U.S. patent application number 11/857721 was filed with the patent office on 2008-03-20 for method and materials for patterning of an amorphous, non-polymeric, organic matrix with electrically active material disposed therein.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Erika Bellmann, James G. Bentsen, Yong Hsu, Manoj Nirmal, Martin B. Wolk.
Application Number | 20080069980 11/857721 |
Document ID | / |
Family ID | 25461042 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080069980 |
Kind Code |
A1 |
Bellmann; Erika ; et
al. |
March 20, 2008 |
METHOD AND MATERIALS FOR PATTERNING OF AN AMORPHOUS, NON-POLYMERIC,
ORGANIC MATRIX WITH ELECTRICALLY ACTIVE MATERIAL DISPOSED
THEREIN
Abstract
In one method of making an organic electroluminescent device, a
transfer layer is solution coated on a donor substrate. The
transfer layer includes an amorphous, non-polymeric, organic matrix
with a light emitting material disposed in the matrix. The transfer
layer is then selectively patterned on a receptor. Examples of
patterning methods include laser thermal transfer or thermal head
transfer. The method and associated materials can be used to form,
for example, organic electroluminescent devices.
Inventors: |
Bellmann; Erika; (St. Paul,
MN) ; Bentsen; James G.; (North St. Paul, MN)
; Hsu; Yong; (Woodbury, MN) ; Nirmal; Manoj;
(St. Paul, MN) ; Wolk; Martin B.; (Woodbury,
MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25461042 |
Appl. No.: |
11/857721 |
Filed: |
September 19, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11337882 |
Jan 23, 2006 |
7276322 |
|
|
11857721 |
Sep 19, 2007 |
|
|
|
10732853 |
Dec 10, 2003 |
7014978 |
|
|
11337882 |
Jan 23, 2006 |
|
|
|
09931598 |
Aug 16, 2001 |
6699597 |
|
|
10732853 |
Dec 10, 2003 |
|
|
|
Current U.S.
Class: |
428/32.8 |
Current CPC
Class: |
C09K 2211/1048 20130101;
H01L 51/0038 20130101; C09K 2211/1007 20130101; H01L 51/0037
20130101; H01L 51/0059 20130101; H01L 51/5016 20130101; C09K 11/06
20130101; H01L 51/0004 20130101; H01L 51/0014 20130101; H01L
51/0013 20130101; Y10S 430/165 20130101; H01L 51/0072 20130101;
H01L 51/0062 20130101; H01L 51/5012 20130101; H01L 51/0015
20130101; H01L 51/0003 20130101; H01L 51/007 20130101; H01L
2251/308 20130101; H01L 51/0081 20130101; C09K 2211/1055 20130101;
C09K 2211/1003 20130101; C09K 2211/1044 20130101; C09K 2211/1059
20130101; C09K 2211/1029 20130101; H01L 51/0095 20130101; H01L
51/0024 20130101; H05B 33/14 20130101; H01L 51/0067 20130101; Y10S
428/917 20130101; H01L 51/0094 20130101; C09K 2211/1014 20130101;
H01L 51/56 20130101; H01L 51/0053 20130101; C09K 2211/1011
20130101 |
Class at
Publication: |
428/032.8 |
International
Class: |
B41M 5/40 20060101
B41M005/40 |
Claims
1. A donor sheet, comprising: a substrate; a light-to-heat
conversion layer disposed on the substrate for converting incident
imaging radiation into heat; a first transfer layer disposed on the
light-to-heat conversion layer, wherein the first transfer layer
comprises an amorphous non-polymeric electroactive material soluble
in a solvent; and at least one additional electroactive transfer
layer disposed on the light-to-heat conversion layer, wherein the
at least one additional transfer layer is susceptible to the
solvent and comprises a light emitting material.
2. The donor sheet of claim 1, wherein the electroactive material
of the first transfer layer comprises a hole blocking material.
3. The donor sheet of claim 1, wherein the electroactive material
of the first transfer layer comprises an electron transport
material.
4. The donor sheet of claim 1, wherein the at least one additional
transfer layer comprises a light emitting material.
5. The donor sheet of claim 1, wherein the at least one additional
transfer layer comprises a hole transport layer.
6. The donor sheet of claim 5, wherein the at least one additional
transfer layer comprises a hole injection layer.
Description
[0001] This application is a divisional of U.S. Ser. No.
11/337,882, filed Jan. 23, 2006, now allowed, which is a divisional
of U.S. Ser. No. 10/732,853, filed Dec. 10, 2003, now U.S. Pat. No.
7,014,978, which is a divisional of U.S. Ser. No. 09/931,598, filed
Aug. 16, 2001, now U.S. Pat. No. 6,699,597, the disclosure of which
are herein incorporated by reference.
BACKGROUND
[0002] Pattern-wise thermal transfer of materials from donor sheets
to receptor substrates has been proposed for a wide variety of
applications. For example, materials can be selectively thermally
transferred to form elements useful in electronic displays and
other devices. Specifically, selective thermal transfer of color
filters, black matrix, spacers, polarizers, conductive layers,
transistors, phosphors, and organic electroluminescent materials
have all been proposed.
SUMMARY OF THE INVENTION
[0003] The present invention provides new thermal transfer donor
elements and methods of patterning using thermal transfer donor
elements. The donors and methods of the present invention are
particularly suited to patterning solvent-coated materials on the
same substrate as solvent-susceptible materials. This can be
especially useful in constructing organic electroluminescent
displays and devices as well as components for organic
electroluminescent displays and devices.
[0004] The present invention is directed to materials and methods
for patterning an amorphous, non-polymeric, organic matrix with
electrically active material disposed in the matrix, as well as the
devices formed using the materials and methods. One embodiment of
the invention includes a method of making an organic
electroluminescent device. A transfer layer is solution coated on a
donor substrate. The transfer layer includes an amorphous,
non-polymeric, organic matrix with a light emitting material
disposed in the matrix. The transfer layer is then selectively
thermally transferred to a receptor. Thermal transfer can include
laser thermal transfer or thermal head transfer.
[0005] Another embodiment is a donor sheet that includes a
substrate and a transfer layer. The transfer layer includes a
solution-coated, amorphous, non-polymeric, organic matrix with a
light emitting material disposed in the matrix. This transfer layer
is capable of being selectively thermally transferred from the
donor sheet to a proximally located receptor. Optionally, the donor
sheet also includes a light-to-heat conversion layer disposed on
the substrate for converting incident imaging radiation into
heat.
[0006] Yet another embodiment is a method of making a donor sheet.
The method includes forming a transfer layer on a substrate by
solution coating a coating composition on the substrate to form an
amorphous, non-polymeric, organic matrix with a light emitting
material disposed in the matrix. Optionally, the method also
includes forming a light-to-heat conversion layer on the
substrate.
[0007] Another embodiment is an electroluminescent device that
includes a first electrode, a second electrode, and a light
emitting layer disposed between the first and second electrodes.
The light emitting layer includes an amorphous, non-polymeric
organic matrix with a light emitting polymer disposed in the
matrix. Such devices include, for example, single OEL devices for,
for example, lighting applications and pixelated devices, such as
displays, which contain multiple OEL devices.
[0008] It will be recognized that electrically active materials
other than light emitting materials can be disposed in an
amorphous, non-polymeric, organic matrix. For example, a conducting
or semiconducting material can be disposed in the amorphous,
non-polymeric, organic matrix. Application examples include the
formation of a hole transport layer or electron transport layer or
other charge conducting layer by disposing a hole transport
material or electron transport material in an amorphous,
non-polymeric, organic matrix. The matrix can be formed using, for
example, any of the materials described above. This structure can
be particularly useful for conducting or semiconducting polymeric
materials to produce a layer with lower cohesive strength than the
polymer itself.
[0009] In addition, these materials and methods can also be useful
for non-thermal printing and transfer methods including, for
example, inkjet printing, screen printing, and photolithographic
patterning.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0011] FIG. 1 is a schematic side view of an organic
electroluminescent display construction;
[0012] FIG. 2 is a schematic side view of a donor sheet for
transferring materials according to the present invention;
[0013] FIG. 3 is a schematic side view of an organic
electroluminescent display according to the present invention;
[0014] FIG. 4A is a schematic side view of a first embodiment of an
organic electroluminescent device;
[0015] FIG. 4B is a schematic side view of a second embodiment of
an organic electroluminescent device;
[0016] FIG. 4C is a schematic side view of a third embodiment of an
organic electroluminescent device;
[0017] FIG. 4D is a schematic side view of a fourth embodiment of
an organic electroluminescent device;
[0018] FIG. 4E is a schematic side view of a fifth embodiment of an
organic electroluminescent device; and
[0019] FIG. 4F is a schematic side view of a sixth embodiment of an
organic electroluminescent device.
[0020] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the
invention.
DETAILED DESCRIPTION
[0021] The present invention contemplates materials and methods for
the thermal patterning of an amorphous, non-polymeric, organic
matrix with an electrically active material disposed therein. Such
methods and materials can be used to form devices including organic
electronic devices and displays that include electrically active
organic materials, and in particular that contain light emitting
polymers or other light emitting molecules. Examples of organic
electronic devices that can be made include organic transistors,
photovoltaic devices, organic electroluminescent (OEL) devices such
as organic light emitting diodes (OLEDs), and the like. In
addition, these materials and methods can also be useful for
non-thermal printing, patterning, and transfer methods including,
for example, inkjet printing, screen printing, and
photolithographic patterning.
[0022] The terms "active" or "electrically active", when used to
refer to a layer or material in an organic electronic device,
indicate layers or materials that perform a function during
operation of the device, for example producing, conducting, or
semiconducting a charge carrier (e.g., electrons or holes),
producing light, enhancing or tuning the electronic properties of
the device construction, and the like. The term "non-active" refers
to materials or layers that, although not directly contributing to
functions as described above, may have some non-direct contribution
to the assembly or fabrication or to the functionality of an
organic electronic device.
[0023] Organic electroluminescent (OEL) display or device refers to
electroluminescent displays or devices that include an organic
emissive material, whether that emissive material includes a small
molecule (SM) emitter, a SM doped polymer, a light emitting polymer
(LEP), a doped LEP, a blended LEP, or another organic emissive
material whether provided alone or in combination with any other
organic or inorganic materials that are functional or
non-functional in the OEL display or devices
[0024] R. H. Friend, et al. ("Electroluminescence in Conjugated
Polymers" Nature, 397, 1999, 12 1.), incorporated herein by
reference, describe one mechanism of electroluminescence as
including the "injection of electrons from one electrode and holes
from the other, the capture of oppositely charged carriers
(so-called recombination), and the radiative decay of the excited
electron-hole state (exciton) produced by this recombination
process."
[0025] Materials for OEL devices can be small molecule (SM) or
polymeric in nature. SM materials include charge transporting,
charge blocking, semiconducting, and electroluminescent organic and
organometallic compounds. Generally, SM materials can be vacuum
deposited or evaporated to form thin layers in a device. In
practice, multiple layers of SMs are typically used to produce
efficient OELs since a given material generally does not have both
the desired charge transport and electroluminescent properties.
[0026] LEP materials are typically conjugated polymeric or
oligomeric molecules that preferably have sufficient film-forming
properties for solution processing. Conventionally, LEP materials
are utilized by casting a solvent solution of the LEP material on a
substrate, and evaporating the solvent, thereby leaving a polymeric
film. Other methods for forming LEP films include ink jetting and
extrusion coating. Alternatively, LEPs can be formed in situ on a
substrate by reaction of precursor species. Efficient LEP lamps
have been constructed with one, two, or more organic layers.
[0027] OELs can also be fabricated with one or more molecular
glasses. Molecular glass is the term used to describe organic, low
molar mass, amorphous, film-forming compounds. Hole transporting,
electron transporting, and bipolar molecular glasses are known
including those described in J. V. Grazulevicius, P. Strohriegl,
"Charge-Transporting Polymers and Molecular Glasses", Handbook of
Advanced Electronic and Photonic Materials and Devices, H. S. Nalwa
(ed.),10, 2001, 233, incorporated herein by reference. The
solubility of the molecular glasses can limit the ways in which
multilayer electronic structures are conventionally created. For
example, it may not be possible to solution coat a light emitting
polymer layer on top of a hole transport layer of a molecular glass
if the materials of the two layers are soluble in the same
solvents. Devices have been previously formed with, for example,
solution coated hole transport layers and vapor deposited emission
and electron transport layers.
[0028] As an example of device structure, FIG. 1 illustrates an OEL
display or device 100 that includes a device layer 110 and a
substrate 120. Any other suitable display component can also be
included with display 100. Optionally, additional optical elements
or other devices suitable for use with electronic displays,
devices, or lamps can be provided between display 100 and viewer
position 140 as indicated by optional element 130.
[0029] In some embodiments like the one shown, device layer 110
includes one or more OEL devices that emit light through the
substrate toward a viewer position 140. The viewer position 140 is
used generically to indicate an intended destination for the
emitted light whether it be an actual human observer, a screen, an
optical component, an electronic device, or the like. In other
embodiments (not shown), device layer 110 is positioned between
substrate 120 and the viewer position 140. The device configuration
shown in FIG. 1 (termed "bottom emitting") may be used when
substrate 120 is transmissive to light emitted by device layer 110
and when a transparent conductive electrode is disposed in the
device between the emissive layer of the device and the substrate.
The inverted configuration (termed "top emitting") may be used when
substrate 120 does or does not transmit the light emitted by the
device layer and the electrode disposed between the substrate and
the light emitting layer of the device does not transmit the light
emitted by the device.
[0030] Device layer 110 can include one or more OEL devices
arranged in any suitable manner. For example, in lamp applications
(e.g., backlights for liquid crystal display (LCD) modules), device
layer 110 might constitute a single OEL device that spans an entire
intended backlight area. Alternatively, in other lamp applications,
device layer 110 might constitute a plurality of closely spaced
devices that can be contemporaneously activated. For example,
relatively small and closely spaced red, green, and blue light
emitters can be patterned between common electrodes so that device
layer 110 appears to emit white light when the emitters are
activated. Other arrangements for backlight applications are also
contemplated.
[0031] In direct view or other display applications, it may be
desirable for device layer 110 to include a plurality of
independently addressable OEL devices that emit the same or
different colors. Each device might represent a separate pixel or a
separate sub-pixel of a pixelated display (e.g., high resolution
display), a separate segment or sub-segment of a segmented display
(e.g., low information content display), or a separate icon,
portion of an icon, or lamp for an icon (e.g., indicator
applications).
[0032] In at least some instances, an OEL device includes a thin
layer, or layers, of one or more suitable organic materials
sandwiched between a cathode and an anode. When activated,
electrons are injected into the organic layer(s) from the cathode
and holes are injected into the organic layer(s) from the anode. As
the injected charges migrate towards the oppositely charged
electrodes, they may recombine to form electron-hole pairs which
are typically referred to as excitons. The region of the device in
which the excitons are generally formed can be referred to as the
recombination zone. These excitons, or excited state species, can
emit energy in the form of light as they decay back to a ground
state.
[0033] Other layers can also be present in OEL devices such as hole
transport layers, electron transport layers, hole injection layer,
electron injection layers, hole blocking layers, electron blocking
layers, buffer layers, and the like. In addition, photoluminescent
materials can be present in the electroluminescent or other layers
in OEL devices, for example, to convert the color of light emitted
by the electroluminescent material to another color. These and
other such layers and materials can be used to alter or tune the
electronic properties and behavior of the layered OEL device, for
example to achieve a desired current/voltage response, a desired
device efficiency, a desired color, a desired brightness, and the
like.
[0034] FIGS. 4A to 4F illustrate examples of different OEL device
configurations. Each configuration includes a substrate 250, an
anode 252, and a cathode 254. The configurations of FIGS. 4C to 4F
also include a hole transport layer 258 and the configurations of
FIGS. 4B and 4D to 4F include an electron transport layer 260.
These layers conduct holes from the anode or electrons from the
cathode, respectively. Each configuration also includes a light
emitting layer 256a, 256b, 256c that includes one or more light
emitting polymers or other light emitting molecules (e.g., small
molecule light emitting compounds) disposed in an amorphous,
non-polymeric, organic matrix, according to the invention. The
light emitting layer 256a includes a hole transport material, the
light emitting layer 256b includes an electron transport material,
and the light emitting layer 256c includes both hole transport
material and electron transport material. In some embodiments, the
hole transport material or electron transport material is a
material that forms the amorphous, non-polymeric, organic matrix
which contains the light emitting polymer or other light emitting
molecules. In other embodiments, a separate matrix-forming material
is used. In addition, the hole transport material or electron
transport material in the light emitting layer 256a, 256b, 256c can
be the same as or different from the material used in the hole
transport layer 258 or electron transport layer 260,
respectively.
[0035] The anode 252 and cathode 254 are typically formed using
conducting materials such as metals, alloys, metallic compounds,
metal oxides, conductive ceramics, conductive dispersions, and
conductive polymers, including, for example, gold, platinum,
palladium, aluminum, calcium, titanium, titanium nitride, indium
tin oxide (ITO), fluorine tin oxide (FTO), and polyaniline. The
anode 252 and the cathode 254 can be single layers of conducting
materials or they can include multiple layers. For example, an
anode or a cathode may include a layer of aluminum and a layer of
gold, a layer of calcium and a layer of aluminum, a layer of
aluminum and a layer of lithium fluoride, or a metal layer and a
conductive organic layer.
[0036] The hole transport layer 258 facilitates the injection of
holes from the anode into the device and their migration towards
the recombination zone. The hole transport layer 258 can further
act as a barrier for the passage of electrons to the anode 252. The
hole transport layer 258 can include, for example, a diamine
derivative, such as
N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (also known as
TPD) or N,N'-bis(3-naphthalen-2-yl)-N,N'-bis(phenyl)benzidine
(NPB), or a triarylamine derivative, such as,
4,4',4''-Tris(N,N-diphenylamino)triphenylamine (TDATA) or
4,4',4''-Tris(N-3-methylphenyl-N-phenylamino)triphenylamine
(mTDATA). Other examples include copper phthalocyanine (CuPC);
1,3,5-Tris(4-diphenylaminophenyl)benzenes (TDAPBs); and other
compounds such as those described in H. Fujikawa, et al., Synthetic
Metals, 91, 161 (1997) and J. V. Grazulevicius, P. Strohriegl,
"Charge-Transporting Polymers and Molecular Glasses", Handbook of
Advanced Electronic and Photonic Materials and Devices, H. S. Nalwa
(ed.), 10, 233-274 (2001), both of which are incorporated herein by
reference.
[0037] The electron transport layer 260 facilitates the injection
of electrons and their migration towards the recombination zone.
The electron transport layer 260 can further act as a barrier for
the passage of holes to the cathode 254, if desired. As an example,
the electron transport layer 260 can be formed using the
organometallic compound tris(8-hydroxyquinolato) aluminum (Alq3).
Other examples of electron transport materials include
1,3-bis[5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazol-2-yl]benzene,
2-(biphenyl-4-yl)-5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazole
(tBuPBD) and other compounds described in C. H. Chen, et al.,
Macromol. Symp. 125, 1 (1997) and J. V. Grazulevicius, P.
Strohriegl, "Charge-Transporting Polymers and Molecular Glasses",
Handbook of Advanced Electronic and Photonic Materials and Devices,
H. S. Nalwa (ed.),10, 233 (2001), both of which are incorporated
herein by reference.
[0038] A number of methods have been used or tried to make OEL
devices. For example, SM light emitting devices have been formed by
sequential vapor deposition of hole transporting, emitting, and
electron transporting molecules. Although the layers are amorphous
when deposited, the layers can crystallize over time, diminishing
their charge transport and emission properties. In general, it can
be difficult to solution cast SM materials since they tend to form
crystallites upon solvent drying or later during the device
lifetime.
[0039] As another example, light emitting layers based on LEP
materials have been fabricated by solution coating a thin layer of
the polymer. This method may be suitable for monochromatic displays
or lamps. In the case of devices fabricated with solution casting
steps, it is much more difficult to create multilayer devices by
multiple solvent casting steps. Multilayer devices could be
produced in which layers are cast from different solvents, a first
insoluble layer is created in situ and a second layer is solvent
cast, a first layer is solution cast and a second layer is vapor
deposited, or one or both of the layers is crosslinked.
[0040] Polymer dispersed small molecule devices have been
fabricated by solution casting a blend of a host polymer (e.g.
polyvinylcarbazole) and a mixture of one or more small molecule
dopants. In general, these devices require high voltages to operate
and are not suitable for display applications. In addition, they
suffer from the same restrictions for patterning as the LEPs.
[0041] Another method of forming devices includes the transfer of
one or more transfer layers by laser thermal patterning as
described in, for example, U.S. Pat. Nos. 6,242,152; 6,228,555;
6,228,543; 6,221,553; 6,221,543; 6,214,520; 6,194,119; 6,114,088;
5,998,085; 5,725,989; 5,710,097; 5,695,907; and 5,693,446, and in
co-assigned U.S. patent application Ser. Nos. 09/853,062;
09/844,695; 09/844,100; 09/662,980; 09/662,845; 09/473,114; and
09/451,984, all of which are incorporated herein by reference. The
patterning process can depend upon the physical properties of the
transfer layer. One parameter is the cohesive, or film strength, of
the transfer layer. During imaging, the transfer layer preferably
breaks cleanly along the line dividing imaged and unimaged regions
to form the edge of a pattern. Highly conjugated polymers which
exist in extended chain conformations, such as
polyphenylenevinylenes, can have high tensile strengths and elastic
moduli comparable to that of polyaramide fibers. In practice, clean
edge formation during the laser thermal imaging of light emitting
polymers can be challenging. The undesired consequence of poor edge
formation is rough, torn, or ragged edges on the transferred
pattern.
[0042] As an alternative to or improvement on these previous
methods and to address some of the above-described difficulties,
light emitting material, such as one or more light emitting
polymers (LEPs) or other light emitting molecules, can be solution
coated as part of a coating composition that includes a material
capable of forming an amorphous, non-polymeric, organic matrix that
resists crystallization. The amorphous nature of the matrix can, in
combination with the non-polymeric nature of the matrix, provide
low cohesive strength, as compared to typical polymer transfer
layers, during transfer from a donor medium to a receptor, as
described below. The amorphous nature of the matrix-forming
material may also act to compatibilize more than one electrically
active material (e.g. two otherwise incompatible LEPs or an LEP and
a phosphorescent emitter). LEPs will be used as an example for the
description below, but it will be recognized that other light
emitting, semiconducting, hole transporting, electron transporting,
or otherwise electrically active molecules could be used in place
of or in addition to one or more LEPs. In addition, laser thermal
transfer will be used as an example of a method for forming light
emitting and other layers, however, it will be recognized that
other transfer, patterning, and printing techniques can be used,
such as inkjet printing, screen printing, thermal head printing,
and photolithographic patterning.
[0043] Any non-polymeric, organic material can be used as long as
the material can be solution coated to form an amorphous matrix and
will resist substantial crystallization during the expected
lifetime of the device under the expected operating and storage
conditions. Examples of suitable materials are described in J. V.
Grazulevicius, P. Strohriegl, "Charge-Transporting Polymers and
Molecular Glasses", Handbook of Advanced Electronic and Photonic
Materials and Devices, H. S. Nalwa (ed.), 10, 233-274 (2001);
Shirota, J. Mater. Chem., 10, 1, (2000); Kreger et al., Synthetic
Metals, 119, 163 (2001); PCT Patent Applications Publication Nos.
WO 99/21935 and WO 00/03565; and Robinson et al., Adv. Mat., 2000,
12(22), 1701, all of which are incorporated herein by reference.
Preferably, this non-polymeric, organic material does not have a
substantial propensity to form or does not form a stable,
crystalline phase under the expected operating and storage
conditions. In addition, preferably, the non-polymeric, organic
material and light emitting material are compatible or soluble in a
common solvent or solvents and do not substantially phase separate
during solution coating and, more preferably, do not phase separate
upon removal of the solvent(s).
[0044] In general, when the amorphous matrix is formed, the
threshold for reducing cohesion in an amorphous matrix/LEP blend is
the point at which the LEP becomes the discontinuous phase (if
there are two observable phases) or the point in which the LEP
chains are dissolved by the amorphous matrix (if there is a single
phase). Generally, the total amount of light emitting polymer or
other light emitting molecule is no more than 50 wt. % of the
solids of a coating composition and can be 40 wt. %, 25 wt. %, or
less of the solids. Typically, the ratio, by weight, of the
non-polymeric, organic material to light emitting material (e.g.,
light emitting polymer or polymers) is at least 1:1 and typically
is in the range of 1:1 to 100:1. Generally ratios of at least 1:1,
and typically at least 2:1 or 3:1 or more, are suitable for thermal
transfer applications.
[0045] In some embodiments, the non-polymeric, organic material is
also a hole or electron transport material. In some of these
embodiments, a hole or electron transport layer is formed using the
non-polymeric, organic material and coated with or coated onto a
light emitting layer containing the same non-polymeric, organic
material as an amorphous matrix for the light emitting
material.
[0046] In some embodiments, a gradient of light emitting material
can be formed by depositing several layers with different
concentrations of light emitting material to achieve a desired
profile. The thermal transfer methods described below can be useful
in creating such structures by sequentially transferring each of
the layers. In addition, layers can be formed using different light
emitting materials to achieve different colors or to produce, for
example, stacked red, green, and blue pixels with intervening
electrodes between each pixel.
[0047] If the non-polymeric, organic material is not a hole or
electron transport material, it can be desirable to include a hole
or electron transport material as part of the coating composition.
Other materials that can be included in the coating composition
include, for example, small molecule dopants (e.g. triplet
emitters); other non-polymeric, organic materials; coating aids,
surfactants; particulate material to, for example, reduce cohesion;
dispersants; stabilizers; and photosensitizers.
[0048] In some embodiments, the non-polymeric, organic material
used to form the amorphous matrix is also a light emitting
molecule. In these embodiments, it is preferred that the materials
and operating conditions be selected to favor emission by the light
emitting polymer instead of the non-polymeric, organic material
which forms the amorphous matrix. For example, the non-polymeric,
organic material may be capable of emitting light in the blue
region of the spectrum. In this instance, a light emitting polymer
could be selected which emits in the red or green regions of the
spectrum. Selection can be based on, for example, the mechanism(s)
of molecular energy transfer and the bandgap of the materials.
[0049] Examples of suitable non-polymeric, organic materials that
can form an amorphous matrix when solution coated include molecules
having a tetrahedral core with pendant electrically active groups.
Examples of such molecules include tetraphenyl methanes 1,
tetraphenyl silanes 2, and tetraphenyl adamantanes 3, as well as
tetraphenyl germanes, tetraphenyl plumbanes, and tetraphenyl
stannanes (i.e., replace Si in 2 with Ge, Pb, or Sn, respectively):
##STR1## Each R is independently a substituent containing one or
more conjugated functional groups (for example, aryl, arylene,
heteroaryl, heteroarylene, alkenyl, or alkenylene) that stabilize
holes (e.g. as cation radicals), electrons (e.g. as anion
radicals), or act as a chromophore. Each R substituent can be the
same as or different from the other R substituents. When all the R
substituents are the same, the molecule typically has some
symmetry. When at least one of the R substituents is different, the
molecule has asymmetry which may further facilitate the formation
and retention of an amorphous matrix. In some instances, R includes
an aromatic ring that is fused to the phenyl group to which R is
attached to form, for example, a substituted or unsubstituted
naphthyl or other fused ring structure. Examples and further
descriptions of such materials can be found in, for example, PCT
Patent Application Publication No. WO 00/03565 and Robinson et al.,
Adv. Mat., 2000, 12(22), 1701, both of which are incorporated
herein by reference.
[0050] In some embodiments, the substituents R include one or more
conjugated structures having, for example, one or more alkenyl,
alkenylene, aryl, arylene (e.g., phenylene, naphthylene, or
anthrylene), heteroaryl, or heteroarylene functional groups. The
substituents can have extended .pi.-conjugated systems which can
include heteroatoms such as nitrogen and oxygen. The conjugated
systems can include electron rich moieties (e.g. a triarylamine) to
stabilize cation radicals (e.g. holes), electron poor moieties to
stabilize anion radicals (e.g. electrons), or a HOMO-LUMO (Highest
Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital) gap
in the ultraviolet to visible range to act as a chromophore.
Examples of suitable R groups include, but are not limited to, the
following: ##STR2## ##STR3##
[0051] Specific examples of suitable tetrahedral core materials
include compounds 4-6: ##STR4## X is C, Si, Ge, Pb, or Sn and
R.sub.2 is H or alkyl. Compounds 5 and 6 include fluorene moieties
that can be chromophoric. These particular fluorenes typically have
band gaps in the blue to ultraviolet range. Such materials can be
useful with LEPs that emit in the red or green regions so that
emission is primarily or exclusively from the LEP.
[0052] Also among this type of compounds are spiro compounds such
as compounds 7-9: ##STR5## where each R is independently a
conjugated structure having one or more alkenyl, alkenylene, aryl,
arylene (e.g., phenylene, naphthylene, or anthrylene), heteroaryl,
or heteroarylene functional groups. The substituents can have
extended .pi.-conjugated systems which can include heteroatoms such
as nitrogen and oxygen. The conjugated systems can include electron
rich moieties (e.g. a triarylamine) to stabilize cation radicals
(e.g. holes), electron poor moieties to stabilize anion radicals
(e.g. electrons), or a HOMO-LUMO (Highest Occupied Molecular
Orbital-Lowest Unoccupied Molecular Orbital) gap in the ultraviolet
to visible range to act as a chromophore.
[0053] Other materials that can be used to form amorphous,
non-polymeric, organic matrices include dendrimers. Dendrimeric
compounds have a core moiety with three or more dendritic
substituents extending from the core moiety. Examples of suitable
core moieties include triphenylamine, benzene, pyridine,
pyrimidine, and others described in PCT Patent Application Ser. No.
WO 99/21935, incorporated herein by reference. The dendritic
substituents typically contain two or more aryl, arylene (e.g.,
phenylene), heteroaryl, heteroarylene, alkenyl, or alkenylene
substituents. In some embodiments, the substituents can be
conjugated structures having one or more alkenyl, alkenylene, aryl,
arylene (e.g., phenylene, naphthylene, or anthrylene), heteroaryl,
or heteroarylene moieties. The dendritic substituents can be the
same or different. Examples of dendrimeric compounds include
starburst compounds based on, for example, triphenylamines, such as
compounds 10-16: ##STR6## ##STR7## Each R.sub.1 and R.sub.2 is
independently H, F, Cl, Br, I, --SH, --OH, alkyl, aryl, heteroaryl,
fluoroalkyl, fluoroalkylalkoxy, alkenyl, alkoxy, amino, or
alkyl-COOH. Each R.sub.3 is independently H, F, Cl, Br, I, alkyl,
fluoroalkyl, alkoxy, aryl, amino, cyano, or nitro. Each X.sub.1 is
independently O, S, Se, NR.sub.3, BR.sub.3, or PR.sub.3. The alkyl,
aryl, and heteroaryl portions of any of these substituents can be
substituted or unsubstituted. Each R.sub.1, R.sub.2, R.sub.3, and
X.sub.1 can be the same as or different from similarly labeled
substituents (i.e., all R.sub.1 substituents can be the same as or
one or more of the R.sub.1 substituents can be different from each
other).
[0054] Other dendrimer compounds can have an aryl or heteroaryl
moiety as a core, such as compounds 17-26: ##STR8## ##STR9## Each
Ar.sub.1 and Ar.sub.2 is independently a substituted or
unsubstituted aryl or heteroaryl, including, for example,
substituted or unsubstituted phenyl, pyridine, pyrole, furan,
thiophene, or one of the following structures: ##STR10## ##STR11##
Each R.sub.1 and R.sub.2 is independently H, F, Cl, Br, I, --SH,
--OH, alkyl, aryl, heteroaryl, fluoroalkyl, fluoroalkylalkoxy,
alkenyl, alkoxy, amino, or alkyl-COOH. Each R.sub.3 is
independently H, F, Cl, Br, I, alkyl, fluoroalkyl, alkoxy, aryl,
amino, cyano, or nitro. Each X.sub.1 and X.sub.2 is independently
O, S, Se, NR.sub.3, BR.sub.3, or PR.sub.3. The alkyl, aryl, and
heteroaryl portions of any of these substituents can be substituted
or unsubstituted. Each R.sub.1, R.sub.2, R.sub.3, X.sub.1, and
X.sub.2 can be the same as or different from similarly labeled
substituents (i.e., all R.sub.1 substituents can be the same as or
one or more of the R.sub.1 substituents can be different from each
other).
[0055] Other amorphous materials include, for example, compounds
27-32: ##STR12## Each Ar.sub.1 and Ar.sub.2 is independently a
substituted or unsubstituted aryl or heteroaryl, n is an integer in
the range of 1 to 6, and each R.sub.1 is independently H, F, Cl,
Br, I, --SH, --OH, alkyl, aryl, heteroaryl, fluoroalkyl,
fluoroalkylalkoxy, alkenyl, alkoxy, amino, or alkyl-COOH. Each
R.sub.3 is independently H, F, Cl, Br, I, alkyl, fluoroalkyl,
alkoxy, aryl, amino, cyano, or nitro. Each X, Xi, and X.sub.2 are
independently O, S, Se, NR.sub.3, BR.sub.3, or PR.sub.3. The alkyl,
aryl, and heteroaryl portions of any of these substituents can be
substituted or unsubstituted. Each R.sub.1, R.sub.2, R.sub.3, X,
X.sub.1, and X.sub.2 can be the same as or different from similarly
labeled substituents (i.e., all R.sub.1 substituents can be the
same as or one or more of the R.sub.1 substituents can be different
from each other).
[0056] Unless otherwise indicated, the term "alkyl" includes both
straight-chained, branched, and cyclic alkyl groups and includes
both unsubstituted and substituted alkyl groups. Unless otherwise
indicated, the alkyl groups are typically C1-C20. Examples of
"alkyl" as used herein include, but are not limited to, methyl,
ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, and isopropyl, and
the like.
[0057] Unless otherwise indicated, the term "alkylene" includes
both straight-chained, branched, and cyclic divalent hydrocarbon
radicals and includes both unsubstituted and substituted alkenylene
groups. Unless otherwise indicated, the alkylene groups are
typically C1-C20. Examples of "alkylene" as used herein include,
but are not limited to, methylene, ethylene, propylene, butylene,
and isopropylene, and the like.
[0058] Unless otherwise indicated, the term "alkenyl" includes both
straight-chained, branched, and cyclic monovalent hydrocarbon
radicals have one or more double bonds and includes both
unsubstituted and substituted alkenyl groups. Unless otherwise
indicated, the alkenyl groups are typically C2-C20. Examples of
"alkenylene" as used herein include, but are not limited to,
ethenyl, propenyl, and the like.
[0059] Unless otherwise indicated, the term "alkenylene" includes
both straight-chained, branched, and cyclic divalent hydrocarbon
radicals have one or more double bonds and includes both
unsubstituted and substituted alkenylene groups. Unless otherwise
indicated, the alkylene groups are typically C2-C20. Examples of
"alkenylene" as used herein include, but are not limited to,
ethene-1,2-diyl, propene-1,3-diyl, and the like.
[0060] Unless otherwise indicated, the term "aryl" refers to
monovalent unsaturated aromatic carbocyclic radicals having one to
fifteen rings, such as phenyl or bipheynyl, or multiple fused
rings, such as naphthyl or anthryl, or combinations thereof
Examples of aryl as used herein include, but are not limited to,
phenyl, 2-naphthyl, 1-naphthyl, biphenyl, 2-hydroxyphenyl,
2-aminophenyl, 2-methoxyphenyl and the like.
[0061] Unless otherwise indicated, the term "arylene" refers to
divalent unsaturated aromatic carbocyclic radicals having one to
fifteen rings, such as phenylene, or multiple fused rings, such as
naphthylene or anthrylene, or combinations thereof. Examples of
"arylene" as used herein include, but are not limited to,
benzene-1,2-diyl, benzene-1,3-diyl, benzene-1,4-diyl,
naphthalene-1,8-diyl, anthracene-1,4-diyl, and the like.
[0062] Unless otherwise indicated, the term "heteroaryl" refers to
functional groups containing a monovalent five- to seven-membered
aromatic ring radical with one or more heteroatoms independently
selected from S, O, or N. Such a heteroaryl ring may be optionally
fused to one or more of another heterocyclic ring(s), heteroaryl
ring(s), aryl ring(s), cycloalkenyl ring(s), or cycloalkyl rings.
Examples of "heteroaryl" used herein include, but are not limited
to, furyl, thiophenyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl,
tetrazolyl, thiazolyl, oxazolyl, isoxazolyl, oxadiazolyl,
thiadiazolyl, isothiazolyl, pyridinyl, pyridazinyl, pyrazinyl,
pyrimidinyl, quinolinyl, isoquinolinyl, benzofuryl,
benzothiophenyl, indolyl, and indazolyl, and the like.
[0063] Unless otherwise indicated, the term "heteroarylene" refers
to functional groups containing a divalent five- to seven-membered
aromatic ring radical with one or more heteroatoms independently
selected from S, O, or N. Such a heteroarylene ring may be
optionally fused to one or more of another heterocyclic ring(s),
heteroaryl ring(s), aryl ring(s), cycloalkenyl ring(s), or
cycloalkyl rings. Examples of "heteroarylene" used herein include,
but are not limited to, furan-2,5-diyl, thiophene-2,4-diyl,
1,3,4-oxadiazole-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl,
1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, pyridine-2,4-diyl,
pyridine-2,3-diyl, pyridine-2,5-diyl, pyrimidine-2,4-diyl,
quinoline-2,3-diyl, and the like.
[0064] Suitable substituents for substituted alkyl, alkylene,
alkenyl, alkenylene, aryl, arylene, heteroaryl, and heteroarylene
groups include, but are not limited to, alkyl, alkylene, alkoxy,
aryl, arylene, heteroaryl, heteroarylene, alkenyl, alkenylene,
amino, F, Cl, Br, I, --OH, --SH, cyano, nitro, --COOH, and
--COO-alkyl.
[0065] It will be recognized that electrically active materials
other than light emitting materials can be disposed in an
amorphous, non-polymeric, organic matrix. For example, a conducting
or semiconducting material can be disposed in the amorphous,
non-polymeric, organic matrix. Application examples include the
formation of a hole transport layer or electron transport layer or
other charge conducting layer by disposing a hole transport
material or electron transport material in an amorphous,
non-polymeric, organic matrix. The matrix can be formed using, for
example, any of the materials described above. This structure can
be particularly useful for conducting or semiconducting polymeric
materials to produce a layer with lower cohesive strength than the
polymer itself.
[0066] A variety of light emitting materials including LEP and SM
light emitters can be used. Examples of classes of suitable LEP
materials include poly(phenylenevinylene)s (PPVs),
poly-para-phenylenes (PPPs), polyfluorenes (PFs), other LEP
materials now known or later developed, and co-polymers or blends
thereof. Suitable LEPs can also be molecularly doped, dispersed
with fluorescent dyes or other PL materials, blended with active or
non-active materials, dispersed with active or non-active
materials, and the like. Examples of suitable LEP materials are
described in Kraft, et al., Angew. Chem. Int. Ed., 37, 402-428
(1998); U.S. Pat. Nos. 5,621,131; 5,708,130; 5,728,801; 5,840,217;
5,869,350; 5,900,327; 5,929,194; 6,132,641; and 6,169,163; and PCT
Patent Application Publication No. 99/40655, all of which are
incorporated herein by reference.
[0067] SM materials are generally non-polymer organic or
organometallic molecular materials that can be used in OEL displays
and devices as emitter materials, charge transport materials, as
dopants in emitter layers (e.g., to control the emitted color) or
charge transport layers, and the like. Commonly used SM materials
include metal chelate compounds, such as tris(8-hydroxyquinoline)
aluminum (Alq3), and
N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD). Other SM
materials are disclosed in, for example, C. H. Chen, et al.,
Macromol. Symp. 125, 1 (1997), Japanese Laid Open Patent
Application 2000-195673, U.S. Pat. Nos. 6,030,715, 6,150,043, and
6,242,115 and, PCT Patent Applications Publication Nos. WO 00/18851
(divalent lanthanide metal complexes), WO 00/70655 (cyclometallated
iridium compounds and others), and WO 98/55561, all of which are
incorporated herein by reference.
[0068] Referring back to FIG. 1, device layer 110 is disposed on
substrate 120. Substrate 120 can be any substrate suitable for OEL
device and display applications. For example, substrate 120 can
comprise glass, clear plastic, or other suitable material(s) that
are substantially transparent to visible light. Substrate 120 can
also be opaque to visible light, for example stainless steel,
crystalline silicon, poly-silicon, or the like. Because some
materials in OEL devices can be particularly susceptible to damage
due to exposure to oxygen or water, substrate 120 preferably
provides an adequate environmental barrier, or is supplied with one
or more layers, coatings, or laminates that provide an adequate
environmental barrier.
[0069] Substrate 120 can also include any number of devices or
components suitable in OEL devices and displays such as transistor
arrays and other electronic devices; color filters, polarizers,
wave plates, diffusers, and other optical devices; insulators,
barrier ribs, black matrix, mask work and other such components;
and the like. Generally, one or more electrodes will be coated,
deposited, patterned, or otherwise disposed on substrate 120 before
forming the remaining layer or layers of the OEL device or devices
of the device layer 110. When a light transmissive substrate 120 is
used and the OEL device or devices are bottom emitting, the
electrode or electrodes that are disposed between the substrate 120
and the emissive material(s) are preferably substantially
transparent to light, for example transparent conductive electrodes
such as indium tin oxide (ITO) or any of a number of other
transparent conductive oxides.
[0070] Element 130 can be any element or combination of elements
suitable for use with OEL display or device 100. For example,
element 130 can be an LCD module when device 100 is a backlight.
One or more polarizers or other elements can be provided between
the LCD module and the backlight device 100, for instance an
absorbing or reflective clean-up polarizer. Alternatively, when
device 100 is itself an information display, element 130 can
include one or more of polarizers, wave plates, touch panels,
antireflective coatings, anti-smudge coatings, projection screens,
brightness enhancement films, or other optical components,
coatings, user interface devices, or the like.
[0071] Organic electronic devices containing materials for light
emission can be made at least in part by selective thermal transfer
of light emitting material from a thermal transfer donor sheet to a
desired receptor substrate. For example, light emitting polymer
displays and lamps can be made coating an LEP and a non-polymeric,
organic material capable of forming an amorphous matrix on a donor
sheet and then selectively transferring the LEP layer alone or
along with other device layers or materials to the display
substrate.
[0072] Selective thermal transfer of layers containing light
emitting materials for organic electronic devices can be performed
using a thermal transfer donor. FIG. 2 shows an example of a
thermal transfer donor 200 suitable for use in the present
invention. Donor element 200 includes a base substrate 210, an
optional underlayer 212, an optional light-to-heat conversion layer
(LTHC layer) 214, an optional interlayer 216, and a transfer layer
218 that comprises an oriented or orientable emissive material or
functional alignment layer. Each of these elements are described in
more detail in the discussion that follows. Other layers can also
be present. Examples of suitable donors or layers of donors are
disclosed in U.S. Pat. Nos. 6,242,152; 6,228,555; 6,228,543;
6,221,553; 6,221,543; 6,214,520; 6,194,119; 6,114,088; 5,998,085;
5,725,989; 5,710,097; 5,695,907; and 5,693,446, and in co-assigned
U.S. patent application Ser. Nos. 09/853,062; 09/844,695;
09/844,100; 09/662,980; 09/662,845; 09/473,114; and 09/451,984, all
of which are incorporated herein by reference.
[0073] In processes of the present invention, emissive organic
materials, including LEPs or other materials, can be selectively
transferred from the transfer layer of a donor sheet to a receptor
substrate by placing the transfer layer of the donor element
adjacent to the receptor and selectively heating the donor element.
Illustratively, the donor element can be selectively heated by
irradiating the donor element with imaging radiation that can be
absorbed by light-to-heat converter material disposed in the donor,
often in a separate LTHC layer, and converted into heat. In these
cases, the donor can be exposed to imaging radiation through the
donor substrate, through the receptor, or both. The radiation can
include one or more wavelengths, including visible light, infrared
radiation, or ultraviolet radiation, for example from a laser,
lamp, or other such radiation source. Other selective heating
methods can also be used, such as using a thermal print head or
using a thermal hot stamp (e.g., a patterned thermal hot stamp such
as a heated silicone stamp that has a relief pattern that can be
used to selectively heat a donor). Material from the thermal
transfer layer can be selectively transferred to a receptor in this
manner to imagewise form patterns of the transferred material on
the receptor. In many instances, thermal transfer using light from,
for example, a lamp or laser, to patternwise expose the donor can
be advantageous because of the accuracy and precision that can
often be achieved. The size and shape of the transferred pattern
(e.g., a line, circle, square, or other shape) can be controlled
by, for example, selecting the size of the light beam, the exposure
pattern of the light beam, the duration of directed beam contact
with the donor sheet, or the materials of the donor sheet. The
transferred pattern can also be controlled by irradiating the donor
element through a mask.
[0074] As mentioned, a thermal print head or other heating element
(patterned or otherwise) can also be used to selectively heat the
donor element directly, thereby pattern-wise transferring portions
of the transfer layer. In such cases, the light-to-heat converter
material in the donor sheet is optional. Thermal print heads or
other heating elements may be particularly suited for making lower
resolution patterns of material or for patterning elements whose
placement need not be precisely controlled.
[0075] Transfer layers can also be transferred from donor sheets
without selectively transferring the transfer layer. For example, a
transfer layer can be formed on a donor substrate that, in essence,
acts as a temporary liner that can be released after the transfer
layer is contacted to a receptor substrate, typically with the
application of heat or pressure. Such a method, referred to as
lamination transfer, can be used to transfer the entire transfer
layer, or a large portion thereof, to the receptor.
[0076] The mode of thermal mass transfer can vary depending on the
type of selective heating employed, the type of irradiation if used
to expose the donor, the type of materials and properties of the
optional LTHC layer, the type of materials in the transfer layer,
the overall construction of the donor, the type of receptor
substrate, and the like. Without wishing to be bound by any theory,
transfer generally occurs via one or more mechanisms, one or more
of which may be emphasized or de-emphasized during selective
transfer depending on imaging conditions, donor constructions, and
so forth. One mechanism of thermal transfer includes thermal
melt-stick transfer whereby localized heating at the interface
between the thermal transfer layer and the rest of the donor
element can lower the adhesion of the thermal transfer layer to the
donor in selected locations. Selected portions of the thermal
transfer layer can adhere to the receptor more strongly than to the
donor so that when the donor element is removed, the selected
portions of the transfer layer remain on the receptor. Another
mechanism of thermal transfer includes ablative transfer whereby
localized heating can be used to ablate portions of the transfer
layer off of the donor element, thereby directing ablated material
toward the receptor. Yet another mechanism of thermal transfer
includes sublimation whereby material dispersed in the transfer
layer can be sublimated by heat generated in the donor element. A
portion of the sublimated material can condense on the receptor.
The present invention contemplates transfer modes that include one
or more of these and other mechanisms whereby selective heating of
a donor sheet can be used to cause the transfer of materials from a
transfer layer to receptor surface.
[0077] A variety of radiation-emitting sources can be used to heat
donor sheets. For analog techniques (e.g., exposure through a
mask), high-powered light sources (e.g., xenon flash lamps and
lasers) are useful. For digital imaging techniques, infrared,
visible, and ultraviolet lasers are particularly useful. Suitable
lasers include, for example, high power (>100 mW) single mode
laser diodes, fiber-coupled laser diodes, and diode-pumped solid
state lasers (e.g., Nd:YAG and Nd:YLF). Laser exposure dwell times
can vary widely from, for example, a few hundredths of microseconds
to tens of microseconds or more, and laser fluences can be in the
range from, for example, about 0.01 to about 5 J/cm.sup.2 or more.
Other radiation sources and irradiation conditions can be suitable
based on, among other things, the donor element construction, the
transfer layer material, the mode of thermal mass transfer, and
other such factors.
[0078] When high spot placement accuracy is desired (e.g., when
patterning elements for high information content displays and other
such applications) over large substrate areas, a laser can be
particularly useful as the radiation source. Laser sources are also
compatible with both large rigid substrates (e.g., 1 m.times.1
m.times.1.1 mm glass) and continuous or sheeted film substrates
(e.g., 100 .mu.m thick polyimide sheets).
[0079] During imaging, the donor sheet can be brought into intimate
contact with a receptor (as might typically be the case for thermal
melt-stick transfer mechanisms) or the donor sheet can be spaced
some distance from the receptor (as can be the case for ablative
transfer mechanisms or material sublimation transfer mechanisms).
In at least some instances, pressure or vacuum can be used to hold
the donor sheet in intimate contact with the receptor. In some
instances, a mask can be placed between the donor sheet and the
receptor. Such a mask can be removable or can remain on the
receptor after transfer. If a light-to-heat converter material is
present in the donor, radiation source can then be used to heat the
LTHC layer (or other layer(s) containing radiation absorber) in an
imagewise fashion (e.g., digitally or by analog exposure through a
mask) to perform imagewise transfer or patterning of the transfer
layer from the donor sheet to the receptor.
[0080] Typically, selected portions of the transfer layer are
transferred to the receptor without transferring significant
portions of the other layers of the donor sheet, such as the
optional interlayer or LTHC layer. The presence of the optional
interlayer may eliminate or reduce the transfer of material from an
LTHC layer to the receptor or reduce distortion in the transferred
portion of the transfer layer. Preferably, under imaging
conditions, the adhesion of the optional interlayer to the LTHC
layer is greater than the adhesion of the interlayer to the
transfer layer. The interlayer can be transmissive, reflective, or
absorptive to imaging radiation, and can be used to attenuate or
otherwise control the level of imaging radiation transmitted
through the donor or to manage temperatures in the donor, for
example to reduce thermal or radiation-based damage to the transfer
layer during imaging. Multiple interlayers can be present.
[0081] Large donor sheets can be used, including donor sheets that
have length and width dimensions of a meter or more. In operation,
a laser can be rastered or otherwise moved across the large donor
sheet, the laser being selectively operated to illuminate portions
of the donor sheet according to a desired pattern. Alternatively,
the laser may be stationary and the donor sheet or receptor
substrate moved beneath the laser.
[0082] In some instances, it may be necessary, desirable, or
convenient to sequentially use two or more different donor sheets
to form electronic devices on a receptor. For example, multiple
layer devices can be formed by transferring separate layers or
separate stacks of layers from different donor sheets. Multilayer
stacks can also be transferred as a single transfer unit from a
single donor element. For example, a hole transport layer and a LEP
layer can be co-transferred from a single donor. As another
example, a semiconductive polymer and an emissive layer can be
co-transferred from a single donor. Multiple donor sheets can also
be used to form separate components in the same layer on the
receptor. For example, three different donors that each have a
transfer layer comprising a LEP capable of emitting a different
color (for example, red, green, and blue) can be used to form RGB
sub-pixel OEL devices for a full color polarized light emitting
electronic display. As another example, a conductive or
semiconductive polymer can be patterned via thermal transfer from
one donor, followed by selective thermal transfer of emissive
layers from one or more other donors to form a plurality of OEL
devices in a display. As still another example, layers for organic
transistors can be patterned by selective thermal transfer of
electrically active organic materials (oriented or not), followed
by selective thermal transfer patterning of one or more pixel or
sub-pixel elements such as color filters, emissive layers, charge
transport layers, electrode layers, and the like.
[0083] Materials from separate donor sheets can be transferred
adjacent to other materials on a receptor to form adjacent devices,
portions of adjacent devices, or different portions of the same
device. Alternatively, materials from separate donor sheets can be
transferred directly on top of, or in partial overlying
registration with, other layers or materials previously patterned
onto the receptor by thermal transfer or some other method (e.g.,
photolithography, deposition through a shadow mask, etc.). A
variety of other combinations of two or more donor sheets can be
used to form a device, each donor sheet forming one or more
portions of the device. It will be understood that other portions
of these devices, or other devices on the receptor, may be formed
in whole or in part by any suitable process including
photolithographic processes, ink jet processes, and various other
printing or mask-based processes, whether conventionally used or
newly developed.
[0084] Referring back to FIG. 2, various layers of the donor sheet
200 will now be described.
[0085] The donor substrate 210 can be a polymer film. One suitable
type of polymer film is a polyester film, for example, polyethylene
terephthalate (PET) or polyethylene naphthalate (PEN) films.
However, other films with sufficient optical properties, including
high transmission of light at a particular wavelength, or
sufficient mechanical and thermal stability properties, depending
on the particular application, can be used. The donor substrate, in
at least some instances, is flat so that uniform coatings can be
formed thereon. The donor substrate is also typically selected from
materials that remain stable despite heating of one or more layers
of the donor. However, as described below, the inclusion of an
underlayer between the substrate and an LTHC layer can be used to
insulate the substrate from heat generated in the LTHC layer during
imaging. The typical thickness of the donor substrate ranges from
0.025 to 0. 15 mm, preferably 0.05 to 0. 1 mm, although thicker or
thinner donor substrates may be used.
[0086] The materials used to form the donor substrate and an
optional adjacent underlayer can be selected to improve adhesion
between the donor substrate and the underlayer, to control heat
transport between the substrate and the underlayer, to control
imaging radiation transport to the LTHC layer, to reduce imaging
defects and the like. An optional priming layer can be used to
increase uniformity during the coating of subsequent layers onto
the substrate and also increase the bonding strength between the
donor substrate and adjacent layers.
[0087] An optional underlayer 212 may be coated or otherwise
disposed between a donor substrate and the LTHC layer, for example
to control heat flow between the substrate and the LTHC layer
during imaging or to provide mechanical stability to the donor
element for storage, handling, donor processing, or imaging.
Examples of suitable underlayers and methods of providing
underlayers are disclosed in co-assigned U.S. patent application
Ser. No. 09/743,114, incorporated herein by reference.
[0088] The underlayer can include materials that impart desired
mechanical or thermal properties to the donor element. For example,
the underlayer can include materials that exhibit a low specific
heat.times.density or low thermal conductivity relative to the
donor substrate. Such an underlayer may be used to increase heat
flow to the transfer layer, for example to improve the imaging
sensitivity of the donor.
[0089] The underlayer may also include materials for their
mechanical properties or for adhesion between the substrate and the
LTHC. Using an underlayer that improves adhesion between the
substrate and the LTHC layer may result in less distortion in the
transferred image. As an example, in some cases an underlayer can
be used that reduces or eliminates delamination or separation of
the LTHC layer, for example, that might otherwise occur during
imaging of the donor media. This can reduce the amount of physical
distortion exhibited by transferred portions of the transfer layer.
In other cases, however it may be desirable to employ underlayers
that promote at least some degree of separation between or among
layers during imaging, for example to produce an air gap between
layers during imaging that can provide a thermal insulating
function. Separation during imaging may also provide a channel for
the release of gases that may be generated by heating of the LTHC
layer during imaging. Providing such a channel may lead to fewer
imaging defects.
[0090] The underlayer may be substantially transparent at the
imaging wavelength, or may also be at least partially absorptive or
reflective of imaging radiation. Attenuation or reflection of
imaging radiation by the underlayer may be used to control heat
generation during imaging.
[0091] Referring again to FIG. 2, an LTHC layer 214 can be included
in donor sheets of the present invention to couple irradiation
energy into the donor sheet. The LTHC layer preferably includes a
radiation absorber that absorbs incident radiation (e.g., laser
light) and converts at least a portion of the incident radiation
into heat to enable transfer of the transfer layer from the donor
sheet to the receptor.
[0092] Generally, the radiation absorber(s) in the LTHC layer
absorb light in the infrared, visible, or ultraviolet regions of
the electromagnetic spectrum and convert the absorbed radiation
into heat. The radiation absorber(s) are typically highly
absorptive of the selected imaging radiation, providing an LTHC
layer with an optical density at the wavelength of the imaging
radiation in the range of about 0.2 to 3 or higher. Optical density
of a layer is the absolute value of the logarithm (base 10) of the
ratio of the intensity of light transmitted through the layer to
the intensity of light incident on the layer.
[0093] Radiation absorber material can be uniformly disposed
throughout the LTHC layer or can be non-homogeneously distributed.
For example, as described in co-assigned U.S. patent application
Ser. No. 09/474,002, non-homogeneous LTHC layers can be used to
control temperature profiles in donor elements. This can give rise
to donor sheets that have improved transfer properties (e.g.,
better fidelity between the intended transfer patterns and actual
transfer patterns).
[0094] Suitable radiation absorbing materials can include, for
example, dyes (e.g., visible dyes, ultraviolet dyes, infrared dyes,
fluorescent dyes, and radiation-polarizing dyes), pigments, metals,
metal compounds, metal films, and other suitable absorbing
materials. Examples of suitable radiation absorbers includes carbon
black, metal oxides, and metal sulfides. One example of a suitable
LTHC layer can include a pigment, such as carbon black, and a
binder, such as an organic polymer. Another suitable LTHC layer
includes metal or metal/metal oxide formed as a thin film, for
example, black aluminum (i.e., a partially oxidized aluminum having
a black visual appearance). Metallic and metal compound films may
be formed by techniques, such as, for example, sputtering and
evaporative deposition. Particulate coatings may be formed using a
binder and any suitable dry or wet coating techniques. LTHC layers
can also be formed by combining two or more LTHC layers containing
similar or dissimilar materials. For example, an LTHC layer can be
formed by vapor depositing a thin layer of black aluminum over a
coating that contains carbon black disposed in a binder.
[0095] Dyes suitable for use as radiation absorbers in a LTHC layer
may be present in particulate form, dissolved in a binder material,
or at least partially dispersed in a binder material. When
dispersed particulate radiation absorbers are used, the particle
size can be, at least in some instances, about 10 .mu.m or less,
and may be about 1 .mu.m or less. Suitable dyes include those dyes
that absorb in the IR region of the spectrum. A specific dye may be
chosen based on factors such as, solubility in, and compatibility
with, a specific binder or coating solvent, as well as the
wavelength range of absorption.
[0096] Pigmentary materials may also be used in the LTHC layer as
radiation absorbers. Examples of suitable pigments include carbon
black and graphite, as well as phthalocyanines, nickel dithiolenes,
and other pigments described in U.S. Pat. Nos. 5,166,024 and
5,351,617. Additionally, black azo pigments based on copper or
chromium complexes of, for example, pyrazolone yellow, dianisidine
red, and nickel azo yellow can be useful. Inorganic pigments can
also be used, including, for example, oxides and sulfides of metals
such as aluminum, bismuth, tin, indium, zinc, titanium, chromium,
molybdenum, tungsten, cobalt, iridium, nickel, palladium, platinum,
copper, silver, gold, zirconium, iron, lead, and tellurium. Metal
borides, carbides, nitrides, carbonitrides, bronze-structured
oxides, and oxides structurally related to the bronze family (e.g.,
WO.sub.2.9) may also be used.
[0097] Metal radiation absorbers may be used, either in the form of
particles, as described for instance in U.S. Pat. No. 4,252,671, or
as films, as disclosed in U.S. Pat. No. 5,256,506. Suitable metals
include, for example, aluminum, bismuth, tin, indium, tellurium and
zinc.
[0098] Suitable binders for use in the LTHC layer include
film-forming polymers, such as, for example, phenolic resins (e.g.,
novolak and resole resins), polyvinyl butyral resins, polyvinyl
acetates, polyvinyl acetals, polyvinylidene chlorides,
polyacrylates, cellulosic ethers and esters, nitrocelluloses, and
polycarbonates. Suitable binders may include monomers, oligomers,
or polymers that have been, or can be, polymerized or crosslinked.
Additives such as photoinitiators may also be included to
facilitate crosslinking of the LTHC binder. In some embodiments,
the binder is primarily formed using a coating of crosslinkable
monomers or oligomers with optional polymer.
[0099] The inclusion of a thermoplastic resin (e.g., polymer) may
improve, in at least some instances, the performance (e.g.,
transfer properties or coatability) of the LTHC layer. It is
thought that a thermoplastic resin may improve the adhesion of the
LTHC layer to the donor substrate. In one embodiment, the binder
includes 25 to 50 wt. % (excluding the solvent when calculating
weight percent) thermoplastic resin, and, preferably, 30 to 45 wt.
% thermoplastic resin, although lower amounts of thermoplastic
resin may be used (e.g., 1 to 15 wt. %). The thermoplastic resin is
typically chosen to be compatible (i.e., form a one-phase
combination) with the other materials of the binder. In at least
some embodiments, a thermoplastic resin that has a solubility
parameter in the range of 9 to 13 (cal/cm.sup.3).sup.1/2,
preferably, 9.5 to 12 (cal/cm.sup.3).sup.1/2, is chosen for the
binder. Examples of suitable thermoplastic resins include
polyacrylics, styrene-acrylic polymers and resins, and polyvinyl
butyral.
[0100] Conventional coating aids, such as surfactants and
dispersing agents, may be added to facilitate the coating process.
The LTHC layer may be coated onto the donor substrate using a
variety of coating methods known in the art. A polymeric or organic
LTHC layer can be coated, in at least some instances, to a
thickness of 0.05 .mu.m to 20 .mu.m, preferably, 0.5 .mu.m to 10
.mu.m, and, more preferably, 1 .mu.m to 7 .mu.m. An inorganic LTHC
layer can be coated, in at least some instances, to a thickness in
the range of 0.0005 to 10 .mu.m, and preferably, 0.001 to 1
.mu.m.
[0101] Referring again to FIG. 2, an optional interlayer 216 may be
disposed between the LTHC layer 214 and transfer layer 218. The
interlayer can be used, for example, to minimize damage and
contamination of the transferred portion of the transfer layer and
may also reduce distortion in the transferred portion of the
transfer layer. The interlayer may also influence the adhesion of
the transfer layer to the rest of the donor sheet. Typically, the
interlayer has high thermal resistance. Preferably, the interlayer
does not distort or chemically decompose under the imaging
conditions, particularly to an extent that renders the transferred
image non-functional. The interlayer typically remains in contact
with the LTHC layer during the transfer process and is not
substantially transferred with the transfer layer.
[0102] Suitable interlayers include, for example, polymer films,
metal layers (e.g., vapor deposited metal layers), inorganic layers
(e.g., sol-gel deposited layers and vapor deposited layers of
inorganic oxides (e.g., silica, titania, and other metal oxides)),
and organic/inorganic composite layers. Organic materials suitable
as interlayer materials include both thermoset and thermoplastic
materials. Suitable thermoset materials include resins that may be
crosslinked by heat, radiation, or chemical treatment including,
but not limited to, crosslinked or crosslinkable polyacrylates,
polymethacrylates, polyesters, epoxies, and polyurethanes. The
thermoset materials may be coated onto the LTHC layer as, for
example, thermoplastic precursors and subsequently crosslinked to
form a crosslinked interlayer.
[0103] Suitable thermoplastic materials include, for example,
polyacrylates, polymethacrylates, polystyrenes, polyurethanes,
polysulfones, polyesters, and polyimides. These thermoplastic
organic materials may be applied via conventional coating
techniques (for example, solvent coating, spray coating, or
extrusion coating). Typically, the glass transition temperature
(T.sub.g) of thermoplastic materials suitable for use in the
interlayer is 25.degree. C. or greater, preferably 50.degree. C. or
greater. In some embodiments, the interlayer includes a
thermoplastic material that has a T.sub.g greater than any
temperature attained in the transfer layer during imaging. The
interlayer may be either transmissive, absorbing, reflective, or
some combination thereof, at the imaging radiation wavelength.
[0104] Inorganic materials suitable as interlayer materials
include, for example, metals, metal oxides, metal sulfides, and
inorganic carbon coatings, including those materials that are
highly transmissive or reflective at the imaging light wavelength.
These materials may be applied to the light-to-heat-conversion
layer via conventional techniques (e.g., vacuum sputtering, vacuum
evaporation, or plasma jet deposition).
[0105] The interlayer may provide a number of benefits. The
interlayer may be a barrier against the transfer of material from
the light-to-heat conversion layer. It may also modulate the
temperature attained in the transfer layer so that thermally
unstable materials can be transferred. For example, the interlayer
can act as a thermal diffuser to control the temperature at the
interface between the interlayer and the transfer layer relative to
the temperature attained in the LTHC layer. This may improve the
quality (i.e., surface roughness, edge roughness, etc.) of the
transferred layer. The presence of an interlayer may also result in
improved plastic memory in the transferred material.
[0106] The interlayer may contain additives, including, for
example, photoinitiators, surfactants, pigments, plasticizers, and
coating aids. The thickness of the interlayer may depend on factors
such as, for example, the material of the interlayer, the material
and properties of the LTHC layer, the material and properties of
the transfer layer, the wavelength of the imaging radiation, and
the duration of exposure of the donor sheet to imaging radiation.
For polymer interlayers, the thickness of the interlayer typically
is in the range of 0.05 .mu.m to 10 .mu.m. For inorganic
interlayers (e.g., metal or metal compound interlayers), the
thickness of the interlayer typically is in the range of 0.005
.mu.m to 10 .mu.m.
[0107] Referring again to FIG. 2, a thermal transfer layer 218 is
included in donor sheet 200. Transfer layer 218 can include any
suitable material or materials, disposed in one or more layers,
alone or in combination with other materials. Transfer layer 218 is
capable of being selectively transferred as a unit or in portions
by any suitable transfer mechanism when the donor element is
exposed to direct heating or to imaging radiation that can be
absorbed by light-to-heat converter material and converted into
heat.
[0108] The present invention contemplates a transfer layer that
includes a light emitting, charge transporting, charge blocking, or
semiconducting material disposed in a non-polymeric, organic
material that forms an amorphous matrix as part of the transfer
layer. The present invention contemplates a transfer layer that
includes a LEP or other light emitting molecules as the light
emitting material. One way of providing the transfer layer is by
solution coating the light emitting material and non-polymeric,
organic material onto the donor to form an amorphous matrix
containing the light emitting material. In this method, the light
emitting material and the non-polymeric, organic material can be
solubilized by addition of a suitable compatible solvent, and
coated onto the alignment layer by spin-coating, gravure coating,
mayer rod coating, knife coating and the like. The solvent chosen
preferably does not undesirably interact with (e.g., swell or
dissolve) any of the already existing layers in the donor sheet.
The coating can then be annealed and the solvent evaporated to
leave a transfer layer containing an amorphous matrix.
[0109] The transfer layer can then be selectively thermally
transferred from the donor element to a proximately located
receptor substrate. There can be, if desired, more than one
transfer layer so that a multilayer construction is transferred
using a single donor sheet. The additional transfer layers can
include an amorphous, non-polymeric, organic matrix or some other
materials. The receptor substrate may be any item suitable for a
particular application including, but not limited to, glass,
transparent films, reflective films, metals, semiconductors, and
plastics. For example, receptor substrates may be any type of
substrate or display element suitable for display applications.
Receptor substrates suitable for use in displays such as liquid
crystal displays or emissive displays include rigid or flexible
substrates that are substantially transmissive to visible light.
Examples of suitable rigid receptors include glass and rigid
plastic that are coated or patterned with indium tin oxide or are
circuitized with low temperature poly-silicon (LTPS) or other
transistor structures, including organic transistors.
[0110] Suitable flexible substrates include substantially clear and
transmissive polymer films, reflective films, transflective films,
polarizing films, multilayer optical films, and the like. Flexible
substrates can also be coated or patterned with electrode materials
or transistors, for example transistor arrays formed directly on
the flexible substrate or transferred to the flexible substrate
after being formed on a temporary carrier substrate. Suitable
polymer substrates include polyester base (e.g., polyethylene
terephthalate, polyethylene naphthalate), polycarbonate resins,
polyolefin resins, polyvinyl resins (e.g., polyvinyl chloride,
polyvinylidene chloride, polyvinyl acetals, etc.), cellulose ester
bases (e.g., cellulose triacetate, cellulose acetate), and other
conventional polymeric films used as supports. For making OELs on
plastic substrates, it is often desirable to include a barrier film
or coating on one or both surfaces of the plastic substrate to
protect the organic light emitting devices and their electrodes
from exposure to undesired levels of water, oxygen, and the
like.
[0111] Receptor substrates can be pre-patterned with any one or
more of electrodes, transistors, capacitors, insulator ribs,
spacers, color filters, black matrix, hole transport layers,
electron transport layers, and other elements useful for electronic
displays or other devices.
[0112] The present invention contemplates polarized light emitting
OEL displays and devices. In one embodiment, OEL displays can be
made that emit light and that have adjacent devices that can emit
light having different color. For example, FIG. 3 shows an OEL
display 300 that includes a plurality of OEL devices 310 disposed
on a substrate 320. Adjacent devices 310 can be made to emit
different colors of light.
[0113] The separation shown between devices 310 is for illustrative
purposes only. Adjacent devices may be separated, in contact,
overlapping, etc., or different combinations of these in more than
one direction on the display substrate. For example, a pattern of
parallel striped transparent conductive anodes can be formed on the
substrate followed by a striped pattern of a hole transport
material and a striped repeating pattern of red, green, and blue
light emitting LEP layers, followed by a striped pattern of
cathodes, the cathode stripes oriented perpendicular to the anode
stripes. Such a construction may be suitable for forming passive
matrix displays. In other embodiments, transparent conductive anode
pads can be provided in a two-dimensional pattern on the substrate
and associated with addressing electronics such as one or more
transistors, capacitors, etc., such as are suitable for making
active matrix displays. Other layers, including the light emitting
layer(s) can then be coated or deposited as a single layer or can
be patterned (e.g., parallel stripes, two-dimensional pattern
commensurate with the anodes, etc.) over the anodes or electronic
devices. Any other suitable construction is also contemplated by
the present invention.
[0114] In one embodiment, display 300 can be a multiple color
display. As such, it may be desirable to position optional
polarizer 330 between the light emitting devices and a viewer, for
example to enhance the contrast of the display. In exemplary
embodiments, each of the devices 310 emits light. There are many
displays and devices constructions covered by the general
construction illustrated in FIG. 3. Some of those constructions are
discussed as follows.
[0115] OEL backlights can include emissive layers. Constructions
can include bare or circuitized substrates, anodes, cathodes, hole
transport layers, electron transport layers, hole injection layers,
electron injection layers, emissive layers, color changing layers,
and other layers and materials suitable in OEL devices.
Constructions can also include polarizers, diffusers, light guides,
lenses, light control films, brightness enhancement films, and the
like. Applications include white or single color large area single
pixel lamps, for example where an emissive material is provided by
thermal stamp transfer, lamination transfer, resistive head thermal
printing, or the like; white or single color large area single
electrode pair lamps that have a large number of closely spaced
emissive layers patterned by laser induced thermal transfer; and
tunable color multiple electrode large area lamps.
[0116] Low resolution OEL displays can include emissive layers.
Constructions can include bare or circuitized substrates, anodes,
cathodes, hole transport layers, electron transport layers, hole
injection layers, electron injection layers, emissive layers, color
changing layers, and other layers and materials suitable in OEL
devices. Constructions can also include polarizers, diffusers,
light guides, lenses, light control films, brightness enhancement
films, and the like. Applications include graphic indicator lamps
(e.g., icons); segmented alphanumeric displays (e.g., appliance
time indicators); small monochrome passive or active matrix
displays; small monochrome passive or active matrix displays plus
graphic indicator lamps as part of an integrated display (e.g.,
cell phone displays); large area pixel display tiles (e.g., a
plurality of modules, or tiles, each having a relatively small
number of pixels), such as may be suitable for outdoor display
used; and security display applications.
[0117] High resolution OEL displays can include emissive layers.
Constructions can include bare or circuitized substrates, anodes,
cathodes, hole transport layers, electron transport layers, hole
injection layers, electron injection layers, emissive layers, color
changing layers, and other layers and materials suitable in OEL
devices. Constructions can also include polarizers, diffusers,
light guides, lenses, light control films, brightness enhancement
films, and the like. Applications include active or passive matrix
multicolor or full color displays; active or passive matrix
multicolor or full color displays plus segmented or graphic
indicator lamps (e.g., laser induced transfer of high resolution
devices plus thermal hot stamp of icons on the same substrate); and
security display applications.
EXAMPLES
Example 1
Preparation of a Receptors
[0118] Three different types of receptors were formed: (A) indium
tin oxide (ITO) only; (B) PDOT (poly(3,4-ethylenedioxythiophene))
on ITO; and (C) mTDATA
(4,4',4''-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine) on
PDOT/ITO. To obtain receptor surface (A), ITO glass (Delta
Technologies, Stillwater, Minn., sheet resistance less than 100
Q/square, 1.1 mm thick) was ultrasonically cleaned in a hot, 3%
solution of Deconex 12NS (Borer Chemie AG, Zuchwil Switzerland).
The substrates were then placed in the Plasma Science Model PS0500
plasma treater (4th State Inc., Belmont, Calif.) for surface
treatment under the following conditions: [0119] Time: 2 minutes
[0120] Power: 500 watt (165 W/cm.sup.2) [0121] Oxygen Flow: 100
sccm
[0122] To obtain receptor surface (B), the ITO was cleaned and
plasma-treated as described for the preparation of receptor surface
(A). Immediately after plasma treatment, the PDOT solution (CH-8000
from Bayer AG, Leverkusen, Germany, diluted 1:1 with deionized
water) was filtered and dispensed through a Whatman Puradisc.TM.
0.45 .mu.m Polypropylene (PP) syringe filter onto the ITO
substrate. The substrate was then spun (Headway Research
spincoater) at 2000 rpm for 30 s yielding a PDOT film thickness of
40 nm. All of the substrates were heated to 200.degree. C. for 5
minutes under nitrogen.
[0123] To obtain receptor surface (C), a PDOT film was deposited
onto ITO as described for the preparation of receptor surface (B).
After the substrates had cooled, a solution of mTDATA (OSA 3939, H.
W. Sands Corp., Jupiter, Fla.) 2.5% (w/w) in toluene was filtered
and dispensed through a Whatman Puradisc.TM. 0.45 .mu.m
Polypropylene (PP) syringe filter onto the PDOT coated ITO
substrate. The substrate was spun (Headway Research spincoater) at
3000 rpm for 30 s yielding an mTDATA film thickness of 40 nm.
Example 2
Preparation of a Donor Sheet without Transfer Layer
[0124] A thermal transfer donor sheet was prepared in the following
manner.
[0125] An LTHC solution, given in Table I, was coated onto a 0.1 mm
thick polyethylene terapthalate (PET) film substrate from Teijin
(Osaka, Japan). Coating was performed using a Yasui Seiki Lab
Coater, Model CAG-150, using a microgravure roll with 150 helical
cells per lineal inch. The LTHC coating was in-line dried at
80.degree. C. and cured under ultraviolet (UV) radiation.
TABLE-US-00001 TABLE I LTHC Coating Solution Trade Parts by
Component Designation Weight carbon black pigment Raven 760
Ultra.sup.(1) 3.55 polyvinyl butyral resin Butvar B-98.sup.(2) 0.63
acrylic resin Joncryl 67.sup.(3) 1.90 dispersant Disperbyk
161.sup.(4) 0.32 surfactant FC-430.sup.(5) 0.01 epoxy novolac
acrylate Ebecryl 629.sup.(6) 12.09 acrylic resin Elvacite
2669.sup.(7) 8.06 2-benzyl-2-(dimethylamino)-1-(4- Irgacure
369.sup.(8) 0.82 (morpholinyl) phenyl) butanone 1-hydroxycyclohexyl
phenyl ketone Irgacure 184.sup.(8) 0.12 2-butanone 45.31
1,2-propanediol monomethyl ether acetate 27.19 .sup.(1)available
from Columbian Chemicals Co., Atlanta, GA .sup.(2)available from
Solutia Inc., St. Louis, MO .sup.(3)available from S. C. Johnson
& Son, Inc., Racine, WI .sup.(4)available from Byk-Chemie USA,
Wallingford, CT .sup.(5)available from Minnesota Mining and
Manufacturing Co., St. Paul, MN .sup.(6)available from UCB Radcure
Inc., N. Augusta, SC .sup.(7)available from ICI Acrylics Inc.,
Memphis, TN .sup.(8)available from Ciba-Geigy Corp., Tarrytown,
NY
[0126] Next, an interlayer, given in Table II, was coated onto the
cured LTHC layer by a rotogravure coating method using the Yasui
Seiki Lab Coater, Model CAG-150, with a microgravure roll having
180 helical cells per lineal inch. This coating was in-line dried
at 60.degree. C. and UV cured. TABLE-US-00002 TABLE II Interlayer
Coating Solution Parts by Component Weight SR 351 HP
(trimethylolpropane 14.85 triacrylate ester, available from
Sartomer, Exton, PA) Butvar B-98 0.93 Joncryl 67 2.78 Irgacure 369
1.25 Irgacure 184 0.19 2-butanone 48.00 1-methoxy-2-propanol
32.00
Example 3
Preparation of Solutions for Transfer Layer
[0127] The following solutions were prepared:
[0128] (a) Covion green. Covion Green PPV Polymer HB 1270 (100 mg)
from Covion Organic Semiconductors GmbH, Frankfurt, Germany was
weighed out into an amber vial with a PTFE cap. To this was added
9.9 g of Toluene (HPLC grade obtained from Aldrich Chemical,
Milwaukee, Wis.). The vial containing the solution was placed into
a silicone oil bath at 75.degree. C. for 60 minutes. The hot
solution was filtered through a 0.45 .mu.m Polypropylene (PP)
syringe filter.
[0129] (b) Covion super yellow. Covion PDY 132 "Super Yellow" (75
mg) was weighed out into an amber vial with a PTFE cap. To this was
added 9.925 g of Toluene (HPLC grade obtained from Aldrich
Chemicals) and a stir bar. The solution was stirred overnight. The
solution was filtered through a 5 .mu.m Millipore Millex syringe
filter.
[0130] (c) mTDATA. Into a container was weighed out 100 mg mTDATA
(OSA 3939 available from H.W. Sands Corp, Jupiter, Fla.). To this
was added 3.9 g of Toluene (HPLC grade obtained from Aldrich
Chemical; Milwaukee, Wis.). The solution was heated at 75.degree.
C. while stirring in silicone oil bath for 25 minutes. The hot
solution was filtered through a Whatman Puradisc.TM. 0.45 .mu.m
Polypropylene (PP) filter.
[0131] (d) t-Butyl PBD. Into a container was weighted out 100 mg
t-butyl PBD
(2-(biphenyl-4-yl)-5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazole,
available from Aldrich Chemical Co., Milwaukee, Wis.). To this was
added 3.9 g of Toluene (HPLC grade obtained from Aldrich
Chemicals). The solution was stirred for 25 minutes and filtered
through a Whatman Puradisc.TM. 0.45 .parallel.m Polypropylene (PP)
filter.
Examples 4-8
Preparation of Transfer Layers on Donor Sheet and Transfer of
Transfer Layers
[0132] Transfer Layers were formed on the donor sheets of Example 2
using blends of the Solutions of Example 3 according to Table III.
To obtain the blends, the above described solutions were mixed at
the appropriate ratios and the resulting blend solutions were
stirred for 20 min at room temperature.
[0133] The transfer layers were disposed on the donor sheets by
spinning (Headway Research spincoater) at about 2000 rpm for 30 s
to yield a film thickness of approximately 100 nm. TABLE-US-00003
TABLE III Parts by Weight of Transfer Layer Compositions Example
Covion Super No. Covion Green Yellow mTDATA t-butyl PBD 4 1 -- -- 2
5 2 -- -- 5 6 1 -- -- 3 7 1 -- 1 1 8 -- 1 3 --
[0134] Donor sheets as prepared in Examples 4-8 were brought into
contact with receptor substrates as prepared in Example 1. Next,
the donors were imaged using two single-mode Nd:YAG lasers.
Scanning was performed using a system of linear galvanometers, with
the combined laser beams focused onto the image plane using an
f-theta scan lens as part of a near-telecentric configuration. The
laser energy density was 0.4 to 0.8 J/cm.sup.2. The laser spot
size, measured at the 1/e.sup.2 intensity, was 30 micrometers by
350 micrometers. The linear laser spot velocity was adjustable
between 10 and 30 meters per second, measured at the image plane.
The laser spot was dithered perpendicular to the major displacement
direction with about a 100 .mu.m amplitude. The transfer layers
were transferred as lines onto the receptor substrates, and the
intended width of the lines was about 100 .mu.m.
[0135] The transfer layers were transferred in a series of lines
that were in overlying registry with the ITO stripes on the
receptor substrates. The results of imaging are given in Table IV.
TABLE-US-00004 TABLE IV Results of Transfer Substrate (A) Substrate
(B) Substrate (C) Example No. ITO ITO/PDOT ITO/PDOT/mTDATA 4
excellent transfer; spotty transfer, no excellent transfer; good
excellent edge continuous lines edge quality quality 5 excellent
transfer; spotty transfer, no excellent transfer; good excellent
edge continuous lines edge quality quality 6 excellent transfer;
spotty transfer, no excellent transfer; good excellent edge
continuous lines edge quality quality 7 excellent transfer; good
transfer; good excellent transfer; excellent edge edge quality
excellent edge quality quality 8 excellent transfer at good
transfer with excellent transfer; high laser dose; some hole
defects; excellent edge quality excellent edge excellent edge
quality quality at high laser dose
Example 9
Preparation of OEL Devices
[0136] The three transfer layer compositions of Examples 4-6 were
used to prepare light-emitting diodes of the construction
ITO/PDOT/mTDATA/Transfer Layer/Ca/Ag. After transfer of the
transfer layer as described in Examples 4-6, Ca/Ag cathodes were
vacuum vapor deposited using the following conditions:
TABLE-US-00005 Thickness Rate Coating time Ca 400 A 1.1 A/s 5 min
51 s Ag 4000 A 5.0 A/s 13 min 20 s
In all cases diode behavior and green light emission were
observed.
[0137] The present invention should not be considered limited to
the particular examples described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention may be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the instant specification.
[0138] Each of the patents, patent documents, and publications
cited above is hereby incorporated into this document as if
reproduced in full.
* * * * *