Metal and electronically conductive polymer transfer Number:7,410,825 from the United States Patent and Trademark Office (PTO) owispatent The invention relates to a donor laminate comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer.<H electronically, conductive, Metal, and, elect, 7410825.html, Patent, pto, 7410825

Title: Metal and electronically conductive polymer transfer

Abstract: The invention relates to a donor laminate comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer.

Patent Number: 7,410,825 Issued on 08/12/2008 to Majumdar, et al.

Inventors: Majumdar; Debasis (Rochester, NY), Irvin, Jr.; Glen C. (Rochester, NY), Madathil; Joseph K. (Rochester, NY), Tutt; Lee W. (Webster, NY), Freedman; Gary S. (Webster, NY), Kress; Robert J. (Rochester, NY)
Assignee: Eastman Kodak Company (Rochester, NY)

Appl. No.: 11/227,591

Filed: September 15, 2005

Current U.S. Class: 438/106 ; 257/E21.499

Current International Class: H01L 21/50 (20060101)

References Cited [Referenced By]

U.S. Patent Documents


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Foreign Patent Documents


0 440 957	Mar., 1996	EP
0 615 256	Sep., 1998	EP
1 079 397	Feb., 2001	EP
0 686 662	Nov., 2002	EP
1 054 414	Mar., 2003	EP
1 524 678	Apr., 2005	EP
WO 97/18944	May., 1997	WO
WO 00/39835	Jul., 2000	WO

Other References

Research Disclosure No. 41548, Nov. 1998, p. 1473, Kenneth Mason Publications Ltd., Hampshire, England. cited by other .
U.S. Appl. No. 10/969,889 filed Oct. 21, 2004, Gates et al. cited by other .
U.S. Appl. No. 11/022,155 filed Dec. 22, 2004, Majumdar et al. cited by other .
Jin-Woo Park et al., "Polyimide as a Plastic Substrate for the Flexible Organic Electroluminescent Device" Mat. Res. Soc. Symp. Proc., vol. 814, 2004, pp. 139-144. cited by other.

Primary Examiner: Geyer; Scott B.
Attorney, Agent or Firm: Leipold; Paul A. Anderson; Andrew J.

Claims

The invention claimed is:

1. A donor laminate comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer, wherein said electronically conductive polymer layer has a peel force of less than 100 grams per inch for separation from said substrate at room temperature.

2. The donor laminate of claim 1 wherein said substrate is transparent.

3. The donor laminate of claim 1 wherein said substrate comprises a surface that is a release material.

4. The donor laminate of claim 1 wherein said electronically conductive polymer layer comprises an electronically conductive polymer in a cationic form and a polyanion.

5. The donor laminate of claim 4 wherein said electronically conductive polymer in a cationic form comprises polythiophene.

6. The donor laminate of claim 4 wherein said electronically conductive polymer in a cationic form comprises polyethylenedioxythiophene.

7. The donor laminate of claim 4 wherein said polyanion comprises polystyrene sulfonate.

8. The donor laminate of claim 1 wherein said electronically conductive polymer layer consists of at least one member selected from the group consisting of substituted or unsubstituted pyrrole-containing, substituted or unsubstituted thiophene-containing polymers and substituted or unsubstituted aniline-containing polymers.

9. The donor laminate of claim 1 wherein said electronically conductive polymer layer further comprises a binder.

10. The donor laminate of claim 1 wherein said metal layer comprises a silver layer.

11. The donor laminate of claim 10 wherein said silver has a thickness of between 5 nanometers and 50 micrometers.

12. The donor laminate of claim 1 wherein said metal layer consists of at least one metal selected from the group consisting of gold, silver, platinum, palladium, copper, aluminum and mixtures thereof.

13. The donor laminate of claim 1 wherein said metal layer has a sheet resistance of between 0.001 and 25 ohm/square.

14. The donor laminate of claim 1 wherein said electronically conductive polymer layer in contact with said substrate, and said metal layer are in a pattern.

15. The donor laminate of claim 1 wherein said metal layer is in a pattern.

16. The donor laminate of claim 1 wherein said electronically conductive polymer layer is in a pattern.

17. The donor laminate of claim 1 wherein said substrate comprises triacetylcellulose.

18. The donor laminate of claim 1 wherein said substrate comprises a flexible polymer sheet.

19. The donor laminate of claim 1 wherein said electronically conductive polymer layer has a thickness of between 5 nanometer and 1 micrometer.

20. The donor laminate of claim 1 wherein said electronically conductive polymer layer has a peel force of less than 50 grams per inch for separation from said substrate.

21. The donor laminate of claim 1 wherein said laminate further comprises an adhesive layer on the side of the metal layer opposite to the substrate.

22. The donor laminate of claim 1 wherein said electronically conductive polymer layer has an FOM less than or equal to 100 wherein FOM is defined as the slope of the plot of 1n (1/T) versus (1/Rs) and wherein T=visual light transmission Rs=sheet resistance in ohms per square FOM=figure of merit and wherein the Rs has a value of less than or equal to 1000 ohms per square.

23. The donor laminate of claim 1 wherein said electronically conductive polymer layer further comprises epoxy silane.

24. The donor laminate of claim 1 wherein said electronically conductive polymer layer is coated utilizing a conductivity enhancing agent.

25. A method of forming a conductive element comprising providing a donor laminate comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer, wherein said electronically conductive polymer layer has a peel force of less than 100 grams per inch for separation from said substrate at room temperature, bringing a receiver sheet into contact with said donor laminate, and transferring said metal layer and electronically conductive polymer layer to said receiver sheet.

26. The method of claim 25 wherein said transferring is carried out by heat.

27. The method of claim 25 wherein said transferring is carried out by pressure.

28. The method of claim 27 wherein said pressure is applied by a patterned roller.

29. The method of Cairn 27 wherein said pressure is applied by acoustic or mechanical force.

30. The method of claim 25 wherein said transferring is carried out utilizing a radiation source.

31. The method of claim 25 wherein said transferring is carried out by thermal resistive head.

32. The method of claim 25 wherein said receiver sheet comprises a flexible polymer sheet.

33. The method of claim 25 wherein said receiver comprises glass.

34. The method of claim 25 wherein said transferring is in a pattern.

35. The method of claim 25 wherein the surface of said substrate in contact with said electronically conductive polymer layer comprises a release material.

36. The method of claim 25 wherein transferring utilizes an adhesive between said metal layer and said receiver element.

Description

FIELD OF THE INVENTION

The present invention relates to a donor laminate for transfer of a conductive layer comprising at least one electronically conductive polymer and a metal layer on to a receiver, wherein the receiver is a component of a device. The present invention also relates to methods pertinent to such transfers.

BACKGROUND OF THE INVENTION

Transparent electrically-conductive layers (TCL) of metal oxides such as indium tin oxide (ITO), antimony doped tin oxide, and cadmium stannate (cadmium tin oxide) are commonly used in the manufacture of electrooptical display devices such as liquid crystal display devices (LCDs), electroluminescent display devices, photocells, solid-state image sensors, electrochromic windows and the like.

Devices such as flat panel displays, typically contain a substrate provided with an indium tin oxide (ITO) layer as a transparent electrode. The coating of ITO is carried out by vacuum sputtering methods which involve high substrate temperature conditions up to 250.degree. C., and therefore, glass substrates are generally used. The high cost of the fabrication methods and the low flexibility of such electrodes, due to the brittleness of the inorganic ITO layer as well as the glass substrate, limit the range of potential applications. As a result, there is a growing interest in making all-organic devices, comprising plastic resins as a flexible substrate and organic electroconductive polymer layers as an electrode. Such plastic electronics allow low cost devices with new properties. Flexible plastic substrates can be provided with an electroconductive polymer layer by continuous hopper or roller coating methods (compared to batch process such as sputtering) and the resulting organic electrodes enable the "roll to roll" fabrication of electronic devices which are more flexible, lower cost, and lower weight.

Electronically conductive polymers have recently received attention from various industries because of their electronic conductivity. Although many of these polymers are highly colored and are less suited for TCL applications, some of these electronically conductive polymers, such as substituted or unsubstituted pyrrole-containing polymers (as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654), substituted or unsubstituted thiophene-containing polymers (as mentioned in U.S. Pat. Nos. 5,300,575, 5,312,681, 5,354,613, 5,370,981, 5,372,924, 5,391,472, 5,403,467, 5,443,944, 5,575,898, 4,987,042, and 4,731,408) and substituted or unsubstituted aniline-containing polymers (as mentioned in U.S. Pat. Nos. 5,716,550, 5,093,439, and 4,070,189) are transparent and not prohibitively colored, at least when coated in thin layers at moderate coverage. Because of their electronic conductivity these polymers can provide excellent process-surviving, humidity independent antistatic characteristics when coated on plastic substrates used for photographic imaging applications (vide, for example, U.S. Pat. Nos. 6,096,491; 6,124,083; 6,190,846;)

EP-A-440 957 describes a method for preparing polythiophene in an aqueous mixture by oxidative polymerization in the presence of a polyanion as a doping agent. In EP-A-686 662 it has been disclosed that highly conductive layers of polythiophene, coated from an aqueous coating solution, could be made by the addition of a di- or polyhydroxy and/or a carbonic acid, amide or lactam group containing compound in the coating solution of the polythiophene.

Many miniature electronic and optical devices are formed using layers of different materials stacked on each other. These layers are often patterned to produce the devices. Examples of such devices include optical displays in which each pixel is formed in a patterned array, optical waveguide structures for telecommunication devices, and metal-insulator-metal stacks for semiconductor-based devices. A conventional method for making these devices includes forming one or more layers on a receiver substrate and patterning the layers simultaneously or sequentially to form the device. In many cases, multiple deposition and patterning steps are required to prepare the ultimate device structure. For example, the preparation of optical displays may require the separate formation of red, green, and blue pixels. Although some layers may be commonly deposited for each of these types of pixels, at least some layers must be separately formed and often separately patterned. Patterning of the layers is often performed by photolithographic techniques that include, for example, covering a layer with a photoresist, patterning the photoresist using a mask, removing a portion of the photoresist to expose the underlying layer according to the pattern, and then etching the exposed layer.

Coated layers of organic electroconductive polymers can be patterned into electrode arrays using different methods. The known wet-etching microlithography technique is described in WO97/18944 and U.S. Pat. No. 5,976,274 wherein a positive or negative photoresist is applied on top of a coated layer of an organic electroconductive polymer, and after the steps of selectively exposing the photoresist to UV light, developing the photoresist, etching the electroconductive polymer layer and finally stripping the non-developed photoresist, a patterned layer is obtained. In U.S. Pat. No. 5,561,030 a similar method is used to form the pattern except that the pattern is formed in a continuous layer of prepolymer which is not yet conductive and that after washing the mask away the remaining prepolymer is rendered conductive by oxidation. Such methods that involve conventional lithographic techniques are cumbersome as they involve many steps and require the use of hazardous chemicals.

EP-A-615 256 describes a method to produce a pattern of a conductive polymer on a substrate that involves coating and drying a composition containing 3,4-ethylenedioxythiophene monomer, an oxidation agent, and a base; exposing the dried layer to UV radiation through a mask; and then heating. The UV exposed areas of the coating comprise non-conductive polymer and the unexposed areas comprise conductive polymer. The formation of a conductive polymer pattern in accordance with this method does not require the coating and patterning of a separate photoresist layer.

U.S. Pat. No. 6,045,977 describes a process for patterning conductive polyaniline layers containing a photobase generator. UV exposure of such layers produces a base that reduces the conductivity in the exposed areas.

EP-A-1 054 414 describes a method to pattern a conductive polymer layer by printing an electrode pattern onto said conductive polymer layer using a printing solution containing an oxidant selected from the group ClO.sup.-, BrO.sup.-, MnO.sub.4.sup.-, Cr.sub.2O.sub.7.sup.-2, S.sub.2O.sub.8.sup.-2, and H.sub.2O.sub.2. The areas of the conductive layer exposed to the oxidant solution are rendered nonconductive.

Research Disclosure, November 1998, page 1473 (disclosure no. 41548) describes various means to form patterns in a conducting polymer, including photoablation wherein the selected areas are removed from the substrate by laser irradiation. Such photoablation processes are convenient, dry, one-step methods but the generation of debris may require a wet cleaning step and may contaminate the optics and mechanics of the laser device. Prior art methods involving removal of the electroconductive polymer to form the electrode pattern also induce a difference of the optical density between electroconductive and non-conductive areas of the patterned surface.

Methods of patterning organic electroconductive polymer layers by image-wise heating by means of a laser have been disclosed in EP 1 079 397 A1. That method induces about a 10 to 1000 fold decrease in resistivity without substantially ablating or destroying the layer.

The application of electronically conductive polymers in display related devices has been envisioned in the past. European Patent Application EP9910201 describes a light transmissive substrate having a light transmissive conductive polymer coating for use in resistive touch screens. U.S. Pat. No. 5,738,934 describes touch screen cover sheets having a conductive polymer coating.

U.S. Pat. Nos. 5,828,432 and 5,976,284 describe conductive polymer layers employed in liquid crystal display devices. The example conductive layers are highly conductive but typically have transparency of 60% or less.

Use of polythiophene as transparent field spreading layers in displays comprising polymer dispersed liquid crystals has been disclosed in U.S. Pat. Nos. 6,639,637 and 6,707,517. However, the polythiophene layers in these patents are non-conductive in nature.

Use of transparent coating on glass substrates for cathode ray tubes using polythiophene and silicon oxide composites has been disclosed in U.S. Pat. No. 6,404,120. However, the method suggests in-situ polymerization of an ethylenedioxythiohene monomer on glass, baking it at an elevated temperature and subsequent washing with tetra ethyl orthosilicate. Such an involved process may be difficult to practice for roll-to-roll production of a wide flexible plastic substrate.

Use of in-situ polymerized polythiophene and polypyrrole has been proposed in U.S. Pat. Appl. Pub. 2003/0008135 A1 as conductive films, for ITO replacement. As mentioned earlier, such processes are difficult to implement for roll-to-roll production of conductive coatings. In the same patent application, a comparative example was created using a dispersion of poly (3,4 ethylene dioxythiophene)/polystyrene sulfonic acid which resulted in inferior coating properties.

U.S. patent application Ser. No. 10/969,889 filed Oct. 21, 2004 and Ser. No. 11/022,155 filed Dec. 22, 2004 disclose donor laminates for transfer of electronically conductive polymers on to suitable receivers wherein the receivers are components of a device. The transfer is accomplished by the application of heat and/or pressure and can be in the form of a pattern. Although quite effective, the conductivity of the transferred layer is limited by that of the electronically conductive polymer, which is often less than metals such as gold or silver. This can put some limitation to applications of the inventions where much higher conductivity is desired.

Although there is considerable art describing various methods to form and pattern electronically conductive polymers, there are some applications where it may be difficult or impractical to involve any wet processing or cumbersome patterning steps. For example, wet processing during coating and/or patterning may adversely affect integrity, interfacial characteristics, and/or electrical or optical properties of the previously deposited layers. Additionally, the device manufacturer may not have coating facilities to handle large quantity of liquid. It is conceivable that many potentially advantageous device constructions, designs, layouts, and materials are impractical because of the limitations of conventional wet coating and patterning. There is a need for new methods of forming these devices with a reduced number of processing steps, particularly wet processing steps. In at least some instances, this may allow for the construction of devices with more reliability and more complexity.

Use of thermal transfer elements and thermal transfer methods for forming multicomponent devices have been proposed previously. For example, Wolk et al. in a series of patents (e.g., U.S. Pat. Nos. 6,114,088; 6,140,009; 6,214,520; 6,221,553; 6,582,876; 6,586,153) disclose thermal transfer elements and methods, for multilayer devices. However, such elements are non-transparent, often including a light-to-heat conversion layer, interlayer, release layer and the like. Construction of such multilayered elements are complex, involved and prone to defects that can get incorporated into the final device. Ellis et al. (U.S. Pat. No. 5,171,650) and Blanchet-Fincher (U.S. Pat. Appl. Pub. 2004/0065970 A1) describe ablative laser thermal transfer of conductive layers. However, such methods are prone to creating dirt and debris that may not be tolerated for many display applications.

It is clear from the prior art that a method to rapidly, cleanly, precisely dry deposit highly conductive materials in continuous or pattern form is needed. Embodiments of the present invention provide such advantages.

PROBLEM TO BE SOLVED BY THE INVENTION

Thus, there is still a need in the art for a suitable donor and a transfer method to form conductive layers, especially those comprising electronically conductive polymers and metal on receiver substrates, and incorporating such receivers in electronic and/or optical devices.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a donor laminate for transfer of an electronically conductive layer to a receiver element.

It is another object to provide methods to transfer an electronically conductive layer to a receiver element.

It is still another object to provide methods to transfer an electronically conductive layer to a receiver element in a pattern.

These and other objects of the invention are accomplished by a donor laminate for transfer of a conductive polymer and a metal comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer.

ADVANTAGEOUS EFFECT OF THE INVENTION

The invention provides a desirable donor laminate and a transfer method to form conductive layers, especially those comprising an electronically conductive polymer and a metal on receiver substrates, and incorporating such receivers in electronic and/or optical devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional representation of a donor laminate of the invention.

FIG. 2 shows a cross-sectional representation of a donor laminate of the invention comprising a substrate, an electronically conductive polymer layer, a metal layer, and two other layers disposed on the metal layer.

FIG. 3 shows a schematic of a display component formed by the methods of the invention comprising a receiver element having conductive layers connected to a power source by an electric lead.

FIG. 4 shows a schematic of a polymer dispersed LC display formed by the methods of the invention.

FIG. 5 shows a schematic of an OLED based display formed by the methods of the invention.

FIG. 6 shows a schematic of a resistive-type touch screen formed by the methods of the invention.

FIG. 7 shows schematic of RFID tags with antennas formed by the methods of the invention.

FIG. 8 shows a cross-sectional representation of a donor laminate of the invention and a receiver element.

FIG. 9 shows a cross-sectional representation of a donor laminate of the invention in contact with a receiver element, as per Example TM-1.

FIG. 10 shows a cross-sectional representation of a receiver element having an electronically conductive polymer layer and a metal layer, transferred by the methods of the invention.

FIG. 11 shows micrographs of stripes of conductive layers on receiver surface, transferred as per Example TM-2.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention relates to donor laminates and methods of using donor laminates for forming devices. The two layers of the invention, namely, the electronically conductive polymer layer and the metal layer can perform multiple functions. The metal layer provides primarily high conductivity and low sheet resistance. The electronically conductive polymer layer provides conductivity as well as protection (from oxidation, scratching, contamination and the like) to the underlying metal layer, upon transfer to the receiver sheet. On the donor sheet, the electronically conductive polymer layer can provide a suitable surface for deposition of the metal layer. It can also act as a release layer to afford clean transfer from the donor to the receiver. In addition, it can also act as a radiation absorber to allow effective transfer by laser, as described in detail through examples herein below. Thus, the present invention effectively addresses multiple problems currently faced in the art.

More particularly, the present invention is directed to a laminate for transfer of a conductive polymer and a metal comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer. Optionally, the laminate further comprises one or more other layers that include operational layers and auxiliary layers of a device.

Another embodiment is a method of forming a conductive element comprising providing a donor laminate comprising in order, a substrate, an electronically conductive polymer layer in contact with said substrate, and a metal layer; bringing a receiver sheet into contact with said donor laminate; and transferring said metal layer and electronically conductive polymer layer to said receiver sheet.

The present invention is applicable to the formation or partial formation of devices and other objects using various transfer mechanisms and donor laminate configurations for forming the devices or other objects.

The donor laminates of the invention can be used to form, for example, electronic circuitry, resistors, bus bars, capacitors, diodes, rectifiers, electroluminescent lamps, memory elements, field effect transistors, bipolar transistors, unijunction transistors, MOS transistors, metal-insulator-semiconductor transistors, charge coupled devices, insulator-metal-insulator stacks, organic conductor-metal-organic conductor stacks, integrated circuits, photodetectors, lasers, lenses, waveguides, gratings, holographic elements, filters (e.g., add-drop filters, gain-flattening filters, cut-off filters, and the like), mirrors, splitters, couplers, combiners, modulators, sensors (e.g., evanescent sensors, phase modulation sensors, interferometric sensors, and the like), optical cavities, piezoelectric devices, ferroelectric devices, thin film batteries, radio frequency identification (RFID) tags, electromagnetic interference (EMI) shields, printed circuit boards (PCB), or combinations thereof; for example, the combination of field effect transistors and organic electroluminescent lamps as an active matrix array for an optical display.

Preferred embodiments are donor laminates for forming a polymer dispersed LC display, an OLED based display, RFID tags, EMI shields, PCB, or a touch screen. The donor laminates include a substrate, an electronically conductive polymer layer and a metal layer, and optionally one or more other layers that are configured and arranged to form, upon transfer to a receiver, at least two operational layers of the device. Embodiments of the present invention also include a polymer dispersed LC display, an OLED based display, RFID tag, EMI shield, PCB, or a touch screen, or other electronic or optical device formed using the donor laminate.

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.

The term, "device", includes an electronic or optical component that can be used by itself and/or with other components to form a larger system, such as an electronic circuit.

The term, "active device", includes an electronic or optical component capable of a dynamic function, such as amplification, oscillation, or signal control, and may require a power supply for operation.

The term, "passive device", includes an electronic or optical component that is basically static in operation (i.e., it is ordinarily incapable of amplification or oscillation) and may require no power for characteristic operation.

The term, "operational layer" includes layers that are utilized in the operation of device, such as a multilayer active or passive device. Examples of operational layers include layers that act as insulating, conducting, semiconducting, superconducting, waveguiding, frequency multiplying, light producing (e.g., luminescing, light emitting, fluorescing or phosphorescing), electron producing, hole producing, magnetic, light absorbing, reflecting, diffracting, phase retarding, scattering, dispersing, refracting, polarizing, or diffusing layers in the device and/or layers that produce an optical or electronic gain in the device.

The term, "auxiliary layer" includes layers that do not perform a function in the operation of the device, but are provided solely, for example, to facilitate transfer of a layer to a receiver element, to protect layers of the device from damage and/or contact with outside elements, and/or to adhere the transferred layer to the receiver element.

Turning now to FIG. 1 there is presented a cross-sectional representation of a donor laminate 16 comprising a substrate 14 having thereon an electronically conductive polymer layer in contact with said substrate 14 and a metal layer 10.

The substrate 14 can be transparent, translucent or opaque, rigid or flexible, and may be colored or colorless. Preferred substrates are transparent. Rigid substrates can include glass, metal, ceramic and/or semiconductors. Flexible substrates, especially those comprising a plastic substrate, are preferred for their versatility and ease of manufacturing, coating and finishing. Flexible plastic substrates can be any flexible self-supporting plastic film that supports the conductive layer. "Plastic" means a high polymer, usually made from polymeric synthetic resins, which may be combined with other ingredients, such as curatives, fillers, reinforcing agents, colorants, and plasticizers. Plastic includes thermoplastic materials and thermosetting materials.

The flexible plastic substrate has sufficient thickness and mechanical integrity so as to be self-supporting, yet should not be so thick as to be rigid. Another significant characteristic of the flexible plastic substrate material is its glass transition temperature (Tg). Tg is defined as the glass transition temperature at which plastic material will change from the glassy state to the rubbery state. It may comprise a range before the material may actually flow. Suitable materials for the flexible plastic substrate include thermoplastics of a relatively low glass transition temperature, for example up to 150.degree. C., as well as materials of a higher glass transition temperature, for example, above 150.degree. C. The choice of material for the flexible plastic substrate would depend on factors such as manufacturing process conditions, such as deposition temperature, and annealing temperature, as well as post-manufacturing conditions such as in a process line of a displays manufacturer. Certain of the plastic substrates discussed below can withstand higher processing temperatures of up to at least about 200.degree. C., some up to 300.degree.-350.degree. C., without damage.

Although the substrate can be transparent, translucent or opaque, for most applications, transparent substrate(s) are preferred. Although various examples of plastic substrates are set forth below, it should be appreciated that the flexible substrate can also be formed from other materials such as flexible glass and ceramic.

Typically, the flexible plastic substrate is a polyester including polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester ionomer, polyethersulfone (PES), polycarbonate (PC), polysulfone, a phenolic resin, an epoxy resin, polyester, polyimide, polyetherester, polyetheramide, cellulose nitrate, cellulose acetate, poly(vinyl acetate), polystyrene, polyolefins including polyolefin ionomers, polyamide, aliphatic polyurethanes, polyacrylonitrile, polytetrafluoroethylenes, polyvinylidene fluorides, poly(methyl x-methacrylates), an aliphatic or cyclic polyolefin, polyarylate (PAR), polyetherimide (PEI), polyethersulphone (PES), polyimide (PI), Teflon poly(perfluoro-alboxy) fluoropolymer (PFA), poly(ether ether ketone) (PEEK), poly(ether ketone) (PEK), poly(ethylene tetrafluoroethylene)fluoropolymer (PETFE), and poly(methyl methacrylate) and various acrylate/methacrylate copolymers (PMMA) natural and synthetic paper, resin-coated or laminated paper, voided polymers including polymeric foam, microvoided polymers and microporous materials, or fabric, or any combinations thereof. Aliphatic polyolefins may include high density polyethylene (HDPE), low density polyethylene (LDPE), and polypropylene, including oriented polypropylene (OPP).

The preferred flexible plastic donor substrates are polyester and cellulose acetate because of their superior mechanical and thermal properties as well as their availability in large quantity at a moderate price.

Most preferred cellulose acetate for use as the donor substrate is cellulose triacetate, also known as triacetylcellulose or TAC. TAC film has traditionally been used by the photographic industry due to its unique physical properties, and flame retardance. TAC film is also the preferred polymer film for use as a cover sheet for polarizers used in liquid crystal displays.

The manufacture of TAC films by a casting process is well known and includes the following process. A TAC solution in organic solvent (dope) is typically cast on a drum or a band, and the solvent is evaporated to form a film. Before casting the dope, the concentration of the dope is typically so adjusted that the solid content of the dope is in the range of 18 to 35 wt. %. The surface of the drum or band is typically polished to give a mirror plane. The casting and drying stages of the solvent cast methods are described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069, 2,739,070, British Patent Nos. 640,731, 736,892, Japanese Patent Publication Nos. 45(1970)-4554, 49(1974)-5614, Japanese Patent Provisional Publication Nos. 60(1985)-176834, 60(1985)-203430 and 62(1987)-115035.

A plasticizer can be added to the cellulose acetate film to improve the mechanical strength of the film. The plasticizer has another function of shortening the time for the drying process. Phosphoric esters and carboxylic esters (such as phthalic esters and citric esters) are usually used as the plasticizer. Examples of the phosphoric esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Examples of the phthalic esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of the citric esters include o-acetyltriethyl citrate (OACTE) and o-acetyltributyl citrate (OACTB). The amount of the plasticizer is in the range of typically 0.1 to 25 wt. %, conveniently 1 to 20 wt. %, desirably 3 to 15 wt. % based on the amount of cellulose acetate.

The particular polyester chosen for use as the donor substrate can be a homo-polyester or a co-polyester, or mixtures thereof as desired. The polyester can be crystalline or amorphous or mixtures thereof as desired. Polyesters are normally prepared by the condensation of an organic dicarboxylic acid and an organic diol and, therefore, illustrative examples of useful polyesters will be described herein below in terms of these diol and dicarboxylic acid precursors.

Preferred polyesters for use in the donor for the practice of this invention include poly(ethylene terephthalate), poly(butylene terephthalate), poly(1,4-cyclohexylene dimethylene terephthalate) and poly(ethylene naphthalate) and copolymers and/or mixtures thereof. Among these polyesters of choice, poly(ethylene terephthalate) is most preferred.

The aforesaid substrate can be planar and/or curved. The curvature of the substrate can be characterized by a radius of curvature, which may have any value. Alternatively, the substrate may be bent so as to form an angle. This angle may be any angle from 0.degree. to 360.degree., including all angles therebetween and all ranges therebetween. The substrate may be of any thickness, such as, for example. 10.sup.-8 cm to 1 cm including all values in between. The preferred thickness of the substrate varies between 1 to 200 .mu.m, to optimize physical properties and cost. The substrate need not have a uniform thickness. The preferred shape is square or rectangular, although any shape may be used. Before the substrate 14 is coated with the electronically conductive polymer layer 12 it may be physically and/or optically patterned, for example by rubbing, by the application of an image, by the application of patterned electrical contact areas, by the presence of one or more colors in distinct regions, by embossing, microembossing, microreplication, etc.

The aforesaid substrate can comprise a single layer or multiple layers according to need. The multiplicity of layers may include any number of additional layers such as antistatic layers, tie layers or adhesion promoting layers, abrasion resistant layers, curl control layers, conveyance layers, barrier layers, splice providing layers, UV, visible and/or infrared light absorption layers, optical effect providing layers, such as antireflective and antiglare layers, waterproofing layers, adhesive layers, release layers, magnetic layers, interlayers, imageable layers and the like.

In one embodiment, the substrate comprises a release layer on the surface of the substrate that is in contact with the conductive layer. The release layer facilitates separation of the conductive layer from the substrate during the transfer process. Suitable materials for use in the release layer include, for example, polymeric materials such as polyvinylbutyrals, cellulosics, polyacrylates, polycarbonates, silicones, and poly(acrylonitrile-co-vinylidene chloride-co-acrylic acid). The choice of materials used in the release layer may be optimized empirically by those skilled in the art.

The polymer substrate can be formed by any method known in the art such as those involving extrusion, coextrusion, quenching, orientation, heat setting, lamination, coating and solvent casting. The substrate can be an oriented sheet formed by any suitable method known in the art, such as by a flat sheet process or a bubble or tubular process. The flat sheet process involves extruding or coextruding the materials of the sheet through a slit die and rapidly quenching the extruded or coextruded web upon a chilled casting drum so that the polymeric component(s) of the sheet are quenched below their solidification temperature. Alternatively, the sheet can be formed by casting a solution of the sheet material on a drum or band and evaporating the solvent.

The sheet thus formed is then oriented by stretching uniaxially or biaxially in mutually perpendicular directions at a temperature above the glass transition temperature of the polymer(s). The sheet may be stretched in one direction and then in a second direction or may be simultaneously stretched in both directions. The preferred stretch ratio in any direction is at least 3:1. After the sheet has been stretched, it can be heat set by heating to a temperature sufficient to crystallize the polymers while restraining to some degree the sheet against retraction in both directions of stretching.

The substrate polymer sheet may be subjected to any number of coatings and treatments, after casting, extrusion, coextrusion, orientation, etc. or between casting and full orientation, to improve and/or optimize its properties, such as printability, barrier properties, heat-sealability, spliceability, adhesion to other substrates and/or imaging layers. Examples of such coatings can be acrylic coatings for printability, polyvinylidene halide for heat seal properties, etc. Examples of such treatments can be flame, plasma and corona discharge treatment, ultraviolet radiation treatment, ozone treatment, electron beam treatment, acid treatment, alkali treatment, saponification treatment to improve and/or optimize any property, such as coatability and adhesion. Further examples of treatments can be calendaring, embossing and patterning to obtain specific effects on the surface of the web.

The electronically conductive polymer layer of the invention can comprise any of the known electronically conductive polymers, such as substituted or unsubstituted pyrrole-containing polymers (as mentioned in U.S. Pat. Nos. 5,665,498 and 5,674,654), substituted or unsubstituted thiophene-containing polymers (as mentioned in U.S. Pat. Nos. 5,300,575, 5,312,681, 5,354,613, 5,370,981, 5,372,924, 5,391,472, 5,403,467, 5,443,944, 5,575,898, 4,987,042, and 4,731,408) and substituted or unsubstituted aniline-containing polymers (as mentioned in U.S. Pat. Nos. 5,716,550, 5,093,439, and 4,070,189). However, particularly suitable are those, which comprise an electronically conductive polymer in its cationic form and a polyanion, since such a combination can be formulated in aqueous medium and hence environmentally desirable. Examples of such polymers are disclosed in U.S. Pat. Nos. 5,665,498 and 5,674,654 for pyrrole-containing polymers and U.S. Pat. No. 5,300,575 for thiophene-containing polymers. Among these, the thiophene-containing polymers are most preferred because of their light and heat stability, dispersion stability and ease of storage and handling.

Preparation of the aforementioned thiophene based polymers has been discussed in detail in a publication titled "Poly(3,4-ethylenedioxythiophene) and its derivatives: past, present and future" by L. B. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik and J. R. Reynolds in Advanced Materials, (2000), 12, No. 7, pp. 481-494, and references therein.

In a preferred embodiment, the layer containing the electronically conductive polymer is prepared by applying a mixture comprising:

a) a polythiophene according to Formula I

##STR00001## in a cationic form, wherein each of R1 and R2 independently represents hydrogen or a C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or a cycloalkylene group, preferably an ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group; and n is 3 to 1000;

and

b) a polyanion compound;

It is preferred that the electronically conductive polymer and polyanion combination is soluble or dispersible in organic solvents or water or mixtures thereof. For environmental reasons, aqueous systems are preferred. Polyanions used with these electronically conductive polymers include the anions of polymeric carboxylic acids such as polyacrylic acids, poly(methacrylic acid), and poly(maleic acid), and polymeric sulfonic acids such as polystyrenesulfonic acids and polyvinylsulfonic acids, the polymeric sulfonic acids being preferred for use in this invention because of its stability and availability in large scale. These polycarboxylic and polysulfonic acids may also be copolymers formed from vinylcarboxylic and vinylsulfonic acid monomers copolymerized with other polymerizable monomers such as the esters of acrylic acid and styrene. The molecular weight of the polyacids providing the polyanions preferably is 1,000 to 2,000,000 and more preferably 2,000 to 500,000. The polyacids or their alkali salts are commonly available, for example as polystyrenesulfonic acids and polyacrylic acids, or they may be produced using known methods. Instead of the free acids required for the formation of the electrically conducting polymers and polyanions, mixtures of alkali salts of polyacids and appropriate amounts of monoacids may also be used. The polythiophene to polyanion weight ratio can widely vary between 1:99 to 99:1, however, optimum properties such as high electrical conductivity and dispersion stability and coatability are obtained between 85:15 and 15:85, and more preferably between 50:50 and 15:85. The most preferred electronically conductive polymers include poly(3,4-ethylene dioxythiophene styrene sulfonate) which comprises poly(3,4-ethylene dioxythiophene) in a cationic form and polystyrenesulfonic acid.

Desirable results such as enhanced conductivity of the conductive layer can be accomplished by incorporating a conductivity enhancing agent (CEA). Preferred CEAs are organic compounds containing dihydroxy, poly-hydroxy, carboxyl, amide, or lactam groups, such as

(1) those represented by the following Formula II:

##STR00002##

wherein m and n are independently an integer of from 1 to 20, R is an alkylene group having 2 to 20 carbon atoms, an arylene group having 6 to 14 carbon atoms in the arylene chain, a pyran group, or a furan group, and X is --OH or --NYZ, wherein Y and Z are independently hydrogen or an alkyl group; or

(2) a sugar, sugar derivative, polyalkylene glycol, or glycerol compound; or

(3) those selected from the group consisting of N-methylpyrrolidone, pyrrolidone, caprolactam, N-methyl caprolactam, dimethyl sulfoxide or N-octylpyrrolidone; or

(4) a combination of the above.

Particularly preferred conductivity enhancing agents are: sugar and sugar derivatives such as sucrose, glucose, fructose, lactose; sugar alcohols such as sorbitol, mannitol; furan derivatives such as 2-furancarboxylic acid, 3-furancarboxylic acid; alcohols such as ethylene glycol, glycerol, di- or triethylene glycol. Most preferred conductivity enhancing agents are ethylene glycol, glycerol, di- or triethylene glycol, as they provide maximum conductivity enhancement.

The CEA can be incorporated by any suitable method. Preferably the CEA is added to the coating composition comprising the electronically conductive polymer and the polyanion. Alternatively, the coated and dried conductive layer can be exposed to the CEA by any suitable method, such as a post-coating wash.

The concentration of the CEA in the coating composition may vary widely depending on the particular organic compound used and the conductivity requirements. However, convenient concentrations that may be effectively employed in the practice of the present invention are about 0.5 to about 25 weight %; more conveniently 0.5 to 10 and more desirably 0.5 to 5.

The electronically conductive polymer layer of the invention can be formed by any method known in the art. Particularly preferred methods include coating from a suitable coating composition by any well known coating method such as air knife coating, gravure coating, hopper coating, curtain coating, roller coating, spray coating, electrochemical coating, inkjet printing, flexographic printing, stamping, and the like.

While the electronically conductive polymer layer can be formed without the addition of a film-forming polymeric binder, a film-forming binder can be employed to improve the physical properties of the layer. In such an embodiment, the layer may comprise from about 1 to 95% of the film-forming polymeric binder. However, the presence of the film forming binder may increase the overall surface electrical resistivity of the layer. The optimum weight percent of the film-forming polymer binder varies depending on the electrical properties of the electronically conductive polymer, the chemical composition of the polymeric binder, and the requirements for the particular circuit application.

Polymeric film-forming binders useful in the electronically conductive polymer layer of this invention can include, but are not limited to, water-soluble or water-dispersible hydrophilic polymers such as gelatin, gelatin derivatives, maleic acid or maleic anhydride copolymers, polystyrene sulfonates, cellulose derivatives (such as carboxymethyl cellulose, hydroxyethyl cellulose, cellulose acetate butyrate, diacetyl cellulose, and triacetyl cellulose), polyethylene oxide, polyvinyl alcohol, and poly-N-vinylpyrrolidone. Other suitable binders include aqueous emulsions of addition-type homopolymers and copolymers prepared from ethylenically unsaturated monomers such as acrylates including acrylic acid, methacrylates including methacrylic acid, acrylamides and methacrylamides, itaconic acid and its half-esters and diesters, styrenes including substituted styrenes, acrylonitrile and methacrylonitrile, vinyl acetates, vinyl ethers, vinyl and vinylidene halides, and olefins and aqueous dispersions of polyurethanes and polyesterionomers. Preferred polymeric film forming binders include polystyrene sulfonates, polyesters, polyurethanes, vinylidene halides polymers and copolymers and mixtures thereof.

Other ingredients that may be included in the electronically conductive polymer layer include but are not limited to surfactants, defoamers or coating aids, charge control agents, thickeners or viscosity modifiers, antiblocking agents, coalescing aids, crosslinking agents or hardeners, soluble and/or solid particle dyes, matte beads, inorganic or polymeric particles, adhesion promoting agents, bite solvents or chemical etchants, lubricants, plasticizers, antioxidants, colorants or tints, and other addenda that are well-known in the art. Preferred bite solvents can include any of the volatile aromatic compounds disclosed in U.S. Pat. No. 5,709,984, as "conductivity-increasing" aromatic compounds, comprising an aromatic ring substituted with at least one hydroxy group or a hydroxy substituted substituents group. These compounds include phenol, 4-chloro-3-methyl phenol, 4-chlorophenol, 2-cyanophenol, 2,6-dichlorophenol, 2-ethylphenol, resorcinol, benzyl alcohol, 3-phenyl-1-propanol, 4-methoxyphenol, 1,2-catechol, 2,4-dihydroxytoluene, 4-chloro-2-methyl phenol, 2,4-dinitrophenol, 4-chlororesorcinol, 1-naphthol, 1,3-naphthalenediol and the like. These bite solvents are particularly suitable for polyester based polymer sheets of the invention. Of this group, the most preferred compounds are resorcinol and 4-chloro-3-methyl phenol. Preferred surfactants suitable for these