Compositions – Electrically conductive or emissive compositions
Reexamination Certificate
2002-07-25
2004-01-13
Kopec, Mark (Department: 1751)
Compositions
Electrically conductive or emissive compositions
C252S299010, C252S299610, C549S081000, C528S377000
Reexamination Certificate
active
06676857
ABSTRACT:
FIELD OF INVENTION
The invention relates to new mono-, oligo- and poly-4-fluorothiophenes, polymerisable liquid crystal materials and anisotropic polymer films, including their oxidatively or reductively doped forms. The invention further relates to their use as semiconductors or charge transport materials in optical, electrooptical or electronic devices including field effect transistors, electroluminescent, photovoltaic and sensor devices. The invention further relates to field effect transistors and semiconducting components comprising the new mono-, oligo- and poly-4-fluorothiophenes. Furthermore the invention relates to a security marking or device and to a charge injection layer, planarising layer, antistatic film or conducting substrate or pattern.
BACKGROUND AND PRIOR ART
Organic materials have recently shown promise as the active layer in organic based thin film transistors and organic field effect transistors (OFETs) [see reference 1]. Such devices have potential applications in smart cards, security tags and the switching element in flat panel displays. Organic materials are envisaged to have substantial cost advantages over their silicon analogues if they can be deposited from solution, as this enables a fast, large-area fabrication route.
The performance of the device is principally based upon the charge carrier mobility of the semiconducting material and the current on/off ratio, so the ideal semiconductor should have a low conductivity in the off state, combined with a high charge carrier mobility (>1×10
−3
cm
2
V
−1
s
−1
). In addition, it is important that the semiconducting material is relatively stable to oxidation, i.e., it has a high ionisation potential, as oxidation leads to reduced device performance.
A known compound which has been shown to be an effective p-type semiconductor for OFETs is pentacene [see reference 2]. When deposited as a thin film by vacuum deposition, it was shown to have carrier mobilities in excess of 1 cm
2
V
−1
s
−1
with very high current on/off ratios greater than 10
6
. However, vacuum deposition is an expensive processing technique that is unsuitable for the fabrication of large-area films.
Regioregular poly(3-hexylthiophene) has been reported with charge carrier mobility between 1×10
−5
and 4.5×10
−2
cm
2
V
−1
s
−1
, but with a rather low current on/off ratio (10-10
3
) [see reference 3]. In general, poly(3-alkylthiophenes) show good solubility and are able to be solution processed to fabricate large area films. However, poly(3-alkylthiophenes) have relatively low ionisation potentials and are susceptible to doping in air [see reference 4].
Fluorinated poly(alkylthiophenes) were studied by L. Robitaille and M. Leclerc [see reference 5]. However, poly[3-(tridecafluorononyl)thiophene] was found to be soluble in octafluorotoluene, a solvent unsuitable for large scale solution processing. Compared to its alkyl analogues, however, it exhibited inferior electronic properties, which was attributed to lower regioregularity. In addition, the bulky fluoroalkyl group dilutes the macroscopic charge transport mobility arising from the conjugated pi-electron component of the molecule. This large group also potentially disrupts the closely packed lammelar morphology, again lowering mobility.
It is an aim of the present invention to provide new materials for use as semiconductors or charge transport materials, which are easy to synthesize, have high charge mobility, good processibility and improved oxidative stability.
Further aims of the present inventions relate to advantageous uses of the mono-, oligo- and polymers, including their oxidatively or reductively doped forms, according to the invention.
Other aims of the invention are immediately evident to those skilled in the art from the following description.
The inventors have found that these aims can be achieved by providing new oligomers and polymers based on regioregular 3-substituted 4-fluorothiophenes, where the subtituant fluorine group withdraws electron density from the conjugated pi-electron molecular system, thus increasing the ionisation potential and rendering the compound less succeptable to loss of electrons.
The compounds according to the invention show a high charge carrier mobility as well as an increased oxidative stability compared to poly-3-alkylthiophenes.
A further aspect of the invention relates to reactive mesogens consisting of a central core comprising one or more 3-substituted 4-fluorothiophene units, and optionally comprising further conjugated moieties that form an extended conjugated system together with the 4-fluorothiophene units, said core being linked, optionally via a spacer group, to one or two polymerisable groups. The reactive mesogens can induce or enhance liquid crystal phases or are liquid crystalline themselves. They can be ordered and aligned in their mesophase and the polymerisable group can be polymerised or crosslinked in situ to form coherent polymer films with a high degree of long range order, or monodomain, thus yielding improved semiconductor materials with high stability and high charge carrier mobility.
A further aspect of the invention relates to liquid crystal polymers, in particular liquid crystal side chain polymers obtained from the reactive mesogens according to the present invention, which are then further processed, e.g., from solution as thin layers for use in semiconductor devices.
A further aspect of the invention relates to the mono-, oligo- and polymers, a material or polymer film according to the invention, which are oxidatively or reductively doped to form conducting ionic species. Another aspect of the invention is a charge injection layer, planarising layer, antistatic film or conducting substrate or pattern for electronic applications or flat panel displays, comprising mono-, oligo- or polymers, a material or polymer film according to this invention.
Definition of Terms
The terms ‘liquid crystalline or mesogenic material’ or ‘liquid crystalline or mesogenic compound’ means materials or compounds comprising one or more rod-shaped, lath-shaped or disk-shaped mesogenic groups, i.e., groups with the ability to induce liquid crystal phase behaviour. The compounds or materials comprising mesogenic groups do not necessarily have to exhibit a liquid crystal phase themselves. It is also possible that they show liquid crystal phase behaviour only in mixtures with other compounds, or when the mesogenic compounds or materials, or the mixtures thereof, are polymerised.
The term ‘polymerisable’ includes compounds or groups that are capable of participating in a polymerisation reaction, like radical or ionic chain polymerisation, polyaddition or polycondensation, and reactive compounds or reactive groups that are capable of being grafted for example by condensation or addition to a polymer backbone in a polymeranaloguous reaction.
The term ‘film’ includes self-supporting, i.e., free-standing, films that show more or less pronounced mechanical stability and flexibility, as well as coatings or layers on a supporting substrate or between two substrates.
SUMMARY OF THE INVENTION
The invention relates to mono-, oligo- and polymers comprising at least one 3-substituted 4-fluorothiophene group.
The invention further relates to the use of mono-, oligo- and polymers according to the invention as semiconductors or charge transport materials, in particular in optical, electrooptical or electronic devices, like for example in field effect transistors (FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications such as electroluminescent displays or backlights of e.g. liquid crystal displays, for photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors and for electrophotographic applications like elec
Farrand Louise
Giles Mark
Heeney Martin
McCulloch Iain
Shkunov Maxim
Kopec Mark
Merck Patent Gesellschaft mit
Millen White Zelano & Branigan P.C.
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