Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Reexamination Certificate
1999-04-27
2002-08-20
Shah, Mukund J. (Department: 1609)
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C136S252000, C430S078000, C252S299010
Reexamination Certificate
active
06437123
ABSTRACT:
This invention relates to triazine compounds and their use in the manufacture of electro-luminescent, electronic and liquid crystal devices. In particular the present invention is concerned with triazine derivatives which are capable of exhibiting a nematic discotic liquid crystal phase, a columnar liquid crystal phase and/or a columnar crystalline phase.
Mesogenic compounds which are capable of exhibiting a discotic columnar liquid crystalline phase are known as electric charge carriers for use in electro-luminescent devices. For example, D. Adam et al, Nature, volume 371, Sep. 8, 1994, pages 141 to 143 disclose that 2,3,6,7,10,11-hexahexylthiotriphenylene is capable of exhibiting a discotic liquid crystal phase and that a highly ordered helical columnar phase of this compound forms by cooling an isotropic liquid melt thereof via the discotic liquid crystal phase. Compounds of this type are suitable for transport of holes. DE-A-4343412 discloses discotic liquid crystal charge transport compounds based on a variety of molecules including triphenylene, phthalocyanine, tricycloquinazoline, perylene, decacyclene and porphyrine. DE-A-4343412 also discloses calamitic liquid crystal compounds based on oxadiazole, thiadiazole, biphenyl, terphenyl, quaterphenyl, stilbene, pyrimidine and oxazoline. DE-A-4325238 also discloses organic charge transporting compounds having liquid crystal properties based on tricycloquinazoline. C. Nuckolls et al, J. Am. Chem. Soc., 1996, volume 118, pages 3767 to 3768 and A. J. Lovinger et al, J. Am. Chem. Soc. 1998, volume 120, pages 264 to 268 describe a highly aggregated fibrous columnar phase of a coloured helicene derivative that may be especially useful for charge transport due to the apparently strong interaction of neighbouring molecular cores in the columnar stack.
D. Goldmann et al (Liquid Crystals, 1996, Vol 21, No 5, 619-623) disclose sheet-shaped mesogens based on 2,4,6-triarylamino-1,3,5-triazine, more specifically 2,4,6-tris(3,4-dialkoxyphenylamino)-1,3,5-triazines. In such compounds, the aryl substituent is connected to the triazine ring via a secondary amino group. The free hydrogen on the secondary amino group is quite reactive and so there would be a tendency for the molecule to decompose, particularly under the conditions experienced in use in electroluminescent devices.
It is an object of the present invention to provide a novel class of triazine compounds which have an electron-deficient central unit that favours transport of negative charges (electrons), which are not coloured and therefore do not absorb light, and which are chemically relatively unreactive since they do not bear reactive groups such as —NH—, and so are less susceptible to unwanted decomposition.
According to the present invention, there is provided a class of triazine compounds of the general formula:
wherein Ar, Ar′ and Ar″ are aromatic moieties and are the same or different; each of R
1
, R
1
′, R
1
″ to R
n
, R
n
′, R
n
″ (hereinafter sometimes simply referred to as “groups R”), which may be the same or different, is an elongated flexible, at least partly aliphatic chain such as to impart liquid-crystalline or columnar crystalline properties to the compound; and —(R
1
, . . . , R
n
), —(R
1
′, . . . , R
n
′) and —(R
1
″, . . . , R
n
″) indicate that there are up to n, n′ and n″ substituent groups R on the respective Ar, Ar′, Ar″ moieties, where n, n′ and n″ are integers which do not exceed the number of available substituent positions on the respective Ar, Ar′, Ar″ moieties.
Some of the compounds of the present invention are capable of exhibiting a columnar liquid crystal phase or a columnar soft crystalline phase which is advantageous in electro-luminescent devices due to the good charge transport properties along the director direction and the lack of pronounced grain boundaries between domains such as known from rigid crystals. Especially advantageous are those compounds of the present invention which exhibit highly ordered (soft crystalline) columnar phases such as reported by Lovinger et al (supra) and Adam et al (supra) but not by Goldmann et al (supra), due to enhanced transport in more ordered systems. An example of such a compound is 2,4,6-tris-(3,4-dinonyloxyphenyl)-1,3,5-triazine.
Furthermore, some of the compounds of the present invention are mesogenic compounds which are capable of exhibiting a discotic nematic phase at room temperature which is advantageous for use in liquid crystal devices due to their elastic properties compared to standard (calamitic) nematics, eg for flexoelectric cholesteric displays, and due to their optical and alignment properties, eg for optical compensation layers to enhance the viewing angle dependence of displays. Such compounds may be those in which R is an acyloxy group such as a (C
5
to C
8
)acyloxy group.
The above property of being capable of exhibiting a columnar liquid crystal phase, columnar soft crystalline phase and/or a discotic nematic phase may be exhibited by the compound either in its pure state or when in admixture with one or more other such triazine compounds or when in admixture with one or more other compounds or both where the amount exceeds 20 wt % (more typically >50 wt %) of the mixture. Such one or more other compounds may be one or more other triazine compounds according to the present invention.
The aromatic moiety in each of Ar, Ar′ and Ar″ may be a single or multiple ring (fused and/or unfused) monoaromatic or heteroaromatic moiety. Conjugation of the aromatic unsaturation in Ar, Ar′ and Ar″ with the central triazine group, combined with the planarising action of the electronic attraction of the nitrogens and inner hydrogens in the above formula, effectively holds the three aromatic and the central triazine group in a planar (discotic) form, thereby facilitating the formation of columnar and nematic phases.
Compounds of the above-defined type have an electron-deficient central unit, because they incorporate nitrogens in the aromatic ring, and thereby facilitate the production of a liquid-crystalline and/or columnar electron transport layer for use in electro-luminescent devices. Such compounds are most preferably colourless, contain no chemically reactive groups such as eg —NH— or —OH and exhibit a liquid crystalline and/or columnar phase at room temperature. The compounds of D. Goldmann et al. (supra) contain —NH— groups.
JP-A-7-157473 and JP-A-8-199163 disclose triazine guiding materials for use in electron-transport in electro-optical devices. However, in such triazine compounds, substituent groups to the triazine contain benzoxazole, benzthiazole, benzimidazole or arylamino moieties and are not capable of exhibiting a liquid crystalline and/or columnar phase because flexible chains are lacking and, in some cases, because heteroatoms in the inner positions or the three aromatic substituents favour high torsion angles between the triazine and the substituent rings.
Some of the compounds of the present invention are rare in being discotic nematics, ie nematics with a negative birefringence. For example, 2,4,6-tris-(3,4-diacyloxyphenyl)-1,3,5-triazines where the acyl group is pentanoyl, hexanoyl, heptanoyl or octanoyl are such compounds. Known discotic nematic compounds are either very large and therefore the phase is highly viscous, or of poor chemical inertness or have very high clearing points. The compounds of D. Goldmann et al. (supra) are not reported as possessing a nematic phase.
Additionally, and especially if at least one of the groups R is polymerisable, the compound of the present invention may be a polymerisable mesogen which has potential use, for example, in the manufacture of optical viewing angle compensation films for electro-optical displays.
Preferably, the groups R are independently selected from alkyl, alkyloxy, alkylthio, alkylamino, acyl, acyloxy, acylthio, acylamino, alkyloxycarbonyl and their alkenyl and alkynyl equivalents, where
Anderson Sally
Bock Harald Reinhart
Fujita Yoshimasa
Hudson Andrew James
Rorison Judy Megan
Balasubramanian Venkataraman
Renner , Otto, Boisselle & Sklar, LLP
Shah Mukund J.
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