Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
2001-04-03
2003-07-22
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
C359S891000, C349S106000
Reexamination Certificate
active
06596446
ABSTRACT:
The invention relates to the use of metal complex pigments in color filters and also to pigment preparations and to their use for producing color filters and also the color filters themselves.
Color filters today are chiefly used in liquid-crystal displays, screens, color resolution instruments and sensors. The flat screens of personal computers are a well-known example. There are various ways to produce color filters, which differ not only in the way the colors are applied but also in the generation of the color element patterns from the primary colors red, green and blue as well as black. The colors may be applied for example by coloring a base layer (e.g. gelatin) by means of soluble dyes or pigments (“Dye Method”, “Dye Dispersion Method”), screen printing, offset printing or inkjet printing of pigment pastes, preparations or inks, electrodeposition of photoresists based on dyes or pigments and also in particular by the pigment dispersion method, which involves the use of pigments dispersed either in a polyimide resin (“non-photosensitive polyimide method”) or in a photoresist (“photosensitive acrylic method”). Associated with the methods mentioned, both the direct generation of the color element patterns by printing and the indirect, photolithographic generation are important, the latter in relation to the abovementioned pigment dispersion method in particular. The technique of the a pigment dispersion method in the form of the “non-photosensitive polyimide method” is disclosed for example in JP-A-10-22392 (1998).
In the pigment dispersion method involving the use of a photoresist, the coloring pigments are present dispersed in a UV-curable photoresist. The photoresist, as well as the pigment, generally consists of binder resin, polymerizable monomer photoinitiator and optionally a solvent. It is prepared for example by first finely dispersing the pigment in the form of a concentrate in a solvent and optionally binder resin and adjusted immediately prior to application together with the monomer and the photoinitiator and optionally further components. The pigmented photoresist is uniformly applied to the substrate, for example glass, for example, by spin coating, predried, UV-irradiated by means of a photomask, developed by means of generally inorganic alkaline solution to form the desired color element patterns, and the coating is cleaned and optionally aftercured. This process is repeated for every color, i.e. generally 3 times for a trichromat in the colors red, green and blue, for example.
The advantages of using pigments in conjunction with the pigment dispersion method are the improved light, moisture and heat resistance of the color filters compared to dye-based coating systems. On the other hand, the transparency and color purity of coatings based on pigments are still unsatisfactory, regardless of the coating method. In particular, the incorporation in the photoresist of various pigments mixed to match the desired color locus values is accompanied by undesirable brilliancy and transparency losses, so that the LCDs have increased energy requirements as a consequence.
Individual pigments used in prior art color filters are disclosed for example in JP-A-10-22392 (Toray 1998), JP-A-10-19183 (Hitachi 1998: specific Pigment Colour Index Pigment Yellow 150) and JP-A-10-19184 (Hitachi 1998). However, these are still in need of improvement with regard to the requirements described. It is an object of the present invention to provide novel pigments for use in color filters having improved color purity and transparency and superior lightfastness. The pigments should further be the readily dispersible in polar and apolar organic media, so that they are stabilizable in finely divided form in the various matrix systems or vehicle media of the aforementioned production methods for color filters.
It was found that, surprisingly, specific metal complex pigments as described in similar fashion in EP-A-73463 very substantially meet the required fastness and coloristic requirements, especially transparency and color purity in mixtures with each other and with other pigments.
The invention accordingly provides for the use of metal complexes of an azo compound which conforms to the formula (I) or to one of its tautomeric structures
where
R and R′ are independently OH, NH
2
, NH—CN, acylamino or arylamino and
R
1
and R
1′
are independently —OH or —NH
2
,
and which host at least one guest compound, the metal complexes corresponding to the mono-, di-, tri- and tetraanions of the azo compounds of the formula (I) with the metals Li, Cs, Mg, Cd, Co, Al, Cr, Sn, Pb, particularly preferably Na, K, Ca, Sr, Ba, Zn, Fe, Ni, Cu, Mn and La, as pigments in color filters for liquid-crystal displays.
Aryl substituents in the formula (I) are preferably phenyl or naphthyl, which may each be substituted, for example by halogens such as F, Cl, Br, —OH, C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy, —NH
2
, —NO
2
and —CN.
Acyl substituents in the formula (I) are preferably selected from the group consisting of (C
1
-C
6
-alkyl)carbonyl, phenylcarbonyl, C
1
-C
6
-alkylsulphonyl, phenylsulphonyl, optionally C
1
-C
6
-alkyl-, phenyl- or naphthyl-substituted carbamoyl, optionally C
1
-C
6
-alkyl-, phenyl- or naphthyl-substituted sulphamoyl or optionally C
1
-C
6
-alkyl, phenyl- or naphthyl-substituted guanyl, where the alkyl radicals mentioned may additionally be substituted, for example by halogen, especially Cl, Br or F, —OH, —CN, —NH
2
and/or C
1
-C
6
-alkoxy and the phenyl and naphthyl radicals mentioned may be substituted for example by halogen especially F, Cl or Br, —OH, C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy, —NH
2
, —NO
2
and/or —CN.
The invention provides in particular for the use of the metal complex pigments prepared on the basis of the mono- and/or dipotassium salts of an azo compound of the formula (1) or one of its tautomeric forms and also the hydrates as pigments in color filters for liquid-crystal displays.
These salts underlying the metal complexes to be used according to the invention preferably contain no or only negligible amounts of diazobarbituric acid, the metal complexes themselves are therefore particularly low in by-products and are therefore very particularly suitable for use in color filters with regard to color purity and transparency.
Metal complexes for the purposes of this application also include metal salts.
Very particularly preferred metal complexes are those of azo compounds of the formula (I), preferably of the potassium salts of these azo compounds, which in the form of their free acid or one of its tautomeric structures conform to the formula (II)
where
R and R′ are independently selected from the group consisting of OH and NHCN,
and which host at least one other compound as guest.
Preference is given in particular to organic metal complexes of azo compounds of the formula (II), preferably of the potassium salts of these azo compounds, which in the form of their free acid or one of the tautomeric structures conform to the formulae (IIa to IIc)
Metal complexes of the mono- or dipotassium salts of the azobarbituric acid of formula (1), especially (IIa), are particularly preferred.
The compounds of the formula (1) are particularly preferably 1:1 azo metal complexes which conform to the formula (Ia) or one of its tautomeric forms
where
Me corresponds to one of the metal centers mentioned above,
R and R′ are each as defined above and
R
1
and R
1′
are independently ═O or ═NH.
Particular preference is given to salts and complexes of the formulae (I, Ia, IIa, IIb, IIc) with bi- or tervalent metals, especially the nickel salts and complexes.
Very particular preference is given to the use of metal complexes where the azobarbituric acid-nickel 1:1 complex corresponds to one of the tautomeric forms of the formula (IIa) and hosts at least one other compound as guest.
Generally the metal complex compound obtainable from the process according to the invention forms a layered crystal lattice in which the bonding within any one layer is substantially
Faubion Kent
Herrmann Udo
Nyssen Peter-Roger
Richter Rolf
Witt Josef
Akorli Godfried R.
Bayer Aktiengesellschaft
Eyl Diderico van
McPherson John A.
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