Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-02-17
2001-09-04
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
Reexamination Certificate
active
06284450
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photosensitive silver salt emulsion and a photosensitive material containing said emulsion. More specifically the invention relates to a silver salt emulsion with improved imaging characteristics and to a method for making said emulsion.
BACKGROUND OF THE INVENTION
A silver halide material used for industrial applications requires a very high flexibility in its practical properties for use, e.g. the light temperature range for exposure, the range or development times in which an optimal image quality can be realized, etc.. On the other hand it is necessary to have the means for the production of tailor-made silver halide materials for special applications which need for instance a well-defined gradation or sensitivity, etc.. One of the means increasingly used in the art, is the introduction of a hole or electron trap in the silver halide crystal, which can be realized by doping with certain metal ligand complexes. Several types of dopants influencing the photographic activity of silver halide materials in different ways are known. The type and strength of the effect of the introduction of a dopant is always the result of the formation of ionic crystal defects in the lattice which in turn can influence the path of photocharges initiated by light absorption in the crystal. The following types of active lattice centres for interaction with photocharges can be distinguished: (i) deep and permanent electron traps, (ii) non-permanent electron traps, (iii) shallow electron traps, (iv) hole traps and (v) recombination centres. A description and definition of the centres mentioned can be found in the following references: R. S. Eachus, M. T. Olm, ‘Crystal Latt. Def. and Amorph. Mat.’, 18,297-31(1989); A. P. Marchetti, R. S. Eachus in ‘Advanced Photochemistry’, 17,145-216(1992); R. S. Eachus, in ‘Phys.Latent Image Form. Halides’, Proc.Int.Symp. Meeting(1983), 249-275; R. S. Eachus, M. T. Olm, Ann.Rep.Prog.Chem., Sect.C,86,3-48(1989); R. S. Eachus, M. T. Olm, J.Soc.Photogr.Sci.Technol.Japan, 54(3),294-303 (1991). An interesting survey in relation with ‘shallow electron traps’ (=SET's) is given in RD36736(November 1994).
Transition metal complexes that can be used as dopant are characterized by the positions of the LUMO and HOMO, where LUMO means ‘lowest unoccupied molecular orbital’ and HOMO ‘highest occupied molecular orbital’ (see D. F. Shriver, P. W. Atkins, C. H. Langford in ‘Inorganic Chemistry’, Oxford University Press(1990)-Oxford-Melbourne-Tokyo). The distance between the energy levels of LUMO and HOMO of a metal ion in a given lattice is among other things determined by the electron-withdrawing strength of the different ligands in the complex. A classification of the ligands with respect to the electron-withdrawing strength is given in the following spectrochemical series as described by Shriver, Atkins and Langford (see above mentioned reference), J. E. Huheey in ‘Inorganic Chemistry: Principles of Structure and reactivity’ (1972)-Harper and Row, New York, or by C. K. Joergensen in ‘Absorption Spectra and Chemical Bonding in Complexes’ (1962)-Pergamon Press, London. The following classification order is generally adopted for the electron-withdrawing strength of a ligand in a metal complex: I
−
<Br
−
<S
2−
<SCN
−
<Cl
−
<NO
3
−
<F
−
<OH
−
<H
2
O<NCS
−
<CH
3
CN <NH
3
<NO
2
−
<<CN
−
<CO.
In spite of this information about the relative strength of a certain ligand it is often difficult to choose a transition metal complex as dopant having the required sensitometric influence in order to use it for a certain application. The relation between the HOMO and LUMO energy levels of a complex in solution (the way it is normally spectrophotometrically measured) and the relative position of these levels in a solid-state situation of a silver halide crystal is not known. An additional factor of uncertainty is the process of incorporating the complex into the crystal.
Excess of halides, high temperatures or extreme pH conditions during precipitation can influence the incorporation of a metal ligand complex into silver halide crystals, this being especially a problem for the asymmetric metal ligand complexes.
In the search for better photographic results new metal complexes are continuously looked for. At this moment metal ligand complexes with at least two different ligands are preferably used in practice. If all the ligands in a metal complex are more electronegative (situated more to the right side of the spectrophotometrical series) the complex is getting more SET (
s
hallow
e
lectron
t
rap) characteristics; if a ligand is becoming less electronegative the trap depth of the metal complex dopant will increase thereby forming a more permanent trapping centre.
Many metal ligand complexes with two or more different ligands are used in materials presently sold in the market. ‘State of the art’ are metal complexes containing halogen ligands used together with another ligand being chosen with respect to the kind of trapping centre needed in the silver halide grains. ‘Mixed’ ligand complexes with halogen ligands as described e.g. in EP-A 0 336 426 (with CN-ligands), EP-A 0 336 427 (with NO- or NS-ligand), EP-A 0 415 480 (with oxo-coordination ligands), EP-A 0 415 481 (with CO-ligand), U.S. Pat. No. 5,360,712 (with organic ligands like azole, diazole, triazole, pyridine, pyrazine, etc.) can be used in photosensitive silver halide materials. So far the activity of the metal halogen-ligand complexes has always been attributed to the ‘other’ ligand as NO, NS, CO, etc.. This is also the case in U.S. Pat. No. 5,500,335 and U.S. Pat. No. 5,474,888 wherein metal complexes with F-ligands are used and wherein the activity of the electronic centres in the crystals are caused by the NO-, CN- or NS-ligand.
The metal complexes described for the first time in the present invention contain one or more F-ligands next to other halogen ligands. These mixed halogen ligand complexes give sensitometric effects that can be fully attributed to the F-ligand, which is unexpected and new in the art.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a photosensitive material containing a silver salt emulsion with improved sensitometric properties, said emulsion containing at least silver halide crystals.
It is a further object of the present invention to provide a photosensitive silver-salt emulsion containing silver halide crystals including a
m
etal-
h
alogen-
f
luorine-complex (called hereinafter ‘MHF’-complex) providing crystal centers able to interact with photoelectrons.
It is another object of the present invention to provide a MHF-complex that can be effectively incorporated into silver-halide crystals.
It is still another object of the present invention to provide a photosensitive image-forming element comprising a photosensitive silver salt emulsion that is thermally developable.
Moreover it is a object of the present invention to provide a method for obtaining a photosensitive element containing silver halide crystals including a MHF-complex as dopant.
Further objects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
The above mentioned objects are realised by providing a photosensitive image-forming element comprising on at least one side of a support a photosensitive layer containing silver halide crystals that are internally doped with a new type of transition metal complex with exclusively halide ligands, more preferably a metal halogen-fluorine-complex (hereinafter called ‘MHF’-complex) represented by general formula (1):
[ML
6−n
F
n
]
m−
(1)
wherein:
M represents a metal selected from the group consisting of the metals belonging both to Group 7, 8, 9 and 10 and to the Periods 4, 5 and 6 of the Periodic System of Elements,
F represents the chemical element fluorine,
L represents one halogen atom or
Höhling Matthias
Reese Ingo
Vandenbroucke Dirk
AGFA-GEVAERT
Breiner & Breiner
Le Hoa Van
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