Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
2001-07-19
2003-05-13
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S502000, C430S503000, C430S508000, C430S570000, C430S572000, C430S574000, C430S576000, C430S577000, C430S581000, C430S585000, C430S567000, C430S510000
Reexamination Certificate
active
06562557
ABSTRACT:
This invention relates to a colour photographic material comprising a transparent support, at least one blue-sensitive, predominantly yellow-coupling silver halide emulsion layer, at least one green-sensitive, predominantly magenta-coupling silver halide emulsion layer (PP-1) and at least one red-sensitive, predominantly cyan-coupling silver halide emulsion layer (BG-1).
It is known from EP 434 044 that the production of a coloured material which has its maximum red sensitivity within the range from 595 to 625 nm and its maximum green sensitivity within the range from 530 to 560 nm is advantageous for high colour saturation and for good reproduction of certain colours.
It is known from U.S. Pat. No. 5,169,746 that certain colours are reproduced well if the red sensitivity at 650 nm is at least 50 % less than the maximum red sensitivity, if no magenta-coloured cyan masking coupler is used at the same time.
U. S. Pat. No. 5,723,280 discloses that a high sensitivity can be attained with certain spectral sensitisers despite their maximum red sensitivity being situated at less than 640 nm. These spectral sensitisers are trimethine cyanine dyes comprising a substituted benzoxazole and a substituted benzthiazole or benzselenazole radical, which contain a condensed phenyl radical and which comprise a 2-sulphoethyl group on a nitrogen atom. According to the teaching of U.S. Pat. No. 5,853,968, similar sensitisers in combination with other red sensitisers also result in improved colour reproduction and in better bleachability.
It is also mentioned in the above patent specifications that the claimed materials can contain filter layers comprising magenta dyes for example. Advantageous inter-actions or a preferred arrangement within the material are not disclosed in connection with these additives, however.
The starting point for each of the aforementioned patent specifications was the discrepancy, which has long been known, between the red sensitivity of the human eye and the red sensitivity of colour films, which is shifted bathochromically with respect to the human eye. The teaching which is emphasised therein is to effect a hypsochromatic shift of the sensitisation to red as far as possible until it corresponds to the red sensitivity distribution of the human eye.
However, because the processing of an exposed film to form a coloured image proceeds differently from the colour processing phenomena in the brain, an accurate adjustment of the sensitisation in the film to match the spectral sensitivity distribution of the human eye is not the solution to all colour reproduction problems. In particular, the colour adaptation of the eye cannot be adjusted thus, which gives rise to more or less pronounced colour casts depending on the ambient illumination. Thus the materials according to the prior art exhibit too high a level of colour when standard daylight is replaced by light of a different colour temperature. In particular, these prior art materials are unsatisfactory for taking photographs in artificial light from fluorescent lamps.
Another disadvantage of these known materials is their sensitivity to short wave red light, which is still unsatisfactory.
Moreover, the colour reproduction according to the prior art is still unsatisfactory for certain colours of flowers, e.g. delphinium, and for some textile colours. All colours are affected which exhibit a significant absorption in the long wave red region or in the infrared region.
Furthermore, no success has been achieved with these prior art materials in fulfilling the severe demands imposed on the stability of modem colour photographic silver halide materials. For the production of all-round colour films in particular, which should be capable of being used worldwide, the stability under humid climatic conditions is still unsatisfactory.
The underlying object of the present invention was thus to identify a colour photo-graphic silver halide material with a high sensitivity to light, which in addition to its colour reproduction in standard light also gives good results in other types of illumination, particularly in the artificial light from fluorescent lamps, which reproduces colours such as that of the delphinium without distortion, and which exhibits high stability on storage under humid climatic conditions.
Surprisingly, it has now been found that this object can be achieved if the spectral sensitivity distribution of the cyan layer in a colour photographic material is adjusted so that the sensitivity maximum is situated in the vicinity of 620 nm, and the sensitivity in the longer wavelength region first of all falls only slightly up to 640 nm and then falls steeply up to 680 nm. This condition is fulfilled by a maximum of unsymmetrical width or preferably by a secondary maximum or by a pronounced shoulder in the spectral sensitivity distribution, wherein the wider part of the red sensitivity curve, the secondary maximum, or the shoulder, is shifted batho-chromatically in relation to the maximum. Expressed numerically, the sensitivity at 640 nm has to be less by a certain extent than the maximum sensitivity which is shifted towards the short wave region, and the sensitivity at 680 nm has to be less by a minimum extent than the maximum sensitivity. This type of red sensitivity distribution differs considerably from the types of red sensitisation which has been used hitherto in photographic materials and from those which have been described hitherto. Surprisingly, the sensitisation according to the invention which was defined above, and which differs considerably from the sensitivity distribution of the human eye, results in better reproduction in artificial light than when the teaching of the prior art is followed.
The present invention therefore relates to a colour photographic material comprising a transparent support, at least one blue-sensitive, predominantly yellow-coupling silver halide emulsion layer, at least one green-sensitive, predominantly magenta-coupling silver halide emulsion layer (PP-1) and at least one red-sensitive, predominantly cyan-coupling silver halide emulsion layer (BG-1), characterised in that the spectral sensitivity distribution of BG-1 is characterised in that
605≦&lgr;
max
≦630 nm,
0.1≦&Dgr;lgE
640
≦0.6 and
1.8≦&Dgr;lgE
680
,
wherein &lgr;
max
represents the wavelength at which the maximum sensitivity occurs, &Dgr;lgE
640
represents the difference of the logarithmic sensitivity at &lgr;
max
minus the logarithmic sensitivity at 640 nm, and &Dgr;lgE
680
represents the difference of the logarithmic sensitivity at &lgr;
max
minus the logarithmic sensitivity at 680 nm, and the sensitivities are determined after exposure and processing of the material at a cyan colour density which is formed by coupling with developer oxidation product and which is 0.5 above the minimum density.
The logarithmic spectral sensitivities are obtained from the spectrogram of the photographic material by plotting logarithmic sensitivity against wavelength, wherein it has proved most useful to measure the sensitivities at a density of 0.5 greater than D
Min
. For this purpose, the test material is processed according to standards or by methods provided for the material.
The strong dependence of the reproduction in artificial light on the shape of the spectrum was particularly surprising. If a departure is made from the aforementioned ranges for &lgr;
max
and for &Dgr;lgE
640
, a significant green cast is obtained for exposures made in the light from fluorescent lamps. Particularly good results, even with regard to delphinium reproduction, are achieved if
610≦&lgr;
max
≦625 nm,
0.2≦&Dgr;lgE
640
≦0.5 and
2.0≦&Dgr;lgE
680
.
PP-1 is preferably further from the support than is BG-1, and at least one green-absorbing dye is contained in BG-1 or in a layer which is situated between PP-1 and BG-1. The at least one green-absorbing dye is most preferably contained in a layer which is situated between PP-1 and BG-1. Even though the green-absorbing dye, the absorption of which always has a certain half-width
Bell Peter
Endres Lothar
Kapitza Detlev
Schütz Heinz
Stetzer Thomas
Agfa-Gevaert
Connolly Bove & Lodge & Hutz LLP
Letscher Geraldine
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