Radiation imagery chemistry: process – composition – or product th – Silver halide colloid tanning process – composition – or product
Patent
1992-10-13
1994-08-30
Neville, Thomas R.
Radiation imagery chemistry: process, composition, or product th
Silver halide colloid tanning process, composition, or product
430592, 430598, G03C 106
Patent
active
053427327
DESCRIPTION:
BRIEF SUMMARY
This invention relates to photographic high contrast silver halide materials and to methods of obtaining high contrast images therewith.
For many years the very high contrast photographic images needed in the graphic arts and printing industries were obtained by developing a `lith` emulsion (usually high in silver chloride content) in a hydroquinone, low sulfite, `lith` developer by the process known as infectious development. However, such low sulfite developers are inherently unstable and are particularly inappropriate for machine processing.
Recently emulsions containing hydrazide nucleating agents have been used and processed in a developer with conventional amounts of sulfite, hydroquinone and possibly metal or a pyrazolidone. Such developers also essentially contain an amine additive as described in U.S. Pat. No. 4,269,929. Other developers containing amines are described in U.S. Pat. Nos. 4,668,605 and 4,740,452.
Many hydrazides have been proposed for use in such materials, for example in U.S. Pat. Nos. 4,323,643, 4,278,748, 4,031,127, 4,030,925 and 4,323,643 and in European Patent 0,333,435.
More recently it has been proposed to incorporate amine boosters in high contrast materials with the advantage that it is not necessary to have a special developer in order to obtain the very high contrast that is demanded by much graphic arts work. Such amine boosters are described in Japanese Patent Publications 140340/85 and 222241/87 and in U.S. Pat. No. 4975354 (European Patent 0,364,166).
U.S. Pat. No. 4,857,450 describes so-called high contrast negative materials suitable for laser scanning applications wherein certain spectral sensitising dyes are used in order to obtain "good long term stability and unexpectedly good sensitivity". The examples given show materials having contrasts in the range 4.88 to 6.29 and (in Example 5) a contrast in the toe region of the characteristic curve of 1.17. Such modest contrasts are inadequate for the high quality now demanded in this field.
The present invention provides high contrast film materials suitable for laser scanning which can be developed in a non-specialist developer to obtain very high contrasts in the range 8 to 16 or more with toe contrasts in the range 4 to 10 or more with good photographic speeds. In addition it has been found that the presently used sensitising dyes provide good safelight handling characteristics to the photographic materials and do not cause any reductions in intrinsic speed.
According to the present invention there is provided a photosensitive photographic silver halide material comprising a support bearing a layer of a silver halide emulsion comprising at least 50% silver chloride which contains in or adjacent the emulsion layer a hydrazide nucleating agent and an amine booster, the combination of which is capable of providing high contrast images, which emulsion is sensitised with a dye of the general formula: ##STR2## wherein each of R.sup.1 and R.sup.2 are individually hydrogen, or halogen atom or an alkyl group of 1-4 carbon atoms, a sulfoalkyl, a trifluoromethyl, or cyano group, R.sup.3 is an alkyl or substituted alkyl group, R.sup.4 is a sulfoalkyl group, and R.sup.5 and R.sup.6 are individually an alkyl or substituted alkyl group, and
Groups which R.sup.1 and R.sup.2 may represent include methyl, ethyl, propyl, butyl, sulfoethyl and sulfopropyl, Cl, Br, CN and CF.sub.3. R.sup.4 may be, for example, a sulfoethyl, sulfopropyl or sulfobutyl group and the counter-ion may be an alkali metal, for example, sodium or potassium. Examples of substituent groups that may be on alkyl groups R.sup.3, R.sup.5 and R.sup.6 are: alkoxy groups, carboxy groups, sulfo groups, sulfonamido groups, and halogen atoms.
The preferred amine boosters to be used in the present invention are those described in the European Patent referred to above wherein they are defined as an amino compound which:
(1) comprises at least one secondary or tertiary amino group,
(2) contains within its structure a group comprised of at least three repeating ethyleneoxy unit
REFERENCES:
patent: 3326689 (1967-06-01), Fix et al.
patent: 3520693 (1970-07-01), Gotze et al.
patent: 4857450 (1989-08-01), Burrows et al.
patent: 4975354 (1990-12-01), Machonkin et al.
patent: 4988604 (1991-01-01), Machonkin et al.
Coldrick Philip J.
Pich Julia
Eastman Kodak Company
Lorenzo Alfred P.
Neville Thomas R.
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