Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Patent
1992-11-13
1994-11-22
Chea, Thorl
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
430539, 430637, 430642, 430643, 252351, G03C 138
Patent
active
053668570
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydrophilic colloid composition for a photographic material. More particularly, it relates to a hydrophilic colloid coating composition containing a fluoroalkyl polyglycidol surface active agent which may be used in the preparation of a photographic material.
In the preparation of a photographic material, a support is usually coated with one or more layers comprising an aqueous solution of a hydrophllic colloid binder e.g. gelatin. Such layers include, for example, silver halide emulsion layers, intermediate layers, antihalation layers, filter layers, antistatic layers, protective layers, and the like. For multilayer materials, the layers may be coated simultaneously.
In the preparation of hydrophilic colloid layers, the coating solutions must be coated uniformly with a minimum of repellency spots, or repellencies. A repellency is a coating unevenness, such as a round, oval, or comet-shaped indentation or crater in the layer or layers. Repellencies are often caused by the presence in the coating composition of finely-divided insoluble materials in the form of addenda, impurities, or contaminants that are surface active. Solutions coated in the preparation of photographic materials often contain dispersed insoluble photographic addenda, such as organic solvents, or addenda to alter certain physical properties, such as lubricants. Many of these addenda are capable of imparting repellencies to coated layers.
Photographic gelatin may contain insoluble residues of certain naturally-occurring animal fats and fatty acids which can impart repellencies to the coated layer. Also, surface active contaminants may be introduced from external sources during preparation of the coating composition or during coating. For example, a layer may be contaminated during or immediately after coating by various oils used to lubricate the coating apparatus or by other airborne surface active particles.
A wide variety of ionic and non-ionic surface active agents have been suggested for use as coating aids to control the uniformity of hydrophilic colloid layers. Ionic e.g. anionic surface active agents can produce unwanted ionic interactions in hydrophilic colloid coating compositions. For example, anionic surface active agents tend to be incompatible with cationic polymers and tend to cause such problems as clouding or precipitation; they also tend to cause large increases in viscosity when added to gelatin solutions and they tend to result in a hydrophobic surface which is not readily wettable.
The use of non-ionic surface active agents can overcome the results of unwanted ionic interactions. For example, U.K. Patent No. 1,524,631 describes the use of certain non-ionic fluoroalkyl polyalkylkeneoxides and polyglycidols as coating aids for use in the preparation of photographic materials. The coating aids are represented by the general formula oxide or polyglycidyl groups. These compounds, however, do not prevent repellencies caused by materials having low surface tension properties, such as silicone fluids used as lubricants and sealants.
In addition to controlling repellencies, surface active agents can affect the electrical charging characteristics of a hydrophilic colloid layer. Dried coatings of aqueous gelatin or aqueous gelatin solutions containing conventional hydrocarbon-based surface active agents charge positively when impacted against surfaces such as stainless steel. Negative charge inducing surface active agents can be incorporated in the coating composition to produce a dried gelatin coating that has a desired charging characteristic. Such measures are of use in minimising the accumulation of electrostatic charge in coated hydrophilic colloid layers.
The invention aims to provide surface active agents for hydrophilic colloid coating compositions which are capable of improved repellency control and have desirable charge control characteristics.
In one aspect, the invention provides a coating composition comprising an aqueous solution of a hydrophilic colloid and a surface active agent present
REFERENCES:
patent: 3470258 (1969-09-01), Tesoro
"Waterproofing and Water-repellancy", J. L. Moillet, 1963, Elsevier Publishing Co., London, p. 142.
Clark Bernard A.
Padday John F.
Pitt Alan R.
Chea Thorl
Eastman Kodak Company
Rice Edith A.
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