Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
2001-06-26
2003-02-18
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Antihalation or filter layer containing
C430S517000, C430S522000, C430S527000, C430S529000, C430S533000, C430S534000, C430S535000, C430S950000, C428S143000, C428S147000, C428S478800, C428S483000, C347S106000
Reexamination Certificate
active
06521398
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved subbed polyester film and to imaging materials having such a polyester as support.
BACKGROUND OF THE INVENTION
Photosensitive materials based on silver halide chemistry are used in a lot of applications, e.g. photographic materials for general amateur and professional photography in black-and white or colour, recording and printing materials for the motion picture industry, and materials for the recording and duplication of medical diagnostic images. Further specific materials are developed for micrography, non-destructive testing and graphic arts pre-press. In graphic arts reproduction processes the original image appearing to have a continuous tone gradation is reproduced in a screening process by a collection of large number of dots, either by optical means in the case of a camera film or by electronic means in case of a recorder film. Apart from camera and recorder films there exist also so-called contact films which are able to duplicate screened images. In several photographic areas but in particular in graphic arts prepress films there is permanent need for lower manufacturing costs, higher covering power, sharper images, and reduced replenishment rates. This can be achieved in principle by lowering the silver coverage and the thickness of the emulsion layer which implies a low gelatin/silver halide ratio, and lowering the thickness of the auxiliary layers which again implies low gelatin coverages. However, this tendency towards low silver and gelatin coverages can lead to severe problems as will be explained hereinafter.
Conventionally graphic arts photographic materials are coated on a polyester support. The most widely used polyester support in the photographic industry is polyethylene terephthalate. In order to ensure a perfect adhesion of hydrophilic layers such as photographic light-sensitive emulsion layers to dimensionally stable polyester film supports, i.e. polyester films that have been biaxially stretched and heat-setted, it is known for long time to apply several intermediate layers between the support and the light-sensitive emulsion layer(s). In most cases two intermediate layers are needed. A first one, known as the adhesive layer or primer layer or resin subbing layer or latex subbing layer, shows a good adhesion to the polyester film and at the same time possesses good attaching properties in respect to the second layer, known as the “gelatin subbing layer” or “gelatin sub layer” or “gel sub layer”, which usually is formed to a great extent of a hydrophilic colloid such as gelatin. For sake of uniformity we will further refer to the first intermediate layer defined above as the latex subbing layer and to the second intermediate layer as the gelatin subbing layer.
It is customary to incorporate in the gelatin subbing layer a certain amount of a spacing agent, also called matting agent, in order to give the surface a certain degree of roughness. When such a spacing agent is absent bad winding up and lateron bad unwinding of the finished polyester is to be expected. In order to be effective such spacing agents must show a certain minimal average particle size, preferably about 3 &mgr;m. However, when using a very thin emulsion layer the top of the spacing agent particles will pierce through the surface of the emulsion layer. When the emulsion layer is exposed and developed each spacing particle piercing through will locally interrupt the black density of the developed silver. When inspected by light in transmittance this gives the so-called “starry night” effect. The problem can be alleviated by choosing less or a smaller spacing agent. However, then the problems with winding up and unwinding must be expected to deteriorate. So there is a need for a solution which avoids the starry night effect but retains the beneficial properties of the presence of the spacing agent.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a polyester support free of problems of winding up and unwinding.
It is a further object of the present invention to provide imaging elements, such as a photographic material, which are free of the starry night effect after processing.
SUMMARY OF THE INVENTION
The above mentioned objects are realised by providing a polyester film having upper and back sides, the upper side bearing, in order, (a) a latex subbing layer, (b) a gelatin subbing layer, characterized in that at least one of said subbing layers (a) and (b) comprises a black spacing agent. Preferably the black spacing agent is incorporated in the gelatin subbing layer (b).
In a preferred embodiment this spacing agent consists of hydrophobic polymeric particles loaded with a mixture of one or more cyan, magenta and yellow dyes in such a mutual ratio that black is obtained. In a further preferred embodiment the polyester film carries on its back side a conductive latex subbing layer (c) and a gelatinous antihalation layer (d).
The polyester film according to the invention can favourably serve as support for several imaging systems, such as a photographic material, a (photo)thermographic material, and an ink jet recording material. Further advantages and embodiments of the present invention will become apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION
The different elements constituting the present invention will now be explained in detail.
The Black Spacing Agent
It is the essence of the present invention that one of the subbing layers, most preferably the gelatin subbing layer (b), contains a black spacing agent.
In a most preferred embodiment the black spacing agents consists of hydrophobic polymer particles or beads, which are loaded with a mixture of cyan, magenta and yellow hydrophobic dyes in such a mutual ratio that the spacing particles appear black.
Methods for associating hydrophobic ingredients, such as hydrophobic dyes, whiteners, and colour couplers, with hydrophobic polymer particles have been described in e.g. U.S. Pat. Nos. 4,230,716, 4,214,047, 4,247,627, 4,304,769 and GB 1504949.
A particularly preferred method for use in the present invention is disclosed in EP 483416. This improved method for making aqueous dispersions of hydrophobic polymer particles loaded with at least one hydrophobic compound comprises the following steps:
dissolving the hydrophobic compound in a water-immiscible organic solvent,
dispersing the solution obtained in an aqueous medium,
mixing the resulting dispersion with a dispersion of hydrophobic particles in another aqueous medium,
stirring the mixture obtained to allow the hydrophobic compound to associate the hydrophobic polymer particles, and
removing the water-immiscible solvent by evaporation.
In practice any of the numerous combinations of hydrophobic cyan, magenta and yellow dyes can be used provided that they can be combined in an appropriate ratio so that the polymeric particle becomes black. In a particularly preferred embodiment a combination of following dyes is used:
Preferred loadable polymer particles include homopolymers or copolymers of acrylic acid, methacrylic acid, and salts and esters thereof, polystyrene, copoly(ethyl acrylate/stearyl methacrylate), copoly(methacrylic acid/methyl methacrylate/stearyl methacrylate), and polymers described in U.S. Pat. No. 4,614,708 and U.S. Pat. No. 4,861,808 mentioned above.
In a most preferred embodiment poly(methyl methacrylate) (PMMA) is used as loadable spacing agent.
Composition of Layers (a) to (d) Coated on the Polyester
An essential ingredient of the latex subbing layer (a) is an adhesion promoting latex. A preferred class of latex polymers for this purpose are vinylidene chloride-containing copolymers having carboxyl functional groups. Illustrative of such polymers are (1) copolymers of vinylidene chloride and an unsaturated carboxylic acid such as acrylic or methacrylic acid, (2) copolymers of vinylidene chloride and a half ester of an unsaturated carboxylic acid such as the monomethylester of itaconic acid, (3) terpolymers of vinylidene chloride, itaconi
Claes Roland
Thillo Etienne Van
Agfa-Gevaert
Guy Joseph T.
Nexsen Pruet Jacobs & Pollard LLC
Schilling Richard L.
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