Permanent records of X rays or radiations of shorter wavelengths are formed on a film substrate by direct exposure to the radiation and heat development. The process is not sensitive to visible radiation and can therefore be carried on in daylight. An X ray photosensitive film containing a halogenated photodegradable polymer and an aryl dye promoter reacting to free radicals is exposed to an X ray image and then heated under conditions which allow the free radical generated by the photodegradation of the polymer to migrate and react with the aryl dye promoter to provide the imaging dye. The X ray photosensitive layer of the X ray photosensitive film or paper includes, in addition to the photodegradable polymer and the aryl dye promoter, a heat activable complexing agent and an organic binder. The process can be carried out using currently available X ray equipment with the advantage of handling the film in daylight and eliminating chemical development.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a novel X ray image recording system. In 
one aspect, the invention relates to the permanent recording of images or 
objects on a sensitive surface by irradiation with X rays or other 
radiations of shorter wavelengths. In another aspect, the invention 
relates to a new image recording substrate sensitive to radiation with 
wavelengths shorter than fifty angstroms. In still another aspect, the 
invention relates to a new and novel X ray photographic process in which 
an image is reproduced without the conventional developing step. 
2. Discussion of the Prior Art 
Present recording systems for X rays use mostly silver halide emulsions. 
The world consumption of X ray films exceeds that of amateur and 
industrial photography. The amount of silver in X ray material is far 
greater than for ordinary photography, and the recent increase in the 
price of silver has already affected the consumer. 
A variety of silver based radiographic films or papers adapted for various 
applications are found on the market. They are produced by major 
photographic companies such as Eastman Kodak, Dupont, Agfa Gevaert, 
Ilford, Fuji, etc. Medical radiography uses mostly films giving negative 
images, paper finds application in industrial radiography and gammagraphy. 
Xerographic systems for radiography have been introduced recently. They are 
presently the only practical alternative for silver halide radiography. 
The method utilizes selenium plates instead of the conventional drum used 
in xerographic photocopy. Such plates, which have been previously 
electrostatically charged, are exposed to the X ray image in the absence 
of light, and transferred into a development machine which applies toner 
selectively on the plate and then transfers and fixes the toner image onto 
a glossy bristol paper or a plastic film. Radioxerography has a 
sensitivity approaching that of silver halide radiography. It generally 
provides a positive image on an opaque substrate, which creates a problem 
for physicians who are accustomed to negative transparencies. It is, 
nevertheless, gradually accepted in the medical world. 
Radioxergaphy, like xerographic photocopy, offers the advantage of dry 
processing, but at the cost of more expensive and cumbersome equipment 
requiring specialized maintenance. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a novel photographic composition 
sensitive to X rays and other ionizing radiations. 
Another object of this invention is to provide a dry process for the 
recording of X ray images. 
Another object of this invention is to provide a process which is not 
sensitive to ambient light but only to X rays and radiations with a 
wavelength shorter than fifty angstroms. 
Still another object of this invention is to provide a more sensitive dry 
process for the recording of X ray images and the like. 
Still another object of this invention is to provide a process which 
requires only the application of heat to produce a permanent image after 
exposure to X rays. 
Yet another object of this invention is to provide a novel X ray sensitive 
film or paper. 
Another object of this invention is to provide a process for developing and 
an image producing composition which can be developed and fixed in a 
single operation. 
Yet another object is to provide an image producing composition which upon 
exposure to X rays may be developed without a separate wet developing 
process or a separate electrostatic process. 
Various other objects and advantages will become apparent to those skilled 
in the art from the accompanying description and disclosure. 
According to the invention, the X ray photographic system comprises an 
image forming compositon and a separate X ray sensitive polymer. The image 
forming system is supported by an X ray sensitive polymer carrier sheet. 
The carrier sheet or sensitive material containing the image reproduction 
system is then exposed to the image or the source of X rays and the 
material to be photographed directly forms a latent image upon exposure. 
This latent image is thereafter developed by exposition to heat. 
The image forming composition of the photographic system is a 
photodegradable polymer which is capable to generate free radicals upon 
photodegration initiated by X ray radiation. The free radicals are made to 
react with a dye forming material to produce a dye which is further 
complexed with a metal salt to increase its contrast. The recording 
mechanism is illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
The photodegradation of polymers is of current occurrence. It is a common 
fact that most of the plastic materials exposed to sunlight lose their 
transparency with time and become colored. Plastic components in X ray 
equipment have a similar behavior when they are exposed to the radiation. 
Photodegradation produces profound modifications in the physical and 
chemical structure of the irradiated material. These modifications can be 
utilized for permanently recording the irradiation of the material and the 
distribution of this irradiation imagewise when such is the case. 
Physical modification affects the optical, thermal, electrical and 
mechanical properties of the material. 
Chemical modification can change the reactivity or the chemical composition 
of the material, producing new active species (new molecules, reactive 
groups, ions, free radicals) which are either localized or free to move in 
the lattice of the material. In the second alternative, the active species 
produced by the photodegradation can be made to move to the surface and 
react with an image forming system to provide a permanent record. 
It is known that polymers are made of the linear repetition of monomeric 
entities forming long polymeric chains. When the monomeric group 
constituting the chain remains reactive, it can react with another 
identical group of another chain, thereby providing a link with the other 
chain and the resulting polymer is therefore called cross-linked. 
The cross-linking of a polymer can involve only certain reactive groups of 
the polymer itself (FIG. 2) or involve a third component which enters into 
the linkage (FIG. 3). 
In linear polymers, the photodegradation can produce a depolymerization by 
breaking the bonds between monomers, extracting monomers or groups of 
monomers (dimers, trimers, etc), or breaking a reactive group in the 
monomer itself. 
In cross-linked polymers, the photodegradation generally breaks the 
cross-linkage, and depending on its complexity and the energy involved, 
the entire link or part of it can be made free. Naturally degradation of 
the linear part of the structure can also take place simultaneously. 
The ability for a polymer to be photodegradable depends on its absorption 
for the radiation responsible for the degradation, as well as the binding 
energy of the bond that will be affected by the degradation. As 
photodegradation always involves the rupture of one or several chemical 
bonds, the absorption of the radiation should be localized on the bond 
itself or in its immediate vicinity, and such a bond should be weak enough 
to be broken by the energy provided during the absorption process. Most of 
the time, the energy will not be absorbed by the bond itself but by 
another structure in its vicinity, and the energy will be transferred to 
the bond with a certain efficiency .eta.. Or the energy will be absorbed 
far away from the breakable bond and be transferred through a secondary 
mechanism (as in charge transfer complexes and sensitizers). 
The two criteria for photodegradation being radiation absorption and bond 
dissociation energy, one can optimize the processes in acting on these two 
parameters. 
It is known in photochemistry that absorption in the higher end of the 
spectrum (UV, visible, IR) can be promoted by spectral sensitization using 
certain dyes which will transfer energy to the sensitized molecule. 
Similar results can be obtained for X rays and higher energy radiation by 
introducing heavy metal atoms in the structure. 
The weakness of the bond to be broken by photodegradation is generally 
depending on the basic chemical structure of the polymer, that is, the 
original monomer or the reactive groups responsible for the cross-linking. 
This particular bond should be in a position to receive the energy 
transferred by the part of the molecule which absorbs the radiation. 
To design and optimize a photodegradable polymer sensitive to X rays, one 
should look for or synthesize polymers containing heavy metal atoms in 
their structure and establish in the structure of such polymer an easy 
transfer of the energy absorbed in the metal to low dissociation energy 
bonds. 
Free radicals are often produced during photodegradation. This is the case 
of the polymers represented in FIG. 4. 
The type of image forming reaction selected for recording makes use of 
halogenated free radicals which are provided by the last example in the 
form of .multidot.CF.sub.3. 
The halogenated free radicals produced by photodegration of halogenated 
polymers will react with an aromatic amine to form a triarylmethane dye by 
condensation, as represented in FIG. 5. 
Alternative mechanisms can be used for image formation starting from the 
same basic reaction. For example, the bromine free radical extracting a 
hydrogen atom gives hydrogen bromide, which can convert a leuco base into 
its colored form. Also, the bromide can be used to oxidize leuco dyes to 
the colored forms. 
These techniques are well known in the graphic arts, and a number of 
organic systems can be made to react with the free radicals produced by 
photodegradation of halogenated polymers. Listed below are some possible 
systems applicable to the present invention: 
Arylindolizines 
Arylamines and aldehydes 
Leuco triphenylmethane 
Leuco-p-diaminostyryl bases 
Leuco cyanine bases 
Leuco xanthine dyes 
Leuco dyes with N-vinylcarbazol 
Leuco merocyanine with N-vinylcarbazol 
4(p-dimethylaminostyryl) quinoline 
Crystal violet lactone 
Spiropyrans. 
The images obtained are generally lower in density than silver halide 
images, and therefore, a complexation of the dye with a metal salt is 
necessary. 
Organic mineral salts such as the metal salts of behenic acid, naphthenic 
acid and stearic acid with such metals as lead, zinc, barium, copper and 
cobalt can be used. 
Generally, the image forming layer includes from 0.01 to 1 gram per square 
meter of the dye former and from about 0.1 to 2 grams per square meter of 
the complexing agent. The dye former and complexing agent are uniformly 
dispersed in an organic binder which is deposited on the film substrate to 
form the image forming layer. An amount of the organic binder sufficient 
to form an image forming layer having a thickness in the range of from 
about 1 to 10 microns is sufficient. Any organic binder which softens at 
the temperature of the heating step, for example, from about 100.degree. 
C. to 150.degree. C., can be used. 
Photodegradable polymers useful for this process include the commercial 
products listed below: 
(a) The polyhexafluoropropylene: 
##STR1## 
(b) The vinylidene fluoride - hexafluoropropylene copolymer: 
##STR2## 
(c) The tetrafluoroethylene - nitrosofluoromethane copolymer: 
##STR3## 
(d) The tetrafluoroethylene - nitrosochloromethane copolymer: 
##STR4## 
(e) The tetrafluoroethylene - nitrosobromomethane copolymer: 
##STR5## 
Complexation of these structures with heavy metals such as Mo, Co, Pb, U 
and Ta, together with cross-linking, considerably improves the sensitivity 
of the system as with the following polymers: 
(f) The copper (II) complex of polyaminoquinone: 
##STR6## 
(g) The copper (I) complex of poly 1,4 phenylenebis (dithiocarbamic acid): 
##STR7## 
The photodegradable halogenated polymer which forms the substrate of the 
photosensitive film according to the invention may have a thickness in the 
range of from about 0.05 to 3 millimeters. 
In carrying out the process of the invention, the photosensitive film is 
photographically exposed to an x-ray image to imagewise photodegrade the 
polymer and selectively generate halogenated free radicals. The exposed 
photosensitive film is then heated to allow the imagewise generated 
halogenated radicals to react with the dye former to thereby form a dye 
image. The dye image forms a complex with the complexing agent to provide 
the final dye complex image. Generally, the heating step can be carried 
out at a temperature in the range of from about 100.degree. C. to about 
150.degree. C. for a time varying from about 0.05 to about 10 seconds. 
The invention will now be described in connection with specific embodiments 
which are provided as illustrative examples only, and not by way of 
limitation. 
EXAMPLE 1 
The following solution is coated on a 3 mm thick sheet of 
polyhexafluoropropylene: 
______________________________________ 
1-methyl-2-phenylindolizine 
0.5 g 
(Preparation described in Bailey J. British Pat. 
No. 999,874) 
4-aminodiphenylamine 0.4 g 
Ethylcellulose 5 g 
Lead naphtenate 0.65 g 
Methylene Chloride 100 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 5 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 110.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a black recording of the image. 
EXAMPLE 2 
The following solution is coated on a 3 mm thick sheet of vinylidene 
fluoride-hexafluoropropylene copolymer: 
______________________________________ 
1-methyl-2-phenylindolizine 
0.4 g 
4-dimethylaminobenzaldehyde 
0.25 g 
Nickel stearate 0.45 g 
Ethylcellulose 3.4 g 
Ethylmethylketone 100 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 5 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 120.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a black-blue recording of the image. 
EXAMPLE 3 
The following solution is coated on a 3 mm thick sheet of 
tetrafluoroethylene-nitrosofluoromethane copolymer: 
______________________________________ 
3-ethylthio-4-carbocyanine 
0.4 g 
Benzene 70 cc 
Acetone 30 cc 
Cellulose acetobutyrate 
3.4 g 
Cobalt naphtenate 0.4 g 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 5 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 150.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a dark green recording of the image. 
EXAMPLE 4 
The following solution is coated on a 3 mm thick sheet of 
tetrafluoroethylene-nitrosochloromethane copolymer: 
______________________________________ 
3'-methyl-spiro(2'H,1'benzopyran-2,2'[2H,1- 
1 g 
benzopyran]) 
Ferric stearate 3.75 g 
Polyvinylidene chloride 30 g 
Methylethylketone 83 cc 
Toluene 17 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 3 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 120.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a dark brown image. 
EXAMPLE 5 
The following solution is coated on a 3 mm thick sheet of 
tetrafluoroethylene-nitrosobromomethane copolymer: 
______________________________________ 
4-dimethylaminodiphenylamine 
1 g 
Copper naphtenate 3.6 g 
Ethylcellulose 5 g 
Methylene chloride 100 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 3 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 150.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a dark image. 
EXAMPLE 6 
The following solution is coated on a 2 mm thick sheet of the copper (II) 
complex of polyaminoquinone copolymerized with polyhexafluoropropylene: 
______________________________________ 
3-ethylthio-4-carbocyanine 
0.4 g 
Cobalt naphtenate 0.4 g 
Lead polyacrylate 3.4 g 
Cellulose acetobutyrate 
3.4 g 
Toluene 70 cc 
Acetone 30 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 0.5 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 110.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a black image. 
EXAMPLE 7 
The following solution is coated on a 2 mm thick sheet of the copper (I) 
complex of poly 1,4 phenylenebis (dithiocarbamide) copolymerized with 
polyhexafluoropropylene: 
______________________________________ 
4-dimethylaminodiphenylamine 
1 g 
Barium naphtenate 4 g 
Ethylcellulose 3 g 
Lead polymethacrylate 
2 g 
Methylene chloride 70 cc 
Acetone 30 cc 
______________________________________ 
to a wet thickness of 10 microns. 
After drying, the film is exposed to an X ray image under the following 
conditions: 
______________________________________ 
Distance to the source: 
50 cm 
Voltage: 150 KV 
Current: 6 mA 
Exposure time: 1 sec. 
______________________________________ 
and passed through heated rollers at a temperature of 120.degree. C. and a 
speed of 6 cm/sec. 
This composition provides a black image.