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U.S. Patent Sep. 30,1997 sheet 4 of 4 5,672,465
POLYETHYLENEIMINE BINDER COMPLEX
CROSS REFERENCE TO RELATED
The instant case is a divisional application of Ser. No. 08/106,131, filed Aug. 12, 1993, now U.S. Pat. No. 5,420, 000, which issued on May 30, 1995, which in turn is a continuation-in-part application of the following U.S. applications: Ser. No. 07/970,986, filed Nov. 2, 1992, now abandoned, which is a continuation application of Ser. No. 07/506,272, filed Apr. 9,1990, now abandoned; and Ser. No. 07/973,192, filed Nov. 2, 1992, now abandoned, which is a continuation application of Ser. No. 07/506,273, filed Apr. 9, 1990, now abandoned.
The major part of this work was supported from Research Grants (R43 CA49347-01, R43 CA49347-02, and R43 CA49347-03) from the National Cancer Institute, U.S. Department of Health and Human Services under the Small Business Innovation Research Program.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation sensitive film for imaging and monitoring high energy ultraviolet, electrons, X-rays, and neutrons utilizing as the radiation sensitive element; a radiation polymerizable diacetylenic composition, which can be fixed during processing simply by heating after exposure. The invention also relates to convertor-complexed polymeric binder compositions useful in the film for converting high energy incident radiation into lower energy radiation to enhance image formation. Processes for preparing emulsions of radiation sensitive compounds for use in the film are also provided.
2. Brief Description of Prior Art
High energy radiation, including that having energy higher than 4 eV, such as short wavelength UV light, X-rays, gamma rays, electrons, neutrons, and laser radiation are used for a variety of applications, such as curing of coatings and cross linking of polymers, recording images and information, radiography, nondestructive testing and diagnostic and radiation therapy.
Currently, silver halide film, composed mainly of an emulsion of silver bromide/iodide in gelatin is widely used as the film for recording images and information, diagnostic and industrial radiography and monitoring radiation therapy and dose. The main advantages of silver halide film are (1) high spatial resolution, (2) image distribution across a plane which can be obtained from a single exposure and (3) information can be stored permanently. However, silver halide film has many disadvantages and drawbacks: (a) it requires protection from ambient light until fixed, (b) the developing and fixing processes are "wet" and chemical based, and require about five minutes developing time, and the concentrations of individual solutions and chemicals, time and temperature of developing and fixing must be strictly controlled. However, it is desired in the art to have a self-developing, fast, dry fixing film which is not affected by white light. There is further a definite need for an inexpensive, dry-processing film for monitoring high energy radiation dosages, storing information and images, nondestructive testing of industrial parts, medical diagnosis, quality control and verification of radiation therapy procedures
which has the advantages and desired features of silver halide film with essentially none of its major disadvantages and drawbacks.
New photosensitive materials are constantly being searched for to provide new film devices. One such group of materials being evaluated are the polymerizable diacetylenes, R—C=C—-C=C—R, where R is a substituent group, which diacetylenes polymerize in the solid state either upon thermal annealing or exposure to high energy radiation [Adv. Polym. Sci., 63, 1 (1984)]. The term diacetylene(s) is used herein to designate a class of compounds having at least one —C=C—Cs^C— functionality. The solid monomers are colorless or white, the partially polymerized diacetylenes are blue or red, while the polydiacetylenes are metallic being usually a copper or gold color. Polydiacetylenes are highly colored because the "pi" electrons of the conjugated backbone are delocalized. The color intensity of the partially polymerized diacetylenes is proportional to the polymer conversion.
Anumber of patents have been issued on the synthesis and use of conjugated polyacetylenic compositions as radiation dosimeters, temperature monitors, and time temperature indicators.
The use of diacetylenes including those having carboxylic acid substituents and their derivatives in photographic and other related arts is disclosed in several U.S. Patents, such as, U.S. Pat Nos. 3,501,297 and 3,679,738 (issued to Cremeans), U.S. Pat. No. 3,501302 (issued to Foitz), U.S. Pat. No. 3,501303 (issued to Foltz et al), U.S. Pat No. 3,501308 (issued to Adelman) and U.S. Pat. Nos. 3,743, 505; 3,844,791 & 4,066,676 (all three issued to Bloom). These patents disclose dispersions in resin, gelatin, or gum matrices of certain diacetylene crystals for directly imaging photo-reactive compositions. Light exposed areas are evidenced by a color change. A quantum efficiency of 8 to 16 is reported. For the use of diacetylenes in diagnostic X-ray film imaging, significantly high quantum yields are required.
Diacetylenes are not sensitive to visible radiation (long wavelength). Luckey and Boer in U.S. Pat. No. 3,772,027 disclose a diacetylenic photosensitive element containing inorganic salts, such as titanium dioxide, zinc oxide, cadmium iodide, and cadmium sulfide as sensitizers to make the element sensitive to visible radiation. Another similar patent (U.S. Pat. No. 3,772,028) issued to Fico and Manthey discloses a photosensitive element sensitized to visible radiation by the addition of pyrylium salts including thiapyrylium and selenapyrylium salts. Amplification of poorly imaged crystalline diacetylenic compositions is obtained in U.S. Pat. No. 3,794,491 (issued to Borsenberger et al), Faint images are enhanced through post-exposure irradiation. These patents describe formulations and processes for making diacetylenes sensitive to longer wavelength (lower energy) radiation, such as visible so that the film can be used as a photographic film for visible light However, there is no report on the sensitization of diacetylenes to shorter wavelength (higher energy) radiation, such as X-rays. Such sensitization to higher energy radiation is desirable for making, for example, diagnostic X-ray film.
In order to increase the spatial resolution of images obtained with diacetylenic imaging compositions, Rasch in U.S. Pat. No. 3,882,134, prepared compositions having a much finer grain structure than reported before. He described the use of vapor deposition to facilitate the isolation of fine micro-crystals.
Ehrlich in U.S. Pat No. 3,811,895 disclosed the use of organometallics as sensitizers and the use of such sensitized
systems as X-ray film media. Lewis, Moskowitz, and Purdy in U.S. Pat. No. 4,734355 disclose a processless recording film made from crystalline polyacetylenic compounds. They also disclosed a process of dispersing crystalline polyacetylenic compounds in a non-solvating medium to a concen- 5 tration of about 2 to 50% polyacetylene crystalline solids and aging said dispersion before drying on a substrate. The sensitivity of the obtained film is low and hence exposure of at least a kilorad of radiation is required to produce the image. Their gelatin/diacetylene mixture requires prolonged 10 aging at low temperature. However, it would be desirable to have a process which does not require aging of the emulsion. Fine crystals (grain size) are desirable for certain applications, such as microfilm and larger crystals can be used for other applications, such as radiation therapy film so 15 that higher radiation sensitivity can be obtained. It is also desirable in the act to have a process to control the diacetylene crystal size.
Guevara and Borsenberger in U.S. Pat. No. 3,772,011 describe print-out elements and methods using photocon- 20 ductors and crystalline polyacetylenic compounds in contact with a photoconductive layer. Visible images are obtained when these layers are contacted with the application of an electric potential. In the absence of an applied potential, the elements described are stable under normal room-light han- 25 dling conditions. Guevera et al in U.S. Pat. No. 3,772,011 provides a diacetylenic composition which undergoes direct image-wise photo-polymerization to a highly colored polymeric product when elaborated into a layer of micro-crystals contiguous to a photo-conductive layer. Such polymeriza- 30 tion takes place upon exposure during the application of an electric potential across the layers. In some cases, an organic photoconductor may be included in the layer of crystalline polyacetylenes.
Use of diacetylenic compositions for photoresists has been disclosed in U.S. Pat. Nos. 3,840369; 4,581,315 and 3,945,831.
Patel in U.S. Pat Nos. 4,235,108; 4,189399; 4,238352; 4,384,980 has disclosed a process of increasing the rate of ^ polymerization by cocrystallization of diacetylenes. Patel and others in U.S. Pat. No. 4,228,126; and 4,276,190 have described an inactive form of diacetylenes for storing and method of rendering them active prior to use by solvent, vapor and/or melt recrystalHzation. 45
Mong-Jon Jun at el (U.S. Pat No. 3,836368) describe 2,4-hexadiyn-l,6-bis(n-hexyl urethane), referred to here in as "166", which turns red upon short wavelength UV irradiation (See Example 3 in the Patent). They prepared a coating formulation by adding water to a solution of 166 in 50 polyvinylpyrrolidone in methanol. The UV exposed coating was red, and it changed to a black color after heating at 55° C. and became inactive to UV light. Although 166 is sensitive to UV radiation, the reactivity is not sufficient to use it for applications, such as diagnostic X-ray film. There 55 is a need to increase the reactivity of 166 so that images can be obtained at a lower radiation dose. We repeated the process described by Jun et al and prepared a coating of 166 by the process disclosed in U.S. Pat No. 3,836368. We obtained undesirably large crystals and hence an opaque go coating. Thus, there is a need in the art for a film device which contains heat fixable diacetylenes, is highly radiation sensitive, preferably transparent and which can be quickly heat fixed in a dry process providing high resolution imaging- 65
None of the above described patents describe a film which is substantially transparent, highly sensitive to short wave
length UV, X-ray, electron, gamma ray, or neutron radiation and contains a radiation sensitive element composed of at least one polymerizable diacetylenic compound and a converter which emits radiation of wavelength shorter than 350 nm when contacted with high energy radiation, which when heated becomes fixed and turns into a blue permanent image. Further, use of a polymeric binder e.g., polyemyleneimine, complexed with a converter material is also not reported. Furthermore, there is no report of a process for making an emulsion of a diacetylene which does not require aging and provides the desired micro-size crystals for preparing transparent films. There are further deficiencies in the prior art with respect to the field of radiation sensitive imaging and monitoring devices as described below.
Silver halide film is not very sensitive to diagnostic X-ray radiation. X-ray images are amplified by placing the film between two fluorescence screens. Intensifying screens are luminescent materials and usually consist of a crystalline host material to which is added a trace of an impurity. Luminescence in inorganic solids usually originates at defects in the crystal lattice (Thomas F. Soules and Mary V. Hoffman, Encyclopedia of Science and Technology, Vol. 14, 1987, pp 527-545). The phosphor of the fluorescence screen absorbs X-rays and emits white light Intensifying screens made with calcium tungstate phosphors have been in use since the time of Roentgen. Around 1972, a new phosphor, gadolinium oxysulfide was developed which emits in the green region and film sensitized to absorb green light was developed. About the same time other phosphors, such as barium fluorochloride and lanthanum oxybromide, which emit in the blue region, were developed. A large number of phosphors have been reported in the literature including terbium activated rare earth oxysulfide (X202S where X is gadolinium, lanthanum, or yttrium) phosphors (T. F. Soules and M. V. Hoffman, Encyclopedia of Chemical Technology, Vol. 14, pp 527-545, 1981 and references quoted therein). Gadolinium and tungsten have very high atomic numbers and also have a high energy absorption coefficient. The following combinations have been used for this purpose: GdOS:Tb(m), LaOS:Tb(in), LaOBr:Tb(m), LaOBr:Tm (IH), and Ba(FCl)2:Eu(H). A number of patents e.g. U.S. Pat Nos. 5,069,982; 5,173,611; 4387,141; and 4,205,234 are representative and have been issued. Among the hundreds of phosphors reported, the literature search reveals that most of them are blue-, green-, or long wave-UV emitting phosphors upon excitation by X-ray. Some of them emit long wavelength blue light, for example, U.S. Pat. No. 4,719,033. No one has so far reported an X-ray screen with a short-wave UV emitting (e.g., wavelength shorter than 275 nm) phosphor.
Convertors/phosphors are usually used as a screen in form of a fine powder dispersed in a polymeric binder. The screens are placed in contact with the emulsion of silver halide film during X-ray irradiation. The prior art does not describe a convertor/phosphor which is in the form of a transparent coating being a solid solution or complex of a converter with a polymeric binder. The use of these converters in the under coat, radiation sensitive coat and top coat of the device is also not described.
Polymers are widely used as binders for a variety of applications including paints and X-ray film coating. Though other polymers are proposed, gelatin is a widely used binder for silver halide and other photosensitive materials including diacetylenes. Many polymers have the ability to form complexes with inorganic compounds. However, there is no report on the use of polymeric complexes as binders for the radiation sensitive formulations, such as diacetylenes.
Polyethyleneimine, referred herein as PEI, farms complexes with a number of inorganic and organic compounds, see Polym. Sci., Vol, 15, pp 751-823,1990 by S. Kobayashi and J. Polymer Science: Part A: Polymer Chem., Vol. 28, pp. 741-758 (1990) by Y. T. Bao and C. G. Pitt. However, there 5 is no report on use of polyethyleneimine and its complexes as binders and converters for radiation sensitive films.
Emulsions are usually prepared by homogenizing/ emulsifying two immiscible liquids, e.g., a water immiscible solvent (e.g., ethylacetate) with water using an emulsifying agent, such as a surfactant For example, U.S. Pat. No. 4,734355 describes this type of system, e.g., diacetylene dissolved in water immiscible solvent, such as ethylacetate and emulsified with gelatin solution in water at high speed. As the solvent used is a good solvent for diacetylenes, the method requires that the emulsion be chilled to a low temperature, and the solvent removed and aged. There is no report on making of an emulsion of diacetylenes without a binder and later mixing the emulsion with a binder. Further, there is no report on preparation of emulsion of a radiation sensitive material, such as diacetylene without using a organic solvent. Further, there is no report on quenching the emulsion to a very low temperature, e.g., liquid nitrogen temperature, to freeze the emulsion and inducing crystal growth by thawing the frozen emulsion.
SUMMARY OF THE INVENTION
We have discovered that a self-developing, dry fixing film device for monitoring, recording and imaging with radiation, such as UV light, electrons, X-rays, neutrons, or gamma rays, can be made by the use of at least one heat fixable conjugated diacetylene, a binder, such as polyemyleneimine, complexed with a converter material, capable upon radiation with high energy electrons, x-rays, gamma rays, neutrons, of generating secondary radiation which is capable of inducing polymerization of the heat fixable diacetylene to form a colored image.
Particularly useful is a specific diacetylene (R—C=C— G=C—R), 166 where [R=—CHjOCONHfCH^Caj and a few closely related diacetylenes which have several unique properties, such as high radiation reactivity, low thermal reactivity, crystallization to an inactive phase from melt, and thus heat fixable, In addition, 166 undergoes a red-to-blue color change when the partially polymerized 166 is heated near or above its melting point, A preliminary toxicity study indicates that 166 is nontoxic.
We have also discovered that certain other diacetylenes such as 155 [R—C=C—C=C—R, where R=—CH2OCONH(CH2)4CH3], 156 [R'-<^C—C=C— R", where R'=—CH2OCONH(CH2)5CH3 and R"=— CH2OCONH(CH2)4CH3] and 16PA [R'—C^C—C=C— R", where R'=—CH2OCOCH2C6H5 and R'=— CHjOCONH^H^CH;,] also have very high radiation reactivity and undergo a phase change, from an active to inactive, when heated near or above their melting points and can be used for making the film.
We have also unexpectedly found that the other related diacetylenes, such as 155,156 and 16PA which can cocrystallize with 166, can increase the radiation reactivity. Specifically, the 85:15 mixture of 166:156 is a preferred diacetylene mixture for the film. We have also discovered that diacetylenes such as 155,156 and 16PAeach have very high radiation reactivity and transform to an inactive phase upon heating near or above their melting points.
By this invention there is provided a self-developing film for developing an image from exposure to X-ray, gamma
ray, electron, or neutron radiation comprising at least one conjugated diacetylene, or cocrystallized mixture thereof, capable of undergoing a color change upon polymerization when contacted with ultraviolet light, X-rays, alpha particles, or electrons, thereby forming an image; a binder; a convertor, wherein said convertor is a material capable of emitting ultraviolet light, low energy X-rays, alpha particles, or electrons upon contact with higher energy X-ray, gamma ray, electron, or neutron radiation; wherein said image is 10 capable of being fixed by heating said diacetylene at or above its melting point, or at the temperature at which the diacetylene undergoes a phase change to a radiation inactive phase.
Further provided is the above film further comprising: (a) 15 at least one layer containing said at least one conjugated diacetylene, or cocrystallized mixture thereof, capable of undergoing a color change upon polymerization induced by ultraviolet light, X-rays, alpha particles, or electrons, thereby forming a colored image; (b) at least one layer 20 containing said binder and said convertor being in combination, being a complex or solid solution, wherein said convertor is a material capable of emitting ultraviolet light, low energy X-rays, alpha particles, or electrons upon contact with higher energy X-ray, gamma ray, electron, or 25 neutron radiation; (c) a substrate upon which said layers (a) and (b) are deposited thereon, wherein layer (a) and layer (b) are capable of being combined into one layer (ab), and said colored image is capable of being fixed by heating said diacetylene at or above its melting point, or at the tempera30 ture at which the diacetylene undergoes a phase change to a radiation inactive phase.
Furthermore, there is also provided: a self-developing film for developing an image from exposure to ultraviolet or laser radiation comprising at least one conjugated 35 diacetylene, or cocrystallized mixture thereof, capable of undergoing a color change upon polymerization when contacted with ultraviolet or laser radiation, thereby fanning an image, and a binder, farming a transparent film, wherein said image is capable of being fixed by heating said diacetylene 40 at or above its melting point, or at the temperature at which the diacetylene undergoes a phase change to a radiation inactive phase.
We have also discovered a process for synthesis of a 45 co-crystallized mixture of two or more diacetylenes in a single step, preferably in one pot. Specifically, the 85:15 mixture of 166:156 can be prepared by first reacting 7.5 mole percent of n-pentyl isocyanate with 2,4-hexadiyn-l,6diol and then adding 92.5 mole percent of 50 n-hexylisocyanate.
By this invention there is further provided a process for producing an asymmetrical diacetylene comprising: (a) contacting a diacetylene diol with a first organic reagent, which can react with one of the alcohol groups of the diol to form 55 a new organic functional group, wherein the molar ratio of the diacetylene diol: first organic reagent is greater than 1:1, in a solvent in the presence of a catalyst and a base at a temperature at 0° to 100° C; (b) contacting the reaction mixture from step (a) with a second organic reagent, in a 60 molar ratio of the starting diacetylene diol: second organic reagent is less than 1:1, which can form the same new functional group as in (a) or a different functional group; (c) recovering said asymmetrical diacetylene from step (b). We have also discovered that polymeric systems which 65 form complexes or solid solutions with organic and inorganic compounds are extremely useful as binder/convertor compositions for radiation sensitive compounds, such as