US 3773508 A
Permanent photochromic images are obtained by selectively exposing a photochromic compound and an organic peroxide in a resin binder to ultraviolet radiation and thereafter heating the element whereby a reaction occurs in the exposed areas to provide the permenent images.
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United States Patent [191 Osada et al.
[ IMAGEWISE EXPOSING AND HEATING A PHOTOSENSITIVE COMPOSITION CONTAINING A SPIROPYRAN COMPOUND AND AN ORGANIC PEROXIDE  Inventors: Chiaki Osada; Hisatake Ono, both of Saitama, Japan  Assignee: Fuji Photo Film Co., Ltd.,
Kanagawa, Japan  Filed: Nov. 16, 1971  Appl. No.: 199,382
 Foreign Application Priority Data Nov. 19, 1970 Japan 45/102198  US. Cl. 915/48 R, 96/48 HD, 96/90 PC  Int. Cl G03c 5/24, G030 1/52  Field of Search ..96/48 R, 96 PC; 252/300 Nov. 20, 1973 Primary Examiner-Norman G. Torchin Assistant Examiner-Won l-l. Louie, Jr. Attorney-Richard C. Sughrue et a].
[5 7] ABSTRACT Permanent photochromic images are obtained by selectively exposing a photochromic compound and an organic peroxide in a resin binder to ultraviolet radiation and thereafter heating the element whereby a reaction occurs in the exposed areas to provide the permenent images.
15 Claims, No Drawings IMAGEWISE EXPOSING AND HEATING A PHOTOSENSITIVE COMPOSITION CONTAINING A SPIROPYRAN COMPOUND AND AN ORGANIC PEROXIDE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new process for forming images, In more detail, the present invention relates to a process for forming images which comprises reacting an organic compound which was altered by ultraviolet radiation absorption with another organic compound.
2. Description of the Prior Art Substances whose color varies upon absorption of ultraviolet rays are generally called photochromic compound. These compounds are usually in a stable colorless state when exciting rays such as ultraviolet rays are not applied thereto. However, when ultraviolet rays are applied thereto, they change into an unstable colored state which has a different absorption spectrum. It is believed that such a change is brought about by the state of the electrons in the molecule of the photochromic compound changing to an unstable high energy state from a stabel low energy state by absorption of the ultraviolet rays. By such a change the molecule is isomerized and the colorless molecule changes into the colored state. However, the colored molecule excited to a high energy state easily returns to the stable low energy state if the exciting rays are removed because the colored molecule is in an unstable state. Many patents are known relating to light-coloring materials in which reversibility a photochromic compound is utilized, and although light-coloring materials containing a photochromic compound can be used for temporary recording of images, these images can not be preserved as permanent images. Several prior art patents, e.g., Belgium Pat. No. 659,192 (Co. U.S. Pat. No. 3,364,023), U.S. Pat. No. 3,341,330, and U.S. Pat. No. 3,441 ,41 1, relate to the stabilization of photochromic images.
SUMMARY OF THE INVENTION The present inventors have discovered a new process for forming permanent images.
The general image forming process of the present invention is as follows. A photochromic compound and an organic peroxide are subject to dissolution in a solution containing a high molecular weight compound. The solution is then applied to paper and dried. A photographic transparent negative film is put onto the resulting element. By applying ultraviolet rays thereto, a positive photochromic image is produced by coloring only the portion of the element through which the ray pass. By leaving the positive image element in the dark or by heating the resulting positive image element, the colored part selectively reacts with the organic peroxide to change into another color. The resulting image does not fade any longer and remains as apermanent image. In the prior light-coloring materials which do not contain an organic peroxide, the formed images automatically fade and return to their initial colorless state. Thus, it becomes possible in accordance with the present invention to obtain permanent images using a photochromic compound. The image recording process of the present invention has the advantage of being a dry treatment because development is not required and the image can be fixed by heating.
The photochromic compound used in the present invention can be represented by the general formula;
Ra Rs 4/ xiqd 2 I N i Q 7 8 7 Rt R z lower alkyl group (carbon atoms: 1-5), substituted alkyl group (carbon atoms: l-5, substituent: carboxyl group, cyano group and ester group) or phenyl group; R and R lower alkyl group (carbon atoms: l-5), phenyl group, or R,+R CH (n 4 or 5); X: hydrogen atom, nitro group, halogen atom, carboxyl group, alkoxycarbonyl group, lower alkyl group or alkoxy group, which prefered carbon atom range for the last three groups being l-5 carbon atoms, though higher carbon atom chains can be used. Y where m is l or 2 and Y is one or more nitro groups, halogen atoms, aldehyde groups or alkoxy groups, with preferred alkoxy groups having l-2 carbon atoms, though higher carbon atom chains can be used. Preferred Examples of Y are as follows:
Such compounds can be formed in accordance with the teaching of U.S. Pat. No. 3,022,318 or No. 2,953,454.
The photochromic compounds can be used solely or as a mixture of two or more thereof.
As the organic peroxide used, there are, for example, diacylperoxides, dialkylperoxides, hydroperoxide, ketoneperoxides and peroxyesters. Organic peroxides which are decomposed at l30C are preferred.
As the resin used as the medium of the layer containing the photochromic compound and the organic peroxide, there can be used any synthetic high molecular weight compound which is soluble in common organic solvents, for example, polyvinyl acetate, polystyrene, polyvinylchloride, polyethylmethacrylate, polymethylmethacrylate, polymethylacrylate, and copolymers of the monomers of the above-mentioned polymers, cellulose butyrate acetate, polyvinylbutyral, cellulose acetate and polyvinylacetal. The high molecular weight compound utilized should illustrate the following characteristics, i.e., the material should have a molecluar weight sufficient to maintain the photochromic compound in suspension, i.e., the resin binder is a solid, it should not be decomposed at heating temperature and it should be substantially transparent. Usually a molecular weight of from about 10,000 to about 70,000 is preferred, with a most preferred molecular weight range being 40,000 to'60,000. Of course, both higher and lower molecular weight materials can be used so long as the resin serves to bind the photochromic material, Preferred organic solvents include acetone, benzene, toluene xylene, cyclohexanone, carbone tetand rachloride, buthyl acetate, ethyl acetate ester, methylethylketone, gamma-butyl lactone, cellosolve, methyl cellosolve, cellosolve acetate, methyl cellosolve acetate etc.
A preferred amount of the photochromic compound is 0.1-l percent (by weight) based on the weight of the resin. Most preferably 2-5 percent. A preferred amount of the organic peroxide is 5-30 percent and especially about percent (by weight) based on the weight of the photochromic compound.
A light-sensitive element is accordance with the present invention can be produced by applying a solution containing the above-mentioned photochromic compound, organic peroxide and resin dissolved in an organic solvent onto a support such as, paperand high molecular weight polymer films, and drying the same. The temperature of drying is not critical and is usually a room temperature to 80C. I
A dianegative is put onto the resulting element. After applying ultraviolet rays thereto, the element is heated to approximately 70-90C for about 5 to about 10 seconds, by which an image is easily obtained in which only the light-exposed part changes into a reddishorange color which is a permanent image.
The following examples are given to describe the invention with respect to several preferred but nonlimiting embodiments.
EXAMPLE 1 A solution composed of 1 part (hereinafter, all parts are by weight) of l,3,3-trimethyl-6'-nitro (indoline-2, 2'-2'H-chromene), 0.05 parts of benzoyl peroxide and 50 parts of a 20 percent benzene solution of polystyrene (m.w. 40,000) was applied to paper having a 80 p. thickness. The resulting element was colorless in the normal state. A dianegative was put on the element and ultraviolet rays were appled. Exposure to ultraviolet rays was carried out using an ultraviolet ray lamp (Toshiba SHL-IOO) as the light source for 30 seconds at a distance of approximately cm. In the following, examples, exposure was also carried out under the same conditions. Only the part of the element which the ultraviolet rays contacted colored blue. The element was then heated to 90C for approximately 30 seconds by which the blue coloring changed to a reddish-orange color. The resulting image did not fade in the dark and remained as a permanent image.
EXAMPLE 2 A solution composed of 1 part of 1,3,3-trimethyl-5- methoxy-6'-nitro spiro(indoline-2,2'-2H-chromene), 0.5 parts of lauroyl peroxide and 50 parts of a percent ethyl acetate solution of polyvinyl acetate (m.w. 30,000) was applied to baryta paper and dried to provide a 5 11. thick layer. After ultraviolet rays were applied to the resulting element by the same procedure as in Example 1, the element was heated, by which a reddish orange permanent image was obtained.
EXAMPLE 3 A solution composed of I part of l-gammaethoxycaronyl-ethyl-3,3-dimethyl-5-chloro-6'-nitro spiro (indoline-2,2'-2H-chromene), 0.1 parts of acetyl peroxide and 100 parts ofa 20 percent ethyl acetate solution of polyethylmethacrylate (m.w. 30,000) was applied to a polyethylene terephthalate film having a 80 1. thickness. A reddish-orange image was obtained by treating the resulting element by the same procedure as in Example I. The resulting image did not fade any longer by heating or by storage after image formation.
EXAMPLE 4 A solution composed of 1 part of 1,3,3-trimethyl-5- ethoxycarbonyl-6-nitro-8-methoxy spiro(indoline- 2,2'-2'H-chromene), 0.2 parts of benzoyl peroxide and 50 parts of a 20 percent ethyl acetate solution of polyvinyl acetate was applied to a paper support. A reddish orange permanent image was obtained by treating the resulting element by the same procedure as in Example 1.
What is claimed is:
l. A process for forming a permanent image which comprises selectively exposing to ultraviolet radiation a composition comprising a photochromic compound, an organic peroxide and a high molecular weight resin as a binder, and thereafter heating said exposed composition, in order to promote the reaction between said peroxide and said photochromic compound, whereby the exposed portion colors reddish-orange, said photochromic compound having the formula:
wherein R, is a lower alkyl group, a substituted alkyl group or a phenyl group; R and R are lower alkyl groups, a phenyl group or R and R, combine to form (Cl-l Where n is 4 or 5; X is a hydrogen atom, nitro group, halogen atom, carboxyl group, alkoxy-carbonyl group, lower alkyl group or alkoxy group; and Ym is one or more member of nitro, halogen, aldehyde or alkoxy, where n is l or 2, said composition comprises 0.1 to l0 percent by weight of said photochromic compound based on said resin and from 5 to 30 percent by weight of said organic peroxide based on said photochromic compound.
2. The process of claim 1 wherein said organic peroxide is selected from the group consisting of diacyl peroxides, dialkyl peroxides, hydroperoxide, ketone peroxides and peroxyesters.
3. The process of claim 1 wherein said high molecular weight resin binder is a synthetic high molecular weight compounds suluble in organic solvents is selected from the group consisting of polyvinyl acetate, polystyrene, polyvinyl chloride, polymethylmethacrylate, polyethylmethacrylate, polymethylacrylate, copolymers of the monomers of the above compounds, cellulose acetate, cellulose butyrate acetate, polyvinyl butyral and polyvinyl acetal.
4. The process of claim 1 wherein the organic peroxide is benzoyl peroxide.
5.-The process of claim 1 wherein the amount of photochromic compound is 2 to 5 percent and the amount of organic peroxide is about 10 percent.
6. The process of claim 1 wherein said heating is to about to about C.
7. The process of claim 6 wherein said heating is for from about 5 to about seconds.
8. The process of claim 1 wherein the peroxide decomposes at 70 to 130C.
13. The process of claim 1 wherein all lower alkyl groups have 1 5 carbon atoms, the substituted alkyl group has 1 5 carbon atoms, and for X the alkoxy carbonyl, or alkoxy group has 1 5 carbon atoms, and for 9. The process of claim 1 wherein the binder has a 5 Y the alkoxy group has 1 2 carbon atoms.
molecular weight of about 10,000 to about 70,000.
10. The process of claim 1 wherein m is 2, and both Y groups are bromine.
11. The process of claim 1 wherein m is 2, and one Y group is NO; and the other is OCH 12. The process of claim 1 wherein m is l and Y is N0 14. The process of claim 1 wherein said substituted alkyl group is carboxyl, cyano or ester group substituted.
15. The process of claim 1, wherein said alkoxycarbonyl group and said alkoxy group have a carbon range of from 1 to 5 carbon atoms.
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