DE1201175B - Light-sensitive layer for producing colored images - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. σ .:

G03c

German class: 57 b-10

Number: 1201175

File number: H 40475 IX a / 57 b

Filing date: September 20, 1960

Opening day: September 16, 1965

The invention relates to light-sensitive layers for producing colored images, the layers from an organic compound which forms halogen radicals on exposure and which is dissolved in an oxygen and Hydrogen is dispersed in the molecule-containing binder.

It is known that such layers under the action of light, especially UV light, suffer a color change because the halogen radicals split off with the binder of the layer react. The resulting image can then continue to be used in a dry way, ζ. Β. by infrared radiation or heating, or fixed by the wet way by dissolving out the light-sensitive substance will.

The object of the invention is to increase the sensitivity of these photosensitive layers and to increase the number of color nuances that can be produced in the images. The subject of the invention starts with a photosensitive layer used to produce colored images from one upon exposure Organic compound which forms halogen radicals and which contains O and H in one of the molecules Binder is dispersed, and is characterized in that the layer also has an in Water or organic acid-base indicator soluble in water-miscible liquids, if appropriate a pigment, optionally a UV absorbing compound and optionally one Contains sensitizer.

A preferred acid-base indicator is Congo red.

A ketone, a stilbene derivative, benzil, salicylic acid phenyl ester is used as a UV-absorbing compound or benzoin is used.

Suitable sensitizers are azo compounds, ζ. B. Ν, Ν'-dimethylphenylazoaniline and 4-phenylazodiphenylamine.

When "acid-base indicators" are mixed with certain organic halogen compounds are dissolved or dispersed in organic binders containing O and H, for a few seconds exposed, they show the typical color change that can be seen from the indicator as a result of a pH change expected from basic to acidic. The color change can be achieved very quickly, that one adjusts the pH of the system before exposure just above the value at which the color change occurs.

In the reactions taking place between the organic halogen compound and the binding agent containing O and H during exposure to light, a light-sensitive layer is used for production
colored pictures

Applicant:

Horizons Incorporated, Cleveland, Ohio

(V. StA.)

Representative:

Dipl.-Ing. E. Prince and Dr. rer. nat. G. Hauser,

Patent attorneys,

Munich-Pasing, Ernsbergerstr. 19th

Named as inventor:

Eugene Wainer, Shaker Heights, Ohio (V. St. A.)

Claimed priority:

V. St. v. America September 22, 1959

there are probably acid and water, which explains the effect on the pH value.

Only layers sensitive to light of the relatively distant ultraviolet can pass through after exposure Coating with a layer of an oxygen-free binder, e.g. B. with polystyrene lacquer, are fixed. Instead of indicators with a color, the hue of which before exposure is relatively light and whose brightness is high and which become dark or low upon exposure, indicators can be used which before exposure in basic medium a color of dark hue and less Have lightness and, when exposed, take on a color with a lighter hue and greater lightness or even become completely colorless. In general, longer exposure times are required for fading required than for a color change to produce a bright color.

The layers according to the invention are not only sensitive to light in the completely dry state, but also even if they are distributed in oxygen-containing solvents such as acetone, alcohol, glycols or the like. Furthermore, the layers can contain plasticizers that are compatible with water. Such plasticizers are glycols, glycerine, glycol ethers or polybasic alcohols.

The layers according to the invention are mainly sensitive to UV light. Your sensitivity

509 687/421

starts at 4000 A and is particularly high for radiation in a range from 2500 to 3500 Å. Through this is the formation of fog despite continued exposure to diffuse daylight or ordinary light Room light is low, which ensures the stability of the exposed layer under these conditions. By adding UV-absorbing compounds, the sensitivity can be reduced in the ultraviolet Increase area further. Such UV absorbing compounds are used in amounts up to to Vio percent by weight, based on the weight of the organic compound forming halogen radicals, added.

The layers according to the invention are transparent before and after exposure; H. they contain transparent dyes and are particularly suitable for copying line art master copies. Halftone images can be achieved by making the layer relatively thick and UV absorbing Connection admits. Another means of obtaining halftone images is to use the Layer add a finely divided inert white pigment in such amounts that the volume of the Pigment does not exceed 35% of the volume of the finished dried layer. Suitable inert white pigments are titanium dioxide, barium sulfate, silica or zirconium oxide.

The most important components of the layers according to the invention are explained in more detail below.

The binder containing O and H is preferable a plastic. Examples of binders and suitable solvents are given in the table. Binder solutions with 5 to 15 percent by weight of binder produced therefrom have a proportionate effect low viscosity and good solubility for the other layer components.

binder

plastic solvent 1. Cellulose acetate 70 acetone + 30 trichloro ethylene 2. Cellulose triacetate ... 70 acetone + 30 3. Cellulose nitrate 50 acetone + 50 ethyl acetate 4. ethyl cellulose 40 toluene + 30 acetone + 30CH ₃ OH 5. Polyethylene glycol .. Methyl alcohol 6. Polyacrylic acid esters 70 acetone + 30 CH ₃ OH 7. Polymethacrylic acid methyl ester 40 ethyl acetate + 30 ace ton + 30 toluene 8. polyvinyl acetate 40 acetone + 40 CH ₃ OH + 20 toluene 9. Polyvinyl alcohol * .. water

* With polyvinyl alcohol, emulsions are obtained which, after drying, give a clear layer.

It is important that the binders used contain hydrogen and oxygen. For example no color changes are achieved when using polystyrene as a binder.

The layers according to the invention can be applied to supports, e.g. B. made of glass, paper, plastic or textiles, to be spread; The shift can also take part in the chemical reaction in question take part. For example, paper and textiles that contain hydroxyl groups can perform the function the oxygen- and hydrogen-containing binders.

Preferred organic compounds which form halogen radicals on exposure are carbon tetrabromide, Iodoform, bromoform, chloroform and carbon tetrachloride. Among these are the two

ίο listed first most suitable as it is at room temperature are solid and practically any amount can be dissolved in a binder. When a If a color reaction is desired in solution, the liquid halogen compounds are suitable.

It was also found that halogen compounds can be produced, some of which are still are more effective than those listed above when using carbon tetrabromide or carbon tetrachloride heated in the dark with a binder containing hydrogen and oxygen. The nature of the products thus obtained is unknown, but it turned out that the use of the products as Binder either alone or mixed with the binders listed in the table. PH changes

he delivers that are larger than the simple ones Halogen compounds obtained. Also, these products seem to be more responsive, so greater sensitivities can be achieved.

Another group of organic compounds that form halogen radicals on exposure, however are generally effective in much narrower pH ranges than those listed above are tetrabromobutane, Hexachloroethane, tetrachlorotetrahydronaphthalene, dichlorobenzene, dibromobenzene and hexachlorobenzene. They can only be used in conjunction with an acid-base indicator, the one changes color completely with a change in pH of 1 or less.

The color reactions obtained are independent of the type of organic compound that occurs on exposure Halogen radicals, d. H. probably a halide free radical and a free radical Fragment delivers the same with the same indicator. It follows from this that there is always water and acid is formed. For example, give carbon tetrabromide, carbon tetrachloride and iodoform, respectively the same color change in Congo red.

The third essential component of the layers according to the invention is the acid-base indicator.

Any of the known acid-base indicators can be practically used and shaped in which effective contrast changes occur when the pH changes.

Of course, there is a color change for all indicators not always equally concise, but it essentially corresponds to that in aqueous solutions usually to be expected for titration with acids or bases.

In the following examples, two types of light sources were used. The first was one 275 watt tungsten filament lamp and the second was a SOO watt high pressure mercury vapor lamp. When using the first lamp, there was generally a complete color change with an in between Exposure for 5 and 20 seconds obtained from a distance of 25 cm. When using the The second lamp has a complete color change due to the much greater intensity of the UV light

a purple cast lasting between 1 and 3 seconds, the exposed parts of the image were pale obtain. yellow.

Example I Example V

A coating liquid of 10 ml of a 10% solution of polyvinyl acetate in a mixture of 40 parts of acetone, 40 parts of methyl alcohol and 20 parts of toluene, 2 ml of a 2% dispersion of Congo red in acetone and 5 ml of a 25% solution of CBr ₄ in acetone was painted in one case on a glass plate and in a second case on a 0.05 mm thick sheet of clear, heat-stabilized polyvinyl chloride. The layers were then allowed to air dry until the solvent was completely removed, after which a portion of each layer was covered and exposed for 3 seconds to a 50 watt high pressure mercury lamp from a distance of 25 cm. The exposed parts of the image were colored deep blue-gray, while the unexposed parts of the image were light red. The image on the glass plate was then kept in a dark room for 30 days and then checked. A slight but noticeable haze had developed in the unexposed parts of the image, which were still remarkably sensitive to UV light. The image on the polyvinyl chloride was at 100 ° C for 30 seconds. heated and then exposed again to UV light. The unexposed parts of the image had lost their sensitivity to light, and the exposed parts of the image showed a slight deepening of color. The image on the polyvinyl chloride was also stored in a dark room for 30 days. After this time there was no evidence of fogging.

35 Example II

A coating liquid composed of 10 ml of a 10 ml solution of methyl polymethacrylate in a mixture of 30 parts of acetone, 40 parts of ethyl acetate and 30 parts of toluene, 1 ml of a 2% solution of ethyl violet (CI. No. 42600) in CH ₃ OH and 10 ml a 25% solution of CBr ₄ in acetone was painted on a glass plate and left to dry until all the solvent had been removed. It was then exposed to the mercury vapor lamp for 15 seconds, whereupon the originally violet color had turned into a light green.

Example III

The coating liquid of Example II was made by adding 5 ml of a 10% solution of Citric acid modified in acetone. The modified coating liquid was applied to a glass plate painted and, after drying, exposed as in Example II, but only for 6 seconds. Also in In this case there was a color change from purple to green.

Example IV

The coating liquid from Example II was modified by adding 10 ml of a 10% solution of oxalic acid in acetone. The modified coating liquid was painted on a glass plate and, after drying, exposed to the mercury vapor lamp for 10 seconds. The unexposed parts of the image were blue with a slight A coating liquid of 10 ml of a 10% solution of cellulose acetate in a mixture of 70 parts of acetone and 30 parts of trichlorethylene, 4 ml of a 3% solution of Orange IV (CI. No. 13080) in CH ₃ OH and 5 ml of a 25% strength solution of CBr ₄ in acetone was painted on a glass plate and allowed to dry. After exposure to the mercury vapor lamp for 3 seconds, a color change from pale yellow to deep gray-brown was produced.

Example VI

A coating liquid of 10 ml of a 10% solution of polyvinyl acetate in a mixture of acetone, toluene and methyl alcohol, 2 ml of a 2% dispersion of Congo red in acetone and 5 ml of a 15% solution of CHI ₃ in acetone was After it had been painted on a glass plate and completely dried, it was exposed for 3 seconds. There was essentially the same color change as in Example I, namely from light red to deep blue-gray.

Example VII

A coating liquid of 10 ml of a 10% solution of polystyrene in toluene, 2 ml of a 2% dispersion of Congo Red in acetone and 5 ml of a 25% solution of CBr ₄ in acetone was painted on a glass plate, allowed to dry and 3 minutes exposed from a distance of 25 cm with the mercury vapor lamp. The original color of the layer was pale pink. Even after this relatively long exposure time, no visible change in color was obtained.

Example VIII

A coating liquid composed of 10 ml of a 10% solution of polyvinyl acetate, 0.05 g of diphenylthiocarbazone and 10 ml of a 25% solution of CBr ₄ in acetone was exposed to a mercury lamp for 10 seconds after being painted on a glass plate and completely dried. The exposed parts of the image were deep red black and the unexposed parts of the image were pale yellow green.

Example IX

A coating liquid composed of 15 ml of a 10% solution of polyvinyl acetate, 3 ml of a 2% dispersion of Congo Red in acetone, 5 ml of a 10% solution of ethylene glycol in acetone, 5 ml of a 25% solution of CBr ₄ in acetone, 0.01 g of benzil and 0.005 g of N, N'-dimethylphenylazoaniline was painted on a glass plate and allowed to dry in a darkroom for 2 hours. It was then exposed to the tungsten filament lamp for 5 seconds from a distance of 25 cm, a color change similar to that of Example I being obtained, except that the developed color was deeper and more purple and the unexposed parts of the image were very pale orange.

Example X

The coating liquid of Example IX was made suitable for pigment use by adding 0.5 g

Modified TiO _2. The modified coating liquid was painted on a glass plate and allowed to dry in a dark room for 5 hours. It was then exposed to the mercury vapor lamp for 15 seconds from a distance of 25 cm through a stepped gray wedge which showed twenty-five different shades of gray. The exposed image showed fifteen different levels. The most exposed steps were very deep blue-gray, while the less exposed steps were more blue than gray.

Example XI

A coating liquid of 1 ml of a lO ° / o solution of polystyrene, 4 ml of a 2% dispersion of Congo red in acetone, 10 ml of a 25 ^fl / o solution of CBr ₄ in acetone, 10 ml of a 10% Äthylenglycollösung in acetone and 10 ml of acetone was applied to cellulose paper by immersing the latter in the coating liquid, soaking it, and then completely drying it over 2 hours. Microscopic examination revealed that the cellulose fibers were pigmented or colored in a pale pink color. The dry paper was exposed to the mercury vapor lamp, which formed the deep blue-gray characteristic of Congo red.

Example XII

A coating liquid composed as in Example I. was painted on a glass plate and left to dry in the darkroom for 2 hours. This layer was then sprayed with a 5% solution of polystyrene in toluene and left to dry. The thickness of the dry polystyrene layer was 12.7 μm. Then became pictorial exposed to UV light, giving the typical color change. The exposed layer was Stored in the darkroom for 30 days after which no evidence of haze was found. A renewed exposure of the unexposed parts of the image with UV light showed that there was still a very weak one Color change occurred, which, however, was nowhere near the extent of the original and which Image usefulness not eliminated.

Example XIII

A brominated polystyrene was produced by polymerizing styrene in the presence of 25 parts of CBr ₄ using toluene as a solvent. The polymerization product was precipitated in solid form by adding acetone. Then, a coating liquid composed of 10 ml of a 10% polyvinyl acetate solution, 1 g of the above brominated polystyrene and 2 ml of a 2% dispersion of Congo red in acetone was painted on a glass plate and allowed to dry. Exposure to a mercury vapor lamp for 2 seconds from a distance of 25 cm gave a blue-gray image from the originally pink-colored layer.

Claims (6)

Patent claims: 1. Photosensitive layer for the production of colored images from an organic compound which forms halogen radicals on exposure which is dispersed in a binder containing O and H in the molecule, and optionally a plasticizer, characterized that it is an organic soluble in water or in water-miscible liquids Acid-base indicator, optionally a pigment, optionally a UV-absorbing one Contains compound and optionally a sensitizer. 2. Photosensitive layer according to claim 1, characterized in that it is used as an acid-base indicator Contains Congo Red. 3. Photosensitive layer according to claim 1, characterized in that it is up to 35 percent by weight of a powdered white pigment. 4. Photosensitive layer according to claim 1, characterized in that it is UV-absorbing Compound contains a ketone, a stilbene derivative, benzil, salicylic acid phenyl ester or benzoin. 5. Photosensitive layer according to claim 1, characterized in that it is used as a sensitizer contains an azo compound. 6. Photosensitive layer according to claim 1, characterized in that it is organic Compound which forms halogen radicals on exposure, a methane derivative with at least 3 halogen atoms in the molecule, preferably carbon tetrabromide. Considered publications:
German patent specification No. 737 289. 509 687/421 9.65 © Bundesdruckerei Berlin