US2067690A - Method and material for obtaining photographic contrasts - Google Patents

Description

Patented Jan. 12, 1937 ED STATES PATENT OFFICE METHOD AND MATERIAL FOR OBTAINING PHOTOGRAPHIC CONTRASTS No Drawing. Application January 11, 1935, Serial No. 1,436. in Germany February 5, 1934 15 Claims.

This invention relates to a method and mate-' rial -for obtaining photographic contrasts with the aid of light.

It is known to obtain photographic contrasts by exposing a carrier which has been sensitized by a diazonium compound, and using metal salts to obtain permanent colored pictures in various tones. For instance, it has been proposed to produce photographic contrasts by means of a sensitized layer containing a mixture of a diazonium compound and a silver salt, which layer upon exposure gives a silver picture. The layer is then treated with an alkaline liquid and subsequently with a fixing agent.

The object of the present invention is to produce with diazonium compounds pictures of better contrast effects than the above mentioned.

According to our invention pictures are produced photochemically by using a diazonium compound and a mercurous salt. Preferably the mercurous salt is embedded in the layer provided with the diazonium compound, although good results can be obtained by using the mercurous salt only after the exposure of the layer contain- 25 ing the diazonium compound. While we believe that. the picture formation is due to the formation of metallic mercury resulting from the reduction of the mercurous salt by the light decomposition product of the diazonium compound,

0 we do not wish to commit ourselves to this explanation.

The fixation of the pictures obtained according to the invention can be efiected in a simple manner by rinsing with water. In contradis- 35 tinction to the prior methods-in which silver nitrate has been used, and in which rinsing could 45 In order to increase the sharpness and contrast effect of the picture, it is advantageous to place, subsequent to the exposure, the layer prepared according to the invention, in an environ-'-- ment which is shut off from the light and which has a high content of water vapor, and to rinse it only after it has remained in such environment for a time, in general for some hours.

The speed of picture formation of such a layer is dependent upon the moisture conditions of 5 the layer, including the amount of moisture prescut at the time of the exposure. The greater the moisture present at the time of exposure the greater is the visibility of the picture directly after the exposure. If a layer contains very little moisture at the time of the exposure, and after exposure is kept in a very dry environment, which is shut oil? from light, substantially no picture formation will take place. However, if the layer, at the time of'the exposure, has the degree of moisture generally obtained by drying in the air, some visible picture formation often occurs immediately after the exposure. degreepfdryness during the exposure other than air-dry isnot preferred. The speed of the picture formation after the exposure can be greatly increased both by a high degree of humidity and by heating, which may be effected by treatment in a. hot water bath or with hot water vapor or steam.

As a rule the resulting color of the picture depends upon the time of exposure and also upon the quantity of the mercurous salt used.

' We have found that the useful properties of the sensitized materials according to the invention are offset to some extent by the disadvantage that with-many carrier materials, for instance paper and linen, the picture produced in accordance with the invention fades out after some time. This is probably due to the subsequent formation by oxidation, first of mercurous compounds and finally of mercuric compounds.

We have found, however, that this fading out may be efiectively prevented by using, in combination with the mercurous salt, the salt of a second metal, which lies higher in the potential series of metals than does mercury, as for instance, silver, gold or platinum.

The combined application of the two metal salts can be carried out in various manner, for instance by treating the picture produced with diaz'onium compound and mercurous salt in accordance with the invention, with a silver nitrate solution, and by subsequently bathing it in a solution of sodium sulphite to remove the excess silver nitrate, as well as any mercury nitrate which may be formed. I

It is also possible to subject the picture pmduced according to the invention, to a short treatment with a silver nitrate solution, and subsequently to a short duration rinsing with distilled water, and to develop the picture with a solution of metol citric acid or of metol tartaric acid. This may be efiected immediately after the exposure. for instance, at a time when the picture is still completely invisible.

A particular Even for pictures, the layer of which consists only of diazonium compound and of a mercurous salt-thus without the use of a second metal salt-a washing with a weak acid solution, for

However, even when using the weak acid'treatment, the pictures tend to ultimately fade out, which is not the case when, in addition to a mer- 1 curous salt, a second metal salt is used, as state above.

Irrespective of whether only a mercurous salt is used, or both a mercurous salt and a second metal 'salt, the initial sharpness and the contrast eifect of the picture are much greater than when using only a silver salt. Thus the initial sharpness and contrast effect of the picture are due to the presence of the mercurous salt, whereas the stabilization of the picture is obtained by the addition of the second metal salt. A further advantage of the images obtained in accordance with the invention is their blackbrown color, which gives a much more pleasing appearance than the yellowish-brown tone pic- If pictures are to be treated in an aurichloride' tures obtained by means of diazonium compounds and silver salts only.

As stated, instead of using silver salts in combination with mercurous salts, salts of other metals which are higher in the electric potential series of metals than is mercury, can be used for the stabilization of the image; for instance, the salts of gold can be used with good results, a suitable gold salt being, for instance, aurichloride.

solution it is, however, necessary to very carefully wash out the picture after its exposure and tains besides the diazonium compound, a mercurous salt and a silver salt. With such sensitized layers beautiful and very stable pictures can be obtained, the stability of this sensitized layer being materially increased for the purpose of conserving it prior to its use.

Images having very high stability can also be obtained without using silver nitrate, by introducing the diazonium compound and the mercurous salt into regenerated cellulose serving as carrier. Excellent results can be so obtained by using a carrier consisting of superficially saponified acetyl cellulose. The picture obtained with superficially saponified acetyl cellulose is particularly well adapted for use as a template or tracing from which prints can be made on socalled printing paper. It has been found that in this manner positive images exhibiting photographic half-tones can be excellently reproduced on the printing paper.

.When the sensitized system according to the invention is provided on a transparent carrier, ior instance on the above-mentioned regenerated cellulose, it is eminently adapted for use with socalled reflex photography. By using transparent sensitized material obtained in the above manner, very beautiful and sharp pictures are obtained. In this case the sensitized material is placed with its sensitized side on the original to be reproduced and is exposed through the transparent sensitized material so that the light reflected by the original causes picture formation.

The invention will be more clearly understood by reference to the following examples:

Example I Paper is soaked in a 2% solution of mercurous nitrate in water and is then dried in the air.

Subsequently it is soaked in a 1% solution of benzene-diazonium-boron-fiuoride in alcohol, whereupon the so-treated paper is again dried in the air and exposed under a tracing for minutes to the light of a 5 kw. incandescent lamp placed at a distance of 25 centimeters therefrom. The exposed paper, on which no picture is visible, is washed in water for one hour and a grey negative picture is obtained. I

It is also possible to use diazonium compounds containing a substitutent, for instance: l-diazoniumbenzenel-sulphonic acid.

Especially suitable are diazonium compounds containing a substitutent which consists of a 'hydroxyl group, for instance, in para-position, of which we may mention the following:

1-hydroxybenzene-4-diazonium-boronfluoride, l-hydroxybenzene-4-diazoniuin-fiuosulphonate, 1-hydroxybenzene-i-diazonium-2-sulphonic acid, l-hydroxybenzene 4 diazonium 2 carboxylic acid, l-hydroxy-2-nitrobenzene-4 diazonium 6 sulphonic acid.

Example II Paper is soaked in a solution of l-hydroxy-benzene-i-potassium diazosulphonate and mercurous nitrate in the ratio of 1 mol. potassium diazosulphonate to 2 mol. mecurous nitrate and then dried in the air. The sensitized material thus obtained is exposed under a tracing for 1 minute to the sunlight. After exposure a negative brown picture appears which, after being washed-in water for about 20 hours, exhibits a grey-black tone and a sharp contrast.

It is also possible to use benzendiazonium compounds in which the substituent consisting of the hydroxyl group is present in the meta-position and of which the following examples are given:

l-hydroxybenzene 3 potassium diazosulphonate,

l hydroxybenzene-5 -diazonium 2 carboxylic acid,

l-hydroxybenzene-5-diazonium-4-sulphonic acidfi-carboxylic acid.

Still better results are achieved when the hydroxyl-group is present in the ortho-position, with respect to the diazonium groups, for instance:

1-hydroxybenzene-2-potassium diazo sulphonate, l-hydroxybenzene 2.- diazonium fiuosulphonate.

Example III the air. When exposing the sci-sensitized paper under a tracing for 2 minutes to the light of a kw. incandescent lamp, and at a distance of 25 centimeters therefrom, a picture is not yet visible. Only after washing in water does a brown-grey negative picture appear.

Example IV Paper, provided with a gelatine layer. is soaked in a 1% solution of l-hydroxy-Z-diazoniumbenzene-l-sulphonic acid and a 2.5% aqueous solution of mercurous nitrate and is then dried in the air. The sensitized paper is then exposed under a film negative for 1 minute to the sunlight. The partly visible positive picture is developed in a 1% aqueous silver nitrate solution. The excess diazonium compound, mercurous salts and silver salts are removed, for instance, by washing with water for one hour.

The print so obtained exhibits a brown-black tone and excellent sharp contrast effects.

Example V positive picture exhibits a brown-grey tone. By

subsequently drying in the air, the color of the picture becomes darker and acquires a blackbrown tone.

Upon rinsing with water at room temperature, the pictures appear in about half an hour. By washing with hot water, for instance water at a temperature of. 50-60 C., the image is developed in 2 to 5 minutes. For fixing it is desirable to again wash with water for a considerable time. By a treatment with 0.01 N. nitric acid or 0.1 N. acetic acid, the fixation can be effected in about one hour.

Example VI water. The picture thus produced is then converted into a silver picture in a 1% solution of silver nitrate.

The positive picture, which exhibits a deep brown tone, is fixed in a sulphite solution and can then be advantageously used as a diapositive for the printing process. If the mercury picture would not be transferred into'a silver picture in the silver nitrate solution, the disadvantage is encountered that it will disappear in the course of about one year.

Example VII Regenerated cellulose is soaked in a 50% alcoform a 3/4% concentration and mercurous nitrate to form a 1.2% concentration, and then dried in the air. The sensitized material thus obtained is exposed under a glass negative for 2 minutes to the light of and at a distance of 40 centimeters from a quartz mercury lamp; it is then exposed for half an hour to an atmosphere having a high content of water vapor and subsequently washed in water, as a result of which a positive picture is developed and rendered visible. Thereupon the picture is stabilized by a treatment with silver nitrate and subsequent rinsing with water.

Example VIII The acetyl cellulose, commercially known under the registered trade-mark Sidacisol, is treated, for instance, in. a shaking machine for two minutes with a 2 N. alcoholic potash lye solution, due to which the acetyl cellulose is superficially saponifled. After thoroughly washing with water, it is dried between filtering paper and subsequently soaked in a 2% mercurous nitrate solution. By means of a rubber squeegeeths layer is squeegeed on a glass and again dried between filtering paper. The material thus obtained is soaked in a 0.75% solution of l-hydroxy-2-diazonlum-G-methylbenzene-4-sulphonic acid containing 1.2% mercurous nitrate and 0.75% of silver nitrate. Thereupon, the sensitized material is conserved in the air for a considerable time, say for five days, in order to obtain a material having the desired properties.

When exposing the sensitized material thus obtained under a photographic glass'negative for 2 to 3 minutes to the light of and at a distance of 25 centimeters from a carbon arc lamp, a slightly visible positive picture exhibiting a brown tone appears, which is then developed for minutes in a 1% silver nitrate solution having a temperature of 40 to 50 C. Thereupon it is washed for about two hours with distilled water, followed by washing for about two hours with tap water and by a short treatment, for instance for about 1 minute, with a 1% sodium sulphite solution and is again washed with water. After exposure it is also possible to develop with a solution containing 2% of metol-and 4% of citric acid; it being desirable, however, to reduce the time of exposure to about 1 minute, followed by washing for one minute with the above-mentioned developer and by rinsing for half an hour with distilled water. Finally it is washed for several hours with tap water and if necessary, after the said treatment with sodium sulphite. It is advisable to finally treat with an approximately 20% solution of glycerin in water in order that the sisting of a hydroxyl group, occupies the orthoposition relatively to the diazonium group, for instance:

l-hydroxy-2-diazonium'benzene-4-su1phonic acid 7 B-carboxylic acid,

1 hydroxy 2 diazonium acid,

1 hydroxy 2 -diazonium benzene-4-chlorine-6- sulphonic acid,

l-hydroxy-G-acetylamino-Z-diazonium benzene- -sulphonic acid.

It is also possible to use diazonium compounds in which two hydroxyl groups are present in. the benzene nucleus, for instance 1-hydroxy-2-diazobenzene-5-carboxylic nium-6-hydroxybenzene-4-sulphonic acid.

Instead of hydroxyl. it is also possible to substitute amino groups in the benzene nucleus and one or both of the hydrogen atoms of such an amino group may be substituted in their turn.

Example IX Example X Paper is repeatedly, say three times, soaked in a 2% solution of mercurous nitrate and subsequently bathed in a 6% sodium sulphate solution and, in order to remove the formed sodium nitrate, it is rinsed with water for one hour. After the paper has been dried in the air, it is soaked in a 1% solution of l-diazonium-Z-hydroxynaphthalene-4-sulphonic acid and it is then again dried in the air. This material may be used in the manner set forth in Example III. After being rinsed with water, the picture, which was not yet visible after the exposure, is developed to a grey negative print.

Example XI Paper is soaked in a 2% solution of mercurous nitrate and is then dried in the air. Subsequently it is soaked in an 80% alcoholic solution containing 1% of 2-hydroxy-l-diazoniumnaphthalenel-sulphonic acid and 1% of silver nitrate and is again dried in the air. The sensitized material is exposed under a film negative for 30 seconds at a distance of 25 centimeters from a 5 kw. incandescent lamp and the not yet visible picture is developed by exposing the material for 24 hours to an atmosphere having a high content of water vapor. In this case the tone of the picture at first becomes brown and later becomes black. In order to fix the picture it is washed with water; the color of the picture not being changed.

Example XII Instead of incorporating the materials referred to in Example XI in paper, they may also be incorporated ina carrier consisting of superficially saponified acetyl cellulose. For preparing the light sensitive material and for producing pictures thereon, one may proceed in accordance with Example VIII.

Example XIII Paper is smeared with a 2% solution of mercurous nitrate, a 1% solution of 1-diazonium-2- hydroxynaphthalene-i-sulphonic acid, and a 2% solution of mercurous nitrate. After each operation the treated paper is dried in the air. Subsequently it is exposed under a tracing for a short time (for 30 seconds at a distance of 25 centime- 5 ters from a 5 kw. incandescent lamp) and developed for 5 minutes in a 1% solution of aurichloride. A negative violet-red picture appears which is stabilized by rinsing with water.

- Since mercurous nitrate reacts with aurichloride, it is advisable to develop after the exposure and to then rinse out thoroughly with water; the picture thus obtained being finally treated with the aurichloride solution.

Example XIV Paper is smeared with a 1% solution of l-diazonium-2-hydroxynaphthalene-4-sulphonic acid and dried in the air. After being exposed under a tracing for a short time (for 30 seconds at a distance of 25 centimeters from a 5 kw. incandescent lamp), the treated paper is smeared with a 2% solution of mercurous nitrate in water. Thus the picture is developed in about 5 minutes whereupon it is washed with water and after 25 that treated with a silver nitrate solution.

It is also possible to rub a veryfine powder of mercurous nitrate into the layer after the exposure, and to subsequently place the so-treated layer in a space having a high content of water 30 vapor. The picture appears after about half an hour and can be stabilized in the manner already set out above.

While we have described our invention in connection with specific examples and in specific 35 applications we do not wish to be limited thereto, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What we claim is:

1. A method of producing photographic con- 40 bringing a mercurous salt into reactive relation- 45 ship with the light-decomposition product of the diazonium compound in the presence of moisture to form the contrasts.

2. A method of producing photographic contrasts comprising the steps, selectively exposing 50 a light-sensitive system containing a'diazonium compound to partly decompose the diazonium compound at selected portions of the system, bringing a mercurous salt into reactive relationship with the light-decomposition product of the 55 diazonium compound in the presence of moisture to form contrasts, and applying to the system to stabilize the contrasts a salt of a metal lying higher than mercury in the electric poten- 60 tial series of metals.

3. A method of producing photographic contrasts comprising the steps, selectively exposing a light-sensitive system containing a diazonium compound and a mercurous salt to partly decom pose the diazonium compound at selected por- 65 tions of the system, and moistening the system to form contrasts by the reaction between the mercurous salt and the light-decomposition product of the diazonium compound.

4. A method of producing photographic contrasts comprising the steps, selectively exposing a light-senstitive system containing a diazonium compound to partly decompose the diazonium compound at selected portions .of the system;

adding a mercurous salt to the system, moistening the system to form contrasts by the reaction between the mercurous salt .and the light-decomposition product of the diazonium compound, and heating the system to increase the speed of contrast formation.

5. A method of producing photographic contrasts comprising the steps, impregnating a carrier of regenerated cellulose with a diazonium compound to form a light-sensitive sysem, selectively exposing said system to partly decompose the diazonium compound at selected portions, and bringing a mercurous salt into reactive relationship with the light-decomposition product of the diazonium compound in the presence of moisture to form the contrasts. I

6. A method of producing photographic contrasts comprising the steps, impregnating a carrier of regenerated cellulose with a diazonium compound and a mercurous salt to form a lightsensitive system therein, selectively exposing the so-iormed system to partly decompose the diazonium compound at selected portions thereof,

I and moistening the carrier to form contrasts by light-decomposition product of the diazonium compound in the presence of moisture to produce the contrasts.

8. A method of producing photographic contrasts comprising the steps, impregnating a carrier of superficially saponifled acetyl cellulose with a diazonium compound to form a lightsensitive system, exposing said system by reflex I photography to partly decompose the diazonium compound at selected portions, and bringing a mercurous salt into reactive relationship with the light-decomposition product 01 the diazonium compound in the presence of moisture to form the contrasts.

9. A material for obtaining photographic contrasts comprising a carrier, and a light-sensitive system supported by said carrier and comprising a diazonium compound and a mercurous salt.

10. A material for obtaining photographic contrasts comprising a carrier, and a light-sensitive system supported by said carrier and comprising a diazonium compound, a mercurous salt, and a stabilizer consisting of a salt of a metal lying higher than mercury in the electric potential series of metals.

11. A material for obtaining photographic contrasts comprising a carrier of regenerated cellulose, and a light-sensitive system within said carrier and comprising a diazonium compound,

and a mercurous salt.

- contrasts comprising a suitable carrier, and a light-sensitive system supported by said carrier and comprising a diazonium compound and mercurous boronfiuoride.

15. A material for obtaining photographic contrasts comprising a suitable carrier, and a light-sensitive system supported by said carrier and comprising a diazonium compound and mercurous sulphate.

ROELOF JAN HENDRIK ALmK. KLAAS HINDERIKUS KLAASSENS. HARKE JAN HOUTMAN.