WO1990012343A1

WO1990012343A1 - Process for treatment of a photographic support, means of implementation and support obtained thereby

Info

Publication number: WO1990012343A1
Application number: PCT/FR1990/000265
Authority: WO
Inventors: Yvon Le Marlec; Christophe Bart
Original assignee: Yvon Le Marlec
Priority date: 1989-04-11
Filing date: 1990-04-11
Publication date: 1990-10-18
Also published as: EP0467982A1; EP0467982B1; DE69005624D1; JPH04506710A; FR2652422A2; AU5557190A; FR2652422B2

Abstract

Process for treatment of a photographic support comprising an image whitened after exposure, development and fixing in order to render said whitened image capable of being developed in daylight or in any other non-inactinic light, characterized by the fact that the photographic support comprising the whitened image is subjected, during a sufficient length of time, to the stabilising action of an acid bath containing an effective quantity of thiourea or equivalent blocking agent.

Description

PROCESS FOR PROCESSING A PHOTOGRAPHIC MEDIUM, MEANS IMPLEMENTED AND MEDIUM THUS OBTAINED

The subject of the invention is a method of treatment 5 of a photographic support capable of allowing the development in daylight or in the presence of any other non-inactinic light of a bleached image contained by said photographic support.

It also targets, as products

10 new industrialists, the means to be implemented within the framework of the above process as well as the photographic support comprising the bleached image and subjected to the above processing process.

Those skilled in the art know that a photographic support must be maintained, before and after exposure and until the final phase of development, namely the action of the fixative, protected from any source of non-light inactive.

Indeed, any exposure of said photographic support 20 to a non-inactinic light source before or after exposure but before the application of the fixative results in the fact that the image to which the support has been exposed and which must appear and continue on the support after the well-known treatment devel- opment ^~ 2 and fixing, is irreparably warped. It has therefore hitherto been impossible to reveal, that is to say to reveal in broad daylight on a photographic support constituted, for example, by a white sheet of photographic paper, an image correctly exposed previously. on the same support. ^• t However, it is easy to conceive of the numerous applications, in particular in the field of communication and

^J education, which would become possible if the above-mentioned impossibility could be overcome. 35 And it is in search of a practical and inexpensive solution to this problem that the Inventors have successfully attached.

Those skilled in the art know that it is possible to "bleach" an image, obtained beforehand on a photographic support after exposure, development and fixation. To do this, it is known to use a rehalogenation of the silver image by forming silver chlorides which must be stabilized because of their photosensitivity, the latter leading to blackening, therefore to a spontaneous reappearance. of the image, in the presence of light.

Those skilled in the art also know that it is possible to make the image thus bleached and stabilized reappear with a particular shade, in particular yellowish, by subjecting it to the action of a thiourea solution. This "development" by the thiourea of a bleached and stabilized image can be carried out in broad daylight but has the disadvantage of "going back" to the light before development.

The invention overcomes these drawbacks and makes it possible to have a photographic support comprising a bleached image capable of being "developed" in daylight by the use of a simple and harmless means.

In fact, the inventors had the merit of finding that an image bleached in a conventional manner, comprising a photographic support which is subjected after the image has been bleached to the action of an acid bath having a content effective in thiourea or any other equivalent blocking agent, could be developed in broad daylight as well as in the presence of any other non-inactinic light source by action on the support thus treated with a dilute alkaline solution.

It follows that the method, in accordance with the invention, of processing a photographic support comprising a bleached image after exposure, development and fixing in order to make the bleached image susceptible to be developed in daylight or in the presence of any other non-inactinic light is characterized in that the photographic support comprising the bleached image is subjected, for a sufficient period, to the stabilizing action of a acid bath with an effective amount of thiourea or an equivalent blocking agent.

Mention may be made, as equivalent blocking agents, of sodium thiocyanate, among others.

The acid bath suitable for being used in the context of the above treatment process and whose pH is from 4.00 to 4.70, preferably close to 4.35, has a concentration of thiourea or any other agent blo¬ equivalent cage of between about 2 and about 3 g / 1, this content preferably being close to 2.5 g / liter. The concentrate targeted by the invention and which, by dilution with an appropriate quantity of water, provides the above-mentioned bath, has a content of thiourea or equivalent blocking agent, of 20 to 30 g / l, preferably close to 25 g / 1; its pH is from 3.11 to 3.40, preferably close to 3.15.

The process, in accordance with the invention, for developing in broad daylight or in the presence of any other non-inactinic light of a bleached image comprised by a photographic support which has been subjected to the treatment in accordance with the invention, consists in subjecting said photographic support to the action of a dilute alkaline solution.

The invention also relates to other arrangements which are preferably used at the same time as those which have just been mentioned; this will be more explicitly discussed below.

And it will be better understood with the aid of the additional description which follows and of the nonlimiting examples which are given by way of illustration and which correspond to advantageous embodiments. Proposing, therefore, to have a photographic medium contain a bleached image capable to be developed in daylight as well as in the presence of any other noninactinic light, this is done as follows or in a technically equivalent manner.

First of all, an image is exposed, it is revealed and it is fixed by subjecting a photographic support to the conventional treatment sequence well known to those skilled in the art, described in all photographic manuals and on which it does not exist. 'is therefore not necessary to insist here.

Then, the photographic support is subjected to a treatment also known in itself and consisting in "whitening" the image previously revealed and fixed.

To do this, a gelatin tanning is preferably carried out by causing an alum to act, for example, then the image is bleached by action, for example, potassium permanganate in an acid medium.

Tanning and bleaching can be simulated and carried out by a single bath.

Advantageously, recourse may be had to the bath, the composition of which is given below by way of example. ¹ ©: potassium permanganate 7 g sodium chloride 20 g acetic acid (80% concentration) 60 ml potassium alum 10 g water qs 1000 ml.

The photographic support comprising the image to be whitened can be immersed in the above-mentioned bath, preferably at room temperature, until the image disappears; in practice, the duration of the action of the bath is approximately 4 minutes.

The support is then rinsed and then discolored by soaking, for example, in a bisulphite bath advantageously containing an alum, preferably at room temperature, for 1 to 2 minutes. The concentration of this bisulfite bath, in particular sodium, is advantageously around 5% by volume and in alum, in particular potassium, of approximately 1% by weight.

The support comprising the image thus bleached and which, moreover, has been discolored as has just been indicated, is then subjected to the stabilization treatment process according to the invention.

This treatment process can be applied immediately after bleaching and bleaching or later; in this second possibility, the support must be protected from light until the stabilization treatment.

This stabilization treatment consists in submitting the discolored photographic support which includes the bleached image to the action, in an acid medium, of thiourea or of an equivalent blocking agent. Thiourea is carried out by means of a bath, the pH of which is brought to a value of 4.00 to 4.70, preferably close to 4.35, using an effective amount of an acid, preferably organic, and even more preferential ent chosen from the group comprising acetic, tartaric, citric and oxalic acids.

Acetic and oxalic acids give the best results.

In practice, the effective amount of acetic acid is 6 to 10 ml, preferably 8 to 10 ml per 1000 ml of bath, oxalic acid is 3.5 to 8 g, preferably 4, 5 to 5.5 g per 1000 ml of bath.

The bath in question, the temperature of which is 18 to 22 ° C., preferably room temperature, preferably also contains a bromide to avoid the too rapid solubilization of the silver chloride and an alum to perfect the tanning. gelatin.

It is applied to the photographic support to be treated for a period fixed between 90 and 120 seconds. Two baths which have led to good results and which are given by way of examples have the following composition: a) Thiourea 2.5 g acetic acid (concentration of 10%) 8 ml

Potassium bromide 1 g Potassium alum 10 g Water q.s.p. 1000 ml. b) Thiourea 2.5 g Oxalic acid 5 g

Potassium bromide 2 g Potassium alum 50 g Water q.s.p. 1000 ml.

In the case of these two baths, the duration of the treatment is approximately 105 seconds.

In general, too high a thio¬ urea concentration and / or a too long treatment time inhibit redevelopment and give a weakened image. Conversely, a concentration of thiourea that is too weak and / or a treatment time that is too short insufficiently stabilizes the bleached image and does not prevent blackening in daylight.

The treatment can be carried out by soaking the photographic support in this bath. It is followed by a sufficiently intense washing to remove from the support all the residues of the above-mentioned bath.

After drying, the photographic support thus treated can be stored in daylight without limitation of duration. The bleached and stabilized image which it carries can be of any kind, so that this support can claim many and varied applications responding in particular educational purposes.

Thus, it is possible to envisage constituting by this support at least certain pages of brochures or books intended for example for educational games. Other applications can be found in all areas of communication.

In order to make the image reappear, whatever it may be, of which the support is a carrier, in other words to reveal or develop this image, in accordance with the invention, action is taken on said support, in daylight or in presence of any other non-inactive light, a dilute aqueous alkaline solution.

The alkalinity can be provided for example by soda, ammonia or sodium carbonate.

The amount of base must be such that the pH of the solution is 11 to 12, preferably close to 11.35.

Advantageously, use will be made of a solution having an NaOH concentration of 1 to 4% by weight. To make the alkaline solution work, it can be applied with a brush.

It is also possible to apply it using a fogger.

Finally, the image can be revealed by dipping the photographic support in the alkaline solution.

Other variants can be envisaged.

Once the image is revealed, it suffices to dry the photographic support; in some cases, it may be advantageous to wipe the support with the aid of an acidified damp sponge to remove traces of alkali which may affect the conservation of the support.

Following what and whatever the embodiment chosen, there is thus a process for the treatment of photographic supports capable of allowing development in daylight or in the presence of any non-inactinic light. a bleached image, of means allowing the implementation of this process and of a support carrying such a stabilized bleached image capable of being revealed in daylight, the characteristics and advantages of which result sufficiently from the above so that there is no need to insist further As goes without saying and as it already follows from the foregoing, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all its variants.

Claims

1. Method for processing a photographic support comprising a bleached image after exposure, development and fixation in order to make said bleached image capable of being developed in daylight or in the presence of any other light not inactivated , characterized in that the photographic support comprising the bleached image is subjected, for a sufficient duration, to the stabilizing action of an acid bath comprising an effective amount of thiourea or of an equivalent blocking agent.

2. Treatment method according to claim 1, characterized in that the pH of the acid bath is from 4.0 to 4.70, preferably close to 4.35.

3. Treatment method according to one of claims 1 and 2, characterized in that the acidity of the bath containing the thiourea or the slow blocking agent is provided by an acid, preferably organic, and more particularly still, chosen from the group comprising acetic, tartaric, citric and oxalic acids.

4. Treatment method according to one of claims 1 to 3, characterized in that the temperature of the acid bath is 18 to 22 ° C, preferably close to 20 ° C and that the duration of action of the bath is 90 to 120 seconds, preferably around 105 seconds.

5. Acid bath comprising a concentration of thiourea or equivalent blocking agent of between approximately 2 g / 1 and approximately 3 g / 1, preferably close to 2.5 g / 1, and intended to be used in the process according to One of claims 1 to 3.

6. Bath according to claim 5, characterized in that it comprises an organic acid preferably chosen from the group comprising acetic, tartaric, citric and oxalic acids.

7. Bath according to one of claims 5 and 6, characterized in that its composition is as follows:

Thiourea 2.5 g Acetic acid (10% concentration) 8 ml Potassium bromide 1 g

Alum potassium 10 g

Water q.s.p. 1000 ml.

8. Bath according to one of claims 5 and 6, characterized in that its composition is as follows:

Thiourea 2.5 g

Oxalic acid 5 g

Potassium bromide 2 g Potassium alum 50 g

Water q.s.p. 1000 ml.

9. Concentrate capable of providing, by dilution with an appropriate amount of water, the bath according to one of claims 5 to 8.

10. Photographic medium, characterized in that it includes a bleached image and that it has been subjected to the method according to one of claims 1 to 4.

11. A method of developing in broad daylight or in the presence of any other non-inactinic light of a bleached image comprised by a photographic support according to claim 10, characterized in that said photographic support is subjected to the action of a dilute alkaline solution.

12. Method according to claim 11, characterized in that the diluted alkaline solution used has a pH of 11 to 12, preferably close to 11.35, and is based on sodium hydroxide, NH ₄ 0H or sodium carbonate.