US2051583A

US2051583A - Method for making reflex copies

Info

Publication number: US2051583A
Application number: US757933A
Authority: US
Inventors: Lodewijk Pieter Frans Grinten
Original assignee: NAAMLOOZE VENNOOTSCHAP CHEMISC
Current assignee: NAAMLOOZE VENNOOTSCHAP CHEMISC
Priority date: 1933-12-19
Filing date: 1934-12-17
Publication date: 1936-08-18
Anticipated expiration: 1953-08-18
Also published as: FR768394A

Description

ug 18, 1936- P, F. VAN DER GRINTEN 2,051,583

METHOD FOR MAKING REFLEX COPIES I Filed Dec. 1v, 19:54

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Patented Aug. 18, 1936 PATENT OFFICE 2,051,583 y METHOD Fon MAKING REFLEX norms Lodewijk Pieter Frans van der Grinten, Venlo,

Netherlands, assignor to Naamlooze Vennootschap Chemische Fabriek L. van der Grinten, Venlo, Netherlands, a limited-liability company of Netherlands Application December 17, 1934, Serial No. 757,933 In the Netherlands December 19, 1933 12 Claims.

, It is known to make reex copies by a method comprising the steps of applying on an original a sheet containing a layer of bromicjsilver emulsion subjecting the original to a radiation through said sheet and subdividing said radiation before it passes through the layer of sensitive material into small areas of lower and higher photochemical power. This method, however, does not give good reflex copies.

Now it has been found that good reflex copies can be obtained by other methods to be further described, whilst the type of the rays employed may be also of importance.

If one compares with the help of the microscope those parts of the reflex copy that were'during u the production of the latter over the dark regions smaller photochemical action has occurred. The

result of this action is hereinafter called the ha1o; vit may for example be practically expressed by the reduction of the covering factor of the screening of the portions in question (the covering factor being the surface of the regions of smaller photochemical action, or the corre spending regions in 'the reflex copy, per unit of surface).

Now it has been-found that the halo exerts a.

large injurious influence on the strength of the picture; The object of the present invention is therefore to limit this halo. Wherever hereinafter reference is made to rays, or to transparency or to capacity of reflexion therefore, this always means that reference is made to rays of A such wave lengths as influence photochemically the sensitive layer or layers employed.

The requirements necessary for the practical avoidance of a halo in the sensitive sheet are dependent on many different factors, vlikewise the importance of the halo.itself.- They are determined inter alia by the kind and the coarseness of the subdivision into regions of greater and of the nature of the sensitive Alayers employed and the diffusion of the rays by these layers.

In order to diminish the halo it is requiredto avoid a diffused radiation into the areas of smaller actinic intensity. It has been found that one necessary condition to obtain this is the use of a sensitive layer, which-at least during a considerable part of the necessary irradiation-has a high coeiiicient of directed propagation for the rays by which the image is formed.

The expression coefficient of directed propagation of a sensitive laye/1 for definite rays is defined as the. reversed ratio between the actinic intensity of a small band (the smallest dimension of which should not exceed the thickness of the layer) of parallel rays of the kind employed as it is measured when perpendicularly impinging upon the front surface of the sensitive layer and. the actinic intensity of this band of rays after passing through the sensitive layer asit is measured in the area which is the perpendicular projection of the area of the front surface upon whichsaid band impinges on the back surface of -said layer.

There are several sensitive layers capable of further be taken into account for example the quantity of sensitive material present and its distribution in the sensitivel sheet. For this reason, for the purpose of reducing lthe halo it is advantageous to have the quantity of the sensitive material as small as possible, which will in many cases present at the same time the advantage that smaller quantities of the radiation suiice for the production of the reflex copy. The

picture production is of course determined simply by the reflected radiation and this radiation is only small owing to the restricted capacityfor reflexion of the originals that occur in'- practice and, i'n the case of covering screening, of the restricted amount of the radiation energy passing into' the system, s'o that for these reasons already the operation is uneconomical as regards the 'useful effect of the radiatibn. -Of -course, with a layer containing less` sensitive material, for instance a thin layer, there is obtained also a smaller picture strength, which, however, may be increased by recopying. Where hereinafter it is a question of strong reflex copies there are meant thereby copies that are strong in relation to the layer employed in the making of them.

In all these cases an improvement is obtained by using a sensitive layer, which-at least during a considerable part of the necessary irradiation by said rays-has not only a high coefficient of directed propagation but in which also the ratio 'between the amount of radiation diffused into the sensitive layer and the radiation leaving the sensitive layer in the direction of the original is small. y f

If dispersion should not be avoided completely it should be caused to take place during the production of the reflex copy merely in the space located between the sensitive layer or the sensitive layers, and the original.

A special selection of the rays to be employed is of course of importance merely for layers that are sensitive over a comparatively wide range of wave lengths. Within such a range the transparency and the ray dispersion may vary with the wave length. In such a case there are preferably chosen, in as far as theselectively reflecting properties of the original allow of this in the sense of what has been said, those wave lengths for which the transparency is the greatest and the ray dispersion is the smallest. As an example for this there may be mentioned the employment of a yellow lter.

It may be here mentioned that in the case of comparative tests for determining an effect according to the invention all the factors that can affect the magnitude and the importance of the halo, other than the nature of the sensitive layers, as, inter alia, the above mentioned factors, must remain constant and only the nature of the sensitive. layer with respect to the rays employed should vary.

It is also to be assumed and taken for granted that the sensitive layers work contrasting to a reasonable extent.

It has further been found that it is not necessary that a high coefficient of directedpropagation exists in the sensitive layer already in the beginning of the process for making the reflex copy. There are sensitive materials wh'ch are decomposed by the radiation into substanc s having a much increased transparency for such rays. In that case the coefiicient of directed propagation increases by the initial irradiation to a maximum when all the sensitive material in the regions of greater actinic intensity has been decomposed. Such layers generally absorb the radiation until they are completely decomposed but do not diffuse the radiation or only to a Very small extent. This makes these layers very suitable for the purpose of the present invention. Examples of such layers are cyanotype layers, layers containing a sensitive iron salt which can be developed by means of galli'c acid and chromate layers that bleach to a colourless substance.

The following examples serve to illustrate the invention which is by no way limited thereto. The examples will be described in connection with the accompanying diagrammatic drawing which shows in crosssection a covering screen, a sensitive sheet and partof an original.

Example 1 An original O (see figure) which consists of a sheet of clear-white paper printed on both sides with black printing, is placed with the side upward from which it is desired to make a reflex copy. On this there is placed with upwardly turned emulsion layer, a celluloid sheet (DR) 0.1 mm. thick, which is provided with a normal silver halide gelatine layer (GL), 0.01 mm. thick,

` and thereon a lined covering screen (R) (made Irradiation is effected through a yellow lter by means of an electric incandescent lamp of watts at a distance of 40 cm. in the middle in front of the system so that the rays impinge rst upon the screen, then upon the sensitive layer, and finally upon the original.

After adequate irradiation, development takes place and xing is effected in an ordinary manner. There is obtained a negative reflex copy in the transparent portions of which (these are consequently the portions that in the making of the reflex copy were laid over the black part of the original Z, indicated in the drawing by hatching in O) the coarseness (by which is meant here the width of the transparent lines that correspond in each case to the covering lines of the screen) is reduced from 0.14 to 0.10, and the covering factor (here consequently the ratio of the transparent surface to the total surface, measured between the limits of the transparent portions) is consequently reduced from 0.82 to 0.59, so that there has occurred a halo of 0.23.

If, instead of working according to the method in which the above mentioned emulsion is employed, there is employed a grainless so-called Lippmann emulsion, which is clear, the halo is too' small to be measured. The coarseness in the transparent portions is then exactly 0.14. In the case of the employment of this emulsilon there'v may be also employed white light (sun ight, incandescent lamp without yellow filter). There is then obtained in the pervious portions o f the negative reex copy a coarseness of 0.13, corresponding to a covering factor of 0.76 and conse- 'quently a halo of 0.82-0.76=0.06.

-In the case of the employment of normal Kodak film there would be obtained for example a coarseness of 0.09, i. e. a halo of 0.29, which is so great that the reflex copy is hardly better than the one lobtainable with the same film in the old way without any screen.

Of course all the measurements were made under exactly like `conditions so that the results were comparable.

Example 2 An original, a sensitive sheet, and a screen for example by sapniflcation. The sensitive solution employed consists of 10 parts by weight of green ferric ammonium citrate 1 part by weight of potassium ferriccyanide,

and 20 parts by volume of water.

The rear side of this sheet is matted that is to say rendered dull for the purpose of increasing the legibility of the reflex copy to be made.

This layer has when unirradiated little transparency to the chemically active rays; during the irradiation this transparency continuously increases and has become comparatively great when the irradiation is finished, and the layer has obtained a. high coeiicient for directed propagation.-

An arc lamp at a distance of 40 cm. serves as the source of radiation.

After completion of the irradiation the sensitive sheet is measured microscopically. The colourless portions have a coarseness of ,0.12 and consequently a halo of 0.12. Washing is now eiected in a dilute potassium ferric cyanide solution and then in water.

A strong negative rei-lex copy is obtained.

If the rear side of the sheet is not matted there is a coarseness of0.l4 and consequently no halo.

Example 3 The operation is exactly like in Example 2 (see the drawing). The'sensitive sheet consists vof a Celluloid sheet 0.10 mm. thick, which is provided with a gelatine sensitive iron salt layer 0.01 mm. thick, which was prepared with a solution of Percent Ferric sulphate Ferric chloride 3 Tartaric acid 5 Percent Gallic acid 0.7 Oxalic acid 0.1

and then immersion in a strong formaline bath.

There is obtained a strong positive reflex copy. When there is employed a lens covering screen the irradiation times are reduced.

Eample 4 For thepurpose of enabling comparison to be made, the operation again takes' place in the manner stated in the foregoing examples (see the drawing).

A sensitive bleaching chromate layer is produced by impregnating on its saponied side a unilaterally saponiiied acetylcellulose sheet with a solution of Parts by weight Bichromate of potassium 1 Phosphoric acid, sp. gr. 1.32 3 Water 2 This layer is yellow coloured and.becomes on irradiation practically colourless. Consequently its transparency to rays at the conclusion of the irradiation is great inthe regions of greater photochemical activity, after .the completion ofcontaining a sensitive layer of the type which exhibits a high coeiiicient of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being selected from the group consisting of Lippman emulsion layer, cyanotype layer, sensitive iron salt layer, bleaching chromate layer, subjecting theoriginal to a radiation through said sheet, and subdividing said radiation before it has passed through said layer into small areas of lower and higher photochemical power.

2. A process for making reex copies comprising the-steps lof applying on an original a sheet containing a sensitive layer of the type which exhibits a high coefficient of directed propagation for the rays by which the image is formed forat least a considerable part of the required irradiation, said layer being a Lippmann emulsion layer, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has passed'through said layer into small areas of lower and higher photochemical power.

3. A process for making rei-lex copies comprising the -steps of applying on an original a sheet containing a sensitive layer of the type which exhibits a high lcoeicient-of directed propagation for the rays by which the image is formed for atleast a considerable part of the required irradiation, said layer being a `cyanotype layer,

subjecting the original to a radiation through said sheet, and subdivlding said radiation before4 it haspassed through said layer into small areas of lower and higher photochemical power.

4. A process for making reflex copies` comprising the steps of applying on'an original a sheet containing a sensitive layer of the type which exhibits a high coeilicient` of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being a bleaching chromate layer, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has -passed through said layer into small areas of lower and higher photochemical power.

5. A process for making reflex copies comprising the steps of A,applying on an original a sheetl containing a sensitive layer of the type which exhibits a high coefficient of directed propagation for the raysby which the image is formed for at least a considerable part of the required irradiation, said layer being selected from the group consisting of Lippmann emulsion layer, cyanotype layer, sensitive iron `salt layer, bleaching chromate layer, subjecting the original to a radiation through said sheet, and subdividing said radiation by the application of a screen before it passes through said layer'into small areas of lower and higher photochemical power.

6. A process for making reflex copies compris- 4ing the steps of applying on an original a sheet containing a sensitive layer of the type which exhibits a high coefcient of directed propagation for the rays by which the image ls formed for at least a considerable part of the required irradiation, said layer being a Lippmann emulsion layer, subjecting the original to a radiation through said sheet, and subdividing said radiation by the application of a screen before it passes through said layer into small areas of lower and higher photochemical power.

7. A process for making reflex copies comprising the steps of applying on an original a. sheet containing a sensitive layer of the type which exhibits a high coefficient of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being a cyanotype layer, subjecting the original to a radiation through said sheet, and subdividing said radiation by the application of a screen before it passes through said layer into small areas of lower and higher photochemical power.

8. A process for making reex copies comprising the steps of applying on an original a sheet containing a sensitive layer yoi the type which exhibits a high coeiiicient of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being -a bleaching chromate layer, subjecting the original to .a radiation through said sheet, and subdividing said radiation by the application of a screen before it passes through said layer into small areas of lower and higher photochemical power.

9. A process for making reflex copies comprising the steps of applying lon an original a sheet Acontaining a sensitive layer of the type which exhibits a high coefficient of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being selected from the group consisting of Lippmann emulsion layer, cyanotype layer, sensitive iron salt layer, bleaching chromate layer, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has passed through said layer into small areas of lower and higher photochemical power, said sheet being diffusing only in the space between the sensitive layer and the original.

10. A process for making reflex copies comprising the steps of applyingv on an origin-al a sheet containing a sensitive layer of the type which exhibits a high coeicient of directed propagation for the rays by which the image is formed for at least a considerable part fof the required irradiation, said layer being a Lippm-ann emulsionlayer, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has passed through said layer into small areas of lower and higher` photochemical power, sai-d sheet being diffusing onlyvin the space between .the sensitive layer and the original.

11. A process for making reflex copies comprising the steps of applying on an origin-a1 a sheetcontaining asensitive layer of the type which exhibits a high coeiiicient of directed propagation for the rays by which the image is formed for at least a considerable part of the required irradiation, said layer being a cyanotype layer, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has passedthrough said layer into small areas of lower and higher photochemical power, said sheet being dilusing only in' the space between the sensitive layer and theI original.

12. A process for making reilex copies comn radiation before it has passed through said layer intoI small areas of lower and higher photochemical power, said sheet being diffusing only in the space between the sensitive layer and the originali LODEWIJ K PIETER FRANS VAN DER GRINTEN.