US2051585A - Process of making reflex copies - Google Patents

Description

Patented Aug. 18, 1936 I UNITED STATES 2,051,585 raocnss or-mxmc nmnx' corms ,Lodewijk Pieter Frans van der Grinten, Venlo,

Netherlands, assignor to Naainloose Vennootschap Chemische Fabriek L. van der Grinten,

Venlo, Netherlands, a of Netherlands limited-liability company No Drawing. Original application September 9, i

1933, Serial No. 688,858. Divided and this application February 4, 1935, Serial No. 4,989.

the Netherlands September 14, 1932 5 Claims. (cl. 95-5) The present invention relates to processes for making reflex copies which comprise the placing of a sheet containing a sensitive layer upon an original, the original and said layer being spaced 5 fromeach other so that there is a distance between the sensitive layer and the original, subjecting the original to a radiation through said sheet, and subdividing said radiation before it has passed through said layer into small areas of 10 lower and higher photochemical power. This application is a division of application Serial No. 688,858, filed September 9, 1933.

For making copies by irradiation of originals which are opaque or slightly transparent to light or of originals carrying an image on both sides, such as sheets written or printed on both sides and the like, it is necessary to use rays reflected by the original.

Apart from processes in which a camera-at least an objectiveis used, processes are known in which the sensitive material is in contact with or in proximity with the original, that is to say, in which the light first passes through the sensitive sheet and is then reflected from the surface of the original back into the sensitive sheet.

Such processes are for instance described by August Albert in Die Reflektographie etc." Halle 1922. An explanation of these processes is given by R. A. Reiss, Eders Jahrbuch' fur 1903, P ge a 110. The present invention is related to these processes and is called conveniently a process of reflectography and the copies obtained by the process are called "reflex copies.

The art of refiectography is still imperfect. In

its application to several photographic processes,

and the possibility of obtaining directlypositive copies, its results are imperfect.

A small improvement is obtained if, as proposed in the French Patent 608,947, there is interposed inthe path of the light in proximityto the sensitive material at the side of the light source a medium which disperses the rays and reflects them to the side of the sensitive material. In this case the radiation remains uniformly distributed but the rays reflected by the original which are not absorbed after passing the sensitive layer are partly reflected again and so retained for the formation of the-image, so that a small increase of the strength of the reflex copies is obtained.

It has been found that in reflectography the I strength of the copies can be increased and other advantages as specified hereafter may be obtained if the radiation which reaches the original does not remain uniformly distributed as in the known processes, but if in any manner care is 1'0. taken that the radiation during its passage through the space limited by the upper and back surface of the sensitive layer or layers," at least before leaving this space, is divided into small areas of more and of less power. ll

The preceding and following use of the term reflectography" implies therefore an extension of that idea with respect to its former meaning, more specifically, the present process corresponds with the known reflectography only in its gen-'20 eral progress and its final result and is so called only with respect to this superficial similarity.

To avoid misunderstanding it is observed that difference in power can exist between radiation of the same intensity if the'rays differ in wave 25 length and difler-in photochemical power. Such areas of the same or nearly the same intensity but different photochemical power may be 'obtained for instance. by the use of prismatic screens.

Preferably as far as possible directed rays are used. The expression directed" or "parallel directed radiation is used in this connection in a definite broad sense in such manner, that for instance the radiation emerging from a light 35 point or a light source resembling a light point and from a distance not substantially greater that the dimensions of the system subjected to radia-,

' tion is also comprised under the expression parallel directed radiation.

Though the rays have then a diflerent direction in distant places of the surface, through which they enterinto the system, but in each of these places and its immediate-surrounding in in the form of lines. In such a case it may be advantageous for the purpose of the present invention, to use a source of radiation in the form of a line or band parallel or nearly parallel to the lines of the division. When using a source of radiation in line or band form as specified above, this radiation must also be considered in the sense of the preceding explanation-at least if the breadth of the source of radiation is not too large'as a parallel directed radiation. It is true that the rays in their projection on a surface vertical to the line like division have a mutually differing direction towards the different distanced lines of division of the surface into which the rays enter, but in these lines themselves and their immediate surrounding in the-surface into which the rays enter, only rays having practically one definite direction in the above mentioned projection are active.

For the sake of clearness it will now be explained what is meant in the following specification and claims by the expressions: carrier, sensitive layer, sensitive material and sheet.

The expression carrier means the plate-, sheetor leaf like material upon which or in which the sensitive substance or substances are applied or extended. The function of the carrier is substantially mechanical as indicated by the expression. a

The sensitive layer" means the space or zone occupied by the substance or substances sensitive to the radiation. The sensitive layer may be outside the carrier, for instance it may be applied on the carrier. It may, however, also form a part of the carrier, for instance if one or both of the sides of the carrier are impregnated with the sensitive substance, or if the carrier over its whole thickness-at least locallyis impregnated with the sensitive substance.

The sensitive material is the substance or substances having the necessary photochemical properties for producing the image by selective radiation.

The sheet or sensitive sheet is the unit, composed of carrier, sensitive material and layer (if the latter is located outside the carrier proper) If, as described hereafter, the sheets carry screens, these screens are considered as belonging to the sheet, therefore to the unit. Possible interruptions of the sheet or its parts (for instance perforations) are also considered to belong to the sheet.

Theeffect according to the invention is obtained in a simple manner if the radiation is caused to pass through a so-called screen which may be applied between the source of radiation and the sensitive sheet, preferably, in the immediate proximity of the sensitive sheet, possibly in direct contact with it. This screen may be a. covering screen i. e. of varying opacity, or a lenticular,

prismatic or similar screen.

When using a separate covering screen it has been found that in certain cases better results are obtained the more the screen surfaceat least at the side directed to the sensitive layer-isreflective, for instance like a mirror. Reflectivity of the covering, parts of the a screen towards the source of radiation has the additional advantage of reflecting the intercepted rays back towards the source of radiation so that-4f this is provided with a reflector, or if for instance the process is carried out in a-cylindrical surface or the like, which may be rotated or notthis energyis not lost, at least not totally lost. Another advantage is that the screen becomes less hot and therefore possibly needs no cooling which might otherwise be desirable in screens having covering parts which absorb rays.

Advantageously, the sensitive sheet may be screened. Preferably thescreening is chosen in such manner that it may be removed from the sensitive sheet, for instance mechanically, by washing with water or other solvents, by washing and mechanical action together or the like. Also in this case it may be advantageous to choose a reflecting screen material. Furthermore in this case one may use a covering or a lenticular or a prismatic screen or the like. The lenses or prisms may be made in the sensitive sheet by a goifer machine.

Also it may be advantageous to apply as a screen material on the sensitive sheet a .sub-' stance which intercepts photochemical active rays, for instance ultra violet rays, but is transparent for other rays.

It is also advantageous to apply a screen material which by a chemical treatment or by radiation or the like may be removed or at least may be made more or less invisible.

If the sensitive sheet contains a material, for

instance the sensitive material itself, which intercepts the photochemical active rays, this material may be advantageously distributed in such manner in the sheet, that small areas with different quantities of. material are formed therein. In other words: the distribution is in the manner of a screen, or in still other words, the sheet may be screened" in such manner that locally less and locally more or all rays can pass.

In the three latter cases it is possible that after the forming of the image nothing needs to be removed. These methods are especially advantageous when combined with processes such as diazo type processes which do not require any removing of substances. The additions required by these processes may be effected if necessary in such manner that they afiect the screer material in the desired way, for instance decolorize it, if the screen material consists of a dyestuif which is decolorized by an agent applied in an after treatment, such asan alkali. Sensitive sheets which are screened or provided with a screen have the advantage that the screening during the radiation cannot shift. They can also be supplied to the trade ready for use. Such sensitive sheets are included in the scope of the present invention.

Screened sensitive sheets or sensitive sheets provided with a screen, may advantageously be supenables the user to use less radiating energy. The

preliminary radiation is effected advantageously with an absorbing background and as much as possible with a directed radiation.

Further it has been found that the nature of the screening,whether of a separate screen or of ascreen combined with a sensitive sheet or sensitive layer, or of a screened sheet or carrier and em on the coarseness.

of the surface, both measured in a definite area, influences the result. This proportion can, be stated generally in an accurate manner for a covering screening and as an average value for a lenticularfprismatic or other screening. Herewill be suflicient but copies of less strength are obtained. By varying the covering factor the. present process may be controlled with respect to the object in view in connection with other conditions. factor will be chosen for copying a weak original and a smaller covering factor for copying a strong original from which only copies are required which do not need to come up to a high standard and by which radiating energy is economized.

It has'also been found that the. coarseness of the screening influences the effect. The coarseness of the screening as used hereafter is defined for the case of a line screening, including also a chess-board kind of screening, as the breadth of the covering parts in millimeters. In otherscreens functiona l l y corresponding measuresare taken.

The effect of a definite coarseness of screening is partly dependent on the distance,-or the average distance, between serisitive material or sensitive layer and the original. This distance is called hereafter image distance and also expressed in millimeters. The amount of radiation required for a total or nearly total photochemical conversion of a definite quantity of sensitive material with a constant covering factor is depend-' Considering for instance a, coarseness 1 and an image distance 0.03 the required radiation decreases if the coarseness is decreased. At the same time the quality of the copy becomes better. The most favorable limits of coarseness for ordinary practice and an image distance -of for instance 0.03 are between the carrier, on a possibly used intermediate layer,.

on a greater or smaller reflective power of the screen material, on the wave lengths of the rays used, on the greater or smaller diffusion thereof, etc. and all this in connection with the requirements made with respect to the copy. By simple experiments the optimum coarseness can be found for any definite case:

Regarding the image distance, it has been found that in most cases it is advantageous that it should be small. At -a small image distance the copy becomes sharper and stronger. A definite image distance can be obtained in practice for instance by choosing a carrier of a definite thickness and also by applying an'intermediate layer. If no intermediate layer is used the image distance'is determined by the location of the layer in the sheet and the thickness of the sheet.

The minimum image distance practically possible So, for instance a larger covering stantially parallel with these edges.

is determined therefore in certain cases by the minimum thickness of the carrier which-can be used in practice, which depends again on the material of the carrier and on the practical possibilities in connection with the position of the layer in the sheet.

'As mentioned above the image distance and the coarseness are controlled advantageously with respect to each other.

The covering as well as the transparent parts of the screening may have the form of lines, points, round or square surfaces, etc. .Hereinbefore as a measure for the coarseness of the screening, for example a line screening, the linear breadth of' the covering parts were taken. In

many cases, however, such as for instance when the transparent parts consist of round surfaces and also in lenticular, prismatic and similar screenings, only amean of several measures can with a small covering factor, may have a drawa back for the copying of lines or other parts of the image which are'parallel with the screening. If this drawback occurs it maybe removed by a suitable position of the screening or by the use of a different screen.

In general, it has been found that it is advan tageous to work with screenings of such form that the zone of the covering parts which is at;

the greatest distance, or the greatest average distance from the edges of these parts, is sub- If the coarseness is small this feature is of minor importance. a

The screening may be obtained in several ways: photographically, by mechanical action, by spraying, atomizing, perforating etc. Total or partial perforation (that is to say a perforation of part of the thickness of the layer or sheet) may be applied with advantage to the sensitive sheets themselves.

If the sensitive material changes or. loses its absorbing power when subjected to radiation .(such as for instance many diazo compounds) the screening of the sheet or the layer may advantageously be obtained by a preliminary radiation through a screen, in which case the sensitive sheet takes over the form of the screening of the screen used during the preliminary radiation.

of light, radiation through definite filters etc. can

also be combined with the present process, but

according to the present invention, practical copies of sufficient strength-are obtained, also without such auxiliary means, even from originals having dark, parts which are not black, but for instance colored, such as originals written or typed with coloredink or the like, and which when copied by means of. a radiation through the original willyield only moderate or bad copies.

' reflex copying processes.

. processes with diazo and similar compounds.

As suitable carriers for the light sensitive materials every suitable transparent carrier may be used. Preferably carriers of a uniform structure having little influence on the direction of the rays and with highest transparency such as for instance glass, celluloid, cellophane (registered trade-mark) gelatine foil and the like are used, but also transfer papers, transfer linen and the like of sumcient transparency may be used.

The sensitive layers may be applied on the carrier on one or both sides and may also be present in the whole mass of the carrier. Best results, however, are obtained with carriers pro-- vided on one side only with sensitive material the sensitive side being then turned away from the original and therefore turned to the screen.

' The invention may' be applied with all usual sensitive layers, such as layers with silver-, diazo and similar compounds, preferably suitable for direct positive processes, such as the positive diazotype process by which positive images in black and different colors may beobtained'directly.

In a silver bromide plate a point screening is applied by a photographic process with a mean coarseness 0.1 and a covering factor 0.6. The

image layer of the screened plate thus obtained is brought into contact with the sensitive layer of a silver bromide film. An original, consisting of a printed page, is placed against the non sensitive side of this fllm. The three parts thus united "are kept together in the usual way in a printing frame and are exposed through the screen during 5 seconds to the light .of an incandescent 50 candle-power lamp at a distance of 20 cm. After the'exposure'the silver bromide fllm is developed in the ordinary way, fixed and washed. A negative copy of the original is obtained of much greater strength than would have been obtained if the exposure had been effected under similar conditions without a screen.

Example 2 on a cellulose film of 0.06 mm. thickness and prepared on both sides with a diazo-l-dimethylamino-i-benzene solution a line screening with a coarseness of 0.5 and covering factor 0.8 is applied on one of the sides. o

The screening material which is printed on the one side may be composed in the following manner: Take parts of water, 6 parts of casein, 6 parts of sugar and add so much aluminum powder that sufficient covering power is obtainedw Between the sensitive sheet and the original a transparent intermediate layer of 0.1 mm. thickness is placed so that the mean-image distance becomes 0.13.

Radiation is carried out with a mercury vapour lamp in such manner that-the screened side is turned to the source of radiation. After the irradiation the fllm is developed in an alkaline solution of an azo component. If the screen material is not already loosened by this development, the surface may be rubbed so that the screen layer is removed. A positive image is obtained of greater strength than the image which would have been obtained under similar conditions without a screen.

If before its use the sheet provided with an ab: sorbing background and with the screen side turned to. the source of radiation is subjected to a preliminary radiation, the-ultimate user may use a shorter time of radiation for obtaining the desired result. This Preliminary radiation is efpower separated by'small areas of lower photochemical power between said beams, and causing said beams to pass through said sensitive layer a and space on to the original.

' 2. A process for making reflex copies which comprises superimposing asensitive layer upon an original so that said layeris spaced from the original by an image distance, subdividing a radiation before it 'has passed through said sensitive layer into small beams of higher photochemical power separated by small areas of lower photo- 7 chemical power between said beams, adjusting the image distance accordingto the coarseness of said areasby interposing between said sensitive layer and the original a support whose thickness is short when the coarseness :of said areas is small and whose thickness is longer when the coarseness of said areas is greater, and causing said beams to pass' through said sensitive layer and support on to the original.

3. A process for making reflex copies which comprises superimposing a sensitive layer upon an original so that said layer is spaced from the original, subdividing a-radiation beforeit has passed through said sensitive layer into small beams of higher photochemical power separated by small areas of lower photochemical power between said beams, adjusting theimage distance according to the coarseness of said areas by interposing between said sensitive layer and the original a support whose thickness is atleast one fourth of the breadth of said areas, and causing said beams to pass through said sensitive layer and'support on to the original. I g.

4. A process for making reflex copies which comprises superimposing a sensitive sheet upon an original in such manner thatthe side of said sheet containing the layer of sensitive material is turned away from the originaland the layer .is

spaced from the original by the carrier portion of said areas is small and longer when the coarseness of said areas is greater, and causing said beanis to pass through said sheet on to the original.

5, A process for making reflex copies which comprises superimposing a sensitive sheet containing a sensitive layer upon an original, subdividing a radiation before it has passed through said sensitive layer into small beams of higher 10 photochemical power separated by small areas of lower photochemical power between said beams,

adjusting the image distance between s'aid'sensitive layer and the original according to the coarseness of said areas by interposing an inter-- mediate layer between said sheet and said original, and causing said beams to pass through said sheet and said intermediate layer on to the original.

' LODEWIJK' PIE'I'ER FRANS VAN DER GRINTEN. 10