US2630484A - Printing - Google Patents

Description

March 3, 1953 R K 2,630,484

' PRINTING Filed Nov. 26, 1947 @Lsz 49 I //VV[N TOR than GAO/1K Patented Mar. 3, 1953 PRINTING Josef Groak, London, England Application November 26, 1947, Serial No. 788,302 In Great Britain September 23, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires September 23, 1966 Claims.

This invention is concerned with improvements in and relating to printing, and consists of a new method and apparatus for making latent or visible images of all kinds such as monochromatic or heterochromatic reproductions of objects, i. e. symbols, scenes, inscriptions and other representations 'of all kinds; or the production of graphic representations of oscillatory phenomena such for example as oscillograms, cardiograms or radar indications.

An object of the present invention is to provide a method and apparatus whereby productions or reproductions may be made utilising a beam of corpuscular energy.

The method according to the invention of making images consists in scanning the surface of a material or body with a beam of corpuscular energy, said material or body consisting of, containing, or being coated with, a heat-sensitive substance or composition which can change its nature under the influence of the heat generated thereon by the scanning beam of corpuscular energy, in such a manner as to produce either direct colour change of said heat-sensitive substance or composition or to render Visible the colour of said heat-sensitive substance or composition, or to initiate colour change in or render visible the colour of, another substance or composition associated with the first-mentioned substance or composition, or to render said firstmentioned substance or composition capable of retaining, combining with, or reacting with a further substance or composition subsequently applied to said first-mentioned substance or com.- position to produce a coloured image.

Further according to the invention a process for making images consists in scanning the surface of a material or body with a beam of corpuscular energy, said material or body being coated with a heat-sensitive coloured substance which is adapted under the influence of the heat generated thereon by the scanning beam of corpuscular energy, to be transformed into a chemical or physical state in which it is substantially unafiected by a reagent capable of removing said coloured substance from said material or body, or destroying its colour, when said substance is in its initial state, i. e. before exposure to heat, and subjecting the said material or body to the action of said reagent, after exposure of the material or body to the action of the scanning beam of corpuscular energy.

In the production of representations or images of oscillatory or other phenomena such as can be expressed in the form of electrical signals, such signals are utilised to modulate the beam of corpuscular energy scanning the surface of the heatsensitive substance or composition.

In the making of reproductions of objects, symbols, scenes, inscriptions and other repre-' sentations of all kinds, the method according to the invention includes the preliminary step of scanning the representation to be reproduced, thereby producing electrical picture signals, and utilising the produced picture signals to modulate the beam of corpuscular energy scanning the surface of the heat-sensitive substance or composition.

Again a reproduction can be made utilising a patterned mask or stencil between a scanning beam of corpuscular energy and the surface of the heat-sensitive substance or composition. In some cases also, a patterned mask may be used in conjunction with the scanning beam for producing the efiects such as are outlined above, and the patterned mask may in such case be disposed on either side of the scanned surface of the heatsensitive substance or composition, in contact therewith.

A production or reproduction may also be made utilising thin material having two surface layers, comprising a first layer of coloured, heat-softenable substance or composition having a low melting point and adapted on melting to yield a liquid of low viscosity, and, on said first layer, a second and porous or absorbent layer of white or coloured substance or composition which remains substantially unafiected at temperatures in the region of the melting point of said first mentioned substance or composition and is of a colour different from that of said first-mentioned substance or composition; said production or reproduction being formed by scanning the first layer through the thin material with a controlled beam of cor puscular energy thereby causing parts of said first layer to melt and to penetrate through .the'

reproduction being formed by scanning the firstlayer through the thin material with a controlled v beam of corpuscular energy thereby causing partsof said first layer to melt and to penetrate through the porous second layer so that some of the undissolved dye dispersed therein is dissolved by the melted parts of said first layer to form a coloured image.

Again, a production or reproduction may be made utilising a material having a black or coloured surface, on which is superimposed a layer of a thermoplastic or readily meltable substance such as paraffin wax itself covered in turn by a layer of transparent or translucent, usually white, material such as a casein solution containing alumina, the image being formed by scanning the transparent or translucent surface with the beam of corpuscular energy so that parts of the layer of wax or other thermoplastic material is softened or melted and corresponding parts of the black or coloured surface become visible through the transparent or translucent layer.

The heat-sensitive substances or compositions, with which the material on which the reproduction is to be directly produced is coated, may consist of any known or suitable substances, or mixture of substances, which, under the influence of heat, change their chemical or physical nature to produce directly'a substantially permanent colour change.

For example, the following compositions using diazosulphonates can be used:

Example 1 The sodium diazosulphonate obtained from 1 dlethylamino, 4 amino, 3 ethoxyben- The sodium diazosulphonate obtained from 1 diethylamino, 4 amino, 3 methoxybenzene gms 1.1 8 methyl, pyrazolone gms 1.0 Thiourea gms 0.? Thiosinamine gms 0.7 Boric acid gms 1.0 Sodium bisulphite grns 0.1 Water mls 50 Example 3 They sodium. 'diazosulphonate obtained from 1 diethylamino, 4 amino, 3 methoxybenzene gms. 1.1 Acetoacetic acid anilide gms 1.0 Thiourea gms 0.7 Thiosinamine gms 0.7 Boric acid gms 1.0 Water mls 50 The surface of the material or body on which the production or reproduction is to be formed, is treated with one of the above aqueous compositions and allowed to dry at about 70 C. The material is then ready to be exposed to the action of heat generated thereon or applied thereto by the controlled beam of corpuscular energy scanning the treated surface of the material or body. The action of heat forms on the material a coloured image, dark violet blue with composition I., dark red with composition 2 and yellow with composition 3. After the coloured image has been formed the material is subjected to the action of daylight or ultraviolet radiation which decomposes the composition not already coloured by the action of the heat, forming a substantially pure White background.

The use of substances which give substantially permanent black products under the influence of heat is also contemplated, either alone or in conjunction with thermosensitive compositions which produce coloured products. Examples of such substances are as follows:

Silver stearate Silver palmitate Silver anthranilate Lead thiobenzoate Alternatively the material or body on which the production or reproduction is to be made may contain or be coated with two substances one of which, under the influence of heat, changes its chemical nature to yielda product which initiates, or catalyses, the formation of a substantially permanent colour change in the other.

For example, the following compositions may be used:

Erami lel Parts Water 100.0

Gelatine 10.0 An oxidising salt (such as nickel nitrate or sodium nitrate) 5.0 Phenolphthalein 0.5

Escamplez Aniline hydrochloride gms 9.8 Gelatine gms 0.026 Potassium nitrate gms 8.0 Water mls 99 Example 3 Nickel nitrate gms 5.0 Sodium thiosulphate gms 3.9 Sodium nitrate gms 3.6 Water mls 100 Gelatin, 1% aqueous solution mls 5 These contain oxidising salts, which, under the influence of heat, bring about a change in the colour of another constituent of the composition.

As an example of the use of a sub-stance or composition which changes its nature under the influence 0f the heat generated upon its surface by the controlled beam of corpuscular energy so as to be capable of retaining or combining with a further substance or composition subsequently applied thereto, may be mentioned the use of a material coated with a thin layer of wax. The wax is melted by the heat generated thereon, in amounts depending upon the variations of the controlled beam, and the melted wax absorbed by the material. The reproduction is then rendered visible by treating the surface of the material with water ink.

Other substances or compositions, which can be used to form a-heat-sensitive layer on the material or body on which the production or reproduction is to be made, include those which, under the. influence of heat, change their nature to yield compounds capable of either reacting with further substances to form coloured products or combining with coloured substances subsequently applied thereto. In the first of these two cases such further substances may be present in the heat-sensitive layer or they may be applied to the heat-sensitive layer after exposure of the latter to the source of heat, 1. e. the controlled beam of corpuscular energy.

For example the material or body is treated with a substance such as albumin which, under the influence of heat, is hardened and made substantially insoluble in water. The treated material or body is exposed to the controlled scanning beam of corpuscular energy, then treated with ordinary printing ink and finally treated with warm water which washes out the unexposed (soluble) portions of the alubumin coating, leaving a black and white or monochromatic reproduction of the object. This procedure is well adapted for use in the production of offset printing plates and letterpress blocks.

. Alternatively the material or body may be coated with a coloured substance such as dyed or pigmented albumin and the black and white or monochromatic reproduction produced directly by exposing the treated material to the action of the controlled scanning beam of corpuscular energy and subsequently washing out the unexposed, and therefore still soluble, portions of the coloured albumin by means of warm water.

An example of an apparatus suitable for use in producing a monochromatic positive reproduction of an object by the method according to the invention, is illustrated in Figure 1 of the accompanying drawings, whilst Figure 2 illustrates diagrammatically an apparatus for making a threecolour reproduction of a coloured object.

For convenience the apparatus may be considered to comprise an exposure unit and a printing unit. The exposure unit comprises a scanning device 5, which is conveniently a television pickup tube such as an iconoscope with associated time base circuits 6 and I by means of which the electron beam in the iconoscope 5 is caused to line-scan and to frame-scan respectively in wellknown manner. The iconoscope 5 performs the operation of scanning picture elements of the image of an object, formed on its mosaic by any suitable optical projection system (no-t shown) in the usual sequence of rows, to develop the picture signals required for the operation of the printing unit yet to be described,

The printing unit comprises a cathode ray tube 8 of such construction as to permit the introduction and withdrawal of strip material on which the reproduction is to be made, into and from the tube without destroying the vacuum therein. The strip material may be a strip of paper 9, bearing a coating of the heat-sensitive substance. The strip of coated paper 9, taken from a supply reel I8, is introduced into the tube 8 through a mechanical seal and a liquid seal, and emerges by way of the same or another liquid seal and a further mechanical seal. The seals are formed by a hollow cup-like container I I having a pair of horizontal opposed branches I2 and I3 at its upper end, the cathode ray tube at its lower end being provided with an open ended tubular extension I4 usually of rectangular section, which pro jects down into a body of liquid I5, usually mercury, in the cup-like container II. Other liquids may, however, be used for this liquid seal subject to their having no deleterious effect on the coated strip material 9. The tubular extension I4 is sealed into the container II at the point of entry 32'.

The outer ends of the branches l2 and I3 are flared, at least on the upper sides as shown at It and in the flared mouths thus formed are mounted pairs of resilient rollers I'I, I8, e. g. of soft rubber, adapted to rotate in pressure contact with one another, or with the strip material 9 when introduced between them, and also with the upper and lower, and also the end walls of the flared mouths of the branches I2 and I3. Screw means I0 are provided to urge the rollers. I1 and I9 towards one another and also into contact with the upper and lower walls of the flared mouths, and resilient linings of air-tight materials also adjustable if desired, may be provided on some or all of the Walls of the flared mouths. Thus are formed at least largely gas-tight mechanical seals between the atmosphere and the interior of the chamber bounded by the walls of the container ll.

Within the chamber II and the branches I2 and I3 are mounted rollers I9, 20, 2I and 22, the rollers 20 and 2| being disposed immediately below two opposite edges of the extension I 4 of the tube 8 and immersed in the mercury in the chamber II. These two rollers 20, 2I, are preferably formed hollow and are apertured to permit entry of the mercury into their interiors to partly overcome buoyancy and all the rollers are mounted on bearing pins (not shown) sealed in the walls of the container II and its branches l2 and I3.

Some degree of leakage may be expected to occur at the mechanical seals in operation and this is counteracted by the use of an exhaust pump (not shown) connected with tubes 23 to maintain a substantially constant air pressure in the branches I2 and I3, less than atmospheric though greater than that within tube 8. The mechanical seals described above permit the pressure diiierence between the interiors of the tube 8 and the container II to be kept small, with a corresponding limitation of the maximum height of the mercury column required in the liquid seal.

Within the lower part of the cathode ray tube 8 is mounted a supporting frame 24 carrying further guide rollers 25, 26, 21 and 28 for the strip material 9, two of said rollers 26 and 21 being disposed so that the plane of the part of the strip 9 extending between them is at right angles to the general direction of the electron beam 32.

In the case illustrated the envelope of the cathode ray tube 8 is formed in two separable parts adapted to be hermetically sealed together in well-known manner along a line of juncture indicated at 29 and the frame 24 carrying the rollers 25, 26, 21 and 28 is detachably mounted in the lower part of the tube 8 by means of wing nuts and bolts 30 passed through lugs 3| provided on the interior of tube 8, so that by opening the tube 8 and removing the frame 24 the first operation of threading a strip 9 through the apparatus is facilitated. The rollers 25 and 28 are carried in bearings at the ends of longitudinally adjustable rods 33 on the frame 24 whereby the direction of movement of the paper strip through the liquid seal and tubular extension I4 may be determined with accuracy.

The emergency end of the strip 9 is in driven engagement with a drum or pulley 34 in turn driven by a motor 35, e. g. through a belt or chain 36, at a predetermined speed such that the strip 9 is drawn thereby through the apparatus at a rate corresponding or related to the frame-scanning speed of the electron beam in the iconoscope. The time base I of the iconoscope 5 is preferably connected through the synchronising circuit 31 with the motor 35 for the purpose of synchronising the rate of movement of the strip 9 through the apparatus with the frame-scanning of the iconoscope 5.

In some cases the supply reel I0 may also be driven positively, to assist movement of the strip 9 at the required speed.

The upper part of the cathode ray tube 8, which in the example illustrated is of glass, is provided on the interior with an anode forming coating 38 of conductive material electrically connected to the power'supply source 39.

' A cathode 40 indirectly heated from a filament 4| is provided in the upper end of the tube 8 and both cathode 49 and filament 4| are connected with the power source 39. 42 is the usual electro-magnetic coil for focussing the electron beam, and 43 the grid to which is applied the scanning signal generated by the iconoscope 5 and amplified by an amplifier 44, and to which suitable bias is applied from the power source 39.

A time base circuit 45, synchronised, through the synchronising circuit 46, with the line-scan time base 6 of the iconoscope 5, is connected to a pair of deflecting coils 47 arranged to cause the electron beam 32 to line-scan in a direction transverse to the direction of movement of the strip material 9 as it passes between the rollers 26 and 21.

The production of a black and white or monochromatic reproduction of an object on the strip 9 is carried out using the above described apparatus as follows.

The image of the object formed on the mosaic of the iconoscope 5, is scanned by the electron beam therein and the picture signals thus obtained are passed through the amplifier 44 to the grid 43 of the cathode ray tube 8. The electron beam 32 of the cathode ray tube 8 is caused by the time base circuit 45 to line-scan, and the coated strip material 9 is drawn by the motor 35 through the apparatus at a speed similar or related to the frame scanning speed in the iconoscope 5.

The electron beam spot which represents the finite area of the electron beam 32 at the focal point 48, scans the coated face of the strip ma terial 9. The electron beam is so modulated by the amplified picture signals applied to the grid 43 that the point to point variation in the instantaneous intensity (i. e. the number of electrons impinging upon the area covered by the spot in unit time) of the scanning electron beam 32 is inversely proportional to the point to point variation in light and shade of the object.

Heat will be generated within the area covered by the electron beam spot due to electron bombardment of the coated strip material 9 within that area, and the amount of heat generated at any point will be proportional to the intensity of the spot at that point. The temperature to which the material within the area covered by the spot will be raised is dependent, among other factors, on the instantaneous value of the beamcurrent supplied to the cathode ray tube 8 and on the rate of scanning. In this example the rate of scanning is assumed to remain substantially constant.

The heat generated on the strip material 9 by the modulated electron beam 32, as it scans across the coated face of the material 9, causes some of the heat-sensitive'substance coated thereon to change colour. the actual extent of the colour change, i. e. the depth of colour,produced at any given point at any instant depending upon the beam current at that instant as determined by the instantaneous amplitude of the modulating picture signal generated by the iconoscope 5 and applied to the grid 43 of the tube 8. Since these picture signals are inversely proportional to the point to point variation in light and shade of the object, a positive reproduction. thereof will be produced on the surface of the strip material 9, the colour of the reproduction being that of the product of the change which the heat-sensitive substance on the strip 9 has undergone under the influence of heat.

The reproduction will be a positive or negative reproduction according to the nature of the iconoscope or other object-scanning device, and also according to the total number of stages of amplification used. When the object-scanning device is of a kind which, with apparatus as described above, would produce a negative reproduction, and a positive reproduction is required, the picture signals generated by the objectscanning device, and used for modulating the electron beam, in addition to being amplified may be inverted with the aid of any known form of electrical inversion means before being applied to the grid 43 of the tube 8.

In order to produce background pattern effects, a patterned mask consisting of thin metal, such for example as a fine wire mesh, or other foraminated material may be interposed between the incident electron beam and the stri material on which the reproduction is to be made.

Alternatively a patterned metal mask of good heat conductivity may, for this purpose, be placed immediately behind and in contact with the material on which the reproduction is to be made.

In the example described above the scanning beam 32 is stated to line-scan only, the strip 9 being moved during the scan at a speed related to the frame-scanning speed of the iconoscope beam.

It is to be understood, however, that the beam 32 may be arranged to both line-scan and framescan, the strip 9 remaining stationary during the operation of such scanning and being moved only when it is necessary to bring a fresh area of the strip into the sphere of influence of the scanning beam 32.

The method according to the present invention may also be applied to the reproduction of a coloured object in substantially its natural colours i. e. to the production of a heterochromatic reproduction of the object. For example a three-colour process, in which the coloured reproduction is built up using the three primary pigmentary colours yellow, red and blue, may readily be carried out, in a, manner yet to be described, using apparatus of the same general kind as that previously described with reference to Figure 1.

Heterochromatic reproductions in the form of coloured transparencies may also be produced using the above described apparatus. For this purpose contiguous areas of transparent strip material are treated with three different heatsensitive substances which, under the influence of heat, will change to yellow, red and blue respectively. Complementary colour filters, i. e. violet, green and orange respectively, are interposed one at a time between the iconoscope and the object to be reproduced and the respective sets of picture signals generated successively by the iconoscope are amplified and inverted and passed to the grid of the cathode ray tube 8, and three successive component reproductions in yellow, red and blue are formed on the contiguous areas of the transparent material. The individual coloured component reproductions are severed from the strip and cemented together in register to form a complete coloured transparent reproduction.

A further apparatus for the production of three-colour reproductions is shown diagrammatically in Figure 2 of the accompanying drawings. It comprises essentially three units of the kind shown in Figure 1 arranged in series one with another, these units being represented by means of blocks marked 49, 50 and 5|. Each of the three printing units 49, 50 and 5i comprises a cathode ray tube, and seals through which the strip material 9, on which the coloured reproduction is to be produced, is introduced into and withdrawn from the evacuated cathode ray tube. Associated with each of the printing units 49, 50 and 5| are material coating units 52, 53, 54, in which the strip material 9 is coated with a heat-sensitive composition of the diazo-sulphonate type hereinbefore described prior to its entry into the related tube 8. Three compositions A, B and C are used which are adapted to be turned yellow, red and blue respectively under the influence of heat; all three compositions being also adapted to be rendered substantially colourless by the action of daylight or ultraviolet radiation.

Also associated with each of the printing units are iconoscopes 55, 56 and 51 respectively, which are exposed towards the object with violet, green and orange colored filters 58, 59 and 60, disposed between them respectively, and the object. The iconoscopes are electrically connected through inverter and amplifier circuits, 6|, E2 and 63, with their associated printing units 49, 50 and 5| in such a manner that the picture signals generated by an iconoscope, as the result of cathode ray scanning of the mosaic on which the appropriate coloured image of the object is formed, may be inverted, amplified and applied to modulate the electron beam of the respective printing unit. Light radiation is excluded from the coating and printing units so that the coated strip material 9 is maintained in darkness until after it has been exposed to the influence of the electron beam at each printing unit. Ultra-violet radiation or mercury vapour lamps 64, 65 and 56 are provided for the purpose of bleaching the unaffected portions of the coated strip material after each exposure in a printing unit. Driving means 68 are provided as before for moving the strip material 9 through the apparatus at a speed related to the speed of frame scanning in the iconoscopes 55, 56 and 51, all arranged to operate from common frame-scan and line-scan time bases (not shown). The electron beams of the printing units are arranged to line-scan only, in planes substantially at right angles to the direction of movement of the strip material 9 through the printing units, by means of a common time base circuit (not shown) electrically synchronised with the corresponding line-scan time base circuit common to the three iconoscopes.

The heterochromatic reproduction is produced as follows. Strip material 9 is fed from the feed roller 69 to the first of the coating units 52 in which it receives a coating of the composition A. The coated material 9 then passes through the printing unit 49, in which it is exposed to the action of the electron beam modulated by the inverted and amplified picture signals generated by the iconoscope 55, the result being the formation of a yellow coloured component reproduction complementary to the violet coloured component image as seen by the iconoscope 55. By component reproduction is understood that coloured reproduction which, when combined with the other component reproductions, forms the required heterochromatic reproduction and by component image is understood a coloured image obtained by passing the normal white radiation reflected from the object through a colour filter. It will be understood that the diazo compound whose final, i. e. heat changed, pigmentary colour, is complementary to that of the particular colour filter disposed between the object and the iconoscope is used and that the picture signals generated by the iconoscope are electrically inverted before being used to modulate the electron beam in order to obtain the final reproduction in the correct combination of colours and against the correct white or dark background. If the picture signals were used without inversion and in combination with the composition whose final, i. e. heat changed, pigmentary colour is the same as that of the particular coloured filter used, the background would not be produced correctly since although red, yellow and blue light radiations combine in the correct proportions to give white light, the corresponding primary pigmentary colours combine to yield black.

The strip material 9 bearing the yellow component of the final reproduction is then passed from printing unit 49 past the ultra-violet or mercury vapour lamp 64, to bleach all unchanged heat-sensitive composition, and thence to the second coating unit 53 wherein it receives a coating of composition B, which turns red under the influence of heat. The second, red component of the final reproduction is formed in register with the previously formed yellow component by means of the electron beam in the second printing unit 50, which is modulated by the amplified and inverted picture signals generated by the iconoscope 56. The material 9 is then passed under the ultra-violet or mercury vapour lamp 65 and into the third coating unit 54 wherein it receives a coating of the composition C, which turns blue under the influence of heat, and the third, blue component of the final reproduction is then formed in the printing unit 5| in register with those formed previously, and the material 9 bearing the final three-colour reproduction is passed under the third lamp and over the driven roller 67.

It will be understood that the apparatus shown in Figure 2 of the drawings is well adapted for the production on strip material of a plurality of coloured reproductions of the same stationary object, it being necessary merely to ensure that the three-coloured component reproductions are printed in register one with another, and this may readily be achieved by suitable control of the speed of movement of the strip 9 and adjustment of the idler and tension rollers provided in the printing units for the purpose of adjusting the exposed portion of the strip relative to the plane of movement of the electron beam.

One or more further colours, or black, may be applied to correct or modify the three-colour reproduction produced by the method last described by providing further coating and printing units in conjunction with the appropriate iconoscopes, colour filters and inverter circuits.

The production of heterochromatic reproductions of a coloured object or scene on transparent material, for example, colour cinematograph films, may also be carried out by the method according to the invention.

The production of single or a small number of heterochromatic reproductions of a stationary coloured object may also be carried out by operating the iconoscopes 55, 56 and 51 one after the other, the separate sets of picture signals gener ated by the iconoscopes 55, 56 and '1 being utilised to modulate the respective electron beams of the printing units 49, 5t} and 55, in timed relationship with one another such that the yellow, red and blue component reproductions are produced in correct register on the strip. In other words, the picture signals from the iconoscope 55, operating with the violet filter 58, are generated and utilised directly in the production of the yellow component reproduction in the printing unit 59, and the picture signals from the corresponding iconoscopes 58 and 51 are generated and utilised respectively in the production of the red and blue component reproductions only when the already made yellow component reproduction has reached the correct position in the printing unit 50;, and the combined yellow and red comp-onent reproduction has reached the correct position in the printing unit 5|.

To produce a single cinematograph film of stationary or moving objects in natural colours, at least three coloured component reproductions must be made on a transparent strip in register with one another in the manner described above with reference to Figure 2 and since it is not possible to proceed by scanning the same area of the transparent material with three electron beams simultaneously, it is necessary to take account of the inevitable time lag which must exist due to the need for the film to travel from the field of one scanning electron beam to the field of the next.

The formation of the three coloured component reproductions in correct register with one another may be accomplished by employing means providing a delay or time lag, introduced between the second and third iconoscopes and the corresponding cathode ray tubes to which they are connected. By this means the picture signals necessary for modulating the first electron beam scanning the heat-sensitive substance which will turn yellow under the influence of heat are transmitted, immediately after inversion and amplification, to modulate the first electron beam, those required for modulating the second electron beam scanning the red heat-sensitive substance are delayed until the yellow component reproduction formed previously reaches the correct position with respect to the second electron beam and those necessary for modulating the third electron beam scanning the blue heat-sensitive substance are delayed still further until the combined yellow and red component reproductions have reached the correct position with respect to the third electron beam so that the blue component reproduction is formed in register with the previously formed yellow and red reproductions.

Alternatively in the production of such a coloured film, two of the component reproductions may be produced simultaneously on opposite sides of the transparent film, previously suitably coated, and the third component reproduction produced subsequently and after application of the third coating composition, but in correct register with the two component re-- productions previously produced, a suitable delay or time lag circuit or mechanism being interposed between the third iconoscope and the respective electron beam so that the third component reproduction is formed in correct register with the other two.

Again, in the production of a heterochromatic reproduction of a stationary or moving coloured object on a film suitable for cinematograph pro jection, the component reproductions may be produced simultaneously upon three separate thin transparent strips and the three strips subsequently brought together so that the simultaneously produced components are in register with one another. Alternatively two films may be employed, two colour component pictures being produced by treatment of the suitably coated two sides of one of the films simultaneously and the third coloured component produced upon the other film, the two films being brought together with the three corresponding component. reproductions in correct register with one another. Since all the colour component reproductions of a single picture are, in this case, produced simultaneously, the provision of, a delay or time lag is unnecessary.

It will be understood that, in some cases the the time required for bringin about the colour change in the heat-sensitive substance may be. such as to make it desirable to scan with. the electron beam at speeds considerably lower than the scanning speeds normally employed in general television practice. For this purpose the picture signals generated by the iconoscopesmay be recorded, usually optically, and the optical records may be made use of subsequently, for the purpose of regenerating at a speed lower than that, at which they were recorded, the required picture signals for modulating the electron beam. The rate of line-scanning of the elec tron beam and also the rate of frame-scanning thereof, or the rate of movement of the strip material as the case may be, are of course correspondingly reduced.

It will be understood: that a heterochromatic reproduction of a stationary object may be made using a single iconoscope, or other object-scanning device, in conjunction with the violet, green and orange colour filters, the object being separately scanned in turn through each of the filters to generate the picture signals corre-- sponding to the three coloured. component repro ductionsv respectively.

In a convenient apparatus, particularly suit-' able for use in conjunction with a single iconoscope, the chamber containing the cathode raytube includes a. carrier belt extending between the outside of. the chamber, through aliquid'seal and, if necessary, a mechanical seal of the kind previously described, and the interior of the chamber. The inner end of the carrier belt is connected with a spring driven roller, the arrangement being such that the belt, together with for example, paper sheets coated with a heat-sensitive substance, may be drawn into the chamberby the, spring driven roller to bring a paper sheet into position in the field of'scan of the electron beam. In such case the electron beam is arranged to both line and frame-scan the coated surface in synchronism With the. line and frame scanning of the object.

It will be understood that the scanning pickup tube or iconoscopemay be connected either directly, or through a radio link with a corresponding printing unit, and the monochromatic, or heterochromatic reproductions may be produced either close to or remote from the object, or scene to be reproduced.

In some cases in the production of monochromatic or heterochromatic reproductions, by the method according to the invention, it may be an advantage to preheat the heat-sensitive substance or composition to a temperature in 13 the region of but below that at which the heatsensitive substance or composition commences to change its colour, or nature, under the infiuence of heat, so as to reduce the amount of heat, required to be generated by the modulated scanning electron beam, to raise the temperature of the heat-sensitive substance to the point at which its change in colour, or nature, occurs.

This preheating may be carried out in a number of ways. For example the surface of the heat-sensitive substance may be scanned with anunmodulated electron beam (i. e. a beam of constant intensity) just before it is scanned by the modulated electron beam, or in cases where a liquid seal is traversed by a coated band on its way to the highly evacuated chamber, the liquid in the liquid seal may be maintained at a temperature to which the coated band is to be preheated. Any other convenient means of preheating, if necessary thermostatically controlled, may however be used.

I claim:

1. Apparatus for making images, said apparatus including an evacuated chamber; a thin basematerial bearing two surface layers comprising a first layer of coloured heat-softenable material of low melting point and capable of yielding a melt of low viscosity, and a second layer, on said first layer, said second layer being of a differently coloured material which is permeable O to the material of the first layer when the material of the first layer is melted, said material being located in said chamber; means for forming an electron beam within said chamber; means for controlling the intensity of said electron beam by modulating said beam; and means for causing the modulated beam to scan said first layer, through the thin base-material on which it is coated, so as to melt parts of said first layer which thereby penetrate through the permeable second layer, so as to form a coloured image against a differently coloured background formed by the said second layer.

2. Apparatus for making images, said appara tus including an evacuated chamber; a thin basematerial located in said chamber and bearing two surface layers comprising a first layer of a heat softenable material of low melting point and capable of yielding a melt of low viscosity and, on said first layer, a second layer, permeable to the material of the first layer, when the material of the first layer is melted, and containing an undissolved dye dispersed therein, which dye is soluble in the material of said first layer; means for forming an electron beam within said chamber; means for controlling the intensity of said electron beam by modulating said beam; and means for causing the modulated beam to scan the first layer through the thin base-material on which it is coated, so as to melt parts of the material of said first layer which thereby penetrate through the permeable second layer, and dissolve some of the undissolved dye dispersed in said second layer, so as to make a coloured image.

3. Apparatus for making a heterochromatic reproduction of a coloured object by making the required number of coloured component reproductions one after the other and all in register with one another, said apparatus including a plurality of evacuated chambers; a strip on which said reproduction is to be made; means for moving said strip through each of said chambers in succession; sensitising means associated with each of said chambers for treating said strip with the appropriate one of an equal plurality of heat- 14 sensitive materials prior to the entry of said strip into a chamber; means for forming discrete electron beams in each of said respective chambers; means for color-scanning said object; means for controlling the intensity of each of said electron beams by modulating each beam with the appropriate set of component-colour picture signals derived from the color-scanning of said object; means for causing the modulated electron beams to scan the surface of the treated strip, whereby to generate heat on said surface by electron bombardment thereofand thereby to change the nature of elemental parts of the corresponding heat-sensitive material and thereby to produce a combination of said elemental parts against a background comprising said material in its unchanged form; and means for treating said strip subsequent to leaving a chamber so that the unchanged heat-sensitive material is substantially colourless and insensitive to any subsequent electron bombardment.

4. Apparatus for making a heterochromatic reproduction of a coloured object containing white or off-white parts by making the required number of coloured component reproductions one after the other and all in register with one another, said apparatus including an evacuated chamber; a surface treated with a heat-sensitive material capable of being changed by heat so as to produce a component reproduction of the required colour with-in said chamber; means for scanning the representation to be reproduced through a colour filter, whose colour is complementary to the pigmentary colour of the particular component reproduction to be produced, whereby to produce a set of electrical picture signals; means for inverting the set of picture signals thus produced; means for generating an electron beam within said chamber; means for modulating said electron beam with said set of inverted picture signals; means for causing the modulated electron beam to scan said surface, whereby to generate heat thereon by electron bombardment thereof and thereby to change the nature of elemental parts of said material so as to produce a comb-ination of said elemental parts against a background comprising said material in its unchanged form; and means for subsequently treating said surface so that the unchanged heat-sensitive material is substantially colourless and insensitive to any subsequent electron bombardment.

5. Apparatus for making a heterochromatic reproduction of a coloured object including white or near white parts, by making the required number of coloured component reproductions one after the other and all in register with one another, said apparatus including an evacuated chamber;

a surface treated with a heat-senstive material which, under the influence of heat, can change its colour to that of the particular component reproduction to be made and which, in its initial state can be rendered substantially colourless by light radiation; means for locating said surface within said chamber; means for scanning said object through a. colour filter whose colour is complementary to the pigmentary colour of the particular component reproduction to be made, whereby to produce a set of electrical picture signals; means for inverting the set of picture signals thus produced; means for generating an electron beam within said chamber; means for modulating said electron beam with said set of inverted picture signals; means for causing the modulated electron beam to scan said surface, whereby to generate heat on said surface by electron bombard- 15 mentl thereof and thereby to cause a colour change in elemental parts of said substance; and means for subsequently exposing the scanned surface to light radiation, so as to render substantialIy colourless those parts of the heat-sensitive material unafiected by the modulated electron beam.

JOSEF GRO'AK.

REFERENCES CITED Number UNITED STATES PATENTS Name Date Morehouse Mar. 22, 1932 Finch Feb. 22, 1938 Finch Aug. 27, 1940 Shankweiler Dec. 3-1, 1940 Carlson Mar. 17, 1942 Bruce Nov. 10, 1942 Marriott Apr; 27, 1943 Goldsmith Apr. 10, 1945 Guerderson' Jan; 7, 1947

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