BE878134A - METHOD AND APPARATUS FOR FORMING IMAGES - Google Patents

Description

       

  Method and apparatus for forming images

  
The present invention relates to a method for forming images on a heat-developable image forming sheet, of the type which is made photosensitive by pre-exposure heating and which is exposed to form a latent image therein, and then hot developed to obtain a visible image. The invention also relates to an apparatus for implementing this method.

  
A hot-developable imaging sheet which is made photosensitive by pre-exposure heating and which is exposed to form a latent image therein, and then heated to obtain an image (a sheet which will be referred to hereinafter simply by "imaging sheet") can be provided with an image visible only by the dry process, and the imaging sheet is not photosensitive before it has been rendered by prior heating .

   Consequently, when only a specific area of the imaging sheet is made photosensitive by preheating and is exposed and then developed hot, an image is formed only in the determined area, but the other areas, which do not have not been made photosensitive at the start, remain non-photosensitive Consequently, the above image-forming sheet allows to record an additional image by preheating and exposing a determined section of an area on which has not recorded an image before, and then developed it by heating.

  
Making such an imaging sheet photosensitive by prior heating is referred to herein as "hot activation", and transforming a latent image into a visible image by heating is hereinafter referred to as "development

  
hot ".

  
In a conventional image recording method employing a process of preheating, exposure and hot developing, for the image forming sheet, it is difficult to obtain a sharp image which is finely contrasted and fine contours. If such a sharp, finely contrasted and well-defined image can be formed on a desired area of the imaging sheet, in a short time, then it is possible to increase the usefulness and interest of the sheet. image formation by allowing an additional image to be recorded therein and thereby providing convenient and useful recording means.

  
The invention aims:
- an image forming method and apparatus which greatly increases the sensitivity of the image forming sheet, so as to obtain a finely contrasted image with sharp outlines, and so as to decrease the time required to obtain a visible image
- an apparatus for forming an image which makes it possible to manipulate the image forming sheet in a lighted room and which is therefore of a simple structure, and which makes it possible to record and develop information on the forming sheet image, by the dry process;

  
- an image forming apparatus which allows, in case the image forming sheet has a number of image forming areas, to remove from the apparatus the sheet on which an image is recorded in the one of the imaging areas, then return this sheet to the apparatus to re-record an image in an imaging area which has not previously received recording.

  
It has now been found that by exposing an image forming sheet in the cooled state, after having previously heated it to make it practically photosensitive, its sensitivity is increased so as to obtain a visible image which is finely contrasted and has contours. clearly demarcated.

  
The subject of the invention is therefore a method for forming a heat-developable image, on an image-forming sheet, which is made photosensitive by heating prior to exposure, and is exposed to form a latent image there, then is developed hot to obtain a visible image, characterized in that after having previously heated the imaging sheet to make it photosensitive in the given area, at least the area rendered photosensitive is cooled before exposure. The invention also relates to an apparatus for implementing this method.

  
Any image forming sheet can be used for the purposes of the invention, as long as it is of the type which becomes photosensitive upon heating prior to exposure and forms a latent image upon exposure, then produces an image visible by hot development.

  
A typical example of this type of imaging sheet is a material called "photosensitive dry matter

  
  <EMI ID = 1.1>

  
minus an oxidizing agent which is an organic salt of silver, and a reducing agent of the silver ion. A more specific example of this imaging material will be given below.

  
A particular example of the imaging sheet for the purposes of the invention is a composition which consists essentially of an oxidizing agent which is an organic non-photosensitive silver salt, a silver halide, or a source halide ion capable of forming the silver halide by reaction on the oxidizing agent based on organic silver salts, a reducing agent for a silver ion, a binder and an ion source mercury. Another example of such a material for an imaging sheet, which can be used for the purposes of the invention, is a composition which consists essentially of an organic, non-photosensitive silver salt, serving as an oxidizing agent. , a reducing agent for a silver ion, a binder, a source of mercuric ion, a carboxylic acid and / or a sensitizing dye.

  
The first composition is described, for example, in U.S. Patents No. 3,802,888, 3,764,329 and
4,113,496, while the latter is described, for example, in United States patent No. 3,816,132 and in the patent application published in Japan under No. 127,719 / 76.

  
As examples of organic non-photosensitive silver salts, of the aforementioned type, there may be mentioned long chain fatty acid silver salts, or silver salts which are organic compounds having an imino group or a group mercapto. The above silver salts include, for example, silver stearate, silver behenate, benzotriazole silver salts, 5-nitrobenzotriazole silver, 5-nitrobenzimidazole silver, silver saccharin, phthalazinone silver, 2mercaptobenzoimidazole silver and 3-mercapto-4-phenyl-1,2,4triazole silver. Among them, the salts are particularly preferred.

  
  <EMI ID = 2.1>

  
gent and the silver behenate. The organic silver salt used as an oxidizing agent is used in an amount of approximately 0.1 to 50 grams per m, and preferably in an amount of 1 to 10 grams per m. As the aforementioned silver halide, mention may be made of silver chloride, silver bromide, silver iodide, silver chlorobromoiodide, silver chlorobromide, silver iodobromide, chlorobromide silver and their mixtures.

  
Silver halide can be used at a rate of

  
0.1 to 40 mol% approximately and preferably at a rate of 0.5

  
at around 20 mol%, based on the total amount of

  
silver salt serving as an oxidizing agent.

  
As examples of a source of halogen ions which are capable of forming a silver halide by reacting on the organic salt of silver serving as oxidizing silver, there may be mentioned a reducible halogenated compound having the structure -CONX- or <EMI ID = 3.1> as described in U.S. Patent No. 3,764,329. Another example of such a source is the halo-

  
  <EMI ID = 4.1>

  
bromine or iodine); organic halides, a particular element of which is one of Ga, Sn, Pb, P, As, Sb, Bi, Se and Te. One can use such a halide for example:

  

  <EMI ID = 5.1>
 

  
  <EMI ID = 6.1>

  
  <EMI ID = 7.1>

  
  <EMI ID = 8.1>

  
sies among bromine, iodine, iodochloride, iodobromide and bromochloride? complexes of halogenated molecules and particular compounds, such as p-dioxane? and organic halogenated compounds, such as triphenylmethyl bromide, triphenylmethyl chloride, iodoform, 2-bromoethanal,

  
  <EMI ID = 9.1>

  
amount of this halogen ion source to be used is between 0.1 to 40 mol% approximately and, preferably between 0.5 and

  
  <EMI ID = 10.1>

  
organic silver serving as an oxidizing agent.

  
A reducing agent suitable for reducing silver ions is a hindered phenol, in which one or two sterically large groups are attached to the carbon atom or to the carbon atom contiguous to the carbon atom carrying the group. hydroxy, so as to sterically hinder this hydroxy group. As examples of such hindered phenols, there may be mentioned 2,6-di-tert-butyl-4-methylphenol, 2,2'methyleneene (4-methyl-6-tert-butylphenol), 2,4,4- trimethyl-

  
  <EMI ID = 11.1>

  
hydroxy-3'-tert-butyl-5'-methylbenzyl) -4-methylphenol. The reducing agent may be used in an amount of 0.1 to 100% by weight and preferably in an amount of 1 to 100% by weight, based on the organic silver salt serving as the oxidizing agent.

  
As a source of mercuric ion, there may be mentioned mercuric acetate, mercuric behenate, mercuric benzoate and mercuric halides.

  
As the organic carboxylic acid, behenic acid, stearic acid, etc. are suitable. The amount of mercuric ion source to be used is 0.1 to 7% of the amount of silver used by the imaging sheet.

  
As a sensitizing dye, merocyanine can be used, and examples of such dyes include those mentioned in "Organic Chemicals List", published by Nippon Kanko Shikiso Kenkyusho (Japan Photosensitive dye institute), pages 102-105, 1969, and pages 25- 27, 1974.

  
As binders, mention may be made of poly (vinyl butyral),

  
  <EMI ID = 12.1> <EMI ID = 13.1> of cellulose, polyvinyl acetate, cellulose acetate propionate, cellulose acetate butyrate, polystyrene

  
and gelatin. [deg.] Among them, it is poly (vinylbutyral) which is particularly suitable as a binder. The binder can be used alone or in the form of a mixture of two or more. of them. It is better to use the binder in an amount such that the weight ratio of the binder to the organic silver salt serving as an oxidizing agent is between approximately 10/1 and 1/10 and, better still, between 1.2 / 1 and 1 / 2.

  
The composition of the image forming sheet for the purposes of the invention may further contain, if necessary, modifiers, such as a toner for a silver image, an agent preventing background blackening and a sensitizer in addition to the above ingredients. As toner for a silver image, there may be mentioned for example phthalazinone and

  
phthalimide. As an agent preventing background darkening, there may be mentioned, for example, tetrabromobutane, hexabromocyclohexane and tribromoquinalidine.

  
The above composition is applied as a coating on a transparent support, such as a polyethylene film, a cellulose acetate film, a polyester film, together with the above-mentioned binder, and a suitable solvent.

  
The thickness of the coating is between 1 and 1000 u approximately

  
  <EMI ID = 14.1>

  
dients of the composition respectively in two or more layers, if desired. The sheet thus obtained is not photosensitive under normal lighting conditions, and

  
it can be handled in a lighted room. When a

  
given area of this sheet is heated beforehand in the dark, this area is made photosensitive.

  
The preheating temperature to make the imaging sheet photosensitive is usually between 80 and 130 [deg.] C, preferably between 90 and 120 [deg.] C. The lower the heating time, the longer the temperature. To make an additional recording, it is necessary that only a desired area, on which one wishes to form an image, be made photosensitive by the preliminary heating. This can be achieved by using a heating plate or block whose heating area is limited to the imaging area of the imaging sheet, <EMI ID = 15.1>

  
red or far infrared rays, which is arranged so that the irradiation range can be limited.

  
If an additional recording is not required, there is no need to limit the heating zone.

  
According to the invention, the prior heating is followed by cooling. As will result from embodiments of the invention, as described below, it is desirable that the temperature of the imaging area of the imaging sheet be made, by this cooling, as low as possible in relation to the preheating temperature. It is better that the temperature of the imaging sheet is, after it has been cooled, lower

  
  <EMI ID = 16.1>

  
lower of this temperature is room temperature.

  
Cooling of the imaging sheet can be achieved for example by placing a metal block or the like, having excellent thermal conductivity, in contact with the sheet, or by blowing air at room temperature, or gas at low temperature on the sheet.

  
For the exposure of the imaging sheet,

  
it is possible, for example, to use a method in which transmitted or reflected light from a subject is projected by projection lenses onto the photosensitive layer of the imaging sheet, so as to expose it to a bright image of the subject. For hot development, the same process can be used as for preheating. The heating temperature for development is between 100

  
and 150 [deg.] C, preferably between 110 and 130 [deg.] C. It is also possible to use the pre-heating means as hot development means, or to use these two means separately.

  
As different conditions are required for the preheating and for the hot development, respectively, in many cases, it is better to provide first heating or preheating means and second heating means for the hot development. In order to form an image on the image forming sheet, at a determined position, and so as to make an additional recording thereon, it is desirable to provide the image forming sheet with <EMI ID = 17.1>

  
transfer means and fixing means, by means of which

  
it can be moved to a prescribed position and kept there fixed for each treatment. In addition, it is better to use means for controlling the operation of the heating means, cooling means, exposure means and hot development means and, if necessary, transfer means and fixing means, as well as their operating times and their operating temperatures.

  
In the image forming apparatus according to the invention, which uses the image forming sheet which is made photosensitive by heating prior to exposure, which is exposed to a light image to form a latent image, and which is developed hot to give a visible image, cooling means are provided for cooling the pre-heated area of the imaging sheet, in the time interval between pre-heating and exposure. ; in addition, means are provided for fixing the imaging sheet to fix it so that

  
its imaging zones to be preheated, cooled, exposed and developed hot are maintained in position in the respective processes. At least two of the means constituted by the pre-heating means and the means

  
cooling, the exposure means and the hot development means are aligned to allow parallel processing by these means.

  
In the appended drawings given solely by way of example:
Figure 1 is a perspective diagram showing the external appearance of the image forming apparatus according to the invention; Figure 2 is a sectional view along line A-A of Figure 1; Figure 3 is a sectional view along line B-B of Figure 2; Fig. 4 is a perspective view illustrating the relationship between the means for transferring the imaging sheet and a tubular body; Figure 5 is a perspective view illustrating, by way of example, the drive mechanism for a frame-shaped member of a heater;

  
  <EMI ID = 18.1> Figure 6 is a perspective view illustrating the state in which the portfolio is placed at an insertion window of the imaging sheet Figures 7, 7A and 7B are sectional views representing examples of the tubular body

  
  <EMI ID = 19.1>

  
perspective of frame-like elements of the tubular body of Figures 7 and 7B seen from the side of an imaging sheet; Figures 9A to 9C are sectional views, respectively, showing other modified shapes of the tubular body of a heater; Fig. 10 is a perspective view showing means for forming an optical path for reading purposes; Figure 11 is a diagram showing the relationship between. the frames of the imaging sheet and the double exposure control elements;

    Figure 12 is a circuit diagram illustrating an example of a means preventing the formation of a double image Figure 13 is a diagram showing the control systems and air passages for heating with hot air and a cooling with air at low temperature; FIG. 14 is a sectional view illustrating another example of a tubular body in the case of heating with hot air and cooling with air at low temperature; Figure 15 is a sectional view illustrating another example of the tubular body in the case of heating by a gas; FIG. 16 is a sectional view illustrating another example of a tubular body in the case of heating by infrared rays;

    Fig. 17 is a chart of times showing the respective positions of the frames of the imaging sheet and the dual exposure control device of pre-heating, cooling, exposure and hot development, during the record ; Fig. 18 is a perspective view showing an example using ratchet wheels to position an imaging sheet; Figure 19 est. a sectional view illustrating the body <EMI ID = 20.1>

  
tubular and the parts associated therewith in a treatment system having only one position; and

  
FIGS. 20 and 21 are graphs giving characteristic photosensitization curves, using as a parameter the degree of cooling of the image-forming sheet, after preliminary heating, but before exposure.

  
The image forming apparatus according to the invention has the appearance

  
exterior as shown, for example, in Figure 1. An envelope 12 is mounted on the rear portion of a base 11 and an object holder 13 is formed on the front portion of the base 11. A part 12a for introducing the light reflected by the object holder 13 in the envelope 12 is mounted thereon, so as to extend above the object holder 13. A control panel 14 is arranged on an upper panel 20 of the base 11 in a corner near the front. Various keys are arranged on the control panel 14 for controlling the image forming apparatus. On the front face of the base 11 is mounted a cover
16 for covering a window for inserting an imaging sheet. A screen 15, on which an image can be projected, is provided on a front face 15 of the envelope

  
on one of its sides.

  
As shown in Figures 2 and 3, a lens

  
18 of projection, which is part of the exposure means, is arranged in the envelope 12, in the center thereof. Leaf
19 for forming an image is placed so as to be able to move, to a position where an image of the object projected by the lens 18 is formed, that is to say to an image exposure position. The sheet 19 is held by a wallet 21, as illustrated in Figure 4, and the wallet is supported by transfer means.

  
The transfer means are arranged, as illustrated in Figures 2 and 3 and on an enlarged scale in Figure_4.

  
  <EMI ID = 21.1>

  
seen the slide 13 is tilted slightly forward and

  
a base plate 22 of the base 11 is also slightly oblique towards the front. As shown in Figure 4, supports
31a, 31b, 32a and 32b are mounted on the base plate, in the vicinity of its four corners.

A threaded shaft 33 is rotatably mounted between the

  
  <EMI ID = 22.1> supports 31a and 32a, so as to extend in a direction perpendicular to the front face of the base 11. One of the end portions of the threaded shaft 33 projects from the support
31a and a motor 34 for displacement in the direction of the Y is mounted on the support 31a on the side of the projecting end portion of the shaft 33. This shaft 33 is driven by a motor
34 drive, in the direction of Y. The shaft 33 is screwed into a threaded hole drilled in a portion 36 of the support formed at one of the end portions of a slide 35, sliding in the direction of Y , which extends in a direction perpendicular to the direction of the threaded shaft 33, so that the slider 35, which slides in the direction of the Y, is moved by the rotation of the threaded shaft 33 along the axis of this last.

   Between the supports 31a and 32a is also mounted a guide rod 37 adjacent and parallel to the shaft
33 threaded, and the guide rod 37 is engaged in a bore formed in the portion 36 forming a support, whereby the slide 35 is held so as to be able to be moved without turning. Similarly, a guide rod 38 is mounted between the support 31b and 32b and is engaged in a hole made in a portion 39 forming a support formed at the other end portion of the slide 35, which allows the latter to move parallel to the base plate 22, in the longitudinal direction of the shaft 33. It is assumed that this direction is the direction of the Y axis, for example. A couple of pieces

  
41 and 42 supports are fixed to the two end portions of the slide 35 which can be moved in the direction of the Y. A threaded shaft 43, extending in the direction of the X, is mounted for rotation between the parts 41 and 42. One end of the threaded shaft 43 extending along the direction of the X protrudes from the part 41 and a motor 44 following drive

  
the direction of the Xs is fixedly mounted on the part 41 on the side of the projecting end of the shaft 43. This shaft 43 is driven by the motor 44. The guide rods 45 and 46, adjacent and parallel to the threaded shaft 43 extending in the direction of the X, count parts 41 and 42. A slide 47 sliding in the direction of the X, is crossed by the shaft
43 and by the guide rods 45 and 46. The slide 47, which moves in the direction of the X, and the threaded shaft 43 which extends in the direction of the X, mesh with each other.

  
  <EMI ID = 23.1>

  
of slide 47 to the right and to the left, that is to say along the direction of the X axis.

  
The slide 47 carries a support 48 having an arm on which the leaf holder 21 is pivotally mounted, as illustrated in FIGS. 2, 4 and 6. Two positioning pins 97, 98 planted on the support 48 are engaged in openings made in a marginal portion of the image forming sheet 19, and the marginal portion of the sheet 19 is pressed by the sheet holder 21, on the support 48. In this case, a helical spring is mounted around the pivot of the holder leaf:
21, although this is not shown, and thanks to this spring the sheet holder 21 is pressed towards the support 48, while the sheet 19 is interposed between them. In the wallet 21 are provided holes for receiving the pins 97 and 98 for positioning.

   To facilitate mounting and dismounting of the imaging sheet, an intermediate portion of the outer marginal portion of the sheet holder 21 projects outward, and constitutes a part 99 for operation. By pressing the part 99, the sheet holder 21 can be easily rotated, against the elastic force of the above-mentioned helical spring.

  
The cover 16 is also arranged to be closed automatically by a spring. When the image forming sheet 19 is mounted on the support 48, or is removed therefrom, the portfolio 21 is brought forward by the motor 34 ensuring the displacement in the direction of the Y, until arriving at the position outermost, where the support 48 pushes the spring 16 forward, through an opening 101 (Figure 6) formed in the front face of the base 11. The cover 16 rotates to open, against of the elastic force of the spring (not shown) so that the sheet holder 21 comes out of the opening 101. This position is a reference position of the portfolio 21 where the image forming sheet 19 can be mounted on the support 48, or be removed therefrom.

   When the support 48 is brought back into the base 11, the cover 16 pivots automatically to cover the opening 101. This thus automatically excludes any penetration of unwanted light into the device.

  
It is better to provide a guide with which the sheet
Image formation 19 held in the wallet 21 is <EMI ID = 24.1>

  
takes for example upper and lower guide plates 103 and 102 fixed to a support 49 for a photographic unit, as illustrated in FIGS. 2 and 4. The distance which separates the plates 103 and 102 gradually decreases as a tubular body 53 , carrying the projection lens 18, is close and the image forming sheet 19 is guided towards the exposure or heating position, under the tubular body 53, passing between the guide plates 103 and 102.

  
In addition, another plate 104 to guide the sheet

  
19 for image formation, after it has passed the tubular body 53, is fixed to a vertical wall 51 of the support 49, so that it extends backwards, from the vicinity of the body tubular 53, under the sheet 19, that is to say on the side of the base plate 22. It is better for these guide plates 102 to 104 to be made of thin elastic sheets of synthetic resin or of phospho-bronze. The guide plates need not always be flat; they can also be curved. Thanks to these guides, the sheet 19, pressed by the wallet 21, on one side, can be brought in securely

  
to a position where it will be photographed without being bent. The guidance is not limited to that which has just been described in a particular way, but may also be of another type. Thus, for example, in the case of a sheet 19 which is curved, it is possible to guide it by belts or rollers rotating towards the position where it must be photographed, while straightening the curvature of the sheet 19.

  
The imaging sheet 19 has several imaging areas called frames 107 arranged in the form of a matrix, as illustrated in Figure 4. The sheet 19 is mounted on the support 48 so that the Any of the frames 107 can be brought exactly to the exposure position or to the heating position. The support 48 is maintained at the aforementioned reference position where the sheet holder 21 is in its outermost position. To achieve this, we can for example, as illustrated in Figure 4, provide a room
108 protruding attached to the slide 47, moving in the direction of the X, so that immediately before this slide 47 reaches the support 42, the protruding part 108 comes into contact with a microswitch 109 attached to the support 42, <EMI ID = 25.1>

  
a protruding part 111 is fixed to the support 41 of the slide

  
35 sliding in the direction of Y and, immediately before this slider 35 reaches the support 32, the part 111 comes into contact with a microswitch 112, interrupting the sliding in the direction of Y. In this way, by exciting the microswitches 109 and 112, the support 48 is stopped at the reference position, that is to say in the position where it is most outward. As motors 44 and 34, drive motors capable of controlling the extent of the displacement are used.

  
  <EMI ID = 26.1>

  
step and, by the number of pulses applied to the motors, one can determine the extent of movement of the sheet 19, from the aforementioned reference position, in the direction of the X axis and in the direction of the Y axis, and detect a precise position of this sheet 19. In the manner described above, we bring that of the frames or areas 107 of image formation that

  
  <EMI ID = 27.1>

  
position.

  
The sheet 19 can take the form not only of a microfilm, on which several frames are arranged in the form of a matrix, but also that of a film in the form

  
roll, on which several frames are placed side by side or even a cut film on which only one frame is formed. Sheet 19 of. microfilm type can be held by the wallet on two sides, or on more than two sides, as well as on one side. However, from the point of view of bringing the sheet 19 into contact with the end face of a heating device over the entire surface, and from the point of view of

  
seen from the pressing of the sheet 19 on the tubular body 53, it is better for the sheet 19 to be held on one side only.

  
Referring now to Figures 2 to 4, to illustrate an example of the heating means, cooling means and exposure means, which form the main part of the apparatus according to the invention, and to describe the arrangement of each of them to the heating, cooling and exposure positions. In the mode of exposure shown, the heating means comprise preliminary heating means, heat development means, which are distinct, and these two means are described in the form of solid bodies. <EMI ID = 28.1>

  
at high temperature, for example of metal blocks. Similarly, the cooling means are constituted by a solid cooling body, for example by a metal block. As illustrated in Figures 3 and 4, the support 49 of the inverted L-shaped photographic unit is fixedly mounted on the base plate 22, at the rear thereof. The vertical wall 51 of the support 49 rises from the base plate 22 at right angles and an upper horizontal plate 52 of the support 22 goes, in the direction of the front face, being practically parallel to

  
the base plate 22. In the upper plate 52 is provided

  
a hole 55 in which the tubular body 53 is properly adjusted and is fixed.

  
The tubular body 53 consists, for example, of a metal block in which is formed a vertical hole 54 passing right through, in the direction of the base plate 22,

  
and the lens 18 is arranged in the hole 54. In the tubular body 53 are formed, to the left and to the right of the hole 54, recesses 57, 57a and 58 which open out towards the base plate 22, each of these recesses having a dimension corresponding to each frame 107 or image-forming zone of the sheet 19. The peripheral edge of each recess is shaped on all sides to the shape of the frame, to constitute part of the means for fixing the sheet 19 during heating.

  
Opposite the recesses 57, 57a and 58, are arranged

  
a first heating device 61 intended for preheating, a cooling device 61a and a second heating device 62 intended to be used for development by heating. The heating devices 61 and 62 and the cooling device 61a are carried respectively at one of the ends of rotary levers 63, 63a and 64 which are perpendicular to the vertical wall 51 of the support 49, as illustrated in FIGS. 4 and 5. The levers 63, 64 and 63a protrude rearwards through an opening 65 formed in the wall
51 vertical to the support 49. The levers 63, 64 and 63a are pivotally mounted, respectively, at an intermediate location, on an axis 95 having two legs 93 and 94 rising from a console 66 fixed to the rear of the wall 51 vertical.

   The rear end portions of the levers 63, 64 and 63a are pivotally mounted on cores 69, 71 and 69a solenoid plungers 67, 68 and
67a, mounted on consoles 66 respectively. By ordering the <EMI ID = 29.1>

  
and 63a so as to bring the heating devices 61 and 62 and the cooling device 61a against the sheet 19. The frames of the sheet 19 are held respectively and fixed by the frame-shaped element of the recess 57 and by heating device 61, by the frame-shaped element

  
of the recess 59 and by the heating device 62 and by the frame-shaped element of the recess 57a and

  
by the cooling device 61a. The end faces of the heating devices 61 and 62 and of the device 61a for re &#65533; cooling, on the side of the sheet 19, have approximately the same dimension as each frame of the sheet 19, but are a little larger than the recesses 57, 58 and 57a.

  
In the foregoing, each of the means for fixing the sheet has been described in the form of a frame, but these fixing means must only fix, during at least the heat treatment, the image-forming zones of the sheet 19 which are subjected to preliminary heating, cooling, exposure to light and development to heat. This is why the fixing means can also be in the form of plates or the like. However, from the point of view of uniformity of treatment, it is better for at least one of each of these fixing means to be formed into a frame. In the case where a layer of photosensitive material is formed on a substrate, it is better that side of the layer of photosensitive material of the imaging sheet is framed. The same applies to the fixing means for the exposure described below.

  
As shown in Figures 2 and 3, the hole 54 of the body
53 tubular is threaded and a tubular body 55, whose peripheral outer face is threaded and which carries the lens 18, is screwed into the hole 54. By rotating the tubular body 55, the position of the lens 18 is adjusted relative to the sheet 19 which is in contact with the end face of the body
53 tubular, thanks to which it is possible to obtain a fine control of the position for which the image of an object is formed. The position of the tubular body 55 and, consequently, the position of the lens 18, is fixed by tightening a nut 56 screwed onto

  
the tubular body 55. The dimension of the open end of the hole 54, on the side of the sheet 19, corresponds to the surface of a frame of the sheet 19 and the peripheral edge defining the open end is also used as a forming frame.

  
part of the means for fixing the sheet 19 during the exposure.

  
As shown in FIG. 5, a rotary lever 72 is interposed between the levers 63a and 64 while being parallel to them

  
so as to be sure that, during the exposure, the sheet 19 is retained in a precise manner in the position where the image of an object is formed. The lever 72 carries, at one of its ends, a second hollow frame 73, intended for the exhibition and is pivotally mounted at the other end on a solenoid 74 mounted on a console 66, while in addition the lever 72 is pivotally mounted in an intermediate position on an axis 95 carried by two legs 93 and 94 rising from the console 66. By controlling the solenoid 74, the lever 72 is rotated, whereby the sheet 19 is pressed by the frame 73, in order to expose, on the peripheral edge similar to a frame of the holes 54 of the tubular body 53 which constitutes the other clamping frame. Consequently, the sheet 19 is clamped between these two frames and is held in a fixed position.

   In this case, the second frame 73 is such with respect to the hole 54 that the sheet 19 is pressed on the tubular body 53. 73 hollow frame can be not only

  
in the form of a frame, but also in the form of a plate, but it is better for it to be in the form of a hollow frame, so that a path of light from a source can form therein.
162 of light, for reading by a reading device which will be described later.

  
FIG. 3 illustrates a preferred arrangement in which the center-to-center distances from the successive imaging areas or frames of the sheet 19 of the recesses
57 and 57a of the hole 54 and the recess 58, are equal and in which these recesses 57 and 57a, this hole 54 and this recess 58 are aligned, the means of prior heating, the means of cooling, the means of exposure and the hot developing means being placed respectively in correspondence with successive areas of image formation. FIG. 9A illustrates a variant of the means for fixing the sheet 19 when the heating means are pressed against it. These fixing means comprise a first and a second frame clamping between them the sheet 19. The second frame
146, intended to press the sheet 19, surrounds the device 62 <EMI ID = 30.1>

  
frame 146 on the first frame formed by the end face of the recess 58, for heating, which is formed in the tubular body 53, one of the zones or frames of the sheet 19 is held by the two frames on both sides. At the same time, even if the temperature of the heating devices 62 becomes too high above a given value, it is possible to avoid the diffusion of heat to the adjacent zones or frames of the sheet. In addition, fixing the sheet 19 during heating makes it possible to uniformly heat the entire imaging area, to obtain the same sensitivity over the entire area and to avoid deformation of the sheet 19 which becomes otherwise produce on heating. This is effective in increasing sensitivity.

  
The second frame 146, illustrated in FIG. 9A, can also be used with the cooling device 61a. It is particularly preferred to activate the heating device 61 or the cooling device 61a after having fixed the sheet 19 in position using the two frames, that is to say fixing means consisting of the first frame 146 and of the end face of the recess of the tubular body 53. In addition, if the frame for heating, the tubular body, the frame for heat development and / or the frame for cooling are respectively the size of one of the areas or frames of the imaging sheet. , and are fixed or are formed in a unitary structure, the arrangement is simplified in comparison with that which is obtained in the case where they are distinct and operate separately.

  
In general, when the sheet has several frames, they are aligned and, therefore, it is desirable that at least the first heating means of the exposure means and the second heating means are also aligned. In particular, it is important that the four means which are the first heating means, the cooling means, the exposure means and the second heating means are aligned.

  
The first heating means, the exposure means and the second heating means are usually adjacent, but other means can also be interposed between them, if necessary.

  
The imaging area of the sheet, after it <EMI ID = 31.1>

  
photosensitive, is moved from a frame and cooled by the above-mentioned cooling means, then shifted from another frame to an exposure position, where the image of an object placed on the object-holder 13 is projected onto this frame of the sheet 19 brought into the exposure position. For this purpose, a plate
114 supporting a lamp is fixed to the underside of the lower end portion of the part 12a, obliquely above the object holder 13, as illustrated in FIG. 2. On the plate 114 are mounted side by side sockets 116 of lamps intended to receive fluorescent oblong lamps 118 - The plate 114 is arranged so that the lights coming from the fluorescent lamps 118 are directed towards the object-holder 13.

  
The light reflected by the object placed on the object holder
13 goes towards the part 12a, in a direction roughly perpendicular to the base 11. A window 121 for receiving light is formed in the part 12a and opens towards the object holder 13. A cover 122 is fixed to the window 121 by extending downward therefrom so as to shield against any outside light. After entering the room 12a, the light reflected by the object falls on a reflector 123 mounted in the room 12a and making an angle of 45 [deg.] Roughly with the base plate 11 and the light reflected by the reflector 123 is reflected by reflector 125 to go to the lens 18 for projecting the tubular body 53, along the optical axis of this lens.

  
In the part 12a and in the envelope 12, there is also a tubular box 126 forming a screen for the light which goes from the inside edge of the cover 122 by surrounding the optical paths comprised between the reflectors 123 and 125 and between the reflector
125 to a shutter 129.

  
As a result, the image of the object on the object holder
13 is reflected by the reflectors 123 and 125 then projected by the lens 18 on the sheet 19. In order to determine the duration of exposure of the sheet 19 to the image of the object, it is provided on the box 126 forming a screen , on the side of the reflector 125, the shutter 129 in order to allow passage to the optical path 128 and to interrupt this path on the side of the projection lens 18. The shutter 129 is driven for example by a solenoid 131 so as to open and close. The shutter 129 is opened by known automatic exposure detection means, although not shown, for a suitable exposure time. It goes without saying that the layer of photosensitive material of the sheet 19 is opposite the hole 54 of the tubular body 53.

  
The probability of accidental re-recording on an already recorded frame, that is, the formation of a double image, can be prevented in various ways. An effective method is to have a strip of reflective material on at least one side, preferably on all sides, of the object holder
13 roughly corresponding to an imaging region of the sheet 19, and to photograph the tape at the same time as

  
  <EMI ID = 32.1>

  
that a highly reflective frame 133 having a high reflection factor is formed on the marginal part of the object-holder 13 from all sides. That is to say that the object-holder 13 consists of a substrate in a color having a low reflectance factor, for example of black color, and is surrounded by a frame 133 square in a white material, by example of aluminum foil or the like, having a high reflectance, and the internal dimension of which is equal to the external dimension of the object-holder 13 corresponding to a frame.

   An object is placed in the highly reflective frame 133 and positioned with respect to this frame 133, and a density recording as a function of the reflection factor of the frame 133 is always provided on the inner marginal part of the image forming area of the sheet
19 corresponding to the marginal part of the object. The highly reflective frame 133 can also be obtained by a projecting conformation on one side or on all sides.

  
To detect an already recorded frame, there is a position located at a distance from a frame of the image 19 from the recess 57 of the tubular body 53 on the opposite side.

  
at hole 54, a detector to avoid the formation of a double image which verifies whether or not the margin of the object is photographed on the frame subjected to verification. This detector preventing the formation of a double image is composed, for example, of a photodiode or of a similar device 134 emitting light, and of a phototransistor or of a similar photodetector 135, between which is interposed the sheet 19.

  
The light emitting device 134 is mounted on an extension of the tubular body 53, while the photodetector
135 is supported so that it can be advanced and removed from the sheet 19 in the same manner as the heater 61, although this is not shown. When the quantity of light received by the photodetector 135 is less than a prescribed value, it is decided that the frame has already

  
received a recording.

  
We will now describe in more detail the means to avoid the formation of the double image. Thus, for example, as shown in FIG. 11, in the case of a frame which has already received a recording, a frame 181 of high density recording forms around the frame 107. corresponding to the highly reflective frame 133 of the object-holder 13 described previously with reference to FIG. 1. Devices
134x and 134y light emitters are arranged opposite the parts in the X direction and in the X direction of the frame
181 recorded respectively and 135x and photodetectors
135y are arranged opposite the light emitting devices 134x and 134y respectively, although they are in the shadow of the sheet 19 in FIG. 11.

  
The light emitting devices 134x and 134y are arranged opposite the photodetectors 135x and 135y respectively, the sheet 19 being interposed between them as illustrated in FIG. 12. In this example, the photodetectors 135x and 135y are phototransistors whose collectors are respectively connected to an input terminal of a comparator 182, via diodes 132x and 132y forming an OR circuit, the other input terminal of the comparator 182 being supplied by a reference voltage.

  
If one of the photodetectors 135x and 135y comes opposite the recording frame 181, the output signal of the photodetector supplied to the comparator 182 increases beyond the reference voltage and the comparator 182 provides an output signal

  
low level. This low level output signal is applied to a 183 PNP transistor to make it conductive and a diode

  
184 emitting light lights up with the result that a photodetector 185 associated with the diode 184 to constitute a photocoupler receives information indicating that the frame has already

  
received a recording.

  
In the event that a couple of photodetectors and available <EMI ID = 33.1>

  
light emitting devices to detect a frame which has already received a recording is provided for each of the X directions

  
and Y. of box 181, as described above, even if the couples

  
photodetectors and light emitting devices are

  
a bit out of position relative. in sheet 19, at least one of the pairs comes opposite the frame 181, which ensures the detection thereof.

  
Above, we used the light transmitted by the frame 181 photographed on the sheet 19 to avoid the formation of a double image, but it is also possible to use for this purpose the light reflected by the frame 181. It is also possible to use the light transmitted or reflected by an image photographed in the frame, without having to provide the frame
133 very reflective nor to photograph it. These means for preventing the formation of a double image are preferably arranged in alignment with the first heating means, the exposure means and the second heating means; in particular, it is better than the means to avoid the formation of a double image, than the first heating means, than the cooling means, than the exposure means and

  
that the second heating means are aligned.

  
When the sheet 19 has been moved in the direction of the X axis to put the frame to be recorded in the position corresponding to the means for preventing the formation of a double image, as illustrated in FIG. 3, the device checks 134 light emitter and by the photodetector 135 if the frame has already received a large number of records or. When it is detected that the frame has not yet received a recording, instructions are given to means for transferring the sheet 19 and the latter is moved a distance corresponding to a frame to the preheating position where the frame is heated for activation. The frame of the sheet 19 thus made photosensitive by activation is then brought to the cooling position where the previously heated frame is cooled.

   The frame of the sheet 19, thus cooled after being activated, is again moved to the exposure position where the image of an object is projected on the frame.

  
The frame thus exposed is then shifted by a distance from a frame to the position of development by heating where the latent image carried by the frame is developed by heating, which completes <EMI ID = 34.1>

  
the registration process performed on a frame.

  
According to the invention, it is better in order to obtain a uniform image formation over the entire area of each frame, to provide pressure means so, when the means of prior heating or the means of development by heat are constituted by a solid body at high temperature or when the cooling means are constituted by a solid body, being able to apply a fluid pressure to the heated or cooled part of the sheet on the opposite face

  
to that where the means are found in the form of solid bodies.

  
Pressure is created using the fluid after, or at the same time as the sheet is fixed in position by the fixing means, preferably while the means using a solid body are in contact with the sheet. As fluid,

  
a gas can be used for this purpose; compressed air is particularly preferred. By uniformly pressing at least one imaging region of the sheet by the fluid toward the heating or cooling solid body, the entire imaging region is brought into close contact with the face of the solid body, with uniform contact pressures, thereby obtaining uniform heating or cooling. As a result, the uniform preload heating makes the imaging area photosensitive over the entire area, while the uniform heat development or uniform cooling provides an increase in sensitivity without dispersion, thereby ensuring image imaging. excellent reproducibility. In addition, it is possible to avoid deformation by

  
the heat from the imaging area caused by the

  
pressurized and by heating the sheet, using heaters during heating. It is desirable that the pressure applied to the sheet, using a fluid, be between 100 and 1000 mm of H2O.

  
As a preferred example of means for pressing the sheet, mention may be made of holes 136, 136a and 137 for entering the

  
gases, arranged respectively in the tubular body 53, so as to go from the bottoms of the recesses 57, 57a and 58 outwards, as shown in FIGS. 3 and 7. The orifices 136,
136a and 137 communicate respectively through the conduits 138,
138a and 139 with bellows 141, 14 la and 142 serving as sources of pressurized gas. On bellows 141, 141a and <EMI ID = 35.1>

  
142, are mounted pivoting solenoid plunger cores.
143, 143a and 144, so that when the solenoids are excited, the bellows contract, which sends air to the recesses 57, 57a and 58. By the conduits which correspond to them.

  
An arrangement for expanding and compressing the bellows 141 is as illustrated for example in FIG. 3. One end of the bellows 141 is fixed to a mounting plate 301, itself fixed to the base plate 22, and the solenoid 143 is also mounted on a mounting plate 302 fixed to the base plate 22. By exciting the solenoid 143, one end of a rod 303 is rotated around an axis 306 carried by two tabs projecting from the plate 302, which presses the other end of the bellows 141 towards the plate 301 and compresses the bellows 141. When the solenoid 143 is de-energized, the bellows 141 is expanded by the spring force of the solenoid 143 in order to return to the initial position. The bellows 141a and 142 are also expanded and compressed by the same arrangement as that which has just been described.

   As the source of pressurized gas, it is preferred to use a pump and, in such a case, the pressure can be properly applied by controlling the pump.

  
Figure 7 is a sectional view on an enlarged scale illustrating the position in which the heating devices 61 and 62, the cooling device 61a and the second frame 73 for exposure are pressed on the tubular body 53 with interposition of the sheet 19. When pressure air is applied to the recesses 57, 58 and 57a in the position where the sheet 19 is pressed on the tubular body 53 by the heating devices 61 and 62 and by the cooling device 61a, the zones of the sheet 19 underlying the recesses 57, 58 and 57a are pressed uniformly on the heating devices 61 and 62 and on the cooling device 61a. Consequently, the. sheet 19 is heated and cooled uniformly over all of its areas.

   The dimensions of the recesses 57, 58 and 57a are chosen to be larger than those of a frame including its margin, so that the marginal parts of the recesses 57, 58 and 57a do not touch the image-forming area, ie that is to say, the marginal portion of each recess is outside the projected image of the highly reflective frame 133 intended to avoid the formation of a double image.

  
In the example of FIG. 7, plates 145, 145a and 145b for distributing the pressure are disposed respectively in the recesses 57, 57a and 58 in an intermediate position opposite the sheet 19. These plates can be made of metal sintered, for example brass or stainless steel, or spongy, porous material, or it may be plates each having perforations distributed in a more or less uniform manner over the entire surface. In short, the pressurized air supplied by inputs 136, 136a and 137 is distributed by the plates
145, 145a and 145b so as to be applied uniformly to sheet 19.

  
However, the above-mentioned dividing plates can be dispensed with by modifying the positions of the inlet ports for the pressurized gas, that is to say by providing the orifices
136, 136a and 137 for entry of pressurized gas into the side walls of the recesses. 57, 57a and 58, as indicated by dashed lines in Figure 7 or by placing the gas inlet orifices as far as possible from the sheet
19.

  
As heating means and as cooling means, particular preference is given to solid bodies at high temperature, and a solid body at low temperature, intended to come into direct contact with the sheet during heating and cooling respectively. In addition, it is desirable that the heating devices and the cooling device are of a dimension greater than the internal dimension of each of the recesses 57, 58 and 57a having marginal portions in the form of a frame on all sides, but not are not large enough to overlap the adjacent frames and to retain the sheet 19 in combination with the marginal portion in the form of a frame (of each of the recesses 57, 58 and 57a.

  
FIG. 8 represents, in perspective, the tubular body 53 and the side on which the devices 61 and 62 are provided. <EMI ID = 36.1>

  
frame 73 for the exhibition. If the tubular body 53 is made of a material having a relatively high thermal conductivity, such as brass, the heating by the heating devices 61 and 62 and by the cooling device 61a is absorbed by the tubular body 53 having a large capacity. thermal crossing the sheet 19, at the marginal portions of the heating devices and the cooling device, which <EMI ID = 37.1>

  
adjacent frames.

  
FIG. 9 illustrates variants of the means for heating or uniformly cooling a single frame of the sheet 19. In FIG. 9A, a second frame-shaped element 146 is provided around the heating device 62 in order to press the sheet 19 onto the tubular body 53. Such an element
146 in the form of a frame prevents thermal diffusion towards the adjacent frames, even if the temperature of the heating device 62 rises unduly and, associated with the pressing of the sheet
19 on the tubular body 53 by the heating device 62, makes it possible to obtain a double seal, so that even if the pressure of the gas under pressure increases, gas does not escape between the sheet 19 and the tubular body 53 , which ensures more uniform heating.

  
In the above, positive pressure is applied

  
to sheet 19 for pressing it, but it is also possible to apply a vacuum to it on the opposite side, to obtain the same results as those obtained by pressing it. FIG. 9B shows, by way of example, an arrangement of this type in which the gas inlet orifice 137, formed in the tubular body 53, in order to open into the recess 58, is no longer provided, the open end of the second frame-shaped element 146 on the opposite side of the sheet 19 being covered with a plate 147 and a shaft 148 for driving the heating device projecting from the plate 147 by a gas-tight packing 149 . A suction orifice 151 is formed in the plate 147 and air located in the second frame-shaped element 146 is sucked through a duct 152 communicating with the orifice 151.

   As a result, the pressure inside the second frame-like member 146 is negative relative to the outside pressure, so that the sheet 19 is pressed uniformly on the heater 62. In FIG. 9C, as the sheet 19 is drawn towards the side of the heating devices, when a vacuum is applied to the sheet, as indicated above, a recess 153 having approximately the same size as the recess 58 of the tubular body 53 is formed in the heating device 62 on the side of the sheet 19. A porous thermal agent 154 having a high thermal conductivity fills the recess 153 and an orifice 151 of depression is formed in the heating device 62 and opens into the recess 153.

   By sucking air through the orifice
151, the sheet 19 is attracted to the heating device and the heat from this device 62 is propagated by the arrangement 54 to the sheet 19. As agent 154, a sintered metal made of stainless steel or the like can be used. Figures 9A to 9C illustrate

  
hot developing means, but these arrangements can also be applied by means of pre-heating or

  
by means of cooling. Although reference has been made above to pressing means using vacuum, pressing using positive pressure is more practical in terms of image quality obtained.

  
Heating or cooling the sheet 19

  
can be carried out by a heating process bringing a gas at high temperature into contact with the sheet, or exposing the sheet to irradiation with infrared rays or having a wavelength going beyond infrared, or by a cooling process bringing a gas at low temperature into contact with the sheet, as well as by the process described above for bringing a solid body into contact at high or low temperature. temperature directly with the imaging sheet.

   As a method of bringing the sheet into contact with a gas at high or low temperature, there may be mentioned a method by which gas at high or low temperature is blown onto the sheet, as well as a method by which a solid body at high temperature or at low temperature in the vicinity, but at a distance, from the sheet, so as to heat or cool gas lying in the very narrow air gap defined between the solid body and the sheet. It is also possible to combine the process using a solid body and that using gas or infrared rays or the like.

  
FIG. 13 shows, by way of example, an arrangement for blowing hot air or low temperature air onto the imaging sheet, for heating or cooling it. A hot air generator 351 is composed of generators 351a and 351b. In the generator 351a, air which is attracted by a duct 353, using a pump 352, is normally sent, by passing through a filter 354 collecting dust, into a reservoir 355 of heated air. In this case, the pump 352 is placed under the control of a part 357 of a

  
  <EMI ID = 38.1>

  
so that the pressure in this tank is maintained at any desired value. The air from the reservoir 355 is always blown by a blower 358 into a device 361 for heating the air via a duct 359. A unit 364 for heating the device 361 is controlled by the output signal from the outlet part 363 of an element 361 for detecting the temperature placed in the tank 365 and the heated air

  
at a predetermined temperature is returned from the device
361 for heating the tank 355, by means of the blower 358. In this way, the air in the tank 355 is controlled and remains at a temperature given in advance.

  
When the sheet 19 is heated or cooled, it is held in advance between the tubular body 53 and the second frame-shaped member 146.

  
In the case where the sheet 19 is heated beforehand, three-way solenoid valves 365 and 366 are open to allow the communication, on the one hand of an air duct 368 and 368a, and on the other hand starts from a duct 372 and 372a for air, and an air blower is driven so that the heated air from reservoir 365 is blown into the recess

  
57, from a jet 369a via the blower
367 from line 368a, solenoid valve 365, line 368 and

  
from the air inlet 369, which heats the sheet 19 beforehand. Then, the air thus blown into the recess

  
57 returns to the reservoir 355 through the orifice 371 for the exit of the air, through the conduit 372, by the solenoid valve 366, by the conduit 372a, by the heating device 361 and by the blower 358.

  
By blowing heated circulating air onto the sheet
19, by the jet 369a, the sheet 19 is activated by heat so as to make it photosensitive.

  
Then, when the sheet 19 is cooled, the solenoid valves 365 and 366 are opened so as to obtain communication between, on the one hand the conduit 368 and the conduit 368b and, on the other hand, the conduit 372 and the conduit 372b, and the air blower 367 is driven. In this case, the air coming from outside via a duct 368a passes through a blower 367a, the duct
368b, the solenoid valve 365, the conduit 368 and the orifice 369 from <EMI ID = 39.1>

  
the sheet 19. The air thus blown into the recess 57 is evacuated towards the outside by the outlet orifice 371, by the conduit 372, by the solenoid valve 370 and by the conduit 372b. In this way, air sucked in from the outside is blown onto the sheet 19 along the jet 369a, whereby the sheet 19 is cooled after having been previously heated.

  
The generator 351b of the generator 351 of hot air is arranged in the same way as the generator 351a described above. Hot air from generator 351b passes through a duct
373 and into an inlet 374 and goes into the recess 58 to heat the sheet 19, then is returned to the generator 351b through an outlet orifice 375 and through a conduit 376. In the way

  
which has just been described, the circulating and hot air coming from the generator 351b is blown on the sheet 19, according to the jet
374a, which means that the sheet 19 is developed under heat. After the heat development process, the sheet 19 can also be cooled by blowing outside air using jet 374a in the same manner as in the case of cooling after activation by heating.

  
The temperature of the hot air produced by the generator
351a is usually set to stay at a pre-set value between 80 and 200 [deg.] C, which is somewhat

  
higher than the temperature at which sheet 19 should

  
be heated. Similarly, the temperature of the hot air produced by the generator 351b is generally maintained between 100 and 220 [deg.] C.

  
As air for cooling, outside air is used at room temperature to cool the sheet.

  
19 at a temperature between 60 [deg.] C and room temperature. It is also possible to set the cooling temperature to a value given in advance of less than 60 [deg.] C, for example between 0 and 60 [deg.] C, using a cooling device. It is also possible to adopt the arrangement illustrated in FIG. 14 according to which the hot air and the cooling air having passed through the orifices 369 and 374 are blown, respectively, into the recesses 57 and 58 by distributing plates 377 and 378 made of porous material. In addition, the hot air and the cooling air can also be blown onto the sheet 19 on the side opposite to the tubular body 53.

   In this case, frame-shaped elements are provided opposite the recesses 57 and 58, on the other side of the sheet.
19, and hot air and cooling air are respectively sent into these frame-shaped elements and are blown onto the sheet 19, if necessary by means of distributor plates.

  
FIG. 15 illustrates a variant of the arrangement for heating the sheet 19, by bringing it into contact with a gas.

  
In Figure 15, high temperature solids are

  
put as close as possible to sheet 19, but do not move with it. The sheet 19 is held between the body

  
53 tubular and the second element 146 in the form of a frame and, during operation, the heating devices 61 and 62 are placed in the immediate vicinity of the sheet 19 in order to heat it. It is believed that the heating of the sheet 19 is effected by a combination of the phenomena of conduction, convection and radiation.

  
As heating means, infrared rays or far infrared rays can also be used. Thus, for example, as indicated in FIG. 16, second elements 132 and 146 in the form of a frame are disposed respectively opposite the recesses 57 and 58 of the tubular body 53, on the other side of the sheet 19 In these second elements 132 and 146 in the form of a frame are arranged generators
401 and 406 of infrared rays respectively. The generator
401 infrared rays includes, for example, a device
402 for heating and an element 403 emitting infrared radiation, for example lanthanum, chromite or the like,

  
which is arranged on the side of the sheet 19. When the heater 402 is operated, the infrared rays irradiate the sheet 19 and heat it. In the recess 57

  
is housed a detector 404 of infrared rays which detects infrared rays coming from the sheet 19, in order to locate the temperature thereof. In such a case, it is also possible to provide a filter 405 for intercepting the wavelength components of the infrared rays which are not absorbed by the sheet 19, i.e. the ray wavelength components infrared which are not necessary for heating the sheet 19 in order to ensure detection only of the component which has heated the sheet 19. The other generator

  
  <EMI ID = 40.1> <EMI ID = 41.1> has just been described. The second elements 132 and 146 in shape

  
frame can constitute a unitary structure with the second element. 73 in the form of a frame arranged opposite the hole 54

  
of the tubular body 53.

  
In the case where, for heating, we do not put a

  
solid body in direct contact with the sheet 19, as it is

  
the case for the heating means illustrated in FIGS. 15 and
16, no deformation of the sheet is caused by direct contact of the latter with the solid body and the surface

  
of the solid body on the side of the sheet 19 need not be made smooth.

  
The heating and cooling means have been illustrated above. As first heating means for pre-heating and as second heating means for

  
heat development, we can use different types of heating means, but it is better to use means

  
of the same type. In general, it is better to use

  
heating means of the type using contact

  
a solid heating body and the imaging sheet. The preferred heating means are those of the type bringing a solid body directly into contact with the imaging sheet, and of the type bringing a gas into contact with the sheet regardless of the heating means. In addition, it is desirable to fix an image forming area of the sheet by fixing means or cooling processes.

  
We will now describe a particular example of operation in which the position of the cooling means and the moment when they operate differs from what has been described so far. The cooling after the preliminary heating can also be carried out without providing the cooling device 61 and the recess 57a. Thus, for example, as shown in Figures 7A and 8A, air at room temperature or cooled air is sent by an air blower
(not shown) in the hole 54 by inlet orifices 136b formed in the peripheral face of this hole 54 and is blown on the sheet 19, then leaves by outlet orifices 136c formed respectively at the periphery of the hole 54 opposite inlet ports 136b.

   It is also possible to adopt an arrangement as shown in dashed lines in FIG. 7A, according to which on the side opposite to the tubular body 53, relative to the sheet. <EMI ID = 42.1>

  
  <EMI ID = 43.1>

  
form of frame in the center thereof, and being parallel to it so that air at room temperature or cooled air is blown onto the sheet 19, from this duct
136d. In this case, the cooling can also be carried out at the same time on the side of the tubular body 53. It is also possible to use an arrangement as illustrated in the figure

  
7B, according to which, after having put the heating device 61 out of contact with the sheet 19, following the preliminary heating of its image-forming zone, air being found in the bellows 141 is sent into the 'recess 57 and directed on the sheet 19 to cool it.

  
The embodiment shown in Figures 1 to 3 is intended that information recorded in the context of the sheet 19 placed in the exposure position are projected

  
on an enlarged scale, to be read. For this purpose, a box
161 containing a light source is mounted on the base plate 22, below the second element 73 in the form of a frame in order to achieve the exposure shown for example in FIG. 2. In the box 161 is provided a light source 162 for reading and, if necessary, a cooling fan 163 which is arranged on the side of the base plate 22. Light rays coming from the light source 162 are reflected by a concave mirror 164 on the reflector 165, parallel to the base plate 22, then deflected by the latter towards the side of the exposure position. The optical axis of the light thus deflected at right angles is aligned with the axis of the second element
37 in the form of a frame and a hole 53.

   Above the reflector 165, a lens 166 is provided, the light beam from which passes through the element 73 in the form of a frame and irradiates the zone of the sheet 19 which is underlying the hole 54. The light transmitted by the sheet 19 passes through the projection lens 18 and is guided on the side of the reflector 125.

  
Between the shutter 129 and the tubular body 53 is provided a rotating mirror 168 which can come in and out of the optical diagram of the image of an object, as illustrated in the figure.

  
10. The rotating mirror 168 is pivotally mounted on a plate 169 fixed to the front face of the casing 12. The shaft of the mirror
168 is driven by a solenoid 171. During recording, the mirror. 168 is kept away from the optical path between the <EMI ID = 44.1>

  
reflector 125 and the tubular body 53, as indicated by the solid lines in FIG. 2. During reading, the mirror 158 is rotated to put it on the aforementioned optical path, so that it makes an angle relative to it, as indicated by the broken lines in FIG. 2. Consequently, the light having passed through the tubular body 53 is reflected by the mirror 168 and still reflected by the reflector 172 mounted on the mounting plate 169 , by the way

  
roughly parallel to the front face 15, then passes through a projection lens 173 with enlargement, then being deflected by a reflector 174 practically at a right angle,

  
so as to be projected onto the screen 175 located on the front face of the envelope 12. During recording, the screen 175 is covered with a cover plate 176, so that there is no there is no light coming from the screen 175. During playback, the cover plate 176 is removed under the control of a solenoid 177 and an image recorded in the imaging area positioned just below the hole

  
54 is projected onto the screen 175, on an enlarged scale.

  
There is a difference between the optical path going

  
from the object-holder 13 to the sheet 19 and the optical path going from the sheet 19 to the screen 175. In a case as described above, the recording on the sheet 19 is clearly projected by the lens 173 on the screen 175 on an enlarged scale. The screen

  
175 need not always be provided on the front face, but it can be placed in any other place. In any case, by incorporating the enlargement lens 173 in the optical path, it is possible to project with magnification the information recorded in any of the frames of the sheet.
19, without putting the sheet 19 in a different position from where it is for the photograph and without mounting the sheet
19 on a separate projector. This is how, while recording information, you can read it immediately after recording it. To be sure that during reading only one frame of the sheet 19 is in the correct position, the sheet 19 is pressed by the second frame-shaped element 73 on the marginal part of the hole 54 of the tubular body 53.

  
As will be understood from the above, the addition of projection means on an enlarged scale requires at least one light source, a lens or a mirror condensing the light and <EMI ID = 45.1>

  
a screen, the other elements being superfluous.

  
The unit for controlling the transfer of heating and the exposure of the sheet 19, the application of a pressure fluid to the sheet 19 and so on, is arranged in a housing 205 placed in the envelope 12, and on the left side, as shown in figure 3. The above command is successful. killed using for example a microcomputer. The temperature control for the heating devices 61 and 62 is also carried out by a microcomputer, while the temperature control of the cooling device 61a can also be natural cooling.

  
In this case, the effect of natural cooling is increased if a radiator fin is provided on the cooling device. It is also possible to use an arrangement for sending air or water to the cooling device, or for cooling the latter by an electronic cooling element.

  
In the case where the means for avoiding the formation of a double image, the means of prior heating, the means of cooling, the means of exposure and the means of development to heat are aligned at the same interval as those of the zones of image formation of sheet 19, it is possible not only to perform recording on a single image formation area of sheet 19, subjecting it successively to the respective processes, but also to obtain speed recording fairly high, by simultaneously submitting multiple imaging areas at any of the respective stages. In the latter case, when a first designated case

  
  <EMI ID = 46.1>

  
  <EMI ID = 47.1>

  
received a recording or has not yet received one. If it has not already received one, the imaging sheet is moved one

  
  <EMI ID = 48.1>

  
pre-heating position, as shown in the figure

  
  <EMI ID = 49.1>

  
next F2 is checked at the same time for double exposure. When it is not feared that the F2 frame may be subjected to double exposure, the imaging sheet is moved from a frame in the direction of the X's,

  
  <EMI ID = 50.1> <EMI ID = 51.1>

  
the following F3 frame at the double exposure verification position

  
  <EMI ID = 52.1>

  
are cooled and preheated respectively and, at the same time, it is checked that the frame F3 is not liable to undergo double exposure.

  
If it turns out that the F3 frame has not yet been registered, the imaging sheet is moved one more frame along the direction of the X axis, which brings

  
  <EMI ID = 53.1>

  
and in the pre-heating position res-

  
  <EMI ID = 54.1>

  
double exposure verification, as shown

  
  <EMI ID = 55.1>

  
exposure, cooling and heating process

  
  <EMI ID = 56.1>

  
  <EMI ID = 57.1>

  
reveals that it has not already received the recording, the imaging sheet is again shifted by a frame along the direction of the X axis, to arrive at the state illustrated in the <EMI ID = 58.1> development position, the second frame F2 is in the exposure position, the third frame F3 is in the

  
  <EMI ID = 59.1>

  
  <EMI ID = 60.1>

  
is in the double exposure verification position. Executives

  
  <EMI ID = 61.1>

  
sition, cooling and pre-heating respectively-

  
  <EMI ID = 62.1>

  
double exposure verification. Then, each time the imaging sheet is similarly shifted by one frame along the direction of the X axis, five frames are checked for double exposure, respectively, heated beforehand. , cooled, exposed and developed

  
to heat, practically at the same time. In the event that such a successive registration is completed, when a last frame

  
  <EMI ID = 63.1>

  
Beforehand, the cooling, the exposure and the development are carried out in parallel, but a double exposure check is not carried out, as illustrated in FIG. 12F. When <EMI ID = 64.1>

  
X-axis direction, cooling, exposure

  
and development takes place in parallel. Then the frames that are still being registered are similarly subjected to the remaining processes one after the other.

  
When the heating means and cooling means, illustrated in FIG. 7A, are used, after a frame intended to receive a recording has been moved to the preheating position, then to the exposure position, the second frame-like member 73 for exposure is pressed onto the imaging sheet and, at the same time, the solenoid of the cooling air supply bellows is excited so as to cool the previously heated frame, then the shutter solenoid is energized. The arrangement illustrated in Figure 7A simplifies the structure of the body

  
53 tubular and requires fewer trips

  
of sheet 19, in comparison with the arrangement of Figure 7. In the arrangement of Figure 7B, after the device 61

  
heating for the preheating has been put out of contact of the sheet 19, air is sent from the recess 57 to

  
sheet 19 to cool it. In this case too, the structure of the tubular body 53 is simple and the number of times that the sheet 19 has to be moved is small in comparison with that

  
that requires the arrangement of Figure 7. In addition, as we

  
does not need the outlet port 136b and the inlet port 136c provided in the arrangement of FIG. 7, the structure

  
of the tubular body 53 is simplified.

  
The conditions for recording, in the previous embodiments, are as follows: the preliminary heating is carried out between 80 and 130 [deg.] C, for a period of between 0.5 and 12 seconds. The exhibition, after returning the sheet

  
photosensitive image formation, is performed by an illumination of for example 2,000 to 10,000 lux. for about 0.5 to 12 seconds and heat development is carried out between
100 and 150 [deg.] C, for about 0.5 to 12 seconds.

  
Above, a stepping motor was used, to drive, position and stop the transfer means

  
of the imaging sheet, but other methods can be used. Thus, for example, as described below, it is also possible to use transfer means which are driven by an ordinary motor, which are brought into position by a signal produced by a combination of an encoder and d 'a photodetector and.which are stopped by a locking latch. Thus, as illustrated in FIG. 18, claws 311 and 312 of a pivoting front bar 308 and a pivoting posterior bar 309 are respectively removed from the hooks
315 and 316 of a front ratchet wheel 313 and of a rear ratchet wheel 314, by the action of a solenoid 307. Next, a motor 317 drives a shaft 323 by means of a clutch 318 and of gears 319, 321 and 322. An encoder 324,

  
the toothed wheel 321 and the ratchet wheels 313 and 314 are fixed relative to each other and form a unitary structure and are arranged so that at each rotation, the shaft 323

  
is driven over the distance of movement of the imaging sheet for a frame. When the gear 321 turns half a turn, a notch 325 in the encoder 324 is detected by

  
a photodetector 326. This detection signal deactivates the solenoid 307 and, by the action of springs 327 and 328, the claws 311 and 312 slide on the outer peripheral face of the ratchet wheels 313 and 314 respectively. When the motor 317 continues to rotate, the ratchet 317 of the wheel 313 strikes

  
the claw 311 of the bar 308 and, at the same time, the claw 312

  
of bar 309 strikes ratchet 316 of wheel 314, which prevents the change of direction of rotation of the toothed wheel

  
321 due to shocks. At the same time, the tree_323 stops spinning. The motor 317 is synchronized so as to continue to rotate for a certain time, even after the toothed wheel 321 is stopped by the aforementioned detection signal from the photodetector 326 and, during this time, an overload of the motor 317

  
is avoided by the clutch 318, until the motor 317 comes to rest after stopping the toothed wheel 321. In this way, the imaging sheet can be shifted and brought into position with great precision. This is why one can also use a transfer mechanism of the type described above.

  
Although the previous embodiments use threaded shafts 33, 43 and 323 to move the imaging sheet, it is possible to use a method using wires, a method using a pinion and a rack or a process using a chain. Among these methods, that of moving the imaging sheet in accordance with the two <EMI ID = 65.1>

  
X and Y directions is effective when the imaging sheet is a microfiche.

  
In the apparatus shown in FIGS. 4 and 5, the heating device 61 for the preliminary heating, the cooling device 61a, the heating device 61 and the second frame-shaped element 73 for the exhibition are put in and out of contact with the image forming sheet, but it is also possible to fix them

  
and to move the tubular body 53 by bringing it into contact

  
and out of contact with the imaging sheet. In general, it is desirable to adopt an arrangement as illustrated

  
in figure 2, in which the side of the tubular body 53 is fixed and the heaters and the second frame-shaped element for the exposure are stationary, so that the imaging position for the image of an object can be fixed easily. Furthermore, the illustrated mechanism for bringing the heaters and the like into contact and out of contact with the imaging sheet is suitable in practice, but this mechanism can also be replaced by others. Similarly, the exposure means can be replaced by other means than those which have been mentioned, but at least one projection lens, for projecting the image of the object on the image forming sheet, and a shutter, are necessary, the other elements being able to be modified according to the position of the object to be placed.

   Thus, for example, the object can be placed at the top of the envelope, facing down. In addition, the exposure conditions can be modified by setting a fixed exposure time beforehand without using an automatic exposure detector.

  
The processing device described above with four positions, according to which preheating, cooling, exposure and development are carried out, in individual positions, allows easy maintenance because each of the different functions is performed in positions different and decreases the recording time, because the recording was carried out successively on several imaging areas, working in parallel. However, exposure, heating and cooling can also be done in the same position. This technique will be referred to as the technique or device at a position.

   This device in one position is particularly suitable for recording said to a frame in which the succession of operations of preliminary heating, cooling, exposure and development is carried out, for each frame, that is to say that the 'information is saved for each frame. The one position apparatus is particularly suitable for an aperture type imaging sheet, but can also be used to record on a single frame a microfiche type sheet having a number of frames.

  
In this case, heaters of the same type can be used for preheating and for heating development, but it is often desirable that the heating temperatures of these two heaters differ. other. This is why it is better, to decrease the recording time on the sheet, to use separate heaters and a cooling device and to make sure that the individual heating devices or the cooling device are put in the same position relative to the image forming sheet, in a certain period of time.

   In addition, in this single position apparatus, the second frame-shaped member 73 for exposure is used in addition to the heating and cooling devices, and pre-heating, cooling, exposure and development are performed while the sheet is held in a fixed position by the tubular body 53 and by the element 73 in the form of a frame.

  
Figure 19 illustrates an apparatus in which preheating, cooling, exposure and development are carried out by the single position process. Two guides 335 and 336 are fixed to the tubular body 53, so that a frame 107 of a punch card 333 with an opening of an imaging sheet can be placed smoothly in the exposure position, that is that is to say in the position corresponding to the lower open end of the hole 54. In the lower guide, an opening slightly larger than the second frame-shaped element 73 is provided in the exposure position, and one end of the guide 305 serves as a stop, so that the punched card 333 is not engaged too far.

  
The face of the image-forming zone 107, on the side of the tubular body 53, comes into contact with the tubular body 53 and the latter is screwed into the tubular body 55 with an orifice
137 pressure gas inlet being provided in the side wall of the tubular body 53. An O-ring 339 to prevent leakage of pressurized gas is interposed between the body
53 tubular and the body 55 tubular. The surface of the image-forming zone 107, on the side opposite the tubular body 53, is pressed by the second frame-shaped element 73 when exposed on the side of the tubular body 53, from the start of heating. prior to the completion of the heat development, which keeps the area in a fixed position-

  
107 image formation.

  
When it maintains the imaging area 107, the frame-shaped member 73 for exposure is located

  
the highest position D indicated by the line in solid lines, but otherwise it is in position E lowered, indicated in the line in broken lines. This upward and downward movement of this element is carried out by means (not shown) for moving it.

  
The heating device 61 for the preheating is normally maintained in the standby position B, but when it is necessary to perform the preheating, it is brought by transfer means (not shown), to an exposure position A by being surrounded by the second frame-shaped element 73 and it heats the image formation zone 107 beforehand and then returns to position B. The cooling device 61a is normally in the standby position F, but in the case where cooling must be carried out, it is brought by means (not shown) to move it to the exposure position A, where it cools the imaging area 107, then is then returned to the position F.

   The heating device 62 for the heat development is normally maintained in the standby position C and is brought, by means
(not shown) to move it, to the exposure position A in order to heat develop the imaging area 107, then is brought back to the position C.

  
In the case where the image forming area 107 of a punch card 333 is manually set to the exposure position, there is no need for means for transferring the image forming sheet. The portion of the punched card 333, except for the image forming area 107, can also <EMI ID = 66.1>

  
only provide a heater and increase the contact time of the heater with the imaging area or change the degree of heating depending on whether the heater is used for preheating or for heat development.

  
Preheating, cooling or heat development can also be done in a position different from that of the exposure. It is also possible to adopt a two-position process, according to which the pre-heating, cooling and development at

  
the heat takes place in the same position which differs from

  
that of the exhibition. Finally, it is also possible to apply a process to a position, as illustrated in FIG. 19, to each image formation zone 107 of the sheet 19, in place of the punched card 333. The cooling of the imaging sheet after it has been preheated has been described above, but to avoid damaging it and causing it to undergo thermal deformation, it is better than after the sheet has been developed to heat, it is cooled by the cooling means such as those used after the preliminary heating.

  
As described above, cooling the imaging sheet after preheating, but before exposure, according to the invention, is useful for obtaining a sharp image with fine contrasts and good contours. delimited. In particular, forced cooling reduces the time required to obtain a visible image and therefore constitutes a very useful process. This will be described in more concrete terms in connection with the following examples.

   With the heat developable image forming apparatus according to the invention, one can record and develop an image on an image forming sheet, frame by frame, without having to have a dark room for manipulate a raw imaging sheet and the developed imaging sheet can be preserved for later reproduction of the recording and, if necessary, reloaded onto the imaging apparatus image to record there again on a frame that has not received sheet recording.

  
Since we don't need a dark room and since <EMI ID = 67.1>

  
the development is not of the wet type, no developer is used. As a result, the image forming apparatus is of a very simple structure, and the image forming sheet can be preserved after subjecting it to recording on one or more of its frames only, and , if necessary, additional recordings can be made on other frames. Furthermore, thanks to the image forming apparatus provided with means for cooling the image forming sheet after it has been previously heated, which is one of the features of the invention, it is possible to have a significant increase in the sensitivity of the imaging sheet, by the fact that it is cooled after the hot activation process, and to produce a visible image with fine contrasts and well-defined contours .

  
The following examples illustrate the invention.

  
EXAMPLE 1

  
The image forming sheet is prepared by the following method. 4 parts by weight of silver behenate and 20 parts by weight of a mixed solution of methyl ethyl ketone and toluene are ground in a ball mill for 24 hours.

  
(in the ratio of 2 to 1 by weight), to prepare a suspension of silver behenate. The following compositions are prepared, using the silver behenate suspension, applied as a coating.

  
  <EMI ID = 68.1>

  
the coating being carried out at room temperature.

  

  <EMI ID = 69.1>
 

  

  <EMI ID = 70.1>


  
After applying the first layer, we apply it

  
  <EMI ID = 71.1>

  
at room temperature.

  
The heating and cooling means illustrated in FIG. 7 are used to obtain a visible image, by prior heating, exposure and development of a given area of the image-forming sheet thus produced.

  
Fig. 20 illustrates the effect produced by the state of the imaging sheet until it has been exposed to a bright image, after having been previously heated.

  
The imaging sheet is made photosensitive by preheating at 100 [deg.] C for 3 seconds, and is irradiated by the light of a 2000 W tungsten lamp via a step shelf , with an illumination of 1000 lux. second, then developed at 120 [deg.] C for 3 seconds. In Fig. 20, curves a, b, c and d indicate the photosensitive characteristics of the imaging sheet in cases where its temperature immediately before exposure is
100 [deg.] C approximately, of 80 [deg.] C approximately, of 60 [deg.] C approximately and the ambient respectively of the abscissas representing the quantity of light on the logarithmic scale and the ordinates, the density of the optical density (OD) image.

  
Using the inverse of the exposure time required to obtain an optical density of 1.0 as a measure of the sensitivity of the imaging sheet, it is found that the specific sensitivity y and the maximum optical density increase and that the minimum optical density decreases in the order of curves a, b, c and d, that is to say as a function of the increase in the degree of cooling of the sheet in the interval between the prior heating and the 'exposure. This indicates that the more the sheet is cooled before exposure, the more <EMI ID = 72.1>

  
the image obtained has a fine contrast and a sharp outline.

  
From the results of FIG. 20, it can be said that it is better for the image formation sheet to be at a temperature

  
  <EMI ID = 73.1>

  
image is exposed immediately after pre-heating

  
without cooling ,. the transmission density of the sheet after development is 0.5 in a white area of an original, 0.2 in a black area, while in the case of an imaging sheet which has been heated beforehand, then cooled down to room temperature before disposal, the transmission density of the sheet is 1.3 in the white area of the original and 0.1 in the black area. As a result, cooling after preheating increases the sensitivity of the imaging sheet, and gives an image with better contrast.

  
EXAMPLE 2

  
Images are formed on the image forming sheet of Example 1, by photographing test grids having different reflection factors, using the image forming apparatus according to the invention. Fig. 21 shows the photosensitive characteristics obtained in cases (a to e) of air-blast cooling on the imaging sheet. In FIG. 21, the ordinates represent the optical densities of the images obtained and the abscissas represent on a logarithmic scale the reflection factors (%) described from tests used, the figures on the abscissa being the reflection factors. The heating is carried out before
100 [deg.] C for 3 seconds. The exposure is carried out by illuminating the test grids with a 20 W fluorescent lamp and the test grids are photographed on a reduced scale.

   Development is carried out at 120 [deg.] C for 3 seconds. The temperature of the imaging sheet, at the time of exposure, is about 95 [deg.] C in the case of curve a, about 70 [deg.] C in the case of curve b , approximately 60 [deg.] C in the case of curve c, approximately 40 [deg.] C in the case of curve d and approximately 30 [deg.] C in the case of curve e. It can be seen in Fig. 21 that a sharp, well-contrasted image can be obtained by cooling the imaging sheet in the time interval between pre-heating and exposure. Furthermore, it can be seen that the temperature of the sheet at the time of <EMI ID = 74.1>

  
the exposure should preferably be lower than 60 [deg.] C and that a temperature of the sheet lower than 40 [deg.] C gives practically the same result as that which one can obtain in the case

  
where the sheet is at room temperature, and therefore this temperature of 40 [deg.] C is not preferred.

  
EXAMPLE 3

  
The imaging sheet is prepared by the method corresponding to that described in United States Patent No. 3,802,888.

  
85 parts by weight of an equiponderal solvent mixture of toluene and methyl ethyl ketone and 15 parts by weight of silver behenate are mixed homogeneously, to prepare a silver behenate paste. Then 35 grams of methyl ethyl ketone 9% polyvinyl butyral are added to 17 grams of the paste, while stirring, to obtain a polyvinyl butyral solution in which silver behenate is dispersed. To this solution is added 0.25 grams of phthalazinone, 0.1 grams of HgBr2 and 0.89 grams of bis- (2-hydroxy-3,5-di-tert-butylphenyl) methane and the mixture is stirred. We apply the mixture in one

  
  <EMI ID = 75.1>

  
and the coating is dried at room temperature. Then, an acetone acetate solution of

  
  <EMI ID = 76.1>

  
and dried at room temperature to obtain a protective layer.

  
After having previously heated to 100 ° C. for 15 seconds, the image-forming sheet thus obtained is cooled by the same cooling process as that used in Example 1, and is irradiated with a tungsten lamp of 500 W, via stepped tablet, at one light

  
of 500,000 lux.second, then we develop at 135 [deg.] C for 10 seconds. It is found that cooling before exposure increases the specific sensitivity and the maximum optical density, as in Example 1.

  
EXAMPLE 4

  
The image forming sheet is prepared by the method corresponding to that described in US Patent No. 3,764,329.

  
15 parts by weight of silver behenate and 85 parts by weight of methyl ethyl ketone are mixed homogeneously to obtain a suspension of silver behenate. To 67 grams of this silver behenate suspension, 60 grams of methyl ethyl ketone, 10 grams of polyvinyl butyral, 0.35 grams of mercuric acetate, 0.49 grams of N-bromosuccinimide and 20 grams of 1-methylpyrrolydine are added. sufficiently mixed and dissolved. The coating mixture is applied in one

  
  <EMI ID = 77.1>

  
in air at room temperature. Then we apply a coating

  
  <EMI ID = 78.1>

  
consisting of 12 parts by weight of cellulose acetate,

  
in 163 parts by weight of acetone, in 2.8 parts by weight of phthalazinone and in 7 parts by weight of 2,4,4-trimethylbenzyl
(2-hydroxy-3,5-dimethylphenyl) methane, then the coating is dried. After having previously heated to 100 [deg.] C for 8 seconds, the imaging sheet thus obtained is cooled by the process used in Example 1, and is irradiated with light from a light bulb. 500 W tungsten, via a stepped tablet, under an illumination of
30,000 lux.second, and we develop at 130 [deg.] C for 10 seconds. It is noted that the cooling before exposure increases the specific sensitivity y and the density and the optics, as

  
this is the case in example 1.

  
EXAMPLE 5

  
The imaging sheet is prepared by the method described in U.S. Patent No. 4,113,496.

  
12 parts by weight of silver behenate, 88 parts by weight of a 2: 1 solvent mixture of methyl ethyl ketone and toluene are mixed in a homogeneous manner to obtain a suspension of silver behenate. Sufficiently 6 grams of the silver behenate suspension are mixed with 4 grams of methyl ethyl ketone, 0.72 grams of polyvinyl butyral, 0.02 grams of mercuric acetate, 0.096 grams of tetrabromobutane, 0.03 grams of dibromide bis- (p-methoxyphenyl) and 1.2 ml of &#65533; &#65533; a solution of sensitizing dyestuff. We apply the

  
  <EMI ID = 79.1>

  
polyester and the coating is dried at room temperature. The sensitizing dye solution is a solution.

  
  <EMI ID = 80.1>

  
lidene) -butalysin] -rhodanine. Then we apply a coating

  
  <EMI ID = 81.1> <EMI ID = 82.1>

  
solution comprising 8.3 grams of acetone, 0.62 grams of cellulose acetate, 0.14 grams of phthalazinone and 0.35 grams of

  
  <EMI ID = 83.1>

  
dries at room temperature.

  
The imaging sheet thus obtained is previously heated to 100 [deg.] C for 3 seconds, cooled as in Example 1, irradiated with light from a

  
  <EMI ID = 84.1>

  
stepped, under an illumination of 10,000 lux.second and it is developed at 120 [deg.] C for 3 seconds. As in Example 1, an improvement in specific awareness y and

  
maximum optical density by pre-heating before exposure.

  
. EXAMPLE 6

  
The imaging sheet is prepared by the process described in U.S. Patent No. 3,816,132 and

  
to the patent application published in Japan under No. 127.719 / 76.

  
17 grams of silver behenate, 13 grams of behenic acid, 40 grams of polyvinyl butyral, 350 ml of toluene and 350 ml of ethanol are mixed in a sufficiently homogeneous manner. The coating mixture is applied in a thickness of 100 p on a polyester film and dried at room temperature.

  
  <EMI ID = 85.1>

  
previous coating, a mixture consisting of 51 grams of

  
  <EMI ID = 86.1>

  
phthalazinone, 0.16 grams of mercuric acid, 0.01 grams of:

  

  <EMI ID = 87.1>


  
10 grams of polyvinyl butyral and 1 liter of ethanol, and dried at room temperature.

  
The image-forming sheet thus obtained is previously heated to 100 [deg.] C for 5 seconds, cooled as in Example 1, irradiated with light from a tungsten lamp at 500 W by via a tiered tablet under an illumination of 200,000 lux.second, and developing at 120 [deg.] C for 5 seconds. It is also established in this example that the specific sensitivity y and the maximum optical density increase when cooling before exposure, as was the case in Example 1.

"CLAIMS *

  
1. A method of forming an image using a heat developable image forming sheet, which normally is not photosensitive, but which can become photosensitive, which consists

  
to heat it beforehand before exposure, to expose it to a bright image to form a latent image there, then to develop it with heat to obtain a visible image, characterized in that after having heated the sheet beforehand, cools it in the area that has been heated prior to exposure.


    

Claims (1)

2. Method according to claim 1, characterized in that the image forming sheet is made of a material containing at least one organic silver salt serving as an oxidizing agent, a silver ion reducing agent and a binder. 3. Method according to claim 2, characterized in that the sheet also contains at least one silver halide and a source of halogen ion capable of forming the silver halide by reacting on an organic silver salt, and a source of mercuric ion. 4. Method according to claim 2, characterized in that the sheet contains at least one organic carboxylic acid, a sensitizing dye and a source of mercuric ion. 5. Method according to claim 2, characterized in that the temperature of the preliminary heating is between 80 and 130 [deg.] C, and the previously heated area of the sheet is cooled to a temperature below 60 [deg.] C. 6. Method according to claim 5, characterized in that the previously heated area of the image is cooled to a temperature below 40 [deg.] C. 7. Method according to claim 1, characterized in that the previously heated zone of the sheet is cooled by a metallic element, capable of coming directly into contact with the sheet. 8. Method according to claim 1, characterized in that the previously heated zone of the sheet is cooled by a gas blown on the sheet. 9. An apparatus for forming an image using a heat developable image forming sheet, which normally is not photosensitive, but which can become photosensitive, by prior heating before exposure, the sheet being <EMI ID = 88.1> then exposed to a light image to form a latent image there, and then developed with heat to obtain a visible image, which comprises one or two heating means for preheating and for developing with heat an image forming area of the sheet,, and exposure means for projecting an optical image of an object onto the image-forming area made photosensitive by the prior heating, characterized by means for cooling the previously heated image-forming area of the sheet before exposure. 10. Apparatus according to claim 9, characterized in that the cooling means comprise a thermally conductive solid body, maintained at a temperature below 60 [deg.] C, and coming into direct contact with the imaging area of the sheet to cool it. <EMI ID = 89.1> by means for applying a pressurized fluid to the sheet on the side opposite that where the solid body is kept in direct contact with the sheet. 12. Apparatus according to claim 11, characterized in that the pressurized fluid is compressed air. 13. Apparatus according to claim 10, characterized by means for producing a vacuum between the solid body and the contact surface of the sheet, when the latter is in direct contact with the latter. 14. Apparatus according to claim 10, characterized by a frame-shaped element, disposed on the side opposite to that on which the solid body which comes into contact with the sheet is located, and by means for introducing a pressurized fluid from the outside into this frame-shaped element, to apply a pressurized fluid to the sheet located in the frame member. 15. Apparatus according to claim 9, characterized in that the cooling means are constituted by means for blowing a gas at a temperature below 60 [deg.] C on the sheet. 16. Apparatus according to claim 15, characterized in that the cooling means are arranged so that the gas is applied to the surface of the image-forming zone of the sheet, from inside the element in the form of a frame arranged in contact with the sheet in the heating or exposure position. 17. Apparatus according to claim 9, characterized in that at least one of the heating means, cooling means and exposure means is provided with means for fixing the image-forming zone of the sheet in position for the corresponding process. 18. Apparatus according to claim 17, characterized in that at least one of the fixing means has a frame-shaped element for holding the sheet in places where it surrounds the image-forming area. 19. Apparatus according to claim 17, characterized in that at least one of the fixing means comprises first and second frame-shaped elements, opposite one another, holding the places of the sheet between them surrounding the imaging area. 20. Apparatus according to claim 17, characterized in that the exposure means comprise a tubular body and the end face of this tubular body, on the side of the sheet, is in the form of a frame, to constitute at least part of the fixing means for the exposure means. 21. Apparatus according to claim 20, characterized in that the fixing means comprise a second frame-shaped element intended for the exposure means, and lying opposite the frame-shaped end face of the tubular body, and the securing means are for holding the sheet between the end face in the form of a frame and the end face of the second element in the form of a frame, surrounding the image forming area of the sheet. 22. Apparatus according to claim 21, characterized by means for projecting light into the interior of the second frame-like element towards the image forming region of the sheet maintained in contact with the second element in the form of a frame, and by means for projecting onto a screen the light which has passed through the image-forming zone and which has passed through a hole in the tubular body. 23. Apparatus according to claim 9, characterized in that the heating means comprise a solid body at high temperature, which is in direct contact with the image-forming zone of the sheet in order to heat it. 24. Apparatus according to claim 23, characterized in that the solid body at high temperature is a thermal conductor, in which a heating device is incorporated and it comprises means for adjusting its temperature to a value given in advance . 25. Apparatus according to claim 23, characterized. by means for applying a fluid under pressure to the sheet on the side opposite to that where it comes into contact with the solid body at high temperature, when the latter is maintained in direct contact with the latter. 26. Apparatus according to claim 25, characterized in that the pressurized fluid is compressed air. 27. Apparatus according to claim 25, characterized in that a frame-shaped element is arranged on the opposite side where the solid body at high temperature is maintained in direct contact with the sheet, and by means for introducing a pressurized fluid outside, into the frame member, for applying the pressurized fluid to the imaging area in the frame member. 28. Apparatus according to claim 23, characterized by means for producing a vacuum between the solid body at elevated temperature and the imaging sheet, coming into contact with it, when the latter is kept in direct contact therewith. this. 29. Apparatus according to claim 9, characterized in that the heating means heat the image-forming zone of the sheet by bringing it into contact with a gas at high temperature. 30. Apparatus according to claim 29, characterized in that the gas at high temperature is air heated between 80 and 220 [deg.] C. 31. Apparatus according to claim 29, characterized in that the gas at high temperature is air which is located between the sheet and a solid body at high temperature disposed in the vicinity, but at a distance, from the sheet, this gas being heated by the solid body at high temperature. 32. Apparatus according to claim 9, characterized in that the heating means irradiate the image-forming zone of the sheet by infrared rays, or far infrared rays. 33. Apparatus according to claim 9, characterized in that the heating means comprise a first means and a second means for respectively pre-heating the sheet and for developing it with heat. 34. Apparatus according to claim 33, characterized in that at least three means among the first heating means, the exposure means and the second heating means are aligned. 35. Apparatus according to claim 33, characterized in that the first heating means for the preliminary heating, the cooling means, the exposure means and the second heating means for the heat development are aligned. 36. Apparatus according to claim 35, characterized in that the first heating means, the cooling means, the exposure means and the second heating means are fixed by being aligned with each other, or constitute a unitary structure. 37. Apparatus according to claim 35, characterized in that it is arranged so that the treatments carried out by the first heating means, the cooling means, the exposure means and the second heating means are carried out in parallel and at the same time for multiple imaging areas of the sheet. 38. Apparatus according to claim 9, characterized by control means to prevent the formation of a double image on an image formation area having already received a recording. 39. Apparatus according to claim 38, characterized in that the control means comprise a light emitting device and a photodetector, the light emitted by the light emitting device being emitted or reflected by the sheet being received by the photodetector, and the formation of a double image being controlled by a comparison of the intensity of the output signal from the photodetector, and of a prescribed value. 40. Apparatus according to claim 39, characterized in that a holder is arranged so that the image of a strip having a reflectance different from the sheet extends along at least l one of the four sides of the sheet imaging area, when the image of an object is formed in this area, the strip in the area of <EMI ID = 90.1> <EMI ID = 91.1> 41. Apparatus according to claim 33, characterized by control means for preventing the formation of a double image in an image formation zone having already received a recording, and at least four means among the control means, the first heating means, exposure means, second heating means are aligned. 42. Apparatus according to claim 33, characterized by control means for preventing the formation of a double image on an image formation area having already received a recording, these control means being adjacent to the first heating means and the means for detecting the first heating means, the cooling means, the exposure means and the second heating means are all aligned. 43. Apparatus according to claim 42, characterized in. what it is arranged so that the treatment by five means are carried out respectively in parallel and at the same time for various areas of image formation of the sheet.