MXPA97001761A - Procedure and printing machine for labor in practice of the procedure and support asiimpr - Google Patents

Abstract

The present invention relates to a method for printing on a support a color image, characterized in that it comprises the steps consisting of: decomposing the image to be reproduced in a composition of colored elementary surfaces, said elementary surfaces are arranged according to a predetermined distribution, the color of each elementary surface is chosen from a predetermined set of base colors and a predetermined set of shades of these base colors, the number of shades for at least one base color is greater than or equal to three, the choice of color The base and the shade attributed to each of said elementary surfaces is carried out in such a way that said composition of colored elementary surfaces visually reconstitutes the image to be reproduced, - printing said composition of colored elementary surfaces on said support by means of inks of which dyes or tones are chosen to be able to reproduce, teni taking into account the color of said support, such base colors and their shades during printing, the hue of a base color attributed to a given elementary surface, is obtained during printing by applying the ratio of each ink within the surface corresponding elementary in the sopor

Description

PROCEDURE AND PRINTING MACHINE FOR THE IMPLEMENTATION OF THE PROCEDURE AND SUPPORT PRINTED SO FIELD OF THE INVENTION The present invention relates to a method of printing in color and in a more particular but not exclusive to a method and a machine for printing offset to dryness.

BACKGROUND OF THE INVENTION It is known to implement, for printing the outer surface of a cylindrical object of revolution such as a drum that serves to contain a liquid, an aerosol pump or a flexible tube, a dry offset printing process comprising the steps consisting of in placing various inks of different colors on a blanket, then transfer by contact of the blanket with the object, the inks on the latter. In practice, a plurality of blankets mounted on a rotating cylinder and loaded successively with the different inks are used. The inks are deposited on each blanket REF: 24228 by means of respective application rollers having raised or raised parts formed on the plates by gravure from a negative. Various procedures can be used to perform these negatives. A known procedure consists in decomposing the original in color to be reproduced in a superposition of monochromatic images in the form of frames, the density variations of each monochromatic image are restored by varying the size of the points of the frame, provided for modulation of amplitude. A corresponding negative is made for each monochromatic image in the form of a frame. The frames of different monochromatic images lean to each other to reduce the phenomenon of iridescent reflection in the print. Such a procedure does not offer complete satisfaction, mainly because it does not allow to avoid, when the image to reproduce presents approximate or similar details and different colors, any superposition of the ink points on the blankets and a mutual contamination of inks, which causes a progressive denaturation of the printed image, and imposes to renew the inks, that also can force to send to the waste or waste a part of the production.

DESCRIPTION OF THE INVENTION The subject of the present invention is a new printing process that mainly allows solving the problem of contamination of the inks placed by the dry offset printing processes of the prior art. The invention is also directed, in a more general way, to be able to print an image rich in shades of color without having to create the colors or nuances of colors by mixing inks of different colors during printing. The invention is also directed to eliminate the phenomena of iridescent reflection when many dyes are printed. The invention achieves this thanks to a method for printing on a support a color image, characterized in that it comprises the steps consisting of: decomposing the image to be reproduced in a composition of colored elementary surfaces, these elementary surfaces are arranged according to a predetermined distribution, the color of each elementary surface is chosen from a predetermined set of base colors and a predetermined set of shades of these base colors, the number of shades for at least one base color is greater than or equal to three, the choice of color The basis and hue assigned to each of said elementary surfaces is carried out so that said composition of colored elementary surfaces visually reconstitutes the image to be reproduced, - printing said composition of colored elementary surfaces on said support by means of inks whose dyes or tones are chosen to be able to reproduce, have Considering the color of said support, such base colors and their shades during printing, the hue of a base color attributed to a given elementary surface is obtained during printing by applying on the ratio of each ink within the elementary surface corresponding on the support. Thanks to the invention, it is possible to print an image without overlapping ink dots in the print, which represents multiple advantages. Firstly, the problem of contamination of the inks, in the particular case of dry offset printing, is considerably limited even eliminated. A substantial economy can thus be realized during the printing of a large number of conditioning devices. It is then possible, thanks to the invention, to visually reconstitute an image without having the mixture of inks intervene in the printing, then without having to previously determine, by calculation or using tests, the colors resulting from the mixture of inks, which does not it is always simple considering mainly the complexity of the mechanism of the perception of colors by the human being. The invention thus finds a general application to all printing devices and exceeds the field of offset printing to dryness. When classic four-color printing uses black, magenta, cyan and yellow inks and restores non-primary colors by the subtraction mixture of magenta, cyan and yellow, it is possible in the invention to use only colored inks that are not primary, for example inks keys dyes or tones are chosen depending on the subject of the image to be printed. Thus, when the image represents, for example, a face, preferably at least one ink whose hue or tone is close to the skin color of the subject will be chosen, and the printed image will have a very close or very close visual reproduction of the image. reality. It is also advantageous to be able to print texts with a single ink thanks to the invention without having to generate the corresponding color by mixing inks in the printing. It is also interesting to be able to choose the color of the inks used for printing because this way you can have colors that are not possible or that are difficult to create by synthesis of subtraction of primary colors. It will be understood that the invention is advantageously used to print objects of great consumption, insofar as the visual perception of the printed image on the objects exposed to the sale, by a potential buyer, can be decisive. The invention can also be used to make reproductions of higher quality pictures or photographs.

In a particular implementation of the invention, the shades of a base color at least have the same saturation but different luminosities. In this case, the nuances of a base color that have the same saturation but different luminosities can be restored during the printing thanks to a more or less large proportion of black ink, inside the elementary surfaces of the support, which are being manipulated for obtaining said nuances during printing. In the case of offset to dryness, to avoid the mixing of inks, when the same elementary surface of the support is put in contact at the same time by a black ink tank and by a deposit of an ink different from the black ink, the The deposit of the black ink and of said ink different from the black ink is done with predetermined reasons for each one of the inks, chosen to avoid the superposition of two inks. In the case of other printing processes for which the overlay of inks in the printing is not a problem, the deposit of the black ink with overlap in at least one other ink already deposited on the support can be effected.

In a particular implementation of the method according to the invention, an ink spot whose shape and size depends on a predetermined ratio of the hue of the base color to be reproduced is printed on each elementary surface on the support. When printing is effected by adjusting the support to the contact of an ink-laden surface, with a direction of displacement substantially tangential to said ink-laden surface, the ink spots advantageously present, when they do not replace the entire extension of the associated elementary surface, a shape adapted to reduce the phenomenon of thickening, and preferably a substantially elongated shape and sharpened or sharpened in the direction of movement of the support. Thus, the phenomenon of thickening, which is translated by a modification of the size of the points in the print, can be reduced, which allows to obtain a printed image closer to the original to be reproduced. Furthermore, it has been found that the number of fully colored elementary surfaces will tend to decrease significantly when the number of shades chosen for each base color increases. Thus, the elementary surfaces are mostly printed only partially and by choosing an adapted arrangement of the ink points inside these elementary surfaces, a set of disconnected ink points can be obtained, which allows avoiding the phenomenon called "de contact "which consists of an exposure of the ink in the contact region of two ink points attached, because of capillary phenomena. This adapted arrangement of the ink points within the corresponding elementary surfaces on the support may consist in centering each ink point on the associated elementary surface. On the other hand, well that a impoverishment of the image can be feared a priori, by the initial choice in the invention of a limited number of base colors in which the decomposition of the original in colors is effected (which can comprise a number of colors much more important than the number of base colors chosen), it has been surprisingly found that the visual reproduction of the printed image may be better than with the prior art printing methods that implement a subtractive blend or of subtraction of primary colors. On the one hand, differences in contrast, for an observer, can be made more important by the invention than in the prior art, due to the choice of non-primary base colors. On the other hand, it is easier to obtain an impression of sweetness or softness restored by a set of shades or dyes at high luminosity using non-primary colors that use a mixture of primary colors as in the prior art. In a particular implementation of the invention, at least one hue is obtained, for at least one of the base colors, by the printing of a predetermined pattern such as a logo. Preferably, several shades of at least one of the base colors are obtained by printing, in a more or less large proportion, a predetermined pattern such as a logo. The drawing is difficult to reproduce because it is invisible to the naked eye, thus providing a means capable of contributing very advantageously with the authenticity of the printed support. The subject of the invention is also a printing machine comprising ink application surfaces respectively loaded by ink dots respectively located within elementary surfaces placed according to a predetermined distribution, to visually reconstitute, during printing on the support, the image to To reproduce, the color of each ink point is chosen from a predetermined set of base colors, each given elementary surface is coated with ink at a chosen ratio depending on the hue to be reproduced, the number of shades is at least three for minus one of the base colors. Another object of the invention is a dry offset printing machine comprising at least one blanket and application rollers carrying reliefs or embossments arranged to deposit on said blanket a set of ink points respectively located within elementary surfaces arranged in accordance with a predetermined distribution to visually reconstitute at the time of printing on a support, the image to be reproduced, the color of each ink point is chosen from a predetermined set of base colors, each given elementary surface is coated with ink in a proportion chosen according to the hue to be reproduced, the number of shades is at least three for at least one of the base colors. Preferably, each relief or enhancement intended to deposit an ink spot within an elementary surface to reproduce an intermediate shade presents a substantially elongated shape and sharp or pointed in the direction of movement of the support at the time of printing to reduce thickening from the point in print. Another object of the invention is a printing medium having an outer surface on which an image consisting of a set of ink points respectively located at the center of the elementary surfaces arranged according to a predetermined distribution, the colors of said points has been printed. of ink are chosen from a predetermined set of base colors, each ink dot of a given base color fills a more or less large proportion of the corresponding elementary surface, according to the hue of said base color to be reproduced, the number of shades is at least three for at least one of the base colors. Preferably, at least one nuance of the printed or printed support is obtained, for one of the base colors, by a predetermined reason such as a logo, more or less printed according to the nuance to be reproduced. Other features and advantages of the present invention resurfaced on reading the detailed description that follows, examples of non-limiting implementation of the method according to the invention, and in the examination of the attached drawing in which: FIG. 1 is a schematic perspective view of a dry offset printing machine, Figure 2 is a diagram illustrating the different steps of a described procedure to better understand the invention, Figure 3 is a diagram illustrating the decomposition of a image constituted by a joint of juxtaposed pixels in a superposition of monochromatic images, figure 4 is a diagram illustrating the different stages of an example of the method according to the invention, figure 5 is a diagram illustrating the decomposition of a composition of colored elementary surfaces in an overlay of monochromatic images, - Figure 6 illustrates different shapes of ink dots arranged within corresponding elementary surfaces, Figure 7 illustrates the restitution of a hue by the printing, in a more or less large proportion, of a predetermined pattern or pattern, Figure 8 is an example of an ink dot shape adapted to limit the thickening phenomenon during printing, Figures 9 to 11 illustrate different distributions of elementary surfaces, Figure 12 is a schematic enlarged view of a printed image conforming to a Prior art method, Figure 13 is a schematic enlarged view of a printed image in accordance with the procedure described with reference to Figure 2, Figure 14 is a schematic enlarged view of a printed image according to the procedure according to the invention described with reference to figure 4, figures 15 to 17 illustrate the decomposition and n monochromatic images of the image depicted on figure 14, - figure 18 illustrates the restitution of shades of a base color by means of the printing, in a more or less large proportion, of a particular pattern. Figure 19 is an example of schematic representation of the color space, Figure 20 illustrates the restitution, during printing, of various shades of the same base color, in accordance with another example of the method according to the invention, - the figure 21 illustrates the obtaining, during printing, shades of different base colors, with black ink tank, according to the example of the method according to the invention described with reference to figure 20, - figure 22 is a schematic illustrating the different steps of the process according to the invention described with reference to figures 20 and 21, and figures 23 and 24 illustrate two ways of realizing the deposit of black ink within an elementary surface on the support. 1 shows, schematically, a dry offset printing machine 1 of a type known per se, comprising a plurality of blankets 2 placed on the periphery of a rotating cylinder 3 to arrive successively, at the moment from the rotation of the latter, to the contact of application rollers 4 destined to deposit in these mantillas 2 the dots of inks of different colors. In the example described, only four application rollers 4 are represented in a desire for clarity of the drawing, but in practice the machine 1 comprises most of the time of six application rollers. These application rollers 4 rotate around axes of rotation parallel to each other and to the axis of rotation of the cylinder 3. Their outer surfaces are constituted for each one by a well-shaped or turned plate having reliefs or enhancements that form protuberances or protrusions radially to the outside and in which an ink is deposited by means of an associated coating roller 5, regularly fed with ink. The objects O to be printed are introduced by means of a carrousel not shown / one after another / each at the contact of a blanket 2 arranged to transfer the inks. Each object O rolls in the blanket 2 associated in such a way that the inks of different colors deposited in the latter are transferred. Now, with reference to FIG. 2, a first example of the method used to make the negatives from which the plates of the application rollers are engraved will be described and that, preferably, it is implemented with the aid of a computer equipped with a display medium such as a videotape. It starts, in the example described, of an original 6 in color, memorized in the computer, which can be either a synthesis image, or an image memorized in numerical form and obtained from a silver or silver photograph, or even an image released by a video camera. As a non-limiting example, the original 6 can be an RVB-coded image exploitable by version 2.5 of the "Photoshop" software, marketed by the "ADOBE SYSTEMS FRANCE" company of Noisy-Le-Grand. In a process step 7, a number n of base colors corresponding substantially, in the particular example described, to the different dyes or shades of inks that will be used in the dry offset printing machine 1 is chosen. Taking into account the number of application rollers usually found in this type of machine, n is chosen most of the time equal to 6. In a subsequent step 8, particular colors are imposed, for example, the dye. Orange is used for printing warning or warning logos for users of aerosol pumps, or a color chosen to print the text. One or more major dyes can also be reacted in the original 6 in color, for example a color that is close to or approximates the color of the subject's skin if the image is a portrait. If the total number n of base colors in which it is desired to effect the decomposition of the original 6 is greater than the number of colors imposed p, then the np colors must be manually or automatically emitted in the following stage 9 of the procedure. remaining, collecting or taking for example the tones or colors statistically majority in the original 6 in color and no longer selected. A composition of colored elementary surfaces that are visualized by means of a video screen connected to the computer or computer is then constituted, in a process step 10, from n base colors. The elementary surfaces are constituted in the example described by regularly juxtaposed squares or squares. The image obtained in step 10 visually reconstitutes the original 6 to be reproduced. In the particular example described, the number of shades for each base color is limited to two, that is, each elementary surface is either colored in its entirety by a base color, or is not colored at all and then appears the color of the background, which is indicated here to be uniformly white. If the visual reproduction of the composition of elementary surfaces is not completely satisfactory, one returns to the preceding step 9 of determining the np colors not imposed, to modify one or more colors and the new image is examined during the return to stage 10. obtained. This can be followed by successive repetitions as illustrated in the scheme of Figure 2 by arrow 11 in dotted line. In the described example, the original 6 in color is an RVB encoded image wherein the color (including hue) of each pixel is coded in 24 bits and is used to constitute the composition of colored elementary surfaces the function of indexed image creation or adjusted from the "Photoshop" software mentioned above. This function allows you to pass from an RVB encoded image where the color (including the hue) of each pixel is encoded in 24 bits to an indexed or classified image where the color (including the hue) of each pixel is encoded with a limited number q of bits that return to the reference colors of which the color (including the hue) is coded in 24 hours. This function is in the original intended to reduce the obstruction in the memory of the computer of images to which it is applied. When the choice of n base colors is satisfactory, the composition of the colored elementary surfaces is decomposed in step 12, in n monochromatic images 12 .., ..., 12 to superimpose. As an example, a fragment 12 of the composition of colored elementary surfaces is shown in FIG. 3. This fragment 12Q is constituted by a set of elementary surfaces of constant dimension and regularly juxtaposed, of which the color is chosen from a predetermined number of base colors, equal to five in the example considered. After the decomposition, five monochromatic images 12 to 12 are obtained, of which the superposition or superposition gives the image again In the following step 13, the negatives 131 to 13 are made, respectively, from n monochromatic images 12 to 12, which will serve in the subsequent engraving, in step 14, of n plates of application rollers 4. During the use of the machine 1, the set of application rollers 4 left in step 15 in each blanket 2 of ink points of the same size, square in the example considered, regularly juxtaposed, and of which the distribution as a function of colorful, they join those different pixels on the image obtained in stage 10 of the procedure. The ink spots deposited in each blanket 2 are transferred during step 16 on the object to be printed. An image obtained by a method according to the prior art has been represented in figure 12. As can be seen in the examination of this figure, the image is constituted by the superposition of monochromatic images in the form of a grid, with the different plot angles, the density variations in the monochromatic images are translated by a variation in the size of the images. points that make up the plot. An image obtained by the implementation of the first example of the method has been represented as an example in figure 13. This image is constituted by a composition of colored elementary surfaces, the elementary surfaces are square or in pictures of the same size and regularly juxtaposed. In the particular example described, the surface of the object on which the image is printed is indicated to be of a uniform, white tone or tint and it will be highlighted in the image shown in Figure 13 the absence, in some parts, of points of ink within said composition of colored elementary surfaces, thus allowing the background color to appear. Of course, a background other than white or non-uniform color may be used and taken into consideration during the generation of monochromatic images in step 12 of the process. The first example of the procedure that must be described, considerably reduces the problem of contamination of inks during offset printing to dryness. However, the visual reproduction of the printed image is also improved by choosing, for one of the base colors at least, a number of shades greater than 2, according to the invention. In an example of the process according to the invention, described with reference to figures 4 to 11, the original 6 in color is decomposed into a composition of colored elementary surfaces with inks selected from n base colors and shades per base color. The number of base colors n and shades m by base colors is indicated in step 7 ', and in the case of step 8' certain base colors and / or shades are imposed. If the total number of dyes or tones in which it is desired to decompose the original 6 in color is greater than the number p of dyes or tones imposed, the remaining dyes or tones will be selected manually or automatically in step 9 '. taking for example the stains or statistically majority tones in the original in color and no longer selected. A composition of colored elementary surfaces is constituted in step 10 'of the process, said elementary surfaces are arranged according to a predetermined distribution, the color of each elementary surface is chosen among the n base colors and their shades, the choice of base color and the hue attributed to each of said elementary surfaces is made so that this composition of colored elementary surfaces visually reconstitutes the image to be reproduced. The decomposition of the original in color in n base colors with m shades per base color can be done using the "Photoshop" software mentioned above, thanks to the step function or transition of an RVB encoded image to a classified or indexed image. The user can visualize in step 10 of the process the composition of colored elementary surfaces by means of a video screen connected to the computer., the elementary surfaces are constituted by regularly juxtaposed squares, as illustrated by figure 9. However, it does not leave the field of the present invention imposing other forms of elementary surfaces and other arrangements of these before effecting the decomposition of the original in color, so before attributing a dye or tone to each elementary surface. For example, one can choose a juxtaposition of hexagons as shown in FIG. 10 or a juxtaposition of triangles as shown in FIG. 11. It can also be proposed, without leaving the frame or scope of the invention, a non-regular arrangement of the elementary surfaces, with a variable spacing between them. The use of regularly juxtaposed squares, however, has the advantage of corresponding to the fixing structure on the video screen of the indexed or classified image of the "Photoshop" software mentioned above. As this has been described above, it is possible to return to step 7 'of choice of base colors and shades if the image obtained in step 10' of the process is not satisfactory, for example because of the choice of certain colors of tax base. It will be noted that the user can easily perform several tests, without it being necessary to proceed to calculations to determine the dyes or tones that result from the mixture of subtraction of primary colors, contrary to the classic printing in four-color. The composition of colored elementary surfaces is then decomposed in step 12 * of the process into a set of monochromatic images. For each monochromatic image corresponding to a base color, the nuance attributed to each elementary surface is translated by the filling of a predetermined proportion of these with this base color.

In the event that the nuances of a base color are encoded in 8 bits, which corresponds to 256 possible shades per base color, the binary value 0 that is translated by the absence of base color that is considered corresponds to a nuance of this base color, in association, for a same base color, at each binary value a respective size or dimension and a point shape, this point fills in a predetermined proportion the corresponding elementary surface. Thus, a slightly saturated hue corresponding to a low binary value will be restored, in the example described, by the filling of a small or small portion only of the total surface area of the associated elementary surface while a very saturated hue corresponds A strong binary value will be translated by filling a large proportion of the total area of the elemental surface. By assigning a non-null binary value to a point size, 255 different point sizes are obtained, and the null binary value is translated by the absence of a point. It is also possible, without leaving the framework or scope of the invention, to attribute a single point size to a predetermined area of binary values. As an example, when the binary value that translates the hue of the base color considered is between 0 and 100, the nuance can be translated by a point that fills 30% for example of the total surface of the associated elementary surface and when said binary value is between 100 and 200, the nuance can be translated by a thicker point that fills in 60 % for example of the elementary surface, etc ... As an example, a fragment 12 'of a composition of colored elementary surfaces has been represented in figure 5 and the reproduction of the nuances of the base colors has been illustrated. by a more or less large filling of each elementary surface. The decomposition of the composition of colored elementary surfaces into monochromatic images 12 'to 125' has also been illustrated in this figure. The person skilled in the art will notice that the monochromatic images obtained from the decomposition of the indexed or classified image obtained in the step 10 'of the procedure, can have the same aptitude in the restitution of details as this one. Thus, the contrast can be localized thanks to the invention, on the printed image precisely with the identical one of the indexed or classified image that has served to realize the monochromatic images. It is then possible to avoid, thanks to the invention, the loss of visual definition found in the prior art methods and due to a difference in resolution between the starting image and the resolution of the monochromatic imagery that serve in plate engraving and obtained from this starting image. Once the monochromatic images have been obtained in which the different nuances are translated by points that fill in a proportion dependent on the nuance to reproduce the elementary surfaces, we proceed to the realization of negatives in stage 13 and then to the engraving of the plates in the step 14. Next, the ink points are deposited in step 15 on each blanket, which are transferred during the step 16 in the object to be printed. In order to avoid that two ink points associated respectively with two adjacent elementary surfaces and which do not completely cover the latter or touch each other during printing, it is preferred that each ink dot be centered on the corresponding elementary surface. Three forms of ink dots corresponding respectively to an increasing or semicircular occupation of the associated elementary surface have been represented as an example in figure 6, to reproduce three shades of a base color corresponding to increasing binary values representative of a nuance increasingly saturated. The choice of the shape of the ink point that allows to restore a shade coating the selected elementary surface in a chosen proportion, it is advantageously carried out taking into account the problems associated with thickening. The shape of the ink dots can also be adapted to the nature of each ink used. Preferably, a shape of sharp and elongated ink dots is chosen in the direction of movement of the medium to be printed during printing. As an example, an ink point of elongated and sharp or pointed shape in the direction of deflection of the substrate to be printed, represented by an arrow in this figure, is shown in FIG. In a particular implementation of the method according to the invention, they are chosen to restore several shades of a base color of the ink spots constituted by the more or less complete pattern of a predetermined theme. As an example, three shapes of ink dots corresponding to three different shades of a base color, these ink dots corresponding to the drawing or progressive design, and preferably according to a random fill are shown in figure 7. , of a predetermined motif or theme that represents an O. By random stuffing, it will be understood the fact of designing the motif or theme to be treated or elementary points randomly distributed within the cover or outer layer of the motif. The complete impression of the pattern inside an elementary surface corresponds to a predetermined hue that has a certain degree of saturation. Any more saturated hue corresponding to a larger proportion of colored surface within the elemental surface is obtained by filling in a given proportion the surface of said elementary surfaces / which is outside the cover or packing of the pattern, preferably in a random Thus, when the hue corresponds to the filling of a greater part of the associated elementary surface, the motif becomes more difficult to discern. From a certain degree of filling, it is no longer possible to recognize the reason. To restore a less saturated hue corresponding to the filling of a weak or smaller proportion only of the elementary surface, the motif is only partly represented. Below a certain proportion of filled elemental surface, it is no longer possible to recognize the reason. FIG. 14 shows a composition of colored elementary surfaces obtained by the method according to the invention, these elementary surfaces are constituted by regularly juxtaposed squares. Each elementary surface is either not colored, in which case it lets the background color appear, or colored by one of the three colors A, B and C, the shades are translated by the respective points of different sizes as illustrated in this figure . The three monochromatic images obtained by decomposing in each of the colors A, B and C the composition of colored elementary surfaces shown in FIG. 14 and which were used in the realization of the negatives used for printing, have been represented in figures 15 to 17. . Figure 18 shows a monochromatic image in which each ink point, arranged inside an elementary surface constituted by a square, represents the same motif or drawing more or less designed or drawn, according to the nuance to be restored. By way of indication, when the elementary surfaces are the squares regularly juxtaposed, each square can have on the printed support 127 μm on the side for example, which will be equivalent to a resolution of 200 lines per inch (79 lines per cm). It is possible, by virtue of the invention, to isolate a point that for example completely fills a square elementary surface of 127 p a side by not filling the adjacent elementary surfaces. By way of indication, in a classic amplitude modulation pattern with 133 lines per inch (52 lines per cm), the size of the points when they are separated by a distance equal to their diameter equals 95 >; um. This dimension is considered as the dimension for which the visibility of an isolated point is optimal, because when the points are less similar or approximate, they are smaller and more difficult to perceive and when the points are closer or similar, they are thicker and it is more difficult to discern each point individually. Thus, in the previous example, in spite of the fact that an isolated point is thicker in the invention than an isolated point of an amplitude modulation frame, it is possible to have a higher resolution thanks to the invention, which is also surprising at first view. The best resolution provided by the invention, can provide the observer with an impression of fineness of the observed image.

On the other hand, when the number of shades is at least three per base color, the points that completely fill an associated elementary surface in the support are minor and it can be tolerated that two points are slightly coated during printing at the rate of thickening phenomenon, without fearing an important problem of contamination of the inks in the printing in the case of offset to dryness. Another example of the method according to the invention will now be described with reference to figures 19 to 24. In a general manner, a color can be defined by its tint or hue, its luminosity and its saturation. An example of a chlorimetric space is shown in FIG. It is conventional to materialize by the projection on an L axis the degree of luminosity of a color, by the angular position around this axis, the tint or tone of the color and by the distance of this axis, the saturation S of the color. Thus, the colors located in this space in the same circle centered on the L-axis have different tints or tones but identical luminosity and saturation. In the example of the implementation of the invention, which has been described above, the nuances of the same base color are obtained by filling more or less an elementary surface, which turns globally to move in the direction D in figure 19 In fact, by decreasing the portion of the elementary surface that is colored, the luminosity is increased and the saturation is decreased and the portion of the elementary surface that is colored increases, the luminosity decreases and approaches the maximum saturation (the background is uniformly white) The example of the method according to the invention which is now described is intended to further extend the number of shades that could serve to reproduce the original in color, varying the luminosity parameter downward, ie according to the direction E in figure 19, from a hue corresponding to the degrees of brightness and saturation given. In this fact, the black ink is deposited in a more or less large proportion within the elementary surface which is otherwise colored in a proportion chosen according to the saturation of the hue to be reproduced. A first range of five elementary surfaces 20, to 20, which are colored in an increasing proportion by a given ink, is shown in FIG. The surface 20, ... is not colored at all and the surface 20, r > It is completely colored. The surfaces 20 ... «and 20 (I.) corresponding each to the given brightness and saturation levels serve to generate, by progressive addition of the black, the second and third families of shades, respectively referred to as 20 (4i). to 20 ... and 20 ... to 20 (5) It is thus understood that the use of black ink allows to increase the number of shades that serve to decompose the original in color, since it allows to restore the luminosity variations to saturation For each base color, it has been possible to restore certain shades using black ink during printing, which is deposited on certain elementary surfaces of the support.The contribution of black ink can be made in a single operation after the deposit from the set of other inks, as illustrated in FIG. 21. Above this figure, a printed support fragment has been represented by deposit within the elementary surfaces of d iferentes inks of color, filling more or less each elementary surface according to the saturation of the shade to be restored. To obtain certain shades, a deposit of black ink has been made. This black ink tank can be made after printing other used colors. The various steps of the process will now be described in detail with reference to Figure 22. It begins with the acquisition of the image to be reproduced in the form of a file 21 of numerical data, for example an RVB encoded file. The distribution 22 of the elementary surfaces, for example one of the distributions illustrated in FIGS. 9 to 11, will be chosen and the set 23 of the base colors and the shades of these base colors in which it is desired to make the decomposition of the original to reproduce. An indexed or classified image 24 is also created, which corresponds to the illumination by the colors and shades of the set 23 of the elementary surfaces defined above, the composition of colored elementary surfaces thus obtained visually restores the image to be reproduced. The indexed image obtained in step 24, in a plurality of monochromatic images, is then decomposed in step 25, each image corresponding to a given base color A, B, C, TLC «• • • Next, in step 26, the monochromatic images A, B, C, ... are decomposed into respective images A * -NA 'B ~ NB' C-NC * *** that rea9ruP n the nuances that do not intervene to the black color and in the respective images N-, N ", N_ ,, ... that make only the black color intervene. The different images N., Nß, N, ... are superimposed in step 27 to obtain a monochromatic image N in black and white. For the plurality of monochromatic images A-NA, B-Nß, C-Nc, ... and N is determined in step 28, for each nuance, the size of the ink spot to be deposited in the support to restore this hue and is attributed to it in the stage 29 at each dot size a pattern occupying the elementary surface of the support in the required proportion. A plurality of monochromatic images M, M, M, ... and M are obtained in which the shades are restored by the presence within each elementary surface of an ink point of predetermined size and shape and are carried out if necessary from these monochromatic images the negatives that are used to make the printing rollers. The support is printed in step 31 with the different basic colors very different from the black color. The black ink is printed in step 32 and a reproduction 33 of the original image is obtained. During the printing process used, it is not a method of offset printing to dryness, the black ink can be deposited directly on the ink previously printed on the support as illustrated in figure 23. During the printing process there is an offset process dryness, to avoid overlapping of inks and mixing problems, it can be when determining the shape of the ink spot that will be deposited on the support to restore a given shade of color, take into account the shape and size of the spot of black ink that will be deposited later to modify the luminosity of the hue considered. More particularly, color ink can not be disposed in the region of the elementary surface which will then be coated with the black ink, as illustrated in FIG. 24. The invention is not limited to the examples of processes that are have described. The invention thus advantageously applies to other printing methods such as dry offset printing, for example screen printing, sublimation or other printing, the shape of printed dots which can be adapted to each printing mode to compensate for faults or defects. By the structure of the final image on the printed support, the invention is particularly well adapted to the printing of the images encoded in the numerical form. The person skilled in the art will understand that the invention can allow to benefit the advantages inherent to conventional frames provided for frequency modulation and amplitude modulation, namely on the one hand the sharpness of the printed image (by the location of the contrast on the identical the starting image) and on the other hand the impression of sweetness or softness (due to the constant spacing of the points of the frame), without the drawbacks of these conventional frames, namely an effect of repercussion for the frame to frequency modulation and a fuzzy or inaccurate effect for the frame to amplitude modulation.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property

Claims (31)

1. A method for printing on a support a color image, characterized in that it comprises the steps consisting of: decomposing the image to be reproduced in a composition of colored elementary surfaces, said elementary surfaces are arranged according to a predetermined distribution, the color of each elementary surface is chosen from a predetermined set of base colors and a predetermined set of shades of these base colors, the number of shades for at least one base color is greater than or equal to three, the choice of the base color and the shade attributed each of said elementary surfaces is carried out in such a way that said composition of colored elementary surfaces visually reconstitutes the image to be reproduced, - printing said composition of colored elementary surfaces on said support by means of inks of which the dyes or shades are chosen for be able to reproduce, taking into account the color of said oporte, such base colors and their shades during printing, the hue of a base color attributed to a given elementary surface, is obtained during printing by applying the ratio of each ink within the corresponding elementary surface on the support.

2. The method according to claim 1, characterized in that the shades of a base color have at least the same saturation but different luminosities.

3. The method according to claim 2, characterized in that the shades of a base color which have the same saturation but different luminosities, are restored during the printing thanks to a more or less large proportion of black ink inside the elementary surfaces of the support that are being manipulated by obtaining such nuances during printing.

4. The method according to claim 3, characterized in that when the same elementary surface of the support is contacted at the same time by a deposit of black ink and by a deposit of an ink different from the black ink, the deposit of the black ink and of said ink different from the black ink, is made with predetermined patterns or drawings for each one of the inks, chosen to avoid the superposition of two inks.

5. The method according to claim 3, characterized in that the deposit of the black ink is made with superposition in at least one other ink already deposited in the support.

6. The method according to any of claims 1 to 4, characterized in that it is applied to offset printing in dry or dry conditions.

7. The method according to any of claims 1 to 6, characterized in that said base colors are non-primary colors.

8. The method according to any of claims 1 to 7, characterized in that at least all the inks except one have dyes or shades chosen among said base colors.

9. The method according to any of claims 1 to 8, characterized in that said elementary surfaces have the same shape.

10. The method according to claim 9, characterized in that said elementary surfaces are deduced or reduced to each other by translation.

11. The method according to any of claims 1 to 10, characterized in that said elementary surfaces are juxtaposed.

12. The method according to any of claims 1 to 11, characterized in that said elementary surfaces are of squares or squares.

13. The method according to any of claims 1 to 12, characterized in that each ink point is centered on the corresponding elementary surface.

14. The method according to any of claims 1 to 13, characterized in that an ink spot is printed on each elementary surface in the support of which the shape and size depend on a predetermined ratio of the hue of the base color to be reproduced.

15. The method according to claim 14, the printing is carried out by bringing the support to be printed on the contact of an ink-laden surface with a direction of displacement substantially tangential to said surface charged with ink, characterized in that said ink points present, when not they fill the entire extension of the associated elementary surface, a shape adapted to reduce the phenomenon of thickening, and preferably a substantially elongate shape and sharp or pointed in the direction of movement of the support.

16. The method according to any of claims 1 to 15, characterized in that a hue is obtained in the printing, for at least one of the base colors, by printing a predetermined pattern such as a logo.

17. The method according to claim 16, characterized in that several shades of at least one of the base colors are obtained by the printing, in a more or less large proportion, of a predetermined motif or theme such as a logo.

18. The method according to any of claims 1 to 17, characterized in that the inks are deposited in the form of ink dots of which the geometry is different according to the ink used.

19. The method according to any of claims 1 to 18, characterized in that said support is white before printing.

20. A printing machine characterized in that it comprises ink application surfaces respectively loaded with ink dots respectively located within the elementary surfaces arranged according to a predetermined distribution, to visually reconstitute, during printing on a support, an image to be reproduced, the color of each ink dot is chosen from a predetermined set of base colors, each given elementary surface is coated with ink in a chosen ratio as a function of the hue to be reproduced, the number of shades is at least three for at least one base color .

21. The printing machine according to claim 20, characterized in that the colors of the ink spots are not primary.

22. The dry or dry offset printing machine, characterized in that it comprises at least one blanket and application rollers carrying or holding reliefs or embossments disposed so as to deposit in said blanket a set of ink dots respectively located within the elementary surfaces arranged according to a predetermined distribution for visually reconstructing during printing on a support, an image to be reproduced, the color of each ink spot is chosen from a predetermined set of base colors, each given elementary surface is coated with ink at a chosen ratio in Depending on the hue to be reproduced, the number of shades is at least three for at least one base color.

23. The dry offset printing machine according to claim 22, characterized in that each relief or enhancement intended to deposit or leave the ink within an elementary surface to reproduce a shade has a substantially elongated shape and sharp or pointed in the direction of travel of the medium to be printed.

24. A printing support characterized in that it has an outer surface in which an image has been printed consisting of a set of ink points respectively located within elementary surfaces arranged according to a predetermined distribution, the colors of said ink dots are chosen from a set predetermined base colors, each ink point of a given base color fills a more or less large proportion of the corresponding elementary surface, according to the hue of said base color to be reproduced, the number of shades is at least three for at least one base color.

25. The printing medium according to claim 24, characterized in that said elementary surfaces have the same shape.

26. The printing medium according to any of claims 24 and 25, characterized in that said elementary surfaces are juxtaposed.

27. The printing medium according to any of claims 24 to 26, characterized in that each elementary surface is constituted by a square.

28. The printing medium according to any of claims 26 to 27, said outer surface is cylindrical, characterized in that said ink points have, when they do not completely fill the corresponding elementary surface, a substantially elongated shape and sharp or pointed in the direction of offset of the support during printing.

29. The printing medium according to any of claims 26 to 28, characterized in that each ink point is centered within the corresponding elementary surface.

30. The printing medium according to any of claims 26 to 29, characterized in that several shades of at least one base color are restored by the printing in a more or less large proportion of a predetermined pattern or subject such as a logo.

31. The printing medium according to any of claims 26 to 30, characterized in that at least one elementary surface has received a black ink dot and a dot of a different black ink, the size of the black ink dot is in function of the luminosity of the hue to be reproduced. SUMMARY OF THE INVENTION The invention relates to a method for printing on a support a color image, characterized in that it comprises the steps consisting of: decomposing the image to be reproduced in a composition of colored elementary surfaces (24), such elementary surfaces are arranged according to a partition predetermined (22), the color of each elementary surface is chosen from a predetermined set of base colors and a predetermined set of shades of these base colors (23), the number of shades for at least one base color is higher or equal to three, the choice of the base color and the shade attributed to each of said elementary surfaces is carried out so that said composition of colored elementary surfaces (24) visually reconstitutes the image to be reproduced. - printing such a composition of colored elementary surfaces on said support by means of inks of which the shades or dyes are chosen to be able to reproduce, taking into account the color of said support, such base colors and their shades during printing, the hue of a base color attributed to a given elementary surface is obtained during printing by applying the ratio of each ink within the corresponding elementary surface on the support.