DE2811787A1 - PRODUCTION OF GRAVURE PRINT PROOF PRINTINGS - Google Patents

Description

Company DAI NIPPON INSATSU KABUSHIKI KAISHA, 12, Kaga-Cho, 1-Chome, Ichigaya, Shinjuku-Ku, Tokyo-To, Japan

Production of rotogravure proofs

The invention relates to proofs and corrections in gravure printing and relates to a simple trial proofing process, which can be used for proofs and corrections in gravure printing.

When printing, it is customary to make test proofs, i.e. to make a test print for the customer or client of the print can determine that the printed matter desired by him is produced. This process is commonly called Designated test and proof prints, but the number of proofs is very small, namely of the order of magnitude of up to ten

Pages and of these a number of sheets. The proofs are also made to check for imperfections in the faces of the printing plates Correct as well as pale print, unevenness and color errors. So you have to expect from the outset that that a printing plate used for the proof is corrected. When the proof of the proof is finally sent to the customer delivered printed matter differs, i.e. from the final

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Print, then they are irrelevant as samples. On the other hand, from the point of view of the test impression, it is not necessary that the proof was made in exactly the same process and operation as the final print. It will for the purpose of so-called proof presses used exclusively for the production of proofs to a large extent.

In the case of gravure printing, which is different from letterpress printing and offset printing differs, proofs are not easily made, and corrections are not easily made during or after the completion of the plate-making process are difficult. For this reason, so-called blue printing or cyan printing is used, in which from the tie & back halftone positive a blue print is made as a proof before plate production begins. While it is possible with Blueprint proofs to check the dimensions and arrangement of the image or characters and letters and the like, however the photographic gradation and other properties that only appear after the plate has been made, as well as the tone effect do not check for intaglio printing. It is therefore necessary in such cases to accept the disadvantages with the main printing press or with a sample press, the structure of which is similar to that of the main press, to produce the sample prints.

It is therefore the object of the invention to provide a simple To create sample printing methods for gravure printing in order to overcome the disadvantages mentioned above.

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Gravure printing and offset printing differ in the printing process, and their grid point structure is also different. This difference in these two printing processes only means that the Procedures for the production of an image identical to the original are different, but not that the prospective one Image cannot be reproduced. The differences between the respective grid dot structure can only be seen with the microscope while the prints are usually viewed directly with the eye. In view of this fact the test print does not need to be carried out in the same process and under the same working conditions as the print of the final edition. It was therefore actually possible to establish that test prints for gravure printing were produced using the offset printing process without having to accept negative results of the test printing process; forms this statement the basis of the invention.

More specifically, according to the invention, there is provided a method of proofing for gravure printing, which is characterized as follows: A contact screen is placed on the light-sensitive layer of a raw plate for offset printing and a halftone film is placed over it (positive or negative) for the gravure printing process; this layering is then exposed from the side of the halftone film, whereby a photo print is produced; this plate is developed to make a printing plate. The developed plate will eventually used to make a proof, in order to produce a proof for gravure and for correction.

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The invention will now be based on the drawing of exemplary embodiments explained in detail. Show it:

1: a schematic sectional illustration of the layering on top of one another a raw plate for offset printing, a contact screen and a halftone film for gravure printing when performing photo printing according to a first embodiment of the invention;

Fig. 2: a diagram showing three print reproduction curves for comparison juxtaposes;

FIG. 3A: a representation similar to FIG. 1, where the main exposure is carried out with a halftone positive according to a second embodiment of the invention;

Figure 3B: an illustrative image showing how the halftone halftone dots in an offset raw plate as a result of the main exposure be formed;

Fig. 4A: a sectional view showing how an additional exposure is carried out; and

Fig. 4B: a diagram which shows the way how halftone dots are formed on the offset raw plate as a result of the additional exposure.

1 shows the basic principle of a first variant of the method shown for proof printing according to the invention. In the method, a raw plate 1 for offset printing is used with a contact grid 2 and a halftone film 3 such as a halftone positive or halftone negative for gravure printing.

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Any plate customary for this purpose can be used as the raw plate 1 for offset printing. These can be polymetallic plates, Deep etching plates, dry offset plates and in advance It is a matter of sensitized plates, all of which have a light-sensitive layer on one surface. Used as halftone film 3 If a halftone positive is used, an offset printing plate with a positive light-sensitive layer that passes through Photolysis is decomposed, while when using a halftone negative a raw plate with a light-sensitive layer is suitable is of the photopolymerizing or photocrosslinking negative type. A plate sensitized in advance is particularly useful for uses a negative type, but their use is desirable for both a positive type and a negative type because of them Advantages in the simple handling when used for the production of test prints.

A grid for gravure printing as well as one for offset printing can be used as the contact grid 2. Screen for offset printing are cheaper.

As the halftone film 3 for the gravure printing process, halftone positives and halftone negatives are used, as already mentioned. A halftone positive is used as a halftone film in almost all cases conventional gravure printing processes used in which as photosensitive Material a carbon foil is used, but in gravure printing, in which an electronic engraving machine

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is used, both a halftone positive and a halftone negative can be used. The halftone positive can be in the form a color separation film, e.g., by photographing an original with a camera or by scanning the original with a color scanner, and the film is then in the required size. The halftone negative can be produced, for example, by photographing the halftone positive shown in above Way was produced as a color separation, obtained with a camera and then obtained as a negative in the required size getting produced.

The contact screen 2 and the halftone film 3 are made in this order arranged one above the other and directly in contact with the light-sensitive layer of the offset printing raw plate 1, and then exposed from the side of the film 3 as indicated by arrows. This exposure can be as with the photo printing process a halftone positive can be carried out in offset printing. Following exposure and photo printing, the plate is made like an ordinary offset printing plate, further processing steps subjected, e.g. to developing, rinsing, sensitization treatment, a repeated washing process, removal, washing, gumming and drying, after which a printing plate is completed is. The aforementioned developing process can be carried out in a common method such as brush development or spray development, be performed.

With a printing plate obtained in this way, the test print is carried out in offset

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process carried out as a normal offset test print, with which a print proof is obtained. In this test prints an attempt _(to approach the low pressure, which is why the use of a highly transparent color is desirable in view of the type used for offset sample print color of the color. It has been shown that the achievable with the gravure printing process Halbtoneindruck can be achieved when a contact grid of such fine lines such as more than 200 lines per inch are used.

The invention makes it clear that with the invention a complete new and very simple test printing process for gravure printing is created, compared to the previously used test printing process for gravure printing brings with it a considerable reduction in working hours and production costs. It should be noted that the invention applies not only to ordinary gravure printing processes with chemical etching processes, but also to gravure printing can be used with electronic engraving processes.

To further clarify the nature and usefulness of what is described Procedure, an example from practice will now be presented.

example 1

A positive type (150 lines per inch) contact grid is provided with its surface facing down on the photosensitive layer

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placed on a sensitized plate, and a halftone positive for intaglio printing is then placed on this grid plate, which is also is placed upside down in close contact.

will
The photo printing process by irradiation through the halftone positive

ten
for minutes with a single metal halide lamp

of 2 kW.

The sensitized plate is then sprayed during one minute (the plate moves one meter in thirty seconds) with a developer solution that passes through Dilute a concentrated developer solution five to six times (caustic soda, sodium silicate) is sprayed for sensitized plates. Then the plate is washed with water, a sensitization treatment with developer color (manufacturer Fuji Shashin Film Kabushiki Kaisha / Fuji Photographic Film Company, Japan) and then washed with water. Unwanted parts are removed with a solution, and then the plate is washed again with water. The plate is finally gummed up and dried, after which a finished one Printing plate is present.

The above procedure is carried out to make printing plates for all four colors, namely cyan, black, magenta and yellow.

With these printing plates, a multicolor print is made on a sample printing press produced in the order of the color separations cyan,

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black, magenta and yellow with printing inks for sample printing (manufactured by Morohoshi Ink K.K. Japan), making printed matter which are suitable as samples for gravure printing.

The print reproduction curve of a print made with a printing plate produced by the first method is represented by curve A in Fig. 2, in which a halftone positive was used as a halftone film. A print reproduction curve of a gravure proof of the output print using a printing plate produced in the ordinary gravure plate making process is generated using the same halftone positive for the low pressure, is with the curve B in Fig. 2 shown. Compared to curve B, curve A shows that in the dark area of the halftone positive the photographic density of the The proof is higher than that of the final print, while the ratio is in the positive light area is reversed. This means that the proof print product is harder than the print product of the final edition and in the Dark zones the tone gradation is poor.

If the exposure is increased to get a good tone gradation in the dark areas, then the tone of the proof will be even harder, and the lack of density in light becomes even more pronounced. In contrast, the exposure is decreased by To counteract the low density in the light to middle parts, then the gradation in the dark areas will still increase

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more serious.

The development of a suitable contact grid with which practical Coincidence of the reproduction curve A for the test print product and the reproduction curve B is also achieved extremely difficult. As a result of studies aimed at improving the first method described, a When halftone positive was used as halftone film, it was found that by taking out only halftone positive for gravure printing later in the first process and applying an additional exposure, the print reproduction curve is very close to the curve of the gravure product can be brought up. This discovery forms the basis for a second embodiment of the invention, which will now be described.

As shown in Fig. 3A, they are sequentially a contact grid 2 and a halftone positive 3a on a photosensitive layer of a Raw plate 1 for offset printing laid on top of one another in layers and are then exposed to light for the photo printing process. This exposure is referred to as "main exposure" hereinafter. An exposure is preferably used in this process step on the order of 60 to 90% of the exposure used in the first embodiment of the invention will.

Fig. 3B is a graphic explanatory image from which it can be seen how the dots on the offset raw plate by the main exposure process are formed. It will in the present case

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Assume that the halftone positive 3A for gravure printing has an area with an optical density distribution indicated at 4 is shown, and in connection therewith a contact grid 2 with an optical density distribution as shown in FIG. 5 is used is indicated. The light passing through then has a distribution as shown in simplified form at 6, which leads to the result of FIG Raster points on the offset raw plate 1 leads.

By using an exposure value in the main exposure process that is smaller than in the case of an additional exposure is carried out, 1 raster points are created on the offset raw plate of larger surface area, and the print density on the imprint becomes higher over the entire area. As a result, it also rises the photographic density in the light and middle areas, and the above-mentioned lack of density in the light to middle areas, which occurred in the first embodiment described has now been corrected.

In this way, the poor density in the light to middle areas is first with the help of the main exposure process corrected. On the other hand, since the amount of light used for exposure has been reduced, the tone gradation produced thereby is darker in the shaded areas than in the case of the first execution game, which is why, in order to correct this, the Halftone positive is removed for the gravure printing process and only the contact grid 2 remains on the raw plate 1, whereupon a additional exposure process from the side of the contact grid

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is made as shown at 4A. At this step, the desirable amount of light is on the order of 0.3 to 7%, in particular 0.5 to 4% of the above-mentioned main exposure process ·

Fig. 4B shows a graphic explanation of how the halftone dots are formed on the offset raw plate for the case that an additional exposure is superimposed on the first-described main exposure is made. The contact grid 2 with

a density distribution as in 5 gives a distribution of the passing through Light according to 6A. As a result, the raster points 7 produced in the main exposure process change into the raster points 7A.

The result of this additional exposure is a change in tone gradation in the dark areas, while the light to middle areas remain almost unaffected. The reason for this is that the density distribution of the vignetted grid points on the contact grid are effectively used. More precisely this means that in the case of the additional exposure, the exposure in the areas of low density of the contact raster 2 has a strong effect, and from this basically results in this tone gradation of the dark areas, which is not completely satisfactory only with the main exposure process can be reproduced. The light to middle areas have received small halftone dots in the main exposure process, which is then almost completely in the additional exposure of the areas of high density of the raster points of the contact raster

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are covered so that they are not influenced. Thus, with the help of the additional exposure, the desired Create tone gradation in the dark areas.

The print reproduction curve of a printed product produced in the test print using one according to the one just described Process produced plate is shown with the curve C in Fig. 2, from which it can be seen that it is very strongly approximates the print reproduction curve B of a product from the intaglio printing process, which in the output printing process with a Plate made using the same halftone positive for gravure printing in the usual manner. That The test print product has no worse properties than the print product that has emerged from normal gravure printing.

To the essence and the usefulness of the just described second embodiment To make the invention more clear, a practical example of this embodiment and a comparative example is given.

Example 2

A positive type (150 lines per inch) contact grid will be placed with its film face down on and over the photosensitive layer of a sensitized plate Screen becomes a halftone positive for gravure printing with its film area

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placed down / so that it is immediately with the one below Grid plate has contact. Thereafter, the main exposure process for photo printing is carried out by exposure through the halftone positive for 8 1/2 minutes with a single metal halide lamp of 2 kW power. Next will just removed the halftone positive for the gravure printing, and after the contact grid plate again firmly attached to the photosensitive Plate is pressed, an additional exposure step carried out for 10 seconds and over the entire area by irradiation from the contact grid side.

The sensitized plate is then developed by spraying for one minute (with a running speed of the plate of 2 m per minute), with a solution that by Dilute to five to six times a stock developer solution (caustic soda or sodium silicate) for those sensitized Plates is won. The plate is then washed with water, subjected to a treatment with developer ink (Manufacturer Fuji Photographic Film Company, Japan) and rinsed again with water. Using a cleaning solution will remove the unwanted Parts removed and the plate then washed again with water. Finally, the plate becomes customary Process gummed up and dried and then ready for printing.

The manufacturing process is carried out so that the four colors cyan, black, magenta and yellow required four color

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Extension panels are made.

By using these printing plates and the printing ink for the test print (manufacturer Morohoshi Ink K.K-, Japan) are in the Sequence cyan, black, magenta and yellow multi-color proofs carried out in a proof press (manufacturer J.G. Mailänder Druckmaschinenfabrik, West Germany) in order to produce print products that are used as rotogravure proofs can.

The printed products that were obtained with the method according to Example 1 could be used as rotogravure test prints, as described, but in comparison with the test prints of Example 2, they were harder in tone, and the tone gradation of dark areas was imperfect.

The test prints obtained by the first and second method examples are not entirely satisfactory in terms of gloss and transparency compared to gravure products from the normal gravure press. this depends to a large extent on the difference between the printing processes, since the transferred color film is thinner in offset printing than in gravure printing, and in order to get the same photographic density as in gravure printing, it is necessary to change the amount of pigment in to increase the printing ink.

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However, since the color film on the print in the case of offset printing is thin, the pigment particles protrude from the film, so that the paint film has an uneven surface. Furthermore, the Pigment content higher than in gravure printing, so that the basic color of the pigment emerges. For these and other reasons there is an improvement the color reproduction is difficult by increasing the picrment content in the color.

This difficulty is overcome with a third embodiment of the invention which will now be described. According to In this embodiment, the printed matter which is used as a test print for gravure printing is obtained in the same process as in the first and second embodiments of the invention, except that it is provided with a transparent resin coating layer as an overlay on the area that has received the pressure. This print is then used as a proof for verification and correction. In order to be able to apply a transparent resin coating layer to the entire printed area of the test printer product, this is done transparent resin dissolved in a solvent, to which, if necessary, additives are added, and the resulting Solution is then applied as a thin layer by rolling it up or the like with an applicator roller. A useful bees

The layering amount of this transparent resin is 5 to ^{45 g / m 2} (solid matter).

The transparent resin to be used is one that is based on the color reproduction and the halftone dot shape that is already on the

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28 Ί1787

Printed product is printed, has no influence and gives a transparency and gloss that is that of a gravure product corresponds, for which five to 60 percent by weight and preferably 10 to 40 percent by weight of resin in the solution are. Useful resins include: hardened rosin, nitrocellulose, polyamides, and vinyl chloride-vinyl acetate copolymers. These resins are very suitable for coating and give transparency and gloss after the coating process similar to that of a rotogravure product. Can be used as a solvent one can use toluene, xylene and normal hexane, each solvent in about the same amount by weight as the transparent resin is mixed. The additives mentioned above can be fillers such as calcium carbonate and magnesium carbonate or other additives, depending on the solution, their amount can be between 10 and 50%.

The transparent resin film can also be applied by a hot melt process. To clarify the advantage and properties of the third embodiment of the invention, a practical example will now be given.

Example 3

The manufacturing steps are as in Example 1 and Example 2 in order to obtain two different print products .

It is now a gravure cylinder with a completely solid top

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surface (depth 30μ) made in an ordinary gravure plate-making process. Two layers of a medium for intaglio printing, consisting of 50 parts by weight of dried rosin and 50 parts by weight of toluene, were applied to the test prints in two different ways on a rotogravure proof proof press and a transparent resin coating with a solids content of about 50 g / m ^{2 was} applied to the two prints.

The two different print products obtained in this way showed one thing Gloss and transparency that came very close to the corresponding values of a low-pressure product, and were no worse, so that they can be used very well as test prints for assessing gravure printing. The two printed products obtained in this way are included a transparent resin coating are in accordance with the printed matter without a transparent resin coating in terms of gloss and transparency Examples 1 and 2 are superior to and come out on top of the gravure printing results closer.

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Claims (11)

PATENT CLAIMS \\ J. Process for the production of test prints for the gravure printing process, characterized in that a contact grid plate (2) and a halftone film (3) for gravure printing are placed over the light-sensitive layer of a raw plate (1) for offset printing and the raw plate (1) is exposed through the film becomes for photo printing, the resulting plate is then developed to make a printing plate, and the plate is printed to print a proof for gravure proofing and proofreading. 2. The method according to claim 1, characterized in that the Halftone film (3) is a halftone positive. 3. The method according to claim 1, characterized in that the halftone film (3) is a halftone negative. 4. The method according to claim 1, characterized in that the Merck banking house. Finck & Co., Munich
(BLZ 70030400) Account no. 254649 809842/0 621 Bank house H. Aufhäuser. Munich (bank code 700 306 00) account no. 261300 Telegram address: patent senior Postal check: Munich (BLZ 70310080) Account number 20904-800 Raw plate (1) is made sensitive in advance. 5. The method according to claim 2, characterized in that after the exposure of the raw plate (1) with light from the side of the halftone positive (3a) forth the halftone positive (3a) is removed, so that only the contact grid plate (2) on the raw plate (1) remains, and this layering is then again subjected to a second exposure process from the side of the contact grid plate (2) will. 6. The method according to claim 5, characterized in that the amount of light of the second exposure process between 0.3 and 7% that of the first exposure. 7. The method according to any one of claims 5, characterized in that after the production of a test impression on the printed one A transparent resin coating is applied to the surface. 8. The method according to claim 7, characterized in that the transparent coating resin by dissolving a transparent resin is obtained in a solvent and this solution by gravure roll coating onto the surface of the test print product or by direct roller coating or reverse roller coating is applied. 9. The method according to claim 8, characterized in that the 8098A2 / 062T 3 - transparent resin is a substance from the following group: hardened rosin, nitrocellulose, polyamides or vinyl chloride-vinyl acetate copolymers, and that the solvent is toluene, xylene or normal hexane. 10. The method according to any one of claims 7 to 9, characterized in that that an additive such as calcium carbonate or magnesium carbonate is added to the resin. 11. The method according to any one of claims 7 to 1O, characterized in that the transparent resin for the coating is applied in an amount of 5 to 45 g / m ² , based on the solids content. 809842/0621