The current status of gravure platemaking (below)

Packaging gravure plate, and color proofing method <br> <br> plate package and the plate is substantially the same publication, but if combined with plastic film and the printed publication is different, the use of multi-color ink, the color is generally 6 , 7 color printing. Therefore, the plate making method that meets these conditions must be considered in the plate making, which is different from publishing printing.

Packaging prints are usually printed in multiple impositions on the same screen, but a single plate is made in the platemaking, and color proofing is also performed in a single frame. The problem of proofing can be said to be the same as that of publishing, but there are many problems with spot colors. In the printing proofing, the spot color ink can be used to correspond, but a color printer is used, and only the basic ink is used together with the method of expression. In such cases, too high quality cannot be expected.

As described above, in the platemaking software unique to packaging plates, there are (1) multi-format imposition function; (2) no-joint ring-and-band image connection function; (3) spot color separation function; (4) trapping function (corresponding to misalignment during printing, outlines of patterns are slightly overlapped, especially during film printing).

Plate making and upper printing plate

No matter how good the film master and digital plate data are, if the accuracy of the printing roller cannot be guaranteed, the quality of the printed matter cannot be guaranteed. This is considered to be the most stringent in gravure printing in various printing plate formats. The following are the contents of the process and processing from the preparation of the roller to the final production of the printing press.

roller

The substrate of the drum is generally an iron pipe, which is due to its low cost and robustness. Weights range from tens of kilograms (related to packaging) to hundreds of kilograms (related to publishing, building materials), and depending on the application, some are nearly one ton. Recently, aluminum has been used. More recently, plastics have also been used for the manufacture of packaging rolls.

The wall thickness of the iron pipe is from 20 mm to 300 mm, and the large diameter roller wall is thicker. No shaft in the drum (for packaging purposes) or with shaft.

Roller copper plating

Regardless of the substrate, copper plating is applied to the surface of the newly manufactured roll. This copper layer is not an engraving and etching layer, but uses this copper plating layer to make the precision of the drum. For example, for cylinders with diameter accuracy within 10 μ and parallelism within 10 μ, the copper plating thickness is 600 μm. In this copper plating layer, the copper layer required for etching and engraving is usually plated, and the thickness is about 80 μm depending on the pattern of the plate. When using the engraving method, hard copper plating is required.

Image formation

After copper plating on the drum, image formation processing was performed on the copper surface. The processing methods include: (1) When a resist film (carbon paper, photosensitive resin, black paint) is used, the resist is transferred or applied onto the copper-plated surface. Image copying is performed on carbon paper or photosensitive resin, an image is formed on a high-sensitivity resin and black paint by a laser, and then chemical etching is performed by using a ferric chloride or the like through a resist film; (2) an engraving method. Engraved directly on the copper surface. Alloys and resin layers have been used instead of copper plating to form images using lasers, but most of them are under development.

The depth of the formed ink groove is generally from several μ to 60 μ. The density of the grooves is from 2 500/cm 2 to 10 000/cm 2 . Laser can be used to make higher density.

Chrome plating

After the ink tank is formed on the copper plating surface, it can be used as a printing roller. However, ink falling outside the groove during printing causes the blade to scratch the copper surface. Therefore, the copper surface is plated with chromium (about 10 μm). After this series of processes, the intaglio printing cylinder was made.

postscript

Gravure printing technology has indeed evolved to high efficiency and high productivity in the prepress digital environment. In recent years, full automation of roller production has become a research topic. At this point, depending on how the ink tank is formed, the development is not the same. The introduction of a chemically etched laser provides excellent detail reproduction, but chemical etching may no longer be used in the future.

In this regard, the engraving method does not have a corrosion process, but it is inferior to the laser method in reproduction and productivity of details. As various ways are still under development, this is also the hope for the future. I want equipment. ”