Magnetic Printing Technology and Mechanical Discussion--Gravure Printing (2)

(3) Basic types of gravure plates

The gravure printing plate has engraving gravure, photo gravure and dot gravure.

1. Engraving intaglio

Gravure engraving plates, according to the different methods of engraving, can be divided into hand-carved, mechanical engraving, chemical etching (etching) and electronic engraving and so on. The printing techniques involving the use of hand-engraved and mechanically-engraved plates for anti-counterfeiting will be described in detail in Chapter 6. Only chemical etching (etching) and electronic engraving are described below.

(1) Chemical etching The method of making gravure plates by means of chemical etching is called chemical etching, also known as etching.

The plate making method is as follows: First, the surface of the pretreated metal plate material is coated with an acid-resistant antiseptic wax layer. Using a sharp steel needle to draw a dotted line on the wax layer, the metal surface of the dotted line portion is exposed, and then it is etched into an intaglio plate with an acidic solution. The printing plate made by using the engraving method combined with the etching and engraving method is very meticulous in printing the dot-line graphic and is difficult to forge. Therefore, engraving and gravure printing is often used to print exquisite packaging and decoration graphics, fine arts and crafts, more suitable for printing a variety of paper money, stamps, bonds and other securities.

(2) Electronic engraving Gravure electronic engraving is a plate making method that uses an electronic engraving machine to directly sculpt pictures on a roller. It has the advantages of simple operation, rapid plate making, clear graphics and rich levels. The principle of traditional engraving platemaking is to place an original with a continuous tone separation image and text on an electronic engraving machine. The scanning head of the electronic engraving machine scans the original and reflects the color of the original on the original. The strength is changed to a current signal; different sizes of electrical signals are output to control the diamond engraving needles so that different shades of light are carved on the roller surface. The dot is light and small, corresponding to the bright part of the manuscript; the dot is deep and large, corresponding to the dark part of the original.

The electronic engraving gravure plate making process is as follows:

1 Make a scan original. Scanned originals can be used as reflective negatives or reflective positives. They are usually photographed with a white, opaque polyester film with low stretchability. If it is a color printing plate, the manuscript must be a color separation sheet that has undergone color correction and correction;

2 Degreasing and derusting copper plated gravure cylinders;

3 The gravure cylinder is mounted on the electronic engraving machine;

4 Mount the scanning original on the original roller;

5 Turn on the engraving machine to engrave the gravure cylinder.

Commonly used electronic stencil machines include Grafima electronic engraving machine and K-200 electronic engraving machine.

With the perfection of the color desktop system and high-end networking system, it has been realized to complete the printing plate production with a filmless electronic engraving system. Since the filmless electronic engraving system eliminates the use of the film and uses digital transmission of image signals, the cost of printing plates is reduced. Low and high quality, so this is the future direction of electronic engraving gravure.

(3) Laser engraved gravure laser engraved gravure engraving system is the essence of the integration of laser technology and electrochemical technology (electrochemical process is different from electro-mechanical process. Electrochemical process is a parallel process, that is, all grids are made at one time; The surface laser and electron beam engraving system is a series of processes, ie, one mesh is made at a time. In a series of processes, a low power and high speed laser controls the diamond carving knife, which is carved into a graphic on the layout surface.

2. Photogravure

Photogravure, also known as photocopying, was first made in England in 1890 using a photographic method. The inventor was Cole. Klietsch.

The feature of the photogravure layout structure is that the dotted line forms the graphic part of the recess, and the depth of each part is not equal; the blank part keeps the original plane of the plate and together make up the gravure plate.

The shades of inscription on the intaglio plate are related to the level of the copy. In the printing process, the deeper the picture on the plate is, the more ink is filled in, and the thicker the ink layer on the printed product is. After printing, the shallower the plate is, the lower the pressure is. After printing, the ink on the corresponding part of the printed product is thinner. In short, the thickness of the ink layer on the printing plate corresponds to the light and dark levels of the original image. The formation of photogravure depth must be achieved through the transfer of graphic and text on carbon paper and the corrosion of acidic solution.

(1) Gravure Photographic Processes Gravity of different dot sizes is expressed by the depth of the image indentation. Therefore, the graphic layers copied by gravure printing are represented by the thinness of the ink, which can truly reproduce the light and dark levels of the original image. This is a difference between photogravure printing and letterpress printing and flat printing, and even different from dot printing.

(2) The manuscript of the gravure plate is divided into continuous lines and texts, but some manuscripts often have both images and text descriptions. Combining the two, they may be monochromatic or colored. At present, there are more photographic manuscripts that have been adopted in China for black and white. No matter which kind of manuscripts, it must be done by photographic methods.

1 Image The photographic image of a positive image was taken as follows. First, the document was remakeed into a continuous smudging picture, corrected by layers, and then legalized. If the original is a color image, blue-violet, red-green, and yellow-color filters should be installed in front of the camera lens. In order, yellow, blue, magenta, and black images of separations should be taken. Corrections and corrections of colors, yellowing, blue, magenta, and black separation positives. After the Yang picture is made, it will be used directly to dry carbon paper. Therefore, the quality of the positive map must be reflected in the printing plate, and if there is a lack of graphics on the plate, it will affect the quality of the printed matter. Therefore, the correction of the positive image is the key during the entire plate making process.

There are many ways to create photo-textures for 2-word texts. The following are commonly used.

a. Proofing photographic method is arranged according to the requirements of the original type of movable type, after proofreading with proofing method to obtain text proofs directly photographed, made of text Yin pictures, and then use the print version of the printing method to make text Yang pictures.

b. Text proofing method Colorless and transparent paper is placed directly on movable type for proofing and clear proofs are printed. This is a positive image.

c. The movable type photographic method applies the carbon ink solution containing alcohol to the arranged movable type plate to fill the gravure part of the movable type, remove the carbon ink on the surface of the movable type, polish it, and then directly take pictures with the movable type plate to obtain black Positive picture of text.

d. The photo-setting method uses a phototypewriter to take a text version and create a text-positive picture.

(3) Imposition Photographs obtained by photographic or other methods, according to construction specifications and technical parameters, are arranged in a printed layout.