Four-color screen printing process points (below)

5. Unsuitable for screen printing manuscripts

Non-applicable originals, ie originals that do not meet the copying requirements. Although this type of manuscript can be copied, it requires a lot of processing adjustments and corrections, and the final copying effect is also unsatisfactory. Such as: 1 image is false and false, there are double shadows, poor clarity; 2 coarse particles, surface pollution, dirty spots, more than road; 3 contrast is too large, too stressed or too thin tone; 4 color cast, old color ;5 Magnification more than 10 times.

6. Uncopyable manuscript

Some manuscripts cannot be copied and should be returned. Such as: 1 serious image imaginary, unclear outline; 2 particles are too rough, magnification is too large; 3 graphics serious wrinkles, pollution. The main part of the image has obvious dirt spots, roads, molds, etc.; 4 serious color cast, the tone is completely distorted.

Whether it is a physical manuscript or an artwork, or a positive edition, these manuscripts determine the quality of future prints. Therefore, the most important thing is that the printer should be able to check and identify the quality of the manuscript, even if the user provides user satisfaction. The manuscript should also be able to correctly identify the quality of the manuscript. Why are you not satisfied with the manuscript? What are the defects and deficiencies in the manuscript? These must be given to the user in advance so that they know the consequences of these defects. If the manuscript was received without prior explanation, it would be too late to say it was rejected by the customer when handing over the screen print. The screen printer was responsible for this.

Fourth, select the original to consider factors

1. Original color

It is also commonly known as "hue." When selecting originals, you should pay attention to selecting those originals with a large range of colors or “hues”. The range of tones is large, and the eyes look like a rainbow. Various blue, green, red, and other colors make people interested and dizzying.

2. Original tone value

Embodies the change from light to dark. When converted to tone dots, the tonal value range of the highlight region is 10 to 15%, the tone value of the four-layer dots is 16 to 35%, the midtone tone is 36 to 65%, and the dot of the 3/4 layer is 66 to 80% The dark tone area is 81 to 100%. These hue values ​​are the light-to-deep dot percentages in any color range for reference in color analysis. When selecting a document, select a document with a wide range of light values ​​from light to dark, and do not select multiple documents with the same local tonal value, because such documents do not appear to have a contrast and are extremely dull and lack of life.

3. Original structure

It is the level or structure of the subtle parts of a manuscript. For example, if you look at a picture, sand grains are clearly visible along the front edge of the grassland. This structural contrast decays with increasing viewing distance. The observer is farther away from the manuscript. The less detailed levels or structures are. If you look at a mountain in the distance, the difference in color or structure of the mountain is very small, usually light blue to lavender. On the contrary, you can see the color difference between the factory and the rock in front of the mountain. When the observation distance increases, All these structures cannot be seen. Changes in structure make people feel the depth and contour of the picture.

4. Original color saturation
Refers to the contrast of color purity. The highly saturated colors consist of secondary colors (magenta, yellow, cyan) secondary colors (purple, orange, and green), which are relatively pure and bright. Mixed colors have a small amount of secondary or composite colors (ie, green with a small amount of cyan or green with a small amount of magenta), and saturated colors are usually in the middle of the hue values ​​in the middle.

5. Manuscript form

Generally refers to the actual appearance of various images in the original works. For example, a geometric building is lined with a beautiful white smoke produced by the extinguishing of candles, giving a sense of beauty and making people's eyes move between these images. Separate them.

The more these five aspects are contained in the original works, the more visual differences the eyes accept. On the other hand, the more objects in the original, the eye's attention is not easy to concentrate, this effect is not desirable in the copy of the tone network, usually pay attention to reduce this effect.

Due to the limitations of the process itself, some colors are difficult to reproduce, such as maroon and dark red. In addition, the fluorescence color cannot usually be duplicated because the film cannot record the wavelength of the fluorescent color. Neutral gray and beige are also not well reproduced. Neutral gray does not belong to any color, it is composed of 5% yellow, magenta and 8% blue. Beige contains all the three primary colors of the same percentage. For all of these colors, the color intensity or dot gain will cause the proportion of the color components to be out of balance. As a result, the beach sand will turn green and the finished concrete will be red. These colors should be noted when selecting the original. However, manuscripts with a high density of neutral grey can be processed using gray component replacement (GCR) technology. 6CB is a new technology for making color separation films and can solve this problem well.

When selecting the original, be careful to avoid selecting originals with the same color and the same tone value, such as a large-area color block or a large cloudless sky. These uniform color blocks are difficult to control, once the colors change, It can be seen at a glance. In addition, you should try not to select the originals with virtual halo effect. For example, in the surface of metal chromium and airbrush paintings, the phenomenon that the color gradually fades to white is often seen on the horizontal line. This is the virtual halo effect. In the screen printing, as the high-light dots gradually disappear, the solvent ink used is likely to dry on the mesh of the high-light dot area, and the tone value may jump from 0 to 1/4 at once, so that the printed image looks rough. But not natural.

Source: "Screen Printing Special Printing"