Plate-reducing techniques for reducing moire

Stretch net

In order to facilitate the printing and printing positioning, it should try to make the color separation film and the frame of the screen parallel (vertical), choose to make the screen dot line and the screen line of each color to be the smallest and the most suitable angle. Its operation method is:

Stretch the net to the required tension on the stretcher, and then affix the film of each separation film face down on the screen. Under light, rotate the film until the moire between the two is minimal or not. The position of the moire, which is the best plate-making position of the image on the screen. And use the pen to mark the best position on the screen as the orientation of the image when printing. Then press this position parallel (vertical) to stick the net, dry, unload the net, and mark the color number of the color separation on the net, namely make the one-color net edition. Other colors are also based on this operation. Note: 1 In the production of screen, the color separation film must be consistent with the fixed position of the stretching network; 2 The tension difference of the color separation screen is not more than 1N/cm; 3 The thickness of the photosensitive film on each screen is the same The surface is smooth.

Another method is to take a stretched screen (0° or 90°) first, and then find the best positions for the four color separation films on this screen, and record the frame and the frame separately according to the color separation. Angle, and then according to the same mesh, tension and angle of the net, and then according to the recording position, stick to the frame, dry, unloading net, making screen. Fine adjustments should be made when printing, so that the effect is better.

2. Platemaking control


The half-tone version of the tanning screen requires a low RZ value and a sharp edge (smoothness). Otherwise, moire is easily generated. Therefore, the coating or film quality should be controlled during the production of the plate.

(1) The thickness of the photosensitive layer on the screen should be controlled to be about 8 μm above the screen (depending on the characteristics of the ink).

(2) After coating with photosensitivity adhesive or attaching a capillary photoconductive film, the screen should be dried with the printing face down. If the plate is made with photopolymer, the last time it is applied should fall on the printing surface, which will help reduce the RZ value. The RZ value is reduced by 50% from the previous one every time the photoresist is applied on the printed surface. If the photosensitive layer on the screen template is very thin, the RZ value will be large, which will cause the screen edges to be uneven and increase the possibility of moiré.

(3) In order to improve the edge sharpness of the network, in the platemaking method, the indirect plate making method should be the first choice, followed by the photosensitive film.

(4) In addition to the above requirements, the following steps must be controlled during the platemaking process, regardless of the use of photosensitive film plate making or photosensitive plate making.

1 Pre-grid coarsening and degreasing. The mesh and the photo-resist layer of the mesh treated before the net are combined firmly, and small dots and thin lines are not easily lost during development.

2 Dry. The photosensitive layer is coated on the screen (Note: If using a photosensitive film, make sure it is affixed with the screen), it must be dry, otherwise:

a. Exposure is not allowed, and the photosensitive layer is easily washed away during development.
b. The thickness of the photosensitive layer is reduced, and the amount of ink is affected in the color printing so that the hue may be deviated and the moiré may be generated.
c. The stencil's resistance to print drops.
d. The dot of the dot-net and the line of the screen are not neat, and there are glitches and jaggies in the graphic and text.
e. The screen is difficult to use or the shadows are generated on the screen after the film is removed.

3 exposure. The correct exposure time should be determined using a exposure scale. When making a fine dot line template, a light exposure zone is generally selected to use less exposure segments within a reasonable exposure time range, and when developing, the halftone dot image on the screen should be partially punched, and high pressure (greater than 4 atmospheres) cannot be used. The squirt guns were flushed with scalloped water. Otherwise, when the small dots on the screen rushed out, the other dots were washed away.

Whether all the highlights and low-profile dots are flushed out, whether the dot-sensitive adhesive is firmly attached to the screen and whether it has been lost, these can be judged by contrasting the color separation film during the plate-checking process.

4 double exposure. The RZ value of the dot surface can be prevented from being increased due to poor development, and the edge sharpness of the dot can be reduced, the moire can be weakened, and the service life of the screen template can be improved.