The four major elements of CD screen copying screen printing quality control (1)

Recently, the mass production of optical discs at home and abroad has opened up yet another new application field for screen printing. The use of screen printing for high-resolution halftone images and continuous tone images on optical disks has become part of the decorator business.

At present, the obvious trend of CD-disc decoration is that there are both halftone original printing images in the reproduced image. There are also color printing images or printing in the field. It is also often observed that on most CDs, the same drawing consists of two different printed images, that is, a screen printing plate is used to simultaneously print the image of the field and the halftone, which requires the decorator to guarantee the mesh. The resolution of the adjusted image and the field printed image is good, the ink is uniform, and the productivity is maximized. At this point, the printer must be able to print two different images of the same ink at the same time, even if the ink can flow well in the solid area, but can also be fixed at the dot.

According to research, a total of 101 variables in screen printing are related to the final printing results. Only careful monitoring of all relevant variables will make the screen printing process more versatile (simultaneously printing both images). Without changing many variables, different jobs can be printed on a single production line. The purpose is to first understand that those variables can remain stable and those variables can change. The four process elements of plate making, printing press adjustment, ink and combination printing will be discussed below.

1, plate making

During the plate making process. The main variables should be baskets, screen tensions, screens, and stencils.

Printed in a CD box. The frame should be firm and stable. Most CD-disc decorators use aluminum mesh frames and use stretch nets and adhesives to make screens. Only a few manufacturers use repeatable stretched frames. To ensure print consistency. The same type of net should be used for the same job.

Same as most screen printing applications. For the printing of a CD disc, the tension of the screen should be kept constant. When printing, the tension value of the screen is usually 22-26 N/cm. Tension is a very important factor. Because it can improve the rebound distance of screen printing plate. This in turn ensures that the fine prints have a very high resolution and edge definition.

For a specific job, or between a job and a job. The produced screen must have the same level of tension. A standard tension level should be used for all jobs, which not only facilitates the rapid transition between different types of jobs, but also reduces and eliminates the inconsistency of many prints. The selection of the screen and the preparation of the template are the variables that you use to meet different printing requirements. You can choose the standard type of screen according to the theoretical amount of ink deposited by the ink manufacturer. Can pass production test. See which screens are easy to use. Then decide which screen to use.

For the template, decorators of CD disks generally use direct liquid emulsions. Capillary photosensitive films are also occasionally used.

Select the stencil system, you can consider according to the requirements of the stencil printing force, the degree of ease of use, and the compatibility with the ink used. Once you have decided on the standard wire mesh type and the applied gluing technology, you It must be decided that in order to print out prints that have both on-site and fine halftone images. Which of these two variables will remain unchanged. Which one can be changed. If you choose a direct liquid emulsion to make a template. You can determine the standard glue application that all templates use. For example, apply wet and wet on both sides of the screen twice. No matter what type of web image you print. If you prepare all the templates using this glue method, then you should consider changing the screen variable. For example, you can choose a 355-mesh, screen-printed block print with a wire diameter of 34u and a 390-mesh screen with a wire diameter of 34u to print a fine image. The 355-mesh screen is more suitable for printing large areas of the field due to its larger opening and the greater amount of missing ink. The 390-mesh screen has a small opening and is suitable for printing dots. Therefore, by changing only the number of screen meshes, two different screen printing plates can be produced to meet the needs of printing jobs. Another way is to change the screen diameter of the screen so that the number of meshes remains the same. For example, you can use a 390-mesh screen with a wire diameter of 31u to print a solid print on the entire surface, and use a 390-mesh screen print screen with a wire diameter of 34u. Because the mesh number is the same, the wire mesh with smaller wire diameter is more suitable for on-the-spot printing, and the wire mesh with larger wire diameter is more suitable for printing fine images.

You can also solve this problem from another angle. For all screen printing plates, the mesh size and wire diameter can be kept unchanged, and only the gluing technique is changed. For example, you can use two different gluing techniques, that is, two sides of a screen plate are wet-pressed and wet-coated with two sensitizing adhesives or wet-pressed and dried to coat each side twice, so that two different thickness stencils are obtained. The principle is that the thicker the stencil layer, the more ink will be attached during printing. Therefore, the thicker stencil printing plate is more suitable for on-the-spot printing, and the thinner stencil printing plate is more suitable for printing. printed matter. By controlling the variables in the platemaking, the problem of inconsistent prints will be greatly reduced, and it will be possible to quickly switch from field printing to fine printing. With regard to the screen parameters and the gluing technology, the above examples may not be suitable for your operation. You must experiment to determine the mesh size, wire diameter, and type of emulsion that are most suitable for your application.