Halftone screen printing market and halftone screen printing process requirements

Halftone screen printing market and halftone screen printing process requirements


(Continued from issue 4, 2001)
3.2 Pre-press color desktop and (FM) network technology The development of modern technology has promoted the technological transformation of the printing industry. Many of the traditional processing methods have been replaced by new and ever-changing technologies, especially the prepress operation system and the computational energy. The increase appeared in the frequency-tone dot-plating process. Its excellent quality and speed had a direct impact on the overall effect and overall benefits of printed copies.
3.2.1 Preprinted color desktop system "Prepress" is understood as "Before Printing". Before the so-called printing, including: creativity, filming, design, plate separation, imposition .... The scope is far more extensive than that of the photoengraving and electronic color separation mechanism. At first glance "filming" may not seem to be included, but on desktop workstations, some hosts have read-out CDs with images such as the sky, green fields, deserts, hills, and background images. In addition to the subject's need to scan input, creative design is generally available. In order to illustrate that the system is a color image, text-compatible, and text-enriched, the word "color" is added before the "desktop system" and understood by the current printing process. The "prepress color desktop system" includes: The sum of all the functions of photosetting, electronic color separation, and full-page imposition. It is also referred to as an integrated plate-making computer.
(1) Color desktop layout input system a. Text and graphics input. Textual information can be entered in a coded manner via a standard computer keyboard. There are two ways to enter the graphics. One is to make the mouse and keyboard draw graphics on the display terminal, and the other is to input graphics through the light pen.
b. Image input. Electrical extension input, rotary drum scan input. In this way, the input can also use the existing electrical extension input part to increase the open interface to connect with the computer and send the scanned electrical signal to the computer.
The color separation of the plane scanner can add one color filter at a time to obtain a considerable color separation signal. It is also possible to divide the color set beam into three types, one for each filter and one for three separate signals.
The quality of the image input by the roller scanner is good, and the resolution is high, especially the dark resolution level of the original is higher.
The quality of the image scanned by the scanner is not as good as that of the drum scanner at present, but it has a fast scanning speed, a relatively simple device structure, and is easy to miniaturize the device.
(2) Color Desktop Publishing Host System The host system refers to the computer part of a color prepress system, that is, a workstation or a microcomputer, which is the core of the entire system.
a. Color drawing software. Mainly used for color line principle of copy processing.
b. Color image editing software. Mainly used for continuous copying of originals.
c. Color publishing software. Mainly used for text, image editing, typesetting processing.
(3) The output text, graphics, and images of the color desktop publishing system are processed, edited, and composed by computer independently, and then summarized by the layout description language to become the result that can be displayed or output on one page. To a special raster image processing part, the summary result is converted into a raster image and finally output by the output device.
a. Page description language. The so-called page description language is based on a page to describe the object. Before this, graphics, text, and images were processed by different dedicated software, and they could be processed independently on different computers. The role of the page description language was to summarize them. Any complicated layout that can be output by a laser printer, an image-setter, or by other means can be described in principle in a page description language.
b. Raster image processor. In image processing, the process of converting lines, arcs, curves, text, etc., into pixel descriptions of pixels is rasterization. Page descriptions are only possible after rasterization on raster output devices such as imagesetters and extensions.
c. The final products produced by the color electronic prepress system through various output devices include: color separation films, color films and various types of proofing products.
The color separation film includes four color plates and spot color plates, which are used for printing plate making, and it is usually convenient to use an imagesetter or an electrical extension to output a color continuous adjustment positive or negative film.
(4) The main features of the color desktop publishing system The development of the color desktop publishing system has experienced two kinds of processes. One is the electronic color separation machine's increase of the open prepress processing interface, the insertion of the host computer system, the introduction of text information, the realization of images and text Page synthesis processing; on the other hand, a computer word processing system represented by a laser photosetter gradually and color image processing system is often referred to as a color desktop publishing system. The process flow firstly enters the text into the computer through text input, uses a scanner or a camera to image and edit the images, prints the results with a printer, and finally performs color separation on the computer's grouped version. . Since the layout on the computer is described in the surface description language, the raster image processor is used to change the layout of the layout into a bitmap image. Finally, these dot matrix data are sent to the laser image photosetter. The film in the photo machine is exposed to light. After that, the C (cyan), M (magenta), Y (yellow), and BK (black) four-color separation films are washed out with a film processor (developer). deal with.
Its development is extremely rapid. The main features of the color prepress system are:
a. It can not only input, process and output the text, image and graphics on the same machine, but also greatly enhance the image processing function.
b. The computer hardware, software and external devices such as scan input and output configured on the device are versatile and open. When the system is collocated, there is no fixed module, and the user can select the combination according to their needs.
c. With the application of computer multimedia technology, input methods are diversified, in addition to text keyboard input, graphic digitized input, image scan input, and dynamic image input device.
d. The output methods are also diversified. In addition to the regular output of plate-making films, various types of printing plates can also be directly produced by using the signals output by computers, and can also be output by ink-jet, electrostatic, and thermal printing.
Utilizing the data from the prepress system, the intermediate media-films can be produced without the need for direct color proofing. Direct digital proofing technologies include inkjet printers, thermal printers, and thermal sublimation printers. It not only images the laser screen, but also can combine text and image output once, without manual imposition, greatly saving time, materials and costs, and high precision. Through high-precision black-and-white printing, it can replace the ink draft; color printing can replace the color draft; the image synthesizer produces synthetic negatives. These are not only available for printing systems but also provide various configurations for advertisements.
(5) Application of pre-press color desktop system in screen printing industry Currently, the market demand for color screen printing products has expanded. Its characteristics are: variety, small format, short cycle. It is reasonable to say that the characteristics of these market requirements are most suitable for screen printing companies and small printing companies to exploit the market to occupy the market. Due to the lack of experience in the production of color separation positives and the lack of professionals, enterprises have lost the favorable opportunity to explore the market and seek their own development. Even if some screen printing companies have equipment for screen making and printing, the processing of color separation at the front end needs to be completed by other large professional printing companies. Small cities, especially township and village enterprises, are far from the road. They are costly and time consuming. This situation has greatly affected the ability of small and medium-sized printing companies to develop the color printing market, and has also restricted the speed of business development.
In today's information age, all industries are rapidly developing. The same is true in the screen printing industry. For example, the screen printing desktop system will give you a new look. This system can be designed, arranged, and creatively created for image and text at any price. . The software in the computer has many functions. In the column of design and creativity, fonts, graphics, and drawings are used to modify the image.
The shade of color can be arbitrarily adjusted, there are color samples and color cards for printing designs, and the proofing design customers can witness the whole process. It is not finalized until the customer is satisfied. Therefore, a substantial increase in business volume is inevitable.
3.2.2 Unconventional (Frequency Modulating) Dot Technology Although the above traditional AM screening technology has excellent color image reproducibility, it has long played an important role in the process of color separation in photo and electronic color separations and screen printing. However, after all, there are still some unsatisfactory areas. In addition to the moiré caused by the misalignment of the stencil angles mentioned above, there are some printing weaknesses: For example, when the printing quality is very demanding, ie high-resolution printing, the splicing and hooking method is difficult to achieve.
The moire phenomenon is inherent in the AM method. It cannot be eradicated and can only be weakened by various technical methods. In particular, the screen-printing moiré is more prominent. Many years of screen printing practice have shown that it is already difficult to reduce the effect of moiré when using four-color inks, and there is also a moiré pattern called rose spot that cannot be overcome. In this case, FM outlets create conditions for screen printing. The development and practicality of the FM network are completed due to the improvement of computer computing functions.
(1) Structural features of the FM network The laser generated grid is smaller than the actual minimum raster grid point that can be simulated. This laser grid can provide simulation network or pursue a new, digital type of net tone. The laser and film recorder are designed solely to reproduce the angle and spacing of the simulated gratings that have been identified. However, the development and popularization of this technology has led to a new replication model, commonly referred to as "FM screening."
The FM network technology enables the continuous tone modulation to be expressed with extremely small and evenly distributed dots. Different coverage rates are achieved by the different number of dots recorded per unit area.
By detecting the network points, it is clear that these distribution points are much finer than the amplitude-modulated screen points, and all the network points have the same size. If we draw a curve with the dot size as the amplitude corresponding to the vertical axis and the dot spacing corresponding to the horizontal axis, the obtained curve has the same amplitude, but the distance between two adjacent peaks is different. The basic characteristics of the curve are consistent with the frequency-adjusted waveforms, which is why we call it "FM screening." Figure 1.
Various methods have been created to locate the site in an optimal state. FM screening produces fairly fine dots on the film, so the color coverage is uniform. It should also be obvious that this type of halftone conversion actually eliminates the moire effect and instead produces powdered and granular dots.
The minimum dot size that can be copied by the FM network point is very important for the screen printer. The diameter of the screen printed web corresponds at least to the two screens of the printing screen plus one cell width.
Now, FM screening can be divided into two forms: first-order and second-order. The first-order FM network points are the particle size representation level of the same size, and this kind of constant size form has a higher requirement for the post-process. In order to match the printing suitability of current equipment and materials, color desktop publishing involves a variety of network size combinations, which are called second-order FM networks. As shown in Figure 2.
(2) FM screening technology FM screening and screening will not produce moire. Because the moiré is the result of periodic structural interactions, the dot distribution of the FM screening is irregular and there is no mesh angle, so the moire is not caused by overlapping several color plates.
Sharpness is good. Because the screen area used by the FM screening is particularly small, the definition is good, and when the separation film is produced, the fine level can be less emphasized and better results can be obtained.
FM screening is insensitive to overlay errors that occur during screen printing. Misalignment between versions has little effect on color and sharpness.
Low-resolution imagesetters also use FM technology to obtain high-quality images, while AM ​​technology requires high-resolution imagesetters. For example, the 1200DPI imagesetter output FM image quality is significantly better than the quality of the 175-mesh AM image output from the 3000DPI image-setter.
The dot distribution in the FM screening is irregular, so that as long as the dots in the FM screening are small enough, the printed matter can fully approach the original and achieve high fidelity.
High productivity. After using FM network, the scanning time can be reduced