With the increasing demand for color prints, silk screen manufacturers are increasingly aware that in order to maintain their competitive advantage, they must have the ability to print in four or more colors. However, it is not an easy task to obtain stable and consistent colors and achieve the quality of products that customers need. In the case of color printing, the design process, screen processing results, and inconsistent color information between the output proofing or printing results often appear. For screen printing (an overview of screen printing machines and technical parameters), this The differences are more pronounced, so a certain color standard has been established in printing methods such as plain printing, gravure printing, etc. to try to solve the problem of color consistency. British researchers began to try to establish a unified standard for the silkscreen production process. Now this work has been carried out in the international arena. Countries have joined together to eliminate color inconsistencies in screen color printing and set out to establish a globally uniform ISO standard. To ensure the stable and reliable image color during screen printing.

This article first introduced the goals to be achieved by the international standards for screen printing, and then introduced the history of screen printing standards and the participation of countries. In particular, the establishment of ISO standards and the progress made have been described. Finally, the impact of the formulation of standards on color screen printing has been described.

First, the color screen printing standard to achieve the goal of color screen printing standard is mainly for those who are directly related to the color reproduction of the production process to define some of the unified parameters and their data, so as to provide guidance for the silk screen manufacturers.

Judging from the goal of color reproduction in the silk screen printing process, the standard must achieve the following objectives: 1. Enable the screen printer to determine the characteristics of the output separation film, which should include the density of the film, the acceptable range of the screen during printing, The size of the screen required for each color separation and the dot characteristics of the color separation.

2. Enables screen printers to determine the number of different mesh lines and the range of tones required for using different ink systems.

3. Can guide the production of proofing, and determine the appropriate conditions for the observation and measurement of the sample.

4. Can guide the screen printer to choose the appropriate printing materials. When using density meter to measure the sample, it should be able to determine the size of the tone value to be achieved.

It will also provide some guidance for those who use screen printing inks to comply with offset standards.

The range of allowable overprint errors allowed between the color separations can be defined.

II. Establishment and Development History of British Standards Countries have made a certain degree of effort in formulating standards for screen color printing.

In January 1990, the UK Screen Printing Association established the ISO standard for color screen printing (SPA) and Gloscat University of the UK (Glascat, a British printing academy) jointly researched and analyzed the screen printing process and tried to formulate Unified standards to achieve color control.

Gloscat's experts studied each process of printing under the auspices of the SPA and 15 famous printing companies in the UK. The focus was on identifying various factors that affect the color reproduction. In the prepress section, the dot shape, size, and dot enlargement, ink density, and ink deposition were analyzed. Various dot angles, mesh lines, and screens of different materials were used to test the results.

By mid-1993, Gloscat's experts decided to conduct more in-depth research. They first contacted the British Ministry of Industry and Trade, and then they worked with the University of Wales and Swansea University and agreed to conduct independent research. The University of Gloscat University's research focuses on determining the parameters that affect replication and the development of appropriate standards, including the establishment of parametric standards for film production, measurement of halftone characteristics, and determination of the quality of printed products. Swansea University has sent a large number of master's and doctoral students, who have made great contributions in measuring dynamic production processes, improving the control capability of printing presses, and improving the quality of printed products and the utilization of equipment. They are not only to determine the allowable range of variables, but to improve and redefine the actual production process. Engineers at Swansea University also used advanced measurement techniques to develop a combination sensor that measures the changing forces on the press, allowing better monitoring of the production process.

III. Extensive International Cooperation In 1994, Gloscat University and Swansea University collaborators submitted a draft standard to the British Standards Institute (BSI) on the basis of extensive research. They thought that if this standard can be more widely The application, extended to the entire European scope, will bring greater benefits. This idea was recognized by the German standards organization. Then, the United Kingdom decided to recommend it to the ISO.

The International Organization for Standardization's Printing Technology Committee first set standards for the color reproduction of the offset printing process, but at the end of the 1980s, it held a conference in the graphic arts field to discuss the establishment of standards for all duplicated color separation processes. This move became more and more necessary with the development of digital prepress systems and other technologies.

In October 1994, the International Organization for Standardization Printing Technology Committee (ISO/TC130) held a meeting in Berlin, where the United Kingdom submitted a draft standard for color screen printing. But this time the TC130 meeting is making final changes to the standard of the offset printing process, and for the screen printing approach it is considered that individual processing is required. The draft was also submitted to Mr. Martin Poller of the German Institute of Printing (Fogra). The Fogra Institute has also conducted some research in this area, and has developed some test films that are specifically designed to verify color accuracy and tonal balance in screen printing. After conducting a series of studies on the UK programme, Mr. Poller concluded that the relevant standards must be developed under various environmental conditions. Part of the reason is that the Fogra Research Institute is based on direct emulsification of screen stencils and flatbed printers, while British researchers are based on capillary membrane screen stencils and cylinder printing presses, according to the results of the Fogra Research Institute by Mr. Martin Polller. The British plan was revised and submitted to the committee at the TC130 meeting held in March 1995. However, after careful study and discussion of Mr. Poller’s proposal by the committee members, it is still considered necessary to improve.

Fourth, the establishment of ISO standards and progress made TC130 is responsible for the establishment of standards for all areas of graphic arts, but because there is no standard model can cover all printing processes including screen printing, it is necessary to establish a unique standard for the silk screen process. . After the decision of each member country, the standardization of screen printing was undertaken by three working groups of TC130. The division of labor is as follows: The first working group is responsible for the standardization of terms in various printing processes, including the terminology used in screen printing.

Because screen printing and other printing methods do not have much in common from a technical point of view, a part of the work group was separated from the members of the third working group to form a special working group to handle the silk screen printing process. They mainly study various parameters from the original image, separation film, screen processing and ink transfer and related processes.

Working Group 4 is mainly responsible for the characteristics of ink processing. The establishment of this working group is mainly due to the fact that the existing standard color ink systems serve for lithography and similar copying processes, and there are no widely applicable standards for screen printing inks.

In addition to the three working groups mentioned above, there is a second working group, but it is dedicated to digital data conversion and has no direct connection with the standardization of silk screen printing. Experts from nine countries including the United Kingdom, the United States, Germany, and Japan participated in these working groups, and research funds mainly come from companies in the trade organizations and participating countries. Cooperation has made progress in the following areas.

1. The terminology standardization The screen printing technology terminology standard is the first to complete the standard, its number is ISO126372:1996.

2. The variables or parameters in the process of standardizing the process parameters are handled by Working Group 3, the main work being conducted in the UK and at the Fogra Institute. The chairman of the working group, Claypole, explained that their work is based on the process to determine the standardization work from prepress to screen printing products or images. Their main process parameters are: the various parameters of the separation process are mainly the quality of the film, transmission density, image size latitude, screen control, screen angle, dot shape and size, maximum and minimum tone values, gray balance And related parameters.

The Working Group on Visual Aspects parameters studied the color, smoothness and gloss of the substrate, the color and gloss of the ink, the range of the dot area and the size of the largest and smallest dots, and the tonal range and latitude involved visual observations. variable.

In addition, they also studied different replication processes for different substances based on different process conditions, compared the direct emulsification stencil with the capillary membrane stencil, and applied two types of inks: water-based UV inks and solvent-based Ink. Finally, based on six commonly used printing materials: matt coated paper, coated paper (copper paper), matt plastic, glossy plastic, coated cardboard, and plastic film, a standard system was created, and a specific type of color was also defined. Standard coated paper for proofing. It must be reminded that the ISO standard is not a panacea. It can only indicate the variables that may be encountered in the processing of the process, and provide some of these variables with a more usable range or determine their possible latitude.

3. Standardization of Ink Properties For screen printing, there is no universal standard for inks. Customers may obtain a color magenta ink from company A and a color magenta ink from company B from another company. C company is different from the previous one. At the same time, the magenta ink designed by Company A for different customers will not be exactly the same. Therefore, the standardization of ink requires the participation of manufacturers. Working Group 4 started to establish ink standards at the end of 1994. It was not until 1997 that the final agreement was reached. This is an important breakthrough.

Fifth, the impact of the standardization For individual businesses, if you want to improve color printing capabilities, improve the status of enterprises, they should use the ISO standard, so as to be successful and gain greater benefits. In the UK, the share of color screen printing is growing at a rate of at least 10 per year. This standard will provide important guidance for print production and thus become a successful starting point for color reproduction.

The ISO standard is trying to make the job more flexible, enabling it to predict the initial state of the image and the relationship between the image and the resulting silkscreen product, thus providing technical guidance for efficient production. However, since the standard only lists the range of parameters that may be achieved in production, screen printers would prefer to know how to implement corrections in the process, so the guidance books published by various agencies may be more popular. It can be foreseen that customers will rely more on screen printing if they can use industrially accepted standards for color control in screen printing production to achieve the desired results.

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