Characteristics and quality specifications of sheet-fed offset printing industry in Taiwan

Note: The author is Xie? Cheng, Director of the Department of Graphic Communication Arts, Taiwan University of the Arts

Director Xie speaking

In the introduction of printing equipment, the quality and quantity of equipment purchased by Taiwanese companies are above the standard. However, in terms of print quality management, Taiwan has not established a complete set of print quality characteristics as a basis for print quality reference. The identification of quality by printers often depends on the subjective visual judgment of operators. Subjective judgment often causes print quality. Unstable. When the printing industry develops towards the international market, it virtually weakens the competitiveness of the industry and reduces many opportunities to open up foreign markets. Therefore, the establishment of a set of printing quality characteristics suitable for the printing industry in Taiwan, in addition to effectively improving the quality of printed matter in Taiwan, is also conducive to the development of the international printing market after Taiwan ’s entry into the World Trade Organization (World Trade Origination, WTO).

1. Industry investigation is conducive to development research

The Ministry of Economy ’s Industrial Development Strategy Planning Report of the Republic of China mentioned in 2008 that Taiwan ’s printing industry focused on cultural and commercial printing. Cultural printing was dominated by books, newspapers, and textbooks, while commercial printing was dominated by advertising materials and packaging. Lithographic printing can best meet the needs of fast, beautiful and cheap in these two printing categories, so lithographic printing has always been the most commonly used printing method in the industry. Therefore, the purpose of this study is to establish a set of quality characteristics of sheet-fed offset printing suitable for the printing industry in Taiwan. This study solicited the sheet-fed lithography industry distributed in the northern, central, southern, and eastern regions of Taiwan to participate in this research case, and provided the printed materials required for this research, and further measured the full version of the printed products provided by the participating manufacturers. Print quality characteristics such as density, dot area expansion, printing contrast, overprint capability, gray balance, chromaticity value, hue difference, gray scale, etc., and use statistical software for various analysis of print quality characteristics. I hope that through experiments and related prints The analysis of quality characteristics can be used to establish a set of lithographic quality characteristics suitable for the printing industry in Taiwan, and to provide printers with a basis for quality control of printed products. In addition, this study also used questionnaires to obtain background information on the printing plants or printing companies participating in this study to conduct industry status surveys, and further explore the location of the factory, the size of the printing plant, and different operating methods (using different printing methods). There are no significant differences in the printing quality characteristics of plate materials, brand printers, printing color sequence, etc.). In addition, the quality characteristics of sheet-fed offset printing from this study are further compared with those of countries such as Europe and the United States.

This research is carried out in two stages. In the first stage, a questionnaire is used to conduct an industrial survey to understand the general situation of the printing industry. The questionnaire includes the location of the factory (sheet-fed offset printing plants distributed in the northern, central, and southern regions of Taiwan) and the size of the printing plant. Size (such as annual turnover, number of employees, the entire pre-press, printing to post-press binding process equipment), the printing machine, ink, printing plate material, paper, printing color sequence, working environment conditions used in the experiment And other projects. The second stage is the printing of printed materials by participating manufacturers. This study invited more than 50 printing companies in the province to participate in the experiment, and finally got 33 printing companies to participate in the experiment, including 21 printing plants in the northern region, 4 printing plants in the central region, and southern printing companies. There are 9 companies with a total of 95 batches of printed materials (each batch is printed with 100 sheets), of which 45 batches are coated paper and 40 batches are uncoated paper.

During the experiment, CD-ROMs or screens containing electronic manuscripts were delivered to the participating manufacturers for printing experiments. Each printing factory officially printed after the full-page concentration reached a custom standard, using coated paper and non-coated paper respectively. Print 100 prints, a total of 200 prints. During the measurement, 35 samples were taken from the coated paper and the non-coated paper respectively by systematic random sampling, and a total of 70 samples were measured. Each print is measured with GretagMacbeth D118C reflective spectrodensitometer to measure the full version density (100%) of the specific area of ​​the print and the percentage of the fine-tone dot area of ​​the highlight (1%, 2%, 3%, 4%, 5%) 、 Dark and detailed tone tone dot area percentage (95%, 96%, 97%, 98%, 99%), general tone tone dot area percentage (10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%), printing contrast percentage, overprinting capacity percentage, hue difference, grayscale and other quality-related characteristics. In addition, the X-Rite530 Spectrodensitometer reflective spectrodensity instrument is used to measure the gray balance and chromaticity value of each specific area of ​​each print. The measured data records are aggregated and statistical software is used for various analysis of print quality characteristics.

2. Accurate data display quality

Due to limited space, the following only summarizes a few important results. A complete and detailed report can be obtained from the host of the plan. The data listed in the table is the average ± tolerance of error (the error value calculated from the 95% confidence interval, Margin of Error).

(1) Solid Ink Density

The full version density refers to "the highest density of the color material printed on the printed material". Generally speaking, the darker the four colors, the higher the density value ("Print Quality Assessment," 2001). For the general printing industry, the more stable the full-page density, the better the print quality (Adams & Sweeney, 1999, P.14).

Table 1 is the descriptive statistics of the concentration of the full version. Among coated papers, the K version has the highest concentration of the full version, with an average value of 1.7098, followed by the C version (1.6856), the Y version (1.3937), and the M version (1.2512) in order. The K version (0.30647), the smallest standard deviation is the M version (0.126), the Y version (0.19234) and the C version (0.24111) are in between. Among the uncoated papers, the full version density of the C version is the highest, with an average value of 1.1086, followed by the K version (1.1075), the Y version (1.0342), and the M version (0.9464). In terms of the degree of variation, the one with the largest standard deviation is also the K version (0.19402), and the one with the smallest standard deviation is the M version (0.12645). Overall, the M-version full-plate density values ​​of coated and uncoated papers are both low, and the standard deviation is also the smallest. The C and K versions of the coated paper are significantly higher than the Y and M versions, while the non-coated paper has a smaller difference in the Y, M, C, and K color versions.

(2) Dot Gain of general tone

Dot expansion refers to the difference in the area of ​​the dots on the screen and the printing plate or on the screen and the paper (Xie? Cheng, 1999, P.33). The dot expansion value referred to in this study is the difference between the dot area on the mesh and paper. For the general printing industry, it is more important to effectively control the expansion of the dot and maintain its stability than the actual measured dot expansion (GRACoL, 2000, S6).

Table 2 summarizes the descriptive statistics of the expanded values ​​of general tone points. For the coated paper, the 10% and 20% tone expansion is the largest in C version, followed by K version, Y version, and M version is the smallest; 25%, 30%, 40%, 50% and other steps The expansion of tone adjustments is based on the K version, followed by the C version, the Y version, and the M version is the smallest; 60%, 70%, 75%, 80%, 90% and other tone expansions are based on the K version Is the largest, followed by Y version, C version, and M version is the smallest. In addition, the K version has the largest network expansion standard deviation at 20%, 25%, 30%, 40%, 50%, 60%, 70% and other levels, and the Y version is at 75%, 80%, 90% and other levels. The standard deviation of the network expansion is also the largest, and the M version is in 10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, etc. The standard deviation of the dot expansion is the smallest.

In the uncoated paper part, the expansion of the dots of 10%, 20%, 25%, 30%, 40%, 50%, 60% and other gradations is the K version, followed by the Y version and the C version. The M version is the smallest; the 70%, 75%, 80%, 90% and other tone expansions are also the K version, the second is the Y version, the M version, and the C version is the smallest. In addition, the K version has the largest standard deviation expansion at 20%, 25%, 30%, 40%, 50%, and 60% tone points, and the C version has 75%, 80%, and 90% tone points. The expanded standard deviation is also the largest, and the expanded standard deviation of the M version at 10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80% and other tone points is The smallest. On the whole, most of the dot expansion characteristics of coated paper and non-coated paper are based on the K version of the dot expansion value, and the M version of the dot expansion value is the smallest.

Figure 1 is a graph of general tone screen dot expansion. The solid line is coated paper, and the dashed line is uncoated paper. It can be seen from the figure that the uncoated paper's dot expansion value is generally higher than that of coated paper. It is worth noting that the part with the highest dot expansion value occurs mostly in the 60% tone part, and the highest expansion in the K and C versions of the uncoated paper occurs in the 40% tone part. In coated paper, except for the 10% and 20% tone, the highest dot expansion value of the other stages is the K version, and the smallest dot expansion value is the M version; in the non-coated paper category, all the tone The dot expansion value of the K version is the highest, the tone expansion value of the M version is the smallest in the 10% to 60% tone part, and the tone expansion value of the C version is the smallest in the tone part of the 70%, 80% and 90% tone.

(3) Print Contrast

Printing contrast is an important indicator for judging the richness and darkness of dark tone levels in the printing process. The higher the printing contrast, the richer the gradation that the dark part can present. Its value is affected by the density of the full version, the brightness of the printed material, the density of 75% tone, and the glossiness (SWOP, 1998, P.44).

Table 3 is the descriptive statistics of printing comparison. Among the coated papers, the printing contrast of the C version is the highest, with an average value of 51.314%, followed by the K version (50.898%), the Y version (42.702%), and the M version (42.696%). In the variation part, the version with the largest standard deviation is the Y version (8.289), and the version with the smallest standard deviation is the M version (5.537). Among the uncoated papers, the printing contrast of the C version is the highest, with an average value of 37.221%, followed by the K version (32.956%), the M version (32.219%), and the Y version (30.342%), with the largest standard deviation. The one is the K version (7.164), and the one with the smallest standard deviation is the M version (5.662). On the whole, the C version printing of coated paper and non-coated paper has a higher contrast, the K version has the largest printing contrast standard deviation, and the M version has the smallest printing contrast standard deviation.

(4) Stacking ability (Trapping)

Overprinting ability refers to the ability of the second-color printing ink to adhere to the first-color ink layer. Generally, the ideal goal of the overprinting ability is 100% overprinting, but for wet overprinting, 75% to 95% are generally used. The acceptable range, the higher the value, the better the overprinting ability (Field, 1988, PP.110 ～ 111).

Table 4 is the descriptive statistics of the printing ability. Among the coated papers, C, Y (G) is the best, and the average is 83.763%, followed by C, M (B), the average is 81.458%, M, Y (R ) Has the worst printing ability, with an average of 69.330. In the variation part, the largest standard deviation is C and M overlay printing ability (7.287), and the smallest standard deviation is C and Y overlay printing ability (5.177). Among the non-coated papers, C, Y (G) is the best, and the average is 81.019%, followed by C, M (B), the average is 67.781%, M, Y ( R) has the worst printing ability, with an average value of 54.997, the largest standard deviation is C, M (B) printing ability (6.041), and the smallest standard deviation is C, Y printing ability (3.624). Overall, both coated and uncoated papers have the best green printing capability and the smallest standard deviation, the red printing capability is poor, and the blue printing capability has the largest standard deviation.

(5) Grayness

The gray scale is the measurement of the proportion of gray in any one-color printing ink of yellow ink, magenta ink or cyan ink. The gray scale is usually measured by a densitometer (Romano FJ & Romano, RM, 1998, P.369). The lower the gray value, the higher the purity of the ink color (Adams & Sweeney, 1999, P.14).

Table 5 is the descriptive statistics of gray scale. Among coated papers, the gray value of the C version is the highest, with an average value of 8.7283, followed by the M version (4.8095), and the gray value of the Y version is the lowest, with an average value of 1.1276. In terms of the degree of variation, the largest standard deviation is the M version (1.0160), and the smallest standard deviation is the Y version (0.7692). Among the uncoated papers, the gray value of the C version is the highest and the average value is 12.962, followed by the M version, the average value is 5.8336, and the gray value of the Y version is the lowest, the average value is 1.2086. For the standard deviation, the largest standard deviation is the C version (1.3370), and the smallest standard deviation is the Y version (0.8357). On the whole, both the coated paper and non-coated paper have a higher gray value in the C version, a lower gray value in the Y version, and a smaller standard deviation.

(6) Hue Error

The total amount or change of colors doped with other colors in a pigment is called a hue difference. The greater the hue difference of a pigment, the more it cannot reproduce colors correctly. Magenta pigments are usually doped with a large amount of yellow pigments and some cyan pigments, and cyan pigments are doped with a little yellow pigments and some magenta pigments (Coudray, 1990, P. 66). Hue difference is also used as the basis for judging the purity of ink color. The lower the hue difference, the higher the purity of ink color (Adams & Sweeney, 1999, P.14).

Table 6 is the descriptive statistics of hue difference. Among coated papers, the M version has the highest hue difference value with an average value of 51.464, followed by the C version with an average value of 26.234, and the Y version with the lowest hue value with an average value of 3.0019. In terms of the degree of variation, the largest standard deviation is the M version (3.865), and the smallest standard deviation is the Y version (0.723). Among the uncoated papers, the M version has the highest hue difference, with an average value of 56.211, followed by the C version, with an average value of 35.118, and the Y version has the lowest hue, with an average value of 4.2814. In terms of the degree of variation, the largest standard deviation is the M version (3.139), and the smallest standard deviation is the Y version (0.783). On the whole, both the coated and uncoated papers have the M version with the highest hue difference and the largest standard deviation, while the Y version has a lower hue difference and the standard deviation is smaller.

(7) Gray Balance

Gray balance is the combination of proper ratio of Cyan, Magenta and Yellow to form neutral gray in color printing. Improper proportion of any one color printing ink will cause the industry to not expect The color cast seen is very important to ensure the stability of the gray balance during proofing and printing (Romano FJ & Romano, RM, 1998, P.369). This study is limited to a study period of only one year, so only three-quarters of the tone (gray balance of 80% outlets) is discussed. Use the X-Rite 530 Spectrodensitometer reflective spectrodensitometer to measure the CIELAB value of each tone (different combination of C, M, and Y percentages) on the three-quarter tone gray balance table of each sheet The combination is the tone with the coordinates of a * and b * that are closest to the origin, so the C, M, and Y tone combinations closest to the origin are calculated by the Pythagorean theorem. As a result, the best C, M, Y order combination, input statistical software, after frequency analysis, the results show that the best combination of coated paper gray balance is c80 / m74 / y66 and c80 / m66 / y66; the best combination of gray balance of uncoated paper It is c80 / m76 / y78 and c80 / m66 / y78.

3. The research achievements have multiple values

The results of this research construct the quality specifications for sheet-fed offset printing in Taiwan and compare them with the relevant quality specifications for offset printing in foreign countries. In terms of application value, the quality specifications of sheet-fed offset lithography in Taiwan constructed by the research results can provide a substantial reference for lithographic operators when performing printing operations. As long as the amount of ink reaches the standard of printing specifications, it can be officially printed, except Shorten the trial printing time and strive for timeliness. Through the definition of printing specifications, it can also reduce the dependence on the professional experience of the operator, and easily maintain good quality and stability. In addition, the printing specifications can provide a standard for printed matter under different printing conditions. Even if printing is performed at different locations and under different printing conditions, the manufacturer can still test the printed matter through the printing specifications to evaluate the quality of the printing quality.

It is worth mentioning that this research is the first complete discussion on the quality characteristics and specifications of lithographic printing in the history of printing in Taiwan. It is also the first study in Asia to construct the quality specifications of sheet-type lithographic printing. Funded by the National Science Committee of the Executive Yuan and supported by the province's sheet-fed offset printing plants, the actual data obtained through the actual operation process of the printing industry. In addition to providing self-assessment by domestic companies, the research results can also provide mutual evaluation by domestic companies, and compare it with relevant print quality specifications abroad. After Taiwan's accession to the WTO, the industry will inevitably face global competition, and the establishment of print quality specifications can become a weapon for the printing industry to know each other and win a battle when exporting. In addition, the various print quality specifications published in Europe, America and other regions do not investigate the attributes of different printing plants (such as turnover, number of employees, etc.), let alone use industrial characteristics as a reference for the analysis and classification of various print quality specifications. Based on this, this study first conducts an industrial survey, and then analyzes, compares, and summarizes the print quality specifications based on the results of the industrial survey, making the entire research result more valuable. Therefore, the results of this study should be extended to the printing industry to provide the manufacturer as a reference for the printing industry in printing quality inspection and printing industry improvement.

In terms of academic value, the results of this research are very suitable for publication in journals or academic conferences related to printing, graphic communication, graphic communication, and industrial technology at home and abroad, such as Visual Communication Journal, Journal of Industrial Technology, China The annual report of the printing technology, the National Association of Industrial Technology international academic conference, the Technical Association of Graphic Arts international academic conference, and the Chinese Academy of Printing Technology annual academic seminars, etc., through the publication of results, can achieve the purpose of academic exchange. In addition, the Graphic Arts Technical Foundation (GATF) is very interested in the results of this study. The author has reached basic consensus with American scholars and research institutions, plans to develop international cooperation, and plans to jointly build a worldwide Lithographic printing quality specifications to help global lithographic printers improve printing quality and increase the competitiveness of the printing industry. (* Acknowledgement: This research was successfully completed. First of all, we would like to thank Sanai Paper, Shixin Publishing Center, Youshi Printing, Tailin, Guoxing Printing, Mountain Watercolor Printing, Contract Art Printing, Lide Printing, Yongfeng Printing , Baike color printing, Shengquan printing, Hongzhan printing, Chinese color printing, autumn rain printing, Yuhua color art, Yongguang printing, Kele printing, Shanghai printing, Jinyi color printing, Shen printing, Zhenqin printing, Xinyi Art, Hongguo printing, Zhexing printing, Xingtai printing, Zhijun printing, Jiade art printing, Yangming packaging printing, Renxiang art printing, Qiuyu printing Tainan factory, Meiyu color printing, Dongyu color printing and other manufacturers fully support and Cooperate to make this study successfully complete the construction of quality specifications for sheet-fed offset printing. During the study, we especially thank the National Science Committee of the Executive Yuan for providing financial support to assist in the purchase of the required measurement equipment and payment of related costs for this study. Completed on schedule. In addition, I would also like to thank Xingcai Printing Communication Culture and Education Foundation for the support of this case and the subsidies for printing funds. The deepest thanks to you. This research also thanks research assistants Wu Yuru, Lin Huafa, Chen Liwen, and the students who participated in the measurement for their continuous assistance, so that the original two-year research plan can be successfully completed within one year.

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