Anti-counterfeiting printing--carbon paper printing technology (I)

Dry carbon paper, also known as disposable anti-counterfeit carbon paper and laminated anti-counterfeiting ticket paper, was invented by Jiangsu Haimen Copying Paper Factory (China Patent No. ZL94 1 1147.0, International Patent No. B41M5/00). It is the fourth generation of high-tech products following ordinary carbon paper, carbon coated paper and carbonless paper. The products have been awarded the titles of “national new products” and “national excellent new products” by the State Economic and Trade Commission, the Ministry of Science and Technology, the State Administration of Taxation, the Ministry of Foreign Trade and Economic Cooperation, the State Bureau of Technical Supervision, and the State Environmental Protection Administration. Torch plan project.

The front of dry carbon paper is a white base paper, and the back is a non-toxic water-based colored coating. The product is divided into flat paper and web, suitable for offset printing, gravure printing, flexo printing, screen printing printing computer tickets, hand counting, roll tickets It can be used without padding. When writing paper, you can get more than one copy, and the color is fast, the writing is clear and bright, can not be altered, not affected by the climate, the file has a long shelf life.

In view of the anti-counterfeiting technical characteristics of the new products of dry carbon paper, the State Administration of Taxation Administration, the Statistics Division, the Post Office of the former Ministry of Posts and Telecommunications, and the Jiangsu Provincial Department of State Taxation and other units have issued trials to the whole country in 1997, and the General Directorate again in July 2001. The document was issued to the nation: “The trials in recent years have proved that dry carbon paper has a significant effect in suppressing and cracking down on the production and sale of fake invoices. It was decided to use the second-generation dry carbon paper developed and produced by the Carbon Paper Factory of Haimen City, Jiangsu Province as an ordinary invoice security paper. Formally put into use."

Now in the technical service and investigation work of the tax paper printing companies in China that use dry carbon paper as a carrier, the printing technology problems and related processing technologies encountered are summarized below for reference of tax paper printing peers.

First, dry copy paper must be well-conditioned before printing to ensure that the process of printing paper feeding, paper feeding and delivery smoothly

In the process of servicing dry carbon paper printing enterprises, it was found that the problems of stretched, curled, and tight edges of dry carbon paper affected printed work. The reasons for these problems after analysis were as follows:

1. Dry carbon paper is coated, dried, cut, and recoiled from the base paper through a non-toxic fatty acid salt solution and a colored coating. The finished product actually becomes a single adhesive tape, and the moisture absorption performance of the positive and negative paper is reversed. There are obvious differences, that is, the moisture absorption performance of the colored coating surface is extremely poor, and the white surface of the base paper is extremely sensitive to moisture absorption, which is one of the main reasons causing the paper curl and tight edges.

2. Dry carbon paper must be transported long-distance or long-term storage after being shipped from the factory. Due to China's vast territory, large and vertical climate variations and frequent changes, such as spring, the room temperature in Heilongjiang is between 18-20%, and the indoor humidity is 20%. Between 30%. In Yinchuan, the indoor temperature and humidity are basically the same, at 18-20% and 18%-20% respectively. The coastal areas and Chongqing, Chengdu, the temperature at 15-20 degrees Celsius, humidity is as high as 60% to 75%. Since the moisture absorption characteristics of dry carbon paper are not compatible with the printing environment of the company, problems such as static electricity and double-sheet wrinkles occur during printing, which brings difficulties to the printing work.

For the above reasons, in order to balance the moisture content of dry carbon paper with the temperature and humidity of the printing shop environment, and ensure the high-quality completion of the E-brush product, the national tax paper printing company has a wealth of experience. For example, at the ticket center of the National Taxation Bureau of Hebei Province, they pay great attention to the balance between the base paper and the printing environment. Generally, two or three days before the printing, they bring the 1000-carbon paper to the workshop and enter natural balance. Another example is the Shanghai Commercial Plant. In addition to the natural balance of the base paper, the printed products are put into plastic bags after they are put into the machine, and then placed in the packing box and then transferred to the next road to fight the code. This effectively ensures that the dry copy paper is high. Quality printing was successfully completed.

Since 2000, I have visited 85 key tax invoice printing companies and related universities and research institutes in various provinces and municipalities across the country. I have collected and summarized their advanced experience in the prepress technology handling of Haitian brand dry carbon paper. :"When the relative humidity of the printing environment changes by 10%, the moisture content of the dry writing paper also changes by about 1%. In general, when the temperature changes by 5 degrees Celsius, the moisture content of the dry copy paper also changes accordingly. 0.15% to 0.2%."

Second, fountain solution, printing pressure and printing speed control

Dry carbon paper will undergo a "quiet" change in printing, and its king has to show two kinds. One is that the paper size changes, that is, the length or direction of the paper is elongated or shortened; the other is the change of the paper on the compression surface, that is, the elastoplastic change of the paper in the vertical direction. The reasons for these two changes are that the paper is subject to changes in the flexibility of the paper due to changes in the printing environment (ie, the moisture content of the paper), and the other is that the paper undergoes elastoplastic changes in the paper after it is subjected to pressure.

For the change rule of dry carbon paper in printing, in order to obtain the ideal minimum change, many printing companies analyzed the factors affecting the expansion and contraction of dry carbon paper. The conclusion is: “Preparing and printing wet paper before printing The fountain solution, printing pressure, and printing speed must be effectively controlled."

After the paper absorbs water, it will expand due to volume expansion, resulting in size reduction after water loss. Therefore, except that the paper is reasonably dampened to the printing environment before printing, it is necessary to control the consumption of the fountain solution. For the offset press, the dampening solution is a normal deformation under the premise of ensuring that the printed image is well-defined, structured, and the layout is separated from the oil and water on the tape and is not pasted. Therefore, the elastoplastic change of the dry copy paper is There is a certain range, beyond the range, dry carbon paper will lose its elasticity, and the deformation of the paper will not be restored. When the dry carbon paper is printed on the printing surface, there will be wrinkles, unevenness, uneven ink layers, and backsides. Colored coatings appear needle-like shedding.

For the control of the embossing force, the ink of the printed product should be gradually pressure-adjusted for the purpose of eliminating scratches, clear graphics, and meeting quality requirements. Due to the different models, there is no single rule. Many of the tax printing companies in China use Weihaitian's WH47 machine. My service practice survey data proves that the printing company's printing pressure scale is most suitable when it is located at 3-4.5.

Printing speed and printing pressure have an important influence on the printing effect of dry carbon paper. This is mainly due to the difference in the length of time the paper stays in the printing zone, and the degree of deformation of the paper is also different. For example, the normal printing speed on the WH47 type machine in the Hebei Provincial Taxation Certificate Center is 6,000 rpm, and the normal printing speed of the Yunnan National Tax Printing Factory WH66NP machine is 500 rpm. When the form machine is printing, such as Shanghai Commercial Factory and Nanjing Special Printing Factory The sun machine, the palace waist machine of Shanghai Enol factory, the Xiaofeng machine of the ticket center of Hebei Province, etc. are basically controlled at a speed of 150 m/min, and normal printing, punching, folding, code printing, page mosaic, and quality of printed products are performed. good.

(to be continued)

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