Analysis of the function and characteristics of bill paper
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With the development of social informatization, bill papers are widely used, such as electricity bills, water bills, bank credit card statements, etc., which are common in life. Bills have their own characteristics: 1 large, tens of thousands, and millions of copies; 2 each bill has the same content, there are some differences, the same content includes descriptive text, advertising patterns, etc. Different content is mainly personalized information, such as personal name, address, related data, etc. 3 Short production cycle, for monthly bills, it is generally required to complete all production within one week.
First, the bill production process
In general, the production of bills goes through three processes: offset printing, printing, and post processing.
1. Offset printing
The bill first uses the traditional offset printing method to pre-print the same graphic and text information, including some descriptive texts or advertisements on the front and back of the bill. These contents occupy a large format, and the direct printing and production cost is high, and the quality is not offset. There are two types of pre-printing of bills: reel and flat, the most common one is reel printing, and the folds are stacked to enter the next printing process; the flat printing method is suitable for small bill production, after printing Cut into a single sheet of paper, printed on a sheetfed printer, the production efficiency is relatively low.
2. Print
The printing mainly completes the printing of personalized information on the bill. Because the personalized information on each bill is different, it can not be completed by offset printing, and can only be realized by personalized printing of variable data by digital printing machine. There are also two ways to print digitally: laser printing and inkjet printing. The former is electrostatic imaging and the latter is inkjet imaging. At present, most of the laser printing methods are used, and the color medium is mostly carbon powder, which is fixed by high temperature and high pressure, and the curing speed is fast. In inkjet printing, a drying process is generally required to speed up ink drying.
3. Post processing
Post-processing is primarily for bills that need to be mailed. After all the graphic information is printed, the machine automatically folds and packages the processing to form a sealed business letter.
Second, the function of bill paper
Billing paper requires two processes of offset printing and printing. The performance requirements of paper are relatively high. Ordinary double-adhesive paper and xerographic paper are only suitable for the production of one process, which cannot meet the requirements. The billing paper needs to have both the offset printing function of the offset paper and the printing function of the xerographic paper.
1. Printing function
The physical properties that determine the printing characteristics of the paper mainly include moisture, surface characteristics, and ink absorbing properties. The main factors that make electrophotographic paper unsuitable for printing are: low water content, strong surface water absorption, poor surface printability, easy powder drop after contact with water, large amount of paper deformation, etc., easy to print off powder, printing wrinkles, overprinting Do not wait for the question.
2. Print function
The printing function mainly requires good paper stiffness, smooth paper feeding, no paper jam; printing is not wrinkled or curled. For laser printing, the paper is required to be resistant to high temperature, not curled under high temperature, and the surface coating is not bonded; the electrostatic imaging performance is good, and the printed graphic information is clear. For inkjet printing, it is required that the paper has good ink absorption performance, no ink flow, and the image is not whitish; at the same time, it is required that the printing ink does not spread, and the graphic is clear.
The main factors that double-adhesive paper is not suitable for printing are: low stiffness, poor paper feeding, easy jamming; high moisture content, high-temperature fixing process, paper curling, paper jam, and paper warpage and unevenness after printing. The paper is not resistant to high temperatures, and the surface coating is easily peeled off and bonded to the high-temperature fixing roller.
In addition, billing papers need to meet some other functions. The paper for billing should be suitable for writing and not for water; secondly, the folding performance of the paper for bills should be good, the paper should be flat, and the folds should not be blasted; the appearance of the paper is good.
Third, the characteristics of bill paper analysis
1. Moisture
The offset paper moisture is about 6%, the moisture of the electrostatic copy paper is about 5%, the moisture of the bill paper should be controlled at 5%, when it is less than 5%, it is easy to absorb water when printing; when it is higher than 5%, the paper stiffness is decreased, printing During the high-temperature fixing process, the water evaporates and the paper is easily curled and deformed.
2. Water absorption
Billing paper requires low water absorption on the surface of the paper, which meets the standard of double-adhesive paper, thereby reducing the water absorption during printing and controlling the moisture of the paper. The water absorption of the paper is related to the surface sizing.
3. Flexibility
The smaller the stretchability of the paper, the more stable the size. When the bill paper is printed, it absorbs water; when printing at high temperature, the water shrinks. The paper has a large stretchability, the paper is easily deformed, and the paper surface becomes uneven.
4. High temperature resistance
The high temperature resistance of billing paper must reach the level of xerographic paper. The low-speed printing fusing temperature is about 120 °C, and the high-speed color printing is about 250 °C. When fixed at high temperature, the paper does not deform or curl, and the surface coating does not fall off or stick.
5. Uniform tension
The roll printing method requires uniform tension of the paper roll. The tension of the paper roll is uneven, and it oscillates left and right during printing, which causes the overprinting to be inaccurate, and the folding of the paper is not uniform, which affects the paper feeding during printing. The tension of the paper roll is related to the weight, thickness, and moisture, and is also affected by the rewinding tension during the production of the paper roll.
6. Stiffness
When the bill is printed, the stiffness of the paper is high. Paper stiffness is poor and paper jams are prone to printing. For high speed printing, the higher the stiffness requirements of the paper. The stiffness of the bill paper must meet the standards for xerographic paper.
7. Conductivity
The conductivity of paper is an important indicator that is easily overlooked. The conductivity has a great influence on the printing effect of paper. The conductivity is too low, the paper tends to accumulate static electricity, the printing paper is not smooth, and it is easy to take double sheets; the conductivity is too high, during the laser printing process, the electrostatic charge of the paper surface is easily lost, the amount of transferred toner is reduced, and the printed image is printed. The text information becomes shallower.
8. Other characteristics
The above paper characteristics are mainly related to the print production suitability of the bill. In addition, there are some characteristic requirements related to the image quality of the paper, such as the whiteness, smoothness and gloss of the paper.
Fourth, the common problems of bill production
There are many problems in the production of bills, especially in the printing process, because the paper has been affected by the printing production, it is more prone to problems. Common paper related issues are:
1. Printing wrinkles
The printed semi-finished product has wrinkles or dead lines. There are several reasons for this: 1 uneven paper tension, wrinkles when the paper roll is placed, and pressed into dead lines during printing; 2 the humidity in the production workshop is too large, and the paper absorbs the wrinkles in the air after the package is unpacked; The amount of printing water is too large, the paper absorbs too much water, and wrinkles; 4 The semi-finished products after printing are not packaged in time with the film, and the moisture in the air is creased.
2. Printing off powder
Printing off powder is a headache for web printing. The paper powder enters the dampening solution, and then is transferred to the blanket cylinder and the plate cylinder, resulting in printing off the plate and getting dirty. It needs to stop the wiping, the loss is very large, the production efficiency is low, the printing plate printing durability is lowered, and the cost is increased. The length of the roll paper roll is generally about 8,000 meters. When the degree of powder drop is slight, the whole roll is not printed.
Printing off powder is related to many factors, including the amount of printing water, ink viscosity, paper surface strength and so on. Electrostatic copy paper is mainly used for offset printing. The surface is highly absorbent, and the surface strength is reduced after water absorption. The fibers and fillers are easy to fall off. In order to reduce the problem of powder drop, the surface printing performance of billing paper needs to meet the standard of double-adhesive paper.
3. Folding paper is not uniform
After printing, the paper folds and stacks the paper, which often causes problems such as tilting of the paper pile and unevenness of the paper surface. Such a semi-finished product is not conducive to packing and packaging, and secondly, paper jam is likely to occur during printing. The main cause of misfeeds is the uneven tension of the paper. Appropriately reducing the tension of the roll printing paper can reduce the unevenness of the paper.
4. Print curl
Printing curl affects the aesthetics of the bill on the one hand, and affects the post-processing of folding, packaging, etc. on the other hand. When the curl is severe, the machine cannot be automatically folded and packaged. The main factors that cause print curl are: paper is not resistant to high temperatures, large moisture, poor stiffness, and the like. Properly reducing the print fusing temperature can reduce the degree of curling.
5. Inkjet diffusion
For inkjet printing production, inkjet diffusion problems often occur. This problem is related to the degree of surface sizing of the paper and the surface tension of the ink. If there is a problem with the paper, it is easy to appear water when writing, the handwriting is enlarged, the writing is blurred, the paper is transparent, etc., and it is not suitable for bill production.
Fifth, the problem of paying attention to the production of bills
The bill production process is relatively complicated, and the environmental requirements for production are relatively high. In order to reduce the occurrence of problems, it is necessary to strictly control the production conditions of each link. From the preparation of raw paper to the delivery of finished products, there are many problems that need attention:
1. Store paper correctly
Control the temperature and humidity of the warehouse, avoid damage to the packaging of the paper, and re-package the returned materials to prevent moisture. Unpack the package when it starts printing on the machine. When the downtime is long, it is best to remove the paper roll and repack it.
2 strictly control the production environment
In the production process, the temperature and humidity of the workshop are controlled to ensure that it is within the normal range. Reduce the impact of air humidity on the paper. Especially in the southern region, the air humidity during the rainy season is very large. During the production process, the paper easily absorbs the moisture in the air, causing problems such as paper deformation and curling.
3. Save the semi-finished products
The printed semi-finished products are immediately packaged in plastic film to avoid exposure to the air for a long time and deformation caused by moisture.
4. Control the printing conditions
In the printing production process, the amount of water supply is reduced as much as possible, thereby reducing the amount of water absorbed by the paper. A better ink can be selected, the ink density is high, the amount of ink required to achieve the same color density is relatively small, and the amount of water during printing is relatively small.
5. Control the printing conditions
The speed of the printer has a certain relationship with the fixing temperature. The faster the speed, the higher the fixing temperature required, and the easier the paper evaporates and the curling problem occurs. Therefore, under the conditions of production, the fixing temperature is lowered as much as possible, and the problem is reduced.
Billing paper is a new type of paper that combines the superior performance of both offset and xerographic paper. Due to their different performances, in the papermaking process, the composition of the billing paper, the papermaking process, etc. are different from the offset paper and the xerographic paper.
At present, some manufacturers have successfully developed billing papers, which have been continuously improved in production applications, and the technology has gradually matured, further promoting the application of bill paper, providing an excellent material carrier for modern information life.