Paper size factors affecting the quality of the UV printing
Time:2016-04-19 10:13Source:sankunClick: Number
Paper size factors affecting the quality of the UV printing
The size of the paper invariance is the one of the major goal of the paper, it has main influence on the quality of printing the same.
Paper also calls the shape stability, size invariability is refers to the paper moisture change when the size of the paper (shape) attack changes, with the size of the paper moisture content before and after the shift change quantity of paper size according to the percentage of performance. General speaking, all kinds of paper fundamentally have receive moisture elongation, shorten the moisture condition. Speed and level of transformation with varieties of fiber raw material differences and differences in paper, the speed of change and the greater the level of the paper form poor stability; On the other hand, the shape stability is good.
Paper the cause of the deformation and its effect on printing quality
In the process of manufacture and use, effect of paper deformation is more, the elements of physical and chemical characteristics of the pulp, beating, chemicals, and the selection of filler, the writing features, in the process of the paper machine equipped with and using of water drop all city influence the size of the paper. Here we only comment on paper in the transportation and the size of the water in the printing process to share off provoked shift.
Paper first consists of cellulose, and cellulose is strong hydrophilic material, it has a strong water imbibition and take off the water. Paper in the store, transport and printing process, because the change of temperature and humidity provoked paper moisture content changes, cause inflation and shorten. Paper moisture change the primary reason of paper size change are: paper moisture change, constitutes a single fiber can receive paper moisture expansion or failed moisture shortened, make the fiber shape transformation, then the size of the paper change; Paper is internal hydrogen bond connecting, paper receiving or lost moisture, the effect of hydrogen bonding for increase or decrease, make the fiber pulled tight or turn to each other.
Paper occur because of the water drop shape change will eventually cause the size of the paper changes, bring whammy effect of printing. Paper moisture content is too large, paper fibers, between filler and rubber connecting force is reduced, easily, in turn, affect the paper surface strength, have showed a loss after printing powder, hair loss and other bad sight attack. And the powder loss, loss of MAO attack decreased, the stiffness of the paper the hardness of the edge and incidental when feed locating problem, formed set off. If the paper moisture content is too low, paper flexibility is poor, when printing dot imprinting easy extension, cause network expansion rate.
Therefore, should not be paper if it does not conform to the high humidity in its moisture content under the printing, and should be carried out under the condition of humidity in printing, which is beneficial to the guaranteeing accuracy. In order to make the paper moisture content in the whole paper adhered to the coherence average, and printing workshop phase with the temperature and humidity, also in order to reduce the paper humidity sensitive level of the situation, the invariance of the progress of paper size, ordinary before printing, to accept the inevitable disposal methods.
The disposal measures to paper deformation
In order to improve the size of the paper invariance, earth want to disposal of paper, disposal method are:
1. The coating. The paper through the level of coating can inevitably improve paper deformation condition. But, after the paper through the one-side coated and boring, because the balance of fiber and water molecules systems have been damaged, will form the paper internal water molecules distribute uneven, internal stress of indeterminacy of dispute, provoked the local disambiguation and the distortion of dispute shorten the inflation rate. If not checked by finishing, will affect paper work eligibility.
Debugging mode is a kind of technological process, it can put the paper in the process of machining have been found in paper not wish some stress alleviation of loss, the paper obtained the average spread on the appropriate moisture, guaranteeing the paper express in normal indoor temperature and humidity in plain, and the same size. So in the process of paper coating processing and disposal, humidifying debugging mode is the main process is often used. Traditional process method there are two kinds roughly: compare with the old way is to hang the sheet in the case of the inevitable humidity or in a sealed space, filled with a lot of steam to form a high temperature and constant humidity space, in this form, according to the degree of sorption equilibrium point, sheet gradually receives the water until the paper moisture content of the absolute moisture content and air around us consistent equilibrium configuration, using the process method, sheet of humidifying the results compare well, but take up the space is larger, the time is long, and not used for paper rolls, so this method has gradually been cut; The second is the commonly used method is to use liquid water to humidifying, inside a small seal installation, or change the shape of the droplets emit distractions, constitute a space atomization, application of electrostatic adsorption principle allow the small droplets in contact with the paper and reach the humidifying goals, but this method can only make your page appearance humidifying, atomized droplets penetrate sheet inside fiber, and very easy to form sheet looks too much water and paper disease such as inflation or stain, and then lower the quality of the paper.
Based on years of production experience and theory, the paper reciprocates humidifying after debugging mode, can eliminate the sheet deformation problem, the invariance of the flatness, size of sheet, calender process after finishing, printing, cutting, packaging has very main significance. When paper on "form", if the width and along the longitudinal water can both average to adjust to the required value, then to the output of the "deformation" relatively flat paper, electrostatic can reduce the risk of trouble, and improve the function of paper on the printing machine operation, compliance progress sheet printing.
2. Wrinkles. Paper deformation will affect the other function of paper and printing quality, but in order to improve the paper features, we can pay to make some folds in the paper, this is corrugate skills. Paper wrinkle can greatly improve the deformation properties of the paper, the progress of the elongation and dynamic strength of paper, breathable, soft and elastic, improved paper receiving characteristics and permeability, and other special properties.
Paper wrinkle to have "plating roller" approach, in addition, the most popular and commonly used is to use scraper wrinkling in the dryer, and the paper from the cylinder surface stripping blade method. Based on contact with scraper sheet of water can be divided into three types: wet wrinkle, paper moisture 40 picture? Wrinkle 60% form; Half dry wrinkles, paper moisture 20 picture? Wrinkle 40% form; Dry wrinkles, paper moisture picture 5? 8% form wrinkles. Whether it is a dry wrinkle still wet wrinkle, fundamentals are similar. Wet wrinkle and half dry wrinkle easily grasp, wrinkle wrinkles than average, but the paper after paper dry hair, board, hard, only suitable for low yield levels used toilet paper.
3. Wet. Damping (dry) disposal, the water cut of components in the moisture content of paper is paper and paper revealed by the percentage of the weight of performance. When the paper containing 0.1% of the water can affect overprint, so control the moisture content of paper is the precondition of guaranteeing overprint precision. Ordinary conditions, the printing paper moisture content should be moderate in 7% plus or minus 1%, and paper and paper in the middle of the surrounding water content error is not more than 1% advisable. Earth hanging paper printing company is 24 hours earlier and put paper or transport to a printing shop in printing workshop temperature and humidity in nearby workshop. Most companies because of the limitation of space, demand printing paper is only a few hours before printing talent turnover in printing workshop, this invariance about paper size is very unlucky. The best practice is in the relative humidity is 6% higher than a printing shop? 8% of the air between paper for humidifying treatment may start on a wet local add wet, then to printing workshop for the balance of moisture, make the average moisture content of paper.
4. Automatic humidification. For offset printing with ink and the sense of separation, due to the moisture absorption when printing paper deformation, on the basis of the paper moisture change lag effect, can be in a formal before printing paper printing again water, automatically increase the moisture content of paper (commonly known as "water"), the paper has a preliminary process of moisture absorption, so much in the official press paper deformation is small. In offset printing, especially after the UV printing, because of the influence of the temperature of dry, paper in the dehumidification process, smaller size of earth. Because after coated or offline glazing by high strength and heat, the influence of the size of the paper deformation is large. Although placed over ten hours or longer time, but is not very clear about the effects of paper moisture, and paper size serious deformation is very difficult to restore. In such conditions can be through automatic humidification way to regulate the moisture content of paper and then make some resilience the size of the paper.
The above several ways have been regulate paper forms to improve the invariance of paper, in addition, still should begin from pre-press, printing to set appropriate disposal, paper deformation for compensation to guaranteeing printing quality.
1. Printing paper wide choice. In typesetting must ponder to the paper deformation condition, divide the paper deformation is divided. Some paper compare with loose texture, very easy by the influence of moisture change. About these paper, layout of wide shoulds not be too big. A lot of the printing company is split wide offset printing equipment, so I hope the paper can produce with split wide, and then progress to produce efficiency. But some of your products on the machining process demands more and the accuracy is higher, if the split wide computer printing, paper also compare with large deformation, forming after processing overprint greatly hard. So much will require the best using full open of paper printing, but sometimes form the waste paper. Therefore, demand according to the detailed requirements of product to make careful processing plan in detail.
2. Paper printing bias. Because the paper fiber length bias on the deformation is greater than the radius of deflection, thus adopting longitudinal axial parallel paper and printing roller for printing, is advantageous to progress overprint precision. We need discussion paper function of moisture absorption and moisture shift invariance size effect rule, and in accordance with the rules of wet printing process and standards, there is also a need to discuss restraint for paper deformation cause overprint banning method, and then cut printing quality divide to progress printing quality.
3. The overprint design position setting. Some print packing box, in particular, demand bronzing or concave and convex overprint, demand attention to the hot stamping design as far as possible when puzzle in close by the side of the body, this is because by the side of politeness are better than on the outside, especially some big size box, on the outside than by alignment is difficult on the side. In accordance with the packaging structure design requirements, the placement of long side to puzzle box when the demand to the paper fiber and the long side of the vertical box, so much can obtain the maximum limit carton strength, but this kind of layout method often unlucky in the alignment of the next working procedure, therefore, overprint pattern design and position setting should especially pay attention to.
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UV printing(6)
