Classification and introduction of commonly used offset substrates Commonly used paper for offset printing is classified according to usage, mainly including the following varieties: An offset newsprint Offset newsprint is mainly used for lithographic newspapers, books and periodicals, but also for offset color newspapers and color children's books. Its packaging form is roll paper. In terms of raw material ratio, mechanical wood pulp accounts for 70-75%, and sulfite chemical wood pulp accounts for 25-30%. No filler is added, and alumina is added in an appropriate amount. The paper has a certain degree of sizing. In order to adapt to the process characteristics of the paper in contact with the wetting fluid in offset printing, the offset newsprint is sized to make the paper have a certain water resistance, and the proportion of chemical wood pulp is also increased, which greatly increases the strength of the paper. Meet the needs of printing. Its main features: First, it has high longitudinal tension, and second, it has good ink absorption. Attention should be paid to the printing of offset newsprint: ⑴ As the paper has good ink absorption and strong water absorption, it is necessary to control the water and ink balance. Offset printing paper Offset paper is generally used for printing books, dictionaries, pictures, inserts, and documents that need to be preserved for a long time, and also for printing tourist maps, book covers, and other products. Offset paper has two packaging forms: offset paper and roll paper. Offset paper is divided into three grades: special number, number one and number two according to the ratio of raw materials, processing technology and technical indicators. There are super calendering and ordinary calendering. Special numbers and No. 1 are used for high-quality prints, and No. 2 is used for ordinary prints. According to the different processing technology and smoothness of offset paper, there are two types of single-sided and double-sided. According to the quantitative difference, double-sided offset paper is seven kinds from 70g /? To 180g / ?, and single-sided offset paper is five kinds from 40g /? To 80g / ?. Raw material ratio of offset paper: Special and No. 1 offset paper's main raw materials are bleached chemical wood pulp or bamboo pulp and bleached chemical cotton pulp, and at the same time, they are equipped with bleaching straw pulp and other pulps not more than 20%, and surface sizing . Bleaching chemical wood pulp or bleaching chemical bamboo pulp and cotton pulp account for about 50% of No. 2 offset paper. In addition, no less than 50% of bleaching chemical straw pulp and reed pulp are used. The amount of filler used in offset paper is 20-30%. Attention should be paid when printing on offset paper: (1) Offset paper has strong water absorption capacity and large expansion and contraction rate, so it is necessary to pay attention to humidity adjustment to keep the paper's intake of wetting fluid to a minimum. Three coated paper Coated paper is also called coated paper or coated paper. Common offset coated paper is made by coating a layer of white paste on a certain paper and then calendering it. The base paper used in coated paper is called base paper or blank, and the coated white slurry is called coating. Coated paper is mainly used for printing high-level and fine color prints, such as picture books, pictorials, calendars, samples, high-level trademarks, etc. It is suitable for printing screen prints. The packaging form of coated paper is mostly lithographic paper. There are two types of double-sided and single-sided. Single-sided coated paper is relatively less used. Double-sided coated paper varies from 80g /? To 250g /? . From 250g /? To 300g /? Coated paper is rarely used. The base paper of coated paper is generally composed of 30% hardwood chemical pulp or rag pulp, combined with 70% softwood chemical pulp, or 50% each of the two types of wood pulp. In order to increase the opacity and thickness of the paper, a certain amount of bleached wood pulp or bleached straw pulp is sometimes added. The base paper generally uses weak sizing or medium sizing, with a filler content of 5-15%. Sometimes, coated paper also directly uses high-quality offset paper as the base paper. The coating is prepared by white pigment, adhesive and other auxiliary agents in a certain proportion. Common white pigments are: kaolin, calcium carbonate, barium sulfate, titanium dioxide, talc, etc. Commonly used adhesives are: casein, soybean casein (soy protein), starch, PVA, CMC, styrene-butadiene latex, acrylic latex. Other auxiliary agents used in coatings are: dispersants, plasticizers, emulsifiers, water repellents, whitening agents, etc. The proportion of pigments in the coating is generally 75-90%, and the adhesive is 10-25%. Coated paper is one of the best quality papers in offset printing, with high whiteness and smoothness, good gloss, strong water resistance, and small stretch rate. In addition, the thickness of the coated paper is uniform, the tightness is high, the opacity is high, the surface strength and other mechanical properties are better, it has an appropriate PH value, lower color shift and gray scale. Coated paper contains a large amount of coating on the surface, so the paper is compact, with poor elasticity and compressibility, poor ink absorption, and high quantitative. Due to the development of the printing industry, new paper varieties are constantly emerging, light coated paper is one example. The so-called light-coated paper, it is between coated paper and offset paper, the performance is close to coated paper, the manufacturing process is similar to the new paper type of offset paper. This kind of paper has not been coated, only the amount of glue applied when the surface is sized. The coating amount is reduced to 1g / ?, so the fiber can be clearly seen on the surface. In the papermaking industry, the coated paper with a fixed basis weight of 50-80g /? Will be light coated paper and the coated paper with a basis weight of 80-300g /? Printing. Pay attention to when printing on coated paper: ⑴Because the elasticity of the coated paper is not high, the printing pressure should not be too large. Four white paper Whiteboard paper is a kind of rigid cardboard with a large thickness, so it is also called white cardboard, which is a higher grade of cardboard. Whiteboard paper is formed by bonding surface layer, core layer and bottom layer. Its packaging form is flat paper. There are two types of whiteboard paper: single-sided and double-sided. Double-sided whiteboard is also called white cardboard. Single-sided whiteboard paper is mainly used in packaging and printing. According to the different surface layers, single-sided whiteboard paper is divided into two categories: ordinary and paint; according to the difference of the bottom layer, there are two kinds of gray background and white background; ordinary whiteboard paper is commonly used according to the quantitative difference. There are four kinds of 300g /? To 450g / ?. The surface layer of whiteboard paper is made of 100% bleached chemical wood pulp, or it is made of bleached rag pulp and bleached straw pulp, and an appropriate amount of whitening agent is added. The core layer is made of mechanical wood pulp or waste paper pulp, reed pulp, straw pulp, etc. The bottom layer is made of waste paper pulp with appropriate filling and sizing. The surface layer of whiteboard is made of bleached chemical wood pulp, with a certain proportion of fillers and rubber materials, and after multiple roller calendering, so the whiteness is good, the smoothness and surface strength are high, and it has certain water resistance and stretchability. Small, moderate ink absorption and relatively uniform. The thickness of whiteboard paper is large, the fiber structure is uniform, the paper is compact, strong, opaque, and the mechanical properties such as tensile strength and folding resistance are high. Whiteboard paper has a high water content, poor water resistance of the core layer and the bottom layer, and large stretchability. During the printing process, pay special attention to: Five aluminum foil paper The unique charm and novel printing effect of aluminum foil paper packaging have made aluminum foil paper printing the mainstream of high-end products. Aluminum foil paper belongs to the category of special paper. It is similar to the printing suitability of glass cardboard and the problems paid attention to in printing. (1) Basic concepts of aluminum foil Aluminum foil, commonly known as "gold (silver) cardboard, gold foil, metal foil". The title of "steel fine paper, steel paper, aluminum paper" is aluminum foil. The so-called foil refers to a metal sheet after special processing in terms of metal materials. The thickness of this sheet is less than 0.2mm. It is called foil. Since the metal material used for foil is different, it shows its properties. , Silver, tin, nickel, aluminum, etc. to show the difference. There are two methods for making aluminum foil paper: one is the composite method of sticking and rolling together aluminum foil and paper, and the other is the vacuum aluminum plating method, which is coated with an aluminum film on the paper surface. However, no matter what kind of aluminum foil paper is made, the surface layer is aluminum foil, and the paper is only its backing. (2) Printability of aluminum foil paper The printability of aluminum foil paper is special because it is a composite of aluminum foil and paper. The aluminum foil or film on the surface has the characteristics of metallic luster, tough texture and smooth surface. During the printing process, the surface characteristics of aluminum foil paper are directly related to the printability of printing presses and inks. Therefore, relatively speaking, the printability of aluminum foil paper is actually the printability of aluminum foil, which is specifically expressed in the following points: (1) The surface strength of aluminum foil paper is very high, it can adapt to the speed of high-speed printing machines, and can also withstand the pull caused by the viscosity of ink, which has good adaptability to improve production efficiency and stabilize printing quality. (2) The smoothness of aluminum foil paper is high, which is conducive to the transfer of ink, and the printed ink film is flat, smooth, graphic, and network lines are clear and complete. (3) The aluminum foil has a tight structure and no voids, and its surface is similar to the mirror effect. Therefore, it does not have the adsorption performance like paper. (4) The curling of aluminum foil paper is caused by the difference in physical properties between the material structures. Aluminum foil has high strength, high density, good stability and is not easy to expand and contract. The paper has low strength, relatively low density, poor stability, and easy expansion and contraction. The performance of aluminum foil and paper is very different. These two materials with different properties are compounded together, which itself has latent curling factors. However, this is only its internal factor. It generally does not curl when the conditions are suitable for it. However, when the ambient temperature and humidity change greatly, it will induce aluminum foil curling. (3) The main points of aluminum foil printing The difficulties of aluminum foil printing on offset presses are mainly the two disadvantages of poor dryness and stickiness of printed products. For this reason, aluminum foil paper should pay special attention to in offset printing: (1) Control the ambient temperature and humidity. (2) When choosing ink, it should be noted that the drying mechanism must be based on oxidized conjunctiva, which is not easy to dry on the ink roller, but can be quickly dried on aluminum foil paper. Existing special ink for aluminum foil paper. (3) Printing ink should not be too thick. Because the surface of aluminum foil paper is smooth and the adsorption force is poor, it is necessary to reduce the adsorption force between the blanket and the ink by increasing the fluidity of the ink, so that it can be smoothly transferred to the aluminum foil paper under the appropriate pressure. (4) Maintain the minimum liquid supply. Aluminium foil paper is not good at absorbing ink at the same time, nor is it good at absorbing wetting liquid. Therefore, the amount of liquid supply can be reduced as much as possible without the printing plate being dirty. (5) Take anti-sticking measures: Six embossed cover paper Embossed book cover paper belongs to the category of special paper, which is a decorative paper used for books, magazines, books, and covers. There is a less obvious pattern on the surface of the paper, and the colors are white, gray, green, beige, pink and other colors. According to the different materials used, it can be divided into three levels: A, B, and C. Level A is used to print the cover of books and magazines with more sophisticated binding. Level B and C can be used as covers for general magazines and books. Of course, embossed cover paper is by no means limited to printing book covers. Embossed book cover paper has high mechanical strength, wear-resistant folding, not easy to break, has good dimensional stability and durability, bright and smooth paper color. The paper weight is generally 120-230g / ?. The embossed book cover paper is mostly flat paper, which does not assess the smoothness, and the color paper does not assess the whiteness. Attention should be paid to the embossed cover paper during the printing process: (1) Reasonably choose embossed cover paper according to the characteristics of the printed product to be printed and the offset printing machine used. Seven Map Paper The map paper mainly prints maps, topographic maps, hydrogeological maps, tourist maps, etc. Its technical indicators are basically similar to offset paper, but have higher requirements in the following aspects: (1) High mechanical strength, especially folding resistance requires folding back and forth dozens of times without breaking, for this reason, some bleached hemp pulp or rag pulp should be added during pulping. Eight carbonless copy paper With the popularization of computers and the development of office automation, Carbonless Copy Paper (CCP) can be more easily printed on computer terminals and is suitable for office automation. Therefore, its scope of application is getting wider and wider. 1 Carbon-free copy paper structure and color development principle Carbonless copy paper can be divided into two kinds of color development and self-color development. The most used is his colorless carbonless copy paper, which is generally composed of three paper pages, namely upper paper, middle paper and lower paper. The upper paper is also called back coated paper (codenamed CB is Coated Back). The backside of the paper has microcapsules containing force sensitive pigment oil, and the middle paper is also called positive and negative double coated paper (codename CFB is Coated Front and Baek) , The front side of the paper is coated with a color developer, and the back side is coated with microcapsules containing force-sensitive pigment oil. The lower paper is also called top-coated paper (codenamed CF is Coated Front), and the paper side is coated with the color developer only. Self-coloring paper (code-named Self-Contained SC) is a microcapsule layer containing force-sensitive pigment oil on the back of the paper, and a developer and microcapsules containing force-sensitive pigment oil on the front. There are two types of coatings on carbonless carbon paper (Figure 2-1), a CF layer containing a color developer and a CB layer containing a color developer. The color developer is a special colorless dye that has been dissolved in nonvolatile The carrier oil is encapsulated by 3-7um microcapsules. The impact pressure of strong writing and printing can crush the microcapsules, so that the colorless dye solution flows out and contacts with the developer, and a chemical reaction occurs to display colored graphics and text, thereby achieving the purpose of copying. There are 45g /? CB paper, 47g /? CF paper, 52g /? CFB paper, etc. according to the quantitative analysis. According to the color of paper, it can be divided into five types: red, yellow, green, blue and white. According to the color traces, it can be divided into blue, yellow, orange, black, red and other colors. (Figure 2-1) Schematic diagram of carbonless carbon paper (1) When purchasing and using carbonless copy paper, it is best to use the same brand of upper, middle and lower paper produced by the same company, and the production date should not be too long apart. (2) When purchasing carbonless carbon paper, consider the printability. For example: surface strength decides whether to lose powder, hair, or paste, high opacity can reduce through-printing, good paper uniformity can reduce printing wrinkles, smoothness determines printing pressure and ink consumption, surface absorption affects ink Absorption, poor absorption is easy to appear blurred and sticky on the reverse side. Tightness reflects the plasticity of the paper. Good plasticity can be printed under less pressure, reduce the printing blue, and improve product quality. (3) Distinguish the functional side of carbonless copy paper during printing, to avoid mistaken functional side and result in scrapped printed matter. In practice, it can be distinguished by looking at it or touching it by hand. When touching the paper by hand, the CF surface is smoother and the CB surface is rougher. When distinguishing by eye, the CF surface is good in gloss and reflective, and the CB surface is rough and uncoated The original paper can be seen fiber by fiber. (4) The printing environment strives for constant temperature and constant humidity. (5) When printing, try to achieve "three small" (small ink, small water, low pressure) as much as possible in the process design with small format printing to avoid overprinting failure. (6) Alcohol cannot be used for printing on carbonless copy paper. Alcohol will cause color development and will temporarily fail. (7) To avoid fluffing and powdering on the CF surface, use inks with low or medium viscosity, reduce the speed of printing, and clean the blanket frequently. (8) Carbonless copy paper is a low-quantity paper, which is light, thin, and soft, and it is often difficult to convey paper. Therefore, the paper positioning should be slightly knocked. Nine synthetic paper Synthetic paper is a very durable and dimensionally stable waterproof paper. It is made of polypropylene (PP) and inorganic fillers, rather than wood fiber. Compared with ordinary paper, synthetic paper has good surface strength, excellent smoothness, and impeccable whiteness. Because synthetic paper has the characteristics of both plastic and paper, it is widely used in many fields: (1) High-quality prints: such as pictorials, pictures, almanacs, etc. Precautions for printing on synthetic paper: 1 Preparation before printing (1) The outer packaging of synthetic paper can be removed before printing. Synthetic paper needs to be stored in the printing shop for 48 hours before printing to adapt to the environment of the printing shop. 2 Printing (1) Because synthetic paper does not absorb water, the water consumption of the layout must be adjusted to a minimum and maintain a balance. The pH value of the wetting liquid should be maintained at 5.5-6. 0, the temperature should be controlled at 25 ℃, the wetting liquid Need to add 10% -15% alcohol. 3 After printing (1) Synthetic paper printed on the delivery table should be stacked with partitions, and the stacking height between the partitions should not exceed 15cm. Ten plastics and composite materials Widely used in plastics and composite materials for offset printing, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyester (PET), nylon, etc. 1. Characteristics of plastics and composite materials: (1) Good mechanical properties, plastic and composite materials have certain transparency, light weight, and most of the density is 1.0-1.4g / ?, has good mechanical strength, such as stretching, compression, impact, bending, etc. . (2) The barrier property is good, and the barrier property mainly includes moisture resistance and water resistance. (3) It has excellent corrosion resistance and good smoothness. Precautions for printing plastics and composite materials. (1) For printing on plastics and composite materials, the surface tension of the ink or coating must be lower than the surface tension of the substrate. If glazing is required, the surface tension of the varnish is lower than that of the ink. (2) Printing with UV ink, unlike most substrates such as paper and cardboard, there are no micropores on the surface of plastics and composite materials that can penetrate ink or paint, but most materials have a bright surface and a matte surface. The matt surface is usually selected as the printing surface to ensure that the ground is not rough, the dots are strong, the adhesion between the ink and the material is strong, the ink is full and no small white spots are exposed, and the printing pressure is increased by 0.02 to 0 compared to the standard pressure .05mm. (3) High requirements for printing equipment: Plastic and composite materials printing have high requirements for printing equipment to ensure accurate overprinting, high stability, easy control of water and ink balance, high pressure control accuracy, and printing dots throughout the printing process. fine. (4) Control the water-ink balance during printing to prevent ink emulsification. (5) Properly increase the air humidity to prevent the generation of static electricity. Baby Comforter,Baby Blankie,Baby Snuggle Toy,Comforting Towel Ningbo Dikai Imp&Exp Co., Ltd , https://www.longkaitoys.com
There are many types of substrates, and paper accounts for the largest proportion, so offset press operators should have an understanding of the characteristics of the paper and the issues to be paid attention to in printing. malfunction.
⑵ Pay attention to the occurrence of paper break.
⑶ When printing color jobs, you must pay attention to the size of the printing pressure, so that the fitting can meet the requirements as much as possible.
(2) After the paper absorbs acidic wetting fluid, it affects the drying speed of the ink. Therefore, the acid value of the wetting fluid should meet the standard.
(3) The proportion of offset paper containing filler is slightly larger. When the ink is too viscous, it will cause the paper to de-powder and fluff, so adjust the ink viscosity and fluidity appropriately.
(4) In the printing process, the appropriate desiccant should be selected according to the performance of various offset papers such as ink absorption, acidity and alkalinity, water content, and the printing form and printing process.
⑵The whiteness of the coated paper is high, and the ink absorption is slightly lower, so it is necessary to use bright or resin ink to match the paper to ensure the brightness of the printed matter.
⑶Coated paper has poor ink absorption, so certain measures should be taken during the printing process to prevent the backside of the printed matter from becoming dirty and drying slowly.
â‘·When printing coated paper, pay special attention to the appropriate adjustment of ink, specifically speaking, the viscosity and viscosity adjustment of ink, so as not to cause powder, hair, delamination and other failures.
⑸ For low-weight coated paper or light-coated paper, because the paper is thin, pay attention to the adjustment of the paper feeding part. [next]
(1) The thickness of whiteboard paper, the thickness of different whiteboard paper is also different, this factor should be taken into account when adjusting the printing pressure and the thickness of the roller lining.
(2) Adjust the gap between the front gauge and the iron table.
(3) Properly adjust the gripping force of grippers.
a Properly increase the amount of desiccant added b. Add a partition paper holder, put a partition paper holder every 50-100 sheets of printed sheets, so that the printed sheets are placed in layers, which can effectively prevent sticking. Because the printing difficulties of aluminum foil paper are often difficult to overcome, UV offset printing is currently widely used.
(2) In the printing process, carefully adjust the ink's suitability, control and reduce the amount of wetting fluid, and prevent the occurrence of powder and hair failure.
(3) When printing, the printing pressure can be increased appropriately, or the ink with greater fluidity and stronger wettability can be used in order to make up for the uneven printing caused by the unevenness of the paper.
(4) Due to the pattern on the surface of the embossed book cover paper, the acceptance of the ink is poor, and the transfer rate is relatively small. Therefore, the color change of the ink must be observed and adjusted accordingly during printing. [next]
(2) The smoothness should be high, reaching 80-140s, so as to print or draw thin lines on the paper.
(3) Good dimensional stability, close to vertical and horizontal expansion ratio, sizing degree> 1.25mm, small deformation when wet.
(4) Good light resistance and less dust to avoid confusion with the symbols on the map.
(5) The basis weight of map paper is generally 55, 100, 120, and 140g / ?. If it is used for printing maps, it has higher requirements on the water resistance and moisture resistance of paper.
2 Points for attention when printing on carbonless carbon paper:
(2) Packaging and printing: such as pharmaceutical packaging, cosmetic packaging, and food packaging.
(3) Special printing: if there is securities, in-mold labels.
(2) Take synthetic paper together for cutting, and always wear gloves when stacking synthetic paper on the paper feeding table of the paper machine.
(3) Check the static eliminator configured on the printing machine, and it must be kept normal.
(2) Because synthetic paper has slight elasticity, the printing pressure should be increased more than ordinary paper. At the same time, try to use an alcohol dampening four-color offset printing machine.
(3) When printing on both sides, print the side with less graphics first, and spray powder as uniformly as possible and minimize it.
(4) The ink used in the printing of synthetic paper adopts a special formula, and the printing speed can reach up to 10,000 sheets / hour (depending on the paper thickness and the size of the printed graphics and text)
(2) Before the printing ink layer is completely dried, do not move it to vibrate the paper pile, so as not to damage the ink layer surface due to the damage of the ink layer, and the back surface will be sticky.
(3) The drying time increases or decreases depending on the type of printing machine and the color density of the printing plate. The surface of the printed product is dried after 4-5 hours and can be subsequently printed. After 12-24 hours, the printed product is completely dry and can be cut. machining.