Types and principles of printing

The difference between plate printing and unplate printing

  Currently, printing and plate making are divided into two categories: “traditional (plate) printing” and “plateless printing”.

  Traditional (printed) printing, including offset printing (offset printing), flexographic printing, gravure printing and screen printing (also based on printing type/principle/number of printing colors/purpose)

principle

   Offset printing is also called “lithographic printing” because the graphic and non-graphic parts of the offset printing plate are basically on the same plane, with only a slight difference in height. It is printed based on the principle of oil-water repulsion. The graphic and text parts of the printing plate are hydrophobic (repellent to ink), and the non-graphic and text parts are hydrophilic (repellent to ink).

process

  During printing, the non-graphic and text parts are wetted first with the help of fountain solution, while the graphic and text parts are not wetted due to their own “fountain solution repellent” properties. On the contrary, the graphic part receives the ink through the ink radial ink transfer, while the non-graphic part repels the ink. The ink received in the graphic part is immediately transferred to the rubber roller and then transferred to the substrate. Therefore, “offset printing” is not a direct printing, but an indirect printing.

application

  In the field of drama printing, “offset printing” is currently the most widely used printing method among all printing methods, and is especially beneficial for the printing of packaging materials such as paper, corrugated boards, and metal flat sheets.

principle

  Flexographic printing can be classified as “letterpress printing”, which is a type of “rotary letterpress printing” that uses a soft, elastic rubber plate or elastomer plate to copy graphics and text.

advantage

  The cost of flexographic printing is low, it can be overprinted in multiple colors, the printing speed is fast, and its printing quality is close to offset printing. At the same time, it can integrate cutting, forming, folding, hot stamping, laminating or glazing and other processes into a production line, thus It helps to improve automation and production efficiency, especially for commercial label and packaging printing applications.

application

  Flexographic printing has wide adaptability and can be applied to different printing materials, such as traditional paper, some non-absorbent printing materials such as cellophane, plastic products, metal foil, glass products, etc., and can be used on some thicker cardboard, corrugated paper, etc. Printing dramas are also performed on the printed matter.
In fact, at present, flexible packaging printing, corrugated box printing, self-adhesive label printing, folding carton printing, etc. almost all use “flexo printing”, and some newspapers and magazines also use “flexo printing”.

The difference between screen printing and digital printing

Screen printing: 1. Substrate and ink. As we all know, screen printing can be described as “universal printing”. It is extremely adaptable to substrates and has great tolerance for inks (printing materials). It is almost impossible to find something it cannot do. When printing, there is almost no ink that it cannot print out. (Screen printing: Using a screen printing plate as a tool to print a pattern on the surface of a material, it can be done manually or mechanically. When printing, the screen printing plate must be in contact with the printing material, so it is called “screen printing” (different kinds of materials are added to the printing paste) Chemical reagents such as reflective particles, luminous particles, expansion reagents and other ingredients can show different effects. The most common printing methods include water slurry, glue, thermosetting ink, thick plate, hot stamping and silver foil, discharge dyeing, flocking, Silicone, foam printing, dripping paste, etc.)

Modern screen printing technology uses photosensitive materials to make screen printing plates through photographic plate making (so that the screen holes in the graphic and text parts of the screen printing plate are through holes, while the screen holes in the non-graphic and text parts are blocked. live).

During printing, the ink is transferred to the substrate through the mesh of the graphic part through the squeezing of the scraper, forming the same graphic and text as the original.

Screen printing equipment is simple, easy to operate, easy to print and plate making, low in cost, and has strong adaptability.

Screen printing has a wide range of applications. Common printed materials include: color oil paintings, posters, business cards, binding covers, product signs, and printed and dyed textiles.

Digital printing: Use a computer to print patterns directly on the material through an inkjet printer without any “plate”. There is no contact between the nozzle and the material during printing, so it is called “plateless printing/or non-contact printing” (water-based inkjet printing) / Laser printing principle such as copying/uv inkjet)

The full name of UV curable digital inkjet is developed on the basis of UV curable printing ink. It has a history of more than 50 years. It is an ancient printing ink variety and has been widely used in the printing industry.

UV inkjet printing means that it uses UV ink, and the drying method of UV ink is UV drying, which means that the ink is cured by UV light. The advantage is that the ink can be printed on any material. It only needs UV light (included with the device) to stop drying, so there is no limit to the printing material.

Spot color printing and four-color printing

Four-color printing uses CMYK (cyan, magenta, yellow, black) four-color overprint to produce the required colors. In layman’s terms, it means using the different superpositions of these four colors to get the desired color. As long as the color has a gradient, it is produced by four-color overprinting. Four-color printing is superimposed by dots. You can see different colors with a magnifying glass. outlets.

Spot color printing refers to a printing process that uses inks other than the four inks of yellow, magenta, cyan, and black to replicate the color of the original. In packaging printing, spot color printing technology is often used to print large-area background colors. Spot color printing is a single color without gradients, the pattern is solid, and the dots cannot be seen with a magnifying glass. (Generally speaking, spot color printing costs slightly more.)

From the perspective of economic benefits, it mainly depends on whether the use of spot color printing technology can save the number of overprints. Because reducing the number of overprints can save both printing costs and prepress production costs.
If a product has both a color gradation picture and a large-area background color, the color gradation picture part can be printed with four colors, while the large-area background color can be printed with spot color.

cost comparison

Screen printing: Traditional screen printing requires film plate making, which costs about 200 yuan per piece. The process is complex and the production cycle is long. Only single-color printing is more expensive, and the finished screen printing dots cannot be eliminated. Mass production is required to reduce costs, and it is impossible to print small batches or individual products (now screen printing will also be divided into stages: printing types are similar Things such as fabrics that cannot be put on semi-automatic or fully automatic machines and large printing presses)

Digital printing does not require a complicated plate-making process and is not subject to any restrictions on the number of prints. It not only greatly reduces costs, but also makes it possible to print in one piece and accept small batch orders. The printed patterns are brightly colored and delicate. Higher clarity. Collective mass customization is printed by screen printing. Compare the two: photos, complex colors, and gradient color patterns need digital hot stamping. Silk screen printing is usually line graphics, text, simple color patterns and LOGOs. Digital hot stamping is priced based on area, and the cost will not differ much if the quantity is large or the quantity is small. Silk screen printing is priced according to the number of colors. The larger the quantity, the lower the cost.

Digital printing does not require a complicated plate-making process and is not subject to any restrictions on the number of prints. It not only greatly reduces costs, but also makes it possible to print in one piece and accept small batch orders. The printed patterns are brightly colored and delicate. Higher clarity. Collective mass customization is printed by screen printing. Compare the two: photos, complex colors, and gradient color patterns need digital hot stamping. Silk screen printing is usually line graphics, text, simple color patterns and LOGOs. Digital hot stamping is priced based on area, and the cost will not differ much if the quantity is large or the quantity is small. Silk screen printing is priced according to the number of colors. The larger the quantity, the lower the cost.

Screen printing has the characteristics of thick ink layer, rich graphics and text levels, strong three-dimensional effect, and wide range of printing materials. As a production tool for screen printing art, screen printing will not change. It is used in high-end tobacco and alcohol, food packaging cartons and other fields. Applications in emerging fields are also gradually increasing. The most prominent advantages of digital printing can be summarized as follows: one-page printing, no plate making required, immediate availability, instant error correction, variable printing, and on-demand printing. The different process characteristics of screen printing and digital printing determine that they have different uses in the printing market. There is no conflict between the two that one can completely replace the other.

Thermal transfer printing and sublimation printing

Thermal transfer printing (divided into film transfer and digital direct printing): Thermal transfer printing does not penetrate into the fabric, but is printed on the surface of the textile. The transferred pattern is very thin, non-breathable, non-sticky, non-cracked, washable and does not fall off. The technology is mainly used on clothes with a very high cotton content.

Process: After printing patterns of various colors on the pet sheet, apply hot melt glue on the back of the pattern (hot melt glue can combine the pattern with clothing), and press it with a press machine at about 150°C. Iron, peel off the PET waste film, and complete the thermal transfer process.

Sublimation printing: Thermal transfer sublimation is to use a machine to print sublimation ink on a specific sublimation paper, and then heat and pressurize the sublimation paper to transfer the pattern of the sublimation paper to the ironing material. The printing material will sublimate through heating and pressure and penetrate into the fabric.

Process: Use a machine to print (or print) disperse dyes (or sublimation ink) on a specific paper in advance, and then use this paper to transfer the pattern on the paper to the object that needs to be printed using high temperature and high pressure.

  1. The temperature and time of hot stamping are different: Generally speaking, the temperature of hot stamping is between 130-150 degrees and the time is about 6-10 seconds, while the temperature of sublimation paper is between 200-230 degrees and the time is about Between 15-20 seconds.

  1. The fabrics used for hot stamping are different: hot stamping can be used on knitted, textile, nylon, non-woven fabrics, Oxford cloth and other fabrics. Sublimation paper can only be ironed on light-colored or white polyester fabrics.
  2. The hand feeling after hot stamping is different: There is hot melt adhesive on the back of the hot stamping, so the hot stamping on the fabric feels hard to the touch. Sublimation paper has ink penetrated into the fabric, so it is called sublimation. It feels like the softness of the fabric.

  1. The colors are different: Heat transfer can achieve the effect of photos. When doing heat transfer, as long as you provide clear original files, you can achieve the effect of photos. The effect of hot stamping on sublimation paper is not as clear as that of heat transfer. The higher the polyester content of the sublimation paper hot stamping fabric, the brighter the color.
  2. There is a difference in the washing fastness: Generally speaking, the washing fastness of heat transfer paper is better than that of non-sublimation paper. However, the quality of heat transfer is distinguished by the quality. The main thing to distinguish the quality of heat transfer is good or bad. Based on: elasticity and wash fastness. Sublimation paper does not have this feature.

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