Overview of label thermal transfer printing

While digital on-demand printing has gradually begun to reach the market, thermal transfer technology with the same personalized characteristics as on-demand printing has also been loved by people because it can print color graphics and text on paper products, Digital competitions on textiles, ceramics, plastics, metals, label papers and other substrates have simple methods, low cost, and personalized strong color printing, thus leading a new trend of transfer printing.

1. Features of transfer printing

Transfer printing is to first print graphics on the carrier to make a transfer material, and then use the printing glue head, thermal transfer printer, transfer printing paper or transfer printing film to transfer the graphics on the transfer material to the substrate. Transfer printing can be printed on the surface of substrates that are not easy to print on the printing machine in various forms, shaped objects or soft materials. Before printing, the image and text are printed on the intermediate transfer carrier, and then this carrier transfers them to the substrate by special technical means, such as heating, wetting, and pressing, to form a printed product. According to the classification of transfer printing technology, it can be divided into cold transfer printing, thermal transfer printing and pressure transfer printing.

1. Cold transfer printing

Can be divided into dry transfer printing and wet transfer printing.
Dry transfer printing: The carrier is generally made of plastic film. The film is pre-coated with RMB in the release layer, then the graphics are printed on the coating, and then a layer of adhesive is printed with the adhesive as the printing ink. It is pasted on the substrate during transfer printing and the carrier film can be removed.
Wet transfer printing: The carrier is usually a paper or film disc printing machine, pre-coated with a water-soluble release layer, and after printing graphics, the back adhesive is printed. The back adhesive is water-soluble. When moistened with water, transfer to the substrate and remove the carrier.

2. Thermal transfer printing

Mainly include sublimation thermal transfer printing, deinking thermal transfer printing, flocking thermal transfer printing, thermal transfer printing, etc.
Sublimation thermal transfer printing: paper is used as the carrier, and sublimation ink is used for printing. During the transfer printing, the heated image can be transferred to the substrate. The ink used is prepared by sublimation dyes for relief printing, which is mostly used for transfer printing of synthetic fiber fabrics.
Deinking thermal transfer printing: paper or film is used as a carrier, and plastic ink is used for printing. Because the ink contains hot-melt link materials, journals are published, and generally no adhesive is printed. During the transfer printing, it is heated and pressurized. After the ink layer is heated, the bonding material melts and adheres to the substrate. When the carrier is removed, the graphic ink layer can be separated from the carrier and transferred to the substrate.
Flocking thermal transfer printing: use paper as a carrier, pre-coat a layer of hot melt adhesive on the paper, then flocking on the adhesive surface, and then use hot melt ink on the velvet surface (actually a hot melt adhesive formulated into a solution ) Printing graphics.
Thermal transfer printing: Simply put, the process of transferring ink from carbon ribbon media to paper or film with heat and pressure is mainly used for label printing. When the label passes through the printer's print head and pinch, heat and pressure transfer the ink to the label.

3. Pressure transfer printing

Such as pressure-sensitive transfer printing, the printing carrier is generally printed with a film Yiwu, pre-coating the release layer and then printing graphics, and the back adhesive is printed with a special pressure-sensitive adhesive as the printing ink. When transferring printing, print on the glossy surface of the film and pressurized coated paper to transfer the graphic to the substrate.

2. Common types of label transfer printing

Label transfer printing is the use of physical and chemical methods to print printed patterns and colors onto the substrate. Common label transfer printing methods are as follows.

1. Wipe transfer printing

Mainly suitable for hard and smooth materials such as paper, wood, plastic, etc., used in art design, photo albums, toy stickers, scratch music, transfer printing paper, etc. When in use, release the release paper on the surface of the finished label, align the pattern with the position to be transferred and print, and evenly rub the back of the pressure-sensitive film with nails or wood chips, tear the transparent film and publish it, and the picture and text transfer is completed.

2. Reverse pressure-sensitive transfer printing

There are three types of reverse pressure-sensitive transfer printing labels: solvent-resistant, scratch-resistant, and baking-resistant. Solvent-resistant type can withstand solvent scrubbing; scratch-resistant type can have good adhesion and scratch-resistant effect without any treatment after transfer printing, but to avoid scratching by hard objects; high-temperature baking type can be transferred during printing After glazing baking treatment, it is also possible to directly perform baking treatment without spraying varnish. Pressure-sensitive transfer printed labels are suitable for surface decoration of hard materials such as metal, plastic, synthetic materials, such as air conditioners, refrigerators, washing machines, water heater housings, fishing rods, clubs, bicycles, etc. When in use, only need to tear the protective film, align the transfer position and paste, evenly squeeze and tear the bottom paper to complete the pattern transfer.

3. Water transfer printing

Can be divided into reverse water transfer printing labels (B, C transfer printing labels), soluble forward water transfer printing labels, peelable film forward water transfer printing labels, etc. The characteristics of water transfer printing labels are exquisite printing, bright colors, a wide range of applicable materials, strong and beautiful labels, and easy to change color printing film, especially for irregular surfaces with good decorative. Because the graphic adhesive film layer of the water transfer printed label has a certain toughness, when drying the moisture under the layer, remember to make the pattern adhere to the uniform on the irregular surface while wiping the water. After drying enough, you can spray varnish and baking on the transfer graphics, but it must be fully dried, otherwise bubbles will appear after baking, resulting in waste products.

4. Thermal transfer printing

Thermal transfer printing is to print a pattern on a special transfer paper or transfer film, and then transfer and print it on the substrate. It is mostly used for ceramic decal printing, textile printing, and commodity label printing. [next]

3. The superiority of label thermal transfer printing

In recent years, with the advancement of science and technology, thermal transfer technology has also undergone rapid development. The main characteristics of thermal transfer are the bright and colorful transfer images, and its effect is not only comparable to ordinary printing At high temperature, the thermal transfer ink can be sublimated by heat, penetrate into the surface of the object, and form a bright color image. Therefore, the thermal transfer product is durable and the image will not fall off, crack and fade. The application range of thermal transfer is very wide, from fabric printing to ceramic, metal, glass and other handicraft surface printing, all kinds of labels, barcodes, stickers printing, especially in label printing has developed rapidly.

To sum up, label thermal transfer printing has many advantages:

(1) A small amount of diverse printing without waste, even if only one sheet can be printed;
(2) Take advantage of the barcode and use it with the scanner to reduce manual processing time and cost;
(3) Various graphic printing machines can be printed according to the needs, especially the company's logo and certification passed mark;
(4) Serial numbers can be printed to track products;
(5) It can be connected to the company's database information, quickly extract the data and print;
(6) It can be used on the production line to track the production of the product at any time to avoid excess materials;
(7) It can be used for warehouse management and keep up to date with the latest inventory;
(8) It can print tickets or various bills with high speed and high quality;
(9) According to the need, you can choose to print labels with high temperature resistance, corrosion resistance or strong adhesion;
(10) The printing speed is fast and the engraving printing can be up to 15cm / s;
(11) It can be cut immediately after printing, which is ideal for tickets;
(12) Computer editing, printing content and printing effect are no worse than printing;
(13) Using system integration solutions, using barcode labels as a medium, comprehensively improve management systems for procurement, production, warehousing, logistics, and sales. With the maturity and popularization of label printing technology, the prices of thermal transfer printers and consumables have been greatly reduced. The cost of label thermal transfer printing has fallen below the ordinary printing cost, greatly enhancing the competitiveness of label thermal transfer.

4. Issues to be noted in label thermal transfer printing

The thermal transfer printing of labels generally goes through two printing processes. First, the raw materials are printed by the label machine, die-cutting, waste disposal and rewinding of the label exhibition, and then the labels in rolls are printed on the bar code printer. The principle is to print after heating. The head is in contact with the ribbon, and the ink on the ribbon is transferred to the label material by heat and contact pressure. Thermal transfer ribbon is coated with wax-based, resin-based or mixed ink polyester or other high-density film on one side, and lubricant on the side without ink to prevent wear and damage of the print head.

The carbon belt is composed of a handle, a front lead belt, a carbon original belt, a rear lead belt, and the like. The handle and front lead are in front of the original carbon belt, and the rear lead is at the end of a roll (some do not have a back lead). The carbon original tape is generally composed of a top coating, an ink layer, an inner coating, a tape base, and a back coating.

Top coat: used to improve the adhesion of ink on the label and enhance the environmental resistance;
Ink layer: used to print and determine the use characteristics of the ribbon;
Inner coating: can make the printing surface smooth Hualian printing, and ensure the consistency of ink release from the tape base;
Tape base: The carrier of other layers determines the performance of heat conduction; Back coating: It is a special coating applied on the back of the carbon tape, which can reduce the wear of the print head 3D printing, reduce the generation of static electricity, and enhance the heat conduction.

The front lead tape is usually transparent or other colors, and its main function is to print the ticket names such as the product name, company name and trademark, which are used for marketing and promotion. Through the front lead belt, the carbon belt can be easily loaded onto the printer, smoothly enter the working state, and protect the original carbon belt during storage and transportation. The rear lead tape mainly serves as a warning to let the printer sense the end of the carbon ribbon. Different printers have different rear lead tapes. There are three main methods: aluminized, transparent, and tension.

Aluminum plating: silver, mainly for reflective sensors, reflected light indicates the end of the ribbon.
Transparent: Used for transmissive sensors, allowing light to pass through indicating that the ribbon is used up.
Tension: used for mechanical sensing, the printer senses the change in tension to indicate that the ribbon is used up.

The ribbon is generally wound on a paper (or plastic) shaft core. The main requirements for the shaft core are that it cannot be deformed and cannot slide during printing. Label thermal transfer is the use of this special ribbon, through the similar working principle of the print head of a fax machine, the toner coating on the ribbon is heated and transferred to paper or other types of materials. The coating material on the carbon ribbon can be selected according to the needs, resulting in strong adhesion, and the choice of printing medium can ensure that the printed handwriting is not affected by the outside world. This heating process, how to heat, can be handed over to the computer to control. The software that has been developed specifically for printing labels is very convenient for users, especially the generation of bar code symbols has become this type. An essential tool for software.

Thermal transfer label paper can be generally divided into two types with and without paint, and their surface ink absorption and smoothness are different. The printing ribbon is divided into wax-based ink, resin-based ink and wax, resin synthetic ink. There are several varieties of bar code printers, and some labels need to be printed on the surface of the ink after printing. Therefore, printers, label paper, ribbons, etc. have a great impact on the printing quality of labels. The quality of the thermal transfer printer determines the effect of label printing. Therefore, when choosing a printer, in addition to considering the price, we must also consider the quality, the technical support of the manufacturer, the guarantee of after-sales service, and the technical capabilities of the seller. Label printing materials are special, and the printing volume is large, and the operating environment is complex. Some imported thermal transfer printers are gorgeous in appearance, but because there is no formal office in China, they only rely on some part-time informal agents to import and sell printed materials, which makes it difficult to meet customer needs in after-sales service and spare parts supply. Once the product has problems, purchasing accessories becomes a big problem. [next]

When purchasing a thermal transfer printer, it is necessary to fully consider the wide and universal suitability of its printing materials, and choose printing materials that are compatible with the printer and have good compatibility, such as label paper and ribbons. In addition to determining the color base (wax base, mixed base or resin base) of the ribbon, the width and length of the ribbon according to the printer when purchasing the ribbon, in order to ensure the print quality, the following issues must also be considered:

1. Printer features

In the thermal transfer printing method, the ribbon and label paper are consumed simultaneously in the length direction. In terms of width, the width of the ribbon should be greater than or equal to the width of the label paper and less than the maximum printing width of the printer. Because the physical size of each printer is different, the maximum paper roll length that can be loaded and the maximum width that can be printed are also different. In addition, the working temperature of the print head and the sensitivity characteristics of the ribbon will also have a great impact on the final printing effect.

2. Features of label paper

The surface of offset paper is relatively rough, and wax-based or mixed-based carbon tape should be used; PET paper has a smooth surface, and resin-based carbon tape should be used.

3. Durability of printed graphics

If you want to print the label content with good durability nationwide, you should choose resin-based carbon tape.

4. Label resistance requirements

If the label is required to be scratch-resistant, smear-resistant, corrosion-resistant, high-temperature resistant, and may be frequently rubbed, the label needs to have strong scratch resistance. In this case, resin ribbon or mixed-based ribbon should also be selected.

5. Print speed

In the case of high-speed printing, select a ribbon with high sensitivity.

6. Print media

Labels of different media need to be matched with different carbon ribbons. From the shape of the media, there are mainly ribbons, cards and labels, and from the material, there are mainly papers, synthetic materials and fabrics. For example, paper: according to the surface gloss, it can be divided into high gloss (such as specular coated paper, glossy paper, etc.), semi-gloss (such as coated paper, etc.) and matt (such as offset paper, etc.), special paper (such as aluminum foil paper, fluorescent paper) , Thermal / thermal transfer paper, etc.). In general, high-gloss paper media is printed with resin-reinforced wax-based or mixed-based carbon tape, especially mirror coated paper, which has a layer of synthetic material light film on its surface, which should be treated as synthetic materials, such as PET, PVC, BOPP, PE , PS, POLYIMIDE, etc .; semi-high gloss paper can use resin-reinforced wax-based and general wax-based carbon tape. Metalized PET mainly includes laser rainbow film, brushed film, gold (silver) color (high gloss, matt), etc. Compared with paper materials, these materials have high strength, beautiful appearance, and a wider range of application to the environment. However, the requirements for carbon ribbons are high, and mixed-based and resin-based carbon ribbons should be used.

7. Cost accounting

Generally speaking, the cost of wax-based carbon ribbon is the lowest, mixed-based carbon ribbon is second, and resin-based carbon ribbon is the highest.

Due to the wide variety of media materials and the large differences between them, in order to obtain satisfactory printing results, multiple tests should be carried out according to their respective circumstances to find a suitable ribbon, and you can also ask the supplier to help you choose.

During the printing of thermal transfer labels, there are not many failures. Generally, the following problems should be noted during printing:

(1) When uneven ink on the label surface, insufficient density, and poor ink printing firmness, the following adjustments should be made: first adjust the print head pressure, then adjust and control the printer speed, check and adjust the print head temperature (heat, according to the Darken level) , Check the replacement ribbon, check the surface smoothness and tension of the label paper, try not to print on the surface of UV printing ink, and the resin-based and water-based ink surface generally have no transfer quality problems.
(2) Due to the phenomenon of rewinding after label printing, pay attention to the drying problem of printing ink. Generally, methods such as reducing the printing speed, controlling the amount of ink supply, prolonging the ink drying time, adding an appropriate amount of quick drying agent to the ink, etc. .

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