Thermal transfer printing is a new printing technology, which has been introduced from abroad for more than 10 years. The printing method of this process is divided into two parts: transfer film printing and transfer processing. The transfer film printing adopts dot matrix printing (resolution up to 300dpi), and the pattern is printed on the surface of the film in advance. The printed pattern is rich in layers, colorful, ever-changing, with small color difference and good reproducibility, which can meet the requirements of designers and is suitable for mass production. In the transfer printing process, the exquisite patterns on the transfer printing film are transferred to the product surface through one-step processing (heating and pressurizing) by a thermal transfer printing machine, and the molded ink layer is integrated with the product surface, which is vivid and beautiful, and greatly improves the product grade. Thermal transfer printing technology is applied to the surfaces of various ABS, PP, plastics, wood, coated metals and other products. At present, thermal transfer printing technology has been widely used in plastics, cosmetics, toys, electrical appliances, building materials, gifts, food packaging, stationery and other industries.
First, the principle and characteristics of thermal transfer printing process
The principle of thermal transfer printing is that color patterns are printed on the heat-resistant substrate film in advance (by release treatment), and then transferred to the product surface by hot stamping with special transfer equipment. The quality of thermal transfer printing process is reliable, the process is stable, and the good material formula is closely matched with the equipment. The characteristics of thermal transfer printing process are: simple operation, few production processes, high efficiency, no pollution, small floor space and low investment. After printing, it has good adhesion, high gloss, clear graphics and text, accurate color matching, bright colors, safety and non-toxicity. After hot stamping, it can be processed by oil injection, sandblasting, secondary injection molding, bending and punching.
Second, the heat transfer process
Due to the continuous progress of technology, the products developed by thermal transfer printing technology are: clothes, cloth bags, hats, pillows, mugs, porcelain plates, tiles, watch cases, mouse pads, coasters, calendars, medals, pennants, work cards, doorplates, mirror boxes, metal hip flask and so on. According to the different transfer materials and equipment, the thermal transfer process is also different. The following is a brief description of several common thermal transfer processes.
1, production process of thermal transfer banner
(1) Computer processing: First, the characters to be printed are processed by the computer;
(2) lettering: engraving the characters or pictures processed by the computer on the transfer paper with a lettering machine;
(3) remove redundant parts as required;
(4) overlapping the composite paper and the transfer printing cloth, and putting them together in a heat transfer printing machine;
(5) After being heated and pressurized by the thermal transfer machine, the disperse dyes on the composite paper will penetrate into the cloth, thus forming banners.
Note: Put the engraved heat transfer paper and blank banner cloth together, with the colored side facing the cloth, and heat it with the pressure of the heat transfer banner machine, and the color of the content on the heat transfer paper will move to the blank banner cloth, thus forming a banner with content.
2, light or white chemical fiber clothing transfer printing process
Choose a printer with thermal transfer ink and plain paper for printing.
(1) Select the picture, print it on the printer with special paper with thermal transfer ink, and select mirror printing;
(2) Place the printed pictures on the transferred clothes repeatedly, determine the specific position and mark them;
(3) Pull up the pressure handle of the bronzing machine, lay the T-shirt flat on the flat plate of the bronzing machine, put the picture face down on the correct position of the transferred clothes, and set the temperature and time of the bronzing machine;
(4) Turn on the power supply, when the temperature of the bronzing machine reaches the set value, the machine will automatically enter the constant temperature state, and press the handle to start hot stamping;
(5) By heating and pressurizing the ironing machine, the buzzer will sound, lift the pressure handle, take out the transferred clothes, and tear off the lining paper, so that you can see that the bright patterns have been transferred to the clothes.
3, light or white cotton clothing transfer printing process
Choose a printer with pigment ink and light color transfer paper for printing.
The method is similar to 2, and there are three main differences:
(1) The paper and ink used are different from 2;
(2) After printing, there is another step, which is to cut off the redundant white edges around the light-colored transfer paper printed paper. If there are many blank positions in the middle of the picture, you can also use scissors to hollow out;
(3) The ironing time is different, and the time for using transfer paper hot stamping is generally slightly shorter.
4. Transfer printing process of dark clothing
Choose a printer with pigment ink and print with dark transfer paper.
(1) printing: after the picture is made, put dark transfer paper into the printer with pigment ink, and mirror printing cannot be used in the printing settings;
(2) Cutting: After printing with dark transfer paper, when the image is completely dried, it must be cut off along the blank edge of the image with scissors (no white edge can be seen after cutting), and some pictures can even be hollowed out in the middle, so that it is not easy to form an airtight transfer part and alleviate the phenomenon of "one board";
(3) Tear: Tear off the sticker on the back of dark transfer paper's picture (otherwise the picture can't be pasted on the cloth), and then stick the picture on the transfer position of the clothes with the pattern facing upwards;
(4) Mask: the picture is facing up. Put a piece of paper on the picture of dark transfer paper for isolation. This kind of paper is called release paper. Release paper is usually used when buying dark transfer paper (a reusable silicone paper). If there is no release paper, you can use the sticker on the back of the torn dark transfer paper picture.
(5) Ironing: Press the handle and add thermal transfer. Finally, remove the release paper and take out the clothes.
5. Cup and plate transfer printing process
Choose a printer with thermal transfer ink, inkjet paper or special paper for printing.
(1) The cups and plates mentioned here are all special cups and plates for bronzing, which have been painted in advance. The external dimensions of cups and plates should be consistent with the molds of cup ironing machine and plate ironing machine;
(2) The size of the printed picture should be equal to or smaller than the size of the transfer position on the cup and tray, and mirror printing must be selected when printing;
(3) The picture faces the cup or plate and is placed in the correct position. The cup also needs to be taped so that there is no gap between the picture and the cup. The temperature of hot stamping on porcelain is higher and the time is longer;
The specific operation of thermal transfer printing seems simple, and it can be completed in a few seconds at most in a few minutes. However, due to different pictures, different transfer films and different transfer methods, especially the nature, thickness, color and even origin of the substrate, the transfer temperature and time are also different, so it is difficult to achieve the best results if you don't master it well.
6. Use an electric iron for thermal transfer.
Due to the limitation of electric iron's calorific value, it is generally not allowed to transfer items of A4 size (about 20×30cm). The electric iron must be adjustable, and the greater the power, the better.
(1) First, adjust the iron to cotton fabric (i.e. 170- 190℃ or so) and preheat it until the heat preservation indicator light is on;
(2) lay the clothes flat on the ironing board, and iron the part to be printed for a few seconds to remove moisture;
(3) The printing surface of transfer paper is laid flat on the part where the clothes are to be transferred, and the four corners of the paper are stuck with self-adhesive to prevent the paper from moving;
(4) Spread the high-temperature resistant flexible asbestos cloth on the clothes with transfer paper, flatten it, and clamp it on the edge of the ironing board with four clamps;
(5) Ironing the part with transfer paper slowly back and forth on the temperature-resistant cloth for 20-30 seconds, and the time can be flexibly controlled according to the size of the pattern;
(6) Take down transfer paper before the clothes get cold, or it will stick.
7, aluminum transfer production process
(1) Roll the thermal transfer film to the required size with a film machine.
(2) According to the size of the workpiece, the cut transfer film is ultrasonically welded into a workpiece packaging bag with a transfer ultrasonic packaging machine.
(3) workers are inserted into the workpiece packaging bag made of transfer film on the packaging platform.
(4) Put the workpiece wrapped with the transfer film on the trolley platform of the thermal transfer machine, and put 18 aluminum material in turn. Connect and lock the vacuum faucets at both ends of aluminum, and turn on the vacuum switch. At this time, the transfer film is closely attached to the aluminum material. The trolley automatically feeds aluminum into the oven, and the oven automatically heats up to 220 degrees and keeps the temperature for 3 minutes, and the trolley automatically exits the oven.
(5) Loosen the vacuum cock and take out the workpiece.
(6) Remove the transfer film and check the quality of the workpiece.