thermal transfer is a new printing process, which was introduced from abroad for more than 1 years. The printing method of this process is divided into two parts: transfer film printing and transfer processing. The transfer film printing adopts dot printing (resolution up to 3dpi), and the pattern is printed on the surface of the film in advance. The printed pattern is rich in layers, colorful and ever-changing, with small color difference and good reproducibility, which can meet the requirements of the designer and is suitable for mass production. The transfer printing process transfers the exquisite patterns on the transfer printing film to the product surface through one-time processing (heating and pressurizing) by a thermal transfer printing machine, and the molded ink layer and the product surface are integrated into one, which is vivid and beautiful, greatly improving 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.
I. Principles and characteristics of thermal transfer printing process
The principle of thermal transfer printing is to print the color pattern on the heat-resistant substrate film in advance (through release treatment), and then transfer it to the surface of the product by hot stamping with special transfer equipment. The quality of thermal transfer printing process is reliable, the technology 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 land occupation and low investment. After printing, it has good adhesion, high gloss, clear graphics and text, accurate color registration, bright colors, safety and non-toxicity, and after hot stamping, it can be processed by oil injection and sandblasting, secondary injection molding, bending and punching.
second, thermal transfer process
due to the continuous progress of technology, the products that have been developed by using thermal transfer technology include: clothes, cloth bags, hats, pillows, mugs, porcelain plates, ceramic tiles, watch cases, mouse pads, coasters, hanging calendars, medals, pennants, work cards, doorplates, mirror boxes, metal hip flask, etc. According to different transfer materials and equipment, the thermal transfer process is different. The following is a brief description of several common thermal transfer processes.
1. Production process of thermal transfer banner
(1) Computer processing: firstly, the characters to be printed are processed by computer;
(2) lettering: using a lettering machine to engrave the characters or pictures processed in the computer to be printed on the transfer paper;
(3) Remove the redundant parts as needed;
(4) overlapping the composite paper and the transfer cloth, and putting them together in the heat transfer 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 a banner.
note: put the engraved thermal transfer paper and blank banner cloth together, with the colored side facing the cloth, and heat it with pressure by the thermal transfer banner machine, so that the color of the content on the thermal transfer paper will move to the blank banner cloth, thus forming a banner with content.
2. The transfer printing process on light-colored or white chemical fiber clothing
The printer with thermal transfer ink and ordinary paper are selected for printing.
(1) Select the pictures, print them on special paper on the printer with thermal transfer ink, and select mirror printing;
(2) Put the printed picture on the transferred clothing repeatedly to determine the specific position and mark it;
(3) Pull up the pressure handle of the hot stamping machine, put the T-shirt flat on the flat plate of the hot stamping machine, and put the picture face down on the correct position of the transferred clothes, and set the temperature and time of the hot stamping machine;
(4) Turn on the power supply, and when the temperature of the hot stamping machine reaches the set value, the machine will automatically enter a constant temperature state, and press the handle to start hot stamping;
(5) By heating and pressurizing the ironing machine, when the time comes, the buzzer will sound, lift the pressure handle, take out the transferred clothes, and tear off the backing paper, so that you can see that the bright patterns have been transferred to the clothes.
3. The transfer printing process on light-colored or white cotton clothing
The printer with pigment ink and light-colored transfer paper are selected 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) One more step after printing is to cut off the extra white edges around the paper printed by light color transfer paper. If there are many blank positions in the middle of the picture, you can also use scissors to hollow them out;
(3) The ironing time is different, so it usually takes a little shorter to use transfer paper hot stamping.
4. The transfer printing process on dark clothing
The printer with pigment ink and dark transfer paper printing are selected.
(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 in dark transfer paper, when the image is completely dry, it must be cut off with scissors along the blank edge of the image (the white edge can't be seen after trimming), and some pictures can even hollow out some blank parts in the middle, so that it is not easy to form airtight transfer parts 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 put the picture on the transfer position of the clothes with the pattern facing upwards;
(4) Masking: The picture is facing up, and a piece of paper is placed on the picture of dark transfer paper for isolation. This paper is called isolation paper. The release paper is usually used when buying dark transfer paper (a kind of silicone paper that can be used repeatedly). 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. The transfer printing process on cups and plates
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 hot stamping, which are coated beforehand. 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 the same as or smaller than the size of the transfer position on the cup or plate, and mirror printing must be selected during printing;
(3) The picture faces the cup or plate, and put it in the correct position. The cup also needs to be glued with adhesive tape, so that there is no gap between the picture and the cup as far as possible. The temperature of hot stamping on porcelain is higher and the time should be longer;
The specific operation of thermal transfer seems simple, and it can be done in a few seconds at most in a few minutes. However, due to different pictures, different transfer films, different transfer methods, especially the properties, thickness, color and even origin of the substrate, the transfer temperature and time are different, and it is difficult to achieve the best effect if you don't master it well.
6. Thermal transfer process by using electric iron
Due to the limitation of the calorific value of electric iron, it is generally not allowed to transfer articles larger than A4 size (about 2×3cm), and the electric iron must be adjustable, and the higher the power, the better;
(1) First, adjust the iron to the cotton file (i.e. about 17-19℃) and preheat it until the heat preservation indicator light is on;
(2) Put the clothes flat on the ironing board and iron the part to be printed for a few seconds to remove moisture;
(3) The printing face of transfer paper is placed flat on the part of the clothes 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 attached, and flatten it and clamp it on the edge of the ironing board with four clamps;
(5) Use an iron to slowly iron the parts with transfer paper on the heat-resistant cloth for 2-3 seconds, and the time can be flexibly controlled according to the size of the pattern;
(6) Take the transfer paper off the clothes before it cools, otherwise it will stick.
7. Production process flow of aluminum material transfer printing
(1) Roll the heat transfer film to the required size with a film machine.
(2) ultrasonically weld the cut transfer film into a workpiece wrapping bag with a transfer ultrasonic packaging machine according to the size of the workpiece.
(3) Insert the worker into the workpiece wrapping 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 materials in turn. Connect the vacuum taps on both ends of the aluminum materials and lock them, and turn on the vacuum switch. At this time, the transfer film is tightly attached to the aluminum materials. The trolley automatically sends aluminum to the baking oven, and the baking oven automatically raises the temperature by 22 degrees and keeps the temperature for 3 minutes, and the trolley automatically exits the baking oven.
(5) Loosen the vacuum tap and remove the workpiece.
(6) Remove the transfer film and check the quality of the workpiece.