How much do you know about printing technology?
1. Roller printing
The process of printing on fabrics with a copper roller engraved with concave patterns is also called copper roller printing. The engraved roller is referred to as a flower cylinder. When printing, first stain the surface of the flower cylinder with color paste, and then use a sharp and flat scraper to scrape off the surface color paste of the unengraved part of the flower cylinder, leaving the color paste in the concave pattern. When the flower cylinder is pressed on the fabric, the color paste is transferred to the fabric and the pattern is printed. Each flower cylinder prints a color paste. If multiple flower cylinders are installed on the printing equipment at the same time, color patterns can be printed continuously.
2. Digital printing
Digital printing is printing using digital technology. Various digital patterns processed by scanning, digital face, image or computer are input into the computer, and then processed by the computer color separation printing system. There is a dedicated RIP software to directly print various special printing dyes (active, dispersed, selected red coatings) between its printing systems onto various fabrics or other media. After processing, various high-precision printing products required are obtained on various textile fabrics.
Digital printing technology can be subdivided into the following categories
1. Classification by printing method
Digital printing is a general term for inkjet printing technology. In order to explain the various printing methods and characteristics more clearly, this article introduces the digital printing of textile fabrics in an all-round, various types and process breakdown.
1. Digital direct printing
Digital direct printing is suitable for disperse, acid dyes, coatings, and active inks. Digital direct printing is a process of direct printing on sizing semi-finished textiles. The process is: select the corresponding ink according to the textile, design the pattern, sizing, and then go to the textile direct printing machine for direct printing, and then dry, steam, wash, dry, soften and set (the coating can be fixed by baking)
2. Thermal transfer method
Thermal transfer printing is to print the textile dye on paper first (coating), and then use the thermal transfer printing machine to transfer the pattern on the paper to the textile. The advantage is that the precision is relatively high, but the printing efficiency is low. It can only be used for textiles with full polyester or high polyester content. The transfer fabrics are all processed semi-finished products and no softener has been added (softeners may affect the coloring rate).
3. Cold transfer method
Like thermal transfer, it is necessary to print the textile dye on paper first, and then use a special machine to press the paper and fabric to achieve the transfer of the pattern.
There are two ways to process the fabric after printing
One is to carry out traditional processing such as steaming, washing, and shaping;
The other is to carry out cold pile chemical reaction treatment to fix the color (the fabric needs to be chemically treated in advance). Use active, disperse, acidic and other dye inks, and this process is applicable to fabrics other than blended fabrics.
2. Classification by dyes and processes
1. Dispersed digital printing
At present, more than 50% of the inks used for printing in my country are disperse dye inks, which are used for printing chemical fiber fabrics such as polyester fibers; disperse dyes are a type of non-ionic dyes with very low water solubility, which exist in a highly dispersed state in water with the help of dispersants when dyeing.
2. Reactive digital printing
Reactive dye inks account for about 29%, mainly used for silk and cotton fabric printing; reactive dyes, also known as reactive dyes. It is a type of dye that reacts chemically with fibers during dyeing. This type of dye contains genes that can react chemically with fibers. When dyeing, the dye reacts with the fiber, forming a covalent bond between the two, becoming a whole, which improves the washing and rubbing fastness. Active dye molecules include two main components: the parent dye and the active group. The group that can react with the fiber is called the active group. At present, it is mainly used on woven and knitted fabrics such as cotton, linen, and silk, or fabrics with a high content of the above ingredients.
3. Acid digital printing
Acid dye ink has a small specific gravity, accounting for about 7%, and is used for printing on fabrics such as wool and nylon. Acid dyes are a type of water-soluble dyes with acidic groups in their structure, which are dyed in an acidic medium. Most acid dyes contain sodium sulfonate salts, which are soluble in water, have bright colors and a complete color spectrum. It is mainly used for dyeing wool, silk, nylon, etc., and can also be used in leather, paper, ink, etc. It generally has no coloring power on cellulose fibers.
4. Pigment ink digital printing
The use of pigment ink in my country is relatively small, less than 2%, and most of them are foreign products. Manufacturers include Huntsman, BASF, DuPont, Klein and other companies.
III. Classification by fabric composition
1. Digital printing mainly based on cotton, but linen, silk, etc. can also use active dye inks;
2. Digital printing mainly based on chemical fiber, produced with dispersed thermal sublimation dye ink and chemical fiber dispersed direct injection digital;
3. Some mixed fabrics such as T/C, which cannot be operated with reactive, disperse, and acid dye inks, are printed with coating inks;
4. Digital printing mainly based on nylon and wool, etc., is produced with acid dye inks, and silk can also be used.
3. Rotary screen printing
Rotary screen printing is a printing method that uses a scraper to print the color paste in the round screen onto the fabric under pressure. Rotary screen printing is different from other screen printing methods in several important aspects. Rotary screen printing is a continuous process like drum printing. The printed fabric is transported to the bottom of the constantly moving round screen flower cylinder through a wide rubber belt. Among screen printing, rotary screen printing has the fastest production speed, which is greater than 3500 yards per hour. Use seamless perforated metal mesh or plastic mesh. The largest round screen circumference is greater than 40 inches, so the largest flower size is also greater than 40 inches. Rotary screen printing machines with more than 20 sets of colors have also been produced, and this printing method is slowly replacing roller printing.
4. Flat screen printing
The printing mold is a polyester or nylon screen (flower plate) fixed on a square frame with a hollow pattern. The pattern on the flower plate can pass through the color paste, and the non-patterned part is sealed with a polymer film layer. During printing, the flower plate is pressed tightly against the fabric, and the color paste is placed on the flower plate. The scraper is used to scrape and press back and forth so that the color paste passes through the pattern and reaches the surface of the fabric. Flat screen printing has low production efficiency, but it has wide adaptability and flexible application. It is suitable for small batch and multi-variety production.
5. Water slurry printing
The so-called water slurry is a water-based slurry. It does not feel strong when printed on clothes, and its covering power is not strong. It is only suitable for printing on light-colored fabrics. The price is relatively low, and it belongs to the lower-end printing type. But it also has an advantage, because it is less likely to affect the original texture of the fabric (the impact is small), so it is more suitable for large-area printing patterns. Water-based printing slurry is soluble in water, and the sauce itself is relatively thin. During printing, the printing paste is evenly leaked through the mesh of the screen printing screen to the part that needs to be printed, so that the pattern can be printed on the T-shirt.
6. Paste printing
The basic process is the same as water slurry printing, but the material used is a paste pigment that will solidify on the fabric after drying, which feels a bit like a piece of ointment sticking to the skin. At present, the most common printed T-shirts on the market are mostly printed with paste.
7. Flocking printing
Flocking is a process with relatively high requirements. Now only a very few factories can do it well, and most factories almost do not have this process. Flocking is also called toothbrush flower. The finished product effect is like a toothbrush whisker standing up. The height of the finished product can reach about 0.3CM. Other colors can be made on it, so it is also called flocking.
8. Pigment printing
(English: pigment print) is also called paint printing. Since the pigment is a non-water-soluble coloring substance and has no affinity for fibers, its coloring must be achieved by the coating of a film-forming polymer compound (adhesive) and the adhesion to the fiber. Pigment printing can be used for processing any fiber textiles. It is more superior in printing blended and interwoven fabrics. It has a simple process, a wide color spectrum, and clear flower outlines, but it has a poor hand feel and low friction fastness.
9. Dye-discharge printing
(English: wash out colors) (discharge print) Select dyes that are not resistant to discharge agents to dye the ground color. After drying, use a color dye printing paste containing a discharge agent or a discharge-resistant agent to print. During post-processing, the ground color dye at the printing site is destroyed and decolorized, forming a white pattern on the color ground or a colored pattern formed by dyeing the color dye. It is also called white discharge or color discharge. Can it make the clothes look like they have been washed? The color of the clothes seems to have been washed away a lot, mottled~~ In fact, this is discharge printing. The principle of discharge printing is to extract the color of the fabric tissue fiber and turn it into another lighter color, like the effect of washing water. It is a cooler printing for men's clothing!