The process of printing dyes, pigments, or coatings onto the surface of cloth, leather, or other objects through a stencil or screen is called printing.
The principle of printing is essentially the same as that of printing.
Fabric printing has a long history.
China has already applied hollow printing during the Warring States Period (see the history of dyeing and finishing in China).
India already had wooden stencil printing in the 4th century BC.
Continuous gravure roller printing began in the 18th century (see roller printing).
Screen printing is developed from hollow patterns and is suitable for small batch and multi-variety printing of easily deformed fabrics.
In the 1960s, metal seamless rotary screen printing began to be applied, which provided conditions for continuous production and its efficiency was higher than flat screen printing.
The transfer printing method appeared in the late 1960s. It uses the sublimation properties of disperse dyes to transfer the dye on the transfer paper to polyester and other fiber fabrics through heating, so that fine patterns can be printed.
In the 1970s, a liquid-jet printing method controlled by an electronic computer program was also developed. Various combinations of nozzles intermittently spray various dyes to form colorful patterns, which are mainly used for carpet printing.
The classification of printed fabrics is divided by technology:
The commonly used ones are direct printing and indirect printing (resist printing, discharge printing and burnout).
Direct printing: It is to directly print dyes or pigments on white or light-colored fabrics, and then obtain patterns through post-processing such as steaming. The process is short and the most widely used.
Indirect printing: The effect cannot be seen during printing, and the effect will appear after post-processing.
·Resistant printing is to first print a substance on the fabric to prevent the dye from staining or developing color, and then dye or develop the color to obtain patterns on the dyed fabric.
Anti-discharge printing is a printing process in which substances are printed on dyed fabrics to eliminate dyes, and patterns are obtained on the dyed fabrics during post-processing.
Burnout usually uses polyester cotton cloth. The base fabric is first dyed in the required color or white, and then the protective material is printed on the cloth. During post-processing, a strong corrosive is used to remove the unprotected cotton. Some of the parts are corroded, and the rest shows the pattern effect.
Divided by the equipment used; usually there are two categories: manual printing and machine printing.
1) Manual printing: Generally, it is done by hand to hold up the flower screen and scrape and print the dye slurry on the cloth in one color and one color. It can be printed partially or the whole piece can be printed. Bottom print.
It is characterized by low investment, convenience and flexibility, and the color registration can be increased or decreased at will, but the output and quality are not as good as machine printing.
2) Machine printing: A. Roller printing.
The pattern is carved on the flower tube, and the dyeing material is printed on the cloth according to the requirements by rolling the flower tube.
Generally, the color combination does not exceed 4 colors.
B. Screen printing.
(Including flat screen printing, rotary screen printing) is to put the pattern on the screen, and then let the dyeing material penetrate into the cloth surface through the mesh, and the color registration can be increased.
Modern science and technology has developed, and many other printing methods have emerged, such as: transfer printing, hot stamping, embossing, spray printing, flocking flowers, and many other types, but fundamentally speaking, none of them can Counts as a print.
It can also be divided by the different raw materials used: cotton printing, polyester-cotton printing, wool printing, silk printing, polyester printing, linen-cotton printing, etc.
Different raw materials have differences in the front and rear finishing processes of printing.
It can also be divided into different base fabrics used: woven fabric printing; knitted fabric printing.
The production process of digital printing is simply to input various digital patterns into the computer through various digital means such as scanning, digital photos, images or computer processing, and then process them through the computer color separation printing system. , special RIP software is used to directly print various special dyes (reactive, dispersed, acidic main coatings) onto various fabrics or other media through its printing system. After processing, it is obtained on various textile fabrics. The various high-precision printing products required have the following advantages compared with traditional printing and dyeing processes: the production process of digital printing greatly shortens the original process route, the order receiving speed is fast, and the proofing cost is greatly reduced.
Because the production process of digital printing gets rid of the color separation, drawing, and screen making processes in the production process of traditional printing, the production time is greatly shortened.
To accept patterns, you can use various advanced means such as CD-ROM and E-mail. Generally, the proofing time does not exceed one working day, while the traditional proofing cycle is generally about a week.
In addition, due to the simplification of the process, the cost of proofing is also greatly reduced.
The shortening of the proofing cycle and the reduction of proofing costs will undoubtedly bring more market opportunities to enterprises under the current market competition rules where time is money and efficiency is life.
The principle of digital printing technology allows its products to break the traditional production of color registration and flower return length, and can achieve high-end printing effects on textile fabrics.
Because digital printing technology can use digital patterns, and use computers to measure, match, and print colors, the colors of digital printing products can theoretically reach 16.7 million, breaking through the color registration of traditional textile printing and dyeing patterns. , especially in the printing of high-precision patterns such as color gradients and moire, digital printing has unparalleled advantages in technology.
In addition, traditional printing patterns are often limited by the length of the "flower return", while the concept of "flower return" does not exist in the digital printing process, thus greatly expanding the space for textile pattern design. Improved product quality.
Digital printing production truly realizes the production process of small batch and quick response, and the production batch is not subject to any restrictions.
Since the entire digital printing production process realizes computerized digital production, production flexibility is greatly improved. Some products can even be delivered on the same day and can be picked up immediately.
In addition, due to the application of computer technology, printing a series of patterns with different tones of the same pattern, and the designer's continuous modification of patterns and colors during the production process have become digital printing production that is different from traditional printing production. A major technical advantage.
The high-precision printing process eliminates the need for water or color paste during the printing process.
The use of dyes during the jet printing process is "distributed on demand" by the computer, so that during the jet printing process, there is no waste of dyeing materials, no waste water is generated, and no waste water is generated during the computer-controlled jet printing process. Noise, so that no pollution is produced during the printing process, and a green production process is realized, thus enabling the production of textile printing to get rid of the high energy consumption, high pollution, and high noise production process in the past, and achieving a low energy consumption, pollution-free production process, giving The production of textile printing and dyeing brings primary technology.
There are several reasons for defects in printing. Poor pattern joints (joint printing) are caused by overlap or mismatch (detachment) of patterns at the joints.
This is mostly caused by improper adjustment of the conveyor belt or improper adjustment of the plate's rule eyes, which affects the accuracy of the flower position.
Pattern misalignment (skewed registration, inaccurate registration) refers to printed products with misaligned patterns.
Most of them occur due to inaccurate pattern alignment, poor engraving, or poor patching.
The printing frame marks (frame printing, overlapping) show abnormal streaks in the shape of the pattern frame.
This is mostly caused by poor conveyor belts, poor installation of pattern frames, etc.
Bending (flower shape skew) means that the pattern is inclined or curved to the warp and weft yarns of the fabric.
Usually it occurs when the printed gray fabric (silk) itself has skewed wefts or poor seams or the plate patch is skewed.
Part of the exposed white warp or weft is flipped or moved to the front or back of the fabric, showing a pattern that resembles the tracks left after being scratched.
This defect is mostly caused by poor penetration of color paste and improper handling after printing (uneven tension, etc.).
The printing color is uneven (spots) and part of the printing becomes speckled like the shape of the skin of a shark.
This defect often occurs when the viscosity of the color paste is inappropriate, the mesh size of the screen is improperly selected, or the patching is uneven.
Bleeding (blooming) is when the color of the printed pattern bleeds out, the outline of the pattern is unclear, and the color appears blurry.
It is caused by low viscosity of color paste, extremely concentrated dye concentration, excessive amount of printing paste or excessive amount of hygroscopic agent.
Stains caused by the color of the printed pattern contaminating other parts.
Most of them occur when the printing platen is not cleaned properly, is not fully dried after printing, overlaps each other, or the fabrics are in contact with each other during the steaming process.
Today, some factories use a control method such as adjusting the tension of the fabric to perform thorough washing under rope conditions.
Double-version color difference (uneven squeegee) shows a certain interval of color depth in the transverse direction of the fabric.
This defect often occurs when the screen frame and scraper are poorly installed or the scraper is uneven.
Level transfer printing first uses a printing method to print pigments on paper to make transfer printing paper, and then transfers the color to the fabric through high temperature (heating and pressure on the back of the paper). It is generally used for chemical fibers. The fabric is characterized by bright colors, fine layers, realistic patterns, and strong artistry, but this process is only suitable for a few fibers such as polyester.
Transfer printing has a simple process, low investment, and flexible production. It is more popular in the market... But to be honest, comparing this transfer printing with other printing types, the price is a bit high, but there are A certain level of discharge printing (discharge printing) uses dyes that are not resistant to discharge agents to dye the ground color. After drying, it is printed with color dyes that contain discharge agents or that contain both discharge-resistant agents. In pulp printing, during post-processing, the ground color dyes at the printing site are destroyed and faded, forming white patterns on the color ground or colored patterns caused by dyeing with floral dyes.
Also known as white pulling or color pulling.
Reduction printing is a process that utilizes the chemical corrosion resistance of different fibers in interwoven or blended fabrics. It uses a printing method to apply a burning agent to partially remove one of the fibers on the fabric, leaving the other fibers to form a translucent form. pattern.
Also called burn-out printing or burnout printing.
Shrink printing uses the printing method to locally apply chemicals that can expand or shrink the fibers on the fabric. Through appropriate treatment, the fibers in the printed parts and the fibers in the non-printed parts will have a difference in puffing or shrinkage, thereby obtaining Products with regular concave and convex patterns on the surface.
For example, pure cotton printed seersucker uses caustic soda as a bulking agent.
Also called embossed printing.
The flat screen printing printing mold is a polyester or nylon screen (pattern) fixed on a square frame and with a hollow pattern.
The patterned areas on the pattern can see through the color paste, while the non-patterned areas are closed with a polymer film layer.
When printing, the pattern is pressed tightly against the fabric, and the pattern is filled with color paste. Use a scraper to scrape and press the pattern back and forth to allow the color paste to penetrate the pattern and reach the surface of the fabric.
Flat screen printing has low production efficiency, but has wide adaptability and flexible application, and is suitable for the production of small batches and multiple varieties.
The rotary screen printing mold is a cylindrical nickel screen with a hollow pattern, which is installed in a certain order above the circulating rubber guide belt and can rotate synchronously with the guide belt.
During printing, the color paste is input into the screen and stored at the bottom of the screen. When the circular screen rotates with the guide belt, the scraper pressed against the bottom of the screen and the floral screen are scraped relative to each other, and the color paste passes through the screen. The pattern reaches the surface of the fabric.
Rotary screen printing is continuous and has high production efficiency. It has the advantages of roller and flat screen printing, but it still has certain limitations in the fineness of patterns and the richness of printing colors.
Remember: Rotary screen printing has certain limitations in color selection.
Pigment printing is also called paint printing. Since pigments are non-water-soluble coloring substances and have no affinity for fibers, their coloring must rely on the coating of film-forming polymer compounds (adhesives) and their adhesion to fibers. function to achieve.
Pigment printing can be used for any fiber textiles, and is more superior in printing blended and interwoven fabrics. The process is simple, the color spectrum is wide, and the flower shape outline is clear, but the hand feel is not good and the rubbing fastness is not good. high.
Zinc plate printing is a printing method in which hollow patterns are carved on the zinc plate, covered on the fabric, and then scraped and coated with color paste to obtain the pattern.
This method is suitable for printing large patterns or thick fabrics, such as scarves, towels, etc.
Chemical etching is now sometimes used instead of hand-engraved patterns.
Roller printing is a process that uses a copper roller with concave patterns to print on fabrics. It is also called copper roller printing.
The engraved roller is called a flower tube for short.
When printing, first coat the surface of the flower tube with color paste, and then use a sharp and flat scraper to scrape off the color paste on the unengraved part of the flower tube, leaving color paste in the concave pattern.
When the flower tube is embossed on the fabric, the color paste is transferred to the fabric and the pattern is printed.
Each flower tube prints a kind of color paste. If multiple flower tubes are installed on the printing equipment at the same time, color patterns can be printed continuously.
Digital printing Digital printing is printing using digital technology.
Digital printing technology is a high-tech product that integrates machinery, computer and electronic information technology and has gradually formed with the continuous development of computer technology. It first appeared in the mid-1990s. This technology The emergence and continuous improvement of technology have brought a new concept to the textile printing and dyeing industry. Its advanced production principles and methods have brought an unprecedented development opportunity to textile printing and dyeing.
Spray printing is a printing method that uses a liquid-containing sprayer to spray the dye liquid onto the fabric through the holes of the patterned mesh or the hollows of the paper.
Also known as liquid spray printing.
In the 1970s, the inkjet printing method controlled by an electronic computer program was developed. Many combinations of nozzles intermittently eject dye liquids of various colors to form patterns of various colors. It is mainly used for carpet printing.
T-shirt screen printing is a relatively common way of printing T-shirts. It has a simple process and is easy to print. It is suitable for printing on T-shirts with many printing materials.
Take printing materials as examples, including water slurry printing, glue printing, hot stamping printing, flocking printing, etc.
Water slurry printing water-based printing slurry is soluble in water, and the slurry itself is relatively thin.
When printing, the printing paste is evenly printed through the mesh of the screen printing screen to the area that needs to be printed, so that the pattern can be printed on the T-shirt.
Its characteristic is that it can only print one color at a time. If you want to print a second color, you must wait for the previous color to dry before proceeding. There is no need to steam and wash after printing; the advantage is that the fabric after printing It has good breathability. As long as it is not printed on a large area, it feels basically soft. If the resolution requirement is not too high, it can be printed with four-color dots.
The disadvantage is: this printing paste is not suitable for printing on dark fabrics.
One point that needs special explanation: the color fastness is related to the color depth of the printed pattern. The lighter the color, the better the color fastness, and vice versa.
The basic process of glue printing is the same as that of water glue printing, except that the material used is glue pigment that will solidify on the fabric after drying, a bit like a plaster that feels close to the skin.
Its characteristic is that it can only print one color at a time. If you want to print a second color, you must wait for the previous color to dry before printing; because the glue is opaque, it can be printed on dark fabrics. It can produce light-colored patterns, but its air permeability is poor and it is not suitable for large-area solid pattern printing.
Scattered flowers or patterns with less rough lines can demonstrate its excellent performance. Currently, the most common printed T-shirts on the market use glue printing.
Foam printing T-shirt foam printing, also known as three-dimensional printing, is developed on the basis of glue printing technology.
The principle is to mix a certain amount of chemical substances with high expansion coefficient into glue printing slurry, commonly known as foaming slurry.
After the printed parts are baked at low temperature, they are pressed at 130-150℃ to create foam.
To achieve a three-dimensional effect similar to relief, the foam printing process can be made into high, medium and low foam according to the specific requirements of the customer.
The biggest advantage of the foam printing printing process is that it has a strong three-dimensional effect and the printing surface protrudes and expands. This printing process is widely used on various needle textile fabrics.
The use of dyestuffs and making dyes and pastes
The fabric must be pre-treated before printing to make it have good wettability.
The dyes used in printing are basically the same as dyeing. Some smaller patterns can use paint (pigment).
In addition, there are also fast pigments, fast amines, fast sulfonates and other dyes specially used for printing.
Different types of dyes can be used to print various patterns on the same fabric.
When printing, dyes or pigments are mixed into color paste.
After printing and drying, it is usually necessary to evaporate, develop or fix the color, and then soap and wash to fully remove the paste, chemicals and floating colors in the color paste.
Printing paste is composed of dye (or pigment), hygroscopic agent, co-solvent, etc. and original paste.
The function of printing paste is to make the color paste have a certain viscosity and fluidity.
It is made of hydrophilic polymer paste. Commonly used pastes include starch, starch degradation products (white dextrin and yellow dextrin), starch ether derivatives, sodium alginate ( or ammonium), hydroxyethyl saponin gum, dragon gum, cellulose ether, polymer electrolyte, etc.
A paste made from water, kerosene and chemicals, sometimes used as printing paste.
The original printing paste should have good stability to the chemicals in the color paste, not interact with the dye, have certain adhesion to the fiber and be easy to wash off the fabric.
The viscosity of printing paste depends on the properties of the original paste.
If the viscosity of the color paste drops too much during printing, it will be difficult to print fine lines; if the viscosity is too high, the color paste will not easily pass through the pores of the screen.
Steaming and its equipment
Steaming is also called steaming.
The fabric printed with color paste is dried and then steamed.
Steam condenses on the fabric, causing the temperature of the fabric to rise, the fiber and paste to swell, and the dye to dissolve and dye. Some dyes also undergo chemical reactions during the steaming process.
Due to the presence of paste, the dyeing process of printing dyes is more complicated, and the steaming time is longer than that of pad dyeing.
There are three types of steaming equipment: ①Steaming box: hang the fabric on the bracket and push it into the box for steaming; ②Continuous steaming machine: hang the fabric in a ring on the roller, Slowly advance, continuous steaming; ③ Various rapid steaming machines.
Steaming box and pendant continuous steaming machine are suitable for silk fabrics, knitted fabrics and fiber fabrics.
The steaming box steams under closed conditions, but cannot produce continuously.
Steaming conditions vary with dye and fiber properties.
When steaming vat dye printed fabrics, the air in the steaming chamber should be removed.
Polyester printed fabrics with disperse dyes can be steamed in a closed steaming oven at around 130°C, or under normal pressure with superheated steam at around 175°C, or they can be baked at around 200°C to fix the color. .
The printing machine is also known as the universal flatbed printer.
The universal flatbed printer can print any material and irregular soft and hard objects, such as: metal, ceramics, crystal, glass, acrylic, stone, PVC, plastic, toys, USB flash drives, cloth , wood, silicone, leather, etc., digital printers can reduce costs, reduce labor, and improve efficiency for you, because digital printers do not need to produce film and plate making, full-color imaging, accurate positioning, and zero scrap rate.
Digital printers have completely replaced traditional processes such as silk screen, pad printing and transfer printing. They are environmentally friendly products and can be exported. They are the trend of special product printing in 2009.
Compared with digital printing, traditional printing has gradually moved away from people’s realization. Let’s take a look at the disadvantages of traditional printing.
Disadvantages of traditional special printing:
1. The cost of film screen printing is high and the printing cost is expensive;
2. Color correction is complex and once the version is finalized Cannot be modified;
3. The process is cumbersome and the production cycle is long;
4. The cost of screen printing plate making is high, and the screen printing points cannot be eliminated, so mass production is required to reduce costs;
p>
5. Thermal transfer printing uses sublimation ink to first print the picture on the transfer paper, and then transfer it to the surface of the medium. There are several difficult problems to solve: color deviation and positioning deviation. The finished picture is also relatively easy to print. If scraped off, the firmness will be poor, and it is generally necessary to spray another layer of protective film.
In addition, transfer printing on special media also requires flexographic printing.
6. Traditional signs generally use the method of engraving, etching, filling with colored paint, or using laser engraving. They can only use monochrome signs and cannot do anything with colored patterns.
7. The rejection rate of multiple overprints is high and the color deviation is large.
8. Skilled printing technicians with many years of experience are required.
9. It requires more personnel and a high proportion of manual work.
The 5 most common printing process methods Printing process is a process of applying printing patterns on textiles using dyes or pigments.
Printing can be divided into fabric printing, top printing and yarn printing, with fabric printing being the main one.
Top printing is used to make mixed-color tweed; yarn printing is used to weave special-style colorful patterned fabrics.
Fabric printing has a long history.
China has already used hollow printing during the Warring States Period (see the history of dyeing and finishing in China).
India already had wood stencil printing in the 4th century BC.
Continuous gravure roller printing began in the 18th century (see roller printing).
Screen printing is developed from hollow patterns and is suitable for small batch and multi-variety printing of easily deformed fabrics.
Let’s take a closer look at several craft methods for environmentally friendly shopping bags.
Glue foam printing
The glue is added with foaming materials, and after printing, it is ironed at high temperature to make the printed parts protrude and appear three-dimensional. This year’s latest foaming technology can be used for color separation in plate making. During the process, layered and color-separated foaming is used to highlight the strong three-dimensional effect and feel.
Thermosetting ink printing
Thermosetting ink printing is mainly used to print exquisite fashionable and unique high-definition pictures of animals, stars, animation games, etc., as well as right angles, rounded corners and different shapes. Thick version special effects formed by printing process, etc.
The thick screen printing process of thermoset ink has become a popular trend in T-shirt clothing and handbag printing.
Because thermoset ink is a non-solvent ink, it can print fine lines, has a smooth surface, and has good fastness. It is non-drying, odorless, has high solid content, and has good scraping fluidity. It can be printed manually or with a fully automatic machine, so we mostly use thermoset ink for thick printing.
Thick version inks include high-coverage spot colors, translucent, transparent and other types.
Advanced water slurry printing
Advanced water slurry printing is the most traditional printing process. The water slurry is transparent and can only be printed on light-colored fabrics such as white. The effect was single and it once faced elimination.
However, judging from the recent international popular printing trends, water-based printing has become the first choice of fashion designers with the improvement of technology. It is highly popular because of its super soft feel, strong breathability and rich expressiveness. favor.
Advanced environmentally friendly glue printing
Environmentally friendly glue printing is characterized by strong color hiding power and is suitable for printing fashionable printing patterns with clear lines, neat edges and accurate color registration. It is mostly used in medium and high-end industries. The printing of high-end fashion and T-shirts is also applicable to the widest range of fabrics.
After printing, it needs to be ironed and shaped at high temperature to obtain high-end printed works with soft feel, strong elasticity and good color fastness.
High elastic thermal transfer printing
Thermal transfer printing is a new printing process. Transfer printing itself also has more than a dozen different technologies. The commonly used one is offset printing, which can print Photo-like delicate effect, suitable for printing photos and detailed gradient transition colors.
But the disadvantage is that the production batch size is relatively large, and generally more than 2,000 pieces can achieve economic cost.
Thermal transfer printing is suitable for cotton and non-woven fabrics, which can greatly improve the product quality of environmentally friendly shopping bags.