(This article is from RTHK Rich network)
Introduction to screen printing
Screen printing belongs to hole plate printing, simple understanding is the use of mesh glue to seal the excess gauze area, leaving the required image or text, through a certain pressure to make the ink through the hole plate holes transferred to the substrate, forming an image or text.
Screen printing substrate can be paper, wood, glass, metal, plastic and many other substrates.
The more common applications of screen printing in life are instructions on products, decorative patterns on home appliances, T-shirt patterns, guide plates, book covers, posters, business cards, etc.
Second, screen printing process
The general process is as follows:
Screen printing document output → film production → Screen board production → color printing → ink curing
01, screen printing file output;
It is a silk screen production document sent by the designer to the manufacturer, because the screen printing production is mostly monochrome or multi-color overprinting, so we need to process the document at the early stage of the design. The document format is best in vector files, such as AI+CDR+EPS+PDF, and if the graphics are small or the clarity requirements are low, the high-definition picture format can also be provided.
Document hierarchical design
Because the narrow sense of screen printing can only be monochrome printing and monochrome overprinting, the designer needs to layer processing on the document, such as the black and red/black and blue need to split the screen printing twice.
Everything is not absolute, there are also some artistic creation, do not need to ensure consistency
What we need to talk about is monochrome printing and monochrome overprinting, which should be single effect or single effect overprinting layering.
Stratification according to a single effect, including stratification according to color, and also according to the type of ink, thickness, transparency, graphic change level, mesh number, film line number, etc.
After the layering is completed, the designer should also pay attention to the order of each layer, and the different order will also affect the effect of the final work of the screen printing.
Designers should conceive the effect they want at the beginning of the design, and then convey it to the manufacturer through the form of documentation. This can not only save costs, but also effectively control the effect output.
After you are familiar with the whole process, you can even recommend the manufacturer to use a manufacturer of a certain effect of ink, glitter, so as to achieve the desired effect. If you are not familiar with it, give it to the manufacturer. You can try more in the model stage, a small change, will produce a lot of subtle changes, will make your program instantaneously different!
02, film production:
When it comes to the word film, many people must be a face mask, is the name of the song is the name of the person or the name of the company...
film:
Film, photographic film and film, film, film, now generally refers to film, can also refer to the printing plate in the negative.
The film in screen printing is like the film of photographs, only the film in screen printing changes the development carrier from photo paper to a screen plate brushed with sensitive glue.
The film substrate used in screen printing production mainly includes pvc, pc, pet, pp, and the size can be satisfied according to the machine size.
Film output:
Is a similar to the old camera film film exposure process, it first through the system to process the graphics into a dot matrix image (that is, composed of dots of graphics), and then convert it into a signal that dominates the laser, using the longitudinal and horizontal movement of the laser relative to the film, the laser point, that is, the dot hit the corresponding position of the film, so that the film is exposed to the corresponding part of the film. Then, through the development and fixing process of the developer, the unexposed part is washed off, and the dot matrix image is formed on the film.
In addition to laser printing film, we commonly use inkjet film, inkjet film in the "Blu-ray film" is now the most widely used in China, it can not only achieve the accuracy of laser film, but also more accurate version of the set, the time step is also greatly reduced.
Traditional laser film production process:
Computer tracing → color separation → Phototypesetting output → Developing → fixing → washing → drying → Printing → Printing
"Blu-ray film" board process:
Computer tracing → color separation → Blu-ray film output → Printing → printing
The specific difference is the difference between cost and quality, for designers as long as they meet the application needs of the product, the rest let the master decide, we only do a simple understanding.
Number of lines in film:
The most important thing for designers to focus on is the number of lines in the film.
Film output is accurate, and this accuracy is expressed by the number of lines. For some beginners and even some of the id, cmf designers working for two or three years, the word must still be very unfamiliar, but for designers engaged in the graphic printing industry should belong to the basic knowledge.
PPI: Image resolution ppi (Pixel per Inch) describes the number of pixels per inch.
DPI: From the point of view of the printing device, the higher the resolution of the image, the more detailed the printed image. The unit used for print resolution is dpi (Dot per Inch), which describes the number of print points expressed per inch.
Line number (LPI): Line number refers to the number of printed lines in each inch (lines per inch, referred to as :lpi, that is, the number of lines per inch), the previous dot is mostly linear, so it is customary to all the dot density is called network cable. In other words, the "number of lines" is the density of the printed network cable. For example, 75 lines means that there are 75 dots in one inch length (25.4MM), that is, 2.95 dots in one millimeter.
The relationship between line number and resolution:
In our lives, we often hear the resolution of the screen is how many pixels, rarely hear the number of lines, in fact, they are related and different: image resolution (ppi) is higher than the printing resolution (lpi), generally more than 2×2 pixels to generate a dot, that is, LPI is about half of DPI.
The use of film in design:
The text in the film is from the point to the line and then to the surface. Usually, the film uses the size and density of the point to explain the depth of the color.
The more the number of theoretical lines, the clearer it is, but this is not absolute, it also depends on the printing process and substrate, different printing processes and substrates can achieve the accuracy of the hanging network is also limited. Ordinary print 150 or 175 lines is good enough, we electric screen printing 35-75 lines is better.
Designers for the use of line number is very diverse, such as gradient processing, sometimes delicate gradient is not conducive to screen printing, if it becomes a dot not only increase the sense of art for the graphics, but also look more delicate.
There is a color half tone in ai, in pixels, we can study it, you can imitate the effect of the number of film lines.
The most direct application of film line number for designers should be the size and density of the point, master the film line number, you will find that this provides a lot of ideas and innovation for your design, and also saves a lot of time for file processing.
Through the processing of the film machine system, the composition of the film pattern can be changed from round points to diamonds and squares. So whether it is round or square, diamond shape, if used properly, the film can be enough to surprise your design.
03, screen printing screen board production:
The screen board includes the screen frame and the screen gauze, which need to be made according to the design document when making, and then brush the photosensitive glue on the finished screen board. After drying, the film is exposed. The black area of the film mainly plays the role of blocking the light, so that the photosensitive glue cannot be cured, and the transparent place is cured by exposure photosensitive glue. After the exposure is complete, wash off the uncured photosensitive glue with water to get the desired graphic text.
The specific process of making the screen board:
Material selection → screen frame grinding → horizontal check → screen frame stretching → screen yarn de-ester → screen board sizing → Exposure → screen board washing → retouching → edge sealing storage
The production process of the net board is complex, and the designer does not need to operate on the ground, but the CMF designer needs to focus on the selection of the net board, the mesh number of the net board, the tension of the net board, and the Angle of the net.
Screen board material selection in the designer notice;
The main selection of mesh frame and gauze, for different materials of substrate and accuracy requirements to select different mesh and mesh frame size, material.
The selection of mesh frame, the main materials used in the production of mesh frame are wood, hollow aluminum profiles, cast aluminum molding frames, steel and other materials, which have their own advantages and disadvantages.
Wood mesh frame, easy to make, light material, mostly used in manual printing, but this mesh frame is not corrosion resistant and easy to deform, affecting the precision of screen printing, so it is mostly used as a hand plate and a small amount of printing.
Hollow aluminum profile, cast aluminum molding frame, is the most widely used mesh frame material, not only easy to operate, but also high strength corrosion resistance, firm and not easy to deformation, suitable for production.
Steel mesh frame, relative to the above several types of mesh frame is the most difficult to deform, but because the steel is more bulky, it is less used in daily production.
The choice of mesh is something that designers must understand, because it requires us to make annotations when we output the design document.
First of all, the most important thing is the choice of mesh number.
Mesh number: It is the precision unit of the mesh board, just like the number of lines in the film, which refers to the number of holes of the mesh board in an inch.
For example, 150 mesh means that there are 150 mesh holes in one inch, because 1 inch =2.54 cm, so there are 5.9 mesh points in 1 mm.
Many times we will hear the master say how much T, T is from where?
T number :T refers to the number of mesh per square centimeter, and 1 inch =2.54 centimeters, so, screen gauze 1T=2.54 mesh, that is, 100T=254 mesh, 300 mesh =118T.
Because the film is also converted in inches, it is easier to mark the screen according to the number of mesh.
In the production of screen printing, 100-400 mesh is generally used:
100 ~ 250 mesh: General printing with glitter or pearlite powder and other large particles of ink, or used in the last back cover, because the fewer the mesh, the larger the mesh, the more ink, the stronger the covering force.
250 ~ 350 mesh: the most commonly used mesh range, this range can be too pearling and can ensure the accuracy of printing, and when printing can reduce the probability of pasting the net, do not wash the net too frequently, and have better control over the cost and time of production, so designers and factories prefer to choose this range.
350 ~ 400 mesh: Generally used when high-precision printing effects are needed, mostly used to print fine text or numbers.
Secondly, the choice of mesh material
When it comes to the accuracy of the mesh, we have to mention the material selection of the mesh, the common mesh on the market has chemical fiber mesh and metal mesh, the same mesh materials have their own advantages and disadvantages, the general production of chemical fiber mesh can meet the needs, but there are some high-precision requirements of the graphics, or to use stainless steel metal mesh.
Tips for designers in pulling nets
The Angle of pulling the net needs to be selected according to the number of lines and graphics of the film. The common problem points in the production are the turtle grain and the plum point, if these two problems occur, it is necessary to check whether the drawing Angle of the mesh board and the number of lines of the film match.
The tension of the mesh, not all the screen is the same tension, its determination needs to be based on the size of the printing area, the fineness, the ink used, the substrate and many other factors, the size of the tension directly affects the accuracy of the printing, the misalignment, the size deviation. When these problems occur, it is necessary for the designer to check the tension of the board.
04, color printing:
The color of screen printing is basically determined at the beginning of the design, but the first color plate is best provided by the designer, which requires the designer to deploy themselves first. Screen printing inks are similar to painting pigments, but with more transparent colors, designers who have learned painting can basically get it done easily.
As for printing, it is divided into two kinds of manual and mechanical, which belong to technical work, so the designer is at ease to the master.
Screen printing inks, like other inks, are mixed with pigments, resins, solvents and auxiliaries.
At present, there are many screen printing ink manufacturers on the market, and there are many varieties, but there are not many fine and complete ones.
In the daily work, the most important channel for designers to get new ink is through the manufacturer's promotion, so designers need to pay more attention to keep in touch with the manufacturer and hold the thigh, not only because these manufacturers will provide different effects of different prices of ink, the most critical is that they will also collect more valuable color effect trend reports through their own channels.
Screen printing ink classification
According to the substrate classification specific: metal ink, plastic ink, glass ink, paper ink, wood ink, fabric ink, special purpose ink and so on.
According to the drying method, there are: ultraviolet drying ink (UV ink), fast setting ink, self-drying ink, low temperature thermosetting ink, high temperature ink, thermal sublimation ink and so on.
According to the state of the ink classification: colloidal ink, such as water-based ink, oily ink, resin ink, starch paste and so on. Solid ink: such as ink powder for electrostatic screen printing.
Designers are a very "stubborn" kind of people, and their classification is different from other industries, so there is a new classification.
According to the classification of ink used by designers, designers often name inks according to the effect, such as glitter (gold onion powder) ink, metal ink, pearl ink, solid color ink, luminous ink, 3d magnetic ink, water ink, uv stereoscopic light oil.
Here are some of the screen printing inks we often use:
Glitter ink is the preparation of glitter into ink, called glitter ink, glitter is made of PET, PVC, OPP metal aluminum film material with high brightness and different thickness electroplating, coating by precision cutting.
About glitter, the industry is mostly known as gold onion powder. There are many kinds of glitter colors, there are gold, silver, red and blue, green, seven colors, magic color, laser, etc., according to different needs can develop a variety of different colors. There are many kinds of glitter colors, there are gold, silver, red, blue, green, seven colors, magic color, laser, etc., according to different needs can be developed a variety of different colors.
Flash powder materials are PET, PVC, OPP, metal aluminum, laser laser materials and so on. PVC flash powder and PVC laser flash powder is not resistant to acid and alkali, not resistant to high temperature, the highest temperature resistance is about 60 degrees; PET glitter and PET laser glitter are acid and alkali resistant and high temperature resistant at about 190 degrees; Metallic flash powder high temperature resistance of about 250 degrees, acid and alkali resistance, mainly used for injection molding.
When designers use glitter ink, in addition to marking the color, we also need to mark the size of glitter particles. At present, the calculation diameter of equivalent volume particles is commonly used in the world to express the particle size, which is expressed in μm or mm.
Glitter particle size can be from 0.004mm-3.0mm can be produced, usually screen printing screen board mostly in 100-400 mesh, glitter particle size corresponding to 150-38μm, there are a lot of comparison table specific use can refer to it.
How designers can tell if their chosen glitter is excellent:
The first is to look at the brightness, from the surface brightness to distinguish, high-quality gold onion powder has high flash, high brightness, and obvious mirror effect.
The second is to see the shape arrangement, this needs to see the shape of the gold onion powder under the microscope, the shape of the rule one, there is no difference in size and powder.
Finally, look at the performance, good glitter acid and alkali corrosion resistance and after performance is excellent, color brightness is enduring.
Different sizes of glitter particles in the ink show different effects. In general, the larger the particle, the stronger the flicker, and the weaker the hiding power of the background color; On the contrary, the smaller the particle, the stronger the hiding power of the background color, the softer the luster.
In addition to granularity, there are many factors that affect the glitter glitter, such as the choice of materials, cutting Angle, etc., which requires designers to make choices according to their own needs.
Pearlescent ink, the difference with glitter ink is the addition of pearlescent powder. Pearlescent powder is mostly made of natural mica and is named for its unique soft pearl luster. Pearlescent color can be adjusted according to demand, because the particles are uniform and delicate for the mesh requirements are low, so it is widely used.
Pearlescent ink is one of the three major optical interference inks, which can be printed on both paper and plastic materials. Optical interference ink simply said that some angles will pale, that is, can not see.
This feature must be a lot of people will think of a thing, yes, a lot of use!
Metal ink, refers to the ink prepared with metal sheet, metallic luster, generally said gold ink, silver ink is this kind of ink. The pigments of metal ink are mainly gold powder and silver powder (copper powder and aluminum powder), and other pigments can also be added to produce ink with special colors, which is called colored metal ink. Our commonly used metal color inks are Tuhao gold, bright silver, electroplated silver, electroplated silver, mirror silver, mirror gold, flash silver and so on.
Under normal circumstances, the larger the particle size of the metal pigment, the higher the metal gloss of the metal ink, but the hiding power and dot reproducibility will become worse. The smaller the particle size of metal pigment, the better the hiding power and dot reproducibility of metal ink, but the metal gloss of metal ink is reduced. Users can choose the appropriate particle size according to their own requirements. But it is not absolute, particle cutting, arrangement and other special treatment will also affect the gloss and hiding power of metal ink.
Solid color ink refers to a monochrome ink that does not add any additional effects, which is widely used in the production of instructions, buttons, low-end silk screen patterns, etc.
UV water bead ink, the surface of the product is like a lotus leaf fell on a lot of different sizes of water. Bead size can be controlled by printing mesh and process conditions. The lower the mesh, the thicker the coating, the larger the water beads, on the contrary, the higher the mesh number, the smaller the water beads. The limitation is that the shape and arrangement of water droplets can not be well controlled, and there are certain differences, so the application can not achieve consistency.
Magnetic ink, the selection of magnetizable pigments, magnetic field treatment is easy to achieve magnetic arrangement, obtain high residual magnetism, added to the ink made of magnetic ink, become magnetic ink. Graphics development needs to open mold in the early stage, the cycle is relatively long, and the price is relatively high.
Ice ink, after printing ink after heating, curing treatment will appear irregular ice flower-like folds, so that the pattern, imprinting produce ice flower-like refraction effect, giving the printed piece special texture effect. Most of this ink is UV ink. The same consistency problem is more difficult to control, the price is higher than ordinary ink, but there are already many in the application.
Glow-in-the-dark ink is made of rare earth luminescent materials through high-tech means. Absorbing sunlight for 10-30min during the day, it will automatically continue to glow for more than 10h, so it will still glow in the middle of the night.
uv stereoscopic gloss oil is the most popular ink used by designers in recent years, which uses uv ultraviolet irradiation to cure ink, and uses transparent gloss oil. Because it has a certain thickness, designers are mostly used to express the texture of the text, and the effect is exquisite and simple.
Compared with ordinary stereoscopic oil, uv stereoscopic oil has a stronger three-dimensional sense, and can also be more refined.
There are a lot of screen printing ink, we can slowly discover their own.
When choosing ink designers should pay attention to the following points:
1, different materials use different inks, must be selected to match the material of the ink, in order to avoid the wrong ink selection caused by adverse consequences, such as screen printing abs ink used on the glass the most common problem is that the adhesion of the ink is not up to standard.
2, different types of ink need to use matching diluents, mainly because various diluents have different dissolution forces for different resin types of ink, the same time in order to avoid bad printing effects.
05, ink curing:
There are many ways, the more common is by drying, volatilization and ultraviolet light curing.
Different curing inks can bring different gloss of the ink after printing, different properties, such as resistance (mechanical resistance, chemical resistance, weather resistance), and the price is also different, so it is necessary to choose the appropriate ink according to the cost in the early stage.
Preservation of screen printing ink, screen printing ink should be stored in a cool and dry place, and avoid lighting.
Third, the problems and solutions in the ink
CMF designers most often follow the process of the first lance must be screen printing, but the most problems in screen printing is in the ink, the following is from the network to sort out some problems and solutions on the ink, I hope to help you!
1, foaming: the reason is that the printing viscosity is too high, drying too fast, the plate and the substrate are too urgent, the layout is poor, the ink itself has problems, etc., can take corresponding measures to adjust according to the above reasons, or add an appropriate amount of defoamer and replace the ink.
2, blocking plate: the reason is too fast drying, printing speed is too slow, printing viscosity is too high, the use of poor and improper diluent, the printing plate is blown by the wind, the ink fineness is not qualified or with impurities. The drying speed should be adjusted appropriately, or the ink should be replaced.
3, pinhole: the reason is that the substrate is too smooth, the printing surface has grease or impurities, the ink itself is poor, so the surface of the substrate must be pre-press treatment, add leveling agent or replace the good ink.
4, poor adhesion: the reason is improper selection of ink, insufficient pre-press treatment, impurities in the substrate, insufficient drying temperature, insufficient time, improper dosage of additives, curing agent, drying agent, two-component ink color overlay printing background color curing hard.
Because PE, PP, PET, aluminum foil and other materials have very low chemical polarity or are too smooth, they are generally treated with electric spark, flame, and strong acid immersion to improve the surface tension of the printed surface. After the ink film of the two-component ink is cured, due to the chemical reaction, the cross-linked ink film is extremely dense, and the ink film after being fully cured is difficult to be etched by the solvent, so when the color is stacked, it can be printed after the base color surface is dry, and other factors can be adjusted by corresponding methods.
5. Drawing: The reason is that the viscosity is too high, the drying is too fast, and the resin used in the ink is not properly matched with the solvent. Appropriate solvents should be used, appropriate viscosity should be adjusted or good ink should be replaced.
6, migration, color: The reason is that the use of improper pigments in the ink, especially a large number of plasticizer soft film, more likely to migrate, should choose the appropriate ink.
7. White or foggy printing surface: The reason is that the diluent contains water, the printing environment air temperature is high, or the printing ink itself is poor.
Because when the printing surface is dry, the solvent volatilization will absorb the surrounding heat, resulting in local water vapor solidification in the ink film or the surface causing white atomization, so you should choose the appropriate drying speed or reduce the space temperature, or replace the excellent ink.
