When the sales of screen-printed clothing has dropped to some extent, designers will be more committed to finding a new visual experience that will draw consumers' attention. Maybe high-density prints are what they are looking for.
This method can print a variety of different colors, and with a little time and effort, a careful printer can master high-density printing. Below, we will make a general discussion on the details of this new method, from design pattern screening, plate making, ink processing to printing and drying. Like other new things, this new solution also needs to be tested or even mistaken to accommodate different printing plants. So don't be afraid of mistakes.
Pattern selection
This is the first step, and perhaps the most important, step you need to consider. Line thickness and pattern size are also determinants of the success of the high-density printing process. For example, after the printing process is completed, the thin lines will look better than the large area. Small-area printing design, especially right angle, compared with large-area printing, the ink is easier to hang on the mesh when printing. In general, you must be very familiar with the types of patterns that are suitable for high-density printing, and eliminate the use of this technique for inappropriate patterns. There are still a lot of tricks that will enhance the visual experience if you use 3D processing. You need to use these to play to your advantage.
Plate making
The screen determines the thickness of the ink layer by the thickness of the mesh yarn and the thickness of the screen. Plate making can be carried out by direct coating of emulsions, direct/indirect methods, or capillary filming methods, which are described below.
For most thick plates, 60-110 mesh (per inch) is often used. You may want to use a mesh tension that is lower than normal, such as 14-20 Newtons. Thicker and thicker ink stacks require a larger screen spacing, perhaps with increased tension. With this concept in mind, don't think about your prints too high. If you think so, you will make the screen distance too close, and make the appropriate grid distance impossible.
In any case, you will need to prepare a suitable degreaser to clean the mesh. After sufficient drying time, apply or patch (indirect film).
Direct emulsions are achieved by repeating the coating on the printing surface until the desired coating thickness is achieved. This will take a day or more. Because each coating requires drying to a moisture content of less than 4% (30 minutes to 1 hour, depending on the emulsion you use and drying conditions) can be applied. After all the coatings have been completed, you will need to allow the stencil to be further dried (eg overnight) before exposure, as screens that are not sufficiently dry will not have good exposure.
How to choose the right emulsion is also the next step. The best option is high solids content. The higher the solid content, the less likely it is to shrink when dry. In addition, a quick exposure of the emulsion is used to minimize exposure time. It takes quite a while to expose the 400-1000 micron film layer.
â—The single component light sensitive polymer emulsion has high solid content and fast exposure speed;
â— The diazo-based photopolymer has a high solid content, but the exposure speed is not fast enough;
â— The diazo-based emulsion has a low solid content and the slowest exposure speed. (The higher the solid content of the diazo-based emulsion, the slower the exposure speed)
Any one is available, but I recommend using a photopolymer because it has the fastest exposure speed and good shrinkage control.
The first step is to apply a wet coating on both sides of the screen and apply a little more on the ink side. This allows the emulsion to "settle" on the printing surface. Place the screen on a horizontal shelf with the printed side facing down.
After drying for a certain period of time, enter the thickening stage:
Thickening can be achieved in several different ways:
1. Standard coating: use a rounded scraper, apply two coats from bottom to top (not dry in the middle), and flip the screen to perform two wet coatings from the opposite direction on the printing surface. Call this a coating 1. Labeling the coating helps you know exactly how many times you have applied the coating. Now let it dry, then repeat the above action until the desired thickness is reached. Allow enough time between each coating to dry. Depending on your thickness requirements, you may be asked for eight, ten or more layers. When applying the third and fourth layers, there may be cases where the middle of the screen is thicker than the edges. If this is the case, you will need to apply one or more times on the edge to achieve the same thickness of the stencil. You can pour a small amount of emulsion around without pouring it in the middle. Repeat twice in each direction to make a standard coating that will leave the emulsion only around the screen. When the eighth or more layers are achieved, multiple iterations are required to achieve uniform thickness. Leave sufficient drying time after the coating is complete. My suggestion is overnight.
2, tape assisted coating: tape along the periphery of the frame, but the width between the tape should not exceed the bucket. This will help to heighten the distance between the bucket and the screen and allow for a thicker emulsion buildup per operation. Calculate how many layers of tape to use based on the base thickness. For example, if your tape thickness is 3 mils (1 mil = 25 microns), for a 300 micron thick film layer, you need 4 layers. In order to achieve the required thickness of the screen, you may need to laminate tape to take into account the shrinkage factor. Apply twice in each direction and carefully keep the bucket "riding" on the tape. Remove the tape before drying to avoid tearing off the dry emulsion. Then place the screen on a horizontal shelf with the printed side facing up. For thicker screens, the operation can be repeated as needed, that is, after each coating is completed, a new tape is laminated and the next round of operation is performed. Allow enough time to dry in the middle of each coat and enough time after completion. My suggestion is still overnight.
3. Scraper coating: This method requires a support plate to provide a flat surface for the screen ink to face down. Correspondingly, this board is smaller than the inner edge of the basket, but higher than the height of the frame, so that it can be connected more closely with the mesh. Apply tape along the outer edge of the screen, but make sure that the width between the tapes does not exceed the coating knife and support. Lay the tape together (as before) to achieve a thickness once to complete the coating (considering shrinkage). At the end of the tape, where the blade starts and stops, leave extra width to remove the unwanted emulsion to keep the screen clean. Now pour the emulsion onto one end of the screen, lower the scraper along the tape at the same end, and then slowly push the scraper steady. When finished, place the screen print side up on a horizontal shelf. Then let it dry for enough time - at least overnight. One disadvantage of this method is that because this time it is coated so thick, it may cause unevenness on the surface. The reason is that the bubbles rise from the emulsion or are surrounded by the emulsion that has been dried near the surface. But this is not the problem itself. What would be the effect of exposing the bottom plate containing bubbles? Moreover, if you do this, you should leave the emulsion long enough to allow the bubbles to emanate before coating and ensure that your technique does not introduce new bubbles in the next steps. This is similar to the straight/indirect method of using a capillary film, which is a film that is pre-coated with a first emulsion, then placed on the table with the film facing up, and the screen printed on the screen. On top, the squeegee is used to apply the emulsion to the ink surface. After drying, a protective film on the back side is peeled off. This method considerably improves the firmness between the film and the mesh.
First you have to consider which type of film to use. Like the emulsion, there are phenanthrene and photoactive compounds. An aspect that does not need to be considered is the solids content. Because the indirect film film itself is dry, it is 100% solids. Don't worry about shrinkage, just simply decide what thickness you need.
Then you need a support plate, a small roller, a blunt or rounded squeegee, and a jade layer emulsion that works with this film. Place the film emulsion face up on the support plate and place the screen printing face down on the film. Tape the inside of the screen, the area is slightly smaller than the film, which helps to deal with the remaining emulsion, and keep the interior of the screen clean. Pour the emulsion at one end, hold the scraper, and slowly push it along the screen with a standard printing technique. This can be applied with a thin layer of emulsion that, after drying, will bond the mesh and the film. Then, it is placed in a dry state, and left for a sufficient period of time to dry, and then the backing protective film is peeled off.
It's time to start exposing, or you can "roll" it on top of it. To do this, you can place the screen ink down on the support plate. Drop a drop of emulsion onto the film and put on the second layer of film, starting with the edge. Then start rolling the film through the roller to get rid of the bubble until the entire film is completed. Leave dry time and peel off the backing layer. (Now at least one company produces a direct/indirect film. Each layer can be glued together before you stick to the screen. And you don't need to use an emulsion; you just need to peel off the protective layer and stick it. On the other layer, then press them together with a roller. By pressing the second or more layers to the thickness you want.)
The capillary film was carefully attached to a wet (water) screen and the emulsion was drawn onto the mesh by capillary action. Although you can stack two or more layers of photographic film together to increase the thickness, if the film has a sufficient thickness, it will have a better effect (the thickness can now be 1000 microns; this film can take you The time to make a screen is reduced from one day to less than one hour; the downside is that they cost $50 or more per piece).
Both direct emulsions and direct/indirect film have a choice of diazo and photoactive compounds. Also, after the film is dried, the solid content is not a problem. Photosensitive compounds are exposed quickly, and what is needed now is to determine the thickness. Capillary photographic film is simpler to use than straight/indirect film because it uses water to adhere the emulsion to the mesh by capillary action. Thick photopolymerizable films are available in a variety of sizes and are currently available in 1000 micron. This eliminates the need to crush several layers together.
The only thing I need to use is a skim version, a film, water and a scraper. The method I chose was to place the film emulsion face up on the support plate and then place the screen print face down on it. Spray a small amount of water with a spray bottle and let it sit for a few seconds to allow the capillary to suck the film onto the mesh, then gently scrape off the excess water with a scraper. After drying, you can take the exposure or crush the second layer of film behind it. (There is also a "roll down" method that is also common in capillary photographic film applications; however, it may not be easy to get used to it. Although both methods can achieve satisfactory results, the one mentioned here It is easier to operate.)
The last thing you need to mention is that you can apply the emulsion to the screen ink to increase the durability of the capillary sensitized film by direct/indirect duty.
How thick do you want to make the screen? Thick printing is harder than the standard version. This requires a little adjustment to achieve the best print, starting with a small amount and then increasing. One of the benefits of printing thermoset inks is that you can dry the first layer instantaneously and then print the next layer. This method allows you to use a less thick template; I recommend starting with a 150-300 micron range and adding it as technology improves.
Ink
How to find an ink that meets various requirements has become the biggest obstacle. You should use the ink that is better released at the beginning. Low viscosity, paste inks are better than high viscosity inks. Then, decide what form you want the finished product to appear, is it smooth and rough? Is it rounded or right angle? Make a decision and then pick from a variety of inks.
Here are some of the things you might use when describing inks:
â— Thicken to increase viscosity. Silica powder is very useful, and this additive is used by most manufacturers and works for all inks;
â— You need a high speed mixer to mix the thickener into the ink. The method of using a power drill and a scraper is good;
â— Concentrated foaming additive or foaming base to form a rough surface;
Lubricant or surface activity increases the fluidity of the ink;
â—The tension additive and the tension primer can increase the elasticity, which avoids cracks in your design pattern;
â— Concentrated pigments increase the intensity and brightness of existing colors. A good idea is to check all available additives or modifiers. You will find that every manufacturer actually has a wide variety of additives and modifiers, so you need to find an additive that you think is suitable for most situations.
Ink manufacturers have begun to produce products that can handle high-density printing. This can save you debugging time. Remember that in the same category they will also appear in a variety of different appearances. So, you will also want to know how to better "handle" these inks in production.
To make a matte (matte) pattern with a flat edge, you need a low-viscosity paste ink. Try what it would look like when you print the ink alone. If there is a smooth matte finish, you don't need to add anything; if not, add a concentrated blowing agent or foaming base and add in small amounts until you get the matte gloss you need. The thickened powder is then added to make it a paste-like state. The thicker the ink, the flatter the edges, but the harder it is to clean the screen. In order to better clean the screen, it may be necessary to use a thinner. Also, it is necessary to gradually increase the amount to avoid the ink layer being too thin. At the same time, you can't lose the right angle edge. If the ink has poor tensile strength, it should be added with a tensile additive or a base. The exact amount of these ingredients depends on the inks and additives you choose. As usual, the “modifications†are recorded in detail, preferably by weight rather than by volume.
A smooth pattern with a flat edge is used in the same way as a matte (rough) pattern, except that the foaming additive is omitted. If you are starting to use matte inks (without adding foaming ingredients), try adding a pull additive, or simply changing to a low viscosity, and having a high gloss ink after drying. Again, the exact amount of these ingredients depends on the type of ink and additive you choose.
High-gloss, high-definition patterns with inlaid edges (or rounded corners) - decorated with plastic pieces that mimic "welding" - can be printed on multi-colored patterns, such as logos. The selected transparent paste requires no milky white or yellow color after drying, which also has a high gloss. The thickened ink is made more viscous if desired. This pattern generally does not require a right angle, so do not care too much about the consistency of the ink.
Make matte (rough) patterns with inlaid edges (or rounded corners), starting with low-viscous inks. Gradually add a small amount of thickener, but also pay attention to the fluidity of the ink, so do not stop when the ink becomes a paste. If necessary, add thinner to increase fluidity. To increase the three-dimensionality of matte (matte), add a little foaming agent. Because you don't need a right angle, you can add a little more, but don't overdo it to make it a standard foaming ink (this will make the finished surface prone to wrinkles and durability).
Printing method
“Making operation†is the key here. Develop a way to keep your production in an uninterrupted state, and if your technology can only be proofed, it is unprofitable.
Any printed pattern must have a good screen, ensuring that there is enough "free" area around the design, which means that the frame is large enough that the printed area does not cover all or almost all of your frame. Choose the appropriate ink squeegee and ink stroke distance. After the screen version is completed, there is no way to expand the size or increase the scratch stroke. Unless you have to do a screen. It is then started with a squeegee of approximately 70 degrees hardness. It is a good idea to have a scraper of various hardnesses. If it is double or triple, it can be better controlled. The ink return plate should adjust the maximum load on the screen (refer to the ink to fully fill the open mesh). If the ink is properly pushed back, the doctor blade will become easier to wipe the ink.
The grid distance is a critical adjustment and is also very important. If there is not enough mesh distance, the ink cannot be released from the screen to the clothes. Because the mesh distance is directly related to the screen tension. A screen with a high tension requires a low mesh distance. Therefore, if necessary, increase the mesh distance of the low tension screen.
At the beginning, the ink and ink return speeds are adjusted to a minimum, and the speed is gradually increased without affecting the printing effect. If the pressure is too high, you will squeeze the ink into the fabric. It is best to let the ink "sit" on the clothes.
If you want the maximum thickness, then dry and stack another layer. Printing two thin layers is much easier than printing a thick layer.
Instant drying
The drying time needs to be carefully calculated to achieve the most suitable drying fixing effect and temperature. Remember that not all instant dryers are the same. For example, the quartz tube dryer heats up quickly. It can quickly dry the surface but an additional 2/3 of the thickness of the ink, which is not heated. Therefore, the first ink layer is inconsistent in physical and chemical state. This may result in the first layer of ink not supporting the second layer of ink very well, which is a problem that often occurs in thick printing. In such cases, an infrared drying panel is more suitable. If the amount of ink is large and must be heated and dried, stay for more time. If you want to superimpose your prints layer by layer, you will need to dry it many times. So you also need a second or more instant dryers.
Final drying
Curing thermoset inks typically use a temperature of 360oF (160°C), in addition to a three times (or higher) ink layer thickness. This thick printing pattern will take longer to reach the drying temperature, so the residence time should be considered when adjusting the oven temperature. You can also increase the drying temperature, but don't try to dry too fast. Drying at high temperatures for a short period of time can cause other problems.
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