Screen printing of UV wrinkle ink
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
With the rapid growth of China's market economy and the diversified development of printing technology, packaging printing has emerged from simple product protection and introductory functions. It is using its special printing effect to improve the quality of goods packaging and increase the value of goods. Adding color, therefore, the share of packaging and decoration printing in the total printing output value has increased from the initial 20% to the current 70%, which is at the top of the printing industry in China. UV wrinkle ink is a special imitation metal ink. It is printed on the surface of the substrate by screen printing. After special conditions, the printed product can produce a three-dimensional, uniform skin-like visual effect. It is widely used in the packaging of high-end and exquisite items such as cigarette packets and wine bags. This article mainly introduces the basic process of UV wrinkle ink printing, as well as the problems that should be paid attention to during printing, for reference only.
The UV wrinkle ink screen printing process is basically the same as the ordinary screen printing process, and mainly includes the following aspects: original design, image processing, positive film negative, and screen stencil. Printing: marquee, net selection, stretch netting, coating, printing, printing, drying.
1. Original document analysis
The manuscript is the basis of screen printing reproduction. The quality of the manuscript is directly related to the quality of plate making and printing products. Therefore, in the manuscript and process design, the manuscript handed in by the customer must be carefully examined to determine whether it conforms to the screen printing. Requirements for master plate making. The standard is: 1 image real, good definition; 2 fine particles, clean and clean; 3 contrast moderate, rich in high, medium and low tone; 4 correct color, bright colors, color balance; 5 copy, magnification No more than 3 to 4 times; 6 originals such as originals and drawings should be flat and free from dirt and dirt.
The above criteria are the basic standard for screen-printed manuscript design, but for UV wrinkle ink printing, the manuscript must include at least five channels of CMYK color separation channels and screen plate channels. Because of this design, the wrinkle effect in the product is achieved by the filter, which is used as an image to separate the color in the four channels of CMYK. In fact, the wrinkle effect is obtained through the post-press process, so Before the original output is plated, it should be re-separated. Otherwise, the final result will not be obtained after printing.
2. Image processing
In general, the originals given by customers are not hierarchical. If the original given by the customer does not meet the printing requirements, that is, it is not suitable for the original for screen printing, the prepress staff must process the original to make it suitable for the original for screen printing. The customer's manuscript to the printing company contains the wrinkle effect, and the prepress personnel must use the PS software to reprocess the color separation before outputting the plate.
The method is to use the software's mapping tool to extract the wrinkle effect part as a new channel storage and be black in the field. This channel is used to output the screen printing plate; the wrinkle effect in the design draft is removed, if not removed, the wrinkle effect It will be separated as an image in the CMYK four-color channel, and the offset printing and final printing effect produced by the separation will not be the final wrinkle effect.
3. Output positive film negatives
In order to faithfully reproduce the original or achieve the effect of the original, ordinary screen printing requires attention to problems such as density, resolution, background color removal of the color separation sheet, and dot enlargement when outputting the film. However, for special effects screen printing, since it is solid printing, the requirements of this part are relatively simple, mainly paying attention to the problems of density and resolution.
The maximum density must be 3.0, and the non-image part grayscale should not exceed 0.05; the resolution of the image can be adjusted as required.
4. Screen selection
Screens are the basis of screen printing. Choosing the right screen is an indispensable part. Due to the wide application range of screen printing, when using the screen, it is necessary to select different screens according to the specific conditions and printing requirements.
4.1 The substrate of this project is paper, printing UV wrinkle ink, and polyester mesh is used.
4.2 choice of mesh size. Since UV wrinkle inks require UV light curing, it is necessary to select different meshes according to the wrinkle effect that needs to be achieved. We know that the higher the precision of the printed matter in screen printing, the larger the number of mesh screens selected, and vice versa. , the lower the number of meshes selected. For wrinkle inks, the higher the number of meshes, the smaller the wrinkle effect, and vice versa. Accordingly, in the selection of the number of meshes, a screen of 100 to 200 mesh is generally available. For example, the printing equipment has high precision, and a mesh having a higher mesh height, such as 200 mesh, can be appropriately selected. When the accuracy of the printing equipment is not too high, the screen with a relatively low mesh number, such as 100 mesh, 150 mesh, etc., should be selected.
5. Stretching net
Stretching is the process of tightening the screen and firmly bonding it to the frame. It is the key to the production of screen printing plates. The tension level directly affects the flatness of the photoresist, and it is related to the quality of the printing. Therefore, the stretched net must reach a certain tension, and the stretch tension of each color plate should be consistent. The method of stretching the net can be done by manual stretching or mechanical stretching.
Steps of stretching the net: roughening and decontamination of the surface treatment of the net frame → coating the adhesive mesh → cutting the wire mesh → distributing the net folder → clamping the net → initial pulling → re-drawing → fixed net → whole side → screen printing. Generally, the material, mesh number, wire diameter grade and stretch date of the wire mesh are marked at the convenient place of the frame.
Note that the angle of the stretched net is not correct, and the printed matter will produce severe moiré, which will affect the appearance of the printed matter. According to practical experience, when the angle of the stretched net is 45°, the tortoise pattern is the most serious. When the angle of the stretched net is 60° and 75°, the moiré pattern is also serious. When the angle of the stretched net is 30°, the moiré is lighter, and the stretched net is stretched. When the angle is 0°, 10°, 20°, and 25°, the printed matter is substantially free of moiré, and therefore, the angle of the stretched net can be determined to be less than 30°.
6. Coating photosensitive adhesive
There are many methods for applying a photoresist on a stretched web, and the most common ones are the bucket method and the rotation method. Pay attention to the number of times of glue application when applying glue, mainly depending on the required template thickness. In order to smooth the surface of the coating, a coating method in which coating and drying are alternately performed is employed. Divided into: general film coating method, thick film coating method, thickening pulp online method.
The screen printing photoresist used in the UV wrinkle ink is mostly printed on the printing surface 2-4 times, the back surface is 2 times, and the coating can be completed in two sides and dried once in the middle.
After the photoresist is applied, it should be fully dried. There are two methods of drying and drying. If the film surface is dusty during drying, pinholes will also occur, so be careful not to get dust when the film surface is dry.
7. Printing version
After the photosensitive film is completely dried, it should be printed as soon as possible. When printing the plate, the film surface of the positive plate should be closely attached to the photosensitive surface for exposure.
7.1 Before the 1st version, the front and back of the positive version must be determined. Check for stains or dust on the glass surface of the positive base, the screen surface and the print frame. Then put the master and template into the printing frame, pay attention to the positive film surface of the positive image and the stencil printing surface, and then check it from the glass surface. If the bottom image is placed in the correct position of the frame, it can be exposed. It is.
7.2 In the whole process of 2 printing, the most important thing is exposure. The amount of exposure determines the degree of hardening of the film. As long as the exposure time is appropriate, the imaging performance is good, and the adhesion force is strong. Otherwise, the adhesion network is poor and the printing durability is lowered. The exposure is mainly determined by factors such as the light source, the distance between the surface of the photoreceptor and the light source, and the exposure time.
7.3 Immerse the exposed plate in water for 1-2 minutes, and shake the frame continuously. After the non-photosensitive part absorbs water and swells, it can be developed by rinsing with water. Development is done as soon as possible in a short time. Sometimes, a spray gun of 3.5 to 5.5 kg/cm2 is used, and water is developed by spraying on both sides.
7.4 The developed screen should be placed in a dust-free drying oven and dried with warm air. After drying, it can be inspected on the light-transmissive inspection table for any contamination marks such as bubbles and trachoma. The edge of the line can be trimmed with glue.
7.5 Before or after the printing plate is dried, the film may be reinforced with a hardener or by applying an anhydrous chromic acid solution.
7.6 In order to protect the surface of the adhesive mesh frame, facilitate the regeneration of the mesh frame, and prevent the solvent of the ink from eroding and affect the adhesive force, the inner side of the frame and the adhesive mesh surface are sealed with a tape, and the place can also be sealed with a solvent-resistant paint.
8. Printing
After the preparation work is completed, it can be printed.
8.1 prepress ink agitation and control additives. Pre-mixing and control additives. U V wrinkle ink must be fully mixed before use. It can be printed directly without dilution. If it is necessary to dilute, it can be diluted with varnish (diluent) for wrinkle ink, the ratio is generally not more than 5%. If you need to color, you can add the corresponding color paste and mix and print, but the amount is generally not more than 3%. U V wrinkle inks of different series and brands are generally not mixed together to avoid adverse reactions affecting the printing effect.
8.2 Install the plate: Mount the prepared screen plate on the press.
8.3 positioning. Put the printed product on the film, align it with the part to be printed, put it on the suction plate for preliminary positioning, and put down the plate to check whether the position of the plate is aligned with the film through the plate. If not, it is appropriate. Adjust the position of the print, then use a slightly thicker film to position the print at three points, and fix three points for the positioning of large quantities of silk screen.
8.4 adjustment of the network distance. According to the printing practice, when the mesh distance is less than 5 mm, the image can be completely displayed on the substrate, and when the mesh distance exceeds 5 mm, the rendering rate of the printed image begins to decrease, and as the mesh distance increases, it appears on the substrate. There are fewer and fewer images on it. According to practical experience, the screen distance can be set to 2 to 5 mm during printing.
8.5 Determination of printing speed. Control the printing speed. The change in printing speed generally does not cause a change in the quality of the product, it can only change the size of the ink wrinkle pattern. The printing speed is fast, the pattern is small, the printing speed is slow, and the pattern is large. Therefore, the printing speed can be adjusted according to the needs of the product.
8.6 Adjust the blade angle. As with the printing speed, the change in the blade angle does not change the quality of the print, only the size of the pattern. The blade angle is small and the pattern is small. On the contrary, the pattern is large. Therefore, the angle of the blade can be adjusted as needed. Generally, when U V light is cured, the optimum printing speed and blade angle are adjusted and controlled with the best pattern effect.
8.7 pay attention to adhesion problems. For some substrates with poor adhesion, it can be printed with the corresponding transparent ink and then printed with U V wrinkle ink to solve the adhesion problem.
8.8 trial printing. The test is printed once, and if there is some deviation in the printed position, the printing table can be adjusted appropriately, and the error is controlled within 1 mm.
9. Dry wrinkle
This process is a unique step in the wrinkle effect printing. Only after this step, the printed product will have a wrinkle effect. This process includes the two lines of UV wrinkle ink marking and curing: low-pressure ultraviolet lamp (sterilization lamp) combined with medium-pressure mercury lamp, short-wavelength germicidal lamp to cure the surface, medium-pressure mercury lamp to complete the overall curing. By changing these two curing steps, different wrinkles can be produced.
UV light curing requires the light-fixing machine to be equipped with a wrinkle device. The light source is 20-40W UV lamp, the power is between 60-100W, and the distance between the UV wrinkle device and the UV light-fixing lamp is at least 1.2 meters. Otherwise, The printed product is not covered by UV light by the UV wrinkle device, and the pattern cannot be extracted and the wrinkle effect cannot be achieved. The power of the UV light-fixing lamp is not less than 3KW, and the speed of the conveyor belt depends on the printing light-solid effect, and is generally between 18 and 25 m/min. The power of the UV crease device and the distance of the conveyor belt directly affect the pattern of the product. The power of the UV crease lamp is large, and the speed of the conveyor belt is fast. Conversely, the power of the UV crease lamp is small, and the speed of the conveyor belt is slow.