There are many types of decals printed, and ceramic decals are an important part of decals. Ceramic decal paper printing according to the decals and glazing with the order and different sintering methods, can be divided into large-film glaze flower paper (standard four open specifications) printing and small-film underglaze flower paper printing. Compared with small film underglaze flower paper printing, large film underglaze flower paper printing is not as good as small film underglaze flower paper printing, but its price is relatively low, the overall printing effect is also relatively ideal, and small film underglaze flower paper Although the printing quality is superior to that of the large-film glaze paper, its price is higher. Therefore, from the current domestic ceramic decals industry, most manufacturers choose to use large-film glaze. Early ceramic decals mainly consisted of plain printing and screen printing. However, with the continuous development of screen printing technology and screen printing, such as low production costs, screens can be reused, regardless of the size and shape of the substrate. With the thick ink layer (up to 2 to 4 microns), bright colors, good reproducibility and strong three-dimensional effect, the screen printing ceramic decal paper technology has become a printing technology that is playing a leading role in this field. Nowadays, it has basically replaced all printing technology of plain-printed ceramic decals.
First, the principle and process flow of ceramic decal paper printing
Ceramic decals Screen printing is a category of screen printing. Its basic principle is: After the plate is made, the part of the pattern on the screen is permeable, and the non-graphic part is non-permeable, and it is attached to the screen cloth. At the time of printing, the squeegee makes the screen contact with the paper, and the ink is immediately printed on the paper through the mesh of the pattern portion to complete one color printing. The principle of superposition of ceramic screen printing and other kinds of screen printing and color packaging printing is different. The general color printing is produced by three primary colors of overprinting, and the ceramic decal-specific pigment is an oil-like powdery organic pigment composed of metal oxides, which has the characteristics of dullness after printing, non-discoloration of the color stack, and discoloration after grilling. Therefore, ceramic decal paper screen printing uses a hierarchical printing method. In general, according to the requirements of the original document, it is necessary to make multiple blocks or even more than a dozen screen printing plates in order to meet the original requirements.
The process flow of ceramic decal paper screen printing is generally as follows: First, according to the user's draft or self-creative design, the color separation of the photographs should be based on the characteristics that ceramic pigments are not discolored. In general, the main red, blue, and green colors are separated, red It should be divided into three times (light, medium, and deep), blue and green in second (light, dark), and finally in black or gray lines. (The desktop system has been used for design and production. The quality and progress have been greatly improved.) . After the good lustration has been checked and the requirements are met, a positive-working small piece (single-patch) is produced, and the proofing is done manually with a small version of the printing plate. After the barbecue, the sample is adjusted in all aspects until it meets the requirements, and the porcelain factory is burned by the test, and the user approves and orders. After mass production on the machine.
Second, the technical problems that each process should pay attention to
1. Screening and Imposition
Ceramic decal color screen printing dot, the lowest line of the screen when the printing / mesh ratio is generally 1/3, in addition, we must fully consider the ceramic decal ink particle size, whether the smooth network, and control the production of moire A variety of comprehensive factors. In the case of color printing, the occurrence of moire is generally controlled and eliminated by changing the number of screen meshes, the screen angle or the stretch angle, the dot type, and the dot arrangement.
When the imposition is made, it can be done according to the user's requirements and the bottom paper standard, but the layout must meet the national standard, that is not less than 43 cm × 34 cm. The pattern is relatively simple and the number of colors can be used for manual imposition, but the manual imposition due to the influence of factors such as technology, its overlay accuracy is often not high enough, especially in the case of a large number of colors, sometimes even not reach a multi-color overlay The quality requirements, while the ceramic flower paper color is generally more than 5 color times, more than 10 times even more than the number of times, so it is best to use imported even drying machine for even drying, so as to ensure the quality of overprint requirements.
2. Plate making
Platemaking includes many processes such as copying, developing, retouching, and stripping. Each process has its own technical requirements and skills. The first is to make screen printing plates, which can use diazo photosensitive adhesive. The edge of the squeegee blade is at an angle of 45 degrees. The smaller the angle of the squeegee, the thinner the photographic solution left on the screen. Apply sensitized adhesive, coat it on both sides and pay attention to evenness. The coated screen plate is dried at a suitable temperature, and the dried screen plate can be delivered to the plate.
(1) Shaiban. Ceramic glaze on the paper screen printing generally use solvent-resistant screen, with oil sexy light or capillary film, or water and oil sensitive emulsion plate, and underglaze flower paper printing used for the water resistant screen, water sexy Optical plastic or water oil two sexy light plastic plate. Before printing, you should wash the plate with detergent or washing powder to remove the dust on the plate surface, handprint and glue, and finally coat the emulsion with a high-pressure water gun after drying.
Sensitive glue is suitable for ceramic decal paper special diazo photosensitive adhesive. Use one or two components as required. One-component photosensitive adhesives have been formulated with photosensitizers and adhesives and can be used directly. Two-component emulsion is the photosensitive agent and glue separately packaged by the user to self-distribution, the method is as follows: Take 10 grams of sensitizer with 50 ml of distilled water or water to fully dissolve, add 950 grams of glue, stir and let stand bubbles Disappeared can be used, can not use metal products, stirring, so as not to affect the stability, with a good emulsion should be low temperature (not less than 5 degrees Celsius) to save light. When coating the sensitized adhesive, avoid direct sunlight. Use a special glue applicator to apply the sensitized adhesive on the woven cloth at about 45 degrees Celsius. Apply the coating on the front and back sides twice. Apply wet or dry wet-pressing. Then put it into the screen drying oven (now overseas has produced automatic photosensitive coating machine, coating quality is quite satisfactory). The coating quality requires uniform coating, uniform service, and uniform thickness. The coated screen should be protected from light.
The most important thing is to control the exposure of the appropriate exposure time, according to practical experience, the general exposure time is controlled in 3 to 7 minutes, the specific operation can first try some samples, adjust the exposure time according to the actual situation, to be the best The exposure data of the printing effect is then mass-printed. In addition, we must also have a good grasp of the light source and the distance between the lights, the light source can generally be used 10 to 15 40-watt row of fluorescent lamps, lights from 25-30 cm, can also be used after the exposure of the screen light version of the water rinse development, revealing . When printing, please pay attention to the design of the sample separation when remember to draw the "10" word rules line, printing a good rule when the rules line, as the screen printing version of the benchmark.
(2) Development and netting. Developing water, put the stencil in clean water, shake for tens of seconds, check whether the pattern is visible, and then use a high-pressure water gun to flush the net. When the net is not washed, the photosensitive part is washed away and the photosensitive part is washed away. (Non-patterned parts) are retained due to photohardening, and are made into screen plates. The water pressure of the water gun should be consistent (about 4MPa) during the net rushing. Grasp the netting time and the net distance. After flushing, flush the glue on the surface with clear water and carefully examine the transparency of the part of the screen pattern. If there is any part that does not work, you should punch it more for that part.
After passing through the screen, pass the water-absorbing paper or sponge to remove the residual water on the screen immediately to avoid the formation of a watermark. Then put it in a screen drying oven. The oven temperature is controlled at 30-45 degrees Celsius, and the temperature is too high to cause deformation of the screen.
(3) revision. In the printing and development, due to the influence of materials, technology, environment and other factors, some of the produced screens have defects and cannot fully meet the quality requirements. If minor common defects are encountered, repairs may be made to make up for the defects. At the time of revision, the screen can be placed on the revised table, and the deformation of the screen can be checked with the film first. The deformation is too large to be put into use, and the cause can be found and re-baked. Revised glue can be added with a small amount of white latex (fastening the drying speed) with the original photoresist or with sealer, carefully inspect the non-patterned part of the trachoma and the plastic part, and finally evenly brush the photoresist on the non-graphic part with a brush. , Into the oven and low-temperature drying (if you do not use the screen to dry naturally better), and finally according to the amount of the amount of the second exposure, increase the screen printing rate. The repaired screen printing plate can deliver the printing process and perform decal screen printing.
(4) Stripping: Stripping is a major advantage of screen printing, as long as the screen fabric is not damaged, the stripping solution can be used to strip off the original film, after washing the other emulsion coating can be used to make other screens, If used properly, a screen can be reused dozens of times.
3. The choice of screen and stretch net
Ceramic decal nets generally use yellow or other color polyester mesh (or nylon mesh), common product meshes are controlled from 180 to 300 mesh (if 250 mesh is selected), and flower surfaces are 220 to 250 mesh, which can produce embossed effect. Fine text with 340 ~ 400 mesh can be, ordinary products as long as the use of domestic that can meet the requirements, so that the price will be relatively low, but for the printing of fine products, in order to ensure quality, can choose to import high mesh (300 or more) Wire mesh, but the price is high. The best choice of aluminum frame is the aluminum frame, it is not easy to deform, light and durable. The stretch net is to cut the screen according to the size of the frame and bond the net cloth to the frame. Before the stretching of the net, the four sides of the frame should be feathered with a file to increase the adhesion of the net and the frame. Stretching machine should use pneumatic stretching machine or mechanical (adhesive) stretch net. When stretching the net, it should be noted that the tension is basically the same and the elasticity is even and the conditions can be tested with a tensiometer. Tensile adhesive can be selected with DS series adhesive or adhesive, and the pressure of the net is kept at 0.4-0.5 MPa. After the adhesive is dry, the adhesive can be removed, and the excess net cloth around is adhered to the frame. Increase the durability of mesh.
Film on the bottom
The film on the bottom paper can be divided into two procedures: film laying and filming.
(1) With film. The proportion of film is generally: polyvinyl butyral resin: methanol (ethanol) = 1:5. For example, when the film is used, about 16 to 18 grams of butyraldehyde can be used. First, the methanol (ethanol) is pumped into the reaction pot according to the amount, and the butyral is uniformly charged under the stirring condition, and the heating switch is turned on (the temperature is controlled at 50 to 60 Celsius) Stir for 3 hours until the butanal is completely dissolved and ready for discharge. The quality of the film must be completely melted, no block, no impurities, and it should be slightly thicker. Methanol can be added properly when the film is on. Ethanol) Adjust the concentration.
(2) on the film. As the paper for the backing paper, the special decal paper (wood pulp paper) should be used. Before use, the paper should be used to trim the four sides of the paper to ensure that the specification size meets the requirements. The upper film generally uses a special filming machine (the principle is similar to the polishing machine). Adjust the gap between the good roll and the print roll so that the film is evenly coated on the base paper. General requirements on the film twice (do not have to turn the head) can be the first time after the first dry, but each time you have to open the paper (fan cooling), the film thickness standard is 0.01 ± 0.001 mm, can be slightly thicker It can not be thin and can be adjusted by measuring with a micrometer.
Film on the drying tunnel should be maintained at 70 ~ 80 degrees Celsius, the temperature is too high, the film is not shiny, and will make the bottom paper scorched, too low will be blistering, dry impermeability, adhesion failure will occur. All in all, the film requires bright, uniform thickness, uniform, no residual film residual pulp, no adhesion, no damage. After drying, the backing paper can be stacked neatly to prevent dust. After a good film is stored for a period of time to make it flat, stereotyped and then used, according to practice, generally mastered in about 15 to 20 days or so. Since the backing paper is composed of paper, plastic film and butyral film, after hot air drying, the deformation of the three materials is also different. Therefore, the bottom paper must be processed before printing. Before the formal printing, the bottom paper is not printed with a wire mesh machine, no squeegee or manual transportation method is used to enter the oven for shaping, that is to say, empty the car, but at this time it is necessary to pay attention to the temperature of the oven must be controlled at the time of the official printing. The temperature is basically the same. By shaping, the deformation of the base paper in the future multi-color printing can be minimized, and the overprint quality of the product can be ensured.
5. Rolling ink
Rolling ink is to add the baked pigment in hot water in proportion to the linking material, artificially stirred and rolled on a three-roller mill. General color rolling 2 to 3 times, the first rough rolling, after the second fine rolling (adjust the roller gap), the rolled pigments should be rolled now, the remaining paint after printing can not be discarded, the following also used again Rolling can be. Screen printing pigments dry quickly without adding any desiccant. Ceramic applique materials include plain printing and screen printing. At present, there are many series of pigments, each with its own characteristics. For example, four-color pigment: the same principle as color printing, good reducibility, quality has reached the international level; high-temperature fast-burning pigments: barbecue temperature 1006 ~ 1200 degrees Celsius, 3 minutes released; lead-free cadmium free pigments: pigments do not contain lead, Cadmium, this series of pigments is powdered before blending, 90% of the particle size is greater than 5 microns. There are more than 10 kinds of basic colors, basically able to meet the color needs of various kinds of flowers; With baking pigments: According to the proportion of the pigments and the amount of printing determined by the proofing, the proportions should be carefully proportioned, and the good pigments should be put into the range of 90-100 degrees Celsius. Baking in the oven for half an hour does not allow moisture in the paint (not more than 0.5%), otherwise it will cause the product to burst and cause waste. Due to the different characteristics of different pigments (high temperature resistance), the range of use is also different. Therefore, appropriate screen printing pigments should be selected according to the requirements of different equipment and printing objects. In addition, special attention should be paid to the miscibility of screen printing pigments and porcelain inks, improper mixing, chemical reaction during sintering, deterioration of color, and even popping of flowers. Therefore, screen printing pigments with good miscibility should be used. And porcelain ink, it is best to use the same manufacturer and the same brand of products. For plain printing, screen printing, high temperature, low temperature and screen printing pigments and porcelain inks produced by different manufacturers and different brands, it is not allowed to mix and use them randomly, so as not to affect the quality.
6. Printing
Screen printing equipment should use roller type flat screen printing machine. Dryer chooses paper hot air dryer. There are related auxiliary equipment. Such as grinding knife machine, vertical racks and so on. In addition, since different ceramic decoration processes use different ceramic decals, the different ceramic decals differ in the printing process, the reticles, and the inks used. Therefore, before the printing of ceramic decals, first of all, we must be clear about the specific ceramic decoration process and decal paper printing process and the use of materials, in order to avoid unnecessary rework and waste products, ensure quality and improve efficiency.
Generally, high-temperature solvent inks are used for printing on glaze decals. The main components are binders (ie, film formers, which mainly use solid resins and organic solvents that dissolve the resin), and coloring agents (which determine the color hue of ceramics after firing). , Mainly series of metal oxides), additives (the role of which is to increase the brightness of the pigment, so that the screen printing porcelain ink is burnt with the ceramic glaze fusion, generally lead glass body, low melting point boron, etc.). The ink printed on the underglaze decal paper is a high-temperature water-based ink, ie, a water-soluble material is used as a binder. Screen printing ceramic decals generally maintain the ambient temperature of the workplace in the range of 22 ~ 26 °C, and the relative humidity is maintained at 65% ~ 70%. For decals used in under-glaze screen printing, the paper should be placed on screen printing sites for a period of time (usually several days) before the screen printing, so that the decals can be stretched to facilitate printing. Registration. For color-coded decals, they should be air-dried for a certain period of time after each color is printed. Check whether they are dry. After drying, make the moisture content of the paper stable. Then, the next color printing can be carried out. If it is not transparent or it takes a long time to dry, you must find out the cause and solve it. If you encounter printing a large area of ​​color blocks dry impervious, you need to erect paper, dry, in short, must be dry before the next color printing. In addition, because screen printing porcelain paper color sequence is more, so before starting the machine should carefully check the operation of machinery and equipment, do oil maintenance work, check all the printing plate is deformed, overprinting is accurate, the angle of the squeegee is reasonable, smooth . In the production process, Sanqin (deep diligence, diligent ink, and ground squeegee) are used to keep the pigments with a certain degree of fluidity. The entire batch of products is consistent in ink color, uniform in thickness, clear in level, and overprinted accurately. In the process of screen printing, the temperature of the oven should generally be maintained between 30 and 40 degrees Celsius, or be flexibly controlled according to changes in the local temperature. With the principle of product drying out of the oven, the entire batch of products should be kept at the same temperature in the printing process. Avoid repeated deformation of the paper caused by high temperature fluctuations. In addition, in the screen printing, the angle of the squeegee, the flatness, the distance between the screen and the ink-removing knife have a great influence on the product quality. The squeegee angle (15 to 30 degrees) should be adjusted according to product requirements. The same point of view is generally applied to the same batch of products to avoid inconsistencies in the thickness of the ink layer caused by adjusting the angle during the printing process. The face of the squeegee must always be carefully ground and held at 90 degrees. The net distance can be adjusted from 4 to 10mm, and the best is 5 to 7mm. It is better to apply the ink evenly and evenly on the screen when the level of the ink-returning blade returns to the ink. If the ink is too high, the ink will not evenly. If the ink is too low, it will scratch the screen.
7. Test burning
Before proofing and mass production of the finished film, one-thousand-thousandth sheet shall be taken for trial burn. First, use a blade to gently scratch the test pattern (note that no force is applied to avoid scratching the bottom film). Apply methanol (ethanol) to water (1:3) to attach the pattern to the porcelain. Blisters, bubbles, and then lightly wipe the pattern with cotton, remove excess moisture, bubbles, make the paper and porcelain tightly integrated, to be dry and put into the electric resistance furnace heating.
According to the selected pigment (high temperature, low temperature, etc.) to set the test firing temperature, the furnace door is not closed first, and the temperature rises to about 200 degrees Celsius to observe that the bottom film turns black and then closes (carbonization of the bottom film). When the temperature rises to the set temperature and the power is turned off automatically, the furnace door is not opened, and the heat is kept for about 15 minutes. Finally, the furnace door is opened. After the furnace temperature drops to room temperature in about 2 hours, the sample can be taken out. Meet the requirements, you can enter the next process.
8. Remove film and inspection
Unmasking and inspection can be carried out simultaneously. When uncovering the film, you can use a knife to pick out the film opening (the whistle should be picked on the film instead of the mouthpiece), then use a smooth bamboo film to take the film, each paper pad a copy of paper for padding, so as not to Sticky. Liner and flower film require smooth, wrinkle-free and neat stacking, and the printed cross paper is basically aligned. For uncovering the film, if the entire unqualified product is rejected, if a flower in a sheet is not qualified, use a red pen to mark the lining paper and count the actual number of sheets. When it isn’t one, it will be supplemented with the entire amount. A good flower film is lined with 100 grams of kraft paper for every 100 sheets, rolled into a roll, and a thick backing sheet (a paper tube or plastic bag is also available) is used to affix the label. The certificate of conformity is one for every ten rolls. Box packing factory. In addition, the amount of lead and cadmium eluted should also be checked to ensure that the product meets the requirements of hygiene and environmental protection. According to the international standards, the products decorated according to the flower design requirements have a lead dissolution of 7×10-6 or less and a cadmium elution amount of 0.5×10-6 or less. For the inspection of lead and cadmium dissolution, it is generally necessary to send Go to a special inspection agency.
Finally, remove the remaining film, dust, and oil traces from the bottom film with a single-sided doctor blade. Be careful not to scratch the backing paper so that the bottom sheet can be reused.
