The pastel material is screen-printed to reproduce the image on the decal. Then it is pasted on the ceramic utensils, and the bright colors are displayed after roasting. This process is called the decoration process of on-glaze pastel decals. It is a ceramic decoration process with a long history and rich national characteristics, but the decoration of silk screen pastel decals in ceramics has only emerged in recent years. Before, the ceramic pastel decoration was all drawn by hand. After the screen printing process was introduced into the pastel ceramic decal decoration, the production process was transferred from hand-made to fully mechanized production, thus saving a lot of labor, and because of the application points.
Color plus screen plate making can produce fine patterns, pastel decals can be completed by full silk screen printing, or by a combination of printing and manual methods.
First, the printing method of domestic silk screen ceramic products
It is understood that the printing technology in domestic enterprises is used on the ceramic tile products that have been fired, and will not be fired after spray painting. This printing method is the main ceramic tile printing method in China at present, because it is not fired by pigments Therefore, the printed product will not be limited by the color of the pigment.
The color is very bright and clear, the picture is rich in layers, almost no difference from the original painting, and it is suitable for porcelain plates and tiles of any specification and surface.
Since the industrialized production of ceramic utensils, there have been three major changes in decoration technology. In the 1920s, the decoration process combining lithography patterns and manual powder rubbing was realized, replacing the hand-engraved plates. The products were finer and the quality was greatly improved, but the production efficiency
The rate is still low, and there is dust pollution. In the late 1950s, an automatic dusting machine appeared to improve the dusting efficiency. The new contradiction was that the printing and dusting speed were not compatible. After several improvements, by the mid-1960s, offset printing was used instead of lithographic printing decals, which improved automation. At this level, the two processes of printing and wiping are matched, thereby realizing a new mechanized production process based on offset printing, which is another major change in the production of ceramic decals. Screen-printed ceramic decals are developing rapidly because of their simple operation, strong adaptability and thick ink layer. Automation began in the 1950s, and at the same time, process technology and silk screen materials have also achieved amazing development. According to statistics, in the 1960s, screen-printed decals accounted for about 20% of the total decals, and in the 1970s, it increased to more than 85%, and almost 100% of glass decals were screen-printed. At the same time, began to use All kinds of special screen. Printing machine. Printing decoration directly on the utensils has reached a very high level in both quality and scale. At present, silk-screen ceramic decals have basically replaced offset-printed ceramic decals and become the main decorative means of ceramic utensils with large output, high efficiency, low cost and strong artistic appeal.
Second, the characteristics of ceramic decal screen printing
Ceramic decal screen printing is a classification of screen printing. Its basic principle is that after plate making, the pattern part on the screen is permeable, and the non-pattern part is impermeable, and it is attached to the screen cloth. When printing, the squeegee makes the screen contact with the paper, and the ink immediately passes through the pattern part
The mesh miss prints on the paper. Complete one color pass printing. Ceramic decal screen printing is different from other types of screen printing and color packaging printing. Generally, color printing is produced by the superimposition of three primary colors, while the special material for ceramic decals is composed of metal oxides. Pigment, it has the characteristics of dullness after printing, no color change after stacking, and color change after roasting. Therefore, the screen printing of ceramic decals adopts the step-by-step printing method. Generally speaking, according to the requirements of the original, multiple or even a dozen screen printing plates can be made to meet the requirements of the original.
Ceramic decal is to move the colored pattern on the flower paper to the ceramic body or glaze by the pasting method, also known as the transfer flower. On-glaze decals include film transfer, water decals and glue decals, etc., and under-glaze decals are posted Flower paper. Only the outline of the pattern is printed on it, and then it is manually filled in after pad printing; there are also those with line colors attached at one time, which are called decals with water. There are two kinds of decals: paper and plastic film. The paper decals must be peeled off, washed and other processes. After the film decal was invented, the process of peeling off the paper is not required, and it is convenient for mechanized and continuous operation.
Ceramic decoration can use several methods of mud coloring, glaze coloring, underglaze coloring and overglaze coloring. The colorant is divided into: the colorant of the blank mud is mixed with the colorant in the blank and fired to form, so this type of colorant is required to have no reaction in each process of making the blank; After firing white porcelain, apply raw glaze on it and then carry out glaze firing. It is required that it should not react with the glaze at normal firing temperature, and should not flow or blur the pattern; the on-glaze colorants are used to decorate the products after the glaze firing. The surface decoration requires a relatively low firing temperature (700 ~900C) can be firmly attached to the glaze, can not penetrate the glaze and flow. Due to its wide range of uses and simple methods, screen printing has played an important role in product decoration in the silicate industry. In addition to the simplicity of the method, the main advantages of screen printing are precise coloration control and direct printing on porcelain blanks with various shapes and irregular surfaces. Ink thickness, which is an important factor for the brightness of many colors and for the mechanical and chemical resistance of the decoration, depends mainly on the type of screen fabric. Screen printing stencils include frame, fabric and stencil film. The frame is used to fix the stretched fabric. The dimensional stability and tensile strength of the frame are the main factors for the accurate printing of the stencil. The screen is used to fix the template to control the tension and ink channels. In the preparation of printed parts, it plays a decisive role in whether it can be printed accurately. The surface decoration of ceramic utensils has been changed from traditional hand-painting and spray painting to simple and easy screen printing decal transfer, but the screen printing technology of ceramic decals is not completely equivalent to ordinary screen printing, ceramic decal screen printing Features: Ceramic decals are mainly used for the pattern and color decoration of ceramic utensils, which can replace the hand-painted and spray-painted techniques used in the past; the resolution of screen printing ceramic decals can reach 40 ~ 50L/cm; After the screen printing ink pattern is attached to the ceramic utensil, it needs to be fired at a high temperature of 700 ~ 800C or 1100 ~ 1350C to be firmly attached. The color depends on the type of color-forming agent in the ceramic; Divided into ceramic glaze. On decals and ceramic underglaze decals. The flower paper is slightly different due to its different composition; due to the strong covering power of the ceramic sleeve ink, the transparency is poor. Therefore, it is not possible to use the principle of three primary colors for printing at present. The dot printing method adopts non-overprinting side-by-side special color ink dot printing ink.
Third, the types of ceramic decals screen printing
There are many kinds of decal printing. Ceramic decal printing is an important part of decal printing. Ceramic decal printing can be divided into large-film on-glaze decal printing (standard four-open size) printing and small-film under-glaze decal printing according to the order of decals and glazing and different firing methods. Compared with the small film underglaze decal printing, although the printing quality of the large film underglaze decal printing is not as good as that of the small film underglaze decal printing, its price is relatively low, and the overall printing effect is ideal. The quality of the printer is worse than that of the large-film glaze paper printing, but its price is higher. Therefore, judging from the current Inner ceramic decal industry, most manufacturers choose large-film glaze decals. Early ceramic decal printing mainly includes two kinds of flat printing and screen printing, but with the continuous development of screen printing technology, and screen printing such as low production costs, the screen can be reused and is not limited by the size and shape of the substrate. It fully reflects the advantages of thick ink layer, bright color, good reproducibility and strong three-dimensional effect, making screen printing ceramic decal technology a leading printing technology in this field, and now it has basically replaced all lithographic ceramics. Decal printing process technology.
Ceramic on-glaze decals can be divided into transfer decals and transfer decals according to different decals. When decorating ceramics with decals, hand coloring, screen printing, etc., some organic adhesives should be used. Such adhesives should be gradually volatilized or burned in the early stage of color firing, and should be melted at the beginning of the flux.
must be completely eliminated before. According to the order of decals and glazing and the different sintering methods, the ceramic decal screen printing process is divided into ceramic on-glaze decal screen printing and ceramic under-glaze decal paper screen printing. Screen printing ceramic on-glaze decals use special printing ink, usually called screen printing porcelain ink. It is an indirect printing material made by repeated rolling and grinding of the ink roller. It must be roasted at a high temperature of 780 ~ 830C to show a specific color and be closely integrated with the ceramic glaze. The ceramic on-glaze decal is to glaze the ceramic utensils first, then decal the paper, and then sinter the pattern. The adhesive (180g/nf) was coated with PVB solution twice (total thickness of 0.01 ~ 0.011mm) on the backing paper. When using, first separate the backing paper from the screen-printed PVB film, then infiltrate the PVB film and transfer it to the glazed surface of the ceramic vessel, and then sinter at 780 ~ 830C, the PVB film is carbonized and decomposed, and the colored pattern is attached to the surface of the ceramic vessel. , Complete the color transfer of ceramic utensils. Ceramic on-glaze decal printing is the main method of ceramic decal printing
It has the characteristics of low price, relatively large format and good overall printing effect, so it is widely used in the ceramic decal industry. Ceramic decal printing, from early lithography, gravure, etc., to later flat printing and screen printing, has basically become the domination of screen printing, mainly because screen printing has simple equipment and easy to master operation techniques. The production cost is low, the screen plate can be reused, not limited by the size and shape of the substrate, and the ink layer is thick (the printing film thickness of screen printing can reach more than 5 ~ 10μm). Bright colors, good reproducibility, strong three-dimensional sense and many other advantages, which are beyond the reach of other printing methods such as lithography. Ceramic underglaze decals are first decals on the embryo of the ceramic utensils, then a layer of transparent enamel is applied, and sintered at high temperature to form colored ceramic utensils. When the ceramic underglaze decal paper is screen printed, the pattern is printed on the decal paper, this kind of.
The flower-carrying paper is obtained by temporarily combining cotton paper and 180g/nt wood pulp paper. The mounting liquid is generally made of adhesive and filling liquid in a certain proportion, and special quilting liquid must be used when mounting. The carrier of the picture and text is cotton paper, also known as leather paper. When using, transfer the flower-carrying paper to the ceramic embryo. After removing the backing paper, apply a layer of transparent enamel to make the glaze cover the entire porcelain embryo. Sintered below 1350C into colored ceramic vessels. In order to improve the ink absorption performance of the decal printing carrier, the embossing film printing process can be used. Patterns are printed directly on dextrin or other types of adhesive layers. Then put a single layer of acrylic resin film on the pattern. Modification of ink absorption performance
It is good for the firmness and clarity of the fine-dot ink, and avoids the phenomenon that a stencil with fine dots can be made but the printed product with fine dots cannot be obtained. The flower transfer film is also conducive to the decal operation of large-area full flower decoration and high-grade display porcelain, art porcelain and other special-shaped porcelain. To prevent the decals from wrinkling and scraping due to the inconsistency of the flat decals and the curved shapes, which may cause the defects of popping after roasting, avoid quality accidents, and ensure the realization of high-grade decoration of decals.
4. Composition of screen printing porcelain ink
Ceramic glazing makes the green body impermeable to liquids and gases, covers the defects on the surface of the green body, and plays a covering role; it improves the surface smoothness of the product, so that the surface can be decorated easily, and it can also improve the strength and Aesthetics: Prevent the green body from contamination, after glazing, it is easy to contaminate even if it is stained
It is used for washing; it interacts with the green body to make the glaze and the green body a whole. The composition of the glaze screen printing porcelain ink: the binder is composed of organic solvents that dissolve solids and resins; the color-forming agent, heavy metal oxide, determines the hue of the ceramic after firing; the auxiliary agent increases the brightness of the color, so that the screen printing porcelain ink can be fired by color. Then, it is fused with the ceramic glaze, and the commonly used additives are generally lead glass body with low melting point boron. The color-forming agent in the screen printing ink is mainly metal oxides, which determine the hue of the color after firing. The particles of the color-forming agent are thicker than those of ordinary color printing ink pigments, and the relative density is also larger. Glaze. The quality of the decals has a big impact, especially on the dot version. Otherwise, it will be difficult to reproduce the small low-number dots. Although the fineness index of screen printing porcelain ink stipulates that its particle fineness should not be less than 92% below 15μm, and the largest particle should not exceed 30μm, it is still difficult to reproduce fine originals. In order to avoid zigzag edges of graphics and text during plate making. It is required to print in a ratio of 1:4, that is to say, if you use a 100-line screen screen, you need to use a screen of 400 mesh or more. The higher the line count of the photographic screen, the smaller the screen aperture used. There are also fewer particles that can pass through the porcelain ink. This results in poor reproducibility of low-to-number dots. The pictures and texts are blurred, and the edges are hairy. Therefore, in order to improve the quality of printed products, the finer the particles of the porcelain ink, the better. The composition of the underglaze screen printing porcelain ink is the same as that of the glaze screen printing porcelain ink, but the connecting material is a water-soluble material. Use yellow or other dyed nylon wire mesh; 270~320 mesh 1 inch wire mesh for ordinary ceramic products: 220~250 mesh 1 inch wire mesh for flower surface, easier to produce relief effect; 340~400 mesh 1 inch for small text products Screen; the proportional relationship between the minimum screen line and the screen mesh for color screen printing is: screen line number: screen mesh = 1: 3. However, the particle thickness of the ceramic ink, the ability to pass through the screen and the absence of moiré must be considered. and other comprehensive factors. The moiré phenomenon produced in color dot printing can be eliminated or reduced by changing the number of screen meshes, the angle of the screen line or the angle of the stretch screen, the type of dots and the arrangement of the dots; the screen used for the on-glaze porcelain ink for screen printing should be solvent-resistant For the screen plate, use oil-based photosensitive glue, water-oil amphoteric photosensitive glue or photosensitive capillary film plate; screen printing underglaze porcelain ink should be a water-resistant screen plate, and use water-resistant photosensitive glue or water-oil amphoteric photosensitive glue to make the plate. When printing ceramic decals, the temperature of the screen printing environment must be maintained at 22 ~ 269C. The relative humidity is 65% ~ 70%; when printing underglaze decals, the paper should be placed in the screen printing place in advance, and the storage time depends on It depends on the ambient temperature and humidity, generally a few days, and then print after the size is stable.

5. The production process and processing points of ceramic infiltrated tile products The indirect ceramic decoration process is divided into two major processes: ceramic on-glaze decal and ceramic under-glaze decal. There are three printing methods for making ceramic decals by indirect method (printing method), namely Hand-engraved copper gravure gravure ceramic decals, offset large film decals and screen-printed film decals. At present, the direct screen printing method is mostly used, with fine printing patterns and high production efficiency. The process flow is roughly as follows: base plate making → screen plate making → printing → enamel preparation → proofing → brick surface treatment – → screen printing. From the above process flow, we can see that the difference between the ceramic tile screen printing and the general screen printing process is the preparation of enamel and the processing of brick blanks. If the process is not properly controlled in production, it will have a greater impact on the quality of the seepage brick. Some of the problems that should be paid attention to in the screen printing process of architectural ceramic infiltration bricks are as follows.
In screen printing, the spacing between the brick and the screen directly affects the accuracy of the printed pattern. With the movement of the scraper, the screen will be deformed to a certain extent, and the pattern printed on the brick is not exactly the same as the pattern on the screen. Therefore, theoretically, the greater the distance between the brick and the screen
Smaller, the higher the precision of the pattern on the adobe. In the actual production control of architectural ceramic infiltration bricks, the spacing can neither be too large nor too small. In the process of screen printing, when the scraper scrapes the screen, the screen must be attached to the mesh before the infiltration glaze is attached. .Leave the surface of the adobe before putting it on, otherwise the edge of the image will be blurred due to the large amount of seepage glaze infiltrating the body. Moreover, if the speed of the wire mesh to leave the brick is too slow, the moisture in the glaze will evaporate with the volatilization of the glaze. The oozing glaze is easy to adhere to the wire mesh, and the oozing glaze particles continue to aggregate, causing the mesh of the mesh to be blocked. The distance between the brick blank and the wire mesh has a direct impact on the speed at which the wire mesh leaves the surface of the blank body. When the distance is small, the deformation of the wire mesh is small during the movement of the scraper, and the upward tension generated by the mesh is also reduced. The speed at which the mesh leaves the surface of the adobe decreases. If the glaze is too large, it may adhere to the mesh and prevent the mesh from leaving the surface of the adobe, resulting in serious printing defects. Of course, the distance between the screen and the brick cannot be too large, which not only reduces the precision of the pattern, but also puts forward higher requirements on the strength of the screen material. and. The speed of the wire mesh leaving the surface of the adobe is too fast, and the amount of infiltrating glaze into the green body is relatively reduced, which will make the pattern shallow and blurred. Therefore, the distance between the screen and the brick is an important parameter, which should be considered comprehensively according to the pattern accuracy requirements and the performance of the glaze.
In a series of performance indicators of the seepage glaze, the viscosity is a very important parameter, which has a great influence on the printing quality. If the viscosity is too large, it is first of all unfavorable to the printing process, and it is easy to produce sticky nets, block nets and damage the green body. Secondly, when the viscosity of the glaze on the surface of the green body is large, the ion diffusion resistance increases, so that the glaze slurry stays on the surface of the green body and it is difficult to penetrate into the interior, and the image is blurred and superficial after high temperature sintering. If the viscosity is too small, there may be two reasons: one is that the amount of penetration aid is too much; the other is that the concentration of the seepage glaze itself is too low. If it is due to the addition of penetration aids
If the viscosity is too low, the coloring ions will infiltrate too deep under the action of the penetration aid, resulting in a decrease in the concentration of the coloring ions in the green body, and the color will become lighter and blurred after high temperature sintering. If the concentration of the seepage glaze itself is too low, the water in the glaze slurry will increase (in fact, water is also a seepage aid), and the concentration of coloring ions will also decrease. The image after high temperature sintering is also blurred and discussed.
Different from the ordinary screen printing process, the performance of the brick blank has a great influence on the color and pattern quality of the product. In actual operation, the blank must maintain a certain humidity and temperature to meet the requirements of the screen printing process. The moisture content of the adobe has an impact on the printing quality.
The moisture content mainly refers to the moisture content when it enters the screen printing process after the drying process. The level of the moisture content has a great influence on the screen printing process. It is quickly absorbed by the brick, which is easy to cause the aggregation and drying of the glaze particles, which will block the mesh and cause difficulties in printing. When the moisture content of the brick blank is too high, the absorption rate of the brick blank to the glaze is slow. If the distance between the brick blank and the wire mesh is too small, after the scraper scrapes, the wire mesh may not be able to adhere to the mesh wire before the brick blank is attached to the mesh. Leave the surface of the adobe, that is, the glaze is easy to adhere to the wire mesh, causing the mesh to be blocked. Therefore, in actual production, it is generally required to control the moisture content of the adobe.
below 0.2%.
If the temperature of the brick blank is too high (higher than 70C), during the printing process, the water in the seepage glaze will evaporate quickly after encountering the high temperature blank, which will increase the viscosity of the seepage glaze, and the sticky glaze will easily block the silk. Mesh mesh, causing printing difficulties. In addition, the coloring ions entering the green body will also migrate with the evaporation of water in the infiltrating glaze, and the coloring ions will be concentrated in a large amount from the inside of the green body to the surface of the green body, resulting in not deep infiltration and blurred patterns. If the temperature of the brick blank is too low (below 30). The capillary pores in the blank body are reduced, and the resistance of the seepage glaze to the blank body increases accordingly, and it is difficult for the coloring ions to enter the interior of the blank body, resulting in the seepage glaze in the green body. The surface of the green body spreads laterally, making the product pattern blurred and the color very light. Therefore, in order to improve the quality of printed products, the temperature of the bricks should be strictly controlled, generally controlled at 45 ~ 65C. The seepage glaze is equivalent to the ordinary screen printing process
It is usually a fluid substance with a certain degree and stable storage (without delamination, precipitation and deterioration) prepared by adding soluble coloring compounds to solid viscosity modifiers, water and active additives. . It is required that the seepage glaze must have the following properties: first, it has a certain viscosity, which produces a high resistance when the scraper moves; second, it has sufficient fluidity and can pass through the mesh holes smoothly; the third is to achieve a certain fineness , to prevent clogging of the mesh.
The selection of the mesh size of the wire mesh is related to the quality requirements of the product pattern on the one hand, and it is closely related to the performance of the infiltration glaze on the other hand. For the seepage glaze with a certain viscosity, if the mesh of the screen is too dense and too small,
When printing, it is difficult for the seepage glaze to reach the surface of the brick body through the screen mesh. Even if it can be printed on the surface of the brick body, it will cause poor seepage effect and shallow and blurred patterns due to the limited number of seepage glazes. If the mesh of the wire mesh is too large, the amount of glaze that penetrates through the wire mesh to the surface of the green body will be more. It is easy to spread out on the surface of the green body, which also causes the pattern to be blurred. In actual production, the mesh number of the mesh should be reasonably selected according to the viscosity of the glaze. The hole should be smaller. Generally speaking, the mesh of the wire mesh can be controlled at 60 ~ 120 mesh 1 inch. The particle size of the glaze paste has a certain influence on the printing quality. If it is too fine, the surface tension will increase, and the glaze layer will be prone to dryness and cracking. After sintering, the glaze shrinks and burnt out. If the particle size of the glaze slurry is too coarse, it will increase the melting temperature, affect the depth of the coloring ions infiltrating the green body, affect the color development ability of the color glaze, and reduce the color concentration of the pattern; It is easy to appear the phenomenon of smearing, and it will also accelerate the wear of the screen and reduce the printing endurance. In actual operation, the control of the size of the glaze slurry generally takes half of the size of the screen mesh opening as the upper limit of the particle size.
The tightness of the screen has a certain influence on the printing process and printing quality. If the screen is too tight, the tension when the screen leaves the blank is relatively large, the speed of leaving the blank is faster, and the contact time between the screen and the blank is relatively large. Reduce, the amount of seepage glaze through screen printing to the surface of the green body is relatively small, at this time
In order to get a clear pattern, the speed of the scraper must be slowed down. If the screen is stretched too loosely, the tension when the screen leaves the green body is relatively small, the speed of leaving the green body is slow, the contact time between the screen and the green body is prolonged, and the glaze is printed on the surface of the green body through the screen. The amount is relatively large. It is easy to cause lateral diffusion of product patterns.
6. Conclusion
Ceramic on-glaze decal printing is the main method of ceramic decal printing. It has the characteristics of low price, relatively large format and good overall printing effect, so it is widely used in the ceramic decal industry. Although the application of screen printing on ceramic infiltration tiles is a relatively new topic, it has developed rapidly in recent years. In actual production, it is necessary to correctly control the distance between the screen and the porcelain blank, and pay attention to the influence of the performance of the seepage glaze and the performance of the porcelain blank on the printing quality. Targeted adjustments should be made in the process operation, the mesh number of the screen should be selected according to the requirements of the specific product and the performance of the seepage glaze, and the tightness of the screen should be adjusted reasonably. Only in this way can a high-quality printed pattern be obtained.