Ceramic printing (2)

(B) ceramic underglaze paper screen printing process

The underglazed porcelain ink is printed on the waxed paper through the screen printing plate (commonly known as cotton paper), and then it is transferred to the porcelain body that has not been burned. The wax paper is peeled off, the graphic is adhered on the porcelain blank, and then the glaze is applied. The layer, after roasting, presents beautiful blue-and-white color graphics. This process is called silk screen decal decoration. The non-toxic glaze coloring material, in addition to decoration in the glaze, is also called lead-free ceramic decoration.

The under-glaze ceramic underglaze decoration has developed in recent years. Prior to this, the ceramic underglazed decal paper process was carried out by gravure printing, and the gravure printing plate was made by hand-engraved copper plates. Since this process is mainly operated by hand, there are limitations in the degree of mechanization, the lack of updating of the flower face, and the inability to print and print colors. The use of screen printing and underglaze printing decoration process not only saves man hours, but also enables rich color layers. Underglaze blue flowers develop to colorful, silk screen printing is an important means.

The process flow of silk screen printing on ceramic glaze paper is shown in Figure 4-3.

Decal paper design principles

With the continuous improvement of people’s living standards, people’s decoration requirements for daily-use ceramics are getting higher and higher. Some problems encountered in the process of designing ceramic applique papers, solutions, and some experiences are briefly described as follows:

(1) When designing ceramic decals, colors should be chosen to use pigments with similar baking temperatures. When designing drawings, most people always follow certain rules, or preferences for certain sub-pigments, or according to the user's requirements. Assortment of pigments is used as you like, and beauty is the standard. However, in the design of ceramic decals, you can not let your own preferences free to gallop, ceramic decals by the paint, utensils, baking and other processes. It is because of these constraints that some very beautiful design drafts, after being made of ceramic decals, can not restore the original appearance of the design drafts, and may even appear tacky. Therefore, designers of ceramic decals must be free to navigate in the field of floral design. First, they must understand and master the properties and characteristics of various ceramic pigments, and try to avoid using pigments with large differences in the baking temperature in the same artwork. , In order to avoid the roasting process, due to the difference in roasting temperature caused by some of the pigment unfamiliar or over-fire.

(2) Do not stack two colors together when designing the artwork. Some of the pigments will affect the hair color. When designing the flower paper, due to the need of color, sometimes the two colors are matched together. The visual effect on the manuscript is very good, but in fact it is not entirely. This is because in the ceramic pigments, due to the different coloring elements of the various pigments, some raw materials may change color during the grilling process, or a pigment may still appear, and the other pigment may become very light or even disappear. The phenomenon, which is called the "eat" phenomenon in the characteristics of ceramic pigments. Such as: cadmium yellow and brown together, brown will eat cadmium yellow, leaving only brown. Therefore, in the design of flower paper, we should master the characteristics of various pigments, and strive not to put together two kinds of pigments that will "eat color." If it is absolutely necessary, the position of the pigment can be staggered. When not tying together or suggesting the addition of a screen cable, the two-colored angle should be staggered, and the color should be restored by the additive color rendering method of juxtaposition of the two color dots.

(3) The color and overlap color of ceramic decal paper cannot be too much. The feature of screen-printing pigments is that the ink layer of printed products is thick and bright in color. Therefore, when designing, it is necessary to design some vivid color papers with fewer color layers; at the same time, not too many colors should be used in the same artwork to avoid increasing the number of sets and lengthening the printing cycle; in the same place as the design draft, such as On a flower, do not stack too much, so as not to mix the upper and lower layers of pigments during the roasting process, so that a flower that looks very good to look at is very gray, very mixed, and very dazzling.

(4) Copying art is a kind of plastic art. The picture pattern copied on decal paper is a graphic art. Daily ceramic products are three-dimensional plastic arts. Different from other color printing products, in addition to concept, composition, and artistic skills, in designing decal paper originals, it is necessary to combine these two modeling arts ingeniously and harmoniously, otherwise it is difficult to achieve perfect decorative effects. The most important dependency relationship between the two is that the plane pattern should take into account the curvature and turning changes of the decorative surface in different parts of the three-dimensional modeling, as well as the relationship between the various parts and the overall layout, to achieve a unified decorative effect, to form a specific decorative style; decorative furnishings ceramics When products are manufactured, consideration must be given to the location of the furnishings, the environment, and people’s viewing angles, as well as illusion changes in sight, color, and shape. In short, the biggest difference from the general color printing products is that it emphasizes the shape and the use of the screen subordinate to the ceramic products.

2. Plate making

(1) Original manuscript processing The manuscript is processed so that the manuscript satisfies both the customer's requirements for the print and the technical requirements for the manuscript for the manuscript. The layout is clear, the text is clear, the lines are smooth, and the proportions are coordinated. Some factories are limited by the technical conditions of the equipment. It is necessary to photograph the black and white manuscripts after the color manuscripts are drawn.
(2) Photo separation Because the color material in the ceramic decal paper material is mostly an inorganic color material made of a metal oxide, its transparency is poor, and its hiding ability is very strong. If the three primary colors of the general color printing are stacked and printed, the hue of the printed decal paper after high-temperature colorization is different from the original hue required for the original, and there are sometimes graphic explosions during the color rendering process. Therefore, when manuscripts of ceramic decals are used for camera color separation, they should be divided into color bottom plates according to the number of hue of the original images, and the colors should be used as far as possible, and color printing should be performed using pre-prepared spot color printing materials. Individual non-foldable colors should also be stacked with active dots. This is a noteworthy issue in the separation of manuscripts from ceramic decals.
(3) The purpose of trimming the bottom plate is to compensate for certain deficiencies in the process of color separation. Such as removing the dirty spots on the layout, repairing the broken lines and broken lines, and adjusting the local contrasts of the pictures, etc., so that the original picture and text conform to the original and printing requirements.
(4) After the sample fitting and trial burn finishing, the pattern bottom plate must pass through the sample fitting and trial burn. The purpose is to check the accuracy of the pattern through the fitting, check whether the color separation is accurate through the test burning, and whether the hue and the original are The requirements are consistent. After the sample fits and the test is burned, if it meets the requirements of the original, the pattern blank will be delivered to the next process and the imposition copy will be made.
(5) Make-up copy The so-called copy make-up is to make full use of the maximum effective printing area of ​​the screen printing machine, and copy two or more patterns of the same color on the same printing plate for screen printing plates. The purpose is to reduce the number of prints, improve printing efficiency, shorten the printing cycle, and reduce printing costs.
(6) After the large-scale finishing and nested imprints are completed, the pre-finishing of the silk-screen printing screens must be carried out before the printing, and in order to distinguish between the pattern-printing pre-removal patterns, it is usually called the “large version” after the copy imposition. The purpose of the large-scale finishing is to make up for the defects of the layout, such as removing surface dirt spots, repairing broken lines, and repairing broken meshes.

After large-scale retouching, proofing should be carried out to check whether the color patterns of the patterns are accurate, whether the hue meets the originals, and comparisons are made based on the small-size patterns. In accordance with the requirements, the large version will be handed over to the printing plate making printing plate, and the large printing plate set will be delivered to the printing room as the standard printing sample when printing.

(7) Production of Screen Printing Plates The colorant particles in the underglaze decals are coarse and irregular in shape. When selecting the net, it is necessary to pay attention to the matching of the mesh hole diameter, and at the same time, the tension of the stretch net and the force of the scraper during printing should be appropriate so as to avoid the irregular blade surface of the printed material particles from scratching the net surface.

3. Decal paper and ink

(1) ceramic decal paper type

1PVB film paper. In the mid-1960s, polyvinyl butyral (PVB) was trial-produced domestically as a decal paper carrier (commonly known as large-membrane paper). This process is characterized by convenient decals and low cost, which greatly reduces the process and time compared with the original glue decals, and does not cause popping after grilling. However, the film quality is still brittle and lacks toughness. It is difficult to decal the large-area decoration and special-shaped vessels, and it cannot be displaced after being attached. Secondly, the carbonization temperature of the PVB film during baking is high, and it is difficult to grasp the low-temperature fast firing products such as enamel and glass. . The PVB membrane structure is shown in Figure 4-4. The PVB film was produced by coating two PVB film liquids on a 180 g/m2 base paper coated with a perchloroethylene adhesive. The first pass was 0.006 mm, and the second pass was 0.004-0.005 mm, and the thickness was 0.01 mm. ±0.001mm thin film. The temperature of the film dryer is controlled below 50°C, which is too high to cause film aging.

PVB film production process shown in Figure 4-5.

2 remove flower film flowers. This is a new type of decal paper widely used in the world. It is composed of paper, hydrosol layer, printing screen, and flower transfer film. Its structure is shown in Figure 4-6. The graphic of the paper film can be printed directly on the paper. The ink absorption is strong and the dot reproducibility is good. Can adapt to fine high-end products. Before decaling, it will be immersed in water, immersed in water, quickly detached from the glue paper, and then attached to a large area or shaped containers. When baking, the film can be completely decomposed below 500° C., leaving no shadow residue on the vessel.
a. Fig. 4-7 shows the process flow of the production of flowers.
b. The material composition of the floral film paper.

Bottom paper material: Double-layer paper type, which is used to hold tissue paper on 180g/m2 wood pulp paper, and then apply dextrin to the tissue paper. After peeling, 180g/m2 paper can be used repeatedly. Single-layer paper type: 80g/m2 paper is generally used.

Floral transfer film carrier: Most of the copolymers of methyl bromide acid monomers and acrylic acid (polyurethanes are also used in foreign countries), the general solution polymerization method, the use of dibenzoyl peroxide as an initiator.
A good film-forming material solution must have good film-forming properties, a certain degree of hardness and flexibility, and suitable for transfer. After silk screen printing, it was dried and reappeared on the screen. When decals were soaked in water, the screen and paper were separated and transferred to porcelain.

Silk screen printing materials: Film removal process is mostly based on 120-mesh metal or nylon mesh screen printing or flat silk printing process. In addition to achieving the general printing activity (dryness, fluidity), the linking material also requires strong conjunctival properties, does not burst after baking, and can be decomposed at lower temperatures, so the main raw materials of the linking materials are Base, then add solvent, thinner and other components.

(2) Ceramic ink Here we mainly introduce screen printing ceramic decal paper ink.

The ceramic ink is mainly composed of a colorant and a solvent. The colorant is a coloring mineral substance, and the solvent is mostly a lead borosilicate glass body, and the two are further processed into a solid melt or a suspension pigment. In order to achieve four-color printing, the key is to use three pigments with good transparency: yellow, magenta, and cyan, as well as a uniform solvent that can be used together with yellow, magenta, cyan, and black pigments.

1 solvent. The main role of the solvent in the pigment is to melt at high temperatures and firmly attach the colorant to the porcelain surface to create a luster. The experiments conducted by the Institute of Silicates show that four-color pigments must use a uniform solvent to achieve the color matching and stacking requirements. Otherwise, there will be some disadvantages in color baking. According to the research experience of high-resistance screen printing pigments, we have rationally screened, used commonality to discard harmful components, used Li2O instead of Na2O, reduced melting temperature, added stable components such as SnO2, ZrO2, and TiO2 to prevent the effect of Li2O on color rendering. Shangyu, improved the chemical stability of the pigment, reduced the coefficient of thermal expansion, and finally determined the common solvent with multi-component PbO-B2O3-SiO2-Al2O3, which is suitable for four-color colorants, but also suitable for the production of porcelain, multi-porcelain Kind of decoration requirements.

2-color agent. The role of the colorant is coloration. Specific requirements are strong coloring and high purity. For this reason, multiple components are avoided and the dopants are reduced.

Magenta: The gold red base is often used, and its composition includes Au-Sn-Al series, Au-Sn-Al-Si series, and Au-Sn series. By using the Au-Sn series as a coloring agent for magenta pigments, the purpose is to eliminate silicon and aluminum components and reduce the color baking temperature of the pigments.

Yellow agent: The use of bismuth lead yellow has the advantages of strong coloring at low temperature and bright coloration. The heat resistance of the colorant depends on the degree of crystallinity of the lead niobate solid solution. Adding ZnO to the composition can increase the crystallinity, improve the heat resistance, and add an appropriate amount of potassium nitrate to avoid the reduction of Pb3O4 and make the yellow color more pure.

Cyan agent: A cobalt aluminum zinc spinel solid solution is used. Cobalt aluminate composition