Discussion on Screen Printing Technology of Ceramic Decal Paper

Ceramic decals use general printing methods (flat, convex, concave) with a print thickness of only 5 to 10 μm. In ceramics, to achieve a three-dimensional pattern pattern, bright color, durable and non-decolorizing, the use of screen printing method is very appropriate. Screen printing equipment is relatively simple and operating techniques are easy to grasp. In domestic and foreign markets, ceramic products decorated with screen printing are gradually replacing ordinary printed paper products.

1. Glazed decal paper screen printing.

1 The production of a wire mesh frame. The frame can be made of wood and aluminum alloy. The wooden net frame needs to use high-quality wood to effectively prevent the net frame from deforming when the oil is touched. The specification is generally 55×35 cm, and the frame timber size is 4×2.5 cm.

2 wire mesh selection. Use 250 mesh nylon mesh.

3 stretch the net. Can be used manually stretching (studing) or machine stretching (adhesive).

4 plate making. According to the pattern designed by the designer, if it is a relatively simple block surface, lines, etc., it can be described on the ordinary transparencies and color separation plate. The stylized lines required are crisp and neat, reaching the design requirements of the design. The ink line should be thick when depicting the pattern, so that the shade is strong and the printing effect is good. Otherwise, there will be defects such as broken lines and poor color leakage. Such as the design of the pattern is more refined, or into a set of tea sets, the use of photoengraving method for plate making. When making plate, remember to draw the “+” character line as the reference for printing.

The screen printing plate can use diazo photosensitive adhesive, the blade of the squeegee blade is at an angle of 45 degrees, and the smaller the angle of the squeegee, the thinner the photographic solution left on the screen. Apply sensitized adhesive, coat both sides, and apply evenly. The coated screen plate is dried at a suitable temperature, and the dried screen plate can be delivered to the plate.

Shaiban light source can be used 10 to 15 40W row fluorescent lamps, light from 25 to 30 cm, exposure time is 5 to 7 minutes. The exposed screen plate was rinsed with warm water and developed. If there is a defect, it is possible to make a supplemental repair. The repaired screen printing plate can be used for the printing process and the decal screen printing.

5 Scratches. Scratch can be used right angle urethane scraper, scraper strip exposed part of the handle to 2 ~ 3 cm is appropriate. It is best to use a two-handed squeegee to print. The printing environment temperature is generally between 20 and 25°C, and the relative humidity should be maintained at about 70%.

2. Glazed decal paper prints.

The printed material of screen printing ceramic glaze paper is a special printing material. In order to distinguish it from other kinds of printing materials, it is usually customary to call it "silk ink."

Silk-printing porcelain ink is a mixture of color-developing agent (metal oxide) and flux (low-melting point boron, lead glass body), adding proper amount of linking material, and indirect printing material made by repeated rolling and grinding by ink-pressing machine. It must be roasted at a high temperature of 780 to 830°C in order to exhibit its specific color and closely blend with the ceramic glaze.

Screen printing porcelain ink also has selective absorption and reflection effects on light. Coloring agents made of different metal oxides also have different light absorption and reflection, so they come in a variety of colors. For example: oxide steel green, oxidation drill purple, silver oxide dark red... .... So the color of screen printing porcelain ink is very extensive.

Silk-screen printing porcelain ink, like common printing ink, also has three basic elements: color, brightness, and saturation. There are also bright and dark. Thick and light points. However, the miscibility of silk-screened porcelain ink is far inferior to that of ordinary color printing inks. Due to improper mixing, chemical reactions occur between the two during the baking process, which presents extremely undesirable colors, and even causes popping and gold rushing. , And make ceramics lose artistic value. Some silk-screened porcelain inks, although they can be mixed, are also subject to certain conditions. Usually, they are uniformly mixed in advance into a special color, and then printed, the color rendering effect is better. It is difficult to achieve the color effect required by the original, such as color printing using the principles of three primary colors. Taking the human skin color as an example, it is better to print the thick yellow and silky red ink of the screen printing porcelain into a special skin color. Such as the use of general color printing overlay printing, not only one more set, it is difficult to get the ideal skin color. This is due to the strong hiding power of the screen printing porcelain ink, poor transparency, different cosolvents contained therein, different baking and firing temperatures, and the formation of chemical reactions between baking and baking. This is also one of the reasons why screen printing ceramic glaze decals cannot be printed using the principle of three primary colors at present.

Knowing the above principles, when designing a manuscript, photographing color separations, and preparing special color printing materials, try to avoid color reset (superimposed colors) and use color juxtaposition, or use a combination of thousands of threads to reduce ink layer overlap. Thickness (must be printed first, then silk screened, which reduces popping and avoids viewing patterns).

Even if the colors are not stacked, besides taking into account the mutual chemical reaction during baking, consideration should also be given to balancing the color temperature between the screen printing porcelain ink as much as possible. When stacking colors, it is necessary to print on the F surface with low color temperature, and the temperature is high on the stack. This is because during the baking process, when the temperature of the lower silk screened porcelain ink layer starts to evaporate and evaporate, the laminated high temperature silk screened porcelain ink layer still has unmelted particle gaps, allowing the lower silk screen printing ink layer to melt. Gas passes to avoid popping flowers.

The same screen printing porcelain ink, baking and coloring temperature is a difference, the general color of the porcelain ink contains more flux, color firing temperature is lower, color deep with less flux, color burning was The color temperature is high. Different fluxes, their pH values ​​are not the same, have a greater impact on color rendering, for example, gold red material with gold as a coloring agent, if you use alkaline flux, color burning effect is good , red and bright. If acid flux is used, color rendering is poor and purple and dark.

The purpose of adding flux in screen printing porcelain ink is to increase the brightness of the pigment, make the color appearing after the burning of the roasted flower more vivid, and make the screen printing porcelain ink fuse with the ceramic glaze by burning the kiln.

Silk-screen printing porcelain inks have more coarse particles and larger specific gravity than ordinary color-printing ink pigments. This has a great influence on the quality of screen-printed ceramic glaze decals, especially for photo dot printing, with a small number of dots. It is difficult to reproduce. Although the fineness index of screen printing porcelain inks stipulates that the grain fineness below 15 microns should not be less than 92%, the maximum grain size should not exceed 30 microns, and it is difficult to duplicate fine manuscripts. In the process of plate making, in order to avoid the sawtooth shape of the edges of the pattern, it is required to print the plate at a ratio of 1:4. That is to say, the bottom plate of the screen with 100 lines of the screen is used for screen printing, and 400 lines or more of screen printing must be used. If the number of photo screens is higher, the aperture of the screen used will be smaller and the number of ceramic ink particles that can pass through will be smaller, which will not only make the reproduction of the low number dots poor. And the pattern is imaginary and the edges are hairy. In order to improve the quality of printed products, the requirement for screen printing porcelain ink is that the finer the particles, the better. During printing, the remaining porcelain ink in the screen should be removed after each printing for a period of time, the new porcelain ink should be replaced, and the printing plate should be cleaned to remove the particles embedded in the mesh to ensure that enough porcelain ink particles are missed. On the substrate.

The linking material for screen printing porcelain ink consists of a solid resin and an organic solvent that dissolves the resin. The main requirements for screen printing porcelain inks on the linking material are good film formation, low decomposition temperature, no popping, no flashing, no wire drawing, good leveling performance, and suitable drying. When selecting the linking material, in addition to noting the above requirements, there is a requirement that the film is not etched.

The printed film on the screen printing ceramic glaze decal paper is polyvinyl chloride film, and its film thickness is only about 0.01mm. When selecting the organic solvent, organic solvent with small amount of alcohol should be used as far as possible, if the alcohol content is too high, It is easy to remove the alcohol film and cause cleaning, which affects the quality of printed products.