This article describes in detail the process of decorating gel coats with decals, from the types of decals, pigments for gel coat decals to the various processes in the decorating process, all of which are explained one by one, and for some links in production Technical specifications, data and suggestions were made to achieve the best decorative effect.
Decal paper printing is a kind of decal paper printing. Decal paper printing can be divided into ceramic decals, metal decals, enamel decals, bamboo and wood decals, rubber decals, glass decals, etc. Ceramic decals can be divided into large-membrane glaze flower paper (standard quarto) and small-membrane flower paper. The former is moderately priced and the overall effect is also good. The latter is better than the former, but the price is higher. As far as the ceramic industry in the province is concerned, most manufacturers choose large-film glaze paper. This technique is slowly being used on the surface of the gel coat.
Decal paper printing can be divided into several types of flat printing and screen printing or a combination of flat screen. At the appointment of "Screen Printing" magazine, we will introduce the decal decoration process to your colleagues. Decal screen printing is different from other types of screen printing, plain printing and color packaging printing. The general color printing is to produce the effect through the overprinting of the three primary colors, and the special decal pigment is an oily powdery organic pigment composed of metal oxides. It has the characteristics of dullness after printing, color change after stacking, and color change after baking. Therefore, the printing method of ceramic decals adopts the step printing method. Generally speaking, according to the requirements of the manuscript, it is necessary to make multiple or even more than ten plates to meet the requirements of the manuscript. The decal printing process sequence is now described as follows.
Trial production stage
Design, photography, color separation: According to the user's manuscript or their own creative design, the color separation of the camera can be separated by camera or manually. According to the characteristics of ceramic pigments that do not change color, generally speaking, the main flower red, blue and green should be separated, red should be divided into three (light, medium and dark), blue and green should be divided into two (light and dark), and finally It is outlined with black or gray lines. (At present, large factories outside the province have used the desktop system for design and production, and the quality and efficiency have been greatly improved.) After making the color check and meeting the requirements, make a small picture (single spell), and use the small version of the plate for manual proofing After roasting, the sample is adjusted in various aspects until it meets the requirements. It is sent to the porcelain factory for trial firing, and after being approved by the user and ordered, mass production is carried out on the machine.
Mass production stage
1. Imposition and continuous drying
The imposition can be carried out according to user requirements and backing paper standards, but the layout should not be less than 43cm × 34cm (national standard). Hand color can be used for less color, and the color of ceramic flower paper is generally not less than 5 colors, more than 10 color times, and the accuracy of overprinting of manual imposition can not meet the requirements. It is best to use a continuous drying machine Perform continuous sun exposure. In this way, the quality requirements for overprinting can be guaranteed.
Second, printing
Because the printing process of screen printing and offset printing is consistent with the general printing requirements, it is omitted.
The photosensitive adhesive should use the diazo photosensitive adhesive special for DS series decals of Beijing Taipingqiao Printing Material Factory. One-component or two-component can be used as required. The single-component photosensitive adhesive has been formulated with the sensitizer and glue, and can be used directly.
3. Coating
The upper membrane can be divided into two stages: distribution membrane and upper membrane.
(1) Film distribution ratio
Polyvinyl butyral resin: methanol (ethanol) = 1: 5
Butyral should be selected for about 16 ~ 18s. First draw methanol (ethanol) into the reaction pot according to the amount, put in butyral with stirring, turn on the heating switch, the temperature is controlled at 50 ~ 60 ℃, stir for 3h, after checking that the butyral is completely dissolved, it can be discharged for use Membrane material needs to be completely melted, no lumps, no impurities, preferably slightly concentrated, methanol (ethanol) can be added to adjust the concentration when the membrane is applied).
(2) Upper membrane
For paper decals dedicated to decals (wood pulp paper), first use a paper cutter to repair the four sides to ensure that the size reaches 54cm × 39cm.
The equipment uses a special coating machine (the principle is similar to the coating machine). Adjust the gap between the material roller and the printing roller, so that the film material is evenly coated on the base paper. Generally requires two times (no need to turn around), the second time after drying for the first time (every time to open the paper, fan cooling), the film thickness standard is 0.01 ± 0.001mm, can not be thick , Can be adjusted by micrometer measurement.
The film drying tunnel should be kept between 70 ～ 80 ℃, the temperature is too high, the color is not bright, the bottom paper is scorched, and if it is too low, it will foam, dry, and form adhesion. In short, the film layer needs to be bright, the thickness is up to the standard, and it is uniform. There is no residual film residue on the edge, no adhesion, and no damage. The dried bottom paper can be piled up neatly after counting the number of shuttles to prevent dust. Generally, it is best to store the film for about 15 to 20 days (leveling, setting).
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Fourth, rolling ink
The decal materials are divided into flat printing and screen printing pigments. Pigments from different manufacturers such as offset printing, screen printing, high temperature and low temperature cannot be mixed. Looking at the domestic manufacturers, the best produced by Shandong Sedek Company is as follows:
3A series: barbecue temperature 800 ～ 850 ℃, best 830 ℃;
3D series: barbecue temperature 780 ～ 800 ℃, best 750 ～ 780 ℃;
Four-color pigment: the same principle as color printing, good reducibility, has reached the international level;
High-temperature fast-burning pigments: Barbecue temperature 1006 ~ 1200 ℃, released in 3 minutes; lead-free and cadmium-free pigments: pigments do not contain lead and cadmium, in line with environmental protection requirements.
The pigments of this series are in powder form before being formulated, and the particle size is 5μm≥90%. There are more than 10 kinds of basic color screen printing and flat printing, which can basically meet the color needs of various floral surfaces.
Mixing baking pigments: carefully mix the pigment components and printing volume determined according to the proofing. The matched pigments should be baked in an oven at 90 ～ 100 ℃ for half an hour. No moisture is allowed in the pigments (not more than 0.5%) ), Otherwise it will cause the product to burst, resulting in waste products.
The baked pigment is added to the screen-printing and flat-printing ceramic special connecting materials according to the proportion while hot. After manual stirring, it is evenly rolled on a three-roll mill. Generally, each color bar is used for 2 to 3 times, the first rough rolling, and then the second fine rolling (adjusting the roller gap). The rolled pigment should be rolled and used. The remaining pigment after printing can not be discarded. Just roll it again.
Five, screen printing
Pre-press processing of base paper: Because the base paper is composed of paper, plastic film and butyral film, after hot air drying, the deformation of the three materials is different, so pre-press processing of the base paper must be performed. Before the official printing, the backing paper is not installed with the screen printing machine, the doctor blade or the manual conveying method is sent into the oven for finalization, so that the deformation of the backing paper in the future multi-color secondary printing is minimized To ensure the overprint quality of the product. This process is called empty car, commonly known as air pressure, and is essential for screen printed ceramic decals. It should be noted that the temperature of the empty car must be controlled to be basically the same as the temperature of the official printing.
The drying method of screen printing pigments is hot air drying, without adding any desiccant to the pigments, so the oven temperature should generally be maintained at 30 ~ 40 ℃, or according to the local temperature changes flexibly grasped, based on the principle of products drying out of the oven Keep the entire batch of products at the same temperature during the printing process, and try to avoid the temperature from suddenly changing to cause the paper to deform multiple times.
Six, flat printing
The pre-press treatment of the paper is also essential. It can be carried out with or without water. The air pressure is performed once. The purpose is the same as screen printing. Flat printing pigments and connecting materials and screen printing connecting materials can not be mixed, should choose ceramic decals for flat printing special connecting materials, flat printing pigments dry slowly, you can add 2% white dry oil, disable red dry oil, after printing a color and stand upright The paper does not need to be heated and is naturally dried. After the first color is completely dried, the next color can be printed. The other printing requirements are consistent with the general flat printing.
Seven, trial burn
Before proofing and uncovering the film in mass production, one-thousandth of a sheet should be drawn for trial firing. First, gently scratch the pattern for trial firing with a blade (note that no force can be used to avoid scratching the base film), and apply the pattern to the porcelain with methanol (ethanol) and water (1: 3). Blisters, bubbles, and then gently wipe the pattern with cotton to eliminate excess water and bubbles, so that the paper and porcelain are tightly combined, and after being dried, put them into a resistance furnace to heat up.
Set the trial firing temperature according to the selected pigment (high temperature, low temperature, etc.). First, do not close the furnace door, wait for the temperature to rise to about 150 ℃ and observe that the bottom film turns black (the bottom film is carbonized). When the temperature rises to the set temperature and the power is automatically cut off, the furnace door is not opened, the temperature is kept for about 15 minutes, and finally the furnace door is opened. After about 2 hours, when the furnace temperature drops to room temperature, the sample can be taken out. If it meets the requirements, it can enter the next process.
8. Inspection and peeling
Inspection and peeling can be performed at the same time. First use a knife to pick out the peeling opening (the picking post should be used instead of the bite), then use a smooth bamboo film to take the film, each flower paper pad is a copy paper Liner to avoid sticking. The backing paper and flower film should be flat and wrinkle-free, stacked neatly, and the printed crosshairs are basically aligned. In the inspection when peeling off the film, when the whole sheet is unqualified, a red pen shall be used to mark the backing paper, and the number of sheets shall be folded according to the actual number of flowers.
The uncovered flower film is rolled into a roll with 100g kraft paper lined per 100 sheets, and a thick lined paper is wrapped (a paper tube or a plastic bag can also be used). A label and a certificate are attached. Boxes are shipped from the factory.
Inspection of lead and cadmium leaching amount: According to international standards, for products decorated according to floral design requirements, the base lead leaching amount is less than 7ppm and cadmium leaching amount is less than 0.5ppm, which needs to be sent to a special agency for inspection.
To clean the film, use a single-sided scraper to brush off the residual film, dust, and oil stains on the bottom film. Be careful not to scratch the backing paper so that the backing paper can be used repeatedly.
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