Analysis of common transfer methods in the most po

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Analysis of common transfer methods of transfer printing

transfer printing refers to a printing method that presents irregular undulations on the surface of some substrates, or objects that have been formed, or soft materials that are not convenient for printing on the printing machine. In order to print images and words on the surface of these substrates, images and words must be printed on a material called intermediate transfer carrier first, and then the carrier transfers them to the substrate through some methods, such as heating, wetting, pressure, etc., and finally forms a printed matter

transfer printing is classified by transfer mode, including direct pad printing and indirect pad printing. Direct pad printing is to use the pad printing head to suck the ink on the concave plate on the special pad printing machine, and then transfer it to the substrate. It is mostly used for irregular concave convex containers, small decorations, toys and tableware on the surface. Indirect pad printing is to use special transfer paper or film to print the pattern first, and then transfer it to the substrate. It is mostly used for ceramic decal printing, textile printing, commodity label printing, etc. According to the classification of transfer technology, there are wet transfer, heat transfer and pressure transfer

direct pad printing is the principle of using gravure printing to brush around key subdivisions such as flexible battery technology, flexible lighting technology, flexible circuit and sensing technology, flexible display technology, flexible neuromorphological devices and systems, that is, after all the ink is coated on the concave plate, the ink on the blank part of the convex surface is engraved with a scraper, leaving only the ink on the pattern part of the concave surface, and then the pad printing head made of silicone rubber is used to apply pressure to stick out the ink, Then transfer to the substrate. Pad printing machine is the main equipment of pad printing, in which pad printing head plays the role of transfer printing. Therefore, pad printing plate, pad printing head and pad printing ink constitute the three elements of pad printing process, and the pad printing process is automatically completed by the pad printing machine. On the premise of determining the pad printing plate and the pad printing head, the quality and performance of the pad printing ink has become the decisive factor of the pad printing effect

indirect pad printing takes transfer printing as an example. The transfer processes include sublimation method, swimming method, melting method and ink layer stripping method

[sublimation method] using the sublimation characteristics of disperse dyes, in the transfer process, when the paper reaches the transfer temperature, the dyes begin to volatilize or sublimate, and form concentration volatilization between the paper and the fiber. When the printed fabric reaches the transfer temperature, the dyes begin to adsorb on the fiber surface until a certain saturation value is reached

[migration method] the dyes in the ink layer of transfer paper still need to be selected by imported quality according to the fiber properties. The fabric is first soaked and rolled with a mixture of color fixing additives and pastes, and then in the wet state, the dye is transferred from the transfer printing paper to the fabric and fixed by hot pressing. Finally, it is wet treated by steaming, washing and so on. When transferring dyes, there should be greater pressure between the fabric and the transfer paper

[ink layer stripping method] use the ink that can produce strong adhesion to the fiber after encountering heat. Under a small pressure, the whole ink layer can be transferred from the transfer paper to the fabric, and then make the corresponding fixation treatment according to the nature of the dye

at present, our common transfer methods are heat transfer and water transfer

heat transfer: use temperature to melt the stripper and adhesive layer of the heat transfer carrier film and apply pressure for transfer

water transfer: use water pressure and activator to dissolve the stripping layer on the water transfer carrier film for transfer

now we will briefly introduce the process problems involved in the printing of pad printing technology on glasses, so that you can understand the general situation of the application of pad printing technology in the glasses industry

1. ink selection

ink selection plays a very important role in pad printing technology, which is widely related to the substrate materials involved in pad printing technology. As the mirror frame is made of metal, the ink is required to have better adhesion on the metal surface. Now the two-component ink is widely used, and the drying method is drying. The printing of lenses requires glass ink, which is usually a two-component ink and dried by drying. The cured ink layer of two-component ink has the characteristics of high hardness and good adhesion, but the operation is a little troublesome

the usage of two-component ink is briefly described as follows:

(1) first add hardener to the ink according to the ink instructions, stir it evenly, and pour it into the oil pan for printing. As the two-component ink will cure slowly, the amount should be controlled

(2) after printing, it should be placed in the drying oven for drying treatment to speed up the drying speed. Generally, the drying time of two-component ink at room temperature is up to 10 hours, which will affect the production efficiency. It is ideal to use the drying method. Generally, the drying temperature is between 150 ℃ ~ 180 ℃, and the drying time is 5 ~ 10 minutes

2. Pad printing adhesive head

the selection of pad printing adhesive head in pad printing process is very important. First of all, the shape of the pad printing adhesive head should be able to print to the specified position, and secondly, the deformation should be small. Because the printing area of the mirror frame is very small, the pad printing rubber head should be slightly pointed. Through the test, aluminum connectors with potential safety hazards are also used. A7 rubber head with a sectional area of 38mm is more suitable. The printing effect of A3 rubber head is also very good, but due to the slightly smaller section, the printing deformation is slightly larger

the hardness of pad printing rubber head is another index that should be considered when selecting. The softer rubber head has wider adaptability, but the printing image and text deformation is large. Especially for printing products as small as spectacle frames, the text font is very small, and the text deformation is large, which is easy to make the text lines adhere and become blurred, so it is better to choose a harder rubber head. Our test result is that the rubber head with a shore hardness of 32 degrees can achieve the best printing quality

for the printing of the nose rest, the rubber head with a smaller cross-sectional area should be selected in consideration of the location limitations. Our test results show that the rubber head with a cross-sectional area of less than 15mm is more suitable, and the hardness should also be more than 32 degrees

3. steel plate

the printing plate of the pad printer is steel plate, and the method of making steel plate is corrosion method. The printed pictures and texts of the mirror frame and lens are very small, so the size of the steel plate does not need to be too large. According to the standards of various industries in pad printing, both 75mm l00mm and 100mm steel plates can be used, and the length of the longest side of the printed text of the spectacle frame is only 20mm, so 75mm 100mm steel plates can be used for the text

the steel plate is made by traditional corrosion method. Because the font is very small and the exposure time is shorter, the steel plate with uniform depth can be obtained

when making steel plates, the depth control is a major indicator. Too deep depth is easy to cause paste, the transfer of ink is affected, and the strokes of the font are easy to be uneven in thickness, the spacing between strokes becomes smaller, and the sharpness decreases. The disadvantage of too shallow depth is also obvious, which is that the color saturation of the font is not high, and the color is difficult to achieve eye-catching effect. Our test result is that the depth of 19 m is the best

4. Pad printing machine

the printing area of the spectacle frame is small, which is only the trademark of the printing company, so it does not involve complex graphics and texts, nor does it involve chromatic registration. It is better to choose a machine with a small area of monochrome pad printing machine

5. Fixture

in the special printing industry, making fixtures is a basic work. Generally speaking, the production fixture is mainly to ensure that the printing area of the substrate and the rubber head have a relatively fixed position, so as to ensure the unity of product printing. At the same time, it is easy to achieve accurate overprint when multi-color overprint is involved, so the position of fixture in pad printing process is indispensable. The inner edge of the spectacle frame is the area for printing pictures and texts, and this position must be clamped by a fixture to ensure that it is parallel to the pad printing rubber head. During the printing process, the spectacle frame cannot be loosened, and it is required to have a good tightening effect. The fixture cast with crystal glue should be the first choice

the method of crystal glue casting is based on the principle that unsaturated polyester resin solidifies under the action of hardener, which is very easy to cure and form according to the shape of the product. No matter how complex the structure of the spectacle frame is, the fixture made by this method can fix the spectacle frame well and meet the printing requirements. The production method is: first mix and stir the resin components a and B evenly and pour them into the prepared paper form until the resin appears gelatinous state, and then take out the spectacle frame

although the pad printing of lens frame and lens is a very simple process, we can see the characteristics of the pad printing process:

pad printing is very suitable for products with small printing area and irregular printing position; It is the special parts of glasses that need to be printed that make the pad printing process wonderful

from the perspective of printing process, in order to achieve exquisite printing effect, selecting high-quality pad printing ink and high hardness pad printing rubber head are two factors that must be paid attention to

the effect of pad printing is closely related to the quality of fixtures

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