Rotogravure production line application of UV curing process

Rotogravure production line application of UV curing process matters needing attention

  At present, there is no mature UV gravure color is put into the actual production of the printing enterprise, usually at the end of the production line for rotogravure printing on a color set UV light oil. This is because the requirements rotogravure printing ink viscosity is low, in about 20 seconds (with 4 # cup measurement), and the UV color with links in the material after joining pigment resin viscosity will slants big, again not adding solvent to reduce viscosity. UV light oil because do not need to add ink, so can achieve rotogravure viscosity requirements. Compared with using common roll coating UV light oil, by way of gravure coating UV light oil, there is a lot of special process technical issues, should pay special attention to.

    (1) substrates with UV light oil adhesion problem

  If on the plastic film coated UV light oil, to ensure that the surface tension of the film is 40 ~ 42 mn/m, or UV light oil will not firm adhesion, under external force in light oil reservoir is very easy to fall off into small flake. In addition, to ensure that the ink completely dry before polishing, such as front-end using water-based ink printing, printing substrates for paper, although the paper on the surface of the ink appears to be dry, but there may still solvent residual, if coated UV light oil at this time, when the UV light oil curing, residual solvent of alcohol can reverse wetting UV light oil reservoir, lead to fall off when UV light oil layer in the next working procedure.

  (2) of UV light oil flow problem
Rotary gravure press speed, UV light oil liquidity is poor, often lead to light oil flow flat, so often appear low brightness, dotted or corrugated UV light oil reservoir. The main factors affecting UV light oil flow flat have anilox roller mesh, UV light oil viscosity and temperature, etc.

  (3) the UV light to produce a large amount of heat, easy to deform the substrates or dehydration
Substrates due to UV lamp at higher temperature, the surface temperature is higher, the UV curing generally adopts chimney water cooling method, but only to prevent the lamps and lanterns is bad, not solve the problem of high temperature of substrates surface. Lower the temperature in the surface of substrates can adopt the following methods.

    ①Using efficient UV lamp. Imported high power UV lamp UV release proportion about 30%, but most domestic UV lamp can reach 15% ~ 15%.

    ②Between UV lamp and the substrates and insulating glass, usually 3 mm thick imported quartz glass absorbs 10% of the ultraviolet light. Although after adding insulating glass can reduce printing speed, but the poor resistance to high temperature of 15 microns below is essential for PVC film printing, printing is not necessary to add other material.

    ③Reduce the amount of UV lamp, improve each UV lamp power. Substrates is situated in the process of heat absorption, the process is slow, so quickly by high temperature can keep heat into the interior of the substrates. According to this principle, the paper under the UV lamp through time as short as possible, this will require less the amount of UV lamp, the opening width of the lampshade is small, and improve the power of each lamp. For example, the British nordson UV lamp shade opening width is only 70 mm, Beijing Mr Bo UV lamp shade opening width is 75 mm, but these two kinds of UV lamp power is very high. Currently, the existing power density on the market for the 400 w/cm of the UV lamp sales.

  (4) the UV lamp energy saving problem

  (1) using a high efficiency of UV lamp.
  (2) the correct matching UV lamp power reservoir thickness, the printing speed and light.
  (3) with low consumed power, internal friction is generally not less than 10% of transformer power supply without transformer power supply, such as Switzerland Pantoc UVC power production consumed less than 1%, and because of the quick start and stepless adjustable power function, but also power saving 30%.
  (4) use of smaller diameter of UV lamp. Ultraviolet light from the center of UV lamp, using molecular collision gradually transfer heat to the outside, the center temperature up to 1700 ℃, but the UV lamp internal molecular collision spend a lot of energy and useless, so you should use a smaller diameter of the UV lamp, such as high power is only 6 mm in diameter water-cooled capillary UV lamp.
  At present, a lot of UV lamp to do small diameter, the reason is that after UV lamp smaller diameter, tube wall load will increase, resulting in wall bulge deformation, the longer the light tube, deformation, the more obvious. Therefore, it is recommended that companies take short and thin tube diameter used after docking.
  (5) reduce the UV light. UV optical path is the UV lamp radiation light to walk on the surface of the substrates and the refractive index of the product. To reduce the UV optical path is to make small reflectors as far as possible, the UV lamp to short distance on the surface of the substrates as far as possible. Measurement results show that the ultraviolet light attenuation and UV is proportional to the square of the optical path, UV light range increased to 10 mm, UV light can reduce about 5%.
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