Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F23/00—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing
  • B41F23/04—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing by heat drying, by cooling, by applying powders
  • B41F23/0403—Drying webs
  • B41F23/0406—Drying webs by radiation
  • B41F23/0409—Ultraviolet dryers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F23/00—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing
  • B41F23/04—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing by heat drying, by cooling, by applying powders
  • B41F23/044—Drying sheets, e.g. between two printing stations
  • B41F23/045—Drying sheets, e.g. between two printing stations by radiation
  • B41F23/0453—Drying sheets, e.g. between two printing stations by radiation by ultraviolet dryers

Definitions

• the present invention relates to an ultraviolet ray apparatus for printing machines and to a printing machine comprising such an apparatus.
• printing machines for example but not only graphic art printing machines, which employ ultraviolet ray light sources for the polymerization of inks, paints, lacquers and the like.
• ultraviolet ray sources are used for the polymerization of inks, paints and the like.
• UV-reactive inks allows to speed up the printing process further and obtain a quick drying of the inks themselves by means of exposure to ultraviolet rays.
• UV lamps ultraviolet ray apparatuses
• UV lamps comprise other components besides a lamp as explained in greater detail below, for drying the inks used in high-speed reel and sheet printing processes on paper and non-paper supports, and the results which can be achieved are good.
• a non-uniform distribution of the ultraviolet rays emitted by the UV lamp regretfully occurs when the exposure is static or at slow speed, i.e. when the sheet remains stationary for the entire exposure or remains partially stationary, e.g. if the support to be printed advances intermittently at slow speed.
• This concentration of UV rays in a focal point creates a non-uniform polymerization of the ink or of the lacquer or of the UV reactive paint and concurrently a temperature increase of the support itself.
• the temperature increase of the printing support is even more harmful when printing uniform backgrounds with glossy or matte inks on supports having very low melting or deformation points.
• this is the case of films or labels or supports made of plastic material in general, in particular of polymeric material, which have very low melting or deformation points.
• the deformation of the support material consequent to the heating caused by the ultraviolet lamp influences printing quality: color registration becomes very difficult if not impossible to obtain because a real expansion or contraction of the support to be printed occurs.
• ultraviolet apparatuses which comprise a reflector, which is - in general - a surface having a parabolic profile on a cross plane, in addition to the UV source (UVA, UVB, UVC ray) itself, i.e. the lamp itself.
• Such a reflector is thus arranged over the lamp, on the side opposite to the support to be printed, as known in the prior art.
• such a reflector is envisaged in order to reflect the UV rays that the lamp emits in all directions to convey the energy towards the support.
• the concentration of UV rays by the reflector also implies the concentration of infrared rays, and thus an accentuation of the heating phenomenon of the support to be printed in the case of static or slow-speed printing processes in particular.
• an ultraviolet ray apparatus of the type comprising at least one source of ultraviolet rays, at least one reflector adapted to reflect the ultraviolet and infrared radiation emitted by said source and arranged, with respect to the lamp, on the side opposite to the support to the printed, and at least one optical element interposed between said source of ultraviolet rays and said support to be printed.
• the apparatus according to the present invention is further characterized in that said optical element is adapted to diffuse the rays emitted by the ultraviolet source either coming directly from the source or reflected by said reflector.
• FIG. 2 shows, in section, a detail of the ultraviolet ray apparatus according to the present invention taken along a vertical cross plane;
• FIG. 3 shows a perspective view of a detail of the apparatus according to the present invention, in particular the optical element adapted to diffuse the rays emitted by the ultraviolet source of said apparatus.
• a printing machine 100 of the type considered here is shown by way of example with particular reference to figure 1 .
• the present invention relates to an ultraviolet ray apparatus of the type adapted to be installed on a printing machine 100, e.g. of the type used in flexography printing processes, in which one or more apparatuses 10 adapted to emit ultraviolet rays are provided to carry out the polymerization of inks, paints and the like.
• the support for example paper but also polymeric material films, is moved so that it passes through various printing stations.
• the ultraviolet ray apparatus 10 comprises at least one source of ultraviolet rays 10a, at least one reflector 10b adapted to reflect the radiation emitted by said source 10a and arranged, with respect to the source, on the side opposite to the support 20 to be printed, and at least one optical element 10c interposed between said source of ultraviolet rays 10a and said support to be printed 20.
• said source 10a of ultraviolet rays is interposed between said reflector 10b and said optical element 10c.
• the ultraviolet ray device 10a of the apparatus 10 according to the present invention emits the light radiation in all directions.
• said light source preferably consists of a discharge lamp, in particular a mercury lamp, which is ionized by effect of an electric arc generated between two electrodes arranged at the ends of said lamp.
• ultraviolet ray sources of this type emit radiations also in the infrared (IR) field. Such radiations are responsible for the heating of the support 20 to be printed, which can reach a temperature of even 80 ° C.
• the UV apparatuses of known type in the prior art have attempted to solve the problem of heating of the support 20 to be printed, which heating, as mentioned, is undesired because it causes expansions of the support itself which prevent maintaining the color print in register, by allowing said support 20 to slide on cooled cylinders.
• the need to provide cooled cylinders complicates the machine making it more complex and consequently more costly and cumbersome.
• a specific cooling system provided with a cooling liquid circulation pump must also be provided in addition to a supplementary cylinder, which must be provided and moved.
• filters are used capable of reflecting the radiation in the infrared wavelength, said filters being interposed between the light source and the support to be printed.
• the infrared filter ends up heating the support 20 in all cases by radiation, not allowing to solve the problem of the heating, and thus of the expansion, of the support 20 to be printed in an effective manner.
• the UV source 10a reaches 800 ° C in operating conditions, while the infrared filter, generally made of quartz, can even reach temperature close to 200 °C.
• the UV apparatus comprises an optical element 10c interposed between said ultraviolet light source 10a and said support 20 to be printed.
• Said optical element 10c is adapted to diffuse the rays emitted by the ultraviolet source either coming directly from the source or reflected by said reflector 10b.
• said optical element 10c will include a concave-convex lens, preferably a concave-convex lens having the two surfaces, the concave and the convex ones having substantially the same center of the radii of curvature.
• such a radius of curvature may be comprised between 50 mm and 300 mm, preferably will be 70 mm.
• said optical element 10c will be interposed between said ultraviolet light source 10a and said support 20 to be printed so as to have the concavity face towards the support.
• the optical element 10c can diffuse the incident radiation.
• the optical element 10c is struck by the radiation emitted directly by the ultraviolet light source 10a and by the radiation reflected by the reflector 10b, and diffuses such a radiation so that the ultraviolet rays are either made to diverge or are parallel to one another.
• the support 20 to be printed is struck by a diffused radiation, not concentrated in a focal point or on a limited area of the said support, as occurs in the prior art.
• the IR infrared component of the radiation is also diffused by the ultraviolet light source 10a, thus solving the problem of heating of the support 20 to be printed.
• the infrared component of the radiation is responsible for the heating of the support and/or of the IR filter directly and then, by radiation, of the support in the apparatus of the type known in the prior art.
• the apparatus of the present invention optimizes the polymerization process of the ink and/or of the light-sensitive ink used in the printing process.
• the diffusion of the ultraviolet and infrared rays avoids the heating of the support 20 to be printed and the excessive polymerization of the ink and/or the paints allowing to control all the steps of the printing process in optimal manner.
• the uniform diffusion of the ultraviolet and infrared rays causes the quantity of energy of the electromagnetic waves which radiate the support 20 to be printed, to be also uniformly distributed and there are no concentrations of energy in a focal point or in a small area of the support 20, thus avoiding in particular the detrimental effect of the concentration of infrared rays, in particular in printing processes on plastic films.
• the concave-convex lens of the optical element 10c is made of quartz glass, or other suitable material, and may have variable size. More in particular, the lens will have the same longitudinal dimension of the lamp to which it is combined, more in general from 60 mm to 2000 mm in length, while the radius of curvature of the lens may be preferably comprised between 50 mm and 300 mm.
• the concave-convex lens may be obtained from a quartz glass tube having thickness of 2 or 3 mm and radius of curvature comprised between 50 mm and 300 mm, preferably 70 mm.
• optical element 10c belonging to the apparatus according to the present invention is shown as consisting of a concave-convex lens, it is apparent that said lens may have any geometry, e.g. meniscus, flat-concave or concave- convex with different radii of curvature for the two surfaces, providing it is a negative lens, i.e. diverging.

Landscapes

• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Supply, Installation And Extraction Of Printed Sheets Or Plates (AREA)
• Printing Methods (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=52682819

Family Applications (1)

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• 2016
  • 2016-02-19 WO PCT/IB2016/050899 patent/WO2016132324A1/en active Application Filing
  • 2016-02-19 EP EP16714527.5A patent/EP3259133A1/de not_active Withdrawn

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