Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C1/00—Forme preparation
  • B41C1/02—Engraving; Heads therefor
  • B41C1/04—Engraving; Heads therefor using heads controlled by an electric information signal
  • B41C1/05—Heat-generating engraving heads, e.g. laser beam, electron beam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F17/00—Printing apparatus or machines of special types or for particular purposes, not otherwise provided for
  • B41F17/001—Pad printing apparatus or machines

Definitions

• This invention relates to a process of engraving an image in a support, wherein said image is provided for pad printing.
• Pad printing is a known technique in the field of printing techniques, which is used for printing and decorating all kinds of objects, made from various materials. This goes from medical tablets to all kinds of caps for closing containers and even electronic apparatus such as fuses and so on. Pad printing is an appropriate technique essentially for printing non-plane surfaces. Pad printing is an indirect printing by means of an elastic pad, which transfers the image to be printed from a deep printing plate to the object to be printed. This technique is described more in detail in EP-A 98870256.9 .
• ink is applied on an engraved printing block or printing plate. Subsequently, the ink is scraped off from the surface of the printing plate, and the ink remains only in the engraved parts of the plate. This remaining ink is taken over with a pad and is deposited subsequently on the surface to be printed. Thanks to the flexibility of a silicone pad, very irregular surface can be printed.
• printing biock plates are used for pad printing, i.e. printing blocks in synthetic material, printing blocks in thin steel with a thickness ranging from 0,2 to 2 mm and thick steel printing blocks with a thickness between 5 mm and 10 mm.
• An image is engraved in the printing block.
• this image has a depth, which is mostly comprised between 10 and 80 ⁇ m.
• an image in the printing blocks for pad printing is almost always carried out in a photochemical way. Firstly a film is thus made from the desired image. Subsequently, the film is put on the printing block, whereby the printing block must be provided with a photosensitive layer. Afterwards, the printing block is exposed together with the film during a few minutes in an exposing apparatus specifically provided therefor. After exposing, the printing block is developed and the image is finally etched out by means of chemical etching products.
• Positioning the film on the printing block with respect to a reference angle of the printing block must be carried out manually and requires thereby the needed precision.
• This invention aims at remedying the aforementioned drawbacks.
• a process as defined in the main claim which is remarkable in that the engraving of said image is effected in that a high energy beam is directed on said support according to a selected image pattern and under set parametric working conditions.
• said energy beam is formed by a high energy ray, particularly a laser beam, which is brought into a relative motion with respect to the support to be engraved under automatic control by an external control unit.
• said energy beam is a pulsed energy beam.
• said support is formed by a plate-like element provided for linear pad printing.
• said plate element is formed by a printing plate which is composed of at least one layer of evaporabte material, wherein the surface to be engraved of the plate element is evaporated selectively under the action of said energy beam thereon.
• a metallic plate is exposed to the action of the energy beam, preferably a steel plate.
• a ceramic plate is exposed to the action of said energy beam.
• a plate of glass material is exposed to the action of said energy beam.
• said support is made from a basis plate and a layer to be treated, which is exposed to the action of said energy beam and which is deposited on the basis plate.
• More particularly said basis plate is made of metal.
• said basis plate is made of a material, the stiffness and/or the hardness of which is greater than the one of the layer to be treated, particularly of a synthethic material.
• said basis plate is made of a composite material.
• said layer to be treated is made of a ceramic layer having a determined thickness, particularly wherein the thickness of said layer to be treated is much smaller that the one of the basis plate.
• the combination thereof with metal as a basic layer shows an advantageous behaviour.
• Said layer to be treated can also be made of an amorphous material, particularly a glass material. According to a remarkable embodiment of the invention, said layer to be treated is made with a thickness which is selected in correspondence with the selected engraving depth in the printing plate.
• said layer to be treated can be selected with a thickness which is greater than the selected engraving depth.
• Figure 1 is a diagrammatic view of an arrangement provided for carrying out the process according to the invention.
• Figures 2 to 5 show a cross section of respective plate elements to be treated according to the process of the invention with variants.
• Figures 6 and 7 represent a respective top view of printing blocks engraved according to said process with a variant.
• the arrangement represented in Figure 1 comprises a laser 7, for example a so-called Yag laser, provided as an engraving means for a printing plate 10 to be used in pad printing, particularly in linear pad printing.
• the laser apparatus emits a preferably pulsed laser beam, which is directed on the plate to be engraved 10.
• the emitted laser beam is deflected 9 by means of a mirror system 8 provided therefor.
• a computer unit (not represented) is further provided for controlling said mirror system 8.
• a part of the surface of the plate 10 corresponding to the places where the laser beam 9 impinges the printing 10 is evaporated.
• the laser beam is passed one or several times on the image 11 thereby to form an engraving 1 with a desired depth as shown on Figure 6.
• the laser beam has a thickness, which is limited, e.g. to some tens of micrometers. Consequently, engraving with said laser beam of a complete surface or of areas with dimensions, which are greater than the available laser beam thickness requires that these areas are filled up with the laser.
• rasters 12 are also used in some cases as shown in Figure 7. This can be carried out by not taking any material away on selected predetermined locations 13 in the image.
• metallic plates are used because they have a long lifetime and because they can be etGhed with chemical products.
• the used metal is mostly a special chromium steel in this case which is submitted to a lap process after a hardening treatment.
• using metallic printing plates 2 in order to engrave by means of a laser causes the problem that an accumulation of metal 14 is created on the edges of the produced engravings 1 , which protrudes over a determined height, up to some micrometers above the metal surface 15 of the plate 2 as shown in Figure 2.
• This accumulation of material 14 is undesired because they render the printing plate unsuitable for use in modern pad printing. This results in the need of a subsequent treatment of the printing plate, e.g. by lapping or polishing.
• An alternative method for remedying thereto consists in modulating the laser beam used to such an extent as to velocity, power and frequency, that this parasitic accumulation of material is not generated.
• this method is very time consuming.
• a further remarkable alternative against the generation of accumulation of material around the engraved areas 1 is proposed according to this invention. It consists in a specific choice of selected materials for the printing plate. In this respect, the choice of ceramics appeared to be very appropriate because of its high resistance to wear on the one hand and the verification of the absence of the generation of accumulations of materials when engraving with laser on the other hand.
• Said basis plate 4 consists advantageously in a more usual, unhardened or lapped material for example, which appears thereby to be cheaper, on which a ceramic layer 3, 5 is further deposited.
• the whole as a superposition of layers appears to be substantially cheaper, the more that it is to be considered that the respective ratios of the layers (bottom and top layer) are not shown at scale in the Figures for a sake of clarity of the representation.
• the top layer 3, respectively 5 in must thinner that the bottom layer 4.
• the top layer forming the layer to be treated may have different thicknesses, depending on the required application.
• a fixed thickness 3 Gan thereby be allocated thereto which is substantially equal to the desired depth of the engraving 1 as shown in Figure 3.
• the laser is set in such a way that the beam 9 takes away only the ceramic layer 3.
• the engraving depth is set yet beforehand for a determined thickness of the ceramic layer 3.
• a thickness which is greater than the desired depth of the engraving can also be allocated to the layer 5 as shown in Figure 3.
• the parameters of the laser beam, in particular the wavelength, the pulse frequency, the velocity of the beam and the power can be set in such a way that the desired depth is engraved.
• This invention can also be used for rotary pad printing.
• the support 10 can be adapted as to its shape for use in rotary pad printing.
• Particularly aluminium and silicon ceramics material can be used as composite materials.
• titanium particularly titanium nitrite and/ or on a chromium basis can also be used advantageously.
• the plate can also advantageously be made of ynthetic material, particularly carbonite having the property of being very light.
• the substrate is made of metal / steel or synthetic material / carbonite.
• the latter is very resistant to wear and tear and is completely Gorrosion-resistant with a resistance to wear which is 3 to 4 times more than the one of hard metal or steel.
• the basis plate can also be made of synthetic material.
• materials we Gan also have TiN (titaniumtin), HG2 ⁇ 3 TiO 2 , Cr 2 O3, Ag.TiN (silvertin).
• Temperatures are comprised between 100 and 200 degrees C. It works perfectly as basis material; it has greater sensitivity to temperatures than titanium on ceramics.
• Bottom plate in metal In this case it is covered with a coating.
• a magnesium coating can be used as a coating.
• the hardness is relatively low in this case and the costs as well.
• Si.C silicon carbide
• Yttria SiC (Silicon carbide)
• SiSiC SiC
• SSiC Cr 2 O 3
• SSN silicon nitride
• metallic support as bottom plate with a substantially thinner layer of ceramic thereon offers a good solution to the problem of fragility of ceramic materials
• the plates present one same material and a relatively greater thickness or possibly also a smaller thickness can be used depending on the application. In the latter case, the final product is cheaper.
• the engraving apparatus comprises a Yag laser having a power ranging between 50 and 120 Watt, and the laser light has a wavelength ranging between 532 and 1064 nm.
• the laser beam is pulsed with a frequency ranging between 10 and 70 kHz.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Plasma & Fusion (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)
• Printing Plates And Materials Therefor (AREA)
• Laser Beam Processing (AREA)
• Printing Methods (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (5)

• 1998
  • 1998-10-26 BE BE9800769A patent/BE1012653A5/nl not_active IP Right Cessation
• 1999
  • 1999-10-26 ES ES99970963T patent/ES2351625T3/es not_active Expired - Lifetime
  • 1999-10-26 EP EP99970963A patent/EP1144194B1/en not_active Expired - Lifetime
  • 1999-10-26 DE DE69942651T patent/DE69942651D1/de not_active Expired - Lifetime
  • 1999-10-26 WO PCT/BE1999/000132 patent/WO2000024582A1/en active Application Filing
  • 1999-10-26 AT AT99970963T patent/ATE476298T1/de active
  • 1999-10-26 AU AU13666/00A patent/AU1366600A/en not_active Abandoned
  • 1999-10-26 DK DK99970963.7T patent/DK1144194T3/da active

Patent Citations (5)

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