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
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N1/00—Printing plates or foils; Materials therefor
  • B41N1/12—Printing plates or foils; Materials therefor non-metallic other than stone, e.g. printing plates or foils comprising inorganic materials in an organic matrix
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/146—Laser beam

Definitions

• the present invention relates to a laser-engravable recording material for the production of relief printing plates, in particular for the production of flexographic printing plates, from one dimensionally stable support and a recording layer Silicone rubbers and inorganic, iron-containing solids and / or soot as an absorber for laser radiation. It continues to affect a process for the production of relief printing plates Engraving of such recording materials by means of a laser, and relief printing plates with a printing relief made of silicone rubbers and inorganic, iron-containing solids and / or Soot.
• photopolymeric relief printing plates to provide laser-writable layers. These exist, for example. from a binder in which carbon black is dispersed. By radiation With an IR laser this layer can be ablated and an image be written into the shift. The image information is thereby transferred directly from the layout computer system to the laser equipment. A mask is thus produced from the laser-ablatable layer, that adheres directly to the photopolymer printing plate. A photographic Negative is no longer needed. Then will exposed and developed the printing plate in the usual way, the remainder of the laser-writable layer also being removed become.
• a major difference between the techniques described is the amount of material that needs to be removed. While the above laser-writable layers are usually only a few ⁇ m thick, so that only small amounts of the materials that make up the IR ablative layer are removed large quantities are required for direct laser engraving of the material from which the printing relief is made become.
• a typical flexographic printing plate is between, for example 0.5 and 7 mm thick and the non-printing depressions in the plate are between 300 ⁇ m and 3 mm deep.
• Essential for the quality of what is obtained by laser engraving Relief is mainly that the material is laser irradiated if possible without melting directly into the Gas phase passes, because otherwise melt edges around the wells be formed around in the plate. Such melting edges lead to a considerable deterioration of the printed image and reduce the resolution of the printing plate and the printed image.
• the sensitivity of the recording material to laser radiation is as high as possible so that the material is as possible can be laser engraved quickly.
• the laser-engravable layer too the important application properties for relief printing plates such as For example, elasticity, hardness, roughness, color acceptance or low Must have swellability in printing inks. Optimizing the Materials with regard to optimal laser engravability must not be used to impair the said application properties to lead.
• US 3,549,733 discloses a recording material made of polyoxymethylene or polychloral for the production of printing plates by means of laser engraving.
• fiberglass or rutile can be used as Fillers are used.
• DE-A 196 25 749 discloses a seamless printing form (sleeve) for the rotary flexographic printing, in which the elastomer layer consists of one cold-curing silicone polymer or a silicone fluoropolymer and Aluminum hydroxide is formed as a filler.
• EP-A 710 573 discloses a laser-engravable printing plate a polyurethane elastomer, nitrocellulose and carbon black.
• the high Amounts of non-elastomeric nitrocellulose 25 to 45% by weight of the laser-sensitive layer, however, cause difficulties the production of flexographic printing plates.
• EP-A 640 043 and EP-A 640 044 disclose single-layer and multi-layer, respectively Elastomeric laser-engravable elements for manufacturing of flexographic printing plates.
• the disclosed elements consist of "reinforced" elastomeric layers.
• a binder come for Flexographic printing plates typical thermoplastic elastomers such as. SBS, SIS or SEBS block copolymers for use.
• the so-called Reinforcement is achieved either through fillers, photochemical cross-linking or thermochemical crosslinking or combinations thereof reached.
• the layer can optionally use IR radiation contain absorbent substances.
• Preferred IR absorbent Material is soot, which also acts as a filler.
• the object of the present invention was to provide an improved material for the production of relief printing plates by means of laser engraving to find that increased sensitivity to laser radiation has and with the relief printing plates without melting edges can be produced.
• a laser-engravable recording material for the production of relief printing plates in particular for the production of flexographic printing plates from a dimensionally stable support and a recording layer made of silicone rubbers and inorganic, ferrous solids and / or soot as absorbers for Laser radiation found.
• a method of manufacture of relief printing plates by engraving such recording materials using a laser and relief printing plates with a printing relief made of silicone rubbers and inorganic, ferrous solids and / or soot as absorbers for Laser radiation found.
• a laser-engravable If necessary, layer with an adhesive layer applied a dimensionally stable carrier.
• suitable Dimensionally stable supports are plates, foils as well as conical and cylindrical sleeves made of metals such as steel, aluminum, Copper or nickel or from plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate, Polyamide, polycarbonate, optionally also fabric and nonwovens, such as glass fiber fabrics and composite materials Glass fibers and plastics.
• PET polyethylene terephthalate
• PEN polyethylene naphthalate
• Polyamide polycarbonate
• optionally also fabric and nonwovens such as glass fiber fabrics and composite materials Glass fibers and plastics.
• Coming as dimensionally stable supports in particular dimensionally stable carrier films such as Polyester films, especially PET or PEN films in question.
• laser-engravable means that the Layer possessing the property of laser radiation, in particular the To absorb radiation from an IR laser, so that it adheres to such Places where they have a laser beam of sufficient intensity is exposed, removed or at least detached.
• the layer is evaporated without melting beforehand or thermally or oxidatively decomposed so that their decomposition products in the form of hot gases, vapors, smoke or small ones Particles are removed from the layer.
• the invention encompasses but also, the residues of the irradiated layer afterwards mechanically removed, e.g. by blasting with a liquid or a gas or for example by suction.
• the laser-engravable layer comprises at least one silicone rubber as a binder.
• Silicone rubbers are made by suitable Crosslinking silicone polymers are formed and are commercial available.
• thermosetting Silicone rubbers HV types
• cold-curing one-component silicone rubbers RTV-1 types
• cold-curing two-component silicone rubbers RTV-2 types
• liquid silicone rubbers LSR types
• silicone rubbers can also also influenced by additives such as fillers or plasticizers become.
• additives such as fillers or plasticizers become.
• Such additives are more commercially available In the context of this invention, silicone rubbers are said to be in The term silicone rubber can be understood to include.
• siloxane block copolymers with siloxane blocks can also be used and thermoplastic hard segments are used.
• hard segment blocks are polycarbonate, polysulfone or Polyimide segments.
• block copolymers have the Properties of thermoplastic elastomers and should Within the scope of this invention also as in the term silicone rubber included to be understood.
• the laser-engravable layer can also be used for other contain polymeric binders other than silicone rubber.
• additional binders can, for example for targeted control of the properties of the elastomeric layer be used.
• Prerequisite for the addition of further binders is that they are compatible with the silicone rubber.
• other rubbers such as ethylene-propylene-diene rubbers are suitable as an additional binder.
• the amount of additional Binding agents are chosen by the skilled worker depending on the desired Properties selected. As a rule, however, should not exceed 25% by weight based on the total amount of binders used, preferably no more than 10% by weight of such additional binders be used.
• the recording layer according to the invention further comprises one inorganic, iron-containing solid and / or soot as absorber for laser radiation.
• Mixtures of several absorbers can also be used
• Laser radiation can be used.
• Suitable absorbers for laser radiation have a high absorption in the range of the laser wavelength on.
• absorbers are suitable that have a high Absorption in the near infrared and in the longer-wave VIS range of the electromagnetic spectrum.
• Such absorbers are particularly suitable for the absorption of radiation from Nd-YAG lasers (1064 nm) as well as IR diode lasers, which are typically Wavelengths between 700 and 900 nm and between 1200 and 1600 nm.
• Suitable solids containing iron are in particular intensely colored iron oxides.
• Such iron oxides are commercially available and are usually used as color pigments or as pigments for magnetic recording.
• Suitable absorbers for laser radiation are, for example, FeO, goethite ⁇ -FeOOH, Akaganeit ⁇ -FeOOH, lepidocrocite ⁇ -FeOOH, hematite ⁇ -Fe 2 O 3 , maghemite ⁇ -Fe 2 O 3 , magnetite Fe 3 O 4 or Berthollide.
• doped iron oxides or mixed oxides of iron with other metals can be used.
• Examples of mixed oxides are Umbra Fe 2 O 3 xn MnO 2 or Fe x A1 (1-x) OOH, in particular various spinel black pigments such as, for example, Cu (Cr, Fe) 2 O 4 , Co (Cr, Fe) 2 O 4 or Cu (Cr, Fe, Mn) 2 O 4 .
• Examples of dopants are, for example, P, Si, Al, Mg, Zn or Cr. Such dopants are generally added in small amounts in the course of the synthesis of the oxides in order to control particle size and shape.
• the iron oxides can also be coated. Such coatings can be applied, for example, in order to improve the dispersibility of the particles.
• These coatings can consist, for example, of inorganic compounds such as SiO 2 and / or AlOOH.
• organic coatings for example organic adhesion promoters such as aminopropyl (trimethoxy) silane, can also be applied.
• Particularly suitable absorbers for laser radiation are FeOOH, Fe 2 O 3 and Fe 3 O 4, most preferably Fe 3 O 4.
• the size of the iron-containing, inorganic solids used, in particular the iron oxides, is selected by the person skilled in the art depending on the desired properties of the recording material. Solids with an average particle size of more than 10 ⁇ m are usually unsuitable. Since iron oxides in particular are anisometric, this information relates to the longest axis.
• the particle size is preferably less than 1 ⁇ m. So-called transparent iron oxides can also be used, which have a particle size of less than 0.1 ⁇ m and a specific surface area of up to 150 m 2 / g.
• ferrous metal pigments are particularly suitable acicular or rice grain pigments with a length between 0.1 and 1 ⁇ m. Such pigments are as magnetic pigments known for magnetic recording. In addition to the iron can also other dopants such as Al, Si, Mg, P, Co, Ni, Nd or Y are present, or the iron metal pigments can be used with it be coated. Ferrous metal pigments are used to protect against corrosion superficially anoxidized and consist of a possibly doped Iron core and a possibly doped iron oxide shell.
• Suitable carbon blacks as absorbers for laser radiation are in particular finely divided types of soot with a particle size between 10 and 50 nm.
• the amount of absorber added is determined by the person skilled in the art material used and according to the desired properties of the recording material selected. In this context it must be taken into account that the added as absorber
• Solids in addition to laser engraving for example also mechanical properties of the recording material such as its Hardness or other properties such as thermal conductivity influence. So, for example, a comparison for flexographic printing plates, harder high-pressure or gravure printing plates are produced, so the expert usually select higher proportions of fillers rather than if manufacturing a flexo plate is intended.
• the amount of the absorber for laser radiation is preferably 0.1 to 20% by weight and particularly preferably 0.5 to 15% by weight.
• the laser-engravable recording layer can also comprise other inorganic materials, in particular oxides or oxide hydrates of metals, as a filler. These fillers are used, for example, to control the mechanical properties or the printing properties of the layer.
• SiO 2 which is often already a component of commercially available silicone rubbers, should be mentioned here.
• TiO 2 metal borides, carbides, nitrides, carbonitrides, oxides or oxides with a bronze structure can be used.
• the laser-engravable recording layer can also still include auxiliaries and additives.
• auxiliaries and additives are dyes, plasticizers, dispersing aids or adhesion promoter.
• the thickness of the laser-engravable recording layer is Standard trap between 0.1 and 7 mm. The thickness is depending on the expert suitable for the intended use of the printing plate chosen.
• the laser-engravable recording element can also have several laser-engravable recording layers of various Include composition on top of each other.
• the recording element according to the invention can also be a thin top layer on the laser-engravable recording layer include.
• Such an upper layer can affect the printing behavior and color transfer essential parameters such as roughness, Abrasiveness, surface tension, surface stickiness or Solvent resistance on the surface can be changed, without the relief-typical properties of the printing form such as for example, to influence hardness or elasticity. Surface properties and layer properties can therefore be independent be changed from one another to achieve an optimal printing result to reach.
• the top layer comprises as a polymeric binder preferably also a silicone rubber, but it can also, for example, in a known manner, SIS or SBS block copolymers include.
• the upper layer can be an absorber for Contain laser radiation without this being absolutely necessary is.
• the composition of the upper class is only limited to the extent that than the laser engraving of those underneath laser-engravable layer must not be impaired and the upper layer must be removable together with this.
• the Top layer should be thin compared to the laser-engravable layer his. As a rule, the thickness of the top layer does not exceed 100 ⁇ m, preferably the thickness is between 5 and 80 ⁇ m, particularly preferably between 10 and 50 microns.
• the recording element according to the invention can be optional also include a sublayer that is not laser-engravable between the support and the laser-engravable layer. With such sub-layers, the mechanical properties the relief printing plates can be changed without the relief typical To influence the properties of the printing form.
• the lower class can also be used as a binder or silicone rubbers also include other polymers.
• the laser-engravable recording element can be optional against mechanical damage from, for example Protective film made of PET, which is located on the top layer.
• the production of the laser-engravable recording elements according to the invention depends on the type of silicone rubber used.
• Essential for the quality of the invention Recording material is that the absorber for the laser radiation and all other components evenly in the silicone rubber are incorporated so that a homogeneous recording material arises.
• they can be made by placing the starting polymer in a suitable solvent such as toluene dissolves the absorber optionally with the addition of further Auxiliaries dispersed therein, the dispersion obtained pour a suitable carrier film, evaporate the solvent lets and crosslinks the silicone polymer. This method is especially when using a cold-curing one-component system advantageous.
• the invention Recording materials can be produced, for example, by the starting components in one without the addition of solvents Dispersing unit, such as a kneader or extruder intensive mixed together and into a plate by pressing, extruding, Round extrusion, injection molding, or by a suitable Combination of measures to form a plate.
• solvents Dispersing unit such as a kneader or extruder intensive mixed together and into a plate by pressing, extruding, Round extrusion, injection molding, or by a suitable Combination of measures to form a plate.
• the silicone rubber used is at room temperature or cured at elevated temperatures.
• the manufacturing process can post-treatment steps such as calendering or include loops. Such steps become advantageous used to make the surface of the recording material as smooth as possible to obtain.
• the laser-engravable recording materials according to the invention serve as the starting material for the production of relief printing plates.
• the procedure includes that the cover film - if available - will be deducted.
• a printing relief in the recording material by means of engraved by a laser.
• Image elements are advantageously engraved, where the edges of the picture elements are initially vertical fall off and only widen in the lower area of the picture element. This ensures that the pixels are well socked however, slight dot gain achieved. But it can also be different designed flanks of the pixels are engraved.
• Nd-YAG lasers (1064 nm), IR diode lasers, which typically have wavelengths between 700 and 900 nm and between 1200 and 1600 nm, and CO 2 lasers with a wavelength of 10640 nm are particularly suitable for laser engraving lasers with shorter wavelengths can also be used, provided the laser is of sufficient intensity.
• a frequency-doubled (532 nm) or frequency-tripled (355 nm) Nd-YAG laser can also be used.
• Such laser devices are commercially available.
• the image information to be engraved is transferred directly from the lay-out computer system to the laser apparatus.
• the lasers can be operated either continuously or in pulsed mode.
• Laser engraving can advantageously be carried out in the presence of an oxygen-containing one Gases, especially air.
• the oxygen-containing gas can be engraved on the recording element be blown.
• a comparatively gentle one Gas flow can be generated, for example, with the aid of a fan. But it can also be a stronger one with the help of a suitable nozzle Be blown over the recording material.
• This embodiment has the advantage that detached solid components the layer can be removed effectively.
• the printing plate obtained can still be cleaned.
• the printing plate can, for example can be cleaned with a brush.
• This cleaning process can with a suitable aqueous and / or organic solvent get supported.
• a suitable solvent is from Expert chosen under the proviso that it is the relief layer not loosen or swell strongly.
• the cleaning can for example, also with compressed air or by suction.
• the present invention encompasses but also to mechanically engrave the recording materials, So for example using suitable knives or other engraving tools.
• relief printing plates are obtained whose printing relief has the same composition, like the laser-engravable recording layer of the above Recording element.
• a pulsed Nd-YAG laser was used to carry out the engraving tests (Type: FOBA-LAS 94S, Fa. Foba GmbH, electronics + laser systems) used with a wavelength of 1064 nm. It was uses a mode aperture of 2 mm, the speed of the Laser beam was 100 mm / s.
• Figure 1 Laser pattern; the shaded areas were evaluated in relation to the engraving depth.
• HTV hot-curing
• silicone rubber Elastosil® R, type. R 300 / 30S, from Wacker
• a starter Lucidol S50S, dibenzoyl peroxide in silicone oil, from Wacker
• a predispersed iron oxide Type H1, Fa. Wacker, 60% by weight Fe 2 O 3 in 40% by weight silicone rubber
• Example 2 The procedure was as in Example 1, except that it was hot-crosslinking Silicone rubber instead of the R 300 / 30S type R 201/80, which has a higher filler content, higher crosslinking and has a higher Shore hardness.
• the networking was carried out at 150 ° C.
• Example 3 was repeated, only iron oxides other than Filler used. The results are summarized in Table 1.
• Example 3 was repeated, only carbon black or mixtures of ⁇ -Fe 2 O 3 and carbon black (Printex U, Degussa) were used as fillers. The results are summarized in Table 1.
• component A 98 parts by weight of component A of 1.5 parts by weight of Fe 2 O 3 of the two-component silicone rubber (Elastosil® RT 426, from Wacker, Kunststoff) were mixed intensively with 2 parts by weight of component B (hardener T-40, from Wacker). The mixture was poured out into a plate and cured at room temperature.
• component B hardener T-40, from Wacker
• a soot-coated, iron-containing silicate pigment (Ebony Novacite® Malvern Minerals Company, iron content approx. 1.6% carbon approx. 3%) was in the A component of the silicone rubber Elastosil® RT 601 (from Wacker) by adding SAZ balls for 6 hours dispersed using a shaker (Red Devil). The dispersion was then treated with Elastosil® RT 601-A and Elastosil® RT 601-B mixed that a ratio of the A component to the B component of 9: 1 was obtained. The mixture contained 10% by weight of the pigment. The mixture was poured into a mold and cured.
• Elastosil® LR 3094/60 A was compared with the B component 1: 1 and additional carbon black (at room temperature) mixed (the A component already contains soot) and the black mass in forms poured. The total content of carbon black was 10% by weight. Subsequently was crosslinked in the drying cabinet at 150 ° C. for 3 hours.
• Example 3 was repeated without using iron oxide as a filler was added.
• the plate obtained was then as above described a laser beam of different pulse frequency and Lamp amperage exposed.
• the plate obtained was not laser-engravable. The results are summarized in Table 2.
• Example 3 was repeated, except that the colorless inorganic materials Al 2 O 3 and Al (OH) 3 were used as fillers.
• the plate obtained was not laser-engravable.
• the material was only foamed and partly colored black.
• Example 3 was repeated, except that colorless TiO 2 was used as the filler. Although the plate was laser-engravable, the sensitivity of the plate to the laser was lower than in example 3.
• EP-A 640 043 10 parts by weight of carbon black (Printex U, from Degussa) and 90 parts by weight of a styrene-isoprene-styrene block copolymer (Kraton®1161, from Shell) were mixed intensively with one another in a kneader and at 150 ° C and 150 bar formed into a plate in a press. The plate obtained was then ablated as described above at various pulse frequencies and lamp currents. The sensitivity was significantly better than in comparative experiments 5 and 6, but the engraved elements had enamel edges. The surface stickiness of the laser engraved plate was higher than before the laser irradiation. The results are summarized in Table 2.
• Soot-filled elastomers such as natural rubber or SIS block copolymers
• lasers can be used engrave, but the results are worse than with the recording materials according to the invention. Disadvantages are particularly the melting edges that occur.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Plasma & Fusion (AREA)
• Manufacturing & Machinery (AREA)
• Printing Plates And Materials Therefor (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)

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• 1999
  • 1999-09-03 DE DE19942216A patent/DE19942216C2/de not_active Expired - Fee Related
• 2000
  • 2000-08-12 DE DE50000120T patent/DE50000120D1/de not_active Expired - Fee Related
  • 2000-08-12 EP EP00117482A patent/EP1080883B1/fr not_active Expired - Lifetime
  • 2000-08-23 US US09/643,727 patent/US6511784B1/en not_active Expired - Fee Related
  • 2000-08-30 JP JP2000260440A patent/JP2001121833A/ja active Pending
• 2002
  • 2002-03-05 US US10/090,229 patent/US6797455B2/en not_active Expired - Fee Related

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