Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
  • B41M5/405—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography characterised by layers cured by radiation

Definitions

• the invention relates to a heat-sensitive recording material having a substrate which carries on its first side at least one heat-sensitive recording layer and on its second side a backside coating.
• the heat-sensitive recording layer has at least one dye precursor and at least one color acceptor, which react color-forming with one another under the action of heat.
• a heat-sensitive recording material of the type specified above is known from DE-C-38 36 660 known.
• the backside coating can here be formed from water-soluble high polymers, such as starch, gelatin, styrene-maleic anhydride copolymer hydrolysates or polyvinyl alcohol, and from water-insoluble polymers, such as latexes. The polymers are used alone or as a mixture.
• the known backside coating is to prevent that when using the known recording material as a label, in particular plasticizers which are present on a provided with the label sheet can penetrate from the back of the recording layer and thus a weakening or deletion of a possible Effect typeface.
• the barrier layer comprises substantially water-soluble polymer materials such as polyvinyl alcohol, various cellulose ethers, starch, gelatin, casein, and polyvinylpyrrolidone, as well as water-dispersed resins such as polystyrene emulsions.
• the function of the barrier layer is to protect against materials such as oils and plasticizers known to cause discoloration or discoloration of the images developed in the recording layer.
• the desired back-printing of a heat-sensitive recording material in the offset and flexographic printing process is the reason for the stated problem in the WO 99/14056 A1 after a backside coating, which is opposite to the Offset and flexographic printing substances used, especially organic solvents, as well as plasticizers, oils and fats has a good barrier effect.
• the backside coating of the known recording material comprises a mixture containing starch, a non-styrene or vinyl acetate acrylate copolymer having a film-forming temperature of less than 5 ° C and preferably less than 2 ° C and an alkaline catalyst such as calcium carbonate.
• a heat-sensitive recording material are taken into account, in addition to the back printability on the front also good stampability and Entwertraj has to be considered that the front and back coatings of a centrally positioned substrate mutually influence each other to take.
• the focus of the invention is not only on the back of the new recording material but also on its front side, that is, on its heat-sensitive recording layer and / or its protective layer covering the heat-sensitive recording layer.
• a recording material is also conceivable which, if appropriate, works with a likewise simply designed protective layer on a completely new recording layer.
• a crosslinking component In addition to the three minimum requirements listed above for a crosslinking component, it was important for the inventors, also in view of the need to ensure the greatest possible flexibility in the production process of thermosensitive recording materials, that this component help to form a coating for the back coating, which is stable over a relatively long period of time, meaning that it will not overly bacterial infest and / or thicken.
• the recording material of the invention has a back coat of a coating color which is storage stable before its application over 5 1/2 days at moderate stirring and thereby does not begin to cure.
• acting as a crosslinking component component it was also important to the inventors that the component has no major impact on the pH of the coating color, since such a change in the pH always, possibly not desired or unpredictable effects the surface properties of the stroke has.
• crosslinking components are not classified as hazardous substances, which makes their handling within the manufacturing process of the recording materials of the invention is not critical and with which of these components at most a negligible hazard to humans and the environment emanates.
• the backcoat comprises binders and in particular starch, styrene-butadiene latex and optionally carboxy- methyl-cellulose.
• binders in sometimes highly divergent mixing ratios is possible and preferred.
• optical brighteners, defoamers and components for viscosity control according to the respective requirements are common additives.
• Particularly positive results can be achieved with a coating weight for the back coating in a range of 2 to 15 g / m 2 .
• a range for the coating weight of the back coating of 2.5 to 4.5 g / m 2
• a range of 8.5 to 12 g / m 2 is very particularly preferred.
• particularly suitable brushing particularly equalizing application devices such as doctor blade and (roll) doctor blade coater and Walzenstreichwerke into consideration, without being limited in any way.
• the heat-sensitive recording layer of the heat-sensitive recording material according to the invention may likewise include in principle all suitable color acceptors, in particular organic color acceptors, suitable for the possible dye precursors, in particular those listed above.
• the heat-sensitive recording layer has at least one color acceptor selected from the list comprising: 2,2 bis (4-hydroxyphenyl) propane, 4 - [(4- (1-methylethoxy) phenyl) sulfonyl] phenol, 4-hydroxy 4'-isopropoxydiphylsulfone, 4,4'-Dlhydroxy-diphenylsulfone, 2,4'-dihydroxy-diphenylsulfone, N- (2-hydroxyphenyl) -2 - [(4-hydroxyphenyl) thio] -acetamide, N- (p-) toluenesulphonyl) -N'-3- (p-toluenesulphonyl-oxy-phenyl) -urea according to the following formula (1)
• this recording layer has a combination of two specific color acceptors which are: N- (p-toluenesulphonyl) -N'-3- (p-toluenesulphonyl-oxy-phenyl) -urea according to Formula (1) and urea-urethane compounds according to formula (2).
• Other color acceptors are not present in the recording layer.
• thermosensitive recording layer In order to obtain as high a whiteness as possible of the thermosensitive recording layer, it is necessary to supply the urea-urethane compounds of the formula (2) to 60 ° C before blending with the other color acceptor and / or other components of the thermosensitive recording layer heat and continue this heat treatment 24 hours continuously.
• the two color acceptors of Formal (1) and Formal (2) can be up to 60% by weight, but preferably in the range of 25 to 35 Gaw% of the heat-sensitive recording layer.
• the effect of the mixture of the two color acceptors in their entirety is a combination resulting from the peculiarities of the two individual dye acceptors: while N- (p-toluenesulphonyl) -N'-3- (p-toluenesulphonyl Oxy-phenyl) -urea according to formula (1) has been recognized as a color acceptor after numerous single and cross experiments, which is expected to high sensitivity of the thermosensitive recording layer to energy action, urea-urethane compounds according to the formula (2) may be more preferred than Such color acceptors are described in which the energy-induced print image has a high stability, especially against environmental influences.
• thermosensitive recording material which has a tendency of little background graying, has a heat-induced printed image resistant to environmental influences, and ensures good stampability and desmeability.
• the recording layer of the heat-sensitive recording material of the present invention for increasing the thermal responsiveness may also preferably have sensitizers having a melting point of preferably from 60 ° C to 180 ° C, more preferably having a melting point from 80 ° C to 140 ° C.
• Such sensitizers are, for example: benzyl p-benzyloxybenzoate, stearamide, N-methylol stearamide, p-benzylbiphenyl, 1,2-di (phenoxy) ethane, 1,2-di (m-methylphenoxy) ethane, m-terphenyl, Dibenzyl oxalate, benzylnaphthyl ether, diphenylsulfone and 2- (2H-benzotriazol-2-yl) -p-cresol, wherein benzylnaphthyl ether, diphenylsulfone, 1,2-di (m-methylphenoxy) ethane and 1,2-di (phenoxy) - ethane are considered preferred.
• the recording layer has as a sole sensitizer 2- (2H-benzotriazol-2-yl) -p-cresol represented by the following formula (3):
• the recording layer it.
• second particularly preferred embodiment of the heat-sensitive recording layer as a color acceptor N- (p-toluenesulphonyl) -N'-3- (p-toluenesulphonyl-oxy-phenyl) urea according to formula (1).
• This color acceptor may be incorporated into the thermosensitive recording layer either in combination with other color acceptors, but preferably as the sole color acceptor.
• the ratio by weight of (%) (atro) of the sensitizer of the formula (3) to the color acceptor of the formula (1) a range of from 5:10 to 9:10 is particularly preferable, and this ratio is independent of the fact that the Color acceptor according to formula (3) is used alone or in combination, is set.
• the heat-sensitive recording layer has not only good printing but also excellent resistance to light.
• 3-dibutylamino-6-methyl-7-anilinofluoran is considered to be the most suitable dye precursor within the second most preferred embodiment, but is not limited to it in any way.
• the dye precursors mentioned by way of example in paragraph [0017] can also be used individually or in combination with one another the heat-sensitive recording layer it. the second embodiment related to the heat-sensitive recording layer and discussed herein.
• Suitable binders for incorporation into the heat-sensitive recording layer are, for example, water-soluble binders such as starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohols, modified polyvinyl alcohols, sodium polyacrylates, acrylamide-acrylate copolymers, acrylamide-acrylate copolymers.
• Methacrylate terpolymers alkali metal salts of styrene-maleic anhydride copolymers or ethylene-maleic anhydride copolymers, which can be used alone or in combination with one another;
• Water-insoluble latex binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers and methyl acrylate-butadiene copolymers are also suitable as binders for incorporation into the heat-sensitive recording layer.
• polyvinyl alcohol in combination with acrylate copolymer are considered to be particularly preferred binders which are incorporated together in the heat-sensitive recording layer in a range from 12 to 21% by weight, based on the total weight of the recording layer.
• the coating composition for forming the heat-sensitive recording layer may further contain slip and release agents, such as higher fatty acid metal salts, for example, zinc stearate, calcium stearate, and waxes for example, paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearamides and castor wax.
• Further constituents of the recording layer are, for example, pigments, preferably inorganic pigments such as, for example, aluminum (hydr) oxide, silica and calcium carbonate, in which case in particular calcium carbonate, preferably in an amount of from 10 to 18% by weight, based on the total weight of the recording layer , should be included in the recording layer, is considered preferred.
• a permanent color or typeface image can be formed in the recording layer under the action of heat.
• the basis weight of the heat-sensitive recording layer is preferably between 2.5 and 12 g / m 2 and more preferably between 3 and 6.5 g / m 2 .
• a brush for applying the heat-sensitive recording layer in particular, offer a doctor blade and (roll) doctor blade coater, curtain coater and air brush.
• the coating color used to form the recording layer is aqueous.
• the subsequent drying of the coating color can be done by means of microwave irradiation. Usually and proven it is just as much to supply heat, as happens by hot-air floatation dryer or contact dryer. Also conceivable is a combination of the listed dry processes.
• a pigment-containing intermediate layer between the substrate layer and the recording layer is the same regardless of which embodiments and variants related to the recording layer.
• pigments of the intermediate layer both organic void pigments and inorganic pigments have proven useful, the latter preferably selected from the group comprising natural and calcined kaolin, silica and in particular bentonite, calcium carbonate and aluminum hydroxide, in particular boehmite here.
• such an intermediate layer can make a positive contribution to the leveling of the base layer surface, which reduces the amount of coating color necessarily required for the heat-sensitive recording layer. For this reason, offer to coat the intermediate layer leveling strokes, such as roller coater, doctor blade and (roll) doctor blade coating.
• the pigments of this intermediate layer can absorb the heat-liquefied wax constituents of the thermosensitive recording layer in the typeface formation and thus promote a safe and rapid operation of the heat-induced recording.
• the basis weight of the pigmented intermediate layer is preferably between 5 and 20 g / m 2 and more preferably between 7 and 11 g / m 2 .
• the recording material according to the invention may have a protective layer which is applied to the heat-sensitive recording layer, regardless of which embodiments and variants, and completely or partially covers them.
• the Protective layer takes on a task, as it must also be partially fulfilled by the backside coating, namely on the one hand the protection of the recording layer arranged under it from environmental influences such as oils, fats, water and plasticizers and on the other hand the improvement of the printability especially in offset and flexographic printing.
• the protective layer itself can be applied by means of conventional brushing, for which, inter alia, a coating color is usable, as described above and for which a surface-related mass in a range of 1.5 to 4.5 g / m 2 is preferred, or the protective layer may alternatively be printed. Processing technology and in terms of their technological properties are particularly suitable such protective layers which are curable by means of actinic radiation.
• actinic radiation UV or ionizing radiation, such as electron beams to understand.
• a variant of the protective layer which completely or partially covers the heat-sensitive recording layer as an alternative to the above-described embodiment provides as binder a polyvinyl alcohol, zinc stearate, as pigment aluminum hydroxide or alternatively also silicon dioxide and one or more crosslinkers, particularly preferred amounts for such a protective layer in Table 1 below: ⁇ u> Table 1: ⁇ / u> product % By weight [otro] Alumininhydroxid 10 - 25 polyvinyl alcohol 55 - 70 zinc stearate 7 - 9 crosslinkers 6 - 7
• thermosensitive recording material of the present invention Since the proposed backcoat of the thermosensitive recording material of the present invention is very easy to dry, both the back coat and the thermosensitive recording layer including the protective layer completely covering it can be applied and dried in a single operation, for example, within a coating machine.
• such a coating machine (a) a rolling device, (b) a first coating, such as a curtain coater, an air brush or a roller blade coating applicator for applying the heat-sensitive recording layer, (c) a first non-contact Schwebetrocknerkanal, (d) a curtain coater or an airbrush for applying the protective layer, (e) optionally and depending on the type, a contactless web guiding system, (f) a film applicator for application of the backside coating, (g) a second non-contact floating dryer channel, (h) an after-dryer section with several drying cylinders, ( i) a remoistening system or a coating installation such as a film applicator for optimizing the flatness or for reducing the roll tendency, (j) an IR drying system, (k) one or more calendering units each having one or more press nips, in particular using zone-controllable and / or shoe press rolls or belt calenders and (I) an A Provide rolling device.
• paper is the substrate that has prevailed on the market with regard to the good environmental compatibility because of good recyclability and is preferred in the context of the invention.
• a paper web of bleached and ground deciduous and softwood pulps with a basis weight of 67 g / m 2 is prepared on a fourdrinier paper machine as the substrate layer with the addition of conventional additives in conventional amounts.
• a mainly calcined kaolin pigment, Styrolbutadienlatex as a binder and starch as Cobinder having intermediate layer of 8 g / m 2 is applied online within the coater with a roller blade coating.
• crosslinkers based on epichlorohydrin resin or oxalic aldehyde that they are both hazardous substances and therefore already for reasons of environmental and human dangers alone are critical.
• Another possible crosslinker, that is ammonium zirconium carbonate was not considered in the experimental series on which this invention is based, because of its extremely strong odor nuisance for ammonia.
• the crosslinking agent according to the invention based on polyurethane can completely convince in terms of low viscosity increase and delayed unfolding of the crosslinking effect in all examples.
• the effectiveness of the crosslinkers used in the examples is examined by 3 days after preparation of the recording material samples are wetted on their back with a few drops of water on a measuring surface and rubbed with a finger under moderate pressure in a circular motion on the moistened measuring surface. It should be considered good if the measuring surface remains smooth on the surface and no particles are released, bad are those samples in which particles are released from the surface or even the entire surface dissolves. Again, only the tried crosslinker based on polyurethane convince. The other crosslinkers have hardly any result-increasing effect in some examples.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Heat Sensitive Colour Forming Recording (AREA)

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• 2007
  • 2007-09-10 DE DE502007002946T patent/DE502007002946D1/de active Active
  • 2007-09-10 AT AT07017657T patent/ATE458623T1/de active
  • 2007-09-10 PL PL07017657T patent/PL2033802T3/pl unknown
  • 2007-09-10 ES ES07017657T patent/ES2339168T3/es active Active
  • 2007-09-10 EP EP07017657A patent/EP2033802B1/fr active Active
• 2008
  • 2008-09-02 WO PCT/EP2008/007151 patent/WO2009033590A1/fr not_active Ceased
  • 2008-09-02 US US12/677,119 patent/US8470732B2/en active Active

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