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
• • 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
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
• • 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
  • B41M5/426—Intermediate, backcoat, or covering layers characterised by inorganic compounds, e.g. metals, metal salts, metal complexes

Definitions

• the invention relates to a heat-sensitive recording material having a substrate layer, on which a pigmented intermediate layer, a color-forming and color-accepting heat-sensitive recording layer and a protective layer are applied in this order, and the use of such a heat-sensitive recording material.
• a heat-sensitive recording material of the type mentioned is known for example from DE-A-101 08 982.
• the well-known recording material has the task of guaranteeing excellent stamp validity as a ticket; there was also a demand for high environmental resistance of the known recording material against water, fats, oils and plasticizers and for good printability, inter alia in offset printing.
• the above-mentioned recording material was convincing in most applications, but the market requirements, particularly with regard to printability, continued to increase, which is why there was a need not only for minor modifications but for fundamental innovations.
• a heat-sensitive recording material with one or more intermediate layers is known, which are arranged between the recording layer and the substrate.
• An intermediate layer contains particles of an oil-absorptive inorganic pigment.
• fine hollow particles of a synthetic resin made of styrene, acrylic or a copolymer of styrene and acrylic are optionally arranged together with other inorganic pigment particles.
• a particle size range (average diameter) of 0.75 ⁇ m to 1.5 ⁇ m for the organic hollow particles is disclosed.
• Calcium and magnesium carbonate, silicon oxide, titanium oxide, kaolin and calcined kaolin are mentioned as suitable inorganic pigments that can be added to the intermediate layer containing organic hollow particles.
• EP-A-1 243437 discloses a heat-sensitive recording material in which a dye precursor dispersion is used, the dye precursor particles of which should not be outside a range from 0.1 ⁇ m to 0.3 ⁇ m, with a proportion of at most 1 % is allowed for particles of 0.07 ⁇ m or less.
• a layer arranged between the recording layer and the substrate should preferably contain hollow particles of a thermoplastic resin, with a particle size of 2 ⁇ m to 10 ⁇ m being particularly preferred. Production difficulties are expected below a particle size of 2 ⁇ m.
• coating compositions are proposed for the intermediate layer which contain either calcined kaolin or organic hollow particles. This document contains no information regarding a certain glass transition temperature.
• An intermediate layer provided on the substrate contains an inorganic pigment with an average particle size of 0.1 ⁇ m to 5 ⁇ m or organic particles with an average particle size of 0.5 ⁇ m to 30 ⁇ m.
• a coating composition for an intermediate layer is disclosed which, in addition to styrene particles, also contains calcined kaolin and calcium carbonate. The document contains no information on the glass transition temperature of the organic particles.
• EP-A-1 134089 discloses an organic pigment, the particles of which are crosslinked and have several cavities, ie multivoided particles. The purpose of these particles is to circumvent the problems in the multi-stage production of spherical particles with only a single cavity.
• the document discloses particle sizes from 0.1 to 2 microns, preferably from 0.5 to 1.5 microns.
• Inorganic pigments are also disclosed as components of the intermediate layer of a heat-sensitive recording material. In contrast, the particle size of the inorganic pigments or their mixing ratio to the particles of the organic pigment are not mentioned.
• a protective layer for covering the recording layer is provided in a general form and without described the components to be used. This disclosed organic pigment has so far had no significance in industrial practice.
• EP-A-0 570 186 describes the intermediate layer of a heat-sensitive recording material which contains crosslinked polymer particles with a particle diameter of 0.2 to 5.0 ⁇ m and an inorganic pigment which has an oil absorption of less than 170 ml / 100 g.
• the document discloses a mixing ratio of organic polymer particles to inorganic pigment in the range from 1: 1 to 1: 9. With regard to the shape of the polymer particles, this document does not contain any information, nor is it disclosed whether particles with a hollow structure are involved.
• the effect of the intermediate layer is explained in the document by the fact that the organic and inorganic pigment particles have a mutual effect and irregularities on the surface of the paper used as a substrate are compensated for or smoothed. Penetration of the components forming the recording layer is to be suppressed in this way and a heat-insulating layer with a high void ratio is to be obtained.
• DE-A-39 01 234 discloses a heat-sensitive recording material with a foamed portion which has tiny spaces in the intermediate layer.
• it is proposed in one of the methods disclosed to introduce tiny hollow plastic particles made of thermoplastic material into such an intermediate layer in an expanded state, air or other gases being contained in the particles produced.
• an intermediate layer is provided which contains an expandable plastic filler which comprises hollow particles made of a thermoplastic material and a solvent with a low boiling point contained in these particles. When heated, the intermediate layer expands and certain voids are created.
• an intermediate layer containing a blowing agent and a thermoplastic material has also been proposed. When heated, an intermediate layer with a cellular structure is formed. While the intermediate layer (s) should have a smoothness of at least 2000 Bekk seconds after calendering, a value of at least 2500 Bekk seconds is disclosed for the smoothness of the recording layer.
• the intermediate layer can be applied to a base layer covering the substrate, which contains inorganic pigment and binder. There is no disclosure in the document for the admixture of inorganic pigment to the intermediate layer. There is also no information in the script on the composition of a possible protective layer.
• the US 4929 590 relates to a heat-sensitive recording material with an intermediate layer containing spherical plastic particles with an average particle size of 0.2 microns to 1.5 microns and a glass transition temperature between 40 ° C and 90 ° C.
• plastic particles with a glass transition temperature of 110 ° C. and an average particle size of 3 ⁇ m are also disclosed, but which have a low recording quality.
• both points help to keep the distance between the heat-sensitive recording layer and the thermal head producing the printed image small.
• the resolution becomes worse, the resolution being approximately inversely proportional to the square of the distance.
• the protective layer must not lose its environmental resistance at the same time, and it should not be deposited or glued to the thermal head, which is why the protective layer should have a rather sealing character.
• the new heat-sensitive recording material should have excellent printability in offset printing, which means in particular a sharp-edged, brilliant printed image and a low tendency to be placed on the printing blanket. While in known cases such a printing blanket can often be cleaned after 3,000 to 6,000 running meters when printing known heat-sensitive recording materials, such a cleaning process with the recording material according to the invention is often only necessary after 24,000 meters. According to popular opinion, an open-pore, voluminous printing base is advantageous, which is in contrast to a smooth, rather sealing surface.
• the solution provides a heat-sensitive recording material with a substrate layer, to which at least the following layers are applied in this order:
• the intermediate layer contains a pigment mixture of an inorganic and an organic pigment
• the organic pigment has a particle size (D 5 o) in a range of 0.75 microns to less than 1.5 microns has,
• the organic pigment has a glass transition temperature greater than or equal to 100 ° C.
• the protective layer contains at least one polyvinyl alcohol and a crosslinking aid.
• the thermal head in the heat-sensitive recording layer which triggers the color-forming reaction of the color formers with the color acceptors causes the wax-like constituents in the recording layer to melt.
• a sealing protective layer is provided which completely covers the recording layer.
• an intermediate layer that completely covers the substrate layer and contains a pigment mixture of an inorganic and an organic pigment is positioned between the substrate layer and the recording layer.
• the inorganic pigments of this intermediate layer cause the melt to be absorbed. It is particularly advantageous if the pigments of the intermediate layer have an oil absorption of at least 80 cm 3/100 g and even better of 100 cm 3 / VI g, determined according to the Japanese standard JIS K 5101. Calcined kaolin, calcium carbonate, silicon dioxide and kaolin have proven particularly useful due to their high absorption capacity. Mixtures of several different types of inorganic pigments are also conceivable.
• the incorporation of organic pigments in the intermediate layer is justified by the fact that such organic pigments to a particular extent a high heat reflectivity of the intermediate layer are beneficial.
• the organic, so-called hollow body pigments arranged in an intermediate layer of a heat-sensitive recording material have air in their interior, which is a good heat insulator.
• the intermediate layer thus optimized as a heat reflection layer increases the response of the recording layer to heat, which significantly increases the resolving power of the heat-sensitive recording material and can also increase the printing speed in the thermal printer.
• the quantitative ratio between organic and inorganic pigment is a compromise of the effects caused by the two types of pigment, which is particularly advantageously solved when the pigment mixture consists of 15 to 50% by weight or better 20 to 50% by weight organic and 85 to 50 wt .-% or better to 80 to 50 wt .-% of inorganic pigment. It is very particularly preferred if the pigment mixture consists of 25 to 40% by weight of organic and 75 to 60% by weight of inorganic pigment.
• the organic pigments have a wall made of thermoplastic resin, which preferably comprises (meth) acrylonitrile copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene acrylate, polyacrylonitrile or polyacrylic acid ester.
• thermoplastic resin which preferably comprises (meth) acrylonitrile copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene acrylate, polyacrylonitrile or polyacrylic acid ester.
• Pigment mixtures of different organic pigments are conceivable.
• a glass transition temperature greater than or equal to 100 ° C. and preferably greater than or equal to 105 ° C. was recognized as essential to the invention because an increased degree of yellowing was found below these temperatures.
• an organic pigment is suitable which comprises spherical particles which consist of only one cavity surrounded by a wall.
• the core of the particles is first filled with water, which evaporates during the drying and smoothing of the intermediate layer through the action of temperature and pressure through the shell, thereby creating the cavity. During this process, the particles largely or completely retain their original shape, volume and diameter.
• the particle size of the present in the intermediate layer is organic pigments before their integration into the intermediate layer as D measured in the delivery state of an aqueous dispersion 5 o value.
• the particle size of the organic pigments in the intermediate layer ideally in a range from 0.75 ⁇ m to less than 1.5 ⁇ m. is particularly preferably in a range from 0.9 ⁇ m to 1.2 ⁇ m. Particle sizes below 0.75 ⁇ m are prohibited due to theological processing difficulties. Particle sizes above 1.5 ⁇ m show too coarse-grained behavior and prevent a preferred leveling effect of the intermediate layer. A particle size of less than 2 ⁇ m, determined as the Dso value, is particularly recommended for the inorganic pigments.
• Pigments which have a particle size distribution of 34 to 40% by weight less than 1 ⁇ m and 57 to 63% by weight less than 2 ⁇ m have proven to be advantageous. Another suitable particle size distribution is obtained when 88% by weight are less than 1 ⁇ m.
• the ratio of the particle size of the organic pigment to the particle size of the inorganic pigment was in a range from 1: 0.38 to 1: 1.5.
• the intermediate layer further comprises a binder selected from the group comprising polyvinyl alcohol, styrene-butadiene latex, starch, carboxy-methyl-celluloseose, cellulose derivatives, styrene-butadiene latex being particularly preferred.
• a binder selected from the group comprising polyvinyl alcohol, styrene-butadiene latex, starch, carboxy-methyl-cellulose, cellulose derivatives, styrene-butadiene latex being particularly preferred.
• the proportion of binder in the intermediate layer preferably consists of 69 to 76% by weight of styrene-butadiene latex.
• an intermediate layer positioned between the substrate layer and the heat-sensitive recording layer can make a positive contribution to the leveling of the substrate layer surface, thus reducing the mass of coating color that is necessarily to be applied for the heat-sensitive recording layer.
• leveling units such as roller doctor blades and doctor blades or blades are preferred for applying the intermediate layer.
• the formation of the intermediate layer with a mass per unit area in a range from 5 g / m 2 to 20 g / m 2 and even better between 7 g / m 2 and 10 g / m 2 has a particularly advantageous effect.
• the heat-sensitive recording layer can in principle contain all known color formers as well as matching color acceptors, in particular organic color acceptors. Are particularly preferred as color formers
• the heat-sensitive recording material according to the invention contains at least one polyvinyl alcohol and a crosslinking agent in its protective layer. tool. It is preferred that the polyvinyl alcohol of the protective layer is modified with carboxyl or silanol groups.
• a protective layer has a high affinity for the preferably UV-curing printing ink used in the offset printing process, which decisively helps to meet the demand for improved printability within offset printing. It is also conceivable to use mixtures of different carboxyl-modified or silanol-modified polyvinyl alcohols.
• Suitable crosslinking aids in the protective layer are, in particular, those selected from the group comprising: boric acid, polyamine, epoxy resin, dialdehyde, formaldehyde oligomers, epiochlorohydrin resin, dimethyl urea, melamine formaldehyde. Mixtures of different crosslinking aids are also possible.
• the ratio by weight of the modified polyvinyl alcohol to the crosslinking aid is in a range from 20: 1 to 5: 1 and particularly preferably in a range from 12: 1 to 7: 1 , It can be said that a ratio of the modified polyvinyl alcohol to the crosslinking aid of 100 parts by volume to 15 to 30 parts by volume has proven successful.
• the protective layer additionally contains an inorganic pigment.
• the inorganic pigment is selected from the group comprising silicon dioxide, aluminum hydroxide, calcium carbonate, kaolin or a mixture of the inorganic pigments mentioned.
• the protective layer it is preferred, for economic reasons, to form the protective layer as single-layered as possible with a mass per unit area in a range from 1.5 g / m 2 to 6 g / m 2 and in particular between 1.8 g / m 2 and 3 g / to apply m 2 .
• a smoothness of the protective layer in the range from 500 and preferably from 800 or even better 1,000 Bekk-seconds (sec) to less than 3,000 Bekk-sec has proven to be advantageous.
• values from 1,000 Bekk-sec to less than 2,500 are Bekk-sec and very particularly preferably from 1,200 Bekk-sec to 2,000 Bekk-sec.
• the gloss of the protective layer is largely determined by the type of smoothing and the roller surfaces and the materials influencing the friction in the smoothing unit and calender.
• a preferred range is between 30% and 50%, and very particularly preferably between 40% and 48%, measured according to Tappi 450 or ISO 2813 at a reflection angle of 75 °.
• Another preferred range is between 10% and 15%, determined according to the same regulations and parameters.
• a particularly good printability for the offset printing process is when the protective layer of the new heat-sensitive recording material has a polar component which is as small as possible of the surface tension to be determined as the sum of the disperse and polar components.
• the determination of the surface tension is carried out according to Owens Wendt as in Journal of Applied Polymer Science, Vol. 13, 1969, pages 1741-1747: Estimation of the Surface Free Energy of Polymers; D. K. Owens, R.C. Wendt stated.
• a suitable range for the measured values of the polar portion of the surface tension is above zero and below 15 mN / m (milli-Newtons per meter).
• a polar component of the surface tension of less than 10 mN / m is particularly preferred.
• a coating base paper that is not surface-treated is to be understood as a coating base paper that has not been treated in a size press or coating device.
• foils made of polyolefin and papers coated with polyolefin as a substrate layer are possible for the invention without such an embodiment having an exclusive character.
• the recording material according to the invention has a backside coating which is on the substrate layer side is applied, which is opposite the side provided with the layer sequence of at least one intermediate layer, heat-sensitive recording layer and protective layer.
• a back coating is proposed, for example, in DE-A-197 48258 and then serves to improve the printability of the recording sheet on the back in offset and flexographic printing processes and to improve the blocking effect of the back against plasticizers, oils and fats.
• application quantities in a range from 1 g / m 2 to 3 g / m 2 and in particular between 1.5 g / m 2 and 2.5 g / m 2 have proven to be advantageous.
• a paper web is produced as a substrate layer from a mixture of bleached and ground softwood sulfate pulp and eucalyptus pulp with a mass per unit area of 63 g / m 2 with the addition of conventional admixtures in conventional amounts.
• the substrate layer is provided on the front side by means of a blade applicator with an intermediate layer of 9 g / m 2 , which completely covers the substrate layer.
• the intermediate layer comprises a pigment mixture of 30% by weight (atro) organic pigment with a particle size (D 50 ) of 1 ⁇ m and 70% by weight (atro) calcined kaolin with a particle size (D 50 ) of 0.9 ⁇ m and an oil absorption of 110 cm 3 / 100g.
• the organic pigment has a glass transition value of 105 ° C.
• the intermediate layer further comprises a binder mixture of 75% by weight styrene-butadiene latex and 25% by weight starch.
• a heat-sensitive recording layer is applied to the intermediate layer with a fluoran color former and 4 - [(4- (1-methylethoxy) phenyl) sulfonyl) phenol as a color acceptor, both with a particle size of 0.9 ⁇ m.
• a protective layer of 2 g / m 2 completely covering the recording layer is applied with a silanol-modified polyvinyl alcohol and a mixture of an epichlorohydrin resin and a dialdehyde as crosslinking aid.
• the ratio of the silanol-modified polyvinyl alcohol to the mixture of the crosslinking aids is 100 parts by volume to 23 parts by volume.
• the protective layer further comprises aluminum hydroxide as a pigment.
• the heat-sensitive recording material thus produced in the first example has a smoothness of 1800 after its calendering Bekk seconds and a gloss value of 40%, measured according to Tappi standard 450 or ISO 2813 at a reflection angle of 75 °.
• a heat-sensitive recording material produced in a second experiment has 1 in comparison to the recording material according to Example 1 above
• the protective layer applied by means of an air brush with 2 g / m 2 has a silanol-modified polyvinyl alcohol and a mixture of epichlorohydrin resin and dialdehyde as cross-linking agents, in contrast to the first example a ratio of the modified polyvinyl alcohol in% by weight to the cross-linking agent mixture in% by weight. -% of 8.5: 1 is set.
• the smoothness in the case of the second example after corresponding calendering is 1,500 Bekk seconds with a gloss of 12%, measured according to Tappi standard 450 or ISO 2813 at a reflection angle of 75 °.
• the polar portion of the surface tension is below 10 mN / m, more precisely in the first example at 9.57 and in the second example at 9.89 mN / m.
• the recording materials according to the invention thus produced have a high environmental resistance and an outstanding offset printability.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Heat Sensitive Colour Forming Recording (AREA)
• Laminated Bodies (AREA)

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• 2002
  • 2002-11-19 DE DE10254070A patent/DE10254070A1/de not_active Ceased
• 2003
  • 2003-11-19 EP EP03779990A patent/EP1565321B1/fr not_active Expired - Lifetime
  • 2003-11-19 AT AT03779990T patent/ATE375258T1/de not_active IP Right Cessation
  • 2003-11-19 AU AU2003288116A patent/AU2003288116A1/en not_active Abandoned
  • 2003-11-19 WO PCT/EP2003/012939 patent/WO2004045862A1/fr not_active Ceased
  • 2003-11-19 DE DE50308369T patent/DE50308369D1/de not_active Expired - Lifetime
  • 2003-11-19 ES ES03779990T patent/ES2295669T3/es not_active Expired - Lifetime

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