Heat-Sensitive Recording Material For Offset Printing

Abstract

A heat-sensitive recording material suitable for offset printing, having a web-shaped substrate, having a front side and a reverse side opposite the front side, a heat-sensitive recording layer disposed at least on one of the two sides of the web-shaped substrate having at least one dye precursor and at least one (color) developer reactive with the dye precursor. The heat-sensitive recording layer has particles including an organic surface whose extent in the direction of the thickness of web-shaped substrate and heat-sensitive recording layer is greater than the thickness of the heat-sensitive recording layer.

Claims

1.-15. (canceled)

16. A heat-sensitive recording material configure for offset printing, comprising: a web-shaped substrate, having a front side and a reverse side opposite the front side; and a heat-sensitive recording layer disposed at least on one of the two sides of the web-shaped substrate, comprising: at least one dye precursor; at least one (color) developer reactive with the at least one dye precursor; and particles having an organic surface whose extent in a direction of a thickness of the web-shaped substrate and the heat-sensitive recording layer is greater than a thickness of the heat-sensitive recording layer, wherein the particles are selected from the group consisting of: microcapsules filled with air and/or water, polyacrylate beads, styrene acrylate beads, and spherical particles of polyolefin.

17. The heat-sensitive recording material as claimed in claim 16, wherein the extent of the particles is from 0.5 μm to 2.0 μm greater than the thickness of the heat-sensitive recording layer.

18. The heat-sensitive recording material as claimed in either of claim 16, wherein the particles have a beadlike form.

19. The heat-sensitive recording material as claimed in claim 16, wherein the particles are incorporated into the heat-sensitive recording layer and have a beadlike form and an equal diameter.

20. The heat-sensitive recording material as claimed in claim 16, wherein the particles are air-filled microcapsules with melamine-formaldehyde-based walls.

21. The heat-sensitive recording material as claimed in claim 16, wherein the heat-sensitive recording material has an interlayer that comprises hollow pigments and is positioned between the web-shaped substrate and the at least one heat-sensitive recording layer.

22. The heat-sensitive recording material as claimed in claim 16, wherein the at least one heat-sensitive recording layer covers over the heat-sensitive recording material toward an outside.

23. The heat-sensitive recording material as claimed in claim 16, wherein the heat-sensitive recording layer comprises at least one (color) developer selected from the group consisting of: 4-[(4-(1-methylethoxy)phenyl)sulfonyl]phenol, N-(p-toluenesulfonyl)-N′-3-(p-toluenesulfonyloxyphenyl)urea, diisopropyldiphenol, 4,4-sulfonyldiphenol, and N-[2-(3-phenylureido)phenyl]benzenesulfonamide.

24. The heat-sensitive recording material as claimed in claim 16, wherein the heat-sensitive recording layer comprises 3-dibutylamino-6-methyl-7-anilinofluoran as the at least one dye precursor.

25. The heat-sensitive recording material as claimed in claim 16, wherein the heat-sensitive recording layer further comprises at least one sensitizer selected from the group consisting of: 1,2-di(phenoxy)ethane, 1,2-di(3-methylphenoxy)ethane, benzyl naphthyl ether, diphenyl sulfone, dimethyl terephthalate, and di(p-methylbenzyl) oxalate.

26. The heat-sensitive recording material as claimed in claim 25, wherein the heat-sensitive recording layer comprises 1,2-di(phenoxy)ethane as the at least one sensitizer.

27. The heat-sensitive recording material as claimed in claim 16, wherein the heat-sensitive recording layer further comprises at least one binder selected from the group consisting of: polyvinyl alcohol, polyvinyl alcohol copolymers, modified polyvinyl alcohols, carboxyl group-modified or silanol-modified polyvinyl alcohols, water-insoluble latex binders styrene-butadiene copolymers, acrylate copolymers, especially: acrylonitrile-butyl acrylate-methacrylate copolymers, and methyl acrylate-methacrylamide copolymers.

28. The heat-sensitive recording material as claimed in claim 16, wherein the web-shaped substrate has a mass per unit area in a range from 100 g/m.sup.2 to 250 g/m.sup.2.

29. The heat-sensitive recording material as claimed in claim 18, wherein the particles are incorporated into the heat-sensitive recording layer and have an equal diameter.

30. The heat-sensitive recording material as claimed in claim 29, wherein the particles are air-filled microcapsules with melamine-formaldehyde-based walls.

31. The heat-sensitive recording material as claimed in claim 21, wherein the at least one heat-sensitive recording layer covers over the heat-sensitive recording material toward an outside.

32. The heat-sensitive recording material as claimed in claim 25, wherein the heat-sensitive recording layer further comprises at least one binder selected from the group consisting of: polyvinyl alcohol, polyvinyl alcohol copolymers, modified polyvinyl alcohols, carboxyl group-modified or silanol-modified polyvinyl alcohols, water-insoluble latex binders styrene-butadiene copolymers, acrylate copolymers acrylonitrile-butyl acrylate-methacrylate copolymers, and methyl acrylate-methacrylamide copolymers.

33. The heat-sensitive recording material as claimed in claim 32, wherein the web-shaped substrate has a mass per unit area in a range from 100 g/m.sup.2 to 250 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The FIGURE is a schematic depiction of a heat sensitive recording material

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0083] The fundamental structure of the heat-sensitive recording material proposed here is further elucidated using the FIGURE.

[0084] On a web-shaped substrate (1), formed in particular of paper with a mass per unit area in a preferred range from 100 g/m.sup.2 to 250 g/m.sup.2, is an interlayer (2), which preferably comprises a combination of organic and inorganic pigments and which, with a mass per unit area in a preferred range from 5 g/m.sup.2 to 20 g/m.sup.2, is able to make a positive contribution to leveling the substrate surface at the top toward the heat-sensitive recording layer (3). This heat-sensitive recording layer (3) is situated on the interlayer (2) and has a mass per unit area in a preferred range from 2 g/m.sup.2 to 6 g/m.sup.2, corresponding in a first approximation to a thickness in a range from 2 μm to 6 μm. Incorporated into this heat-sensitive recording layer (3) there are spherical particles (4) having an organic surface, the extent of which in the direction of the thickness of web-shaped substrate (1) and heat-sensitive recording layer (3) is greater than the thickness of the heat-sensitive recording layer (3). The FIGURE clearly shows how the particles (4) protrude in a bumplike manner from the otherwise flat heat-sensitive recording layer (3), the protrusion being preferably within a range from 0.5 μm to 4.0 μm.

[0085] The invention is to be elucidated in more detail with reference to the following two inventive examples and the one comparative example:

[0086] A base paper with a mass per unit area of 140 g/m.sup.2 is produced as web-shaped substrate on a Fourdrinier paper machine from bleached and ground softwood and hardwood pulps with addition of 0.6 wt % (bone dry) of resin size, based on the total solids content (bone dry) of the pulp supplied to the paper machine, and also with addition of further customary adjuvants. On-line within the paper machine, this web-shaped substrate is provided on the front side, by a coating knife applicator, with an interlayer of 9 g/m.sup.2, which fully covers over the web-shaped substrate. The interlayer comprises a pigment mixture of 18 wt % (bone dry) of organic pigment having a particle size (D50) of 1 μm and 82 wt % (bone dry) of calcined kaolin having a particle size (D50) of 0.9 μm and an oil absorption of 110 cm.sup.3/100 g. The organic pigment has a glass transition FIGURE of 105° C. The interlayer further comprises a binder mixture of 75 wt % of styrene-butadiene latex and 25 wt % of starch. The interlayer is dried by contact drying through a multiplicity of drying cylinders.

[0087] To form samples of the inventive 1st example, a heat-sensitive recording layer having a thickness after drying of 3.0 μm is applied to the interlayer in a separate coating machine, using a roller blade applicator, the heat-sensitive recording layer being formed using the following formulation as per table 1. Final drying of the heat-sensitive recording layer is accomplished by a combination of a multiplicity of drying cylinders in a drying section assigned to the coating machine used, with the recording material along with web-shaped substrate, interlayer, and heat-sensitive recording layer being passed meanderingly through this drying section, and of a plurality of hot air flotation dyers.

TABLE-US-00001 TABLE 1 Component Tradename Wt % (bone dry) Dye precursor 3-dibutylamino-6-methyl- ODB-2 5.8 7-anilinofluoran (Color) developer 4-[(4-(1-methylethoxy)phenyl)- D8 19.0 sulfonyl]phenol Sensitizer 1,2-di(phenoxy)ethane EGPE 9.4 Particles with organic Air-filled microcapsules with — 0.5 surface melamine-formaldehyde- (spherical, average based walls diameter: 4.5 μm) Binder Combination of acrylonitrile-butyl — 10.0 acrylate-methacrylate copolymers Mowiol 15-99 10.0 and methyl acrylate- methacrylamide copolymers polyvinyl alcohol Inorganic pigment Calcium carbonate Socal P3 41.0

[0088] To form samples of the inventive 2nd example, a heat-sensitive recording layer having a thickness after drying of 2.5 μm is applied to the interlayer in a separate coating machine, using a roller blade applicator, the heat-sensitive recording layer being formed using the following formulation as per table 2. Final drying of the heat-sensitive recording layer is accomplished by a combination of a multiplicity of drying cylinders in a drying section assigned to the coating machine used, with the recording material along with web-shaped substrate, interlayer, and heat-sensitive recording layer being passed meanderingly through this drying section, and of a plurality of hot air flotation dyers.

TABLE-US-00002 TABLE 2 Component Tradename Wt % (bone dry) Dye precursor 3-dibutylamino-6-methyl- ODB-2 6.3 7-anilinofluoran (Color) developer 4-[(4-(1-methylethoxy)phenyl)- D8 19.2 sulfonyl]phenol Sensitizer 1,2-di(phenoxy)ethane EGPE 8.4 Particles with organic Spherical polyolefin particles — 0.5 surface (spherical, average diameter: 4 μm) Binder Combination of acrylonitrile-butyl — 14.0 acrylate-methacrylate copolymers Mowiol 15-99 5.0 and methyl acrylate- methacrylamide copolymers polyvinyl alcohol Inorganic pigment Combination of aluminum Martifin OL 107 42.0 hydroxide and silica Sipernat 350

[0089] To form samples of the comparative example, a heat-sensitive recording layer having a thickness after drying of 2.5 μm is applied to the interlayer in a separate coating machine, using a roller blade applicator, the heat-sensitive recording layer being formed using the following formulation as per table 3. Final drying of the heat-sensitive recording layer is accomplished by a combination of a multiplicity of drying cylinders in a drying section assigned to the coating machine used, with the recording material along with web-shaped substrate, interlayer, and heat-sensitive recording layer being passed meanderingly through this drying section, and of a plurality of hot air flotation dyers.

TABLE-US-00003 TABLE 3 Component Tradename Wt % (bone dry) Dye precursor 3-dibutylamino-6-methyl- ODB-2 6.2 7-anilinofluoran (Color) developer 4-[(4-(1-methylethoxy)phenyl)- D8 16.4 sulfonyl]phenol Sensitizer 1,2-di(phenoxy)ethane EGPE 7.0 Binder Combination of acrylonitrile-butyl — 13.6 acrylate-methacrylate copolymers Mowiol 15-99 2.3 and methyl acrylate- methacrylamide copolymers polyvinyl alcohol Inorganic pigment Combination of aluminum Martifin OL 107 46.0 hydroxide and silica Sipernat 350

[0090] After the samples have been readied, black and white checkered thermal test printouts are produced on each of the samples using an Atlantek 400 instrument from Printrex (USA), employing a thermal head with resolution of 300 dpi and an energy per unit area of 16 mJ/mm.sup.2. The specimens thus processed are subsequently first viewed under a scanning electron microscope, in order to assess the behavior of the samples of inventive examples 1 and 2 under the heat of a thermal head. Here it is found that the elevations protruding in a domelike manner from the otherwise flat heat-sensitive recording layer—referred to here as bumps—, formed in the inventive 1st example by air-filled microcapsules, very largely retain their original form without restriction, under the influence of a heat-emitting thermal head, and therefore continue to protrude as they originally did from the heat-sensitive recording layer. As expected, the spherical polyolefin particles according to the inventive 2nd example are slightly and partially melted, but also still protrude significantly as elevations from the otherwise flat recording layer.

[0091] On subsequent printing, these findings are further confirmed: the printing, and particularly the passage through the turnover bar assemblies within the offset printing machines employed, are completely unproblematic in the case of the samples of inventive examples 1 and 2; in particular, on passage through the turnover bar assemblies, there are no instances at all of discoloration in the recording layers. This was exactly the objective of the invention, and can exactly be achieved with absolute conviction with heat-sensitive recording materials in accordance with the present invention—in contrast to recording materials from the known prior art having relatively high masses per unit area and having heat-sensitive recording layers without the particles with organic surface, as represented here by the samples of the comparative example: these samples exhibit distinct discolorations in the recording layer, owing to pressure, friction, and rubbing in the turnover bar assemblies of the offset printing machines employed.

[0092] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.