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
  • B41M5/40—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
• • 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

Definitions

• the present invention relates to a heat-sensitive recording material, more particularly, to a highly sensitive heat-sensitive recording material that has rapid thermal response and that causes minimum deposition of tailings on the surface of a thermal head.
• Heat-sensitive recording materials are generally comprised of a support such as paper, plastic film or syn­thetic paper that is coated with one or more heat-sensitive color-forming layers that contain a binder and a thermally color-forming substance as main ingredients.
• Heat-sensitive recording materials need only be heated to produce an image and they can be used with rela­tively simple and compact recording apparatus. Because of these and other advantages, heat-sensitive recording materials are extensively used in information recording applications.
• a heat-sensitive recording material that comprises a support coated with a heat-sensitive recording layer con­taining an electron donating colorless dye and an electron accepting compound, which recording material is charac­terized in that an undercoat layer containing both poly­styrene and a pigment that is capable of oil absorption in an amount of less than 100 ml/100 g is provided between the support and the heat-sensitive color-forming layer.
• an inorganic pigment is incorporated as an additional filler to provide an improved capability for absorbing tailings, whereby a desirable heat-sensitive recording material is obtained that has not only high recording sensitivity but also a greater ability to absorb tailings.
• Polystyrene has a sufficiently high heat conductivity to provide a high recording sensitivity.
• the polystyrene to be used is generally a fine particulate polystyrene that has an average particle size of up to 5 ⁇ m, preferably in the range of 0.5 - 2 ⁇ m. Polystyrene particles larger than 5 ⁇ m are incapable of forming a highly smooth undercoat layer. On the other hand, it should be taken into consideration that polystyrene particles smaller than 0.5 ⁇ m have a tendency to deteriorate, rather than improve, the ability to absorb tailings.
• the pigment to be incorporated in the undercoat layer together with polystyrene is such that it absorbs an oil in an amount of less than 100 ml/100 g (JIS K 5101).
• examples of the pigment that satisfies this requirement include calcined clay, clay, talc, calcium carbonate and magnesium carbonate.
• Pigments that absorb 100 ml or more of an oil per 100 g contribute to an improvement in the ability to absorb tailings but, on the other hand, the density of prints obtained by printing with high energy is not satis­factorily high.
• Polystyrene and the pigment capable of oil absorption in an amount of less than 100 ml/100 g are used in combina­tion, typically at ratios of 1:4 to 4:1 (by weight). If the pigment to polystyrene ratio exceeds 4, it is impossible to maintain a desirably high recording sensitivity. On the other hand, if the polystyrene to pigment ratio exceeds 4, it is impossible to maintain a desirably high ability to absorb tailings.
• An adhesive is used to form an undercoat layer that contains the polystyrene and the pigment capable of oil absorption in an amount of less than 100 ml/100 g.
• the adhesive is used in an amount of 1 - 20 parts (by weight) per 100 parts of the sum of the polystyrene and the pigment.
• water-soluble polymeric aqueous emulsions may be used as pigments and specific examples are listed below: polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, starch, starch derivatives, styrene/maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyamide, SBR latex, polystyrene-acrylate ester emulsion, and polyvinyl acetate emulsion.
• the polystyrene, the pigment capable of oil absorp­tion in an amount of less than 100 ml/100 g, and the adhe­sive are dispersed in a desired order in an aqueous medium and they are mixed to prepare a coating solution, which is then applied onto a support to form an undercoat layer having a dry weight of 1 - 15 g/m2. Coating operations can be performed with conventional applicators.
• the support to be used in the present invention may be selected from among appropriate materials such as paper, plastic films, synthetic paper and metal foils.
• the so formed undercoat layer is then overlaid with a heat-sensitive color-forming layer, which may be formed in the usual manner.
• the colorless or pale-colored electron donating dye may be selected from among the following compounds: Crystal violet lactone 3-(N-ethyl-N-isopentylamino)-6-­methyl-7-anilinofluoran; 3-diethylamino-6-methyl-7-anilinofluoran; 3-diethylamino-6-methyl-7- (o,p-dimethylanilino)fluoran; 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran; 3-pyrrolidino-6-methyl-7-anilinofluoran; 3-dibutylamino-6-methyl-7-anilinofluoran; 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran; 3-diethylamino-7- (o-chloro
• the following compounds may be enumerated as typical examples of electron accepting compounds (developing agents): Bisphenol A; Benzyl-p-hydroxybenzoate; n-butyl di(4-hydroxyphenyl)acetate Bisphenol S; 4-hydroxy-4′ -isopropyloxydiphenylsulfone; 1,1-di(4-hydroxyphenyl)cyclohexane; and 1, 7-di(hydroxyphenylthio)-3,5-dioxaheptane.
• electron accepting compounds developer agents
• heat-sensitive color-forming layers Materials that are conventionally incorporated in heat-sensitive color-forming layers may be contained, as appropriate, in the heat-sensitive color-forming layer of the present invention.
• known heat-fusible organic compounds that melt at 50 - 150°C may be used as sensitizers and typical examples thereof are listed below: Phenyl p-hydroxynaphthoate; p-benzylbiphenyl; Benzyl naphthyl ether; Benzyl terephthalate; Benzyl p-benzyloxybenzoate; Diphenyl carbonate; and Dinitrile carbonate.
• organic and inorganic pigments that can be used in the present invention are not limited in any particular way such as with respect to the oil absorbing capability, and the following may be used as required: inorganic fine particulate compounds such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clays, talc, as well as surface-­treated calcium carbonate and silica; and organic fine particulate compounds such as urea-formaldehyde resin, styrene/methacrylic acid copolymer and polystyrene resin.
• inorganic fine particulate compounds such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clays, talc, as well as surface-­treated calcium carbonate and silica
• organic fine particulate compounds such as urea-formaldehyde resin, styrene/methacrylic acid copoly
• waxes may also be incorporated as required in the heat-sensitive color-forming layer, and known waxes may be used such as paraffin, amide-based waxes, bisimide-based waxes and metal salts of higher aliphatic acids.
• Useful adhesives include the following: water-­soluble polymers such as polyvinyl alcohols with various molecular weights, starches, derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethyl cellu­lose, methyl cellulose and ethyl cellulose, poly(sodium acrylate), polyvinylpyrrolidone, acrylamide/acrylate ester copolymer, acrylamide/acrylate ester/methacrylic acid terpolymer, alkali salts of styrene/maleic anhydride copolymer, polyacrylamide, sodium alginate, gelatin and casein; and latices of polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butad
• the present invention provides a heat-sensitive recording material that has a sufficiently rapid heat response to insure high sensitivity, that prevents the production of a dark image even if color formation is effected with high energy, and that yet causes little deposition of tailings on the surface of a thermal head.
• Example 1 Water 100 parts Calcined clay ("Ansilex” of Engelhard Minerals & Chemicals Corporation; oil absorption, 80 ml/100 g) 20 parts Dispersion of polystyrene particles ("L 8801” of Asahi Chemical Industry Co., Ltd.; solids content, 48%; average particle size, 0.5 ⁇ m) 40 parts
• a coating solution for heat-sensitive color-forming layer was prepared by the following procedure.
• composition consisting of these ingredients was pulverized with a sand grinder to an average particle size of 2 ⁇ m.
• Dispersion B Benzyl p-hydroxybenzoate 20 parts Polyvinyl alcohol (10% aq. sol.) 10 parts Water 70 parts
• composition consisting of these ingredients was pulverized with a sand grinder to an average particle size of 2 ⁇ m.
• Dispersion A 75 parts
• dispersion B 125 parts
• calcium carbonate 30 parts
• 10% aqueous polyvinyl alcohol 200 parts
• 30% paraffin dispersion 17 parts
• a dis­persion of 30% zinc stearate 17.1%
• Example 2 Water 100 parts Precipitated calcium carbonate ("Calulite SA” of Shiraishi Central Laboratory Co., Ltd.; oil absorption, 60 ml/100 g) 20 parts Dispersion of polystyrene particles ("L 8801” of Asahi Chemical Industry Co., Ltd.; solids content, 48%) 40 parts
• Example 1 Water 100 parts Synthetic silica ("Sorex CM" of Tokuyama Soda Co., Ltd.; oil absorption, 150 ml/100 g) 20 parts Dispersion of polystyrene particles ("L 8801" of Asahi Chemical Industry Co., Ltd.; solids content, 48%) 40 parts
• Example 2 Water 100 parts Ansilex 40 parts
• Example 2 Water 100 parts Dispersion of polystyrene particles ("L 8801" of Asahi Chemical Industry Co., Ltd.; solids content, 48%) 82 parts
• Example 1 These ingredients were dispersed with a homogenizer for 5 minutes and subsequently processed as in Example 1 to prepare a coating solution for undercoat layer. This solu­tion was applied onto a sheet of wood-free paper (50 g/m2) to form an undercoat layer, which was overlaid with a heat-­sensitive color-forming layer as in Example 1.
• Table 1 shows that the samples of the present invention not only exhibited a high color density at the two energies applied but they also had high resistance to the deposition of tailings.
• the ability of these samples to maintain a constant color density over a broad range of energies ( ⁇ 0.1 mJ) is very desirable for the purposes of designing machines such as printers and producing good image quality on heat-sensitive recording materials.
• the sample prepared in Comparative Example 1 used a pigment capable of greater oil absorption than 100 ml/100 g and the image density obtained at 0.54 mJ was lower than when an energy of 0.44 mJ was applied.
• the sample prepared in Comparative Example 2 did not use polystyrene and it was incapable of producing a high color density at either of the energies applied.
• the sample prepared in Comparative Example 3 used polystyrene alone. Although it exhibited high color densities over a broad range of energies, this sample was unacceptable in terms of resistance to the deposition of tailings.
• Sensitivity measurements were conducted with a test apparatus adapted from a commercial thermal facsimile. Pulse width modulation was effected to achieve a line speed of 10 msec/line and a scan density of 8 ⁇ 8 dots/mm, and 64 lines were printed with an energy of 0.44 mJ or 0.54 mJ being applied per dot. The resulting color densities were measured with a Macbeth densitometer RD- 514 and used as indices of recording sensitivity.
• tailings on the thermal head was inspected visually and the results were evaluated by the following criteria: 0, completely acceptable with little deposition of tailings; ⁇ , reasonably acceptable despite some deposition of tailings; X, unacceptable on account of extensive deposition of tailings.

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

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Publications (1)

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Cited By (4)

Citations (4)

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• 1989
  • 1989-05-23 JP JP1129772A patent/JPH089269B2/ja not_active Expired - Fee Related
• 1990
  • 1990-05-22 EP EP90305548A patent/EP0399785A1/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (2)

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