HEAT SENSITIVE TRANSFERRING RECORDING MEDIUM

Abstract: A heat-sensitive transferring recording medium comprises a heat-resistant substrate, a heat-sensitive releasing layer and a heat-sensitive transferring ink layer, and the ink layer mainly comprises 50 - 80 wt.% polyethylene resin having a melting point or softening point of 60 - 150°C, molecular weight of 1,000 - 100,000, penetration of 20 or less (at 25°C)(JIS K 2235), and melting viscosity of 100 - 10,000 cps (at 140°C), 0 - 30 wt. % wax having a melting point of 50 - 110°C, and 5 - 45 wt.% coloring agent. A heat-sensitive transferring recording medium comprises a heat-resistant substrate, a heat-sensitive releasing layer melting at 50 - 100°C and a heat-sensitive transferring ink layer.

Description: This invention relates to a heat-sensitive transferring recording medium and more particularly, to a heat-sensitive transferring recording medium used for a heat-sensitive transferring recording apparatus such as thermal facsimile and thermal printer. Related Background Art Non-impact type heat-sensitive recording systems have recently drawn public attention since they are of less noise and easy handling. The conventional heat-sensitive recording systems are free from noise and do not need any development and fixation, and the handling is easy, but have some problems of falsifying and storaging. In order to solve such problems, there have been proposed heat-sensitive transferring recording methods which comprise forming a heat melting ink layer on a substrate and superposing a receiving paper (recording paper) on the heat melting ink layer, heating the substrate with a thermal head, and melting the heat melting ink layer to transfer the melted portion of the heat melting ink layer to a receiving paper composed of a plain paper. However, these heat-sensitive transferring recording methods suffer from the following problems. That is, though good print can be obtained when the degree of smoothness of the receiving paper composed of a plain paper is high, unevenness of the surface of the receiving paper results in that there are some portions contacting the receiving paper and some portions not contacting the receiving paper when the degree of smoothness of the receiving paper is low, for example, Bekk smoothness is 50 sec. or less, and as a result, the transferring efficiency becomes low to form voids and lower the sharpness, and moreover, fluidity of the heat melting ink is so high that the heat melting ink penetrates the receiving paper and reaches the inside resulting in less density. Therefore, good print cannot be produced. EPO application 0 194 860, unpublished at the date of the present application, describes ink manufacturing methods in which a hot melt type coating material or an organic solvent type coating is used and the content of resin components is at most 20% by weight. In the case of hot melt ink, the more the content of resin component, the higher is the melt viscosity, and thereby coating is not possible. In the case of organic solvents type inks, it is difficult to dissolve or disperse waxes and, further, remove the organic solvent from the wax dissolved or dispersed in the organic solvent for drying. SUMMARY OF THE INVENTION An object of the invention is to provide a heat-sensitive transferring recording medium of high transferring efficiency and producing sharp and clear print of high density free from void. According to the present invention, there is provided a heat-sensitive transferring medium which comprises a heat-resistant substrate, a heat-sensitive releasing layer and a heat-sensitive transferring ink layer laminated in this order, the heat-sensitive transferring ink layer mainly comprising (a) a polyethylene resin having a melting point or softening point of 60 - 150°C, molecular weight of 1,000 - 100,000, penetration of 20 or less (at 25°C)(JIS K 2235) and melting viscosity of 100 - 10,000 cps (at 140°C), (b) a wax having a melting point of 50 - 110°C, and (c) a coloring agent, and the contents of (a), (b) and (c) components being 50 - 80 % by weight, 0 - 30% by weight and 5 - 45% by weight after dried, the total of (a), (b) and (c) being 100% by weight. DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat-resistant substrate used in the present invention includes a thin paper of 20 µ or less thick such as glassine, condenser paper and the like, and a heat-resistant film of 10 µ or less thick such as polyester, polyimide, nylon, polypropylene films and the like. Plastic films of 2 - 10 µ thick are preferred. In order to enhance the heat resistance of a heat-resistant substrate, there may be provided a heat-resistant protective layer. As polyethylene in the heat-sensitive transferring ink layer used in the present invention, there may be used low molecular weight polyethylene of oxide type having an acid value of 5 - 30, low molecular weight polyethylene of a copolymer type containing 5 - 40% by weight of vinyl acetate, low molecular weight polyethylene of a copolymer type containing 5 - 15 % by weight of an organic acid (for example, acrylic acid), and their emulsions or dispersions. As waxes used in the heat-sensitive transferring ink layer of the present invention, there may be used paraffin wax, microcrystalline wax, carnauba wax, shellac wax, montan wax and higher fatty acids. Emulsions thereof may be also used. For example, as a wax emulsion, there may be used emulsions of paraffin wax, microcrystalline wax, canauba wax, shellac wax and montan wax. A coloring agent for the heat-sensitive transferring ink layer used in the present invention, there may be mentioned pigments such as carbon black, iron oxide, prussian blue, lake red, titanium oxide and the like, and dyes such as basic dyes, neozapon dyes and the like. As other components for the heat-sensitive transferring ink layer, there may be used a filler, for example, extender pigments such as calcium carbonate, clay and the like and a softening agent such as various animal oils, vegetable oils, mineral oils and the like. Further, it is effective for decreasing an energy necessary for heat-sensitive head to provide a heat-sensitive releasing layer between a substrate and a heat-sensitive transferring ink layer. The releasing layer may be formed by using silicone, celluloses, and waxes, alone or in combination. Further, they may be used together with pigments such as carbon black, calcium carbonate, clay, talc and the like dispersed therein. Preferably a releasing layer capable of melting at 50 - 100 °C is used. Examples of composition of the releasing layer are as shown below. (In each of A and B below, the total of the components is 100 wt.%.) A : Wax 90 - 40 wt.% Thermoplastic resin 0 - 40 wt.% Softening agent 0 - 30 wt.% B : Wax 100 - 30 wt.% mp.50 - 100°C One or more thermoplastic resins 10 - 60 wt.% mp.60 - 150°C Softening agent 0 - 30 wt.% liquid at room temperature C : One or more selected from rosin and its derivatives, terpene resin, hydrocarbon resins, α-methylstyrene-vinyltoluene copolymer, low molecular weight styrene resins, and coumarone-indene resin. D : Wax emulsions Components for the releasing layer melting at 50 - 100°C used in the present invention are as shown below. Waxes such as paraffin wax, microcrystalline wax, carnauba wax, shellac wax, montan wax, higher fatty acids, higher fatty acid amides, higher alcohols, higher fatty acid metal soap, and the like. As wax emulsions, emulsions of the above-mentioned various waxes may be used. Thermoplastic resins such as ethylene-vinyl acetate copolymer, polyamide, polyethylene, polyester, and the like. Resins exhibiting low viscosity when melted such as rosin and its derivatives, terpene resin, hydrocarbon resins of aliphatic type, aromatic type, aliphatic/aromatic copolymer type, alicylic compound type, or the like, α-methylstyrene-vinyltoluene copolymer, low molecular weight styrene resin, coumrrone-indene resin, and the like. They may be used alone or in combination. When they are used together with hydrogenated hydrocarbon resins or low molecular weight styrene resins, good results are obtained. As a softening agent, there may be used various animal oils, vegetable oils or mineral oils. As a heat-resistant protective layer, there may be used higher fatty acid, fluorocarbon resin, silicone resin or the like. Where the heat-sensitive releasing layer can melt at a temperature ranging from 50°C to 100°C, a conventional heat-sensitive transferring ink layer may be used, and it is preferred that the heat-sensitive transferring ink layer is composed of the components (a), (b) and (c) (50 - 80 % by weight, 0 - 30 % by weight and 5 - 45 % by weight, respectively) as mentioned above. The heat-sensitive transferring recording medium may be produced by the following method. The above-mentioned wax, thermoplastic resin, and softening agent, or wax-emulsion, or a styrene oligomer, and hydrogenated petroleum resin are mixed or dispersed, and the resulting mixture or dispersion is applied to a heat-resistant substrate by hot-melt coating or solvent coating followed by drying to produce a heat-sensitive releasing layer. Then, to the surface of the heat-sensitive releasing layer is applied a mixture of the above-mentioned polyethylene resin, wax and coloring agent dispersed in a solvent or a molten mixture of the components. When the emulsion or dispersion is used, polyethylene emulsion, wax emulsion, and coloring agent are dispersed in water by means of a dispersing machine such as a ball-mill or attritor, to produce an ink. When a commercially available coloring agent dispersion is used as a coloring agent, it is necessary only to simply mix and agitate the above-mentioned components. The resulting ink coating material is applied to a substrate by means of a hot melt type or solvent type coating machine followed by solidifying or drying. Where a heat-resistant protective layer is provided on a surface of the substrate opposite to the ink layer, a component such as higher fatty acid, fluoro-carbon resin, silicone resin or the like as mentioned above is mixed with and dispersed in a solvent and applied to the opposite surface followed by drying. The thickness of the heat-sensitive transferring ink layer is preferably 2 - 10 µ. EXAMPLES 1 - 19 To the upper surface of a 4 µ thick PET (polyethylene terephthalate) was applied a fatty acid amide in the thickness of 1 µ to form a heat-resistant protective layer, and to the other surface was applied a coating material comprising a resin such as silicone, ethyl cellulose polyamide, polyethylene, and coumarone-indene and the like, wax such as microcrystalline wax, montan wax and the like, a wax emulsion such as microcrystalline wax emulsion, montan wax emulsion and the like and/or a plasticizer and others as shown in the examples in the following tables, to produce a 2 µ thick heat-sensitive releasing layer. To the surface of the resulting heat-sensitive releasing layer was applied a coating material composed of a resin such as low molecular weight polyethylene and the like, and/or wax such as carnauba wax, paraffin wax, emulsions thereof and the like, and/or a softening agent, and a coloring agent to produce a 4 µ thick heat-sensitive transferring ink layer. The heat-sensitive transferring recording mediums produced according to the above-mentioned examples were tested by using a heat-sensitive printer (cycle, 1.2 m sec; impressed pulse width, 0.9 m sec; power, 0.5 W/DOT) and receiving paper having Bekk smoothness test of 16 sec, Hammermill bond paper (JIS P8119). The results show that the products in Examples 1 and 2 (conventional products) gave many voids and low density while the products of Examples of 3 - 19 gave less void and good prints of high density, except for Example 5 which is a comparative example. See "Test Result" ( infra ).

Claims: A heat-sensitive transferring recording medium which comprises a heat-resistant substrate, a heat-sensitive releasing layer and a heat-sensitive transferring ink layer laminated in this order, the heat-sensitive transferring ink layer mainly comprising (a) a polyethylene resin having a melting point or softening point of 60 - 150°C, molecular weight of 1,000 - 100,000, penetration of 20 or less (at 25°C)(JIS K 2235) and melting viscosity of 100 - 10,000 cps (at 140°C), (b) a wax having a melting point of 50 - 110°C, and (c) a coloring agent, and the contents of (a), (b) and (c) components being 50 - 80 % by weight, 0 - 30% by weight and 5 - 45% by weight after dried, the total of (a), (b) and (c) being 100% by weight. A heat-sensitive transferring recording medium according to claim 1 in which the heat-resistant substrate is constituted of a plastic film provided with a heat-resistant protective layer. A heat-sensitive transferring recording medium according to claim 1 in which the polyethylene resin is a low molecular weight polyehtylene of oxide type having acid value of 5 - 30. A heat-sensitive transferring medium according to claim 1, in which the polyethylene resin is a low molecular weight polyethylene of a copolymer type containing 5 - 40% by weight of vinyl Acetate. A heat-sensitive transferring recording medium according to claim 1 in which the polyethylene resin is a low molecular weight polyethylene of a copolymer type containing 5 - 15% by weight of an organic acid. A method of manufacturing a heat-sensitive transferring recording medium according to any one of claims 1 - 5, in which the polyethylene resin is applied in the form of an emulsion and/or aqueous dispersion. A heat sensitive transferring recording medium according to claim 1, in which the heat-sensitive releasing layer melts at 50 - 100 degrees C. A heat-sensitive transferring recording medium according to claim 7 in which the releasing layer comprises 40 - 90% by weight of wax, 0 - 40% by weight of a thermoplastic resin and 0 - 30% by weight of a softening agent, total contents of the wax, thermoplastic resin and softening agent being 100% by weight. A heat-sensitive transferring recording medium according to claim 7 in which the releasing layer comprises (a) a wax having a melting point of 50 - 100 degrees C, (b) one or more of thermoplastic resins having a softening point or a melting point of 60 - 150 degrees C, and (c) a softening agent which is liquid at the normal temperature, the contents of (a), (b) and (c) being 100 - 30% by weight, 10 - 60% by weight,and 0 - 30% by weight, respectively, and the total contents of (a), (b) and (c) being 100% by weight. A heat-sensitive transferring recording medium according to claim 7 in which the releasing layer comprises at least one member selected from the group consisting of rosin, its derivatives, terpene resin, hydrocarbon resins, α-methylstyrene-vinyltoluene copolymer, low molecular weight styrene resins, and coumarone-indene resins. A method of manufacturing a heat-sensitive transferring recording medium according to claim 7, in which the releasing layer is applied in the form of a wax emulsion. A heat-sensitive transferring recording medium according to any one of claims 7 - 10, or made by a method according to claim 11, in which the heat-resistant substrate is a plastic film provided with a heat-resistant protective layer.

Inventors: UEYAMA, SEIJI
Applicants: GENERAL COMPANY LIMITED
Application year: 1986
Main classification: B41M5
IPC codes: B41M5