Ink ribbon for sublimation transfer type hard copy

Abstract: An ink ribbon for transfer type hard copy is described in which such ink ribbon containing a dye and a printing paper are in contact with each other and a picture image is formed on said printing layer by a selective heat-treatment wherein said ink ribbon includes a plastic film of polyethylene terephthalate substantially free of water content, an ink layer formed on the surface of said plastic film, said ink layer comprising a dye sublimable upon heating, a heat-resistant treating layer formed on another surface of said plastic film and a lubricating layer on said heat-resistant treating layer.

Description: TECHNICAL FIELD The present invention relates to an ink ribbon for a sublimation transfer type hard copy used to produce a hard copy of a still picture image such as a picture image taken by a video camera or a television picture image. BACKGROUND ART Fig. 1 shows an example of a prior art printer for a sublimation transfer type hard copy. This printer comprises a platen 2 having wound therearound a printing paper 1 and which is rotatable in the direction shown by an arrow a and a thermal print head 4 which is urged against the platen across an ink ribbon 3 for use in thermal transfer recording. On the point of the thermal print head 4, there are arranged heat generating elements 4a whose total number corresponds to the number of picture elements in one scanning line of, for example, a television picture image. The ink ribbon 3 for use in thermal transfer recording tightly pressed between the thermal print head 4 and the printing paper 1 is formed of a film base 9 on which, for example, an yellow ink layer Y, a magenta ink layer M, a cyan ink layer C and a black ink layer B each having a configuration corresponding to a configuration of a picture screen of a television picture image are repeatedly arranged in turn. Further, ink portion position detecting marks 5Y, 5M, 5C and 5B are respectively formed on one side edge of the film base at the positions of the corresponding color ink portions so as to detect the positions of the ink portions and a block position detecting mark 6 is formed on the other side edge of the film base so as to detect each combination group of four colors of Y, M, C and B. Under the condition that the yellow ink layer Y, for example, is urged against the printing paper 1 as described above, by an information corresponding to yellow, for example, a color signal corresponding to yellow of a television video signal, each head element 4a of the thermal print head 4 is heated with a pattern corresponding to the picture elements of one scanning line to thereby thermally transfer the yellow sublimation dye contained in the yellow ink layer Y to the printing paper 1 in accordance with the heated pattern. At every line corresponding to each scanning line, the platen 2 is intermittently rotated in the direction shown by the arrow a to thereby carry out the thermal transfer of information of each line. When the platen 2 is rotated one turn, the yellow color of one picture screen amount is transferred. Then, a similar transfer treatment is carried out with respect to the magenta color and subsequently, the cyan color and the black color are sequentially transferred repeatedly to thereby superpose the transferred picture images of the sublimation dyes of the yellow, magenta, cyan and black sublimation dyes one another, thus a color picture image being printed on the printing paper. In this case, detecting means are provided to detect the marks 5 (5Y, 5M, 5C and 5B) and 6 in the ink layers Y, M, C and B of respective colors for the purpose of supplying the signals corresponding to the respective color signals to the head elements 4a of the thermal print head 4. This detecting means includes, for example, a light source 7 for emitting a light ray for use in detection, for example, an infrared ray emitting diode and a detecting element 8 for detecting the infrared ray in which case, both of them are disposed in opposing relation to each other at both sides of the ink ribbon 3 for use in thermal transfer recording at which the marks 5 and 6 are provided. In the detecting means, the detecting element 8 produces a detected signal dependent on the presence or absence of the marks 5 and 6 whereby to detect the positional relation of the ink ribbon 3 for use in thermal transfer recording relative to the thermal print head 4. As the ink ribbon for such sublimation transfer type hard copy, there is used in the art such one that is formed such that on a film base 9 made of a paper such as a condenser paper, which is thin, uniform and dense, there is formed a coating layer made of an ink in which a sublimation dye is dissolved and dispersed into resin and solvent. As described above, since in the prior art ink ribbon, the paper is used as the film base 9, when the ink ribbon 3 is heated by the thermal print head 4, the water component contained in the paper is evaporated and the film base 9 is considerably shrunk to thereby produce wrinkles between the printing paper and the ink ribbon 3, thus lowering the picture quality. Although the amount of water component contained in the paper is very small, the water is boiled up momentarily by the thermal print head 4 heated around 400°C, producing a bubble spot in the film base 9. The fact that the heat is absorbed by the water upon boiling decreases sublimation amount of dye in the ink ribbon 3 and causes the bubble spot in the picture image as a density spot, thus lowering the picture quality considerably. On the other hand, on the surface of the printing paper 1 which is the transferred paper, after the sublimation dye is transferred thereto, there is provided a protecting layer. This protecting layer is to avoid such defects that when the protecting layer is not provided, the dye which is not diffused into the coating composition layer formed on the printing paper 1 but adhering to its surface is rubbed to be dropped in color and that if this dye is left as it is, the dye is transferred to pollute other materials. Further, since the dye coagulated on the coating composition layer can not produce the color inherent to the dye if the dye is left as it is, it is necessary that the coagulated dye is diffused sufficiently into the protecting layer to complete the coloring inherent to the dye. As a method for forming such protecting layer available to the above-described objects, the present applicant has previously proposed a method for forming a cover film by a laminator or a method for forming a protecting layer in which without using the laminator, the cover film layer formed on the ink ribbon is pressed by the same thermal print head so as to produce the protecting layer. By virtue of such technique, the protecting layer can be formed on the printing paper 1 very easily. However, since the film base of the ink ribbon on which the cover film layer is formed is made of condenser paper similarly to the prior art, there are the following problems. That is, when a resin layer which becomes the cover film layer is formed on the surface of the condenser paper, the releasing treatment must be carried out so as to prevent the resin layer and the condenser paper from being melt bonded. However, the dye coating layer must be bonded well to the condenser paper so that it is difficult to carry out the releasing treatment available only to the necessary portion and to carry out the complete releasing treatment in a manufacturing standpoint. Further, even if the releasing treatment is carried out, to the surface of the protecting layer the form of concavity and convexity peculiar to the condenser paper is transferred and hence the protecting layer having the smooth surface is not formed, thus the protecting layer being made insufficient in external appearance. DE-A-2 022 704 discloses a print ribbon, where in order to allow high thermal head temperatures and eliminate sticking, the base of a thermal transfer print ribbon is formed by a heat-resistant plastic or by placing a heat-resistant layer between an ordinary plastic base and a thermal head. In view of the above-described aspect, the problem underlaying this invention is to provide an ink ribbon for sublimation transfer type hard copy which is free of shrinkage of the film base, does not form bubble spots in the film base by heat generated upon transfer so that an excellent picture quality can be obtained. DISCLOSURE OF INVENTION This invention relates to an ink ribbon for sublimation transfer type hard copy, in which such ink ribbon containing a dye and a printing paper are in contact with each other and a picture image is formed on said printing paper by a selective heat treatment, which is characterized in that said ink ribbon includes a plastic film of polyethylene terephthalate substantially free of water content, an ink layer formed on the surface of said plastic film, said ink layer comprising a dye sublimable upon heating, a heat-resistant treating layer formed on another surface of said plastic film, and a lubricating layer on said heat-resistant treating layer. According to such an ink ribbon, it is possible to protect the plastic film base from being shrunk and producing a bubble spot therein due to heat generated upon transfer. Accordingly, the quality of a transferred picture image can be improved. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a perspective view of a prior art printer for sublimation transfer type hard copy; Fig. 2 is a cross-sectional view showing an embodiment of an ink ribbon according to the present invention; Fig. 3 is a perspective view of an ink ribbon for a color picture image; Fig. 4 is a side view showing the ink ribbon of the present invention which is in its use mode; Fig. 5 is a perspective view of an ink ribbon for a black and white picture image; Figs 6 to 8 are respectively perspective views showing other embodiments of the ink ribbon according to the present invention; and Fig. 9 is a side view showing the ink ribbon of the above embodiments which is in its use mode. BEST MODE FOR CARRYING OUT THE INVENTION Fig. 2 shows an embodiment of this invention comprising a plastic film base 16 with a plastic film 14 of polyethylene terephthalate substantially free of water content, on the surface of which is formed a heat-resistant treating layer 15 which does not have a melting point and, on the surface of the plastic film on which the heat-resistant treating layer 15 is not formed, there is formed a sublimation dye coating layer 13. A lubricant layer 35 is formed on the heat-resistant treating layer 15 of the ink ribbon 11. This lubricant layer ensures that the ink ribbon can slide on the thermal print head smoothly. This lubricant layer can be formed by coating on the layer a releasing agent such a silicone resin. The heat-resistant treating layer 15 made of a substance which does not have a melting point is formed such that a resin such as nitrocellulose and polyimide lacquer which begin to be carbonized or decomposed before being melted by heat or a heat curable heat-resistant resin such as melamine resin, aminoalkyd resin, epoxy resin, silicone denatured epoxy resin or unsaturared polyester and unsaturated oligomer such as epoxy acrylate is mixed with a curing agent, coated and then cured. Alternatively, the heat-resistant treating layer may be made of coating layer containing a denatured silicone resin denatured by a resin such as alkyd resin, epoxy resin, acrylic resin or urethane resin. Then, the denatured silicone resin is mixed with melamine resin or imidasol, coated and then cured to thereby form the heat-resistant treating layer. The thickness of the treating layer 15 is not limited particularly,but preferably selected in a range from 1µm to 10µm. A coating material in which a heat-resistant powder is dispersed into the resin available for forming the heat-resistant treating layer may be used to form the heat-resistant treating layer 15 of this ink ribbon 11. The heat-resistant powder may be inorganic powder such as silica, calcium carbonate, titanium oxide, carbon or graphite, heat-resistant organic powder such as teflon, silicone or cellulose powder. As described above, since the heat-resistant treating layer 15 contains the heat-resistant powder, the friction coefficient between the ink ribbon 11 and the thermal print head can be lowered to thereby enable the ink ribbon to smoothly slide on the thermal print head. Although the heat-resistant treating layer 15 is formed on the surface of the plastic film, if the ink ribbon is exposed in a high temperature of about 400°C for a long time, the treating layer 15 and the plastic film 14 are both melted. However, the heating by the thermal print head lasts for a very short time of period ranging from several tens microseconds to several tens milliseconds so that the plastic film 14 is not melted and thus the heat-resistant property of the treating layer 15 can prevent the ink ribbon 11 from being melt bonded and deformed. As described above, as the plastic film base of the ink ribbon for sublimation transfer type hard copy, the plastic film base having formed thereon the heat-resistant treating layer is used so that such film base contains no water component, thus the picture image becomes free of the bubble spot completely. Further, contrary to the condenser paper, the plastic film is swollen a little by the heating so that the ink ribbon in contact with the printing paper is not wrinkled. Accordingly, it is possible to increase the quality of the transferred picture image considerably. Fig. 3 illustrates another embodiment of the present invention which utilizes the fundamental structure of the above-described present invention. Particularly in this case, the present invention is applied to an ink ribbon for a color picture image in which after the picture image is formed, the protecting layer can be formed successively. In this embodiment, on one surface of the plastic film base 16 on which the heat-resistant treating layer is formed, the coating layers 13 mainly made of the sublimation dye are formed sequentially as in the order of yellow Y, magenta M, cyan C and black B (this can be provided as required). Between the adjacent combinations of the ink layers 13 (Y, M, C and B) of 4 colors, there is formed a protecting layer or a cover film layer 10 to thereby form an ink ribbon 31 for a color picture image. This cover film layer 10 is made of a transparent resin layer which can not be bonded to the plastic film base 16 but can easily be melt bonded to the surface of the printing paper. The thickness of the cover film layer 10 is in a range from 1 to 10 µm. The material of this cover film layer may be polyester resin, epoxy resin, cellulose acetate resin, nylon resin or polyvinylpyrrolidone resin, each having a melt bonding property. As required, the releasing treatment can be carried out between the base film 16 and the cover film layer 10. The cover film layer 10 may contain an ultraviolet absorbent or phosphor whitener, if necessary. Reference numeral 22 designates a sensor mark for use in determining the position. Fig. 4 illustrates a state of a transfer treatment which uses such an ink ribbon 31. Reference numeral 17 designates a printing paper in which a dye diffusing layer 19 is formed on the surface of a base 18. Reference numeral 23 designates a platen which moves the printing paper 17 and reference numeral 21 designates a thermal print head which is provided at its point with heat generating elements whose number is corresponding to the number of the picture elements in one scanning line of the picture image. The ink ribbon 31 is tightly pressed against the printing paper 17 by the thermal print head 21. In this ink ribbon 31, in like manner described in connection with Fig. 1, each heat generating element of the thermal print head 21 is supplied with the electric power in accordance with the video signal so as to sequentially sublimate and transfer the dyes of yellow Y, magenta M, cyan C and black B in response to the heated amount, thus forming a color picture image on the printing paper 17. Thereafter, the ink ribbon 31 is heated at its portion of the cover film layer 10 by the thermal print head 21 to thereby melt bond the cover film layer 10 to the printing paper 17. When the cover film layer 10 is melt bonded to the printing paper, a dye coagulated material 24 of picture image transferred from the ink ribbon 31 is diffused into the cover film layer 10 and the dye diffusing layer 19 of the printing paper 17. Reference numeral 25 designates the dye that is diffused as mentioned above. As set forth above, at the same time when the color picture image is formed, the cover film layer is formed. According to such ink ribbon 31 for a color picture image, as the film base thereof, there is used the heat-resistant plastic film base 16 so that the bubble spot caused by the evaporation of water component and the wrinkles will not appear and in addition, the protecting layer having the smooth surface can be formed. In the plastic film base 16, if necessary, the releasing treatment may be carried out over the portion of the protecting layer and further, a primer treatment may be carried out over the portion in which each color coating layer is formed. Practical examples of the ink ribbon 31 for a color picture image will be described next. An ink ribbon 32 for a black and white picture image is formed such that as shown in Fig. 5, the coating layer B of black color ink and the cover film layer 10 are sequentially formed. [Reference Example] A base material 14 was made by a polyester film having a thickness of 8µm. On one surface of this base material 14, there was coated a resin liquid having the following composition by a pipe coater such that the heat-resistant treating layer 15 might have a thickness of 3µm after being dried. Thereafter, at a temperature of 130°C, it was heated and then cured for an hour. After the heat-resistant treating layer 15 was made by the resin liquid having the above-described composition, on the surface opposing to the surface in contact with the thermal print head 4, there was coated a resin liquid having the following composition to thereby form the ink layer 13 of thermal transfer property, thus an ink ribbon for sublimation transfer recording being formed. [Example 1] The ink ribbon 11 for sublimation transfer recording which was formed in the above-described Reference Example was manufactured. Then, on the upper surface of the heat-resistant treating layer 15, there was coated a resin liquid having the following composition available for the purpose of lowering the friction coefficient upon transportation by using a gravure coater through a printing plate having a depth of 20µm and 200 lines 2.54 cm (inch). This product was placed at a temperature of 130°C for 5 minutes and then cured to form the lubricant layer 35 (see Fig. 2), thus an ink ribbon for sublimation transfer recording of this example being produced. When this ink ribbon for sublimation transfer recording was used to carry out the printing test, a clear picture image having no scattering in the printing density and which was free of the sticking and so on was stably obtained. After 1000 prints were made continuously, the head element 4a and the nearby portion thereof were observed by the microscope. In this case, no deposition of resin was discovered therefrom. Next, to confirm the effects of [Example 1], [Comparative example 1] will be described. [Comparative example 1] On one surface of a condenser paper (H-14 manufactured by Honshu Paper Co., Ltd.) having a thickness of 14µm used as a base material, there was coated a thermal. transfer ink layer having the following composition by using the gravure coater so as to have the thickness of 1µm after being dried, thus the ink ribbon for thermal transfer recording of this comparative example being formed. After the ink ribbon of this comparative example was used and 1000 prints were continuously printed similarly to the above-described examples, the results were observed by the microscope. In this case, it was confirmed that the resin component contained in the condenser paper which was used as the base material was deposited to the thermal print head 4. Fig. 6 illustrates a further embodiment of this invention. In the embodiment in Fig. 3, for the purpose of preventing the coagulated material of the sublimation dye deposited on the printing paper 17 from losing a color and the like purpose, after the dyes of 4 colors were transferred, the cover film layer 10 was formed on the printing paper 17. However, in practice, it is cumbersome to form such protecting layer and in addition, when the cover film layer 10 is formed on the thin printing paper 17, a deformation such as a curl will frequently be caused on the printing paper 17. This embodiment is to remove such defects. In this embodiment, as shown in Fig. 6, next to the last coating layer of the respective color coating layers of sublimation dyes necessary for forming one picture image, or the coating layer B of the black color ink in this embodiment, there is formed a portion 26 of an area equal to or larger than a picture image and in which no coating layer is formed to thereby form an ink ribbon 33. After the picture image of the coating layers Y, M, C and B of 4 colors is formed on the printing paper 17, as shown in Fig. 9, the portion 26 without the coating layer is successively urged against the printing paper 17 and the picture image is once again heated from the back of the ink ribbon by the thermal print head 21. By virtue of such re-heating, the coloring inherent to the dye can be developed and a coagulated material 24 of dye deposited on the printing paper 17 can be diffused well into the dye diffusing layer 19. The heat amount of the thermal print head 21 for such re-heating of the picture image is free from the restriction put by the signal that forms the picture image and becomes an electric power required by the whole of the resistor elements of the thermal print head 21 to diffuse the dye well. Such re-heating can be carried out a plurality of times by using the same portion 26 in which no coating layer is formed and this ensures that the dye can be fixed more completely. Further, as shown in Fig. 7, if a thin film 27 which is hard to be diffused with the dye is formed on the portion 26 in which no coating layer is formed, when the picture image is heated once again, the dye can be prevented from being dropped from the picture image and this enables the dye to be thermally fixed effectively. The thin film 27 which is hard to be diffused with the dye can be obtained by coating casein, coating and curing a curable heat-resistant resin such as polyimide resin, silicone resin or melamine resin, metal plating, and metal thin film treatment. According to this ink ribbon 33, the picture image can be fixed without using the protecting layer. Since the protecting layer is not used, the printing paper can be protected from the deformation such as curl. Fig. 8 illustrates an embodiment in which the above-described structure is applied to an ink ribbon 34 for a black and white picture image. In this case, next to the black color coating layer B, there is formed the portion 26 having no coating layer. As set forth above, according to the present invention, as the film base of the ink ribbon for sublimation transfer type hard copy, there is used a plastic film of polyethylene terephthalate having formed thereon a heat-resistant treating layer and a lubricating layer. Consequently, such film base contains no water component and produces no bubble unlike the prior art so that the bubble spot is removed from the picture image completely. Further, unlike the prior art condenser paper, the film base can be prevented from being shrunk largely by the heating and the film base is rather swollen a little so that no wrinkle is produced between the film base and the printing paper. Thus, the quality of the transferred picture image can be improved.

Claims: An ink ribbon for transfer type hard copy in which such ink ribbon containing a dye and a printing paper are in contact with each other and a picture image is formed on said printing paper by a selective heat treatment, characterized in that said ink ribbon includes a plastic film of polyethylene terephthalate substantially free of water content, an ink layer formed on the surface of said plastic film, said ink layer comprising a dye sublimable upon heating, a heat-resistant treating layer formed on another surface of said plastic film, and a lubricating layer on said heat-resistant treating layer. The ink ribbon for sublimation transfer type hard copy according to claim 1, characterised in that a cover film layer made of a transparent resin layer which is to be melt bonded and transferred on a printed printing paper is further formed on said film base. The ink ribbon for sublimation transfer type hard copy according to claim 1, characterized in that coating regions of yellow, magenta and cyan dyes are formed on the plastic film in turn in the longitudinal direction of said film. The ink ribbon for sublimation transfer type hard copy according to claim 3, characterized in that dye coating regions of yellow, magenta, cyan and black are formed on said film in turn in the longitudinal direction of said film. The ink ribbon for sublimation transfer type hard copy according to claim 3, characterized in that dye coating regions of yellow, magenta and cyan and a cover film region are formed on said film in turn in the longitudinal direction of said film. The ink ribbon for sublimation transfer type hard copy according to claim 3, characterized in that dye coating regions of yellow, magenta, cyan and black and a cover film region are formed on said film in turn in the longitudinal direction of said film. The ink ribbon for sublimation transfer type hard copy according to claim 1, characterized in that said heat-resistant treating layer is made of a resin having no melting point. The ink ribbon for sublimation transfer type hard copy according to claim 7, characterized in that said heat-resistant treating layer is formed by curing a denatured silicone resin denatured by a resin which is selected from alkyd resin, urethane resin, epoxy resin or acrylic resin.

Inventors: ABE TETSUYA C O SONY CHEMICALS, FUJIWARA YOSHIO C O SONY CHEMI, KOBAYASHI NAOTAKE C O SONY CHE, SHINOHARA SATORU C O SONY CHEM, ABE, TETSUYA, FUJIWARA, YOSHIO, KOBAYASHI, NAOTAKE, SHINOHARA, SATORU, ABE, TETSUYA, C/O SONY CHEMICALS CORP., FUJIWARA, YOSHIO, C/O SONY CHEMICALS CORP., KOBAYASHI, NAOTAKE, C/O SONY CHEMICALS CORP., SHINOHARA, SATORU, C/O SONY CHEMICALS CORP.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: B41M5
IPC codes: B41M5