An embodiment of the invention will be described below with reference to the drawings.
In
The operation of the thermal transfer printer will now be described. In an initial state before printing, the thermal head 3 is lifted and separated from the platen roll 4. When the ribbon supply roll 1 is mounted, the edge of the ribbon 10 is passed between the conveying rollers 5. The edge of the ribbon 10 is then passed between a heat roller 8a and a pressure roller 8b that constitute a heating unit 8, while covering the top of the bending unit 7. The edge of the ribbon 10 is then fixed around the take-up roll 9. The edge of the receiver sheet 11, on the other hand, is drawn from the receiver sheet supply roll 2, and held between conveying rollers (not illustrated) and fixed.
During printing, the thermal head 3 is lowered by a pressing mechanism (not illustrated) to press the ribbon 10 and the receiver sheet 11 together between the thermal head 3 and platen roll 4. The thermal head 3 with a plurality of heat resistors then records on the receiver sheet 11 by selectively heating the sheet according to image information on the thermal head 3.
When printing is completed, the pressing mechanism (not illustrated) lifts the thermal head 3, whereupon the pressure between the ribbon 10 and the receiver sheet 11 is released. A predetermined length of the receiver sheet 11 is drawn by conveying rollers (not illustrated), and conveyed to an ejector (not illustrated). The used ribbon 12, on the other hand, is conveyed by the conveying rollers 5 to the processing mechanism 6. The bending unit 7 forms a bend line in the ribbon 12 delivered to the processing mechanism 6, and then the ribbon 12 is delivered to the heating unit 8. In the bending unit 7, the first bending member 7a causes the ribbon 12 to curve upwardly, and then the second bending member 7b with an acute apex forms a bend line in the used ribbon 12 in the longitudinal direction. The ribbon 12 with a bend line is passed between the heat roller 8a and pressure roller 8b, and is thereby folded along the bend line, which causes the opposing dye layers to be fused together. The used ribbon 12 that has passed through the processing mechanism 6 is subsequently wound onto the take-up roll 9.
The first bending member 7a is a plate material whose upper edge has an arch-shaped curved surface. Contacting the ribbon 12 with this arch portion allows the ribbon to curve upwardly. This reduces the tension that is generated when the bend line is formed by the second bending member 7b. The second bending member 7b may be composed of a plate material with an acute apex in the center, and more specifically, a plate material with an isosceles triangle-shaped top. The vertical angle θ of the isosceles triangle is preferably from 90 to 150°. This is because an angle of less than 90° produces great tension, whereas an angle of more than 150° makes it difficult to form a bend line. Note that the apex of the second bending member 7b may not necessarily have an acute edge, as long as it is acute enough to form a bend line.
While typical plastic materials such as ABS and styrene are usable as the first and second bending members 7a, 7b, materials such as silicone-modified resin are particularly preferable because they can reduce the frictional resistance between these members and the ribbon.
Further, as shown in
The second bending member 7b is positioned at a distance from the first bending member 7a. This distance D is at least 1/4 , and preferably not less than 1/4 and not more than 1/1, of the width of the used ribbon. If the distance D is shorter than the width of the used ribbon, the used ribbon cannot be curved sufficiently with the first bending member 7a, and the effect of reducing the tension cannot be obtained.
Although the figures show an example of the structure in which the first bending member 7a and the second bending member 7b are separate, a bending unit in which the first bending member 7a and the second bending member 7b form a single molded product may also be used. Moreover, when the first bending member 7a and the second bending member 7b are separate, as shown in
In order to thermally fuse the dye layers together, the temperature of the heat roller 8a must be equal to or higher than the glass transition temperature of the binder resin contained in the dye layers. The temperature is, for example, from 100 to 200° C., and preferably from 110 to 180° C.
In the above-described embodiment, the heating unit performs both heating and folding of the ribbon. That is to say, the folder and the heater according to the invention are formed integrally. These components, however, may also be separate, for example, as shown in
The term “low-capacity heat source” as used herein denotes a heating member in which the heat source has a very low heat capacity, and the temperature of the heat source after the supply of heat to the heat source is stopped rapidly decreases to 30 to 50° C. The definition of a “very low heat capacity” denotes a heat capacity such that the amount of heat remaining in the heat source immediately after heating has been stopped is so small that even if the heat is applied intensively to one area of a ribbon that has stopped being conveyed, the film used as the ribbon base, such as PET, is not heated to its melting point (around 250° C.), thereby preventing the ribbon from breaking due to excess heating. While the state described by “the supply of heat to the heat source is stopped” may depend on the heating element selected, in the case of a thermal head, this denotes a state in which the application of electricity is stopped. The term “rapidly” is defined as a period of about one second.
Alternatively, the heating members 20a, 20b may generate electromagnetic waves such as microwaves, so as to heat only the dye layers of the ribbon without heating other portions that do not require heating.
Note that the ribbon is not continuously conveyed, but stops, for example, at the instance before and after printing, as described below. In such an instance, excess heat is applied to the ribbon that is being exposed to heat by the heater 20, possibly breaking the ribbon. For this reason, as shown in
In the case of color printing, a ribbon is typically used which has repeated coatings of dye layers of cyan C, magenta M and yellow Y formed sequentially in the longitudinal direction of the base. These dye layers are sequentially printed and superimposed onto the receiver sheet. During color printing, when the receiver sheet is returned to its initial position by the supply roll 2 every time a single color is printed thereon, the receiver sheet is conveyed after all of the dyes have been superimposed. The ribbon is also positioned upstream of each ink every time a single color is printed. For example, when yellow Y is printed, the thermal head 3 is positioned on the upstream end of yellow Y, as shown in
During this color printing, the ribbon moves in the direction opposite to the conveyance direction, causing a great load to be applied to the ribbon that is being bent by the bending unit 7, thus possibly breaking the ribbon. In order to prevent this, a buffer unit 30 may be provided, as shown in
The buffer unit is illustrated in detail in
The buffer unit may also have a structure such as that shown in
While the use of the first bending member 7a with one curved portion and the second bending member 7b with one apex has been shown as an example in the above-described embodiment, first and second bending members 7a, 7b with a plurality of curved portions or apexes can also be used. In that case, multiple bend lines which are not limited to two, such as three, four, etc., can be formed in a ribbon. Examples of such bending units will be described below.
As shown in
The bending unit may also have a structure as shown in
In the aforementioned examples, the ribbon is folded with the first and second folding members and subsequently heated; however, the ribbon may be bound in the width direction instead of being folded, so as to become unreadable. Such an example is now described referring to
With this structure, the ribbon is bound in the width direction and then heated, which causes the dye surfaces to be fused together, thereby preventing the reading of information from the ribbon. While the ring 50 is used for binding the ribbon in this example, any suitable member capable of reducing the width of the ribbon can be used, such as a U-shaped member. Moreover, while the ribbon is bound with the ring 50 and then heated in this example, this order of steps may be the opposite. That is to say, the ribbon may be heated and softened, and then bound with the ring 50.
Note that the take-up roll 9 can be made to reciprocate in the axial direction (i.e., the direction vertical to the paper of
Moreover, in the case of color printing with a printer that uses such a ring 50, the ribbon may be conveyed upstream during printing. In this case, as shown in
Moreover, the following structure is also possible. The portion of the ribbon that passes by the heater 20 while the ribbon is unwound is designed not to be heated by the heater 20 within the rewinding distance G that starts from its downstream end. As shown in
Furthermore, the thermal transfer printer may also have a structure as shown in
The ribbon is not particularly limited as long as it has a dye layer on one surface of its base, but preferably has a bottom-surface layer on the other surface thereof. The base of a thermal transfer sheet may be any known material with a certain degree of heat resistance and strength. Examples of materials include polyethylene terephthalate films, 1,4-polycyclohexylene dimethylene terephthalate films, polyethylene naphthalate films, polyphenylene sulfide films, polystyrene films, polypropylene films, polysulfone films, aramid films, polycarbonate films, polyvinyl alcohol films, cellophane, cellulose derivatives such as cellulose acetate, polyethylene films, polyvinyl chloride films, nylon films, polyimide films, ionomer films and the like. Among these examples, polyethylene terephthalate films are preferable. The thickness of the material used is about 0.5 to about 5.0 μm, and preferably about 1 to about 10 μm.
A dye layer may be formed of a single monochrome layer, or a plurality of dye layers with different phases of colors may be repeatedly formed sequentially on the same surface of the same base. Dye layers support a sublimable color on an optional binder. Dyes used in known dye-sublimation transfer sheets, which are thermally melt, diffused or transferred by sublimation, may be used in the invention. These dyes can be selected in consideration of their color phase, printing density, light resistance, shelf life, solubility in binders and the like.
Examples of dyes include diarylmethine, triarylmethine, thiazoles, methines such as merocyanine and pyrazolone methine, azomethines such as indoaniline, acetophenoneazomethine, pyrazoloazomethine, imidazoleazomethine, imidazoazomethine and pyridoneazomethine, xanthenes, oxazines, cyanomethylenes such as dicyanostyrene and tricyanostyrene, thiazines, azines, acridines, benzeneazos, azos such as pyridone azo, thiophene azo, isothiazole azo, pyrrole azo, pyrazolo azo, imidazol azo, thiadiazole azo, triazole azo and disazo, spiropyrans, indolino spiropyrans, fluorans, rhodamine lactams, naphthoquinones, anthraquinones, quinophthalones and the like.
Any known binder resin may be used as a binder for the dye layer. Preferable examples of such binders include cellulose resins such as ethyl cellulose, hydroxyethylcellulose, ethylhydroxycellulose, hydroxypropylcellulose, methylcellulose, cellulose acetate and cellulose butyrate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone and polyacrylamide, polyester resin, phenoxy resin and the like. Especially preferable among these examples are cellulose resins, acetal resins, polyvinyl butyral resins, polyester resins and phenoxy resins, in view of their good heat resistance, dye transferability and the like.
A dye layer may incorporate any of the aforementioned dyes, binders, and various known additives, as necessary. Examples of additives include organic particles such as polyethylene wax, inorganic particles, silicone oil and phosphoric ester, for improving the releasability from receiver sheets and the suitability of inks for application. Such a dye layer can be typically formed by adding any of the aforementioned dyes, binders and optional additive(s) to a suitable solvent, dissolving or dispersing these components to prepare a coating dispersion, and then applying the resulting dispersion onto a base and drying. Coating can be accomplished by a known means, such as gravure printing, screen printing, or reverse roll coating using a gravure plate. The amount of the thus formed dye layer is from 0.2 to 6.0 g/m2, and preferably from 0.2 to 3.0 g/m2, as measured after drying.
A heat-resistant sliding layer can be used as a bottom-surface layer. The heat-resistant sliding layer serves to control the sliding properties of the base on the thermal head to improve the heat resistance of the base. Examples of resins forming the heat-resistant sliding layer include cellulose resins such as ethyl cellulose, hydroxyethylcellulose, ethylhydroxy cellulose, hydroxypropyl cellulose, methylcellulose, cellulose acetate and cellulose butyrate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, and polyacrylamide, polyester resin, polyurethane resin, polyamide-imide resin, silicone-modified polyamide-imide resin and silicone-modified or fluorine-modified resin.
The heat-resistant sliding layer of the invention can be formed by, for example, the following method. Any of the aforementioned resins or a filler dissolved or dispersed in a suitable solvent is applied on a base to prepare a heat-resistant-sliding-layer coating dispersion. The resulting dispersion is applied by a means such as gravure printing, screen printing, or reverse roll coating using a gravure plate, and dried. The amount of the dried heat-resistant sliding layer is preferably from 0.1 to 3.0 g/m2.
Examples of usable receiver sheets include natural pulp papers, coated papers, tracing papers, plastic films, metals, ceramics, wood and cloths.
The invention will hereinafter be described in greater detail with reference to the Examples, which are not intended to limit the invention.
A heat-resistant-sliding-layer coating dispersion with the composition shown below was applied by gravure coating onto an untreated surface of a thin-film base (PET film 4WF597, a polyethylene terephthalate film, manufactured by Toray, thickness: 4.5 μm) in an amount of 0.5 g/m2 as measured after drying, and dried to form a heat-resistant sliding layer. A dye-layer coating dispersion with the composition shown below was then applied by gravure coating onto the surface (which was treated to facilitate adhesion) of the thin-film base opposite to the surface with the heat-resistant sliding layer, in an amount of 0.7 g/m2 as measured after drying, and dried. A thermal-transferable-protective-layer coating dispersion with the composition shown below was then applied to the dye layer in an amount of 1.0 g/m2 as measured after drying, and dried to form a thermal-transferable protective layer. A sensor mark for position detection was then formed on the dye layer and thermal-transferable protective layer, so as to yield a ribbon.
The ribbon prepared according to the method described above was mounted in the thermal transfer printer shown in
By using the used ribbon processing mechanism of the invention, only the dye layers were fused together. The ribbon showed no breakage.
For comparison, evaluation was also carried out in the same manner as described above, using only a second bending member with an acute top. Although the dye layers were fused together, some of the tested ribbons were partially broken, showing that stable fusion of ribbons was difficult.
Number | Date | Country | Kind |
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2006-235970 | Aug 2006 | JP | national |
2006-313541 | Nov 2006 | JP | national |
2006-313550 | Nov 2006 | JP | national |