METHOD FOR PRODUCING MULTI-COLOR INK RIBBONS

Abstract: This improved multi-colour ink ribbon is impregnated with liq. inks of different colours between border lines. The ribbon is made of a cloth base formed from yarns that are heat-meltable. The ink non-impregnatable border lines are formed by melting the yarns of the cloth base under non-contact conditions. The border lines are formed by irradiation with heat rays in a non-contact manner, by which means the irradiated yarns of the cloth base are melted. The irradiated yarns lie at the positions where it is desired to form the border lines. Laser light beams are used as heat rays. The laser beam is focused with a lens to an oval shape, the long axis of which lies along the direction in which the irradiation is scanned along the cloth base.

Description: This invention relates to a method for producing multicolor ink ribbons for typewriters or printers provided with a mechanism for impact printing. As multi-color ink ribbons for use with typewriters or impact type printers of word processors, computers and other devices, there are known two-color ink ribbons comprising a textile substrate saturated with black and red liquid inks on both sides of an ink-resistant borderline and four-color or other multi-color ink ribbons comprising a substrate fabric similarly saturated with, for example, black, cyan, magenta and yellow liquid inks. This type of multi-color ink ribbon has the drawback of "migration", an intermingling of the inks of different colors from the adjacent ink-saturated lanes during storage, distribution or use, and a variety of preventive countermeasures have been proposed. For example, JP-U1- 65012/1976 discloses the art of forming a borderline between ink-saturated lanes by hot melting technique or by impregnation with a plastic composition. JP-A- 128412/1978 discloses the art of forming a borderline by causing the substrate fabric to contact a thermal means such as a hot roller. JP-U1- 134516/1979 teaches the technique of forming a borderline wherein the substrate fabric is melted under pressure by means of the pressure tip of an ultrasonic welder. JP-A- 140285/1983 teaches the technique of forming a borderline by coating the substrate fabric with a water repellent agent such as silicone oil, paraffin, wax, a fluorine-containing resin, or the like. However, the method in which the borderline is formed by coating the substrate fabric with a plastic material or a water repellent agent is disadvantageous in that if one tries to assure a sufficient penetration of the coating agent into the substrate fabric to prevent formation of pinholes, the coating agent will diffuse too much into the substrate so that a broad ink-resistant zone is formed in the substrate fabric. As a result, the ribbon must have a fairly large width and this, in turn, makes it essential to scale up both the ribbon feed mechanism and the shifting mechanism for color change. Furthermore, it is technically difficult to accurately construct a borderline of uniform width by any of such coating techniques. The method of forming a borderline by melting the substrate fabric with a heating means such as the hot roller or pressure tip of a high frequency welding machine is disadvantageous in that the heating means picks up the molten masses of the substrate to cause an irregular travel of the fabric and a variation in heating temperature. Such troubles result in a local under-melting or over-melting at the points of contact so that pinholes are formed in the borderline to cause a migration of inks from the adjacent ink-saturated lanes. In addition, as shown in Fig. 4, which is a partially expanded view (a schematic tracing of a micrograph) showing the borderline formed by the above method employing a heating means, a portion of the melted fiber collects and is solidified to form resin build-ups 5a along both edges of the borderline (5), and these resin build-ups 5a tend to interfere with the operation of the ribbon shift guide during the use of the ink ribbon or cause an instability of the direction of travel; the result is irregular traveling. In Fig. 4, the numeral 3 denotes the substrate fabric, 3a the warp fiber of the same, 3b the weft fiber of the same, and 5 the borderline. Furthermore, it is known to obtain the ink-impervious borderlines between adjacent color saturated lanes of an ink ribbon by focusing a CW laser on the travelling ribbon with sufficient intensity to melt the nylon filaments of the ribbon so that they fuse together and form borderlines between the colored lanes of the ribbon (IBM Technical Disclosure Bulletin Vol. 26 No. 12, May 1984). However, a laser beam focused in its true round shape onto a substrate fabric is liable to cause local over-heating or over-melting or under-melting in the borderline so that unevennesses occur and pin holes are formed in the borderline which allow migration of ink from adjacent ink-saturated lanes of the ribbon. Also, it is difficult to achieve smooth control of the method in forming the borderlines. It is the object of the present invention to provide multi-color ink ribbons manufactured thus that the border lines between the different liquid ink colors are narrow and effectively avoid migration of ink colors. By the invention a multi-color ink ribbon comprising a substrate fabric constructed of heat-meltable fiber and saturated with liquid inks of different colors in distinct lanes separated by one or more borderline from each other is obtained, each of said borderlines being an ink-impervious narrow linear zone formed by melting the fiber corresponding thereto under no compressive stress. The invention consists in a method of producing multi-color ink ribbons comprising a substrate fabric constructed of heat-meltable fiber and saturated with liquid inks of different colors in distinct lanes separated by one or more borderlines from each other, which comprises melting the fiber in a linear zone corresponding to each of said borderlines by irradiation with thermal radiation without physical contact and which operates in accordance with the characterizing portion of the single method claim. This invention is described below in further detail. The substrate fabric to be employed in this invention is a textile material constructed of heat-meltable fiber. As heat-meltable fibers mentioned above various filament fibers of heat-meltable materials such as nylon 6, nylon 66, polyester and so on can be employed. Formation of the borderlines is effected by irradiating the corresponding linear zone of the substrate fabric with thermal radiation, whereby the fiber in said linear zone is melted without physical contact to form an ink-impervious borderline. Upon the above irradiation, the fiber in the borderline-forming zone melts under no compressive stress, whereby an ink-impervious linear zone is formed. The thermal radiation may be a beam of infrared light or laser light, for instance, but the use of laser light is particularly beneficial for commercial purposes. As laser source or oscillator, there may be employed any one of carbon dioxide gas laser (wavelength 10,600 nm), ruby laser (694 nm), YAG laser (10,600 nm), glass laser (1,065 nm), He-Ne laser, semiconductor laser, and so on. The laser oscillator is driven and controlled to output a narrow beam of, for example, about 0.1 to 0.2 mm in diameter and projected through an appropriate optics to the substrate fabric traveling at a constant speed. Depending on cases, the diameter of the laser beam may be less than 0.1 mm or in excess of 0.2 mm. In irradiating the substrate fabric with a laser beam, an accurate borderline can be formed with good reproducibility when the laser light is deformed into an oblong beam by means of a dome-shaped lens and projected to the substrate fabric with the major axis of the oblong beam oriented in the direction of travel of the substrate fabric. The incident angle of laser light on the substrate fabric is generally 90 degrees but the irradiation may be carried out at an inclination of, for example, 30°, 45° or 60°. The direction of travel of the substrate fabric for the purpose of irradiation may be vertical, horizontal or oblique. The formation of a borderline by irradiation with such a thermal radiation is preferably carried out prior to saturation of the fabric with liquid inks from the standpoint of preventing color migration but may be performed simultaneously with the saturation procedure or after the same procedure. Liquid inks of various colors can be used for saturation of the substrate fabric. For example, the two-color combination of black and red, the three-color combination of black, red and magenta, and the four-color combination of black and the three primary colors, namely cyan, magenta and yellow. In the case of the four-color combination last mentioned, the blue, green and red colors are produced by the superimposition of cyan and magenta, cyan and yellow, and magenta and yellow, respectively, and these seven colors plus the white background of the printing paper (eight colors in total) constitute the prints of characters, pictures, graphs and so on. In the multi-color ink ribbon according to this invention, the fiber forming the linear zone corresponding to said borderline is melted without physical contact to form an ink-impervious linear pattern. Thus, the molten fabric material fills the inter-fiber voids and is solidified in situ to thereby positively prevent the diffusion of liquid inks to the neighboring ink-saturated lanes. It has been found that if a laser beam, even a relatively low energy level beam, is deformed into an oblong beam by means of a dome-shaped lens before it is projected onto a substrate fabric with the major axis of the beam being oriented in the direction of travel of the substrate fabric, a very narrow and even borderline can be produced with good reproducibility and with even properties avoiding the problem of local over-heating, under-melting or over-melting so that no undue pin holes are present in the thus formed borderlines. As shown in the partially enlarged cross-section view (a schematic tracing of a micrograph) showing the multi-color ink ribbon of this invention in Fig. 1, the selective melting of the substrate fabric with thermal radiation without physical contact does not give rise to the resin pooling and build-ups which are produced along the edges of the borderline when the conventional contact method is employed, so that a stable travel of the fabric is assured during the formation of the borderline or in use of the ink ribbon. This invention provides the following effects. In the multi-color ink ribbon of this invention, the borderline assures a positive prevention of diffusion of liquid inks into the neighboring ink-saturated lanes. In addition, since the melt does not collect and coagulate to form buildups along edges of the borderline of the multi-color ink ribbon, the travel of the substrate fabric in the borderline forming stage and the travel of the product ink ribbon are both very smooth. When the laser beam used as the thermal radiation is deformed into an oblong beam by means of a dome-shaped lens before it is incident on the fabric and projected with the major axis of the oblong beam oriented in the direction of travel of the substrate fabric, a narrow or very narrow borderline can be produced with good reproducibility without the under-melting or over-melting problem. Fig. 1 is a partially enlarged cross-section view (a schematic tracing of a micrograph) showing the multi-color ink ribbon of this invention; Fig. 2 is a schematic side elevation view outlining the apparatus for practicing the method of this invention; Fig. 3 is a perspective view showing the cardinal parts involved in the practice of the method, and Fig. 4 is a partially enlarged cross-section view (a schematic tracing of a micrograph) showing the borderline formed by the heating element contact method. In the figures, the following reference numerals or symbols are used: (1) - laser oscillator; (2) - lens (dome-shaped lens); (3) - substrate fabric; (3a) - warp fiber; (3b) - weft fiber; (4) - laser beam; (5) - borderline; (5a) - build-up. The following embodiments are further illustrative of this invention. Example 1 In Fig. 2, the reference numeral 1 represents a laser oscillator and the numeral 2 represents a dome-shaped lens as an example of the optics used in the method of the invention. A substrate fabric 3 is traveling in vertical direction indicated by an arrowmark. The fabric 3 is a woven fabric of nylon 6 filaments, which are an example of the heat-meltable fiber to be used in this invention. The reference numeral 4 designates a laser beam deformed to assume an oblong cross-section. The borderline formed by irradiation with the above-mentioned beam 4 is indicated at 5. The beam output from the laser oscillator 1 is deformed by the lens 2 into an oblong beam 4 which is incident on the substrate fabric 3 where it melts the fiber in the zone corresponding to the borderline to be formed without physical contact and under no compressive load. As the traveling substrate fabric 3 is thus irradiated with the oblong laser beam 4, a borderline 5 with a line width of 0.2 mm is produced in the irradiated zone. When the lane of the substrate on one side of the above borderline is saturated with black liquid ink and the lane on the other side with red liquid ink, the diffusion of each ink is arrested exactly at the edge of the borderline. Neither of the inks diffuses into the borderline so that the borderline remains as white as it has been. In an experiment in which, after the two lanes on both sides of such a borderline were saturated with dye-based liquid inks and one of the lanes was used, there occurred no capillary diffusion of the ink from the unused lane into the consumed lane. The traveling characteristic of the fabric during the borderline forming stage and that of the product ink ribbon were also investigated. It was found that, in both cases, the traveling stability was excellent. The multi-color ink ribbon according to this invention is of great benefit as typewriter ribbon or as ribbon for the impact type printers of word processors, computers and other devices.

Claims: 1. Method for producing multi-color ink ribbons comprising a substrate fabric (3) constructed of heat-meltable fiber and saturated with liquid inks of different colors in distinct lanes separated by one or more borderlines (5) from each other, which comprises melting the fiber in a linear zone corresponding to each of said borderlines by irradiation with laser light without physical contact, characterized in that the laser light is passed through a dome-shaped lens (2) to give an oblong beam (4) which is projected to the substrate fabric (3) with the major axis of the oblong beam (4) oriented in the direction of travel of said substrate fabric (3).

Inventors: KITAMURA, ATSUSHI, OKUSHIMA, SHIGERU RESEARCH LAB. OF FUJI KAGAKUSHI
Applicants: FUJI KAGAKUSHI KOGYO CO., LTD., KITAMURA, ATSUSHI
Application year: 1987
Main classification: B41J31
IPC codes: B41J31