Ink ribbon for printer and ink therefor

Abstract: An ink ribbon for a printer, particularly an impact type printer such as a wire dot printer or daisy wheel printer, as well as a black ink to be used for an ink ribbon for a printer.

Description: Field of the Invention The present invention relates to an ink ribbon for a printer, more particularly to an ink ribbon for an impact type printer for a computer, such as a wire dot printer or daisy wheel printer. Description of the Related Art Impact type printers such as wire dot printers or daisy wheel printers are now widely used, due to the increase in the use of computers and office automation. The cloth ink ribbons to be used in such printers usually comprise cotton cloth, silk cloth or nylon cloth as the base cloth, and contain an ink prepared by dissolving or dispersing dyes or colorants such as dyes in various solvents and coated on or impregnated in such a base cloth. Cotton cloth, however, although having a good ink retentivity, has a problem of a lack of printing sharpness due to a thick cloth thickness. A silk cloth, although having a good ink retentivity and printing sharpness, has the problems of a poor durability and a high cost. On the other hand, the nylon fiber cloth now in use, although having an excellent durability, has a thickness as thick as 120 to 140 µm. Accordingly, the problem that a sharply printed character cannot be transferred arises, and thus a sharp print is difficult to obtain even when the wire of the printing head is made finer. Furthermore, in the prior art, soft dyes having absorption bands at visible regions of about 400 to less than 700 nm have been exclusively used, but these colorants have no absorption band at the near infrared region (700 nm to 900 nm), which is the wave-length of most bar codes now in use, and therefore, can not be used for that purpose. Therefore, a hard pigment has been used in the prior art as the colorant having an absorption band in the infrared region (700 nm or higher) such as carbon black, black titanium oxide, or metal oxide, and accordingly, the wire of the printer was susceptible to abrasion by the hard pigment on which the wire is impacted through the ink ribbon. Also, this abrasion of the wire is caused by an adhering of the ink to the wire and a penetration of the hard pigment into the gap between the wire and the wire guide. As described above, the ink ribbon for the impact type printer, such as a wire dot printer or daisy wheel printer, of the prior art has the problems of a poor durability or printing sharpness and cannot cope with a high-speed operation of a printing head. Furthermore, the ink ribbon for an impact type printer, such as a wire dot printer or daisy wheel printer, of the prior art has the problems of a poor durability or printing sharpness and cannot cope with a high-speed operation of a printing head. Various printers are widely used as the printing recording means of terminals of computers, etc., and various inks are used for the ribbons of printers such as a wire dot printer. The ink is impregnated in such printing ribbons (printing ribbons), and particularly for black printing ribbons, a carbon black alone or together with, for example, a black oil soluble dye such as nigrosine or aniline black, is used. The black ink ribbon of the prior art as mentioned above contains carbon black as the colorant, and thus has problems such as an abrasion of the wire of the printer head or a generation of print blurring due to the presence of the black oil soluble dye generally used therewith in combination. To maintain the blackness, sharpness and light-resistance of a printed character, however, it is impossible to exclude a considerable amount of carbon black from the ink formulation. It has been necessary to use a large amount of a black oil-soluble dye, to prolong the life of the ink ribbon, by lowering the amount of carbon black formulated, and to inhibit the abrasion of the wire while maintaining the print characteristics at as high a level as possible. EP-A-0168045 discloses a multiple-use pressure-sensitive transfer recording medium in which a liquid ink paste is used. As the liquid ink paste, a pigment or an oil-soluble dye is included as a colouring agent. Examples of the pigments are carbon black and black toners and examples of the oil-soluble dyes are Nigrosine Base, Spirit Black, Special Black, Victoria Blue Base and Methyl Violet Base. Summary of the Invention According to the present invention, an ink ribbon, suitable for use in a printer, comprises a base cloth and, coated thereon or impregnated therein, an oil-soluble ink containing 0.1 to 10.% by weight of an IR-absorptive aminium compound of the formula [(R)₂N-Ph]₂N-Ph-N[Ph-N(R)₂]₂. (HX) n wherein Ph is 1,4-phenylene, R is H or C₁₋₁₂ alkyl, X is SbF₆ or ClO₄, and n is 1 or 2. Description of the Invention Preferably, the base cloth used in this invention is of 6-nylon, 6,6-nylon, silk or polyester. More preferably, it is of 6,6-nylon, 70 to 110 µm thick, having 15 to 25 warp filaments with a monofilament fineness of 10 to 25 denier and 15 to 30 weft filaments with a monofilament fineness of 15 to 30 denier, a warp density of 8.7 to 11.8 monofilaments/mm (220 to 300 monofilaments/inch) and a weft density of 4.7 to 7.1 monofilaments/mm (120 to 180 monofilaments/inch). Such a cloth preferably has 15 to 20 warp filaments with a monofilament fineness of 15 to 25 denier and 15 to 25 weft filaments with a monofilament fineness of 20 to 30 denier. More preferably, such a cloth has a warp density of 8.6 to 9.8 monofilaments/mm (225 to 250 monofilaments/inch) and a weft density of 4.9 to 5.9 monofilaments/mm (125 to 150 monofilaments/inch). By thus constituting the base cloth of the ink ribbon for a printer, the cloth thickness can be 70 to 110 µm, preferably 80 to 100 µm (in the prior art 120 to 140 µm), and the printing width can be reduced by 5 to 10%, to enable sharp printing. The wire of the printing head and the copying capacity (number of papers capable of being sharply printed at one printing) also can be increased by 20%, and yet an ink ribbon for a printer having an excellent durability can be obtained. As described above, according to the present invention, by reducing the thickness of the ink ribbon for a printer, the printing gap can be reduced and a high-speed printing head operation can be effected. Also, according to the present invention, the printing quality and sharpness are excellent, and the copying capacity is improved. By the use of an aminium compound in accordance with the present invention, absorption in the infrared region can be obtained without the use of carbon black. This compound has the particular effect of not corroding and abrading metals, and thus is useful for reducing the abrasion of the wire of the printer. According to the present invention, by formulating an oil-soluble ink according to conventional formulation (e.g. 10 to 20% by weight of oil-soluble dye other than the aminium compound, 10 to 40% by weight of mineral oil, 15 to 35% by weight of a higher fatty acid, and 5 to 25% by weight of surfactant) and coating or impregnating this ink onto a 6-nylon cloth, a 6,6-nylon cloth, a silk cloth, or a polyester cloth, an ink ribbon has an absorption band in the near infrared region, and can therefore be used effectively for bar code printing. Since the organic dye is soft, the ink ribbon causes substantially no abrasion of the wire of a printer. These effects mean that it is possible to read bar codes (IR-region) by machine even when they are difficult to read with the naked eye (visible light region), and the ink ribbon can be suitably used for a card information recording to be used for an optical reading device (OCR). A typical example of the oil-soluble dye is nigrosine base. Typical examples of the mineral oils are liquid paraffin and various lubricating oils. Typical examples of the higher fatty acids are oleic acid, stearic acid and lauric acid. Typical examples of the surfactants are sorbitan monooleate, sorbitan trioleate, polyoxyethylene sorbitan monooleate, and polyoxyethylene monolaurate. The following Example illustrates the invention. Example An ink for a printer ribbon was obtained by stirring and mixing 5 parts by weight of bis(p-dimethylaminophenyl)-(N,N-bis(p-dimethylaminophenyl-p-aminophenyl)aminiumhexafluoroantimonic acid ester (prepared by the method described in US-A-4699863), 20 parts by weight of a black oil-soluble dye (nigrosine base), 40 parts by weight of a mineral oil, and 30 parts by weight of a surfactant (sorbitane sesquinoleate). This ink was then coated on a fabric made of 6,6-nylon, in an amount of 15 g/m². Using this ink ribbon, printing was effected 2 x 10⁸ times by a dot printer DPK24GH manufactured by Fujitsu K.K., and it was found that the amount of wire abrasion was 5 µm or less. By way of comparison, the procedure of the Example was repeated using 5 parts by weight of carbon black in place of the organic dye. The amount of wire abrasion of the printer was about 40 µm.

Claims: An ink ribbon, suitable for use in a printer, comprising a base cloth and, coated thereon or impregnated therein, an oil-soluble ink containing 0.1 to 10.% by weight of an IR-absorptive aminium compound of the formula [(R)₂N-Ph]₂N-Ph-N[Ph-N(R)₂]₂.(HX) n wherein Ph is 1,4-phenylene, R is H or C₁₋₁₂ alkyl, X is SbF₆ or ClO₄, and n is 1 or 2. An ink ribbon as claimed in claim 1, wherein the base cloth is of 6-nylon, 6,6-nylon, silk or polyester. An ink ribbon as claimed in claim 2, wherein the base cloth is of 6,6-nylon, 70 to 110 µm thick, having 15 to 25 warp filaments with a monofilament fineness of 10 to 25 denier and 15 to 30 weft filaments with a monofilament fineness of 15 to 30 denier, a warp density of 8.7 to 11.8 monofilaments/mm (220 to 300 monofilaments/inch) and a weft density of 4.7 to 7.1 monofilaments/mm (120 to 180 monofilaments/inch). An ink ribbon as claimed in claim 3, wherein the cloth has 15 to 20 warp filaments with a monofilament fineness of 15 to 25 denier and 15 to 25 weft filaments with a monofilament fineness of 20 to 30 denier. An ink ribbon as claimed in claim 3 or claim 4, wherein the cloth has a warp density of 8.6 to 9.8 monofilaments/mm (225 to 250 monofilaments/inch) and a weft density of 4.9 to 5.9 monofilaments/mm (125 to 150 monofilaments/inch). An ink ribbon as claimed in any of claims 2 to 5, wherein the cloth is 80 to 100 µm thick. An ink ribbon as claimed in any preceding claim, wherein the oil-soluble ink comprises 10 to 20% by weight of an oil-soluble dye other than the aminium compound, 10 to 40% by weight of a mineral oil, 15 to 35% by weight of a higher fatty acid and 5 to 25% by weight of a surfactant. An ink ribbon as claimed in any preceding claim, wherein the oil-soluble ink contains 1 to 5% by weight of the aminium compound. Use of an ink ribbon as claimed in any preceding claim, in a printer.

Inventors: KUBOTA MASAYUKI, SATO MINAKO, SEKIOKA CHIAKI, SUZAWA HIROMICHI, TANAKA MASAYUKI, UEMURA HISASHI - AZA HAKKOUCHI, KUBOTA, MASAYUKI, SATO, MINAKO, SEKIOKA, CHIAKI, SUZAWA, HIROMICHI, TANAKA, MASAYUKI, UEMURA, HISASHI, SATO, MINAKO, 32-3 AZA HIGASHISHINDEN, UEMURA, HISASHI, 4-8, AZA HAKKOUCHI
Applicants: FUJITSU ISOTEC LTD, FUJITSU ISOTEC LIMITED
Application year: 1990
Main classification: B41J31
IPC codes: B41J31, B41M5