RECORDING HEAD FOR USE IN AN ELECTRICALLY EXCITED TRANSFER RECORDING DEVICE

Abstract: In an electrically excited transfer recording device which transfers an image or images formed in a recording film (18) onto a recording chart (19), a recording head (1) is comprised of a head base (2) of resin having insulating properties and a plurality of electrode needles (9) formed on the head base (2). During the printing, a resistance layer formed in the recording film (18) is electrically charged by the electrode needles (9) and ink contained in the recording film (18) is fused upon generation of heat in the resistance layer to be transferred onto the recording chart (19).

Description: The present invention generally relates to a recording head for use in an electrically excited transfer recording device, and more particularly, to the structure of a recording head for use in a transfer recording device of the type in which the transfer is executed by utilizing heat generated by electricity. In an electrically excited transfer recording device, a resistance layer formed in a recording film is charged with electricity by a plurality of electrode needles provided in a recording head, thereby to generate heat so that ink contained in the recording film is fused by the heat and transferred onto a recording chart. Fig. 1 depicts an end portion of one of the conventional recording heads according to Japanese Patent Laid-open applications JP-61-179760 and JP-61-43585. The recording head, generally shown by 15, is comprised of an insulating head base 16 and a plurality of electrode needles 17 disposed on the surface of the head base 16. A recording film 18 having therein an ink layer, a conductive layer and a resistance layer is pressed against a recording chart 19 by the recording head 15, with the recording chart 19 being carried by a platen 20. The recording head 15 is then charged with electricity while sliding with respect to the recording film 18. Upon generation of heat in the resistance layer, the ink contained in the ink layer is fused so that an image or images formed in the recording film 18 may be transferred onto the recording chart 19. In this way, since the recording head 15 slides with respect to the resistance layer of the recording film 18, the resistance layer partly comes off or peels off the recording film 18 due to the heat generated by mutual friction, the electricity or the like. The resistance layer which has peeled off turns to film waste, film refuse or the like and is caused to adhere to the end portion of the recording head 15 during printing operation. Upon repeated printing operation, the film waste gradually accumulates and lowers the quality of printed image. The sliding movement between the recording head 15 and the recording film 18 wears the end portion of the recording head 15, and therefore, a length A of contact gradually increases, within which the recording film 18 is pressed against the recording chart 19. As this length A of contact increases, the pressure between the recording film 18 and the recording head 15 decreases, thus resulting in unstable contact between the recording head 15 and the recording film 18. This fact occasionally lowers the transfer properties of the ink or deteriorates the quality of the printed image. Conventionally, certain hard ceramic such as forstelite or the like is occasionally used in the head base 16 of the recording head 15 having on its surface a plurality of electrode needles 17. In such a construction, the film waste can hardly be removed and the quality of the printed image is undesirably lowered before long. Because of this, should the occasion arise, the end portion of the recording head 15 is lapped by a grinding sheet or the like so that any particles or waste material adhering thereto may be removed for improvement of the quality of the printed image. Such work, however, consumes much time and not only be inconvenient for the user, but results in increased cost during the use of the recording device. Furthermore, in the aspect of manufacture, the formation of a pattern of the electrode needles with respect to the hard ceramic, firing process required therefor or the like costs disadvantageously relatively high. In the case of the head base 16 employing therein resinous material, the sliding movement between the recording head 15 and the recording film 18 wears the end portion of the recording head 15 by a considerable amount. The length A of contact, therefore, increases relatively rapidly and the transfer properties are deteriorated before long, thus resulting in the shortened life of the recording head 15. Furthermore, the increase of the length A of contact increases the area of contact and lowers the pressure between the recording head 15 and the recording film 18. Accordingly, since it becomes troublesome to remove the film waste and the amount of adhesion or accumulation thereof increases, the quality of the printed image tends to be deteriorated. The IBM-technical disclosure bulletin volume 27 No. 9 Febuary 1985, pages 5188 and 5189 discloses a resistive ribbon print head profile which prevents build-up of debris on the electrodes of a thermal print head through relieving the pressure on the portions of the ribbon extending beyond the electrode functional area. This produces a substantially uniform pressure in the electorde functional area so that arcing does not occur to generate the debris. The Japanese Laid-open JP-62-3966 A discloses a termal transfer-recorder, in which the ink ribbon is brought into contact with a recording paper supported on a platon on the back side and a slant surface type thermal head being disposed with an end in contact with the ribbon. US-A 4605936 discloses a thermal head comprising a substrate providing a flat surface and an oblique surface. The oblique surface is close to the surface of a recording paper positioned on a platon of a recording apparatus. Accordingly, the present invention has been developed with a view to substantially eliminating the above described disadvantages inherent in the prior art recording head for use in an electrically excited transfer recording device, and has for its essential object to provide an improved recording head in which the quality of printed image can be desirably stably kept for a long period. Another important object of the present invention is to provide a recording head of the above described type which is simple in construction and stable in functioning, and can be manufactured at a low cost. In accomplishing these objects, a recording head according to one preferred embodiment of the present invention comprises a head base; and a plurality of electrode needles on said head base, whereby a resistance layer formed in the recording film is electrically charged by said eletrode needles and ink contained in the recording film is fused upon generation of heat in the resistance layer to be transferred onto the recording chart, wherein a plurality of grooves extending in a direction longitudinally of the recording head between adjacent ribs are formed in the rear of an end portion at the area of contact between said recording head and said recording film to a bottom surface of said head base, said grooves reducing an amount of the recording head which contacts the recording film as the recording head wears in response to contact with the travelling recording film. The recording head is brought into contact at its end portion with a recording film with the end portion being of a construction as shown by either one of the following: (1) a plurality of grooves are formed in the rear of the end portion in a direction parallel to the electrode needles (2) the end portion is chamfered in the rear thereof from an edge of the surface of contact between the recording head and the recording film, combined with (1) As the material of a head base constituting the main body of the recording head is employed resin having insulating properties, for example, polyimide, polyamide, polyphenylenesulfide, or ceramic, for example, Photoveel (name used in trade and manufactured by Photon Ceramics Co., Ltd.), forstelite, alumina or the like. Moreover, the recording head may be chamfered at its end portion end of a construction in which a plurality of grooves are formed in the end portion. Because of this, the increase of the length of contact between the recording head and the recording film or the increase of the area of contact therebetween is relatively small. This fact restricts the deterioration of the transfer properties of the ink, the adhesion or the accumulation of the film waste onto the recording head so that the life of the recording head can be prolonged. These and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and in which: Fig. 1 is a side view of an end portion of the conventional recording head during the printing: Fig. 2 is a fragmentary perspective view of the end portion of the recording head according to a first embodiment of the present invention; Fig. 3 is a fragmentary perspective view of the end portion of the recording head according to a second embodiment of the present invention; and Fig. 4 is a side view of the end portion of the recording head of Fig. 3 during the printing. Fig. 2 illustrates the end portion of the recording head 1a according to a first embodiment of the present invention. The recording head 1a is comprised of an insulating head base 7, a heat-resisting insulating layer 8 and a plurality of electrode needles 9, as in the first embodiment. The material of these components 7, 8 and 9 of the recording head 1a are the same as that used in the first embodiment, and also, the electrode needles 9 are quite the same both in size and in arrangement as those of the first embodiment. In this embodiment, however, a plurality of grooves 7a extending in a direction longitudinally of the recording head la and having a suitable depth are formed in the rear of the end portion of the head base 7 and each between adjacent ribs 7b. Each groove 7a and each rib 7b are 0.8 mm and 0.2 mm wide, respectively. Fig. 3 illustrates the end portion of the recording head 1b according to a second embodiment of the present invention. In this embodiment, the recording head 1b is comprised of an insulating head base 10, a heat-resisting insulating layer 11 and a plurality of electrode needles 12, as in the first and second embodiments. The material of these components 10, 11 and 12 of the recording head 1b are the same as that used in the first and second embodiments, and also, the electrode needles 12 are quite the same both in size and in arrangement as those of the first and second embodiments. A plurality of grooves 10a and ribs 10b having the same dimensions as those in the second embodiment have are alternately formed in the rear of the end portion of the head base 10. In this embodiment, however, the ribs 10b are chamfered at an angle of 45 degrees from the vicinity of an edge of the contact surface 14 between the end portion of the recording head 1b and the recording film 18. In other words, the chamfered portions 13 are formed in the rear of the end portion of the recording head 1b by removing corners of the ribs 10b as shown by dotted lines in Fig. 3. Several experiments have been made with respect to the conventional recording head 15 of Fig. 1 having neither the grooves nor the chamfered portions and to the recording head 1, 1a or 1b of the present invention. The result of the experiments will be explained hereinafter. With respect to the conventional recording head 15 having the head base 16 of a ceramic base of forstelite, the adhesion of the film waste has gradually lowered the quality of the printed image after the recording film 18 of about 100 m was used for the printing. In contrast, with respect to the conventional recording head 15 having the head base 16 of a resin base 16 of polyimide, the quality of the printed image has been lowered little even after the recording film of about 6 km was used for the printing. The printing followed by the use of the recording film of 400 m has worn the end portion of the recording head 15 by an amount of 2.9/10³ mm³ and 2.1/10² mm³ per 1 cm contact length of the recording head 15, respectively with respect to the ceramic base 16 and to the resin base 16. That is to say, the recording head 15 having the resin base 16 wears by an amount approximately 10 times more than that having the ceramic base does, and therefore, the end portion of the recording head 15 is considered to be continuously ground. This fact is greatly effective against the adhesion of the film waste or the accumulation thereof. In the conventional recording head 15 having the end portion on which no processing has been executed, after the recording film of about 7 km has been consumed by the printing, the transfer properties of the ink have lowered due to the increase of the contact length A between the recording head 15 and the recording film 18. In the recording head 1a according to the first embodiment, since the contact length A at locations where the grooves 10a are formed does not exceed a certain length determined by the thickness t (Fig. 3) of the base 10 in which the ribs 10b and the grooves 10a are alternately formed, the transfer properties of the ink never be lowered. However, an area of a portion of the recording head 1a in contact with the recording film 18 increases with the progress of wear and the quality of the printed image is lowered, since the film waste is caused to increasingly adhere to the end portion of the recording head 1a and accumulates thereon. This phenomenon has become conspicuous upon consumption of the recording film 18 of about 13 km. In the recording head 1b according to the second embodiment, the contact length A does not increase so much with respect to the same amount of wear. In this case, the recording film 18 of about 20 km has been used for the printing until the quality of the printed image has been found lowered. As is clear from the above described experiments, the recording head 1b according to the second embodiment can be used for the printing with respect to the longest recording film 18. As described above, according to the present invention, the resin having the insulating properties is utilized as the material of the head base constituting the recording head for use in the electrically excited transfer recording device. The recording head of the present invention can, therefore, reduce the adhesion or the accumulation of the film waste onto the end portion of the recording head, and the quality of the printed image is hard to lower. The resin base having such characteristics is fully utilized in the recording head of the present invention and is of advantage in remarkably saving time or trouble during the maintenance by using the grinding sheet or the like. Moreover, the grooves formed in the rear of the recording head can prevent a change for the worse in transfer properties caused by the increase of the contact length between the recording head and the recording film so that the life of the recording head may be prolonged. In addition, the chamfer processing can limit the increase of the contact length or area and make a contribution to the prolonged life of the recording head. It is to be noted here that although the ceramic of forstelite, alumina or the like is disadvantageous in resistance to wear or in processing properties as compared with the resin base, this fact never denies the utilization of all of the ceramic base. It is needless to say that, in various kinds of ceramics, the one to which the film waste hardly adheres or the one having the resistance to wear or the processing properties similar to that of the resin is applicable to the present invention.

Claims: A recording head (1a, 1b) for use in an electrically excited transfer recording device which transfers an image or images formed in a recording film (18) onto a recording chart (19), said recording head (1a, 1b) comprising: a head base (7, 10); and a plurality of electrode needles (9, 12) on said head base (7, 10), whereby a resistance layer formed in the recording film (18) is electrically charged by said electrode needles (9, 12) and ink contained in the recording film (18) is fused upon generation of heat in the resistance layer to be transferred onto the recording chart (19), characterised in that, a plurality of grooves (7a, 10a) extending in a direction longitudinally of the recording head (1a, 1b) between adjacent ribs (7b, 10b) are formed in the rear of an end portion at the area of contact between said recording head (1a, 1b) and said recording film (18) to a bottom surface of said head base (7, 16), said grooves (7a, 10a) reducing an amount of the recording head (1a, 1b) which contacts the recording film (18) as the recording head (1a, 1b) wears in response to contact with the travelling recording film (18). The recording head as claimed in Claim 1 wherein said end portion of said recording head (1a, 1b) is chamfered in the rear thereof from an edge or the vicinity thereof of the surface of contact (14) between said recording head (1a, 1b) and said recording film (18) . The recording head as claimed in Claim 1, wherein said end portion has a generally flat and uninterrupted surface in both a longitudinal and transverse direction. The recording head as claimed in Claim 1, wherein said end portion has a generally straight surface from the edge of the area of contact between the recording head (1a, 1b) and the recording film (18) to the bottom surface of the head base (7, 10). The recording head as claimed in Claim 1, wherein said end portion has at least two surfaces meeting at an obtuse angle, said at least two surfaces extend from the edge of the area of contact between the recording head (1b) and the recording film (18) to the bottom surface of the head base (10) at least when said recording head (1a, 1b) is installed in said electrically excited transfer recording device.

Inventors: ASAI, SHIGEMI, IWAMATSU, TADASHI, NAKAI, SHUNJI, SAWAI, HIROYUKI, TOYOSHIMA-TETSURO
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: B41J2
IPC codes: B41J2