Output sheet for image forming device and image forming device by use of the sheet

Abstract: The present invention concerns output sheet having optical transparency of an image forming device which supports a toner image and then fixes the toner image by passing through a heating fixing device, and an image forming device by use of such sheet. For enabling detection of the conveying state of the sheet at high precision, a colored ink containing metallic powder is printed at a part of the sheet to provide a mark portion for recognition.

Description: This invention relates to a recording material to be used for image forming device such as electrophotographic device or electrostatic recording device. Particularly, it relates to a sheet which is the recording material which can be used for the above device for detecting the running situation and presence of the recording material within the device by an optical means, and to an image forming device by use of the sheet. In the prior art, as the recording material of this kind, there is, for example, a transparent polyethylene terephthalate (PET) film sheet provided for an overhead projector (OHP). In an electrophotographic device which passes such PET film sheet as the recording material, for detection of an accident such as paper jamming, etc., for example, light from a light source is irradiated on the recording material, and presence of the reflected light or presence of the transmitted light is detected by an optical detection means for improving detection precision or accuracy. Whereas, a PET sheet permits the light to transmit therethrough and detection with an optical detection means is hardly possible, various proposals have been made about improvements of the recording material in order to improve the detection precision. For example, Japanese Patent Application Laid-open No. 58-106550 proposes to provide peelable spaced opaque members at e.g. the corners of a transparent film. Also, Japanese Patent Application Laid-open No. 58-105157 proposes formation of a peripheral band coating with an opaqueness of 60% or more according to JIS P-8138 in order to shield visible light, and further Japanese Patent Application Laid-open No. 59-7367 proposes one having a vapour deposited metal film on the side end part or whole of the sheet in order to shield IR-ray. United States Patent US 4,637,974 discloses a transparent sheet having a printed ink border. Notably Japanese Patent Application Laid-open No. 58-150966 discloses a transparent sheet having a printed band at one end and/or along one or both side edges, which printed band comprises a binder and a pigment such as TiO₂ metallic powder. However, in the case of the prior art as described above, for example, in the case of providing an opaque member, there was a fear that the recording material may be obstructed within the electrophotographic device during paper passage due to the stepped difference of the opaque member, or the toner image of the unfixed portion may be disturbed by the paper passage shock by the stepped difference portion. On the other hand, the coating layer for shielding visible light is poor in shielding characteristic against the light of IR level from an LED light source conventionally used as inexpensive light source, and the detection time of the signal becomes shorter in the case of further narrower coating width, whereby detection precision is lowered. Further, according to metalvapour deposition on the whole sheet, visible light transmittance of the film itself becomes lower, and when it is provided for OHP as the transmissive image, the image will become dark, and moreover, there was a drawback that vapour deposition by use of a vacuum device resulted in increased cost of the film itself. On the other hand, the transmission type detection means has a light source and a photosensor arranged with an interval apart from each other, whereby the positional precision can be guaranteed only with great difficulty, and also due to unstable detection precision, there have been made proposals to enhance reliability by using a detection means of the reflection type of higher precision, or by using separately both within one device. However, there has existed no transfer material such as transparent sheet, etc. satisfying both characteristics of reflection and transmission (shielding). An object of the present invention is to provide a solution to the problems possessed by sheets of the prior art as described above. According to the present invention there is provided a sheet for use in an image forming device, this sheet being optically transparent and having on its surface a marked portion for optical sensor recognition, said marked portion being marked with a coloured ink; which sheet is characterised in that: said coloured ink contains a metallic powder consisting of scale-like particles. By using scale-like particles of metallic powder, the effective area occupied by the metallic powder at the reflection surface can be made larger, whereby reflection characteristic can be improved. Also, by setting the weight ratio of the metallic powder occupied in the ink containing metallic powder at 2 to 30%, lowering in reflection characteristic which may be caused by too low content of metallic powder can be prevented, and also the S/N ratio in the shielding characteristic can be made greater, whereby it becomes possible to prevent generation of erroneous actuations on account of contamination with toner powder within the device. As will be described, using ink containing a metallic powder obtained by mixing metallic powder into a coloured ink for printing, IR-light having a wavelength of 800 to 1000 nm can be transmitted at 30% or lower, and further a reflectance of 60% or higher can be obtained, whereby both good shielding and good reflection characteristics can be attained. In the accompanying drawings:- Figs. 1A to 1D are plan and cross-section views showing different variants of marked sheet recording material according to a first example of the present invention; Fig. 2 is an illustration showing the detection state of the sheet recording material shown in Fig. 1; Figs. 3A to 3D are plan and cross-section views showing different variants of marked sheet recording material according to a second example of the present invention; and Fig. 4 shows a sectional view of an electrophotographic copying device which is an example of an image forming device to which the present invention is applicable. Referring now to the examples shown in the drawings, the present invention will be described. The following description is given by way of example only. Figs. 1A to 1D illustrate the recording material according to an example of the present invention, wherein numeral 1 is a transparent sheet (hereinafter called "film") as the recording material, 2 an opaque portion according to the present invention which is printed on the transparent film 1 using an ink containing metallic powder obtained by mixing metallic powder with a coloured ink for printing. This is a detection portion which is detectable by optical detection means. The transparent film 1 is a heat-resistant resin film with the maximum use temperature of 100°C or higher, and a resin of polyester, polyamide, polyamideimide, etc. may be employed. Particularly, polyethylene terephthalate (PET) is preferable with respect to heat resistance and transparency. The film thickness is required to be 50 µm or more so that no wrinkle may be generated by heating during fixing in an electrophotographic device, and preferably 200 µm or less for ensuring transparency. The surface of the transparent film 1 also may be applied with roughening treatment called matting, antistatic treatment, formation of a coating layer for improvement of fixability, etc., if desired. The opaque portion 2, as shown in Fig. 1A to Fig. 10, is provided along the edge of the transparent film 1, and may be provided, for example, at one side of the four sides as shown in Fig. 1A, or two sides of the four sides as shown in Fig. 1B. Further, although not shown, it can be also formed at three sides or all the four sides. Also, the opaque portion 2, as shown in Fig. 1C may be also provided partially along the edge corresponding to the detection position of a photosensor provided within an electrophotographic device which performs image formation using the transparent film 1 as a recording medium. The width L of the opaque portion 2 may be set conveniently depending on the paper passage speed and the sensitivity of the photosensor of the device used, but it is required to be at least the thickness of the transparent film employed. For, if it is less than the film thickness, the detection level of the opaque portion 2 by the photosensor becomes equal to the detection level by diffused reflection at the film edge surface, etc., whereby signal can be distinguished from noise only with difficulty. Also, the upper limit of the width may be selected adequately with the balance with the image forming width, although the sensitivity of the photosensor can be lowered if it is broader. The thickness H of the opaque portion 2 shown in Fig. 1D is 1 µm to 100 µm, preferably 40 µm or less. If it is more than 100 µm, the image in the vicinity of the opaque portion 2 is affected by the influence from the stepped difference. On the other hand, if it is less than 1 µm, there can be erroneous actuation due to printing irregularity of the opaque portion 2. The reflection and shielding characteristics relative to IR-ray demanded for the material of the opaque portion should be such that the light in the IR-ray region of wavelength 800 to 1000 µm should be transmitted at only 30 % or lower, and 60 % or more should be reflected by reflection (not normal reflection, but diffused reflection by 45° incident light, as shown in Fig. 2). With a transmittance over 30 %, when the window material, surface of the LED 11 which becomes the light source side is contaminated with dust in the air, toner, paper powder, etc. within the device, it becomes difficult to discriminate the level of the signal by printing from that by contamination. Preferably, a transmittance is 10 % or less. However, this condition is the case of the measuring condition when the light receiving device exhibits a photocurrent of 304 µA at the peak of 900 nm, when the radiation output is 46 mW/sr (driving current I F =50 mA) by use of LED of 940 nm peak. For reflection, using of the LED 11 shown in Fig. 2, light having the above radiation output and wavelength is irradiated on the opaque portion 2 on the transparent film 1 as the body to be measured from an angle of 45°, and the diffusion reflected light is measured by a light receiving device (sensor) 12. The reflectance at this time is shown by the ratio of the output by the marked portion of the present invention relative to an output when the body to be measured is a white plain paper. As the reflectance, 60 % or more of the reflected light output of the plain paper as described above is preferable, and in the case of the marked portion not satisfying this condition, reflection noise by metallic parts such as bonded steel plate, etc. within the device and the above reflection signal can be hardly discriminated from each other other, thus causing an erroneous actuation to occur. Further, when an output of 80 % or more is obtained, it is more preferable because detection becomes possible even if the distance between the sheet surface and the reflection type sensor may more or less change. As those satisfying the above reflectance and transmittance, there may be included metallic powder containing ink in which metallic powder is mixed into conventional colored ink for printing as described above, such as gravure ink, heating curable type ink, UV-ray curable type ink, etc. In the following, specific examples are described. Printing ink satisfying the above stated conditions may comprise a mixture of a thermosetting resin as represented by polyester resin, acrylic resin, polyolefin resin, polyacetal, polyamide, polystyrene, halo-containing resin, silicon resin, polyether, polycarbonate, vinyl acetate resin, cellulose type resin, and copolymers of these, or a thermosetting resin as represented by single substance or copolymer of phenol resin, xylene resin, petroleum resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicon resin, furan resin, etc., mixed with at least one of white, black and further colored pigments and metallic powder of aluminum, gold, copper, silver, palladium, zinc, nickel, tin, etc., which is dissolved in a solvent of the ester type, the ketone type, the alcohol type, etc. and adjusted to a suitable viscosity. The proportions may be 5 to 30 % by weight of pigment component such as white, black, gray and colored pigments, 2 to 30 % by weight of metallic powder, with the balance being the above resin and known auxiliary agents for aiding dispersion of the pigment and metallic powder, based on the total weight of the ink. Also, depending on the curing condition of the ink, there is no problem in containing a catalyst of the heat cure type, and a photoinitiator of the photocure type. Further, for enhancing the strength of the ink, monomer components of resin may be mixed as the curing agent, or for imparting flexible strength to the ink, a polymeric component of resin or a filler having a molecular weight of 10 to 1000-fold of the prepolymer of ink may be also mixed. To describe next about the content percentage of metallic powder to be used in detail, if the amount of the metallic powder such as aluminium is less than 3 % by weight, in the reflection characteristic, no great difference from the black coating internally of the device can be taken, whereby there is only a reflection intensity of 2.5-fold relative to the black coating according to the measuring method as mentioned above and there is possibility of erroneous actuation. Preferably, there should be an amount of 6 % by weight mixed. Further, when there is possibility that the distance between the printing portion of the transfer material and the reflection type sensor changes by 50 % or more, the amount of metallic powder is required to be made 10 % by weight or more. On the other hand, if the metallic powder exceeds 20 % by weight, the metallic powder may be dropped off from the marked portion, whereby the device, particularly the photosensitive member, may be internally damaged. However, in the case of the ink containing the filler as described above mixed therein, 30 % by weight of metallic powder can be contained in the ink. And, the shape of the metallic powder particles is thin, so called scale-shape, with a thickness of 1 µm or less and a width of 5 to some 10 µm to the maximum of about 50 µm. Next, to describe the pigment for printing which is the base, it is preferable to use a gray pigment comprising a mixture of a white pigment with Chinese ink or a gray pigment, and when a coloured dye or pigment such as yellow, grass colour is employed, it is preferably used as a mixture with white or Chinese ink. Also, for intensifying the reflection characteristic, a dye or pigment of purple, indigo, blue, etc. is not so preferred. If it dare be used, metallic powder is required in a slightly larger amount. Also, the pigment which can be used in the above description may be any pigment known in the art as the printing ink without any problem. The present invention is described in more detail below by way of Examples by referring to the components containing metallic powder. First example Five kinds of ink containing metallic powder were obtained by mixing a pigment comprising a mixture of a white pigment and Chinese ink pigment at a ratio of 1 : 8 mixed at the respective ratios into aluminium powder at the respective percentage by weight of 20 %, then 12, 10 and 6 %, and as Comparative example, 2.0 %. The resin of the ink employed is an ink of the UV-ray curable urethane resin type. Next, onto a PET film with a thickness of 100 µm and a heat-resistant temperature of 150 °C (transparent film 1) was screen printed the above five kinds of ink to a thickness H=15 µm and a printed width L=8 mm, and this was cured by UV-ray from a light pressure mercury lamp. The printed, namely the opaque portion 2 obtained has silver gray colour. However, one with 0 % of transmission had a dark gray colour. Table 1 below shows the reflectance and transmission characteristics, and the paper passage tests in an electrophotographic device having an optical detection means comprising an LED 11 (wavelength 980 nm) and a sensor 12. As shown in Table 1, by mixing of aluminium metallic powder, reflected dose of IR-ray can be increased without lowering the shielding characteristic of IR-ray, whereby both shielding characteristic and reflection characteristic are valid. Besides, the reflectance of IR-light of 800 to 1000 nm is enhanced to 2-fold or more as compared with the case when containing no aluminium powder. Also, it can be understood that not only the transmittance of IR-light can be lowered stably between 1/10 to 1/100 than when using an ink of the white type, but also the shielding ratio is improved by aluminium powder. However, in the case of Examples 1 and 2, erroneous recognition may sometimes occur if the distance from the refection type sensor is deviated by 10 %. Column of working state indicates paper passage characteristic. ○: good X: no paper passage Reflectance is represented with a paper of 84 % of whiteness and 60 seconds of smoothness as being 100 %. Second example By use of 10 % by weight of a mixture comprising a 1:1 mixture of a white pigment and a yellow pigment, and mixing therewith 20 % of silver powder in terms of percent by weight, and by use of an unsaturated polyester as the resin, styrene monomer, a accelerator catalyst accelerator, etc. were mixed thereinto to prepare a printing ink (metal containing ink). Next, on the edge surface of the above PET film (transparent film 1), printing was performed by use of a screen of 200 mesh to a thickness of 30 µm and a width of 8 mm, followed by drying. The printing obtained (opaque portion 2) was gold in colour. For the opaque portion 2, the reflection characteristic was measured by use of an IR-LED light of 980 nm, whereby 90 % or more of reflectance was exhibited, with the transmittance being 0.05 % or less, thus exhibiting a good shielding characteristic. When the transparent film 1 was mounted on an electrophotographic device having optical detection means comprising a sensor 12 forming a pair with the above LED 11 for paper passage test, good results were obtained without any erroneous detection at all. Also, sufficient reflection intensity could be obtained even if the distance between the reflection type sensor and the above printed surface may vary by 20 % or more. Third example With the use of a mixture of white pigment 11 and black pigment 3 as the pigment and aluminium powder as the metal powder, a heat ray curable acrylic resin ink comprising 15 % by weight of the pigment and 30 % by weight of the metal powder was prepared. Also, in the resin ink was mixed 30 % by weight of an amino resin having a molecular weight of 30000 as the filler. This ink was printed by use of a screen of 350 mesh with a thickness of 15 µm and a width of 8 mm on the surface of a PET film coated on the surface with a polyester resin having a melt viscosity at 130°C of 2 x 10⁴ poise to a thickness of 15 µm. This was also subjected to the same experiments as in the second example, and as a result, a reflectance of 98 %, and a transmittance of 0.008 % were exhibited, and also the paper passage test was good. However, when the printed portion was polished with a plain paper, the ink was found to be slightly peeled off. In contrast, by reducing the metal powder by about 1 %, there was substantially no peel-off. When an ink was prepared without change of the ratios of the respective components except for removing the filler from the above printing ink, the strength of the ink after curing was low, and peeling occurred in the thermal fixer in the electrophotographic device. For prevention of this peeling, the content of the metal powder was required to be made 20 % or less. When the ink containing metallic powder shown in the above second and third examples from which the metallic powder was removed were printed similarly on the PET film and subjected to the paper passage test, the ink corresponding to the second example was not detected by either optical detection means of the reflection type and the transmission type. On the other hand, in the ink corresponding to the third example, erroneous actuation was generated in the reflection type. Fourth example With the use of a mixture of white pigment and yellow pigment mixed at 1:1 as the pigment, and mixing copper metal powder therewith to 18 % by weight, a printing ink (metal containing ink) was prepared with a vinyl acetate as the resin. Next, on the end surface on the release paper side of a label paper (transparent film 1) comprising a seal paper and a release paper both consisting of a PET film was printed the ink to a thickness of 17 µm and a width of 8 mm, followed by drying. The printing obtained (opaque portion 2) had a reddish copper colour To the opaque portion 2, reflection characteristics were measured by use of IR-LED ray of 980 nm. As a result, 92 % of reflectance was exhibited with transmittance being 0.1 %, thus exhibiting good shielding characteristic. When the paper passage test was conducted by subjecting the transparent film 1 to an electrophotographic device having optical detection means comprising a sensor 12 forming a pair with the same LED 11 as mentioned above arranged at several places, good results were obtained without any erroneous detection at all. In the above examples, as the recording material sheet, resins films such as PET films were shown as examples, but these are also inclusive of films applied with matting treatment, antistatic treatment, etc., for the purpose of improving conveyability or transferability within the device. Otherwise, as the recording material to which the present invention is applicable, there is a film for transferring the toner image formed on the recording material to an image receiving member by use of label paper or iron. These recording materials applicable to the present invention are recording materials transmissive to the light source wavelength of the optical sensor which is the means for discriminating the paper and the light transmissive sheet in an electrophotographic device, etc., and the present invention is applicable to all the recording materials satisfying this condition as is apparent from the descriptions in the examples of the present invention. The present invention has the constitution and the action as described above, and by printing the opaque portion with the use of a metallic powder containing ink obtained by mixing metallic powder into a coloured ink for printing, IR-ray having a wavelength of 800 to 1000 nm can be shielded at 70 % or more with the ink components, and also a reflectance of 60 % or more obtained with the metallic powder to give both shielding characteristic and reflection characteristic, whereby a transmissive sheet capable of corresponding to both the transmission and reflection types by use of IR-ray can be prepared, and since IR-ray inherently receives influence from external light with difficulty, it becomes possible to effect detection with higher reliability in an electrophotographic device where contamination with powder, etc., is liable to occur. Also, reflectance of IR-ray can be enhanced by mixing with metallic powder, and the opaque portion can be prepared more simply and at lower cost as compared with, for example, metallic vapour deposition of the prior art. Further, since the opaque portion is formed by printing, the stepped difference can be set at the minimum level on the transmissive sheet to give an excellent paper passage characteristic. By making the particles of metallic powder shaped in scales, the area occupied by the metallic powder on the reflection surface can be made larger, whereby reflection characteristic can be improved. Also, by setting the weight ratio of the metallic powder in the metallic powder containing ink at 2 to 30 %, it is possible to prevent lowering in reflection characteristic caused by too small amount of metallic powder, or drop-off of the metallic powder from the printed opaque portion caused by too much amount of powder. Further, by mixing a polymer having a molecular weight which is 10 to 1000-fold as compared with the prepolymer of the resin in the resin which plays the role as the binder of ink, the printing strength is increased to enable increase of the metallic powder content, whereby both reflection and shielding characteristics can be stabilized. Whereas, by use of an ink containing metallic powder mixed therein, when, for example, defective conveyance may sometimes occur in the course of receiving such action as charging from the printing side in an electrophotographic device and yet the material to be conveyed thrusted into the charger, current may sometimes leak through printing even leading to fuming of the printed portion by heat generation. To cope with such problem, the electrical resistivity of the ink which becomes the mark portion is lot lowered so much. For example, it is effective to set the electrical resistivity of ink to a value approximate to the electrical resistivity of the sheet surface. In the following, examples by taking such electrical resistivity into consideration are described in detail. Fifth example Fig. 3 illustrates a transfer material according to the fifth example of the present invention, wherein those having the same functions as in the above examples are affixed with the same symbols. Numeral 1 in the Figure is a transparent film as the transfer material, 2 the opaque portion according to the present invention, which is printed on the transparent film 1 by use of a metallic powder containing ink obtained by mixing metallic powder into a coloured ink for printing, corresponding to the detection portion by an optical detection means. As the transparent film 1, those of the above examples are applicable. The opaque portion 2, as shown in Fig. 3A to Fig. 3C, is provided along the edge of the transparent film 1, and may be provided, for example, at one side of the four sides as shown in Fig. 3A, or at two sides of the four sides as shown in Fig. 3B. Further, although not shown, it may be also provided at three sides or all of the four sides. Also, the opaque portion 2 may be provided partially along the edge corresponding to the detection position of the photosensor provided within the electrophotographic device which performs image formation by providing the transparent film 1, as shown in Fig. 3C. However, practically printing is commonly performed from end to end on one side, partially because of appearance including the printed portion of the transparent film 1, etc. At this time, for example, by utilizing other portions which actuate the optical sensor, a LOGO such as a note or an arrowhead during paper passage of the transparent film through the electrophotographic device is written. When metal powder is contained in the printing ink, the transparent film 1 used which becomes its base generally has a surface resistivity of about 10⁸ to 10¹⁴ ohm.cm. As the material to be used for the base material, PET in general has a surface resistivity of 10¹⁶ ohm.cm. This is because antistatic treatment for prevention of disturbance of toner image on the transfer material by electrostatic charges caused by such factor as corona, etc. used during image formation within the electrophotographic device is applied. Also, in a transfer material to be applied for an electrophotographic device which forms a colour image using a multiple transfer device which transfers toner images on a photosensitive drum successively repeatedly, also because the electrostatic charges accumulated on the transfer material are increased, a film with relatively lower surface resistivity of 10⁸ to 10¹⁰ ohm.cm is used. Whereas, when the surface resistivity is measured under the printing state where the optical system jam detecting sensor within the electrophotographic device as described below can be normally actuated, it was confirmed to fall within the range of from 10⁵ to 10⁹ ohm.cm. However, when printing is effected with the resistivity shown by this resistivity value, for example, in the course of receiving the action of charging, etc. from the printing side within the electrophotographic device, defective conveyance occurs and yet the materials thrusts into the charger, the current is leaked through printing sometimes leading to fuming by heat generating at the printing portion, as described in the prior art example. Accordingly, when the surface resistivity of the printing portion to be printed partially on the film surface is lower than the surface resistivity of the film, a printing pattern is used comprising a printing portion which is substantially equal to the surface resistivity of the film and an electrically conductive portion. In the Figure, X is the portion with surface resistivity equal to that of the film which is, for example, a portion without printing. Y is the portion printed with the metal powder containing ink to be used in the present invention. Whereas, the inventors have found as the result of investigation about the relationship with the surface resistivity of printing in the case when the current is leaked through the printing portion as described above that there is no problem if the surface resistivity is 10⁸ ohm.cm or higher. Accordingly, the surface resistivity of printing which can sufficiently make avail of the present invention is 10⁸ ohm.cm or higher. When the width of the portion equal in surface resistivity to the film which divides the printing portions based on the result is determined, it may be said to be 1 mm or more when the surface resistivity of the film is 10⁸ ohm.cm. Similarly, when the surface resistivity of the film is 10⁹ ohm.cm, it can be understood that an interval of 0.1 mm or more may be taken. However, in practical application, it is preferable to take a distance 3 to 5-fold of this value for the purpose of security. Meanwhile, the printing portion according to the present invention is required to actuate normally a photosensor within the electrophotographic device. The width L between the printing portion and the opaque portion 2 may be set conveniently depending on the paper passage speed and the sensitivity of the photosensor, but is required to be at least the thickness of the transparent film employed. For, with a thickness lower than the film thickness, the detection level of the opaque portion 2 becomes equal to the detection level by diffused reflection at the film end surface, etc., whereby signal can hardly be distinguished from noise. On the other hand, the upper limit of the width L may be selected adequately in view of the balance with the image forming width, although the sensitivity of the photosensor can be made lower as the width is broader. The thickness of the opaque portion 2 shown in Fig. 3D may be 1 µm to 100 µm, preferably 40 µm or less. If it is more than 100 µm, the image in the vicinity of the opaque portion 2 is affected due to the influence by the stepped difference. On the other hand, if it is less than 1 µm, there can be erroneous actuation due to printing irregularity of the opaque portion 2. Further, when current passage was effected for one second with one end of the printing portion located on the earth and the other connected to AC of 10 kvpp, there was no fuming, etc. Sixth example By use of 10 % by weight of a mixture of white pigment and yellow pigment mixed at 1:1 as the base pigment, silver powder was mixed therewith to 20 % by weight, and an unsaturated polyester was used as the resin and styrene monomer, polymerization catalyst accelerator, etc. were mixed therewith to prepare a printing ink (metal containing ink). Next, on the end surface of a PET film used in the foregoing first example 1 (transparent film 1), printing was performed by use of a screen of 200 mesh to a thickness of 30 µm, a width of 8 mm and a distance between printing of 1 mm, followed by drying. The printing obtained (opaque portion 2) was gold in colour and the surface resistivity of the printing 10⁶ ohm.cm. When the reflection characteristic was measured for the opaque portion 2 by use of an IR-LED ray of 980 nm, 90 % or more of reflectance was exhibited, with transmittance being 0.05 %, thus exhibiting a good shielding characteristic. When the transparent film 1 was subjected to an electrophotographic device having optical detection means comprising a sensor 12 forming a pair with the above LED 11 at several places for paper passage test, good results were obtained without any erroneous detection at all. Also, even when the distance between the reflection type sensor and the above printing surface may vary by 20 % or more, sufficient reflected light intensity was obtained. Further, no fuming, etc. occurred even when one end of the printing portion was located at the earth, and the other end connected to AC of 10 kVpp (i.e. peak-to-peak). Seventh example With the use of a mixture of white pigment 11 and black pigment 3 as the pigment, aluminium powder as the metallic powder, a heat-ray curable acrylic resin ink was prepared with 15 % of the pigment and 30 % by weight of the metallic powder. Also, 30 % by weight of an amino resin having a molecular weight of 30000 was mixed as the filler in the resin ink. The ink was coated by use of a screen of 350 mesh on the surface of a PET film with a surface resistivity of 10¹⁰ ohm.cm coated with a polyester resin with a melt viscosity at 130 °C of 2 x 10⁴ poise to a thickness of 15 µm, a width of 8 mm and a distance X between printing of 1 mm. The surface resistivity of printing at this time was found to be 10⁷ ohm.cm. When this was subjected to the same test as in the first example and the second example, a reflectance of 98 % and a transmittance of 0.008 % were exhibited, and also the paper passage test was good. Further, no fuming, etc. occurred when current was passed for one second with the one end of the printing portion located on the earth, and the other end connected to AC of 10 kVpp. Eighth example With the use of a mixture of white pigment and yellow pigment mixed at 1:1 as the pigment, and mixing 20 % by weight of the pigment and 18 % by weight of copper metal powder therewith, a printing ink (metal containing ink) was prepared with a vinyl acetate as the resin. Next, on the end surface on the release paper side of a label paper (transparent film 1) comprising a seal paper and a release paper both consisting of a PET film was printed the ink to a thickness of 17 µm and a width of 8 mm, followed by drying. The printing obtained (opaque portion 2) had a reddish copper colour. The printing portion has a surface resistivity of 10⁷ ohm.cm. For the opaque portion 2, reflection characteristics were measured by use of IR-LED ray of 980 nm. As the result, 92 % of reflectance was exhibited with transmittance being 0.1 %, thus exhibiting good shielding characteristic. When the paper passage test was conducted by subjecting the transparent film 1 to an electrophotographic device having optical detection means comprising a sensor 12 forming a pair with the same LED 11 as mentioned above arranged at several places, good results were obtained without any erroneous detection at all. Further, no fuming, etc. occurred when current was passed for one second with one end of the printing portion located on the earth and the other end connected to AC of 10 kVpp. From the fifth to eighth examples as described above, when the surface resistivity of the printing portion to be printed on a part of the film surface is lower than the surface resistivity of the film, by making a pattern comprising a portion with a surface resistivity substantially equal to that of the film and a printing containing metallic powder, the following inconveniences can be prevented. That is, in a transfer material for recording, by the printing portion which has a printing pattern having insulating property to the electrical device arranged in the conveying route from the paper feeding to the paper discharging within the image forming device, defective conveyance is generated in the course of receiving of charging, etc. from the printing side within the electrophotographic device, and in such case when the material is thrusted into the charger, the current is leaked through printing and fuming may sometimes occur by heat generation of the printing portion. Further, a recording material for image forming device capable of corresponding to the reflection type sensor and the transmission type sensor of the optical system jam detection sensor arranged in the conveying route within the image forming device can be provided. In the following, an example of the image forming device to which the above film is applicable is to be described. Fig. 4 shows schematically a sectional view of the electrophotographic device capable of forming a fullcolour image as the image forming device to which the film of the present invention is applied. In the Figure, there are broadly classified the recording material conveying system I provided from the right side of the main device 100 to approximately the centre of the main device, the latent image forming portion II provided near the transfer drum constituting the above recording material conveying system I at approximately the central portion of the main device 100, and the developing means arranged near the above latent image forming portion II (namely the rotatory developing device III). The recording material conveying system I as mentioned above has trays 101 and 102 for feeding recording material freely detachable relative to the opening formed on the right side (right side in Fig. 1) of the above main device 100, rollers 103 and 104 for paper feeding arranged approximately immediately above said trays 101 and 102, paper feeding guides 4A, 4B equipped with the paper feeding roller 106 arranged near the rollers for paper feeding 103 and 104. The transfer drum 8 provided in the vicinity of the above paper feeding guide 4B has the roller for contact 7, the gripper 6, the deelectrifier 12a for separation of the recording material, the separation nail or paw 14 arranged from the upstream side to toward the downstream side of the rotational direction in the vicinity of its outer peripheral surface, and also the transfer charger 9, the deelectrifier for separation of recording material 13 arranged within the inner peripheral side. Further, it comprises the conveying belt means 15 provided near the above separation nail 14, and the fixer 16 near the tray for discharging freely detachable relative to the main device 100 extending outwardly of the main device 100 arranged near the conveying direction terminal end side of said conveying belt means 15. The above latent image forming portion II has an image carrying member with its outer peripheral surface arranged in contact with the outer peripheral surface of the above transfer drum 8 and also freely rotatable in the arrowhead direction in Fig. 4 (namely the photosensitive drum 2a), a deelectrifier 10 arranged from the upstream side to the downstream side in the rotation direction of said photosensitive drum 2 in the vicinity of the outer peripheral surface of said photosensitive drum 2a, a cleaning means 11a, a primary charger 3 and an exposure means such as laser beam scanner for forming electrostatic latent images on the outer peripheral surface of the above photosensitive drum 2a, and an exposure portion from an image exposure reflection means such as a polygon mirror. The above rotatory developing device III has a freely rotatable case member (hereinafter called "rotary member") 4a, a yellow developer 4Y, the magenta developer 4M, the cyan developer 4C and the black developer 4BK mounted respectively on said rotatory member 4a and constituted so as to visualize (namely develop) electrostatic images formed on the outer peripheral surface of the above photosensitive drum 2a at the position opposed to the outer peripheral surface of the above photosensitive drum 2a. The sequence of the image forming device as a whole with the constitution as described above is explained by referring to an example in the case of full colour mode. When the photosensitive drum 2a as described above rotates in the arrowhead direction in Fig. 1, the photosensitive material on said photosensitive drum 2a is charged uniformly by the primary charger 3. When uniform charging is effected to the photosensitive material with the primary charger 3, image exposure is effected with the laser beam E modulated by the yellow image signal, whereby electrostatic images are formed on the photosensitive member 2a and the above electrostatic latent images are developed by the yellow developer 4Y fixed previously at the developing position by rotation of the rotary member 4a. On the other hand, when the recording film according to the present invention is a film, it is conveyed toward the paper feeding roller 106 from the trays for feeding 101 or 102 by the respective rollers 103, 104 for feeding. In the conveying route, a photosensor as the photodetection means, and in the drawing, a transmission type photosensor equipped with a LED light source (emitting device) 110 and a light receiving device 111 comprising a phototransistor is provided. The sheet passes between the light source 110 and the light receiving device 111, and during the passage, presence of the film is judged depending on whether the light from the light source 110 is shielded or not. When it is judged that the film is conveyed under normal state, the film is held by the gripper 6 of the transfer drum at a predetermined timing via the paper feeding roller 106, the paper feeding guide 4A and the paper feeding guide 4B, and wound up electrostatically on the transfer drum 8 by the roller 7 for contact and the electrode opposed to said roller for contact 7. However, when it is judged that the film is not under the normal state, actuation of the device will automatically be stopped. Also, a photosensor for judging whether the wound up film is on the transfer drum 8 at the correct position is arranged by the combination of the light source 113 and the light receiving device 112, and here the transfer drum will continue to rotate, if the film is judged to be under normal wound-up state. The transfer drum 8 rotates in the arrowhead direction in Fig. 4 as synchronized with the photosensitive drum 2a, and the sensible image developed by the yellow developer 4 is transferred onto the film by the transfer charger 9 at the area where the outer peripheral surface of the above photosensitive drum 2a is in contact with the outer peripheral surface of the above transfer drum 8. The transfer drum 8 continues to rotate as such to be prepared for transfer of the next colour (magenta in Fig. 4). On the other hand, the photosensitive drum 2a is deelectified by the above charger for deelectrification 10, cleaned by the cleaning means 11a, and then again charged by the primary charger 3, and receives image exposure as described above from the next magenta image signal. The above rotatory developing device rotates when an electrostatic latent image with the magenta image signal is formed on the photosensitive drum 2a by the above image exposure to fix the magenta developer 4M at the predetermined position as described above to effect a predetermined magenta developing. Subsequently, the process as described above is practiced also for cyan colour and black colour and on completion of transfers corresponding to four colours, the multi-colour sensible image is deelectrified by the respective deelectrifiers 12a, 13, whereby grippage of the film by the above gripper is released and also said film is separated from the transfer drum 8 by the separation nail 14. Also, in this case, by judging whether separation has been done normally by the photosensor comprising the light source 115 and the light receiving device 114 similarly as described above, the film is sent to the fixer by the conveying belt when it was separeted normally to be fixed by heat and pressure to complete a series of full colour print sequence, thereby forming a full colour print image on the film. The fixer 16 is equipped with a heating fixing roller 161, a pressurizing roller 162 and a coating means 163 for feeding silicone oil to the heating fixing roller 161. The heating fixing roller 161 should preferably have a surface layer having excellent release characteristic such as silicone rubber. Also, the surface layer of the pressurizing roller 163 should preferably be formed of a fluorine type resin. In the device as described above, detection of the position was possible at high precision in the film to which the present invention has been applied.

Claims: A sheet for use in an image forming device, this sheet (1) being optically transparent and having on its surface a marked portion (2) for optical sensor recognition, said marked portion being marked with a coloured ink; which sheet is characterised in that: said coloured ink contains a metallic powder consisting of scale-like particles. A sheet according to claim 1, wherein said scale-like particles of metallic powder have a thickness of 1 µm or less, and a width of 5 to 50 µm, preferably 5 to 10 µm. A sheet according to claim 1, wherein said ink comprises 2 to 30% by weight of the metallic powder. A sheet according to claim 1, wherein said marked portion (2) is in the shape of one or more bands at the edge of at least one side of said sheet (1). A sheet according to claim 1, wherein said marked portion (2) has a thickness (H) of 1 µm to 100 µm, preferably 1 µm to 40 µm. A sheet according to claim 4, wherein said sheet (1) is a transparent resin film, having a thickness of 50 µm to 200 µm, and the width of the marked portion (2) is not narrower than the thickness of the sheet (1). A sheet according to claim 1, wherein said marked portion (2) has an electrical resistivity value similar to the surface resistivity of the sheet portion (1). A sheet according to claim 7, wherein said marked portion (2) has a surface resistivity of 10⁸ to 10⁹ ohm.cm.

Inventors: AMEMIYA KOJI C O CANON KABUSHI, TAKEUCHI TATSUO C O CANON KABU, AMEMIYA, KOJI, C/O CANON KABUSHIKI KAISHA, TAKEUCHI, TATSUO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: G03G7
IPC codes: G03G15, G03G7