GB2204508A

GB2204508A - Image recording system

Info

Publication number: GB2204508A
Application number: GB08807789A
Authority: GB
Inventors: Takemi Yamamoto; Hitoshi Nakai; Jun Sakai; Mitsuru Ohta
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1987-03-31
Filing date: 1988-03-31
Publication date: 1988-11-16
Anticipated expiration: 2008-03-31
Also published as: GB2204508B; GB8807789D0; FR2613501A1

Abstract

A system for reproducing an image using either negative or positive originals (6) employs a bi-polar developer (16) which is electrostatically positively or negatively chargeable. Developing roll (18) is selectively connectable via switches (SW1) and (SW2) to power sources (HV1) and (HV2) for applying high and low bias voltages so as to transfer positive or negatively charged toner to the photosensitive drum (11). Toner is transferred to a belt (19) using transfer roll (21) which is selectively connectable via switches (SW3) and (SW4) to further power sources (HV3) and (HV4) so as to charge the belt to a polarity opposite that of the toner. Belt (19) may be light-transparent so that, through the use of a second exposure unit (4), an image is transferred to microcapsule - bearing photosensitive sheet (26). <IMAGE>

Description

IMAGE RECORDING SYSTEM CAPABLE OF USING BOTH NEGATIVE AND POSITIVE ORIGINALS FOR REPRODUCING A PRINT The present invention relates to an image recording or forming system capable of reproducing a negative or positive image on a photosensitive medium, by using either of a negative or a positive original.

The following photographic techniques are generally known, for reproducing a positive color print, from a negative or positive image on an original film or transparency which is prepared in a photographic process using silver halide salts.

Fof reproducing a positive print from a positive original image, a positive-to-positive photosensitive paper is exposed to a radiation through a film or transparency which bears the positive original image. The imagewise exposed photosensitive paper is developed by using a developer liquid, and the developed image is fixed by a fixing liquid. This process is known as "direct-print photography". Alternatively, an instant photography film such as "SUNPACK AUTOZOOM VIEW PRINTER" (available from NIPPON POLAROID KABUSHIKI KAISHA) is exposed through a positive slide film, whereby a positive print is prepared.

The most familiar and generally practiced method for reproducing a positive print from a negative original film is carried out by exposing a negative-positive photosensitive paper through the negative original film, and developing the exposed photosensitive paper by a developer liquid.

In the known methods described above, only the negative or positive film can be used as the original subject to reproduce a positive print. In other words, the known methods are not capable of using both negative and positive original films, to reproduce a positive print from either of the negative and positive films. Further, if the photographic process requires the use of a developer liquid, the process tends to be complicated, and requires consumables such as developing and fixing liquids, in addition to the photosensitive medium.

Therefore, i the overall photographic system becomes expensive, and the cost of reproduction of a print is comparatively high. These problems are serious particularly when a positive print is reproduced in an enlarged scale with respect to the original size Moreover, the known direct print photography involves cumbersome disposal of the used developing and fixing liquids.

The present invention was developed in the light of the prior art problems discussed above. It is accordingly an object of the present invention to provide an image recording system which permits less costly reproduction of a negative or positive image, by using either of a negative and a positive original.

The above object of the invention may be attained according to the principle of the present invention which provides an image recording system comprising: (a) a first medium for bearing an electrostatic latent image formed on a surface thereof by local potential differences on the surface, the surface having high-potential portions and low-potential portions; (b) a second medium for bearing a bi-polar material which is electrostatically positively and negatively chargeable; and (c) depositing means for supporting the first and second media such that the surface of the first medium is adjacent to a surface of the second medium, and for moving the first and second media relative to each other, thereby electrostatically transferring the bi-polar material to the surface of the first medium.The depositing means includes deposition-voltage applying means for applying a controlled voltage to the bi-polar material. The deposition-voltage applying means is adapted to operate in one of a low-potential mode and a high-potential mode, such that the controlled voltage provides a high potential difference with respect to a potential of the highpotential portions of the first medium in the high potential mode, and a low potential difference with respect to a potential of the low-potential portions of the first medium when the deposition-voltage applying means is placed in the lowpotential mode, and such that the controlled voltage provides a high potential difference with respect to the potential of the low-potential portions of the first medium, and a low potential difference with respect to the potential of the high-potential portions of the first medium.Accordingly, an image corresponding to the electrostatic latent image is formed on the first medium, by the bi-polar material which is deposited on the highpotential and low-potential portions in different conditions.

In the image recording system of the present invention constructed as described above, an electrostatic latent image is formed by high-potential portions and lowpotential portions of the first medium which are established 'according to a negative or positive image of an original subject to be reproduced.The bi-polar material which is electrostatically transferred from the second medium to the electrostatically imaged surface of the first medium is electrostatically positively or negatively charged by a controlled voltage applied thereto by the deposition-voltage applying means, so that the bipolar material is deposited on the high-potential and lowpotential portions in different conditions so that an image corresponding to the previously formed electrostatic latent image is formed by the bi-polar material differently deposited on the high-potential and lowpotential portions of the first medium.

The deposition-voltage applying means is operable selectively in one of the low-potential mode and the high-potential modes, depending upon whether the electrostatic latent image is a positive image or a negative image with respect to the original image to be reproduced. Since the potential differences with respect to the high-potential and low-potential- portions of the first medium are changed by the controlled voltage applied to the bi-polar material, depending upon the operating mode of the deposition-voltage applying means, the conditions in which the bi-polar material is electrostatically deposited on the high-potential and lowpotential portions of the first medium can be switched as required to form a desired positive or negative image corresponding to the electrostatic latent image, which may be a positive or a negative image with respect to the original image.

If the instant image recording system is used to reproduce a negative or positive print by using a slide film which may be either a positive transparency or a negative transparency. Accordingly, the instant system may accept both positive and negative transparencies. In other words, positive prints can be reproduced on the same type of photosensitive recording medium, even if source image information is changed from a positive image to a negative image or vice versa. Further, the instant image recording system does not require conventionally used developing and fixing liquids, and consequently eliminates cumbersome handling and disposal of the used liquids.

The bi-polar material used in the instant recording system may be a powdered material or toner.

In one form of the present invention, the deposition-voltage applying means electrostatically positively or negatively charges the bi-polar material to electrostatically deposit the positively or negatively charged bi-polar material selectively to the highpotential portions and the low-potential portions of the first medium, depending upon- the low-potential mode or high-potential mode in which the deposition-voltage applying means is selectively placed as described above.

Thus, a visible image corresponding to the latent image is formed by the negatively or positively charged bi-polar material deposited on either the high-potential portions or the low-potential portions of the first medium. In this connection, it is desirable that the bi-polar material has a magnetic property, and that the second medium includes a magnet in order to provide a magnetic attracting force acting on the bi-polar magnetic material, for preventing electrostatic attraction of the magnetic material to one of the high-potential and low-potential portions of the first medium to which the controlled voltage applied to the bi-polar magnetic material provides the low potential difference. Namely, the magnetic attracting force provided by the magnet is greater than an electrostatic force acting on the bi-polar magnetic material borne on the second medium.

In an alternative form of the present invention, the deposition-voltage applying means electrostatically positively or negatively charges the bi-polar material to electrostatically deposite the positively and negatively charged bi-polar material to the high-potential portions and the low-potential portions of the first medium, such that a first electrostatic attracting force acting on the bi-polar material attracted to one of the high-potential and low-potential portions is s greater than a second electrostatic attracting force acting on the bi-polar material attracted to the other of the high-potential and low-potential portions, when the deposition-voltage applying means is placed in one of the low-potential and high-potential modes, and such that the first electrostatic attracting force is smaller than the second electrostatic attracting force when the volt ate applying means is placed in the other of the modes. In this case, the image recording system further comprises an eraser body disposed adjacent to the surface of the first medium, for removing the bi-polar material from the surface of the first medium, and erasure-voltage applying means for applying to the eraser body an erasure voltage which is switchable between a positive level and a negative level, to remove the bi-polar material from the high-potential or low-potential portions of the first medium to which the controlled voltage applied to the bi-polar material provides the low potential difference.That is, the highpotential portions or low-potential portions from which the bi-polar material is removed by the eraser body are determined depending upon whether the deposition-voltage applying means is place in the high-potential mode or in the low-potential mode. In the instant arrangement, too, a visible image corresponding to the electrostatic latent image is eventually formed by the bi-polar material electrostatically deposited on the high-potential portions or low-potential portions of the first medium.

According to one arrangement of either of the above-described two forms of the instant recording system, the bi-polar material has a light-shielding property, and the image recording system further comprises: a third medium; means for holding the third medium adjacent to the first medium which bears a light-shielding image consisting of the bi-polar material deposited on the highpotential portions or the low-potential portions thereof; transfer-voltage applying means for applying to the third medium a transfer voltage for transferring the lightshielding image from the first medium to the third medium, such that the transfer voltage is switcheable between a positive level and a negative level; and recording-medium exposing means for exposing a photosensitive recording medium, under an influence of the light-shielding image on the third medium, so that an image corresponding to the light-shielding image is formed on the photosensitive recording medium. In this arrangement, the recording medium may be of a type which has microcapsules each of which contains a chromogenic material and whose mechanical strength varies with an amount of exposure to a radiation.

In this case, developing means is provided for pressing the photosensitive recording medium in the presence of a developing material, and thereby rupturing the microcapsules according to their mechanical strength, for chemical reaction with the developing material so as to produce the visible image.

In the above arrangement, the first medium may be provided with a plurality of electrostatic images at different times and/or in different portions of the surface theF'eof. In this case, the depositing means is adapted to form the light-shielding image corresponding to each of the plurality of electrostatic images, and the transfer-voltage applying means operates to transfer each light-shielding image corresponding to each electrostatic image to the third medium. Further, the recording-medium exposing means is adapted to expose the photosensitive recording medium to radiations having different wavelengths, under the influence of the corresponding light-shielding images on the third medium.

According to another arrangement of either of the two alternative forms of the invention described above, the recording system further comprises means for holding a recording medium adjacent to the first medium which bears the bi-polar material deposited on the highpotential portions or the low-potential portions thereof, and transfer-voltage applying means for applying to the recording medium a transfer voltage for transferring the bi-polar material from the first medium to the recording medium. The transfer voltage is switcheable between a positive level and a negative level. In this case, the bipolar material may comprise at least one chromogenic material corresponding to at least one color, respectively. The image recording system further comprises means for fixing the chromogenic material or materials transferred to the recording medium.

In the above arrangement, the bi-polar material comprises i C plurality of chromogenic materials corresponding to a plurality of colors, respectively, and the first medium bears a plurality of electrostatic image patterns at different times and/or in different portions of the surface thereof. In this instance, the depositing means is operable to deposite on the first medium each of the plurality of chromogenic materials according to a corresponding one of the plurality of electrostatic image patterns. The means for holding a recording medium and the transfer-voltage applying means cooperate to transfer the chromogenic materials corresponding to the electrostatic image patterns, to the recording medium such that patterns formed by the chromogenic materials are superposed on each other, whereby a visible color image is formed.

In a further form of the invention, electrostatic charging means is provided for uniformly charging the surface of the first medium, and first-medium exposing means is provided for exposing the surface of the first medium under an influence of source image information on an original, thereby forming on the surface of the first medium the latent electrostatic image which corresponds to the source image information.

The above and optional objects, features and advantages of the present invention will become more apparent by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which: Fig. 1 is a schematic view of one embodiment of an image recording system of the present invention in the form of a color imaging apparatus; Fig. 2 is a schematic view in perspective of a belt feeding unit and second exposing means of the apparatus of Fig. 1; Fig. 3(a) is a graph indicating spectral transmission factors of three primary colors of light of an interference filter used in the apparatus of Fig. 1; Fig. 3(b) is a graphical view indicating spectral reflection factors of three primary colors (cyan, magenta and yellow) of an original;; Fig. 4 is a fragmentary elevational view in vertical cross section of a pressure-sensitive photosensitive sheet; Fig. 5(a) is a view showing different potentials in exposed and non-exposed areas of the surface of a photosensitive drum, and a condition in which a toner is attracted to the drum, where an image formed by the toner is reversed with respect to a negative image on a slide film; Fig. 5(b) is a view showing different potentials in the exposed and non-exposed surface areas of the drum, and a condition in which the toner is attracted to the drum, where 1the image formed by the toner is not reversed with respect to a positive image on the slide film; Fig. 6 is a block diagram showing an electric control system of the color imaging apparatus of Fig. 1;; Fig. 7 is a schematic view corresponding to that of Fig. 1, showing another embodiment of a color imaging apparatus according to the present invention; Fig. 8 is a diagram illustrating a driver circuit for selectively applying a controlled voltage to four developing rolls of the color imaging apparatus of Fig. T; Figs. 9(a) and 9(b) are views corresponding to those of Figs. 5(a) and 5(b), in connection with the embodiment of Fig. 7; Fig. 10 is a schematic view corresponding to that of Fig. 1, showing a further embodiment of the invention; Figs. 11(a) and 11(b) are views explaining a process in which a positive print is reproduced from a negative slide film; and Figs. 12(a) and 12(b) are views explaining a process in which a positive print is reproduced from a positive slide film.

Referring first to Figs. 1 and 2, there is shown a color imaging apparatus which includes a first exposing unit 1 as fdrst exposing means, a xerography unit 2 as toner depositing means, a belt feeding unit 3 as feeding means, a second exposing unit 4 as second exposing means, and a paper supply unit 5.

In the first exposing unit 1, a transparency or slide film 6 corresponding to a desired source or original image to be reproduced is interchangeably placed in position. The slide film 6, which bears a positive or negative image with respect to the original image, is irradiated with a scanning radiation produced by a light source 7 which is driven by a suitable driver. The radiation which has passed through the slide film 6 is incident upon a plane mirror 10 through a focusing lens 8 and an interference filter 9. The radiation is reflected by the mirror 10 toward the surface of a photosensitive drum 11 of the xerography unit 2, whereby the reflected light is focused on the surface of the drum 11. The interference filter 9 has three filter elements 9R, 9G, 9B which selectively transmit rays of light having wavelengths corresponding to red, green and blue colors, respectively.These filter elements 9R, 9G and 9B for the red, green and blue colors have spectral transmittances or transmission factors as indicated in Fig. 3(a). The focusing lens 8 has a variable magnifying ratio m.

Depending upon a selected magnifying ratio m of the focusing lens 8, the speed of scanning the slide film 6 with the radiation is adjusted by the driver device of the light source 7. Thus, the size of an electrostatic latent image to be formed on the photosensitive drum 11 can be varied as desired.

Along the periphery of the photosensitive drum 11 of the xerography unit 2, there are disposed a discharger 13, an electrostatic charger 14 connected to a high voltage source Hvo, a first developing device 15 as first developing means, and a cleaning device 12, in the order corresponding to a rotating direction of the drum 11 (indicated by arrow A in Fig. 1).

As the photosensitive drum 11 is rotated, a residual electrostatic charge on the drum is removed by the discharger 13, and the discharged circumferential surface of the drum 11 is uniformly electrostatically charged to -650V. When the negatively charged surface is irradiated with a radiation representative of the original image information, the surface potential Vi in the unexposed areas slightly decreases to -600V, while the electrostatic charge in the exposed areas disappears to a considerable degree, with the surface potential Vl in the exposed areas decreasing to -50V. As a result, a pattern of electrostatic surface potential difference is formed by the exposed and unexposed portions of the photosensitive drum 11, whereby an electrostatic latent image corresponding to the source image information is formed on the drum 11.

The first developing device 15 includes a toner container 17 for accommodating a mass of a positively and negatively electrostatically charageable, bi-polar black toner 16. The first developing device 15 further includes a developing roll 18 made of a non-magnetic material, which serves as a medium for bearing the toner 16. The developing roll 18 incorporates a cylindrical permanent magnet (not shown), and the toner 16 includes a magnetic powder, so that the toner 16 is attracted to the developing roll 18 by a magnetic force of the magnetic powder. With the roll 18 rotated, the toner 16 in the container 17 is moved toward the surface of the photosensitive drum 11. The developing roll 18 is connected via disconnect switches SW1 and SW2 selectively to one of two power sources HV1 and HV2.These power sources HVl, HV2 serve as bias voltage applying means for applying high and low bias voltages -500V, -100V to the developing roll 18. With the appropriate one of the disconnect switches SW1, SW2 placed in its ON or closed position, the high or low developing bias voltage is applied to the developing roll 18, whereby a potential between the photosensitive drum 11 and the developing roll 18 is changed between two values. More specifically, a positively charged toner 16a or negatively charged toner 16b of the bi-polar toner mass 16 is electrostatically attracted or transferred to the exposed or unexposed surface areas of the photosensitive drum 11, depending upon the potential and polarity in the exposed and unexposed areas. Since the toner 16 is a light-shielding material, a visible light-shielding image 22 corresponding to the electrostatic latent image is formed by the toner 16. While the light-shielding image 22 is transferred to a light-transparent endless belt 19 as described below, there may be left some amount of the toner 16 on the circumferential surface of the drum 11. The residual toner mass is removed by a cleaning blade 12a of the cleaning device 12. The removed toner mass is stored in a recovery casing 12b.

The belt feeding unit 3 has a pair of feed rolls 20, 20 which are rotated by suitable means (not shown). An intermediate medium in the form of the transparent endless sheet belt 19 made of polyethylene terephthalate (PET) is supported by the feed rolls 20, so as to extend horizontally therebetween so that the endless belt 19 is rotated in a direction indicated by arrow B in Fig. 1.

Below an upper run of the endless belt 19, there is disposed image transfer means in the form of a transfer roll 21 which is located below the photosensitive drum 11, such that the transfer roll 21 and the drum 11 cooperate to pinch the upper run of the endless belt 19 therebetween. The transfer roll 21 is connected via disconnect switches SW3 and SW4 selectively to one of two power sources HV3 and HV4. These power sources HV3, HV4 serve as transfer voltage applying means for applying negative and positive high voltages to the transfer roll 21. The disconnect switches SW3 and SW4 are closed and opened in response to the corresponding actions of the disconnect switches SW1 and SW2, respectively.The transfer roll 21 serves to electrostatically charge the transparent endless belt 19, with a polarity opposite to that of the positively or negatively charged toner 16a, 16b which is electrostatically deposited on the photosensitive drum 11 as the visible light-shielding image 22. The amount of the electrostatic charge applied to the transfer roll 21 is determined so as to be sufficient to transfer the toner 16a, 16b (i.e. visible light-shielding pattern or image 22) onto the endless belt 19. Thus, the visible light-shielding image 22 is transferred from the drum 11 to the transparent endless belt 19.

The second exposing unit 4 is disposed above a downstream portion (left-hand side portion in Fig. 1) of the upper run of the endless belt 19. This second exposing unit 4 includes an illuminating lamp 23, a light collector 24, and an interference filter 25 which consists of three filter elements 25R, 25G and 25B having the same spectral transmission factors as the corresponding filter elements 9R, 9G and 9B of the interference filter 9 of the first exposing unit 1.

As shown in Fig. 2, the paper supply unit 5 is disposed alongside the path of the endless belt 19. The unit 5 includes a storage cassette 27 for accommodating a stack of pressure-sensitive photosensitive cut sheets 26, and a pair of feed rollers 28, 28 for delivering the photosensitive sheets 26 from the cassette 27 toward the endless belt 19. The paper supply unit 5 further includes a sheet guide 30 for guiding each photosensitive recording sheet 26 fed by the feed rollers 28 to an exposing position just below the lower surface of the downstream portion of the upper run of the endless belt 19, which is aligned with the second exposing unit 4.

In the present embodiment, the pressuresensitive photosensitive sheet 26 is of a color imaging type, having a paper substrate 26a, and a multiplicity of microcapsules 26b and a developing material which are formed on the substrate 26a, as well known in the art. The microcapsules 26b contain a radiation-curable resin, and different chromogenic materials corresponding to the primary color pigments; cyan, magenta and yellow. The chromogenic materials are capable of chemically reacting with the developing material, so as to produce the respective colors. The upper surface of the upper run of the endless belt 19 on which the visible image 22 lies is irradiated by a suitable amount of radiation which is emitted from the exposing device 4 via the filter elements 25R, 25G and 25B which are selectively placed in the operative position.As a result, the photosensitive sheet 26 is imagewise exposed to the radiation through the endless belt 19, under an influence of the visible image 22. Described in more detail, the radiation-curable resin in the microcapsules 26b in the exposed areas of the photosensitive sheet 26 is cured, while the radiationcurable resin in the microcapsules 26b in the unexposed areas corresponding to the light-shielding toner of the visible image 22 is left uncured. Thus, when the photosensitive sheet 26 is exposed through the endless belt 19 to a radiation transmitted through each of the three filter elements 25R, 25G, 25B, a latent image corresponding to the visible light-shielding image 22 is formed on the sheet 26, for each of the three colors.

A second developing device in the form of a pair of presser rolls 29, 29 is disposed alongside the endless belt 19, on the side opposite to the paper supply device 5, as shown in Fig. 2. The presser rolls 29 are movable toward and away from each other. The photosensitive sheet 26 exposed by the second exposing device 4 is guided by the above-indicated sheet guide 30, into a pressure nip of the presser rolls 29, 29. As a result, the microcapsules 26b whose resin is left uncured are ruptured, and the chromogenic materials flow out of the ruptured microcapsules, whereby the chromogenic materials chemically react with the developing material also provided on the sheet 26. In this manner, a visible color image is formed on the pressure-sensitive photosensitive sheet 26.

Another cleaning device 31 is disposed below the left end of'the endless belt 19 near the second exposing unit 4. The device 31 has a cleaning blade 31a, and a recovery casing 31b. The visible light-shielding image on the transparent endless belt 19, which has been used as a photomask, is removed from the belt 19 by the blade 31a and stored in the recovery casing 31b.

Referring to Fig. 6, an electric control system of the color imaging apparatus constructed as described above will be described.

The control system uses a CPU (central processing unit) 32 which serves as control means for controlling the operation of the apparatus. To the CPU 32 are connected an operator's control panel 33 and a sensor S1. The control panel 33 has control switches which include a start switch for starting the operation, and selector switches for selecting a desired number of copies to be reproduced, a desired image density and other operating conditions. The sensor S1 is provided to detect the presence of the slide film 6 in the first exposing unit 1. To the CPU 32, there are also connected a ROM (read-only memory) 34 and a RAM (random-access memory) 35.

The ROM 34 stores control programs for controlling the operation of the imaging apparatus, and the RAM 35 temporarily stores data signals from the operator's control panel 33 and sensor S1. According to the control programs stored in the ROM 34, the CPU 32 controls the first exposing unit 1, xerography unit 2, belt feeding unit 3, second exposing unit 4 and paper supply unit 5.

The CPU 32 incorporates judging means 32a which is responsive to a signal from the control panel 33, to determine whether the slide film 6 is a positive transparency or a negative transparency. According to the determination by the judging means 32a, the CPU 32 controls the disconnect switches SW1 through SW4 for the developing roll 18 and the transfer roll 21.

There will be described an operation to reproduce a color print on the instant color imaging apparatus, according to a negative image or a positive image on the slide film 6, which is prepared in a known silver salt photographic process.

When the slide film 6 is a negative transparency, the imaging operation is performed in the following manner: The image on the negative slide film 6 consists of colors which are complementary to the colors of an original image to be reproduced. Described more specifically, the image on the negative slide film 6 consists of three primary colors of light, i.e., red, green and blue, which correspond to the complementary colors of the three primaries, namely, cyan, magenta and yellow pigments on the original positive image. These complementary colors (cyan1 magenta and yellow) have spectral reflection factors as indicated in Fig. 3(b). In the first exposing unit 1, the red-color filter element 9R of the interference filter 9 is initially placed in the operative position on the optical path.In this condition, the negative slide film 6 is scanned by a radiation from the light source 7, and the radiation travels through the focusing lens 8 and the filter element 9R. More precisely, only the light rays corresponding to the red-colored portions of the negative film 6 (cyan portions of the original image) are transmitted through the filter element 9R. Thus, a negative latent image corresponding to the cyan portions of the original image is electrostatically formed on the photosensitive drum 11. The drum 11 therefore serves as a medium for bearing the electrostatic latent image.

While the photosensitive drum 11 is rotated with the thus formed electrostatic latent image of cyan moving toward the developing roll 18 (developing station), the switch SW1 is held closed while the switch SW2 is held open. Namely, the high voltage source HV1 is connected to the developing roll 18, whereby -500V bias voltage is applied to the developing roll 18. As a result, there exists a positive potential difference of +450V = -50V 500V), between the exposed surface areas of the photosensitive drum 11 and the developing roll 18, as indicated in Fig. 5(a).Therefore, the negatively charged toner 16b of the bi-polar toner 16 is electrostatically attracted and thereby transferred to the exposed areas of the drum 11, whereby the visible light-shielding positive image 22 corresponding to the cyan portions of the original image is formed, with the toner 16b deposited in the exposed areas of the drum 11. Thus, the negative image on the negative slide film 6 is reversed into the positive image 22 consisting of the light-shielding toner 16b. On the other hand, there exists a negative potential difference of -100V = -600V - (-500V) between the unexposed surface areas of the drum 11 and the developing roll 18. Consequently, the negatively charged toner 16b will not be electrostatically attracted to the unexposed portions of the drum 11.Although an electrostatic attracting force acts on the positively charged toner 16a on the developing roll 18, the toner 16a will not be attracted to the drum 11 since a magnetic force between the magnetic powder of the toner and the permanent magnet in the developing roll 18 is greater than the electrostatic attracting force. acting on the toner 16a.

In response to the closing and opening actions of the switches SW1 and SW2, the switches SW3 and SW4 are closed and opened, respectively, so that the positive high voltage source HV3 is connected to the transfer roll 21.

As a result, an electric field is produced by the transfer roll 21, in a direction from the roll 21 toward the drum 11 through the endless belt 19. Consequently, an electrostatic force acts on the toner 16b, so as to attract the toner 16b onto the endless belt 19. Since the endless belt 19 is positively charged while the toner 16b on the drum 11 is negatively charged, the toner 16b forming the visible light-shielding positive image 22 is transferred from the drum 11 onto the endless belt 19, as the drum 11 and endless belt 19 are rotated.

In the same manner as described above, visible light-shielding positive images 22 corresponding to magenta and yellow portions of the original image are formed on the drum 11, and transferred to the endless belt 19 rotating in the direction B, by selecting the greenand blue-color filter elements 9G and 9B of the interference filter 9.

As the endless belt 19 is rotated in the direction B, a portion of the belt 19 bearing the visible light-shielding positive image 22 corresponding to the cyan portions of the original image becomes opposite to the second exposing unit 4. In the meantime, the pressuresensitive photosensitive sheet 26 is delivered from the paper supply unit 5, and brought into the exposing position. In this condition, the red-color filter element 25R of the interference filter 25 is selected into position, and the portion of the belt 19 bearing the lightshielding cyan image 22 is irradiated by a radiation which is emitted by the illuminating lamp 23 and transmitted through the filter element 25R. As a result, the microcapsules 26b of the photosensitive sheet 26 which correspond to the cyan are imagewise exposed corresponding to the light-shielding image 22.That is, the microcapsules 26b in the unexposed portions of the sheet 26 protected by the light-shielding toner 16b of the photomask pattern 22 are left uncured, while the microcapsules 26b in the exposed portions of the sheet 26 are cured due to exposure to the radiation. In this way, a latent positive cyan image is formed on the photosensitive sheet 26.

Latent positive t ive magenta and yellow images are formed on the sheet 26, in the same manner as described above with respect to the cyan image. Namely, the portions of the endless belt 19 bearing the visible light-shielding positive images 22 for magenta and yellow are aligned with the second exposing unit 4, and the appropriate green- and yellow-color filter elements 25G and 25B of the filter 25 are selectively placed in the operative position. In this condition, the photosensitive sheet 26 is imagewise exposed to a radiation transmitted through the appropriate filter element 25G, 25B and the photomask 22 for magenta or yellow. The magenta and yellow microcapsules 26b in the exposed portions of the sheet 26 are radiation-cured.

After the latent images for cyan, magenta and yellow have been formed on the pressure-sensitive photosensitive sheet 26, the sheet 26 is passed through the pressure nip of the presser rolls 29 of the second developing device. As a result, the uncured microcapsules 26b for the three colors are ruptured, and the chromogenic materials come out of the ruptured microcapsules 26b, causing a chemical reaction between the chromogenic materials and the developer material of the photosensitive sheet 26, thereby producing a positive color print corresponding to the original positive image. As described above, the reproduction of the positive image on the photosensitive sheet 26 is effected in the following manner and order: 1) The negative slide film 6 corresponding to the original image is placed in position in the first exposing unit 1; 2) The negative image on the slide film 6 is converted by the exposing unit 1, into an electrostatic negative image formed on the photosensitive drum 11; 3) The electrostatic negative image is reversed by the first developing unit 2, into the visible light-shielding positive image 22 consisting of the toner 16b; 4) The visible positive image 22 is transferred onto the transparent endless belt 19, as a light-shielding photomask; and 5) A latent image is formed on the photosensitive sheet 26, by exposure of the sheet to the radiation from the second exposing unit 4, through the light-shielding photomask 22, or under the influence of the lightshielding image 22. This latent image is developed by the second developing device 29, 29, into a positive image corresponding to the positive image on the negative slide film 6.

Where the slide film 6 is a positive film, the imaging operation is performed in the following manner: The positive image on the slide film 6 consists of the same colors as the positive image on the original image. Described more specifically, the image on the positive slide film 6 consists of cyan, magenta and yellow (complementary colors of the three primary colors of light), which appear on the original positive image. When a latent image corresponding to the cyan image of the positive slide film 6 is formed on the pressure-sensitive photosensitive sheet 26, the red-color filter element 9R of the interference filter 9 in the first exposing unit 1 is initially placed in the operative position on the light path, as in the case of reproducing a positive image from the negative slide film 6.In this condition, the positive slide film 6 is scanned by a radiation from the light source 7, and the radiation travels through the focusing lens 8 and the filter element 9R. More precisely, only the light rays corresponding to the red-colored portions of the positive film 6 (i.e., magenta and yellow portions of the original image) are transmitted through the filter element 9R. Thus, a positive latent image corresponding to the non-cyan portions of the original image is electrostatically formed on the photosensitive drum 11.

The switch SW2 is held closed while the switch SW1 is held open. Namely, the low voltage source HV2 is connected to the developing roll 18, whereby -100V bias voltage is applied to the developing roll 18. As a result, there exists a negative potential difference of -500V = 600V - (-100V) between the unexposed surface areas of the photosensitive drum 11 and the developing roll 18, as indicated in Fig. 5(b). Therefore, the positively charged toner 16a of the bi-polar toner 16 is electrostatically attracted to the unexposed areas of the drum 11, whereby the visible light-shielding positive image 22 corresponding to the cyan portions of the original image is formed, with the toner 16a deposited in the unexposed areas of the drum 11.On the other hand, there exists a positive potential difference of +50V = -50V - (-100V) between the exposed surface areas of the drum 11 and the developing roll 18. Therefore, the positively charged toner 16a will not be electrostatically attracted to the exposed portions of the drum 11. Although an electrostatic attracting force acts on the negatively charged toner 16b on the developing roll 18, the toner 16b will not be attracted to the drum 11, since a magnetic force between the magnetic powder of the toner 16b and the permanent magnet in the developing roll 18 is greater than the electrostatic attracting force acting on the toner 16b.

In response to the closing and opening actions of the switches SW2 and SW1, the switches SW4 and SW3 are closed and opened, respectively, so that the negative high voltage source HV4 is connected to the transfer roll 21.

As a result, an electric field is produced by the transfer roll 21, in a direction from the roll 21 toward the drum 11 through the endless belt 19. Consequently, an electrostatic force acts on the toner 16a, so as to attract the toner 16a onto the endless belt 19, whereby the toner 16a forming the visible light-shielding positive image 22 is transferred from the drum 11 onto the endless belt 19, as the drum 11 and endless belt 19 are rotated.

Similarly, visible light-shielding positive images 22 corresponding to the magenta and yellow portions of the original image are formed on the drum 11, and are transferred to the endless belt 19, by selecting the green and blue-color filter element-s 9G' and 9B of the interference filter 9.

After the light-shielding positive images 22 corresponding to the cyan, magenta and yellow portions of the original image are formed on the endless belt 19, the photosensitive sheet 26 is imagewise exposed by the second exposing unit 4, in the same manner as described above with respect to the color imaging operation using the negative slide film 6. Since the photomasks consisting of the light-shielding patterns of the toner 16a are positive images, the microcapsules 26b in the unexposed portions of the photosensitive sheet 26 corresponding to the cyan, magenta and yellow image portions of the positive slide film 6 are left uncured, whereby a latent image is formed on the photosensitive sheet 26.When the thus imagewise exposed photosensitive sheet 26 is subsequently developed by the prltesser rolls 29, a positive color image corresponding to the positive image on the positive slide film 6 appears on the photosensitive sheet 26. As described above, the positive color print is obtained from the positive slide film 6 in the following manner and order:: 1) The positive slide film 6 corresponding to the original positive image is placed in position in the first exposing unit 1; 2) The positive image on the slide film 6 is converted by the exposing unit 1, into an electrostatic positive image formed on the photosensitive drum 11; 3) The electrostatic positive image is converted by the first developing unit 2, into the visible positive image 22 consisting of the light-shielding toner 16a; 4) The visible positive image 22 is transferred onto the transparent endless belt 19, as a light-shielding photomask; and 5) A latent image is formed on the photosensitive sheet 26, by exposure of the sheet to the radiation from the second exposing unit 4, through the light-shielding photomask 22, and this latent image is developed by the second developing device 29, 29, into a positive image corresponding to the positive image on the positive slide film 6.

As described above, when the slide film 6 is a negative film, the visible light-shielding positive image 22 is formed by the negatively charged toner 16b attracted to the exposed portions of the photosensitive drum 11.

When the slide film 6 is a positive film, the visible positive image 22 is formed by the positively charged toner 16a attracted to the unexposed portions of the drum 11. Thus, the visible image 22 is obtained from either the negative slide film 6 or the positive slide filom 6, by simply operating the switches SW1-SW4 as described above.

A positive image corresponding to the original image is formed on the photosensitive sheet 26, as a result of exposure of the sheet through the light-shielding positive image 22 made of the light-shielding toner 16a, 16be irrespective of whether the slide film 6 is a negative film or a positive film.

Generally, the spectral characteristics of the exposing light sources 7, 23, photosensitive drum 11 and photosensitive sheet 26 are not flat. Further, the cyam and magenta pigments of a negative color film or transparency produced in a silver salt photography process tends to have incomplete spectral absorptance. Therefore a so-called "orange mask" is usually used with respect to the cyan and magenta pigments, in the manufacture of negative films. For this reason, the unexposed portions of a negative film tend to be orange-colored. In view of this tendency, a suitable compensation filter (not shown) is provided on the light path in the first exposing unit 1 of the instant embodiment, for eliminating the color distortion on a reproduced color print.

In the present image recording system, a positive color print can be reproduced from either a negative or a positive slide or transparency, by simply switching the disconnect switches SW1-SW4, without changing or replacing any component parts of the system.

Furthermore, the prevent recording system eliminates developing and fixing liquids and related units or components, as required in the silver salt photography process. Accordingly, the operation and maintenance of the system are made easier, and the operation cost is reduced, without using any consumables except for the photosensitive recording medium 26. Thus, the instant system permits inexpensive reproduction of a color print.

Moreover, the size of the image reproduced on the photosensitive sheet 2 can be readily changed as desired, by changing the magnifying ratio m of the focusing lens 8.

Referring to Fig. 7, there is shown a modified embodiment of the present invention, wherein the same reference characters as used in the preceding embodiment are used to identify the corresponding elements. The present apparatus uses an exposing unit 1 similar to the first exposing unit 1 of the preceding embodiment.

However, the exposing unit 1 of the present embodiment includes an interference filter 107 which is different from the interference filter 9 of Fig. 1. Namely, the interference filter 107 has four filter elements 107R, 107G, 107B and lOTY. The filter elements 107R, 107G and 107B have the same functions as the filter elements 9R, 9G and 9B of the filter 9. The filter element 107Y additionally provided on the present filter 107 permits transmission of light rays having wavelengths corresponding to all of the three colors, red, green and blue, and is used to form a black image (black-and-white image).

The xerography unit 2 includes the cleaning device 12, discharger 13 and electrostatic charger 14, which have the same functions as described above with respect to the first embodiment. However, the xerography unit 2 uses four developing devices 113, 114, 115 and 116 which are disposed along the periphery of the photosensitive drum 11, in the order of description (corresponding to the rotating direction A of the drum).

As previously described, the surface of the drum 11 is negatively charged to -650V by the charger 14. As a result of exposure to a radiation through each filter element 107R, 107G, 107B, 107Y, the surface potential in the unexposed portions of the drum 11 slightly decreases to 600V, while that in the exposed portions greatly decreases to -50V.

The developing devices 113-116 include respective developing rolls 113a, 114a, 115a and 116a, and respective toner containers 113b, 114b, 115b and 116b. The containers 113b, 114b, 115b, 116b accommodate four different toners, respectively, i.e., cyan toner 117, magenta toner 118, yellow toner 119 and black toner 120, which correspond to the red, green, blue and black filter elements 107R, 107G, 107B and 107Y, respectively. The toners 117, 118, 119 and 120 are electrostatically positively and negatively chargeable bi-polar materials, and include chromogenic materials or pigments corresponding to cyan, magenta, yellow and black. The developing rolls 113a, 114a, 115a, 116a are connected to a switching circuit 112 as shown in Fig. 8, so that a controlled bias voltage is applied to the developing rolls in a controlled sequence as described below.

The switching circuit 112 is connected to the power sources HV1, HV2 through the disconnect switches S91, SW2. For simplificatinn and easy undertandJng, each power source HVl, HV2 and the corresponding switch SW1, SW2 in its closed position are indicated in Fig. 8 as a power source 126. The switching circuit 112 includes four variable resistors R1, R2, R3 and R4, and four relays RAl, RA2, RA3 and RA4. A sliding contact of each variable resistor R1-R4 is connected to one of two fixed terminals of the corresponding relay RA1-RA4. This fixed terminal is normally disconnected from a movable terminal of the corresponding relay. The other fixed terminal is grounded.

The movable terminals of the relays RA1-RA4 are connected to the respective four developing rolls 113a116a. The relays RA1-RA4 are controlled by a suitable control device as shown at 32, 34, 35 in Fig. 6 of the preceding embodiment.

Normally, the relays RA1-RA4 are placed in their open position, and all the developing rolls 113a, plea, 115a, 116a are connected to the earth through the movable terainals of the relays. In this condition, the toners 117- 120 are not transferred to the surface of the photosensitive drum 11. When the developing devices 113116 are activated, one at a tine, according to signals from the control device, the output voltage of the power source 126 (HV1 or HV2) is divided by the corresponding variable resistor R1-R4, whereby the controlled bias voltage is applied to the respective developing roll 113a116a through the respective relay RA1-RA4. Thus, the four developing devices 113-116 are sequentially activated.

As described above, each of the developing rolls 113a-116a is connected to the power sources HV1, HV2 through the switching circuit 112. With the switch SW1 placed in the closed position, a bias voltage of -500V is applied to the selected developing roll 113a-116a. With the switch SW2 in the closed position, a bias voltage of 100V is applied to the selected developing roll. These bias voltages are selected so as to transfer the positively or negatively charged toners 117-120 to the exposed or unexposed portions of the photosensitive drum 11, depending upon whether the image on the slide film 6 is a positive image or a negative image with respect to an original image to be reproduced.

With the cyan, magenta, yellow and black toners 117-120 electrostatically transferred from the developing rolls 113a-116a to the photosensitive drum 11, as described later in more detail, corresponding cyan, magenta, yellow and black images 22 are formed on the drum 11. These images are transferred to a recording medium 125 in the form of a cut sheet stored in a stack in a cassette 103. The recording medium 125 fed from the cassette 103 is delivered onto an endless belt 123, while being guided by a guide 122. The endless belt 123 has a gripper on its outer surface for gripping the leading end of the recording medium 125 when delivered from the cassette 103.

Contrary to the endless belt 19 used in the first embodiment, the endless belt 123 need not be lighttransparent, and is used as means for supporting the recording medium 125 and moving the same between the drum 11 and a transfer roll 121, and between two image-fixing rolls in the form of heating rolls 124, 124.

The transfer roll 121, which is similar to the roll 21 used in the apparatus of Fig. 1, is disposed adjacent to the photosensitive drum 11. This transfer roll 121 is also connected to the power sources HV3 or HV4 through the corresponding disconnect switch SW3, SW4, so that a controlled transfer voltage is applied to the transfer roll 121 and to the recording medium 125, so that the images.22 formed on the drum 11 are electrostatically transferred to the recording medium 125 supported on the endless belt 123.

In a first printing cycle, the red-color filter element 107R is selected, and the cyan toner 117 is electrostatically transferred to the imagewise exposed surface of the drum 11, whereby the cyan image 22 is formed on the drum 11. In the meantime, the endless belt 123 is loaded with the recording medium 125. As the medium 125 is fed with the moving upper run of the rotating endless belt 123, the cyan image 22 consisting of the cyan toner 117 is transferred to the medium 125. The transferred cyan image 22 is fixed on the medium 125 while the medium 125 is passed through the nip of the heating rolls 124.

The endless belt 123 is stopped after the recording medium 125 bearing the cyan image 22 is returned to a predetermined original position. Then a second printing cycle is initiated.

In the second printing cycle, the green-color filter element 107G is selected, and the magenta toner 118 is electrostatically transferred to the imagewise exposed surface of the drum 11, as the drum 11 is rotated. The magenta toner 118 is electrostatically transferred as the magenta image 22 to the recording medium 125, such that the magenta image 22 is superposed on the previously formed cyan image 22.

Såmilarly, a third printing cycle is effected to form the yellow image 22 on the medium 125, which yellow image 22 corresponds to an electrostatic latent image formed on the rotating drum 11, as a result of exposure to a radiation through the blue-color filter element 107B.

The yellow image 22 consisting of the yellow toner 119 is superposed on the cyan and magent images 22 previously formed on the medium 125.

In a fourth printing cycle, an electrostatic latent image is formed on the rotating drum 11, as a result of exposure to a radiation through the black filter element 107Y. In this cycle, the black toner 129 for adjusting the tone of a color print to be reproduced on the medium 125 is transferred to the drum 11 and to the medium 125, as the black image 22 superposed on the cyan, magenta and yellow images 22. It is noted that the last printing cycle for the black image 22 may be eliminated.

In this case, the filter element 107Y and the fourth developing device 116 are not used or operated.

Where the slide film 6 is a negative transparency, the disconnect switches SW1 and SW2 are placed in the closed and open positions, respectively.

Therefore, in the first printing cycle, the high bias voltage of -500V is applied to the first developing roll 113a through the relay RAl of the switching circuit 112 shown in Fig. 8. As a result, there arises a potential difference of +450V = -50V - (-500V), between the surface potential Vi of the exposed portions of the drum 11, and the potential of the developing roll 113a. Therefore, the negatively charged cyan toner 117 is electrostatically attracted to the exposed portions of the drum surface, as indicated in Fig. 9(a). Thus, the negative image on the slide film 6 is reversed into the positive cyan image 22, which corresponds to the cyan image of the original. On the other hand, a potential difference of -1OOV = -600V (-500V) is present between the unexposed portions of the drum 11 and the developing roll 113a.Consequently, the negatively charged cyan toner 117 will not be attracted to the unexposed portions of the drum 11. Further, the positively charged cyan toner 117 will not be attracted to the drum 11, because of a magnetic force produced by a permanent magnet provided in the developing roll 113a, as described before with respect to the first embodiment of Fig. 1.

The cyan image 22 thus formed on the drum 11 is electrostatically transferred to the recording medium 125, by the high positive transfer voltage applied from the power source HV3 to the transfer roll 121, through the closed switch SW3, in the same manner as described before in connection with the first embodiment.

In the second, third and fourth printing cycles, the appropriate relays RA2-RA4 are sequentially activated to apply the high bias voltate of -500V to the corresponding developing rolls 114a, 115a, 116a. As a result, the magenta, yellow and black toners 118-120 are transferred as the positive magenta, yellow and black images 22 to the drum 11 and the recording medium 125, in the same manner as described above. Thus, the cyan, magenta, yellow and black images 22 are superposed on each other on the recording medium 125, whereby a positive color print is produced.

Where the image on the slide film 6 is a positive image with respect to the original image to be reproduced, the switch SW2 is closed and the switch SW1 is opened, and the comparatively low bias voltage of -100V is applied from the power source HV2 to the developing rolls 113a, 114a, 115a, 116a, through the corresponding relays RA1-RA4. Therefore, there arises a negative potential difference of -500V = -600V - (-100V) between the exposed portions of the photosensitive drum 11 and the developing roll 113a, 114a, 115a, 116a, whereby the positively charged toner 117-120 is electrostatically attracted to the unexposed portions of the drum 11, as indicated in Fig. 9(b). Thus, the positive image on the slide film 6 is converted into the positive cyan, magenta, yellow or black image 22 formed on the drum 11.Since there exists a positive potential difference of +50V = -50V - (-100V) between the exposed portions of the drum 11 and the appropriate developing roll 113a-116a, the positively charged toner 117-120 will not be attracted to the exposed portions of the drum 11.

In response to the closing and opening actions of the switches SW2 and SW1, the switches SW4 and SW3 are closed and opened, whereby the high negative transfer voltage is applied from the power source HV4 to the transfer roll 121. As a result, the positively charged toners 117-120 or images 22 are transferred from the drum 11 to the medium 125. Thus, a positive color print is formed on the medium 125, from the positive image on the slide film 6.

Referring further to Figs. 10, 11(a), 11(b), 12(a) and 12(b), a third embodiment of the present invention will be described. In the interest of brevity and simplification, the same reference characters as used in the preceding embodiments will be used to identify the corresponding components.

This modified apparatus is adapted to reproduce a monocrome print, as distinguished from a color print as reproduced by the preceding embodiments. Namely, the xerography unit 2 of the present embodiment uses a developing device 213 which accommodates a black toner 217. The developing device 213 has a developing roll 213a which is connected to the power source HV1 (-500V) or HV2 (-100V) via the disconnect switch SW1 or SW2, as described before with respect to the embodiments of Figs. 1 and 7.

Further, the photosensitive drum 11 is uniformly negatively charged by the electrostatic charger 14, as previously described.

Further, the instant embodiment is different from the preceding embodiment of Fig. 7, in that the xerography unit 2 of the present monochrome imaging apparatus includes a selective erasing device generally indicated at 222 in Fig. 10. This erasing device 222 is disposed between the developing roll 213a, and the transfer roll 121 disposed below the drum 11. The device 222 includes a toner removing hollow drum 221 which is rotatable in a direction B indicated in Fig. 10, and an image-selection roll 214 disposed within the hollow drum 221. The image-selection roll 214 is connected through disconnect switches SW5, SW6 selectively to two power sources HV5, HV6. Adjacent to the hollow drum 221, there is disposed a container 215 for storing the black toner 218 which is removed from the drum 11, by the hollow drum 221 in cooperation with the image-selection roll 214, as described below.The disconnected switches SWl-SW6 are controlled by a suitable controlled as indicated at 32, 34, 35 in Fig. 6.

There will be described an operation of the present apparatus, in which a black-and-white monochrome print is reproduced, by using a monocrome negative transparency in the form of the slide film 6.

The bright and dark portions of the negative image on the slide film 6 are reversed with respect to the bright and dark portions of the original image to be reproduced. The negatively charged surface of the photosensitive drum 11 is imagewise exposed to a radiation under an influence of the negative image on the slide film 6, such that the exposed portions of the drum surface correspond to the bright portions of the negative image of the film 6, which in turn corresponds to the dark or black portions of the original image. In the meantime, the switches SW1 and SW2 are closed and opened, respectively, to apply the high negative bias voltage of -500V to the developing roll 213a.As a result, there arises a positive potential difference of +450V = -50V - (-500V), between a surface potential Vl of the exposed portions of the drum 11, and a surface potential of the developing roll 213a, as indicated in Fig. ll(a). Therefore, the negatively charged black toner 217 is electrostatically attracted to the exposed portions of the drum 11. At the same time, there exists a negative potential difference of -100V = 600V - (-500V) between a surface potential Vi of the unexposed portions of the drum 11 and the potential of the developing roll 213a. As a result, the positively charged black toner 217 is electrostatically attracted to the unexposed portions of the drum 11. Thus, the toner 217 is deposited in the exposed and unexposed portions of the drum 11, in different conditions.Before the toner 217 deposited on the drum 11 approaches the selective erasing device 222, the switches SW5 and SW6 are closed and opened, respectively, so that a high negative erasure voltage is applied from the power source HV5 to the imageselection roll 214. Accordingly, the positively charged toner 217 deposited in the unexposed portions of the drum 11 is electrostatically attracted to the surface of the hollow drum 221, while the negatively charged toner 217 is left on the exposed portions of the drum 11, as indicated in Fig. ll(b). The remaining negatively charged toner 217 is electrostatically transferred to the recording medium 125 by the transfer roll 121, in the presence of the positive transfer voltage applied to the roll 121 from the power source HV3 via the switch SW3.Since the areas of the medium 125 on which the toner 217 is deposited correspond to the bright or white portions of the negative image on the slide film 6, the visible black image reproduced on the medium 125 is a positive image with respect to the original image.

Where the slide film 6 is a positive transparency in which the bright and dark portions correspond to the bright and dark portions of the original to be reproduced.

In this case, the switches SW2 and SWI are closed and opened, respectively, so that the low bias voltage of -1OOV is applied to the developing roll 213a.

As a result, there arises a positive potential difference of +50V = -50V - (-100V), between the surface potential Vl of the exposed portions of the drum 11, and the surface potential of the developing roll 213a, as indicated in Fig. 12(a). Therefore, the negatively charged black toner 217 is electrostatically attracted to the exposed portions of the drum 11. At the same time, there exists a negative potential difference of -500V = -600V - (-100V) between the surface potential Vi of the unexposed portions of the drum 11 and the potential of the developing roll 213a. As a result, the positively charged black toner 217 is electrostatically attracted to the unexposed portions of the drum 11. Thus, the toner 217 is deposited in the exposed and unexposed portions of the drum 11, in different conditions. In the present case, the switches SW6 and SW5 are closed and opened, respectively, so that a high positive erasure voltage is applied from the power source HV6 to the image-selection roll 214. Accordingly, the negatively charged toner 217 on the exposed portions of the drum 11 is removed by the toner removing hollow drum 221, and the positively charged toner 217 is left on the exposed portions of the drum 11, as indicated in Fig.

12(b). The remaining positively charged toner 217 is electrostatically transferred to the recording medium 125 by the transfer roll 121, in the presence of the negative transfer voltage applied to the roll 121 from the power source HV4 via the switch SW4. Since the areas of the medium 125 on which the toner 217 is deposited correspond to the dark or black portions of the positive image on the slide film 6, the visible black image reproduced on the medium 125 is a positive image with respect to the original image.

Iv the present modified embodiment, the amount of the toner 217 to be deposited on the drum 11 increases with the potential difference (absolute value) between the surfaces of the drum 11 and developing roll 213a. In the case of reproduction of a positive print by using a negative slide film, a comparatively large amount of the toner is deposited in the exposed portions of the drum 11, while a comparatively small amount of the toner 217 is deposed in the unexposed portions of the drum 11. In the case where a positive print is reproduced from a positive slide film, a comparatively large amount of the toner 217 is deposited in the unexposed portions of the drum 11, while a comparatively small amount of the toner 217 is deposited in the exposed portions of the drum 11.Thus, simple switching actions of the disconnect switches SW1 and SW2 for the developing device 213 allows for a change in the conditions in which the toner 217 is deposited in the exposed and unexposed portions of the drum 11, so that the comparatively small amount of the toner 217 is removed from the unexposed or exposed portions of the drum 11, in order to form a visible positive image to be transferred to the recording medium 125.

While the present invention has been described in its presently preferred embodiments with a certain degree of particularity, it is to be understood that the invention is not limited to the details of the illustrated embodiments, but may be embodied with various changes, modifications and improvements which may occur to those skilled in the art, in the light of the foregoing description. For instance, the following changes or modifications may be made in the invention: a) While the photosensitive drum 11 used in the illustrated embodiments of Figs. 1, 7 and 10 is negatively charged before it is imagewise exposed to a radiation, it is possible to positively charge the photosensitive drum.

b) While the positive slide film 6 used in the illustrated embodiments is prepared in a silver salt photographic process, it is possible to use a slide film prepared in other methods. For example, a film or other type of transparency on which an image is printed painted, drawn or otherwise provided may be used.

c) Although the pressure-sensitive photosensitive sheet used in the illustrated embodiment of Fig. 1 has both microcapsules (containing chromogenic material and radiation-curable resin) and developer material on a paper substrate, the pressure-sensitive photosensitive sheet may have only the microcapsules. In this case, the developing material is provided on a separate recording sheet on which a desired image is reproduced.

d) The imaging apparatus of Fig. 1 may use a pressure-sensitive photosensitive medium all microcapsules of which contain the same chromogenic material for black, yellow, magenta, cyan, etc. In this case, a monochrome image may be reproduced on the photosensitive medium.

The imaging apparatus of Fig. 1 may use a pressure-sensitive photosensitive medium which includes a layer of microcapsules formed on at least one of opposite surfaces of a light-shielding substrate. This substrate has a multiplicity of minute light-transparent portions.

In this case, the light-transparent endless belt 19 is disposed in close contact with the surface of the photosensitive medium on which the microcapsule layer is formed. In operation, the photosensitive medium is irradiated by a radiation produced by the second exposing unit 4 disposed on the side of the photosensitive medium.

The microcapsule layer of the photosensitive medium which faces the endless belt 19 is imagewise exposed to the radiation reflected by the light-shielding image or photomask 22.

f) In the second and third embodiments of Figs.

7 and 10, the toners 117-120 and 217 contain chromogenic materials or pigments corresponding to cyan, magenta, yellow and black, which directly produce color images on the ordinary recording medium 125. However, the toners 117120, 217 may consist of a mass of microcapsules which includes an appropriate chromogenic material and a radiation-curable resin. In this case, a recording medium (125) has a layer of a developing material, and presser rolls are provided for rupturing the uncured microcapsules, so that the chromogenic material flowing from the ruptured microcapsules chemically reacts with the developing material on the recording medium.

g) Although the exposing device 1 used in the illustrated embodiments is adapted such that a radiation from the light source 7 is transmitted through the slide film 6, it is possible that the photosensitive drum 11 is imagewise exposed to a radiation which is reflected by the slide film 6.

Claims

1. An image recording system, comprising:

a first medium for bearing an electrostatic latent image formed on a surface thereof by local potential differences on differences on said surface, so that said surface has high-potential portions and low-potential portions; a second medium for supporting a bi-polar material which is electrostatically positively or negatively chargeable; and means for supporting said first and second media such that said surface of the first medium is adjacent to a surface of said second medium, and for moving said first and second media relative to each other, thereby electrostatically transferring said bi-polar material to the surface of said first medium, and depositionvolt age applying means for applying a controlled voltage to said bi-polar material said deposition-voltage annoying means being operable in a low-potential mode or a h ighpotential mode, such that said controlled voltage provides a high potential difference with respect to the potential ofsaid high-potential portions of said first medium, and a low potential difference with respect to the potential of said low-potential portions of said first medium when said deposition-voltage applying means is in ~ the low-potential mode, and such that said controlled voltage provides a high potential difference with respect to the potential of said low-potential portions of said first medium, and a low potential difference with respect to the potential of said highpotential portions of said first medium,-nhen said depositionvoltage applying means is in the high potential mode whereby an image corresponding to said latent image is formed on said first medium, by said bi-polar material which is differentially deposited on said highpotential and low-potential portions.

2. An image recording system according to claim 1, wherein said bi-polar material consists of a powdered material.

3. An image recording system according to claim 1 or 2, wherein said deposition-voltage applying means electrostatically positively or negatively charges said bi-polar material to electrostatically deposit the positively or negatively charged bi-polar material selectively to said high-potential portions and said low-potential portions, depending upon said low-potential mode or highpotential mode in which said deposition-voltage applying means is selectively placed, whereby a visible image corresponding to said latent image is formed on said first medium

4.An image recording system according to claim 1, 2 or 3, wherein said bi-polar material has a magnetic property, and said second medium includes a magnet which provides a magnetic attracting force that is greater than an electrostatic force acting on said bipolar material borne on said second medium, in a direction that causes said bi-polar material to be attracted to one of said high-potential and low-potential portions of said first medium with respect to which said controlled voltage applied to said bi-polar material provides said low potential difference.

5. An image recording system according to claim 1, 2, fi or 4 wherein said deposition-voltage applying means positively or negatively charges said bi-polar material to electrostatically deposite the positively and negatively charged bi-polar material to said highpotential portions and said low-potential portions of said first medium , a first electrostatic attracting force acting on the bi-polar material attracted to one of said high-potential and low-potential portions being greater than a second electrostatic attracting force acting on the bi-polar material attracted to the other of said highpotential and low-potential portions, when said deposition voltage applying means is placed in one of said lowpotential and high-potential modes, and said first electrostatic attracting force being smaller than said second electrostatic attracting force when said voltage applying means is placed in the other of said modes, and said image recording system further comprising: an eraser body adjacent to said surface of said first medium , for removing said bi-polar material from said surface of the first medium; and erasure-voltage applying means for applying to said eraser body an erasure voltage which is switchable between a positive level and a negative level, to remove said bi-polar material from said other of the high-potential and low-potential portions of said first medium when said deposition-voltage applying means is placed in said one mode, and from said one of the bi gh-potential and low-potential portions when said deposition-voltage applying means is placed in said other mode, whereby a visible image corresponding to said latent image is formed on said first medium.

6. An image recording system according to any one of claims 1-5, wherein said bi-polar material has a light-shielding property, and said image recording system further comprises: a third medium; means for holding said third medium adjacent to said first medium which bears a lightshielding image consisting of said bi-polar material deposited on said high-potential portions or said lowpotential portions thereof; transfer-voltage applying means for applying to said third medium a transfer voltage for transferring said light-shielding image from said first medium to said third medium, said transfer voltage being switcheable between a positive level and a negative level; and recording-medium exposing means for exposing a photosensitive recording medium, under the influence of said light-shielding image on said third medium, so that an image corresponding to said light-shielding image is formed on said photosensitive recording medium

7. An image recording system according to claim 6, wherein said photosensitive recording medium has microcapsules each of which contains a chromogenic material and whose mechanical strength varies with the amount of exposure to radiation, said image recording system further comprising: developing means for pressing said photosensitive recording medium in the presence of a developing material, and thereby rupturing said microcapsules , depending upon the mechanical strength thereof, fora chemical reaction with said developing material so as to produce said visible image.

8. An image recording system according to claim 6 or 7, wherein said first medium bears a plurality of electrostatic images at different times and/or in different portions of the surface thereof 1 and said depositing means operating to form said lightshielding image corresponding to each of said plurality of electrostatic images, said transfer-voltage applying means operating to transfer each light-shielding image corresponding to said each electrostatic image to said third medium and said recording-medium exposing means exposing said photosensitive recording medium to radiations having different wavelengths, under the influence of the corresponding light-shielding images on said third medium.

9. An image recording system according to any one of claims 1-5, further comprising: means for holding a recording medium adjacent to said first medium which bears said bipolar material deposited on said highpotential portions or said low-potential portions thereof; and transfer-voltage applying means for applying to said recording medium a transfer voltage for transferring said bi-polar material from said first medium to said recording medium, said transfer voltage being switchable between a positive level and a negative level.

10. An image recording system according to claim 9, wherein said bi-polar material comprises at least one chromogenic material corresponding to at least one color, respectively, said image recording system further comprising means fixing said at least one chromogenic material on said recording medium

11.An image recording system according to claim 10, wherein said at least one chromogenic material of-zvsaid bi-polar material comprises a plurality of chromogenic materials corresponding to a plurality of colors, respectively, and said first medium bears a plurality of electrostatic image patterns at different times and/or in different portions of the surface thereof, said depositing means operating to deposite on said first medium each of said plurality of chromogenic materials according to a corresponding one of said plurality of electrostatic image patterns, said means for holding a recording medium and said transfer-voltage applying means cooperating to transfer said chromogenic materials corresponding to said electrostatic image patterns, to said recording medium -such that patterns formed by said chromogenic materials are superposed on each other, whereby a visible color image is formed.

12. An image recording system according to any one of claims 1-11, further comprising electrostatic charging means for uniformly charging the surface of said first medium and first-medium exposing means for exposing the surface of said first medium to influence of source image information on an original, thereby forming on the surface of said first medium said latent electrostatic image which corresponds to said source image information.

13. An image recording system, comprising: a photosensitive medium whose electrostatic charge is variable due to exposure thereof to a radiation; first exposing means for exposing said photosensitive medium so as to selectively form one of a first and a second electrostatic latent image due to a difference in the potential between said exposed and unexposed portions, said first electrostatic latent image being a positive image with respect to an original image to be reproduced, said second electrostatic latent image being a negative image with respect to said original image; a bi-polar light-shielding material which is electrostatically positively or negatively chargeable;; first developing means disposed opposite to said photosensitive medium , for electrostatically transferring said light-shielding material to said photosensitive medium, to thereby form a visible image on said photosensitive medium; judging means for determining whether the electrostatic latent image formed on said photosensitive medium is said first image or said second image; deposition-voltage applying means responsive to said judging means, for applying a controlled bias voltage to said first developing means , so as to electrostatically positively or negatively charge said light-shielding material, 4 W to electrostatically deposit the positively or negatively charged light-shielding material selectively to said exposed and unexposed portions, depending upon the result of determination by said judging means;; an intermediate medium disposed adjacent to said photosensitive medium transfer means for electrostatically transferring said visible image consisting of the deposited light-shielding material from said photosensitive medium to said intermediate medium; transfer-voltage applying means for applying to said transfer means a controlled transfer voltage, to transfer said positively or negatively charged light-shielding material as said visible image to said intermediate medium depending upon said result of determination by said judging means; feeding means for feeding said intermediate medium bearing said visible image , to a position aligned with a photosensitive recording medium disposed remote from said photosensitive medium;; second exposing means for exposing said recording medium to a radiation under an influence of said visible image , and thereby forming a latent image on said recording medium; and second developing means for developing said latent image on said recording medium into a visible image.

14. An image recording system, comprising: a photosensitive medium having a surface on which an electrostatic image is formed due to exposure thereof to a radiation; exposing means for selectively forming one of a positive and a negative latent image on said photosensitive medium, said first latent image being a positive image with respect to an original image to be reproduced, said second latent image being a negative image with respect to said original image; developing means for depositing an electrostatically charged material on the surface of said photosensitive medium , according tc the latent image formed on said photosensitive medium;; transfer means for electrostatically charging an image-bearing medium with a polarity opposite to that of said electrostatically charged material , and thereby electrostatically transferring said electrostatically charged material to said image-bearing medium; said electrostatically charged material comprising at least three chromogenic materials corresponding to cyan, magenta and yellow, said three chromogenic materials being positively and negatively chargeable; said developing means including depositionvoltage applying means for applying a controlled bias voltage to said electrically chargeable material , said controlled bias voltage being changed depending upon whether the electrostatic latent image formed on said photosensitive medium is said first or second latent image; and said transfer means including switching means determining the polarity of said image-bearing medium such that the polarity of the image-bear'ing medium in opposite to that of said electrostatically charged material.

15. An image recording system, comprising: latent-image forming means for exposing a uniformly elecctrostatically charged surface of a photosensitive medium to a radiation under the influence of a selected one of a positive and a negative original image, and electrostatically forming an electrostatic latent image corresponding to the selected positive or negative original image, such that exposed and non-exposed portions of the surface of the photosensitive medium have different potentials; ; depositing means for applying a controlled voltage to an electrostatically positively or negatively chargeable bi-polar material, and'thereby electrostatically depositing said bipolar material on said exposed and unexposed portions of said photosensitive medium such that the polarity of the bi-polar material deposited on said exposed portions is opposite to that of the bi-polar material deposited on said unexposed portions; and erasing means for selectively removing the positively or negatively charged bi-polar material from the corresponding exposed or unexposed portions of said photosensitive medium

16. An image recording system according to claim 15, further comprising transfer means, for transferring to a recording medium (125) said positively or negatively charged bi-polar material (21?) which is left on said photosensitive medium (11).

17. An image recording system constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.