Method and apparatus for decolorization, and image forming apparatus

Abstract: A sheet (106) of paper, plastic or the like on which an image is formed with using a toner that is photochemically decolorizable due to the absorption of near infrared rays is illuminated with near infrared rays under the state that the image is heated to a temperature equal to or higher than the glass-transition temperature of a binding resin of the toner, whereby the color of the toner can be easily and rapidly eliminated. This enables the reuse of the sheet (106) to be realized easily and at a low cost.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method according to claim 1 and apparatus according to claim 10 for decolorizing toner images formed on a sheet from a toner which can be photochemically decolorized, and also to an image forming apparatus as claimed in claim 25. 2. Description of the Related Art Recently, in view of the conservation of nature, particularly the conservation of forests and the reduction of wastes in an urban area, the reuse and regeneration of used paper have attracted public attention again. As a part of such a recycle, the reuse of waste copy sheets, printed matter, facsimile sheets or the like which have been used in offices has been studied. Since the majority of such waste paper consists of confidential documents which are generally company secrets, however, it is very difficult to collect such waste paper outside the company to regenerate the paper. Furthermore, it is very difficult to erase recorded or printed portions of printed matter and copy sheets, and therefore printed matter and copy sheets are forced to be burned or shredded. Consequently, the general recognition is that it is substantially impossible to reuse such paper. In view of the above-mentioned state, the inventors had earnestly conducted studies to find a near infrared-decolorizing pigment which absorbs near infrared rays to be decolorized, and developed a toner using such a pigment. This toner was proposed in Japanese patent application No. HEI3-277725 (1991). When an electrostatic copy operation is conducted using that toner, images or characters formed on a sheet such as a copy sheet can be erased only by the illumination of near infrared rays, and after this erasure an electrostatic copy operation or printing can be further conducted on the sheet, thereby allowing the sheet to be reused. When such used sheets are to be disposed of, recorded images or characters can be erased only by the illumination of near infrared rays. Therefore, there are many advantages such as that sheets can be collected to be reused in a company without leaking secrets outside. However, the rate of decolorization performed only by the illumination of near infrared rays is low. For example, the process of decolorizing a toner image formed on the entire surface of a recording sheet of A4 size of JIS (Japanese Industrial Standard) requires several tens seconds. Namely, this decolorizing process has a problem in that it can process only a few sheets per minute. When an electrostatic photography copier or printer which forms an image on a recording sheet using such a decolorizable toner, and decolorizing means for decolorizing an image-formed recording sheet to make it colorless to be reused are independently installed, there arises another problem in that they require a large installation space. Even if the recording has been done with using a decolorizable toner, image-formed recording sheets cannot be reused unless decolorizing means is available. Therefore, it is cumbersome to separately install electrostatic photography image forming means and decolorizing means so as to be paired with each other. A currently used electrostatic photography copier or printer and a toner therefore are constructed to function in pairs. Namely, a most suitable toner is selected for each kind of copiers and printers. Therefore, there is no toner that can be suitably and commonly used for all kinds of copiers and printers. Copiers and printers are designed and adjusted so that various toners of different characteristics achieve optimum image qualities. Even if many kinds of decolorizable toners with different characteristics become available, therefore, a decolorizable toner and electrostatic photography image forming means which is designed and adjusted to be optimum for the use of that decolorizable toner must be used in pairs. Consequently, a decolorizable toner, electrostatic photography image forming means and decolorizing means are realized so that their characteristics relate to each other. When electrostatic photography image forming means and decolorizing means are constructed independently of each other, it is required to separately prepare individual image forming means and decolorizing means in accordance with a decolorizable toner to be used. This involves cumbersome works. In the case that decolorizable toner, electrostatic photography image forming means and decolorizing means are combined in an unsuitable manner, it may be impossible to form optimum images on recording sheets or to sufficiently achieve the decolorization. In EP-0 468 465 document falling under article 54(3) EPC a near infrared ray-decolorizable recording material is contemplated. This material comprises a near infrared ray-absorbing cationic dye-borate anion complex with a cationic dye having absorptions in the near infrared region; further the material comprises four groups, which independently represent an alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl, silyl, alicyclic, or saturated or unsaturated heterocyclic group, substituted alkyl, substituted aryl, substituted alkaryl, substituted allyl, substituted aralkyl, substituted alkenyl, substituted alkynyl, or substituted silyl, with the proviso that at least one of the four groups represents an alkyl group having 1 to 8 carbon atoms. SUMMARY OF THE INVENTION It is an object of the invention to provide a decolorizing method which can solve the above-mentioned problems and greatly improve the rate of decolorizing a toner image formed on a sheet. In order to accomplish the object, the decolorizing method of the invention comprises the steps of: heating a toner image formed on a sheet from a photochemically decolorizable toner, at least to a temperature equal to or higher than the glass-transition temperature of the binding resin of the toner; and illuminating the toner image with near infrared rays, concurrently with or soon after heating the toner image. According to the invention, when a toner image formed on a sheet from a photochemically decolorizable toner is to be decolorized, the toner is heated by heating means at least to a temperature equal to or higher than the glass-transition temperature of a binding resin of the toner, thereby increasing the heat momentum of molecules constituting the toner on the sheet. Since the toner has a structure that exhibits the decolorizing effect in the case of absorption of near infrared rays, this heating causes the toner on the sheet to be transferred from a solid state to a rubber-like elastic state or a melting state. When the toner in such a state is illuminated with near infrared rays, this illumination of near infrared rays allows the decolorization to easily occur. In this way, the sheet can be reused. The decolorization is a chemical reaction, and the decolorizing reaction in the invention is irreversible. Since the heated toner is in a state in which the molecules constituting the toner are excited and its appearance is at least in a state of rubber-like elasticity, the chemical reaction of decolorizing the toner by the illumination with near infrared rays proceeds very rapidly as compared with a toner in a solid state, thereby improving the rate of decolorization. Furthermore, the decolorizing reaction is realized by an irreversible chemical reaction, so that decolorized toner images on the sheet is prevented from being unwillingly changed in decolorizing/coloring state or discolored depending on the ambient temperature, illumination or non-illumination of usual white light or chemical conditions. Sheets which can be made reusable by the invention include all kinds of sheets of paper, plastic film or the like for an office or business use that can be subjected to the electrostatic copy operation, for example, recording sheets used in a conventional electrostatic photography, OHP (Over Head Projector) films, magnetic cards, plastic film sheets for display, etc. When characters formed on a plastic film sheet are to be decolorized, the thermal deforming temperature of the plastic film sheet must be equal to or higher than the glass-transition temperature of the toner to be used. In a preferred embodiment of the invention, the decolorizing method further comprises: applying physical deformation such as rubbing or pressing to the toner layer of the toner image, concurrently with or before illuminating the toner image with near infrared rays. According to the invention, when a toner image formed on a sheet from a photochemically decolorizable toner is to be decolorized, the toner is heated by heating means at least to a temperature equal to or higher than the glass-transition temperature of a binding resin of the toner. This heating causes the toner on the sheet to be transferred from a solid state to a rubber-like elastic state or a melting state. The toner in such a state is physically deformed by deforming means for performing an action such as rubbing or pressing. Means for illuminating with near infrared rays means illuminates the toner which has been physically deformed or is being physically deformed, with near infrared rays. Since the toner has a structure that exhibits the decolorizing effect in the case of absorption of near infrared rays, this illumination of near infrared rays allows the decolorization to easily occur. Since the toner in a solid state on the sheet is heated to be transferred into a state having at least rubber-like elasticity so as to increase the heat momentum of molecules constituting the toner, and then physically deformed, the toner transfers into a state in which a chemical reaction between molecules constituting the toner easily occurs. Moreover, the deformation of a toner in a rubber-like elastic or a melting state greatly increases the chance of causing a chemical reaction between molecules constituting the toner. In a further preferred embodiment of the invention, decolorizing method further comprises: partially removing the toner layer of the toner image in the thickness direction by performing shaving, peeling or the like on the toner layer. According to the invention, when a toner image formed on a sheet from a photochemically decolorizable toner is to be decolorized, the toner of the toner image is partially removed in the thickness direction by performing shaving, peeling or the like on the toner, and thereat or thereafter the remaining toner is illuminated with near infrared rays , whereby the decolorizing reaction in the deep portion of the toner layer is promoted. As a result, the rate of decolorizing the toner image formed on the sheet is greatly improved. Since the toner is partially removed in the thickness direction to reduce the layer thickness, traces of the decolorized toner image on the sheet become inconspicuous. In a further preferred embodiment of the invention, in the step of illuminating the toner image with near infrared rays, light from a light source converges to illuminate the toner image and light except direct light converges on the area illuminated with direct light from the light source. According to the invention, the light density in the area illuminated with near infrared rays increases, thereby the period of time for decolorizing become reduced. In a further preferred embodiment of the invention, in the step of illuminating the toner image with near infrared rays, both sides of the sheet are illuminated with near infrared rays. According to the invention, the light density in the area illuminated with near infrared rays increases greatly, and the deep portion of the toner layer close to the sheet is efficiently illuminated because the light can travel thorough the thin sheet. According to the invention, the process of illuminating with near infrared rays and that of heating can be simultaneously conducted on the toner, so that the overall period required for decolorizing the toner is greatly shortened and this prevents a temperature of the toner after heating from decreasing. It is another object of the invention to provide a decolorizing apparatus which can efficiently decolorize a photochemically decolorizable toner, and has a short decolorizing time per a sheet, and can be manufactured in a light and compact structure. In order to accomplish the object, a decolorizing apparatus of the invention is as claimed in claim 10. According to the invention, the near infrared ray illuminating means illuminates a toner in a rubber-like elastic or a melting state with near infrared rays, whereby the toner is made colorless to be decolorized. In this way, a sheet can be made reusable. Moreover, the decolorization is caused by a chemical reaction, and the decolorizing reaction can be irreversible. Since the heated toner is in a state in which the toner has at least rubber-like elasticity, the chemical reaction of decolorizing the toner by the illumination of near infrared rays proceeds very rapidly as compared with that conducted in a toner of a solid state, thereby improving the rate of decolorization. In a further preferred embodiment of the invention, the decolorizing apparatus further comprises: means for applying physical deformation such as rubbing or pressing to the toner layer of the toner image at a predetermined position of the transporting path illuminated with near infrared rays or in the upstream side therefrom along the transporting direction of the sheet. According to the invention, a toner image formed on a sheet by a photochemically decolorizable toner is heated to a temperature which is equal to or higher than the glass-transition temperature, preferably the softening point of a binding resin of the toner, so that the toner is transferred at least into a rubber-like elastic state or a melting state. While or after applying physical deformation such as rubbing, pressing, the toner is illuminated with near infrared rays. This greatly increases the chance of causing an irreversible chemical reaction among molecules constituting the toner by which the toner is decolorized, so that the period required for completing the decolorization of the toner is remarkably shortened. In a further preferred embodiment of the invention, the decolorizing apparatus further comprises: means for partially removing the toner layer of the toner image in the thickness direction by performing shaving, peeling or the like on the toner layer at a predetermined position of the transporting path illuminated with near infrared rays or in the upstream side therefrom along the transporting direction of the sheet. According to the invention, when a toner image formed on a sheet by a photochemically decolorizable toner is to be decolorized, the toner of the toner image is partially removed in the thickness direction of the layer by performing shaving, peeling or the like on the toner, and thereat or thereafter near infrared rays are illuminated, whereby the decolorizing reaction in the deep portion of the toner layer is promoted. As a result, the rate of decolorizing the toner image formed on the sheet is greatly improved. Since the toner is partially removed in the thickness direction to reduce the layer thickness, traces of the decolorized toner image became inconspicuous. In a further preferred embodiment of the invention, the means for illuminating the toner image with near infrared rays comprises: a light source; and means for converging near infrared rays at a predetermined position of the transporting path, disposed between the light source and the transporting path. According to the invention, the light utilization efficiency of the light source is improved, and the size of the light source can be reduced. Furthermore, this can prevent the temperature of a heated sheet which has been elevated to the predetermined one by the heating means from lowering while the sheet in the path moving to the light condensing portion. In a further preferred embodiment of the invention, a heat resisting glass plate for blocking the air flowing from the means for illuminating with near infrared rays toward the predetermined position, is disposed between the means for illuminating with near infrared rays and the predetermined position. According to the invention, the plate of heat resisting glass prevents an air the temperature of which is raised by the heat of the light source from moving toward the transporting path and its periphery, and allows an air flow in the vicinity of the light source to be smoothly conducted. In a further preferred embodiment of the invention, the transporting means comprises a member having a reflective surface toward the transporting path, disposed at a position which is more distant from the means for illuminating with near infrared rays than from the transporting path of the sheet and in the vicinity of the predetermined position of the transporting path illuminated with near infrared rays. According to the invention, the member having a reflective surface toward the transporting path can converge the light from the light source on the light condensing portion, whereby the light utilization efficiency of the light source can be further improved. In a preferred embodiment of the invention, at least one of the heating means and the means for illuminating with near infrared rays can displace off the transporting path from a position predetermined in time of decolorizing. According to the invention, when a sheet is blocked in the transporting path, namely there happens a jam, therefore, the displacement of the heating means and/or the means for illuminating with near infrared rays forms a large space in the transporting path so that the user can easily perform the jam-removing operation, and safely and easily check and clean these means. According to the invention, the process of the illumination of near infrared rays and that of heating can be simultaneously conducted on the toner, so that the overall period required for decolorizing the toner is remarkably shortened. In a further preferred embodiment, the light source is a flashlamp. In a further preferred embodiment of the invention, the transportation speed of the sheet transported by the transporting means is variable. According to the invention, when sheets having various decolorizing characteristics which change depending on the adhering amount or thickness of the fixed toner are to be decolorized, therefore, sheets which are easy to be decolorized may be transported at a high speed so that the period required for decolorization is shortened, and sheets which are difficult to be decolorized may be transported at a low speed so that the heating amount and light illuminating amount per one sheet are increased, thereby surely performing the decolorization operation. Accordingly, it is possible to arbitrarily decide in accordance with the user's request which is given with preference, the degree of decolorization residue which remains to be decolorized or the period required for decolorization. It is a further object of the invention to provide an image forming apparatus with a function of decolorization which can be installed in a small space, form optimum images with using a decolorizable toner, and surely conduct the decolorization operation. In order to accomplish the object, an image forming apparatus is as claimed in claim 25. According to the invention, in a single body of a copier or printer, the electrostatic photography image forming means and the decolorizing means are arranged in series or juxtaposed in parallel in the transporting path of sheets. The electrostatic photography image forming means forms images on a sheet using the electrostatic photography technique and a photochemically decolorizable toner to perform the recording operation, and the decolorizing means illuminates the toner on the sheet with light for decolorization, whereby the toner is made colorless to be decolorized. In this way, the sheet can be made reusable. In the image forming apparatus with such a function of decolorization, since the electrostatic photography image forming means and the decolorizing means are accommodated in one body of the apparatus, it is not necessary to separately provide image forming means and decolorizing means, with the result that the space for installation becomes small. Moreover, this allows the combination of a toner, image forming means and decolorizing means to be done in an optimum manner so that images of high quality can be formed and that the decolorization operation can be surely conducted, thereby preventing troubles such as the deteriorated image quality and insufficient decolorization which may caused by a wrong combination of a toner, image forming means and decolorizing means. BRIEF DESCRIPTION OF THE DRAWINGS Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: Fig. 1 is a sectional view showing the configuration of a decolorizing apparatus for a decolorizing method; Fig. 2 is a graph illustrating experimental results; Fig. 3 a sectional view showing the configuration of a decolorizing apparatus for a decolorizing method; Fig. 4 is a sectional view showing the configuration of a decolorizing apparatus for a decolorizing method; Fig. 5 is a sectional view showing the configuration of a decolorizing apparatus for a decolorizing method; Fig. 6 is a sectional view showing the configuration of a decolorizing apparatus 60c for a decolorizing method; Fig. 7 is a sectional view showing the configuration of a decolorizing apparatus 60d for a decolorizing method; Fig. 8 is an enlarged sectional view of the vicinity of an abrasive roller 138 shown in Fig. 7; Fig. 9 is a sectional view showing the configuration of a decolorizing apparatus 60f for a decolorizing method; Fig. 10 is a sectional view showing the configuration of a decolorizing apparatus 60g for a decolorizing method; Fig. 11 is an enlarged sectional view of the vicinity of a reverse transfer roller 143 shown in Fig. 10; Fig. 12 is a sectional view showing the configuration of a decolorizing apparatus 60h for a decolorizing method; Fig. 13 is a fragmentary side elevation view showing the configuration of the decolorizing apparatus 60h of Fig. 12; Fig. 14 is a sectional view showing the state in which a light source unit 70 of the decolorizing apparatus 60h of Fig. 12 is rotated on an axis 71 to open; Fig. 15 is an exploded perspective view showing a decolorizing unit 80; Fig. 16 is a partial view showing the configuration of an optical system of a light source 12 and a light condensing portion P; Fig. 17 is a partial view showing the state of the heat exhaustion in the vicinity of the light source 12 and a pair of heating rollers 10 and 11; Fig. 18 is a fragmentary front view showing an operation panel 91 of the decolorizing apparatus 60h of Fig. 12; Fig. 19(a) is a sectional view showing the configuration of a decolorizing apparatus 60i for a decolorizing method, and Fig. 19(b) is a plan view of the apparatus; Fig. 20 is a graph showing a typical emission spectrum of a xenon flashlamp; Fig. 21 is a graph showing a temperature elevation curve of a sheet and toner; Fig. 22 is a sectional view showing the configuration of a decolorizing apparatus 60j which is disposed as a part of an image forming apparatus; Fig. 23 is a sectional view of the whole of an image forming apparatus 300; Fig. 24 is a partially cutaway plan view diagrammatically showing the image forming apparatus 300; Fig. 25 is a block diagram showing the electrical configuration of the image forming apparatus 300 shown in Figs. 22 to 24; Fig. 26 is a flowchart illustrating the operation of a processing circuit 348 shown in Fig. 25; and Fig. 27 is a sectional view showing another embodiment of the image forming apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the drawing, preferred embodiments of the invention are described below. The process of forming images on sheets using a decolorizable toner which is useful in the invention is conducted in, for example, an electrostatic copier. The toner used in this electrostatic copier is a photochemically decolorizable toner which can be decolorized by the absorption of near infrared rays. Various examples of the composition of such a decolorizable toner and the detail of the manner of decolorizing toners of the various compositions are described in aforesaid Japanese patent application No. HEI3-277725 (1991). Therefore, only several decolorizable toners are exemplified in the following description of embodiments. The invention is not restricted to the embodiments described below, and includes wide variety of modifications according to the scope of the appended claims. An example of the decolorizable toner has a structure in which a pigment and organic boron ammonium salt are dispersed or dissolved in a styrene resin. The pigment is represented, for example, by Formula (1) or Formula (2) below: The styrene resin is widely used as a binding resin for a toner. The pigment represented by Formula (1) or (2) is a cyanine pigment which, when illuminated with near infrared rays having a wavelength of about 820 nm in the presence of organic boron ammonium salt, absorbs the near infrared rays to cause an irreversible reaction, resulting in that the pigment vanishes its blue color to become colorless. As the organic borate ammonium salt, tetrabutylammonium n-butyl triphenyl borate represented by following Formula (3) may be used: Ten decolorizable toners S1-S10 listed in Table 1 were prepared to be used in the embodiments described below. (Unit: Parts by weight) S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 RE1 100 - - 100 - - 100 - 100 - RE2 - 100 - - 100 - - 100 - 100 RE3 - - 100 - - 100 - - - - Wax 5 5 5 5 5 5 5 5 5 5 DY1 2 2 2 - - - 4 4 - - DY2 - - - 2 2 2 - - 4 4 Sensitizer 3.4 3.4 3.4 5.0 5.0 5.0 3.4 3.4 5.0 5.0 In Table 1 above, the symbols RE1-RE3 indicate binding resins such as a styrene acrylic resin, RE1 indicates HYMER SBM-100 supplied by SANYO CHEMICAL INDUSTRIES, LTD. which has a softening point MP of 104 °C and a glass-transition temperature TG of 60°C. RE2 indicates HYMER TB-1000 supplied by SANYO CHEMICAL INDUSTRIES, LTD. which has a softening point MP of 145°C and a glass-transition temperature TG of 58°C, and RE3 indicates HYMER ST-125 supplied by SANYO CHEMICAL INDUSTRIES, LTD. which has a softening point MP of 125°C and a glass-transition temperature TG of 50°C. The symbols DY1 and DY2 indicate pigments, i.e., DY1 is the pigment represented by above Formula (1), and DY2 is the pigment represented by above Formula (2). The sensitizer in Table 1 is an organic boron ammonium salt which is tetrabutylammonium n-butyltriphenyl borate represented by foregoing Formula (3). Examples of the wax shown in Table 1 include polypropylene wax supplied by SANYO CHEMICAL INDUSTRIES, LTD., and as an example VISCOL 550P (trade name) was used. Each of the mixtures S1-S10 listed in Table 1 was kneaded and mixed in a pressurized kneader at a temperature of 120°C for 15 minutes. Then, it was solidified by cooling, and the solidified product was pulverized by a jet mill. The powder product was passed through a classifier to obtain a toner having a particle diameter of about 5 to 20 µm and the mean particle diameter of about 10 µm. To the toner, 0.5 parts by weight of silica fine powder was added as an additive per 100 parts by weight of the toner, and then the toner is mixed in a Henschel mixer. The silica fine powder adheres to the surface of the toner and functions to make the charged polarity of the toner uniform (e.g., to the negative polarity), thereby improving the charge capacity of the toner and preventing the toner from aggregating to be solidified. The carrier to be mixed with the toner of the embodiments was Cu-Zn ferrite, more specifically FB-810 (trade name) supplied by KANTO DENKA KOGYO CO.. LTD. The 95 parts by weight of the carrier and 5 parts by weight of the above-mentioned toner were placed in a propylene vessel and mixed at 50 rpm for 30 minutes to obtain a developer. Copy paper No. V602 supplied by FUJI XEROX CO., LTD. on which a toner image "TONER" consisting of characters of about 4 mm square was printed by a laser beam printer KX-P4420 supplied by KYUSYU MATSUSHITA ELECTRIC CO., LTD. was used as a sheet. The thickness of the toner image formed on the sheet was about 35µm. (First Embodiment) When a toner image formed from the photochemically decolorizable toner having the structure described above is to be decolorized, the toner image is heated to a temperature equal to or higher than the glass-transition temperature Tg of the binding resin such as the styrene resin of the toner. More preferably, the toner image is heated to a temperature which is equal to or higher than the softening point MP of the binding resin and lower than the decomposition temperatures of the components constituting the toner such as the binding resin, the near infrared ray-absorbing pigment, the sensitizer such as organic boron ammonium salt. When heated to a temperature equal to or higher than the glass-transition temperature Tg, the binding resin transfers from a solid state to a rubber-like elastic state, and, when heated to a temperature equal to or higher than the softening point MP, it transfers to a melting state. In this embodiment, the toner of such a state is illuminated with near infrared rays of the above-mentioned wavelength using the light source, thereby increasing the rate of decolorizing the photochemically decolorizable toner. Hereinafter, the principle of achieving the above-mentioned function and effects by heating the toner prior to the illumination of near infrared rays will be described. The inventors performed the operation of heating the above-mentioned photochemically decolorizable toner prior to the illumination of near infrared rays, and measured the surface temperatures of the sheets and periods of the illumination of near infrared rays required for completing decolorization. Fig. 1 is a diagram of a decolorizing apparatus for a decolorizing method, which was used in the above-mentioned measurement. This measurement was conducted using the apparatus of Fig. 1 placed in a darkroom. In the apparatus, a cylindrical heat insulated cover 153 which upward opens is hermetically disposed on a heater 133, and a transparent heat resisting glass plate 154 is hermetically fixed to the opening of the heat insulated cover 153, thereby forming an internal space 155 which is hermetically sealed from the exterior. A sheet 106 on which the toner image consisting of the photochemically decolorizable toner is formed is placed on a supporting plate 152 which is disposed on the heater 133 and made of a heat insulating material, and then heated by the heater 133. A light source 135 such as a tungsten halogen lamp is disposed above the sheet 106. In the apparatus, the heater 133 heats the air in the internal space 155, and the heated air in turn heats the sheet 106. The temperature of the sheet 106, i.e., the temperature of the internal space 155 is measured by a thermometer 156 which protrudes through the heat insulated cover 153 into the internal space 155. The procedure of the experiment of decolorizing the toner on the sheet 106 using the apparatus of Fig. 1 will be described. At first, the heater 133 heats the air in the internal space 155, and the temperature of the internal space 155 measured by the thermometer 156 is set as a predetermined temperature. When the temperature of the internal space 155 reaches the predetermined temperature, this state is maintained for about 5 minutes, and then the light source 135 illuminates the sheet 106 with near infrared rays. As the decolorizable toner and the sheet 106, used were the toners S1 to S6 listed in Table 1 in the form of developers obtained by respectively mixing the toners with the above-mentioned carrier, and sheets that were the aforesaid copy paper on which a toner image had been formed by the laser beam printer. A tungsten halogen lamp of the aluminum coat type which emits near infrared rays was used as the light source 135, and the illumination was conducted at the rating of the lamp, IS volt and 150 watt. The results obtained in these measurements are shown in the graph of Fig. 2. In this experiment, the completion of decolorization was judged by ten observers. The shortest period prolonging until when six among the ten observers judged decolorization to be completed was determined as the period required for the completion of decolorization. This shortest period was set as the illumination period required for decolorization. The softening point MP of the toners was measured in accordance with Japanese Industrial Standard JIS K-2207 (1990) "Ring and ball method", and the measurement of the glass-transition temperature was performed using a thermal analyzer (DSC) by the measuring method specified in a U.S. standard, ASTM D3418-82. As seen from Fig. 2, there exists in the vicinity of 50 to 60°C a changing point Ta1 at which the lamp illumination period required for decolorization rapidly decreases. After this point, the illumination period gradually changes with the rise of the temperature, to form in the vicinity of about 100 to 150°C a second changing point Ta2 at which the lamp illumination period rapidly decreases again. The changing point Ta1 is caused by the glass-transition temperature TG of the binding resin used in the toners, and the changing point Ta2 is caused by the softening point MP of the binding resin. Namely, Fig. 2 shows the phenomenon in which the decolorizing reaction rapidly proceeds at the time when the binding resin reaches a rubber-like elastic state, and then the decolorizing reaction at the rubber-like elastic state saturates, and the binding resin melts to fluidity, whereby the decolorizing reaction proceeds again at a high speed. From the experimental results described above, it will be noted that it is effective in improving the rate of decolorization to perform the decolorizing method comprising the steps of: heating a toner image formed on a sheet from a photochemically decolorizable toner, at least to a temperature equal to or higher than the glass-transition temperature of a binding resin of the toner; and illuminating the heated toner with near infrared rays. (Second Embodiment) When a toner image formed from the photochemically decolorizable toner having the structure described above is to be decolorized, the toner image is heated to a temperature equal to or higher than the glass-transition temperature TG of the binding resin such as the aforesaid styrene resin of the toner. More preferably, the toner image is heated to a temperature which is equal to or higher than the softening point MP of the binding resin and lower than the decomposition temperatures of the near infrared ray-absorbing pigment constituting the toner. The decomposition temperature of the near infrared ray-absorbing pigment of Formula (1) is about 140°C, and that of the pigment of Formula (2) is about 180°C. When heated to a temperature equal to or higher than the glass-transition temperature TG, the binding resin transfers from a solid state to a rubber-like elastic state, and, when heated to a temperature equal to or higher than the softening point MP, it transfers to a melting state. The toner is further subjected to physical deformation such as rubbing and pressing. When the toner under heating and application of physical deformation is illuminated with near infrared rays, photochemical decolorization of the toner due to the illumination of near infrared rays is performed rapidly. Experiments were conducted to confirm the degree of the reduction in the period required for decolorization according to the invention. Fig. 3 is a diagram of a decolorizing apparatus for a decolorizing method, used in such experiments. This measurement was conducted using the apparatus of Fig. 3 placed in a darkroom. In the apparatus, a cylindrical heat insulated cover 153 which upward opens is hermetically disposed on a heater 133, and a transparent heat resisting glass plate 154 is hermetically fixed to the opening of the heat insulated cover 153, thereby forming an internal space 155 which is hermetically sealed from the exterior. A sheet 106 on which the toner image consisting of the photochemically decolorizable toner is formed is placed on a supporting plate 152 which is disposed on the heater 133 and made of a heat insulating material, and then heated by the heater 133. A light source 135 such as a tungsten halogen lamp is disposed above the sheet 106. In the apparatus, the heater 133 heats the air in the internal space 155, and the heated air in turn heats the sheet 106. The temperature of the sheet 106, i.e., the temperature of the internal space 155 is measured by a thermometer 156 which protrudes through the heat insulated cover 153 into the internal space 155. The procedure of the experiment of decolorizing the toner on the sheet 106 using the apparatus of Fig. 3 will be described. At first, the heater 133 heats the air in the internal space 155, and the temperature of the internal space 155 measured by the thermometer 156 is set as a predetermined temperature. When the temperature of the internal space 155 reaches the predetermined temperature, this state is maintained for about 5 minutes, and then the light source 135 illuminates the sheet 106 with near infrared rays. At this time, the surface of the sheet 106 is rubbed by a brush member 196 having a front end to which heat resisting fibers are implanted, at a rate of, for example, one cycle per second. A tungsten halogen lamp of the aluminum coat type which emits near infrared rays is used as the light source 135, and the illumination is conducted at the rating of the lamp, 15 volt and 150 watt. The results obtained in these measurements are shown in Table 2. In these experiments, the completion of decolorization was judged by ten observers. The shortest period prolonging until when six among the ten observers judged decolorization to be completed was determined as the period required for the completion of decolorization. This shortest period was set as the illumination period required for decolorization. The softening point MP and glass-transition temperature were measured in the same manner as described above. Compound No. of decoloraizable toner Glass -transistion temperature of binding resin (°C) Softening point of binding resin (°C) Temperature of recording sheet (°C) Physical deformation (Yes or No) Near IR ray illumination period required for decolorization (sec.) Example 1 S1 60 104 60 Yes 24 2 S1 60 104 110 Yes 4 3 S2 58 145 100 Yes 9 4 S3 50 125 130 Yes 5 5 S4 60 104 110 Yes 10 6 S5 58 145 60 Yes 47 7 S5 58 145 100 Yes 37 8 S5 58 145 145 Yes 15 9 S6 50 125 130 Yes 14 Comparative Example 1 S1 60 104 40 No 185 2 S1 60 104 60 No 58 3 S1 60 104 110 No 11 4 S2 58 145 100 No 25 5 S2 58 145 150 No Pigment was decomposed to become yellow 6 S3 50 125 40 No 180 7 S3 50 125 130 No 15 8 S4 60 104 40 No 218 9 S4 60 104 110 No 20 10 S5 58 145 40 No 220 11 S5 58 145 60 No 110 12 S5 58 145 100 No 75 13 S5 58 145 145 No 30 14 S6 50 145 40 No 210 15 S6 50 125 130 No 25 As apparent from Table 2, the rate of decolorization in the case that near infrared rays are illuminated when the temperature of the sheet is equal to or higher than the glass-transition temperature of the binding resin of the toner is substantially greater than that in the case that near infrared rays are illuminated when the temperature of the sheet is lower than the glass-transition temperature of the binding resin. An object of the invention is to further improve the rate of decolorization. Examples 1 to 9 show the rate of decolorization obtained when the surface of the recording sheet was rubbed by the brush member 196. It will be noted that the rate of decolorization is remarkably improved in all cases of using the decolorizable toners S1 to S6, i.e., irrespective of the kind of the toner (Table 1), as compared with Comparative Examples 1 to 15. From the above-mentioned experimental results, it will be noted that it is effective in further improving the rate of decolorization to heat the decolorizable toner to a temperature equal to or higher than the glass-transition temperature of a binding resin of the toner, more preferably than the softening point of the binding resin, and to then illuminate the heated toner with near infrared rays while applying physical deformation such as rubbing and pressing. Furthermore, the decolorizing reaction is realized by an irreversible chemical reaction, so that decolorized toner images on the sheet 106 is prevented from being unwillingly changed in decolorizing/coloring state or discolored depending on the ambient temperature, illumination or non-illumination of usual white light or chemical conditions. (Third Embodiment) Experiments relating to the decolorizing method of the invention were conducted in the manner described below. A recording sheet on which an image of the above-mentioned decolorizable toner had been formed in a thickness of about 35 µm was used. The toner image was shaved off to a thickness of about 10 µm by an abrasive member such as so-called sandpaper, in the manner described later, and then illuminated with near infrared rays. In this case, the near infrared ray illumination period prolonging until the toner image on the sheet was completely decolorized was measured. In other experiments, heating rollers heated to about 110 to 130 °C were pressed to the surface of a recording sheet having a toner layer of a thickness of about 35 µm, so that the toner image was reversely transferred to the heating rollers, thereby reducing the thickness of the toner layer of the sheet to about 15 µm. Immediately after the toner image was reversely transferred from the sheet to the heating rollers, the sheet was illuminated with near infrared rays, and the illumination period prolonging until the toner image on the sheet was completely decolorized was measured. The thickness of the toner layer on the sheet was measured by cutting the sheet together with the toner layer and observing the section through a microscope. These experiments relating to the decolorizing method of the invention were conducted using the experimental apparatus shown in Figs. 4 and 5 placed in a darkroom. Fig. 4 is a diagram of the decolorizing apparatus for a decolorizing method, used in the above-mentioned measurement. In the apparatus, a cylindrical heat insulated cover 153 which upward opens is hermetically disposed on a heater 133, and a transparent heat resisting glass plate 154 is hermetically fixed to the opening of the heat insulated cover 153, thereby forming an internal space 155 which is hermetically sealed from the exterior. A sheet 106 on which the toner image consisting of the photochemically decolorizable toner is formed is placed on a supporting plate 152 which is disposed on the heater 133 and made of a heat insulating material. A processing member 136 has a cylindrical body 132 which is supported by a supporting piece 134. An abrasive material 131 such as sandpaper is attached on the outer periphery of the cylindrical body. While being supported by the supporting piece 134, the processing member 136 can reciprocate on the sheet 106 in the direction indicated by the arrow, so as to abrade and remove the toner layer on the sheet 106. After this processing, the sheet 106 is heated by the heater 133. A light source 135 such as a tungsten halogen lamp is disposed above the recording sheet 106. In the apparatus, the heater 133 heats the air in the internal space 155, and the heated air in turn heats the sheet 106. The temperature of the sheet 106, i.e., the temperature of the internal space 155 is measured by a thermometer 156 which protrudes through the heat insulated cover 153 into the internal space 155. The procedure of decolorizing the toner on the sheet 106 using the decolorizing apparatus of Fig. 4 will be described. Initially, the processing member 136 abrades the toner layer on the sheet 106. Then, the heater 133 heats the air in the internal space 155, and the temperature of the internal space 155 measured by the thermometer 156 is set as a predetermined temperature. When the temperature of the internal space 155 reaches the predetermined temperature, this state is maintained for about 5 minutes, and then the light source 135 illuminates the sheet 106 with near infrared rays. A tungsten halogen lamp of the aluminum coat type which emits near infrared rays is used as the light source 135, and the illumination is conducted at the rating of the lamp, 15 volt and 150 watt. Fig. 5 is an enlarged sectional view of a decolorizing apparatus for a decolorizing method. This decolorizing apparatus is similar in structure to that of Fig. 4, and the corresponding portions are designated by the same reference numerals. The decolorizing apparatus of Fig. 5 is characterized in that the decolorizing apparatus of Fig. 4 is modified so that the processing member 136 comprises a metal reverse-transfer roller 143 which builts in a heat source 145 such as a heater and that the toner image on the sheet 106 is melted by the heat of the heat source 145 while the reverse-transfer roller 143 is held by the supporting piece 134. The reverse transfer in this context means a process in which a toner layer transferred onto the sheet 106 is heated to a temperature equal to or higher than the glass-transition temperature TG so as to become at least a rubber-like elastic state, preferably a melting state, and the toner in such a state is transferred to a belt, roller or the like. When the reverse-transfer roller 143 is rotated on the sheet 106, a melting toner 175 adheres to the surface of the reverse-transfer roller 143 to form a reverse transfer layer 146 thereon. In this way, the toner 175 on the sheet 106 is peeled off and removed so that the thickness of the toner layer is reduced prior to the illumination of near infrared rays. In the decolorizing procedure using the decolorizing apparatus of Fig. 5, which is substantially the same as that using the decolorizing apparatus of Fig. 4, the toner 175 is reversely transferred by the reverse-transfer roller 143, namely, the surface layer portion of the toner layer is peeled off and removed from the sheet 106, and then the above-mentioned heating process and the near infrared ray illumination process are performed by the heater 133 and the light source 135, respectively. The embodiment of the decolorizing method can achieve the same effects as described in conjunction with the forgoing embodiments. The results obtained in the measurements using the toners S7 to S10 listed in Table 1 are shown in Table 3. In these experiments, the completion of decolorization was judged by ten observers. The shortest period prolonging until when six among the ten observers judged decolorization to be completed was determined as the period required for the completion of decolorization. This shortest period was set as the illumination period required for decolorization. Compound No. of decolorizable toner Sheet to be decolorized Near IR ray illumination period required for decolorization (sec) Inconspicuousness of decolorized toner Thickness of toner layer (µm) Process of removing toner Temp. at illumination of near IR rays (°C) Example 10 S7 About 10 Abrasion 60 44 ○ 11 S7 About 10 Abrasion 110 8 ○ 12 S7 About 15 Reverse transfer 110 10 ○ 13 S8 About 10 Abrasion 60 48 ○ 14 S8 About 10 Abrasion 130 10 ○ 15 S8 About 15 Reverse transfer 130 8 ○ 16 S9 About 10 Abrasion 60 84 ○ 17 S9 About 10 Abrasion 110 22 ○ 18 S9 About 15 Reverse transfer 110 22 ○ 19 S10 About 10 Abrasion 60 88 ○ 20 S10 About 10 Abrasion 130 19 ○ 21 S10 About 15 Reverse transfer 130 20 ○ Comparaative Example 16 S7 About 35 No 60 75 × 17 S7 About 35 No 110 17 × 18 S8 About 35 No 60 65 × 19 S8 About 35 No 130 20 × 20 S9 About 35 No 60 130 × 21 S9 About 35 No 110 36 × 22 S10 About 35 No 60 120 × 23 S10 About 35 No 130 30 × It will be noted from Table 3 that, when the toner layer of the sheet having a thickness of about 35 µm is thinned by the abrasion process as in Examples 10, 11, 13, 14, 16, 17, 19 and 20 so as to have a thickness of about 10 µm, the period of the illumination of near infrared rays required for complete decolorization is remarkably shortened as compared with that required when the thickness of the toner layer to be decolorized remains to be about 35 µm. Similarly, when the thickness of the toner layer on the sheet 106 is reduced by the above-mentioned reverse transfer process as in Examples 12, 15, 18 and 21, the period of the illumination of near infrared rays required for complete decolorization is remarkably shortened as compared with that required when the thickness of the toner layer to be decolorized remains to be about 35 µm. When the inconspicuousness of the toner print portion on the decolorized sheet 106 having a toner layer thickness of about 35 µm is compared with that of the toner print portion having a toner layer thickness of about 10 to 15 µm, it will be noted that the toner print portion having a toner layer thickness of about 10 to 15 µm is more inconspicuous. The estimate of the inconspicuousness was conducted, for example, in such a manner that the toner print portion after being subjected to the decolorizing process was observed with the naked eye, and, when the rising of the toner layer was obviously recognized, this decolorization was judged to be failure and indicated by "X", and, when the rising of the toner layer was not obviously recognized, this decolorization was judged to be success and indicated by "○" in the table. It will be noted from the above that the decolorized toner print portion can be made inconspicuous by abrading the toner layer on the sheet 106 or performing the reverse transfer so that the toner layer is partially removed at least in the thickness direction to reduce the thickness of the toner layer. According to the embodiment, when a toner image formed from a decolorizable toner is to be decolorized, the toner layer on the sheet is partially removed in the thickness direction prior to the illumination of near infrared rays, and thereafter near infrared rays are illuminated, whereby the rate of decolorization in the deep portion of the toner layer is improved. Since the toner is decolorized under the condition that the thickness of the toner layer is reduced, it is possible to make traces of the decolorized toner image inconspicuous. The decolorizing method of the invention is not restricted to the examples in which a toner layer on the sheet 106 having a thickness of about 35 µm is thinned to have a thickness of about 10 µm in such a manner as described in the embodiment. Namely, the invention includes a wide range of modifications in which, irrespective of the thickness of a toner layer on the sheet 106, the surface portion of the toner layer is removed by performing the shaving, peeling or the like, and then the thinned toner layer is subjected to the illumination of near infrared rays. (Fourth Embodiment) Fig. 6 is a sectional view of a decolorizing apparatus 60c. A light source 135 for illuminating near infrared rays is disposed inside a roller 157 which is made of transparent glass. A pair of rollers 158a and 158b are disposed in the vicinity of the roller 157 and with leaving a distance from each other along the periphery direction of the roller 157. Another roller 158c is disposed at a position which is separated from the roller 157. A belt 164 for transporting the sheet 106 is wound around the rollers 158a, 158b and 158c so that the portion of the belt 164 between the rollers 158a and 158b elongates along and contacts with the roller 157 made of transparent glass. In the vicinity of the portion of the belt 164 contacting with the roller 157, disposed is a heater 133. The roller 157 and the belt 164 are driven in such a manner that their peripheral velocities are different from each other. The sheet which has been transported along the direction of arrow A1 is further transported while being sandwiched between the belt 164 and the roller 157, and heated by the heater 133 during this transportation. At the same time, the sheet 106 is rubbed or subjected to physical deformation owing to the difference in peripheral velocity between the belt 164 and the roller 157. During this deformation, the light source 135 inside the roller 157 illuminates the sheet through the roller 157 with near infrared rays, thereby performing the decolorization process. The decolorized sheet is transported along the direction of arrow A2. (Fifth Embodiment) Fig. 7 is a sectional view of a decolorizing apparatus 60d for a decolorizing method and Fig. 8 is an enlarged sectional view of the decolorizing apparatus 60d. The decolorizing apparatus 60d comprises a tray 183 on which sheets 106 to be decolorized are stacked. The sheets 106 on the tray 183 are taken out by a sheet supply roller 184 and supplied by resist rollers 185 to an endless belt 164 for transporting the sheet 106. A processing device 137 is disposed in the upstream side of the endless belt 164 in the direction A1 along which the sheet 106 is transported. The processing device 137 comprises a duct 140 which covers the entire width of the endless belt 164 and opens downward. An abrasive roller 138 which has a roughened outer surface or to which sandpaper is fixed is disposed inside the duct 140 and positioned in such a manner that the roller can abrade the toner layer 175 on the sheet 106 to a layer thickness of about 10 µm. The abrasive roller 138 is rotated in the direction of arrow A2. A cleaning brush 139 is disposed inside the duct 140 and positioned in such a manner that the brush 139 slidingly contacts with the outer surface of the abrasive roller 138. In order to remove the toner adhered to the abrasive roller 138, the cleaning brush 139 has a cylindrical member on which electrically insulating fibers are implanted. The air in the duct 140 is sucked from the outside to have a negative pressure. Therefore, the toner which has been removed from the abrasive roller 138 by the cleaning brush 139 is pulled outside by the suction, and then collected by a dust collector (not shown). A supporting member 141 is positioned in such a manner that the endless belt 164 and the sheet 106 are pressed between this member 164 and the abrasive roller 138. A heating unit 159 which comprises a heat insulated wall 161 made of a heat insulating material is disposed in the downstream side of the processing device 137 in the direction A1 of transporting the sheet 106. The endless belt 164 elongating between the pair of rollers 162 and 163 runs under the heat insulated wall 161. A press roller 186 is disposed in the space surrounded by the endless belt 164 and between the pair of rollers 162 and 163, and a heating roller 187 is disposed at a position opposite to the press roller 186 toward the endless belt 164, whereby the sheet 106 sandwiched between the rollers 186 and 187 is heated at least to a temperature equal to or higher than the glass-transition temperature TG, preferably the softening point MP of the binding resin of the toner, so that the toner which is at least in a rubber-like elastic state is spread out. Transporting rollers 188 and 189 which are respectively disposed on the rollers 162 and 163 transport the sheet 106 in collaboration with the endless belt 164. A light source 135 is disposed inside the heat insulated wall 161. A fan 190 is disposed above the light source 135 so that the sheet 106 on the endless belt 164 is illuminated with near infrared rays from the light source 135 while being pressed down toward the endless belt 164. The decolorized sheet 106 is stacked on a tray 191. The embodiment can achieve the same effects as those described in conjunction with the forgoing embodiments of the decolorizing method. (Sixth Embodiment) Fig. 9 is a sectional view of a decolorizing apparatus 60f for a decolorizing method. This embodiment is similar in structure as the embodiment shown in Fig. 7, and the corresponding portions are designated by the same reference numerals. The decolorizing apparatus 60f comprises in the downstream side of resist rollers 185 a pair of endless belts 164a and 164b, for transporting a sheet 106, which respectively elongate between two pairs of rollers 162a and 163a, and 162b and 163b. A heater 165 is disposed in the space surrounded by the endless belt 164a and between the pair of rollers 162a and 163a. Inside the endless belt 164b and between the rollers 162b and 163b, disposed are a plurality of press rollers 192 which press the endless belt 164b against the heater 165 through the endless belt 164a. A fan 168 for cooling the melted toner which adheres to the endless belt 164a to solidify the toner is disposed above the endless belt 164a. Since the toner image on the sheet 106 is heated by the heater 165 to become a rubber-like elastic state or melt, the endless belt 164a is provided with a brush-like cleaning member 193 which is rotated to remove the toner adhering to the endless belt 164a. The waste toner which has been removed by the cleaning member 193 is stored in a storage tank 194. A separating claw 195 for separating the sheet 106 from the endless belt 164a is disposed in such a manner that it contacts from the outside with the portion of the endless belt 164a which contacts with the roller 163a. An illumination unit 170 which illuminates the sheet 106 with light including above-mentioned near infrared rays is disposed in the downstream side of the endless belts 164a and 164b along the transporting direction Al of the sheet 106. The illumination unit 170 comprises a list source 172 disposed inside a heat insulated wall 161. A platform 171 is disposed below the light source 172. A pair of fixing rollers 173 are disposed in the downstream side of the platform 171 along the transporting direction A1. The decolorized toner remaining on the sheet 106 is pressed between the pair of fixing rollers 173 to be extended over the entire surface of the sheet 106, whereby the surface of the sheet 106 is made relatively smooth. In the downstream side of the fixing rollers 173 along the transporting direction, disposed are a pair of discharging rollers 174 that discharge the sheet 106 on which toner images have been decolorized, to the outside of the decolorizing apparatus 60f. The discharged sheet 106 is placed on a tray 191. The embodiment can achieve the same effects as those described in conjunction with the forgoing embodiments. (Seventh Embodiment) Fig. 10 is a sectional view of a decolorizing apparatus 60g for a decolorizing method and Fig. 11 is an enlarged sectional view of the decolorizing apparatus 60g. This embodiment is similar in structure as the embodiment shown in Fig. 7, and the corresponding portions are designated by the same reference numerals. In the decolorizing apparatus 60g, a processing device 137c is disposed in the upstream side of an endless belt 164 along the transporting direction A1 of the sheet 106. The processing device 137c comprises a duct 140 which covers the entire width of the endless belt 164 and opens downward. Inside the duct 140, disposed is a reverse-transfer roller 143 which is rotated in the direction of arrow A2 on an axis parallel to the width direction of the endless belt 164. The reverse-transfer roller 143 incorporates a heater 144, and is formed into a cylindrical shape from a material to which the above-mentioned toner can adhere. A cleaning brush 139 on which electrically insulating fibers are implanted in order to remove the toner on the reverse-transfer roller 143 is disposed inside the duct 140 and positioned in such a manner that the brush slidingly contacts with the reverse-transfer roller 143. The air in the duct 140 is sucked from the outside to have a negative pressure. Therefore, the toner which has been removed from the surface of the sheet 106 by the cleaning brush 139 is pulled out by the suction, and then collected by a dust collector (not shown) or the like. The embodiment can achieve the same effects as those described in conjunction with the forgoing embodiments. Embodiments of the invention include applications in which the configurations of the embodiments shown in Figs. 7-11 are incorporated in electrostatic copiers to function as decolorizing means. (Eighth Embodiment) Fig. 12 is a front sectional view showing the configuration of a decolorizing apparatus 60h for a decolorizing method. The decolorizing apparatus 60h comprises a heating roller pair which consists of a heating roller 10 and a press roller 11, a light source 12 such as a tungsten halogen lamp, reflecting mirrors 13a and 13b having a concave shape, heat resisting glass plates 14 and 15, supply rollers 31 and 32, transporting rollers 34, 35, 38 and 39 and discharge rollers 22 and 23 which transport a sheet 106 such as paper or plastic sheet, guide members 33, 36, 37, 40, 41, 16 and 17 for smoothly guiding the sheet 106, exhaust ducts 61, 63, 65 and 67 and exhaust fans 62 and 66 which discharge to the outside the heat generated from the heating roller pair 10 and 11 and the light source 12, and so on. The plural sheets 106 to which the above-mentioned photochemically decolorizable toner is fixed are accommodated in a sheet supply cassette 30. The sheet 106 is taken out by the supply rollers 31 and 32, and then transported along a one-dot chain line in the figure to the heating roller pair 10 and 11 by the guide members 33, 36, 37, 40 and 41 and transporting rollers 34, 35, 38 and 39. The heating roller 10 is a hollow cylinderical roller which is made of a metal or glass and the surface of which is coated with fluorocarbon polymers or the like. A heater 10a such as a tungsten halogen lamp is incorporated in the shaft portion of the roller 10, so that the energization of the heater 10a causes the surface to be heated to a predetermined temperature. The press roller 11 has a structure in which the surface of a metal roller is coated with a thick layer of silicone rubber, and is forced at a predetermined pressure toward the heating roller 10, so that the silicone rubber elastically deforms along the outer shape of the heating roller 10, thereby maintaining a predetermined contacting area. When the sheet 106 is transported while being sandwiched between the heating roller pair 10 and 11, the toner is heated to a temperature equal to or higher than its glass-transition temperature of the bonding resin. In the discharging side of the heating roller pair 10 and 11, light including near infrared rays emitted from the light source 12 is efficiently converged by the reflecting mirrors 13a and 13b, etc., thereby forming a light condensing portion having a high light illumination density. As soon as discharged from the heating roller pair 10 and 11, therefore, the sheet 106 is illuminated with light of near infrared rays, with the result that the color of the toner is efficiently erased. The decolorized sheet 106 is guided by the guide members 16 and 17 and discharged to the outside by the discharge rollers 22 and 23 to be placed on a discharge tray 42. The guide member 16 consists of a plurality of linear members which are formed by bending wires, etc., elongate along the transporting direction of the sheet and are arranged at predetermined intervals perpendicular to the transporting direction of the sheet. In this way, during when the sheet 106 on which images are once formed from the toner is transported from the sheet supply cassette 30 to the discharge tray 42, the toner image is efficiently and quickly decolorized. Cleaning rollers 20 and 21 into which a parting agent such as silicone oil is impregnated respectively contact with the heating roller 10 and press roller 11 of the heating roller pair, so that the surface of the heating roller pair 10 and 11 is wetted by the parting agent. This prevents the toner fixed to the sheet 106 from adhering to the roller pair and also the sheet 106 from winding round the roller pair. Separating claws 24 and 25 contact with the heating roller 10 and the press roller 11 in the discharging side, respectively. Even when the sheet 106 is closely attracted to the heating roller 10 or press roller 11, the sheet 106 can be separated from the roller by the tip of the separating claw 24 or 25, thereby preventing the sheet 106 from winding round the roller. Sheet detection sensors 51 and 52 such as a photocoupler or microswitch are disposed optionally at various positions along the transporting path (indicated by a one-dot chain line in Fig. 12) of the sheet 106, for example, at the upper potion of the guide member 36, and in the discharging side of the discharge rollers 22 and 23. These sensors are used in the timing control and the detection of a jam. Electric discharge brushes 56 and 57 are disposed at various positions along the transporting path of the sheet 106 and of the rollers, for example, on the surface of the press roller 11 and in the discharging side of the discharge rollers 22 and 23, thereby preventing the sheet 106 from being electrostatically attracted to the rollers or the like. A temperature sensor 53 such as a bimetal or a thermistor is disposed on the surface of the heating roller 10 so as to control the temperature of the heating roller 10. Furthermore, thermal fuses 54, 55 and 56 are disposed at positions where the temperature rise is notable, for example, on the surface of the heating roller 10, the reflecting mirror 13b and the guide member 17, thereby preventing the generation of an abnormal high temperature. A large amount of heat is generated in the vicinity of the heating roller pair 10 and 11 and the light source 12. Therefore, the exhaust ducts 61 and 65 are disposed at the both sides of the transporting path of the sheet 106, and the air is forcedly exhausted to the outside by the exhaust fans 62 and 66 such as a sirocco fan through the exhaust ducts 63 and 67 and vent holes 64 and 68, thereby preventing the excessive temperature rise of the apparatus. Fig. 13 is a fragmentary side elevation view showing the configuration of the decolorizing apparatus 60h of Fig. 12. The heating roller 10, press roller 11, and cleaning rollers 20 and 21 are rotatably supported by a frame 6 and an auxiliary side plate 7. The heater 10a such as a tungsten halogen lamp is incorporated in the shaft portion of the heating roller 10. When any of the rollers 10, 11, 20 and 21 is to be replaced, therefore, the roller to be replaced can be accessed only by removing the auxiliary side plate 7 and without disassembling the whole of the frame 6, thereby improving the workability of the maintenance operation. As shown in the center of the fragmentary portion of Fig. 13, a plurality of the discharge rollers 22 and 23 are rotatably supported along the width direction of the sheet 106 with predetermined intervals. Similarly, a plurality of the separating claws 24 and 25 are disposed along the width direction of the sheet 106 with predetermined intervals. The separating claws 24 and 25 are respectively provided with coil springs 24a and 25a so that their tips are forced to contact with the surface of the heating roller 10 and press roller 11 at a predetermined pressure. As shown in Fig. 12, one end of the coil spring 24a which forces the separating claw 24 is elongated to the axis of the discharge rollers 22 and bent to form a smooth curve, so that the elongated portion can function also as the guide member 16. The exhaust fan 62 is driven by a motor 62a. Fig. 14 is a front view showing the state in which a light source unit 70 of the decolorizing apparatus 60h of Fig. 12 is rotated around an axis 71 to open. When the sheet 106 is blocked in the subsequent stage of the heating rollers pair 10 and 11, i.e., there happens a so-called jam, this jam can be removed in the following manner. In the state of Fig. 12, the discharge tray 42 is removed, and thereafter an engaging member 72 disposed at the upper portion of the light source unit 70 is manually operated to unlock the engagement between a claw 73 of the engaging member 72 and a hole 74 formed on a housing 5. Then, the light source unit 70 is rotated to swing outward, so that a large space is formed in the discharging side of the heating roller pair 10 and 11 and that the inside of the light source unit 70 can be easily observed. This allows the user to remove a jam in safety and with ease. After the removal of a jam, the light source unit 70 is pushed into the housing 5, whereby the engagement between the claw 73 of the engaging member 72 and the hole 74 of the housing 5 is easily made again. In this way, the opening and closing facility of the light source unit 70 facilitates the jam removing operation. The light source unit 70 may be constructed so as to horizontally move along linear guiding means such as a rail. An axis which is detachably mounted to the housing may be used as the axis 71 so that the light source unit 70 can be detached from the body of the decolorizing apparatus. Fig. 15 is an exploded perspective view showing a decolorizing unit 80. The decolorizing unit 80 comprises the heating roller pair 10 and 11, the cleaning rollers 20 and 21, the guide members 40 and 41, the light source unit 70, and a bottom plate 4, frame 6 and auxiliary side plate 7 which support these components. The exhaust duct 65 is mounted at a portion between the heating roller pair 10 and 11 and the bottom plate 4, and a top cover 81 to which the exhaust duct 61 is unitedly attached is mounted above the heating roller pair 10 and 11. The press roller 11 is forced toward the heating roller 10 by a coil spring 82. The auxiliary side plate 7 by which the heating roller pair 10 and 11 and the cleaning rollers 20 and 21 are rotatably supported through bearings is detachably mounted to the frame 6 by fixing members 7a such as a screw. As described above, therefore, it is possible to easily and quickly perform the maintenance operation of the rollers 10, 11, 20 and 21. Fig. 16 is a partial view showing the configuration of an optical system of the light source 12 and a light condensing portion P. Although one portion of the light emitted from the light source 12 directly reaches the light condensing portion P, most portion of the light is reflected by reflecting mirrors 13a, 13b and 13c. The light reflected by the reflecting mirror 13b is directed toward the light condensing portion P. The light reflected by the reflecting mirrors 13a and 13c proceeds to the guide member 17 having a mirror surface, and is again reflected by the guide member 17 to converge on the light condensing portion P. In addition to the formation of the mirror surface, the guide member 17 may be further optically processed in order to improve the light converging efficiency in a greater degree. Namely, the guide member 17 may be formed into a triangular wave shape, so that the light source 12 and the light condensing portion P are positionally set in the direction of regular reflection. Therefore, the guide member 17 functions as means for smoothly transporting the sheet 106 and also improving the light converging efficiency. Even when the sheet 106 moves over the guide member 17, the light from the light source 12 can transmit through the sheet 106 with an attenuation of a small degree, thereby allowing the light converging function of the guide member 17 to continue. In the case that the light source 12 has a large output power, the separating claw 24 made of a resin may be overheated and deformed. Hence, it is preferable that a metal protective cover 18 is disposed in front of the separating claw 24. Fig. 17 is a partial view showing the heat exhaustion in the vicinity of the light source 12 and the heating roller pair 10 and 11. In addition to an improved light converging efficiency of the optics from the light source 12 to the light condensing portion P, also a large output power of the light source 12 will contribute the efficient and rapid decolorization of the decolorizable toner. Therefore, it is required to exhaust a hot air to the exterior of the apparatus while reducing the effect of the waste heat of the light source on the other members. The light source 12 emits light having a wavelength distribution ranging from visible light to far infrared rays and generates a large amount of heat. Members which directly receive light from the light source 12 absorb the light to elevate their temperature, resulting in that the air in the vicinity of the light source 12 and the heating roller pair 10 and 11 becomes hot. Accordingly, the exhaust duct 61 to which the exhaust fan 62 is connected is disposed in the upper portion of the apparatus, and the exhaust duct 65 to which the exhaust fan 66 is connected is disposed in the lower portion of the apparatus. The provision of the heat resisting glass plates 14 and 15 between the light source 12 and the light condensing portion P enables the air flow to be smoothly conducted without substantially interrupting the light from the light source 12, thereby preventing the air from continuing to stay in the interior. The exhaustion from the upper and lower sides of the transporting path of the sheet 106 improves the ventilation efficiency and prevents the sheet 106 from being subjected to the deformation such as a warp, flapping which is caused by the exhaustion pressure difference between the both sides of the sheet 106, thereby suppressing the occurrence rate of a jam. Fig. 18 is a fragmentary front view showing an operation panel 91 of the decolorizing apparatus 60h of Fig. 12. When an operation switch 92 on the operation panel 91 is pressed, the sheets 106 in the sheet supply cassette 30 are taken out one by one, and the decolorization operation is continuously carried out. The apparatus may be modified so that one of the sheets 106 is processed for each operation of the switch. By operating a speed control dial 93, the rotational speed of a driving motor 90 which drives the rollers 34, 35, 38, 39, 10, 11, 22 and 23 is controlled so that the transporting speed of the sheet 106 is set to a desired value. When the sheet 106 carrying a toner which is easily decolorized is to be processed or the color of a toner is allowed to remain appearing in a some degree, the sheet 106 may be transported at a higher speed so that the decolorization operation is rapidly conducted. In contrast, when the sheet 106 carrying a toner which is difficult to be decolorized is to be processed, the transporting speed of the sheet 106 may be set to a lower speed so that the sheet is subject to the sufficient heating and light illumination, whereby the decolorization is surely conducted. In the case that the sheet 106 carrying a toner which cannot be decolorized by one decolorization process, the sheet 106 may be returned to the sheet supply cassette 30 so that the decolorization process is repeatedly conducted, whereby the decolorization is more surely conducted. (Tenth Embodiment) Fig. 22 is a sectional view showing part of an image forming apparatus which has a decolorizing function and shows a decolorizing means 60j disposed in a transporting path 301a for a sheet 106. The decolorizing means 60j is mounted in a body 304 of a copier 300 shown in Fig. 23. Electrostatic photography image forming means 305 is disposed in the upstream side of the transporting path 301a for a sheet 106. Sheets 106a from a manual sheet supply port 310 are supplied one by one by a sheet supply roller 307, and sheets 106b stacked on a supply cassette 308 are supplied one by one by a sheet supply roller 309. The sheets 106a and 106b may be generally designated by reference numeral 106. In the electrostatic photography image forming means 305, a right cylinderical photoconductive body 311 is rotated in the direction of arrow 312. The surface of the photoconductive body 311 is electrically charged by a corona charger 313, and in an exposure region 314 an original image is exposed to form a latent image. The latent image is visualized into a toner image by, for example, a magnetic brush of a developer 315, and the toner image of the photoconductive body 311 is transferred by the transfer corona discharger 316 to the sheet 106 transported through transporting path 301b. Then, the sheet 106 is separated from the photoconductive body 311 by a separation corona discharger 317. The sheet 106 bearing the thus transferred toner image is transported by an endless belt 318 such as an aramid film belt or the like, which is disposed in the transporting path 301a. The toner remaining on the photoconductive body 311 after the transfer is removed by cleaning means 319. In order to form an original image in the exposure region 314, an original 321 is placed on a transparent platen 320 which is horizontally disposed in the upper portion of the body 304, and then covered by a cover 322. The original 321 is illuminated through the transparent platen 320 by a light source 323, and the original image is directed to the exposure region 314 through an optical system 327 which includes a reflecting mirror 324, a lens 325 and a reflecting mirror 326. By relatively moving the original 321 with respect to one portion of the optical system 327 in the right and left direction as viewed in Fig. 23, the slit exposure is carried out. The sheet after the transfer process is transported onto the endless belt 318, and sandwiched to be subjected to the thermal fixing process, by the pressure roller 329 and heating roller 330 of a fixing device 328 which is disposed in the downstream side in the transporting direction of the sheet. The sheet which has been subjected to the thermal fixing process is discharged onto a discharge tray 332 by discharging rollers 331. The decolorizing means 60j mounted in the body 304 has a configuration shown in Fig. 22. A light source 335 emitting near infrared rays for decolorization is disposed in a housing 334 which is made of a light-shielding material such as a metal. The light source 335 may be a tungsten halogen lamp, a light emitting diode, a semiconductor laser device, or the like. The light emitted from the light source 335 as indicated by arrows 336 impinges onto the upper surface of the sheet 106 on the conveyor 318, through an opening 337 formed in the lower portion of the housing 334. An image formed from the toner has been already fixed to the upper surface of the sheet 106. When the toner on the sheet 106 is illuminated with near infrared rays emitted through the opening 337 from the light source 335, the toner image becomes colorless, resulting in that the decolorized sheet 106 can be made reusable. A cooling fan 338 for cooling the light source 335 is disposed in the housing 334 so that an air is sucked in through an opening 339 formed in the upper portion of the housing 334 to be directed to the light source 335. The cooling air is exhausted from the opening 337. In the opening 337, a plurality of wires 340 horizontally elongating along the transporting direction of the sheet 106 or the right and left direction as viewed in Fig. 22 are arranged with leaving intervals in a direction perpendicular to the transporting direction. The wires are fixed to the lower portion of the housing 334. Even when the sheet 106 rises on the belt 318, this configuration prevents the sheet 106 from entering into the opening 337 or caught on the wires 340, resulting in that the sheet 106 can be smoothly transported and prevented from jamming. Members for safety such as a temperature detection element 341 and a fuse may be disposed in the housing 334. Fig. 24 is a partially cutaway plan view showing the image forming apparatus 303 in a simplified manner. A print button 343 which is operated to start the copy operation of the image forming means 305, and display/input means 344 for the display and input operation are disposed on the front and upper portion of the body 304. A changeover switch 345 for switching the copying and decolorization operations, and a switch 346 for starting the decolorization operation are further disposed. As shown in Fig. 23, a sensor 347 for detecting whether or not a toner image is formed on the upper surface of the sheet 106 is disposed in the transporting path 301b. Fig. 25 is a block diagram showing the electrical configuration of the embodiment shown in Figs. 22 to 24. The print button 343, display/input means 344, switches 345 and 346 and sensor 347 produce signals which are then supplied to a processing circuit 348 that is constituted of a microcomputer or the like, thereby controlling the decolorizing apparatus 60j, the image forming means 305 and driving means 349 for the belt 318. The driving means 349 includes a pair of roller 350 and 351 between which the belt 318 elongates, and drives the roller 351 in a speed-variable manner. Fig. 26 is a flowchart illustrating the operation of the processing circuit 348. The process proceeds from step a1 to step a2, and it is checked whether or not the copying/decolorization changeover switch 345 and the decolorization operation switch 346 are operated to carry out decolorization. When decolorization is not to be carried out, the process proceeds to the next step, i.e., step a3 to check whether or not the print button 343 is operated to start the copying. When the copying is not to be done, the process proceeds to step a4. In step a4, on the basis of the signal of the sensor 347, it is judged whether or not a toner image is formed on the upper surface of the sheet transported in the transporting path 301b. When no image is formed, i.e., the transported sheet 306 is white, the process proceeds to step a5. In step a5, the image forming means 305 performs the electrostatic image formation operation to form the original image of the original 321 on the upper surface of the sheet 106, and after the fixation the sheet 106 is discharged onto the discharge tray 332. When the print button 343 is operated in step a3, the process jumps to step a5. When the copying/decolorization changeover switch 345 and the decolorization operation switch 346 are operated to start the decolorization operation, the process proceeds from step a2 to step a6. In step a6, the light source 335 of the decolorizing means 60j is energized to illuminate the toner image on the sheet 106 with near infrared rays to be subjected to the decolorization operation. In step a7, in order that decolorization is surely achieved, the driving means 349 is controlled so that the transporting speed of the belt 318 during the decolorization operation is lower than that during the image forming operation. This enables the sheet 106 to be illuminated with a sufficient amount of light so that the decolorization operation is surely conducted, whereby the sheet 106 can be made reusable. When the sheet 106 carrying a toner image thereon is transported in the transporting path 301b, the sensor 347 detects the existence of the image, and the decolorization operation is automatically conducted in steps a6 and a7. When, after operating the print button 343 or the copying/decolorization changeover switch 345 to instruct the start of the copying operation, the operator finds that this instruction is wrong, the operator can immediately operate the copying/decolorization changeover switch 345 or the decolorization operation switch 346. This causes the process to jump steps a6 and a7 to conduct the decolorization operation. In this way, when in the middle of the copying operation the operator finds that this copying is not necessary, the operator can control the image forming apparatus to immediately interrupt the unnecessary copying operation and start the decolorization operation, so that the sheet 106 on which at least one portion of the copying operation has been conducted can be subjected to the decolorization operation. During the image forming means 305 conducts the copying operation in step a5, the decolorizing means remains to stop, and the discharging rollers 331 continue to operate. Similarly, when the decolorizing means 60j conducts the decolorizing operation in step a6, the image forming means 305 remains to stop, the fixing device 328 continues its thermal fixing operation, and the discharging rollers 331 continue to operate. According to the thus configured embodiment, the sheet 106 on which an unnecessary copying operation has been done can be made reusable, thereby enabling resources to be effectively utilized. Since the electrostatic image forming means 305 and the decolorizing means 60j are housed in the sole body 303, the embodiment can be constructed in a reduced size and installed in a small space, as compared with the case wherein these components 60j and 305 are separately installed. This configuration in which the image forming means 305 and the decolorizing means 60j are housed in the sole body 303 allows the manual sheet supply port 310, the sheet supply cassette 308, the discharge tray 332, etc. to be used commonly in both the copying and decolorization operations, whereby the decolorizing means 60j can be easily incorporated and the configuration can be simplified as compared with the case wherein the decolorizing means 60j and the image forming means 305 are separately installed. Furthermore, the decolorizing means 60j which can perform optimum decolorization on the toner used in the developing device 315 of the image forming means 305 is disposed in the common body 304. Therefore, the apparatus can conduct the copying of a high quality using the toner, and surely attain decolorization of the toner, with the result that the sheet 106 carrying the toner that has been made colorless and transparent can be surely made reusable. (Eleventh Embodiment) Fig. 27 shows an embodiment in which a near infrared ray illumination device is disposed in the downstream side of a fixing device. More specifically, a decolorizing means 60j comprising a light source 335 is disposed in the downstream side of a fixing device 328. In this case, since the sheet has been already heated by a heating roller 330, the decolorizing effect due to the illumination of near infrared rays is improved in accordance with this heating. The invention can be applied not only to the embodiments described above, but also to a wide range of printers and other electrostatic photography image forming means. The method and apparatus of the invention are not restricted to the application on a toner which is contained in a developer for an electrostatic copier as described in the embodiments, but also applicable to decolorizable ink for printing, stamp or writing which contains the pigment of Formula (1) or (2), or wide variety of other pigments. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.

Claims: A decolorizing method comprising the steps of: separately providing a heater and a near infrared ray source; heating an electrostatic toner image formed on a sheet (106) from a photochemically decolorizable toner having a binding resin to at least the glass-transition temperature of the binding resin of the toner with the heater; and illuminating the toner image with near infrared rays from the near infrared ray source. A decolorizing method according to claim 1 comprising the step of: illuminating the toner image with near infrared rays concurrently with or after said step of heating. The decolorizing method of claim 2, wherein said step of heating further comprises heating the toner image to at least the softening point of the binding resin. The decolorizing method of claim 2, wherein said step of heating comprises heating the toner image to a temperature lower than the decomposition temperature of the components of the photochemically decolorizable toner. The decolorizing method of claim 2, wherein said step of heating changes the binding resin from a solid state to a melting state. A decolorizing method according to claim 1 comprising the step of: physically deforming the toner image no later than said step of illuminating the toner image with near infrared rays. The decolorizing method of claim 6, wherein said step of physically deforming comprises rubbing and pressing the toner image. A decolorizing method according to claim 1 comprising the step of: removing at least partially a layer of the toner image so as to reduce the thickness thereof. The decolorizing method of claim 2 or 6, wherein said step of illuminating comprises illuminating both sides of the sheet (106) with near infrared rays. A decolorizing apparatus (60c, 60d, 60f, 60g, 60h, 60i) comprising: a transport path for transporting an electrostatic toner image sheet (106) along a transport path, the toner image sheet (106) having a toner image thereon formed from photochemically decolorizable toner comprising a binding resin transported thereby; heating means (133, 187, 165, 10, 240) disposed along said transport path, for heating the toner image to at least the glass-transition temperature of the binding resin of the toner; and illuminating means (135, 172; 12, 13a-13c; 240, 241) provided along said transport path, for illuminating the toner image with near infrared rays concurrently with or after heating of the toner image by said heating means. A decolorizing apparatus according to claim 10 comprising: means (157, 164, 188, 189; 38, 39, 40, 41, 16, 17; 212, 213, 223, 224) for transferring the toner image sheet (106) to said heating means and said near infrared illuminating means along said transport path. The decolorizing apparatus of claim 10 or 11, wherein said heating means is for heating the toner image to at least the softening point of the binding resin. The decolorizing apparatus of claim 10 or 11, wherein said heating means is for heating the toner image to a temperature lower than the decomposition temperature of the components of the photochemically decolorizable toner. The decolorizing apparatus of claim 10 or 11, wherein said heating means is further for changing the binding resin from a solid state to a melting state. The decolorizing apparatus (60h) of claim 10, wherein said illuminating means (12) is further for illuminating both sides of the toner image sheet (106) with near infrared rays. A decolorizing apparatus (60c, 60d, 60f, 60g) according to claim 10 wherein the transport path comprises a belt conveyor (164, 164a-164b) for transporting a toner image sheet along a transport path. A decolorizing apparatus (60g, 60h, 60i) according to claim 10 wherein the transport path comprises a roller (188, 189; 38, 39; 212, 213) for transporting a toner image sheet along a transport path. A decolorizing apparatus (60c, 60f) according to claim 10 comprising: deforming means (157, 164; 192) for physically deforming the toner image no later than when said illuminating means illuminates the toner image with near infrared rays. The decolorizing apparatus of claim 20, wherein said deforming means deforms the toner image by rubbing the toner image and/or pressing the toner image. A decolorizing apparatus (60d, 60g) according to claim 10 comprising: means (137, 137c) for partially removing the toner image in the thickness direction no later than when said illuminating means illuminates the toner image with near infrared rays concurrently with or after heating of the toner image by said heating means. The decolorizing apparatus of claim 20, wherein said means for at least partially removing a layer of the toner image removes the layer by one selected from the group consisting of shaving the layer from the toner image and peeling the layer from the toner image. The decolorizing apparatus (60h) of any one of claims 10, 11, 16, 17, and 18, wherein a heat resisting glass plate (15) for blocking the air flowing from the means for illuminating with near infrared rays toward the predetermined position is disposed between the means for illuminating with near infrared rays and the predetermined position. The decolorizing apparatus (60h) of claim 22, wherein the transporting means comprises a member (17) having a reflective surface toward the transporting path, disposed at a position which is more distant from the means for illuminating with near infrared rays than from the transporting path of the sheet and in the vicinity of the predetermined position of the transporting path illuminated with near infrared rays. The decolorizing apparatus (60h) of any one of claims 10, 11, 16, 17 and 18, wherein at least one of the heating means and the illuminating means is removable from the transporting path from a position predetermined in time of decolorizing. An electrostatic image forming apparatus (300) comprising: means (305) for forming toner images on a cut sheet (106) with a photochemically decolorizable toner by an electrostatic photocopy process; and a decolorizing apparatus (60j) as claimed in claim 10 for decolorizing the toner image on cut sheet (106) by heating the toner image to at least the glass-transition temperature and illuminating the toner image with decolorizing light; wherein said means (305) for forming and said decolorizing apparatus (60j) are selectively operable.

Inventors: ABE YUKI, HOSODA YOSHIKAZU, INOUE SHIGEKI, KOUZUKI RIKUZOU, MIKATA YASUNORI, MUROFUSHI KATSUMI, OKAMOTO MASAKAZU, TABATA MASATSUGU, TANIMOTO SADAO, UCHIMOTO YOSHIHIRO, ABE, YUKI, HOSODA, YOSHIKAZU, INOUE, SHIGEKI, KOUZUKI, RIKUZOU, MIKATA, YASUNORI, MUROFUSHI, KATSUMI, OKAMOTO, MASAKAZU, TABATA, MASATSUGU, TANIMOTO, SADAO, UCHIMOTO, YOSHIHIRO, Abe, Yuki, c/o Bando Chemical Ind., Ltd., Hosoda, Yoshikazu, c/o SHOWA DENKO K. K., Inoue, Shigeki, c/o BANDO CHEMICAL IND., LTD., Kouzuki, Rikuzou, c/o BANDO CHEMICAL IND., LTD., Mikata, Yasunori, c/o BANDO CHEMICAL IND., LTD., Murofushi, Katsumi, c/o SHOWA DENKO K. K., Okamoto, Masakazu, c/o BANDO CHEMICAL IND., LTD., Tabata, Masatsugu, c/o BANDO CHEMICAL IND., LTD., Tanimoto, Sadao, c/o BANDO CHEMICAL IND., LTD., Uchimoto, Yoshihiro, c/o YUNIKO KABUSHIKI KAISHA
Applicants: BANDO CHEMICAL IND, SHOWA DENKO KK, BANDO CHEMICAL INDUSTRIES, LIMITED, SHOWA DENKO KABUSHIKI KAISHA
Application year: 1992
Main classification: G03G9
IPC codes: G03G13, G03G9