Heat developing apparatus and heat developing method

This heat developing method includes a step of forming a latent image on a heat developing photosensitive film sheet and a step of developing the film sheet, while the film sheet on which a latent image is formed is being conveyed, by heating with segmented heaters which are formed by dividing the total heating area into plural segments in the direction perpendicular to the conveyance direction, and which are independently temperature controllable, wherein the film sheet is so conveyed that no film sheets of different sizes are simultaneously in contact with any segmented heater.

This application is based on Japanese Patent Application No. 2004-151816 filed on May 21, 2004, in Japanese Patent Office, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a heat developing apparatus and a heat developing method for developing and visualizing a latent image which has been formed on a heat-developing photosensitive film sheet.

The following Patent Document 1 discloses a heat-developing photosensitive material recording device in which a film, being an exposed recording material, is conveyed into a heat-developing section and developed as it is in contact with a heating drum and thereby heated. In this case, since the size of film varies depending upon the photographed object (photographed portion), the type of film conveyed to the heat-developing section also varies from time to time. Since the film is developed as it passes through a heating unit, accordingly, if the heating unit employs a heating drum, for example, the temperature of the area that is utilized for development (the area that is actually in contact with the film, which is called the “developing area” below) becomes lower than in other areas because the film removes heat from that contact area.

If the same area on the heating drum surface is always utilized for development, the temperature of the developing area is almost stable even when a plurality of recording films are developed in series, and therefore stable development becomes possible. When the film size is changed, however, the position, dimensions and shape of the developing area are different from the previous development operation. Consequently, problems tend to arise in that the temperature distribution in the new developing area does not become uniform immediately after changing to a different film size, and uneven development is easily caused.

This problem is remarkably found particularly when the recording material is changed from a small size to a large size. Since high image quality is required in the medical field, high image-quality recording film is employed. But, because the effect of heat on high image-quality recording film like the above during development is very much, the above-mentioned uneven development tends to occur.

The following Patent Document 2 discloses an image forming apparatus in which, in order to prevent overheating of the sheet non-passage area on a fixing roller when recording material is continuously fed into the fixing unit, the feeding interval of the recording material is changed during the continuous feed between fixing at the first set temperature and fixing at the second set temperature. In a fixing unit like the above, however, temperature non-uniformity is caused on the fixing roller surface, because, although the surface temperature of the recording material passage area on the fixing roller becomes lower while the recording material passes through it, heat is hard to be removed from the recording material non-passage area of the fixing roller. This temperature non-uniformity is remarkably evident when the recording material continuously passes through the fixing roller surface. If the temperature is set high enough for the sheet passage area in this operation, the sheet non-passage area becomes excessively hot. This tendency is particularly marked when the set temperature of the fixing roller is changed, when the size of recording material is changed, and for a while after the fixing roller surface reaches the temperature for image forming.

The following Patent Document 3 discloses a heat-developing apparatus, using a heat-developing method that can control image-quality degradation due to the temperature drop of heating members resulting from continuous processing, and also continuously heat-develops the heat-developing sheets of different sizes on which an exposed latent image has been formed, to reduce the continuous process time, in which the minimum required temperature restoration time for heat-developing the following heat-developing sheet is determined from the physical data of the heat-developing sheet currently being developed, and the development of the following heat-developing sheet to be developed next is started after the minimum temperature restoration time has elapsed.

The heat-developing apparatus of Patent Document 3 employs the same method as for Patent Document 2, the temperature of which is controlled by a single sensor in the lateral direction and the apparatus carries out nothing but waiting until the temperature distribution in the lateral direction becomes uniform. Processing capacity cannot improve when the size of the recording material or heat-developing sheet is changed frequently.

The following Patent Document 4 discloses a fixing device provided on a copying machine, printer, facsimile machine, or the like. A fixing device of this type is equipped with a heating member, where the surface temperature of fixing roller is sensed by a thermal sensor and the surface temperature of the fixing roller is controlled via signals to maintain at a specified temperature by varying the heat from the heating member. That is to say, it is in an ON/OFF system, by which power to the heating member is turned ON if the surface temperature of the fixing roller is lower than the specified temperature and turned OFF if higher, or electrical power to the heating member is controlled accordingly. This temperature control is achieved using signals from a thermal sensor such as thermistor installed in contact with or close to the fixing roller surface, where the surface temperature of the fixing roller is sensed at one location.

However, it frequently happens that the surface temperature of the fixing roller is not at a constant temperature particularly across its whole width in the axial direction resulting from airflow inside or outside the apparatus, operating conditions, sheet size, or inherent differences among machines. Consequently, the surface temperature of the fixing roller near the portion where the thermal sensor is installed is controlled to the specified temperature but the specified temperature may not be maintained at portions away from the thermal sensor. Under this condition, problems arise in that fixing characteristics do not become uniform so that stable and favorable fixing cannot be achieved.

In Patent Document 4, in order to maintain nearly constant temperature across the whole width of the fixing roller in the fixing device, even when the temperature condition of the fixing roller is different in the axial direction, the fixing roller is divided into two heating areas, nearly equally divided into right and left portions in the axial direction. A high-temperature heating member of each heater is provided across the whole heating area, a thermal sensor for sensing the surface temperature of each heating area is provided, and temperature balance on the fixing roller surface is controlled so that each heating area is maintained at the specified temperature.

The following Patent Document 5 discloses an apparatus in which a film sheet is subjected to heating and conveyed while it is wound around a heating drum and pressed by opposed rollers. This apparatus is capable of processing three different sized sheets of film of 14×17 inch, 14×14 inch and 11×14 inch having the same width, by the same heater pattern. When processing of 10×12 inch or 8×10 inch is also desired, however, the apparatus requires a stand-by time until the drum is restored to a uniform temperature due to the changed size. This stand-by time can become much longer when the size is changed after continuous processing of film sheets of the same size because the temperature difference between the film-passage portion and non-passage portion becomes much greater. The stand-by time also varies depending upon the type of film and temperature setting for heat-development. Accordingly, the processing capacity per unit time is tremendously low.[Patent Document 1] Tokkai Hei No. 11-65070[Patent Document 2] Tokkai Hei No. 05-6043[Patent Document 3] Tokkai No. 2002-244266[Patent Document 4] Tokkai Hei No. 05-53463[Patent Document 5] Tokuhyou Hei No. 10-500497

SUMMARY OF THE INVENTION

In view of the above problems in the prior art, an object of the present invention is to offer a heat-developing apparatus and heat-developing method that can supply a specific quantity of heat to the heat-developing photosensitive material, which is conveyed while being heated, and to maintain stable finished image density by using a heating method in which heating area is divided into multiple heater patterns corresponding to film passage phases.

In order to achieve the above object, the heat-developing apparatus of the present invention is composed of a film loading means on which heat-developing photosensitive film sheets of different sizes can be loaded, a conveying means for conveying the heat-developing photosensitive film sheets from the film loading means, an exposing means for forming a latent image on the conveyed heat-developing photosensitive film, a heat-developing means for developing and visualizing a heat-developing photosensitive film on which a latent image has been formed, including a heating means for heating the heat-developing photosensitive film sheet, and an auxiliary means for heating and conveying the heat-developing photosensitive film sheet while pressing the film against the heating means. It also is composed of a controlling means for controlling the conveying means, the exposing means and the heat-developing means. The heating means is composed of a heater that is divided into at least multiple areas, in the direction perpendicular to the conveying direction of the heat-developing photosensitive film sheets, each of which is capable of independently controlling the temperature. Further a control means controls the conveyance of the heat-developing photosensitive film sheet so that heat-developing photosensitive film sheets of different sizes can not simultaneously be in contact with any of the multiple segmented heater sections.

With this heat-developing apparatus, the temperature distribution across the width direction can be controlled to become uniform by independently controlling the multiple segmented heaters, corresponding to the film passage phase. When a heat-developing photosensitive film sheet of some size is heated by a set of segmented heaters and then a different sized heat-developing photosensitive film sheet is conveyed, the conveyance of that film sheet is so controlled that the foregoing and following heat-developing photosensitive sheets of film can not simultaneously be in contact with each segmented heater section, and hence a different sized heat-developing film sheet can be conveyed and heated after the temperature of each heater section has become suitable for that size of heat-developing photosensitive film sheet. Accordingly, even when the size of a sheet of heat-developing photosensitive film is changed, a specific quantity of heat can always be supplied to a specific sized sheet of the heat-developing photosensitive film and thus stable finished image density can be maintained.

In the above heat-developing apparatus, the heating means is not practically divided in the conveyance direction and, when different sized heat-developing photosensitive film sheets are conveyed, the control means stops conveying the following different sized film sheet to the heating means until the trailing edge of the foregoing film sheet being another size has been detached from the heating means, and hence the following different sized heat-developing photosensitive film sheet can be conveyed and heated after the temperature of each segmented heater section has been suitably controlled for the following heat-developing photosensitive film sheet.

In the above apparatus, the heat developing means can be so constructed to comprise a heating drum that is equipped with a sheet heater on the interior of its sleeve and driven to rotate and opposed rollers which are installed around the circumference of the heating drum.

By constructing the apparatus so that the heater of the heating means is divided into multiple segments, also in the conveyance direction, the temperature of each of which is capable of being independently controlled, and that, when different sized heat-developing photosensitive film sheets are conveyed, the control means controls the conveyance of the heat-developing photosensitive film so that the foregoing and following heat-developing photosensitive sheets of film can not simultaneously be in contact with any segmented heater section in the conveyance direction, the following different sized heat-developing photosensitive film sheet can be conveyed and heated after the temperature of each segmented heater has been suitably controlled for the following sheet of heat-developing photosensitive film.

In the above case, the heating means divided into multiple segments can be constructed as fixed plate heaters and the auxiliary means can be constructed as opposed rollers installed opposite to the plate heaters.

The heat-developing method according to the present invention includes a step of forming a latent image on a conveyed sheet of heat-developing photosensitive film and a step of heating and developing the sheet of heat-developing photosensitive film with a latent image formed thereon while conveying it, by a heater which is divided into multiple segments, in the direction perpendicular to the conveyance direction, each segment of which is capable of independently controlling the temperature, wherein the sheets of heat-developing photosensitive film are so conveyed that different sized heat-developing photosensitive film sheets can not simultaneously be in contact with any of the multiple segmented heaters.

With this heat-developing method, the temperature distribution across the width direction can be controlled to become uniform by independently controlling the multiple segmented heaters corresponding to film passage phase. When a sheet of heat-developing photosensitive film of some size is heated by segmented heaters and then a different sized heat-developing photosensitive film sheet is conveyed to the heater section, the conveyance of the sheet of film is so controlled that the foregoing and following sheet of heat-developing photosensitive film can not simultaneously be in contact with any segmented heater, and hence the following different sized sheet of heat-developing film can be conveyed and heated after the temperature of each heater section has been suitably controlled. Accordingly, even when the sheet size of heat-developing photosensitive film is changed, a specific quantity of heat can always be supplied to the heat-developing photosensitive film and stable finished image density can be maintained.

In the above heat-developing method, when different sized sheet of heat-developing photosensitive film are conveyed, conveyance of a different sized sheet of following film into the heating means is temporary stopped until the trailing edge of another sized sheet of foregoing film has been detached from the heating means, and hence the different sized sheet of following heat-developing photosensitive film can be conveyed and heated after the temperature of each segmented heater has been suitably controlled.

In the above heat-developing apparatus and heat-developing method, when the upstream heat-developing photosensitive film is controlled to stand by, due to a change of the film size, this stand-by time T can theoretically be constantly defined by the following equation in which the heater section length is L and the conveyance velocity is V, irrespective of the heat-developing time setting, type of film sheet, whether or not there has been a change of the film sheet size after continuous processing and heating size pattern to be changed to.
T=L/V

According to the heat-developing apparatus and heat-developing method of the present invention, a specific quantity of heat can be always supplied to the heat-developing photosensitive material, which is conveyed while being heated, and stable finished image density can be maintained by using a heating method where the heating area is divided into multiple heater patterns corresponding to film sheet passage phases through a heating means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments for realizing the present invention are described below, using figures.

The First Embodiment

FIG. 1is a front view showing major portions of the heat-developing apparatus according to the first embodiment.FIG. 2is a schematic figure showing the exposure section of the heat-developing apparatus inFIG. 1.

As shown inFIG. 1, heat-developing apparatus100is composed of supply section110incorporating first and second loading sections11and12for loading a package containing a specified number of sheets of heat-developing photosensitive material, i.e. heat-developing photosensitive film (hereinafter, sometimes simply called “film”) and conveying section5for conveying successive sheets of film one after another for exposure and development, exposure section120which exposes the film supplied from supply section110and which forms a latent image on the film, heat-developing section130for heat-developing the film with a latent image formed thereon, and cooling and conveying section150including densitometer200for measuring the image density of the developed film and also for obtaining image density information, and sets of conveying rollers144A.

Different sized film sheets are loaded each into first and second loading sections11and12of supply section110, from which the film sheets are sequentially conveyed either from first loading section11or second loading section12in arrowed direction (1) inFIG. 1by conveying section5and paired conveying rollers139,140and141, which convey individual sheet of film downward to exposure section120.

Next, the film is conveyed horizontally in arrowed direction (2) and, while sub-scanning conveyance of the sheet of film is conducted by paired conveying rollers142, a laser beam is irradiated onto it by exposure section120and a latent image is formed on the film.

The film is next conveyed in arrowed direction (3) by paired sets of conveying rollers146,145,144and143, which convey the film sheet carrying a latent image formed thereon upward to heat-developing section130.

Then, the latent image on the film is visualized in the heat-developing section130, conveyed further in arrowed direction (4) by paired sets of conveying rollers144A, and then passes through cooling and conveying section150, after which it is discharged into discharge section160. Paired conveying rollers139,141,142,146,145,144and143are driven to rotate by motor151(FIG. 5).

The exposure section will now be described. As shown inFIG. 2, exposure section120employs laser beam L to form a latent image on film sheet F, wherein laser beam L the intensity of which has been modulated based on image signals S is deflected through rotating polygonal mirror113so as to carry out main-scanning on film sheet F, and also film sheet F is moved relative to laser beam L in a direction substantially perpendicular to the main scanning direction so that sub-scanning is also conducted on film sheet F.

The detailed structure of exposure section120is described hereunder. InFIG. 2, image data outputted from external image signal output device121is received via the Internet and image signals S, i.e. digital signals of the image data are converted into analog signals by D/A converter122and then inputted to modulator123. Modulator123controls driver124of laser light source110abased on the above analog signals so that the modulated irradiating laser beam L is emitted from laser light source110a.

Laser beam L irradiated from laser light source110ais transmitted through lens112and then, after being converged only in the vertical direction through cylindrical lens115, enters rotating polygonal mirror113, rotating in arrowed direction A′ inFIG. 2, as a line image perpendicular to the drive axis of the mirror. Rotating polygonal mirror113reflects and deflects laser beam L in the main scanning direction, and deflected laser beam L passes through fθ lens114, including a cylindrical lens composed of two combined lenses. Then the beam is reflected by mirror116located according to the main scanning direction in the light path so as to carry out main-scanning repeatedly in arrowed direction X on scanning surface117of film sheet F, which is being conveyed (sub-scanned) in arrowed direction Y by paired conveying rollers142. In short, entire scanning surface117of film sheet F is scanned by laser beam L.

The cylindrical lens of fθ lens114is designed to converge incident laser beam L on scanning surface117of film sheet F only in the sub-scanning direction, and the distance from fθ lens114to the scanning surface is equal to the focal length of the whole fθ lens114. Since exposure section120is provided with fθ lens114, including the cylindrical lens, and mirror116, and laser beam L is once converged only in the sub-scanning direction by rotating polygonal mirror113as explained above, the scanning position of laser beam L will not shift in the sub-scanning direction but equally pitched scanning lines can be formed on scanning surface117of film sheet F even if inclination of the face or an axial offset is caused on rotating polygonal mirror113. Compared to a galvanometer mirror or other optical polarizers, rotating polygonal mirror113has the advantage of excellent scanning stability. Accordingly, a latent image is formed on film sheet F based on image signals S.

Heat-developing section130for heating film sheet F is described below, usingFIGS. 1,3and4.FIG. 3is a schematic front view showing the major portions of heat-developing section130inFIG. 1.FIG. 4is a schematic plan view showing the construction of the segmented heater, viewing the interior surface from the exterior circumference of the heating drum inFIG. 3.

As shown inFIGS. 1 and 3, heat developing section130employs heating drum14as a heating member which heats film sheet F while it is adhered to the drum. By keeping the temperature of film sheet F above a prescribed minimum heat development temperature for a prescribed heat development time, heating drum14functions to visualize the latent image on film sheet F. Here, the minimum heat development temperature is the minimum temperature, for example 95° C. in which a latent image formed on film sheet F starts to develop. On the other hand, heat development time is the duration during which the temperature of film sheet F is maintained above the minimum heat development temperature to obtain desired development characteristics of the latent image on film sheet F. It is preferable that film sheet F can not be heat-developed substantially below 40° C.

As also shown inFIGS. 1 and 3, around the exterior of heating drum14, a plurality of rotatable opposed rollers16(auxiliary means), with a smaller diameter compared to heating drum14, are installed, as guiding members and pressing members, and face the circumferential surface of heating drum14and further opposed rollers16are arranged parallel to the axis of heating drum14.

As shown inFIGS. 1 and 3, heating drum14is equipped with cylindrical aluminum sleeve36and heater32as a heat source adhered on the interior surface of sleeve36. Further, on the outer surface of heating drum14, an elastic layer and a smooth surface layer are formed. By controlling electrical current supplied to heater32, heating drum14is heated to a prescribed temperature.

Motive force of micro step motor155(FIG. 5) is transmitted to shaft22to rotate heating drum14, whereby the film sheet is pinched between the circumferential surface of heating drum14and opposed rollers16and transported while being heated in direction (3) inFIG. 1while opposed rollers16press film sheet F against heating drum14.

Heater32formed as a segmented heater pattern on the inner surface of heating drum14as shown inFIG. 4, is composed of segmented heaters32a,32b,32c,32dand32e, which are arranged by dividing the surface into 5 sections in width direction W perpendicular to the film conveyance direction (3) which is the circumferential direction of the drum. Central segmented heater32cis the widest in width direction W and is structured so that segmented heaters32band32dadjacent to segmented heater32care wider than segmented heaters32aand32eat both ends of the drum.

Thermal sensors33a,33b,33c,33dand33eare located on the circumferential surface of heating drum14corresponding to each of segmented heaters32a-32eas shown inFIG. 4. These sensors detect the temperature of each drum area corresponding to each of segmented heaters32a-32efor independent temperature control of each of segmented heaters32a-32ebased on respective detected temperatures. Thermal sensors33a-33eare structured of common thermocouples or temperature thermistors, or the like.

Segmented heaters32a-32eheat the widest drum area G in width direction W inFIG. 4, and drum area G corresponds to 17 inches of, for example, a 14×17″ size sheet. On the other hand, segmented heaters32b,32cand32dheat drum area H, which is narrower than drum area G in width direction W, and drum area H corresponds to 10 inches of an 8×10″ size sheet. For example, when drum area H is heated for development of an 8×10″ size sheet, segmented heaters32band32dare controlled to a lower temperature than that of drum area G corresponding to a 14×17″ size sheet. Further, both outer segmented heaters32aand32eare not energized or controlled to a lower temperature than segmented heaters32band32d. As mentioned above, by controlling individually energizing of a plurality of segmented heaters32a-32ecorresponding to the film passage phase such as drum areas G or H, it becomes possible to control temperature distribution on heating drum14in the width direction to become uniform in a relatively short time.

Further, light transmission type photosensor159is installed to detect the leading edge and subsequently the trailing edge of the film sheet upstream of paired conveying rollers143located at the most downstream point of the conveying means to feed the film sheet to heating drum14and it detects the leading edge and subsequently the trailing edge of the film sheet fed in film conveyance direction (3). This detection enables motor151(FIG. 5) to control driving the upstream side conveying system, including paired conveying rollers143.

Next, the control system of the heat developing apparatus inFIG. 1will be explained referring toFIG. 5, which is a block diagram showing the controlling system of the heat developing apparatus inFIG. 1.

Controller152is composed of a central processing unit (CPU) and conducts the total control of the apparatus. As shown inFIG. 5, controller152controls electrical current supplied to segmented heaters so as to maintain the temperature of each drum area via each respective heater to a set temperature, based on the temperatures detected by thermal sensors33a-33e. Controller152further controls conveying section5and paired conveying rollers139to convey a film sheet of the corresponding size from loading section11or12, based on the film size information, included in supplementary information of image data transferred from exterior image signal output device121, shown inFIGS. 2 and 5, to heat developing apparatus100.

Controller152judges that the film sheet size has been changed, based on the film size information attached to the received image data. In the case of a change of film sheet size, when photosensor159detects the leading edge of film sheet F2, as shown inFIG. 3, controller152stops motor151and controls following film sheet F2to stand by while pinched between paired conveying rollers143for example, until the foregoing film sheet F1is detached from heating drum14.

Based on the rotation speed of heating drum14driven by micro step motor155and the diameter of heating drum14, stand-by time T, until the trailing edge of the foregoing film sheet F1is detached from heating drum14, is calculated, and so controlled that after stand-by time T has elapsed after the conveyance starting time of the trailing edge of foregoing film sheet F1on heating drum14, controller152controls conveyance of following film sheet F2to heating drum14by paired conveying rollers143, as well as conducting temperature control of segmented heaters32a-32ecorresponding to the film sheet size.

Stand-by time T can be theoretically determined by an equation T=L/V, where the circumferential length of heating drum14is L (shown inFIG. 3) and the conveying speed is V, regardless of heat development temperature setting, the type of the film, whether or not there has been a size change after continuous processing or a change of size pattern. Practically, it is preferable to be T+α in consideration of inherent differences among the apparatuses such as the conveying speed or the diameter of the drum.

Next, the operation of heat developing apparatus100inFIGS. 1-5will be explained referring to the flowchart ofFIG. 6.

Initially, when image data, outputted from an exterior image signal output device121shown inFIGS. 2 and 5, are inputted into heat developing apparatus100(S01), a sheet of film of the size corresponding to the film size information included in the supplementary information of the image data, is conveyed from loading section11or12by conveying section5and paired conveying rollers139,140,141and142(S02), and the film sheet is exposed to form a latent image based on image signals S of the image data (S03).

Next, as well as the sheet of film on which a latent image has been formed is conveyed by paired rollers146,145and144(S04), whether the film sheet size has been changed or not is judged compared to previously developed film sheet F1as shown inFIG. 3, based on the film size information included in the supplementary information of the image data (S05). If the film sheet size has been changed, as shown inFIG. 3, when photosensor159detects the leading edge of following film sheet F2which has been conveyed near paired conveying rollers143(S04), motor151is stopped to stop film conveyance while pinching the leading edge of film sheet F2between paired conveying rollers143and controlled to stand by in this state (S07).

Next, the conveyance starting time of the trailing edge of foregoing film sheet F1on heating drum14is determined based on the time when photosensor159detects the trailing edge of foregoing film sheet F1, and whether or not the foregoing film sheet has been detached from heating drum14is judged based on whether or not the stand-by time has elapsed since the starting time (S08). If stand-by time T has elapsed, temperature control of each heater32a-32eis conducted to correspond to the size of following film sheet F2(S09), after which following film sheet F2is conveyed to heating drum14by paired conveying rollers143(S10).

The following film sheet F2is conveyed while heated in heat developing section130to visualize the latent image by heat development (S11) and is further conveyed while cooled in cooling and conveyance section150(S12) and discharged to discharge section160(S13).

As mentioned above, according to heat developing apparatus100inFIGS. 1-6, when a different sized sheet of film F2is conveyed due to a change of film sheet size after foregoing film sheet F1of a prescribed size is heated by segmented heaters32a-32e, so as to prevent two sequential sheets of film F1and F2from being simultaneously in contact with each of segmented heaters32a-32e, after the foregoing film sheet has been detached from heat drum14, following film sheet F2is conveyed to the heating drum for heat development as well as temperature control via segmented heaters32a-32eis conducted to suit the size of the following sheet of film. Therefore, in the case of a change of film sheet size, the prescribed heat can be provided to each following different sized sheet of film to obtain uniform density of the finished film sheet.

A detailed example of the segmented heaters illustrated inFIG. 4is also shown inFIG. 9and the detailed example of segmented heaters inFIG. 9are arranged by dividing the drum surface into five sections in width direction W. The width of middle heater (1) is 215±5 mm, the width including middle heater (1) and both adjacent heaters (2) and (3) is 354 mm, and each width of heaters at both ends (4) and (5) is 25±2 mm. A 14 inch width (354 mm) film sheet such as a 14×17″ size film sheet is positioned to correspond to the total width of heaters (1), (2) and (3), and a 10 inch width (252 mm) film sheet such as a 10×12″ size film sheet is positioned to correspond to the width including the total width of heater (1) and partial width of heaters (2) and (3), and further an 8 inch (201 mm) size film sheet such as an 8×10″ size film sheet is positioned to correspond to the width of heater (1). The relationship between the position of each segmented heater and that of film sheet of each size is arranged as shown inFIG. 9, and by controlling electric current supplied to each heater (1)-(5), quick resetting of uniform temperature distribution in the width direction W corresponding to each film sheet size can be realized.

The Second Embodiment

FIG. 7is a schematic side view of the heat developing apparatus of the second embodiment.FIG. 8is a schematic plan view of the segmented heaters.

As shown inFIG. 7, heat developing apparatus300is a combination of first heating section210, second heating section220and the third heating section230. First heating section210is positioned obliquely to convey the film sheet obliquely upward, the second heating section220is positioned vertically to convey the film sheet upward and the third heating section230is positioned obliquely to convey the film sheet obliquely upward so that as a whole they basically form a substantial arc shape.

In heat developing apparatus300inFIG. 7, paired conveying rollers161are located upstream of first heating section210, and further, exposure section120, being the same as inFIG. 2is located upstream of paired conveying rollers161. In exposure section120, by means of applying main scanning of laser beam L onto the sheet of film in the perpendicular direction, while sub-scanning conveyance in conveying direction J is conducted to film sheet F, a latent image is formed on film sheet F based on the image data. Paired of conveying rollers161feed film sheet F, which has been conveyed in horizontal conveying direction J, into first heating section210.

Reflective type photosensor162is located so as to detect the leading edge and the trailing edge of the sheet of film near the upstream side of paired conveying rollers161. On the upstream side of exposure section120, a prescribed sized film sheet can be fed toward exposure section120from plural loading sections (not illustrated) in which film sheets of different sizes are loaded the same as in the first embodiment.

First heating section210, second heating section220and third heating section230are opposed by a plurality of auxiliary rollers240,250and260respectively to convey film sheet F in the directions of arrows “a” (obliquely upward), “b” (vertically) and “c” (obliquely upward) consecutively as shown inFIG. 7. Further each heating section210,220and230has guide surface170, which has a straight or curved surface in the conveyance direction and a concave surface in the direction perpendicular to the conveyance direction and internal sheet-shaped heaters211,212and213.

Heater211of heating section210has a segmented heater pattern as shown inFIG. 8and is structured of segmented heaters211a,211b,211c,211dand211ewhich are arranged by dividing the surface into 5 sections in width direction “w” perpendicular to film conveyance direction “a”. Middle segmented heater211cis the widest in width direction “w”, and segmented heaters211band211dadjacent to segmented heater211care wider than segmented heaters211aand211eon both ends of heater211.

A thermal sensor is located to correspond to each of segmented heaters211a-211eof heating section210, whereby temperature of the heating area corresponding to each segmented heater is detected, and the temperature of each segmented heater211a-211ecan be independently controlled based on these detected temperatures.

Segmented heaters211a-211eheat the widest heating area “g” in width direction “w” so that the heating area “g” corresponds to 17 inches of for example a 14×17″ sized sheet of film. On the other hand, segmented heaters211b,211cand211dheat heating area “h”, which is narrower than heating area “g” in width direction “w” and corresponds to 10 inches of an 8×10″ size sheet. For example, when heating area “h” is heated for development of an 8×10″ size sheet, segmented heaters211band211dare controlled to have lower temperature than in the case of heating area “g” corresponding to a 14×17″ size sheet, and therefore, both outer segmented heaters211aand211eare not energized or are controlled to have a lower temperature than segmented heaters211band211d. As mentioned above, by individually energizing to a plurality of segmented heaters211a-211ecorresponding to film passage phase such as heating areas “g” or “h”, it becomes possible to control temperature distribution in heating section210across the width to become uniform in a relatively short time.

Second heating section220and third heating section230are structured the same as first heating section210, and each of the heaters is also controlled individually, and further, first, second and third heating sections210,220and230also have their temperatures independently controlled.

Each set of auxiliary rollers240,250and260is driven by a motor (not illustrated) to convey film sheet F in the conveyance directions “a”, “b” and “c” while pressing film sheet F against each heating section210,220and230. Film sheet F sent from third heating section230is fed in horizontal direction “d” and is discharged by paired conveying rollers270.

Heat developing apparatus300inFIG. 7is controlled by a controlling system similar to the one inFIG. 5and is operated basically the same as shown inFIG. 6. First, image data are inputted into heat developing apparatus300from an exterior apparatus, and a sheet of film, of the size corresponding to the film size information included in the supplementary information of the image data, is conveyed from a loading section and exposed to form-a latent image based on image signals S of the image data in exposure section120.

Next, as the sheet of film, on which a latent image has been formed, is conveyed, whether the film sheet size has been changed or not is judged compared to the previously developed sheet of film based on the film size information included in the supplementary information of the image data. If the film sheet size has been changed, when photosensor162detects the leading edge of film sheet F2which has been carried to near paired conveying rollers161, as shown inFIG. 7, motor151is stopped to stop film conveyance while pinching the leading edge of the film sheet between the paired conveying rollers161and is controlled to stand by in this state.

Next, the conveyance starting time of the trailing edge of the foregoing film sheet in heating section is obtained based on the time when photosensor162detects the trailing edge of the foregoing film sheet, and whether or not the foregoing film sheet has been detached from first heating section210is judged based on whether or not the stand-by time has elapsed since the starting time. If stand-by time T has elapsed, temperature control of each heater211a-211eof first heating section210is conducted to suit the size of the following film sheet and the following film sheet is conveyed to first heating section210by paired conveying rollers161.

Similarly, after the trailing edge of the foregoing film sheet has passed second heating section220, temperature control of second heating section220is conducted to suit the size of the following film sheet and the following film sheet is conveyed there, and subsequently to third heating section230after the trailing edge of the foregoing film sheet has passed there, where temperature control of the same manner as in the previous heating sections is conducted. After having been heated for heat development, the film sheet is then discharged by paired conveying rollers270in horizontal direction “d”.

Stand-by time T mentioned above, can be determined from film conveying speed of auxiliary rollers240and the length of heating section210in conveyance direction “a”. The film sheet is conveyed at the same speed also in heating sections220and230. The length of each heating section210,220and230in each conveyance direction “a”-“c” is identical. Accordingly, by conveying the following film sheet after the above stand-by time T has elapsed, there is no possibility for two sequential film sheets to be simultaneously in contact with each of three heating section210,220and230.

In the case of the second embodiment, it is preferable to set extra time a to be a little longer in consideration of inherent differences among length of each heater L1, L2and L3in the film sheet conveyance path. Further, in the case that the length L1, L2and L3are obviously different, stand-by time T needs to be determined by the longest length of the three.

As mentioned above, according to heat developing apparatus300inFIGS. 7 and 8, when a different sized film sheet is conveyed due to a change of sheet size after the foregoing film sheet of a prescribed size is heated by segmented heaters211a-211eof first heating section210, so as to prevent two sequential film sheets from being simultaneously in contact with segmented heaters211a-211e, after the foregoing film sheet has been detached from first heating section210, the following film sheet is conveyed into first heating section210for heating as well as temperature control, via segmented heaters211a-211eto suit the size of the following film sheet. The following film sheet is fed into second heating section220, and further third heating section230for heating at similar intervals avoiding being heated together with the foregoing film sheet in the same heating section and temperature control of the segmented heaters of each heating section can be conducted. Therefore, in the case of a change of film sheet size, prescribed heat capacity can be provided to the following different sized film sheet to obtain uniform image density of the finished film sheet.

The best practical embodiments are explained above, however the invention is not limited to these and the embodiments can be modified within the range of the technical theory of this invention. For example, the number of the film loading sections is two inFIG. 1, but could also be three or more. Also, three or more loading sections can be similarly installed inFIG. 7. InFIGS. 3 and 7, although light-transmission type photosensors159and162are employed, light-reflective type photosensors can be employed.

Further, inFIGS. 3 and 7, to prevent sequential sheet of film of different sizes from existing in the same heating section at the same time, the conveyance interval is controlled by the stand-by time, however this invention is not limited to this, for example, by employing a photosensor near the exit of film sheet from heating drum14inFIG. 3(a photosensor is located between heating sections210and220inFIG. 7), the photosensor can detect that the trailing edge of the film sheet is detached from heating drum14or heating section210.