Patent Publication Number: US-6213593-B1

Title: Image-forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image-forming apparatus capable of forming an image by applying an image-forming solvent appropriately on an image-recording material such as a light-sensitive material or an image-receiving material. 
     2. Description of the Related Art 
     Image-forming apparatuses, which record images by using two types of image-recording materials such as a light-sensitive material and an image-receiving material, are known. 
     The image-forming apparatus of this type includes therein an image-forming solvent application section having a tank for storing an image-forming solvent to be applied to a light-sensitive material, and a thermal development-transfer section including a heating drum and a pair of endless pressure belts adapted to rotate with the heating drum in pressure-contact with the outer periphery of the heating drum. 
     The light-sensitive material, on which an image has been exposed while the material is held and conveyed through the image-forming apparatus, is immersed in the water stored in the image-forming solvent tank of the image-forming solvent application section. After being coated with water in this way, the light-sensitive material is sent into the thermal development-transfer section. The image-receiving material is also sent into the thermal development-transfer section in a manner similar to the light-sensitive material. 
     In the thermal development-transfer section, the light-sensitive material coated with water is superposed with the image-receiving material, and the superposed light-sensitive material and image-receiving material are wound in close contact on the outer periphery of the heating drum. Further, the two materials are held and conveyed between the heating drum and an endless pressure belt. The light-sensitive material thus is thermally developed, while at the same time, the image is transferred to the image-receiving material so as to form (record) a predetermined image on the image-receiving material. 
     After the light-sensitive material is immersed in and coated with the water which is provided as an image-forming solvent in the tank, the water that has contacted the light-sensitive material still remains in the tank. As a result, bacteria propagate in the tank by using the slight amount of organic materials, which has eluted from the light-sensitive material, as a source of nutrition. Consequently, the water is liable to be contaminated, which may deteriorate both the image-forming apparatus and the image quality. 
     A possible solution to this drawback is to keep the water supplying elements such as the tank out of contact with the light-sensitive material and to eject and apply water drops to the light-sensitive material from the water supply. The mere ejection of water drops, however, causes uneven application of atomized water to the light-sensitive material, with the result that the portions of the water drops contacting each other coalesce whereas there are portions of the light-sensitive material to which water is not applied, so that it is difficult to achieve uniform application. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned, an object of the present invention is to provide an image-forming apparatus capable of forming a uniform coat (film) of a solvent on an image-forming material. 
     According to one aspect of the present invention, there is provided an image-forming apparatus having an application device for applying an image-forming solvent onto an image-recording material, wherein the application device includes a plurality of nozzle holes for ejecting and applying the image-forming solvent onto the image-recording material, and the application device applies the image-forming solvent such that sets of three drops of the image-forming solvent, which are ejected from the plurality of nozzle holes and applied onto the image-recording material adjacent to one another, are applied onto the image-recording material so as to contact each other without any spaces therebetween. 
     The image-forming apparatus according to this aspect has the following effects. 
     The application device includes a plurality of nozzle holes for ejecting and applying the image-forming solvent to the image-recording material. Each set of three drops of the image-forming solvent, which are ejected from the nozzle holes and applied to the image-recording material adjacent to one another, are applied onto the image-recording material so as to contact each other without any spaces therebetween. 
     In this way, the image-forming solvent can be ejected from the nozzle holes of the application device and drops of the image-forming solvent can adhere to the image-recording material uniformly and without any spaces therebetween. Therefore, a uniform coat (film) of solvent can be formed on the image-recording material even by an application device which does not contact the image-recording material. 
     According to another aspect of the present invention, there is provided an image-forming apparatus having an application device for applying an image-forming solvent onto an image-recording material, wherein the application device includes a plurality of nozzle holes for ejecting and applying the image-forming solvent onto the image-recording material, the diameter D of each drop of the image-forming solvent adhering to the image-recording material is expressed as              D   =       2   ·   sin                       θ              [       3   ·   V       π   ·     {     2   -       3   ·   cos                   θ     +       (     cos                 θ     )     3       }         ]       1   /   3                 (   1   )                         
     where V is the volume of a drop of the image-forming solvent ejected from a nozzle hole and θ is the contact angle at which a drop of the image-forming solvent adheres to the image-recording material, and the pitch P between adjacent nozzle holes of the application device is less than or equal to (3)·D/2. 
     The image-forming apparatus according to this aspect has the following effects. 
     The application device includes a plurality of nozzle holes for ejecting and applying the image-forming solvent to the image-recording material, and the pitch P between adjacent nozzle holes is set to less that or equal to (3)·D/2. 
     The diameter D of each drop of the image-forming solvent attached to the image-recording material is obtained from the above equation (1). 
     Water drops can be made to uniformly adhere to the image-recording material without any spaces therebetween on the basis of the relation between the pitch P between adjacent nozzle holes and the diameter D of each drop of the image-forming solvent. In the same way as in the previously-described aspect of the invention, therefore, it is possible to form a uniform film (coat) of solvent on the image-recording material even by an application device which does not contact the image-recording material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic structural view of an image-recording device according to a first embodiment of the present invention. 
     FIG. 2 is a schematic structural view of an application device according to the first embodiment of the invention. 
     FIG. 3 is an enlarged perspective view showing an ejection tank according to the first embodiment of the invention. 
     FIG. 4 is a bottom view showing a state in which a light-sensitive material is conveyed under the ejection tank according to the first embodiment of the invention. 
     FIG. 5 is an enlarged view of the main portions in FIG.  4 . 
     FIG. 6 is a sectional view of the ejection tank according to the first embodiment of the invention. 
     FIG. 7 is a sectional view showing the manner in which water is ejected from the ejection tank according to the first embodiment of the invention. 
     FIG. 8 is a sectional view schematically showing the manner in which a water drop is ejected from a nozzle hole of the ejection tank and adheres to the light-sensitive material according to the first embodiment of the invention. 
     FIG. 9 is a diagram for explaining the positions of the nozzle holes of the ejection tank as projected on the light-sensitive material according to the first embodiment of the invention. 
     FIG. 10 is a plan view showing the light-sensitive material onto which water drops have been ejected from the nozzle holes of the ejection tank and applied according to the first embodiment of the invention. 
     FIG. 11 is an enlarged view schematically showing three water drops out of those which have adhered to the light-sensitive material to which water drops have been ejected and applied from the ejection tank according to the first embodiment of the invention. 
     FIG. 12 is an enlarged view of a thermal development-transfer section according to the first embodiment of the invention. 
     FIG. 13 is a diagram for explaining the positions of the nozzle holes of the ejection tank as projected on the light-sensitive material according to a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a schematic structural view of an image-recording apparatus  10  which is an image-forming apparatus according to a first embodiment of the present invention. 
     A light-sensitive material magazine  14  for accommodating a light-sensitive material  16  is disposed in a housing  12  of the image-recording apparatus  10  shown in FIG.  1 . The light-sensitive material  16  is taken up in a roll form in the light-sensitive material magazine  14  such that the light-sensitive (exposure) surface of the light-sensitive material  16  is directed to the left when the light-sensitive material  16  is withdrawn from the light-sensitive material magazine  14 . 
     A pair of nip rollers  18  and a cutter  20  are disposed in the vicinity of the light-sensitive material withdrawal opening of the light-sensitive material magazine  14 . The light-sensitive material  16  that has been withdrawn from the light-sensitive material magazine  14  by a predetermined length can be cut by this cutter  20 . The cutter  20  is a rotary type cutter including a fixed blade and a movable blade, for example, and can cut the light-sensitive material  16  with the movable blade moved vertically by a rotating cam or the like to mesh with the fixed blade. 
     A plurality of conveying rollers  24 ,  26 ,  28 ,  30 ,  32 ,  34  are arranged in that order downstream of the cutter  20  in the direction in which the light-sensitive material  16  is conveyed. A guide plate (not shown) is interposed between each pair of the conveying rollers. The light-sensitive material  16  cut to a predetermined length is conveyed first to an exposure section  22  disposed between the conveying rollers  24 ,  26 . 
     An exposure unit  38  is disposed at the left of the exposure section  22 . The exposure unit  38  includes three types of LDs (laser diodes), a lens unit, a polygonal mirror and a mirror unit (none of which are shown). A light beam C is emitted from the exposure unit  38  to the exposure section  22  to expose the light-sensitive material  16 . 
     Further, a U-turn section  40  for conveying the light-sensitive material  16  along a U-shaped curved path and a water application section  50  for applying an image-forming solvent are disposed above the exposure section  22 . In the present embodiment, water is used as the image-forming solvent. 
     The light-sensitive material  16  that has been conveyed upward from the light-sensitive material magazine  14  and exposed in the exposure section  22  is conveyed while being held between the conveying rollers  28 ,  30 , and thus is sent into the water application section  50  along the upper portion of the U-turn section  40  of the conveying path. 
     As shown in FIG. 2, an ejection tank  312 , which is a portion of a solvent application device  310  is disposed at the portion of the water application section  50  which opposes the conveying path A of the light-sensitive material  16 . 
     As shown in FIG. 2, a water bottle  332  for storing water to be supplied to the ejection tank  312  is disposed at the lower left of the ejection tank  312 . A water filter  334  is disposed above the water bottle  332 . The water bottle  332  and the filter  334  are connected by a water pipe  342  along which a pump  336  is disposed. 
     Further, a subtank  338  for storing water supplied from the water bottle  332  is disposed at the right of the ejection tank  312 . A water pipe  344  extends from the filter  334  to the subtank  338 . 
     When the pump  336  is activated, water is sent from the water bottle  332  to the filter  334 , and the water filtered through the filter  334  is supplied to the subtank  338  where it is stored temporarily. 
     A water pipe  346  for connecting the subtank  338  and the ejection tank  312  is arranged between the ejection tank  312  and the subtank  338 . The water sent by the pump  336  from the water bottle  332  through the filter  334 , the subtank  338 , and the water pipe  346  is filled into the ejection tank  312 . 
     A tray  340  connected to the water bottle  332  by a circulation pipe  348  is disposed under the ejection tank  312 . The water which overflows from the ejection tank  312  is collected in the tray  340  and returned through the circulation pipe  348  to the water bottle  332 . Further, the circulation pipe  348  extends so as to project into the subtank  338 , and is connected to the subtank  338 . The excess water stored in the subtank  338  is returned to the water bottle  332  through the circulation pipe  348 . 
     Further, as shown in FIGS. 4 and 6, a nozzle plate  322  formed by bending an elastically deformable, rectangular, thin plate is provided at a portion of the ejection tank  312  which is a portion of the wall surface of the ejection tank  312  and which opposes the conveying path A of the light-sensitive material  16 . 
     As shown in FIGS. 3 to  5 , the nozzle plate  322  has a plurality of nozzle holes  324  (several tens of μm in diameter, for example) arranged at regular spatial intervals in two staggered rows over the entire width of the light-sensitive material  16  linearly at an angle to the direction A in which the light-sensitive material  16  is conveyed. The water filled in the ejection tank  312  is released from and ejected toward the light-sensitive material  16  by way of the nozzle holes  324 . 
     As shown in FIG. 5, each of the nozzle holes  324  is formed in a circle having the same inner diameter of d, and therefore, water drops L of substantially the same volume can be ejected from each nozzle hole  324 . Further, sets of three adjacent nozzle holes  324  are arranged on the nozzle plate  322  in such a manner that the centers S of the three nozzle holes  324  are the vertices of an equilateral triangle. 
     As shown in FIGS. 2 and 3, an exhaust pipe  330  extends from the upper portion of the ejection tank  312  so as to provide communication between the outside and inside of the ejection tank  312 . Further, a valve (not shown) for opening and closing the exhaust pipe  330  is installed along the route of the exhaust pipe  330 . The opening/closing operation of this valve permits the interior of the ejection tank  312  to communicate with or be shut off from the exterior environment. 
     The end portions of the nozzle plate  322  positioned in the direction orthogonal to the longitudinal direction of the nozzle hole row formed by the plurality of nozzle holes  324  arranged linearly are, as shown in FIG. 6, bonded by an adhesive or the like to a pair of lever plates  320 . The nozzle plate  322  is thus adhesively coupled with the pair of lever plates  320 . The lever plates  320  are fixed to a pair of side walls  312 A of the ejection tank  312 , respectively, via narrow support portions  312 B formed under the side walls  312 A. 
     A pair of top walls  312 C contact each other and form the top side of the ejection tank  312 . Portions of these top walls  312 C protrude to the outer sides of the ejection tank  312 , and a plurality of piezoelectric elements  326  (three on each side in accordance with the present embodiment) serving as actuator means are adhered to the lower sides of the protruding portions of the top walls  312 C. The lower surfaces of the piezoelectric elements  326  are bonded to the outer ends of the lever plates  320  so as to be connected to the lever plates  320 . 
     The piezoelectric elements  326 , the lever plates  320  and the support portions  312 B form a lever mechanism. When the outer side ends of the lever plates  320  are moved by the piezoelectric elements  326 , the inner side ends of the lever plates  320  move in the opposite direction. The piezoelectric elements  326  are formed of laminated piezoelectric ceramics, for example, to ensure a greater axial displacement of the piezoelectric elements  326 . The piezoelectric elements  326  are connected to a power supply (not shown) to which voltage is applied at a timing controlled by a controller (not shown). The above-described valve for opening and closing the exhaust pipe  330  is also connected to the controller, and the opening and closing operation of the value is controlled by the controller. 
     The lever plate  320 , the side wall  312 A, the support portion  312 B and the top wall  312 C each form a portion of an integrated frame  314 . As shown in FIG. 6, a pair of the frames  314  are overlaid and screwed to each other by bolts (not shown). In this way, the outer frame of the ejection tank  312  is made up of a pair of the lever plates  320 , a pair of the side walls  312 A, a pair of the top walls  312 C and a pair of the support portions  312 B respectively arranged in opposed relations to each other. 
     As shown in FIGS. 3 and 4, a thin sealing plate  328  is bonded to the pair of the frames  314  at a position defined by each end pair of the frames  314  and each longitudinal end of the nozzle plate  322 . 
     Further, an elastic adhesive such as silicon rubber, for example, is filled, at the inner sides of the sealing plates  328 , to prevent water leakage from the gap defined between the sealing plates  328 , the longitudinal ends of the nozzle plate  322 , and the longitudinal ends of the frame pair  314 . The space in the ejection tank  312  thus is sealed by the elastic adhesive without adversely affecting the movement of the longitudinal ends of the nozzle plate  322 . Alternatively, the longitudinal ends of the ejection tank  312  may be sealed only by the elastic adhesive without using the thin sealing plates  328 . 
     When power is supplied to the piezoelectric elements  326  from a power supply, as shown in FIG. 7, the piezoelectric elements  326  extend so as to rotate the lever plates  320  around the support portions  312 B. Accordingly, the nozzle plate  322  is displaced while being deformed by the piezoelectric elements  326  via the lever plates  320  such that the central portion of the nozzle plate  322  is raised in the direction of arrow B. The deformation of the nozzle plate  322  increases the internal pressure of the ejection tank  312 , with the result that water drops L which are a small amount of water are collectively ejected linearly from the nozzle holes  324  which are aligned in two rows. 
     The water drops L can be continuously ejected from the nozzle holes  324  by supplying power to and extending the piezoelectric elements  326  repeatedly. 
     As shown in FIG. 8, the diameter D of each drop of water L on the light-sensitive material  16  is obtained from the following equation              D   =       2   ·   sin                       θ              [       3   ·   V       π   ·     {     2   -       3   ·   cos                   θ     +       (     cos                 θ     )     3       }         ]       1   /   3                 (   1   )                         
     where V is the volume of each drop of water L ejected from a nozzle hole  324  and θ is the contact angle at which the water drop L adheres to the light-sensitive material  16 . 
     The volume V of a drop of water L can be obtained from Graph 1 below showing the results of an experiment conducted by changing the conditions of the variation width (nozzle amplitude h) at points corresponding to the nozzle holes  324  at the time of displacement of the nozzle plate  322  by the piezoelectric elements  326 . In the data employed for this case, the diameter d of the nozzle hole  324  is given as 30 μm or 80 μm.                    
     Three water drops L ejected from the nozzle holes  324  adhere to the light-sensitive material  16  adjacent to each other without any space between them. 
     In other words, as shown in FIG. 11, the pitch which is the distance between centers S 1  of water drops L is equal to the pitch P which is the distance between centers S of adjacent nozzle holes  324 . As a result, if the pitch P is a value obtained from the equation given below, the three water drops L adhere to the light-sensitive material  16  closely to each other without any space therebetween.              P   ≦         3     2     ·   D             (   2   )                         
     Further, water is ejected at a proper timing conforming to the conveying rate of the light-sensitive material  16 , i.e., at the moment the nozzle holes  324  are positioned at points above the portions indicated by dotted lines  324 A. Then, water drops L are ejected when the nozzle holes  324  are positioned at the point above the portions indicated by solid lines  324 B in FIG.  9 . As a result, as shown in FIG. 10, water drops L adhere to the surface of the light-sensitive material  16  in such an arrangement that the lines connecting the centers S 1  of the water drops L form equilateral triangles. 
     Actually, however, the water drops L adhered to the surface of the light-material  16  may contact and interfere with each other. In such a case, the water drops L tend to coalesce in an attempt to reduce the surface energy. The water drops L thus overlaid immediately coalesce and are integrated with one another. 
     As shown in FIG. 1, an image-receiving material magazine  106  for accommodating the image-receiving material  108  is disposed at the upper left corner of the housing  12  in FIG.  1 . The image-forming surface of the image-receiving material  108  is coated with a dye-fixing material having a mordant. The image-receiving material  108  is taken up in roll form in the image-receiving material magazine  106  in such a manner that the light-receiving material  108  is withdrawn from the image-receiving material magazine  106  with the image-forming surface thereof facing down. 
     A pair of nip rollers  110  are disposed in the vicinity of the image-receiving material withdrawal opening of the image-receiving material magazine  106 . The nip rollers  110  nip the image-receiving material  108  out of the image-receiving material magazine  106 . The nipping of the image-receiving material  108  by the nip rollers  110  can also be cancelled. 
     A cutter  112  is disposed next to the nip rollers  110 . Similarly to the cutter  20  for the light-sensitive material described above, the cutter  112  is a rotary type cutter including a fixed blade and a movable blade, for example. The movable blade of the cutter  112  is moved vertically by a rotary cam or the like into engagement with the fixed blade to thereby cut the image-receiving material  108  withdrawn from the image-receiving material magazine  106  to a length shorter than the light-sensitive material  16 . 
     Conveying rollers  132 ,  134 ,  136 ,  138  and a guide plate (not shown) are disposed next to the cutter  112  so as to convey the image-receiving material  108  which has been cut to predetermined length toward the thermal development-transfer section  120 . 
     As shown in FIGS. 1 and 12, the thermal development-transfer section  120  includes a pair of endless belts  122 ,  124  vertically entrained in loops about a plurality of suspension rollers  140 . When any one of the suspension rollers  140  is driven to rotate, the endless belts  122 ,  124  entrained about the suspension rollers  140  begin to rotate. 
     A flat heating plate  126  is vertically disposed in the loop of the endless belt  122  so as to oppose the inner peripheral surface of the endless belt  122 . The heating plate  126  has disposed therein a linear heater (not shown) to heat the surface of the heating plate  126  to a predetermined temperature. 
     The light-sensitive material  16  is fed between the endless belts  122 ,  124  of the thermal development-transfer section  120  by the last conveying rollers  34  on the conveying path of the light-sensitive material  16 . The image-receiving material  108  is fed synchronously with the light-sensitive material  16 . The image-receiving material  108  is, by the last conveying rollers  138  on the conveying path of the image-receiving material  108 , fed in between the pair of endless belts  122 ,  124  and superposed with the light-sensitive material  16 , with the light-sensitive material  16  being conveyed a predetermined length ahead of the image-receiving material  108 . 
     The image-receiving material  108  is smaller in both width and length than the light-sensitive material  16 . The image-receiving material  108  and the light-sensitive material  16 , therefore, are overlaid on each other with the four peripheral sides of the light-sensitive material  16  extending beyond the periphery of the image-receiving material  108 . 
     The light-sensitive material  16  and the image-receiving material  108  overlaid by the endless belts  122 ,  124  in the manner described above are held and conveyed by the endless belts  122 ,  124  in this overlaid state. Once the overlaid light-sensitive material  16  and the image-receiving material  108  are completely accommodated between the endless belts  122 ,  124 , the endless belts  122 ,  124  stop rotating, so that the light-sensitive material  16  and the image-receiving material  108  are heated by the heating plate  126 . The light-sensitive material  16  is thus heated through the endless belt  122  and the heating plate  126  both while being conveyed and while in a stationary state. As the heating progresses, the movable dye is released and transferred from the light-sensitive material  16  to the dye fixing layer of the image-receiving material  108  to thereby form an image on the image-receiving material  108 . 
     A separation pawl  128  is disposed downstream of the endless belts  122 ,  124  in the direction in which the materials are supplied. The separation pawl  128  is adapted to engage with only the leading end portion of the light-sensitive material  16  held and conveyed between the endless belts  122 ,  124 . The leading end portion of the light-sensitive material  16  projecting from between the endless belts  122 ,  124  can thus be separated from the image-receiving material  108 . 
     Light-sensitive material delivery rollers  148  are disposed to the left (in FIG. 1) of the separation pawl  128 . The light-sensitive material  16  guided leftward by the separation pawl  128  can thus be fed further toward a waste light-sensitive material accommodation section  150 . 
     The waste light-sensitive material accommodation section  150  includes a drum  152 , on which the light-sensitive material  16  is wound, and a belt  154 , a portion of which is entrained around the drum  152 . The belt  154 , is also entrained about a plurality of rollers  156 . Due to the rotation of the rollers  156 , the belt  154  is turned thereby to rotate the drum  152 . When the light-sensitive material  16  is fed in while the belt  154  is driven by the rotation of the rollers  156 , the light-sensitive material  16  can be accumulated around the drum  152 . 
     Image-receiving material delivery rollers  162 ,  164 ,  166 ,  168 ,  170  are arranged in that order to convey the image-receiving material  103  leftward in FIG. 1 from under the endless belts  122 ,  124 . As a result, the image-receiving material  108  that has been delivered from the endless belts  122 ,  124  is conveyed by the material delivery rollers  162 ,  164 ,  166 ,  168 ,  170  into a tray  172 . 
     Operation of the present embodiment will be explained below. 
     In the image-recording apparatus  10  having the above-described structure, after the light-sensitive material magazine  14  is set in position, the nip rollers  18  are activated so as to withdraw the light-sensitive material  16 . As soon as the light-sensitive material  16  is withdrawn by a predetermined length, the cutter  20  is activated to cut the light-sensitive material  16  to a predetermined length, and the cut light-sensitive material  16  is conveyed to the exposure section  22  with the light-sensitive (exposure) surface thereof directed to the left in FIG.  1 . While the light-sensitive material  16  is passing through the exposure section  22 , the exposure unit  38  is activated so as to scan-expose an image on the light-sensitive material  16  located in the exposure section  22 . 
     When exposure has been completed, the light-sensitive material  16  thus exposed is conveyed to the water application section  50 . The water application section  50  delivers the light-sensitive material  16  toward the ejection tank  312  by driving the conveying rollers  32 , as shown in FIG.  4 . 
     The ejection tank  312  ejects water and applies the water to the light-sensitive material  16  fed along the conveying path A. The operation and effects at this time will now be explained. 
     First, the valve of the exhaust pipe  330  is closed by the controller. When water is to be atomized and ejected from the nozzle plate  322  in this state, voltage is applied to the piezoelectric elements  326  from a power supply controlled by the controller, so as to deform all of the piezoelectric elements  326  by extending all of the piezoelectric elements  326  at the same time. 
     When the piezoelectric elements  326  are deformed in this way, the displacement thereof is transmitted to the nozzle plate  322  via the pair of lever plates  320  rotating around the support portions  312 B, so that the nozzle plate  322  is displaced in such a way as to apply pressure to the water in the ejection tank  312 . As a result, the water filled in the ejection tank  312  is ejected while being atomized from the nozzle holes  324  as shown in FIG. 7, and can be made to adhere to the light-sensitive material  16  which is being conveyed. 
     The water can be applied to the entire surface of the light-sensitive material  16  by ejecting the water from the nozzle holes  324  a multiplicity of times at an arbitrary timing conforming with the conveying rate of the light-sensitive material  16 . 
     A plurality of the nozzle holes  324  for ejecting water are arranged in two rows over the entire width of the light-sensitive material  16  in the nozzle plate  322  provided at the ejection tank  312  as a portion of the wall of the ejection tank  312 . As described above, the volume V of each of the water drops L ejected from the nozzle holes  324  can be determined from the inner diameter of the nozzle hole  324  and the nozzle amplitude h. 
     Assuming that the pitch P between the nozzle holes  324  is a value in the range defined by the above equation, each of three water drops L which have adhered to the light-sensitive material  16  adjacent to each other have a diameter D. These water drops L, therefore, adhere to the light-sensitive material  16  so as to contact each other and without any space therebetween. 
     It is thus possible for the water drops L ejected from the nozzle holes  324  of the ejection tank  312  to adhere to the light-sensitive material  16  uniformly without any space therebetween, on the basis of the relation between the diameter D of the water drop L and the pitch P between adjacent nozzle holes  324 . Consequently, a uniform water film (coat) can be formed on the light-sensitive material  16  even in a case in which the light-sensitive material  16  does not contact the ejection tank  312 . 
     In other words, coating irregularities can be eliminated by arranging the nozzle holes  324  in such a manner as to make all of the water drops coalesce so as to form a uniformly-coalesced water film on the light-sensitive material  16  promptly after landing on the light-sensitive material  16 . 
     The water drops L are applied to the light-sensitive material  16  in such a manner that the centers S of the water drops L after landing on the light-sensitive material  16  constitute the vertices of equilateral triangles, respectively, and that the gravitational center of each equilateral triangle is fully covered by the water drops L. In this way, all of the water drops can be made to coalesce with a minimum amount of water. 
     As described above, a film (coat) of water can be formed uniformly on the light-sensitive material  16  without any deterioration of the image-recording apparatus  10  or the image quality which otherwise might be caused by the contamination of water. 
     Since the ejection tank  312  has nozzle holes  324  from which water is ejected, a smaller amount of water is required than with an application device which applies water to a light-sensitive material or the like by immersing the light-sensitive material in a tank filled with water. The light-sensitive material  16  thus can be dried in a shorter time. 
     Furthermore, since the ejection tank  312  has the plurality of nozzle holes  324  arranged over the entire width of the light-sensitive material  16  and water is ejected simultaneously from these nozzle holes  324  by a single displacement of the piezoelectric elements  326 , water can be applied over a wide area along the entire width of the light-sensitive material  16  by a single ejection. Consequently, the nozzle plate  322  need not be scanned on a two-dimensional plane, and water application to a larger area in a shorter time is made possible, thereby reducing the overall time required for water application. 
     Further, the lever plates  320  are coupled to the end portions of the nozzle plate  322  which end portions are at the direction perpendicular to the longitudinal direction of the rows formed by the nozzle holes  324 , and the nozzle plate  322  is coupled to the piezoelectric elements  326  through the lever plates  320 . As a result, the plurality of nozzle holes  324  can be collectively displaced stably by the same amount of displacement. Water can thus be applied more uniformly to the light-sensitive material  16 . 
     All that is required to manufacture the solvent application device  310  is to form a plurality of the nozzle holes  324  in the nozzle plate  322 . Therefore, there is no need for an integration technique, and the solvent application device  310  can be manufactured at a lower cost. 
     Further, when water is ejected from the nozzle holes  324  of the nozzle plate  322 , the amount of water in the ejection tank  312  is progressively reduced. Although the amount of water in the ejection tank  312  is successively reduced, the subtank  338  has the function of keeping the water level in the ejection tank  312  constant by refilling water thereto. Therefore, the water pressure in the ejection tank  312  during atomization operation is kept constant by the water supplied from the subtank  338 . Continuous water ejection is thus ensured. 
     Thereafter, the light-sensitive material  16 , to which water serving as an image-forming solvent has been applied by the water application section  50 , is fed between the endless belts  122 ,  124  of the thermal development-transfer section  120  by means of the conveying rollers  34 . 
     As the light-sensitive material  16  is scan-exposed, on the other hand, the image-receiving material  108  is withdrawn and conveyed by the nip rollers  110  from the image-receiving material magazine  108 . When the image-receiving material  108  is withdrawn by a predetermined length, the cutter  112  is activated to cut the image-receiving material  108  to a predetermined length. 
     After the cutting operation of the cutter  112 , the image-receiving material  108  thus cut is guided by the guide plate and conveyed by the conveying rollers  132 ,  134 ,  136 ,  138 . When the leading end portion of the image-receiving material  108  comes to be held by the conveying rollers  138 , the image-receiving material  108  is set in a standby state directly before the thermal development-transfer section  120 . 
     As the light-sensitive material  16  is fed between the endless belts  122 ,  124  by the conveying rollers  34  as described above, the image-receiving material  108  begins to be conveyed again. The image-receiving material  108  thus is fed integrally with the light-sensitive material  16  between the endless belts  122 ,  124 . 
     As a result, the light-sensitive material  16  and the image-receiving material  108  are superposed on each other, and while being heated by the heating plate  126 , are held and conveyed so that an image is formed on the image-receiving material  108  by thermal development and transfer. 
     Further, after the light-sensitive material  16  and the image-receiving material  108  are delivered from the endless belts  122 ,  124 , the leading end portion of the light-sensitive material  16 , which precedes the image-receiving material  108  by a predetermined length, engages with the separation pawl  128  so as to be separated from the image-receiving material  108 . The light-sensitive material  16  is further conveyed by the light-sensitive material delivery rollers  148  so as to be fed into and accumulated in the waste light-sensitive material accommodation section  150 . At this time, the light-sensitive material  16  is dried very quickly, and therefore no heater or the like is required to dry the light-sensitive material  16 . 
     On the other hand, the image-receiving material  108  that has been separated from the light-sensitive material  16 , is conveyed by the image-receiving material delivery rollers  162 ,  164 ,  166 ,  168 ,  170  and delivered into the tray  172 . 
     In the case of recording a plurality of image frames, the above-mentioned processes are repeated successively. 
     The image-receiving material  108  on which a predetermined image has been formed (recorded) by thermal development and transfer between the endless belts  122 ,  124  is delivered out from the endless belts  122 ,  124 . The image-receiving material  108  thus delivered is discharged to the exterior of the apparatus by being held and conveyed by the plurality of image-receiving material delivery rollers  162 ,  164 ,  166 ,  168 ,  170 . 
     The positions of the nozzle holes  324  of the ejection tank  312  relating to the second embodiment of the present invention, which positions are projected onto the light-sensitive material  16 , are illustrated in FIG.  13  and described hereinafter. The same component parts as those described in the first embodiment are designated by the same reference numerals respectively, and will not be described again. 
     As shown in FIG. 13, the nozzle plate  322  of the ejection tank  312  according to the present second embodiment is formed with a plurality of the linearly-aligned, water-ejecting nozzle holes  324  in a staggered fashion at regular spatial intervals in two rows at an angle to the direction A in which the light-sensitive material  16  is conveyed. 
     More specifically, the nozzle holes  324  are arranged in four rows and water drops L are repeatedly ejected at a timing shown by dotted lines  324 C and solid lines  324 D. This not only has the same effects as the first embodiment but also can improve the redundancy of atomization accompanying the ejection. 
     In other words, should any one of the nozzle holes  324  be clogged, other nozzle holes  324  can compensate for the clogging, and therefore no coalescence irregularities occur. 
     According to the first embodiment, the nozzle holes  324  are arranged in two rows at positions such that the lines connecting the centers S of a given set of three nozzle holes  324  form an equilateral triangle. The two nozzle hole rows, however, are not necessarily disposed at positions at which the lines connecting the centers S of a given set of three nozzle holes form an equilateral triangle. Instead, the two rows may be disposed at a distance from each other. Further, more than two rows of nozzle holes may be used. The actuator means can be driven a lesser number of times by increasing the number of nozzle hole rows. 
     The relation between the pitch P and the diameter D of the water drops L was explained by the critical value above. Actually, however, allowing for irregularities in the direction in which the water drops L fly and the tolerance in diameters of the water drops L, the nozzle holes  324  can be arranged more closely (densely) than in the above-described embodiments to ensure that all of the water drops coalesce when the water drops L having a minimum diameter fly in the most irregular directions. 
     The volume V of the water drop L in the first and second embodiments described above may be in the range of 0.00001 to 0.01 mm 3 , the contact angle θ may be 40 degrees or less, and the thickness of the water film formed on the light-sensitive material  16  may be in the range of 1 to 100 μm. The invention, however, is not limited to these values. 
     Further, each nozzle hole row may be arranged in a direction other than a direction perpendicular to the direction in which the material is conveyed, unlike in the above-described embodiments. For example, the nozzle holes may be arranged diagonally to the direction in which the material is conveyed. 
     In the above-described embodiments, the light-sensitive material  16  and the image-receiving material  108  are used as image-recording materials, water is applied by means of the ejection tank  312  of the solvent application device  310  to the light-sensitive material  16  after exposure thereof, the light-sensitive material  16  and the image-receiving material  108  are superposed, and thermal development and transfer are carried out. However, the present invention is not limited to the same, and water may be ejected toward and applied to the image-receiving material  108 . 
     Furthermore, another image-recording material in sheet or roll form may be used in place of the above-mentioned materials. Moreover, a solvent other than water may be used as the image-forming solvent. The present invention is applicable also to the application of a developer onto a photographic printing paper in a developing device, the application of water in a printing press, the coating machine, and the like. 
     It can thus be understood from the foregoing description that the image-forming apparatus according to the present invention has the great advantage that a uniform film can be coated on an image-recording material.