Patent Description:
In the related art, there is known a layer transfer device that includes a supply reel around which a multilayer film is wound and a wind-up reel that winds up the multilayer film from the supply reel. In a state where a sheet conveyed from a sheet conveying unit is overlapped with the multilayer film supplied from the supply reel, the layer transfer device transfers a transfer layer onto a toner image of the sheet (see, for example, Patent Literature <CIT>, <CIT>, <CIT>).

In such a layer transfer device, in particular the one known from <CIT>, after the sheet and the multilayer film are caused to pass a nip part of a heating roller and a pressing roller and to perform thermal transfer in a state where the sheet and the multilayer film are overlapped each other, the sheet and the multilayer film are conveyed along a direction of a tangent line of the heating roller at a downstream end of the nip part in a conveying direction. Further, when the multilayer film passes a peeling roller provided on the tangent line of the heating roller, the multilayer film which has been thermal transferred is peeled off from the sheet and is wound by the wind-up reel.

The sheet which passes the nip part of the heating roller and the pressing roller and which is conveyed in a tangent line direction tends to curl to conform to a shape of the heating roller. When the sheet curls, the sheet is to be partially peeled off from a contact surface shared with the multilayer film before reaching the peeling roller.

When such a force is applied before the sheet reaches the peeling roller, the transfer layer which is softened due to heating in the vicinity of the toner image may be pulled by the sheet and adhere to the sheet. As a result, an excess transfer layer is transferred around the toner image, so that so-called burrs may be generated, the transfer layer may be excessively transferred with respect to the toner image, and the transfer layer may be insufficient with respect to the toner image.

Therefore, an object of the present invention is to provide a layer transfer device capable of preventing action of a force of peeling a sheet from a multilayer film when the sheet passes from a nip part of a heating roller and a pressing roller to a peeling roller, and capable of transferring a transfer layer onto a toner image without causing excess or deficiency in a transfer portion.

In order to solve the problems described above, the present invention provides a layer transfer device that overlaps a multilayer film having a plurality of layers with a surface of a sheet on which a toner image is formed, the layer transfer device being configured to transfer at least one layer of the multilayer film onto the toner image, the layer transfer device including: a sheet conveying unit configured to convey the sheet; a supply reel around which the multilayer film is wound; a wind-up reel configured to wind up the multilayer film from the supply reel; a film transfer unit configured to perform transfer in a state where the multilayer film supplied from the supply reel is overlapped with the sheet conveyed from the sheet conveying unit; and a peeling roller disposed between the film transfer unit and the wind-up reel in a conveyance path of the multilayer film, the peeling roller contacting the multilayer film having passed the film transfer unit, the peeling roller being configured to peel off the multilayer film from the sheet when a conveying direction of the multilayer film having passed the film transfer unit is changed to a direction different from a conveying direction of the sheet due to the wind-up reel winding up the multilayer film.

The film transfer unit includes: a first roller provided at a position to contact the sheet; and a second roller provided at a position to contact the multilayer film, and the film transfer unit overlaps the sheet with the multilayer film and is configured to heat and press the sheet and the multilayer film at a nip part of the first roller and the second roller.

Further, a tangent line of the second roller at a downstream end of the nip part in the conveying direction of the sheet passes between a center of the second roller and a center of the peeling roller, and an angle formed by the tangent line and a film tension portion of the multilayer film tensed between the nip part and the peeling roller is <NUM> degrees to <NUM> degrees.

According to this configuration, since the tangent line of the second roller passes between the center of the second roller and the center of the peeling roller and the angle formed by the tangent line and the film tension portion is <NUM> degrees to <NUM> degrees, the sheet that is heated and pressed at the nip part of the first roller and the second roller and that curls along the shape of the second roller can be corrected by the multilayer film in the vicinity of an exit of the nip part.

Therefore, when moving from the nip part to the peeling roller, the sheet overlapped with the multilayer film is in close contact with the multilayer film and the peeling is not performed, and after the transfer layer thermally transferred at the nip part is sufficiently cooled, the multilayer film is peeled off from the sheet by the peeling roller. Therefore, image quality that edges are sharp and that burrs are few in a transfer portion can be obtained. In other words, a foil is transferred to a portion on the sheet where the toner image is formed and the foil is not transferred to a portion on the sheet where the toner image is not formed, and accordingly there is no excess transfer layer on an edge portion of the toner image and a good image quality can be obtained.

In the above-described layer transfer device, the first roller has lower hardness than the second roller, and since a surface of the first roller is recessed with respect to the second roller at the nip part so that the nip part can have a circular arc shape.

Accordingly, since the nip part is formed in the circular arc shape, the conveyance path of the sheet can be made in a curved shape. Therefore, since members close to the first roller and the second roller can be laid out in proximity to the first roller and the second roller, a size of the layer transfer device can be reduced.

For example, in the above-described layer transfer device, the first roller has a rubber layer on the surface of the first roller and the second roller is a rigid body having no rubber layer, and the rubber layer of the first roller can have JIS-A hardness of <NUM>° to <NUM>°. Alternatively, each of the first roller and the second roller has a rubber layer on respective surfaces, the rubber layer of the first roller has JIS-A hardness of <NUM>° to <NUM>°, and the rubber layer of the second roller can have JIS-A hardness of <NUM>° to <NUM>°.

The rubber layer can be made of silicone rubber.

In the above-described layer transfer device, the angle formed by the tangent line and the film tension portion can be <NUM> degrees to <NUM> degrees.

Accordingly, image quality that edges are cleaner in the transfer portion can be obtained.

In the above-described layer transfer device, the first roller is a pressing roller, and the second roller can be a heating roller.

Further, the first roller is driven, and the second roller can be rotated by rotation of the pressing roller.

In the above-described layer transfer device, a pair of conveying rollers configured to convey the sheet can be arranged downstream of the peeling roller, and a peripheral speed of the conveying roller can be made greater than a peripheral speed of the first roller.

Accordingly, since the sheet can be conveyed in a state where tension is applied to the sheet between the nip part of the first roller and the second roller and a nip part of the conveying rollers, the multilayer film can be peeled off cleanly at the time of peeling by the peeling roller. As a result, image quality that the edges are cleaner in the transfer portion can be obtained.

In order to solve the problems described above, the present invention provides an image forming apparatus including: the above-described layer transfer device, and an image forming unit configured to form the toner image on the sheet.

The layer transfer device includes a holding member sandwiching the sheet and the multilayer film with the peeling roller, and a distance from the holding member to the nip part of the conveying rollers is equal to or larger than a distance from a leading end of the sheet to a leading end of a range where the image forming unit is capable of forming the toner image on the sheet.

Accordingly, by providing the holding member that sandwiches the sheet and the multilayer film with the peeling roller, the leading end of the sheet from which the multilayer film is peeled off by passing the peeling roller can be prevented from floating in a direction of separating from the peeling roller, and vibration of the sheet due to the peeling can be suppressed.

Further, since the conveying roller can be spaced apart by a distance equal to or larger than the distance (leading end margin length) from the leading end of the sheet to be conveyed to a range (image forming region) where the image forming part is capable of forming the toner image on the sheet, the degree of freedom of the layout of the layer transfer device can be increased.

In order to solve the problems described above, the present invention provides an image forming apparatus including: the above-described layer transfer device, and an image forming part unit configured to form the toner image on the sheet.

In the layer transfer device, a distance from the peeling roller to the nip part of the conveying rollers is less than the distance from the leading end of the sheet to the leading end of the range where the image forming unit is capable of forming the toner image on the sheet.

Accordingly, since the distance from the peeling roller to the nip part of the conveying roller is less than the leading end margin length of the sheet, the multilayer film is peeled off from the image forming region of the sheet after the leading end of the sheet is nipped by the nip portion of the conveying rollers. Therefore, image quality that the edges are cleaner can be obtained.

According to the present invention, action of a force of peeling a sheet from a multilayer film when the sheet passes from a nip part of a heating roller and a pressing roller to a peeling roller can be prevented, and a transfer layer can be transferred onto a toner image without causing excess or deficiency in a transfer portion.

Embodiments of the present invention will be described in detail with reference to an appropriate drawing. In the following description, first, an entire configuration of a foil transfer device is briefly described, and thereafter a peripheral structure of a heating roller and a pressing roller will be described.

In the following description, directions will be described with directions shown in <FIG>. That is, a right side of <FIG> is set as "front", a left side of <FIG> as "rear", a front side of a paper surface of <FIG> as "left", and a back side of the paper surface of <FIG> as "right". Upper and lower sides of <FIG> are set as "upper" and "lower" respectively.

A foil transfer device <NUM> as an example of a layer transfer device is, for example, a device that, after an image forming apparatus such as a laser printer forms a toner image on a sheet, transfers a foil such as a gold foil onto the toner image of the sheet.

As shown in <FIG>, the foil transfer device <NUM> includes a main body housing <NUM>, a sheet tray <NUM> that is provided at a rear portion of the main body housing <NUM> and on which a sheet S such as a piece of paper or an OHP film is placed, a sheet supply port <NUM> through which the sheet S supplied from the sheet tray <NUM> passes, a sheet discharge port <NUM> that is provided at a front portion of the main body housing <NUM>, and a sheet discharge tray <NUM> on which the sheet S discharged through the sheet discharge port <NUM> is placed.

The main body housing <NUM> mainly includes, in an inner portion thereof, a sheet conveying unit <NUM> that conveys the sheet S along a conveyance path SP extending from the sheet supply port <NUM> to the sheet discharge port <NUM>, a film supply unit <NUM> that supplies a multilayer film F so as to overlap the multilayer film F with the sheet S conveyed from the sheet conveying unit <NUM>, and a film transfer unit <NUM> that heats and presses the sheet S and the multilayer film F in a state where the sheet S and the multilayer film F are overlapped each other.

The sheet conveying unit <NUM> mainly includes a sheet supply mechanism <NUM> that includes a plurality of pairs of rollers and that conveys the sheet S supplied through the sheet supply port <NUM> toward the film transfer unit <NUM>, and a pair of conveying rollers <NUM> that conveys the sheet S which has passed the film transfer unit <NUM> toward the sheet discharge port <NUM>.

The sheet conveying unit <NUM> conveys the sheet S placed on the sheet tray <NUM> one by one toward the film transfer unit <NUM> by the sheet supply mechanism <NUM> in a state where a surface (front surface) of the sheet S on which the toner image is formed is directed downward. The sheet conveying unit <NUM> guides the sheet S which passes the film transfer unit <NUM> and on which a foil is transferred toward the sheet discharge port <NUM> by the conveying rollers <NUM>.

The film supply unit <NUM> includes the multilayer film F, a supply reel <NUM>, a wind-up reel <NUM>, a support roller <NUM>, a peeling roller <NUM>, and a holding member <NUM>.

The multilayer film F has, on a tape-like support layer made of a polymer material, a release layer and a foil layer that serves as a transfer layer. The foil is a thin metal such as gold, silver, copper, or aluminum.

The multilayer film F is mainly made of a polymer material.

The supply reel <NUM> includes a rotatable supply shaft <NUM>, and the multilayer film F is wound around the supply shaft <NUM>.

The wind-up reel <NUM> includes a rotatable wind-up shaft <NUM>, and a leading end of the multilayer film F is fixed to the wind-up shaft <NUM>.

The wind-up reel <NUM> is rotationally driven by a drive part (not shown) provided in the main body housing <NUM>. When the wind-up reel <NUM> rotates, the multilayer film F wound around the supply reel <NUM> is drawn out, and the drawn-out multilayer film F is wound around the wind-up shaft <NUM>.

The support roller <NUM> is disposed downstream of the sheet supply mechanism <NUM> in a conveying direction of the sheet S and below the conveyance path SP of the sheet S. More specifically, in a conveyance path of the multilayer film F, the support roller <NUM> is disposed upstream of the film transfer unit <NUM> and between the supply reel <NUM> and the wind-up reel <NUM>.

The support roller <NUM> is a roller that guides the multilayer film F supplied from the supply reel <NUM> with the transfer layer directed upward so as to overlap with the sheet S conveyed from the sheet supply mechanism <NUM> with the toner image directed downward. The support roller <NUM> changes a conveying direction of the multilayer film F drawn out from the supply reel <NUM> and guides the multilayer film F to be substantially parallel to the conveyance path SP of the sheet S.

The peeling roller <NUM> is disposed downstream of the film transfer unit <NUM> in the conveying direction of the sheet S and below the conveyance path SP of the sheet S. More specifically, in the conveyance path of the multilayer film F, the peeling roller <NUM> is disposed downstream of the film transfer unit <NUM> and between the supply reel <NUM> and the wind-up reel <NUM>. The peeling roller <NUM> is a roller that contacts the multilayer film F having passed the film transfer unit <NUM>, and that changes the conveying direction of the multilayer film F having passed the film transfer unit <NUM> to a direction different from the conveyance path SP of the sheet S due to the wind-up reel <NUM> winding up the multilayer film F.

The multilayer film F which passes the film transfer unit <NUM> and which is conveyed in a state of being overlapped with the sheet S is guided in a direction different from a direction of the sheet S when passing the peeling roller <NUM>, and is peeled off from the sheet S.

The holding member <NUM> is disposed downstream of the film transfer unit <NUM> in the conveying direction of the sheet S and at a position facing the peeling roller <NUM> above the conveyance path SP of the sheet S.

The holding member <NUM> sandwiches the sheet S and the multilayer film F with the peeling roller <NUM>.

The film transfer unit <NUM> includes a pressing roller <NUM> serving as an example of a first roller and a heating roller <NUM> serving as an example of a second roller. The film transfer unit <NUM> overlaps the sheet S and the multilayer film F with each other, and heats and presses the sheet S and the multilayer film F at a nip part NP of the pressing roller <NUM> and the heating roller <NUM>.

The pressing roller <NUM> is disposed above the conveyance path SP of the sheet S and at a position to contact a back surface of the sheet S (a surface opposite the surface formed with the toner image).

The pressing roller <NUM> is a roller in which a cylindrical core metal <NUM> provided at a center portion thereof is covered with a rubber layer <NUM> made of silicone rubber. The rubber layer <NUM> has JIS-A hardness of <NUM>° to <NUM>°, and a thickness of the rubber layer <NUM> is <NUM> to <NUM>. The pressing roller <NUM> has a diameter of <NUM> to <NUM>. The JIS-A hardness conforms to ISO <NUM>-<NUM>.

Both end portions of the pressing roller <NUM> are rotatably supported by the main body housing <NUM>, and the pressing roller <NUM> is rotationally driven by a motor (not shown). When the pressing roller <NUM> is pressed against the heating roller <NUM>, the sheet S and the multilayer film F are held between the pressing roller <NUM> and the heating roller <NUM>, and the heating roller <NUM> is rotated by rotation of the pressing roller <NUM>.

The heating roller <NUM> is disposed below the conveyance path SP of the sheet S and at a position to contact the multilayer film F.

The heating roller <NUM> is a roller in which a heater (not shown) is disposed inside a metal tube formed in a cylindrical shape. The heating roller <NUM> has a diameter of <NUM> to <NUM>. The heating roller <NUM> is a rigid body having no rubber layer.

The pressing roller <NUM> has lower hardness than the heating roller <NUM>, and in a state where the pressing roller <NUM> is pressed against the heating roller <NUM>, a surface of the pressing roller <NUM> is recessed with respect to the heating roller <NUM>. Therefore, the nip part NP of the pressing roller <NUM> and the heating roller <NUM> has a circular arc shape by the recessed pressing roller <NUM>.

A rubber layer made of silicone rubber can be provided on a surface of the heating roller <NUM>. In this case, the rubber layer <NUM> of the pressing roller <NUM> has JIS-A hardness of <NUM>° to <NUM>° and the rubber layer of the heating roller <NUM> has JIS-A hardness of <NUM>° to <NUM>°, so that the hardness of the pressing roller <NUM> is relatively lower than the hardness of the heating roller <NUM>.

A thickness of the rubber layer of the heating roller <NUM> and the thickness of the rubber layer <NUM> of the pressing roller <NUM> are <NUM> to <NUM>.

In the foil transfer device <NUM> configured as described above, the sheet S which is placed on the sheet tray <NUM> with the front surface thereof directed downward is conveyed one by one toward the film transfer unit <NUM> by the sheet supply mechanism <NUM>.

Upstream the film transfer unit <NUM>, the sheet S conveyed along the conveyance path SP of the sheet S is overlapped with the multilayer film F supplied from the supply reel <NUM> along the conveyance path of the multilayer film F, and is conveyed to the film transfer unit <NUM> in a state where the toner image of the sheet S and the transfer layer of the multilayer film F are in contact with each other.

In the film transfer unit <NUM>, when the sheet S and the multilayer film F pass the nip part NP of the pressing roller <NUM> and the heating roller <NUM>, the sheet S and the multilayer film F are heated and pressed by the heating roller <NUM> and the pressing roller <NUM>, and the foil is thermally transferred onto the toner image.

After the foil is thermally transferred, the sheet S and the multilayer film F are conveyed to the peeling roller <NUM> in a state of being in close contact with each other. When the sheet S and the multilayer film F pass the peeling roller <NUM>, the conveying direction of the multilayer film F is changed to a direction different from the conveying direction of the sheet S, and thus the multilayer film F is peeled off from the sheet S.

The multilayer film F peeled off from the sheet S is wound around the wind-up shaft <NUM> of the wind-up reel <NUM>. Meanwhile, the sheet S from which the multilayer film F is peeled off is conveyed toward a nip part of the conveying rollers <NUM>.

Further, the sheet S having passed the conveying rollers <NUM> is discharged from the sheet discharge port <NUM> to the sheet discharge tray <NUM> in a state where the front surface on which the foil is transferred is directed downward.

Next, a configuration on a downstream side of the film transfer unit <NUM> will be described, which is a characteristic of the present invention.

As shown in <FIG>, the peeling roller <NUM> is disposed upward than a tangent line TL passing through the nip part NP of the pressing roller <NUM> and the heating roller <NUM>. More specifically, the tangent line TL of the heating roller <NUM> at a downstream end of the nip part NP of the pressing roller <NUM> and the heating roller <NUM> in the conveying direction of the sheet S passes between a rotation center 61A of the heating roller <NUM> and a rotation center 43A of the peeling roller <NUM>.

Further, a film tension portion FT of the multilayer film F conveyed along the conveyance path of the multilayer film F is tensed between the nip part NP and the peeling roller <NUM>, and forms an angle θ with the tangent line TL. The angle θ formed by the tangent line TL and the film tension portion FT is set within a predetermined range.

the peeling roller <NUM> is disposed such that the film tension portion FT is located upward than the tangent line TL, so that the sheet S, which passes the nip part NP of the pressing roller <NUM> and the heating roller <NUM> and is heated and pressed and is about to curl along a shape of the heating roller <NUM>, can be corrected by the multilayer film F in the vicinity of an exit of the nip part NP.

The holding member <NUM> sandwiches the sheet S, of which the curl is corrected, with the film tension portion FT and guides the sheet S. The sheet S and the multilayer film F which are in close contact with each other after passing the film transfer unit <NUM> are guided along the holding member <NUM>, and thus are conveyed to the peeling roller <NUM> in a state of being in close contact with each other without occurrence that a force acts to peel off the sheet S from the multilayer film F before the sheet S reaches the peeling roller <NUM>; meanwhile, the transfer layer softened by heating is sufficiently cooled.

The holding member <NUM> prevents the leading end of the sheet S, from which the multilayer film F is peeled off by passing the peeling roller <NUM>, from floating in a direction of separating from the peeling roller <NUM>, and also plays a role of suppressing vibration of the sheet S caused by the peeling.

The conveying rollers <NUM> rotate at a peripheral speed larger than a peripheral speed of the pressing roller <NUM>.

The conveying rollers <NUM> can be disposed at a position such that a distance from the holding member <NUM> to the nip part of the conveying rollers <NUM> is equal to or larger than a distance (hereinafter, referred to as "leading end margin length") from the leading end of the sheet S to be conveyed to a leading end of a range (image forming region) where an image forming apparatus is capable of forming the toner image on the sheet S. More specifically, the conveying rollers <NUM> can be spaced apart from the peeling roller <NUM> such that a distance D1 from a position, where the sheet S and the multilayer film F are sandwiched by a leading end portion of the holding member <NUM> and the peeling roller <NUM>, to the nip part of the conveying rollers <NUM> is equal to or larger than the leading end margin length of the sheet S.

In the foil transfer device <NUM> configured as described above, the curl of the sheet S having passed the film transfer unit <NUM> is corrected in the vicinity of the exit of the nip part NP of the pressing roller <NUM> and the heating roller <NUM>, and thereafter the sheet S is guided by the film tension portion FT and the holding member <NUM> and is conveyed in a state of being in close contact with the multilayer film F. Therefore, a force acts to peel off the sheet S from the multilayer film F before the sheet S reaches the peeling roller <NUM>, and while the sheet S moves from the nip part NP to the peeling roller <NUM>, the transfer layer of the multilayer film F is sufficiently cooled in a state of being in close contact with the toner image of the sheet S. Accordingly, the foil can be reliably transferred onto the toner image.

Thereafter, the leading end of the sheet S from which the multilayer film F is peeled off by passing the peeling roller <NUM> is conveyed toward the nip part of the conveying rollers <NUM>.

Further, since the peripheral speed of the conveying roller <NUM> is larger than the peripheral speed of the pressing roller <NUM>, the sheet S of which the leading end reaches the conveying roller <NUM> is conveyed in a state where tension is applied to the sheet S between the nip part NP and the nip part of the conveying rollers <NUM>. Meanwhile, since the multilayer film F which passes the peeling roller <NUM> and which is to be peeled off from the sheet S is peeled off from the sheet S that is in a state where tension is applied to the sheet S, the multilayer film F can be peeled off cleanly.

Next, a reason for determining the predetermined range of the angle θ formed by the film tension portion FT and the tangent line TL (experimental result) will be described.

The inventors of the present application conducted an experiment in which an angle θ, which is formed by a tangent line of a heating roller at a downstream end of a nip part of a pressing roller and the heating roller in a conveying direction of paper and a film tension portion of a multilayer film tensed between the nip part and a peeling roller, was variously changed to determine an angle range of θ at which generation of burrs in a transfer portion could be prevented and good image quality could be obtained.

Paper used in the experiment was Neenah Paper Exact Index (manufactured by Neenah Paper) with a basis weight of <NUM>/m<NUM>. In a foil transfer device used in the experiment, diameters of a pressing roller and a heating roller are both <NUM>, and a thickness of a rubber layer of the pressing roller is <NUM>. Measurement was performed in an environment with a temperature of <NUM> and a humidity of <NUM> %.

Specifically, a curl amount (input curl amount) of the paper at a time when a toner image was formed by a laser printer was measured, and then another curl amount (output curl amount) of the paper after a foil was transferred thereto by the foil transfer device was measured. Further, a paper curl ratio defined by output curl amount/input curl amount was determined.

When the paper curl ratio is larger than <NUM>, it means that the curl amount of the paper is increased after the paper passes the film transfer unit of the foil transfer device.

The measurement of the curl amount was performed as follows:.

In addition, for paper on which a toner image was formed by the laser printer, area of the toner image was measured as pre-print area, and area of the foil transferred onto the toner image by the foil transfer device was measured as foil transfer area. Further, a foil transfer ratio defined by foil transfer area/pre-print area was calculated.

When the foil transfer ratio is large, it means that the area of the foil transferred is larger with respect to the area of the toner image. That is, an excess foil is transferred around the toner image, indicating that a so-called burr has occurred. The foil transfer ratio being at a value close to <NUM> means image quality that there are few burrs and that edges are sharp in a transfer portion.

The paper curl ratio and the foil transfer ratio described above were determined while changing the angle θ formed by the tangent line and the film tension portion. <FIG> is a graph in which the output curl amount/input curl amount is taken on a vertical axis, the angle θ formed by the tangent line and the film tension portion is taken on a horizontal axis, and the paper curl ratio and the foil transfer ratio are plotted.

As a limit of the configuration of the foil transfer device, θ needs to be set to <NUM> degrees or less.

Referring to <FIG>, it was confirmed that, with the angle θ formed by the tangent line and the film tension portion being at <NUM> degrees or more, the paper curl ratio was <NUM> or less and the value of the foil transfer ratio also fell within an allowable range.

Further, it was confirmed that, with θ being in a range of <NUM> degrees to <NUM> degrees, the paper curl ratio was sufficiently small and the curl of the paper was greatly corrected. At this time, the value of the foil transfer ratio was also <NUM> or less, and image quality that there were few burrs and that edges were sharp in the transfer portion could be obtained.

The paper used in the foil transfer device is preferably thick paper such as the above-described Neenah Paper Exact Index (manufactured by Neenah Paper) with a basis weight of <NUM>/m<NUM> or Mondi Color Copy (manufactured by Mondi) with a basis weight of <NUM>/m<NUM>.

According to the above, the following effects can be obtained in the present embodiment.

When the peeling roller <NUM> is disposed such that the tangent line TL of the heating roller <NUM> passes between the rotation center 61A of the heating roller <NUM> and the rotation center 43A of the peeling roller <NUM>, and the angle formed by the tangent line TL and the film tension portion FT is <NUM> degrees to <NUM> degrees, the sheet S which is heated and pressed at the nip part NP of the pressing roller <NUM> and the heating roller <NUM> and which is about to curl along the shape of the heating roller <NUM> can be corrected by the film tension portion FT in the vicinity of the exit of the nip part NP.

Therefore, when moving from the nip part NP to the peeling roller <NUM>, the sheet S overlapped with the multilayer film F is in close contact with the multilayer film F and the peeling is not performed, and after the foil thermally transferred at the nip part NP is sufficiently cooled, the multilayer film F is peeled off from the sheet S by the peeling roller <NUM>. Therefore, image quality that edges are sharp and that burrs are few in a transfer portion can be obtained. In other words, the foil is transferred to a portion on the sheet S where the toner image is formed and the foil is not transferred to a portion on the sheet S where the toner image is not formed, and accordingly there is no excess transfer layer on the edge portion of the toner image and a good image quality can be obtained.

Further, when the angle formed by the tangent line TL and the film tension portion FT is <NUM> degrees to <NUM> degrees, image quality that edges are cleaner in the transfer portion can be obtained.

The pressing roller <NUM> has lower hardness than the heating roller <NUM>, and the surface of the pressing roller <NUM> is recessed with respect to the heating roller <NUM> in the nip part NP so that the nip part NP has a circular arc shape. Accordingly, the conveyance path SP of the sheet S can be curved. Therefore, members close to the pressing roller <NUM> and the heating roller <NUM> can be laid out in proximity to the pressing roller <NUM> and the heating roller <NUM>, and thus a size of the foil transfer device <NUM> can be reduced.

Since the pair of conveying rollers <NUM> that convey the sheet S is disposed downstream of the peeling roller <NUM> in the conveying direction of the sheet S and the peripheral speed of the conveying rollers <NUM> is larger than the peripheral speed of the pressing roller <NUM>, the sheet S can be conveyed in a state where tension is applied to the sheet S between the nip part NP and the nip part of the conveying rollers <NUM>. Therefore, at the time of peeling the multilayer film F off from the sheet S by the peeling roller <NUM>, the peeling can be performed cleanly. As a result, image quality that the edges are cleaner in the transfer portion can be obtained.

By providing the holding member <NUM> which sandwiches the sheet S and the multilayer film F with the peeling roller <NUM>, the leading end of the sheet S from which the multilayer film F has been peeled by passing the peeling roller <NUM> can be prevented from floating in a direction away from the peeling roller <NUM>, and vibration of the sheet S due to peeling can be suppressed.

Further, since the conveying roller <NUM> can be disposed at a position spaced apart by a distance equal to or larger than the leading end margin length of the sheet S to be conveyed, the degree of freedom in the layout of the foil transfer device <NUM> can be increased.

In the following description, the same components as those of the above-described embodiment are denoted by the same reference numerals, and a detailed description thereof is omitted.

As shown in <FIG>, in the foil transfer device <NUM> according to a second embodiment, the holding member is not provided at a position facing the peeling roller <NUM>, and a distance D2 from the peeling roller <NUM> to the nip part of the conveying rollers <NUM> is less than the leading end margin length of the sheet S.

According to such a foil transfer device, since the distance D2 from the peeling roller <NUM> to the nip part of the conveying rollers <NUM> is less than the leading end margin length of the sheet, the multilayer film F is peeled off from the image forming region of the sheet S after the leading end of the sheet S is nipped by the nip part of the conveying rollers <NUM>. Therefore, image quality that the edges are cleaner can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. The specific configurations may be appropriately modified without departing from the spirit of the present invention.

For example, although the foil transfer device has been described as a stand-alone device in the embodiments described above, the foil transfer device can be configured as an optional product of an image forming apparatus, or can be configured as a foil transfer unit attached to the image forming apparatus.

<FIG> shows a configuration in which a foil transfer device serving as an example of a layer transfer device is mounted on a color laser printer serving as an example of an image forming apparatus.

In the following description, directions will be described with directions shown in <FIG>. That is, a right side of <FIG> is set as "front", a left side of <FIG> as "rear", a front side of the paper surface of <FIG> as "left", and a back side of the paper surface of <FIG> as "right". Upper and lower sides of <FIG> are set as "upper" and "lower" respectively.

As shown in <FIG>, a color laser printer <NUM> mainly includes a paper feeding unit <NUM> and an image forming unit <NUM> in a housing <NUM>. A foil transfer device <NUM> serving as an optional product is mounted to an upper portion on a rear side of the housing <NUM>.

The foil transfer device <NUM> has a configuration similar to that of the foil transfer device <NUM> shown in <FIG>.

In the color laser printer <NUM>, the sheet S supplied from the paper feeding unit <NUM> is conveyed one by one to the image forming unit <NUM>, and a toner image is formed on a front surface of the sheet S in the image forming unit <NUM>. The sheet S on which the toner image is formed is conveyed to a fixing device <NUM>, with its front surface being directed upward, and the toner image is thermally fixed to the sheet S when the sheet S passes the fixing device <NUM>. Thereafter, the sheet S is discharged onto a first sheet discharge tray <NUM> through a first sheet discharge port <NUM> of the housing <NUM>, in a state where the front surface on which the toner image is thermally fixed is directed downward.

At this time, a flapper <NUM> is switched to a position indicated by a solid line, and the sheet S is guided toward the first sheet discharge port <NUM> by a front face of the flapper <NUM>.

When a foil is transferred to the toner image of the sheet S, the sheet S is conveyed toward the foil transfer device <NUM> by switching the position of the flapper <NUM> to a position indicated by a broken line.

The sheet S having passed the fixing device <NUM> passes over a back face of the flapper <NUM>, and passes the film transfer unit <NUM> of the foil transfer device <NUM> in a state where its front surface on which the toner image is thermally fixed is overlapped with the multilayer film F supplied from the supply reel <NUM>. When the toner image of the sheet S passes the pressing roller <NUM> and the heating roller <NUM> of the film transfer unit <NUM>, the front surface on which the toner image is thermally fixed by the fixing device <NUM> melts and the foil is thermally transferred.

The sheet S on which the foil is thermally transferred is conveyed toward the conveying rollers <NUM>, and the multilayer film F after the foil being thermally transferred is wound around the wind-up reel <NUM> via the peeling roller <NUM>.

Thereafter, the sheet S is discharged onto a second sheet discharge tray <NUM> through a second sheet discharge port <NUM> by the pair of conveying rollers <NUM> and a pair of second conveying rollers <NUM> in a state where the front surface on which the foil is thermally fixed is directed downward.

The foil transfer device <NUM> can have a configuration similar to that of the foil transfer device shown in <FIG> without a holding member.

According to the foil transfer device <NUM> of the color laser printer <NUM>, the same effects as those of the foil transfer devices in the embodiments described above can be obtained.

In the above-described embodiments and modification, the film transfer unit <NUM> includes the pressing roller <NUM> as a first roller provided at a position to contact the sheet S and a heating roller <NUM> as a second roller provided at a position to contact the multilayer film F, and alternatively, the film transfer unit can be configured to include a heating roller as a first roller provided at a position to contact the sheet S and a pressing roller as a second roller provided at a position to contact the multilayer film F.

In this configuration, when the heating roller has lower hardness than the pressing roller and is pressed against the pressing roller, a surface of the heating roller is recessed with respect to the pressing roller, and accordingly a nip part has a circular arc shape.

In addition, in the above-described embodiment, instead of the holding member <NUM>, a roller that sandwiches the sheet S and the multilayer film F with the peeling roller <NUM> can be provided.

Claim 1:
A layer transfer device (<NUM>) that overlaps a multilayer film (F) having a plurality of layers with a surface of a sheet (S) on which a toner image is formed, the layer transfer device (<NUM>) being configured to transfer at least one layer of the multilayer film (F) onto the toner image, the layer transfer device (<NUM>) comprising:
a sheet conveying unit (<NUM>) configured to convey the sheet (S);
a supply reel (<NUM>) around which the multilayer film (F) is wound;
a wind-up reel (<NUM>) configured to wind up the multilayer film (F) from the supply reel (<NUM>);
a film transfer unit (<NUM>) configured to perform transfer in a state where the multilayer film (F) supplied from the supply reel (<NUM>) is overlapped with the sheet (S) conveyed from the sheet conveying unit (<NUM>); and
a peeling roller (<NUM>) disposed between the film transfer unit (<NUM>) and the wind-up reel (<NUM>) in a conveyance path of the multilayer film (F), the peeling roller (<NUM>) contacting the multilayer film (F) having passed the film transfer unit (<NUM>), the peeling roller (<NUM>) being configured to peel off the multilayer film (F) from the sheet (S) when a conveying direction of the multilayer film (F) having passed the film transfer unit (<NUM>) is changed to a direction different from a conveying direction of the sheet (S) due to the wind-up reel (<NUM>) winding up the multilayer film (F),
wherein the film transfer unit (<NUM>) includes: a first roller (<NUM>) provided at a position to contact the sheet (S); and a second roller (<NUM>) provided at a position to contact the multilayer film (F), and the film transfer unit (<NUM>) overlaps the sheet (S) with the multilayer film (F) and is configured to heat and press the sheet (S) and the multilayer film (F) at a nip part (NP) of the first roller (<NUM>) and the second roller (<NUM>), and
wherein a tangent line (TL) of the second roller (<NUM>) at a downstream end of the nip part (NP) in the conveying direction of the sheet (S) passes between a center (61A) of the second roller (<NUM>) and a center (43A) of the peeling roller (<NUM>), and an angle (θ) formed by the tangent line (TL) and a film tension portion (FT) of the multilayer film (F) tensed between the nip part (NP) and the peeling roller (<NUM>) is <NUM> degrees to <NUM> degrees.