JP2002162842A - Image forming method and image forming device for non- fixation type image-receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve toner particle transferability and toner particle maintainability onto a non-fixation type image-receiving sheet in an image forming method and an image forming device for non-fixation type image- receiving sheet. SOLUTION: In the method for forming an image on a non-fixation type image receiving sheet, many recessed parts for receiving toner particles and many projecting parts for protecting are formed on the surface of the image receiving sheet S. As the preceding process before transferring a toner image onto the image receiving sheet by a transfer device 21, a sheet electrifying device 42 electrifies the surface of the image receiving sheet S with the polarity opposite to the electrified polarity of the toner particles. In such an electrified state, the image receiving sheet S is fed to the transfer device 21, and the toner particles on the photoreceptor are stuck onto the image receiving sheet S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming an image on a non-fixable image receiving sheet to which toner particles are removably attached.

[0002]

2. Description of the Related Art [Fixed image receiving sheet] In a printer currently used for output from a personal computer, a printing method generally used is to heat toner particles onto an image receiving sheet made of paper, plastic, or the like. A typical example is an electrophotographic system for fixing, or an inkjet system for drying and fixing ink on an image receiving sheet.

In each of the above-mentioned fixing methods, printing time is required, consumables such as electricity bills and ink are required, and running costs are increased. Also, due to the recent trend toward reduction of environmental load, there is a demand for reduction of energy consumption of printers and reduction of paper consumption.

[0004] On the other hand, paper output from a printer or the like is temporarily required, but once viewed, it is no longer necessary and is often discarded.

[Non-Fixed Image-Receiving Sheet] A method of reusing transfer paper in the above-described system is also known. For example, as a method of separating the toner from the transfer paper, a method of passing the transfer paper between a pair of heat rollers to melt and peel off the solidified toner, and a method of deinking using an aqueous solution of a surfactant or the like are known. Have been.

[0006] However, a large amount of energy is required for heating and removal of water that has penetrated, and the removed toner cannot be reused because it has been melted and solidified.

Therefore, Japanese Patent Application Laid-Open No. 6-43682 discloses that
With the aim of solving such a problem, fine projections are dispersedly formed on the surface of the image receiving sheet, and after transferring the toner image to the image receiving sheet surface having a large number of such fine projections, the image is formed by fixing with pressure, and thereafter, It has been proposed that the toner is detached from the image receiving sheet by a mechanical method, and the image receiving sheet and the toner are reused.

FIG. 7 shows a transfer apparatus (image forming apparatus) used for forming a toner image on a non-fixed image receiving sheet as described above.
And is composed of a drum-shaped photoconductor 127 and a transfer roller 128 opposed thereto.
Is provided around the transfer section 130 which is in contact with the transfer roller 128.
, A toner wiping unit (scraping unit) 131, an image charging unit 132, an exposing unit 133, and a developing unit 134 are arranged in this order from the drum rotation direction R side.

A bias for attracting toner particles is applied to the transfer roller 128. When the transfer is performed by such a transfer device, if the toner particles are charged on the negative electrode, the transfer roller 128 is charged on the positive electrode by applying a bias as shown in FIG.
The negatively charged toner particles are attracted by the positively charged toner particles and adhere to the surface of the image receiving sheet S.

[0010]

As shown in FIGS. 7 and 8, a method or an apparatus for transferring only attraction of toner particles by the charge of the transfer roller 128 at the time of transfer uses a transfer roller and a transfer roller. The distance from the toner particles on the surface of the photoreceptor is greater than the thickness of the image receiving sheet, which weakens the electric field, and there is a limit to improving the transferability and the holding ability only by adjusting the applied voltage. .

If the minute projections described in JP-A-6-43682 also describe the problem of the dispersion type image receiving sheet itself, the minute projections serve as spacers above the sheet, and the surface To prevent toner particles from adhering to the back of the upper sheet,
It hardly fulfills the function of mechanically and reliably holding the toner particles attached to the sheet surface.

Further, since the minute projections are merely formed in a dispersed manner, the image receiving sheet after the image formation may be handled while the toner adheres to the minute projections of the image receiving sheet. Although it is fixed to the protrusions by the pressure treatment, the fixing of the toner is only of a degree that can be mechanically removed from the image receiving sheet. It can be lost.

Further, since the minute projections formed on the image receiving sheet are each formed in an isolated dot shape, they are easily bent or deformed when subjected to an external force, so that an object easily enters between the projections and the image is disturbed. Due to the action, the toner image cannot be sufficiently protected.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to improve the transferability and retention of toner particles in an image forming method and an image forming apparatus for a non-fixable image receiving sheet.

[0015]

According to a first aspect of the present invention, there is provided an image forming method for a non-fixing type image receiving sheet to which toner particles are removably adhered.
A large number of concave portions for receiving the toner particles and a large number of convex portions for protecting the toner particles are formed.As a step before transferring the toner image to the image receiving sheet, the surface of the image receiving sheet is opposite in polarity to the charged polarity of the toner particles. It is characterized by being electrically charged.

According to a second aspect of the present invention, in the image forming apparatus for a non-fixing type image receiving sheet to which toner particles are removably attached, a large number of concave portions for receiving toner particles and toner particles are formed on the surface of the image receiving sheet. A number of convex portions for protection are formed, a transfer device that transfers the toner image to the surface of the image receiving sheet, and before the transfer process by the transfer device, the surface of the image receiving sheet is set to the polarity opposite to the charging polarity of the toner particles. It is characterized in that a sheet charging device for charging is arranged.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Structure of Non-Fixed Image-Receiving Sheet] FIG. 1 is an enlarged partial cross-sectional perspective view of a non-fixed type image-receiving sheet S used in the image forming method of the present invention. , The sheet surface layer 2 and the sheet core layer 3 form a laminated structure (two-layer structure). The surface of the sheet surface layer 2 is
It has an uneven surface on which a large number of concave portions 5 and convex portions 6 are formed.

The concave portion 5 is formed in a continuous groove shape, and the convex portion 6 is connected to the ridge shape along the groove-shaped concave portion 5, and is formed as a so-called convex portion.

The groove recesses 5 are provided regularly, for example, in parallel with the same width W1 to receive the toner 10. It is desirable that the width W1 of each recess 5 has a width that is at least twice the average particle size of the toner 10. For example,
The width W1 of each groove-shaped concave portion 5 is preferably 20 μm to 500 μm, and the depth D (convex portion height H) is 20 μm to 100 μm with respect to the average particle size of the toner 10 of 2 to 30 μm.
μm is preferred. It is preferable that the width W2 of the convex portion 6 is not more than 1/2 and not less than 1/50 of the width W1 of the groove-shaped concave portion 5.

The image receiving sheet S can be formed of various materials such as paper, synthetic resin (polyester, polyethylene terephthalate, polyolefin (polypropylene, polyethylene, etc.), polyimide, polyamide, etc.) or a combination thereof.

As shown in FIG. 1, the concave portion 5 is formed as a continuous groove, and the convex portion 6 is formed as a ridge-shaped convex line 6 along the continuous groove-shaped concave portion 5, so that the convex line 6 has a width W1 of the concave portion 5. And serves as a space for the upper space, mechanically stably holds the toner adhered to a predetermined position on the bottom surface of the groove concave portion 5, and even if the image sheets on which images have been formed are stacked, the upper image sheet The back surface is not stained by the toner, and even if the surface of the image sheet is touched with the hand, the protrusions 6 protect the toner particles, so that the hand becomes dirty or the image receiving sheet surface becomes dirty. Nor.

[Method of Manufacturing Non-Fixed Image-Receiving Sheet] In FIG. 1, as a method of forming the sheet surface layer 2 on the sheet core layer 3, a synthetic resin (for example, polyethylene) is formed on the sheet core layer 3 made of paper or the like. Or a thermoplastic resin such as acrylic or polyester) or a layer of a sheet surface material obtained by kneading a white pigment, an extender, or the like with titanium oxide, zinc oxide, silica, alumina, clay, talc, or the like in the resin, in a predetermined continuous groove. A concave and convex surface is formed by molding with a mold (for example, a master roller) having a pattern in which the concave portion 5 can be formed. The resin may be cast into a molding die.

Further, a method of forming a polymer film used as a so-called resist on the sheet core layer 3 and subjecting it to an exposure treatment through a light-shielding mask to remove a portion corresponding to the continuous groove-shaped concave portion 5, a more specific example For example, a method in which a film of a photopolymerizable polymer is formed on the sheet core layer 3 and exposed through a light-shielding mask, and then a portion corresponding to the continuous groove-shaped concave portion 5 is removed by washing with water or the like can also be exemplified.

[Image Forming Apparatus] FIG. 2 shows an example of an image forming apparatus to which the invention of the present application is applied. A sheet cleaning apparatus (toner removing apparatus) 20 is arranged in order from the transport start side (left side in FIG. 2) of the image receiving sheet. And a sheet charging device 42 for pre-charging, a transfer device 21, and a ridge cleaning device (a ridge toner removing device) 22. That is, the sheet charging device 42 is disposed on the transport start end side of the transfer device 21 as a process before the transfer process.

The sheet cleaning device 20 includes a collection conductive brush roller 25 and an opposing roller 26.

The sheet charging device 42 is composed of a pair of sheet charging rollers 40. One roller 40 is connected to a power supply capable of adjusting an applied voltage, the other roller 40 is grounded, for example. Image receiving sheet S between 40
, A bias voltage is applied, and the surface of the image receiving sheet is charged to a desired polarity and charge amount. When the toner particles are negatively charged, the surface of the image receiving sheet is positively charged. Although the roller type is shown in FIG. 2 as the sheet charging device 42, a charger or a discharger may be used.

The transfer device 21 comprises a drum-shaped photosensitive member 27 and a transfer roller 28 opposed thereto.
7, a toner wiping unit (scraping unit) 31, an image charging unit 32, an exposing unit 33, and a developing unit 34 in order from the transfer unit 30 abutting on the transfer roller 28 to the drum rotation direction R side.
Is arranged. The transfer roller 28 is applied with a bias to attract toner particles.

The ridge cleaning device 22 includes a charging roller 35 and an opposing roller 36.
5 is provided with a toner wiping unit 37.

[Image Forming Method] An image forming method using the image forming apparatus of FIG. 2 will be described. (1) The transfer device 21 uniformly charges the surface of the photoconductor 27 to about −900 V in the image charging unit 32,
The exposure is performed in accordance with the image data to form an electrostatic latent image on the surface of the photoconductor 27. The exposed portion of the surface of the photoreceptor 27 is attenuated to about -100V, and the unexposed portion is maintained at about -900V. Thereafter, toner particles (negative polarity) are adhered to the photoconductor 27 in the developing section 34 in accordance with the electrostatic latent image.

(2) When the image receiving sheet S is reused, the toner particles in the groove concave portion 5 are once removed by the cleaning device 20, and the surface is cleaned as necessary even when the image receiving sheet S is not reused. , Sheet charging device 42
Transported to

(3) In the sheet charging device 42, the surface of the image receiving sheet S is charged to the opposite polarity (positive polarity) to the charged polarity (negative polarity) of the toner particles. For example, a voltage of +1000 V to +2000 V is applied to the sheet charging roller 40, so that the surface of the image receiving sheet S is approximately + 2V.
+ 800V is applied from 00V. Thus, the image receiving sheet S
After the surface of the transfer unit 21 is charged with a positive charge,
Transported to 0.

(4) In the transfer section 30 of the transfer device 21, the toner particles of the electrostatic latent image adhered to the photoreceptor 27 are transferred to the uneven surface of the image receiving sheet S conveyed.
At this time, the bias applied to the transfer roller 28 is adjusted to several hundred volts so as to obtain an optimum image density in consideration of the charge amount charged on the image receiving sheet itself, and is applied.

FIG. 3 is an enlarged view of the transfer section 30. The negatively charged toner particles 10 adhering to the surface of the photosensitive member 27 are
The positive charges charged on the surface of the image receiving sheet S and the positive charges charged on the transfer roller 28 are attracted and transferred to the surface of the image receiving sheet.

Most of the toner particles to be transferred are
, But also partially adheres to the ridges 6.

(5) Image receiving sheet S on which toner image has been transferred
Is transported to the ridge cleaning device 22 shown in FIG. 2, and the toner particles 10 attached to the ridge 6 are collected by the electrostatic force of the charging roller (positive charge) 35 as shown in FIG.
At this time, a bias of about +300 V is applied to the charging roller 35, and the opposing roller 36 is grounded.

(6) When the image receiving sheet S on which an image has been formed is to be reused, the sheet cleaning apparatus 20 shown in FIG.
And the toner particles adhered to the concave portion 5 are collected.
5, at this time, a bias of about +1 kV having a polarity opposite to the charged polarity of the toner particles is applied to the collected conductive brush roller 25. The opposing roller 26 is grounded.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Table 1 below shows a continuous groove-shaped recess 5 as shown in FIG.
And image receiving sheet S on which ridge-shaped convex ridges 6 are formed.
And transferability and holding when a toner image is formed by an image forming apparatus having a sheet charging device 42 as shown in FIG. 2 and the roller application voltage of the sheet charging device 42 is set to various magnitudes. 4 is a table comparing the properties and cleaning.

As a specific method of manufacturing the image receiving sheet used in Table 1, a thermoplastic resin (high-density polyethylene) is uniformly applied on the sheet core layer 3 and then a shape forming mold (silicone rubber) is used. The sheets were stacked and hot-pressed (10 kg / cm ^{2 at} 120 ° C. for 30 minutes), then cooled and separated to transfer the surface shape. At this time, the concavo-convex shape in FIG. 1 is such that the concave portion width W1 = 200 μm, the convex portion width W2 = 10 μm,
The height D (H) was 50 μm. As the material of the sheet core layer 3, plain paper used in a normal copying machine or printer was used.

Instead of applying the resin, a high-density polyethylene sheet film (Toyobo Co., Ltd., thickness: 30 μm)
m) is placed on plain paper, a mold for forming a shape is placed in the same manner, hot-pressed (120 ° C., 30 minutes, 10 kg / cm ² ), then cooled and separated to transfer the surface shape. .

As the bias applied to the transfer roller 28 of the transfer device 21, when the applied voltage of the sheet charging device 42 is 0, a bias voltage of about +1 kV is applied, and the other applied voltages are 500 to 4000V. In Case of,
The voltage was adjusted to several hundred volts to obtain an optimum image density.

[Evaluation of Transfer Property] The amount of toner transferred onto the image receiving sheet S was measured with respect to the amount of toner deposited on the photoreceptor 27 before transfer, and the ratio of the transferred toner particles was 9
0% or more was rated as excellent (（), 80% or more good (○), and less than or equal to unacceptable (x).

[Evaluation of Retention] A plurality of image-receiving sheets S on which images were formed were superimposed, and the back dirt of the sheets was visually evaluated. (○), others were not allowed (×).

[Evaluation of Cleaning Property] The image-receiving sheet S on which an image was formed was passed through the sheet cleaning device 20, and the residual image of the image-receiving sheet immediately before transfer was visually evaluated. Is (x).

[0044]

[Table 1]

As shown in the uppermost column of the numerical part in Table 1,
When the voltage applied to the roller by the sheet charging device is 0, that is, even when pre-charging is not performed, for example, by setting the voltage applied to the transfer roller 28 at the time of transfer to about +1 kV,
Good results have been obtained for transferability and retention.

As shown in the third to fifth columns of the numerical part of Table 1, when the pre-charging is performed and the roller applied voltage is set to 1000, 1500 and 2000 V, the pre-charging is performed. The transferability and the retention were improved as compared with the case where no treatment was performed, and the best results were obtained. Regarding the cleaning property, at least in the range where the roller applied voltage in the pre-charging was up to 2500 V, even if the image receiving sheet was charged with the opposite polarity to the toner particles, the cleaning property was not affected and the performance did not change.

When the voltage applied to the roller is, for example, 400
When the voltage is too high, such as 0 V, it has been found that a discharge phenomenon occurs at the time of transfer, and on the contrary, transferability and retention are reduced.

[0048]

[Other Embodiments] (1) The present invention can of course be applied to an image forming method or an image forming apparatus in which toner particles are charged to a positive electrode to perform transfer. Is negatively charged.

(2) In the image forming apparatus, instead of the dry sheet cleaning device (image removing device) 20 shown in FIG. 2, a liquid is applied to the image receiving sheet as shown in FIG. Image removing device 210 that removes toner in the concave portion and reproduces the sheet in a reusable state
It is also possible to use. Hereinafter, the image removing device 210 of FIG. 6 will be described.

Schematic Configuration of Image Removal Apparatus The image removal apparatus 210 generally includes a sheet supply unit 212 that stores and supplies an image receiving sheet S reproduced by the apparatus 210.
And the image receiving sheet S sent from the sheet supply unit 212
Immersing section 214 for applying a liquid to the sheet to wet the image receiving sheet S
A toner removing unit 216 for removing toner from the image receiving sheet S to which the liquid has been applied; and a foreign substance such as toner remaining on the image receiving sheet S by spraying a liquid on the image receiving sheet S from which the toner has been removed. A rinsing unit 218 for removing, a liquid removing unit 220 for removing liquid attached to the surface of the image receiving sheet S from which the toner has been removed, and a drying unit 222 for drying the image receiving sheet S from which the liquid has been removed until the image receiving sheet S can be reused. ,
Sheet discharging unit 2 for discharging and receiving the dried image receiving sheet S
24.

Sheet Supply Unit The sheet supply unit 212 has a supply tray 226 that stores the image receiving sheets S. The sheet supply unit 212 also has a separation mechanism 22 for sending out only the uppermost sheet from the plurality of image receiving sheets S stacked and stored on the supply tray 226.
8 and a feeding mechanism 232 that feeds the uppermost sheet separated from the lower layer sheet by the separating mechanism 228 along the sheet conveying path 230. In the present embodiment, as the separating mechanism 228, a separating device having a pickup roller in contact with the uppermost sheet and a separating pad in contact with the outer peripheral surface of the pickup roller is used. However, a separating device of another form is used. You may. Also, the delivery mechanism 23
2 generally has a first shaft connected to a drive system and a second shaft arranged in parallel with the first shaft, and a plurality of rollers (for example, rubber rollers )
A roller transport device, which is conventionally used as a paper transport device of a copying machine or a printer, is used in which a sheet is nipped and transported by a roller attached to one axis and a roller attached to the other axis. .

Immersion Unit The immersion unit 214 has a container 236 that stores a cleaning liquid (liquid) 234. Water is used as the cleaning liquid 234. In order to easily remove the toner adhering to the image receiving sheet S, a surfactant is used in an amount of about 0.1.
01% (= weight of surfactant / weight of water) may be added. Further, if necessary, another material may be added to the cleaning liquid 23.
4 may be added.

An inner space of the container 236 is provided with an overflow tank 238 for immersing the image receiving sheet S by an overflow wall 238.
And the cleaning liquid 23 overflowing from the immersion tank 240
4 and an overflow tank 242 for accommodating the same. Container 2
36, a step of sending the cleaning liquid 234 flowing from the immersion tank 240 through the overflow wall 238 to the overflow tank 242 again into the immersion tank 240 and sending the cleaning liquid 234 from the overflow tank 242 to the immersion tank 240. A liquid circulating unit 244 for collecting foreign matter (for example, toner) contained in the cleaning liquid 234 is additionally provided.

The liquid circulation section 244 has a liquid circulation path 248. One end of the liquid circulation path 248 is connected to the overflow tank 242, and the other end is located above the immersion tank 240. Therefore, the cleaning liquid 234 accumulated in the overflow tank 242
Is supplied to the immersion tank 240 from above the liquid level. The liquid circulation path 248 includes a pump 250 for forcibly circulating the cleaning liquid 234 along the liquid circulation path 248,
It has a filter section 252 for removing foreign matter contained in the cleaning liquid 234.

In order to keep the liquid level in the overflow tank 242 constant, the liquid level is measured. When the water level in the overflow tank 242 becomes lower than a predetermined level, the cleaning liquid is transferred from a preliminary tank (not shown) to the immersion tank 240. 234 may be replenished.

In the immersion tank 240 of the container 236, a plurality of image receiving sheets S sent from the sheet supply unit 212 are transported along the sheet transport path 230 in the cleaning liquid 234 in the immersion tank 240. A transport mechanism 256,
A guide member (not shown) that guides the image receiving sheet S between the plurality of transport mechanisms 256 is provided. Transport mechanism 2
Reference numeral 56 denotes the above-described roller transport device. As a guide member, a pair of guide plates (the cleaning liquid 2) that face each other with a predetermined interval across the sheet conveyance path 230.
It is possible to suitably use a guide wire (a plurality of wires extending in the sheet conveyance direction and arranged at predetermined intervals in a direction perpendicular to the sheet conveyance direction) or a guide wire (a plate having a plurality of openings through which the sheet 34 can enter and exit).

Toner Removal Unit The toner removal unit 216 has a pair of brush rollers 258 facing each other with the sheet conveyance path 230 interposed therebetween. These brush rollers 258 use a shaft connected to a drive system, and a base cloth on which nylon fibers are planted around the shaft. The brush roller 258 is used for the image receiving sheet S conveyed along the sheet conveyance path 230. The bristles of each brush roller 258 are arranged so as to contact the front and back surfaces. The image receiving sheet S contacts the toner adhering to the front surface or the back surface of the image receiving sheet S passing between the brush rollers 258.
Are respectively connected to motors (not shown) to remove toner from the toner.

The peripheral speed of the brush roller 258 is set to several times to several tens times the conveying speed of the image receiving sheet S.
The rotation direction of the brush roller 258 will be briefly described. When the leading end of the image receiving sheet S enters the opposing portion of the brush roller 258, the bristle of the brush roller 258 moves in the sheet conveying direction, and the leading end of the image receiving sheet S It is preferable to control the drive motor of the brush roller 258 so that the bristle tip moves in the direction opposite to the sheet conveyance direction after passing through the facing portion.

In FIG. 6, the brush roller 258 is used as a member that comes into contact with the image receiving sheet S and removes toner from the image receiving sheet S, but a soft member such as a sponge or cloth is attached around the rotation shaft. Rollers can also be used.

The rinsing unit 218 is provided to supply the cleaning liquid 234 to the front and back surfaces of the image receiving sheet S that has passed between the pair of brush rollers 258 or has passed therethrough.
It has a spray nozzle 260 disposed between the brush roller 258 and the brush nozzle 258. This spray nozzle 26
Numeral 0 is connected to the other end of the liquid circulation path 248 described above so that the cleaning liquid 234 purified by the liquid circulation path 248 is supplied. Note that, in the present embodiment, the spray nozzle 260 is formed by folding a tube having liquid injection holes formed at predetermined intervals by 180 ° in the middle thereof.

As shown in the figure, the brush roller 258 and the spray nozzle 260 are provided on both sides of the sheet conveying path because the uneven surface of the image receiving sheet is arranged on the supply tray 226 with the lower side or the upper side. This is to ensure that the image is also removed.

Liquid Removal Unit The liquid removal unit 220 has a pair of squeezing rollers 262 formed of two rollers that face each other with the sheet conveyance path 230 interposed therebetween and come into contact with each other on the sheet conveyance path 230. One of the two rollers constituting the squeezing roller pair 262 is drivingly connected to a motor (not shown).

Drying Unit The drying unit 222 is disposed downstream of the liquid removing unit 220 in order to dry the image receiving sheet S from which the cleaning liquid 234 has been removed until it can be reused in the image forming apparatus. In the present embodiment, as the drying unit 222, two rollers 264, 2 opposed to each other with the sheet conveyance path 230 interposed therebetween and in contact with each other on the sheet conveyance path 230.
It consists of 66. At least one of the rollers 264 and 266 has a heater 268 therein as a heating source.

As the drying means of the drying section 222, for example, instead of the roller-type heater described above, for example, a blower that only blows normal-temperature air to a sheet, or a built-in heater that can blow out hot air is used. A type blower may be used. Further, a configuration in which air dried by a dehumidifier is blown may be used.

Sheet Discharge Unit The sheet discharge unit 224 has a discharge tray 270 that stores the image receiving sheets S dried in the drying unit 222 in a stacked manner.

Sheet Reproduction Processing The operation of the image removing apparatus 210 having the above configuration will be described. Specifically, the image receiving sheet S to be reproduced is in the supply tray 2
26 are stacked and accommodated. When the apparatus 210 is started in this state, the plurality of image receiving sheets S stored in the supply tray 226 are sequentially sent out from the uppermost sheet by the separating mechanism 228, and the immersion unit 214 is sent out by the sending mechanism 232.
Supplied to

Image receiving sheet S supplied to dipping section 214
Is transported by the transport mechanism 256 while being guided by the guide member, and the cleaning liquid 234 in the immersion tank 240 is
The cleaning liquid 234 permeates into the concave portions of the surface layer of the image receiving sheet S for a predetermined time. As a result, the adhesive force between the toner adhering to the recesses on the surface of the image receiving sheet S and the surface is lost, and the toner can be separated only by applying a mechanical force. The image receiving sheet S discharged from the cleaning liquid 234 of the immersion tank 240 is subjected to the rubbing force of the pair of brush rollers 258 on the front and back surfaces, and the toner adhering to these front and back surfaces is removed. At this time, the cleaning liquid 234 is sprayed from the spray nozzle 260 onto the front and back surfaces of the image receiving sheet S, and the toner adhering to the sheet portion that has passed through the facing portion of the brush roller 258 is washed away. In addition, brush roller 2
The toner adhering to 58 is washed off into immersion tank 240.

The toner dropped into the immersion tank 240 and the toner separated from the image receiving sheet S while the image receiving sheet S is being conveyed through the immersion tank 240 overflow the overflow wall 238 from the immersion tank 240. It flows into the overflow tank 242 together with the cleaning liquid 234 flowing in the tank 242. The toner contained in the cleaning liquid 234 in the overflow tank 242 is sent through the liquid circulation path 248 by the pump 250 and
52. The cleaning 234 from which the toner has been removed is transferred from the spray nozzle 260 to the image receiving sheet S.
Are sprayed on the front and back surfaces of the brush roller 258 and the brush roller 258.

The image receiving sheet S from which the toner has been removed is squeezed by the pair of squeezing rollers 262 of the liquid removing section 220,
The cleaning liquid 234 on the surface is removed. continue,
After the image receiving sheet S is sent to the drying unit 222 and dried,
The sheet is discharged onto the discharge tray 270 of the sheet discharge unit 224.

[0070]

As described above, according to the present invention, (1) in the process before transferring a toner image to an image receiving sheet, the surface of the image receiving sheet is charged to a polarity opposite to the charging polarity of the toner by a sheet charging device ( (Pre-charging), the transfer electric field is substantially increased in the transfer step, and transferability is improved.

(2) Since the surface of the image receiving sheet is charged to a polarity opposite to the charging polarity of the toner particles, since the charged charges are present on the surface side of the image receiving sheet, the toner particles can be stably held electrostatically. Image retention is improved.

(3) Since the image receiving sheet itself is charged, the toner particles are firmly electrostatically adhered to the surface of the sheet. There is no set-off phenomenon that the toner moves during printing.

(4) Since a non-fixing type image receiving sheet to which toner particles are removably adhered is adopted, the image receiving sheet can be reused, the paper consumption can be reduced, and the energy and the energy of the fixing type can be reduced. Consumables become unnecessary, and the toner collected from the image receiving sheet can be reused, so that the running cost can be reduced.

(5) By forming a large number of concave portions for receiving the toner particles and a large number of convex portions for protecting the toner particles on the surface of the image receiving sheet, the toner particles are mechanically strongly held in the concave portions, Moreover, the mechanical holding is strengthened by a large number of convex portions, and the convex portions function as spacers, thereby reliably preventing contact of foreign matter (finger or other sheet back surface) from above, and Can be improved.

[Brief description of the drawings]

FIG. 1 is a partially enlarged longitudinal sectional view of a non-fixing type image receiving sheet used in an image forming method according to the present invention.

FIG. 2 is a simplified side view of an image forming apparatus to which the present invention is applied.

FIG. 3 is an enlarged vertical sectional view of a transfer unit of the image forming apparatus.

FIG. 4 is an enlarged longitudinal sectional view of the ridge cleaning device.

FIG. 5 is an enlarged vertical sectional view of a cleaning device (image removing device).

FIG. 6 is a simplified side view of a wet cleaning device (image removing device).

FIG. 7 is a simplified side view showing an example of a conventional image forming apparatus.

FIG. 8 is an enlarged vertical sectional view showing a transfer step in a conventional transfer section.

[Explanation of symbols]

 Reference Signs List 2 sheet surface layer 3 sheet core layer 5 groove-shaped concave portion 6 convex portion (projected ridge portion) 10 toner particle 42 example of sheet charging device for pre-charging

Continuation of the front page (72) Ryuharu Kurita, 2-3-13 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Masafumi Yamamoto 2--3, Azuchicho, Chuo-ku, Osaka City, Osaka No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H032 AA05 BA04 BA05 BA12 BA13 BA28

Claims (2)

[Claims] 1. A method for forming an image on a non-fixable image receiving sheet to which toner particles are removably attached, wherein a number of concave portions for receiving toner particles and a number of convex portions for protecting toner particles are provided on the surface of the image receiving sheet. Wherein the surface of the image receiving sheet is charged to a polarity opposite to the charging polarity of the toner particles as a step before transferring the toner image to the image receiving sheet. 2. An image forming apparatus for a non-fixing type image receiving sheet to which toner particles are removably attached, wherein a number of concave portions for receiving toner particles and a number of convex portions for protecting toner particles are provided on the surface of the image receiving sheet. A transfer device for transferring the toner image to the surface of the image receiving sheet, and a sheet charging device for charging the surface of the image receiving sheet to a polarity opposite to the charging polarity of the toner particles before the transfer step by the transfer device. An image forming apparatus for a non-fixing type image receiving sheet, wherein the image receiving apparatus is disposed.