JP7527883B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device that forms an image on a sheet.

Conventionally, when creating documents such as pay slips that require confidentiality and therefore need to be sealed, preprinted paper with adhesive applied to it was prepared in advance, variable data was printed on the preprinted paper, and then the paper was sealed as a post-processing step. This method took time to create the preprinted paper, which required the application of adhesive, and was inefficient when only a small number of documents were required.

Patent Document 1 proposes an image forming device that uses an adhesive toner (powder adhesive) in addition to an image forming toner using an electrophotographic process to output a sealed document using a single device while using plain paper. The adhesive toner is designed to melt at a lower temperature than the image forming toner, and is applied to a sheet, which is a recording medium, by being transferred in the same electrophotographic process as the image forming toner. The sheet is then folded so that the surfaces on which the adhesive toner image is formed face each other, and finally the sheets are adhered to each other by heating the sheets while the adhesive surfaces are in close contact with each other via the adhesive toner. This method is efficient even for applications requiring a small number of items, since the printing process and adhesive process are completed in a single image forming device. In addition, the method of adhesion by heating and melting the adhesive does not require strong pressure, which is advantageous for making the device smaller and quieter.

JP 2006-171607 A

However, when the printing process and the bonding process are performed in one image forming apparatus as in the above document, the following problems may occur. In the bonding process, the outer surface of the folded sheet comes into contact with a heating member such as a heating roller or a heating film and is heated, and the heat is transmitted inside the sheet to heat the powder adhesive applied to the inner surface of the sheet. Therefore, the temperature rise of the powder adhesive is slower than when the powder adhesive is in direct contact with the heating member. On the other hand, since the sheet is heated while being transported at a preset transport speed, the time that the sheet is in contact with the heating member is limited. Therefore, it is possible to set the heating temperature in the bonding process very high in order to soften the powder adhesive, but there are cases where sufficient adhesive strength cannot be obtained with this method.

Therefore, the present invention aims to obtain sufficient adhesive strength when printing a finished product bonded using a powder adhesive.

An image forming apparatus according to one aspect of the present invention includes image forming means for forming a toner image on a sheet using a printing toner and applying a powder adhesive to the sheet, fixing means for heating the toner image formed on the sheet by the image forming means and the powder adhesive applied to the sheet to fix the toner image to the sheet, folding means for folding the sheet that has passed through the fixing means with the surface on which the powder adhesive has been applied facing inward, and bonding means for heating the sheet folded by the folding means to bond the inner surfaces of the folded sheet with the powder adhesive, wherein the image forming apparatus includes image forming means for forming a toner image on a sheet using a printing toner and applying a powder adhesive to the sheet, and a fixing means for fixing the toner image to the sheet by heating the sheet folded by the folding means .

An image forming apparatus according to another aspect of the present invention is an image forming apparatus comprising: an image forming means having a photosensitive member, a developing unit which supplies powder adhesive to an electrostatic latent image formed on the photosensitive member, and a transfer unit which transfers the powder adhesive from the photosensitive member to a sheet; a fixing unit which heats the powder adhesive layer transferred to the sheet to fix the powder adhesive to the sheet; a folding unit which folds the sheet which has passed through the fixing unit with the surface to which the powder adhesive has been transferred facing inward; and an adhesive unit which heats the sheet folded by the folding unit to adhere the inner surfaces of the folded sheet to each other with the powder adhesive, wherein the maximum temperature reached by the powder adhesive when heated by the fixing unit is Tmax1 [°C] and the maximum temperature reached by the powder adhesive when heated by the adhesive unit is Tmax2 [°C], Tmax1 is higher than the melting point of the powder adhesive, Tmax2 is lower than the melting point of the powder adhesive and equal to or higher than the glass transition temperature of the powder adhesive, and Tmax1>Tmax2 .

According to the present invention, sufficient adhesive strength can be obtained when printing a product bonded using a powder adhesive.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. 3A and 3B are diagrams for explaining attachment of a post-processing unit to an apparatus body of the image forming apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a sheet transport path in the image forming apparatus according to the first embodiment. 6 is a diagram illustrating another sheet transport path in the image forming apparatus according to the first embodiment. FIG. 4A to 4F are diagrams for explaining the contents of a folding process according to the first embodiment. FIG. 1 is a perspective view showing an external appearance of an image forming apparatus according to a first embodiment. 3A and 3B are diagrams illustrating examples of products output by the image forming apparatus according to the first embodiment. FIG. 2 is a schematic diagram of a process cartridge according to the first embodiment. FIG. 4 is a schematic diagram of a first fixing unit according to the first embodiment. FIG. 2 is a schematic diagram of the inside of a post-processing unit according to the first embodiment. Schematic diagram of sheet adhesion mechanism (A, B). Schematic diagram (A to C) of the process of melting the powder adhesive in the first fixing unit. Schematic diagram (A, B) of the process of applying powder adhesive using a second fixing device. 1A and 1B are conceptual diagrams showing the state of a powder adhesive when the ratio of the amount of heat supplied in the bonding process to the amount of heat supplied in the fixing process is less than 1.0. 1A to 1C are conceptual diagrams showing the state of a powder adhesive when the ratio of the amount of heat supplied in the bonding process to the amount of heat supplied in the fixing process is 2.2 or more. 10A to 10C are diagrams illustrating a product output by the image forming apparatus according to the second embodiment and image defects. 1 is a conceptual diagram showing a cause of image defects.

An exemplary embodiment of the present invention will now be described with reference to the drawings.

(Overall device configuration)
First, the overall configuration of the image forming apparatus will be described with reference to Figures 1, 2, and 6. Figure 1 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus 1 including an image forming apparatus main body (hereinafter referred to as an apparatus main body 10) according to a first embodiment and a post-processing unit 30 connected to the apparatus main body 10. The image forming apparatus 1 is an electrophotographic image forming apparatus (electrophotographic system) including the apparatus main body 10 equipped with an electrophotographic printing mechanism and the post-processing unit 30 as a sheet processing device.

Figure 6 is a perspective view showing the exterior of the image forming device 1. The post-processing unit 30 is attached to the top of the device body 10. The image forming device 1 has a sheet cassette 8 at the bottom, an openable tray 20 on the right side, and a first discharge tray 13 on the top.

First, the internal structure of the device main body 10 will be described. As shown in FIG. 1, the device main body 10 includes a sheet cassette 8 as a sheet storage section that stores sheets P as a recording medium, an image forming unit 1e as an image forming means, a first fixing device 6 as a fixing means, and a housing 19 that houses these. The device main body 10 has a printing function that forms a toner image on a sheet P fed from the sheet cassette 8 by the image forming unit 1e, and creates a printed matter that has been subjected to a fixing process by the first fixing device 6. It should be noted that, for example, paper is used as the sheet P as a recording medium.

The sheet cassette 8 is inserted into the housing 19 at the bottom of the device main body 10 so that it can be pulled out, and stores a large number of sheets P. The sheets P stored in the sheet cassette 8 are fed from the sheet cassette 8 by a feeding member such as a feeding roller, and are transported by the transport roller 8a in a state where they are separated one by one by a separation roller pair. It is also possible to feed sheets set in the open tray 20 (Figure 6) one by one.

The image forming unit 1e is a tandem-type electrophotographic unit equipped with four process cartridges 7n, 7y, 7m, and 7c, a scanner unit 2, and a transfer unit 3. A process cartridge is a unit in which multiple parts that are responsible for the image forming process are integrated and replaceable. The device main body 10 is provided with a cartridge support section 9 supported by a housing 19, and each of the process cartridges 7n, 7y, 7m, and 7c is removably mounted in mounting sections 9n, 9y, 9m, and 9c provided on the cartridge support section 9. The cartridge support section 9 may be a tray member that can be pulled out from the housing 19.

Each process cartridge 7n, 7y, 7m, 7c has a substantially common configuration, except for the type of powder contained in the four powder containers 104n, 104y, 104m, 104c. That is, each process cartridge 7n, 7y, 7m, 7c includes a photosensitive drum 101 which is an image carrier, a charging roller 102 which is a charger, a powder container 104n, 104y, 104m, 104c which contains the powder, and a developing roller 105 which performs development using the powder.

Of the four powder containers, the three powder containers 104y, 104m, and 104c on the right side of the figure contain yellow, magenta, and cyan printing toners Ty, Tm, and Tc, respectively, as toners (first powder, powder developer) for forming a visible image on the sheet P. In contrast, the powder container 104n on the leftmost side of the figure contains powder adhesive Tn, which is a toner (second powder) for performing an adhesive process after printing. The powder containers 104y, 104m, and 104c are all examples of first containers that contain printing toner, and the powder container 104n is an example of a second container that contains powder adhesive. In addition, the process cartridges 7y, 7m, and 7c are all examples of first process units that form a toner image using printing toner, and the process cartridge 7n is an example of a second process unit that forms an image of powder adhesive in a predetermined application pattern.

In this embodiment, when printing black images such as text, they are expressed using process black, which is a combination of yellow (Ty), magenta (Tm), and cyan (Tc) toners. However, for example, a fifth process cartridge using black printing toner may be added to image forming unit 1e, so that black images can be expressed using black printing toner. This is not a limitation, and the type and number of printing toners can be changed depending on the application of image forming device 1.

The scanner unit 2 is disposed below the process cartridges 7n, 7y, 7m, and 7c and above the sheet cassette 8. The scanner unit 2 is an exposure means in this embodiment that irradiates the photosensitive drum 101 of each process cartridge 7n, 7y, 7m, and 7c with laser light G to write an electrostatic latent image.

The transfer unit 3 is equipped with a transfer belt 3a as an intermediate transfer body (secondary image carrier). The transfer belt 3a is a belt member wound around a secondary transfer inner roller 3b and a tension roller 3c, and its outer circumferential surface faces the photosensitive drums 101 of each process cartridge 7n, 7y, 7m, and 7c. On the inner circumferential side of the transfer belt 3a, a primary transfer roller 4 is disposed at a position corresponding to each photosensitive drum 101. In addition, a secondary transfer roller 5 as a transfer means is disposed at a position facing the secondary transfer inner roller 3b. The transfer nip 5N between the secondary transfer roller 5 and the transfer belt 3a is a transfer section (secondary transfer section) where a toner image is transferred from the transfer belt 3a to the sheet P.

The first fixing device 6 is disposed above the secondary transfer roller 5. FIG. 9 is a detailed view of the first fixing device 6. The first fixing device 6 has a cylindrical fixing film (endless belt) 6a, a heater 6a1 that contacts the inner surface of the fixing film 6a, and a pressure roller 6b that forms a fixing nip 6N with the heater 6a1 through the fixing film 6a. The fixing film 6a and the pressure roller 6b function as a pair of rotating bodies (first rotating body pair) that rotate while sandwiching the sheet P. The fixing film 6a has a base layer with a thickness of 30 to 70 μm made of heat-resistant resin such as polyimide, polyamide, PEEK, or metal such as stainless steel. The fixing film 6a has an elastic layer with a thickness of 0.1 to 1 mm made of silicone rubber or the like and a release layer with a thickness of 5 to 30 μm made of fluororesin such as PFA or PTFE on the base layer. The surface roughness (Rz value) of the fixing film surface is set to 6 μm or less so as to be sufficiently smooth. The surface roughness (Rz value) shown here is the value measured using a surface roughness measuring instrument SE-3400 (manufactured by Kosaka Laboratory Co., Ltd.). The surface layer of the fixing film 6a is the surface that comes into contact with the molten toner and powder adhesive, and the toner surface after the fixing process is smoothed to match the surface shape of the fixing film 6a, as described below.

The pressure roller 6b has a core 6b1 made of iron or aluminum, an elastic layer 6b2 made of silicone rubber or the like and having a thickness of 2 to 4 mm, and a release layer made of a fluororesin such as PFA or PTFE provided on the outermost surface.

The heater 6a1 as the heating means (first heating means) has a heating resistor 6a12 such as Ag/Pd (silver palladium) that generates heat when electricity is applied, and an insulating protective layer (glass layer in this embodiment) 6a13 on a thin plate-shaped substrate 6a11 mainly composed of ceramics such as alumina. A temperature detection element 6a2 such as a thermistor is in contact with the substrate 6a11 and is connected to a CPU 6a3 as a control unit mounted on the image forming apparatus 1. The heater 6a1 heats up by supplying electricity to the heating resistor 6a12. The temperature rise is detected by the temperature detection element 6a2, and the CPU 6a3 controls the current to the heating resistor 6a12 via the triac 6a4. For example, if the temperature detected by the temperature detection element 6a2 is lower than a predetermined set temperature, the amount of power supplied to the heating resistor 6a12 is increased so that the heater 6a1 heats up, and if the temperature detected by the temperature detection element 6a2 is higher than the set temperature, the amount of power is decreased so that the heater 6a1 cools down, thereby keeping the heater 6a1 at a constant temperature.

The heater 6a1 is held by a holding member 6a5 made of a heat-resistant resin such as LCP (liquid crystal polymer). The holding member 6a5 also has a guide function for guiding the rotation of the fixing film 6a. A force is applied to the holding member 6a5 in a direction approaching the pressure roller 6b from a spring (not shown) attached to a metal stay 6a6. The pressure roller 6b is pressed toward the heater 6a1 via the fixing film 6a with a total pressure of 10 to 30 kgf by a pressure means such as a spring member (not shown). As a result, a fixing nip 6N with a width of 5 to 11 mm in the sheet conveying direction is formed between the pressure roller 6b and the heater 6a1 and holding member 6a5 that constitute the nip portion forming unit.

The pressure roller 6b receives power from a motor (not shown) and rotates in the direction of the arrow r1 in FIG. 9. The rotation of the pressure roller 6b causes the fixing film 6a to rotate accordingly. The sheet P carrying an unfixed toner image is transported in the sheet transport direction through the fixing nip 6N together with the fixing film 6a while the surface (image surface) of the sheet P carrying the toner image and powder adhesive Tn is brought into close contact with the outer surface of the fixing film 6a in the fixing nip 6N. This configuration is characterized by the fact that the thermal capacity of the fixing film and heater is particularly small, and the holding member 6a5 is also made of a material with high thermal insulation properties, making it possible to heat the surface of the fixing film 6a to a high temperature more quickly with a small amount of heat supply.

The housing 19 is provided with a discharge port 12 (first discharge port) which is an opening for discharging the sheet P from the device body 10, and a discharge unit 34 is disposed in the discharge port 12. The discharge unit 34, which is the discharge means in this embodiment, uses a so-called triple roller system having a first discharge roller 34a, an intermediate roller 34b, and a second discharge roller 34c. In addition, a switching guide 33, which is a flap-shaped guide that switches the transport path of the sheet P, is provided between the first fixing device 6 and the discharge unit 34. The switching guide 33 can rotate around the shaft portion 33a so that the tip 33b reciprocates in the direction of the arrow c in the figure.

The device main body 10 is equipped with a mechanism for performing double-sided printing. A motor (not shown) is connected to the discharge unit 34, and the rotation direction of the intermediate roller 34b can be rotated forward and backward. In addition, a double-sided conveying path 1r is provided as a conveying path connected in a loop to the main conveying path 1m. The sheet P, on which an image is formed on the first side while passing through the main conveying path 1m, is sandwiched and conveyed by the first discharge roller 34a and the intermediate roller 34b by the switching guide 33 rotated clockwise (broken line position). After the trailing end of the sheet P in the traveling direction passes through the switching guide 33, the switching guide 33 rotates counterclockwise (solid line position) and the intermediate roller 34b rotates in reverse, and the sheet P is reversed and conveyed to the double-sided conveying path 1r. Then, while the sheet P passes through the main conveying path 1m again in an inverted state, an image is formed on the second side of the sheet P. After double-sided printing, the sheet P is guided to the switching guide 33 (solid line position) rotated counterclockwise, is sandwiched and transported between the intermediate roller 34b and the second discharge roller 34c, and is discharged from the device body 10.

In addition, the conveying path passing through the conveying roller 8a, the transfer nip 5N, and the fixing nip 6N in the device main body 10 constitutes the main conveying path 1m where an image is formed on the sheet P. When viewed from the main scanning direction during image formation (the width direction of the sheet perpendicular to the conveying direction of the sheet conveyed through the main conveying path 1m), the main conveying path 1m extends from below to above passing one side of the horizontal direction relative to the image forming unit 1e. In other words, the device main body 10 of this embodiment is a so-called vertical conveying type (vertical path type) printer in which the main conveying path 1m extends in a substantially vertical direction. Note that when viewed vertically, the first discharge tray 13, the intermediate path 15, and the sheet cassette 8 overlap each other. Therefore, the movement direction of the sheet when the discharge unit 34 discharges the sheet P in the horizontal direction is opposite to the movement direction of the sheet when the sheet P is fed from the sheet cassette 8 in the horizontal direction.

1 (when viewed in the main scanning direction during image formation), it is preferable that the horizontal occupancy of the main body portion of the post-processing unit 30, excluding the second discharge tray 35, is within the occupancy of the device main body 10. By storing the post-processing unit 30 in the space above the device main body 10 in this way, it is possible to install the image forming device 1 with adhesive printing function in an installation space approximately the same as that of a normal vertical pass printer.

(Post-processing unit)
2, the post-processing unit 30 is attached to the upper part of the apparatus main body 10. The post-processing unit 30 is a post-processing unit in which a folder 31 as a folding means and a second fixing device 32 as an adhesive means (second fixing means) are housed in a housing (second housing) 39 and integrated with each other.

The second fixing device 32 in this embodiment has the same configuration as the first fixing device 6 as shown in FIG. 10. It has a cylindrical heating film (endless belt) 32b and a pressure roller 32a, and the sheet P folded by the folder 31 is sandwiched and conveyed in an adhesive nip 32N (second fixing nip) which is a nip between the heating film 32b and the pressure roller 32a. The heating film 32b and the pressure roller 32a function as a pair of rotating bodies (second rotating body pair) that rotate while sandwiching the sheet P. On the inner surface side of the heating film 32b, a heater 32b1 and a temperature detection element 32b2 are provided as heating means, as in the first fixing device 6. The heating film 32b rotates in response to the pressure roller 32a that rotates in the direction of the arrow r2, so that the sheet P is sandwiched and conveyed in the adhesive nip 32N. In the process, the sheet P is heated and pressurized, so that the powder adhesive Tn applied to the sheet P is softened again, and the sheet P is adhered in a folded state.

The post-processing unit 30 is provided with a first discharge tray 13 that rotatably holds the tray switching guide 13a, an intermediate path 15, and a second discharge tray 35. The first discharge tray 13 is provided on the upper surface of the post-processing unit 30 and is located on the upper surface of the entire image forming apparatus 1 (FIG. 1). The functions of each part of the post-processing unit 30 will be described later.

The post-processing unit 30 is provided with a positioning portion (e.g., a convex shape that engages with a concave portion of the housing 19) for positioning the housing 39 relative to the housing 19 (first housing) of the device body 10. The post-processing unit 30 is also provided with a drive source and control unit separate from the device body 10, and is electrically connected to the device body 10 by connecting the connector 36 of the post-processing unit 30 with the connector 37 of the device body 10. This allows the post-processing unit 30 to operate based on commands from the control unit provided in the device body 10 using power supplied via the device body 10.

(Process cartridge)
As described above, each of the process cartridges 7n, 7y, 7m, and 7c has a substantially common configuration, except for the type of powder contained in the four powder containers 104n, 104y, 104m, and 104c. Here, the process cartridge 7n will be described as a representative. FIG. 8 is a cross-sectional view showing a schematic configuration of the process cartridge 7n. The process cartridge 7n is composed of a photoconductor unit CC including a photoconductor drum 101 and the like, and a development unit DT including a development roller 105 and the like.

The photosensitive drum 101, which is a drum-shaped electrophotographic photosensitive member (image carrier), is rotatably attached to the photosensitive unit CC via a bearing (not shown). The photosensitive drum 101 receives a driving force from a motor serving as a driving means (driving source) (not shown) and is driven to rotate in a clockwise direction (arrow w) in the figure during image formation. In addition, the photosensitive unit CC has a charging roller 102 for charging the photosensitive drum 101 and a cleaning member 103 arranged around the photosensitive drum 101.

The developing unit DT is provided with a developing roller 105 as a developer carrier that contacts the photosensitive drum 101 and rotates in a counterclockwise direction (arrow d) in the figure. The developing roller 105 and the photosensitive drum 101 each rotate so that their surfaces move in the same direction at the opposing portion (contact portion).

The developing unit DT is also provided with a developer supply roller (hereinafter simply referred to as "supply roller 106") as a developer supply member that rotates in a clockwise direction (arrow e) in the figure. The supply roller 106 and the developing roller 105 rotate so that their surfaces move in the same direction at the opposing portion (contact portion). The supply roller 106 supplies powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) onto the developing roller 105. At the same time, the supply roller 106 acts to strip off the powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) remaining on the developing roller 105 from the developing roller 105. The developing unit DT is also provided with a developing blade 107 as a developer regulating member that regulates the layer thickness of the powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) supplied onto the developing roller 105 by the supply roller 106.

The powder storage section 104n stores a powder adhesive (printing toner in the case of the process cartridges 7y, 7m, and 7c). A rotatably supported transport member 108 is provided within the powder storage section 104n. The transport member 108 rotates in a clockwise direction (arrow f) in the figure to agitate the powder stored in the powder storage section 104n and transport the powder to the development chamber 109 in which the development roller 105 and supply roller 106 are provided.

Here, the photoconductor unit CC and the development unit DT can be separately configured as a photoconductor unit cartridge and a development unit cartridge, respectively, and can be configured to be detachable from the main body of the image forming apparatus. Also, it is possible to configure a powder cartridge that has only the powder storage section 104 and the transport member 108 and is detachable from the main body of the apparatus, separate from the process cartridge having the photoconductor and developer carrier.

(Printing toner)
As the printing toners Tm, Tc, and Ty of this embodiment, conventionally known printing toners can be used. Among them, printing toners using a thermoplastic resin as a binder resin are preferred. The thermoplastic resin is not particularly limited, and those used in conventional printing toners such as polyester resin, vinyl resin, acrylic resin, and styrene-acrylic resin can be used. A plurality of these resins may be contained. Among them, printing toners using styrene-acrylic resin are more preferred. In addition, the printing toner (printing developer) may contain a colorant, a magnetic material, a charge control agent, a wax, and an external additive.

(powder adhesive)
In addition, as the powder adhesive Tn of this embodiment, a powder adhesive containing a thermoplastic resin can be used. The thermoplastic resin is not particularly limited, and examples thereof include known thermoplastic resins such as polyester resin, vinyl resin, acrylic resin, styrene-acrylic resin, polyethylene, polypropylene, polyolefin, ethylene-vinyl acetate copolymer resin, and ethylene-acrylic acid copolymer resin. A plurality of these resins may be contained.

The powder adhesive Tn preferably further contains a wax. The wax may be any known wax, such as an ester wax, which is an ester of an alcohol and an acid, or a hydrocarbon wax, such as paraffin wax.

The powder adhesive Tn may also contain a colorant. Known colorants such as black colorants, yellow colorants, magenta colorants, and cyan colorants can be used as the colorant. The content of the colorant in the powder adhesive is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Furthermore, the powder adhesive Tn may contain a magnetic material, a charge control agent, a wax, and an external additive.

In order to form an adhesive portion on a sheet P using a powder adhesive by electrophotography, the weight average particle diameter of the powder adhesive Tn is preferably 5.0 μm or more and 30 μm or less, and more preferably 6.0 μm or more and 20 μm or less. Note that printing toner may be used as the powder adhesive Tn as long as it satisfies the adhesive properties.

(Example of powder adhesive manufacturing)
A method for producing the powder adhesive Tn will be exemplified below. First, the following materials were prepared.
Styrene 75.0 parts n-Butyl acrylate 25.0 parts Polyester resin 4.0 parts (Polyester resin having a weight average molecular weight (Mw) of 20,000, a glass transition temperature (Tg) of 75° C., and an acid value of 8.2 mgKOH/g)
Ethylene glycol distearate 14.0 parts (ester wax obtained by esterifying ethylene glycol and stearic acid)
Hydrocarbon wax (HNP-9, manufactured by Nippon Seiro) 2.0 parts Divinylbenzene 0.5 parts

The mixture of the above materials was kept at 60°C and stirred at 500 rpm using a T.K. Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to dissolve uniformly, preparing a polymerizable monomer composition.

Meanwhile, 850.0 parts of 0.10 mol/L-Na ₃ PO ₄ aqueous solution and 8.0 parts of 10% hydrochloric acid were added to a vessel equipped with a high-speed stirring device Clearmix (manufactured by M Technique Co., Ltd.), the rotation speed was adjusted to 15,000 rpm, and the mixture was heated to 70° C. 127.5 parts of 1.0 mol/L-CaCl ₂ aqueous solution was added thereto to prepare an aqueous medium containing a calcium phosphate compound.

After adding the above polymerizable monomer composition to the aqueous medium, 7.0 parts of the polymerization initiator t-butyl peroxypivalate was added, and the mixture was granulated for 10 minutes while maintaining a rotation speed of 15,000 rpm. The high-speed agitator was then replaced with a propeller agitator, and the mixture was reacted at 70°C for 5 hours while refluxing, after which the liquid temperature was increased to 85°C and the mixture was reacted for an additional 2 hours.

After the polymerization reaction was completed, the resulting slurry was cooled, and hydrochloric acid was added to the slurry to adjust the pH to 1.4 and the slurry was stirred for 1 hour to dissolve the calcium phosphate salt. The slurry was then washed with three times the amount of water, filtered, dried, and classified to obtain powder adhesive particles.

Then, 2.0 parts of silica fine particles (number average particle size of primary particles: 10 nm, BET specific surface area: 170 ^m2 /g) that had been hydrophobized using dimethyl silicone oil (20% by mass) were added as an external additive to 100.0 parts of the powder adhesive particles. The powder adhesive particles to which the silica fine particles had been added were mixed at 3000 rpm for 15 minutes using a Mitsui Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) to obtain a powder adhesive. The weight average particle size of the obtained powder adhesive was 6.8 μm.

(Method of measuring glass transition temperature (Tg))
The glass transition temperature (Tg) of the powder adhesive Tn can be measured using a differential scanning calorimeter "Q1000" (manufactured by TA Instruments). The melting points of indium and zinc are used for temperature correction of the detector of the device, and the heat of fusion of indium is used for heat correction.

Specifically, 1 mg of sample is weighed out and placed in an aluminum pan, with an empty aluminum pan used as a reference. Using the modulation measurement mode, measurements are taken in the range of 0°C to 100°C with a heating rate of 1°C/min and temperature modulation conditions of ±0.6°C/60 seconds. Since the specific heat change is obtained during the heating process, the glass transition temperature (Tg) is determined as the intersection of the line midway between the baselines before and after the specific heat change and the differential thermal curve. The glass transition temperature (Tg) of the obtained powder adhesive Tn was 52°C.

(Example of the production of printing toner)
Next, a method for producing the printing toners Ty, Tm, and Tc will be exemplified. First, the following materials were prepared.
Styrene 60.0 parts Colorant 6.5 parts (C.I. Pigment T Blue 15:3, Dainichi Seika Chemicals Co., Ltd.)

The above materials were placed in an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and further dispersed using zirconia particles with a diameter of 1.7 mm at 220 rpm for 5 hours to obtain a pigment dispersion.

In addition, the following materials were prepared:
Styrene 15.0 parts n-Butyl acrylate 25.0 parts Polyester resin 4.0 parts (Polyester resin having a weight average molecular weight (Mw) of 20,000, a glass transition temperature (Tg) of 75° C., and an acid value of 8.2 mgKOH/g)
Behenyl behenate 12.0 parts (ester wax obtained by esterifying behenic acid and behenyl alcohol)
Divinylbenzene 0.5 parts

The above materials were mixed and added to the pigment dispersion. The resulting mixture was kept at 60°C and stirred at 500 rpm using a T.K. Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to dissolve and disperse uniformly, preparing a polymerizable monomer composition.

Meanwhile, 850.0 parts of 0.10 mol/L-Na ₃ PO ₄ aqueous solution and 8.0 parts of 10% hydrochloric acid were added to a vessel equipped with a high-speed stirring device Clearmix (manufactured by M Technique Co., Ltd.), the rotation speed was adjusted to 15,000 rpm, and the mixture was heated to 70° C. 127.5 parts of 1.0 mol/L-CaCl ₂ aqueous solution was added thereto to prepare an aqueous medium containing a calcium phosphate compound.

After adding the above polymerizable monomer composition to the aqueous medium, 7.0 parts of the polymerization initiator t-butyl peroxypivalate was added, and the mixture was granulated for 10 minutes while maintaining a rotation speed of 15,000 rpm. The high-speed agitator was then replaced with a propeller agitator, and the mixture was reacted at 70°C for 5 hours while refluxing, after which the liquid temperature was increased to 85°C and the mixture was reacted for an additional 2 hours.

After the polymerization reaction was completed, the resulting slurry was cooled, and hydrochloric acid was added to the slurry to adjust the pH to 1.4. The slurry was then stirred for one hour to dissolve the calcium phosphate salt. The slurry was then washed with three times the amount of water, filtered, dried, and classified to obtain toner particles.

Then, 2.0 parts of silica fine particles (number average particle diameter of primary particles: 10 nm, BET specific surface area: 170 ^m2 /g) that had been hydrophobized using dimethyl silicone oil (20% by mass) were added as an external additive to 100.0 parts of the toner particles. The toner particles to which the silica fine particles had been added were mixed at 3000 rpm for 15 minutes using a Mitsui Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) to obtain a toner. The weight average particle diameter of the obtained printing toner was 6.5 μm.

(Method of measuring weight average particle size)
The weight average particle diameter of the printing toners Ty, Tm, Tc and the powder adhesive Tn is calculated as follows. The measurement device is a precision particle size distribution measurement device using the pore electrical resistance method with a 100 μm aperture tube, "Coulter Counter MulTisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.). The measurement conditions are set and the measurement data is analyzed using the accompanying dedicated software, "Beckman Coulter MulTisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.). The measurement is performed with an effective measurement channel count of 25,000 channels.

The electrolyte solution used for the measurements is one in which special grade sodium chloride is dissolved in ion-exchanged water to give a concentration of 1% by mass, for example "ISOTON II" (manufactured by Beckman Coulter).

Before performing measurements and analysis, the dedicated software is set as follows. On the "Change Standard Measurement Method (SOM)" screen of the dedicated software, the total count number in the control mode is set to 50,000 particles, the number of measurements is set to 1, and the Kd value is set to the value obtained using "Standard particle 10.0 μm" (manufactured by Beckman Coulter). The threshold and noise level are automatically set by pressing the "Threshold/Noise Level Measurement Button". In addition, the current is set to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and "Flush aperture tube after measurement" is checked. On the "Pulse to particle size conversion setting" screen of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin to 256 particle size bin, and the particle size range to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour 200 mL of the electrolyte solution into a 250 mL round-bottom glass beaker made exclusively for the MulTisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "Aperture Tube Flush" function of the dedicated software.
(2) 30 mL of the aqueous electrolyte solution is placed in a 100 mL flat-bottom glass beaker, and 0.3 mL of a dilution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments with a pH of 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted 3 times by mass with ion-exchanged water is added thereto as a dispersant.
(3) Prepare an ultrasonic disperser "UlTransonic Dispersion SysTem TeTora150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W. Place 3.3 L of ion-exchanged water in the water tank of the ultrasonic disperser, and add 2 mL of Contaminon N to this water tank.
(4) The beaker (2) is set in the beaker fixing hole of the ultrasonic disperser described above, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolyte solution in the beaker is maximized.
(5) While the electrolyte solution in the beaker in (4) is being irradiated with ultrasonic waves, the toner or powder adhesive is added to the electrolyte solution in small amounts of 10 mg at a time and dispersed. The ultrasonic dispersion process is then continued for another 60 seconds. During the ultrasonic dispersion process, the water temperature in the water tank is appropriately adjusted to be 10°C or higher and 40°C or lower.
(6) Using a pipette, the electrolyte solution (5) in which the toner or powder adhesive is dispersed is dropped into the round-bottom beaker (1) placed in the sample stand to adjust the measurement concentration to 5%. Measurements are then continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using dedicated software provided with the device to calculate the weight average particle diameter.

(Image formation operation)
Next, the image forming operation performed by the image forming apparatus 1 of this embodiment will be described with reference to Figures 1 to 8. Figures 3 and 4 are diagrams showing the sheet transport path in the image forming apparatus 1. Figures 5(a to f) are diagrams for explaining the contents of the folding process.

When data of an image to be printed and a command to execute printing are input to the image forming device 1, the control unit of the image forming device 1 starts a series of operations (image forming operation) in which the sheet P is transported to form an image and, if necessary, post-processing is performed by the post-processing unit 30. In the image forming operation, first, as shown in FIG. 1, the sheets P are fed one by one from the sheet cassette 8 and transported toward the transfer nip 5N via the transport roller 8a.

In parallel with the feeding of the sheet P, the process cartridges 7n, 7y, 7m, and 7c are driven in sequence, and the photosensitive drum 101 is rotated in the clockwise direction (arrow w) in the figure. At this time, the photosensitive drum 101 is uniformly charged on its surface by the charging roller 102. The scanner unit 2 also irradiates the photosensitive drum 101 of each process cartridge 7n, 7y, 7m, and 7c with laser light G modulated based on image data, forming an electrostatic latent image on the surface of the photosensitive drum 101. Next, the electrostatic latent image on the photosensitive drum 101 is developed into a powder image by the powder carried by the developing roller 105 of each process cartridge 7n, 7y, 7m, and 7c.

The powder adhesive layer formed on the photosensitive drum 101 by development with the powder adhesive Tn differs from a toner image (normal toner image) of printing toner used to record images such as figures and text on a recording medium in that it is not intended to transmit visual information. However, in order to apply the powder adhesive Tn to the sheet P in a predetermined application pattern, the layer of powder adhesive Tn developed in a shape corresponding to the application pattern by the electrophotographic process may also be considered as one of the "toner images."

The transfer belt 3a rotates in the counterclockwise direction (arrow v) in the figure. The toner images formed in each process cartridge 7n, 7y, 7m, and 7c are primarily transferred from the photosensitive drum 101 to the transfer belt 3a by the electric field formed between the photosensitive drum 101 and the primary transfer roller 4.

As shown in FIG. 1, process cartridge 7n, which uses powder adhesive Tn, is located most upstream of the four process cartridges in the rotation direction of transfer belt 3a. Yellow, magenta, and cyan process cartridges 7y, 7m, and 7c are lined up in this order from process cartridge 7n toward the downstream side in the rotation direction of transfer belt 3a. Therefore, when the four types of toner images are superimposed on transfer belt 3a, powder adhesive Tn becomes the bottom layer (the layer in contact with transfer belt 3a), and yellow (Ty), magenta (Tm), and cyan (Tc) printing toners are superimposed on top of it in this order.

The toner image carried by the transfer belt 3a and reaching the transfer nip 5N is secondarily transferred to the sheet P transported along the main transport path 1m by the electric field formed between the secondary transfer roller 5 and the secondary transfer inner roller 3b. At that time, the toner layer is turned upside down. That is, on the sheet P that has passed through the transfer nip 5n, the printing toners of cyan (Tc), magenta (Tm), and yellow (Ty) are layered from the bottom layer (the layer that contacts the sheet P), and a layer of powder adhesive Tn is formed on top of that. Therefore, in the toner image transferred to the sheet P, the layer of powder adhesive Tn becomes the outermost surface.

Then, the sheet P carrying the unfixed toner image is sandwiched and transported through the fixing nip 6N together with the fixing film 6a while the image side of the sheet P is in close contact with the outer surface of the fixing film 6a. During this sandwiching and transporting process, heat from the heater 6a1 is applied to the image side of the sheet P through the fixing film 6a, and the printing toners Ty, Tm, Tc and the powder adhesive Tn melt and are fixed onto the sheet P. Having passed through the fixing nip 6N, the sheet P is curvature-separated from the fixing film 6a while still retaining the fixed toner image, and the image fixed to the sheet P is obtained.

Regardless of whether single-sided or double-sided printing is being performed, the sheet P discharged from the device body 10 is sandwiched between the intermediate roller 34b and the second discharge roller 34c as shown in Figures 3 and 4, and is transported to the first path R1 or the second path R2 by the tray switching guide 13a.

The first path R1 shown in FIG. 3 is a path along which the sheet P that has passed through the first fixing device 6 is discharged to the first discharge tray 13 by the discharge unit 34 in a normal printing mode that does not use the post-processing unit 30. The second path R2 shown in FIG. 4 is a path along which the sheet P that has passed through the first fixing device 6 is discharged to the second discharge tray 35 via the discharge unit 34, the folder 31, and the second fixing device 32 in an adhesive printing mode.

Between the first fixing device 6 and the folder 31 in the second route R2, an intermediate path 15 is provided. The intermediate path 15 is a sheet transport path that passes through the upper surface (top surface) of the image forming device 1, and extends below the first discharge tray 13 and approximately parallel to the first discharge tray 13. The intermediate path 15 and the first discharge tray 13 are inclined vertically upward toward the folder 31 with respect to the horizontal direction. Therefore, the entrance of the folder 31 (the guide roller pair (31c, 31d) described below) is located vertically above the exit of the device main body 10 (the nip between the intermediate roller 34b and the second discharge roller 34c).

The folder 31 has four rollers, a first guide roller 31c, a second guide roller 31d, a first folding roller 31a, and a second folding roller 31b, and a retraction section 31e. The first guide roller 31c and the second guide roller 31d are a pair of guide rollers that sandwich and transport the sheet P received from the transport path (intermediate path 15 in this embodiment) upstream of the folder 31. The first folding roller 31a and the second folding roller 31b are a pair of folding rollers that send out the sheet P while folding it.

The distance M (FIG. 1) from the second discharge roller 34c to the first guide roller 31c in the sheet transport direction along the second path R2 is configured to be shorter than the overall length L (FIG. 5(a)) of the sheet P in the transport direction before folding. In other words, the distance M from the second discharge roller 34c to the first guide roller 31c determines the lower limit of the length of the sheet in the transport direction that can be processed by the post-processing unit 30. This configuration allows the sheet P to be transferred smoothly from the discharge unit 34 to the pair of guide rollers.

The folding process by the folder 31 will be described with reference to Figures 5(a-f). When performing the folding process, the first guide roller 31c and the first folding roller 31a rotate in a clockwise direction in the figure, and the second guide roller 31d and the second folding roller 31b rotate in a counterclockwise direction in the figure. First, the leading edge q of the sheet P sent out from the discharge unit 34 is pulled into the pair of guide rollers (31c, 31d) as shown in Figure 5(a). As shown in Figure 5(b), the leading edge q of the sheet P is guided downward by the guide wall 31f and contacts the first folding roller 31a, and is then pulled into the opposing first folding roller 31a and second guide roller 31d and abuts against the wall 31g of the pull-in section 31e.

As the sheet P is pulled in by the pair of guide rollers (31c, 31d), the leading edge q slides against the wall 31g and advances further into the pull-in section 31e. Eventually, the leading edge q hits the end 31h of the pull-in section 31e as shown in FIG. 5(c). The pull-in section 31e forms a space below the intermediate path 15 that extends approximately parallel to the intermediate path 15, and at the stage shown in FIG. 5(c), the sheet P is wrapped around the second guide roller 31d and bent into a U-shape.

When the sheet P is further pulled in by the guide roller pair (31c, 31d) from the state shown in FIG. 5(c), it starts to bend at the middle part r as shown in FIG. 5(d). Eventually, as shown in FIG. 5(e), the middle part r comes into contact with the second folding roller 31b, and is pulled into the nip of the folding roller pair (31a, 31b) by the frictional force it receives from the second folding roller 31b. Then, as shown in FIG. 5(f), the sheet P is folded with the middle part r as the crease, and is discharged by the folding roller pair (31a, 31b) with the middle part r at the front.

Here, the depth N of the retraction section 31e (FIG. 5(e)), i.e., the distance from the nip of the pair of folding rollers (31a, 31b) to the end 31h of the retraction section 31e, is set to half the total length L of the sheet P. This allows the folder 31 to fold the sheet P in half (center folding). Note that by changing the depth N of the retraction section 31e, the position of the fold can be changed as desired.

The folder 31 described above is an example of a folding means, and a folding mechanism may be used that, for example, presses a blade against the sheet P and pushes it into the nip between a pair of rollers to form a crease. The folding process is not limited to folding in half, and a folding mechanism that performs, for example, a Z-fold or a triple fold may be used. Since the folder 31 of this embodiment is composed of rotating rollers and a fixed retraction section 31e, the drive mechanism can be simplified compared to a folding mechanism that uses a reciprocating blade. Furthermore, since the folder 31 of this embodiment only requires the retraction section 31e with a depth N of half the sheet length in addition to the four rollers, the post-processing unit 30 can be made smaller.

The sheet P folded by the folder 31 is transported to the second fixing device 32, where it is subjected to a bonding process in which it is heated and pressurized while being sandwiched and transported through the bonding nip 32N. The sheet P is subjected to a bonding process (a second thermal fixation of the image surface to which the powder adhesive has been applied) so that it is bonded while still in the folded state as shown in FIG. 10. That is, when the sheet P passes through the bonding nip 32N, the powder adhesive Tn on the sheet P is heated and pressurized again in a softened state, so that the inner surfaces of the sheets P are bonded (bonded) together via the powder adhesive Tn.

As shown in FIG. 4, the sheet P that has been subjected to the adhesive process by the second fixing device 32 is discharged to the left side in the figure from the discharge outlet 32c (second discharge outlet) provided in the housing 39 of the post-processing unit 30. It is then stored in the second discharge tray 35 (see FIG. 1) provided on the left side surface of the device main body 10. This completes the image formation operation when the sheet P is transported along the second path R2.

Figure 7(a) shows an example of a powder adhesive Tn application pattern, and Figure 7(b) shows a paper bag 54, which is an example of an adhesive print that is a fully adhesive product (output product of the image forming device 1). In this case, the image forming unit 1e applies powder adhesive Tn to a U-shaped region 53a so that when the sheet P is folded, three sides including the crease 53b are joined. Then, the sheet P is folded so that the layers of powder adhesive Tn applied to the region 53a face each other, and then an adhesive process is performed, forming the paper bag 54 of Figure 7(b) with an opening on one side.

As described above, the image forming apparatus 1 of this embodiment can output a product that is bonded by an adhesive process from a base paper such as blank paper that is not preprinted paper. The bonding points of the folded sheet P can be changed by applying the powder adhesive Tn to the sheet P in a different pattern. For example, it is possible to create semi-adhesive products that are intended to be peeled off later, such as envelopes for enclosing documents or pay slips. Furthermore, the image recorded by the image forming apparatus 1 using printing toner can include a format (unchanging part) when preprinted paper is used, and a variable part such as personal information. Furthermore, the image forming apparatus 1 of this embodiment can be used for applications in which preprinted paper is used as a recording medium and printing and adhesive processes are performed on the variable parts.

(Conditions of the first heat treatment and the second heat treatment)
Here, we will explain the condition settings for the fixing process (first fixing process, first heating process) in which the sheet P is heated by the first fixing device 6, and the adhesion process (second fixing process, second heating process) in which the sheet P is heated by the second fixing device 32.

When outputting a fully bonded product such as the paper bag 54 shown in FIG. 7(b), it is sufficient for the adhesive part made of powder adhesive to have a strength equal to or greater than the tear strength of the base paper, sheet P, in order to fulfill the purpose of the paper bag. In other words, the adhesive part needs to have an adhesive strength (mechanical strength) such that when an external force is applied in a direction to pull the sheet surfaces bonded to each other in the paper bag 54 apart, the sheet surfaces do not peel apart, and the strength of the paper, sheet P, reaches its limit and breaks first. This adhesive strength is generally higher than the strength obtained when normal printing toner is fixed to the sheet P by the fixing process in normal printing.

First, the difference in heating efficiency between the fixing process and the bonding process will be explained. In the fixing process, as shown in FIG. 9, the fixing film 6a, which is a heating member, directly contacts the layer of powder adhesive Tn on the sheet P to supply heat, so that the powder adhesive Tn is heated with high efficiency. On the other hand, in the bonding process, as shown in FIG. 10, the sheet P is folded so that the layer of powder adhesive Tn is on the inside, and the heating film 32b, which is a heating member, contacts the outer surface of the sheet P to supply heat. In other words, the layer of powder adhesive Tn is heated by the heat transmitted from the heating film 32b through the sheet P, so the heating efficiency of the powder adhesive Tn is lower than in the fixing process.

Therefore, if it is assumed that the powder adhesive Tn reaches exactly the same maximum temperature in the fixing process and the bonding process, it is necessary to supply a larger amount of heat to the sheet P in the bonding process than in the fixing process. In other words, it is considered necessary to set the temperature control temperature of the heating film 32b higher so that a larger amount of heat can be supplied to the sheet P in a short period of time.

In particular, in the case of an image forming apparatus with high productivity (fast sheet transport speed), the sheet P passes through the adhesion nip 32N in a short time. In such a case, if it is assumed that the powder adhesive Tn reaches exactly the same maximum temperature in the fixing process and the adhesion process, it is assumed that the amount of heat supplied to the adhesion process must be much greater (for example, about two to several times) than the amount of heat supplied to the fixing process. In other words, it is assumed that the temperature control temperature of the heating film 32b must be set very high so that a large amount of heat is transferred to the sheet P in a short time.

However, if the controlled temperature of the heating film 32b is set high, hot offset may occur during the bonding process, as described below. In addition, a high controlled temperature of the heating film 32b may result in inconveniences such as increased power consumption and heat generation by the image forming device 1.

In this embodiment, therefore, the conditions of the fixing and bonding processes are proposed to obtain strong bonding with the powder adhesive while minimizing the amount of heat supplied to the sheet during the bonding process. Hereinafter, the amount of heat supplied per unit area of the sheet P in the fixing process is referred to as "amount of heat supplied in the fixing process Q1," and the amount of heat supplied per unit area of the sheet P in the bonding process is referred to as "amount of heat supplied in the bonding process Q2." In other words, Q1 is the Joule heat supplied per unit area of the sheet P from the fixing film 6a during the period from when the sheet P reaches the bonding nip 32N until it leaves the fixing nip 6N. Q2 is the Joule heat supplied per unit area of the sheet P (unit area of the outer surface of the sheet in a folded state) from the heating film 32b during the period from when the sheet P reaches the bonding nip 32N until it leaves the bonding nip 32N.

In this embodiment, the amount of heat supplied in the fixing step is set to be greater than the minimum necessary amount, and the amount of heat supplied in the bonding step is set to the minimum necessary amount.
(a) As a specific condition, preferably, the ratio of the amount of heat Q2 supplied in the adhesion step to the amount of heat Q1 supplied in the fixing step is between 1.0 and 2.2 (1.0≦Q2/Q1≦2.2).
(b) More preferably, the ratio of the amount of heat Q2 supplied in the adhesion step to the amount of heat Q1 supplied in the fixing step is between 1.3 and 1.9 (1.3≦Q2/Q1≦1.9).

The maximum temperature (Tmax1) of the powder adhesive Tn in the fixing process is set to a temperature range that exceeds the melting point of the powder adhesive Tn and where the melt viscosity approaches that of a liquid. On the other hand, the maximum temperature (Tmax2) of the powder adhesive in the bonding process is set to near the glass transition temperature Tg (softening point) that is lower than the melting point of the powder adhesive Tn. By adopting such a heat distribution, it is possible to obtain a strong adhesive strength even though the amount of heat supplied in the bonding process is minimized, as will be explained in detail later. The calculation method is explained in detail below.

In this embodiment, the sheet conveying speed of the first fixing device 6 and the second fixing device 32 is the same value, specifically, 210 mm/sec. Hereinafter, a case will be considered in which a sheet P made of A4 size paper (width 210 mm × length (length in conveying direction) 297 mm) is folded in half by adhesive printing to output a product. In this case, the area of the sheet P is ⁶²³⁷⁰ mm2, and the time required for the sheet P to pass through the fixing nip 6N of the first fixing device 6 is approximately 1.41 sec. In the adhesive process, the sheet P is folded in half to become half the size (width 210 mm × length 148.5 mm), the area is 31185 ^mm2 , and the time required for the sheet P to pass through the adhesive nip 32N of the second fixing device 32 is approximately 0.71 sec (Table 1).

The temperature control conditions and power for the fixing process and adhesion process under the above conditions are summarized in Table 2 below. Power was measured by connecting a power meter (Digital Power Meter WTn310, manufactured by Yokogawa Measurement Corporation) in series with the heater 6a1, 32b1 of the first fixing unit 6 or the second fixing unit 32, and reading the average power consumption while the paper was passing through. The adhesiveness evaluation result of "○" indicates that when an external force was applied in the direction of peeling off the adhesive surface of the product, the adhesive surface did not peel off, and the strength of the paper sheet P reached its limit first and it broke.

The maximum temperatures Tmax1 and Tmax2 of the powder adhesive Tn were measured as follows. First, a thermocouple with a small heat capacity of the temperature detection part (for example, a K-type thermocouple wire with a diameter of 50 μm or less, manufactured by Anritsu Keiki Co., Ltd.) was prepared. When measuring the maximum temperature Tmax1 of the powder adhesive Tn in the fixing process, the thermocouple was attached to the surface of the sheet P, and the sheet P was passed through the fixing nip 6N and recorded. When measuring the maximum temperature Tmax2 of the powder adhesive Tn in the bonding process, a thermocouple was attached to the sheet P before it was folded by the folder 31 after the fixing process, and the sheet P was passed through the bonding nip 32N in a folded state with the thermocouple sandwiched inside, and recorded. Then, the potential difference signal output from the thermocouple was measured with a memory high-corder manufactured by Hioki E.E. Corporation, and the maximum temperatures were identified from the temperature change over time and were set as Tmax1 and Tmax2.

The temperature control temperature (target temperature of heater 6a1) in the fixing process was 170°C, and the average power consumption during paper passage was 415 W. The time required for sheet P to pass through fixing nip 6N was 1.41 sec, so the input heat amount can be calculated as 415 [W] x approximately 1.41 [sec] = 586.9 [J]. Since the sheet area was 62370 ^mm2 , the heat amount (Q1) applied per unit area was 586.9 ÷ 62370 = approximately 0.009 [J/ ^mm2 ]. Under these conditions, the maximum temperature Tmax1 of powder adhesive Tn was 120°C.

The controlled temperature in the bonding process (the target temperature of the heater 32b1) was 220°C, and the average power consumption during paper passage was 617 W. The time required for the sheet P to pass through the bonding nip 32N was 0.71 sec, so the input heat amount can be calculated as 617 [W] x approximately 0.71 [sec] = 436.3 [J]. The sheet area was 31185 ^mm2 , so the heat amount (Q2) applied per unit area was 436.3 ÷ 31185 = approximately 0.014 [J/ ^mm2 ]. Under these conditions, the maximum temperature Tmax2 of the powder adhesive Tn was 80°C.

The results are summarized in Table 2. It is preferable that the maximum temperatures Tmax1 and Tmax2 of the powder adhesive Tn have a relationship of Tmax1 > Tmax2. Furthermore, for reasons described below, it is preferable to set Tmax2 higher than the glass transition temperature Tg (52°C in this embodiment).

The state of the adhesive joint formed by the fixing and adhesion processes of this embodiment will be described below. First, ideal adhesion is when smooth surfaces come into close contact with each other, the objects to be adhered are close enough to each other that intermolecular forces can reach them, and a direct bond is created at the molecular level. In this case, stronger bonding strength can be obtained if the objects to be adhered have similar molecular structures. It is generally known that very strong bonding strength can be obtained by polishing the surfaces of similar solids with metal or the like and then adhering them together.

Figure 11 (A) is an enlarged cross-sectional view of the surface of the paper used as sheet P. Paper is a light and strong medium due to the entanglement of cellulose fibers, and when observed under a microscope, it has countless irregularities P1 with heights of several μm to several tens of μm caused by the cellulose fibers. Therefore, the surface of paper is generally not in a very favorable condition for use as an adherend.

By the way, liquid glue is a means that achieves practical adhesive strength even with such papers. As shown in Figure 11 (B), liquid glue GL has good wettability with cellulose and can fill the gaps caused by the unevenness P1 between the opposing paper surfaces. When the water is evaporated in this state and the liquid glue GL is dried and solidified, intermolecular forces act between the cellulose and the solidified liquid glue GL, and an overall mechanical bond (anchor effect) is obtained via the solidified material, resulting in strong adhesion.

As described above, in this embodiment, the sheet P is bonded using the powder adhesive Tn. Therefore, by going through the process described below, an adhesive strength close to that achieved by the liquid glue GL can be obtained.

(Fixing process)
First, as shown in FIG. 12A, the image forming unit 1e transfers the powder adhesive Tn onto the paper used as the sheet P, and applies the powder adhesive Tn in a predetermined pattern. Then, as shown in FIG. 12B, in the fixing nip 6N of the first fixing device 6, heat from the heater 6a1 is applied to the powder adhesive Tn via the fixing film 6a. As a result, the temperature of the powder adhesive Tn rises to 120° C., which is a temperature (Tmax1) that is higher than the maximum temperature (Tmax2) during the bonding process described below. As a result, the powder adhesive Tn melts and becomes liquid, and a layer of the adhesive Tn1 that penetrates into the unevenness of the paper (wetting the surface of the paper) is formed. The maximum temperature Tmax1 during this fixing process is preferably 40° C. or higher than the glass transition temperature (Tg) of the powder adhesive Tn, and more preferably 50° C. or higher than Tg.

After that, when it passes through the fixing nip 6N, the adhesive Tn1 solidifies while filling the unevenness between the paper as shown in FIG. 12(C), and the cellulose and adhesive Tn1 have a sufficient contact area, which allows intermolecular forces (van der Waals forces) to act. At the same time, the adhesive Tn1 becomes entangled with the paper fibers, which creates a mechanical bonding force between the adhesive Tn1 and the paper (anchor effect). Furthermore, the surface of the adhesive Tn1 is smoothed by being leveled by the fixing film 6a, to the same degree of surface roughness as the surface of the fixing film 6a (in this embodiment, the surface of the release layer made of fluororesin).

If the amount of heat applied to the powder adhesive Tn in the fixing process is insufficient, the adhesive Tn1 will not penetrate the unevenness of the paper sufficiently (will not be sufficiently wetted), and the surface of the adhesive Tn1 will not be sufficiently smooth. On the other hand, if too much heat is applied to the powder adhesive Tn in the fixing process, the viscosity of the molten powder adhesive Tn will drop too much and it will penetrate into the inside of the paper, resulting in an insufficient amount of adhesive remaining on the surface of the paper and an insufficient surface of the adhesive Tn1.

In this way, by supplying a power slightly higher than that required for normal image fixing, the viscosity of the molten powder adhesive can be appropriately reduced, resulting in a smooth surface.

(Bonding process)
13A, the sheets P are folded so that the surfaces (image surfaces) coated with the adhesive Tn2 face each other when they reach the second fixing device 32. At this point, although the surfaces of the adhesive Tn2 are smooth, the surfaces of the adhesive Tn2 are not in close contact with each other and gaps remain, so that the sheets P are not in an adhesive state.

From this state, the sheet P is pressurized and heated in the adhesive nip 32N of the second fixing device 32, and the temperature of the adhesive Tn2 rises to, for example, 80°C. The maximum temperature Tmax2 reached in this adhesive process is preferably 10°C or more higher than the glass transition temperature (Tg) of the powder adhesive Tn, and more preferably 20°C or more higher than Tg. However, the maximum temperature Tmax2 reached in the adhesive process is lower than the maximum temperature Tmax1 reached in the fixing process.

By being heated in the adhesive nip 32N, the softened adhesive Tn3 comes into close contact with the other parts as shown in FIG. 13(B). In this state, the same types of adherends are close enough to each other to create a direct bond at the molecular level, so the upper and lower sheets P in the figure are firmly adhered together via the adhesive Tn3.

Comparative Example
As comparative experimental results, the adhesiveness of the adhesive prints obtained by varying the heat supply Q1 in the fixing process (i.e., varying the power supplied to the heater 6a1 of the first fixing unit 6) is evaluated, and the results are shown in Table 3. The adhesiveness was evaluated by applying a force to the adhesive surface of the paper bag in a direction to peel it off by hand. In this case, those that were not adhered at all were marked with an X, those that were adhered but the adhesive surface peeled off were marked with a △, and those in which the adhesive surface did not peel off and the paper was torn first were marked with an O. Good results were obtained in Comparative Examples 3 and 4, but in Comparative Examples 2 and 5, although the adhesive surface was adhered, it peeled off before the paper was torn (△). Comparative Examples 1 and 6 were not adhered (X).

The following describes the case of Comparative Example 1, in which the ratio Q2/Q1 of the amount of heat supplied in the bonding process Q2 to the amount of heat supplied in the fixing process Q1 is lower than 1.0. In this case, as shown in FIG. 14(A), the amount of heat supplied in the fixing process Q1 is too high, so that the adhesive Tn4 melts excessively and penetrates into the cellulose fibers, and after passing through the first fixing device 6, the surface of the adhesive Tn4 shows the unevenness of the surface of the paper itself. Even if the bonding process is performed in this state, sufficient adhesive strength cannot be obtained because there are few contact points of the adhesive Tn5 as shown in FIG. 14(B).

Next, the case of Comparative Example 6 in which the ratio Q2/Q1 of the heat supply Q2 in the adhesion process to the heat supply Q1 in the fixing process is higher than 2.2 will be described. In this case, as shown in FIG. 15(A), the heat supply Q1 in the fixing process is too small, so that the adhesive Tn6 is insufficiently melted, resulting in an uneven surface as shown in the figure, and the adhesive Tn6 is also insufficiently melted at the interface between the adhesive Tn6 and the paper. Even if the adhesion process is performed in this state, there is not enough contact area between the cellulose and the adhesive Tn6, so that intermolecular attraction (van der Waals force) is not obtained, and mechanical bonding (anchor effect) is not obtained. Therefore, if the adhesion process is performed with the heat supply Q2 of 0.0140 J/ ^mm2 , which is the same as in Example 1, even if the surfaces of the adhesive Tn6 are bonded to each other as shown in FIG. 15(B), the bond between the adhesive Tn6 and the paper is weak, so that the adhesion between the papers via the adhesive Tn6 is insufficient. Even if the adhesive Tn6 is heated further to above its melting point in this state, the adhesive Tn7 will penetrate into the cellulose fibers of the paper, as shown in Fig. 15C, and the adhesive strength will not increase. Therefore, it is clear that the balance between the amounts of heat Q1 and Q2 supplied in the fixing process and the adhesion process is important.

As described above, according to this embodiment, the maximum temperature Tmax2 of the powder adhesive Tn in the bonding process is set lower than the maximum temperature Tmax1 of the powder adhesive Tn in the fixing process. This allows the state of the powder adhesive Tn to be appropriately changed in each of the fixing process and bonding process, without setting the heating temperature in the bonding process excessively high, and allows the sheet P to be firmly bonded via the powder adhesive Tn.

In this embodiment, a method for increasing the adhesive strength of the powder adhesive Tn and reducing the occurrence of image defects in images formed with printing toner is described. In the following, elements with the same reference numerals as in embodiment 1 have substantially the same configuration and function as in embodiment 1, and the following description focuses on the parts that are different from embodiment 1.

As described above, the image forming device 1 is capable of applying powder adhesive Tn in a predetermined application pattern in parallel with the operation of recording an image on one or both sides of a sheet P using printing toner, and outputting a product (glued printed product) that has been subjected to folding and gluing processes. Therefore, it is possible to output a product that has been glued by gluing and has printing information added from base paper such as blank paper that is not preprinted paper.

Figure 16(a) shows an example of a coating pattern of powder adhesive Tn, and Figure 16(b) shows a paper bag 54 for a medicine bag, which is an example of an adhesive print. The paper bag 54 is coated with powder adhesive Tn in the area shown in Figure 16(a), folded in half at crease 53b, and then subjected to a bonding process to form a bag shape. In addition, an image 53c is recorded on the surface of the paper bag 54 with printing toner. When outputting such a product, one side of the sheet P used as the base paper becomes the outside of the product, and the other side becomes the inside of the product. Therefore, as the image formation operation for the first side in double-sided printing, an image 53c for the outer surface is formed with printing toner, and as the image formation operation for the second side, powder adhesive Tn is applied in a predetermined coating pattern.

In this case, depending on the temperature and power conditions of the bonding process, an image defect 53d called hot offset may occur, as shown in FIG. 16(c). Hot offset occurs for the following reasons:

As shown in FIG. 17, the powder adhesive Tn is applied to the inside of the folded sheet P. When the power supply in the bonding process is increased to melt the powder adhesive Tn, the temperature of the heating film 32b increases. If the temperature of the heating film 32b becomes excessively high, the image 53c on the front side of the sheet P that is in direct contact with the heating film 32b melts excessively and becomes liquid, adhering to the heating film 32b as stains. The adhering stains are again adhered to the sheet P when the heating film 32b rotates once, and become apparent as the image defect 53d in FIG. 16(B). In order to suppress the occurrence of this hot offset, it is necessary to supply the necessary amount of heat to the powder adhesive Tn while preventing the temperature of the heating film 32b from becoming too high.

In this embodiment, we propose to supply the necessary amount of heat to the powder adhesive Tn while setting the temperature of the heating film 32b low by setting the sheet conveying speed in the second fixing device 32 slowly. In other words, if the sheet conveying speed in the first fixing device 6 is V1 and the sheet conveying speed in the second fixing device 32 is V2, then V1 > V2.

Specifically, the sheet conveying speed V1 of the first fixing device 6 is 210 mm/sec, the same as in Example 1, and the sheet conveying speed V2 of the second fixing device 32 is 104.5 mm/sec, which is slower than 210 mm/sec. At that time, the temperature setting of the heater 32b1 was adjusted so that the amount of heat received by the sheet P in the adhesion process was approximately the same as in Example 1. Table 4 also shows Comparative Example 1, in which the sheet conveying speed V2 of the second fixing device 32 was set to 157.5 mm/sec, and Comparative Example 2, in which it was set to 70 mm/sec. The adhesiveness evaluation result "○" indicates that when an external force was applied in the direction of peeling off the adhesive surface of the product, the adhesive surface did not peel off, and the strength of the paper sheet P reached its limit first and it broke.

In Example 2 and Comparative Examples 1 and 2, in which the sheet conveying speed V2 and heater temperature were adjusted as described above, the adhesiveness evaluation results were all rated as "good." It can be seen that by appropriately adjusting the amount of heat Q2 supplied per unit area to the sheet P in the fixing and bonding processes, it is possible to appropriately change the state of the powder adhesive Tn in the fixing and bonding processes, as explained in Example 1, and achieve strong adhesion.

From Table 4, it can be seen that the slower the sheet conveying speed V2 of the second fixing device 32, the lower the temperature of the heater 32b1 and the heating film 32b. This is because the slower the sheet conveying speed V2, the longer the time required to pass through the adhesion nip 32N, and therefore the lower the temperature of the heater 32b1 and the heating film 32b required to supply the same amount of heat Q2 (0.0140 J/ ^mm2 ) to the sheet P. In other words, by making the sheet conveying speed V2 in the adhesion process slower than the sheet conveying speed V1 in the fixing process, it is possible to keep the heating temperature of the heater 32b1 and the heating film 32b low while maintaining good adhesion. As a result, excessive melting of the printing toner in the adhesion process is less likely to occur, and hot offset is less likely to occur.

As shown in Table 4, in Example 2 and Comparative Examples 1 and 2, in which the temperature of the heater 32b1 and the heating film 32b is lower than in Example 1, hot offset is less likely to occur. In particular, hot offset did not occur in Example 2 and Comparative Example 2. Moreover, the conditions of Example 2 are more advantageous than the conditions of Comparative Example 2 in that higher productivity can be achieved without causing hot offset.

The sheet conveying speed in the fixing process and the gluing process can be appropriately selected depending on the printing speed of the entire image forming apparatus and the folding method of the sheet P. For example, if the sheet conveying speed in the fixing process is 210 mm/sec and a bonded print is output in which the sheet P is folded in half and bonded, the sheet conveying speed in the bonding process can be reduced to half, 105 mm/sec, with almost no loss in overall productivity. In other words, it is preferable to set the sheet conveying speeds V1 and V2 in the fixing process and the gluing process so that, for example, 0.5≦V2/V1≦0.75 holds.

As explained above, in this embodiment, by slowing down the sheet transport speed in the adhesion process relative to the sheet transport speed in the fixing process, it is possible to obtain sufficient adhesive strength while keeping the heating temperature in the adhesion process as low as possible, thereby reducing the possibility of hot offset occurring.

Other Embodiments
In the first and second embodiments, a film-type image heating device having excellent quick start properties is used as the first and second fixing devices 6 and 32, but the configuration of the image heating device is not limited to this. For example, an image heating device that heats the toner and powder adhesive on the sheet P via a heating roller that is in pressure contact with the pressure rollers 6b and 32a may be used as the first and/or second fixing devices 6 and 32. The heating roller is, for example, a metal cylinder having an elastic layer such as silicone rubber and a release layer such as fluororesin formed on its outer periphery. In addition, the nip forming unit in the film type is not limited to one in which the heater directly contacts the inner surface of the film, but may be configured such that the heater contacts the film via a sheet material having high thermal conductivity such as iron alloy or aluminum. In addition, the heating means is not limited to one using a heating resistor, but may be, for example, a halogen lamp or an induction heating mechanism.

1...Image forming device / 1e...Image forming means (image forming unit) / 6...Fixing means (first fixing device) / 31...Folding means (folding device) / 32...Adhesive means (second fixing device) / Tn...Powder adhesive / Ty, Tm, Tc...Printing toner

Claims (9)

an image forming means for forming a toner image on a sheet using a printing toner and applying a powder adhesive to the sheet;
a fixing means for heating the toner image formed on the sheet by the image forming means and the powder adhesive applied to the sheet, thereby fixing the toner image to the sheet;
a folding means for folding the sheet that has passed through the fixing means so that the surface on which the powder adhesive is applied is inward;
an adhesive means for heating the sheet folded by the folding means and adhering inner surfaces of the folded sheet to each other with the powder adhesive;
An image forming apparatus comprising:
The maximum temperature of the powder adhesive when heated by the fixing means is Tmax1 [°C].
The maximum temperature of the powder adhesive when heated by the adhesive means is Tmax2 [°C].
Tmax1 is higher than the melting point of the powder adhesive;
Tmax2 is lower than the melting point of the powder adhesive and is equal to or higher than the glass transition temperature of the powder adhesive;
Tmax1>Tmax2;
1. An image forming apparatus comprising: an image forming means including a photoconductor, a developing section for supplying a powder adhesive to an electrostatic latent image formed on the photoconductor, and a transfer section for transferring the powder adhesive from the photoconductor to a sheet;
A fixing means for heating the powder adhesive layer transferred to the sheet to fix the powder adhesive to the sheet;
a folding means for folding the sheet that has passed through the fixing means so that the surface to which the powder adhesive has been transferred is inward;
an adhesive means for heating the sheet folded by the folding means and adhering inner surfaces of the folded sheet to each other with the powder adhesive;
An image forming apparatus comprising:
The maximum temperature of the powder adhesive when heated by the fixing means is Tmax1 [°C].
The maximum temperature of the powder adhesive when heated by the adhesive means is Tmax2 [°C].
Tmax1 is higher than the melting point of the powder adhesive;
Tmax2 is lower than the melting point of the powder adhesive and is equal to or higher than the glass transition temperature of the powder adhesive;
Tmax1>Tmax2;
1. An image forming apparatus comprising: The glass transition temperature of the powder adhesive is Tg [°C].
Tmax1 ≧ Tg + 40 and Tmax2 ≧ Tg + 10;
3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. The glass transition temperature of the powder adhesive is Tg [°C].
Tmax1 ≧ Tg + 50 and Tmax2 ≧ Tg + 20;
3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. The amount of heat per unit area applied to the sheet by the fixing means is Q1 [J/mm ² ],
If the amount of heat per unit area applied to the sheet by the adhesive means is Q2 [J/mm ² ], then
Q1<Q2;
5. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. The relationship between Q1 and Q2 is 1.0≦Q2/Q1≦2.2.
6. The image forming apparatus according to claim 5 , The relationship between Q1 and Q2 is 1.3≦Q2/Q1≦1.9.
6. The image forming apparatus according to claim 5 , the fixing unit includes a first pair of rotating bodies that rotate while holding a sheet therebetween, and a first heating unit that heats the sheet conveyed by the first pair of rotating bodies;
the bonding means includes a second pair of rotating bodies that rotate while holding the sheet therebetween, and a second heating means that heats the sheet conveyed by the second pair of rotating bodies;
The sheet conveying speed by the first rotating body pair is V1 [mm/sec],
If the sheet conveying speed by the second rotating body pair is V2 [mm/sec],
V1>V2;
8. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. the folding means is capable of folding the sheet in half so that the length in the sheet conveying direction is halved;
The relationship between V1 and V2 is 0.5≦V2/V1<0.75.
9. The image forming apparatus according to claim 8 ,

Images