JP7600194B2 - Method for manufacturing pressure-bonded sheet and image forming apparatus - Google Patents

Description

The present invention relates to a method for manufacturing a pressure-sealed sheet such as a pressure-sealed postcard, and an image forming apparatus having a means for manufacturing the pressure-sealed sheet.

Sealed postcards that seal confidential information such as invoices and pay slips need to have a certain adhesive strength to prevent them from coming off during delivery, but at the same time, it is important that they can be easily peeled off so that they can be opened after arriving at the user's hands.
Furthermore, the printer that creates the above-mentioned laminated postcards is extremely convenient because it is simple and space-saving: it prints letters and images on a paper medium (hereinafter referred to as paper), and then transports the paper as is, folds it, and laminates it to create the laminated postcards.
It is desirable for such a printer to have a simple configuration in which a process cartridge filled with a developer for printing (hereinafter referred to as toner) and a powder adhesive for pressing (hereinafter referred to as glue) is attached to the same printer body, and printing is performed using a conventional electrophotographic image formation process, while a folding unit and a pressing unit can be added to handle both printing and pressing.
However, problems occur when two different types of powder are used in a series of image formation processes. Specifically, if the physical properties and conditions of the toner and glue are not optimized, they will dissolve or mix with each other, and when a postcard in which glue 2 and toner 8 are bonded with folded-over paper 4 is opened as shown in Fig. 2A, the toner printed on paper 4 may peel off together with glue 2, causing the toner 8 to be transferred to the white area of the opposite side (hereinafter referred to as peeling offset).
As for the material of this adhesive, Patent Document 1 clearly states that a hydrocarbon resin (such as polyethylene) is suitable.

JP 2007-45861 A

However, in order to solve the problem of peeling offset, the adhesive specifications as in Patent Document 1 are insufficient for the manufacture of pressure-bonded postcards, which perform printing and pressure-bonding processes in a single process, and for printers. It is necessary to select the material, type, form, etc. of both, including the toner, based on their physical properties.
In view of the above situation, the present invention aims to propose an effective method for manufacturing a pressure-bonded sheet and an image forming apparatus that uses an image forming apparatus that can perform printing and pressure-bonding processes in a single flow, while suppressing the peeling offset that occurs when a pressure-bonded postcard is opened.

The above object can be achieved by using the following configuration.
That is, the present invention is a method for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state,
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The method for producing a pressure-bonding sheet is characterized in that the difference in solubility parameter (SP value) between the printing toner and the powder adhesive is 1.0 (cal/cm ³ ) ^1/2 or more.

The present invention also provides an image forming apparatus for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable manner, comprising:
a means for forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing means for heating the composite layer formed on the sheet to fix it to the sheet;
a means for overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or on a different sheet to which another composite layer is fixed, and a pressing means for pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The present invention relates to an image forming apparatus, wherein the difference in solubility parameter (SP value) between the printing toner and the powder adhesive is 1.0 (cal/cm ³ ) ^1/2 or more.

The present invention also provides a method for producing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable manner, comprising the steps of:
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The printing toner contains a wax,
When the storage modulus of the printing toner at the temperature in the fixing step is G'(A1), the storage modulus of the printing toner at the temperature in the pressure bonding step is G'(A2), the storage modulus of the powder adhesive at the temperature in the fixing step is G'(B1), and the storage modulus of the powder adhesive at the temperature in the pressure bonding step is G'(B2),
G'(A1)>G'(A2)
G'(B1)>G'(B2)
G'(B1)>G'(A1)
Fulfilling
This relates to a method for manufacturing a pressure-bonded sheet, characterized in that the temperature in the fixing step is a temperature between the start point onset temperature and the end point onset temperature of the change region caused by melting in the storage elastic modulus curve of the powder adhesive.

The present invention also provides a method for producing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable manner, comprising the steps of:
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The method for producing a pressure-bonded sheet is characterized in that the difference in average particle size between the toner and the powder adhesive is less than 25 μm, and the powder adhesive has a broader particle size distribution or a larger half-value width than the toner.

Furthermore, the present invention provides an image forming apparatus for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising:
a means for forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing means for heating the composite layer formed on the sheet to fix it to the sheet;
a means for overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or on a different sheet to which another composite layer is fixed, and a pressing means for pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The toner and the powder adhesive have an average particle size difference of less than 25 μm, and the powder adhesive has a broader particle size distribution or a larger half-value width than the toner.

By adopting the configuration of the present invention, in an image forming device that can perform printing and bonding processes in a single flow, it is possible to make the printing toner and the powder adhesive (glue) less likely to dissolve or mix with each other. This makes it possible to suppress the occurrence of peeling offset when the bonded postcard is opened.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to the present invention. 2A and 2B are diagrams illustrating the peel offset phenomenon. FIG. 3 is an explanatory diagram showing the viscoelastic properties in the examples of the present invention and the comparative examples. FIG. 4 is an explanatory diagram showing the temperatures during fixing and pressure bonding in addition to the viscoelastic properties in the examples of the present invention and the comparative examples. FIG. 5 is an explanatory diagram showing the temperature and viscoelasticity characteristics of the developer (toner) and powder adhesive (glue) during fixing and compression in an embodiment of the present invention. FIG. 6 is an explanatory diagram showing the temperature and viscoelasticity characteristics when the powder adhesive (glue) is fixed in an embodiment of the present invention. FIG. 7 is an explanatory diagram showing the temperature and viscoelasticity characteristics of the developer (toner) and powder adhesive (glue) during fixing in an embodiment of the present invention. FIG. 8 is an explanatory diagram showing the temperature and viscoelastic properties of the future developer (toner) and powder adhesive (glue) during fixing and pressing in an embodiment of the present invention, as well as the viscoelastic properties of the future developer (toner). 9A, 9B and 9C are schematic diagrams showing an image forming apparatus in an embodiment of the present invention, the contact state between the image carrier (drum) and intermediate transfer belt (ITB) at the 1st station, and the contact state between the image carrier (drum) and intermediate transfer belt (ITB) at the 2nd station. 10A and 10B are schematic diagrams showing the states immediately before and after the contact between the image carrier (drum) and intermediate transfer belt (ITB) of the second station when there is an average particle size difference in an embodiment of the present invention. 11A and 11B are schematic diagrams showing the state of a pressure-bonded postcard before and after peeling when there is a difference in average particle size in an embodiment of the present invention. 12A and 12B are schematic diagrams showing the state immediately before and after contact between the image carrier (drum) and intermediate transfer belt (ITB) at the 2nd station in an embodiment of the present invention when there is a difference in average particle size and the particle size distribution is wide. 13A and 13B are schematic diagrams showing the state of a pressure-bonded postcard before and after peeling in an embodiment of the present invention when there is a difference in average particle size and the particle size distribution is wide. 14A and 14B are diagrams showing the average particle size and particle size distribution in an embodiment of the present invention. 15A and 15B are schematic diagrams illustrating the gaps between particles of developer (toner) and powder adhesive (glue) in an embodiment of the present invention.

<Overall overview of the device>
The method for producing a pressure-bonded sheet and the image forming apparatus of the present invention, which produce a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, are based on the steps (or means) of:
(i) forming a composite layer on a sheet by laminating an adhesive layer formed as a surface layer using a powder adhesive on a toner image formed using a printing toner;
(ii) a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
(iii) a process of overlapping an area on the sheet where the composite layer has been formed and fixed with an area on the same sheet or a different sheet where another composite layer has been fixed, and (iv) a pressing process of pressing the overlapping areas of the composite layer and the other composite layer under heat.

Here, in step (iii), when "different sheets" are overlapped, the sheet does not necessarily need to be folded. However, when "same sheets" are overlapped, the sheet does need to be folded. Therefore, for the sake of convenience, the above step (iii) is referred to as a "folding step," and the means for this step are sometimes referred to as a "folding means" or a "folding unit."

Figure 1 is a schematic cross-sectional view showing an example of an image forming apparatus according to the present invention, which is based on a conventional full-color image forming apparatus and has a configuration in which a folding unit 6 and a pressing unit 7 have been added.

The process cartridge filled with glue 2 is installed in the most upstream station of the four image formation stations, and the other stations are equipped with process cartridges of the colors yellow (hereafter referred to as Y), magenta (hereafter referred to as M), and cyan (hereafter referred to as C). However, the configuration is not limited to the above. Specifically, monochrome, or the order and proportion of process cartridges of each color of glue or toner installed in each station can be set arbitrarily according to needs. It should also be noted that the number of stations is not limited to four.

Next, we will explain in detail the image formation process (charging, developing, transferring, fixing) used to create laminated postcards, as well as the flow of the folding and lamination processes.

(Explanation of the image formation process, folding process, and bonding process)
In the image forming apparatus of Fig. 1, each station has an image carrier (hereinafter referred to as drum) 1 having an OPC photosensitive layer (organic photoconductor), which can rotate in the direction of the arrow at a predetermined process speed. The surface of the drum 1 is charged to a predetermined polarity and potential by a charging roller 12 to which a charging bias is applied, and then receives an exposure beam from a laser beam scanner 16 to form an electrostatic latent image. Then, for the electrostatic latent image, a powder adhesive (hereinafter referred to as glue) 2 is transported from a developer container to a developer carrying member 17, and the glue 2 is transferred to the drum 1 by a developing means (contact charging and developing bias), i.e., the electrostatic latent image is developed.

The glue on the drum 1 is then (primarily) transferred to an intermediate transfer belt (hereafter referred to as ITB) 3 that comes into contact with the drum by a predetermined transfer pressure and transfer bias from a transfer roller 14, and the glue 2 on the ITB 3 is carried to the next station. Some of the glue 2 on the drum that was not transferred is scraped off with a cleaning blade or the like, and then the drum 1 is charged, exposed, and developed again, allowing repeated image formation. The scraped off glue 2 is then stored and collected in a cleaning container 13. The components that perform this series of processes (drum 1, charging roller 12, developing container 2, cleaning container 13) are integrated into a cartridge called a process cartridge, and four process cartridges, each with a different powder, are lined up and stored in the main body.

In the next station, the same process is followed, but this time Y toner (yellow toner) 8 is transferred from the drum 11 to the ITB. The transfer is then repeated in sequence from the next station onwards, resulting in at least two layers of powder (glue and toner of one other colour, up to a maximum of glue, Y toner 8, M toner (magenta toner) 9 and C toner (cyan toner) 10) being stacked in order on the ITB. Then, the toner image is (secondarily) transferred from the ITB 3 to the paper 4 by the transfer bias of the secondary transfer roller 15 for the conveyed recording material (hereinafter referred to as paper) 4. As a result, the order of stacking is reversed on the ITB 3 on the paper 4, and a composite layer is formed in which the glue, which is the surface layer, is stacked on top of the toner image, so that the papers 4 can be stacked facing each other and pressed together with the glue. For this reason, in a device that uses an intermediate transfer member such as an intermediate transfer belt, it is desirable to install the glue in the most upstream station in image formation.

Then, the adhesive is heated and pressurized by the fixing unit 5, melting it together with the toners 8, 9, and 10, and is fixed onto the paper 4. At this time, it is important that most of the adhesive 2 is fixed in a moderately softened state while still melting. The reason for this is that if the toners 8, 9, and 10 and the adhesive 2 melt all at once during fixing, they will tend to become compatible with each other, which will reduce the peel-off offset properties, and the present invention incorporates the techniques described in each of the embodiments below.

The paper is then sent to the folding unit 6, where it is folded into the specified shape, and then heat-bonded by the bonding unit 7 under pressure to create a bonded postcard. During bonding, it is important to carry out this bonding process at a temperature that melts the glue, in order to maintain the adhesive strength of the bonded postcard while suppressing peel offset.

The reason why the glue and toner are not melted at once during fixing, but rather melted during pressing, is as follows. The reason is that by fixing only to the extent that the glue does not melt completely during fixing but only softens, heat is transferred to the glue more slowly than to the toner during pressing. This creates a difference in how easily the two melt, making it difficult for them to dissolve at their interface, or the toner layer that has melted once during fixing has wax on its surface, which acts as a wall that makes it difficult for the glue to dissolve in the toner layer, making it difficult for the two to dissolve in each other.

<Explanation of peel offset and its causes>
The laminated postcard created through the above process is delivered to the user and then opened. However, as mentioned above, peel offset may occur depending on the physical properties of the toner and adhesive and the conditions.

The present inventors have investigated the melting state and compatibility of printing toner and paste, and have found that
It was found that good peelability can be obtained by controlling either: 1. the difference in solubility parameters (SP values) between the toner and the glue; or 2. the difference in viscoelastic properties between the toner and the glue.

In addition, the powder characteristics of the toner and glue were examined.
3. It was found that good peelability can be obtained by controlling the difference in average particle size and particle size distribution between the toner and the paste.

The three control points are explained in order below.

(About toner and glue)
Before describing the three factors that contribute to the peel offset, the toner and adhesive according to the present invention will be described.

The toner used in the present invention contains a thermoplastic binder resin such as styrene acrylic resin, polyester resin, vinyl resin, or acrylic resin, and further contains wax, colorant, external additive, charge control agent, magnetic material, etc. as necessary. The shape of each toner particle is spherical or amorphous, and the average particle size is approximately 6 μm ± 2 μm. However, the material and physical properties are not limited to the above. In particular, to suppress the occurrence of peeling offset, the material and physical properties (structure) of the toner may be changed to match the material and physical properties of the glue, and a toner with a different SP value, viscoelasticity properties, average particle size, and particle size distribution may be used.

On the other hand, powder particles of polyethylene are preferably used as the glue. The powder particles of polyethylene can be produced by a polymerization method or a pulverization method, and external additives may be added to the surface. The shape of each particle is spherical or amorphous, and the average particle size is about 6 to 30 μm. However, the material and physical properties are not limited to the above. In particular, to suppress the occurrence of peeling offset, the material and physical properties (structure) of the glue may be changed to match the material and physical properties of the toner, and a glue with a different SP value, viscoelastic properties, average particle size, and particle size distribution may be used.

[Example 1] (1. Difference in solubility parameter (SP value) between toner and glue)
As mentioned above, the level of peeling offset varies depending on the compatibility and mixing condition of the toner and the adhesive. Therefore, it is necessary to form an image and create a pressure-bonded postcard when the toner and the adhesive are poorly compatible or poorly mixed.

Therefore, we focused on an index called the SP value, which represents the compatibility of two types of materials. The SP value indicates the solubility of the two substances in question, and is a unique value determined by the materials and molecular structure. In addition, two different substances have a characteristic that if their SP values are far apart, they are less compatible, and if their SP values are close, they are more compatible. Next, we will explain how to calculate the SP value.

(Method of calculating solubility parameter (SP value))
The SP value in the present invention was determined using the following Fedors formula. The values of Δei and Δvi here were based on the evaporation energy and molar volume (25°C) of atoms and atomic groups in Tables 3 to 9 of "Basic Science of Coating" pp. 54-57, 1986 (Maki Shoten). Ev is the evaporation energy, V is the molar volume, Δei is the evaporation energy of an atom or atomic group of component i, and Δvi is the molar volume of an atom or atomic group of component i. For example, a substance called hexanediol is composed of atomic groups (-OH) x 2 + (-CH ₂ ) x 6, and the SP value is determined by the following exemplary formula, with the SP value (δi) being 11.95.
SP value calculation formula δi = [Ev/V] ^1/2 = [Δei/Δvi] ^1/2
Example) SP value of hexanediol δi = [Δei/Δvi] ^1/2 = [{(5220) x 2 + (1180) x 6}/{(13) x 2 + (16.1) x 6}] ^1/2 = 11.95

In this specification, the unit of the SP value is (cal/cm ³ ) ^1/2 , where (cal/cm ³ ) ^1/2 = 0.48888 × (J/cm ³ ) ^1/2 .

In this specification, the SP value of the toner is the SP value of the binder resin.

In this example, the toner used had the following formula. The binder resin was changed to that shown in Table 1 below. Note that "parts" refers to "parts by weight."

(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, manufactured by 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 having 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 (weight average molecular weight (Mw) 20,000, glass transition temperature (Tg) 75°C, acid value 8.2 mgKOH/g)
Behenyl behenate 12.0 parts 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, thereby preparing a polymerizable monomer composition.

Meanwhile, 850.0 parts of a _0.10 mol/L- _Na3PO4 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 a 1.0 mol/L-CaCl2 _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 t-butyl peroxypivalate, a polymerization initiator, was added and granulated for 10 minutes while maintaining a rotation speed of 15,000 rpm. After that, the agitator was changed from the high-speed agitator to a propeller agitator, and the mixture was reacted at 70°C for 5 hours while refluxing, and then 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 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 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 (printing toner). The weight average particle size of the obtained toner was about 6 μm.

Next, to investigate the compatibility of these toners with glue (powder adhesive), several glues with different resin types, as shown in Table 1, were used, the image formation process described above was carried out, and test samples of pressure-bonded postcards as shown below were created to check the peel offset.

The test samples were prepared by printing two types of materials - glue and one of the three colors of toner, Y, M, or C - all over the inside of a 3 cm x 4 cm area of a strip of paper (Canon GF-C081) prepared as a substitute for a pressure-bonded postcard, and one printed entirely with glue and one printed entirely with glue alone, then stacking them with the printed sides facing inwards, fixing and bonding them together. In this experiment, the process conditions for image formation (applied bias, settings for each component, temperature conditions, etc.) were set to be roughly the same for glue and toner, but they may be set separately for each powder. In the test described below, when high-density polyethylene was used as the glue, the fixing and bonding temperatures were raised to perform fixing and bonding.

The peel test was performed using an ORIENTEC TENSILON Model RTG-1255 tensile tester. Both ends of the strip were clamped to the test device and peeled at a pulling speed of 50 mm/min.

To check for peeling offset, the peeled surface of the strip peeled off with TENSILON was checked to see if any toner was transferred to the strip where only the glue was printed. The results are explained below using Table 1.

When the toner and glue are made of the same polyester resin as in Table 1, the SP value for both is 9.30 since they are the same material. When a test sample was created in this state and a peel test was performed, the peeling surfaces became compatible with each other and did not separate properly, resulting in peel offset. It was also confirmed that when the toner and glue were both made of the same styrene acrylic resin, they became compatible with each other and peel offset occurred.

Next, a peeling test was conducted by changing the toner to polyester resin and the glue to polypropylene resin with a similar SP value. The results confirmed that the toner and glue were compatible and did not separate well. This shows that the ease of compatibility is due not to the materials, but to the similarity of the SP values.

Next, we will explain the case where the difference in SP value is large. This time, we conducted a similar test using two polyethylenes with different structures, namely low-density polyethylene and high-density polyethylene, as the glue. The SP value of low-density polyethylene was 7.93 (the difference in SP value with the polyester contained in the toner was 1.37), and the SP value of high-density polyethylene was 8.29 (the difference in SP value with the polyester contained in the toner was 1.01). As a result, it was found that the separation surfaces of both polyethylenes were not compatible with each other, and the peeling surfaces were cleanly separated and peeled off in a smooth and glossy state. Therefore, it was found that if the difference in SP value is at least 1.0 or more, compatibility with each other can be suppressed. Incidentally, low-density polyethylene allows image formation under almost the same process conditions as toner, and in this respect it is preferable to high-density polyethylene.

The above are the test results regarding the SP value, but next we carried out a model experiment to examine the peel offset under conditions outside the range of normal use while changing the toner and adhesive materials from the above combination. The purpose of this model experiment is twofold:

The first is to investigate whether compatibility can be suppressed even if the difference in SP value is less than 1.0, i.e., to find out how much margin there is, for example, whether 1.0 is an appropriate value, and the second is to investigate whether the threshold value of a difference in SP value of 1.0 is a condition that can only be achieved with the combination of the above-mentioned polyester resin for the toner and the polyethylene resin for the glue, i.e., to find out whether the same results can be obtained with other combinations.

The model experiment is explained in detail. In this model experiment, the amount of toner and glue on the strip mentioned above was made uneven so that peeling offset would occur easily. By making the coating uneven, the toner will not bond to the surrounding toner as it melts (the toner will be more likely to become isolated), and it will be more likely to peel off from the paper.

Therefore, in this model experiment, when the toner and glue have the same SP value, the peel offset worsens. The results are shown in Table 2.

First, as shown in Table 2, the above model experiment was carried out using polyester resin as the toner and low-density polyethylene and high-density polyethylene as the glue. In the case of high-density polyethylene, where the difference in SP value is 1.01, slight peeling offset occurred. On the other hand, in the case of low-density polyethylene, where the difference in SP value is 1.37, no peeling offset occurred.

In addition, when the toner was styrene acrylic resin and the glue was low-density polyethylene and high-density polyethylene, both regular peeling offset tests and model experiments were conducted. The difference in SP value between the toner and glue was 1.47 and 1.11, respectively. When regular peeling tests and model experiments were conducted under these conditions, it was found that no peeling offset occurred with either low-density polyethylene, which has an SP value difference of 1.47, or high-density polyethylene, which has an SP value difference of 1.11.

Therefore, it has become clear that good results can be obtained if the difference in SP value that suppresses peel offset is 1.0 or more. More preferably, the difference in SP value is 1.1 or more.

[Example 2] (2. Difference in Viscoelastic Properties between Toner and Adhesive)
Next, the viscoelastic property, which is another factor in the peel offset, will be described. The reason for focusing on this viscoelastic property will be described later.

From the viewpoint of viscoelastic properties, in the present invention, when the storage modulus at the temperature in the fixing step of the toner is G'(A1), the storage modulus at the temperature in the pressure bonding step is G'(A2), the storage modulus at the temperature in the fixing step of the adhesive is G'(B1), and the storage modulus at the temperature in the pressure bonding step is G'(B2),
G'(A1)>G'(A2)
G'(B1)>G'(B2)
G'(B1)>G'(A1)
and the temperature in the fixing step must be between the start and end onset temperatures of the change region caused by melting in the storage elastic modulus curve of the glue.

Here, the viscoelastic property is an index showing the energy stored in the powder for a given strain, and is expressed as the storage modulus with respect to temperature. In the case of powder such as thermoplastic resin as in this embodiment, when the toner or glue is heated and the temperature is increased, the viscoelastic property changes and the storage modulus decreases. This state indicates that the toner or glue has melted and become soft (hereinafter referred to as softened).

If the glue is close to being a single material, the softening temperature will be close to the melting point, and the viscoelasticity will tend to change suddenly near that temperature range. However, if it contains multiple materials, such as toner, the range in which the viscoelasticity changes differs for each substance, so there tends to be fewer areas where the viscoelasticity changes suddenly, and the viscoelasticity changes gradually depending on the heating temperature. Next, we will explain how to measure the viscoelastic properties of toner and glue.

(Measurement of viscoelastic properties and storage modulus of toner and glue)
The viscoelastic properties of the toner and glue, that is, the storage modulus, were measured using a DMA8000 (manufactured by Perkin Elmer), a compression fixture (product number: N533-0320), and a heating furnace (product number: N533-0267). First, as a measurement sample, a tablet molder (e.g., NT-100H, manufactured by NPA Systems) was used in an environment of 25°C to pressure-mold (compression-mold at about 10 MPa for about 60 seconds) the toner or glue (about 2.0 g) into a disk shape with a diameter of 7.9 mm and a thickness of 2.0±0.3 mm to create a sample, which was measured while being heated, and a graph of the storage modulus versus heating temperature was created.

In this embodiment, the toner used in the viscoelasticity measurements was the same as that used in Example 1 in terms of the components, manufacturing process, and particle size.

That is, the toner uses a styrene acrylic resin as a binder resin, contains wax as a release agent, and uses polyethylene as glue, but the materials of the toner and glue are not limited to these. In particular, it is sufficient if the toner and glue are made of materials with different viscoelastic properties, and if the storage modulus of the glue is higher than that of the toner, at least at the fixing temperature, peeling offset can be suppressed, so the materials of the toner and glue are not limited to these.

Figure 3 shows the results of the viscoelasticity measurements. The horizontal axis shows the temperature at which the powder was heated under specified conditions, and the vertical axis shows the storage modulus of each powder at that time. It was found that the viscoelastic properties of each of the three powders tended to be as follows:

The toner shown by the solid line has a high storage modulus at low temperatures and is therefore hard. However, as the temperature increases, the storage modulus gradually decreases, and a tendency for the toner to soften in an almost linear fashion is observed.

On the other hand, the glue shown by the dashed line was softer than the toner before heating, but its storage modulus hardly changed up to a certain temperature, and it showed the characteristic of softening rapidly at temperatures close to the melting point.

However, there are two types of polyethylene: low-density polyethylene and high-density polyethylene, which have different structures. Low-density polyethylene, shown by the dashed line, has a higher branched structure than high-density polyethylene, shown by the dotted line, and therefore has a lower melting point. As a result, it softens at a lower temperature. Conversely, the molecular structure of high-density polyethylene is mainly linear, so it has a higher melting point and softening temperature.

(Improvement of peeling offset by viscoelastic properties)
As mentioned above, the level of peeling offset varies depending on the compatibility and mixing condition of the toner and the adhesive. Therefore, it is necessary to form an image and create a pressure-bonded postcard when the toner and the adhesive are poorly compatible or poorly mixed.

Therefore, we focused on an index called viscoelasticity, which indicates how easily a material softens. When actually creating laminated postcards, there are two heating timings: fixing and lamination. We found that by using these two temperatures and the difference in viscoelasticity between the toner and glue to create a situation in which they are less compatible with each other, we could improve peel offset. Next, we will explain the specific viscoelasticity properties that we obtained this time.

Figure 4 is an addition to Figure 3 of the actual paper temperature during fixing and the paper temperature during pressing (i.e. the temperature of the toner and glue on the paper). The paper temperature during fixing is shown by vertical solid line A, and the paper temperature during pressing is shown by vertical solid line B. In this embodiment, the temperature during pressing B was set higher than the temperature during fixing A.

The viscoelastic properties of each powder at fixing time A are explained below. At fixing time A, the toner was almost completely melted, and the low-density polyethylene, which acts as a glue, was slightly melted. However, the high-density polyethylene was barely melted.

Next, the viscoelastic properties of each powder at compression time B will be explained. At compression time B, it was found that while the toner and low-density polyethylene were almost completely melted, the high-density polyethylene had not melted and was not fixed. In this example, the glue was fixed at the same temperature setting as the toner, so it is desirable to use low-density polyethylene for the glue rather than high-density polyethylene, which does not fix easily. Therefore, from here on, we will use low-density polyethylene for the glue and explain how to suppress peeling offset.

Figure 5 is a graph that uses black and white circles to show the storage modulus of the toner and the storage modulus of the glue (low-density polyethylene) at the temperatures during fixing and pressing, making it easier to explain the relationship between viscoelastic properties and peel offset. In Figure 5, the fixing of the glue is simply and easily expressed as (1), the pressing of the glue as (2), the fixing of the toner as (3), and the pressing of the toner as (4). It has been found that the suppression of peel offset is improved in the following three states, which will be explained in order.

The first reason is that in this embodiment, as shown in Figure 5, the paper temperature during pressing is set higher than during fixing, so the viscoelasticity is in the order of (1) > (2) and (3) > (4).

Secondly, as shown in Figure 6, the glue does not need to melt completely when it is fixed. It melts when it is pressed, which is why it is possible to apply pressure. Therefore, (1) can be used when it is slightly softened and beginning to melt. In other words, (1) should be used within the softening region of the viscoelastic properties as shown in Figure 6.

The third condition is considered to be the most important condition for suppressing peel offset, and it is to satisfy the relationship (1)>(3) at the temperature of fixation A as shown in Figure 7. Here, it is preferable that the difference between the storage modulus of (1) and the storage modulus of (3) at the temperature of fixation A is not less than |Log10( ^1x105 )-Log10( ^3x104 )| and not more than |Log10( ^3x106 )-Log10( ^6x104 )|.

The reason for this is that if the viscoelastic properties of the toner and glue are similar and both powders melt all at once during fixing, they will become more compatible, and it has been found that they are already compatible enough to cause peeling offset when fixing is complete. Therefore, in order to improve peeling offset, it is necessary to fix the glue only slightly softened rather than completely melted during fixing. In other words, by fixing the glue in a slightly softened state during fixing, it is possible to make the entire glue melt only when it is pressed against the glue. In other words, the two powders do not become molten during fixing, creating a situation in which they are less likely to become compatible, and peeling offset can be improved.

Also, depending on the type of toner, by mainly melting the toner during fixing, a layer of wax can be formed on the toner surface in a state where it is incompatible with the adhesive. This acts as a wall of toner that is difficult to dissolve in the adhesive when pressed, suppressing compatibility.

Regarding temperature and pressure conditions during bonding, if the bonding process is performed at a very high temperature or pressure, peeling offset is likely to occur, so the conditions for bonding are preferably a paper temperature of about 105°C to 115°C, a paper speed of 100 mm/s, and a pressure of 32 kg (one-sided load of 16 kg x 2).

From the above, it was found that in order to improve peeling offset due to viscoelastic properties, it is sufficient to satisfy the following relationships: viscoelasticity of the glue at the time of fixing > viscoelasticity at the time of pressing ((1) ≥ (2)), viscoelasticity of the toner at the time of fixing > viscoelasticity at the time of pressing ((3) ≥ (4)), the viscoelasticity of the glue at the time of fixing ((1)) is within the range of the softening region in the viscoelastic properties, and the viscoelasticity of the glue at the time of fixing ≥ viscoelasticity of the toner ((1) ≥ (3)).

We also considered the possibility that future development of toner materials would lead to the slope of change in the viscoelastic properties of the toner (the slope of the softening region) becoming steeper than that of the glue. Figure 8 shows this assumed situation.

The solid line in Figure 8 shows the viscoelasticity of the toner, which is sharper melting (easier to soften) than the glue shown by the dashed line. Even if one were to try to change the positional relationship of (3) and (4), the position of (3) is inevitable because the toner itself melts when fixed, so it is expected that the positional relationship of (3) and (4) will always be as shown in Figure 8 (because it is a thermoplastic resin, the viscoelasticity of (4) is lower than that of (3)). In other words, it was found that the positional relationship of (1) (2) (3) and (4) will not change, simply by changing the solid line part with a lower temperature than (3).

As a result, if the above relationship is maintained, the glue can be fixed in a slightly softened state, and only when the glue is pressed can the entire glue melt. This prevents the toner and glue from melting all at once during fixing, making them less compatible, which is expected to improve peel offset.

In this embodiment, the fixing temperature (paper temperature during fixing) was 95° C., and the pressing temperature (paper temperature during pressing) was 105° C. The storage elastic modulus of the glue at the fixing temperature was 3×10 ⁶ Pa, the storage elastic modulus of the glue at the pressing temperature was 2×10 ⁴ Pa, the storage elastic modulus of the toner at the fixing temperature was 6×10 ⁴ Pa, and the storage elastic modulus of the toner at the pressing temperature was 2×10 ⁴ Pa.

[Example 3] (3. Difference in average particle size and particle size distribution between toner and paste)
As mentioned above, the level of peeling offset varies depending on the compatibility and mixing condition of the toner and adhesive. Therefore, it is necessary to form an image in a state where the toner and adhesive are poorly compatible or poorly mixed, and to create a pressure-bonded postcard.

Therefore, we focused on the state in which the toner and adhesive exist as powder before fixing and bonding, and thought that peeling offset could be suppressed by improving the state in which they are mixed with each other.

When the average particle size and particle size distribution of the toner and glue were varied, it was found that if the average particle size and particle size distribution of the toner and glue were the same, peeling offset did not occur even when a laminated postcard was created through a series of image formation processes and peeled off. However, it was found that peeling offset occurred significantly when the average particle size of the toner and glue was different and the average particle size of the glue was about 25 μm larger than that of the toner. On the other hand, it was found that even if the average particle size of the glue was about 25 μm larger than that of the toner, the particle size distribution was wide (i.e. the half-width of the particle size distribution was large) or there were many particles smaller than the average particle size of the glue, the suppression of peeling offset was improved. Therefore, the mechanism of this improvement is explained below and the necessary conditions are presented. The average particle size and particle size distribution were measured using the following method.

(Measuring average particle size and particle size distribution)
The average particle size and particle size distribution of the toner and glue, i.e., the weight-average particle size, are calculated as follows. The measuring device used is a precision particle size distribution measuring device using the pore electrical resistance method, "Coulter Counter Multisizer 3" (registered trademark, product name, manufactured by Beckman Coulter, Inc.), equipped with a 100 μm aperture tube. 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.

The electrolyte solution used for the measurement is one in which special grade sodium chloride is dissolved in ion-exchanged water to a concentration of 1 mass%, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.) can be used. Before performing the measurement and analysis, the dedicated software is set as follows. In 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, Inc.). 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 is set to 2, the electrolyte is set to ISOTON II, and "Flush aperture tube after measurement" is checked. In 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 is set to 256 particle size bin, and the particle size range is set 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 obtained by diluting "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) three 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, and the ultrasonic disperser is operated. Then, the height 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 irradiated with ultrasonic waves, add the toner or paste to the electrolyte solution in small amounts of 10 mg at a time and disperse it. Then, continue ultrasonic dispersion for another 60 seconds. During ultrasonic dispersion, adjust the water temperature in the water tank appropriately so that it is between 10°C and 40°C.
(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%. Then, measurements are 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.

(Identifying the location where toner and glue mix)
Next, in a state where the above-mentioned peel offset occurs, the location where the toner and the adhesive are mixed is identified.

In the image formation process, the steps where toner and glue exist in powder form are the development step where development is performed from the developer carrying member to the drum, the primary transfer step where transfer is performed from the drum to the ITB, and the secondary transfer step where transfer is performed from the ITB to paper. We then tried to identify the location of the problem by forcibly stopping the drive of the main unit, and found that it was occurring in the primary transfer step, as shown in Figure 9C. In this step, both glue 2 and toner 8 have been transferred onto the ITB 3, and they are mixed at this stage.

Figure 10A is a schematic diagram of the state before transfer pressure is applied, and the toner and glue are regularly carried on the drum according to the print pattern. However, when transfer pressure is applied, glue particles about 25 μm larger than the toner disrupt the toner image on the drum as shown in Figure 10B, and it was confirmed that the toner gets into the gaps between the larger glue particles. This is thought to be because the larger particles are heavy and difficult to move, and the lighter smaller particles move and enter the gaps. When this state occurs on the ITB, when secondary transfer is performed to paper, a layer of glue is placed on top of the disrupted toner layer on the paper, and the particles are mixed together even more. As a result, the toner is fixed in an isolated position different from the normal position during fixing as shown in Figure 11A, and when the paper 4 is peeled off after pressure bonding as shown in Figure 11B, the isolated toner peels off together with the glue, which was found to be the cause of the peeling offset.

On the other hand, if the average particle size of the toner and glue is the same, there are many contact points between the layers at the time of mixing, and the transfer pressure can be absorbed by the surface, so neither the toner nor the glue is disturbed on the ITB. Therefore, it is believed that peeling offset does not occur.

And, when the average particle size of the glue is about 25 μm larger than that of the toner and there are many particles smaller than the average particle size of the glue (the glue has a wider particle size distribution than the toner, or the half-width of the particle size distribution is larger), small glue particles fill the gaps between the large glue particles on the ITB in advance as shown in FIG. 12A. Therefore, even when the toner is transferred from the drum to the ITB at the downstream station in image formation and transfer pressure is applied, the toner can be prevented from entering the gaps between the large glue particles as shown in FIG. 12B, so mixing of the toner and glue on the ITB can be suppressed. In this way, the toner and glue do not mix with each other during fixing, and are fixed while maintaining their respective layers as shown in FIG. 13A. When the paper 4 is peeled off after pressing as shown in FIG. 13B, the toner and glue peel off without being disturbed at their interface, and peeling offset does not occur.

In addition to the above combinations of toner and glue, other combinations such as those shown in Table 3 are also possible. Table 3 shows that peeling offset occurs when the toner has a small average particle size and the glue has a large average particle size, and that peeling offset is better suppressed with a large particle size distribution than with a small particle size distribution. It can be seen that the effect of a large particle size distribution of glue is particularly large.

However, since the data in parentheses indicates that the contribution of peel offset is low, in this embodiment, we will focus on combinations with large particle size differences, namely, toner with small average particle size (approximately 6 μm) and glue with small average particle size (approximately 6 μm) and large average particle size (approximately 30 μm).

Next, we will explain why peel offset suppression is improved by increasing the particle size distribution of the glue. Figures 14A and 14B are graphs for the upper right corner of Table 3, that is, when the difference in average particle size and particle size distribution between the toner and glue is large. Figure 14A shows the glue with a large average particle size and large particle size distribution, and Figure 14B shows the toner with a small average particle size and small particle size distribution. In this case, since the particle size distribution of the glue is wide (i.e., the half-width of the particle size distribution is large), particles of various glue sizes fill the gaps on the ITB at the most upstream of image formation, and a smooth surface can be formed before the toner is printed at the next station. In particular, since the gaps are filled with glue with a small average particle size similar to that of the toner particles, if the particle size distribution of the glue is wider than that of the toner, that is, if there are many particles close to the particle size of the other side in advance, they will be less likely to mix with each other, and peel offset can be suppressed.

Next, we will explain why peel offset improves when the threshold value for the difference in average particle size between toner and glue is less than 25 μm. Figures 15A and 15B are schematic diagrams showing what size toner particles can get into the gaps in glue with a maximum average particle size of 30 μm (these are diagrams of the ITB surface viewed from the planar side rather than the cross-sectional side).

As shown in Figure 15A, when the toner is 5 μm, the glue is 30 μm, and the average particle size difference is 25 μm, the toner will come into contact with the gaps in the glue and penetrate, making it easier for the powders to mix, resulting in worsening peel offset. On the other hand, as shown in Figure 15B, when the toner is 6 μm, the glue is 30 μm, and the average particle size difference is 24 μm, it becomes physically difficult for the toner to penetrate into the gaps in the glue, making it difficult for the powders to mix. This makes it possible to suppress peel offset.

Table 4 shows the relationship between the particle size difference and the peel offset.

For the values in Table 4, the average particle size is assumed to be a maximum of 30 μm, since the electrophotographic image formation process is used for both toner and glue. Therefore, even if the average particle size of the toner and glue changes, the figures will be similar to those in Table 4, so the situation in which penetration is easiest is when the average particle size is 30 μm, which means that the situation is most severe when the average particle size difference in Table 4 is 25 μm. Therefore, it was found that peel offset can be suppressed by making the difference in average particle size smaller than 25 μm.

From the above, it became clear that in terms of the average particle size and particle size distribution of the toner and glue, the difference in average particle size between the toner and glue is less than 25 μm, and the particle size distribution of the glue is wider than the particle size distribution of the toner, i.e., the half-value width is larger, which improves the suppression of peel offset.

<Summary>
The advantages of the examples of the present invention are shown in Table 5.

In this case, the SP value difference between the toner and the glue is set to 1.0 (cal/cm ³ ) ^1/2 or more, so that the toner and the glue are less likely to be mixed together even in a molten state. Also, by making the viscoelastic properties of the toner and the glue different during fixing, it is possible to avoid the two powders from melting all at once, and to make them less likely to be mixed together even when the molten and powder states are mixed. Also, by making the average particle size difference between the toner and the glue less than 25 μm and making the particle size distribution of the glue larger than that of the toner, small particles of the glue can be inserted in advance into the gaps between the large particles of the glue, forming a smooth surface, so that the toner and the glue are less likely to be mixed together even in a powder state. As a result, peeling offset can be effectively suppressed. Also, the image quality and gloss of the peeling surface are improved (adhesion strength is also partially improved).

Furthermore, by combining all of the above-mentioned configurations of SP value difference, viscoelasticity difference, average particle size and particle size distribution difference, it is possible to further improve the image quality and gloss (adhesion strength) of the peel surface in addition to the peel offset.

1: Image carrier (drum: 1st station), 2: Powder adhesive (glue), 3: Intermediate transfer belt (ITB), 4: Recording material (paper), 5: Fixing unit, 6: Folding unit, 7: Pressing unit, 8: Toner (Y: yellow), 9: Toner (M: magenta), 10: Toner (C: cyan), 11: Image carrier (drum: 2nd station), 12: Charging roller, 13: Cleaning container, 14: Transfer roller, 15: Secondary transfer roller, 16: Laser beam scanner, 17: Developer carrying member

Claims (10)

A method for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising the steps of:
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
A method for producing a pressure-bonding sheet, wherein the difference in solubility parameter (SP value) between said printing toner and said powder adhesive is 1.0 (cal/cm ³ ) ^1/2 or more. The method for manufacturing a pressure-bonded sheet according to claim 1, wherein the powder adhesive contains low-density polyethylene. An image forming apparatus for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising:
a means for forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing means for heating the composite layer formed on the sheet to fix it to the sheet;
a means for overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or on a different sheet to which another composite layer is fixed, and a pressing means for pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
an image forming apparatus comprising: a toner for printing and a powder adhesive, the toner and the powder adhesive each having a solubility parameter (SP value) difference of 1.0 (cal/cm ³ ) ^1/2 or more; The image forming apparatus according to claim 3, wherein the powder adhesive contains low-density polyethylene. A method for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising the steps of:
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The printing toner contains a wax,
When the storage modulus of the printing toner at the temperature in the fixing step is G'(A1), the storage modulus of the printing toner at the temperature in the pressure bonding step is G'(A2), the storage modulus of the powder adhesive at the temperature in the fixing step is G'(B1), and the storage modulus of the powder adhesive at the temperature in the pressure bonding step is G'(B2),
G'(A1)>G'(A2)
G'(B1)>G'(B2)
G'(B1)>G'(A1)
Fulfilling
A method for manufacturing a pressure-bonded sheet, characterized in that the temperature in the fixing process is a temperature between the start onset temperature and the end onset temperature of the change region due to melting in the storage modulus curve of the powder adhesive. The method for manufacturing a pressure-bonded sheet according to claim 5, wherein the powder adhesive contains low-density polyethylene. A method for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising the steps of:
A step of forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing step of heating the composite layer formed on the sheet to fix it to the sheet;
a step of overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or a different sheet to which another composite layer is fixed, and a pressing step of pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
The method for producing a pressure-bonded sheet is characterized in that the difference in average particle size between the toner and the powder adhesive is less than 25 μm, and the powder adhesive has a broader particle size distribution or a larger half-value width than the toner. The method for manufacturing a pressure-bonded sheet according to claim 7, wherein the powder adhesive contains low-density polyethylene. An image forming apparatus for manufacturing a pressure-bonded sheet in which sheets are pressure-bonded to each other in a peelable state, comprising:
a means for forming an unfixed composite layer on a sheet by laminating an adhesive layer formed using a powder adhesive as a surface layer on an unfixed toner image formed using a printing toner;
a fixing means for heating the composite layer formed on the sheet to fix it to the sheet;
a means for overlapping an area on the sheet to which the composite layer is fixed with an area on the same sheet as the sheet or on a different sheet to which another composite layer is fixed, and a pressing means for pressing the overlapping area of the composite layer and the other composite layer under heat and pressure;
having
an image forming apparatus, characterized in that the difference in average particle size between said toner and said powder adhesive is less than 25 μm, and said powder adhesive has a broader particle size distribution or a larger half-value width than said toner; The image forming apparatus according to claim 9, wherein the powder adhesive contains low-density polyethylene.

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