JP4577148B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to a technique for forming a highly glossy and borderless image.

  With the widespread use of digital still cameras, there is an increasing demand to easily print out photographic images taken with digital still cameras at convenience stores and photo shops in town. In general, a photographic image formed on photographic paper or the like is preferred to have a high gloss and edgeless finish (hereinafter referred to as “photographic image quality”). Therefore, there is a need for a technique that can easily and inexpensively form photographic quality images.

  As an example of such a technique, an electrophotographic image forming apparatus described in Patent Document 1 can be cited. The image forming apparatus described in Patent Document 1 heats and cools a sheet while being closely attached to a fixing belt to make the image highly glossy, and cuts four sides of the sheet after fixing, thereby obtaining a photographic image quality image. Easy to get.

  In order to form a photographic image using an electrophotographic image forming apparatus, a paper (hereinafter referred to as “coated paper”) in which various resin layers are coated on the surface of a base material portion such as cellulose is used. Is desirable. By using such paper, it is possible to obtain gloss similar to that of photographic paper, and at the same time, by embedding the toner in a softened resin layer at the time of fixing, it is possible to reduce surface irregularities caused by the toner. . In addition, since the resin layer of the coated paper loses the air permeability from the surface, the base material portion of the paper expands and curls due to moisture absorption of the base material portion, or the toner image is pulled along with the curl and cracks occur. It can also be prevented from occurring.

In consideration of productivity and cost of image formation, it can be said that it is desirable to cut a large size sheet and divide it into a plurality of sheets. In general, it takes less time to form one image (for example, A4 size) twice that size than to form two images of a certain size (for example, A5 size). This is because the unit price per area is cheaper for large format paper. The timing for cutting the paper in the electrophotographic image forming process may be before transfer (for example, see Patent Document 2) or after fixing (for example, see Patent Documents 1 and 3). However, considering the ease of paper conveyance and image formation, the timing for cutting the paper is preferably after fixing rather than before transfer. In particular, as described in paragraph 0007 of Patent Document 1, in order to obtain an image without a border by electrophotography, a configuration in which an image with a margin is formed in advance and the margin is cut after fixing is preferable. It is.
JP 2004-109900 A JP 11-84777 A JP 2002-362823 A

  By the way, when using a sheet provided with the resin layer as described above, a higher amount of heat is required for fixing the toner image. However, when such paper is heated at a high temperature, moisture or gas contained in the base material part expands, and a phenomenon called so-called “blister” occurs in which the surface of the heated and softened resin layer is broken or inflated. Occur. Blisters cause innumerable irregularities on the surface of the paper and impair aesthetics, which is a serious image quality defect especially in photographic image quality.

  In other words, in order to form a photographic image using coated paper, it is necessary to perform the fixing process at a temperature at which the toner is satisfactorily embedded and at the same time the blister is suppressed. However, since the temperature at which toner is satisfactorily embedded and the temperature at which blisters are likely to occur are very close to each other, it has conventionally been difficult to stably maintain good image quality.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for stably obtaining a high-gloss and borderless image while satisfactorily suppressing blisters.

In order to achieve the above object, the present invention provides a toner for forming a toner image having an image area smaller than the size of the recording material on a sheet-like recording material having a resin layer formed on the surface on which the toner image is formed. An image forming unit, a cutting unit that cuts the recording material on which the toner image is formed by the toner image forming unit into a size corresponding to an image area of the toner image formed on the recording material, and the cutting unit An image forming apparatus including a heating unit that heats and pressurizes the recording material to reduce a step between the resin layer and the toner image is provided.
According to such an image forming apparatus, since the recording material is cut before the heat treatment by the heating unit and the size of the recording material is reduced, moisture and gas inside the recording material (particularly the central portion) that cause blistering can be easily performed. It is emitted to the outside.

  The image forming apparatus according to the present invention is configured so that a plurality of image data having an image area smaller than the size of the recording material on which a toner image is formed do not overlap each other and fit within the size of the recording material. The toner image forming means forms a toner image based on the arrangement made by the arrangement means, and the cutting means uses the plurality of recording materials on which the toner images are formed. It is more preferable that the image data is cut at a size corresponding to each image area. In this way, since a plurality of images are formed from a single recording material, the productivity of image formation can be increased.

  Further, the toner image forming means fixes a toner image formed on the recording material by heating a transfer means for transferring the toner image to the recording material and a recording material on which the toner image is transferred by the transfer means. It is preferable that a temperature at which the heating unit heats the recording material is equal to or higher than a temperature at which the fixing unit heats the recording material. At this time, it is desirable that the temperature at which the heating means heats the recording material is such that the resin layer on the surface of the recording material is softened. In this way, the toner image transferred to the recording material is cut once in a state where the toner image is fixed by the fixing unit, and then the toner image is embedded in the layer on the surface of the recording material by the heating unit, and then cut. Processing is performed so as to eliminate cracks in the vicinity of the cut surface that accompany this.

  The present invention can also be specified as an image forming method performed by the above-described image forming apparatus. That is, in this image forming method, a toner image forming process of forming a toner image having an image area smaller than the size of the recording material on a sheet-like recording material having a resin layer formed on the surface on which the toner image is formed; A cutting process in which the recording material on which the toner image is formed in the toner image forming process is cut into a size corresponding to an image area of the toner image formed on the recording material, and the recording material cut in the cutting step is heated. And a heating process of applying pressure to reduce the step between the resin layer and the toner image.

  As described above, according to the present invention, it is possible to stably obtain a high-gloss and borderless image while satisfactorily suppressing blisters.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a so-called tandem color image forming apparatus that forms toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K) using an intermediate transfer belt will be described as an example. . However, of course, the toner and transfer method used in the present invention are not limited to such an embodiment.

[1. Constitution]
1 and 2 are diagrams showing a configuration of an image forming apparatus 100 according to an embodiment of the present invention. FIG. 1 is a block diagram schematically showing the configuration of the image forming apparatus 100, and FIG. 2 is a diagram showing the configuration of each part of the image forming apparatus 100 in more detail. 2, illustration of the operation part 7 and the control part 8 is abbreviate | omitted.

  The configuration of the image forming apparatus 100 includes a toner image forming unit 1, a paper feeding unit 2, a primary fixing unit 3, a conveyance switching unit 4, a cutting unit 5, a secondary fixing unit 6, an operation unit 7, It is roughly divided into a control unit 8. The image forming apparatus 100 can form a photo image with high gloss and no border. Therefore, the image forming apparatus 100 is suitably used for so-called digital camera prints (photographic quality prints) in which image data is printed on paper as if photographic film is printed on photographic paper. Hereinafter, the configuration of each part of the image forming apparatus 100 will be described with reference to FIGS. 1 and 2.

  The toner image forming unit 1 includes image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 11, a drive roll 12, a secondary transfer roll 13, and a backup roll 14. Note that the alphabets attached to the end of the reference numerals of the image forming units 10Y, 10M, 10C, and 10K merely indicate the color of the toner. There is no difference. Therefore, in the following description, these alphabets may be omitted as appropriate and may be collectively referred to as “image forming unit 10”. Similarly, each part of the image forming unit 10 will be described by omitting the alphabet as appropriate.

The image forming unit 10 includes a photosensitive drum 101, a charger 102, an exposure device 103, a developing device 104, a primary transfer roll 105, a drum cleaner 106, and a charge removal device 107. The photosensitive drum 101 is an image carrier having a photoconductive layer formed on the surface thereof, and is rotated in the direction of arrow A in FIG. The charger 102 generates a predetermined potential difference on the surface of the photosensitive drum 101 and uniformly charges it. The exposure device 103 is provided with a beam emission source such as a laser diode, and the charged light on the surface of the photosensitive drum 101 is irradiated with beam light so that the charge of the irradiated portion disappears, and according to the input image data of each color. An electrostatic latent image is formed. The developing device 104 includes toner of any one of Y, M, C, and K, and forms a toner image by applying toner to the electrostatic latent image on the surface of the photosensitive drum 101. In the present embodiment, toner having a melting temperature of about 110 ° C. and a viscosity of about 10 ⁴ Pa, mainly composed of styrene acrylic, is used. The primary transfer roll 105 faces the photosensitive drum 101 via the intermediate transfer belt 11, and transfers the toner image to the intermediate transfer belt 11 at the facing position. The transferred toner image is conveyed in the direction of arrow B in FIG.

  The drum cleaner 106 collects untransferred toner remaining on the surface of the photosensitive drum 101 after the toner image is transferred. The neutralization device 107 neutralizes the surface of the photosensitive drum 101. In other words, the drum cleaner 106 and the charge removal device 107 remove unnecessary toner and charges from the photosensitive drum 101 and prepare the photosensitive drum 101 to perform the next image forming process.

  The intermediate transfer belt 11 is an endless belt member. The intermediate transfer belt 11 is rotated in the direction of arrow B in FIG. 2 by the drive roll 12, and conveys the toner image formed in the image forming unit 10 to the nip area formed by the secondary transfer roll 13. The secondary transfer roll 13 is electrically grounded (grounded) via its shaft, and generates a potential difference with the backup roll 14 connected to a power source (not shown). The toner image on the surface of the intermediate transfer belt 11 is moved by this potential difference, and the sheet of paper supplied from the paper feeding unit 2 at a position where the secondary transfer roll 13 and the backup roll 14 face each other (hereinafter referred to as “secondary transfer position”). Adhere to the surface.

  The paper feed unit 2 includes paper trays 20 and 21, a plurality of transport rolls 22, and a registration roll 23. The paper trays 20 and 21 store different types of paper, and the paper in each tray is different in size and quality. The transport roll 22 transports the paper supplied from the paper trays 20 and 21. The registration roll 23 adjusts the timing at which the sheet enters the secondary transfer position.

  Here, the paper used in this embodiment will be described. In this embodiment, two types of recording materials, “plain paper” and “coated paper”, are used as paper. Here, the plain paper is a so-called PPC (Plain Paper Copier) paper usually used for image formation, and is a paper mainly made of cellulose. The coated paper is a paper in which cellulose or the like similar to PPC paper is used as a base material layer and various layers are coated on the upper and lower sides thereof.

FIG. 3 is a cross-sectional view showing the configuration of the coated paper. As shown in the figure, the coated paper comprises a base material layer L ₁ , a moisture-proof layer L ₂ and an image receiving layer L ₃ . The moisture-proof layer L ₂ is made of a resin such as polyethylene, and is formed on both surfaces of the base material layer L ₁ . The thickness of the moisture-proof layer L ₂ is about several μm. Since the moisture-proof layer L ₂ prevents moisture from entering the base material layer L ₁ , the coated paper prevents the base material layer L ₁ from curling with moisture even under a high humidity environment. Further, the image receiving layer L ₃ is a layer mainly composed of a thermoplastic resin such as polyester, and is formed on the surface (recording surface) on which the toner image is formed. The thickness of the image receiving layer L ₃ is about 5 to 20 μm, more preferably about 10 μm. The melting temperature of the image receiving layer L ₃ is about 130 ° C.

  In the present embodiment, the paper stored in the paper tray 20 is plain paper, and the paper stored in the paper tray 21 is coated paper. The size of the coated paper is assumed to be A4 size (210 × 297 mm). Of course, these are merely examples, and the size and type of paper to be stored are arbitrary.

  Here, the description returns to each part of the image forming apparatus 100. The primary fixing unit 3 fixes the toner image by heating and pressurizing the paper on which the toner image is transferred at the secondary transfer position. As shown in FIG. 4, the primary fixing unit 3 includes a fixing roll 30, a pressure belt 31, and a pressure pad 32.

  For example, the fixing roll 30 has an elastic layer 302 made of silicone rubber having a rubber hardness (JIS-A) of about 33 ° on the surface of a core 301 made of aluminum having a thickness of 1.5 mm, an outer diameter of 25 mm, and a length of 380 mm. The release layer 303 made of a 30 μm thick PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) tube is further coated on the surface of the elastic layer 302. It is a roll-shaped member. A heat source 304 such as a halogen lamp is provided inside the fixing roll 30. The heat source 304 is heated from the inside so that the surface temperature of the fixing roll 30 becomes a predetermined temperature. The temperature at which the fixing roll 30 heats the paper depends on the melting temperature of the toner, but is about 120 to 140 ° C. in this embodiment.

  The pressure belt 31 is a belt-like member in which a release layer composed of a PFA tube having a thickness of 30 μm is formed on the surface of a polyimide belt having a thickness of 75 μm, an outer diameter of 30 mm, and a length of 330 mm. The pressure pad 32 urges the pressure belt 31 from the inside to form a nip region with the fixing roll 30. The load urged by the pressure pad 32 is, for example, 336 N, and the nip width at this time is about 6.5 mm.

The conveyance switching unit 4 includes a switching member 40 and conveyance rolls 41 and 42. The switching member 40 is rotatably provided on the upper part of the primary fixing unit 3 and switches the conveyance direction of the sheet discharged from the primary fixing unit 3 to the right direction or the left direction. The sheet conveyed in the left direction is discharged to the discharge tray T ₁ by the conveyance roll 41, and the sheet conveyed in the right direction is conveyed to the cutting unit 5 by the conveyance roll 42.

  The cutting unit 5 includes a slitter 50 that cuts the paper in the transport direction (the direction of arrow C in FIG. 2), reciprocating cutters 51 and 52 that cut the paper in a direction perpendicular to the transport direction, and a plurality of transports that transport the paper. A roll 53 for conveying and cutting the paper. Details of each part are as follows.

  FIG. 5 is a view showing the slitter 50 from the direction in which the paper enters. The slitter 50 includes shafts 501 and 502, and rotary blades 503a to 503h, conveying rolls 504a to 504h, and urging springs 505a to 505d are provided at appropriate positions of the shafts 501 and 502. The rotary blades 503e to 503h are fixed to the shaft 502, and rotate together with the shaft 502 rotated by a driving device (not shown). The intervals between the rotary blades 503e and 503f and the rotary blades 503g and 503h are both 89 mm. The interval between the rotary blades 503f and 503g is 16 mm. The rotary blades 503a to 503d are provided so as to be slidable with respect to the axial direction of the shaft 501, but are urged by the urging springs 505a to 505d and pressed to the rotary blades 503e to 503h, respectively, and their positions are fixed. ing. The contact pressure between the rotating blades facing each other is 3 to 10 N, and each lapping margin is about 1 mm. The conveyance rolls 504a to 504h are fixed to the shaft 501 or 502 and assist the conveyance of the paper at the time of cutting.

FIG. 6 is a perspective view showing the configuration of the reciprocating cutter 51. The reciprocating cutter 51 includes a fixed blade 511 and a movable blade 512. The movable blade 512 is moved up and down by a driving device (not shown). The fixed blade 511 is fixed at a position that properly meshes with the movable blade 512 that has moved downward.
The reciprocating cutter 52 also has the same configuration as the reciprocating cutter 51. The interval between the reciprocating cutters 51 and 52 is 127 mm.

  Next, the configuration of the secondary fixing unit 6 will be described with reference to FIG. The secondary fixing unit 6 includes a fixing roll 60, a pressure roll 61, a fixing belt 62, a cooler 63, a peeling roll 64, a steering roll 65, and a conveyance roll 66. The fixing roll 60 is a roll member formed by forming a release layer 603 made of a PFA tube or the like around a metal core 602 having high thermal conductivity, and includes a heat source 601 such as a halogen lamp inside the core 602. . The fixing roll 60 is rotated in the direction D in the drawing by a driving device (not shown) and the surface thereof is heated to a predetermined temperature (140 to 160 ° C. in the present embodiment).

  The pressure roll 61 is covered with an elastic body layer 613 made of silicone rubber or the like having a rubber hardness (JIS-A) of about 40 ° around a metal core 612 having high thermal conductivity, and the surface thereof is fixed. A release layer 614 similar to the release layer 603 of the roll 60 is formed. The core 612 includes a heat source 611 such as a halogen lamp. The pressure roll 61 is rotated in the direction E by a driving device (not shown) and the surface thereof is heated to a predetermined temperature (140 to 160 ° C. in the present embodiment).

  The fixing belt 62 is a belt member in which a coating layer having high smoothness made of fluorine rubber or silicone rubber is formed on the surface of an endless film made of, for example, thermosetting polyimide. The fixing belt 62 is provided on the fixing roll 60, the peeling roll 64, and the steering roll 65. It is stretched and rotated following the fixing roll 60. The coating layer is desirably about 35 μm, and the polyimide serving as the base material is desirably 75 μm or more.

  The cooler 63 is in contact with the inner peripheral surface of the fixing belt 62 between the fixing roll 60 and the peeling roll 64, and cools the heated paper by absorbing the heat of the fixing belt 62. As the cooler 63, for example, an air-cooled heat sink made of aluminum can be used. Although the cooling temperature of the cooler 63 differs depending on the type of toner and paper used, it is desirable to cool the paper so that the recording surface of the paper is about 60 to 80 ° C.

The peeling roll 64 rotates following the movement of the fixing belt 62. When the peeling roll 64 is stretched while winding the fixing belt 62, the paper is naturally peeled from the fixing belt 62 by the rigidity of the paper itself. Paper that has been separated from the fixing belt 62 is discharged to the discharge tray T ₂ is transported by the transport roller 66.
The steering roll 65 stretches the fixing belt 62 and causes a bias (a phenomenon in which the fixing belt 62 moves toward one end of the steering roll 65) that occurs when the fixing belt 62 is continuously circulated. Correct it.

  The operation unit 7 includes a touch panel type display and hard buttons (not shown), and accepts an operator input. The input contents of the operator are supplied to the control unit 8. In this embodiment, the operator can instruct the image forming mode via the operation unit 7. There are two types of image forming modes in the present embodiment: a “normal mode” for forming an image on plain paper and a “photo quality mode” for forming an image on coated paper. In the “photo quality mode”, an image is formed in a so-called L size (89 × 127 mm). The function of the operation unit 7 may be delegated to an external device such as a computer.

  The control unit 8 includes a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a memory, a communication interface, and the like (not shown), and controls the operation of each unit of the image forming apparatus 100 described above. The control unit 8 operates each unit of the image forming apparatus 100 in response to an input from the operator, and forms an image based on image data supplied from an external device (not shown) on a sheet.

[2. Operation]
Based on the above configuration, the image forming apparatus 100 forms an image by performing an operation according to the image forming mode based on the input image data. In the “normal mode”, the image forming apparatus 100 forms an image using plain paper. At this time, the control unit 8 causes the paper supply unit 2 to supply plain paper, and causes the conveyance switching unit 4 to convey the paper after the toner image transfer to the left. That is, in the normal mode, the fixing process by only the primary fixing section 3 with respect to the plain paper is performed, plain paper on which the image is formed is discharged to the discharge tray T _1.

On the other hand, in the “photo image quality mode”, the image forming apparatus 100 forms an image using coated paper and performs a two-stage fixing process using the primary fixing unit 3 and the secondary fixing unit 6. The fixing process (primary fixing process) in the primary fixing unit 3 is a process for melting and fixing the toner image on the surface of the coated paper, and the fixing process (secondary fixing process) in the secondary fixing unit 6 is a process for fixing the toner image. embedded in the image receiving layer T ₃ of the softened coated paper is a process for finishing the coated paper surface with high smoothness. In the secondary fixing unit 6, the fixing roll 60 and the pressure roll 61 heat the coated paper to soften the image receiving layer T _{3, and} are then cooled by the cooler 63 in close contact with the highly smooth fixing belt 62. As a result, the surface of the coated paper is finished with a high smoothness.

Here, the fixing process in the photo image quality mode will be described. FIG. 8 is a cross-sectional view showing the surface properties of the paper after the fixing process at each stage. As shown in FIG. 8A, at the stage where the primary fixing process is completed, the toner image IM is only attached to the surface of the image receiving layer L ₃ of the coated paper. For this reason, on the surface of the coated paper, a step d is formed between the region where the toner image is formed and the region where the toner image is not formed, and this step d appears as minute unevenness. If the surface of the coated paper is uneven, the reflection and scattering of light will be uneven, resulting in a decrease in the glossiness of the coated paper surface. Therefore, the coated paper surface at this stage is in a state of low gloss.

When the secondary fixing process is performed after the primary fixing process, the toner image IM is embedded in the image receiving layer L ₃ of the coated paper as shown in FIG. This is because the temperature at which the secondary fixing unit 6 heats the coated paper is higher than that of the primary fixing unit 3 and the image receiving layer L ₃ is softened. Since the toner image IM is embedded, the level difference disappears from the surface of the coated paper, so that the surface of the coated paper after the secondary fixing is in a state of higher gloss than that before the secondary fixing process.

  In the photo quality mode, the image forming apparatus 100 divides the region so that four L-size (89 × 127 mm) images are formed on one A4 size (210 × 297 mm) coated paper. Do. At this time, the control unit 8 arranges the input four pieces of image data so as to be one A4 size, and controls the cutting unit 5 to cut the coated paper. Note that the input image data may be originally L size or different size. When the image data is different from the L size, the image data is enlarged or reduced to the L size after cutting.

FIG. 9 is a diagram illustrating a state in which the paper is cut in the photographic image quality mode. In the figure, the hatched area indicates an image area, that is, an area where a toner image is formed, and broken lines l _{1 to} l ₈ indicate sheet cutting positions. The rotary blades 503a and 503e of the cutting unit 5 cut the paper at the position of the broken line l _1. Similarly, the rotary blades 503b and 503f, the rotary blades 503c and 503g, and the rotary blades 503d and 503h are respectively broken lines l ₁ and l. Cut the paper at positions ₂ , l ₃ and l ₄ . The reciprocating cutter 51 of the cutting unit 5 cuts the paper at the positions of the broken lines l ₅ and l ₇ , and the reciprocating cutter 52 cuts the paper at the positions of the broken lines l ₆ and l ₈ .

  In FIG. 9, the toner image is formed slightly larger than the L size (specifically, about 2 mm on each side). This is to prevent a margin from entering the edge of the image due to a shift in the sheet conveyance timing or cutting timing. However, of course, the image area of each toner image may be equal to the L size.

  By forming an image as described above, the image forming apparatus 100 of the present embodiment can form four L-size images from one A4 size sheet in the photographic image quality mode. Therefore, the image forming apparatus 100 can perform image formation per sheet at high speed and at low cost.

Further, according to the image forming apparatus 100 of this embodiment, after the cutting unit 5 cuts the sheet, the secondary fixing unit 6 performs the fixing process at a temperature at which the image receiving layer L ₃ is softened. even cracking occurs in the toner and the image receiving layer L ₃ in the vicinity of the surface, it is possible to overcome this cracking.

  Furthermore, according to the image forming apparatus 100 of the present embodiment, it is possible to satisfactorily suppress the generation of blisters. This effect is presumed to be achieved by securing a “escape” of moisture and gas that cause blistering by cutting the paper to a smaller size before secondary fixing. In order to verify the validity of this inference, the present inventor conducted the following experiment.

<Experiment 1>
Using the image forming apparatus 100 of this embodiment, an experiment was performed to evaluate the surface properties of the paper while changing the surface temperature of the fixing roll 60 and the pressure roll 61 of the secondary fixing unit 6. In this experiment, A4 size coated paper was used, one was imaged with a razor cut (see FIG. 10) in the center, and the other was nothing (no cut). Formation was performed. The toner image formed on the paper surface at this time is a black (process black) patch image formed with toners of four colors Y, M, C, and K.

  The configuration of the secondary fixing unit 6 used in this experiment will be described in detail. Both the fixing roll 60 and the pressure roll 61 have a width of 320 mm and an outer diameter of 50 mm, and the cores (602, 612) are aluminum having a thickness of 7 mm. The rubber layer 613 of the pressure roll 61 has a rubber hardness of 60 °. The power of the heat source 601 is 500 W, the power of the heat source 611 is 350 W, and the surface temperature of the pressure roll 61 is set to be about 10 ° C. lower than the surface temperature of the fixing roll 60. The load applied to the paper by the fixing roll 60 and the pressure roll 61 is 2150N. The fixing belt 62 is made of polyimide having a width of 320 mm and a thickness of 80 μm, and has a silicone rubber coating layer having a rubber hardness of 47 °. The conveyance speed of the fixing belt 62 is 50 mm / s.

FIG. 11 shows the results of this experiment. In the figure, the horizontal axis indicates the surface temperature of the fixing roll 60, and the vertical axis indicates the level of the toner step (see FIG. 8) after fixing. When this level is about 2 or less, the step becomes invisible to the human eye. Further, the temperature T ₁ is a temperature at which blisters start to be generated in the coated paper having no cut, and the temperature T ₂ is a temperature at which blisters start to be generated in the coated paper having the cut. In either case, blisters frequently occurred at the center of the paper and rarely occurred at the edge.

As is clear from the experimental results, when the cut is made in the coated paper, the temperature at which the blister is generated can be increased by about 10 ° C. as compared with the case where there is no cut. That is, when the cut is made in the coated paper, both the level difference caused by the toner and the blister can be suppressed by controlling the fixing roll 60 to a temperature of 140 ° C. or higher and lower than T ₂ . On the other hand, when no cut is made in the coated paper, the temperature at which the level of the step becomes 2 or less is almost equal to the temperature at which the blister starts to be generated. It is difficult to understand.

<Experiment 2>
In this experiment, the evaluation was tried using different sheets while using the same configuration as in Experiment 1 described above. In this experiment, the surface properties were evaluated using one A4 size coated paper and four L size coated papers. The L-sized coated paper was image-formed in a state where two sheets were arranged vertically and horizontally so as to be approximately the same size as the A4 size. That is, the state of the paper is closer to the state before the secondary fixing in the photo image quality mode of the present embodiment.

FIG. 12 shows the results of this experiment. As is apparent from the figure, also in this experiment, the temperature (T ₃ and T ₄ ) at which blisters start to occur can be increased by about 10 ° C. by using four sheets of L size. Therefore, it has been clarified that by cutting the paper before the secondary fixing, the step and the blister can be more easily suppressed than when cutting after the fixing.

Based on these experimental results, the operation of the present invention will be considered. As mentioned above, the blister from that frequently occurs in the center of the sheet, in the edge of the paper, moisture and gas contained in the substrate layer L ₁ is, the end portion which is exposed in the substrate layer L ₁ It is recognized that it diverges from the outside. That is, it is recognized that the blister is caused by moisture or gas that has not been able to reach the end of the paper in the course of primary fixing or secondary fixing.

  Here, the process of cutting the sheet leads to shortening the path until moisture or gas reaches the edge of the sheet, that is, the “escape” of moisture or gas. Therefore, when the paper is cut, the rate at which moisture and gas are diffused to the outside increases, and blisters are less likely to occur until the fixing roll 60 reaches a relatively high temperature. In other words, the above experiment proves that by cutting the paper to a smaller size before the secondary fixing, the “escape” of moisture and gas that causes blisters is secured and blisters are less likely to occur. It was.

[3. Modified example]
Thus far, the present invention has been described with reference to one preferred embodiment. However, the present invention is not limited to the above-described embodiments, and various modifications can be made. Therefore, a part of the modification will be described here.

  In the above-described embodiment, a description has been given using a so-called tandem color image forming apparatus, but the present invention can also be applied to other image forming apparatuses. For example, the image forming apparatus may be a so-called rotary developing method, or the toner may be other than four colors. In short, the present invention can cut a sheet after a toner image is formed on the sheet and before performing a process (secondary fixing process) for making the sheet highly smooth. Any image forming apparatus may be used.

  Therefore, the details of the image forming apparatus can be modified. For example, the above-described embodiment is configured to include two reciprocating cutters, but even with one, it is possible to cut the paper into L size. In this case, there is an advantage that the image forming apparatus can be reduced in size, but in this case, the size of the image to be formed is changed because the size of the paper changes according to the conveyance speed and cutting timing of the paper. It has the disadvantage that it is difficult to maintain good accuracy.

  Further, as a means for cutting the paper in the direction orthogonal to the transport direction, a circular cutter as shown in FIG. 13 can be used in addition to the above-described reciprocating cutter. The circular cutter 51a of FIG. 13 includes a plate-shaped fixed blade 511a and a rotating disk-shaped movable blade 512a, and the movable blade 512a reciprocates along the fixed blade 511a to cut the paper. is there.

  In the above-described embodiment, the configuration in which A4 size coated paper is cut and divided into four L size sizes is shown, but the mode of cutting the paper is not limited to this. For example, a coated paper of A3 size (297 × 420 mm) may be cut and divided into eight L sizes, or the divided image may be a size different from the L size. FIG. 14 shows an example in which a postcard size (100 × 150 mm) sheet is cut into an L size. In the figure, the hatched area is an image area, and the broken line indicates the position to be cut.

  In this way, when cutting at a position different from the above-described embodiment, it is necessary to change the blades of the slitter 50 and the reciprocating cutters 51 and 52 to appropriate positions, but depending on the size of the paper and the image. It is good also as a structure from which the position of a blade changes. In this way, images of various sizes can be formed using various sizes of paper.

  Further, the paper used in the “photo image quality mode” in the above-described embodiment is not limited to the coated paper described with reference to FIG. In the present invention, the paper, that is, the recording material, may be any paper as long as it has a layer that prevents the air permeability of the base material layer. This is because such a sheet has an effect of suppressing blisters. In addition, the above-described layer that impedes air permeability is generally formed of a resin, but does not necessarily need to be a resin.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of an image forming apparatus in detail. It is sectional drawing which showed the structure of the coated paper used in the embodiment. FIG. 3 is a diagram illustrating a primary fixing unit of the image forming apparatus. FIG. 6 is a diagram illustrating a configuration of a slitter of a primary fixing unit. It is the perspective view which showed the structure of the reciprocating cutter of a primary fixing part. FIG. 3 is a diagram illustrating a configuration of a secondary fixing unit of the image forming apparatus. FIG. 6 is a cross-sectional view illustrating the surface properties of a sheet after fixing processing at each stage. It is the figure which showed a mode that the paper was cut in the photograph image quality mode of the embodiment. It is the figure which showed the paper of the state which made the notch with the razor. It is the figure which showed the experimental result. It is the figure which showed the experimental result. It is the figure which showed the structure of the circular cutter used as a modification of a reciprocating cutter. FIG. 6 is a diagram illustrating a state in which a postcard-size sheet is cut into an L size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 1 ... Toner image forming part, 2 ... Paper feeding part, 3 ... Primary fixing part, 4 ... Conveyance switching part, 5 ... Cutting part, 6 ... Secondary fixing part, 7 ... Operation part, 8 ... Control unit

Claims (4)

Toner image forming means for forming a toner image having an image area smaller than the size of the recording material on a sheet-like recording material having a resin layer formed on the surface on which the toner image is formed;
Cutting means for cutting the recording material on which the toner image is formed by the toner image forming means into a size corresponding to the image area of the toner image formed on the recording material;
An image forming apparatus comprising: a heating unit that heats and pressurizes the recording material cut by the cutting unit to reduce a step between the resin layer and the toner image. A plurality of image data having an image area smaller than the size of the recording material on which a toner image is formed, and an arrangement means for arranging the image data in positions that do not overlap each other and fit within the size of the recording material,
The toner image forming unit forms a toner image based on the arrangement performed by the arrangement unit;
The image forming apparatus according to claim 1, wherein the cutting unit cuts the recording material on which the toner image is formed with a size corresponding to each image area of the plurality of image data. The toner image forming unit includes:
Transfer means for transferring a toner image to the recording material;
Fixing means for fixing the toner image formed on the recording material by heating the recording material onto which the toner image has been transferred by the transfer means;
The image forming apparatus according to claim 1, wherein a temperature at which the heating unit heats the recording material is equal to or higher than a temperature at which the fixing unit heats the recording material. An image forming apparatus is an image forming method for forming an image on a sheet-like recording material having a resin layer formed on a surface on which a toner image is formed,
A toner image forming process for forming a toner image having an image area smaller than the size of the recording material on the recording material;
A cutting process in which the recording material on which the toner image is formed in the toner image forming process is cut into a size corresponding to the image area of the toner image formed on the recording material;
An image forming method comprising: heating and pressurizing the recording material cut in the cutting step to reduce a step between the resin layer and a toner image.

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