JP2015022053A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus having such functions that when at least a shielding toner image is formed and transferred onto a colored recording medium except for a white color or a transparent recording medium, a finish image including the shielding toner image can be formed to have picture qualities ensuring the shielding property without influenced by the recording medium as a base.SOLUTION: The image forming apparatus includes: an image forming unit for forming at least either of a shielding toner image and a non-shielding toner image and transferring the image onto a recording medium; a fixing unit for fixing at least either of the shielding toner image and the non-shielding toner image transferred to the recording medium in the image forming unit, to the recording medium; and control means for controlling in such a way that, when a shielding toner image is formed and transferred to a colored recording medium except for a white color or a transparent recording medium in the image forming unit, fixing conditions for a shielding toner image in the fixing conditions set by three elements of fixing temperature, fixing pressure and fixing time in the fixing unit are determined, based on the conditions for fixing a non-shielding toner image, by decreasing at least one element in the above three elements, or by decreasing at least a fixing pressure to zero.

Description

  The present invention relates to an image forming apparatus.

  Conventionally, a white toner image is formed between a normal toner image and a transfer material as an image forming apparatus that prevents the image quality from deteriorating due to the color of the background such as the color of the transfer material. In addition, there is known an image forming apparatus having a configuration in which image data for forming a normal toner image is used as image data for a white toner image, and a process for attaching a substantially constant amount of white toner to a toner image forming unit is performed. (Patent Document 1).

  In addition, as an image forming apparatus that can always perform good fixing by switching the amount of fixing heat given according to the image forming mode, the type of recording paper, etc., when performing image formation on an OHP film or forming an image with high glossiness When copying in the OHP / gloss mode for cases, the initial fixing speed is slower than the initial fixing speed in the normal mode, and the deceleration is set lower than the deceleration in the normal mode. An image forming apparatus configured to perform fixing under fixing conditions is known (Patent Document 2).

  Further, as an image forming apparatus capable of obtaining a good product with no fixing failure and no show-through, there is an image forming apparatus having a configuration in which the fixing pressure is changed depending on whether or not the white toner image is formed. Known (Patent Document 3). In Patent Document 3, for example, when a white toner image is formed and fixed on thin paper such as high-quality paper or gloss coated paper, the pressing force at the time of fixing may be changed to a pressure higher than the fixing pressure at the normal time. It is shown. Japanese Patent Application Laid-Open No. 2004-228561 discloses that a white color single-color image forming apparatus and a four-color full color image forming apparatus may be arranged side by side to form a full color image after forming a white toner image in advance. .

Furthermore, as an image forming method in which the white toner in contact with the transfer material does not excessively penetrate into the transfer material and can be melted to such an extent that the fixing property is not impaired, the white toner is superposed on a plurality of colored toners. An image forming process for forming a white toner image between the transfer material and the multicolor toner image by developing and transferring the toner image according to the toner image, and the multicolor toner image and the white toner image on the transfer material. A fixing step for fixing, and a storage elastic modulus G ′ _(T) (W) at a temperature reached in the fixing nip of the white toner image at the time of the fixing step is an individual value at the time of the fixing step. The storage elastic modulus G ′ _(T) (W) at the temperature reached in the fixing nip of the white toner during the fixing step is higher than the storage elastic modulus at the temperature reached in the fixing nip of the colored toner. in the range (dyn / cm ²⁾ Image forming methods are known that (Patent Document 4). In Patent Document 4, according to this image forming method, excessive penetration of a multicolor toner image into the transfer material is prevented by the white toner transferred in the vicinity of the transfer material, and the color toner on the image surface is also disclosed. Is sufficiently melted, and as a result, it has been shown that a high-quality image having a uniform glossiness on the image surface and good fixability without a decrease in image density can be obtained.

JP 2002-99127 A Japanese Patent Laid-Open No. 08-95425 JP 2012-98655 A JP 2006-209090 A

  In the present invention, when at least a shielding toner image is formed and transferred to a colored or transparent recording medium other than white, the finished image including the shielding toner image is shielded without being affected by the underlying recording medium. It is an object of the present invention to provide an image forming apparatus capable of forming images with assured image quality.

The image forming apparatus of the present invention (A1)
An image forming unit that forms and transfers at least one of a shielding toner image and a non-shielding toner image to a recording medium;
A fixing unit for fixing at least one of the shielding toner image and the non-shielding toner image transferred to the recording medium in the image forming unit to the recording medium;
In the case where the shielding toner image is formed in the image forming unit and transferred to a colored or transparent recording medium other than white, the fixing condition set by three elements of fixing temperature, fixing pressure and fixing time in the fixing unit is set. Control means for controlling the fixing condition of the shielding toner image to reduce at least one of the three elements in the fixing condition of the non-shielding toner image or to control to at least fix the fixing pressure to zero. It is characterized by being.

  The image forming apparatus of the invention (A2) is the image forming apparatus of the invention A1, wherein the control means is a recording medium having a Wang Ken type smoothness of 1000 s or less as the recording medium or a surface roughness of toner. In the case of using a recording medium having a roughness equal to or larger than the average particle diameter, the control for reducing at least one of the three elements or the fixing pressure of the fixing toner image is reduced to zero. The control is performed.

  Further, in the image forming apparatus of the invention (A3), in the image forming apparatus of the invention A1 or A2, the fixing condition of the shielding toner image controlled by the control means is that the shielding toner image after fixing is The conditions are set so that the particles of the shielding toner constituting the toner image are also present on the projections of the surface irregularities of the recording medium in a state where the particle shape can be identified.

The image forming apparatus of the invention (A4) is the image forming apparatus of any one of the inventions A1 to A3.
The shielding toner image is fixed on the recording medium according to the fixing condition of the shielding toner image controlled by the control unit in the fixing unit after the shielding toner image is formed and transferred to the recording medium in the image forming unit. A first action to be performed;
After the first operation, a non-shielding toner image is formed in the image forming unit, transferred to the recording medium on which the shielding toner image is fixed, and then the fixing condition of the non-shielding toner image in the fixing unit. Then, the second operation of fixing the non-shielding toner image on the recording medium is performed.

  According to the image forming apparatus of the invention A1, when at least a shielding toner image is formed and transferred to a colored or transparent recording medium other than white, the shielding toner image is blocked depending on the fixing condition of the shielding toner image controlled by the control means. The finished image including the toner image can be formed with an image quality in which the shielding property is ensured without being affected by the recording medium as a base.

  In the invention A2, it is possible to accurately form a finished image including at least a light-shielding toner image with an image quality in which shielding properties are ensured without being affected by the recording medium having the Oken-type smoothness or surface roughness. it can.

  In the invention A3, the finished image including at least the light-shielding toner image is not affected by the underlying recording medium as compared with the case where the fixing condition of the shielding toner image is different from the condition controlled by the control means. Therefore, it can be reliably formed with an image quality in which shielding is ensured.

  In the invention A4, as compared with the case without the configuration of the invention, a finished image including at least a light-shielding toner image is surely formed with an image quality in which shielding properties are ensured without being affected by a recording medium as a base. be able to.

1 is a schematic explanatory diagram illustrating a main part of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic block diagram conceptually showing a configuration relating to fixing condition selection means in the image forming apparatus of FIG. 1. 3 is a flowchart showing control contents of a fixing operation during image formation by the image forming apparatus of FIG. 1. FIG. 2 is a schematic cross-sectional view conceptually showing a state of a finished image obtained by forming each of three image patterns by the image forming apparatus of FIG. 1. FIG. 2 is a schematic cross-sectional view showing an enlarged state of a finished image obtained by forming at least a shielding toner image on a colored or transparent recording medium other than white, and (a) is a view when fixed under normal fixing conditions. The state of the finished image obtained is shown, and (b) shows the state of the finished image obtained when fixing is performed under special fixing conditions. It is a graph which shows a part of conditions of the evaluation test 1, and the result at that time. It is a graph which shows the result of the evaluation test 2. It is a schematic explanatory drawing which shows an example (the principal part) of the image forming apparatus which concerns on other embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a schematic explanatory diagram showing an outline of the image forming apparatus according to the first embodiment.

  The image forming apparatus 1A according to the first embodiment includes a first image forming unit 2A that forms a shielding toner image and transfers the image to the recording medium 9, and a fixing unit 5A that fixes the shielding toner image on the recording medium 9. Image forming apparatus 10 </ b> A, image forming unit 2 </ b> B that forms a non-shielding toner image and transfers it to recording medium 9, and fixing unit 5 </ b> B that fixes the non-shielding toner image on recording medium 9. It is configured by connecting the device 10B. For example, the entire image forming apparatus 1A is configured as a printer.

  Among these, the first image forming apparatus 10A includes an image forming unit 2A that forms a shielding toner image in an internal space of the housing 11A and transfers the image to the recording medium 9, and a recording medium 9 that is supplied to the image forming unit 2A. A medium supply unit 4A that accommodates and sends out and a fixing unit 5A that fixes the shielding toner image transferred by the image forming unit 2A to the recording medium 9 are mainly disposed.

  Here, the shielding toner is a dry developer toner (colored fine powder) used to shield (conceal) the color and surface state of the recording medium 9 by mainly reflecting light. It is. In the image forming unit 2A, for example, white (W) toner (Tw), gold (G) toner (Tg), and silver (S) toner (Ts) are used as shielding toners. It is configured such that a shielding toner image (Iw, Ig, Is) with toner can be individually formed.

  The image forming unit 2A includes three image forming units 20W, 20G, and 20S that individually form a shielding toner image (Ia) composed of the white toner (Tw), the gold toner (Tg), and the silver toner (Ts). A belt-type intermediate transfer unit 30 is included.

The image forming units 20W, 20G, and 20S employ a recording method such as a known electrophotographic method, and have almost the same configuration except that the shielding toner used in the developing device is different.
That is, the image forming unit 20 (W, G, S) has a surface (image holding surface) of the photosensitive drum 21 around the photosensitive drum 21 that is rotationally driven in a direction indicated by an arrow (a clockwise direction in FIG. 1). A charging device 22 such as a contact method that charges the surface of the photosensitive drum 21 to a required potential, and an LED that forms an electrostatic latent image having a required potential by irradiating the charged surface of the photosensitive drum 21 with light based on image data (signal). An exposure device 23 comprising an array, a laser scanning device and the like, and a developing device 24 (developing the electrostatic latent image with a corresponding type of shielding toner (Tw, Tg, Ts) to form a shielding toner image (Ia) W, G, S), and a drum cleaning device (not shown) for cleaning the surface of the photosensitive drum 21 after transfer. Necessary image data for forming a shielding toner image is transmitted from an image processing unit (not shown) to the exposure device 23 of each image forming unit 20.

  The intermediate transfer unit 30 transfers the shielding toner images (Ia) formed on the respective photosensitive drums 21 in the image forming units 20W, 20G, and 20S to the recording medium 9 by relaying them with an intermediate transfer belt described later. . The intermediate transfer unit 30 is rotationally driven in the direction indicated by the arrow (counterclockwise direction in FIG. 1) while passing through the primary transfer position of each photosensitive drum 21 in the image forming unit 20 (W, G, S). An endless belt-shaped intermediate transfer belt 31, a plurality of belt support rolls 32 a to 32 d that rotatably support the intermediate transfer belt 31, and a shield for each photosensitive drum 21 of the image forming unit 20 (W, G, S). A primary transfer device 33 that primarily transfers a toner image to the outer peripheral surface of the intermediate transfer belt 31; and a contact system that secondary-transfers the shielding toner image primarily transferred to the intermediate transfer belt 31 to the recording medium 9. A secondary transfer device 35 and a belt cleaning device 36 for cleaning the outer peripheral surface of the intermediate transfer belt 31 after the secondary transfer are configured.

  The medium supply unit 4A has a tray type storage body 41 for storing a plurality of recording media 9 of a required size, type, etc. in a stacked state, and one recording medium 9 stored in the storage body 41. It is composed of a delivery device 42 or the like of a roll system that feeds it to the conveyance path one by one. A plurality of containers 41 (sending devices 42) are provided according to the usage mode. As the recording medium 9, cut paper cut to a required size is used. The type of the recording medium 9 is not particularly limited as long as a toner image can be formed. Color recording paper other than white, such as white recording paper, and transparent (colorless transparent or colored transparent) Recording film or the like is possible.

  Between the medium supply unit 4A and the secondary transfer position of the image forming unit 2A, a conveyance roll 43a and a belt conveyance for conveying and supplying the recording medium 9 sent from the medium supply unit 4A to the secondary transfer position A supply conveyance path 43 including an apparatus 43b, a conveyance guide member, and the like is provided. Further, between the secondary transfer position of the image forming unit 2A and the fixing unit 5A, relay conveyance configured by a belt conveyance device 44a and the like for conveying the recording medium 9 after the secondary transfer to the fixing unit 5A. A path 44 is provided. A two-dot chain line in FIG. 1 indicates a main conveyance path of the recording medium 9.

The fixing unit 5A is driven to rotate inside a dedicated housing (not shown) at a required speed in a direction indicated by an arrow (a counterclockwise direction in the figure) and to keep the surface temperature at the required temperature. A roll type, a belt type, etc., which are heated by means, such as a roll type, a belt type, etc., and a roll type, belt type, etc. The fixing device 50 </ b> A is provided with a pressing rotator 53.
In the fixing by the fixing device 50A, as a general rule, the unfixed shielding toner image (Ia) is transferred to the contact portion where the heating rotator 52 and the pressing rotator 53 rotate in a heated state. When the recording medium 9 is introduced and passes through the contact portion, the recording medium 9 is heated and pressurized (for a required time). On the recording medium discharge side of the fixing unit 5A, a discharge conveyance path 45 including a discharge roll 45a and the like for discharging the recording medium 9 after fixing to the outside of the housing 11A is provided.

  As the fixing device 50A in the first embodiment, a belt-type fixing device is applied. This belt-type fixing device 50A uses a heating roll that is rotationally driven as the heating rotator 52, and an endless belt as the pressing rotator 53 is required from the inside to the heating roll by the pressure pad 54 or the like. A structure having a structure in which it is pressed with a width and a pressure to be brought into contact with each other in a rotatable manner is used. About a heating roll, it heats with the heater installed in the inside of the roll.

  On the other hand, the second image forming apparatus 10B forms an unshielded toner image in the internal space of the casing 11B and transfers it to the recording medium 9, and the image forming unit 2B (shielding toner image). The medium supply unit 4B for supplying the recording medium 9 and the fixing unit 5B for fixing the shielded toner image transferred by the image forming unit 2B to the recording medium 9 are mainly arranged.

  Here, the non-shielding toner is a toner as a dry developer used for forming an image, which does not require shielding like the shielding toner. In the image forming unit 2B, yellow (Y), magenta (M), cyan (C), and black among colored toners that transmit light (or absorb without reflecting light) as non-shielding toners. The four color toners (Ty, Tm, Tc, Tk) of (K) are employed, and the non-shielding toner images (Ib) with the respective non-shielding toners (Ty, Tm, Tc, Tk) are individually used. Or it is comprised so that it can form combining two or more.

  The image forming unit 2B includes four image forming units 20Y, 20M that individually form each non-shielded toner image (Ib) composed of yellow (Y), magenta (M), cyan (C), and black (K). 20C and 20K, and a belt-type intermediate transfer unit 30.

The image forming units 20Y, 20M, 20C, and 20K employ a recording method such as a known electrophotographic method, and have almost the same configuration except that the non-shielding toner used in the developing device is different.
That is, in the image forming unit 20 (Y, M, C, K), the direction indicated by the arrow (clockwise direction in FIG. 1) is almost the same as the case of the image forming unit 20 (W, G, S). A charging device 22 such as a contact method that charges the surface of the photosensitive drum 21 to a required potential around the photosensitive drum 21 that is rotated and the surface of the photosensitive drum 21 that has been charged is irradiated with light based on image data. An exposure device 23 for forming an electrostatic latent image having a required potential, and developing the electrostatic latent image with a corresponding type of non-shielding toner (Ty, Tm, Tc, Tk). The developing device 24 (Y, M, C, K) to be Ib) and a drum cleaning device (not shown) for cleaning the surface of the photosensitive drum 21 after transfer are arranged. Necessary image data for forming a non-shielding toner image is transmitted from an image processing unit (not shown) to the exposure device 23 of each image forming unit. The intermediate transfer unit 30 has substantially the same configuration as the intermediate transfer unit 30 of the image forming unit 2A in the first image forming apparatus 10A.

  The medium supply unit 4B conveys and supplies the recording medium 9 on which the shielding toner image is formed (transferred and fixed) in the first image forming apparatus 1A to the secondary transfer position of the image forming unit 2B. The medium supply unit 4B in the first embodiment feeds the recording medium 9 discharged through the discharge path 45 to the outside of the housing 11A in the first image forming apparatus 1A, and forms an image therein. A belt conveying device 46 and the like for conveying to the secondary transfer position of the section 2B are arranged. Between the secondary transfer position of the image forming unit 2B and the fixing unit 5B, a relay conveyance path 47 including a belt conveyance device 47a and the like for conveying the recording medium 9 after the secondary transfer to the fixing unit 5B. Is arranged.

The fixing unit 5B is driven to rotate at a required speed in a direction indicated by an arrow (a counterclockwise direction in the drawing) in a dedicated housing (not shown) so that the surface temperature is maintained at the required temperature. A roll type, a belt type, etc., which is rotated by a contact with a required pressure so as to be substantially along the axial direction of the heating rotary body 52, such as a roll type, a belt type, etc. heated by a heating means. And a fixing device 50B provided with a pressure rotating body 53.
In the fixing by the fixing device 50B, in principle, an unfixed non-shielding toner image (Ib) is transferred to a contact portion where the heating rotator 52 and the pressing rotator 53 that rotate in a heated state contact each other. When the recording medium 9 is introduced and passed through the contact portion, the recording medium 9 is heated and pressurized (for a required time). On the recording medium discharge side of the fixing unit 5B, a discharge conveyance path 48 including a discharge roll 48a and the like for discharging the fixed recording medium 9 to the outside of the housing 11B is provided.

  As the fixing device 50B in the first embodiment, an electromagnetic induction heating (IH) type fixing device is applied. This IH type fixing device 50B uses a pressure roll that is rotationally driven as the pressure rotator 53, and an endless belt having a conductive layer as a heating rotator 52 from the inside by a pressing roll or a pad 55 or the like. A structure is used in which a heating means 56 for pressing the endless belt against the pressure roll in a required width so as to be able to rotate, and for electromagnetic induction heating of the endless belt is disposed.

The image forming apparatus 1A is configured to perform image formation distinguished by the following three patterns.
That is, by forming a shielding toner image in the first image forming apparatus 10A, an image pattern 1 for forming a finished image consisting only of the shielding toner image and a shielding toner image in the first image forming apparatus 10A are formed. After that, the second image forming apparatus 10B forms a non-shielding toner image to form a finished image composed of the shielding toner image and the non-shielding toner image, and the second image forming apparatus 10B It is an image pattern 3 that forms a finished image consisting only of a non-shielding toner image by forming a non-shielding toner image.

  The image formation of the image pattern 1 is performed roughly as follows.

First, in the intermediate transfer unit 30 after a shielding toner image (Ta) made of white toner or the like (Tw or the like) is formed in any image forming unit 20W or the like in the image forming unit 2A of the first image forming apparatus 10A. On the other hand, the desired recording medium 9 is conveyed from the medium supply unit 4A to the secondary transfer position of the image forming unit 2A via the supply conveyance path 43, and is transferred to the secondary transfer position. The shielding toner image is secondarily transferred to the recording medium 9 at the secondary transfer position.
Subsequently, the recording medium 9 onto which the shielding toner image (Ta) has been transferred in the image forming unit 2A is conveyed to the fixing unit 5A through the relay conveyance path 44, and is heated and pressed for a required time in the fixing unit 5A. Thus, the shielding toner image (Ta) is fixed on the recording medium 9. Thereafter, after the fixing recording medium 9 is sent out to the second image forming apparatus 10B via the discharge conveyance path 45, the medium supply unit 4B and the relay conveyance path 47 in the second image forming apparatus 10B. Then, the toner is discharged to a discharge container (not shown) outside the housing 11B through the discharge conveyance path 48.

  With the above operation, a recording medium 9 on which a finished image (Ia) consisting only of the shielding toner image (Ta) is formed as shown in FIG. 4A is obtained (output). At the time of this image formation, in the image forming unit 2B in the second image forming apparatus 10B, the secondary transfer device 35 moves to a separated position away from the intermediate transfer belt 31, and the recording medium 9 is passed through. In the fixing unit 5B, the pressurizing rotator 53 moves to a separated position away from the heating rotator 52 and passes through the recording medium 9 (no fixing process).

  In addition, the image formation of the image pattern 2 is performed roughly as follows.

First, a recording medium 9 on which a required shielding toner image (Ta) is formed is obtained by the operations in the image forming unit 2A and the fixing unit 5A of the first image forming apparatus 10A (first operation). Is sent to the second image forming apparatus 10 </ b> B via the discharge conveyance path 45. At this time, the shielding toner image (Ta) is uniformly formed on the entire surface of the recording medium 9, or a partial area of the recording medium 9 where the non-shielding toner image (Tb) described later is formed or It is formed in a region slightly wider than that region.
Subsequently, in the intermediate transfer unit 30 after a non-shielding toner image (Tb) made of non-shielding toner is formed in one or a plurality of image forming units 20 in the image forming unit 2B of the second image forming apparatus 10B. The primary transfer and the secondary transfer position are carried. On the other hand, the recording medium 9 having the shielding toner image (Ta) is conveyed to the secondary transfer position of the image forming unit 2B by the medium supply unit 4B. The non-shielding toner image (Tb) is secondarily transferred onto the shielding toner image (Ta) of the recording medium 9 at the secondary transfer position.
Subsequently, the recording medium 9 having the shielding toner image (Ta) onto which the non-shielding toner image (Tb) is transferred by the image forming unit 2B is conveyed to the fixing unit 5B through the relay conveyance path 44, and is required in the fixing unit 5B. The non-shielding toner image (Tb) is fixed to the recording medium 9 having the shielding toner image (Ta) by being heated and pressurized for the time (second operation). Thereafter, the recording medium 9 after the fixing is discharged through a discharge conveyance path 48 to a discharge container (not shown) outside the casing 11B.
With the above operation, as illustrated in FIG. 4B, the recording medium 9 on which the finished image (Ib) including the shielding toner image (Ta) and the non-shielding toner image (Tb) is formed is obtained.

  Further, the image formation of the formation pattern 3 is performed in the general manner as follows.

First, after the non-shielding toner image (Tb) made of non-shielding toner is formed in one or a plurality of image forming units 20 in the image forming unit 2B of the second image forming apparatus 10B, the primary transfer is performed in the intermediate transfer unit 30. It is transferred and conveyed to the secondary transfer position. On the other hand, a desired recording medium 9 passes from the medium supply unit 4A of the first image forming apparatus 10A to the medium supply unit of the second image forming apparatus 10B via the supply conveyance path 43, the relay conveyance path 44, and the discharge conveyance path 46. 4B is transported to the secondary transfer position of the image forming unit 2B. Then, the non-shielding toner image (Tb) is secondarily transferred to the recording medium 9 at the secondary transfer position.
Subsequently, the recording medium 9 on which the non-shielding toner image (Tb) has been transferred by the image forming unit 2B is conveyed to the fixing unit 5B through the relay conveyance path 47, and is heated and pressurized for a required time in the fixing unit 5B. As a result, the non-shielding toner image (Tb) is fixed to the recording medium 9. Thereafter, the recording medium 9 after the fixing is discharged through a discharge conveyance path 48 to a discharge container (not shown) outside the casing 11B.

  With the above operation, the recording medium 9 on which the finished image (Ic) consisting only of the non-shielded toner image (Tb) is formed as illustrated in FIG. 4C is obtained. At the time of this image formation, in the image forming unit 2A in the first image forming apparatus 10A, for example, the secondary transfer device 35 is moved to a separated position away from the intermediate transfer belt 31, and the recording medium 9 is passed through. Further, in the fixing unit 5A, the pressing rotator 53 moves to a separated position away from the heating rotator 52 to pass the recording medium 9 (no fixing process).

  In the image forming apparatus 1A, for example, the operation of each component in the image forming apparatuses 10A and 10B is comprehensively controlled by the control device 6 disposed on the first image forming apparatus 10A side, for example. It is configured.

  The control device 6 is mainly composed of an arithmetic processing device, a storage means, a control means, an input / output means, etc., and includes a control program set according to the operation of each component and other related information. Based on this, a predetermined control operation is performed. In addition, the control device 6 is configured to control each piece of information such as image data and operation instruction data transmitted from devices such as an image reading device, a personal computer (PC), and a storage medium reading / writing device that are connected to or equipped with the image forming apparatus 1A. Even grasp and necessary post-processing.

  Further, in this image forming apparatus 1A, the control device 6 is configured to perform control to make the fixing condition of the fixing unit 5A in the first image forming apparatus 10A that forms the shielding toner image (Ta) a desired condition. ing.

  Here, the fixing condition is a condition set by three elements of a fixing temperature, a fixing pressure, and a fixing time. The fixing temperature corresponds to the heating and holding temperature at the time of fixing the heating rotator 52 in the fixing device 50. The fixing pressure corresponds to a pressure holding pressure at the time of fixing of the pressure rotating body 53 in the fixing device 50. The fixing time is a time required for the recording medium 9 to be fixed to pass through the contact portion between the heating rotator 52 and the pressing rotator 53 in the fixing device 10 to perform the fixing process, and the moving direction of the contact portion. This length corresponds to a value obtained by dividing the length by the rotation speed of the heating rotator 52 that rotates.

  When the control device 6 forms a shielding toner image (Ta) in the image forming unit 2A of the first image forming apparatus 10A and transfers it to a colored or transparent recording medium 9B other than white, the first image is formed. Regarding the fixing condition of the shielding toner image (Ta) in the fixing unit 5A of the forming apparatus 10A, a condition in which at least one of the three elements in the fixing condition of the non-shielding toner image (Tb) is reduced or at least the fixing pressure is set. Control is performed to make the condition zero. Incidentally, when the control device 6 forms the shielding toner image (Ta) on the recording medium 9 (white recording medium 9 or the like) other than the colored or transparent recording medium 9B other than white, at least one of the above three elements is used. The fixing conditions for the non-shielding toner image (Tb) can be selected without selecting the conditions for reducing the elements or at least the conditions for fixing the fixing pressure to zero (hereinafter, these conditions are also referred to as “special conditions”). Fixing can be performed under certain “normal fixing conditions”.

  Examples of the color or transparent recording medium 9B other than white, which can be used as a guide when selecting the special conditions, include the above-described black (black), yellow (Y), magenta (M), cyan (C), and red. Colored recording media (recording paper, etc.) 9B such as blue, green, and light colors (for example, when black is gray), colorless transparent or colored transparent recording media (resin film such as OHP, 9B is a target.

Further, the control device 6 records at least the surface 9Ba on the side on which the shielding toner image is formed, in the colored or transparent recording medium 9B other than white, in the range of 1000 s (seconds) or less. When the recording medium 9B having a surface roughness of the medium 9B or its surface 9Ba having a roughness equal to or larger than the average particle diameter of the toner is used, control is performed so as to make the fixing conditions special. . The surface roughness at this time is represented by the depth of fine irregularities on the surface. The roughness having a surface roughness equal to or greater than the average particle diameter of the toner refers to a state in which the depth of the fine irregularities is a dimension equal to or greater than the average particle diameter of the toner. Each of the toners used in Embodiment 1 has an average particle diameter of 6 μm. Incidentally, as for the recording medium 9B, both the Oken smoothness and the surface roughness both fall within the above numerical range, but there are those that fall within either numerical range.
The Oken type smoothness is measured according to the smoothness test method of “P8155 (2010)” in Japanese Industrial Standard (JIS). Further, the surface roughness substantially corresponds to a range where the arithmetic average roughness Ra is 8 μm or more when expressed by the arithmetic average roughness (Ra). The arithmetic average roughness Ra in this case is obtained in accordance with the measurement method and calculation formula of “B0601 (1994)” (“B0031 (1994)”) in JIS.

  The recording medium 9B having such surface characteristics is relatively inferior in surface smoothness (in other words, the surface has fine irregularities), but the recording medium 9B having such surface characteristics is used. In this case, fixing is performed under special conditions (or fixing is not performed), so that the finished image (Ia or Ib) is not affected by the underlying recording medium 9B and is blocked by the shielding toner. It is possible to accurately form the image with assured image quality. In FIG. 4, a recording medium 9B having fine irregularities on the surface is shown as a recording medium, and in particular, the fine irregularities on the surface 9Ba are exaggerated. Further, the unevenness of the surface 9Ba in the recording medium 9B is, for example, the unevenness existing due to the pulp fibers constituting the paper being exposed on the surface, or the unevenness when the surface 9Ba is roughened. And so on.

Among the special conditions of the above fixing conditions (hereinafter also referred to as “special fixing conditions”), as a condition for reducing at least one of the three elements, only one of the fixing temperature, fixing pressure or fixing time (one element) is used. Examples include conditions for reducing, conditions for reducing only two elements of the fixing temperature, fixing pressure, and fixing time, and conditions for reducing all three elements of fixing temperature, fixing pressure, and fixing time.
In this case, the reduction ratio of the fixing temperature, the fixing pressure, and the fixing time, which are the three elements, can be set by experiment or the like. The fixing pressure is also reduced to about 0.6 to 0.9 times the fixing temperature in the fixing conditions), and the fixing pressure is reduced to about 0.4 to 0.8 times the fixing pressure under the normal fixing conditions. The fixing time may be reduced to about 0.3 to 0.7 times the fixing time under normal fixing conditions.
Among the special conditions of the above fixing conditions, at least the fixing pressure is set to zero, the fixing temperature is set to zero (in this case, the fixing time is completely zero), and heating is slightly performed. Conditions (in this case, the heating temperature is lower than the fixing temperature of the main body. Also, the fixing time is a little as much as it is heated at the heating temperature).

  Further, this special condition is that, for example, the particles of the shielding toner (Tw, etc.) constituting the shielding toner image (Ta) after fixing can be discriminated (without being completely crushed) in a state where the particle shape can be identified. It is preferable to set the condition set based on the determination criterion that the protrusions on the surface unevenness are also present (see FIG. 5c). The special condition is set to a setting condition in which at least one of the three elements of the fixing condition is reduced from the viewpoint of satisfying this determination criterion.

For example, as shown in FIG. 2, the control device 6 includes a changing unit 71 for actually changing the fixing condition of the fixing unit 5A, and a selection input unit for actually selecting and inputting the special condition as the fixing condition. 72.
As shown in FIG. 2, the changing means 71 is configured as a part of the fixing control unit 62 </ b> A (fixing condition changing unit) of the fixing unit 5 </ b> A in the control device 6. The selection input means 72 is a selection input unit (button, selection screen, etc.) included in an operation panel provided on the outer surface of the housing 11A of the first image forming apparatus 10A as shown by a two-dot chain line in FIG. Or a selection input screen displayed by driver software on a terminal such as a PC connected to the image forming apparatus 1A. Regarding the selection input means 72, based on the setting information and detection information of the type of the recording medium 9 used for image formation, the recording medium 9 at that time is a recording medium 9B that preferably selects a special fixing condition. It is also possible to configure by software so that special fixing conditions are automatically selected (output as selected information). When the selection input unit 72 is configured as the selection input screen displayed on an external device separate from the image forming apparatus 1 </ b> A, it is sufficient that the control unit 6 is connected to only the changing unit 71. is there.
In the control device 6, information (control signal) regarding whether or not the fixing condition has been changed is transmitted to the fixing condition changing unit 71 of the fixing control unit 62 </ b> A based on the input information input by the selection input means 72. Further, as shown in FIG. 2, the fixing control unit 62A is connected to a three-element control unit 55 that actually changes three elements (fixing temperature, fixing pressure, and fixing time) relating to the fixing conditions of the fixing device 50A. The three-element control unit 55 includes a heating control unit, a pressurization control unit, a rotation speed control unit, and the like.

  When the fixing device 50A of the fixing unit 5A in the first image forming apparatus 10A whose fixing conditions are changed by the control device 6 receives an instruction from the control device 6 to control to the special fixing conditions, the fixing control unit 62A described above. The three-element control unit 55 controls at least one of the fixing temperature, the fixing pressure, and the fixing time to be decreased, or at least controls the fixing pressure to be zero. More specifically, as for the fixing temperature, the set temperature of the heater in the heating roll 52 is lowered by a predetermined amount, and as for the fixing pressure, the set pressure of the pressure pad 54 in the belt-type pressurizing rotating body 53 is lowered by a predetermined amount. For the fixing time, the rotation speed of the heating roll 52 is decreased by a predetermined amount. Further, at least the control for setting the fixing pressure to zero specifically refers to the case where the fixing pressure is set to zero and the fixing temperature is set to a normal setting, or the fixing pressure is set to zero and the fixing temperature is set to zero. It is a case where it sets to. In the former case, the recording medium to be fixed is not pressurized and is heated slightly (that is, in this case, a little heat fixing is performed). In the latter case, the recording medium or the like to be fixed is neither heated nor pressed (that is, this case corresponds to not performing the fixing process). The fixing device 50A is set to normal fixing conditions while the special fixing condition is not selected from the control device 6. In the fixing device 5B of the fixing unit 5B in the second image forming apparatus 10B that forms the unshielded toner image (Ib), the normal fixing conditions are always set.

  In the image forming apparatus 1A having the control device 6 for controlling such fixing conditions, when the image formation by the image patterns 1 and 2 is performed, the control device 6 sets the special conditions as the fixing conditions in the fixing unit 5A. It is possible to select. In principle, this selection is performed by the user of the image forming apparatus 1A as necessary. However, as described above, when the recording medium 9B is used as the recording medium 9, a special condition is automatically selected. In such a case, the image forming apparatus 1A automatically performs it.

  When the image formation is performed by the image patterns 1 and 2 in the image forming apparatus 1A, the fixing operation of the fixing unit 5A in the first image forming apparatus 10A in which the shielding toner image (Ta) is formed is controlled. The following control is performed by the device 6.

  That is, when image formation by the image patterns 1 and 2 is requested, as shown in FIG. 3, the control device 6 confirms the fixing conditions (step 10: hereinafter abbreviated as “S10”) and is special. It is determined whether or not fixing conditions are selected (S11).

  At this time, if a special fixing condition is not selected, the fixing condition is set to a normal fixing condition in the fixing device 50A of the fixing unit 5A that fixes the shielding toner image (Ta). The fixing operation for the shielding toner image (Ta) is performed under normal fixing conditions (S12), and is continued until all the fixing operations under the fixing conditions are completed (S13). When the shielding toner image (Ta) is fixed under normal fixing conditions, for example, the recording medium 9 is a recording medium that is not a colored or transparent recording medium 9B other than the white color or a recording medium that does not have the surface characteristics. The case where it uses is mentioned.

  On the other hand, when a special fixing condition is selected, in the fixing device 50A of the fixing unit 5A that fixes the shielding toner image (Ta), the fixing condition is changed in the fixing condition of the fixing control unit 62 shown in FIG. The three-element control unit 55 of the fixing device via the unit 71 changes the set value of the necessary elements of the three elements to a set value that is smaller than the normal fixing condition or at least a set value that makes the fixing pressure zero (S14). Subsequently, the fixing operation for the shielding toner image (Ta) is performed under special fixing conditions (S15), and is continuously performed until all the fixing operations under the fixing conditions are completed (S16).

  In the image formation with the image patterns 1 and 2, when the fixing operation of the shielding toner image (Ta) is performed under special fixing conditions, particles of the shielding toner (Tw or the like) are formed as illustrated in FIG. 5c. In a state where the shape can be identified, it also exists on the projections on the surface unevenness of the recording medium 9B, and the finished image (Ia, Ib) at that time is influenced by the color, uneven shape, etc. of the recording medium 9B as the base. Therefore, it is possible to obtain an image with good image quality in which the shielding property by the shielding toner is secured.

According to the studies by the present inventors, when the shielding toner image (Ia) transferred to the recording medium 9B is fixed under the normal fixing conditions for the non-shielding toner image (Tb), the following is performed. It has been found that poor image quality occurs.
That is, in this case, as illustrated in FIG. 5a, in the fixing under normal fixing conditions, the particles of the shielding toner (Tw, etc.) constituting the shielding toner image (Ia) are sufficiently crushed to form a film shape. In the portion where the convex portion on the surface irregularity exists in a state like a film having a relatively thin thickness, there may be a tendency to concentrate mainly on the concave portion on the irregular surface of the recording medium 9B. Then, a portion b of the incident light h1 passes through the portion of the shielding toner image (Ia) whose concealability is reduced in the thin film state, reaches the convex portion on the surface of the recording medium 9B, and is reflected. As a result, the finished image (Ia) may appear dull in color due to the influence of the color of the recording medium 9B, and the desired image quality may not be obtained. Further, even when the non-shielding toner image (Ib) is formed on the shielding toner image (Ia) as shown by a two-dot chain line in FIG. Both the Ib) and the portion of the shielding toner image (Ia) whose concealability is reduced due to the thin film state are transmitted and reach the convex portion on the surface of the recording medium 9B to be reflected.
For example, as shown in FIG. 5b, this point is a state in which the particles of the shielding toner (Tw, etc.) constituting the shielding toner image (Ia) are not crushed, but the projections on the surface irregularities of the recording medium 9B. Even when the particles of the shielding toner (Tw or the like) existing in the recording medium 9B are moved so as to be pushed into the concave portions of the surface unevenness by the action of fixing pressure or the like, a part b of the incident light h1 is recorded on the recording medium 9B. As a result, the finished image (Ia) looks dull in color due to the influence of the color of the recording medium 9B, and the desired image quality is not achieved. Sometimes. Further, even when the non-shielding toner image (Ib) is formed on the shielding toner image (Ia) as shown by a two-dot chain line in FIG. Ib) is transmitted, reaches the convex portion on the surface of the recording medium 9B, and is reflected.

In contrast, when the shielding toner image (Ta) transferred to the recording medium 9B is fixed under special fixing conditions for the shielding toner image (Ta), the occurrence of image quality defects is reduced as follows. Turned out to be.
That is, in this case, as illustrated in FIG. 5c, the state of the particles of the shielding toner (Tw, etc.) constituting the shielding toner image (Ta) can be identified by fixing under special fixing conditions. Thus, it also exists on the projections on the surface irregularities of the recording medium 9B. Thereby, in the portion of the shielding toner image (Ta), light is scattered (reflected) by the particles of the shielding toner (Tw or the like) (scattered light b1, b2, b3,...). As a result, the light transmittance is lowered and the concealability is ensured. For this reason, the incident lights h1 and h3 incident on the projections on the surface irregularities of the recording medium 9B on which the shielding toner image (Ta) is present are scattered (reflected) by the particles of the shielding toner (Tw or the like) and recorded. The light is normally reflected by the shielding toner image (Ta) or the non-shielding toner image (Tb) without reaching the convex portion 9B and reflecting. This is the same even when the non-shielding toner image (Ib) is formed on the shielding toner image (Ia) as shown by a two-dot chain line in FIG. 5C. As a result, the finished images (Ia, Ib) at that time are less affected by the color of the recording medium 9B and can be obtained with the desired image quality. When the finished image (Ia) having only the shielding toner image (Ta) is formed (see FIG. 4a), the image is obtained without the non-shielding toner image (Tb) in FIG. 5c.

<Evaluation Test 1>
Hereinafter, an evaluation test performed using the image forming apparatus 1A will be described.

  This test 1 is performed when a test image consisting only of the following shielding toner is formed on various recording media 9 and 9B shown in FIG. 6 and fixed under the following normal fixing conditions or special fixing conditions. The color of the finished test image and the grade of image intensity were examined. The result of this evaluation test 1 is shown in FIG.

As the shielding toner image (Ta) of the test image, an image (image area ratio: Cin = 100%) that spreads over the entire surface of one side of the recording medium was formed using white toner (Tw).
Normal fixing conditions were a fixing temperature of about 160 ° C., a fixing pressure of about 4 kgf / cm ² (≈40 N / cm ² ), and a fixing time of about 80 ms (milliseconds). On the other hand, special fixing conditions were a fixing temperature of about 130 ° C., a fixing pressure of about 4 kgf / cm ² , and a fixing time of about 80 ms. Incidentally, the special condition at this time is a condition for reducing only the fixing temperature. In this way, the control to make the special condition by lowering the fixing temperature is advantageous in that it can be easily performed with relatively few other structural restrictions.

For the white density grade, the density of the obtained finished test image (shielding toner image Ia) is measured in a L ^* , a ^* , b ^* color system using a density measuring device (X-Rite: 938 spectral densitometer). The L ^* value was measured, and the L ^* value at that time was classified into five coloring grades according to the following criteria. Good results are obtained when the white density grade is 3 or more. Note that the white density of the recording medium of the transparent film is measured by placing a reference black paper under the transparent film.
White density grade 1: When the L ^* value is 59 or less White density grade 2: When the L ^* value is 60 to 64 White density grade 3: When the L ^* value is 65 to 69 White density grade 4: L ^When the value of ^* is 70 to 74 White density grade 5: When the value of L ^* is 75 or more

The image strength grade is determined by scratching (scratching) the obtained finished test image (a portion where the shielding toner image Ia and the non-shielding toner image Ib overlap) with a pencil having different hardness (pencil hardness 6H to HB to 6B). The minimum hardness at which the test image was not destroyed was examined, and the hardness at that time was classified into five image intensity grades according to the following criteria. Good results are obtained when the image intensity grade is 4 or higher.
Image strength grade 1: When pencil hardness is 6B-4B Image strength grade 2: When pencil hardness is 3B-B Image strength grade 3: When pencil hardness is HB-H Image strength grade 4: Pencil hardness is 2H-4H In case of image strength grade 5: When pencil hardness is 5H-6H

  From the results shown in FIG. 6, from the shield toner image to the recording medium (embossed paper, high-quality paper) 9B in which the Oken smoothness is in the range of 1000 s or less or the arithmetic average roughness Ra of the surface is 8 μm or more. In the case of forming a test image, when a special fixing condition is applied, the obtained finished test image has a sufficient white density as compared with a test image obtained by adopting a normal fixing condition. I understand that. In addition, special fixing conditions are applied to recording media (coated paper, black film, colorless transparent film) in which the Oken smoothness and surface roughness are both out of the above numerical range even in a colored or transparent recording medium 9B other than white. When the test image is formed in this way, the resulting finished test image has a white density sufficiently higher than the test image obtained by adopting the normal fixing conditions, but the image strength is greatly increased. It turns out that it falls to.

<Evaluation Test 2>
Further, an evaluation test 2 performed using the image forming apparatus 1A will be described.

  In this test 2, the high-quality paper in the evaluation test 1 (FIG. 6) was used as the recording medium 9B, and when the same test image as in the evaluation test 1 was formed and fixed under various fixing conditions shown in FIG. The white density grade of the finished test image was examined. The white density grade was measured and classified by the same method as in Test 1, and the white density blade was evaluated as “◯” when 3 or more and “×” when 2 or less. The results of this evaluation test 2 are shown in FIG.

The normal fixing conditions are those indicated by * 1 in FIG. 7a. Specifically, as in Test 1, the fixing temperature is about 160 ° C., the fixing pressure is about 4 kgf / cm ² (≈40 N / cm). ² ) The fixing time was about 80 ms (milliseconds). The other fixing conditions are such that at least one of fixing temperature, fixing pressure and fixing time is decreased or increased as shown in FIG.

  From the results shown in FIG. 7, when the fixing condition is a condition where one of the three elements of the normal fixing condition is reduced (corresponding to the “special condition”), the finished test image obtained at that time It can be seen that the white density is all improved. On the other hand, it is also found that when the fixing condition is a condition in which one of the three elements of the normal fixing condition is increased, the white density of the finished test image obtained at that time decreases.

  According to the studies by the present inventors, a test comprising a shielding toner image on a recording medium (embossed paper, high-quality paper) 9B having a surface roughness of not less than the average particle diameter of toner (6 μm in this example). In the case of forming an image, if special fixing conditions are applied, the obtained finished test image is a normal fixing image as in the case where the test image is formed on the recording medium having the arithmetic average roughness Ra in Evaluation Test 1. It has been confirmed that a sufficient white density can be obtained compared to a test image obtained by adopting the conditions. In addition, a test image composed of a shielding toner image is fixed on a recording medium (embossed paper, high-quality paper) 9B having a surface roughness equal to or greater than the average particle diameter of the toner under various fixing conditions shown in FIG. Even in this case, it has been confirmed that the white density of the finished test image obtained at that time is all improved.

[Other Embodiments]
The image forming apparatus having the control device 6 that controls the fixing conditions is not limited to the image forming apparatus 1A according to the first embodiment, and an image forming apparatus having another configuration (form) can be applied.

  For example, as shown in FIG. 8, the image forming unit 2C capable of forming both the shielding toner image (Ta) and the non-shielding toner image (Tb), and the shielding toner image (Ta) and the non-shielding image. An image including a fixing unit 5C that can fix the toner image (Tb) under normal fixing conditions or special fixing conditions, and a medium supply unit 4C that stores and sends out the recording medium 9 supplied to the image forming unit 2C. It is possible to apply the forming apparatus 1B. The medium supply unit 4C has substantially the same configuration as the medium supply unit 4A in the first image forming apparatus 10A.

  The image forming unit 2C includes five image forming units 20W, 20Y, 20M, 20C, and 20K that individually form a shielding toner image (Ta) and a non-shielding toner image (Tb), and a belt-type intermediate transfer unit 30. It consists of and. The image forming unit 20W that forms the shielding toner image (Ta) uses, for example, white toner (Tw) as the shielding toner, and has the same configuration as the image forming unit 20W in the image forming unit 2A in the first embodiment. It will be. The image forming units 20Y, 20M, 20C, and 20K that form the non-shielding toner image (Tb) apply, for example, the four color toners (Ty, Tm, Tc, and Tk) as the non-shielding toner. It has the same configuration as the image forming units 20Y, 20M, 20C, and 20K in the image forming unit 2B in the first embodiment. The intermediate transfer unit 30 has substantially the same configuration as the intermediate transfer unit 30 of the image forming unit 2A in the first image forming apparatus 10A or the like.

  Further, when compared with the image forming units 2A and 2B in the first embodiment, the image forming unit 2C retransmits the recording medium 9 after being fixed by the fixing unit 5C so as to be merged with the middle portion of the supply conveyance path 43. The difference is that the conveyance path 49 is additionally provided. The retransmission conveyance path 49 is a conveyance path that connects a middle portion of the discharge conveyance path 48 on the recording medium discharge side of the fixing unit 5C and a middle portion of the supply conveyance path 43, and includes a plurality of conveyance roll pairs 49B to 49B. 49e, a conveyance guide member and the like. A transport destination switching device for switching the transport destination of the recording medium 9 (not shown) to either the discharge transport path 48 or the retransmission transport path 49 is disposed in the middle of the discharge transport path 48.

The fixing unit 5C is driven to rotate inside a dedicated housing (not shown) at a required speed in a direction indicated by an arrow (counterclockwise direction in the figure) and the surface temperature is maintained at the required temperature. A roll type, a belt type, etc., which are heated by means, such as a roll type, a belt type, etc., and a roll type, belt type, etc. The fixing device 50 </ b> C is provided with a pressing rotator 53.
The fixing by the fixing device 50C is, as a general rule, the unfixed shielding toner image (Ia) and the non-shielding image at the contact portion where the heating rotator 52 and the pressing rotator 53 rotate in a heated state. The recording medium 9 onto which at least one of the toner images (Ib) has been transferred is introduced, and is heated and pressed when passing through the contact portion (for a required time).

  As the fixing device 50C, for example, a roll nip type fixing device is applied. The roll nip type fixing device 50 </ b> C uses a heating roll that is rotationally driven as the heating rotator 52, and a pressure roll that is driven to rotate as the pressing rotator 53. The heating roll is configured to be heated by a heater installed inside the roll. Moreover, about a pressurization roll, it is comprised so that the pressure at the time of a contact with a heating roll can be changed.

In this image forming apparatus 1B, as in the case of the image forming apparatus 1A according to the first embodiment, it is possible to perform image formation that is distinguished by the following three patterns (image patterns 1 to 3). Has been.
That is, the image pattern 1 is a finished image (Ia) composed only of the shielding toner image (Ta) by operating the image forming unit 20w in the image forming unit 2C and the fixing unit 5C to form and fix the shielding toner image. ). The image pattern 2 is a recording medium on which the shielding toner image (Ta) is formed after the image forming unit 20w is operated in the image forming unit 2C and the fixing unit 5C to form and fix the shielding toner image (Ta). 9 is retransmitted to the image forming unit 2C through the retransmission conveyance path 49, and one or more of the image forming units 20 (Y, M, C, K) are operated in the image forming unit 2C and the fixing unit 5C again. This is a pattern in which a shielding toner image (Tb) is formed and fixed, thereby forming a finished image (Ib) composed of a shielding toner image (Ta) and a non-shielding toner image (Tb). The image pattern 3 forms an unshielded toner image (Tb) by operating any one or more of the image forming units 20 (Y, M, C, K) in the image forming unit 2C and the fixing unit 5C. In this pattern, a finished image (Ic) made up of only the non-shielding toner image (Tb) is formed by fixing.

  The image forming apparatus 1B also includes a control device 6 that controls the fixing conditions as in the case of the image forming apparatus 1A according to the first embodiment, and forms a shielding toner image (Ta). A desired condition can be selected as the fixing condition of the fixing unit 5A in one image forming apparatus 10A. That is, when the control device 6 forms a shielding toner image (Ta) in the image forming unit 2C and transfers it to a colored or transparent recording medium 9B other than white, the control device 6 applies the shielding toner image (Ta) in the fixing unit 5C. As the fixing condition, it is possible to select a special condition including a condition in which at least one of the three elements is reduced in the fixing condition of the non-shielding toner image (Tb) or a condition in which the fixing pressure is reduced to zero. ing.

  In the fixing device 50C of the fixing unit 5C whose fixing condition is to be changed by the control device 6, when the control device 6 performs control for selecting a special fixing condition, as shown in FIG. 6 is controlled so that at least one of the fixing temperature, the fixing pressure, and the fixing time is decreased, or at least the fixing pressure is controlled to be zero. The

  In addition, as the image forming apparatus having the control device 6 that controls the fixing conditions, for example, an image forming apparatus having the following configuration can be applied. As an example, the image forming unit 2A for forming the shielding toner image and the image forming unit 2B for forming the non-shielding toner image in the first embodiment, the fixing unit 5C in the other embodiments, and the recording medium 9 are used. And a post-processing transport that feeds the recording medium 9 after fixing of the fixing section 5C to either of the image forming sections 2A and 2B. And an image forming apparatus.

  Incidentally, the image pattern 2 by this image forming apparatus is obtained by operating the image forming unit 20w or the like in the image forming unit 2A to form a shielding toner image (Ta) and fixing it by the fixing unit 5C. The recording medium 9 on which (Ta) is formed is conveyed to the image forming unit 2B through the post-processing conveyance path, and any one or more of the image forming units 20 (Y, M, C, K) are transferred in the image forming unit 2C. By operating, a non-shielding toner image (Tb) is formed and fixed by the fixing unit 5C, thereby forming a finished image (Ib) composed of the shielding toner image (Ta) and the non-shielding toner image (Tb). It will be.

  As other examples, the image forming unit 2C and the medium supply unit 4C in the other embodiments, the fixing unit 5A and the fixing unit 5B in the first embodiment, and the post-transfer discharged from the image forming unit 2C. The recording medium 9 is conveyed to one of the fixing unit 5A and the fixing unit 5B, and the re-transmission conveyance path is used to retransmit the recording medium 9 discharged from the fixing unit 5A to the image forming unit 2C. Image forming apparatus. In this image forming apparatus, the fixing unit 5A can perform fixing according to either a normal fixing condition or a special fixing condition in accordance with a selection result from the control device 6.

  In addition, the image forming apparatus 1 only needs to be capable of forming a shielding toner image and a non-shielding toner image. Regarding the image forming method of the image forming unit, the configuration and presence / absence of the intermediate transfer method, and the like The present invention is not limited to the configuration exemplified in Embodiment 1 or other embodiments.

  The fixing device 50 constituting the fixing unit 5 whose fixing conditions are selectively changed by the control device 6 is also particularly limited in its form as long as it can switch between normal fixing conditions and special fixing conditions. Not.

  Further, the recording medium 9 is not limited to the cut paper exemplified in the first embodiment, and other continuous paper (including film-type ones) conveyed in, for example, a winding form may be applied. Good. When this continuous sheet is applied, the image forming apparatus can be employed in, for example, the image forming apparatus 1A according to the first embodiment.

1A, 2B ... Image forming apparatuses 2A, 2B, 2C ... Image forming sections 5A, 5B, 5C ... Fixing section 6 ... Control device (control means)
9 ... Recording medium 9B ... Non-white or colored or transparent recording medium Ta ... Shielding toner image Tb ... Non-shielding toner image

Claims (4)

An image forming unit that forms and transfers at least one of a shielding toner image and a non-shielding toner image to a recording medium;
A fixing unit for fixing at least one of the shielding toner image and the non-shielding toner image transferred to the recording medium in the image forming unit to the recording medium;
In the case where the shielding toner image is formed in the image forming unit and transferred to a colored or transparent recording medium other than white, the fixing condition set by three elements of fixing temperature, fixing pressure and fixing time in the fixing unit is set. Control for controlling the fixing condition of the shielding toner image to a condition in which at least one of the three elements in the fixing condition of the non-shielding toner image is reduced or a condition in which the fixing pressure is made zero. And an image forming apparatus.   The control means uses the recording toner in the case where a recording medium having a Oken type smoothness in the range of 1000 s or less or a recording medium having a surface roughness greater than the average particle diameter of the toner is used as the recording medium. 2. The image forming apparatus according to claim 1, wherein an image fixing condition is controlled so that at least one of the three elements is reduced or the fixing pressure is made zero.   The fixing condition of the shielding toner image controlled by the control means is that the shielding toner image after fixing has a surface roughness of the recording medium in a state where the particle shape of the shielding toner particles constituting the toner image can be identified. The image forming apparatus according to claim 1, wherein the conditions are set so as to be present also on the convex portion. The shielding toner image is fixed on the recording medium according to the fixing condition of the shielding toner image controlled by the control unit in the fixing unit after the shielding toner image is formed and transferred to the recording medium in the image forming unit. A first action to be performed;
After the first operation, a non-shielding toner image is formed in the image forming unit, transferred to the recording medium on which the shielding toner image is fixed, and then the fixing condition of the non-shielding toner image in the fixing unit. 4. The image forming apparatus according to claim 1, wherein a second operation of fixing the non-shielding toner image to the recording medium is performed.

Images