JP2015166792A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem of an image forming apparatus having a pressure fixing apparatus: an unfixed toner image can be fixed on only limited media.SOLUTION: Transparent or white toner is melted on a recording sheet before forming a color toner image, to reinforce paper fiber. The color toner can be sufficiently crushed by pressure fixing means, thereby obtaining a sufficiently fixed image.

Description

  The present invention provides an image forming apparatus including a pressure fixing device that fixes a non-fixed toner image by inserting a recording medium paper on which the non-fixed toner image is formed between a pair of rollers that are pressed to contact each other. Relates to the device.

  In general, a pressure heating fixing method is widely used in image forming apparatuses such as printers and copiers using an electrophotographic process. However, in the case of the above-described thermal pressure fixing device, there is a problem that electric power for heating the fixing roller to a predetermined temperature is required and it is difficult to save energy.

  Accordingly, a fixing device using a pressure fixing method that is superior in terms of energy saving and instant start has been devised (see Patent Document 1), and is in practical use particularly in a small-sized image forming apparatus.

Japanese Patent Laid-Open No. 5-107985

  However, in the pressure fixing method, when fixing toner on a recording paper having a rough surface such as embossed paper or soft recording paper, the pressure applied between the rollers is absorbed by the recording paper, and the toner is not sufficient. Since no proper pressure was applied, fixing failure occurred.

  In other words, the image forming apparatus provided with the conventional pressure fixing device has a problem that a medium capable of fixing an unfixed toner image is limited.

  An image forming apparatus according to the present invention includes a transparent / white toner arrangement unit for placing a transparent or white toner on a recording paper, a heating unit for heating and fusing the transparent / white toner image and fusing it on the recording paper, and an image on the recording paper. An image forming apparatus comprising: a color toner image forming unit that places a color toner on a forming portion; and a pressure fixing unit that fixes the color toner image on a recording sheet by a pressure member without using heat. The image forming means solves the above problem by forming a color toner image on the portion where the transparent or white toner is fused.

  The image forming apparatus according to the present invention reinforces the paper fiber by melting transparent or white toner into the recording paper, even if it is soft recording paper, so that the color toner can be sufficiently crushed and sufficient fixability can be obtained. Is obtained. Therefore, the media to which the pressure fixing device can be applied can be expanded as compared with the prior art.

1 is a cross-sectional view of an image forming apparatus according to Embodiment 1 of the present invention. It is a flowchart which concerns on control of Example 1 of this invention. It is a block diagram concerning Example 2 of the present invention. It is a flowchart which concerns on control of Example 2 of this invention. It is a table which concerns on control of Example 2 of this invention.

  Hereinafter, the present invention will be described with reference to the drawings.

  The white toner used in the present invention is white toner particles containing a white pigment, an antioxidant and a binder. Instead of the white toner, a colorless transparent toner that does not contain a color pigment and is transparent to visible light may be used.

<Example 1>
FIG. 1 shows an image forming apparatus of this embodiment.

  In this embodiment, paper physical property detection means (not shown) is provided upstream of the transparent / white toner arrangement means. The paper physical property detection means has a light emitting element such as an LED and a light receiving element such as a photodiode. The light emitting element emits light to the measurement site, and the regular reflection light or irregular reflection light is detected from the measurement site by the light receiving device. The surface roughness Rz1 of the recording paper is measured by the output.

  FIG. 2 is a flowchart showing the control of this embodiment.

  When the measured surface roughness Rz1 is equal to or greater than a predetermined value a (for example, 10 μm), the recording paper is determined as embossed paper and the present invention is carried out. On the other hand, if Rz1 is less than the predetermined value a, it is determined that the recording paper is plain paper, and only the color toner image forming unit and the pressure fixing unit are implemented.

  When the recording paper is plain paper, the transparent / white toner arrangement unit A, the heating unit B, and the cooling unit C before the color toner image forming unit D may be omitted. Since plain paper has a sufficiently high degree of smoothness, unfixed color toner can be crushed by the pressure fixing means E to obtain sufficient fixability.

  Thus, by omitting the transparent / white toner arrangement means A, heating means B, and cooling means C according to the recording paper to be used, it is possible to reduce the power required for fixing the coated paper to zero. The energy saving merit of the fixing device can be increased.

  Hereinafter, an embodiment will be described in which paper physical property detection means (not shown) recognizes embossed paper as recording paper.

(A) Transparent / white toner arrangement means 1a is a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a drum) as an image carrier, and is rotated at a predetermined speed in the clockwise direction of an arrow. The peripheral surface of the rotating drum 1a is uniformly charged to a predetermined polarity and potential by the primary charger 2a. The charged surface of the drum 1a is image-exposed by a laser scanner 3a as an image exposure device, and an electrostatic image (electrostatic latent image) of image information is formed. The scanner 3a outputs a laser beam modulated in accordance with the input image information, and scans and exposes the uniformly charged surface of the drum 1a. Thereby, an electrostatic image corresponding to the image information subjected to the scanning exposure is formed on the drum surface. The electrostatic image is developed as an unfixed white toner image by the white developing device 4a.

  The amount of white toner to be developed is a sufficient amount of toner so that Rz1> Rz2 when the surface roughness of the initial embossed paper is Rz1 and the surface roughness of the recording paper P after the process is Rz2. It has been adjusted.

  On the other hand, a paper feeding mechanism (not shown) is driven to feed the recording paper P. The recording paper P is fed by a registration roller pair 7a that is rotationally driven at a predetermined control timing, and is guided by a pre-transfer guide member 8a to be a transfer portion T that is a facing portion between the drum 1a and the transfer charger 5a. To be introduced.

  The recording paper P is brought into close contact with the surface of the drum 1a at the transfer portion T by the back surface of the recording paper P being charged by the transfer charger 5a in the opposite polarity to the charging polarity of the white toner, and the recording paper P The unfixed white toner image on the 1a surface is sequentially electrostatically transferred.

  The recording paper P exiting the transfer portion T is separated from the surface of the drum 1a, guided by the post-transfer guide member 9a, and introduced into the heating means B.

  The transfer residual toner remaining on the drum 1a surface after separation of the recording paper is removed from the drum surface by the drum cleaning device 6a, and the drum 1 is repeatedly used for image formation.

  In this embodiment, a white toner image is formed on the recording paper by the transparent / white toner arrangement means A as described above.

(B) Heating means In this embodiment, the heating means B is an induction heating type non-contact heating device, and is induction-heated suspended between a driving roller 22 and a driven roller 23 arranged in parallel. An endless recording paper conveyance belt 21 is provided. In addition, an induction coil unit 24 is provided on the upper side of the ascending belt portion of the belt 21 so as to be opposed to the belt at a predetermined interval from the belt. The unit 24 is fixedly supported so as not to contact the belt 21 with respect to a fixing unit frame (not shown).

  A temperature sensor (thermistor) TH <b> 1 that detects the temperature of the belt 21 is disposed inside the ascending belt portion of the belt 21 so as to face the unit 24. A control unit (not shown) adjusts the temperature of the belt 21 to a predetermined temperature so that the temperature detection information input from the temperature sensor TH1 is maintained in a predetermined temperature information range. The belt 21 is heated and temperature-controlled during the image forming operation of the image forming apparatus.

  The recording paper P that has passed through the transparent / white toner arrangement means is conveyed by the rotational movement of the belt 21 with the unfixed toner image carrying surface facing upward on the upper surface of the belt 21 of the heating means. The belt 21 is heated to a predetermined temperature by induction heat generation by the magnetic flux generated by the unit 24. In the process of being conveyed by the belt 21, the recording paper P is heated and melted from the back side by the heat of the belt 21, and the white toner image on the front side is fused to the recording paper.

  110 ° C. above the softening point (temperature after heating the toner by the heating means) until the toner of the white toner image on the recording paper P moves at a predetermined speed from the recording paper inlet to the outlet of the heating means. To be fused on the recording paper P.

(C) Cooling means The recording paper P that has passed through the heating means B is guided by the guide member 32 and introduced into the color toner image forming means D. In this embodiment, a Peltier element 31 is provided as a cooler on the back surface of the guide member 32, and serves as a cooling means for cooling the recording paper P that has passed through the heating means.

  The guide member 32 is a hard thin plate having high thermal conductivity such as metal. The Peltier element 31 is disposed such that the heat absorbing portion side is in close contact with or adhered to the back surface of the guide member 32.

  The recording paper P that has passed through the heating means B is transferred onto the guide member 32 of the cooling means C, and is conveyed while the back surface slides on the upper surface of the guide member 32. In the conveying process, the recording paper P is cooled from the back surface by the guide member 32 cooled by the Peltier element 31, and the toner of the white toner image on the recording paper P is cooled and solidified.

  In this embodiment, the glass transition point of the toner is set to 60 ° C., and the cooling temperature of the guide member 32 by the Peltier element 31 is set to 25 ° C. or less. By this setting, the toner of the fused toner image on the recording paper P is cooled to 40 ° C. (temperature after cooling of the toner by the cooling means C) below the glass transition point until the cooling means C moves. The toner surface solidifies.

(D) Color toner image forming means A yellow developing unit Y, a magenta developing unit M, a cyan developing unit C, and a black developing unit respectively storing yellow, cyan, magenta, and black toners mounted on a rotating body of the developing device 4d. The developing unit of the first color in the unit Bk is moved to the developing position facing the photosensitive drum 1d by the rotation of the rotating body, and a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 1d is applied to the color developing unit 4d. When applied, color toner is attached to the electrostatic latent image on the photosensitive drum 1d to develop it as a color toner image. Further, the transfer process is performed in the same manner as before.

(E) Pressure Fixing Unit The pressure fixing unit E is a pressure fixing device having a pressure roller pair of a fixing roller 51 and a pressure roller 52.

  In this embodiment, the fixing roller 51 has a heat-resistant elastic body layer formed on the outer peripheral surface of a metal hollow roller core made of aluminum, stainless steel, iron or the like with a thickness of about 0.1 to 1 mm. A resin layer as a release layer is formed with a thickness of about 1.0 to 40 μm.

  The pressure roller 52 is provided with a relatively thick elastic layer (for example, about 5 to 10 mm) such as silicone rubber, fluorine rubber, or fluorosilicone rubber on the outer peripheral surface of a metal roller core, and further serves as a release layer thereon. A fluororesin layer is provided with a thickness of about 30 to 50 μm.

  The fixing roller 51 and the pressure roller 52 are arranged substantially in parallel in the vertical direction and are brought into pressure contact with each other with a predetermined pressing force, thereby forming a pressure fixing nip portion N having a predetermined width with respect to the recording paper conveyance direction. The fixing roller 51 is driven to rotate in the clockwise direction indicated by an arrow at a predetermined speed. The pressure roller 52 rotates following the rotation of the fixing roller 51.

  In this embodiment, the pressing force of the fixing roller 51 and the pressure roller 52 is set to 3.3 × 10 5 Pa, and the width of the fixing nip portion N is set to 10 mm.

  The recording paper P that has passed through the color toner image forming means D enters a pressure fixing nip portion N that is a pressure contact portion between the fixing roller 51 and the pressure roller 52 of the pressure fixing means E, and is nipped and conveyed by the nip portion N. The In the nipping and conveying process, the color toner image on the recording paper is pressure-fixed on the recording paper surface by the contact pressure of the fixing roller 51.

  As described in this embodiment, by controlling each image forming process so that the unevenness on the surface of the transfer material is made smaller than that before image formation according to the recognized surface roughness of the transfer material with white toner. Further, pressure can be applied to the color toner by the pressure fixing means, and sufficient fixing property can be obtained.

  Further, as described in claim 3, it is preferable that the applied amount of the white toner is smaller than the applied amount of the color toner. By doing so, it is possible to make "the power necessary for improving the smoothness of the recording paper (power consumed by the heating means C)" smaller than "the power for fixing the color toner by the thermal pressure fixing means" The energy saving merit of this embodiment can be made superior to the thermal pressure fixing means.

<Example 2>
In the first embodiment, whether or not to implement the present invention is determined based on the measurement result of the recording paper measuring unit. In the second embodiment, the downstream pressure fixing is performed based on the recording paper information input from the operation unit by the user. The region and amount of white toner are optimally controlled so that the color toner image can be sufficiently fixed by means E.

  Except for the white toner arrangement control, the configuration and control of this embodiment are the same as those of the first embodiment.

  FIG. 3 is a block diagram relating to the second embodiment. FIG. 4 shows a flowchart relating to the control of the second embodiment. FIG. 5 is a table relating to the control of the second embodiment.

  First, from the image data converted by the image processing unit, the white toner placement control unit determines the placement position of the white toner so that the white toner is placed under the color toner image formation position on the recording paper.

  Further, the “reinforcing area” and “applied amount” of the white toner are calculated by the area calculating unit and the applied amount calculating unit from the recording paper information input by the user from the operation unit.

  The calculation result of “applied amount” is input as the exposure condition Vcont of the transparent / white toner arrangement unit A. For example, as shown in FIG. 5, in the case of smooth recording paper with Rz ≦ 1.0 μm, Vcont = 200 V, whereas for the recording paper with low smoothness of Rz ≧ 10 μm, Vcont = 300 V is controlled.

  The calculation result of the “reinforcement region” is input as “the number of pixels around the edge of the color toner image as the reinforcement region to which the white toner is applied” as the exposure condition of the transparent / white toner arrangement unit A. For example, as shown in FIG. 5, in the case of a smooth recording paper with Rz ≦ 1.0 μm, the reinforced area is controlled to the surrounding 5 pixels, whereas in the case of a recording paper with low smoothness of Rz ≧ 10 μm, the reinforcement is made. The area is controlled to 15 pixels around.

  Thus, in this embodiment, the transparent or white toner is not placed on the entire surface of the recording paper, but the amount of the transparent or white toner applied is minimized according to the recording paper. Accordingly, the recording paper can be reinforced by fusing the transparent or white toner with a minimum amount of power. Therefore, the power required for the heating means B can be minimized, and the loss of the energy saving merit of the pressure fixing device can be minimized.

A Transparent / white toner arrangement means B Heating means C Cooling means D Color toner image forming means E Pressure fixing means 1a, 1d Image carrier (electrophotographic photosensitive drum)
2a, 2d Primary charger 3a, 3d Laser scanner 4a White developer 4d Color developer 5a, 5d Transfer charger 6a, 6d Cleaning device 7a Registration roller pair 8a, 9a Guide member 21 Recording material conveyance belt 22 Drive roller 23 Driven roller 24 Induction heating unit 31 Peltier element 32 Guide member 51 Fixing roller 52 Pressure roller

Claims (6)

Transparent / white toner arrangement means for placing transparent or white toner on the recording paper;
Heating means for heating and melting the transparent white toner image and fusing it on the recording paper;
Color toner image forming means for placing color toner on the image forming portion on the recording paper;
In an image forming apparatus having pressure fixing means for fixing the color toner image on a recording paper with a pressure member only by pressure action without using heat,
The color toner image forming means forms a color toner image on a portion where transparent or white toner is fused. 2. The image forming apparatus according to claim 1, further comprising a cooling unit between the heating unit and the color toner image forming unit to cool the fused transparent and white toner image into a solidified state. The image forming apparatus according to claim 1, wherein a loading amount of the transparent or white toner is smaller than a loading amount of the color toner. The user has an input means that allows the user to select the type of recording paper, a paper physical property detection means for detecting the physical property value of the recording paper, and a loading amount control means for changing the loading amount of the transparent or white toner placed on the recording paper. 4. The amount of the transparent or white toner to be placed on the recording paper is changed based on the input result of the type of the selected recording paper or the detection result of the paper physical property detection means. The image forming apparatus according to any one of the above. The user has an input means that allows the user to select the type of recording paper, a paper physical property detection means for detecting the physical property value of the recording paper, and an area control means for changing the area on the recording paper of transparent or white toner to be placed on the recording paper. The region on the recording paper of transparent or white toner to be placed on the recording paper is changed based on the input result of the type of the recording paper selected by the above or the detection result of the paper physical property detection means. Item 4. The image forming apparatus according to any one of Items 3 to 3. 2. The image forming apparatus according to claim 1, wherein only the color toner image forming unit and the pressurizing unit are operated according to the type of recording paper.