JP4396456B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having two or more of these functions, and more particularly to an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus, generally, an electrostatic latent image is formed on an image forming body such as a photoreceptor, and the formed electrostatic latent image is developed to form a toner image. The formed toner image Is transferred onto a recording material such as recording paper, and the transferred toner image is fixed to form an image on the recording material.

  In the color image forming apparatus, the toner image formed on the image forming body is transferred to the intermediate transfer body, the toner image is transferred from the intermediate transfer body to the recording material, and the toner image transferred to the recording material is fixed. Therefore, an image forming process for forming an image on a recording material is often used.

  In the electrophotographic image forming process, various recording materials are used. That is, in addition to plain paper, thin paper, thick paper, glossy paper provided with a gloss layer on the surface on which an image is formed, OHT, and the like are used as the recording material.

  Since these recording materials are not the same in characteristics that affect image formation by electrophotography, such as transportability, resistance value, heat capacity, etc., conditions corresponding to the recording materials are set in development, transfer and fixing. Need to do.

  For example, Patent Document 1 proposes switching print sequence conditions based on designation information for designating the type of recording material.

The printing sequence conditions, the developing sleeve peripheral speed, a developing bias, a primary transfer bias, secondary transfer bias, secondary transfer speed and the fixing speed is ani Gerare.

  In Patent Document 1, image scattering, fogging, voids, and the like caused by differences in recording materials are prevented.

  Recently, the use as an output means of a digital camera has increased, and glossy paper is often used as a recording material. However, as a problem when using glossy paper, the problem of fog is particularly large. Countermeasures are needed. This is due to the following phenomenon.

In glossy paper, the molten toner does not penetrate into the recording material in the fixing step or the degree of penetration is low, and the molten toner spreads laterally along the surface of the recording material and is fixed. Therefore, phenomenon that will leave also fixed as a dot having a large area with toner of a small volume to form a fog occurs.

Such phenomena, for example good urchin fog measured on the photosensitive member, even at low levels as a fog unfixed toner image, the higher the image after fixation, may exceed acceptable levels .

  The above-described fogging problem that occurs when glossy paper is used is particularly noticeable when a high-quality image is formed using a small particle size toner.

  In Patent Document 1, anti-fogging control corresponding to the difference in characteristics of the recording material is performed. However, even if the level of fog does not pose a problem when the toner image is measured in the unfixed stage as described above. Since no countermeasure has been taken against the fog phenomenon that becomes noticeable by the fixing process, the fog prevention is insufficient when glossy paper is used.

  The present invention solves the problem that the countermeasures against the difference in recording materials in the prior art are not sufficient, and in particular, image formation capable of forming a high-quality image on glossy paper, which is sufficient to prevent fogging on glossy paper. An object is to provide an apparatus.

The object of the present invention is achieved by any of the following inventions.
1. Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoconductor is developed using a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoconductor under a developing bias having a DC component Vdc. Developing means for forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
A light emitting element that emits a light beam toward the recording material, a light receiving element that receives reflected light from the recording material, a surface property detecting means for detecting the surface property of the recording material, and a control means,
The control means discriminates whether or not the recording material is glossy paper on the basis of the output of the surface property detection means, and when the discrimination result is glossy paper, by controlling the charging potential Vh, the fog margin Vh− An image forming apparatus characterized in that Vdc is increased as compared with the case of plain paper .
2. Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoconductor is developed using a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoconductor under a developing bias having a DC component Vdc. Developing means for forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
Having designation means and control means for designating glossy paper,
When the glossy paper is designated by the designation means, the control means controls the charging potential Vh to increase the fog margin Vh-Vdc as compared with the case of plain paper. .
3. Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoreceptor is charged with a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoreceptor under a developing bias having a direct current component and an alternating current component. Developing means for developing and forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
A light emitting element that emits a light beam toward the recording material, a light receiving element that receives reflected light from the recording material, a surface property detecting means for detecting the surface property of the recording material, and a control means,
The control means discriminates whether or not the recording material is glossy paper based on the output of the surface property detection means, and when the discrimination result is glossy paper, the frequency of the AC component is higher than that of plain paper. An image forming apparatus.
4). Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoreceptor is charged with a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoreceptor under a developing bias having a direct current component and an alternating current component. Developing means for developing and forming a toner image on the photoreceptor;
Means for transferring the toner image on the photosensitive member to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
Having designation means and control means for designating glossy paper,
The control means increases the frequency of the AC component when the glossy paper is designated by the designation means as compared with the case of plain paper .

  According to the invention of any one of claims 1 to 3, since an appropriate fog level is set for recording materials having various surface properties, high-quality images that are not affected by the type of recording material used are stabilized. Formed.

  According to the third aspect of the present invention, even when an image is formed on glossy paper, image forming conditions are set in consideration of fog appearing on the image after the fixing process. A high quality image is formed.

  According to the invention of any one of claims 4 to 6, since the operator designates the type of the recording material, the image forming condition corresponding to the designation is set, so that an image with high image quality in the fog is formed.

  According to the sixth aspect of the invention, even when an image is formed on glossy paper, image forming conditions are set in consideration of fog appearing in the image after the fixing process. A high-quality image without fogging is formed by designation.

<Image forming apparatus>
FIG. 1 is a diagram showing a color image forming apparatus according to an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer unit, a sheet feeding / conveying device, and a fixing unit 24. A document image reading device SC is disposed above the color image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer unit 5Y, and a cleaning unit 6Y disposed around the photoreceptor 1Y. The image forming unit 10M that forms a magenta image includes a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer unit 5M, and a cleaning unit 6M arranged around the photoreceptor 1M. The image forming unit 10C that forms a cyan image includes a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer unit 5C, and a cleaning unit 6C disposed around the photoreceptor 1C. The image forming unit 10K that forms a black image includes a charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer unit 5K, and a cleaning unit 6K disposed around the photoreceptor 1K.

  The belt-like intermediate transfer member 7 is semiconductive and is wound around a plurality of rollers and supported so as to be able to circulate.

  By the image forming means comprising the charging means 2Y, the exposure means 3Y and the developing means 4Y, charging, exposure and development are performed on the photoreceptor 1Y, and a yellow toner image is formed on the photoreceptor. Similarly, a magenta toner image is formed on the photosensitive member 1M by the image forming unit including the charging unit 2M, the exposing unit 3M, and the developing unit 4M, and the image forming unit including the charging unit 2C, the exposing unit 3C, and the developing unit 4C. A cyan toner image is formed on the photoconductor 1C, and a black toner image is formed on the photoconductor 1K by the image forming unit including the charging unit 2K, the exposure unit 3K, and the developing unit 4K. These single color toner images are transferred to the intermediate transfer body 7 by the primary transfer means 5Y, 5M, 5C, and 5K, and are superimposed to form a multicolor toner image.

  The recording material P stored in the recording material storage unit 20 such as a paper feed cassette or a paper feed tray is fed by a paper feeding device 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D and a registration roller 23. The multi-color toner on the recording material P is collectively transferred by the secondary transfer unit 5A. The recording material P onto which the multicolor toner image has been transferred is fixed by the fixing unit 24, conveyed to a paper discharge roller 25, and discharged onto a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording material P by the secondary transfer unit 5A, the intermediate transfer member 7 passes through the cleaning unit 6A, and the residual toner is removed from the intermediate transfer member 7.

  As the photoconductors 1Y, 1M, 1C, and 1K, known ones such as an OPC photoconductor and an aSi photoconductor are used, but an OPC photoconductor is preferable, and a negatively chargeable OPC photoconductor is particularly preferable. In this case, a negatively chargeable OPC photoreceptor is used.

  As the charging means 2Y, 2M, 2C, and 2K, a corona discharge device such as a scorotron or a corotron is used, and a scorotron discharge device is preferably used.

  As the exposure units 3Y, 3M, 3C, and 3K, light emitting elements that emit light according to image data, such as lasers and LED arrays, are used.

  As the developing means 4Y, 4M, 4C, 4K, there are a developing means using a two-component developer mainly composed of a carrier and a toner, or a developing means using a one-component developer mainly composed of a toner without including a carrier. Although used, a two-component developing means using a small particle size toner is preferable. In addition, a developing device that performs development by regular development or a reversal development method can be used as the developing means. However, a developing bias having the same polarity as the charging of the photosensitive member is applied to the developing sleeve 41 (shown in FIG. Reversal development in which development is performed with toner charged to the same polarity as the charge of the body is preferable. In this embodiment, development is performed by reversal development using negatively charged toner.

  The toner having a volume average particle size of 4 to 8 μm is preferable as the small particle size toner.

  The volume average particle diameter is an average particle diameter based on volume, and is a value measured by “Coulter Counter TA-II” or “Coulter Multisizer” (both manufactured by Coulter, Inc.) equipped with a wet disperser.

  A high-quality image having a high resolving power can be formed by such a small particle size toner. A toner having a volume average particle diameter of more than 8 μm weakens the characteristics of high image quality.

  When a toner having a volume average particle size smaller than 4 μm is used, the image quality is likely to deteriorate due to fogging.

  In the present invention, spherical toner is desirable, and the degree of spheroidization is desirably 0.94 or more and 0.98 or less.

Degree of spheroidization = (perimeter of a circle with the same area as the particle projection image) / (perimeter of the particle projection image)
The degree of spheroidization was obtained by taking a picture of resin particles enlarged 500 times with a scanning electron microscope or a laser microscope for 500 resin particles, and using an image analyzer “SCANNING IMAGE ANALYSER” (manufactured by JEOL Ltd.) Then, the photographic image is analyzed, the circularity is measured, and the arithmetic average value can be obtained. Moreover, as a simple measuring method, it can measure with "FPIA-1000" (made by Toa Medical Electronics Co., Ltd.).

  When the degree of spheroidization is less than 0.94, it is crushed as a result of being subjected to strong stress in the developing means, and fog and toner scattering are likely to occur. If the sphericity is greater than 0.98, it may be difficult to maintain high cleaning performance.

  For the toner having a small particle diameter and a high sphericity as described above, it is desirable to use a polymerized toner.

  The polymerized toner means a toner obtained by forming a binder resin for toner and forming the toner shape by polymerization of a raw material monomer or prepolymer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a step of fusing particles between them. In a polymerized toner, a raw material monomer or prepolymer is uniformly dispersed in an aqueous system and then polymerized to produce a toner, so that a toner having a uniform toner particle size distribution and shape can be obtained.

  Specifically, a polymer is produced by emulsion polymerization of a monomer in a liquid of an aqueous medium to which an emulsion is added or a suspension polymerization method, and then an organic solvent, agglomeration is produced. It can manufacture by the method of adding an agent etc. and making it associate. A method of preparing by mixing with a dispersion liquid of a release agent or a colorant necessary for the constitution of the toner at the time of association, or a toner component such as a release agent or a colorant dispersed in a monomer Examples thereof include emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  Semi-conductive rubber rollers are used for the primary transfer means 5Y, 5M, 5C, 5K and the secondary transfer means 5A, and a transfer voltage is applied to the primary transfer means 5 by a power source.

  Cleaning means 6A, 6Y, 6M, 6C and 6K perform cleaning with a cleaning blade made of a rubber blade.

  Above the recording material storage unit 20, a surface property detection means 30 for detecting the surface property of the recording material is provided. As shown in FIG. 2, the surface property detection means 30 includes a light emitting element 30A such as an LED and a light receiving element 30B such as a phototransistor. The light emitting element 30A is a light source that emits a light beam in a certain direction, and the light receiving element 30B is a directional light receiving element that receives light incident from a certain direction.

  When the recording material P specularly reflects light like glossy paper, the light receiving intensity of the light receiving element 30B is strong, and when the recording material P reflects diffused light like plain paper, the light receiving intensity of the light receiving element 30B is low. .

FIG. 3 shows a change in the output of the surface property detecting means 30 due to the difference in surface property of the recording material P. As shown in the figure, the output is rough paper <plain paper <glossy paper, and a threshold level Lr, which is a level between the plain paper and the glossy paper, is provided, and control described later is performed.
<Embodiment 1>
FIG. 4 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention.

  In the first embodiment shown in FIG. 4A, the control means CR reads the output of the surface property detection means 30, and controls the charging means 2 based on the read output. Control is performed as shown in FIG. That is, the photosensitive members 1Y, 1M, 1C, and 1C are charged from the charged potential Vh0 of the photosensitive members 1Y, 1M, 1C, and 1K in the case of plain paper, which is a normal recording material P, to the potential Vh1 that is higher than Vh0 in the case of glossy paper. Charge 1K. As a result, the normal fog margin ΔV0 (Vh0−Vdc) is raised to a high fog margin ΔV1 (Vh1−Vdc), and image formation is performed under an image forming condition in which the gloss level is lower than normal. .

As an actual control mode, the output of the surface property detection means 30 is discriminated by a predetermined threshold Lr shown in FIG. Then, control for selecting and setting the fog margins ΔV0 and ΔV1 is performed.
<Embodiment 2>
As shown in FIG. 4B, the developing sleeve 41 of the developing units 4Y, 4M, 4C, and 4K is applied with a developing bias in which the DC voltage Vdc from the DC power supply Edc is superimposed on the AC Vac from the AC power supply Eac. .

  The control means CR reads the output of the surface property detection means 30 and controls the frequency f of the output of the AC power supply Eac based on the read output. That is, when the recording material P is glossy paper, the control means CR controls the AC power supply Eac so that the frequency f is higher than usual.

As a result, the fog level is low when glossy paper is used, and fogging that tends to occur when glossy paper is used is well prevented.
<Embodiment 3>
FIG.4 (c) is a block diagram of the control system of Embodiment 3 of this invention.

  The present embodiment has an operation unit OP as a designation means that can be set as a type of recording material having a different surface state, for example, plain paper or glossy paper.

  The control means CR controls at least one of the AC power supply Eac and the power supply 20E based on the designation information set by the operator in the operation unit OP.

  Whether the recording material P to be used is plain paper or glossy paper is set by the operator using the operation unit OP, and the control means CR is fogged if it is glossy paper as described above based on the designation information by the setting. The output of the power source 20E is set high so that the level of The fog level may be lowered by controlling the AC power supply Eac and setting the frequency f high.

<Example 1>
Using a negatively charged toner having a volume average particle diameter of 6 μm and a developing bias of DC component Vdc = −400 V, AC component Vac (peak-peak voltage) = 1.0 kV, frequency 5 kHz, the fog margin ΔV shown in Table 1 = Vh-Vdc was set to form an image.

  As a result, high-quality images without fogging were obtained on both plain paper and glossy paper.

<Example 2>
A negatively charged toner having a volume average particle diameter of 6 μm is used. The charging potential Vh of the photoreceptor is −500 V, and the developing bias is DC component Vdc = −400 V and AC component Vac (peak-peak voltage) = 1.0 kV. An image was formed by setting the frequency f (kV) shown in Table 2.

  As a result, high-quality images without fogging were obtained on both plain paper and glossy paper.

<Example 3>
Using a negatively charged toner having a volume average particle diameter of 5 μm, the fog margin shown in Table 1 under the conditions of DC component Vdc = −400 V, AC component Vac (peak-peak voltage) = 1.0 kV, and frequency 5 kHz as a developing bias An image was formed by setting.

  As a comparative example, when the fog margin is glossy paper, an image is formed with the same value 100 V as that of plain paper.

  As a result, as shown in Table 3, in the comparative example, fog was generated in the case of glossy paper, and the fine line was formed thick, and the reproducibility of the fine line was not good.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the structure of a surface property detection means. It is a figure which shows the output of the surface property detection means with respect to various recording materials. 2 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. It is a figure which shows control of fog margin Vh-Vdc.

Explanation of symbols

1Y, 1M, 1C, 1K photoconductor 2Y, 2M, 2C, 2K charging means 3Y, 3M, 3C, 3K image exposure means 4Y, 4M, 4C, 4K developing means 5Y, 5M, 5C, 5K primary transfer means 5A secondary Transfer means CR control means 30 Surface property detection means

Claims (4)

Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoconductor is developed using a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoconductor under a developing bias having a DC component Vdc. Developing means for forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
A light emitting element that emits a light beam toward the recording material, a light receiving element that receives reflected light from the recording material, a surface property detecting means for detecting the surface property of the recording material, and a control means,
The control means discriminates whether or not the recording material is glossy paper on the basis of the output of the surface property detection means, and when the discrimination result is glossy paper, by controlling the charging potential Vh, the fog margin Vh− An image forming apparatus characterized in that Vdc is increased as compared with the case of plain paper . Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoconductor is developed using a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoconductor under a developing bias having a DC component Vdc. Developing means for forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
Having designation means and control means for designating glossy paper,
When the glossy paper is designated by the designation means, the control means controls the charging potential Vh to increase the fog margin Vh-Vdc as compared with the case of plain paper. . Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoreceptor is charged with a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoreceptor under a developing bias having a direct current component and an alternating current component. Developing means for developing and forming a toner image on the photoreceptor;
Transfer means for transferring a toner image on the photoreceptor to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
A light emitting element that emits a light beam toward the recording material, a light receiving element that receives reflected light from the recording material, a surface property detecting means for detecting the surface property of the recording material, and a control means,
The control means discriminates whether or not the recording material is glossy paper based on the output of the surface property detection means, and when the discrimination result is glossy paper, the frequency of the AC component is higher than that of plain paper. An image forming apparatus. Photoconductor,
Charging means for charging the photosensitive member to a charging potential Vh;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image on the photoreceptor;
The electrostatic latent image on the photoreceptor is charged with a toner having a volume average particle diameter of 4 μm to 8 μm charged to the same polarity as the charge polarity of the photoreceptor under a developing bias having a direct current component and an alternating current component. Developing means for developing and forming a toner image on the photoreceptor;
Means for transferring the toner image on the photosensitive member to a recording material; and
In an image forming apparatus having fixing means for fixing a toner image on a recording material,
Having designation means and control means for designating glossy paper,
The control means increases the frequency of the AC component when the glossy paper is designated by the designation means as compared with the case of plain paper .

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