JP2002116597A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device preventing an image defect caused by a releasing agent from appearing without complicating the device. SOLUTION: This image forming device is provided with plural toner image forming means for forming a toner image with different color toner on an image carrier, an intermediate transfer body, a transfer means for primarily transferring the toner image from the image carrier in the toner image forming means to the intermediate transfer body, a heating means for heating and melting the toner image on the intermediate transfer body at a specified position, and a transfer and fixing means for secondarily transferring and fixing the toner image on the intermediate transfer body on a recording medium simultaneously by heating and pressuring the toner image while holding it between the intermediate transfer body and the recording medium at the specified position, and forms a color image by using the releasing agent. The toner image forming means using the toner of the color whose lightness difference from the recording medium is the smallest is arranged on the most upstream side out of the plural toner image forming means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used as an electrophotographic copying machine, a printer, a facsimile, and the like. The present invention relates to an image forming apparatus that transfers a toner image on a transfer body to a recording medium and simultaneously fixes the toner image to form an image.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus such as an electrophotographic copying machine or a printer, an electrostatic latent image is formed on a photosensitive drum, and the electrostatic latent image is developed with dry toner to form a toner image. Then, a toner image developed on the photosensitive drum is electrostatically transferred to a recording medium and fixed to form an image, so that an image is widely used. In such an image forming apparatus, there is a problem that density unevenness occurs in an image or powder toner is scattered in a transfer portion, resulting in inferior resolution and dot reproducibility.

[0003] This is largely due to the transfer process of electrostatically transferring the toner image on the photosensitive drum to the recording medium. That is, the transfer method using the electrostatic transfer method cannot transfer the toner image formed on the photosensitive drum uniformly and efficiently. The transfer efficiency of the toner image depends on the electric field applied to the toner layer (hereinafter referred to as “E
t ". ), But when the electric field reaches a certain magnitude, a so-called Paschen discharge occurs, and Et
And the transfer efficiency starts to decrease. That is, the transfer efficiency has a peak at a certain value of Et. It is said that the peak value of the transfer efficiency is not 100% but a maximum of about 95% (Electrostatic transfer of toner image, Journal of the Society of Electrophotography, 19th.
No. 1, Vol. 25-32, (1981)).

Since the transfer efficiency of the toner layer depends on Et, unless the Et is kept constant regardless of the thickness of the toner layer, unevenness of a recording medium represented by paper, and unevenness of electrical properties, the transfer efficiency becomes large. Or at each transfer position on the recording medium. When the toner image formed on the photosensitive drum is monochromatic and has a small layer thickness, image unevenness mainly occurs due to unevenness of the recording medium and unevenness of electrical properties. This is the same when a single-color toner image formed independently on the photosensitive drum is transferred onto the recording medium in a superimposed state, and image unevenness occurs due to unevenness of the recording medium and unevenness in electrical properties. In other words, the difference between the portion to be overlap-transferred and the portion to transfer a single color without overlap transfer can be electrostatically suppressed, but it is difficult to compensate for unevenness of the recording medium and unevenness in electrical properties.

On the other hand, in the so-called intermediate transfer, in which a single-color toner image independently formed on a photoreceptor drum is transferred onto an intermediate transfer medium whose physical properties are controlled without any unevenness, so-called intermediate transfer is performed. Can obtain a uniform image without unevenness of the surface or unevenness of electric properties. Even if the toner image on the intermediate transfer member is multicolored, three or more layers of each single color overlap in many places, and 1
Layer or less. Even if the toner layers are electrostatically and uniformly transferred to a recording medium represented by paper, it is difficult to apply a constant electric field over the entire area of the toner image. Becomes non-uniform for each part.

Therefore, in the electrostatic transfer system, all of the color images superimposed on the intermediate transfer member are not transferred to the recording medium, but partially remain on the intermediate transfer member. In addition, due to the unevenness of the surface of the paper as the recording medium, the paper and the intermediate transfer body do not completely adhere to each other, resulting in a non-uniform gap, disturbing the electrostatic electric field, and the Coulomb repulsion between the powder toners. And the toner is scattered, thereby deteriorating the quality of the image.

To solve this problem, Japanese Patent Publication No. 46-4167
No. 9 discloses a method of adhesively transferring a toner image formed on a photoreceptor drum to an intermediate medium, and then transferring the toner from the intermediate medium to a recording medium by fusion heat. In this method, since the transfer of the toner image to the recording medium is performed in a non-electrostatic manner, the deterioration of the image quality in the transfer step as described above is less likely to occur.

For example, Japanese Patent Application Laid-Open No. Hei 2-108072 discloses that toner images of different colors are electrostatically superimposedly transferred on an intermediate transfer member, and a multicolor multi-toner image is fused on the intermediate transfer member. Then, a technique is disclosed in which the fused multiple toner image is transferred to a recording medium and a fixed color image is obtained. According to this method as well, the toner image is transferred to the recording medium in a non-electrostatic manner, so that the image quality hardly deteriorates as described above. This method is referred to as a simultaneous transfer and fixing method.

An image forming apparatus using this simultaneous transfer and fixing system is disclosed in US Pat.
-19642, JP-A-5-107950,
JP-A-5-249798, JP-A-10-6302
Japanese Patent Application Laid-Open No. 8 (1996) -1995 discloses that the intermediate transfer body and the recording medium are heated and pressurized in close contact with each other so that the toner image is completely transferred from the intermediate transfer body to the recording medium. There is disclosed a technique in which the recording medium is cooled until the adhesive strength with the intermediate transfer member becomes larger, and after the cooling, the recording medium is separated from the intermediate transfer member.

According to the image forming apparatus using the simultaneous transfer and fixing method, the transfer efficiency of the toner image is high, the color balance is good, and the image gloss and the color reproducibility are excellent regardless of the image density and the image area ratio. It is possible to obtain an image having no unevenness in color, excellent in graininess, and excellent in uniformity of image gloss and transparency of toner.

[0011] The intermediate transfer member is unlikely to be affected by the environment (temperature and humidity), unlike paper, which is a general recording medium.
Since the physical properties such as surface properties and resistance are stable, electrostatic transfer from the photosensitive drum to the intermediate transfer body can be performed closely.
If proper physical property values are given, there is a feature that toner images are hardly disturbed or uneven due to disturbance of the electrostatic transfer electric field. As an example of the intermediate transfer member, a two-layer structure including a base layer and a surface layer is formed, and the base layer has a volume for transferring the toner image from the photosensitive drum to the intermediate transfer member electrostatically without image disturbance. The surface layer is made of a material whose resistivity can be adjusted.The surface layer has elasticity so that the toner image is sandwiched between the intermediate transfer body and the recording medium, and the adhesion between the intermediate transfer body and the recording medium is improved during simultaneous transfer and fixing from the intermediate transfer body to the recording medium. The material used is used. For example, when a polyimide film to which carbon black is added is used as the material of the base layer, the volume resistivity can be adjusted by changing the amount of carbon black added. Examples of the surface layer material include silicone rubber.
Silicone rubber has elasticity, and its surface shows adhesiveness to toner at room temperature.In addition, in order to transfer the toner to the recording medium efficiently, it has the property of easily releasing the melted and fluidized toner. Therefore, it is most suitable for the surface layer of the intermediate transfer member.

In the transfer / fixing section, the intermediate transfer member, which is an image holding member, the toner image and the recording medium are integrally brought into close contact with each other and heated, so that the powder toner is brought into a molten state and the individual toners are fused. It is desirable to form one smooth film. At this time, the intermediate transfer body and the recording medium need to be in close contact with each other for the purpose of efficiently transferring heat to the toner image and sinking the molten toner into the recording medium to form an image without irregularities. If air enters in some places, the heat capacity changes in places where air is present and where it does not exist, the toner image is not melted uniformly, and uneven transfer / fixing results in minute uneven gloss. As the heat and pressure roll, a metal roll or a roll having a heat-resistant elastic layer such as silicone rubber on a metal roll can be used. A heat source is disposed inside the heating roll, and the heating temperature is set and controlled so as to be higher than the toner softening point upstream of the intermediate transfer member transferring and fixing the toner on the recording medium. In the heating area, the nip pressure is set so that the photosensitive drum and the toner image and the recording medium are sufficiently adhered to each other in the heating area so that partial lifting does not occur, and wrinkling and displacement do not occur in the recording medium.

The recording medium onto which the toner has been transferred is conveyed in a state in which the recording medium is in close contact with the intermediate transfer member, and is separated at a separation position. When peeling, the surface temperature of the recording medium that is in contact with the intermediate transfer body is lower than the toner softening point so that the toner is sufficiently coagulated and solidified and can be fixed to the recording medium surface with strong adhesive force. Desirably, it is separated from the transfer member. A cooling means for lowering the surface temperature of the recording medium is not always necessary, and a suitable peeling state can be obtained by, for example, increasing the distance from the transfer / fixing position to the peeling position or lowering the ambient temperature. However, by providing the cooling means downstream of the transfer / fixing position and upstream of the peeling position, an image having a suitable surface state can be formed more efficiently. For peeling off the recording medium, for example, there is a method in which the recording medium is separated from the intermediate transfer body together with the toner by the strength of the recording medium itself using a roll having a small curvature.
As a result, regardless of the image density and the image area ratio, it is possible to obtain an image having excellent image gloss and color reproducibility, no occurrence of color unevenness, excellent graininess, and excellent image gloss uniformity. Becomes

[0014]

However, the prior art described above has the following problems. That is, JP-A-2-108072, US Pat.
990278, JP-A-5-19642, JP-A-5-107950, JP-A-5-249798
As disclosed in Japanese Patent Application Laid-Open No. H10-63028 and the like, in an image forming apparatus using the simultaneous transfer and fixing method, as the number of prints increases from tens to hundreds of thousands, However, due to stresses such as discharge and heating, the adhesive force with the toner increases, and fine toner that cannot be transferred to the recording medium gradually remains on the intermediate transfer body, and the surface roughness of the intermediate transfer body deteriorates. I know it will come. For this reason, it is difficult to form a smooth toner image by transfer and fixing, and as a result, there arises a problem that the gloss of the image deteriorates.

In order to suppress the deterioration of gloss, it is necessary to suppress the increase in the adhesive force between the intermediate transfer member and the toner due to discharge or heating. As a countermeasure, a release agent represented by wax is arranged between the intermediate transfer body and the toner, for example,
Experiments have shown that it is effective to use a release agent-containing toner or to apply a release agent to the surface of the intermediate transfer member, and it is possible to reduce deterioration in gloss. On the other hand, regarding the use of the release agent, the release agent is offset on the intermediate transfer body after the recording medium is peeled off, and when the intermediate transfer body is cooled, the release agent solidifies, and the release agent remains on the intermediate transfer body. However, there is a problem that it remains as floating release agent particles. If the release agent remains on the intermediate transfer body, the release agent is gradually re-transferred from the intermediate transfer body to the photosensitive drum, causing filming, fogging the white background, and lowering or lowering the density of the image area. This causes an image defect in which density unevenness is caused.

For such an image forming apparatus using a release agent, several methods have been proposed for removing the release agent once applied to the intermediate transfer member.

For example, Japanese Patent Application Laid-Open No. 5-107950 discloses a method of applying a silicone oil as a release agent to an intermediate transfer member to prevent offset, and removing the release agent adhering to the intermediate transfer member by a web to prevent offset. A way to do that has been proposed. In this method, a web is sandwiched between a contact portion between a pressure roller for removal and an intermediate transfer member, and a release agent is transferred to the web. If the release agent is continuously taken on the same surface of the web, the removal ability is reduced due to clogging or the like. Therefore, it is necessary to pull the web from the web roll by the take-up roll and switch to a new surface at a certain frequency. Therefore, there is a problem that the release agent cannot be completely removed and the apparatus becomes complicated. Further, in the above-described means, the release agent is also removed while uniformly abrading the surface of the intermediate transfer member, and as a result, the life of the intermediate transfer member is shortened. In addition, roll,
When an attempt is made to remove the release agent by itself such as a web, it is difficult to remove the release agent only because it is stretched while being attached.

On the other hand, with respect to the transfer of the release agent to the intermediate transfer member and the photosensitive drum, in a double-sided printing apparatus having a fixing device using a release agent to prevent toner offset to the fixing device, a fixing roll or paper is used. There is a problem that the release agent migrates to the intermediate transfer member or the photosensitive drum from the image, causing white spots or the like of the image. Similarly, a method of removing the release agent attached to the intermediate transfer member or the photosensitive drum has been proposed. I have.

For example, the means disclosed in Japanese Patent Application Laid-Open No. 7-261566 removes impurities such as a release agent on the surface of the intermediate transfer member by contacting a member using a material that decomposes impurities. is there. However, with this means, it is difficult to develop a material that does not affect other functional components and decomposes and removes only a specific release agent, for example, when there is a coat layer on the surface of the intermediate transfer body. There is a problem that is.

The means disclosed in Japanese Patent Application Laid-Open No. 5-1077993 is to provide a rubbing member downstream of the cleaning device for the image carrier to remove the release agent adhering to the image carrier. However, this means removes the release agent while uniformly abrading the surface of the image carrier, and has a problem that the life of the image carrier is consequently shortened. In addition, even if the release agent is not removed, it is difficult to remove the release agent by simply using a roll, a web, or the like.

Further, Japanese Patent Application Laid-Open No. 2000-39778 discloses that the release agent removing powder held on the surface of the release agent removing member which is in rotational contact with the intermediate transfer member causes the release agent adhering to the surface of the intermediate transfer member. Means for entanglement of the release agent is disclosed, but not only the removal efficiency of the release agent is not sufficient, but also a secondary obstacle occurs because the release agent removing powder adheres to the surface of the intermediate transfer member. There is a fear.

Further, Japanese Patent Application Laid-Open No. 2000-137403 proposes a method of removing a release agent by an electric field, but the method is limited to a material capable of electrostatically adsorbing the material of the release agent. Therefore, there is a problem that the range of material selection becomes narrow.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to make image defects caused by a release agent visible without complicating the apparatus. An object of the present invention is to provide an image forming apparatus that does not allow the image forming apparatus to perform the operation.

Another object of the present invention is to provide an image forming apparatus capable of obtaining a high-quality image without image defects due to adhesion of a release agent to an intermediate transfer member and an image carrier. Is to do.

[0025]

In order to solve such a problem, an image forming apparatus according to the present invention forms a toner image on an image carrier using toners of different colors. A plurality of toner image forming means, an intermediate transfer body, a transfer means for primarily transferring a toner image from the image carrier of each of the toner image forming means to the intermediate transfer body, and a predetermined position on the intermediate transfer body. Heating means for heating and melting the toner image; and heating and pressing the toner image on the intermediate transfer body at a predetermined position between the intermediate transfer body and the recording medium, thereby applying the toner image to the recording medium. An image forming apparatus for forming a color image using a release agent, the toner image forming means being formed of a toner of a color having the smallest lightness difference from the recording medium. , Of in the toner image forming means, it is characterized in that arranged on the most upstream.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the present invention, wherein a plurality of toner image forming means for forming toner images on the image carrier using toners of different colors, an intermediate transfer body, Transfer means for primarily transferring a toner image to the intermediate transfer member from the image carrier of each toner image forming means;
Heating means for heating and melting the toner image on the intermediate transfer body at a predetermined position, and applying heat while pressing the toner image on the intermediate transfer body between the intermediate transfer body and the recording medium at a predetermined position; A transfer fixing unit for fixing the toner image at the same time as the secondary transfer to the recording medium, and forming a color image using a release agent. Is characterized in that the toner image forming means of the above-mentioned toner is arranged at a position other than the uppermost stream among a plurality of toner image forming means.

Further, in the image forming apparatus according to the present invention, an image carrier on which a toner image is formed, an intermediate transfer member, and a toner image from the image carrier on the intermediate transfer member. Transfer means for primary transfer, and heating and pressing the toner image on the intermediate transfer body at a predetermined position between the intermediate transfer body and the recording medium while heating and pressurizing, and secondary transferring the toner image to the recording medium. In an image forming apparatus having a transfer fixing unit for simultaneously fixing and a unit for applying a release agent to the intermediate transfer body, the temperature of the intermediate transfer body at a position where the image carrier comes into contact with the intermediate transfer body is the same as the above. It is characterized in that it is configured to be lower than the melting point temperature of the release agent.

It is an object of the present invention that the release agent remaining on or transferred to the intermediate transfer member is
This is to solidify where it comes into contact with the image carrier and to make it difficult to transfer to the image carrier.

Further, in the image forming apparatus according to the present invention, the image of the area where the release agent adheres to the surface of the image carrier and the image of the region where the release agent adheres to the surface of the image carrier are provided. The image forming apparatus further comprises means for adjusting the developing conditions so that the color difference between the image in the non-existing area and the image is within one.

The object of the present invention according to claim 4 is that, in addition to the invention according to claim 3, when the release agent is transferred to the image carrier,
The development conditions are adjusted so that the effect of the release agent does not appear on the development characteristics. The development conditions mentioned here include the development bias applied to the development roll, the distance between the image carrier and the development roll, the development roll. But not limited to this.

Further, in the image forming apparatus according to the present invention, the means for adjusting the developing condition adjusts an amplitude voltage in an AC component of a developing bias applied to the developing roll. .

An object of the invention described in claim 5 is that when there is a release agent formed into a solidified film on the image carrier, the amplitude voltage in the AC component of the developing bias applied between the image carrier and the developing roll is reduced. It is to increase the adhesion between the image carrier and the toner by adjusting, preferably strengthening.

Further, in the image forming apparatus according to the present invention, the means for adjusting the developing condition adjusts the amplitude voltage of the AC component of the developing bias applied to the developing roll to 1 KV or more. Features.

An object of the invention described in claim 6 is that when there is a solidified film-forming release agent on the image carrier, the amplitude voltage in the AC component of the developing bias applied between the image carrier and the developing roll is reduced. By setting it to 1KV or more,
An object of the present invention is to surely increase the adhesion between the image carrier and the toner.

According to a seventh aspect of the present invention, in the image forming apparatus according to the present invention, the means for applying the release agent to the intermediate transfer member includes an external or internal addition of the release agent to the toner. It is characterized in that a release agent is applied to the intermediate transfer member.

An object of the present invention is to add a release agent to or inside the toner, thereby eliminating the need for a new release agent application device and reducing the cost of the device. .

[0037]

First, the operation of the present invention will be described.

The release agent on the intermediate transfer member comes into contact with the most upstream image carrier, and most of the agent is transferred to the surface of the image carrier. Then, in the developing process, fog / dirt and density unevenness are caused. On the other hand, since a large amount of the release agent has been transferred to the surface of the image carrier, the amount of the release agent on the intermediate transfer member decreases. Therefore, the image carrier on the downstream side is less contaminated by the release agent.

Also, fog and stains due to black toner are easy to see on white paper, and fog and stains due to yellow toner are difficult to see. The same applies to uneven density. That is, the toner image of the color with the smallest brightness difference from the recording medium has less fog / dirt and uneven density, and the toner image of the color with the largest brightness difference with the recording medium has fog / dirt and uneven density. Is easy to see.

That is, according to the first aspect of the present invention, the release agent adhering to the intermediate transfer member is transferred to the most upstream image carrier, causing fog / dirt and density unevenness. Since the toner image has the smallest brightness difference from the recording medium, the toner image is not visually recognized as an image defect.

According to the second aspect of the present invention,
Because the toner image has a large difference in brightness from the recording medium, it is easy to see if fog, dirt, or uneven density occurs, but because it is located downstream, contamination by the release agent is reduced.
Image defects do not occur.

Next, the operation of the invention described in claims 3 to 7 will be described.

In order to solve the above problems, the present inventors first confirmed that the density was reduced and where the unevenness due to the density reduction was caused in the image forming process. Typical methods for supplying the release agent include a method using silicone oil as the release agent and a method using solid wax as the release agent by adding it internally to the toner. The results are shown below.

<Case where Silicone Oil is Used as Release Agent> As disclosed in Japanese Patent Application Laid-Open No. 5-107950, dimethyl silicone oil is used as a release agent, and an embodiment of the present invention described later is used. In the image forming apparatus having the configuration shown in FIG. 2, although not shown, a release agent supply device for supplying a release agent onto the intermediate transfer body 50 is arranged between the rolls 56 and 57, and has a predetermined width. Only the mold release agent was supplied to verify the process in which image defects occurred. as a result,
At the stage of the developed image on the photoreceptor, it was found that the amount of development was rather large in the area where the silicone oil was attached, rather than in the density reduction and unevenness due to the density reduction. However, in the image on the intermediate belt 50 after the primary transfer, it was found that in the area where the silicone oil was adhered, the density was reduced and unevenness due to the density reduction was generated.

That is, when a liquid release agent typified by silicon oil adheres to the photoconductor (image carrier), the non-electrostatic adhesion between the photoconductor and the developer (toner) Therefore, although the amount of toner to be developed is increased, the primary transfer cannot be performed. As a result, it is considered that the density is reduced and unevenness due to the density reduction is generated.

<Case where Solid Wax is Internally Added to Toner as Release Agent> Carnauba wax having a melting point of 85 ° C. was used as a release agent. The temperature at the transfer fixing unit is 150 ° C., and at this temperature, the wax is molten, but the belt temperature at which the photoconductor and the intermediate belt contact each other is 55 ° C.,
At this temperature, the wax has solidified. In the image forming apparatus having the structure shown in FIG.
A release agent supply device that supplies a release agent onto the intermediate transfer body 50 is disposed between the roller and the roll 57, and the release agent is supplied only to a predetermined width to verify a process in which an image defect has occurred. did. As a result, it was found that in the stage of the developed image on the photoreceptor, density reduction and unevenness due to the density reduction occurred in the area where the wax was attached. In the image on the intermediate transfer belt after the primary transfer, an image defect considered to be caused by the primary transfer process is not observed, and the decrease in density on the photoconductor caused in the developed image is directly transferred to the intermediate belt. I understand.

Although the mechanism is not clear, the contact between the intermediate belt and the photosensitive member causes the wax to
It is considered that the film is thinly formed on the photoreceptor in a solidified state. It is presumed that the thin filming of the wax increases the non-electrostatic adhesion between the photoconductor and the developer (toner), and reduces the amount of development due to alienation of the movement of the toner.

That is, it is necessary to remove the release agent, such as silicone oil, which adheres in a liquid form onto the photoreceptor from the belt, and the above-described removing means is required.

However, the release agent which solidifies on the photoreceptor to form a film does not cause an image defect in the primary transfer process. There is no need to use a means for removing the release agent as described.

That is, in order to achieve the above object,
4. An image carrier on which a toner image is formed, an intermediate transfer body, a transfer unit for primarily transferring the toner image from the image carrier to the intermediate transfer body, and a predetermined position. A transfer and fixing unit that heats and presses the toner image on the intermediate transfer member between the intermediate transfer member and the recording medium, and simultaneously performs secondary transfer of the toner image to the recording medium; In the image forming apparatus having means for applying a release agent to the intermediate transfer body, the temperature of the intermediate transfer body at a position where the image carrier contacts the intermediate transfer body is lower than the melting point temperature of the release agent. It is configured as follows.

FIG. 15 is a view showing a transfer fixing device for explaining the operation of the invention described in claims 3 to 7 of the present invention.

In FIG. 15, an intermediate transfer member 100 as an image carrier is formed in an endless shape, is tensioned by a tension roll 104 at a constant tension, and transfers the toner on the photosensitive member 107 onto the intermediate transfer member 101. Transfer unit T, intermediate transfer body 101
A heating unit A for melting the toner by a heating plate 106 provided on the back surface of the printer, a transfer fixing unit B for transferring and fixing the toner on the intermediate transfer body 101 to paper P as a recording medium, and a cooling unit C for cooling and solidifying the toner Then, the sheet P is circulated through a peeling section D that peels the sheet P from the intermediate transfer body 101.

The heating section A is an area for performing preheating for simultaneous transfer and fixing in the transfer and fixing section B.
May be omitted if a sufficient amount of heat is given.

The transfer / fixing section B includes a heating roll 102 and a pressure roll 103. The two rolls are brought into contact with each other, and the intermediate transfer body 101 and the paper P are sandwiched therebetween to pressurize and heat.

In the transfer fixing section B, the intermediate transfer member 10
The toner image 1, the toner image, and the paper P as a recording medium are integrally brought into close contact with each other and heated, so that the powder toner is in a molten state, and the individual toners are fused to form a single film.

The toner image transferred and fixed to the recording medium in the transfer fixing section B is cooled while being transported to the peeling section D,
Agglomerates and solidifies, producing a strong adhesive force with the recording medium. Although not shown, a cooling device may be provided between the transfer fixing section B and the peeling section D. The intermediate transfer body 101 and the recording medium P cooled by the cooling unit C are conveyed to a separation unit D including a separation roll 105 having a small radius of curvature, and the recording medium P is separated by the rigidity of the recording medium P itself. An output image is completed by being peeled off from the sheet 101 together with the toner. The surface of the toner image transferred and fixed to the recording medium P is the intermediate transfer body 1
No. 01 and the surface is smoothed and has high gloss.

After the recording medium P is peeled at the peeling section D,
The toner on the photoconductor 107 is transferred to the intermediate transfer body 101 again at the transfer unit T.

The release agent is used to suppress an increase in adhesive force due to repeated use of the intermediate transfer member 101.
For example, a release agent is internally or externally added to the toner to be developed.

When the release agent is internally or externally added to the toner, the release agent is melted in the transfer and fixing section B to generate its function, and is interposed between the intermediate transfer body 101 and the toner image. In addition, the adhesive force between the intermediate transfer member 101 and the toner image is reduced. Therefore, after the recording paper P is peeled at the peeling section D, a certain amount of the release agent remains on the intermediate transfer member 101.

That is, if a release agent is used in an image forming apparatus of the simultaneous transfer and fixing type using the intermediate transfer member 101, the release agent contacts the photosensitive member 107 while leaving the release agent on the intermediate transfer member 101. The problem of transfer of the mold agent occurs.

As a result of the present inventors' investigation into this problem, as described above, when a liquid release agent typified by silicon oil adheres to the photoconductor 107, Non-electrostatic adhesion to the agent (toner) increases, thereby reducing the amount of toner developed and
It was found that the primary transfer could not be performed, and as a result, density reduction and unevenness due to the density reduction occurred.

Further, when the solidified wax adhered to the photosensitive member 107, it was found that in the stage of the developed image, the density was decreased in the region where the wax was adhered, and unevenness due to the decreased density occurred. In the image on the intermediate transfer belt 101 after the primary transfer, no image defect considered to be caused by the primary transfer process is observed, and the density reduction on the photoconductor 107 generated in the developed image is directly transferred to the intermediate transfer belt. I knew it was there.

The area on the photoconductor 107 where the release agent has adhered and the area where the release agent has not adhered can be determined by measuring the contact angle of the surface of the photoconductor 107 with water. The area where the release agent is not attached has a contact angle with water of less than 80 °, and when the release agent is attached, the contact angle with water becomes 90 ° or more.

The present inventors consider that if the release agent migrates to the photoreceptor 107 and solidifies to form a film, it does not affect the primary transfer performance. There is a requirement that a mold agent film can be formed, and a requirement that there is no difference in development performance between an area where the solidified release agent film is formed on the photoreceptor 107 and an area where the mold release agent is not transferred. We thought this problem could be solved if we made it clear.

That is, the requirement for forming a solidified release agent film on the photoreceptor 107 is that the melting point temperature of the release agent is determined by the temperature of the intermediate transfer member at the position where the photoreceptor 107 contacts the intermediate transfer member 101. Lower than that of the photoconductor 1
The requirement that there is no difference in the developing performance between the region where the release agent is solidified on the film 07 and the region where the release agent has not been transferred is that the non-electrostatic charge of the photoconductor 107 and the toner The purpose is to lower the adhesion and increase the movement of the toner.

[0066]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a configuration diagram showing an image forming apparatus according to Embodiment 1 of the present invention.

This image forming apparatus, as shown in FIG.
It has four image forming units 1Y, 1M, 1C, and 1K that form toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K). The units 1Y, 1M, 1C, and 1K are arranged along the horizontal direction at regular intervals. These four image forming units 1Y, 1M, 1C, and 1K have the same configuration except that only the color of the toner image to be formed is different.

The yellow (Y), magenta (M), cyan (C), and black (K) image forming units 1Y, 1Y
M, 1C, and 1K denote photosensitive drums 2Y, 2Y as image carriers using an organic photoconductor (OPC), an inorganic photoconductor, or the like.
M, 2C, and 2K.
Y, 2M, 2C, and 2K are rotationally driven at a predetermined speed along a direction indicated by an arrow by driving means (not shown). After the surfaces of the photosensitive drums 2Y, 2M, 2C, and 2K are uniformly charged to a predetermined potential by charging devices 3Y, 3M, 3C, and 3K including scorotrons and the like, the light scanning devices 4Y and 4K are charged.
Laser light is scanned and exposed by M, 4C, and 4K according to image information, and an electrostatic latent image is formed. Photoconductor drum 2
The electrostatic latent images formed on Y, 2M, 2C, and 2K are the developing devices 5Y, 5M, 5C,
It is developed by 5K to become a toner image.

Each image forming unit 1Y, 1M, 1C, 1
The toner images formed on the K photoconductor drums 2Y, 2M, 2C and 2K are transferred to transfer devices 6Y and 6 made of corotron or the like.
By M, 6C, and 6K, primary transfer is performed in the order of yellow, magenta, cyan, and black on the intermediate transfer belt 7 as an intermediate transfer body in a state of being superimposed on each other. Note that the photosensitive drums 2Y after the completion of the primary transfer,
The surfaces of 2M, 2C and 2K are drum cleaners 8Y and 8
M, 8C, and 8K remove residual toner and the like.

The intermediate transfer belt 7 is an endless belt, and includes a belt drive roll 9 and a tension roll 10
, A belt-side transfer fixing roll 11, and a paper peeling roll 1
2 and at a predetermined tension. Recording paper 1 as a recording medium is placed on the belt-side transfer fixing roll 11.
A paper-side transfer / fixing roll 14 for transferring and fixing the toner image from the intermediate transfer belt 7 at the same time is pressed against the intermediate transfer belt 7.
A paper-side transfer / fixing roll cleaner 15 for cleaning the surface of the paper-side transfer / fixing roll 14 is arranged in contact with the paper-side transfer / fixing roll 14. Then, the intermediate transfer belt 7 is rotationally driven by the belt driving roll 9 at the same rotational speed as the photosensitive drums 2Y, 2M, 2C, and 2K. The intermediate transfer belt 7 is composed of a base layer and a surface layer. Here, a polyimide film whose resistivity is adjusted by adding a conductive agent such as carbon black to the base layer, and silicone rubber for the surface layer. Each is used.

A belt heating plate 16 for heating the belt 7 to a predetermined temperature is provided between the tension roll 10 and the belt-side transfer fixing roll 11 on the back side of the intermediate transfer belt 7.
Are arranged. As the belt heating plate 16, for example, a belt heating plate with a planar heater attached to the back surface is used.

The belt-side transfer / fixing roll 11, the paper-side transfer / fixing roll 14, and a belt cleaner opposing roll 18, which will be described later, use a metal roll coated with silicone rubber, and provide a heat source inside to control the temperature. It is possible. On the other hand, a belt cleaner 17 and a paper-side transfer / fixing roll cleaner 15, which will be described later, are provided on a metal roll having a heat source whose temperature can be controlled as a surface layer. (About 11
(3 ° C.).

The toner image primarily transferred onto the intermediate transfer belt 7 passes through the tension roll 10 and
Is conveyed to the belt heating plate 16 set to. The toner image is heated and melted while passing over the belt heating plate 16, and is formed on a sheet 13 as a recording medium at a nip formed between the belt-side transfer fixing roll 11 and the paper-side transfer fixing roll 14. Is transferred and fixed simultaneously. The sheet 13 on which the toner image has been transferred and fixed is cooled by natural heat radiation until it reaches the sheet peeling roll 12, and the toner image is transferred to the sheet 13.
In a state where the paper 13 is sufficiently anchored, the paper 13 is peeled by the paper peeling roll 12 having a small radius of curvature with the rigidity of the paper 13 itself, and is discharged to an output tray (not shown).

Incidentally, the belt cleaner 17 removes residual toner and the like from the surface of the intermediate transfer belt 7 after the peeling step of the paper 13 is completed. On the back side of the belt cleaner 17, the belt cleaner 17 is
The belt cleaner opposing rolls 18 that are in pressure contact with each other are disposed to oppose each other.

The heating temperature of the belt-side transfer / fixing roll 11 and the paper-side transfer / fixing roll 14 is set to 95 ° C., and the pressing load between the belt-side transfer-fixing roll 11 and the paper-side transfer / fixing roll 14 is 735 N. Is set. The paper-side transfer fixing roller 14 is pressed against the intermediate transfer belt 7 after driving in order to reduce the load immediately after the start of the intermediate transfer belt 7,
It is configured to be separated from the intermediate transfer belt 7 before the stop.

Here, the toner image transferred to the intermediate transfer belt 7 will be described. In addition to the toner image transferred as a print image on the sheet 13, other types of toner images are transferred to the intermediate transfer belt 7. For example, as shown in FIG. 2, a control image (hereinafter, referred to as a “patch image”) 19 for controlling the toner density and the transfer position of the four color toner images is exemplified. The patch image 19
May be transferred onto the paper 13, but usually, while being transferred to the intermediate transfer belt 7, the toner concentration and the position of the image are detected by a sensor (not shown) and removed by the belt cleaner 17. . Further, extremely low-density toner, which is called fog toner and adheres to the photosensitive drum 2 other than the toner image, is also transferred to the intermediate transfer belt 7 as a toner image.

Therefore, even after the image is transferred and fixed on the sheet 13, the toner image remains on the intermediate transfer belt 7 and adheres to the sheet-side transfer fixing roll 14. Thus, the paper-side transfer / fixing roll cleaner 15 prevents the toner image attached to the paper-side transfer / fixing roll 14 from attaching to the back surface of the paper 13 to be transported next. The temperature of the paper-side transfer fixing roll cleaner 15 is set to 115 ° C., and the pressing load between the paper-side transfer fixing roll cleaner 15 and the paper-side transfer fixing roll 14 is set to 98N. The paper-side transfer / fixing roll cleaner 15 nips the paper-side transfer / fixing roll 14 after driving the intermediate transfer belt 7 to reduce the load immediately after the start of the intermediate transfer belt 7. It is configured to be separated.

Next, the toner image remaining on the intermediate transfer belt 7 is conveyed to the belt cleaner 17 in a state of being once cooled. Therefore, the belt cleaner 17 sets the intermediate transfer belt 7 at a temperature of 120 ° C. higher than the softening point of the toner.
, And the pressure applied between the belt cleaner 17 and the cleaner opposing roll 18 is set to 196N. Have been. Thereby, the cooled toner image is heated by the belt cleaner 17 and the cleaner opposing roll 18,
It is melted again, and the adhesive force with the intermediate transfer belt 7 can be reduced. Further, by using a roll in which a polyester resin is coated on a metal roll as the belt cleaner 17, the contact area between the belt cleaner 17 and the cleaner opposing roll 18 is increased by the elasticity of the polyester resin, and the belt cleaner 17 is used. The cleaning property can be improved. As a result, the intermediate transfer belt 7 can be reliably cleaned. In addition, belt cleaner 1
Numeral 7 is configured to contact the intermediate transfer belt 7 after driving in order to reduce the load immediately after the start of the intermediate transfer belt 7, and to separate from the intermediate transfer belt 7 before stopping. In addition,
The toner and the like removed by the belt cleaner 17 are removed by removing means (not shown).

By the way, the toner for forming the toner image contains carnauba wax as a release agent.
An increase in the adhesive force between the toner and the intermediate transfer belt 7 due to repeated stresses such as discharge and heating is suppressed. The toner image formed on the intermediate transfer belt 7 is made of toner and carnauba wax, and only the carnauba wax remains offset on the intermediate transfer belt 7 when the paper 13 is peeled off. The carnauba wax remaining on the intermediate transfer belt 7 is melted by the belt cleaner 17 and partially cleaned at the same time as the toner, but in the melted state, it cannot be sufficiently cleaned and passes through the belt cleaner 17. The carnauba wax is cooled when passing through the belt drive roll 9, and is present on the intermediate transfer belt 7 as floating wax particles, and contacts and adheres to the surface of the photosensitive drum 2.

Next, an image defect caused by the attachment of wax to the photosensitive drum 2 will be described.

When the patch image 19 as shown in FIG. 2 is continuously written, filming occurs on the photosensitive drum 2 by the wax which has made a round of the belt. Then, as shown in FIG. 3, when a solid image 20 is formed on the paper 13,
In the area 21 indicated by light hatching in the figure, band-like fogging and density unevenness occur, and in the solid image 20, the density decreases. This is considered to be because the non-electrostatic adhesive force on the surface of the photosensitive drum 2 was increased due to the adhesion of the wax, and the developing characteristics were changed.

FIG. 4 shows four image forming units 1Y and 1Y.
When the first, second, third, and fourth photosensitive drums are sequentially arranged from the upstream side among the photosensitive drums M, 1C, and 1K, the contact angle of the surface of each photosensitive drum 2 with water It is shown. FIG. 4 also shows the contact angle with water when the surface of the photosensitive drum 2 is completely covered with wax. It can be evaluated that the larger the contact angle with water, the more wax is attached. The water droplet used had a diameter of 2 mm.

As is clear from FIG. 4, the patch image 19
Wax adheres to the position (recording position) where
The largest amount of wax adheres to the uppermost first photosensitive drum 2, that is, the contact angle with water on the surface of the photosensitive drum 2 is large, is reduced to about 1/10 in the second, and is reduced to the third and fourth. It can be seen that the second photosensitive drum 2 is equivalent to a state where the wax at the non-recording position is not attached.

FIGS. 5 and 6 show the case where only the developing device 4 is replaced with respect to each photosensitive drum 2 to which the wax has adhered, and the color of the toner image formed on each photosensitive drum 2 is changed. That is, when the colors of the toner images formed on the first, second, third, and fourth photosensitive drums 2 are switched to yellow, magenta, cyan, and black, respectively,
FIG. 9 shows the result of evaluating the difference between the number of fogging toners at an image defect portion and the periphery of the toner weight when a solid image is recorded.

FIGS. 7 and 8 show the evaluation of the fog and the density unevenness at that time.

FIG. 9 shows the toner weight and color development of a solid image as characteristics of the toner used for evaluation. The characteristics of the toner are not significantly different from the toner values used in many color copying machines such as a color copying machine Acolor 930 manufactured by Fuji Xerox. FIG. 9 also shows the color developing properties of the white paper 13 used for the evaluation.

As is apparent from FIGS. 5 and 6, it can be seen that there is no difference in the number of fog toners and the difference between the toner weight and the periphery due to the color of the toner. That is, regardless of whether any of yellow, magenta, cyan, and black toner images are formed on the first, second, third, and fourth photosensitive drums 2, the number of fog toners and the peripheral weight of the toner It can be seen that there is no difference in the difference.

On the other hand, as is apparent from FIGS. 7 and 8, even if there is no difference between the number of fog toners and the toner development weight, the visibility of fog and density unevenness is large depending on the toner color. It turns out that they are different. That is, the difference between the number of fog toners and the toner development weight is the first, second,
Regardless of the yellow, magenta, cyan, or black toner image formed on each of the third and fourth photosensitive drums 2, there is almost no difference between the colors, but the visibility of fog and density unevenness. Is significantly different depending on whether a yellow, magenta, cyan, or black toner image is formed on each of the first, second, third, and fourth photosensitive drums 2. On the body drum 2, yellow has the best band-like fogging grade, and then magenta and cyan are almost the same so that they are faintly visible. For black, the band-like fog is clearly visible. bad. The grade of the band-shaped density unevenness is yellow, magenta, and cyan on the first photosensitive drum 2 and is of such an extent that both can be seen when viewed with care. It looks good and is the worst.

As described above, even if wax adheres to the surface of the photosensitive drum 2 on the uppermost stream, the influence of the wax on the photosensitive drum 2 is unlikely to appear as visibility of fog and density unevenness. It can be seen that the use of the yellow toner having a small difference in brightness from that of No. 13 significantly reduces image defects.

Further, it can be seen that the image defect is greatly improved by not using the black toner having a large difference in brightness from the paper 13 in the uppermost stream. Further, regarding the black toner, even when used for the second photosensitive drum 2, the visibility of fog and density unevenness is relatively poor as compared with the toners of other colors, so It is desirable to do.

Therefore, in the first embodiment, as shown in FIG. 1 in the most upstream first image forming unit 1,
The developing device 4 uses a yellow toner, and the first photosensitive drum 2 is configured to form a yellow toner image.

Further, in the first embodiment, as shown in FIG. 1, a black toner is used as the developing device 4 in the fourth most downstream image forming unit 1, and the fourth photosensitive drum 2 is used in the fourth photosensitive drum 2. , So as to form a black toner image.

The above is the configuration when white paper is used as a general recording medium. If the recording medium is black paper, the positions of the yellow toner and the black toner are interchanged. .

Embodiment 2 FIG. 10 shows Embodiment 2 of the present invention. In Embodiment 2, an image bearing member on which a toner image is formed, an intermediate transfer member, and the image bearing member A transfer unit that primarily transfers a toner image to the intermediate transfer body from above, and heats and presses the toner image on the intermediate transfer body at a predetermined position while sandwiching the toner image between the intermediate transfer body and a recording medium. In an image forming apparatus having a transfer and fixing unit for fixing an image at the same time as secondary transfer onto the recording medium and a unit for applying a release agent to the intermediate transfer body, a position where the image carrier comes into contact with the intermediate transfer body. , The temperature of the intermediate transfer member is lower than the melting point temperature of the release agent.

In the second embodiment, the color difference between the image of the area where the release agent adheres to the surface of the image carrier and the image of the area where the release agent does not adhere to the surface of the image carrier is different. ,
There is provided a means for adjusting the developing conditions so as to be within one.

Further, in the second embodiment, the means for adjusting the developing condition is configured to adjust the amplitude voltage in the AC component of the developing bias applied to the developing roll.

In the second embodiment, the means for adjusting the developing conditions is configured to adjust the amplitude voltage of the AC component of the developing bias applied to the developing roll to 1 KV or more.

Further, in the second embodiment, the means for applying the release agent to the intermediate transfer body includes adding or releasing the release agent to or from the toner, thereby adding the release agent to the intermediate transfer body. It is configured to be applied.

FIG. 10 is a configuration diagram showing an image forming apparatus according to Embodiment 2 of the present invention.

In FIG. 10, reference numeral 50 denotes a belt-shaped intermediate transfer member. The intermediate transfer belt 50 has a curved heating plate 51, an intermediate transfer member position control roll 52, a heating roll 53, Rolls 54, 55, 5
It is circulated in the direction of the arrow shown in FIG. A pressure roll 58 is arranged to face the heating roll 53. The heating roll 53 and the pressure roll 58 can be arranged in reverse, and the pressure roll 58 may be a heating roll having a heat source inside. The heating plate 51
It consists of a plate with a heat source.

A photosensitive drum 60 is disposed above the intermediate transfer belt 50. After the surface of the photosensitive drum 60 is uniformly charged by the primary charger 61, the surface is exposed by a light beam scanning device 63 which is turned on and off by a light beam pulse width modulator 62 according to a density signal, and an electrostatic latent image is formed. It is formed. As the photoconductor drum 60, various organic photoconductors (OPC) can be used in addition to various inorganic photoconductors (Se, a-Si, a-SiC, CdS, etc.).
The electrostatic latent image on the photosensitive drum 60 is developed by the developing device 64, and a so-called digital image toner image representing the density by area modulation is formed on the photosensitive drum 60.

The toner image is transferred onto the intermediate transfer belt 50 by the primary transfer device 65, and a toner image is formed on the intermediate transfer belt 50. On the upstream side of the primary transfer device 65,
A heating plate 66 is provided, and the temperature of the intermediate transfer belt 50 at the primary transfer position T is controlled by the heating plate 66.

The toner image formed on the intermediate transfer belt 50 is heated and melted while moving in the area A in contact with the heating plate 51 and moving. The pressure roll 58 is disposed so as to be able to freely contact with and separate from the heating roll 53, and synchronizes with the feeding of the recording paper 68 from the paper feeding tray 67.
3 is pressed. After that, the intermediate transfer drum 50 holding the toner image and the recording paper 68 move between the heating roll 53 and the pressure roll 58 at the same time, and are heated under pressure. The toner heated above the melting temperature is softened and melted, penetrates into the recording paper 68, and is then solidified, whereby transfer and fixing are performed. The cooling unit C includes the intermediate transfer drum 50 and the recording paper 6 that are integrally transported from the heating area B.
8. This cools the toner, which causes the toner to coagulate and solidify,
A strong adhesive force is generated between the recording paper 68 and the recording paper 68. The intermediate transfer drum 50 and the recording paper 68 cooled by the cooling unit C are
Further, the recording paper 68 is separated from the intermediate transfer belt 50 together with the toner by the stiffness (bending hardness) of the recording paper 68 itself on the roll 54 having a small radius of curvature, and a color image is formed on the recording paper 68. It is formed. The surface of the toner image transferred and fixed on the recording paper 68 is smoothed to have a high gloss following the surface of the intermediate transfer belt 50.

As the intermediate transfer belt 50, for example, one having a two-layer structure of a base layer and a surface layer is used. A 70 μm thick polyimide film to which carbon black has been added is used for the base layer. In this embodiment, the toner image is transferred from the photosensitive drum 60 to the intermediate transfer belt 50.
The volume resistivity of the base layer is adjusted to 10 ¹⁰ Ω · cm by changing the addition amount of carbon black in order to transfer electrostatically and without image disturbance. As the base layer, for example, a highly heat-resistant sheet having a thickness of 10 to 300 μm can be used, and polyester, polyethylene terephthalate, polyether sulfone, polyether ketone, polysulfone, polyimide, polyimide amide, and polyamide It is possible to use a polymer sheet or the like.

[0106] The surface layer in order to transfer not disturbed electrostatically Moreover image a toner image from the photosensitive drum 60 to the intermediate transfer belt 50, a volume resistivity of 10 ¹⁴ Ω · cm
To the recording paper 68 from the intermediate transfer belt 50.
In order to improve the close contact between the intermediate transfer belt 50 and the recording paper 68 via the toner image when the transfer and fixing to the
A silicone copolymer is used. The silicone copolymer has elasticity, and its surface shows tackiness to the toner at normal temperature, and furthermore, in order to transfer the toner to the recording medium 68 efficiently, the toner which has been melted and fluidized is easily released. Because of its properties, it is most suitable for a surface layer. As for the surface layer, in addition to the silicone copolymer,
Fluoro rubber, fluoro resin, or the like may be used. In the present embodiment, a DX35-547A / B silicone copolymer made of Toray Dow Silicone having a rubber hardness of 30 degrees and a thickness of 50 μm is used.

The primary transfer unit 65 is adjusted to apply a charge to the back surface of the intermediate transfer belt 50 so that the toner on the photosensitive drum 60 is efficiently transferred to the intermediate transfer belt 50. In the present embodiment, a corotron is used and 31
The voltage applied to the corotron wire is adjusted to give a charge density of 5 μC / m ² .

As the heating plate 51, a silicon rubber heater attached to the back of an aluminum plate having a thickness of 2 mm and a length of 220 mm in the circulation direction of the intermediate transfer belt 50 is used. The heating temperature is set and controlled so that the toner temperature in a region where the intermediate transfer belt 50 contacts the recording paper 68 is equal to or higher than the toner melting temperature. In addition, a ceramic heater or the like can be used as the heating plate 51.

As the heating and pressing rolls 53 and 58, a metal roll or a roll having a heat-resistant elastic layer such as silicone rubber on a metal roll can be used. A heat source is arranged inside the heating roll 53, and the heating temperature is:
The toner temperature in the heating area is set and controlled so as to be equal to or higher than the toner melting temperature. In the present embodiment, a 50 mm outer diameter roll obtained by laminating a silicone rubber having a hardness of 30 degrees and a thickness of 2 mm on a hollow aluminum roll is used as the heating roll 53 and the pressure roll 58. A halogen lamp is used as a heat source. In addition, the pressing force of the heating and pressure rolls 53 and 58 was changed and adjusted so that the holding width between the two rolls was 7.5 mm.

The toner is mainly composed of a thermoplastic binder containing a coloring matter, and a known material can be used.
Here, a toner using a polyester resin is used.

With respect to 100 parts by weight of the polyester resin,
4 parts by weight of carbon black and 5 parts by weight of carnauba wax having a melting point of 85 ° C. are mixed and melted by an extruder, kneaded, cooled, pulverized by a jet mill, and the pulverized material is classified to obtain a volume average diameter. 7 μm black toner was obtained.

The developing device 64 is provided with a cylindrical developing roll that conveys the developer by holding the developer on the surface and rotating the developing roller. Development bias is applied,
An electric field formed at a development position close to the photosensitive drum 60 causes toner having a charge to adhere to the electrostatic latent image. This applied voltage makes the DC component have the same polarity as the charging potential of the photosensitive drum 60, and develops the potential contrast (the DC component voltage and the entire exposure voltage of the photosensitive drum 60) against the entire exposed portion potential of the photosensitive drum 60. Difference) is 3
It is set to be about 00V.

The distance (DRS) between the photosensitive drum 60 and the developing roll at the position where the photosensitive drum 60 and the developing roll are closest to each other was set to 0.5 mm. The AC component of the developing bias voltage had an amplitude value of 0.5 kV in peak-to-peak value (Vpp), a frequency of 9 kHz, and a rectangular waveform. Further, the ratio Vs / Vp of the moving speed Vs of the developing roll to the moving speed Vp of the photoconductor is 2.

With the above configuration, the toner image transport speed (transfer fixing speed) of the intermediate transfer body 50 is 260 mm / s, the toner temperature in the heating area B is heated to the toner melting temperature, and the intermediate transfer in the primary transfer area T is performed. The body temperature is appropriately controlled with a heating plate, and after using the toner described above, an image A shown in FIG. 11A is output, and then a uniform density image B shown in FIG.
Was intended, and the resultant image B shown in FIG. 11C was evaluated for a decrease in density. The evaluation was made based on the color difference ΔE in the Lab uniform color space between the two areas where the density was not reduced and the area where the density was reduced. If the color difference ΔE is larger than 1, it exceeds the detection limit of humans and is recognized as a decrease in density.

FIG. 12 shows the relationship between the temperature of the intermediate transfer member 50 in the primary transfer area T and the color difference ΔE of the image B. As is clear from the figure, the temperature of the intermediate transfer body 50 in the primary transfer area T is equal to the melting point of the release agent (85 ° C.).
From the above, it can be seen that the color difference ΔE sharply increases and the density is significantly reduced. Below the melting point (85 ° C.) of the release agent, the color difference ΔE was within 1, which was a level at which no functional decrease in density was recognized.

Embodiment 3 The temperature of the primary transfer area T described in Embodiment 2 is 50
11C, the temperature of the heating plate 66 is controlled to change the developing condition as shown in FIG. 13, and after outputting 1000 images A shown in FIG. 11A, the image shown in FIG. A uniform density image B is intentionally output, and the resulting FIG.
Evaluation of the density reduction of the image B shown in (c) was performed.

As is clear from the results shown in FIG. 13, even when the temperature of the primary transfer area T is lower than the melting point of the toner, the color difference ΔE due to the decrease in density may exceed 1 due to continuous image output. However, by changing the developing conditions, that is, by sandwiching the distance (DRS) between the photoconductor and the developing roll so as to increase the adhesive force between the photoconductor and the toner, the electric field strength between the photoconductor and the developing roll is increased, Vs /
By increasing Vp, the toner supply ability was improved, and the color difference ΔE due to the decrease in density could be kept within one.

Embodiments 4 and 5 As described in Embodiment 2, the temperature of the primary transfer area T is set to 50.
11C, the temperature of the heating plate is controlled to change the developing conditions as shown in FIG. 14, and after 1000 images A shown in FIG. 11A are output, the uniformity shown in FIG. A density image B is intentionally output and the resulting FIG.
Evaluation of the density reduction of the image B shown in (c) was performed.

As is clear from the results shown in FIG. 14, even when the temperature of the primary transfer area T is equal to or lower than the melting point of the toner, the color difference ΔE due to the density decrease may exceed 1 due to the continuous image output. However, by changing the developing bias, that is, by increasing the voltage applied between the photosensitive member 60 and the developing roll so as to increase the adhesive force between the photosensitive member 60 and the toner, the color difference ΔE due to the density reduction is kept within one. Was completed.

[0120]

As described above, since the image forming apparatus of the present invention has the above-described configuration, it is possible to provide an apparatus which does not make the image defect due to the release agent visible without complicating the apparatus. .

The present invention has the above-described structure and operation. Even if a release agent for improving the life of the intermediate transfer member is used, transfer of the release agent to the photosensitive member is suppressed. Even when the release agent migrates to the photoreceptor, a decrease in image density is prevented, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram showing a sample of an image to be formed.

FIG. 3 is a schematic diagram showing a sample of an image to be formed.

FIG. 4 is a graph showing the relationship between the position of the photosensitive drum and the contact angle of water on the surface of the photosensitive drum.

FIG. 5 is a graph showing the relationship between the photosensitive drum and the number of fog toners measured at different positions of the photosensitive drum.

FIG. 6 is a graph showing the result of measuring the relationship between the photosensitive drum and the solid toner weight at different positions of the photosensitive drum.

FIG. 7 is a graph showing the relationship between the photoreceptor drum and the band-shaped fogging grade measured at different positions of the photoreceptor drum.

FIG. 8 is a graph showing the relationship between the photoreceptor drum and the band-like density unevenness grade measured at different positions of the photoreceptor drum.

FIG. 9 is a table showing physical properties of a toner.

FIG. 10 is a configuration diagram showing an image forming apparatus according to Embodiment 2 of the present invention.

FIG. 11 is a schematic diagram showing a sample of an image to be formed.

FIG. 12 is a graph showing the relationship between the temperature of the intermediate transfer member of the primary transfer portion and the color difference.

FIG. 13 is a chart showing experimental conditions and results of the third embodiment.

FIG. 14 is a table showing experimental conditions and results of the fourth and fifth embodiments.

FIG. 15 is a configuration diagram for explaining the operation of the image forming apparatus according to the present invention.

[Explanation of symbols]

1Y: Image forming unit for forming a yellow (Y) toner image 1M: Image forming unit for forming a magenta (M) toner image 1C: Image forming unit for forming a cyan (C) toner image 1K: Image forming units 2Y, 2M, 2C, 2K for forming black (K) toner image: photosensitive drum 7: intermediate transfer belt.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 372 G03G 15/06 101 2H078 15/06 101 15/16 101 15/16 101 15/20 102 15/20 102 104 104 15/24 15/24 9/08 361 (72) Inventor Yasuhiro Oda 430 Nakai-cho, Ashigarugami-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. (72) Inventor Yuichi Fukuda Nakai-cho, Ashigara-gun, Kanagawa Prefecture Sakae 430 Green Tech Nakai Fuji Xerox Co., Ltd. (72) Inventor Norihiro Katsuta 430 Sakai Nakaicho, Ashigara-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. F-term (reference) 2H005 AA06 AA08 AA21 CA13 CA14 2H030 AA06 AB02 AD04 BB22 BB34 BB42 BB43 BB46 BB61 BB71 2H032 AA14 AA15 BA01 BA05 BA09 B A21 BA23 2H033 AA01 AA39 BA11 BA24 BA41 BA58 BB01 BB17 BB28 BB34 BE09 2H073 AA01 BA03 BA13 BA21 CA22 2H078 AA08 BB01 CC06 DD38 DD42 DD51 DD57 DD61 DD73

Claims (7)

[Claims] A plurality of toner image forming means for forming toner images on the image carrier with toners of different colors; an intermediate transfer member; and a toner image from the image carrier of each of the toner image forming means. Transfer means for primary transfer to the intermediate transfer member,
Heating means for heating and melting the toner image on the intermediate transfer body at a predetermined position, and applying heat while pressing the toner image on the intermediate transfer body between the intermediate transfer body and the recording medium at a predetermined position; And an image forming apparatus for forming a color image using a release agent, the image forming apparatus having a transfer fixing unit that fixes the toner image to the recording medium at the same time as the secondary transfer. The toner image forming means by the toner of the plurality of toner image forming means,
An image forming apparatus, which is arranged at the most upstream. A plurality of toner image forming means for forming toner images on the image carrier with toners of different colors, an intermediate transfer member, and a toner image from the image carrier of each toner image forming means. Transfer means for primary transfer to an intermediate transfer member,
Heating means for heating and melting the toner image on the intermediate transfer body at a predetermined position, and applying heat while pressing the toner image on the intermediate transfer body between the intermediate transfer body and the recording medium at a predetermined position; And an image forming apparatus for forming a color image using a release agent, the image forming apparatus having a transfer-fixing unit for fixing the toner image to the recording medium at the same time as the secondary transfer. The toner image forming means by the toner of the plurality of toner image forming means,
An image forming apparatus, which is arranged at a position other than the most upstream. 3. An image carrier on which a toner image is formed, an intermediate transfer body, a transfer unit for primarily transferring a toner image from the image carrier to the intermediate transfer body, and A transfer and fixing unit that heats and pressurizes the toner image between the intermediate transfer body and the recording medium while performing secondary transfer of the toner image to the recording medium, and simultaneously releases the toner image from the intermediate transfer body. Wherein the temperature of the intermediate transfer member at a position where the image carrier contacts the intermediate transfer member is lower than the melting point temperature of the release agent. Characteristic image forming apparatus. 4. A color difference between an image of an area where the release agent is attached to the surface of the image carrier and an image of an area where the release agent is not attached to the surface of the image carrier is within one. The image forming apparatus according to claim 3, further comprising a unit that adjusts a developing condition. 5. The image forming apparatus according to claim 4, wherein the means for adjusting the developing condition adjusts an amplitude voltage in an AC component of a developing bias applied to the developing roll. 6. The image forming apparatus according to claim 5, wherein the means for adjusting the developing condition adjusts an amplitude voltage of an AC component of a developing bias applied to the developing roll to 1 KV or more. 7. A means for applying a release agent to the intermediate transfer body, wherein the release agent is applied to the intermediate transfer body by internally or externally adding the release agent to the toner. The image forming apparatus according to claim 3.