JP3521712B2 - Intermediate transfer member, manufacturing method thereof, and image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in which a toner image formed on a photoconductor is primarily transferred to an intermediate transfer body, and the toner image that is primarily transferred is transferred and fixed on a recording paper. The present invention relates to an intermediate transfer member, an image forming apparatus, and a method for manufacturing the intermediate transfer member, which are used in the method.

[0002]

2. Description of the Related Art Conventionally widely used, an electrostatic latent image is formed on a photoconductor, which is developed as a toner image with a dry toner, and then the toner image is electrostatically transferred onto a recording medium,
In the image forming technique for fixing, there is a problem that density unevenness occurs in an image or powder toner is scattered at a transfer portion, resulting in poor resolution and dot reproducibility.

This is largely due to the transfer process in which the toner image on the photoconductor is electrostatically transferred to the recording medium.

Since the transfer efficiency of the toner layer depends on Et, the transfer efficiency must be constant unless Et is constant irrespective of the toner layer thickness, unevenness of a recording medium typified by paper, and unevenness of electrical properties. The transfer position of the recording medium will be different.
When the toner image formed on the photoconductor is monochromatic and the layer thickness is thin, image unevenness occurs mainly due to unevenness of the recording medium and uneven electrical properties. This is the same as when a color image is formed by transferring a single-color toner image independently formed on a plurality of photoconductors onto a single recording medium. This causes image unevenness. In other words, the difference between the portion to be over-transferred and the portion to be transferred in a single color without being over-transferred can be electrostatically suppressed, but it is difficult to compensate the unevenness of the recording medium and the unevenness of electrical properties.

On the other hand, a monochromatic toner image formed independently on each of a plurality of photoconductors is an intermediate medium whose physical properties are controlled without unevenness, that is, an intermediate transfer body (for example, belt, drum).
A method is known in which a color image is transferred onto a recording medium by superimposing and transferring the color image onto the recording medium. In this case, a uniform image without unevenness can be obtained on the intermediate transfer member. However, the toner image on the intermediate transfer member is multi-layered, and has three or more layers in a large number and one layer or less in a small number, and these toner layers are electrostatically collectively and uniformly formed on a recording medium typified by paper. It is difficult to apply a constant electric field to transfer
As a result, Et becomes non-uniform. Therefore, in this electrostatic transfer method, all the color images overlaid on the intermediate transfer member are not transferred to the recording medium, and some of them remain on the intermediate transfer member. Further, the residual amount varies depending on the thickness of the toner layer formed on the intermediate transfer member. Therefore, the color balance of the color image obtained on the recording medium is deviated, and the desired color image cannot be obtained. In addition, a recording medium such as paper has irregularities on its surface,
The image quality is deteriorated because the toner does not completely adhere to the intermediate transfer member, a non-uniform gap is generated, the transfer electric field is disturbed, and the Coulomb repulsive force between the powder toners causes the toner to scatter.

To address this problem, Japanese Patent Publication No. 46-4167
No. 9 discloses a method in which a toner image formed on a photoconductor is adhesively transferred to an intermediate transfer member, and then the toner is melted and thermally transferred from the intermediate transfer member to a recording medium. In this method, since the toner image is transferred to the recording medium in a non-electrostatic manner, the deterioration of the image quality in the electrostatic transfer process as described above is less likely to occur.

Further, for example, in Japanese Unexamined Patent Publication No. 2-108072, after toner images of different colors are electrostatically superposed and transferred onto an intermediate transfer member, and then a multi-color multiple toner image is melted on the intermediate transfer member. , A technique for obtaining a color copy by transferring the fused multiple toner image to a recording medium is disclosed.
This method also non-electrostatically transfers the toner image to the recording medium, so that the deterioration of the image quality as described above is less likely to occur (this method is called a transfer fixing method).

An image forming apparatus using this transfer fixing method is disclosed in US Pat. No. 2,990,278 and Japanese Patent Laid-Open No. 5-1.
9642, JP-A-5-107950, JP-A-5-249798, etc., the intermediate transfer member and the recording medium are closely contacted so that the transfer of the toner image from the intermediate transfer member to the recording medium is completed. After heating and pressurizing, a technique is disclosed in which the recording medium is peeled off from the intermediate transfer body after cooling until the cohesive force between the toners becomes larger than the adhesive force between the toner and the intermediate transfer body (at least below the melting point). ing. According to this, it is possible to obtain a high-quality image having high toner transfer efficiency, good color balance, high gloss, and excellent toner transparency. In order to make effective use of this advantage, continuous research is being conducted especially on the construction of the uppermost layer of the intermediate transfer member.

For example, as a material having heat resistance and toner releasability, a silicone resin, a fluorine resin, or a fluorine resin dispersed in a fluorine rubber as used in a conventional fixing device. Things are being considered.

In the apparatus using the intermediate transfer member, since the intermediate transfer member is in contact with the surface of the photosensitive member, a releasing agent such as silicone oil is attached to the surface of the intermediate transfer member like the conventional fixing device. Can't give. Therefore, for the purpose of preventing the toner image from being offset on the surface of the intermediate transfer body during transfer fixing and reducing defects in image quality, the material of the surface of the intermediate transfer body has good releasability from the toner. Silicone rubber, which has advantages, is often used.

[0011]

However, even when an intermediate transfer member coated with silicone rubber is used, the following problems occur.

On the surface of the photosensitive member, a large number of isolated toners called fog toners exist in addition to the toner image to be an image. When the toner image on the surface of the photoconductor is directly transferred to the recording paper by using the electrostatic force, the selective transfer using the electrostatic force is performed on the fog toner, and the level is unrecognizable even if the transfer is performed on the recording paper. However, when the above intermediate is used, the fog toner is almost transferred to the surface of the intermediate transfer member due to the elasticity and adhesiveness of the silicone rubber. As a result, there is a problem that the image quality deteriorates.

In the case of using a silicone rubber, if the toner image once melted is cooled to a temperature below the melting point and then peeled off, no offset phenomenon occurs on the surface of the intermediate transfer member. The toner image on the recording medium peeled off from the surface becomes the surface shape of the intermediate transfer member. In other words, the surface of the toner image roughly copies the surface shape of the intermediate transfer body like a mold, and if the surface of the intermediate body is smooth, the toner image becomes very glossy, that is, gloss is high, while If the body surface is rough or cloudy, the toner image has a low gloss. Therefore, in order to obtain high gloss, it is necessary to keep the surface of the silicone rubber smooth.
This is due to the good leveling properties of silicone rubber,
It is easily achievable. However, in that case, another problem arises. That is, in order to copy and print a color image, toner images of three or more colors are superposed and a color is developed. At that time, registration of each color, that is, a positional deviation has an important influence on image quality. Then, the following problem occurs.

A smooth intermediate transfer member coated with silicone rubber has a high coefficient of friction with a very smooth surface such as a photoconductor. As a result, a slip occurs between a member (for example, a drive roll) that drives the intermediate transfer body and the back surface of the intermediate transfer body. When the friction coefficient between the drive roll and the back surface of the intermediate transfer member is increased to increase the driving force,
It is good for the intermediate transfer member if the direction of the force received from the drive roll and the direction of the force received from the photoconductor are the same, but usually there is also a problem with mechanical accuracy, and those directions are not exactly the same. , The intermediate transfer member is wavy due to mutual pulling, and the flat surface cannot be maintained. As a result, there is a problem that the toner image on the surface of the photoconductor cannot be faithfully transferred and an image defect is generated.

Usually, in order to reduce the friction coefficient of rubber,
A method of roughening the surface is used. There are several known methods. One of them is a method of roughening the spray coating by changing the conditions such that the silicone rubber during spraying is not easily atomized, for example, the coating conditions such as temperature, humidity, distance from the spray gun, and the viscosity of the silicone rubber. . However, in this method, even if fine undulations are generated, the surface of the undulations remains smooth, so that the friction coefficient does not decrease significantly. The other is a blasting process in which grains of sand or steel are applied, and this method makes the rubber surface as a whole rough like recesses. However, the coefficient of friction is only slightly reduced, and the transfer rate of fog toner cannot be reduced. Moreover, not only the gloss of the image is greatly reduced, but also it is difficult to uniformly roughen the image, resulting in unevenness, which greatly deteriorates the image quality. Other coating methods such as blade coater and dipping are also used, but even if both have large undulations, the surface becomes a mirror surface, which is a problem to be overcome by the inventors of the present invention. I can't solve it.

There are some prior arts that describe the surface roughness of the intermediate transfer member. JP-A-59-50473 describes that the surface roughness is controlled by spray coating, but the friction coefficient with the photoconductor is set so that it can be controlled by sliding the intermediate transfer member with respect to the photoconductor. Neither can it be lowered or the fog toner transfer can be lowered to an unrecognizable level. In addition, JP-A-59-202477
JP-A-5-19642, JP-A-5-333711
JP-A-6-102782 and JP-A-7-43992.
JP-A-8-185061 exists, but the purpose is to improve the durability of rubber on the surface of an intermediate transfer member, improve transferability, improve image gloss, prevent transfer omission, and improve adhesion to a transfer material. Roughness of the intermediate transfer body is specified for the purpose of preventing offset of the toner to the surface of the intermediate transfer body and for improving the storability of the release material for preventing the adverse effect of the release material such as oil. , Even if the surface roughness disclosed in those publications is achieved, the high gloss desired as a color image of the intermediate transfer member, which is a problem of the present inventors, is affected by the unevenness of the surface of the intermediate transfer member on the image. There is a need to achieve this without visual inspection, and to have good drive running controllability of the intermediate transfer member (that is, the coefficient of friction with the photoconductor is low) to prevent image misalignment, and to reduce the transfer rate of fog toner. All satisfied Can not.

Therefore, in view of the above drawbacks, the first object of the present invention is to form an image by transferring and fixing a toner image from a photoreceptor to a recording medium by using an intermediate transfer member having a surface of silicone rubber or the like. In the device, the image gloss can take a desired high value for a color image, and the friction coefficient with the photoconductor is lowered to facilitate the drive / run control of the intermediate transfer member, and further, the transfer rate of the fog toner is reduced to deteriorate the image quality. It is to provide an intermediate transfer member capable of preventing

A second object of the present invention is to provide a suitable method for producing the intermediate transfer member.

A third object of the present invention is to provide an image forming apparatus utilizing the intermediate transfer member.

[0020]

The above first object can be achieved by the following intermediate transfer member. That is, the photoreceptor on which the electrostatic latent image is formed is developed with a developer containing toner, the developed toner image is primarily transferred to an intermediate transfer body, and then the toner image that is primarily transferred is
An intermediate transfer member used in an image forming method of contacting a recording medium and transferring a toner image to the recording medium at least by heating, the surface to which the image is primarily transferred (hereinafter, also referred to as image primary transfer surface) is The convex portion on the smooth surface is an intermediate transfer member in which they (that is, the smooth surface and the convex portion) are scattered so that they can be distinguished from each other.

In the present invention, "the smooth surface and the convex portion are distinguishable" means that when the enlarged image or enlarged photograph of the image primary transfer surface is observed, the smooth surface and the convex portion are objectively observed. It is identifiable (that is, the person skilled in the art can recognize the existence of the two types without any doubt). This applies everywhere in the observation area. Therefore,
The image primary transfer surface in the present invention is distinct from unevenness, but it is clearly different from a surface where a smooth surface is not clear, that is, a surface where the surface is sandblasted.

According to the present invention, since the individual convex portions existing on the image primary transfer surface are scattered, the image transferred from the surface to the recording medium is less affected by the convex portions (that is, The concave portions of the image after transfer corresponding to the convex portions become invisible) and have high gloss. On the other hand, due to the convex portion, the friction between the intermediate transfer member and the photosensitive member is reduced,
Also, the transfer of fog toner is prevented. As a result, the above object can be achieved.

The above-mentioned first object can also achieve the following invention by the same or similar action.

That is, in the intermediate transfer member used in the above-mentioned image forming method, the surface on which the image is transferred is a smooth surface with convex portions scattered so that they can be distinguished. , The relationship between the ratio [Cin (%)] of the area of the smooth surface of the intermediate transfer member and the height [h (μm)] of the convex portion is expressed by the empirical formula h ≦ 19 · (1-Cin / 100) ^{−1 / 2} −24.5 ... (1), wherein the height of the convex portion is 2 μm or more. Cin is, for example, 50 to 95%.

Further, in the intermediate transfer member used in the above-mentioned image forming method, the surface on which the image is transferred is a smooth surface on which convex portions are scattered, and the presence of the convex portions. Thus, the intermediate transfer member, wherein the image primary transfer surface has a coefficient of friction smaller than that in the absence thereof.

The second object is a method for manufacturing the intermediate transfer member, wherein a surface corresponding to the surface to which an image is primarily transferred is formed on the surface of the intermediate transfer member before the surface is finally cured. It can be achieved by a manufacturing method having a step of pressing the mold.

The third purpose is to record a photosensitive member, a developing device for supplying a developer containing toner to the photosensitive member, an intermediate transfer member in contact with the photosensitive member, and a recording medium sent to the intermediate transfer member for contact. At least a medium conveying means and a heating means for heating a contact portion thereof are provided, an electrostatic latent image is formed on a photoconductor by using light, and the electrostatic latent image is developed by a developer containing toner, The developed toner image is primarily transferred to an intermediate transfer body, and then the primary transferred toner image is
In an image forming apparatus that carries out an image forming method in which a toner image is transferred to a recording medium by contacting the recording medium with at least heating, the surface of the intermediate transfer member on which the image is primarily transferred has a convex portion on a smooth surface. To make them distinguishable,
It can be achieved by an image forming apparatus that is a scattered surface.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

FIG. 1 is for explaining one embodiment of the present invention, and is a schematic view showing an outline of an intermediate transfer member according to the present invention and an image forming apparatus using the intermediate transfer member.

The intermediate transfer member 50 is belt-shaped and has a two-layer structure of a base layer and a surface layer. Materials that can be used as the base layer (base material) of the intermediate transfer member include polyimide, polyether ether ketone (PEEK), polyarylene sulfide (PAS), polyimide amide, polyether sulfone (PES), polyether nitrile ( PE
N), thermoplastic polyimide, etc. are mentioned, but polyimide is preferable from the viewpoint of heat resistance and mechanical strength.

The surface layer preferably has a volume resistivity of 10 ¹² Ωcm to 10 ¹⁵ Ωcm in order to electrostatically transfer the toner image from the photosensitive member to the intermediate transfer member without image disturbance.

When performing simultaneous transfer and fixing from the intermediate transfer body to a recording medium (paper or the like), the toner image is sandwiched to improve the adhesion between the intermediate transfer body and the recording medium, and the releasability and heat resistance of the toner are taken into consideration. The surface layer is preferably a silicone rubber coat layer. However, depending on the case, a fluororesin, a coat layer in which a fluororesin is dispersed in fluororubber, or the like can be used. Usually, the rubber hardness of the surface layer is 20 to 70.
The thickness and thickness are 20 to 300 μm.

In FIG. 1, a belt-shaped intermediate transfer member 50.
Is arranged vertically above and below the rollers 5-1 and 5-2, and horizontally separated from both the rollers 5-1 and 5-2, and between the rollers 5-1 and 5-2. It is supported by a heating roll 2 having a diameter substantially equal to the distance between the highest point and the lowest point, and is rotatable in the arrow direction. An intermediate transfer member is sandwiched between the heating roll 2 and the pressure roll 3
Are facing and arranged. As the heating and pressing roll, a metal roll or a roll having a heat resistant elastic layer such as silicone rubber can be used. A heat source is arranged inside the heating roll, and its heating temperature is
The toner temperature in the heating area is set and controlled so as to be higher than the toner melting temperature. The heating roll 2 and the pressure roll 3 may be arranged in reverse, and the pressure roll 3 may be a heating roll having a heat source inside.

The drum-shaped photoconductors 1-1, 1-2, 1-3, 1-4 are parallel to each other in contact with the surface of the upper moving surface of the intermediate transfer member 50 and along the belt moving direction. The chargers 10-1 and 10- that are arranged and installed side by side
2, 10-3, 10-4 can be uniformly charged. As the photoconductors 1-1, 1-2, 1-3, 1-4, in addition to various inorganic photoconductors (Se, a-Si, a-SiC, CdS, etc.), various organic photoconductors can be used. it can.

A light beam scanning device 2 for turning on and off each photoconductor by a light beam pulse width modulation device according to a density signal.
0 is arranged across each photoconductor. Developers 11, 12, 13, and 14 containing black, yellow, magenta, and cyan toners are arranged on the respective photoconductors. The color toner is composed of a thermoplastic binder containing dyes such as yellow, magenta and cyan, and known materials can be used. The amount of toner on the recording paper for each color is about 0.4 m depending on the content of the dye.
g / cm ² ~0.7mg / cm ² to become such, the exposure condition or the developing conditions are set.

Photoreceptors 1-1, 1-2, 1-3, 1-4
Underneath, via the intermediate transfer body 50, the transfer device 50-1,
50-2, 50-3, 50-4 are arranged.

Between the pressure roll 2 and the pressure roll 3,
The recording paper P from the tray 6 can be fed.

The recording paper is sandwiched between the pressure roll 2 and the pressure roll 3.
The holding part (nip part), that is, the heating area,
The intermediate transfer body 50, the toner image, and the recording paper P are sufficiently dense.
It does not wrinkle on the recording paper P as it is worn
It is set so that it does not occur. The nip pressure is
1 × 10 for the above toner^Five Pa ~ 1 x 10 ⁶ 
The range of Pa is suitable.

Immediately after passing through the heating area, a heating area outlet cooling device 7 facing the recording paper P is provided. The heating area outlet cooling device 7 is intended to lower the toner temperature immediately after passing through the heating area, and the same effect can be obtained by cooling not only the paper side but also immediately after passing through the heating area from the intermediate transfer body side. The same applies when the cooling is performed from both sides immediately after passing through the heating area. By cooling, the cohesive force of the toner is increased and the toner is prevented from being offset to the intermediate transfer body 50 at the time of peeling.

The cooling device 4 disposed below the lower moving surface of the intermediate transfer member cools the intermediate transfer member 50 and the recording paper P which are integrally conveyed from the heating area.

The device having the above structure functions as follows. Each photoconductor is exposed by the light beam scanning device 20 according to an image signal, and an electrostatic latent image is formed. The electrostatic latent images on the photoconductors are developing units 11, 12, 13, and 14 containing black, yellow, magenta, and cyan toners, respectively.
The toner image of each color of a so-called digital image, which is developed by the above method and represents the density by area modulation, is formed on each photoreceptor. The toner images of the respective colors are sequentially transferred to the transfer devices 50-1 and 50.
-2, 50-3, and 50-4, primary transfer is performed to the intermediate transfer body 50, and toner images of a plurality of colors are formed on the intermediate transfer body 50.

The pressure roll 3 is a recording paper P from the tray 6.
As the paper is fed, it is pressed against the heating roll 2. After that, the intermediate transfer body 50 holding the toner images of the plurality of colors and the recording paper P
However, the heating roll 2 and the pressure roll 3 are matched in timing.
It moves between and is heated under pressure. The toner heated to the melting temperature or higher is softened and melted, penetrates into the recording paper P, and then solidifies to perform transfer fixing.

The intermediate transfer member 50 and the recording paper P cooled by the heating area outlet cooling device 7 and the cooling device 4 are conveyed, and the recording paper P is stiff on the roll 5-2 having a small radius of curvature. By this, the toner is separated from the intermediate transfer member 50 together with the toner, and a color image is formed. The surface of the toner image transferred and fixed on the recording paper P has an intermediate transfer member 50.
The surface is smoothed and becomes high gloss.

The image primary transfer surface of the intermediate transfer member according to the present invention used in the image forming apparatus as described above is
The convex portions are scattered on the smooth surface. Then, the intermediate transfer member is defined by the combination of the requirements described below.

The smooth surface and the convex portion on the image primary transfer surface are scattered in a distinguishable manner. Also, due to the presence of the convex portion, from the friction coefficient when it does not exist,
The image primary transfer surface has a low coefficient of friction.

The height of the convex portion is preferably 2 μm or more,
It is 12 μm or less, more preferably 3 μm or more and 9 μm or less.

Further, the interval between the convex portions is preferably
It is 10 μm or more and 200 μm or less.

Furthermore, the ratio [Cin (%)] of the area of the smooth surface on the image primary transfer surface and the height [h (μ
m)] preferably satisfies the empirical formula h ≦ 19 · (1-Cin / 100) ^−1/2 −24.5 ·· (1) (see Examples below).

The shape and arrangement pattern of the convex portions are not limited, and various patterns can be adopted including those with or without order. For example, the shapes shown in FIGS.

FIG. 2 is a sectional view of the intermediate body. This intermediate body has a base layer 21 on which a silicone rubber 24 having a smooth portion 22 and a convex portion 23 is provided. Other FIGS. 3 to 7
FIGS. 6A to 6C are diagrams showing a pattern of convex portions as viewed from above. As shown in FIG. 3 or 4, the convex portions may be isolated (FIG. 3 shows the same pattern in each column and each row of the convex portions,
Indicates a pattern in which the convex portions are offset every other line),
It may be linear as shown in FIGS.
Is a line perpendicular to the longitudinal direction of the intermediate body, FIG. 6 is a line parallel to the direction, and FIG. 7 is a pattern of lines oblique to the direction).

Further, it is preferable that the heights of the convex portions are as uniform as possible, but this is not always the case.

Although any method can be used to obtain the intermediate transfer member of the present invention, it can be prepared by, for example, embossing. For example, a mold in which a minute recess is formed on a smooth surface by processing a metal may be used, but the following method can also be preferably used.

As shown in FIG. 8, a toner image 81 having no toner (resultingly a concave portion) is transferred and fixed to a recording medium (paper or the like) 82 at a position corresponding to the convex portion of the intermediate transfer member, and the recording is performed. This is a method in which the medium 82 is used as an embossing mold and is pressed against an intermediate transfer member before being cured (that is, an intermediate transfer member before rubber or resin is hardened).

At this time, the interval between the recesses, the depth of the recesses, and the size of the recesses are created by changing the number of overlapping toners, the number of lines / inch, and the area ratio of the toner image. For example, when toner is used to form a convex portion on the surface of the intermediate transfer member by using a paper type having one color, 200 lines / inch, and a toner image area ratio of 85%, the convex portion on the surface of the intermediate transfer member may be formed depending on the transfer fixing condition. Height is 3μm to 4μm, spacing is 100μm
To 125 μm, and the area ratio of the smooth portion can be changed from 85% to 90%. At this time, the roughness of the smooth portion is 0.10.
μmRa, and the gloss of this smooth part is 1 from FIG.
It exceeds 00%.

The intermediate transfer member may be a drum or the like in addition to the above belt.

[0056]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples on which the invention was completed.

In these examples, a polyimide film having a thickness of 80 μm and containing carbon black was used as the base layer of the belt-shaped intermediate transfer member, and the toner image was electrostatically transferred from the photosensitive member to the intermediate transfer member without image disturbance. Therefore, the volume resistivity of the base layer was adjusted from 10 ⁸ Ωcm to 10 ¹² Ωcm by changing the amount of carbon black added.

For the surface layer of the intermediate transfer member, a silicone rubber having a thickness of 50 μm (specific materials will be described later) was coated on the base layer.

Color toner to be used The amount of toner for each color on the recording paper was set so that the content of each dye was 0.65 mg / cm ² .

The device used is a device substantially corresponding to the device shown in FIG. As a roll corresponding to the heating / pressurizing roll shown in FIG. 1, a laminate of silicone rubber having a hardness of 55 degrees and a thickness of 3 mm on a hollow aluminum roll was used, and a halogen lamp was used as a heat source inside the heating roll. used. The nip pressure is 5.5 × 10.
^It was set to ⁵ Pa. [Comparative Example] The present inventors firstly uniformly roughened the surface of the intermediate transfer member and examined the relationship between the surface roughness and the gloss. As a method of uniformly roughening the silicone rubber surface,
A material with uniform roughness on the surface of silicone rubber, in fact, an embossing method in which a wrapping film (trade name: Imperial Wrapping Film, made by Sumitomo 3M) is pressed (that is, the surface of the wrapping film is projected onto the silicone rubber surface) ) Tried.

Specifically, the surface of a conductively treated polyimide belt has a silicone rubber having a rubber hardness of 40 Hs (trade name: Silicone rubber KE4895, manufactured by Shin-Etsu Chemical Co., Ltd.) and a silicone rubber having a rubber hardness of 65 Hs (prototype, Toray Dow Corning). -Silicone Co., Ltd.) was coated to a thickness of about 50 μm, a wrapping film was placed on the surface before cross-linking, peeled off after a certain period of time, and the remaining cross-linking step was performed. At that time, the number of the wrapping film, the timing of placing it on the silicone rubber surface, the time, etc. were changed to prepare intermediate transfer bodies having various surface roughnesses. FIG. 9 shows the result of examining the relationship between the gloss and the roughness of the image by using the intermediate transfer member thus created by embossing.

Here, the apparatus and the like used for image formation and evaluation will be specifically shown. Evaluation Copier Product name: Acolor 935, toner manufactured by Fuji Xerox Co., Ltd. Toner for Acolor 935, paper manufactured by Fuji Xerox Co., Ltd. Product name: J-coated paper, Fuji Xerox Co., Ltd. gloss meter Gloss Meter Model GM-26D for 75 ° Murakami Color Research Laboratory Surface Roughness Meter Profile Micrometer VF7500 / 7510, manufactured by Keyence Co., Ltd. From FIG. 9, it can be seen that there is no great difference in gloss due to the difference in hardness of the silicone rubber. It is considered that this is because the recording paper on which the toner image is transferred and fixed is peeled off from the intermediate transfer body after being cooled.

By the way, it is said that the desired high gloss for a color image is 70% or more. According to FIG. 9, when the entire surface of the intermediate transfer member is uniformly roughened, the surface roughness is smaller than Ra 0.3 μm. There must be.

Next, FIG. 10 shows the results of examining the friction coefficient of the embossed intermediate transfer member with the photosensitive member. in this case,
A difference occurs depending on the rubber hardness, and the higher the rubber hardness, the lower the friction coefficient. It is considered that when the rubber hardness is low, it is easily deformed when pressure is applied. The friction coefficient measuring device used is Peeling / Slipp manufactured by Heidon.
ing / Scratching Tester Hei
It is don-14. The speed was 100 mm / sec and the load was 10 gf / mm.

Here, the allowable range of the friction coefficient between the intermediate transfer member and the photosensitive member will be described. FIG. 11 is an explanatory diagram showing a relationship of forces acting on the photoconductor 111, the intermediate transfer belt 112, and the intermediate transfer body driving roll 113 that drives the intermediate transfer belt 112. There is a limit to the mechanical working accuracy, a speed difference occurs between the speed of the surface of the photoconductor 111 and the moving speed of the intermediate transfer belt 112, and the photoconductor 111 and the drive roll 11
The situation is shown when there is an error with respect to the parallel of 3.

The friction coefficient μ between the photoconductor 111 and the intermediate transfer belt 112 is between the photoconductor 111 and the intermediate transfer belt 112.
And a frictional force Fs determined by the transfer pressure Fn acts.
Here, the transfer pressure Fn is the sum of the electrostatic attraction force and the mechanical pressing force that accompany transfer, and is generally at least 0.5 g / m.
It is said to require a value of m ² . In addition, between the back surface of the intermediate transfer belt 112 and the intermediate transfer roller driving roll 113,
A conveying force Fd for moving the intermediate transfer belt 112 acts. On the other hand, the intermediate transfer belt 112 itself has bending rigidity Fr.

When the belt bending rigidity Fr is sufficient,
When the frictional force Fs is larger than the transporting force Fd, slippage occurs between the intermediate transfer body driving roll 113 and the back surface of the intermediate transfer body belt 112, and the moving speed of the intermediate transfer body belt 112 becomes uncontrollable, and the expansion and contraction of an image or Color misregistration will occur.

On the other hand, when the conveying force Fd is sufficient with respect to the frictional force Fs, but the belt bending rigidity Fr is insufficient, the intermediate transfer belt 112 is wavy, and the moving speed of the intermediate transfer belt 112 increases. The control becomes uncontrollable, and expansion and contraction of the image and misregistration of color overlap occur.

FIG. 12 shows whether control is actually possible when the friction coefficient μ between the photosensitive member and the intermediate transfer member (belt) or the thickness of the belt is changed. From this, when the belt is thin and the rigidity is low, when the belt bends due to the corrugation of the belt, and when the belt bending rigidity is increased due to the thickness of the belt, etc., the threshold is determined by the slip of the intermediate transfer member drive roll. In any case, it can be seen that control is not possible unless the friction coefficient is 1.2 or less. This result is the transfer pressure Fn.
Is the result when the minimum value is 0.5 g / mm ² , and it is desirable that the coefficient of friction is smaller.

Therefore, from FIG. 10 in which the coefficient of friction of the embossed intermediate transfer member with the photosensitive member was examined, in order to reduce the value to 1.2 or less, the surface roughness of the intermediate transfer member varies slightly depending on the rubber hardness. Is required to be greater than 0.5 μmRa.

Next, FIG. 13 shows the transfer rate of the fog toner of the embossed intermediate transfer bodies. The hatched portion in the figure is the transfer rate in the case of conventionally transferring the toner image on the photosensitive member directly onto the recording medium by electrostatic transfer. Therefore, in order to obtain the conventional level, the roughness of the surface of the intermediate transfer member must be about 0.6 μmRa or more.

From the above results, when the surface of the intermediate transfer member is uniformly roughened to a surface roughness of 0.6 μmRa or more, the friction coefficient is 1.2 or less and the fog toner transfer rate is equal to or less than that of the conventional electrostatic transfer. Can be achieved, but the gloss is reduced to 40%
It turns out that it becomes the following. [Example (some control examples)] As a result of the above, the present inventors
Rather than uniformly roughening the surface of the intermediate transfer member, an attempt was made to leave it with a smooth surface. That is, 70% or more of high gloss is obtained by leaving a smooth high gloss surface on the surface of the intermediate transfer body at a high area ratio. The objective was to lower the friction coefficient and the fog toner transfer rate.

What must be taken into consideration here is that the convex portion on the surface of the intermediate transfer member forms a concave portion on the surface of the toner image in the image on the recording medium. Normally, the visual function (VT) shown in FIG.
From the figure of F), at least 150 lines / inch or more are required. That is, the distance between the convex portions is preferably 170 μm or less. However, as a result of sensory evaluation as a distance that is not noticeable even when visually recognized, it was found that the distance may be about 200 μm. Therefore, FIG. 15 shows the result of evaluation of how much the area of the smooth portion is actually set so that the gloss of the image becomes 70% or more by changing the height of the convex portion. The result is that, in practice, a recording paper having the above-mentioned toner image is used as a mold to form an intermediate transfer member coated with silicone rubber having a rubber hardness of 40 Hs, and the area of the smooth portion and the height of the convex portion are changed to change the toner. It was obtained by transferring and fixing the image on a recording paper and measuring the gloss.

From FIG. 15, in order to obtain a desired high gloss for a color image, it was found that the relationship between the height of the convex portion and the area ratio of the smooth portion should be above the solid line in FIG. .

The relationship between the area ratio of the smooth portion and the height of the convex portion is expressed by the following equation. Height of convex portion [h] ≦ 19 · (1−Cin / 100) ^−1/2 −24.5 (Equation (1) Unit of height of convex portion: μm Unit of Cin:% For example, smooth portion If the area ratio (Cin) is 85%, the height (h) of the convex portion may be about 10 μm or less.

The distance between the convex portions cannot be largely changed depending on the conditions under which the mold for pressing the surface of the intermediate transfer member is formed.
From m to around 200 μm, there was no great difference in the relationship between the gloss value and the area ratio of the smooth portion and the height of the convex portion in FIG.

Next, FIG. 16 and FIG. 17 show the measurement results of the friction coefficient with the photoconductor and the transfer rate of the fog toner, which are the other two required items. These are 40Hs and 65
In the intermediate transfer member of the silicone rubber surface of Hs, the friction coefficient and the fog with the photoconductor are used by using the intermediate transfer member having the convex portions of various heights with the area ratio of the smooth portion between 55% and 95%. The transfer rate of the toner is measured.

From FIG. 16, the coefficient of friction with the photosensitive member originally depends on the area ratio of the smooth portion. From this measurement, when the area ratio of the smooth portion is 55% to 95%, the height of the convex portion is 2 μm or more. It was found that the friction coefficient was 3.0 or less.

The area ratio of the smooth portion being 0.55 or more means that the area ratio of the convex portion is 0.45 or less. Since the contact area is about ⅓, the friction coefficient should simply be reduced to about ⅓ of that on a smooth surface. However, it is considered that the reason why this is not the case is the deformation of the silicone rubber. The friction coefficient needs to be 1.2 or less from the viewpoint of driving and driving control of the intermediate transfer member, but from this experiment, even if the variation in the area ratio of the smooth portion is taken into consideration, the height of the convex portion is 2 μm or more. It turned out to be good.

Regarding the transfer rate of the fog toner, the experimental result shows that if there is a convex portion to some extent, the area ratio of the smooth portion is not so much influenced, and if the height of the convex portion is also 2 μm or more, it is caused by the conventional electrostatic force. It has been found that the transfer rate decreases to the same level or less in the case of direct transfer to the recording medium. The average particle diameter of the color toner used this time is about 7 μm, and it also comes into contact with the recessed smooth portion. Nevertheless, the transfer rate of the fog toner decreased because the pressure applied to the fog toner from the smooth portion of the intermediate transfer member decreased due to the presence of the convex portion, and therefore the adhesion force of the fog toner to the photoconductor was decreased. May be stronger than the adhesive force with the surface of the intermediate transfer body,
It is considered that the transfer rate of the entire fog toner has decreased.

From the above results, when the friction coefficient between the intermediate transfer member and the photosensitive member is reduced (in this embodiment, 1.2 or less), a smooth portion is provided on the silicone rubber on the surface of the intermediate transfer member. A convex portion with a height of 2 μm or more is provided there, and the formula (1)
The height of the convex portion and the area ratio of the smooth portion may be determined so that By doing so, the gloss of the image is high and the transfer rate of the fog toner can be made equal to or lower than the transfer rate in the case of the direct transfer to the recording medium by the conventional electrostatic force.

The desired gloss for the color image is 70%, but if 60% is acceptable, for example, from the relationship between the area ratio of the smooth portion and the height of the convex portion in FIG.
The required area ratio of the smooth portion and the height of the convex portion may be obtained.

The present invention is not limited to the above embodiments, but should be determined by the gist of the present invention and its idea.

[0084]

According to the present invention, in image formation in which a toner image is transferred and fixed from a photoreceptor to a recording medium using an intermediate transfer member, a high gloss desired as a color image can be obtained, and the intermediate transfer is performed to prevent image shift. The drive / run controllability of the body can be favorably maintained. In addition, the transfer rate of the fog toner on the photoconductor can be reduced to the same level as or lower than the conventional direct transfer to the recording medium by electrostatic force.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus using an intermediate transfer member according to the present invention.

FIG. 2 is a schematic cross-sectional view of an example of an intermediate transfer member according to the present invention.

FIG. 3 is a schematic plan view of an example of an intermediate transfer member according to the present invention.

FIG. 4 is a schematic plan view of another example of the intermediate transfer member according to the present invention.

FIG. 5 is a schematic plan view of still another example of the intermediate transfer member according to the present invention.

FIG. 6 is a schematic plan view of another example of the intermediate transfer member according to the present invention.

FIG. 7 is a schematic plan view of still another example of the intermediate transfer member according to the present invention.

FIG. 8 is a schematic view showing an example of a die for embossing the surface of the intermediate transfer member so that the convex portions are scattered on the smooth portion.

FIG. 9 is a view showing the relationship between the roughness of the surface of an intermediate transfer member provided with unevenness and image gloss.

FIG. 10 is a diagram showing the relationship between the roughness and the coefficient of friction of the surface of an intermediate transfer member on which unevenness is uniformly provided.

FIG. 11 is a schematic diagram showing a relationship between forces acting on an intermediate transfer member and an intermediate transfer member driving roll that drives the intermediate transfer member.

FIG. 12 is a diagram showing a relationship of running controllability of the intermediate transfer body when the friction coefficient between the intermediate transfer body and the photoconductor is changed.

FIG. 13 is a diagram showing the relationship between the roughness of the surface of an intermediate transfer member provided with unevenness and the transfer rate of fog toner.

FIG. 14 is a diagram showing a relationship between a spatial frequency and a visual function value.

FIG. 15 is a diagram showing the relationship between the area ratio of the smooth portion of the surface of the intermediate transfer member, which is embossed so that the convex portions are scattered on the smooth portion, and the image gloss when the height of the convex portion of the surface is changed. Is.

FIG. 16 is a diagram showing the relationship between the height of the protrusions on the surface of the intermediate transfer member, which is embossed so that the protrusions are scattered on the smooth portion, and the friction coefficient.

FIG. 17 is a diagram showing the relationship between the height of the convex portions on the surface of the intermediate transfer member, which is embossed so that the convex portions are scattered on the smooth portion, and the transfer rate of the fog toner.

[Explanation of symbols]

1 1-1, 1-2, 1-3, 1-4 Photoreceptor 2
Heating roll 3 Pressure roll 4 Cooling device 5
0 Intermediate transfer member 5-1, 5-2, 5-3 Roll 6
Paper tray 7 Heating area outlet cooling device 10-1, 10-2, 10-3, 10-4 Charging device 11, 12, 13, 14 Developing device 20 Exposure device P Recording paper

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Riki Ando 430 Nakai-cho, Nakai-cho, Ashigaragami-gun, Kanagawa Green Tech Nakakai Fuji Xerox Co., Ltd. (72) Inventor Kaku Kitano 430 Sakai, Nakai-cho, Ashigarashami-gun, Kanagawa Green Tech Nakakai Fuji Xerox Co., Ltd. Yasuo Sakaguchi 1600 Takematsu, Minamiashigara City, Kanagawa Fuji Xerox Co., Ltd. (56) References JP 59-50475 (JP, A) JP 4-303870 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114

Claims (18)

(57) [Claims] 1. A photosensitive member on which an electrostatic latent image is formed is developed with a developer containing toner, the developed toner image is primarily transferred to an intermediate transfer member, and then the primary transferred toner. An intermediate transfer member used in an image forming method in which an image is brought into contact with a recording medium and a toner image is transferred onto the recording medium at least by heating, and the surface on which the image is primarily transferred has a smooth surface and a convex portion. , Intermediate transfer bodies, which are the surfaces that are scattered, distinguishable from each other. 2. The height of the convex portion is 2 μm or more and 12 μm or more.
The intermediate transfer member according to claim 1, which has a thickness of m or less. 3. The distance between the convex portions is 10 μm or more, 20
The intermediate transfer member according to claim 2, which has a size of 0 μm or less. 4. The relationship between the ratio [Cin (%)] of the area of a smooth surface on the surface to which the image is primarily transferred and the height [h (μm)] of the convex portion is expressed by an empirical formula h ≦ 19. The intermediate transfer member according to claim 2, which satisfies (1-Cin / 100) ^-1/2 -24.5 ... (1). 5. The intermediate transfer member according to claim 4, wherein the Cin is 50 to 95%. 6. The gloss of the surface on which the image is primarily transferred is 6
The intermediate transfer member according to claim 5, which is 0% or more. 7. The gloss of the surface on which the image is primarily transferred is 7
The intermediate transfer member according to claim 5, which is 0% or more. 8. The intermediate transfer member according to claim 1, wherein the surface on which the image is primarily transferred is made of silicone rubber. 9. A photosensitive member on which an electrostatic latent image is formed is developed with a developer containing toner, the developed toner image is primarily transferred to an intermediate transfer member, and then the primary transferred toner is transferred. An intermediate transfer member used in an image forming method in which an image is brought into contact with a recording medium and a toner image is transferred onto the recording medium at least by heating, and the surface on which the image is primarily transferred has a smooth surface and a convex portion. , Which are the surfaces that are scattered so that they can be distinguished, and the ratio [Cin (%)] of the area of the smooth surface on the surface to which the image is primarily transferred and the height [h (μm)] of the convex portion The following relationship is satisfied by the empirical formula h ≦ 19 · (1-Cin / 100) ^−1/2 −24.5 (1), and the height of the convex portion is 2 μm or more. 10. The intermediate transfer member according to claim 9, wherein the Cin is 50 to 95%. 11. A photoreceptor on which an electrostatic latent image is formed is developed with a developer containing toner, the developed toner image is primarily transferred to an intermediate transfer body, and then the transferred toner image is transferred. Is an intermediate transfer member used in an image forming method in which a toner image is transferred to a recording medium at least by contacting it with a recording medium, and the surface to which the image is primarily transferred has a smooth surface with convex portions, The intermediate transfer member, which is a scattered surface, has a coefficient of friction smaller than a coefficient of friction when the image does not exist due to the presence of the convex portion. 12. The intermediate transfer member according to claim 11, wherein the smooth surface and the convex portions are dispersed so as to be distinguishable from each other. 13. The relationship between the ratio [Cin (%)] of the area of a smooth surface on the surface to which the image is primarily transferred and the height [h (μm)] of the convex portion is expressed by an empirical formula h ≦ 19 · (1 -Cin / 100) ^-1/2 -2
The intermediate transfer member according to claim 12, which satisfies 4.5. 14. The intermediate transfer member according to claim 13, wherein the height of the convex portion is 2 μm or more. 15. The intermediate transfer member according to claim 14, wherein the Cin is 50 to 95%. 16. The method of manufacturing an intermediate transfer member according to claim 1, wherein the surface of the intermediate transfer member has a surface corresponding to a surface on which an image is primarily transferred before the surface is finally cured. A method for manufacturing an intermediate transfer member, comprising a step of pressing a mold. 17. The method for producing an intermediate transfer member according to claim 16, wherein the mold comprises a recording medium and a toner image transferred on the surface thereof. 18. A photosensitive member, a developing device for supplying a developer containing toner to the photosensitive member, an intermediate transfer member in contact with the photosensitive member, and a recording medium conveying means for feeding and contacting a recording medium to the intermediate transfer member. At least a heating unit for heating the contact portion is used, an electrostatic latent image is formed on a photoconductor by using light, the electrostatic latent image is developed by a developer containing toner, and the developed toner In an image forming apparatus for carrying out an image forming method in which an image is primarily transferred to an intermediate transfer member, and thereafter, the toner image that is primarily transferred is brought into contact with a recording medium and at least the toner image is transferred to the recording medium by heating, An image forming apparatus in which the surface of the intermediate transfer member on which the image is primarily transferred is a smooth surface with convex portions scattered so that they can be distinguished.