JPH08194385A - Intermediate transfer device for color image forming device - Google Patents

Abstract

PURPOSE: To realize an intermediate transfer device having high transfer efficiency and uniform transfer performance of plural colors free from transfer defects and image defects with simple constitution and high reliability at a low cost. CONSTITUTION: This intermediate transfer device is provided with a resin layer 14B having elasticity and a surface layer 14C having release property from toners on a base material 14A consisting of a conductor. The surface layer 14C is composed of a resin consisting essentially of a polyorganosiloxane. The resin layer 14B having the elasticity and the surface layer 14C are otherwise provided with a layer having affinity to the respective layers therebetween. The ends of the cylindrical conductor base material 14A on the drum are formed to a shape inclined or stepped in a generator direction within the ranges where the toner images are not transferred. These ends are provided with the resin layers 14B, 14C up onto these slopes or stepped surfaces. As a result, the intermediate transfer device is constituted without impairing the uniform resistance value and the dimensional accuracy of the outside diameter of the drum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer device in a color image forming apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art As an image forming method for obtaining a color image, a toner image obtained by developing a latent image on a latent image holding means by developing means of a plurality of different colors one by one is transferred from the latent image holding means to an intermediate transfer means. There is a method in which the toner images of a plurality of colors are formed by sequentially repeating the above steps, and the toner images of the plurality of colors are transferred onto a transfer material to form a color image of a plurality of colors.

As an example of an image forming apparatus using such an intermediate transfer means, there is one which uses a cylindrical drum as the intermediate transfer means, as disclosed in JP-A-1-198773.

[0004]

Generally, there are various image forming methods for forming an image of a plurality of colors by using the intermediate transfer means as in the above-mentioned known examples. However, image forming using these methods is possible. The apparatus sequentially transfers toner images of different colors from the latent image holding means to the intermediate transfer means one by one, and transfers the toner images of the plurality of colors onto the transfer material to form a multicolor image. To do. In this way, when a plurality of transfers are performed, unless the transfer of the first color and the transfer of the plurality of colors are substantially the same, the transfer may be different and the hues may be different. Furthermore,
Not only in the case of transferring a plurality of colors but also in the case of transferring only a single color, if the transfer from the intermediate transfer unit onto the transfer material is not uniform, image defects such as color unevenness and color density decrease occur.

Further, when the toner images are overlapped to form an image, there is a possibility of color misregistration between the toner images of respective colors.

Problems such as color misregistration and color unevenness due to the transfer of the toner image are particularly important problems in a color image forming apparatus, and color reproducibility and hue stabilization cannot be obtained, so that a desired image is obtained. Cannot be formed, which is a major technical problem in a color image forming apparatus using an electrophotographic process such as a copying machine or a laser printer.

In order to improve the transfer efficiency from the intermediate transfer means onto the transfer material, there has been proposed a method of improving the toner releasability by treating the toner holding surface of the intermediate transfer means with a fluororesin. However, in the case of a toner in which hydrophobic silica is used as an external additive in order to improve the fluidity of the toner, the releasability from the fluororesin is not sufficient and transfer unevenness occurs. In the method of transferring the toner image by the potential difference between the intermediate transfer means and the transfer material, the transfer efficiency can be improved by increasing the potential difference between the intermediate transfer means and the transfer material. In order to obtain a sufficient transfer efficiency, the applied potential becomes high, which may cause discharge breakdown.

When a surface layer having releasability for toner is formed on a resin layer having elasticity provided on a conductive base material, the surface layer having releasability for toner forms a uniform thin layer. Although necessary, if the wettability of these two layers is not good, the desired uniform thin layer cannot be formed because the material does not spread uniformly when the material for the surface layer is applied.

Further, it is necessary for the intermediate transfer device to contact the latent image holding means or transfer the toner in a minute void.
Since a potential of several hundred volts is applied on the surface of the latent image holding means,
Electric discharge leaks from the end of the conductive base material of the intermediate transfer member, but this point is not taken into consideration in the above-mentioned known example. In the case of a drum-shaped intermediate transfer member, it is possible to insulate the end face in order to prevent discharge leakage from the end, but when the insulating material is applied, if the coating material rises in the radial direction of the drum, Since the image transfer cannot be performed uniformly, it is unavoidable to perform processing only on the end face, but pinholes are likely to occur at the end face edge portion, and reliability becomes a problem. Furthermore, the number of steps is increased due to the insulating treatment of the end faces, resulting in a high cost. As another method, a method of forming a resin layer up to the end surface of the drum-shaped conductor base material is also conceivable, but in this case, since the resin layer projects from the base material, the resin layer protrudes from both ends due to contraction during formation of the resin layer. The protruding resin portion is pulled in the generatrix direction and also rises from the transfer surface of the drum-shaped intermediate transfer member. An object of the present invention is to solve these problems and to configure an intermediate transfer device having a uniform transfer performance for a plurality of colors, and to provide a high quality color image forming apparatus using the same.

[0010]

In order to achieve the above object, an intermediate transfer device is composed of a resin layer having elasticity on a base material of a conductor and a resin layer having releasability for toner.

In the case of a toner using hydrophobic silica as an external additive, a resin layer containing polyorganosiloxane as a main component is provided as a resin layer having releasability from the toner of the intermediate transfer device.

The elastic resin formed on the conductor substrate has a volume resistivity of 10 ⁴ to 10 ¹⁵ Ω · cm, and a surface layer having a releasability to toner is 0.1 to 5.
It has a thickness of 0 μm.

Further, a layer having an affinity for at least each of them is provided between the elastic resin layer provided on the conductor substrate and the surface layer having the releasability for the toner. Further, when a drum-shaped cylindrical member is used as the conductor base material, its end portion is inclined with respect to the generatrix direction within a range where the toner image is not transferred, and the inclined surface is formed on the base material. A resin layer is provided.

Alternatively, when a drum-shaped cylindrical member is used as the conductor base material, its end portion has a step shape within a range where the toner image is not transferred, and the step surface is formed on the base material. A resin layer is provided.

[0015]

Since the intermediate transfer member having the above-described structure is composed of a member having elasticity on the base material of the conductor and a member having a peeling property for the toner, the toner image on the intermediate transfer member and the transfer target material is formed. During the transfer process, the elastic member on the conductive base material makes the contact between the intermediate transfer member and the transferred material uniform, and the surface layer is releasable from the toner to improve transfer efficiency and transfer with uniformity. It will be possible.

Further, in order to improve the fluidity of the toner, the use of hydrophobic silica as an external additive is a general method in the field of electrophotography, but hydrophobic silica has a very small surface energy. However, the fluidity is improved by suppressing the aggregation of toners, but on the other hand, it does not necessarily have sufficient releasability for a fluororesin which is generally said to have high releasability. On the other hand, in the case of a silicone resin whose main component is a polyorganosiloxane having a silicon atom in its skeleton, the hydrophobic silica, which is an external additive of the toner, has excellent water repellency with respect to the silicone resin which is an organic silicon. Therefore, by forming a silicone resin containing polyorganosiloxane as a main component in the surface layer of the intermediate transfer member,
Good transfer performance for toner can be obtained.

In general, since a silicone resin containing polyorganosiloxane as a main component has a high electric resistance, when it is formed as a surface layer, in order to obtain a semiconductive resistance value required for an intermediate transfer member, the above-mentioned poly (polysiloxane) is used. It is necessary to form the organosiloxane surface layer uniformly and thinly. Furthermore, desired semiconductivity can be obtained by controlling the volume specific resistance value of the elastic body provided on the conductor substrate. In this case, the surface layer has a high resistance, and it is preferable that the thickness of the surface layer is thin in order to obtain the semiconductivity required for the intermediate transfer member, but a uniform film having no film defects such as pinholes is formed. Therefore, an appropriate thickness is required, and therefore, the thickness of the surface layer having releasability for toner is preferably 0.1 to 50 μm. By making the surface layer of the high-resistance body a thin layer, the contribution of the surface layer to the semiconductive resistance value required for the intermediate transfer member can be reduced, so the resistance value is mainly determined by the volume resistivity of the elastic member, The value is preferably 10 ⁴ to 10 ¹⁵ Ω · cm, more preferably 10 ⁷ to 10 ¹³ Ω · cm.

Further, between the elastic resin layer on the base material of the electric conductor and the surface layer having the releasability for the toner,
By providing a layer that has an affinity for at least each of them, the wettability of the surface layer material is improved when the surface layer is formed, and the elongation when applied is uniform, so that film thickness accuracy without pinholes It is possible to form a uniform thin layer having a high temperature.

Further, since the intermediate transfer device and the latent image holding means transfer the toner in a contact state or in a minute gap state, a conductor group is applied to a potential of several hundred volts applied on the surface of the latent image holding means. It is necessary to perform insulation treatment from the end of the material in order to prevent discharge leakage. When a drum-shaped cylindrical conductor substrate is used, its end is inclined in the generatrix direction within the range where the toner image is not transferred, so that the spatial distance between the conductor substrate and the surface to which voltage is applied is increased. It can be sufficiently taken, and further, by forming a resin layer on the inclined surface, discharge leakage can be prevented. Alternatively, in the range where the toner is not transferred, the drum-shaped cylindrical conductor base end is formed into a step shape, and the end portion has a sufficient space distance from the voltage surface, and a resin layer is formed on the step surface. By doing so, discharge leakage can be prevented. These slanted shapes or stepped shapes can be formed within the range where toner is not transferred, and do not affect the print image quality. With the above structure, an intermediate transfer device having a uniform transfer performance for a plurality of colors can be realized with a simple structure and with high reliability, and a high-quality color image forming apparatus using the same can be provided.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows an external view of a color laser printer which is an image forming apparatus according to an embodiment of the present invention. Body 1
A paper cassette 2 is provided on the lower side of the right side of the. or,
Printed sheets are stacked on the upper lid 3 of the upper surface of the main body 1. A panel 4 for displaying print control and messages is provided on the front surface of the main body 1. A controller 5 for controlling a printing process and an interface with a computer is arranged inside the rear side of the main body 1.

FIG. 5 is a schematic view of the internal structure of the color laser printer of this embodiment. 3 on the right center of the main body 1
A photoreceptor belt 11 is provided which is a latent image forming means on a belt stretched by two rotatable shafts 10.
The photoconductor belt 11 has a photoconductor layer (for example, OP
C) and a two-layer structure having a conductive layer (for example, aluminum) underneath (not shown), and a voltage for transferring toner to the intermediate transfer means is applied to the lower conductive layer. You can do it. Since the belt has a seam, the length of the photoreceptor belt 11 must be at least the desired image length or longer. In this embodiment, in addition to the length of two images, a margin of 8 cm, which is much larger than the environment of the photosensitive belt 11 and the change in the circumferential length due to changes over time, is additionally provided. A belt mark is provided at the end of the photoconductor 11 at a position several mm from the seam of the belt. Further, the photosensitive belt 11 is adapted to move in the X direction. In the vicinity of the photoconductor belt 11, the photoconductor charger 1 is sequentially installed along the X direction.
2, exposure means 17, developing means 13a, 13b, 13c,
13d, an intermediate transfer unit 14, a charge eliminating lamp 15, a belt position detecting unit 18, and a cleaner 16 are provided. or,
Around the intermediate transfer means 14, an intermediate transfer cleaner 24, a pre-charger 25, and a drum position detection means 26 are provided.

The photoconductor charger 12 is a scorotron charger, and charges the photoconductor by discharging the corotron wire and controlling the voltage of the grid plate.

The exposure means 17 is capable of forming a spot image of the light of a semiconductor laser (not shown) on the photosensitive belt, and by scanning exposure, the photosensitive belt 1 is exposed.
A latent image is formed on 1.

Developing means 13a, 13b, 13c, 13d
The four developing devices are of the same type but store different color toners, for example, yellow, magenta, cyan and black, and develop each color. or,
Each is designed to work independently.

FIG. 1 is an external view of the intermediate transfer means, and FIG. 2 is a sectional view thereof. FIG. 3 shows a sectional view of the intermediate transfer means 14 of another embodiment.

The intermediate transfer means 14, as shown in FIG.
On a drum-shaped cylindrical conductor substrate (eg, diameter 108
(mm aluminum drum) 14A is formed by applying or molding an elastic resin (for example, with a thickness of 1 mm, the material is silicone rubber, urethane rubber, nitrile rubber, chloroprene rubber, etc. Adjusted value). Further, a coating layer 14C of one layer is further applied to the surface of the elastic member 14B, and the coating material is a resin such as a silicone resin or a fluorine resin, which has a releasability for the toner. In this embodiment, a silicone resin containing polyorganosiloxane as a main component is coated as the surface layer 14C. Since it is necessary to uniformly form a thin layer for coating the surface layer 14C, spray coating or pulling by dipping can be used as the method. However, in the case of the silicone resin containing polyorganosiloxane as the main component used in this example, the viscosity of the coating solution changes with time because the curing reaction proceeds after the coating solution is adjusted, and the film is not removed by pulling by dipping. It is extremely difficult to keep the thickness constant, and spray coating is optimal.

Further, in FIG. 3, a resin layer 14B having elasticity and a resin layer 14C having releasability for toner are provided on a conductive base material 14A, and between these two layers,
A layer 14D having an affinity for each layer is provided. In this embodiment, silicone resin is used as a main component having elasticity and is subjected to a conductive treatment for adjusting the resistance value, but the wettability of the surface layer 14C with the polyorganosiloxane is not good. Therefore, the primer layer 14D that imparts the affinity is provided. The primer mentioned here is used for the purpose of improving the adhesiveness to the elastic layer 14B which is the adherend, the coating property (leveling property), etc., in order to form the polyorganosiloxane surface layer 14C. The primer is usually composed of a film-forming agent, a silane coupling agent, a solvent, a catalyst, and additives (pigments and others). Its function is to achieve the purpose through the process of solvent evaporation → hydrolysis and condensation → adhesive film formation. The most important part of the primer composition is the silane coupling agent, which is carefully selected and used according to the material of the adherend. For example,

[0029]

Embedded image

Etc. are used. By providing this layer, the wettability is improved when the polyorganosiloxane is spray-coated, and there is no repelling phenomenon on the surface, and thin and uniform coating is possible.

In the toner of this embodiment, a polyester resin is used as a base material, a pigment or a dye is dispersed as a colorant, and hydrophobic silica is added as an external additive to improve the fluidity of the toner. . This hydrophobic silica is used as the surface layer 14
It has a high peeling property with respect to the polyorganosiloxane of C, and therefore, the efficiency of transferring the toner from the intermediate transfer unit 14 to the sheet 50 can be increased. Therefore, even with a relatively small amount of toner, sufficient image density can be obtained on paper,
It is possible to minimize the adverse effect caused by the increase in the diameter due to the increase in the toner layer thickness on the intermediate transfer unit 14.

In order to obtain the semiconductivity necessary for the intermediate transfer member, the resin layer 14B having elasticity has a volume resistivity value of 10 ⁴ to 10 ¹⁵ Ω · cm and a thickness of 0.2 to 10 mm, The desired semiconductivity can be obtained by setting the thickness of the resin layer 14C having a peeling property to the toner to be 0.1 to 50 μm.

Further, as shown in FIG. 6, the intermediate transfer means 14 has both ends of the conductor base material 14A which are inclined with respect to the generatrix direction in the range where the toner image is not transferred, and reach the inclined surface. Resin layers 14B and 14C are configured. As another method, as shown in FIG. 7, both ends of the conductor base material 14A have a step shape within a range where the toner image is not transferred, and the resin layer 14B reaches the step surface.
14C is configured. As described above, the drum-shaped transfer body 1 to which a high voltage is applied by forming the inclined or stepped shape
Even in the portion where the conductor 14A is exposed from the transfer surface of No. 4 to the conductor layer 14A, a sufficient spatial distance can be provided, and discharge leakage can be prevented also in this end face. The spatial distance from the transfer surface to the conductor base material is 1 mm or more, and more preferably 1.5 mm or more, including the thickness of the resin layers 14B and 14C formed on the surface of the drum-shaped intermediate transfer member 14.

The drum-shaped cylindrical conductor base material 14A is
It is electrically grounded. An encoder 14E is provided at the right end of the intermediate transfer means 14, and 32 holes at equal pitches are formed. The intermediate transfer means 14 is pressed against the photosensitive belt 11 with an appropriate pressure and is in contact with the nip width of 5 to 20 mm. The nip width can be widely formed because the photoconductor belt 11 has a belt shape, and the transfer is performed well. Further, since the nip width is formed wide, it is possible to drive the photoconductor belt 11 and move the intermediate transfer means 14 accordingly.

The charge eliminating lamp 15 is used for the photosensitive belt 1 after transfer.
The residual potential on 1 is removed by light irradiation.

The belt position detecting means 18 uses an optical sensor to detect the mark on the photosensitive belt 11.

Similarly, the intermediate transfer cleaner 24 removes the toner remaining on the intermediate transfer means 14 after the sheet is transferred. The intermediate transfer cleaner 24 is so arranged as to retract while the toner image is formed on the intermediate transfer means 14.

The pre-charger 25 works only immediately before the transfer of the sheet, and adjusts the potential of the toner on the intermediate transfer means 14. The drum position detection means 26 uses an optical sensor to detect the hole position of the encoder 14E at the right end of the intermediate transfer means 14.

A paper cassette 2 is provided below the photosensitive belt 11 of the main body 1. A conveyance roller 19 is provided inside the upper body 1 of the paper cassette 2, whereby the paper 50 is pulled out from the paper cassette 2, passes through the registration roller 20, the transfer roller 21, the static eliminator 22, and the fixing device 23. It is discharged onto the upper lid 3.

The registration roller 20 is for adjusting the leading edge of the paper 50. The transfer roller 21 is used to transfer the toner image formed on the intermediate transfer means 14 onto the paper 50, and has a metal cored bar and an appropriate resistance value (10 ⁴ to 10 ^10).
Ω) elastic layer (not shown). Appropriate voltage is applied to the metal core to optimize the transfer of toner from the intermediate transfer means 14 to the paper. Further, the transfer roller 21 is retracted so as not to contact the intermediate transfer means 14 while the toner image is formed on the intermediate transfer means 14. The static eliminator 22 uses an AC corona charger, and
The paper 50 is neutralized by the radiation of the corona. Fixing device 2
3 fixes the toner on the paper 50.

Next, the operation of the embodiment of the present invention constructed as above will be described. First, when a print command is input from the computer to the controller 5, the photoconductor belt 11 starts to move, the belt position detection means 18 detects a mark representing the seam of the photoconductor belt 11, and an encoder immediately after the signal. The drum position detecting means 26 detects the hole 14E. By the signal, the photoconductor charger 1
The exposure means 1 is provided on the photoconductor belt 11 charged by 2
Exposure is started from 7 and a latent image is formed. This latent image is developed by any one of the developing means 13a, 13b, 13c, 13d. The developed toner image is
The image is transferred onto the intermediate transfer unit 14. The above steps are repeated to form toner images of a plurality of colors on the intermediate transfer unit 14. However, the exposure when forming the toner images of the second and subsequent colors was detected at the start of exposure of the toner images of the first color. It is started by the same position detection signal after one round after being detected by the encoder 14C.

As described above, since the exposure start timing is the same for each color with reference to one position on the intermediate transfer means 14, a plurality of toner images can be accurately overlapped. In addition, in the exposure of the first color, the seam of the photoconductor belt 11 is detected by the belt position detection means 18, and the seam of the photoconductor belt 11 is included in the image area while the toner images of at least four colors are superposed. Since it is avoided, the image defect is eliminated.

In addition, since the intermediate transfer device 14 can be configured to have an optimum semiconductive resistance value which is uniform and even on the entire surface, the intermediate transfer device 14 can perform optimum transfer under substantially the same conditions even in repeated transfer. became. Also, various high voltages are applied during transfer. Here, for example, in the case of an intermediate transfer member configured by coating a semi-conductive rubber belt on a drum-shaped conductor base material, a small air layer present on the back surface of the belt is agglomerated by the application of a high voltage and becomes large. Although the phenomenon of agglomeration occurred and transfer failure occurred, in this embodiment, the resin layer 14 was directly formed on the surface of the drum-shaped cylindrical substrate 14A.
Since B and 14C are formed by coating, no air layer is formed, and transfer defects do not occur.
In addition, it is not necessary to perform bonding to prevent the rubber belt from being displaced.

Next, the toner images of a plurality of colors formed on the intermediate transfer means 14 are pre-charged by the pre-charger 25 and transferred by the transfer roller 21 to the paper 50 pulled out from the paper cassette 2 by the conveying roller 19. To be done.
Next, the sheet 50 is transferred to the intermediate transfer unit 14 by the static eliminator 22.
Further, the charge is removed and peeled off, and the paper is sent to the fixing device 23 and fixed, and then discharged onto the upper lid 3 of the main body 1.

With the above-described structure, according to this embodiment, an intermediate transfer device having uniform semiconductivity and transferability and high transfer efficiency can be realized as the intermediate transfer device 14, and good transfer performance can be established. .

[0046]

With the above construction, according to this embodiment,
Optimal transfer to the intermediate transfer device 14 is possible, and an intermediate transfer device of a high-quality color image forming apparatus having excellent transfer performance can be provided with high productivity and at low cost.

[Brief description of drawings]

FIG. 1 is an external view of an intermediate transfer device according to an embodiment of the present invention.

FIG. 2 is a sectional view of an intermediate transfer device according to an embodiment of the present invention.

FIG. 3 is a sectional view of an intermediate transfer device according to an embodiment of the present invention.

FIG. 4 is an external view of an image forming apparatus according to an embodiment of the present invention.

FIG. 5 is a vertical sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 6 is a partially enlarged view of a sectional view of an intermediate transfer device according to an embodiment of the present invention.

FIG. 7 is a partially enlarged view of the cross-sectional view of the intermediate transfer device according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printer main body, 11 ... Photosensitive belt, 12 ... Photosensitive charger, 13a, 13b, 13c, 13d ... Developing means, 14
... intermediate transfer means, 14A ... conductive base material, 14B ... elastic member, 14C ... coating layer, 14D ... primer layer,
14E ... Encoder, 15 ... Static elimination lamp, 16 ... Cleaner, 17 ... Exposure means, 18 ... Belt position detection means, 19
... conveying roller, 20 ... registration roller, 21 ... transfer roller, 22 static eliminator, 23 ... fixing device, 24 ... intermediate transfer cleaner, 25 ... precharger, 26 ... drum position detecting means, 5
0 ... paper.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Akasaki 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Electric Appliances Division, Electric Appliances Division Taga Headquarters (72) Inventor Masashi Yamamoto Omika, Hitachi-shi, Ibaraki 7-1-1, Machi, Hitachi, Ltd., Hitachi Research Laboratory, Inc. (72) Inventor, Masahiko Saito 1-1-1, Higashi-Taga-cho, Hitachi, Hitachi, Ibaraki (72) Invention, Hitachi, Ltd. Electric Appliances Division Makoto Kobayashi 1-1-1 Higashitaga-cho, Hitachi-shi, Ibaraki Co., Ltd. Electrical Equipment Division, Hitachi, Ltd., Taga Headquarters (72) Inventor Hiroyuki Onodera 1-1-1 Higashi-taga-cho, Hitachi-shi, Ibaraki Hitachi (72) Inventor Masahiro Nakano, 1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Stock Company Nissha Co., Ltd. Manufacturing electrical appliance division Taga in the headquarters (72) inventor Shizuo Tsuruta Hitachi City, Ibaraki Prefecture Higashitaga-cho, 1 Chome, Co., Ltd., Hitachi Home Appliances Division Taga within headquarters

Claims (5)

[Claims] 1. A latent image holding means is exposed with an image to form a latent image, and the latent image formed on the latent image holding means is developed by one of developing means having different toners. The transferred toner image is transferred onto the intermediate transfer device, and this is repeated multiple times to form an image in which a plurality of different toner images are superposed, and then transferred from the intermediate transfer means to the transfer target to form a color image. In the color image forming apparatus, the intermediate transfer device includes an elastic resin layer on a base material of a conductor and a resin layer whose surface layer having releasability for toner is composed mainly of polyorganosiloxane, A color image characterized in that a toner for forming an image comprises a thermoplastic resin as a base material and at least a pigment or a dye as a coloring agent and a hydrophobic silica as an external additive. An intermediate transfer device forming device. 2. The elastic resin layer formed on a conductor substrate according to claim 1, which is made of a resin having a volume resistivity of 10 ⁴ to 10 ¹⁵ Ω · cm and has a releasability to toner. An intermediate transfer device for a color image device, wherein the surface layer has a thickness of 0.1 to 50 μm. 3. A latent image is formed by exposing an image on the latent image holding means, and the latent image formed on the latent image holding means is developed by one of developing means having different toners. The transferred toner image is transferred onto the intermediate transfer device, and this is repeated multiple times to form an image in which a plurality of different toner images are superposed, and then transferred from the intermediate transfer means to the transfer target to form a color image. In the color image forming apparatus, the intermediate transfer device is provided with a resin layer having elasticity and a resin layer containing polyorganosiloxane having peeling property for toner as a main component on the base material of the conductor, and these two layers are provided. An intermediate transfer device of a color image forming apparatus, characterized in that a layer having an affinity for each of them is provided between them. 4. The base material as a conductor according to claim 1, wherein the shape of the base material is a drum-like cylindrical shape, and its end portion is inclined with respect to the generatrix direction within a range where a toner image is not transferred. An intermediate transfer member for a color image device, comprising a resin layer formed on the substrate up to an inclined surface. 5. The base material as a conductor according to claim 1, wherein the base material is a drum-shaped cylinder, and the end portion thereof has a step shape within a range where a toner image is not transferred. An intermediate transfer member for a color image device, comprising a resin layer formed on the base material.