JPH09146385A - Intermediate transfer body for color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the fine smoothness of the surface of an intermediate transfer body and the evenness of volume resistance values by casting liquid rubber on a conductive substrate and then, fixing the liquid rubber into a prescribed shape for generating a cross-linking reaction, so as to form a semiconductor rubber layer and covering the surface with an insulating layer having high mold releasability for toner, that is, adopting two-layer structure. SOLUTION: The intermediate transfer body 14 is constituted in such a manner that the semiconductor rubber layer 14B having rubber elasticity is formed on a drum- like cylindrical conductive substrate 14A. Then, fine carbon power is compounded into liquid urethane, so that the resistance between the substrate 14A and the insulating layer 14C is 10<9> Ω for instance. Then, the volume resistance value (preferably, 10<4> -10<12> Ωm) of the rubber layer 14B is adjusted to 10<12> Ωcm and the thickness (preferably, 0.2-3mm) is adjusted to 1.5mm. Thus, on the surface of the rubber layer 14B, the fine smoothness and the evenness of the volume resistance values are secured by casting work, so that a defect in an image and irregularities in image density caused by the omission of the contact of the surface of the intermediate transfer body 14 with a photoreceptor and a recording medium are never generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a copying machine or a laser beam printer, and in particular, a toner image formed on a photosensitive member is once transferred onto an intermediate transfer member, and the color toner image is formed there. The present invention relates to an intermediate transfer member in a forming method.

[0002]

2. Description of the Related Art Before transferring a toner image formed on a photoconductor onto a recording medium, the toner image is transferred onto an intermediate transfer member, the toner image is transferred from the intermediate transfer member onto the recording medium, and the toner image is transferred onto the recording medium. The image forming method of fixing an image on a recording medium with a fixing device to form an image is adopted in a color image forming device because a multicolor image can be easily formed. As an example of an intermediate transfer member of an image forming apparatus adopting such an intermediate transfer system, as shown in JP-A-1-198773, a three-layer structure of an elastic member, a conductive member, and an insulating member is sequentially arranged on the outer side of a substrate. There is something. Also, in Japanese Patent Laid-Open No. 4-335381, there is one having a three-layer structure of a conductive sponge, a conductive intermediate layer, and a dielectric film in that order on the outside of the substrate. In addition, JP-A-4-287070
The publication discloses an intermediate transfer member having a two-layer structure composed of a conductive sponge and a dielectric film on a metal drum.

[0003]

Generally, in order to obtain a high quality color image, two points of fine smoothness of the surface of the intermediate transfer member and uniformity of the volume resistance value are important. By the way, there are roughly two factors that can be considered as factors that make unevenness on the surface by the conventional method and hinder the fine smoothness and the uniformity of the volume resistance value.

The first factor is that the surface roughness of the surface is not sufficiently smooth, and the second factor is the variation of the electric resistance value in the thickness direction depending on the part.

There are two possible causes for the first factor, surface smoothness. One of them is that when a conventional semiconductor rubber layer of a conventional system is attached to a substrate via an adhesive, the surface of the existing semiconductor layer has been cut and finished due to the restriction of the processing process. However, since the semiconductor rubber layer is made of a rubber-like material, it was not possible to obtain the smoothness required for finishing a hard material. As mentioned above, the insulating layer having excellent toner releasability is applied on the rough finish surface, and the material composition of this coating material is variously devised so that the leveling property is imparted to make the surface smooth. However, it is the current situation that a cutting mark on the surface of the base semiconductor rubber layer remains on the surface of the insulating layer. Another cause of lowering the surface smoothness is due to uneven application of the adhesive. That is, since the ready-made semiconductor rubber layer is fixed on the substrate through the adhesive, unevenness in the thickness of the adhesive between the substrate and the semiconductor rubber layer causes unevenness on the surface, resulting in a defective image.

The second cause of the volume resistance unevenness is that when a millable rubber material is used to form a semiconductor rubber layer as in the conventional case, a raw rubber is mixed with a crosslinking agent, a stabilizer, etc. When performing, the bubbles are easily mixed because the material itself has a very high viscosity. When using this semiconductor rubber layer in a relatively thin shape like this configuration, even minute air bubbles have a problem of affecting the electric resistance value in the thickness direction, which directly affects the image quality. To do. In addition, when bubbles are present, when the surface of the semiconductor rubber layer is cut, as described above, the cutting is performed while continuing to press with a constant pressure, which causes a problem that only the bubble portion is deeply cut. As a result, the surface of the above-mentioned first factor has irregularities, which may be a cause of indirectly lowering the image quality.

An object of the present invention is to provide an intermediate transfer member which solves the above-mentioned problems and ensures the fine smoothness of the surface of the intermediate transfer member and the uniformity of the volume resistance value.

[0008]

According to the present invention, a liquid rubber is cast on a conductive substrate and then a cross-linking reaction is caused to adhere the liquid rubber to a predetermined shape to form a semiconductor rubber layer. Is a two-layer structure in which the toner is covered with an insulating layer having good toner releasability.

Since the liquid rubber is directly cast on the substrate, it can be molded between the substrate and the semiconductor rubber layer without the use of an adhesive, and the liquid rubber having a sufficiently low viscosity is cast, and after being put into the mold, it is cured. Therefore, there is no problem that air bubbles are trapped in the gap between the base and the semiconductor rubber layer or in the semiconductor rubber layer.

Further, in order to increase the adhesiveness with the substrate, an additive for improving the adhesiveness is dispersed and blended in the liquid rubber itself, or the same component is added to the surface of the substrate before the casting step. It is also possible to perform a pre-treatment for applying the drug to be held.

Further, by finishing the inner wall surface of the casting mold to be a mirror surface, the mirror surface is transferred to the surface of the semiconductor rubber layer which is a cured product, and the cutting and polishing steps as a post-process are not required. . Therefore, the insulating layer on the surface does not have unevenness and maintains fine smoothness. Moreover, the conventional intermediate transfer member has a three-layer structure, but the present invention has a two-layer structure because no adhesive is used, and can be easily processed at low cost.

Since the surface of the semiconductor rubber layer is mirror-finished, the adhesion between the surface of the intermediate transfer member and the surface of the photoconductor or the recording medium is improved, and image defects due to contact leakage between the toner latent image and the surface of the intermediate transfer member are eliminated. It was Further, since it is a liquid rubber, it is mixed with a defoaming agent and mixed well before casting. Therefore, the unevenness of the partial volume resistance value due to nonuniform substances such as bubbles in the semiconductor rubber layer is eliminated, and the charged toner is charged. Is uniformly transferred from the intermediate transfer member to the recording medium.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, the device configuration and operating principle of a color image forming device incorporating the intermediate transfer member of the present invention as a component will be described with reference to FIGS. 2 and 3.

FIG. 2 is an external view of a color laser printer which is an image forming apparatus according to an embodiment of the present invention. A paper cassette 2 is provided on the lower right side of the main body 1. Further, printed sheets are stocked 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. 3 is a schematic view of the internal structure of the color laser printer of this embodiment. A belt-shaped photosensitive belt 11 stretched around three rotatable shafts 10 is provided in the center of the main body 1 from the right. The photoconductor belt 11 has a two-layer structure (not shown) having a photoconductor layer (for example, OPC) on the surface and a conductive layer (for example, aluminum) under the photoconductor layer (not shown). Can apply a voltage for transferring the toner to the intermediate transfer member. Since the belt has a seam, the length of the photoconductor 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 photoconductor belt 11 and the change in circumferential length due to changes over time, is added. A belt mark is provided at the end of the photoconductor belt 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 12, the exposure unit 17, the developing units 13a and 13b, in order along the X direction.
13c and 13d, an intermediate transfer member 14, a charge eliminating lamp 15, a belt position detecting means 18, and a cleaner 16 are provided. Further, around the intermediate transfer body 14, an intermediate transfer cleaner 24, a pre-charger 25, and a drum position detecting means 26 are provided.

The paper 50, which is a recording medium, is fed from the paper cassette one by one by the conveying roller 19, and the registration roller 20 corrects the direction and inclination of the paper 50 and stands by. When the color toner image is completed on the intermediate transfer body 14, the timing is adjusted and the color toner image is conveyed to the transfer roller 21. The transfer roller 21 and the static eliminator 22 are retracted until the color toner image is completed on the intermediate transfer member. When the color toner image is completed, the transfer roller 21 is brought into contact with the intermediate transfer body 14, and the space between the intermediate transfer body 14 and the transfer roller 21 is set to the sheet 5
While passing 0, the color toner image on the intermediate transfer member is transferred to the paper. The paper 50 on which the color toner image is transferred is conveyed to the fixing device 23. By being heated and pressed here, the color toner image is fixed on the paper 50 and is discharged to the outside of the main body 1. The intermediate transfer cleaner 24 contacts the intermediate transfer body after the color toner image is transferred onto the sheet 50, and the intermediate transfer cleaner 24 is placed on the sheet 5 on the intermediate transfer body 14.
The residual toner that has not been transferred to 0 is cleaned.

The photoconductor charger 12 is a scotron 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 of the same type are of the same type, but different color toners, such as yellow, magenta,
It contains cyan and black toner, and develops each color. In addition, each is designed to operate independently.

The intermediate transfer member 14 is shown in FIGS.
As shown in (B), a semiconductor rubber layer 14B having rubber elasticity is formed on a drum-shaped cylindrical conductive base (for example, an aluminum drum having a diameter of 108 mm) 14A. The material of the semiconductor rubber layer is a liquid urethane using polyoxypropylene glycol as the polyol component and methylene diisocyanate as the isocyanate component, and the viscosity of the mixture before curing is
It is 350 mPa · s.

If the resistance value in the thickness direction of the intermediate transfer member is too high, the transfer from the photosensitive belt to the recording medium is difficult, so that the resistance between the surface of the substrate 14A and the surface of the insulating layer 14C is 10%.
Tokai Black # 5500P, a fine carbon powder manufactured by Tokai Carbon Co., was mixed with liquid urethane so as to have a resistance of ⁹ Ω, and the volume resistance value of the semiconductor rubber layer 14B (generally 10 ⁴ to
May be set to 10 ¹² [Omega] cm to) in this embodiment is adjusted to 10 ¹² [Omega] cm by blending the thickness was 1.5 mm.

A mold release agent made of a fluororesin was thinly applied to the mold before casting in order to make it easy to remove from the mold after the semiconductor rubber layer 14B was cured. At the time of casting, liquid pressure was applied by applying air pressure of 5 kgf / cm ² with a dispenser.
After casting, it was cured by heating at 80 ° C. for 60 minutes. The adhesive force between the semiconductor rubber layer 14B and the base 14A in this configuration is
When the semiconductor rubber layer 14B was peeled off at 10 mm / min by the 90 ° peeling method, it was about 30 g / cm.

With this constitution, sufficient reliability can be obtained with this adhesive force, but if higher adhesive force is required, additives for improving the adhesive property are dispersed and blended in the liquid rubber to be cast. It is effective to perform a pretreatment in which a chemical having a similar component is applied to the surface of the substrate 14A before the casting or the casting process. Silane-based coupling agents and titanium-based coupling agents are typical materials as the components for improving the adhesiveness mentioned here.
Further, one layer of insulating layer 14C is formed outside the semiconductor rubber layer 14B. The material of the insulating layer 14C is fluororesin. Spray coating was performed so that the thickness was 30 μm, and heat curing was performed at 170 ° C. for 17 minutes. Fluororesin,
It is suitable for forming a surface layer because it has releasability to toner when a color toner latent image is transferred from an intermediate transfer member to a recording medium.

Next, another embodiment will be described.

In this embodiment, the base 14A and the insulating layer 14C are used.
The material and shape are the same as in the previous embodiment. The difference is that the thickness of the semiconductor rubber layer 14B is 2 mm, which is thicker than that of the first embodiment so that a thick casting nozzle can be used, and the casting and the die cutting of the liquid rubber can be performed faster than in the previous embodiment. For that reason, the volume resistance value of the semiconductor rubber layer 14B is adjusted to be as low as 10 ¹¹ Ωcm by using a conductive plasticizer as a compounding component for adjusting the volume resistance value. Therefore, the resistance between the base 14A and the surface of the insulating layer 14C is adjusted to 10 ⁹ Ω as in the previous embodiment. The conductive plasticizer is
It is M-170 manufactured by Kyowa Fermentation Co., Ltd. and has a viscosity of 300 mP.
The volume resistance value is 10 ⁷ Ωcm at a · s. The processing method after adjusting the volume resistance value of the liquid rubber is the same as that of the previous embodiment.

The present invention is not limited to the blending components and dimensions illustrated in the above examples. Inorganic filling components such as calcium carbonate, talc and glass, coloring pigments, or phosphoric acid ester, and flame retardancy-imparting components such as antimony trioxide and aluminum hydroxide are dispersed and mixed into the liquid casting component as required. It doesn't matter. Further, in this embodiment, liquid urethane is used as the base resin component, but it is not limited to this. Any material can be used as long as it is a type of liquid resin in which a crosslinking agent and a curing agent are mixed, and energy such as heat and ultraviolet rays is applied to react and cure. As these examples, materials having rubber elasticity such as silicone type, fluorine type, acrylic type and chloroprene type are suitable.

[0027]

As described above, since the surface of the semiconductor rubber layer 14B of the intermediate transfer member of the present invention is subjected to the casting process to ensure the fine smoothness and the uniformity of the volume resistance value, the intermediate transfer is performed. Image defects and image density unevenness due to contact leakage of the surface of the body 14 with the photoconductor or the recording medium do not occur. In addition, the simplification of the two-layer structure facilitates the processing of the intermediate transfer member 14.

[Brief description of the drawings]

FIG. 1 is a diagram showing an intermediate transfer member according to an embodiment of the present invention.

FIG. 2 is an external view of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of the image forming apparatus according to the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main body, 2 ... Paper cassette, 10 ... Shaft, 11 ... Photosensitive belt, 12 ... Photosensitive charger, 13a, 13b, 13c,
13d ... Developing means, 14 ... Intermediate transfer body, 14A ... Conductive substrate, 14B ... Semiconductor rubber layer, 14C ... Insulating layer, 14
D ... 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, 50
… Paper.

Front page continuation (72) Inventor Tetsuo Ishikawa 1-1-1, Higashi-Taga-cho, Hitachi-shi, Ibaraki Hitachi Electric Co., Ltd. Electric Appliance Division, Taga Headquarters (72) Inventor Masahiro Nakano 1-chome, Higashi-Taga-cho, Hitachi-shi, Ibaraki No. 1 No. 1 Inside the Taga Headquarters, Electric Appliance Division, Hitachi, Ltd.

Claims (7)

[Claims] 1. Toner images of different colors formed on a photosensitive member are sequentially transferred onto an intermediate transfer member to form a color toner image, and the color toner image is transferred onto a recording medium to form an image. In an intermediate transfer member of a color image forming apparatus, the intermediate transfer member is formed by casting liquid rubber on a conductive substrate and then causing a cross-linking reaction to fix the liquid rubber to a predetermined shape to form a semiconductor rubber layer. An intermediate transfer member of a color image forming apparatus is characterized in that the surface of the semiconductor rubber layer is covered with an insulating layer having good toner releasability. 2. The semiconductor rubber layer according to claim 1,
An intermediate transfer member for a color image forming apparatus, which is made of liquid rubber such as polyurethane rubber, silicone rubber, fluororubber, acrylonitrile-butadiene rubber, or polychloroprene rubber. 3. The intermediate transfer member for a color image forming apparatus according to claim 1, wherein the insulating layer outside the semiconductor rubber layer is made of a fluoropolymer as a base material. 4. The intermediate transfer member of a color image forming apparatus according to claim 1, wherein the semiconductor rubber layer has a volume resistance value of 10 ⁴ to 10 ¹² Ωcm. 5. The intermediate transfer member for a color image forming apparatus according to claim 1, wherein the adhesive force between the semiconductor rubber layer and the substrate is 20 g / cm or more. 6. The intermediate transfer member for a color image forming apparatus according to claim 1, wherein the thickness of the semiconductor rubber layer is 0.2 to 3 mm. 7. The intermediate transfer member for a color image forming apparatus according to claim 1, wherein the hardness of the semiconductor rubber layer is 30 to 95 degrees on a Shore A hardness scale.