JP3320241B2 - Image forming device - 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 apparatus using an electrophotographic system, and more particularly, to a method in which a toner image formed on a first image carrier is temporarily transferred onto an intermediate transfer member and then transferred to a second image carrier.
And an image forming apparatus such as a copying machine, a printer, a facsimile, etc., for obtaining an image formed product by further transferring the image on an image carrier.

[0002]

2. Description of the Related Art An image forming apparatus using an intermediate transfer member includes:
A color image forming apparatus, a multi-color image forming apparatus, or a color image forming apparatus that sequentially transfers a plurality of component color images of color image information or multi-color image information and outputs an image formed product by combining and reproducing a color image or a multi-color image. The image forming apparatus is effective as an image forming apparatus having a forming function and a multicolor image forming function, and can obtain an image without overlapping deviation (color deviation) of each component color image.

FIG. 1 schematically shows an example of an image forming apparatus which is a transfer apparatus using an intermediate transfer body having a roller shape.

FIG. 1 shows a color image forming apparatus (copier or laser beam printer) using an electrophotographic process. Medium resistance elastic roller 2 as intermediate transfer member
0 is used.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) which is used repeatedly as a first image carrier, and rotates at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. Driven.

In the course of rotation, the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a primary charger (corona discharger) 2 and then subjected to image exposure means (not shown) for color analysis / connection of a color original image. An image exposure optical system, a scanning exposure system using a laser scanner that outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information, etc.) to receive a first image of a target color image. An electrostatic latent image corresponding to a color component image (for example, a magenta component image) is formed.

Next, the electrostatic latent image is transferred to the first developing device 41.
(Magenta developing device) is developed with magenta toner M as the first color. At this time, the second to fourth developing devices 4
2, 43, and 44 (developing units for cyan, yellow, and black) are turned off and do not act on the photosensitive drum 1, and the magenta toner image of the first color is used for the second to fourth magenta toner images.
Of the developing units 42 to 44.

The intermediate transfer member 20 is rotated at the same peripheral speed as the photosensitive drum 1 in the counterclockwise direction indicated by the arrow.

The intermediate transfer member 20 is made of a pipe-shaped metal core 21.
And an elastic layer 22 formed on the outer peripheral surface thereof.

[0010] The first type formed and supported on the photosensitive drum 1
In the process in which the magenta toner image of the color passes through the nip between the photosensitive drum 1 and the intermediate transfer body 20, an outer peripheral surface of the intermediate transfer body 20 is generated by an electric field generated by a temporary transfer bias applied to the intermediate transfer body 20. The intermediate transfer is sequentially performed.

After the transfer of the first color magenta toner image onto the intermediate transfer member 20, the surface of the photosensitive drum 1 is cleaned by the cleaning device 14.

Hereinafter, similarly, a cyan toner image of the second color,
The third color yellow toner image and the fourth color black toner image are sequentially superimposed and transferred onto the intermediate transfer body 20 to form a composite color toner image corresponding to the target color image.

Reference numeral 25 denotes a transfer roller, which is provided in parallel with the intermediate transfer member 20 and in contact with the lower surface thereof.

The first transfer from the photosensitive drum 1 to the intermediate transfer body 20
The primary transfer bias for the sequential superimposed transfer of the toner images of the fourth to fourth colors has a polarity (+) opposite to that of the toner and a bias power source 6
Applied from 1. The applied voltage is, for example, +2 kV to +
The range is 5 kV.

First transfer from the photosensitive drum 1 to the intermediate transfer member 20
The transfer roller 25 and the intermediate transfer member cleaner 35 can be separated from the intermediate transfer member 20 in the process of sequentially transferring the toner images of the fourth to fourth colors.

The transfer of the composite color toner image superimposed and transferred on the intermediate transfer member 20 to the transfer material 24 as the second image carrier is performed while the transfer roller 25 is in contact with the intermediate transfer member 20 and The transfer material 24 is fed from the paper cassette 9 to a contact nip between the intermediate transfer body 20 and the transfer roller 25 at a predetermined timing, and at the same time, a secondary transfer bias is applied to the transfer roller 25 from the bias power supply 29. With this secondary transfer bias, the composite color toner image is transferred from the intermediate transfer member 20 to the transfer material 24 as the second image carrier. The transfer material 24 to which the toner image has been transferred is introduced into the fixing device 15 and is fixed by heating.

After the image transfer to the transfer material 24 is completed, the transfer residual toner on the intermediate transfer member 20 is cleaned by contacting the intermediate transfer member cleaner 35.

A color electrophotographic apparatus having an image forming apparatus using the above-mentioned intermediate transfer member is a conventional technique, in which a second image carrier is stuck or adsorbed on a transfer drum, and the first image carrier is stuck thereon. A color electrophotographic apparatus having an image forming apparatus for transferring an image from a carrier, for example,
It is superior to the transfer method as described in JP-A-3-301960 in the following points. That is, there is little color shift at the time of superimposing the toner images of each color. Next, as shown in FIG. 1, the image from the intermediate transfer body is not required for the second image carrier without any processing or control (for example, gripping by a gripper, adsorbing, giving a curvature, etc.). Can be transferred, so that the second image carrier can be variously selected. For example, thin paper (40 g / m ²
Paper) to thick paper (200 g / m ² paper). Transfer is possible regardless of the width of the second image carrier or the length of the second image carrier. Further, it can be applied to envelopes, postcards, label paper, and the like.

Further, since the intermediate transfer member is excellent in rigidity, it is difficult for dimensional accuracy such as dents and strain deformation to occur due to repeated use, so that the frequency of replacement of the intermediate transfer member can be reduced.

As described above, due to the advantages of using the intermediate transfer member, a color copying machine, a color printer, and the like using the image forming apparatus have already started operating in the market.

However, these color electrophotographic apparatuses are:
At present, the device does not function sufficiently as a device that makes full use of the above-mentioned advantages and that is truly expected and satisfactory to users. That is, when the image forming apparatus using the intermediate transfer member is repeatedly used in various environments, the following problems still remain.

(1) The transfer efficiency from a first image carrier, for example, a photosensitive drum to an intermediate transfer member, and the transfer efficiency from the intermediate transfer member to a second image carrier, for example, paper or an OHP sheet, are sufficiently high. It has not become something. Therefore, a cleaning device to be provided in the photosensitive drum and the intermediate transfer member is indispensable, and a load on the device is increased to clean a large amount of transfer residual toner, and the cleaning device becomes considerably complicated in structure and expensive. It has become something.

(2) An image transferred to the intermediate transfer member and a part of the image transferred to the second image carrier are not transferred as shown in FIG. May be. This is caused by the fact that the transfer efficiency has not reached 100% as described in (1). As the cause, the material used for the intermediate transfer member, the surface properties, the resistance, or the magnitude and timing of the applied bias at the time of transfer, or the mechanical configuration of the image forming apparatus are considered to act in combination, The main cause is unknown. However, it is known that it deteriorates as the durability of the intermediate transfer member advances or as the environment becomes lower in temperature and humidity.

(3) The surface properties and resistance of the intermediate transfer member may change as the intermediate transfer member is repeatedly used and the durability is advanced. In extreme cases, abrasion occurs on the surface of the intermediate transfer member, and it becomes impossible to maintain good transfer efficiency and a uniform image obtained at the beginning.

(4) As shown in FIG. 1, the intermediate transfer member 20 is provided with an intermediate transfer member cleaner 35. This is an apparatus for removing untransferred toner from the intermediate transfer member before the next series of transfer steps starts. There are various cleaning methods such as blade cleaning, fur brush cleaning, or a combination thereof, but toner is transferred to the surface of the intermediate transfer member 20.
When the cycle of demolding is repeated thousands or tens of thousands of times,
The toner that has not been completely removed by the cleaner 35 gradually accumulates on the surface of the intermediate transfer body 20, so that so-called filming is formed. When this happens, the first
In this case, the transferability of the toner from the image carrier is deteriorated, resulting in an image having a spot-like white spot due to poor transfer of the filmed portion, resulting in lower image quality or lowering the overall transfer efficiency.

(5) To express the function of the intermediate transfer member,
In many cases, the elastic layer is made of rubber, elastomer, resin, or the like, and a coating layer or the like is used as an upper layer as necessary. For example, JP-A-4-81786, JP-A-4-88385, JP-A-3-242667, and JP-A-5-333725 have already disclosed some preferable materials and compositions.
Nothing has yet been found that satisfies all the characteristics, has a wide and stable resistance, and can be used.

[0027]

SUMMARY OF THE INVENTION However, the present invention proposes an image forming apparatus using an intermediate transfer member which solves the above-mentioned problem.

Accordingly, an object of the present invention is to provide an image forming apparatus having extremely high transfer efficiency from the first image bearing member to the intermediate transfer member and very high transfer efficiency from the intermediate transfer member to the second image bearing member. Is what you do.

Another object is that the uniform and uniform image quality without transfer failure of a minute portion of an image, that is, without a so-called hollow image, depends on the type of paper or OHP sheet as the second image carrier. An object of the present invention is to provide an image forming apparatus which can be obtained without using the above.

Another object is to provide good adhesion between the elastic layer and the coating layer even under severe and durable use such as repeated use of the intermediate transfer member, and hardly cause changes such as surface shaving and roughness. It is intended to provide an image forming apparatus capable of maintaining the same characteristics as described above.

Another object of the present invention is to provide an image forming apparatus which does not cause filming due to toner adhesion to the surface of the intermediate transfer member.

[0032]

That is, the present invention provides an image forming method in which an image formed on a first image carrier is transferred onto an intermediate transfer member and then further transferred onto a second image carrier. In the apparatus, the intermediate transfer member may include at least a dicarboxylic acid, a dialcohol, and the following general formula (1)

[0033]

Embedded image (Wherein, R is an alkylene group having 2 to 3 carbon atoms, R ₁ and R
₂ is hydrogen or an alkyl group having 1 to 3 carbon atoms;
An integer satisfying ≦ a + b ≦ 5, and n is a positive integer. And polyester selected from di- and triisocyanate compounds.
An image forming apparatus characterized by having a coating layer made of a polyester polyurethane resin which is a polymer with at least one isocyanate compound.

The concept of the resin used in the present invention is to be used as a polymer in a broad sense including the concepts of rubber, elastomer, polymer, plastics and the like.

The polyester polyurethane resin using the polyester obtained by adding and reacting the compound represented by the general formula (1) (compound (1)) of the present invention is more applicable to the coating layer than the non-added polyurethane resin. It is possible to provide a more flexible coating and to provide a stronger coating, and to simultaneously add a coating for preparing the coating, for example, a powdery or solid additive to impart conductivity or mold release properties. Even if a large amount is added, a uniform coating surface can be formed and the film surface can be kept smooth. By these effects, the transfer efficiency and the image quality of the intermediate transfer body could be improved.

Addition of an appropriate amount of the compound (1) to the polyester can improve the adhesion between the coating layer and the elastic layer thereunder, and can improve the durability by repeated use.

However, excessive addition increases the hardness of the coating layer and lowers the flexibility, reduces the resistance to abrasion and scratches, and reduces the slipperiness of the coating layer surface. Filming is easily induced.

However, the addition amount of the compound (1) is preferably 2 to 30% by weight based on the polyester polyurethane resin. If the content is less than 2% by weight, no substantial effect can be obtained, and excessive addition outside this range may cause the above-mentioned problems.

In the polyester polyurethane resin of the present invention, dicarboxylic acid and dialcohol, which are monomers used for obtaining the polyester, are used as components having relatively low molecular weights, so that the obtained coating film surface is dense and the hardness is increased. In addition, the friction resistance and the abrasion resistance can be improved. When the number of methylene groups in the dicarboxylic acid or dialcohol is increased and the molecular weight is increased, the film has some flexibility, but the hardness is considerably reduced.

In the present invention, preferred embodiments of the dicarboxylic acid and the dialcohol are as follows.

HOOC- (CH_Two )_A -COOH, A =
HO- (CH _Two )_B -OH, B =
Range of 2 to 5 or CH_Three -CH (OH) -CH_Two -OH
And more preferable ranges are A = 0 to 4, B = 2
~ 3.

Although the selection of the composition and the amount of the isocyanate is important in forming the polyurethane coating film, in the present invention, the selection of the monomer constituting the polyester is more effective in achieving the object of the present invention. I found that

A polyether polyol compound may be added to the polyester polyurethane resin of the present invention as long as the effects of the present invention are not impaired. For example, poly (oxypropylene) glycol, poly (oxypropylene) poly (oxyethylene) glycol, poly (oxybutylene) glycol, poly (oxytetramethylene)
Poly (oxyalkylene) glycols such as glycol, poly (oxypropylene) triol, poly (oxypropylene) poly (oxyethylene) triol, poly (oxyalkylene) triols such as poly (oxybutylene) triol, ethylenediamine, pentaerythritol And poly (oxyalkylene) polyols such as poly (oxypropylene) polyol and poly (oxypropylene) poly (oxyethylene) polyol using sorbitol, sucrose, starch and the like as initiators.

Examples of the isocyanate compound used in the present invention include aromatic isocyanate compounds such as tolylene diisocyanate, meta-xylylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl isocyanate; hydrogenated products of the above isocyanates; Isocyanate compounds, and blocked isocyanate compounds in which isocyanate groups of these isocyanate compounds are blocked with phenol, ketoxime, aromatic secondary amine, tertiary alcohol, amide, lactam, heterocyclic compound, sulfite, and the like.

As a catalyst for accelerating the formation of a polymer,
Naphthenates such as magnesium naphthenate and cobalt naphthenate, tin compounds such as dibutyltin dilaurate, dimethyltin dilaurate, stannous chloride, triethylenediamine, N-methylmorpholine, N, N, N ',
An amine compound such as N'-tetramethylpolymethylenediamine may be added. The addition amount of the catalyst is preferably 0.05 to 5% by weight based on the polymer.

As a method for obtaining the coating layer of the present invention, a dicarboxylic acid, a dialcohol and a compound (1) preferably selected are subjected to a condensation reaction to obtain a polyester in advance. By further reacting with a cyanate compound, a desired polyester urethane resin is obtained. Next, this is dissolved and decomposed in an appropriate solvent.

At this time, a resistance controlling agent, a lubricant, a release agent and the like are simultaneously dispersed and mixed to obtain a coating material for coating. After coating, it reacts and cures to obtain a coating layer.

As the coating method, a spray coating method,
Dip coating, roll coater coating, curtain flow coating, and the like can be used.

In order to control the electric resistance of the coating layer of the present invention, if necessary, an electron conductor or an ionic conductor can be added as a resistance control agent.

Examples of preferred electron conductors include conductive metal oxides, graphite, and metals (copper, aluminum,
Nickel and silver) and conductive polymers (polyaniline,
Polypyrrole, polythiophene, polyacetylene, polypyridine, polyacene, polyazulene, polydiphenylbenzidine, polyvinylcarbazole, poly-3-alkylthiophene, and the like. Of these, metals, polyaniline, polypyrrole and polythiophene are particularly preferred. Examples of preferred ionic conductors include metal salts and ammonium salts. Examples of the metal salt include salts of metals of Group I or Group II, and among them, salts of Li, Na and K having a relatively small cation radius are particularly preferable. Examples of the anions constituting these metal salts include halogen ions (F, Cl, Br and I, etc.), thiocyanate ions, perchlorate ions, trifluoromethanesulfonate ions, and fluoroborate ions.
Of these, particularly preferred are thiocyanate, perchlorate, trifluoromethanesulfonate and fluoroborate. As the ammonium salt, carboxylic acids (adipic acid, phthalic acid,
Ammonium salts of acids such as azelaic acid), phosphoric acid, boric acid, sulfonic acids (such as arylsulfonic acids) and borofluoric acid. Among these ammonium salts, ammonium carboxylate, ammonium phosphate and ammonium borate are particularly preferred. The electron conductor and the ionic conductor may be used as a mixture.

When these resistance control agents are used as a coating layer and are added to a coating, it is preferable to add them in an amount of 1.0% by weight to 200% by weight based on the solid resin component in the coating. If the amount is less than 1.0% by weight, the electric resistance cannot be stably controlled, and a surface having a uniform resistance may not be formed. On the other hand, if it exceeds 200% by weight, it becomes difficult to form a tough continuous film. In extreme cases, a stable film cannot be formed, and a film in which independent particles are weakly bonded to each other results.

The intermediate transfer member used in the present invention has, for example, a roller shape having at least an elastic layer made of rubber, elastomer, or resin on a rigid cylindrical conductive support.
Further, various forms such as a roller shape having one or more coating layers on the upper layer of the elastic layer or a belt shape as shown in FIG. 5 can be selected as required for various purposes. The example is shown in FIGS.

Considering the prevention of color misregistration in image superposition and the durability due to repeated use, a more preferred embodiment of the present invention is a roller shape.

In each of the figures, 100 is a rigid cylindrical conductive support, 101 is an elastic layer, 102 and 103 are coating layers, and 104 is an intermediate transfer belt.

As the cylindrical conductive support, a metal or alloy such as aluminum, iron, copper and stainless steel, a conductive resin in which carbon and metal particles are dispersed, and the like can be used. Such a cylinder, a cylinder having a shaft penetrating the center of the cylinder, a cylinder having a reinforced interior, and the like can be given.

Other rubbers, elastomers, and resins used in the elastic layer and the coating layer of the intermediate transfer member used in the present invention include, for example, styrene-butadiene rubber, high styrene rubber, butadiene rubber, Isoprene rubber, ethylene-propylene copolymer,
Examples thereof include nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicone rubber, fluorine rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, and norbornene rubber. Further, as resins, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene- Vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, Styrene-
Octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer,
Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylate copolymer Styrene-based resins such as coalesced copolymers (homopolymers or copolymers containing styrene or styrene substituents), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic acid resins, phenolic resins, epoxy resins,
Polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin,
Examples include a silicone resin, a ketone resin, an ethylene-ethyl acrylate copolymer, a xylene resin, and a polyvinyl butyral resin.

The thickness of the elastic layer is 0.5 mm or more,
mm or more, particularly preferably 1 mm to 10 mm. The thickness of the coating layer is preferably a thin layer for transmitting the flexibility of the lower elastic layer to the upper layer or to the surface of the photoreceptor, specifically 3 mm or less, more preferably 2 mm or less, and particularly 5 μm. It is preferably about 1 mm.

The volume resistivity of the intermediate transfer member used in the present invention is preferably from 10 ¹ to 10 ¹³ Ω · cm, particularly preferably from 10 ² to 10 ¹⁰ Ω · cm. The volume resistivity of at least the surface layer is preferably within these ranges.

A photosensitive member such as a roller belt can be used as the first image carrier used in the present invention.
The roller shape can minimize the deviation of high transfer efficiency and image registration (registration),
It is suitable in the present invention. It is presumed that this is because the rigid intermediate transfer member and the rigid photosensitive drum are in contact with each other, and the above-described favorable effects occur.

The photosensitive layer of this photoreceptor is made of OPC
(Containing organic photoconductor) A photosensitive layer, particularly a photosensitive layer having a layer containing fluorine resin particles having a particle size of 0.1 to 100 μm, for example, polytetrafluoroethylene particles, polyvinylidene fluoride particles, etc. When a photosensitive drum coated on the surface of a rigid roller is used, friction between the intermediate transfer member and the photosensitive member is reduced, high durability of the intermediate transfer member is obtained, transfer efficiency is improved, and partial transfer failure is caused. There is an advantage such as prevention of the above, and the performance can be further improved by combination with the present invention.

The intermediate transfer member of the present invention is manufactured, for example, as follows.

First, a metal roll as a cylindrical conductive support is prepared. An elastic layer is provided by molding rubber, elastomer resin, or the like on a metal roll by melt molding, injection molding, dip coating, spray coating, or the like.

Next, as described above, the coating layer is provided by forming the material of the coating layer on the elastic layer by melt molding, injection molding, dip coating or spray coating.

[0064]

The present invention will be described below in detail with reference to examples. (Examples 1 and 2 and Comparative Examples 1 and 2) An elastic layer was formed by transfer molding a rubber compound having the following composition on the surface of an aluminum cylindrical roller having a diameter of 182 mm, a length of 320 mm and a thickness of 5 mm using a mold. The obtained roller (1) was obtained.

Rubber compounding NBR rubber 100 parts (parts by weight, the same applies hereinafter) Zinc oxide 2 parts Conductive carbon black 10 parts Paraffin oil 30 parts Vulcanizing agent (sulfur) 2 parts Vulcanization accelerator (dibenzothiazyl disulfide, MBTS) 3) Next, in order to obtain a coating layer on the upper layer, a coating material for a coating layer was prepared based on the following formulation and production method.

Glutaric acid 10 parts, adipic acid 40 parts, propylene glycol 30 parts, and the following compound (A)

[0067]

Embedded image 10 parts were condensed to obtain a polyester (1). Next, as an isocyanate compound, 25 parts of tolylene diisocyanate, 10 parts of hexamethylene diisocyanate, and 0.05 part of triethylenediamine were added and a polymerization reaction was performed to obtain a polyester polyurethane resin (1).
00 parts were dissolved in toluene. Further, 60 parts of conductive tin oxide as an electric resistance adjusting agent and 80 parts of polyvinylidene fluoride fine powder as a lubricant were added to the toluene solution,
The mixture was dispersed and mixed in a ball mill for about 3.0 hours, and then 10 parts of toluene was added, followed by stirring and mixing with a homomixer for 1.0 hour to obtain a coating material for a coating layer.

A coating layer having a thickness of about 50 to 200 μm is formed on the surface of the roller (1) by spray coating with the above coating material, and then dried and cured at 80 ° C. for 1.5 hours to obtain the intermediate transfer body (1) of the present invention. I got

The intermediate transfer member (1) was mounted on the full-color electrophotographic apparatus shown in FIG. 1, and a full-color image copying test was repeatedly performed using an OPC photosensitive drum having a photosensitive layer on an aluminum cylinder as a photosensitive member. . Table 1 shows the results.

The image forming conditions of this embodiment will be described below.

Photoreceptor: OPC photosensitive drum (having a coating layer in which polytetrafluoroethylene particles having a particle size of 0.1 μm are dispersed on the surface layer) Surface potential: -700 V Color developer (for all four colors): non-magnetic one component Toner Primary transfer voltage: +900 V Secondary transfer voltage: +3400 V Process speed: 120 mm / s Development bias: -500 V

Example 2 A durability test was performed in the same manner as in Example 1 except that the coating material for the coating layer was changed as follows. In terms of image quality, a good full-color image was obtained, which was the same as the initial one even after 10,000 sheets. Table 1 shows the results.

Adipic acid 50 parts, diethylene glycol 10 parts, propylene glycol 25 parts, and the following compound (B)

[0074]

Embedded image 10 parts were condensed to obtain a polyester (2).

Next, as an isocyanate compound, MD
Polymerization reaction was carried out with 30 parts of I and 0.07 parts of triethylenediamine to obtain a polyester polyurethane resin (2). Thereafter, a coating material for a coating layer was obtained in the same manner as in Example 1.

Example 3 The coating material for the coating layer used in Example 1 was applied to the surface of an endless polytetrafluoroethylene belt to obtain a belt-shaped intermediate transfer member. Using the full-color electrophotographic apparatus shown in FIG. 5, the belt was subjected to an endurance test of 10,000 sheets. As a result, the same advantageous effects as in Example 1 were obtained.

(Comparative Example 1) A durability test was carried out in the same manner as in Example 1 except that an intermediate transfer member (having only an elastic layer) in which no covering layer was formed was used.
Filming gradually occurs on the surface of the intermediate transfer member from 000 sheets, and after 10,000 sheets, a fine streak appears as if raining on the image, resulting in an adverse effect of filming. It was impossible. In addition, the image quality was initially an ignorable minute hollow image, which was negligible, but after 10,000 copies, the defective image was clearly missing the center of the character. Table 1 shows the results.

(Comparative Example 2) A coating material for a coating layer was prepared in the same manner as in Example 1 except that the compound (A) used in Example 1 was omitted from the coating layer. And a durability test.

In the image quality after 10,000 sheets, the rough image and the roughness of the halftone portion increased compared to the initial image.
For the time being, it could be evaluated as a practical lower limit level. On the surface of the intermediate transfer member coating layer after 10,000 sheets, there was a slight judgment that filming occurred at the beginning, but no substantial defect on the image caused by this was found.

In this comparative example, the durability up to 10,000 sheets was obtained, but it was judged that the further improvement of the durability required the coating layer to be further improved.

[0081]

[Table 1]

[0082]

As described above, according to the image forming apparatus of the present invention, the transfer efficiency from the first image bearing member to the intermediate transfer member and from the intermediate transfer member to the second image bearing member are both high. Regardless of the type of paper or OHP sheet, it is possible to obtain a homogeneous image free from image defects such as image dropout. Good properties are maintained even after durability. Further, filming due to toner adhesion to the intermediate transfer member does not occur.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrophotographic apparatus having an intermediate transfer member of the present invention.

FIG. 2 is a schematic sectional view of one example of an intermediate transfer member of the present invention.

FIG. 3 is a schematic sectional view of one example of an intermediate transfer member of the present invention.

FIG. 4 is a schematic sectional view of one example of an intermediate transfer member of the present invention.

FIG. 5 is a schematic sectional view of an electrophotographic apparatus having an intermediate transfer member of the present invention.

FIG. 6 is an example of a missing image.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 5/147 502 G03G 15/01 114

Claims (6)

(57) [Claims] 1. An image forming apparatus for transferring an image formed on a first image carrier onto an intermediate transfer member, and further transferring the image onto a second image carrier, wherein the intermediate transfer member includes at least Dicarboxylic acid, dialcohol and the following general formula (1) (Wherein, R is an alkylene group having 2 to 3 carbon atoms, R ₁ and R
₂ is hydrogen or an alkyl group having 1 to 3 carbon atoms, a and b are integers satisfying 0 ≦ a + b ≦ 5, and n is a positive integer. And polyester selected from di- and triisocyanate compounds.
An image forming apparatus characterized by having a coating layer composed of a polyester polyurethane resin which is a polymer with at least one isocyanate compound. 2. The image forming apparatus according to claim 1, wherein the intermediate transfer member is a roller having an elastic layer. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer member is a roller having an elastic layer and a coating layer. 4. The apparatus according to claim 1, wherein said intermediate transfer member is a belt.
The image forming apparatus as described in the above. 5. The image bearing member according to claim 1, wherein the first image bearing member is a photosensitive drum having a photosensitive layer on a conductive rigid roller, the intermediate transfer member is a rigid roller having an elastic layer, and the apparatus is for electrophotography. The image forming apparatus according to claim 1, wherein 6. The photosensitive drum has a surface layer containing fluororesin particles, and the apparatus is for electrophotography.
The image forming apparatus as described in the above.