JP3337834B2 - 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 or a multi-color image forming apparatus or a multi-color image forming apparatus that sequentially outputs a plurality of component color images of the color image information or the multi-color image information and outputs an image formed by combining and reproducing the color image or the 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 is a schematic diagram of an example of an image forming apparatus which is a transfer apparatus using an intermediate transfer member 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 20 as an intermediate transfer member
You are using

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) which is repeatedly used as a first image carrier, and rotates at a predetermined peripheral speed (process speed) clockwise as 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 the image exposure means shown in FIG. An image-forming 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. (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 42,
43,44 (cyan, yellow, black developing units)
Is turned off and does not act on the photosensitive drum 1,
The first color magenta toner image is not affected by the second to fourth 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 of this embodiment comprises a pipe-shaped 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 portion 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 formed by a primary 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 corresponding to 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 step of sequentially transferring the toner images of the fourth to fourth colors.

The transfer of the composite color toner image superimposed and transferred onto the intermediate transfer member 20 onto a transfer material 24 as a second image carrier is performed while the transfer roller 25 is brought into contact with the intermediate transfer member 20 and supplied. The transfer material 2 is transferred from the paper cassette 9 to the contact nip between the intermediate transfer body 20 and the transfer roller 25 at a predetermined timing.
4 is fed, 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.

In a color electrophotographic apparatus having an image forming apparatus using the above-mentioned intermediate transfer member, a second image carrier is stuck or adsorbed on a transfer drum, which is a conventional technique,
A color electrophotographic apparatus having an image forming apparatus for transferring an image thereon from a first image carrier, for example,
It is superior to the transfer method described in JP-A-301960 in the following points.

(1) Color shift at the time of superimposing toner images of each color is small.

(2) As shown in FIG. 1, an image from the intermediate transfer member can be transferred to the second image carrier without any processing or control (for example, gripping by a gripper, adsorbing, giving a curvature, etc.). Since the image can be transferred, the second image carrier can be selected in a wide variety. For example envelopes, postcards, labels, etc., thin paper (40 g / m ² paper)
It is possible to transfer from the second image carrier to a thick paper (200 g / m ² paper) regardless of the width of the second image carrier, the length of the second image carrier, or the thickness of the second image carrier.

(3) Because the rigidity of the intermediate transfer member is excellent, the dimensional accuracy such as dents, distortion, deformation and the like hardly occurs 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.

[0023]

However, these color electrophotographic apparatuses do not function as apparatuses which fully utilize the above-mentioned advantages and which are truly expected and satisfied by users. It is. That is, when the image forming apparatus using the intermediate transfer body is actually used repeatedly in various environments, there are still the following problems.

(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 for 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, which makes the cleaning device considerably complicated in configuration and expensive. It will be something.

(2) An image transferred to the intermediate transfer member and a part of the image transferred to the second image support are not transferred as shown in FIG. In some cases). This is caused by the fact that the transfer efficiency has not been achieved at 100% as described in (1). As the cause, the material used for the intermediate transfer body, surface properties, resistance, or the magnitude of the applied bias at the time of transfer, its timing or the mechanical configuration of the image forming apparatus, etc. are considered to act in combination, The main cause is unknown. However, as the durability of the intermediate transfer member progresses,
Or, it is known that it becomes worse in a low temperature and low humidity environment.

(3) The surface properties and resistance of the intermediate transfer member may change as the durability of the intermediate transfer member is increased by repeated use. 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. The cleaning method includes various methods such as blade cleaning, fur brush cleaning, or a combination thereof. When a cycle of transferring, adhering, and releasing the toner on the surface of the intermediate transfer body 20 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. In this case, the transferability of the toner from the first image carrier is deteriorated, resulting in an image having a spot-like white spot due to poor transfer of the filmed portion, and lowering the image quality or lowering the overall transfer efficiency. Invite.

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

An object of the present invention is to provide an image forming apparatus in which transfer efficiency from the first image carrier to the intermediate transfer member and transfer efficiency from the intermediate transfer member to the second image carrier are extremely high. It is. Another object is to obtain a uniform and homogeneous image quality that does not cause transfer failure of a minute portion of an image without depending on the type of paper or OHP sheet that is the second image carrier and that has no so-called hollow image. An image forming apparatus is provided. Another object of the present invention is to provide an image forming apparatus which does not change even when subjected to severe endurance use due to repeated use of the intermediate transfer member, and can maintain the same characteristics as the initial state. Another object is to provide an image forming apparatus which does not cause filming due to toner adhesion to the surface of an intermediate transfer member.

[0030]

That is, the present invention relates to an image forming apparatus comprising: an image formed on a first image carrier; an elastic layer; and a coating layer formed by applying a coating material for the coating layer on the elastic layer. In the image forming apparatus, after the transfer on the intermediate transfer member having the following, the coating layer further transfers a ferroelectric substance having a relative dielectric constant of 5 or more to an average particle diameter of 0.1 to 10 μm. to contain those powdered, those the powdered relative to the resin solids content of the coating layer in the coating material is Ri 1-300 wt% der, the
Ferroelectric is an image forming apparatus according to claim substance der Rukoto represented by the following general formula. General formula: MTiO ₃ , M = Ca, Sr, Ba.

The present invention also relates to a method for forming a first image carrier on a first image carrier.
The formed image is coated with an elastic layer and a coating material for a coating layer on the elastic layer.
Onto an intermediate transfer member having a coating layer formed by applying
After forming, image formation is further transferred onto a second image carrier.
In the apparatus, the coating layer is a ferroelectric substance having a relative dielectric constant of 5 or more.
Containing 0.1 to 10 μm average particle size
The powder was then powdered with respect to the resin solid content in the coating material for the coating layer.
Is 1 to 300% by weight, and the ferroelectric is titanium oxide.
And an image forming apparatus. Also,
According to the present invention, the image formed on the first image carrier is
Formed by applying a coating material for a coating layer on the elastic layer and the elastic layer.
After transfer onto the intermediate transfer member having the covered layer, the second image
In an image forming apparatus for further transferring an image on an image bearing member,
The covering layer is made of a ferroelectric substance having a relative dielectric constant of 5 or more, having an average particle size of 0.1 to
Containing 10 μm powder, contained in the coating for the coating layer
1 to 300 weight of the powdered resin based on the resin solid content
%, And the ferroelectric is a polyvinylidene fluoride resin.
An image forming apparatus comprising:

Hereinafter, the present invention will be described in detail.

The reason why the transfer efficiency is improved by adding a ferroelectric substance is considered as follows. That is, the electric field applied between the first image bearing member and the intermediate transfer member is represented by E
1. Assuming that the electric field applied between the intermediate transfer member and the second image carrier is E2, E1 and E2 can be written as follows.

[0034] _{E1 = (V h1 -V c)} / (d m / ε m + d t1 / ε t + d c / ε c + g 1) ... (1) E2 = (V h2 -V p) / (d c / ε _c + d _t2 / ε _t + d _p / ε _p + g ₂ ) (2) where V _h1 : surface potential on the toner layer on the first image carrier V _c : surface potential on the intermediate transfer body V _h2: the surface potential V of the toner layer on the intermediate transfer member _p: a second surface potential of the image carried on member d _m: the first image carrier thickness d of the recording layer of _t1: first image bearing member Thickness of upper toner layer d _c : Thickness of elastic layer and coating layer of intermediate transfer member d _t2 : Thickness of toner layer on intermediate transfer member d _p : Thickness of second image carrier ε _m : First image The relative permittivity of the recording layer of the carrier ε _t : the relative permittivity of the toner layer ε _c : the relative permittivity of the elastic layer and the coating layer of the intermediate transfer body ε _p : the relative permittivity of the second image carrier g ₁ : First An image bearing member and the intermediate transfer member gap width between g _2: transfer efficiency in the electrostatic transfer of the gap width toner and the second image bearing member and the intermediate transfer member, the electric field E applied to the gap between the transfer material and the toner layer Is known to be proportional to Then, as is clear from Expressions (1) and (2), it is found that E1 and E2 increase as ε _c increases. Therefore, when ε _c is increased, the transfer efficiency of the toner from the first image carrier to the intermediate transfer member (hereinafter referred to as primary transfer efficiency) and the transfer efficiency of the toner from the intermediate transfer member to the second image carrier (hereinafter referred to as primary transfer efficiency) (Referred to as secondary transfer efficiency).

Since the intermediate transfer member of the present invention contains a ferroelectric, the intermediate transfer member has a large relative dielectric constant. This is considered to be the reason that the intermediate transfer member of the present invention exhibits high transfer efficiency. Further, high transfer efficiency also means that the transfer residual toner is small. Therefore, even if the intermediate transfer member is repeatedly used and the durability is advanced, filming hardly occurs and a good image can be maintained.

Further, since the ferroelectric substance contained in the intermediate transfer member of the present invention is a fine powder, the surface of the intermediate transfer member can be made smooth, and a good image without a hollow image or the like can be obtained. Obtainable.

Further, the ferroelectric substance contained in the intermediate transfer member of the present invention has a dramatic change in the relative dielectric constant in the temperature range (10 ° C. to 35 ° C.) in actual use, and therefore, the relative dielectric constant is practically used. It can be said that the rate does not depend on the environment. Therefore, the intermediate transfer member of the present invention always shows a high transfer efficiency stably regardless of the use environment.

Examples of the ferroelectric fine powder to be contained in the intermediate transfer member of the present invention include fine powders of inorganic compounds such as calcium titanate, strontium titanate, barium titanate and titanium oxide, and organic compounds such as polyvinylidene fluoride. Can be used.

The measurement of the relative permittivity of the ferroelectric material in the present invention was performed as follows. (1) A measurement sample is formed into a disk shape having a thickness of 10 to 10000 μm and a diameter of 20 mm or more. (2) LCR meter (manufactured by Yokogawa Hewlett-Packard Company, HP4284A + electrode for dielectric measurement: HP164)
51B (B type)). (3) 1 Vrms (1000 Hz) is applied, and “Cp−
Measure the value of Cp in "Rp" mode. (4) Based on the obtained Cp, the relative dielectric constant ε of the measured substance is calculated by the following equation.

Ε = Cp (pF) × d (μm) /173.85 where d: thickness of the sample.

As the ferroelectric substance of the present invention, particularly, one obtained by sintering calcium titanate, strontium titanate, and barium titanate into fine powder once and having a relative dielectric constant of several thousands to ten thousands is extremely high. To indicate a high value,
The addition of a small amount can increase the relative dielectric constant of the intermediate transfer member.

The relative dielectric constant of titanium oxide is about 80, and the relative dielectric constant of the intermediate transfer member can be increased. In addition, by using a conductive titanium oxide which has been subjected to a surface treatment to have conductivity, the relative permittivity of the intermediate transfer member can be increased and the resistance can be adjusted.

Although the relative permittivity of the polyvinylidene fluoride resin is 7 to 8, it has an effect of increasing the relative permittivity of the intermediate transfer member. However, the degree is naturally smaller than that of the aforementioned ferroelectric. Nevertheless, the intermediate transfer member containing the fine powder of polyvinylidene fluoride resin shows high transfer efficiency. This is because polyvinylidene fluoride has a high releasability, so when it is contained in the coating layer of the intermediate transfer body, the releasability of the toner increases, thereby contributing to an improvement in transfer efficiency. I think that the.

The average particle size of the ferroelectric fine powder in the present invention was determined according to the following procedure. (1) Both the elastic layer and the coating layer are cut out from a part of the intermediate transfer body and subjected to ion sputtering to prepare a sample for observation with an electron microscope. (2) Observe the above sample with an electron microscope at an arbitrary magnification. (3) Arbitrarily select from 20 ferroelectric particles in the field of view.
Select individual particles. 10 or more particles in the field of view 20
If it is less than one, select all particles. If the number of particles in the visual field is less than 10, all the particles are selected, the visual field is moved, and this operation is repeated a plurality of times. (4) Of the straight lines connecting the ends of the selected particles,
The longest length is defined as the particle size of the particles, and an average value is determined from the particle sizes of the particles. This value is defined as the average particle size.

The ferroelectric fine powder of the present invention is added to the upper coating layer of the elastic layer of the intermediate transfer member.

The shape of the ferroelectric fine powder is preferably spherical, granular, rod-like or scaly. Also,
The average particle size of the fine powder of the ferroelectric is 10μm or less.
When it is larger than 10 μm, the surface roughness of the coating layer becomes large, which causes deterioration of image quality.

The ferroelectric fine powder is applied to the elastic layer of the intermediate transfer member .
When used in the coating material for the coating layer, it is added in an amount of 1% by weight to 300% by weight based on the resin solid content in the coating material because it is used for the upper coating layer. If the amount is less than 1% by weight, there is no effect of increasing the relative dielectric constant of the intermediate transfer member by adding a ferroelectric substance, so that transfer efficiency cannot be improved. On the other hand, if it exceeds 300% by weight, it becomes difficult to form a tough continuous film. In extreme cases, a stable coating surface cannot be formed, resulting in a coating in which independent particles are weakly bound.

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 cylindrical conductive support, and one or more coating layers on the elastic layer. Alternatively, the belt shape and various aspects as shown in FIG. 5 can be selected for the purpose and need. The example is shown in FIGS.

In consideration of the color misregistration of 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 drawings, reference numeral 100 denotes a rigid cylindrical conductive support, 101 denotes an elastic layer,
Numerals 2 and 103 indicate a coating layer, and 104 indicates 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, metal particles, and the like 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.

The rubber, elastomer, and resin used for the elastic layer and the cover layer of the intermediate transfer member used in the present invention include:
For example, as the elastomer or rubber, styrene-butadiene rubber, high styrene rubber, butadiene rubber, isoprene rubber, ethylene-propylene copolymer, chloroprene rubber, butyl rubber, silicone rubber, fluorine rubber,
Examples include acrylonitrile butadiene rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, polynorbornene rubber, and the like. Further, as resins, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl oxide copolymer, styrene-maleic acid copolymer, styrene -Acrylate copolymers (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer) Styrene-methacrylic ester copolymers (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-chloroacrylic acid Methyl copolymer, styrene-acrylonitrile-acryl Styrene resins such as acrylate copolymers (mono- or copolymers containing styrene or styrene substituents), methyl methacrylate resin, butyl methacrylate resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic Resins (silicone-modified acrylic resin, vinyl chloride resin-modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, rosin-modified maleic resin, phenol resin , Epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, fluorine resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene Resins and polyvinyl butyral resins, polyamide resins, modified polyphenylene oxide resins.

The thickness of the elastic layer is preferably 0.5 mm or more, more preferably 1 mm or more, and particularly preferably 1 mm to 10 mm. Further, the thickness of the coating layer is preferably a thin layer for transmitting the flexibility of the lower elastic layer further to the upper layer or the surface of the photoreceptor, specifically 1 mm or less, more preferably 500 μm or less. In particular, the thickness is preferably 1 μm to 200 mm.

The resistance value of the intermediate transfer member used in the present invention is 1
It is preferably 0 ⁴ ~10 ¹⁰ Ω.

In order to control the resistance as described above, it is necessary to add a conductive agent in some cases. The conductive agent can be added as appropriate as long as the object of the present invention is not hindered. For example, carbon, aluminum powder, nickel powder, or the like can be used. However, when conductive titanium oxide is used, the resistance can be adjusted and the relative dielectric constant can be improved.
It is also conceivable to use a conductive resin instead of dispersing a conductive agent in the resin. Specific examples include quaternary ammonium salt-containing polymethyl methacrylate, polyvinylaniline, polyvinylpyrrole, polydiacetylene, and polyethyleneimine. Among these, a conductive particle-dispersed resin is preferred from the viewpoint of controlling the conductivity.

As the first image carrier, a photosensitive drum having a photosensitive layer on a conductive rigid roller, and a fine powder of ethylene tetrafluoride resin (PTFE) is provided on at least the outermost layer of the photosensitive drum. It is preferable to use a photosensitive drum containing the photosensitive drum. In particular, when a photosensitive drum containing at least the outermost layer containing PTFE fine powder is used, higher primary transfer efficiency can be obtained. This is considered to be because the surface energy of the outermost layer of the photoreceptor is reduced by containing the fine powder of PTFE, and the releasability of the toner is improved.

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

[0058]

The present invention will be described in detail below with reference to examples. (Example 1) Diameter 182 mm, length 320 mm, thickness 5
A roller having an elastic layer was obtained by subjecting a rubber compound having the following composition to transfer molding using a mold on the surface of a cylindrical roller made of aluminum having a thickness of 1 mm.

Rubber compounding NBR rubber 100 parts (parts by weight, the same applies hereinafter) Vulcanizing agent (precipitated sulfur) 1.5 parts Vulcanization aid (zinc oxide) 5 parts Vulcanization accelerator (TBTD) 1.5 parts Vulcanization Accelerator (MBTS) 1.2 parts Conductive agent (graphite) 10 parts Dispersion aid (stearic acid) 1 part Plasticizer (naphthenic process oil) 45 parts Next, barium titanate is sintered at 1370 ° C. for 2 hours. Then, it was pulverized into fine powder having an average particle size of 5 μm. Using this fine powder, a coating material was prepared based on the following composition, and used as a coating material for a coating layer for obtaining a coating layer on the elastic layer.

Coating composition for coating layer 50 parts of polyurethane prepolymer 3 parts of curing agent (isocyanate) 3 parts of conductive agent (graphite) 10 parts of barium titanate 10 parts 40 parts of toluene 40 parts of methyl ethyl ketone Thickness 100
A coating layer having a thickness of μm was formed, and thereafter, heating was performed at 85 ° C. for 1 hour to remove the residual solvent, and the coating layer was crosslinked to obtain an intermediate transfer member having a tough surface layer. The resistance of the intermediate transfer member was 3 × 10 ⁷ Ω.

Next, the coating layer and the elastic layer of the intermediate transfer member and the aluminum cylindrical roller were peeled off, and the relative permittivity of the coating layer and the elastic layer was measured using the LCR meter. The measurement was performed in two environments: a low-temperature and low-humidity environment (15 ° C./10% RH) and a high-temperature and high-humidity environment (32.5 ° C./85% RH). The result is ε = 14, 32.5 ° C at 15 ° C / 10% RH.
At ８５ / 85% RH, almost no change was observed at ε = 16, and the sample was stable.

This intermediate transfer member was mounted on a full-color electrophotographic apparatus shown in FIG. 1, and a full-color image was printed on 80 g / cm ² paper using an OPC photosensitive drum as a photosensitive member. Defined and measured. Primary transfer efficiency (transfer efficiency from photosensitive drum to intermediate transfer body); image density on intermediate transfer body / (transfer residual image density on photosensitive drum + image density on intermediate transfer body). Secondary transfer efficiency (transfer efficiency from intermediate transfer body to paper); image density on paper / (image density on paper + transfer residual image density on intermediate transfer body).

As a result of measuring the transfer efficiency at 23 ° C./50% RH, the primary transfer efficiency was 96%, and the secondary transfer efficiency was 94%.
Met. The full-color print image had characters and fine lines without any voids, and the solid image had uniform image quality. Even after the endurance test of 10,000 sheets, the same image quality as in the initial stage was obtained, and the secondary transfer efficiency was 93%, which was almost not reduced.

The presence or absence of filming with toner was determined by observation with an optical microscope. Observation of the surface of the intermediate transfer member of Example 1 after the endurance of 10,000 sheets revealed that no filming by the toner was present.

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

Photoreceptor: OPC photosensitive drum 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 / sec Development bias: -500 V

Example 2 An intermediate transfer member was prepared in the same manner as in Example 1 except that the coating composition for the coating layer was changed as follows in Example 1, and the measurement of the relative dielectric constant and the transfer efficiency were performed. And a durability test. In terms of image quality, a good full-color image was obtained which was not different from the initial state even after the endurance of 10,000 sheets.
Table 1 shows the results.

Coating composition for coating layer Polyurethane prepolymer 50 parts Curing agent (isocyanate) 3 parts Conductive titanium oxide 30 parts Toluene 50 parts Methyl ethyl ketone 50 parts

Example 3 An intermediate transfer member was prepared in the same manner as in Example 1 except that the composition of the coating material for the coating layer was changed as follows in Example 1, and the measurement of the relative dielectric constant and the transfer efficiency were performed. And a durability test. In terms of image quality, a good full-color image was obtained which was not different from the initial state even after the endurance of 10,000 sheets.
Table 1 shows the results.

Coating composition for coating layer Polyurethane prepolymer 50 parts Curing agent (isocyanate) 3 parts Conductive agent (graphite) 10 parts Polyvinylidene fluoride fine powder 50 parts Toluene 50 parts Methyl ethyl ketone 50 parts

[0071]

[0072]

Example 4 The photosensitive drum containing the fine powder of PTFE in the outermost layer and the intermediate transfer member of Example 1 were mounted on the full-color electrophotographic apparatus shown in FIG. 1, and the transfer efficiency was measured and the durability test was performed. went.
Compared with Example 1, the primary transfer efficiency was further improved. Table 1 shows the results.

(Comparative Example 1) Measurement of relative permittivity and measurement of transfer efficiency in the same manner as in Example 1 except that an intermediate transfer member (having only an elastic layer) in which a coating layer was not formed was used. And the durability test was performed, but filming occurred on the surface of the intermediate transfer member gradually from about 3,000 sheets, and after 10,000 sheets, it appeared on the image as a thin streak like rain, and the image quality was It was not practical. As for the degree of hollowing out, at the beginning, only a negligible hollowing-out image quality could be seen, but after 10,000 sheets of durability, it was a defective image in which the center of the character was clearly missing. Table 1 shows the results.

Comparative Example 2 An intermediate transfer member was prepared in the same manner as in Example 1 except that barium titanate was not added in the formulation of the coating material for the coating layer of Example 1, and the relative dielectric constant was measured.
A transfer efficiency measurement and a durability test were performed. Although a good image could be obtained in the initial stage, the secondary transfer efficiency was rather low, and the image became rough as the durability was improved. That is, practically, the durability was only about 6000 to 8000 sheets, and the environment dependency of the dielectric constant was poor. Table 1 shows the results.

[0076]

[Table 1]

[0077]

As described above, the present invention provides the first
An image forming apparatus for transferring an image formed on an image carrier to an intermediate transfer member and further transferring the image on a second image carrier, wherein the intermediate transfer member has a relative dielectric constant of 5 or more. The intermediate transfer member has a large relative dielectric constant. Therefore, the following effects can be obtained by using the image forming apparatus of the present invention. (1) Both primary transfer and secondary transfer exhibit high transfer efficiency. Therefore, the transfer residual toner is small, and the size of the cleaning device can be reduced. (2) Since the transfer efficiency is high, a good image can be obtained without occurrence of a hollow image. (3) Since the transfer efficiency is high, occurrence of filming due to durability can be suppressed. (4) Since the environment dependency of the relative permittivity of the intermediate transfer member is small, a good image can be obtained without being affected by the use environment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a color image output apparatus using a roller-shaped intermediate transfer member.

FIG. 2 is a cross-sectional view of a roller-shaped intermediate transfer body of the present invention having an elastic layer.

FIG. 3 is a sectional view of a roller-shaped intermediate transfer member of the present invention having a coating layer on an elastic layer.

FIG. 4 is a cross-sectional view of a roller-shaped intermediate transfer body of the present invention having a plurality of coating layers on an elastic layer.

FIG. 5 is a schematic diagram of a color image output device using an intermediate transfer belt.

FIG. 6 is a diagram illustrating an example of a hollow image;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 primary charging device 3 image exposure means 9 paper feed cassette 14 photosensitive drum cleaning device 15 fixing device 20 intermediate transfer body 21 metal core 22 elastic layer 24 transfer material 25 transfer roller 35 intermediate transfer body cleaner 41 magenta color development Apparatus 42 Cyan developing apparatus 43 Yellow developing apparatus 44 Black developing apparatus 61 Bias power supply 100 Core metal 101 Elastic layer 102 Coating layer 103 Coating layer 104 Belt-shaped intermediate transfer body

Continued on front page (72) Inventor Takashi Kusaba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsunetori Ashbe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon stock JP-A-6-19254 (JP, A) JP-A-6-130835 (JP, A) JP-A-5-303294 (JP, A) JP-A-5-210314 (JP, A) JP-A-6-149085 (JP, A) JP-A-6-324550 (JP, A) JP-A-6-67551 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/01 114 G03G 15/16-15/16 103 G03G 5/05 103

Claims (7)

(57) [Claims] An image formed on a first image carrier is transferred onto an intermediate transfer member having an elastic layer and a coating layer formed by applying a coating material for the coating layer on the elastic layer. An image forming apparatus for further transferring the image on a second image carrier, wherein the coating layer contains a ferroelectric substance having a relative dielectric constant of 5 or more powdered to an average particle diameter of 0.1 to 10 μm; The powdered material is 1 to 3 with respect to the resin solid content in the coating material for the coating layer.
00 wt% der is, the ferroelectric body represented by the following general formula
An image forming apparatus comprising material der Rukoto. General formula: MTiO ₃ , M = Ca, Sr, Ba. 2. An image formed on a first image carrier.
Is formed by applying a coating material for a coating layer on the elastic layer and the elastic layer.
After transfer onto an intermediate transfer body having a coating layer formed,
In the image forming apparatus for further transferring the image on the image carrier 2
The coating layer has a ferroelectric material having a relative dielectric constant of 5 or more having an average particle size.
0.1 to 10 μm powder, containing the coating layer
1 to 3 with respect to the resin solid content in the paint
00% by weight, and the ferroelectric is titanium oxide
An image forming apparatus comprising: 3. An image formed on a first image carrier.
Is formed by applying a coating material for a coating layer on the elastic layer and the elastic layer.
After transfer onto an intermediate transfer body having a coating layer formed,
In the image forming apparatus for further transferring the image on the image carrier 2
The coating layer has a ferroelectric material having a relative dielectric constant of 5 or more having an average particle size.
0.1 to 10 μm powder, containing the coating layer
1 to 3 with respect to the resin solids in the coating composition
And the ferroelectric is polyvinylidene fluoride
An image forming apparatus comprising a resin. 4. The apparatus according to claim 1, wherein said intermediate transfer member is a roller.
The image forming apparatus according to any one of claims 1 to 3 , wherein 5. The apparatus according to claim 1, wherein the intermediate transfer member is a belt.
The image forming apparatus according to any one of claims 1 to 3 , wherein 6. The first image bearing member, an image forming apparatus according to any one of claims 1 to 5 conductive rigid roller onto a photosensitive drum having a photosensitive layer. 7. The image forming apparatus according to claim 6 , wherein at least the outermost layer of the photosensitive drum contains a fine powder of an ethylene tetrafluoride resin.