JPH0766219B2 - Copy method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a copy image such as electrophotography and electrostatic recording. More specifically, the present invention relates to a copying method in which transfer is performed in two steps using an intermediate transfer member to obtain a high quality image.

[Prior Art] In an electrophotographic method, a photoconductive layer formed on a conductive substrate is uniformly charged, and then, an electrostatic latent image is formed by imagewise discharging by an exposure operation. This latent image is visualized by a colored resin called toner. The visualized developed image is transferred to transfer paper such as paper by electrostatic attraction, and then fused and fixed on the transfer paper through a fixing roll to obtain a permanent image.

In the transfer process, a corotron or a biased roll is generally used.

In such a copying method, it is known that the quality of the final fixed image is often deteriorated due to the image disturbance during the transfer process.

In view of this point, a copying method in which an electrostatic transfer step is omitted is also proposed.

For example, Japanese Examined Patent Publication No. 37-11646 discloses a method in which a toner image formed on a photoconductor is directly superposed on a transfer paper and transferred and fixed by a heating roll or the like.

In Japanese Patent Publication No. 46-41679, an intermediate transfer medium formed of silicon rubber or the like is used to transfer the toner image once formed on the photoreceptor to the intermediate transfer medium in a non-electrostatic manner (a kind of adhesive transfer). Then, a copying method is disclosed in which the intermediate transfer medium and the heating roll are brought into contact with each other through the transfer paper, and the toner image on the intermediate transfer medium is transferred to the transfer paper and fixed at the same time.

Further, Japanese Patent Publication No. Sho 22-22763 discloses a thermal transfer fixing method in which a conductive magnetic toner and an intermediate transfer medium of silicon rubber are combined.

Further, JP-A-56-138742 discloses a thermal transfer fixing method using a charge holding layer made of a heat resistant resin and an intermediate transfer medium such as silicon rubber.

These copying methods were started with the aim of simplifying the process, but gradually improve the quality of copied images,
That is, the toner image is disturbed on the transfer paper in the copying method using the electrostatic force by the conventional corotron etc.,
It has attracted attention as a means for avoiding the drawbacks of causing disturbance around the line image in the final fixed image, lowering of resolution, and lowering of graininess of the solid image.

[Problems to be Solved by the Invention] In the prior art, the quality of a copied image is improved by simply using a non-electrostatic means only in the transfer step. That is, through a series of processes of latent image formation, development, transfer, and fixing, a high-quality image, especially a halftone dot image of 100 to 200 lines / inch, can be faithfully reproduced on the original without impairing its gradation. To provide.

[Means for Solving Problems] The present invention provides an electrostatic latent image on a smooth recording medium in which the unevenness having a centerline average roughness of 0.5 μ or more has a frequency of 1 cycle / mm or less and a depth of 1 μ or less. Forming process, 10 ¹² to 10 ¹⁴ Ωcm (10
⁴ V / cm) high resistance toner is attached to the electrostatic latent image to develop it, and a pickup roll is brought close to the toner image formed in the developing step to adjust the height of the toner image on the recording medium. Suppression step of 10 ~ 20μ, the toner image on the recording medium that has undergone the suppression step is measured according to JIS B0601 and the surface roughness is 0.5μ or more
Transferring and fixing the toner image on the intermediate transfer medium by pressing it with a heating roll with the recording sheet interposed between the step of transferring it onto a smooth intermediate transfer medium having a depth of 3 μm or less at e / mm or less. The present invention provides a copying method characterized by comprising steps.

As shown in FIG. 1, in the copying method of the present invention, for example, the photosensitive belt 1 is first uniformly charged by a corotron (first
(A)), and then imagewise exposure to form an electrostatic latent image (Fig. 1 (b)), and this electrostatic latent image is developed with a high resistance toner (Fig. 1 (c)) to obtain the image. The toner image is temporarily non-electrostatically transferred to the intermediate transfer medium 2 by the pressing roll 13 (first transfer).
(D)), and then the primary transfer image is secondarily transferred and fixed onto the recording sheet 3 using the heating roll 15 to form a permanent image (FIG. 1 (e)).

The present invention will be described in detail below with reference to an example of a copying system for carrying out the method of the present invention shown in FIG.

(1) Latent Image Forming Step The photosensitive body is uniformly charged and then imagewise exposed to form an electrostatic latent image. In the system shown in FIG. 2, the latent image is formed by the exposure 5 after the belt-shaped photoconductor 1 moving in the a direction is charged by the charger 4.

The photoconductor does not necessarily have to have a belt shape, and a drum shape can also be used.

As the material of the photoreceptor, Se as an inorganic amorphous material,
Se / As, As ₂ Se ₃ , Se / Te / Si / S, CdS and Cd as crystalline materials
It is possible to use those composed of a charge generation material such as Se, ZnO, TiO ₂ , an organic bisazo pigment, a phthalocyanine pigment, and a squarium pigment, and a charge transport material such as an aromatic amine and hydrazone.

The surface characteristics and PIDC (Photo Induced Decay Curve) are the required characteristics of the photoconductor to obtain high quality copied images.
Properties and surface resistance can be mentioned.

Regarding the surface shape, for example, in the case of a dispersion type photoreceptor such as ZnO, the surface roughness has a frequency of 5 cy of unevenness with a depth of 0.5 μ or more.
When the toner image is formed on the photoconductor, it is cle / mm, and the depth is 7μ, and the toner particles enter the concave part and the toner particles embedded in the concave part of the photoconductor are intermediately transferred during the primary transfer to the intermediate transfer medium. Not only the white spots in the image transferred to the medium are generated, but also a load occurs in cleaning the photoconductor.

Evaporation type photoreceptors such as Se-based ones can obtain very good primary transfer characteristics, but even dispersion type photoreceptors such as ZnO can obtain good primary transfer characteristics by smoothing the surface. You can Experimentally, the surface roughness is 0.5μ deep
It was confirmed that almost 100% primary transfer can be achieved when the frequency of the unevenness is 1 cycle / mm or less and the depth is 1 μm or less.

Regarding the PIDC characteristic, a steep, ie, binary characteristic is particularly preferable for halftone dot reproduction.

The PIDC characteristics (sensitometry) can be adjusted by controlling the exposure amount to the photoconductor, the charging potential, and the like. Regarding the surface resistance, it is preferable to form a dielectric film or an insulating coating by spray coating on the photoconductive layer in order to suppress the latent image charge from leaking due to entanglement with the developer. It is also possible to mix conductive metal fine powder in the film to suppress the resistance.

Further, a-Si is preferable from the viewpoint of heat resistance, and similarly, an inorganic photoconductive material such as CdS, CdSSe, CdSe, ZnSe,
Those obtained by dispersing ZnCdS, TiO ₂ , ZnO, CdS / CdCO ₃ in a heat resistant resin can be applied. As the heat resistant resin, fluorine resin, polyimide resin, polyamide resin, polyimide amide resin, polyaryl sulfone resin, polyphenylene sulphate resin, thermosetting acrylic resin, thermosetting alkyd resin, epoxy resin, and mixtures thereof. ,
What is widely used as a heat resistant resin in this field is used.

Specific examples of these heat resistant resins include poly-tetrafluoroethylene and tetrafluoroethylene-6- as fluorine-containing resins.
Fluorinated propylene copolymer, poly- (ethylene trifluoride chloride), poly-vinylidene fluoride, ethylene trifluoride chloride-vinylidene fluoride copolymer, poly-perfluoroalkylene (PPA), poly-vinylheptafluoro Butyrate, Amisin (nylon 6), Zytel (nylon 6)
6), Kapton (polyimide resin), Ryton PPSV-1
Type [polyphenylene sulfite resin, Hodogaya Chemical Co., Ltd.], Astrel-560 [polyarylsulfone resin, 3M]. Among the heat-resistant resins described above, a fluorine resin, a polyimide resin, a polyamide resin, a polyimideamide resin, a polyphenylene sulfide resin, or a mixture thereof is preferable.

In the latent image forming process, contact transmissive exposure using a transmissive original is preferable, but the complexity of the original is required, and a device such as suction is required to increase the contact accuracy, which is restricted by the complexity and size of the device. . In practical terms, tracking error,
In order to suppress velocity error and the like, it is preferable to use a belt-shaped photoreceptor and perform static exposure using a plane or exposure in a state where the relative position with respect to the original does not change.

In consideration of speeding up, flash exposure with a belt-shaped photoreceptor is particularly suitable.

(2) Developing Step After forming a latent image faithful to the original, toner development is performed by the developing device 6.

In this development process, the spread of the image in the transfer, which is the primary process,
It is essential to carry out uniform thin layer development in consideration of crushing.
In particular, the height of the toner image (pile height) is more important than the particle size of the toner. Experimentally, the line image spreads in the range of 10 to 20 μ, and in the case of a halftone image, the highlight (area ratio to 5
%) To the shadow area (area ratio 85% ~), and it is possible to suppress crushing.

As a concrete method of the uniform thin layer development, use of a conductive one-component toner has brought good results.

Resistance of the toner is experimentally 10 ³ v / cm at the electric field 10 ³ to 10 ¹¹
It was confirmed that Ω · cm was suitable.

Although both magnetic and non-magnetic toners can be used, the so-called magnetic brush developing method using a conductive magnetic one-component toner is preferable from the viewpoints of carrying and feeding, downsizing of the developing device, and the like.

However, the conductive magnetic one-component toner has the following disadvantages.

(I) Coloring problem, that is, even if a dye is mixed, the content of magnetic powder is high and the blackness is high, so that only a color toner having low lightness can be obtained. (Ii) The problem of fixing, that is, the content of magnetic powder In the case of conductive toner, it is as high as 50 to 80%, so a large amount of heat energy is consumed during fixing. Therefore, there is a problem in terms of speeding up and low power consumption, and (iii) the problem of bias leak, that is, toner is removed when a developing bias is applied in order to remove stains (fogging) on the background portion of the photoconductor. It has a problem that it becomes an electric path and leak occurs.

To solve the above problems, toner has a resistivity of 10 ¹² to 10
^{A material of 14} Ω · cm (electric field 10 ⁴ V / cm) is preferable.

In the region of this resistance, it is possible to develop by induction or polarization, and it is not necessary to provide a special charge applying means,
The device can be downsized, and the magnetic powder content can be suppressed to a low value of 40 to 60%, and the above problems can be alleviated.

However, the toner having a resistivity of 10 ¹² to 10 ¹⁴ Ω · cm causes disorder in the periphery of the line image in the final fixed image, and irregularities in the dot shape and crushing of the shadow portion in the case of a halftone image.

It has been found that the cause of this is that the toner particles attached to the latent image form a layer and are arranged in a tower shape, which are crushed during the primary transfer to induce spread and reduce the final image quality.

As a result of intensive studies by the present inventors, in the developing step, a step of positively adhering toner to the latent image and a step of positively picking up excessively adhered toner are provided.
This problem was solved by adopting a so-called function separation type developing method and performing uniform thin layer development.

That is, in the first developing step, each parameter is set to increase the developing electric field and the toner density in the developing nip area, and in the second developing suppressing step, the developing electric field, the toner density in the developing nip area, and the magnetic high speed force are set. The above problem was solved by setting the parameter in the weakening direction.

FIG. 3 is a schematic view of an example of an apparatus for carrying out the function-separated developing process. The first developing process is carried out by the developing roll 6a ₁ and then the excessively attached toner is removed by the pickup roll 6a _2. is there. The pickup roll is a rotatable conductive metal roll (charging roll). A bias voltage having a polarity opposite to that of the toner is applied to the roll so that the toner in the upper layer portion of the developed image on the photoconductor is on the metal roll side. Aspirate into. Since the developed image on the photoconductor has a weaker electrostatic adhesion to the photoconductor in the upper layer portion, the toner layer can be made into a uniform thin layer state by adjusting the distance between the pickup roll and the photoconductor and the applied voltage. .

FIG. 4 is a schematic view of another example of the developing device, in which the toner image is restored by using the negative pressure of air by the suction device 6c after the _first development is carried out by the developing roll 6a _1. .

The material and characteristics of the toner used in the developing process will be further described.

It has been experimentally confirmed that the toner has a particle size (average particle size) of 10 μm or less, preferably 1 to 5 μm. Considering the particle size of the printing ink and liquid developer, it is fine to improve the image quality (particularly the graininess and resolution of the low-density solid image, the dot shape of the halftone image, and the _Dmax ). Although good results are obtained, there are limitations due to manufacturing restrictions and handling.

The particle size distribution is preferably narrower in consideration of the transitions in selective development, primary transfer, and secondary transfer (that is, it is desirable that the pressing force acts uniformly on each toner particle).
Experimentally, it was found that 2 to 4 give good results with the distribution index d ₉₀ / d ₁₀ .

As the toner material, a release agent may be added to the toner from the viewpoint of preventing offset to the photosensitive member in the primary transfer and preventing offset to the intermediate transfer medium in the secondary transfer.

The release agent may be a binder resin for toner having release properties, or may be added as a release agent.

The binder resin for toner having release property is a polymer of styrene-based monomer, a polymer of other vinyl-based monomer, or a styrene-based monomer and other vinyl-based monomer. And a copolymer thereof.

Examples of the styrene-based monomer include styrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene and p-methoxy. Styrene, p-phenyl styrene, styrene such as 3,4-dichlorostyrene and derivatives thereof can be mentioned, and styrene monomer is most preferable. Examples of other vinyl-based monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride and vinylidene chloride; vinyl acetate, vinyl benzoate, vinyl butyrate, etc. Vinyl esters of
Methyl acrylate, ethyl acrylate, isobutyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-chloromethyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate Α-methylene aliphatic monocarboxylic acid esters such as 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate;
Acrylic acid or methacrylic acid derivatives such as acrylonitrile and acrylamide; vinyl ethers such as vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone; N-vinyl compounds such as N-vinylpyrrole and N-vinylcarbazole; vinylnaphthalene, etc. Can be mentioned.

Specific examples of the copolymer include styrene-vinyl acetate copolymer, styrene-methyl methacrylate copolymer, styrene-methyl acrylate copolymer, styrene-2-ethylhexyl methacrylate copolymer, styrene-acrylic acid 2
-Chloroethyl copolymer or styrene-phenyl methacrylate copolymer. And these polymers have a weight average molecular weight of 3,000 or more, preferably 3,000 to 50.
It preferably has a molecular weight of 0,000.

Further, these polymers preferably have a weight average molecular weight / number average molecular weight of 3.5 or more.

Examples of the releasing agent as an additive include low molecular weight olefin polymers, fatty acid metal salts, higher fatty acids, fatty acid amides, higher alcohols, hydrocarbon lubricants, and fatty acid esters.

The low molecular weight olefin polymer used in the developer of the present invention is an olefin polymer containing only olefin as a monomer component or an olefin copolymer containing a monomer other than olefin as a monomer component. It is a small molecule. The olefin as a monomer component includes, for example, ethylene, propylene, butene-1, octene-1, or homologues thereof having different positions of unsaturated bonds, or, for example, 3-methyl-1-butene, 3-
All olefins such as propyl-5-methyl-2-hexene and the like into which an alkyl group is introduced as a branched chain are included.

Further, as a monomer component other than the olefin as a monomer component forming a copolymer with the olefin, for example, vinyl ethers such as vinyl methyl ether and vinyl phenyl ether, vinyl esters such as vinyl acetate, and tetrafluoroethylene, for example. , Vinyl chloride, vinylidene chloride, tetrachloroethylene and other haloolefins such as methyl acrylate, ethyl acrylate,
Acrylic esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, stearyl methacrylate, N, N-dimethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, or methacrylic acid Examples thereof include acid esters, acrylic type derivatives such as acrylonitrile and N, N-dimethylacrylamide, organic acids such as acrylic acid and methacrylic acid, diethyl fumarate and β-pinene.

The low molecular weight olefin polymer is an olefin polymer composed of only olefins containing at least two kinds of olefins as a monomer component, such as ethylene-
Propylene copolymer, ethylene-butene copolymer, ethylene-pentene copolymer, propylene-butene copolymer, propylene-pentene copolymer, ethylene-3-methyl-1-butene copolymer, ethylene-propylene- An olefin copolymer containing butene copolymer or the like or at least one olefin as described above and at least one monomer other than the above olefin as a monomer component, for example, an ethylene-vinyl acetate copolymer. ,
Ethylene-vinyl methyl ether copolymer, ethylene-
Vinyl chloride copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic acid copolymer, propylene-vinyl acetate copolymer, propylene-vinyl ethyl ether copolymer,
Propylene-ethyl acrylate copolymer, propylene-
Methacrylic acid copolymer, butene-methyl methacrylate copolymer, pentene-vinyl acetate copolymer, hexene-vinyl acetate copolymer, ethylene-propylene-vinyl acetate copolymer, ethylene vinyl acetate-vinyl methyl ether It is a copolymer or the like.

In the low molecular weight olefin polymer containing a monomer other than olefin as a monomer component, it is desirable that the olefin component contained in the copolymer is as large as possible. Because, in general, the smaller the content of the olefin component, the smaller the releasability, and the fluidity of the toner,
This is because characteristics such as image quality tend to deteriorate.

Therefore, it is desirable that the content of the olefin component in the copolymer is as high as possible, and particularly, the one containing about 50 mol% or more of the olefin component is effectively used.

The molecular weight of the low molecular weight olefin polymer may be one that is included in the concept of low molecular weight referred to as an ordinary polymer compound, but is generally 1,000 to 45,000 in weight average molecular weight, preferably 2,000 to 6,000. .

Low molecular weight olefin polymers have a softening point of 100-180 ° C, especially
Those having 130-160 ° C are preferred.

The amount of low molecular weight olefin polymer used is the resin component of the toner.
It is 1 to 20 parts by weight, preferably 3 to 15 parts by weight, per 100 parts by weight. If it is 1 part by weight or less, it may not have a sufficient releasability imparting effect. It is not preferable because it tends to decrease.

As another example of the release agent used in the developer of the present invention,
As a metal salt of a fatty acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, caprylic acid, caproic acid, linoleic acid, ricinoleic acid or ricinoleic acid lead, zinc, magnesium, cobalt, Metal salts of copper, calcium, cadmium, iron, nickel, aluminum or barium are mentioned, and higher fatty acids are usually decanoic acid having 8 or more carbon atoms, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid. Alternatively, ricinoleic acid may be used, and fatty acid amides include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidic acid amide, behenic acid amide, oleic acid amide, linoleic acid amide, linolenic acid amide, and gadrenic acid amide. , Elka Acid amide, ceracoleic acid amide; bis fatty acid amides include bislauric acid amide, bismyristic acid amide, bispalmitic acid amide, bisstearic acid amide, N, N′-didodecanoyl-ethylenediamine, and lauryl alcohol as a higher alcohol. , Myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol or oleyl alcohol, fatty acid esters include esters of fatty acids with monohydric alcohols or full or partial esters of fatty acids with polyhydric alcohols, and hydrocarbons Examples of the lubricant include natural paraffin, synthetic paraffin, micro wax, and chlorinated paraffin.

The amount of these release agents added to the developer is 0.1 to 65% by weight, preferably 0.2 to 20% by weight, based on the developer.

The general additive and manufacturing method of the developer will be described.

The toner contains not only the above-mentioned releasing agent but also a binder resin for toner. These resins may have the releasability described above, or may have no releasability, for example, an epoxy resin, a polyester resin, or a polyamide resin.

Any colorant such as a pigment or a dye may be added to the toner according to the present invention, if necessary. These colorants are known, for example, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate. , Lamp black, oil black, azo oil black, rose bengal and mixtures thereof. or,
Where conventional xerographic reproduction of printed documents is desired, the toner may be made from a black dye such as a black dye such as carbon black or Amraplast black dye.

The addition amount of the colorant used in the toner of the present invention is widely adopted, but it is usually 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin for toner.

When the toner is used as a one-component developer, any magnetic material can be added.

The magnetic substance that can be used is a substance that is strongly magnetized in that direction by a magnetic field, preferably black, well dispersed in resin and chemically stable, and has a particle size of 1 μm.
It is desirable that the following fine particles can be easily obtained, and magnetite (ferric tetroxide) is most preferable. Typical magnetic or magnetizable materials include cobalt, iron,
Metals such as nickel; aluminum, cobalt, copper,
Alloys of metals such as iron, lead, magnesium, nickel, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium and mixtures thereof; aluminum oxide, iron oxide, copper oxide, Metal compounds containing metal oxides such as nickel oxide, zinc oxide, titanium oxide and magnesium oxide; refractory nitrides such as vanadium nitride, chromium nitride; carbides such as tungsten carbide and silica carbide; ferrites and them A mixture of It is desirable that these ferromagnetic materials have an average particle size of about 0.1 to 1 .mu.m, and the amount contained in the toner is preferably about 50 to 500 parts by weight with respect to 100 parts by weight of the binder resin component for toner. Preferably 80 to 2 per 100 parts by weight of the resin component
00 parts by weight.

Other charge control agents, fluidizing agents and the like may be added to the toner as appropriate.

The toner is manufactured by any manufacturing method such as a so-called kneading method and a polymerization method.

The kneading method is, for example, mixing a binder resin for toner, a release agent, a colorant, a charge control agent, a magnetic material, etc., melt kneading, cooling,
It is a method of crushing and manufacturing.

On the other hand, the polymerization method is a method in which a release agent, a colorant, a charge control agent, a magnetic material, and the like are mixed with the monomer of the binder resin for toner, and the toner is manufactured all at once by, for example, suspension polymerization.

(3) Primary transfer step The toner image on the photoconductor belt is then transferred to the intermediate transfer medium 2 which moves in the direction b by a non-electrostatic method, that is, between the support roll 12 and the pressing roll 13 and the photoconductor belt is intermediate. Primary transfer is performed by a method of passing the transfer belts in an overlapping manner.

The intermediate transfer medium used in this primary transfer has a transfer rate in the primary transfer and the secondary transfer, and a missing image portion (toner particles enter the concave portion of the intermediate transfer medium by the primary transfer and contact the recording sheet by the secondary transfer). The area becomes insufficient, resulting in white spots on the final image.This development causes a drop in dot _{Dmax in} the case of a halftone image and impairs gradation.) Furthermore, it is easy to clean the intermediate transfer medium. Considering that, the smoothness of the surface is important.

According to the experiment, the surface roughness of the intermediate transfer medium has a depth of 0.5μ.
It was found that good results can be obtained with a frequency of 2 cycles / mm or less and a depth of 3 μm or less.

As the intermediate transfer medium having such a surface roughness, a heat resistant resin film provided with layers of various elastomers and rubber materials is used. Specific examples of the surface layer include TSE387RTV, TSE388W, TSE389C (above trade name) manufactured by Toshiba Silicone Co., Ltd., and KR271, KR272, KE130, KE13 manufactured by Shin-Etsu Chemical Co., Ltd.
6-V, KE12RTV, KE17RTV, KE42RTV, KE113RTV, KE1800ABCRTV
Etc. (the above product name), SH-780, SE made by Toray Silicone Co., Ltd.
9140, SH850, SH748V, SRX475V, SH1603V, etc. (all product names), Bayer EVW-1018, EV-1840, etc. (all product names), Nippon Polyurethane Co., Coronate C-4046, Nipporan 4038, all product products First name).

Further, carbon black or metal powder may be dispersed for the purpose of preventing static electricity.

In the primary transfer step, the charge of the intermediate transfer medium is removed by the charge remover 11 before the transfer in order to perform good transfer in a non-electrostatic manner.

(4) Secondary Transfer Fixing Step Next, the primary fixing toner image is transferred and fixed by pressing the heat fixing roll 15 against the support roll 14 with the transfer paper 3 moving in the c direction interposed.

In this transfer fixing step, the toner image on the intermediate transfer medium is heated by the preheater 9, and the transfer paper is also heated by the preheater 16.

The intermediate transfer medium after the secondary transfer fixing is cleaned by the cleaning device 10 and is prepared for the next cycle.

Further, the photoconductor belt after the primary transfer is also cleaned by the cleaning device 8 after the charge is removed by the charge remover 7, and the process proceeds to the next copying cycle.

[Examples] Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

Se-based photoconductor as the photoconductor (surface roughness is 1 cycle / mm of uneven frequency with a depth of 0.5μ or more, depth 0.5μ: measured by SLOAN DEKTAKII), and an exposure system made by Fuji Photo Film Co., Ltd. "ELP280" and as an intermediate transfer medium, silicone RTV (manufactured by Shin-Etsu Chemical Co., Ltd., thickness 100μ, surface roughness 0.5 μ or more depth uneven frequency 1 cycle / mm, depth 2.5
.mu.) and the surface temperature of the heat fixing roll was 180.degree. C. under the same conditions, and only the developing conditions were changed, and the copy tests of the following comparative examples and examples were conducted.

Comparative Example A styrene-acrylic resin as a toner containing 50% of magnetic powder and an electric resistance of 9 × 10 ¹² Ω · cm, d ₅₀ 7.2 μ, d ₉₀ / d
₁₀ 3.1 used, development is internal rotation type 12 poles 750 Gaus
s, sleeve diameter 30φ, rotation speed 1,200 rpm, one magnet roll, development bias 250v (photoconductor potential: image area 80
A copying test was performed under the conditions of 0 v, non-image part 150 v), trimming gap 0.3 mm, and photoconductor-developing roll gap 0.6 mm.

Example The same toner as in the comparative example was used as the toner, and the development was performed using the first developing roll [roll diameter 30φ, 12 poles, 750 Gauss, rotation speed 1, 2
00 rpm, developing bias 250 v (photoconductor potential: same as in comparative example), trimming gap 0.3 mm, photoconductor-developing roll gap 0.6 mm) and second pickup roll [roll diameter 30φ, 12 poles, 250 Gauss, rotation speed 1,200 rpm , A developing bias of 500 v (photoreceptor potential: the same as in the comparative example), a trimming gap of 0.3 mm, and a photoconductor-developing roll gap of 0.7 mm].

The image quality obtained in the comparative example and the example is shown in the following table.

Also, when the developed image on the photoconductor was observed with a microscope, it was found that the toner layer height (the line image portion corresponding to **) was found in the comparative example.
It was as high as 40μ, and was 15μ in the example.

EFFECTS OF THE INVENTION The present invention is a latent image forming, uniform thin layer using high resistance toner in a copying method in which a toner image is temporarily non-electrostatically primary-transferred using an intermediate transfer medium and then transferred and fixed on a recording paper. developing,
The present invention provides a novel copying method capable of obtaining a high quality final image by combining a series of processes of primary transfer and secondary transfer fixing.

[Brief description of drawings]

FIG. 1 is an explanatory view of an image forming process in the copying method of the present invention, FIG. 2 is a schematic view of an example of a system for carrying out the copying method of the present invention, and FIGS. 3 and 4 are developments used in the present invention. It is a schematic diagram of an example of a device. Reference numeral: 1 ... photosensitive belt; 2 ... intermediate transfer belt; 3 ... transfer paper; 4 ... charger; 5 ... exposed; 6 ... developing machine; 6a ₁ ... developing roller; 6a ₂ ... pickup roll; 6b _1, 6b ₂ ... Toner layer thickness regulating plate; 6c ... Suction device; 7, 11 ... Static eliminator; 8, 10 ... Cleaning device; 9 ... Toner preheater; 12, 14 ... Support roll; 13 ... Press roll; 15 ... Heating roll 16: Transfer paper preheater; a, b, c ... Direction of movement.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-36752 (JP, A) JP 59-19980 (JP, A) JP 59-202477 (JP, A) JP 59- 206855 (JP, A) JP 57-128352 (JP, A) JP 57-62077 (JP, A) JP 56-78846 (JP, A)

Claims (1)

[Claims] 1. A process for the center line average roughness frequency of more uneven 0.5μ depth below 1 cycle / mm to form an electrostatic latent image on a smooth recording medium is less than 1 [mu], 10 ¹² to 10 ¹⁴ Ω ・ cm
A step of adhering (10 ⁴ V / cm) high-resistance toner to the electrostatic latent image to develop, and a toner image formed in the developing step is brought close to a pickup roll to increase the toner image on the recording medium. The toner image on the recording medium that has undergone the suppressing step has a frequency of 2 cycles / mm or less and a depth of 3 μm or less. A copying method comprising: a step of transferring the toner image on a smooth intermediate transfer medium in an overlapping manner; and a step of transferring and fixing the toner image on the intermediate transfer medium to a recording sheet by pressing it with a heating roll with a recording sheet interposed.