JP2002229245A - Image forming device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to stably provide an electrostatic latent image according to a writing voltage to a latent image carrier, to achieve excellent resolution and to provide a latent image carrier. Prevents filming on holding body,
An object of the present invention is to provide an image forming apparatus having a long life of a latent image carrier. SOLUTION: An image forming apparatus 1 according to the present invention has a charge injection layer on a surface, and a latent image carrier 2 on which an electrostatic latent image is formed;
Writing electrode 3 for writing the electrostatic latent image on latent image carrier 2
b, and a developing device 4 for reversal developing the electrostatic latent image with negatively charged toner, wherein the writing electrode 3b is brought into contact with the latent image carrier 2 in a rotating direction. Accordingly, in the image forming apparatus for forming an electrostatic latent image, the work function of the surface of the toner particles forming the negatively charged toner is made larger than the work function of the surface of the writing electrode.

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 for forming an image by forming an electrostatic latent image on a latent image carrier by bringing a writing electrode of a writing device into contact with the latent image carrier. About.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrostatic copying machine or a printer, generally, the surface of a photoconductor is uniformly charged by a charging device, and a laser beam is applied to the surface of the uniformly charged photoconductor. Alternatively, an electrostatic latent image is written on the surface of the photoconductor by exposing light of an exposure device such as LED lamp light. Then, the electrostatic latent image on the surface of the photoreceptor is developed by a developing device to form a developer image on the surface of the photoreceptor, and the developer image is transferred to a transfer material such as paper by a transfer device, and the image is formed. Has formed. In such a conventional general image forming apparatus, the exposing device, which is a writing device for an electrostatic latent image, is constituted by a laser light generating device, an LED lamp light generating device, or the like. And it has a complicated configuration.

Therefore, as an apparatus for writing an electrostatic latent image, an image forming apparatus for writing an electrostatic latent image on the surface of a latent image carrier using a needle electrode without using a laser beam or an LED lamp light is disclosed in Japanese Patent Publication No. Sho.
It has been proposed in JP-A-3-45014 and JP-A-59-33969. The image forming apparatus disclosed in the former publication has a multi-stylus having a large number of needle electrodes, and the needle electrode of the multi-stylus is simply brought into contact with the inorganic glass layer on the surface of the latent image carrier. Then, when a voltage is applied to the corresponding stylus electrode of the multi-stylus according to the input signal of the image information, the stylus electrode forms an electrostatic latent image on the latent image carrier.
According to the image forming apparatus disclosed in this official gazette, a conventional exposure apparatus is not used as a writing apparatus, and accordingly, the image forming apparatus has a small and relatively simple configuration.

However, in this image forming apparatus, since a large number of needle electrodes of the multi-stylus are simply brought into contact with the inorganic glass layer on the surface of the latent image carrier, the large number of needle electrodes are connected to the latent image carrier. It is difficult to make stable contact with the inorganic glass layer on the surface of. Therefore, it is difficult to stably charge the surface of the latent image carrier, and there is a problem that it is difficult to obtain a good image. In addition, in order to prevent the surface of the latent image carrier from being damaged by the contact of a large number of needle electrodes, it is necessary to provide an inorganic glass layer on the surface of the latent image carrier, and the configuration of the latent image carrier becomes more complicated. Become.
Moreover, since the inorganic glass layer has the property of physically adsorbed water and the charged charges of the latent image carrier leak, it is necessary to provide a means for drying the surface to prevent the influence of the physically adsorbed water. There is a problem that the size is further increased. Furthermore, simply contacting a large number of needle electrodes with the surface of the inorganic glass layer is not sufficient, and there is a high possibility that ozone (O ₃ ) is generated by the discharge from the needle electrodes, and rust on parts in the apparatus. As well as NO
Nitric acid (HNO ₃ ) generated by reacting with _x may corrode resin parts, and there is a problem that it is necessary to provide a sufficient exhaust system for discharging ozone from the inside of the apparatus.

In Japanese Patent Application Laid-Open No. 59-33969, a latent image is recorded on a dielectric layer serving as a latent image carrier by using a discharge from a needle electrode. The same problem as that of ozone generation occurs.

Further, an image forming apparatus for writing an electrostatic latent image on a latent image carrier by controlling ions generated by a corona discharger by a non-contact ion control electrode provided at the tip of an insulating substrate. Has been proposed in JP-A-6-166206. Even in the image forming apparatus disclosed in this publication, an exposure apparatus is not used as a writing device, so that the image forming apparatus has a small and relatively simple configuration. However, since the ion control electrode controls the ions generated by the corona discharger and does not directly inject the electric charge into the latent image carrier, not only does the image forming apparatus have to be large, but also However, there is a problem that the configuration becomes extremely complicated. Moreover, it is difficult to stably write an electrostatic latent image on the latent image carrier due to charging by ions. Further, since ozone is basically generated due to generation of ions, a problem similar to that of the image forming apparatus disclosed in the above-mentioned official gazette occurs.

Japanese Patent Laid-Open Publication No. Hei 6-3921 discloses that when charging a latent image carrier uniformly by using a charging roll or a charging blade, the charge is injected into the surface of the latent image carrier. Although an electrophotographic apparatus provided with a layer is described, an exposure apparatus such as a laser beam or an LED lamp light is used for writing an electrostatic latent image. As described above, the image forming apparatus is large-sized. In addition, there is a problem that the configuration becomes complicated.

For the purpose of solving such a problem, the inventors of the present invention previously disclosed in Japanese Patent Application No. 2000-298925, etc., a latent image carrier on which an electrostatic latent image is formed and a latent image carrier. A writing device including a plurality of writing electrodes for writing the electrostatic latent image; and a developing device for developing the electrostatic latent image on the latent image carrier, wherein the writing device holds the latent image. An image forming apparatus for writing an electrostatic latent image by contacting the body with a small pressing force and developing the electrostatic latent image written on the latent image carrier to form an image; It has been proposed that the imaging device can be simplified and an image device that does not generate ozone or the like can be obtained. However, since the transfer residual toner is present, filming occurs on the writing electrode and the latent image carrier, and the electrostatic latent image is latent. Influences the stability when applied to the image carrier and Or cause, also, there is a problem that affects the prolonged life of the latent image carrier.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus proposed by the present inventors in which an electrostatic latent image corresponding to a writing voltage is stably formed on a latent image carrier. An object of the present invention is to provide an image forming apparatus which can provide excellent resolution and prevent filming on the latent image carrier and make the latent image carrier have a long life.

[0010]

An image forming apparatus according to the present invention has a latent image carrier on which a charge injection layer is formed on the surface and on which an electrostatic latent image is formed, and the electrostatic latent image on the latent image carrier. A writing device having a writing electrode for writing an image, and at least a developing device for reversely developing the electrostatic latent image with negatively charged toner,
In the image forming apparatus for forming an electrostatic latent image by bringing the writing electrode into contact with the rotating direction of the latent image carrier in contact therewith, the work function of the surface of the toner particles forming the negatively charged toner is determined by the writing electrode. It is characterized in that the work function is larger than the work function of the surface.

The difference between the work function of the surface of the toner particles forming the negatively charged toner and the work function of the surface of the writing electrode is 0.15 eV or more.

Further, the work function of the surface of the charge injection layer is larger than the work function of the surface of the writing electrode and smaller than the work function of the surface of toner particles (hereinafter referred to as toner particles) forming negatively charged toner. It is characterized by.

The contact portion of the writing device with the latent image carrier is formed by a plurality of electrodes arranged in the rotation axis direction of the latent image carrier and a separating member arranged between the plurality of electrodes. Wherein the difference between the work function of the surface of the separating member and the work function of the surface of the charge injection layer is less than 0.15 eV.

Further, a contact portion of the writing device with the latent image carrier is pressed with a linear pressure of 0.05 N / mm or less with respect to the rotation direction of the latent image carrier. I do.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a negative charge is injected from a write electrode into a charge injection layer while a negative write electrode is in contact with the surface of the charge injection layer in a latent image carrier. It is possible to reduce the voltage compared to the discharge method,
Further, the charge injection layer has a charge retention property, is excellent in charge injection property, and is excellent in electron injection efficiency upon contact charging, unlike the low resistance layer. Further, since the electrostatic latent image is formed by bringing the writing electrode into contact with the rotating direction of the latent image carrier in opposition, the cleaning function of the residual toner on the latent image carrier is performed by the writing electrode. It has.

In such a system, the transfer residual toner on the latent image carrier may be in a positively charged state such as fog, and is deposited on the contact portion between the writing electrode and the latent image carrier. Tend to. The image forming apparatus of the present invention is in a reversal development system in which a writing electrode has a negative polarity and a negatively charged toner is used. A potential barrier can be provided to facilitate the flow of electrons from the writing electrode side to the toner particles when the positively charged transfer residual toner comes into contact with the writing electrode, thereby shifting the transfer residual toner to the negatively charged toner. be able to. In addition, since the negatively charged toner having a small charge amount is more negatively charged, the toner particles are prevented from depositing on the contact portion between the writing electrode and the latent image carrier due to the repulsive force with the writing electrode. it can. In addition, the transfer residual toner charged to the negative side is transferred in the next transfer process, and the transfer residual toner can be collected on the developer carrier by electric force in the simultaneous development cleaning system. Therefore, the transfer residual toner is prevented from remaining on the latent image carrier, filming on the latent image carrier can be prevented, image deterioration can be prevented, and the life of the latent image carrier can be extended. Things.

If the work function of the charge injection layer is larger than the work function of the surface of the writing electrode and smaller than the work function of the surface of the toner particles, the latent image carrier has a structure that easily receives electrons from the writing electrode. The writing charge can be performed quickly, and the image quality such as white spots does not occur in the developing section at the time of reversal development by the negatively charged toner because the charge amount of the negatively charged toner is not reduced. And can be.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a basic configuration of an image forming apparatus according to the present invention.

As shown in FIG. 1, an image forming apparatus 1 according to the present invention includes a latent image carrier 2 on which an electrostatic latent image is formed, and a latent image carrier 2 which comes into contact with the latent image carrier 2. A writing device 3 for writing an electrostatic latent image of a negative polarity on the developing device 4 and a developing device 4 for reversal developing the electrostatic latent image on the latent image carrier 2 with a negatively charged developer carried and conveyed by a developer carrier 4a And a transfer device 6 for transferring the developer image on the latent image carrier 2 developed by the developing device 4 onto a transfer material 5 such as paper, and transferring the charge remaining on the latent image carrier 2 after transfer. At least a static eliminator 7 for eliminating static is provided.
In the following description, all the latent image carriers 2 are described as being grounded, but this is for convenience of explanation, and the present invention is limited to the case where the latent image carrier 2 is grounded. is not.

FIG. 2A is a diagram illustrating a basic process of image formation in the image forming apparatus 1 according to the present invention, and a dielectric layer is formed on a substrate made of a conductive material as a latent image carrier 2. A multilayer latent image carrier having a charge injection layer laminated thereon is used. Further, a charge eliminating roller 7b is used as the charge eliminating device 7. The writing electrode 3b of the writing device 3 comes into contact with the charge injection layer, which is the surface layer of the latent image carrier, and negatively charges the non-image portion. Developer carrier 4a of developing device 4
Has a (-) DC bias voltage applied to it,
The developer carrier 4 a is configured to convey the negatively charged developer 8 toward the latent image carrier 2. Incidentally, a bias voltage in which an alternating current is superimposed on a direct current (-) can be applied to the developer carrier 4a. Further, an AC bias voltage is applied to the charge eliminating roller 7b.

In this image forming process, the charge removing roller 7b is in contact with the charge injection layer, and the charge of the latent image carrier is removed by the charge removal roller 7b, and the charge injection layer surface is charged with 0V. After being brought into a uniform charge state close to the latent image carrier 2 by the writing electrode 3b of the writing device 3,
The upper non-image portion is (-) charged, and an electrostatic latent image is written on the latent image carrier. Then, the negatively charged developer 8 conveyed by the developer carrier 4a of the developing device 4 adheres to the (−) non-charged image portion near 0 V on the latent image carrier, and the electrostatic latent image is reversely developed. You.

In the present invention, the latent image carrier is replaced with a multilayer latent image carrier having a dielectric layer and a charge injection layer laminated on a conductive layer. A photoconductor in which layers are stacked may be used. An image forming process using a photoconductor will be described with reference to FIG. In FIG. 2B, a static elimination lamp 7 a is used as the static eliminator 7 together with the photoconductor 2. Further, the writing electrode 3 of the writing device 3
“b” contacts the photoconductor 2 and charges the non-image portion of the photoconductor 2 (−). Further, a bias voltage in which an alternating current is superimposed on a direct current (−) is applied to the developer carrier 4 a of the developing device 4, and the developer carrier 4 a applies the negatively charged developer 8 to the photoconductor 2. To be transported to The developer carrier 4a may be applied with a (-) DC only bias voltage.

In the image forming process of this embodiment, the charge on the surface of the photosensitive member 2 is removed by the charge removing lamp 7a, and the charge on the photosensitive member 2 is reduced to a uniform charge state close to 0V. The non-image portion on the photoconductor 2 is (-) charged by the writing electrode 3b of the loading device 3, and an electrostatic latent image is written on the photoconductor 2. Then, the negatively charged developer 8 conveyed by the developer carrying member 4a of the developing device 4 adheres to the (-) uncharged image portion near 0 V on the photoreceptor 2, and the electrostatic latent image is reversely developed. You.

In the present invention, as described above,
Although a photoconductor may be used as the latent image carrier, hereinafter, a dielectric layer on a substrate made of a conductive material as the latent image carrier,
A description will be mainly given of a case where a multilayer latent image carrier in which a charge injection layer is laminated is used.

FIG. 3 is a diagram for explaining the configuration of the contact portion between the writing electrode 3b and the latent image carrier 2, and FIG.
FIG. 3 is a perspective view for explaining an arrangement relationship between the writing electrode 3b and the latent image carrier 2, and FIG. 3B is a perspective view of the writing electrode 3b and the latent image carrier viewed from the rotation axis direction of the latent image carrier 3. It is an enlarged view of the contact state with 2. FIG. 4 is an enlarged view of the contact state between the writing electrode 3 b and the latent image carrier 2 as viewed from the rotation direction of the latent image carrier 3.

As shown in FIGS. 3A and 3B, in the image forming apparatus of the present invention, the writing device 3 includes a writing electrode 3a.
Is brought into contact with the surface of the latent image carrier 2 rotating in the direction of the arrow, and the writing electrode, which is driven and controlled by the driver 11, mainly performs charge injection and imparts charges to the latent image carrier. is there. Further, as shown in FIG. 3B, the latent image carrier 2 has a dielectric layer 2 on a base material 2c made of a conductive material.
d, a multilayer latent image carrier on which the charge injection layer 2b is laminated. The contact portion between the writing device and the latent image carrier is formed by contact between the plurality of writing electrodes and the charge injection layer of the latent image carrier, and as shown in FIG. May be formed by the plurality of electrodes 3b arranged in the rotation axis direction of the latent image carrier and the separating member 3c arranged between the plurality of electrodes 3b. Good.

The base material 3a of the writing device 3 supports the writing electrode 3b, for example, a silicon rubber plate (work function: 5.26 eV), an ethylene propylene copolymer rubber plate (EPDM, 5.23 eV), or the like. It is preferable to use an insulating rubber plate having a high insulating property with a volume resistance of 10 ¹⁰ Ω · cm or more, a relatively soft, flexible base material having a JISA hardness of 10 to 50 °, and bending of the base material 3a. This allows the writing electrode to be lightly pressed and brought into contact with the charge injection layer of the latent image carrier with a weak elastic restoring force.

In the image forming apparatus of the present invention, the pressing force of the writing electrode against the latent image carrier rotating at a predetermined speed v is not more than 15 N at a width of 300 mm, that is, not more than 0.05 N / mm, preferably not more than 0.05 N / mm. Is 0.005 to 0.0
5 N / mm, more preferably 0.01 to 0.03 N /
mm, so that the charge injection can be performed stably. However, from the viewpoint of abrasion, it is desirable to reduce the linear pressure as much as possible while maintaining the state of keeping the contact stable.

As the write electrode material, for example, titanium (3.57 eV), zinc (4.33 eV), iron (4.6)
0eV), copper (5.02eV), Ni (5.22e
V), platinum (5.63 eV), and the like, which are appropriately selected depending on the relationship with the work function on the surface of the toner particles and the work function on the charge injection layer described later.

As a method of providing a writing electrode on a base material,
A concave portion corresponding to the write electrode shape is formed on the surface of the base material by a method such as etching, and a write electrode material is vacuum-deposited on the concave portion,
It may be formed by filling by a method such as plating,
A metal foil may be stuck on a base material, or a metal film may be formed by laminating by vapor deposition, plating, or the like, and then patterned into an electrode shape. The film is formed with a thickness of 3 μm to 20 μm. Good. The volume resistance at the writing electrode is 10 ^-1
Ω · cm or less, and the surface of the write electrode 3b may be covered with a thin protective layer that easily tunnels electrons so long as the above-mentioned function is not impaired.

Further, a separating member 3c may be provided between the writing electrodes, if necessary, to make contact with the surface of the latent image carrier together with the writing electrodes. When the write electrode is embedded in the surface of the base material, the spacing member is made of the same material as the base material, but it is necessary to select a material whose work function is similar to the work function of the charge injection layer described later. In the case where a separating member is provided between the write electrodes provided on the flat base material, the work function of the charge injection layer described later is less than 0.15, preferably a work function having almost no difference. For example, the same material as the charge injection layer described later is used as an example, and is formed by coating between electrodes. The potential for injecting charges from the write electrode into the charge injection layer and charging it is several hundred volts, and the difference in work function between the separating member and the charge injection layer is 0.15.
If it is less than the above, charging due to friction can hardly occur, and even if it occurs, it can be ignored.

Next, as shown in FIG. 3B, the latent image carrier 2 is made of a conductive material having a volume resistance of 10 ^-1 Ω · cm or less, such as aluminum, and is grounded in a cylindrical shape. Material 2c and dielectric layer 2 formed on the outer periphery of substrate 2c
d, the charge injection layer 2b.

The dielectric layer 2d is made of polyester resin such as polyethylene terephthalate, polycarbonate resin, polystyrene resin, fluororesin, cellulose resin, vinyl chloride resin, polyurethane resin, acrylic resin, epoxy resin, silicone resin, alkyd resin, melamine resin,
Examples of phenolic resin, polyamide resin, vinyl chloride-vinyl acetate copolymer resin alone, or two or more polymer alloys, etc., are formed by coating on a base material or by sticking a film-like material. Formed, film thickness 5 to 2
It is good to be 00 μm, preferably 5 to 50 μm. 5μ
If it is thinner than m, it will not function as a dielectric layer. The relative dielectric constant (ε) of the dielectric is 1 to 10, preferably 2 to
8

The charge injection layer 2b is preferably formed from (1) a resin obtained by mixing and dispersing a conductive material described in the dielectric layer, and (2) a conductive polymer material.

In the case of (1), the resin is, for example, a solvent-soluble polyester resin, polycarbonate resin, fluorine resin, polyurethane resin, acrylic resin, epoxy resin, alkyd resin, melamine resin, phenol resin, or polyamide resin. The use of a paint binder makes it easy to disperse and mix the conductive material, and the charge injection layer can be formed only by the drying step of the coating layer.

In the case where a resin other than a paint resin such as a polystyrene resin, a cellulose resin, a vinyl chloride resin, a silicone resin, a vinyl chloride-vinyl acetate copolymer resin, or the like is used, melt kneading with a conductive material is performed. Therefore, it is necessary to uniformly disperse the conductive material in the resin, to melt-extrude the resin, or to form a film for sticking. To uniformly disperse the conductive material in a highly viscous resin even at high temperatures, a long-term kneading operation with the addition of a surfactant is required,
It has the advantage of high bonding between resins and excellent abrasion resistance, and is suitable as a binder for a charge injection layer in contact with a writing electrode.

As the conductive material to be mixed, zinc oxide, tin oxide, antimony oxide, titanium oxide, barium sulfide, aluminum oxide, strontium titanate, and magnesium oxide are doped with antimony, indium, carbon, and the like, respectively. Processed, and
Copper, aluminum, nickel, stainless steel, metal particles and metal fibers such as iron, other, carbon black, silicon carbide, silicon oxide, silicon nitride, carbon fibers, perchlorate and the like, as a volume average particle size, It is only necessary that the distance be smaller than the distance between the electrode pitches.
It is as follows.

Among the conductive materials described above, the surface tension of the metal oxide subjected to the conductivity treatment is about 100 dyne / cm.
The metal particles are about 1000 dyne / cm, but the surface tension of the binder resin is about 40 dyne / cm,
Conductive metal oxides having a surface tension value close to the surface tension of the binder resin have higher compatibility with the binder resin and are more suitable for uniform dispersion. In addition, a dispersant or the like is appropriately added.

When a paint binder is used, examples of the solvent include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, dimethyl sulfoxide, hexane, and toluene.

The conductive material is mixed at a ratio of 5 to 100 parts by weight, preferably 20 to 80 parts by weight with respect to 100 parts by weight of the binder resin to form a coating solution.
The charge injection layer may be formed by coating on the dielectric layer, or may be formed into a film and then pasted on the dielectric layer.

Further, the charge injection layer may be formed from a conductive polymer material. Examples of the conductive polymer material include polyacetylene, poly-p-phenylene, poly-p-phenylene sulfide, polypyrrole, polychenylene, and polyaniline alone or a conductive polymer material such as A
Examples thereof include those doped with sF ₅ , I ₂ , BF _{4, and the} like.

The thickness of the charge injection layer is from 0.01 μm to
100 μm, preferably 0.1 μm to 20 μm,
When the film thickness is large, the lateral charge of the latent image is undesirably diffused.
The volume resistance of the charge injection layer is 10 ³ to 10 ¹⁵ Ω · c.
m, preferably in the range of 10 ⁷ to 10 ¹² Ω · cm. If the volume resistance is low, the diffusion of the latent image charge is likely to occur,
In particular, it easily occurs under high temperature and high humidity. On the other hand, if the volume resistance is too high, the function as the charge injection layer is reduced. The work function of the surface of the charge injection layer is in the range of 4 to 6 eV. When the latent image carrier is a photoconductor made of a photoconductive layer, the charge injection layer needs to be transparent, so that a transparent conductive material such as tin oxide is used as the conductive material. .

Next, as the negatively charged toner used in the image device of the present invention, base particles obtained by melt-kneading a binder resin, a pigment, a release agent, a negative charge control agent, and the like, and pulverizing and classifying the same. And toner particles having an external additive attached thereto.

Examples of the binder resin include polystyrene and copolymers thereof, for example, hydrogenated styrene resin, styrene-isobutylene copolymer, styrene-propylene copolymer, etc .; polyester resins and copolymers thereof; Copolymers and the like are exemplified. Examples of the pigment include carbon black, nigrosine, rhodamine-based, copper phthalocyanine, carnamin-based, quinacridone, solar pure yellow, and the like, and 5 to 15 parts by weight, preferably 6 to 12 parts by weight based on 100 parts by weight of the binder resin. Contained. Examples of the release agent include polypropylene wax, polyethylene wax, and the like, and 0.5 to 10 parts by weight, preferably 2 to 8 parts by weight based on 100 parts by weight of the binder resin. Examples of the negative charge control agent include an electron-accepting organic complex, a chlorinated polyester, and a pyridinyl salt.
0.001 to 5 parts by weight with respect to 100 parts by weight of the binder resin,
Preferably, the content is 0.001 to 3 parts by weight. In addition, metal soaps, dispersants such as ethylene glycol, zinc stearate, zinc oxide, and magnetic agents are appropriately added.

The toner of the present invention is obtained by kneading and pulverizing the above-described materials into base particles using a kneading and pulverizing method, a spray drying method, and a polymerization method. Metal salt fine particles, or fine particles obtained by hydrophobically treating organic fine particles such as acrylic resin fine particles, etc., are externally added by a spraying method, and have a volume average particle diameter of 3 to 12 μm, preferably 5 to 9 μm. The volume resistivity is preferably 10 ¹² Ω · cm or more, and the work function is in the range of 4.8 to 6.0 eV.

In the present invention, the relationship between the work function of the writing electrode and the work function of the toner particles is as follows:
The work function of the surface of the toner particles is made larger than the work function of the surface of the writing electrode, thereby providing a potential barrier that facilitates the flow of electrons in the direction from the writing electrode to the toner particles. Therefore, the work function of the toner particles is at least 0.15 eV, preferably 0.3 eV, higher than the work function of the writing electrode.
V or more is preferable.

When the work function of the surface of the charge injection layer is larger than the work function of the surface of the writing electrode and smaller than the work function of the surface of the toner particles, the work function of the charge injection layer is defined as The difference between the work function of the electrode and the work function of the toner particles is at least 0.15.
eV or more, preferably 0.3 eV or more.

In the image forming apparatus of the present invention, for example, when the work function of the toner particles is 5.68 and the work function of the charge injection layer is 5.18 eV, the work function of the writing electrode is It is good to be 5.18 eV or less, for example, titanium (3.57 eV), zinc (4.33 eV),
A write electrode made of a material such as iron (4.60 eV) or copper (5.02 eV) may be used.

The image forming apparatus of the present invention may be a method using an intermediate transfer member. In this case, the toner image on the latent image carrier is once transferred to a belt-shaped or roll-shaped intermediate transfer body, and then transferred to a transfer material such as paper using a transfer roll or the like. . Further, as negatively charged toner, cyan,
When developing yellow, magenta, and black color toners, after developing the electrostatic latent image on the latent image carrier, each color is sequentially transferred onto the intermediate transfer body, and the color formed on the intermediate transfer body is It is preferable that the toner is collectively transferred to the receiving paper.

[0050]

The present invention will be described below in detail with reference to examples. The work function (φ) defined in the image apparatus of the present invention is a surface analysis apparatus (AC-1 manufactured by Riken Keiki Co., Ltd.).
Is measured by

(Preparation method of toner) Binder resin (polyester resin) 89 parts by weight Colorant (copper phthalocyanine) 5 parts by weight Negative charge control agent (pyridinyl salt) 3 parts by weight Release agent (polypropylene wax) 3 parts by weight After uniformly mixing the above composition at 3000 rpm for 1 minute using a Henschel mixer 20B (Mitsui Mining Co., Ltd.), a twin-screw kneading extruder (PCM manufactured by Ikegai Chemical Co., Ltd.) -30)
And the additives were dispersed and fixed in the resin. The kneaded product was roll-cooled and coarsely pulverized with a feather mill.

Next, after finely pulverizing using a jet pulverizer {200 APG (manufactured by Hosokawa Micron)}, base particles were obtained using an air classifier {100 ATP (manufactured by Hosokawa Micron)}.

Then, based on 100 parts by weight of the base particles, silica fine particles whose surface was treated with hexamethyldisilazane (particle diameter: 10 nm, “Cavoseal TG8” manufactured by Cabot Corporation)
10G "), and 2800 minutes by using a Henschel mixer 20B (Mitsui Mining Co., Ltd.).
The toner was uniformly mixed at rpm and externally treated with silica.

The average particle size of the obtained toner particles is 7.5 μm.
m, volume resistivity 10 ¹⁶ Ω · cm, work function 5.68 eV
Met.

(Image Forming Apparatus) A polycarbonate resin film (with a relative dielectric constant of 2.80) was formed on an aluminum pipe having an outer diameter of 28.86 mm.
7, a volume resistivity of 1 × 10 ¹⁵ Ω · cm and a thickness of 70 μm) is formed by a coating method to form a dielectric film, and then a polyamide resin (manufactured by Lead City Co., Ltd., FR- 104) 1
00 parts by weight and conductive titanium oxide TiO ₂ (manufactured by Titanium Co., Ltd., FC-300, volume average particle diameter 20 n)
m) 33% by weight of ethanol and a solid content of 33%
After applying the dispersion prepared as above, the mixture was heated at 150 ° C. and 3
After drying under the conditions of time, a charge injection layer having a film thickness of 1 μm was formed to form a latent image carrier.

The volume resistance of the charge injection layer is increased by Hiresta IP.
(Mitsubishi Yuka Co., Ltd.), 7.6 × 10
^{It was 10} Ω · cm, and the work function was 5.18 eV.

On the other hand, a 1 mm thick silicon rubber plate (JISA hardness 30) was used as a base material in the writing device shown in FIG.
After forming a writing electrode-shaped recess (depth 10 μm) on the surface having a work function of 5.26 eV), the recess is filled with an iron film (work function 4.60 eV) by plating to create a writing device. did.

The obtained latent image carrier and the writing device are incorporated in an image forming apparatus shown in FIG. 2A, the rotation speed of the latent image carrier is set to 20 cm / s, and the writing electrode is connected to a line. The latent image carrier was brought into contact with the charge injection layer surface at a pressure of 0.02 N / mm, and a voltage of -300 V was applied to the writing electrode to form an electrostatic latent image on the latent image carrier. The charge injection layer surface potential is -3
00V, and the injection efficiency was excellent.

Next, the toner obtained above was used as a negatively charged developer, the electrostatic latent image on the latent image carrier was reversely developed, and an image was formed on the transfer paper. No image omission, excellent developability, no toner adhered to non-image areas, no image deterioration, and no filming on the latent image carrier was observed.

[0060]

According to the image forming method of the present invention, the electrostatic latent image corresponding to the writing voltage can be stably applied to the latent image carrier, the resolution can be improved, and the latent image carrier can be obtained. Filming of the latent image can be prevented, and the life of the latent image carrier can be extended.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a basic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating a basic process of image formation in the image forming apparatus of the present invention.

3A and 3B are diagrams illustrating a contact state between a writing electrode of a writing device and a latent image carrier, and FIG. 3A is a perspective view illustrating an arrangement relationship between the writing electrode and the latent image carrier. (B) is an enlarged view of the contact state between the writing electrode and the latent image carrier viewed from the rotation axis direction of the latent image carrier.

4A and 4B are diagrams showing a contact state between a writing electrode of a writing device and a latent image carrier, and FIG. 4C shows a state of contact between the writing electrode and the latent image carrier viewed from the rotation direction of the latent image carrier. It is an enlarged view of a contact state.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 image forming apparatus 2 latent image carrier 3 writing apparatus 3
a: base material, 3b: writing electrode, 4: developing device, 5: transfer material, 6: transfer device, 7: static eliminator, 8: developer

Continued on the front page (72) Inventor Kenjiro Yoshioka 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko-Epson Corporation (reference) 2C162 AE21 AE44 AE47 AE74 AE82 AE84 EA20 2H005 DA02 2H029 AA06 AB03 AB04 AB10 AE01 2H068 AA08

Claims (5)

[Claims] A latent image carrier having a charge injection layer on its surface and on which an electrostatic latent image is formed; and a writing device having a writing electrode for writing the electrostatic latent image on the latent image carrier. An image forming an electrostatic latent image by bringing the writing electrode into contact with the latent image carrier in a rotating direction, the developing device being configured to reversely develop the electrostatic latent image with negatively charged toner. In the image forming apparatus, the work function of the surface of the toner particles forming the negatively charged toner is larger than the work function of the surface of the writing electrode. 2. The difference between the work function of the surface of the toner particles forming the negatively charged toner and the work function of the surface of the writing electrode is 0.15.
2. The image forming apparatus according to claim 1, wherein the voltage is eV or more. 3. The work function according to claim 1, wherein the work function of the surface of the charge injection layer is larger than the work function of the surface of the writing electrode and smaller than the work function of the surface of the toner particles forming the negatively charged toner. Image forming device. 4. A contact portion of the writing device with a latent image carrier includes a plurality of electrodes arranged in a rotation axis direction of the latent image carrier and a separating member arranged between the plurality of electrodes. Wherein the difference between the work function of the surface of the separating member and the work function of the surface of the charge injection layer is less than 0.15 eV.
Or the image forming apparatus according to claim 2. 5. A contact portion of a writing device with a latent image carrier has a linear pressure of 0.05 N / s with respect to a rotation direction of the latent image carrier.
The image forming apparatus according to any one of claims 1 to 3, wherein the image is pressed at a distance of not more than mm.