JP3000919B2 - Method and apparatus for developing electrostatic latent image - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for developing an electrostatic latent image in an electrophotographic apparatus such as a copying machine or a printer or an electrostatic recording apparatus.

[0002]

2. Description of the Related Art In an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, a developer is applied to an electrostatic latent image formed on a latent image holding member such as a photosensitive drum. It is advantageous to use a one-component developer as a developer in the developing process of visualizing the electrostatic latent image by supplying the developer from the viewpoints of downsizing, cost reduction, and high reliability of the developing device.

Conventionally, a one-component developer (hereinafter referred to as toner) is supplied to a latent image holding member such as a photosensitive drum holding an electrostatic latent image, and toner adheres to the electrostatic latent image on the latent image holding member. Let
Developing methods for visualizing the electrostatic latent image include a powder cloud method in which toner particles are used in a spray state, a contact developing method in which toner particles are directly contacted with the latent image surface of a photosensitive drum for development, and a method in which toner particles are charged. Development methods such as a jumping development method in which the electrostatic latent image is developed without contacting the latent image surface of the photosensitive drum with an electric field, and a magnetite method in which a conductive toner having magnetism is brought into contact with the electrostatic latent image surface and developed. Are known.

[0004] The contact developing method will be described. For example, as shown in FIG. 1, a toner application roller 2 for supplying toner and a photosensitive drum (electrostatic holding body) 3 holding an electrostatic latent image are used. A developing roller 1 having a conductive elastic layer is disposed in contact with or close to the photosensitive drum 3, and the developing roller 1, the photosensitive drum 3, and the toner applying roller 2 rotate in the directions indicated by arrows in FIG. As a result, the toner 4 is supplied to the surface of the developing roller 1 by the toner applying roller 2, and the toner is arranged in a uniform thin layer by the layering blade 5. In this state, the developing roller 1 comes into contact with the photosensitive drum 3 or By rotating while approaching, the toner formed in a thin layer adheres to the electrostatic latent image 10 of the photosensitive drum 3 from the developing roller 1 and the latent image is visualized. In the figure, reference numeral 6 denotes a transfer unit, which transfers a toner image to a recording medium 7 such as paper. Reference numeral 8 denotes a cleaning unit, which is a cleaning blade 9 for transferring the toner image to the surface of the photosensitive drum 3 after transfer. The remaining toner is removed.

Here, in the reversal development used in a printer or the like, it is necessary to charge the toner to the same polarity as the charge on the latent image carrier, and in general, when an organic photoreceptor is used as the latent image carrier. Has a negative charge potential,
The charge of the toner must also be negative, and if a positively charged photoreceptor such as an amorphous silicon photoreceptor is used, the charge potential is positive, so the charge of the toner must also be positive. In this case, since the frictional charging with the developing roller surface is greatly involved in the charging of the toner, it is necessary to control the compatibility between the toner and the developing roller by designing the materials of both the toner and the developing roller, and the compatibility between the toner and the developing roller is poor. Fog, image memory, and the like are likely to occur in the initial image, and the occurrence of these image defects is remarkable particularly in a high-temperature, high-humidity or low-temperature, low-humidity environment. Even if there is no problem in the initial image, there is a case where problems occur such as a decrease in image density and a decrease in charge amount during repeated image output.

Therefore, conventionally, the toner side is controlled by a method such as blending a charge control agent according to the material of the layering blade and the developing roller, and the material is selected based on the triboelectric sequence. Control of the developing roller is performed to control compatibility between the toner and the developing roller.

[0007] However, these compatibility control methods have the following problems. In other words, the control on the developing roller side cannot be carried out by using only the triboelectric charging order as a reference. In the case of an elastic roller having conductivity, a conductive powder or a salt is added to impart conductivity, and thus the addition thereof changes the charging property. In the case of an elastic roller, selection of materials is limited in order to prevent contamination of the photoconductor. In addition, control of the toner side involves the following problems: (1) Since the effects of additives are not quantified, it takes time to develop a prescription suitable for a blade or a developing roller. -Control is limited due to problems such as CCA contamination. There are problems such as. Furthermore, in the conventional method, when the developing roller and the toner are combined, there is no method of judging compatibility except by actually performing image output or measuring and evaluating the toner charge amount, and the compatibility is easily evaluated. There is also a problem that it is not possible.

The present invention has been made in view of the above circumstances, and it is possible to easily and surely control the compatibility between toner and a developing roller, and to obtain a good image without causing image defects such as fog and image memory. It is an object of the present invention to provide a method and an apparatus for developing an electrostatic latent image capable of reliably reproducing the image over a long period of time.

[0009]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to achieve the above object, the present inventor has developed a developing roller having a conductive layer formed on the outer periphery of a good conductive shaft. The developer is carried on the surface to form a thin layer of the developer, and the developer is charged by frictional charging, and the developing roller is brought into contact with a drum-shaped latent image holding member holding an electrostatic latent image on the surface. Or, by rotating the latent image holding member and the developing roller in close proximity to each other to supply a developer to the surface of the latent image holding member to visualize the electrostatic latent image on the surface of the latent image holding member, It has been found that the compatibility between the developer and the developing roller can be easily and reliably controlled by evaluating the ionization potential of both surfaces as an index. As a result of further study, the ionization potential of the developer surface has been found. Is set to 4.5 to 5.5 eV, and the ionization potential of the developing roller surface is set to be lower than the ionization potential of the developer by using carbon black having a pH of 5 or more as a conductive material in the conductive layer in the case of negative charging. In the case of positive charge, by adjusting the ionization potential of the developer to be higher than the ionization potential of the developer by using an inorganic or organic ionic conductive material as a conductive material in the conductive layer, and performing development, image defects such as fog and image memory It has been found that a good image can be reliably reproduced over a long period of time without causing the problem, and the present invention has been completed.

Accordingly, the present invention provides a developing roller having a conductive layer formed on the outer periphery of a good conductive shaft, carrying a developer for negative charging on the surface of the developing roller to form a thin layer of the developer.
The developer is negatively charged by frictional charging, and the developing roller is brought into contact with or close to a drum-shaped latent image holding member holding an electrostatic latent image on its surface to rotate the latent image holding member and the developing roller. In the developing method of supplying a negatively charged developer to the surface of the latent image holding member to visualize the electrostatic latent image on the surface of the latent image holding member, the conductive layer may be a carbon black having a pH of 5 or more as a developing roller. Is used as a conductive material, and the ionization potential of the developer surface is adjusted to 4.5 to 5.5 eV, and the ionization potential of the development roller surface is adjusted to be equal to or less than the ionization potential of the developer to perform development. A method for developing an electrostatic latent image, wherein a positively charged developer is carried on the surface of a developing roller having a conductive layer formed on the outer periphery of a good conductive shaft. While forming a thin layer of the image agent, the developer is positively charged by triboelectric charging, and the developing roller is brought into contact with or in proximity to a drum-shaped latent image holding member having an electrostatic latent image on its surface to form a latent image. A developing method for rotating a holding member and a developing roller to supply a positively charged developer to the surface of the latent image holding member to visualize an electrostatic latent image on the surface of the latent image holding member. The conductive layer contains an inorganic or organic ionic conductive material as a conductive material, the ionization potential of the developer surface is 4.5 to 5.5 eV, and the ionization potential of the developing roller surface is Provided is a method for developing an electrostatic latent image, wherein the development is performed by adjusting the ionization potential to be equal to or higher than the ionization potential of a developer.

According to the present invention, there is provided an apparatus for developing an electrostatic latent image by the developing method of the present invention, wherein a rotatable drum-like latent image holder capable of holding an electrostatic latent image on a surface is provided. A conductive roller formed on the outer periphery of the conductive shaft; and a developing roller rotatably disposed in a state of being in contact with or in proximity to the surface of the latent image holding member. By carrying a negatively chargeable developer and forming a thin layer of the developer, the developer is negatively charged by frictional charging, and in this state, the developing roller and the latent image holder are rotated. An electrostatic latent image developing device that supplies a negatively charged developer to the surface of the latent image holding member to visualize the electrostatic latent image on the surface of the latent image holding member, wherein the conductive layer is used as a developing roller. It contains carbon black with a pH of 5 or more as a conductive material. As a reference, and the developer,
A developing device for an electrostatic latent image, wherein a device having a surface ionization potential of 4.5 to 5.5 eV is used, and the ionization potential of the developing roller surface is adjusted to be equal to or less than the ionization potential of the developer. A rotatable drum-shaped latent image holding member capable of holding an electrostatic latent image on the surface thereof, and a conductive layer formed on the outer periphery of a good conductive shaft, in contact with or in proximity to the surface of the latent image holding member. And a developing roller rotatably disposed in a state where a positively chargeable developer is carried on the surface of the development roller to form a thin layer of the developer, and the developer is triboelectrically charged. By rotating the developing roller and the latent image holding member in this state, a positively charged developer is supplied to the surface of the latent image holding member to thereby supply the surface of the latent image holding member. Visualization of electrostatic latent image of In an electrostatic latent image developing apparatus, a developing roller in which the conductive layer contains an inorganic or organic ionic conductive material as a conductive material and the developer has a surface ionization potential of 4.5 to 5 is used. .
A developing device for an electrostatic latent image, characterized in that a developing device of 5 eV is used and the ionization potential of the surface of the developing roller is adjusted to be equal to or higher than the ionization potential of the developer.

Note that the ionization potential is the energy required to separate one electron from an atom or molecule in a ground state in a gas to infinity and dissociate it into a cation and a free electron. The developer and the developing roller are directly irradiated with ultraviolet light (3.5 to 6.2 eV), respectively, and the photoelectrons emitted at this time are measured and easily obtained from the threshold value of the power plot of the quantum efficiency. it can.

Hereinafter, the present invention will be described in more detail.
As described above, the method and apparatus for developing an electrostatic latent image according to the present invention control the compatibility between the charging roller and the developer by using the ionization potential of both surfaces as an index. Potential of 4.5
The ionization potential on the surface of the developing roller is adjusted to be lower when negatively charged and higher when positively charged.

As the developer, a one-component developer is usually preferably used, and the ionization potential of the surface is 4.5.
-5,5 eV, preferably 5.1 in the case of a negatively chargeable developer.
To 5.4 eV, 4.8 to 5.3 e for a positively chargeable developer
V, and a commercially available one-component developer can be suitably used. In this case, it is practically difficult to make the ionization potential on the developer surface larger than 5.5 eV, and even if it can be initially controlled with a charge control agent or the like, it cannot be stable. On the other hand, if the ionization potential of the developer surface is smaller than 4.5 eV, it is difficult to reduce the ionization potential of the developing roller to less than that, and in the case of negative charging, proper chargeability of the developer may not be obtained. In the case of positive charging, it may be difficult to properly control the charging property.

Next, as described above, the developing roller is
A conductive layer is formed on the outer periphery of a good conductive shaft,
In this case, any shaft may be used as long as it has good electrical conductivity, but it is usually a metal core made of a metallic solid body or a metal cylindrical body hollowed inside. And the like.

The conductive layer formed on the outer periphery of the shaft is obtained by mixing conductive powder or magnetic powder into various resins when developing is performed in a state where the latent image holding member and the developing roller are not in contact with each other. When the development is performed in a state where the latent image holding member and the developing roller are in contact with each other, a relatively soft elastic body is used due to the necessity of the developing nip. And as a base component of such a conductive layer, polyurethane, natural rubber, butyl rubber, nitrile rubber, polyisoprene rubber, polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, acrylic rubber, And a mixture thereof, and the like. In the present invention, polyurethane or silicone rubber is particularly preferably used. In this case, the conductive layer may be a layer composed of a single layer of an elastomer or a foam material or a layer composed of a plurality of layers obtained by laminating these layers. Further, a coating film may be formed on these base layers using a resin such as polyamide, fluororesin, acrylic, polyurethane, or polycarbonate, or a mixture of these with a conductive material.

The polyurethane preferably used as a base component of the conductive layer will be described. The polyurethane elastomer and the foam material may be any of those produced by various methods. For example, carbon black may be blended in a polyurethane prepolymer. Then, it can be obtained by a known method in which a conductive material is blended with a polyhydroxyl compound, and the resulting mixture is reacted with a polyisocyanate by a one-shot method.

In this case, examples of the polyhydroxyl compound include polyols used for producing general flexible polyurethane foams and urethane elastomers, for example, polyether polyols having a polyhydroxyl group at the end, polyester polyols, and copolymers of both. In addition to polyester polyether polyols, general polyols such as polyolefin polyols such as polybutadiene polyol and polyisoprene polyol, and so-called polymer polyols obtained by polymerizing an ethylenically unsaturated monomer in a polyol can be used.

Examples of the polyisocyanate compound include polyisocyanate, which is also used for producing general flexible polyurethane foam and urethane elastomer.
That is, tolylene diisocyanate (TDI), crude TD
I, 4,4-diphenylmethane diisocyanate (MD
I), crude MDI, an aliphatic polyisocyanate having 2 to 18 carbon atoms, an alicyclic polyisocyanate having 4 to 15 carbon atoms, and a mixture or a modified product of these polyisocyanates, for example, partially reacted with a polyol. Prepolymers and the like are used. Particularly, in the present invention, in the case where development is performed by negatively charging the developer, a polyisocyanate such as tolylene diisocyanate is used in order to favorably adjust the ionization potential of the surface to the above range. The use of is recommended.

As a suitable polyisocyanate, xylylene diisocyanate can be exemplified in addition to tolylene diisocyanate.

When a silicone rubber is used as a base material, an organopolysiloxane raw rubber can be used after being crosslinked with a crosslinking agent or the like by a conventional method. In this case, the organopolysiloxane raw rubber used in the present invention may be any one as long as it is used for a silicone rubber compound for molding, but at least two alkenyl groups (eg, vinyl group, allyl group) in one molecule. Or the like). Such organopolysiloxanes include, for example, dimethylpolysiloxane having dimethylvinylsilyl groups at both ends, dimethylsiloxane / methylvinylsiloxane copolymer having dimethylvinylsilyl groups at both ends, dimethylsiloxane having methylphenylvinylsilyl groups at both ends -Methylphenylsiloxane-methylvinylsiloxane copolymer, methyl (3,3,3-trifluoropropyl) polysiloxane having a dimethylvinylsilyl group at both ends blocked.

When the conductive layer is formed of various rubber materials, a crosslinking agent and a vulcanizing agent can be added. In this case, a vulcanization aid, a vulcanization accelerator, a vulcanization acceleration aid, a vulcanization retarder, and the like can be used in both cases of organic peroxide crosslinking and sulfur crosslinking. Furthermore, peptizing agents, foaming agents, plasticizers, softeners, tackifiers, antiblocking agents, separating agents, release agents, extenders, and coloring agents that are commonly used as rubber compounding agents in addition to the above. Etc. can be added.

For example, nigrosine, triaminophenylmethane, cationic dye, and the like are used for the purpose of controlling the charge amount of the one-component developer on the surface when used as a developing roller. And various fine particles such as silicone resin, silicone rubber and nylon. In this case, the amount of these additives is preferably 1 to 5 parts by weight, and the fine powder is preferably 1 to 10 parts by weight, based on 100 parts by weight of the polyurethane or silicone rubber.

The conductive layer is usually blended with a conductive material for imparting conductivity. In this case, as the conductive material,
First, Ketjen Black EC,
Carbon black such as acetylene black, SAF, I
SAF, HAF, FEF, GPF, SRF, FT, MT
Such as carbon for rubber, carbon for color (ink) that has been subjected to oxidation treatment, pyrolytic carbon, natural graphite,
Examples include powders of artificial graphite, metals such as antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, and germanium and metal oxides, and conductive polymers such as polyaniline, polypyrrole, and polyacetylene. In addition, inorganic ionic conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride, and further modified aliphatic dimethylammonium ethosulfate, stearylammonium acetate, laurylammonium acetate, octadecyltrimethylammonium perchlorate Organic ionic conductive substances such as salts and tetrabutylammonium borate can be used alone or in combination with the above powder. The amount of the conductive material is appropriately adjusted depending on the type of the conductive material, but is usually 0.01 to 50 parts by weight, particularly 0.1 to 100 parts by weight based on 100 parts by weight of the base component.
It is used in the range of 1 to 30 parts by weight.

Other conductive materials include electron acceptors that can form charge transfer complexes, such as tetracyanoethylene and its derivatives, tetracyanoquinodimethane and its derivatives, benzoquinone and its derivatives, chloranil and its derivatives, Examples include anthraquinone and its derivatives, anthracene and its derivatives, dichlorodicyanobenzoquinone and its derivatives, ferrocene and its derivatives, and phthalocyanine and its derivatives. One of these can be used alone, or two or more can be used in combination.
Among these, tetracyanoquinodimethane and tetracyanoethylene are particularly preferably used. The amount of the electron accepting substance capable of forming the charge transfer complex is 0.001 to 20 parts by weight based on 100 parts by weight of the polymer substance as the base component.
Parts by weight, preferably 0.01 to 1 part by weight.

Here, in the present invention, when the developer is charged negatively to perform the development, the pH is 5 or more, preferably the pH is 5 or more.
6 to 11 carbon blacks are used. Thereby, the ionization potential of the conductive layer surface can be easily reduced, and the ionization potential of the conductive layer can be easily made lower than that of the developer. In this case, the resistance of the conductive layer is made to be 10 ³ to 10 ¹⁰ Ωcm, particularly 10 ⁴ to 10 ⁸ Ωcm by the addition of the carbon black.
When the resistance value is less than 10 ³ Ωcm, the electric charge may leak to the latent image holding member, or the developing roller itself may be broken by the voltage, and on the other hand, 10 ¹⁰
If it exceeds Ωcm, ground fog is likely to occur. The pH of the carbon black was determined by boiling the sample in distilled water, centrifuging it, removing the supernatant, and separating sludge.
This can be easily known by measuring the pH with a pH meter as a measurement sample.

On the other hand, in the present invention, when the developer is charged positively for development, the above-mentioned inorganic ionic conductive material or organic ionic conductive material is used as the conductive material, and is not particularly limited. It is preferable not to use conductive powder such as carbon. The reason is that the conductive powder itself generally has a property of easily emitting electrons, and therefore has a low ionization potential of itself, and therefore, when it is blended, the ionization potential as a base resin tends to be low. This is because the object of the present invention may not be sufficiently achieved. In this case, when the conductive powder is blended, not only the case where the conductivity is controlled thereby, but also the case where carbon or the like is blended for coloring. In addition, as long as the ionization potential can be adjusted to a predetermined value, the addition of the conductive powder itself may be used. A preferable resistance value in the case of positive charging is 1
0 ⁵ to 10 ¹⁰ Ωcm.

In the present invention, when the developer is negatively charged and the development is performed, stearyl stearate, lauryl laurate and the like are provided on the conductive layer of the developing roller for the purpose of adjusting the ionization potential of the conductive layer. Lubricants such as monoester lubricants such as acrylates, fatty acid ester lubricants such as methyl oleate and methyl palmitate, and ester-type nonionic surfactants such as polyoxyethylene monolaurate and polyoxyethylene monostearate; Sorbitan ester-type nonionic surfactants such as soribitan monolaurate and sorbitan monopalmitate; sorbitan ether ester-type nonionic surfactants such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monopalmitate Formulated with a nonionic surfactant It is possible, it is possible to easily reduce the ionization potential of the conductive layer by blending these lubricants and surfactants adjusted to be lower than the ionization potential of the developer.

Although the hardness of the conductive layer is not limited, particularly when the development is carried out in contact with the latent image holding member,
It is preferably set to 60 ° or less, particularly 25 to 55 ° on the JIS-A scale. In this case, if the hardness exceeds 60 °, the contact area with a latent image holding member such as a photosensitive drum becomes small, and good development may not be performed. Conversely, if the hardness is too low, the compression set becomes large. If the developing roller is deformed or eccentric for some reason, density unevenness occurs in the image. For this reason, even when the hardness of the elastic layer is set to be low, it is preferable to reduce the compression set as much as possible.
It is preferably set to 0% or less.

The surface roughness of the conductive layer, that is, the surface roughness of the developing roller is not particularly limited.
10-point average roughness of 15 μm Rz or less, especially 1 to 10 μm
It is preferably Rz. When the surface roughness exceeds 15 μmRz, the thickness of the toner layer of the one-component developer (toner) and the uniformity of charging may be impaired. However, when the surface roughness is 15 μmRz or less, the adhesion of the toner can be improved. In addition to this, it is possible to more reliably prevent image deterioration due to roller wear during long-term use.

According to the developing method and the developing device of the present invention, the ionization potential of the surface of the developing roller is equal to or higher than the ionization potential of the developer when the developer is negatively charged. When the developer is positively charged, the developer is adjusted so as to be equal to or larger than the ionization potential of the developer of 4.5 to 5.5 eV. is there. In this case, preferably, the ionization potential of the developing roller surface is set to be smaller or larger than the ionization potential of the developer by about 0.1 to 0.5 eV. More specifically, the ionization potential of the developing roller surface is negatively charged. In the case of (1), it is preferable to adjust to 4.5 to 5.3 eV, and in the case of positive charge, it is preferable to adjust to 4.7 to 5.5 eV. In this case, the ionization potential can be adjusted by selecting a material for forming the conductive layer and blending additives such as the conductive agent, the lubricant, and the surfactant.

In this case, the ionization potential is measured by preparing a sheet-like sample of the conductive layer and directly irradiating it with ultraviolet light (3.5 to 6.2 eV) as described above. And the quantum efficiency can be easily obtained from the threshold value of the power plot of the quantum efficiency. In addition, as a measuring device, Riken Keiki Co., Ltd. A
A commercially available surface analyzer such as C-1M can be used.

Here, the developing method and the developing apparatus of the present invention adjust the developer and the ionization potential of the surface of the developing roller as described above to prevent the occurrence of image fogging and image memory and to obtain a good image. Although it can be obtained, the reason why the occurrence of image fogging and image memory is favorably prevented by the present invention is presumed to be as follows.

That is, as shown in FIG. 2, image fogging is a phenomenon in which a sandy image appears in a portion which is originally a white image, and the occurrence is caused by the presence of a weakly charged developer or a reversely charged developer. However, as described above, the ionization potential adjusted in the present invention dissociates one electron from an atom or molecule in the ground state to infinity and dissociates it into a cation and a free electron. For example, when developing with negatively charged developer, the ionization potential carried on the surface of the developing roller is set by setting the ionization potential on the surface of the developing roller low. The electrons are easily transferred to the high-developable developer, whereby the developer can be reliably and negatively charged to a high potential. On the other hand, when the developer is positively charged, Conversely, by setting the ionization potential on the surface of the developing roller to be high, electrons can easily move from the developer having a low ionization potential carried on the surface of the developing roller to the surface of the developing roller, so that the developer can be reliably and highly charged. It can be considered that a positive charge can be applied to the potential, and in either case of the negative charge or the positive charge, the generation of the weakly charged developer or the oppositely charged developer is surely prevented, and a good image is surely obtained.

Further, with respect to the image memory, for example, when an image including a black background is partially printed, most of the developer on the developing roller in the black background is developed and consumed, so that the developer on the roller is newly supplied. Will be replaced. In this case, if the charge rise of the developer is slow, the charge amount becomes nonuniform between the black printed portion on the roller and other portions, and if a portion such as a halftone exists after the black background on the image, the half A history of a black background portion may remain on a tone, which is a so-called image memory. Therefore, in order to avoid the occurrence of the image memory, it is necessary to improve the charge rise of the developer, and it is considered that the adjustment of the ionization potential in the present invention is effective for this purpose.

The developing method and the developing apparatus of the present invention
The developer is carried on the surface of the developing roller to form a thin layer of the developer, and the developing roller is brought into contact with or in proximity to a drum-shaped latent image holding member having an electrostatic latent image held on the surface thereof. By rotating the image holding member and the developing roller, a developer is supplied to the surface of the latent image holding member to visualize an electrostatic latent image on the surface of the latent image holding member. The development can be performed by the mechanism shown in FIG. In this case, in FIG. 1, development is performed in a state where the developing roller 1 and the latent image holding member 3 are in contact with each other.
It is also possible to carry out development in a non-contact state in which the and the latent image holding member 3 are close to each other.

[0037]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 Glycerin was added with propylene oxide and ethylene oxide to give a molecular weight of 500.
100 parts by weight of polyether polyol (Exenol 828 from Asahi Glass Co., Ltd.) (OH value: 33) (parts by weight,
The same applies hereinafter), 1.0 part of 1,4-butanediol, and a silicone surfactant (L-520, manufactured by Nippon Yunika).
5 parts, 0.5 parts of nickel acetylacetonate, 0.01 parts of dibutyltin dilaurate and 1.0 part of acetylene black (manufactured by Denka Co., pH 6.9) were added, and the mixture was preliminarily mixed using a mixer and then painted. Acetylene black was uniformly dispersed by kneading with a roll to prepare a polyol composition.

The polyol composition was stirred under reduced pressure to remove bubbles, and 17.5 parts of urethane-modified MDI (Sumitole PF, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was added thereto.
Stir for a minute and then pour into a mold heated to 110 ° C.
After curing for 2 hours, a conductive layer was formed on the outer periphery of the metallic shaft to obtain a roller. The surface of the obtained roller was polished to adjust the surface to a JIS 10-point average roughness of 7 μmRz to obtain a developing roller.

On the other hand, a sheet sample similar to the conductive layer of the developing roller was prepared, and the ionization potential was measured using the obtained sheet sample.
V.

The above roller is mounted on the developing unit shown in FIG. 1 as a developing roller 1, an organic photosensitive drum for negative charging is used as a photosensitive drum 3, and a toner for a printer cp500 (Ionization potential 5.3e manufactured by Casio) is used as a toner 4.
Using V), development was performed under the conditions of a photoconductor charging potential of -820 V, a developing bias of -400 V, and a linear velocity of 60 mm / sec, and the toner charge amount and image evaluation were performed based on the following measurement methods. Table 1 shows the results.

Example 2 Development was performed in the same manner as in Example 1 except that toner for NEC printer PC-PR1000E / 4 (ionization potential: 5.1 eV) was used as the toner, and the toner charge amount was similarly changed. Was measured and the image was evaluated. Table 1 shows the results.

Example 3 Monoester lubricant Unistar M9676 (manufactured by NOF Corporation) was added to 100 parts of a polyisoprene polyol having a molecular weight of 2500 (OH value = 47.1).
And 3.32 parts of acetylene black, and stirred for 30 minutes. Thereafter, the glue MDI (NCO% = 31.
7.33) and dibutyltin dilaurate in 0.033 parts
01 parts were added and stirred for 3 minutes. Next, a shaft was arranged, and the reaction mixture was poured into a mold heated to 90 ° C. in advance, and a curing reaction was performed at 90 ° C. for 12 hours to obtain a roller. The obtained roller surface was polished to obtain an average roughness of 7 μm Rz.
To obtain a developing roller.

A sheet sample similar to the conductive layer of this developing roller was prepared, and the ionization potential of the obtained sheet sample was measured to be 5.0 eV.

Using the developing roller described above, development was performed in the same manner as in Example 1, and measurement of toner charge and image evaluation were performed in the same manner. Table 1 shows the results.

[0046]

[0047]

Example 5 A surface treatment was conducted by immersing the developing roller prepared in Example 1 in a 10% by weight solution of a fluororesin (fluoroolefin vinyl ether copolymer) in toluene and pulling it up and drying it by heating. Do
This was used as a developing roller. When the ionization potential of this developing roller was measured in the same manner, it was 5.0 eV.

The obtained developing roller was developed in the same manner as in Example 1, and the toner charge amount was measured and the image was evaluated in the same manner. Table 1 shows the results.

Example 6 1.0 part of sodium perchlorate was mixed with 100 parts of polytetramethylene ether glycol (OH value = 56), and the mixture was stirred while controlling the temperature at 100 ° C., and then 4,4 ′ 13.48 parts of difinylmethane diisocyanate (NCO% = 33.6) was added and stirred,
Mixed. Next, this reaction mixture was cast into a mold previously heated to 90 ° C., and a curing reaction was carried out at 90 ° C. for 12 hours to obtain a roller having a conductive layer formed on the outer periphery of a metallic shaft. The surface of the obtained roller is polished and the surface is JIS10
The point average roughness was adjusted to 5 μmRz to obtain a developing roller.

On the other hand, a sheet sample similar to the conductive layer of the developing roller was prepared, and the ionization potential was measured using the obtained sheet sample.
V.

The above-mentioned roller is mounted on the developing unit shown in FIG. 1 as a developing roller 1, and a positively charged organic photosensitive drum is used as a photosensitive drum 3 and a styrene-acrylic toner (ionization potential: 4.9 eV) is used as a toner 4. Photoconductor charging potential +750 V, developing bias -350 V,
Development was performed under the condition of a linear velocity of 60 mm / sec, and the toner charge amount and image evaluation were similarly performed. Table 1 shows the results.

Comparative Example 1 A developing roller was prepared in the same manner as in Example 1 except that 0.01 part of sodium perchlorate was used instead of acetylene black, and its ionization potential was measured. 0.4 eV.

The obtained developing roller was developed in the same manner as in Example 1, and the toner charge amount was measured and the image was evaluated in the same manner. Table 1 shows the results.

[Comparative Example 2] A method similar to that of Example 6 except that a developing roller prepared in Example 1 (ionization potential: 5.0 eV) and a polyester toner (ionization potential: 5.3 ev) were used as the toner. , And similarly the measurement of the toner charge amount and the image evaluation were performed. Table 1 shows the results.

Measurement Method Toner charge amount: Each roller was mounted on the developing unit shown in FIG. 1 as a developing roller and rotated at a peripheral speed of 50 mm / sec to form a uniform thin toner layer on the surface of the developing roller.
The thin toner layer was sucked by air and introduced into a Faraday gauge, and the charge amount was measured. Image output: Each roller is attached to the developing unit shown in FIG. 1 as a developing roller, and an image is output by reversal development while rotating at a peripheral speed of a linear speed of 60 mm / sec.
The sharpness was evaluated. In a high temperature and high humidity environment (33
At 85 ° C. and a humidity of 85%).
The evaluation of the image memory was performed using an image chart in which only the leading end of the image was solid black and the subsequent portions were halftone.

[0057]

[Table 1]

[0058]

According to the method and apparatus for developing an electrostatic latent image of the present invention, the compatibility between the toner and the developing roller can be easily and reliably controlled without causing image defects such as fog and image memory. A good image can be reliably reproduced over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the developing device of the present invention.

FIG. 2 is a reference diagram illustrating an example of an image in which fogging has occurred.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Development roller 2 Toner application roller 3 Photosensitive drum (latent image holding body) 4 Toner (one-component developer) 5 Layering blade 6 Transfer unit 7 Recording medium 8 Cleaning unit 9 Cleaning blade

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-233477 (JP, A) JP-A-4-191752 (JP, A) JP-A-59-90857 (JP, A) JP-A-3-1990 187732 (JP, A) JP-A-9-190074 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 9/08

Claims (6)

(57) [Claims] 1. A developing roller having a conductive layer formed on an outer periphery of a good conductive shaft, a negatively charged developer is carried on a surface of the developing roller to form a thin layer of the developer, and the developer is triboelectrically charged. By rotating the latent image holding member and the developing roller by contacting or approaching the developing roller with a drum-shaped latent image holding member holding an electrostatic latent image on its surface,
In a developing method of supplying a negatively charged developer to the surface of the latent image holding member to visualize an electrostatic latent image on the surface of the latent image holding member, the conductive layer serves as a developing roller for conducting carbon black having a pH of 5 or more. And the ionization potential of the developer surface is adjusted to 4.5 to 5.5.
A method for developing an electrostatic latent image, wherein the development is performed by adjusting the ionization potential of the developing roller to be equal to or less than the ionization potential of the developer. 2. The method according to claim 1, wherein the conductive layer constituting the developing roller comprises one or more lubricants selected from monoester lubricants and fatty acid ester lubricants, and / or ester nonionic surfactants, and sorbitan ester lubricants. 2. The development of an electrostatic latent image according to claim 1, comprising one or more nonionic surfactants selected from nonionic surfactants and sorbitan ether ester type nonionic surfactants. Method. 3. A developing roller having a conductive layer formed on the outer periphery of a good conductive shaft, a developer for positive charging is carried on the surface of the developing roller to form a thin layer of the developer, and the developer is triboelectrically charged. By positively charging the developing roller by contacting or approaching the developing roller with a drum-shaped latent image holding member holding an electrostatic latent image on the surface to rotate the latent image holding member and the developing roller,
In a developing method of supplying a positively charged developer to the surface of the latent image holding member to visualize an electrostatic latent image on the surface of the latent image holding member, the conductive layer may be an inorganic or organic ionic conductive material as a developing roller. Is used as a conductive material, and the ionization potential of the developer surface is set to 4.5 to 5.5.
A method for developing an electrostatic latent image, wherein the developing is performed by adjusting the ionization potential of the developing roller to eV and the ionization potential of the developer to be equal to or higher than the ionization potential of the developer. 4. The electrostatic latent image developing method according to claim 3, wherein the conductive layer constituting the developing roller does not contain conductive powder. 5. A rotatable drum-shaped latent image holder capable of holding an electrostatic latent image on its surface, and a conductive layer formed on the outer periphery of a good conductive shaft. A developing roller rotatably disposed in contact with or in proximity to the developing roller. The developing roller carries a negatively charged developer on the surface of the developing roller to form a thin layer of the developer. The developer is negatively charged by frictional charging, and in this state, the developing roller and the latent image holding member are rotated to supply a negatively charged developer to the surface of the latent image holding member, thereby supplying the latent image to the latent image holding member. In a developing device for an electrostatic latent image for visualizing an electrostatic latent image on a surface of a holding member, a developing roller in which the conductive layer contains carbon black having a pH of 5 or more as a conductive material, and the developing agent includes: Has an ionization potential of 4.5 to 4.5.
A developing device for an electrostatic latent image, wherein the developing device uses 5.5 eV and the ionization potential of the surface of the developing roller is adjusted to be equal to or less than the ionization potential of the developer. 6. A rotatable drum-shaped latent image holder capable of holding an electrostatic latent image on a surface thereof, and a conductive layer formed on the outer periphery of a good conductive shaft. A developing roller rotatably disposed in contact with or in proximity to the developing roller. The developing roller carries a positively chargeable developer on the surface thereof to form a thin layer of the developer. The developer is positively charged by frictional charging, and in this state, the developing roller and the latent image holding member are rotated, thereby supplying a positively charged developer to the surface of the latent image holding member to supply the latent image to the latent image holding member. In a developing device for an electrostatic latent image for visualizing an electrostatic latent image on a surface of a holding member, a developing roller in which the conductive layer contains an inorganic or organic ionic conductive material as a conductive material, and as the developer , Surface ionization potential is 4.5-
A developing device for an electrostatic latent image, wherein the developing device uses 5.5 eV and the ionization potential of the surface of the developing roller is adjusted to be equal to or higher than the ionization potential of the developer.