JP2006064738A - Electrifying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device in which easy, steady, uniform injection charging is ensured for a long time and to provide an image forming apparatus having the charging device. <P>SOLUTION: The charging device electrifies a body to be charged, by applying an charging voltage to a low-volatile, conductive gel medium disposed in contact with the surface of the body to be. The image forming apparatus includes: the body to be charged; the charging device for uniformly electrifying the surface of the body to be electrified; an exposure device for forming an electrostatic latent image on the charged body; a developing device for forming a toner image by developing the electrostatic latent image; and a transfer device for transferring the toner image onto a transferred material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging device, in particular, a contact charging device, and an image forming apparatus including the charging device.

  Conventionally, in an image forming apparatus such as an electrophotographic apparatus, a corona charger using corona discharge has been mainly used as means for charging an object to be charged such as an electrophotographic photosensitive member. The corona charger is placed in non-contact with the object to be charged, for example, a high voltage is applied to a wire electrode or a needle electrode to cause corona discharge, and a part of the discharge current is passed through the object to be charged. The charged body is charged to a predetermined potential.

  However, since this corona charger uses corona discharge, a large amount of ozone is generated, which adversely affects the human body, and discharge products from the corona discharge adhere to the surface of the object to be charged, shortening the life of the object to be charged. There was a problem to do. Furthermore, a high voltage power source is necessary, and there is a disadvantage that the power source cost is high.

  In recent years, many contact chargers have been proposed and put to practical use because they have advantages such as low ozone and low power compared to corona chargers.

  The contact charger applies a predetermined charging bias to a conductive electrode brought into contact with an object to be charged to charge the surface to be charged to a predetermined polarity / potential. As the electrode, for example, a charging roller, a fur brush, a magnetic brush, a blade, or the like is used.

  It is known that there are two types of contact charging mechanisms. One is a charging mechanism by discharge, and the other is a mechanism in which charges are directly injected from an electrode to an object to be charged.

  In the discharge charging mechanism, a discharge phenomenon that occurs in a minute gap between an object to be charged and an electrode is used. For this reason, although it can be charged at a lower voltage than the corona charging, it is necessary to apply a voltage obtained by adding a threshold voltage to a desired charging potential to the electrode. In addition, although the amount of ozone generated is smaller than that of corona charging, the charging method using the discharge phenomenon is unavoidable due to discharge products.

  In the injection charging mechanism, a charge is directly injected from a contact electrode to an object to be charged without going through a discharge phenomenon. Even if the voltage applied to the electrode is equal to or lower than the discharge threshold, the surface of the object to be charged can be charged to a voltage substantially equal to the applied voltage. Available at low voltage. Further, since no discharge occurs and no ions are generated, there is no harmful effect caused by the discharge product.

Specifically, a method of using a fluid such as a liquid, powder, or gel as a charge transfer medium to an object to be charged is known as an injection charging mechanism (Patent Document 1). By using a fluid as the charge transfer medium, the charge transfer medium can maintain close contact with the surface of the charged body, so that direct injection charging with excellent uniformity and high charging ability can be performed. Direct injection charging is effective for contact charging of the member to be charged by the contact electrode. Furthermore, it is known that using a gel as a fluid makes it easier to handle and process without causing problems such as volatilization, scattering, and leakage, compared to the case of using a liquid or powder.
Japanese Patent Laid-Open No. 9-305003 JP 2004-133347 A

However, hydrogels using water as a solvent for conventional charging gels have the following problems.
(1) The volume of the gel is likely to decrease due to the volatilization of the solvent, and stable charging cannot be maintained due to a decrease in the contact area with the charged body; and (2) Peripheral processes such as the developing unit and the transfer unit Adversely affects the development, causes development unevenness and transfer unevenness, and cannot maintain stable image formation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a charging device that realizes simple and stable uniform injection charging over a long period of time, and an image forming apparatus including the charging device.

  The present invention relates to a charging device for charging a charged object by applying a charging voltage to a gel-like conductive medium disposed in contact with the surface of the charged object whose surface moves. The present invention relates to a charging device in which a conductive medium has low volatility.

  The present invention also provides an object to be charged whose surface is moved, the above-described charging device for uniformly charging the object to be charged, an exposure device for forming an electrostatic latent image on the object to be charged, and developing the electrostatic latent image. The present invention relates to a developing device that forms a toner image and an image forming device that includes a transfer device that transfers the toner image to a transfer target.

  In the charging device of the present invention, by interposing a gel-like conductive medium as a charge transfer medium to the object to be charged, substantially ozone-less charge injection from the electrode to the object to be charged can be performed efficiently and simply. it can. Furthermore, by using a low-volatile material as the gel-like conductive medium, there is no need to particularly increase the sealing quality, and the effects of deterioration in image quality, workability, and capacity change due to volatile components are suppressed and stable over a long period of time. The object to be charged can be charged efficiently and uniformly.

The charging device according to the present invention includes at least a gel-like conductive medium disposed in contact with the surface of an object to be charged, and the gel-shaped conductive medium disposed so as to be electrically connected to the gel-shaped conductive medium. It comprises an electrode for applying a charging voltage. In the present invention, the configuration and arrangement of the gel-like conductive medium and the electrode are particularly limited as long as the surface of the object to be charged can be uniformly charged by applying a charging voltage to the gel-like conductive medium by the electrode. is not.
Hereinafter, an embodiment of the charging device of the present invention will be described with reference to the drawings showing an image forming apparatus provided with the charging device. However, as long as the charging device of the present invention has the above-described gel-like conductive medium and electrode, It should be clear that they should not be construed as limited to those embodiments.

(First embodiment)
FIG. 1A is a schematic configuration diagram illustrating an example of an image forming apparatus including the charging device of the present invention. The image forming apparatus of FIG. 1A includes a charged body 1 whose surface moves, a charging apparatus 2 that uniformly charges the charged body, an exposure apparatus 3 that forms an electrostatic latent image on the charged body, A developing device 4 that develops an electrostatic latent image to form a toner image and a transfer device 5 that transfers the toner image to a transfer target 6 are provided.

  A member to be charged is a so-called photosensitive member that performs charging, exposure, development, and the like on the surface while moving the surface, and usually has a cylindrical shape, and the surface moves by rotating about its axis. The surface of the member to be charged is preferably subjected to a coating treatment from the viewpoint of preventing adhesion of the gel-like conductive medium over a long period of time. The coating treatment is performed by applying a solution obtained by dissolving the coating material in a solvent to the surface of the member to be charged and drying it. Examples of the coating material include polyurethane resin, silicone resin, fluorine-containing resin, and phosphazene resin. The solvent is not particularly limited as long as it can dissolve the coating material, and examples thereof include methyl ethyl ketone, isopropanol, hexane, toluene, and THF. The coat thickness is not particularly limited, and usually 1 to 20 μm, particularly 2 to 10 μm is preferable.

  In the first embodiment of the charging device of the present invention, as shown in FIG. 1A, the charging device 2 includes a gel-like conductive medium 2a arranged in contact with the surface of the body 1 to be charged, and the electrode 2b being charged. A flat plate-type structure in which the gel-type conductive medium 2a is held by the flat-plate electrode 2b in a non-contact state with respect to the charged body 1 downstream of the gel-type conductive medium 2a in the moving direction of the body surface. Have. FIG. 1B is a schematic sketch of an electrode, a gel-like conductive medium, and an object to be charged when the image forming apparatus of FIG. 1A is viewed from the x direction. As described above, since the electrode for applying a voltage to the gel-like conductive medium is arranged on the downstream side of the gel-like conductive medium in the moving direction of the member to be charged, the electrode can be reliably contacted and applied with the voltage. . Further, since the electrode also has a function of holding the gel-like conductive medium, it is not necessary to separately provide a holding material for the gel-like conductive medium, and the apparatus can be simplified.

  The gel-like conductive medium 2a is continuously struck while being rubbed with the surface of the body to be charged, or rotating and renewing contact / peeling by the frictional force with the surface. In contact with the surface, the surface of the member to be charged is charged. In FIG. 1A, the gel-like conductive medium may be placed on the surface of the member to be charged so as to be in contact with the electrode.

  In the present invention, “gel” means a state in which a solvent is incorporated in a three-dimensional network structure, and the shape and viscosity are not particularly limited.

  Such a gel-like conductive medium has low volatility, that is, is composed of a low volatility solvent having a vapor pressure lower than that of water as a solvent. The network structure constituting the gel-like conductive medium may be composed of a polymer or a network structure by intermolecular bonds such as hydrogen bonds, electrostatic bonds, coordination bonds, van der Waals bonds, and molecular entanglement bonds. It may be composed of a low molecular compound that can be converted into a low molecular weight compound.

  The lower the volatility of the gel-like conductive medium is, the better. In the present invention, the gel-like conductive medium only needs to have a vapor pressure lower than that of water. Specifically, the vapor pressure at 25 ° C. is 3167.5 Pa or less, preferably 300 Pa or less, more preferably 3 Pa or less.

The conductivity of the gel-like conductive medium may be such that the volume resistivity is 1 × 10 ¹⁰ Ωcm or less. This is because the member to be charged can be sufficiently charged. From the viewpoint of securing a sufficient charge amount even when the image forming apparatus is used at a process speed of 150 mm / sec or higher, the volume resistivity of the gel-like conductive medium is 1 × 10 ⁸ Ωcm or less, particularly 1 X10 ⁶ Ωcm or less is preferable. On the other hand, the lower limit of the volume resistivity of the gel-like conductive medium is not particularly limited, but if it is 0.01 Ωcm or more, stable charging can be performed without excessive current flowing on the surface of the charged body. Preferably it is 0.1 Ωcm or more, particularly 1 Ωcm or more.

  In this specification, the volume resistivity is a value measured by a TOA ultra-high precision conductivity meter (product name: digital super insulation / micro ammeter). However, it does not have to be measured by the above-mentioned device, and may be measured by any device that can measure according to the same principle and principle as the above-mentioned device.

  Such a conductive property of the gel-like conductive medium is obtained by using a conductive material as a solvent, using a conductive material as a network constituent molecule, and dispersing conductive powder in the gel-like medium. It can be achieved by the method of making it. Preferably, a method of using a conductive material as a solvent and a method of dispersing conductive powder in a gel-like medium are employed. These methods may be employed alone or in combination.

A so-called ionic liquid can be used as the conductive solvent. Examples of the ionic liquid include imidazolium salts, pyridinium salts, ammonium salts, and the like. Specific examples of ionic liquids, for example, ethyl methyl imidazolium cation _{(CF 3 SO 2) 2 N} - as a salt, N- methyl -N'- methoxy-methylimidazolium bromide, N- methyl -N'- methoxy Examples thereof include ethyl imidazolium bromide and 1-ethyl-3-methyl imidazolium bromide. These ionic liquids can be synthesized, for example, according to the method disclosed in Japanese Patent Application No. 2000-184298. By using an ionic liquid, high conductivity and low volatility of the gel-like conductive medium can be realized at the same time.
Moreover, the electrolysis solution which melt | dissolved the supporting electrolyte in the below-mentioned nonelectroconductive solvent can also be used as an electroconductive solvent. As the supporting electrolyte, for example, alkali metal ions, quaternary alkyl ammoniums, halogen ions, sulfate ions, perchlorate ions and the like can be used.
Two or more types of conductive solvents that are compatible with each other may be used in combination.

Conductive polymers and conductive low molecular compounds can be used as the conductive molecules that can form a network structure.
Examples of the conductive polymer include a π-electron conjugated polymer, a non-conductive polymer to be described later doped with I ₂ or Br ₂ to increase conductivity, a polymer charge transfer complex, and the like. The π-electron conjugated polymer is a linear or branched polymer having a π-electron conjugated unit in the main chain, a branched polymer having a π-electron conjugated unit in the side chain, and a three-dimensional cross-linked product thereof. . Specific examples of such conductive polymers such as polyacetylene, polythiophene, polyethylene doped with I _2, segmented polyurethane, and the like.
The conductive polymer can be obtained by polymerization of olefins and acetylenes, polycondensation of aromatic dihalides, oxidative polymerization of pyrrole, thiophene, aniline and the like. The conductivity can be increased by iodine doping of the obtained polymer.
Examples of the polymer charge transfer complex include polyvinyl carbazole-trinitrofluorenone series, polyvinyl pyridine-iodine series, polycation ionomer-tetracyanoquinodimethane series, and the like.

Examples of the conductive low molecular weight compound include organic charge transfer complexes and ion radical salts, or glymes. Examples of the organic charge transfer complex include cetothiafulvalene-tetracyanoquinodimethane complex. Examples of the ion radical salt include ammonium ion-tetracyanoquinodimethane complex. Examples of the glyme salt include diethoxyethane and propoxyethane.
Two or more kinds of conductive molecules may be used in combination.

  As electroconductive powder, metal oxides, such as electroconductive carbon, metal powder, electroconductive zinc oxide, etc. are mentioned, for example. The average primary particle size of the conductive powder is preferably 0.01 to 100 μm, particularly 0.02 to 50 μm, from the viewpoint of the production cost and dispersibility of the particles. Two or more kinds of conductive powders may be used in combination.

  In preparing the gel-like conductive medium, non-conductive molecules and non-conductive solvents may be used as long as the resulting gel-like conductive medium has the desired conductivity and low volatility.

Non-conductive molecules are non-conductive molecules that can form a network structure, and non-conductive polymers and non-conductive low-molecular compounds can be used.
Examples of the non-conductive polymer include silicone, cellulose, polybutadiene, polyether, polyester, acrylic, a copolymer thereof, and a three-dimensional crosslinked product. Ethyl cellulose is available as etosel (Nisshin Kasei), acrylic is 2-dimethylaminoethyl methacrylate (Wako), and silicone is KSG-15 (Shin-Etsu Silicone).

（式中、Ｒ_１及びＲ_２はそれぞれ独立して炭素数２以上のアルキル基を示し、Ｒ_３及びＲ_４はそれぞれ独立して炭素数２〜２０のアルキレン基を示し、Ｒ_５は下記式（１）〜（９）：

からなる群から選ばれる糖アミド基を示す。またｎは１又は２の整数を示す。）で表される有機化合物、Ｎ−ラウロイル−Ｌ−グルタミン酸−α，β−ビス−ｎ−ブチルアミド、１，２，３，４−ジベンジリデン−Ｄ−ソルビトール、１２−ヒドロキシステアリン酸、コレステロール誘導体、シクロヘキサンジアミン誘導体等が挙げられる。中でも、一般式（ＩＩ）；

で表される有機化合物、およびＮ−ラウロイル−Ｌ−グルタミン酸−α，β−ビス−ｎ−ブチルアミドが好ましい。 As non-conductive low molecular weight compounds, compounds that can form fibrous aggregates by intermolecular interactions such as hydrogen bonds, and bond / three-dimensionalize the aggregates by van der Waals force can be used. .
Specific examples of the non-conductive low molecular weight compound include, for example, the general formula (I);

(In the formula, R ₁ and R ₂ each independently represent an alkyl group having 2 or more carbon atoms, R ₃ and R ₄ each independently represent an alkylene group having 2 to 20 carbon atoms, and R ₅ represents the following formula: (1) to (9):

A sugar amide group selected from the group consisting of: N represents an integer of 1 or 2. ), N-lauroyl-L-glutamic acid-α, β-bis-n-butyramide, 1,2,3,4-dibenzylidene-D-sorbitol, 12-hydroxystearic acid, cholesterol derivatives, And cyclohexanediamine derivatives. Among them, general formula (II);

And N-lauroyl-L-glutamic acid-α, β-bis-n-butyramide are preferable.

The organic compound represented by the general formula (I) can be prepared by utilizing various synthetic methods. For example, a primary amine having an ether group corresponding to R _{1 to} R ₄ in the general formula (I) is reacted with two carboxyl groups of an amino group protected amino acid to form two sets of amide bonds, After removing the protecting group of the obtained compound, this is reacted with gluconolactone to form a sugar amide moiety (R ₅ ).

For example, N-lauroyl-L-glutamic acid-α, β-bis-n-butyramide and 12-hydroxystearic acid are commercially available from Wako Pure Chemical.
Two or more kinds of non-conductive molecules may be used in combination.

  A non-volatile solvent having a low volatility having the above-mentioned vapor pressure is used. For example, hydrocarbon liquids such as isoparaffin and paraffin, silicone liquid such as dimethylpolysiloxane, fluorine compound liquid, vegetable oil, triethylene glycol, etc. And low vapor pressure solvents. Two or more non-conductive solvents that are compatible with each other may be used in combination.

The gel-like conductive medium can be prepared by mixing the network constituent molecules with a solvent and optionally a conductive powder.
The ratio of the network-constituting molecule to the solvent is usually 1/1 to 1/500, and preferably 1/10 to 1/100, in terms of weight ratio (network-constituting molecule / solvent).

The usage-amount of a conductive molecule, a conductive solvent, and conductive powder is not restrict | limited especially as long as a gel-like conductive medium has desired electroconductivity.
For example, when the conductivity of the gel-like conductive medium is achieved only by using a conductive solvent, the amount of the conductive solvent used is usually 50 to 99.9% by weight based on the total amount of the gel-like conductive medium, 80 to 99% by weight is particularly suitable.
Also, for example, when the conductivity of the gel-like conductive medium is achieved only by using the conductive powder, the amount of the conductive powder used is usually 0.01 to 50 with respect to the total amount of the gel-like conductive medium. % By weight, in particular 0.1 to 30% by weight is preferred.

  The amount of the gel-like conductive medium used in the charging device is not particularly limited as long as the object of the present invention can be achieved. For example, when a cylindrical charged body having an axial length of 250 mm and a diameter of 30 mm is used, 1 to 50 g, particularly 5 to 30 g is preferred.

  The electrode 2b may be made of any material as long as it is electrically connected to a power source (not shown) and can apply a charging voltage to the gel-like conductive medium. For example, the electrode 2b is made of a conductive material such as a metal such as aluminum or a conductive polyurethane. Examples thereof include resins.

The gap (y ₁ ; see FIG. 1) between the electrode 2b and the member to be charged 1 is not particularly limited as long as it can hold the gel-like conductive medium and does not discharge, and the flow of the gel-like conductive medium Although it depends on the properties, 0 to 20 mm, usually 0.05 to 10 mm is preferable.

  The charging voltage applied to the gel-like conductive medium 2a by the electrode 2b is not particularly limited. For example, −800 to −300 V is preferable in terms of DC voltage, but it is not limited to this range. The charging voltage may be a charging bias in which an AC voltage is superimposed on a DC voltage. In this case, the AC peak voltage is preferably 50 to 2000 V, the frequency is 500 to 2000 Hz, and the DC voltage is preferably −800 to −300 V. In the present invention, when a voltage is applied to the gel-like conductive medium by the electrode, the applied voltage is applied as it is to the surface of the member to be charged in the contact area between the gel-like conductive medium and the member to be charged. The surface is uniformly charged to the voltage potential. Such charging can be continued by continuously applying a voltage to the gel-like conductive medium even when the surface of the object to be charged moves continuously.

  The exposure device 3 forms an electrostatic latent image corresponding to the print data on the surface of the charged object 1 uniformly charged by the charging device. For example, a laser exposure device incorporating a laser diode, a polygon mirror, and an fθ optical element can be used.

  The developing device 4 supplies charged toner to the electrostatic latent image formed on the surface of the member to be charged. When the charged toner is supplied, the toner is attracted to the member to be charged by electrostatic force, the electrostatic latent image is visualized, and a toner image is formed. The toner stored in the developing device may be either a one-component toner or a two-component toner.

  The transfer device 5 transfers the toner image formed on the surface of the charged body to a transfer body 6 such as paper.

  The image forming apparatus may be provided with a cleaning member (not shown) for cleaning the surface of the charged body upstream of the gel-like conductive medium and downstream of the transfer apparatus in the moving direction of the charged body. Good (the same applies to other embodiments). By providing the cleaning member, the gel-like conductive medium is hardly contaminated with residual toner and the like, and the conductive performance of the gel is stabilized for a longer period.

(Second Embodiment)
In the first embodiment, the gel-like conductive medium 2a is held by the electrode 2b, but if the gap between the electrode and the object to be charged is too large and the electrode cannot hold the gel-like conductive medium, it is held. A new material may be provided. That is, in the second embodiment, as shown in FIG. 2A, the holding material 12c is not in contact with or in contact with the charged body 1 on the downstream side of the electrode 12b in the moving direction of the surface of the charged body. The gel-like conductive medium 12a is held and held by the holding material 12c. At this time, the holding material 12c may be disposed at any position as long as the gel-like conductive medium 12a can be held and retained while securing the electrical contact between the gel-like conductive medium 12a and the electrode 12b. Is fixed in contact with the electrode 12b. FIG. 2B is a schematic sketch of the electrode, the gel-like conductive medium, the holding material, and the member to be charged when the image forming apparatus of FIG. 2A is viewed from the x direction.

The gel-like conductive medium 12a and the electrode 12b have the gel-like conductivity shown in FIG. 1A except that the gap between the electrode and the member to be charged is too large and the gel-like conductive medium is held by the holding material. The same as the medium 2a and the electrode 2b. In FIG. 2A, the gel conductive medium may be placed on the surface of the member to be charged so as to be in contact with the electrode and the holding material.
The gap (y ₂ ; see FIG. 2) between the electrode 12b and the member to be charged 1 is not particularly limited as long as electrical contact between the electrode and the gel-like conductive medium can be ensured, and depends on the amount of the gel-like conductive medium. However, usually 0.05 to 20 mm, particularly 0.1 to 10 mm is preferable.

  The constituent material of the holding member 12c is not particularly limited as long as the gel-like conductive medium can be held and held, and may be any material from conductive to non-conductive. Examples thereof include metals such as aluminum, conductive resins such as conductive polyurethane, and insulating rubbers such as urethane rubber.

The gap (z ₁ ; see FIG. 2) between the holding member 12c and the member 1 to be charged is not particularly limited as long as the gel-like conductive medium can be held and held, and depends on the fluidity of the gel-like conductive medium. Usually, a range of 0 to 20 mm, particularly 0.05 to 10 mm is preferable. From the viewpoint of the action of cleaning the surface of the member to be charged, the holding material is preferably disposed in contact with the member to be charged. At this time, it is not necessary to separately provide a cleaning member, so that the apparatus can be simplified. On the other hand, from the viewpoint of reducing wear of the member to be charged, it is preferable that the holding material is disposed in non-contact with the member to be charged.

  2A and 2B is the same as that shown in FIGS. 1A and 1B except that the charging device is the charging device 12 having the above-described configuration. Since the same reference numerals as those in FIGS. 1A and 1B in FIGS. 2A and 2B are the same, the description thereof is omitted.

(Third embodiment)
In the second embodiment, when the holding material has conductivity, the holding material may be provided between the electrode and the gel-like conductive medium. That is, in the third embodiment, as shown in FIG. 3A, the holding material 22c is upstream of the electrode 22b in the moving direction of the surface of the charged body, and is downstream of the gel-like conductive medium 22a. The gel-like conductive medium 22a is held and held by the holding material 22c in a non-contact state or in contact with the member 1 to be charged. At this time, the holding member 22c is electrically connected to the gel-like conductive medium 22a and the electrode 22b and is in a conductive state. FIG. 3B is a schematic sketch of the electrode, the gel-like conductive medium, the holding material, and the member to be charged when the image forming apparatus of FIG. 3A is viewed from the x direction.

The gel-like conductive medium 22a and the electrode 22b have the gel-like conductivity shown in FIG. 1A except that the holding material 22c is arranged between them and the gel-like conductive medium is held by the holding material 22c. The same as the medium 2a and the electrode 2b. Note that in FIG. 3A, the gel-like conductive medium may be placed on the surface of the member to be charged so as to be in contact with the holding material.
The gap (y ₃ ; see FIG. 3) between the electrode 22b and the member 1 to be charged is not particularly limited as long as electrical contact between the electrode and the holding material can be secured, and is usually 0.05 to 20 mm, particularly 0.1 to 0.1 mm. 10 mm is preferred.

  The constituent material of the holding member 22c is not particularly limited as long as it can hold the gel-like conductive medium and has conductivity, and examples thereof include metals such as aluminum and conductive resins such as conductive polyurethane.

The gap (z ₂ ; see FIG. 3) between the holding material 22c and the member 1 to be charged is not particularly limited as long as the gel-like conductive medium can be held and held, and depends on the fluidity of the gel-like conductive medium. Usually, a range similar to the gap (z ₁ ) between the holding material 12c and the member 1 to be charged in FIG.

  3A and 3B is the same as that shown in FIGS. 1A and 1B except that the charging device is the charging device 22 having the above-described configuration. The same reference numerals as those in FIGS. 1A and 1B in FIGS. 3A and 3B are the same as those in FIGS.

(Fourth embodiment)
In the first embodiment, a shaft-shaped holding material may be newly provided to rotate and hold the gel-like conductive medium. That is, in the fourth embodiment, as shown in FIG. 4A, the holding material 32c is disposed so as to penetrate the gel-like conductive medium 32a upstream from the electrode 32b in the moving direction of the surface of the charged body. As the holding material 32c rotates, the gel-like conductive medium 32a is rotated and held around the holding material 32c. As a result, the flow (replacement) of the gel-like conductive medium existing in the contact area with the member to be charged 1 is promoted, and the entire gel-like conductive medium can be used more effectively, so that more stable charging can be achieved efficiently. . 4B is a schematic sketch of the electrode, the gel-like conductive medium, the holding material, and the member to be charged when the image forming apparatus of FIG. 4A is viewed from the x direction.

The gel-like conductive medium 32a and the electrode 32b are different from those shown in FIG. 1A except that the gap between the electrode and the member to be charged is set within a range in which electrical contact between the electrode and the gel-like conductive medium can be secured. This is the same as the gel-like conductive medium 2a and the electrode 2b. In FIG. 4A, the gel-like conductive medium may be placed on the surface of the member to be charged so as to be in contact with the electrode while penetrating the holding material.
The gap (y ₄ ; see FIG. 4) between the electrode 32b and the member to be charged 1 depends on the amount of the gel-like conductive medium, but is usually 0 to 20 mm, particularly preferably 0.05 to 10 mm.

  The holding member 32c may rotate at any direction and circumferential speed as long as the gel-like conductive medium 32a can be rotated and held. The holding member 32c is preferably adjusted so as to rotate in the same direction and at the same peripheral speed as the member 1 to be charged in the region between the member 1 and the member 1 to be charged.

  From the viewpoint of more effectively achieving the holding of the gel-like conductive medium, the holding member 32c preferably has irregularities (not shown) such as protrusions and depressions on the surface, or it is also preferable to adjust the surface roughness.

  The constituent material of the holding member 32c is not particularly limited as long as the gel-like conductive medium can be rotated and held, and may be any material from conductive to non-conductive. For example, the constituent material similar to the holding material 12c is mentioned. Further, when the holding member 32c has conductivity, a charging voltage may be applied to the electrode 32b instead of or both. In the former case, the holding material 32c is regarded as the electrode 32c, the electrode 32b is regarded as the retaining material 32b, and the material of 32b may be insulative.

  The gap between the holding member 32c and the member to be charged 1 is not particularly limited as long as the gel-like conductive medium can be rotated and held.

  The image forming apparatus shown in FIGS. 4A and 4B is the same as that shown in FIGS. 1A and 1B except that the charging device is the charging device 32 having the above-described configuration. Since the same reference numerals as those in FIGS. 1A and 1B in FIGS. 4A and 4B are the same, the description thereof is omitted.

(Fifth embodiment)
In the fifth embodiment, as shown in FIG. 5A, the charging device 42 has a shaft coat type configuration in which a gel-like conductive medium 42a is coated around a shaft electrode 42b. 42 is arranged so that the gel-like conductive medium 42 a is in contact with the member 1 to be charged. At this time, the charging device 42 may rotate at any direction and circumferential speed as long as the charging of the surface of the member to be charged can be achieved, or may be fixed. Usually, the charging device 42 is adjusted to rotate in the same direction and at the same peripheral speed in the contact area with the member 1 to be charged. FIG. 5B is a schematic sketch of the electrode, the gel-like conductive medium, and the member to be charged when the image forming apparatus of FIG. 5A is viewed from the x direction.

The gap (y ₅ ; see FIG. 5) between the electrode 42b and the member 1 to be charged is determined depending on the coating thickness of the gel-like conductive medium, and is usually 0.001 to 10 mm, particularly preferably 0.1 to 5 mm. It is.

  The gel-like conductive medium 42a and the electrode 42b are the same as the gel-like conductive medium 2a and the electrode 2b in FIG. 1A, respectively, except that they have the configuration and shape as described above. In FIG. 5A, the gel-like conductive medium may be disposed so as to contact the surface of the member to be charged while coating the shaft-like electrode.

5A and 5B, the holding member 42c is provided, but it may not be provided. The gap (Z ₃ ; see FIG. 5) between the holding member 42c and the member 1 to be charged is usually 0 to 20 mm, particularly preferably 0.05 to 10 mm.

  The image forming apparatus shown in FIGS. 5A and 5B is the same as that shown in FIGS. 1A and 1B except that the charging device is the charging device 42 having the above-described configuration. Since the same reference numerals as those in FIGS. 1A and 1B in FIGS. 5A and 5B are the same, the description thereof will be omitted.

(Sixth embodiment)
In the sixth embodiment, as shown in FIG. 6A, the charging device 52 is a flat coat type in which one end face parallel to the axis of the flat electrode 52b is coated with a gel conductive medium 52a. The charging device 52 is configured such that the gel-like conductive medium 52a is in contact with the member 1 to be charged. FIG. 6B is a schematic sketch of the electrode, the gel-like conductive medium, and the member to be charged when the image forming apparatus of FIG. 6A is viewed from the x direction.

The gap (y ₆ ; see FIG. 6) between the electrode 52b and the member to be charged 1 is determined depending on the coating thickness of the gel-like conductive medium, and is usually 0 to 20 mm, particularly preferably 0.05 to 10 mm. .

  The gel-like conductive medium 52a and the electrode 52b are the same as the gel-like conductive medium 2a and the electrode 2b in FIG. 1A, respectively, except that they have the above-described configuration and shape. In FIG. 6A, the gel-like conductive medium may be disposed so as to be in contact with the surface of the member to be charged while coating one end face of the flat electrode.

  The image forming apparatus shown in FIGS. 6A and 6B is the same as that shown in FIGS. 1A and 1B except that the charging device is the charging device 52 having the above-described configuration. Since the same reference numerals as those in FIGS. 1A and 1B in FIGS. 6A and 6B are the same, the description thereof is omitted.

  All of the image forming apparatuses shown in the above embodiments are for monochrome, each having only one member to be charged and one developing device, but may be applied to full color.

  As a full-color image forming apparatus, for example, a so-called four-cycle type in which four developing devices of each color are provided around one charged body, and four charged bodies corresponding to each color are intermediate transfer. There is a so-called tandem type that is provided along the moving direction of the body (corresponding to the transfer body). In any of these types of full-color image forming apparatuses, it is sufficient if the charging device of the present invention is provided as a charger for charging the surface of the object to be charged. Usually, one book is provided for one object to be charged. The inventive charging device is used.

<Preparation of gel-like conductive medium>
A gel-like conductive medium was prepared by the following method.
(Gel A)
10 parts by weight of conductive zinc oxide (Pazette CK: manufactured by Hakusui Tech Co., Ltd.) was mixed with 100 parts by weight of silicone gel (KSG-16: manufactured by Shin-Etsu Silicone) to obtain Gel A.

(Gel B)
First, the organic compound of the general formula (II) was synthesized according to the following reaction scheme.

Synthesis of compound (A);
In a 200 ml eggplant-shaped flask, 4.3 g (17.8 mmol) of 3-lauryloxypropyl-1-amine (manufactured by Acros Co., Ltd., Mw: 243.43), t-butyloxycarbonyl-L-glutamic acid (Boc-L- Glu-OH, manufactured by Kokusan Chemical Co., Ltd., Mw: 247.11) 2.0 g (8.1 mmol), and triethylamine (produced by Kishida Chemical Co., Ltd., Mw: 101.6) 1.8 g (17.8 mmol) Was dissolved in 150 ml of dry tetrahydrofuran (THF). While stirring with ice cooling, 2.9 g (17.8 mmol) of diethyl cyanophosphate (DEPC, manufactured by Aldrich, Mw: 163.11) was added. After stirring at room temperature for 2 days, THF was distilled off under reduced pressure, chloroform was added to the oily residue, and a 5% aqueous sodium carbonate solution was further added, followed by shaking twice. The chloroform phase was separated and excess water was removed using anhydrous sodium sulfate. The solvent chloroform was distilled off under reduced pressure, and acetone was added to the residue for recrystallization to obtain a colorless powder (compound (A), yield = 3.71 g, yield = 65%).

Synthesis of compound (B);
The above compound (A) (Mw: 698.07) 3.7 g (5.3 mmol) was dissolved in 100 ml of dry dichloromethane and stirred with trifluoroacetic acid (TFA, manufactured by Kishida Chemical Co., Ltd., Mw: 114. 02) was added so that it might become 20 weight% of the whole, and it stirred at room temperature for 3 hours. Thereafter, trifluoroacetic acid and dichloromethane were distilled off under reduced pressure, and acetone was added to dissolve the oily residue. Under ice-cooling, 1 ml of 35 wt% aqueous hydrochloric acid was added, and the resulting precipitate was separated by filtration. This was recrystallized from ethyl acetate to obtain a colorless powder (compound (B), yield = 2.56 g, yield = 76%).

Synthesis of organic compound (II);
The above compound (B) (Mw: 634.42) 2.56 g (4.0 mmol) and triethylamine (Kishida Chemical Co., Ltd. Mw: 101.6) 0.61 g (6.0 mmol) were dissolved in chloroform, and further ionized. Added exchange water and shaken. The chloroform phase was separated and dried using anhydrous sodium sulfate. Chloroform was distilled off under reduced pressure, ethanol was added to the residue and dissolved, and 0.56 g (3.1 mmol) of glucono-δ-lactone (Kishida Chemical Co., Ltd. Mw: 178.14) was added, followed by stirring under reflux. . Two days later, analysis by thin layer chromatography (TLC-FID, CHCl ₃ : CH ₃ OH = 10: 1) showed that the peak of the raw material (compound (B)) remained. 5 g was added and reflux stirring was performed for 2 days. After the reflux was stopped, the ice-cooled precipitate was filtered off and recrystallized with ethanol to obtain a colorless powder of organic compound (II) (yield = 1.4 g, yield = 45%).

  Next, the organic compound (II) was added to 1-ethyl-3-methylimidazolium bromide (manufactured by Acros) to a concentration of 10 mM, dispersed by heating, and allowed to stand for 6 hours to obtain Gel B.

(Gel C)
N-lauroyl-L-glutamic acid-α, β-bis-n-butyramide (white oil (Molesco White P40 manufactured by Matsumura Oil Research Institute) added with 2% by weight of metal soap (Molesco Amber SB50N: manufactured by Moresco) Wako) was mixed at 3% by weight, heated and stirred for 10 minutes, and then allowed to stand at room temperature to obtain Gel C.

(Gel D)
24 g of PVA (Kuraray K polymer KM-618) powder and 276 g of pure water were stirred with a stirrer for 1 hour while being heated to 70 ° C. 1 g of anhydrous sodium tetraborate (manufactured by Wako) and 166 g of pure water were stirred with a stirrer for 1 hour while being heated to 70 ° C. An anhydrous sodium tetraborate aqueous solution was mixed with an aqueous PVA solution (an anhydrous sodium tetraborate aqueous solution) at 3% wt and stirred.

(Physical properties of the gel)
Gel A: Vapor pressure 10Pa, volume resistivity 1 × 10 ⁶ Ωcm
Gel B: vapor pressure 0.01 Pa, volume resistivity 2 × 10 ² Ωcm
Gel C: vapor pressure 0.8 Pa, volume resistivity 1 × 10 ⁴ Ωcm
Gel D: vapor pressure 3168 Pa, volume resistivity 1 × 10 ³ Ωcm

<Evaluation>
The obtained gel was mounted on the image forming apparatus of various embodiments, and the following items were evaluated. The surface to be charged was subjected to the following treatment. The dimensions of the member to be charged were an axial length of 250 mm and a diameter of 30 mm.
(Surface treatment method)
A solution in which 70 parts of PTFE is added to 100 parts of polycarbonate and dissolved in a solvent in which THF / toluene is mixed in 9/1 is applied to the surface of the object to be charged in a thickness of 7 μm and dried in an oven at 120 ° C. for 40 minutes. Thus, a surface layer was formed.

(Average charge during initial and endurance)
Regarding the average withstand voltage, the surface potential of the object to be charged was measured in an environment of 25 ° C. and 50% RH. As for the surface potential, the surface potential V0 of the object to be charged when DC-500V is applied to the charging electrode to charge the object to be charged is the surface potential meter MODEL344 manufactured by Trek Japan Co., Ltd., probe 6000B-16. It measured using. The measurement results were evaluated according to the following criteria, and “◎” and “判断” were judged to be practically acceptable levels.
◎; | V0 |> 470V
○: 430V ≦ | V0 | ≦ 470V
×; | V0 | <430V

(Electric charge unevenness in initial and durability)
For evaluation of charging unevenness, half-image formation was performed in an environment of 25 ° C. and 50% RH, and the roughness of the image was judged by a sensory test. A halftone pattern of 2 dots × 2 dots was adopted as an image pattern in image formation. For the image quality evaluation, the visual observation results were evaluated according to the following criteria.
◎: Uneven image is not recognized;
○: Image unevenness is recognized, but there is no practical problem;
X: Image unevenness is remarkably problematic in practical use.

  The results are shown in the table below. In addition, a figure number indicating the configuration of the used image forming apparatus, apparatus conditions, and the like are collectively shown. Durability means after printing 5000 sheets of A4 images in an environment of 25 ° C. and 50% RH.

(A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction. (A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction. (A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction. (A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction. (A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction. (A) is a schematic block diagram of an example of an image forming apparatus provided with the charging device of the present invention, and (B) is a schematic sketch when the image forming apparatus of (A) is viewed from the x direction.

Explanation of symbols

1: Charged body (photoconductor), 2: 12: 22: 32: 42: 52: 62: charging device, 2a: 12a: 22a: 32a: 42a: 52a: gel-like conductive medium, 2b: 12b: 22b : 32b: 42b: 52b: electrode, 3: exposure device, 4: developing device, 5: transfer device, 6: transfer target, 12c: 22c: 32c: holding material.

Claims (5)

  A charging device for charging a charged object by applying a charging voltage to a gel-like conductive medium placed in contact with the surface of the charged object whose surface moves. A charging device characterized by low volatility.   The charging device according to claim 1, wherein the gel-like conductive medium is composed of a solvent having a vapor pressure lower than that of water.   The charging device according to claim 1, wherein the gel-like conductive medium is a gel containing an ionic liquid.   The charging device further includes a holding material arranged in a non-contact state or a contact state with respect to the charged body downstream of the gel-like conductive medium in the moving direction of the surface of the charged body, and the holding material is a gel-like conductive material. The charging device according to claim 1, wherein the conductive medium is held and held. An object to be charged whose surface moves, the charging device according to claim 1 for uniformly charging the object to be charged, an exposure device for forming an electrostatic latent image on the object to be charged, an electrostatic latent An image forming apparatus comprising: a developing device that develops an image to form a toner image; and a transfer device that transfers the toner image to a transfer target.

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