JP6965528B2 - Image forming device and removal method - Google Patents

Description

The present invention relates to an image forming apparatus and a removing method .

The following Patent Document 1 describes, in an image forming apparatus using a photoconductor drum provided with a low-wear surface layer, a developing roll at a portion facing the photoconductor drum and a developing roll when developing an electrostatic latent image of the photoconductor drum. The configuration is disclosed in which the moving direction of the photoconductor drum is opposite to the moving direction of the photoconductor drum. Further, in this image forming apparatus, a cleaning blade that comes into contact with the surface of the photoconductor drum after the transfer of the toner image on the surface of the photoconductor drum is provided.

Japanese Unexamined Patent Publication No. 2005-10363

The present invention has a single layer as compared with a configuration in which the developer holder is continuously moved in the same direction as the movement direction of the latent image holder at the facing portion between the latent image holder and the developer holder after the transfer of the toner image. It is an object of the present invention to obtain an image forming apparatus and a removing method in which deposits are suppressed from accumulating on the surface of a latent image holder provided with a type photosensitive layer.

The image forming apparatus according to the first aspect is provided with a single-layer type photosensitive layer on a conductive substrate, and is arranged to face a rotating latent image holder and the latent image holder, and the latent image holder is arranged. After the transfer of the developer holder that develops the electrostatic latent image formed on the latent image holder as a toner image while moving with respect to the latent image holder and the toner image formed on the surface of the latent image holder, the latent image is said to be latent. It has a moving mechanism that moves the developer holding body in a direction opposite to the moving direction of the latent image holding body at a portion facing the image holding body and the developing agent holding body.

The image forming apparatus according to the second aspect has an elastic deformation rate of 43.5% or less of the latent image holder in the image forming apparatus according to the first aspect.

The image forming apparatus according to the third aspect is the latent image forming apparatus according to the first or second aspect when the developer holder is moved in a direction opposite to the moving direction of the latent image holder. The speed ratio of the developer holder to the image holder is 1.6 or more and 1.8 or less.

The image forming apparatus according to a fourth aspect is the image forming apparatus according to any one aspect of the first aspect to the third aspect, to transfer the toner image on the surface of the latent image holding member to a transfer member A cleaning member that contacts the surface of the latent image holder and cleans the surface is not provided on the downstream side of the transfer portion and upstream of the exposure position where the electrostatic latent image is formed on the latent image holder. ..
The removal method according to the fifth aspect is a removal method for removing deposits remaining on the surface of the latent image holder using the image forming apparatus according to any one of the first to third aspects. After the toner image formed on the surface of the latent image holder is transferred by the moving mechanism, the developer holding the developer is held at the facing portion between the latent image holder and the developer holding body. By moving the body in the direction opposite to the moving direction, the deposits remaining on the surface of the latent image holder are scraped off by the developer on the developer holder.

According to the image forming apparatus according to the first aspect , after the toner image is transferred, the developer holder is moved in the same direction as the movement direction of the latent image holder at the opposite portion between the latent image holder and the developer holder. As compared with the subsequent configuration, the accumulation of deposits on the surface of the latent image holder provided with the single-layer type photosensitive layer is suppressed.

According to the image forming apparatus according to the second aspect , the elastic deformation rate of the latent image holder is accumulated on the surface of the latent image holder by the developer holder as compared with the case where the elastic deformation rate is larger than 43.5%. The kimono is easily scraped off.

According to the image forming apparatus according to the third aspect , the speed ratio of the developer holder to the latent image holder when the developer holder is moved in the direction opposite to the moving direction of the latent image holder is 1.6. Compared with the case where the size is smaller, the effect that the deposits accumulated on the surface of the latent image holder are easily scraped off is improved. Further, when the developer holder is moved in the direction opposite to the moving direction of the latent image holder, the speed ratio of the developer holder to the latent image holder is larger than 1.8, and the latent image is retained. The decrease in sensitivity due to wear of the photosensitive layer of the body is suppressed.

According to the image forming apparatus according to the fourth aspect , the number of parts is reduced while suppressing the accumulation of deposits, as compared with the configuration in which the cleaning member is provided to contact the surface of the latent image holder to clean the surface. be able to.
According to the removal method according to the fifth aspect, after the toner image is transferred, the developer holder is continuously moved in the same direction as the movement direction of the latent image holder at the opposite portion between the latent image holder and the developer holder. Compared with the configuration, the accumulation of deposits on the surface of the latent image holder provided with the single-layer type photosensitive layer is suppressed.

It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 1st Embodiment, and is the figure which shows the state which develops the electrostatic latent image of the surface of a photoconductor by a developing apparatus. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 1st Embodiment, and is the figure which shows the state which cleans the surface of a photoconductor by a developing roll after transfer | transfer of a toner image. It is a block diagram which shows the conductive substrate on the surface side of the photoconductor and the single-layer type photosensitive layer. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 2nd Embodiment, and is the figure which shows the state which develops the electrostatic latent image of the surface of the photoconductor of each color by a developing apparatus. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on 1st Embodiment, and is the figure which shows the state which cleans the surface of the photoconductor of each color with a developing roll after transfer | transfer of a toner image. It is a figure which shows the experimental result of the image quality durability, and the color point evaluation when the elastic deformation rate of a photoconductor, the rotation direction of a developing roll, and the peripheral speed ratio of a developing roll with respect to a photoconductor are changed.

Hereinafter, embodiments of the image forming apparatus of the present invention will be described with reference to the drawings.

[First Embodiment]
(overall structure)
FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the first embodiment. As shown in FIG. 1, the image forming apparatus 10 according to the first embodiment includes a process cartridge 12 including an electrophotographic photosensitive member (hereinafter, abbreviated as “photoreceptor”) 14 as an example of a latent image holder. An exposure device 16 that forms an electrostatic latent image on the surface of the photoconductor 14, and a transfer roll that transfers a toner image formed on the surface of the photoconductor 14 to a recording medium P (for example, paper) as an example of a transfer target. It has 18. Here, the facing portion between the transfer roll 18 and the photoconductor 14 is an example of the transfer portion. In the image forming apparatus 10, the exposure apparatus 16 is arranged at a position where the photoconductor 14 can be exposed through the opening 13A of the housing 13 of the process cartridge 12.

The process cartridge 12 develops a photoconductor 14 that rotates in the direction of arrow A, a charging device 22 that charges the surface of the photoconductor 14, and an electrostatic latent image formed on the surface of the photoconductor 14 in the housing 13. It is provided with a developing device 24 for forming a toner image. In the image forming apparatus 10, the transfer roll 18 is arranged outside the housing 13 (lower side of the housing 13 in the present embodiment) and downstream of the developing apparatus 24 in the rotation direction of the photoconductor 14. Further, the process cartridge 12 is detachably provided with respect to the image forming apparatus 10. The process cartridge 12 is on the downstream side of the transfer portion of the toner image in the rotation direction of the photoconductor 14 (downstream side of the transfer roll 18) and upstream of the exposure position where an electrostatic latent image is formed on the surface of the photoconductor 14. A cleaning device such as a cleaning blade that comes into contact with the surface of the photoconductor 14 is not provided on the side. In other words, a cleaning device such as a cleaning blade that comes into contact with the surface of the photoconductor 14 after the toner image on the surface of the photoconductor 14 has been transferred and before the electrostatic latent image is formed on the surface of the photoconductor 14. Is not provided.

The image forming apparatus 10 is provided with an endless transport belt 30 that transports the recording medium P to the transfer position of the toner image. The transport belt 30 is stretched on a plurality of (four in this embodiment) rolls 32, and one of the plurality of rolls 32 is a drive roll for driving the transport belt 30. The transport belt 30 transports the recording medium P in the same direction (arrow C direction) as the moving direction of the photoconductor 14 at the portion facing the photoconductor 14. By supplying the recording medium P onto the transfer belt 30, the recording medium P is conveyed between the photoconductor 14 and the transfer roll 18 by the movement of the transfer belt 30.

Although the image forming apparatus 10 includes a transport belt 30 for transporting the recording medium P, the image forming apparatus 10 includes an intermediate transfer belt instead of the transport belt 30, and transfers the toner image on the surface of the photoconductor 14 to the intermediate transfer belt. It may be configured to be used. In this configuration, the image forming apparatus is a secondary transfer apparatus that transfers the toner image on the intermediate transfer belt to the recording medium on the downstream side of the transfer position of the toner image on the surface of the photoconductor 14 in the moving direction of the intermediate transfer belt. I have.

As shown in FIG. 3, the photosensitive member 14 includes, for example, a conductive substrate 40, and a single-layer type photosensitive layer 42 is directly provided on the conductive substrate 40. The single-layer photosensitive layer 42 contains at least a charge generating material and a charge transporting material, and may contain other components if necessary. The photoconductor 14 may be provided with another layer, if necessary. Examples of other layers include an undercoat layer provided between the conductive substrate 40 and the single-layer type photosensitive layer 42, a protective layer provided on the single-layer type photosensitive layer 42, and the like. The configuration of each member of the photoconductor 14 will be described later.

As shown in FIG. 1, as the charging device 22, for example, a conductive or semi-conductive charging roller is used. Further, as the charging device 22, in addition to the charging roller described above, a contact type charging device using a charging brush, a charging film, a charging rubber blade, a charging tube, or the like is used. Further, a non-contact type roller charger, a scorotron charger using corona discharge, a corotron charger, or the like, which is known per se, is also used.

Examples of the exposure apparatus 16 include an optical system device that exposes light such as a semiconductor laser beam, an LED light, and a liquid crystal shutter light on the surface of the photoconductor 14 in a predetermined image pattern. The wavelength of the light source is within the spectral sensitivity region of the photoconductor 14.

Examples of the developing device 24 include a developing device that develops by bringing a developing agent into contact with the surface of the photoconductor 14. The developing device 24 has a function of adhering a developing agent to the photoconductor 14. For example, the developing apparatus 24 includes a developing roll 26 as an example of a developer holder that rotates by holding a one-component developer or a two-component developer on the surface. In the developing apparatus 24, the developing roll 26 is in contact with the photoconductor 14, or the developing roll 26 is arranged close to the photoconductor 14, and the developing agent on the developing roll 6 is in contact with the photoconductor 14. There is.

A motor 28 as an example of a moving mechanism for rotating the developing roll 26 is connected to the developing roll 26. As shown in FIG. 1, when developing an electrostatic latent image on the surface of the photoconductor 14, the developing roll 26 is directed by the motor 28 in the same direction as the photoconductor 14 at the opposite portion between the photoconductor 14 and the developing roll 26 (arrows). It is configured to be rotated in the B direction). In the present embodiment, when the electrostatic latent image of the photoconductor 14 is developed, the peripheral speed of the developing roll 26 is rotationally driven so as to be constant with the peripheral speed of the photoconductor 14, but the present invention is not limited to this. No.

Further, a power supply (not shown) is connected to the developing roll 26 so that a developing bias is applied to the developing roll 26 when developing an electrostatic latent image on the surface of the photoconductor 14. Further, although not shown, the photoconductor 14 is grounded. In the image forming apparatus 10 of the present embodiment, for example, the surface of the photoconductor 14 is negatively charged by the charging device 22, and the toner having a negative charge is transferred to the exposed portion of the electrostatic latent image on the surface of the photoconductor 14. As a result, the electrostatic latent image is visualized and a toner image is formed.

Further, as shown in FIG. 2, in the developing roll 26, after the toner image on the surface of the photoconductor 14 is transferred to the recording medium P, the developing roll 26 is placed at the opposite portion between the photoconductor 14 and the developing roll 26. It is configured to be rotated in the direction opposite to that of the photoconductor 14 (direction of arrow D). In the present embodiment, the development roll 26 is rotated in the direction opposite to that during development by rotating the motor 28 in the reverse direction with respect to the rotation direction of the motor 28 during development. After the toner image on the surface of the photoconductor 14 is transferred to the recording medium P, the developing roll 26 cleans the surface of the photoconductor 14 by rotating in the direction opposite to the photoconductor 14 at the portion facing the photoconductor 14. It is designed to do (clean). When cleaning the surface of the photoconductor 14 with the developing roll 26 after transferring the toner image on the surface of the photoconductor 14, no bias is applied to the developing roll 26 from a power source (not shown). The timing and time for cleaning the photoconductor 14 with the developing roll 26 are set such that the developing roll 26 and the photoconductor 14 are idled for 10 seconds every time 500 sheets are printed.

When the developing roll 26 shown in FIG. 2 is rotated in the reverse direction, the speed ratio (peripheral speed ratio) of the developing roll 26 to the photoconductor 14 is preferably 1.6 or more and 1.8 or less, and 1.6 or more and 1.7. The following is more preferable.

The developer used in the developing apparatus 24 may be a one-component developer using only toner or a two-component developer containing toner and a carrier. Further, the developer may be magnetic or non-magnetic. In the present embodiment, a two-component developer containing toner and a carrier is used, and the two-component developer adhering to the surface of the developing roll 26 is a photoconductor during development and cleaning of the photoconductor 14 by the developing roll 26. It comes into contact with 14 to form a sliding contact portion.

In the present embodiment, as the photoconductor 14, a single-layer type photosensitive layer 42 is directly provided on the conductive substrate 40, and the deposits remaining on the single-layer type photosensitive layer 42 are the developing roll 26 or the developing roll. It is designed to be scraped off by the above developer (for example, a two-component developer).

The elastic deformation rate of the photoconductor 14 is preferably 43.5% or less, more preferably 41.5% or less. Here, the elastic deformation rate of the photoconductor 14 is calculated as follows. The photoconductor to be measured is set in a measuring device (PICODENTOR HM500) manufactured by Fisher Instruments in an environment of a temperature of 23 ° C. and 30% RH, and a Vickers indenter is applied to the surface of the photoconductor (photosensitive layer). The load is continuously increased using the test load when pushed in by 0.5 μm, divided by the surface area of the indenter, and the elastic deformation rate of the photosensitive layer is measured. The measurement points are 5 points at a position of 40 mm, a position of 80 mm, and a central portion from both ends in the axial direction of the photoconductor, and the average value thereof is calculated as the “elastic deformation rate of the photosensitive layer”. The axial length of the photoconductor 14 is, for example, 240 mm or more.

The transfer roll 18 is in contact with the photoconductor 14 via the transport belt 30, and transports the recording medium P supplied on the transport belt 30. A voltage (bias) opposite to the charging polarity of the toner is applied to the transfer roll 18 from a power source (not shown) so that the toner image on the surface of the photoconductor 14 is electrostatically transferred to the recording medium P. It has become.

Here, each layer of the photoconductor 14 will be described.
(Conductive substrate)
Examples of the conductive substrate include metal plates containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.), metal drums, metal belts, and the like. Can be mentioned. The conductive substrate includes, for example, a paper, a resin film, a belt or the like coated, vapor-deposited or laminated with a conductive compound (for example, a conductive polymer, indium oxide, etc.), a metal (for example, aluminum, palladium, gold, etc.) or an alloy. Can also be mentioned. Here, "conductive" means that the volume resistivity is less than ^{10 13 Ωcm.}

(Single layer type photosensitive layer)
The single-layer type photosensitive layer includes, for example, a binder resin, a charge generating material, and a hole transporting material and an electron transporting material as charge transporting materials. The monolayer type photosensitive layer may contain other additives if necessary.

<Bundling resin>
The binder resin is not particularly limited, but for example, polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene. Copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin , Poly-N-vinylcarbazole, polysilane and the like. These binder resins may be used alone or in admixture of two or more.

Among these binder resins, polycarbonate resin and polyarylate resin are preferable from the viewpoint of mechanical strength of the photosensitive layer and the like.
Further, from the viewpoint of film forming property of the photosensitive layer, at least one of a polycarbonate resin having a viscosity average molecular weight of 30,000 or more and 80,000 or less and a polyarylate resin having a viscosity average molecular weight of 30,000 or more and 80,000 or less may be used.

The viscosity average molecular weight is a value measured by the following method. 1 g of the resin ^{is dissolved in 100 cm 3} of methylene chloride, and the specific viscosity ηsp is measured with an Ubbelohde viscometer in a measurement environment of 25 ° C. Then, the ultimate viscosity [η] (cm ³ / g) was obtained from the relational expression of ηsp / c = [η] + 0.45 [η] ² c (where c is the concentration (g / cm ^{3)), and H.I.} The viscosity average molecular weight Mv is obtained from the relational expression [η] = 1.23 × 10 ^-4 Mv ^{0.83 given by Schnell.}

The content of the binder resin with respect to the total solid content of the photosensitive layer is, for example, 35% by mass or more and 60% by mass or less, preferably 40% by mass or more and 55% by mass or less.

-Charge generating material-
The charge generating material is not particularly limited, but it is desirable to use at least one selected from, for example, a hydroxygallium phthalocyanine pigment and a chlorogallium phthalocyanine pigment. As these charge generating materials, they may be used alone or in combination of two or more. A hydroxygallium phthalocyanine pigment is preferable from the viewpoint of increasing the sensitivity of the photoconductor.
When the hydroxygallium phthalocyanine pigment and the chlorogallium phthalocyanine pigment are used in combination, the ratio of the hydroxygallium phthalocyanine pigment to the chlorogallium phthalocyanine pigment is a mass ratio. It is preferably 3: 7 (preferably 9: 1 to 6: 4).

The hydroxygallium phthalocyanine pigment is not particularly limited, but a V-type hydroxygallium phthalocyanine pigment is preferable.

The content of the charge generating material with respect to the total solid content of the single-layer type photosensitive layer is preferably 0.8% by mass or more and 5% by mass or less, and 0.8% by mass or more and 4% by mass, from the viewpoint of suppressing the generation of ghosts. The following is more preferable, and 0.8% by mass or more and 3% by mass or less is further preferable.
Another cause of ghosts (particularly positive ghosts) is that the electric charge generated in the process of exposing the surface of the photoconductor was accumulated in the single-layer type photosensitive layer, and the photoconductor was charged in the next image formation. The accumulated charge is released at that time, and the electric potential on the surface is lowered. That is, it is considered that the ghost (particularly the positive ghost) is generated by adding the potential difference between the image portion and the non-image portion generated in the formation of the previous image and the electric charge accumulated in the formation of the previous image. .. Therefore, while reducing the content of the charge generating material within the range that functions as a photoconductor and suppressing the amount of charge accumulated in the single-layer type photosensitive layer, the potential difference can be increased by using a proximity charging method charging means having a high charging ability. It is presumed that the decrease further suppresses the occurrence of ghosts.
When a plurality of types of charge generating materials are used, the content of the charge generating materials means the total content of all the charge generating materials used.

<Hole transport material>
The hole transport material is not particularly limited, but is, for example, an oxaziazole derivative such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole; 1,3,5-tri Pyrazoline derivatives such as phenyl-pyrazolin, 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline; triphenylamine, N, N'-bis (3, Aromatic tertiary amino compounds such as 4-dimethylphenyl) biphenyl-4-amine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline; N, N'-bis (3-methylphenyl)- Aromatic tertiary diamino compounds such as N, N'-diphenylbenzidine, 3- (4'-dimethylaminophenyl) -5,6-di- (4'-methoxyphenyl) -1,2,4-triazine, etc. 1,2,4-Triazine derivatives; Hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone; Kinazoline derivatives such as 2-phenyl-4-styryl-quinazoline; 6-Hydroxy-2,3-di ( Benzofuran derivatives such as p-methoxyphenyl) benzofuran; α-stilben derivatives such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline; enamine derivatives; carbazole derivatives such as N-ethylcarbazole; poly-N -Vinylcarbazole and derivatives thereof; and the like; a polymer having a group composed of the above-mentioned compound in the main chain or the side chain; and the like. These hole transporting materials may be used alone or in combination of two or more.

<Electronic transport material>
The electron transport material is not particularly limited, but for example, quinone compounds such as chloranyl and bromoanyl; tetracyanoquinodimethane compounds; 2,4,7-trinitro-9-fluorenone, 2,4,5,7. Fluolenone compounds such as −tetranitro-9-fluorenone, 9-dicyanomethylene-9-fluorenone-4-carboxylate octyl; 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3 Oxa such as 4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4-oxadiazole, 2,5-bis (4-diethylaminophenyl) 1,3,4-oxadiazole, etc. Diazole compounds; Xantone compounds; Thiophene compounds; Dinaftquinone compounds such as 3,3'-di-tert-pentyl-dinaftoquinone;3,3'-di-tert-butyl-5,5'-dimethyl Diphenoquinone compounds such as diphenoquinone, 3,3', 5,5'-tetra-tert-butyl-4,4'-diphenoquinone; a polymer having a group composed of the above compounds in the main chain or side chain. ; And so on. These electron transporting materials may be used alone or in combination of two or more.

(Action and effect)
Next, the operation and effect of the image forming apparatus 10 of the present embodiment will be described.

As shown in FIG. 1, in the image forming apparatus 10, when the photoconductor 14 rotates in the direction of arrow A, the photoconductor 14 is charged by the charging device 22, and the photoconductor 14 is irradiated with image light by the exposure device 16. An electrostatic latent image is formed on the surface of 14. Further, the electrostatic latent image on the surface of the photoconductor 14 is developed by the developing device 24 to form a toner image. At that time, the developing roll 26 in the developing apparatus 24 is rotated in the same direction as the photoconductor 14 (in the direction of arrow B) by the motor 28 at the portion facing the photoconductor 14, and is developed from a power source (not shown) on the developing roll 26. When the bias is applied, the toner is transferred to the exposed portion of the electrostatic latent image on the surface of the photoconductor 14, and the toner image is formed. After that, a voltage opposite to the charging polarity of the toner is applied to the transfer roll 18, so that the toner image on the surface of the photoconductor 14 is transferred to the recording medium P which is conveyed between the photoconductor 14 and the transfer roll 18. Transcribed. The toner image transferred to the recording medium P is conveyed to a fixing device (not shown) to fix the toner image on the recording medium P and form an image.

Further, as shown in FIG. 2, after the toner image on the surface of the photoconductor 14 is transferred, the motor 28 is rotated in the reverse direction so that the developing roll 26 and the photoconductor 14 face each other to the photoconductor 14. On the other hand, the developing roll 26 is rotated (idle) in the opposite direction (arrow D direction). In the present embodiment, the developing roll 26 is rotated in the reverse direction with respect to the photoconductor 14 in a state where the developing agent of the developing roll 26 (for example, a two-component developer) is in contact with the surface of the photoconductor 14.

The reverse rotation (idle rotation in the reverse direction) of the developing roll 26 may be performed every time the toner image on the surface of the photoconductor 14 is transferred to one recording medium P, or may be performed for each predetermined job. May be good. For example, the timing and time for cleaning the photoconductor 14 with the developing roll 26 are set so that the photoconductor 14 and the developing roll 26 are idled for 10 seconds every time 500 sheets are printed, for example. As a result, the deposits remaining on the surface of the photoconductor 14 after the transfer of the toner image are scraped off by the developing roll 26 or the developing agent (for example, the two-component developing agent) on the developing roll 26, and adheres or transfers to the developing roll 26. .. Therefore, the deposits remaining on the surface of the photoconductor 14 are removed from the surface of the photoconductor 14, and the single-layer type photosensitive layer 42 on the surface of the photoconductor 14 is refreshed. The residue adhering to or transferred to the developing roll 26 is mixed or discharged into, for example, a toner box (not shown) of the developing apparatus 24.

In the image forming apparatus 10, the single-layer type photosensitive layer is compared with a configuration in which the developing roll is continuously moved in the same direction as the moving direction of the photoconductor at the portion facing the photoconductor and the developing roll after the toner image is transferred. Accumulation of deposits on the surface of the photoconductor 14 provided with 42 is suppressed. As a result, image quality defects due to deposits accumulated on the surface of the photoconductor 14 are suppressed.

Further, in the image forming apparatus 10, the elastic deformation rate of the photoconductor 14 is, for example, 43.5% or less. In the image forming apparatus 10, the deposits accumulated on the surface of the photoconductor 14 are easily scraped off by the developing roll 26 as compared with the case where the elastic deformation rate of the photoconductor is larger than 43.5%.

Further, in the image forming apparatus 10, the speed ratio (peripheral speed ratio) of the developing roll 26 to the photoconductor 14 when the developing roll 26 is rotated in the reverse direction is 1.6 or more and 1.8 or less. In the image forming apparatus 10, the effect is that the deposits accumulated on the surface of the photoconductor 14 are easily scraped off as compared with the case where the speed ratio (peripheral speed ratio) of the developing roll to the photoconductor is smaller than 1.6. improves. Further, as compared with the case where the speed ratio (peripheral speed ratio) of the developing roll to the photoconductor is larger than 1.8, the decrease in sensitivity due to the wear of the photosensitive layer of the photoconductor 14 is suppressed.

Further, in the image forming apparatus 10, the surface of the photoconductor 14 is located on the downstream side of the transfer portion of the toner image on the photoconductor 14 and on the upstream side of the exposure position where the electrostatic latent image is formed on the surface of the photoconductor 14. There is no cleaning member provided to contact and clean the surface. In the image forming apparatus 10, the number of parts can be reduced while suppressing the accumulation of deposits on the photoconductor 14, as compared with the configuration having a cleaning member that contacts the surface of the photoconductor and cleans the surface. can. In the image forming apparatus 10, cost reduction and space saving can be achieved by reducing the number of parts. Further, in the image forming apparatus 10, wear of the single-layer type photosensitive layer 42 of the photoconductor 14 is suppressed as compared with a configuration having a cleaning member that contacts the surface of the photoconductor and cleans the surface.

Further, in the image forming apparatus 10, the photoconductor 14 is provided with a single-layer type photosensitive layer 42 on the surface thereof. As a result, the image forming apparatus 10 suppresses wear on the surface of the single-layer type photosensitive layer 42 as compared with a configuration having a cleaning member that contacts the surface of the photoconductor and cleans the surface of the photoconductor. That is, when a photoconductor without a protective layer is applied to an image forming apparatus provided with a cleaning device for cleaning the surface of the photoconductor with a cleaning blade, for example, the surface of the photoconductor may be worn with use. However, since the image forming apparatus 10 of the present embodiment does not include a cleaning member such as a cleaning blade that comes into contact with the photoconductor 14, even if the photoconductor 14 does not have a protective layer, it is on the surface of the photoconductor 14. Wear is unlikely to occur.

[Second Embodiment]
Next, the image forming apparatus according to the second embodiment will be described with reference to FIGS. 4 and 5. The same components as those of the above-described first embodiment are designated by the same numbers, and the description thereof will be omitted.

As shown in FIG. 4, the image forming apparatus 50 is an image forming apparatus that forms a multicolor image. The image forming apparatus 50 of the present embodiment includes, for example, four image forming units 52Y in which four process cartridges 12 of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in parallel. It is configured to include 52M, 52C, and 52K. In the image forming apparatus 50, the endless conveying belt 54 for conveying the recording medium P is arranged at a position straddling the image forming portions 52Y, 52M, 52C, and 52K. The transport belt 54 is stretched on a plurality of rolls (4 in this embodiment) and moves in the direction of arrow C. A transfer roll 18 is arranged at the transfer position of the photoconductor 14 of each color via a transport belt 54, and the toner image on the surface of the photoconductor 14 is directly transferred to the recording medium P for each color. ing.

In this image forming apparatus 50, at the time of developing the electrostatic latent image on the surface of the photoconductor 14 of each color, the developing roll 26 is in the same direction as the photoconductor 14 by the motor 28 at the opposite portion between the photoconductor 14 and the developing roll 26. It is rotated in the direction of arrow B).

Further, as shown in FIG. 5, in the developing roll 26 of each color, after the toner image on the surface of the photoconductor 14 of each color is transferred to the recording medium P, the developing roll 26 is formed at the opposite portion between the photoconductor 14 and the developing roll 26. The developing roll 26 is rotated by the motor 28 in the direction opposite to that of the photoconductor 14 (in the direction of arrow D). After the toner image on the surface of the photoconductor 14 is transferred to the recording medium P, the developing roll 26 of each color is rotated in the opposite direction at the portion facing the photoconductor 14 to clean the surface of the photoconductor 14. It is designed to (clean).

In the above image forming apparatus 50, a single-layer type photosensitive layer is compared with a configuration in which the developing roll is continuously moved in the same direction as the moving direction of the photoconductor at a portion facing the photoconductor and the developing roll after the toner image is transferred. Accumulation of deposits on the surface of the photoconductor 14 of each color including 42 (see FIG. 3) is suppressed.

The image forming apparatus 50 includes a transport belt 54 for transporting the recording medium P, but instead of the transport belt 54, an intermediate transfer belt is provided, and a toner image on the surface of the photoconductor 14 of each color is transferred to the intermediate transfer belt. It may be configured to be overlaid and transferred. In this configuration, the image forming apparatus collectively transfers the toner image on the intermediate transfer belt to the recording medium on the downstream side of the transfer position of the toner image on the surface of the four-color photoconductor 14 in the moving direction of the intermediate transfer belt. It is equipped with a secondary transfer device. Further, the present invention may be applied to an image forming apparatus for a multicolor image provided with a plurality of rotary developing apparatus at a position facing the photoconductor.

Further, although the present invention has been described in detail with respect to a specific embodiment, the present invention is not limited to such an embodiment, and various other embodiments are possible within the scope of the present invention. It is obvious to the trader.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

As shown in FIG. 6, three types of photoconductors (A, B, C) having an elastic deformation rate of 43.5%, 41.5%, and 45% were used with respect to the rotation direction and peripheral speed ratio of the developing roll. The following evaluation was carried out for the combination.

In Examples 1 to 6, the direction of rotation of the developing roll of the developing apparatus is set so that the moving directions of the developing agent roll and the photoconductor are opposite to each other in the facing portion (rubbing portion) between the developing roll and the photoconductor. In Comparative Examples 1 to 4, the moving direction W of the developing agent roll and the photoconductor was set to be the same in the facing portion (rubbing portion) between the developing roll and the photoconductor. The time at this time is defined as the time for cleaning the photoconductor with the developing roll. The cleaning time of the photoconductor with the developing roll was set, for example, to allow the developing roll and the photoconductor to idle for 10 seconds every time 500 sheets were printed.

<Color point evaluation>
When 2000 sheets of halftone images with an image density of 50% are output on A4 size paper in an environment of temperature 28 ° C. and humidity 85%, the image forming apparatus is stopped overnight, and the blank paper is conveyed into the image forming apparatus the next morning. The number of color dots generated on a blank sheet of paper was counted. The evaluation criteria are as follows, and the results are shown in FIG. 6 (“color dots” in the table of FIG. 6).

The evaluation criteria for color points are as follows.
-Evaluation criteria for color points-
A: No color spots have occurred.
B: The number of color points is 1 or more and 9 or less.
C: The number of color points is 10 or more.

<Image quality durability>
In an environment of temperature 20 ° C. and humidity 40%, 12,000 halftone images with an image density of 30% are output on A4 paper, and the density of the 10,000th print image is what percentage of the density of the first print image. It was measured whether it became.

The evaluation criteria for the concentration are as follows.
-Evaluation criteria-
A: The density of the 10,000th print image is 95% or more of the density of the 1st print image.
B: The density of the 10,000th print image is less than 95% and 90% or more with respect to the density of the 1st print image.
C: The density of the 10,000th print image is less than 90% and 85% or more with respect to the density of the 1st print image.
D: The density of the 10,000th print image is less than 85% of the density of the 1st print image.

The evaluation results are shown in FIG. As shown in Examples 1 to 6 of FIG. 6, when the elastic deformation rate of the latent image holder is 43.5% or less, the evaluation of the color point is relatively good and the image quality defect is suppressed. You can see that. This is because the developing roll scrapes off the deposits accumulated on the surface of the photoconductor having the single-layer type photosensitive layer, so that the refreshability of the single-layer type photosensitive layer on the surface of the photoconductor is improved, and the photoconductor It is considered that image quality defects due to deposits accumulated on the surface of the image processing are suppressed.

Further, it can be seen that when the peripheral speed ratio of the developing roll to the photoconductor is 1.6 or more and 1.8 or less, image quality defects due to deposits accumulated on the surface of the photoconductor are suppressed. At the same time, the evaluation criteria for the concentration are also good, and it can be seen that the decrease in sensitivity due to the wear of the single-layer type photosensitive layer of the photoconductor is suppressed.

10 Image forming apparatus 14 Photoreceptor (example of latent image holder)
26 Development roll (example of developer holder)
28 Motor (an example of moving mechanism)
30 Image density 40 Conductive substrate 42 Photosensitive layer 50 Image forming apparatus P Recording medium (example of transfer target)

Claims (3)

A rotating latent image holder with a single-layer photosensitive layer on a conductive substrate,
A developer holder which is arranged to face the latent image holder and develops an electrostatic latent image formed on the latent image holder as a toner image while moving with respect to the latent image holder.
After the transfer of the toner image formed on the surface of the latent image holder, the developer holder is moved in the direction opposite to the moving direction of the latent image holder at the facing portion between the latent image holder and the developer holder. A moving mechanism having a structure in which deposits remaining on the surface of the latent image holder after transfer are scraped off by the developer on the developer holder.
Have,
The speed ratio of the developer holder to the latent image holder when the developer holder is moved in the direction opposite to the moving direction of the latent image holder is 1.6 or more and 1.8 or less.
The latent image holder is located on the downstream side of the transfer unit that transfers the toner image on the surface of the latent image holder to the transferred body, and on the upstream side of the exposure position where the electrostatic latent image is formed on the latent image holder. There is no cleaning member that comes into contact with the surface of the surface and cleans the surface .
When the surface of the latent image holder is cleaned by the developer holder after the transfer of the toner image on the surface of the latent image holder, no bias is applied to the developer holder.
Image forming device. The image forming apparatus according to claim 1, wherein the elastic deformation rate of the latent image holder is 43.5% or less. There is a removal method for removing deposits remaining on the surface of a latent image holder using the image forming apparatus according to claim 1 or 2.
After the transfer of the toner image formed on the surface of the latent image holder by the moving mechanism, the developer holder is placed on the latent image holder at a portion facing the latent image holder and the developer holder. A removal method in which deposits remaining on the surface of the latent image holder are scraped off by the developer on the developer holder by moving the latent image holder in the direction opposite to the moving direction.

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