JP2021001940A - Image forming apparatus and image forming method - Google Patents

Abstract

To provide an image forming apparatus that can reduce the occurrence of charging unevenness on a printed material while preventing a deterioration of a photosensitive layer of an image carrier.SOLUTION: An image forming apparatus 1 comprises an image carrier 50, a charging unit 51, a first static eliminating unit 61, a charging control unit, and a static elimination control unit. The charging unit 51 has a charging body 51a and an application unit 51b. The charging body 51a charges a peripheral surface 50a of the image carrier 50. The application unit 51b applies voltage to the charging body 51a. The first static eliminating unit 61 irradiates the peripheral surface 50a of the image carrier 50 with light to eliminate static electricity on the peripheral surface 50a of the image carrier 50. The charging control unit controls the application unit 51b so that the potential of the peripheral surface 50a of the image carrier 50 becomes a target value. The static elimination control unit controls the first static eliminating unit 61 based on the target value. The peripheral surface 50a of the image carrier 50 the static electricity of which is eliminated by the first static eliminating unit 61 is located on the upstream side in the direction of rotation R of the image carrier 50 with respect to the peripheral surface 50a of the image carrier 50 charged by the charging body 51a.SELECTED DRAWING: Figure 2

Description

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

The image forming apparatus described in Patent Document 1 includes a photoconductor, a charging roller, and a fuse lamp. The photoconductor rotates. The fuse lamp removes static electricity from the upstream portion of the proximity surface where the peripheral surface of the photoconductor and the surface of the charging roller are close to each other. As a result, it is possible to suppress the occurrence of image defects in the printed matter.

Japanese Unexamined Patent Publication No. 5-341626

However, in the image forming apparatus described in Patent Document 1, since the charge is always removed from the upstream portion, the amount of current for charging the image carrier such as the photoconductor increases. The more current flows through the image carrier, the more easily the photosensitive layer of the image carrier deteriorates. As a result, when the toner remaining on the photosensitive layer of the image carrier was recovered, the amount of wear of the photosensitive layer of the image carrier increased.

By the way, it has been found by the studies by the present inventors that the occurrence of uneven charging such as image defects is affected by the potential of the peripheral surface of the image carrier. For example, when the potential of the peripheral surface of the image carrier is within a predetermined range, charging unevenness may occur unless static electricity is removed. On the other hand, when the potential of the peripheral surface of the image carrier is not within a predetermined range, uneven charging is unlikely to occur even without static elimination. As a result, it was found that it is preferable to eliminate static electricity on the peripheral surface of the image carrier only when necessary, based on the potential of the peripheral surface of the image carrier.

The present invention has been made in view of the above problems, and an object of the present invention is an image forming apparatus and image forming capable of reducing the occurrence of uneven charging in printed matter while suppressing deterioration of the photosensitive layer of an image carrier. To provide a method.

The image forming apparatus of the present invention includes an image carrier, a charging unit, a first static elimination unit, a charging control unit, and a static elimination control unit. The image carrier has a photosensitive layer and rotates. The charged portion includes a charged body and an application portion. The charged body charges the peripheral surface of the image carrier. The application unit applies a voltage to the charging unit. The first static elimination unit irradiates the peripheral surface of the image carrier with light to eliminate static electricity on the peripheral surface of the image carrier. The charge control unit controls the application unit so that the potential on the peripheral surface of the image carrier becomes a target value. The static elimination control unit controls the first static elimination control unit based on the target value. The peripheral surface of the image carrier from which the first static elimination unit is statically eliminated is located upstream of the peripheral surface of the image carrier charged with the charged body in the rotational direction of the image carrier.

The image forming method of the present invention includes a rotation step, an application step, a charging step, and a static elimination step. In the rotation step, the image carrier having the photosensitive layer rotates. In the application step, a voltage is applied to the charged body so that the potential on the peripheral surface of the image carrier becomes a target value. In the charging step, the peripheral surface of the image carrier is charged. In the static elimination step, the peripheral surface of the image carrier located upstream of the peripheral surface of the image carrier charged with the charged body in the rotation direction of the image carrier is irradiated with light to carry the image. Remove static electricity from the peripheral surface of the body. The static elimination step is executed based on the target value.

According to the image forming apparatus of the present invention and the image forming method of the present invention, it is possible to reduce the occurrence of uneven charging in the printed matter while suppressing the deterioration of the photosensitive layer of the image carrier.

It is sectional drawing which shows the image forming apparatus which concerns on embodiment of this invention. It is a figure which shows the photoconductor and the peripheral part thereof provided with the image forming apparatus shown in FIG. It is a partial cross-sectional view which shows an example of the photoconductor provided in the image forming apparatus shown in FIG. It is a partial cross-sectional view which shows an example of the photoconductor provided in the image forming apparatus shown in FIG. It is a partial cross-sectional view which shows an example of the photoconductor provided in the image forming apparatus shown in FIG. It is a block diagram which shows the structure of the image forming apparatus shown in FIG. It is a flowchart which shows an example of the processing of the control part which concerns on this embodiment.

First, the terms used in the present specification will be described. A compound and its derivatives may be generically referred to by adding "system" after the compound name. When the polymer name is represented by adding "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

[Image forming device]
Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and the description is not repeated. In this embodiment, the X-axis, Y-axis, and Z-axis are orthogonal to each other, the X-axis and Y-axis are parallel to the horizontal plane, and the Z-axis is parallel to the vertical line.

First, an outline of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. The image forming apparatus 1 according to the present embodiment is a full-color printer. The image forming apparatus 1 includes a feeding unit 10, a conveying unit 20, an image forming unit 30, a discharging unit 70, an operating unit 76, and a control unit 95.

The feeding unit 10 includes a cassette 11 that accommodates a plurality of sheets P. The feeding section 10 feeds the sheet P from the cassette 11 to the transport section 20. The sheet P is made of, for example, paper or synthetic resin. The transport unit 20 transports the sheet P to the image forming unit 30.

The image forming unit 30 includes an exposure device 31, a magenta unit (hereinafter, M unit) 32M, a cyan unit (hereinafter, C unit) 32C, a yellow unit (hereinafter, Y unit) 32Y, and a black unit (hereinafter, BK unit) 32BK. The transfer belt 33, the secondary transfer roller 34, and the fixing device 35 are included. Each of the M unit 32M, the C unit 32C, the Y unit 32Y, and the BK unit 32BK includes a photoconductor 50, a charging unit 51, a developing roller 52, a primary transfer roller 53, and a cleaner 55.

The exposure device 31 irradiates each of the M unit 32M to BK unit 32BK with light based on the image data, and forms an electrostatic latent image in each of the M unit 32M to BK unit 32BK. The M unit 32M forms a magenta toner image based on the electrostatic latent image. The C unit 32C forms a cyan toner image based on the electrostatic latent image. The Y unit 32Y forms a yellow toner image based on the electrostatic latent image. The BK unit 32BK forms a black toner image based on the electrostatic latent image.

The photoconductor 50 has a drum shape. The photoconductor 50 rotates around the center of rotation. A charging portion 51, a developing roller 52, a primary transfer roller 53, and a cleaner 55 are arranged around the photoconductor 50 from the upstream side in the rotation direction of the photoconductor 50 in the order described. The charging unit 51 positively charges the peripheral surface 50a, which is the surface of the photosensitive layer of the photoconductor 50. For example, the charging unit 51 charges the peripheral surface 50a of the photoconductor 50 so that the potential of the peripheral surface 50a of the photoconductor 50 becomes 500 V.

As described above, the exposure apparatus 31 exposes the peripheral surface 50a of the charged photoconductor 50 to form an electrostatic latent image on the peripheral surface 50a of the photoconductor 50. The wavelength of the light emitted from the exposure apparatus 31 is, for example, 780 nm. The exposure amount of the exposure apparatus 31 is, for example, 1 μJ / cm ² .

The developing roller 52 supplies toner to the electrostatic latent image and develops the electrostatic latent image into a toner image. As a result, a toner image is formed on the peripheral surface 50a of the photoconductor 50. The toner image contains toner.

The transfer belt 33 comes into contact with the peripheral surface of the photoconductor 50 by 50a. The primary transfer roller 53 primary transfers the toner image formed on the peripheral surface 50a of the photoconductor 50 to the transfer belt 33 (more specifically, the outer surface of the transfer belt 33). Toner images of four colors are superimposed on the outer surface of the transfer belt 33 and primaryly transferred. The four-color toner image is a magenta-colored toner image, a cyan-colored toner image, a yellow-colored toner image, and a black-colored toner image. By the primary transfer, a color toner image is formed on the outer surface of the transfer belt 33. The secondary transfer roller 34 secondarily transfers the color toner image formed on the outer surface of the transfer belt 33 to the sheet P. The fixing device 35 heats and pressurizes the sheet P to fix the color toner image on the sheet P. The sheet P on which the color toner image is fixed is discharged to the discharge unit 70. After the primary transfer, the cleaner 55 recovers the toner remaining on the peripheral surface 50a of the photoconductor 50.

The control unit 95 includes a processor such as a CPU (Central Processing Unit).

The operation unit 76 accepts various user operations. For example, the operation unit 76 accepts a print job. Specifically, the operation unit 76 includes a display unit and an operation key unit.

The photoconductor 50 corresponds to an image carrier. The developing roller 52 corresponds to a developing unit. The primary transfer roller 53 corresponds to a transfer unit. The transfer belt 33 corresponds to the transferred body. The cleaner 55 corresponds to a cleaning unit. The exposure device 31 corresponds to an exposure unit.

Next, the image forming apparatus 1 according to the present embodiment will be further described with reference to FIG. FIG. 2 shows the photoconductor 50 and its peripheral portion. As shown in FIG. 2, the image forming apparatus 1 includes a charging unit 51, a developing roller 52, a primary transfer roller 53, a cleaner 55, a first static elimination unit 61, a second static elimination unit 62, and the like. It further includes a third static elimination unit 63.

<Developing roller>
The developing roller 52 attracts and supports the carrier CA carrying the toner T by a magnetic force. When a development bias (development voltage) is applied to the developing roller 52, a potential difference is generated between the potential of the developing roller 52 and the potential of the peripheral surface 50a of the photoconductor 50, and is formed on the peripheral surface 50a of the photoconductor 50. The toner T moves and adheres to the electrostatic latent image.

<Charging part>
The charging unit 51 has a charging roller 51a and an application unit 51b. The charging roller 51a has a drum shape. The charging roller 51a rotates around the rotation center 51X. The surface of the charging roller 51a is arranged so as to be in contact with the peripheral surface 50a of the photoconductor 50. The charging roller 51a corresponds to a charged body.

The application unit 51b applies a charging voltage (charging bias) to the charging roller 51a. Then, the application unit 51b is controlled by the control unit 95. Specifically, the application unit 51b applies a predetermined value of charging voltage (charging bias) to the charging roller 51a by the control unit 95. The charging voltage (charging bias) is a DC voltage. When the charging voltage is a DC voltage, the amount of discharge from the charging roller 51a to the photoconductor 50 is smaller than when the charging voltage is a superposed voltage, and the amount of wear on the peripheral surface 50a of the photoconductor 50 can be reduced.

<Primary transfer roller>
At the time of primary transfer, a transfer voltage (transfer bias) is applied to each primary transfer roller 53 to charge each primary transfer roller 53. Each toner image carried on the peripheral surface 50a of each photoconductor 50 is rotated by a potential difference (transfer electric field) between the surface potential of the peripheral surface 50a of each photoconductor 50 and the surface potential of each primary transfer roller 53. The primary transfer is performed on the outer peripheral surface of the transfer belt 33.

<Cleaner>
The cleaner 55 includes a cleaning blade 81 and a toner seal 82. The cleaning blade 81 is located downstream of the primary transfer roller 53 in the rotation direction R of the photoconductor 50. The cleaning blade 81 is pressed against the peripheral surface 50a of the photoconductor 50 and collects the toner T remaining on the peripheral surface 50a of the photoconductor 50. The remaining toner T is the toner T remaining on the peripheral surface 50a of the photoconductor 50 after the primary transfer. Specifically, the tip of the cleaning blade 81 is pressed against the peripheral surface 50a of the photoconductor 50, and the direction from the base end to the tip of the cleaning blade 81 is the circumference of the tip of the cleaning blade 81 and the photoconductor 50. At the contact point with the surface 50a, the rotation direction R is opposite to that of the surface 50a. The cleaning blade 81 is in so-called counter contact with the peripheral surface 50a of the photoconductor 50. As a result, the cleaning blade 81 is strongly pressed against the peripheral surface 50a of the photoconductor 50 so that the cleaning blade 81 bites into the photoconductor 50 as it rotates. By being strongly pressed in this way, the occurrence of cleaning defects can be further suppressed. The cleaning blade 81 is, for example, a plate-shaped elastic body, and more specifically, a plate-shaped rubber. The cleaning blade 81 makes line contact with the peripheral surface 50a of the photoconductor 50.

<1st static elimination unit>
The first static elimination unit 61 irradiates the peripheral surface 50a of the photoconductor 50 with light to eliminate static electricity from the peripheral surface 50a of the photoconductor 50. The peripheral surface 50a of the photoconductor 50 to be statically eliminated by the first static elimination unit 61 is located upstream of the peripheral surface 50a of the photoconductor 50 charged by the charging roller 51a in the rotation direction R of the photoconductor 50. Specifically, the first static elimination unit 61 is arranged so as to face the peripheral surface 50a on the downstream side of the cleaner 55 in the rotation direction R of the photoconductor 50. The first static elimination unit 61 is, for example, a static elimination lamp.

The first static elimination unit 61 is controlled by the control unit 95. Specifically, when the ON signal is input from the control unit 95, the first static elimination unit 61 emits light. On the other hand, when the ON signal is not input from the control unit 95, the first static elimination unit 61 does not emit light.

The wavelength of the light emitted from the first static elimination unit 61 is preferably 680 nm or more and 880 nm or less. Furthermore, charge removal amount of the first charge removing unit 61 is preferably at 0μJ / cm ² or more 4μJ / cm ² or less, and more preferably 0μJ / cm ² or more 2μJ / cm ² or less. When the amount of static light removed by the first static elimination unit 61 is 0 μJ / cm ² , it means that the photoconductor 50 is not statically eliminated by the first static elimination unit 61.

The amount of static elimination light indicates the amount of light that reaches the peripheral surface 50a of the photoconductor 50. Specifically, an optical power meter (“optical power meter 3664” manufactured by Hioki Electric Co., Ltd.) was used to measure the amount of light reaching the peripheral surface 50a of the photoconductor 50.

<Second static elimination unit>
The second static elimination unit 62 eliminates static electricity on the peripheral surface 50a of the photoconductor 50 after transfer by the primary transfer roller 53. Specifically, the second static elimination unit 62 eliminates static electricity from the peripheral surface 50a of the previous photoconductor 50 for 20 ms or more, preferably 50 ms or more, than the time for charging by the charging unit 51. Specifically, the second static elimination unit 62 is arranged so as to face the peripheral surface 50a on the downstream side of the primary transfer roller 53 in the rotation direction R of the photoconductor 50 and on the upstream side of the cleaner 55. The second static elimination unit 62 is, for example, a static elimination lamp.

The second static elimination unit 62 is controlled by the control unit 95. Specifically, when the operation unit 76 receives a print job, an ON signal is input from the control unit 95, and the second static elimination unit 62 emits light.

The wavelength of the light emitted from the second static elimination unit 62 is preferably 680 nm or more and 880 nm or less, and more preferably longer than the wavelength of the light emitted from the first static elimination unit 61.

Furthermore, charge removal amount of the second discharger 62 is preferably at 0μJ / cm ² or more 10 .mu.J / cm ² or less, and more preferably 0μJ / cm ² or more 5 .mu.J / cm ² or less. When the amount of static light removed by the second static elimination unit 62 is 10 μJ / cm ² or less, the amount of charge trapped in the photoconductor 50 is reduced, and the charging ability of the photoconductor 50 can be improved. Further, the amount of light elimination from the second static elimination unit 62 is preferably equal to or greater than the amount of static elimination light from the first static elimination unit 61. When the amount of static elimination light of the second static elimination unit 62 is 0 μJ / cm ² , it means that the system is static elimination-less.

<Third static elimination unit>
The third static elimination unit 63 removes static electricity from the peripheral surface 50a of the photoconductor 50 after being charged by the charging unit 51 and before being transferred by the primary transfer roller 53. Specifically, the third static elimination unit 63 eliminates static electricity from the peripheral surface 50a of the previous photoconductor 50 for 20 ms or more, preferably 50 ms or more, than the time for charging by the charging unit 51. Specifically, the third static elimination unit 63 is arranged so as to face the peripheral surface 50a on the downstream side of the developing roller 52 in the rotation direction R of the photoconductor 50 and on the upstream side of the primary transfer roller 53. The third static elimination unit 63 is, for example, a static elimination lamp.

The third static elimination unit 63 is controlled by the control unit 95. Specifically, when the operation unit 76 receives a print job, an ON signal is input from the control unit 95, and the third static elimination unit 63 emits light.

The wavelength of the light emitted from the third static elimination unit 63 is preferably 680 nm or more and 880 nm or less, and more preferably longer than the wavelength of the light emitted from the first static elimination unit 61.

Furthermore, charge removal amount of the third static eliminator 63 is preferably 0μJ / cm ² or more 10 .mu.J / cm ² or less, and more preferably 0μJ / cm ² or more 5 .mu.J / cm ² or less. When the amount of static elimination light of the third static elimination unit 63 is 10 μJ / cm ² or less, the amount of charge trapped in the photoconductor 50 is reduced, and the charging ability of the photoconductor 50 can be improved. Further, the amount of light elimination from the third static elimination unit 63 is preferably equal to or less than the amount of static elimination light from the first static elimination unit 61. When the amount of static elimination light of the third static elimination unit 63 is 0 μJ / cm ² , it means that the system is static elimination-less.

<Photoreceptor>
Hereinafter, the photoconductor 50 included in the image forming apparatus 1 will be described with reference to FIGS. 3 to 5. 3 to 5 show an example of a partial cross-sectional view of the photoconductor 50, respectively. The photoconductor 50 is, for example, an OPC (organic photoconductor) drum.

As shown in FIG. 3, the photoconductor 50 includes, for example, a conductive substrate 501 and a photosensitive layer 502. The photosensitive layer 502 is a single layer (one layer). The photoconductor 50 is a single-layer electrophotographic photosensitive member including a single-layer photosensitive layer 502. The photosensitive layer 502 contains a charge generator, a hole transport agent, an electron transport agent, and a binder resin. The film thickness of the photosensitive layer 502 is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 15 μm or more and 35 μm or less.

As shown in FIG. 4, the photoconductor 50 may include a conductive substrate 501, a photosensitive layer 502, and an intermediate layer 503 (undercoat layer). The intermediate layer 503 is provided between the conductive substrate 501 and the photosensitive layer 502. As shown in FIG. 3, the photosensitive layer 502 may be provided directly on the conductive substrate 501. Alternatively, as shown in FIG. 4, the photosensitive layer 502 may be provided on the conductive substrate 501 via the intermediate layer 503. The intermediate layer 503 may be a single layer or a plurality of layers.

As shown in FIG. 5, the photoconductor 50 may include a conductive substrate 501, a photosensitive layer 502, and a protective layer 504. The protective layer 504 is provided on the photosensitive layer 502. The protective layer 504 may be a single layer or a plurality of layers.

(Charging capacity ratio)
A ghost image tends to occur particularly when the charging roller 51a is arranged in contact with the peripheral surface 50a of the photoconductor 50 and the charging voltage is a DC voltage. The ghost image is an image in which the image before the photoconductor 50 makes one rotation appears as an afterimage in the printed matter. However, when the photoconductor 50 satisfies the formula (1), even when the surface of the charging roller 51a is arranged in contact with the peripheral surface 50a of the photoconductor 50 and the charging voltage is a DC voltage, a ghost image is obtained. Can be suppressed.

In the formula (1), Q represents the charge amount (unit: C) of the photoconductor 50. S represents the charged area (unit: m ² ) of the photoconductor 50. d represents the film thickness (unit: m) of the photosensitive layer 502 of the photoconductor 50. ε _r represents the relative permittivity of the binder resin contained in the photosensitive layer 502 of the photoconductor 50. ε ₀ represents the permittivity of vacuum (unit: F / m). In addition, "d / ε _r · ε ₀ " means "d / (ε _r × ε ₀ )". V is a value calculated from the following formula (2).
V = V ₀ −V _r・ ・ ・ (2)

V _r in the formula (2) represents the first potential of the peripheral surface 50a of the photoconductor 50 before being charged by the charging roller 51a. V ₀ in the formula (2) represents the second potential of the peripheral surface 50a of the photoconductor 50 after being charged by the charging roller 51a.

Hereinafter, the value represented by the following formula (1') in the formula (1) may be referred to as a chargeability ratio. The chargeability ratio represented by the formula (1') is the photoconductor 50 with respect to the theoretical chargeability (theoretical value) of the photoconductor 50 when the peripheral surface 50a of the photoconductor 50 is charged by the charging roller 51a. The ratio of the actual charging ability (measured value) of is shown.

The photosensitive layer 502 contains a charge generator, a hole transport agent, an electron transport agent, and a binder resin. The photosensitive layer 502 may further contain an additive, if necessary. Hereinafter, suitable combinations of charge generators, hole transport agents, electron transport agents, binder resins, additives, and materials will be described.

(Charge generator)
The charge generator is not particularly limited. Examples of the charge generator include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, and cyanine. Pigments, powders of inorganic photoconductive materials (eg, selenium, selenium-tellu, selenium-arsenic, cadmium sulfide or amorphous silicon), pyrylium pigments, anthanthrone pigments, triphenylmethane pigments, slen pigments, toluidine pigments, Examples thereof include pyrazoline pigments and quinacridone pigments. The photosensitive layer 502 may contain only one type of charge generator, or may contain two or more types of charge generator.

In order to suppress the generation of ghost images, the phthalocyanine pigment is preferably metal-free phthalocyanine, titanyl phthalocyanine, or chloroindium phthalocyanine, and more preferably titanyl phthalocyanine.

The content of the charge generator is preferably more than 0.0% by mass and 1.0% by mass or less, and more than 0.0% by mass and 0.5% by mass or less with respect to the mass of the photosensitive layer 502. More preferably. When the content of the charge generator is 1.0% by mass or less with respect to the mass of the photosensitive layer 502, the chargeability ratio can be increased. The mass of the photosensitive layer 502 is the total mass of the materials contained in the photosensitive layer 502. When the photosensitive layer 502 contains a charge generator, a hole transporting agent, an electron transporting agent, and a binder resin, the mass of the photosensitive layer 502 is the mass of the charge generating agent, the mass of the hole transporting agent, and the mass of the electron transporting agent. And the mass of the binder resin. When the photosensitive layer 502 contains a charge generator, a hole transport agent, an electron transport agent, a binder resin, and an additive, the mass of the photosensitive layer 502 is the mass of the charge generator, the mass of the hole transport agent, and the electron transport. It is the sum of the mass of the agent, the mass of the binder resin, and the mass of the additive.

(Hole transport agent)
The hole transporting agent is not particularly limited. Examples of the hole transporting agent include nitrogen-containing cyclic compounds and condensed polycyclic compounds. Examples of the nitrogen-containing ring compound and the condensed polycyclic compound include a triphenylamine derivative; a diamine derivative (more specifically, N, N, N', N'-tetraphenylbenzidine derivative, N, N, N. ', N'-tetraphenylphenylenediamine derivative, N, N, N', N'-tetraphenylnaphthylene diamine derivative, di (aminophenylethenyl) benzene derivative, N, N, N', N'-tetraphenyl Phenantrine diamine derivatives, etc.); Oxadiazole compounds (more specifically, 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, etc.); Styryl compounds (more specifically) Specifically, 9- (4-diethylaminostyryl) anthracene, etc.); carbazole-based compounds (more specifically, polyvinylcarbazole, etc.); organic polysilane compounds; pyrazoline-based compounds (more specifically, 1-phenyl- 3- (p-Dimethylaminophenyl) pyrazoline, etc.); Hydrazone compounds; Indol compounds; Oxadiazole compounds; Isooxazole compounds; Thiazol compounds; Thiaziazole compounds; Imidazole compounds; Pyrazole compounds; and Triazole compounds Can be mentioned. The photosensitive layer 502 may contain only one kind of hole transporting agent, or may contain two or more kinds of hole transporting agents.

The content of the hole transport agent is preferably greater than 0.0% by mass and 35.0% by mass or less with respect to the mass of the photosensitive layer 502, and is preferably 10.0% by mass or more and 30.0% by mass or less. More preferably.

(Binder resin)
Examples of the binder resin include thermoplastic resins, thermosetting resins, and photocurable resins. Examples of the thermoplastic resin include polycarbonate resins, polyarylate resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic acid polymers, and styrene-acrylic acid copolymers. Polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate Examples thereof include resins, ketone resins, polyvinyl butyral resins, polyester resins, and polyether resins. Examples of the thermosetting resin include silicone resin, epoxy resin, phenol resin, urea resin, and melamine resin. Examples of the photocurable resin include an acrylic acid adduct of an epoxy compound and an acrylic acid adduct of a urethane compound. The photosensitive layer 502 may contain only one kind of binder resin, or may contain two or more kinds of binder resins.

The viscosity average molecular weight of the binder resin is preferably 10,000 or more, more preferably 20,000 or more, further preferably 30,000 or more, and even more preferably 50,000 or more. , 55,000 or more is particularly preferable. When the viscosity average molecular weight of the binder resin is 10,000 or more, the abrasion resistance of the photoconductor 50 tends to be improved. On the other hand, the viscosity average molecular weight of the binder resin is preferably 80,000 or less, and more preferably 70,000 or less. When the viscosity average molecular weight of the binder resin is 80,000 or less, the binder resin tends to be easily dissolved in the solvent for forming the photosensitive layer, and the photosensitive layer 502 tends to be easily formed.

The content of the binder resin is preferably 30.0% by mass or more and 70.0% by mass or less, and preferably 40.0% by mass or more and 60.0% by mass or less with respect to the mass of the photosensitive layer 502. More preferred.

(Electronic transport agent)
Examples of the electron transporting agent include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, and the like. Examples thereof include dinitroanthracene-based compounds, dinitroacridine-based compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroaclydin, succinic anhydride, maleic anhydride and dibromomaleic anhydride. Examples of the quinone compound include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds. The photosensitive layer 502 may contain only one kind of electron transporting agent, or may contain two or more kinds of electron transporting agents.

The content of the electron transporting agent is preferably 5.0% by mass or more and 50.0% by mass or less, and 20.0% by mass or more and 30.0% by mass or less with respect to the mass of the photosensitive layer 502. Is more preferable. When the photosensitive layer 502 contains two or more kinds of electron transporting agents, the content of the electron transporting agent is the total content of the two or more kinds of electron transporting agents.

(Additive)
The photosensitive layer 502 may further contain an additive, if necessary. Examples of the additive include an antioxidant (more specifically, an antioxidant, a radical scavenger, a quencher, an ultraviolet absorber, etc.), a softener, a surface modifier, a bulking agent, a thickener, and a dispersion. Stabilizers, waxes, donors, surfactants, and leveling agents. When the additive is contained in the photosensitive layer 502, the photosensitive layer 502 may contain only one kind of additive, or may contain two or more kinds of additives.

(Middle layer)
The intermediate layer 503 contains, for example, inorganic particles and a resin (resin for the intermediate layer) used for the intermediate layer 503. By interposing the intermediate layer 503, it is possible to suppress an increase in electrical resistance by smoothing the flow of current generated when the photoconductor 50 is exposed while maintaining an insulating state to the extent that leakage can be suppressed.

Examples of the inorganic particles include metal particles (more specifically, aluminum, iron, copper, etc.) and metal oxides (more specifically, titanium oxide, alumina, zirconium oxide, tin oxide, zinc oxide, etc.). Particles and particles of non-metal oxides (more specifically, silica, etc.). One type of these inorganic particles may be used alone, or two or more types may be used in combination. The inorganic particles may be surface-treated. The resin for the intermediate layer is not particularly limited as long as it can be used as the resin for forming the intermediate layer 503.

<Memory>
Next, the configuration of the image forming apparatus 1 will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the image forming apparatus 1. As shown in FIG. 6, the image forming apparatus 1 further includes a storage unit 90 and a detection unit 75.

The detection unit 75 detects the film thickness of the photosensitive layer 502 of the photoconductor 50. The detection unit 75 measures, for example, the total number of rotations of the photosensitive member 50 from the initial stage to calculate the thickness of the photosensitive layer 502. The storage unit 90 stores the reduction rate of the photosensitive layer 502 with respect to the unit rotation speed of the photoconductor 50. Then, the detection unit 75 calculates the film thickness of the photosensitive layer 502 based on the total rotation speed and the reduction rate of the photosensitive layer 502 with respect to the unit rotation speed of the photoconductor 50, and sends a signal indicating the value to the control unit 95. Output.

The storage unit 90 includes a storage device and stores a computer program. Specifically, the storage unit 90 includes a main storage device such as a semiconductor memory and an auxiliary storage device such as a semiconductor memory and / or a hard disk drive.

Specifically, the storage unit 90 stores the relationship between the potential, the film thickness, and the uneven charging in the image forming apparatus 1. Table 1 is a table showing the relationship between the potential, the film thickness, and the occurrence of uneven charging in the first photoconductor 50. Table 2 is a table showing the relationship between the potential, the film thickness, and the occurrence of uneven charging in the second photoconductor 50.

As shown in FIG. 3, the first photosensitive member 50 includes a conductive substrate 501 and a photosensitive layer 502. Then, the first photoconductor 50 satisfies the formula (1). On the other hand, the second photoconductor 50 includes a conductive substrate 501 and a photosensitive layer 502, as shown in FIG. Then, the second photoconductor 50 does not satisfy the formula (1).

In Tables 1 and 2, the vertical axis represents the potential of the peripheral surface 50a of the photosensitive layer 502, and the horizontal axis represents the film thickness of the photosensitive layer 502. In Tables 1 and 2, ◯ indicates that charging unevenness does not occur, and × indicates that charging unevenness occurs. Charging unevenness means, for example, that white spots are visualized in a printed matter on which a solid image is printed. Tables 1 and 2 are tables in the case where the image forming apparatus 1 is installed at a temperature of 32.5 ° C. and a relative humidity of 80% RH, and the first static elimination unit 61 does not eliminate static electricity.

As shown in Table 1, in the first photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, charging unevenness occurs when the potential is 400 V or more and 650 V or less. On the other hand, when the potential is not 400 V or more and 650 V or less, charging unevenness does not occur. Further, in the first photoconductor 50 having a film thickness of the photosensitive layer 502 of 30 μm, uneven charging occurs when the potential is 500 V or more and 600 V or less. On the other hand, when the potential is not 500 V or more and 600 V or less, charging unevenness does not occur.

Further, as shown in Table 2, in the second photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, charging unevenness occurs when the potential is 500 V or more and 600 V or less. On the other hand, when the potential is not 500 V or more and 600 V or less, charging unevenness does not occur. Further, in the second photoconductor 50 having a film thickness of the photosensitive layer 502 of 30 μm, uneven charging does not occur.

As shown in FIG. 6, the control unit 95 includes a charge control unit 95a and a static elimination control unit 95b. Then, the processor of the control unit 95 functions as the charge control unit 95a and the static elimination control unit 95b by executing the computer program stored in the storage device of the storage unit 90.

The charge control unit 95a controls the application unit 51b so that the potential of the peripheral surface 50a of the photoconductor 50 becomes a target value. The target value is, for example, a numerical value input by the user or the manufacturer in the operation unit 76 in order to form an image. Specifically, the charge control unit 95a controls the application unit 51b based on the input signal from the operation unit 76. Specifically, the charge control unit 95a controls the application unit 51b so that the potential of the peripheral surface 50a of the photoconductor 50 becomes the target value indicated by the input signal from the operation unit 76.

The static elimination control unit 95b controls the first static elimination control unit 61 based on the target value. Specifically, the static elimination control unit 95b determines whether or not the target value indicated by the input signal from the operation unit 76 is within a predetermined range. In the image forming apparatus 1 including the first photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, the static elimination control unit 95b outputs an ON signal to the first static elimination unit 61 when the target value is 400 V or more and 650 V or less. .. On the other hand, when the target value is not 400 V or more and 650 V or less, the static elimination control unit 95b does not output an ON signal to the first static elimination unit 61. Table 3 is a table showing the relationship between the potential, the film thickness, and the occurrence of uneven charging in the first photoconductor.

In Table 3, the vertical axis represents the potential and the horizontal axis represents the film thickness. In Table 3, ◯ indicates that charging unevenness does not occur, and × indicates that charging unevenness occurs. As shown in Table 3, charging unevenness does not occur in all combinations of the potential of 300 V to 700 V and the film thickness of 15 μm to 35 μm.

Further, in the image forming apparatus 1 including the second photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, when the target value is 500 V or more and 600 V or less, the static elimination control unit 95b sends an ON signal to the first static elimination unit 61. Output. On the other hand, when the target value is not 500 V or more and 600 V or less, the static elimination control unit 95b does not output an ON signal to the first static elimination unit 61. Table 4 is a table showing the relationship between the potential, the film thickness, and the occurrence of uneven charging in the second photoconductor.

In Table 4, the vertical axis represents the potential and the horizontal axis represents the film thickness. In Table 4, ◯ indicates that charging unevenness does not occur, and × indicates that charging unevenness occurs. As shown in Table 4, charging unevenness does not occur in all combinations of the potential of 300 V to 700 V and the film thickness of 15 μm to 35 μm.

Therefore, according to the image forming apparatus 1 according to the present embodiment, the peripheral surface 50a of the photoconductor 50 can be statically eliminated only when necessary, based on the potential of the peripheral surface 50a of the photoconductor 50. As a result, it is possible to suppress the flow of unnecessary current through the photoconductor 50. Therefore, it is possible to reduce the occurrence of uneven charging in the printed matter while suppressing the deterioration of the photosensitive layer 502 of the photoconductor 50.

Specifically, in the image forming apparatus 1 provided with the first photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, when the target value is not 400 V or more and 650 V or less, the static elimination control unit 95b is the first static elimination unit 61. Since the static electricity is not removed, the deterioration of the photosensitive layer 502 of the photoconductor 50 can be suppressed. Further, in the image forming apparatus 1 including the second photoconductor 50 having a film thickness of the photosensitive layer 502 of 35 μm, the static elimination control unit 95b does not eliminate static electricity at the first static elimination unit 61 when the target value is not 400 V or more and 650 V or less. Therefore, deterioration of the photosensitive layer 502 of the photoconductor 50 can be suppressed.

Further, when the cleaner 55 is provided, deterioration of the photosensitive layer 502 of the photoconductor 50 can be suppressed, so that the amount of wear of the photosensitive layer 502 of the photoconductor 50 can be suppressed even if the photosensitive layer 502 is strongly pressed by the cleaner 55.

Then, when the photoconductor 50 satisfies the formula (1), the generation of a ghost image can be suppressed.

Further, it is preferable that the static elimination control unit 95b controls the first static elimination control unit 61 based on the target value and the film thickness. Specifically, as the image is formed, the photosensitive layer 502 is worn by the cleaner 55, and the film thickness of the photosensitive layer 502 becomes thinner. Therefore, in the first photoconductor 50, when the film thickness of the photosensitive layer 502 was 35 μm, charging unevenness occurred when the target value was 400 V or more and 650 V or less, but the film thickness of the photosensitive layer 502 became 30 μm. When it becomes, charging unevenness occurs when the target value is 500 V or more and 600 V or less. That is, the predetermined range in which uneven charging occurs changes. As a result, the static elimination control unit 95b acquires the film thickness of the photosensitive layer 502 from the detection unit 75. Then, the static elimination control unit 95b determines whether or not the target value indicated by the input signal from the operation unit 76 is within a predetermined range based on the film thickness of the photosensitive layer 502 acquired from the detection unit 75. 95b determines.

Therefore, according to the image forming apparatus 1 according to the present embodiment, even if the film thickness of the photosensitive layer 502 changes, the first static elimination unit 61 is controlled according to the film thickness of the photosensitive layer 502, so that when necessary. Only the peripheral surface 50a of the photoconductor 50 can be statically eliminated. As a result, it is possible to reduce the occurrence of uneven charging in the printed matter while suppressing the deterioration of the photosensitive layer 502 of the photoconductor 50.

The image forming apparatus 1 according to the present embodiment has been described above. Although the charging roller 51a has been described, the charging device arranged so as to be in contact with the peripheral surface 50a of the photoconductor 50 may be a charging brush. Further, although the case where the charging voltage is a DC voltage has been described, the present invention is also applicable when the charging voltage is an AC voltage or a superposed voltage. The superimposed voltage is a voltage obtained by superimposing a DC voltage and an AC voltage. Further, although the developing roller 52 using the two-component developer containing the carrier CA and the toner T has been described, the present invention is also applicable to a developing device using the one-component developer. Further, although the image forming apparatus 1 adopting the intermediate transfer method has been described, the present invention is also applicable to the image forming apparatus adopting the direct transfer method.

[Image formation method]
Next, an image forming method executed by the image forming apparatus 1 according to the present embodiment will be described. This image forming method includes a rotation step, an application step, a charging step, and a static elimination step. In the rotation process, the photoconductor 50 rotates. In the application step, a voltage is applied to the charging roller 51a so that the potential of the peripheral surface 50a of the photoconductor 50 becomes a target value. In the charging step, the peripheral surface 50a of the photoconductor 50 is charged. In the static elimination step, the peripheral surface 50a of the photoconductor 50 located on the upstream side of the rotation direction R of the photoconductor 50 with respect to the peripheral surface 50a of the photoconductor 50 charged by the charging roller 51a is irradiated with light to cause the photoconductor 50. The peripheral surface 50a is statically eliminated. The static elimination process is executed based on the target value.

The processing of the control unit 85 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing an example of processing by the control unit 85.

As shown in FIG. 7, first, in step S101, the charge control unit 95a controls the application unit 51b so that the potential of the peripheral surface 50a of the photoconductor 50 becomes a target value.

Next, in step S102, the static elimination control unit 95b determines whether or not the target value is within the predetermined range. When the static elimination control unit 95b determines that the target value is within the predetermined range (YES in step S102), the process proceeds to step S103. On the other hand, when the static elimination control unit 95b determines that the target value is not within the predetermined range (NO in step S103), the process ends.

In step S103, the static elimination control unit 95b outputs an ON signal to the first static elimination unit 61. Then, the process ends.

According to the image forming method executed by the image forming apparatus 1 according to the present embodiment, the peripheral surface 50a of the photoconductor 50 can be statically eliminated only when necessary, based on the potential of the peripheral surface 50a of the photoconductor 50. .. As a result, it is possible to suppress the flow of unnecessary current through the photoconductor 50. Therefore, it is possible to reduce the occurrence of uneven charging in the printed matter while suppressing the deterioration of the photosensitive layer 502 of the photoconductor 50.

The image forming apparatus according to the present invention can be used to form an image on a recording medium.

1: Image forming apparatus 31: Exposure apparatus (exposure unit)
33: Transfer belt 50: Photoreceptor (photoreceptor drum)
50a: Peripheral surface 51: Charging part 51a: Charging roller 51b: Applying part 52: Developing roller (developing part)
53: Primary transfer roller (transfer section)
55: Cleaner (cleaner part)
61: 1st static elimination unit 62: 2nd static elimination unit 63: 3rd static elimination unit 75: Detection unit 81: Cleaning blade 95: Control unit 95a: Calculation unit 95b: Static elimination control unit

Claims (8)

An image carrier that has a photosensitive layer and rotates,
A charged portion having a charged body that charges the peripheral surface of the image carrier and an application portion that applies a voltage to the charged body.
A first static elimination unit that irradiates the peripheral surface of the image carrier with light to eliminate static electricity on the peripheral surface of the image carrier.
A charge control unit that controls the application unit so that the potential on the peripheral surface of the image carrier becomes a target value,
A static elimination control unit that controls the first static elimination unit based on the target value is provided.
An image forming apparatus in which the peripheral surface of the image carrier to be statically eliminated by the first static elimination unit is located upstream of the peripheral surface of the image carrier charged with the charged body in the rotational direction of the image carrier. A detection unit for detecting the film thickness of the photosensitive layer of the image carrier is further provided.
The image forming apparatus according to claim 1, wherein the static elimination control unit controls the first static elimination control unit based on the target value and the film thickness. The image forming apparatus according to claim 1 or 2, further comprising a cleaning unit arranged on the upstream side of the image carrier in the rotation direction of the first static elimination unit. An exposed portion that exposes the peripheral surface of the image carrier after being charged by the charged portion to form an electrostatic latent image on the peripheral surface of the image carrier.
A developing unit that develops the electrostatic latent image with toner to form a toner image on the peripheral surface of the image carrier.
A transfer unit that transfers the toner image to the transfer target, and
Further provided with a second static elimination section for statically eliminating the peripheral surface of the image carrier after transfer by the transfer section.
The image forming apparatus according to claim 3, wherein the cleaning unit recovers the toner remaining on the peripheral surface of the image carrier after static elimination by the second static elimination unit. The fourth aspect of the present invention further comprises a third static elimination unit that irradiates the peripheral surface of the image carrier before development by the transfer unit with light after development by the developing unit to eliminate static electricity on the peripheral surface of the image carrier. The image forming apparatus described. The image carrier includes a conductive substrate and the single-layer photosensitive layer.
The image forming apparatus according to any one of claims 1 to 5, wherein the photosensitive layer contains a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin. The image forming apparatus according to claim 6, wherein the image carrier satisfies the formula (1).

(In the above formula (1),
Q represents the amount of electric charge of the image carrier.
S represents the charged area of the image carrier.
d represents the film thickness of the photosensitive layer.
ε _r represents the relative permittivity of the binder resin contained in the photosensitive layer.
ε ₀ represents the permittivity of vacuum
V is a value calculated from the equation V = V ₀ −V _r .
V _r represents the first potential of the peripheral surface of the image carrier before being charged by the charged portion.
V ₀ represents the second potential of the peripheral surface of the image carrier after being charged by the charged portion. ) A rotation process in which the image carrier having the photosensitive layer rotates,
An application step of applying a voltage to the charged body so that the potential of the peripheral surface of the image carrier becomes a target value, and
A charging step of charging the peripheral surface of the image carrier and
The peripheral surface of the image carrier, which is located upstream of the peripheral surface of the image carrier charged with the charged body in the rotation direction of the image carrier, is irradiated with light to cover the peripheral surface of the image carrier. Including the static elimination step of static elimination
An image forming method for executing the static elimination step based on the target value.

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