JP5625307B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, it is proposed that the intermediate layer provided between the base material and the photosensitive layer includes a resin and metal oxide particles generated by a plasma method. Since the metal oxide particles generated by the plasma method have a small average particle size of 100 nm or less, in Patent Document 1, the dispersibility of the metal oxide particles in the resin is improved to suppress the deterioration of the image quality. .

  In Patent Document 2, the image carrier is formed with a subbing layer having a metal oxide and a receptive compound and a photosensitive layer, and is formed last time by adjusting the volume resistance of the subbing layer. It has been proposed to suppress fogging when using a recording medium wider than the recording medium.

JP 2006-184512 A JP 2002-169317 A

  The present invention provides an image forming apparatus that realizes both the suppression of chain-like white spots and the suppression of contamination on the end face of a recording medium, as compared with a configuration that does not use the image carrier and the transfer device of the present invention. The purpose is to provide.

According to a first aspect of the present invention, there is provided an image carrier having an undercoat layer containing metal oxide particles and a photosensitive layer on a cylindrical conductive substrate , and charging the image carrier. Charging device, a latent image forming device for forming an electrostatic latent image on the image carrier charged by the charging device, and development for developing the electrostatic latent image formed on the image carrier with toner And a transfer device that has a voltage dependency of 2.2 or less represented by the following formula (1) and transfers the toner image formed on the image carrier to the recording medium by the developing device. An image forming apparatus.

P = R1 / R2 (1)

In formula (1), P represents the voltage dependence of the resistance with respect to the transfer voltage of the transfer device, and R1 represents the resistance of the transfer device when a transfer voltage of 1 kV is applied at a temperature of 22 ° C. and a humidity of 55% RH. indicates the value, R2 is shows the resistance value of said transfer device when the transfer voltage of 2kV is applied at a temperature 22 ° C. humidity 55% RH,
R1 and R2 are measuring devices including the transfer device, a cylindrical member having the same material as the base material of the image carrier, the same diameter and the same length in the width direction, a voltage applying device, and a current measuring device. Measured by
The voltage application device is a device that applies a voltage between the cylindrical member and the transfer device, and the current measurement device is configured such that when the voltage is applied by the voltage application device, the cylindrical member And a device for measuring a current value of a current flowing between the transfer device and the transfer device,
The cylindrical member and the transfer device are arranged in contact with each other so as to have the same linear pressure as the linear pressure between the transfer device and the image carrier in the image forming apparatus, and the cylindrical member is rotated. With the arrangement, the transfer device is rotated so that
R1 is a state in which the cylindrical member is rotated at a linear velocity of 300 mm / s under the environment of a temperature of 22 ° C. and a humidity of 55% RH, and the transfer device is driven and rotated from the voltage application device to the cylinder. Calculated from the average current value measured by the current measuring device in 3 seconds from 2 seconds after applying a voltage of 1 kV between the transfer member and the transfer device, and the applied voltage (1 kV) ,
R2 is a state in which the cylindrical member is rotated at a linear velocity of 300 mm / s in an environment of a temperature of 22 ° C. and a humidity of 55% RH, and the transfer device is also driven to rotate, and the cylinder from the voltage application device to the cylinder. Calculated from the average current value measured by the current measuring device in 3 seconds from 2 seconds after applying a voltage of 2 kV between the transfer member and the transfer device, and the applied voltage (2 kV) The

  According to the first aspect of the present invention, both the suppression of chained white spots and the suppression of smearing of the end face of the recording medium are realized as compared with the configuration in which the image carrier and the transfer device of the present invention are not used. An image forming apparatus is provided.

Furthermore, according to the invention of claim 1, as compared with the case outside the scope of the content of the metal oxide particles contained in the undercoat layer is defined in claim 1, further contamination of the end surface of the recording medium It is suppressed.

Further, the invention according to claim 1, as compared with the case where the voltage dependence of transfer device exceeds 1.8, chain-shaped white spots is further suppressed.

1 is a schematic diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic diagram which shows an example of a structure of a transfer apparatus. It is a schematic diagram which shows the voltage dependence measuring apparatus. It is a schematic diagram which shows an example of a structure of (A)-(D) image holding body. (A) is a schematic plan view which shows an example of the circular electrode which measures volume resistance, (B) is a schematic sectional drawing which shows an example of the circular electrode which measures volume resistance.

Hereinafter, an embodiment of the image forming apparatus of the present embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment is provided with an image holding body 12 as an image holding body. The image carrier 12 has a cylindrical shape, and is rotationally driven (in the direction of arrow A in FIG. 1) by a motor (not shown).

  Around the image carrier 12, a charging device 15, an exposure device 16, and a developing device 18 are sequentially arranged along the rotation direction of the image carrier 12.

  The charging device 15 charges the surface of the image carrier 12. The charging device 15 is provided in contact or non-contact with the surface of the image carrier 12, and includes a charging roll 14 for charging the surface of the image carrier 12, and a power supply 28 for charging and applying a voltage to the charging roll 14. It consists of The power supply 28 is electrically connected to the charging roll 14. The charging roll 14 charges the surface of the image carrier 12 with the voltage applied from the power supply 28. Examples of the charging roll 14 include a corotron charger and a scorotron charger.

  The exposure device 16 irradiates the surface of the image carrier 12 charged by the charging device 15 with a laser beam L modulated based on the image data of the image to be formed, and the image data on the image carrier 12. An electrostatic latent image corresponding to the image is formed.

  A developer containing at least toner is stored in the developing device 18. Examples of the developer include a two-component developer. As the two-component developer, a known two-component developer including a toner and a carrier is applied. The toner is stored in a state of being charged to a predetermined charge amount by being stirred by a stirring mechanism (not shown) in the developing device 18. Examples of the toner contained in the two-component developer include a toner having a volume average particle diameter of 3 μm or more and 9 μm or less obtained by a polymerization method.

  Further, the developing device 18 includes a developing roll 18A for developing the electrostatic latent image formed on the image carrier 12 with toner. The developing roll 18A holds the developer stored in the developing device 18 on the surface, and supplies the toner contained in the developer from the developing device 18 to the surface of the image carrier 12. The toner supplied onto the image carrier 12 adheres to the electrostatic latent image on the image carrier 12 by electrostatic force. As a result, the electrostatic latent image on the image carrier 12 is developed by the toner supplied from the developing roll 18 </ b> A, and a toner image corresponding to the electrostatic latent image is formed on the image carrier 12.

  A transfer device 20 is provided around the image holding body 12 and downstream of the position where the developing roller 18 </ b> A is disposed in the rotation direction of the image holding body 12. The transfer device 20 has a cylindrical shape, and sandwiches and conveys the recording medium P with the image carrier 12. A transfer power supply 30 for applying a transfer voltage to the transfer device 20 is electrically connected to the transfer device 20.

  When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the image carrier 12 is applied from the transfer power supply 30, the image is held in the region between the image carrier 12 and the transfer device 20. An electric field having an electric field strength is generated to move each toner constituting the toner image on the body 12 from the image holding body 12 to the transfer device 20 side by electrostatic force.

The recording medium P is stored in a paper storage unit (not shown), and is transported (in the direction of arrow B in FIG. 1) along the transport path 34 by a plurality of transport rollers (not shown) from the paper storage unit. It reaches the area where the image carrier 12 and the transfer device 20 face each other (transfer area 32 in FIG. 1). The toner constituting the toner image on the image carrier 12 is transferred to the recording medium P reaching the transfer area 32 by an electric field formed in the transfer area 32 when a transfer voltage is applied to the transfer device 20. Is done. That is, the toner image is transferred onto the recording medium P by the movement of the toner from the surface of the image carrier 12 to the recording medium P.
The transfer area 32 indicates an area where the toner image on the image carrier 12 is transferred to the recording medium P side in an area where the image carrier 12 and the transfer device 20 face each other.

A fixing device 26 is provided on the transport path 34 of the recording medium P on the downstream side in the transport direction from the transfer region 32. The fixing device 26 fixes the toner image transferred onto the recording medium P to the recording medium P by heat or heat and pressure.
That is, the recording medium P that has been transferred along the transport path 34 and has passed the transfer region 32 between the image carrier 12 and the transfer device 20 and has the toner image transferred thereon is further transported by a transport roller (not shown). When the installation position of the fixing device 26 is reached along 34, the toner image on the recording medium P is fixed. The recording medium P on which the toner image is fixed, that is, on which an image is formed, is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance rollers (not shown).

  A cleaning device 22 and a charge eliminating device 24 are disposed downstream of the transfer region 32 in the rotational direction of the image carrier 12 in the rotational direction of the image carrier 12 (in the direction of arrow A in FIG. 1).

  The cleaning device 22 removes deposits such as residual toner and paper dust on the image carrier 12. Examples of the cleaning device 22 include a configuration having a blade member that contacts the image carrier 12 at a linear pressure of 10 g / cm to 150 g / cm. The static eliminator 24 removes residual charges on the image carrier 12.

  After the toner image transferred to the recording medium P is removed, the image carrier 12 is removed by the cleaning device 22 by rotation, and then the residual charge is removed by the static eliminator 24 and charged again by the charging device 15.

  As described above, the image forming apparatus 10 forms an image on the recording medium P.

Here, in the conventional image forming apparatus, chained white spots may occur in the image formed on the recording medium P. This chain-like white spot is a phenomenon in which a white spot-like white spot is generated in an image formed on the recording medium P in a direction intersecting the conveyance direction of the recording medium P, and occurs in the transfer area 32. It is thought to be caused by a discharge phenomenon.
The chained white spots become more conspicuous as the image is formed in the image forming apparatus 10 at a higher speed and in a low temperature and low humidity environment. The “end surface of the recording medium P” indicates an end surface of the recording medium P that intersects the thickness direction of the recording medium P.

  As a result of intensive studies, the inventors have made the above-described chain-like white spots by making the voltage dependency of the resistance to the transfer voltage of the transfer device 20 included in the image forming apparatus 10 2.2 or less. Found to be suppressed.

More specifically, the chain-like white spots are described in detail before the recording medium P reaches the transfer region 32 and the toner image on the image holding body 12 is transferred to the recording medium P. This is considered to be a transfer failure that occurs when a part of the toner constituting the toner image held on the image holding body 12 is charged with a reverse polarity due to a discharge occurring between them.
The ratio of the toner constituting the toner image held on the image holding body 12 to the opposite polarity due to the discharge is considered to depend on the discharge energy at the time of the discharge. This discharge energy is considered to be so small that the resistance of the transfer device 20 functions as a resistance that limits the discharge energy.
Therefore, by setting the voltage dependency of the resistance with respect to the transfer voltage of the transfer device 20 to 2.2 or less, the discharge energy between the recording medium P and the image carrier 12 is suppressed, and the chain white It is thought that omission is suppressed.

  The voltage dependency of the transfer device 20 on the transfer voltage may be 2.2 or less, but the smaller the value, the better, for example, 1.8 or 1.6 or 1.6 or less.

  The voltage dependency of the transfer device 20 is expressed by the following formula (1).

  P = R1 / R2 (1)

In the above formula (1), P indicates the voltage dependency of the resistance with respect to the transfer voltage of the transfer device 20, and R1 is the transfer device 20 when a transfer voltage of 1 kV is applied at a temperature of 22 ° C. and a humidity of 55% RH. R2 represents a resistance value, and R2 represents a resistance value of the transfer device 20 when a transfer voltage of 2 kV is applied at a temperature of 22 ° C. and a humidity of 55% RH.

More specifically, the voltage dependency of the transfer device 20 is measured using a measuring device 21 shown in FIG.
Specifically, the measurement device 21 is made of the same material and the same size as those of the transfer device 20 and a later-described base material (base material 60 in FIG. 4 described later) of the image carrier 12 provided in the image forming apparatus 10. The cylindrical member 40, the voltage application device 42, and the current measurement device 44 are included.

  The voltage application device 42 is a device that applies a voltage between the cylindrical member 40 and the transfer device 20. The current measuring device 44 is a device for measuring a current value of a current flowing between the cylindrical member 40 and the transfer device 20 when a voltage is applied by the voltage applying device 42.

The cylindrical member 40 may be the same material and the same size as a later-described base material (base material 60 in FIG. 4 described later) of the image carrier 12 provided in the image forming apparatus 10. Therefore, the diameter of the member 40 is the same as the diameter of a base material 60 described later of the image carrier 12 provided in the image forming apparatus 10, and the width direction length of the member 40 is the width direction of the base material 60. It is the same as the length (and the length in the width direction of the transfer device 20).
Then, the cylindrical member 40 and the transfer device 20 are arranged in contact with each other so as to have the same linear pressure as the linear pressure between the transfer device 20 and the image carrier 12 in the image forming apparatus 10. The transfer device 20 is arranged to rotate (in the direction of arrow B in FIG. 3) as the member 40 rotates (in the direction of arrow A in FIG. 3).

  R1 in the above formula (1) (resistance value when a transfer voltage of 1 kV is applied) rotates the cylindrical member 40 at a linear velocity of 300 mm / s in an environment of a temperature of 22 ° C. and a humidity of 55% RH. In the state where the transfer device 20 is also driven to rotate, current measurement is performed 2 seconds later and 3 seconds after a voltage of 1 kV is applied between the cylindrical member 40 and the transfer device 20 from the voltage application device 42. It is calculated from the average current value measured by the device 44 and the applied voltage (1 kV).

In addition, R2 (resistance value when a transfer voltage of 2 kV is applied) in the above formula (1) is the linear velocity of 300 mm / s for the cylindrical member 40 in an environment of a temperature of 22 ° C. and a humidity of 55% RH. In the state where the transfer device 20 is also driven and rotated, the voltage application device 42 applies a voltage of 2 kV between the cylindrical member 40 and the transfer device 20, 2 seconds later and 3 seconds later. It is calculated from the average current value measured by the current measuring device 44 and the applied voltage (2 kV).
Thereby, the voltage dependency of the resistance with respect to the transfer voltage of the transfer device 20 is calculated.

  The voltage dependency of the transfer device 20 may be 2.1 or less, but the value of R1 represented by the above formula (1) is preferably in the range of 1 MΩ or more and 1 GΩ or less for reasons of transfer power supply restrictions.

  Here, as described above, when the voltage dependency of the resistance with respect to the transfer voltage of the transfer device 20 provided in the image forming apparatus 10 is set to 2.2 or less, the chained white spots are considered to be suppressed. However, the present inventors have found that the contamination of the end face of the recording medium P increases as the chained white spots are suppressed. Note that “dirt of the end surface of the recording medium P” indicates an end surface of the recording medium P that intersects the thickness direction of the recording medium P.

  For this reason, as a result of further earnest studies, the present inventors have made the undercoat layer (the undercoat layer 62 in FIG. 4) constituting the image carrier 12 contain metal oxide particles, which will be described later. As a result, it has been found that both the suppression of chain-like white spots and the suppression of stains on the end face of the recording medium are realized.

When metal oxide particles are contained in the undercoat layer 62 of the image carrier 12, accumulation of electric charges in the undercoat layer 62 of the image carrier 12 or at the interface between the undercoat layer 62 and the upper layer is suppressed. However, the resistance of the image carrier 12 is considered to be lower than that in the case where no metal oxide particles are contained. For this reason, generally, by including metal oxide particles in the undercoat layer 62 of the image carrier 12, the discharge energy described above rises and chain white spots are remarkably generated. It was thought.
However, the present inventors set the voltage dependency of the resistance with respect to the transfer voltage of the transfer device 20 to 2.2 or less, and include metal oxide particles in the undercoat layer 62 of the image carrier 12, so that It has been found that the smearing of the end face of the recording medium P is further suppressed while suppressing the white voids in the shape.

  Hereinafter, the image carrier 12 and the transfer device 20 used in the image forming apparatus 10 of the present embodiment will be described in detail.

  4A, 4B, 4C, and 4D show examples of cross-sectional views of the image carrier 12. FIG. As shown in FIG. 4A, the image carrier 12 includes a conductive base material 60 configured in a columnar shape, an undercoat layer 62 formed on the base material 60, and an upper surface of the undercoat layer 62. And a photosensitive layer 63 formed thereon. The photosensitive layer 63 may have a two-layer structure of a charge generation layer 65 and a charge transport layer 66 as shown in FIG. 4B, and is 0 as shown in FIGS. 4C and 4D. The protective layer 64 may be provided on the photosensitive layer 63.

  In the image carrier 12 of the present embodiment, a conductive substrate is used as the substrate 60. The base material 60 includes a cylindrical member made of metal such as aluminum, copper, iron, nickel, and a cylindrical member made of glass or plastic, such as aluminum, copper, gold, silver, platinum, palladium, titanium, Nickel-chromium, stainless steel, cylinder-deposited metal such as indium, or a well-known cylinder-shaped conductive material treated by depositing a conductive metal compound such as indium oxide or tin oxide, or laminating a metal foil These materials are used.

As described above, the undercoat layer 62 includes metal oxide particles. The metal oxide particles have a resistance of 10 ² Ω · cm to 10 ¹¹ Ω · cm, 10 ⁴ Ω · cm to 10 ¹⁰ Ω · cm, or 10 ⁷ Ω · cm to 10 ¹⁰ Ω · cm. The metal oxide particle which has is mentioned.

  Examples of the metal oxide particles having the resistance value include metal oxide particles such as tin oxide, titanium oxide, and zinc oxide. The particle size of the metal oxide particles is 500 nm or less from the viewpoint of obtaining the dispersibility of the metal oxide particles in the coating liquid used for forming the undercoat layer 62 and suppressing the gelation of the coating liquid. 10 nm or more and 200 nm or less are mentioned.

  In addition, as this metal oxide particle, you may use in mixture of 2 or more types, such as a thing from which surface treatment differs, or a particle diameter.

  Examples of the content of the metal oxide particles contained in the undercoat layer 62 include 30% by volume or more and 60% by volume or less from the viewpoint of effectively suppressing contamination of the end face of the recording medium P.

  As the metal oxide particles contained in the undercoat layer 62, those subjected to surface treatment may be used. The surface treatment agent is selected from known materials as long as desired characteristics such as a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and a surfactant can be obtained. In particular, a silane coupling agent is good from the viewpoint of giving good electrophotographic characteristics. Further, a silane coupling agent having an amino group is preferable from the viewpoint of giving good blocking property to the undercoat layer 62. As the surface treatment method, any known method can be used, but a dry method or a wet method may be used.

  What is necessary is just to adjust the quantity of the silane coupling agent with respect to the metal oxide particle in the undercoat layer 62, a titanate coupling agent, and an aluminum coupling agent according to an electrophotographic characteristic.

The undercoat layer 62 preferably includes a receptive compound.
This accepting compound is a compound having an electron-withdrawing structure and having the property of extracting electrons out of holes and electrons generated in the charge generation pigment by light irradiation.
Examples of the accepting compound include a compound having a group that reacts with the metal oxide particles. Examples of the compound having a group that reacts with the metal oxide particles include a compound having a hydroxyl group or a quinone group, and the quinone group includes a compound having an anthraquinone structure. Furthermore, a receptive compound having an anthraquinone structure having a hydroxyl group is preferable. Examples of the compound having an anthraquinone structure having a hydroxyl group include a hydroxyanthraquinone compound and an aminohydroxyanthraquinone compound. Examples of the compound having an anthraquinone structure include anthraquinone, hydroxyanthraquinone, aminoanthraquinone, and aminohydroxyanthraquinone, and more specifically, alizarin, quinizarin, anthralfin, and purpurin.

The content of the accepting compound in the undercoat layer 62 is in the range of 0.01% by mass to 20% by mass and 0.05% by mass to 10% by mass with respect to the metal oxide particles contained in the undercoat layer 62. The range of mass% or less is mentioned.
By containing the acceptor compound within the above range in the undercoat layer 62, it is considered that the aggregation of the metal oxide particles is suppressed and the function of accepting the electrons of the metal oxide particles is also expressed.

Examples of the binder resin contained in the undercoat layer 62 include acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, and polyvinyl chloride. Resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenolic resin, phenol-formaldehyde resin, melamine resin, urethane resin and other known polymer resin compounds, and charge transport Examples thereof include charge transporting resins having a functional group and conductive resins such as polyaniline. Among these, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, epoxy resin and the like are preferable as the resin insoluble in the photosensitive layer 63.
The ratio of the accepting compound, metal oxide particles, and binder resin in the coating solution used to form the undercoat layer 62 may be adjusted according to the image carrier 12 to be produced.

  The undercoat layer 62 is prepared by dissolving the binder resin used in the undercoat layer 62 in a solvent, and further adding and dispersing metal oxide particles and, if necessary, the accepting compound. It is formed by applying the applied coating solution on the substrate 60.

  A known organic solvent may be used as a solvent used for adjusting the coating solution for the undercoat layer 62. In addition, a known method such as a roll mill may be used as a method for dispersing the metal oxide particles in the coating solution for the undercoat layer 62, and a known coating method such as a blade coating method may be used. This method may be used.

  The thickness of the undercoat layer 62 may be a preferable thickness from the viewpoint of realizing suppression of both the chain-like white spots and the contamination of the end face of the recording medium P in the image forming apparatus 10. A thickness of 15 μm or more and 20 μm or more and 50 μm or less can be mentioned.

The volume resistance of the undercoat layer 62 is preferably 10 ⁸ Ω · cm or more and 10 ¹³ Ω · cm or less, and may be 10 ⁸ Ω · cm or more and 10 ¹¹ Ω · cm or less.
If the volume resistance of the undercoat layer 62 is within the above range, it is considered that the suppression of both the chained white spots and the contamination of the end face of the recording medium P in the image forming apparatus 10 is effectively realized.
The volume resistance of the undercoat layer 62 may be measured in accordance with JIS K6911 using a circular electrode (for example, HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). Specifically, for example, it is measured using a circular electrode shown in FIG. FIG. 5 is a schematic plan view (A) and a schematic cross-sectional view (B) showing an example of a circular electrode for measuring volume resistance. The circular electrode shown in FIG. 5 includes a first voltage application electrode A ′ and a second voltage application electrode B ′. The first voltage application electrode A ′ has a cylindrical electrode part C ′ and a cylindrical shape having an inner diameter larger than the outer diameter of the cylindrical electrode part C ′ and surrounding the cylindrical electrode part C ′ at a constant interval. Ring-shaped electrode portion D ′. The undercoat layer 62 to be measured is sandwiched between the cylindrical electrode portion C ′ and the ring-shaped electrode portion D ′ and the second voltage application electrode B ′ in the first voltage application electrode A ′, and the first voltage application electrode A ′. The current I (A) flowing 5 seconds after the voltage V (V) is applied between the cylindrical electrode portion C ′ and the second voltage applying electrode B ′ in FIG. The resistance ρv (Ωcm) may be calculated. Here, in the following formula (3), t indicates the thickness of the undercoat layer 62.

  Formula (3) ρv = 19.6 × (V / I) × t

  A known photosensitive layer 63 may be used as the photosensitive layer 63 formed on the undercoat layer 62.

  For example, the charge generation layer 65 may be made of a known charge generation material and binder resin. As the charge generation material, a metal phthalocyanine pigment is preferable.

  Examples of the binder resin include organic photoconductive polymers such as poly-N-vinyl carbazole, polyvinyl anthracene, polyvinyl pyrene, and polysilane. Specifically, as the binder resin, polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide Resins, acrylic resins, polyacrylamide resins, polyvinyl pyridine resins, cellulose resins, urethane resins, epoxy resins, caseins, polyvinyl alcohol resins, polyvinyl pyrrolidone resins, and the like. You may use these individually or in mixture of 2 or more types.

  The charge generation layer 65 is formed by applying and drying a solution in which a charge generation material and a binder resin are dissolved in a solvent. Generally, the thickness of the charge generation layer 65 is 0.1 μm or more and 5 μm or less, or 0.2 μm or more and 2.0 μm or less.

  As the charge transport layer 66, a layer formed by a known technique may be used. For example, the charge transport layer 66 is formed containing a charge transport material and a binder resin, or is formed containing a polymer charge transport material.

  Examples of the charge transport material include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [ Pyrazoline derivatives such as pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline Aromatic tertiary amino compounds such as N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine and the like, 3- (4′-dimethylaminophenyl) 1,2,4-triazine derivatives such as -5,6-di- (4'-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzene Hydrazone derivatives such as zaldehyde-1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran, p Hole transport materials such as α-stilbene derivatives such as-(2,2-diphenylvinyl) -N, N-diphenylaniline, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and derivatives thereof Quinone compounds such as chloranil and broanthraquinone, tetraanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, xanthone compounds , Electron transport materials such as thiophene compounds, and Examples thereof include a polymer having a group composed of the above-mentioned compound in the main chain or side chain. These charge transport materials are used alone or in combination of two or more.

  Examples of the binder resin used for the charge transport layer 66 include acrylic resin, polyarylate, polyester resin, polycarbonate resin such as bisphenol A type or bisphenol Z type, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer. Examples thereof include insulating resins such as coalescence, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorine rubber, and organic photoconductive polymers such as polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene. The charge transport layer is formed by applying and drying a solution in which the charge transport material and the binder resin shown above are dissolved in a solvent.

  The film thickness of the charge transport layer 66 may be 5 μm or more and 50 μm or less, 10 μm or more and 40 μm or less.

  When the protective layer 64 is provided on the photosensitive layer 63, the protective layer 64 may be formed by including a curable resin, a cured resin film having a charge transporting compound, and a conductive material in the binder resin. . The film thickness of the protective layer 64 is 0.5 μm or more and 20 μm or less, and 2 μm or more and 10 μm or less.

  Next, the transfer device 20 used in the image forming apparatus 10 of the present embodiment will be described in detail.

  As shown in FIG. 2, the transfer device 20 is configured such that an elastic layer 20 </ b> B is provided on the outer peripheral surface of a cylindrical core body 20 </ b> A.

The core body 20A is a columnar member that functions as an electrode and a support member of the transfer device 20, and has conductivity. In the present embodiment, “conductive” means that the volume resistivity is less than 10 ¹³ Ωcm. As for the measurement method, the measurement method described for the volume resistivity of the undercoat layer 62 may be used.

  The core 20A is made of a conductive material such as a metal or alloy such as free-cutting steel, aluminum, copper alloy, or stainless steel; iron plated with chromium or nickel; a conductive resin; Any of these materials can be used as the core body 20A of the transfer device 20 in terms of strength and electrical characteristics.

  The outer diameter of the core 20A may be adjusted according to the image forming apparatus 10 to which the transfer device 20 is applied.

  An elastic layer 20B is laminated on the outer peripheral surface of the core body 20A. In the present embodiment, a case in which the elastic layer 20B is provided on the core 20A will be described, but a configuration in which another layer is interposed may be used. For example, an adhesive layer (not shown) may be provided between the core body 20A and the elastic layer 20B.

  Examples of the adhesive constituting this adhesive layer include polyolefin, chlorine rubber, acrylic, epoxy, polyurethane, nitrile rubber, vinyl chloride, vinyl acetate, polyester, phenol, and silicone rubber. Adhesives such as resins and silane coupling agents are used and are not particularly limited.

  The adhesive layer may be used alone or in combination with a plurality of layers. In addition, this adhesive layer includes carbon black such as conductivity imparted ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide Fine powders such as various metal oxide particles such as titanium oxide, tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution; The thickness of the adhesive layer is not particularly limited, but may be 5 μm or more and 100 μm or less, or 10 μm or more and 50 μm or less for reasons of adhesiveness, thickness variation, and resistance variation.

  The elastic layer 20B may be composed of only a non-foamed layer, or may have a non-foamed layer on the surface (outside) of the foamed layer. A plurality of foamed layers and non-foamed layers may be used. The elastic layer 20B is a layer made of a material that can be restored to its original shape even when deformed by applying an external force of 100 Pa.

The elastic layer 20B has a configuration in which a conductive agent is dispersed in a rubber material.
As the rubber material constituting the elastic layer 20B, epichlorohydrin, polyurethane, nitrile rubber, isoprene rubber, butadiene rubber, epichlorohydrin-ethylene oxide rubber, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR) ), Chlorinated polyisoprene, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), hydrogenated polybutadiene, butyl rubber, silicone rubber, or the like, or a material obtained by blending two or more thereof. Among these, urethane rubber, nitrile rubber, epichlorohydrin-ethylene oxide rubber, and ethylene-propylene-diene rubber (EPDM) are preferable. Since these rubber materials have elasticity, all are suitably used as materials constituting the elastic layer 20B. In particular, a synthetic rubber containing epichlorohydrin as a main component is excellent because the rubber itself has a certain level of electrical conductivity (ionic conductivity).

  When the elastic layer 20B is composed of a non-foamed layer and a foamed layer, the rubber material is preferably composed mainly of epichlorohydrin rubber, and other one or more kinds of organic rubbers such as NBR, EPDM, and SBR. , CR, etc. may be blended. Examples of epichlorohydrin rubber mainly used for the non-foamed layer and the foamed layer include, for example, Gechron 1100, Gechron 3100, Gechron 3101, Gechron 3103, Gechron 3103, and Gechron 3105 manufactured by Nippon Zeon Co., Ltd., each having different volume resistance values. , Gechron 3106 or the like may be used, and two or more grades may be used in combination in order to obtain the target voltage dependency.

As the conductive agent contained in the elastic layer 20B, an electronic conductive agent or an ionic conductive agent is used. From the viewpoint of adjusting the voltage dependency of the transfer device 20 to 2.2 or less, an ionic conductive agent is preferably used.
Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide, titanium oxide, oxide Examples thereof include various metal oxides such as tin-antimony oxide solid solution and tin oxide-indium oxide solid solution; and the like.
Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; alkaline earth metal perchlorates and chlorates; Can be mentioned. These conductive agents may be used alone or in combination of two or more.

  The hardness of the elastic layer 20B may be in the range of 15 ° to 90 ° in terms of Asker C hardness. Further, the thickness of the elastic layer 20B is sufficiently deformed when the outer peripheral surface of the transfer device 20 is placed in contact with the image carrier 12 or the recording medium P, so that the contact portion is stably formed and the size of the device can be reduced. From a viewpoint, the range of 1.5 mm or more and 7 mm or less and the range of 2 mm or more and 5 mm or less are mentioned.

  The elastic layer 20B may be formed directly on the core body 20A or via the adhesive layer or the like, and then the elastic layer surface may be polished to adjust the shape and outer diameter. Although there is no restriction | limiting in particular as a grinding | polishing method, Well-known methods, such as a cylindrical grinding | polishing (traverse and plunge) method and a centerless grinding | polishing method, are utilized.

Here, as described above, the voltage dependency on the transfer voltage of the transfer device 20 of the present embodiment is set to 2.2 or less.
As a method of adjusting the voltage dependency to be 2.2 or less, the type of material constituting the elastic layer 20B, the type and content of the electronic conductive agent and the ionic conductive agent contained in the elastic layer 20B are adjusted. Is mentioned.
In addition, as a conductive agent contained in the elastic layer 20B, it is better to use an ionic conductive rubber or an ionic conductive agent for voltage dependency reasons than to use an electronic conductive agent. In the case of using an electronic conductive agent, it is difficult to make the dispersion uniform. Therefore, it is preferable to use a large amount of a conductive agent having low conductivity so as to improve the dispersibility of the conductive agent.

  As described above, in the image forming apparatus 10 according to the present embodiment, the voltage dependency of the resistance with respect to the transfer voltage of the transfer apparatus 20 is set to 2.2 or less, and the undercoat layer 62 of the image carrier 12 is subjected to metal oxidation. It is considered that both the suppression of chain-like white spots and the suppression of stains on the end face of the recording medium P are realized by including the product particles.

  Hereinafter, the image forming apparatus of the present embodiment will be specifically described with reference to examples, but the present invention is not limited to these examples. Further, unless otherwise specified, “part” represents “part by mass” and “%” represents “mass%”.

<Production of transfer device 1 to transfer device 5>
-Production of transfer device 1-
-Formation of elastic layer-
-Epichlorohydrin rubber (trade name: 3106, manufactured by Nippon Zeon Co., Ltd.) 30 parts by mass-) Acrylic nitrile-butadiene rubber (trade name: DN401LL manufactured by Nippon Zeon Co., Ltd.) 70 parts by mass- Calcium carbonate (trade name: Whiten SB, 5 parts by mass blowing agent (trade name: N1000 # S, manufactured by Eiwa Chemical Co., Ltd.) 5
・ Vulcanization accelerator (stearic acid, manufactured by NOF Corporation) 1 part by mass ・ Vulcanizing agent: Sulfur (trade name: Parnock R, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass ・ Vulcanization accelerator: Thiuram (product) Name: Noxeller TET-G, manufactured by Ouchi Shinsei Chemical)
2 parts by mass, vulcanization accelerator: thiazole (trade name: Noxeller DM-P, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
1.5 parts by mass

  After the epichlorohydrin rubber of the elastic layer forming material is masticated with a 12-inch open roll for 3 minutes, during the rotation of the open roll, foaming of the elastic layer forming material is performed. A raw rubber was prepared by gradually adding an agent, calcium carbonate, and an ionic conductive agent, and finally kneading for 5 minutes after mixing the vulcanizing agent and the two types of vulcanization accelerators.

  As the core, a surface of a shaft (cylindrical member) having a diameter of 8 mm, a length of 310 mm, and a material SUM24L was subjected to nickel plating and chromate treatment.

  A cylindrical shape having an inner diameter of 7 mm was molded by an extruder using a dummy core and vulcanized at 150 ° C.

After vulcanization, the core was pressed and left for 4 hours. Then, the diameter (outer diameter) of this roll member was finished to Φ14 mm with a traverse grinding machine equipped with a grindstone particle size of # 60. The volume resistivity of this elastic layer was 3 × 10 ⁷ Ω · cm in an environment of 22 ° C. and 55% RH.
Thereby, the transfer apparatus 1 was produced.

  The voltage dependency of the produced transfer device 1 was measured and found to be 1.6.

This voltage dependence measurement was performed using the measuring device 21 described with reference to FIG.
Specifically, a cylindrical member made of aluminum having a diameter (outer diameter) of 30 mm, a length of 310 mm, and a thickness of 1 mm was prepared as the same member as the substrate 60 used for forming the image carrier 12. A line between the transfer device 20 and the image carrier 12 in an image forming apparatus (Fuji Xerox Co., Ltd., DocuCenter Color-III 4000 a450) on which the transfer device 20 is mounted on the cylindrical member 40. It was pressed with a spring load of 800 gf on one side so as to be the same as the pressure. As a result, the transfer device 20 is arranged to rotate (in the direction of arrow B in FIG. 3) as the cylindrical member 40 rotates (in the direction of arrow A in FIG. 3).

  Then, after being left in an environment of temperature 22 ° C. and humidity 55% RH for 24 hours, the cylindrical member 40 is rotated at a linear velocity of 300 mm / s in this environment (at this time, the transfer device 20 is also driven to rotate). A current value measured by the current measuring device 44 for 3 seconds after 2 seconds after applying a voltage of 1 kV between the cylindrical member 40 and the transfer device 20 from the voltage applying device 42; From the applied voltage (1 kV), R1 (resistance value when a transfer voltage of 1 kV was applied) in the above formula (1) was determined.

  In addition, the cylindrical member 40 is rotated at a linear velocity of 300 mm / s under the environment of the temperature of 22 ° C. and the humidity of 55% RH (the transfer device 20 is also driven to rotate), and the voltage application device 42 forms a cylindrical shape. From the current value measured by the current measuring device 44 for 2 seconds to 3 seconds after the voltage of 2 kV is applied between the member 40 and the transfer device 20 and the applied voltage (2 kV), the above formula is obtained. R2 (resistance value when a transfer voltage of 2 kV was applied) in (1) was determined.

  Then, the voltage dependency of the transfer device 1 was obtained by calculating Expression (1) (R1 / R2) from the values of R1 and R2.

-Production of transfer device 2-
In the production of the transfer device 1, instead of the epichlorohydrin rubber (trade name: 3106, manufactured by Nippon Zeon Co., Ltd.) used in the elastic layer in the transfer device 1, epichlorohydrin rubber (product name: EPION301, manufactured by Daiso Corporation) The same material and the same structure as the transfer device 1 except that acrylonitrile-butadiene rubber (trade name: DN401 made by Nippon Zeon Co., Ltd.) was used instead of acrylonitrile-butadiene rubber (trade name: DN401LL made by Nippon Zeon Co., Ltd.). The transfer device 2 was manufactured with the same content and the same manufacturing method.

  The voltage dependency of the produced transfer device 2 was measured by the same method as that of the transfer device 1 and found to be 1.8.

-Production of transfer device 3-
In the production of the transfer device 1, epichlorohydrin rubber (trade name: 3106, manufactured by Nippon Zeon Co., Ltd.) used in the elastic layer of the transfer device 1, 35 parts by mass of carbon black (trade name: FW200, manufactured by Cabot Japan) The transfer device 3 was manufactured with the same material, the same configuration, the same content, and the same manufacturing method as the transfer device 1 except that 25 parts by mass of epichlorohydrin rubber and 75 parts by mass of acrylonitrile-butadiene rubber were used. .

  The voltage dependency of the produced transfer device 3 was measured by the same method as that of the transfer device 1 and found to be 2.2.

-Production of transfer device 4-
In the production of the transfer device 1, the transfer device except that the carbon black (trade name: FW200 manufactured by Cabot Japan) of the transfer device 3 was replaced with 25 parts by mass of carbon black (trade name: FW1 manufactured by Cabot Japan). The transfer device 4 was manufactured using the same material, the same configuration, the same content, and the same manufacturing method as in FIG.

  The voltage dependency of the produced transfer device 4 was measured by the same method as that of the transfer device 1 and found to be 3.0.

-Production of transfer device 5-
In the production of the transfer device 4, the same material as the transfer device 4 except that the epichlorohydrin rubber in the transfer device 4 is 15 parts by mass, 75 parts by mass of acrylonitrile-butadiene rubber, and carbon black 35. The transfer device 5 was manufactured with the same configuration, the same content, and the same manufacturing method.

  The voltage dependency of the produced transfer device 5 was measured by the same method as that of the transfer device 1 and found to be 5.2.

<Preparation of image carrier 1 to image carrier 5>
-Production of image carrier 1-
First, a base material made of aluminum having a diameter (outer diameter) of 30 mm, a length of 310 mm, and a thickness of 1 mm was prepared as the base material 60.

Next, a coating solution for the undercoat layer 62 was prepared. First, 100 parts by mass of zinc oxide: (average primary particle diameter 70 nm: manufactured by Teika Co., Ltd .: specific surface area value 15 m ² / g) is stirred and mixed with 500 parts by mass of tetrahydrofuran, and a silane coupling agent (KBM603: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 .25 parts by mass was added and stirred for 2 hours. Tetrahydrofuran was then distilled off under reduced pressure and baked at 120 ° C. for 3 hours to prepare zinc oxide surface-treated with a silane coupling agent as metal oxide particles.

  And, the metal oxide particles, 162 parts by mass, 14.5 parts by mass of alizarin as the accepting compound, and 13.5 parts by mass of a curing agent (blocked isocyanate (Sumidule 3175: manufactured by Sumitomo Bayern Urethane Co., Ltd.)) , 15 parts by mass of butyral resin (ESLEC BM-1: manufactured by Sekisui Chemical Co., Ltd.), 38 parts by mass of a solution obtained by dissolving 85 parts by mass of methyl ethyl ketone, and 25 parts by mass of methyl ethyl ketone, For 2 hours to obtain a dispersion. As a catalyst, 0.005 parts by mass of dioctyltin dilaurate and 4.0 parts by mass of silicone resin particles (Tospearl 145: manufactured by GE Toshiba Silicone) were added to the resulting dispersion to prepare a coating solution for the undercoat layer 62. .

  The prepared coating solution for the undercoat layer 62 is applied on the above-mentioned base material (aluminum base material having a diameter of 30 mm, a length of 310 mm, and a thickness of 1 mm) by a dip coating method, and dried at 170 ° C. for 40 minutes. Curing was performed to obtain an undercoat layer 62 having a thickness of 25 μm.

The content (volume%) of the metal oxide particles contained in the undercoat layer 62 is cross-sectional observed with a scanning electron microscope, and the number of metal oxide particles contained in the cross-sectional unit area is determined. Find the number per volume, further determine the equivalent circle diameter of each metal oxide particle included in the unit area of the cross section, determine the average diameter of the particles included in the unit area from the value, from there, from that, per unit volume The content (% by volume) of the metal oxide particles contained in the film was determined from the ratio between the total volume obtained from the number of particles and the average diameter and the unit volume of the film, and found to be 50% by volume.
Further, as described above, the amount of the accepting compound contained in the undercoat layer 62 was 7% by mass.

  Next, a photosensitive layer was formed on the undercoat layer 62. First, X-ray diffraction spectrum Bragg angles (2θ ± 0.2 °) using Cukα as a charge generating material are at least 7.3 °, 16.0 °, 24.9 °, and 28.0 °. A mixture consisting of 15 parts by mass of hydroxygallium phthalocyanine having a diffraction peak, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) as a binder resin, and 200 parts by mass of n-butyl acetate, Dispersion was performed in a sand mill for 4 hours using 1 mmφ glass beads. To the obtained dispersion liquid, 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added and stirred to obtain a coating solution for a charge generation layer. The charge generation layer coating solution was dip coated on the undercoat layer 62 and dried at room temperature to form a charge generation layer 65 having a thickness of 0.2 μm.

Next, 1 part by mass of tetrafluoroethylene resin particles, 0.02 part by mass of the fluorine-based graft polymer, 5 parts by mass of tetrahydrofuran, and 2 parts by mass of toluene were sufficiently stirred and mixed to obtain a tetrafluoroethylene resin particle suspension. . Next, 4 parts by mass of N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine, a bisphenol Z-type polycarbonate resin ( Viscosity average molecular weight 40,000) After mixing and dissolving in 6 parts by mass, tetrahydrofuran 23 parts by mass, toluene 10 parts by mass, after adding the tetrafluoroethylene resin particle suspension and stirring and mixing, a fine flow path is provided. Using a high-pressure homogenizer equipped with a through-type chamber (trade name LA-33S, manufactured by Nanomizer Co., Ltd.), the dispersion treatment with the pressure increased to 400 kgf / cm ² was repeated 6 times to obtain a tetrafluoroethylene resin particle dispersion. It was. Further, 0.2 part by mass of 2,6-di-t-butyl-4-methylphenol was mixed to obtain a coating solution for the charge transport layer 66. This coating solution was applied onto the charge generation layer 65 and dried at 115 ° C. for 40 minutes to form a charge transport layer 66 having a thickness of 32 μm. In this way, the image carrier 1 was produced.

-Production of image carrier 2-
In the production of the image carrier 1, the content of the metal oxide particles in the coating liquid for the undercoat layer 62 of the image carrier 1 is 303 parts by mass, and the receptive compound (alizarin) in the coating liquid is used. An image carrier 2 was produced using the same material, the same configuration, the same content, and the same manufacturing method as the image carrier 1 except that the content was 25.2 parts by mass.

The content (volume%) of the metal oxide particles contained in the undercoat layer 62 of the produced image carrier 2 was measured under the same conditions and method as the image carrier 1 and found to be 60%.
Further, as described above, the amount of the accepting compound contained in the undercoat layer 62 was 7% by mass.

-Production of image carrier 3-
In the production of the image carrier 1, the content of the metal oxide particles in the coating liquid for the undercoat layer 62 of the image carrier 1 is 58.7 parts by mass, and the receptive compound (alizarin) in the coating liquid is used. The image carrier 3 was produced with the same material, the same structure, the same content, and the same manufacturing method as the image carrier 1 except that the content of) was 6.8 parts by mass.

The content (volume%) of the metal oxide particles contained in the undercoat layer 62 of the produced image carrier 3 was measured under the same conditions and method as the image carrier 1 and found to be 30%.
Further, as described above, the amount of the accepting compound contained in the undercoat layer 62 was 7% by mass.

-Production of image carrier 4-
In the production of the image carrier 1, the content of the metal oxide particles in the coating liquid for the undercoat layer 62 of the image carrier 1 is 12.4 parts by mass, and the receptive compound (alizarin) in the coating liquid is used. The image carrier 4 was produced with the same material, the same composition, the same content, and the same manufacturing method as the image carrier 1, except that the content of) was 0 mass%.

The content (volume%) of the metal oxide particles contained in the undercoat layer 62 of the produced image carrier 4 was measured under the same conditions and method as the image carrier 1 and found to be 10%.
Further, as described above, the amount of the accepting compound contained in the undercoat layer 62 was 0% by mass.

-Production of image carrier 5-
In the production of the image carrier 1, the content of the metal oxide particles in the coating liquid for the undercoat layer 62 of the image carrier 1 is 0 part by mass, and the accepting compound (alizarin) in the coating liquid is used. An image carrier 5 was produced with the same material, the same configuration, the same content, and the same manufacturing method as the image carrier 1 except that the content was 2.44 parts by mass.

The content (volume%) of the metal oxide particles contained in the undercoat layer 62 of the produced image carrier 5 was measured under the same conditions and method as the image carrier 1 and found to be 0%.
Further, as described above, the amount of the accepting compound contained in the undercoat layer 62 was 7% by mass.

(Examples 1 , 2, 4, 5, Reference Examples 1-8 , Comparative Examples 1 to 13)
Each of the adjusted image carrier 1 to image carrier 5 and transfer device 1 to transfer device 5 is combined in the combinations shown in Tables 1 and 2 to form an image forming apparatus (manufactured by Fuji Xerox Co., Ltd., DocuCenter Color-III 4000 a450). The A4 size recording medium (manufactured by Fuji Xerox Interfield, trade name P paper, weighing 64 g / m ² ) is the same as the transport direction of the recording medium. Thus, a running test was performed in which half-tone images with a 30% density were continuously formed on 100 sheets on the entire surface of the recording medium.

  In this running test, the charging potential of the image carrier by the charging device was −650 V, the exposure potential by the exposure device was −250 V, and the developing potential by the developing device was set to −450 V. Further, a transfer current of 12 μA / 100 mm / s was supplied to the transfer device.

  The running test is performed on each of the linear speeds (process speeds) 200 mm / s, 300 mm / s, 400 mm / s, and 500 mm / s of the outer peripheral surface of the image carrier and the transfer device by modifying the image forming apparatus. It was.

―Evaluation of chained white spots―
In the running test, the image formed on the 100th sheet was evaluated for the presence of chained white spots. The evaluation criteria were as follows. The evaluation results are shown in Tables 1 and 2.
G0: When no white spots appear on the entire surface of the paper G1: When no white spots appear on the paper except for the leading and / or trailing edges of the paper G2: White white that appears within 1/3 of the paper When missing parts are observed G3: When continuous white spots are seen on 1/3 or more sheets of paper

―Evaluation of dirt on the edge of recording media―
In the running test, the stain on the end face of each of the first to 100th recording sheets was evaluated. The evaluation criteria were as follows. The evaluation results are shown in Tables 1 and 2.
G0: When there is no end surface contamination G1: When end surface contamination is limited to within 2 mm G2: When end surface contamination is between 2 mm and 5 mm G3: When end surface contamination is 5 mm or more

As shown in Tables 1 and 2, Examples 1 , 2, 4, 5 and Reference Examples 1 to 2 in which metal oxide particles are contained in the undercoat layer and the voltage dependency of the transfer device is 2.2 or less . 8 , the metal oxide is not contained in the undercoat layer, or the voltage dependency of the transfer device exceeds 2.2, and the outer peripheral surfaces of the image carrier and the transfer device are higher than those of Comparative Examples 1 to 13. Until the linear velocity reached from a low speed of 200 mm / s to a high speed of 500 mm / s, both occurrence of chain white spots and contamination of the end face of the recording medium were suppressed.

Further, among Examples 1 , 2, 4, 5 and Reference Examples 1 to 8 , Example 1, Example 2, Example 4, Example 5, Reference Example 3 having a voltage dependency of 1.8 or less, In Reference Example 4 , Reference Example 6 , and Reference Example 7 , compared with Reference Example 1 , Reference Example 2 , Reference Example 5 , and Reference Example 8 in which the voltage dependence exceeds 1.8 and is 2.2 or less. As a result, it was difficult to generate chain-like white spots.

In Examples 1, 2, 4 and 5, among the Reference Example 1-8, Example 1 the content of the metal oxide particles is 60 vol% or less than 30 vol%, 2,4,5, reference example As for 1-5 , compared with the reference examples 6-8 whose content is outside this range, the result that both the chain-like white spots and the contamination of the end face are reduced even at higher speed (G1 or less) is obtained. It was.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image holding body 15 Charging apparatus 16 Exposure apparatus 18 Developing apparatus 20 Transfer apparatus 26 Fixing apparatus 60 Base material 62 Undercoat layer 63 Photosensitive layer

Claims (1)

On a conductive base material configured in a cylindrical shape, an undercoat layer containing metal oxide particles, and a photosensitive layer,
An image carrier in which the content of the metal oxide particles in the undercoat layer is 50% by volume or more and 60% by volume or less;
A charging device for charging the image carrier;
A latent image forming device that forms an electrostatic latent image on the image carrier charged by the charging device;
A developing device for developing the electrostatic latent image formed on the image carrier with toner;
A voltage dependency represented by the following formula (1) is 1.8 or less, and a transfer device that transfers a toner image formed on the image carrier to the recording medium by the developing device;
An image forming apparatus.
P = R1 / R2 (1)
(In formula (1), P represents the voltage dependency of the resistance with respect to the transfer voltage of the transfer device, and R1 represents the transfer device when the transfer voltage of 1 kV is applied at a temperature of 22 ° C. and a humidity of 55% RH. indicates resistance, R2 is shows the resistance value of said transfer device when the transfer voltage of 2kV is applied at a temperature 22 ° C. humidity 55% RH,
R1 and R2 are measuring devices including the transfer device, a cylindrical member having the same material as the base material of the image carrier, the same diameter and the same length in the width direction, a voltage applying device, and a current measuring device. Measured by
The voltage application device is a device that applies a voltage between the cylindrical member and the transfer device, and the current measurement device is configured such that when the voltage is applied by the voltage application device, the cylindrical member And a device for measuring a current value of a current flowing between the transfer device and the transfer device,
The cylindrical member and the transfer device are arranged in contact with each other so as to have the same linear pressure as the linear pressure between the transfer device and the image carrier in the image forming apparatus, and the cylindrical member is rotated. With the arrangement, the transfer device is rotated so that
R1 is a state in which the cylindrical member is rotated at a linear velocity of 300 mm / s under the environment of a temperature of 22 ° C. and a humidity of 55% RH, and the transfer device is driven and rotated from the voltage application device to the cylinder. Calculated from the average current value measured by the current measuring device in 3 seconds from 2 seconds after applying a voltage of 1 kV between the transfer member and the transfer device, and the applied voltage (1 kV) ,
R2 is a state in which the cylindrical member is rotated at a linear velocity of 300 mm / s in an environment of a temperature of 22 ° C. and a humidity of 55% RH, and the transfer device is also driven to rotate, and the cylinder from the voltage application device to the cylinder. Calculated from the average current value measured by the current measuring device in 3 seconds from 2 seconds after applying a voltage of 2 kV between the transfer member and the transfer device, and the applied voltage (2 kV) The )