JP2012242506A - Electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member which has ease of controlling volume resistivity and small environmental dependence of conductivity, and reduces the occurrence of ghost due to an increase in the cumulated number of printings.SOLUTION: The electrifying member includes a conductive base and an elastic layer, and the elastic layer contains particles including at least one of (A) crystal of an iron lithium phosphate containing carbon and (B) crystal of an iron lithium phosphate containing at least one or more kinds of metal elements selected from a group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti.

Description

  The present invention relates to a charging member.

In recent years, in an electrophotographic apparatus, a charging member used for contact charging of an electrophotographic photosensitive member generally has a configuration including a conductive base and a conductive elastic layer formed on the base. The volume resistivity of the conductive elastic layer in the charging member is usually adjusted within the range of 1 × 10 ² Ω · cm to 1 × 10 ⁹ Ω · cm. For adjusting the volume resistance of the elastic layer, an ion conductive agent or electronic conductive particles are used.

  An elastic layer made conductive using electron conductive particles has a small change in volume resistivity with respect to a change in content in the elastic layer, although the volume resistivity is less dependent on the environment. On the contrary, the volume resistivity of the ionic conductive agent hardly changes even if the content in the elastic layer varies. However, there is a problem that the volume resistance is highly dependent on the environment.

  Therefore, Patent Documents 1 and 2 disclose an image forming apparatus in which the volume resistivity is less dependent on the environment and the change in the volume resistivity with respect to the change in the content is small by using both the electronic conductive agent and the ionic conductive agent. An electrically conductive roller is disclosed.

JP-A-6-73286 JP 2007-154123 A

However, in the recent trend of improving the process speed and the number of printable pages in an electrophotographic apparatus, a conventional charging member has been examined. As the number of printed sheets increases, ghost images are likely to occur. The present inventors have found that
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a charging member that has a stable volume resistivity and hardly causes ghosts in an electrophotographic image even when a large number of electrophotographic images are formed.

According to the present invention, a charging member having a conductive substrate and an elastic layer,
The elastic layer provides a charging member containing particles containing at least one crystal selected from the group consisting of the following (A) and (B):
(A) a crystal of lithium iron phosphate containing carbon,
(B) A crystal of lithium iron phosphate containing at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti.

  According to the present invention, it is possible to obtain a charging member that is easy to control the volume resistivity and has a small environmental dependency and is less likely to generate a ghost accompanying an increase in the cumulative number of printed sheets.

It is sectional drawing which shows an example of the charging member of this invention. It is a schematic diagram showing an example of an electrophotographic apparatus using the charging member of the present invention. It is a schematic diagram for demonstrating the volume resistivity measurement of the charging roller in this invention. It is a schematic diagram which shows the crystal structure of lithium iron phosphate in this invention.

The present invention is described in detail below. However, the present invention is not limited to this embodiment.
In order to achieve the above-mentioned object, the present inventors have investigated the cause of the ghost that is likely to occur in the electrophotographic image over time in the conventional charging member. As a result, the repeated discharge from the charging member to the electrophotographic photosensitive member causes the polymer in the elastic layer of the charging member to deteriorate, resulting in a decrease in ionic conductivity and a decrease in the amount of charged charge supplied. I found out.
Therefore, the present inventors developed a stable volume resistivity by expressing ionic conduction in the particles dispersed in the polymer, not in the polymer, and making the ionic conduction mechanism in the particles difficult to break. It has been found that a charging member can be obtained which has a large number of electrophotographic images and hardly causes ghosts in the electrophotographic images. The present invention is based on such new findings.
FIG. 2 shows a schematic configuration of an electrophotographic apparatus to which the present invention can be applied, and has a charging member. The electrophotographic photosensitive member 21 as a member to be charged is a drum-shaped electrophotographic photosensitive member having a conductive base 21b such as aluminum and a photosensitive layer 21a formed on the base 21b as basic constituent layers. It is rotationally driven at a predetermined peripheral speed in the clockwise direction in the figure around the support shaft 21c.

  Here, a charging roller which is one of charging members will be described. The charging roller 1 is disposed in contact with the electrophotographic photosensitive member 21 to charge (primary charging) the electrophotographic photosensitive member to a predetermined polarity and potential. The charging roller 1 is composed of a conductive substrate 11 and an elastic layer 12 formed on the conductive substrate 11, and the both ends of the conductive substrate 11 are driven by rotation of the electrophotographic photosensitive member 21 by pressing means (not shown). Followed rotation.

  When a predetermined direct current (DC) bias is applied to the conductive substrate 11 from the power source 22 and the rubbing power source 23, the electrophotographic photosensitive member 21 is contact-charged to a predetermined polarity and potential. The electrophotographic photosensitive member 21 whose peripheral surface is charged by the charging roller 1 is then subjected to exposure of target image information (laser beam scanning exposure, slit exposure of a document image, etc.) by an exposure device 24, so that the peripheral surface has a target. An electrostatic latent image corresponding to the image information is formed.

  The electrostatic latent image is then successively visualized as a toner image by the developing member 25. This toner image is then synchronized with the rotation of the electrophotographic photosensitive member 21 from a paper feeding means (not shown) by the transfer member 26 and transferred at a proper timing between the electrophotographic photosensitive member 21 and the transfer member 26. Are sequentially transferred to the transfer material 27 conveyed to the substrate. The transfer member 26 in this example is a transfer roller, and the toner image on the electrophotographic photosensitive member 21 side is transferred to the transfer material 27 by charging with the reverse polarity to the toner from the back of the transfer material 27.

The transfer material 27 having received the transfer of the toner image on the surface is separated from the electrophotographic photosensitive member 21 and conveyed to a fixing means (not shown) to receive image fixing and output as an image formed product. Alternatively, in the case of forming an image on the back side, it is conveyed to a re-conveying means to the transfer unit.
The peripheral surface of the electrophotographic photosensitive member 21 after the image transfer is subjected to pre-exposure by the pre-exposure device 28, and residual charges on the electrophotographic photosensitive drum are removed (static elimination). Known means can be used for the pre-exposure device 28. For example, an LED chip array, a fuse lamp, a halogen lamp, and a fluorescent lamp can be preferably exemplified.

The peripheral surface of the electrophotographic photosensitive member 21 from which the charge has been removed is cleaned by the cleaning member 29 after removal of adhering contaminants such as toner remaining after transfer, and is repeatedly used for image formation.
The charging roller 1 may be driven and driven by the electrophotographic photosensitive member 21 driven to move the surface, may not be rotated, or has a predetermined circumference in the forward or reverse direction in the surface moving direction of the electrophotographic photosensitive member 21. You may make it actively rotate at a speed.

  When the electrophotographic apparatus is used as a copying machine, the exposure is reflected light or transmitted light from the original, or the original is read as a signal, and a laser beam is scanned or the LED array is driven based on this signal. Alternatively, the liquid crystal shutter array may be driven. Examples of the electrophotographic apparatus that can use the charging member of the present invention include a copying machine, a laser beam printer, an LED printer, or an electrophotographic application apparatus such as an electrophotographic plate making system.

The charging member according to the present invention has a conductive base and an elastic layer, and at least one crystal of lithium iron phosphate selected from the group consisting of the following (A) and (B) is contained in the elastic layer. Containing particles.
(A) Crystal of lithium iron phosphate containing carbon.
(B) A crystal of lithium iron phosphate containing at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr and Ti.

The crystal structure of lithium iron phosphate is an olivine structure (FIG. 4) in which oxygen is a hexagonal close-packed structure, lithium and iron have a hexacoordinate octahedron, and phosphorus has a tetracoordinate tetrahedron. Since the —PO bond is strong, the crystal structure is stable.
Here, in the crystal of lithium iron phosphate, since iron atoms are isolated in the crystal and have a strong crystal structure, the electronic conductivity and the diffusion coefficient of lithium ions are low, and the conductivity is low. Therefore, it was possible to improve the electronic conductivity and the lithium ion diffusion rate by incorporating different metal elements such as carbon, Co, and Nb into the lithium iron phosphate crystal.
And, the present inventors made the elastic layer stable by including particles containing lithium iron phosphate crystals combined with carbon atoms or specific metal elements as described above in the elastic layer. It has been found that conductivity can be imparted.

  That is, as described above, conventionally, as a means for facilitating control to a desired volume resistivity at the time of manufacturing a charging roller, or as a means for reducing fluctuations in volume resistivity with respect to changes in the charging roller usage environment, an ionic conductive agent, A method of using electronically conductive particles in combination is known. Conventionally, as an ionic conductive agent, an electrolyte such as an alkaline salt such as lithium perchlorate is used, and in the polymer, the ion is ionized into a cation and an anion. To express. In such a case, ions are diffused and moved by the movement of the polymer chain, so that the ionic conductivity is affected by the polymer structure. In the charging roller, the polymer is deteriorated due to the influence of discharge during charging, and the ion conductivity is lowered. For the above reasons, a ghost image is generated because the charged charge supply amount decreases.

On the other hand, since the crystal of lithium iron phosphate in the particles according to the present invention has both electronic and ionic conductivity properties, it can be easily controlled to have a desired volume resistivity and is less dependent on the environment. . In addition, since lithium ions diffuse and move within the lithium iron phosphate crystal, it is less susceptible to polymer degradation.
Furthermore, since the crystal structure of lithium iron phosphate has high stability, the crystal structure is not easily broken even when discharge energy is applied when the charging roller is used. For this reason, the ion conductivity is stably maintained, and the supply of charged charges is unlikely to be lowered with respect to long-time use.

  The crystal (A) of lithium iron phosphate containing carbon includes the following production method. A mixed solution containing a carbon-containing compound, a lithium-containing compound, an iron-containing compound, and a phosphorus-containing compound is heated in a mist state and thermally decomposed to produce a fine powder composed of a lithium iron phosphate precursor containing carbon, followed by firing. There is a way. There is also a method in which, after synthesis of lithium iron phosphate, mixed and pulverized with a carbon-containing compound, heated in an inert gas atmosphere such as argon gas or nitrogen gas, the carbon-containing compound is thermally decomposed and coated. As for content of carbon in the crystal | crystallization (A) of lithium iron phosphate, 1-12 mass% is preferable with respect to lithium iron phosphate. When the content is 1% by mass or more, the conductivity of the particles is sufficient, and the charged charge supply amount is not insufficient, so that the ghost image is further reduced. When the content is 12% by mass or less, ion conductivity in the particles becomes sufficient, and the volume resistivity can be easily controlled in the charging roller.

(B) A crystal of lithium iron phosphate containing at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti has the following manufacturing method. . Contains lithium iron phosphate materials such as Li ₂ CO ₃ , NH ₄ H ₂ PO _4, Fe ₂ C ₂ O ₄ .2H ₂ O, and the metal element groups Co, Mn, Mg, Mo, Nb, Zr, and Ti A small amount of acetone is added to the compound to be pulverized and mixed with a zirconia ball mill. Then, there is a method of drying by vacuum drying, heating at 300 to 400 ° C. in an inert gas atmosphere in a rotary furnace such as a rotary tube furnace, and then firing at 700 to 800 ° C. Compounds containing Co, Mn, Mg, Mo, Nb, Zr, Ti include cobalt sulfate heptahydrate, manganese methoxide, manganese acetate tetrahydrate, magnesium sulfate, magnesium oxalate dihydrate, chloride Examples include molybdenum, niobium phenoxide, zirconium ethoxide, titanium methoxide, and titanium sulfate. The content of at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti in the lithium iron phosphate crystal (B) includes Fe and the contained metal element. 1-10 mol% is preferable with respect to the total molar amount. If it is 1 mol% or more, the conductivity of the particles becomes sufficient, and the charged charge supply amount is not insufficient, so that the ghost image is reduced. When the amount is 10 mol% or less, the stability of the crystal structure peculiar to lithium iron phosphate is maintained, and even when the discharge energy is applied when using the charging roller, the ion conductivity is not lowered and the ghost image is reduced. .

  It is preferable that at least one crystal of lithium iron phosphate selected from the group consisting of (A) and (B) is blended in an amount of 1 part by mass to 60 parts by mass with respect to 100 parts by mass of the base polymer. When the amount is 1 part by mass or more, it is easy to control the volume resistivity of the charging roller and has low environmental dependency, and the occurrence of ghosts associated with an increase in the number of accumulated prints is reduced. Moreover, at 60 mass parts or less, the deterioration of workability by the viscosity of an unvulcanized rubber composition rising too much can be prevented.

1A and 1B are schematic views of a charging roller 1 as an example of the charging member of the present invention. FIG. 1B includes a cored bar 11, a semiconductive elastic layer 12 provided on the outer periphery thereof, and a surface layer 13. FIG. 1A shows a single-layer configuration in which only the semiconductive elastic layer 12 is mounted on the core metal 11. From the viewpoint of productivity such as the number of steps, a single layer configuration is more preferable.
The elastic layer is a mixture of base polymer and additives. The base polymer is not particularly limited as long as it is a material exhibiting rubber elasticity in the actual use temperature range of the charging member. Examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene (SBR), butyl rubber (IIR), ethylene-propylene-diene terpolymer rubber (EPDM), epichlorohydrin. Homopolymer (CHC), epichlorohydrin-ethylene oxide copolymer (CHR), epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (CHR-AGE), acrylonitrile-butadiene copolymer (NBR), acrylonitrile-butadiene copolymer Examples thereof include a hydrogenated polymer (H-NBR), chloroprene rubber (CR), and acrylic rubber (ACM, ANM). Moreover, thermoplastic elastomers such as polyolefin-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and vinyl chloride-based thermoplastic elastomers are also included. Two or more of these base polymers may be blended. In addition, fillers, processing aids, crosslinking aids, crosslinking accelerators, crosslinking accelerators, crosslinking retarders, dispersants, etc. that are commonly used as rubber compounding agents are added to the base polymer as necessary. Sometimes.

Further, in the present invention, carbon materials such as carbon black and graphite; oxides such as titanium oxide and tin oxide; metals such as Cu and Ag; conductive particles obtained by coating the surface of the particles with oxides or metals and the like. An electronic conductive agent may be used in combination.
Examples of the mixing method of these raw materials include a mixing method using a closed mixer such as a Banbury mixer and a pressure kneader, and a mixing method using an open mixer such as an open roll.

  As a method for forming the elastic layer, an unvulcanized semiconductive rubber composition is extruded into a tube shape by an extruder, vulcanized and molded with a vulcanizing can, and a conductive substrate is press-fitted. There is a method of polishing to a desired outer diameter. Further, an unvulcanized semiconductive rubber composition is coextruded into a cylindrical shape around a conductive substrate by an extruder equipped with a cross head, fixed inside a mold having a desired outer diameter, vulcanized, The method etc. which obtain a molded object can also be mentioned.

The surface of the elastic layer may be subjected to surface modification by ultraviolet irradiation, electron beam irradiation, or the like so that dirt such as toner and paper powder does not easily adhere. A surface layer may be applied. As a method for forming the surface layer, the surface layer material as described above is dissolved or dispersed in a solvent, and the surface of the elastic layer is coated by a coating method such as dipping, ring coating, beam coating, roll coater or spraying. And the like. As the surface layer, a known coating layer is generally used. For example, a binder polymer such as acrylic polymer, polyurethane, polyamide, polyester, polyolefin, silicone, carbon black, graphite, titanium oxide, tin oxide, etc. Oxides: Metals such as Cu and Ag, conductive particles obtained by coating the surface of the particles with oxides and metals, and conductive particles; ionic electrolytes such as LiClO ₄ , KSCN, NaSCN, and LiCF ₃ SO ₃ are dispersed in appropriate amounts. Therefore, a sol-gel film made of polysiloxane having a desired electric resistance value or an oxyalkylene group is used.

In the present invention, a good image is obtained when the surface layer is not provided, and a single layer is more preferable in consideration of cost.
The charging roller according to the present invention may be provided with functional layers such as an adhesive layer, a diffusion prevention layer, a base layer, and a primer layer in addition to the elastic layer and the surface coating layer as necessary.

The present invention will be described in more detail with reference to the following examples, but these examples do not limit the present invention. Hereinafter, unless otherwise specified, commercially available high-purity products were used unless otherwise specified.
(Preparation of lithium iron phosphate particles)
The production examples of lithium iron phosphate particles (A) or (B) used in the present invention are shown below.

(Production Example 1) Sample 1: Production of particles containing carbon-encapsulated lithium iron phosphate crystals.
LiNO ₃ , Fe (NO) ₃ , and (H ₃ PO ₄ ) are mixed at a molar ratio of Li: Fe: P = 1: 1: 1 so that the LiNO ₃ concentration is 0.1 mol / L. Adjusted. 60% by mass of sucrose is added to this aqueous solution, and ultrasonic waves of 1.6 MHz are added to this solution to form a mist, which is then introduced into a horizontal reaction tube set to 1.5 m at 400 ° C. with an air flow rate of 5 L / min. The precursor particles were obtained. The precursor particles were calcined at a temperature of 800 ° C. for 2 hours to obtain particles containing carbon-encapsulated lithium iron phosphate crystals.
(Carbon content analysis)
The measurement of the carbon content was performed using a trace carbon analyzer (EMIA-100 type, manufactured by Horiba), and the value obtained by rounding off the two digits after the decimal point was defined as the carbon content. When the obtained carbon-encapsulated lithium iron phosphate particles were measured, the carbon content was 12.0% by mass.

(Production Example 2) Sample 2: Production of particles containing LiFe _0.97 Ti _0.02 Co _0.01 PO ₄ crystal.
A 60 L reaction vessel was charged with 40 L of an aqueous solution containing 23 mol of NaOH and 11 mol of Na ₂ CO ₃ , and replaced with nitrogen gas, and maintained at a temperature of 60 ° C. To this, 20 L of an aqueous solution containing 18 mol of FeSO ₄ and 0.9 mol of Fe ₂ (SO ₄ ) ₃ was added with nitrogen aeration and stirring to obtain a suspension containing iron hydroxide particles at a temperature of 60 ° C. For 60 minutes. Next, with the temperature kept at 60 ° C., air was aerated at 10 L / min, and an oxidation reaction was performed for 2 hours. The obtained suspension was filtered, washed and dried to obtain fine-particle iron oxide.

6 L of the suspension obtained after oxidation (1.8 mol as Fe) was charged into a 15 L reaction vessel, and 1 L of an aqueous solution having a Na ₂ CO ₃ concentration of 0.54 mol / L was added and mixed. While mixing at room temperature, 1 L of an aqueous solution in which 0.036 mol of Ti (SO ₄ ) ₂ and 0.018 mol of CoSO ₄ .7H ₂ O were dissolved was added dropwise over 1 hour. The obtained suspension was filtered, washed, and dried to obtain particles containing Ti and Co-treated fine iron oxide crystals.

Ti, Co-treated fine particle iron oxide 0.05 mol (0.15 mol as a metal content), Li ₂ CO ₃ 0.079 mol, (NH ₄ ) ₂ HPO ₄ 0.15 mol and glucose 6 g were put in an 80 mL zirconia ball mill. Further, 20 mL of pure water was added and mixed at 250 rpm for 24 hours. After drying at a temperature of 150 ° C., the mixture was pulverized in an agate mortar and calcined in a nitrogen atmosphere at a temperature of 800 ° C. for 6 hours to obtain LiFe _0.97 Ti _0.02 Co _0.01 PO ₄ crystal-containing particles.

(Production Example 3) Sample 3: Production of particles containing LiFe _0.96 Ti _0.02 Mn _0.02 PO ₄ crystal.
A 60 L reaction vessel was charged with 40 L of an aqueous solution containing 24 mol of NaOH and 12 mol of Na ₂ CO ₃ , nitrogen gas was passed through and replaced, and the temperature was maintained at 60 ° C. To this, 20 L of an aqueous solution containing 18 mol of FeSO ₄ , 0.9 mol of Fe ₂ (SO ₄ ) ₃ , 0.4 mol of Ti (SO ₄ ) ₂ and 0.4 mol of MnSO ₄ was added while stirring with nitrogen. Then, a suspension containing iron hydroxide particles was prepared and mixed at 60 ° C. for 60 minutes. Next, with the temperature kept at 60 ° C., air was aerated at 10 L / min, and an oxidation reaction was performed for 2 hours. The obtained suspension was filtered, washed and dried to obtain fine-particle iron oxide.

Ti, Mn-doped iron oxide 0.05 mol (0.15 mol as a metal content) obtained above, 0.080 mol of Li ₂ CO ₃ , 0.15 mol of (NH ₄ ) ₂ HPO ₄ and 5 g of glucose in a zirconia ball mill I put it in. Further, 20 mL of pure water was added and mixed at 250 rpm for 24 hours. After drying at a temperature of 150 ° C., the mixture was pulverized in an agate mortar and calcined at a temperature of 800 ° C. for 12 hours in a nitrogen atmosphere to obtain LiFe _0.96 Ti _0.02 Mn _0.02 PO ₄ crystal-containing particles.

(Production Example 4) Sample 4: Production of LiFe _0.98 Mg _0.02 PO ₄ crystal-containing particles.
Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, MgC ₂ O ₄ .2H ₂ O were changed to Li: Fe: Mg: P = 1: 0.98: 0.02: 1. The mixture was mixed at a molar ratio, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain a LiFe _{0.98 Mg 0.02} PO ₄ crystal containing particles.

(Production Example 5) Sample 5: Production of LiFe _0.99 Mo _0.01 PO ₄ crystal-containing particles.
LiOH.H ₂ O, NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, and MoCl ₅ have a molar ratio of Li: Fe: Mo: P = 1: 0.99: 0.01: 1. A small amount of acetone was added, and pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain a LiFe _{0.99 Mo 0.01} PO ₄ crystal containing particles.

Preparation Example 6 Sample 6: Preparation of LiFe _0.99 Nb _0.01 PO ₄ Crystal-Containing Particles Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, Nb (C ₆ H ₅ O) ₅ was mixed at a molar ratio of Li: Fe: Nb: P = 1: 0.99: 0.01: 1, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain a LiFe _{0.99 Nb 0.01} PO ₄ crystal containing particles.

Preparation Example 7 Sample 7: Preparation of LiFe _0.99 Zr _0.01 PO ₄ Crystal-Containing Particles Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, Zr (C ₂ H ₅ O) ₄ was mixed at a molar ratio of Li: Fe: Zr: P = 1: 0.99: 0.01: 1, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain a LiFe _{0.99 Zr 0.01} PO ₄ crystal containing particles.

Preparation Example 8 Sample 8: Preparation of LiFe _0.98 Ti _0.02 PO ₄ Crystal-Containing Particles A 60 L reaction vessel was charged with 40 L of an aqueous solution containing 55.2 mol of NaOH and purged with nitrogen gas to replace the temperature. Maintained at 80 ° C. To this, 20 L of an aqueous solution containing 6 mol of FeSO ₄ , 6 mol of Fe ₂ (SO ₄ ) ₃ and 0.36 mol of Ti (SO ₄ ) ₂ was added with nitrogen aeration and stirring, and the temperature was 80 ° C. for 3 hours. Mixed. The obtained suspension was filtered, washed and dried to obtain fine particle Ti-doped iron oxide.
In the above, 0.05 mol of Ti-doped iron oxide (0.15 mol as a metal content), 0.079 mol of Li ₂ CO ₃ , 0.153 mol of (NH ₄ ) ₂ HPO ₄ and 4 g of glucose were placed in an 80 mL planetary ball mill container. Furthermore, 20 mL of pure water was added and mixed at 250 rpm for 12 hours. After drying at a temperature of 120 ° C., the mixture was pulverized in an agate mortar and fired at 800 ° C. for 6 hours in an N ₂ atmosphere to obtain LiFe _0.98 Ti _0.02 PO ₄ crystal-containing particles.

(Production Example 9) Sample 9: Production of carbon-coated LiFe _0.99 Mo _0.01 PO ₄ crystal-containing particles LiOH.H ₂ O, NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, MoCl ₅ The mixture was mixed so that the molar ratio of Li: Fe: Mo: P = 1: 0.99: 0.01: 1 was added, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Thereafter, refined coal pitch with a softening temperature of 250 ° C. was added, pulverized and mixed, and then fired at 800 ° C. for 10 hours to obtain carbon-coated LiFe _0.99 Mo _0.01 PO ₄ crystal-containing particles.

(Production Example 10) Sample 10: Production of carbon-containing lithium iron phosphate crystal-containing particles LiNO ₃ , Fe (NO) ₃ , and (H ₃ PO ₄ ) in a molar ratio of Li: Fe: P = 1: 1: The aqueous solution was adjusted so that the concentration of LiNO ₃ was 0.1 mol / L. 2% by mass of sucrose is added to this aqueous solution, and 1.6 MHz ultrasonic waves are added to this solution to form a mist, which is introduced into a horizontal reaction tube set at a temperature of 1.5 m at a temperature of 400 ° C. with an air flow rate of 5 L / min. As a result, precursor particles were obtained. The precursor particles were calcined at a temperature of 800 ° C. for 2 hours to obtain carbon-containing lithium iron phosphate crystal-containing particles.

(Production Example 11) Sample 11: Production of carbon-containing lithium iron phosphate crystal-containing particles.
LiNO ₃ , Fe (NO) ₃ and (H ₃ PO ₄ ) are mixed at a molar ratio of Li: Fe: P = 1: 1: 1 so that the concentration of LiNO ₃ is 0.1 mol / L. The aqueous solution was adjusted so that 5% by mass of sucrose is added to this aqueous solution, and 1.6MHz ultrasonic waves are added to this solution to form a mist, which is introduced into a horizontal reaction tube set at a temperature of 1.5 m at a temperature of 400 ° C. with an air flow rate of 5 L / min. As a result, precursor particles were obtained. The precursor particles were calcined at a temperature of 800 ° C. for 2 hours to obtain carbon-containing lithium iron phosphate crystal-containing particles.

(Production Example 12) Sample 12: Production of carbon-containing particles containing lithium iron phosphate crystals.
LiNO ₃ , Fe (NO) ₃ and (H ₃ PO ₄ ) are mixed at a molar ratio of Li: Fe: P = 1: 1: 1 so that the concentration of LiNO ₃ is 0.1 mol / L. The aqueous solution was adjusted so that 70% by mass of sucrose is added to this aqueous solution, and 1.6 MHz ultrasonic waves are added to this solution to form a mist, which is introduced into a horizontal reaction tube set at a temperature of 1.5 m at a temperature of 400 ° C. with an air flow rate of 5 L / min. As a result, precursor particles were obtained. The precursor particles were calcined at a temperature of 800 ° C. for 2 hours to obtain carbon-containing lithium iron phosphate crystal-containing particles.

(Production Example 13) Sample 13: Production of LiFe _0.999 Mg _0.001 PO ₄ Crystal-Containing Particles Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, MgC ₂ O ₄ .2H ₂ O was mixed at a molar ratio of Li: Fe: Mg: P = 1: 0.999: 0.001: 1, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain LiFe _{0.999 Mg 0.001} PO ₄ crystal containing particles.

(Preparation Example 14) Sample 14: Preparation of LiFe _0.9 Mg _0.1 PO ₄ crystal-containing particles.
Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, MgC ₂ O ₄ .2H ₂ O are mixed with Li: Fe: Mg: P = 1: 0.9: 0.1: 1. The mixture was mixed at a molar ratio, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain LiFe _{0.9 Mg} 0.1 PO ₄ crystal containing particles.

(Production Example 15) Sample 15: Production of LiFe _0.85 Mg _0.15 PO ₄ crystal-containing particles.
Li ₂ CO ₃ , NH ₄ H ₂ PO ₄ , FeC ₂ O ₄ .2H ₂ O, MgC ₂ O ₄ .2H ₂ O are Li: Fe: Mg: P = 1: 0.85: 0.15: 1 The mixture was mixed at a molar ratio, a small amount of acetone was added, and the mixture was pulverized and mixed in a zirconia ball mill for 24 hours. Then, it vacuum-dried and it heated at the temperature of 350 degreeC by argon tube atmosphere in argon atmosphere for 10 hours. Then, they fired at a temperature 800 ° C. 10 hours _to obtain a LiFe _{0.85 Mg 0.15} PO ₄ crystal containing particles.
Table 1 summarizes the types of metal elements contained, the metal element content, and the carbon content of the above-described Samples 1-15.
The metal element content is the content of the metal element group with respect to the total molar amount of Fe and at least one metal element group selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr and Ti. It means the sum of mol%.

[Example 1]
(Preparation of rubber material)
The materials shown in Table 2 were kneaded and mixed with A using a 6 liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin). A kneading mixing conditions were set to a filling rate of 60 vol%, a blade rotation number of 35 rpm, and mixing for 16 minutes to obtain an A kneading rubber composition.

A kneading mixing conditions were set to a filling rate of 60 vol%, a blade rotation number of 35 rpm, and mixing for 16 minutes to obtain an A kneading rubber composition.
The materials shown in Table 3 were mixed with 177 parts by mass of this A-kneaded rubber mixture using an open roll having a roll diameter of 12 inches. The mixing conditions were a front roll rotational speed of 8 rpm, a rear roll rotational speed of 10 rpm, and a roll gap of 2 mm for 20 minutes to obtain an unvulcanized rubber composition for an elastic layer.

(Molding of elastic layer)
Conductive vulcanizing adhesive (Metaloc U-20; manufactured by Toyo Chemical Laboratories Co., Ltd.) in the axial central portion 228 mm of the cylindrical surface of a cylindrical conductive substrate (steel, surface is nickel-plated) having a diameter of 6 mm and a length of 252 mm Was applied and dried at a temperature of 80 ° C. for 30 minutes.
Next, the unvulcanized rubber composition is simultaneously extruded into a cylindrical shape coaxially around the conductive substrate by extrusion molding using a cross head, and the outer periphery of the conductive substrate is coated with the unvulcanized rubber composition. An unvulcanized rubber roller was prepared. As the extruder, an extruder having a cylinder diameter of 45 mm (Φ45) and L / D = 20 was used, and the temperature during extrusion was a head of 100 ° C., a cylinder of 110 ° C., and a screw of 110 ° C.
The obtained unvulcanized rubber composition was vulcanized by heating in a heating furnace in air at atmospheric pressure at a temperature of 160 ° C. for 30 minutes. The rubber after the vulcanization was cut off at both ends of the rubber to make the length of the rubber part 232 mm, and then the rubber part was polished with a polishing machine (LEO-600-F4-BME made by Mizuguchi Seisakusho). A rubber roller having a crown-shaped elastic layer having a diameter of 4 mm and a central diameter of 8.5 mm was obtained.
The surface of the obtained rubber roller was subjected to surface modification treatment by ultraviolet irradiation. The irradiation conditions were such that a low-pressure mercury lamp (manufactured by Harrison Toshiba Lighting Co., Ltd.) was used to irradiate ultraviolet rays having a wavelength of 254 nm so that the integrated light amount was 8500 mJ / cm ² . The charging roller 1 was produced as described above.

(Durable image evaluation)
The produced charging roller was incorporated into an electrophotographic process cartridge, and this process cartridge was incorporated into an A4 paper longitudinal output electrophotographic apparatus (trade name: LBP5050 manufactured by Canon Inc.) for image evaluation.
The image evaluation was performed under an environment of a temperature of 15 ° C. and a humidity of 10% RH, and a halftone image (width in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member) output after printing 6000 sheets at a printing density of 1% (after durability). Evaluation was performed based on an image in which a 1-dot line was drawn at intervals of 2 dots.
A solid image of 15 mm square was formed on the first round of the photosensitive drum, and a halftone image was output immediately thereafter. A ghost image rank was assigned to image defects due to an afterimage that appeared after the second round of the drum. Table 4 shows the evaluation criteria.

Above C rank is a practical level.

(Volume resistivity measurement)
FIG. 3 shows a schematic diagram of a volume resistivity measuring apparatus. An aluminum sheet 31 having a width of 1.5 cm is wound around the central portion of the charging roller 1 so as to be in close contact with the elastic layer without any gap. In this state, a DC voltage was applied to the cored bar portion 11 of the charging roller 1 using the power source 32, and the electric resistance of the elastic layer was measured from the voltage applied to the resistor 33 connected in series to the aluminum sheet 31.
The elastic layer has an electrical resistance of 15 ° C. and 10% R.H. H. (Also referred to as L / L) in the environment, temperature 32.5 ° C., humidity 80% H. Under the environment (also referred to as H / H), the apparatus of FIG. 3 was used, and measurement was performed by applying a DC voltage of 200 V between the metal core and the aluminum sheet.
From the measured electric resistance value (Ωd), the roller outer diameter is 8.5 mm, the aluminum sheet width is 1.5 cm, and the elastic layer thickness is 1.5 mm. Therefore, the volume resistivity (ρd )
Ρd = (Ωd × 0.85 × π × 1.5) /0.15 (1)
100 charging rollers 1 were produced and measured once for each, and the average value was taken as the value of volume resistivity.

(Environment dependency)
The volume resistivity ratio measured under H / H and L / L environments was evaluated as environment dependency, and those showing values of 2 or less were judged to have good (small) environment dependency.

(Easy adjustment of resistance)
100 charging rollers 1 were produced, and the ratio between the maximum value and the minimum value of the volume resistivity (under H / H environment) was determined. The smaller this value, the easier it is to adjust the volume resistivity between the charging members.
Table 11 shows the measurement results and evaluation results of the charging roller according to this example.

[Example 2]
A charging roller 2 was produced and evaluated in the same manner as in Example 1 except that the blending number of Sample 1 (see Production Example 1) was 10 parts by mass.
Example 3
The materials shown in Table 5 were mixed in the same manner as in Example 1 to obtain an unvulcanized rubber composition (A kneaded rubber composition).

Table 6 shows materials mixed with the A-kneaded rubber composition and the open roll.

Except for the above, the charging roller 3 was produced and evaluated in the same manner as in Example 1.

[Examples 4 and 21]
The charging rollers 4 and 21 were prepared and evaluated in the same manner as in Example 3 except that the composition of the elastic layer forming mixture was changed as shown in Tables 11 and 13.
[Examples 5, 7 to 13, 25, 28 to 33]
The charging rollers 5, 7 to 13, 25, and 28 to 33 were produced and evaluated in the same manner as in Example 1 except that the composition of the elastic layer forming mixture was changed as shown in Tables 11 to 14.
[Examples 6 and 23]
The charging rollers 6 and 23 were prepared and evaluated in the same manner as in Example 5 except that the composition of the elastic layer forming mixture was changed as shown in Tables 11 and 13.
[Examples 14 to 20]
The charging rollers 14 to 20 were produced and evaluated in the same manner as in Example 2 except that the composition of the elastic layer forming mixture was changed as shown in Table 12.
[Example 22]
A charging roller 22 was produced and evaluated in the same manner as in Example 4 except that sample 1 was changed to sample 6.
Example 24
A charging roller 24 was produced and evaluated in the same manner as in Example 6 except that Sample 1 was changed to Sample 6.

Example 26
The materials shown in Table 7 were mixed in the same manner as in Example 1 to obtain an unvulcanized rubber composition (A kneaded rubber composition).

Table 8 shows materials mixed with the A-kneaded rubber composition and the open roll.

Except for the above, the charging roller 26 was produced and evaluated in the same manner as in Example 1.

Example 27
The materials shown in Table 9 were mixed in the same manner as in Example 1 to obtain an unvulcanized rubber composition (A kneaded rubber composition).

Table 10 shows the materials mixed with the A-kneaded rubber composition and the open roll.

Except for the above, the charging roller 27 was produced and evaluated in the same manner as in Example 1.

[Comparative Examples 1-3]
Except for the changes shown in Table 14, charging rollers 34 to 36 were produced and evaluated in the same manner as in Example 1.

The above Examples and Comparative Examples are summarized in Tables 11-14. As is clear from the table, in the examples using at least one lithium iron phosphate particle selected from the group consisting of (A) and (B), lithium perchlorate and sodium phosphate, which are conventional ionic conductive agents, are used. The ghost image was improved as compared with the comparative example using. At this time, it was confirmed that the resistance was easily adjusted and the environmental dependency was not deteriorated and was compatible.
In Example 25, lithium iron phosphate particles containing carbon and containing Mo element are used, and the ghost image and environment dependency are improved compared to the comparative example.
In the case of Example 26, the sample 1 containing no metal element and the sample 5 containing a predetermined metal element and carbon are used in combination, and the ghost is improved and the resistance is adjusted as compared with the comparative example. It is both easy and environmentally dependent.
In the case of Example 27, Sample 4 and Sample 7 are used together, and the ghost is improved and the resistance is easily adjusted and the environment dependency is compatible with that of the comparative example. Both sample 4 and sample 7 contain a predetermined metal element and carbon.
In the case of Example 28, the ghost is improved as compared with the comparative example, but the ghost is not improved as much as in Example 29 and Example 1. This is because the sample 10 does not contain at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti, and in the lithium iron phosphate particles (A) This is because the carbon content was less than 1% by mass, the conductivity of the particles was insufficient, and the amount of charged charge supplied was insufficient.
In the case of Example 30, the ghost is improved and the environment dependency is better than that of the comparative example, but the ease of adjusting the resistance is not improved as much as in Example 29 and Example 1. This is because the carbon content of sample 12 was more than 13% by mass, so the content of lithium iron phosphate in the particles was small, the ion conductivity in the particles was insufficient, and the volume resistivity was difficult to control. It is because it has become.
In Examples 31 and 33, the ghost is improved compared to the comparative example, but the ghost is not improved as much as in Example 9. This is because the content of Mg element is outside the range of 1 to 10 mol% with respect to the total molar amount of Fe and the contained metal element.
Since Comparative Example 3 is a system in which lithium perchlorate is added as a conductive agent and only an ionic conductive agent is blended, the environmental dependency is worse than that of the example.

DESCRIPTION OF SYMBOLS 1 Charging roller 11 Core metal 12 Elastic layer 13 Surface layer

Claims (3)

A charging member having a conductive substrate and an elastic layer,
The elastic layer contains particles containing at least one crystal selected from the group consisting of the following (A) and (B):
(A) a crystal of lithium iron phosphate containing carbon,
(B) A crystal of lithium iron phosphate containing at least one metal element selected from the group consisting of Co, Mn, Mg, Mo, Nb, Zr, and Ti.   The charging member according to claim 1, wherein the particles include the crystal of (A), and the content of carbon in the crystal is 1% by mass or more and 12% by mass or less. 2. The particle includes the crystal of (B), and the content of the metal element in the crystal is 1 mol% or more and 10 mol% or less with respect to the total molar amount of the metal element and Fe. Or the charging member of 2.