JP2020098247A - Charging roller and method for manufacturing charging roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging roller capable of sufficiently improving the adhesiveness between a resin on the surface layer of the charging roller and particles, and a method for producing the charging roller. A charging roller of the present invention includes a shaft member, a base layer, and a surface layer that forms a surface, and the surface layer includes a main body particle portion and a binder resin for the surface layer that covers the surface of the main body particle portion. A coating film containing a resin of the same resin type, and at least a part of particles of the coating particles, wherein a part of the particles are present so as to protrude from the surface of the surface layer. To do. Further, the method for producing the charging roller of the present invention is a method for producing the above-mentioned charging roller, and has a step of preparing the coating particles before the step of forming the surface layer, In the forming step, the coated particles are mixed with a raw material containing a binder resin for forming the surface layer, and the obtained raw material is used to form the surface layer. [Selection diagram] Figure 2

Description

The present invention relates to a charging roller and a method for manufacturing the charging roller.

Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile, first, the surface of a photoconductor is uniformly charged, and an image is projected from the optical system onto the photoconductor to expose it to light. An electrostatic latent image is obtained by an electrostatic latent image process that forms a latent image by erasing the electrostatic charge of the charged portion, and then the toner image is formed by the adhesion of toner and the toner image is transferred to a recording medium such as paper. , The method of printing is adopted.
A charging roller is generally used to charge the surface of the photoconductor (photosensitive drum). Specifically, in a minute gap formed when the charging roller is brought into contact with the photoconductor, a voltage is applied to a voltage. Discharge occurs from the charging roller to which the voltage is applied to the photoconductor, and the surface of the photoconductor is uniformly charged thereby.

JP, 2010-134452, A

Here, the charging roller may include particles in its surface layer in order to facilitate formation of a minute gap with the photoreceptor (see, for example, Patent Document 1), but the charging roller contacts the photoreceptor. Since the load continues to be added to the particles contained in the surface layer each time they come into contact with each other, it is required that sufficient adhesion be formed between the resin on the surface layer and the particles so that the particles do not detach from the surface layer of the charging roller. There is.

Therefore, the present invention is capable of sufficiently improving the adhesiveness between the resin and particles on the surface layer of the charging roller, and sufficiently improves the adhesiveness between the resin and particles on the surface layer of the charging roller and the charging roller. An object of the present invention is to provide a method of manufacturing a charging roller for obtaining a charging roller that can be improved.

The charging roller of the present invention is a charging roller comprising a shaft member, a base layer positioned radially outside the shaft member, and a surface layer positioned radially outside the base layer and forming a surface,
The surface layer includes a main body particle portion, and a coating particle having a coating that covers the surface of the main body particle portion and that contains a resin of the same resin type as the binder resin of the surface layer,
At least a part of the particles of the coating particles are present so that a part of the particles protrude from the surface of the surface layer.
According to the charging roller of the present invention, the adhesiveness between the resin and the particles on the surface layer of the charging roller can be sufficiently improved.

In the charging roller of the present invention, the main body particle portion of the coating particles is made of at least one resin selected from the group consisting of acrylic resin, melamine resin, silicone resin, phenol resin, polyamide resin, polystyrene resin and fluororesin. It is preferably formed. According to this configuration, the performance of the particles can be similarly ensured even after the coating treatment.

In the charging roller of the present invention, the surface layer preferably has a thickness of 5 to 30 μm. According to this configuration, it is possible to easily hold the coated particles sufficiently, and it is possible to reduce the number of the coated particles that do not protrude from the surface of the surface layer and are included inside.

In the charging roller of the present invention, with respect to the surface area of the surface layer, the ratio of the total area of the coating particles protruding from the surface of the surface layer among the coating particles in a plan view viewed from the radial direction of the charging roller, It is preferably more than 60%. With this configuration, it is possible to sufficiently reduce the micro jitter (horizontal stripe) that may occur when printing is performed on a recording medium such as paper.

In the charging roller of the present invention, the average particle size of the coating particles is preferably 3 to 20 μm. With this configuration, it is possible to further reduce the micro jitter of the image printed on the recording medium and improve the image quality.

The method for producing a charging roller of the present invention produces the above-described charging roller, which includes a step of forming the base layer radially outside the shaft member and a step of forming the surface layer radially outside the base layer. A method of manufacturing a charging roller for:
Before the step of forming the surface layer, has a step of preparing the coating particles,
In the step of forming the surface layer, the coating particles are mixed with a raw material containing a binder resin for forming the surface layer, and the obtained raw material is used to form the surface layer radially outside the base layer. Is characterized by.
According to the method of manufacturing the charging roller of the present invention, the adhesiveness between the resin and the particles on the surface layer of the charging roller can be sufficiently improved.

According to the present invention, the adhesiveness between the resin and particles on the surface layer of the charging roller can be sufficiently improved, and the adhesiveness between the resin and particles on the surface layer of the charging roller is sufficiently improved. It is possible to provide a method of manufacturing a charging roller for obtaining a charging roller that can be improved.

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus including a charging roller according to an exemplary embodiment of the present invention. It is sectional drawing which shows the charging roller which concerns on one Embodiment of this invention by the cross section along an axial direction. It is an expanded sectional view which shows a part of surface layer of the charging roller of FIG. 2 by the cross section along an axial direction.

An embodiment of the present invention will be described below as an example with reference to the drawings.
The charging roller of this embodiment can be used in an image forming apparatus (for example, a laser printer) as shown in FIG. 1. As shown in the axial sectional view of FIG. 2, the charging roller 1 of this embodiment has a shaft. The member 2 includes a base layer 3 located radially outside the shaft member 2, and a surface layer 4 located radially outside the base layer 3 and forming a surface of the charging roller 1.
The charging roller 1 of the present embodiment is not limited to the base layer 3 and the surface layer 4 as the layers formed on the shaft member 2, and may be formed between the base layer 3 and the surface layer 4 or between the shaft member 2 and the base layer 3. In between, a single layer or a plurality of other layers can be optionally formed.

In addition, in the charging roller 1 of the present embodiment, as shown in FIG. 3, the surface layer 4 is made of the same resin species as the binder resin of the surface layer 4 that covers the main body particle portion 5 and the surface of the main body particle portion 5. A coating film 6 containing a resin is included, and at least some of the particles of the coating film 7 are present such that a part of the particles protrudes from the surface of the surface layer 4. By doing so, since the coating 6 of the coating particles 7 is of the same resin type as the binder resin of the surface layer 4, the affinity between the coating 6 and the binder resin is improved, and thus the surface layer 4 of the charging roller 1 is improved. The adhesiveness between the binder resin and the portion of the coated particles 7 located in the surface layer 4 (the portion buried in the surface layer 4) can be sufficiently improved, and the coated particles 7 fall off from the surface layer 4. Can be sufficiently suppressed.

The "same resin type" means that the resins have the same skeleton in the molecular chain and are, in terms of classification, resins belonging to the same group, for example, urethane resin, acrylic resin, melamine resin, silicone resin, They are those belonging to the group such as phenol resin, polyamide resin, polystyrene resin and fluororesin.
The coated particles 7 have a constant distribution of one or more particles. Further, “at least a part of the particles of the coated particles 7 are present so that a part of the particles protrudes from the surface of the surface layer 4 ”, a part of the particles of the coated particles 7 is a surface layer 4 There is a case where the particles are completely buried inside, but it means that at least a part of the particles of the coated particles 7 are not completely buried inside the surface layer 4.

Here, in the present embodiment, the coating particles 7 have a coating as described above, but 80% or more of the surface area of the main body particle portion of one coating particle 7 is covered with the coating. Is preferable, more preferably 90% or more, and further preferably all.
As described above, the coating 6 of the coating particles 7 is not particularly limited as long as it is the same resin type as the binder resin of the surface layer 4, but among them, a urethane resin that can be suitably used as the binder resin, urethane resin It is preferable to include.
The thickness of the coating 6 of the coating particles 7 is not particularly limited, but is preferably 0.01 to 3.0 μm, and more preferably 0.05 to 1.0 μm.
Further, the film 6 may be blended with an additive that can be contained together with the binder resin of the surface layer 4. As long as the coating 6 contains a resin of the same resin type as the binder resin of the surface layer 4, the additives other than the resin in the coating 6 may be the same as or different from the additives other than the binder resin of the surface layer 4. Good. However, it is preferable that the film 6 is formed only of the resin of the same resin type as the binder resin of the surface layer 4.

In the present embodiment, the main particle portion 5 of the coated particle 7 is not particularly limited, but is substantially spherical and is selected from the group consisting of acrylic resin, melamine resin, silicone resin, phenol resin, polyamide resin, polystyrene resin and fluororesin. Preferably, it is formed of at least one resin. Thereby, the performance of the particles can be similarly ensured even after the coating treatment.
Further, the main body particle portion 5 of the coated particle 7 is more preferably formed of acrylic resin from the viewpoint of image quality when printed on a recording medium such as paper.

In the present embodiment, the average particle diameter of the coating particles 7 is 1 to 1 from the viewpoint of forming a minute gap when the charging roller 1 is brought into contact with the photosensitive member and effectively discharging the charging roller 1 to the photosensitive member. The thickness is preferably 30 μm, more preferably 3 to 20 μm.
The average particle size of the particles means the volume average particle size (Mv) obtained by the laser diffraction/scattering method. Further, the average particle size of the particles is, when the particles contained in the surface layer 4 are a mixture of plural kinds of particles (when the shape of the particle size distribution curve of the particles contained in the surface layer is multimodal), It is an average particle diameter measured in a state where a plurality of types of particles are mixed.

In the present embodiment, the content of the coating particles 7 contained in the surface layer 4 forms a minute gap when the charging roller 1 is brought into contact with the photoconductor to effectively discharge the charge roller to the photoconductor. From the viewpoint, it is preferably 10 to 200 parts by mass, more preferably 50 to 150 parts by mass, and further preferably 90 to 120 parts by mass with respect to 100 parts by mass of the binder resin contained in the surface layer 4.

Here, in the present embodiment, the total area of the coating particles 7 of the coating particles 7 protruding from the surface of the surface layer 4 with respect to the surface area of the surface layer 4 in a plan view viewed from the radial direction of the charging roller 1. The proportion is preferably more than 60%, more preferably 70% or more. By doing so, it is possible to sufficiently reduce the micro jitter (horizontal stripe) that may occur when printing is performed on a recording medium such as paper. Specifically, when the charging roller 1 is brought into contact with the photosensitive member in order to charge the photosensitive member, a large number of coating particles 7 on the surface of the surface layer 4 come into contact with the surface of the photosensitive member, so that the charging roller 1 and the photosensitive roller are exposed. It is easy to make minute gaps (gap) formed by being supported by a large number of coated particles 7 uniformly between the body over the entire surface layer 4. Then, since the charging roller 1 to which the voltage is applied uniformly discharges the photoconductor to the photoconductor by the uniformly present minute gaps, the surface of the photoconductor is uniformly charged, which may be caused by uneven charging. Jitter (horizontal stripe) can be sufficiently reduced.
The ratio of the total area of the coating particles 7 of the coating particles 7 protruding from the surface of the surface layer 4 in the plan view viewed from the radial direction of the charging roller 1 to the surface area of the surface layer 4 is 85% or less. It is preferable to have.

In the present embodiment, the total area of the coating particles 7 protruding from the surface of the surface layer 4 is photographed by a laser microscope at the center in the axial direction of the surface layer 4, both sides (positions 25 mm inward from both ends of the surface layer 4). It is obtained by using the photograph (1000 times). Specifically, a photograph (1000 times) taken by a laser microscope was binarized using image processing software so that the portions confirmed as particles became black, and the total of the black portions were By calculating the area and arithmetically averaging the total areas obtained from the three photographs, the total area of the coating particles 7 protruding from the surface of the surface layer 4 is obtained.
Further, the ratio of the total area of the coating particles 7 protruding from the surface of the surface layer 4 to the surface area of the surface layer 4 is obtained by dividing the total area obtained by the above method by the total photographed area of the photograph (1000 times). Get by.
In addition, the part confirmed as particles in the photograph (1000 times) photographed by the laser microscope is the part which is confirmed to project more than the portion where the surface of the surface layer 4 is flat in the photograph. Further, the coating 6 of the coating particles 7 is also calculated as the above total area.

In the present embodiment, as described above, the total area of the coating particles 7 of the coating particles 7 protruding from the surface of the surface layer 4 in plan view as seen from the radial direction of the charging roller 1 with respect to the surface area of the surface layer 4. When the ratio is more than 60% (hereinafter, also referred to as “when the particle protrusion ratio is more than 60%”), the average particle size of the coated particles 7 is preferably 3 to 30 μm, and It is preferably 3 to 20 μm. By setting the average particle size of the coating particles 7 to 3 μm or more, it is easy to form a minute gap on the surface layer 4 sufficiently uniformly while the length of the minute gap between the charging roller 1 and the photoconductor is moderate. Therefore, the micro jitter can be further reduced. Further, by setting the average particle size of the coating particles 7 to 30 μm or less, the discharge from the charging roller 1 to the photoconductor can be appropriately generated, and the discharge failure called white spot can be suppressed. Can be effectively secured.

In the present embodiment, when the particle protrusion ratio is more than 60%, the content of the coated particles 7 is preferably 70 to 160 parts by mass with respect to 100 parts by mass of the binder resin contained in the surface layer 4, It is preferably 90 to 120 parts by mass. By setting the content of the coating particles 7 to 80 parts by mass or more, it is possible to easily make a minute gap uniformly exist over the entire surface layer 4 of the charging roller 1, and the content is set to 160 parts by mass or less. This makes it easier to secure the storage stability of the layer forming raw material for forming the charging roller 1.

Here, in the charging roller 1 of the present embodiment, as the layer-forming raw material constituting the surface layer 4 other than the coated particles 7, a urethane acrylate oligomer as a binder resin, a photopolymerization initiator, and a conductive agent are used. An ultraviolet curable resin composition containing Various additives may be added to the layer-forming raw material as long as the object of the present invention is not impaired.

As the urethane acrylate oligomer used as the layer forming raw material, a polyol represented by the following formula (I),
y≦0.6/x+0.01 (I)
(In the formula, x is a hydroxyl value (mgKOH/g) of the polyol, and y is a total degree of unsaturation (meq/g) of the polyol). synthesized using together have acryloyloxy groups (CH ₂ = CHCOO-) one or more, it is possible to use a compound having a plurality of urethane bonds (-NHCOO-).
Such urethane acrylate oligomer is obtained by, for example, adding an acrylate having a hydroxyl group to a urethane prepolymer synthesized from (i) a high-purity polyol alone or a mixture of a high-purity polyol and another polyol, and polyisocyanate, (ii) An acrylate having a hydroxyl group is added to a urethane prepolymer synthesized from a high-purity polyol alone or a mixture of a high-purity polyol and another polyol, and a polyisocyanate, and a mixture of a urethane prepolymer synthesized from another polyol and a polyisocyanate. It can be synthesized. The high-purity polyol used for synthesizing the urethane prepolymer is, for example, diethyl zinc, iron chloride, metalloporphyrin, complex metal cyanide complex, or cesium compound in the presence of a catalyst such as ethylene glycol, propylene glycol, glycerin, neopentyl. Polyhydric alcohols such as glycol, trimethylolpropane, pentaerythritol, and compounds obtained by reacting these with alkylene oxide can be synthesized by adding alkylene oxide such as propylene oxide or ethylene oxide to unsaturated polyhydric alcohol. It has less mono-ol by-products and higher purity than conventional polyols.

By forming a layer by ultraviolet irradiation using a urethane acrylate oligomer synthesized by using a high-purity polyol satisfying the relationship of the above formula (I), the residual compressive strain is reduced and the contamination property of the charging roller 1 to the adjacent member is reduced. Can be reduced. From the viewpoint of obtaining such effects, the total degree of unsaturation of the high-purity polyol is preferably 0.05 meq/g or less, more preferably 0.025 meq/g or less, and 0.01 meq/g or less. It is more preferable that there is.

The high-purity polyol used for the synthesis of the urethane acrylate oligomer preferably has a weight average molecular weight (Mw) of 1,000 to 16,000. By setting the molecular weight of the high-purity polyol to 1,000 or more, the hardness of the layer can be suppressed to a low level and good image quality can be ensured. On the other hand, if it is 16,000 or less, the compression residual strain can be reduced. It is possible to suppress an increase in the image quality and to suppress the occurrence of image defects due to the deformation of the charging roller 1.

In the synthesis of the urethane acrylate oligomer, the other polyol that can be used together with the high-purity polyol is a compound having a plurality of hydroxyl groups (OH groups), and specific examples of the polyol include polyether polyol and polyester. Examples thereof include polyols, polybutadiene polyols, alkylene oxide-modified polybutadiene polyols and polyisoprene polyols. The polyether polyol can be obtained, for example, by adding an alkylene oxide such as ethylene oxide or propylene oxide to a polyhydric alcohol such as ethylene glycol, propylene glycol, or glycerin. Examples of the polyester polyol include polyhydric alcohols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, trimethylolethane, and trimethylolpropane, adipic acid, and glutaric acid. , Succinic acid, sebacic acid, pimelic acid, suberic acid, and other polycarboxylic acids. These polyols may be used alone or in a blend of two or more.

In the synthesis of the urethane acrylate oligomer, when another polyol (a2) is used together with the high purity polyol (a1), the mass ratio (a1/a2) of the high purity polyol (a1) and the other polyol (a2) is , 100/0 to 30/70 is preferable. By setting the proportion of the high-purity polyol (a1) in the total amount (a1+a2) of the high-purity polyol (a1) and the other polyol (a2) to 30% by mass or more (that is, the proportion of the other polyol (a2) is By setting the content to 70% by mass or less), it is possible to sufficiently reduce the stain resistance of the adjacent member such as the photoconductor while reducing the compressive residual strain of the layer.

The polyisocyanate that can be used to synthesize the urethane acrylate oligomer is a compound having a plurality of isocyanate groups (NCO groups), and specifically, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and crude diphenylmethane diisocyanate. (Crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hexamethylene diisocyanate (HDI), and isocyanurate modified products, carbodiimide modified products, glycol modified products thereof and the like. These polyisocyanates may be used alone or in combination of two or more.

In the synthesis of the urethane acrylate oligomer, it is preferable to use a catalyst for urethanization reaction. Examples of the urethane-forming reaction catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate, and monobutyltin oxide; stannous chloride and the like. Inorganic tin compounds; organic lead compounds such as lead octenoate; monoamines such as triethylamine, dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine, tetramethylhexanediamine; pentamethyldiethylenetriamine, pentamethyldipropylene Triamines such as triamine and tetramethylguanidine; cyclic amines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine, dimethylimidazole and pyridine; dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethyl Alcohol amines such as ethanolamine, methylhydroxyethylpiperazine and hydroxyethylmorpholine; ether amines such as bis(dimethylaminoethyl) ether and ethylene glycol bis(dimethyl)aminopropyl ether; p-toluenesulfonic acid, methanesulfonic acid, Organic sulfonic acids such as fluorosulfuric acid; inorganic acids such as sulfuric acid, phosphoric acid, perchloric acid; bases such as sodium alcoholate, lithium hydroxide, aluminum alcoholate, sodium hydroxide; tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate, etc. Titanium compounds; bismuth compounds; quaternary ammonium salts and the like. Among these catalysts, the organic tin compound is preferable. These catalysts may be used alone or in combination of two or more. The amount of the catalyst used is preferably 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the polyol.

Furthermore, acrylates having a hydroxyl group that can be used in the synthesis of the urethane acrylate oligomer, a hydroxyl group and having 1 or more, a compound having one or more acryloyloxy groups (CH ₂ = CHCOO-). The acrylate having a hydroxyl group can be added to the isocyanate group of the urethane prepolymer. Examples of the acrylate having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, pentaerythritol triacrylate and the like. These acrylates having a hydroxyl group may be used alone or in combination of two or more.

The photopolymerization initiator used as the raw material for forming the layer has a function of initiating the polymerization of the urethane acrylate oligomer described above and further the acrylate monomer described later by being irradiated with ultraviolet rays. As such a photopolymerization initiator, 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, 2,2-dimethoxy-2-phenylacetophenone, acetophenone diethyl ketal, alkoxyacetophenone, benzyldimethyl ketal, benzophenone 3,3- Benzophenone derivatives such as dimethyl-4-methoxybenzophenone, 4,4-dimethoxybenzophenone and 4,4-diaminobenzophenone, alkyl benzoylbenzoates, bis(4-dialkylaminophenyl)ketones, benzyl derivatives such as benzyl and benzylmethylketal, Benzoin derivatives such as benzoin and benzoin isobutyl ether, benzoin isopropyl ether, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexylphenyl ketone, xanthone, thioxanthone and thioxanthone derivatives, fluorene, 2,4,6-trimethylbenzoyldiphenyl Phosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2-methyl-1-[4-( Methylthio)phenyl]-2-morpholinopropane-1,2-benzyl-2-dimethylamino-1-(morpholinophenyl)-butanone-1 and the like. These photopolymerization initiators may be used alone or in combination of two or more.

The conductive agent used as the layer forming raw material has a function of imparting conductivity to the elastic layer. As such a conductive agent, one that can transmit ultraviolet rays is preferable, an ionic conductive agent or a transparent electronic conductive agent is preferably used, and an ionic conductive agent is particularly preferably used. Since the ion conductive agent is transparent in addition to being dissolved in the urethane acrylate oligomer, when the ion conductive agent is used as the conductive agent, even if the layer forming raw material is applied thickly on the shaft member, the ultraviolet ray is sufficiently emitted. It is possible to reach the inside of the coating film and sufficiently cure the layer forming raw material. Here, as the ion conductive agent, perchlorates such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium and modified fatty acid dimethylethylammonium, chlorates, hydrochlorides, bromates Ammonium salts such as salts, iodates, borofluorides, sulfates, ethylsulfates, carboxylates and sulfonates; alkali metals such as lithium, sodium, potassium, calcium and magnesium, and alkaline earth metals Perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, sulphates, trifluoromethyl sulphates, sulphonates and the like can be mentioned. Further, as the transparent electron conductive agent, fine particles of metal oxide such as ITO, tin oxide, titanium oxide, zinc oxide; fine particles of metal such as nickel, copper, silver, germanium: conductive titanium oxide whiskers, conductive titanium Examples thereof include conductive whiskers such as barium acid whiskers. Further, as an electronic conductive agent, conductive carbon such as Ketjen black and acetylene black, carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, carbon for color subjected to oxidation treatment, etc. Black, pyrolytic carbon black, natural graphite, artificial graphite, etc. may be used. These conductive agents may be used alone or in combination of two or more.

The layer forming raw material preferably further contains an acrylate monomer. Acrylate monomer is a monomer having acryloyloxy groups (CH ₂ = CHCOO-) 1 or more to act as a reactive diluent, i.e., in addition to curing by ultraviolet radiation, to lower the viscosity of the raw material for the layer formation It is possible. The number of functional groups of the acrylate monomer is preferably 1.0 to 10, and more preferably 1.0 to 3.5. The molecular weight of the acrylate monomer is preferably 100 to 2000, more preferably 100 to 1000.

Examples of the acrylate monomer include isomyristyl acrylate, methoxytriethylene glycol acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isoamyl acrylate, glycidyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, and phenoxyethyl acrylate. , 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, pentaerythritol triacrylate and the like. These acrylate monomers may be used alone or in combination of two or more.

In the layer forming raw material, the mass ratio of the urethane acrylate oligomer and the acrylate monomer (urethane acrylate oligomer/acrylate monomer) is preferably in the range of 100/0 to 10/90. By setting the ratio of the urethane acrylate oligomer in the total amount of the urethane acrylate oligomer and the acrylate monomer to 10% by mass or more (that is, by setting the ratio of the acrylate monomer to 90% by mass or less), a low level suitable for the charging roller 1 can be obtained. It is possible to obtain the base layer 3 having hardness and low compressive residual strain.

The amount of the photopolymerization initiator compounded in the layer-forming raw material is preferably in the range of 0.2 to 5.0 parts by mass based on 100 parts by mass of the urethane acrylate oligomer and the acrylate monomer in total. By setting the amount of the photopolymerization initiator to be 0.2 parts by mass or more, the effect of initiating the ultraviolet curing of the layer forming raw material can be surely obtained, while by setting it to 5.0 parts by mass or less. In addition, it is possible to suppress deterioration of physical properties such as compression residual strain and improve the cost performance of the layer forming raw material.

Further, the compounding amount of the conductive agent in the layer forming raw material is preferably in the range of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the total of the urethane acrylate oligomer and the acrylate monomer. By setting the amount of the conductive agent to be 0.1 part by mass or more, the conductivity of the layer can be sufficiently ensured and the desired conductivity can be imparted to the charging roller 1, while 5.0 parts by mass can be provided. With the following, it is possible to appropriately suppress the conductivity of the layer, suppress deterioration of physical properties such as residual compression strain, and secure a good image.

A polymerization inhibitor may be further added to the layer-forming raw material in an amount of 0.001 to 0.2 parts by mass based on 100 parts by mass of the total amount of the urethane acrylate oligomer and the acrylate monomer. By adding a polymerization inhibitor, it is possible to prevent thermal polymerization before irradiation with ultraviolet rays. As the polymerization inhibitor, hydroquinone, hydroquinone monomethyl ether, p-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, butylhydroxyanisole, 3 -Hydroxythiophenol, α-nitroso-β-naphthol, p-benzoquinone, 2,5-dihydroxy-p-quinone and the like can be mentioned.

The thickness of the surface layer 4 is preferably 5 to 30 μm. When the thickness of the surface layer 4 is 5 μm or more, the coated particles 7 can be easily held sufficiently, while when it is 30 μm or less, the number of the coated particles 7 that do not protrude from the surface of the surface layer 4 and are contained inside is reduced. be able to.

Next, in FIG. 2, the shaft member 2 is composed of a metal shaft 2A and a highly rigid resin base material 2B arranged on the outer side in the radial direction thereof. However, the shaft member 2 of the charging roller 1 of the present embodiment is There is no particular limitation as long as it has good conductivity, and it may be composed of only the metal shaft 2A, or may be composed of only the highly rigid resin base material 2B, or a metal whose inside is hollowed out. It may be a cylindrical body made of high-rigidity resin or the like.

When a highly rigid resin is used for the shaft member 2, it is preferable to add/disperse a conductive agent to the highly rigid resin to ensure sufficient conductivity. Here, as the conductive agent dispersed in the high-rigidity resin, carbon black powder or graphite powder, carbon fiber, metal powder such as aluminum, copper, nickel, etc., metal oxide powder such as tin oxide, titanium oxide, zinc oxide, conductive A powdery conductive agent such as a transparent glass powder is preferable. These conductive agents may be used alone or in combination of two or more. The compounding amount of the conductive agent is not particularly limited, but is preferably in the range of 5 to 40 mass% and more preferably in the range of 5 to 20 mass% with respect to the entire high rigidity resin.

Examples of the material of the metal shaft 2A and the metal cylindrical body include iron, stainless steel, aluminum and the like. The material of the high-rigidity resin substrate 2B includes polyacetal, polyamide 6, polyamide 6.6, polyamide 12, polyamide 4.6, polyamide 6/10, polyamide 6/12, polyamide 11, polyamide MXD6, poly. Butylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polyether sulfone, polycarbonate, polyimide, polyamideimide, polyetherimide, polysulfone, polyetheretherketone, polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, polypropylene, ABS resin, Examples thereof include polystyrene, polyethylene, melamine resin, phenol resin and silicone resin. Among these, polyacetal, polyamide 6.6, polyamide MXD6, polyamide 6.12, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, and polycarbonate are preferable. These high-rigidity resins may be used alone or in combination of two or more.

When the shaft member 2 is a metal shaft or a shaft member having a highly rigid resin base material provided on the outside thereof, the outer diameter of the metal shaft is preferably in the range of 4.0 to 8.0 mm. When the shaft member 2 is a shaft member in which a highly rigid resin base material is arranged on the outer side of a metal shaft, the outer diameter of the resin base material is preferably in the range of 10 to 25 mm. By using a high-rigidity resin for the shaft member 2, it is possible to suppress an increase in the mass of the shaft member 2 even if the outer diameter of the shaft member 2 is increased.

The charging roller 1 according to the present embodiment includes a base layer 3 located radially outside the shaft member 2. As the layer-forming raw material forming the base layer 3, the same layer-forming raw material forming the surface layer 4 can be used, except that the coated particles 7 contained in the surface layer 4 are not an essential component. ..

The Asker C hardness of the base layer 3 formed of the layer forming raw material is preferably 30 to 70 degrees. Here, the Asker C hardness is a value when a flat surface portion of a cylindrical sample having a height of 12.7 mm and a diameter of 29 mm is measured. If the Asker C hardness is 30 degrees or more, a sufficient hardness can be secured as the charging roller 1, while if it is 70 degrees or less, the followability with other rollers and blades is good.

In addition, the base layer 3 preferably has a residual compression set (compression set) of 3.0% or less. Here, the compressive residual strain can be measured according to JIS K 6262 (1997), and specifically, for a cylindrical sample having a height of 12.7 mm and a diameter of 29 mm, a specified heat treatment condition (22 at 70° C.) is used. Time), the sample can be obtained by compressing the sample in the height direction by 25%. If the compressive residual strain of the base layer 3 is 3.0% or less, pressure contact marks due to other members are less likely to occur on the surface of the charging roller 1 and streaky image defects are less likely to occur in the formed image.

Further, the base layer 3 preferably has a thickness of 1 to 3000 μm. When the thickness of the base layer 3 is 1 μm or more, the charging roller 1 has sufficient elasticity. On the other hand, when the thickness is 3000 μm or less, the ultraviolet rays sufficiently reach the deep part of the base layer 3 upon irradiation with ultraviolet rays, and thus the layer forming layer is formed. The raw material can be surely ultraviolet-cured, and the amount of expensive ultraviolet-curable resin raw material used can be reduced.

Furthermore, the base layer 3 is preferably, but not limited to, having a volume resistivity of 10 ⁴ to 10 ⁸ Ω·cm. Here, the resistivity of the base layer 3 is set to 100 V between the shaft member 2 and the counter electrode by pressing the outer peripheral surface of the roller having only the base layer 3 formed on the shaft member 2 against a flat plate or a cylindrical counter electrode with a predetermined pressure. The voltage can be applied and the current value can be obtained. The charging roller 1 preferably has a volume resistivity of 10 ⁴ to 10 ⁸ Ω·cm. Here, regarding the resistivity of the charging roller 1, the outer peripheral surface of the roller is pressed against a flat plate or a cylindrical counter electrode with a predetermined pressure, a voltage of 100 V is applied between the shaft member 2 and the counter electrode, and a current value at that time is applied. Can be obtained from

Further, in the charging roller 1 of the present embodiment, the base layer 3 can be formed of polyurethane foam. In this case, for example, the base layer 3 made of polyurethane foam can be directly supported on the outer side in the radial direction of the metal shaft 2A.

As the polyurethane resin used for the polyurethane foam forming the base layer 3, conventionally known materials can be appropriately selected and used, and are not particularly limited. The foaming ratio of the polyurethane foam is not particularly limited, but is preferably 1.2 to 50 times, particularly preferably about 1.5 to 10 times, and the foam density is 0.1 to 0.7 g/ It is preferably about cm ³ .

A conductive agent can be added to the polyurethane foam constituting the base layer 3, whereby conductivity can be imparted or adjusted to a predetermined resistance value. The conductive agent is not particularly limited, and the same conductive agents that can be blended with the above-mentioned ultraviolet curable resin can be used alone or in combination of two or more kinds as appropriate. The amount of these conductive agents blended is appropriately selected according to the type of composition, and is usually adjusted so that the volume resistivity of the base layer 3 falls within the above range.

When formed of polyurethane foam, the base layer 3 may include, in addition to the above-mentioned conductive agent, a water-proofing agent, a wetting agent, a foaming agent, a foam stabilizer, a curing agent, a thickener, and a deodorant, if necessary. Known additives such as a foaming agent, a leveling agent, a dispersant, a thixotropy-imparting agent, an antiblocking agent, a cross-linking agent, and a film forming aid can be added in appropriate amounts.
The thickness of the base layer 3 is preferably 1.0 to 5.0 mm, more preferably 1.0 to 3.0 mm. By setting the thickness of the base layer 3 within the above range, spark discharge can be prevented.

In addition, in the charging roller 1 of the present embodiment, the material for forming the intermediate layer between the base layer 33 and the surface layer 4 is not particularly limited, and a moisture curing type resin may be used, or an acrylate may be used. A UV curable resin in which an amide-containing monomer such as an acryloylmorpholine monomer is mixed with the contained oligomer may be used.

Next, a method of manufacturing the charging roller 1 according to the embodiment of the present invention for manufacturing the charging roller 1 of the above-described embodiment will be described.
The method of manufacturing the charging roller 1 according to the present embodiment includes the step of forming the base layer 3 on the outer side of the shaft member 2 in the radial direction and the step of forming the surface layer 4 on the outer side of the base layer 3 in the radial direction. It is a manufacturing method of a charging roller for manufacturing. The method of manufacturing the charging roller 1 of the present embodiment has a step of preparing the coating particles 7 before the step of forming the surface layer 4, and the prepared coating film is included in the step of forming the surface layer 4 described above. The particles 7 are mixed with a raw material containing a binder resin for forming the surface layer 4, and the particles 7 are used to form the surface layer 4 on the radially outer side of the base layer 3.
In the present embodiment, by manufacturing the charging roller 1 in the above steps, the adhesiveness between the resin of the surface layer 4 of the charging roller 1 and the coated particles 7 can be sufficiently improved.

Here, in the step of preparing the coating particles 7, specifically, a resin of the same resin type as the binder resin of the surface layer 4 is formed on the surface of the main particle portion 5 of the coating particles 7 before coating to be contained in the surface layer 4. The coating film 6 is formed by preparing the coating particles 7.
When the base layer 3 is formed from the above-mentioned layer forming raw material, in the step of forming the base layer 3, the base layer 3 is formed by applying the above layer forming raw material to the outer surface of the shaft member 2 and then irradiating with ultraviolet light. can do. Further, in the step of forming the surface layer 4, the surface forming layer 4 can be formed by applying the above-mentioned layer forming raw material containing the coating particles 7 to the surface of the formed base layer 3 and irradiating with ultraviolet rays.
By these steps, the charging roller 1 of the above-described embodiment can be easily manufactured, so that it is possible to manufacture the charging roller 1 in a short time without requiring a large amount of heat energy. Moreover, since a curing furnace or the like is unnecessary for manufacturing, a large amount of equipment cost is not required.
Examples of the method of applying the above-mentioned layer forming raw material to the outer surface of the shaft member 2 or the surface of the base layer 3 include a spray method, a roll coater method, a dipping method, and a die coating method. Examples of the light source used for ultraviolet irradiation include a mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp and the like. The conditions of ultraviolet irradiation are appropriately selected according to the components, composition, coating amount, etc. contained in the layer forming raw material, and the irradiation intensity, integrated light amount, etc. may be appropriately adjusted.

In the method for manufacturing the charging roller 1 of the present embodiment, when the base layer 3 is formed of polyurethane foam, in the step of forming the base layer 3, the base layer 3 is formed on the outer periphery of the shaft member 2 using a cylindrical mold. It can be formed by supporting polyurethane foam by molding or the like.

Next, FIG. 1 shows a schematic view of an example of an image forming apparatus including the charging roller 1 of the above-described embodiment.
The illustrated image forming apparatus supplies a photoconductor 10 holding an electrostatic latent image, a charging roller 1 located near the photoconductor 10 (upper side in the figure) for charging the photoconductor 10, and a toner 11. Toner supply roller 12, a developing roller 13 disposed between the toner supply roller 12 and the photoconductor 10, a layering blade 14 provided near the development roller 13 (upper side in the drawing), and a photoconductor. A transfer roller 15 located near (downward in the figure) 10 and a cleaning roller 16 disposed adjacent to the photoconductor 10 are provided. The illustrated image forming apparatus may further include known components (not shown) that are commonly used in the image forming apparatus.

In the illustrated image forming apparatus, first, the charging roller 1 is brought into contact with the photoconductor 10 and a voltage is applied between the photoconductor 10 and the charging roller 1 to charge the photoconductor 10 to a constant potential. An electrostatic latent image is formed on the photoconductor 10 by an exposure device (not shown). Next, the photoconductor 10, the toner supply roller 12, and the developing roller 13 rotate in the direction of the arrow in the figure, so that the toner 11 on the toner supply roller 12 is sent to the photoconductor 10 via the developing roller 13. To be The toner 11 on the developing roller 13 is formed into a uniform thin layer by the stratifying blade 14, and the developing roller 13 and the photoconductor 10 rotate while coming into contact with each other, so that the toner is removed from the developing roller 13 to the photoconductor 10. The latent image is visualized by adhering to the latent image. The toner attached to the latent image is transferred to a recording medium such as paper by the transfer roller 15, and the toner remaining on the photoconductor 10 after the transfer is removed by the cleaning roller 16.

Although the embodiments of the present invention have been described with reference to the drawings, the charging roller and the method for manufacturing the charging roller of the present invention are not limited to the above examples, and the charging roller and the charging roller of the present invention are not limited thereto. The manufacturing method can be appropriately modified.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

First, the materials used for manufacturing the charging rollers of Examples and Comparative Examples will be described.
(Urethane acrylate oligomer)
Bifunctional, high-purity polyol with a molecular weight of 4,000 (Preminol S-X4004, manufactured by Asahi Glass Co., Ltd., polyol consisting of PO chains, hydroxyl value = 27.9 mgKOH/g, total unsaturation = 0.007 meq/g, formula Right part of (I) (0.6/x+0.01)=0.03) 100 parts by mass, isophorone diisocyanate 8.29 parts by mass (isocyanate group/hydroxyl group of polyol=3/2=1.50 (molar ratio)) And 0.01 part by mass of dibutyltin dilaurate were heated and stirred to react at 70° C. for 2 hours to synthesize a urethane prepolymer having isocyanate groups at both ends of the molecular chain. Further, 2.88 parts by mass of 2-hydroxyethyl acrylate (HEA) was stirred and mixed with 100 parts by mass of this urethane prepolymer and reacted at 70° C. for 2 hours to synthesize a urethane acrylate oligomer having a molecular weight of 9,000. The obtained urethane acrylate oligomer had a viscosity of 80,000 mPas/sec at 25° C. measured by a B-type viscometer.

(Photopolymerization initiator)
IRGACURE 819 (manufactured by BASF Japan Ltd.)

(Conductive agent)
Conductive agent (i): Potassium metal ion Conductive agent (ii): Ketjen Black (manufactured by Kao Corporation)

Next, a method of manufacturing the charging roller of each of Examples and Comparative Examples will be described.
(Examples and comparative examples)
Obtained by blending 3 parts by mass of the photopolymerization initiator and 3 parts by mass of the conductive agent (i) with respect to 100 parts by mass of the urethane acrylate oligomer on the outer surface of the metal shaft having an outer diameter of 6.0 mm. The layer forming raw material thus obtained was applied to a thickness of 1500 μm by a die coater and cured by spot UV irradiation while applying to form a base layer. The base layer-formed roller thus obtained was further irradiated with UV at a UV irradiation intensity of 700 mW/cm ² for 5 seconds while rotating in a nitrogen atmosphere.
Next, with respect to 100 parts by mass of the urethane acrylate oligomer, 3 parts by mass of the photopolymerization initiator, 3 parts by mass of the conductive agent (ii), and particles of the type and content prepared in advance shown in Table 1. And are mixed to obtain a layer-forming raw material, and the obtained layer-forming raw material is applied to the surface of the base layer-formed roller obtained above by a roll coater and irradiated with UV to have a thickness of 15 μm. A surface layer was formed by using the above to obtain test rollers of each Example and Comparative Example. Table 1 below shows the results of evaluation of each of the test rollers according to the following.

Next, a method of evaluating the charging roller of each of Examples and Comparative Examples will be described.
(Adhesiveness)
The adhesion between the resin and particles on the surface layer of each test roller was measured by the following method. After each test roller was left in an environment of a temperature of 35° C. and a humidity of 80% for 24 hours, it was incorporated into an electrophotographic apparatus as a charging roller. After printing 10,000 sheets, the surface of the roller at the center in the axial direction and the surface at a position of 25 mm from both ends were observed with a laser microscope (1000 times) for the presence or absence of particles, and the following criteria were used. evaluated.
The obtained results were evaluated for adhesiveness according to the following criteria. The results are shown in Table 1.
○: No dropout ×: Dropped (If even one place is dropped ×)

(Micro jitter)
Each test roller was attached to the cartridge as a charging roller, and it was left for 24 hours in an environment of a temperature of 35° C. and a humidity of 80%. Then, the cartridge was installed in an actual machine, printing was performed under the same environmental conditions, and micro jitter (horizontal stripe) was evaluated according to the following criteria. The results are shown in Table 1.
○: No micro jitter (horizontal stripes) Δ: Partially confirmed ×: Confirmed in the entire printing area

According to the present invention, the adhesiveness between the resin and particles on the surface layer of the charging roller can be sufficiently improved, and the adhesiveness between the resin and particles on the surface layer of the charging roller is sufficiently improved. It is possible to provide a method of manufacturing a charging roller for obtaining a charging roller that can be improved.

1: charging roller, 2: shaft member, 3: base layer, 4: surface layer,
5: main body particle portion, 6: coating film, 7: coating particle, 10: photoconductor, 11: toner,
12: toner supply roller, 13: developing roller, 14: layering blade,
15: Transfer roller, 16: Cleaning roller

Claims (6)

A charging roller comprising a shaft member, a base layer located radially outside the shaft member, and a surface layer located radially outside the base layer and forming a surface,
The surface layer includes a main body particle portion, and a coating particle having a coating that covers the surface of the main body particle portion and that contains a resin of the same resin type as the binder resin of the surface layer,
The charging roller, wherein at least a part of the coating particles are present such that a part of the particles protrudes from the surface of the surface layer. The main body particle portion of the coated particles is formed of at least one resin selected from the group consisting of acrylic resin, melamine resin, silicone resin, phenol resin, polyamide resin, polystyrene resin and fluororesin. 1. The charging roller according to 1. The charging roller according to claim 1, wherein the surface layer has a thickness of 5 to 30 μm. The ratio of the total area of the coating particles protruding from the surface of the surface layer among the coating particles to the surface area of the surface layer in a plan view viewed from the radial direction of the charging roller is more than 60%. Item 4. The charging roller according to any one of Items 1 to 3. The charging roller according to claim 4, wherein the coating particles have an average particle diameter of 3 to 20 μm. Charging for manufacturing the charging roller according to claim 1, comprising a step of forming the base layer radially outside of the shaft member, and a step of forming the surface layer radially outside of the base layer. A method of manufacturing a roller,
Before the step of forming the surface layer, has a step of preparing the coating particles,
In the step of forming the surface layer, the coating particles are mixed with a raw material containing a binder resin for forming the surface layer, and the obtained raw material is used to form the surface layer radially outside the base layer. A method of manufacturing a charging roller, comprising:

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