JP2019105663A - Conductive roller and image forming apparatus - Google Patents

Abstract

To provide a conductive roller that can prevent a reduction in print density caused by a deterioration in toner conveyance performance.SOLUTION: In order to solve the above-mentioned problem, a conductive roller 1 of the present invention is a conductive roller 1 comprising a shaft 2, and at least an elastic layer 3 and a surface layer 4 on an outer peripheral side of the shaft 2, wherein the surface layer 4 is formed of a composition for a surface layer containing polyol, isocyanate, and a crosslinking agent; the molecular weight of the polyol is 500 to 8000; the isocyanate index of the composition for a surface layer is 1.2 to 2.0; the cohesive force of the surface layer is 4 to 11 nN.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a conductive roller and an image forming apparatus.

  Generally, as shown in FIG. 1, a developing unit in an electrophotographic image forming apparatus such as a copying machine or a printer includes an image forming member such as a photosensitive member 11 which holds an electrostatic latent image, and the image forming member. A developing roller 1 for visualizing an electrostatic latent image by contacting and bearing toner 15 carried on the surface, and a toner supply roller 13 for supplying the toner to the developing roller 1 are provided. Image formation is performed by a series of processes in which the toner 15 is transported from the toner storage unit 14 to the image forming body (photosensitive member 11) via the toner supply roller 13 and the developing roller 1.

Here, there is a need to increase the number of printed sheets in the electrophotographic image forming apparatus described above. However, it is known that as the number of printed sheets increases, the deterioration of the toner 15 progresses and the toner tends to aggregate. The toner 15 which has become easy to be aggregated becomes clumps when being conveyed by the developing roller 1, and there is a possibility that conveyance unevenness may easily occur. Then, when the conveyance unevenness of the toner 15 occurs, the printing is whitened like a sand, and a problem occurs that the printing density is lowered.
Therefore, there has been a demand for the development of a technology capable of improving the reduction in print density caused by uneven transport of toner.

  Therefore, an object of the present invention is to provide a conductive roller capable of suppressing a decrease in print density caused by the deterioration of toner conveyance performance. Another object of the present invention is to provide an image forming apparatus excellent in print density.

  The present inventors examined in order to solve the above-mentioned subject about a conductive roller provided with a shaft, an elastic layer, and a surface layer at least on the outer peripheral side of the shaft. As a result, attention was paid to the fact that the cohesion of the roller surface (the adhesion of the surface such as tackiness) largely affects the reduction of the toner conveyance performance. The inventors of the present invention conducted further intensive studies, and as a result, when the surface layer of the conductive roller is composed of a composition for surface layer containing a polyol, an isocyanate and a crosslinking agent, the molecular weight of the polyol and the isocyanate index are adjusted. By controlling the cohesion of the surface layer of the roller (cohesive force obtained from the force curve measured using AFM (Atomic Force Microscope)) within the appropriate range (4 to 11 nN), the conveyance performance such as toner conveyance unevenness It has been found that the deterioration can be suppressed and the reduction in print density can be prevented, and the present invention has been completed.

That is, the conductive roller of the present invention is a conductive roller provided with a shaft, and at least an elastic layer and a surface layer on the outer peripheral side of the shaft,
The surface layer comprises a surface layer composition comprising a polyol, an isocyanate and a crosslinking agent,
The molecular weight of the polyol is 500 to 8000, and the isocyanate index of the surface layer composition is 1.2 to 2.0,
The cohesion of the surface layer is 4 to 11 nN.
With the above configuration, it is possible to provide a conductive roller capable of suppressing a decrease in print density due to the deterioration of toner conveyance performance.

  In the conductive roller of the present invention, the polyol preferably contains at least one selected from the group consisting of a hydrogenated polybutadiene polyol, a polycarbonate polyol, a polytetramethylene ether glycol and a polypropylene glycol. This is because the reduction in print density can be suppressed more reliably.

  Furthermore, in the conductive roller of the present invention, the surface layer composition preferably further includes 0.1 to 5 parts by mass of silicone with respect to 100 parts by mass of the urethane component. This is because a decrease in print density can be suppressed without causing an increase in torque or deterioration of toner.

  Furthermore, in the conductive roller of the present invention, the silicone preferably contains an acrylate-modified silicone having an acrylate group having a molecular weight of 500 to 2,000 per one. This is because a decrease in print density can be more reliably suppressed without causing an increase in torque or toner deterioration.

An image forming apparatus according to the present invention is characterized by comprising the above-described conductive roller according to the present invention.
According to the above configuration, it is possible to suppress the decrease in print density and to realize excellent image quality.

  According to the present invention, it is possible to provide a conductive roller capable of suppressing a decrease in print density caused by the deterioration of toner conveyance performance. Further, according to the present invention, an image forming apparatus excellent in print density can be provided.

FIG. 1 is a partial cross-sectional view schematically showing an example of an image forming apparatus. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically one Embodiment of the electroconductive roller of this invention.

Hereinafter, an embodiment of the present invention will be described using the drawings as needed.
Here, FIG. 1 is a cross-sectional view schematically showing an embodiment of the conductive roller of the present invention, and FIG. 2 shows a part of the surface layer of the embodiment of the conductive roller of the present invention. It is expanded and shown schematically.
<Conductive roller>
The conductive roller of this embodiment is a conductive roller 1 provided with a shaft 2 and at least an elastic layer 3 and a surface layer 4 on the outer peripheral side of the shaft 2 as shown in FIG.

Here, as an example of the conductive roller according to the present invention, specifically, a charging roller for uniformly charging an image carrier such as a photosensitive member, a developing roller for carrying and transporting a developer and supplying it to the image carrier, A developer supply roller that supplies the developer while charging the developer, a fixing roller that fixes the developer image transferred to the recording medium such as recording paper, a cleaning roller that removes the developer etc. attached to the image carrier Etc.
Among these, the conductive roller of the present invention is preferably used as a developing roller. In particular, the developing roller is a member that is required to be able to suppress the reduction in print density caused by the deterioration of the toner conveyance performance, and therefore, it is possible to effectively enjoy the benefits of the problem solving of the present invention.

Hereinafter, each constituent member of the conductive roller of the present embodiment will be described.
(Elastic layer)
The elastic layer 3 which comprises the electroconductive roller 1 of this embodiment is a layer located in the lowest part of the electroconductive roller 1 (adjacent to the shaft 2), as shown in FIG.

  There is no restriction | limiting in particular about the material which comprises the said elastic layer, According to the objective, it can select suitably, For example, a polyurethane resin, a rubber elastic body, a polyamide resin, polyester resin, a polyimide resin, a silicone resin, an acrylic resin, Polyvinylidene fluoride resin, polyvinyl butyral resin, ethylene-tetrafluoroethylene copolymer resin, melamine resin, fluorine resin, epoxy resin, polycarbonate resin, polyvinyl alcohol resin, cellulose resin, polyvinylidene chloride resin, polyvinyl chloride resin, polyethylene resin , Ethylene-vinyl acetate copolymer resin, and the like. These may be used alone or in combination of two or more. Among these, polyurethane resins are preferable in that they can realize good flexibility.

The polyurethane resin is not particularly limited as the polyurethane resin, and can be appropriately selected according to the purpose. For example, polyester-based urethane resin, polyether-based urethane resin, polycarbonate-based urethane resin, and the like can be mentioned. These may be used alone or in combination of two or more.
Among these, polyether-based urethane resins are preferable in that the resin has a low resistance value and hydrolysis is less likely to occur. Moreover, it can be made to be ultraviolet-ray cured by irradiating an ultraviolet-ray as it is a polyurethane resin which has a (meth) acrylate group. In particular, a polyurethane in which a (meth) acrylate group is introduced at the end of the polyurethane is preferable in that the efficiency of ultraviolet curing is excellent.

Here, the elastic layer is formed of a composition for an elastic layer.
The composition for the elastic layer is not particularly limited as long as it is a composition capable of forming the elastic layer, and can be appropriately selected according to the purpose.
When forming the elastic layer of the said polyurethane resin, it is preferable to contain components, such as a polyol, an isocyanate, a urethane bond catalyst, a solvent, a filler, etc. as said composition for elastic layers. Moreover, when forming the elastic layer of the said polyurethane foam, it is preferable to further include a foam stabilizer.
The composition for the elastic layer may contain, in addition to the above components, an ion conductive agent, a plasticizer, a softener, a tackifier, an antiblocking agent, a separating agent, a release agent, an extender, a colorant, as necessary. It may contain a crosslinking agent, a vulcanizing agent, a polymerization inhibitor, and the like.

In addition, there is no restriction | limiting in particular as said polyol, According to the objective, it can select suitably. For example, polyether polyol, polyester polyol, polytetramethylene glycol, polybutadiene polyol, alkylene oxide modified polybutadiene polyol, polyisoprene polyol, etc. may be mentioned. These may be used alone or in combination of two or more.
Among these, polyether polyols are preferable in terms of reducing the flexibility and permanent compression strain of the resin.

Moreover, there is no restriction | limiting in particular as said isocyanate, According to the objective, it can select suitably. For example, tolylene diisocyanate (TDI), prepolymerized tolylene diisocyanate (prepolymerized TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tri Di-isocyanate, hexamethylene diisocyanate (HDI); these isocyanurate modified products, carbodiimide modified products, glycol modified products, etc .; These may be used alone or in combination of two or more.
Among these, prepolymerized tolylene diisocyanate (prepolymerized TDI) is preferable in that it has high urethane reaction activity and easily improves the elasticity of the elastic layer and hence the conductive roller.

There is no restriction | limiting in particular as said urethane bond catalyst, According to the objective, it can select suitably. For example, dibutyltin dilaurate, dioctyltin acetate, dioctyltin bis (ethyl malate), dibutyltin bis (oleyl malate), dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate , Monobutyl tin oxide, and the like. These may be used alone or in combination of two or more.
Among these, dibutyltin dilaurate is preferable in terms of high catalytic activity.

There is no restriction | limiting in particular as said foam stabilizer, According to the objective, it can select suitably. For example, silicone type foam stabilizers, ionic surfactants, nonionic surfactants, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, silicone-based foam stabilizers are preferable in that the foam uniformity of the foam is good.
Moreover, it is preferable that the said silicone type foam stabilizer has a functional group. There is no restriction | limiting in particular as a functional group of the said silicone type foam stabilizer, According to the objective, it can select suitably, For example, OH (hydro acid) group, a thiol group, an amino group, an imino group, a nitro group, a nitroso Groups, carboxyl groups, acroyl groups, alkyl groups, alkenyl groups, alkoxy groups and the like. These may be used alone or in combination of two or more. Among these, when an isocyanate (OH) group is contained in a composition for an adhesive layer described later, the isocyanate is a urethane bond with an OH (hydroxy acid) group derived from a silicone-based foam stabilizer in an elastic layer. In that the adhesion between the elastic layer and the adhesive layer can be further improved. If the moisture-curable adhesive described later contains MDI having two or more isocyanate groups, the MDI has high electron-withdrawing property and is easily chemically reacted with OH of the foam stabilizer, so it has high reaction efficiency and adhesiveness. Can be particularly improved.

  There is no restriction | limiting in particular as said solvent, According to the objective, it can select suitably. For example, alcohols such as methanol, ethanol and isopropyl alcohol; butyl acetate; dimethyl sulfone; dimethyl sulfoxide; These may be used alone or in combination of two or more. Among these, butyl acetate is preferred in view of its high volatilization rate.

In addition, when forming an elastic layer by the said composition for elastic layers, after apply | coating the said composition for elastic layers to the outer surface of a shaft, the electroconductive roller of this invention forms an elastic layer by irradiating an ultraviolet-ray. be able to. Therefore, the roller of the present invention can be manufactured in a short time without requiring a large amount of heat energy. In addition, since a curing furnace or the like is unnecessary for production, a large amount of equipment cost is not required. In addition, as a method of apply | coating the raw material for said layer formation to the outer surface of a shaft, or the surface of an elastic layer, a spray method, a roll coater method, a dipping method, the die coating method etc. are mentioned. Moreover, as a light source used for ultraviolet irradiation, a mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp etc. are mentioned. The conditions of the ultraviolet irradiation may be appropriately selected according to the components, the composition, the application amount, and the like contained in the layer forming raw material, and the irradiation intensity, the integrated light amount, and the like may be appropriately adjusted.
When the elastic layer is formed of polyurethane foam, the elastic layer can be formed, for example, by directly supporting the composition for an elastic layer including the polyurethane foam on the radially outer side of the shaft.

(Surface)
The surface layer 4 constituting the conductive roller 1 of the present embodiment is a layer formed on the elastic layer 3 directly or via an intermediate layer such as an adhesive layer, as shown in FIG.

  And in this invention, the said surface layer consists of a composition for surface layers containing a polyol, an isocyanate, and a crosslinking agent, The molecular weight of the said polyol is 500-8000, and the isocyanate index of the composition for surface layers is 1.2- The cohesion of the surface layer is 4 to 11 nN.

The reduction of the conveyance performance such as toner conveyance unevenness of the conductive roller which is the main cause of the reduction of the printing density is caused by the low cohesion of the surface of the conductive roller (surface layer surface). It has been found that the toner conveyance performance of the conductive roller can be enhanced by enhancing the. However, if the cohesion of the surface layer is too high, it will cause an increase in torque due to an increase in surface stickiness, and promotion of tray deterioration.
Therefore, in the present invention, by adjusting the molecular weight of the polyol in the composition for surface layer and the isocyanate index, the torque of the surface layer is controlled by keeping the cohesion of the surface layer within a specific range (specifically, 4 to 11 nN). It is possible to enhance the toner conveyance performance and to suppress the decrease in print density without causing problems such as the increase of toner density and the deterioration of toner.

Here, the cohesion of the surface refers to the cohesion within the material that constitutes the surface (a force that indicates whether the materials can be integrated without being separated), and in the present invention, the AFM (Atomic Force Microscope): It can be obtained from a force curve measured using an atomic force microscope. The force curve refers to the distance between the probe and the sample and the force acting on the cantilever by moving the fixed point up and down by setting the upper and lower limits of the distance between the probe and the sample at the time of measurement by AFM It is a curve obtained as a result of plotting the relationship with the deflection amount of the cantilever. As the AFM, for example, a commercially available microscope such as Hitachi High-Technologies NanoNavi S-image can be used.
In addition, the cohesion of the surface layer needs to be in the range of 4 to 11 nN from the viewpoint of enhancing the toner conveyance performance and suppressing the decrease in the printing density without causing problems such as an increase in torque and toner deterioration. . Furthermore, it is preferable to set it as 4-8 nN from the same viewpoint, and it is more preferable to set it as 5-8 nN.

Here, the surface layer is formed of a surface layer composition.
The surface layer composition contains a polyol, an isocyanate, and a crosslinking agent, the molecular weight of the polyol is 500 to 8000, and the isocyanate index of the surface layer composition is 1.2 to 2.0.
In addition, about the said composition for surface layers, well-known additives, such as a electrically conductive agent, can be suitably contained unless the objective of this invention is impaired other than the component mentioned above.

Here, the molecular weight (weight average molecular weight) of the polyol is required to be 500 to 8000, preferably 800 to 8000, and more preferably 1000 to 6000.
As the molecular weight of the polyol tends to increase as the molecular weight of the polyol increases and decreases as the molecular weight of the polyol decreases, the toner can be transported without causing problems such as an increase in torque and toner deterioration. The molecular weight is set to 500 to 8000 in order to enhance the performance. In addition, when the molecular weight of the polyol is 800 or more, the base layer is softened, so that the surface layer mixture is easily penetrated into the hardened base layer, and when it is 8000 or less, the adhesion between the layers can be improved. There is also.
In addition, the molecular weight (weight average molecular weight) of the said polyol can be calculated | required as a value of polystyrene conversion using gel permeation chromatography.

Here, the polyol is not particularly limited as long as it has the above-described molecular weight, and can be appropriately selected according to the purpose. Examples of the type of the polyol include polyether polyols, polyester polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, alkylene oxide-modified polybutadiene polyols, polyisoprene polyols, and the like. In addition, the polyol mentioned above may be used individually by 1 type, and may use 2 or more types together.
Moreover, it is preferable that the said polyol contains at least 1 type selected from the group which consists of a hydrogenated polybutadiene polyol, polycarbonate polyol, polytetramethylene ether glycol, and a polypropylene glycol among the above-mentioned. The toner conveyance performance can be further enhanced, and the reduction in print density can be suppressed more reliably.

Moreover, as an isocyanate, if it can have the isocyanate index mentioned later, there will be no restriction | limiting in particular, According to the objective, it can select suitably. For example, tolylene diisocyanate (TDI), prepolymerized tolylene diisocyanate (prepolymerized TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tri Di-isocyanate, hexamethylene diisocyanate (HDI); their isocyanurate modified products, carbodiimide modified products, glycol modified products, etc .; These may be used alone or in combination of two or more.
Among these, isophorone diisocyanate is advantageous in that it is easy to adjust the viscosity in the production process, it is easy to ensure the flexibility of the base layer, and the like.

Here, as an isocyanate index of the composition for surface layers, it is required that it is 1.2-2.0, and it is preferable that it is 1.2-1.8.
The higher the isocyanate index of the surface layer composition, the lower the cohesion described above, and the lower the isocyanate index, the higher the cohesion described above. Therefore, the isocyanate index is in the range of 1.2 to 2.0 in order to enhance the toner transport performance without causing problems such as an increase in torque and toner deterioration. Moreover, it is advantageous at the point which the viscosity adjustment in a manufacturing process surface becomes easy to carry out that the said isocyanate index is in the said suitable range, and the point which is excellent in the softness | flexibility of a base layer.

  In addition, the composition for surface layer can contain other components as needed. There is no restriction | limiting in particular about another component, According to the objective, it can select suitably. Other components include, for example, elastomers other than urethane components, catalysts, photopolymerization initiators, foam stabilizers, conductive agents, fillers, fine particles, peptizers, foaming agents, plasticizers, softeners, tackifiers, Antiblocking agents, separating agents, releasing agents, extenders, coloring agents, vulcanizing agents, polymerization inhibitors, etc. may be mentioned. These may be used alone or in combination of two or more.

  The surface layer composition may also contain an elastomer other than the urethane component formed from the above-described polyol and isocyanate. There is no restriction | limiting in particular as said elastomer, According to the objective, it can select suitably. For example, silicone, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), polynorbornene rubber Butyl rubber (IIR), chloroprene rubber (CR), acrylic rubber, epichlorohydrin rubber (ECO), ethylene-vinyl acetate copolymer (EVA), mixtures thereof, and the like. These may be used alone or in combination of two or more.

Moreover, it is preferable that the said composition for surface layers contains a silicone among the elastomer mentioned above. Since the silicone has the effect of reducing the cohesion of the surface layer, the cohesion of the surface layer can be adjusted more effectively by including an appropriate amount in the composition for the surface layer, resulting in an increase in torque and toner deterioration. This is because the decrease in print density can be suppressed.
The content of the silicone is not particularly limited, but is preferably 0.1 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the urethane component.

Moreover, about the said silicone, as above-mentioned, it should just be an effect which reduces the cohesion force of surface layer, and it does not specifically limit about a kind.
However, it is preferable to contain a modified silicone having a functional group such as a hydroxyl group, an epoxy group, a methacryloxy group, an acrylate group or a methacrylate group as the silicone from the viewpoint that the surface toner conveyance performance can be more reliably enhanced. Among them, it is more preferable to contain an acrylate modified silicone having an acrylate group having a molecular weight of 500 to 2,000 per one. Moreover, by containing these silicones, there is also an effect that compatibility with a urethane component becomes high.

Examples of the catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, tin octenoate, monobutyl tin oxide, and the like; inorganic substances such as stannous chloride Tin compounds; organic lead compounds such as lead octenoate; monoamines such as triethylamine and dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; pentamethyldiethylenetriamine and pentamethyldipropylenetriamine Triamines such as tetramethylguanidine; triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethylamine Cyclic amines such as noethyl morpholine, dimethylimidazole and pyridine; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethyl ethanolamine, methyl hydroxyethyl piperazine and hydroxyethyl morpholine; bis (dimethylaminoethyl) ether Ether amines such as ethylene glycol bis (dimethyl) aminopropyl ether; organic sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, fluorosulfuric acid; inorganic acids such as sulfuric acid, phosphoric acid, perchloric acid; sodium alcoholate, Bases such as lithium hydroxide, aluminum alcoholate and sodium hydroxide; Titanium compounds such as tetrabutyl titanate, tetraethyl titanate and tetraisopropyl titanate; Bismuth compounds; quaternary ammonium salts, and the like. Among these catalysts, organotin compounds are preferred. One of these catalysts may be used alone, or two or more thereof may be used in combination.
The amount of the catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the polyol.

  Moreover, it is preferable that the said surface layer uses an ultraviolet curable polyurethane. In that case, as the photopolymerization initiator contained in the composition for surface layer, 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, 2,2-dimethoxy-2-phenylacetophenone, acetophenone diethyl ketal, alkoxyacetophenone Benzophenone derivatives such as benzyl dimethyl ketal, benzophenone and 3,3-dimethyl-4-methoxybenzophenone, 4,4-dimethoxybenzophenone, 4,4-diaminobenzophenone, alkyl benzoylbenzoate, bis (4-dialkylaminophenyl) ketone And benzyl derivatives such as benzyl and benzyl methyl ketal; benzoin derivatives such as benzoin and benzoin isobutyl ether; benzoin isopropyl ether; Nonone, 1-hydroxycyclohexyl phenyl ketone, xanthone, thioxanthone and thioxanthone derivatives, fluorene, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentyl phosphine oxide Bis (2,4,6-trimethyl benzoyl) -phenyl phosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (Morpholinophenyl) -butanone-1 etc. can be used. One of these photopolymerization initiators may be used alone, or two or more thereof may be used in combination.

There is no restriction | limiting in particular as said foam stabilizer, According to the objective, it can select suitably. For example, a silicone type foam stabilizer, an ionic surfactant, a nonionic surfactant, etc. are mentioned. These foam stabilizers may be used alone or in combination of two or more.
Further, among the above-described foam stabilizers, silicone foam stabilizers are preferable in that the foam uniformity of the foam is improved.

  The conductive agent has the function of imparting conductivity to the elastic layer. As such a conductive agent, one capable of transmitting ultraviolet light is preferable, an ion conductive agent or a transparent electron conductive agent is preferably used, and an ion conductive agent is particularly preferably used. Since the ion conductive agent dissolves in the urethane acrylate oligomer and has transparency, when an ion conductive agent is used as the conductive agent, ultraviolet rays are sufficiently coated even if the material for layer formation is thickly coated on the shaft It reaches the inside of the film, and the layer forming material can be sufficiently cured. Here, as the ion conductive agent, perchlorate such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium, chlorate, hydrochloride, bromate Ammonium salts such as salts, iodates, borohydrofluorides, sulfates, ethyl sulfates, carboxylates, sulfonates and the like; alkali metals such as lithium, sodium, potassium, calcium and magnesium, and alkaline earth metals Perchlorate, chlorate, hydrochloride, bromate, iodate, borohydrofluoride, sulfate, trifluoromethyl sulfate, sulfonate and the like can be mentioned. In addition, as a transparent electron conductive agent, fine particles of metal oxide such as ITO, tin oxide, titanium oxide, zinc oxide, etc .; fine particles of metal such as nickel, copper, silver, germanium, etc .: conductive titanium oxide whisker, conductive titanium And conductive whiskers such as barium whiskers. Furthermore, conductive carbons such as ketjen black and acetylene black, carbon blacks for rubbers such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, etc., carbons for color, and carbons for color treatment subjected to oxidation treatment etc. Black, pyrolytic carbon black, natural graphite, artificial graphite, etc. may be used. One of these conductive agents may be used alone, or two or more thereof may be used in combination.

(Other layers)
The conductive roller of the present invention comprises a shaft 2, an elastic layer 3 and a surface layer 4 as shown in FIG. 2, but may further comprise other layers as required.
There is no restriction | limiting in particular as said other layer, According to the objective, it can select suitably, For example, the intermediate | middle layer formed between the elastic layer 3 and the surface layer 4, and between the surface layer 3 and the shaft 2 The intermediate layer etc. which are formed are mentioned. The intermediate layer is not particularly limited, and can be appropriately selected according to the types of the elastic layer and the surface layer. For example, a moisture-curable resin may be used, or an ultraviolet-curable resin in which an amide-containing monomer such as an acryloyl morpholine monomer is blended with an acrylate-containing oligomer may be used.

(shaft)
The conductive roller of the present invention comprises a shaft 2 as shown in FIG. The material constituting the shaft 2 is not particularly limited as long as it has good conductivity, and can be, for example, a shaft made of metal, a shaft made of a highly rigid resin substrate, or a combination of these. It may be a metal or highly rigid resin cylinder or the like hollowed out inside.

  In addition, when using a highly rigid resin for the said shaft, it is preferable to add and disperse | distribute an electrically conductive agent to highly rigid resin, and to ensure electroconductivity sufficiently. Here, as the conductive agent to be dispersed in the high rigidity resin, carbon black powder, graphite powder, carbon fiber, metal powder such as aluminum, copper, nickel etc., metal oxide powder such as tin oxide, titanium oxide, zinc oxide etc., conductivity Powdered conductive agents, such as crystalline glass powder, are preferred. 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% by mass, and more preferably in the range of 5 to 20% by mass, with respect to the entire high rigidity resin.

  Examples of the material of the metal shaft and the metal cylinder include iron, stainless steel, aluminum and the like, which may be plated with zinc or nickel. The material of the highly rigid resin base material 1B is 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, polyamide imide, polyether imide, poly sulfone, polyether ether ketone, polyethylene terephthalate, polyarylate, liquid crystal polymer, polytetrafluoroethylene, polypropylene, ABS resin, Polystyrene, polyethylene, melamine resin, phenol resin, silicone resin and the like can be mentioned. 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.

<Image forming apparatus>
An image forming apparatus according to the present invention is characterized by including the above-described electrically conductive roller according to the present invention.
By providing the conductive roller of the present invention in the image forming apparatus, it is possible to effectively suppress the decrease in printing density due to the deterioration of the toner conveyance performance.

Here, FIG. 5 schematically shows an embodiment of the image forming apparatus of the present invention, but in the image forming apparatus of the present embodiment, the conductive roller 1 of the present invention is used as a developing roller. ing. In the image forming apparatus of the present embodiment, a photosensitive member 11 holding an electrostatic latent image, a charging roller 12 for charging the photosensitive member 11 located in the vicinity (upper side in the figure) of the photosensitive member 11, toner 24 A toner supply roller 13 for supplying toner, a developing roller 1 disposed between the toner supply roller 13 and the photosensitive member 11, and a cleaning blade 17 provided in the vicinity (upper side in the figure) of the developing roller 1; A transfer roller 18 located in the vicinity (downward in the drawing) of the photosensitive member 11 and a cleaning roller 19 disposed adjacent to the photosensitive member 11 are provided.
The image forming apparatus of the present embodiment can further include known components (not shown) generally used in the image forming apparatus.

  In the image forming apparatus shown in FIG. 5, first, the charging roller 1 is brought into contact with the photosensitive member 11, a voltage is applied between the photosensitive member 11 and the charging roller 12, and the photosensitive member 11 is charged to a constant potential. Thereafter, an electrostatic latent image is formed on the photosensitive member 11 by an exposure device (not shown). Next, as the photosensitive member 11, the toner supply roller 13 and the developing roller 1 rotate in the direction of the arrow in the figure, the toner 15 on the toner supply roller 13 passes through the developing roller 1 and is supplied to the photosensitive member 11. Be The toner 15 on the developing roller 1 is prepared in a uniform thin layer by the cleaning blade 17 and is rotated while the developing roller 1 and the photosensitive member 11 are in contact with each other. The latent image is visualized by adhering to the electrostatic latent image. The toner 24 attached to the latent image is transferred to a recording medium such as paper by the transfer roller 18, and the toner 15 remaining on the photosensitive member 11 after transfer is removed by the cleaning roller 19.

  EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

<Samples 1 to 27>
Each sample of the developing roller was produced according to the conditions described below.

(Preparation of elastic layer)
A mixture of isophorone diisocyanate (manufactured by Evonik Japan Co., Ltd.) as an isocyanate is used as an isocyanate index 1.6, using both end hydroxyl group polypropylene diol ("Sannicks PP-2000" manufactured by Sanyo Chemical Industries, Ltd.) as a polyol I put it together. Furthermore, in order to introduce a (meth) acrylate group into polyurethane, 2-hydroxypropyl acrylate which is a (meth) acrylate containing a hydroxyl group (manufacturing company: Kyoeisha Chemical Co., Ltd., trade name: light ester HOP-A (N)) Was added to react equivalently with the isocyanate group. The reaction was followed by IR, and when the isocyanate peak disappeared, the reaction was terminated to obtain urethane acrylate for the elastic layer. The composition for elastic layers was adjusted so that IRGACURE184 (made by BASF Corporation) may be included as this with 1 mass part with respect to 100 mass parts of urethane acrylates as a photoinitiator.
The prepared composition for an elastic layer was applied by a die coater to a thickness of 1500 μm, and while being applied, it was cured by spot UV irradiation to form an elastic layer. The elastic layer-formed roller thus obtained was further subjected to UV irradiation for 5 seconds at a UV irradiation intensity of 700 mW / cm ² while rotating in a nitrogen atmosphere.

(Preparation of surface layer)
In order to introduce a (meth) acrylate group into the polyurethane using a polyol described in Table 1 and an appropriate amount of isocyanate described in Table 1 to satisfy the isocyanate index as shown in Table 1, for capping of the terminal isocyanate Of 2-hydroxyethyl acrylate ("Light Ester HOA (N)" manufactured by Kyoeisha Chemical Co., Ltd.) in an amount of 4.5 parts by mass with respect to 100 parts by mass of a polyol, Irg. A surface layer composition containing 1 part by mass of 907 (manufactured by BASF Corp.) with respect to 100 parts by mass of a polyol was prepared. The content of silicone contained in the surface layer composition and the isocyanate index of the surface layer composition are shown in Table 1.
Next, the prepared composition for surface layer is applied by a roll coater on the surface of the elastic layer-formed roller obtained, and UV irradiation is performed to form a surface layer with a thickness of 6 μm, and a developing roller for each sample is obtained. Made.

(Evaluation)
The following evaluation was performed about each sample of the produced developing roller.

(1) Cohesive Force On the surface of each sample of the developing roller, a force curve was created using AFM (atomic force microscope, manufactured by Hitachi High-Technologies Corporation), and the cohesive force (nN) was derived. The obtained cohesion is shown in Table 1.

(2) Hardness For each sample of the developing roller, a sheet sample (tensile test sample) having a thickness of 1 mm was separately prepared for the surface layer material, and the sample was measured according to the method defined in JIS K7161. A tensile test sample was prepared with a No. 3 dumbbell punching jig, and the prepared sample was subjected to a tensile test using EZ-TEST manufactured by Shimadzu Corporation. The tensile rate was 10 mm / min, and the modulus of elasticity (MPa) was calculated from strain and stress between 3% and 4%. When the elastic modulus of the developing roller is high, uneven conveyance and the like may cause the image quality to deteriorate. The measured elastic modulus is shown in Table 1.

(3) Uneven Transport of Toner Each sample of the developing roller was attached to a printing apparatus (“HL-L2360DN” manufactured by Brother Industries, Ltd.) to print 3000 sheets of 1% density images. Thereafter, the state of the toner adhering to the surface of each sample was observed at 1000 times with a Keyence laser microscope, and evaluated according to the following criteria. The evaluation results are shown in Table 1.
:: The area occupied by toner particles in the field of view is 90% or more ○: The area occupied by toner particles in the field of view is 80% or more and less than 90% ×: The area occupied by toner particles in the field of view is less than 80%

(4) Printing density About each sample of a development roller, it attaches to a printing apparatus ("HL-L2360DN" by Brother Kogyo Co., Ltd.) and carries out solid black printing (all black printing), and obtains a printed image obtained The reflection density of K color was measured with a reflection densitometer "eXact" manufactured by X-Rite. The measured reflection density results are shown in Table 1.

(5) Other printing problems Each sample of the developing roller is attached to a printing apparatus ("HL-L2360DN" manufactured by Brother Industries, Ltd.), and 3000 sheets of 1% density images are implemented. It was visually observed whether there was a problem. The observed printed images were evaluated according to the following criteria, and the results are shown in Table 1.
:: no problem: no white vertical streaks or the like in the black solid image ×: occurrence of streaks or occurrence of blur

* 1: For polyols,
PPG is polypropylene glycol ("PP-2000" manufactured by Sanyo Chemical Industries, Ltd.),
PTMG is polytetramethylene ether glycol ("PTG-200 SN" manufactured by Hodogaya Chemical Co., Ltd.),
The ester diol is (Plascel 220, manufactured by Daicel Industries, Ltd.),
Polycarbonate diol is (Asahi Kasei Chemicals Corporation "T5652"),
The hydrogenated polybutadiene is shown to be (“GI-2000” manufactured by Nippon Soda Co., Ltd.).
* 2: For isocyanate,
IPDI is isophorone diisocyanate ("VESTANAT IPDI" manufactured by Evonik Co., Ltd.),
TDI is toluene diisocyanate (Toron Co., Ltd. "Corronate T-80"),
MDI is diphenylmethane diisocyanate (manufactured by Tosoh Corp. "Millionate MT"),
It shows that HDI is hexamethylene diisocyanate ("Duranate 50M-HDI" manufactured by Asahi Kasei Corporation).
* 3: Silicone without acrylate modification, manufactured by NOF Corporation "FS-7101"
* 4: Acrylate modified silicone, manufactured by Shin-Etsu Chemical Co., Ltd. “X22-2457”, molecular weight 1000 per acrylate group
* 5: Acrylate modified silicone, manufactured by Shin-Etsu Chemical Co., Ltd. “X 22-2458”, molecular weight 300 per acrylate group

  From the results in Table 1, it was found that the samples of the developing roller, which belong to the range of the example, were excellent in the toner conveyance performance without causing a problem of printing, and show good results with respect to the printing density. On the other hand, the sample of the developing roller belonging to the range of the comparative example had a problem in any of the evaluation items.

  According to the present invention, it is possible to provide a conductive roller capable of suppressing a decrease in print density caused by the deterioration of toner conveyance performance. Further, according to the present invention, an image forming apparatus excellent in print density can be provided.

1 Developer roller (conductive roller)
Reference Signs List 2 shaft 3 elastic layer 4 surface layer 11 photoreceptor 12 charging roller 13 toner supply roller 14 toner storage unit 15 toner 17 cleaning blade 18 transfer roller 19 cleaning roller

Claims (5)

A conductive roller comprising a shaft, and at least an elastic layer and a surface layer on the outer peripheral side of the shaft,
The surface layer comprises a surface layer composition containing a polyol, an isocyanate and a crosslinking agent,
The molecular weight of the polyol is 500 to 8000, and the isocyanate index of the surface layer composition is 1.2 to 2.0,
The conductive roller, wherein the cohesion of the surface layer is 4 to 11 nN.   The conductive roller according to claim 1, wherein the polyol comprises at least one selected from the group consisting of a hydrogenated polybutadiene polyol, a polycarbonate polyol, a polytetramethylene ether glycol and a polypropylene glycol.   The conductive roller according to claim 1 or 2, wherein the composition for surface layer further comprises 0.1 to 5 parts by mass of silicone with respect to 100 parts by mass of the urethane component.   The conductive roller according to any one of claims 1 to 3, wherein the silicone contains an acrylate-modified silicone having an acrylate group having a molecular weight of 500 to 2,000 per one.   An image forming apparatus comprising the conductive roller according to any one of claims 1 to 4.

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