JP2012181229A - Toner carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrier that has an elastic layer formed of a single layer, reduces damage to toner and improves toner-scraping property at the same time, and provides high-quality images in a duration test.SOLUTION: A toner carrier 10 comprises a shaft 1, and a single-layered polyurethane foam layer 2 carried on the outer periphery of the shaft 1. The polyurethane foam layer 2 comprises conductive solution containing a conductive material and a binder impregnated therein. The polyurethane foam layer 2 has the Asker F hardness of 75 to 84 degrees from the surface to 1 mm toward the inside and the IFD hardness of 220 to 240 N from 1 mm from the surface toward further inside of the layer.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner carrier, and more specifically, in an image forming apparatus such as a copying machine or a printer, a toner (developer) is conveyed to an image forming body such as a photoreceptor or paper to form a visible image on the surface. The present invention relates to a toner carrier used for supplying toner to a roller.

  In general, as shown in FIG. 3, an image forming body 11 such as a photoconductor that holds an electrostatic latent image, and the image forming body are provided in a developing unit in an electrophotographic image forming apparatus such as a copying machine or a printer. A developing roller 12 that makes the electrostatic latent image visible by attaching toner 20 held on the surface in contact with the toner 11 and a toner carrier 13 for supplying toner to the developing roller 12 are provided. Yes. In such a developing unit, image formation is performed by a series of processes in which the toner 20 is transported from the toner storage unit 14 to the image forming body 11 via the toner carrier 13 and the developing roller 12. In the figure, reference numeral 15 denotes a transfer roller, 16 denotes a charging portion, 17 denotes an exposure portion, and 18 denotes a blade for scraping toner.

  Among them, the toner carrier 13 has a function of carrying toner 20 on the surface by frictional charging and supplying (conveying) the toner to the developing roller 12, and a cleaning member for scraping off unnecessary toner remaining on the surface of the developing roller 12. As a function. Therefore, the toner carrier 13 is required to have toner transportability, toner chargeability, and toner scraping property. In particular, considering the realization of high image quality and high durability in image formation, the toner carrier 13 can improve the scraping property of residual toner while reducing damage to the toner accompanying image formation. Desired.

  The toner carrier 13 generally has a roller shape in which an elastic layer such as polyurethane foam is provided on the outer periphery of a shaft via an adhesive layer. As an improved technique related to the conductive roller, for example, Patent Document 1 discloses a conductive roll used for a charging roll or the like, in which a conductive elastic body layer is formed concentrically on the outer periphery of a shaft body. A conductive roll is disclosed in which the surface of an elastic layer is coated with a resin dielectric layer in which conductive particles having a predetermined electric resistance are distributed. Patent Document 2 discloses a conductive roller that can be used as a developing roller, which includes a roller body made of a conductive resin porous body, and a conductive shaft that is inserted through the roller body. The porous body is obtained by impregnating and drying a conductive resin solution, and the conductive resin formed by drying is not only adhered to the inside of the roller body, but also the outer peripheral surface is a conductive resin layer. A conductive roller coated with is disclosed.

JP-A-1-66675 (Claims etc.) JP 2003-43805 A (Claims etc.)

  In the toner carrier, from the viewpoint of reducing damage to the supplied toner, it is preferable to reduce the contact pressure of the toner carrier. For that purpose, at least the inside of the polyurethane foam layer constituting the elastic layer of the toner carrier must be softly formed. On the other hand, from the viewpoint of scraping off of the residual toner, it is preferable to form the surface of the polyurethane foam layer hard in order to efficiently collect the toner. Therefore, it is difficult for the toner carrying member to satisfy both the demand for the reduction of the toner damage and the improvement of the toner scraping property, and these have a contradictory relationship.

  In response to such a demand, it is conceivable to lower the hardness inside the polyurethane foam layer constituting the toner carrier and increase the surface hardness. However, in the structure composed of two layers having different hardnesses as disclosed in Patent Document 1, the production process becomes complicated and the number of members increases. Therefore, it has been desired to establish a technique for achieving both reduction of toner damage and improvement of toner scraping property in the toner carrier without causing such other problems.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and achieve both reduction of toner damage and improvement of toner scraping property in a toner carrier having an elastic layer composed of a single layer, even during durability. An object of the present invention is to provide a toner carrier capable of obtaining a high-quality image.

  As a result of intensive studies, the present inventors have found the following. That is, conventionally, a polyurethane foam layer used for a conductive roller is uniformly and uniformly impregnated with a conductive solution containing a conductive material and a binder therein as disclosed in Patent Document 2. Therefore, the surface hardness and the internal hardness were made substantially the same. Therefore, when this is applied to a toner carrier, it is difficult to scrape off the toner in the developing roller that is in contact with it while reducing toner damage.

  From this viewpoint, the present inventors have further studied, and as a result, by adjusting the amount of the conductive solution impregnated in the polyurethane foam layer constituting the single elastic layer of the toner carrier, The inventors have found that the hardness can be changed between the inside and the present invention, and have completed the present invention.

That is, the present invention provides a toner carrier in which a single polyurethane foam layer is carried on the outer periphery of a shaft.
The polyurethane foam layer is impregnated with a conductive solution containing a conductive material and a binder, and the hardness of the polyurethane foam layer from the surface to 1 mm is 75 to 84 degrees in Asker F hardness, and from the surface The internal hardness is 220 to 240 N in terms of IFD hardness from 1 mm.

In the present invention, the amount of the conductive solution impregnated in the polyurethane foam layer is preferably in the range of 9 to 13 g / L. Moreover, in this invention, it is preferable to form the said polyurethane foam layer using the polyurethane foam which has the air permeability in the range of 30-70 cc / cm < ² > / sec. Furthermore, the solid content concentration of the conductive solution is preferably in the range of 19.0 to 22.0 mass%.

  According to the present invention, with the above configuration, in the toner carrier having an elastic layer composed of a single layer, it is possible to achieve both reduction in toner damage and improvement in toner scraping property, It has become possible to realize a toner carrier capable of obtaining a high-quality image even during durability. As described above, a conductive roller in which the hardness of the vicinity of the surface and the inside thereof is changed in a single elastic layer has not existed conventionally.

3 is a schematic perspective view illustrating an example of a toner carrier of the present invention. FIG. It is a graph which shows the relationship between the surface vicinity and internal hardness of the polyurethane foam layer before impregnation of an electroconductive solution, and the surface vicinity and internal hardness of the polyurethane foam layer after an electroconductive solution impregnation. FIG. 3 is a schematic diagram illustrating a configuration example of a developing unit of the image forming apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic perspective view showing an example of the toner carrier of the present invention. As shown in the figure, the toner carrier 10 of the present invention comprises a single polyurethane foam layer 2 carried on the outer periphery of a shaft 1.

  In the toner carrier 10 of the present invention, the polyurethane foam layer 2 is impregnated with a conductive solution containing a conductive material and a binder, and the hardness of the polyurethane foam layer 2 from the surface to 1 mm is Asker F hardness. It is 75 to 84 degrees, and the internal hardness is 220 to 240 N in terms of IFD hardness from 1 mm from the surface. As described above, the hardness is individually controlled in the vicinity and inside of the polyurethane foam layer 2 so that the vicinity of the surface is hard and the inside is soft, thereby improving the toner scraping property during printing durability. However, toner damage can be reduced. In the present invention, this makes it possible to obtain a toner carrier capable of obtaining a high-quality image even at the end of printing durability. Further, since the toner carrier of the present invention has a single polyurethane foam layer, it has the merit that the number of members and the manufacturing process can be reduced as compared with the case of the two-layer structure.

  In the present invention, the hardness of the polyurethane foam layer 2 from the surface to 1 mm and the internal hardness from 1 mm from the surface are a problem. The surface of the polyurethane foam layer 2 that can be measured based on each hardness measurement method. It defines the neighborhood and the interior. That is, about the surface vicinity, the hardness from the surface of the polyurethane foam layer 2 to 1 mm is measured by the measuring method of Asker F hardness. In addition, since the IFD hardness is compressed by 50% in the thickness direction, the inner portion of the thickness, for example, when the foam thickness is 6 mm, the hardness at a location 3 mm from the surface is measured. The inside is defined from 1 mm.

  In the present invention, the hardness from the surface of the polyurethane foam layer 2 to 1 mm is 75 to 84 degrees, preferably 80 to 82 degrees in terms of Asker F hardness. If the hardness in the vicinity of the surface is too low, the toner scraping property is lowered, and if it is too high, the toner damage is increased. In any case, a high-quality image cannot be obtained for a long time. Further, the internal hardness from 1 mm from the surface of the polyurethane foam layer 2 is 220 to 240 N, preferably 230 to 235 N in terms of IFD hardness. If the internal hardness is too low, a sufficient force is not applied to the toner, so that the toner cannot be charged because friction does not occur, and if it is too high, the toner damage increases. Can not be obtained for a long time. In particular, it has been found that the higher the internal hardness, the greater the effect on the image quality.

  In the present invention, the hardness of the polyurethane foam layer 2 can be controlled mainly by adjusting the amount of the conductive solution impregnated into the polyurethane foam layer 2. Specifically, in the present invention, the amount of the conductive solution impregnated into the polyurethane foam layer 2 is preferably in the range of 9 to 13 g / L, more preferably in the range of 12 to 12.5 g / L. is there. If the amount of the conductive solution impregnated in the polyurethane foam layer 2 is too small, the surface hardness is lowered. On the other hand, if the amount is too large, the conductive solution penetrates into the inside, and the internal hardness increases simultaneously with the surface hardness. In any case, the desired effect of the present invention may not be obtained. Here, since the solid content of the conductive solution to be impregnated substantially consists of a conductive material and a binder, the amount of impregnation is substantially the conductive material adhering to the surface and inside of the polyurethane foam layer 2 and It means the mass of the binder.

  In the present invention, by adjusting the impregnation amount of the conductive solution within the above range, as described above, different hardness can be obtained in the vicinity of the surface and in the interior in a single polyurethane foam layer. This is because the conductive solution is impregnated only in the vicinity of the surface without penetrating into the polyurethane foam layer by making the impregnation amount of the conductive solution relatively small. This is considered to be due to a difference in hardness between the vicinity of the surface and the inside. Here, in the toner carrier, it is necessary to have a desired conductivity in order to take power from the shaft. From this point of view, it is desirable that all of the thickness direction is impregnated. In order to satisfy, it is sufficient that the area of the polyurethane foam layer impregnated with the conductive solution is 16 to 17% of the total thickness from the surface.

  Further, the hardness in the vicinity and inside of the polyurethane foam layer 2 varies depending on the blending of the polyurethane foam, the air permeability, the density, and the like, as well as the blending of the conductive solution. Become.

  In the toner carrier of the present invention, the shaft 1 is not particularly limited. For example, a steel material such as sulfur free cutting steel or lead free cutting steel plated with nickel or zinc, iron, It is possible to use a metal core made of a solid metal such as stainless steel or aluminum, a metal shaft such as a metal cylinder hollowed inside.

  In the toner carrier of the present invention, the polyurethane foam used for the polyurethane foam layer 2 is not particularly limited. For example, two or more active substances can be obtained by the technique disclosed in Japanese Patent No. 3,480,028. A compound produced by stirring and mixing a compound having hydrogen and a compound having two or more isocyanate groups together with additives such as a catalyst, a foaming agent, and a foam stabilizer and foaming and curing is preferable. The film removal treatment after foam curing may or may not be performed.

  Specifically, the polyurethane foam by the method disclosed in the above-mentioned Patent No. 3,480,028 is obtained by mixing a mixture of single diols containing two kinds of single diols having an average molecular weight difference of 800 to 3600 with a polyol. It can be produced by mixing a polyether polyol containing a total amount of 50% by mass or more with respect to the components, an isocyanate, water, a catalyst, and a foaming agent, allowing them to foam, and allowing them to stand.

  Here, “single diol” is used to collectively refer to one diol or a group of two or more diols having an average molecular weight difference of 400 or less. Further, the “average molecular weight difference” represents a difference in average molecular weight of each diol as a target, and is used to mean the maximum difference particularly when there are many kinds of combinations.

  The polyether polyol used in producing the polyurethane foam is (1) a polyether polyol of a type in which only propylene oxide is added to, for example, diethylene glycol, or (2) a block of propylene oxide and ethylene oxide, for example, in diethylene glycol. Randomly added types of polyether polyols, (3) In the above (1) or (2), including, for example, polyether polyols of a type grafted with acrylonitrile or styrene, etc., but not particularly limited, (1) A type of polyether polyol.

  Examples of the initiator used for producing the polyether polyol include polyhydric alcohols, polyhydric phenols, mono- or polyamines, preferably polyhydric alcohols and polyhydric phenols, particularly preferably polyhydric alcohols. It is. Specific examples include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, and among them, diethylene glycol is particularly preferable.

  The polyether polyol component may contain a polyol component other than the diol. As such a polyol component, trifunctional, which is usually used in the production of polyurethane foam, for example, glycerin base added with alkylene oxide, for example, propylene oxide, two types of alkylene oxide, for example, propylene oxide Examples of those obtained by adding ethylene oxide in a random or block manner and polyfunctional ones include polyether polyols obtained by adding the same ones as described above to a sucrose base.

  As the isocyanate, tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate and the like can be used alone or in combination. Of these, tolylene diisocyanate is particularly preferable.

  As a compound used for a catalyst and a foaming agent, there is no restriction | limiting in particular in a kind and usage-amount, A well-known thing is used. Specifically, for example, amine catalysts such as triethylenediamine, tetramethylenehexadiamine, dimethylcyclohexylamine, and organic tin catalysts such as stannous octoate and dibutyltin dilaurate are used as the catalyst. As the foaming agent, methylene chloride, Freon 123, Freon 141b or the like is used.

  In addition to the above, various additives such as flame retardants, antioxidants, ultraviolet absorbers, foam stabilizers and the like can be appropriately blended with the polyurethane foam used in the present invention. Among these, examples of the foam stabilizer include various siloxanes and polyalkylene oxide block copolymers.

In the present invention, the breathability of the polyurethane foam used for the polyurethane foam layer 2 is preferably 30 to 70 cc / cm ² / sec. If the air permeability of the polyurethane foam is too low, the function of supporting the toner as a toner carrier may be impaired. If it is too high, it becomes difficult to control the vicinity of the surface and the inside to the desired hardness. By setting the air permeability within the above range, it is easy to control the impregnation region of the conductive solution as desired, and to control the vicinity of the surface and the inside to the target hardness. The air permeability is a value measured according to JIS K 6400.

Moreover, as a density of the said polyurethane foam, the range of 50-70 kg / m < ³ > is preferable. If the density is too low or too high, it becomes difficult to control the vicinity of the surface and the inside to the desired hardness.

  Furthermore, the average cell diameter of the polyurethane foam is preferably about 300 to 500 μm. If the average cell diameter is too small, the toner fluidity and toner transportability are lowered, and if it is too large, it becomes difficult to control the vicinity of the surface and the inside to the desired hardness.

  Furthermore, the number of cells of the polyurethane foam is preferably about 50 to 83 / inch. If the average number of cells is too small, it will be difficult to control the vicinity of the surface and the inside to the desired hardness, and if it is too large, the toner fluidity and toner transportability will deteriorate.

  Next, in the present invention, the conductive material used in the conductive solution includes carbonaceous particles such as carbon black and graphite, metal powder such as silver and nickel, and conductive metal oxide such as tin oxide, titanium oxide, and zinc oxide. 1 selected from the group consisting of a single substance, or an insulating fine particle such as barium sulfate coated with the above conductive metal oxide wet, conductive metal carbide, conductive metal nitride, conductive metal boride and the like 1 Used in combination of species or multiple species. In the present invention, carbon black can be preferably used, and ketjen black is more preferably used. As the conductive material, it is preferable to use fine particles having an average particle size of 100 nm or less, particularly about 50 nm or less.

  In addition, as a binder used for the conductive solution, acrylic resin such as acrylic resin, polyacrylic ester resin, acrylic acid-styrene copolymer resin, acrylic acid-vinyl acetate copolymer resin, polyvinyl alcohol, polyacrylamide, Examples thereof include polyvinyl chloride resin, urethane resin, vinyl acetate resin, butadiene resin, epoxy resin, alkyd resin, melamine resin, chloroprene rubber and the like. Among these, acrylic resin, urethane resin, and chloroprene rubber are preferably used. These binders can be used alone or in admixture of two or more. The conductive material alone cannot be firmly bonded to the foam wall of the polyurethane foam. However, by using a conductive solution containing a binder, the conductive material adheres firmly to the foam wall of the polyurethane foam, so that stable conductivity can be achieved. The conductive layer can be formed in the foam of the polyurethane foam.

  In this invention, it is preferable that the solid content density | concentration of an electroconductive solution exists in the range of 19.0-22.0 mass%. If the solid content concentration of the conductive solution is too low, toner damage will increase, and if it is too high, sufficient force will not be applied to the toner, so there will be no friction and the toner will not be charged. .

  The compounding ratio of the conductive material and the binder in the conductive solution is preferably such that the solid content of the conductive material is 10 to 110 parts by weight, particularly 30 to 50 parts by weight, with respect to 100 parts by weight of the solid content of the binder. If the conductive material has too much solid content, the adhesive force to the polyurethane foam may be insufficient, and if it is too small, the surface resistance of the toner carrier may not be stable.

  In addition to the conductive material and the binder, an appropriate amount of water, an organic solvent such as toluene or ethyl acetate can be added to the conductive solution. These solvents are preferably added so that the viscosity of the conductive solution is about 5 to 300 cps (25 ° C.). When the viscosity of the conductive solution is within this range, the work of impregnating and attaching the conductive solution to the polyurethane foam becomes easier.

  If necessary, other additives such as mineral oil-based antifoaming agents, silicon-based antifoaming agents, surfactants, charge control agents, and the like can be further added to the conductive solution. These are preferably added in an amount of 0.001 to 10 parts by weight, particularly 0.001 to 0.1 parts by weight, based on 100 parts by weight of the conductive solution.

  In the toner carrier of the present invention, an adhesive layer can be provided between the shaft 1 and the polyurethane foam layer 2 as desired in order to ensure adhesion between the two. The adhesive layer can be formed using, for example, a two-component polyurethane adhesive, an epoxy adhesive, a polyester adhesive, an acrylic adhesive, an acrylic emulsion adhesive, a urethane emulsion adhesive, or the like.

  The toner carrier of the present invention can be manufactured, for example, as follows. That is, first, a block-like polyurethane foam is cut out in a desired size from a polyurethane foam produced in an appropriate shape, a hole is made, and the shaft 1 is passed through an adhesive layer as desired. Thereafter, the surface of the block-like polyurethane foam is polished and finished into a cylindrical shape to obtain a roller shape. Next, conductivity is imparted to the polyurethane foam using the conductive solution. Specifically, for example, a conductive solution is prepared by dispersing and containing a powdered conductive agent and a binder in water or an organic solvent together with other additives as necessary. The polyurethane foam with a shaft is immersed, and the conductive solution is impregnated into the foam of the polyurethane foam. After that, the polyurethane foam with a shaft is taken out from the conductive solution, compressed to remove excess conductive solution, and then dried by heating to remove moisture and the like, so that the conductive agent is put together with the binder in the bubbles of the polyurethane foam. Can be fixed.

Hereinafter, the present invention will be described in more detail with reference to examples.
A toner carrier having a single polyurethane foam layer carried on the outer periphery of the shaft as shown in FIG. 1 was produced as follows. First, a block-like polyurethane foam is cut out in a desired size from a polyurethane foam produced in an appropriate shape, a hole is made, and a shaft (material: SUM22, diameter 6.0 mm, length 300 mm) is passed through an adhesive layer. I passed. Thereafter, the surface of the block-like polyurethane foam was polished and finished into a cylindrical shape, and the polyurethane foam layer had a roller shape with a diameter of 13.0 mm and a length of 250 mm (thickness on the shaft of 6 mm). The surface and internal hardness, density, and air permeability values before impregnation of the used polyurethane foams A to C are shown in Table 1 below.

  Next, a conductive solution was prepared with the formulation shown in Table 2 below, and the polyurethane foam with the shaft was immersed in the conductive solution, and the conductive solution was impregnated in the foamed foam. Thereafter, the polyurethane foam with a shaft was taken out of the conductive solution and compressed to remove excess conductive solution, and then dried by heating to remove moisture and the like, to obtain toner carriers of the examples and comparative examples. . FIG. 2 shows the relationship between the surface vicinity and internal hardness of the polyurethane foam before impregnation with the conductive solution and the surface vicinity and internal hardness of the polyurethane foam after the impregnation with the conductive solution, respectively.

＊１）対ウレタン比率とは、ポリウレタンフォーム層の密度に対する質量％を示す。

* 1) The ratio of urethane to urethane indicates mass% with respect to the density of the polyurethane foam layer.

(Image quality evaluation during printing durability)
Each obtained toner carrier was incorporated into a commercially available printer, and printing was performed up to 20000 sheets with a 1% printing pattern. As a result, the case where fading has occurred between 0 and 10000 sheets x, the case where fading has occurred between 10,000 sheets and 15000 sheets, the case where fading has occurred between 15000 sheets and 20000 sheets, and the case where up to 20000 sheets have been blurred. The case where it did not occur was evaluated as ◎. The results are shown in Table 3 below together with the constitution and physical properties of each toner carrier.

  As shown in Table 3 above, the toner carrying member of Example 1 that satisfies the near-surface and internal hardnesses according to the present invention has good printing durability performance with no blurring up to 20000 sheets. It was confirmed. Further, from Tables 2 and 3, it can be seen that the amount of carbon impregnated in the polyurethane foam affects the surface hardness after impregnation.

DESCRIPTION OF SYMBOLS 1 Shaft 2 Polyurethane foam layers 10 and 13 Toner carrier 11 Image forming body 12 Developing roller 14 Toner accommodating portion 15 Transfer roller 16 Charging portion 17 Exposure portion 18 Toner scraping blade 20 Toner

Claims (4)

In the toner carrier formed by carrying a single polyurethane foam layer on the outer periphery of the shaft,
The polyurethane foam layer is impregnated with a conductive solution containing a conductive material and a binder, and the hardness of the polyurethane foam layer from the surface to 1 mm is 75 to 84 degrees in Asker F hardness, and from the surface A toner carrier having an IFD hardness of 220 to 240 N from 1 mm.   The toner carrier according to claim 1, wherein an impregnation amount of the conductive solution to the polyurethane foam layer is 9 to 13 g / L. The toner carrier according to claim 1, wherein the polyurethane foam layer is formed using a polyurethane foam having air permeability within a range of 30 to 70 cc / cm ² / sec.   The toner carrier according to claim 1, wherein a solid content concentration of the conductive solution is in a range of 19.0 to 22.0 mass%.

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