JP2012159676A - Toner carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrier that has improved toner-scraping property than before.SOLUTION: A toner carrier 10 carries a polyurethane foam layer 2 on an outer periphery of a shaft 1. The polyurethane foam layer 2 has been subjected to membrane exclusion treatment, and has an average cell diameter in the range of 200 to 300 μm. The polyurethane foam layer 2 preferably has density in the range of 85 to 110 g/L, and resistance value in the range of 3 to 7 LogΩ.

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. 4, 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.

  As such a toner carrier, there is one in which a polyurethane foam imparted with conductivity is carried on the outer periphery of a shaft. As an improvement technique related to a toner carrier using polyurethane foam, for example, Patent Document 1 stirs and mixes a predetermined polyurethane foam raw material containing polyol, polyisocyanate, catalyst, foaming agent, foam stabilizer, additive, and the like. The obtained polyurethane foam is composed of a specific polyether polyol as a polyol, a specific amount of phosphate ester as an additive, and after stirring and mixing these raw materials, the mixture is poured into a cylindrical mold. An elastic member that is closed and foamed under pressure and can be used as a toner supply member for an image forming apparatus is disclosed.

  The polyurethane foam used for the toner carrier includes a so-called independent cell (bubble) type and a continuous cell type. For example, since the polyurethane foam described in Patent Document 1 is chemically foamed and resinated in a mold, bubbles are held inside the foam, and the properties are close to an independent cell structure. Moreover, the polyurethane foam manufactured by the free foaming which does not use a mold has a structure which consists of a continuous cell fundamentally.

Japanese Patent Laid-Open No. 2003-137756 (Claims etc.)

  Various techniques for improving the toner scraping property of the toner carrier have been studied in the past, but this is not sufficient, and the realization of a toner carrier with improved toner scraping property is required. It was.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a toner carrier that solves the above problems and has improved toner scraping performance as compared with the prior art.

  As a result of investigations to solve the above problems, the present inventor has found the following. In the toner carrier using the polyurethane foam as described above, in order to improve the toner scraping performance, the surface of the foam carrying the toner has irregularities for scraping off the toner and has a large surface area. Is required. In particular, since the toner carrier is used in a state where it is in pressure contact (nip) with another member, it is important that the surface area be large in the state where it is in pressure contact with the other member. Such irregularities on the surface of the foam are formed by cells exposed on the surface. Conventionally, polyurethane foams used for toner carriers have a pressure contact in both the independent cell and continuous cell structures. Since the number of cells exposed on the surface in the state is limited, further improvement in the toner scraping property cannot be expected.

  From this viewpoint, as a result of further investigations, the present inventors have found that the polyurethane foam used for the toner carrier is exposed to the foam surface at the time of pressure contact by using a polyurethane foam having a cell diameter in a specific range. The inventors have found that the surface area can be increased by increasing the number of cells, and as a result, the toner scraping property can be improved, and the present invention has been completed.

That is, the present invention provides a toner carrier having a polyurethane foam layer carried on the outer periphery of a shaft.
The polyurethane foam layer is subjected to a film removal treatment, and the polyurethane foam layer has an average cell diameter in the range of 200 to 300 μm.

  In this invention, it is preferable that the density of the said polyurethane foam layer is the range of 85-110 g / L. The toner carrier of the present invention preferably has a resistance value in the range of 3 to 7 LogΩ.

  According to the present invention, with the above-described configuration, it is possible to realize a toner carrier having further improved toner scraping performance as compared with the related art.

3 is a schematic perspective view illustrating an example of a toner carrier of the present invention. FIG. With the cell membrane on the surface removed, (a) a polyurethane foam surface with a continuous cell structure subjected to film removal treatment, and (b) a polyurethane foam surface with an independent cell structure without film removal treatment It is explanatory drawing which shows the state seen from. (A1) is Example 1 (without pressure contact), (a2) is Example 1 (with pressure contact), (b1) is Comparative Example 5 (without pressure contact), and (b2) is polyurethane of Comparative Example 5 (with pressure contact). It is a photograph figure which shows the change of the contact area (surface area) of a foam layer. 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 polyurethane foam layer 2 carried on the outer periphery of a shaft 1.

  In the toner carrier 10 of the present invention, it is important that the polyurethane foam layer 2 is subjected to film removal treatment, and the average cell diameter of the polyurethane foam layer is in the range of 200 to 300 μm. Here, the film removal treatment (Scott treatment) refers to a treatment for removing the foam surface and the internal cell membrane by subjecting the polyurethane foam to a blast treatment, a combustion treatment, a treatment using a solvent, or the like. As a result, the skeleton portion of the foam structure mainly remains, so that the polyurethane foam has a substantially three-dimensional network structure.

FIG. 2 shows (a) a polyurethane cell surface having a continuous cell structure that has undergone film removal treatment, and (b) a polyurethane foam having an independent cell structure that has not undergone film removal treatment, with the cell membrane on the surface removed. Explanatory drawing which shows the state which looked at the surface from upper direction is shown. As shown in the figure, in the polyurethane foam of the continuous cell structure subjected to the film removal treatment, since the cell membrane is removed, the cell exposed on the surface is different from the case of the independent cell structure not subjected to the film removal treatment. through the opening of the C _S, in a state where the cell C _I and skeletal portions thereof inside can be observed present in the lower layer. Therefore, when this polyurethane foam is pressed against another member, the internal cells and its skeleton are exposed to the surface through the opening on the surface, and as a result, the surface area of the foam that contacts the other member is increased. And can contribute to improvement of toner scraping property. In contrast, in the polyurethane foam of a conventional closed cell structure, although it is possible to increase the surface area by reducing the cell diameter, even when pressed, only a cell C _S present on the surface can be exposed to the surface Therefore, the number of cells exposed on the surface is small as compared with the case of the continuous cell structure subjected to the film removal treatment, and thus cannot contribute to the improvement of the toner scraping property.

  In the present invention, the film removal treatment can be performed according to a conventionally known method, and is not particularly limited. Preferably, for example, the following procedure can be used. First, polyurethane foam is put in a kettle, and the inside is brought into a state close to vacuum. Thereafter, the gas is filled so as to have a ratio of oxygen: hydrogen = 2: 1, ignition is performed, and a process of burning the cell film in a processing time of about 1 hour is performed. Thereafter, the kettle is cooled to make the inside of the kettle the same as the external pressure, and the treated polyurethane foam is taken out from the kettle.

  Moreover, in this invention, the average cell diameter of the polyurethane foam layer 2 is 200-300 micrometers, Preferably it is the range of 240-270 micrometers. By setting it as the polyurethane foam layer 2 which has the fine cell of the said range, favorable toner scraping property is realizable with the foam structure formed by the said film removal process. If the average cell diameter is too small, the toner fluidity and toner transportability are lowered. If the average cell diameter is too large, sufficient toner scraping property cannot be obtained, and in any case, the desired effect of the present invention can be obtained. Absent.

  In the polyurethane foam having a continuous cell structure used in the present invention, as a method for obtaining a fine cell diameter in the above-mentioned range, each raw material may be used before and / or during the mixing of raw material components during the production of the polyurethane foam. A method of pressurizing components or mixed raw material components can be mentioned. Thereby, it is considered that the bubbles filled in the raw material component are refined, and as a result, a polyurethane foam having a fine cell diameter can be obtained.

  In the present invention, the density of the polyurethane foam layer is preferably 85 to 110 g / L, more preferably 90 to 100 g / L. If the density of the polyurethane foam is too low, desired fine cells may not be obtained. On the other hand, when the density of the polyurethane foam is too high, the foaming speed at the time of foaming is not constant, and cell regulation (uniformity) is impaired.

  In the toner carrier of the present invention, the desired effect of the present invention can be obtained as long as it has the above-mentioned specific average cell diameter and a polyurethane foam layer subjected to film removal treatment. The specific structure and material of the other toner carrier are not particularly limited, and can be appropriately configured according to a conventional method.

  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.

  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 air permeability of the polyurethane foam used for the polyurethane foam layer 2 is preferably 10 to 50 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 (specifically, the toner does not enter the polyurethane foam layer and the toner cannot be conveyed). If it is too high, the toner may slip through the toner carrier and cannot carry the toner, which is not preferable. The air permeability is a value measured according to JIS K 6400.

  Furthermore, the number of cells of the polyurethane foam is preferably about 80 to 100 cells / inch. If the average number of cells is too small, the desired toner scraping property cannot be obtained, and if it is too large, the toner fluidity and toner transportability are lowered.

  In the present invention, the conductivity can be imparted to the toner carrier by impregnating the polyurethane foam with a conductive solution containing a conductive material and a binder. The resistance value of the toner carrier of the present invention is preferably in the range of 3 to 7 LogΩ, particularly 3.0 to 6.0 LogΩ. By setting the resistance value within this range, a solid black image having a uniform density can be obtained. If the resistance value is too low, the density becomes high and becomes thin in the latter half of the printing durability. If the resistance value is too high, the density becomes low.

  Examples of the conductive material used in the conductive solution include carbonaceous particles such as carbon black and graphite, metal powder such as silver and nickel, a simple substance of conductive metal oxide such as tin oxide, titanium oxide, and zinc oxide, or barium sulfate. One or a plurality of combinations selected from those obtained by coating the above-mentioned conductive metal oxide wet with the insulating fine particles as a core, conductive metal carbide, conductive metal nitride, conductive metal boride, etc. Used in 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 cell wall of the polyurethane foam. However, by using a conductive solution containing a binder, the conductive material adheres firmly to the cell wall of the polyurethane foam, so that stable conductivity can be achieved. The functional layer can be formed in the cells of the polyurethane foam.

  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, subjected to the above-described film removal treatment, then drilled, and a shaft through an adhesive layer as desired. Pass 1 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. Then, the polyurethane foam with a shaft is taken out from the conductive solution, compressed to remove excess conductive solution, and then heated and dried to remove moisture and the like, so that the conductive agent is put into the polyurethane foam cell together with the binder. Can be fixed.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1-3 and Comparative Examples 1-4>
A toner carrier having a polyurethane foam layer carried on the outer periphery of the shaft as shown in FIG. First, a block-like polyurethane foam was cut out from a polyurethane foam produced in an appropriate shape at a desired size, and each example was subjected to film removal treatment according to the following procedure. About each comparative example, the film removal process was not performed. All of these polyurethane foams had a continuous cell structure.

(Film removal treatment)
The cut out block-like polyurethane foam was placed in a dedicated pot, and the inside was brought to a state close to vacuum. Thereafter, the gas was filled so as to have a ratio of oxygen: hydrogen = 2: 1, ignition was performed, and combustion treatment was performed in a treatment time of about 1 hour. Thereafter, the kettle was cooled to make the inside of the kettle the same as the external pressure, and the treated polyurethane foam was taken out from the kettle.

  A hole was made in the obtained polyurethane foam, and a shaft (material: SUM22, diameter 6.0 mm, length 300 mm) was passed through the adhesive layer. 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).

  Next, a conductive solution was prepared according to the formulation shown in Table 1 below, and the polyurethane foam with the shaft was immersed in this conductive solution, and the conductive solution was impregnated in the bubbles of the polyurethane foam. Thereafter, the polyurethane foam with a shaft was taken out from the conductive solution and compressed to remove excess conductive solution, and then dried by heating to remove moisture and the like, thereby obtaining toner carriers of the respective examples. In the toner carrier of each example, the resistance value was adjusted by the amount of carbon adhered to the polyurethane foam layer. The average cell diameter was adjusted by changing the density of the polyurethane foam and the pressure condition of the isocyanate tank and / or the head portion where the polyol and isocyanate were stirred in the polyurethane foam production apparatus. For example, for the toner carrier of Comparative Example 4, neither the isocyanate tank nor the head portion was pressurized during the production.

* 1) The ratio of urethane to urethane indicates mass% with respect to the density of the polyurethane foam layer.
* 2) Carbon type A: W311N (Lion Corporation, Ketjen Black)
* 3) Carbon type B: PSM black (manufactured by Gokoku Color Co., Ltd.)
* 4) Binder: BS050301 (manufactured by Enex Co., Ltd., acrylic resin)
* 5) Antifoaming agent: KS502 (Shin-Etsu Chemical Co., Ltd., silicone oil)

<Comparative Example 5>
A toner carrier of Comparative Example 5 was produced in the same manner as in Comparative Example 1 and the like except that the polyurethane foam was obtained by foaming and curing in a mold. This polyurethane foam had an independent cell structure.

<Image evaluation>
Each obtained toner carrier was incorporated into a commercially available printer, and the uniformity of the black solid image and the presence or absence of development ghost were evaluated. The results, for the uniformity of the solid black image, density is uniform with paper one side, if the ○ has reached the prescribed concentration, but uniform paper one side, the case does not reach the prescribed concentration ○ ^-, paper one side not The case where it was uniform but reached the specified density was indicated by Δ, and the case where it was non-uniform across the paper and did not reach the specified density was indicated as x. For development ghosts, the case where the specific pattern is not transferred continuously at the rear end of the paper (the rear end side of the print on one side of the paper) is indicated by ○ ⁻ , and the rear end of the paper (the rear end of the print on the entire side of the paper). specific pattern on the side) is, as transcribed to the first sheet printing, the case 2 and subsequent sheets disappear △ ^+, a specific pattern to the paper rear end (rear end side of the printing paper one side), two printing The pattern is transferred up to the eye, but the case where the third and subsequent sheets disappear is Δ, and the specific pattern is transferred up to the third printed sheet on the rear end of the paper (the rear end side of the printing on one side of the paper). The case where it disappears is indicated by Δ ⁻ , and the case where a specific pattern is transferred up to the fourth sheet is indicated by ×.

<Transmission density evaluation>
First, the toner was uniformly applied to the surface of a SUS roller (outer diameter: 20 mm) that was regarded as a developing roller. Thereafter, in a state where each obtained toner carrier is pressed against the SUS roller at a nip amount of 1.5 mm, the SUS roller is mechanically rotated, and each toner carrier is driven to rotate. The toner on the surface of the SUS roller was scraped off by each toner carrier. After 5 rotations, the residual toner on the surface of the SUS roller was transferred, and the amount of the residual toner was evaluated based on the transmission density. For measuring the transmission density, a Macbeth transmission density measuring device was used. The lower the transmission density, the better the toner scraping property.
These results are shown in the table below.

  As shown in the above table, in the toner carrier of each example having a polyurethane foam layer subjected to film removal treatment and the average cell diameter satisfying a specific range, the toner scraping property is improved, It was confirmed that good image evaluation results were obtained. Furthermore, when the resistance value is in the range of 3 to 7 LogΩ, the uniformity of the black solid image is also good.

<Contact area in pressure contact>
About the toner carrier of Example 1 and Comparative Example 5, the vicinity of the surface of the polyurethane foam layer was colored pink, and the change in contact area (surface area) due to the presence or absence of pressure contact was observed. The more pink parts are seen, the higher the contact area. The result is shown in FIG. In the figure, (a1) is Example 1 (without pressure contact), (a2) is Example 1 (with pressure contact), (b1) is Comparative Example 5 (without pressure contact), and (b2) is Comparative Example 5 (with pressure contact). FIG.

  As shown in FIG. 3, in the polyurethane foam of Comparative Example 5 having an independent cell structure, there is no difference in contact area due to the presence or absence of pressure contact. On the other hand, it can be seen that the surface area of the polyurethane foam of Example 1 having the continuous cell structure subjected to the film removal treatment is increased at the time of pressure contact.

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 (3)

In the toner carrier formed by supporting a polyurethane foam layer on the outer periphery of the shaft,
A toner carrier, wherein the polyurethane foam layer is subjected to film removal treatment, and an average cell diameter of the polyurethane foam layer is in the range of 200 to 300 μm.   The toner carrier according to claim 1, wherein the density of the polyurethane foam layer is in the range of 85 to 110 g / L.   The toner carrier according to claim 1, wherein the resistance value is in the range of 3 to 7 LogΩ.