JP7101186B2 - Conductive endless belt - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention supplies a developer to the surface of an image forming body such as a latent image holder holding an electrostatic latent image on the surface in an electrostatic recording process in an electrophotographic device such as a copying machine or a printer or an electrostatic recording device. The present invention relates to a conductive endless belt (hereinafter, also simply referred to as “belt”) used when transferring a toner image formed in the above process to a recording medium such as paper.

Conventionally, in the electrostatic recording process in a copying machine, a printer, or the like, first, the surface of a photoconductor (latent image holder) is uniformly charged, and an image is projected onto the photoconductor from an optical system to be exposed to light. An electrostatic latent image is formed by erasing the charge on the portion, and then toner is supplied to the electrostatic latent image to form a toner image by electrostatic adhesion of the toner, which is used as paper, OHP, or printing paper. A method of printing is adopted by transferring to a recording medium such as.

In this case, even in a color laser printer or a color copier, printing is basically performed according to the above process, but in the case of color printing, four color toners of magenta, yellow, cyan, and black are used to adjust the color tone. In order to reproduce, a step of superimposing these toners at a predetermined ratio to obtain a required color tone is required, and several methods have been proposed for performing this step.

Among them, as a general-purpose method, a printing method for forming a color image by using an endless transfer belt as shown in FIG. 2 is known. In the illustrated apparatus, the first developing unit 12a to the fourth developing unit 12d for developing the electrostatic latent images on the photoconductor drums 11a to 11d with yellow, magenta, cyan, and black, respectively, are sequentially arranged along the transfer belt 10. Has been done. The transfer belt 10 is circulated and driven in the direction of the arrow in the drawing, and the four-color toner images formed on the photoconductor drums 11a to 11d of the developing units 12a to 12d are sequentially transferred onto the transfer belt 10. A color toner image is formed on the surface of the paper, and the toner image is transferred onto a recording medium 13 such as paper to print out. Here, in the apparatus shown in the figure, the arrangement order of the toners used for development is not particularly limited and can be arbitrarily selected. In the figure, reference numeral 14 indicates a drive roller or tension roller for circulatingly driving the transfer belt 10, 15 is a secondary transfer roller, 16 is a recording medium feeder, 17 is a heating image on a recording medium, and the like. The fixing device to be fixed by is shown.

As a base resin for a belt that can be used in such an electrophotographic image forming process, a thermoplastic resin has conventionally been widely used. For example, in Patent Document 1, the resin base material comprises (a) a thermoplastic polyalkylene naphthalate resin and / or (b) a thermoplastic polyalkylene terephthalate resin, and (c) a thermoplastic polyester-based elastomer. , (C) is disclosed as a conductive endless belt in which the compounding ratio of the component is in the range of 1 to 15 parts by weight with respect to 100 parts by weight of the component (a) and / or (b).

Japanese Unexamined Patent Publication No. 2007-25130

Generally, in a belt, in order to exhibit stable performance even if the usage environment changes, it is required that the electric resistance does not depend on voltage, that is, the electric resistance does not fluctuate due to a change in voltage. However, in recent years, depending on the specifications of the printer, belts that are voltage-dependent or have various resistance values have been required, and further improvements have been required.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a conductive endless belt in which the electric resistance is voltage-dependent.

As a result of diligent studies to solve the above problems, the present inventors can solve the above problems by using a combination of a specific thermoplastic resin as the base resin of the belt and defining the ratio of the thermoplastic resin. The present invention was completed.

That is, the present invention relates to an endless belt-shaped conductive endless belt used in an image forming apparatus.
The base resin contains a thermoplastic polyalkylene naphthalate resin, a thermoplastic polybutylene terephthalate resin, and a thermoplastic elastomer, and the thermoplastic polybutylene terephthalate resin is used with respect to the total amount of the base resin. It is characterized by containing 36% by mass or more and containing the thermoplastic elastomer in an amount of 10% by mass or more and 40% by mass or less.

In the belt of the present invention, the thermoplastic polyalkylene naphthalate resin is a thermoplastic polybutylene naphthalate resin, and the mass ratio of the thermoplastic polybutylene naphthalate resin to the thermoplastic polybutylene terephthalate resin is , It is preferably in the range of 0.64 to 1.50.

The belt of the present invention is particularly useful as a transfer belt.

According to the present invention, it is possible to realize a conductive endless belt in which the electric resistance is voltage-dependent by the above configuration. Further, in particular, by using a thermoplastic polybutylene naphthalate resin and a thermoplastic polybutylene terephthalate resin in combination as the base resin and setting the mass ratio of these in a predetermined range, the resin has voltage dependence and curl. It is possible to use a conductive endless belt that suppresses the occurrence of.

It is a cross-sectional view in the width direction which shows one structural example of the conductive endless belt of this invention. It is sectional drawing in the width direction which shows the other structural example of the conductive endless belt of this invention. It is a schematic diagram which shows an example of the image forming apparatus which concerns on this invention. It is explanatory drawing which concerns on the evaluation method of winding habit in an Example. It is another explanatory diagram relating to the evaluation method of curl in an Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A and 1B are cross-sectional views in the width direction showing a configuration example of the conductive endless belt of the present invention. The endless belt-shaped conductive endless belt generally includes a belt with a joint and a belt without a joint (so-called seamless belt), but in the present invention, any one may be used, and a seamless belt is preferable. be. The conductive endless belt of the present invention can be used as a transfer belt or the like in an image forming apparatus such as a copying machine or a printer.

When the conductive endless belt of the present invention is, for example, the transfer belt 10 shown in FIG. 2, it is arranged between the developing units 12a to 12d provided with the photoconductor drums 11a to 11d and the recording medium 13 such as paper. The four-color toner images formed on the surfaces of the photoconductor drums 11a to 11d, which are circulated and driven by a driving member such as the driving roller 14, are once transferred and held, and then transferred to the recording medium 13. Form a color image. Although the case where the toner has four colors is described here, it goes without saying that the number of toner colors is not limited to four colors.

In the belt of the present invention, the base resin constituting the belt contains a thermoplastic polyalkylene naphthalate resin and a thermoplastic polybutylene terephthalate resin (PBT), and 36 mass of PBT is added to the total amount of the base resin. It is characterized by containing% or more.

PBT is a material used for the base resin of belts, but if it is blended in too much, the curl tends to worsen, so conventionally, in combination with other resins, only a small amount of less than 36% by mass is used. It has not been used. On the other hand, the present inventors have found that by adding more PBT than before, a belt having a voltage dependence on electric resistance can be obtained. It is considered that when PBT is contained in a large amount of 36% by mass or more, uneven distribution of the conductive agent occurs, which causes voltage dependence. The content of PBT needs to be 36% by mass or more with respect to the total amount of the base resin, preferably 36% by mass or more and 60% by mass or less, and more preferably 36% by mass or more and 44% by mass or less. Is.

Specific examples of the thermoplastic polyalkylene naphthalate resin used in combination with PBT in the present invention include thermoplastic polyethylene naphthalate resin (PEN) and thermoplastic polybutylene naphthalate resin (PBN). PBN is preferably used.

In the present invention, in particular, PBN and PBT are used in combination as a base resin, and the mass ratio of PBN to PBT (mass of PBN / mass of PBT) is within the range of 0.64 to 1.50. It is preferably in the range of 1.05 to 1.50, and more preferably in the range of 1.05 to 1.50. By defining the mass ratio of PBN and PBT in the above range, it is possible to obtain a belt having voltage dependence of electric resistance and suppressing the occurrence of curl. Here, the winding habit refers to a phenomenon in which a mark remains on the belt due to the shape in which the belt is fixed when the belt is fixed for a certain period of time. In order to obtain the above-mentioned mass ratio of PBN and PBT, the blending amount of PBN is preferably, for example, 46% by mass or more, and preferably 54% by mass or less, based on the total amount of the base resin.

In the present invention, the base resin preferably further contains a thermoplastic elastomer, whereby it is possible to obtain an effect of improving durability such as breakage resistance of the belt. The thermoplastic elastomer used in the present invention is not particularly limited, and examples thereof include polyester-based, polyamide-based, polyether-based, polyolefin-based, polyurethane-based, styrene-based, acrylic-based, and polydiene-based. Of these, thermoplastic polyester elastomers are preferable. In the present invention, among the thermoplastic polyester-based elastomers, the PBN elastomer can be preferably used, whereby the belt can be softened and the durability of the belt can be further improved. The blending amount of the thermoplastic elastomer in the present invention can be 40% by mass or less, preferably 30% by mass or less, and preferably 5% by mass or more with respect to the total amount of the base resin.

The polyester-based material such as the thermoplastic polyalkylene naphthalate resin or PBT used as the base resin in the present invention has a drawback that it tends to cause a decrease in molecular weight due to hydrolysis during molding and heating. Therefore, it is preferable to add a compound having a carbodiimide group to the belt of the present invention and recrosslink the polyester-based material by the reaction between the carbodiimide group and the carboxylic acid to suppress the decrease in molecular weight. This makes it possible to prevent embrittlement of the belt and improve the crack resistance of the belt during durability. Such a carbodiimide compound is easily available on the market, and examples thereof include trade name: carbodilite manufactured by Nisshinbo Chemical Co., Ltd. The carbodiimide compound can also be used in the form of pellets or the like that have been master-batched in advance. For example, trade names: Carbodilite E pellets, B pellets and the like manufactured by Nisshinbo Chemical Co., Ltd. can be preferably used.

The amount of the carbodiimide compound added is not particularly limited, but is preferably 0.05 part by mass or more, more preferably 0.1 part by mass or more, and preferably 0.1 part by mass or more with respect to 100 parts by mass of the base resin. Is in the range of 30 parts by mass or less, more preferably 5 parts by mass or less.

In addition, a conductive agent can be appropriately added to the belt of the present invention in order to adjust the conductivity. The conductive agent is not particularly limited, and known electronic conductive agents, ionic conductive agents and the like can be appropriately used.

Among these, as the electronic conductive agent, specifically, for example, conductive carbon such as Ketjen black and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, MT, oxidation treatment and the like. Color (ink) carbon, pyrolysis carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium and other metals and metal oxides, polyaniline, Conductive polymers such as polypyrrole and polyacetylene, carbon whisker, graphite whisker, titanium carbide whisker, conductive potassium titanate whisker, conductive barium titanate whisker, conductive titanium oxide whisker, conductive whisker such as conductive zinc oxide whisker, etc. Can be mentioned.

Specific examples of the ion conductive agent include perchlorates such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium and modified fatty acid dimethylethylammonate, and chloratesates. Ammonites such as hydrochlorides, bromines, iodates, borohydrides, sulfates, ethyl sulfates, carboxylates, sulfonates, alkali metals such as lithium, sodium, potassium, calcium and magnesium. , Alkaline earth metal perchlorate, chlorate, hydrochloride, bromine salt, iodate, borohydrochloride salt, sulfate, trifluoromethyl sulfate, sulfonate and the like.

In the present invention, the above-mentioned conductive agent may be used alone or in combination of two or more, and for example, an electronic conductive agent and an ionic conductive agent may be used in combination. It is possible to stably develop conductivity even with fluctuations in the applied voltage and changes in the environment.

The blending amount of the conductive agent is usually 100 parts by mass or less, particularly 80 parts by mass or less, particularly 50 parts by mass or less, for example, 1 part by mass with respect to 100 parts by mass of the base resin. More than parts by mass, especially more than 5 parts by mass. The ionic conductive agent is usually 0.01 part by mass or more, particularly 0.05 part by mass or more, and usually 10 parts by mass or less, particularly 5 parts by mass or less, with respect to 100 parts by mass of the base resin. It is a range. In the present invention, it is particularly preferable to use carbon black as the conductive agent and add it in an amount of 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the base resin.

Further, it is possible to appropriately add other functional components in addition to the above-mentioned components to the belt of the present invention as long as the effects of the present invention are not impaired. Flame retardants, antioxidants, compatibilizers, coupling agents, lubricants, surface treatment agents, pigments, ultraviolet absorbers, antistatic agents, dispersants, neutralizers, foaming agents, cross-linking agents and the like can be appropriately blended. .. Further, a colorant may be added for coloring.

The thickness of the belt of the present invention is appropriately selected according to the form of the applied member or the like, but is preferably in the range of 50 μm or more and 200 μm or less. The surface roughness thereof is preferably 10 μm or less, particularly 6 μm or less, and further 3 μm or less in JIS 10-point average roughness Rz. Further, the volume resistivity is preferably adjusted within the range of 102 Ω · cm or ^more and 10 ¹³ Ω · cm or less. Furthermore, the tensile elastic modulus of the belt of the present invention is preferably 1000 MPa or more, particularly preferably 1500 MPa or more, and preferably 3000 MPa or less.

Further, as shown by the alternate long and short dash line in FIGS. 1A and 1B, the belt of the present invention is formed on the drive member on the surface of the image forming apparatus of FIG. 2 on the side in contact with the drive member such as the drive roller 14. A fitting portion to be fitted with a fitting portion (not shown) may be formed, and the conductive endless belt of the present invention is provided with such a fitting portion and the fitting portion provided on the drive member. By fitting it with (not shown) and running it, it is possible to prevent the conductive endless belt from being displaced in the width direction. In this case, the fitting portion is not particularly limited, but as shown in FIGS. 1A and 1B, a continuous convex line is formed along the circumferential direction (rotational direction) of the belt, and this is a drive roller or the like. It is preferable to fit the drive member into a groove formed along the circumferential direction on the peripheral surface of the drive member.

In addition, in FIG. 1A, an example in which one continuous convex strip is provided as a fitting portion is shown, but in this fitting portion, a large number of convex portions are arranged in a row along the circumferential direction (rotational direction) of the belt. It may be provided so as to project, two or more fitting portions may be provided (FIG. 1B), or the belt may be provided at the center portion in the width direction. Further, instead of the convex stripes shown in FIGS. 1A and 1B, a groove is provided as the fitting portion along the circumferential direction (rotational direction) of the belt, and this is provided in the circumferential direction on the peripheral surface of the drive member such as the drive roller. It may be fitted with the ridges formed along the line.

The belt of the present invention can be suitably manufactured by extrusion molding of a resin composition containing the above-mentioned base material resin, a conductive agent and the like, and specifically, for example, a resin composition containing the above-mentioned various compounding components by a twin-screw kneader. The product can be produced by kneading the product and extruding the obtained kneaded product using an annular die. Alternatively, a powder coating method such as electrostatic coating, a dip method or a centrifugal casting method can also be suitably adopted.

Hereinafter, the present invention will be described in more detail with reference to examples.
Pellets were obtained by mixing and dispersing with a twin-screw kneader according to the formulation shown in the table below. Using these pellets, an endless shape transfer belt was formed with an inner diameter of 220 mm, a thickness of 120 μm, and a width of 250 mm by extrusion molding with a molding machine equipped with a cylindrical die at the tip of a single shaft extruder. ..

<Evaluation of voltage dependence>
Regarding the obtained transfer belt, at a temperature of 25 ° C. and a relative humidity of 50%, a ring probe UR-100 connected to a high-restor-UX MCP-HT800 manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used as a measuring device. The surface resistance at the measured voltages of 100 V and 250 V was measured, and the difference was taken to evaluate the voltage dependence of the surface resistance. If this value is 0.20 or more, it can be said that there is voltage dependence.

<Evaluation of curl>
The obtained transfer belt was evaluated for the presence or absence of curl according to the following.
A test piece having a length of 100 mm and a width of 10 mm is cut out from each belt, and a load of 200 g (400 g in total) on one side is applied to both ends of the test piece 20 under an environment of a temperature of 30 ° C. and a relative humidity of 80%, as shown in FIG. 3A. It was hung and left for 12 days in a state of being hung on a metal shaft 21 having a diameter of 18 mm. After that, the load was removed, the mixture was left in an environment with a temperature of 25 ° C. and a relative humidity of 50% for 24 hours, and as shown in FIG. 3B, the angle θ of the habit attached to the test piece 20 was measured and evaluated according to the following. ..
⊚: When the curl angle θ is 45 ° or more and 180 ° or less.
◯: When the curl angle θ is 30 ° or more and less than 45 °.
X: When the curl angle θ is 0 ° or more and less than 30 °.

These results are also shown in the table below.

＊１）ＰＢＮ，帝人株式会社製、商品名ＴＱＢ－ＯＴ
＊２）ＰＢＴ，ウィンテックポリマー株式会社製、商品名ジュラネックス７００ＦＰ
＊３）熱可塑性エラストマー，東洋紡株式会社製、商品名ペルプレンＥＮ－１６０００
＊４）カルボジイミド化合物，日清紡ケミカル株式会社製 商品名カルボジライトＨＭＶ－８ＣＡ
＊５）カーボンブラック，デンカ株式会社製 商品名デンカブラック（アセチレンブラック）

* 1) PBN, manufactured by Teijin Limited, trade name TQB-OT
* 2) PBT, manufactured by Wintech Polymer Ltd., trade name Juranex 700FP
* 3) Thermoplastic elastomer, manufactured by Toyobo Co., Ltd., trade name Perprene EN-16000
* 4) Carbodiimide compound, manufactured by Nisshinbo Chemical Co., Ltd. Product name Carbodilite HMV-8CA
* 5) Carbon black, manufactured by Denka Co., Ltd. Product name Denka Black (acetylene black)

As shown in the above table, in the belt of each example in which the base resin contains a thermoplastic polyalkylene naphthalate resin and PBT and the PBT content is 36% by mass or more, good voltage dependence is obtained. Was confirmed to be obtained. Furthermore, it was found that by using PBN as the thermoplastic polyalkylene naphthalate resin and setting the mass ratio of PBN to PBT to 0.64 to 1.50, the curl is surely eliminated.

10 Transfer belts 11a to 11d Photoreceptor drums 12a to 12d Development unit 13 Recording medium 14 Drive roller or tension roller 15 Secondary transfer roller 16 Recording medium feeder 17 Fixing device 20 Test piece 21 Metal shaft

Claims (3)

In an endless belt-shaped conductive endless belt used in an image forming apparatus,
The base resin contains a thermoplastic polyalkylene naphthalate resin, a thermoplastic polybutylene terephthalate resin, and a thermoplastic elastomer, and the thermoplastic polybutylene terephthalate resin is used with respect to the total amount of the base resin. A conductive endless belt containing 36% by mass or more and containing the thermoplastic elastomer in an amount of 10% by mass or more and 40% by mass or less . The thermoplastic polyalkylene naphthalate resin is a thermoplastic polybutylene naphthalate resin, and the mass ratio of the thermoplastic polybutylene naphthalate resin to the thermoplastic polybutylene terephthalate resin is 0.64 to 1. The conductive endless belt according to claim 1, which is within the range of 50. The conductive endless belt according to claim 1 or 2 , which is a transfer belt.

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