JP2015169703A - Conductive endless belt and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive endless belt that suppresses separation of fluorine from the surface of a surface layer to prevent the occurrence of filming by paper powder and wear of a blade, and thereby improving durability while ensuring good transferability and cleaning, and an image forming apparatus using the same.SOLUTION: A conductive endless belt 100 includes an intermediate layer 102 and a surface layer 103 sequentially on a base material layer 101. The surface layer includes a fluororesin composition having a silanol group, and the intermediate layer includes a UV curable resin containing a hydroxyl group-containing acrylate.

Description

  The present invention supplies a developer to the surface of an image forming body such as a latent image holding body holding an electrostatic latent image on the surface in an electrostatic recording process in an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus. The conductive endless belt used when transferring the toner image formed in this way onto a recording medium such as paper, and an image forming apparatus using the conductive endless belt (hereinafter also simply referred to as “belt” and “apparatus”) About.

  Conventionally, in an electrostatic recording process in a copying machine, a printer, etc., first, the surface of a photosensitive member (latent image holding member) is uniformly charged, and an image is projected onto the photosensitive member from an optical system and exposed to light. An electrostatic latent image is formed by erasing the charged portion, and then toner is supplied to the electrostatic latent image to form a toner image by electrostatic adhesion of the toner, which is formed on paper, OHP, photographic paper For example, a method of printing by transferring to a recording medium such as the above is employed.

  In this case, color laser printers and color copiers basically perform printing according to the above process. However, in the case of color printing, the color tone is adjusted using toners of four colors, magenta, yellow, cyan, and black. In order to reproduce the image, a process for obtaining a necessary color tone by superimposing these toners at a predetermined ratio is required, and several methods have been proposed for performing this process.

  Among these, a printing method for forming a color image using an endless transfer belt as shown in FIG. 2 is known as a general-purpose method. In the illustrated apparatus, a first developing unit 12 a to a fourth developing unit 12 d for developing electrostatic latent images on the photosensitive drums 11 a to 11 d with yellow, magenta, cyan, and black, respectively, are sequentially arranged along the transfer belt 10. Has been. The transfer belt 10 is driven to circulate in the direction of the arrow in the figure, and the four color toner images formed on the photosensitive drums 11a to 11d of the developing units 12a to 12d are sequentially transferred, whereby the transfer belt 10 A color toner image is formed on the recording medium, and the toner image is transferred onto a recording medium 13 such as paper to perform printout. Here, in the illustrated apparatus, the arrangement order of the toners used for development is not particularly limited, and can be arbitrarily selected. In the figure, reference numeral 14 denotes a driving roller or tension roller for circulatingly driving the transfer belt 10, 15 is a secondary transfer roller, 16 is a recording medium feeding device, 17 is an image heated on the recording medium, etc. 1 shows a fixing device for fixing.

  As a belt usable in such an electrophotographic image forming process, for example, Patent Document 1 discloses a multilayer structure having a base layer and a surface layer, and the surface layer is made of n-dodecane with a pencil hardness of 4H or more. A conductive endless belt formed by a hard coat layer having a contact angle of 20 ° or more is disclosed. In this Patent Document 1, the surface layer is improved to prevent the surface layer from being scratched and the toner releasability is improved to improve the transfer efficiency by a synergistic effect. In particular, an ultraviolet (UV) curable material containing a fluorine component or a silicone-based paint is used.

JP 2009-192901 A (Claims etc.)

  As described above, by containing a fluorine component or the like on the outermost surface of the belt, the fluorine is unevenly distributed in the vicinity of the surface, and the toner releasability is improved to improve transferability and toner cleaning properties. It is known to improve this. However, in a belt having a structure in which a surface layer is provided on a resin base material layer, it is necessary to provide the surface layer with a thickness of about several μm in order to level the surface state and improve the glossiness. . At this time, if the hardness of the surface layer is too high, the flexibility of the belt is remarkably lowered, so that the intended durability may not be obtained. Among image forming apparatuses, in particular, in medium to high speed machines, the transfer belt is required to have a life equal to or longer than that of the apparatus itself, which is a problem.

  Also, in the surface layer containing a fluorine component, the fluorine component is present only near the surface of the surface layer, so the fluorine component present on the surface falls off due to paper passing or friction with the OPC (photoreceptor drum). There is. Therefore, not only the toner releasability is lowered, but also filming of paper dust occurs, and particularly when a blade is used as a cleaning member, the friction coefficient between the surface layer and the blade increases due to an increase in the coefficient of friction between the surface layer and the blade. By promoting the wear, there is a problem that an image defect due to a cleaning defect occurs, resulting in a decrease in durability.

  Therefore, the object of the present invention is to suppress the falling of fluorine from the surface of the surface layer, thereby preventing the occurrence of film dusting and blade wear, and ensuring good transferability and cleaning properties while maintaining durability. It is an object of the present invention to provide a conductive endless belt and an image forming apparatus using the same.

  As a result of intensive studies, the present inventor has provided an intermediate layer between the base material layer and the surface layer, and formed the surface layer with a fluororesin composition having a silanol group, and blended the intermediate layer with a hydroxyl group-containing acrylate. Thus, it has been found that the hardness of the belt can be appropriately secured while obtaining strong adhesion between the surface layer and the intermediate layer. As a result, it has been found that a good toner releasability can be obtained while suppressing the detachment of fluorine from the surface of the surface layer, and a belt having excellent durability can be realized, and the present invention is completed. It came to.

That is, the conductive endless belt of the present invention is a conductive endless belt comprising a base layer and an intermediate layer and a surface layer in order,
The surface layer includes a fluorine-based resin composition having a silanol group, and the intermediate layer includes an ultraviolet curable resin containing a hydroxyl group-containing acrylate.

  In the belt of the present invention, the ultraviolet curable resin preferably contains 10 to 30% by mass of the hydroxyl group-containing acrylate. In the present invention, the hydroxyl group-containing acrylate preferably has a linear alkyl group, and the linear alkyl group preferably has 2 or more carbon atoms.

  An image forming apparatus according to the present invention includes the conductive endless belt according to the present invention.

  According to the present invention, it is possible to prevent the occurrence of paper dust filming and blade wear by suppressing the falling off of fluorine from the surface of the surface layer, and while maintaining good transferability and cleaning properties, it is durable. It has become possible to realize a conductive endless belt and an image forming apparatus using the same.

It is sectional drawing of the width direction which shows one structural example of the electroconductive endless belt of this invention. 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. It is the schematic which shows the rotation testing machine used in the Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Generally, there are conductive endless belts with joints and belts without joints (so-called seamless belts), but any of them may be used in the present invention, and a seamless belt is preferable. As described above, 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, the conductive endless belt is disposed between the developing units 12 a to 12 d including the photosensitive drums 11 a to 11 d and the recording medium 13 such as paper. The toner images of four colors formed on the surfaces of the photosensitive drums 11a to 11d are temporarily transferred and held by a driving member such as the driving roller 14 and then transferred to the recording medium 13, A color image is formed. Although the case where the toner has four colors is described here, it is needless to say that the number of toner colors is not limited to four.

  FIG. 1 is a cross-sectional view in the width direction showing a configuration example of the conductive endless belt 100 of the present invention. As shown in the figure, the conductive endless belt 100 of the present invention comprises an intermediate layer 102 and a surface layer 103 in this order on a base material layer 101.

  The belt of the present invention is characterized in that the surface layer 103 includes a fluorine-based resin composition having a silanol group, and the intermediate layer 102 includes an ultraviolet curable resin containing a hydroxyl group-containing acrylate. In the past, only the surface layer with high hardness was formed on the base material layer, and it had various functions such as leveling of the belt surface, improvement of glossiness, and toner releasability. In the invention, the problem is solved by separating the function into two layers of the surface layer 103 and the intermediate layer 102.

  That is, in the present invention, the surface layer 103 that forms the outermost surface of the belt is formed of a fluorine-based material, so that good toner releasability can be secured and good transferability can be obtained. On the other hand, since the surface layer 103 made of a fluorine-based material does not have sufficient adhesiveness to the base material layer 101, in the present invention, an intermediate layer 102 containing a hydroxyl group-containing acrylate is provided in the lower layer of the surface layer 103. Thereby, the surface layer 103 and the intermediate | middle layer 102 can be adhere | attached firmly. This is considered to be due to the reaction between the silanol group in the surface layer 103 and the hydroxyl group in the intermediate layer 102. Accordingly, the fluorine component can be prevented from dropping from the surface of the surface layer 103, and good toner releasability and, in turn, good transfer efficiency can be maintained. In addition, the removal of fluorine components from the belt surface is suppressed, so it is possible to prevent an increase in torque and friction coefficient due to filming of paper dust, and even when a blade is used as a cleaning member, it prevents the occurrence of blade wear. Thus, the durability can be improved while ensuring the cleaning property. Therefore, according to the present invention, among the image forming apparatuses, a belt having durability corresponding to the belt life required particularly in a medium to high speed machine can be obtained.

  The surface layer 103 includes a fluororesin composition having a silanol group. Specifically, for example, Fluorosurf FG-5080 (manufactured by Fluoro Technology Co., Ltd.) can be used as such a fluorine-based resin composition. In the present invention, since the surface layer 103 is provided on the base material layer 101 via the intermediate layer 102, the thickness of the surface layer 103 can be reduced as compared with the prior art, and the material of the surface layer 103 has high hardness. Even when is used, by using a relatively soft material for the intermediate layer 102, it is possible to prevent the overall hardness of the belt from becoming too high. The thickness of the surface layer 103 can be in the range of 1 to 20 nm, for example, and is preferably in the range of 2 to 6 nm.

  The intermediate layer 102 includes an ultraviolet curable resin containing a hydroxyl group-containing acrylate. Specific examples of such ultraviolet curable resins include polyester resins, polyether resins, epoxy resins, amino resins, polyamide resins, acrylic resins, acrylic urethane resins, urethane resins, alkyd resins, phenol resins, melamine resins, urea. Examples thereof include resins, silicone resins, polyvinyl butyral resins, and the like, and these can be used alone or in combination.

  Among the above ultraviolet curable resins, in particular, those using polyfunctional acrylate monomers having two or more (meth) acryloyl groups such as dipentaerythritol hexaacrylate, and (meth) acrylate series containing (meth) acrylate oligomers An ultraviolet curable resin is preferred. Examples of such (meth) acrylate oligomers include urethane (meth) acrylate oligomers, epoxy (meth) acrylate oligomers, ether (meth) acrylate oligomers, ester (meth) acrylate oligomers, and polycarbonate (meth). Examples include acrylate oligomers, and fluorine-based and silicone-based (meth) acrylic oligomers. Specifically, for example, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer (manufactured by Kyoeisha Chemical Co., Ltd., UA306H) or PEG600 # diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., light acrylate 14EG-A) is used. it can. In particular, when a polyfunctional acrylate and PEG600 # diacrylate are used in combination and the content of PEG600 # diacrylate is increased, a film having both adhesiveness and flexibility can be formed.

  Specific examples of the hydroxyl group-containing acrylate include 4-hydroxybutyl acrylate (4HBA), hydroxyethyl methacrylate (HEMA), and pentaerythritol triacrylate (PE-3A). Among them, in the present invention, it is preferable to use a hydroxyl group-containing acrylate having a linear alkyl group, which increases the degree of freedom of reaction and makes the terminal hydroxyl group easier to move. By exposing the hydroxyl group to the surface, it is considered that the reactivity with the silanol group in the surface layer 103 is improved, and as a result, the durability of the fluorine coating on the surface layer is improved. In particular, the straight-chain alkyl group preferably has 2 or more carbon atoms, more preferably 4 or more, whereby the reactivity between the hydroxyl group and the silanol group can be further improved. For example, the use of the above 4HBA is preferable because the linear alkyl group portion is long, so that the hydroxyl group is easily exposed on the surface of the intermediate layer 102 and the reactivity with the silanol group is improved.

  As content of the hydroxyl-containing acrylate in ultraviolet curable resin, the range of 10-30 mass% is preferable. By containing the hydroxyl group-containing acrylate at 10% by mass or more, the adhesion between the surface layer 103 and the intermediate layer 102 can be further strengthened, and the falling off of the fluorine component from the surface can be more reliably prevented. The occurrence of filming can be prevented. Further, by containing the hydroxyl group-containing acrylate at 30% by mass or less, it is possible to appropriately secure the belt hardness and obtain better transferability.

  Further, the intermediate layer 102 contains a photopolymerization initiator for accelerating the initiation of the curing reaction by irradiation with ultraviolet rays. Such a photopolymerization initiator is not particularly limited, and known ones can be used. Specifically, for example, α-aminoacetophenone, acylphosphine oxide, thioxanthoneamine, and the like can be used. Specific examples thereof include bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide. 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one and the like. In addition, 2,2-dimethoxy 1,2 diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy 2-methyl-1-phenylpropan-1-one, 1- [4- (2hydroxy Ethoxy) phenyl] 2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1- [4-phenyl] -2-morpholinopropan-1-one, and the like can also be used.

  As a compounding quantity of this photoinitiator, it can be 0.1-10 mass parts with respect to 100 mass parts of ultraviolet curable resin.

  A conductive material is added to the intermediate layer 102 in order to ensure conductivity. As the conductive material, a known electronic conductive agent or ionic conductive agent can be used. Of these, specific examples of the electronic conductive agent include conductive carbon such as ketjen black and acetylene black, carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, oxidation treatment, and the like. Carbon for color (ink), pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium and other metal and metal oxides, polyaniline, polypyrrole And conductive polymers such as polyacetylene.

  Specific examples of the ion conductive agent include perchlorates such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified fatty acid dimethylethylammonium, chlorate, Ammonium salts such as hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate and sulfonate, alkali metals such as lithium, sodium, potassium, calcium and magnesium And alkaline earth metal perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, sulfates, trifluoromethyl sulfates, sulfonates, and the like.

  One of these conductive materials may be used alone, or two or more thereof may be used in appropriate combination. For example, an electronic conductive agent and an ionic conductive agent may be used in combination.

  The compounding amount of the conductive material in the intermediate layer 102 is usually 100 parts by mass or less, for example 1 to 100 parts by mass, particularly 1 to 80 parts by mass, especially 100 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin. 5 to 50 parts by mass. Moreover, about an ion conductive agent, it is 0.01-50 weight part normally with respect to 100 mass parts of ultraviolet curable resin, Especially 1-20 weight part is the range.

In the present invention, the conductivity of the coating film may satisfy the following relationship by appropriately adjusting the blending amount of the conductive material in the intermediate layer 102 and the base material layer 101 described later within a suitable range. preferable. In addition, for the measurement of the resistivity at this time, for example, a resistivity meter Hiresta UX MCP-HT800 / UR-100 probe manufactured by Mitsubishi Chemical Analytech Co., Ltd. can be used. It can be used as a resistivity.
−0.5 digit <[Surface resistivity after forming the intermediate layer (10 V) −Surface resistivity only of the base material layer (10 V)] <0.5 digit
When the value of [surface resistivity after forming intermediate layer (10V) −surface resistivity of substrate layer only (10V)] is −0.5 digits or less, an image in which toner is scattered due to electric charge escaping from the surface On the other hand, if it is 0.5 digit or more, a predetermined current does not flow, leading to a decrease in density. Here, for example, when the measurement result is (1) 1E + 10 [Ω / □], the logarithmic display is 10.0, and when the measurement result is (2) 3E + 10 [Ω / □], the logarithm Since the display is about 10.5, the difference (2) − (1) = 0.5 digits.

  The film thickness of the intermediate layer 102 can usually be in the range of 0.5 to 10 μm, preferably in the range of 2 to 5 μm.

  Further, as described above, the intermediate layer 102 is preferably flexible. Furthermore, as the film physical properties of the intermediate layer 102, the elongation at break is preferably 30% or more, for example, 5 to 10%.

  The resin material used for the base material layer 101 can be appropriately selected and used as a belt material from conventionally known general-purpose thermoplastic resins, thermoplastic elastomers, blends and alloys thereof, and the like.

  Among these, specific examples of the thermoplastic resin include polyalkylene naphthalate resin (for example, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, etc.) and polyalkylene terephthalate resin (for example, polyethylene terephthalate). Polyester resins such as (PET) resin, glycol-modified PET (PETG) resin, polybutylene terephthalate (PBT) resin, etc.), polyamide (PA) (for example, PA11, PA12, PA6, PA66, PA610, PA612, PA46, aroma Group nylon (nylon 6T, 9T, MXD6, etc.), acrylonitrile-butadiene-styrene (ABS) resin, polyacetal (POM), polyarylate (PAR), polycarbonate (PC), polyphenylene sal Aido (PPS), polyphenylene ether (PPE), polysulfone, polyether sulfone, polyether imide, polyether ether ketone, polyimide, polyamide-imide, polyethylene, polypropylene, polystyrene and the like.

  Examples of thermoplastic elastomers include polyester, polyamide, polyether, polyolefin, polyurethane, styrene, acrylic, polydiene, and the like. Among them, thermoplastic polyester elastomer Is preferred. Such thermoplastic polyester elastomers include both polyester-polyester type using polyester for hard segment and soft segment, and polyester-polyether type using polyester for hard segment and polyether for soft segment. It can be used suitably. In addition, although the hard segment of the polyester-type elastomer generally uses PBT or PBN as a main component, all can be used in this invention.

  A conductive material is added to the base material layer 101 in order to ensure conductivity. As the conductive material, known electronic conductive agents and ionic conductive agents similar to those mentioned for the intermediate layer 102 can be used with the same content.

  The film thickness of the base material layer 101 is usually in the range of 5 to 200 μm, preferably in the range of 70 to 140 μm.

  In addition to the above-mentioned components, other functional components can be appropriately added to each layer of the belt of the present invention as long as the effects of the present invention are not impaired. For example, various fillers and reinforcing materials , Flame retardant, Antioxidant, Compatibilizer, Coupling agent, Antioxidant, Lubricant, Surface treatment agent, Pigment, Ultraviolet absorber, Antistatic agent, Dispersant, Neutralizing agent, Foaming agent, Crosslinking agent, Surface A modifier etc. can be mix | blended suitably. Furthermore, you may color by adding a coloring agent.

  In the belt of the present invention, as shown by a one-dot chain line in FIG. 1, a fitting portion that fits with the fitting portion formed on the driving member is formed on the surface of the image forming apparatus that contacts the driving member. Alternatively, the conductive endless belt of the present invention is provided with such a fitting portion, and is fitted with a fitting portion (not shown) provided on the drive member so as to travel, thereby making the conductive endless belt. Deviation in the width direction of the belt can be prevented. For example, as shown in FIGS. 1A and 1B, the fitting portion has one or two ridges continuous along the circumferential direction (rotation direction) of the belt, and this is a driving roller or the like. It can be made to fit in the groove | channel formed along the circumferential direction in the surrounding surface of this drive member. Conversely, a groove along the circumferential direction (rotation direction) of the belt is provided as the fitting portion, and this is fitted to the convex strip formed along the circumferential direction on the circumferential surface of the drive member. Good.

  There is no restriction | limiting in particular as a manufacturing method of the belt of this invention, A known method is employable. For example, for the base material layer 101, a resin composition comprising a resin component and a functional component such as a conductive material is kneaded with a biaxial kneader, and the obtained kneaded product is extruded using an annular die. In addition, a powder coating method such as electrostatic coating, a dip method, or a centrifugal casting method can also be suitably employed. Next, a paint for forming the intermediate layer 102 containing an ultraviolet curable resin, a photopolymerization initiator, a conductive material, and the like is prepared, and this paint is applied on the base material layer 101 and dried, followed by ultraviolet irradiation. Thus, the intermediate layer 102 can be formed on the base material layer 101. Next, a belt of the present invention can be obtained by coating and curing a silanol group-containing fluororesin composition on the intermediate layer 102 to form the surface layer 103.

  The image forming apparatus of the present invention may be any apparatus provided with the conductive endless belt of the present invention, and examples thereof include an apparatus using a transfer system using a transfer belt as shown in FIG. Since the image forming apparatus of the present invention includes a belt capable of maintaining toner releasability, it has a long life as an apparatus, and is particularly useful in medium to high speed machines.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Base material layer>
18 parts by mass of carbon black (acetylene black) was blended with 100 parts by mass of the PPS resin, and mixed and dispersed with a biaxial kneader to obtain pellets. An endless base material layer having an inner diameter of 220 mm, a thickness of 120 μm, and a width of 250 mm was formed by extrusion molding with a molding machine equipped with a cylindrical die at the end of a single-screw extruder.

<Intermediate layer>
3 parts by mass of Irgacure 184 (manufactured by BASF Japan Ltd., alkylphenone photopolymerization initiator) as a photopolymerization initiator with respect to 100 parts by mass of the total amount of the resin components shown in Table 1 below, and addition of fluorine 0.5 part by mass of Megaface RS-72-K (manufactured by DIC Corporation, UV reaction type surface modifier) as an agent (surface modifier) and conductive metal oxide (ATO as a conductive material) -T-7722G-496, manufactured by Resino Color Industry Co., Ltd., solid content concentration 40% by mass) and 20 parts by mass (as solid content), diluted with a solvent (PMA (propylene glycol monomethyl ether acetate)), It coated on the said base material layer with the spray coating machine so that the film thickness after drying might be set to 2 micrometers. This coating film was dried by heating and then cured by UV irradiation to form an intermediate layer. For Comparative Example 5, no intermediate layer was formed.

<Surface>
On the intermediate layer, Fluorosurf FG-5080 (silanol group-containing fluorine-based resin material, manufactured by Fluoro Technology Co., Ltd.) is applied by brushing and cured with a curing time of 8 hours or more. A surface layer of 6 nm was formed, and conductive endless belts of Examples and Comparative Examples were produced. About Comparative Examples 1-3, the intermediate | middle layer was not formed.

<Coating elongation at break>
A coating film having only an intermediate layer was prepared, and the elongation to break was measured under the following conditions.
Equipment: Shimadzu Corporation, EZ-test
Sample: strip shape (length 100 mm x width 10 mm x standard thickness 100 μm)
Tensile speed: 5mm / sec
Data sampling interval: 100 msec
Measuring method: inclination at 0.5 to 0.6% elongation (when described, tangent method described in JIS)
Measurement environment: Room temperature (23 ± 3 ° C, 55 ± 10% RH)

<Paint pencil hardness>
About the surface layer surface of the belt of each Example and a comparative example, pencil hardness was measured using the commercially available pencil scratch hardness tester based on the prescription | regulation of JISK5600-5-4.

<Rotational durability test>
The belts 100 of the examples and comparative examples each having a protruding rib on both inner sides and a reinforcing tape on the outer surface are set in an endurance tester as shown in FIG. After standing for 24 hours, a continuous rotation test was performed at a linear speed of 150 mm / sec. The durability time was 500 hours (h). In the figure, reference numeral 21 denotes a driving roller (φ24.0), reference numeral 22 denotes a secondary transfer roller backup roller (φ24.0), reference numeral 23 denotes a tension roller (φ12.0), and reference numeral 24 denotes a primary transfer roller. Reference numeral 25 denotes a cleaning blade. An arrow indicates the direction of rotation of the belt.

<Calcium carbonate rubbing test>
A rubbing test was performed on the surface of the belt layer of each example and comparative example, in which a cotton seagull containing calcium carbonate was reciprocated 100 times at a load of 1 kg. Thereafter, the calcium carbonate was removed with a urethane sheet assuming a cleaning blade. Measure the coefficient of friction of the surface layer before and after the test, ○ if the rate of change is within 20%, ○ △ if it is over 20% and within 50%, △, 100 if it is over 50% and within 100%. When exceeding%, it was set as x.

<Transferability>
The belts of the examples and comparative examples were set on a commercially available color laser printer, and a purple image was printed. During the secondary transfer, the front cover is opened, and the toner remaining as a transfer residue between the secondary transfer roller nip portion on the belt and the cleaning portion is attached to a mending tape manufactured by Sumitomo 3M Co., Ltd., and this is applied to the OHP sheet. Pasted. The value calculated based on the following formula was defined as the secondary transfer efficiency, with C1 being the value measured with a Macbeth densitometer and C2 being the value of the Macbeth densitometer of the image printed on the recording medium.
Secondary transfer efficiency = 1-C1 / (C1 + C2)
In comparison with a transfer belt mounted as a reference, the transfer belt improved as ◯, the same level as Δ, and the worse as X.

  These results are also shown in the table below.

＊１）樹脂（１）：ペンタエリスリトールトリアクリレートヘキサメチレンジイソシアネートウレタンプレポリマー（共栄社化学（株）製，ＵＡ３０６Ｈ）
＊２）樹脂（２）：ＰＥＧ６００＃ジアクリレート（共栄社化学（株）製，ライトアクリレート１４ＥＧ−Ａ）
＊３）樹脂（３）：４−ヒドロキシブチルアクリレート（日本化成（株）製，４ＨＢＡ（炭素数４の直鎖アルキル基を有する水酸基含有アクリレート））

* 1) Resin (1): Pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer (manufactured by Kyoeisha Chemical Co., Ltd., UA306H)
* 2) Resin (2): PEG600 # diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., light acrylate 14EG-A)
* 3) Resin (3): 4-hydroxybutyl acrylate (manufactured by Nippon Kasei Co., Ltd., 4HBA (hydroxyl group-containing acrylate having a linear alkyl group having 4 carbon atoms))

＊４）樹脂（４）：２−ヒドロキシエチルメタクリレート（三菱ガス化学（株）製，ＨＥＭＡ（炭素数２の直鎖アルキル基を有する水酸基含有アクリレート））
＊５）樹脂（５）：ペンタエリスリトールトリアクリレート（共栄社化学（株）製，ライトアクリレートＰＥ−３Ａ（炭素数１の直鎖アルキル基を有する水酸基含有アクリレート））

* 4) Resin (4): 2-hydroxyethyl methacrylate (Mitsubishi Gas Chemical Co., Ltd., HEMA (hydroxyl group-containing acrylate having a straight-chain alkyl group having 2 carbon atoms))
* 5) Resin (5): Pentaerythritol triacrylate (manufactured by Kyoeisha Chemical Co., Ltd., light acrylate PE-3A (hydroxyl group-containing acrylate having a linear alkyl group having 1 carbon atom))

  From the results in the above table, each example in which an intermediate layer mainly composed of an ultraviolet curable resin containing a hydroxyl group-containing acrylate and a surface layer composed of a fluororesin composition having a silanol group was provided on the base material layer. In this belt, the increase in the coefficient of friction was suppressed, and it was confirmed that the predetermined durability was obtained while maintaining good transferability. Further, from the results of Examples 1 to 5 in which only the content of the hydroxyl group-containing acrylate in the intermediate layer was changed, good results were obtained in all the performances when the content of the hydroxyl group-containing acrylate was 10 to 30% by mass. You can see that Further, from the results of Examples 2, 6, and 7 in which the hydroxyl group-containing acrylates having different carbon numbers of the linear alkyl group were used, the increase in the coefficient of friction was suppressed as the number of carbons was increased to 2, or more, particularly 4 or more. When it is, it turns out that it is very effective for suppression of the raise of a friction coefficient.

  On the other hand, the durability of the belt of Comparative Example 1 was lowered because the intermediate layer provided on the base material layer was hard, the transferability was insufficient, and the friction coefficient was increased. The belt of Comparative Example 2 contains the resin (2), so that the intermediate layer is more flexible than Comparative Example 1, so that the durability is improved compared to Comparative Example 1. The rise has not improved. Further, the belt of Comparative Example 3 has the resin (2) compounded in an amount greater than that of Comparative Example 2, so that the intermediate layer becomes more flexible than Comparative Example 2 and the durability is further improved compared to Comparative Example 2. However, the increase in transferability and friction coefficient has not been improved. Furthermore, in the belt of Comparative Example 4, a surface layer made of a fluororesin composition having a silanol group is provided on the intermediate layer, but since the intermediate layer does not contain a hydroxyl group-containing acrylate, Comparative Examples 1 to 3 Although the transferability has improved, the increase in the coefficient of friction has not been improved. Furthermore, the belt of Comparative Example 5 showed good results because only the initial evaluation was made with respect to transferability. However, since the intermediate layer was not provided, the hardness was high and the friction coefficient also increased.

11a to 11d Photosensitive drums 12a to 12d Developing unit 13 Recording medium 14 Driving roller or tension roller 15 Secondary transfer roller 16 Recording medium feeding device 17 Fixing device 21 Driving roller 22 Secondary transfer roller backup roller 23 Tension roller 24 Primary Transfer roller 25 Cleaning blade 100 Conductive endless belt 101 Base material layer 102 Intermediate layer 103 Surface layer

Claims (5)

In a conductive endless belt comprising an intermediate layer and a surface layer in sequence on a base material layer,
The conductive endless belt, wherein the surface layer includes a fluorine-based resin composition having a silanol group, and the intermediate layer includes an ultraviolet curable resin containing a hydroxyl group-containing acrylate.   The conductive endless belt according to claim 1, wherein the ultraviolet curable resin contains 10 to 30% by mass of the hydroxyl group-containing acrylate.   The conductive endless belt according to claim 1, wherein the hydroxyl group-containing acrylate has a linear alkyl group.   The conductive endless belt according to claim 3, wherein the linear alkyl group has 2 or more carbon atoms.   An image forming apparatus comprising the conductive endless belt according to claim 1.

Images