Electrophotographic belt and electrophotographic image forming apparatus

Abstract

To provide a conductive electrophotographic belt composed of a base layer and a surface layer by which a large quantity of light is regularly reflected from a surface of the electrophotographic belt and good optical sensor characteristics for image control can be obtained, despite provision of a plurality of grooves extending in a circumferential direction in a surface of the surface layer of the electrophotographic belt and provision of a plurality of grooves in a surface of the base layer in contact with the surface layer.SOLUTION: An electrophotographic belt has an endless shape. The electrophotographic belt has a base layer and a surface layer provided directly on the base layer. A plurality of first grooves extending in a circumferential direction of the electrophotographic belt are provided in an outer surface of the surface layer. A plurality of second grooves are provided in a surface of the base layer in contact with the surface layer. The second grooves each form an acute angle of ±20° or less with respect to a direction orthogonal to the circumferential direction of the electrophotographic belt.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic belt and an electrophotographic image forming apparatus equipped with the electrophotographic belt. [Background technology]

[0002] In electrophotographic image forming apparatuses, for example, an electrophotographic belt is used as an intermediate transfer belt that temporarily transfers and holds a toner image. Toner remaining on the surface of the electrophotographic belt after transfer from the electrophotographic belt to paper or the like (hereinafter also referred to as "transfer residual toner") is cleaned using a cleaning blade made of an elastic material such as urethane rubber. In recent years, there has been a trend toward requiring electrophotographic image forming apparatuses to have even longer service lives in order to reduce environmental impact and costs, and electrophotographic members that can maintain excellent toner cleaning properties even when the number of printed sheets increases are needed. Patent Document 1 discloses that a cleaning blade is prevented from being caught in the electrophotographic transfer belt by providing a plurality of fine grooves extending in the circumferential direction on the toner image carrying surface (hereinafter also referred to as the "outer surface") of the electrophotographic transfer belt as shown in Fig. 1. The disclosure discloses a technology that enables the residual toner after transfer to be stably cleaned over a long period of time by providing such grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4590237 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent electrophotographic image forming apparatuses, the following control may be performed to achieve high color reproducibility. That is, a corrective toner image may be formed on an intermediate transfer belt, the corrective toner image may be detected by an optical sensor, and image control such as color misregistration correction may be performed based on the detection result. The optical sensor detects the corrective toner image using the difference (contrast) between the amount of light reflected from an area where the corrective toner image is not formed and the amount of light reflected from an area where the corrective toner image is formed.

[0005] Therefore, if the amount of reflected light from the surface of the electrophotographic belt on which no corrective toner image is formed is small, a clear difference cannot be obtained between the amount of reflected light from the portion on which the corrective toner image is formed, which may result in unstable image control. For this reason, it is required that the amount of reflected light from the surface of the electrophotographic belt is large. Meanwhile, electrophotographic belts are being required to have a longer life, and therefore, in electrophotographic belts having a surface layer laminated on a base layer, grooves may be provided on the surface of the base layer that contacts the surface layer to improve adhesion between the base layer and the surface layer.

[0006] According to the inventors' investigations, in an electrophotographic belt having grooves extending in the circumferential direction on the outer surface and also having grooves on the surface of the base layer that contacts the surface layer, there are cases where the corrective toner image cannot be accurately detected. One aspect of the present disclosure is directed to providing an electrophotographic belt having a plurality of grooves in the circumferential direction on its outer surface and grooves on the surface of a base layer in contact with the surface layer, while still achieving a large amount of reflected light and favorable image control optical sensor characteristics. Another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus capable of stably forming electrophotographic images with high color reproducibility over a long period of time. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, An electrophotographic belt having an endless shape, a base layer and a surface layer provided directly on the base layer; a plurality of first grooves extending in the circumferential direction of the electrophotographic belt are provided on the outer surface of the surface layer, a plurality of second grooves are provided on a surface of the base layer on the side in contact with the surface layer, The electrophotographic belt is provided such that each of the second grooves forms an acute angle of ±20° or less with respect to a direction perpendicular to the circumferential direction of the electrophotographic belt. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described electrophotographic belt as an intermediate transfer belt. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to obtain an electrophotographic belt having high adhesion between a surface layer and a base layer, having good image control optical sensor characteristics, and capable of stable toner cleaning over a long period of time. According to another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images over a long period of time. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram showing the angle of the grooves (first grooves) in the surface layer of the electrophotographic belt according to the present disclosure. [Figure 2] 1 is a schematic diagram showing a cross section of an electrophotographic belt according to the present disclosure, taken in a direction perpendicular to the circumferential direction. [Figure 3] FIG. 3 is a schematic view showing the angle of the grooves (second grooves) in the base layer of the electrophotographic belt according to the present disclosure. [Figure 4] 1 is a schematic diagram showing a cross section of an electrophotographic belt according to the present disclosure in a direction parallel to the circumferential direction. [Figure 5] FIG. 1 is a schematic diagram showing an example of the configuration of an intermediate transfer type image forming apparatus. [Figure 6] FIG. 2 is a schematic diagram showing an example of the configuration of a concentration detection sensor. [Figure 7] FIG. 1 is a schematic diagram of a reflected light amount measuring tool used in the examples. [Figure 8]FIG. 2 is a schematic diagram of a processing device used to form a base layer groove used in the examples. [Figure 9] FIG. 2 is a schematic diagram of a processing device used to form surface layer grooves used in the examples. [Figure 10] FIG. 2 is a schematic view showing an example of a cross-sectional shape of a cylindrical mold used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present disclosure, the expressions "XX or more and YY or less" and "XX to YY" that represent a numerical range mean a numerical range that includes the endpoints, that is, the lower limit and the upper limit, unless otherwise specified. We investigated the reason why the amount of reflected light decreases in an electrophotographic belt having a plurality of grooves extending in the circumferential direction on its outer surface and a plurality of grooves on the surface of the base layer that contacts the surface layer (hereinafter simply referred to as the "surface of the base layer"). As a result, we found that the decrease in the amount of reflected light depends on the extension direction of the grooves on the surface of the base layer. That is, we found that the decrease in the amount of reflected light is significant when the extension direction of the grooves on the surface of the base layer coincides with the extension direction of the grooves on the outer surface of the electrophotographic belt. That is, the base layer specularly reflects light that is incident on non-grooved portions of the surface of the base layer, while diffusely reflects light that is incident on the groove side and groove bottom. This is thought to result in an increase in the amount of diffusely reflected light and a decrease in the amount of specularly reflected light. An electrophotographic belt according to one embodiment of the present disclosure has an endless shape and includes a base layer and a surface layer provided directly on the base layer. A plurality of first grooves extending in the circumferential direction of the electrophotographic belt are provided on the outer surface of the surface layer. A plurality of second grooves are provided on the surface of the base layer that contacts the surface layer, and each of the second grooves forms an acute angle of ±20° or less with respect to a direction perpendicular to the circumferential direction of the electrophotographic belt.

[0011] The present inventors have conducted research to obtain an electrophotographic belt that reflects a large amount of light to an optical sensor and has good optical sensor characteristics for image control.

[0012] The light reflected from an electrophotographic belt includes not only the light reflected from the outermost surface, but also the light reflected from the surface of the base layer in a multi-layer belt having a base layer below the surface layer. A part of the incident light irradiated from the image control optical sensor passes through the surface layer and is reflected by the surface of the base layer. Furthermore, it has been confirmed that when grooves are formed on the surface of the base layer, the amount of reflected light changes depending on the angle of the grooves (hereinafter also referred to as "base layer grooves") with respect to the direction perpendicular to the circumferential direction of the electrophotographic belt.

[0013] Based on the above results, the present inventors have come to the following idea: In an electrophotographic belt having a plurality of grooves on the outer surface of the surface layer and on the surface of the base layer in contact with the surface layer, the amount of light reflected from the base layer can be controlled by controlling the angle of the base layer grooves with respect to the direction perpendicular to the circumferential direction of the electrophotographic belt. An electrophotographic belt according to one embodiment of the present disclosure will be described in detail below, although the present disclosure is not limited to the following embodiment.

[0014] <Electrophotographic belt> 1 is a schematic explanatory diagram of the outer peripheral surface of an electrophotographic belt (hereinafter, sometimes simply referred to as a "belt") 101 according to one embodiment of the present disclosure. Reference numeral 101a denotes the circumferential direction of the belt 101, 101b denotes a direction perpendicular to the circumferential direction 101a, and 102 denotes grooves formed on the outer surface of the belt 101. The electrophotographic belt has an endless shape and comprises a base layer and a surface layer, the surface layer being provided directly on the base layer. Materials that can be used for the base layer include thermoplastic resins, such as polyamide, polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, thermoplastic polyimide, polyether ether ketone, etc. These can also be used in combination of two or more types. Materials that can be used for the surface layer include curable resin materials that are cured by exposure to heat or active energy rays, and for example, acrylic materials can be used.

[0015] <Groove on the surface layer: First groove> 1, a plurality of first grooves 102 are provided in the outer peripheral surface of the surface layer of an electrophotographic belt 101, and the first grooves 102 are provided in the approximately circumferential direction of the electrophotographic belt 101. Reference numeral 103 in FIG. 1 denotes an example of a surface perpendicular to the circumferential direction of the electrophotographic belt 101. Figure 2 is a schematic diagram showing a cross section of the belt in a direction perpendicular to the circumferential direction. 201 indicates the base layer and 202 indicates the surface layer. W1 indicates the groove width, H1 indicates the groove depth, and P1 indicates the interval between adjacent grooves. The number n of the first grooves is not particularly limited as long as it can stably perform toner cleaning, but for an electrophotographic belt having a width of 250 mm in a direction perpendicular to the circumferential direction of the electrophotographic belt, it is preferably 2,000 to 120,000. That is, the number of grooves per mm of width in a direction perpendicular to the circumferential direction of the electrophotographic belt is preferably 8 to 480. By setting the number to 2,000 or more (i.e., 8 grooves per mm of width), it is possible to prevent an excessive increase in the area of ​​the cleaning blade contacting the portion where no first grooves are provided. This also prevents an increase in the frictional force generated between the cleaning blade and the electrophotographic belt. Furthermore, by setting the number to 120,000 or less (i.e., 480 grooves per mm of width), it is possible to maintain good toner secondary transfer efficiency.

[0016] There are no particular restrictions on the interval P1 between adjacent grooves as long as the number of grooves is within the above range, but it is preferable that the intervals be approximately equal from the viewpoint of toner cleaning.

[0017] The width W1 of the first groove is preferably 0.10 μm to 3.0 μm, and more preferably 0.20 μm to 2.0 μm. By setting it to 0.10 μm or more, it is possible to prevent the grooves from disappearing due to wear on the surface of the electrophotographic belt. Furthermore, by setting it to 3.0 μm or less, it is possible to maintain good secondary transfer properties of toner. Furthermore, the depth H1 of the first groove is preferably 0.10 μm to 5.0 μm, and more preferably 0.20 μm to 2.0 μm. By setting it to 0.10 μm or more, it is possible to prevent the grooves from disappearing due to wear on the surface of the electrophotographic belt. Furthermore, by setting it to 5.0 μm or less, it is possible to maintain sufficient strength of the electrophotographic belt.

[0018] <Base groove Second groove> As shown in Fig. 3, a plurality of second grooves 203 are provided on the surface of the base layer 201 that contacts the surface layer (not shown in Fig. 3) of the electrophotographic belt. Each of the second grooves 203 is provided so that the acute angle θ with respect to a direction 101b perpendicular to the circumferential direction of the electrophotographic belt is ±20° or less. Reference numeral 304 in Fig. 3 denotes an example of a plane in the circumferential direction of the electrophotographic belt.

[0019] 4 is a schematic diagram showing a circumferential cross section of the belt 5, showing a case where the acute angle is 0°. The second grooves 203 preferably have a ten-point average roughness Rzjis measured on the surface of the base layer 201 of 1.85 μm to 3.10 μm. If Rzjis is less than 1.85 μm, sufficient adhesion between the surface layer 202 and the base layer 201 may not be obtained, which is undesirable. If Rzjis exceeds 3.10 μm, the influence of the second grooves 203 of the base layer 201 on the surface shape of the surface layer 202 increases, which may impair the smoothness of the portions of the surface layer 202 other than the first grooves 102, which is undesirable.

[0020] The number of second grooves is preferably 50 to 600 per 1 mm of width in the direction perpendicular to the direction in which the second grooves extend. If the number of second grooves is less than 50, sufficient adhesion between the surface layer 202 and the base layer 201 may not be obtained, which is not preferable. If the number of second grooves exceeds 600, the influence of the second grooves 203 in the base layer 201 on the surface shape of the surface layer 202 increases, which may impair the smoothness of the portions of the surface layer 202 other than the first grooves 102, which is not preferable.

[0021] The width of the second grooves is preferably 0.4 μm to 10 μm. If the width of the second grooves is less than 0.4 μm, when the coating liquid for forming the surface layer 202 is applied, the coating liquid has difficulty penetrating into the groove portions of the base layer 201, which may result in insufficient adhesion, which is undesirable. If the width of the second grooves exceeds 10 μm, the influence of the second grooves 203 of the base layer 201 on the surface shape of the surface layer 202 increases, which may impair the smoothness of the portions of the surface layer 202 other than the first grooves 102, which is undesirable.

[0022] The base layer can be formed by a molding method using a known thermoplastic resin. For example, the thermoplastic resin composition can be pelletized and molded by a known molding method such as continuous melt extrusion molding, injection molding, stretch blow molding, or inflation molding to obtain a base layer for an electrophotographic belt in an endless belt shape. Among these, continuous melt extrusion molding is more preferred because it allows continuous molding and is suitable for mass production.

[0023] It is preferable to clean the surface of the molded base layer to remove foreign matter. For example, the base layer is held by a cylindrical or multi-axis roller and rotated at a constant speed while pressing a cleaning member against the surface of the base layer to remove foreign matter. The cleaning member can be, but is not particularly limited to, a nonwoven fabric, a rubber blade, a brush, or the like. Grooves can be formed on the surface of the base layer using known processing methods such as polishing, cutting, and imprinting, but polishing is preferred from the viewpoint of providing a high degree of freedom in processing.

[0024] The surface layer can be formed by any known method, such as dip coating, spray coating, flow coating, shower coating, roll coating, spin coating, ring coating, etc. By using these methods, the surface layer can be formed on the base layer. Grooves can be formed on the surface of the surface layer by known methods such as cutting, etching, imprinting, etc. Imprinting is preferred from the viewpoints of high reproducibility of the grooves and low processing costs. In order to reduce the amount of transmitted light irradiated from the image control optical sensor, the thickness of the electrophotographic belt is preferably 30 μm or more, and particularly preferably 50 μm or more.

[0025] <Electrophotographic image forming apparatus> FIG. 5 shows an example of an image forming apparatus incorporating an electrophotographic belt according to the present disclosure as an intermediate transfer member, configured as an electrophotographic apparatus. This image forming apparatus forms color images on a recording medium S, such as paper, supplied from a paper feed cassette 20 using four color toners, represented by C, M, Y, and K, respectively. Image forming stations for each color are arranged side by side in a substantially horizontal direction. These image forming stations are equipped with photosensitive drums 1c, 1m, 1y, and 1k, respectively. The subscripts "c," "m," "y," and "k" are added to reference numerals to indicate which color image forming station the reference numeral belongs to: "cyan," "magenta," "yellow," or "black." The image forming apparatus is equipped with a laser scanner 3, a laser optical unit, which emits laser beams 3c, 3m, 3y, and 3k corresponding to image signals for each color toward the photosensitive drums 1c, 1m, 1y, and 1k, respectively.

[0026] Since all the image forming stations have the same structure, the image forming station for K (black) will be described here. Surrounding the photosensitive drum 1k are a conductive roller 2k, which is a contact charging device, a developing unit 4k, a conductive roller 8k, which is a primary transfer roller, and a toner recovery blade 14k, which is used to clean the photosensitive drum 1k. The developing unit 4k is provided with a developing roller 41k, which is a developer carrier that develops the latent image on the photosensitive drum 1k, a developing container 42k that holds toner supplied to the developing roller 41k, and a developing blade 43k that regulates the amount of toner on the developing roller 41k and applies an electric charge.

[0027] The electrophotographic belt 5 is configured as an endless belt and is provided in common to the image forming stations for each color. It is stretched over a secondary transfer opposing roller 92, a tension roller 6, and a drive roller 7, and is rotated in the direction of the arrow in the figure by the drive roller 7. The electrophotographic belt 5 comes into contact with the surfaces of the photosensitive drums 1c, 1m, 1y, and 1k in succession in the section between the tension roller 6 and the drive roller 7, and is pressed against the photosensitive drums 1c, 1m, 1y, and 1k by primary transfer rollers 8c, 8m, 8y, and 8k, respectively. As a result, the toner images formed on the surfaces of the photosensitive drums 1c, 1m, 1y, and 1k are transferred to the surface of the electrophotographic belt 5, which serves as an intermediate transfer member.

[0028] A secondary transfer roller 9 is provided opposite the counter roller 92, and the electrophotographic belt 5 is pressed against the counter roller 92 by the secondary transfer roller 9. A secondary transfer voltage is applied to the secondary transfer roller 9 from a power source via a current detection circuit 10. The secondary transfer roller 9 and the counter roller 92 form a secondary transfer unit. The recording medium 5 passes through the nip between the electrophotographic belt 5 and the secondary transfer roller 9 at the position of the counter roller 92 via a feed roller 12 and a transport roller 13, whereby the toner image held on the outer surface of the electrophotographic belt 5 is transferred. In this way, an image is formed on the surface of the recording medium S. The recording medium S with the transferred toner image passes through a fixing device 15 consisting of a roller pair of a heating roller 151 and a pressure roller 152, where the image is fixed, and the recording medium S is discharged to a paper output tray 21.

[0029] A cleaning blade 11 is provided at the position of the tension roller 6 to come into contact with the outer peripheral surface of the electrophotographic belt 5. Toner that has not been transferred to the recording medium S and remains on the outer peripheral surface of the electrophotographic belt 5 is scraped off and removed by the cleaning blade 11. The cleaning blade 11 is a member that extends in a direction substantially perpendicular to the direction in which the electrophotographic belt 5 moves. The cleaning blade 11 is not particularly limited as long as it is suitable for toner cleaning. Examples include urethane rubber, acrylic rubber, nitrile rubber, and EPDM rubber, and from the viewpoint of toner cleaning, urethane rubber is preferred.

[0030] The color of printed matter changes depending on the conditions of the image forming device, such as the environment in which it is used. For this reason, it is necessary to measure the density as needed and provide feedback to the control mechanism within the device. The toner image for density correction is transferred to the surface of the electrophotographic belt 5, and then transported to the position of the drive roller 7 as the electrophotographic belt 5 rotates. The toner density is detected by a density detection sensor 160, which is located on the opposite side of the electrophotographic belt 5 from the drive roller 7.

[0031] 6 is a schematic diagram of the density detection sensor 160. The density detection sensor 160 is composed of a light-emitting element 161, a diffuse reflection light-receiving element 162, and a specular reflection light-receiving element 163. The light-emitting element 161 emits infrared light, which is reflected by the surface of the toner image T. The diffuse reflection light-receiving element 162 is disposed in a position where it can receive light reflected in directions other than the specular reflection direction relative to the position of the toner image T, and detects the diffuse reflection light at the position of the toner image T. The specular reflection light-receiving element 163 is disposed in a position where it can receive light reflected in the specular reflection direction relative to the toner image T, and detects the specular reflection light at the position of the toner image T. [Example]

[0032] EXAMPLES The present disclosure will be specifically described below with reference to examples and comparative examples, but the present disclosure is not limited to the configurations embodied in the examples.

[0033] (Methods for measuring and evaluating characteristic values) The evaluation methods (1) to (4) for the electrophotographic belts according to the examples and comparative examples will be explained below.

[0034] (1) Evaluation of the roughness of the base surface The surface roughness was measured using a surface roughness measuring instrument (product name: Surfcom 1500SD, manufactured by Tokyo Seimitsu Co., Ltd.) The ten-point average roughness Rzjis was measured in accordance with JIS B0601 (2001) under the conditions of a cutoff wavelength of 0.25 mm, a measurement reference length of 0.25 mm, and a measurement length of 1.25 mm.

[0035] Here, the ten-point average roughness Rzjis of the base layer surface was measured by scanning the stylus of a measuring instrument in a direction perpendicular to the direction in which the grooves formed on the outer circumferential surface of the base layer belt extend. Five base layer belts were produced under the same conditions, and this measurement was carried out on one of the base layer belts at eight points (two points in the direction perpendicular to the circumferential direction and four points in the circumferential direction), and the ten-point average roughness Rzjis was calculated by arithmetically averaging the obtained values. When no grooves were found on the outer peripheral surface of the base layer belt, the above measurement was carried out by scanning the stylus of the measuring instrument in a direction perpendicular to the circumferential direction of the base layer belt.

[0036] The surface roughness of the base layer can be measured even after the surface layer is formed on the base layer. Specifically, the belt consisting of the base layer and surface layer is cut into sheets at the roughness measurement points (two points perpendicular to the circumferential direction x four points circumferentially). The cut sheets are immersed in an alkaline solution and then removed after the surface layer has dissolved. The distance between two points perpendicular to the circumferential direction is half the width of the base layer belt, and the distance between two adjacent points on the four circumferential directions is one-quarter the circumference of the base layer belt. While the cut sheets are immersed in the alkaline solution, an ultrasonic device can be used to accelerate the dissolution of the surface layer. Next, the entire surface of the removed sheet is rinsed with pure water and then dried with dry air to remove any remaining moisture. This process removes the surface layer, exposing the surface of the base layer that was in contact with the surface layer. The subsequent measurement of the surface roughness of the base layer is as described above.

[0037] (2) Measurement of the base layer groove angle The base layer groove angle was measured using a non-contact three-dimensional surface profiler (trade name: NewView 6300, manufactured by Zygo Corporation). Five electrophotographic belts were produced under the same conditions, and the measurement was carried out on one of the electrophotographic belts at eight points (two points in the direction perpendicular to the circumferential direction and four points in the circumferential direction), each within an evaluation length of 300 μm, by the following method. The surface of the electrophotographic belt was observed at a magnification of 50 times using a non-contact three-dimensional surface profiler, and the angle formed between the extending direction of the base layer grooves 203 and the direction perpendicular to the circumferential direction of the electrophotographic belt was measured from the obtained base layer groove image, as shown in Fig. 3. The smaller angle (an angle of 90° or less) was defined as the angle θ of the base layer groove. Regarding the sign of the angle, the angle θ shown in Fig. 3 with respect to the circumferential direction of the belt was taken as positive.

[0038] (3) Evaluation of reflected light amount The amount of reflected light was measured using a reflected light amount measurement tool configured as shown in Fig. 7. Belt 5 was stretched over three axes 703, a glass plate 702 was placed on the backside of the measurement surface, and measurement was performed using a gloss meter (product name: PG-2, manufactured by Nippon Denshoku Industries Co., Ltd.) 701. The direction of the light projection axis of the light emitting element 161, which is the light source, was set to a direction perpendicular to the circumferential direction of the electrophotographic belt. The light projection and reception angle was set to 60°. Five electrophotographic belts were produced under the same conditions, and this measurement was performed on one of the belts at eight points: two points in the direction perpendicular to the circumferential direction and four points in the circumferential direction. The arithmetic mean of the obtained values ​​was determined as the amount of reflected light. The distance between two points in the direction perpendicular to the circumferential direction was set to half the belt width, and the distance between two adjacent points of the four circumferential directions was set to one-quarter of the belt's circumferential length.

[0039] (4) Evaluation of adhesion Using an electrophotographic image forming apparatus having the configuration shown in FIG. 5, an electrophotographic belt was attached as an intermediate transfer member, and the adhesion performance between the surface layer and the base layer was evaluated when blade cleaning was performed. This evaluation was carried out under an environment of a temperature of 25°C and a relative humidity of 50%, using an Extra (basis weight 80 g / m) manufactured by OCE as the recording medium S. 2 ) and JIS A4 size paper were used, and 600,000 sheets were printed intermittently with two sheets. The presence or absence of surface layer peeling was determined based on the presence or absence of residual toner. If the surface layer peels, the toner will be buried in the peeled area and will not be able to follow the elastic deformation of the blade cleaning, causing it to slip through the cleaning blade 11.

[0040] Specifically, first, with the secondary transfer voltage turned off (0 V), laser beams 3y and 3m were irradiated onto photosensitive drums 1y and 1m to record a red image (Y toner and M toner) over the entire A4 size surface. After that, the secondary transfer voltage was set to an appropriate value, and three blank sheets were passed continuously. Since no secondary transfer voltage is applied, the Y toner and M toner transferred from the photosensitive drums 1y and 1m to the entire surface of the electrophotographic belt 5 is hardly transferred to the recording medium S at the secondary transfer portion and rushes into the cleaning blade 11. If the toner is removed from the electrophotographic belt 5, the three sheets that pass thereafter will be output as completely blank sheets, but if the toner is not removed, the transfer residual toner that has slipped through the cleaning blade 11 will be transferred to the recording medium S at the secondary transfer portion. In other words, it will be transferred onto the blank sheet and output as a toner cleaning failure image on the recording medium S.

[0041] The above evaluation was carried out at the time points of 200,000 sheets, 400,000 sheets, and 600,000 sheets, and based on the evaluation results, the electrophotographic belts were ranked according to the following criteria. Good: No cleaning failures occurred during the 600,000 sheet paper feed process. ×: Cleaning failure occurred during the process of passing 600,000 sheets.

[0042] [Example 1] (Base layer manufacturing) The base layer was produced by a production method including the following steps. The following materials were mixed using a Henschel mixer (Nippon Coke and Engineering Co., Ltd., FM-150L / I) at a blade rotation speed of 1515 rpm, a processing amount of 30 kg, a processing time of 5 minutes, and a processing temperature of 50°C to obtain a mixture (A). Polyether ether ketone resin (450G, manufactured by Victrex Co., Ltd.) 83 parts by weight Carbon black (Touka Black #7270SB, manufactured by Tokai Carbon Co., Ltd.) 17 parts by weight

[0043] Next, the obtained mixture (A) was mixed using a twin-screw kneader (Ikegai Corporation, PCM43) at an extrusion rate of 6 kg / h, a screw rotation speed of 225 rpm, and a barrel control temperature of 330°C to obtain a pellet-shaped mixture (B). The obtained mixture (B) was then molded using a single-screw extruder (Plastic Technology Research Institute Co., Ltd.) equipped with a spiral cylindrical die at the tip under the conditions of an extrusion rate of 6 kg / h and a die temperature of 380°C or less to obtain the base layer of the intermediate transfer belt. The base layer of the obtained intermediate transfer belt had a thickness of 60 μm, a circumferential length of 792 mm, and a width of 250 mm.

[0044] (Formation of basement groove) Groove processing was performed on the base layer surface using the processing device shown in Fig. 8. Groove processing was performed on the base layer of the belt by pressing an abrasive film against it to form grooves on the surface of the base layer. Specifically, as shown in Fig. 8, the base layer 201 of the belt was held on the outer peripheral surface of a cylindrical holding mold, and an abrasive film 803 (trade name: Lapica WA2000, manufactured by Kovacs Co., Ltd.) for base layer groove processing, which was installed on the outer peripheral surface of an abrasive film holding roller 802, was pressed against it. The abrasive film 803 was pressed against the base layer 201 at a contact surface pressure of 0.08 kg / mm 2 While the abrasive film was pressed against the surface, the roller holding the abrasive film was moved at 100 mm / sec in a direction perpendicular to the circumferential direction of the belt while the cylindrical holder mold was rotated to the desired angle. The process was repeated until no unprocessed areas remained, thereby forming grooves on the surface of the base layer. The groove pattern on the surface of the base layer obtained by the above steps was as follows: Number of grooves: 482 The width and spacing of the grooves shown in Figure 4 are: W2 = 1.1 μm, P2 = 4.6 μm

[0045] (Preparation of coating liquid) The acrylic resin composition shown in Table 1 was weighed out, and the solution was subjected to a coarse dispersion treatment, and then dispersed using a high-pressure emulsifying disperser (product name: Nanovaita, manufactured by Yoshida Kikai Kogyo Co., Ltd.). This dispersion treatment was continued until the 50% average particle size of the contained PTFE reached 200 nm. The obtained dispersion was used as a coating liquid for the surface layer.

[0046] [Table 1]

[0047] (Formation of surface layer) The base layer was fitted onto the outer periphery of a cylindrical mold (circumferential length 792 mm), the edges were sealed, and the mold was then immersed in a container filled with the coating liquid (curable composition). The base layer was then pulled up at a constant relative speed between the liquid surface of the curable composition and the base layer, forming a coating film of the coating liquid on the surface of the base layer. The desired film thickness can be obtained by adjusting the pulling speed (the relative speed between the liquid surface of the curable composition and the base layer) and the solvent ratio of the curable composition. In this example, the pulling speed was set to 10 to 50 mm / sec, and the surface layer thickness was adjusted to 5 μm.

[0048] In this example, the coating direction refers to the direction opposite to the direction in which the base layer is pulled up. In other words, the location where the base layer is first pulled up from the coating liquid is the most upstream. The base layer coated with the coating liquid was removed from the cylindrical mold and dried for 1 minute in an exhausted environment at a temperature of 23°C. The drying temperature and drying time were adjusted appropriately depending on the type of solvent, solvent ratio, and film thickness. Thereafter, a UV irradiator (product name: UE06 / 81-3, manufactured by Eye Graphics Co., Ltd.) was used to dry the base layer with an accumulated light dose of 600 mJ / cm. 2 The coating was cured by irradiating it with ultraviolet light until it reached a temperature of 100°C.

[0049] (Formation of grooves in the surface layer) Using the imprint processing device shown in Figure 9, grooves were formed in the coating film. The imprint processing device is composed of a cylindrical mold 901 for providing grooves and a cylindrical belt holding mold 900, and the cylindrical mold 901 can apply pressure while maintaining its axis parallel to the cylindrical belt holding mold 900. At this time, the cylindrical mold 901 and the cylindrical belt holding mold 900 rotate synchronously without slippage. Cylindrical mold 901 is made of electroless nickel-plated carbon steel and has a diameter of 120 mm and a length of 250 mm. Convex portions corresponding to the shape of the grooves are formed on the surface of cylindrical mold 901, and the convex pattern is formed in a spiral shape at an angle of 0.1° with respect to the circumferential direction of the cylindrical mold. The cross-sectional shape of the protrusions corresponding to the grooves formed on the cylindrical mold used in this example, in a direction perpendicular to the circumferential direction, was a trapezoid as shown in Figure 10, and the respective dimensions were H = 3.5 μm, Wb = 2.0 μm, Wt = 0.2 μm, and P = 6 μm.

[0050] Next, a base layer with a coating film formed thereon was fitted onto the outer periphery of the cylindrical belt holding mold 900 (circumferential length 792 mm). This was rotated at a peripheral speed of 1 mm / sec together with a cylindrical mold 901 heated to 130°C (the rotation directions were opposite for both). While maintaining their axial centerlines parallel to each other, the cylindrical mold 901 was brought into contact with the belt, and the pressure was increased to 22.0 kN at a rate of 1.0 kN / s. Then, while maintaining the pressure at 22.0 kN, the cylindrical belt holding mold 900 and the cylindrical mold 901 were rotated, and the groove-imparting cylindrical mold 901 was released upon completion of imprint processing for one revolution of the belt. As a result, the convex pattern of the groove-imparting cylindrical mold 901 was transferred to the surface of the belt, forming grooves. The groove pattern of the surface layer obtained through the above steps was as follows: Number of grooves: 41,667 The width, depth, and spacing of the grooves shown in Figure 2 are: W1 = 0.6 μm, H1 = 0.6 μm, P1 = 6 μm

[0051] The thickness of the surface layer was measured by destructive testing, in which an electrophotographic belt separately produced under the same conditions was cut and the cross section was observed with an electron microscope (product name: XL30-SFEG, manufactured by FEI Corporation). As a result of the destructive testing, the thickness of the surface layer was found to be 5.0 μm. When the reflected light amount of the electrophotographic belt was evaluated using a reflected light amount measuring tool shown in FIG. 7, all values ​​exceeded the reference value (=30). The electrophotographic belt was mounted in an electrophotographic image forming apparatus shown in FIG. 5, and adhesion was evaluated. It was confirmed that no peeling of the surface layer occurred after printing 600,000 sheets.

[0052] [Examples 2 to 6] An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the roughness of the base layer surface and the angle of the base layer grooves were set to the values ​​shown in Table 2. The evaluation results are shown in Table 2.

[0053] [Table 2]

[0054] [Comparative Examples 1 to 8] An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the roughness of the base layer surface or the angle of the base layer grooves were set to the values ​​shown in Table 3. The evaluation results are shown in Table 3. The angle of the base layer groove in Comparative Examples 1 to 8 was too large relative to the direction of light projection from the gloss meter, which acted to hinder the gloss meter from receiving light, and as a result, sufficient reflected light was not obtained from the base layer, resulting in insufficient reflected light (<30) in all cases.

[0055] [Table 3] [Explanation of symbols]

[0056] 1 Photosensitive drum 2 Conductive roller 3. Laser scanner 4 Developer 5 Electrophotographic belt 6 Tension roller 7 Drive Roller 8 Primary transfer roller 9 Secondary transfer roller 10 Current detection circuit 11 Cleaning blade 12 Feeding roller 13 Conveyor roller 14 Toner collection blade 15 Fixing unit 20 Paper cassette 21 Paper output tray 41 Developing roller 42 Developer container 43 Developing blade 101 Electrophotographic belt 101a Rotation direction 101b perpendicular direction (direction perpendicular to the rotation direction 101a of the electrophotographic belt 101) 102 Groove 160 Concentration detection sensor 161 Light-emitting element 163 Regular reflection photodetector 201 Base layer 202 Surface layer 203 Base groove 701 Glossmeter 702 Glass plate 703 axes 802 Polishing film holding roller 803 Polishing Film 900 Cylindrical Belt Retention Type 901 Cylindrical mold

Claims

1. An electrophotographic belt having an endless shape, a base layer and a surface layer provided directly on the base layer; a plurality of first grooves extending in a circumferential direction of the electrophotographic belt are provided on an outer surface of the surface layer; a plurality of second grooves are provided on a surface of the base layer on the side in contact with the surface layer; The electrophotographic belt is characterized in that each of the second grooves forms an acute angle of ±20° or less with respect to a direction perpendicular to the circumferential direction of the electrophotographic belt.

2. 2. The electrophotographic belt according to claim 1, wherein the ten-point average roughness Rzjis measured on the surface on which the second grooves are formed is 1.85 μm to 3.10 μm.

3. 3. The electrophotographic belt according to claim 1, wherein the number of said second grooves is 50 to 600 per 1 mm of width in a direction perpendicular to the direction in which said second grooves extend.

4. 4. The electrophotographic belt according to claim 1, wherein the width of the second groove is 0.4 μm to 10 μm.

5. 5. The electrophotographic belt according to claim 1, wherein the number of the first grooves is 8 to 480 per 1 mm of width in a direction perpendicular to the circumferential direction of the electrophotographic belt.

6. 6. The electrophotographic belt according to claim 1, wherein the width of the first groove is 0.10 μm to 3.0 μm.

7. 7. The electrophotographic belt according to claim 1, wherein the depth of the first groove is 0.10 μm to 5.0 μm.

8. An electrophotographic image forming apparatus comprising an endless intermediate transfer belt and an optical sensor for detecting a toner image formed on an outer peripheral surface of the intermediate transfer belt, the direction of the light projection axis of the optical sensor is perpendicular to the circumferential direction of the surface of the intermediate transfer belt; 8. An electrophotographic image forming apparatus, wherein the intermediate transfer belt is the electrophotographic belt according to claim 1.

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