JP2010164706A - Image forming device - Google Patents

Abstract

An endless belt body is effectively and effectively maintained for a long period of time.
A sheet 10a supplied from a sheet feeding unit 10 is conveyed to each photosensitive drum 11 by an endless belt body (for example, a conveyor belt) 14. Each photosensitive drum 11 whose surface is charged by each charging roll 15 forms an electrostatic latent image by each LED head 12. Each developing unit 13 supplies toner onto each photosensitive drum 11 and develops the electrostatic latent image to become a visible image. The visible image on each photosensitive drum 11 is transferred to the paper 10 a by each transfer roll 16. The transferred paper 10a is sent to the fixing unit 17, where it is fixed and discharged. The belt 14 after separating the paper 10 a is cleaned by a cleaning blade 18 that removes toner and other foreign matters remaining on the belt 14. The Young's modulus of the conveyor belt 14 is 2.0-5. It is OGPa and the specularity is 60-130.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer provided with an endless belt body, other multifunction peripherals, and facsimile machines, and more particularly to a technique for cleaning an endless belt body.

  2. Description of the Related Art Conventionally, an image forming apparatus such as an electrophotographic printer is in contact with a photosensitive drum, which is an image carrier, as described in Patent Document 1 below, for carrying a recording material, which is an endless belt. A conveyor belt is provided. In general, for the purpose of removing (cleaning) toner remaining on the conveyance belt, a structure in which a cleaning blade made of urethane rubber is brought into contact with the conveyance belt is employed.

JP 2006-79001 A

  However, since the conventional image forming apparatus has a structure in which the toner remaining on the conveyance belt is removed by a urethane rubber cleaning blade in contact with the conveyance belt, the cleaning on the conveyance belt is effectively performed for a long time. There was a problem that it was difficult to maintain.

  The image forming apparatus of the present invention includes a plurality of image carriers, a movable endless belt provided in contact with each of the image carriers, and the endless belt in contact with the endless belt. The endless belt body has a Young's modulus of 2.0 to 5.0 GPa and a specularity of 60 to 130.

  According to the present invention, by setting the Young's modulus of the endless belt body to 2.0 to 5.0 GPa and the specularity of 60 to 130, the reliability of the cleaning performance of the endless belt body by the cleaning member can be improved.

FIG. 1 is a schematic configuration diagram showing an image forming apparatus in Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram illustrating another image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a schematic configuration diagram illustrating the specularity measuring apparatus used in the first embodiment. FIG. 4 is a block diagram showing the pattern projection plate in FIG. FIG. 5 is a waveform diagram showing a digital signal converted by the A / D converter in FIG. FIG. 6 is a table showing a cleaning performance evaluation table for the belts 14 and 24 of the first embodiment. FIG. 7 is a graph showing a cleaning performance evaluation for the belts 14 and 24 of the first embodiment. FIG. 8 is an enlarged cross-sectional view showing a belt in Embodiment 2 of the present invention.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Image Forming Apparatus of Example 1)
FIGS. 1A and 1B are schematic configuration diagrams showing an image forming apparatus according to Embodiment 1 of the present invention. FIG. 1A is a side view of the whole, and FIG. It is a side view of the endless belt body drive device in figure (a).

  The image forming apparatus 1 shown in FIG. 1A has, for example, four colors (black (K), yellow (Y), magenta (M), and cyan (M) on a sheet 10a that is a recording material stored in a sheet feeding unit 10. C)) is an electrophotographic color printer for printing characters, images, and the like, and includes four photosensitive drums 11 serving as electrostatic latent image carriers.

  Around each photosensitive drum 11, each light-emitting diode (LED) head 12, which is an exposure device that forms an electrostatic latent image on the photosensitive drum 11, and the electrostatic latent image on the photosensitive drum 11. Each developing unit 13 that is a developing member that supplies toner to the toner and develops the electrostatic latent image, a common endless belt body (for example, a belt that is a conveying member that carries the paper 10a) 14, and the surface of the photosensitive drum Each charging roll 15 is a charging member that charges the toner, and each transfer roll 16 is a transfer member that transfers the toner image from the photosensitive drum 11 to the paper 10a. A fixing unit 17 as a fixing member for fixing the toner image on the paper 10 a is disposed on the paper delivery side of the belt 14, and further, the toner remaining on the belt 14 is brought into contact with the belt 14. A cleaning blade 18 which is a cleaning member to be removed is provided.

  The endless belt body driving device shown in FIG. 1B is a device that drives a belt 14 that is an endless belt body. For example, the belt 14 is stretched with a tension force of 6 ± 10% kg by a tension means (not shown) and is rotated by a driving roll 19. A flange-shaped guide member (hereinafter referred to as “flange”) 21 for preventing meandering of the belt 14 while being rotated following the belt 14 is provided at a position in contact with the side portion of the belt 14.

  The flange 21 can be added to other rotating means as needed, or can be added to both sides of the belt 14. It can also be added to a belt support member (not shown). A cleaning blade 18 for removing residual toner is in contact with the belt 14.

  FIGS. 2A and 2B are schematic configuration diagrams illustrating another image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 2A is a side view of the whole, and FIG. FIG. 2 is a side view of the endless belt body driving device in FIG. 2 (a) and 2 (b), elements common to those in FIGS. 1 (a) and 1 (b) are denoted by common reference numerals.

  An image forming apparatus 1A shown in FIG. 2A is an intermediate transfer type image forming apparatus provided with an endless belt body driving device, and is replaced with another endless belt body in place of the belt 14 in FIG. (For example, an intermediate transfer belt body that directly carries a toner image visualized by development, hereinafter simply referred to as “belt”) 24 is provided.

  The endless belt body driving device shown in FIG. 2B is a device that drives the belt 24. The belt 24 is stretched by a stretching means (not shown), rotated by a driving roll 19, and provided with a flange 21 for preventing meandering of the belt 24 while being in contact with the side of the belt and rotating following the belt 24. ing. As in FIG. 1B, the flange 21 can be added to other rotating means as needed, or can be added to both sides of the belt 24. It can also be added to a belt support member (not shown).

(Detailed configuration of component parts of image forming apparatus)
The materials of the belts 14 and 24 (for example, 14) are prepared by appropriately adjusting various polyamideimides (hereinafter referred to as “PAI”), blending an appropriate amount of carbon black for the expression of conductivity, and N-methylpyrrolidone (hereinafter “ NMP ")) Mixing and stirring in the solution, casting into a cylindrical mold, heating at 80 to 120 ° C for a predetermined time while rotating, and then raising the temperature to 200 to 350 ° C for a predetermined time After heating, the mold was removed to obtain a belt original tube having a thickness of 100 ± 10 μm and a circumference of 624 ± 1.5 mm, and then cut into a width of 228 ± 0.5 mm.

  The PAI structure is a polymer in which an amide group and one or two imide groups are bonded via an organic group and are repeated as one unit. Depending on whether the organic group is aliphatic or aromatic, it is classified into aliphatic PAI or aromatic PAI. In Example 1, aromatic PAI is preferable from the viewpoint of durability and mechanical properties. . The meaning of this aromatic also means that the organic group to which the imide group or amide group is bonded is basically one or two benzene rings.

  PAI may be in the stage of amide acid that is completely imide ring-closed or not imide ring-closed, but it should be at least 50% or more, preferably 70% or more imidized. . This is because if there are too many amidic acid stages, the dimensional change rate tends to be large.

Note that the imidization ratio, the intensity of the Fourier transform infrared spectrophotometer (hereinafter referred to as "FT-IR".) At the absorption derived from the imide groups (1780Cm- ¹⁾ and absorption attributable to benzene rings (1510Cm- ¹⁾ It can be calculated from the ratio.

  As a method for increasing the Young's modulus of the belt 14, it is generally achieved by forming a molecular structure having a large number of aromatic rings and imide groups. On the other hand, as a method of lowering, it is brought about by making a molecular structure having few structures.

  The material of the belt 14 is not limited to the PAI used in the first embodiment. From the viewpoint of durability and mechanical characteristics, a material in which the tensile deformation at the time of driving the belt is within a certain range is desirable. It is desirable that the material be resistant to damage such as side wear, side breakage, and cracking due to repeated sliding with the meandering prevention means. For example, similar to the PAI used in Example 1, polyimide (PI), polycarbonate (PC), polyamide (PA), polyetheretherketone (PEEK) having a Young's modulus of 2.0 GPa or more, preferably 3.0 GPa or more. ), A resin such as polyvinylidene fluoride (PVdF), ethylene-tetrafluoroethylene copolymer (ETFE), and a mixture mainly composed of these resins may be used.

  When the belt 14 is produced by rotational molding, the solvent is appropriately determined depending on the material used, but an organic polar solvent is often used, and N, N-dimethylacetamides are particularly useful. For example, N, N -Dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, dimethylsulfoxide, NMP mentioned above, pyridine, tetramethylenesulfone, dimethyltetramethylenesulfone and the like. These may be used alone or in combination.

  The rotational speed of the cylindrical mold in the rotational molding is 5 to 1000 rpm, preferably 10 to 500 rpm from the viewpoint of the thickness accuracy of the belt 14 and the thickness profile.

  The same applies to a method in which a belt 14 is formed in the gap using a cylindrical mold having a combination of large and small diameters, or in the case where the belt 14 is formed by coating or dipping on the outer peripheral surface of the cylindrical mold. .

  On the other hand, in the case of so-called extrusion molding and inflation molding, molding can be performed without a solvent.

  Carbon black includes furnace black, channel black, ketjen black, acetylene black, and the like. These may be used alone or in combination with a plurality of types of carbon black. The type of these carbon blacks can be appropriately selected depending on the intended conductivity. However, the belt 14 used in the image forming apparatus 1 and 1A (for example, 1) in the first embodiment is particularly suitable for channel black. Furnace black is preferably used, and depending on its use, it is preferable to use one that prevents oxidative deterioration such as oxidation treatment or graft treatment, or one that has improved dispersibility in a solvent. The carbon black content is appropriately determined depending on the type of carbon black to be added according to the purpose, but the belt 1 used in the image forming apparatus 1 in the first embodiment is required to have the required mechanical properties. From strength etc., it is 3-40 weight% with respect to belt composition resin solid content, Preferably it is 5-30 weight%, More preferably, it is 5-25 weight%.

  The specularity of the belt 14 can be obtained by appropriately adjusting how the inner peripheral surface of the cylindrical mold is polished.

  As the toner, a styrene-acrylic copolymer was used as a main constituent composition by an emulsion polymerization method, 9 parts by weight of paraffin wax was included, an average particle diameter of 7 μm and a sphericity of 0.95 were used. This was selected because image sharpness and high image quality could be obtained by performing development with improved transfer efficiency, no fixing release agent, and excellent dot reproducibility and resolution.

  The cleaning blade 18 was set to a linear pressure of 4.3 g / mm with urethane rubber having a rubber hardness of JIS A 72 ° and a thickness of 1.5 mm. This is because the blade system made of an elastic material such as urethane rubber is excellent in the function of removing residual toner, foreign matter, etc., and its configuration is simple, compact, and low cost. Also, as the rubber material, urethane rubber having high hardness and high elasticity and excellent in wear resistance, mechanical strength, oil resistance, ozone resistance, etc. is optimal.

  In general, the urethane rubber used as the cleaning blade 18 as in Example 1 to maintain the cleaning property has a hardness of JIS A 60-90 °, more preferably 70-85 °, and an elongation at break of 250-500%, more preferably. Is preferably 300 to 400%, permanent elongation is 1.0 to 5.0%, more preferably 1.0 to 2.0%, rebound resilience is 10 to 70%, more preferably 30 to 50%. . Each of the physical properties can be measured according to JISK6301.

  The linear pressure is 1 to 6 g / mm, preferably 2 to 5 g / mm. This is because if it is too small, the adhesion to the belt 14 is insufficient, and thus cleaning failure is likely to occur. On the other hand, if it is too large, the contact with the belt 14 becomes a surface contact, the frictional resistance becomes excessive, the pressing force is superior to the scraping force, and problems such as poor cleaning such as so-called filming phenomenon and turning over are likely to occur. Because.

  In the first embodiment, the shaft diameter of the belt drive roll 19 is φ25. However, the shaft drive roll 19 is not limited to this diameter, and generally has a diameter of 10 to 50 due to cost and downsizing of the apparatus. Often used.

  As a means for stretching the belt 14, in the first embodiment, a spring is used and the belt 14 is stretched with a force of 6 ± 10% kg. However, the method of stretching the belt 14 is not limited to this. Further, the force for tensioning the belt 14 is also appropriately selected depending on the belt material to be used and the belt driving means. In general, the belt 14 is stretched with a force of 2 to 8 ± 10% kg. There are many cases.

  In the above description, the belt 14 and the like used in the image forming apparatus 1 in FIG. 1 have been described. However, the same applies to the belt 24 and the like used in the other image forming apparatus 1A in FIG.

(Specularity measuring device used in Example 1)
FIG. 3 is a schematic configuration diagram illustrating the specularity measuring apparatus used in the first embodiment. FIG. 4 is a block diagram showing the pattern projection plate in FIG.

  A specularity measuring apparatus 30 shown in FIG. 3 includes a pattern projecting device 31, a photoelectric conversion element 32, and a signal processing device 33. The pattern projection device 31 is provided with a light source 31a and a pattern projection plate 31b. The pattern projection plate 31b shown in FIG. 4 is, for example, a stainless steel plate having a thickness of 0.5 mm having an opening 31b1 having a width of 1 mm, and the surface is matte so as not to reflect light. The pattern projection device 31 is held so as to irradiate the object surface 34 with light at an angle θ.

  The photoelectric conversion element 32 is held such that this optical axis is on the same plane as the optical axis of the pattern projection device 31 and is at an angle of (180-2θ) degrees. The photoelectric conversion element 32 uses a charge coupled device (hereinafter referred to as “CCD”) array in which a large number of light receiving portions are arranged linearly (one-dimensionally) or two-dimensionally. A signal processing device 34 is connected to the output side of the photoelectric conversion element 33.

  The signal processing device 34 is, for example, a device that calculates the specularity of the measurement object surface 34 from the reflection intensity signal S32 of the measurement object surface 34 output from the photoelectric conversion element 32. For example, an analog reflection intensity signal is used. An analog / digital conversion unit (hereinafter referred to as “A / D conversion unit”) 33a that converts S32 into a digital signal is provided. A maximum (Max) and minimum (Min) detection unit 33b, a calculation unit 33c, and a display unit 33d are connected to the output side of the A / D conversion unit 33a.

(Operation of Image Forming Apparatus of Example 1)
In the image forming apparatus 1 of FIG. 1, the paper 10 a supplied from the paper supply unit 10 is conveyed to each photosensitive drum 11 by the belt 14. Each photosensitive drum 11 whose surface is charged by each charging roll 15 forms an electrostatic latent image by each LED head 12. Each developing unit 13 supplies toner onto each photosensitive drum 11 and develops the electrostatic latent image to become a visible image. The visible image on each photosensitive drum 11 is transferred to the paper 10a by each transfer roll 16, and sequentially transferred by the belt 14 carrying the paper 10a. The transferred paper 10a is sent to the fixing unit 17, where it is fixed and discharged. The belt 14 after separating the paper 10 a is cleaned by a cleaning blade 18 that removes toner and other foreign matters remaining on the belt 14.

  On the other hand, in the image forming apparatus 1A of FIG. 2, the toner image is directly carried on the belt 24 and transferred to the paper 10a. Other operations are almost the same as those of the image forming apparatus 1 of FIG.

(Operation of Specularity Measuring Device of Example 1)
FIG. 5 is a waveform diagram showing a digital signal converted by the A / D converter 33a in FIG.

  In the specularity measuring apparatus 30 of FIG. 3, a parallel light beam is irradiated from the light source 31 a to the pattern projection plate 31 b, and a light / dark pattern of light is projected onto the surface of the object to be measured 34. The pattern projected on the measurement object surface 34 is imaged by the photoelectric conversion element 32 and converted into an electrical signal. The analog reflection intensity signal S32 output from the photoelectric conversion element 32 is converted into a digital signal as shown in FIG. 5 by the A / D conversion unit 33a in the signal processing device 33.

  The maximum / minimum detection unit 33b detects the maximum value (Max) and the minimum value (Min) of each digital signal waveform, and the calculation unit 33c detects the maximum value (Max)) and minimum value (Min). ) Average Max (Ave.) and average Min (Ave.), respectively, and Max (Ave.) and Min (Ave.)

が計算される。この（１）式より、理想表面をもった被測定物表面の値は「１」となる。よって、便宜上理想表面をもった被測定物表面３４を基準とし、次式（２）を用いて鏡面度が算出される。鏡面度とは表面性状の写像性を数値化したものである。

Is calculated. From this equation (1), the value of the surface of the object having the ideal surface is “1”. Therefore, for convenience, the specularity is calculated using the following equation (2) with the measured object surface 34 having an ideal surface as a reference. The specularity is a numerical value of the mapping of the surface texture.

  Conventionally, methods for quantitatively measuring the fine shape of the surface include surface roughness, glossiness, etc., but these are only a part of the characteristics, and image clarity is measured by visual evaluation. Was common.

  On the other hand, the specularity in the first embodiment is based on the clearness of the reference pattern (reflected image) reflected on the surface of the object to be measured 34 based on the variation of the luminance value (brightness) distribution as described above. It is calculated by the relative value between the piece and the object. The surface property is better as the numerical value of the specularity is larger than the reference specularity of 1000 of the ideal surface.

(Evaluation of cleaning property of Example 1)
6A and 6B are diagrams showing a table of cleaning performance evaluation for the belts 14 and 24 of the first embodiment, and FIG. 7 is a table of cleaning performance evaluation for the belts 14 and 24 of the first embodiment. It is a figure which shows a graph.

  The conditions and evaluation results of the cleaning performance evaluation for the belts 14 and 24 of the first embodiment will be described.

  For the cleaning property evaluation, a printer C5800n manufactured by Oki Data Corporation was used. The linear velocity of the belts 14 and 24 is approximately 90 mm / sec. It is. A4 size was used as the paper 10a, and the YMCK horizontal line was printed at a density of 0.5% per paper. The printing conditions were 3P / J (page / Job: 1Jo has 3 pages of comparison data), that is, an operation of printing 3 sheets and pausing for 7 seconds.

  The Young's modulus was measured according to JISK7127. Specifically, a test piece was punched out with a type 2 punch, the thickness was measured with a micrometer, and the test speed was 50 mm / min. With a tensile tester manufactured by Orientec Co., Ltd. (Tensilon RTM-100). I went there.

  In FIG. 6A, the determination “O” indicates that there is no cleaning failure, and “x” indicates that there is a cleaning failure. From the results of FIG. 6A and FIG. 7, the Young's modulus of the belts 14 and 24 is 2.0-5. It is preferable that it is OGPa and the specularity is 60-130. Hereinafter, the reason will be described.

  The more uneven the belt surface is, the more likely it is that the contact substance will be attached, and the cleaning blade 18 will not be scraped off. This can be explained from the following.

  Generally, as printing proceeds, toner-derived or recording material such as paper 10a, mainly paper-derived material, adheres and accumulates on the belts 14 and 24. Once attached, the same substances are easily attracted to each other, and the attachment easily proceeds. This is because an increase in intermolecular force and compatibility are improved.

  On the other hand, the toner-derived or paper-derived substance mainly includes silica and calcium carbonate, and the substance is extremely hard and scratches and wears the belts 14 and 24 as contact members to generate scratches. The phenomenon has a Young's modulus of 2. The lower the OGpa and the lower the specularity than 60, the easier it is to generate and proceed.

Hereinafter, the reason for the effect will be described in detail.
First, if the specularity is lower than 60, it becomes difficult for the cleaning blade 18 to ensure a uniform linear pressure on the belts 14 and 24, and the toner is likely to slip through. This becomes easier to slip through as the sphericity of the toner increases. Further, as the particle size of the toner becomes smaller, it becomes easier to obtain high image quality. However, since the specific surface area also becomes larger, the adhesion force of the toner to the belts 14 and 24 per unit weight becomes larger, and the belts 14 and 24 become larger. The cleaning property tends to deteriorate. Furthermore, since the fluidity deteriorates as the particle size of the toner becomes smaller, more additives, mainly silica and wax, are required. However, the lower the specularity, the more the additives remain on the belt surface. It becomes easy to slip through. In some cases, slipping causes a local shearing force to be applied to the cleaning blade 18, causing local edge chipping (chipping), leading to destruction of the cleaning blade 18.

  Second, if the Young's modulus of the belts 14 and 24 is lower than 2.0 GPa, scratches are likely to occur on the belt surface. This is because the smaller the Young's modulus, the higher the hardness of the silica or calcium carbonate described above, the scratches are generated on the belt surface every time printing is performed, and the smaller Young's modulus advances the scratches. As a result, the cleaning blade 18 As a result, the adhesion between the belts 14 and 24 is deteriorated, and cleaning failure is likely to occur. This indicates that it is not sufficient that the mirror degree is high. That is, although the cleaning property is good in the initial state, the surface of the belt is scratched every time printing is performed, and the cleaning performance is deteriorated.

  Third, as the Young's modulus of the belts 14 and 24 is lower than 2.0 GPa and the specularity is lower than 60, the belt surface becomes uneven, which causes microslip between the belts 14 and 24 and the recording material printing surface. The wax and external additives in the vicinity of the surface of the printing surface are easily scraped off, which causes the belt to adhere to the belt surface. The adhering wax and the external additive stay in the cleaning blade edge part, and as a result, the cleaning blade 18 passes through and becomes a cause of poor cleaning. Further, when the residue on the belts 14 and 24 increases, the degree of adhesion and affinity between the cleaning blade 18 and the residues on the belts 14 and 24 increase, and a phenomenon of increasing the frictional force occurs. This increase in the frictional force increases the shear stress between the belt surface and the cleaning blade, and as a result, a fatal phenomenon such as local edge chipping or turning-up of the cleaning blade 18 may occur.

  In order to compensate for the above-described problems, a method has been proposed in which the linear pressure of the cleaning blade 18 is increased to reduce the cleaning failure. However, the burden on the cleaning blade 18 becomes extremely large, and the edge of the cleaning blade 18 may be damaged. , The turning phenomenon is likely to occur. In addition, increasing the linear pressure is not preferable because there is a side surface that accelerates the generation of scratches on the belt surface.

  On the other hand, when the specularity is higher than 130, the adhesion between the cleaning blade 18 and the belts 14 and 24 is increased, and the friction is remarkably increased. As a result, an increase in torque for driving the belts 14 and 24 and an enlargement of a power supply device for covering the same are accompanied. Further, the increase in the frictional force increases the shear stress between the belt surface and the cleaning blade, and as a result, a fatal phenomenon such as local edge chipping or turning-up of the cleaning blade 18 is likely to occur.

  On the other hand, the belts 14 and 24 having a Young's modulus higher than 5.0 Gpa are very difficult from a technical point of view, and it is extremely difficult to manufacture the belts 14 and 24. And time is needed. As a result, the yield decreases and the cost increases, and it is practically impossible to use the image forming apparatuses 1 and 1A as in the first embodiment.

(Effect of Example 1)
According to the first embodiment, the reliability of the belts 14 and 24 can be improved by setting the Young's modulus of the belts 14 and 24 to 2.0 to 5.0 GPa and the specularity 60 to 130.

(Configuration of Example 2)
FIG. 8 is an enlarged cross-sectional view showing a belt in Embodiment 2 of the present invention.

  In the image forming apparatus according to the second embodiment of the present invention, a belt 34 having a two-layer structure is used instead of the belts 14 and 24 in the image forming apparatuses 1 and 1A according to the first embodiment. The belt 34 having a two-layer structure is constituted by a surface layer 34-1 on the paper transport surface 34a side and a lower layer 34-2 on the back surface side. Other configurations are the same as those of the first embodiment.

  That is, in Example 2, various types of belts having different Young's moduli of each layer were appropriately adjusted, and cleaning performance was evaluated. The inner surface of the cylindrical mold is appropriately adjusted so that the belt specularity is 100, and is divided into two stages so that the surface layer is 10 ± 10% μm and the lower layer is 90 ± 10% μm by rotational molding. By casting, a belt 34 having a layer structure as shown in FIG. 8 is prepared and provided in the image forming apparatuses 1 and 1A shown in FIG.

(Operation of Example 2)
Evaluation methods, evaluation conditions, and determination methods were the same as in Example 1.

  From the table shown in FIG. 6B, by making the difference between the Young's modulus of the surface layer 34-1 and the Young's modulus of the lower layer 34-2 of the belt 34 within 40%, the entire belt is elastic while maintaining the cleaning property. Due to the deformation, it is possible to prevent a character or line image from being omitted. Further, due to the contribution of the elastic deformation, there is also a secondary effect of absorbing the load fluctuation at the time of driving the belt and reducing meandering.

  The void is caused by the fact that the pressing force at the time of transfer and fixing concentrates on the toner layer, the toner aggregates and the charge density increases, so that discharge occurs inside the toner layer and the toner polarity changes. is there. This is generally said to occur easily when a belt having a high Young's modulus is used, and is because the amount of elastic deformation with respect to the pressing force is small.

  If the difference in Young's modulus of the surface layer 34-1 in the belt 34 is more than 40%, it is excellent in preventing hollowing out, but the amount of deformation of repeated bending of the belt 34 is different, which causes delamination with use. Inferior in durability. Further, since the deformation of the belt 34 with respect to the stress at the time of driving increases, unevenness in the conveyance accuracy of the belt 34 occurs, resulting in a color misalignment image defect.

  If the surface layer thickness of the belt 34 is too large, the effect of preventing hollowing out cannot be expected. On the other hand, reducing the thickness of the surface layer is extremely difficult in terms of manufacturing and as a result causes an increase in cost. Thus, it is substantially impossible to use it in the image forming apparatuses 1 and 1A as in the second embodiment. Is possible. Further, the unevenness of the Young's modulus difference due to the thickness variation is relatively large, and image defects are likely to occur.

(Effect of Example 2)
According to the second embodiment, the Young's modulus of the surface layer 34-1 in the belt 34 is 2.0 to 5.0 GPa and the specularity is 60 to 130, and the difference in Young's modulus between the surface layer 34-1 and the lower layer 34-2. Is within 40%, it is possible to reduce image quality defects such as voids while maintaining the reliability of the cleaning performance of the belt 34.

(Modification)
The present invention is not limited to the above-described embodiments, and various usage forms and modifications are possible. For example, the following forms (a) and (b) are used as the usage form and the modified examples.

  (A) In the first and second embodiments, the image forming apparatuses 1 and 1A to which the endless belt body of the electrophotographic printer is applied have been described. However, the image forming apparatuses 1 and 1A may be changed to configurations other than those illustrated. . The present invention can also be applied to multifunction devices other than printers, facsimile machines, and the like.

  (B) In the first and second embodiments, the transport belt 14 in FIG. 1 and the belt (intermediate transfer belt body) 24 in FIG. 2 have been described as endless belt bodies, but the present invention can also be applied to other belts such as a fixing belt. is there.

DESCRIPTION OF SYMBOLS 1,1A Image forming apparatus 11 Photosensitive drum 14, 24, 34 Belt 18 Cleaning blade 30 Specular degree measuring device 34-1 Surface layer 34-2 Lower layer

Claims (7)

A plurality of image carriers;
A movable endless belt provided in contact with each image carrier;
A cleaning member that contacts the endless belt body and removes the residue on the endless belt body,
The endless belt body has a Young's modulus of 2.0-5. An image forming apparatus having an OGPa and a specularity of 60 to 130.   The image forming apparatus according to claim 1, wherein the endless belt body includes at least two layers, and a difference in Young's modulus between the surface layer and the lower layer is within 40%.   3. The image forming apparatus according to claim 1, wherein in the endless belt body, the relationship between the film thickness of the surface layer and the film thickness of the lower layer is such that surface layer> lower layer.   4. The image forming apparatus according to claim 1, wherein substantially nothing is interposed between a surface layer and a lower layer in the endless belt body.   5. The image forming apparatus according to claim 1, wherein the surface layer and the lower layer of the endless belt body are substantially the same material. 6. The image carrier is a photoreceptor,
The image forming apparatus according to claim 1, wherein the endless belt body is a conveyance belt that carries a recording material.   The image forming apparatus according to claim 1, wherein the endless belt is an intermediate transfer belt that directly carries a toner image visualized by development.

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