Image forming roller, charging roller, method for inspecting image forming roller, and method for inspecting charging roller

Abstract

A charging roller includes: a base; and a surface layer formed on an outer peripheral surface of the base, wherein a contact angle between the surface layer and toluene is 6° or more, and a contact angle between the surface layer and tetradecane is 22° or more.

Description

Technical Field

[0001] The present invention relates to image forming rollers, such as charging rollers, for electrophotographic image formation. Background Technology

[0002] In electrophotographic image forming apparatus, roller components such as charged rollers or developing rollers are arranged around photoconductors. For example, Patent Document 1 discloses a configuration in which the surface roughness of the conductive roller, such as the charged roller, is optimized. Patent Document 2 discloses a configuration in which the surface layer of the conductive roller is formed from two types of particles with different diameters.

[0003] Related technical documents

[0004] [Patent Documents]

[0005] [Patent Document 1]

[0006] Japanese Patent Application Publication No. 2019-191519

[0007] [Patent Document 2]

[0008] Japanese Patent Application Publication No. 2019-219498 Summary of the Invention

[0009] The problem to be solved by the present invention

[0010] Typically, electrophotographic image forming apparatuses are configured with a cleaning blade that removes toner adhering to the surface of roller members, such as charged rollers. However, in practice, toner components that cannot be completely removed by the cleaning blade may remain as a thin film (toner film formation) over a wide area of ​​the roller member's surface. In view of these circumstances, one aspect of the present invention aims to reduce the adhesion of toner components to the surface of the image forming roller.

[0011] Problem-solving methods

[0012] An image forming roller according to one embodiment of the present invention includes: a roller core; and a surface layer formed on the outer peripheral surface of the roller core, wherein the surface layer has a contact angle of 6° or greater with toluene and a contact angle of 22° or greater with tetradecane. In a more specific embodiment, the contact angle between the surface layer and toluene is 13° or greater, and the contact angle between the surface layer and tetradecane is 25° or greater. In another embodiment, the surface layer comprises a material comprising a silicon-based urethane resin.

[0013] A charging roller according to another embodiment of the invention is used in an electrophotographic device, and the charging roller includes: a body; and a surface layer formed on the outer peripheral surface of the body, wherein the surface layer has a contact angle of 6° or greater with toluene and a contact angle of 22° or greater with tetradecane. In a more specific embodiment, the contact angle between the surface layer and toluene is 13° or greater, and the contact angle between the surface layer and tetradecane is 25° or greater.

[0014] A method for inspecting an image forming roller according to an embodiment of the present invention is used to determine whether the image forming roller is in good condition. The image forming roller includes: a body; and a surface layer formed on the outer peripheral surface of the body. The method includes determining that the image forming roller is in good condition when the contact angle between the surface layer and toluene is 6° or greater and when the contact angle between the surface layer and tetradecane is 22° or greater. In a more specific embodiment, the image forming roller is determined to be in good condition when the contact angle between the surface layer and toluene is 13° or greater and when the contact angle between the surface layer and tetradecane is 25° or greater.

[0015] A method for inspecting a charging roller according to another embodiment of the present invention is used to determine whether the charging roller is in good condition. The charging roller includes: a substrate; and a surface layer formed on the outer peripheral surface of the substrate. The method includes determining that the charging roller is in good condition when the contact angle between the surface layer and toluene is 6° or greater and when the contact angle between the surface layer and tetradecane is 22° or greater. In a more specific embodiment, the charging roller is determined to be in good condition when the contact angle between the surface layer and toluene is 13° or greater and when the contact angle between the surface layer and tetradecane is 25° or greater.

[0016] Effects of the present invention

[0017] According to the present invention, the adhesion of toner components to the surface of the image forming roller can be reduced. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating the construction of an image forming apparatus according to an embodiment.

[0019] Figure 2 This is a cross-sectional view of the charging roller.

[0020] Figure 3 This is a cross-sectional view of the toner particles.

[0021] Figure 4 A flowchart for inspecting the charging roller is shown. Detailed Implementation

[0022] A: Image forming equipment

[0023] Figure 1 This is a diagram illustrating an image forming apparatus 100 according to a configuration of the present invention. The image forming apparatus is an electrophotographic printing device (e.g., a multifunction printer) that forms images on a sheet recording medium 200 such as printing paper. The image forming apparatus 100 includes a photoconductor drum 11, a charging roller 12, an exposure unit 13, a supply roller 14, a developing roller 15, a transfer roller 16, a pair of fixing rollers 17, and a cleaning blade 18. The charging roller 12, supply roller 14, developing roller 15, transfer roller 16, and fixing roller 17 are cylindrical roller components (image forming rollers) for forming electrophotographic images.

[0024] The charging roller 12 is a conductive roller that uniformly charges the surface of the photoconductor drum 11. The exposure device 13 forms an electrostatic latent image on the photoconductor drum 11 by exposing light to the surface of the drum. The supply roller 14 supplies charged toner to the surface of the developing roller 15. The developing roller 15 attaches the toner to the electrostatic latent image on the surface of the photoconductor drum 11. The transfer roller 16 transfers the toner attached to the surface of the photoconductor drum 11 to the recording medium 200. The fixing roller 17 fixes the transferred toner to the surface of the recording medium 200. The cleaning blade 18 removes any remaining toner from the surface of the photoconductor drum 11.

[0025] B: Charging roller 12

[0026] Figure 2 This is a cross-sectional view of the charging roller. (For example...) Figure 2 As shown, the charging roller 12 is a cylindrical roller member having a roller core 20 and a surface layer 30. The roller core 20 has a core member 21 and an elastic member 22. The core member 21 is a cylindrical member and constitutes the axis of rotation of the charging roller 12. For example, the core member 21 is formed of a metallic material such as SUS alloy or a resin material such as polyimide.

[0027] The elastic member 22 is a cylindrical portion formed on the outer peripheral surface of the core member 21. The elastic member 22 is formed of a conductive elastic material. Examples of materials for the elastic member 22 include various rubber materials, such as polyurethane rubber (PUR), epichlorohydrin rubber (ECO), nitrile rubber (NBR), styrene rubber (SBR), chloroprene rubber (CR), etc. Another layer, such as an adhesive layer, may be formed between the outer peripheral surface of the core member 21 and the inner peripheral surface of the elastic member 22 to improve the adhesion between them.

[0028] Surface layer 30 is a film formed on the outer peripheral surface of roller core 20. Specifically, surface layer 30 is formed over the entire area of ​​the outer peripheral surface of elastic member 22 with a substantially uniform thickness. The thickness of surface layer 30 can be freely chosen and, for example, is equal to or greater than 2 μm and equal to or less than 40 μm. The outer peripheral surface of surface layer 30 includes the surface of charging roller 12. As described below, surface layer 30 includes a substrate comprising a silicone-based urethane resin.

[0029] C: Manufacturing method of charging roller 12

[0030] A method for manufacturing the charging roller 12 will now be described. However, the method for manufacturing the charging roller 12 is not limited to the following example.

[0031] First, prepare the core 20 of the charging roller 12. For example, the elastic member 22 of the core 20 is formed from vulcanized epichlorohydrin rubber (ECO) with a hardness of 50° to 64°. The surface roughness (maximum height Rz conforming to JIS 82) of the outer peripheral surface of the elastic member 22 is 3 μm. Perform mechanical polishing on the core 20. Mechanical polishing includes dry polishing and wet polishing. Dry polishing is mechanical polishing using a grinding stone; while wet polishing is mechanical polishing using waterproof sandpaper. Wet polishing can be omitted.

[0032] A surface layer 30 is formed on the outer peripheral surface of the roller core 20. More specifically, a coating liquid of a predetermined composition is agitated using, for example, ultrasonic waves and then applied to the outer peripheral surface of the roller core 20. The coating method used for the coating liquid can be freely chosen. For example, spraying is suitable. The surface layer 30 is then fired using, for example, an electric furnace. The temperature of the electric furnace is set, for example, to 80°C or higher and 160°C or lower. The firing time is set to an appropriate time of not less than 20 minutes and not more than 60 minutes.

[0033] D: Characteristic Study of Surface Layer 30

[0034] In one configuration, the surface layer 30 of the charging roller 12 and the components contained in the toner (hereinafter referred to as "toner components") have a high affinity. Residual toner components remaining on the surface of the photoconductor drum 11 after using the cleaning blade 18 may remain as a thin film over a wide area of ​​the surface of the charging roller 12. When residual toner components remain on the surface of the charging roller 12 (toner film formation), errors may occur in the size of the nip where the photoconductor drum 11 and the charging roller 12 contact each other, or in the design value of the gap between the photoconductor drum 11 and the charging roller 12 around this nip. Therefore, the discharge efficiency from the charging roller 12 to the photoconductor drum 11 may decrease, resulting in a reduction in image quality. Therefore, it is important to reduce the affinity between the surface layer 30 of the charging roller 12 and the toner components. In view of these circumstances, the inventors of the present invention have considered reducing the wettability of the surface layer 30 of the charging roller 12 relative to the toner components.

[0035] Figure 3 This is a cross-sectional view of the toner particles in this embodiment. Figure 3 As shown, the toner particle 40 includes a spherical toner core 41 and a shell 42 formed on the surface of the toner core 41. The shell 42 completely or partially covers the surface of the toner core 41.

[0036] In addition to color materials such as pigments, the toner core 41 also contains additives such as waxes. The waxes, for example, are composed of materials containing aliphatic hydrocarbons as the main component. The shell layer 42, for example, is composed of materials containing styrene-acrylic resin as the main component. In view of these circumstances, the inventors of the present invention conceived of aliphatic hydrocarbons and styrene-acrylic resin as toner components capable of adhering to the surface layer 30 of the charging roller 12.

[0037] The wax in the toner core 41 is characterized by its high hydrocarbon content, which contains aliphatic hydrocarbons. On the other hand, the styrene-acrylic resin in the shell layer 42 is classified as an aromatic hydrocarbon. In order to reduce the wettability of the toner components relative to the surface layer 30 of the charging roller 12, the inventors considered the characteristics of the wax with a high hydrocarbon content and the characteristics of the shell layer 42 being an aromatic hydrocarbon, and selected a silicone urethane resin from several resin materials as the substrate of the surface layer 30 of the charging roller 12.

[0038] Carbonate urethane resin was also considered as a candidate material for the surface layer 30 of the charging roller 12. However, similar to waxes, carbonate urethane resin has a high hydrocarbon content and is classified as aromatic hydrocarbons, similar to shell 42. Therefore, carbonate urethane resin is considered to have a high affinity for the toner component. In contrast, silicone urethane resin has a low hydrocarbon content and does not contain aromatic hydrocarbons. Therefore, silicone urethane resin is considered suitable as a material for the surface layer 30 of the charging roller 12 to reduce the wettability of the toner component.

[0039] Similar to waxes (aliphatic hydrocarbons), tetradecane, with its high hydrocarbon content, is conceived as a solvent for waxes. Toluene, similarly classified as an aromatic hydrocarbon to shell 42 (styrene-acrylic resin), is conceived as a solvent for shell 42. Therefore, when tetradecane and toluene are conceived as toner solvents, the wettability (contact angle) between the toner solvent and the surface layer 30 of the charging roller 12 is considered.

[0040] Table 1 below is a graph showing the results of evaluating the contact angle between surface layer 30 and tetradecane, the contact angle between surface layer 30 and toluene, and the presence of toner film in several samples (Example 1, Example 2 and Comparative Example) under different conditions of surface layer 30 of charging roller 12.

[0041] Table 1

[0042]

[0043] The contact angles (°) in Table 1 are indicators of the wettability of the solvent to the surface layer 30 of the charging roller 12. For example, each contact angle in Table 1 was measured by the contact angle droplet method to analyze the shape of the solvent droplets dropped onto the surface of the surface layer 30. Specifically, the contact angle was calculated by observing the droplets 10 seconds after 0.1 μL of solvent was dropped onto the surface of the surface layer 30.

[0044] Table 1 also includes evaluation results of the formation of a thin film of solvent (toner film) on the surface of the charging roller 12. Specifically, after printing the same image on a total of 10,000 sheets of printing paper using the image forming apparatus 100, a visual inspection of the formation of a toner film on the surface of the charging roller 12 is performed.

[0045] Examples 1 and 2 include samples where the surface layer 30 of the charging roller 12 is formed from a substrate containing a silicone urethane resin. On the other hand, the comparative example includes a sample where the surface layer 30 of the charging roller 12 is formed from a substrate containing a carbonate urethane resin. Table 2 is a graph showing the composition of the coating liquid used to form the surface layer 30. It will be understood from Table 2 that the compositions in Example 1 and Example 2 are different from each other.

[0046] Table 2

[0047]

[0048]

[0049] As can be clearly seen from Table 1, in the comparative example, the contact angle between surface layer 30 and toluene is 2°, and the contact angle between surface layer 30 and tetradecane is 17°. In the comparative example, the substrate of surface layer 30 of charging roller 12 comprises carbonate urethane resin. Due to the small contact angle (high wettability) as described above, toner film formation was observed.

[0050] On the other hand, as can be clearly seen from Table 1, in Example 1, the contact angle between surface layer 30 and toluene is 13°, and the contact angle between surface layer 30 and tetradecane is 25°. In Example 1, the substrate of surface layer 30 of charging roller 12 comprises a silicone-based urethane resin. In Example 1, no toner film formation was observed. In Example 2, the substrate of surface layer 30 comprises a silicone-based urethane resin, the contact angle between surface layer 30 and toluene is 6°, and the contact angle between surface layer 30 and tetradecane is 22°. In Example 2, no toner film formation was observed either.

[0051] From the above results, it will be understood that, from the viewpoint of preventing toner film formation on the surface of the charging roller 12, a configuration in which the contact angle between the surface of the charging roller 12 and toluene is 6° or greater and the contact angle between the surface of the charging roller 12 and tetradecane is 22° or greater (Example 2) is suitable. Even more suitable is a configuration in which the contact angle between the surface of the charging roller 12 and toluene is 13° or greater and the contact angle between the surface of the charging roller 12 and tetradecane is 25° or greater (Example 1).

[0052] As described above, according to this embodiment, the affinity of the toner component for the surface layer 30 of the charging roller 12 is reduced, thereby preventing toner film formation on the surface layer 30. With the above configuration, the dimensional error of the gap between the photoconductor drum 11 and the charging roller 12 in contact with each other, or the error of the gap between the photoconductor drum 11 and the charging roller 12 around the gap, is reduced. Therefore, the reduction in discharge efficiency from the charging roller 12 to the photoconductor drum 11 is reduced, thus enabling the formation of a high-quality image by the image forming apparatus 100.

[0053] E: Inspection of charging roller 12

[0054] Figure 4 This is a flowchart illustrating the inspection process used to determine whether the charging roller 12 is in good condition. After manufacturing the charging roller 12 using the manufacturing method described above, the following steps are performed: Figure 4 The inspection process is shown. The manufacturing method of the charging roller 12 may include... Figure 4 The inspection process is shown.

[0055] First, the charging roller 12 to be inspected is prepared (process S1). After process S1, in process S2, it is determined whether both a first condition and a second condition are met. The first condition is that the contact angle between the surface layer 30 of the charging roller 12 and toluene is 6° or greater, and the second condition is that the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 22° or greater. When both the first and second conditions are met (S2: Yes), the charging roller 12 is determined to be in good condition. On the other hand, when at least one of the first or second conditions is not met (S2: No), the charging roller 12 is determined to be in bad condition.

[0056] As described above, during the inspection process, the charging roller 12 is determined to be in good condition when the contact angle between the surface layer 30 of the charging roller 12 and toluene is 6° or greater, and when the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 22° or greater. As described above, when the above conditions are met, toner film formation on the surface layer 30 of the charging roller 12 is prevented. Therefore, a charging roller 12 capable of maintaining a high level of image quality formed by the image forming apparatus 100 can be provided.

[0057] In the above description, examples are given of a first condition where the contact angle between the surface layer 30 of the charging roller 12 and toluene is 6° or greater, and a second condition where the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 22° or greater. A configuration is also assumed where, in the first condition, the contact angle between the surface layer 30 of the charging roller 12 and toluene is 13° or greater, and where, in the second condition, the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 25° or greater. In other words, when the contact angle between the surface layer 30 of the charging roller 12 and toluene is 13° or greater and the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 25° or greater, it can be determined that the charging roller 12 is in good condition.

[0058] F: Modify

[0059] Examples of modifications to the above embodiments are illustrated below. Two or more forms freely chosen from the following examples may be appropriately combined, provided they do not contradict each other.

[0060] (1) The material of the surface layer 30 of the charging roller 12 is not limited to urethane resin. In other words, if the contact angle between the surface layer 30 of the charging roller 12 and toluene is 6° or greater and the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 22° or greater, or more preferably, the contact angle between the surface layer 30 of the charging roller 12 and toluene is 13° or greater and the contact angle between the surface layer 30 of the charging roller 12 and tetradecane is 25° or greater, then any material can be used to form the surface layer 30.

[0061] (2) In the above embodiments, an example of a construction in which the roller core 20 includes a core member 21 and an elastic member 22 has been given. However, the roller core 20 is not limited to the above example. For example, the roller core 20 may include a single cylindrical element. Thus, in this invention, the distinction between the core member 21 and the elastic member 22 is not necessary. Another layer, such as an adhesive layer to improve the adhesion of the surface layer 30, may be formed on the outermost layer of the roller core 20. In other words, another layer may be inserted between the elastic member 22 and the surface layer 30.

[0062] (3) In the above embodiments, examples of applying the present invention to the construction of the charging roller 12 have been given. However, the scope of application of the present invention is not limited to the charging roller 12. For example, the present invention can be applied to any roller component (image forming roller) used for electrophotographic image formation. More specifically, in addition to the charging roller 12 described in the above embodiments, the present invention can be similarly applied to... Figure 1 The various components shown in the figure (supply roller 14, developing roller 15, transfer roller 16 and fixing roller 17).

[0063] In the above embodiments, the inspection process of the charging roller 12 is given. Figure 4 Examples are provided. However, the same inspection process can be applied to any image forming roller other than charging roller 12. In other words, for example, if the contact angle between the surface layer of the image forming roller and toluene is 6° or greater, and the contact angle between the surface layer of the image forming roller and tetradecane is 22° or greater, then the image forming roller is determined to be in good condition. When the contact angle between the surface layer of the image forming roller and toluene is 13° or greater, and when the contact angle between the surface layer of the image forming roller and tetradecane is 25° or greater, the image forming roller can be determined to be in good condition.

[0064] Description of reference numerals in the attached figures

[0065] 100...Image forming apparatus, 200...Recording medium, 11...Optical guide drum, 12...Charging roller, 13...Exposure device, 14...Supply roller, 15...Developing roller, 16...Transfer roller, 17...Fixing roller, 18...Cleaning blade, 20...Roller core, 21...Core component, 22...Elastic component, 30...Surface layer, 40...Toner particles, 41...Toner core, 42...Shell layer.

Claims

1. An image forming roller, comprising: Roller core; as well as A surface layer is formed on the outer peripheral surface of the roller core, wherein, The contact angle between the surface layer and toluene is 6° or greater, and The contact angle between the surface layer and tetradecane is 22° or greater. The contact angle between the surface layer and toluene was calculated by observing the droplet 10 seconds after 0.1 μL of toluene was dropped onto the surface of the surface layer. The contact angle between the surface layer and tetradecane was calculated by observing the droplet 10 seconds after 0.1 μL of tetradecane was dropped onto the surface of the surface layer.

2. The image forming roller according to claim 1, wherein, The contact angle between the surface layer and toluene is 13° or greater, and The contact angle between the surface layer and tetradecane is 25° or greater.

3. The image forming roller according to claim 1 or 2, wherein, The surface layer includes a substrate comprising a silicone-based urethane resin.

4. A charging roller for an electrophotographic device, comprising: main body; as well as A surface layer is formed on the outer peripheral surface of the body, wherein, The contact angle between the surface layer and toluene is 6° or greater, and The contact angle between the surface layer and tetradecane is 22° or greater. The contact angle between the surface layer and toluene was calculated by observing the droplet 10 seconds after 0.1 μL of toluene was dropped onto the surface of the surface layer. The contact angle between the surface layer and tetradecane was calculated by observing the droplet 10 seconds after 0.1 μL of tetradecane was dropped onto the surface of the surface layer.

5. The charging roller according to claim 4, wherein, The contact angle between the surface layer and toluene is 13° or greater, and The contact angle between the surface layer and tetradecane is 25° or greater.

6. A method for inspecting an image forming roller, the image forming roller comprising a body and a surface layer formed on an outer peripheral surface of the body, the method being used to determine whether the image forming roller is in good condition. The method includes: The image forming roller is considered to be in good condition when the contact angle between the surface layer and toluene is 6° or greater, and when the contact angle between the surface layer and tetradecane is 22° or greater. The contact angle between the surface layer and toluene was calculated by observing the droplet 10 seconds after 0.1 μL of toluene was dropped onto the surface of the surface layer. The contact angle between the surface layer and tetradecane was calculated by observing the droplet 10 seconds after 0.1 μL of tetradecane was dropped onto the surface of the surface layer.

7. The method for inspecting an image forming roller according to claim 6, wherein, The image forming roller is determined to be in good condition when the contact angle between the surface layer and toluene is 13° or greater and when the contact angle between the surface layer and tetradecane is 25° or greater.

8. A method for inspecting a charging roller, the charging roller comprising a substrate and a surface layer formed on the outer peripheral surface of the substrate, the method being used to determine whether the charging roller is in good condition. The method includes: The charging roller is considered to be in good condition when the contact angle between the surface layer and toluene is 6° or greater, and when the contact angle between the surface layer and tetradecane is 22° or greater. The contact angle between the surface layer and toluene was calculated by observing the droplet 10 seconds after 0.1 μL of toluene was dropped onto the surface of the surface layer. The contact angle between the surface layer and tetradecane was calculated by observing the droplet 10 seconds after 0.1 μL of tetradecane was dropped onto the surface of the surface layer.

9. The method for inspecting a charging roller according to claim 8, wherein, The charging roller is determined to be in good condition when the contact angle between the surface layer and toluene is 13° or greater and when the contact angle between the surface layer and tetradecane is 25° or greater.

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