Developing roller

Abstract

The developing roller includes a metal core material, an elastic layer around the core material, and a surface layer around the elastic layer. In this developing roller, the value X is 65.6 N / mm 3 or more, and the value Y is 229 μm or more. The value X is calculated according to X = P1 / (D1·A) to P2 / (D2·A). P1 is the load required to press a metal probe in the shape of a frustum of a cone with a tip diameter of 40 μm against the developing roller to cause the developing roller to displace 100 μm deeply in the radial direction. D1 is the displacement of the developing roller caused by the load P1. A is the tip area of the probe. P2 is the load required to press the probe against a material roller without a surface layer to cause the material roller to displace 100 μm deeply in the radial direction. D2 is the displacement of the material roller caused by the load P2. The value Y is the displacement of the developing roller when the probe is pressed against the developing roller to pierce the surface layer.

Description

Technical Field

[0001] The present invention relates to a developing roller in an image forming apparatus using an electrophotographic method. Background Art

[0002] In an image forming apparatus using an electrophotographic method, a developing device for supplying a developer, i.e., toner, to a photosensitive drum is provided. The developing device includes a toner container and a developing roller. The toner attached to the outer peripheral surface of the developing roller is supplied to the photosensitive drum as the developing roller rotates. An electrostatic latent image is formed on the photosensitive drum, and toner particles are transferred from the developing roller to the electrostatic latent image, thereby generating a toner image (Patent Document 1).

[0003] The developing device also has a member called a restricting blade or a doctor blade. The doctor blade restricts the amount of toner particles attached to the developing roller and transported from the toner container. The doctor blade contacts the developing roller with a certain degree of force.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-372855 Summary of the Invention

[0007] The developing roller contacts the photosensitive drum with a certain degree of force. As described above, the developing roller is also subject to a force from the doctor blade. It is necessary to improve the durability of the developing roller used in such a force-applied environment.

[0008] Therefore, the present invention provides a developing roller having high durability.

[0009] A developing roller according to one aspect of the present invention is used in an image forming apparatus using an electrophotographic method. The developing roller includes a metal core material, a rubber elastic layer disposed around the core material, and a surface layer disposed around the elastic layer. In this developing roller, the value X is 65.6 N / mm 3 Hereinabove, the value Y is 229 μm or more. Here, the value X is calculated according to the following formula:

[0010] X = P1 / (D1·A) - P2 / (D2·A)

[0011] P1 is the load required to press a frustum-shaped metal probe with a front-end diameter of 40 μm against the developing roller to cause the developing roller to displace 100 μm deeper in the radial direction. D1 is the displacement of the developing roller caused by the probe under the load P1. A is the front-end area of the probe. P2 is the load required to press the probe against a material roller having the core material and the elastic layer but not having the surface layer to cause the material roller to displace 100 μm deeper in the radial direction. D2 is the displacement of the material roller caused by the probe under the load P2. The value Y is the displacement of the developing roller caused by the probe when the probe is pressed against the developing roller to displace the probe in the radial direction of the developing roller and pierce the surface layer.

[0012] The value X is an index of the compressive strength of the surface layer. In this method, the value X is 65.6 N / mm 3 or more, and the wear of the surface layer is small. The value Y is an index of the compressive toughness of the surface layer. In this method, by making the value Y 229 μm or more, the surface layer is not easily peeled off from the elastic layer. Therefore, when the value X is 65.6 N / mm 3 or more and the value Y is 229 μm or more, the developing roller has high durability and a long life.

[0013] The developing roller according to one aspect of the present invention is used in an image forming apparatus using an electrophotographic method. The developing roller includes a metal core material, a rubber elastic layer disposed around the core material, and a surface layer disposed around the elastic layer. In this developing roller, the value Z is 6.56 N / mm 2 or more, and the value Y is 229 μm or more. Here, the value Z is calculated according to the following formula:

[0014] Z = (P1 - P2) / A

[0015] P1 is the load required to press a frustum-shaped metal probe with a front-end diameter of 40 μm against the developing roller to cause the developing roller to displace 100 μm deeper in the radial direction. P2 is the load required to press the probe against a material roller having the core material and the elastic layer but not having the surface layer to cause the material roller to displace 100 μm deeper in the radial direction. A is the front-end area of the probe. The value Y is the displacement of the developing roller caused by the probe when the probe is pressed against the developing roller to displace the probe in the radial direction of the developing roller and pierce the surface layer.

[0016] The value Z is an index of the compressive strength of the surface layer. In this method, the value Z is 6.56 N / mm 2 or more, and the wear of the surface layer is small. The value Y is an index of the compressive toughness of the surface layer. In this method, by making the value Y 229 μm or more, the surface layer is not easily peeled off from the elastic layer. Therefore, when the value Z is 6.56 N / mm2 When it is above the above value and the value Y is 229 μm or more, the developing roller has high durability and a long life. Description of the Drawings

[0017] Figure 1 It is a diagram showing the usage state of the developing roller according to the embodiment of the present invention.

[0018] Figure 2 It is a cross-sectional view of the developing roller according to the embodiment.

[0019] Figure 3 It is a front view of the developing roller in the compression test.

[0020] Figure 4 An enlarged cross-sectional view of the developing roller in the compression test.

[0021] Figure 5 An enlarged cross-sectional view of the developing roller in the compression test.

[0022] Figure 6 It is a load-displacement graph obtained from the compression test.

[0023] Figure 7 It is a plan view of the developing roller showing the wear marks that may occur on the surface of the developing roller.

[0024] Figure 8 It is a plan view of the developing roller showing the peeling of the surface layer of the developing roller.

[0025] Figure 9 It is a cross-sectional view of the developing roller showing the peeling of the surface layer of the developing roller.

[0026] Figure 10 It is a table showing the measurement results of the surface layer indexes of multiple samples of the developing roller and the results of the durability test of these samples. Detailed Embodiments

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The scale of the drawings is not necessarily accurate, and sometimes some features are exaggerated or omitted.

[0028] As Figure 1 shown, the image forming apparatus using the electrophotographic method has a photosensitive drum 10 and a developing device 11. The photosensitive drum 10 rotates in the arrow direction. The developing device 11 supplies toner particles 12 as a developer to the photosensitive drum 10. An electrostatic latent image is formed on the surface of the photosensitive drum 10 by a latent image forming device (not shown in the figure), and the toner particles 12 are transferred from the developing device 11 to the electrostatic latent image, thereby generating a toner image based on the toner particles 12 on the outer peripheral surface of the photosensitive drum 10.

[0029] The developing device 11 includes: a toner container 14 that stores a collection 13 of toner particles; an elastic roller 15 that is entirely disposed within the toner container 14; a developing roller 20, a part of which is disposed within the toner container 14; and a blade 16 (limiting blade) that is supported by the toner container 14. The elastic roller 15 is pressed against the developing roller 20, and the developing roller 20 is pressed against the photosensitive drum 10. The elastic roller 15 and the developing roller 20 rotate in the directions indicated by the arrows, and a substantially constant amount of toner particles within the toner container 14 adhere to the developing roller 20. Accordingly, a thin layer of toner particles is formed on the outer peripheral surface of the developing roller 20. As the developing roller 20 rotates, the toner particles adhering to the developing roller 20 are transported toward the photosensitive drum 10. The blade 16 disposed at the toner particle outlet of the toner container 14 is pressed against the outer peripheral surface of the developing roller 20, and adjusts the amount of toner particles that adhere to the developing roller 20 and are transported from the toner container 14. Accordingly, the developing roller 20 contacts each of the photosensitive drum 10, the elastic roller 15, and the blade 16 with a certain degree of force.

[0030] Although not shown in the figures, in the developing device 11, components for stirring the collection 13 of toner particles within the toner container 14, a screw for transporting the toner particles within the toner container 14, etc. may also be provided.

[0031] As Figure 2 shown, the developing roller 20 includes a cylindrical core material 21 made of metal, an elastic layer 22 made of rubber with a uniform thickness disposed around the core material 21, and a surface layer 23 made of rubber with a uniform thickness disposed around the elastic layer 22. The diameter of the core material 21 is several millimeters, the thickness of the elastic layer 22 is 1 - 3 mm, and the thickness of the surface layer 23 is several micrometers to several tens of micrometers.

[0032] Both the elastic layer 22 and the surface layer 23 are formed of rubber. In the embodiment, both the elastic layer 22 and the surface layer 23 are formed of silicone rubber. However, the elastic layer 22 is provided to ensure the elasticity of the developing roller 20, and the surface layer 23 is provided to improve the wear resistance of the surface of the developing roller 20. Accordingly, the composition of the material of the surface layer 23 is different from the composition of the material of the elastic layer 22.

[0033] In the embodiment, the surface layer 23 is manufactured as follows.

[0034] First, in the first stage, the following materials are mixed:

[0035] Polyurethane-modified hexamethylene diisocyanate with a solid content of 80 wt% (grade "E402 - 80B" of "DURANATE" (trade name) manufactured by Asahi Kasei Corporation (Tokyo, Japan)), 16.5 wt%;

[0036] Reactive silicone oil ("X-22-160AS" (trade name), manufactured by Shin-Etsu Chemical Co., Ltd. (Tokyo, Japan)), 36.7% by weight;

[0037] Butyl acetate as a diluting solvent, 46.8% by weight.

[0038] Then, by allowing the mixture to stand at 120 °C for 3 hours, the reaction of the components was promoted to form a prepolymer.

[0039] Next, in the second stage, the following materials were mixed:

[0040] The prepolymer formed in the first stage;

[0041] As an adhesive, isocyanate with a solid content of 75% by weight ("Desmodur L75" (trade name), manufactured by Sumika Covestro Urethane Co., Ltd. (Hyogo, Japan));

[0042] Carbon dispersion with a solid content of 20 - 30% by weight ("MHI-BK" (trade name), manufactured by Mikuni Shikiso Co., Ltd. (Hyogo, Japan));

[0043] Butyl acetate was used as a diluting solvent, 44.7% by weight.

[0044] Furthermore, in the third stage, 2.6% by weight of silicone rubber particles were added to the mixture obtained in the second stage to obtain a coating liquid. The silicone rubber particles are "EP-2720" (trade name) manufactured by DuPont Toray Specialty Materials Co., Ltd. (Tokyo, Japan). The hardness of the silicone rubber particles measured using a hardness tester (Type A according to the standards of "JIS K 6253" and "ISO 7619") is 70 degrees. The average particle diameter of the silicone rubber particles is 2 μm.

[0045] In the fourth stage, the coating liquid was coated around the elastic layer 22 and dried to form the surface layer 23.

[0046] The applicant adjusted the material composition of the surface layer 23 and manufactured multiple samples with different properties of the surface layer 23. Specifically, the ratios of the prepolymer, isocyanate, and carbon dispersion in the second stage were changed.

[0047] In each sample, the diameter of the core material 21 is 6 mm, the thickness of the elastic layer 22 is 1.5 mm, and the thickness of the surface layer 23 is 10 μm ± 2 μm. However, in one sample (Sample 20), the thickness of the surface layer 23 is 20 μm.

[0048] The applicant measured the indices X and Y representing the durability of the surface layer 23 of these samples. In addition, the applicant actually installed these samples in a printer and tested the durability of the samples.

[0049] Figures 3 to 5 The situation of a compression test for measuring the index representing the durability of the surface layer 23 of the sample is shown. In the compression test, a compression testing machine 30 was used. The compression testing machine 30 has a cylindrical movable shaft 31 and a probe 32 formed at the front end of the movable shaft 31. The movable shaft 31 and the probe 32 are made of metal. The compression testing machine 30 can measure the displacement of the probe 32 and the load applied to the probe 32 while automatically pressing down the movable shaft 31.

[0050] As the compression testing machine 30, “LNP nano touch” manufactured by Ludwig Nano Prazision GmbH (Nordheim, Germany) was used. The probe 32 has a frustum - of - cone shape with a smaller diameter as it is farther from the movable shaft 31, and the front - end diameter d of the probe 32 is 40 μm. The apex angle θ of the frustum of the cone is 30 degrees.

[0051] As Figure 3 shown, the front end of the probe 32 is brought into contact with the center in the longitudinal direction of the developing roller 20, the movable shaft 31 is driven, and the probe 32 is pressed into the normal direction (radial direction) of the outer peripheral surface of the developing roller 20. By selecting the V - control mode in “LNP nano touch”, the pressing - in speed is approximately constant, about 50 μm / s. The maximum pressing - in depth is set to be slightly smaller than the thickness of the elastic layer 22, which is 1.5 mm.

[0052] During the pressing - in process, the displacement of the probe 32 and the load applied to the probe 32 are recorded. In “LNP nanotouch”, the resolution of the displacement (the reading scale of the displacement) is 10 nm. Based on the recording results, value X1, value Y, and value Z1 are obtained.

[0053] Value X1 and value Z1 are calculated by the following formulas:

[0054] X1 = P1 / (D1·A)

[0055] Z1 = P1 / A

[0056] Here, P1 is the load required to press the metal probe 32 with a frustum - of - cone shape having a front - end diameter d of 40 μm against the developing roller 20 and displace the developing roller 20 deeper in the radial direction by 100 μm. That is, P1 is Figure 4 the load applied to the probe 32 in the state of Figure 4The displacement of the probe 32 in the state of , thus approximately 100 μm, is the reading value when the reading value of the displacement of the probe 32 in the pressing process first exceeds 100 μm. More precisely, P1 is also the load when the reading value of the displacement of the probe 32 in the pressing process first exceeds 100 μm.

[0057] A is the front-end area of the probe 32, which is calculated by the following formula.

[0058] A = π·(d / 2) 2

[0059] The value Y is the displacement of the developing roller 20 brought about by the probe 32 when the probe 32 presses against the developing roller 20 and is displaced in the radial direction of the developing roller 20 to pierce the surface layer 23, as Figure 5 shown. Figure 6 is the load-displacement graph obtained from the compression test. The value Y is Figure 6 the displacement amount at the time of a sharp load drop as shown. The value Y is a value obtained from the compression test and corresponds to the elongation at break in the tensile test. Among them, the elongation at break is the strain obtained by dividing the amount of deformation by the original total length, that is, a dimensionless quantity, and the value Y is the amount of deformation, expressed in μm. The value Y is an index of the compressive toughness of the surface layer 23.

[0060] On the other hand, the value X1 can be regarded as an index of the compressive strength (briefly, hardness) of the developing roller 20. However, X1 is affected not only by the hardness of the surface layer 23 but also by the hardness of the elastic layer 22. Therefore, a material roller having a core material 21 and an elastic layer 22 and not having a surface layer 23 (not shown in the figure) is prepared, and for the material roller, the values X2 and Z2 are calculated according to the following formula.

[0061] X2 = P2 / (D2·A)

[0062] Z2 = P2 / A

[0063] Here, P2 is the load required to press the probe 32 against the material roller and displace the material roller deeper in the radial direction by 100 μm. D2 is the displacement of the material roller brought about by the probe 32 under the load P2. D2 is approximately 100 μm, which is the reading value when the reading value of the displacement of the probe 32 in the pressing process first exceeds 100 μm. More precisely, P2 is also the load when the reading value of the displacement of the probe 32 in the pressing process first exceeds 100 μm.

[0064] Then, the values X and Z with the influence of the hardness of the elastic layer 22 offset are calculated according to the following formula.

[0065] X = X1 - X2

[0066] Z = Z1 - Z2

[0067] Therefore, the values X and Z can be calculated according to the following formulas.

[0068] X = P1 / (D1·A) - P2 / (D2·A)

[0069] Z = (P1 - P2) / A

[0070] The values X and Z can be regarded as indicators of the compressive strength (briefly, hardness) of the surface layer 23. Specifically, the value X is substantially equal to the value obtained by dividing the difference between the force required to radially displace the developing roller 20 by 100 μm by the probe 32 and the force required to radially displace the material roller by 100 μm by the probe 32 by the volume of the probe 32 of the piercing roller. The value Z is equal to the value obtained by dividing the difference between the above forces by the front area of the probe 32.

[0071] In the durability test, each sample was installed in a color printer "HL-L8360CDW" (trade name) manufactured by Brother Industries, Ltd. (Aichi, Japan). Then, printing was performed using the printer. After each sample was printed on 6000 A4 sheets, it was visually judged whether the surface layer 23 had wear marks and whether the surface layer 23 had peeled off. During printing, a uniform image with a concentration of 1% was formed on the entire surface of each sheet.

[0072] As Figure 7 shown in the plan view of the developing roller 20, excessive wear of the surface layer 23 is manifested as linear wear marks 40 on the surface layer 23. The wear marks 40 extend in the circumferential direction of the developing roller 20. This is because a part of the blade 16 contacts the outer peripheral surface of the rotating developing roller 20, causing wear of the surface layer 23.

[0073] As Figure 8 (plan view) and Figure 9 (cross-sectional view) shown, peeling of the surface layer 23 results in the exposure of the elastic layer 22.

[0074] Figure 10 The values X, Y, Z of multiple samples and the results of the durability test of these samples are shown. In Samples 1 to 12 and 20, neither wear marks nor peeling occurred on the surface layer 23. In Samples 13 to 19, wear marks or peeling occurred on the surface layer 23.

[0075] From Figure 10 the results shown, it can be seen that preferably the value of X is 65.6 N / mm 3 or more, and the value of Y is 229 μm or more. In addition, it can be seen that preferably the value of Z is 6.56 N / mm 2 or more, and the value of Y is 229 μm or more. The values X and Z are a kind of indicators of the compressive strength of the surface layer 23. The value of X is 65.6 N / mm 3When it is above, the wear of the surface layer 23 is less. The value of Z is 6.56 N / mm 2 When it is above, the wear of the surface layer 23 is less. In samples 13 to 15 with smaller values of X and Z, wear marks were generated on the surface layer 23.

[0076] The value of Y is an index of the compressive toughness of the surface layer 23. By making the value of Y 229 μm or more, the surface layer 23 is not easily peeled off from the elastic layer 22. In samples 16 to 19 with a smaller value of Y, peeling of the surface layer 23 occurred.

[0077] Therefore, the value of X is 65.6 N / mm 3 When it is above and the value of Y is 229 μm or more, the developing roller 20 has high durability and a long life. Similarly, when the value of Z is 6.56 N / mm 2 When it is above and the value of Y is 229 μm or more, the developing roller 20 has high durability and a long life.

[0078] The preferred upper limits of the values of X, Y, and Z are not clear, but for sample 12 with the value of X being 215.5 N / mm 3 and the value of Z being 21.55 N / mm 2 no wear marks or peeling occurred on the surface layer 23, and for sample 1 with the value of Y being 890 μm, no wear marks or peeling occurred on the surface layer 23. Therefore, the preferred range of the value of X includes at least 65.6 N / mm 3 to 215.5 N / mm 3 The preferred range of the value of Y includes at least the range of 229 μm to 890 μm. The preferred range of the value of Z includes at least 6.56 N / mm 2 to 21.55 N / mm 2 The range.

[0079] The thickness of the surface layer 23 of sample 20 is 20 μm, which is larger than the thickness of the surface layer 23 of other samples. The material composition of the surface layer 23 of sample 20 is the same as that of the surface layer 23 of sample 2. The difference between samples 2 and 20 lies only in the thickness of the surface layer 23. Samples 2 and 20 have substantially the same results. Therefore, even if the thickness of the surface layer 23 is different, it is preferred that the value of X is 65.6 N / mm 3 When it is above and the value of Y is 229 μm or more. Similarly, it is preferred that the value of Z is 6.56 N / mm 2 When it is above and the value of Y is 229 μm or more.

[0080] Above, the present invention has been illustrated with reference to the preferred embodiments of the present invention. However, those skilled in the art should understand that without departing from the scope of the invention described in the claims, formal and detailed changes can be made. Such changes, alterations, and modifications should be included within the scope of the present invention.

[0081] Symbol Explanation

[0082] 20 Developing Roller

[0083] 21 Core Material

[0084] 22 Elastic Layer

[0085] 23 Surface Layer

Claims

1. A developing roller used in an image forming apparatus employing an electrophotographic method, characterized in that, Comprising: A core made of metal; An elastic layer made of rubber, which is disposed around the core; And A surface layer, which is disposed around the elastic layer; Wherein, The value of X is 65.6 N / mm 3 Above, The value Y is 229 μm or more, Here, the value X is calculated by the following formula: X = P1 / (D1·A) - P2 / (D2·A) P1 is the load required to press a metal probe in the shape of a frustum of a cone with a front-end diameter of 40 μm against the developing roller to cause the developing roller to displace 100 μm deeper in the radial direction. D1 is the displacement of the developing roller caused by the probe under the load P1. A is the front-end area of the probe. P2 is the load required to press the probe against a material roller having the core and the elastic layer but not having the surface layer to cause the material roller to displace 100 μm deeper in the radial direction. D2 is the displacement of the material roller caused by the probe under the load P2. The value Y is the displacement of the developing roller caused by the probe when the probe is pressed against the developing roller to displace the probe in the radial direction of the developing roller and pierce the surface layer. The value of X is 215.5 N / mm 3 Next, The value Y is 890 μm or less.

2. A developing roller used in an image forming apparatus employing an electrophotographic method, characterized in that, Comprising: A core made of metal; An elastic layer made of rubber, which is disposed around the core; And A surface layer, which is disposed around the elastic layer; Wherein, The value of Z is 6.56 N / mm 2 above The value Y is 229 μm or more, Here, the value Z is calculated by the following formula: Z = (P1 - P2) / A P1 is the load required to press a metal probe in the shape of a frustum of a cone with a front-end diameter of 40 μm against the developing roller to cause the developing roller to displace 100 μm deeper in the radial direction. P2 is the load required to press the probe against a material roller having the core and the elastic layer but not having the surface layer to cause the material roller to displace 100 μm deeper in the radial direction. A is the front-end area of the probe. The value Y is the displacement of the developing roller caused by the probe when the probe is pressed against the developing roller to displace the probe in the radial direction of the developing roller and pierce the surface layer. The value of Z is 21.55 N / mm 2 Next, The value Y is 890 μm or less.

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