Cleaning blade

Abstract

The cleaning blade has a front end portion that contacts the photosensitive member and is formed of polyurethane having a tan δ of 0.35 or more at 23°C, a loss modulus of 5.59 MPa or more at 23°C, and a rebound modulus of 21% or less at 23°C.

Description

Technical Field

[0001] The present invention relates to a cleaning blade used in an image forming apparatus. Background Art

[0002] In an image forming apparatus utilizing electrophotography (eg, a copier or printer), a toner image formed on the surface of a photosensitive drum is transferred to a moving sheet. Toner remaining on the surface of the photosensitive drum is removed by a cleaning blade.

[0003] It is desirable that the cleaning blade have appropriate elasticity to cause moderate deformation and have appropriate wear resistance to ensure long life. Generally speaking, the cleaning blade is made of a thermosetting polyurethane resin or a thermosetting polyurethane elastomer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2017 / 111061 Summary of the Invention

[0007] In image forming devices, a photosensitive drum and its surrounding components are often provided as a single unit. In this case, the life of the unit is determined by the component with the shortest life. The cleaning blade is a component with a short life, and it is desired to further extend its life.

[0008] The present invention provides a cleaning blade having a longer life.

[0009] One embodiment of the present invention provides a cleaning blade. The cleaning blade has a tip portion that contacts a photosensitive member. The tip portion is formed from a polyurethane having a tan δ of 0.35 or greater at 23°C, a loss modulus of 5.59 MPa or greater at 23°C, and a rebound modulus of 21% or less at 23°C.

[0010] In this aspect, the wear resistance of the front end portion of the cleaning blade can be improved, thereby extending the life of the cleaning blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A diagram showing a cleaning blade in use according to an embodiment of the present invention.

[0012] Figure 2 This is a table showing the characteristics and test results of samples produced to investigate the preferred range of the present invention.

[0013] Figure 3 This is a diagram showing the form of a wear test of a cleaning blade for examining the preferred range of the present invention.

[0014] Figure 4It is a diagram showing a form of measuring the wear of the cleaning blade. DETAILED DESCRIPTION

[0015] Below, with reference to the attached Figure 1 The embodiments of the present invention will be described below. The drawings are not necessarily accurate to scale, and some features may be exaggerated or omitted.

[0016] like Figure 1 As shown, the cleaning blade 10 of the embodiment is disposed near a photosensitive drum (photosensitive member) 1 of an image forming apparatus utilizing electrophotography. As is well known, a transfer device 2 is disposed near the photosensitive drum 1. As a paper sheet S, conveyed by a conveying device (not shown), passes through the nip between the photosensitive drum 1 and the transfer device 2, the toner image formed on the photosensitive drum 1 is transferred to the sheet S.

[0017] Toner remaining on the surface of the photosensitive drum 1 without being transferred to the sheet S is removed by the cleaning blade 10. The image forming apparatus includes a plurality of other components as is well known to those skilled in the art, but descriptions of the other components are omitted.

[0018] The cleaning blade 10 includes a bracket (supporting member) 11 made of hard plastic or metal and an elastic member 12 fixed to the bracket 11. Both the bracket 11 and the elastic member 12 extend parallel to the axial direction of the photosensitive drum 1. The bracket 11 is fixed to a predetermined position of the image forming apparatus and supports the elastic member 12. The bracket 11 has high rigidity, while the elastic member 12 has moderate elasticity. The front end portion 13 of the elastic member 12 contacts the outer peripheral surface of the photosensitive drum 1. The front end portion 13 in contact with the photosensitive drum 1 scrapes off the residual colorant on the photosensitive drum 1. The elastic member 12, especially the front end portion 13, receives a reaction force from the photosensitive drum 1, thereby causing elastic deformation.

[0019] It is desirable to improve the wear resistance of the front end portion 13 of the cleaning blade 10 and extend the life of the cleaning blade 10. The applicant prepared a plurality of samples of the elastic member 12, measured the characteristics of these samples, and conducted a wear test.

[0020] Figure 2 The materials and properties of each sample are shown.

[0021] Each sample of the elastic member 12 manufactured is polyurethane. The polyol used is an ester polyol (molecular weight 2000). The isocyanate used is 4,4'-diphenylmethane diisocyanate (MDI), which is "MILLIONATE MT" manufactured by Tosoh Corporation (Tokyo, Japan). Trimethylolethane (TME) and 1,1,1-trimethylolpropane (TMP) used as cross-linking agents are both manufactured by Korei Chemical Industry Co., Ltd. (Tokyo, Japan). 1,3-Propanediol (1,3PD) and 1,4-Butanediol (1,4BD) used as chain extenders are both manufactured by Mitsubishi Chemical Corporation (Tokyo, Japan).

[0022] The rebound modulus, loss elastic modulus, and storage elastic modulus were measured at an air temperature of 23° C. and a humidity of 55% RH.

[0023] The rebound modulus was measured using a Lubbock-type rebound measuring device (“VR-6512” manufactured by Ueshima Manufacturing Co., Ltd. (Tokyo, Japan)) in accordance with JIS K6255 (2013).

[0024] The loss modulus and storage modulus were measured on a test piece made for each sample. The test piece had a thickness of 2 mm, a width of 3 mm, and a marking interval of 20 mm.

[0025] These test pieces were deformed with an amplitude of 2 μm and a frequency of 10 Hz, and the phase difference between dynamic stress and dynamic strain was measured. The measurement machine was a "Rheogel-E4000HP" manufactured by UBM Co., Ltd. (Tokyo, Japan). Furthermore, the strain was applied to a known formula to calculate the loss modulus and storage modulus. The viscosity / elasticity ratio (tan δ) was obtained by dividing the loss modulus by the storage modulus.

[0026] The wear amount was measured using the following experiment. The wear amount was also measured at an air temperature of 23°C and a humidity of 55% RH. Figure 3 As shown, the sample of the elastic member 12 has a protruding length L of 9 mm protruding from the end of the bracket 11 and a thickness t of 2 mm. The length L is measured when the elastic member 12 is in a straight state.

[0027] like Figure 3 As shown, a 0.3 μm thick abrasive film 20 is wound around the outer circumference of a rotatable cylinder 19. Cylinder 19 is a glass cylinder coated with polycarbonate, and resembles photosensitive drum 1. Abrasive film 20 is "Abrasive Polishing Paper #15000A3-0.3SHT" available from 3M Japan Co., Ltd. (Tokyo, Japan). The reason for winding abrasive film 20 around cylinder 19 is to accelerate the wear of the front end portion 13 of elastic member 12 using an abrasive.

[0028] Next, the elastic member 12 of the cleaning blade 10 was brought into contact with the cylinder 19 on which the abrasive film 20 was wound, at a contact angle θ and a contact load of 0.18 N / cm. The contact angle θ was 20 degrees. The photosensitive drum 1 was then rotated at a peripheral speed of 460 mm / s and slid relative to the elastic member 12 by a distance of 1485 mm (the total length of five A4-size sheets).

[0029] After that, the wear amount of the front end portion 13 of the elastic member 12 was measured. In the wear amount measurement, a laser microscope "VK-X250" manufactured by Keyence Co., Ltd. (Osaka, Japan) was used to photograph the edge of the front end portion 13 using an objective lens with a magnification of 150 times, and the area of the worn portion 22 in the photographed image was calculated. Although the photographing direction was tilted with respect to the longitudinal direction of the elastic member 12 ( Figure 4 The arrow in the figure shows the shooting direction), but the area of the worn portion 22 perpendicular to the longitudinal direction of the elastic member 12 can be calculated by calculation correction. Three locations in the longitudinal direction of the elastic member are photographed. The average value of the areas obtained based on the three locations is recorded in Figure 2 .

[0030] According to the test results, the wear amount of samples 1 to 3 was very small, while that of samples 4 to 8 was large.

[0031] Therefore, at least the tip portion 13 of the elastic member 12 is preferably formed from a polyurethane having a viscosity / elasticity ratio (tan δ) of 0.35 or greater at 23°C, a loss modulus of 5.59 MPa or greater at 23°C, and a rebound modulus of 21% or less at 23°C. The tip portion 13 having these characteristics, due to its low rebound modulus, has high shock and vibration absorption capabilities. Furthermore, the high viscosity / elasticity ratio (tan δ) improves the ability to dissipate frictional energy generated during sliding movement with the photosensitive drum 1 as heat, resulting in high wear resistance. Consequently, the life of the cleaning blade 10 can be extended.

[0032] While the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that modifications may be made in form and detail without departing from the scope of the invention as set forth in the claims. Such modifications, variations, and corrections are intended to be within the scope of the present invention.

[0033] For example, in the above embodiment, the cleaning blade contacts the outer peripheral surface of the photosensitive drum 1 to clean the photosensitive drum 1. However, the cleaning blade of the present invention may contact a photosensitive belt wound around a plurality of rollers instead of the photosensitive drum 1 to clean the belt.

[0034] Description of Reference Numerals

[0035] 1 Photosensitive drum (photosensitive member)

[0036] 2 Transfer device

[0037] 10 Cleaning blade

[0038] 11 Bracket (supporting member)

[0039] 12 Elastic components

[0040] 13 front end

[0041] S sheet

Claims

1. A cleaning blade, characterized in that: The cleaning blade has a front end portion that contacts the photosensitive member, The tip portion is formed of polyurethane having a tan δ of 0.35 or greater at 23° C., a loss modulus of 5.59 MPa or greater at 23° C., and a rebound modulus of 21% or less at 23° C.

2. The cleaning blade according to claim 1, wherein The polyurethane has a tan δ of 0.50 or less.

3. The cleaning blade according to claim 1, wherein The loss elastic modulus of the polyurethane is 12.10 MPa or less.

4. The cleaning blade according to claim 1, wherein The polyurethane has a rebound modulus of more than 16%.

5. The cleaning blade according to claim 1, wherein The crosslinking agent of the polyurethane is trimethylolethane.

6. The cleaning blade according to claim 1, wherein The chain extender of the polyurethane is 1,3-propylene glycol.

Images