WO2019164071A1

WO2019164071A1 - Cleaning blades, and electrophotographic imaging apparatuses and electrophotographic cartridges employing the same

Info

Publication number: WO2019164071A1
Application number: PCT/KR2018/008919
Authority: WO
Inventors: Soon Cheol Jeong; Moon Young Kim
Original assignee: Hp Printing Korea Co., Ltd.
Priority date: 2018-02-20
Filing date: 2018-08-07
Publication date: 2019-08-29
Also published as: KR20190099955A

Abstract

Provided is a cleaning blade to remove residual toner on a surface of an electrophotographic photoreceptor. When storage moduli at certain temperatures and the difference between the storage moduli are obtained by dynamic viscoelastic measurement conducted as a function of temperature, The obtained storage moduli and the difference between the storage moduli satisfy certain conditions.

Description

CLEANING BLADES, AND ELECTROPHOTOGRAPHIC IMAGING APPARATUSES AND ELECTROPHOTOGRAPHIC CARTRIDGES EMPLOYING THE SAME

In electrophotographic imaging apparatuses such as facsimile machines, printers, copy machines, and the like, the inside of a developing cartridge is filled with toner particles upon which external additives having a size of several to several tens of nanometers are physically coated. In a developing process, toner particles are transferred onto a surface of an electrophotographic photoreceptor drum.

When the developing process is completed, toner particles, external additive particles, or the like may remain on the surface of the photoreceptor drum. Thus, it is necessary to perform a cleaning process of removing the residual particles from the surface of the photoreceptor drum before performing the subsequent toner image forming cycle.

Although there are various cleaning methods for removing toner particles and the like, a method of scraping off residual toner or external additive particles on a surface of a photoreceptor drum by using cleaning blades is widely used.

As used herein, the term "and/or" includes any and all combinations of at least one of the associated listed items.

Hereinafter, a cleaning unit including a cleaning blade according to some examples of the present disclosure, and an electrophotographic cartridge and an electrophotographic imaging apparatus each including the cleaning unit will be described in detail.

The above and other features of certain examples of the present disclosure will be explained from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view illustrating a cleaning unit including a cleaning blade according to an example of the present disclosure;

FIG. 2 is a schematic cross-sectional view illustrating an electrophotographic imaging apparatus and an electrophotographic cartridge each including a cleaning unit according to an example of the present disclosure;

FIG. 3 illustrates a change in storage modulus of a polyurethane rubber constituting a cleaning blade manufactured according to Example 1; and

FIG. 4 illustrates storage modulus master curves obtained for polyurethane rubbers constituting each of cleaning blades manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2.

FIG. 1 is a schematic cross-sectional view of a cleaning unit 2 including a cleaning blade 3 according to an example of the present disclosure.

Referring to FIG. 1, the cleaning unit 2 includes the cleaning blade 3 configured to remove toner and other residues remaining on a surface of an electrophotographic photoreceptor 1 after an image is transferred, and a support member 4 attached to at least a portion of the cleaning blade 3 and configured to support the cleaning blade 3. A portion of the cleaning blade 3, which is not attached to the support member 4, is referred to as a free length of the cleaning blade 3. The toner may be, for example, a styrene-acrylate-based toner or a polyester-based toner. The support member 4 is configured to support the cleaning blade 3 and may be fixed to a waste toner collector (not illustrated) located at a lower portion of the cleaning unit 2 or fixed to a main body (not illustrated) of an imaging apparatus (illustrated in FIG. 2, discussed below). The support member 4 may be manufactured using, for example, stainless steel.

In the cleaning unit 2, the cleaning blade 3 scrapes toner or the like remaining on the surface of the electrophotographic photoreceptor 1 by applying a blade pressure N to the surface of the electrophotographic photoreceptor 1 such that the toner is removed. Cleaning performance of the cleaning blade 3 may be obtained by increasing the blade pressure N or increasing a cleaning angle θ. However, when the blade pressure N is increased, the electrophotographic photoreceptor 1 becomes worn out, resulting in reduced lifespan. Thus, in consideration of this, the cleaning performance may be maintained by reducing the blade pressure N and increasing the cleaning angle θ. However, when the cleaning angle θ is too large, the cleaning blade 3 may be rolled up in a direction in which the electrophotographic photoreceptor 1 rotates (in a direction illustrated by an arrow), and thus care should be taken.

The cleaning blade 3 may be made of a polyurethane. A polyurethane cleaning blade is cheap in terms of raw material costs. However, since a polyurethane has rapidly reduced elasticity in a low-temperature environment, cleaning performance of a cleaning blade made of a polyurethane is likely to rapidly deteriorate when an image is formed not only in a low-temperature environment, i.e., about 10 ℃ to about 20 ℃, but also in an ultra-low-temperature environment, i.e., about -5 ℃ to about 0 ℃. In addition, the cleaning blade made of a polyurethane has sufficient elasticity in a high-temperature environment, and thus has excellent cleaning performance, but is likely to have poor abrasion resistance and poor durability, and cracks or the like may form easily. In particular, in a high temperature and high humidity environment, rebound resilience of the polyurethane cleaning blade becomes too large during a stick-slip movement such that a restoring force with respect to a rubber strain increases, resulting in cracks and poor cleaning performance.

However, in the present disclosure, physical properties of the polyurethane cleaning blade are controlled based on a storage modulus value obtained by dynamic viscoelastic measurement, instead of being based on a tan δ peak value. In particular, in the present disclosure, performance of the cleaning blade is controlled based on a storage modulus G' (MPa) at -5 ℃; a storage modulus G' at 23 ℃; a difference therebetween, i.e., △G' (MPa); the degree of swelling (%) in a toluene solvent; and a variation of storage modulus at t=1 year (G'(MPa) @ t = 1 year) with respect to storage modulus at initial t=0 sec (G'(MPa) @ t = 0 sec) from a storage modulus master curve obtained using a time-temperature superposition principle (TTSP). The inventors of the present disclosure have discovered that when this method is used, a cleaning blade may maintain stable cleaning characteristics even during long-term use under all environmental conditions, ranging from a low-temperature environment to a high-temperature environment, in which it is difficult for the cleaning blade to exhibit cleaning performance, and the cleaning blade may have a long lifespan and allow a high photoreceptor drum linear velocity and high-quality image formation.

That is, the cleaning blade 3 is controlled such that a storage modulus at -5 ℃, i.e., G'(MPa) @ -5 ℃ (unit: MPa), a storage modulus at 23 ℃, i.e., G'(MPa) @ 23 ℃ (unit: MPa), and a difference therebetween, i.e., ΔG'(MPa)(-5 ℃ - 23 ℃) (unit: MPa), satisfy the following conditions (i), (ii), and (iii), wherein these values are obtained by dynamic viscoelastic measurement conducted as a function of temperature at a temperature ranging from about -80 ℃ to about 50 ℃ in a nitrogen atmosphere and at a measurement frequency of 10 Hz, a heating rate of about 2.0 ℃/min, and an initial strain of about 0.03%:

27 < G'(MPa) @ -5 ℃ < 32... (i);

10 < G'(MPa) @ 23 ℃ < 16... (ii); and

12 < ΔG'(MPa) (-5 ℃ - 23 ℃) < 21... (iii).

The storage modulus G', loss modulus G" and shear modulus G* have a relation in which the square root of the sum of (storage modulus G')² and (loss modulus G")² is equal to shear modulus G*, i.e., G* = (G'² + G"²)^1/2. More particularly, condition (i) may be 27.5 <　G'(MPa) @ -5 ℃ < 32.0, condition (ii) may be 10.2 < G'(MPa) @ 23 ℃ < 15.5, and condition (iii) may be 12.2 < ΔG'(MPa)(-5 ℃ - 23 ℃) < 20.5. More particularly, condition (i) may be 27.67 ≤ G'(MPa) @ -5 ℃ ≤ 31.93, condition (ii) may be 10.23 ≤ G'(MPa) @23 ℃ ≤ 15.38, and condition (iii) may be 12.29 ≤ ΔG'(MPa)(-5 ℃ -23 ℃) ≤ 20.22.

When the cleaning blade 3 does not satisfy all of conditions (i) to (iii), as can be seen from examples and comparative examples below, it is difficult to satisfy all the above-described properties. Thus, when the cleaning performance of the cleaning blade 3 is poor, residual toner adheres to a charging roller such that the charging roller becomes contaminated. As a result, a charging property of contaminated surface areas of the charging roller decreases, resulting in a poor imaging quality due to streaks in areas of the printed image corresponding to the contaminated surface areas where the charging property has decreased.

The cleaning blade 3 may include a polyurethane or may be made of a polyurethane. The degree of swelling of the polyurethane in a toluene solvent, which is calculated based on Equation 1 below, may be controlled to satisfy the following condition:

21 < degree of swelling (%) < 34,

Degree of swelling = [(Wb - Wa)/Wa] X 100(%)........ (1),

wherein Wa and Wb are defined as follows: Wa denotes an initial weight of polyurethane rubber, which is equal to 1 g, and Wb denotes a post-swelling weight (unit: g) obtained after 1 g of the polyurethane rubber is immersed in 20 ml of toluene and then maintained for 4 hours.

The cleaning blade 3 may also be controlled such that, when a storage modulus master curve is obtained using the time-temperature superposition principle under the following measurement conditions through a dynamic mechanical analysis (DMA) method described in ASTM D4056, a variation of storage modulus at t=1 year, i.e., G'(MPa) @ t = 1 year, with respect to storage modulus at initial t=0 sec, i.e., G'(MPa) @ t = 0 sec, from the master curve, satisfies the following condition (iv):

(G'(MPa) @ 1 year/G'(MPa) @ t = 0 sec) X 100(%) < 20% ... (iv),

[Measurement Conditions]

Measurement mode: tensile mode (dynamic measurement)

Step type: frequency & temperature simultaneous sweep test

Measurement frequency (Hz): 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz (10 points)

Strain: about 0.2 % to about 1.45%

Measurement temperature: about -40 ℃ to about 100 ℃ (36 points at intervals of 4 ℃)

Atmosphere: nitrogen atmosphere.

Since the cleaning blade 3 further satisfies condition (iv), the cleaning blade 3 may maintain stable cleaning characteristics even during long-term use under all environmental conditions, ranging from a low-temperature environment to a high-temperature environment, in which it is difficult for the cleaning blade 3 to exhibit cleaning performance.

The variation of storage modulus at t=1 year, i.e., G'(MPa) @ t = 1 year, with respect to storage modulus at initial t=0 sec, i.e., G'(MPa) @ t = 0 sec, from the master curve, may be controlled to be, for example, less than about 10%, for example, less than about 7%.

The cleaning blade 3 may be made of a polyurethane rubber or a polyurethane elastomer as a main material. The cleaning blade 3 may be essentially made of a polyurethane rubber or a polyurethane elastomer. The polyurethane rubber or the polyurethane elastomer may be obtained by preparing a urethane prepolymer and then further reacting the urethane prepolymer with a curing agent.

The urethane prepolymer may be obtained by reacting a first polyol compound containing two or more hydroxyl groups per molecule with an aromatic polyisocyanate compound containing, per molecule, two or more isocyanate groups, for example, two to four isocyanate groups, for example, two to three isocyanate groups. The urethane prepolymer may be produced by a reaction between the first polyol compound and the aromatic polyisocyanate compound in such amounts that a ratio of equivalents of the hydroxyl groups of the first polyol compound to the isocyanate groups of the aromatic polyisocyanate compound ranges from about 1:1.1 to about 1:5. When the ratio of equivalents thereof is less than 1:1.1, a hydroxyl group-terminated urethane prepolymer may be obtained, and when the ratio of equivalents thereof is greater than 1:5, it may be difficult to increase a molecular weight of the urethane prepolymer.

In preparation of the urethane prepolymer, the first polyol compound may be a polyether-based polyol, a polyester-based polyol, a polyetherester polyol, or a mixture thereof, have a number average molecular weight of about 1,000 to about 8,000, and contain, for example, 2 to 6 hydroxyl groups, for example, 2 to 5 hydroxyl groups. For example, the first polyol compound may be a polyether-based polyol such as a polyethylene glycol, a polypropylene glycol, a polybutylene glycol, or the like obtained by addition polymerization of ethylene oxide, propylene oxide, tetrahydrofuran (THF), or the like using, as an initiator, an alcohol compound containing two to six hydroxyl groups, for example, two to five hydroxyl groups, such as ethylene glycol, glycerol, butane diol, trimethylolpropane, pentaerythritol, or the like. In addition, a modified polyol such as an acryl-modified polyol, a silicone-modified polyol, or the like may be used as the first polyol compound.

Examples of the aromatic polyisocyanate compound which may be used in preparing a urethane prepolymer include toluene diisocyanate (TDI), 4,4'-methylene diphenyl diisocyanate (MDI), xylene diisocyanate (XDI), isophorone diisocyanate (IPDI), polymethylene polyphenyl polyisocyanate, and the like. In addition, a mixture or modified product of these compounds may be used as the aromatic polyisocyanate compound. Further, an aliphatic diisocyanate such as hexamethylene diisocyanate (HDI) or the like may also be used.

As described above, when the urethane prepolymer is allowed to further react with a curing agent, a polyurethane rubber or elastomer may be obtained.

The curing agent may include a second polyol compound containing two or more hydroxyl groups per molecule. The second polyol compound may be the same as the first polyol compound. In addition, the curing agent may further include a multifunctional chain extender containing, per molecule, two or more of hydroxyl groups, amino groups, or a combination of these, a catalyst for catalyzing an addition reaction between isocyanate terminal groups of the urethane prepolymer and hydroxyl groups of the second polyol compound, and a plasticizer.

As the second polyol compound used in the curing agent, the aforementioned examples of the first polyol compound used in preparing the urethane prepolymer as a main material may also be used.

A ratio of equivalents of isocyanate groups of the urethane prepolymer to a sum of hydroxyl groups of the second polyol compound and functional groups of the chain extender in the curing agent may range from about 1:0.5 to about 1:5.0. When the ratio of equivalents thereof is less than 0.5, the polyurethane may not be sufficiently cured, and when the ratio of equivalents thereof is greater than 5.0, the polyurethane may have excessively high hardness.

As the chain extender, water, a low-molecular-weight multifunctional alcohol such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, glycerol, trimethyl propane, or the like, and/or a multifunctional polyamine compound such as hydrazine, ethylene diamine, propylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, 1,2-dimethylethylene diamine, 2-methylpentamethylene diamine, diethylenetoluene diamine, 4,4'-diaminodiphenylether, 2,3-diaminotoluene, 2,4- or 4,4'-diaminodiphenylmethane, 1,3- or 1,4-diphenyldiamine, naphthalene-1,5-diamine, 1,3-dimethyl-2,4-diaminobenzene, 1,3,5-triethyl-2,4-diaminobenzene, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4,4'-(1,3-phenyleneisopropylidene)bisaniline, 4,4'-(1,4-phenyleneisopropylidene)bisaniline, or the like may be used, and these may be used alone or in combination of two or more of these materials. The amount of the chain extender may range from about 0.5 wt% to about 10 wt%, for example, about 1 wt% to about 5 wt%, with respect to a total weight of reactants, in view of molecular weight control of the polyurethane.

As a curing catalyst for catalyzing the addition reaction, tin acetate, dibutyl tin acetate, dibutyl tin dilaurate, dioctyl tin dilaurate, tetrabutyl titanate, dibutyl tin maleate, stannous octate, lead octoate, N'-tetramethyl-1,3-butanediamine, or the like may be used, and these materials may be used alone or in combination of two or more. The amount of the curing catalyst may range from about 0.05 wt% to about 5 wt%, for example, about 1 wt% to about 3 wt%, with respect to the total weight of reactants, in view of workability and a curing rate.

When reacting the urethane prepolymer with the curing agent, an acid for controlling a reaction rate by controlling the pH of a reaction system may be further used. When mixing the urethane prepolymer with the curing agent, pH may be controlled to about 4 to about 6.5. If the pH is less than 4 or greater than 6.5, the reaction rate may slow down.

Non-limiting examples of the plasticizer include phthalates such as dibutyl phthalate and dioctyl phthalate; adipates such as dibutyl adipate and dioctyl adipate; and octoates such as lead octoate, and these materials may be used alone or in combination of two or more. The amount of the plasticizer may range from about 1 wt% to about 10 wt% with respect to a total weight of reactants. When the amount of the plasticizer is greater than 10 wt%, mechanical and physical properties of the polyurethane may deteriorate, and thus durability thereof may rapidly decrease.

The cleaning unit according to an example of the present disclosure may be integrated into electrophotographic cartridges or electrophotographic imaging apparatuses such as laser printers, photocopiers, facsimiles, and the like.

An electrophotographic imaging apparatus according to an example of the present disclosure includes: an electrophotographic photoreceptor; a charging apparatus configured to charge the electrophotographic photoreceptor by contacting the electrophotographic photoreceptor; an exposure apparatus configured to form an electrostatic latent image on a surface of the electrophotographic photoreceptor; a developing apparatus configured to form a visible image by developing the electrostatic latent image; a transfer apparatus configured to transfer the visible image to an image-receiving member; and a cleaning unit configured to remove residual toner on the surface of the electrophotographic photoreceptor, wherein the cleaning unit includes the cleaning blade according to an example of the present disclosure.

An electrophotographic cartridge according to an example of the present disclosure includes an electrophotographic photoreceptor; and a cleaning unit configured to remove residual toner on a surface of the electrophotographic photoreceptor after a visible image formed on the electrophotographic photoreceptor is transferred onto an image-receiving member, wherein the electrophotographic cartridge integrally supports the electrophotographic photoreceptor and the cleaning unit, and is attachable to and detachable from the electrophotographic imaging apparatus, and the cleaning unit includes the cleaning blade according to an example of the present disclosure.

FIG. 2 is a view illustrating an electrophotographic imaging apparatus and an electrophotographic cartridge each including the cleaning unit according to an example of the present disclosure.

Referring to FIG. 2, an electrophotographic photoreceptor drum 11 is charged by a charging roller 13 arranged to contact the electrophotographic photoreceptor drum 11. Subsequently, an electrostatic latent image is formed on the electrophotographic photoreceptor drum 11 by exposing an image portion to laser light. The electrostatic latent image is converted into a visible image, for example, a toner image, by a developing apparatus 15, and then the toner image is transferred to an image-receiving member 19 by a transfer roller 17 to which a voltage is applied. Toner remaining on a surface of the electrophotographic photoreceptor drum 11 after transfer of the toner image is removed by a cleaning unit 21 according to an example of the present disclosure, in particular a cleaning blade. Subsequently, the electrophotographic photoreceptor drum 11 may be provided to be used again to form an image in the next cycle. The developing apparatus 15 includes a toner layer regulating blade 23, a developing roller 25, a toner supplying roller 27, and the like.

The electrophotographic cartridge 29 may integrally support the electrophotographic photoreceptor drum 11 and, if needed, the charging apparatus 13, the developing apparatus 15, and the cleaning unit 21 according to an example of the present disclosure, and may be detachably attached to the electrophotographic imaging apparatus 31.

Hereinafter, the present disclosure will be described in further detail with reference to the following examples. However, these examples are provided for illustration and are not intended to limit the scope of the present disclosure.

Examples 1 to 3 and Comparative Examples 1 to 6: Manufacture of Cleaning Blades

As shown in Table 1 below, an amount of 4,4'-diphenylmethane diisocyanate (MDI) with a NCO content of 10.4 % to 16.9 % was added to a mixture of ethylene glycol adipate and polyethylene adipate in a mixing ratio of 100: 50-82, and allowed to react in a nitrogen atmosphere at about 80 ℃ for about 3 hours to obtain a NCO group-terminated urethane prepolymer (main component).

1,4-butanediol and trimethylol propane as curing agents were weighed in parts by weight, as shown in Table 1, and added to the NCO group-terminated urethane prepolymer heated at about 80 ℃, and then mixed by spinning mixing screws at a high speed at about 2,000 rpm for about 1 minute, followed by a defoaming process in a vacuum to prevent air bubbles from being generated. The resulting reactive composition was subjected to centrifugal molding for a cleaning blade, whereby the reactive composition was added in a predetermined amount to a centrifugal mold having a diameter of about 800 mm, to a thickness of about 2 mm. The mold was heated to about 120 ℃ and spun at about 1,200 rpm for about 40 minutes to cure the reactive composition. The cured reaction product, i.e., polyurethane rubber, was taken out of the mold, and then maintained for aging at room temperature for 4 days to allow the NCO terminal groups remaining in trace amounts on a surface of the polyurethane rubber to react with moisture in air.

The resulting polyurethane elastic sheet was cut into a rectangular shape having a width of 343 mm, which is a standard A3 size, and adhered by pressing to a SECC steel bracket (galvanized steel obtained by performing Zn plating on cold rolled steel) using a thermosetting polyurethane hot-melt adhesive to have a free length of about 8.5 mm, so that the resulting steel could be assembled with an SL-X7600 (manufactured by Samsung Electronics) developing unit.

Various characteristics of the cleaning blades manufactured according to Examples 1 to 3 and Comparative Examples 1 to 6 were evaluated.

	NCO group-terminated urethane prepolymer main component			Curing agent
	Mixing amount of ethylene glycol adipate (pbw^&)	Mixing amount of polyethylene adipate(Mn=2,000) (pbw)	NCO %*** of the main component	1,4-butane diol(pbw)	Trimethylol propane(pbw)	Amine curing agent*(pbw)
Example 1	100	73	13.7%	6.74	4.12	-
Example 2	100	67	10.9%	7.85	4.75	-
Example 3	100	79	16.9%	6.52	3.95	trace**
CE ⁺ 1	100	50	16.4%	5.03	3.03	trace
CE
2	100	55	13.7%	5.44	3.31	-
CE 3	100	62	13.7%	6.92	4.15	-
CE 4	100	82	14.5%	8.42	5.14	-
CE 5	100	76	10.4%	7.78	4.88	trace
CE 6	100	79	11.7%	8.36	5.06	-

* N'-tetramethyl-1,3-butanediamine;

** Less than 300 wt ppm based on the total weight of the polyurethane;

*** Percentage (%) of isocyanate groups at end groups of the obtained urethane prepolymer assuming that the total weight of the main component (ethylene glycol adipate + polyethylene adipate + MDI) is 100.

& pbw: parts by weight

+ CE: Comparative Example

Hardness Measurement

Hardness of each of the specimens having a thickness of about 2 mm was evaluated using an IRHD rubber hardness tester available from Bareiss Prufgeratebau GmbH after being maintained in an environment of 23±2 ℃ and 50±10% relative humidity (RH) for 8 hours or more.

Evaluation of Young's Modulus and Modulus

Mechanical and physical properties, i.e., Young's modulus and modulus, of each of the cleaning blades of the examples and the comparative examples were measured using a Shimadzu EZ-Test L Type Universal Testing Machine (UTM). Specimens used were in accordance with a dumbbell No. 3 standard and were about 2 mm thick. Measurement was performed in an environment of 23 ℃ and 55 % RH.

Herein, Young's modulus is a modulus value measured when the specimens were elongated to 5 % at a rate of 10 mm/min. Modulus at an elongation of 100 % and modulus at an elongation of 300 % were measured under a condition of elongation of each specimen at a rate of 500 mm/min.

Rebound Resilience Evaluation

Rebound resilience of each specimen was evaluated using a Lupke-type rebound resilience tester (Model: VR-6500 Series) available from SATRA-HAMPDEN in an environment of about 23 ℃ and about 55% RH in accordance with the JIS K 6255 standard. At this time, six sheets of circular specimens (total thickness: about 12 mm) each having a diameter of about 30 mm and a thickness of about 2 mm were stacked, and then each of the stacked products was hit three times with a strike rod, and a measurement value at the fourth hit was recorded.

To record the measurement values, an initial height of the tip of the strike rod of the Lupke-type rebound resilience tester was set to 100 %, a height at which the tip of the strike rod returned after hitting a stacked portion of the six sheets of specimens was recorded, and the return height with respect to the initial height was expressed as a percentage (%).

Method of Measuring Degree of Swelling: Evaluation of Crosslinking Density of Polyurethane Rubber

Polyurethane rubber, which is a material of the cleaning blade, is a polymer composed of polymer chains of various molecular weights that are crosslinked. In some cases, since some of the polymer chains do not participate in the crosslinking reaction or some of them are cross-linked, the polyurethane rubber may be dissolved in a solvent. In a case in which a solvent permeates into an empty space between the polymer chains, the polyurethane rubber swells. Because of this, the crosslinking density of the cleaning blade may be evaluated, and in the case of low crosslinking density, the polyurethane rubber has low strength under a high-temperature condition such as an H/H environment, and thus the cleaning blade may have poor edge abrasion resistance.

Crosslinking is a phenomenon in which polymer chains are chemically linked to each other, and the crosslinking density of a polyurethane rubber is affected by mixing with raw material components used in synthesis of the polyurethane rubber and may be defined by the number of crosslinking points. Thus, in the case of chains of a polymer having a relatively small molecular weight, the number of crosslinking points per unit volume increases, and crosslinking density increases accordingly. In addition, the larger the amount of a crosslinking agent, the greater the number of crosslinking points, resulting in increased crosslinking density. That is, crosslinking density is inversely proportional to the molecular weight of a polyurethane prepolymer such that as the molecular weight of the polyurethane prepolymer increases, the number of crosslinking points relatively decreases, and is proportional to the amount of a crosslinking agent.

In terms of functional and physical properties of the cleaning blade material in an electrophotographic apparatus, the higher the crosslinking density, the higher the modulus. When the modulus increases, abrasion resistance increases, resulting in high durability, but when the modulus increases to a certain range or more, permanent deformation (plastic deformation) or, in other words, permanent strain increases. Accordingly, it is necessary for the cleaning blade material to have crosslinking density within a certain range.

[Method of Measuring Degree of Swelling]

① 1 g of polyurethane rubber of each cleaning blade was accurately cut and put in a 20 ml glass vial.

② The glass vial was filled with 20 ml of toluene such that the cut polyurethane rubber was completely and sufficiently immersed therein.

③ After 4 hours, toluene on a surface of the polyurethane rubber was removed and then the post-swelling weight of the rubber was measured. The steps ① to ③ were performed under a condition of 23±2 ℃.

The degree of swelling of polyurethane rubber may be calculated by the Equation below:

Degree of swelling = [(Wb - Wa)/Wa] X 100(%),

wherein Wa and Wb are defined as follows: Wa denotes an initial weight of the polyurethane rubber, which is equal to 1 g; and Wb denotes a post-swelling weight (unit: g) obtained after 1 g of the polyurethane rubber is immersed in 20 ml of toluene and then maintained for 4 hours.

Cleaning Performance Test

An electrophotographic apparatus (X7600 manufactured by Samsung Electronics Co., Ltd.) equipped with each of the cleaning blades of the examples and the comparative examples was maintained for 24 hours or more in a climatic chamber, the temperature of which was adjustable to -5 ℃. Thereafter, after confirming that the temperature of the climatic chamber was -5 ℃ or less, 50 sheets of solid images for each of the colors (yellow, magenta, cyan, and black) were printed under conditions where an electrophotographic apparatus processing speed was 70 ppm to 80 ppm (330 mm/sec to 390 mm/sec) and the free length and thickness of a cleaning blade of an electrophotographic photoreceptor drum were set to about 7.8 mm and about 2 mm, respectively, and cleaning performance of each cleaning blade when used at -5 ℃ was evaluated from the quality of the printed material. Evaluation standards were as follows:

◎: cleaning performance of non-image region of the printed material was good,

○: no image defects after five sheets of images were printed,

×: occurrence of vertical black lines or white lines due to cleaning defects in non-image region of the printed material,

when cleaning defects occur in a non-image region of the printed material, image defects appear as vertical black lines in the printed image, and when a surface of a charging roller was contaminated with an external additive of a toner or a toner itself, image defects appear in the form of white lines.

Abrasion Resistance Test

An electrophotographic apparatus (X7600 manufactured by Samsung Electronics Co., Ltd.) equipped with each of the cleaning blades of the examples and the comparative examples was maintained for 24 hours or more in a climatic chamber, the temperature of which was adjustable to a normal temperature/normal humidity (N/N) environment (23 ℃/50 % to 60% RH) and a high temperature/high humidity (H/H) environment (30 ℃/80 % to 90 % RH). Thereafter, after confirming that the temperature and humidity of the climatic chamber were 23 ℃/50 % to 60 % RH or 30 ℃/80 % to 90 % RH, cleaning performance (abrasion resistance) according to environmental changes was evaluated according to a method described below under conditions where an electrophotographic apparatus processing speed was 70 ppm to 80 ppm (330 mm/sec to 390 mm/sec) and the free length and thickness of a cleaning blade of an electrophotographic photoreceptor drum were set to about 7.8 mm and about 2 mm, respectively.

First, each electrophotographic apparatus was maintained for 24 hours or more, and then one sheet of an image was printed using the electrophotographic apparatus in a user environment having a small toner consumption (text printing, 1 % coverage), and an imaging unit was stopped for 37 seconds, followed by printing, and this printing process was repeated. At this time, abrasion resistance of each cleaning blade was evaluated by counting the number of printed images without vertical black streaks in non-image areas. As the number of printed images with good quality increases, a printing time taken until cracks occur in an edge area of the cleaning blade increases, such that a long lifespan may be achieved. As the temperature in each electrophotographic apparatus increases from the N/N environment to the H/H environment, the cleaning blade exhibits reduced hardness, and thus an abrasion level of the cleaning blade is increased due to friction between the cleaning blade and a drum, resulting in reduced durability.

The suitability criteria for durability evaluation of the cleaning blades used in the present test were determined such that when an image count of 185K was reached in the N/N environment and an image count of 151K was reached in the H/H environment, cleaning performance was secured and abrasion resistance of each cleaning blade was good.

Storage Modulus Measurement

Storage modulus at -5 ℃, i.e., G*(MPa) @ -5 ℃, storage modulus at 23 ℃, i.e., G*(MPa) @ 23 ℃, and a difference therebetween, i.e., △G'(MPa)(-5 ℃ - 23 ℃), of the polyurethane rubbers constituting each of the cleaning blades of the examples and the comparative examples were measured according to a sine wave oscillation method by using an ARES measuring tool provided with a dynamic mechanical analyzer (DMA) manufactured from the Rheometric Scientific, Inc. under the measuring conditions indicated below:

- Measurement conditions: temperature ranging from about -80 ℃ to about 50 ℃, frequency: 10 Hz, strain of about 0.03 %, and heating rate: about 2 ℃/min;

- Size of specimen: 3 mm x 60 mm;

- Grip gap: 20 mm; and

- Atmosphere: nitrogen atmosphere.

FIG. 3 illustrates a change in storage modulus of the polyurethane rubber of the cleaning blade of Example 1, wherein the change was measured under the above conditions.

The reason why storage modulus is significant in a temperature range between -5 ℃ to 25 ℃ is as follows. When storage modulus is high at -5 ℃, the cleaning blade is vulnerable to permanent strain (permanent deformation) and is likely to undergo glassification, thus losing elasticity, and accordingly, it is difficult to form nip pressure between the cleaning blade and the electrophotographic photoreceptor drum. As a result, low-temperature cleaning performance deteriorates. On the other hand, when the crosslinking density of the rubber of a cleaning blade is low, the rubber becomes soft and storage modulus thereof at 25 ℃ decreases. Thus, an abrasion level of the cleaning blade is increased due to friction between the cleaning blade and the electrophotographic photoreceptor drum, resulting in deteriorated cleaning performance. That is, physical properties suitable for cleaning blades in -5 ℃, N/N, and H/H environments have a trade-off relationship.

The above-described evaluation results are summarized in Tables 2 and 3 below.

	Hardness	Young'sModulus(MPa)	Rebound resilience			Modulus(MPa)		Degree of swelling*(%)	Cleaning performance			Blade abrasion resistance(crack resistance)
	Hardness	Young'sModulus(MPa)	10℃	23℃	55℃	100%elongation	300%elongation	Degree of swelling*(%)	-5℃	N/N	H/H	N/N	H/H
Example1	72	5.4	21	33	61	3.6	21.5	34	◎	◎	◎	>185K	>151K
Example 2	79	9.8	10	32	49	5.7	30.2	27	○	◎	◎	>185K	>151K
Example 3	78	8.1	11	23	68	5.4	19.6	21	◎	◎	◎	>185K	>151K
CE** 1	72	5.9	18	49	62	5.1	17.8	39	◎	x	x	60K	92K
CE
2	78	13.1	13	35	64	5.9	10	44	◎	○	x	>120K	34K
CE 3	83	11.6	15	46	73	5.1	10.9	48	◎	△	x	92K	68K
CE 4	75	7.8	11	21	48	4.6	22.3	23	x	◎	○	>185K	>151K
CE 5	76	8.5	13	25	53	4.7	24.9	17	x	○	○	>120K	>151K
CE 6	71	6.8	10	18	50	3.5	27.5	15	x	◎	◎	>185K	>151K

* The degree of swelling in toluene;

N/N: 23 ℃, 50 % to 60 % RH, H/H: 30 ℃, 80 % to 90 % RH.

** CE: Comparative Example

	G'(MPa)　@　23 ℃	G'(MPa)　@　-5 ℃	△G'(MPa)(-5 ℃ - 23 ℃)
Example 1	10.23	28.15	17.92
Example 2	11.71	31.93	20.22
Example 3	15.38	27.67	12.29
Comparative Example 1	9.54	14.24	4.70
Comparative Example 2	8.84	23.61	14.77
Comparative Example 3	7.17	16.92	9.75
Comparative Example 4	13.33	43.21	29.88
Comparative Example 5	9.97	36.16	26.19
Comparative Example 6	13.01	21.75	8.74

Referring to Tables 2 and 3, it is confirmed that although the hardness, Young's modulus, rebound resilience, modulus, and degree of swelling in toluene exhibited by the cleaning blades of Examples 1 to 3 are similar to those of the cleaning blades of Comparative Examples 1 to 6, the cleaning blades of Examples 1 to 3 exhibit much higher cleaning performance at a low temperature and much higher abrasion resistance and cleaning performance in a H/H environment than those of the cleaning blades of Comparative Examples 1 to 6, through control of storage modulus characteristics such that the above-described conditions (i) to (iii) are satisfied.

Prediction of Cleaning Performance Change Over Time ( Lifespan Prediction Test)

Due to a decrease in nip pressure (line pressure) due to permanent strain of a cleaning blade according to long-term use of an electrophotographic apparatus, it is difficult to obtain long-lifespan characteristics of a photoreceptor drum unit. Thus, if it is possible to predict and measure an elastic loss zone of a cleaning blade material, a cleaning blade with long-lifespan characteristics may be obtained. For this, when an accelerated lifespan prediction method using the William-Landel-Ferry (WLF) equation or the Arrhenius equation is used, the lifespan of a cleaning blade may be predicted.

In particular, a function of time may be converted to a function of temperature based on the time-temperature superposition principle where the higher the temperature, the longer the time in the WLF equation (in other words, higher temperature corresponds to longer time). Particularly, measurement values corresponding to frequencies, i.e., 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz at each temperature are plotted in a frequency domain in a temperature range between -40 ℃ and 100 ℃ at intervals of 4 ℃. Under this 4 ℃ interval condition, storage modulus G' corresponding to each frequency is obtained, and then storage modulus measurement values at temperatures ranging from -40 ℃ to 100 ℃ (4 ℃, 36 points) based on a storage modulus measurement value at a reference temperature of 50 ℃ are plotted on a graph with the x axis (unit: Hz) converted to time. Using this method, a storage modulus master curve may be obtained through time-temperature superposition principle, usually automatically by measuring devices used in the art. When the storage modulus master curve is used, the elastic loss zone of a polyurethane rubber may be predicted.

FIG. 4 illustrates storage modulus master curves obtained under the following given conditions for polyurethane rubbers constituting each of the cleaning blades of Examples 1 and 2, abbreviated as E1 and E2 in the figure, and Comparative Examples 1 and 2, abbreviated as CE1 and CE2 in the figure. That is, FIG. 4 illustrates storage modulus master curves obtained using the time-temperature superposition principle under the following conditions through a dynamic mechanical analysis method described in ASTM D4065. Table 4 shows results obtained from each master curve by calculating a variation of storage modulus at t=1 year (G'(MPa) @ t = 1 year) with respect to storage modulus at initial t=0 sec (G'(MPa) @ t = 0 sec).

Lifespan Prediction Test Conditions

Measurement mode: tensile mode (dynamic measurement)

Step type: frequency & temperature simultaneous sweep test

Measurement Hz: 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz (10-Point)

Strain: 0.2 % to 1.45 %

Measurement temperature: -40 ℃ to 100 ℃ (interval of 4 ℃, 36 points)

Atmosphere: nitrogen atmosphere.

From these master curves, elasticity retention and changes in elasticity or elastic loss zones of the cleaning blades at the temperatures ranging from about -40 ℃ to about 100 ℃ may be predicted. In addition, the loss of nip pressure of each cleaning blade may be indirectly identified from a decreased variation of storage modulus after a certain period of time has passed, compared to storage modulus at the initial t=0 sec. From these results, changes in cleaning performance of the cleaning blades may be predicted.

		1 sec(1 sec)passed	24 h(8.64E+04sec) passed	1 week(6.05E+05sec) passed	30 days(2.59E+06sec) passed	1 year(3.15E+07sec) passed
Example1	G'(MPa)	7.50E+06	7.05E+06	7.42E+06	7.27E+06	7.33E+06
Example1	Variation(%)	Initial	6.0	1.1	3.1	2.3
Example 2	G'(MPa)	9.24E+06	8.72E+06	8.96E+06	8.75E+06	8.65E+06
Example 2	Variation (%)	Initial	5.6	3.0	5.3	6.4
Example 3	G'(MPa)	4.24E+06	4.04E+06	3.78E+06	3.64E+06	3.41E+06
Example 3	Variation (%)	Initial	4.7	10.8	14.2	19.6
CE^* 1	G'(MPa)	1.20E+07	9.18E+06	9.02E+06	8.92E+06	8.16E+06
CE^* 1	Variation (%)	Initial	23.5	24.8	25.7	32.0
CE 2	G'(MPa)	9.38E+06	8.64E+06	8.58E+06	-	-
CE 2	Variation (%)	Initial	7.9	8.5	-	-
CE 3	G'(MPa)	3.32E+06	2.89E+06	2.71E+06	2.45E+06	2.41E+06
CE 3	Variation (%)	Initial	13.0	18.4	26.2	27.4
C4	G'(MPa)	5.97E+06	5.52E+06	5.31E+06	4.98E+06	4.75E+06
C4	Variation (%)	Initial	7.5	11.1	16.6	20.4
CE 5	G'(MPa)	5.12E+06	4.59E+06	4.16E+06	3.49E+06	-
CE 5	Variation (%)	Initial	10.4	18.8	31.8	-
CE 6	G'(MPa)	6.22E+06	6.07E+06	5.77E+06	5.49E+06	5.26E+06
CE 6	Variation (%)	Initial	2.4	7.2	11.7	15.4

* CE: Comparative Example

Referring to Table 4, it is confirmed that the cleaning blades of Examples 1 to 2 according to the present disclosure exhibit a much lower variation of storage modulus at t=1 year (G'(MPa) @ t = 1 year) with respect to storage modulus at initial t=0 sec (G'(MPa) @ t = 0 sec) than that of each of the cleaning blades of Comparative Examples 1 and 2, through the control of storage modulus characteristics such that the above-described conditions (i) to (iii) are satisfied. Thus, it is evaluated that, even at t=1 year, a nip pressure between a photoreceptor drum and a cleaning blade according to the present disclosure may continue to maintain a good level compared to a nip pressure at initial t=0 sec, and accordingly, the cleaning blade according to the present disclosure may maintain good cleaning performance even after long-term use thereof.

As is apparent from the foregoing description, a cleaning blade according to an example of the present disclosure may maintain stable cleaning characteristics even after long-term use under all environmental conditions, ranging from a low-temperature environment to a high-temperature environment, in which it is difficult for the cleaning blade to exhibit cleaning performance. In addition, the cleaning blade has a long lifespan and allows a high photoreceptor drum linear velocity and high-quality image formation. The cleaning blade has excellent cleaning performance when an image is formed in a low-temperature environment, particularly between -5 ℃ and 0 ℃, and has excellent abrasion resistance and excellent durability in a high-temperature/high-humidity environment. Therefore, an electrophotographic cartridge and an electrophotographic imaging apparatus each including a cleaning unit including the cleaning blade according to an example of the present disclosure may provide high-quality images over a long period of time even when used in consecutive imaging operations under various environmental conditions and under conditions of high process speed. That is, the cleaning blade according to an example of the present disclosure may achieve the following effects, among other things:

(1) Since the cleaning blade can satisfactorily remove residual toner, contamination of an electrophotographic photoreceptor and other developer members is minimized, and accordingly, high-quality images may be provided over a long period of time under various environmental conditions such as an ultra-low-temperature environment, a high-temperature/high-humidity environment, and the like.

(2) Since the cleaning blade exhibits a long lifespan, replacement costs of the cleaning blade, which is a consumable product, may be reduced.

While example(s) have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.

Claims

A cleaning blade to remove residual toner present on a surface of an electrophotographic photoreceptor,

wherein, when

a storage modulus of the cleaning blade at -5 ℃ (G'(MPa)@-5℃) (unit: MPa),

a storage modulus of the cleaning blade at 23 ℃ (G'(MPa)@23℃) (unit: MPa), and

a difference between the G'(MPa)@-5 ℃ and the G'(MPa)@23℃ (ΔG'(MPa)(-5℃ - 23℃) (unit: MPa)

are obtained by dynamic viscoelastic measurement conducted as a function of temperature

at a temperature ranging from about -80 ℃ to about 50 ℃,

in a nitrogen atmosphere,

at a measurement frequency of 10 Hz,

a heating rate of 2.0 ℃/min, and

an initial strain of 0.03%,

the G'(MPa)@-5℃, the G'(MPa)@23℃, and the ΔG'(MPa)(-5℃ - 23℃) of the cleaning blade satisfy following conditions (i), (ii), and (iii):

27 MPa < G'(MPa)@-5 ℃ < 32 MPa (i);

10 MPa < G'(MPa)@23 ℃ < 16 MPa (ii); and

12 MPa < ΔG'(MPa)(-5 ℃ - 23 ℃) < 21 MPa (iii).
The cleaning blade of claim 1, wherein the cleaning blade includes a polyurethane.
The cleaning blade of claim 2, wherein, when a degree of swelling of the polyurethane is obtained based on Formula 1 below,

Degree of swelling = [(Wb - Wa)/Wa] X 100(%) ..... (1)

where Wa denotes an initial weight of the polyurethane rubber, the initial weight being equal to 1 g, and

Wb denotes a post-swelling weight (unit: g) obtained after 1 g of the polyurethane rubber is immersed in 20 ml of toluene and then maintained for 4 hours,

the obtained degree of swelling of the polyurethane satisfies the following condition:

21 % < the obtained degree of swelling (%) < 34 %.
The cleaning blade of claim 1, wherein, when a storage modulus master curve of the cleaning blade is obtained using a time-temperature superposition principle through a dynamic mechanical analysis method described in ASTM D4056 under the following measurement conditions:

measurement mode: tensile mode (dynamic measurement),

step type: frequency & temperature simultaneous sweep test,

measurement frequency (Hz): 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz (10 points),

strain: about 0.2 % to about 1.45 %,

measurement temperature: about -40 ℃ to about 100 ℃ (interval of 4 ℃, 36 points), and

atmosphere: nitrogen atmosphere,

a variation of storage modulus at t = 1 year (G'(MPa)@t=1year) with respect to storage modulus at initial t = 0 sec (G'(MPa)@t=0sec), from the storage modulus master curve, satisfies the following condition:

( G'(MPa)@t=1year / G'(MPa)@t=0 sec ) X 100(%) < 20%.
An electrophotographic cartridge attachable to and detachable from an electrophotographic imaging apparatus, the electrophotographic cartridge comprising:

an electrophotographic photoreceptor, onto which a visible image is to be formed;

an image receiving member onto which the visible image formed onto the electrophotographic photoreceptor is to be transferred; and

a cleaning unit to remove residual toner on a surface of the electrophotographic photoreceptor after the visible image formed on the electrophotographic photoreceptor has been transferred onto the image-receiving member,

wherein

the electrophotographic cartridge is to integrally support the electrophotographic photoreceptor and the cleaning unit,

the cleaning unit includes a cleaning blade to remove residual toner present on the surface of the electrophotographic photoreceptor, and

when

a storage modulus of the cleaning blade at -5 ℃ (G'(MPa)@-5 ℃) (unit: MPa),

a storage modulus of the cleaning blade at 23 ℃ (G'(MPa)@23℃) (unit: MPa), and

a difference between the G'(MPa)@-5℃ and the G'(MPa)@23℃ (ΔG'(MPa)(-5℃ - 23℃) (unit: MPa)

are obtained by dynamic viscoelastic measurement conducted as a function of temperature

at a temperature ranging from about -80 ℃ to about 50 ℃,

in a nitrogen atmosphere,

at a measurement frequency of 10 Hz,

a heating rate of 2.0 ℃/min, and

an initial strain of 0.03%,

the G'(MPa)@-5 ℃, the G'(MPa)@23 ℃, and the ΔG'(MPa)(-5 ℃ - 23 ℃) of the cleaning blade satisfy following conditions (i), (ii), and (iii):

27 MPa < the G'(MPa)@-5 ℃ < 32 MPa (i);

10 MPa < the G'(MPa)@23 ℃ < 16 MPa (ii); and

12 MPa < the ΔG'(MPa)(-5 ℃ - 23 ℃) < 21 MPa (iii).
An electrophotographic imaging apparatus comprising:

an electrophotographic photoreceptor;

an image receiving member;

a charging apparatus to charge the electrophotographic photoreceptor by contacting the electrophotographic photoreceptor;

an exposure apparatus to form an electrostatic latent image on a surface of the electrophotographic photoreceptor;

a developing apparatus to form a visible image by developing the electrostatic latent image;

a transfer apparatus to transfer the visible image onto the image-receiving member; and

a cleaning unit to remove residual toner on the surface of the electrophotographic photoreceptor, the cleaning unit including a cleaning blade to remove the residual toner,

wherein, when

a storage modulus of the cleaning blade at -5 ℃ (G'(MPa)@-5 ℃) (unit: MPa),

a storage modulus of the cleaning blade at 23 ℃ (G'(MPa)@23 ℃) (unit: MPa), and

a difference between the G'(MPa)@-5 ℃ and the G'(MPa)@23 ℃ (ΔG'(MPa)(-5 ℃ - 23 ℃) (unit: MPa)

are obtained by dynamic viscoelastic measurement conducted as a function of temperature

at a temperature ranging from about -80 ℃ to about 50 ℃,

in a nitrogen atmosphere,

at a measurement frequency of 10 Hz,

a heating rate of 2.0 ℃/min, and

an initial strain of 0.03%,

the G'(MPa)@-5 ℃, the G'(MPa)@23 ℃, and the ΔG'(MPa)(-5 ℃ - 23 ℃) of the cleaning blade satisfy following conditions (i), (ii), and (iii):

27 MPa < the G'(MPa)@-5 ℃ < 32 MPa (i);

10 MPa < the G'(MPa)@23 ℃ < 16 MPa (ii); and

12 MPa < the ΔG'(MPa)(-5 ℃ - 23 ℃) < 21 MPa (iii).
The electrophotographic cartridge of claim 5, wherein

the cleaning blade includes a polyurethane, and

when a degree of swelling of the polyurethane is obtained based on Formula 1 below,

Degree of swelling = [(Wb - Wa)/Wa] X 100(%) ..... (1)

where

Wa denotes an initial weight of the polyurethane rubber, the initial weight being equal to 1 g, and

Wb denotes a post-swelling weight (unit: g) obtained after 1 g of the polyurethane rubber is immersed in 20 ml of toluene and then maintained for 4 hours,

the obtained degree of swelling of the polyurethane satisfies the following condition:

21 % < the obtained degree of swelling (%) < 34 %.
The electrophotographic cartridge of claim 5, wherein, when a storage modulus master curve of the cleaning blade is obtained using a time-temperature superposition principle through a dynamic mechanical analysis method described in ASTM D4056 under the following measurement conditions:

measurement mode: tensile mode (dynamic measurement),

step type: frequency & temperature simultaneous sweep test,

measurement frequency (Hz): 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz (10 points),

strain: about 0.2 % to about 1.45 %,

measurement temperature: about -40 ℃ to about 100 ℃ (interval of 4 ℃, 36 points), and

atmosphere: nitrogen atmosphere,

a variation of storage modulus at t = 1 year (G'(MPa)@t=1year) with respect to storage modulus at initial t = 0 sec (G'(MPa)@t=0sec), from the storage modulus master curve, satisfies the following condition:

(G'(MPa)@t=1 year / G'(MPa)@t=0 sec ) X 100(%) < 20%.
The electrophotographic imaging apparatus of claim 6, wherein, when a degree of swelling of the polyurethane is obtained based on Formula 1 below,

Degree of swelling = [(Wb - Wa)/Wa] X 100(%) ..... (1)

where Wa denotes an initial weight of the polyurethane rubber, the initial weight being equal to 1 g, and

Wb denotes a post-swelling weight (unit: g) obtained after 1 g of the polyurethane rubber is immersed in 20 ml of toluene and then maintained for 4 hours,

the obtained degree of swelling of the polyurethane satisfies the following condition:

21 % < the obtained degree of swelling (%) < 34 %.
The electrophotographic imaging apparatus of claim 6, wherein

the cleaning blade includes a polyurethane, and

when a storage modulus master curve of the cleaning blade is obtained using a time-temperature superposition principle through a dynamic mechanical analysis method described in ASTM D4056 under the following measurement conditions:

measurement mode: tensile mode (dynamic measurement),

step type: frequency & temperature simultaneous sweep test,

measurement frequency (Hz): 0.1 Hz, 0.3 Hz, 0.5 Hz, 0.7 Hz, 1.0 Hz, 3 Hz, 5 Hz, 7 Hz, 10 Hz, and 30 Hz (10 points),

strain: about 0.2 % to about 1.45 %,

measurement temperature: about -40 ℃ to about 100 ℃ (interval of 4 ℃, 36 points), and

atmosphere: nitrogen atmosphere,

a variation of storage modulus at t = 1 year (G'(MPa)@t=1 year) with respect to storage modulus at initial t = 0 sec (G'(MPa)@t=0 sec), from the storage modulus master curve, satisfies the following condition:

( G'(MPa)@t=1 year / G'(MPa)@t=0 sec ) X 100(%) < 20%.