JP2015225164A - Cleaning blade, image forming unit, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of passing of a developer between a cleaning blade and a developer conveyance member even when an image is formed for a long period.SOLUTION: A cleaning blade is formed from a plate-like rubber material for scraping a developer adhered on a developer conveying member accompanied with a movement of the developer conveying member which disposes an edge in contact with a contact point in the developer conveyance member. A rebound resilience Rb at 23[°C]is 5% or more and 22[°C] or less. In a loss tangent tan δ measured by a measurement frequency of 1[Hz], a variation of the loss tangent tan δ at the time of increasing the temperature from a peak top temperature Tp by 50[°C] is 0.58 or more and 0.75 or less. Even when an image is formed for a long period in an image forming device, the occurrence of passing of the developer between a cleaning blade 32 and the developer conveyance member can be suppressed.

Description

  The present invention relates to a cleaning blade, an image forming unit, and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copier, a facsimile machine, a multifunction machine, for example, an electrophotographic printer, includes an image forming unit (process cartridge), and a photosensitive member as a developer conveying member in the image forming unit. The surface of the drum is charged by a charging roller, and is exposed by an LED head to form an electrostatic latent image. The toner as a developer thinned by a developing blade on the developing roller is formed on the electrostatic latent image. Is electrostatically attached to form a toner image.

  The toner image is transferred onto a sheet conveyed through the sheet conveyance path by a transfer roller, and the toner image on the sheet is fixed by a fixing device.

  Incidentally, the toner remaining on the photosensitive drum after the toner image is transferred to the paper is removed by a cleaning device. The cleaning device includes a plate-like cleaning blade as a cleaning member disposed so as to be pressed against the surface of the photosensitive drum. The cleaning blade is made of an elastic material such as urethane rubber, and is rotated with the rotation of the photosensitive drum. Then, the toner is slid with the surface of the photosensitive drum to scrape off the toner (for example, see Patent Document 1).

JP 2002-49288 A

  However, in the conventional printer, when an image is formed over a long period of time, toner slips between the cleaning blade and the photosensitive drum.

  The present invention solves the problems of the conventional printer and suppresses the developer from slipping between the cleaning blade and the developer conveying member even when an image is formed over a long period of time. An object of the present invention is to provide a cleaning blade, an image forming unit, and an image forming apparatus.

  Therefore, in the cleaning blade of the present invention, the edge is disposed in contact with the contact point of the developer conveying member, and the developer adhering to the developer conveying member is scraped as the developer conveying member moves. It consists of a plate-shaped rubber material.

  The rebound resilience at 23 [° C.] is made 5 [%] or more and 22 [%] or less.

  In addition, in the loss tangent measured at a measurement frequency of 1 [Hz], the amount of change in loss tangent when the temperature is increased by 50 [° C.] from the peak top temperature is 0.58 or more and 0.75 or less. The

  According to the present invention, in the cleaning blade, the edge is disposed in contact with the contact point of the developer conveying member, and the developer adhering to the developer conveying member is scraped off as the developer conveying member moves. It consists of a plate-shaped rubber material.

  The rebound resilience at 23 [° C.] is made 5 [%] or more and 22 [%] or less.

  In addition, in the loss tangent measured at a measurement frequency of 1 [Hz], the amount of change in loss tangent when the temperature is increased by 50 [° C.] from the peak top temperature is 0.58 or more and 0.75 or less. The

  In this case, the temperature of the cleaning blade at the loss tangent measured at a measurement frequency of 1 [Hz] is set at a rebound resilience at 23 [° C.] of 5 [%] or more and 22 [%] or less. Since the amount of change in loss tangent when the temperature is increased by 50 [° C.] from the peak top temperature is 0.58 or more and 0.75 or less, even if an image is formed over a long period in the image forming apparatus, the cleaning blade And the developer transport member can be prevented from slipping through.

FIG. 2 is a conceptual diagram of an image forming unit in the embodiment of the present invention. 1 is a conceptual diagram of a printer in an embodiment of the present invention. It is a 1st figure which shows the relationship between the variation | change_quantity of loss tangent and count value in embodiment of this invention. It is a 2nd figure which shows the relationship between the variation | change_quantity of loss tangent and count value in embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a color printer as an image forming apparatus will be described.

  FIG. 1 is a conceptual diagram of an image forming unit in the embodiment of the present invention, and FIG. 2 is a conceptual diagram of a printer in the embodiment of the present invention. In the present embodiment, the image forming units (process cartridges) 13Bk, 13Y, 13M, and 13C for the respective colors of black, yellow, magenta, and cyan differ only in the color of the toner as the developer, and have the same structure. FIG. 1 shows only the image forming unit 13Bk.

  In the figure, Cs is a housing of the printer, 11 is a sheet cassette as a medium accommodating section that is disposed in the lower part of the casing Cs and accommodates a sheet P as a medium, and 12 is a pair of registration rollers. Each of the image forming units 13Bk, 13Y, 13M, and 13C is disposed in an upper portion of the housing Cs, and serves as an image carrier and a photosensitive drum 19 as a first developer conveying member and a charging device. Charging roller 20, a developing roller 22 as a developer carrying member, a toner cartridge 30 as a developer containing portion for containing toner, a cleaning device 31 and the like.

  Reference numeral 21 denotes an LED head as an exposure device disposed to face the photosensitive drum 19 of each of the image forming units 13Bk, 13Y, 13M, and 13C, and u1 is below the image forming units 13Bk, 13Y, 13M, and 13C. The transfer unit u1 is stretched by a driving roller R1, a driven roller R2 disposed at a predetermined distance from the driving roller R1, and the driving roller R1 and the driven roller R2. In this embodiment, the transfer belt 14 is disposed as a belt member that is disposed so as to be movable in the direction of the arrow A, and as the second developer conveying member. A transfer roller 15 serving as a transfer member disposed so as to face each of the photosensitive drums 19 via the belt 14, and an edge (tip) are connected to the transfer belt 1. To abut against comprises a cleaning blade 18 as a first cleaning member arranged. The cleaning blade 18 is disposed to scrape off toner adhering to the transfer belt 14, toner of a toner image formed on the transfer belt 14 for density adjustment, and the like from the photosensitive drum 19.

  Reference numeral 16 denotes a fixing device as a fixing device disposed adjacent to the transfer unit u1, and 17 denotes a conveying roller pair. The fixing device 16 includes a heating roller r1 as a first fixing member, and the heating roller. A pressure roller r2 is provided as a second fixing member disposed to face the roller r1.

  Next, the operation of the printer will be described.

  When a hopping roller (not shown) disposed at the front end of the paper cassette 11 is rotated, the paper P in the paper cassette 11 is fed one by one in the direction of the arrow and sent to the registration roller pair 12. The registration roller pair 12 corrects the skew of the paper P by temporarily stopping the paper P that has been fed, and sends it between the image forming units 13Bk, 13Y, 13M, and 13C and the transfer unit u1.

  In each of the image forming units 13Bk, 13Y, 13M, and 13C, the surface of the photosensitive drum 19 is uniformly charged by the charging roller 20, exposed by the light emitting element of the LED head 21, and a static image as a latent image. An electrostatic latent image is formed. The toner contained in the toner cartridge 30 is supplied to the developing roller 22 by a toner feed roller (not shown) as a developer supply member formed of urethane sponge or the like, and the developer roller 22 serves as a developer regulating member. After being thinned by a developing blade (not shown), it is attached to the electrostatic latent image, and a toner image as a developer image is formed on the photosensitive drum 19.

  The sheet P sent from the registration roller pair 12 is conveyed between each photosensitive drum 19 and the transfer roller 15 as the transfer belt 14 travels. At this time, a voltage having a polarity opposite to the polarity of the toner image is applied to each transfer roller 15, and the toner images on the respective photoconductive drums 19 are sequentially transferred onto the paper P by electrostatic force, and the color toner is transferred to the paper P. An image is formed.

  Subsequently, the paper P is sent to the fixing device 16 where the color toner image is heated by the heating roller r1, pressurized by the pressure roller r2, and fixed on the paper P. The sheet is conveyed by the conveying roller pair 17 and is discharged out of the printer casing Cs by a discharge roller pair (not shown).

  Incidentally, after the toner image on the photosensitive drum 19 is transferred to the paper P, the toner adheres to the surface of the photosensitive drum 19, that is, remains, but the toner remaining on the surface of the photosensitive drum 19 In the present embodiment, the movement 19 is scraped and removed by the cleaning device 31 as it rotates.

  Next, details of the cleaning device 31 will be described. In the present embodiment, the outer diameter of the photosensitive drum 19 is set to 30 [mm].

  The cleaning device 31 includes a plate-shaped cleaning blade 32 as a second cleaning member, and a holder 33 that is attached to a case of the image forming units 13Bk, 13Y, 13M, and 13C and holds the cleaning blade 32. The edge of the cleaning blade 32 is in the counter direction with respect to the rotational direction of the photosensitive drum 19 (so that the edge of the cleaning blade 32 is opposite to the moving direction of the surface of the photosensitive drum 19). The toner remaining on the surface of the photosensitive drum 19 in contact with the photosensitive drum 19 is scraped off by the cleaning blade 32 as the photosensitive drum 19 rotates.

  The cleaning blade 32 is made of an elastic body made of a rubber material, and the holder 33 is made of a material having rigidity such as a metal material. In the present embodiment, SECC is used as a material having rigidity.

  In the cleaning blade 32, when the length of the deformable portion not held by the holder 33 is a free length, the cleaning blade 32 has a free length of 6 in order to increase the mounting accuracy of the cleaning blade 32 with respect to the holder 33. .5 [mm] or more and 7.8 [mm] or less, and the tolerance of the free length is ± 15 [mm]. The thickness of the cleaning blade 32 is 1.5 [mm] or more and 2.0 [mm] or less.

  In the present embodiment, the contact point is the portion of the surface of the photosensitive drum 19 where the edge of the cleaning blade 32 comes into contact. The moving direction of the photosensitive drum 19, in this embodiment, the rotational direction (the direction of arrow B). ) Between the portion downstream of the contact point and the cleaning blade 32 (hereinafter referred to as “cleaning angle”) and the pressure at which the cleaning blade 32 presses the photosensitive drum 19 at the contact point (hereinafter referred to as “linear pressure”). .) Was changed to determine whether or not toner slipped between the cleaning blade 32 and the photosensitive drum 19 due to wear of the edge of the cleaning blade 32. .

  The test results are shown in Table 1.

  In Table 1, “◯” indicates that no toner slipping occurred even when the count value of the drum counter reached 5000 or more (even if the photosensitive drum 19 rotated 5000 times or more), and “×” represents the drum This means that the toner has passed through until the count value of the counter reaches 5000. Based on the result of the simple test in Table 1, in the present embodiment, the cleaning angle is set to 9 [°] or more and 16 [°] or less, the linear pressure is set to 10 [gf / cm] or more, and 25 [gf / cm] or less.

  Next, a method for manufacturing the cleaning blade 32 will be described.

  In the present embodiment, polyurethane (polyurethane elastomer) manufactured using polyol, isocyanate, and a curing agent as raw materials is used as the elastic body made of the rubber material that is the material of the cleaning blade 32.

  The polyol is not particularly limited as long as it is usually used for producing polyurethane, and polyethylene adipate, polybutylene adipate, polyethylene butylene adipate, etc. are used alone or in combination of two or more. Is done.

  The isocyanate is not particularly limited as long as it is usually used for producing polyurethane. Tolylene diisocyanate, 4,4-diphenylmethane diisocyanate (MDI), hexamethylene isocyanate, 1, 4 -Cyclohexane diisocyanate or the like, or isomers thereof.

  As the curing agent, a mixture of a high molecular weight polyol, a low molecular weight diol and a low molecular weight triol is used. The high molecular weight polyol is not particularly limited as long as it is usually used for producing polyurethane, and polyethylene adipate (average molecular weight 2000) is used. Further, the low molecular weight diol is not particularly limited as long as it is usually used for producing polyurethane. 1,4-butanediol, ethylene glycol, diethylene glycol, 1,6-hexanediol, Neopentyl glycol or the like is used. The low molecular weight triol is not particularly limited as long as it is usually used for producing polyurethane, and trimethylolpropane, triisopropanolamine and the like are used.

  The cleaning blade 32 made of polyurethane is manufactured, for example, as shown below.

  That is, the polyol and the isocyanate are subjected to a dehydration treatment, the dehydrated polyol and the isocyanate are mixed, and a temperature of 70 [° C.] to 140 [° C.] is 10 [min] to 120 [min]. The curing agent was added to the prepolymer obtained by this reaction, and the mixture was poured into a mold of a centrifugal molding machine preheated to a temperature of 150 [° C.] and cured for 25 [min] to 50 [min]. Thereafter, a sheet body having a cylindrical shape is taken out from the mold, and the cleaning blade 32 is formed by a blade member obtained by cutting the sheet body into a strip shape.

  By the way, when the temperature at which the loss tangent tan δ is the highest is the peak top temperature Tp, the rubber material such as polyurethane is in a glass state when the temperature is lower than the peak top temperature Tp, and the temperature is equal to or higher than the peak top temperature Tp. In some cases, the rubber material is known to be in a rubbery state. Therefore, when the cleaning blade 32 is used at a temperature lower than the peak top temperature Tp, the cleaning blade 32 is in a glass state, and the edge of the cleaning blade 32 is brought into contact with the surface of the photosensitive drum 19 when the photosensitive drum 19 is rotated. On the other hand, since it becomes difficult to deform | transform, the followable | trackability with respect to the photosensitive drum 19 will become low, and it will become easy to generate | occur | produce stick-slip movement. As a result, the edge of the cleaning blade 32 is likely to be worn, chipped, etc., and the toner is likely to slip through.

  Therefore, it is preferable to use the cleaning blade 32 at a temperature higher than the peak top temperature Tp.

In this case, the loss tangent tan δ has a loss elastic modulus E ″ and a storage elastic modulus E ′.
tan δ = E ″ / E ′
It represents how much of the energy applied to the rubber material is absorbed by the material when the rubber material is deformed. Accordingly, when the cleaning blade 32 is used at the peak top temperature Tp, the value of the loss elastic modulus E ″ with respect to the storage elastic modulus E ′ is large, so that the cleaning blade 32 easily absorbs the force applied from the photosensitive drum 19 and rebound resilience. The rate Rb becomes small.

  That is, when the cleaning blade 32 is used at the peak top temperature Tp, the edge of the cleaning blade 32 is easily deformed with respect to the surface of the photosensitive drum 19 when the photosensitive drum 19 is rotated, Since the followability can be enhanced, the occurrence of stick-slip motion can be suppressed. As a result, the edge of the cleaning blade 32 is less likely to be worn, chipped, and the like, so that toner can be prevented from slipping through.

  However, when the temperature at which the cleaning blade 32 is used becomes higher than the peak top temperature Tp and the loss tangent tan δ becomes small, the value of the storage elastic modulus E ′ with respect to the loss elastic modulus E ″ increases. It is difficult to absorb the force applied from the drum 19 and the rebound resilience Rb is increased.

  As a result, when the photosensitive drum 19 is rotated, the edge of the cleaning blade 32 is not easily deformed with respect to the surface of the photosensitive drum 19, and the followability to the photosensitive drum 19 is reduced. Occurrence is less likely to be suppressed. As a result, the edge of the cleaning blade 32 is likely to be worn, chipped, etc., so that it is not possible to prevent toner from slipping through.

When Young's modulus is E,
E = √ (E ' ² + E " ² )
And
E '> E "
So
E ≒ E '
Can be considered.

  Therefore, when the storage elastic modulus E ′ is large, the Young's modulus E is also large, and the cleaning blade 32 becomes hard. As a result, the edge of the cleaning blade 32 is likely to be chipped.

  Therefore, in the present embodiment, the loss tangent tan δ is measured at a measurement frequency of 1 [Hz] using a “dynamic viscoelasticity measuring device DMS6100” manufactured by Hitachi High-Tech, and the temperature is changed from the peak top temperature Tp to 50 [ [° C.] The amount of change in loss tangent tan δ when the temperature is increased is set to 0.58 or more and 0.75 or less. In this case, as described later, the peak top temperature Tp is set to 10 [° C.] or less.

  Note that the amount of change in loss tangent tan δ can be changed by adjusting the blending ratio of the high molecular weight polyol, low molecular weight diol, and low molecular weight triol used as the curing agent.

  At this time, the rebound resilience Rb of the cleaning blade 32 measured by the measurement method standardized in JIS K6255 is set to 5% or more and 22% or less at 23 [° C.]. .

  In general, when the rebound resilience Rb is low, the peak top temperature Tp is high. For example, when the rebound resilience Rb is lower than 5 [%], the peak top temperature Tp is higher than 10 [° C.]. End up. In this case, the cleaning blade 32 is in a glass state, and the toner slips easily as described above. Therefore, in the present embodiment, the rebound resilience Rb is set to 5% or more and 22% or less. The peak top temperature Tp is set to 10 [° C.] or less.

  In the present embodiment, an experiment was conducted to determine whether toner slipped out when the toner remaining on the photosensitive drum 19 was scraped off by the cleaning blade 32.

  In this experiment, an image forming unit acceleration tester was used, and “c710dn” manufactured by Oki Data Co., Ltd. was used as the image forming units 13Bk, 13Y, 13M, and 13C, and only the cleaning blade 32 was varied under normal temperature and humidity. This was done by forming an image. As the cleaning blade 32, 13 types of samples A to M having different impact resilience Rb were used.

  In the experiment, a polymerized toner having a particle size of 7.0 [μm] was used as the toner. A plurality of external additives having a particle size of 12 nm to 200 nm was used for the toner.

  In the image forming unit acceleration tester, the image forming units 13Bk, 13Y, 13M, and 13C continuously supply toner to the surface of the photoconductive drum 19 while rotating the photoconductive drum 19 at a rotation speed equivalent to 50 ppm. The toner on the photosensitive drum 19 is scraped off by the cleaning blade 32.

  The time for rotating the photosensitive drum 19, that is, the on-time was set to 12 [seconds], and the time for stopping the photosensitive drum 19, that is, the off-time was set to 4 [seconds].

  Each time the drum counter counts 7000, the image forming units 13Bk, 13Y, 13M, and 13C are disassembled, and the toner is attached (wound) to the charging roller 20 caused by the toner slipping, and the cleaning blade The state of 32 edges was observed. In the observation, “Optical Microscope VIIX-100” (magnification 100 to 1000 times) manufactured by Keyence Corporation and “Laser Microscope VK-8510” (magnification 1000 times) manufactured by Keyence Corporation were used.

  Then, the count value of the drum counter when the toner adheres to the charging roller 20 and the state of the edge of the cleaning blade 32 in the portion where the slipping occurred are confirmed. As experimental results, physical properties of samples A to M (the amount of change in loss tangent tan δ and the rebound resilience Rb when the temperature is higher by 50 [° C.] than the peak top temperature Tp), and the adhesion of toner to the charging roller 20 Table 2 shows the count value of the drum counter when this occurs.

  FIG. 3 is a first diagram showing the relationship between the loss tangent variation and the count value in the embodiment of the present invention. In the figure, the horizontal axis represents the amount of change in loss tangent tan δ, and the vertical axis represents the count value.

  As shown in the figure, when the amount of change in the loss tangent tan δ when the temperature is 50 ° C. higher than the peak top temperature Tp is 0.58 or more and 0.75 or less, the toner to the charging roller 20 When the toner adheres, the count value of the drum counter becomes 70000 or more, and it has been found that the toner does not easily slip through.

  Further, when the change amount of the loss tangent tan δ is smaller than 0.58 or larger than 0.75 and the edge of the cleaning blade 32 is observed with respect to the sample in which the toner slips out, the edge is missing and the toner is removed from the edge. I found out.

  Subsequently, based on the experimental results in Table 2, the samples A to M were samples having a rebound resilience Rb of 23 [° C.] greater than 22%, 5% or more, and 22% or less. It was divided into those.

  FIG. 4 is a second diagram showing the relationship between the amount of change in loss tangent and the count value of the drum counter in the embodiment of the present invention. In the figure, the horizontal axis represents the amount of change in loss tangent tan δ, and the vertical axis represents the count value of the drum counter.

  In the figure, ♦ indicates a sample having a rebound resilience Rb greater than 22%, and ● indicates a sample having a rebound resilience Rb of 5% or more and 22% or less.

  As can be seen from the figure, when the amount of change in the loss tangent tan δ is set to the same level, the cleaning blade 32 having a rebound resilience Rb of 5% or more and 22% or less is less than the rebound resilience Rb of 22%. It can be seen that the count value is larger than that of the large cleaning blade 32 and the durability is improved.

  When the change amount of the loss tangent tan δ is 0.58 or more and 0.75 or less, the count value becomes 100,000 or more, and the durability of the cleaning blade 32 can be greatly improved.

  As described above, when the value of the rebound resilience Rb is small and the change amount of the loss tangent tan δ is small, it is possible to suppress the occurrence of chipping or wear of the edge on the cleaning blade 32, and toner slip occurs. Can be suppressed.

  Therefore, in the present embodiment, the rebound resilience Rb at 23 [° C.] of the cleaning blade 32 is set to 5% or more and 22% or less, and the temperature at the measurement frequency of 1 [Hz] is set. Is set to 0.58 or more and 0.75 or less when the loss tangent tan δ is increased by 50 ° C. from the peak top temperature Tp.

  Accordingly, even when an image is formed over a long period of time in the printer, it is possible to prevent the cleaning blade 32 from being chipped, worn, etc., and toner slips between the cleaning blade 32 and the photosensitive drum 19. Can be suppressed.

  As a result, the durability of the cleaning device 31 can be improved, and the life of the image forming units 13Bk, 13Y, 13M, and 13C and the printer can be extended.

  In the above embodiment, the cleaning blade 32 for scraping off the toner adhering to the photosensitive drum 19 is described. However, the present invention is applied to the cleaning blade 18 for scraping off the toner adhering to the transfer belt 14. Can be applied.

  Although the printer has been described in the above embodiment, the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction machine.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

14 Transfer belt 18, 32 Cleaning blade 19 Photosensitive drum

Claims (8)

In a cleaning blade made of a plate-shaped rubber material, which is disposed with its edge in contact with a contact point on the developer conveying member, and scrapes off the developer attached to the developer conveying member as the developer conveying member moves. ,
(A) the rebound resilience at 23 [° C.] is 5% or more and 22% or less,
(B) In the loss tangent measured at the measurement frequency of 1 [Hz], the change in loss tangent when the temperature is increased by 50 [° C.] from the peak top temperature is 0.58 or more and 0.75 or less. A cleaning blade characterized by being made.   2. The cleaning blade according to claim 1, wherein a cleaning angle formed by a portion downstream of the contact point in the moving direction of the developer conveying member and the cleaning blade is 9 ° or more and 16 ° or less. .   The cleaning blade according to claim 2, wherein a linear pressure at which the cleaning blade presses the developer conveying member at the contact point is 10 gf / cm or more and 25 gf / cm.   The cleaning blade according to claim 1, wherein the peak top temperature is set to 10 ° C. or lower.   The cleaning blade according to claim 1, wherein the developer conveying member is an image carrier.   The cleaning blade according to claim 1, wherein the developer conveying member is a belt member.   An image forming unit on which the cleaning blade according to claim 1 is mounted.   An image forming apparatus on which the image forming unit according to claim 7 is mounted.

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