JP2013080075A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean a spherical toner excellent in developability and transferability by a simple blade cleaning system.
A displacement-load curve when a toner on a blade is pressed with a flat indenter in a micro hardness tester is a downward convex shape having a displacement amount a (μm) as an inflection point. The toner and blade are used under the condition that the toner is plastically deformed.
[Selection] Figure 3

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that employs an electrophotographic system or electrostatic recording system.

  In recent years, an image forming apparatus using an electrophotographic system has been required to output higher image quality than before. For this purpose, it is essential to develop a toner image faithful to the electrostatic latent image on the drum on the drum and efficiently transfer the toner image onto paper. It is widely known that toner spheroidization is an effective means for securing such developability and transferability.

  However, there are some problems in using the spherical toner in the electrophotographic system, and the most important one is the problem of poor cleaning. In general, the electrophotographic system is equipped with a cleaning means for removing toner remaining on the drum surface after transfer in order to repeatedly use the drum for image formation. As a cleaning means, blade cleaning that scrapes toner by bringing an elastic blade such as rubber into contact with the drum in the counter direction is the most simple, low-cost, and stable method, and is widely put into practical use. However, when the spherical toner is to be cleaned with a rubber blade, the toner often slips between the blade and the drum, resulting in poor cleaning. A defective cleaning causes an image defect and a charging device contamination, so that the reliability of the apparatus is remarkably impaired. Also, as a countermeasure against such slip-through, increasing the contact pressure of the blade against the photosensitive drum to increase the scraping force of the toner increases the frictional force between the photosensitive drum and the blade, and the blade that is in contact with the counter The possibility of failure of the cleaning system itself increases.

  The reason why the spherical toner is likely to cause a cleaning failure as compared with the irregular toner will be described with reference to FIG. By optimizing the contact pressure and contact angle of the cleaning blade, the toner cannot sink into the cleaning nip in the initial stage of the image forming apparatus, so that it is possible to perform good cleaning. However, as the apparatus continues to be used, the blade contact state changes due to a change in drum surface property and the replacement of intervening substances in the blade nip, and a state in which toner enters the cleaning nip occurs. More specifically, when the friction coefficient between the blade and the drum is increased, the leading end of the blade is drawn in the traveling direction of the photosensitive drum, and the wedge angle of the cleaning nip in FIG. A state that makes it easy to enter the nip occurs. FIG. 1a schematically shows the state of the cleaning nip when cleaning irregularly shaped toner, and FIG. 1b schematically shows the state of the cleaning nip when cleaning spherical toner. When the toner has entered the cleaning nip, the irregular toner is trapped in the cleaning nip as shown in FIG. 1a, so that it is still cleaned, whereas the spherical toner shown in FIG. 1b. More specifically, as shown in FIG. 1c, the toner receives a moment (a counterclockwise moment in the figure) that rotates due to friction with the drum, and rolls through the nip and slips through.

  The following techniques are disclosed as techniques for solving this problem. In Patent Document 1, the C, M, and Y developing units in a full-color multifunction peripheral are spherical toners. However, the toner of the Bk developing unit is changed to an irregular toner, and the irregular toner is supplied to the cleaning nip to improve the cleaning performance. I am letting. Patent Document 2 describes a technique for improving cleaning properties by pulverizing toner using a brush upstream of a cleaning blade. Furthermore, Patent Document 3 describes a technique for cleaning spherical toner by deforming spherical toner in a transfer nip and retaining the deformed toner in a wedge portion of a cleaning blade.

JP-A-8-254873 JP 2001-188452 A JP 2006-17796 A

  In the prior art, the cleaning of the spherical toner has been achieved by newly introducing a member for cleaning the spherical toner, or by making significant changes to other processes such as development and transfer. Such an achievement means causes adverse effects on other processes and increases in cost. In Patent Document 1, since the transferability of Bk toner is reduced by making the Bk toner indefinite, black character quality is sacrificed. Further, in Patent Document 2, a brush must be newly introduced in the process of pulverizing the toner on the image carrier, and the brush may damage the photosensitive drum. In Patent Document 3, in order to deform the toner at the transfer nip, it is necessary to apply a transfer nip pressure larger than usual by using a hard transfer body, and there is a concern about problems such as hollowing out in the transfer process.

  The problem to be solved by the present invention is to stably clean the spherical toner with a simple configuration.

The above problems are solved by the image forming apparatus described below.
(1) In an image forming apparatus having a cleaning unit for cleaning residual toner remaining on the image carrier after the toner image formed on the image carrier is transferred to a recording material, the cleaning unit includes the image A cleaning blade in contact with the carrier, wherein the microhardness of the surface of the image carrier is larger than the microhardness of the surface of the blade, and the average circularity of the toner is 0.97 or more. The displacement pressure-load curve obtained when the contact pressure is 20 g / cm or more and 70 g / cm or less and the toner and the blade are integrally deformed by pressure in the microhardness meter is changed in the displacement amount a (μm). An image forming apparatus having a downward convex shape as a bending point, and the toner undergoes plastic deformation at a displacement amount a.
(2) The image forming apparatus according to (1), wherein the toner has a core / shell structure.
(3) The image forming apparatus according to (1) or (2), wherein the cleaning blade is subjected to a treatment having a surface hardness higher than that inside.
(4) The image forming apparatus according to any one of (1) to (3), wherein the cleaning blade is made of polyurethane, and a surface layer thereof is treated with an isocyanate.

  A mechanism that is effective in the above-described image forming apparatus will be described with reference to the drawings. FIG. 3 is a diagram schematically showing the microhardness measurement of the toner on the blade. After the flat indenter detects the toner surface, a load is applied to the toner, and the load versus displacement at that time is measured. An example of the measurement result is shown in FIG. It can be seen that the load-displacement curve has a downwardly convex inflection point. The reason why such a curve is obtained will be described with reference to FIG. First, the indenter detects the toner surface and starts applying a load. This is the state (I) in the figure. Then, the blade is deformed downward by the toner, and eventually reaches a state where the toner is buried in the blade (II). The amount of displacement at that time is a (μm). At that time, the end of the indenter comes into contact with the blade, and a larger load is felt than when only the toner is pushed. Accordingly, when the load-displacement curve received by the indenter is shown in the figure, it has a downwardly convex inflection point as shown in FIG.

  That is, in the regions (I) to (III) in the figure, the indenter comes into contact with not only the toner but also the blade around the toner as shown in FIG. It becomes more difficult to displace than in the cases (I) to (II). This is the reason why downward convex inflection points occur.

  When the surface of the image carrier is harder than the blade, the state (II) in which the toner is buried in the blade is equal to the state in which the toner on the image carrier has entered the cleaning nip.

  When the toner on the blade is subjected to the inflection point load (II) (= displacement amount a) and the toner is not plastically deformed, when the spherical toner on the actual image carrier sinks into the cleaning nip, FIG. As shown in FIG. 6, since the toner can rotate in the nip, the toner receives a rotational moment from the frictional force with the image carrier, and slips while rolling downstream in the traveling direction. On the other hand, when the toner on the blade is plastically deformed when it reaches the displacement amount a, when the spherical toner on the image carrier enters the cleaning nip, as shown in FIG. Since the toner is plastically deformed, the toner cannot rotate in the nip and cannot travel further in the nip in the downstream direction.

  In order to verify this mechanism, the inventors conducted an experiment using a visualization apparatus as shown in FIG. A spherical toner is adhered to a glass plate coated with polycarbonate, which is a typical surface layer of an image carrier, and the state of scraping off the toner is observed with a high-speed camera from the back of the glass. The glass plate moves from the left to the right in the figure while maintaining the contact angle with the blade. In this manner, the toner behavior in the cleaning nip can be visualized and observed in a situation close to cleaning on the image carrier. Since we want to observe the behavior of the toner when it sinks, the blade angle is 30 °, which is larger than the contact angle in the actual device (the larger the set angle, the rust as shown in FIG. 1). Since the angle of is small, the toner tends to sink into the blade nip. The load applied to the blade was 35 g / cm.

  The flat plate moves at 10 mm / second and images at a speed of 6000 frames / second. The angle of view is 356 μm × 356 μm, and the resolution is 1024 × 1024 pixels.

  When the toner on the blade is a combination of a toner and a blade that does not undergo plastic deformation with a displacement amount a, the toner that has sunk rolls through the blade nip as shown in FIG. 1c. Also in this visualization device, slipping occurred in a part of the blade length, and by observing the part, it was possible to confirm a phenomenon that the toner rolls through the blade nip (FIG. 9). Further, even when the blade edge after cleaning was observed with a microscope, almost no toner that had undergone plastic deformation was found (FIG. 10a).

  On the other hand, when the combination of the blade and the toner is such that the toner on the blade is plastically deformed by the displacement amount a, the toner stays in place even if the toner sinks into the nip under the same setting conditions, and the cleaning is performed well. Was observed. Further, when the blade edge after cleaning was observed, it was confirmed that the toner was plastically deformed in the vicinity of the edge (FIG. 10b).

  Through these experiments, the inventors have been convinced of the mechanism by which the above-described image forming apparatus is effective.

  As described above, according to the invention of (1), even when the spherical toner enters the cleaning nip, the toner is plastically deformed by the blade surface layer, so that the toner on the photosensitive drum can be continuously cleaned well. .

  In addition, as the conditions under which the effects of the invention are sufficiently exhibited, the following three points are listed in the invention of (1). The first point is that the microhardness of the carrier is greater than the microhardness of the blade surface. If this condition is not met, the surface of the image carrier will be deformed rather than the blade. The state in which the toner has entered the blade nip does not match the state of the displacement amount a when the microhardness meter is measured. The second point is the condition that the circularity of the toner used is 0.97 or more. The present invention is effective only after blade cleaning of toner having excellent developability and transferability. It has been found by the inventors that good developability and transferability are secured with toner having a circularity of 0.97 or more. The third point is a condition that the contact pressure of the cleaning blade is 20 g / cm or more and 70 g / cm or less. In the visualization apparatus shown in FIG. 8, the behavior of the toner was observed by varying the contact pressure of the blade. When the toner entered the cleaning blade at 20 g / cm or less, even when the toner was plastically deformed with a displacement amount a. A phenomenon was observed in which the entire blade was lifted and slipped through. When the toner enters the blade nip, the entire blade is not lifted, and the blade contact pressure is required so that the blade surface layer remains at a minute deformation for one toner.

Consider further the value of 20 g / cm. When observing the cleaning nip, it can be seen that the toners buffer each other and all the toner does not enter the cleaning nip at the same time. Let P be the ratio of the toner that enters the cleaning nip within a certain time width (the time required for one toner to enter the cleaning nip). Further, when the force applied to the toner is N (gf) and the toner particle diameter is d (μm) at the displacement amount a of the microhardness measurement, the maximum number of toners is arranged in the longitudinal width of 1 cm (10000 / d). The force F (g / cm) for the toner to lift the blade per unit length is
F = N × (10000 / d) × P
It is represented by As an example, if N = 0.15 (gf) and d = 6 (μm),
F = 250 × P
It becomes. If the contact pressure of 20 g / cm is present, even if the toner enters the nip, considering that the cleaning is performed by plastic deformation in the nip, P = 0.08. In this example, 8% of the total toner is in the nip. You are going to dive. Although P depends on the particle size distribution of the toner and the fluidity of the toner, the inventors consider that this number has a certain degree of validity when observing the appearance of the toner entering the nip by visualization. . Conversely, when P = 1, that is, toner having a uniform particle diameter of 6 μm enters the cleaning nip at the same time in the closest state, cleaning cannot be performed without a contact pressure of 250 g / cm. In fact, even if the contact pressure is not so high, if the conditions of the present invention are satisfied, the toner is satisfactorily cleaned. Therefore, all the toner does not sink into the cleaning nip at the same time. It is reasonable from the viewpoint of visualization to think that it is in the nip. When cleaning is performed for a certain period of time, the toner that has entered the blade nip and plastically deformed is accumulated in the blade nip, resulting in a state as shown in FIG. From the above consideration, it is not a mysterious phenomenon to clean the toner without lifting the blade with a contact pressure of 20 g / cm or more.

  On the other hand, when the load is 70 g / cm or more, the frictional force between the photosensitive drum and the blade increases, and the possibility that the cleaning system breaks down due to turning of the blade in contact with the counter is increased. For the above reasons, in the present invention, it is necessary to bring the cleaning blade into contact with the image bearing member with a contact pressure of 20 g / cm or more and 70 g / cm or less.

  In the toner having the configuration (2), since the toner shell is broken when the toner is plastically deformed, a larger deformation occurs, so that the effect of the invention described in (1) is easily exhibited.

  In the configuration (3), since the blade base layer is soft and the blade surface layer is hard, the toner that has entered the cleaning nip can be plastically deformed while maintaining stable contact with the photosensitive drum. Therefore, the effects of the invention described in (1) and (2) are more easily exhibited.

  In the configuration of (4), since the configuration of (3) can be easily realized and the surface hardness of the blade can be easily controlled, the effects of the inventions of (1) to (3) are easily exhibited.

Difference in behavior of irregularly shaped toner (a) and spherical toner (b) in the cleaning nip. (C) is an enlarged view of a spherical toner. 1 is a schematic cross-sectional configuration diagram of an embodiment of an image forming apparatus according to the present invention. Explanation of measurement of micro hardness of toner on blade. The measurement result example of the micro hardness measurement of the toner on a blade. FIG. 4 is a schematic diagram during measurement of micro hardness of toner on a blade. FIG. 6 is a schematic diagram when toner is not plastically deformed at a cleaning nip. FIG. 6 is a schematic diagram when toner is plastically deformed in a cleaning nip. Schematic of the visualization apparatus which inventors conducted experiment. An observation image when toner passes through. Microscopic image of the blade edge after cleaning. (A) A combination of a toner and a blade in which the toner has not undergone plastic deformation at the displacement amount a. (B) A combination of a toner and a blade in which the toner has undergone plastic deformation at the displacement amount a. FIG. 3 is a configuration diagram of the cleaning unit 10. Comparison of toner cross-sectional shapes before and after microhardness measurement in Example 1. Relationship between blade penetration and contact load. Comparison of toner cross-sectional shapes before and after microhardness measurement in Comparative Example 1.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

[Example 1]
First, the overall configuration of the image forming apparatus according to the present embodiment will be described. FIG. 2 shows a schematic cross-sectional configuration of the image forming apparatus 100 of the present embodiment. The image forming apparatus 100 of this embodiment is a tandem type electrophotographic laser beam printer.

  The image forming apparatus 100 according to the present exemplary embodiment includes first, second, third, and fourth image forming units (stations) SY, SM, SC, and SK as a plurality of image forming units. The first, second, third, and fourth image forming units SY, SM, SC, and SK form yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. It is supposed to be.

  In this embodiment, the configurations and operations of the image forming units SY, SM, SC, and SK are substantially the same except that the color of the toner used is different. Accordingly, in the following, when no particular distinction is required, the subscripts given to the reference numerals in the drawings will be omitted to indicate that they are elements provided for any color, and the description will be made comprehensively.

  The image forming unit S includes a drum-type electrophotographic photosensitive member, that is, a photosensitive drum 1 as an image bearing member that carries toner. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 (counterclockwise) in the drawing. Around the photosensitive drum 1, there are a charging roller 2 as a contact charging member as a charging means, a laser beam scanner 3 as an exposure means (image information writing means), a developing device 4 as a developing means, and a cleaning device as a cleaning means. 10 is arranged. Further, an intermediate transfer device 60 is disposed so as to face the photosensitive drums 1 of all the image forming units S.

  The intermediate transfer device 60 includes an intermediate transfer belt 6 that is an endless belt-like member as an intermediate transfer member that can move in contact with the photosensitive drum 1. The intermediate transfer belt 6 is wound around a driving roller 61, a driven roller 62, and a secondary transfer backup roller 7b as a plurality of support members. When the driving force is transmitted to the driving roller 61, the intermediate transfer belt 6 rotates in the direction of arrow R2 (clockwise) in the drawing. Further, it is a rotatable primary transfer member serving as a primary transfer unit so as to come into contact with the inner peripheral surface (back surface) of the intermediate transfer belt 6 at a position facing each photosensitive drum 1 of each image forming unit S. A next transfer roller 5 is disposed. Each primary transfer roller 5 presses the intermediate transfer belt 6 toward the photosensitive drum 1. Thus, the intermediate transfer belt 6 is sandwiched between the photosensitive drum 1 and the primary transfer roller 5 to form the primary transfer portion N1. Further, the secondary transfer roller 7a is disposed so as to contact the outer peripheral surface (front surface) of the intermediate transfer belt 6 at a position facing the backup roller 7b. The secondary transfer roller 7 a is in pressure contact with the intermediate transfer belt 6. As a result, the intermediate transfer belt 6 is sandwiched between the secondary transfer roller 7a and the backup roller 7b to form the secondary transfer portion N2. Each of the secondary transfer roller 7a and the backup roller 7b is a rotatable secondary transfer member constituting a secondary transfer unit.

  Next, an image forming operation will be described taking full color image formation as an example.

  First, the surface of the photosensitive drum 1 is uniformly charged to a predetermined potential having a predetermined polarity (negative polarity in this embodiment) by the charging roller 2. The photosensitive drum 1 rotates at a peripheral speed (surface movement speed) of 210 mm / sec in the direction of arrow R1 in the figure. The peripheral speed of the photosensitive drum 1 corresponds to the process speed of the image forming apparatus 100.

  The surface of the charged photosensitive drum 1 is scanned and exposed by a laser beam scanner (image exposure device) 3 with a laser beam L modulated by an image signal. As a result, an electrostatic image (latent image) is formed on the photosensitive drum 1.

  The electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developer toner by the developing device 4. In this embodiment, the developing device 4 develops the electrostatic image on the photosensitive drum 1 by a reversal development method. That is, toner charged to the same polarity (negative polarity in this embodiment) as the charged polarity of the photosensitive drum 1 is attached to the image portion (bright portion) of which charge has been attenuated by exposure on the surface of the charged photosensitive drum 1. Thus, the electrostatic image on the photosensitive drum 1 is developed.

  The toner images of the respective colors formed on the respective photosensitive drums 1 are transferred onto the intermediate transfer belt 6 at the primary transfer portion N1 where the primary transfer roller 5 and the photosensitive drum 1 face each other with the intermediate transfer belt 6 interposed therebetween. Are sequentially superimposed and transferred (primary transfer). At this time, the primary transfer roller 5 is supplied with a primary transfer bias (primary transfer voltage) having a polarity opposite to the normal charging polarity of the toner, which is output from a primary transfer power supply 51 as a primary transfer bias applying unit. Is applied.

  The toner images superimposed on four colors on the intermediate transfer belt 6 are transferred onto a recording sheet or the like at the secondary transfer portion N2 where the secondary transfer roller 7a and the backup roller 7b face each other with the intermediate transfer belt 6 interposed therebetween. The material P is collectively transferred (secondary transfer). At this time, the secondary transfer roller 7a has a secondary transfer bias (secondary transfer voltage) output from a secondary transfer power supply 71 serving as a secondary transfer bias applying unit and having a polarity opposite to the normal charging polarity of the toner. Is applied. In this embodiment, the secondary transfer bias is applied to the secondary transfer member in contact with the outer peripheral surface of the intermediate transfer belt 6, but the secondary transfer bias reverses the polarity and is applied to the inner peripheral surface of the intermediate transfer belt 6. You may apply to the secondary transfer member which contacts.

  Here, the transfer material P is taken out from the transfer material cassette 8 by a supply roller or the like, and is supplied to the secondary transfer portion N2 via a transport roller, a transport guide, and the like.

  The transfer material P onto which the toner image has been transferred is separated from the intermediate transfer belt 6 and conveyed to a fixing device (heat roller fixing device) 9 as fixing means. The unfixed toner image on the transfer material P is fixed on the transfer material P by being heated and pressed by the fixing device 9.

  Toner remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 6 after the primary transfer process (primary transfer residual toner) is removed from the surface of the photosensitive drum 1 by the cleaning device 10 and collected. A schematic diagram of the cleaning device 10 is shown in FIG. The cleaning blade is in contact with the traveling direction of the photosensitive drum 1 at a pressure of 35 g / cm in the direction of the counter, and an angle between the blade side surface and the drum tangent is 27 °. The photosensitive drum 1 from which the primary transfer residual toner has been removed is repeatedly used for image formation.

(Blade contact pressure measurement method)
In the apparatus of this embodiment, the amount of penetration of the blade into the photosensitive drum is defined, and the contact pressure is calculated and defined from the amount of penetration. The relationship between the amount of penetration of the blade into the photosensitive drum and the contact pressure is measured using a dedicated measuring device.

  The apparatus includes a drum, a cleaning blade, and a support member of the image forming apparatus according to the present exemplary embodiment, and further includes a load cell that measures a load applied to the drum. The blade support member is movable, and the amount of blade penetration into the drum can be changed. By measuring the load applied to the load cell when the intrusion amount is changed in increments of 0.2 mm, the relationship between the blade contact load and the intrusion amount is obtained. The contact pressure (g / cm) is obtained by dividing the contact load (g) by the blade longitudinal width (cm).

  Finally, the toner remaining on the surface of the intermediate transfer belt 6 without being transferred to the transfer material P after the secondary transfer process (secondary transfer residual toner) is removed from the surface of the intermediate transfer belt 6 by the intermediate transfer belt cleaner 64. To be recovered. The intermediate transfer belt cleaner 64 scrapes off the toner on the intermediate transfer belt 6 by an intermediate transfer belt cleaning member such as an elastic blade (cleaning blade). The intermediate transfer belt cleaner 64 may be attached to the surface of the intermediate transfer belt 6 so as to be able to contact / separate. Further, during the primary transfer process, the intermediate transfer belt cleaning member can be separated from the surface of the intermediate transfer belt 6 so that the toner image before the secondary transfer is hardly disturbed.

  The image forming apparatus 100 can also form a single-color or multi-color image by forming a toner image using only one desired image forming unit or only four of the four image forming units. Also in this case, the image forming operation is the same as that in the above-described full-color image formation except that there is an image forming portion that does not form a toner image.

  Next, main components of the image forming apparatus 100 will be described in more detail.

(About the cleaning blade)
The cleaning blade used in this example was a polyurethane resin-based blade, and the JIS-A hardness defined by JIS K 6253 was 85 degrees. A polymer polyol, polyisocyanate, and a crosslinking agent were reacted to form a blade.

  As the polymer polyol, polyester polyol, polyether polyol, caprolactone ester polyol, polycarbonate ester polyol, silicone polyol and the like are used. A weight average molecular weight of 500 to 5000 is usually used, but is not limited thereto.

  Examples of the isocyanate include, but are not limited to, diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and hexamethylene diisocyanate.

  Examples of the crosslinking agent include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, trimethylolpropane and the like. Examples of the catalyst include, but are not limited to, triethylenediamine.

  As a molding method of the blade, the above-mentioned components are mixed at once, and the one-shot method in which the components are cast and molded into a mold or a centrifugal molded cylindrical mold. The isocyanate and polyol are reacted in advance to form a prepolymer, and then A prepolymer method in which a cross-linking agent is mixed and cast into a mold or a centrifugal molded cylindrical mold, a semi-prepolymer obtained by reacting an isocyanate with a polyol, and a curing agent obtained by adding a polyol to the cross-linking agent are reacted. For example, a semi-one shot method in which a mold or a centrifugally-molded cylindrical mold is cast and molded can be used.

  In this way, a polyurethane blade having a thickness of 2 mm, a width of 345 mm, and a depth of 15 mm was formed.

  The surface hardness of the created blade was measured with an ultrafine hardness tester ENT1100 manufactured by Elionix. When a maximum load of 100 mgf (step interval: 10 milliseconds, number of divisions: 1000) was measured using a triangular indenter (opposite angle of 115 °), a displacement of about 2.5 μm was observed.

(About toner)
The toner particles used in the present invention may be produced by any method. However, as a main production method, the toner produced by the pulverization method is subjected to mechanical treatment or heat treatment to be substantially spherical. And a production method of granulating in an aqueous medium such as a suspension polymerization method or an emulsion polymerization method. Among these production methods, the suspension polymerization method is a relatively simple method for granulating a spherical toner having a core-shell structure encapsulating wax, and is one of the preferred production methods from the viewpoint of production cost such as not using a solvent. is there.

  The suspension polymerization method, which is one of the preferred toner production methods for application to the present invention, will be described below. A polymerizable monomer, a colorant, a wax component, and other additives as required are uniformly dissolved or dispersed by a disperser such as a homogenizer, a ball mill, a colloid mill, or an ultrasonic disperser, and then a polymerization initiator. Is dissolved to prepare a polymerizable monomer composition. Next, toner particles are produced by suspending the polymerizable monomer composition in an aqueous medium containing a dispersion stabilizer and performing polymerization. The polymerization initiator may be added simultaneously with the addition of other additives to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. In addition, a polymerization initiator dissolved in a polymerizable monomer or solvent may be added immediately after granulation and before starting the polymerization reaction.

  The toner particles thus obtained have a capsule structure in which a wax component is encapsulated. The surface hardness of the toner can be changed by changing the molecular weight distribution and composition of the toner particle outer shell.

  Examples of the binder resin used in the toner include commonly used styrene-acrylic copolymers, styrene-methacrylic copolymers, epoxy resins, and styrene-butadiene copolymers. As the polymerizable monomer, a vinyl polymerizable monomer capable of radical polymerization can be used. As the vinyl polymerizable monomer, a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer can be used.

  The following are mentioned as a polymerizable monomer for producing | generating a binder resin. Styrene monomer: o- (m-, p-) methylstyrene, m- (p-) ethylstyrene, and the like. Acrylic acid ester monomer or methacrylic acid ester monomer: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, acrylic acid Octyl, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, stearyl acrylate, stearyl methacrylate, behenyl acrylate, behenyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl acrylate, methacrylic acid Dimethylaminoethyl, diethylaminoethyl acrylate, diethylaminoethyl methacrylate. Ene monomers: butadiene, isoprene, cyclohexene, acrylonitrile, methacrylonitrile, acrylic amide, methacrylic amide.

  Further, by adding a low molecular weight polymer to the polymerizable monomer composition, the molecular weight distribution of the toner can be optimized, and the low-temperature fixability and offset resistance can be controlled. Examples of the low molecular weight polymer include low molecular weight polystyrene, low molecular weight styrene-acrylic acid ester copolymer, and low molecular weight styrene-acrylic copolymer.

  A preferable addition amount of the low molecular weight polymer is 1 part by mass or less and 50 parts by mass or less, and more preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  In addition, a polar resin having a carboxyl group such as a polyester resin or a polycarbonate resin can be used in combination with the above binder resin.

  For example, in the case of directly producing toner particles by a suspension polymerization method, when a polar resin is added during the polymerization reaction from the dispersion step to the polymerization step, a polymerizable monomer composition that becomes toner particles and an aqueous dispersion medium are exhibited. Depending on the balance of polarity, the added polar resin forms a thin layer on the surface of the toner particles, or the presence state of the polar resin is controlled so that it exists with a gradient from the toner particle surface toward the center. Can do. That is, the addition of the polar resin can reinforce the shell portion of the core-shell structure, thus affecting the mechanical strength of the toner.

  A preferable addition amount of the polar resin is 1 part by mass or more and 25 parts by mass or less, and more preferably 2 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the binder resin. If the amount is less than 1 part by mass, the presence state of the polar resin in the toner particles tends to be non-uniform. On the other hand, if it exceeds 25 parts by mass, the polar resin layer formed on the surface of the toner particles becomes thick.

  Examples of the polar resin used in the toner include polyester resins, epoxy resins, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and styrene-maleic acid copolymers. In particular, a polyester resin having a molecular weight of 3000 to 10,000 in terms of the main peak molecular weight is preferable as the polar resin because the fluidity and negative frictional charging characteristics of the toner particles can be improved.

  Furthermore, in order to control the mechanical strength of the toner particles, a crosslinking agent may be used when the binder resin is synthesized.

  Examples of the bifunctional crosslinking agent include the following. Divinylbenzene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1, 6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200, # 400, # 600 diacrylate, dipropylene glycol diacrylate, Polypropylene glycol diacrylate, polyester type diacrylate (MANDA Nippon Kayaku), and dimethacrylate instead of the above diacrylate Thing was.

  The following are mentioned as a polyfunctional crosslinking agent. Pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, diallyl phthalate, tri Allyl cyanurate, triallyl isocyanurate and triallyl trimellitate. The addition amount of these crosslinking agents is preferably 0.05 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer.

  The following are mentioned as a polymerization initiator used for this toner. 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis Azo or diazo polymerization initiators such as -4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl Peroxide-based polymerization initiators such as peroxide, lauroyl peroxide, tert-butyl-peroxypivalate.

  Although the usage-amount of these polymerization initiators changes with the target degree of polymerization, generally they are 3 mass parts or more and 20 mass parts or less with respect to 100 mass parts of polymerizable vinylic monomers. The kind of the polymerization initiator varies slightly depending on the polymerization method, but is used alone or in combination with reference to the 10-hour half-life temperature.

  The toner contains a colorant as an essential component in order to impart coloring power. Examples of the colorant used in the toner include the following organic pigments, organic dyes, and inorganic pigments.

  Examples of organic pigments or organic dyes as cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds.

  Examples of the organic pigment or organic dye as the magenta colorant include the following. Condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, perylene compounds.

  Examples of the organic pigment or organic dye as the yellow colorant include compounds typified by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

  Examples of the black colorant include carbon black and those prepared by using the above yellow colorant / magenta colorant / cyan colorant to black.

  These colorants can be used alone or in combination and further in the form of a solid solution. The colorant used in the present toner is selected from the viewpoints of hue angle, saturation, brightness, light resistance, OHP transparency, and dispersibility in the toner.

  The colorant is preferably used by adding 1 part by mass or more and 20 parts by mass or less to 100 parts by mass of the polymerizable monomer or binder resin.

  As an example of the dispersion stabilizer used when preparing the aqueous medium, known inorganic and organic dispersion stabilizers can be used.

  Specifically, the following are mentioned as an example of an inorganic dispersion stabilizer. Tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, magnesium carbonate, calcium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina .

Examples of the organic dispersant include the following. Polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose sodium salt, starch.
Commercially available nonionic, anionic and cationic surfactants can also be used. Examples of such surfactants include the following. Sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate.

  As the dispersion stabilizer used in preparing the aqueous medium used in the present toner, an inorganic poorly water-soluble dispersion stabilizer is preferable, and it is preferable to use a poorly water-soluble inorganic dispersion stabilizer that is soluble in acid.

  In the present toner, when a water-insoluble inorganic dispersion stabilizer is used and an aqueous medium is prepared, the amount of these dispersion stabilizers used is 0.2 mass relative to 100 mass parts of the polymerizable monomer. It is preferable that it is at least 2.0 parts by mass. In this toner, it is preferable to adjust the aqueous medium using 300 parts by mass or more and 3000 parts by mass or less of water with respect to 100 parts by mass of the polymerizable monomer composition.

  In the present toner, when preparing an aqueous medium in which the poorly water-soluble inorganic dispersion stabilizer as described above is dispersed, a commercially available dispersion stabilizer may be used as it is. In order to obtain particles of a dispersion stabilizer having a fine uniform particle size, a water-based inorganic dispersion stabilizer may be produced in a liquid medium such as water under high-speed stirring to adjust the aqueous medium. For example, when tricalcium phosphate is used as a dispersion stabilizer, a preferable dispersion stabilizer is obtained by mixing sodium phosphate aqueous solution and calcium chloride aqueous solution under high speed stirring to form tricalcium phosphate fine particles. Can do.

  In the present toner, a charge control agent can be mixed with toner particles and used as necessary. By adding a charge control agent, the charge characteristics can be stabilized, and the optimum triboelectric charge amount can be controlled according to the development system.

  As the charge control agent, a known one can be used, and a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable. Further, when the toner particles are produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous medium is preferable.

  Examples of the charge control agent that control the toner to be negatively charged include the following. Organic metal compounds and chelate compounds are effective, and monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic dicarboxylic acids, oxycarboxylic acids, and dicarboxylic acid-based metal compounds. Other examples include aromatic oxycarboxylic acids, aromatic mono- and polycarboxylic acids and metal salts thereof, anhydrides, esters, and phenol derivatives such as bisphenol. Further examples include urea derivatives, metal-containing salicylic acid compounds, metal-containing naphthoic acid compounds, boron compounds, quaternary ammonium salts, calixarene, and resin charge control agents.

  The present toner can contain these charge control agents singly or in combination of two or more.

  A preferable blending amount of the charge control agent is 0.01 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer or the binder resin. . However, it is not essential to add a charge control agent to the toner, and it is not always necessary to include the charge control agent in the toner by actively utilizing the triboelectric chargeability with the magnetic carrier.

  In order to improve fluidity, inorganic fine powder is added to the toner particles.

  Examples of the inorganic fine powder externally added to the toner particles include silica fine powder, titanium oxide fine powder, alumina fine powder, and double oxide fine powders thereof. The particle size of these inorganic fine powders is preferably 120 nm or less at most.

Examples of the silica fine powder include dry silica or fumed silica produced by vapor phase oxidation of silicon halide, and wet silica produced from water glass. As the inorganic fine powder, dry silica having less silanol groups on the surface and inside of the silica fine powder and less NaO ₂ and SO ₃ ²⁻ is preferable. In addition, the dry silica may be a composite fine powder of known metal oxide produced by using a metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound in the production process.

  The inorganic fine powder is externally added to the toner particles in order to improve the fluidity of the toner and make the toner particles uniformly charged. By hydrophobizing the inorganic fine powder, it is possible to adjust the charge amount of the toner, improve the environmental stability, and improve the characteristics in a high-humidity environment. It is preferable to use it. When the inorganic fine powder added to the toner absorbs moisture, the charge amount as the toner is reduced, and the developability and transferability are easily lowered.

  As treatment agents for the hydrophobic treatment of inorganic fine powder, unmodified silicone varnish, various modified silicone varnishes, unmodified silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, organotitanium Compounds. These treatment agents may be used alone or in combination.

  The measurement of the average particle diameter and the circularity of the prepared toner will be described.

(Measurement of average particle diameter of toner)
The number average particle size of the toner was measured using a Coulter Multisizer (manufactured by Coulter), connected to an interface (manufactured by Nikkiki) that outputs the number distribution and volume distribution, and a PC 9801 personal computer (manufactured by NEC). Measured according to

  Specifically, first, a 1% NaCl aqueous solution was prepared using primary sodium chloride as the electrolyte. As the electrolytic solution, commercially available ISOTON R-11 (manufactured by Coulter Scientific Japan) can also be used. To 100 ml of the electrolytic aqueous solution, 5 mg of a measurement sample (toner) and 0.1 ml of a contamination aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) are added. The electrolyte in which the sample is suspended is dispersed for about 1 minute with an ultrasonic disperser, and the volume and number of toner particles of 2.0 μm or more are measured with the Coulter Multisizer using a 100 μm aperture, and the number average particle diameter is measured. Asked.

(Measurement of average circularity of toner)
The average circularity of the toner was measured by using a flow type particle image measuring device “FPIA-2100 type” (manufactured by Toa Medical Electronics Co., Ltd.) according to the operation manual of the device, and the circularity was obtained.

The circularity can be obtained by (equivalent circle diameter × π / periphery length of particle projection image), and equivalent circle diameter = (particle projection area / π) ^1/2 × 2. Here, the particle projection area is the area of the binarized toner particle image, and the peripheral length of the particle projection image is defined as the length of the contour line obtained by connecting the edge points of the toner particle image. The degree of circularity is an index indicating the degree of unevenness of toner particles. When the toner particles are spherical, the degree of circularity is 1.000. The more complicated the surface shape, the smaller the degree of circularity.

  As a specific measuring method, first, 10 ml of ion-exchanged water from which impure solids are removed in advance is prepared in a container. After adding a surfactant, preferably an alkyl benzene sulfonate, as a dispersant, 0.02 g of a measurement sample is further added and dispersed uniformly. As a means for dispersion, an ultrasonic disperser “Tetora 150 type” (manufactured by Nikka Ki Bios) is used for 2 minutes to obtain a dispersion for measurement. In that case, it cools timely so that the temperature of this dispersion liquid may not become 40 degreeC or more. In order to suppress variation in circularity, the installation environment of the apparatus is controlled at 23 ° C. ± 0.5 ° C. so that the temperature inside the flow type particle image analyzer FPIA-2100 is 26 to 27 ° C. Preferably, autofocus is performed using 2 μm latex particles every 2 hours.

  The concentration of the dispersion is readjusted so that the toner density at the time of measurement is 3000 to 10000 / μl, and 1000 or more toners are measured. After the measurement, using this data, data having an equivalent circle diameter of less than 2 μm is cut, and the average circularity of particles having an equivalent circle diameter (number basis) of 2.0 μm or more is obtained.

  In the present invention, since the transfer property required by the image forming apparatus is achieved, the effect is exhibited by using toner having a circularity of 0.97 or more.

  In this example, toner A having an average particle diameter of 6 μm and a circularity of 0.98 prepared by the above-described manufacturing method was used.

(About photoconductor)
The photoconductors used in Examples and Comparative Examples of the present invention are negatively charged OPC photoconductors, and the following first to fourth functional layers are sequentially arranged from the bottom on a φ30 mm aluminum drum base. It is provided. The first layer is an undercoat layer, and is a conductive layer having a thickness of about 20 μm provided to smooth the surface of an aluminum drum base (hereinafter referred to as an aluminum base) and to prevent the occurrence of moire due to reflection of laser exposure. Is a layer. The second layer is a positive charge injection preventing layer, and serves to prevent the positive charge injected from the aluminum substrate from canceling the negative charge charged on the surface of the photoreceptor, and is made of 10 ⁶ by polyamide resin and methoxymethylated nylon. It is a medium resistance layer with a resistance adjusted to about Ω · cm and a thickness of about 1 μm. The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon receiving laser exposure. The fourth layer is a charge transport layer, which is a P-type semiconductor, in which hydrazone is dispersed in polycarbonate resin or polyarylate resin. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.

  A film having the same composition as the charge transport layer as the outermost layer was formed on a glass plate with an ultrafine hardness meter ENT1100 manufactured by Elionix, and the surface hardness was measured. Using a triangular indenter and measuring with a maximum load of 100 mgf (step interval 10 milliseconds, number of divisions 1000), a displacement of 0.25 μm was observed. It was found that the surface layer was harder than any blade used in Examples and Comparative Examples of the present invention.

(Measurement of micro hardness of toner on blade)
The microhardness measurement in this example was performed using an ultra-microhardness meter ENT1100 manufactured by Elionix Corporation. This device obtains a load-displacement curve by continuously measuring the load applied to the indenter and the indentation depth (that is, the displacement of the sample) when the indenter is pushed into the sample during loading and unloading. From this curve, the microhardness and elastic modulus of the sample are obtained.

  The tip of the used indenter is a flat square of 20 μm × 20 μm. The measurement environment is a temperature of 23 ° C. and a humidity of 45% RH. A piece of the cleaning blade (hereinafter referred to as blade 1) used in this embodiment is placed on a smooth base, and the back surface of the blade is fixed with an adhesive having a high hardness after curing, such as Aron Alpha. The toner used in this example is toner A, and the average particle size is 6 μm. The toner was sprayed with air and sparsely adhered onto the blade. The toner size was measured from the microscopic image of the toner measured before the microhardness measurement, and it was confirmed that the average particle size of the toner A was within ± 10%, that is, between 5.4 μm and 6.6 μm. The maximum load was set to 300 mgf, the step interval was set to 10 milliseconds, the number of divisions (number of measurement data) was set to 1000, and the toner on the blade was measured. This is a process in which after the indenter comes into contact with the toner surface, the maximum load is applied for 10 seconds, the maximum load is held for 1 second, and then unloading is performed for 10 seconds.

  The measurement results in this example are shown in FIG. Although the displacement increases almost linearly as the load is increased at the time of loading, there is an inflection point where the slope of the load versus displacement changes in the middle ((II) in the figure). The state of the blade and the toner at that time is the state of (II) in FIG. 5, which is the same as the state where the toner on the photosensitive drum has entered the blade in the cleaning process (the photosensitive drum is sufficiently more than the toner and the blade). Under hard conditions).

  In the regions (II) to (III) in FIG. 4, the indenter comes to contact not only the toner but also the blade around the toner as shown in FIG. ) To (II), it becomes more difficult to displace. This is the reason why downward convex inflection points occur. Further, the displacement at the inflection point was almost the same as the measured toner particle diameter. If the toner shape is a substantially spherical shape, the toner particle size estimated from the microscopic image before the measurement and the displacement of the inflection point almost coincide.

  As a more specific method of obtaining the inflection point, in the example of FIG. 4, it can be obtained in the form of an intersection of a straight line from 50 mgf to 150 mgf and a straight line from 200 mgf to 300 mgf.

  From the above measurement, the load when the toner was buried in the blade by the indenter was obtained. Since the measurement results vary slightly depending on the toner solid, the same measurement was performed on five toners having a particle diameter within ± 10% of the average particle diameter, and the average was obtained. The average load was 172 mgf.

  Further, five toners having a particle diameter within ± 10% of the average particle diameter were evaluated as to whether or not the toner was plastically deformed when 172 mgf, which was the obtained load, was applied to the toner on the blade.

  Evaluation was performed using a Violet laser microscope VK9500 manufactured by Keyence Corporation. First, the height of the toner on the blade to be measured is measured with VK9500. The objective lens was 150 times and the height measurement step interval was 0.2 μm. After a load of 172 mgf was applied to this toner with a microhardness meter, the height was measured again with a laser microscope, and the toner shape before and after the measurement was as shown in FIG. The toner height is clearly reduced by about 2 μm after the measurement, and it can be seen that the toner base is plastically deformed. The same evaluation was performed on five toners, and it was found that when a load of 172 mgf was applied, plastic deformation occurred in all the toners.

  Factors that change the toner shape before and after the microhardness measurement can occur in addition to plastic deformation. For example, this may be caused by embedding an external additive in the toner base or rolling the toner during measurement. However, considering the particle size of the external additive and the circularity of the toner, the shape change this time is larger than such change, and the toner base is plastically deformed because the flat surface is exposed. It can be clearly determined.

  Further, the circularity of the cross section of the plastically deformed toner is about 0.86, and the circularity of the pulverized toner used in Comparative Example 2 described later is 0.94. If the toner has a degree of circularity, the toner is cleaned well without rolling at the cleaning nip. As a definition of plastic deformation, it is also possible to make it a condition that the film is deformed to a circularity that can be cleaned well.

  When the blade and the toner have such a relationship, when the toner on the photosensitive drum sinks into the cleaning blade, the toner is plastically deformed in the cleaning nip as shown in FIG. 7, so that the toner rotates in the nip. And stable cleaning becomes possible.

  The blade 1 was actually attached to the apparatus, and a durability test was performed using the toner A. When an image having a printing rate of 5% was continuously output, no defective cleaning occurred even when 500,000 sheets were output.

[Example 2]
The cleaning blade used in this example has a hardened layer on the surface layer based on polyurethane resin.

  The polyurethane resin used as the base material is made of polyurethane having a JIS-A hardness of 75 degrees defined by JIS K 6253, so that the blade as a whole is flexible and rich in rubber elasticity. The polyurethane that forms this base material is a product obtained by reacting a polymer polyol, polyisocyanate, and a crosslinking agent. The same as 1 blade.

(Regarding the formation of a hardened surface layer)
A method for forming a hardened surface layer on the molded substrate will be described. The surface hardened layer is formed by reacting an isocyanate compound and a polyurethane resin by impregnating a blade serving as a base material with an isocyanate compound for a predetermined time and then heat-curing.

  The hardened layer does not need to be formed on the entire surface of the blade, and may be formed about 3 mm inside from the edge where the blade contacts the photoreceptor.

  A specific process for forming the hardened layer will be described. As a method for impregnating the blade base material with the isocyanate compound, first, a method in which the temperature is such that the polyisocyanate compound is in a liquid state and the blade member is immersed therein is exemplified. In addition, a method of impregnating a fibrous or porous material with an isocyanate compound and applying it to a blade member may be employed. Further, it may be applied by spraying. Similarly, the temperature of the isocyanate compound after being applied, during and after being immersed in the isocyanate liquid is preferably a temperature at which the isocyanate compound is liquid. In this way, the urethane is impregnated with the isocyanate compound, and after a certain time, the isocyanate compound remaining on the urethane surface is wiped off. Thereafter, the reaction between the impregnated isocyanate compound and the polyurethane resin is allowed to proceed.

  The longer the impregnation time, the thicker the cured layer and the greater the microhardness of the blade surface. If the time for impregnation is short, the cured layer is thin and the microhardness of the blade surface is small. In addition, the degree depends on the type of isocyanate compound used and the type of catalyst. By changing these conditions, blades having different surface microhardnesses can be produced.

  The specific impregnation time of the isocyanate compound is preferably 6 minutes or more and 120 minutes or less. The impregnation temperature is preferably 10 ° C. or higher and 100 ° C. or lower.

  The time for reacting the impregnated isocyanate compound and the polyurethane resin is preferably 5 minutes or longer and 120 minutes or shorter from the viewpoint of reaction efficiency and thermal degradation of the polyurethane resin. The reaction temperature is preferably 30 ° C. or higher and 160 ° C. or lower.

  The isocyanate compound impregnated in the blade has one or more isocyanate groups in the molecule, and those having one isocyanate group can be aliphatic monoisocyanates such as octadecyl isocyanate, aromatic monoisocyanates and the like.

  Those having two or more isocyanate groups are 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), m-phenylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate. 4,4 ′, 4 ″ -triphenylmethane triisocyanate, 2,4 ′, 4 ″ -biphenylmethane triisocyanate, 2,4,4 ″ -diphenylmethane triisocyanate and the like, but are not limited thereto. In addition to these, modified products and multimers having two or more isocyanate groups can be used.

  Of these, aliphatic monoisocyanates with little steric hindrance and MDI with a low molecular weight are preferred from the viewpoint of permeability.

  In order to accelerate the polymerization reaction of the isocyanate compound, the polyurethane resin may be impregnated with a polymerization catalyst of the isocyanate compound in addition to the isocyanate compound.

  As the multimerization catalyst used together with the isocyanate compound, a quaternary ammonium salt, a carboxylate or the like can be used. Examples of the quaternary ammonium salt include DABCO TMR catalyst, NCX211 and NCX212 (both manufactured by Sankyo Air Products). Although these polymerization catalysts contain a hydroxyl group, the function of the polymerization catalyst is to polymerize the isocyanate compound, and does not participate in the crosslinked structure itself, and is different from the active hydrogen compound. Examples of the carboxylate include potassium acetate and potassium octylate such as P-15 and k-15 manufactured by Sankyo Air Products.

  Since these polymerization catalysts have a very high viscosity or are solid at the time of impregnation, it is preferable that they are dissolved in a solvent in advance and then added to an isocyanate compound and impregnated in a polyurethane resin. As the solvent, those having no active hydrogen capable of reacting with an isocyanate compound are used. Specifically, MEK, toluene, tetrahydrofuran, ethyl acetate and the like can be raised. The dilution ratio is preferably 1.5 to 15 times in terms of mass ratio. Moreover, the addition rate of the polymerization catalyst with respect to the isocyanate compound is preferably 1 ppm by mass or more and 1000 ppm by mass or less at the final concentration. In addition, since a polymerization reaction is started when an isocyanate compound and a polymerization catalyst are mixed, the mixing of the isocyanate compound and the polymerization catalyst is preferably performed immediately before impregnation of the isocyanate compound.

  The surface hardness of the created blade was measured with an ultrafine hardness meter ENT1100 manufactured by Elionix. When a maximum load of 100 mgf (step interval: 10 milliseconds, number of divisions: 1000) was measured using a triangular indenter (opposite angle of 115 °), a displacement of 2 μm was observed.

  The blade formed in this way is used in this embodiment, and this is called blade 2.

  The blade 2 has only a hard surface, and the blade as a whole is in soft contact with the photosensitive drum, so that the allowable range of mechanical tolerances is wider than that of the blade 1. As shown in FIG. 13, in the relationship between the amount of penetration of the blade into the photosensitive drum and the load, the inclination of the blade 2 is smaller than the inclination of the blade 1, and the fluctuation of the load is small relative to the fluctuation of the mechanical penetration amount. It can be said that a more stable contact state is realized.

  In this example, the same toner A as in Example 1 was used as the toner, and the blade 2 was used as a cleaning blade.

  In the same manner as in Example 1, the microhardness of the toner on the blade was measured. A downward convex inflection point could be confirmed, and the average load at the inflection point was 182 mgf. When five toners having an average particle diameter of ± 10% were selected and a load of 182 mgf was applied to the toner on the blade, it was confirmed that all the toners were plastically deformed.

  The toner after plastic deformation still has a circularity of about 0.86, and good cleaning properties are promised.

  It can be seen that the blade 2 has a structure in which the blade base layer is soft and the blade surface layer is hard, so that the toner that has entered the cleaning nip can be plastically deformed while maintaining stable contact with the photosensitive drum. The blade 2 was actually attached to the apparatus, and a durability test was performed using the toner A. When an image having a printing rate of 5% was continuously output, no defective cleaning occurred even when 500,000 sheets were output.

[Comparative Example 1]
The blade that is the base material of the blade 2 created in Example 2 is referred to as a blade 3. It is a polyurethane having a JIS-A hardness of 75 degrees as defined by JIS K 6253, and the blade as a whole is flexible and rich in rubber elasticity. In this comparative example, the toner A was used as the toner, and the blade 3 was used as the cleaning blade.

  As a result of the microhardness measurement, a downward convex inflection point was confirmed, and the average load at the inflection point was 64 mgf. When five toners with an average particle size of ± 10% are selected and a load of 64 mgf is applied to the toner on the blade, it is confirmed that there is no change in the shape of all the toners, even if they are within the measurement error range. It was. Naturally, there is no change in the toner circularity. An example of the shape measurement result is shown in FIG. In such a relationship between the toner and the blade, as shown in FIG. 6, since the toner keeps a spherical shape when the toner enters the cleaning nip, the toner rolls and slips through the nip.

  The blade 2 was actually attached to the apparatus, and a durability test was performed using the toner A. When an image with a printing rate of 5% was continuously output and about 10,000 sheets were output, a cleaning failure due to toner slipping occurred.

[Example 3]
In this example, toner B having an average particle diameter of 6 μm and an average circularity of 0.98 was used, and the blade 3 was used as a cleaning blade. The basic preparation method of the toner B is the same as that of the toner A. However, the toner B is more easily plastically deformed than the toner A by changing the addition amount of the low molecular weight polymer, the polar resin, and the crosslinking agent.

  As a result of measuring the micro hardness of the toner on the blade, a downward convex inflection point was confirmed, and the average load at the inflection point was 65 mgf. When five toners having an average particle size of ± 10% were selected and a load of 65 mgf was applied to the toner on the blade, it was confirmed that all the toners were plastically deformed.

  When the shape of the toner after plastic deformation was measured, the amount of deformation was about 1.5 μm, and when converted to circularity, it was about 0.88.

  The blade 2 was actually attached to the apparatus, and a durability test was performed using the toner B. When an image having a printing rate of 5% was continuously output, no defective cleaning occurred even when 500,000 sheets were output.

[Comparative Example 2]
In this comparative example, pulverized toner having an average particle diameter of 6 μm and an average circularity of 0.94 was used, and the blade 3 was used as a cleaning blade.

  As a result of measuring the microhardness of the toner on the blade, a downward convex inflection point was confirmed, and the average load at the inflection point was 70 mgf. When five toners having an average particle diameter of ± 10% were selected and a load of 65 mgf was applied to the toner on the blade, the shape of the toner hardly changed before and after the measurement.

  The blade 3 was actually attached to the apparatus, and a durability test was performed using the pulverized toner. When an image having a printing rate of 5% was continuously output, no defective cleaning occurred even when 500,000 sheets were output.

  Incidentally, when the behavior of this toner in the cleaning nip is observed with the visualization device of FIG. 8, it can be seen that the toner in the vicinity of the nip hardly moves, and the toner sandwiched in the nip is cleaned together with the blade.

  The durability results of Examples 1 to 3 and the comparative example are summarized in Table 1. It can be seen that good durability results were obtained in the examples of the present invention. Since the pulverized toner was used in Comparative Example 2, the durability result was good, but the transferability was sacrificed.

  Further, in Example 3, the scope of the present invention is set by using a toner that is easily plastically deformed. However, it is also conceivable that an adverse effect is caused by softening the toner shell. For example, when the toner is continuously agitated and the toner is continuously stirred, the external additive is embedded in the toner base and loses its function. However, if the toner shell is soft, this phenomenon is likely to occur. In addition, a toner having a soft shell generally has a low glass transition point and has a characteristic of being easily deteriorated by heat. Therefore, if the toner is left standing at a high temperature, the characteristic of the toner may be easily deteriorated. From such a viewpoint, as in the first and second embodiments, the means for matching the material of the blade to the application range of the present invention is more preferable for the toner having excellent characteristics.

  In this embodiment, only the verification for the toner having an average particle size in the particle size distribution of the toner is described. However, the toner on the blade is very small with respect to the toner deviating from the average particle size (large or small). Even if the hardness measurement was performed, the presence or absence of the occurrence of plastic deformation was not covered. A small toner has a small inflection point load, and a large toner has a large curvature, but a small toner has a large curvature with respect to an indenter and a blade, and a large toner has a small curvature. Difficult to plastically deform. As a result, as long as the material of the toner shell does not have a large particle size dependency, the presence or absence of the occurrence of plastic deformation has little effect.

Durability results of Examples 1 to 3 and Comparative Example

100 Image forming apparatus 1 Photosensitive drum 2 Charging roller

Claims (4)

  In the image forming apparatus having a cleaning unit for cleaning the residual toner remaining on the image carrier after the toner image formed on the image carrier is transferred to the recording material, the cleaning unit is disposed on the image carrier. A cleaning blade that contacts the surface of the image carrier, the microhardness of the surface of the image carrier is greater than the microhardness of the surface of the blade, the average circularity of the toner is 0.97 or more, and the contact pressure of the cleaning blade is The displacement amount-load curve obtained when the toner and the blade are integrally deformed by pressure in a micro hardness tester is 20 g / cm or more and 70 g / cm or less. The displacement amount a (μm) is an inflection point. An image forming apparatus, wherein the toner is plastically deformed at a displacement amount a. The image forming apparatus according to claim 1, wherein the toner has a core-shell structure. The image forming apparatus according to claim 1, wherein the cleaning blade is subjected to a process having a higher surface hardness than the inside. The image forming apparatus according to claim 1, wherein the cleaning blade is made of polyurethane, and a surface layer thereof is treated with an isocyanate.