JP5147578B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material such as a sheet, and more particularly to a developing device and a process cartridge applied to these apparatuses. is there.

  Conventionally, in a developing device of a non-magnetic one-component developing system, the surface of the developing roller is intentionally roughened for the purpose of carrying and transporting toner as a developer in a developing roller as a developer carrying member. Is generally provided.

  In recent years, in order to cope with high image quality and energy saving, the toner has been made smaller in particle size and lower in melting point.

  However, as a common problem in these toners, image degradation caused by so-called toner degradation, in which the toner is stressed in the developing portion and the external additive is embedded in or released from the toner base, is a problem. Yes. In particular, when the surface of the developing roller is large, problems such as filming, fogging, density unevenness, and roughness may occur when the developing device is used continuously for a long period of time.

To solve this problem, it has been proposed to appropriately reduce the surface roughness of the developing roller (see Patent Document 1).
Japanese Patent Application Laid-Open No. 09-127783

  However, when the surface roughness of the developing roller is reduced, so-called blade fusion, in which deposits such as fine powder and free external additives that adhere to the regulating blade as the developer regulating member adhere firmly, is very likely to occur. There was a concern that it would end up.

  The cause of blade fusion is considered as follows. That is, deposits such as fine powder and free external additives temporarily adhering to the surface of the regulating blade are rubbed against the regulating blade at a portion where the developing roller has a high roughness in a conventional developing roller having a relatively large surface roughness. This is thought to be because the effect of rubbing and peeling off became smaller.

  The present invention has been made in view of the circumstances as described above, and suppresses blade fusion even with a developing roller having a low surface roughness, thereby preventing filming, fogging, The object is to prevent the occurrence of problems such as density unevenness and roughness.

In order to achieve the above object, the present invention provides:
Developer,
A developer carrying member carrying the developer;
A developer regulating member that is made of a conductive material and regulates the developer on the developer carrying member;
Regulation bias applying means for applying a bias to the developer regulating member;
Developing bias applying means for applying a bias Vdev to the developer carrying member;
In a developing apparatus of a non-magnetic one-component development system having
The developer carrier is composed of a base layer made of a rubber-like elastic body and a surface layer made of a SiOx thin film,
The regulation bias applying means applies an AC voltage to the developer regulating member,
The surface roughness of the developer carrier is Ra [μm] ,
Of the voltages applied to the developer regulating member by the regulating bias applying means, the maximum voltage on the charging polarity side of the developer is Vb_H, and the minimum voltage is Vb_L.
When the rotation speed of the surface of the developer carrying member is v [m / sec] and the application time of the minimum voltage Vb_L applied to the developer regulating member by the regulating bias applying unit is Tl [sec],
0.05 ≦ Ra ≦ 0.2,
| Vdev−Vb_L | ≦ | Vdev−Vb_H |,
100V ≦ | Vb_H−Vb_L | ≦ | Vb_H− Vdev | ≦ 500V,
And,
30 × 10 ⁻⁶ / v ≦ Tl ≦ 120 × 10 ⁻⁶ / v
It is characterized by satisfying.

  According to the present invention, even with a developing roller having a small surface roughness, blade fusion is suppressed, thereby preventing problems such as filming, fogging, density unevenness, and roughness caused by toner deterioration. It becomes possible to do.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings and examples. Here, the following embodiments will be described with reference to image forming apparatuses applicable to all experimental examples including examples and comparative examples. Note that the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the following embodiments do not limit the scope of the present invention to these unless otherwise specified.

[Image forming apparatus having non-magnetic one-component developing device]
FIG. 2 is a schematic sectional view of the image forming apparatus 1 according to the embodiment of the present invention. In the present embodiment, a printer using electrophotographic technology will be described as an example of an image forming apparatus.

  The image forming apparatus 1 has a process cartridge 2 and is detachably disposed on the image forming apparatus main body. The process cartridge 2 includes a photosensitive drum (photosensitive member) 4 as an image carrier, a charging roller 3 as a charging device, a cleaning blade 9 as a cleaning device, and a developing device 100 that develops the photosensitive drum 4. included. Bias supplied to various process parts is applied through a process cartridge 2 from a high voltage power source (not shown).

  Hereinafter, an image forming process in the image forming apparatus 1 will be described.

  The recording material 6 fed from the feeding unit is conveyed to the transfer unit and the fixing unit, and then discharged to the discharge unit 7.

  In the transfer portion, an image of toner 101 as a developer formed on the photosensitive drum 4 is transferred onto the recording material. In the present exemplary embodiment, so-called negative polarity toner, which is a negative polarity toner 101, is used, so that the toner 101 is attracted from the photosensitive drum 4 to the transfer roller 5 disposed facing the photosensitive drum 4. Apply a positive bias.

  The toner image on the photosensitive drum attracted to the bias of the transfer roller via the recording material 6 adheres on the recording material 6. The so-called transfer residual toner remaining on the photosensitive drum 4 without being transferred is peeled off from the photosensitive drum 4 by a cleaning blade 9 disposed on the surface of the photosensitive drum 4 and collected in a waste toner container 8. .

  Next, the recording material 6 onto which the toner image has been transferred is conveyed to the fixing device 10. In the fixing device 10, the recording material onto which the toner image is transferred is sandwiched between a pair of rollers whose temperature is adjusted to a predetermined temperature in the fixing nip portion, and receives heat and pressure simultaneously. As a result, the toner 101 melts. At this time, for example, when paper is used as the recording material, the melted toner is entangled with the surface of the paper fiber. Then, after passing through the fixing nip portion, the toner 101 is collected and fixed on the recording material as it is cooled by the outside air.

  The recording material 6 on which the toner image is fixed is discharged to the discharge unit 7, where one image forming process is completed. In the case where images are continuously formed, the above process is sequentially repeated.

[Process cartridge]
The process cartridge 2 shown in FIG. 2 includes a developing device 100, a photosensitive drum 4, a charging roller 3, and a cleaning blade 9.

  The photosensitive drum 4 is composed of a semiconductor thin film of about 20 to 25 μm formed on the base layer of the aluminum base tube. The charging roller 3 is pressed on the surface of the photosensitive drum 4 and is driven to rotate. In order to charge the photosensitive drum 4 to a uniform potential, a bias is applied to the charging roller 3 to generate a discharge due to a potential difference from the conductive base layer of the photosensitive drum 4.

  The charging roller 3 is provided with a conductive rubber layer around the metal core, and its surface is chemically treated so that the external additive of the toner 101 that has passed through the cleaning blade 9 is difficult to adhere.

  The portion charged by the charging roller 3 on the photosensitive drum enters the exposure portion by being rotationally driven. In the exposure unit, the surface potential of the photosensitive drum 4 is partially lowered by exposure from the exposure device 11, and an electrostatic latent image of 600 dpi (dot / inch) is sequentially formed.

  The exposure apparatus 11 uses a semiconductor laser as a light source, and scans the photosensitive drum by reflecting the laser beam to a polygon mirror that rotates at high speed.

  The cleaning blade 9 is composed of an elastic member and its supporting metal plate. The elastic member is made of rubber or resin such as hard urethane or silicon, and is in contact with the photosensitive drum 4 at a predetermined angle and pressure. The cleaning blade 9 has a function of peeling off the transfer residual toner from the photosensitive drum 4 and storing it in the waste toner container 8.

[Developer]
FIG. 1 is a schematic cross-sectional view of a non-magnetic one-component developing type developing apparatus in the present embodiment.

  The function of the developing device 100 is to visualize the electrostatic latent image formed on the photosensitive drum 4 as a toner image by the charging and exposure process.

  The developing device 100 includes a toner container portion 102 filled with the toner 101, and agitates the toner 101 while being transported to the vicinity of the supply roller 104 as a developer supply member by a rotationally driven stirring blade 103 as a stirring member. As a member for forming a latent image on the photosensitive drum 4 with the toner 101 conveyed by the stirring blade 103, a supply roller 104, a regulating blade 105 as a developer regulating member, and a developing roller as a developer carrying member 106.

[toner]
Hereinafter, the toner 101 applicable to the present embodiment will be described.

  The toner 101 is basically charged by being rubbed by the regulating blade 105, and the movement can be controlled by an electric field. That is, the toner 101 is regulated by the regulation blade 105, so that it becomes a uniform toner layer and has a charge, and the latent image can be developed by the action of the electric field between the photosensitive drum 4 and the developing roller 106 in the developing unit. It becomes.

The toner 101 used in the developing device of the non-magnetic one-component developing system is roughly composed of a toner 101 base material and an external additive. The base material of the toner 101 is prepared by a method such as a suspension polymerization method, an emulsion polymerization method, or a pulverization method using the materials (1), (2), (3), and (4) exemplified below.
(1) Thermoplastic resin (binder): styrene acrylic polymer, polystyrene, polyester, polyvinyl bratil, polyamide resin, polyethylene, epoxy resin, and the like. Alternatively, a mixture of the above.
(2) Pigment (colorant): Black is carbon black, benzine derivative for yellow, rhodamine B lake for magenta, copper phthalocyanine, sulfonamide derivative for cyan.
(3) Charge control agent: In the case of a negative toner, an electron-accepting organic complex, chlorinated paraffin, chlorinated polyester, excess base polyester, chlorinated copper phthalocyanine, and the like. In the case of a positive toner, nigrosine electron donating dyes, alkoxylated amines, alkylamides, chelates, pigments, quaternary ammonium salts, and the like.
(4) Filler: calcium carbonate, clay, talc, pigment, etc.

External addition of the external additive to the toner base is performed by stirring, heat treatment or the like using the external additive exemplified below.
External additives: silica (hydrophobic, colloidal, etc.), metal oxides (titanium oxide, zinc oxide, tin oxide), metal complexes, charge control agents, etc.

  Further, as the typical physical property values relating to the toner 101, the following are used.

  The volume average particle diameter of the toner 101 is, for example, about 4 to 15 μm when measured with a Coulter Counter TA-II type manufactured by Beckman Coulter, Inc.

  The measuring device is connected to a volume average particle size and number average particle size output device and a personal computer. In the measurement using a Coulter counter, first, several g of the toner 101 to be measured is dispersed in a 1% aqueous sodium chloride solution, and a few drops of a surfactant are added. A good dispersion state can be obtained by using an ultrasonic cleaner. Thereafter, the particle size of the toner 101 is measured using a 100 μm aperture, and then processed by a personal computer to calculate the volume average particle size and the particle size distribution.

Regarding the shape of the toner 101, the value of the shape factor SF-1 measured by the image analyzer is preferably 100 to 140, and the value of the shape factor SF-2 is preferably 100 to 130. Further, by satisfying the above conditions and setting the value of (SF-2) / (SF-1) to 1.0 or less, not only the characteristics of the toner 101 but also matching with the image analysis apparatus is extremely good. It will be something.

The coefficients SF-1 and SF-2 are parameters defined by values obtained as follows. First, using a FE-SEM (S-800) manufactured by Hitachi, Ltd., 100 toner images enlarged at a magnification of 500 times are randomly extracted. Then, the image information is introduced into the image analysis apparatus (Luxex 3) manufactured by Nicole via the interface and analyzed, and the coefficients SF-1 and SF-2 are defined by values obtained by calculating from the following equations. .
SF-1 = {(MXLNG) ² / AREA} × (π / 4) × 100
SF-2 = {(PERI) ² / AREA} × (1 / 4π) × 100
AREA: toner projected area MXLNG: absolute maximum length PERI: circumference

  The toner shape factor SF-1 indicates the degree of roundness of the toner particles, and the larger the value, the more spherical the shape becomes irregular. SF-2 indicates the degree of unevenness of the toner particles, and the larger the value, the more prominent the unevenness of the toner surface. In particular, the use of toner having SF-1 of 100 to 140 and SF-2 of 100 to 130 in terms of transferability and image quality may raise the effect of this embodiment.

Further, when the mass per unit area of the toner layer after passing through the developer regulating member is M / S [mg / cm ² ], the M / S is about 0.2 to 0.8 [mg / cm ² ]. preferable. In this embodiment, the negative toner is assumed.

[Regulating blade]
Below, the control blade 105 applicable to this embodiment is demonstrated.

  The function of the regulating blade 105 is to regulate the toner 101 (layer thickness (amount) thereof) on the developing roller 106 (on the developer carrying member) and to frictionally charge the toner 101 to achieve uniform toner coating layer and development. The necessary charge is imparted to the toner 101.

  The regulating blade 105 is attached to the regulating blade support sheet metal 110. As the material of the regulating blade support sheet metal 110, stainless steel having a thickness of about 1 mm is preferable. In particular, when a voltage is applied, a conductive path from the power source to the regulation blade 105 can be easily created by using the conductive regulation blade support sheet metal 110. The material of the regulating blade 105 is preferably an elastic member such as stainless steel, phosphor bronze, resin, or rubber.

  In the present embodiment, a conductive material is used for the regulation blade 105 because a bias is applied by a power source Vb as regulation bias application means. In the regulation blade 105 in the present embodiment, by using a metal material, stable conductivity can be ensured even if the temperature and humidity change.

[Supply roller]
Below, the supply roller 104 applicable to this embodiment is demonstrated.

The function of the supply roller 104 is to convey and supply the toner 101 to the surface of the developing roller 106 and to peel off the returned toner 101 without being developed on the surface of the developing roller 106. The supply roller 104 is preferably brought into contact with the developing roller 106 with an intrusion amount of about 0 to 3 mm and is driven to rotate in the counter direction with respect to the developing roller 106 as indicated by an arrow in FIG.

  The supply roller 104 includes a cored bar and a sponge layer provided around the cored bar. The material of the metal core is preferably a material that can withstand a certain load during rotational driving, such as metal (stainless steel, iron, aluminum, brass, etc.), plastic, ceramics, and the like.

  The sponge layer is preferably made of foamed urethane, silicon or the like, and the surface foam cell diameter is preferably about 50 to 1000 μm. If necessary, a conductive agent or carbon may be mixed to provide conductivity and a bias may be applied. Further, the sponge layer may be not only a single layer but also two or three layers.

  As the physical properties of the supply roller 104, the hardness is set to an appropriate hardness in consideration of the amount of penetration into the developing roller 106 and the difference in outer diameter. Further, the resistance value needs to be adjusted to a resistance value as necessary when a bias is applied.

[Development roller]
Hereinafter, the developing roller 106 of this embodiment will be described.

  The toner 101 supplied onto the developing roller 106 by the supply roller 104 enters the restricting portion that is a contact portion between the developing roller and the restricting blade by the rotation of the developing roller 106, and about 1 to 3 layers by the restricting blade 105. To a uniform toner layer. At the time of toner regulation, the toner 101 is rubbed between the regulation blade 105 and the developing roller 106, and thus can have a charge.

  The uniform toner layer on the developing roller 106 formed by the regulating blade 105 develops the electrostatic latent image on the photosensitive drum 4 in the developing unit. In the contact development method, the developing roller 106 rotates with a peripheral speed ratio of about 1.1 to 1.6 times with respect to the photosensitive drum 4. Further, a toner 101 having a charge on the developing roller is applied to the developing roller 106 by applying a potential having a value between the potentials of the exposed portion and the non-exposed portion on the photosensitive drum 4 from the power source Va. Can be transferred onto the photosensitive drum 4 to develop the latent image. Here, the power source Va corresponds to a developing bias applying unit.

  The developing roller 106 is composed of a base layer composed of one or more rubber-like elastic bodies having appropriate conductivity around a core bar made of metal such as stainless steel, and a surface layer formed of a SiOx film. Has been. The rubber-like elastic body (rubber material) is a commonly used rubber such as silicon rubber, urethane rubber, acrylic rubber, natural rubber, and EPDM (ethylene propylene diene rubber). The resistance value of the base layer can be obtained by dispersing carbon, carbon resin particles, metal particles, an ionic conductive agent, or the like.

The resistance value of the developing roller 106 is preferably 2 × 10 ^{4 to} 5 × 10 ⁸ Ω · cm. Below this range, the current flowing through the elastic layer increases and the required electric capacity increases. On the other hand, if it exceeds this range, the current flowing during development tends to be hindered.

  As the surface roughness in this embodiment, an arithmetic average roughness Ra that is an index of the surface roughness of the developing roller 106 is used. And the measurement of arithmetic average roughness Ra used surface roughness tester SE-30 by the Kosaka laboratory based on JISB0601. Three measurement points are measured in the circumferential direction at three points, that is, a portion near the left and right ends in the rotation axis direction (hereinafter referred to as the longitudinal direction) of the developing roller 106, and an average value of a total of nine points is measured in this embodiment. Surface roughness.

The hardness of the developing roller 106 in this embodiment is measured by the Japan Rubber Association standard SRIS0.
This was measured using an Asker C-type spring rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with 101. The measured value is taken as 30 seconds after the hardness meter is brought into contact with the developing roller 106 left at room temperature and normal humidity (23 ° C., 55% RH) for 12 hours or more with a force of 10 N. The hardness is preferably 40 to 75 ° so that the nip portion formed by pressing the regulating blade 105 against the developing roller 106 stably exists in the longitudinal direction. In the case of the contact development method, it is necessary to adjust the hardness according to the contact state with the photosensitive drum.

  In Examples and Comparative Examples described later, as the surface layer of the developing roller 106, a (SiOx) thin film layer and a urethane resin layer mainly containing silicon oxide containing carbon atoms are used. The SiOx layer is a base layer of the developing roller 106 by a dry method such as a chemical vapor deposition (CVD) method, a physical vapor deposition (PVD) method, or vacuum deposition, or a wet method such as dip coating, spray coating, or roll coating. Formed on top. Specific examples of the PVD method include sputtering and ion plating. Further, specific examples of the CVD method include plasma CVD, thermal CVD, and laser CVD.

  The SiOx film in the present embodiment was formed by the following method by plasma CVD.

  A roller having only a base layer, in which a core metal is coated with EPDM rubber as a base layer, is placed in a vacuum chamber, and a plate electrode is placed in close proximity to the roller. Thereafter, the chamber is filled with a gasified organosilicic compound serving as a source gas for the SiOx film and, if necessary, an inert gas, an oxidizing gas, or the like. Then, high-frequency power is supplied between the flat plate electrodes while rotating the roller having only the base layer to generate plasma, and source gas molecules grow on the surface of the base layer to form a surface layer film. It should be noted that the thickness and composition of the SiOx film formed in this way can be changed by parameters such as the composition of the source gas, the pressure concentration in the chamber of the source gas, and the plasma irradiation time.

  If the composition ratio of SiO and SiC is different, the physical properties change, but a characteristic change is a change in hardness. Specifically, when the composition ratio is biased toward SiO alone or SiC alone, the SiOx film tends to be hard and loses flexibility, and problems such as cracking are likely to occur. In the present embodiment, it has been confirmed that the above-described problems such as cracking do not occur within the ranges described below for the composition ratio and the film thickness.

  For measurement of the composition ratio, an X-ray photoelectron spectrometer “Quantum 2000” (manufactured by ULVAC-PHI Co., Ltd.) was used. Then, by using AlKα as the X-ray source, the binding energy of the Si 2p orbit and O and C 1s orbits on the surface of the developing roller are measured, and the abundance ratio of each atom is calculated from each peak value (O / The composition ratio of Si) and (C / Si) was determined.

  Further, the thickness of the formed SiOx film was measured at three locations at equal intervals from the end in the longitudinal direction of the developing roller 106 using a thin film measuring apparatus “F20-EXR” (trade name, manufactured by FILMETRICS). It is an average of the values obtained by measuring a total of nine places at three equal intervals in the direction.

(Operation of this embodiment)
Below, the effect | action of this embodiment is demonstrated using FIG.

  In this embodiment, the developing roller 106 having a SiOx film characterized by a high hardness as a material is provided on the surface of an elastic roller made of a rubber material base layer, and the bias applied to the regulating blade 105 is varied. It is characterized by.

As a result, even with a developing device using a developing roller having a small surface roughness that is likely to cause fusion of fine powder and external additives to the regulating blade 105, the above-mentioned problem is maintained while maintaining the effect of reducing the load on the toner 101. Can be suppressed. Hereinafter, the fusion of fine powder and external additives to the regulating blade 105 is referred to as blade fusion.

  FIG. 3 is an enlarged schematic view of a nip portion (regulation blade nip) formed by the developing roller 106 and the regulation blade 105, and is a schematic cross-sectional view showing a state in which a variation bias in the nip portion acts on the toner. 3A shows the toner coating by the normal regulating blade 105, whereas in FIG. 3B, the regulating blade bias is instantaneously changed, so that the toner 101 is clogged at the entrance of the nip portion, and the surface of the developing roller. It shows a state where the surface of the regulating blade is rubbed directly. Note that the arrows shown in FIGS. 3A and 3B indicate the rotation direction of the developing roller 106.

  In order to create the state shown in FIG. 3B, the potential of the regulating blade 105 is set higher than the potential of the developing roller 106 on the polarity side of the toner 101 (the state of FIG. 3A), and from there The potential of the regulating blade 105 may be changed to the potential of the developing roller 106.

  When the potential of the regulating blade 105 is high, the toner 101 passes through the nip portion so as to be pressed against the developing roller 106, and thus the amount of toner 101 passing through the regulating blade is large. If the potential of the regulating blade 105 is suddenly lowered from this state, the force that the toner 101 is pressed against the developing roller 106 becomes weak, so that the amount that can flow in is limited. If this potential is maintained, the flow becomes stagnant at the nip entrance. , Toner coating blanks.

  The generation mechanism of blade fusion is closely related to the surface of the developing roller.

  When the surface roughness is rough, there is a high probability that a portion having a high roughness when viewed from the developing roller base layer directly rubs against the regulating blade 105 without the toner 101 in the nip portion. For this reason, even if there is a deposit on the regulation blade 105, it can be peeled off with a strong local pressure.

  However, the toner 101 in the highly rough portion is likely to be locally subjected to the conveying force of the developing roller 106, causing toner deterioration.

  Thus, it has been found that the stress on the toner 101 is reduced if the surface roughness is suppressed and the mirror surface is used. However, when the surface roughness is suppressed to a mirror surface, the toner deterioration can be suppressed, but as described above, it is difficult to peel off the adhered matter. For this reason, what is initially attached becomes firmly attached by heat or rubbing due to toner regulation to become a fused product.

  The SiOx film is a hard material because the toner 101 has high releasability and is closer to glass than the surface of rubber or resin. For this reason, as shown in FIG. 3B, when rubbing directly with the regulating blade 105 without using the toner 101, a very high abrasiveness is exhibited even with a slight roughness, and fine powders and external additives adhered to the regulating blade surface. It is thought to scrape off.

  On the other hand, for example, when the developing roller 106 having a resin film such as urethane formed on the surface layer is used, the hardness when viewed from a microscopic viewpoint of the film is smaller than that of the SiOx film. There is a concern that a sufficient stripping effect cannot be exhibited.

  Further, unlike the SiOx film, when the surface is a resin or rubber material surface, there is tackiness, so that the toner 101 tends to remain on the surface of the developing roller even when a variable bias that strongly restricts the toner 101 is applied.

  Using a developing roller formed with a urethane resin film as the surface layer, the same examination was performed with the same development configuration as in the following experimental example. At least when the surface roughness Ra was 0.2 μm or less, blade fusion occurred. Was. That is, it is difficult to suppress the occurrence of blade fusion with a conventional resin film such as urethane.

<< Experimental example >>
Hereinafter, experimental examples for verifying differences between examples and comparative examples described later will be described.

  There are five developing rollers A to E used in the experiment, each having a surface layer with a different roughness.

  Table 1 shows the surface roughness of the developing rollers A to E. All of these five were made to have an outer shape of φ12 mm, and the base layer was made of EPDM rubber material. The surface roughness was made larger than φ12 mm, which is the target outer diameter of the EPDM base layer, and then the polishing conditions of the polishing machine were changed to create a surface roughness within the range of Ra 0.02 to 0.3 μm.

  Martens hardness and film thickness were used to confirm the physical properties of the surface layer of each developing roller. One of the points of this embodiment is to use a hard and thin material for the surface layer while maintaining the hardness of the entire roller including the base layer in the above-described Asker C-type hardness measurement. Although it is generally difficult to measure the hardness of a thin film of nano to micron order (particularly, the hardness of the material itself as in this embodiment), it is considered that it can be roughly grasped by the Martens hardness and thickness.

Martens hardness is a value based on ISO14577, and is a physical property value obtained by pushing into an object to be measured while applying a load to an indenter,
(Test load) / (Surface area of indenter under test load) [N / mm ² ]
As required.

  The Martens hardness can be measured using an ultra micro hardness test system Picodenter HM500 (trade name, manufactured by Fisher Instruments Co., Ltd.). In this measuring device, a square pyramid indenter or a triangular pyramid indenter is pushed into a measurement object while applying a predetermined relatively small test load, and when the predetermined indentation depth is reached, the indenter is removed from the indentation depth. The surface area in contact is obtained, and the Martens hardness is obtained from the above formula. That is, when the indenter is pushed into the measurement object under the constant load measurement condition, the stress at that time with respect to the pushed-in depth is defined as Martens hardness.

In the present embodiment, the measurement was performed by pressing the square pyramid-shaped indenter to a depth of 0.8 μm from the surface of the developing roller in a direction perpendicular to the surface at a constant load application speed (1 mN / mm ² / sec). The measurement points were measured at three points, which are positions obtained by dividing the longitudinal direction of the developing roller 106 into four equal parts, and the arithmetic average value was taken as the Martens hardness of the developing roller surface.

  The SiOx film thickness of the developing roller surface layer was set to about 1.75 μm in the developing rollers A to E.

  This is because the SiOx film having a composition ratio (O / Si) of 1.00 or more and 1.95 or less and a composition ratio (C / Si) of 0.05 or more and 1.00 or less is less than 5 μm. This is because the following problems were confirmed when the thickness was increased. That is, it was confirmed that cracking and peeling occurred without being able to follow the flexible deformation of the rubber elastic body when it was set in the developing device. On the other hand, if the thickness is 0.05 μm or less, uniform coating becomes difficult, and problems such as oil component seepage from the base layer are likely to occur. Here, in the SiOx film, the composition ratio (O / Si) is 1.00 or more and 1.95 or less, and the composition ratio (C / Si) is 0.05 or more and 1.00 or less. The thickness is preferably 0.05 μm or more and 5 μm or less.

  Here, the Martens hardness on the surface of the developing roller before forming the thin film described above is H1, and the Martens hardness in a state where the SiOx film as the surface layer is formed on the base layer is H2. In this case, the surface hardness of the developing rollers A to E used in this experimental example was about 2.9 [N / mm] for H1 and about 1.2 [N / mm] for H2. Although the SiOx film was very thin, a clear difference was found in the Martens hardness.

  On the other hand, the hardness by the Asker C-type hardness meter indicating the hardness of the entire developing roller was 63 ° with the developing rollers A to E, regardless of whether the SiOx film was formed or not.

  Table 2 shows the AC bias potential and frequency applied to the developing roller 106 and the regulating blade 105.

  Although the fluctuation bias of the regulation blade 105 does not necessarily have a rectangular waveform, it is easy to implement. Therefore, in this embodiment, a rectangular AC bias with a duty of 50% is used as the fluctuation bias. Therefore, half of the reciprocal of the value of the frequency f is the application time Tl of the minimum voltage Vb_L applied to the regulating blade 105 in this embodiment.

In this experimental example, the frequency was fixed at 1200 Hz. In Table 2, the potential of the developing roller is the bias Vdev. In addition, among the voltages applied to the regulating blade 105, the maximum voltage and the minimum voltage on the charging polarity side of the toner 101 are Vb_H and Vb_L, respectively, and the potential difference corresponding to the amplitude of fluctuation is | Vb_H−Vb_L |. Also, the potential difference applied between the developing roller 106 and the regulating blade 105 was | Vb_H− Vdev |.

  FIG. 4 is a diagram showing the relative potential relationship of each bias in the present embodiment. FIG. 5 is a diagram showing a relative potential relationship of each bias in the prior art.

The biases A to D have a potential relationship as shown in FIG. Since the bias E has an amplitude of 0, only the DC bias is applied. The bias F is set such that the regulating blade potential is lower than the developing roller potential, that is, on the side opposite to the polarity of the toner 101, and has a potential relationship as shown in FIG.

  A durability experiment in a normal environment (temperature 24 ° C./humidity 50%) was performed by combining each developing roller shown in Table 1 and each bias shown in Table 2.

  The variable bias was applied to the regulating blade 105 whenever the developing roller was rotating. In the durability experiment, a printer as an image forming apparatus as shown in FIG. 2 was used.

The rotation speed v of the developing roller (surface) was 120 mm / sec. The toner filling amount was 100 g. A two-sheet intermittent printing paper endurance test was performed with an image pattern having a printing rate of 1%, and the image was evaluated when up to 11,000 sheets were passed.

  The presence or absence of occurrence of blade fusion due to unevenness in the solid image was determined. In addition, the evaluation of the rough image was visually judged from a solid image to a thin halftone. Note that the rough image is a disturbance in the image caused by so-called toner deterioration such that the external additive of the toner 101 is peeled off or released.

  Table 3 summarizes the combinations of experimental conditions and the resulting problems. In Table 3, combinations of developing rollers A to E and biases A to F are shown. The biggest problem that occurred in each combination is listed at that location.

  In the case of using the bias A, discharge traces are generated regardless of the configuration of the developing roller.

This is thought to be because the maximum potential difference | Vb_H− Vdev | in Table 2 exceeded 500V. Assuming from Paschen's discharge start voltage, the discharge threshold is around 600 V, but the toner 101 may be present in the nip portion, and it is considered that the discharge has started locally. Therefore, an unintended pattern such as a spot has occurred in the image. That is,
| Vb_H- Vdev | ≦ 500V
By satisfying this relationship, the occurrence of discharge traces can be prevented.

  In the case of using the bias B, no major problem occurred in the developing rollers A to C. In the developing roller D, blade fusion occurred despite the AC bias being applied.

  This is presumably because the surface roughness of the developing roller was close to a mirror surface and rubbed against the surface of the regulating blade regardless of the bias, but the effect of peeling off the deposits could not be exhibited. Further, in the case of using the developing roller E, a rough image due to the rough surface of the roller was generated regardless of the biases A to F.

In the case of using the biases C and D, like the bias B, good images were obtained on the developing rollers A to C.

Therefore, the surface roughness Ra [μm] of the developing roller is
0.05 ≦ Ra ≦ 0.2
The occurrence of a major problem can be prevented by setting.

  In the case of using the bias E, blade fusion occurred in the developing rollers A to D.

  This is presumably because the bias E is a DC bias, and the development roller surface with extremely small surface roughness and the regulating blade 105 are endured without rubbing, and the deposits are fused to the regulating blade surface. In the case of the developing roller E, since the surface roughness is relatively large, the blade is not rubbed even with a DC bias because the developing roller E directly rubs against the regulating blade 105 at a portion where the roughness crest is high. However, the load on the toner 101 is increased due to the roughening action, and in particular, the roughness is observed in the halftone image.

  Therefore, by making the bias applied to the regulating blade 105 an AC bias (AC voltage), it is possible to prevent the occurrence of blade fusion and the occurrence of roughness.

  The image using the bias F generated a rough image regardless of the configuration of the developing roller.

This is considered as follows. The bias F is used in Table 2, in which the value of | Vb_H−Vb_L | corresponding to the amplitude of the AC bias is larger than the maximum potential difference | Vb_H− Vdev |, that is, the potential as shown in FIG. Become a relationship. For this reason, the force of the electric field received by the toner 101 is reversed, resulting in an AC bias having a large stirring / vibrating action as seen in the past, and the base material and the external additive of the toner 101 are easily separated from the toner 101. This is probably because

Therefore, the potential relationship shown in FIG.
| Vb_H−Vb_L | ≦ | Vb_H− Vdev |
| Vdev−Vb_L | ≦ | Vdev−Vb_H |
Satisfaction can be prevented by satisfying this relationship.

From Table 2 ,
100V ≦ | Vb_H−Vb_L |
It can be seen that the relationship is established.

  From the above experimental results, the developing rollers D and E have problems under all bias conditions, and the biases A, E, and F have problems with all developing rollers. It can be seen that no problem occurred depending on the setting of the surface roughness of the developing roller.

That is, from these experimental results,
0.05 ≦ Ra ≦ 0.2
100V ≦ | Vb_H−Vb_L | ≦ | Vb_H− Vdev | ≦ 500V
| Vdev−Vb_L | ≦≦ Vdev−Vb_H |
It can be seen that the occurrence of the problem can be prevented when the above relationship is satisfied.

  Based on the above experimental examples, examples and comparative examples are shown below.

<Examples and Comparative Examples>
Table 4 shows the developing roller configuration, the bias of the regulating blade 105, the frequency, and the like of the example and the comparative example. Also in the examples and comparative examples, image evaluation similar to that in the experimental example is performed, and a summary of the results is shown in the image evaluation column. The bias applied to the regulating blade 105 is also an AC bias of DUTY 50%, as in the experimental example. The application time of the minimum potential Vb_L of the regulating blade bias converted from the frequency is also shown in the table.

  In Example 1, the developing roller A and the bias B shown in the experimental example are combined, and the frequency of the regulating blade bias is changed. The image evaluation was a good image without problems.

  In Example 2, the developing roller B and the bias C shown in the experimental example are combined, and the frequency of the regulating blade bias is changed. The image evaluation was a good image without problems.

  In Example 3, the developing roller C and the bias D shown in the experimental example are combined, and the frequency of the regulating blade bias is changed. The image evaluation was a good image without problems.

  In the fourth and fifth embodiments, the Vb_L application time Tl is changed in the first embodiment.

  In Example 4, the time Tl was long, and a line that was difficult to confirm by visual observation was observed on the image.

  In Example 5, although the time Tl was short and there was no blade fusion, a slight amount of fine powder adhered to the blade was confirmed. A non-problematic level of unevenness was observed on the image.

  In Comparative Example 1, the developing roller A and the bias B shown in the experimental example are combined, and the frequency of the regulating blade bias is changed. In the image evaluation, stripe unevenness, which was thought to be caused by blade fusion, occurred, and when the regulated blade surface was observed, blade fusion was confirmed.

  In Comparative Example 2, the developing roller A and the bias B shown in the experimental example are combined, and the frequency of the regulating blade bias is changed. In the image evaluation, a clear line due to the AC bias cycle was generated without waiting for the paper passing durability result.

From Table 4, the appropriate range of the Vb_L application time Tl at the rotation speed v = 120 × 10 ⁻³ [m / sec] of the developing roller is
0.00025 ≦ Tl [sec] ≦ 0.001
It is thought that. This is converted into the length that the developing roller surface advances with respect to the blade during the application time Tl.
30 × 10 ⁻⁶ ≦ (Tl × v (= 120 × 10 ⁻³ )) [m] ≦ 120 × 10 ⁻⁶
Can be expressed.

The effect of the present invention is obtained by rubbing the developing roller surface and the blade surface during the Vb_L application time Tl. Therefore, not the proper range of the application time Tl at v = 120 × 10 ⁻³ [m / sec] used in the example, but the length that the developing roller surface advances with respect to the blade during the application time Tl, that is, If the value of the product of Tl and v is in an appropriate range, it is considered that the same effect can be obtained even if Tl and v are changed.

In other words, using the values obtained from this example, for any Tl and v,
^{30 × 10 -6 ≦ (Tl ×} v) [m] ≦ 120 × 10 -6
As long as is satisfied.

From the above, when an arbitrary developing roller rotation speed v is determined, the appropriate range of the Vb_L application time Tl is
30 × 10 ⁻⁶ / v ≦ Tl [sec] ≦ 120 × 10 ⁻⁶ / v
It can be determined by the following formula.

(Consideration on action)
In Examples 1 to 5, since the surface roughness of the developing roller, the bias potential setting, and the bias frequency were appropriate, good results were obtained in image evaluation. This is because, in the blank area of the toner coating on the surface of the developing roller due to the fluctuation of the bias, the hard and moderately rough SiOx thin film developing roller surface rubbed against the regulating blade surface. It is thought that it was able to be washed away.

  On the other hand, in Comparative Example 1, although the same developing roller and bias setting as in Example 1 were used, blade fusion occurred. This is presumably because a sufficient blank area of the toner coating could not be obtained because the bias frequency was too high with respect to the rotation speed v of the developing roller (Vb_L was too short).

  In Comparative Example 2, it is considered that the blank area of the toner coating was conspicuous because the frequency was too low.

  In addition, although the frequency was changed in the developing roller D having the smallest surface roughness, blade fusion also occurred in this case. This is presumably because sufficient friction could not be obtained on a mirror-like surface and the deposit on the regulating blade could not be swept away.

  From the above experimental examples and examples, the surface layer is formed of a SiOx thin film having a surface roughness Ra of 0.05 to 0.2, and the base layer is made of an elastic developing roller. It can be seen that a good image can be obtained by setting as described above.

That is,
100V ≦ | Vb_H−Vb_L | ≦ | Vb_H− Vdev | ≦ 500V,
30 × 10 ⁻⁶ / v ≦ Tl [sec] ≦ 120 × 10 ⁻⁶ / v
It can be seen that a good image can be obtained by setting so as to satisfy the above relationship.

  As described above, in the present embodiment, the developing roller 106 having the hard and thin surface layer and the rubber elastic base layer is provided, and the variation bias is applied to the regulating blade 105. By setting it as such a structure, the effect | action which scrapes off the deposit | attachment adhering to the control blade 105 can be acquired. Therefore, even when a developing roller having a surface with a small roughness is used in the developing device for high image quality or high durability, it is possible to prevent the occurrence of a non-uniform image due to so-called blade fusion. Can do. As a result, problems such as filming, fogging, density unevenness, and roughness due to toner deterioration can be prevented, and a good image can be obtained.

  In this embodiment, the configuration in which the variable bias is always used while the developing roller is rotating is described. However, the same effect can be obtained by using the same variable bias only during non-image formation or image formation.

  Further, the developing device and the process cartridge according to the present embodiment can be applied to a color image forming apparatus.

1 is a schematic cross-sectional view of a nonmagnetic one-component developing device in an embodiment of the present invention. 1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing a state where a variable bias at a nip portion acts on toner according to an embodiment of the present invention. The figure which shows the relative electric potential relationship of each bias for describing embodiment of this invention. The figure which shows the relative electric potential relationship of each bias in a prior art for demonstrating embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 100 Developing apparatus 101 Toner 104 Supply roller 105 Regulating blade 106 Developing roller

Claims (3)

Developer,
A developer carrying member carrying the developer;
A developer regulating member that is made of a conductive material and regulates the developer on the developer carrying member;
Regulation bias applying means for applying a bias to the developer regulating member;
Developing bias applying means for applying a bias Vdev to the developer carrying member;
In a developing apparatus of a non-magnetic one-component development system having
The developer carrier is composed of a base layer made of a rubber-like elastic body and a surface layer made of a SiOx thin film,
The regulation bias applying means applies an AC voltage to the developer regulating member,
The surface roughness of the developer carrier is Ra [μm] ,
Of the voltages applied to the developer regulating member by the regulating bias applying means, the maximum voltage on the charging polarity side of the developer is Vb_H, and the minimum voltage is Vb_L.
When the rotation speed of the surface of the developer carrying member is v [m / sec] and the application time of the minimum voltage Vb_L applied to the developer regulating member by the regulating bias applying unit is Tl [sec],
0.05 ≦ Ra ≦ 0.2,
| Vdev−Vb_L | ≦ | Vdev−Vb_H |,
100V ≦ | Vb_H−Vb_L | ≦ | Vb_H− Vdev | ≦ 500V,
And,
30 × 10 ⁻⁶ / v ≦ Tl ≦ 120 × 10 ⁻⁶ / v
A developing device characterized by satisfying the above.   A process cartridge comprising the developing device according to claim 1, wherein the process cartridge is detachably attached to the image forming apparatus. An image carrier;
The developing device according to claim 1, which performs a developing action on the image carrier;
An image forming apparatus comprising:

Images