JP2000081759A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make toner hardly adhere to the surface of a contact electrifying member, to maintain the uniformity of the electrification of an image carrier by the electrifying member and to stably obtain a uniform image over a long term by constituting developer of the toner and additive and making the same additive as the above-mentioned additive previously adhere to the surface of the electrifying member. SOLUTION: An electrifying roller 2 has structure provided with a conductive elastic layer 2b on a conductive supporting body 2a and a surface layer 2d having releasing property from the toner on the layer 2b, and the additive 9 is made to adhere to the layer 2b in an isolated state. The additive 9 is the same additive as the additive added to the toner. It is desirable to set the adhesive amount Q(g) of the additive 9 within the range of 0.1S<Q<50S when the surface area of the outermost surface of the roller 2 is defined as S m2. In the roller 2 the surface of which the additive 9 adheres to, the adhesion of the toner left after transfer on a photoreceptor drum to the roller 2 is drastically reduced, and the electrification characteristic and the durablity of the roller 2 are remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for charging an image bearing member,
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., in which an image is exposed and developed, and the obtained visible image is transferred to a transfer material to obtain an image. The present invention relates to an improvement of a charging member suitable for the charging.

[0002]

2. Description of the Related Art Many types of electrophotography have been conventionally known. In general, a photoreceptor using a photoconductive substance is used as an image carrier, and the surface of the photoreceptor is charged by a charging means. Is uniformly charged to the polarity and potential of the photosensitive member, and the photosensitive member is exposed to light by an image exposing means to form an electrostatic latent image. Then, the latent image is developed with toner to be visualized. The toner image is transferred to a transfer material, and thereafter, the toner image is fixed to the transfer material by heating, pressurizing, or the like, to obtain a copy or printed matter. Transfer residual toner remaining on the photoreceptor without being transferred to the transfer material is removed by cleaning with a cleaning device.

As a charging means in such an electrophotographic method, a corona charger using a corona discharge called a corotron or a scorotron has been used. However, at the time of corona discharge, when a negative or positive corona is generated, Since a large amount of ozone is generated, it is necessary to provide a filter for capturing ozone in the electrophotographic apparatus, and there have been problems such as an increase in the size of the apparatus or an increase in running cost.

As a technique for solving this problem, a charging member is brought into contact with a photoreceptor to form a narrow space in the vicinity of the contact portion, and to form a discharge which can be interpreted by the so-called Paschen's law. As a result, a contact charging method which minimizes the generation of ozone has been developed. For example, Japanese Patent Application Laid-Open Nos. 57-178257 and 56-10435
1, JP-A-58-40566, JP-A-58-13915
6. This technology is known in Japanese Patent Application Laid-Open No. 58-150975.

However, recently, there has been a demand for further downsizing of the image forming apparatus utilizing such electrophotography. For example, the charging apparatus as described above is downsized. There was a limit only in miniaturization of the equipment used for each process.

Therefore, in recent years, the transfer residual toner remaining on the photoreceptor is not removed by a dedicated cleaning device as described above, but the transfer residual toner is collected by a developing means. Cleaning methods have been devised. For example, JP-A-59-33573, JP-A-62-203182, JP-A-63-133179, JP-A-64-20587, JP-A-2-51168, JP-A-2-302772, JP-A-5-2287, JP-A-5-2287 -2
289, JP-A-5-53482 and JP-A-5-61383.

[0007] As a conventional cleaning device dedicated to a photoreceptor, an elastic blade is brought into contact with a photoreceptor to scrape off residual toner on the photoreceptor, or an elastic blade or an elastic roller is brought into contact with the photoreceptor. There is a method in which a bias having a polarity opposite to that of the transfer residual toner on the photoconductor is applied to these to electrostatically collect the toner. However, in any of these methods, the size of the apparatus is increased, and the cleaning member is applied to the photoconductor. There are also adverse effects such as abrasion of the photoconductor due to pressing, shortening of service life, and generation of memory (drum memory) due to long-term contact with the photoconductor in contact with the cleaning member.

In the simultaneous development cleaning method, the transfer residual toner transferred from the transfer section to the development section by the movement of the photosensitive member is used in the next and subsequent developments by the DC voltage applied to the developer carrier of the developing means and the photosensitive member. The toner is collected on the developer carrier by the potential difference of the surface potential. Since the dedicated cleaning device can be omitted, the size of the image forming apparatus can be further reduced.

[0009]

In the above-mentioned simultaneous cleaning method for development, at the time of development or at the time of blank before and after development,
A potential to apply a DC or AC component bias so that the toner from the developer carrier can adhere to the latent image on the photoconductor and the transfer residual toner on the photoconductor can be transferred to the developer carrier at the same time. The important factors at this time are the charge polarity and charge amount of the transfer residual toner.

When a toner image formed on a photoconductor by development using a negatively charged photoconductor and a negatively charged toner is transferred to a transfer material by a positive transfer voltage, the transfer voltage and the type of the transfer material are used. The charge polarity of the transfer residual toner varies from plus to minus depending on the relationship between (difference in thickness, resistance, dielectric constant, etc.) and image area.

[0011] Even if the charge polarity of the transfer residual toner on the photoreceptor changes to positive due to the application of the transfer voltage in the transfer step, not only the photoreceptor but also the photoreceptor during the next image formation is charged. The toner is also uniformly negatively charged. For this reason, after charging, image exposure is performed to form a latent image of the next image, and when the latent image is developed by applying a developing bias to a developer carrying member of a developing unit, the latent image and the non-image portion of the photosensitive member are developed. The transfer residual toner present in the dark potential portion (non-exposed portion) is attracted to the developer carrier due to the development electric field,
Transfer residual toner does not remain in the non-image area.

On the other hand, the transfer residual toner existing in the light portion potential portion (exposure portion) serving as the image portion of the photosensitive member stops at the light portion potential portion as it is due to the development electric field. There is no problem because new toner adheres from the body to form a toner image.

According to the study of the present inventor, when the photosensitive member is charged by an AC charging method in which a DC voltage in which an AC component is superimposed is applied to a contact charging member, the polarity of the transfer residual toner cannot be controlled by the charging. Therefore, it has been found that this method cannot be applied to simultaneous development cleaning, and it is necessary to adopt a DC charging method in which only a DC voltage capable of changing transfer residual toner to a negative polarity is applied.

However, the DC simultaneous development cleaning has the following problems. In this method, when transfer residual toner adheres to the contact charging member, the charging characteristics of the charging member change, and for example, problems such as a decrease in the charging potential of the photoconductor surface due to an increase in the resistance of the charging member and uneven charging of the photoconductor surface are caused. And image defects such as fog and uneven density are likely to occur. In this regard, the AC charging method is more advantageous, and the effect of toner adhesion to the contact charging member is very small.

For this reason, it is necessary for the contact charging member to make it difficult for toner to adhere, and to prevent deterioration of charging characteristics even if toner adheres. For example, JP-A-7-43980 and JP-A-8-18
In 5013, a fluorine-based resin is used on the surface of the contact charging member to enhance the releasability from the toner so that the toner does not easily adhere. However, when the amount of toner attached to the contact charging member is not small as in the configuration using the simultaneous development cleaning, it is difficult to maintain the initial charging characteristics for a long period of time.

On the other hand, for example, in JP-A-6-348106 and JP-A-7-128954, a toner layer is provided on the surface of a contact charging member, and the thickness of the toner layer is regulated by a regulating member. Even if toner adheres to the surface, so that the charging characteristics of the charging member do not change,
The regulation of the regulation member is intended to ensure a toner layer of a constant thickness at all times.

However, if an elastic blade or a sponge member is used as a regulating member, and these are brought into contact with the surface of the contact charging member so as to control the thickness of the toner layer, the regulating member may not contact the charging member. A strong pressure is required, which causes damage to the charging member, deformation or lack of the regulating member due to long-term use, and makes it difficult to uniformly control the thickness of the toner layer. In the case of a charging member such as a charging roller,
Even when the charging member does not rotate, unevenness in the thickness of the toner layer occurs between the contact portion and the non-contact portion of the charging member.

An object of the present invention is to prevent the toner from adhering to the surface of the contact charging member and prevent the transfer residual toner on the image carrier from adhering even when the charging member is used in the simultaneous developing and cleaning system. An object of the present invention is to provide an image forming apparatus capable of maintaining uniformity of charging of an image carrier by a member and capable of stably obtaining a uniform image for a long period of time.

[0019]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention relates to a static image formed by contacting an elastic charging member with the surface of an image carrier, uniformly charging the surface of the image carrier, and exposing the charged image carrier. The electrostatic latent image is developed by a developing unit using a developer, the obtained visible image is transferred to a transfer material, and the remaining transferable developer remaining on the image carrier passes through the charging member, and is then transferred to the transfer member by the developing unit. When developing the latent image of the image, in an image forming apparatus that recovers by a potential difference between the image carrier and the developer carrier of the developing means, the developer is composed of at least a toner and an external additive thereof, An image forming apparatus, wherein the same external additive as the external additive is previously attached to a surface of a charging member. Preferably, the adhesion amount Q (g) of the external additive to the surface of the charging member is 0.1% when the surface area of the outermost surface of the charging member is S (m ² ).
S <Q <50S.

According to the present invention, the charging member may have a structure in which a conductive elastic layer is provided on a cylindrical conductive substrate, and a surface layer having a releasability from toner is provided on the elastic layer. it can. The surface layer can be formed by coating a tube of the material constituting the surface layer on the elastic layer. Further, an intermediate layer having elasticity can be provided between the elastic layer and the surface layer of the charging member. The charging member may be formed in a roller shape.

According to the present invention, the external additive can be a metal oxide subjected to a hydrophobic treatment. The average particle size of the external additive is 1 μm or less, and the particle resistance of the external additive is 1 μm.
0 ¹² Ωcm or more. Preferably, the toner is a spherical particle produced by a polymerization method. The toner has a shape factor SF-1 of 100 to 140,
2 is 100 to 120.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of the image forming apparatus of the present invention.

This image forming apparatus includes a drum-shaped electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 1, and a charging roller 2 as a contact charging member, a developing device 3, and a transfer member around the photosensitive drum 1. A roller 4 is provided, a registration roller 5 is provided on the upstream side in the moving direction of the transfer material P passing through the transfer portion between the photosensitive drum 1 and the transfer roller 4, and a fixing device 7 is provided on the downstream side. An exposure device (not shown) is provided above the photosensitive drum 1.

In order to form an image, first, the photosensitive drum 1 is rotated in the direction of the arrow in the figure, and in the course of the rotation, the surface of the photosensitive drum 1 is charged by a charging roller 2 contacting the photosensitive drum 1 with a potential of a predetermined polarity. In the present embodiment, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by uniformly charging to a negative potential and performing image exposure 6 from an exposure device (not shown). Then, the latent image is reversely developed by the developing device 3 to which a developing bias is applied, and is visualized as a toner image. The toner image is transferred to the transfer material P supplied to the photosensitive drum 1 at a predetermined timing by the registration roller 5. The transfer is performed by the action of the transfer roller 4 to which the transfer bias is applied. The transfer material P on which the toner image has been transferred is conveyed from the photosensitive drum 1 to the fixing device 7, where the toner image is fixed by heating and pressing.
Image formation ends.

The image forming apparatus employs a simultaneous development cleaning method, and the transfer residual toner remaining on the photosensitive drum 1 is collected by the developing unit 3 when the next image is developed by the developing unit 3.

The developing device 3 contains a one-component developer and a negatively chargeable non-magnetic toner inside, and has a developing roller 31 at an opening facing the photosensitive drum 1.
Are driven to rotate in the same direction at the portion facing the photosensitive drum 1. The developing roller 31 is provided with an application roller 32 and a regulating blade 33 downstream of the developing roller in the rotation direction of the developing roller in contact with each other, and is connected to a power source.

The application roller 32 rotates in contact with the developing roller 31 to frictionally charge the toner contained in the developing device 3 at the contact portion, and supplies the toner to the developing roller 31 to carry it. The toner carried on the developing roller 31 is conveyed to a contact portion with the regulating blade 33 with the rotation of the developing roller 31, is regulated by the regulating blade 33, is further charged by friction, and has a predetermined thickness. Formed in layers.

As the developing roller 31 rotates, the toner formed on the toner layer is conveyed to a developing section facing the photosensitive drum 1. The toner that has reached the developing section is transferred and attached to a latent image (exposed section) on the photosensitive drum 1 by a developing bias applied to the developing roller 31 from a power source, reversely develops the latent image, and is visualized as a toner image.

The simultaneous development cleaning will be described.
As described above, when the toner image formed by the negatively charged toner on the negatively charged photosensitive drum 1 is transferred to the transfer material P by a positive transfer bias, the toner image is not completely transferred onto the transfer material P and remains on the photosensitive drum 1. The transferred remaining toner includes the toner that has been converted to a positive polarity by receiving the above-described positive polarity transfer bias. These transfer residual toners pass through the charging roller 2 with the rotation of the photosensitive drum 1, but the toner having a positive polarity due to the negative charging of the photosensitive drum 1 by the charging roller 2 for the next image formation. Is also converted to negative polarity.

As described above, the photosensitive drum 1 is subjected to image exposure 6 of the next image in a state where all of the untransferred toner has passed the charging roller 2 and has a negative polarity. The electro-latent image is reversely developed in the same manner as described above.

In the reversal development, new negatively charged toner on the developing roller 31 is developed by attaching an exposed portion (a bright portion potential portion). At this time, a developing bias applied to the developing roller 31 is applied to the photosensitive drum. 1 is located at a potential between the non-exposed portion and the exposed portion, an electrostatic force acts on the transfer residual toner of negative polarity existing on the non-exposed portion of the photosensitive drum 1 so as to be attracted to the developing roller 31 side. The transfer residual toner on the non-exposed portion can be collected by attaching to the developing roller 31.

With respect to the transfer residual toner of negative polarity existing on the exposed portion of the photosensitive drum 1, the above-described developing bias acts as a force to stop the photosensitive drum 1 as it is. There is no problem because it is the part that forms

As described above, by controlling the charge polarity of the transfer residual toner on the photosensitive drum 1, simultaneous cleaning with development can be performed and a cleaner-less image formation can be realized. When the toner adheres to the surface, the controllability of the charging polarity of the transfer residual toner on the photosensitive drum 1 by the charging roller 2 and the charging property of the photosensitive drum 1 are reduced, and it is difficult to perform the simultaneous cleaning with development.

When the transfer residual toner on the photosensitive drum 1 is cleaned by a cleaning device having a cleaning member such as a blade or a fur brush as in the prior art, the transfer residual toner is applied to the charging roller 2. Adhesion is small, and a low surface energy resin or a resin having a large contact angle is used on the surface of the charging roller 2, or highly releasable particles are dispersed in the resin on the surface to form a toner with the toner on the charging roller 2. By improving the releasability, it is possible to sufficiently cope with toner adhesion to the charging roller.
Even if these measures are taken, it is not possible to sufficiently prevent toner from adhering to the charging roller.

In order to adopt the simultaneous development cleaning method, as described above, it is necessary to use a DC charging method in which only a DC voltage is applied to the charging roller 2. This DC charging method uses an AC voltage. The charging roller 2 is more susceptible to toner contamination than the AC charging method that applies a superimposed DC voltage.

For this reason, the charging roller 2 needs to have a new configuration. Therefore, in the present invention, the charging roller 2 has a configuration in which the same external additive as the external additive added to the toner is adhered to the surface thereof. FIG. 2 is a sectional view of the charging roller 2 according to the present invention.

The charging roller 2 shown in FIG. 2A has a structure in which a conductive elastic layer 2b is provided on a conductive support 2a, and a surface layer 2d having releasability from toner is provided on the elastic layer 2b. The external additive 9 is attached to the surface layer 2d in a free state. This external additive 9 is the same external additive as the external additive added to the toner. The charging roller 2 shown in FIG. 2B has a structure in which an intermediate layer 2c having elasticity is provided between a conductive elastic layer 2b and a surface layer 2d on a conductive support 2a. The external additive 9, which is the same as the external additive added to the toner, is attached to the surface layer 2d in a free state.

The one-component developer toner includes a styrene resin,
To a binder resin such as a polyester resin, an acrylic resin, a phenol resin, and an epoxy resin, a colorant, a charge control agent and other additives (internal additives) are added, mixed and kneaded, and the obtained kneaded material is cooled, After pulverization, it is obtained by adjusting to a desired particle size distribution by air classification or the like. The obtained toner is used by adding an external additive for the purpose of stabilizing the chargeability of the toner, imparting fluidity, and imparting abrasiveness to the photoconductor.

As the external additive, a metal oxide is used, and silicon, aluminum, and the like mainly used as a fluidity imparting agent are used.
In addition to oxides such as titanium, metal oxides such as iron oxide, zinc oxide, cerium oxide, metal titanate, and various ferrites can be used. Depending on the purpose of use, these metal oxides are preferably subjected to a hydrophobic treatment in view of stability of charging of the toner under a high humidity environment. As the hydrophobizing agent, silazane, alkylalkoxysilane, silicone oil or the like is used.

According to the charging roller 2 having such an external additive adhered to the surface, the adhesion of the transfer residual toner on the photosensitive drum 1 to the charging roller 2 is greatly reduced, and the charging characteristics and durability of the charging roller 2 are improved. Sex is greatly improved.

The reason why the adhesion of the transfer residual toner to the charging roller is reduced is considered as follows. The transfer residual toner particles conveyed to the charging roller 2 with the rotation of the photosensitive drum 1 tend to come into contact with the surface of the charging roller, but the external additive is present on the surface of the charging roller in a free state. Therefore, before the toner particles adhere to the surface of the charging roller, the external additive moves to the toner particle side and is scraped off, so that the toner particles do not come into contact with the charging roller,
Since the scraped external additive is returned to the photosensitive drum together with the scraped external additive, toner adhesion to the charging roller is reduced.

The transfer residual toner that has returned to the photosensitive drum 1 with the external additive is negatively charged again by a minute discharge downstream of the contact nip between the charging roller 2 and the photosensitive drum 1, and then the above-described operation is performed. Similarly, due to the potential difference between the developing bias applied to the developing roller 31 of the developing device 3 and the photosensitive drum 1, the toner adheres to the developing roller 31 and is collected.

In the above description, it is necessary that the external additive previously attached to the surface of the charging roller 2 is the same as the external additive added to the toner currently used. Even if an external additive of the toner is added to the surface of the charging roller 2, an external additive to be added to a different kind of toner from the toner currently being used may cause the toner on the photosensitive drum 1 to be charged.
When the external additive is taken in from the developer and the toner is collected in the developing device 3, the toner having a different formulation of the external additive is mixed into the developing device 3, and the distribution of the charge amount portion of the toner is not correct. It is not suitable because it stabilizes and causes uneven development and uneven transfer.

According to the study of the present inventor, if other particles which are not the external additive of the toner are previously adhered to the surface of the charging roller 2 and the particles are formed as fine particles having an average particle diameter of 1 μm or less, the charging is performed. The toner can be prevented from adhering to the surface of the roller 2. Therefore, the effect of preventing the adhesion of the toner is as follows.
It is considered that the diameter of the particles attached to the surface of the charging roller 2 is particularly greatly affected. However, in any case, if particles other than the external additive of the toner are attached, This is not possible because toners with different external additive formulations will be mixed into the toner.

In the present invention, the average particle diameter of particles such as an external additive of the toner is in the range of 0.05 to 200 μm using a laser diffraction particle size distribution analyzer HEROS manufactured by JEOL Ltd.
The measurement was carried out by dividing the logarithm by two, and was represented by an average particle diameter of 50% by volume.

As described above, the external additive adhering to the surface of the charging roller 2 is scraped off by the transfer residual toner and is collected in the developing device 3. On the other hand, it is supplied little by little from the developing device 3. Therefore, during long-term use, if the initial amount of the external additive adhering to the surface of the charging roller 2 is adjusted according to the number of sheets used, the charging roller 2 can be charged without an external additive supply device. It is possible to maintain an amount of the external additive sufficient to prevent the toner from adhering to the surface of the roller 2.

In the present invention, it is particularly preferable that the external additive has an insulating property with a resistance (particle resistance) of 10 ¹² Ωcm or more. If the particle resistance of the external additive is 10 ¹² Ωcm or less, the transfer efficiency deteriorates, so that the transfer residual toner is increased. It is inevitable that toner adheres.

The resistance of the external additive is determined by filling the external additive in a cylinder, arranging a pair of electrodes so as to sandwich the filled external additive from above and below, and applying a voltage between the electrodes. The current flowing at that time was measured. The measurement conditions were 23 ° C., 65% environment, and the contact area between the external additive and the electrode was 2%.
cm ² , the thickness of the external additive charged is 1 mm, the load on the upper electrode is 10 kg, and the applied voltage is 100 V.

Adhesion amount Q of external additive to surface of charging roller 2
(G) is preferably in the range of 0.1 S <Q <50 S, where Sm ² is the surface area of the outermost surface of the charging roller 2.

The adhering amount of the external additive on the surface of the charging roller 2 is 0.
In the case of 1 Sg or less, the supply of the external additive from the developing device 3 cannot be performed in time, and the external additive becomes insufficient on the surface of the charging roller, causing the toner to adhere to the charging roller, and the durability is reduced. If the amount of the external additive adhered to the surface of the charging roller 2 is 50 Sg or more, there is a possibility that the external additive drops from the charging roller.

The adhesion of the external additive to the charging roller 2 can be effected by direct coating of an external additive such as an electrostatic powder coating method, a fluid immersion coating method, an electrostatic fluid immersion coating method, or a sprayed powder coating method. is there. Alternatively, a method in which an external additive is mixed and diluted in a solvent such as acetone, methanol, or N-hexane, and the external additive is sprayed onto the surface of the charging roller by spray coating, has the same adhesion state as the powder coating described above. Is obtained. On the other hand, in a method in which a surface layer is formed on a charging roller with a resin and an external additive is dispersed in the resin as disclosed in Japanese Patent Application Laid-Open No. 9-204089, for example, I can't get it.

In the present invention, the binder resin constituting the toner may be, for example, a homopolymer of styrene or a substituted product thereof such as polystyrene, poly-p-chlorostyrene and polyvinyl toluene; styrene-p-chlorostyrene copolymer. Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-
Acrylic acid-2-ethylhexyl copolymer, styrene-
Octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-
Acrytonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene- Acrylonitrile-indene copolymer,
Styrene-based copolymers such as styrene-maleic acid copolymer and styrene-maleic acid ester copolymer; polymethyl methacrylate; polybutyl methacrylate; polyvinyl chloride; polyvinyl acetate; polyethylene; polypropylene; polyester; polyurethane; polyamide; Epoxy resin; polyacrylic acid resin; rosin; modified rosin;
Terpene resins; phenolic resins; aliphatic or alicyclic hydrocarbon resins; aromatic petroleum resins; chlorinated paraffins; These are used alone or in combination of two or more.

Any known coloring agent can be used. For example, dyes and pigments such as carbon black, iron black, graphite, nigrosine, metal complexes of monoazo dyes, ultramarine, copper phthalocyanine, methylene blue, chrome yellow, quinoline yellow, hansa yellow, benzine yellow, Dupont oil red, quinacridone various lake pigments, etc. No.

The charge control agent is added as needed to control the charge polarity and charge amount of the toner. A known appropriate charge control agent may be appropriately selected depending on the polarity and charge amount of the target toner, and is not particularly limited. Examples of the charge control agent include metal complex salt azo dyes and nigrosine dyes.

The toner is not particularly limited as long as it has been subjected to an external additive treatment, but there is a preferred form in terms of transfer efficiency due to toner scattering. That is, if the amount of the transfer residual toner in contact with the charging roller 2 is small, the absolute amount of the toner involved in the scattering is reduced, so that it is suitable for use in combination with the image forming apparatus of the present invention. Toner shape factor SF-1 is 100 to 140, SF-2 is 100 to 1
Those having a range of 20 tend to have good transferability. In particular, it is formed by a polymerization method, and has shape factors SF-1 and SF-2.
Is within the above range, since transferability is particularly good.

The shape factors SF-1 and SF-2 of the toner are as follows:
It is measured as follows. For example, using a scanning electron microscope FE-SEM (S-800) manufactured by Hitachi, Ltd., 10
100 pieces of toner particles of 2 μm or more enlarged at a magnification of 00 times or more are sampled at random 100 pieces, and the image information of the toner particle image is introduced into an image analysis device Lusex3 manufactured by Nicole, for example, via an interface, and analyzed. SF1 = {(MXLNG) ² / AREA} × (π / 4)
× (100) SF2 = {(PERE) ² / AREA} × (1 / 4π)
× (100) (however, MXLNG: absolute maximum length of toner particles, PE
(RI: perimeter of particle, AREA: projected area of particle) It was defined as a value calculated from the above equation.

The shape factor SF-1 indicates the degree of roundness of the toner particles, and SF-2 indicates the degree of unevenness of the toner particles.

The charging roller 2 will be further described. The conductive elastic layer 2b of the charging roller 2 has a role of stabilizing the nip width between the charging roller 2 and the photosensitive drum 1, and is formed using rubber or an elastomer. The intermediate layer 2c and the surface layer 2d formed on the elastic layer 2b need to prevent contamination of the photosensitive drum due to leakage of components in the elastic layer 2b. Similarly, the intermediate layer 2c and the surface layer 2d are formed using rubber or elastomer, and further formed using resin. It can also be formed using.

The rubbers and elastomers used include styrene-butadiene rubber, styrene rubber, butadiene rubber, isoprene rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicon rubber, fluorine rubber, nitrile rubber. , Urethane rubber, acrylic rubber, epichlorohydrin rubber, norbonene rubber and the like. As the resin to be used, polystyrene, chloropolystyrene, poly-α-
Methylene styrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer) Copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate, copolymer styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic ester copolymer (styrene) -Methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl methacrylate copolymer, styrene-acrylonitrile-acrylate copolymer Such as styrene resin (styrene or Homopolymers containing styrene substituted or copolymer), vinyl chloride resin, styrene - vinyl acetate copolymer, rosin-modified maleic acid resins, phenol resins,
Epoxy resin, polyester resin, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, fluororesin, polycarbonate resin, polyamide resin, polyvinyl butyral resin, and the like. Examples include polymers and mixtures.

As the conductive support 2a of the charging roller 2,
Metals and alloys such as aluminum, iron, copper, and stainless steel can be used, and a conductive resin in which conductive particles such as carbon and metal particles are dispersed can be used. The shape of the support 2a is a cylindrical body, and a shaft can pass through the center of the cylindrical body, and the inside of the cylindrical body can be reinforced.

The intermediate layer 2c and the surface layer 2d of the charging roller 2
Can be formed as follows. A general method is to disperse a conductive pigment in a resin or rubber or the like constituting the surface layer 2d, then dissolve it in an organic solvent, and apply the resulting solution to a dipping method, a roll coating method, a spray coating method, or the like. To obtain a coating on the elastic layer 2b.

However, a preferred method is to form a surface layer by extruding a rubber or elastomer constituting the surface layer into a tube shape by extrusion or the like and coating the tube on the elastic layer. Performance is improved,
This leads to cost reduction of the charging roller 2. The charging roller 2 coated with this tube by the simultaneous development cleaning method
As a result, the charging area near the nip is enlarged and the polarity of the transfer residual toner is easily controlled. In view of this performance, the surface layer 2d of the charging roller 2 is also used.
Is preferably formed by a tube.

Hereinafter, a specific example of the first embodiment will be described.

As an electrophotographic apparatus, a laser beam printer (Laser Jet manufactured by Hewlett-Packard Company) is used.
4plus) was prepared. This printer is of a process cartridge type and uses a charging roller as a charging member for a photosensitive drum.

By modifying the above printer, the printer shown in FIG.
An image forming apparatus having the configuration of this embodiment shown in FIG.

First, the cleaning blade of the photosensitive drum was removed to use the cartridge as a cleaner-less system. Next, instead of a stainless steel sleeve, a medium-resistance rubber roller (outer diameter 18 mm) made of urethane foam was attached, and this was brought into contact with the photosensitive drum 1 as a developing roller 31. The rotation of the developing roller 31 was in the same direction at the contact portion with the photosensitive drum 1, and was driven so as to be 150% of the peripheral speed of the photosensitive drum 1. For regulating the layer thickness of the toner on the developing roller 31, a stainless steel blade coated with a resin was attached as the regulating blade 33.

Next, the charging roller 2 to which a DC voltage is applied
Was modified so that the surface of the photosensitive drum 1 was charged to a predetermined primary charging potential Vd by a DC charging method.

In the device thus modified, the transfer residual toner on the photosensitive drum 1 is made to have the same polarity as the charging polarity of the photosensitive drum 1 by the charging roller 2 and, at the same time, the surface of the photosensitive drum 1 is uniformly charged. While maintaining the transfer residual toner on the charged photosensitive drum 1 at the same polarity as the charged polarity of the photosensitive drum 1, an image portion is exposed by a laser beam to form an electrostatic latent image, and the latent image is negatively charged. And a process of transferring the obtained toner image to a transfer material by a transfer roller to which a voltage is applied.

In the present embodiment, the charging roller 2 is provided as shown in FIG.
The configuration shown in FIG. This charging roller 2 was manufactured as follows.

First, 40 parts by weight of conductive carbon black, 50 parts by weight of paraffin oil, an appropriate amount of a foaming agent, a crosslinking agent and other compounding agents are added to 100 parts by weight of EPDM, and these are kneaded to prepare a conductive compound. did. Next, a stainless steel cylinder having a diameter of 6 mm was used as the conductive substrate (core bar) 2a, and the above compound was vulcanized and formed on the cylindrical body, and the outer surface of the molded product was polished to form a 3 mm thick cylinder. The conductive elastic layer 2b of the foam was formed.

Next, 14 parts by weight of conductive carbon black were blended with 100 parts by weight of the ether-based thermoplastic elastomer, and these were mixed at 180 ° C. for 1 hour using a pressurized kneader.
The mixture was melt-kneaded for 0 minutes. After cooling, the kneaded material was pulverized with a pulverizer, and then pelletized using a single screw extruder. The pellets were extruded using a tube extruder and had an inner diameter of 1
A seamless tube having a thickness of 0.5 mm and a thickness of 250 μm was obtained. This tube serves as an intermediate layer 2c of the charging roller 2, and is referred to as a tube A.

Next, 100 parts by weight of a thermoplastic elastomer in which a polyethylene molecular chain is covalently bonded to one end of an ethylene butylene rubber molecular chain and an olefin crystal is covalently bonded to the other end,
13 parts by weight of conductive carbon black was blended and melt-kneaded at 200 ° C. for 10 minutes by a pressure kneader. After cooling the kneaded product, it was pulverized with a pulverizer and pelletized using a single screw extruder. The pellets were extruded using a tube extruder to obtain a seamless tube having an inner diameter of 11 mm and a thickness of 250 μm. This tube serves as a surface layer 2d of the charging roller 2, and is referred to as a tube B.

Subsequently, air is blown into the tube A to increase the outer diameter, and the base 2a provided with the elastic layer 2b is formed.
To cover the tube A on the elastic layer 2b, and then cover the tube B on the outside thereof in the same manner to form the intermediate layer 2c and the surface layer 2d. The structure shown in FIG. Was obtained. The surface area of the outermost surface of the charging roller was 87 cm ² (8.7 × 10 ⁻³ m ² ).

The charging roller 2 thus manufactured is referred to as charging roller No. 1.

Thereafter, the surface layer 2d of the charging roller 2
Then, the same hydrophobic additive-treated silica as that used for the toner described later is applied so that the adhesion amount becomes 0.09 g, and as shown in FIG. An external additive was used as a pre-adhered configuration.

The application of the hydrophobized silica was performed as follows. The hydrophobized silica was dissolved in an acetone solution, and a homogenizer was used to prepare a 100% dilute solution that was uniformly dispersed.
Was applied to the surface. At this time, the above solution is applied using a spray coating machine in advance, and the coating efficiency of the spray coating machine is checked in advance. When the coating solution is actually applied to the surface of the charging roller 2, the coating efficiency is determined based on the coating efficiency. The amount of adhesion was determined. In this way, hydrophobic silica was applied to the surface of the charging roller 2 so that the amount of adhesion was 0.09 g.

The photosensitive drum 1 was of a type in which four functional layers were provided on an aluminum cylinder having an outer diameter of 30 mm.

The lowermost first layer is a subbing layer that smoothes defects of the aluminum substrate and prevents the occurrence of moire due to reflection by laser exposure, and is formed of a conductive layer having a thickness of about 20 μm. The second layer thereon is a positive charge injection preventing layer,
It serves to prevent positive charges injected from the aluminum substrate from canceling out negative charges charged on the surface of the photoreceptor. The positive charge injection preventing layer is a medium resistance layer having a thickness of about 1 μm and made of an alamin resin and methoxymethylated nylon and having a resistance adjusted to about 10 ⁶ Ωcm.

The third layer is a charge generation layer that generates positive and negative charge pairs upon receiving laser exposure, and has a thickness of about 0.3 μm in which a titanyl phthalocyanine pigment is dispersed in a resin.
Layers. The fourth layer as the uppermost layer is a charge transporting layer, and is composed of a 15 μm thick layer of a P-type semiconductor in which hydrazone is dispersed in a polycarbonate resin. Negative charges charged on the photoreceptor surface cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the photoreceptor surface.

The surface resistance of the photosensitive drum 1 having the above configuration was 3 × 10 ¹⁵ Ωcm in the case of the charge transport layer alone.

The toner produced was as follows.

[0088] 88 parts by weight of styrene, 12 parts by weight of n-butyl acrylate, 3 parts by weight of low molecular weight polypropylene, 4 parts by weight of carbon black, 1.2 parts by weight of a metal-containing azo dye, and 3 parts by weight of an azo initiator are dispersed and mixed. This was added to 500 parts by weight of pure calcium phosphate in which 4 parts by weight was dispersed, and dispersed by a homomixer, followed by polymerization at 70 ° C. for 8 hours. The obtained polymer was filtered, washed, and dried and classified to obtain a toner plastic. Subsequently, the silica fine powder (BET specific surface area: 135 m ² / g) synthesized by the dry method was previously treated with hexamethyldisilazalane, and then treated with dimethylsilicone oil (100 cSt) diluted with hexane and heated. Thus, hydrophobized silica was obtained.

The above toner composition was treated with hydrophobic silica 1.5
wt% and strontium titanate 0.8 wt% were externally added to prepare a toner having a weight average particle diameter of 6.3 μm. The externally added hydrophobized silica has an average particle size of 0.02 μm and a particle resistance of 10 ¹⁶ Ωcm or more, and the strontium titanate has an average particle size of 1.8 μm and a particle resistance of 10 μm.
^It showed insulation of ¹⁶ Ωcm or more.

The above toner is referred to as toner a. Toner a
Was prepared by the polymerization method as described above, and when the toner particles were observed with an electron microscope, the particles were spherical. The shape factor SF-1 of the toner is 125 and SF-2 is 1
It was 15.

The bias applied to the charging roller 2 is DC-12.
00 V, the charging potential of the photosensitive drum 1 (bright portion potential Vd)
Is about -600 V, and the exposed portion potential by image exposure (bright portion potential V
1) was set to about -150 V to form an electrostatic latent image. The reversal development of the latent image by the developing device 3
The bias applied to 1 was set to DC-400V.

Under the above conditions, a temperature of 15 ° C. and a humidity of 10
% Low temperature and low humidity environment (L / L), 23 ° C, 60% normal environment (N / N), 30 ° C, 80% high temperature and high humidity environment (L / L)
In each environment of L), an image forming test was continuously performed on 10,000 sheets, and the fog of a white background of the image and the density uniformity of halftone were evaluated at the initial stage of image formation and at the time of 1,000 and 10,000 sheets. 75 g / m ² plain paper was used as the transfer material.

The fog on the white background is TOKYO DENSH
OKU CO., LTD. Reflection densitometer (ODELTC
-6DS). The fog amount = Ds−Dr, where Ds is the worst value of the reflection density of the white background after printing, and Dr is the average reflection density of the paper before printing. When the fog amount is 2% or less, a good image having substantially no fog is obtained, and when it exceeds 5%, an unclear image in which fog is conspicuous. The density uniformity on the halftone was visually evaluated.

Table 1 shows the prescription of the charging roller of the first embodiment.
Table 2 shows the evaluation results of the images. In Table 2, the meanings of the symbols are as follows. A: Neither fog nor density unevenness occurs. ：: Minor fog or density unevenness is found in part of the image. Δ: slight fog or density unevenness in the entire image, but practically acceptable. X: Either poor fog or poor density nonuniformity occurs, which is practically impossible.

[0090]

[Table 1]

[0091]

[Table 2]

Example 2 A weight average particle size of 6.3 was obtained in the same manner as in the toner a of Example 1.
A μm toner was prepared, but the silica fine powder used in Example 1 was externally added to the toner without using a hydrophobic treatment.
This toner is referred to as toner b. The charging roller 2 used was the same as the charging roller No. 1 in Example 1, but the surface thereof was coated with silica having no hydrophobic treatment.

The toner b was prepared by a polymerization method. When the toner particles were observed with an electron microscope, the toner particles showed a spherical shape. The shape factor SF-1 of the toner is 121, and the shape factor SF-2 is 1
145. The untreated silica externally added exhibited an insulating property with an average particle size of 0.02 μm and a particle resistance of 10 ¹⁶ Ωcm or more.

Otherwise, an image forming test was performed in the same manner as in Example 1 to evaluate the image. Table 1 similarly shows the prescription of the charging roller of Example 2 and Table 2 shows the evaluation results of the image.

As shown in Table 2, according to the second embodiment, the chargeability of the toner slightly deteriorated in the H / H environment, and the transfer efficiency was lowered. Only slight density unevenness was confirmed, and a good image was maintained.

Example 3 In Example 1, strontium titanate was applied to the surface of the charging roller No. 1 instead of hydrophobically treated silica. Otherwise, the procedure was the same as in Example 1. Tables 1 and 2 show the prescription of the charging roller of this example and the evaluation results of the image as in the past.

As shown in Table 2, according to Example 3, since the average particle diameter of the external additive applied to the charging roller was slightly large, there was a concern about the releasability of the toner. In a H / H environment, even after the end of the test on 10,000 sheets, only a slight density unevenness was confirmed in some parts, and good images were obtained.

Examples 4 and 5 In Example 1, the amount of the hydrophobized silica applied to the charging roller was reduced to 0.0007 g, and 0.52 g
And tried to increase. Others were the same as Example 1.

As shown in Table 2, in Example 4, the amount of the hydrophobic silica applied to the charging roller was slightly insufficient. Although this occurred, this state could be maintained after 10,000 sheets, and there was no practical problem. In Example 5, part of the silica spilled onto the photosensitive drum probably due to an excessive amount of the hydrophobic silica applied, and this part appeared as a white spot image on the halftone of the first image. But image formation 5
The white spot image disappeared within the number of sheets, and there was no practical problem. In Example 5, good images were obtained in each environment without fog and density unevenness in the image after 10,000 sheets.

Examples 6 and 7 In Example 6, the toner c produced as described below was used, and the charging roller was coated with a titanium oxide obtained by hydrophobizing an external additive used for the toner c. In Example 7, the toner d produced as described below was used, and the charging roller was coated with silica subjected to the hydrophobic treatment of an external additive used for the toner d.

The method for producing the toner c is as follows. The same strontium titanate 0.8 watt as that externally added in Example 1 was added to the toner composition prepared in Example 1 in the process of producing the toner a.
t%, and 1.5 wt% of titanium oxide which has been hydrophobized therewith
Was externally added to prepare a toner having a weight average particle size of 6.3 μm, which was designated as toner c. The average particle size of the hydrophobized titanium oxide is 0.02 μm, and the particle resistance is 10 ¹¹ Ωcm.
Met.

The titanium oxide subjected to the hydrophobic treatment is obtained by oxidizing titanium tetrapropoxide in a gas phase at 400 ° C.
Spherical hydrophilic titanium oxide (BET specific surface area: 155 m ² /
g), and this is obtained by adding and mixing the coupling agent at a ratio of 20% to the titanium fine particles so that the particles do not coalesce, and then drying and crushing the resulting mixture while stirring and mixing in an aqueous system. Was done.

The method for producing the toner d is as follows. 100 parts by weight of a polyester resin, 2 parts by weight of a metal-containing azo dye, 3 parts by weight of low-molecular-weight polypropylene, and 5 parts by weight of carbon black are dry-mixed and set at 150 ° C. The mixture was kneaded by a shaft kneading extruder. The obtained kneaded material was cooled, pulverized with an air-flow pulverizer, and then subjected to air classification to obtain a toner composition having a controlled particle size distribution. To this toner composition, 1.5 wt% of the hydrophobized silica used in Example 1 and 0.8 wt% of strontium titanate were externally added to prepare a toner having a weight average particle diameter of 6.3 μm. The toner d
And

As shown in Table 2, in each of Examples 6 and 7, the transfer efficiency was slightly lowered in each environment.
Even after the zero-sheet test, only slight density unevenness was confirmed in some parts, and a good image was obtained.

Examples 8 to 14 In Examples 8 to 14, the charging roller 2 had the structure shown in FIG. 2A and was manufactured as described below. Otherwise, an image forming test was performed in the same manner as before, and the image was evaluated.

To 100 parts by weight of EPDM, 30 parts by weight of conductive carbon black, 20 parts by weight of paraffin oil, an appropriate amount of a crosslinking agent and other compounding agents were added, and these were kneaded to prepare a conductive compound. Next, the above compound is heated and vulcanized at 150 ° C. for 15 minutes on a 6 mm-diameter stainless steel cylinder as a conductive substrate (core metal) 2a to obtain a rubber roller having a 3 mm-thick conductive elastic layer 2b. Was.

Subsequently, 100 parts by weight of a fluororesin (toluene / xylene = 1/1 solution, solid content 40%, fluoroolefin-vinyl ether copolymer) was added to conductive titanium oxide (surface treatment with tin oxide, average primary particles). Diameter: 0.
1 [mu] m, the powder resistivity: 10 ⁰ [Omega] cm) was added 25 parts by weight, was dispersed using a small bead mill, an isocyanate (curing agent) were mixed 20 parts by weight, by crosslinking, to prepare a fluororesin coating material. This fluororesin paint was dipped and applied on the rubber roller by dipping,
By drying by heating for 30 minutes, a surface layer 2d was formed to a thickness of 20 μm, and a charging roller 2 having the structure of FIG. 2A was obtained.

The surface area of the elastic portion of the charging roller is 87
cm ² . The charging roller 2 thus obtained is referred to as charging roller No. 2.

Thereafter, the same hydrophobicizing silica, untreated silica, strontium titanate, or hydrophobicizing titanium oxide as the external additive used for the toner was applied to the surface layer 2d of the charging roller 2, and FIG. As shown in ()), the charging roller 2 was used as a configuration in which an external additive was attached to the surface.

As shown in Table 2, each of Examples 8 to 14
In both cases, the durability tends to be deteriorated as compared with the case where the surface layer is formed with a tube, probably due to the effect of the decrease in the contact nip area with the photosensitive drum due to the insufficient elasticity of the charging roller, but in each case, In the environment, the practical level can be maintained even after the test of 10,000 sheets.

Comparative Examples 1 and 2 As the charging roller 2, Comparative Example 1 was the charging roller No. 1.
In Comparative Example 2, the charging roller No. 2 was used, but in each case, the external additive was not applied to the surface of the charging roller, and used in the image forming test. The photosensitive drum 1 was the photosensitive drum manufactured in Example 1, and the toner was toner a.

As shown in Table 2, in Comparative Example 1, N
In the H / H environment, the practical level was maintained even after the test of 10,000 sheets, but in the H / H environment, fog occurred on the entire image at about 8,000 sheets, and the density unevenness was conspicuous. Was.

In Comparative Example 2, the practical level could be maintained even after the test of 100 million sheets in the L / L environment.
9000 sheets in H / H environment, about 5000 in H / H environment
Fogging occurred in the entire image near the sheet, and particularly in the H / H environment, the level of fog and density unevenness were poor, and image formation was stopped around 6000 sheets.

In both Comparative Examples 1 and 2, H
A considerable amount of toner is visually adhered to the surface of the charging roller tested in the / H environment, and is incorporated in the image forming apparatus again, and a bias of DC-1200 V is applied to charge the photosensitive drum 1 (dark section potential). When Vd) was measured,
It had dropped to about -450V.

In the above, a charging roller was used as a contact charging member of the photosensitive drum 1. However, the present invention is not limited to this, and conductive blades, brushes, etc., which contact the photosensitive drum and charge it, can be used. It may be a charging member. As the image carrier, a photosensitive belt or the like can be used in addition to the photosensitive drum.

[0116]

As described above, according to the present invention,
The same external additive as the external additive externally added to the toner of the developer used in the developing device is previously attached to the surface of the charging member having elasticity which comes into contact with and charges the image carrier. As a result, it is difficult for toner to adhere to the surface of the contact charging member, and even when the charging member is used in the simultaneous development cleaning method, adhesion of toner remaining after transfer on the image carrier is prevented, and the image bearing by the charging member is carried out. Uniform charging of the body can be maintained, and a uniform image can be stably obtained over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration example of a charging roller according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 charging roller 2a conductive support 2b conductive elastic layer 2c intermediate layer 2d surface layer 3 developing device 9 external additive 31 developing roller

Claims (11)

[Claims] An electrostatic latent image formed by contacting an elastic charging member with a surface of an image carrier, uniformly charging the surface of the image carrier, and exposing the charged image carrier to light. Is developed using a developing means by a developing means, the obtained visible image is transferred to a transfer material, and the transfer remaining developer remaining on the image carrier is passed through a charging member, and then the next image of the next image is developed by the developing means. In the image forming apparatus, when developing the latent image, the developer is recovered by a potential difference between the image carrier and the developer carrier of the developing unit, wherein the developer is composed of at least a toner and an external additive thereof, and An image forming apparatus, wherein the same external additive as the external additive is previously adhered to the surface. 2. The amount Q (g) of the external additive adhering to the surface of the charging member is in the range of 0.1S <Q <50S, where S (m ² ) is the surface area of the outermost surface of the charging member. Item 1. The image forming apparatus according to Item 1. 3. The image forming apparatus according to claim 1, wherein said charging member is provided with a conductive elastic layer on a cylindrical conductive substrate, and a surface layer having releasability from toner on said elastic layer. apparatus. 4. The image forming apparatus according to claim 3, wherein a tube of a material constituting said surface layer is coated on an elastic layer to form a surface layer. 5. The image forming apparatus according to claim 3, wherein an intermediate layer having elasticity is provided between the elastic layer and the surface layer of the charging member. 6. The image forming apparatus according to claim 1, wherein said charging member is formed in a roller shape. 7. The image forming apparatus according to claim 1, wherein the external additive is a metal oxide subjected to a hydrophobic treatment. 8. The image forming apparatus according to claim 1, wherein the external additive has an average particle size of 1 μm or less. 9. The image forming apparatus according to claim 1, wherein the external additive has a particle resistance of 10 ¹² Ωcm or more. 10. The image forming apparatus according to claim 1, wherein the toner is spherical particles manufactured by a polymerization method. 11. The shape factor SF-1 of the toner is 10
The image forming apparatus according to claim 1, wherein SF-2 is 100 to 120 and 0 to 140.