JP2005010797A - Development method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development method capable of suppressing variation in the charge amount of toner on a developing roller, thereby uniformly depositing the toner substantially into a single layer on the developing roller. <P>SOLUTION: In the development method, a developer is moved to the latent image region of a latent image carryer by depositing a developer on the peripheral face of a developing roller and regulating the thickness of the developer layer by a rubber elastic developing blade for the developing roller. The blade is brought into contact with the developing roller in the upper part of the roller at the position opposite to the latent image carrying body. The contact angle between the tangential line of the peripheral face of the developing roller passing the contact point with the blade and the top end face of the blade is controlled to 75° to 85°. The developer used is a nonmagnetic single component developer prepared by externally adding an inorganic oxide having 5 to 20 nm average particle size and an inorganic oxide having >20 nm and ≤2 μm average particle size to spheric toner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing method by electrophotography.

  An image forming apparatus using an electrophotographic method, such as an electrophotographic printer, has a charging means for uniformly and uniformly charging the surface of a latent image carrier (photosensitive drum), and a surface of the uniformly charged photosensitive drum. A latent image forming means such as a laser device for writing an electrostatic latent image; a developing means for developing the electrostatic latent image with a developer (toner); and a transfer means for transferring the developed toner image to a transfer material such as transfer paper; It has.

  As a developing means of such an image forming apparatus, a developing apparatus including a developing roller, a developing roller blade, a developer containing means (accommodating casing), and a developer supplying means (supplying roller) is known. When the developing roller is rotated in the developing device, the toner in the developer containing means adheres to the outer peripheral surface due to electrostatic force caused by friction. The developing roller blade contacts the outer peripheral surface of the rotating developing roller and adjusts the thickness of the toner layer formed on the outer peripheral surface of the developing roller. That is, the developing roller blade scrapes off part of the toner particles adhering to the developing roller, adjusts the layer thickness of the toner particles, and acts to uniformize the charge amount of the passing toner.

  Part of the toner adhering to the outer peripheral surface of the developing roller selectively moves to the surface of the photosensitive drum in a latent image pattern when the surface of the developing roller comes close to the surface of the photosensitive drum, The electrostatic latent image is developed, and a toner image is formed on the surface of the photosensitive drum. This toner image is transferred to a transfer material (transfer paper), and an image is formed on the transfer paper.

  The developing roller blade used in such a developing device is expected to play a role of depositing a uniform and thin toner on the outer peripheral surface of the developing roller. If the toner does not uniformly adhere to the outer peripheral surface of the developing roller, the photosensitive member fog is generated when the electrostatic latent image on the surface of the photosensitive drum is developed. Photoreceptor fogging is a phenomenon in which toner having a polarity opposite to that of the toner to be adhered to the photosensitive drum adheres to the photosensitive drum, making uniform charging difficult and causing problems such as deterioration in image quality.

  As a conventional developing roller blade, for example, a stainless steel blade is known. However, when this stainless steel blade is used, the toner charge amount on the developing roller is likely to vary, and the filming phenomenon in which the toner is fused by frictional heat to form a film is likely to occur. Moreover, it is difficult for the stainless steel blade to form the toner substantially uniformly in a single layer on the developing roller.

A blade made of a rubber elastic material has also been proposed as a blade for the developing roller, but when the blade is in contact at any contact angle, a substantially single toner layer is formed on the outer peripheral surface of the developing roller. It was not clear as to what could be done. For example, a developing device has been proposed in which the contact angle is approximately 90 degrees (the blade tip surface is approximately 90 degrees with respect to the tangent to the developing roller) so that the blade surface and the roller surface overlap each other (Patent Document 1). . However, in the developing device in which the blade is in contact with the developing roller at a contact angle close to 90 degrees, the toner charge amount is likely to vary, and the toner is uniformly formed on the developing roller so as to be substantially a single layer. It was difficult to adhere.
JP 62-118372 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing method capable of suppressing toner charge amount variation on a developing roller and uniformly adhering the toner so that the toner becomes a substantially single layer on the developing roller. is there.

  Another object of the present invention is to provide a developing method using a developer that is excellent in fluidity and image density, has small photoreceptor fogging, and has good durability.

  As a result of intensive studies on the blade for the developing roller, the present inventors have configured the blade with a rubber elastic body, and by setting the contact angle of the blade to the developing roller within a predetermined range, the charge amount of the toner on the developing roller It has been found that the toner can be uniformly deposited on the developing roller so that the toner becomes substantially a single layer.

  Further, in a method of developing by forming a substantially single toner layer on the developing roller, a spherical toner is used as a developer, an inorganic oxide having an average particle shape of 5 to 20 nm, and an average particle shape of 20 nm. It has been found that by using a developer containing an excess of 2 μm or less of inorganic oxide mixed and added externally, the photoreceptor fog is extremely small, the printing density is good, and a good image quality can be formed even after a continuous printing test. . The present invention has been completed based on these findings.

Thus, according to the present invention, the developing roller is disposed opposite to the latent image carrier, the developer accommodated in the developer accommodating means is attached to the outer peripheral surface of the developing roller, and the developing roller made of a rubber elastic body The blade is brought into contact with the rotating developing roller to regulate the layer thickness of the developer layer adhering to the outer peripheral surface of the developing roller, and adhered to the outer peripheral surface of the developing roller in the latent image area of the latent image carrier. In the development method of developing by moving the developer,
(1) The developing roller blade is brought into contact with the developing roller at a predetermined position on the opposite side to the latent image carrier on the developing roller, and a tangent line on the outer periphery of the developing roller passing through a point where the developing roller blade contacts with the developing roller; The contact angle formed with the tip surface of the developing roller blade is 75 to 85 degrees, and
(2) A non-magnetic one-component developer obtained by externally mixing a spherical toner with an inorganic oxide (a) having an average particle diameter of 5 to 20 nm and an inorganic oxide (b) having an average particle diameter exceeding 20 nm and not exceeding 2 μm. There is provided a developing method characterized by using and developing.

The spherical toner includes at least a binder resin and a colorant obtained by suspension polymerization of a polymerizable monomer composition containing at least a vinyl monomer and a colorant, and has a volume average particle diameter (dv). 3-15 μm, ratio of volume average particle size (dv) to number average particle size (dn) (dv / dn) of 1.00-1.40, area of circle having absolute maximum length of particle as diameter (Sc) (Sc / Sr) divided by the actual projected area (Sr) of the particles is 1.00 to 1.30, and the specific surface area (A) (m ² / g) by the BET method and the number average particle diameter (dn ) (Μm) and true specific gravity (D) are preferably substantially spherical with a product (A × dn × D) of 5 to 10, and the charge amount (Q) (μc / g) and specific surface area ( A nonmagnetic monocomponent spherical toner having an absolute value of the ratio (Q / A) of A) in the range of 50 to 150 is preferable.

  The spherical toner used in the present invention can be obtained as a so-called polymerized toner by suspension polymerization of a polymerizable monomer composition containing at least a vinyl monomer and a colorant. The developer is used as a nonmagnetic one-component developer.

  In the developer and the development method, the mixing ratio of the inorganic oxide to 100 parts by weight of the spherical toner is 0.1 to 3.0 parts by weight of the inorganic oxide (a) having an average particle diameter of 5 to 20 nm, and the average particle The inorganic oxide (b) having a diameter exceeding 20 nm and not more than 2 μm is preferably 0.1 to 3.0 parts by weight. The mixing ratio (a: b weight ratio) of the inorganic oxide (a) and the inorganic oxide (b) is preferably in the range of 1: 5 to 5: 1. These inorganic oxides are preferably hydrophobized.

  According to the present invention, by setting the contact angle of the developing roller blade with respect to the developing roller to 75 to 85 degrees, and using a developer in which inorganic oxides having different average particle diameters are mixed and added to the spherical toner, Appropriate developer layer thickness (substantially a single layer) can be formed, the developer charge amount and adhesion amount are stabilized, and the photoreceptor fog, paper fog, and image density fluctuation are less likely to occur. Become.

  The present invention uses a developer in which inorganic oxides (a) and (b) having different average particle diameters are mixed and externally added (mixed as an external additive) to a spherical toner, and the developer is placed on a developing roller. The method is characterized in that it is a method of developing by forming a substantially single toner layer.

  As a method of forming a substantially single toner layer on the developing roller, a developing roller blade made of a rubber elastic body is brought into contact with the rotating developing roller, and at that time, the latent image carrier above the developing roller and Is a predetermined position on the opposite side, and the developing roller blade is brought into contact with the developing roller, and the contact angle formed between the tangent to the outer periphery of the developing roller passing through the point where the developing roller blade contacts and the tip surface of the developing roller blade A method of adjusting the angle to 75 to 85 degrees. Here, the contact angle is an angle formed by a tangent line on the outer periphery of the developing roller that passes through a point where the developing roller blade contacts the developing roller and a tip surface of the blade.

Image forming apparatus An image forming apparatus using electrophotography generally has a charging means for charging the surface of a latent image carrier, and a latent image for writing an electrostatic latent image on the surface of the charged latent image carrier. The image forming apparatus includes a forming unit, a developing unit for developing the electrostatic latent image with a developer (toner), and a transfer unit for transferring the developed toner image to a transfer material.

  FIG. 1 shows a cross-sectional view of an example of an image forming apparatus for applying the developer and the developing method of the present invention. In this image forming apparatus, a photosensitive drum 1 is mounted as a latent image carrier so as to be rotatable in the direction of an arrow. The photoreceptor drum 1 usually has a structure in which a photoconductive layer is provided on the outer periphery of a conductive support drum body. The photoconductive layer is composed of, for example, an organic photoreceptor, a selenium photoreceptor, a zinc oxide photoreceptor, an amorphous silicon photoreceptor, or the like.

  Around the photosensitive drum 1, a charging unit 3, a latent image forming unit 4, a developing unit 5, a transfer unit 6, and a cleaning unit 2 are arranged along the circumferential direction. The charging unit 3 has a function of uniformly charging the surface of the photosensitive drum 1 positively or negatively, and includes, for example, a corona discharge device, a charging drum, a charging blade, and the like. The latent image forming means 4 irradiates the uniformly charged surface of the photosensitive drum with light corresponding to the image signal in a predetermined pattern to form an electrostatic latent image on the irradiated portion (reversal development method). Alternatively, an action of forming an electrostatic latent image (regular development method) is performed in a portion not irradiated with light. The latent image forming unit 4 is configured by, for example, a combination of a laser device and an optical system, or a combination of an LED array and an optical system.

  The developing means 5 performs an action of attaching a developer (toner) to the electrostatic latent image formed on the surface of the photosensitive drum 1. The developing means 5 is usually a developing device provided with a developing roller 8, a developing roller blade 9, a developer 10 accommodating means (accommodating casing) 11, and a developer supplying means (supply roller) 12. The developing roller 8 is disposed so as to face the photosensitive drum 1, and is usually disposed in close proximity so that a part of the developing roller 8 contacts the photosensitive drum 1, and is rotated in a direction opposite to the photosensitive drum 1. . The supply roller 12 contacts the developing roller 8 and rotates in the same direction as the developing roller 8, and supplies the toner 10 to the outer periphery of the developing roller 8.

  When the developing roller 8 is rotated in the developing device, the toner 10 in the developer containing means 11 adheres to the outer peripheral surface due to electrostatic force caused by friction. The developing roller blade 9 abuts on the outer peripheral surface of the rotating developing roller 8 and adjusts the thickness of the toner layer formed on the outer peripheral surface of the developing roller 8.

  In the reverse development method, the toner is attached only to the light irradiation portion of the photosensitive drum 1, and in the regular development method, the toner is attached only to the light non-irradiation portion. A bias voltage is applied between them.

  The transfer means 6 is for transferring the toner image on the surface of the photosensitive drum 1 formed by the developing means 5 to a transfer material (transfer paper) 7, and is composed of, for example, a corona discharge device, a transfer roller, and the like. .

  The cleaning means 2 is for cleaning the toner remaining on the surface of the photosensitive drum 1, and is constituted by, for example, a cleaning blade. However, this cleaning means is not always necessary in the case of a system in which a cleaning action is performed simultaneously during development.

<Developing roller>
The material of the developing roller used in the present invention is not particularly limited, but it is preferable that at least the surface is made of a rubber elastic body. The friction coefficient of the surface of the developing roller is usually 0.1 to 1.2, preferably 0.15 to 0.8, and more preferably 0.2 to 0.6.

By setting the coefficient of friction of the rubber elastic body surface within the above range, it becomes easy to stably form a toner layer on the surface of the developing roller at a density of 0.2 to 0.4 mg / cm ² by the layer thickness regulating blade 9, As a result, the toner can be frictionally charged uniformly, and the photoreceptor fog and paper fog can be reduced. Further, by setting the friction coefficient within the range, even if a virgin developing roller is used, normal printing can be performed without idling. In the developing roller having a friction coefficient smaller than 0.1, the surface of the roller may be slipped too much and the toner layer may not be formed uniformly. When the friction coefficient is larger than 1.2, the toner layer becomes too thick, and the photosensitive member fog and the paper fog tend to increase.

  The rubber elastic body constituting the surface of the developing roller is not particularly limited. For example, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, epichlorohydrin rubber, urethane rubber, silicon rubber, A blend of two or more of these may be mentioned. Among these, a blend rubber of epichlorohydrin rubber and acrylonitrile-butadiene copolymer rubber is preferably used.

  The developing roller used in the present invention is manufactured, for example, by covering the outer periphery of a conductive shaft with a rubber elastic body. The conductive shaft is made of a metal such as stainless steel, for example. In order to coat the outer periphery of the conductive shaft with the rubber elastic body, the rubber elastic body may be attached to the outer periphery of the conductive shaft by means of press molding or extrusion molding and vulcanized. In this case, extrusion molding is particularly suitable for mass production, and unlike press molding, a split mold line is not formed, which is preferable.

  As a means for setting the surface of the developing roller to have a friction coefficient within the above range, after polishing the outer peripheral surface of the developing roller with a cylindrical cutting machine or the like, ultraviolet irradiation is performed to crosslink the unsaturated portion of the rubber elastic body, A method of adjusting the friction coefficient can be adopted. The conditions for ultraviolet irradiation are, for example, conditions in which a light source of 80 W / cm is used for irradiation for 2 to 3 minutes. The polishing of the developing roller is preferably performed first with a coarse cutting file or a grindstone, and finally with a fine file or grindstone.

When the developing roller used in the present invention is composed of a conductive shaft and a rubber elastic body, the electrical resistance between the surface of the rubber elastic body and the surface of the conductive shaft is 10 ⁵ to 10 ⁸ Ω (500 V Preferably, the volume resistivity is 10 ⁷ to 10 ¹⁰ Ω · cm. If the resistance of the rubber elastic body is too low, current may flow from the developing roller to the latent image carrier (photosensitive drum), and the charge of the toner may leak to the developing roller. If the resistance of the rubber elastic body is too high, the surface may be charged by friction, which may adversely affect development.

  Each surface roughness in the circumferential direction and the axial direction of the developing roller used in the present invention is usually 10 μm or less. When the surface roughness in the circumferential direction is larger than 10 μm, there is a higher tendency to cause photoconductor fog and paper fogging along the circumferential direction, and when the surface roughness in the axial direction is larger than 10 μm, it follows the axial direction. As a result, there is a higher tendency to cause photoreceptor fog and paper fog. In the present invention, the surface roughness refers to the ten-point average roughness (Rz) of the curve by tracing the developing roller surface with a pointer, recording the movement, and expressing the uneven shape of the surface as a surface roughness curve. . Each surface roughness in the circumferential direction and the axial direction may be close to 0 as long as it is 10 μm or less, but is preferably about 6 to 8 μm in view of mass productivity and economy. By setting the surface roughness in the circumferential direction and the axial direction to 10 μm or less, the toner layer becomes uniform, and the photoreceptor fog and paper fog can be further reduced. In order to make the surface roughness within the above range, the outer peripheral surface of the rubber elastic body may be polished with a cylindrical grinder or the like.

  In the present invention, the friction coefficient is a coefficient obtained by the Euler belt type friction coefficient measuring method shown in FIG. As shown in FIG. 5, first, a measurement paper (usually copy paper) 53 is cut into a certain width (for example, about 20 mm). Next, approximately 90 degrees of the measurement paper is wound around the developing roller 8 (measuring roller), a weight 54 having a predetermined weight is attached to one end, and a tension gauge 55 is attached to the other end.

Next, the measurement paper 53 on the surface of the developing roller 8 is pulled at a constant speed (about 100 ± 20 mm / min) in a state where the weight 54 is not shaken. The scale of the tension gauge 55 at the moment when the measurement paper 53 starts to move on the surface of the developing roller is read. A numerical value obtained by substituting the measured value F read by the tension gauge 55 and the weight W of the weight 54 into the following formula is the friction coefficient μ _s in the present invention.

  It is preferable that a bias voltage is applied to the conductive shaft of the developing roller. In the case of reversal development, a voltage having the same polarity as that of the electrostatic latent image on the latent image carrier is applied to the conductive shaft of the developing roller.

<Development roller blade>
The developing roller blade preferably used in the present invention has a belt shape that contacts the outer peripheral surface along the axial direction of the developing roller. The tip of the blade is not fixed and is configured to contact the surface of the developing roller. It is preferable that the other end of the blade is fixed to a holder made of a rigid body so that the angle at which the blade contacts the developing roller can be adjusted.

  The length of this blade (length from the fixed end to the free end: free end length 1) is not particularly limited, but is preferably 10 to 12 mm. The thickness t of the blade is preferably about 1.2 to 1.5 mm. The width of the blade has a length corresponding to the axial length of the developing roller. The free end of the blade may have a shape that draws a gentle arc, or may have a shape having an acute angle, a right angle, or an obtuse angle.

  As shown in FIG. 1, a layer thickness regulating blade 9 as a developing roller blade is provided around the developing roller 8 at a position between the contact point with the developer supply roller 12 and the contact point with the photosensitive drum 1. Has been placed. The blade 9 is made of, for example, a conductive rubber elastic body. As shown in a cross section in FIG. 2, the blade 9 is usually in the shape of a strip plate, and the base end portion is held by the holder 50. The holder 50 is made of a metal that is a conductive material.

  The compression set of the developing roller blade is preferably 10% or less, more preferably 4 to 8%. The compression set is measured according to JIS K-6262. By setting the compression set to 10% or less, the permanent set generated in the blade in pressure contact with the developing roller is reduced, and the linear pressure of the blade against the developing roller is prevented from decreasing over time. Can be formed.

The rebound resilience of the developing roller blade is preferably 30 to 50%. The rebound resilience is measured by the Rüpke method (JIS K-6255). When the rebound resilience is 30 to 50%, the thickness of the toner layer is easily made substantially a single layer. Young's modulus of the blade 9 is preferably 80~120kg / cm ^2, more preferably 90~110kg / cm ^2. When the Young's modulus of the blade 9 is in the above range, the thickness of the toner layer can be made substantially close to a single layer. When the Young's modulus is too large, the rotational torque to the developing roller increases and a phenomenon such as jitter (horizontal stripes corresponding to the number of teeth of the developing roller driving gear) occurs.

The electrical resistance between the portion of the blade 9 that touches the phenomenon roller 8 and the portion of the conductive holder 50 that fixes the blade 9 is usually 10 ⁶ Ω or less, and preferably 10 ⁴ to 10 ⁶ Ω. This electrical resistance is preferably low, but in the manufacturing method of the conductive blade made of rubber elastic body, conductive particles such as carbon black are added to lower the electrical resistance, so that the content of conductive particles increases. Naturally, there is a restriction because the elasticity of the rubber elastic body tends to decrease too much.

More specifically, a voltage of −200 V to −600 V is preferably applied to the developing roller blade in order to inject charge into the toner. For this reason, the electric resistance of the blade is 10 ⁶ Ω or less. Preferably there is. As shown in FIG. 4, the measuring method of the electric resistance of the blade for the developing roller is such that the tip of the corner where the blade 9 touches the developing roller 8 is brought into contact with the conductive plate 51 and the electric power between the holder 50 and the holder 50 for fixing the blade 9 is fixed. Resistance is measured with an insulation resistance meter 52 (applied voltage: 500 V).

  The rubber elastic body constituting the developing roller blade is not particularly limited. For example, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, Silicon rubber etc. are mentioned, Among these, urethane rubber, NBR, etc. are preferably used.

  In order to set the compression set, rebound resilience, and Young's modulus of the developing roller blade within the above ranges, vulcanization conditions such as the amount of vulcanizing agent contained in the rubber elastic body constituting the blade may be selected. . For example, when the rubber elastic body constituting the blade is made of urethane rubber, the total amount of the rubber elastic body is 100% by weight, the addition amount of the vulcanizing agent is 1.0 to 4.0% by weight, and the vulcanization temperature. If the temperature is 150 to 170 ° C. and the vulcanization time is 20 to 50 minutes, the compression set, the rebound resilience, and the Young's modulus can be set within the above ranges.

The electric resistance of the developing roller blade is set to 10 ⁶ Ω or less by adjusting the content of conductive particles such as carbon black contained in the rubber elastic body constituting the blade. For example, when the rubber elastic body constituting the blade is made of urethane rubber, the total amount of the rubber elastic body is 100% by weight, and the addition amount of carbon black having an average particle diameter of 40 nm is 5 to 30% by weight. The electric resistance can be set within the above range.

  In the developing device used in the present invention, the blade for the developing roller is attached at an angle such that the contact angle with respect to the developing roller is 75 to 85 degrees, preferably 77 to 83 degrees. If the contact angle is less than 75 degrees, the toner layer formed on the surface of the developing roller tends to be too thin, and if the contact angle is too small, the blade may be turned up by the rotation of the developing roller. . When the contact angle is larger than 85 degrees, the toner layer becomes too thick, and when the contact angle becomes too large, the abdomen of the blade comes into contact with the outer peripheral surface of the developing roller, and the toner layer becomes extremely thick. .

  Specifically, as shown in FIG. 2, the blade 9 made of a rubber elastic body has a free end bent with respect to the developing roller 8 in a direction opposite to the rotation direction of the developing roller 8 and a contact angle θ. Is attached to be 75 to 85 degrees. That is, the developing roller blade is brought into contact with the developing roller at a predetermined position on the developing roller upper side opposite to the latent image carrier, and the tangent line on the outer periphery of the developing roller passing through the point where the developing roller blade contacts with the developing roller. The contact angle formed with the tip surface of the roller blade is set to 75 to 85 degrees.

  As shown in FIG. 2, the contact angle θ is an angle formed by a tangent line T on the outer periphery of the developing roller passing through a point where the blade 9 contacts the developing roller 8 and the tip surface S of the blade 9. When the tip surface of the blade 9 is a plane or curved surface other than a right angle with respect to the blade abdominal surface, the tip surface S of the blade 9 is a surface substantially perpendicular to the bending line U along the free end of the blade 9. Defined.

  The blade 9 is preferably attached to the developing roller 8 so that the linear pressure is 0.7 to 2 g / mm. Here, the linear pressure f is defined by the following mathematical formula.

  In this equation, t is the thickness of the blade, δ is the deflection of the blade, E is the Young's modulus of the blade, and l is the free end length of the blade (see FIG. 2).

Reversal Development System In the present invention, a system in which reversal development is performed using the above-described image forming apparatus (however, the cleaning unit 2 is not provided) and cleaning is performed simultaneously with the development can be employed.

In order to perform reversal development, the surface of the photosensitive drum 1 is uniformly charged to about V _C = −500 V, for example, as shown in FIG. 3A by the charging unit 3 shown in FIG. Next, the latent image forming means 4 shown in FIG. 1 irradiates light with a predetermined pattern, partially uncharges the charged surface of the photosensitive drum 1, and forms an electrostatic latent image with the predetermined pattern. To do. The potential of the region where the electrostatic latent image is formed is, for example, a voltage close to zero V.

The electrostatic latent image on the surface of the photosensitive drum 1 is developed by the developing means 5 shown in FIG. On the surface of the developing roller 8 of the developing means 5, the layer thickness is regulated by the action of the developing roller blade 9, and a substantially single layer of the spherical toner 10 is formed. As shown in FIG. 3B, a bias voltage is applied between the developing roller 8 and the photosensitive drum 1 so that the surface potential V _D of the developing roller 8 is, for example, −200V. For this reason, the negatively charged toner 10a adhering to the peripheral surface of the developing roller 8 moves to the surface of the photosensitive drum 1 in a pattern of an electrostatic latent image as a light irradiating portion, and the photosensitive drum 1 As shown in FIG. 3C, a toner image with an electrostatic latent image pattern is formed on the surface.

  As shown in FIG. 3B, the negative residual toner 10b adhering to a region other than the electrostatic latent image on the photosensitive drum 1 is an electric field based on the surface potential of the photosensitive drum and the surface potential of the developing roller 8. As a result, it moves to the developing roller 8 side. As a result, the surface of the photosensitive drum 1 can be cleaned simultaneously with development. Therefore, in this reversal development method, the cleaning means 2 shown in FIG. 1 is not necessary.

The condition for carrying out the simultaneous development cleaning is that when the charging potential of the surface of the photosensitive drum 1 is V _C and the surface potential of the developing roller 8 is V _D , the absolute value of V _C −V _D is 50V. That is all you need. The tip of the potential of the blade 9 shown in Figure 1 and _{V BL,} when the surface potential of the supply roller 12 was set to _{V S} is preferably a _{V D ≧ V BL ≧ V S} . When the charging polarity of the toner 10 and the polarity of the surface potential of the photosensitive drum 1 are positive, the absolute value of V _C −V _D is 50 V or more, and the absolute value of V _D ≦ the absolute value of V _BL ≦ V _Any relationship of the absolute value of _S may be used. This relationship is the same in the case of simultaneous development cleaning in regular development.

Developer In the present invention, as a developer, an inorganic oxide (a) having an average particle diameter of 5 to 20 nm and an inorganic oxide (b) having an average particle diameter exceeding 20 nm and not more than 2 μm are externally added to a spherical toner. A non-magnetic one-component developer is used.

<Spherical toner>
The spherical toner contains at least a binder resin and a colorant, and has a volume average particle diameter (dv) of 3 to 15 μm, preferably 5 to 10 μm, and a ratio of the volume average particle diameter (dv) to the number average particle diameter (dn) ( (dv / dn) is 1.00 to 1.40, and the value (Sc / Sr) obtained by dividing the area (Sc) of the circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle is 1.00. To 1.30, and the product (A × dn × D) of the specific surface area (A) (m ² / g), number average particle diameter (dn) (μm), and true specific gravity (D) by the BET method is 5 Is preferably substantially spherical, and the absolute value of the ratio (Q / A) of the charge amount (Q) (μc / g) to the specific surface area (A) is in the range of 50 to 150. A magnetic one-component spherical toner is preferable.

The method and apparatus for measuring the physical properties of the spherical toner are as follows.
(1) Sc / Sr is a value measured and analyzed by the image processing analyzer under the following conditions.
Image processing analyzer: Luzex IID [Nikole Co., Ltd.]
Particle area ratio to frame area: Max 2%
Total number of processed particles: 1000 Sc / Sr value is represented by an average number of 1000 particles.

(2) The specific surface area (A) according to the BET method is a value measured using a specific surface area automatic measuring apparatus 2200 manufactured by Shimadzu Corporation.

(3) The volume average particle diameter (dv) and the number average particle diameter (dn) are values measured by a Coulter counter [model TA-II type, manufactured by Nikkiki Co., Ltd.].

(4) True specific gravity (D) is a value measured by a Beckman hydrometer.

(5) The charge amount (Q) (μc / g) is a value measured by a blow-off method after a toner is blended with the carrier TEFV150 / 250 so as to have a concentration of 5% and stirred at 150 rpm for 30 minutes. The charge amount (Q) and the ratio (Q / A) are expressed as absolute values regardless of positive charge or negative charge.

  The spherical toner can be obtained by polymerizing a polymerizable monomer composition containing a vinyl monomer and a colorant by a suspension polymerization method. As a specific suspension polymerization method, for example, a mixture containing a vinyl monomer, a colorant, a radical polymerization initiator, and various additives as required is uniformly dispersed with a ball mill or the like to obtain a uniform mixed solution (polymerizability). Monomer composition) is prepared, and then the homogeneous mixed solution is finely dispersed in water by high shear stirring to granulate fine droplets, and then heated to a temperature of usually 30 to 200 ° C. And suspension polymerization.

  Examples of vinyl monomers include aromatic vinyl such as styrene, vinyl toluene, and α-methylstyrene; acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, acrylic acid 2 -Derivatives of acrylic acid or methacrylic acid such as ethylhexyl, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, acrylonitrile, acrylamide; olefins such as ethylene, propylene, butylene; Vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl methyl keto , Vinyl ketones such as methyl isopropenyl ketone; 2-vinylpyridine, 4-vinylpyridine, nitrogen-containing vinyl compounds such as N- vinyl pyrrolidone. These vinyl monomers can be used alone or in combination of two or more.

  An arbitrary cross-linking agent can be used together with these vinyl monomers. Examples of the crosslinking agent include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline and divinyl ether And a compound having 3 or more vinyl groups. These crosslinking agents can be used alone or in combination of two or more.

  Examples of the colorant include carbon black, aniline black, crystal violet, rhodamine B, malachite green, ligrosin, copper phthalocyanine, azo dye, and other pigments and dyes. These colorants can be used alone or in combination of two or more.

  Further, nigrosine dye, monoazo dye, metal-containing dye, zinc hexadecyl succinate, alkyl ester or alkyl amide of naphthoic acid, nitrohumic acid, N, N′-tetramethyldiamine benzophenone, N, N′-tetramethylbenzidine, You may contain 1 type, or 2 or more types of strong polar substances called a charge control agent in this field | area, such as a triazine and a salicylic acid metal complex. The charge polarity of the toner can also be adjusted to positive (+) or negative (−) by selecting the type of charge control agent.

  The spherical toner can be internally or externally added with an additive for controlling chargeability, conductivity, fluidity, or adhesion to the photosensitive drum or the fixing roller. Examples of such additives include mold release agents such as low molecular weight polypropylene, low molecular weight polyethylene, various waxes, and silicone oil, and inorganic fine powders such as carbon black and calcium carbonate.

<Inorganic oxide>
In the present invention, for example, silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, tin oxide, barium titanate, strontium titanate or the like can be used as the inorganic oxide to be externally added to the spherical toner. These inorganic oxides are preferably hydrophobized. Of these inorganic oxides, hydrophobized silicon dioxide is particularly preferred.

  As the inorganic oxide, a first inorganic oxide (a) having an average particle diameter of 5 to 20 nm, preferably 7 to 18 nm, and a second inorganic oxide having an average particle diameter of more than 20 nm and not more than 2 μm, preferably 30 nm to 1 μm. The oxide (b) is used in combination. The average particle diameter of the inorganic oxide is an average value of particle diameter values measured for 100 inorganic oxide particles (n = 100 particles) with a transmission electron microscope.

  The mixing ratio of the first inorganic oxide (a) to 100 parts by weight of the spherical toner is usually 0.1 to 3.0 parts by weight, preferably 0.2 to 2.0 parts by weight. The mixing ratio of b) is usually 0.1 to 3.0 parts by weight, preferably 0.2 to 2.0 parts by weight. The weight ratio (a: b) of the first inorganic oxide (a) to the second inorganic oxide (b) is usually 1: 5 to 5: 1, preferably 3:10 to 10: 3.

  In the present invention, in the method of developing by forming a substantially single developer layer on the developing roller, the spherical toner is used as the developer and the inorganic oxides (a) and (b )), A substantially single developer layer can be easily formed on the developing roller even after the initial and continuous printing tests. Although it can be multi-layered or formed as a single layer, it can prevent the adhesion amount from decreasing, (2) it can maintain good fluidity, and (3) it can maintain image density at a good level. It is possible to achieve excellent effects such as (4) prevention of the photosensitive drum and paper fogging, and (5) printing with good image quality even with the cleaner-less method.

  When the first inorganic oxide (a) is not mixed or the mixing ratio is too small, a developing device in which the developing roller blade is attached to the developing roller so that the contact angle is 75 to 85 degrees may be used. The developer layer formed on the developing roller is small, the image density is lowered, and fogging occurs. If the mixing ratio of the first inorganic oxide (a) is excessive, it becomes difficult to ensure proper fluidity of the developer. If the average particle size of the first inorganic oxide (a) is too small, the charge amount distribution becomes broad, and there is a possibility that a photoreceptor and paper fogging occur.

  When the second inorganic oxide (b) is not mixed or when the mixing ratio is too small, a developing device in which the developing roller blade is attached to the developing roller so that the contact angle is 75 to 85 degrees may be used. The fluidity and image density after continuous printing are lowered, and fogging tends to occur. If the mixing ratio of the second inorganic oxide (b) is excessive, the image quality may be deteriorated due to a decrease in fluidity. If the average particle size of the second inorganic oxide (b) is excessive, filming of the inorganic oxide tends to occur on the photosensitive drum due to poor cleaning.

  By using a developer in which the first inorganic oxide (a) and the second inorganic oxide (b) are mixed and added to the spherical toner, the contact angle of the developing roller blade with respect to the developing roller is 75 to 85 degrees. When it is applied to a developing device attached so that a substantially single-layer developer layer can be formed on the developing roller, excellent fluidity and image density, and good image quality without fogging can be obtained. In addition, even after the continuous printing test, these characteristics can be maintained at a high level. Further, by setting the weight ratio (a: b) of the first inorganic oxide (a) to the second inorganic oxide (b) in the range of 1: 5 to 5: 1, it is possible to prevent deterioration of image quality. .

In the present invention, a substantially single layer of developer is formed on the developing roller by the developing method using the developing device in which the developing roller blade is attached to the developing roller so that the contact angle is 75 to 85 degrees. As for the developer, by using a developer in which two types of inorganic oxides having different average particle diameters are mixed and added to the spherical toner, the developer has good fluidity, and on the developing roller. Thus, a single layer of the developer can be reliably formed, the charge amount and the adhesion amount of the developer can be stabilized, and an image with high image density and no fog can be formed. Moreover, the present invention provides a developing method that is excellent in fluidity and image density and can maintain high image quality even after long-term operation (after continuous printing).

According to the present invention, the developer layer around the developing roller is substantially a single layer (developing roller surface) by using a developing device that uses a specific developer and combines the above-described preferred developing roller and developing blade. Developer density of 0.2 to 0.4 mg / cm ² ), and a stable image can be obtained. Even when a virgin developing roller is used, normal printing can be performed without idling.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited only to these Examples. In the following examples and comparative examples, parts and% are based on weight unless otherwise specified. The physical properties are measured as follows.

(1) Photosensitive fog The developer in the fogged part on the photosensitive drum is transferred onto paper with a mending tape, and the reflectance measured with a whiteness meter (Nippon Denshoku) This was done by comparing the value obtained by subtracting the reflectance when pasted on paper from the value measured with a whiteness meter. The larger this value, the more photosensitive member fog.

(2) Image density Using a Macbeth densitometer, the image density was measured by measuring the black solid part.

(3) Fluidity Using a powder tester (manufactured by Hosokawa Micron Co., Ltd.), sieves with openings 149, 74, and 44 μm are stacked on the upper, middle, and lower stages, respectively, and 4 g of developer is placed on the sieve with an upper stage opening of 149 μm. (Toner) is placed, and vibration is applied for 15 seconds with an amplitude of 0.2 mm. After the vibration is stopped, the aggregation degree is obtained by the following operation.
(Weight of toner on 149 μm aperture sieve / 4 g) × 100 (1)
(Toner weight on 74 μm aperture sieve / 4 g) × 100 × (3/5) (2)
(Toner weight on 44 μm aperture sieve / 4 g) × 100 × (1/5) (3)
The total of the above three calculated values is used as the degree of aggregation (%), and the fluidity is obtained by the following formula. Fluidity (%) = 100-cohesion degree (%)

[Example 1]
<Image forming apparatus>
A rubber elastic body composed of a blend rubber of epichlorohydrin rubber and acrylonitrile-butadiene copolymer rubber was formed on the outer periphery of a stainless steel shaft having a diameter of 10 mm to a thickness of 3.9 mm by extrusion molding. Thereafter, the outer peripheral surface of the rubber elastic body was polished with a cylindrical cutting machine, so that the surface roughness of the outer peripheral surface was 4 μm in the axial direction and the circumferential direction. Next, while rotating the rubber elastic body, the surface was irradiated with ultraviolet rays under a condition of 2 minutes using a lamp of 80 W / cm. As a result, the friction coefficient of the surface of the rubber elastic body was 0.6.

  The developing roller 8 thus obtained was placed in contact with the photosensitive drum 1 so that the contact width was about 2 mm, as shown in FIG. As the photosensitive drum 1, an organic photosensitive drum having an outer diameter of 30 mm was used. As the charging means 3, a corona discharge device is used in which the surface potential of the photosensitive drum 1 is uniform at about VC = -600V. As the electrostatic latent image forming unit 4, an apparatus combining a laser device and an optical system was used. As the supply roller 12, a sponge roller made of urethane rubber having an outer diameter of 13 mm was used. The supply roller 12 was brought into contact with the developing roller 8 so that the contact width was about 2 mm.

The layer thickness regulating blade 9 which is a developing roller blade is composed of a rubber elastic body made of urethane, and has a compression set of 6%, a Young's modulus of 85 kg / cm ² and a rebound resilience of 30%. A flat blade of 222 mm × 1.2 mm was used. The electrical resistance of this blade was 5 × 10 ⁵ Ω when measured by the measuring method shown in FIG. As shown in FIG. 2, the blade 9 was attached in contact with the outer periphery of the developing roller 8 so that the contact angle θ with respect to the developing roller 8 was 80 degrees. At this time, the linear pressure F with respect to the developing roller 8 was about 1.66 g / mm, and the deflection amount δ was 4.54 mm.

In this embodiment, a method of developing simultaneously with cleaning by a reversal development method is adopted, and a bias voltage is applied between the developing roller 8 and the photosensitive drum 1 so that the surface potential V _D of the developing roller 8 becomes −200V. Applied. A bias voltage was applied so that the potential at the tip of the layer thickness regulating blade 9 was V _BL = −220 V, and a bias voltage was applied so that the surface potential V _S of the supply roller 12 was −600 V. In this embodiment, since the simultaneous development cleaning (cleaner-less) method is adopted, the cleaning means 2 shown in FIG. 1 is not necessary. The photosensitive drum 1 is rotated in the arrow direction at a peripheral speed of 40 mm / second, the developing roller 8 is rotated in the arrow direction at a peripheral speed of 100 mm / second, the supply roller 12 is rotated in the arrow direction at a peripheral speed of 50 mm / second, and the transfer is performed. Transferred to paper 7 10 times.

<Developer>
As the spherical toner 10 accommodated in the developing means 5, toner obtained by the following manufacturing method was used.

  90 parts of styrene, 10 parts of stearyl methacrylate, 4 parts of low molecular weight polypropylene, 7 parts of carbon black (trade name Black Pearl 130), 0.5 part of chromium-based dye (trade name Bontron S-34), and 2,2'-azobis 2 parts of (2,4-dimethylvaleronitrile) was ball milled to obtain a uniform mixed solution.

  Next, the above mixed solution was added to 400 parts of pure water in which 4.5 parts of calcium phosphate was finely dispersed to obtain an aqueous dispersion. The aqueous dispersion was subjected to high shear stirring from a rotor-stator type homomixer under a pH of 9 or more, and the mixture was finely dispersed in water. This aqueous dispersion was put into a reactor equipped with a stirring blade, and polymerization was carried out at 65 ° C. for 4 hours with stirring.

The dispersion liquid containing the polymer thus obtained was sufficiently washed with acid and water, and then separated and dried to obtain a toner material (polymerized toner). The resulting polymerized toner was substantially spherical particles. That is, the polymerized toner has a volume average particle diameter (dv) of 6.5 μm and a ratio (dv / dn) of the volume average particle diameter (dv) to the number average particle diameter (dv) of 1.18. A value (Sc / Sr) obtained by dividing the area (Sc) of a circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle is 1.07, and the specific surface area (A) by the BET method The product was a spherical toner having a product (A × dn × D) of 5.6 (m ² / g), number average particle diameter (dn) (μm) and true specific gravity (D). The absolute value of the ratio (Q / A) of the charge amount (Q) (μC / g) to the specific surface area (A) was 120.

  The non-magnetic one-component developer is prepared by adding 1.0 part by weight of hydrophobic silica “AEROSIL RX-170” (manufactured by Nippon Aerosil Co., Ltd., average particle size of 15 nm) to 100 parts of the above polymerized toner, and hydrophobic silica “AEROSIL RX-50”. 1.0 parts by weight (manufactured by Nippon Aerosil Co., Ltd., average particle size 40 nm) was added and mixed to prepare.

<Result>
An image forming experiment was performed using the image device and the developer. As a result of observing the photoreceptor fog, the numerical value quantified with respect to the photoreceptor fog was 0.5%, which was confirmed to be small. As a result of observing the image density (print density), the quantified numerical value was 1.41, which was an appropriate range. When a continuous printing test for 10,000 sheets was performed, it was confirmed that the image quality was maintained at 1.4% and the image density was 1.40. Further, the developer had good fluidity and maintained high fluidity even after continuous printing of 10,000 sheets.

[Example 2]
In Example 1, as a developer, 0.3 part by weight of hydrophobic silica “AEROSIL RX-170” and 0.3 part by weight of hydrophobic silica “AEROSIL RX-50” are added to 100 parts of polymerized toner. Except for using a non-magnetic one-component developer by mixing, an image formation experiment was conducted in the same manner as in Example 1. As a result, the quantified value of the photoreceptor fog was 0.4%. The image density was also good. When a continuous printing test was conducted for 10,000 sheets, it was confirmed that the photosensitive member fog was 2.3% and the image density was 1.39, maintaining good image quality. Further, the developer has good fluidity and maintained high fluidity even after continuous printing of 10,000 sheets.

[Example 3]
In Example 1, as a developer, 1.0 part by weight of hydrophobic silica “AEROSIL RX-170” and 0.3 part by weight of hydrophobic silica “AEROSIL RX-50” are added to 100 parts of polymerized toner. Except for using a non-magnetic one-component developer by mixing, an image formation experiment was conducted in the same manner as in Example 1. As a result, the quantified value of the photoreceptor fog was 0.4%. The image density was also good. When a continuous printing test was conducted for 10,000 sheets, it was confirmed that the photosensitive member fog was 1.8% and the image density was 1.40, maintaining good image quality. Further, the developer has good fluidity and maintained high fluidity even after continuous printing of 10,000 sheets.

[Example 4]
In Example 1, 0.3 parts by weight of hydrophobic silica “AEROSIL RX-170” and 1.0 part by weight of hydrophobic silica “AEROSIL RX-50” are added to 100 parts of polymerized toner as a developer. Except for using a non-magnetic one-component developer by mixing, an image formation experiment was conducted in the same manner as in Example 1. As a result, the quantified value of the photoreceptor fog was 0.5%. The image density was also good. When a continuous printing test was conducted for 10,000 sheets, it was confirmed that the photosensitive member fog was 1.3% and the image density was 1.39, maintaining good image quality. Further, the developer has good fluidity and maintained high fluidity even after continuous printing of 10,000 sheets.

[Comparative Example 1]
In Example 1, as a developer, only 1.0 part by weight of hydrophobic silica “AEROSIL RX-170” is added to 100 parts of polymerized toner and mixed to obtain a nonmagnetic one-component developer. Except that, the image formation experiment was conducted in the same manner as in Example 1. As a result, the numerical value obtained by quantifying the photoreceptor fog was 0.6%, and the initial printing was good with an image density of 1.42. When the 10,000 sheets continuous printing test was conducted, the photoreceptor fog increased rapidly to 15.3%, the image density decreased to 1.23, and good image quality could not be maintained. Further, the flowability of the developer also decreased after continuous printing of 10,000 sheets.

[Comparative Example 2]
In Example 1, as a developer, only 1.0 part by weight of hydrophobic silica “AEROSIL RX-50” is added to 100 parts of polymerized toner and mixed to obtain a nonmagnetic one-component developer. Except for this, an image forming experiment was conducted in the same manner as in Example 1. As a result, the amount of developer formed on the developing roller was small, the image density was as low as 1.28, and it was not durable.

[Comparative Example 3]
In Example 1, an image forming experiment was performed in the same manner as in Example 1 except that the image forming apparatus was used so that the contact angle θ of the layer thickness regulating blade 9 with respect to the developing roll 8 was 88 degrees. As a result, the developer layer formed on the developing roller became a multilayer of two or more layers, the photosensitive member fog increased, and it could not be used.

[Comparative Example 4]
In Example 1, an image forming experiment was performed in the same manner as in Example 1 except that the image forming apparatus was used so that the contact angle θ of the layer thickness regulating blade 9 with respect to the developing roll 8 was 70 degrees. As a result, the amount of developer formed on the developing roller was small, the image density was low, and it could not be used.

  These results are collectively shown in Table 1.

  The developing method of the present invention can be used for developing an electrostatic image by electrophotography.

FIG. 1 is a schematic view of an image forming apparatus used in the present invention. FIG. 2 is a schematic view showing the positional relationship between the layer thickness regulating blade (developing roller blade) and the developing roller shown in FIG. FIG. 3 is a schematic view showing the effect of simultaneous development cleaning (cleaner-less method) in reversal development. FIG. 4 is a conceptual diagram showing a method for measuring electrical resistance. FIG. 5 is a conceptual diagram showing a method for measuring the friction coefficient of the developing roller.

Explanation of symbols

1: latent image carrier (photosensitive drum), 2: cleaning means,
3: charging means, 4: latent image forming means, 5: developing means,
6: transfer means, 7: transfer material (transfer paper), 8: developing roller,
9: Blade for developing roller (layer thickness regulating blade),
10: developer (toner), 12: developer supply roller,
50: Holder, 51: Conductive plate, 52: Insulation resistance meter,
53: Measuring paper, 54: Weight, 55: Tension gauge.

Claims (1)

A developing roller is arranged opposite to the latent image carrier, and the developer contained in the developer containing means is attached to the outer peripheral surface of the developing roller, and the developing roller blade made of a rubber elastic body is rotated on the developing roller. The thickness of the developer layer adhering to the outer peripheral surface of the developing roller is regulated by contacting, and the developer adhering to the outer peripheral surface of the developing roller is moved to the latent image area of the latent image carrier for development. In the development method,
(1) The developing roller blade is brought into contact with the developing roller at a predetermined position on the opposite side to the latent image carrier on the developing roller, and a tangent line on the outer periphery of the developing roller passing through a point where the developing roller blade contacts with the developing roller; The contact angle formed with the tip surface of the developing roller blade is 75 to 85 degrees, and
(2) A non-magnetic one-component developer obtained by externally mixing a spherical toner with an inorganic oxide (a) having an average particle diameter of 5 to 20 nm and an inorganic oxide (b) having an average particle diameter exceeding 20 nm and not exceeding 2 μm. A development method characterized by using and developing.

Images