JPH06250435A - Image forming method - Google Patents

Abstract

PURPOSE:To provide an image forming method including an electrification process which prevents electrification defect due to contamination or scratches with the developer on an electrification member or the surface of a body to be electrified. CONSTITUTION:An electrifying member having the surface layer consisting of polyester resin with 0.3-2.5mum center line average roughness is used. The magnetic toner containing magnetic iron oxide used in this method has the following properties. (1) The weight average particle size is <=13.5mum in the distribution of particle size of the magnetic toner, and 50wt.% of the toner is particles having >=12.7mum particle size. (2) The amt. of silicon atoms in the magnetic iron oxide is 0.5-4wt.% of the iron atoms. The amt.(B) of silicon atom present in a 20wt.% dissolution rate of iron atom in the magnetic iron oxide and the amt.(A) of silicon atom in the magnetic iron oxide satisfy B/A = 44 to 84%. The amt.(C) of silicon atom present in the surface of the magnetic iron oxide satisfies C/A=10-55%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in electrophotography. More specifically, the present invention relates to an image forming method including a charging step of bringing a charging member to which a voltage is applied from the outside into contact with a member to be charged for charging, and a cleaning step of removing a developer from the member to be charged.

[0002]

2. Description of the Related Art Conventionally, a corona discharger has been known as a charging means in an electrophotographic apparatus or the like. However, the corona discharger has problems that a high voltage must be applied and that the amount of ozone generated is large.

Therefore, recently, it has been considered to use the contact charging means without using the corona discharger. Specifically, a voltage is applied to a conductive roller, which is a charging member, to bring the roller into contact with a photosensitive member, which is a member to be charged, so that the surface of the photosensitive member is charged to a predetermined potential. If such a contact charging means is used, the voltage can be lowered and the amount of ozone generated can be reduced as compared with the corona discharger.

However, when the contact charging means is used, there is a problem that charging failure occurs if sufficient contact cannot be maintained with the body to be charged. In addition, if residual developer is present on the surface of the photoconductor at the contact area, the residual developer adheres to the charging member and the surface of the photoconductor because the charging member has a predetermined contact pressure, which affects the image. It also has the problem of being lost.

When such a phenomenon occurs, a defect occurs in the latent image formation of the latent image carrier or a transfer omission occurs,
This will result in defective image copying.

Therefore, the surface characteristics of the charging member are important and need to be strictly controlled. However, the control of the material and surface shape, the ease of manufacturing including matching with the inner layer, and the cost Considering the above, it is difficult to make a charging member having surface characteristics that satisfy all the surfaces.

On the other hand, in recent years, small-sized, inexpensive and high-speed personal use copying machines and laser printers have appeared,
From the standpoint of maintenance-free, these small machines use a cartridge system that integrates the photoconductor, developing device, cleaning device, etc., and since the structure of the developing device can be simplified as a developer, magnetic one-component developing It is desirable to use agents.

Further, these developers tend to be made finer in order to realize high image quality. In such a magnetic developer, the polishing effect of the developer itself is strong, and the surface of the photoconductor is strongly rubbed during image formation, so that the surface of the photoconductor is often scraped or scratched. There is a problem such as fusion of the developer. This problem is prominent when an abutting member such as the above-mentioned charging member that is in contact with the surface of the photoconductor with a predetermined abutting pressure is used, and is designed in consideration of applicability between the charging member and the developer. ,
It tends to be difficult.

Further, in the contact charging device as described above, the charging member is used by applying a DC voltage or a DC voltage superimposed with an AC voltage. At this time, in the vicinity of the contact portion between the charging member and the photosensitive drum, Abnormal charging of the residual developer and repeated flight motions are repeated, which makes it easier to electrostatically attract or embed the residual developer to the surface of the charging member or the photoconductor drum. It is very different from the case of using the non-contact charging means. Especially this problem
As the developer is made finer, the developer becomes more prominent, and as a new problem, there is a concern that the life of the charging member will be shortened, that is, frequent replacement is required.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method which solves the above problems.

That is, the object of the present invention is to prevent the charging member and the surface of the member to be charged (photosensitive member) from being contaminated, such as sticking of the residual developer, so that the contact between the charging member and the member to be charged is sufficiently achieved. An object of the present invention is to provide an image forming method that has a charging step that can be maintained and does not cause charging failure or uneven charging, and finally achieves a long service life of the charging member, that is, a reduction in replacement frequency.

Further, an object of the present invention is that the image density is high,
An object is to provide an image forming method with excellent image reproducibility.

A further object of the present invention is to provide an image forming method which can obtain a good image without fog even when used for a long time.

[0014]

That is, according to the present invention, a charging member containing at least a polyester resin and having a surface layer having a center line average roughness (Ra) of 0.3 to 2.5 μm is charged. In the image forming method, there is provided an image forming method including a charging step of contacting the body and applying a voltage to the charging member from the outside to charge the body to be charged, and a cleaning step of removing the developer from the body to be charged. As a magnetic toner containing at least a binder resin and magnetic iron oxide, the magnetic toner has a weight average particle diameter of 13.5 μm or less, and the particle diameter distribution of the magnetic toner is 12.
The content of the magnetic toner particles of 7 μm or more is 50% by weight or less, and the magnetic iron oxide has a silicon element content of 0.5 to 4% by weight based on the iron element. The ratio (B / A) × 100 of the content B of the silicon element present in the magnetic iron oxide having a dissolution rate of the iron element of up to 20% by weight and the total content A of the silicon element of the magnetic iron oxide × 100 is 44 to 84.
%, And the ratio (C / A) of the content C of the silicon element present on the surface of the magnetic iron oxide to the content A (C / A) × 100 is 10
The image forming method is characterized by using a developer of 55%.

First, the contact charging step applicable to the image forming method of the present invention will be specifically described.

FIG. 1 is a schematic diagram showing an embodiment of a contact charging device for carrying out the contact charging process according to the present invention. In the figure, reference numeral 1 is a photosensitive drum which is a member to be charged, and is formed by forming an organic photoconductor (OPC) 1b which is a photosensitive layer on an outer peripheral surface of a drum base body 1a made of aluminum. Rotate at the speed of. Reference numeral 2 denotes a charging roller which is a charging member brought into contact with the photosensitive drum 1 with a predetermined pressure. The metal cored bar 2a is provided with a conductive rubber layer 2b, and the surface layer 2c which is a releasable coating film is further provided on the peripheral surface thereof. Provided. Surface layer 2
In view of matching with the developer and the image forming method of the present invention, c is preferably a release film.

Further, since electricity is applied in the diametrical direction, both the conductive rubber layer 2b and the surface layer 2c must have a specific resistance in the medium resistance region. The resistance value in the present invention is preferably 10 ³ to 10 ⁶ Ω in the conductive rubber layer 2b, and 10 ⁴ to 10 ⁹ Ω with the surface layer 2c.
As shown in FIG. 3, the resistance value is measured by winding a metal foil 4 having a width of 1 cm around the charging member,
Is applied between the metal foil part 4 and the metal foil part 4, and the current value one minute later is measured by the ammeter 6, and the resistance is 250 [V] / current value [A] = measurement part resistance [Ω]. To measure.

As the conductive rubber layer 2b, JIS K63 is used.
The hardness specified by the A type hardness tester of 01 is 20 to
A hardness of 80 ° is preferred.

Reference numeral E denotes a power supply section for applying a voltage to the charging roller 2 and supplies a predetermined voltage to the core metal 2a of the charging roller 2. In FIG. 1, E indicates a DC voltage, but it may be a DC voltage superimposed with an AC voltage.

In the present invention, the adhesion between the conductive rubber layer and the surface layer and the material / property of the surface layer dominate the strength of the charging member itself, and determine the state of contact with the surface of the photoreceptor. I found it.

That is, it has been found that by adjusting them and, in addition, combining them with a developer having a good matching, the contamination of the surface of the charging member or the surface of the photoconductor can be reduced and the life of the charging member can be extended. .

In the charging roller shown in FIG. 1, as the conductive rubber layer 2b, for example, a polyether urethane layer in which carbon black is dispersed is used, and the surface is polished in consideration of cost and ease of production. Shaped.

On top of that, polyester, which is a good material having good film-forming property, is coated by dipping to form a surface layer, and the center line average roughness Ra is 0.3 to 2.5 μm in accordance with JIS standard (B0601). I adjusted it so that.

If Ra is less than 0.3 μm, the surface of the charging member and the surface of the photoconductor are likely to come into close contact with each other. Therefore, when a developer is interposed in the gap, fusing, filming, or other contamination occurs on each surface. It is easy, but generally hard to reach as long as the surface of the conductive rubber layer is polished. Further, it is possible to further roughen the surface of the conductive rubber layer so that Ra of the surface layer exceeds 2.5 μm. In that case, the adhesion between the charging member surface and the photoreceptor surface Is worse, the developer is more likely to be buried in the concave portions on the surface of the charging member, and the contamination is more likely to proceed.

As the resin material used for the conductive rubber layer in the present invention, in addition to polyether urethane, for example, EPDM / EPT / EPM / NBR / BR / BR / C.
A synthetic rubber such as R, a thermosetting elastomer such as natural rubber, or a thermoplastic elastomer such as vinyl chloride, vinyl acetate polyester, PVA, etc. may be used alone or in combination.

The conductive particles added to impart conductivity to the conductive rubber layer include carbon black.
Conductive particles such as zinc oxide, titanium oxide, and metal powder are used.

The polyester used in the surface layer of the charging member of the present invention is obtained by condensation of alcohol and carboxylic acid, and conventionally known ones are used.

Examples of the alcohol used include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol and 1,4-butenediol. Dihydric alcohols such as diols, 1,4-bis (hydroxymethyl) cyclohexane, and etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropyleneized bisphenol A. Examples of the carboxylic acid include maleic acid, fumaric acid, mesaconinic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid. Adipic acid, sebacic acid, malonic acid, anhydrides of these acids, dimers of lower alkyl ester and Rirein acid, divalent organic acids such as.

Further, a polyhydric alcohol having a valence of 3 or more and / or
Alternatively, a trivalent or higher polyvalent carboxylic acid may be used.

Examples of polyhydric alcohols having 3 or more valences include sorbitol, 1,2,3,6-hexanetetrol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose,
1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,
3,5-trihydroxymethylbenzene and the like can be mentioned. Examples of the trivalent or higher polyvalent carboxylic acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid and 2,5,7-naphthalene. Tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, 1,2,
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2
-Methylene carboxy propane, tetra (methylene carboxyl) methane, 1,2,7,8-octane tetracarboxylic acid, employer trimer acid, and acid anhydrides thereof.

It is also possible to use a combination of polyester and another resin material for the surface layer. As the resin material to be combined, a material having flexibility at room temperature such as polyamide, polyimide, fluororesin, silicon resin, PVA, etc. is used. In order to impart conductivity, carbon black, zinc oxide, titanium oxide, You may add electroconductive particles, such as a metal powder.

In the present invention, the conductive rubber layer is preferably flame-retardant because it is used to support the electrode, and particularly has a flame-retardant property of 94 HB or more in UL-94 standard. preferable.

The thickness of the conductive rubber layer is preferably 1 to 5 mm. The thickness of the surface layer is 1 to 500 μm.
Is preferred.

Further, although the charging member is composed of the conductive rubber layer and the releasable coating in the above-mentioned embodiment, the invention is not limited to this, and it is possible to prevent a leak between the conductive rubber layer and the surface of the releasable coating to the photoreceptor. Therefore, a high resistance layer, for example, a hydrin rubber layer having a small environmental change may be formed.

FIG. 2 is a schematic diagram showing another embodiment of the contact charging device for carrying out the contact charging step according to the present invention. The same members as those of the apparatus shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The contact charging member 2'of this embodiment is a blade-like member which is brought into contact with the photosensitive drum 1 in the forward direction with a predetermined pressure, and this blade 2'is a metal supporting member 2'to which a voltage is supplied. A conductive rubber 2'b is supported by a, and a surface layer 2'c serving as a releasable coating is provided at the contact portion with the photosensitive drum 1. According to this embodiment, there is no problem such as adhesion between the blade and the photoconductor drum, and the same working effect as that of the above embodiment can be obtained.

Further, the mechanical or electrical pressure applied between the charging member and the photosensitive member is a factor related to the gist of the present invention, and the contact pressure of the charging member on the photosensitive member is 5 to 500 g.
/ Cm, the DC voltage applied to the charging member has an absolute value of 20
0-900V, when applying an AC voltage, peak-peak voltage 500-5000V, frequency 50-3000H
It is preferable that each of them is adjusted to z.

Although the roller-shaped or blade-shaped charging member is used in the above-described embodiments, the present invention is not limited to this, and the present invention can be applied to other shapes.

As the photoconductor used in the present invention, in addition to organic photoconductor, amorphous silicon, selenium, Zn
It is also possible to use O or the like. In particular, when amorphous silicon is used for the photoconductor, compared to the case where other materials are used, if the softening agent of the conductive rubber layer adheres even a little to the photoconductor, the image deletion will be worse, so that it will be on the outside of the conductive rubber layer. The effect obtained by forming the insulating film is great.

In the cleaning step according to the present invention, generally, the photosensitive drum after the toner image transfer is cleaned by being wiped off by the cleaning member such as a blade or roller of a cleaner to wipe off the residual toner after transfer and other contaminants. It is surfaced and repeatedly used for image formation.

It is also possible to perform the cleaning step at the same time as the charging step, the developing step, or the transfer step related to the electrophotography.

Examples of the surface material of the latent image bearing member used in the present invention include silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate and polycarbonate. There is no limitation, and other monomers or copolymers or blends between the exemplified resins can be used.

The present invention is particularly effective for an image forming apparatus in which the latent image carrier has a diameter of less than 30 mm. This is because in the case of a small-diameter drum, the pressure is likely to be concentrated at the abutting portion because the curvature is large even with the same linear pressure.

It is considered that the same phenomenon occurs in the belt photosensitive member, and it is effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer portion.

Next, the developer applicable to the developing step and the cleaning step in the image forming method of the present invention will be described.

The developer according to the present invention has a magnetic toner containing at least a binder resin and magnetic iron oxide, and the magnetic toner has a weight average particle diameter of 13.5 μm or less.
In the particle size distribution of the magnetic toner, the content of magnetic toner particles having a particle size of 12.7 μm or more is 50% by weight or less,
The content of silicon element in the magnetic iron oxide is 0.5 to 4% by weight based on the iron element, and the dissolution rate of iron element in the magnetic iron oxide is up to 20% by weight. The ratio (B / A) × 100 of the content B of the silicon element and the total content A of the silicon element of the magnetic iron oxide is 100 to 44%, and the content of the silicon element existing on the surface of the magnetic iron oxide. C
(C / A) × 100 is 10 to 55%
Is characterized in that.

The developer of the present invention, having the above-mentioned constitution, adheres to the surface of the charging member or the surface of the photosensitive drum even if some residual developer is left on the photosensitive drum after the cleaning process. Is extremely unlikely to occur, and contamination itself is reduced, so that the charging member itself can have a long life and the frequency of replacement can be reduced.

From the above, the developer according to the present invention is
It is possible to provide an image forming method in which matching with the charging step according to the present invention is extremely good, the capability of the charging step according to the present invention can be sufficiently exhibited, and always good image formation can be provided, and the number of discarded charging members can be provided. It is possible to contribute ecologically by reducing

The reason why the above effects are obtained in the developer according to the present invention is not always clear, but it is presumed as follows.

By improving the magnetic iron oxide in the developer of the present invention, the fluidity of the magnetic toner itself is improved, and the releasability from the photoreceptor is improved. As a result, the residual developer after the cleaning process, which is a cause of toner sticking to the charging member and the photoconductor, is reduced.

Further, by using the charging member of the present invention, even if some residual developer is present, the special surface property of the charging member makes it extremely difficult for the developer to be fixed.

Further, the magnetic iron oxide of the present invention has a large bonding strength with the resin in the developer, the amount of free magnetic material from the developer is reduced, and the charging member and the photoconductor are damaged due to them. It gets harder.

That is, in the magnetic toner according to the present invention, the weight average particle size is 13.5 μm or less (preferably 3.5 to 13.5 μm), and the particle size distribution of the magnetic toner is 12.7 μm or more. One of the characteristics is that the specific magnetic iron oxide containing a silicon element is used for the magnetic toner containing 50% by weight or less of the magnetic toner particles.

The weight average particle diameter of the magnetic toner is 13.5 μm.
Or the content of the magnetic toner particles having a particle diameter of 12.7 μm or more exceeds 50% by weight, the magnetic toner containing a large amount of relatively coarse magnetic toner particles is generally used conventionally. It is possible to stabilize the charging of the magnetic toner even by using the above-mentioned magnetic iron oxide.

The weight average particle diameter of the magnetic toner particles is 3.5 μ.
When it is smaller than m, the fluidity of the magnetic toner becomes low even if the special magnetic iron oxide of the present invention is used, and problems such as toner fusion due to poor cleaning, filming, etc., and fog due to poor charging, density. Since a problem such as thinning is likely to occur, the weight average particle diameter is preferably 3.5 μm or more.

That is, in the magnetic toner according to the present invention, remarkable effects such as improvement in charging stability and fluidity as compared with the conventional example are observed, and the weight average particle diameter is 13.5 μm or less (preferably 3. 5 to 13.5 μm, more preferably 5.0 to 13.0 μm) and a particle size of 12.7 μm.
This is the case where the content of the magnetic toner particles of m or more is 50% by weight or less (more preferably 40% or less).

Further, in the present invention, the content of silicon element in the magnetic iron oxide used in the magnetic toner is 0.5 to 4.0% by weight (more preferably 0.8 to 3.0) based on the iron element.
%, And more preferably 0.9 to 3.0% by weight) is one of the characteristics. The content rate of silicon element is 0.
When the amount is less than 5% by weight, the effect of improving the magnetic toner (particularly, the improvement of the fluidity of the magnetic toner) is weak, and when the content of silicon element is more than 4.0% by weight, the silicic acid component is magnetically oxidized. It is not preferable because it is unnecessarily retained on the surface of iron and adversely affects the magnetic properties.

Further, in the present invention, the total content A of the silicon element present in the magnetic iron oxide used for the magnetic toner and the content B of the silicon element present in the magnetic iron oxide having a dissolution rate of the iron element of up to about 20%. The ratio B / A × 100 (%) is 44 to 8
4% (preferably 60 to 80%), and the content C and the content A of the silicon element existing on the surface of the magnetic iron oxide particles.
One of the features is that the ratio C / A × 100 (%) with 10 to 55% (preferably 25 to 40%). B /
When A × 100 (%) is less than 44%, a large amount of silicon element more than necessary is present in the central portion of the magnetic iron oxide, which easily deteriorates the production efficiency and causes the magnetic properties to be unstable. May be iron oxide.

When B / A × 100 (%) exceeds 84%, too much silicon element is present in the surface layer of the magnetic iron oxide, and a large amount of silicon element is layered on the surface of the magnetic iron oxide. Since the surface of the magnetic iron oxide is present and becomes brittle against mechanical shock, many adverse effects are likely to occur when it is used for a magnetic toner.

On the other hand, when C / A × 100 (%) is less than 10%, the silicon element on the surface of the magnetic iron oxide is small and it is difficult to obtain good fluidity for the magnetic iron oxide and the magnetic toner. In addition, the charge amount and volume resistivity of the magnetic iron oxide are reduced, and the charge stability and environmental stability of the magnetic toner are likely to be impaired.

When C / A × 100 (%) is more than 55%, the irregularities on the surface of the magnetic iron oxide are conspicuous, and the irregularities on the surface of the magnetic iron oxide become fragments when the magnetic toner is manufactured. It is dispersed in the toner and tends to adversely affect the magnetic toner characteristics.

That is, in order to obtain good magnetic toner characteristics, it is necessary that the distribution of the silicon element present in the magnetic iron oxide increases continuously or stepwise from the inside toward the surface as described above. preferable.

Further, in the present invention, the charge amount of the magnetic iron oxide is −25 to −70 μc / g (preferably −40 to −60 μm).
c / g) and the volume resistivity of magnetic iron oxide is 1
× 10 ⁴ to 1 × 10 ⁸ Ω · cm (preferably 5 × 10 ⁴
It is preferably about 5 × 10 ⁷ Ω · cm).

When the charge amount of the magnetic iron oxide is less than -25 μc / g, when the magnetic toner is repeatedly used for a long period of time, the charge amount required by the magnetic toner tends to be lost, and problems such as reduction in image density and image fog occur. Occurs. On the other hand, when the charge amount of magnetic iron oxide exceeds -70 μc / g,
Since the charge amount of the magnetic toner becomes too high, the image density tends to decrease in a low temperature and low humidity environment.

The volume resistivity of magnetic iron oxide is 1 ×
When it is less than 10 ⁴ Ω · cm, it becomes difficult to maintain the charge amount required by the magnetic toner, and the image density is apt to decrease. On the other hand, when the volume resistivity of the magnetic iron oxide exceeds 1 × 10 ⁸ Ω · cm, the charge amount tends to increase more than necessary when repeatedly used in a low temperature and low humidity environment, and the image density decreases. Easy to get caught.

Further, in the present invention, the degree of aggregation of magnetic iron oxide is preferably 3 to 40% (preferably 5 to 30%).

When the coagulation degree of the magnetic iron oxide is less than 3%, blowing out of the magnetic toner, which is called flushing, is likely to occur at the time of producing the magnetic toner, and it is difficult to efficiently produce the magnetic toner.

On the other hand, when the cohesion exceeds 40%,
It is not easy to sufficiently disperse the magnetic iron oxide in the magnetic toner, and the image density, fog and the like are likely to be adversely affected. Further, in the present invention, the fluidity of the magnetic iron oxide is reflected in the fluidity of the magnetic toner, and when the magnetic iron oxide having an aggregation degree of more than 40% is used, the fluidity of the magnetic toner is sufficiently high. It is difficult to obtain, and a large amount of residual developer that is not removed in the cleaning process is generated on the photosensitive drum, toner fusion to the photosensitive drum and charging member is observed, and it adversely affects the charging property of the magnetic toner. Occurrence of fogging, etc. tends to occur.

Further, in the present invention, the smoothness D of the magnetic iron oxide is preferably 0.2 to 0.6 (preferably 0.3 to 0.5).

When the smoothness D is less than 0.2, the irregularities on the surface of the magnetic iron oxide are conspicuous, and the irregularities become fragments during the production of the magnetic toner, which are easily dispersed in the magnetic toner and adversely affect the toner characteristics.

On the other hand, when the smoothness D is larger than 0.6, it is difficult to obtain sufficient adhesiveness between the binder resin used for the magnetic toner and the magnetic iron oxide, and the magnetic toner surface gradually increases after repeated use. The magnetic iron oxide is removed, and adverse effects such as reduction in image density are likely to occur.

Further, in the present invention, the sphericity ψ of the magnetic iron oxide is
Is preferably 0.8 or more.

When the sphericity ψ is less than 0.8, the individual particles of magnetic iron oxide come into surface-to-surface contact,
With small magnetic iron oxide particles having a particle size of about 0.1 to 1.0 μm, the magnetic iron oxide particles cannot be easily separated from each other even with a mechanical shearing force. May not be sufficiently dispersed.

Further, the magnetic iron oxide used in the present invention preferably has an average particle size of 0.1 to 0.4 μm, more preferably 0.1 to 0.3 μm.

The method of measuring various physical property data in the present invention will be described in detail below. (1) Toner particle size distribution The toner particle size distribution can be measured by various methods.
In the present invention, a Coulter counter is used.

That is, a Coulter Counter TA-II type (manufactured by Coulter) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) were connected. , Electrolyte is 1st class sodium chloride
% NaCl aqueous solution is prepared. As a measuring method, a surfactant (preferably an alkylbenzene sulfonate) as a dispersant was added to 0.1 to 100 ml of the electrolytic aqueous solution.
Add ~ 5 ml, and then add 2 to 20 mg of the measurement sample.
The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of the toner is measured by the Coulter Counter TAII type using an aperture of 100 μm to 2 to 40 μm. Calculate the volume distribution and number distribution of the particles. Then, according to the present invention, the weight-based weight average diameter D ₄ obtained from the volume distribution (the central value of each channel is a representative value for each channel), and the weight-based 12.7 μ obtained from the volume distribution is used.
Determine the weight distribution of m or more. (2) Content of elemental silicon In the present invention, the content C of elemental silicon on the surface of the magnetic iron oxide can be determined by the following method. For example, about 3 liters of deionized water is placed in a 5 liter beaker and heated in a water bath at 50 to 60 ° C. About 25 g of magnetic iron oxide slurried with about 400 ml of deionized water is added to a 5 liter beaker together with the deionized water while being washed with about 300 ml of deionized water.

Next, while maintaining the temperature at about 60 ° C. and the stirring speed at about 200 rpm, special grade sodium hydroxide was added to form a sodium hydroxide solution of about 1N, and the magnetic iron oxide concentration was adjusted to about 5 g / l. Initiation of dissolution of silicon compounds such as silicic acid on the surface of iron oxide particles. Thirty minutes after the start of dissolution, 20 ml is sampled, filtered through a 0.1 μ membrane filter, and the filtrate is collected. The filtrate is quantified for silicon element by plasma emission spectroscopy (ICP).

The content C of the elemental silicon is the unit weight of magnetic iron oxide in the aqueous sodium hydroxide solution (5 g of magnetic iron oxide /
It corresponds to the elemental silicon concentration per 1) (mg / l).

In the present invention, the content of silicon element (based on iron element), the dissolution rate of iron element, and the content of silicon element A and B of magnetic iron oxide can be determined by the following method. it can. For example, about 3 liters of deionized water is placed in a 5 liter beaker and heated in a water bath at 45 to 50 ° C. About 25 g of magnetic iron oxide was slurried with about 400 ml of deionized water to about 3
While washing with 00 ml of deionized water, add together with the deionized water into a 5 liter beaker.

Next, while maintaining the temperature at about 50 ° C. and the stirring speed at about 200 rpm, special grade hydrochloric acid is added to start the dissolution. At this time, the magnetic iron oxide concentration is about 5 g / l and the hydrochloric acid aqueous solution is about 3 N. Approximately 20 ml is sampled several times from the start of dissolution to the time when everything is dissolved and becomes transparent, filtered through a 0.1 μ membrane filter, and the filtrate is collected. The filtrate is quantified for iron element and silicon element by plasma emission spectroscopy (ICP).

The iron element dissolution rate for each sample is calculated by the following equation.

[0082]

[Equation 1] The content and content of elemental silicon for each sample are calculated by the following equation.

[0083]

[Equation 2] The total content A of the silicon oxide in the magnetic iron oxide corresponds to the silicon element concentration (mg / l) per unit weight of the magnetic iron oxide after being dissolved, 5 g / l of the magnetic iron oxide.

The content B of the elemental silicon in the magnetic iron oxide is the elemental silicon concentration (mg) per unit weight magnetic iron oxide 5 g / l of the magnetic iron oxide detected when the dissolution rate of the magnetic iron oxide is 20%. / L).

As a method for measuring the contents A, B and C, a magnetic iron oxide sample is divided into two and the content of silicon element and the contents A and B are measured, while the content C is Method of measuring separately, and measuring the content C of the magnetic iron oxide sample, and then using the sample after measurement, the content B '(content B minus the content C) and the content A' Examples include a method of measuring (content A minus content C) and finally calculating the contents A and B. (3) Charge amount of magnetic iron oxide About 2 g of magnetic iron oxide and carrier iron powder (TEFV200 to 3)
00 mesh) (Nippon Iron Powder Co., Ltd.) 500 g of about 198 g
Weigh it in ml polybin, shake it by hand for 10 seconds, then shake it with a V-type blender for 20 minutes, and measure the charge amount of magnetic iron oxide using a blow-off powder charge amount measuring device (Toshiba Chemical Co., Ltd.) To do. At this time, a 400 mesh mesh made of stainless steel was set to the Faraday gauge for measurement, a measurement sample amount of about 0.4 g was weighed, and the value was calculated by performing blow-off for 30 seconds. (4) Volume resistivity of magnetic iron oxide 10 g of magnetic iron oxide is put into a measuring cell and molded by a hydraulic cylinder (pressure 600 Kg / cm ² ). After releasing the pressure, a resistance meter (YEW MODEL 2506A manufactured by Yokogawa Electric Corporation)
DIGITAL MALTIMER) is set, and a pressure of 150 kg / cm ² is applied again by the hydraulic cylinder. Start the measurement and read the measured value after 3 minutes. Furthermore, the thickness of the sample is measured and the volume resistivity value is measured by the following formula.

[0086]

[Equation 3] (5) Aggregation degree of magnetic iron oxide 10 g of magnetic iron oxide was crushed with a mixer to obtain 200 mesh.
Weigh 2 g of the powder that has passed the screening. From the top to the powder tester (Hosokawa Micron Co., Ltd.),
The sieves are set in three steps in the order of 100 mesh and 200 mesh, 2 g of the sample weighed is gently placed on the sieve, vibration of 1 mm amplitude is given for 65 seconds, and the weight of the magnetic iron oxide remaining on each sieve is measured. Then, the degree of aggregation is calculated according to the following formula.

[0087]

[Equation 4] (6) Smoothness of Magnetic Iron Oxide In the present invention, the smoothness D of magnetic iron oxide is determined as follows.

[0088]

[Equation 5] (7) BET BET specific surface area of magnetic iron oxide is obtained by Yuasa Ionics Co., Ltd., fully automatic gas adsorption amount measuring device: Autosorb 1, and nitrogen is used as an adsorption gas by the BET multipoint method. The sample is pretreated by degassing at 50 ° C. for 1 hour. (8) Average Particle Size and Magnetic Iron Oxide Surface Area Photographed at 10,000 times with an applied voltage of 100 KV using a magnetic iron oxide sample treated with a collodion film copper mesh with an electron microscope (Hitachi H-700H). Then, the baking magnification is set to 3 times and the final magnification is set to 30,000 times. With this, the shape is observed and the maximum length of each particle (μm)
Is measured, 100 particles are randomly selected, and the average is taken as the average particle diameter.

For the calculation of the surface area, it is assumed that the average particle diameter of the magnetic iron oxide is a sphere, and the density of the magnetic iron oxide is measured by a usual method to obtain the surface area value. (9) Sphericity of magnetic iron oxide The sphericity ψ of the magnetic iron oxide in the present invention is calculated as follows.

[0090]

[Equation 6] For the sphericity ψ, 100 magnetic iron oxide particle specimens are randomly selected from the photograph, the maximum length and the minimum length are measured, and then the calculated values are averaged.

The maximum length and the minimum length of the magnetic oxide material follow the method for obtaining the average particle diameter.

While the cubic magnetic normal iron oxide has a sphericity ψ of less than 0.8 of about 0.6 to 0.7, the sphericity ψ preferably used in the present invention is 0.8 or more. The magnetic iron oxide (preferably 0.85 or more, more preferably 0.9 or more) has a shape close to a spherical shape without angular ends.

When the sphericity ψ is less than 0.8, the dispersibility in the binder resin is inferior to that in the case where the silicon element is unevenly distributed on the surface of the magnetic iron oxide particles, so that The developing characteristics of the obtained magnetic toner are likely to be deteriorated, and the magnetic toner tends to be inferior in dot reproducibility.

The magnetic iron oxide used in the magnetic toner of the present invention is 20 parts by weight to 2 parts by weight with respect to 100 parts by weight of the binder resin.
It is preferred to use 00 parts by weight. It is more preferable to use 30 to 150 parts by weight.

In some cases, the magnetic iron oxide used in the magnetic toner of the present invention may be treated with a silane coupling agent, a titanium coupling agent, titanate, aminosilane or the like.

On the other hand, the binder resin in the toner according to the present invention is one obtained by polymerizing one or more kinds of monomers selected from styrenes, acrylic acids, methacrylic acids and their derivatives in view of development characteristics and charging characteristics. preferable.
Examples of monomers that can be used include styrenes such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene. Acrylic acids, methacrylic acids and their derivatives include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-tetradecyl acrylate, n-acrylic acid. Acrylic esters such as hexadecyl, lauryl acrylate, cyclohexyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylate, etc. can be mentioned, as well as methacrylic acid, methyl methacrylate / ethyl methacrylate, propyl methacrylate, butyl methacrylate. , Amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, silyl methacrylate. Rohekishiru, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, methacrylic acid esters such as stearyl methacrylate. In addition to the above-mentioned monomers, a small amount of other monomers such as acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, vinylcarbazole, vinylmethyl ether, butadiene, isoprene, maleic anhydride, malein within a range that can achieve the object of the present invention. Acids, maleic acid monoesters, maleic acid diesters, vinyl acetate and the like may be used.

As the cross-linking agent used in the toner resin according to the present invention, as a bifunctional cross-linking agent, divinylbenzene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-
Butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetra Ethylene glycol diacrylate, polyethylene glycol # 200, # 400, #
Examples include 600 diacrylates, dipropylene glycol diacrylate, polypropylene glycol diacrylate, polyester type diacrylate (MANDA Nippon Kayaku), and those obtained by replacing the above acrylates with methacrylates.

As a polyfunctional crosslinking agent, pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxy, Polyethoxyphenyl) propane, diallyl phthalate, triallyl cyanurate,
Examples thereof include triallyl assocyanurate, triarylallysocyanurate, triallyl trimellitate, and diaryl chlorendate.

In the toner using the resin according to the present invention, in addition to the above-mentioned binder resin component, within the range not adversely affecting the effect of the present invention, the content of the binder resin component is less than the following content. A compound may be included.

For example, silicone resin, polyester,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin such as low molecular weight polyethylene or low molecular weight polypropylene, aromatic petroleum resin, chlorinated paraffin, For example, paraffin wax.

A colorant may be used in the toner according to the present invention, if necessary. As the colorant, generally known dyes and pigments can be used, and for example, carbon black, nigrosine dye, lamp black, etc. can be applied.

As the charge control agent contained in the toner according to the present invention, a conventionally known charge control agent is selected. Specific examples of the positive charge control agent generally include nigrosine and 2 carbon atoms.
Azine dyes containing 16 to 16 alkyl groups (Japanese Examined Patent Publication No.
1627), basic dyes (for example, CI Bas
ic Yellow 2 (C.I. 41000), C.I.
I. Basic Yellow 3, C.I. I. Basi
c Red 1 (C.I. 45160), C.I. I. Ba
sic Red 9 (C.I. 42500), C.I. I.
Basic Violet 1 (CI.4253
5), C.I. I. Basic Violet 3 (C.
I. 42555), C.I. I. Basic Violet
10 (C.I. 45170), C.I. I. Basic
Violet 14 (C.I. 42510), C.I. I. B
asic Blue 1 (C.I. 42025), C.I.
I. Basic Blue 3 (C.I. 5100
5), C.I. I. Basic Blue 5 (C.I.4
2140), C.I. I. Basic Blue 7 (C.
I. 42595), C.I. I. Basic Blue 9
(C.I. 52015), C.I. I. Basic Blu
e 24 (C.I. 52030), C.I. I. Basic
Blue 25 (C.I. 52025), C.I. I. B
asic Blue 26 (C.I. 44025),
C. I. Basic Green 1 (C.I. 420
40), C.I. I. Basic Green 4 (C.
I. 42000), etc., and lake pigments of these basic dyes (as a laking agent, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide, etc.) , C.I. I. Sovent Black
3 (C.I. 26150), Hansa Yellow G (C.I.
I. 11680), C.I. I. Mordant Bla
ck11, C.I. I. Pigment Black 1
etc.

Or, for example, a quaternary ammonium salt such as benzolmethyl-hexadecylammonium chloride or decyl-trimethylammonium chloride, a vinyl polymer containing an amino group, a polyamide resin such as a condensation polymer containing an amino group, etc. may be mentioned. ,
Preferred examples include nigrosine, quaternary ammonium salts, triphenylmethane-based nitrogen-containing compounds and polyamides.

Specific examples of the negative charge control agent include monoazo dyes described in JP-B-41-20153, JP-B-42-27596, JP-B-44-6397, and JP-B-45-26478. Metal complexes of nitramic acid and salts thereof described in JP-A No. 50-133338 or C.I. I. Dyes and pigments such as 14645, JP-B-55-42752, JP-B-58
-41508, Japanese Patent Publication No. 58-7384, Japanese Patent Publication No. 59-7385, and the like, Zn, Al, and C of salicylic acid, naphthoic acid, and dicarboxylic acid.
Examples thereof include metal complexes of o, Cr and Fe, sulfonated copper phthalocyanine pigments, nitro groups, halogen-introduced styrene oligomers and chlorinated paraffins. Particularly, from the viewpoint of dispersibility, metal complex salts of monoazo dyes, metal complexes of salicylic acid, alkylsalicylic acid, naphthoic acid, and dicarboxylic acid are preferable. The amount of these charge control agents added keeps good triboelectric chargeability as described above, while minimizing the adverse effects such as a reduction in developing power and a reduction in environmental stability due to contamination of the developing sleeve surface by the charge control agents. Therefore, the addition amount of 0.1 to 3 parts by weight is preferable with respect to 100 parts by weight of the binder resin.

In the toner according to the present invention, an ethylene olefin polymer may be used as a fixing auxiliary together with a binder resin.

Here, as the ethylene-based olefin homopolymer or ethylene-based olefin copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer is used. There are coalesced products, ionomers having a polyethylene skeleton, and the like, and the above copolymer preferably contains 50 mol% or more (more preferably 60 mol% or more) of an olefin monomer.

The magnetic toner according to the present invention is preferably mixed with an inorganic fine powder or a hydrophobic inorganic fine powder.
For example, it is preferable to add and use silica fine powder.

The fine silica powder used in the present invention includes both so-called dry method produced by vapor phase oxidation of a silicon halogen compound or dry silica called fumed silica and so-called wet silica produced from water glass. Although usable, dry silica, which has few silanol groups on the surface and inside and has no production residue, is preferable.

Further, the silica fine powder used in the present invention is preferably hydrophobized. The hydrophobic treatment is applied by chemically treating with an organic silicon compound or the like that reacts with or physically adsorbs to the fine silica powder. As a preferred method, a method of treating dry silica fine powder generated by vapor phase oxidation of a silicon halogen compound with a silane coupling agent, or simultaneously treating with a silane coupling agent and an organosilicon compound such as silicone oil Is mentioned.

Examples of the silane coupling agent used for the hydrophobic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyl. Dichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane,
Chlormethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldimethyl Examples include siloxane and 1,3-diphenyltetramethyldisiloxane.

Examples of the organosilicon compound include silicone oil. As a preferred silicone oil, one having a viscosity of about 30 to 1,000 centistokes at 25 ° C. is used, and for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified. Silicone oil or the like is preferable.

As the method for treating the silicone oil, for example, silica fine powder treated with a silane coupling agent and silicone oil may be directly mixed by using a mixer such as a Henschel mixer, or silica as a base may be mixed with silicone oil. The method of injecting Alternatively, it may be produced by dissolving or dispersing silicone oil in an appropriate solvent, mixing with silica fine powder of the base, and removing the solvent.

If necessary, external additives other than silica fine powder may be added to the magnetic toner according to the present invention.

For example, a charging auxiliary agent, a conductivity-imparting agent, a fluidity-imparting agent, an anti-caking agent, a releasing agent at the time of heat roll fixing,
Resin fine particles or inorganic fine particles that act as a lubricant, an abrasive, etc.

The inorganic fine powder or hydrophobic inorganic fine powder to be mixed with the magnetic toner is used in an amount of 0.1 to 5 parts by weight (preferably 0.1 to 3 parts by weight) per 100 parts by weight of the magnetic toner. good.

To prepare a magnetic toner for developing an electrostatic image according to the present invention, magnetic powder and a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or dye as a colorant, if necessary, charge control Agents, other additives, etc., are thoroughly mixed with a mixer such as a ball mill, and then melted, kneaded and kneaded with a heat kneader such as a heating roll, kneader or extruder to make the resins compatible with each other. The magnetic toner according to the present invention can be obtained by dispersing or dissolving a pigment or a dye therein, cooling and solidifying the mixture, followed by pulverization and strict classification.

The magnetic iron oxide containing elemental silicon according to the present invention is produced, for example, by the following method.

After adding a predetermined amount of silicic acid compound to the aqueous solution of ferrous salt, an equivalent amount or an equivalent amount or more of alkali such as sodium hydroxide is added to the iron component to prepare an aqueous solution containing ferrous hydroxide. . The pH of the prepared aqueous solution is pH 7
Air is blown while maintaining the above (preferably pH 8 to 10), the ferric hydroxide is oxidized while the aqueous solution is heated to 70 ° C. or higher, and seed crystals that form the core of the magnetic iron oxide particles are first generated. To do.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals, based on the amount of alkali added previously. While maintaining the pH of the solution at 6 to 10, the reaction of ferrous hydroxide is promoted while air is blown in, and magnetic iron oxide particles are grown around the seed crystal. The pH of the liquid shifts to the acidic side as the oxidation reaction progresses,
The pH of the liquid is preferably not less than 6. By adjusting the pH of the solution at the final stage of the oxidation reaction, it is preferable that a predetermined amount of the silicic acid compound is unevenly distributed on the surface layer and the surface of the magnetic iron oxide particles.

Examples of the silicic acid compound used for addition include silicates such as commercially available sodium silicate and silicic acid such as sol-like silicic acid produced by hydrolysis. Other additives such as aluminum sulfate and alumina may be added as long as they do not adversely affect the present invention.

As the ferrous iron salt, iron sulfate generally produced as a by-product in the production of titanium by the sulfuric acid method and iron sulfate produced as a result of cleaning the surface of a steel sheet can be used, and further iron chloride or the like can be used. is there.

In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / l is generally used in view of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the thinner the concentration of iron sulfate, the finer the particle size of the product tends to be. In addition, during the reaction, the larger the amount of air and the lower the reaction temperature, the easier the particles become.

According to the above-mentioned manufacturing method, the magnetic iron oxide particles having a silicic acid component were mainly composed of spherical particles having a curved surface having no plate-like surface, as observed by transmission electron microscopy. Produces magnetic iron oxide containing almost no surface particles,
It is preferable to use the magnetic iron oxide in the toner.

[0124]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples. Number of copies or% given in the examples
Indicates parts by weight or% by weight.

(Production Example 1) Sodium silicate was added to an aqueous solution of ferrous sulfate so that the content of silicon element was 1.8% with respect to iron element. 0 to
1.1 equivalent of caustic soda solution was mixed to prepare an aqueous solution containing ferrous hydroxide.

The pH of the aqueous solution is adjusted to pH 7 to 10 (eg pH
While maintaining at 9), air was blown in to carry out an oxidation reaction at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Next, an aqueous ferrous sulfate solution was added to this slurry liquid so that the amount of the alkali was 0.9 to 1.2 equivalents based on the initial alkali amount (sodium component of sodium silicate and sodium component of caustic soda), and then the slurry was added. PH of liquid 6-10
The pH was adjusted to 8 (for example, while maintaining the pH at 8), the pH was adjusted at the end of the oxidation reaction, and the silicic acid component was unevenly distributed on the surface of the magnetic iron oxide particles. The produced magnetic iron oxide particles were washed, filtered and dried by a conventional method, and then the aggregated particles were crushed to obtain magnetic iron oxide having the characteristics shown in Table 2.

The data obtained by measuring the dissolved amounts of the iron element and the silicon element every 10 minutes are shown in Table 1, and FIG. 3 shows the relationship between the dissolution rates of the iron element and the silicon element in the magnetic iron oxide.

In the magnetic iron oxide obtained in Production Example 1, the results shown in FIG.
The content C of the silicon element derived from a silicon compound such as silicic acid, which is eluted with alkali and is present on the surface C of the magnetic iron oxide particles shown in FIG. 1, is 17.9 mg / l, and the surface layer B of the magnetic iron oxide particles shown in FIG. Content B of the silicon compound derived from the silicon compound present in 3 is 38.8 mg / l, and the content A is 5
It was 9.7 mg / l.

[0130]

[Table 1]

Production Example 2 As shown in Table 2 in the same manner as in Production Example 1, except that sodium silicate was added so that the content ratio of silicon element to iron element was 2.9% in Production Example 1. A magnetic iron oxide having various characteristics was obtained.

Production Example 3 As shown in Table 2 in the same manner as in Production Example 1, except that sodium silicate was added so that the content ratio of the silicon element to the iron element was 0.9% in Production Example 1. A magnetic iron oxide having various characteristics was obtained.

(Manufacturing Example 4) As shown in Table 2 in the same manner as in Manufacturing Example 1, except that sodium silicate was added so that the content ratio of the silicon element to the iron element was 1.7%. A magnetic iron oxide having various characteristics was obtained.

(Comparative Production Example 1) A magnetic iron oxide having the properties shown in Table 2 was obtained in the same manner as in Production Example 1 except that sodium silicate was not added in Production Example 1.

(Comparative Production Example 2) With respect to 100 parts of the magnetic iron oxide obtained in Comparative Production Example 1, 1.5 parts of fine silicic acid powder was mixed with a Henschel mixer to have the characteristics shown in Table 2. Magnetic iron oxide was obtained.

[0136]

[Table 2]

Example 1 -Styrene-n-butyl acrylate copolymer 100 parts (copolymerization weight ratio 8: 2, Mw 300,000) -Magnetic iron oxide 100 parts of Production Example 1-Negative charge control agent (dialkyl salicylic acid-based Chromium complex) 1 part ・ Low molecular weight polypropylene 2 parts The above mixture is melt-kneaded in a twin-screw extruder heated to 140 ° C., and the cooled kneaded product is coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. Then, the obtained finely pulverized powder was classified by a fixed wall type air classifier to produce classified powder. Furthermore, the obtained classified powder is a multi-division classifier utilizing the Coanda effect (Elbowjet classifier manufactured by Nittetsu Mining Co., Ltd.).
Strictly classifying and removing ultrafine powder and coarse powder simultaneously to obtain a negatively chargeable magnetic toner having a weight average particle diameter (D ₄ ) of 6.8 μm (content of magnetic toner particles having a particle diameter of 12.7 μm: 0.2%). Obtained.

A magnetic developer was prepared by mixing 100 parts of this magnetic toner with 1.2 parts of hydrophobic silica fine powder which had been treated with hexamethyldisilazane and then treated with silicone oil using a Henschel mixer.

Next, the photosensitive drum and the charging roller are: outer diameter of the photosensitive drum: 24 mmφ outer diameter of the charging roller: 12 mmφ hardness of the charging roller: 54.5 ° (ASKER-C) conductive rubber layer: carbon black Polyetherurethane layer having a thickness of 3 mm dispersed Surface layer: Polyester layer having Ra of 0.9 μm (thickness of about 5 μm) In the contact charging device shown in FIG. 1, the contact pressure to the photoreceptor is 60 g / cm. , The voltage applied to the charging member is DC-3
Using an image forming apparatus (Canon LBP-LX remodeling machine) of 45 V, 1700 Vpp AC, and 150 Hz frequency, the developer was sequentially replenished with a printing speed of 4 sheets (A4) / min. , A real-time test of forming an image by the reversal development method for 6000 times at room temperature and normal humidity (25 ° C, 60% RH), high temperature and high humidity (30 ° C, 90% R
H) and low temperature and low humidity (15 ° C., 10% RH), and printout images were evaluated.

Image density measured by Macbeth reflection densitometer, whiteness of transfer paper measured by reflectometer (manufactured by Tokyo Denshoku Co., Ltd.) and solid white were calculated by comparison with whiteness of transfer paper after printing. Table 3 shows the results of dot reproducibility of the fog and the image drawing test of the pattern shown in FIG.
Shown in.

At the same time, the states of the charging member and the surface of the photosensitive member were observed, but in any of the environments, the residual developer was not fixed on the surface of the charging member and the photosensitive drum.

Therefore, when the developer was replenished, the photoconductor was exchanged, and the actual copying test was continued, after the actual copying of 20,000 sheets, the fixing of the developing agent and the severe stain were observed on the surface of the charging member. There wasn't.

Example 2 Styrene-2-ethylhexyl acrylate-100 parts Maleic acid n-butyl half ester copolymer (copolymerization weight ratio 7: 2: 1, Mw 250,000) 80 parts of magnetic iron oxide of Preparation Example 2 -Negatively charged control agent (monoazo dye-based chromium complex) 0.8 part-Low molecular weight polypropylene 3 parts The above mixture was melt-kneaded with a twin-screw extruder heated to 140 ° C, and the cooled kneaded product was roughly roughened with a hammer mill. The mixture was pulverized, and the coarsely pulverized product was finely pulverized with a jet mill. The finely pulverized powder obtained was subjected to air classification to obtain a weight average particle diameter (D ₄ ) of 13 μ.
m (content of magnetic toner particles having a particle size of 12.7 μm or more 4
5%) of negatively chargeable magnetic toner was obtained.

100 parts of the magnetic toner obtained and 0.6 part of hydrophobic colloidal silica treated with dimethyl silicone oil were mixed with a Henschel mixer to prepare a magnetic developer.

Next, using this developer, except that the contact charging member was a blade type (see FIG. 2) having a surface layer (thickness: 10 μm) made of polyester resin with Ra of 1.5 μm. Then, in the same manner as in Example 1, 10,000 copies were tested in each environment. The results are shown in Table 3.

Further, in any of the respective environments, the residual developer did not adhere to the surface of the charging member and the photosensitive drum.

Further, in the same manner as in Example 1, the developer was replenished, the photoconductor was replaced, and the actual copying test was continued.
After the actual copying of 50,000 sheets, there was no particular abnormality on the surface of the charging member.

Example 3 100 parts of styrene-n-butyl acrylate (copolymerization weight ratio 8: 2, Mw 270,000) 100 parts of magnetic iron oxide of Production Example 3 negative-charge controlling agent (monoazo dye-based chromium complex) 2 parts Low molecular weight polypropylene 3 parts Using the above materials, a magnetic toner having a weight average particle diameter (D ₄ ) of 4 μm (content of magnetic toner particles having a particle diameter of 12.7 μm or more 0%) was obtained in the same manner as in Example 1. Obtained.

A magnetic developer was prepared by mixing 100 parts of the obtained magnetic toner and 1 part of hydrophobic colloidal silica treated with silicone oil with a Henschel mixer.

Next, using this developer, except that the contact charging member shown in FIG. 1 having a surface Ra of 0.4 μm was used, the same test as in Example 1 was performed on 6000 sheets in each environment. Was done. The results are shown in Table 3.

Further, in any of the respective environments, the residual developer did not adhere to the surface of the charging member and the photosensitive drum.

Further, in the same manner as in Example 1, the developer was replenished, the photoconductor was replaced, and the actual copying test was continued. As a result, after the actual copying of 15,000 sheets, the residual toner remained on the surface of the charging member. There was no sticking of the developer.

Example 4 Styrene-n-ethylhexyl acrylate-maleic acid 100 parts n-butyl half ester copolymer (copolymerization weight ratio 7.5: 1.5: 1, Mw 300,000) -Magnetic property of Production Example 4 Iron oxide 50 parts-Negatively charged property control agent (dialkylsalicylic acid-based chromium complex) 1 part-Low molecular weight polypropylene 1 part Weight average particle diameter (D ₄ ) 8.5 μm (particles) in the same manner as in Example 1 using the above materials. A magnetic toner having a content of magnetic toner particles having a diameter of 12.7 μm or more of 4%) was obtained.

A magnetic developer was prepared by mixing 100 parts of the magnetic toner thus obtained with 1.6 parts of hydrophobic colloidal silica fine powder which had been treated with hexamethyldisilazane and then treated with silicone oil in a Henschel mixer. .

Next, using this developer, the surface Ra was set to 2.3 μm, and the charging member shown in FIG. 1 having an electric resistance of 10 ⁸ Ωcm when a direct current of 100 V was applied was used in the same manner as in Example 1 except that Under each environment, a live-action test of 4000 sheets was conducted.

As a result, dot-like adhered matter was observed at several places on the surface of the photoconductor under a high temperature and high humidity environment. However, no image defect was recognized on the image. In other environments, no adherence of residual developer was found on the charging member and the photosensitive drum. The evaluation results are shown in Table 3.

Further, the developer was replenished as it was, the photoconductor was exchanged, and the real-photographing test was continued. Was observed, but no image defect was observed on the image. In other environments, on the surface of the charging member,
There was nothing special.

Example 5 Styrene-n-butyl acrylate copolymer 100 parts (copolymerization weight ratio 8: 2, Mw 300,000) 70 parts magnetic iron oxide of Production Example 1 negative charge control agent (monoazo dye type Chromium complex) 0.8 parts-Low molecular weight polypropylene 4 parts Weight average particle diameter 1 using the above materials in the same manner as in Example 1.
A magnetic toner of 1 μm (content of magnetic toner particles having a particle size of 12.7 μm or more: 33%) was obtained.

100 parts of the magnetic toner obtained and a fine powder of hydrophobic colloidal silica treated with silicone oil.
4 parts were mixed with a Henschel mixer to prepare a magnetic developer.

This developer was used in the same manner as in Example 1 to obtain 40
A 00 live-action test was conducted. The results are shown in Table 3.

Further, in any of the respective environments, no sticking substance of the residual magnetic material was observed on the surface of the charging member and the photosensitive drum.

Further, the developer was replenished and the photoconductor was replaced, and 20,000 actual copies were continued, but there was no particular abnormality on the surface of the charging member in each environment.

Comparative Example 1 The weight average particle diameter was 8 μm (particle diameter 12.7) in the same manner as in Example 1 except that the magnetic iron oxide of Comparative Production Example 1 was used.
A magnetic toner having a content of magnetic toner particles of 5 μm or more (5%) was obtained. A magnetic developer was prepared in the same manner as in Example 1 using the obtained magnetic toner.

Next, using this developer, in the same manner as in Example 1, an actual copying test was performed on 4000 sheets in each environment.
As a result, in the high temperature and high humidity environment, spots of unique substances were found on the surface of the photoconductor and the surface of the charging member. In addition, dot-shaped white spots, so-called white spots, occurred on the image. Table 3 shows the evaluation results
Shown in. The developer was replenished, the photoconductor was replaced, and the actual shooting test was continued, but the white spots on the image gradually deteriorated, and 6
At the time of 000 sheets, the charging member had to be replaced.

Comparative Example 2 Comparative Example 2 was repeated except that the magnetic iron oxide prepared in Comparative Example 2 was used.
In the same manner as in Example 2, the weight average particle size was 7 μm (particle size 12.
A magnetic toner having a content of magnetic toner particles of 7 μm or more (0.7%) was obtained. Example 2 was performed using the obtained magnetic toner.
A magnetic developer was prepared in the same manner as in.

Next, using this developer, the same procedure as in Example 1 was carried out except that the surface was not subjected to polishing and a blade type charging member having Ra of 0.1 μm (see FIG. 2) was used. In each environment, 2000 live-action tests were conducted. As a result, streak-like adhered substances were observed on the surface of the photoconductor and the surface of the charging blade in a high temperature and high humidity environment. The obtained image lacked sharpness due to a difference in image density in addition to a partial whiteout phenomenon. The evaluation results are shown in Table 3.

Further, the developer was replenished, the photosensitive member was exchanged, and the actual copying test was continued, but while the image defect was aggravated,
At the time of 5000 sheets, the charging member had to be replaced.

Comparative Example 3 Using the magnetic developer of Example 1, Ra on the surface was 3.0 μm.
Except for the above, the actual shooting test of 4000 sheets was performed in each environment in the same manner as in Example 1. as a result,
In the high temperature and high humidity environment, innumerable spot-like unique substances were observed on the surface of the charging member and the photoconductor. Also, so-called white spots were generated on the image. The evaluation results are shown in Table 3. Further, the developer was replenished, the photoconductor was exchanged, and the actual copying test was continued, but the white spots on the image deteriorated, and the charging member had to be replaced at the time of 6000 sheets.

Comparative Example 4 The magnetic iron oxide of Production Example 1 was used, and the magnetic substance having a weight average particle diameter of 14.5 μm (content of magnetic toner particles having a particle size of 12.7 μm or more of 65%) was obtained in the same manner as in Example 1. Get toner,
A magnetic developer was prepared in the same manner as in Example 1, and in the same manner as in Example 1, a test for actual copying of 6000 sheets was performed in each environment. The results are shown in Table 3.

In each environment, no sticking of the residual developer was found on the charging member and the surface of the photosensitive member. However, on the image, the dot reproducibility was inferior to that of the magnetic developer of Example 1, and toner dust was observed.

[0171]

[Table 3]

[0172]

As described above, according to the present invention, the good contact state between the charging member and the member to be charged (photoreceptor) can be sufficiently maintained, and the developer can be applied to the charging member and the member to be charged. By improving the adhesiveness, it is possible to prevent charging failure due to contamination of the surface of the charging member and the surface of the member to be charged with the developer, and always form a good image.

Further, by reducing the contamination of the charging member, it is possible to prolong the service life, and it is possible to contribute to the reduction of waste by prolonging the replacement cycle.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a charging roller of the present invention.

FIG. 2 is a view showing an outline of a blade which is another embodiment of the present invention.

FIG. 3 is an explanatory diagram of a resistance measuring method of the charging device according to the present invention.

FIG. 4 is a diagram showing a dissolution curve of magnetic iron oxide.

FIG. 5 is a schematic diagram of magnetic iron oxide for explaining the distribution of silicon compounds.

FIG. 6 is an explanatory diagram of a checker pattern for testing the developing characteristics of magnetic toner.

[Explanation of symbols]

 1, 1'Charged member (photosensitive drum) 2, 2'Charging member 4 Electrode (50 μm aluminum sheet) 5 DC current 6 DC ammeter

Claims (2)

[Claims] 1. A charging member containing at least a polyester resin and having a surface layer having a center line average roughness (Ra) of 0.3 to 2.5 μm is brought into contact with a member to be charged, and a voltage is applied to the charging member from the outside. In the image forming method, which comprises a charging step of applying a voltage to charge the charged body, and a cleaning step of removing the developer from the charged body, the developer contains at least a binder resin and magnetic iron oxide. The magnetic toner has a weight average particle diameter of 13.5 μm or less, and in the particle size distribution of the magnetic toner, the content of magnetic toner particles having a particle diameter of 12.7 μm or more is 50% by weight or less. In the magnetic iron oxide, the content of silicon element in the magnetic iron oxide is 0.5 to 4% by weight based on the iron element, and the dissolution rate of iron element in the magnetic iron oxide is up to 20% by weight. Existing in The ratio (B / A) × 100 is 44 to 84% of the total content A of silicon element content B and magnetic iron oxide, the content of silicon element present in the magnetic iron oxide surface C
(C / A) × 100 is 10 to 55%
And an image forming method. 2. The image forming method according to claim 1, wherein the developer contains a hydrophobic colloidal silica fine powder.