JP3101784B2 - Image forming method - Google Patents

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 charging a charging member to which a voltage is externally applied by bringing the charging member into contact with a member to be charged, and a cleaning step of removing a developer from the charging member.

[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, corona dischargers have problems such as the need to apply a high voltage and the generation of a large amount of ozone.

Therefore, recently, the use of contact charging means without using a corona discharger has been studied. More specifically, a voltage is applied to a conductive roller serving as a charging member, and the roller is brought into contact with a photosensitive member serving as a charged member to charge the surface of the photosensitive member to a predetermined potential. If such a contact charging means is used, the voltage can be reduced as compared with a corona discharger, and the amount of generated ozone can be reduced.

[0004] However, when the contact charging means is used, there is a problem that poor charging occurs if sufficient contact with the member to be charged cannot be maintained. In the contact portion, if the residual developer is present on the surface of the photoreceptor, since the charging member has a predetermined contact pressure, the residual developer adheres to the surface of the charging member and the photoreceptor, and the image is affected. There is also a problem that is.

[0005] When such a phenomenon occurs, the latent image formation of the latent image carrier may be lost, or the transfer may be omitted.
The result is a defective image copy.

For this reason, the surface characteristics of the charging member are important and need to be strictly controlled. However, management of the material and the surface shape, and easiness of manufacturing including matching with the inner layer, and cost reduction. In consideration of the above, it is difficult to produce a charging member having surface characteristics satisfying all surfaces.

On the other hand, in recent years, small-sized, inexpensive and high-speed personal use copying machines and laser printers have emerged.
These small machines use a cartridge system that integrates a photoconductor, a developing unit, and a cleaning device from the standpoint of maintenance-free operation. It is desirable to use an agent.

Further, these developers tend to be further finely divided in order to realize high image quality. In such a magnetic developer, the developer itself has a strong polishing effect, and the surface of the photoconductor is strongly rubbed during image formation, so that the surface of the photoconductor is often scraped or damaged. There was a problem that the developer was fused. This problem is conspicuous when a contact member such as the above-mentioned charging member that is in contact with the surface of the photoreceptor with a predetermined contact pressure is used. ,
It can be difficult.

Further, as described above, in the contact charging device, a DC voltage or a DC voltage superimposed with an AC voltage is applied to the charging member and used. At this time, around the contact portion between the charging member and the photosensitive drum, Unusual charging of the residual developer and repetition of flying motion are repeated, which makes it difficult for the residual developer to be electrostatically attracted and embedded on the charging member and the surface of the photosensitive drum. Is very different from the case where non-contact charging means is used. In particular, this problem
The finer the developer, the more noticeable it appears. As a new problem, there is a concern that the life of the charging member is 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-mentioned problems.

That is, an object of the present invention is to prevent contact between the charging member and the member to be charged (photoconductor) by preventing contamination such as sticking of the residual developer to the surface of the member to be charged (photoconductor). An object of the present invention is to provide an image forming method which has a charging step that can be maintained and does not cause charging failure and charging unevenness, and finally achieves a longer life of the charging member, that is, a reduction in replacement frequency.

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

It is a further object of the present invention to provide an image forming method capable of obtaining a good image without fogging even when used for a long time.

[0014]

That is, the present invention provides a method of charging a charging member having at least a polyester resin and having a surface layer having a center line average roughness (Ra) of 0.3 to 2.5 μm. An image forming method comprising: a charging step of applying a voltage to a charging member from the outside while being in contact with a body to charge the charged body; and a cleaning step of removing the developer from the charged body. A magnetic toner containing at least a binder resin and magnetic iron oxide, the magnetic toner having a weight average particle diameter of 13.5 μm or less, and a particle diameter of 12.3 in the particle size distribution of the magnetic toner.
The content of 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 when the dissolution rate of the iron element of the magnetic iron oxide is up to 20% by weight and the total content A of the silicon element of the magnetic iron oxide is 44 to 84.
%, And the ratio (C / A) × 100 between the content C of the silicon element present on the surface of the magnetic iron oxide and the content A is 10 to 10%.
An image forming method using a developer which is 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 one embodiment of a contact charging device for performing a contact charging step according to the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum which is a member to be charged, which is formed by forming an organic photoconductor (OPC) 1b which is a photosensitive layer on an outer peripheral surface of a drum base 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, provided with a conductive rubber layer 2b on a metal core 2a, and further provided with a surface layer 2c which is a release coating on the peripheral surface thereof. Provided. Surface layer 2
c is preferably a release film in view of matching with the developer and the image forming method of the present invention.

Further, in order to conduct electricity in the diameter direction, both the conductive rubber layer 2b and the surface layer 2c need to have a specific resistance in a medium resistance region. The resistance value in the present invention is preferably 10 ³ Ω to 10 ⁶ Ω for the conductive rubber layer 2b, and 10 ⁴ Ω to 10 ⁹ Ω when the surface layer 2c is provided.
As shown in FIG. 3, a method of measuring the resistance value is to wind a metal foil 4 having a width of 1 cm around a charging member,
250 V is applied between the metal foil part 4 and the current value one minute later is measured by the ammeter 6, and the resistance is obtained from the relationship of 250 [V] / current value [A] = resistance of the measurement part [Ω]. Is measured.

JIS K63 is used as the conductive rubber layer 2b.
20 at a hardness defined by an A-type hardness tester of No. 01
Preferably, the hardness is 80 °.

Reference numeral E denotes a power supply unit for applying a voltage to the charging roller 2 to supply a predetermined voltage to the metal core 2a of the charging roller 2. In FIG. 1, E indicates a DC voltage, but may be obtained by superimposing an AC voltage on a DC voltage.

In the present invention, the adhesion between the conductive rubber layer and the surface layer and the material and properties of the surface layer govern 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 combining them with a developer having good matching, the contamination of the surface of the charging member and the surface of the photosensitive member can be reduced, and the life of the charging member can be prolonged. .

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

Further, polyester, which is a low-cost material having good coating properties, is coated thereon by dipping to form a surface layer, and has a center line average roughness Ra of 0.3 to 2.5 μm according to JIS standard (B0601). It was adjusted to become.

When Ra is less than 0.3 μm, the surface of the charging member and the surface of the photoreceptor easily adhere to each other. If a developer is interposed in the gap, contamination such as fusion or filming occurs on each surface. However, it is generally difficult to reach as long as the surface of the conductive rubber layer is formed by polishing. The surface of the conductive rubber layer can be further roughly polished and formed so that Ra of the surface layer exceeds 2.5 μm. In this case, however, the adhesion between the surface of the charging member and the surface of the photoreceptor can be improved. Adverse effects, such as deterioration of the developer, the possibility that the developer is easily buried in the concave portions of the charging member surface, and that the contamination easily proceeds.

As the resin material used for the conductive rubber layer in the present invention, besides polyether urethane, for example, EPDM, EPT, EPM, NBR, BR, BR, C
Thermosetting elastomers such as synthetic rubber such as R, natural rubber, etc., and thermoplastic elastomers such as vinyl chloride / vinyl acetate polyester / PVA are used alone or in combination.

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

The polyester used for the charging member surface layer of the present invention is obtained by condensation of an alcohol and a carboxylic acid, and conventionally known polyesters 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, 1,4-butenediol and the like. Dihydric alcohols such as diols, 1,4-bis (hydroxymethyl) cyclohexane, and etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylene bisphenol A Examples of the carboxylic acid include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, and 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 trihydric or higher polyhydric alcohol and / or
Alternatively, a trivalent or higher valent polycarboxylic acid may be used.

Examples of trihydric or higher polyhydric alcohols 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. Examples of the trivalent or higher polycarboxylic 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-naphthalenetricarboxylic acid, 1,2,2
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2
-Methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empol trimer acid, and acid anhydrides thereof.

It is also possible to use polyester and other resin materials in combination for the surface layer. As the resin material to be combined, a material having flexibility at normal temperature, such as polyamide, polyimide, fluororesin, silicon resin, and PVA, is used. In order to further impart conductivity, carbon black, zinc oxide, titanium oxide, Conductive particles such as metal powder may be added.

In the present invention, since the conductive rubber layer is used to support the electrodes, the conductive rubber layer is preferably flame-retardant, and particularly preferably has a flame retardancy of 94 HB or more according to 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.

In the above-described embodiment, the charging member is composed of the conductive rubber layer and the release coating. However, the present invention is not limited to this. For preventing leakage to the photoconductor between the conductive rubber layer and the surface of the release coating. For this purpose, a high resistance layer, for example, a hydrin rubber layer with small environmental fluctuation may be formed.

FIG. 2 is a schematic diagram showing another embodiment of the contact charging device for performing the contact charging step according to the present invention. The same members as those of the apparatus of FIG. 1 described above are denoted by the same reference numerals, and the description thereof will not be repeated.

The contact charging member 2 'of this embodiment is in the form of a blade which is brought into contact with the photosensitive drum 1 in a forward direction at a predetermined pressure, and the blade 2' is a metal supporting member 2 'to which a voltage is supplied. The conductive rubber 2'b is supported by a, and a surface layer 2'c serving as a releasable film is provided at a contact portion with the photosensitive drum 1. According to this embodiment, the same operation and effect as those of the above embodiment can be obtained without any trouble such as adhesion between the blade and the photosensitive drum.

The mechanical or electrical pressure applied between the charging member and the photosensitive member is an element according to the gist of the present invention, and the contact pressure of the charging member with the photosensitive member is 5 to 500 g.
/ Cm, the DC voltage applied to the charging member has an absolute value of 20
When an AC voltage is applied to 0 to 900 V, the peak-peak voltage is 500 to 5000 V, and the frequency is 50 to 3000 H.
It is desirable that z be adjusted respectively.

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

The photoreceptor used in the present invention includes, in addition to organic photoconductors, amorphous silicon, selenium, Zn
O or the like can also be used. In particular, when amorphous silicon is used for the photoconductor, compared to the case where other materials are used, even if the softening agent of the conductive rubber layer adheres to the photoconductor even to a small extent, the image flow becomes severe, so The effect of providing the insulating coating is great.

In the cleaning step according to the present invention, the photosensitive drum after transfer of the toner image is generally cleaned by wiping and removing residual toner and other contaminants after transfer by a cleaning member such as a blade or roller of a cleaner. The surface is formed and repeatedly used for image formation.

Further, such a cleaning step can be simultaneously performed in a charging step, a developing step, or a transfer step related to the electrophotographic method.

The surface material of the latent image carrier used in the present invention includes silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate, polycarbonate and the like. There is no limitation, and other monomers or copolymerization or blending between exemplified resins can be used.

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

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

Next, a 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. The magnetic toner has a weight average particle size of 13.5 μm or less.
In the particle size distribution of the magnetic toner, the content of the magnetic toner particles having a particle size of 12.7 μm or more is 50% by weight or less,
In the magnetic iron oxide, the content of the silicon element in the magnetic iron oxide is 0.5 to 4% by weight based on the iron element, and the solubility of the 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 to the total content A of the silicon element in the magnetic iron oxide is 44 to 84%, and the content of the silicon element present on the surface of the magnetic iron oxide C
And the ratio (C / A) × 100 of the content A is 10 to 55%
It is characterized by being.

The developer of the present invention, having the above-described structure, can adhere to the surface of the charging member or the surface of the photosensitive drum even if a small amount of the residual developer remains on the photosensitive drum after the cleaning step. Is extremely unlikely to occur, and the contamination itself is reduced, so that the life of the charging member itself can be prolonged, and the frequency of replacement can be reduced.

From the above, the developer according to the present invention is:
Matching with the charging step according to the present invention is extremely good, and it is possible to provide an image forming method that makes full use of the ability of the charging step according to the present invention and always performs good image formation. It is possible to contribute ecologically by reducing.

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

By improving the magnetic iron oxide, the developer of the present invention improves the fluidity of the magnetic toner itself and improves the releasability from the photoreceptor. As a result, the amount of the residual developer after the cleaning process, which causes the toner to adhere to the charging member and the photosensitive member, is reduced.

Further, by using the charging member of the present invention, even if a small amount of the residual developer is present, the developer is extremely unlikely to be fixed due to the special surface property of the charging member.

Further, the magnetic iron oxide of the present invention has a large bonding strength with the resin in the developer, reduces the amount of free magnetic material from the developer, and causes damage to the charging member and the photosensitive member. It becomes difficult.

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

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

The weight average particle diameter of the magnetic toner particles is 3.5 μm.
When the diameter 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 the fogging and density due to problems such as toner fusion, filming due to poor cleaning, and charging failure. The weight average particle size is preferably 3.5 μm or more because problems such as lightening are likely to occur.

That is, in the magnetic toner according to the present invention, remarkable effects such as improvement in charge stability and fluidity are seen as compared with the conventional example because 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 magnetic toner particles having a particle size of m or more is 50% by weight or less (more preferably 40% or less).

Further, in the present invention, the content of the silicon element in the magnetic iron oxide used for the magnetic toner is 0.5 to 4.0% by weight (more preferably 0.8 to 3.0) based on the iron element.
%, More preferably 0.9 to 3.0% by weight). When the content of silicon element is 0.
When the content is less than 5% by weight, the effect of improving the magnetic toner (particularly, the fluidity of the magnetic toner) is weak, and when the content of the silicon element is more than 4.0% by weight, the silicic acid component is It is not preferable because it remains on the iron surface more than necessary or 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 when the dissolution rate of the iron element of the magnetic iron oxide is up to about 20% are obtained. B / A × 100 (%) is 44 to 8
4% (preferably 60-80%), the content C and the content A of the silicon element present on the surface of the magnetic iron oxide particles.
Is 100 to 55% (preferably 25 to 40%). B /
When A × 100 (%) is smaller than 44%, a large amount of silicon element more than necessary is present in the central portion of the magnetic iron oxide, and the production efficiency is easily deteriorated. May be iron oxide.

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

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 in the magnetic iron oxide and the magnetic toner. In addition, the charge amount and the volume resistivity of the magnetic iron oxide are reduced, and the charge stability and environmental stability of the magnetic toner are easily 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 easily dispersed in the toner and has an adverse effect on magnetic toner characteristics.

In other words, in order to obtain good magnetic toner characteristics, the distribution of the silicon element present in the magnetic iron oxide must increase 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 .mu.c / g (preferably -40 to -60 .mu.c / g).
c / g) and the magnetic iron oxide has a volume resistivity of 1
× 10 ⁴ to 1 × 10 ⁸ Ω · cm (preferably 5 × 10 ⁴ Ω · cm)
To 5 × 10 ⁷ Ω · cm).

When the charge amount of the magnetic iron oxide is less than −25 μc / g, if the magnetic toner is used repeatedly for a long period of time, the magnetic toner cannot easily have the required charge amount, resulting in a problem such as a decrease in image density and image fog. Occurs. On the other hand, when the charge amount of the magnetic iron oxide exceeds -70 μc / g,
Since the charge amount of the magnetic toner becomes too high, the image density tends to be reduced in a low-temperature and low-humidity environment.

The magnetic iron oxide has a volume resistivity of 1 ×.
If it is smaller than 10 ⁴ Ω · cm, it becomes difficult to maintain the required charge amount of the magnetic toner, and the image density tends to decrease. On the other hand, when the volume resistivity of the magnetic iron oxide exceeds 1 × 10 ⁸ Ω · cm, the charge amount is likely to be higher than necessary when repeatedly used in a low-temperature and low-humidity environment, and a decrease in image density is observed. Easy to be.

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

When the degree of aggregation of the magnetic iron oxide is less than 3%, the blowing of the magnetic toner called flushing is apt to occur at the time of manufacturing the magnetic toner, and it is difficult to efficiently manufacture the magnetic toner.

On the other hand, when the degree of aggregation exceeds 40%,
It is not easy to sufficiently disperse the magnetic iron oxide in the magnetic toner, and this tends to have an adverse effect on image density, fog, and the like. Further, in the present invention, the fluidity of the magnetic iron oxide is reflected on the fluidity of the magnetic toner, and when the magnetic iron oxide having a cohesion degree of more than 40% is used, the fluidity of the magnetic toner is not sufficiently increased. 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, causing toner fusion to the photosensitive drum and the charging member, and adversely affecting the chargeability of the magnetic toner. , Fog and the like tend to be observed.

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

If 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, and are easily dispersed in the magnetic toner to easily adversely affect the toner characteristics.

On the other hand, when the smoothness D is larger than 0.6, it is difficult to obtain a sufficient adhesion between the binder resin used for the magnetic toner and the magnetic iron oxide, and the surface of the magnetic toner gradually decreases after repeated use. Magnetic iron oxide is removed, which tends to cause adverse effects such as a decrease in image density.

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

When the sphericity ψ is less than 0.8, the individual particles of the magnetic iron oxide come into face-to-face 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 for measuring various physical property data in the present invention will be described in detail below. (1) Particle size distribution of toner The particle size distribution of toner can be measured by various methods.
In the present invention, this is performed using a Coulter counter.

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 a number distribution and a volume distribution and a CX-1 personal computer (manufactured by Canon) were connected. The electrolyte is 1 grade using primary sodium chloride.
% NaCl aqueous solution is prepared. As a measuring method, a surfactant (preferably an alkylbenzene sulfonate) is used as a dispersant in 100 to 150 ml of the aqueous electrolytic solution.
Add 5 ml, and further add 2-20 mg of the measurement sample.
The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of the toner were measured using the Coulter Counter TAII, using a 100 μm aperture as the aperture, and measuring 2 to 40 μm. The volume distribution and the number distribution of the particles are calculated. Then, according to the present invention, the weight-based weight average diameter D ₄ obtained from the volume distribution (the median value of each channel is a representative value for each channel), and the weight-based 12.7 μm obtained from the volume distribution.
Find a weight distribution of m or more. (2) Content of Silicon Element In the present invention, the content C of the silicon element 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 to 50 to 60 ° C. About 25 g of magnetic iron oxide slurried with about 400 ml of deionized water is added to the 5 liter beaker with the deionized water while washing with about 300 ml of deionized water.

Then, while maintaining the temperature at about 60 ° C. and the stirring speed at about 200 rpm, a special grade sodium hydroxide is added to make a 1N sodium hydroxide solution. At this time, the magnetic iron oxide concentration is about 5 g / l. The dissolution of silicon compounds such as silicic acid on the surface of the iron oxide particles is started. Thirty minutes after the start of dissolution, 20 ml is sampled, filtered through a 0.1 μm membrane filter, and the filtrate is collected. The filtrate is subjected to quantitative determination of silicon element by plasma emission spectroscopy (ICP).

The content C of the silicon element is determined by the unit weight of the magnetic iron oxide in the aqueous sodium hydroxide solution (magnetic iron oxide 5 g /
1) corresponding to the silicon element concentration (mg / l).

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

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 dissolution. At this time, the concentration of the magnetic iron oxide is about 5 g / l, and the aqueous hydrochloric acid solution is about 3N. Approximately 20 ml of the sample is sampled several times from the start of dissolution until it is completely dissolved and clear, filtered through a 0.1 μ membrane filter, and the filtrate is collected. The filtrate is subjected to quantitative determination of 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 the silicon element for each sample are calculated by the following equations.

[0083]

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

The content B of the silicon element of the magnetic iron oxide is determined based on the silicon element concentration (mg per unit weight of magnetic iron oxide 5 g / l) 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 parts, and while the contents of silicon elements and the contents A and B are measured, the contents C are measured. Separately measuring method, measuring the content C of the sample of magnetic iron oxide, using the sample after the measurement, then using the content B '(the amount obtained by subtracting the content C from the content B) and the content A' (The amount obtained by subtracting the content C from the content A), and finally calculating the contents A and B. (3) Charge of magnetic iron oxide About 2 g of magnetic iron oxide and carrier iron powder (TEFV200-3)
00mesh) (Nippon Iron Powder Co., Ltd.)
weighed into a ml polybin, shaken by hand for 10 seconds, shaken with a V-type blender for 20 minutes, and measured the charge of magnetic iron oxide using a blow-off powder charge meter (Toshiba Chemical Corporation) I do. At this time, a 400 mesh stainless steel net is set on the Faraday gauge for measurement, and about 0.4 g of the measurement sample is weighed and calculated from the value when blow-off is performed for 30 seconds. (4) Volume specific resistance of magnetic iron oxide 10 g of magnetic iron oxide is put into a measuring cell and molded (pressure 600 kg / cm ² ) by a hydraulic cylinder. After releasing the pressure, use a ohmmeter (YEW MODEL2506A manufactured by Yokogawa Electric Corporation).
DIGITAL MULTIMETOR), and apply a pressure of 150 Kg / cm ² again with a hydraulic cylinder. Start the measurement and read the measured value 3 minutes later. Further, the thickness of the sample is measured, and the volume resistivity is measured by the following equation.

[0086]

(Equation 3) (5) Aggregation degree of magnetic iron oxide 10 g of magnetic iron oxide was pulverized with a mixer and 200 mesh
2 g of the sample passed through the sieve is weighed. 60mesh from above on powder tester (Hosokawa Micron Co., Ltd.)
Three screens are set in the order of 100 mesh and 200 mesh, and 2 g of the weighed sample is gently placed on the screen, and a vibration having an amplitude of 1 mm is applied for 65 seconds to measure the weight of the magnetic iron oxide remaining on each screen. Then, the degree of aggregation is calculated according to the following equation.

[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 determined by a BET multipoint method using a fully automatic gas adsorption amount measuring apparatus: Autosorb 1, manufactured by Yuasa Ionics Co., Ltd., using nitrogen as the adsorbed gas. In addition, as pretreatment of a sample, degassing is performed at 50 ° C. for 1 hour. (8) Average particle size and surface area of magnetic iron oxide Using an electron microscope (H-700H, Hitachi, Ltd.), using a sample of magnetic iron oxide treated on a copper mesh of a collodion film, photographing at 10,000 × at an applied voltage of 100 KV. Then, the printing magnification is 3 times, and the final magnification is 30,000 times. With this, the shape is observed and the maximum length of each particle (μm)
Is measured, 100 pieces are randomly selected, and the average is defined as the average particle size.

In calculating the surface area, the magnetic iron oxide is assumed to be spherical with the average particle diameter as the diameter, and the density of the magnetic iron oxide is measured by an ordinary method to determine the value of the surface area. (9) Sphericity of Magnetic Iron Oxide The sphericity 磁性 of magnetic iron oxide in the present invention is calculated as follows.

[0090]

(Equation 6) The sphericity ψ is obtained by randomly selecting 100 magnetic iron oxide particle specimens from a photograph, measuring the maximum length and the minimum length, and then averaging the calculated values.

The maximum length and the minimum length of the oxidized magnetic material follow the method for determining the average particle size.

The sphericity of a cubic ordinary magnetic iron oxide is about 0.6 to 0.7 and less than 0.8, whereas the sphericity 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 a square end.

When the sphericity ψ is less than 0.8, even if the silicon element is unevenly distributed on the surface of the magnetic iron oxide particles, the dispersibility in the binder resin is inferior to the case where the silicon element is 0.8 or more. The magnetic toner obtained tends to have poor developing characteristics, and tends to be a magnetic toner having poor dot reproducibility.

The magnetic iron oxide used in the magnetic toner of the present invention is used in an amount of 20 to 2 parts by weight based on 100 parts by weight of the binder resin.
It is preferable 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 obtained by polymerizing one or more monomers selected from styrenes, acrylic acids, methacrylic acids and derivatives thereof. preferable.
Examples of monomers that can be used include styrenes such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene. Examples of acrylic acids, methacrylic acids and derivatives thereof include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-tetradecyl acrylate, and n-acrylate. Examples include acrylates such as hexadecyl, lauryl acrylate, cyclohexyl acrylate, diethylaminoethyl acrylate, and dimethylaminoethyl acrylate. Similarly, methacrylic acid, methyl methacrylate ヽ ethyl methacrylate, propyl methacrylate, and butyl methacrylate , Amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, silicon methacrylate Rohekishiru, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, methacrylic acid esters such as stearyl methacrylate. Besides the above-mentioned monomers, a small amount of other monomers within the range that can achieve the object of the present invention, such as acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, vinylcarbazole, vinylmethylether, butadiene, isoprene, anhydrous maleic, maleic Acids, maleic acid monoesters, maleic acid diesters, vinyl acetate and the like may be used.

As the crosslinking agent used in the resin for toner according to the present invention, 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 diacrylate (MANDA Nippon Kayaku), and methacrylates of the above acrylates.

As polyfunctional crosslinking agents, pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxy, Polyethoxyphenyl) propane, diallyl phthalate, triallyl cyanurate,
Triallyl asocyanurate, triallyl isocyanurate, triallyl trimellitate, diarylchlorendate and the like.

In the toner using the resin according to the present invention, in addition to the above-mentioned binder resin component, the following content is selected in a proportion smaller than the content of the binder resin component as long as the effect of the present invention is not adversely affected. A compound may be contained.

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.

In the toner according to the present invention, a coloring agent can be used if necessary. As the colorant, generally known dyes / pigments can be used, and for example, carbon black, nigrosine dye, lamp black and the like 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. As specific examples of the positive charge control agent, generally, nigrosine, carbon number 2
Azine dyes containing up to 16 alkyl groups (Japanese Patent Publication No.
No. 1627), basic dyes (for example, CI Bas)
ic Yellow 2 (CI.41000), C.I.
I. Basic Yellow 3, C.I. I. Basi
c Red 1 (CI. 45160), C.I. I. Ba
sic Red 9 (CI. 42500), C.I. I.
Basic Violet 1 (CI. 4253)
5), C.I. I. Basic Violet 3 (C.I.
I. 42555), C.I. I. Basic Violet
10 (CI. 45170), C.I. I. Basic
Violet 14 (CI. 42510), C.I. I. B
asic Blue 1 (CI. 42025), C.I.
I. Basic Blue 3 (CI. 5100)
5), C.I. I. Basic Blue 5 (CI.4
2140), C.I. I. BasicBlue 7 (C.I.
I. 42595), C.I. I. Basic Blue 9
(CI. 52015), C.I. I. Basic Blu
e24 (CI. 52030), C.I. I. Basic
Blue 25 (CI.52025), C.I. I. B
asic Blue 26 (CI.44025),
C. I. Basic Green 1 (CI. 420)
40), C.I. I. Basic Green 4 (C.I.
I. Lake pigments of these basic dyes (for example, phosphotungstic acid, phosphomolybdic acid, phosphomolybdic 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. Moldrant Bla
ck11, C.I. I. Pigment Black 1
etc.

Further, for example, polyamide resins such as quaternary ammonium salts such as benzolmethyl-hexadecyl ammonium chloride and decyl-trimethyl ammonium chloride, vinyl polymers containing amino groups, and condensation polymers containing amino groups, etc. ,
Preferred are nigrosine, quaternary ammonium salts, triphenylmethane-based nitrogen-containing compounds, polyamides and the like.

Specific examples of the negative charge control agent include monoazo dyes described in JP-B-41-20153, JP-A-42-27596, JP-A-44-6397, and JP-A-45-26478. Metal complexes, furthermore, nitroamine acids and salts thereof described in JP-A-50-133338 or C.I. I. Dyes and pigments such as 14645, JP-B-55-42752, JP-B-58
No. 41508, JP-B-58-7384, JP-B-59-7385 and the like, Zn, Al, C of salicylic acid, naphthoic acid and dicarboxylic acid
Metal complexes such as o, Cr, Fe, etc., sulfonated copper phthalocyanine pigments, nitro groups, styrene oligomers into which halogens are introduced, and chlorinated paraffins can be exemplified. In particular, from the viewpoint of dispersibility, a metal complex salt of a monoazo dye, and a metal complex of salicylic acid, alkyl salicylic acid, naphthoic acid, and dicarboxylic acid are preferable. The addition amount of these charge control agents minimizes adverse effects such as a reduction in developing power and a decrease in environmental stability due to contamination of the developing sleeve surface by the charge control agents while maintaining good triboelectricity as described above. Therefore, the addition amount is preferably 0.1 to 3 parts by weight based on 100 parts by weight of the binder resin.

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

Here, those applied as the ethylene-based olefin homopolymer or ethylene-based olefin copolymer include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer. There is an ionomer having a polyethylene skeleton, or 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 inorganic fine powder or hydrophobic inorganic fine powder.
For example, it is preferable to add silica fine powder for use.

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

Further, the silica fine powder used in the present invention is preferably subjected to a hydrophobic treatment. The hydrophobizing treatment is applied by chemically treating with an organic silicon compound or the like which reacts or physically adsorbs with the silica fine powder. A preferred method is to treat the dry silica fine powder produced by the vapor phase oxidation of the silicon halide compound with a silane coupling agent or simultaneously with the silane coupling agent and an organic silicon compound such as silicone oil. Is mentioned.

Examples of the silane coupling agent used in the hydrophobic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyl. Dichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane,
Chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldi Siloxane and 1,3-diphenyltetramethyldisiloxane.

Examples of the organosilicon compound include silicone oil. Preferred silicone oils are those having a viscosity of about 30 to 1,000 centistokes at 25 ° C., for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, fluorine-modified Silicon oil and the like are preferred.

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

An external additive other than the fine silica powder may be added to the magnetic toner according to the present invention, if necessary.

For example, a charging auxiliary, a conductivity-imparting agent, a fluidity-imparting agent, an anti-caking agent, a release agent for fixing with a hot roll,
These are resin fine particles and inorganic fine particles that function as a lubricant, an abrasive and the like.

The inorganic fine powder or the hydrophobic inorganic fine powder 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) based on 100 parts by weight of the magnetic toner. good.

To prepare a magnetic toner for developing an electrostatic image according to the present invention, a magnetic powder, a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or a dye as a colorant as required, a charge control And other additives are thoroughly mixed by a mixer such as a ball mill, and then melted, kneaded and kneaded using a hot kneader such as a heating roll, kneader or extruder to mutually dissolve the resins. The pigment or dye is dispersed or dissolved therein, and after cooling and solidifying, pulverization and strict classification are performed to obtain the magnetic toner according to the present invention.

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

After a predetermined amount of the silicate compound is added to the aqueous ferrous salt solution, an equivalent or an equivalent or more of alkali such as sodium hydroxide is added to the iron component to prepare an aqueous solution containing ferrous hydroxide. . Adjust the pH of the prepared aqueous solution to pH 7
Air is blown in while maintaining the above (preferably pH 8 to 10), and the ferrous hydroxide is oxidized while the aqueous solution is heated to 70 ° C. or higher, and a seed crystal serving as a core of magnetic iron oxide particles is first generated. I do.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate based on the amount of the alkali previously added is added to the slurry-like liquid containing the seed crystals. The reaction of ferrous hydroxide is promoted while blowing air while maintaining the pH of the solution at 6 to 10 to grow magnetic iron oxide particles with the seed crystal as a core. As the oxidation reaction proceeds, the pH of the solution shifts to the acidic side,
It is preferable that the pH of the liquid is not less than 6. By adjusting the pH of the solution at the end of the oxidation reaction, it is preferable that a predetermined amount of the silicate 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 commercially available silicates such as sodium silicate and silicic acids such as sol silicic acid generated by hydrolysis or the like. In addition, 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 salt, iron sulfate generally produced as a by-product in the production of titanium sulfate, iron sulfate produced as a by-product of cleaning the surface of a steel sheet, and iron chloride and the like can be used. is there.

The method for producing magnetic iron oxide by the aqueous solution method generally uses an iron concentration of 0.5 to 2 mol / l from the viewpoint of preventing an increase in viscosity during the reaction and the solubility of iron sulfate. Generally, the lower the concentration of iron sulfate, the smaller the particle size of the product tends to be. Further, in the reaction, as the amount of air is larger and the reaction temperature is lower, the particles are easily atomized.

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

[0124]

EXAMPLES The present invention will be described below in more detail with reference to Production Examples and Examples. Number of copies or% described in Examples
Indicates parts by weight or% by weight.

(Production Example 1) Sodium silicate was added to an aqueous ferrous sulfate solution so that the content ratio of silicon element to iron element was 1.8%. 0 to
An aqueous solution containing ferrous hydroxide was prepared by mixing 1.1 equivalents of a sodium hydroxide solution.

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

Next, an aqueous solution of ferrous sulfate was added to the slurry so that the amount thereof became 0.9 to 1.2 equivalents relative to the initial alkali amount (sodium component of sodium silicate and sodium component of caustic soda). PH of liquid 6-10
(Eg, pH 8), the oxidation reaction was promoted while blowing air, 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 properties shown in Table 2.

Table 1 shows data obtained by measuring the dissolution amounts of the iron element and the silicon element every 10 minutes, 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, FIG.
The content C of a silicon element derived from a silicon compound such as silicic acid eluted with alkali 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. Is 38.8 mg / l, and content A is 58.8 mg / l.
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 to iron was 2.9%. A magnetic iron oxide having excellent characteristics was obtained.

(Production Example 3) Table 2 was produced 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 0.9%. A magnetic iron oxide having excellent characteristics was obtained.

(Production Example 4) Table 2 was produced 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 1.7%. A magnetic iron oxide having excellent 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.

(Comparative Production Example 2) To 100 parts of the magnetic iron oxide obtained in Comparative Production Example 1, 1.5 parts of silicic acid fine powder was mixed with a Henschel mixer and had the characteristics shown in Table 2. A magnetic iron oxide was obtained.

[0136]

[Table 2]

Example 1 100 parts of styrene-n-butyl acrylate copolymer (copolymerization weight ratio 8: 2, Mw 300,000) 100 parts of magnetic iron oxide of Production Example 1 Negative charge control agent (dialkylsalicylic acid type) Chromium complex) 1 part ・ Low molecular weight polypropylene 2 parts Then, the obtained finely pulverized powder was classified by a fixed wall air classifier to produce a classified powder. In addition, the obtained classified powder is multi-divided using the Coanda effect (Nippon Mining Co., Ltd. elbow jet classifier)
The ultrafine powder and the coarse powder are strictly classified and removed simultaneously to obtain a negatively chargeable magnetic toner having a weight average particle diameter (D ₄ ) of 6.8 μm (the 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 and 1.2 parts of hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil using a Henschel mixer.

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

The image density measured by a Macbeth reflection densitometer, the whiteness of the transfer paper measured by a reflectometer (manufactured by Tokyo Denshoku Co., Ltd.) and the whiteness of the transfer paper after printing solid white were calculated. Table 3 shows the results of dot fogging and dot reproducibility by performing an image test for the pattern shown in FIG.
Shown in

At the same time, the appearance of the charging member and the surface of the photoreceptor was observed, but no residual developer was fixed on the charging member and the surface of the photosensitive drum in any of the environments.

Then, the developer was further replenished, the photosensitive member was replaced, and the actual photographing test was further continued. As a result, even after the actual photographing of 20,000 sheets, the developer was firmly adhered to the surface of the charging member and severe stains were observed. Did not.

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

A magnetic developer was prepared by mixing 100 parts of the obtained magnetic toner and 0.6 parts of hydrophobic colloidal silica treated with dimethyl silicone oil using a Henschel mixer.

Next, the contact charging member was changed to a blade type (see FIG. 2) having a Ra of 1.5 μm and a surface layer (thickness of 10 μm) made of a polyester resin using this developer. In the same manner as in Example 1, a real image test of 10,000 sheets was performed under each environment. Table 3 shows the results.

In any of the respective environments, no residual developer was fixed on the charging member and the surface of the photosensitive drum.

Further, in the same manner as in Example 1, the developer was replenished, the photosensitive member was replaced, and the actual photographing test was continued.
After the actual printing 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 control agent (monoazo dye-based chromium complex) 2 parts-Low molecular weight polypropylene 3 parts A magnetic toner having a weight average particle diameter (D ₄ ) of 4 μm (the 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 using the above materials. 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 using a Henschel mixer.

Next, in the same manner as in Example 1 except that this developer was used and the contact charging member shown in FIG. Was done. Table 3 shows the results.

In any of the environments, no residual developer was fixed on the charging member and the surface of the photosensitive drum.

Further, in the same manner as in Example 1, the developer was further replenished, the photosensitive member was replaced, and the actual printing test was continued. 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) Iron oxide 50 parts-Negative charge control agent (dialkylsalicylic acid-based chromium complex) 1 part-Low molecular weight polypropylene 1 part Using the above materials, in the same manner as in Example 1, weight average particle diameter (D ₄ ) 8.5 µm (particles) A magnetic toner having a content of magnetic toner particles having a diameter of 12.7 μm or more (4%) was obtained.

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

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

As a result, spot-like fixed matters were observed at several places on the surface of the photoreceptor under a high temperature and high humidity environment. However, no image defect was found on the image. In other environments, no sticking of the residual developer was found on the charging member and the photosensitive drum. Table 3 shows the evaluation results.

Further, the developer was replenished as it was, the photosensitive member was replaced, and the actual photographing test was continued. As a result, in a high-temperature and high-humidity environment after 10,000 sheets of actual photographing, dot-like unique substances were found at several places on the photosensitive member surface. However, no image defect was observed on the image. In other environments, on the surface of the charging member,
There was no particular abnormality.

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

100 parts of the obtained magnetic toner and 0.1 parts of hydrophobic colloidal silica fine powder treated with silicone oil.
4 parts 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 live-action test of 00 sheets was performed. Table 3 shows the results.

In any of the respective environments, no residual magnetic material was fixed on the surface of the charging member and the surface of the photosensitive drum.

Further, the developer was replenished and the photosensitive member was replaced, and actual photographing of 20,000 sheets was continued as it was. However, there was no particular abnormality on the surface of the charging member in any of the environments.

Comparative Example 1 A weight average particle diameter of 8 μm (particle diameter of 12.7) was obtained 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 magnetic toner particle content 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, a photographic test of 4000 sheets was performed in each environment in the same manner as in Example 1.
As a result, under the high-temperature and high-humidity environment, dot-like unique substances were recognized on the surface of the photoconductor and the surface of the charging member. Further, spot-like white spots, so-called white spots, occurred on the image. Table 3 shows the evaluation results.
Shown in Further, the developer was replenished, the photosensitive member was replaced, and the actual photographing test was continued, but the white spots on the image gradually deteriorated.
At the time of 000 sheets, the charging member had to be replaced.

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

Next, the same procedure as in Example 1 was carried out except that this developer was used, and the surface was not polished and molded, and a blade-type charging member (see FIG. 2) having Ra of 0.1 μm was used. In each environment, 2,000 live-action tests were performed. As a result, streaks were found on the surface of the photoreceptor and the surface of the charging blade under a high temperature and high humidity environment. The obtained image had a density difference in image density in addition to a partial white spot phenomenon, and lacked sharpness. Table 3 shows the evaluation results.

Further, the actual photographing test was continued by replenishing the developer and exchanging the photoreceptor.
At the time of 5000 sheets, the charging member had to be replaced.

Comparative Example 3 Using the magnetic developer of Example 1, the surface Ra was 3.0 μm.
Except for the following, a real image test of 4000 sheets was performed in each environment in the same manner as in Example 1. as a result,
In a high-temperature and high-humidity environment, countless dot-like unique substances were recognized on the surface of the charging member and the photosensitive member. In addition, so-called white spots occurred on the image. Table 3 shows the evaluation results. Further, the developer was replenished, the photosensitive member was replaced, and the actual photographing test was continued. However, white spots on the image deteriorated, and the charging member had to be replaced at 6,000 sheets.

Comparative Example 4 Using the magnetic iron oxide of Production Example 1, a magnetic material having a weight average diameter of 14.5 μm (content of magnetic toner particles having a particle diameter of 12.7 μm or more: 65%) in the same manner as in Example 1. Get the toner,
A magnetic developer was prepared in the same manner as in Example 1, and a 6000-sheet actual photographing test was performed in each environment in the same manner as in Example 1. Table 3 shows the results.

In each environment, no residual developer was fixed on the charging member and the surface of the photoreceptor. However, on the image, compared with the magnetic developer of Example 1, the dot reproducibility was inferior, and toner dust was observed.

[0171]

[Table 3]

[0172]

As described above, according to the present invention, a good contact state between the charging member and the member to be charged (photosensitive member) can be sufficiently maintained, and the developer can be applied to the charging member and the member to be charged. By improving the fixing property, it is possible to prevent poor charging due to contamination of the developer on the charging member and the surface of the member to be charged, thereby always forming a good image.

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

[Brief description of the drawings]

FIG. 1 is a view schematically showing a charging roller of the present invention.

FIG. 2 is a view schematically showing a blade according to another embodiment of the present invention.

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

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

FIG. 5 is a schematic view of a magnetic iron oxide for explaining the distribution of a silicon compound.

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

[Explanation of symbols]

 1, 1 'charged body (photosensitive drum) 2, 2' charging member 4 electrode (50 μm aluminum sheet) 5 DC current 6 DC ammeter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-231060 (JP, A) JP-A-2-151873 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/083

Claims (2)

(57) [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 externally applied to the charging member. And a cleaning step of removing the developer from the charged body, wherein the developer contains at least a binder resin and a 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 the magnetic toner particles having a particle diameter of 12.7 μm or more is 50% by weight or less. Wherein the content of silicon element in the magnetic iron oxide is 0.5 to 4% by weight based on the iron element, and the solubility of the iron element in the magnetic iron oxide is up to 20% by weight. Silicon source present 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
And the ratio (C / A) × 100 of the content A is 10 to 55%
An image forming method, characterized in that: 2. The image forming method according to claim 1, wherein the developer contains a hydrophobic colloidal silica fine powder.