JPH08334960A - Image forming method - Google Patents

Abstract

PURPOSE: To provide an image forming method provided with a contact electrifying process capable of obtaining an excellent image having a high density by never or hardly causing the fusing of toner on a photoreceptor. CONSTITUTION: In the image forming method provided with an electrifying process and using the toner incorporating inorganic grains having 0.1 to 5μm average grain size and an electrostatic charge latent image carrier consisting of an organic photoreceptor, in a developing process, voltages for bringing back the toner from the latent image carrier to a toner carrier and for making the toner fly from the toner carrier to the latent image carrier are applied to the toner carrier for time T1 at least once, between the latent image carrier and the toner carrier in a developing region and after that, a voltage in a direction where the toner is made to fly to an image part and brought back into an nonimage part, is applied to the toner carrier for time T2 . Further, the ratio of the time T1 to the time T2 , T2 /T1 is >=0.1.

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 for visualizing an electrostatic latent image in an image forming method such as electrophotography, electrostatic recording and electrostatic printing. More specifically, an electrophotographic method including at least a charging step of contacting an electrostatic latent image holding member with a charging member to which a voltage is applied from the outside to perform charging, and a developing step of developing the electrostatic latent image with toner. The present invention relates to an image forming method used in.

[0002]

2. Description of the Related Art A corona discharger has been known as a charging means in an electrophotographic apparatus or the like. However, the corona discharger has a problem that a large amount of ozone is generated because a high voltage must be applied. Therefore, recently, a charging means using a contact charging means without using a corona discharger has been studied. JP-A-63-149
In Japanese Patent Laid-Open No. 668 and Japanese Patent Laid-Open No. 63-149669, a voltage is applied to a conductive roller which is a charging member,
It is described that the roller is brought into contact with a photosensitive member (electrostatic latent image holding member) which is a member to be charged to charge the surface of the photosensitive member to a predetermined potential. When such a contact charging means is used, the voltage can be lowered and the ozone generation amount can be reduced as compared with the corona discharger. However, in the contact charging means using the contact charging device as described above, a DC voltage or a voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging member. Particularly in the vicinity of the contact area, abnormal charging of the residual toner having a small particle size and light weight and repeated flight motion are repeated, and electrostatic adsorption or embedding of the residual toner on the surface of the photosensitive drum is likely to occur. The toner is fused to the surface of the photosensitive drum. In particular, this tendency is remarkable when an electrostatic latent image carrier having an organic photoconductor is used. As described above, the use of the contact charging means is very different from the case of using the conventional non-contact charging means using a corona discharger, and has a unique problem.

On the other hand, in recent years, compact and inexpensive personal-use copying machines, laser printers, etc. have appeared, and in these small machines, a cartridge in which a photoconductor, a developing device, a cleaning device, etc. are integrated from the standpoint of maintenance-free. It is desirable to use the magnetic one-component toner because the method is used and the structure of the developing device can be simplified as the toner.

In order to obtain a good image in the method using such a magnetic one-component toner, the toner should be more uniform.
It is necessary to have a charging property that allows the charging to be performed more quickly. Therefore, for example, JP-A-62-6107
No. 2, etc., it is proposed to add and mix inorganic particles to toner powder. However, when a toner containing such inorganic particles is used in an image forming apparatus having the above-mentioned contact charging device and an organic photoconductor, the inorganic particles in the toner easily scratch the photoconductor, Toner fusion onto the surface of the photoreceptor is particularly likely to occur.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming method which solves the problems of the prior art as described above. That is, an object of the present invention is to provide an image forming method having a contact charging step, in which toner fusion does not occur on a photosensitive member or toner fusion does not easily occur. Another object of the present invention is to provide an image forming method capable of obtaining a good image with high image density.

[0006]

The above object can be achieved by the present invention described below. That is, according to the present invention, a charging step in which a charging member to which a voltage is applied from outside is brought into contact with the electrostatic latent image holding member to perform charging, and an electrostatic latent image is formed on the charged electrostatic latent image holding member. And a developing step of developing the electrostatic latent image formed on the electrostatic latent image holding member with a toner layer disposed on a toner carrier to form a toner image, and the electrostatic latent image holding member. An image forming method comprising at least a transfer step of forming a transfer image by transferring the toner image formed on the transfer material to a transfer material, and having an average particle diameter of 0.1 to 5 μm.
Developing area using the electrostatic latent image holding member composed of the toner containing the inorganic particles and the organic photoconductor, and the electrostatic latent image holding member and the toner carrier facing the electrostatic latent image holding member in the developing step. Between the electrostatic latent image carrier and the toner carrier, a voltage for pulling the toner back from the electrostatic latent image carrier to the toner carrier and a voltage for causing the toner to fly to the electrostatic latent image carrier are set. After the toner is applied to the toner carrier at least once for T ₁ time, the toner is ejected to the image area and the voltage for returning the toner to the non-image area is applied to the toner carrier for T ₂ hours. And the T ₁ hour and T
_The image forming method is characterized in that the ratio T ₂ / T ₁ with respect to ₂ hours is 0.1 or more.

[0007]

In the present invention, the toner containing inorganic particles and the organic photoconductor having a relatively low hardness have a charging step of contacting and charging by using the special bias as described above. However, the toner fusion to the electrostatic latent image carrier (organic photoconductor) is effectively prevented. The reason for this is considered to be as follows.

Normally, due to the force of the developing electric field applied to the developing area, the toner flies from the toner carrier toward the photoconductor, which is the electrostatic latent image carrier, and collides with the surface of the photoconductor.
At this time, an impact is applied from the toner to the surface of the photoconductor, and in some cases, the surface of the photoconductor is scratched. Since the toner used in the present invention contains inorganic particles having a relatively large particle size and a relatively high hardness, scratches are generated on the surface of the organic photoreceptor having a relatively low hardness used in the present invention. easy. Toner is easily embedded in the scratches by a charging roller or the like that is in contact with the photoconductor, and toner fusion on the photoconductor surface is likely to occur.

The impact force of the toner on the surface of the photosensitive member depends on the magnitude of the developing electric field applied to the developing area.
It is almost determined by the magnitude of the voltage (peak-to-peak) of the AC component of the bias applied from the outside to the toner carrier. However, in order to obtain a sufficient image density, it is necessary to make the value of the voltage of this AC component a certain amount, and it cannot be made smaller than a certain value. On the other hand, when a discontinuous AC component of the developing electric field used in the present invention as shown in FIG. 2 is applied, a continuous AC component as shown in FIG. Compared to the case where the voltage is applied, the number of times the toner collides with the surface of the photoconductor is smaller, and the time during which the toner is pressed against the surface of the photoconductor by the strong electric field can be shortened. It is considered that the occurrence of scratches on the surface of the photoconductor due to the above can be prevented, and the fusion of the toner on the surface of the photoconductor can be prevented. As a result, according to the present invention, even in the image forming method including the contact charging step, the toner fusion is not generated on the photoconductor or hardly occurs, and a good image having a high image density is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to the preferred embodiments of the present invention. The image forming method of the present invention comprises a charging step in which a charging member to which a voltage is applied from the outside is brought into contact with an electrostatic latent image holding member (photoreceptor) to perform charging, and an electrostatic latent image holding member charged is electrostatically charged. A step of forming a charge latent image, a developing step of developing the electrostatic latent image formed on the electrostatic latent image holding member by a toner layer arranged on a toner carrier to form a toner image, An image forming method comprising at least a transfer step of transferring a toner image formed on an electrostatic latent image holder onto a transfer material to form a transferred image, wherein the electrostatic latent image carrier is an organic photoconductor. In the developing step, a toner containing inorganic particles having an average particle diameter of 0.1 to 5 μm is used, and the developing area is composed of an electrostatic latent image holding member and a toner carrier facing the electrostatic latent image holding member. ,
Between the electrostatic latent image holder and the toner carrier, a voltage for pulling the toner back from the electrostatic latent image carrier to the toner carrier and a voltage for causing the toner to fly to the electrostatic latent image carrier are carried on the toner carrier. After the toner is applied at least once for ₁ hour to the body, the toner is ejected to the image portion and the voltage to pull back the toner to the non-image portion is applied to the toner carrier.
_{It is} applied for ₂ hours, and the ratio of the T ₁ and T ₂ hours is T ₂ / T ₁
Is 0.1 or more.

In the present invention, in the charging step, a charging device for contacting with a charging member to perform charging is used as a temporary charging device. Examples of the contact charging method that can be used in the present invention include a method using a charging member such as a roller, a blade, or a brush. Among these, the method using a roller is particularly preferable. FIG. 1 shows an example of an image forming apparatus to which the image forming method of the present invention is applied. In the image forming apparatus of FIG. 1, the surface of the electrostatic latent image carrier (hereinafter, referred to as a photoconductor) 1 is charged by the charging roller 7. The basic configuration of the charging roller 7 is composed of a central cored bar 7A and a conductive elastic layer 7B forming the periphery thereof. As shown in FIG. 1, since the charging roller 7 is pressed against the surface of the photoconductor 1 with a pressing force, the charging roller 7 is driven to rotate as the photoconductor 1 rotates. When a bias is externally applied to such a charging roller 7, the surface of the photoconductor 1 is first charged to a predetermined polarity and potential. Then, an electrostatic latent image is formed on the photoconductor 1 by image exposure 8, and the electrostatic latent image is sequentially visualized as a toner image by developing means such as the developing device 2.

When the charging roller 7 as shown in FIG. 1 is used, preferable process conditions are as follows.
The contact pressure of the photosensitive drum 1 with the photosensitive member 1 of 4.9 to 490 N / m (5 to
500 g / cm), and when a bias in which a DC voltage is superimposed with an AC voltage is used, the AC voltage =
It is preferable that 0.5 to 5 kV _pp , AC frequency = 50 to 5 kHz, and DC voltage = ± 0.2 to ± 1.5 kV. The contact pressure is calculated by the following formula. (Contact pressure) [N / m] = (Force applied to transfer member) [N] ÷ (Abutting length) [m]

A releasable coating may be provided on the surface of the above charging roller 7 used in the present invention in order to prevent fusion of toner. As the release film, nylon resin, PVDF (polyvinylidene fluoride), PVDC
It is possible to apply materials such as (polyvinylidene chloride). As described above, the charging roller 7 includes, for example, the core metal 7A at the center and the conductive elastic layer 7B forming the outer periphery, and the conductive elastic layer 7B is made of urethane in which a conductive material such as carbon is dispersed. Resistance value of ethylene-propylene-diene terpolymer (EPDM) etc. 10 ⁶ to 1
It is made of an elastic material of about 0 ¹⁰ Ω · cm. Of course, the contact charging method that can be used in the present invention is not limited to this.

In the present invention, an organic photoconductor is used as the photoconductor 1 (electrostatic latent image carrier) against which the charging roller 7 is pressed. The organic photoreceptor may be a so-called single-layer type photoreceptor in which the photosensitive layer contains a charge generating substance and a substance having a charge transporting property in the same layer, and also has a function having a charge transporting layer and a charge generating layer respectively. It may be a separate type photoreceptor. A function-separated laminated photoreceptor having a structure in which a charge generation layer and then a charge transport layer are laminated in this order on a conductive substrate is one of the preferable examples of the photoreceptor used in the present invention. The aspect of the laminated type photoreceptor 1 used in the present invention will be described below. First, as the conductive substrate, metal such as aluminum or stainless steel, plastic having a coating layer of aluminum alloy or indium oxide-tin oxide alloy, paper or plastic impregnated with conductive particles, plastic having conductive polymer, etc. Cylindrical cylinders and films made of the above materials are preferably used.

On these conductive substrates, the adhesion of the photosensitive layer is improved, the coatability is improved, the substrate is protected, the defects on the substrate are covered, the charge injection from the substrate is improved, and the electrical damage of the photosensitive layer is prevented. An undercoat layer may be provided for the purpose of protection and the like. This undercoat layer is formed of, for example, polyvinyl alcohol, poly-
N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose,
It is formed of a material such as ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymerized nylon, glue, gelatin, polyurethane, aluminum oxide. The film thickness is usually 0.1 to 10 μm, preferably 0.1 to 3 μm.

The charge generation layer formed on such a conductive substrate includes azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, Triphenylmethane dye: A charge generating substance such as an inorganic substance such as selenium or amorphous silicon is dispersed in an appropriate binder and coated, or formed by vapor deposition or the like. The binder used at this time can be appropriately selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol Resin, silicone resin, epoxy resin,
Examples thereof include vinyl acetate resin. The amount of the binder contained in the charge generation layer is appropriately selected within the range of 0 to 80% by mass, preferably 0 to 40% by mass. The thickness of such a charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.

The charge transport layer laminated on the charge generation layer as described above has a function of receiving charge carriers from the charge generation layer and transporting them in the presence of an electric field. The charge transport layer having such a function is formed by dissolving a charge transport substance together with a binder resin in a solvent, if necessary, and applying the solution on the charge generation layer. The film thickness is 5-40μ
m, preferably about 10 to 30 μm. As the charge transport material used in this case, polycyclic aromatic compounds having a structure such as biphenylene, anthracene, pyrene, phenanthrene in the main chain or side chain; nitrogen-containing ring such as indole, carbazole, oxadiazole, pyrazoline Formula compounds; hydrazone compounds; styryl compounds and the like. As the binder resin in which these charge transporting substances are dispersed, resins such as polycarbonate resin, polyester resin, polymethacrylate polystyrene resin, acrylic resin and polyamide resin; organic light such as poly-N-vinylcarbazole and polyvinylanthracene Conductive polymers and the like are mentioned. Among these binder resins,
Polycarbonate resin, polyester resin, and acrylic resin are preferable. That is, In the case of the image forming method of the present invention,
The use of these materials is particularly preferable because they have good cleaning properties, and cleaning defects, toner fusion to the photoreceptor, and filming of external additives do not easily occur. The amount of the binder resin in the charge transport layer is preferably 40 to 70% by mass.

On the photoreceptor 1 having the above structure,
The exposure 8 forms an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 2. At that time, a bias is applied between the developing sleeve 9 (toner carrying member) and the photoconductor 1 (electrostatic latent image holding member) to cause the toner to fly onto the photoconductor to visualize the electrostatic latent image. . In the present invention, in the developing step, a voltage for pulling the toner back from the electrostatic charge latent image carrier to the toner carrier and a electrostatic latent image from the toner carrier as a bias between the electrostatic latent image carrier and the toner carrier. After the voltage for causing the holding body to fly is applied to the toner carrier at least once for T ₁ time, the toner is caused to fly to the image area and the toner is pulled back to the non-image area. Is applied for T ₂ hours. On this occasion,
T ₂ / T ₁ is, to like a 0.1 or more. In the present invention, by using the special bias as described above, even though the toner containing the inorganic particles is used, the electrostatic latent image holding member (organic photoreceptor) as described above is obtained. Toner fusion is effectively prevented. The reason for this is
As I mentioned earlier, I think it is as follows.

Usually, the toner is transferred from the toner carrier 9 to the electrostatic latent image carrier by the force of the external developing electric field applied to the developing area composed of the electrostatic latent image carrier 1 and the toner carrier 9 facing it. It flies toward a certain photoconductor 1 and collides with the surface of the photoconductor 1. At this time, an impact is applied from the toner to the surface of the photoconductor, and in some cases, the surface of the photoconductor is scratched. Since the toner used in the present invention contains inorganic particles having a relatively large particle size and a relatively high hardness, the surface of the organic photoreceptor having a relatively low hardness used in the present invention is It is easily scratched. Toner is easily embedded in the scratches by the charging roller 7 that is in contact with the photoconductor 1, and toner fusion on the photoconductor surface is likely to occur.

The impact force of the toner on the surface of the photosensitive member depends on the magnitude of the developing electric field applied to the developing area, which is the magnitude of the voltage (peak to peak) of the AC component of the bias applied from the outside to the toner carrier. Almost depends on the size. However, in order to obtain a sufficient image density, it is necessary to set the value of the voltage of this AC component to a certain level, and even if it is to prevent toner fusion on the surface of the photoconductor, Can not be made smaller. On the other hand, when a discontinuous AC component of the developing electric field used in the present invention as shown in FIG.
Compared to the case of applying a continuous AC component as shown in,
Since the number of times the toner collides with the surface of the photoconductor is small, and the time during which the toner is pressed against the surface of the photoconductor by the strong electric field is short, the occurrence of scratches on the surface of the photoconductor due to the collision of toner can be prevented. As a result, it is considered that the fusion of the toner on the surface of the photoconductor can be prevented.

In the present invention, as shown in FIG. 2, a voltage for returning the toner from the electrostatic latent image holder to the toner carrier and the toner carrier between the electrostatic latent image carrier and the toner carrier. After the voltage for causing the electrostatic latent image holding member to fly from the body is applied to the toner carrier at least once for T ₁ hour, the toner is made to fly to the image portion and the toner is pulled back to the non-image portion. A voltage is applied to the toner carrier for T ₂ hours, at which time the ratio of T ₁ hours to T ₂ hours is 0.
It may be set such that 1 ≦ T ₂ / T ₁ , but more preferably 0.2 ≦ T ₂ / T ₁ ≦ 10, further preferably 0.3 ≦ T ₂
/ T ₁ ≦ 6. If the value of T ₂ / T ₁ is smaller than 0.1, there is no effect of preventing toner fusion to the photosensitive member, and T
_If the value of ₂ / T ₁ is larger than 10, the reproducibility of isolated dots tends to be poor, which is not preferable.

The magnitude of the electric field of the AC component (V _pp / SD) superimposed in the developing area is 4.0 × 10 ⁶ ≦
V _pp /SD≦8.00×10 ⁶ (V / m), and further 5.
The present invention is particularly effective in the range of 0 × 10 ⁶ ≦ V _pp /SD≦8.00×10 ⁶ (V / m). Here, V _pp is the value of the peak-to-peak voltage of the bias applied to the gap between the electrostatic latent image holder and the toner carrier, and SD is the gap between the electrostatic latent image carrier and the toner carrier. . In the case of 4.0 × 10 ⁶ > V _pp / SD, sufficient image density cannot be obtained, and 8.00 × 10 ⁶ <V _pp / SD.
In that case, leakage of the photosensitive member occurs, which is not preferable. Further, the frequency (f) of the discontinuous AC component superimposed on the DC component as the developing electric field used in the present invention as described above is in the range of 100 ≦ f ≦ 3,000 (Hz). Is preferred. In addition, T ₁ that actually applies the voltage
The time is preferably 0.15 to 2.5 msec.

The toner image developed as described above is
In the transfer step, it is transferred to a transfer target material (not shown) by a transfer charger. In the present invention, the transfer roller 4 is used as the transfer charger. The transfer roller 4 has a basic core metal 4A and a conductive elastic layer 4B that forms the outer periphery thereof. As shown in FIG. 1, the transfer roller 4 is pressed against the surface of the photoconductor 1 with a pressing force, and is rotated at a constant speed or a peripheral speed different from the peripheral speed of the photoconductor 1. The material to be transferred is conveyed between the photoconductor 1 and the transfer roller 4, and at the same time, a bias having a polarity opposite to that of the toner is applied from the transfer bias current 10 to the transfer roller 4, so that the toner image on the photoconductor 1 is covered. It is transferred to the surface side of the transfer material. As the material of the transfer roller 4 that can be used in the present invention, the same material as the charging roller 7 described above can also be used. Further, the preferable transfer process condition is that the contact pressure of the roller is 4.9 to 490 N / m.
(5 to 500 g / cm), DC voltage ± 0.2 to ± 1
It is 0 kV. The transfer roller 4 is composed of a core metal and a conductive elastic layer, and the conductive elastic layer has a volume resistance 10 such as urethane and ethylene-propylene-diene terpolymer (EPDM) in which a conductive material such as carbon is dispersed. ^{6 ~10 10 Ω} · c
It is made of elastic material of about m.

Next, the toner used in the image forming method of the present invention will be described. The toner used in the present invention contains inorganic particles having an average particle diameter of 0.1 to 5 μm. If the average particle size is less than 0.1 μm, the effect of uniform charging cannot be obtained, and if it is larger than 5 μm, the photoreceptor is significantly damaged, which is not preferable. Specific examples of the inorganic particles used in the present invention include metal oxides such as magnesium, zinc, aluminum, cerium, cobalt, iron, zirconium, chromium, manganese, strontium, tin and antimony; calcium titanate; Complex metal oxides such as magnesium titanate and strontium titanate; metal salts such as calcium carbonate, magnesium carbonate and aluminum carbonate; clay minerals such as kaolin; phosphoric acid compounds such as apatite; silicon compounds such as silicon carbide and silicon nitride; carbon Examples thereof include carbon powder such as black and graphite.

The type of the binder resin constituting the toner used in the present invention is, for example, polystyrene, poly-p-chlorostyrene, polyvinyltoluene, or other styrene and its substitution homopolymers; styrene- p-chlorostyrene copolymer, styrene-vinyltoluene copolymer,
Styrene-vinyl naphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether Styrene-based copolymers such as copolymers, styrene-vinyl ethyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers ; Polyvinyl chloride, phenol resin, natural resin modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, Cyclohexylene resins, polyvinyl butyral, terpene resin, coumarone-indene resins, the use of petroleum-based resin and the like can. A crosslinked styrene resin is also a preferable binder resin.

As a comonomer for the styrene monomer of the styrene copolymer, for example, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, acrylic acid-
A monocarboxylic acid having a double bond such as 2-ethylhexyl, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, and acrylamide, or a substituted form thereof. A dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; and a substituted product thereof; a vinyl ester such as vinyl chloride, vinyl acetate, vinyl benzoate, etc. Ethylenic olefins such as ethylene, propylene, butylene, etc .; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc .; for example, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc. Such vinyl ethers; vinyl monomers such as may be used alone or in combination. A compound having two or more polymerizable double bonds is mainly used as the cross-linking agent, and examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol. A carboxylic acid ester having two double bonds such as dimethacrylate and 1,3-butanediol dimethacrylate; a divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and 3 or more vinyl groups. The compound having; can be used alone or as a mixture.

As the binder resin for toner used for pressure fixing, for example, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer,
Ethylene-acrylic acid ester copolymer, higher fatty acid,
Examples thereof include polyamide resin and polyester resin. These are used alone or in combination.

Further, in the present invention, it is also preferable to include the following waxes in the toner from the viewpoint of improving the releasability from the fixing member during fixing and the fixing property. Paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, carnauba wax and its derivatives, etc., where the derivatives are oxides and block copolymers with vinyl monomers. , Including graft modified products. In addition, alcohols, fatty acids, acid amides, esters, ketones, hydrogenated castor oil and its derivatives, plant waxes, animal waxes, mineral waxes, petrolactam and the like can be used.

As the magnetic powder used in the toner used in the present invention, an alloy or compound powder containing a ferromagnetic element is preferably used. Examples thereof include alloys and compounds of iron, such as magnetite and maghemite ferrite, cobalt, nickel, manganese, zinc, and other ferromagnetic alloys, which are conventionally known as magnetic materials.

In the toner used in the present invention, a charge control agent may be blended with toner particles (internal addition) or mixed with toner particles (external addition). The charge control agent further enables optimum charge amount control according to the developing system. For controlling the toner to be negatively charged, for example, an organic metal complex and a chelate compound are effective, and a monoazo metal complex, an acetylacetone metal complex,
There are metal complexes based on aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids. Other examples include negative charge control agents such as aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol.

The following substances are used to control the positive charge. For example, modified products of nigrosine and fatty acid metal salts; tributylbenzylammonium-1
-Hydroxy-4-naphthosulfonate, quaternary ammonium salts such as tetrabutylammonium tetrafluoroborate, and onium salts such as phosphonium salts which are analogs thereof, lake pigments thereof, triphenylmethane dyes and lakes thereof Pigments, (as a laker, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid,
Ferricyanide, ferrocyanide, etc.) Metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate, dicyclohexyltin borate; These can be used alone or in combination of two or more. The charge control agent as described above is preferably used in the form of fine particles added to the toner. In this case, the number average particle diameter of these charge control agents is preferably 4 μm or less, and more preferably 3 μm or less. When these charge control agents are internally added to the toner, the amount is 0.1 to 2 with respect to 100 parts by mass of the binder resin.
The range of 0 parts by mass is preferable, and it is particularly preferable to use 0.2 to 10 parts by mass. As the coloring material which can be further added to the toner used in the present invention, conventionally known carbon black, copper-phthalocyanine, etc. can be used.

The toner used in the present invention contains, for example, fine powder of silicic acid, titanium oxide, or fine powder of inorganic material such as aluminum oxide in order to improve charge stability, developability, fluidity and storage stability. To be used. A case where, for example, silica fine powder is used as the inorganic fine powder will be described. As the silicic acid fine powder that can be used in the present invention, a so-called dry method produced by vapor phase oxidation of a silicon halide or an alkoxide or a dry silica called fumed silica,
Also, both so-called wet silica produced from water glass or silicon alkoxide can be used, but there are few silanol groups on the surface and inside the silica fine powder, and
Dry silica having less production residue such as Na ₂ O and SO ₃ ²⁻ is preferable. Further, in the case of dry silica, it is possible to obtain a composite fine powder of silica and another metal oxide by using another halogen compound such as aluminum chloride and titanium chloride together with a silicon halogen compound in the manufacturing process. , Including those. The silica fine powder used in the present invention has a specific surface area of 30 m ² / g or more by nitrogen adsorption measured by the BET method, and particularly 50 to 400 m ² / g.
It is preferable to use 0.01 to 8 parts by mass, preferably 0.1 to 5 parts by mass of fine silica powder with respect to 100 parts by mass of the toner. Further, the silica fine powder used in the present invention is, if necessary, a silicone varnish, various modified silicone varnishes, silicone oils, various modified silicone oils, for the purpose of hydrophobizing, controlling chargeability, etc.
It is also possible and preferable to be treated with a treating agent such as a silane coupling agent, a silane coupling agent having a functional group, or an organic silicon compound, or in combination with various treating agents.

A lubricant powder such as Teflon powder, zinc stearate powder and polyvinylidene fluoride powder may be used in the toner used in the present invention. The toner used in the present invention contains a binder resin, a wax, a metal salt or a metal complex, a pigment or a dye as a colorant, a magnetic substance, a charge control agent, if necessary, and other additives. After sufficiently mixing with a mixer such as, a metal compound, a pigment, a dye, and a magnetic substance are melt-kneaded with a heat kneader such as a heating roll, a kneader, or an extruder to make the resins compatible with each other. Can be obtained by dispersing or dissolving, and solidifying by cooling and then pulverizing and classifying.

[0034]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. [Example 1] 100 parts by mass of magnetic iron oxide 100 parts by mass of styrene-butyl acrylate copolymer 2 parts by mass of iron complex of monoazo dye (negative charge control agent) 3 parts by mass of low molecular weight polyolefin (release agent) Parts The above materials were mixed in a blender, melt-kneaded in a twin-screw extruder heated to 130 ° C., and the cooled kneaded material was coarsely pulverized with a hammer mill, and the coarsely pulverized material was finely pulverized with a jet mill to obtain The finely pulverized product was strictly classified by an air classifier to obtain magnetic toner particles having a weight average particle size of 7 μm. Based on the obtained magnetic toner particles, dry silica (BET specific surface area 200 m ² / g) hydrophobized with 1.2 parts by mass of silicone oil, and 1.0 part by mass of strontium titanate having an average particle size of 1.0 μm. Parts were added and mixed with a mixer to obtain a magnetic toner.

An image was formed using the obtained toner A with the configuration shown in FIG. A rubber roller (diameter 12 mmφ, contact pressure 49 N / m (50 g / cm)) in which conductive carbon coated with nylon resin is dispersed is used as the primary charging roller 7 in the configuration of FIG. 1, and a DC voltage is −700 V. , AC voltage: 2.2 kV (peak to peak) is applied, the outermost surface layer is charged on an organic cylindrical photoreceptor (OPC drum) with a diameter of 30 mmφ, which is formed of a styryl compound and a polycarbonate resin, and laser exposure is performed. Dark potential VD = -700V, bright potential VL =-
It was set to 150V. As a toner carrier, a developing sleeve was prepared in which a resin layer having the following configuration was formed on an aluminum cylinder having a diameter of 16 mm. Phenolic resin 100 parts by weight Graphite (particle size about 7 μm) 90 parts by weight Carbon black 10 parts by weight

Then, the gap between the photosensitive drum and the developing sleeve is 200 μm, the developing magnetic pole is 70 mT (700 gauss),
As a toner control member, thickness 1.0mm, free length 10mm
The urethane rubber blade of 14.7 N / m (15 g /
The contact was made with a linear pressure of (cm). Peripheral speed V of electrostatic latent image carrier
Is 96 mm / sec, and the developing bias is the bias of the waveform shown in FIG. 2 (however, the DC bias component V _dc = −500).
V, voltage for causing toner to fly from toner carrier to electrostatic latent image carrier (maximum development accelerating voltage) = -1,100 V, voltage for pulling toner back from electrostatic latent image carrier to toner carrier (maximum retract voltage) = 100V, T ₁ = 0.56m
sec, T ₂ / T ₁ = 2.0) was used. Furthermore, as a photoconductor cleaning blade, the thickness is 2.0 mm and the free length is 8 m.
24.5 N / m (25 g
/ Cm) with a linear pressure. Magnetic toner is used as the toner, and it is continuously used in an environment of 23 ° C. and 65% RH for 8,000
0 images were printed. As a result, no toner fusion occurred on the photoconductor. Further, the image density was high, and good image quality and image were obtained.

[Examples 2 to 5 and Comparative Example 1] Same as Example 1 except that the value of T ₂ / T _{1 in} the image forming apparatus used in Example 1 was changed as shown in Table 1 below. I made a picture. Table 1 shows the evaluation results. In the comparative example, the image density was low and toner fusion occurred. Further, the waveform in Comparative Example 1 when T ₂ = 0 is shown in FIG.

[Embodiments 6 to 8] The peak-to-peak voltage value (V _pp ) of the bias applied to the gap between the electrostatic latent image carrier and the toner carrier in the image forming apparatus used in Example 1.
Was imaged in the same manner as in Example 1 except that was changed as shown in Table 1. Table 1 shows the evaluation results.

[Embodiment 9 and Embodiment 10] The gap (SD) between the electrostatic latent image holder and the toner carrier in the image forming apparatus used in Embodiment 1 is changed as shown in Table 1. Images were printed in the same manner as in Example 1 except for the above. Table 2 shows the evaluation results.

[Examples 11 and 12] The inorganic particles of the developer used in Example 1 were silicon carbide (3 μm) in Example 11, and cerium oxide (2 μm) in Example 12.
Images were printed out in the same manner as in Example 1 except that each was replaced with. Table 1 shows the evaluation results.

[Example 13] 80 parts by mass of magnetic iron oxide 100 parts by mass of styrene-butyl acrylate copolymer 2 parts by mass of triphenylmethane dye (positive charge control agent) Low molecular weight polyolefin (release) Agent) 4 parts by mass The above materials are mixed in a blender, melt-kneaded in a twin-screw extruder heated to 130 ° C., and the cooled kneaded material is coarsely crushed with a hammer mill, and the coarsely pulverized material is finely crushed with a jet mill. The obtained finely pulverized product was strictly classified by an air classifier to obtain magnetic toner particles having an average particle size of 8.5 μm. Based on the obtained magnetic toner particles, dry silica (BET specific surface area 100 m ² / BET specific surface area of 100 m ² / BET) which was hydrophobized with 0.6 parts by mass of an aminosilane coupling agent and hexamethyldisilazane
g) and 1.0 part by mass of strontium titanate having an average particle size of 1.0 μm were added and mixed in a mixer to obtain a magnetic toner used in this example.

In the configuration of FIG. 1, a rubber roller (diameter 12 mm, contact pressure 50 N / m (5
0 g / cm)), and a DC voltage of -700 V and an AC voltage of 2.2 kV (peak to peak) are applied,
An organic cylindrical photosensitive member (OPC drum) having a surface layer with a diameter of 30 mmφ is charged with polycarbonate, and a halogen lamp causes a dark potential VD = -700 V and a bright potential VL =-.
It was set to 150V. As a toner carrier, an aluminum cylindrical developing sleeve having an outer diameter of 16 mmφ whose surface was roughened by blasting with Alundum # 400 was prepared.

Then, the gap between the photosensitive drum and the developing sleeve is set to 200 μm, the developing magnetic pole is 70 mT (700 gauss), the thickness of the toner regulating member is 1.0 mm, and the free length is 1.
A 0 mm urethane blade made of 9.8 N / m (1.
The contact was made at a linear pressure of 0 kg / m). The peripheral speed V of the electrostatic latent image carrier is 96 mm / sec, the ratio Vt / V of the peripheral speed Vt of the toner carrier to the peripheral speed V of the electrostatic latent image carrier is 1.5,
As the developing bias, the bias having the waveform shown in FIG. 2 (however, DC bias component V _dc = −200 V, voltage for causing toner to fly from the toner carrier to the electrostatic charge latent image carrier (maximum development accelerating voltage) = + 400 V, toner being electrostatic charge) Voltage (maximum pullback voltage) V = − for pulling back from the latent image carrier to the toner carrier
800 V, T ₁ = 0.56 msec, T ₂ / T ₁ = 2.
0) was used. Further, as a photosensitive member cleaning blade, a urethane rubber blade having a thickness of 2.0 mm and a free length of 8 mm was brought into contact with the linear pressure of 24.5 N / m (25 g / cm). Magnetic toner is used as toner, 23 ° C 65%
8,000 sheets were continuously printed under the RH environment. As a result, no fusion occurred on the photoreceptor. In addition, the image density was high and an image of good quality was obtained. Table 1 shows the evaluation results.

[Comparative Example 2] Image formation was performed in the same manner as in Example 13 except that T ₂ / T ₁ in the image forming apparatus used in Example 13 was changed to 0. The evaluation results are shown in Table 1. The toner adhesion was remarkable and the image density was low. T
The waveform when ₂ = 0 is shown in FIG.

[Evaluation Method and Evaluation Criteria] 1. After continuous image formation of 8,000 sheets of toner fused , the photoreceptor was visually observed and evaluated according to the following criteria. ◯ is not generated at all on the photoconductor. ◯ Δ is slightly generated on the photoconductor, but is not generated on the image. In the case of x, fusion is clearly visible on the image. 2. Image density Image density was evaluated using a solid black image. The image density was measured with a reflection densitometer.

Table 1 * SD = Gap between photosensitive drum and developing sleeve * V _pp / SD: × 10 ⁶ (V / m)

[0047]

As described above, according to the present invention,
Provided is an image forming method having a contact charging step, in which toner fusion does not occur or hardly occurs on a photoreceptor. Further, according to the present invention, a high image density and a good image are provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an image forming method of the present invention.

FIG. 2 is a waveform of a developing bias according to the first exemplary embodiment.

FIG. 3 is a waveform of a developing bias in Comparative Example 1.

[Explanation of symbols]

 1: Photoconductor 2: Developing device 4: Transfer roller 6: Photoconductor cleaning blade 7: Charging roller 8: Exposure 9: Development sleeve 10: Transfer bias current

Claims (4)

[Claims] 1. A charging step of charging an electrostatic charge latent image carrier by bringing a charging member to which a voltage is applied from outside into contact with the electrostatic latent image carrier, and a step of forming an electrostatic latent image on the charged electrostatic latent image carrier. And a developing step of developing the electrostatic latent image formed on the electrostatic latent image holding member with a toner layer arranged on a toner carrier to form a toner image, and the electrostatic latent image holding member on the electrostatic latent image holding member. A toner containing at least an inorganic particle having an average particle size of 0.1 to 5 μm, the image forming method comprising: , An electrostatic latent image holding member made of an organic photoconductor is used, and in the developing step, the electrostatic latent image holding member is formed in a developing region made up of the electrostatic latent image holding member and a toner carrying member facing the electrostatic latent image holding member. Between the toner carrier and the toner carrier, A voltage pull back the toner carrying member from the holding member, and a voltage to the toner carrying member to fly from the toner carrying member to the electrostatic latent image bearing member, T ₁ hour at least
After applying it twice, the toner is ejected to the image area,
Applying T ₂ hours a voltage of returning the toner to the toner carrying member to the non-image area, and the ratio T ₂ of the with the time T ₁ and T ₂ hours
An image forming method characterized in that / T ₁ is 0.1 or more. 2. The image forming according to claim ₁ , wherein the value of the ratio T ₂ / T ₁ of the time T _{1 to the} time T ₂ is 0.2 to 10, more preferably 0.3 to 6.0. Method. 3. A voltage applied between the electrostatic latent image carrier and the toner carrier in the developing step to pull back the toner from the electrostatic latent image carrier to the toner carrier and the electrostatic latent image carrier from the toner carrier. The difference (V _pp ) from the voltage to fly the body,
The value (V _pp / SD) divided by the gap (SD) between the electrostatic latent image carrier and the toner carrier is 4.0 to 8.0 × 10 ⁶ (V
/ M) is the image forming method according to claim 1. 4. The thickness of the toner layer disposed on the toner carrier is smaller than the gap between the electrostatic latent image carrier and the toner carrier, according to any one of claims 1 to 3. Image forming method.