JP2568244B2 - Image forming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming method using a one-component developer containing negatively chargeable toner and positively chargeable resin particles, and more specifically, on an electrostatic image carrier. And an image forming method including a step of satisfactorily transferring the toner image to a transfer material.

[Background technology]

Conventionally, in an electrophotographic apparatus, a normal developing method for developing a non-exposed portion is generally used. In this method, since the reflected light from the document is optically processed and then projected on a photoreceptor, development is performed on a non-exposed portion (character portion of the document) having no reflected light.

Recently, the electrophotographic system has been used for a printer or the like used for the output of a computer, in addition to obtaining a copy image. In the case of a printer, a light emitter (such as a semiconductor laser) is turned on and off according to an image signal, and the light is projected on a photoreceptor.
At this time, the printing rate (the ratio of the printing area per page) is usually 30% or less, and the method of exposing the character portion (reversal development) is superior in terms of the life of the light emitter.

Further, the reversal development is used for an apparatus (for example, a microfilm output apparatus) that outputs a positive image and a negative image from the same original, and further, the normal development is performed in order to develop two or more colors in the same apparatus. And, it has come to be used in an apparatus or the like in which reversal development is combined.

However, the reversal development has the following problems.
The transfer electric field in normal development (hereinafter referred to as positive development) has the same polarity as that of primary charging, and even if the transfer electric field is applied to the photoconductor after passing through the image carrier (hereinafter referred to as paper), the effect thereof is erase exposure ( It is erased at (6) in FIG.

On the other hand, the transfer electric field in the reversal development has a polarity opposite to that of the primary charge, and even after passing through the paper or the like, when the transfer electric field is applied, the charge of the opposite polarity occurs on the photoconductor, and the image cannot be erased by the erase exposure, resulting in a dark and light image. Appears. This is a development called "paper mark".

As measures against paper marks, there are means such as lowering the transfer current after the paper or the like has passed, as seen in JP-A-60-256173, but this method requires various parts (microswitches, etc.). This is necessary, and the cost of the device increases as the device becomes complicated. Further, a means of lowering the transfer electric field to make it a range where charging of the opposite polarity does not occur on the photoconductor is conceivable. However, in this method, since the transfer efficiency is lowered, image quality is deteriorated due to poor transfer. Another side effect of the reversal development method is that the photoconductor and the paper are charged with opposite polarities, so that the photoconductor and the paper are electrostatically adsorbed when charged by a strong electric field, It does not separate even after the transfer process is completed, and paper or the like enters and causes a paper jam or the like until the next process (cleaning process, etc.). This is a development called "wrapping". As a measure against wrapping, there is a means for preventing the photoreceptor and the paper from adhering to each other, as disclosed in JP-A-56-60470. However, this method is not always effective in reversal development. That is, it is considered that this is because adhesion at the time of separation in the transfer step of reversal development is stronger than that in the normal development system. As another method, as can be seen in U.S. Pat. No. 3,357,400, there is a device provided with a separation charging or belt separation as an auxiliary means for separation. As a result, although it is effective for the winding development, it is not effective for the paper trace phenomenon. This is because the separation charge is smaller than the transfer charge and does not affect the potential on the photoconductor.

As another means, there is a means for lowering the electrostatic field by lowering the transfer electric field, but this method is apt to cause image quality deterioration due to transfer failure as described above. In addition, when the transfer electric field is lowered, the transfer efficiency is lowered, and postcards and OH
I cannot answer to various needs such as P film. Also, if the transfer electric field is lowered,
In the area where the developer is likely to concentrate (edge development area), "difference in transfer", which is part of transfer failure, occurs. It is considered that this is because the amount of the developer in the edge developing portion is larger than that in the normal portion, the developer agglomeration is likely to occur, and the response to the transfer electric field is lowered. Therefore, a high-quality image faithful to the latent image can be obtained. Has a problem that it becomes difficult.

[Object of the Invention]

An object of the present invention is to provide an image forming method which solves the above-mentioned problems.

An object of the present invention is to provide a transfer step capable of obtaining a high-quality image faithful to a latent image in an image forming method requiring transfer by a low transfer electric field, such as a reversal developing method, regardless of conditions of a transfer carrier. An object is to provide an image forming method.

An object of the present invention is to provide an image forming method in which there is no phenomenon such as "paper mark", "wrapping", "transfer no void", or the phenomenon is suppressed.

An object of the present invention is to provide an image forming method using a developer that gives a high quality image without fog even when a thick transfer paper is used.

Further, an object of the present invention is an image forming method using a negatively chargeable magnetic one-component developer that is stable against environmental changes such as high temperature and high humidity and low temperature and low humidity and can always exhibit good characteristics. To provide.

A further object of the present invention is to provide an image forming method using a negatively chargeable magnetic one-component developer suitable for developing a digital latent image used in a digital copying machine, a laser beam printer and the like.

An object of the present invention is to provide an image forming method which does not cause hollow image development even under a low transfer electric field as in a reversal developing device and has good durability.

[Outline of Invention]

The present invention provides an image forming method of developing an electrostatic charge image on an electrostatic image carrier with a one-component developer, and electrostatically transferring a toner image formed on the electrostatic image carrier onto a transfer material. i) 100 parts by weight of negatively chargeable toner, (ii) average particle size of 0.1 to 1.0 μ
0.1 to 3.0 parts by weight of resin particles having m and having tribocharge characteristics of +50 to +600 μc / g, and (iii) a hydrophobicity of 90
% Or more, and the tribocharge characteristics are −100 to −300 μc / g
Containing at least 0.01 to 3 parts by weight of silica fine powder treated with a silane coupling agent, silicone oil, or both, and the mixing ratio of the silica fine powder and the resin particles is 1: 0.1 to 1: 100. Using a certain one-component developer, transfer the toner image on the electrostatic image carrier under the condition that the ratio (V _tr / V _pr ) of the primary charging electric field V _pr and the transfer charging electric field V _tr is negative. The present invention relates to an image forming method characterized by performing electrostatic transfer to an image.

[Specific Description of the Invention]

The present inventors have found that by adding resin fine particles having a positive charging property to a one-component developer, a satisfactory result can be obtained in the transfer step in reversal development.

The positively chargeable resin fine particles added to the developer used in the image forming method of the present invention have an average particle size of 0.1 to 1 μm and a triboelectric charge amount of +50 μc / g to +600 μc / g, preferably +100 μc / g. To +600 μc / g is used. The resin particles are fixed on the surface of the toner particles in the developer by electrostatic force, and voids are formed between the toner particles and between the toner particles and the surface of the photoconductor to reduce the adhesive force, thereby improving the electrostatic transfer. It is thought that it can be done.

If the average particle size is smaller than 0.1 μm, the transfer efficiency is not improved, while if it is larger than 1 μm, it is not stably fixed on the surface of the toner particles, so that the density is lowered and black spots, fog, etc. are developed. The above problem occurs. Further, if the charge amount is lower than +50 μc / g, the toner is not stably fixed on the surface of the toner particles, and the above-mentioned development problems occur. On the other hand, if the charge amount is higher than +600 μc / g, the toner particle surface is electrostatically charged. However, since the chargeability is high, there are problems in development such as thin lines.

The addition amount of the positively chargeable resin particles is preferably 0.1 to 3.0 parts by weight, more preferably 0.2 to 1.0 part by weight, based on 100 parts by weight of the toner.
If the amount is less than 0.1 part by weight, the effect of addition is not obtained and the transfer efficiency is not improved. If the amount is more than 3.0 parts by weight, excessive resin particles are present in the developer, which causes a problem in development. The charge amount of the resin particles is measured as follows. Carrier fine iron powder not covered with resin (for example, EFV200 manufactured by Nippon Iron & Powder Co., Ltd.) having resin fine particles 0.2g and main particle size of 200 to 300 mesh left to stand overnight in an environment of 25 ° C, 50 to 60% RH / 300) 99.8g and put in an aluminum pot having a volume of about 200c.c. in the above environment, and after mixing for 60 minutes, using an aluminum cell having a 400 mesh screen, 0.5kg / cm ^At the blow pressure of ² , the charge amount of the resin fine particles is measured by the blow-off method. The average particle size of the resin particles is measured with a Coulter Counter N4 (manufactured by Nikkaki Co., Ltd.) in a state of being ultrasonically dispersed in a solvent. In addition, a virtually monodisperse product obtained by a polymerization method or the like may be measured by a scanning electron microscope photograph (SEM image).

The resin particles used in the present invention are characterized in that they behave together with the developer, and the behavior thereof together is characterized in that the attraction force between the developer and the photoconductor is adjusted. This is completely different from the method disclosed in JP-A-56-60470, in which particles are positively placed on a non-image to lower the attraction between the transfer material and the photoconductor.

According to the method of Japanese Patent Laid-Open No. 56-60470, the winding phenomenon can be improved without lowering the transfer electric field, but it is not effective against the paper trace phenomenon and the transfer rate is improved under a low transfer electric field. It has no effect.

The transfer process used in the present invention includes a corona discharge charger,
An electrostatic transfer method using an electric field generated by a contact roller charger or the like may be used. The transfer conditions are measured as follows. Referring to FIG. 1 of the accompanying drawings, a description will be given of a cleaning device 8, a developing device 9, a transfer charging device 3 from an image forming device.
The photosensitive member (photosensitive drum) 1 serving as an electrostatic image holding member is charged by the primary charger 2. After the leakage light is shielded substantially completely and one round of the photoconductor 1 is charged, the surface potential of the photoconductor is measured by a surface electrometer. The value of the surface potential at this time is V _pr [V]. Next, the surface of the photoconductor is wiped with a cloth impregnated with alcohol to remove the charge on the surface of the photoconductor, and then the primary charger 2 is removed and the transfer charger 3 is attached to charge one round of the photoconductor 1. After that, the surface potential of the photoconductor is measured. The value of the surface potential at this time is V
_tr [V]. In the present invention, the value of V _tr / V _pr is negative, preferably the absolute value of V _tr / V _pr Is preferably 0.5 to 1.6. When the absolute value is less than 0.5, the transfer electric field is too low and image deterioration is likely to occur during transfer. On the other hand, when the absolute value is more than 1.6, the transfer electric field is too strong and the photoreceptor is easily charged positively. , The paper trace phenomenon and the winding phenomenon are likely to occur. The absolute value The more preferable range of is 0.9 to 1.4.

INDUSTRIAL APPLICABILITY The present invention is effective for an image forming method (apparatus) using an organic photoconductor (hereinafter referred to as OPC photoconductor), and the OPC photoconductor is composed of a multilayered OPC including at least a charge generation layer and a charge transport layer. It is particularly effective for the image forming method of the reversal development method using the. In the OPC photoreceptor, when the photosensitive layer is charged in the opposite polarity, the movement of the charge is slow, and particularly in the laminated OPC, this tendency becomes remarkable, and the paper trace is likely to occur, so that the present invention exhibits a particularly advantageous effect. To do.

The value of V _pr used in the present invention is −300 to −1,000.
[V] is preferable, and -500 to -900 [V] is particularly preferable. If it is less than −300 [V], it is difficult to secure a potential difference during development, and the image tends to become unclear.
If it exceeds 000 [V], dielectric breakdown of the photosensitive layer due to the electric field occurs, and image quality deterioration such as black spots easily occurs. From the viewpoint of durability and the like, -500 to -900 [V] is particularly preferable.

In the image forming method of the present invention, the transfer material is separated from the photoconductor by the elastic force of the transfer material (paper or the like), the curvature of the photoconductor, and the static elimination means such as the static elimination brush without using a mechanical separating means.
It is particularly effective for an image forming method (apparatus). The separation state in an apparatus having no mechanical separation mechanism depends on the transfer conditions, and winding is likely to occur, so that the present invention is particularly effective.

The present invention is particularly effective for an image forming method (apparatus) in which the diameter of the photoconductor 1 (“φ” in FIG. 1 is 50 mm or less is used. In an apparatus in which a photoconductor drum of φ50 mm or less is used. For the purpose of downsizing, it is necessary to reduce the number of parts, and the separating step is usually constituted by the separating and static eliminating brush 7 and the like only by the elastic force of the paper (see FIG. 2). In the static elimination step, static electricity is erased only from paper and the like, and usually does not act on the surface potential of the photoconductor.

The image forming process will be described with reference to FIG. The surface of the photoconductor is negatively charged by the primary charger 2, a latent image is formed by image scanning by exposure 5 with a light source or laser light, and a developing sleeve 4 including a magnetic blade 11 and a magnet is provided. In the container 9, the latent image is reversely developed with the one-component magnetic developer 13. In the developing section, a bias is applied between the photosensitive drum 1 and the developing sleeve 4 by the bias applying means. When the transfer paper P is conveyed and reaches the transfer portion, the transfer charger 3 charges the positive polarity from the back surface (the surface opposite to the photosensitive drum side) of the transfer paper P to form a negatively charged toner image on the photosensitive drum surface. Is transfer paper P
Electrostatically transferred to the top. Immediately after passing through the transfer charger 3, the charge removing brush 10 removes charges on the back surface of the transfer paper, and separates the transfer paper P from the photosensitive drum 1 by curvature separation. On the transfer paper P separated from the photosensitive drum 1 by the curvature separation, the toner image on the transfer paper P is fixed by the heating and pressure roller fixing device 7.

The one-component developer remaining on the photosensitive drum after the transfer process is removed by the cleaning device 8 having a cleaning blade. The photosensitive drum 1 after cleaning is erased by erase exposure 6 and the process starting from the charging process by the primary charger 2 is repeated again. Next, the negatively chargeable toner used in the present invention will be described.

In the present invention, as the binder resin of the toner, for example,
A homopolymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, and the like, or a substitution product thereof.
Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-
Methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate Copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer Polymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Styrene-based copolymers such as isoprene copolymer and styrene-acrylonitrile-indene copolymer; polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, silicone resin, polyester, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene Resins, phenol resins, xylene resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes, etc. may be used alone or in combination.

In the present invention, among these resins, a styrene-acrylic copolymer is preferably used, and a styrene-n-butyl acrylate (St-nBA) copolymer and a styrene-n-butyl methacrylate (St) are particularly preferred. -NBMA) copolymer, styrene-n-butyl acrylate-2-ethylhexyl methacrylate (St-nBA-2EHMA) copolymer and the like are preferably used.

As the coloring material that can be added to the toner according to the present invention, conventionally known carbon black, copper phthalocyanine, iron black and the like can be used.

As the magnetic fine particles contained in the magnetic toner according to the present invention, a substance that is magnetized when placed in a magnetic field is used.
Powders of ferromagnetic metals such as iron, cobalt and nickel, or alloys and compounds such as magnetite, γ-Fe ₂ O ₃ and ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area by the nitrogen adsorption method of ^{2 to 20} m ² / g, particularly 2.5 to 12 m ² / g, and a magnetic powder having a Mohs hardness of 5 to 7 is preferable. The content of the magnetic powder is preferably 10 to 70% by weight with respect to the amount of toner.

Further, the toner of the present invention may optionally contain a charge control agent, and a negative charge control agent such as a metal complex salt of a monoazo dye; a metal complex salt of salicylic acid, alkylsalicylic acid, cyalkylsalicylic acid or naphthoic acid is used. To be

Further, the magnetic toner according to the present invention has a volume resistivity of 10
It is preferably at least ¹⁰ Ω · cm, particularly preferably at least 10 ¹² Ω · cm, in view of triboelectric charge and electrostatic transferability. The volume resistivity here means that the toner is molded at a pressure of 100 kg / cm ² and
It is defined as a value converted from the current value one minute after the application of an electric field of V / cm.

The triboelectric charge amount of the negatively chargeable magnetic toner used in the present invention must be -8 μc / g to -20 μc / g. -8
When it is less than μc / g, the image density tends to be low, and the effect is particularly remarkable under high humidity. On the other hand, if it exceeds −20 μc / g, the toner charge is too high and the line image and the like are fine, and the image becomes poor especially under low humidity.

The negatively chargeable toner particles of the present invention are at 25 ° C. and 50 to 60% RH.
10g of toner particles left overnight in the environment of 200 to 300 mesh and 90g of carrier iron powder not covered with resin (for example, EFV200 / 300 manufactured by Nippon Iron Powder Co., Ltd.) Mix well in an aluminum pot with a volume of about 200 c.c. (hold by hand and shake about 50 times up and down) and use a standard blow-off using an aluminum cell with a 400 mesh screen. The triboelectric charge amount of the toner particles is measured by the method. By this method, toner particles whose measured triboelectric charge becomes negative are regarded as negatively charged toner particles.

The volume average particle diameter of the toner particles is 5 to 30 μm, preferably 7 to 15 μm. The content of 4 μm or less in the number distribution is 2% to 20%, preferably 2 to 18%.

A Coulter Counter TA-II type (manufactured by Coulter) is used as a device for measuring the particle size of the toner, and an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) that output a number average distribution and a volume average distribution. Connect the electrolyte, and use 1st grade sodium chloride as the electrolyte.
% NaCl aqueous solution is prepared. As the measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate as a dispersant is added to 100 to 150 ml of the electrolytic aqueous solution, and 0.5 to 50 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the particle size distribution of particles of 2 to 40μ is measured by the Coulter Counter TA II type using a 100μ aperture as an aperture. To obtain the volume average distribution and number average distribution.

The toner according to the present invention is generally manufactured as follows.

The binder resin and optionally the magnetic substance, dyes and pigments as colorants, etc. are uniformly dispersed by a mixer such as a Henschel mixer.

The dispersion obtained as described above is melt-kneaded with a kneader, extruder, roll mill or the like.

The kneaded product is roughly pulverized by a cutter mill, a hammer mill or the like and then finely pulverized by a jet mill or the like.

The finely pulverized material is classified using a zigzag classifier or the like, and the particles are classified to obtain a toner.

In addition, as a method for producing the toner, a polymerization method, a capsule method, or the like can be used. The outline of these production methods is described below.

(Polymerization Toner) A polymerizable monomer, and if necessary, a polymerization initiator, a colorant, and the like are granulated in an aqueous dispersion medium.

The granulated monomer composition particles are classified into an appropriate particle size.

The monomer composition particles having a specified internal particle diameter obtained by the classification are polymerized.

After the dispersant is removed by an appropriate treatment, the polymerization product obtained above is filtered, washed with water and dried to obtain a toner.

(Capsule Toner) Resin and, if necessary, magnetic powder and the like are kneaded with a kneader or the like to obtain a toner core material in a molten state.

The toner core is placed in water and stirred vigorously to produce a fine particle core.

The core fine particles are placed in a shell material solution, and a poor solvent is dropped while stirring, and the core material is encapsulated by covering the surface of the core material with the shell material.

The resulting capsule is filtered and dried to obtain a toner.

Next, a method for producing resin particles having an average particle diameter of 0.1 to 1.0 μm will be described. The insulating resin used for the resin particles in the present invention may be the same as the binder resin used for the toner described above, and may be a spray dry method, a suspension polymerization method, an emulsion polymerization method, a soap-free polymerization method, a seed polymerization method, or a machine. A method capable of producing spherical fine particles such as a pulverization method can be used. Among them, the soap-free polymerization method is particularly suitable because it has no residual emulsifier and thus has advantages such as obtaining a polymer having a narrow particle size distribution without inhibiting the charging property of the toner. However, it is not particularly limited.

The resin particles used in the present invention include methyl methacrylate, dimethylaminoethyl methacrylate,
Diethylaminoethyl methacrylate, N-methyl-N-
It is preferable to use a resin synthesized from a composition containing a monomer such as phenylaminoethyl methacrylate, diethylaminoethyl methacrylamide, dimethylaminoethyl methacrylamide, 4-vinylpyridine or 2-vinylpyridine.

It is essential that the resin particles are charged with the opposite polarity to the toner particles, and may be subjected to particle surface treatment if necessary. As the surface treatment method, a metal such as iron, nickel, cobalt, copper, zinc, gold, silver or the like is subjected to surface treatment by a vapor deposition method or a plating method, or a metal oxide such as the above metal, magnetic material or conductive zinc oxide. A method of fixing an object or the like by ion adsorption or external addition, a pigment or a dye, and a triboelectrically chargeable organic compound such as a polymer resin may be supported by coating or external addition.

In any case, spherical fine particles having a specific resistance of 10 ⁸ to 10 ¹⁴ Ω · cm are preferable. If the specific resistance is lower than 10 ⁸ Ω · cm, the charge amount of the toner particles is remarkably reduced especially in a high temperature and high humidity environment, and as a result, the image density is lowered, which is not preferable. Further, if a resist having a specific resistance higher than 10 ¹⁴ Ω · cm is used, “black spots” fog is likely to occur in the non-image area on the paper due to the flight of toner particles. It can be considered that this is because the electrification amount of the spherical particles of opposite polarity is remarkably increased, and the toner particles existing in the vicinity of the particles are electrostatically adsorbed and the reversal development is performed, but the details are not clear.

The particle size of the resin particles needs to be smaller than the toner particle size because it is necessary to increase the contact area with the toner particles, and 0.1 to 1 μm is required for toner particles of about 12 μm.
It is preferably in the range of m.

Further, it is advantageous for the spherical fine particles to be as close to a true sphere as possible for fluidity of the developer and uniform charging.

The amount of spherical fine particles added is 0.1 with respect to the insulating magnetic toner.
-3% by weight, more preferably 0.3-0.5% by weight. 0.
If it is less than 1% by weight, the effect of addition does not appear, while if it is more than 3% by weight, the image density decreases, which is not preferable.

The volume resistivity in the present invention is measured by, for example, the device shown in FIG. In the figure, 31 is a pedestal. Reference numeral 32 is a pressing means, which is connected to a hand press and has a pressure gauge 33 attached thereto. 34 is a hard glass cell with a diameter of 3.100 cm,
Put sample 35 inside. 36 is a brass press ram,
Diameter 4.266 cm, area 14.2857 cm ² . 37 is a stainless steel push rod having a radius of 0.397 cm and an area of 0.496 cm ² , and the pressure from the press ram 36 is applied to the sample 35. 38 is a brass base, 39 and
40 is an insulating plate made of bakelite. 41 is Pressham 36 and stand 38
An ohm meter connected to the reference numeral 42 is a dial gauge.

In the device shown in Fig. 3, the hand press has a hydraulic pressure of 20 kg / cm ²
When the pressure is applied to the sample, a pressure of 576 kg / cm ² is applied to the sample. The resistance is read from the ohmmeter 41, multiplied by the cross-sectional area of the sample, and divided by the height of the sample read from the dial gauge 42 to obtain the volume resistivity.

The developer used in the image forming method of the present invention preferably further contains a hydrophobic silica fine powder.

In the case of a negatively chargeable magnetic one-component developer, it contains negatively chargeable hydrophobic silica fine powder treated with a silane coupling agent, silicone oil or both and positively chargeable resin fine particles, and has 100% by weight of the negatively chargeable magnetic toner. It is preferable that 0.01 to 3 parts by weight of the silica and 0.02 to 3 parts by weight of the resin fine particles are contained with respect to 1 part by weight.

The fine silica powder used in the present invention is so-called dry silica or fumed silica produced by vapor phase oxidation of a silicon halogen compound, and the surface thereof is treated with a silane coupling agent and / or silicone oil. It is a fine silica powder.

Hexamethyldisilazane (HMDS) is a preferred silane coupling agent. Moreover, as a preferable silicone oil, the viscosity at 25 ° C. is about 50-
Thousands of 1,000 centistokes are used, such as dimethyl silicone oil, methyl phenyl silicone oil,
α-Methylstyrene modified silicone oil, chlorphenyl silicone oil, fluorine modified silicone oil and the like are preferable. For the purposes of the present invention, -OH groups, -COOH groups, -NH
Silicone oil containing a large amount of _two or the like is not preferable.

A known technique is used for the method of treating silicon oil,
For example, silica fine powder and silicone oil may be directly mixed by using a mixer such as a Henschel mixer, or a method of injecting silicone oil onto silica as a base may be used. Alternatively, it may be prepared by dissolving or dispersing silicon oil in an appropriate solvent, mixing it with the silica fine powder of the base, and removing the solvent.

As the hydrophobicity of the silica fine powder in the present invention, a value measured by the following method is used. Of course, other measuring methods can be applied while referring to the measuring method of the present invention.

100 ml of pure water and 1 g of a sample are placed in a sealed stopper-type container, and shaken with a shaker for 10 minutes. After shaking, for example, let stand for a few minutes, after separating the silica powder layer and the water layer, collect the water layer and measure the transmittance at a wavelength of 500 nm with reference to pure pure water containing no silica fine powder. However, the value of the transmittance is used as the hydrophobicity of the treated silica.

The hydrophobicity of the silica fine powder in the present invention is 90% or more (more preferably 93% or more). If the degree of hydrophobicity is less than this, it becomes impossible to obtain a high-quality image due to moisture adsorption of the silica fine powder under high humidity.

 The fine silica powder has a negative charging property.

The tribo value of negatively charged silica fine particles is measured by the following method. That is, 2 g of silica fine powder left overnight in an environment of 25 ° C and 50 to 60% RH, and carrier iron powder not covered with resin, which has a main particle size of 200 to 300 mesh (for example, Nippon Iron Powder Co., Ltd. EFV200 / 300) 98 g of EFV200 / 300) mixed thoroughly in an aluminum pot having a volume of about 200 c.c. under the above environment (hold in your hand and shake about 50 times up and down) and a 400 mesh screen. The amount of triboelectric charge of the silica fine particles is measured by an ordinary blow-off method using the aluminum cell. The silica fine particles whose measured triboelectric charge is negative by this method are defined as negatively chargeable silica fine particles. In the present invention, the tribo charge amount is −
Silica fine particles having a concentration of 100 μc / g to −300 μc / g are used.

The silica fine particles are used in an amount of 0.0 to 100 parts by weight of the toner particles.
Effective when 1 to 3 parts by weight, particularly preferably,
It is intended to provide a developer having excellent stability when added in an amount of 0.05 to 2 parts by weight.

If the amount is less than 0.01 parts by weight, the image density will be lowered, and if it exceeds 3 parts by weight, fog cannot be suppressed, which is not preferable.

To describe a preferable mode of addition, it is preferable that 0.01 to 1.5 parts by weight of the treated silica fine particles adhere to the toner particle surface with respect to the weight of the developer.

It is preferable that the weight ratio of the silica used in the present invention to the resin particles is in the range of silica: resin fine particles = 1: 0.1 to 1: 100. If the ratio of the resin fine particles to the silica amount 1 is less than 0.1, there is almost no effect on fog. Further, if the ratio of the resin fine particles to the silica amount 1 exceeds 100, it is not preferable because it causes a decrease in concentration.

Hereinafter, the present invention will be further described with reference to Examples.

Example 1 The above mixture was melted and kneaded with a twin-screw extruder heated to 160 ° C. and then cooled, and the cooled product was roughly crushed with a hammer mill (mechanical crusher) to a mesh having an opening diameter of 2 mm, and then a jet mill ( With a wind-powered crusher)
Finely ground to a degree. The finely pulverized product was classified by a DS classifier (wind classifier) so that the volume average particle diameter measured by a Coulter counter was 11.5 μm, to prepare a negatively charged insulating magnetic toner.

The insulating magnetic toner had a triboelectric charge of −13 μc / g as measured by a blow-off method with respect to the iron powder carrier.

With respect to 100 parts by weight of the negatively chargeable magnetic toner, spherical positively chargeable resin particles (average diameter 0.4 μm, having a structural unit derived from a methyl methacrylate monomer as a main constituent component)
Tribocharge + 400 μc / g, sphericity about 1.0, containing nitrogen-containing compound, specific electric resistance 6.5 × 10 ¹¹ Ω ・ cm; Nippon Paint PT
P-2) 0.4 part by weight and hydrophobic silica fine powder (BET specific surface area 130 m ² / g dry silica treated with hexamethyldisilazane and then treated with dimethyl silicone; hydrophobicity 95%, tribocharge Amount-190 μc / g) 0.4 part by weight was added and mixed with a Henschel mixer to give a one-component developer.

The obtained developer was used as a commercial copying machine FC-5 (manufactured by Canon Inc .; OPC laminated negative charging photoreceptor, curvature separation type using drum diameter φ30, static elimination needle biased at -1.0 kV).
Was modified for reversal development (see Fig. 1), V _pr was -700V, Under the transfer condition (V _tr = + 700V) where 1.0 is 1.0, a non-contact gap is set between the photosensitive drum and the developer layer on the developing drum (including magnet), and AC bias (f = 1,800Hz, V _pp = 1,600V) ) And a DC bias (V _DC = -500 V) were applied to the developing drum to perform image formation. The toner-fixed image on which the image was formed and fixed on the heating / pressurizing roller was evaluated as follows. The results are shown in Table 1.

(1) Image density: ordinary copy paper (75 g / m ² ) 1,00
It was evaluated by maintaining the image density when passing 0 sheets.

○ (Good): 1.35 or more, △ (Available): 1.0 to 1.34, × (Improper): 1.0 or less (2) Transfer condition: Strict transfer conditions, 120g / m ² thick paper is passed, and transfer is missing evaluated.

◯: Good, Δ: Practical, X: Practical (3) Winding condition: 1,000 thin sheets of 50 g / m ² were passed and the state of paper jam was evaluated.

○: Within 1 time / 1,000 sheets, △: 2 to 4 times / 1,000 sheets, ×: 5 times or more / 1,000 sheets (4) Paper trace: All solid images were output and evaluated by the uniformity.

◯: Density difference within 0.05, Δ: same as 0.06 to 0.15, ×: same as 0.16 or more (5) Image quality: Toner scattering, rubbing, etc. were visually evaluated.

◯: Good, Δ: Practical, X: Practical Example 2 Image was produced in the same manner as in Example 1 except that the transfer condition was changed so that the ratio of V _tr / V _pr was −0.5. I did it.
The results are shown in Table 1.

Example 3 Images were printed in the same manner as in Example 1 except that the transfer conditions were changed so that the ratio of V _tr / V _pr was −0.6.
The results are shown in Table 1.

Example 4 Images were printed in the same manner as in Example 1 except that the transfer conditions were changed so that the V _tr / V _pr ratio was −2.0.
The results are shown in Table 1.

Example 5 A developer was prepared in the same manner as in Example 1 except that spherical resin particles having an average particle diameter of 0.1 μm and a triboelectric charge amount of +450 μc / g were used as the positively chargeable resin particles. It was prepared and imaged in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

Example 6 A developer was prepared in the same manner as in Example 1 except that spherical resin particles having an average particle size of 1.0 μm and a tribocharge amount of +380 μc / g were used as the positively chargeable resin particles. It was prepared and imaged in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

Example 7 A developer was prepared in the same manner as in Example 1 except that spherical resin particles having an average particle size of 0.4 μm and a tribo charge amount of +50 μc / g were used as the positively chargeable resin particles. It was prepared and imaged in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

Example 8 A developer was prepared in the same manner as in Example 1 except that spherical resin particles having an average particle size of 0.4 μm and a tribocharge amount of +600 μc / g were used as the positively chargeable resin particles. It was prepared and imaged in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

Example 9 As the positively chargeable resin particles, spherical resin particles having an average particle size of 0.4 μm and a tribo charge amount of +400 μc / g were used.
A developer was prepared in the same manner as in Example 1 except that 1 part by weight was used, and images were formed and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 10 A developer was prepared in the same manner as in Example 1 except that the amount of the positively chargeable resin particles added was 2.0 parts by weight. . The results are shown in Table 1.

Comparative Example 1 A developer was prepared in the same manner as in Example 1 except that positively chargeable resin particles were not used, and images were formed and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 As the positively chargeable resin particles, spherical resin particles having an average particle diameter of 0.05 μm and a tribo charge amount of +800 μc / g were used.
A developer was prepared in the same manner as in Example 1 except that 4 parts by weight was used, and images were formed and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 As positively chargeable resin particles, spherical resin particles having an average particle size of 1.5 μm and a triboelectric charge amount of +30 μc / g were used.
A developer was prepared in the same manner as in Example 1 except that parts by weight were used, and images were formed and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 11 Volume average particle diameter 12μm by kneading, crushing and classifying the above materials
Negatively charged one-component magnetic toner (tribo charge -10 μc /
g) was obtained.

Spherical resin particles (PMMA, particle size 0.4μ, specific resistance)
0.5 parts by weight of 10 ⁹ Ω · cm, tribo charge amount +450 μc / g), silicon oil treated silica (tribo charge amount −200 μc / g)
0.4 parts by weight were mixed with a Henschel mixer to obtain a negatively chargeable one-component magnetic developer. This is a commercially available reversal development method, using a LBP-SX (Canon) laser beam printer with V _tr / V _pr of -1.0 at room temperature and normal humidity (23 ° C, 65% R
In H), 4,000 printout durability tests were conducted.
The results are shown in Table 2.

Example 12 A printout durability test was conducted using the same developer as in Example 11 except that the charge amount of the resin fine particles was +300 μc / g. The results are shown in Table 2.

Example 13 The same developer as in Example 11 was used except that the charge amount of the resin fine particles was +100 μc / g. The results are shown in Table 2.

Example 14 Volume average particle size by melting, kneading, crushing and classifying the above materials
11 μm negatively chargeable magnetic one-component toner (tribo charge amount −11
μc / g) was obtained. Resin fine particles prepared from 0.4 parts by weight of silica fine powder (hydrophobicity 98%, tribo charge amount −200 μc / g) treated with dimethyl silicone oil in 100 parts by weight of the toner and a composition containing methyl methacrylate monomer as a main component. (Tribo charge amount + 350μc / g, average particle size 0.5μm)
Two parts by weight were added and mixed to obtain a negatively-charged one-component developer.

The developer is a commercially available laser beam printer LBP-SX.
(Canon) was used and evaluated under normal temperature and normal humidity (20 ℃, 60% RH), low temperature and low humidity (15 ℃, 10% RH), and high temperature and high humidity (35 ℃, 85% RH). . As a result, a good image having no fogging of cardboard and having durability without environment dependence was obtained.

Example 15 A completely similar developer was obtained except that the addition amount of the resin fine particles in Example 14 was changed to 0.5 part.

Example 16 Example 1 was repeated except that 0.5 parts of silica fine powder (hydrophobicity 99%, tribocharge amount −150 μc / g) treated with olefin modified silicone oil in place of the silica fine particles of Example 14 was added.
A developer similar to that of 4 was obtained.

[Brief description of drawings]

In the accompanying drawings, FIG. 1 is a schematic view of an image forming apparatus used in an embodiment of the present invention, and FIG. 2 shows a transfer portion to which an AC bias and a DC bias are applied to a charge eliminating brush. FIG. 3 is an enlarged view, and FIG. 3 is a view schematically showing a measuring device for measuring the specific electric resistance value of powder. 1 ... Photosensitive drum 2 ... Primary charging device 3 ... Transfer charging device 4 ... Development sleeve 5 ... Exposure 6 ... Erase exposure 7 ... Heating / pressurizing roller fixing device 8 ... Blade cleaning device 9 ... Development Device 10 ... static elimination brush 11 ... blade 12 ... bias applying means

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshiyuki Ochi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Manabu Ono 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Tetsuto Kuwashima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP 54-30039 (JP, A) JP 53-106035 (JP) , A) JP 61-59361 (JP, A) JP 60-169872 (JP, A) JP 60-186853 (JP, A) JP 63-52151 (JP, A) JP 60-186876 (JP, A) JP-A-60-186875 (JP, A) JP-A-60-186866 (JP, A)

Claims (5)

(57) [Claims] 1. An image forming method, wherein an electrostatic charge image on an electrostatic image carrier is developed with a one-component developer, and a toner image formed on the electrostatic image carrier is electrostatically transferred onto a transfer material. (I) 100 parts by weight of negatively chargeable toner, (ii) average particle size 0.1 to 1.0 μ
0.1 to 3.0 parts by weight of resin particles having m and having tribocharge characteristics of +50 to +600 μc / g, and (iii) a hydrophobicity of 90
% Or more, and the tribocharge characteristics are −100 to −300 μc / g
Containing at least 0.01 to 3 parts by weight of silica fine powder treated with a silane coupling agent, silicone oil, or both, and the mixing ratio of the silica fine powder and the resin particles is 1: 0.1 to 1: 100. The ratio of the primary charging electric field V _pr to the transfer charging electric field V _tr (V _tr / V _pr ) using a certain one-component developer
An image forming method characterized in that a toner image on an electrostatic image carrier is electrostatically transferred onto a transfer material under the condition that is negative. 2. A toner image is electrostatically transferred onto a transfer material under the condition that the absolute value of the ratio (V _tr / V _pr ) of the primary charging electric field V _pr and the transfer charging electric field V _tr is 0.5 to 1.6. The image forming method according to the first item of the range. 3. The image forming method according to claim 1 or 2, wherein, following the transfer step for electrostatically transferring the toner image onto the transfer material, the charge removing step by the charge removing means is performed on the transfer material. 4. The image forming method according to claim 1, wherein the charge eliminating means is a charge eliminating brush or a charge eliminating needle. 5. The image forming method according to claim 1, wherein the electrostatic image carrier is a photosensitive drum having a diameter of 50 mm or less, and the transfer material is separated from the photosensitive drum by curvature separation.