JP3060150B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a positively chargeable one-component developer.

[0002]

2. Description of the Related Art An electrostatic latent image formed on an image carrier is developed using a carrier-free developer contained in a two-component developer, a so-called one-component developer (hereinafter also simply referred to as toner). Developing devices for performing such processes are known.

[0003] Such a developing device comprises a developer carrier for carrying a toner to develop an electrostatic latent image on an image carrier, and a toner layer which comes into contact with the developer carrier and is conveyed to a developing section. A regulating member for regulating the thickness.

Strictly speaking, at the time of forming the developer layer, the above-mentioned regulating member and an elastic member which comes into contact with the developer carrier downstream of the developer regulating member described later are:
It is not directly in contact with the developer carrier, but a thin developer layer exists between the developer carrier and the developer layer, and this developer layer is pressed against the developer carrier. In a state where the developer is not present, the developer is urged so as to directly contact the developer carrier, so for the sake of convenience in the present specification, such a regulating member or the elastic member is used for developing even when the developer layer thickness is regulated. It comes into contact with the agent carrier.

A developer carrier (usually a sleeve or a roller; hereinafter, simply referred to as a developing sleeve unless necessary) is generally made of a metal such as aluminum, to which a developing bias voltage is applied. Further, the toner is rubbed on the surface of the developing sleeve, and has a triboelectric charge having a polarity for developing the electrostatic latent image.

The important points in this developing method are how to give a uniform amount of triboelectric charge to the toner and to form a uniform thin toner layer. In the regulating portion of the toner layer on the developing sleeve, the regulating member (for example, an elastic blade) that contacts the developing sleeve regulates the toner to a predetermined layer thickness. However, the toner once thinned is not all developed, and is rubbed again by the regulating member. At this time, the frictional charge amount of the toner becomes excessive,
Charge is strongly attached to the sleeve, and the charge imparting ability of the sleeve is reduced. In addition, the amount of charge tends to be different from the toner that has been frictionally charged many times and the newly replenished toner.
Toners have a distribution in particle size, have a large surface area per volume, and a large amount of triboelectric charge per mass.Because the toner is difficult to develop, it adheres to the lowermost layer of the sleeve, causing friction between the toner and the sleeve. There is a problem that charging is significantly inhibited.

As a result, a sufficient amount of triboelectric charge is not applied to the toner, so that not only the image density is reduced, but also a large amount of rubbing occurs between the toners, and the toner is triboelectrically charged to a polarity opposite to the desired triboelectric charge polarity. So-called inverted toner is generated, and so-called inverted fogging that adheres to the background portion of the latent image on the photosensitive drum occurs.

As a countermeasure against this, the present inventors have proposed a method in which the developer regulating member is provided at a position on the upstream side in the rotation direction of the developing sleeve.
It was thought that this could be solved by installing an elastic roller in contact with the developing sleeve. It has been determined that the toner on the undeveloped sleeve can be scraped off by the elastic roller, and the amount of triboelectric charge of the toner can always be kept uniform by supplying fresh toner.

[0009] However, some problems remain in order to realize the above configuration. When a positively charged toner is used, the elastic roller is made of an open-celled foam having a foam skeleton structure such as silicone rubber having a strong negative property in terms of charge application. Become. In this case, it is possible to scrape the undeveloped toner and supply the toner onto the sleeve by the appropriate irregularities on the surface of the open-cell foam. However, when the developing operation is repeated many times, the following problems occur.

In the open-cell foam, since the cells are communicated with each other, the inside thereof is clogged with toner, and as a result, the elastic roller is hardened. For this reason, the contact pressure of the elastic roller against the sleeve becomes excessive, and the function of rubbing the toner by the elastic roller onto the sleeve is too strong, causing toner fusion on the sleeve and deterioration of the physical properties of the toner, resulting in image deterioration. And the driving torque of the sleeve and the elastic roller is significantly increased.

Since the degree of toner clogging in the elastic roller tends to be non-uniform in the longitudinal direction of the roller, the function of the elastic roller for applying and scraping the toner to the sleeve can be uneven in the longitudinal direction. In addition, unevenness in image density due to tribo of the toner layer on the sleeve and unevenness of the layer thickness occurs.

On the other hand, with respect to the toner, if the fluidity of the toner on the sleeve is poor, the toner cannot be scraped off by the elastic member, so that the toner layer on the sleeve becomes uneven, causing image disturbance and fogging. In addition, the charge amount becomes excessive. When so-called charge-up occurs, unevenness similarly occurs. Therefore, the performance required of the toner is required to have extremely good fluidity and the amount of triboelectric charge is always constant without being affected by the environment.

Conventionally, hydrophobic silica fine powder is generally added to improve the fluidity of the toner. However, since the hydrophobic silica fine powder is strongly negatively charged, the charge amount decreases or changes negatively, which is not preferable. Positively-charged silica fine powder has also been proposed by a method such as oil treatment.However, coarse particles are generated during the treatment and the fluidity-imparting ability is reduced. Occurred and did not fully meet the aforementioned requirements.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method using a positively chargeable one-component toner which has solved the above-mentioned problems.

That is, an object of the present invention is to provide an image forming method in which a toner layer is always formed uniformly on a sleeve and unevenness does not occur.

Another object of the present invention is to provide an image forming method in which the amount of triboelectricity of the toner is stable in each environment, no charge-up or the like occurs, and no fogging or the like occurs.

[0017]

According to the present invention, a positively chargeable one-component developer carried on a developer carrying member is regulated by a developer regulating member in contact with the developer carrying member. While forming a thin layer of the developer on the developer carrier, the developer is transported by the developer carrier to a developing unit opposed to an image carrier, and the image is formed by the developer at the developing unit. In the image forming method for developing and visualizing a latent image formed on a carrier, a single-cell foam rubber contacting the developer carrier is provided at a position upstream of the developer regulating member in the rotation direction. It has a rotatable elastic roller, the positively chargeable one-component developer contains at least a colorant-containing resin particle and an external additive, and at least a weight average particle size of 0.01 to 0.2 μm as the external additive And hydrophobic hydrophobic oxide treated with a coupling agent. Containing emissions particulates, it relates to an image forming method comprising.

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention.

In FIG. 1, reference numeral 2 denotes a developing container containing a one-component toner 6, and the developing device comprises a photosensitive member 1 of an image carrier which rotates in the direction of arrow a in FIG. And a developing sleeve 3 opposed to the photosensitive member 1.
The upper electrostatic latent image is developed and visualized as a toner image. The developing sleeve 3 protrudes into the developing container 2 at a substantially right peripheral half in the drawing, and exposes a substantially semi-peripheral left surface to the outside of the developing container 2. Has been established. A slight minute interval is provided between the developing sleeve 3 and the photoconductor 1. The developing sleeve 3 is driven to rotate in the direction of arrow b with respect to the rotation direction a of the photoconductor 1.

Incidentally, the developer carrying member is provided with the developing sleeve 3.
Not limited to the cylindrical body (sleeve) as described above, an endless belt that is driven to rotate may be used. Further, a conductive rubber roller may be used.

Further, in the developing container 2, an elastic blade 4 is provided as an elastic regulating member above the developing sleeve 3, and an elastic roller 5 is provided at a position upstream of the elastic blade 4 in the rotation direction of the developing sleeve 3. Is provided.
Note that an elastic roller may be used as the elastic regulating member.

The elastic blade 4 is provided so as to be inclined downward toward the upstream side in the rotation direction of the developing sleeve 3, and is in contact with the upper outer peripheral surface of the developing sleeve 3 in the rotation direction.

The elastic roller 5 is in contact with a portion of the developing sleeve 3 opposite to the photosensitive member 1 and is rotatably supported.

In the developing device, the elastic roller 5 rotates in the direction of arrow c, and carries the toner 6 by the rotation of the elastic roller 5 to supply the toner 6 to the vicinity of the developing sleeve 3. The toner 6 on the elastic roller 5 rubs against the developing sleeve 3 at the contact portion (nip portion) where the toner 5 comes into contact with the developing roller 3, so that the toner 6 adheres to the developing sleeve 3.

Thereafter, as the developing sleeve 3 rotates, the toner 6 adhering to the developing sleeve 3 enters between the elastic blade 4 and the developing sleeve 3 at a contact portion between the elastic blade 4 and the developing sleeve 3. The surface of the sleeve 3 and the elastic blade 4
Rubbed by both of them, and receive sufficient triboelectric charging.

The toner 6 charged as described above is
After coming out of the contact portion between the elastic blade 4 and the developing sleeve 3, a thin layer of the toner 6 is formed on the developing sleeve 3, and is conveyed to the developing unit facing the photoreceptor 1 at a small interval. . In the developing section, an alternating voltage in which DC and AC are superimposed is applied as a developing bias between the developing sleeve 3 and the photoconductor 1, so that the toner 6 on the developing sleeve 3 becomes an electrostatic latent image on the photoconductor 1. Correspondingly, the toner image is transferred to the electrostatic latent image, developed and visualized as a toner image.

The toner 6 remaining on the developing sleeve 3 without being consumed in the development in the developing section is collected into the developing container 2 from a lower portion of the developing sleeve 3 as the developing sleeve 3 rotates.

The collected toner 6 is peeled off from the developing sleeve 3 by the elastic roller 5 at a contact portion with the developing sleeve 3. At the same time, new toner 6 is supplied onto the developing sleeve 3 by the rotation of the elastic roller 5, and the new toner 6 is transported again to the contact portion between the developing sleeve 3 and the elastic blade 4.

On the other hand, most of the stripped toner 6 is conveyed and mixed into the toner 6 in the developing container 2 with the rotation of the elastic roller 5, and the stripped toner 6 is removed.
Is dispersed.

A first feature of the present invention resides in that a single-cell foam rubber is used for an elastic roller abutting on the developer carrying member on the downstream side of the developer regulating member. When the roller is made of a single-cell foam rubber, the roller can be easily applied with toner, scraped, and charged well with moderate unevenness due to a single foam on the roller surface, and hard due to toner clogging in the roller. Can be prevented. The material is silicone rubber, EPDM rubber, CR rubber, etc.
Although known materials can be used, silicone rubber that is easily negatively charged is particularly preferable in consideration of compatibility with the positively chargeable toner.

The sliding width W between the elastic roller and the developing sleeve is preferably 2.0 mm to 6.0 mm. If it is wider than 6.0 mm, there is a possibility that the toner is fused on the developing roller and the toner is deteriorated due to an increase in driving torque and an excessive load on the developing roller and the toner. On the other hand, when the width is smaller than 2.0 mm, the contact of the elastic roller with the developing roller tends to be non-uniform, and as a result, the toner may be unevenly applied to and scraped from the sleeve of the elastic roller.

Further, the hardness of the elastic roller is preferably in the range of 8 ° to 25 ° under a 300 g load of Asker C. If the hardness is lower than 8 °, the low molecular weight component (oil component) in the roller exudes, and this oil adheres to the developing roller at the sliding contact with the developing roller, which may cause contamination. In addition, when the hardness is increased more than 25 °,
There is a possibility that problems such as fusion of the toner on the developing roller and occurrence of toner deterioration may be advanced.

A second feature of the present invention is that the positively chargeable nonmagnetic one-component toner contains at least a colorant-containing resin particle and an external additive, and the external additive has a weight average particle size of 0.01 to 0.01. It is to contain hydrophobic titanium oxide fine particles of 0.2 μm.

The inventors of the present invention have conducted intensive studies on the positively chargeable one-component toner used in the image forming apparatus having the above-described structure. Extremely effective for application and charge stabilization,
It has been found that it is extremely well suited to the image forming apparatus having the above-described configuration.

That is, a sufficiently good fluidity can be obtained, the charge amount in each environment is stable, no charge-up occurs even under low humidity, and even in the image forming apparatus having the above structure,
Since the undeveloped toner is peeled off by the elastic roller and the fresh toner is supplied satisfactorily, a uniform thin layer of the toner can always be formed on the developing sleeve, and no reversal fog occurs.

This cannot be achieved by the generally known hydrophobic silica fine particles as a fluidity improver. The reason is that silica fine particles have strong negative chargeability, whereas titanium fine particles have almost neutral chargeability. In addition, silica fine particles that have been changed to positive charge by oil treatment, etc. are concerned about coarse particles generated during treatment and a decrease in fluidity imparting ability due to aggregation, and further, charge up to the positive side under low humidity. And satisfactory performance was not obtained.

Further, the inventors of the present invention have found that the hydrophobic titanium oxide is particularly preferably a hydrophobic titanium oxide which is surface-treated while being hydrolyzed while mechanically dispersing titanium oxide fine particles in an aqueous system so as to have a primary particle size. I found something.

Conventionally, it has been proposed to add hydrophobic titanium oxide. However, titanium oxide fine particles originally had a smaller surface activity than silica, and the hydrophobicization was not always sufficiently performed. For this reason, under high temperature and high humidity, the charge amount of the toner is reduced, and toner scattering and fogging are caused.
In addition, when using a large amount of a processing agent or the like, or using a high-viscosity processing agent or the like, although the degree of hydrophobicity is certainly increased, coalescence and the like of the particles occurs, and the ability to impart fluidity is reduced, Compatibility of charging stability and imparting of fluidity has not always been achieved, and cannot be applied to the developing device of the present invention.

According to the present invention, however, the titanium oxide fine particles are surface-treated while being hydrolyzed while mechanically dispersing the titanium oxide fine particles to have a primary particle size. It was also found that the surface treatment of the titanium oxide fine particles was almost in the form of primary particles due to the effect of the charge repulsion between the particles due to the treatment.

The feature of the present invention is that the surface of the titanium oxide is treated while the coupling agent is hydrolyzed in an aqueous system. At this time, a mechanical force is applied to disperse the titanium oxide fine particles to a primary particle size. It is not necessary to use a coupling agent that generates gas like chlorosilanes or silazanes, and it is not necessary to use high-viscosity particles in the gas phase. Coupling agents can also be used, and the effect of hydrophobization is enormous.

The coupling agent usable in the present invention may be any of a silane coupling agent and a titanium coupling agent. Particularly preferred are silane coupling agents, which are represented by the general formula R _m SiY _n R: alkoxy group m: an integer of 1 to 3 Y: alkyl group, amino group, vinyl group, glycidoxy group, meltcapto group, methacryl group, Ureido group n: represented by an integer of 1 to 3, for example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-aminopropyltriethoxysilane, N-dimethylaminophenyltriethoxysilane, aminoethylaminomethylphenethyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane Hydroxypropyl trimethoxysilane, phenyltrimethoxysilane, n- hexadecyl trimethoxy silane, can be mentioned n- octadecyl trimethoxysilane.

The treatment amount is 1 to 50 parts by weight, preferably 3 to 40 parts by weight, based on 100 parts by weight of titanium oxide, and the degree of hydrophobicity is 40 to 90%, preferably 50 to 80%.
You can do it.

That is, if the degree of hydrophobicity is less than 40%, there is a problem that the charge amount is greatly reduced due to long-term storage under high humidity, and a mechanism for accelerating the charge on the hardware side is required, and the apparatus becomes complicated. On the other hand, if the degree of hydrophobicity exceeds 90%, it is difficult to control the charging of titanium oxide itself, and as a result, the toner is charged up under low humidity.

The particle size is preferably 0.01 to 0.2 μm from the viewpoint of imparting fluidity. If the particle size is larger than 0.2 μm, toner charging becomes non-uniform due to poor fluidity, resulting in toner scattering and fogging. On the other hand, when the thickness is smaller than 0.01 μm, the toner is easily embedded on the surface of the toner, the toner is quickly deteriorated, and the durability is reduced. The particle size of titanium oxide in the present invention was measured by a transmission electron microscope.

In the present invention, the method of treating titanium oxide is not particularly limited, but the treatment is carried out by hydrolyzing the coupling agent while mechanically dispersing the titanium oxide in an aqueous system so as to have a primary particle size. This method is effective and is preferable in that no solvent is used.

Further, the treated titanium oxide is 400 n
The light transmittance at a light length of m is preferably 40% or more.

That is, when the titanium oxide of the present invention is used as a full-color toner, if the transmittance with respect to visible light is poor, the projected image of the OHP is blurred, and a clear image cannot be obtained. The measurement of transmittance in the present invention will be described later.

In recent years, as the demand for higher image quality has increased, and the toner has been required to have a further smaller particle size.
Again, the titanium oxide of the present invention is extremely effective. When the particle size of the toner is reduced, the surface area per weight increases, and charge-up due to sliding of the elastic roller poses a serious problem. However, by using the titanium oxide of the present invention, stable charging performance can be obtained.

On the other hand, the colorant-containing resin particles contain a colorant and a binder resin as main components and, if necessary, additives such as a charge control agent. The particle size of the resin particles is preferably in the range of 3.5 to 10.0 μm from the viewpoints of developability and chargeability.

The coloring agent that can be used in the toner of the present invention includes any suitable pigment or dye. Toner colorants are well known and include pigments such as carbon black, aniline black, acetylene black, naphthol yellow, hansa yellow, rhodamine lake, alizarin lake, bengara, phthalocyanine blue, and indanthrene blue. These are used in an amount necessary and sufficient to maintain the optical density of the fixed image.
0.1 to 20 parts by weight, preferably 2-1 to 0 parts by weight
The addition amount of 0 parts by weight is good. A dye is further used for the same purpose. For example, there are azo dyes, anthraquinone dyes, xanthene dyes, methine dyes and the like, and 0.1 to 20 parts by weight, preferably 0.3 to 3 parts by weight, per 100 parts by weight of the resin is good.

As the binder resin used in the toner of the present invention, all known binder resins can be used. For example, polystyrenes such as polystyrene, poly (P-chlorostyrene), and polyvinyltoluene, and homopolymers of substituted styrenes 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 Polymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Styrene-based copolymers such as polymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, and polystyrene Le, polyurethane, polyamide,
Epoxy resin, polyvinyl butyral, amide,
Polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination.

The charge controlling agent to be added as necessary further includes an amino compound, a quaternary ammonium compound, an organic dye, particularly a basic dye and a salt thereof, a nigrosine base,
And a salicylic acid chelate compound.

Hereinafter, the measuring method of the present invention will be described.

(1) Method for Measuring Charge Amount FIG. 3 is an explanatory view of a charge amount measuring apparatus. Using this device, the suction port 31 is pressed against the recording material to suck the developer,
The sample is collected on the filter 32 of the inner cylinder. At this time, the inner cylinder is electrostatically shielded from the outside, and the amount of charge of the developer accumulated therein is measured by the connected Faraday gauge 33, and the weight of the sucked developer is increased by the weight of the filter. From this, the amount of charge of the developer on the recording material (the amount of charge per unit weight) is calculated from this.

(2) Method of measuring transmittance 0.10 g of sample 13.20 g of alkyd resin (Veccosol 1323-60-EL manufactured by Dainippon Ink) 3.30 g of melamine resin (Super-Beckamine J-820-6 manufactured by Dainippon Ink)
0) Thinner 3.50g (Aramic thinner manufactured by Kansai Paint) Glass media 50.00g

The above composition was collected in a 150 cc glass bottle,
Disperse for 1 hour with Red Devil Paint Conditioner.

After the dispersion, 2 mi is added to the PTP film.
1 with a doctor blade.

Is heated at 120 ° C. for 10 minutes to perform baking.

The sheet No. was manufactured by U-BEST manufactured by JASCO.
Measure the transmittance in the range of 320-800 nm at 50,
Compare.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Developing devices (1) to (5), one-component toner (a) to
(E) was prepared.

Developing device (1): Takes the configuration shown in FIG. 1, and the elastic roller 5 has a hardness of 10 ° on a metal core 51 having an outer diameter of 4 mm.
(Asker C, 300 g load) Silicone single-cell foamed rubber covered with a roller having a thickness of 4 mm and an outer diameter of 12
The width W of sliding contact with the developing sleeve 3 having an outer diameter of 16 mm was set to 4.0 mm. Further, the closed cell roller has a relative speed to the sleeve,
m / s.

Developing device (2): Same configuration as the developing device (1) except that the sliding contact width W is set to 5.0 mm.

Developing device (3): The structure is the same as that of the developing device (1) except that a continuous foam of polyurethane is used for the supply roller.

Developing device (4): The structure is the same as that of the developing device (1) except that the sliding contact width W is set to 7.0 mm.

Developing device (5): The structure is the same as that of the developing device (1), except that the hardness of the silicone single-cell foam rubber is 5 ° (Asker C, 300 g load).

Toner (a): styrene-acrylic resin 100 parts by weight Carbon black 3.5 parts by weight Charge control agent (nigrosine) 5.0 parts by weight

The raw materials of the above formulation are sufficiently premixed by a Henschel mixer, melt-kneaded by a twin-screw extruder, cooled, roughly ground to about 1-2 mm using a hammer mill, and then air-jetted. And pulverized with a pulverizer. Further, the obtained finely pulverized product is classified by a multi-segment classification device to classify 8.5 μm (colorant-containing resin particles).
I got

While mixing and stirring the hydrophilic titanium oxide fine particles generated in the aqueous system, γ-aminopropyltriethoxysilane is added and mixed so as to be 30% by weight with respect to the titanium oxide fine particles so that the particles do not coalesce. Dry and pulverized to prepare a hydrophobic titanium oxide having a hydrophobicity of 70%, an average particle size of 0.05 μm, and a transmittance at 400 nm of 55%, added to the above classified product by 1.0% and mixed with a mixer. Thus, a toner (that is, a positively chargeable one-component developer) (a) was obtained.

Toner (b): Styrene-acrylic resin 100 parts by weight Copper phthalocyanine pigment 5.0 parts by weight (CI Pigment Blue 15) Charge control agent (quaternary ammonium salt) 4.0 parts by weight

The raw materials having the above formulation were kneaded, crushed and classified in the same manner as in the toner (a) to obtain a 8.2 μm classified product. To this, 0.8% of the same hydrophobic titanium oxide as that prepared for the toner (a) was added and mixed with a mixer to obtain a toner (b).

Toner (c): Toner (a) was prepared in the same manner as toner (a) except that hydrophilic titanium oxide fine particles (having a hydrophobicity of 0%) not treated with a coupling agent were used.

Toner (d): Same as toner (a) except that hydrophobic silica fine powder (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) is used instead of hydrophobic titanium oxide fine particles in toner (a). Prepared.

Toner (e): Toner (a) was prepared in the same manner as toner (a) except that hydrophobic silica fine powder surface-treated with amino-modified silicone oil was used instead of hydrophobic titanium oxide fine particles.

Example 1 The toner (a) was put into the developing device (1), and was incorporated into a laser beam printer (organic photoconductor was used for the photosensitive drum 1) having the structure shown in FIG.
800 Hz, an AC voltage V _PP (peak-to-peak voltage) of 1800 V, and a DC voltage V _{DC of} −500 to −100 V are applied to make the distance between the developing sleeve 3 and the photosensitive drum 1 20.
Non-contact development was carried out at a setting of 0 μm.

As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve, and the charge amount of the toner was +10 μC /
g, and a good image having a reflection density of 1.5 was obtained. In addition, 200 ° C under low temperature and low humidity of 15 ° C and 10%.
When a printing durability test was performed on 0 sheets, a uniform toner layer was maintained on the sleeve until the end, and the charge amount of the toner did not change from the initial value, and density unevenness, reduction in image density, fog, etc. occurred. Did not.

Example 2 The toner (b) was charged into the developing device (1), and non-contact development was performed in the same manner as in Example 1. As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
This was a good value of 14 μC / g, and a good image having a reflection density of 1.5 was obtained. When a printing test was performed on 3000 sheets at a low temperature and low humidity of 15 ° C. and 10%, a uniform toner layer was maintained on the sleeve until the end, and the charge amount of the toner remained unchanged from the initial value. Unevenness, lower image density,
No fog or the like occurred.

Example 3 The toner (a) was charged into the developing device (2), and non-contact development was performed in the same manner as in Example 1. As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
This was a good value of 11 μC / g, and a good image having a reflection density of 1.5 was obtained. Further, when a printing durability test was performed on 2,000 sheets at a low temperature and a low humidity of 15 ° C. and 10%, the toner layer on the sleeve and the charge amount of the toner did not change from the initial state. Did not occur.

Comparative Example 1 When the toner (c) was charged into the developing device (1) and non-contact development was performed in the same manner as in Example 1, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
A good value of 10 μC / g was obtained, and a good image having a reflection density of 1.5 was obtained. However, when a printing test was performed on 3,000 sheets at a high temperature and high humidity of 30 ° C. and 80%, the charge amount of the toner was significantly reduced, and the toner scattering and fog were extremely deteriorated.

Comparative Example 2 When the toner (d) was charged into the developing device (1) and non-contact development was performed in the same manner as in Example 1, the charge amount of the toner was +
The drop was as large as 2 μC / g, resulting in uneven density and toner scattering.

Comparative Example 3 When the toner (e) was charged into the developing device (1) and non-contact development was performed in the same manner as in Example 1, the toner charge amount was +1.
2 μC / g, which was appropriate, but the fluidity of the toner was poor.
The toner layer on the sleeve was uneven. In addition, 15
When a printing test was performed on 3000 sheets at a low temperature and a low humidity of 10% at ℃, toner charge-up occurred, resulting in uneven density and
The image density decreased.

Comparative Example 4 The toner (a) was charged into the developing device (3), and non-contact development was performed in the same manner as in Example 1. As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
This was a good value of 11 μC / g, and a good image having a reflection density of 1.5 was obtained. However, when a printing durability test of 3,000 sheets was performed under normal temperature and normal humidity, the toner penetrated into the open-cell foam of the elastic roller and was hardened, toner fusion on the sleeve occurred, and further toner deterioration occurred. Fog worsened.

Comparative Example 5 The toner (a) was charged into the developing device (4), and non-contact development was performed in the same manner as in Example 1. As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
A good value of 12 μC / g was obtained, and a good image having a reflection density of 1.5 was obtained. However, when a printing durability test was performed on 3,000 sheets under normal temperature and normal humidity, toner fusion on the sleeve occurred.

Comparative Example 6 The toner (a) was charged into the developing device (5), and non-contact development was performed in the same manner as in Example 1. As a result, a uniform coating layer of about 30 μm was obtained on the developing sleeve. +
A good value of 10 μC / g was obtained, and a good image having a reflection density of 1.5 was obtained. However, when a printing durability test was performed on 3,000 sheets under normal temperature and normal humidity, the low molecular weight component of the elastic roller adhered to the sleeve, and the amount of toner decreased.

[0084]

As described above, by using the present invention, in the image forming method using the one-component developer, the toner layer is always formed uniformly on the sleeve, and no unevenness is generated. The amount of triboelectricity of the toner is stable in each environment, no charge-up or the like occurs, and an image forming method without reversal fog can be obtained. It can be seen that the present invention is industrially useful.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the vicinity of a developing device of an image forming apparatus according to the present invention.

FIG. 2 shows a configuration of a laser beam printer used in Examples and Comparative Examples.

FIG. 3 is an explanatory diagram of a charge amount measuring device.

[Explanation of symbols]

 Reference Signs List 1 photoconductor (image carrier) 3 developing sleeve (toner carrier) 4 elastic blade 5 elastic roller 6 toner 21 scanner unit 22 folding mirror 23 laser beam 24 primary charger 25 developing device 26 transfer charger 27 recording material 28 fixing device 29 Cleaning device

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-181352 (JP, A) JP-A-6-11887 (JP, A) JP-A-59-137305 (JP, A) JP-A-5-137305 273848 (JP, A) JP-A-7-110621 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 9/08

Claims (5)

(57) [Claims] The positively chargeable one-component developer carried on a developer carrying member is regulated by a developer regulating member in contact with the developer carrying member, and the developer is transferred onto the developer carrying member. While forming a thin layer, the developer is conveyed by the developer carrier to a developing section facing the image carrier, and the developing section forms a latent image formed on the image carrier by the developer. In the image forming method of developing and visualizing, a rotatable elastic roller made of a single-cell foam rubber contacting the developer carrier is provided at a position on the upstream side in the rotation direction of the developer regulating member, positively chargeable one-component developer contains at least a colorant-containing resin particles and an external additive, Ri least the weight average particle diameter 0.01~0.2μm der as external additive, coupling loop
An image forming method, comprising hydrophobic titanium oxide fine particles treated with a coloring agent . 2. The sliding contact width between the elastic roller made of the single-cell foam and the toner carrier is from 2.0 mm to 6.
The image forming method according to claim 1, wherein the distance is within a range of 0 mm. 3. The hardness of the elastic roller made of the single-cell foam is 8 ° to 25 ° (Asker C, 300 g load).
The image forming method according to claim 1, wherein: 4. The image forming method according to claim 1, wherein a material of the elastic roller made of the single-cell foam is silicone rubber. 5. The hydrophobic titanium oxide has a weight average particle diameter of 0.01 to 0.2 μm, surface-treated while hydrolyzing a coupling agent in an aqueous system, a degree of hydrophobicity of 40 to 90%, and 40.
5. The image forming method according to claim 1, wherein the titanium oxide has a light transmittance of 40% or more at 0 nm.