JP2552828B2 - Image forming method - Google Patents

Description

The present invention relates to a developing method for forming a brush of a small amount of magnetic particles on a toner holding member by using a dry developer and using the brush for development.

[Prior Art] Various methods have been proposed and put to practical use as dry development methods.

For example, in a developing method using a two-component developer, when the image portion of the latent image is developed by the developer applied on the developing roller, the toner in the developer is the toner applied on the developing roller. Use less than a few percent of This is extremely inefficient considering the developing device configuration. This is because it is necessary to apply a large amount of the developer on the developing roller with a constant amount and uniform toner concentration each time the developing roller rotates in order to obtain a predetermined sufficient developing concentration. Therefore, the size of the developing device is increased.
It was complicated. Of course, attempts have been made to improve the developing efficiency even in this type of developing method. For example, the present applicant has proposed JP-A-55-32060, 55-133058, 56-70560, and NP 8
It has been put to practical use in 500 copiers. According to this, although the development density can be increased and the development efficiency can be increased, the development efficiency close to 100% cannot be achieved in the image area, and this type of development method still has room for improvement. Is left.

In terms of improving development efficiency, the one-component development method is two
Better than the component development method. Among them, especially in Japanese Patent Application Laid-Open No. 54-43037 filed by the applicant of the present invention, a toner thin layer having a thickness of 200 μm or less is formed on a developing roller, and the toner applied on the sleeve is developed to almost 100% in the image area. Developing at a high rate. Therefore, downsizing of the developing device configuration
It could be simplified and put into practical use. This was achieved because a thin layer of 200 μm or less could be formed on the developing roller. However, it is extremely difficult to form a thin layer of a dry developer in either one-component development or two-component development. Therefore, even in the one-component development, a relatively thick layer is formed by anyone other than the applicant. Forming the device. From the viewpoint of image quality, at the present time, it is required to improve the sharpness and resolution of a developed image, and development of a thin layer forming method of a dry developer and its apparatus is indispensable.

By the way, the above-mentioned applicant's method relates to the formation of a thin layer of the magnetic toner. In order to give the magnetic toner magnetism, it is necessary to internally add a magnetic substance to the toner. This is because of poor fixability when thermally fixing a developed image transferred onto a transfer paper, and the magnetic substance is internally added to the toner itself. Therefore (the magnetic substance is usually black), there is a problem such as poor color when reproducing the color.

Therefore, as a method for forming a thin layer of non-magnetic toner, a soft brush such as beaver hair is made into a cylindrical brush, and toner is adhered and applied to the brush, or a developing roller whose surface is made of fiber such as velvet. There has been proposed a method of coating with a doctor blade or the like.

However, when an elastic blade is used as the doctor blade in the fiber brush, the amount of toner can be regulated, but uniform application is not performed, and rubbing the fiber brush on the developing roller only causes Since the triboelectric charge is not applied to the toner existing in the above, there is a problem that fogging or the like is likely to occur.

Further, magnetic toners can easily prevent toner scattering by utilizing magnetic force, but non-magnetic toners cannot utilize magnetic force and toners are easily scattered inside the machine. The inconveniences described above occur not only during copying but also when vibration or shock is applied during transportation of the apparatus.

The applicant of the present invention uses a non-magnetic toner and magnetic particles as a developing device which is completely different from the above-mentioned conventional method, provides a magnetic particle restraining member facing the toner carrying member, and restrains the magnetic particle with respect to the moving direction of the surface of the holding member. A method has already been proposed in which a magnetic brush of magnetic particles is formed upstream of the member by the magnetic force of the magnetic field generating means, the magnetic brush is restricted by the magnetic particle restriction member, and a thin layer of non-magnetic toner is formed on the toner holding member. (JP-A-58-143360). According to this method, the gap between the latent image carrier and the toner carrier in the developing section is set wider than the toner layer thickness, and an alternating electric field is applied to obtain a non-magnetic toner developed image on the surface of the latent image carrier. It was put to practical use. As a result, it is possible to obtain a color developed image with a small and simple developing device configuration that has extremely high developing efficiency. Especially in two-component magnetic brush rubbing development,
A good quality solid image was obtained without rubbing marks generated in the solid image portion. However, there has been a demand for further improvement in development image quality, for example, development of a development system that further improves gradation.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned conventional circumstances, and it is a development method capable of obtaining a developed image which has extremely high development efficiency and is not inferior to the conventional development method. For the purpose of provision.

In particular, a main object of the present invention is to provide a simple image forming method for forming a stable image even under special conditions such as high temperature and high humidity, low temperature and low humidity.

[Means and Actions for Solving Problems] Specifically, according to the present invention, a latent image holding member for holding a latent image and a developer carrying member facing the latent image holding member are provided. In the formed developing area, the latent image is formed by a two-component developer containing a non-magnetic toner and magnetic particles while applying an alternating electric field between the developer carrying body containing a magnet inside and the latent image holding body. In an image forming method of developing with a formed magnetic brush, the amount of magnetic particles conveyed to a developing area is regulated and the magnetic particles are circulated in a developer supply container, and a two-component system on the developer carrier is provided. conveying the developer to the developing area, the developing area of the developer carrying member in the magnetic particles, the presence of the magnetic particles form a magnetic brush so that 5 to 100 mg / cm ^2, amino acrylic monomers as constituents 2-15% by weight of body
Fine particles of fluororesin 0.1 to 5 per 100 parts by weight of the non-magnetic toner containing 30% by weight or more of the copolymer contained in the binder resin.
Forming a non-magnetic toner image on the latent image carrier while reciprocating the non-magnetic toner to which the weight part is added externally between the surface of the developer carrier and the surface of the magnetic brush and the latent image carrier in the developing area. The present invention relates to an image forming method.

The non-magnetic toner referred to here is an external magnetic field 5000e,
A toner that exhibits a magnetization of 10 emμ / g or less and cannot substantially behave as a magnetic toner.

Further, the development area referred to here means an area of about 10 mm centering on the closest position between the latent image carrier and the developer carrier on the developer carrier.

The inventors of the present invention have proposed the above-mentioned Japanese Patent Application Laid-Open No. 58-143360, and as a result of earnest research on the improvement thereof, as a result, a clear developing magnetic pole is formed in the developing portion to perform locally concentrated development. In the one-component developing method, the triboelectric charge is imparted to the toner mainly between the surface of the sleeve and the surface area of the sleeve is substantially increased, whereby the triboelectricity of the toner is stabilized and the sleeve is stabilized. It has been found that stabilization of the toner supply to the top and improvement of image quality such as gradation and uniformity are achieved. Furthermore, the developer coating method used in the present invention is applied to the present development system, and environmental changes, particularly high temperature and high humidity,
It has been found that it produces an effect of stably providing a high-quality image even when the environment changes such as low temperature and low humidity. Although the detailed mechanism has not been completely clarified yet, it is generally estimated as follows from the experiments so far.

That is, the positively chargeable copolymer containing aminoacryl originally has a strong positive chargeability, while the fluororesin has a relatively strong negative chargeability. Therefore, when the fluorine-containing resin fine particles are present around the colored particles containing the positively chargeable copolymer, the fluorine-containing resin fine particles are slightly separated from the colored particles in a certain environment to charge the colored particles as if they were carriers. Serves to strengthen, and in other environments,
It adheres to the amino groups on the colored particles and rather serves to suppress the charging of the colored particles. Therefore, it is considered that the toner as a whole is always adjusted to an appropriate charged state.

Hereinafter, the main developing method will be described with reference to Examples. First
The figure is an embodiment according to the present invention. In FIG.
3 is a latent image holding member, 21 is a toner supply container, 22 is a non-magnetic sleeve, 23 is a fixed magnet, 24 is a non-magnetic blade, 26 is a magnetic particle circulation region limiting member, 27 is magnetic particles, 28 is non-magnetic toner, Reference numeral 29 is a developer collecting container portion, 30 is a scattering prevention member, 31 is a magnetic member, 32 is a developing region, and 34 is a bias power source. The sleeve 22 rotates in the b direction, and the magnetic particles 27 circulate in the c direction accordingly. This causes contact and rubbing between the sleeve surface and the magnetic particle layer to form a non-magnetic toner layer on the sleeve surface. Further, while the magnetic particles circulate in the c direction, a part of the magnetic particles is regulated to a predetermined amount by the gap between the nonmagnetic blade 24 and the sleeve 22, and is applied onto the nonmagnetic toner layer. That is, the non-magnetic toner is applied on both the surface of the sleeve and the surface of the magnetic particles, and the effect equivalent to that of substantially increasing the surface area of the sleeve is exhibited.

In the developing area 32, one of the magnetic poles of the fixed magnet 23 is opposed to the latent image surface to form a clear developing pole, and the alternating electric field causes the toner to fly and develop on the sleeve and from the magnetic particles. (This development will be described later.)
After development, the magnetic particles and the undeveloped toner are collected in the developing container as the sleeve rotates.

The sleeve 22 may be a paper cylinder or a synthetic resin cylinder, but if the surface of these cylinders is subjected to a conductive treatment or is made of a conductor such as aluminum, brass or stainless steel, it can be used as a developing electrode roller.

The coating amount of the magnetic particles on the downstream sleeve surface of the non-magnetic blade 24 in the present invention is 5 to 100 mg / cm ² , preferably 10 to 80 mg / cm ² in order to fully utilize both the magnetic brush and the sleeve 22 surface. A small amount of about cm ² is desirable. If the amount of magnetic particles present on the surface of the sleeve is too large, the regulation force by the non-magnetic blade 24 is weakened, the sliding force between the sleeve and the magnetic particles is reduced, and the toner can be smoothly charged. Can not. Further, the magnetic particles also fly during the flight development of the toner, and the latent image carrier 3
There is a drawback that it adheres to the top. On the contrary, if the amount of the magnetic particles existing on the sleeve surface in the developing area 32 is too small, the amount of toner applied to the developing area is reduced, resulting in uneven density and reduced image density. The abundance of magnetic particles on the surface of the sleeve is mainly the gap between the sleeve 22 and N _{1 of the} fixed magnet 23.
It can be adjusted by the position of the pole and the magnetic density of the S ₁ pole.

The method for measuring the abundance of magnetic particles in the present invention is described below. First, a magnetic brush made of only magnetic particles was formed on the sleeve, and the magnetic particles in the portion corresponding to the developing area were sucked using a smooth filter paper as a filter, and the weight M (mg) was measured. Next, the remaining magnetic particles on the sleeve after the magnetic particles were attracted were sampled with a transparent adhesive tape, and the occupied area S (cm ² ) of the attracted magnetic particles was determined. The abundance m (mg / cm ² ) of magnetic particles was calculated as follows.

The gap distance d between the tip of the non-magnetic blade 24 and the surface of the developing sleeve 22 at the position of m = M / S point 25 is 50 to 750 μm, preferably 100 to 600 μm. If the distance d is less than 50 μm, magnetic particles, which will be described later, will be clogged, and the sleeve will be damaged. On the other hand, if it is larger than 700 μm, a large amount of non-magnetic toner and magnetic particles, which will be described later, leak out and a thin layer cannot be formed.

In FIG. 1, reference numeral 26 is a magnetic particle circulation region limiting member whose lower surface is in contact with the upper surface side of the non-magnetic blade 24 and whose front end surface is an undercut surface.

Denoted at 27 and 28 are magnetic particles and non-magnetic toner that are sequentially accommodated in the toner supply container 21.

The bottom plate of the toner supply container 21 is extended below the developing sleeve 22, which is a toner holding member, to prevent the toner from leaking to the outside. In order to further prevent the leakage of this toner to the outside, a leakage toner collection container portion 29 that receives and restrains the leakage toner and a scattering toner along the length of the tip edge of the extension bottom plate are provided on the upper surface of the extension bottom plate. Prevention member
30 is provided. A voltage described later is applied to this member 30.

The magnetic particles 27 generally have an average particle size of 30 to 100 μm, preferably 40 to 80 μm. Each magnetic particle may be composed of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more kinds of magnetic particles. Then, by first inserting the magnetic particles 27 into the toner supply container 21, the magnetic particles 27 from the toner supply container 21 in which the magnetic particles 27 face the inside of the container 21, that is, the sleeve 22 are arranged. Alternatively, the magnetic particle layer in the sleeve 22 is attracted and held by each magnetic field by the magnet 23 in the sleeve 22 in each part of the sleeve surface area from the magnetic member 31 for preventing the leakage of the toner to the tip of the non-magnetic blade 24 which is the magnetic particle restraining member. The entire surface area is covered. When the magnetic toner 28 is charged into the container 21 after the magnetic particles 27 are charged, a large amount of the magnetic toner 28 is stored outside the magnetic particle layer as the first layer with respect to the sleeve 22 and exists as the second layer.

It is preferable that the magnetic particles 27 to be initially charged contain about 2 to 70% (weight) of the non-magnetic toner 28 based on the magnetic particles, but the magnetic particles may be magnetic particles only. Further, once the magnetic particles 27 are adsorbed and held as a magnetic particle layer on the sleeve surface area, they do not substantially flow to one side even if the apparatus is vibrated or the apparatus is tilted to a large extent. The overall covered state is retained.

Thus, in the state where the magnetic particles 27 and the non-magnetic toner 28 are sequentially charged and contained in the container 21 as described above, the magnetic pole of the magnet 23 is
A magnetic brush of magnetic particles is formed in the magnetic particle layer portion near the surface of the sleeve corresponding to the S ₂ position by a strong magnetic field of the magnetic pole.

Further, the magnetic particle layer portion near the tip of the non-magnetic blade 24, which is a magnetic particle regulating member, is regulated based on the effect of gravity and magnetic force and the presence of the non-magnetic blade 24 even if the sleeve 22 is driven to rotate in the direction of arrow b. Due to the balance between the force and the conveying force of the sleeve 22 in the moving direction, it accumulates at a point 25 on the surface of the sleeve 22 and forms a stationary layer which can move a little but is dull.

When the sleeve 22 is rotated in the direction of the arrow b, the magnetic brush circulates in the direction of the arrow c near the magnetic pole S ₂ by appropriately selecting the position of the magnetic pole and the fluidity and magnetic characteristics of the magnetic particles 27. Form a circulating layer. In the circulation layer, the magnetic particles that are relatively close to the sleeve 22 rise from the vicinity of the magnetic pole S ₂ onto the stationary layer on the downstream side of the rotation of the sleeve by the rotation of the sleeve 22. That is, it receives the force of pushing it up. The magnetic particles pushed up, the magnetic particle circulation region limiting member 26 provided on the upper portion of the non-magnetic blade 24, because the upper limit of the circulation region is determined, it does not climb onto the non-magnetic blade 24. , It falls by gravity and returns to the vicinity of the magnetic pole S ₂ again. In this case, the magnetic particles having a small push-up force, which are received far away from the sleeve surface, may drop before reaching the magnetic particle circulation limiting member 26. That is, in the circulation layer, the magnetic brush circulates the magnetic particles as indicated by the arrow c due to the magnetic force and the frictional force due to the gravity and the magnetic poles and the fluidity (viscosity) of the magnetic particles.
During this circulation, the magnetic brush sequentially takes in the non-magnetic toner 28 from the toner layer on the magnetic particle layer and stores it in the developer supply container.
Returning to the lower part in 21, the circulation is repeated with the rotation driving of the sleeve 22.

As the developing bias voltage 34, an alternating voltage having the same peak voltage on the positive side and the negative side or a DC voltage superimposed on this alternating voltage can be used. For example, for an electrostatic latent image with a dark latent image potential of -600 V and a bright latent image potential of -200 V, as an example, a DC voltage of -300 V is superimposed on the sleeve 22 and the peak voltage of the waveform is
An alternating voltage selected in the range of V _pp 300 to 2000 V and frequency 200 to 3000 Hz is applied to hold the photosensitive drum 3 at the installation potential. Generally, the electric resistance of a magnetic brush is relatively high (greater than 10 ⁸ Ωcm), in which case the peak voltage width V _pp of the developing bias should be high (eg 800 V or higher) and the frequency should be 600 Hz or higher, preferably 800 Hz. More preferably 1k
Good image quality with sufficient density was obtained at higher frequencies above Hz. However, even if only V _pp is high, if the frequency is low, the density is low and it is difficult to obtain good image quality. In any case, the upper limit of V _pp is determined by the gap discharge limit value of the developing unit, and the lower limit is determined by the toner flight limit value on the sleeve and the magnetic particles.

Regarding the resistance of the entire developing magnetic brush, it is preferable that the resistance in the thickness direction of the developing brush is 10 ⁸ Ωcm or more when the developing brush is in contact with the latent image carrier 1.

Incidentally, the resistance value of the magnetic particles and the magnetic brush described in the present invention means the developing sleeve 22 by the developing device shown in FIG.
A magnetic brush of 50 mg / cm ² magnetic particles is formed on the top, a developing sleeve and a metal drum with a gap of about 300 μm are provided opposite to this, and a circuit of about 1 MΩ resistance is connected in series to these circuits. This is calculated and obtained from the value of the current flowing when the voltage is applied.

The development in the developing section 32 will be described below regarding the developing method according to the present invention.

2 and 3 are enlarged explanatory views of the developing section in the developing method according to the present invention. 50 is the latent image charge in the dark area on the latent image carrier. 28 is a non-magnetic toner. 34 is an alternating voltage source on which a DC component is superimposed. 2 shows the case where a plus waveform component of the alternating voltage is added to the sleeve 22, and FIG. 3 shows the case where a minus waveform component of the alternating voltage is added. The polarity of the latent image charge is shown as negative and the polarity of the developer is shown as positive.

Since the resistance of the developing brush 51 is relatively large (greater than about 10 ⁸ Ωcm), the developing brush 51 depends on the charging / discharging time constant of the charge due to the material of the developing brush 51 itself, etc. Alternatively, there is a charge injected by the mirror charge, the latent image electric field on the latent image carrier 3 and the alternating electric field between the latent image carrier 3 and the sleeve 22.

When the electric field due to the latent image charge 50 in the dark portion on the latent image carrier 3 and the electric field due to the alternating electric field coincide with each other, the developing brush 51 is in the maximum sagging state in the sleeve 22 direction.

When the direction of the electric field due to the latent image charge on the latent image carrier 3 and the direction of the electric field due to the alternating electric field do not match, the yielding of the developing brush 51 becomes small.

In any case, as described above, the developing brush is generated by the alternating electric field.
51 is in a fine but violent vibration state, and the fog toner excessively attached to the latent image holding member is rubbed by the developing brush, removed from the latent image holding member 3, and pulled back onto the brush. Further, due to the above vibration of the brush 51, the toner is easily separated from the brush 51 and easily supplied to the latent image holding member 3, so that the image density is also improved. Also a brush
The above vibration of 51 loosens the toner in the brush 51, which contributes to the improvement of image density and the prevention of ghost. Further, when this vibration state is severe, a part of the magnetic brush separates from the brush or the sleeve and reciprocates between the latent image carrier and the sleeve surface. The kinetic energy of this reciprocating brush is large and efficient, and the effect of the above-mentioned vibration is expected. The above behavior of the magnetic particles in the developing section is a phenomenon observed as a result of high-speed photography of 8000 frames per second with a high-speed camera.

The toner coating magnetic particles used in the present invention include:
Any material with a true specific gravity of 6 g / cm ³ or less can be used.For example, surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium, rare earth metals, and their alloys or oxides are used. However, a metal oxide or the like can be preferably used. Further, there is no particular limitation as a manufacturing method thereof.

Further, the surface of the magnetic particles may be coated with resin or the like.
As the treatment method, a method of mixing with powder and melting or softening with heat to adhere to the magnetic particles, a method of dissolving or suspending in a solvent and coating and adhering to the magnetic particles, a method of simply mixing with powder Any conventionally known method such as the above can be applied.

The positively chargeable copolymer used in the present invention, in order to reliably exhibit its performance and have a positive positive charge,
It is preferable that the binder resin contains 30% by weight or more, more preferably 50% by weight or more.

Further, the aminoacryl monomer as a constituent of the copolymer used in the present invention is preferably contained in the copolymer in an amount of 2 to 15% by weight. You can use all known ones,
Generally, the one represented by the following structural formula is effective.

R ₁ is hydrogen or a methyl group or an ethyl group R ₂ is an alkylene group having 1 to 4 carbon atoms R ₃ , R ₄ is an alkyl group having 1 to ₄ carbon atoms Among them, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylamino Ethyl methacrylate and diethylaminoethyl methacrylate are preferable. Further, in the present invention, all the conventionally known monomers can be used as the constituent components other than aminoacryl, but in general, vinyl monomers, particularly styrene-70% by weight of an acrylic comonomer. It is desirable to include the above. Examples of the styrene-based monomer include styrene,
Acrylic monomers such as vinyltoluene and α-methylstyrene are acrylic acid, acrylic acid methyl / ethyl / propyl / butyl / 2-ethylhexyl esters / methacrylic acid, and methacrylic acid methyl / ethyl / propyl. -Esters of butyl 2-ethylhexyl and the like can be mentioned, respectively.

In the present invention, as a method for polymerizing the copolymer, all the conventionally known methods can be used, but a homogeneous system such as bulk polymerization or solution polymerization is particularly preferable.

As the fluorine-containing resin in the present invention, all conventionally known resins can be used, but vinylidene fluoride, tetrafluoroethylene, trifluoroethylene chloride, hexafluoropropylene, hexafluoroisopropyl methacrylate and the like are preferable. Polymers or copolymers are preferable, and polyvinylidene fluoride and polytetrafluoroethylene are more preferable.

It is desirable that the fluorine-containing resin has an average particle size of 5 μm or less, preferably 2 μm or less, in order to sufficiently exhibit its ability when mixed with colored particles. The mixing ratio is such that the weight ratio of colored particles / fluorine-containing resin fine particles 10
0 / 0.1 to 100/5, more preferably 100 / 0.2 to 100/3 is desirable. As the mixing method, a device having a shearing force such as a conventionally known Henschel mixer, a tumbler blender, a device having no shearing force such as a ball mill,
Alternatively, any device such as a Nauta mixer may be used.

In the present invention, it is possible to add other resins, polymers and the like to the toner in addition to the copolymer. Examples thereof include polystyrene, polystyrene-butanediene copolymers, styrene-copolymers such as styrene-based copolymers, polyethylene, polyethylene-vinyl acetate copolymers, polyethylene-vinyl alcohol copolymers such as ethylene-based copolymers. Examples thereof include a compound, a phenol resin, an epoxy copolymer, a phenol resin, an epoxy resin, an allyl phthalate resin, a polyamide resin, a polyester resin, and a maleic acid resin. In addition, the manufacturing method and the like of each resin is not particularly limited.

As the coloring material used in the toner of the present invention, conventionally known coloring materials such as carbon black, dyes and pigments can be used.

Further, a fluidity improver such as silica or alumina may be added to the toner.

It is also possible to implement the constitution of the present invention in the microcapsule toner by using the core material, the shell material, or both of them.

EXAMPLES The present invention will be described in more detail with reference to examples. Parts shown in the examples are parts by weight.

 As the developing device, the one shown in FIG. 1 was used.

In the apparatus of the embodiment, the photosensitive drum 3 is 60
It rotates at a peripheral speed of mm / sec. 22 is a stainless steel with an outer diameter of 32 mm and a thickness of 0.8 mm that rotates at a peripheral speed of 66 mm / sec in the direction of arrow b (S
US304) sleeve, the surface of which was subjected to irregular sandblasting using # 600 alundum abrasive grains, and the circumferential surface roughness was set to 0.8 μm (R _Z =).

On the other hand, a ferrite sintered type magnet 23 is fixedly arranged in the rotating sleeve 22, and the magnetic pole arrangement is such that the maximum value of the surface magnetic flux density is about 800 gauss as shown in FIG.

As the non-magnetic blade 24, 1.2 mm-thick non-magnetic stainless steel was used so that the amount of magnetic particles present on the sleeve was 30 to 60 mg / cm ^2, and the blade-freeb gap was 300 μm.

On the surface of the photosensitive drum 3 facing the sleeve 22,
As an electrostatic latent image, a charge pattern of -150 V in the dark part and -150 V in the light part was formed, and the distance from the sleeve surface was set to 300 μm. Then, a frequency of 800 Hz is generated by the power source 34 with respect to the sleeve,
Development was performed by applying a voltage having a peak-to-peak value of 1.4 kV and a center value of -300V.

Example 1 100 parts by weight of styrene-2-ethylhexyl acrylate-diethylaminoethyl methacrylate copolymer (80: 17: 3) 100 parts by weight of red powder (that is, non-magnetic toner) consisting of 5 parts by weight of rhodamine pigment and having an average particle diameter of 12 μm. Part, 0.5 parts by weight of positively charged colloidal silica, polyvinylidene fluoride fine particles (average particle size 0.5 μ
m) 0.5 part by weight was added externally to obtain a non-magnetic toner having positively chargeable colloidal silica and polyvinylidene fluoride fine particles as external additives.

Non-magnetic toner containing the above external additive 10 parts by weight and particle size 25
When 100 parts by weight of ferrite particles between 0-350 mesh were mixed and applied to the developing device of FIG. 1 and images were produced in various environments, the image reflection densities were as high as 1.2 to 1.3.
It was a good image without fog. Also 35 ° C, 90% RH and 15
The initial image after standing for 1 month in a special environment of ℃ and 10% RH was also good.

Comparative Example An image development test was conducted in the same manner as in Example 1 except that the fine particles of polyvinylidene fluoride were not added to the developer. Before leaving it, a clear image with an image density of 1.2 to 1.3 was obtained, but when it was left for 1 month in an environment of a temperature of 35 ° C and a humidity of 90% RH, an image development test was conducted, the image density dropped to 1.1. However, fogging occurred in the non-image area.

Example 2 Styrene-butyl methacrylate-dimethylaminoethyl acrylate copolymer (80: 15: 5) 60 parts by weight Styrene-butadiene resin (80:20) 40 parts by weight Phthalocyanine pigment 4 parts by weight Blue having an average particle size of 11 μm 100 parts by weight of particles (that is, non-magnetic toner), 0.8 parts by weight of positively charged colloidal silica, polytetrafluoroethylene fine particles (average particle size 0.8 μ
m) When 1 part by weight was externally added and the same test as in Example 1 was conducted, the same good result was obtained.

Example 3 The procedure of Example 2 was repeated, except that a styrene-butyryl acrylate-dimethylaminoethyl methacrylate copolymer (82: 8: 10) was used as the positively chargeable copolymer, and the same good results were obtained. Results were obtained.

[Effects of the Invention] As described above, according to the present invention, in a developing device using magnetic particles with a simple structure, by interposing a small amount of magnetic particles in the developing area, there is no background fog and good gradation is obtained. In addition, good image quality without negative characteristics could be obtained in various environments.

Further, by effectively distributing the toner that contributes to the development on the sleeve and the magnetic particles and performing the flight development from both of them, it was possible to achieve a development efficiency of nearly 100% in an alternating electric field. This is a compact developing device configuration.
This enables simplification.

Further, the brush of magnetic particles according to the present invention was brought into contact with the latent image holding member and vibrated at least by the alternating electric field, whereby the value fog toner adhering to the latent image holding member could be removed.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a developing device according to the developing method according to the present invention, and FIGS. 2 and 3 are enlarged explanatory views of a developing portion according to the developing method according to the present invention. Developer supply container, 22 ... Non-magnetic sleeve, 23 ... Fixed magnet, 24 ... Non-magnetic blade, 26 ... Magnetic particle circulation region limiting member, 27 ... Magnetic particles, 28 ... Non-magnetic toner, 29 ... … Developer collection container part, 30 …… Scatterproof member, 31 …… Magnetic member, 32 …… Development area, 34 …… Bias power supply, 50 …… Electrostatic latent image, 51 …… Magnetic brush.

Claims (1)

(57) [Claims] 1. A developer carrying device having a magnet inside in a developing region formed between a latent image carrying member for holding a latent image and a developer carrying member facing the latent image carrying member. In an image forming method, a latent image is developed with a magnetic brush formed of a two-component developer containing a non-magnetic toner and magnetic particles while applying an alternating electric field between the body and the latent image carrier. The amount of magnetic particles conveyed to the developer carrier, the magnetic particles are circulated in the developer supply container, and the two-component developer on the developer carrier is conveyed to the developing area. In the developing area, a magnetic brush is formed so that the amount of magnetic particles present is 5 to 100 mg / cm ^2, and a copolymer containing 2 to 15% by weight of an aminoacryl monomer as a constituent is contained in the binder resin. Per 100 parts by weight of non-magnetic toner containing 30% by weight or more of The non-magnetic toner on which 0.1 to 5 parts by weight of particles are externally added is reciprocated between the surface of the developer carrying member and the surface of the magnetic brush and the latent image holding member in the developing area, and the non-magnetic toner is formed on the latent image holding member. An image forming method, which comprises forming an image.