JPH0797237B2 - Reverse 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 developer carrying member by using a dry developer and using the dry developer, and particularly to a developing method. The present invention relates to a so-called reversal development method in which toner is attached to a non-image portion of a latent image to form a visible image.

[Prior Art] Various methods have heretofore been proposed and put into 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 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 applicant has proposed JP-A-55-32060, 55-133058, 56-70560, and NP-85.
00 Practical use in 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 addition, there is room for further improvement in the life of the developer due to deterioration such as spent of the carrier.

In terms of improving the development efficiency, the one-component development method has two
Better than the component development method. Among them, in Japanese Patent Application Laid-Open No. 54-43037, which was previously filed by the applicant of the present invention, a toner thin layer of 200 μm or less is formed on the developing roller, and the toner applied on the sleeve is developed to almost 100% in the image area. Developing with efficiency. Therefore, it was possible to put the developing device into a compact and simple structure for 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. Configure the device. From the viewpoint of image quality, it is now required to improve the sharpness and resolution of a developed image. Therefore, development of a thin layer forming method for a dry developer and its apparatus are 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 a magnetic blade is used as a doctor blade for the fiber brush, the amount of toner can be regulated, but uniform coating is not performed, and the fiber of the brush is simply rubbed by rubbing the fiber brush on the developing roller. Since triboelectrification charges are not applied to the toner existing between them, there is a problem that fogging or the like is likely to occur.

Further, magnetic toners can easily prevent the toner from scattering by utilizing magnetic force, but non-magnetic toners cannot utilize magnetic force, and the 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 extremely high developing efficiency and with a small and simple developing device configuration. Particularly, in the two-component magnetic brush rubbing development, a good quality solid image was obtained without any rubbing marks generated in the solid image portion.

However, in the social situation where the application of the electrophotographic method to printers, microfilm reader printers, etc. is becoming active, there is an increasing demand for a developing method and a developer that are matched by the reversal developing method. That is, in a so-called reversal development method in which toner is attached to a non-image portion of an electrostatic latent image to form a visible image, due to its peculiarity, a development method and a developer that are more efficient than a more uniform electrostatic charge retention of the toner are required. Is required. There is also a demand for a long-life reversal development method and a developer which are not found in conventional non-magnetic toner reversal development methods.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to obtain a reversal developed image which has extremely high developing efficiency and is not inferior to the conventional developing method and the developer. The purpose is to provide a reversal development method that can be performed.

It is a further object of the present invention to provide a reversal development method in which the toner, the magnetic particles, and the developer carrying member are smoothly charged, and the toner is evenly charged and good reversal development is performed to stabilize the image. To provide.

A further object of the present invention is to provide a long-life reversal development method without deterioration such as so-called spent formation.

[Means and Actions for Solving Problems] That is, according to the present invention, the developer carrier and the latent image carrier are provided in the developing area of the developer carrier facing the latent image carrier for holding the latent image. In a reversal image forming method in which a latent image is reversal developed with a non-magnetic toner while applying an alternating electric field between it and the maximum magnetic field of 50 to 90emu which has a true specific gravity of 6 or less and is coated with an electrically insulating resin. The amount of magnetic particles present in the developing area of the developer carrier is 5 to 80 mg.
The magnetic brush is formed to be / cm ^2, and in the developing area, while the latent image carrier and the magnetic brush are in contact with each other, the non-magnetic toner (however with silicone oil is transferred from the surface of the developer carrier to the latent image carrier) (Excluding the case of having treated silica fine powder), and further, non-magnetic toner is transferred from the surface of the magnetic brush to the latent image carrier, and the latent image is reversely developed with the non-magnetic toner. The present invention relates to a reverse image forming method.

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

The reversal development method is a method in which toner is attached to the non-image portion of the electrostatic charge image formed on the latent image carrier, and the relative potential between the developer carrier and the latent image carrier. Relationship is
There is no difference from the regular development method. However, from the viewpoint of the latent image potential and the absolute value of the electrostatic charge of the toner, it can be understood that the development is unreasonably forced. For example, in the regular development method, toner having an electrostatic charge of −20 μC / g on the developer carrier set to + 100V is attached to the + 600V latent image in the image area, and the + 50V latent image in the non-image area is adhered. The development is carried out so as not to adhere to, and development according to Coulomb's law is possible. However, in the reversal development method, the toner having an electrostatic charge of +20 μC / g on the developer carrying member set to the level of + 550V must be attached to the non-image portion in the latent image of + 50V. That is, both developing methods have a relative potential difference of 55
Although the development is 0V, the former is not unreasonable according to Coulomb's law regarding the adhesion between the latent image and the toner, and the latter may be contrary to it. Due to such unavoidable characteristics, the following characteristics are required for the reversal development method. That is, (a) The transfer of toner on the latent image from the developer carrying member is smooth. Since the toner adhesion to the latent image can never be determined only by the cloning force, if the toner transfer is not smooth, the difference between the image part and the non-image part is less likely to occur, and the phenomenon such as a decrease in image reflection density and an increase in fog are likely to occur. .

(B) The electrostatic charge held by the toner is uniform and stable. In addition, it must be equipped with a mechanism that can charge the toner. If the amount of electrostatic charge on the toner is often disturbed, (a)
It is difficult to achieve the item.

The inventors of the present invention have made diligent studies on a developing method for a non-magnetic toner that satisfies the above characteristics and is small and simple, and as a result, the inventors have found that a clear developing magnetic pole is formed in the developing portion, Focus on 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 to stabilize the impartment of the triboelectric charge to the toner. It has been found that the toner supply to the toner is stabilized and the adaptability to reversal development is improved. Further, the magnetic particles used in the present invention are applied to the present development system, and the adhesion between the toner and the magnetic particles or the adhesion to the toner carrier,
By appropriately adjusting the interactions such as mold release and charging,
They have found that the flying development ability of the toner can be maximized and a good reverse image can be stably supplied over a long period of time.

Hereinafter, a) a description of the developing method, b) details of the developing mechanism, and c) the constitution of the materials will be described in this order.

a) Description of Development Method Hereinafter, the present reversal development method will be described with reference to Examples. FIG. 1 shows an example of a developing device used in the present invention. In FIG. 1, 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 magnetic or non-magnetic blade, 26 is a magnetic particle circulation region limiting member, 27 is magnetic particles, 28 is non-magnetic toner, 29 is a developer collection container part, and 30 is scattering. Preventing member, 31 is a magnetic member, 32 is a developing area, 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 magnetic or 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 same effect as that of substantially increasing the surface area of the sleeve is exhibited. From this, it is clear that the magnetic particles are different from the conventional carrier that imparts triboelectric charge to the toner. Therefore, deterioration of the developer such as spent is basically not possible.

Further, 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 definite developing pole, and the toner is fly-reversal developed on the sleeve and from the magnetic particles by the alternating electric field. (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 magnetic particles used in the present invention preferably have a high electrical resistance in order to remove discharge between the sleeve and the latent image carrier due to an alternating electric field, and the surface thereof is entirely or uniformly covered with an electrically insulating resin. It is preferably partially covered. The electrical insulating property referred to here means 10 ⁸ Ω · cm or more.

Furthermore, the magnetic particles used in the present invention are such that the magnetic brush constituted by them can behave lightly by an alternating electric field,
Further, in order to prevent external scattering, it is desirable that the specific gravity is small and the maximum magnetization is appropriate, specifically, the true specific gravity is 6 or less and the maximum magnetization is 50 to 90 emu / g.

In the present invention, the coating amount of the magnetic particles on the surface of the downstream sleeve of the magnetic or non-magnetic blade 24 is the magnetic brush and the sleeve.
In order to make full use of both surfaces, it is desirable that the amount is as small as 5 to 80 mg / cm ² , preferably 10 to 60 mg / cm ² . If the amount of magnetic particles present on the surface of the sleeve is too large, the regulation force of the blade 24 is weakened, and the frictional force between the sleeve and the magnetic particles is reduced, so that the toner cannot be charged smoothly. Further, there is a drawback that the magnetic particles also fly during the flight development of the toner and adhere to the latent image carrier 3. 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 amount of magnetic particles present on the surface of the sleeve mainly depends on the gap between the sleeve 22 and N of the fixed magnet 23.
_It can be adjusted by the position of the ₁ pole, the density of the S ₁ pole as much as possible, and the like.

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, magnetic particles in a portion corresponding to the developing area were sucked using a cylindrical filter 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.

m = M / S The developing area means an area having a width of 10 mm in the front-rear direction in the sleeve circumferential direction with the closest position between the latent image holding member and the developer carrying member as the center.

The gap distance d between the tip of the non-magnetic blade 24 and the surface of the developing sleeve 22 at the point 25 is 50 to 650 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 650 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 magnetic or 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 introducing the magnetic particles 27 into the toner supply container 21, the magnetic particles 27 from the toner supply container 21 in which the sleeve surface region where the magnetic particles 27 face the inside of the container 21, that is, the sleeve 22 is disposed. Or, a sleeve is provided on each part of the sleeve surface area from the magnetic member 31 for preventing the leakage of toner to the tip of the blade 24 which is a magnetic particle restraining member.
A magnetic particle layer is attracted and held by the magnetic field of the magnet 23 inside the layer 22, and the sleeve surface region is entirely covered as a magnetic particle layer.
The non-magnetic toner 28 is charged into the container 21 after the magnetic particles 27 are charged therein, so that a large amount of the non-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 in the sleeve surface area, they do not substantially drift even if the apparatus is vibrated or the apparatus is tilted considerably, and the sleeve surface area is prevented from flowing. The overall covered state is retained.

With the magnetic particles 27 and the non-magnetic toner 28 successively charged and stored in the container 21 as described above, the magnetic particle layer portion near the sleeve surface corresponding to the magnetic pole S ₂ position of the magnet 23 has a strong magnetic pole. The magnetic field forms a magnetic brush of magnetic particles.

Further, the magnetic particle layer portion in the vicinity of the tip of the blade 24, which is a magnetic particle restricting member, has a restricting force based on the effect of gravity and magnetic force and the presence of the blade 24 even if the sleeve 22 is rotationally driven in the direction of arrow b, By the balance with 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.

Further, when the sleeve 22 is rotated in the direction of arrow b, the magnetic brush circulates in the direction of 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. , Forming a circulation layer. In the circulation layer, the magnetic particles that are relatively close to the sleeve 22 rise up 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 are
Since the magnetic particle circulation area limiting member 26 provided on the upper portion of the blade 24 determines the upper limit of the circulation area, it does not ride on the blade 24, 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, such as being located far from the sleeve surface, may fall before reaching the magnetic particle circulation region 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 gravity and magnetic poles and the fluidity (viscosity) of the magnetic particles. The non-magnetic toner 28 is sequentially taken in from the toner layer above the layer and returned to the lower portion in the developer supply container 21, and this circulation is repeated as the sleeve 22 is rotationally driven.

The present inventors have found that in order to apply a smooth charge to the toner, the circulation of magnetic particles in the C direction and the contact and rubbing of the sleeve surface with the magnetic particle layer are important. Furthermore, these phenomena cause the maximum magnetization of magnetic particles (external magnetic field 5000
It has been found that it is greatly affected by the magnetization at e or the saturation magnetization at an external magnetic field of less than that.

That is, when the maximum magnetization of the magnetic particles is large, the magnetic field formed by the magnetic brush on the sleeve and the magnet in the sleeve is large, and the contact between the magnetic particles and the sleeve surface,
Although this is desirable for rubbing, if this magnetic field is too strong, the magnetic particles are strongly bound to the strong magnetic poles of the magnet, and the circulation movement of the magnetic particles due to the rotation of the sleeve described above is hindered, causing streaks in the non-magnetic toner coating layer. And unevenness are likely to occur. Therefore, a weaker magnetic field tends to be desirable in order to promote the circulating motion of magnetic particles. However, if the magnetic field is too weak, the problem that magnetic particles adhere to the latent image carrier in the developing area 32 may occur. This tendency is more remarkable in the reversal development in which the uniformity of the charge application to the toner is required more.

In order to obtain a high-quality image by smooth and uniform charge application to toner suitable for reversal development, the inventors of the present invention have clarified the phenomenon as described above to obtain the maximum magnetization of magnetic particles (at an external magnetic field of 5000e). We have found that the magnetization value or the saturation magnetization value in an external magnetic field below that should be set to 50 to 90 emu / g.

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, with respect to an electrostatic latent image with a dark portion latent image potential of −600 V and a bright portion latent image potential of −50 V, for example, a DC voltage of −500 V is superimposed on the sleeve 22 to change the frequency and peak-to-peak voltage of the AC component. When development was performed, a correlation diagram as shown in FIG. 4 was obtained.

If the frequency is less than 1000 Hz, the vibration and flight of the magnetic particles are not sufficient, and the magnetic brush marks are likely to appear in the developed image, which is not preferable. On the other hand, if it exceeds 3000 Hz, both the toner and the magnetic particles will not follow the electric field, resulting in a thin image and easy fog, which is not preferable. The area shaded by a vertical line is an area where discharge easily occurs between the sleeve and the photoconductor, and this value becomes even lower in the area where the high atmospheric pressure is low. The region shaded with a horizontal line is a region where background fog is likely to occur in the background portion, and the region shaded with a diagonal line is a region in which magnetic particles do not fly sufficiently in voids. Therefore, it is preferable to perform the development in the area surrounded by these lines. Further, from the viewpoint of image density gradation (fogging, latitude, etc.), it is more preferable that the frequency is in the range of 1.2 to 2 KHz and V _pp is in the range of 800 to 1500 V.

More preferably, the range of 1.4 to 1.8 KHz and 1000 to 1350 V _pp is good. Similarly, the SD (sleeve-photoreceptor) interval is 25
When the development was carried out under the same setting by changing the thickness from 0 to 700 μm, the best image was obtained when the alternating electric field shown in Table 1 was applied.

From a similar experiment, in practical use, the frequency is 1 to 2.2 KHz, V _pp 800
˜2200, SD gap 250 to 700 μm, almost good images were obtained. If the SD gap is set to 800 μm or more, it is not preferable because even if the alternating electric field voltage is increased, the reproduction of fine lines is deteriorated.

In any case, the upper limit of V _pp is determined by the gap discharge limit value of the developing section, and the lower limit thereof is determined by the toner flight limit value on the sleeve and the magnetic particles.

Taking the above into consideration, the resistance of the entire developing magnetic brush is preferably 10 ⁸ Ωcm or more in the thickness direction of the developing brush when the latent image holding member 3 is in contact with the developing brush.

The resistance value of the magnetic particles and the magnetic brush described in the present invention means that the developing sleeve 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.

b) Details of developing mechanism The phenomenon 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 reversal 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 power supply on which a DC component is superimposed. FIG. 2 shows the case where a minus waveform component of the alternating voltage is applied to the sleeve 22, and FIG. 3 shows the case where a plus 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 negative.

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 do not match, 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 coincide with each other, the sagging of the developing brush 51 becomes small, and the developing brush 51 comes into contact with the latent image carrier.

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 vibration of the brush, the toner is easily separated from the brush 51 and is easily supplied to the latent image holding member 3, so that the image density is also improved. Also brush 51
The above-mentioned vibration loosens the toner in the brush 51, which contributes to improvement of image density and prevention of ghost. further,
When this vibrating 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.

c) Composition of Material As the magnetic particles for toner coating used in the present invention, any magnetic particles having a true specific gravity of 6 or less and a maximum magnetization of 50 to 90 emu / g can be used, for example, surface-oxidized or unoxidized iron. ,
Metals such as nickel, cobalt, manganese, chromium, and rare earths, and alloys or oxides thereof can be used, but metal oxides, more preferably ferrite particles, can be used. Further, there is no particular limitation as a manufacturing method thereof.

Further, as a method of coating the surface of the magnetic particles with a resin or the like, a method of dissolving or suspending a coating material such as a resin in a solvent and applying the coating material onto a carrier, a method of simply mixing with a powder, and the like are conventional. Any known method can be applied.

The coating resin for the surface of the carrier varies depending on the toner material, but for example, polytetrafluoroethylene / monochlorotrifluoroethylene polymer / polyvinylidene fluoride / silicone resin / polyester resin / ditertiary butyl salicylic acid metal complex, styrene resin -Acrylic resin, polyacid, polyvinyl butyral, nigrosine, aminoacrylate resin, basic dye and its lake, silica fine powder, alumina fine powder, etc. are suitable, but not limited thereto.

The amount of the above compound to be treated may be appropriately determined so that the carrier satisfies the above conditions, but in general, the total amount is preferably 0.1 to 30% by weight (preferably 0.5 to 20% by weight) based on the carrier of the present invention.

On the other hand, as the binder resin of the toner used in the present invention,
Polystyrene, homopolymers of styrene such as poly-p-chlorostyrene, polyvinyltoluene and the like and substituted products thereof; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-vinyl. Naphthalene 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-acryl-aminoacrylic copolymer, styrene-
Amino acrylic copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer Styrene-based copolymers such as polymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acryloylyl-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer ; Polymethylmethacrylate,
Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin-modified rosin, terpene resin, phenol resin, aliphatic or alicyclic carbonization Hydrogen resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination.

In the toner, any suitable pigment or dye can be used as a colorant. For example, there are known facial cleansers such as carbon black, iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow.

Further, as a charge control agent, an amino compound, a quaternary ammonium compound and an organic dye, particularly a basic dye and a salt thereof,
Benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride, nigrosine base, nigrosine hydrochloride, safranine γ and crystal violet, metal-containing dyes, salicylic acid-containing metal compounds and the like may be added. Further, magnetic powder may be added to the extent that the effects of the present invention are not impaired.

The above toner composition may be used for a toner by a commonly used mixing-pulverizing method, or may be used for a wall material or a core material of a micro couple toner, or both.

EXAMPLES The present invention will be described in more detail with reference to examples. Parts given 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 in the direction of arrow a.
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 so that the roughness of the circumferential surface was 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 poles are arranged as shown in FIG.
The maximum value of surface magnetic flux density was about 800 gauss.

The blade 24 was made of 1.2 mm thick non-magnetic stainless steel. The blade-sleeve gap was 200 μm.

On the surface of the photoconductor drum 3 facing the sleeve 22, an electric charge pattern of a dark portion of −600 V and a light portion of −150 V was formed as an electrostatic latent image, and the distance from the sleeve surface was set to 300 μm. Then, a reversal development was carried out by applying a voltage of 1800 Hz, a peak-to-peak value of 1.4 kV and a center value of -450 V to the sleeve by a power source 34.

Example 1 Polyester resin 100 parts To a blue powder having an average particle diameter of 12 μm consisting of 5 parts phthalocyanine pigment, 0.3% by weight of colloidal silica surface-treated with dimethylsilane was added,
Toner.

In addition, ferrite particles (particle size 200 to 300 mesh, true specific gravity 5.1, maximum magnetization 63 emu / g) surface-coated with styrene-methyl methacrylate copolymer (electrical resistance 10 ¹⁴ Ωcm or more) were prepared as magnetic particles.

The toner and magnetic particles are mixed at a weight ratio of 12: 100,
The negative electrostatic latent image shown in FIGS. 1 and 2 was applied to a developing device for visualizing the latent electrostatic image by reversal development, and the amount of magnetic particles present on the sleeve in the developing portion was m = 45 mg / cm ² . When the image is output with the settings so that a clear image with good gradation and no fog is obtained, the image reflection density is 1.
It was 45.

Further, almost no adhesion of magnetic particles on the photosensitive drum 22 or toner scattering from the developing device was observed.

Further, when the durability of the developer was examined to determine the durability of 100,000 sheets, a clear image without fog (image density 1.43) was obtained as in the initial stage. On the other hand, when the same image was produced in a high temperature and high humidity environment (30 ° C, 90% RH),
The image density was 1.39, and an image free from problems such as fog was obtained. In addition, clear and fog-free images were obtained even in low-temperature and low-humidity environments (10 ° C, 10%).

Comparative Example 1 The same operation as in Example 1 was carried out except that the amount of magnetic particles present in the developing portion was set to m = 200 mg / cm ^2, and the resulting image was good, but toner scattering / latent image Many magnetic particles adhered to the surface and mechanical troubles of the device occurred frequently.

Comparative Example 2 Spherical iron powder surface-coated as magnetic particles as in Example 1 (particle size 200 to 300 mesh, true specific gravity 8.1, maximum magnetization 180 emu /
Example 1 was repeated except that g) was used.
The alternating electric field leaked to the photoconductor through the magnetic brush, resulting in damage to the photoconductor. Therefore, when the amount of resin coated on the surface was increased by 20 times (true specific gravity 7.1, maximum magnetization 150emu / g), somehow the leak was subsided, but the treated iron powder could not be evenly present on the sleeve surface, which was good. No image was obtained.

Example 2 Ferrite particles surface-coated with a silicone resin (particle size 25
All were carried out in the same manner as in Example 1 except that 0 to 350 mesh, true specific gravity 4.7, and maximum magnetization 81emu / g) were used as magnetic particles so that m = 15 mg / cm ^2. Good results were obtained.

Example 3 The same procedure as in Example 2 was carried out except that m = 85 mg / cm ² was set, but adhesion of magnetic particles to the latent image was slightly observed, but a good image was obtained without any particular problem. Was given.

Example 4 The electrical performance of the developing device of Example 1 was reversed so that a positive charge latent image could be reversed-developed.

Next, styrene-2-ethylhexyl acrylate-dimethylamino ethyl acrylate copolymer 100 parts (85: 12: 3) Rhodamine pigment 5 parts To a red powder having an average particle size of 11 μm, 0.5% of positively charged colloidal silica was added. , And toner.

As the magnetic particles, styrene-butyl methacrylate copolymer 80 parts and magnetite fine powder 120 parts were kneaded, pulverized, and classified to have an average particle diameter of 60 μm (true specific gravity 2.4, maximum magnetization 51 emu / g). .

When 10 parts of the above toner and 100 parts of magnetic particles were mixed and charged into the above apparatus and set to m = 12 mg / cm ² to produce an image, the same good results as in Example 1 were obtained. Was obtained.

Comparative Example 3 The same procedure as in Example 4 was carried out except that m = 1 mg / cm ² was set. As a result, the image was thin as a whole, and the image density at the trailing edge of the image was reduced particularly in the case of a large consumption document. Was noticeable.

Comparative Example 4 As magnetic particles, 120 parts of styrene-butyl methacrylate copolymer and 80 parts of magnetite fine powder were kneaded, pulverized and classified to have an average particle diameter of 60 μm (true specific gravity of 1.5, maximum magnetization of 41 emu / g). Was carried out in the same manner as in Example 4, and remarkable adhesion of magnetic particles was observed on the photoconductor.

[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 reversal image quality without negative characteristics could be obtained.

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, the development efficiency of nearly 100% could be achieved in the alternating electric field. This is a compact developing device configuration.
This enables simplification.

Further, the magnetic particles used in the present invention have a function of increasing the sleeve surface area and improving the developing efficiency, unlike a so-called carrier, which is a triboelectrification-imparting agent for toner, so that it is called so-called carrier spent. There was no deterioration of the developer, and the durable life was dramatically increased.

Further, at least the alternating electric field caused the brush of magnetic particles according to the present invention to come into contact with the latent image carrier and vibrate, whereby the background fog toner adhering to the latent image carrier could be removed.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a developing device according to the developing method of the present invention, FIGS. 2 and 3 are enlarged explanatory views of a developing section in the developing method of the present invention, and FIG. 4 is development of the developing device of the present invention. It is a figure which shows the example of a characteristic curve. 3 ... Latent image holding member, 21 ... Developer supply container, 22 ... Non-magnetic sleeve, 23 ... Fixed magnet, 24 ... Magnetic or non-magnetic blade, 26 ... Magnetic particle circulation region limiting member, 27 ... … Magnetic particles, 28 …… Non-magnetic toner, 29 …… Developer collection container, 30 …… Scattering prevention member, 31 …… Magnetic member, 32 …… Development area, 34 …… Bias power supply, 50 …… Static Electric latent image, 51 ... Magnetic brush.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G03G 15/08 507 L 15/09 Z (72) Inventor Hiroyuki Kobayashi 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 Canon Inc. (72) Inventor Mitsuru Uchida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-61-277962 (JP, A)

Claims (1)

[Claims] 1. A latent image is formed by applying an alternating electric field between the developer carrying body and the latent image carrying body in a developing area of the developer carrying body facing the latent image carrying body for holding the latent image. In a reversal image forming method of reversal development with a non-magnetic toner, development of a developer carrier is carried out by magnetic particles having a true specific gravity of 6 or less and a maximum magnetization of 50 to 90 emu / g covered with an electrically insulating resin. The amount of the magnetic particles present in the region is 5 to 80 mg
The magnetic brush is formed to be / cm ^2, and in the developing area, while the latent image carrier and the magnetic brush are in contact with each other, the non-magnetic toner (however with silicone oil is transferred from the surface of the developer carrier to the latent image carrier) (Excluding the case of having treated silica fine powder), and further, non-magnetic toner is transferred from the surface of the magnetic brush to the latent image carrier, and the latent image is reversely developed with the non-magnetic toner. Reverse image forming method.