JPH0797236B2 - Image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image developing method using magnetic brush development which can be preferably used in a digital printer or the like operating electrophotography.

[Prior Art] Conventionally, various methods have 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 a uniform toner concentration each time the developing roller rotates in order to obtain a predetermined sufficient developing concentration. For this reason, the structure of the developing device has become large and complicated. Of course, attempts have been made to improve the developing efficiency even in this type of developing method. For example, the applicant
Proposed 55-32060, 55-133058, 56-70560, and NP-8500
It has been put to 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.

The one-component developing method is superior to the two-component developing method in terms of improving the developing efficiency. 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 can be formed by anyone other than the applicant. It constitutes a developing 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 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, with the diversification of the output information from the reader unit that reads the image of the document, the printer unit is also desired to be able to meet such diversification,
In particular, as a digital printer, in order to develop a latent image formed with a laser beam spot diameter of about 50 to 150 μm with high resolution, it is desired to develop a developing method and a developer that further improve the developed image quality. It was rare.

[Problems to be Solved by the Invention] As described above, in order to sufficiently exhibit the excellent functions of the digital printer, it is necessary for the developer to have high performance and to be an optimal developing method for the developer.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to provide an image forming method capable of obtaining a solid developed image having extremely high developing efficiency and not inferior to the conventional developing method.

A further object of the present invention is to provide an image forming method in which a solid image is stabilized by smoothly charging the toner, the magnetic particles and the developing roller.

A further object of the present invention is to provide an image forming method that reduces the adhesion of magnetic particles to an electrostatic holder and the scattering of toner.

A further object of the present invention is to provide a high resolution image forming method capable of faithfully reproducing a latent image formed with a spot diameter of about 50 to 150 μm.

[Means and Actions for Solving Problems] That is, the present invention converts an image of a document into an electric signal,
An electrostatic latent image is formed on the latent image carrier according to the electric signal,
Then, the electrostatic latent image is developed with a non-magnetic toner while applying an alternating electric field between the latent image carrier and the developer carrier in the developing area of the developer carrier which faces the latent image carrier. In the image forming method described above, the non-magnetic toner is provided with a triboelectric charge of 3 to 30 μC / g in absolute value, the true specific gravity is 6 or less, and the electrical insulation is substantially the same as the binder resin of the non-magnetic toner. A magnetic brush is formed by the magnetic particles coated with a functional resin so that the amount of the magnetic particles present is 5 to 80 mg / cm ^{2 in} the developing area of the developer carrying member. And the magnetic brush are brought into contact with each other, the non-magnetic toner is transferred from the surface of the developer carrying member to the latent image holding member, and the non-magnetic toner is transferred from the surface of the magnetic brush to the latent image holding member. Develop the image with non-magnetic toner (except for reversal development) An image forming method, characterized in that.

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 inventors of the present invention proposed the above-mentioned Japanese Patent Application Laid-Open No. 58-143360 and, as a result of diligent research on its improvement, as a result, a clear developing magnetic pole was formed in the developing section to perform locally concentrated development. In the one-component developing method, the triboelectrification 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 triboelectrification of the toner. It was found that the toner supply can be stabilized and image quality such as gradation and uniformity can be improved. Further, the magnetic particles and the non-magnetic toner used in the present invention have an appropriate interaction such as adhesion, release, charging, etc. with the magnetic particles of the toner or with the toner carrier when applied to the present developing method. It has been found that by adjusting the value to 1, the ability of the toner to fly can be maximized and a good image can be stably supplied over a long period of time.

That is, the spot diameter is 50 to 150 μm only when the main developing method is applied to the developer used in the present invention.
It became possible to faithfully reproduce the latent image formed to a certain degree, and it became possible to control the density of the developed image and to control the thickening / thinning of the developed image.

The present inventors consider this reason as follows. That is, unlike the conventional two-component development method, by combining the main developer and the main development method, it is possible to increase the development efficiency to nearly 100% and stabilize the toner development amount on the high potential side of the latent image potential. Has been achieved, which is ideal for ON-OFF development of digital printers. More specifically, since the surface of the magnetic particles is covered with an electrically insulating resin having substantially the same structure as the non-magnetic toner, the non-magnetic toner flies well from the magnetic particles in the developing area, and the developing efficiency is improved. I think it has become possible to raise it. Further, since the magnetic particles and the toner particles have good stirring property and dispersibility, the toner particles are provided as individual particles for development.
We believe that the spot diameter of μm can be faithfully reproduced. Furthermore, since light magnetic particles are used, it is considered that the developer is less likely to be deteriorated due to the light load, the developing property is not deteriorated due to the durability, and the agglomeration does not occur, so that a stable developed image can be always obtained.

The latent image forming method used in the present invention may be any as long as the light source or the optical path is turned on and off according to an electric signal, but generally a semiconductor laser light source or a liquid crystal shutter is often used. .

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 main 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, 1 is a latent image holding member, 2 is a toner supply container, 3 is a non-magnetic sleeve, 4 is a fixed magnet, 5 is a magnetic or non-magnetic blade, 7 is a magnetic particle circulation region limiting member, and 8 is magnetic particles. ,
Reference numeral 9 is a non-magnetic toner, 10 is a developer collecting container portion, 11 is a scattering prevention member, 12 is a magnetic member, 13 is a developing region, and 14 is a bias power source. The sleeve 3 rotates in the b direction, and the magnetic particles 8 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 non-magnetic blade 5 and the sleeve 3, and is applied onto the non-magnetic 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.

In the developing region 13, one of the magnetic poles of the fixed magnet 4 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 3 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.

Further, the magnetic particles used in the present invention preferably have a low specific gravity so that the magnetic brush constituted by the magnetic particles can behave smoothly by an alternating electric field, and specifically, the true specific gravity is preferably 6 or less.

The coating amount of the magnetic particles on the downstream sleeve surface of the magnetic or non-magnetic blade 5 in the present invention is 5 to 80 mg / cm ² , preferably 10 to 10 in order to fully utilize both the magnetic brush and the surface of the sleeve 3. It is desirable that the amount is as small as 60 mg / cm ² . If the amount of the magnetic particles present on the surface of the sleeve is too large, the regulation force of the blade 5 is weakened, and the rubbing 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 1. Further, as the sleeve peripheral speed becomes faster, the regulation by the fixed magnet becomes weaker and the scattering of the developer becomes remarkable. On the contrary, when the amount of the magnetic particles existing on the sleeve surface in the developing area 13 is too small, the amount of toner applied to the developing area is reduced, resulting in uneven density and image density. The amount of magnetic particles present on the surface of the sleeve can be adjusted mainly by the gap with the sleeve 3, the position of the N ₁ pole of the fixed magnet 4, the maximum density of the S ₁ pole, 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 of 10 mm in the front and rear in the sleeve circumferential direction with the closest position between the latent image holding member and the developer carrying member as the center.

The tip of the blade 5 and the developing sleeve 3 at the point 6 position
The distance d between the surface and the surface is 50 to 650 μm, preferably 100 to
It is 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, 7 is a magnetic particle circulation region limiting member in which the lower surface is in contact with the upper surface side of the blade 5 and the front end surface is an undercut surface.

Reference numerals 8 and 9 denote magnetic particles and non-magnetic toner that are sequentially accommodated in the toner supply container 2.

The bottom plate of the toner supply container 2 is extended below the developing sleeve 3, 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 10 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
11 are provided. A voltage described later is applied to this member 11.

The magnetic particles 8 generally have an average particle size of 30 to 65 μm, preferably 35 to 60 μm. If the particle size is smaller than 30 μm, the magnetic particles are likely to be developed on the latent image carrier, and the latent image carrier and the cleaning blade are easily damaged. On the other hand, if the particle size is
If it is larger than 65 μm, the ability of the magnetic particles to retain the toner is deteriorated, resulting in non-uniformity of a solid image, toner scattering, and fog.
The non-uniformity of the solid image is a fatal defect because the digital printer is on-off development for the latent image. 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 8 into the toner supply container 21, the magnetic field from the toner supply container 2 in which the magnetic particles 8 face the inside of the container 2, that is, the sleeve 3 is disposed. In addition, the sleeve surface area from the magnetic member 12 for preventing the leakage of the toner to the tip of the blade 5 serving as the magnetic particle restraining member is attracted and held by the magnetic field of the magnet 4 in the sleeve 3 to the sleeve surface area as a magnetic particle layer. It will be in a state of covering the whole. The non-magnetic toner 9 is stored in a large amount outside the magnetic particle layer as the first layer with respect to the sleeve 3 by being charged into the container 2 after the magnetic particles 8 are charged, and is present as the second layer.

The magnetic particles 8 to be initially charged preferably originally contain about 2 to 30% by weight of the non-magnetic toner 9 with respect to the magnetic particles, but may include only the magnetic particles. Further, once the magnetic particles 8 are adsorbed and held as a magnetic particle layer in 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 state of covering the whole is maintained.

Thus, in the state where the magnetic particles 8 and the non-magnetic toner 9 are sequentially charged and contained in the container 2 as described above, the magnetic particle layer portion near the sleeve surface corresponding to the magnetic pole S ₂ position of the magnet 4 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 5 serving as a magnetic particle regulating member has a regulating force based on the effect of gravity and magnetic force and the presence of the blade 5 even if the sleeve 3 is rotationally driven in the direction of the arrow b, and the sleeve. By the balance with the conveying force of 3 in the moving direction, it accumulates at the point 6 position on the surface of the sleeve 3 and forms a stationary layer which can move a little but is difficult to move.

Further, when the sleeve 3 is rotated in the direction of the arrow b, the magnetic brush is arranged 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 8.
Circulates in the direction to form a circulation layer. In the circulation layer,
The magnetic particles relatively close to the sleeve 3 swell from the vicinity of the magnetic pole S ₂ onto the stationary layer on the downstream side of the rotation of the sleeve 3 by the rotation of the sleeve 3. That is, it receives the force of pushing it up. The amount of the magnetic particles thus pushed up is determined by the magnetic particle circulation region limiting member 7 provided on the upper part of the blade 5, and the upper limit of the circulation region is determined. Then
It 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 7. That is, in the circulation layer, the magnetic brush of magnetic particles is circulated as indicated by an arrow c due to the magnetic force and frictional force due to gravity and magnetic poles, and the fluidity (viscosity) of the magnetic particles. The non-magnetic toner 9 is sequentially taken in from the toner layer on the upper side and returned to the lower portion in the developer supply container 2, and this circulation is repeated as the sleeve 3 is rotationally driven.

As the developing bias power source 14, 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 3 to develop the AC component by changing the frequency and the peak-to-peak voltage. As a result, the correlation diagram as shown in FIG. 6 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 carrier 1 is in contact with the developing brush.

The resistance value of the magnetic particles and the magnetic brush described in the present invention means the developing sleeve 3 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.

b) Details of developing mechanism The phenomenon in the developing section 13 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. Reference numeral 21 is the latent image charge in the dark area on the latent image carrier. 9 is a non-magnetic toner. 14 is an alternating voltage power source on which a DC component is superimposed. FIG. 2 shows a case where a negative waveform component of the alternating voltage is applied to the sleeve 3, and FIG. 3 shows a case where a positive 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 22 is relatively large (greater than about 10 ⁸ Ωcm), the developing brush 22 depends on the charging / discharging time constant of the electric charge due to the material of the developing brush 22 itself, etc. Alternatively, there is an electric charge injected by the mirror charge, the latent image electric field on the latent image carrier 1 and the alternating electric field between the latent image carrier 1 and the sleeve 3.

When the electric field due to the latent image charge 21 in the dark portion on the latent image carrier 1 and the electric field due to the alternating electric field do not match, the developing brush 22 is in the maximum sagging state in the sleeve 3 direction.

When the direction of the electric field due to the latent image charge on the latent image carrier 1 and the direction of the electric field due to the alternating electric field coincide with each other, the yield of the developing brush 22 becomes small and the developing brush 22 comes into contact with the latent image carrier.

In any case, as described above, the developing brush is generated by the alternating electric field.
22 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 1, and pulled back onto the brush. Further, due to the above-mentioned vibration of the brush, the toner easily comes off from the brush 22 and is easily supplied to the latent image holding body 1, so that the image density also improves. Further, the above vibration of the brush 22 loosens the toner in the brush 22,
This contributes to improvement of image density and 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.

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 can be used, for example, surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium. , Metals such as rare earths, and alloys or oxides thereof can be used, but preferably metal oxides, more preferably ferrite particles can be used. Moreover, there is no particular limitation in the manufacturing method.

Further, as a method of coating the surface of the magnetic particles with a resin, a conventionally known method such as a method of dissolving or suspending a resin in a solvent and applying it to adhere to the magnetic particles, a method of simply mixing with a powder, etc. Both are applicable.

The resin for coating the magnetic particles may be an electrically insulating resin having substantially the same structure as the non-magnetic toner (including those having different ratios). For example, it is suitable to use a polyester resin, a styrene resin, an acrylic resin, etc. alone or in combination. Among them, polyester is preferable in view of charging stability, dispersion and stirring stability of magnetic particles and non-magnetic toner. Resins are preferred. Further, for the purpose of stabilizing the charging between the magnetic particles and the non-magnetic toner, silica fine powder, alumina fine powder, polytetrafluoroethylene, within a range that does not reduce the flight property of the non-magnetic toner from the magnetic particles in the developing region, Monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin and the like may be contained in the polyester resin alone or in plural.

The treatment amount of the above resin may be appropriately determined so that the magnetic particles satisfy 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 magnetic particles.

The coating resin for the magnetic particles and the polyester resin for the non-magnetic toner used in the present invention are synthesized from an aliphatic acid, an aromatic acid and a bisphenol alcohol. Preferred aliphatic acids include, for example, succinic acid, adipic acid, fumaric acid, maleic acid, sebacic acid, glutaric acid, and examples of preferred aromatic acids include phthalic acid, isophthalic acid, terephthalic acid or their An acid anhydride or the like is used. Further, as preferable bisphenol alcohols, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) ethane, 2,2
-Bis (4-hydroxyphenyl) methane, 4,4'-dihydroxydiphenyl ether and the like are used.

Further, if necessary, polystyrene, poly (p-chlorostyrene), homopolymers of styrene such as polyvinyltoluene, and substitution products thereof; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers. Coal, 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-acryl-aminoacrylic copolymer, styrene-aminoacrylic 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-butadiene copolymer, styrene -Styrene-based copolymers such as isoprene copolymer, styrene-acryloylyl-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, poly Vinyl chloride, poly Vinyl acid, polyethylene, polypropylene, polyester, polyurethane, polyamide,
Epoxy resin, polyvinyl butyral, 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 mixed and used. .

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

Further, the non-magnetic toner needs to contain a charge control agent. Examples of such charge control agents include metal-containing dyes and salicylic acid metal-containing compounds. In particular, the effect of the present invention is further exhibited by containing an alkylsalicylic acid or a metal chelate of salicylic acid. Further, magnetic powder may be added to the extent that the effects of the present invention are not impaired. In particular, the effect of the present invention is further exhibited by containing an alkylsalicylic acid or a metal chelate of salicylic acid.

At that time, the charge amount of the magnetic particles and the toner is 3 to 30 μC / g.
(Preferably 5 to 25 μC / g) is desirable. If the charge amount is larger than 30 μC / g, the separation between the toner and the magnetic particles is poor and the developability deteriorates, resulting in uneven density and density. On the contrary, if the charge amount is smaller than 3 μC / g, the magnetic particles restrain the toner. , Toner scattering, fog, etc. occur.

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 macrocapsule toner or both.

Here, a method of measuring the triboelectric charge amount of the magnetic particles of the toner in the present invention will be described in detail with reference to the drawings.

FIG. 4 is an explanatory diagram of the triboelectric charge amount measuring device. 400 at the bottom
A magnetic brush (on the toner and the magnetic particles) on the developer carrier for measuring the triboelectric charge amount in a metal measuring container 42 having a conductive screen 43 of a mesh (which can be appropriately changed to a size through which magnetic particles do not pass). Mixture) put a metal lid
Play 44 At this time, the weight of the entire measuring container 42 is weighed and W ₁
(G). Next, in the suction device 41 (at least the portion in contact with the measurement container 42 is an insulator), suction is performed from the suction port 47 to adjust the air volume control valve 46 to adjust the pressure of the vacuum gauge 45 to 70 mmHg. In this state, suction is sufficiently performed (for about 1 minute) to remove the toner by suction. The potential of the electrometer 49 at this time is V (volt). Here, 48 is a condenser, and the capacity is C
(ΜF). The weight of the entire measuring container after suction is weighed and is W ₂ (g). The triboelectric charge amount T (μC / g) is calculated by the following formula.

However, the measurement conditions are 23 ° C and 50% RH.

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 1 is 60 mm in the direction of arrow a.
Rotate at a peripheral speed of / second. 3 is stainless steel with an outer diameter of 32 mm and a thickness of 0.8 mm that rotates in the direction of arrow b at a peripheral speed of 66 mm / sec (SUS
304) sleeve, the surface of which was subjected to irregular sand blasting 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 4 is fixedly arranged in the rotating sleeve 3, 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. The blade 5 used was 1.2 mm thick non-magnetic stainless steel. Blade-sleeve clearance is 200
μm. An amorphous silicon drum was used as a latent image holder facing the sleeve 3, and a charge pattern of a bright portion +90 V was formed at a dark portion 450 V as an electrostatic latent image, and the distance from the sleeve surface was set to 300 μm. Then, a voltage of 1500 Hz, a peak-to-peak value of 1.4 kV and a center value of 200 V was applied to the sleeve by the power source 14 to perform development.

The latent image forming device shown in FIG. 5 was used.

The laser light is turned on / off in response to the electric signal sent from the reader to reproduce the bright and dark parts of the original on the latent image carrier 1. The laser light emitted from the laser unit 51 is applied to a polygonal mirror (polygon mirror 53) that rotates at high speed by a scanner motor 52, and the reflected light is passed through an imaging lens 54 to the surface of the latent image holder 1. It is illuminated to form a latent image.

Example 1 Succinic acid and 2,2-bis (4-hydroxyphenyl)
Polyester resin consisting of propane (5: 5) 100 parts Rhodamine pigment 5 parts Chromium complex compound of 3,5-di-t-butylsalicylic acid 2 parts To a red powder having an average particle size of 11 μm, 0.5% by weight of colloidal silica is added. The toner was added.

As the magnetic particles, ferrite particles (particle size) coated with 2 parts of the polyester resin in which a rhodamine dye is dispersed are used.
Between 250 to 350 mesh, average particle size 46 μm, true specific gravity 5.1) were prepared.

The above toner and magnetic particles were mixed at a weight ratio of 9:91 and applied to the developing device shown in FIG. 1, and the amount of magnetic particles present on the sleeve in the developing section was set to m = 40 mg / cm ^2. When the image was printed out, a high-resolution image without fog was obtained, and the solid image reflection density was 1.3. The charge amount at this time was −10.2 μC / g (23 ° C., 65%). In addition, the adhesion of magnetic particles on the latent image carrier 22 and the toner scattering from the developing device were hardly seen. Further, when the durability of the developer was examined to test 10,000 sheets, a clear image (solid image density 1.25) without fog was obtained as in the initial stage. When the developer was taken out after 10,000 sheets and the charge amount was measured, it was -11.3 μC / g. Also, clear and fog-free images (image density 1.15) were obtained even in low-temperature and low-humidity environments (15 ° C, 10% RH).

Comparative Example 1 The same procedure as in Example 1 was carried out except that the amount of magnetic particles present in the developing area, m = 85 mg / cm ² , was set. Scribbles were observed, and the resolution of the line image was further reduced.

Comparative Example 2 The coating of the magnetic particles of Example 1 further contained the metal salicylate complex contained in the toner to coat the surface of the magnetic particles.

When the image formation was carried out in the same manner as in Example 1 using the above toner and magnetic particles, only an image having a fog in image density was obtained. When the charge amount at this time was measured,
It was −2.6 μC / g, and the toner and magnetic particles were likely to be separated.

Comparative Example 3 When line drawing was performed in the same manner as in Example 1 except that ferrite particles having a particle size of 150 to 250 mesh, an average particle size of 75 μm, and a true specific gravity of 5.1 were used, the line image was good. However, uneven density occurred in the solid image. The charge amount at this time was −14.5 μC / g.

Comparative Example 4 As a ferrite particle, 500 mesh or less 20%, average particle size 2
Example 1 except that the one having 9 μm and the true specific gravity of 5.0 was used.
When an image was formed in the same manner as in 1., a large number of ferrite particles adhered to the latent image carrier. The charge amount at this time is -8.1 μC
It was / g.

Comparative Example 5 Image formation was performed in the same manner as in Example 1 except that the negative charge control agent (chromium complex compound of 3.5-di-t-butylsalicylic acid) was not used. The image reflection density was 0.53, and fog and toner scattering occurred. Was remarkable. At this time, the charge amount of the toner and magnetic particles was −2.2 μC / g.

Comparative Example 6 Images were produced in the same manner as in Example 1 except that as magnetic particles, ferrite particles surface-coated with an aminoacrylate copolymer (particle size 250 to 350 mesh, average particle size 44 μm, true specific gravity 5.1) were used. As a result, an image with a solid image reflection density of 1.05 was obtained at 23 ° C. and 65%. However, under low temperature and low humidity (15 °, 10%), the reflection density of the solid image decreased to 0.75. The charge amount at this time was −33 μC / g (23 ° C., 65%).

Comparative Example 7 Magnetic particles surface-coated with 100 parts of iron powder and 25 parts of the resin used in Example 1 (particle size between 250 and 350 mesh, average particle size)
45 μm, true specific gravity 6.6) were prepared.

When the above-mentioned magnetic particles were used and image formation was carried out in the same manner as in Example 1, the application of the developer on the developer carrying member was uneven, and uneven density occurred in the image. The charge amount at this time is −
It was 16 μC / g.

Example 2 Images were produced in the same manner as in Example 1 except that a polyester resin composed of adipic acid and 2,2-bis (4-hydroxyphenyl) propane (5: 5) was used. Good results have been obtained.

Example 3 Image formation was performed in the same manner as in Example 1 except that the polyester resin used in Example 1 was used as a coating resin without containing a rhodamine-based pigment, and good results were obtained as in Example 1. It was

[Effects of the Invention] As described above, according to the present invention, in a developing device using magnetic particles with a simple structure, a small amount of magnetic particles are interposed to obtain a uniform and good image quality of a solid image without fog. I was able to.

Further, by effectively distributing the toner that contributes to the development onto 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 not only enables the development device to be compact and simple, but it also enables ON-OFF development of an electrostatic latent image formed in response to an electrical signal with high resolution. Is.

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 holding member and vibrate, whereby the 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, FIGS. 2 and 3 are enlarged explanatory views of a developing portion in the developing method according to the present invention, and FIG. FIG. 5 is a schematic diagram of a latent image forming apparatus according to the present invention, and FIG. 6 is a diagram showing an example of a developing characteristic curve of a developing device according to the present invention. 1 ... Latent image holder, 2 ... Developer supply container, 3 ... Non-magnetic sleeve, 4 ... Fixed magnet, 5 ... Blade, 7 ...
Magnetic particle circulation region limiting member, 8 ... Magnetic particles, 9 ... Non-magnetic toner, 10 ... Developer collecting container portion, 11 ... Scattering prevention member, 12 ... Magnetic member, 13 ... Development area, 14 ...... Bias power supply, 21 …… Electrostatic latent image, 22 …… Magnetic brush 41 …… Suction machine, 42 …… Measuring container, 43 …… Conductive screen, 44 ……
Lid, 45 ... Vacuum gauge, 46 ... Air flow control valve, 47 ... Suction port, 48 ... Condenser, 49 ... Electrometer, 51 ... Laser unit, 52 ... Scanner motor, 53 ... Polygon mirror, 54 …… Imaging lens, 55 …… Mirror.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 15/09 Z (72) Inventor Hiroyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo 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. An image of a document is converted into an electric signal, an electrostatic latent image is formed on a latent image holding member in response to the electric signal, and then a developing agent carrying member facing the latent image holding member is developed. In an image forming method of developing the electrostatic latent image with a non-magnetic toner while applying an alternating electric field between the latent image holding member and the developer carrying member in a region, the non-magnetic toner has an absolute value of 3 to A developer carrier is provided with magnetic particles that impart a triboelectric charge of 30 μC / g, have a true specific gravity of 6 or less, and are coated with an electrically insulating resin that has substantially the same structure as the binder resin of a non-magnetic toner. In the developing area, a magnetic brush is formed so that the amount of the magnetic particles is 5 to 80 mg / cm ^2, and in the developing area, the latent image carrier and the magnetic brush are brought into contact with each other from the surface of the developer carrier. The non-magnetic toner is transferred to the latent image carrier, and the non-magnetic toner is transferred from the surface of the magnetic brush. Image forming method, characterized in that the electrostatic latent image is developed with a non-magnetic toner (except in the case of reversal development).