JPS61162060A - Magnetic particle material for toner coating and toner coating method using said magnetic particle material - Google Patents

Abstract

PURPOSE:To obtain a developed image having high quality even in the case of color copying by using a magnetic particle material having the specific relation between the specific surface area of the magnetic particles prior to resin coating and the specific surface area of the resin-coated magnetic particle material. CONSTITUTION:The magnetic particle material for toner coating is formed by coating the surface of the magnetic particles with the resin and the relation between the specific surface area (S1) of the magnetic particles prior to the resin coating and the specific surface area (S2) of the resin-coated magnetic particle material satisfies S2<=0.95XS1. The size of the magnetic particles is preferably in the grain size range of 60-400 meshes. Various high polymers are adequately adoptable for the material to coat the surface of the magnetic particles; for example, polytetrafluoroethylene or the like is usable. The preferable amt. of the high-polymer material to be used is a 0.5-20wt% range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a multifunctional magnetic particle for toner coating in electrophotography, and a toner coating method using the magnetic particle.

[Description of prior art]

As the electrophotographic method, US Pat.
Various methods are described in Japanese Patent No. 24748, etc., but all of these methods involve applying a total electrostatic charge to the surface of an electrophotographic photoreceptor having a photoconductive layer using means such as corona discharge, and discharging this charge. An electrostatic latent image is formed by irradiating the photoconductive layer with a light image corresponding to the original, and then the electrostatic latent image is developed using a colored fine powder called toner. After the image is transferred onto a transfer material such as paper, it is permanently fixed using heat, pressure, solvent vapor, etc. to obtain a copy.

The process of developing the electrostatic latent image described above involves attracting toner particles charged with a polarity opposite to that of the electrostatic latent image by electrostatic attraction, and causing them to adhere to the electrostatic latent image. This makes the entire latent image visible. The methods of developing a darkening electrostatic latent image using toner can be roughly divided into two-component development methods that use carrier particles as a means to transport the toner to the electrostatic latent image, and one-component development methods that do not use carrier particles. There is a law.

In the two-component development method, a mixture of carrier particles and toner particles is inevitably used as a developer, and since the toner particles are normally consumed in much larger quantities than the carrier particles during the development process, the mixing ratio of the two is This not only causes fluctuations in image density, but also causes various problems. For example, if the toner content is less than the optimum content, the carrier may adhere to the photoreceptor or paper surface, causing various defects. On the other hand, if the toner content is excessive, it may cause roughness and fog in non-image areas. This may cause poor cleaning, and may easily cause scattering and contamination inside the device due to electrostatic repulsion between excess toner particles.

On the other hand, various one-component developing methods have been proposed that do not cause the problem of fluctuations in the mixing ratio, but in any of these developing methods, it is extremely difficult to form a uniform thin layer of toner, and it is extremely difficult to form a uniform thin layer of toner. Therefore, most of them formed a relatively thick layer of goner. However, as improvements in the clarity, resolution, etc. of developed images are currently being sought, there is a desire to develop a method for forming a uniform thin layer of toner in a -component type development method.

As a method for forming a thin layer in a one-component developing method known so far, there is a method described in JP-A-54-43037, which has been put into practical use. This method uses magnetic toner as a developer to form a magnetic brush, thereby forming a thin layer, but in order to make magnetic toner magnetic, a magnetic substance must be added to the toner. First, since a dark-colored magnetic material is added thereto, there is a problem of poor color in color electrophotography. Further, there is a problem in that the internal addition of a magnetic substance has a negative effect on the fixing performance when fixing the toner, resulting in poor fixing performance.

In order to avoid these problems, there is also a method of forming the entire thin layer using non-magnetic toner. For example, toner may be applied using a cylindrical brush made of soft bristles such as beaver hair, or the toner may be applied using a doctor blade or the like to a developing roller whose surface is made of fibers such as velvet. There is a way. However, when an elastic blade is used as a doctor blade on the fiber brush, it is possible to control the amount of toner, but it is difficult to apply it uniformly, and in addition, simply rubbing the fiber brush on the developing roller can Since the toner present between the fibers of the brush is not sufficiently charged by frictional charging, there are problems such as ghosting and the like being likely to occur. Furthermore, in methods using these non-magnetic toners, it is difficult to prevent toner from leaking from the developing device.

[Purpose of the invention]

The purpose of the present invention is to provide a simple dry electrostatic latent image development method that solves the various problems of the conventional methods by focusing on magnetic particles and can produce the excellent images required even for color copying. It is about providing.

Another object of the present invention is to provide magnetic particles for toner application.

Still another object of the present invention is to form a magnetic brush independently in a system where a large amount of toner exists, and to fluidly circulate and move the toner in the system without passing through a metal or a regulating member. An object of the present invention is to provide a magnetic particle body for toner application, which allows toner to be accurately supplied onto a toner carrier.

Yet another object of the present invention is to provide a simple dry electrostatic latent image development method using the magnetic particles.

[Structure of the invention]

The magnetic particles for toner application of the present invention were developed as a result of repeated trial and error research on magnetic particles from various angles in order to solve the various problems seen in the conventional methods described above by focusing on magnetic particles. If the magnetic particles are resin-coated magnetic particles and the relationship between the specific surface area and fluidity with respect to the magnetic particles satisfies specific conditions, a magnetic brush is formed in a system where a large amount of toner exists, and the regulating member The toner can be smoothly circulated through the system without passing through the toner, with an appropriate restraining force generated by the magnetic field, and not only can the toner be charged, but also a predetermined amount of toner can be supplied onto the toner carrier. This has been completed after experimentally confirming that this is the case.

That is, the magnetic particles for toner coating of the present invention are formed by coating the surfaces of magnetic particles with a resin, and the specific surface area (S1) of the magnetic particles before resin coating and the magnetic particles coated with the resin differ from each other. The relationship between the specific surface area (S2) of cm2/
Measured at f (for example, K, using powder specific surface area measuring device 5S-100 manufactured by Shimadzu Corporation), formula: S2≦0.95 X S, ...
(1), the fluidity of the resin-coated magnetic particles (f2) and the fluidity of the magnetic particles before resin coating (f1)
) is measured in seconds 1501 (JISZ250
2), formula f2<f+ ・・・・・・・・・・・・・・・
・・・・・・・・・ (2) Fully satisfied.

As the magnetic particles of the magnetic material for toner coating of the present invention, known ones can be used, and examples thereof include surface oxidized or unoxidized iron, nickel, cobalt, manganese, chromium,
Examples include metals such as rare earths, alloys and oxides thereof, and the like. However, the present invention is not limited to these, and other materials may also be used.

The shape of the magnetic particles can be arbitrary, such as spherical or oval. The size of the magnetic particles is 60~
Particle sizes in the 400 mt size range are preferred.

The substance that coats the surface of the magnetic particles needs to be considered depending on the type of magnetic particles and the type of toner, but in general, various polymeric materials can be used as appropriate, such as polytetrafluoroethylene, monochlorotrifluoride, etc. Fluoroethylene polymers, polyvinylidene fluoride, silicone resins, polyester resins, styrene resins, acrylic resins, polyamides, polyvinyl butyral, aminoacrylate resins, and the like can be used alone or in an appropriate mixture. In addition, when coating the surface of the magnetic particles with such a polymeric material, in the polymeric material,
If necessary, a metal complex of ditar/yari-butylsalicylic acid, a charge control agent such as a basic dye such as Nipron, a surface treatment agent such as glue powder or fine alumina powder, etc. can be dispersed.

When the surface of the magnetic particles is coated with such a polymer material, the obtained magnetic particles have the formulas (1) and (
2) The amount of the polymeric material that coats the surface of the magnetic particles and is fixedly formed thereon is important because it must be completely satisfactory. In terms of quantity, the polymeric material used is generally in an amount of 0.1 to 30% by weight, preferably in the range of 0.5 to 20% by weight, based on the magnetic particles.

The method of coating and fixing the polymer material on the surface of the magnetic particles to obtain the desired magnetic particles includes a method of melting or softening the sample with heat and making it adhere to the magnetic particles;
Any conventionally known method can be applied, such as a method of dissolving or suspending the material in a solvent and adhering it to magnetic particles by a coating means.

In order to efficiently produce the magnetic particles of the present invention according to these methods, it is first necessary to select the method to be adopted, set the conditions and implement the method on a laboratory scale, and create model magnetic particles first. Once an optimal model magnetic material has been obtained, the method is generally scaled up and carried out based on the conditions adopted in that case. The process diagram for either method is as follows: classification of magnetic particles of a predetermined size → fixation of a coat of polymer material on the surface of the classified magnetic particles → classification of a magnetic material of a predetermined size and shape → magnetic material of the present invention. Become.

For toners used with the magnetic materials of the present invention, any suitable pigment or dye can be used as a colorant. For example, there are known facial cleansers such as carbon blank, iron black, phthalonoamine blue, ultramarine blue, quinacriteno, and benzidine yellow.

In addition, as the binder resin of the toner used, monopolymers of styrene/and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene;
-Chlorstyrene copolymer, styrene/-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer , styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acrylic-aminoacrylic copolymer, styrene-aminoacrylic copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer,
Styrene/-vinyl methyl ether copolymer, styrene rubinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer , styrenic copolymers such as styrene-maleic acid copolymer, styrene/-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate,
Polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin , paraffin wax, etc. can be used alone or in combination.

In addition, as a charge control agent, amino compounds, quaternary ammonium compounds and organic dyes, especially basic dyes and their salts,
Benzyldimethyl-hexadenolammonium chloride, derutrimethylammonium chloride, nigrosine base, nigeroa/hydrochloride, safranin γ and crystal violet, metal-containing dyes, salicylic acid metal-containing compounds, etc. may be added.

Furthermore, the magnetic powder may be added in its entirety to the extent that it does not impede the effects of the present invention.

When the magnetic particles of the present invention are used in combination with such a toner, the toner can be uniformly applied onto the toner carrier by taking in and regulating the toner, and the circulation of the magnetic brush can be constantly stabilized. etc., can bring even better effects.

Toner application using the magnetic particles of the present invention requires a developer container that stores toner and magnetic particles for toner application, a toner carrier that conveys the toner to a latent image carrier, and a toner outlet of the developer container. It is more efficient and effective to carry out the method using a system in which a magnet forming a magnetic brush made of toner applying magnetic particles is placed in contact with the toner carrier on the upstream side of the toner carrier.

The present invention includes a toner application method that efficiently exhibits the above-mentioned functions possessed by the magnetic particles of the present invention, and the method uses a developing device shown in FIG. 1 or 2. It can be implemented by

First, to explain the method of using the developing device (cross-sectional view) shown in FIG. The entire developing position rotates in the direction of arrow a and passes through.

A non-magnetic sleeve 2, which is a toner carrier that carries toner, faces the photosensitive drum 1 with a predetermined gap therebetween, and this sleeve 2 rotates in the direction indicated by the arrow. A container 3 made of a non-magnetic material such as resin or aluminum is located above the sleeve 2 and stores the toner 4 and a mixture of the toner 4 and magnetic particles 5. , the magnetic blade 6 is screwed.

On the other hand, a magnet 7 is provided on the opposite side of the sleeve 20 to the magnetic blade 6. The mounting position of this magnet is determined by the relationship between the position of the magnetic pole and the magnetic blade 6.
Is the magnetic pole actually slightly upstream of the magnetic blade 60 position? Due to the effect of the magnetic field formed by providing the magnetic field, better results can be obtained in terms of preventing the magnetic particles from flowing out and uniformly applying the toner.

In the above configuration, the magnetic particles 5 in the container 3 form a magnetic brush 8 due to the magnetic field generated between the S pole of the magnet 7 and the magnetic blade 6. Then, as the sleeve 2 rotates, the magnetic particles and toner are stirred and mixed while the magnetic plate 78 is held. In this state, on the magnetic blade side of the container 3, due to the presence of the blade 6, the mixture of magnetic particles and toner is prevented from moving by the blade, rises, and circulates in the direction of arrow C.

As a result, the pl-ner is triboelectrically charged by the sleeve 2 or the magnetic particles by mixing with the magnetic particles. The charged toner is uniformly and thinly applied to the surface of the sleeve 2 by a mirror force by a magnetic plate 8 formed near the magnetic blade 6, and reaches a position facing the photoreceptor drum.

By the way, the magnetic particles 5 constituting the magnetic brush 8 do not flow onto the sleeve 2 by setting the restraining force due to the magnetic field of the magnet 7 to be stronger than the conveying force caused by frictional force. If there is toner within the area of the magnetic plan 8, the ratio of the magnetic particles of the magnetic plan 8 to this toner is
The rotation of the sleeve 2 keeps the value almost constant. Even if this occurs and the toner on the sleeve is consumed, toner is automatically supplied to the area of the magnetic plan 8. Therefore, it is possible to always supply and apply a constant amount of toner onto the sleeve 2.

The developing device (cross-sectional view) shown in FIG. 2 is a modification of the developing device shown in FIG. The N pole of one magnetic pole is located at the center O of the sleeve 2 with respect to the magnetic blade 6.
There is no difference from the developing device shown in FIG. 1 except that the developing device is set at an angle of 30 degrees (θ in the drawing) from the line connecting the tip of the blade.

The latent image holder is a drum-shaped or belt-shaped member having a photoreceptor layer and an insulating layer, and the magnetic pole is a magnet roller with magnetic poles of the same polarity or different polarity magnetized in the axial direction. Alternatively, a plurality of rod-shaped magnets can be bonded onto a fixed support member. Furthermore, as the rotating toner carrier, it is possible to use a sleeve made of non-magnetic metal such as aluminum, copper, stainless steel or brass, or a synthetic resin material, or an endless belt made of resin or metal. A roughened surface or an uneven pattern may be provided in order to improve the electrostatic properties and charging characteristics. In addition, if necessary, a regulating member installed on the outlet side of the developer container may be made of magnetic material such as iron, aluminum, copper, etc.
Blade plates and walls entirely made of non-magnetic material such as resin can be used.

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. In Examples and Comparative Examples, parts are parts by weight, and % by weight.

Examples The developing device shown in FIG. 2 was used.

In FIG. 2, the same members as in FIG. 1 are given the same reference numerals. In the apparatus of this embodiment, the photosensitive drum 1 rotates in the direction of arrow a at a circumferential speed of 60 questions/second. 2 is 6 in the direction of the arrow
32mm outer diameter, 0.8m thick, rotating at a circumferential speed of 6 gourds/second
The sleeve is made of stainless steel (SUS304), and its surface is sandblasted with irregular sand blasting using +-600 alundum abrasive grains, and the roughness of the circumferential surface is reduced to 0.8 μm (
Rz=).

On the other hand, a sintered ferrite type magnet 7 is fixedly disposed inside the rotating sleeve 2, and its first magnetic N pole is connected to a line connecting the center O of the sleeve 2 and the tip of the blade with respect to the magnetic blade 6. It is set at an angle of 30 degrees (θ in the figure).

The magnetic blade 6 is made of iron, and its surface is nickel-plated to prevent rust. The distance between the blade 6 and the surface of the sleeve 20 was set to 200 μm.

Next, magnetic particles for toner application were manufactured as follows.

That is, styrene-methyl methacrylate copolymer (
Molar ratio 20:80) 50 S' i xylene x
After removing xylene, immerse amorphous iron powder I K9 with particle size between 150 and 250 mesh in the solution.
The resin coating was completed by heating to 300°C. (The processing amount is 5 parts of resin for 100 parts of iron powder.) The specific surface area and fluidity before and after resin coating are determined by mixing the materials from the bottom, melting and kneading, cooling, crushing and classifying to obtain particles with an average particle size of 12μ. To this, 0.6% colloidal silica was externally added to prepare a toner.

Then, after thoroughly mixing 7 parts by weight of the toner and 50 parts by weight of magnetic particles, they are placed in the container 3. Then toner 20
Add 0 parts by weight from above and place in container 3. The mixture of toner and magnetic particles in the container 3 could be observed to move smoothly in circulation as the magnetic particles were conveyed by the sleeve under the magnetic field, especially when the amount of toner was low.

In the developing device configured as described above, as the sleeve rotated, a uniform thin layer made only of toner could be formed on the surface of the sleeve 2.

On the surface of the photosensitive drum 1 facing the sleeve 2, a charge pattern of 600 V in the dark part and +150 V in the bright part was formed as an electrostatic latent image, and the distance from the sleeve surface was set to 300 μm. Then, power supply E is applied to the sleeve at a frequency of 800 Hz and a peak-to-peak value of 1.4 KV.
When a voltage with a center value of 300 V was applied, a high-quality clear blue developed image without uneven development, ghost images, or fogging could be obtained, and this state continued intermittently until the toner ran out.

In addition, good images were obtained even under special environments of high temperature and high humidity, and low temperature and low humidity.

Furthermore, regarding the mixture in container 3, only the toner was consumed for development, with almost no magnetic particles being consumed.

In addition, the developing function remains stable until most of the toner is consumed. After the developer was consumed, the developing device was removed from the main body and the lower part of the sleeve 2 was looked at, and it was found that not only magnetic particles but also almost no toner had leaked there.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the magnetic particles were not treated. However, a faint image was not obtained, and as the number of copies was increased, the toner on the sleeve was charged up and it became difficult to produce an image. Ta.

When I removed the toner on top, the brush was not circulating at all.

Comparative Example 2 Magnetic particles were produced in the same manner as in Example 1 except that the amount of resin coating was 0.1 part per 100 parts of iron powder. The specific surface area and fluidity before and after resin coating were as shown in the table below. There was no residual difference, and the conditions of the present invention were not satisfied.

When development was carried out in the same manner as in Example 1 using the magnetic particles, unlike in Comparative Example 1, the circulation of the brush was extremely poor and only a thin image was obtained.

Example 2 Magnetic particles were obtained in the same manner as in Example 1, except that 3 parts of dimethylboria and 0 xane were used for resin coating and 100 parts of iron powder.The specific surface area and fluidity before and after resin coating were as shown in the table below. It was like that.

On the other hand, the following materials were mixed, melted and kneaded, cooled, crushed and classified to obtain particles with an average particle size of 13 μm, to which 0.5% colloidal silica was added externally to form a toner.

Hereinafter, the same procedure as in Example 1 was carried out, and the dark area was +500V.

Frequency 1600 for bright area +100 V electrostatic latent image
Hz% Peak-to-peak value 1300V% center value + 2
When a voltage of 00 V was applied to the sleeve and developed,
Good results were obtained.

Comparative Example 3 Magnetic particles were obtained in the same manner as in Example 2, except that the resin coating amount was 0.2 parts with respect to 100 parts of iron powder, and development was carried out in the same manner as in Example 2 using the magnetic particles. The specific surface area and fluidity before and after the resin coating were as shown in the table below, which did not satisfy the conditions of the present invention, and the circulation of the brush was intermittent, resulting in uneven images.

[Summary of effects of the invention]

The present invention simplifies the dry electrostatic latent image development method by using magnetic particles in which the magnetic particles are not coated with a resin, and a predetermined amount of toner is constantly transferred onto the toner carrier or the latent image is retained. It can be applied onto the body and form the desired uniform toner thin layer.

Furthermore, by using the magnetic particles, even in the case of color copying, it is possible to obtain clear and high-quality developed images without causing problems such as ghost images or fogging during development. Furthermore, in the method using the magnetic particles, the magnetic particles do not pass through the regulating member, and not only the magnetic particles but also the toner do not leak.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one example of a developing device suitable for using the magnetic particles for toner application of the present invention. FIG. 2 is a sectional view of a developing device used in an embodiment of the present invention. 1... Photosensitive drum which is a latent image holding member 2... Non-magnetic sleeve which is a toner carrier 3... Container 4... Toner 5... Magnetic particles for toner application 6... Regulation Magnetic blade 7.7C, which is a member...Magnet 8.8a...Magnetic plan E...Power source a...Arrow b indicating the rotation direction of the photosensitive drum...Arrow indicating the rotation direction of the sleeve C...Arrow showing the circulation of the mixture of magnetic particles and toner

Claims (4)

[Claims] (1) Specific surface area of magnetic particles before resin coating (S_1) and specific surface area of resin-coated magnetic particles (S_2)
A magnetic particle body for toner application, wherein the relationship satisfies the following formula: S_2≦0.95×S_1. (2) Fluidity of resin-coated magnetic particles (f_2
) and the fluidity (f_1) of the magnetic particles before resin coating satisfies the following formula: f_2<f_1. The magnetic particles for toner application according to claim (1). (3) Specific surface area of magnetic particles before resin coating (S_1) and specific surface area of resin-coated magnetic particles (S_2)
A toner application method characterized by using magnetic particles having a relationship satisfying the following formula: S_2≦0.95×S_1. (4) The magnetic particle body has its own fluidity (f_2),
The toner coating method according to claim (3), wherein the relationship between the fluidity (f_1) of the magnetic particles before resin coating satisfies the following formula: f_2<f_1.