JPS6350700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel developing method applied to electrophotography.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Many methods are known, as described in Japanese Patent No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Various methods are also known for visualizing electrical latent images using toner.

For example, the magnetic brush method described in US Pat. No. 2,874,063, the cascade development method described in US Pat. No. 2,618,552, the powder cloud method and fur brush development method described in US Pat. No. 2,221,776, and liquid development. A number of developing methods are known, such as the method.

Among these developing methods, in particular, a magnetic brush method using a developer mainly consisting of toner and carrier,
Cascade method, liquid development method, etc. are widely put into practical use. All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such drawbacks, various development methods using a one-component developer made only of toner have been proposed, among which many methods are superior to methods using a developer made of magnetic toner particles.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. In this method, a conductive magnetic developer is supported on a cylindrical conductive toner carrier (sleeve) having magnetism inside, and is brought into contact with an electrostatic image to develop it. At this time, a conductive path is formed by the toner particles in the developing section between the recording medium surface and the sleeve surface, and through this conductive path, the sleeve conducts charge to the toner particles, which creates a Coulomb force between the electrostatic image and the image area. The toner particles are deposited on the image area and developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, because the toner is conductive, the developed image can be transferred from the recording medium to the final product such as plain paper. It has the disadvantage that it is difficult to electrostatically transfer it to a permanent support member.

As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, JP-A-52-94140 discloses a developing method that utilizes dielectric polarization of toner particles. However, such a method has drawbacks such as an inherently slow development speed and an inability to obtain a developed image with sufficient density, making it difficult in practice.

Another developing method using high-resistance magnetic toner is a method in which the toner particles are triboelectrified by friction between the toner particles or friction between the toner particles and a sleeve, etc., and the toner particles are brought into contact with an electrostatic image holding member for development. It has been known. However, these methods tend to cause insufficient frictional charging due to the small number of times of contact between the toner particles and the friction member, and the Coulomb force between the charged toner particles and the sleeve increases and they tend to aggregate on the sleeve. It has drawbacks and is difficult to implement in practice.

Toner was brought into contact with both the image area and the non-image area on the surface of the electrostatic image holder indiscriminately, and the toner was left in the image area, which could be called indiscriminate contact development. A system described in Japanese Patent No. 9475, which can be called jumping development, has been proposed in which toner is caused to fly to non-image areas.

In the former indiscriminate contact method, it is unavoidable that some toner remains on the non-image area on the surface of the electrostatic image holder, which is the so-called fog phenomenon, but in the latter jumping method, the fog phenomenon occurs. It is known that it can be almost eliminated. However, while many of the former have been put into practical use and are used in various types of copying machines, the latter have not been put into full-scale practical use. The reasons for this are that although the latter method does cause fogging, it is difficult to support the toner uniformly, it is difficult to stabilize the flight of the toner, and it also causes density unevenness in the image area and toner particles in the periphery of the image area. There was a risk that irregular flying would occur, resulting in blurred images.

The present applicant previously proposed a new developing method that eliminates the above-mentioned drawbacks in JP-A-54-43036. This is done by applying a very thin layer of magnetic toner on the sleeve, triboelectrically charging it, and then bringing it very close to the electrostatic image under the action of a magnetic field and facing it without contact, causing the toner to fly. It is to be developed.

According to this method, by applying an extremely thin layer of magnetic toner onto the sleeve, the degree of contact between the sleeve and the toner is increased, and sufficient frictional electrification is possible.The toner is supported by magnetic force, and the magnetic toner is By moving the toner relatively, the toner particles are disaggregated and are sufficiently rubbed against the sleeve, the toner is supported by magnetic force, and the toner is opposed to the electrostatic image without coming into contact with it. Excellent images can be obtained by preventing background fog through development.

In this toner flying development, the magnetic toner on the sleeve needs to be uniformly scattered onto the electrostatic image carrier in order to perform the development by flying toner. An important condition is that the magnetic toner be applied uniformly on the sleeve having a magnetic toner.

The present inventors focused on the cohesiveness of toner, and
When various magnetic toners were applied onto the sleeve, toners with high agglomeration values measured at room temperature and humidity were found to be difficult to spread evenly onto the sleeve when toner flight development was performed in a high humidity environment. In some cases, the caking toner may slip on the rotating sleeve, resulting in a developed copy image with low image density and some white areas that are not developed. Occurred. On the other hand, if the degree of aggregation is extremely small, the fine toner particles may scatter inside the copying machine, which may cause the apparatus to become dirty or cause fogging, which is disadvantageous.

The object of the present invention is to provide a new development method which improves the above-mentioned drawbacks. That is, an object of the present invention is to provide a developing method with high fidelity to the original and stable image quality. Furthermore, it is an object of the present invention to provide a developing method that eliminates the background fog phenomenon even when the environment changes, especially when the humidity is high, and provides a high-resolution image with uniform density and sufficient density in the image area.

The feature is that an electrostatic image carrier that holds an electrostatic image on its surface and a toner carrier that carries an insulating magnetic toner on its surface are arranged with a certain gap in the developing section, and An insulating magnetic toner having an agglomeration degree of 0.1 to 30% (more preferably 1 to 20%) at a humidity of 60% is supported on a toner carrier to a thickness thinner than the gap, and the toner is placed under the action of a magnetic field. The developing method includes transferring the electrostatic image carrier to the electrostatic image holder and developing the image.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 shows a schematic configuration of an example of a copying device or a recording device to which the developing method according to the present invention can be applied, but the present invention is not limited thereto.

1 corresponds to an electrostatic image holder, and is a photosensitive drum containing a photoconductive layer.It can be used with or without an insulating layer on the surface. A similar shape is also possible. Reference numeral 2 represents a known photosensitive charging device, and 3 represents a light image irradiation device that projects an original image, a light image, or a light beam modulated by an image signal. As a result, an electrostatic image is formed on the photoreceptor 1. A developing device 4 has a developer carrier 4a, and forms a toner particle visible image in accordance with the electrostatic image on the photoreceptor 1. 5 is a device for transferring the toner image onto a transfer material 6. Incidentally, in order to improve transferability, a charge may be applied to the visible image in advance by corona discharge or the like before transfer. Furthermore, it is also possible to adopt a so-called electrostatic image transfer method in which the electrostatic image on the photoreceptor 1 is temporarily transferred to another image carrier, and then converted into a visible image by the developing device 4. 7, the toner image is transferred to a member 6;
This is a fixing device for fixing images on a paper, and is composed of at least two rollers having pressure or heating means. Reference numeral 8 denotes a cleaning device for cleaning and removing residual toner on the photoreceptor 1 after transfer, so that the photoreceptor 1 can be reused.

Each step of the electrophotographic method applied to the method of the present invention will be explained below.

First, the process of forming an electrical latent image will be described.

Electrophotographic photoreceptors have various configurations in order to obtain predetermined characteristics or depending on the type of electrophotographic process to which they are applied. 2. Description of the Related Art As typical electrophotographic photoreceptors, there are photoreceptors having a photoconductive layer formed on a support and photoreceptors having an insulating layer on the surface, which are widely used. The photoreceptor, which is composed of a support and a photoconductive layer, is produced by the most common electrophotographic process. That is, it is used for charging, image exposure, development, and, if necessary, image formation by transfer. In addition, for photoreceptors equipped with an insulating layer, this insulating layer protects the photoconductive layer, improves the mechanical strength of the photoreceptor, improves dark decay characteristics, or
It is provided for the purpose of application to a specific electrophotographic process (furthermore, to eliminate pollution). Examples of electrophotographic processes using photoconductors having such insulating layers or photoconductors having insulating layers are disclosed in U.S. Pat. Publication No. 46-3713, Special Publication No. 42-19747,
It is described in Japanese Patent Publication No. 36-4121, etc.
In particular, a typical specific electrophotographic process includes a process that uses charge injection from the support side during charging to move the charge between the insulating layer and the photoconductive layer. Such a process is described in Japanese Patent Publication No. 42-23910,
As disclosed in Publication No. 42-24748, etc., primary charging, secondary charging with opposite polarity to primary charging, or AC
This is a process of forming an electrostatic image by removing static electricity, simultaneous image exposure, and full-surface exposure (full-face exposure may be omitted if necessary). In addition, Special Publication No. 19748, Special Publication No. 13437, and Special Publication No. 49
As disclosed in Japanese Patent No. 44902, image exposure may be performed before or after secondary charging or AC neutralization in the above process.

A predetermined electrophotographic process is applied to the electrophotographic photoreceptor to form an electrostatic image, and this electrostatic image is developed and made visible.

Some typical other image holding members are those used in the following electrophotographic process.

(1) As described in Japanese Patent Publication No. 32-7115, Japanese Patent Publication No. 8204, and Japanese Patent Publication No. 43-1559, the electrophotographic The electrostatic image formed on the body is transferred to another holding member for development, and then the toner image is transferred to the transfer member. (2) Or as another electrophotographic process in which an electrostatic image is formed on another image holding member in correspondence with the electrostatic image formed on the electrophotographic photoreceptor, for example, Japanese Patent Publication No. 45-30320,
As described in Japanese Patent Application Laid-open No. 48-5063 and Japanese Patent Application Laid-Open No. 51-341, an electrostatic image is formed on a screen-shaped electrophotographic photoreceptor having a large number of fine openings by a predetermined electrophotographic process. By applying corona charging to another image holding member through this electrostatic image, the ion flow of the corona is modulated to form an electrostatic image on the other image holding member, which is then developed with toner. Examples include a process of transferring the image to a transfer member to form a final image. (3) According to another electrophotographic process, an electrostatic image corresponding to the electrical signal can be formed on the surface of the image holding member by applying an electrical signal to (multiple) needle electrodes. Image holding members used in electrophotographic processes such as (1) to (3) need only have an insulating electrostatic holding surface and do not require a photoconductive layer. As described above, various types of surface insulating members are generally used as image holding members on which electrostatic images are formed, including electrophotographic photoreceptors.

The developing process used in the present invention will be explained with specific examples. FIG. 2 shows a cross-sectional view of one embodiment of the developing process used in the present invention. In the figure, when the electrostatic image holding surface 1 moves in the direction of the arrow, the multipolar permanent magnet 9 is fixed so as not to rotate.
By rotating the non-magnetic cylinder 4b, which is a toner carrier (sleeve), in the same direction as the electrostatic image holding surface 1,
A one-component insulating magnetic toner 11 sent from a developer container 12 is applied onto a non-magnetic cylindrical surface, and friction between the cylindrical surface and the toner particles gives the toner particles a charge of opposite polarity to the electrostatic image charge. . Furthermore, a doctor blade 10 made of iron is placed close to the cylindrical surface (at intervals).
50μ to 500μ) and are arranged opposite to one magnetic pole (pole B in the figure) of the multipolar permanent magnet 9, thereby regulating the thickness of the toner layer to be thin (30μ to 300μ) and uniform. By adjusting the rotational speed of the cylinder 4b, the surface speed and preferably the internal speed of the toner layer are made to be substantially the same as, or close to, the speed of the electrostatic image bearing surface.
As the doctor blade 10, a permanent magnet may be used instead of iron to form opposing magnetic poles. Further, in the developing section, an alternating current bias may be applied between the toner carrier and the electrostatic image holding surface.

As mentioned above, in this developing process, in order to stably hold the one-component magnetic toner on the sleeve,
A nonmagnetic cylinder 4b containing a multipolar permanent magnet 9 was used. In addition, in order to form a thin and uniform toner layer,
A doctor blade 10 made of a magnetic thin plate or a permanent magnet was placed close to the surface of the cylinder 4b. Using a magnetic doctor blade in this way,
Opposing magnetic poles are formed between the magnetic poles of the permanent magnet contained in the sleeve, forcing the toner particle chains to stand up between the doctor blade and the sleeve, causing them to spread to other parts of the sleeve, such as the electrostatic image surface. It is advantageous to keep the toner layer thin in the opposing areas. Further, by applying such forced movement to the toner, the toner layer becomes more uniform, thereby achieving a thin and uniform toner layer formation that could not be achieved with a non-magnetic doctor blade.

The development phenomenon according to the present invention is such that in the non-image area of the electrostatic image holding surface, the toner layer is maintained in a non-contact manner, and in the image area, such a toner layer is formed in which the toner is transferred to the electrostatic image holding surface. Then, the image is developed. The image area of the electrostatic image holding surface referred to here is:
This is the area to which toner particles should adhere during development, and the non-image area refers to the background area to which toner particles should not adhere. During the transfer, the toner layer corresponding to the image area is attracted by the electric field and increases in thickness in the direction of the electric field, and the magnetic field acts on the toner layer in this area, causing the toner in this area to grow erect like an elongated ear at the magnetic pole position (hereinafter referred to as This phenomenon is called the "toner elongation" phenomenon. Therefore, when the surface layer of the toner layer and the electrostatic image holding surface are close to each other, the elongated part of the toner comes into direct contact with the image area of the electrostatic image holding surface, causing the sleeve to When the electrostatic image bearing surfaces are separated from each other, toner remains on the electrostatic image bearing surfaces to complete development. This method differs from the so-called contact development method or jumping development method in that during development, toner does not come into contact with non-image areas, but does come into contact with image areas due to the above-mentioned toner elongation phenomenon. it is conceivable that. If the gap between the surface layer of the toner layer and the electrostatic image holding surface is larger than the above, in addition to the development state due to the phenomenon that the toner stretches as described above, the toner may stretch but still not contact the electrostatic image holding surface. It is thought that a developing state may occur in which the toner that has not been used also stands up in the electric field and flies as if the tips of its spikes are torn off and reaches the electrostatic image holding surface.

Of course, according to the present invention, depending on the gap between the electrostatic image holding surface and the sleeve, development can be carried out in which the above-described toner elongation developer and the accompanying flying phenomenon are added. In this way, by utilizing the toner elongation phenomenon in which the toner layer stands up and grows in the image area of the electrostatic image holding surface and develops by coming into direct contact with the electrostatic image holding surface,
By reducing the amount of toner flying through the development gap, the effect of the airflow flowing through the gap, the gravity of the toner itself, and vibrations of the electrostatic image holding surface and sleeve can be minimized, resulting in high fidelity. It is possible to obtain a microscopic image of excellent image quality with excellent image reproducibility and no background fog, and it is good if the gap size of each part is set to meet this condition. In order to sufficiently ensure toner elongation as described above, the gap between the toner surface layer (in the non-image area where no upright growth occurs) and the electrostatic image holding surface must be kept to three times or less the thickness of the toner layer. In addition, the acceptable conditions for development that mainly involves the above-mentioned toner elongation and also allows the toner to fly is to make the above-mentioned gap 10 times or less the thickness of the toner layer.

According to experiments and theoretical analysis including the above-mentioned considerations, the gap D in the developing section between the sleeve and the electrostatic image holding surface is preferably 50μ≦D≦500μ. The upper limit value is a value determined to develop fine print (100μ) printed with commercially available smallest type with good resolution, and the lower limit is an appropriate value determined in relation to the thickness of the toner layer. According to experiments, the thickness a of the toner layer supported on the sleeve is 30μ≦a≦
A thin layer of about 300μ was preferred. During development, the toner layer stands up due to the presence of a magnetic field, but as mentioned above, the height of the toner layer is thought to be about three times the thickness of the toner layer, so it takes a long time for the toner surface layer to reach the electrostatic image holding surface. It is necessary that the gap b between the toner surface layer and the electrostatic image holding surface satisfies b≦300μ.
In general, good results were obtained when b≧a/5.

As explained above, in the developing process in the electrophotographic method of the present invention, it is necessary for the toner to generate an appropriate frictional charge with the sleeve surface and to have an appropriate magnetic moment, and in addition, it is necessary to prevent the toner from elongating. In order to develop the main body and also allow the flying of toner to coexist, the thickness a of the toner layer on the sleeve must be adjusted to optimize the gap D between the toner surface layer and the electrostatic image holding surface.
It is necessary to form a thin layer of about 30μ≦a≦300μ.
In order to obtain such an extremely thin toner layer, first, it must be extremely uniform on the sleeve and the individual toner particles must not aggregate and have appropriate fluidity. If a toner with low fluidity is used, a toner layer of a certain thickness will not be formed, and such a toner layer will not be able to approach the image area of the electrostatic image holding surface with an appropriate gap, and the image will not be It tends to cause unevenness. In more severe cases, toner may cause blocking or caking within the developing device or on the sleeve, resulting in a decrease in image density or even no development at all.

This phenomenon is particularly noticeable when the developing method of the present invention is applied at high humidity. In other words, 25℃ humidity
Toner cohesion is 30% when measured under 60% conditions
In the case of toner that exhibits the above value, in a high humidity environment where the humidity condition during development exceeds 85%, the toner will not be applied uniformly on the sleeve, causing unevenness and streaks, and the image density will be significantly lower. The image quality also deteriorates, making it impractical.

The dynamic phenomena of these toner particles are extremely complex, and the factors related to the degree of aggregation include the particle size distribution and shape of the toner particles, the magnetic material, binder resin, and additives used, and the friction coefficient of the particle surface. , adhesion, electrostatic properties, porosity, degree of compaction, adsorbed moisture,
It includes many physical conditions such as temperature.

The method for measuring the degree of aggregation used in the present invention is to place toner on a sieve, apply vibrations, and measure the proportion of toner remaining on the sieve.

According to this method, the greater the proportion of toner remaining on the sieve, the greater the degree of toner aggregation, indicating that toner particles tend to aggregate and behave. Specifically, it is measured using a powder tester manufactured by Nomicrometics Laboratory under conditions of a temperature of 25±1°C and a humidity of 60±5%.

Arrange the 60 mesh, 100 mesh, and 200 mesh sieves in this order from above and set them on the shaking table.
2g of toner was placed on a 60 mesh sieve, and a voltage of 47V was applied to the vibration system to vibrate for 40 seconds.

After completion, the weight of the toner remaining on each sieve is measured, weighted by 0.5, 0.3, and 0.1, and added to express the degree of aggregation as a percentage.

The toner used in the present invention consists of a binding substance, magnetic powder, and additives.

As the binder resin for the toner used in the present invention, known binder resins can be used, including monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene, and styrene-P-chlorostyrene. Styrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid Butyl copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-a chlormethacrylate acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer,
Styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-
Styrenic copolymers such as butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, polymethyl methacrylate, Butyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic resin group hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Parafine wax and the like can be used alone or in combination.

The magnetic powder used in the present invention includes ferromagnetic elements and alloys and compounds containing them, including alloys and compounds of iron such as magnetite, hematite, and ferrite, cobalt, nickel, and manganese, and other ferromagnetic elements. There are substances that are conventionally known as magnetic materials, such as alloys. This magnetic powder is contained in the developer in an amount of 10 to 70% by weight, preferably 15 to 35% by weight.
It is preferable to include it by weight%. With this content, an appropriate magnetic moment is activated in the above-mentioned developing method, a good image can be created, and the fixing property is also excellent.

Further, as additives, carbon black, ultramarine blue, nigrosine, metal complex dyes, colloidal silica, etc. can be used for the purpose of coloring charge control, prevention of aggregation, and the like.

In the electrophotographic method of the present invention, it is appropriate to limit the degree of aggregation of the toner provided to 30% or less.
Although it is clear from the above description, it will become clearer from the following examples.

(Example 1) 70 parts by weight of styrene-butyl maleate copolymer, 30 parts by weight of magnetic powder (magnetite, average particle size 0.25μ)
2 parts by weight of a metal complex dye (trade name: Zapon First Black B, manufactured by BASF) using a ball mill, and melt-kneaded using a roll mill.
After cooling, it is coarsely pulverized using a hammer mill, and then finely pulverized using a supersonic jet pulverizer. The obtained powder was classified and 1 to 40 microns were used as toner. The particle size distribution at this time was about 0.2% by weight of particles of 5μ or less, about 20% by weight of particles of 20 to 35μ, and about 3% of particles larger than 35μ. Image printing was performed using this toner.

The surface of the insulating layer of the photosensitive drum, which consists of three layers: an insulating layer made of polyester resin, a photosensitive layer made of CdS and acrylic resin, and a conductive substrate, is uniformly charged by +6 KV corona discharge at a speed of 168 mm/sec on the cotton surface of the drum. and then at the same time as the original image irradiation.
After performing a 7KV alternating current corona discharge, the entire surface is uniformly exposed to form a latent image on the surface of the photoreceptor. A developer with a sleeve diameter of 50 mm, a magnetic flux density on the sleeve surface of 700 Gauss, and a distance between the sleeve made of aluminum and an iron tipping blade of 0.1 mm as shown in FIG. It was developed using Next, apply +7KV from the back of the transfer paper.
When the powder image was transferred while being irradiated with a direct current corona and fixed using the fixing device of a commercially available dry type electrophotographic copying machine (manufactured by Canon, NP5000), the image density was 1.35.
was sufficiently high, and a high-quality, high-resolution image without fogging was obtained. Observation of the sleeve revealed that the toner layer on the sleeve was approximately 70 microns and was extremely uniformly applied. According to the measurement method described above, the degree of aggregation of toner is 19
It was %. When the environmental conditions during development were set to 30°C and 85% humidity, a high quality image with an image density of 1.25 was obtained.

(Example 2) 65% by weight polystyrene, magnetic powder (ferrite,
Average particle size 0.53μ) 35 parts by weight, Carbon Black 2
A toner consisting of 1 part by weight and 2 parts by weight of a metal complex dye was prepared in the same manner as in Example 1, and after classification, 0.3 parts by weight of hydrophobic colloidal silica was added and imaged at room temperature and humidity in the same manner as in Example 1. When the image was taken out, the image density was 1.47, and a clear image with no fog or image disturbance was obtained. The thickness of the toner layer on the sleeve was approximately 75μ and was uniformly applied. The degree of cohesion of the toner was 5%. environmental conditions
At 30°C and 85% humidity, a high quality image with an image density of 1.3 was obtained.

(Example 3) The same procedure as in Example 1 was carried out at normal temperature and humidity, except that the toner formulation was 100 parts by weight of styrene-butyl maleate-butyl acrylate and 70 parts by weight of magnetite (average particle size 0.25μ). However, a clear image with no fog and a high image density of 1.33 was obtained. The degree of cohesion of the toner was 85%. environmental conditions
When the temperature was 30°C and the humidity was 85%, a high quality image with an image density of 1.12 was obtained.

(Example 4) The distance between the sleeve surface and the blade in Example 1 was
200μ, the distance between the sleeve surface and the photosensitive drum insulating layer surface is 300μ, and the sleeve surface in the developing section is 200μ.
The same procedure as in Example 1 was performed except that an AC bias of 500 V at Hz was applied, and the same results as in Example 1 were obtained. The thickness of the toner layer was approximately 120μ.

(Example 5) A toner was prepared in the same manner as in Example 1 except that the toner formulation of Example 1 was changed to 100 parts by weight of polyester; 100 parts by weight of magnetite; and 2 parts by weight of carbon black. After classification, a toner was prepared using 0.3 parts by weight of hydrophobic colloidal silica. When images were produced at room temperature and humidity in the same manner as in Example 1 using parts by weight, the image density was 1.37.
Clear images with no fog were obtained. The thickness of the toner layer on the sleeve was approximately 70μ and was uniformly applied. The cohesion degree of the toner was 19%. environmental conditions
At 30°C and 85% humidity, a high quality image with an image density of 1.25 was obtained.

(Comparative Example 1) The toner formulation was changed to styrene-butyl maleate.
A toner was prepared in the same manner as in Example 1 using 100 parts by weight of butyl acrylate and 50 parts by weight of magnetite.
The degree of aggregation of this toner at 25°C and 60% humidity is 40%.
It was hot. When copies were made using this toner at room temperature and humidity in the same manner as in Example 1, images with almost no fog and an image density of 1.25 were obtained. However, when the environmental conditions were set to 30°C and humidity to 85%, the image density became as low as 0.8.

(Comparative Example 2) The toner formulation was changed to styrene-butyl maleate-
A toner was prepared in the same manner as in Example 1 using 100 parts by weight of butyl acrylate, 2 parts by weight of polyethylene, and 70 parts by weight of magnetite. This toner's 25℃ humidity 60
The degree of aggregation in % was 48%. When copies were made using this toner at room temperature and humidity in the same manner as in Example 1, images with almost no fog and an image density of 1.16 were obtained. However, when the environmental conditions were set to 30°C and 85% humidity, the image density became as low as 0.7.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an example of a copying device or a recording device to which a developing method according to the present invention can be applied. FIG. 2 is a sectional view of one embodiment of the developing process used in the present invention. 1... Photosensitive drum, 4... Developing device, 4a...
Toner carrier, 4b...Nonmagnetic cylinder, 9...Magnet roll, 10...Doctor blade, 11
...Insulating magnetic toner.

Claims (1)

[Scope of Claims] 1. An electrostatic image carrier that holds an electrostatic image on its surface and a toner carrier that carries an insulating magnetic toner on its surface are arranged with a certain gap in a developing section,
An insulating magnetic toner having an agglomeration degree of 0.1 to 30% at 60% humidity at 60% humidity is supported on a toner carrier to a thickness thinner than the gap, and the toner is transferred to the electrostatic image carrier under the action of a magnetic field. A developing method characterized in that the developing method is carried out by moving to 2 Claim 1 in which the degree of cohesion is 1 to 20%
Development method described in section. 3. The developing method according to claim 1, wherein an alternating current bias is applied between the toner carrier and the electrostatic image holding surface in the developing section.