JPS6132858A - Image forming method - Google Patents

Abstract

PURPOSE:To form stably a sharp image having high density without fogging for a long period of time in image formation including a stage for developing the latent image of a carrying body by using a toner at a ratio within a specific range with a carrier when the average grain size and true specific gravity of the toner and carrier are specified to prescribed values. CONSTITUTION:The toner concn. Tc of the two-component developer, i.e., the ratio (wt%) of the content of the toner with respect to the carrier is maintained within the range shown by the formula where the average grain size of the toner is designated as r1mum, the average grain size of the carrier as r2mum, the true specific gravity of the toner as rho1 and the true specific gravity of the carrier as rho2. The carrier consists of the particle powder which is formed by dispersing and incorporating the pulverous powder of a magnetic material into a binder resin such as styrene or vinyl ketone and has 10-50mum average grain size. Metals such as iron and cobalt including ferrite and magnetite exhibiting strong magnetisum or the alloy thereof, etc. are used for the magnetic material used for the pulverous powder of the magnetic material. The average grain size of the pulverous powder of the magnetic material is about 0.05-3mum and the ratio of te content of the pulverous magnetic material powder is 40-90wt% by the weight of the carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming method including a step of developing a latent image formed by a method or the like with a two-component developer.

[Prior art]

Currently, in order to form a visible image from image information, methods using electrostatic latent images or magnetic latent images, such as electrophotography, are widely used. For example, according to an example of electrophotography, an electrostatic latent image formed on a latent image carrier, which is a photoconductive photoreceptor, through a charging process and an exposure process, is formed by a developer consisting of electroscopically colored particles called toner. The toner image is usually transferred and fixed onto a transfer material to obtain a visible image.

The developer used to develop such an electrostatic latent image or a magnetic latent image includes a so-called two-component developer consisting of a mixture of toner and a carrier, and a carrier consisting of a magnetic toner containing a magnetic substance. There is a so-called one-component developer that is used alone without being charged, but in the system using a two-component developer, the toner is charged by friction, so it is necessary to select the characteristics of the carrier, stirring conditions, etc. It is possible to control the charge polarity and charge amount of the toner to a considerable extent, and in this respect, one-component developers are also superior.

Development methods using such a two-component developer include a magnetic brush method and a cascade method, among which the magnetic brush method is preferably used. What is this magnetic brush method?
A developer layer is formed on the developer transporting carrier by magnetic force in the form of spikes, and this developer layer is rubbed on the surface of the latent image carrier to adhere toner particles to the latent image. This method requires at least development.

Conventionally, the two-component developer used in such a magnetic brush method generally consists of toner particles with an average particle size of about 10-odd μm and magnetic carrier particles with an average particle size of about 70 to 200 μm. It is true. In such a two-component developer, only the toner is consumed as development progresses, so there is a problem that the toner concentration in the developer changes and the image quality deteriorates. It is necessary to replenish toner and control the toner concentration so that it is within a certain allowable range.

However, in the above-mentioned two-component developer containing a carrier with a larger diameter than the toner, the allowable range of toner concentration is narrow and extremely sophisticated technology is required to control the toner concentration. The problem is that the device for controlling the toner concentration is expensive. Moreover, because the carrier has a large diameter, the brush-like bristles of the developer are inevitably rough, resulting in poor reproducibility and poor latent image development. There is a problem that it is difficult to obtain images.

For this reason, a small-diameter carrier was developed in which fine magnetic particles were dispersed in a binder resin (Japanese Patent Laid-Open No. 54-66134).

According to a two-component developer using such a carrier, the surface area of the entire carrier particles is significantly increased compared to the same amount of large-diameter carrier, which increases the chances of frictional contact between the toner particles and the carrier particles. The smaller the variation in image quality caused by changes in toner density, the wider the allowable range of toner density, making it easier to control toner density. Moreover, as the diameter of the carrier particles becomes smaller, the spikes of the developer that stand up like a brush are present in a higher density, thus forming a sharp image with no blemishes and excellent fine line reproducibility. There is a possibility that it can be done.

However, the small-diameter carrier made by dispersing magnetic fine powder in a binder resin as described above has a particle size that is not much different from that of the toner, and is easily scattered. Since it is difficult to make the particles have large magnetic properties because it is not possible to contain a large amount of magnetic material, it is difficult to make the particles have large magnetic properties. Therefore, a problem arises in that a large amount of carrier particles adhere to the latent image carrier together with toner particles during development, and as a result, the benefits of reducing the diameter of the carrier cannot be sufficiently obtained.

(5td4n)day ^h) The present invention was made based on the above-mentioned circumstances, and its object is to use a two-component developer containing a small-diameter carrier so that capri is not generated. An object of the present invention is to provide an image forming method capable of stably forming a high density and clear image for a long period of time.

[Structure of the invention]

The above purpose is to form a developer layer of a two-component developer consisting of toner and carrier on a developer transport carrier, and to supply this developer layer to a development space that generates an oscillating electric field to form a latent image. An image forming method including a developing step of developing a latent image on a carrier, wherein the two-component developer has an average of 0 particles of toner and a diameter of r1 μm1 carrier.
If the average particle size is r2μm1, the true specific gravity of the toner is ρ4, and the true specific gravity of the carrier is now, then the ratio TC of toner to carrier is within the range expressed by the following formula. This is achieved by an image forming method.

However, 10≦r2≦50.0.3≦1≦0.6.

r2- The present invention will be explained in detail below.

In the present invention, a developer transport carrier is disposed opposite to a latent image carrier carrying a latent image with a certain space in which development is performed, that is, a development space, and within this developer transport carrier, for example, developer is held. A two-component developer containing a specific carrier, the details of which will be described later, is raised like a brush on the surface of a developer transport carrier. A state in which a developer layer is formed and the developer layer is not in contact with the latent image carrier, that is, the height of the developer spike is the shortest distance between the latent image carrier and the developer transport carrier in the development space. It is supplied to the developing space in a very small state, and on the other hand, a vibrating electric field is applied to this developing space, and the particles forming the developer layer are oscillated and dispersed, thereby forming a latent image carrier and the developing agent. The toner particles are caused to reciprocate with the agent transporting carrier, thereby causing the toner particles to adhere to the latent image carried on the latent image carrier and developing the latent image to form a toner image.

Next, the toner image is transferred to a transfer material such as paper, and the transferred image is fixed in a fixing device by, for example, a contact heat fixing method using a heating roller, thereby forming a visible image.

Next, the two-component developer used in the method of the present invention will be explained.

The two-component developer used in the method of the present invention has a toner concentration TC%, that is, a content ratio of toner to carrier (weight %), an average particle diameter of the toner of 112 m, an average particle diameter of the carrier of 9 μto, and a true specific gravity of the toner. If ρ1 is ρ1 and the true specific gravity of the carrier is now, it is characterized in that it falls within the range expressed by the following equation (1).

s o (-L) (Q)≦Tc≦140 <-! i＞
r4> (1) r2 r, but 10≦r2≦50.0.3≦11 / r2≦
It is 0.6.

The above formula α) was derived from the viewpoint that the surface area ratio of the toner and the carrier is an important factor in obtaining an appropriate charging state through contact between the carrier and the toner. That is, although the details are omitted, formula α) specifically indicates that the portions K to + of the surface area of the carrier particles are occupied by the toner adhering to the surface of the carrier, and such conditions The results below were obtained based on the experimental confirmation that the frictional charging between toner and carrier was successful.

The carrier is composed of fine magnetic powder dispersed in a binder resin and has an average particle size of 10 to 50.
The particle size is preferably 15 to 40 μm/1 m.

Various binder resins can be used to constitute such a carrier, such as styrenes such as styrene, parachlorostyrene, and α-methylstyrene;
Methyl acrylate, ethyl acrylate, n-acrylate
Propyl, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate,
α-methylene aliphatic monocarboxylic acid esters such as n-butyl methacrylate, 2-ethylhexyl methacrylate, and phenyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine; N-vinyl cyclic compounds such as N-vinylpyrrolidone; vinylmethylketone, vinylethylketone,
Vinyl ketones such as methyl isopropenyl ketone; unsaturated hydrocarbons such as propylene, ethylene, isoprene, butadiene; polymers of monomers such as halogenated unsaturated hydrocarbons such as chloroprene; 2
Copolymers in combination of more than one species, mixtures thereof, non-vinyl condensation resins such as rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyester resins, polyurethane resins, polyimide resins, or mixtures of these and the above-mentioned vinyl resins. can be mentioned.

The magnetic material used for the magnetic fine powder constituting the carrier includes ferrite, magnetite, iron, cobalt, nickel, and other ferromagnetic metals or alloys, or compounds containing these elements, or ferromagnetic elements. alloys that do not contain manganese but become ferromagnetic through appropriate heat treatment, such as alloys called Heusler alloys that contain manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or Examples include chromium dioxide and others. The average particle size of the magnetic fine powder is preferably about 0.05 to 3 μm, and the content of the magnetic fine powder is 40 to 90% by weight, preferably 55 to 80% by weight based on the carrier. It is.

If the fine magnetic powder is exposed in a bare state on the surface of the trenched carrier particles, the triboelectric charging properties of the carrier particles may be adversely affected by the triboelectric charging properties of the fine magnetic powder. It is desirable to previously coat the surface of the magnetic fine powder with a resin or higher fatty acid before incorporating the fine powder into the binder resin. Examples of higher fatty acids that can be used for this purpose include stearic acid, palmitic acid, and oleic acid. Coating can be easily carried out by ``dipping treatment''.

The carrier is preferably insulating and has a specific resistance of 1015Ω or more. If the value of this specific resistance is low, when a bias voltage is applied to the developer transport carrier,
Charges are injected into the carrier particles, causing a problem in which the carrier particles tend to adhere to the surface of the image carrier, or breakdown of the bias voltage tends to occur.

The specific resistance was determined by placing carrier particles in a container with a cross-sectional area of 0.50 mm, tapping them, applying a load of I K9/cm on the packed particles, and applying 1 K9/cm between the load and the bottom electrode. This value is obtained by reading the current value when a voltage that generates an electric field of '000 V/cm is applied.

The carrier can contain various property improvers as required, and the property improvers include charge control agents,
Fluidity improvers and other known agents can be used.

As such a charge control agent, for example, Japanese Patent Publication No. 41-
Fettschw HBN (Fettschw HBN) having positive triboelectric charging properties as described in Japanese Patent No. 2427.
arz HBN; C0I, A 2 6
150), alcohol-soluble Nigrosin; C01, A30
415), Sudan Chief Shubarut BB (Suda
n tiefschwarz BB; 7 /I/Bent Bratak 3; C, 1, A26150), Brilliant Spirit Schwarz TN (Brillantsp
ritschwarz TN; 77 /l/pen,
Fabriken, manufactured by Baia), Zabonsparz X (Z
aponschwarz
Hoechst), negatively triboelectrically charged Ceresschwarz@G (Ceresschwarz@G:
77 yv Behenfapriken (manufactured by Bahia), Riha Morgenschwa 71/tsu EiTOO (Chromoge)
n schwarz ETOO; C0I, A146
45), Azo Oil Black (FQ (Azo-Of
l-Black (R); National, manufactured by Aniline Co., Ltd.), Spiron Black TR) I (manufactured by Hodogaya Chemical Co., Ltd.), Bontron 834 (OIJ: r, manufactured by Hodogaya Chemical Co., Ltd.), Nigrosine SO (manufactured by Orient Chemical Co., Ltd.) ) and other dyes such as phthalocyanine blue fxF are self-soothing with a mixture of dyes and phthalocyanine blue fxF → Carbon black that has been oxidized and resins that have positive or negative charge control groups are considered to be a type of charge control agent. be able to.

Further, in order to improve the compatibility of these charge control agents with the resin component, they can be added in the form of salts formed with higher fatty acids, or a compatibility improver can be added separately.

Further, examples of the fluidity improver include inorganic materials such as silica and alumina.

The carrier can be manufactured as follows. For example, a binder resin, magnetic fine powder, and other property improving agents added as necessary are premixed using a ball mill or the like, and uniformly mixed and dispersed. Next, the mixture is kneaded using heated rolls, and then cooled and pulverized. Next, in order to obtain a carrier having a desired particle size, classification is performed as necessary to produce a carrier.

Further, it is preferable that the carrier has a spherical shape because it can improve the fluidity, and in this way, when using a spherical carrier, for example, a pulverized carrier obtained according to the above manufacturing method is used. A suitable method is to further spray the carrier particles into hot air using a known spray dryer method or the like, thereby instantaneously melting the surface of the carrier particles and making the carrier particles spherical by surface tension. be.

Still another method for producing the carrier is a method in which a monomer component of a binder resin is polymerized in the presence of fine magnetic powder to form a polymer, and this method is industrially stable. This is preferable because it is easy to assemble.

Specifically, the following methods can be mentioned, for example.

(a) A method in which ordinary bulk polymerization is carried out in a solvent-free state under a nitrogen stream at a temperature of 60 to 120°C.

(b) In water at a temperature of 60 to 12,010 degrees Celsius under a nitrogen stream, for example, powders of gelatin, starch, polyvinyl alcohol, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, silicic acid, or metal oxides, etc. A method in which suspension polymerization is carried out by a conventional method in the presence of a dispersant.

Emulsion polymerization is carried out by a conventional method using an aqueous polymerization initiator in the presence of a surfactant such as fj sodium dodecylbenzene sulfonate, an alkyl sulfate type anion emulsifier, and sodium dodecyl sulfonate under a nitrogen stream at a temperature of 40 to 90 °C. How to do it.

2) Examples of solvents C that are suitable at temperatures of 60 to 120°C under nitrogen flow! - A method in which solution polymerization is carried out by a conventional method in a diluted state with (habenzene, xylene, ethanol, methyl ethyl ketone).

The toner that constitutes the two-component developer together with the carrier described above is made by dispersing toner components such as colorants in a binder resin, and various thermoplastic resins can be used as the binder resin. used. Specific examples include styrene, parachlorostyrene,
Styrenes such as α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-methacrylate
α-methylene aliphatic monocarboxylic acid esters such as -butyl, diuryl methacrylate, and e2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine: Vinyl ethers such as vinyl methyl ether and vinyl butyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; Unsaturated hydrocarbons such as ethylene, pyrene, isoprene, and butadiene, and their halides; Polymers of monomers such as halogenated unsaturated hydrocarbons such as chloroprene, copolymers obtained by combining two or more of these monomers, mixtures thereof, or, for example, rosin-modified phenol formalin. Examples include non-vinyl condensation resins such as resins, oil-modified epoxy resins, polyester resins, polyurethane resins, polyimide resins, cellulose resins, and polyether resins, or mixtures of these and the above-mentioned vinyl resins. Colorants include, for example, carbon black, nigrosine dye, aniline blue, calco oil blue, lime yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or mixtures thereof. Toner components other than the i-coloring agent include a charge control agent, an anti-offset agent, a fluidity improver, and the like, and if necessary, fine magnetic powder may be contained.

Such a toner can be obtained by a conventionally known toner manufacturing method, and has an average particle size of 25 μm or less, particularly 10 to 1
A 6 μm toner is preferred.

The two-component developer used in the method of the present invention has been described above.Next, a specific developing process for developing, for example, an electrostatic image using such a developer will be described.

The developer transport carrier for supplying the developer to the development space is
A conventional device capable of applying a bias voltage can be used, and a structure in which a rotating magnet having a plurality of magnetic poles is provided inside a sleeve on which a developer layer is supported is particularly preferable. Can be used. In such a developer transport carrier, the rotation of the rotating magnet causes the developer layer carried on the surface of the sleeve to move in an undulating manner, so that new developer is continuously supplied. Furthermore, even if there is some degree of non-uniformity in the thickness of the developer layer on the surface of the sleeve, the above-mentioned wave-like undulations sufficiently cover the effect so that it does not become a problem in practice. It is preferable that the developer conveying speed due to the rotation of the rotating magnet or the rotation of the sleeve is almost the same as or faster than the moving speed of the electrostatic image carrier. Also,
The conveyance direction due to the rotation of the rotating magnet and the rotation of the sleeve is
The same direction is preferred. Image reproducibility is better in the same direction than in the opposite direction. However, it is not limited to these.

Further, it is preferable that the developer layer supported on the developer transport carrier has a uniform thickness. For example, the developer adhering to the developer transport carrier is sufficiently scraped off with a blade that regulates the thickness. A uniform layer is preferred. The gap between the developer transport carrier and the electrostatic image carrier is several 10
~2000 μm is preferable, and if the gap between the developer transport carrier and the electrostatic image carrier is too narrow than several tens of μm,
It is difficult to form magnetic brush ears that can develop uniformly in the developing space, and it is also impossible to supply a sufficient amount of toner particles to the developing space, making it difficult to perform stable development. On the other hand, if the gap greatly exceeds 2000 μm, the opposing electrode effect will deteriorate and sufficient image density will not be obtained. The edge effect of increasing toner adhesion also increases.

In addition, it is especially important to set the gap and the thickness of the developer layer so that the ears of the magnetic brush do not come into contact with the surface of the electrostatic image carrier without applying an oscillating electric field, and are as close as possible to the surface of the electrostatic image carrier. preferable. This is because the toner image is prevented from having scratches or fogging caused by the rubbing of the magnetic brush.

Preferably, the oscillating electric field is created by applying an oscillating bias voltage to the sleeve of the developer transport carrier. Further, as the bias voltage, it is preferable to use a voltage obtained by superimposing a DC voltage, which prevents toner particles from adhering to non-image areas, with an AC voltage, which makes it easier for the toner particles to separate from the carrier particles. However, the present invention is not limited to these methods.

An example of a specific apparatus that can be used to perform the developing step in the method of the present invention is shown in FIG. In FIG. 1, reference numeral 1 denotes a drum-shaped electrostatic image carrier such as a photoreceptor such as Be, which rotates in the direction of the arrow, and an electrostatic image is formed on its surface by a charging exposure device (not shown). 2 is a sleeve made of a non-magnetic material such as aluminum; 3 is a magnet body provided inside the sleeve 2 and having a plurality of N and S magnetic poles along the circumference; the sleeve 2 and the magnet body 3 form a developer transport carrier; is configured. The sleeve 2 and the magnet 3 are relatively rotatable, and in the illustrated example, the sleeve 2 is rotated in the direction of the arrow, and the magnet 3 is fixed.

The N and S magnetic poles of the magnet body 3 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the magnetic force creates a layer of developer material in the form of a brush on the surface of the sleeve 2, that is, a magnetic brush. Form. 4 is the height of the magnetic brush,
A regulating blade 5 made of a magnetic or non-magnetic material regulates the amount, and a cleaning blade 5 removes the magnetic brush that has passed through the developing space A from above the sleeve 2. sleeve 2
Since the surface of 7 comes into contact with the developer at the developer reservoir, the developer is supplied.
is a stirring screw that stirs the developer in the developer reservoir to make the components uniform. Since toner particles in the developer reservoir at the top of the developer reservoir are consumed when development is performed, toner particles T in the toner hopper 8 are replenished as appropriate. Reference numeral 9 denotes a supply roller having a concave portion on its surface for dropping the toner particles T into the developer reservoir. A bias power supply 10 applies a bias voltage to the sleeve 2 via a protective resistor 11. A bias voltage having an oscillating alternating current component is applied by the bias power supply 10 between the grounded base 1a of the electrostatic image carrier 1 and the sleeve 2. This bias voltage is, for example, a superimposed voltage of a DC voltage and an AC voltage.The DC component prevents fogging, and the AC component vibrates the magnetic pusher to improve the developing effect. For this DC voltage component, a voltage of, for example, 50 to 600 V, which is approximately equal to or even higher than the potential of the insertion part, is used, and for the AC voltage component, a frequency of 100 Hz to 10 kHz, preferably 1 to 10 kHz is used.
A voltage of 100V to 5KV at 5kHz is used.

Note that, when the toner particles contain a magnetic substance, the DC voltage component may be lower than the valve surface potential. If the frequency of the AC voltage component is too low, the effect of imparting vibration will be small, and if it is too high, the developer will not be able to follow the vibrations of the electric field, resulting in a decrease in image density and the inability to obtain a clear, high-quality image. A trend appears. In addition, the voltage of the AC voltage component is also related to the frequency, but the higher the voltage, the more the magnetic brush will vibrate and the more effective it will be, but if it is too high, it will easily cause fogging, and it will cause problems such as lightning strikes. This is not preferable because dielectric breakdown is likely to occur.

In the above-described apparatus, if the gap between the sleeve 2 and the electrostatic image carrier 1 is set to be in the range of several tens to 2000 μm, the electrostatic image on the electrostatic image carrier l is developed. , the magnetic pushin formed on the surface of the sleeve 20 is
As the magnetic flux density on the surface of the sleeve 20 changes as the sleeve 20 rotates, it moves on the sleeve 2 while vibrating, thereby stably and smoothly passing through the gap with the electrostatic image carrier l. At this time, on the surface of the electrostatic image carrier 1,
It provides a uniform development effect, making it possible to stably develop images with high density.

Although an example of the apparatus that can be used in the method of the present invention has been described above with reference to FIG. 1, the present invention is not limited thereto. For example, several electrode wires may be stretched around the developing area between the developer transport carrier and the electrostatic image carrier, and an oscillating voltage may be applied to them to vibrate the magnetic brush and produce a developing effect. can be improved.

In that case as well, a direct current bias voltage may be applied to the developer transport carrier, or oscillating voltages of different frequencies may be applied. Furthermore, the method of the present invention can be similarly applied to reversal development and the like. In that case, the DC voltage component is set to a voltage approximately equal to the receiving potential in the non-image background portion of the electrostatic image carrier. Furthermore, the method of the present invention can be applied even when the image to be developed is a magnetic latent image.

[Function and effect of the invention]

In the image forming method of the present invention, by applying an oscillating electric field to the developing space in the developing step, even if a small-diameter carrier is used as the carrier constituting the developer, this carrier can be prevented from adhering to the latent image carrier. is suppressed, and good development can be achieved. That is, by applying an oscillating electric field to the developing space, the particles constituting the developer fly between the developer layer and the latent image carrier in the state of unit particles as the electric field changes. Therefore, it is possible to selectively adhere toner particles to the electrostatic latent image based on strictly defined Coulomb attraction, and therefore adhesion of carrier particles to the latent image carrier is inhibited.

As a result, the effects of reducing the diameter of the carrier are: (1) the tolerance range of toner concentration in the two-component developer is wide, making toner replenishment easy, and (2) the spike-like spikes in the developer layer are high. It is possible to fully exhibit effects such as being able to obtain high-quality images with high density and no unevenness.

Furthermore, in the image forming method of the present invention, since the developer used has a toner concentration within a specific range defined by the average particle diameter and true specific gravity values of the carrier and toner, the toner and carrier As a result, the toner can be properly charged, and as a result, clear images with no fog and high density can be produced, as is clear from the examples described below. can be formed.

[Embodiments of the invention]

Examples of the present invention will be described below, but the present invention is not limited thereto. Note that "parts" represent parts by weight.

<Production of carrier> l) Carrier A Styrene-acrylic resin (monomer composition ratio of styrene, butyl methacrylate and methyl methacrylate: 50:
20:30. Softening point: 133℃) 40 parts Magnetite "BL-100" (manufactured by Titan Kogyo Co., Ltd.) 70
Partial charge control agent "Spiron Black TRHJ (manufactured by Hodogaya Chemical Co., Ltd.) 2 or more parts of the substance are mixed in a ball mill, further kneaded with two rolls, then crushed and classified, and the average particle size is 20.4 μm, true specific gravity is 1. 92 microcarriers were obtained, which will be referred to as "carrier A".

2) Carrier B A carrier was obtained in the same manner as Carrier A except that the average particle diameter of 20.4 μm in Carrier A was changed to 40 μm. This will be referred to as "Career B."

3) Carrier C Styrene-acrylic resin (monomer composition ratio of styrene, butyl methacrylate and methyl methacrylate: 50:
20:30) 25 parts magnetite rBPT
-1000J (manufactured by Toda Kogyo Co., Ltd.) 70 parts of the charge control agent "Spiron Black TRHJ" Using 2 parts or more of the substance, the average particle size was 24 in the same manner as in the case of carrier A.
．． A carrier with a true specific gravity of 2.02 was obtained. This will be referred to as "Carrier C."

<Manufacture of toner> 1) Toner a Styrene-acrylic resin (monomers of styrene, phthyl acrylate and methyl methacrylate, composition ratio 75:
15:10. Weight average molecular weight Mw/number average molecular number MN=
10.1, softening point 128℃)
100 parts carbon black "Mogul L" (manufactured by Cabot) 10 parts boriglobylene r660PJ (manufactured by Sanyo Chemical Co., Ltd.) 3 parts charge control agent "Nigrosine 80j (manufactured by Orient Chemical Co., Ltd.) 2 or more parts were mixed in a ball mill, and further 2 parts After kneading with this roll, it was crushed and classified to obtain a non-magnetic toner powder with an average particle size of 11.0 μm and a true specific gravity of 1.06.Additionally, this toner powder was supplemented with hydrophobic silica fine powder equivalent to over 0.2 weight of the toner powder. [几-972J (manufactured by Nippon Aerosil Co., Ltd.) was added and mixed to prepare a toner.

This is referred to as "toner a".

2) Toner b A toner was obtained in the same manner as Toner a, except that the average particle size of the toner powder in Toner a, 11.02 m, was changed to 16.5 μm. This is referred to as "toner b".

Examples 1 and 2 and Comparative Examples 1 and 2 Carrier A and toner a were used, and the content ratio (wt%) Tc of toner to carrier was the value shown in Table 1. Two types of examples and two comparative examples were used. A total of four types of developers were prepared. Furthermore, this carrier A
In the developer composed of toner a and toner a, the range of the content ratio Tc of the toner that satisfies the above-mentioned formula (1) is approximately 20 to 42.

The device shown in Figure 1 using each developer listed in Table 1 and above? Two live-action tests were conducted using the camera, and the following evaluation items were examined.

The results are also listed in Table 1.

<Evaluation Items> (1) Capri Capri, that is, occurrence of toner adhesion to the background area other than the image area to which the toner should adhere was visually observed. The evaluation was rated as "○" if there was almost no occurrence of capri, "△" if there was some occurrence of capri, and "x" if there was significant occurrence of capri.

(2) Carrier Adhesion Carrier adhesion was visually observed for carrier adhesion on the transferred image. The evaluation was given as "○" if there was almost no carrier adhesion, "Δ" if there was some carrier adhesion, and "x" if there was significant carrier adhesion.

(3) Image Alignment Image alignment was determined by visually observing the transferred image. For evaluation, those with sufficient image density and practical use were evaluated as rOJ, those with slightly low image density and edge effects were evaluated as "Δ," and those with low image density and noticeable edge effects were evaluated as "x."

The equipment used for the live-action test had the following conditions. That is, the electrostatic charge image carrier 1 is an organic photoconductive (OPC) photoconductor, its circumferential speed is 150 m/sec, the highest potential of the electrostatic image formed on the charge image carrier 1 is -500 cm, and the sleeve 2 is The outer diameter is 30 m, the rotation speed is 10° rpm, the magnetic flux density of the N and S magnetic poles of the magnet body 3 is 500 Gauss, the rotation speed is 11000 rpm, and the thickness of the developer layer in the developing space is 0.
2■, gap between sleeve 2 and electrostatic image carrier 1 0.3+
s, that is, the bias voltage applied to the 300 μm 1 sleeve 2 has a DC voltage component of -250V.

The AC voltage component was 1.5kHz and 400V. Further, for fixing, a heat roller fixing device with a heat roller surface temperature of 180° C. was used.

Examples 3 to 5 and Comparative Example 3 Using carrier A and toner b, the content ratio (weight %) of toner to carrier was set to the value shown in Table 2.
A total of four types of developers were prepared, three types for Examples and one type for Comparative Examples. In addition, in the developer composed of carrier A and toner b, the range of the content ratio Tc of toner that satisfies the above-mentioned condition 2α) is approximately 36 to 63.
It is.

For each of these developers, an actual photographic test was conducted using the apparatus described above. The results are shown in Table 2.

Table 82 Examples 6 and 7 and Comparative Examples 4 and 5 Using carrier B and toner a, the content ratio (weight and weight) of toner to carrier was set to the value shown in Table 3.
A total of four types of developers were prepared, two types for Examples and two types for Comparative Examples. In addition, in the developer composed of this carrier B and toner a, the above formula (1) is satisfied.
The content ratio Tc of the toner that satisfies the range is approximately 12 to 2
It is 2.

For each of these developers, an actual photographic test was conducted using the apparatus described above. The results are shown in Table 3.

Table 3 Examples 8 and 9 and Comparative Examples 6 and 7 Using carrier B and toner b, the content ratio (weight ratio) of toner to carrier was set to the value shown in Table 4.
A total of four types of developers were prepared, two types for Examples and two types for Comparative Examples. In addition, in the developer composed of carrier B and toner b, the above formula (1) is satisfied.
The content ratio Tc of the toner that satisfies the range is approximately 18 to 3
It is 2.

For each of these developers, an actual photographic test was conducted using the apparatus described above. The results are shown in Table 4.

Table 4 Example 10.11 and Comparative Examples 8 and 9 Using carrier C and toner a, the content ratio (weight %) of toner to carrier was set to the value shown in Table 5.
A total of four types of developers were prepared, two types for Examples and two types for Comparative Examples. In addition, in the developer composed of carrier C and toner a, the range of the content ratio Tc of toner that satisfies the above-mentioned formula (1) is approximately 19 to 33.
It is.

For each of these developers, an actual photographic test was conducted using the apparatus described above. The results are shown in Table 5.

According to the results shown in Table 5 and above, in all of the examples of the present invention, high-quality visible images with good reproducibility without capri, carrier adhesion, and image distortion are produced within the appropriate range of toner density. It has been confirmed that it can be obtained.

On the other hand, the comparative examples were inferior in all evaluation items; if the toner density is too low, carrier adhesion and image distortion occur significantly, and if the toner density is too high, fogging occurs. It turned out to be significant.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view schematically showing an example of a developing device that can be used to perform a developing step in carrying out the method of the present invention. 1... Electrostatic image carrier 2... Sleeve 3...
Magnet body 4... Regulation blade 5... Cleaning blade

Claims (1)

[Claims] 1) A developer layer of a two-component developer consisting of toner and carrier is formed on a developer transport carrier, and this developer layer is supplied to a development space in which an oscillating electric field is generated. An image forming method including a developing step of developing a latent image on a latent image carrier, wherein the two-component developer has the following characteristics: an average particle size of toner of r_1 μm, an average particle size of carrier of r_2 μm, and a true specific gravity of toner. An image forming method characterized in that the ratio T_C of toner to carrier is within a range expressed by the following formula, where ρ_1 is the true specific gravity of the carrier and ρ_2 is the true specific gravity of the carrier. 80 (r_1/r_2) (ρ_1/ρ_2)≦T_C≦
140 (r_1/r_2) (ρ_1/ρ_2) However,
10≦r_2≦50, 0.3≦r_1/r_2≦0.6
It is.