JPS63174054A - Electrostatic image developer and electrostatic image developing method - Google Patents

Abstract

PURPOSE:To impart triboelectrified charge of an adequate electrostatic charge quantity to a toner by incorporating a carrier coated with a silicone compd., toner contg. a prescribed copolymer and fine inorg. particles to be electrostatically charged positive into a developer. CONSTITUTION:The fine magnetic material particles coated with the silicone compd., for example, rubber, varnish or resin consisting of polysiloxane having a methyl group or phenyl group are used for the carrier of the developer. The styrene/acrylic copolymer polymerized by an azo-bis initiator is used for the binder of the toner and a coloring agent and other additives are dispersed therein. The fine inorg. particles (e.g.; silica particles) which are subjected to a surface treatment by an amino modified silicone compd., etc. and are electrostatically charged positive are further incorporated therein. The positive triboelectrified charge of the adequate electrostatic charge quantity is imparted to the toner according to this constitution and, therefore, the images having a high image density without having fogging are stably obtd. many times.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrostatic image used for developing an electrostatic latent image formed in electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to a developer and an electrostatic image developing method for developing an electrostatic latent image formed on the surface of a photoreceptor made of an organic photoconductive semiconductor using the electrostatic image developer,
In particular, the present invention relates to an electrostatic image developer and an electrostatic image developing method suitable for developing a negative electrostatic latent image formed on the surface of a photoreceptor made of an organic photoconductive semiconductor.

(Background of the Invention) In general, in electrophotography, a photoreceptor having a photosensitive layer made of a photoconductive material is given a uniform electrostatic charge, and then image exposure is performed to create a static charge on the surface of the photoreceptor. An electrostatic latent image is formed, and this electrostatic latent image is developed with a developer to form a toner image.The obtained toner image is transferred to a transfer material such as paper, and then fixed by heating or pressure. to form a copy image.

Examples of the photoconductive material used to form the photosensitive layer of the photoreceptor include inorganic photoconductive materials such as selenium, zinc oxide, and cadmium sulfide, and organic photoconductive materials made of high molecular compounds or low molecular weight compounds such as polyvinyl carbazole. There are known materials such as carbonaceous materials.

However, although photoreceptors having photosensitive layers formed from these photoconductive materials have one advantage in forming electrostatic latent images, they also have drawbacks specific to various photoreceptors. have.

For example, in a photoreceptor having a photosensitive layer formed of selenium, the photosensitive layer easily crystallizes due to heat or metal compounds contained in the developer or transfer material, deteriorating its properties, resulting in an electrostatic latent image. There is a problem that the potential of the image decreases, resulting in a decrease in image density or partial image blanking. In addition, under high humidity environmental conditions, the photoconductivity of the photosensitive layer decreases and static charges remain in the non-image areas of the photoreceptor, resulting in fogging and making it difficult to obtain clear images. First, there is a problem that good images cannot be formed many times under high-temperature environmental conditions, and durability is low.

Additionally, photoreceptors having a photosensitive layer formed of cadmium sulfide or a photoreceptor having a photosensitive layer formed of zinc oxide typically have a photoconductive material, ie, cadmium sulfide or zinc oxide, dispersed in a binder resin. A photosensitive layer is formed, but it is quite difficult to uniformly disperse such a photoconductive material in the form of fine particles in a binder resin, and as a result, the resulting photoreceptor has low sensitivity and is unsuitable for high-speed copying. In addition, the photosensitive layer tends to deteriorate early in the corona charging process or exposure process that is normally used to form an electrostatic latent image, making it difficult to maintain a good image over a long period of time. Furthermore, under high-humidity environmental conditions, the characteristics of the photosensitive layer change due to moisture, making it impossible to obtain the desired electrostatic latent image potential, resulting in a low image density. There is a point.

On the other hand, organic photoreceptors having a photosensitive layer formed from a polymeric photoconductive material typified by polyvinylcarbazole have good film-forming properties and can be manufactured at low cost. It has been attracting attention in recent years due to its advantages such as non-toxicity, but on the other hand, it has low sensitivity and is prone to early deterioration during the corona charging process or exposure process, resulting in poor durability. Since the charge retention ability is easily changed, it is still inferior to photoreceptors having a photosensitive layer made of an inorganic photoconductive material, and the development of a high-performance photoconductive material is desired.

On the other hand, in order to overcome the above-mentioned problems, in recent years there has been a decline in the use of low molecular weight organic photoconductive materials. Since the low molecular weight organic photoconductive material has good dispersibility in the binder resin, the resulting photosensitive layer has the organic photoconductive material uniformly dispersed in the form of fine particles. It is possible to obtain a photoreceptor with relatively high sensitivity, and by forming the photosensitive layer by dispersing an organic photoconductive material in a binder resin, film forming properties are good, and therefore the photoreceptor can be processed with high productivity. In addition, there are many types of low molecular weight photoconductive materials that can be used, and therefore, by using appropriately selected low molecular weight photoconductive materials, it is possible to create photoreceptors with superior performance than conventional ones. It is possible to obtain. Thus, organic photoreceptors having a photosensitive layer formed of a low molecular weight organic photoconductive material are preferred over conventional photoreceptors.

However, since organic photoconductive materials usually exhibit photoconductivity through the movement of positive charges, it is difficult to form photoconductive materials on the surface of an organic photoreceptor that has a photosensitive layer formed from the organic photoconductive material. The polarity of the electrostatic latent image is preferably negative. In order to develop a negative electrostatic latent image, it is necessary to use a developer containing positively charged toner.

However, in the conventionally widely used photoreceptor having a photosensitive layer made of selenium, etc., the polarity of the electrostatic latent image formed on the surface is positive, so it is difficult to develop the electrostatic latent image. A developer containing a negatively charged toner is used, and a considerable amount of research and development has been done on developing a developer containing a negatively charged toner. Research and development of developers containing toner is still lagging behind, and the reality is that a developer containing a sufficiently positively charged toner has not been obtained.

On the other hand, wet developing methods and dry developing methods are known as methods for developing electrostatic latent images. The former wet development method uses a liquid developer, which has the problem of emitting a bad odor, and also requires high energy to dry the transfer material, making high-speed copying difficult. The latter dry developing method does not have such problems and can be preferably used as a developing method for electrostatic latent images.

The developers used in the dry development method include a so-called one-component developer consisting only of a magnetic toner containing a magnetic substance, and a so-called two-component developer consisting of a non-magnetic toner that does not contain a magnetic substance and a magnetic carrier. type developer is known.

The former one-component developer consists only of magnetic toner and does not have a carrier, so there is some frictional electrification caused by the toners and the height of the toner and the developing sleeve or developer layer placed in the developing device is controlled. The toner is charged by frictional charging with the regulating blade, etc., and as a result, both positively charged toner and negatively charged toner exist, and the amount of PJ frictional electrification is small, so development basically fails. There is a problem that it tends to become stable. Specifically, for example, toner may adhere to non-image areas on the photoreceptor,
There is a problem that capri occurs in the final fixed image, or the amount of toner adhering to the image area on the photoreceptor becomes insufficient, resulting in a low density of the final fixed image.

In addition, the magnetic material used in magnetic toner usually has hydrophilic properties, and since this hydrophilic magnetic material is often contained in an exposed state on the surface of toner particles, the toner becomes triboelectrically charged due to moisture. Charge tends to leak, and in high-temperature environments, electrostatic transfer to the transfer paper normally used as a transfer material becomes defective during the transfer process, resulting in a low toner transfer rate to the transfer paper. There is a problem that the density of the final fixed image decreases (also, since the magnetic material used for magnetic toner usually has negative chargeability,
It is difficult to positively charge magnetic toner with an appropriate amount of charge, and as a result, a large proportion of toner with opposite polarity exists.
As a result, there are problems in that the density of the final fixed image decreases and image unevenness occurs.

On the other hand, the latter two-component developer is composed of toner and carrier, and the carrier has the function of charging the toner to a desired polarity. It is possible to impart a triboelectric charge depending on the amount, and it is possible to obtain a developer having much superior triboelectric chargeability compared to the one-component developer described above.

Further, by selecting a carrier having desired characteristics, it is possible to control the amount of charge of the toner to a considerable extent.

However, in order to obtain a good final fixed image, it is not enough that the developer has good triboelectric chargeability, and particles of the developer to which triboelectric charge has been applied do not aggregate in the developing device. It is necessary that the film be transported to the developing space in good condition without any damage.

In other words, in a two-component developer, if the toner tends to aggregate and form lumps due to electrostatic aggregation, it becomes difficult to disperse the toner particles in the carrier particles at a uniform concentration. The triboelectricity of the toner and carrier decreases, and the proportion of toner with low triboelectricity increases, and in the developing process, toner adheres to non-image areas on the photoreceptor, causing fog in the final fixed image. In addition, there is a large amount of weakly charged toner, and the electrostatic adhesion force between the toner and the carrier is small. Therefore, in the magnetic brush development method, the toner particles attached to the carrier particles are removed while rotating the carrier particles by magnetic force. When conveyed to the developing space, toner particles scatter due to centrifugal force due to the rotation of the carrier particles, and as a result, they contaminate various devices such as the charger and exposure optical system installed in the copying machine, and the final fixation is interrupted. There is a problem that image defects such as image unevenness occur in the image.

However, in conventional negatively charged toners, fine silica particles having a smaller diameter than the toner particles are mixed with the toner particles to attach the fine silica particles to the surface of the toner particles, thereby preventing the toner from clumping. This is done to obtain high liquidity.

However, conventionally used silica fine particles have strong negative chargeability, so when obtaining a positively chargeable toner, if silica fine particles are mixed with the toner and attached to the surface of the toner particles, the resulting toner will be negatively charged. It becomes electrostatic,
As a result, the polarity becomes the same as the negative electrostatic latent image formed on the photoreceptor, and there is a problem that electrostatic development cannot be performed.

[Problem that the invention seeks to solve]

Under these circumstances, research and development of positively chargeable fine particles has been progressing recently, but it has been found that there is a new problem.

In other words, the positively charged a-free fine particles are mixed with the toner and kept attached to the toner particles, and when mixed with the carrier particles and stirred, they impart a positive charge to the toner. RAM charge is applied, but since conventional two-component developers use a carrier made of iron powder particles, when the toner and carrier are stirred in the developing device, the toner particles are Positively charged inorganic fine particles adhering to the surface begin to transfer to the surface of the carrier particle due to physical or electrostatic adhesion, and the amount of transfer increases each time the carrier is used repeatedly. As a result, the frictional charging characteristics between the toner and the carrier change, and the amount of weakly charged toner increases, and furthermore, the amount of toner that is negatively charged increases, resulting in fogging and image distortion. Phenomenon in which a part of the image is missing (image missing), a phenomenon in which a difference in shading appears in the image (image unevenness), a phenomenon in which the density in the peripheral area of the image decreases
There is a problem in that a phenomenon in which band-shaped differences in shading appear in an image (referred to as "image blurring") occurs, and the image becomes unclear.

Further, when an image is formed many times, the positive chargeability of the toner is significantly reduced, resulting in a problem that the image density becomes low and unclear at an early stage, and the durability of the developer is low.

In addition, weakly charged toner or toner of opposite polarity tends to scatter, which contaminates the inside of the apparatus, resulting in the problem that the image becomes smudged and unclear.

On the other hand, in toner, styrene is used as a binder.
Acrylic copolymers are widely used. However, conventional styrene-acrylic copolymers generally have
Because it is obtained through a polymerization reaction using benzoyl peroxide as an initiator, the copolymer contains a large amount of benzoic acid, which is a decomposition product of benzoyl peroxide, as a constituent unit. As a result, the negative chargeability caused by the benzoic acid appears strongly in the toner, and there are problems in that the positive triboelectricity of the toner is inhibited and the rise characteristics of the triboelectricity are poor. In other words, the required stirring time from the start of stirring of the developer in the developing device until the amount of triboelectric charge of the toner reaches the appropriate value required for development is considerably long, and as a result, a lot of fogging occurs, especially in the early stages of image formation. However, there is a problem that the initial image becomes unclear.

This problem becomes particularly serious when the developer is left unstirred for a long time, such as when images are formed first thing in the morning.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its objects are as follows: (1) to have good positive chargeability, to produce high-quality images with high image density and no fog over and over again; (2) To provide an electrostatic image developer that can stably form good images regardless of environmental conditions; (3) To provide an electrostatic image developer that can stably form good images regardless of environmental conditions. ) To provide an electrostatic image developer that has good triboelectric charging properties and can form a clear image without fogging even in the initial stage of image formation; An object of the present invention is to provide an electrostatic image developing method that can satisfactorily develop a negative electrostatic latent image without causing toner scattering.

[Means for solving problems]

The electrostatic image developer of the present invention comprises a carrier comprising magnetic particles coated with a silicone compound, a toner comprising a styrene-acrylic copolymer polymerized with an azobis initiator, and the carrier. Inorganic fine particles that become positively charged due to friction with other objects (hereinafter also referred to as "positively chargeable inorganic fine particles").

).

The electrostatic image developing method of the present invention includes a carrier formed by coating magnetic particles with a silicone compound, a toner containing a styrene-acrylic copolymer polymerized with an azobis-based initiator, and the carrier. Electrostatic image developer (hereinafter referred to as "electrostatic image developer") containing inorganic fine particles that become positively charged by friction with
Also referred to as "specific developer." ) to develop a negative electrostatic latent image formed on the surface of a photoreceptor (hereinafter also referred to as "organic photoreceptor") made of an organic photoconductive semiconductor by a contact magnetic brush development method. do.

[Function and effect of the invention]

According to the electrostatic image developer of the present invention, a carrier having a coating layer made of a silicone compound, a toner containing a specific copolymer, and a positive charge that are positively charged due to friction between the carrier and the carrier. Since it contains chargeable inorganic fine particles, the synergistic effect of these makes it possible to reliably impart a positive and appropriate amount of triboelectric charge to the toner, resulting in an image with a high 4 degree and no capri. Images of good quality can be stably formed many times. In addition, good positive triboelectric charging properties of the toner can be stably obtained regardless of environmental conditions, so even under high-temperature environmental conditions, high-quality images with high image density and no capri are produced repeatedly. can be formed into Moreover, since the developer has good triboelectric charging properties, it is possible to form an initial image of good quality without capri even in the initial stage of image formation.

In other words, since the styrene-acrylic copolymer contained in the toner is polymerized with an azobis-based initiator, it contains carboxylic acid compounds such as benzoic acid that cause damage to the positive triboelectric charging properties of the toner. is not contained in the unit, so that the toner has good positive triboelectric charging properties, and
The rise characteristics of triboelectric charging with carriers are improved.

Therefore, even if the developer is left unstirred for a long time, the necessary stirring time is required from the time the developer starts stirring in the developing device until the amount of triboelectric charge on the toner reaches the appropriate value required for development. As a result, capri does not occur even in the initial stage of image formation, and an initial image of good quality can be formed.

In addition, since the specific styrene-acrylic copolymer contained in toner generally has hard properties, the physical adhesion of the toner is low, and as a result, the toner cannot be sufficiently uniformly dispersed and mixed into the carrier. , it is possible to impart a stable triboelectric charge to the toner with a high probability. Also,
Since the toner contains a specific styrene-acrylic copolymer, the positively charged inorganic fine particles have high adhesion to the toner particles, and even when agitated in the imager, the positively charged inorganic fine particles form. is stably held in the toner particles, and the toner's 4'R triboelectric charging properties are stably exhibited.

As described above, since the toner has positive triboelectric chargeability and the electrostatic image developer contains positively chargeable inorganic fine particles, the toner has even better positive triboelectricity. Since the carrier has a coating layer made of a silicone-based compound, the surface energy of the carrier particles is reduced and the surface slipperiness is improved, so that the adhesion of positively charged inorganic fine particles to the carrier particles is reduced. This makes it difficult for the toner substance to adhere to the carrier particles, and as a result, the toner can stably exhibit good positive triboelectric charging properties over a long period of time. Also,
A carrier having a coating layer made of a silicone compound has stable triboelectric charging properties even under changes in environmental conditions, so it is capable of imparting a stable triboelectric charge to toner even under high temperature environmental conditions. This makes it possible to create an excellent developer with low environmental dependence. Further, a carrier having a coating layer made of a silicone compound can be used repeatedly many times and has excellent durability.

Furthermore, since the electrostatic image developer of the present invention is made of a combination of a specific carrier, a specific toner, and specific inorganic fine particles, an appropriate triboelectric charge can be immediately imparted to the toner by slight agitation in the developing device. Therefore, even when images are formed intermittently, good images can be formed without fogging or deterioration in image quality caused by insufficient toner charge.

According to the electrostatic image developing method of the present invention, a negative image formed on the surface of an organic photoreceptor, that is, a photoreceptor made of an organic photoconductive semiconductor, is formed by a contact magnetic brush development method using a specific developer as described above. To develop a negative electrostatic latent image formed on the organic photoreceptor, the negative electrostatic latent image formed on the organic photoreceptor can be developed without toner particle scattering, without sacrificing the advantages of organic photoreceptors such as low production cost and non-toxicity. Good development can be achieved without any problems. In other words, since the specific developer mentioned above has excellent positive charging properties, it becomes positively charged with an appropriate amount of charge, so that the carrier particles and toner particles form a uniform brush shape on the developing sleeve. The developer layer (magnetic brush) is carried in a thin layered form arranged side by side, and the developer layer (magnetic brush) in this form is stably transported to the developing space while maintaining this form, which reduces contamination due to scattering of toner particles. Occurrence can be prevented. In addition, the presence of positively charged inorganic particles gives the developer excellent fluidity, making it possible to form a uniform and uniform magnetic brush on the developing sleeve. This makes it possible to achieve good development.

In conclusion, according to the developer and developing method of the present invention, clear and good quality images without capri are generated and are free from image unevenness, image blanking, image blurring, and image fading, regardless of environmental conditions. It can be stably formed many times.

[Specific structure of the invention]

The carrier constituting the electrostatic image developer of the present invention is constructed by providing a coating layer made of a silicone compound on the surface of magnetic particles.

The silicone compound for forming the carrier coating layer is not particularly limited, and various silicone compounds can be used. In a carrier having a coating layer made of a silicone compound, the surface energy of the carrier is considerably small, and as a result, transfer and adhesion of toner substances or inorganic fine particles to the carrier particles is difficult to occur, and contamination of the carrier can be considerably suppressed. This makes it possible to obtain a developer with excellent durability.

As the silicone compound, for example, a silane coupling agent, silicone oil, silicone rubber, silicone varnish, silicone resin, or a cured product thereof can be preferably used. Further, a plurality of types of silicone compounds may be used in appropriate combination.

In addition, as silicone rubber, silicone varnish, and silicone resin, those having an organic group such as an alkyl group or an aromatic group as a constituent unit are preferable, and those having an organic group such as a methyl group or a phenyl group are particularly preferable. Specific examples of the silicone compound having an organic group include dimethylsiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, and modified products thereof. In particular, polysiloxane having a methyl group or a phenyl group has an excellent negative charging property, and when a coating layer made of the polysiloxane is provided and a carrier C and a toner are triboelectrically charged, the toner is positively charged. have an effect. By appropriately selecting the content ratio of methyl groups and phenyl groups among the above organic groups, it is possible to adjust the properties such as hardness, toughness, and triboelectric charging properties of the coating layer of the carrier. The requirements for toners used in combination with
There is an advantage that the range of toner selection is wide.

As the silicone varnish, for example, “SR210
1j, rsH997J, rsH994j, rsR220
2J, rR-4-31174, rSR914
0J, ``5) 1643 J, r S H2O
47J, r J CR6100J, “JCR61
01J, r J CR6102J, rsH6103J
(all manufactured by Toray Silicone), rKR271
J, rKR272J, rKR274J, rKR21
6J, “KR280J, rKR282J, rKR261
J, rKR260'', rKR255J, rKR266J
, rKR251J, rKR155J, rKR152J,
rKR214J, “KR220J, rX-40-171
J,rX-40-172J,rX-40-19
02J, rX-40-1903J, rX-40-1
905J,rX-40-2605BJ,rKR2
01J, rSA-4J, rK R5202J, rK
R5203J, rKR3093J, rEcloolJ
, rX-41-9701'' (all manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

Examples of the silicone rubber include rSH410.
, rSH432J, rSH433J, rSH7
40J, rsH745UJ, rsH746UJ, rsH
747UJ, rsH748UJ, rsH35UJ, rs
H55UJ, rsH75UJ, rsH52UJ, rsH
82Uj, rs) (841Uj, rs) (851
tJJ, rS H1125U j.

rsH1150UJ, rsH1603UJ, r
sH665Uj, rsE955UJ, rsH50
2UJ, rSRX-440UJ (manufactured by Toray Silicone), etc. can be used.

Examples of the silicone resin include rSH804.
, rsH805J, rsH806A, J, rSH808
”, “5) (840J, rsR2107j, rsR21
08J, r S R2400J, rSR620J (
(manufactured by Toray Silicone), etc. can be used.

Furthermore, when forming the coating layer of the carrier using the silicone compound described above, a curing agent may be used as necessary. Examples of such curing agents include peroxides such as hensyl peroxide, 2,4-dichlorohensyl peroxide, dicumyl peroxide, ditertiary butyl peroxide, and tertiary glutyl perbenzoate; octylic acid, naphthene; Acids such as lead, iron, cobalt,
Metal soaps such as manganese and zinc; organic amines such as ethanolamine; and the like.

When the coating layer of the carrier is formed using the silicone-based compound as described above, the adhesive strength with the magnetic particles is sufficiently high, so that the impact resistance of the carrier is significantly excellent.

In addition, in forming the coating layer of the carrier, other resins may be used in addition to the silicone compounds described above. Examples of such other resins include styrene-acrylic resins, polyurethane, polyester, etc. can be used.

In the present invention, the magnetic particles constituting the carrier include 'Th1i, which is strongly magnetized in the direction of the magnetic field.
For example, metals or alloys that exhibit ferromagnetism such as iron, ferrite, and magnetite, such as iron, nickel, and cobalt, or compounds that contain these elements, and metals that do not contain ferromagnetic elements but can exhibit ferromagnetism by appropriate heat treatment. It is possible to use particles made of an alloy such as Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide.

In the present invention, the method for producing a carrier having a coating layer made of a silicone compound on the surface of magnetic particles is not particularly limited, but in specific examples, for example, a silicone compound component or A coating liquid prepared by dissolving a curing agent or the like used as needed in a solvent is applied to the surface of the magnetic particles, and then the solvent is evaporated off by heating and drying. The carrier used in the present invention can be manufactured by thermally curing the coating layer during or after drying, if necessary.

The coating method for applying the above-mentioned coating liquid to the surface of the magnetic particles is not particularly limited, but includes, for example, a dipping method in which powder of the magnetic particles is immersed in the coating liquid, and a method in which the coating liquid is sprayed onto the magnetic particles. A spray method, a fluidized bed method in which magnetic particles are suspended with fluidized air and a coating is sprayed onto the suspended magnetic particles, and a method in which magnetic particles are transferred onto a surface where a coating liquid is present. Can be used.

In particular, when the fluidized bed method is used, it is possible to form a uniform coating film on the surface of the magnetic particles, and a coating layer with uniform properties can be stably formed.

A coating method using the fluidized head method is described, for example, in Japanese Patent Application Laid-Open No. 54-155049.

Additives may be added to the coating liquid as necessary. The solvent is not particularly limited as long as it dissolves the silicone compound component, but examples include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran, dioxane, higher alcohols, and A mixed solvent of these can be used.

The thickness of the coating layer in the carrier is not particularly limited, but it is preferably a thickness that can impart a positive triboelectric charge to the toner by frictional charging with the toner, specifically, 0.01 It is preferable that it is about ~5.0μ, and it is particularly preferable that it is about 0.1 to 3n. If the thickness of the coating layer is too small, the durability of the carrier may be reduced, while if the thickness of the coating layer is too large, the coating layer is likely to peel off, and as a result, the image may become unclear. Further, the quantitative ratio of the coating layer to the magnetic particles is preferably 0.01 to 10% by weight, particularly preferably 0.05 to 5% by weight. If this ratio is too small, the durability of the carrier may be reduced, while if the ratio is too large, the coating layer is likely to peel off, and as a result, the image may become unclear.

In the present invention, the average particle size of the carrier is 5 to 500n.
It is preferable that it is, and it is especially preferable that it is 20-150p. When the average particle size of the carrier is too small,
A so-called carrier adhesion phenomenon occurs in which the carrier adheres to the electrostatic latent image and forms a fixed image, and as a result, the image may become unclear.On the other hand, if the average particle size of the carrier is too large, image distortion occurs. There are cases.

In the present invention, the carrier particles have a spherical shape and
Specifically, the ratio of the major axis to the minor axis (major axis/minor axis) of the carrier particles is preferably 1.0 to 1.
It is preferable that it is 2. If the value of the ratio is too large, the magnetic brush formed on the developing sleeve may become non-uniform, resulting in a decrease in the image formation properties, resulting in an unclear image, and in some cases, the durability of the carrier may decrease.

In the present invention, the average particle size (weight) of the carrier is “
Defined as the value measured using "Micro Track" (manufactured by Nikkiso Co., Ltd.). Further, the long axis of the carrier represents the maximum value of the outer diameter, and the short axis represents the minimum value of the outer diameter.

The inorganic fine particles constituting the electrostatic image developer of the present invention are positively chargeable inorganic fine particles that are positively charged by friction with a carrier.

In the present invention, positively charged particles are defined as follows.

That is, 0.2 g of positively charged inorganic fine particles left overnight under environmental conditions of a temperature of 20° C. and a relative humidity of 40%, and a coating layer made of a silicone compound on the surface of the carrier, that is, the magnetic particles used in the present invention. One of the carriers that has
9.8 g and approximately 20 cc under the above environmental conditions.
The amount of triboelectric charge on the inorganic particles was measured by shaking for 5 minutes in a glass sample container with a volume of Those that are positively charged are defined as positively charged inorganic particles.

The positively chargeable inorganic fine particles used in the present invention have a triboelectric charge of →1 M/g or more, especially +30 m/g in the above measurement.
It is preferable that the weight ratio is 〆/g or more.

When the amount of triboelectric charge is too small, the positive triboelectricity of the toner deteriorates and the amount of triboelectricity decreases, which may result in fogging or a decrease in the durability of the developer.

As such inorganic fine particles, for example, those having a positively charged substance on their surfaces can be preferably used. Specifically, inorganic fine particles whose surfaces have been treated with an amino-modified silicone compound and which have the amino-modified silicone compound or its cured product on the surface can be preferably used. According to such inorganic fine particles, the presence of amino groups makes the inorganic fine particles excellent in positively charging properties, and the functional groups of the silicone compound and the hydrophilic groups such as hydroxyl groups present on the surface of the free fine particles. are strongly bound together, resulting in inorganic fine particles that have excellent moisture resistance and durability, and have stable positive triboelectric charging properties that are not affected by environmental conditions.

As the amino-modified silicone compound, amino-modified silane cuff pulling agents, amino-modified silicone oils, amino-modified silicone varnishes, amino-modified silicone rubbers, amino-modified silicone resins, etc. can be used. In terms of moisture resistance and durability,
Amino-modified silicone varnish, amino-modified silicone rubber, and amino-modified silicone resin are preferred.

As the amino-modified silane coupling agent, for example, the following compounds can be preferably used.

HzN CHtCHzCHtSi(OCHs)sHtN
CHtCHtCH*5i(OCtHs)s Hs ■ Ht N CH* CHyoCHtsi (OCH3)
tCH.

■ Hm N CHt CHt N HCHtCHtCHg
5i(OCHs)tHxN CON HCHzCHxC
HtSi(OCtHs)sHtNCH*CH*NHCH
tCHmCHgSi(OCHs)iH* N CHt
CHt N HCHx CHz N HCHt-100tCHtSi(OCHz)s Hs Ct OCOCHx C) I z N HCHt
C1(z CHz-3i(OCHs)s Hs Cx OCOCHt CHz N HCHz C
HtNH--CHtCHtCHxSi(OCHs)
sHSC wealth OCOCHt CHz N HCHz CH
tNH--CHICHtN HCHtCHoNHC
Hffi--CHtCHtSi(OCHs)s l(sCOCOC)(xCHtN HCHtCHtN
H--CHtCHtCHtSi(OCHs)zHsC
Mushroom N CHzCHxCHtSi(OCHs)sl HSC寞一３５(OCHs)s H,C CHtCHtSi(QC)(ツ)3 HOCH鵞CHt N CH,CHxc HxSi(OCHs'IsHOC
HtCHt (H Co) 5iCHxCHtCHtNHCH*(H
3CO) KO5iCHOCHt CHt N HCHt(
HsCzO)ssicHtcHmcHtH (I(scto,)ssicHtcHmcHtHsCN
HCHICHtCHzSi(OCtl(s)sHt
N (CHz CHt N H) z CHz C)I
2 CHt -5i(OCH3)3 HxCN HCON Hz 02Hisi(OCH3)x Furthermore, the above compound may be in a form in which the alkoxy group is substituted with a chlorine atom.

These compounds may be used alone or in combination.

As the amino-modified silicone oil, for example, one represented by the following general formula (1) can be preferably used.

General formula (1) (RI' represents an alkylene group, an aryl group, an aminoalkylene group, etc., R'' and R'2 each represent a hydrogen atom, a hydroxyl group, an alkyl group, an aryl group, etc., x, y each represents an integer of 1 or more.) Furthermore, the amino-modified silicone oil preferably has an amino equivalent of 4 in the range of 200 to 22,500, particularly preferably in the range of 300 to 10,000. When the value of amino equivalent is too small, the effect of imparting positive chargeability by the inorganic fine particles is small, resulting in foggy and unclear images. On the other hand, when the value of amino equivalent is too large, the inorganic fine particles are transferred to the carrier particles. It tends to adhere, and the durability of the formed image agent may be reduced.

The amino-modified silicone oil preferably has a viscosity of 10 to 10,000 cps at 25°C, particularly preferably 20 to 3,500 cps. If the viscosity is too low, the stickiness of the inorganic particles may be On the other hand, when the viscosity is excessive, proper surface treatment becomes difficult, and as a result, the positive chargeability of the toner becomes unstable and the developer becomes Durability may decrease.

Examples of commercially available amino-modified silicone oils that can be preferably used include those listed in Table 1 below.

Table 1 Examples of the silicone varnish used to obtain the amino-modified silicone varnish include methyl silicone varnish, phenylmethyl silicone varnish, etc., and methyl silicone varnish is particularly preferred.

Methyl silicone varnish is T1 shown by the following structural formula.
Unit, D! It is a polymer consisting of 1 unit, M'' unit,
And T! It is a three-dimensional polymer containing a large amount of 1 unit.

(Tt1 unit) (n!1 unit) 0
CHs Hs CH3Si O- CH.

In addition, methyl silicone varnish or phenyl methyl silicone varnish is specifically represented by the following structural formula (1).
It is a substance that has the chemical structure shown below.

Structural formula (1) (R11 represents a methyl group or a phenyl group) In the above silicone varnish, in particular, the T'' unit is a unit effective for imparting good thermosetting properties and forming a three-dimensional network structure. Inorganic fine particles whose surfaces have been treated with silicone varnish containing such T" units have a hard and tough film on their surfaces, and therefore have excellent impact resistance, moisture resistance, and mold release properties. becomes. Above T! ' unit in the silicone varnish in an amount of 10 to 90 mol%, especially 30
It is preferably contained in a proportion of ~80 mol%. Current 39
If the ratio of T ''' units is too small, the toner becomes soft and the adhesiveness increases, and the stability of moisture resistance, durability, and triboelectric charging properties may decrease. In particular, the cleaning performance of the toner decreases, and Toner scattering may occur, resulting in image unevenness, fogging, etc., and furthermore, the durability of the fixing device may be reduced.On the other hand, when the proportion of the T" units is excessive, toner particles may be formed on the surface of inorganic fine particles. The coating layer may become non-uniform and the stability and durability of triboelectric charging properties may decrease.

Further, such silicone varnish has a hydroxyl group at the end or side chain of its molecular chain, and is cured by dehydration condensation of this hydroxyl group.

Examples of hardening accelerators that can be used to accelerate this hardening reaction include fatty acid salts such as zinc, lead, cobalt, and tin; amines such as triethanolamine and butylamine; and the like. Among these, amines can be particularly preferably used.

In order to make the silicone varnish as described above into a 7mino-modified silicone adhesive, it is necessary to replace some of the methyl groups or phenyl groups present in the T'' units, D!+ units, and M'' units with amino groups. What is necessary is to substitute with a group. Examples of the group having an amine group include those represented by the following structural formula.

CHt CH! N Hz -CHz(CHz)t NHz -CHt(CHz)x NH(CHz)z NHz
The silicone rubber used to obtain the amino-modified silicone rubber is, for example, a long-chain polymer consisting of only D3131 represented by the following structural formula, and has a viscosity of, for example, 10' to 10''cps at a temperature of 25°C.
For example, those having an average molecular weight of 104 to 101+ can be preferably used. Especially when the viscosity is 10h=
10'' cps and an average molecular weight of 105 to 10? When the molecular weight is too large, it becomes difficult to uniformly treat the surface, and as a result, triboelectric charging properties become unstable, which tends to result in foggy and unclear images, and durability and moisture resistance may deteriorate.

[D3131 Single R3 autoO5i-0- (R31 and R3g each represent an alkyl group such as a methyl group or an ethyl group, an aromatic group such as a phenyl group, a polyether, etc.) R1 is preferably a methyl group or a phenyl group, particularly preferably a methyl group, and in order to give the silicone rubber a crosslinked structure, R1 is a methyl group or a phenyl group, and in order to make the silicone rubber have a crosslinked structure, R1 may be a methyl group or a phenyl group. It is preferable to carry out copolymerization using a single amount of D3333.

[D3232 units ([>33 units] CHs
CHs-O-3i-0-
-○-5i-0-CHs
By making the silicone rubber have a crosslinked structure in this way, the inorganic fine particles whose surfaces have been treated with the silicone rubber have a hard and tough film on their surface, which increases impact resistance and strength. It has excellent moisture resistance and mold releasability.

In addition, such silicone rubber preferably has a hydroxyl group at the end of the molecular chain or at the side chain, and curing is accelerated by dehydration condensation of the hydroxyl group, and the hydroxyl group is combined with the functional group on the surface of the inorganic fine particles. It becomes possible to form a film through reaction and strong chemical bonds. Known vulcanization agents can be used to accelerate this curing reaction. Specifically, for example, benzoyl peroxide, bis-2,
Organic peroxides such as 4-dichlorobenzoyl peroxide, di-t-butyl peroxide, and dicumyl peroxide can be preferably used.

Further, in order to make the silicone rubber into an amino-modified silicone rubber as described above, R31 and R3 of the D31 unit! may be partially substituted with a group having an amino group. Examples of the group having an amino group include, but are not limited to, those represented by the following structural formula.

CHz G Hz N H! -G Hz (CHz)z N Hz CHz (CHz)z N H (CHri3 N H!
+CHzNHz The silicone resin used to obtain the amine-modified silicone resin has T" units, D
It is a polymer composed of "units, D4 units, and M" units, and unlike silicone oil, it is a polymer that contains a large amount of T" units.

[T4■ unit) CD'1 unit]] 7゛[lvt 41 unit) (Dat unit] R
44R46 CH2Si OOSi O- I CH= CH! (R41, R4寞 R43, R44, R45, RJ& are each an alkyl group such as a methyl group or an ethyl group,
Represents an organic group such as an aromatic group such as a phenyl group. ) Such silicone resins have many branches and a large number of fine networks formed by crosslinking, so they have hard properties, and the above T" units are effective units for creating a crosslinked structure, and , an effective unit for forming a cyclic structure within the molecule, making silicone resins both strong and flexible.In addition, silicone resins have siloxane bonds. Since a considerable amount of silanol groups with OH groups remain freely without forming f
It reacts with the functional groups present on the surface of the i19 fine particles or forms siloxane bonds during the curing stage, resulting in the silicone resin having even stronger properties.

Therefore, inorganic fine particles whose surfaces have been treated with such silicone resin have a tough yet flexible film on their surfaces, and therefore have excellent impact resistance, moisture resistance, and mold release properties. .

In order to make the silicone resin as described above into an amine-modified silicone resin, the above-mentioned T" units, D" units, D"
unit, an organic group present in the M'' unit (R41, R=2.
R43, R44, R4S, R46) may be partially substituted with a group having an amino group. Examples of the group having an amino group include those represented by the following structural formula.

-CHt G Hz N Ht -CHx(CHz)t NHx CHz(CHz>t NH(CHz)s NH
z Examples of inorganic fine particles whose surfaces are treated with the above compounds include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, chromium oxide, cerium oxide, and dioxide. Examples include fine particles of antimony, zirconium oxide, silicon carbide, and the like. It is preferable that the average particle size of the primary particles (particles separated into individual unit particles) of such inorganic fine particles is within the range of 3 u to 2 μ.

In particular, silica fine particles can be preferably used as the free fine particles. Silica fine particles are 5i-0-Si
Fine particles having a bond may be produced by either a dry method or a wet method, but those produced by a dry method are preferable, and in particular, silica fine particles produced by vapor phase oxidation of a silicon halide compound. It is preferable that In addition, as silica fine particles, silicon dioxide (
silica), aluminum silicate, sodium silicate, calcium silicate, potassium silicate, zinc silicate,
Although fine particles made of silicate such as magnesium silicate may be used, those containing 85% by weight or more of SiO□ are preferable.

Known techniques can be used to treat the surface of the inorganic fine particles with the above compounds, and specifically, for example, after dispersing the inorganic fine particles in a solution in which the above compounds are dissolved in a solvent. , removing the solvent by filtration or spray drying, and then curing by heating, or spraying a solution of the above compound in a solvent onto inorganic fine particles using a fluidized bed device, and then drying by heating. A method of curing the film by removing the solvent by removing the solvent can be used.

The particle size of the positively chargeable inorganic fine particles whose surface has been treated with the above-mentioned compound thus obtained is such that the average particle size of the primary particles is 3u to 2n, particularly 51p to soo p.
It is preferable that it is within the range of .

In addition, the specific surface area according to the BET method is 20 to 500 m1
7 g is preferable. If the average particle size is too small or the specific surface area is too large, for example, inorganic fine particles easily slip through during cleaning using a blade-type cleaning device, resulting in poor cleaning. There is. On the other hand, when the average particle diameter is too large or the specific surface area is too small, the fluidity of the developer decreases, resulting in poor developability, which may result in a decrease in image density or the occurrence of image unevenness.

The positively chargeable inorganic fine particles are added to and mixed with the toner particles from the outside so that they are attached or implanted onto the surface of the toner particles, and a carrier is further mixed therein.

The content ratio of the positively chargeable inorganic fine particles is 0.1 to 0.1 in the toner.
It is preferably 5% by weight, especially 0.1 to 2% by weight.
When the content ratio of the positively chargeable JA fine particles is too small, the fluidity of the developer may decrease, resulting in poor triboelectric charging properties of the toner, which is not suitable for the toner. It becomes difficult to apply a positive charge amount, and fogging and image unevenness may occur. Furthermore, when the content ratio is excessive, some of the positively chargeable inorganic particles may exist in a free state from the toner particles, and as a result, the free positively chargeable inorganic particles may adhere to and transfer to the carrier particles. , or the inner wall of the developing device,
It adheres and accumulates on the developing sleeve, regulating blade, etc., and eventually the triboelectricity of the toner becomes poor, making it difficult to apply an appropriate amount of positive charge to the toner, resulting in fogging and a decrease in image density. This may occur.

The toner used in the present invention is a toner containing a styrene-acrylic copolymer polymerized with an azobis-based initiator, and basically contains a binder made of the styrene-acrylic copolymer. It is a particulate powder containing a colorant and other additives, and the average particle size thereof is usually preferably about 5 to 20 nm.Other additives include, for example, those for improving fixing properties. A charge control agent, a cleaning performance improving agent, etc. can be used.

The styrene-acrylic copolymer is basically a copolymer obtained by polymerizing a styrene monomer and an acrylic monomer in the presence of an azobis initiator. In particular, in the presence of an azobis-based initiator,
A copolymer obtained by polymerizing a styrene monomer and acrylic acid or its ester and/or methacrylic acid or its ester can be preferably used. The styrene-based component can impart suitable release properties to the toner, improving offset resistance, and can also harden the toner, resulting in suitable positive triboelectrification due to friction with the carrier. It is possible to obtain clear images with good image formation properties and transfer properties. Acrylic acid or its ester and/or methacrylic acid and its ester component can impart good fixing properties to the toner and form an image with excellent fixing strength.

In the styrene-acrylic copolymer, the styrene component is preferably contained in a proportion of 60 to 90 percent of the copolymer, while the acrylic component is contained in a proportion of 40 to 90 percent of the copolymer. If the proportion of the styrene component, which is preferably contained in a proportion of 10% by weight, is too small and the proportion of the acrylic component is too large, the copolymer constituting the toner tends to transfer and adhere to the carrier particles. As a result, the properties of the carrier may be impaired and the durability of the developer may be reduced. On the other hand, if the proportion of the styrene component is too large and the proportion of the acrylic component is too small, the fixing performance may be reduced.

The styrene-acrylic copolymer has a weight average molecular weight of 60.000 to soo, ooo, a number average molecular weight of 1Mn of 1,000 to 30,000, and a ratio Mw of these.
/Mn values within the range of 5.0 to 40 can be preferably used. By using a material within such a preferable range, a toner with excellent offset resistance and fixing properties can be obtained. On the other hand, when the weight average molecular weight M-1 number average molecular weight M1 and the ratio Mw/MnO value are outside the above ranges, the offset resistance and fixing properties may deteriorate.

Further, as the styrene-acrylic copolymer, one having a glass transition point Tg within the range of 45 to 70°C can be preferably used. If the glass transition point Tg is too low, the toner's fluidity may be reduced due to increased tackiness, while if the glass transition point Tg is too large, the fixing performance may be reduced.

Specific examples of styrenic jIL polymers that can be used to obtain the styrene-acrylic copolymer include:
For example, styrene, O-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-
Ethylstyrene, 2,4-dimethylstyrene, p-n-
Butylstyrene, p-tert-butylstyrene, p-
n-hexylstyrene, p-n-octylstyrene, p
-n-nonylstyrene, p-n-decylstyrene, p-
Examples include n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene. These monomers may be used alone or in combination.

Further, examples of the acrylic component that can be used to obtain the styrene-acrylic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, rIIn-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate,
α of 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.
-methylene aliphatic monocarboxylic acid esters; acrylic acid or methacrylic acid derivatives; and others. These monomers may be used alone or in combination.

In addition, the styrene-acrylic copolymer may include other components such as vinyl esters such as vinyl acetate, vinyl butyrate, and vinyl benzoate; vinyl methyl ether;
Vinyl ethers such as vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone; dienes such as butadiene and isoprene; unsaturated carboxylic acids such as malemoleic acid and fumaric acid; etc. may be contained as structural units.

Examples of the azobis-based initiator include 2,2°-azobisisobutyronitrile, 2,2′-azobis(2°4
-dimethylvaleronitrile), 212°-azobis(4
-methoxy-2,4-dimethyl/slleronitrile),
Dimethyl 2.2'-azobisisobutyrate and the like can be preferably used.

The styrene-acrylic copolymer obtained by polymerization using such an azobis-based initiator has suitable positive chargeability, and as a result, the toner exhibits excellent positive triboelectric chargeability. . However, when penzoyl peroxide is used as an initiator as in the past, the resulting styrene-acrylic copolymer contains a large amount of benzoic acid units as its constituent units. As a result, the toner cannot obtain proper positive triboelectric chargeability.

The method for producing the styrene-acrylic copolymer is not particularly limited, and various methods can be used.

Specifically, for example, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, etc. can be used.

Examples of the colorant contained in the toner used in the present invention include carbon black, phthalocyanine blue, benzidine yellow, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, and methylene blue chloride. Dyes and pigments such as , malachite green offsalate, lamp black, and rose bengal can be used. These substances may be used alone or in combination, and the content of the colorant is usually preferably 1 to 15% by weight of the toner.

In addition, examples of the fixability improver include polyolefin,
Fatty acid metal salts, fatty acid esters and fatty acid ester waxes, higher fatty acids, higher alcohols, liquid or solid paraffin waxes, amide waxes, polyhydric alcohol esters, silicone varnishes, aliphatic fluorocarbons, and the like can be used.

Further, as the charge control agent, for example, metal complex dyes, aminotriphenylmethane dyes, nigrosine dyes, quaternary ammonium salt compounds, nitrogen-containing compounds, or polymers can be used.

Further, as the cleaning property improving agent, for example, fatty acid metal salts such as zinc stearate, calcium stearate, and stearic acid, and polymer particles such as methyl methacrylate particles and styrene particles can be used.

In the present invention, the glass transition point Tg is the extension line of the baseline below the glass transition point when measured using a differential scanning calorimeter "low temperature DSCJ (manufactured by Rigaku Denki Co., Ltd.) at a heating rate of 10°C/sin." This is the temperature at the intersection of the curve and the tangent line showing the maximum slope from the rising edge of the peak to the top of the peak.

In addition, the values of weight average molecular weight M- and number average molecular weight Mn can be determined by various methods, and there are slight differences depending on the measurement method, but in the present invention, the values determined by the following measurement method are as follows: It is defined as

That is, the weight average molecular weight, Mn, and peak molecular weight are measured by gel perminusion chromatography (GPC) under the conditions described below. At a temperature of 40°C, the solvent (tetrahydrofuran)
was flowed at a flow rate of 1.2-min/min, and the concentration was 0.2 g/20d.
To measure the molecular weight of the sample, inject 3B of tetrahydrofuran sample solution as the sample weight, and measure the molecular weight of the sample using the logarithm of the molecular weight and count number of the calibration curve prepared using several types of monodisperse polystyrene standard samples. Select measurement conditions that fall within the range where is a straight line.

The reliability of the measurement results is based on the NB5706 polystyrene standard sample (weight average molecular weight M
w=28.8×lO'+number average molecule 11Mn=13.7
×10' + Mw/ Mn -2-11) ratio Mw/
This is confirmed by checking that the Mn value is 2.11±0.10.

As the GPC column to be used, any column may be used as long as it satisfies the above conditions. Specifically, for example, TSK-GEL, GMH, (manufactured by Toyo Soda Co., Ltd.), etc. may be used. Can be done.

Next, the electrostatic image developing method of the present invention will be explained.

In the electrostatic image developing method of the present invention, a negative electrostatic latent image formed on the surface of an organic photoreceptor is coated with a specific carrier as described above, a specific toner as described above, and the positively chargeable non-81
A toner image is formed by developing with a specific electrostatic image developer containing the toner particles.

The organic photoreceptor is usually constructed by laminating a photosensitive layer containing a photoconductive semiconductor made of an organic compound on a conductive support. The photosensitive layer may be composed only of a photoconductive semiconductor made of an organic compound, or may be composed of the photoconductive semiconductor dispersed in a binder made of a resin.

The photosensitive layer includes a carrier generation layer containing a carrier generation substance that absorbs visible light and generates charged carriers, and a carrier generation layer that transports either or both of positive and negative carriers generated in this carrier generation layer. It is preferable to use a so-called functionally separated type photosensitive layer configured by combining a carrier transport layer containing a carrier transport substance. In this way, by assigning the two basic functions necessary for the photosensitive layer, namely carrier generation and carrier transport, to separate layers, the range of materials that can be used in the composition of the photosensitive layer is widened, and each It becomes possible to independently select the substance or material system that optimally performs the function.
In addition, by doing so, it is possible to achieve excellent characteristics required in the image forming process, such as high surface potential when charged, high charge retention capacity, high photosensitivity, and high stability during repeated use. It becomes possible to construct an organic photoreceptor having specific characteristics.

As carrier-generating substances in the photosensitive layer, for example, anthrone pigments, perylene derivatives, phthalocyanine pigments, azo dyes, indigoid dyes, etc. can be used. Examples of carrier transport substances include carbazole derivatives, oxadiazole derivatives, triarylamine derivatives, poly7arylalkane derivatives, hydrazone derivatives, pyrazoline derivatives, stilbene derivatives,
Styryl triarylamine derivatives and the like can be used. It is preferable that the carrier generation layer has a thickness of usually 0.01 to 2 μm, and the carrier transport layer has a thickness of usually 1 to 30 nm.

When forming a photosensitive layer by dispersing a photoconductive semiconductor made of an organic compound in a binder made of a resin, examples of the resin that can be used as the binder include polyethylene, polypropylene, acrylic resin, methacrylic resin, chloride resin, etc. Addition polymer resins, polyaddition resins, polycondensation resins such as vinyl resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and these Copolymer resins containing two or more of the repeating units of the resin, such as vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, styrene-acrylic copolymer resins, etc. Examples include insulating resins, and polymeric organic semiconductors such as poly-N-vinylcarbazole.

In the organic photoreceptor, a metal sheet made of, for example, aluminum, nickel, copper, zinc, palladium, metal, indium, tin, platinum, gold, stainless steel, steel, or brass can be used as the conductive support.

The specific structure of the organic photoreceptor is not particularly limited, and various structures can be adopted. Further, an organic photoreceptor whose surface potential when charged is, for example, -400 to -1000 V can be particularly preferably used.

FIG. 1 is an explanatory diagram showing an example of a developing device that can be suitably used to carry out the electrostatic image developing method of the present invention.

Reference numeral 10 denotes an organic photoreceptor, and this organic photoreceptor 10 has a rotating drum-like form that is rotated in the direction of arrow The photosensitive layer 10B containing is laminated. A charger and an exposure optical system (not shown) are arranged upstream of the development space 24, and the charger first sets the surface of the organic photoreceptor 10 to be developed at a temperature of -400 to -1, for example.
It is charged to a constant negative potential within the range of 000V,
Next, an exposure optical system (not shown) projects an optical image of the original onto the developed surface of the organic photoreceptor 10, and an electrostatic latent image corresponding to the original is formed on the developed surface, and this electrostatic latent image is moved to the developing space 24, and the electrostatic latent image is developed in the developing space 24.

11 is a developing sleeve, and this developing sleeve 11 is
The developing sleeve 11 has a rotating drum shape made of a non-magnetic material such as aluminum, and a magnet 12 is disposed inside the developing sleeve 11 . This magnet body 12 is made up of a plurality of N and S poles arranged along the circumference of the developing sleeve 11. These developing sleeve 11 and magnet body 12 constitute a developer transport carrier, and in a specific example,
The developing sleeve 11 is rotated to move, for example, in the direction of arrow Y, that is, in the same direction as the moving direction of the organic photoreceptor 10 in the developing space 24, and the magnet body 12 is fixed, for example. In the present invention, the rotation direction of the developing sleeve 11 is not particularly limited, and the magnet body 12 may be rotated in an appropriate direction.

The N and S magnetic poles constituting the magnet body 12 are magnetized so that the magnetic flux density on the surface of the developing sleeve is usually about 500 to 1,500 Gauss, and the particles of the developer 22 are distributed on the surface of the developing sleeve 11 by the magnetic force. A developer layer (magnetic brush) 23 is formed in which the developer layer (magnetic brush) is made to stand up like a brush.

Reference numeral 13 denotes a regulating blade, which is made of a magnetic or non-magnetic material and is used to regulate the height and amount of the developer N23 reaching the developing space 24. Reference numeral 14 denotes a cleaning blade, and this cleaning blade 14 is used to scrape off and remove the developer remaining on the surface of the developing sleeve 11 after development.

The surface of the developing sleeve 11 that has been cleaned by the cleaning blade 14 comes into contact with the developer 22 again in the developer reservoir 15, and a new magnetic brush is formed on the surface, and after this magnetic brush is regulated by the regulating blade 13, it enters the developing space. 24.

15 is a developer reservoir; 16 is a stirring screw; in the developer reservoir 15, toner and carrier constituting the developer 22 are mixed and dispersed by the stirring screw 16;
This makes the toner density uniform. Also,
The carrier of the developer 22 is used repeatedly, while the toner is consumed each time development is performed. Therefore, new toner in the toner hopper 17 is transferred to the developer reservoir 15 by the supply roller 18 having a recessed portion on its surface. will be replenished accordingly.

Reference numeral 19 denotes a bias power supply, and 20 denotes a protective resistor. The bias power supply 19 applies a bias voltage necessary for development to the developing sleeve 11 via the protective resistor 20. This bias voltage is preferably a DC voltage of, for example, about 50 to 500 μm.

In developing an electrostatic latent image, in order to achieve uniform development, it is preferable that the tip of the magnetic brush come into shallow contact with the surface of the photoreceptor 10. Therefore, the tip of the regulating blade 13 and the surface of the developing sleeve 11 should be in close contact with each other. The distance (Hcut) between the organic photoreceptor 10 and the developing sleeve 11 in the developing space 24 is
It is preferable to set the distance to about 0.8 times the gap (D sd). Further, the gap (D sd) is, for example, 0.1 to 4
．． It is preferable to set it to 01. If the gap (D sd) is too large, developing performance may deteriorate or toner scattering may occur. On the other hand, if the gap (D sd) is too small, toner scattering or carrier adhesion to the image area may occur. This may occur and the image may become unclear.

In the apparatus configured as described above, when the developing sleeve 11 rotates, the magnitude and direction of the magnetic field on its surface sequentially change, so that the carrier particles in the magnetic brush formed on the surface of the developing sleeve 11 rotate and vibrate. At the same time, the toner particles are moved to the developing space 24 following the rotational movement of the developing sleeve 11, and as a result, the toner particles attached to the surface of the carrier particles by electrostatic force are conveyed to the developing space 24.

Next, an image forming method using the developer and developing method of the present invention will be described.

First, a negative electrostatic latent image is formed on the surface of the organic photoreceptor (latent image forming step), this electrostatic latent image is developed with the specific developer (developing step), and the toner image obtained by development is A fixed visible image is formed by electrostatically transferring the toner image onto a transfer material (transfer step) and fixing the toner image on the transfer material by contact heating with a heat roller, for example, and fixing the toner image on the transfer material after the transfer step. The developer remaining on the surface of the photoreceptor is cleaned using a cleaning blade (cleaning step) to restore the surface of the organic photoreceptor to its original clean state.

In the latent image forming step, the surface of the organic jδ photoreceptor is charged to a uniform negative potential (charging step), and then a light image of the document is projected onto the charged surface of the organic photoreceptor (exposure step). As a result, an electrostatic latent image made of electrostatic charges is formed on the surface of the organic photoreceptor.

Specifically, in the charging step, the entire image forming area on the surface of the organic photoreceptor is charged to a potential of, for example, about -400 to -1000V using, for example, a corona charger, and in the exposure step, the charging An exposure optical system comprising, for example, a light source, a reflecting mirror, and a lens produces a reflected light image or a transmitted light image of the document on the surface of the organic photoreceptor whose surface is charged to a uniform negative potential during the process. The image is formed, thereby forming a negative electrostatic latent image corresponding to the original on the surface of the organic photoreceptor.

In the transfer step, an electrostatic transfer method can be preferably used. Specifically, for example, a transfer device that generates an alternating current corona discharge is placed so as to face the organic photoreceptor through the transfer material, and the alternating current corona discharge is applied to the transfer material from the back side of the organic photoreceptor. The toner carried on the surface is transferred to the surface of the transfer material.

In the cleaning step, a cleaning blade is used. This cleaning blade is preferably made of urethane rubber, for example, and in this case, cleaning performance and durability are improved. The cleaning blade is usually placed in a state in which it is lightly and elastically pressed against the surface of the photoreceptor, and cleaning is accomplished by scraping off toner remaining on the surface of the photoreceptor.

In order to facilitate cleaning, it is preferable to add a static elimination process to neutralize the surface of the organic photoreceptor before the cleaning process. This static elimination step can be performed, for example, using a static eliminator that generates AC corona discharge.

In the fixing step, it is preferable to carry out fixing by a contact heating method using a heat roller fixing device having a heat roller, and the heat roller is formed by coating the surface with a fluororesin or a silicone resin. can be preferably used. A heat roller fixing device usually includes a heat roller, a backup roller placed in opposition to the heat roller, and a heat source for heating the heat roller.
Alternatively, a cleaning roller may be further arranged in opposition to the heat roller. Specifically, as a heat roller,
For example, a core material made of a metal such as iron or aluminum and a coating layer made of a fluororesin such as Teflon (polytetrafluoroethylene manufactured by DuPont) or a silicone resin can be preferably used. . Further, as the backup roller, one constructed by providing a coating layer made of silicone rubber or the like on the surface of a metal core material can be preferably used.

FIG. 2 is an explanatory diagram showing an example of an image forming apparatus that can be suitably used to form an image by applying the developer and developing method of the present invention.

30 is a cabinet, and at the top of this cabinet 3° is a glass original for placing the original 31! 32 and a platen cover 33 that covers the document 31.
and is provided. A paper feed tray 41 into which transfer paper 40 is placed is provided at one end of the cabinet 30, and a paper discharge tray 42 is provided at the other end. 43 and 44 are paper feed rollers, and 45 is a paper discharge roller.

Reference numeral 50 denotes an organic photoreceptor for forming a negative electrostatic latent image, and this organic photoreceptor 50 has a rotating drum shape. Around this organic photoreceptor 50, corona chargers 51.
n-point optical system 52, magnetic brush development.

A container 53, an electrostatic transfer device 54, a separator 55, and a blade type cleaning device 56 are arranged.

The exposure optical system 52 includes a first mirror unit 63 consisting of a light source 61 and a first mirror 62, and a second mirror unit 63 consisting of a pair of mirrors arranged in order along the optical path from the first mirror unit 63 to the organic photoreceptor 50. 2 mirror unit 64
, a lens 65 , a mirror 66 , and a groic mirror 67 . The first mirror unit 63 is provided below the layer stacking table 32 so as to be movable so as to be scanned with respect to the document placing table 32, and the second mirror unit 64 is arranged to move from the document scanning point to the organic photoreceptor 50. The first mirror unit 63 is provided movably in accordance with the moving speed of the first mirror unit 63 so as to maintain a constant optical path length. Original table 3
When the original 31 placed on the original 2 is illuminated with slit-shaped illumination light scanned by the exposure optical system 52, the slit-shaped reflected light images of the original 31 sequentially formed by scanning are rotated. The images are sequentially projected onto the developing surface of the organic photoreceptor 5o.

Reference numeral 70 denotes a contact heating type heat roller fixing device. It is configured.

In the above apparatus, the surface to be developed of the organic photoreceptor 50 is charged to a uniform negative potential by the corona charger 51, and then imagewise exposed by the exposure optical system 52, so that the surface of the organic photoreceptor 50 is
A negative electrostatic latent image corresponding to the original is formed on the surface to be developed. This negative electrostatic latent image is then developed by the magnetic brush developer 53 to form a corresponding toner image on the document.

The toner image on the organic photoreceptor 5o is electrostatically transferred onto the transfer paper 4o by the electrostatic transfer device 54, and the toner image on the transfer paper 40 is heated and fixed by the heat roller fixing device 70 to form a fixed image. On the other hand, the surface of the organic photoreceptor 50 that has passed through the electrostatic transfer device 54 is rubbed by a blade-type cleaning device 56, and the toner remaining on the surface is scraped off, resulting in the original clean surface. In addition to that,
It will be subjected to the charging process by the corona charger 51 again.

According to the above-described image forming means, the positive chargeable inorganic fine particles impart suitable mold releasability to the developer, so that the physical adhesion force to the surface of the organic photoreceptor is small, and therefore, in the transfer process. Good transfer can be performed using an electrostatic transfer means, and it is possible to reliably form a clear image with high image density (and no image unevenness).

In addition, since the transferability of the developer is good, it can be used even after the transfer process. A small amount of developer remains on the photoreceptor, and therefore, the remaining developer can be easily cleaned in the cleaning process, and the presence of the positively charged state Ia particles allows the developer to have suitable release properties. Because of this, the adhesion of the developer to the organic photoreceptor is small.
As a result, it becomes possible to easily clean the developer using a cleaning blade.

In addition, since the cleaning properties of the developer are good, it is possible to achieve good cleaning even with a small pressure contact force of the cleaning blade against the organic photoreceptor, so that the surface of the organic photoreceptor is not worn away by the cleaning blade. This prevents the characteristics of the organic photoreceptor from deteriorating early, and the service life of the organic photoreceptor can be significantly extended.

In addition, in the fixing process, positively charged inorganic fine particles are present between the surface of the molten developer and the hot cola, and the positively charged inorganic fine particles provide a mold release effect, allowing the heated roller of the developer to Transfer and adhesion to the heat roller is prevented, and developer is prevented from accumulating in the minute grooves of the heat roller. As a result, image staining caused by the offset phenomenon can be prevented.

[Specific examples]

Hereinafter, specific examples and comparative examples of the present invention will be described, but the present invention is not limited to these examples.

(Manufacture of carrier) (1) Carrier C1 (for the present invention) 8 parts by weight of silicone varnish rsR-2101J (manufactured by Le Silicone Co., Ltd.) was mixed into spherical copper particles with an average particle size of 100 nm using a fluidized bed device. −Zinc ferrite particles (
(manufactured by Nippon Tetsuko Co., Ltd.) was spray-coated to 100 parts by weight, further heat-treated at 200°C for 5 hours to sinter, and then the aggregates were sieved to form a coating layer made of sintered silicone varnish. We have manufactured a new carrier. This is called "carrier CIJ. This carrier C1 has an average particle size of 1
02x, and the ratio of the major axis to the minor axis (major axis/minor axis) is 1.05.

(2) Carrier C2 (for the present invention) In the production of carrier C1, silicone rubber
5 parts by weight of H-2047J (manufactured by Le Silicone), 0.05 parts by weight of benzoyl peroxide, and an average particle size of 88
P-weight spherical copper-zinc ferrite particles (manufactured by Nippon Tetsuko Co., Ltd.)
A carrier having a coating layer made of sintered silicone rubber was produced by the same treatment except that 100 parts by weight was used. This is referred to as "carrier C2J." This carrier C2 has an average particle size of 901 and a ratio of major axis to minor axis (major axis/minor axis) of 1.04.

(3) Carrier C3 (for the present invention) Spherical copper particles with an average diameter of 50 μm were added to a coating solution prepared by dissolving 2 parts by weight of Soricone resin rSR-2400J (manufactured by Toray Silicone Co., Ltd.) in 50 parts by weight of xylene. - After immersing 100 parts by weight of zinc ferrite particles (manufactured by Nippon Tetsuko Co., Ltd.), it is heated to volatilize and remove the solvent xylene, and then heat-treated at 200°C for 5 hours to sinter, and then the aggregates are removed. The mixture was sieved to produce a carrier having a coating layer made of a sintered silicone resin. This is referred to as "carrier C3J. This carrier C3 has an average particle size of 52n1 and a ratio of the major axis to the minor axis (major axis/minor axis) of 1.03.

(4) Carrier C4 (for the present invention) In the production of carrier C3, silicone varnish rKR
-216J (manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part by weight was used, but the same treatment was carried out to produce a carrier having a coating layer made of a sintered silicone varnish. This is called “Carrier C4J.

This carrier C4 has an average particle diameter of 5 In and a ratio of major axis to minor axis (major axis/breadth axis) of 1.02.

(Manufacture of inorganic fine particles) (1) Inorganic fine particles Al (for the present invention) 100 parts by weight of silica fine particles with an average particle size of 12 mm and a specific surface area of 200 m''/g [Aerosil 200J (manufactured by Nippon Aerosil Co., Ltd.)] were added to a high-speed rotating mixer. and then N
-β (aminoethyl)γ-aminopropyltrimethoxysilane rKBM 603J (manufactured by Shin-Etsu Chemical Co., Ltd.)
8 parts by weight and hexamethyldisilazane "526079J"
(manufactured by Torre Silicone) in 100 parts by weight of hexane was added dropwise to the high-speed rotating mixer to perform surface treatment, and then the contents of the mixer were transferred to a flask. By heating for 5 hours with stirring at a temperature of 100 to 150 °C in an inert gas atmosphere, the hexane solvent was removed and the reaction was proceeded, and the average particle size of the primary particles was 12 toughness, BET
Positively chargeable inorganic fine particles with a specific surface area of 190 m''/g by the method were produced. These are referred to as inorganic fine particles All. These inorganic fine particles A1 have a triboelectric charge amount of +50 to +200 C/g with carriers 01 to C4. Within this range, especially the amount of frictional electrification with carrier CI is +64 me/g.

(2) Inorganic fine particles A2 (for the present invention) In the production of i-free fine particles AI, the amino equivalent is 3500
．． 10 parts by weight of amino-modified silicone oil rS,F 8417J (manufactured by Le Silicone Co., Ltd.) having a viscosity of 1200 cps at 25°C and 8 parts by weight of hexamethyldisilazane rsZ6079J (manufactured by Le Silicone Co., Ltd.). Other than using the same process, the average particle size of the primary particles was 13u, and the specific surface area by BET method was 180.
m''/g of positively chargeable inorganic fine particles were obtained. These are referred to as [inorganic fine particles A2.J. These inorganic fine particles A2 have a triboelectric charge amount of 50 to +200 A/g with carriers C1 to C4. Yes, especially the frictional electrification with carrier C1 is +
It is 10Jjc/g.

3) i-free fine particles A3 (for the present invention) In the production of Kuroiso fine particles AI, silica fine particles "Aerosil 13" with an average particle diameter of 16Q and a specific surface area of 13"/g were used.
0J (manufactured by Nippon Aerosil Co., Ltd.) and a treatment solution prepared by dissolving 20 parts by weight of an amino-modified silicone varnish having a structural unit represented by the following structural formula in 100 parts by weight of xylene. The average particle diameter of the primary particles is 16u, and the specific surface area by BET method is 92n.
+"/g positively charged point a fine particles were obtained. These are referred to as [a-free fine particles A3J.

The inorganic fine particles A3 have a triboelectric charge amount with the carriers 01 to C4 within a range of +50 to +200 m/g, and particularly a triboelectric charge amount with the carrier C1 of +106 m/g.

(x, y, z are each !i! numbers of 1 or more, and x
:y:z=1:4:5. ) (4) @a fine particles A4 (for the present invention) In the production of inorganic fine particles A1, silica fine particles "Aerosil 3" having an average particle size of 7 mm and a specific surface area of 30 On+''/g were used.
00J (manufactured by Nippon Aerosil Co., Ltd.) 100 parts by weight, 25 parts by weight of amino-modified silicone rubber having a structural unit represented by the following structural formula, and 0.2 parts by weight of benzoyl peroxide are dissolved in 125 parts by weight of xylene. The treatment was carried out in the same manner except that the treatment liquid was used, and the average particle size of the primary particles was 7.
Positively charging inorganic fine particles with a specific surface area of 166 m''/g were obtained by the BET method. These are referred to as inorganic fine particles A4J. These inorganic fine particles A4 have a triboelectric charge amount of +50 to +200 with the carrier Cl-C4. In particular, the amount of frictional electrification with the carrier C1 is +185/g.

(x, y, z are each integers greater than or equal to 1, and x: y
:z=1:1:2. ) (5) A-free fine particles A5 (for the present invention) As constituent units, the following DI unit, the following D2 unit, the following A
D' unit, the following T1 unit, and the molar ratio of these is 4.
s:o, s: 1:4 for amino-modified silicone resin and 0.5 for this amino-modified silicone resin.
A treatment solution was prepared by dissolving % by weight of benzoyl peroxide in xylene.

CD’ unit　　　　　　　　　　[D2 unit] CH, CH.

-O-5i-0- -〇-5i-0-CHs
CH= CHz (T' unit)
CAD' unit] CH3 -O-3iO--0-5i-0- CH, CH, (CHt), NH2 Next, put silica fine particles "Aerosil 300J (manufactured by Nippon Aerosil Co., Ltd.) into a mixer, and mix the silica fine particles with After spraying a treatment solution containing 20% by weight of the above-mentioned amino-modified silicone resin, the mixture was placed in a flask, and the solvent xylene was removed at a temperature of 120°C for 5 hours while stirring. The amino-modified silicone resin was subjected to a curing reaction to obtain positively chargeable non-m fine particles having an average primary particle size of 7 particles and a specific surface area of 135 m''/H by BET method. This is referred to as "inorganic fine particles A5J.

The Ja-free fine particles A5 have a frictional charge amount of +50 to +20 (Ic/H) with the carriers C1 to C4, and in particular, a frictional charge amount of +1951!c/g with the carrier C1.

(Production of toner) (1) Toner TI (for the present invention) 2,2°-azobisisobutyronitrile 3 as an initiator
Styrene 70 in a toluene solution using parts by weight.
20 parts by weight of n-butyl acrylate and 10 parts by weight of methyl methacrylate to form a styrene-n-butyl acrylate-methyl methacrylate copolymer (weight average molecular weight Mw=85,
000, number average molecular weight Mn=is, ooo, Miy/M
n=5.7, glass transition point Tg=58°C). This will be referred to as "Copolymer 1".

100 parts by weight of the above copolymer 1 and carbon black [
10 parts by weight of Mogul Lj (manufactured by Cabo Soto) and
Nigrosine Sol (manufactured by Orient Chemical Industry Co., Ltd.) 2
After mixing with the ilt part, 100 to 1
Thoroughly melted and kneaded at 30°C, then cooled, coarsely pulverized with a hammer mill, further finely pulverized with a jet mill, and then classified. A toner of .0x was obtained. This is referred to as "toner T 1 j."

(2) Toner T2 (for the present invention) Using 3.5 parts by weight of 2.2''-azobis(2,4-dimethylvaleronitrile) as an initiator, 65 parts by weight of styrene and 35 parts by weight of n-butyl methacrylate. and:,
By conducting a polymerization reaction, styrene-n
-Butyl methacrylate copolymer (weight average molecule itM
w=103. ooO, number average molecule IMn = 16.0
00, Mw/'Mn=6.4, glass transition point Tg=6
0°C) was obtained. This will be referred to as "Copolymer 2".

A toner was obtained in the same manner as in the production of toner T1, except that 100 parts by weight of the above copolymer 2 was used instead of copolymer 1. This is referred to as [Toner T2J.

(3) Toner T3 (for the present invention) Using 3 parts by weight of 2,2'-azobis(4-methoxy-2'4-dimethylvaleronitrile) as an initiator, 82 parts by weight of styrene and 2 parts by weight of styrene in a toluene solution. - Styrene-2-ethylhexyl acrylate copolymer (weight average molecular weight Mw = 112,000-
Number average molecular weight Mn=14. OOO, Mw/Mn=8.0
, glass transition point Tg = 60°C) was obtained.

This will be referred to as "Copolymer 3".

A toner was obtained in the same manner as in the production of toner T1, except that 100 parts by weight of the above copolymer 3 was used instead of copolymer 1. This is referred to as [Toner T3J.

(4) Toner T4 (for comparison) Using 5 parts by weight of benzoyl peroxide as an initiator, 70 parts by weight of styrene, 20 parts by weight of n-butyl acrylate, and 10 parts by weight of methyl methacrylate were polymerized to produce styrene. A -n-butyl acrylate-methyl methacrylate copolymer was obtained. This is called “Copolymer 4
”.

This copolymer 4 contained benzoic acid, and its content was 4.1% by weight.

A toner was obtained in the same manner as in the production of toner T I, except that 100 parts by weight of the above copolymer 4 was used instead of copolymer 1. This is called "Toner T4J.

Examples 1 to 9 and Comparative Example 1 In each of the Examples and Comparative Examples, a developer was prepared using carrier, toner, and positively chargeable inorganic fine particles in combinations and amounts shown in Table 2 below.

That is, first, positively chargeable inorganic fine particles are added to the toner from the outside, and these are mixed using a Henschel mixer, so that the positively chargeable inorganic fine particles are attached or implanted onto the surface of the toner particles and retained, and then these are transferred to the carrier. A developer was prepared by mixing.

The developers obtained in Examples 1 to 9 were each referred to as "Developer 1".
~ "Developer 9" and the developer obtained in Comparative Example 1 are referred to as "Comparative Developer 1."

Table 2 <Live-action test> (1) Test 1 (Live-action test under normal temperature environmental conditions) An organic photoreceptor for forming a negative electrostatic latent image, a contact magnetic brush developer, and an alternating current corona discharge. A corona transfer device, a heat roller with a diameter of 30φ whose surface layer is made of Teflon (polytetrafluoroethylene manufactured by Depon Co., Ltd.), and a silicone rubber surface layer rKE-1300RT.
An electrophotographic copying machine r U-Bix comprising a heat roller fixing device made of a backup roller formed by VJ (manufactured by Shin-Etsu Chemical Co., Ltd.) and a cleaning device having a cleaning blade made of urethane rubber.
A photocopy test in which a modified 1550MRJ (manufactured by Konishiroku Photo Industry Co., Ltd.) was used to continuously form copied images 130,000 times using each of the above developers under room temperature environmental conditions of a temperature of 20°C and a relative humidity of 40%. and evaluated each of the following items. In addition, the live-action test is 500
The test was performed intermittently, with a one-day rest period between each test.

The results are shown in Tables 3 and 4 below.

The above-mentioned organic photoreceptor has a negatively chargeable two-layer photosensitive layer formed using an anthrone-based pigment as a carrier-generating substance and a carbazole derivative as a carrier-transporting substance, and a rotating drum-shaped aluminum conductive layer. It is constructed by laminating layers on a support.

The surface potential (highest potential) of the organic photoreceptor during charging is -600V, the gap (Dsd) between the photoreceptor and the developing sleeve in the development space is 0.6 mm, and the distance between the tip of the regulating blade and the developing sleeve (Hcut) is 0.5
8 mm, the magnet body is a fixed type, the magnetic flux density on the surface of the developing sleeve is 800 Gauss, and the bias voltage applied to the developing sleeve is -1120 cm in DC voltage.

■Capri “Sakura Densitometer” (manufactured by Konishiroku Photo Industry Co., Ltd.)
The determination was made by measuring the relative density of a white background portion with a document density of 0.0 with respect to a copied image. Note that the white background reflection density is OoO. For evaluation, if the relative concentration is less than 0.01, it is marked as "○", and if it is 0.01 or more and less than 0.03, it is marked as "○".
Δ", and cases of 0.03 or more were marked "x".

■Image density "Sakura densitometer" (manufactured by Konishiroku Photo Industry Co., Ltd.)
was used to measure the relative density of the white background portion of the original with a density of OIO to the copied image. For evaluation, when the image density was 1.0 or more, it was evaluated as "○", when it was 0.7 or more and less than 1.0, it was evaluated as "△", and when it was less than 0.7, it was evaluated as "x".

The 0-quality copied images were visually judged from five points: image missing, image unevenness, image blur, image fading, and sharpness. The evaluation was ``x'' if it was poor and had a practical problem, ``Δ'' if it was slightly defective but at a practical level, and ``○'' if it was good.

"Image missing" refers to a phenomenon in which part of an image is missing, "image unevenness" refers to a phenomenon in which differences in shading occur in an image, and "image blur" refers to a phenomenon in which the density in the peripheral areas of an image decreases. "Image fading" refers to a phenomenon in which band-like differences in shading appear in an image.

■ Toner scattering Visually observe the inside of the copying machine and the copied image. If there is almost no toner scattering and it is in good condition, it is rOJ, and if there is some toner scattering, but it is at a practical level, it is "△
”, and cases where a large amount of toner scattering was observed and there was a problem in practical use were rated “×”.

(2) Cleaning properties After repeated image formation, the surface of the photoreceptor was visually observed immediately after being cleaned with a cleaning blade, and judgment was made based on the presence or absence of deposits on the surface of the photoreceptor. The evaluation is "○" if the product is in good condition with almost no deposits observed, "Δ" if some deposits are observed but at a practical level, and "Δ" if there are many deposits found and there are problems in practical use. was marked as "x".

(2) Heat roller dirt The heat roller constituting the fixing device was visually observed and determined. The rating is "x" if there is a lot of heat roller dirt and it is a practical problem, "△" if there is some heat roller dirt but it is at a practical level, and "△" if there is almost no heat roller dirt. The case where there was no OJ was defined as rOJ.

(2) Test 2 (live-action test under high-temperature environmental conditions) A live-action test was conducted in the same manner, except that the environmental conditions were a high-temperature environment of 30°C and 80% relative humidity, and each of the above items was evaluated. . The results are shown in Table 5 below.

As can be understood from the results in Tables 3 to 5, developers 1 to 9 of the present invention have good toner triboelectric charging properties and fluidity, and therefore, in the developing process, magnetic brush A negative electrostatic latent image formed on an organic photoreceptor by a developing method can be developed well without toner scattering,
In the transfer process, electrostatic transfer means can perform transfer at a high transfer rate, and in the cleaning process, a cleaning blade with a simple structure can perform good cleaning, and in the fixing process, a heated roller The fixing device allows for good fixing without the occurrence of offset phenomena, and as a result, fogging,
It is possible to form a good image with clear image quality without image missing, image unevenness, image blur, or image fading, and with high image density.

Further, even in the initial stage of image formation, the rise characteristics of triboelectric charging properties are good, and an initial image of good image quality without wrinkles can be formed.

Further, even when performing an image forming process many times, the heat roller and bank-up roller in the heat roller fixing device are not contaminated, and the usable life of the rollers is significantly extended.

Furthermore, good images can be stably formed many times even under high temperature environmental conditions.

On the other hand, according to Comparative Developer 1, since toner T4 contains a styrene-acrylic copolymer polymerized using benzoyl peroxide as an initiator, Due to the benzoic acid present in the toner, triboelectric charging properties are poor at the initial stage of image formation, resulting in an initial image that is foggy and unclear with low image density. Furthermore, in intermittent image formation every 5,000 times, the rise characteristics of triboelectric charging after a pause are poor, resulting in an image at the beginning of image formation that is foggy and unclear with low image density. Further, in image formation performed many times, fog gradually increases even after the initial stage of image formation after a pause, and the image density gradually decreases, resulting in an image that becomes unclear at an early stage. Furthermore, under high-temperature environmental conditions, more fogging occurs than under normal-temperature environmental conditions, and image density decreases and image blurring increases.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an electrostatic image developing apparatus that can be suitably used to carry out the electrostatic image developing method of the present invention, and FIG. FIG. 2 is an explanatory diagram showing an example of an image forming apparatus that can be suitably used when forming an image. DESCRIPTION OF SYMBOLS 10... Organic photoreceptor 10A... Conductive support 10B... Photosensitive layer 11... Developing sleeve 12... Magnet body 13... Regulating blade 23... Developer M (magnetic brush) 24...Development space 30...Cabinet 31...Document 32...Document mounting table 4
0... Transfer paper 50... Organic photoreceptor 51
...Corona charger 52...Exposure optical system 53.
...Magnetic brush developer 54...Electrostatic transfer device 56...
・Blade type cleaning device 70...Heat roller fixing device

Claims (1)

[Scope of Claims] 1) A carrier comprising magnetic particles coated with a silicone compound, a toner comprising a styrene-acrylic copolymer polymerized with an azobis initiator, and the carrier. An electrostatic image developer characterized by containing inorganic fine particles that are positively charged by friction. 2) Positively charged due to friction between a carrier formed by coating magnetic particles with a silicone compound, a toner containing a styrene-acrylic copolymer polymerized with an azobis-based initiator, and the carrier. A negative electrostatic latent image formed on the surface of a photoreceptor made of an organic photoconductive semiconductor is developed by a contact magnetic brush development method using an electrostatic image developer containing inorganic fine particles. An electrostatic image development method.