JPS63169660A - Electrostatic image developer and electrostatic image developing method - Google Patents

Abstract

PURPOSE:To improve durability and to obtain an excellent image of a high density without having fogging by using a developer contg. a carrier consisting of specific magnetic material particles and a toner as well as fine inorg. particles which are electrostatically charged positive by friction with the carrier. CONSTITUTION:The negative electrostatic latent image formed on the surface of a photosensitive body consisting of an org. photoconductive semiconductor is developed by a contact type magnetic brush developing method using the electrostatic image developer constituted by incorporating the carrier consisting of the magnetic material particles contg. copper, zinc and iron as essential components, the toner contg. styrene/ acryl copolymer and the fine inorg. particles which are electrostatically charged positive by friction with the above-mentioned carrier into the developer. The positive triboelectrostatic charge of an adequate electrostatic charge quantity is surely imparted to the toner by the synergistic effect of the carrier, the toner and the positive- chargeable fine inorg. particles contained in the above-mentioned developer; in addition, the good triboelectrostatic chargeability is not affected by environmental conditions such as high humidity. The good image of the high density having no fogging is thereby stably obtd. even after repetitions of many times without being affected by environmental conditions.

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]

Generally, in electrophotography, a photoreceptor having a photosensitive layer made of a photoconductive material is given a uniform electrostatic charge, and then an electrostatic latent image is formed on the surface of the photoreceptor by performing image exposure. 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 materials such as high-molecular compounds such as polyvinylcarbadul or low-molecular weight compounds. Photoconductive materials and the like are known.

However, although photoreceptors with photosensitive layers formed from these photoconductive materials have one advantage in forming electrostatic latent images, they also have disadvantages 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-temperature 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. However, under high-temperature environmental conditions, good images cannot be formed many times 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 the exposure process that is normally used to form an electrostatic latent image, so that it cannot be used for a long period of time. There is a problem that it is not possible to form an image, and furthermore, under high-temperature environmental conditions, the characteristics of the photosensitive layer change due to moisture, making it impossible to obtain the desired potential of the electrostatic latent image, resulting in low image density. There is a problem.

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 problems, it has recently been proposed to use low molecular weight organic photoconductive materials. Since low molecular weight organic photoconductive materials generally have good dispersibility in binder resins, the resulting photosensitive layer has the organic photoconductive materials uniformly dispersed in the form of fine particles, resulting in a high sensitivity. By forming the photosensitive layer by dispersing an organic photoconductive material in a binder resin, it is possible to obtain a photoreceptor with relatively high performance, and by forming the photosensitive layer by dispersing an organic photoconductive material in a binder resin, the film forming property is good, and therefore the photoreceptor can be manufactured 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 obtain photoreceptors with better performance than conventional ones. It is possible. Thus, an organic photoreceptor having a photosensitive layer formed of a low molecular weight organic photoconductive material is more preferable than 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. Developers containing negatively charged toner are used, and considerable research and development efforts have been made on developing agents containing 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 is
Since a liquid developer is used, there is a problem in that it emits a bad odor, and there is also a problem in that high-speed copying is difficult because high energy is required to dry the transfer material. 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 because the amount of triboelectric charge is small, development is basically unstable. There are some problems that can easily become a problem. Specifically, for example, toner may adhere to non-image areas on the photoreceptor, causing fog in the final fixed image, or the amount of toner adhering to the image area on the photoreceptor may be insufficient, resulting in There is a problem that the fixed image has a low fourth degree.

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. In addition, since the magnetic material used in magnetic toner usually has negative chargeability, it is difficult to positively charge the magnetic toner with an appropriate amount of charge, and as a result, there is a large proportion of toner that is reverse scratchable. In contrast, the latter two-component developer is composed of toner and carrier, and the carrier adjusts the toner to the desired polarity. Because it has the function of charging, it is possible to apply triboelectric charge to the toner with the appropriate polarity and in the appropriate amount, and it has much superior triboelectric charging properties compared to the one-component developer mentioned above. It is possible to obtain a developer having

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 necessary to use 1? It is not enough to have good triboelectric properties; it is necessary that developer particles to which triboelectric charges are applied in the developing device be transported to the developing space in a good condition without agglomeration.

In other words, in a two-component developer, if the toner tends to aggregate and form clumps due to electrostatic cohesive force, it becomes difficult to disperse the toner particles in the carrier particles at a uniform concentration. The triboelectricity between the toner and the carrier decreases, and the proportion of toner with a low triboelectricity increases, and during the development process, l.
toner adheres and causes 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, the centrifugal force caused by the rotation of the carrier particles causes the l/ner particles to scatter, which contaminates the charger, exposure optical system, and other equipment installed in the copying machine. There is a problem that image defects such as image unevenness occur in the final fixed 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 that of the negative static N, WI image formed on the photoreceptor, resulting in the 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, this positive chargeability is 8! By being mixed with the toner, the fine particles are held in a state adhered to the toner particles, and by being mixed with the carrier particles and stirred, the fine particles give the toner a positive Pi! A triboelectric 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 The positively charged non-81 fine particles adhering to the surface become transferred to the surface of the carrier particle due to physical or electrostatic adhesion force, 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, the amount of weakly charged toner increases, and furthermore, the amount of toner that is negatively charged increases, resulting in fogging and image formation. A 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 at the periphery of the image decreases (image blur), a phenomenon in which a band-like difference in shading appears in the image ( There is a problem that 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.

[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. ) An object of the present invention is to provide an electrostatic image developing method capable of satisfactorily developing a negative electrostatic latent image formed on a photoconductive photoreceptor without toner scattering.

[Means for solving problems]

The electrostatic image developer of the present invention is characterized by the friction between a carrier made of magnetic particles containing copper, zinc, and iron as essential components, a toner containing a styrene-acrylic copolymer, and the carrier. It is characterized by containing inorganic fine particles that are electrically charged (hereinafter also referred to as "positively chargeable inorganic particles").

The electrostatic image developing method of the present invention uses a carrier made of magnetic particles containing copper, zinc, and iron as essential components, a toner containing a styrene-acrylic copolymer, and the carrier to form a positive image by friction between the carrier and the carrier. An electrostatic image developer (hereinafter also referred to as "specific developer") containing inorganic fine particles that are electrically charged.
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 is developed using a contact magnetic brush development method. .

[Function and effect of the invention]

According to the electrostatic image developer of the present invention, friction between a carrier made of magnetic particles containing copper, zinc, and iron as essential components, a toner containing a styrene-acrylic copolymer, and the carrier Since it contains positive chargeable inorganic fine particles that are positively charged, the synergistic effect of these makes it possible to reliably impart a positive and appropriate amount of triboelectrification to the toner, resulting in a high image density. It is possible to stably form fog-free, high-quality images many times. In addition, since good positive triboelectric charging properties of the toner can be stably obtained regardless of environmental conditions, the image density is high and there is no fogging even under high temperature environmental conditions.
! A high-quality image can be stably formed many times.

In other words, the styrene-acrylic copolymer contained in the toner generally has hard properties, so the physical adhesion of the toner is low, and as a result, the toner can be sufficiently uniformly dispersed and mixed in the carrier, and the toner It is possible to impart a stable triboelectric charge with a high degree of probability. In addition, since the toner contains a styrene-acrylic copolymer, the positively charged inorganic fine particles have high adhesion to the toner particles, and even when the positively charged inorganic fine particles are stirred in the imager. is stably held in the toner particles, and the excellent triboelectric charging properties of the toner 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 is made of magnetic particles containing copper, zinc, and iron as essential components, the surface of the carrier particles has high slipperiness, and therefore the positively charged non-11Ha particles are less likely to adhere to the carrier particles. Furthermore, adhesion of the toner substance to the carrier particles becomes less likely to occur, and as a result, the toner can stably exhibit good positive triboelectric charging properties over a long period of time.

In addition, carriers made of magnetic particles containing copper, zinc, and iron as essential components have stable triboelectric charging properties even under changes in environmental conditions, so toner particles are stable even under high-temperature environmental conditions. It is possible to impart a triboelectric charge, making it an excellent developer with little environmental dependence.

Further, since the excellent properties of such a carrier can be stably obtained over a long period of time, it can be used repeatedly many times, and the durability of the developer is significantly improved.

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, an image is formed on the surface of an organic photoreceptor, that is, a photoreceptor made of a photoconductive semiconductor, by a contact magnetic brush development method using a specific developer as described above. Since the negative electrostatic latent image is developed, the negative electrostatic latent image formed on the organic photoreceptor can be transferred to the toner without sacrificing the advantages of the organic photoreceptor such as low production cost and non-toxicity. Good development can be achieved without scattering of particles. 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 the developing method of the present invention, it is possible to produce clear and good quality images without fogging and without image unevenness, image blanking, image blurring, or image fading, regardless of environmental conditions. (Can be stably formed many times.

[Specific Structure of the Invention] The electrostatic image developer of the present invention basically contains a carrier made of magnetic particles containing copper, zinc and iron as essential components, and a styrene-acrylic copolymer. With toner,
It contains inorganic fine particles that are positively charged by friction with the carrier.

The carrier constituting the electrostatic image developer of the present invention is composed of magnetic particles containing copper, zinc and iron as essential components.

Such magnetic particles contain copper, zinc and iron as essential components, and may contain these metals in the form of metal oxides, and may further contain other ferromagnetic metal elements. It's okay. Examples of other ferromagnetic metal elements include manganese, aluminum, tin, and chromium.

As the magnetic particles, those made of ferrite can be particularly preferably used. Ferrite is a general term for magnetic oxides containing iron, especially MO and Fe.
A spinel type ferrite represented by xOs (M is a divalent metal) can be preferably used. Ferrite can have various magnetic properties and triboelectric charging properties by appropriately changing the composition of the contained metal components, so it is possible to select the one with the optimum characteristics in combination with the toner used in the present invention. . In addition, since ferrite is an oxide, its specific gravity is smaller and lighter than metal powders such as metal iron powder, and it can be easily mixed and stirred with toner, thus making it easier to remove toner from the developer. As a result, the amount of triboelectric charge of the toner can be made stable. In addition, the resistivity of ferrite is usually within the range of 10'' to 10 Ω·cl, which is higher than that of metal powder such as metal iron powder. When applied, excellent developability is obtained.

Further, as the ferrite, one having a saturation magnetization σ of 45 to 75 erau/g in a magnetic field of 10,000 s can be preferably used, and a ferrite having a resistivity of lXl
0' to I XIO"Ω'C11% specific gravity is 4.0 to 5.
5. Those having a bulk density of 2.0 to 3.0 g/cm3 can be preferably used.

If the saturation magnetization σ is too small, there is a risk that carrier particles will adhere to the electrostatic latent image and form part of the image. Damage to the roller surface can significantly shorten the service life of the hot roller fuser, and carrier particles can fly off the developer sleeve, contaminating the device and resulting in smeared images. On the other hand, when the saturation magnetization σ1 is excessive, it becomes difficult to form a uniform magnetic brush on the developing sleeve when applying the magnetic brush development method, and the resulting image quality deteriorates, resulting in an unclear image. There are cases.

Furthermore, when the bulk density is too low, it becomes difficult to mix the carrier and toner uniformly, and as a result, the amount of triboelectric charge of the toner becomes unstable, resulting in foggy and unclear images. On the other hand, when the bulk density is too large, it becomes difficult to form a uniform and dense magnetic brush on the developing sleeve when applying the magnetic brush development method, and as a result, the image may become blurred and unclear.

In the present invention, the average particle size (weight) of the carrier is 30
~150p, especially 40~110μ
It is preferable that 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, which may result in problems such as damage to the heat roller. can be,
On the other hand, if the average particle diameter of the carrier is too large, image distortion may occur.

In the present invention, the carrier particles preferably 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 1.0 to 1.2.
It is preferable that By using such a preferable spherical carrier, it is possible to form an image with high resolution and excellent gradation reproducibility. 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.

Further, the bulk density of the carrier is defined as a value measured according to JI322504. However, the drying process is omitted. -Specifically, from a funnel with a 2.5φ hole, 2
Drop the sample into a 5 cm3 cylindrical container, and
The value is the bulk density expressed in units of rg/cm'J based on the weight of '.

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 inorganic fine particles are defined as follows.

That is, 0.2 g of positively charged inorganic fine particles left overnight under the environmental conditions of a temperature of 20° C. and a relative humidity of 40% and 19.8 g of the carrier used in the present invention were mixed under the above environmental conditions. Shake for 5 minutes in a glass sample container with a volume of about 20 cc, and then measure the amount of triboelectric charge of the positively charged inorganic fine particles by the usual blow-off method using a stainless steel cell with a 400 mesh screen, Those whose triboelectric charge becomes positive as a result are defined as positively charged inorganic particles.

The positively chargeable inorganic fine particles used in the present invention have a triboelectric charge of +10 uc/g or more, especially +
304/g or more is preferable.

When the amount of friction 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 8g-free fine particles, the existence of amino groups makes them Jim-free particles with excellent positive chargeability, and the hydrophilicity such as the functional groups of the silicone compound and the hydroxyl groups present on the surface of the free fine particles. Since the groups are strongly bonded, the inorganic fine particles 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 coupling agents, amino-modified silicone oils, amino-modified silicone varnishes, amino-modified silicone rubbers, amine-modified silicone resins, etc. can be used. In particular, it offers excellent 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.

HzNCH, CHzCHzSi (OCH3H2N C
H2CHICHzSi(OCtHs)iCHl HtN CHtCHzCHzSi(OCI4z”)x
Hi HgN CHzCHtN HCHzCHzCHxSi(
OCH-+)zH□N CON HCH□CHzCHz
Si(OCzHs)sHtN CHtCHzN HCH
tCHzCHtSi(OCH3)IHtN CHtCH
tN I]CHzCHzN HCHz--CHICHt
Sl(OCHff)s H5C, OCOCH, CHEN HCH2CH2C[(
, -5i(OCH3)TSH5C10COCH2CHffiNHCH2CH,N+
(-CHzCHzCHxSi(OCHs)+H5C!0
COCH□CH2N HCHtCHtN H-CHtC
HtN 11CHICHtN HCH2-CHICHz
si(OCH3)3 HICOCOCHffiCHffiNHCH2CH! N
H-CHzCHzCHzSi(OCH3)3HS G
! N CHz CHz CH□Si (OCH3) aH
s Ct Si<0CR3)3 H3C CHt CHzsi(OCHs) a HOCHz G Hz N CHzCHzCHzSi(OCR3).

HOCHz CHt (HsCO)+SiCHzCHtCHzN HCHz(
HsC0) isic H□CHz CHz N HCH
t(HsCzO)zsiCHzCHzCHzH 硼(HsCzO), 1sicHzcH□CHtl(jCN
HCH,CH,CH2S1(OCzHs)zHzN(
CHtCHxNH)zCHzCHzCHz-5t(O
Ct(s)+ HsCN HCON Hz ■ C3HaSi(OCHs)+ Moreover, in the above compound, the alkoxy group may be 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) (R11 represents an alkylene group, aryl group, aminoalkylene group, etc., R+z and R13 each represent a hydrogen atom, hydroxyl group, alkyl group, oryl group, etc., x, y are Each represents an integer of 1 or more.) Furthermore, as the amino-modified silicone oil, those having an amino equivalent value within the range of 200 to 22,500 are preferable, and those within the range of 300 to 10,000 are particularly preferable.

When the amino equivalent value 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 amino equivalent value is too large, the inorganic fine particles become carrier particles. It is easy to transfer and adhere to the particles, and the durability of the image forming 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. When the viscosity is too low, the stickiness of the inorganic fine particles becomes high, which may reduce the durability of the image forming agent.On the other hand, when the viscosity is too high, proper surface treatment becomes difficult, and as a result, the toner The positive chargeability of the developer may become unstable and the durability of the developer 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 T” shown by the following structural formula.
unit, D21 unit, M'' unit,
It is a three-dimensional polymer containing a large amount of T'' units.

[Tz' unit) CD'' unit] [OCHff I CHs St OCHs Si O-+
1 (Mtl unit) Ha CHs Si O- Hs In addition, methyl silicone varnish or phenyl methyl silicone varnish is specifically, for example, represented by the following structural formula (1)
It is a substance that has the chemical structure shown below.

Structural formula (1) %Formula% (R1 represents a methyl group or a phenyl group) In the above silicone varnish, in particular, the T'' unit is used to impart good thermosetting properties and to form a three-dimensional network structure. Inorganic fine particles whose surfaces are treated with silicone varnish containing such TEL units have a hard and tough film on their surfaces, and therefore have excellent impact resistance, moisture resistance, and mold release properties. The above-mentioned T" unit is contained in the silicone varnish in an amount of 10 to 90 mol%, especially 30 to 90 mol%.
It is preferably contained in a proportion of 80 mol%. Right! );
T! If the ratio of 1 unit is too small, the stickiness may increase due to softening, and the stability of moisture resistance, durability, and triboelectric charging properties may decrease.In particular, the cleaning performance of the toner may decrease, and toner scattering may occur. This results in image unevenness,
Capri and the like may occur, and furthermore, the durability of the fixing device may be reduced. On the other hand, if the proportion of the 39 Tt + units is too large, the coating layer formed on the surface of the am-free particles may become non-uniform, and the stability and durability of triboelectric charging properties may deteriorate.

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 above silicone varnish into an amino-modified silicone varnish, some of the methyl groups or phenyl groups present in the Ttl units, D" units, and M" units may be substituted with groups having an amino group. Examples of the group having an amino group include those represented by the following structural formula.

CHz CHt -N HI CHz(CHz)t N Hz -CHz(CHz)t-NH(CHt)* NH2 As the silicone rubber used to obtain the above amino-modified silicone rubber, for example, D represented by the following structural formula
A long-chain polymer consisting of only 31 units, with a viscosity of 10' to 10' cps at a temperature of 25°C,
Those having an average molecular weight of, for example, 104 to 10" can be preferably used. Particularly, those having a viscosity of 1O& to 1Q"
cps and an average molecular weight of 105 to 107 is preferred. When the viscosity is too low or the average molecular weight is too low, durability and moisture resistance may decrease, while when the viscosity is too high or the average molecular weight is too high, uniform surface treatment becomes difficult, resulting in friction. Charging properties become unstable, which tends to result in foggy and unclear images, and durability and moisture resistance may deteriorate.

[D11 unit] -0-3i-0- 3g (R21 and Ro 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.) R3g is preferably a methyl group or a phenyl group, particularly preferably a methyl group. In addition, in order to make the silicone rubber have a crosslinked structure, the D'''' unit shown by the following structural formula,
It is preferable to copolymerize using a small amount of D'' units represented by the following structural formula.

(()0431st) CD” unit] CH,
C.I.

-O-5i-0--0-5i-0- CH,CH=CH2 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 It has a hard and tough film, and therefore has excellent impact resistance, 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 vulcanizing 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.

Furthermore, in order to make the silicone rubber as described above into an amino-modified silicone rubber, a portion of R31 and RIm of the Dff+ unit may be 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 Ht CR2 (CHz)z N Hz -CH, (CI(,)!-NH-(CHI)!-NH!
The silicone resin used to obtain the amine-modified silicone resin has a T4' unit represented by the following structural formula,
It is a polymer consisting of 41 [) units, [) 4 g units, and M'' units, and unlike silicone oil, it is a polymer that contains a large amount of T'' units.

[T41 unit] (D” unit) 0
R"R"-3i-0-R"-5i-0- [M41 unit) CD" unit] R44R4
6 CH3Si OOSt O- R” CH-CH.

(R41, R4t, Ru, R44, R45, R
o represents an organic group such as an alkyl group such as a methyl group or an ethyl group, or an aromatic group such as a phenyl group, respectively. ) 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. , which becomes 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 O H groups remain, which do not form and exist freely, these silanol groups react with functional groups present on the surface of the inorganic fine particles or form siloxane bonds during the curing stage. It became like this,
As a result, the silicone resin has stronger properties, and the inorganic fine particles whose surfaces have been treated with such a silicone resin have a tough yet flexible film on their surface, which makes them more durable. It has excellent impact strength, moisture resistance, and mold releasability.

In order to make the silicone resin as described above into an amino-modified silicone resin, the T" units, D" units, pa
t unit, organic i (R41, R
4! , R43, R44, R4S, R4&)
(Part of D may be substituted with a group having an amino group. Examples of the group having an amino group include those represented by the following structural formula.

-CH2G Hz N Ht -CH, (CH□)tNHz -CH (CHl)! -NH-(CHI)3-NH Process 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, and Examples include fine particles of zinc, chromium oxide, cerium oxide, antimony dioxide, 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 mμ to 2 μl.

In particular, silica particles can be preferably used as the inorganic particles. Silica fine particles are 5i-0-3i
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. In addition, as the 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 5i01 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 charged 8g machine particles whose surface has been treated with the above-mentioned compound obtained in this way is such that the average particle size of the primary particles is 3u to 2μ layer, especially 5IIp to 50μ layer.
It is preferable that it be within the range of 0.03μ.

In addition, the specific surface area according to the BET method is 20 to 500 m"
/g is preferable. If the average particle size is too small or the specific surface area is too large, for example, when cleaning using a blade type cleaning device,
a Fine particles may easily slip through, resulting in poor cleaning. 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.
Preferably 5% by weight, especially 0.1-2% by weight
It is preferable that When the content ratio of the positively chargeable inorganic fine particles is too small, the fluidity of the developer may decrease, resulting in poor triboelectric charging properties of the toner and imparting an appropriate amount of positive charge to the toner. This may cause capri or image unevenness to 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. Otherwise, it may adhere and accumulate on the inner wall of the developing device, the developing sleeve, the regulating blade, etc., and eventually the triboelectric charging properties of the toner become poor, making it difficult to apply an appropriate amount of positive charge to the toner, resulting in fogging. or a decrease in image density may occur.

The toner used in the present invention is a toner containing a styrene-acrylic copolymer, and basically contains a colorant and other additives in a binder made of the styrene-acrylic copolymer. The average particle size is usually preferably about 5 to 20 μ layers.

In addition, other additives include, for example, a fixability improver,
A charge control agent B, a cleaning performance improving agent, etc. can be used.

The styrene-acrylic copolymer is basically a copolymer obtained from a styrene monomer and an acrylic monomer, and in particular, a styrene monomer, acrylic acid or its ester, and Copolymers obtained by polymerization with/or methacrylic acid or esters thereof can be preferably used. The styrene-based component can impart suitable release properties to the toner and improve offset resistance, and can also harden the toner and provide 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 an amount of 60 to 90% by weight of the copolymer, while the acrylic component is contained in an amount of 40 to 10% by weight of the copolymer. It is preferably contained in a proportion of % by weight. When the proportion of the styrene component 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, which impairs the properties of the carrier and reduces the durability of the developer. It may decrease. 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 JIMw of 60. OOO to 500,000, number average molecular weight Mn of 1,000 to 30,000, and ratio Mw/Mn of these values in the range of 7.4 to 40 can be preferably used. By using a toner within such a preferable range, a toner with excellent anti-offset properties and fixing properties can be obtained. On the other hand, when the values of weight average molecular weight h, number average molecular weight Mn, and ratio Mw/Mn are outside the above ranges, 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. When the glass transition point Tg is too small, the toner's fluidity may be reduced due to high tackiness; on the other hand, when the glass transition point Tg is too large, the fixability may be reduced.

Specific examples of styrene monomers that can be used to obtain the styrene-acrylic copolymer include styrene, 0-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, pn-decylstyrene, pn-
Examples include 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, acrylic 1ln-butyl 1. Isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methacryl acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-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 maleile acid and fumaric acid; etc. may be contained as structural units.

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

! 4. Physically, 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, a metal complex dye or the like can be used.

Further, as the cleaning property improving agent, for example, fatty acid metal salts such as zinc stearate, calcium stearate, stearic acid, etc., polymer particles such as methyl methacrylate a particles, styrene fine particles, etc. 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/111in]. 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 weight average molecule 11Mw and the number average molecule llMn
The value can be determined by various methods, and there are some differences depending on the measurement method, but in the present invention, it is defined as the value determined by the following measurement method.

That is, the weight average molecule is 11 Mw, the number average molecule is 3j1 Mn, and the peak molecular weight is measured by gel permeation 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/min.
Measurement is performed by injecting 3 mg of a 20 d tetrahydrofuran sample solution as a sample weight. When measuring the molecular weight of a sample, select measurement conditions in which the molecular weight of the sample falls within a range where the logarithm of the molecular weight and the count number of the calibration curve prepared using several types of monodisperse polystyrene standard samples are linear. .

The reliability of the measurement results is based on the NB5706 polystyrene standard sample (weight average molecular weight M
w=28.8X 10'+number average molecule IMn=13
．． 7XIO', Mw/Mn=2.11) ratio Mw/
This is confirmed by checking that the Mn value is 2.11±0.10.

Note that any GPCO column may be used as long as it satisfies the above conditions.Specifically, for example, TSK-C;EL, GMH&(
(manufactured by Toyo Soda Co., Ltd.), etc. can be used.

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 formed using a specific carrier as described above, a specific toner as described above, and the positively charged inorganic fine particles. A toner image is formed by developing with a specific electrostatic image developer containing.

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 photosensitive layer constructed by combining a carrier transporting layer containing a carrier transporting substance. By assigning two basic functions to separate layers, the range of materials that can be used to construct the photosensitive layer is widened, and it is possible to independently select the materials or material systems that optimally perform each function. Then,
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 the carrier-generating material 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, polyarylalkane 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 nm, 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, silver, indium, tin, platinum, gold, stainless steel, steel, brass, etc. 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, which has the shape of a rotating drum that is rotated in the direction of arrow The angry light layer 10B containing the following 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 a light image of the original onto the developing surface of the organic photoreceptor 10, and a static image corresponding to the original is projected onto the developing surface of the organic photoreceptor 10. A 1iWI image is formed, and this electrostatic latent image is moved to the development space 24, where the electrostatic latent image is developed.

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 consists of a plurality of N and S magnetic 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 applied to 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]t2i23 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 it possible to make the toner concentration 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, it is preferable that the tip of the magnetic brush make shallow contact with the surface of the organic photoreceptor 10 in order to achieve uniform development. The distance (Hcut) between the organic photoreceptor 10 and the developing sleeve 11 in the developing space 24 is
It is preferable that the gap (D sd) is approximately 0.8 times the gap (D sd) between
It is preferable to set it as Qmm. 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 air brush formed on the surface of the developing sleeve 11 are The toner particles are moved to the developing space 24 following the rotational movement of the developing sleeve 11 while vibrating, 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 by contact heating the toner image on the transfer material with a heat roller (fixing 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 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 an organic photoreceptor through a transfer material, and an alternating current corona discharge is applied to the transfer material from the back side of the photoreceptor. The toner carried on the surface of the transfer material 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 bank up roller disposed 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 Devon Co., Ltd.) 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.

Reference numeral 30 denotes a cabinet, and at the top of the cabinet 30 there are provided a glass document mounting table 32 on which a document 31 is placed, and a platen cover 33 that covers the document 31. A paper feed tray 4I into which the 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 the organic photoreceptor 50, from the upstream side to the downstream side in the rotational direction, a corona charger 51, an exposure optical system 52, a magnetic brush developer 53, and an electrostatic transfer device 54 are arranged.
, 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 dichroic ink mirror 67 . The first mirror unit 63 is movably provided below the document mounting table 32 so that the document [7 table 32] is scanned, and the second mirror unit 64 moves the organic photoreceptor 50 from the document scanning point. The first mirror unit 63 is provided so as to be movable 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 50.

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

In the above apparatus, the surface to be developed of the organic photoreceptor 50 is charged to a uniform negative potential by the corona 4Ff electric device 51,
Next, imagewise exposure is performed by the exposure optical system 52 to form a negative electrostatic latent image corresponding to the original on the developed surface of the organic photoreceptor 50. This negative electrostatic latent image is then developed by the magnetic brush developing device 53 to form a toner image corresponding to the original. The toner image on the organic photoreceptor 50 is electrostatically transferred onto the transfer paper 40 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, it is 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, only a small amount of developer remains on the organic photoreceptor after the transfer process.
Therefore, in the cleaning process, it is easy to clean the remaining developer, and since the developer has suitable release properties due to the presence of positively charged inorganic particles, the developer is not easily removed from the organic photoreceptor. The adhesive force is small, and as a result, the developer can be easily cleaned using a cleaning blade.

In addition, since the cleaning properties of the developer are good, it is possible to achieve good cleaning with a small pressure contact force of the cleaning blade against the organic photoreceptor. This prevents premature deterioration of the characteristics of the organic photoreceptor due to abrasion, and the service life of the organic photoreceptor can be significantly extended.

In addition, in the fixing process, positively chargeable inorganic fine particles are present between the surface of the molten developer and the heat roller, and the positively chargeable non-W1 particles provide a mold release effect, resulting in the release of the developer. Transfer and adhesion to the heat roller is prevented, developer is prevented from accumulating in minute grooves of the heat roller, and as a result, image stains 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.

(Carrier) (1) Carriers 01 to C7 (for the present invention) Magnetic particles made of ferrite particles having the composition and characteristics shown in Table 2 below were used as carriers.

These are respectively labeled as “Carrier CIJ ~ [Carrier C7J
shall be.

(2) Carrier C8 (for comparison) Iron powder particles rr) SP-138J (manufactured by Dowa Iron Powder Co., Ltd.) was used as a carrier. This is called “Carrier C8J.

(Inorganic fine particles) (1) Inorganic fine particles AI (for the present invention) Average particle size is 12 mtr, specific surface area is 20 (1w”/g
100 parts by weight of silica fine particles "Aerosil 200" (manufactured by Nippon Aerosil Co., Ltd.) were placed in a high-speed rotating mixer, and then N-β (aminoethyl) γ-aminopropyltrimethoxysilane rKBM 603J (manufactured by Shin-Etsu Chemical Co., Ltd.) was added.
8 parts by weight and hexamethyldisilazane [5Z6079J
A treatment solution prepared by dissolving 8 parts by weight of <Tou μ Silicone Co., Ltd.) 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 as a carrier was removed and the reaction was proceeded, and the average particle size of the primary particles was 121μ, B
Positively charging inorganic fine particles having a specific surface area of 190 m''/H were produced by the ET method. These are referred to as [Inorganic fine particles All].

The inorganic fine particles A1 have a triboelectric charge amount with the carriers 01 to C7 within a range of +30 to +200 tlg, and particularly a triboelectric charge amount with the carrier C1 of +63 uc/g.

(2) Inorganic fine particles A2 (for the present invention) In the production of inorganic fine particles A1, the amino equivalent is 3500
．． 10 parts by weight of amino-modified silicone oil rsF8417J (manufactured by Le Silicone Co., Ltd.) having a viscosity of 1200 cps at 25°C, and hexamethyldisilazane rs
Z6079J (manufactured by I-Re Silicone Co., Ltd.) was treated in the same manner except that 8 parts by weight was used, and the average particle size of the primary particles was 13 mm, and the specific surface area by BET method was 180 m''/
g of positively charged inorganic fine particles were obtained. This is called “Inorganic fine particles A
Let it be 2J. These inorganic fine particles A2 are carriers 01 to C
The amount of triboelectric charge with carrier C1 is within the range of +30 to +200 tl-7g, and especially the amount of triboelectricity with carrier C1 is +71 m/g.

(3) Am-free particles A, 3 (for the present invention) In the production of inorganic fine particles AI, the average particle size is 16171
100 parts by weight of silica fine particles with a % specific surface area of 130 m''7 g [Aerosil 130J (manufactured by Nippon Aerosil Co., Ltd.)] and 20 parts by weight of an amine-modified silicone varnish having a structural unit represented by the following structural formula were dissolved in 100 parts by weight of xylene. Processed in the same manner except that a processing solution consisting of
Positively charged inorganic fine particles having an average primary particle diameter of 15 mg and a specific surface area of 92 m''7 g by the BET method were obtained. These are referred to as "inorganic fine particles A3J."

The inorganic fine particles A3 have a triboelectric charge amount with the carrier C1-C7 within a range of +30 to +200&/g, and particularly a triboelectric charge amount with the carrier C1 of +93ttC/g.

(x, y, z are each integers of 1 or more, X:)
':z=1:4:5. ) (4) Inorganic fine particles A4 (for the present invention) In the production of inorganic fine particles A1, 100 parts by weight of silica fine particles "Aerosil 300J (manufactured by Nippon Aerosil Co., Ltd.) with an average particle diameter of 7 μm and a specific surface area of 300 m"/g were used. ,
The same treatment was carried out, except that a treatment solution prepared by dissolving 25 parts by weight of an amino-modified silicone rubber having a structural unit represented by the following structural formula and 0.2 parts by weight of hendiyl peroxide in 125 parts by weight of xylene was used. , the average particle size of the primary particles is 71
Positively charged inorganic fine particles with a specific surface area of 166111"/g were obtained by μ, BET method.
shall be. The inorganic fine particles A4 have a triboelectric charge amount of +30 to +200 f:,/g with the carriers 01 to C7, and especially a triboelectric charge amount of +145 with the carrier CI.
aC/g.

(x, y, z are each integers greater than or equal to 1, and x: y
:z=7:1:2. ) (5) Inorganic fine particles A5 (for the present invention) have the following D1 unit, the following minor unit, the following AD' unit, and the following TI unit as their constituent units, and the molar ratio of these is 4.5:0.5 : 1 : 4 for amino-modified silicone resin and 0 for this amino-modified silicone resin.
．． A treatment solution was prepared by dissolving 5% by weight of benzoyl peroxide in xylene.

(D' unit) (D" unit] CH3CH3 -O-3i-0--0-5i-0- CHs CH"" CHt (T' unit) CAD' unit] 0
CH.

-O-3i-0--0-3i-0- I CH GHz(CHt)zNHtNext, silica fine particles [Aerosil 300J (manufactured by Nippon Aerosil Co., Ltd.)] were placed in a mixer, and the above amino acid was added to the silica fine particles. After spraying a treatment solution with a proportion of 20% by weight of modified silicone resin, these were placed in a flask, and the solvent xylene was removed at a temperature of 120°C for 5 hours while stirring, and the amino-modified silicone resin was removed. A curing reaction is performed, and the average particle size of the primary particles is 7 μμ,
Positively charged inorganic fine particles having a specific surface area of 13,511"7 g by the BET method were obtained. These were referred to as "inorganic fine particles A5J.

The inorganic fine particles A5 have a triboelectric charge amount of +30 to +200 7 g with the carrier Cl-C7, and especially a triboelectric charge amount of +160 me/g with the carrier C1.

(Toner) (1) Toner TI (for the present invention) Styrene-n-butyl acrylate-methyl methacrylate copolymer polymerized using benzoyl peroxide as an initiator (copolymerization weight composition ratio -7:2:1) , weight average molecular weight Mw=130.OOO, number average molecular weight 51 Mn
-10,000, Mw/Mn=13, glass transition temperature Tg
= 60°C), 10 parts by weight of carbon black [Mogul LJ (manufactured by Cabot), and 2 parts by weight of metal-containing dye, and then mixed with two rolls.
Thoroughly melt-kneaded at 00 to 130°C, then cooled, coarsely pulverized with a hammer mill, further finely pulverized with a jet mill, and then classified to obtain particles with an average particle size of 11. On toner was obtained. This is referred to as [toner TIJ.

(2) Toner T2 (for the present invention) In the production of toner T1, a styrene-n-butyl methacrylate copolymer polymerized using benzoyl peroxide as an initiator (copolymerization type WIMi composition ratio = 65:35)
, weight average molecular weight Mw = 120.000, number average molecular fiMn = 8,000, Mw/Mn = 15.0,
Gas transition point Tg = 55℃) 100! A toner having an average particle size of 10.5 μm was obtained in the same manner except that the Iti part was used. This is referred to as [Toner T2J.

Examples 1 to 7 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 3 below.

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

The developers obtained in Examples 1 to 7 were each referred to as "Developer 1".
~ "Developer 7", and the developer obtained in Comparative Example 1 is referred to as "Comparative Developer 1".

Table 3 Live-action test> (1) Test 1 (Live-action test under room temperature environmental conditions) An organic photoreceptor for forming a negative electrostatic latent image, a contact magnetic brush developer, and an AC corona discharge were used. A corona transfer device, a heat roller with a diameter of 30φ whose surface layer is made of Teflon (polytetrafluoroethylene manufactured by DuPont), 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 photocopying test in which a modified 1550MRJ (manufactured by Konishiroku Photo Industry Co., Ltd.) was used to continuously form copied images 50,000 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. The results are shown in Table 4 below.

The above-mentioned organic photoreceptor has a negatively chargeable two-layer photosensitive layer formed using an anthrone interlayer 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 it on a support.

The surface potential (highest potential) of the organic photoreceptor when it is charged is -700■, the gap (Dsd) between the photoreceptor and the developing sleeve in the developing space is 0.6 m+m, and the gap between the tip of the regulating blade and the developing sleeve is The distance (Hcut) is 0
．． The 55 mm, 611 stone body is of 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 -150 V 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 was set to 0.0. 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 "○".
Cases of 0.03 or more were marked as "x".

■Image level "Sakura densitometer" (manufactured by Konishiroku Photo Industry Co., Ltd.)
was used to measure the relative density of a white background portion with an original density of 0.0 with respect to a copied image. For evaluation, when the image density was 1.0 or more, rOJ was given, when it was 0.7 or more and less than 1.0, it was given "Δ", and when it was less than 0.7, it was given "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, ``△'' if it was slightly defective but at a practical level, and rOJ 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. It represents the northern phenomenon, and ``image fading'' refers to a phenomenon in which a band-like difference in shading appears 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, mark it as "○." If there is some toner scattering, but it is at a practical level, mark it as "Δ."
”, 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 ``rob'' when there are almost no deposits observed and the condition is good, ``△'' when there are some deposits but at a practical level, and ``△'' when there are many deposits and there are problems in practical use. I marked it with an “×”.

(2) Durability of the fixing device Judgment was made based on the occurrence of an off-cent phenomenon, the occurrence of paper jams, and the staining of the back side of the transfer paper, which are caused by dirt on the heat roller and buffer roller that constitute the fixing device. Evaluation,
A case where the result is poor and has a practical problem is rated as "x", a case where it is slightly poor but at a practical level is rated as "△", and a case where it is good is rated as "○".

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 the above items were evaluated. did. The results are shown in Table 5 below.

As can be understood from the results in Tables 4 and 5,
According to the developers 1 to 7 of the present invention, the toner has good triboelectric charging properties and fluidity, and therefore, in the developing process,
A negative electrostatic latent image formed on an organic photoreceptor by magnetic brush development can be developed well without toner scattering, and in the transfer process, it can be transferred at a high transfer rate by electrostatic transfer means. In addition, in the cleaning process, a cleaning blade with a simple structure can perform good cleaning, and in the fixing process, a hot roller fixing device can perform good fixing without causing an offset phenomenon. As a result, it is possible to form a good image with clear image quality without fogging, image missing, image unevenness, image blurring, and image fading, and with high image density.

Further, even when the image forming process is performed many times, the heat roller and backup 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 the carrier is made of iron powder particles, there is no problem with separate installation at the initial stage of image formation, but as the image formation is repeated, the triboelectricity of the toner increases. As a result, when the image forming process is performed many times, fog gradually increases and the image density gradually decreases, resulting in an early blurred image. In addition, under high temperature environmental conditions,
The carrier is significantly affected by humidity and becomes stable in FtJ triboelectric chargeability, resulting in significant fogging occurring at an early stage, image density being considerably reduced, and image blurring becoming significant.

[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... Angry light layer 11... Developing sleeve 12... Magnet body 13... Regulation blade 23... Developer layer (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 Miyako 2Z

Claims (1)

[Claims] 1) A carrier made of magnetic particles containing copper, zinc, and iron as essential components, a toner containing a styrene-acrylic copolymer, and a toner that is positively charged by friction between the carrier and the carrier. An electrostatic image developer characterized by containing inorganic fine particles. 2) Contains a carrier made of magnetic particles containing copper, zinc, and iron as essential components, a toner containing a styrene-acrylic copolymer, and inorganic fine particles that are positively charged by friction with the carrier. An electrostatic image characterized in that 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 made of Development method.