JPS59164562A - Developing method - Google Patents

Abstract

PURPOSE:To enable development superior in durability, such as repeated use characteristics, by holding an insulating magnetic developer contg. a fine silica powder subjected to silane coupling agent treatment and hydrophobicness raising treatment after heat treatment in a thin layer on a carrying body to carry out development. CONSTITUTION:An electrostatic image bearing body for bearing it on the surface and a developer carrying body for holding an insulating magnetic developer on the surface are arranged at a prescribed constant gap. The insulating magnetic developer to be used contains a fine silica powder produced by vapor phase oxidation of silicon halide, heat treated at >=400 deg.C, and treated with a silane coupling agent having the formula in which R is alkoxy or Cl; m is 1-3; Y is a hydrocarbon group having at least one of amino, vinyl, ureido, etc.; and n is 3-1. Said powder is raised in hydrophobicness to 30-80 hydrophobic degree measured by the methanol titration method. The electrostatic image is developed by carrying said developer contg. said powder held in a layer thinner than said gap and transferring the developer to the electrostatic image bearing body at a developing section.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method using an insulating magnetic developer.

Conventionally, developing units and methods used in electrophotography, electrostatic recording, etc. are roughly divided into dry developing methods and wet developing methods. The former method is further divided into a method using a two-component developer and a method using a -component developer. Depending on the type of carrier used to transport the toner, two-component developing methods include the magnetic brush method using an iron powder carrier, the cascade method using bead carriers, and the fur brush method using fur. .

In addition, those belonging to the -component type development method include a powder cloud method in which toner particles are sprayed, and a contact development method (contact development, or (also referred to as toner development), the toner particles are not brought into direct contact with the electrostatic latent image surface, but the toner particles are charged and directed toward the electrostatic latent image surface using the electric field of the electrostatic latent image.
There is a jumping development method in which a magnetic conductive toner is brought into contact with an electrostatic latent image surface, and a magnetry method in which development is performed by bringing a magnetic conductive toner into contact with an electrostatic latent image surface. In the two-component development method, a mixed developer of carrier particles and toner particles is inevitably used, and during the normal development process, the toner particles are used in much larger quantities than the gear particles, and the gear particles are used for a long time. It inherently has drawbacks such as deterioration in image quality due to deterioration caused by.

On the other hand, in -component-based development methods, the Magne Dry method using magnetic toner and the contact development method not using magnetic toner, the toner contacts the entire surface of the surface to be developed, that is, the image area and the non-image area, indiscriminately. As a result, there is a problem in that toner tends to adhere even to non-image areas, resulting in so-called smearing. (This fog staining problem also occurs in two-component developing methods.)
Further, even in the powder cloud method, it is unavoidable that toner particles J in a powder state adhere to non-image areas, and similarly, it has the disadvantage that soil blur cannot be removed.

Furthermore, in the so-called jumping development method, which belongs to the component-based development method, after toner is uniformly applied to a carrier such as a sheet, it is held facing an electrostatic holding surface with a distance FJt-, and an electrostatic image is transferred from the toner carrier. A method is known in which toner is attracted and attached to a holding surface by the charges of an electrostatic image, and developed. 3 (U.S. Pat. No. 2,839,400, etc.). In the non-image area, where the toner is not drawn, or because the toner and the non-image surface do not come into contact with each other, the above-mentioned capri is less likely to appear.

Furthermore, since carrier particles are not used, there is no variation in the mixing ratio as described above, and there is no deterioration of gear particles.

However, in this method, an electric field is applied in advance to adhere the toner to the toner carrier sheet, but it is difficult to apply the toner uniformly and thinly, and uneven application is likely to occur. Another drawback is that when a single layer of applied toner faces an electrostatic image, it is difficult to release the toner uniformly onto the electrostatic image.

In this regard, JP-A-54-43027, JP-A-55-186
In the developing device proposed in No. 56, which has magnetic toner, a movable toner carrier (sleeve roller), and a stationary magnet inside the carrier, a magnetic toner is proximate to the outer surface of the sleeve roller, facing the magnetic pole of the magnet. A developing device (l,
It can be said that it is an electrostatic image developing device that eliminates the above drawbacks and has high fidelity and stable image quality.

An object of the present invention is to provide a developing method with excellent durability such as continuous use characteristics.

Another object of the present invention is to provide a developing method that is stable against environmental changes such as high temperature and high humidity, and low temperature and low humidity.

The feature is that an electrostatic image carrier that holds an electrostatic image on the entire surface and a developer carrier that carries an insulating magnetic developer on its surface are arranged with a certain gap in the developing section. A fine silica powder produced by vapor phase oxidation of a silicon halide compound, wherein the fine silica powder is heated at a temperature of 400°C or higher (preferably 450°C to 1500°C, particularly preferably 500 to 1000°C). (R is an alkoxy group or a chlorine atom, m is an integer of 1 to 3, Y is at least one of an amine group, a vinyl group, a glint group, a mercapto group, a methacrylic group, and a ureido group) hydrocarbon group containing one or more types, n is an integer of 3 to 1)
Treated with a silane coupling agent shown in
An insulating magnetic developer containing fine silica powder that has been hydrophobized so as to exhibit a value in the range of 80 is supported on a developer carrier to a thin thickness across the gap, and the developer is transferred to the developing section. A developing method includes transferring the electrostatic image carrier to the electrostatic image holder and developing the image.

If copying is continued repeatedly using the conventionally known jumping developer, the uniformity of the developer layer carried on the developer carrier may be impaired, and the circumference of the carrier may become uneven. Coating defects with streaks occurring in the direction, the thickness of the supported developer layer being extremely thick in some areas compared to the initial thickness, spot-like unevenness occurring, and splatter-like Coating defects occur. The former is observed as white streaks on the image when developed, and the latter is observed as uneven density in the form of dots or waves. This phenomenon rarely occurs during normal repeated copying, but it may occur especially when used continuously for long periods of time under extremely low temperature and low humidity environmental conditions.1 Furthermore, even under high temperature and high humidity conditions, the developer layer The thickness often changes and becomes thinner, and wrinkles may cause a decrease in image density, which is undesirable.

As a result of repeated studies on this point, we found that one of the reasons for this is the stability and reliability of the charge control component, and these causes cause the developer powder to stick to the sleeve and the developer powder to flow from the sleeve. We found that this is due to changes in the transcription of .

More specifically, this phenomenon is caused by the occurrence of non-uniform areas of triboelectric charge in the developer layer supported on the carrier due to changes in environmental conditions. That is,
Under ultra-low temperature and low humidity environmental conditions, friction between the surface of the carrier and the developer generates components with extremely large triboelectric charges, and the mirroring force resulting from this charge causes the development of the carrier. Extremely large components of such triboelectric charges tend to accumulate near the body, and this affects the uniformity of the developer coating on the upper layer of the developer layer and the ease of development due to continuous durability, etc. , the above-mentioned white streaks and
Dot-like unevenness and serpentine coating defects occur.

In addition, the decrease in the thickness of the developer layer at high temperatures and high humidity is also caused by uneven triboelectric charging between the developer and the carrier. be.

Conventionally, known charge control agents used in such dry developing toners include amino compounds, quaternary ammonium compounds, and organic dyes, especially basic dyes and their salts, including benzyl dimethyl, hexadecyl ammonium chloride, Decyl-trimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin γ, crystal violet, and the like are used.

Nigrosine base and nigrosine hydrochloride are often used as positive charge control agents. These are usually added to thermoplastic resins, heated, melted and dispersed, and then
It is finely pulverized and adjusted to an appropriate particle size as necessary before use.

However, these dyes used as charge control agents have complex structures, uniform properties, and poor stability. In addition, decomposition or deterioration occurs due to decomposition, mechanical shock, friction, changes in temperature and humidity conditions, etc. during thermal crosstalk, resulting in a phenomenon in which charge controllability is deteriorated.

Therefore, when a toner containing these dyes as a charge control agent is used for development in a copying machine, as the number of copies increases,
The dye decomposes or changes in quality, causing toner deterioration during durability.

Furthermore, since it is extremely difficult to uniformly disperse these dyes as charge control agents in thermoplastic resins, this has the fatal drawback of causing a difference in the amount of triboelectric charge between toner particles obtained by pulverization. have. For this reason, various methods have been used to more uniformly disperse these dyes into resins. For example, basic nigrosine base is used by forming salts with higher fatty acids in order to improve compatibility with thermoplastic resins, but unreacted fatty acids or salt dispersion products are often exposed on the toner surface. This contaminates the carrier or toner carrier, causing a decrease in toner fluidity, capri, and image density. Alternatively, in order to improve the dispersion of these dyes into the resin, a method of mechanically pulverizing and mixing dye powders and resin powders and then heat-melting and kneading them is also used. In reality, poor dispersion cannot be avoided, and charge uniformity sufficient for practical use has not yet been obtained.

Most charge-controlling dyes are hydrophilic, and due to poor fractionation into the resin, the dye is exposed on the toner surface when it is melted and kneaded and then crushed. When these toners are used under high humidity conditions, they have the disadvantage that good quality images cannot be obtained due to the hydrophilic nature of these dyes.

In this way, when used in a conventional toner containing a wild dye, the toner particles may be dispersed between the toner particles, between the toner and the carrier, or between the toner and the toner carrier such as a sleeve. The amount of charge generated on the surface varies, causing problems such as development fog, toner scattering, and carrier contamination. Moreover, these problems become particularly noticeable when a large number of copies are made, resulting in a result that is practically unsuitable for copying machines.

Furthermore, under high humidity conditions, the toner image transfer efficiency is significantly reduced, making it unusable. Also 1. When the toner is stored for a long period of time even at room temperature and humidity, due to the instability of the charge control dye used, the toner often aggregates and cannot be used again.

The inventor of the present invention has conducted extensive research with the aim of solving the various problems associated with conventional charging and injection toners as described above, and producing high-quality images by being uniformly and strongly charged and by visualizing the electrostatic charge image. , the vapor phase of the silicon halide compound is a fine silica powder produced by chemical reaction, and after the fine silica powder is heat-treated at a temperature of 400°C or higher, m is an integer of 1 to 3, Y is a hydrocarbon group containing at least one or more of amino groups, vinyl groups, glycidoxy groups, mercapto groups, methacrylic groups, and ureido groups; n is an integer of 3 to 1)
treated with a coupling agent such as
It has been discovered that by incorporating fine silica powder that has been hydrophobized so as to exhibit a value in the range of 80 into a highly magnetic developer, an electrophotographic developer exhibiting various excellent properties can be obtained. Furthermore, it was discovered that it is very effective to apply this developer to a developing device having a sleeve roller.7.
The developing process used in the present invention will be explained.

FIG. 1 shows an embodiment of the magnetic cylinder 2 in the developing process used in the present invention.
rotates in the same direction as the surface of the electrostatic image holder in the developing section. Inside the non-magnetic cylinder 2, there is a multipolar permanent magnet 3.
is arranged so that it does not rotate. The one-component insulating magnetic developer 11 sent from the developer container 6 is applied onto the non-magnetic cylindrical surface, and due to the friction between the cylindrical surface and the toner particles,
Gives toner particles a charge of opposite polarity to the electrostatic image charge. Furthermore, an iron doctor
By arranging the toner so as to face the S pole (in the figure), the thickness of the toner layer can be controlled to be thin (30 μm to 300 μm) and uniform. By fully adjusting the circuit speed of this cylinder 2,
The surface velocity and preferably the internal velocity of the developer layer are made to be substantially equal to or close to the velocity of the electrostatic image bearing surface. As the doctor blade 5, opposing magnetic poles may be formed using a permanent magnet in an iron bar. Furthermore, an alternating current bias may be applied between the developer carrier and the electrostatic image holding surface in the developing section. This AC Baianu is f
is 200-4000Hz, Vpp is 500-300
It is sufficient if it is 0V.

As described above, in this developing step, the non-magnetic cylinder 2 containing the multipolar permanent magnet 3 was used in order to stably hold the one-component magnetic developer on the developer carrier. In addition, in order to uniformly form the developer carrier, a doctor blade 10 made of a thin magnetic plate and a permanent magnet is placed close to the surface of the cylinder 2, and an opposing magnetic pole is formed between the doctor blade and the magnetic pole of the stone. It is not necessary to force the toner particle chains to stand up between the developer carriers, and to force the toner particle chains to stand up on other parts of the developer carrier, for example, facing the electrostatic image surface (in order to thinly control the developer particles in the developing area). It's advantageous.

Furthermore, by imparting such forced movement to the developer, the developer layer becomes more uniform, thereby achieving a thin and uniform layer of toner that could not be achieved with a non-magnetic doctor blade. Moreover, since the gap between the doctor blade and the sleeve can be set wide, there is also the effect of preventing the destruction and aggregation of toner particles. When the toner particles are transferred in the developing area, they are transferred to the electrostatic image side due to the attraction action of the electrostatic image or the action of an alternating current bias. As the toner binder resin used in the developing method of the present invention, various gain resins conventionally known as toner binder resins for electronic photography can be used.

If kept, polystyrene, polystyrene-butadiene copolymer, styrene-based industrial polymers such as styrene-acrylic copolymer, polyethylene, polyethylene-vinyl acetate copolymer,
These include ethylene copolymers such as polyethylene vinyl alcohol copolymers, phenol resins, epoxy resins, allyl phthalate resins, polyamide resins, polyester resins, maleic acid resins, and the like. Furthermore, there are no particular restrictions on the manufacturing method of any of the resins. This is because conventionally, resins produced by emulsion polymerization or the like tend to contain impurities and are difficult to use, but the present invention allows them to be used easily, and the range of resin selection is greatly expanded. This is also a great effect of the present invention.

The magnetic powder to be contained in the toner includes ferromagnetic elements, alloys and compounds containing these, magnemate,
There are conventionally known shimagnetic materials such as hemamate, ferrite, alloys and compounds of iron, cobalt, nickel, and manganese, and nine other ferromagnetic alloys.

The average particle size of the magnetic powder usually used is 0.0.
The thickness is preferably 5 to 5μ, preferably 0.1 to 1μ. This magnetic powder is KIO to 70% by weight in the toner, preferably 15 to 35% by weight.
It is preferable to include it by weight%.

With this content, an appropriate magnetic moment is activated in the above-mentioned developing method, a good image can be created, and the fixing property is also excellent.

As the coloring material used in the toner, conventionally known carbon black, iron black, etc. can be used, and conventionally known positively charged materials such as carbon black and iron black can be used. 1
All dyes as additives can be used in combination with the treated silica fine powder used in the present invention.

Examples are various dyes such as benzyldimethyl-hexadecyl ammonium chloride, dentrotrimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin gamma and crystal violet.

The silica fine powder produced by vaporization of a silicon halogen compound used in the present invention is so-called dry process silica or humidified silica, and is produced by a conventionally known technique. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride scum in an oxyhydrogen flame, and the basic reaction formula is as follows.

S 1clA+ 2 H2+02→SiO2+4HC1
In this production process, for example, by using other metal halogen compounds such as aluminum chloride or titanium chloride together with silicon halogen compounds, it is also possible to obtain composite fine powders of silica and other metal oxides. Also includes. The particle size is o, o as the average primary particle size.
It is desirable that the particle size is within the range of o i to 2μ, and particularly preferably, it is good to use silica fine powder within the range of 0.002 to 0.2μ.

Commercially available silica fine powders produced by vapor phase oxidation of silicon-logen compounds used in the present invention include, for example, those with the following trade names.

AERO8I'L 130 (Japan Aerosil Co., Ltd.) 200 00 80 T600 0X80 0X170 0K84 Ca -0-8iL M -5 (CABO
T Co, Ltd.) Ms-'7M S-75 S-5 H-5 Wacker HDK N 20 V 15 (W
ACKER-CHEIVII E ■ Company) N 20 E
30 40 D -CFine 5ilica (Dow Corning Co., Inc.) Fransol (Fransi 1 Co.) The silica fine powder used in the present invention is obtained by heat-treating these silica fine powders at a temperature of 400°C or higher, but the heat treatment may be performed by, for example, electric The pulverized powder may be placed in a furnace and left at a temperature of 400 DEG C. or higher for an appropriate period of time, for example, 10 minutes to 10 hours. There are no particular restrictions on the heat treatment method, and any method can be applied as long as it does not significantly deteriorate the properties of the developer. Further, the heat treatment temperature is preferably 450°C to 1500°C, and particularly preferably 500°C to 100°C.

Examples of adding these fine silica powders to toner are conventionally known. However, such substances are not necessarily stable in terms of stability, and addition of such silica to toners that require positive charge controllability changes the chargeability, making them unsuitable.

These silica fine powders have the general formula % (R is an alkoxy group or a chlorine atom is an integer of 1 to 3, Y is at least one of an amino group, a vinyl group, a glycidoquine group, a mercapto group, a methacrylic group, a ureido group, or hydrocarbon group containing two or more types, n is an integer of 3 to 1)
Treated with a silane coupling agent shown in
It is hydrophobized to show a value in the range of 80. A developer used in the developing method of the present invention can be obtained by incorporating the treated silica fine powder into a toner.

The following 7-run coupling agents are applicable to the present invention.

As a compound containing a vinyl group FLt　C=　CH8iC4 H2C=CH8i (OC2le).

H2C=CHCHt SiCmulC=CHCruS i (CHs) C4f(,C=
CHCL Si (CH,)2 C1H2C=CHCH
25i (QC2 quick) 3Ht C=CH8i (QC2H
4QCHa )s (Lc=CHC)t SxC'4 (Hz C=CH)t 5i(OC2x)2(H2C=
CH)35iQC,H5 is CL CHCH20CHt CH2CH2S” (OC
Hs ) sCHHz CHCHz QC LeC Quick C Quick 5tC
n.
As those containing a C2 mercapto group, HS C
Ht CH2Cru5i (OCRs)sH8CH,CH
2C Xinsi (QC2I (5)! For those containing methacrylic group, for those containing ureido group, 1 (2NC0NHCH2CH2C mountain 5i (OCtl-1
5) i ゛ is lifted.

The preferred 7-run coupling agent for use in the present invention is a compound containing an amine group and is represented by the following formula Jm.

f(2NCf(tCH2CruSi(OCL)sL
NCf(2CL CHt S: (OCt lis
)s
)3H2NCruCH1NHCH,CH2CruSi (Q
CHs )a しんCH,、C几■C しんCH2NHCHt
CH2CH2Si (QCHs)sH,Ct oc
oc H,CNHCH,CruCH,5t(OCHa
)sLC,0COCH,CH,NHClC:Fii
NHCHt CH,CxinSi (0CHa) 3Hs
C20COCHtCH,NHC几ClNHClClNH
C Ning C XunNH・CH2C几Cru5z(OCru)3 H3C0COCH20Ht NHCH,CK,NHCH
2CK CH2si (001%)sHsN-@-4
(OCi horse).

@-NHOHs C bird OH5 (OOHI) IHllNC
H, OH, NHCH, -@-cz (& SIL (o
cz).

Bird NCH, -@-c Bird C Horse & (OCHs) a) i, N
OH, OH, NHOH, → To C bird C horse 5t (00 horse).

(,Ha C20)3sicHz CH2CH2R3C
NHCH2CL C1(2Si (OC2Hs)sH
2N(CH2CH2NH)2 CH2CH2CH25
Examples include i(OCR,)3Ha CNHC0NHCs H6S (OCR3)3. Further, the alkoxy group of the above compound may be a chlorine atom. These silane coupling agents may be used alone or in a mixed system of two or more.

In addition, in order to perform the hydrophobization treatment so that the degree of hydrophobization required for the silica fine powder used in the present invention, that is, the degree of hydrophobization measured by a methanol titration test is in the range of 30 to 80, conventional methods are required. A known hydrophobization method is used, and the hydrophobicity is imparted by chemical treatment with an organosilicon compound that reacts with or physically adsorbs fine silica powder. A preferred method is to treat fine silica powder produced by vapor phase oxidation of a silicon-based compound with an organosilicon compound after or simultaneously with a silane coupling agent.

Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane.

Dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, penzyldimethylchlorosilane, bromomethyldimethylchlorosilane.

α-Chlorethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganonylmerbutane, trimethylsilylmercaptan, triorganosilylacrylate, vinyl, dimethylacetoxysilane, dimethylethoxysilane.

Dimethyldimethoxysilane, diphenylshedkinsilane, hexamethyldisiloxane, 1゜3-divinyltetramethyldisiloxane, 1゜i'3-diphenyltetramethyldisiloxane, and one molecule containing 2 to 12 siloxane units. There are dimethylpolysiloxanes and the like containing one hydroxyl group bonded to St in each unit located at the end. These may be used alone or in a mixture of 2 m or more.

The preferred weight ratio of the silane coupling agent and the hydrophobizing agent used to treat the silica fine powder is is:ss~8
5:1.5, and by changing this ratio, the triboelectric charge value of the developer containing the silica fine powder can be set to a desired value. This ratio can be arbitrarily selected and varies depending on the type of aminosilane compound and hydrophobizing agent used. The total amount of the 7-rank purin agent and the hydrophobizing agent is 0.1 to 30 wt% based on the silica fine powder.
(more preferably 0.5 to 20 wt%). The final treated silica fine powder can be used in the development method of the present invention if it is hydrophobized to show a value in the range of 30 to 80 as measured by a methanol titration test. A preferred developer is obtained.

The methanol titration test is an experimental test to confirm the degree of hydrophobization of fine silica powder with a hydrophobized gold coating.

“Methanol Titration Test” is defined herein to evaluate the degree of hydrophobization of treated silica fine powder.
is done as follows. 0.2g of sample silica fine powder in a capacity of 2
Add to 50 mA of D water (5.0 m/!) in an Erlenmeyer flask. Titrate methanol from the burette until the entire amount of silica is wetted. At this time, constantly stir the solution in the flask with a magnetic stirrer. The end point is observed when the entire amount of fine silica powder is suspended in the liquid, and the degree of hydrophobization is expressed as the percentage of methanol in the liquid mixture of methanol and water when the end point is reached.

In addition, the effect is exhibited when the amount of these treated silica fine powders is 0.01 to 20% based on the weight of the developer, and particularly preferably when it is added 0.1 to 3%. Shows stable positive chargeability. The preferred form of addition is 0.01 to 3 based on the weight of the developer.
It is preferable that % by weight of the treated silica fine powder be attached to the surface of the toner particles.

In the developing method of the present invention configured in this manner, since the developer used contains the above-described fine silica powder as a charge control component, it is applied to the developer layer supported on the developer carrier. The frictional charge amount is made uniform, and only the excess charge that tends to occur during durability at ultra-low temperature and low humidity is leaked through the silica fine powder to an appropriate saturation value, resulting in the formation of a stable developer layer. At high temperatures and high humidity, it is easy to maintain the amount of triboelectric charge necessary to provide a stable coating state, and no concentration drop occurs.

Another feature is that it is easy to form a stable developer layer, which eliminates development fog and toner scattering around the edges of latent images, which were previously unresolved problems, and high image density can be obtained. ,/・- The reproducibility of the foottone is good.

Furthermore, even when the developer used in the developing method of the present invention is stored at high temperature and high humidity for a long period of time, the amount of triboelectric charge decreases very little and copy quality hardly deteriorates, which is believed to be due to the following reasons. That is, the silica fine powder produced by vapor phase oxidation of a silicon halogen compound has many hydroxyl groups formed on its surface. These are of the following types:

1. The silanol groups on the surface, which are spatially distant from other silanol groups and therefore have no possibility of interaction with each other within their active area and are therefore isolated,
Or it can be called "free 7-ranol group".

2. A silanol group that is itself the same type as 1, but in close enough proximity that it can interact through hydrogen bridges;
Therefore, it can be called a "bonded (hydrogen-bridged) silanol group."

3. Hydroxyl groups of water adsorbed on the surface.

It is thought that this is because the hydroxyl groups on the silica surface undergo condensation among the silanol groups by heat treatment at a temperature of 400° C. or higher, resulting in stabilization of the surface. 40
When heat treated at a temperature below 0°C, adsorbed water is removed during heating and the water content of the silicic acid fine powder decreases, but when the temperature is returned to room temperature, water is absorbed again and the water content becomes the same amount as before the heat treatment.

However, when heat treated at 400°C or higher, the hydroxyl groups on the surface of the silicic acid fine powder particles condense and release water.
Even if the temperature is returned to room temperature, the water content will be significantly lower than before the heat treatment. Although the number of hydroxyl groups is not completely removed, this amount is favorable for subsequent steps and organic treatments.

In the present invention, the heat treatment time varies depending on the treatment temperature, the particle size of the silicic acid fine powder, and other characteristics, but is approximately 1 minute to 10 minutes.
The time range may be determined based on the fact that the amount of moisture absorbed as a result of the heat treatment is approximately 5% by weight or less (particularly preferably 3% by weight or less). The amount of moisture absorbed was determined by heating the heat-treated silicic acid fine powder left on a saturated aqueous solution with a liquid base of sodium thiosulfate for about one week at 20°C, that is, at a humidity of 78%, using a thermobalance at 2°C/
The heating loss curve is measured from room temperature to 400° C. with a temperature increase of 10 minutes, and the amount of decrease is determined as the amount of moisture absorbed.

The basic configuration and features of the present invention have been described above, and the method of the present invention will be specifically explained below based on Examples. However, this does not limit the embodiments of the present invention in any way.

[Example 1] The above materials were thoroughly mixed in a blender and then kneaded with two rolls heated to 150°C. The kneaded product was left to cool naturally and then coarsely ground using a cutter mill to obtain a fine powder of die.

Next, silica fine powder Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) was heat-treated at 800°C for 1 hour, and the resulting silica fine powder was placed in a closed Henschel mixer heated to 70°C, and the silica was subjected to silane coupling. γ-Aminopropyltriethoxysilane diluted with alcohol was added dropwise to the mixture to give a treatment amount of 10% by weight while stirring at high speed. The obtained fine powder was dried at 120° C., then put into the Henschel mixer again, and while stirring, dimethyldichlorosilane was sprayed to the silica at a concentration of 10% by weight. The mixture was stirred at high speed for 2 hours at room temperature, further stirred at 80°C for 24 hours, and then the mixer was opened to atmospheric pressure. The mixture was further dried at low speed at atmospheric pressure at 60° C. for 5 hours. The degree of hydrophobicity was 55.

The treated silica fine powder was added in an amount of 0.6% by weight to the above fine powder and mixed in a Henschel mixer to prepare a developer.

Next, the OPC photoreceptor was subjected to corona discharge of -6 KV to uniformly charge the entire surface, and then an original image was irradiated to form an electrostatic latent image.

The developer carrier was a stainless steel cylindrical sleeve with an outer diameter of 50 mm. The sleeve surface magnetic flux density was 700 Gauss, and the distance between the ear cutting blade and sleeve surface was 02 mm. This sleeve rotation magnet fixation (sleeve peripheral speed is the same as that of the drum, rotation direction is opposite) type developing device was set at a distance between the photosensitive drum surface and the sleeve surface of 0.251 mm, and the sleeve was set at 400 Hz.

An alternating current of 1000V and a direct current bias of -150V were applied.

The powder image was developed using the developer described above, and then the powder image was transferred while irradiating a direct current corona of -7 KV from the back side of the transfer paper to obtain a copy image. For fixing, use a commercially available plain paper copier (product name: N
P-5000, manufactured by Canon). The resulting transferred image had a sufficiently high density of 1.38, had no fogging, and had no toner scattering around the image, resulting in a good image with high resolution. At this time, the weight per unit area of the single layer of toner coated on the sleeve is 1.5
It was 1O-3(f/cx2).

Transfer images were continuously created using the above developer and their durability was examined, but the transferred images after 100,000 copies were also completely dull compared to the initial images.

Next, when the environmental conditions were set to 35°C and 85%, the image density was 1.30, which was almost the same value as normal temperature and humidity, and a clear image was obtained without fogging or scattering, and the durability was 1000 sheets. Until then, there had been no change. At this time, the weight per unit area of one layer of toner is 1.40 x 1O-3
(97cm2).

Next, when a transferred image was obtained at a low temperature and low humidity of 10°, 010%, the image density was as high as 1.31, and solid black was developed and transferred extremely smoothly, and the image was excellent with no scattering or hollow spots. Durability was carried out under these environmental conditions, and the density fluctuation was ±0.1 up to 100,000 copies, which was sufficient for practical use, and no white streaks or unevenness occurred. The change in the weight per unit area of one layer of the toner at this time is shown by A in FIG. 2, and there was almost no change. Furthermore, when it was stored and developed at 35° C. 90% for one month, there was almost no change from before storage.

[Comparative Example 1] A developer was obtained in the same manner as in Example 1, except that Aerosil 200 was not treated with γ-aminopropyltrinitoxysilane and dimethyldichlorosilane, and development and transfer were performed, but an inverted image was obtained. The amount of triboelectric charge was -3,
It exhibited negative chargeability of 2 μc/f.

[Comparative Example 2] A developer was obtained in the same manner as in Example 1, except that the treatment with dimethyldichlorosilane was not performed, and an image was obtained in the same manner.

At room temperature and humidity, there was little fog, but the image density was low at 0.82, line drawings were scattered, and solid black was noticeably rough. Durability was investigated, and the density decreased to 0.61 after 5,000 sheets were printed.

When an image was obtained under the condition of 35°085%, the image density was as low as 0.63, and fogging, cracking, and roughness increased, making it unusable. The transfer efficiency was also as low as 70%. At this time, the weight per unit area of one layer of toner is:
o, 70 x 10-3 sea, ivy.

When an image was obtained under the condition of 10"010%, the density was 0.40 after about 500 sheets, making it unusable. At this time, the initial toner per unit area of one layer The weight was 1.7XIF3y/cm2, and at the time of 500 sheets, it was 3.5x1O-3f/crn2, causing uneven waves.

[Comparative Example 3] Example 1 except that the amount of dimethyldichlorosilane was changed to 0.1% by weight based on the silica.
I did the same thing. The degree of hydrophobicity of the silica at this time was 15. At room temperature and humidity, good images were obtained up to 100,000 sheets, and the toner weight per unit area of the toner layer did not change, but at 35'C! At 85%, the initial image density is 1.2 and at 5000 sheets, it becomes 0.78.
It declined to . The toner layer was 1.4xlO-39/cx2, but when 5000 sheets were produced, it was 0.75 x 10
"-31/G: Decreased to rIL2.

When I stored it for one month under the condition of 10°010% and tested it for durability in a loofah environment, the initial image density was as high as 1.4 and good results were obtained, but after 5000 sheets there was a problem with unevenness. The image density decreased to 0.62, and white streaks appeared on the image after 7,000 sheets were printed. Tona Ichiyori at this time was 4. OX 1O
It had increased to -3f/am2.

The change in toner weight per unit area of one layer of toner at this time is shown by B in FIG.

[Examples 2 to 9] - The heat treatment temperature of Aerosil 200 was set to 430°0, respectively.
, 480°C, 500°0, 600°0, 700°C
1900°C, 1000°C, 1200°0. Good results were obtained when the procedure was carried out in substantially the same manner as in Example 7, except that . The degree of hydrophobicity of silica is 50 respectively.
,50,55,58.70. It was '65. 35℃9
A 0% storage test for 1 month also showed good results.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a developing process applicable to the present invention. Figure 2 shows the temperature at 10% in Example 1 and Comparative Example 3.
FIG. 3 is a diagram showing a change in toner weight per unit area of one layer of toner during durability in an environment of . 1... Electrostatic image holder, 2... Non-magnetic cylinder, 5...
Doctor blade, 6... Insulating developer. A...Results of Example 1, B...Results of Comparative Example 3.

Claims (1)

[Scope of Claims] An electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic developer on its surface are arranged with a certain gap in a developing section, A fine silica powder produced by vapor phase oxidation of a silicon halide compound, wherein the fine silica powder is heat-treated at 400° C. or higher at a temperature of 7:20° C. and then formed into a compound of the general formula 1% (R is an alkoxy group or a chlorine atom). , m is an integer of 1 to 3, Y is a hydrocarbon group containing at least one or more of amine group, vinyl group, glycidoxy group, mercapto group, methacrylic group, and ureido group, n is an integer of 3 to 1 )
Treated with a silane coupling agent shown in
A flat-edge magnetic developer containing fine silica powder that has been hydrophobized so as to exhibit a value in the range of 80 is supported on a developer carrier to a thin thickness across the gap, and the developer is developed. A developing method comprising transferring the electrostatic image to the electrostatic image holder and developing the image in the third step.