JPS649626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single component developer consisting of magnetic toner particles applied from a magnetic brush to a latent latent image without the use of a carrier material.

The majority of electrophotographic reproduction methods used today are
By forming an electrostatic charge pattern on a suitable recording means corresponding to the pattern of the bright and dark image to be copied, and placing the marking substance on the recording means by the force generated by this potential pattern, It consists of developing.

Xerography is the most widely known of these techniques. Even if the substrate is photoconductive, as in the case of selenium, as taught in U.S. Pat. No. 2,297,691, U.S. Pat.
It may be a conventional insulating substrate coated with a photoconductive layer as described in US Pat. No. 3,536,483 and a few other examples.

After forming the electrostatic charge pattern, the potential pattern is developed by conventional means of applying fine developer powder to the electrostatic latent image. In a common technique, a fine insulating powder is cascaded onto a potential pattern support member. In the conventional method, this fine powder is triboelectrically charged to a predetermined polarity and selectively adheres to areas of the surface that have a large amount of charge of the opposite polarity.
Triboelectric charges are generated by providing carrier beads within the powder mixture. This development technique is called a cascade development method.

Another form of development, called magnetic brush development, uses a magnetic carrier or magnetic toner. In this technique, magnetic forces adhere the toner-carrier mixture to the support member and apply it to the image support member. Compared to the cascade development method, the magnetic brush development method is more satisfactory in solid black areas, is easier, and is dependent on the gravity of the carrier to apply toner to the surface and the location of the development station. do not.

Yet another form of electrostatic pattern development involves
As described in U.S. Pat. No. 3,166,432,
Conductive monocomponent toners are used by providing a conductive support member that supports a layer of finely divided conductive toner powder in contact with a charge pattern support member. In this case, the toner is held on a support member by van der Waalska, and a bias is applied to the conductive support member during development. This technique is satisfactory in solid black areas and requires only one component in the developer.

While all of the above techniques have advantages in certain conditions, each also has drawbacks that reduce its usefulness in actual machines.

In conventional cascade development techniques, the toner-carrier mixture has a predetermined charge polarity that cannot be reversed without changing the toner or carrier. In this way, positive images and negative images cannot be easily created. In addition, the image has blank areas, solid black areas are not filled, and the fidelity to the charge pattern of the original image is low. The triboelectric properties of the toner during development are
raises important questions. The non-uniform force between the carrier and the toner causes the toner to have varying threshold levels, causing the toner to be non-uniformly charged and deposited on the background areas. Also, because toner retains its charge for a long time, during the cascade process some toner escapes the development area and enters other parts of the device, causing mechanical problems. These problems, combined with the problems inherent in two-component systems when only a single component is missing, limit the usefulness of this technique.

Magnetic brush developers also use a carrier, so some of the aforementioned drawbacks remain, even though they overcome other drawbacks. As mentioned above, this technique has little effectiveness other than being able to fill solid black areas. However, it still requires triboelectric toners with the attendant problems mentioned above. Also, due to mechanical brushing and other electrical characteristics, this technique has high background area adhesion and low machine latitude.

The method described in U.S. Pat. No. 3,166,432 is
There are many advantages over the cascade technique. However, it has drawbacks that limit its applicability. Van der Waalska, which acts to adhere the toner onto the conductive support member, is a counterforce to the imaging electrical force generated by the electrostatic charge pattern and must be selectively overcome to cause the toner to adhere. Must be. This van der Waalska is weak and not uniform from one toner to adjacent toners. Also, high contrast is difficult to achieve. Since van der Waalska is not directly controlled and is largely dominated by the surface properties of the contained materials, the equipment becomes extremely sensitive to changes in the development characteristics due to deterioration of the surface quality or changes in ambient conditions of temperature and humidity. There is.

In liquid development technology, most of the problems of cascade development systems exist in addition to other problems unique to liquid development systems. This technique requires triboelectric charging, which makes image conversion difficult, as discussed above. Also, as in the case of cascade development, the variation of a given toner is not well controlled, resulting in high background area adhesion, low machine latitude, and large spots characteristic of large dark or gray areas. will occur.
Copying machines also present unique problems with processing fluids, usually solvents.

To date, magnetic development devices that do not use carrier materials have been proposed. One such device is described in US Pat. No. 2,846,333. This specification discloses a magnetic brush development process in which toner particles of ferrite and resinous materials are applied to develop an electrostatic latent image. The difficulty of this method is that
The conductivity of the toner makes electrostatic transfer difficult.

The magnetic development method that does not use a carrier is covered by US Patent No.
No. 3909258, which describes an electrostatic development method using a carrierless magnetic brush. This US Patent No. 3909258
Toners suitable for use in the process described therein are disclosed in US Pat. No. 3,639,245, which discloses dry toner powders having specific electrical conductivity. This toner is formed by blending magnetite with a resin and, after blending, pulverizing it to a small particle size. The particles are then mixed with conductive carbon black embedded in their surface, followed by small particles of SiO ₂ to form the toner and improve its flowability. A disadvantage of this toner is that it is difficult to transfer from a photoconductive substrate to ordinary bond paper.

Accordingly, there remains a need for toners suitable for use in single component magnetic development devices. There is also a need for toners suitable for high speed development equipment that have good electrostatic transfer properties for transfer from photoconductive surfaces to conventional bond paper.

It is an object of the present invention to provide a toner that overcomes the above-mentioned drawbacks.

Another object of the present invention is to provide a sharp, sharp image by developing an electrostatic image with a magnetic brush without a carrier.

It is a further object of the present invention to provide a toner that is electrostatically transferred from a photoreceptor to conventional bond paper.

Another additional object of the present invention is to form a toner suitable for high speed development with a magnetic brush device without the use of a carrier.

Furthermore, it is an object of the present invention to provide a toner whose electrical resistance is dependent on the electric field.

Furthermore, an additional object of the invention is to form an electric field dependent toner by a simple method.

Another object of the present invention is to form a toner that adheres well by electrostatic forces without image disturbance upon processing after transfer to paper and before fusing.

These and other objects of the present invention are comprised of a magnetically attractable material and a resin, the magnetically attractable particles of which are compatible with the resin of the toner and which are located on the magnetite surface. This is accomplished by forming the toner coated with a thin coating material that has a strong affinity for and is also compatible with the solvent used to form the toner.
The toner of the present invention is preferably formed by spray drying from a slurry solution.

In a particular embodiment according to the invention, stearic acid is neutralized with ammonium hydroxide to form a water-soluble ammonium compound. Magnetite pigment is added to the aqueous solution with stirring, so that the ammonium compound adheres to the surface of the pigment. This substance also decomposes upon heating and returns to stearic acid. The material is filtered, washed and dried, then the pigment is dispersed in an aqueous solution of toluene and styrene butylene methacrylate resin and spray dried. The magnetite may be 50 weight percent of the weight of the resin and magnetite dispersion.

The weight of the solvent accounts for 2/3 of the total weight of the spray dried slurry solution. Magnetite coated in other ways is also suitable for the present invention.

Generally speaking, the toner of the present invention has a resistance that is dependent on the electric field strength. It becomes conductive under a high electric field during development, but becomes conductive under a low electric field during transfer.
It has a powder resistance of 10 ⁷ to 10 ¹⁷ ohms/cm. Due to this resistance change that strongly depends on the electric field, toner can be transferred using ordinary electrostatic transfer technology without using specially treated paper, pressure, adhesive, or other special transfer technology. Can be transcribed. Furthermore, toner becomes conductive under high electric fields,
This allows easy development by the dielectric method. The toner of the present invention has a low electric field of about 10 volts/cm (which corresponds to 1 in common logarithm, hereinafter 1logE).
Expressed as volt/cm. ) under about 10 ¹² ohms/
It has a resistance of cm or more. at least 100 volts/
Field strengths below 2 logE volts/cm are preferably held at about 10 ¹² ohms/cm, which provides greater transfer latitude. The preferred initial resistance under no electric field is 10 ¹⁴ ohm cm (corresponding to 14 in common logarithm, hereafter 14 log P ohm cm).
(expressed as cm) or more, and image transfer is good in this range. The toner of the present invention exhibits a nearly constant and stable resistance when the electric field intensity is increased, and with a sharp break point as the boundary, the vertical axis is the common logarithm of the resistance (ohm/cm) and the horizontal axis is the common logarithm of the electric field (volt/cm). When plotted as a graph of logP versus logE, it decreases with a slope of about 5 or more. A preferred slope is 10 or more. A slope of 10 or higher is preferred as it provides excellent electrostatic transfer and good development.

The toner of the present invention and the magnetic pigment contained therein are treated as magnetic substances because they are attracted by a magnet. However, it is not itself a magnet. The toner is held to the magnetic brush roller or belt by magnetic forces. The magnetic brush is biased to induce a charge on the toner particles of a polarity opposite to that of the charge on the photoreceptor. The outer toner adheres to the electrostatic latent image area and develops the electrostatic latent image when its electrostatic force exceeds the magnetic force. U.S. Patent No. 3909258
The number shows the force during the development process using a magnetic brush on a carrier-free developer.

The magnetic pigment used in the toner of the present invention can be any suitable particle that provides the desired magnetic properties. Typical of such materials are ferrites, iron particles and nickel alloys. Preferred for the present invention is magnetite, which is black, inexpensive, and exhibits excellent magnetism. Particle sizes generally range from 0.02 microns to 1 micron. The preferred average particle size of the magnetite particles is about 0.1-0.5 microns. Preferably, the particles are circular or cubic in shape.

The transfer efficiency of the toner of the present invention is about 70% or more, compared to about 85% in ordinary electrostatic transfer.

The coated magnetic pigment should be used in an appropriate amount such that the toner forms a magnetic field dependent toner. It has been found that a suitable range includes about 40 to 70 percent magnetic pigment by weight of the resulting toner. For good development characteristics and good transfer, it is preferred that the coated magnetite be present at about 45 to 55 weight percent.

The material coating the magnetic particles is one that is compatible with the toner resin and that will firmly bond to the magnetic particles during spray drying when mixed with a solvent for the toner resin. Bye. Generally such substances are surfactants. The magnetic particle coating has an affinity for magnetite surfaces such as carboxylic acid groups, sulfate groups, sulfonate groups, phosphate groups, ester groups, alcohol groups, amine groups, amide groups, quaternary ammonia compounds, or mixtures thereof. and long-chain aliphatic components containing 6 to 22 carbon atoms or 6
and other components that exhibit an affinity for solvents and resins, such as aromatics containing ~22 carbon atoms. Preferred are stearic acid and stearic acid derivative materials, which exhibit good dispersion properties and produce the desired toner semiconductivity to aid transfer. Preferably, typical coating amounts range from 0.1 to 10 weight percent. The preferred range of coating material for magnetite is about 1 to 5 weight percent, which provides good insulation under low electric fields.

Any suitable toner resin may be used as long as it is compatible with the magnetite coating.

Any suitable material can be used in the present invention as long as it has the properties described above, but representative resins include polyamide, polyurethane, epoxy resin, vinyl resin, diol consisting of diphenol, dicarboxylic acid, and esterified polymer products. Suitable vinyl resins for use in the toners of the present invention include homopolymers or copolymers of two or more vinyl monomers. Representative examples of such vinyl monomer units include the following. Namely, styrene; p-chlorostyrene; vinylnaphthalene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl Vinyl esters such as butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-
Esters of α-methylene aliphatic monocarboxylic acids such as chloroethyl acrylate, phenyl acrylate, methyl-α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; acrylonitrile such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, etc. , methacrylonitrile,
Ether of acrylamide; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; Vinylidene halides such as vinylidene chloride, vinylidene chloride fluoride; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N - N-vinyl compounds such as vinylpyrrolidene; and mixtures thereof.

It is generally known that toner resins containing relatively high amounts of styrene are preferred because they provide high image formation and density. The styrenic resin used is preferably a styrene homopolymer or styrene homologue or styrene copolymer together with other monomer groups, such as a single methylene group linked to the carbon atom by a double bond. The representative monomer units mentioned above are preferably copolymerized with styrene by addition polymerization.
Styrenic resins may be formed by polymerization of a mixture of two or more unsaturated monomeric materials and styrene monomer. Addition polymerization techniques include well known polymerization techniques such as free radical polymerization processes, anionic, and cationic polymerization processes. These vinyl resins may, if desired, be a mixture of two or more resins, preferably different vinyl resins that ensure good triboelectric properties and uniform resistance to physical degradation. However, non-vinyl thermoplastic resins can also be used, including resin-modified phenol formaldehyde resins, oil-modified epoxy resins, polyurethane resins, polyether resins, and mixtures thereof.

Esterified polymeric products of diols consisting of diphenols and dicarboxylic acids may be used as the preferred resin material for the toner compositions of the present invention.

The diphenol reactant has the general formula:

Here, R represents substituted and unsubstituted alkylene radicals having 1 to 12 carbon atoms, alkylidene radicals having 1 to 12 carbon atoms, and cycloalkylidene radicals having 3 to 12 carbon atoms, and R′ and R″ represents substituted and unsubstituted alkylene radicals with 2 to 12 carbon atoms, alkylenearylene radicals with 8 to 12 carbon atoms and arylene radicals, X and X' are hydrogen or have 1 to 4 carbon atoms represents an alkyl radical, n ₁ and n ₂ are each at least 1, and the average sum of n ₁ and n ₂ is less than 21. R is 2 to 4
an alkylidene radical having a carbon atom,
Diphenols in which R' and R'' are alkylene radicals having 3 to 4 carbon atoms are preferred, as they provide increased blocking resistance and more complete electrophotographic image formation and toner image transfer.
Optimal results are obtained with diols in which R is an isopropylene radical and R' and R'' are selected from the group consisting of propylene and butylene radicals, since the resins formed from these diols This is because it has high resistance to agglomeration and high-speed penetration into the image-receiving sheet during heat fixing.Dicarboxylic acids having 3 to 5 carbon atoms strongly inhibit the formation of a thin film on the image forming surface and prevent copying. Preferred results are obtained due to the narrow image formation during machine operation. Preferred results are obtained by using alpha-unsaturated carboxylic acids, including fumaric acid, maleic acid, or maleic anhydride, since the toner's physical This is because maximum resistance to deterioration and high-speed melting properties can be obtained.An appropriate diphenol can be used as long as it satisfies the above general formula.A typical diphenol is 2,2-
Bis(4-βhydroxyethoxyphenol)propane; 2,2-bis(4-hydroxyisopropoxyphenyl)propane; 2,2-bis(4
-βhydroxyethoxyphenyl)pentane;
2,2-bis(4-βhydroxyethoxyphenyl)-butane; 2,2-bis(4-hydroxy-propoxy-phenyl)-propane; 2,2
-bis(4-hydroxy-propoxy-phenol)propane; 1,1-bis(4-hydroxy-
ethoxy-phenyl)-butane; 1,1-bis(4-hydroxyisopropoxyphenyl)heptane; 2,2-bis(3-meryl-4-β-hydroxyethoxy-phenyl)propane; 1,
1-bis(4-βhydroxyethoxyphenyl)-cyclohexane; 2,2′-bis(4-βhydroxyethoxyphenyl)-norbornane;
2,2'-bis(4-βhydroxyethoxyphenyl)norbornane;2,2-bis(4-βhydroxystyryloxyphenyl)propane; 2
Polyoxyethylene ether of isopropylene diphenol in which one phenolic hydroxyl group is oxyethylated and the average number of oxyethyl groups per mole is 2.6; one mole of oxypropylene group in which two phenolic hydroxyl groups are oxyethylated The average number of hits is 2.5 2
- polyoxypropylene ether of butylidene diphenol; etc. Diphenols in which R is an alkylidene radical with 2 to 4 carbon atoms and R' and R'' are alkylene radicals with 3 to 4 carbon atoms are preferred. This increases the blocking resistance and improves the electrophotographic image. The degree of formation and the transfer of the toner image are more complete.Optimal results are obtained by using diols in which R is isopropylidene and R' and R'' are selected from the group consisting of propylene and butylene. can get. This is because resins formed from these diols have high agglomeration inhibiting power and high-speed penetration into image-receiving sheets during heat fixing.

A suitable dicarboxylic acid can be reacted with a diol such as those described above to form the toner composition of the present invention. This dicarboxylic acid may be substituted or unsubstituted, saturated or unsaturated, and has the general formula: HOOCR _o3 COOH.

where R is a substituted or unsubstituted alkylene radical having 1 to 12 carbon atoms, or 10 to 12
It is an alkylene radical with a carbon atom, n ₃
is less than 2. Typical dicarboxylic acids containing such anhydrides include malonic oxalate, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,
Phthalic acid, mesaconic acid, homophthalic acid, isophthalic acid, terephthalic acid, o-phenyleneacetic acid-β-
Examples include propionic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, phthalic anhydride, traumatic acid, and citraconic acid. Dicarboxylic acids having 3 to 5 carbon atoms are preferred because they strongly inhibit the formation of thin films on the imaging surface and produce narrow images during copier operation. α- containing fumaric acid, maleic acid or maleic anhydride
Favorable results are obtained by using unsaturated dicarboxylic acids. This is because it provides the toner with maximum resistance to physical deterioration and fast melting properties. The esterified polymer product may itself be copolymerized or mixed with one or more thermoplastic resins, preferably aromatic resins, aliphatic resins or mixtures thereof. Representative thermoplastic resins include resin-modified phenol formaldehyde resins, oil-modified epoxy resins, polyurethane resins, cellulose resins, vinyl-based resins, and mixtures thereof. If additive resin is included in the resin component of the toner, it should not exceed about 50 weight percent of the total amount of resin in the toner. It is preferred that the resin component of the toner is a polymerized condensation product of diol and dicarboxylic acid in a relatively high proportion. This is because the fixing temperature can be lowered significantly depending on the amount of additive material. Furthermore, the presence of a high proportion of polymerized condensation products of diols and dicarboxylic acids in the toner provides sharp and dense images. Any suitable mixing technique may be used to add the additive resin to the toner. The resulting resin mixture is almost homogeneous and exhibits high coexistence with pigments and dyes. Colorants may be suitably added before, during, or after the mixing or polymerization step.

styrene-butyl methacrylate copolymer,
Styrene-vinyltoluene copolymers, styrene-acrylate copolymers, polystyrene resins. Image formation can be obtained.

Any method of forming toner particles that provides the desired properties to the toner may be used. Typical of such methods include hot melt formation and mastication followed by grinding the toner particles to the appropriate size. A preferred method of the present invention is to form a solvent in which magnetite and toner resin are dispersed and spray dry the dispersion medium, so that the magnetite is concentrated on the surface of the toner particles, giving the toner good magnetic and electrostatic properties. , which enables wonderful magnetic induction phenomena and electrostatic transfer to plain paper. Although not bound by any particular theory as to why the toner of the present invention exhibits electric field-dependent properties, the properties are to some extent related to the concentration of magnetic particles on the toner surface, and the magnetic pigment coating is believed to be contributed in higher concentrations by spray drying.

The solvent used in spray drying can be any substance that can dissolve the toner resin and magnetite coating without causing them to adhere. Solvents for toner resins include well-known hydrocarbons, alcohols, ketones, esters, amides, fluorinated hydrocarbons, chlorinated hydrocarbons, and other well-known solvents.
Preferred solvents include toluene for use with styrene polymer resins and styrene polymer mixtures, resulting in no solvent in the toner, and which are inexpensive and relatively non-toxic. Chloroform has been found to be a preferred solvent for polyester toner resins because it is easy to use, non-flammable, and only a small amount remains in the toner. Chloroform and toluene are both compatible with the preferred fatty acid and derivative coatings on magnetite. The solvent is generally used in an amount such that the volume of slurry solids is in the range of 5 to 20 weight percent. As used herein, the solids content refers to the solids produced by spray drying and includes resin, magnetite, and other additives such as colorants.

Methods of coating magnetite for use in the present invention are disclosed in US patent applications. Magnetite coated by this method is not sensitive to humidity. This is an advantage in toner formation, which furthermore easily disperses in solvents and resins without affecting the properties of the coating. This method is performed as follows. First, stearic acid fatty acid or its derivatives are neutralized with anhydrous ammonia to produce a water-soluble ammonia compound. The pigment, preferably magnetite, is added to the aqueous solvent by stirring.
The ammonia compound adheres to the pigment surface and is decomposed by heating to return to fatty acids or derivatives thereof. The aqueous solution is filtered, washed and dried. The pigment coated by this method is hydrophobic and also has the property of being well dispersed in organic matrices like polymer resins and organic solvents. Suitable fatty acids and derivatives thereof include myristic acid, pentadecanoic acid, palmitic acid, lauric/margaric acid, oleic acid, linoleic acid and mixtures thereof. In order to obtain good coverage and electrical properties, stearic acid and mixtures thereof, other fatty acids having 14 to 18 carbon atoms are preferred.

Methods for forming toners are disclosed in other US patent applications. This toner forming method is a method of forming a toner by spray drying a dispersion medium of magnetite coated with a fatty acid or a derivative thereof and a resin. A dispersion of magnetite and fatty acids in a solvent is
Stir or heat with reflux and agitation for a period of time prior to polymer addition and spray drying.

In a specific example, 50 parts by weight of magnetite, 2 parts by weight of stearic acid, and 50 parts by weight of toluene are mixed and stirred at reflux for about 1 hour to a temperature of about 110°C.
heated to. After heating, the mixture is mixed with a polymer solution of styrene in toluene. The dispersion medium was spray dried to form a toner. The toner is 10 ⁶ ohm cm to 10 ¹⁷ ohm cm depending on the electric field strength.
It was found that the powder had a powder resistance of cm.

The time for stirring or heating and stirring the magnetite and fatty acid or its derivative in the solution may be set to a length such that the toner has a desired electric field dependence after spray drying. Generally, this heating is carried out with reflux for about 30 minutes to 3 hours. The preferred heating time is about 1 hour with reflux, which allows a toner with the desired field dependence to be produced without requiring a very long time. The reflux heating temperature is selected depending on the volatility of the solvent used. Heating temperatures of about 100°C to 150°C have been found to be typical for standard solvents.

Other methods of coating stearic acid or its derivatives on magnetite can also be used. Among these methods, there is a method of coating the magnetite particles directly, preferably by rolling with a fatty acid material under low heat. Another coating method involves coating magnetite with ammonium stearate or other fatty acid ammonium salts and heating the coated particles to restore the fatty acids coating the particles.

Although the above description does not mention adding additives to the solvent prior to spray drying, pigments, humidity control substances, dyes, etc. may be added prior to toner formation in the present invention. The preferred magnetite material is black and is suitable for most electrophotographic reproduction applications without the need for color additives. however,
Other less dark colored magnetic materials may require pigment or dye additives to obtain the appropriate toner color. Such pigments or dyes themselves are not required to be electrically sensitive.

Additionally, post-treatments such as classification may be required depending on the particle size obtained by spray drying.

The method for forming the toner of the present invention used for electrophotography will be described below. Percentages are by weight unless otherwise stated.

EXAMPLE 100 g of styrene-butyl methacrylate resin (ratio 65/35) are dissolved in 500 g of toluene. After dissolving the resin with toluene, it is added to a Kady mill containing 100 g of Pfizer MO4431 coated magnetite and milled for 30 minutes.
Magnetite coated with Faiza has a length of about 0.1 micron to 1 micron and a diameter of about 0.02 micron to 1 micron.
It consists of 0.2 micron needle-like particles. The particles are coated with a stearic acid coating consisting of a mixture of fatty acids and calcium salts. Calcium salts are hydrophilic substances that are slightly moisture sensitive. After finely pulverizing, the dispersion was heated to a temperature of 83.2℃ (180〓).
to 104.4°C (220°C) at a rate of 200ml/min to a Bowen spray dryer. Toner particles having an average size of 15 microns and ranging from 5 microns to 30 microns are collected. These toners can be developed at high speeds using carrierless magnetic devices and are successfully transferred by electrostatic transfer at low humidity with transfer efficiencies of about 75 percent. However, this toner is somewhat moisture sensitive, with approximately 5% humidity at 86% humidity.
has a slope of The field resistivity of this toner at 17% relative humidity is shown in FIG.

Example: 96 g of Piccolastic D-125, a polystyrene polymer, instead of the polymer.
The method of the example is repeated except that 104 g of the coated magnetite is used. This toner exhibits excellent transfer properties. This property is the same as the example except that it is more moisture sensitive.

EXAMPLE The method of the example is repeated except that chloroform is used instead of toluene and 100 g of polyester resin is used instead of the resin of the example.
This toner also exhibits good electrical properties and transfers well. Its characteristics are the same as the toner of the example.

EXAMPLE The method of the example is repeated except that 120 g of coated magnetite and 80 g of resin are used. The toner of this example also exhibits excellent transfer properties and good development properties. This characteristic is the same as the toner of the example.

EXAMPLE The method of the example is repeated except that 130 g of coated magnetite and 70 g of resin are used. This toner also exhibits good transfer and development properties. This characteristic is the same as the toner of the example.

EXAMPLE The toner of Example A described in US Pat. No. 3,639,245 is formed as a control agent. When utilized in an electrostatic transfer device, this toner has approximately 30%
When a percentage is transferred, it is not transferred efficiently.

Example: 96g of Picocolastic D-125, a polystyrene polymer, was used instead of the polymer, and Cities Service Mapicoblack, a magnetite coated with stearic acid, was used instead of magnetite.
The method of Example 1 is repeated, except that 104 g of Mapico Service is used. Mapikobrak magnetite is composed of three-dimensional lattice particles of about 0.02 microns to about 0.8 microns. This toner exhibits excellent development and transfer properties.

Example The previous example is repeated, except using 70 g of resin and 130 g of coated magnetite. This toner also has excellent development and transfer properties.

Example 100 g of a dispersion of Phizer magnetite MO-4232,
The uncoated magnetite, about 4 g of stearic acid, and about 100 g of toluene are mixed and heated to about 100° C. for 1 hour at reflux with gentle stirring. This heating is performed using a three neck flask. After heating, the mixture is combined with a polymer solution containing about 96 g of polystyrene resin (Picocolastic D-125) in about 1000 g of toluene. Next, average this dispersion to
Spray dry to 12 micron size particles. As a result, the resulting toner has excellent electric field properties. As shown in FIG. 2, the initial resistivity is greater than 14 ohm-cm, and the resistivity drops rapidly at a certain point. This toner is
Moreover, as shown in FIG. 2, it exhibits almost no moisture sensitivity. This toner can be developed at high speed using a carrierless magnetic device and was found to be transferred by electrostatic transfer with a transfer efficiency of 75 percent.

Example Instead of the polystyrene resin of the example, 98 g of styrene-butyl methacrylate resin (ratio 35/
The toner is formed as described in the Examples except using 65). This toner has excellent transfer properties and particularly desirable electric field dependent properties.

This toner resistivity is given by line 2 in FIG.

Example XI The procedure of the example is repeated except that about 2 g of stearic acid and 98 g of the styrene-butyl methacrylate (ratio 65/35) of the example are used. This toner has also been found to have desirable field dependent properties. The resistivity of this toner is illustrated by line 1 in FIG. 3 of the drawings.

Example XII The procedure of the example is repeated except that about 6 g of stearic acid and 94 g of the styrene-butyl methacrylate resin of the example (65/35 ratio) are used. This toner also has desirable resistivity characteristics, illustrated by line 3 in FIG. 3 of the drawings.

Example: Approximately 104 g of magnetite MO-4232 as a control agent.
When a toner is formed by spray drying a slurry of 48 percent Picolastic D- ¹²⁵ and about 400 grams of toluene and tested over the same range as illustrated in FIG. cm and
It varies only between 10 ^{and 17} ohm cm. In comparison, the low electrical conductivity of the toner of the present invention ranges from 10 to about ¹⁴ ohm cm at low electric fields of about 40 volts/cm.
Approximately 10 ⁸ ohm cm in an electric field of 8000 volts/cm
changes up to.

The toner resistivity measurement method used in this case is as follows:
It is determined by the following method. Measurements on powders are complex because the results are influenced by the powder compounds as well as the shape and size characteristics of the powder particles. Therefore, in order to relate the properties to toner behavior during development, measurements were made by forming pellets into test specimens. Measurement diameter 5.08 to measure the DC resistance of toner
A Bulsbaugh cell with 2 inch (cm) electrodes was used. The spacing between the electrodes is 1.27 mm (0.05 inch). This toner is packed between the two electrodes of the battery by vibrating it until it reaches a certain level. 1.27mm above
The current is measured as a function of the applied voltage between two electrodes with a spacing of . Charging time is 1 minute as recommended by ASTM regulations. After each measurement the specimen is repacked by vibration. The resistance is calculated according to Ohm's law, and the data in the drawings are shown as the logarithm of the resistance value versus the logarithm of the electric field strength.

Transfer efficiency in this case is measured by comparing the weight of toner transferred to the paper to the weight of residual toner that is removed by adding adhesive tape to the photoreceptor after transfer is complete.

Although specific materials and conditions have been described in the foregoing examples of toner formation methods and methods of use of the present invention, these are intended solely to illustrate the present invention. Various other substitutes and methods, such as those described above, may be used in place of the methods of the above examples to achieve the same results. In addition to the methods used for the toners of the present invention, other methods and variations may be used. For example, toner may be sorted before it is used for development and transfer. Additionally, other substances such as colorants may be added.

After reading this specification, one skilled in the art will be able to make other variations of the invention. These would be included within the scope of this invention. For example, the present invention can be used in a conventional magnetic development apparatus for zinc oxide paper without transfer. Additionally, the toners of the present invention can be used in processes that require the development of magnetic images rather than electrostatic latent images.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram of resistivity versus electric field intensity of the toner of the present invention. FIG. 2 is a characteristic diagram of resistivity versus electric field strength of the moisture-insensitive toner of the present invention. FIG. 3 shows the effect of varying the amount of magnetite coating agent in the toner of the present invention.

Claims (1)

[Claims] 1 toner particles, the toner particles comprising a resin and a magnetic material coated with a surfactant, the surfactant being present in an amount of about 0.1 to 10 weight percent of the magnetic material, and the magnetic material disposed inside the toner particle. For electric field-dependent single-component developers that exist in higher concentrations near the surface of toner particles,
In low electric fields less than cm, the resistivity is greater than 10 ¹² ohm cm, but in electric fields greater than 100 volts/cm, the resistivity is less than 10 ¹² ohm cm; A developer characterized in that, when plotting the logarithmic value of powder resistance, resistivity is shown along a line with a slope of 5 or more.