JP2962040B2 - Method for developing one-component insulating magnetic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for developing an electrostatic latent image by an electrophotographic method, an electrostatic recording method or the like using an insulating magnetic one-component toner.

[0002]

2. Description of the Related Art In recent years, dry-type electrophotographic developers widely used not only in copiers but also in printers, facsimiles, and the like are mainly of the dry type in terms of ease of handling. Dry developers include two-component developers that use a mixture of carrier particles and toner particles, and one-component developers that do not require a carrier. A developing method using a two-component developer (hereinafter referred to as a two-component developer)
The component developing method is currently the most proven and widely used, and has relatively good image quality, but has the following disadvantages.

(1) The developer consumes only toner during development, so that a toner replenishing means and an adjusting mechanism for keeping the toner concentration constant are required, and the machine becomes large and complicated. (2) In order to frictionally charge the toner and the carrier, the developer must be sufficiently and quickly stirred, requiring a large amount of power and increasing the size of the developing device. (3) The life of the developer is short due to contamination of the carrier surface by the toner and the like. (4) Due to the problem described in (3) above, the developer needs to be replaced from time to time, the inside of the machine tends to be dirty due to toner scattering due to a decrease in the toner charge amount, and sometimes the machine needs to be cleaned extensively. Maintenance by persons with specialized knowledge is indispensable. (5) The frictional charging property of the toner is easily affected by the environmental humidity, and the problem of fogging and a decrease in image density is likely to occur.

However, in recent years, electrophotographic copying machines,
As printers and facsimile machines are rapidly becoming smaller and more personalized, they are small, simple and do not require the above-mentioned maintenance, and are stable in any use environment, especially under high temperature and high humidity. It has become increasingly important to establish a one-component developing method for obtaining images. Further, when a two-component developing method is used for a large-sized machine or a high-speed machine, the developing mechanism becomes more complicated and larger, and
Developer replacement work during maintenance becomes very difficult,
The increase in downtime associated with this has been a major obstacle in use, and there is a growing demand for these improvements.

The one-component toner containing no carrier particles includes a magnetic one-component toner containing a magnetic powder therein and developed by a magnetic brush developing method, and a non-magnetic one-component toner containing no magnetic powder therein. The non-magnetic one-component toner has a feature that a vivid color toner is possible, and various developing methods have already been proposed. However, despite the one-component developing method, a stable toner charge amount and image quality are always maintained. Is difficult to maintain, and the lives of the toner and the developing device are short.

On the other hand, magnetic one-component toners are also relatively widely used because high quality images can be obtained by a conventional magnetic brush developing method. At first, a conductive magnetic toner as disclosed in U.S. Pat. Nos. 3,639,245 and 3,909,258 was used as the magnetic one-component toner. Unlike the insulating toner, the developing using the conductive toner is performed by using the charge induced by the electric field from the electrostatic induction action, and thus has the following advantages as compared with the insulating toner.

(1) Since the electrostatic charge due to the triboelectric charge is not used, the influence of the image deterioration due to the humidity can be eliminated. (2) When selecting a resin, a pigment, an additive, and the like, which are constituent components of the toner, it is not necessary to consider the charging polarity, so that the range of selection is wide. (3) Since uniform charge can be applied to the toner, an image with less background smear and excellent resolution can be obtained. (4) One-component development without difficulty becomes possible. (5) Since the frictional charging mechanism is unnecessary, the structure of the developing device is simplified, and the size can be reduced. (6) Both normal development and reverse development can be performed with the same toner.

[0008] Despite the many advantages described above,
The conductive toner is applied to plain paper by a plain paper transfer method using electrostatic force, that is, a conductive or dielectric roller to which a corona discharge or bias is applied, which is widely used in a process using an insulating toner. Due to the biggest drawback that good transfer is difficult, plain paper copiers (PP
C), facsimile is impossible, and at present, it is hardly used except for those using a large-size and low-efficiency adhesive transfer method.

The reason why the transferability of the conductive toner deteriorates in the plain paper transfer system using electrostatic force is presumed to be as follows. That is, in principle, the conductive toner performs development and transfer using electrostatic induction charges generated by an electric field. For this reason, it is considered that, particularly under high humidity, the electric resistance value decreases due to the transfer paper absorbing moisture, and as a result, the injected electric charge leaks through the paper, so that an effective electric field does not work on the conductive toner and transfer is not performed. . Therefore, in order to prevent this phenomenon, electrostatic recording paper which has been subjected to insulation treatment has been used conventionally, but the paper becomes thick and expensive.

Therefore, in order to enable PPC, an attempt has been made to improve the transferability by increasing the electric resistance of the toner as disclosed in, for example, Japanese Patent Application Laid-Open No. 50-92137. However, as the electric resistance of the toner increases, the polarization mainly due to the electrostatic induction or dielectric polarization of the toner becomes insufficient and the developability deteriorates, and especially when it exceeds 10 @ 12 .OMEGA.cm, it is not practical at all. Therefore, the magnetic one-component developing method is
In order to make this possible, the following measures were considered.

(1) Developing with a conductive toner having relatively high resistance as described in, for example, JP-A-53-39752 and JP-A-53-131044, and transferring by devising transfer paper. Improve the problem. (2) Use a toner exceeding 10 ¹² Ωcm (hereinafter referred to as an insulating toner) to improve its developability.

As for the above-mentioned method (1), sufficient results have not yet been obtained, but some useful methods have been found in (2). Here, the insulating toner needs to be further classified according to its charging mechanism.

Although many documents have been reported on the charging mechanism of the insulating magnetic one-component toner, they are roughly classified into a method that does not use frictional charging and a method that uses frictional charging. However, at present, the development mechanism utilizing triboelectric charging is mostly adopted because the development mechanism is well understood. Examples of the developing method utilizing such triboelectric charging include a developing method called "BMT developing method" disclosed in Japanese Patent Publication No. 59-44627 and Japanese Patent Application Laid-Open No. 55-1.
Japanese Patent Application Laid-Open No. 57-114 discloses a developing method called "magnetic jumping developing method" as disclosed in JP-A-8656.
No. 163, etc., "FEED development method" and the like. These developing methods actually provide a compact, simple and maintenance-free developing device which is an advantage of the above-described one-component developing method. However, since these use frictional charging for development, the charge amount of the toner becomes insufficient particularly under high humidity, and the charge amount tends to be high under low humidity, and a stable image is always obtained regardless of the use environment. Is still not enough for that purpose.

Therefore, in order to simultaneously achieve the object of always obtaining a stable image regardless of the use environment,
It is absolutely necessary to put into practical use an insulative magnetic one-component developing method utilizing charge by charge injection or electrostatic induction or dielectric polarization, in which the charging mechanism is not affected by the use environment in principle. U.S. Pat. No. 3,645,770, Japanese Unexamined Patent Publication No. Sho 50-1 can also use a method of applying a charge other than charge injection or electrostatic induction without using frictional charging.
Although it is disclosed in, for example, Japanese Patent No. 17432, it is not yet sufficient mainly in terms of stability.

An example of the insulating magnetic one-component developing method utilizing charge injection is a developing method disclosed in US Pat. No. 4,121,931. For the development mechanism of this development method, see Field, "A MODEL TO DESCRIBE ERECTROGRAPHI
C DEVELOPMENT OF RESISTIVEONE-COMPONENT TONER SYST
EMS ", IEEE / IAS Conference Records p.973, which is an excellent one-component developing method that is less susceptible to the environment because it does not use triboelectric charging for toner charging. The law still has the following problems:

(1) In an electric field created by an electrostatic latent image on a photoreceptor, the toner is brought into electrical contact with a toner carrier (mainly a magnetic sleeve) having a conductive portion (electrode). Charge is injected from the substrate and is forcibly charged. At this time, adding a power supply to the electrodes is almost a necessary requirement for enhancing the effect, but as a result, the mechanism becomes complicated. In addition, the application of a voltage for injecting a charge having a polarity opposite to that of the photoreceptor has an effect of a reverse bias at the time of development, which causes fogging. Also,
According to the methods described in this publication and the literature, when actually examined, the developability greatly changes depending on the type of the photoconductor, the type of the toner, the magnetic force of the magnetic sleeve, and the like. Because of this factor, a practical one-component magnetic toner developing method cannot be obtained from this method alone.

(2) The toner particles into which electric charges have been injected from the magnetic sleeve must move quickly to the upper layer of the toner layer to develop the electrostatic image. Therefore, high-speed and intense physical disturbance of the toner layer is required, and the mechanism of the developing device is complicated. Further considering the principle of development, this method addresses the poor developability of the insulating toner as described above by increasing the toner moving speed to transport the toner to the electrostatic image at a high speed of 10 cm / sec or more. However, the high-speed contact between the electrostatic image and the toner, on the contrary, promotes the cleaning effect of the photoreceptor by the toner magnetic brush on the magnetic sleeve and lowers the developing efficiency. Further, since a shearing force is applied to the toner due to strong stirring as described above, problems such as accelerated deterioration of the toner also occur. As a method for solving such a problem related to the rotation of the magnetic sleeve, for example, Japanese Unexamined Patent Application Publication No.
Japanese Patent Application Laid-Open No. 55-126266 discloses a method in which only the sleeve is rotated to limit the speed difference between the sleeve and the photoreceptor to a predetermined range. A method of setting the speed, direction, and number of magnetic poles to predetermined values is disclosed.
Although these measures are intended to improve various problems relating to the rotation of the magnetic sleeve, when actually examined, the developability also greatly changes depending on the type of the photoreceptor, the type of the toner, and the like. Since the selection is a very large factor, it is not possible to obtain a practically stable magnetic one-component toner developing method only by this method.

On the other hand, an insulative magnetic one-component developing system utilizing an electrostatic induction effect is disclosed in, for example, JP-A-54-1346.
There is a method disclosed in Japanese Patent Publication No. 40-240. In this development method, toner having a surface in which charge-movable regions such as carbon black are mainly scattered in an insulating main region is used, and an insulating toner carrier constituting a developing unit is used. And the toner is set to a charged state that can be developed by the latent image charges in the image area. The developing mechanism is described in more detail below. Using magnetic toner particles in which conductors such as carbon are dispersed,
Considering two toner particles in which the exposed carbon portions are in contact with each other, positive and negative charges are induced in the carbon portions of the respective toners by electrostatic induction through the contact points.
The toner particles in a charged state that can contribute to development develop the latent image when they come into contact with the latent image. That the toner charge is not due to charge injection (from the sleeve)
It is clear from the fact that an insulating material is used in the developing section as the toner carrier. However, this developing method has the following problems.

Considering the easiness of the electrostatic induction, it is desirable that the above-mentioned charge-transferable region has a low electric resistance such as carbon black. However, when the resistance becomes low, polarization is likely to occur, but at the same time, the charge neutralization rate when the toner particles separate again increases, and this publication does not consider this point. High developability cannot be obtained.

Thus, in the various developing systems which have been proposed as described above, there has been much discussion about which mechanism, such as triboelectric charging, charge injection, or electrostatic induction, is dominant. The general view is that all effects exist, albeit in greater or lesser magnitude, and that no single mechanism works. It is clear that even if an insulative toner is used in the developing section as the toner carrier, good charge development is possible without any charge injection from the sleeve. The toner carrier is desirably conductive from the viewpoint of reducing the moving speed of the carrier (sleeve, internal magnet) and improving the image quality.

As a method utilizing electrostatic induction (polarization), there is another method disclosed in, for example, JP-A-58-186765. This is described in Japanese Patent Application Laid-Open No. 54-13 / 1979.
Since the discussion is based only on the resistance value of the toner particles and not on the microscopic consideration as in JP-A-4640, the developability is not sufficient, and the photoconductors that can be used are limited.

Japanese Unexamined Patent Publication No. 57-58162 discloses a charge control method such that the surface potential of a toner layer when a magnetic toner carrier and / or a magnet roll is rotated has the same polarity as an electrostatic image. A high-resistance magnetic one-component toner is disclosed. Among them, the added charge control agent has an effect of facilitating the charge injection by the charge injection or the electrostatic induction from the conductive toner carrier or the like, in addition to the control of the frictional charge performance, which is the intended purpose. Although there is a description suggesting the existence of, there is no description of a specific method or the like.

In order to obtain a good image by the insulative magnetic one-component development, it is very important to select the type of toner to be used in addition to the mechanical and electrical problems of the developing mechanism. Regarding the physical properties of the toner, see, for example, JP-A-54-365.
In Japanese Patent Application Laid-Open No. 54-139545, there is disclosed a method in which not only the electrical resistance value of the toner but also the relative dielectric constant is taken into consideration and the developability and the transfer property are compatible by setting the value within an appropriate range. A method is disclosed in which the electrical resistance of the toner is changed within a specific range by a voltage, and the developability and the transfer rate are improved by setting the dielectric constant to a specific value.
In many other patent publications, attempts have been made to improve the above-mentioned problem by specifying the physical properties of the toner. However, in practice, even if the physical properties of the toner are the same, there are many differences in the developing property and the transfer rate, Unless the physical properties of the individual materials are selected, a practical magnetic one-component toner developing method cannot be obtained. Further, during a long-term printing test in an actual machine, the cause is not fixed, but as a phenomenon, a change in toner charge amount causes a large change in image density and, as a result, a problem of aggregation. This phenomenon is also described in the above-mentioned Japanese Patent Application Laid-Open No. 54-134640. In this case, in order to prevent accumulation of toner particles having opposite polarity charges, it is necessary to provide a reverse polarity charge removing means. It is necessary. This phenomenon may be caused by a specific toner composition except that a second electric means for forcibly adding or removing charge to the toner is provided, as disclosed in, for example, JP-A-56-130664. Cannot be prevented.

[0024]

From the above discussion, the inventors of the present invention have found that a development system that does not use triboelectric charging is most advantageous for the development of an insulating magnetic one-component toner. Has come to the conclusion that the problem can be solved. However, as described above, there have been various problems in the conventional developing method utilizing charge by charge injection or electrostatic induction. Therefore, as a result of intensive studies, the present inventors have found that, when the toner composition used in a specific developing device satisfies a specific requirement, the toner is charged mainly by electrostatic induction and a good electrostatic latent image is obtained. The image was found to develop.

[0025]

That is, the present invention comprises at least a resin, a magnetic powder, a colorant and a charge stabilizer, wherein the resin has a volume resistivity of about 1 × 10 ¹⁴ Ωcm or more. Is about 1 × 10 ⁴ to 1 × 10 ¹² Ωcm
Wherein the magnetic powder and the coloring agent have a volume resistivity of about 1 ×.
10 ⁴ to 1 × 10 ¹² Ωcm and a volume resistivity of about 1
0 ⁴ [Omega] cm the magnetic one-component toner which is substantially free of the following materials, using a magnetic held to at least the developing field surface conductive toner carrier is, electrostatic formed electrostatic image bearing member A latent image is visualized by bringing said magnetic one-component toner into contact with a latent image and mainly charging by electrostatic induction or dielectric polarization by an electric field of said electrostatic latent image; It relates to a developing method.

The present invention will be described more specifically. The volume resistivity of the toner and the toner composition used in the present invention is measured as follows. A commercially available tableting device for infrared absorption spectrum measurement (a circle with a molding inner cross section of 20 mm)
About 0.8 g of the toner left for 24 hours in a thermo-hygrostat at 50 ° C. and 50% RH was put into a constant pressure / humidity bath at 400 kg / cm ² using a hydraulic press.
To produce a cylindrical pellet having a thickness of about 2 mm and a circular shape with both end faces having a diameter of 20 mm. A main electrode having a diameter of 10 mm is applied in close contact with the center of both circular end faces of the pellet by applying a silver paste, and one end is grounded. next,
A guard electrode with one end grounded is provided along the outer periphery of the pellet, a DC voltage is applied to the main electrode, the current flowing between the main electrodes is read directly by an ammeter, and the volume specific resistance value is calculated from the current value at a stable stage. Is calculated.

The one-component insulating magnetic toner used in the present invention is required to have a predetermined specific volume resistance value of the composition. The method for producing the insulating magnetic one-component toner used in the present invention includes a binder component containing a thermoplastic resin as a main component, a magnetic powder, a colorant, a charge stabilizer, and other components that are added as necessary. After hot-melt kneading using a kneader such as an axial extrusion kneader, a two-roll mill, and a pressure kneader, the mixture is cooled, solidified, and finely pulverized using a pulverizer such as a jet mill. It is common to adjust to. In recent years, various methods for directly producing toner particles by a suspension polymerization method, an emulsion polymerization method, and the like have been proposed, and toners produced by these methods can also be used. The toner needs to have a volume-based average particle size of 5 to 15 μm. If the upper limit is exceeded, the roughness of the image becomes remarkable.
The developing method is not preferable because the replenishability due to the fluidity of the toner deteriorates remarkably.

The thermoplastic resin may be any of those usually used for toners, such as polystyrene, copolymers containing styrene with acrylate or methacrylate, acrylonitrile or maleate, Examples include polyacrylate, polymethacrylate, polyester, polyamide, epoxy, phenol, hydrocarbon, and petroleum resins.

Known magnetic powders such as various ferrites, magnetites and hematites can be used, and various shapes such as cubic, octahedral, spherical, and acicular can be used. In this case, the particle diameter is desirably 1 μm or less from the problems of uneven distribution of the amount of magnetic powder between toner particles and generation of free magnetic powder. In terms of magnetic properties, the saturation magnetization is not particularly limited as long as it is about 50 emu / g or more, but the coercive force is desirably 200 Oe or less mainly due to the problem of the mobility of the toner particles on the toner carrier. More preferably, it is 120 Oe or less and 40 Oe or more. There is no problem if magnetic powder is used as it is,
When used after being subjected to surface treatment with a fatty acid, a silane coupling agent, or the like, if necessary, by improving the wettability to the resin when hot melt kneading the thermoplastic resin and coating the magnetic powder itself, Exposure of the magnetic powder to the toner surface can be prevented. As a result, environmental resistance, image quality, and the like may be improved due to the effect of preventing frictional electrification between toners.

Regarding the amount of magnetic powder to be added, a necessary amount is added depending on the strength of the magnetic field on the toner carrier in order to impart a magnetic force for holding the toner particles on the toner carrier. From the relationship between the binding force on the toner and the attractive force on the electrostatic latent image, the amount is preferably 20 to 60% by weight based on the toner.

As the charge stabilizer, a specific charge stabilizer is used from various charge control agents which have been used in various developing methods using ordinary triboelectric charging. More specifically, an excellent effect has been recognized on a substance having a predetermined volume specific resistance, which is capable of frictionally charging a thermoplastic resin in a polarity opposite to that of an electrostatic latent image on an electrostatic image carrier. The polarity of the electrostatic latent image is opposite to that of the potential when uniformly charging the surface of the photoreceptor during regular development, and the unexposed portion becomes the ground potential due to the bias voltage during reversal development. It has the same polarity as the potential when the body surface is uniformly charged.

The charge stabilizer used in the present invention includes those known per se. However, the charge stabilizer is basically not provided with triboelectricity as in the prior art, but is obtained by adding the charge in an insulating binder component. Stabilizer generates charge by electrostatic induction or dielectric polarization, has the effect of retaining the generated charge and the effect of preventing the same polarity charge as the latent image charge from accumulating in the toner during actual development running In this respect, it has an effect completely different from the conventional one. That is, the triboelectrification property of the conventional charge control agent itself has a secondary relationship with the developability of the present invention, and the charge stabilizer of the present invention mainly has a problem with its resistance. The property that the thermoplastic resin can be frictionally charged to the opposite polarity to the electrostatic latent image on the electrostatic image carrier has a correlation with the retention of the resulting charge. Unreported so far. As has already been verified in many documents, the effects of friction, charge injection, and electrostatic induction are rarely independent of each other in the development of the insulating one-component development method, and the effects of each are small at the same time. Exist. However, at least, it can be said that this toner and this developing method facilitated application of electric charge and stabilization of environment and printing durability as compared with any conventional magnetic one-component developing method.

The effect of the charge stabilizer will be described in more detail. FIG. 1 is a conceptual diagram of a toner charging mechanism in the developing method according to the present invention. The toner 3 held by the magnet 2 on the toner carrier 1 forms a magnetic brush and is in contact with the electrostatic image carrier 4. Basically, whether the surface of the toner carrier is conductive or insulative, the electrostatic latent image on the electrostatic image carrier can be developed. However, the conductive property improves the developability. Next, toner particles 3 close to the electrostatic image carrier
Let us focus on a and 3b. The following two mechanisms are considered for the toner particles to acquire a charge that can contribute to development. One is as shown in FIG. 1 (a), where an electric field generated between the electrostatic latent image 5 and the toner present in the vicinity thereof causes the electrostatic latent image 5 to contact or contact the latent image due to the action of the charge stabilizer dispersed in the binder resin. Electrostatic induction or dielectric polarization occurs between the adjacent toner particles, and the toner particles 3a close to the electrostatic latent image have charges of the opposite polarity to the electrostatic latent image, and are developed by the Coulomb force with the electrostatic latent image. Here, an important function of the charge stabilizer is a property of retaining a charge having a polarity contributing to development and not retaining a charge having the same polarity as a latent image generated by polarization. Of course, if the resistance value is within the predetermined range, the magnetic powder has the same effect. Alternatively, the same applies to the contact between the magnetic powder and the charge stabilizer. However, for this reason, it is assumed that the same polarity charge of the toner particles 3b is lost due to dissipation into the air or contact with the toner carrier or other developing device surface. Therefore, as another mechanism, as shown in FIG. 1 (b), it is also conceivable that a charge having the same polarity as the latent image generated by the polarization of a single particle is scattered from the toner surface and consequently obtains a charge that contributes to development. Further, such polarization does not occur only between the uppermost two particles in the toner layer, but also transfers the electric charge to the third and lower layers from the top as shown in FIG. It seems to be. The actual charge transfer in a system in which a pigment or the like is dispersed in an insulating binder resin is determined by the PIP method (Persistent Internal Polarization).
ization), Photographic Science & Engineer 6 # 2 p-65
, 70, '62, Kallmann & Rennert, and an electron avalanche phenomenon with a single-layer phthalocyanine photoreceptor (see JP-A-2-302759). It is considered that charge injection from the electrostatic image carrier to the toner particles did not occur. This is because in this case, the same polarity charge as that of the electrostatic latent image is injected into the toner.

Of course, as already mentioned, the effect of the triboelectric charging of the charge stabilizer on the release of charges of the same polarity cannot be denied. However, even if the effects on the triboelectrification are almost the same, there is a case where the above-mentioned same-polarity charge releasing effects are greatly different and the development properties are different, so it is certain that the development mechanism of FIG. 1 is dominant. It is considered that the electrostatic induction or the dielectric polarization does not occur only in the charge stabilizer but also in the contact between the exposed magnetic powders or the contact between the magnetic powder and the charge stabilizer. However, in any case, since the magnetic powder does not have the ability to selectively retain the specific polarity of the polarized charge, the charge stabilizer is still an essential component.

Since the toner used in the developing method according to the present invention utilizes charges induced by electrostatic induction in the initial image, an electrostatic latent image of either polarity is good regardless of whether the polarity is positive or negative. Develop. However, when a charge stabilizer having a triboelectric charge property with respect to the binder resin having the same polarity as that of the electrostatic latent image is used, charges having the same polarity as the latent image accumulate in the toner layer as the image is developed as described above. The concentration decreases. In such a case, the triboelectricity of the binder resin is positive and negative by using both positive and negative.
It is possible to stably develop an electrostatic latent image of either negative polarity.

The charge stabilizer that can contribute to such a charging mechanism has a particle diameter that does not separate from toner particles when melt-kneaded and dispersed in a toner, then pulverized and classified.
A material having a volume resistivity of about 10 ⁴ to 10 ¹² Ωcm and a property of being capable of frictionally charging a thermoplastic resin in the opposite polarity to the electrostatic latent image on the electrostatic image carrier is effective. Almost all of the toners used as charge control agents for the toner can be used. Examples of such substances include nigrosine-based oil-soluble dyes, crystal violet, triphenylamine, quaternary ammonium salts, azo-based metal complex salts, varatin dyes, and metal complex salt dyes such as orazole dyes. In addition, various pigments such as various non-ferrous metal oxides, zinc white, yellow iron oxide, Hansa yellow, disazo yellow, quinoline yellow, permanent yellow, red bengal, lithol red, and wool are suitable as long as the volume resistivity and the charging polarity are appropriate. Chang red calcium salt, Watchang red manganese salt, pyrazolone red, lake red C, lake red D, brilliant carmine 3B, navy blue, phthalocyanine blue, titanium oxide and the like can be used.

The coloring agent is not necessarily required because the magnetic powder is black, brown or dark blue, but pigments and dyes which are usually used can be used. Metal oxide, zinc white, yellow iron oxide,
Hansa Yellow, Disazo Yellow, Quinoline Yellow, Permanent Yellow, Bengala, Lisor Red, Watchang Red Calcium Salt, Watchang Red Manganese Salt, Pyrazolone Red, Lake Red C,
Pigments such as Lake Red D, Brilliant Carmine 3B, navy blue, phthalocyanine blue and titanium oxide, or oil-soluble dyes can be used.

With respect to the amount of the colorant to be added, a necessary amount for imparting the desired coloring property to the toner is added. If the amount is too large, free colorant particles serve as a triboelectric charging aid. From the viewpoint that the toner carrier, the electrostatic image carrier and the like are stained, it is desirable that the content is 10% by weight or less based on the toner. Heretofore, carbon black has been most commonly used as a black colorant in terms of price, versatility, and the like, but is determined to be unsuitable in the present invention because of its low volume resistivity.

Other necessary components include lubricants such as various waxes. Further, in order to improve the fluidity, the toner is dry-blended with silica or the like as necessary.

For the resistance value of the toner, the above-described measurement method is used. However, the volume specific resistance value may change depending on the applied voltage. Particularly, in the case of a toner in which a low-resistance substance such as carbon black is dispersed, Notable. As a conventional method of applying charge to toner using electrostatic induction, there is a method of utilizing a phenomenon in which the volume resistivity decreases as the applied voltage increases. However, such a property is rather unsuitable for the toner used in the present invention. So, for example, 10,
It is not preferable that the resistance is 10 ¹² Ωcm or less under an electric field of 000 V / cm. The toner according to the present invention is about 500 to 20.
When measured under a low electric field of about 00 V / cm, it shows a substantially constant resistance value.

As shown in FIG. 2, for example, the toner carrier has a plurality of magnetic poles 6 therein, and a mechanism for transporting the toner layer regulated by the doctor blade 8 when the conductive sleeve 7 rotates. Is the most common. The internal magnetic pole 6 may be fixed or rotated. This conductive sleeve generates an electric field in the developing field between the electrostatic latent image and
Further, from the viewpoint of leaking electric charges of the same polarity as the latent image on the toner, it is preferable that the electric charges are electrically grounded. In addition, in the case of an organic or inorganic photoreceptor, if there is a residual potential in the background due to insufficient exposure, etc., it is necessary to apply a DC bias having the same polarity as the electrostatic latent image for the purpose of preventing background contamination. is there. However, application of a DC voltage to the sleeve may cause a decrease in image density due to charge injection into the toner. Therefore, it is desirable to suppress the absolute value to about 300 V or less. However, in the case of reversal development, since the bias acts in the direction of improving the image density, there is no problem even if 300 V or more is applied.

The gap between the toner carrier and the doctor blade and the distance between the toner carrier and the electrostatic image carrier need to be adjusted so that the toner layer contacts or comes very close to the electrostatic image carrier. The gap between the toner carrier and the doctor blade is preferably about 0.2 mm or more and about 1 mm or less.
When the thickness is less than about 0.2 mm, the effect of frictional charging between the toner and the sleeve increases, and the environmental stability and running stability of the image deteriorate. The gap between the toner carrier and the doctor blade, and the gap between the toner carrier and the electrostatic image carrier can be made larger than usual, because the dimensional accuracy in mechanical design can be roughened. It is extremely advantageous for copiers and the like, and further has the advantage that the performance between machines is stabilized because fine adjustment is not required.

As a method for forming an electrostatic latent image on the electrostatic image carrier, inorganic photosensitive members such as Se-based and a-silicon-based
After uniformly distributing the charge by using a corona discharge or the like without applying light to the electrostatic image carrier such as an organic photoreceptor, the image information is exposed to form an electrostatic latent image It is most common to do so. In addition, a method of directly recording an electrostatic latent image on an electrostatic recording paper or the like using a needle-shaped electrode, an ion flow recording, or the like may be used. Thereafter, when a toner carrier holding the toner is brought into contact with the electrostatic latent image by, for example, a magnetic force, the toner selectively adheres to the electrostatic latent image by the mechanism described above and develops the toner.

Here, it is apparent from the following phenomena that the developing method according to the present invention is different in principle from the conventional method using charge injection and the conventional method utilizing mutual friction. Regarding the mechanism in which the toner injected from the conductive toner carrier is transferred to the upper layer of the toner layer by physical disturbance of the toner layer and is developed by contacting the electrostatic latent image, the toner carrier is made of an insulator. However, it can be seen from the development that this is not the case. Further, in the present invention, it is desirable that carbon black or the like is attached to the surface as a charge injection site.
0 ⁴ [Omega] cm or less of the material since it is better not substantially contained is good, the mechanism is seen quite different.

Also, the mechanism utilizing frictional charging between toner particles is clearly different from the following points. (1) Assuming that the magnetic powder is charged positively and the resin is negatively charged due to mutual friction between the binder resin portion on the toner surface and the exposed magnetic powder portion, the amount of the magnetic powder is reduced by 5%.
Even if it is changed from 50% to 55%, a large change in developability does not appear. (2) The toner used in the present invention does not actively expose the magnetic powder to the toner surface. (3) Developability is not affected by the environment because triboelectric charging is not used. Regarding the developability of the electrostatic latent image, 7 ° C. 20% RH
From 30 ° C. to 85% RH, a stable and constant image quality can be obtained.

Of course, as described above, in the developing method according to the present invention, electrostatic induction or dielectric polarization is dominant, but it cannot be denied that there are some effects of charge injection and mutual friction.

[0047]

According to the present invention, the thermoplastic resin has a volume resistivity of about 1 × 10 ¹⁴ Ωcm or more, and the charge stabilizer has a volume resistivity of about 1 × 10 ⁴ to 1 × 10 ¹² Ωcm. Powder and colorant have volume resistivity of about 1 × 10 ⁴ to 1 × 10 ¹² Ω
cm. and a magnetic one-component toner substantially free of a substance having a volume resistivity of about 10 ⁴ Ωcm or less. A toner carrier having a conductive surface at least in a developing field is used. It is characterized in that the latent image is visualized by being mainly charged by electric induction or dielectric polarization.

The use of the insulating magnetic one-component toner has the following characteristics. (1) Suitable for electrostatic transfer due to insulating toner, PPC
Is possible. (2) Because of the one-component developing method, the developing mechanism is simplified and the size can be reduced. Also, maintenance is easier or unnecessary than before.

Further, since the developing method according to the present invention does not utilize triboelectric charging or charge injection, it has the following features. (1) There is no dependence on the operating environment (especially humidity). This greatly improves printing quality and machine reliability. (2) The amount of charge of the toner was extremely stable even in long-term printing without using any special electric means, and the reliability of the image was greatly improved. (3) The developing speed can be increased, and the developing device in a large-scale machine can be simplified and maintenance-free. (4) The dimensional accuracy of the developing device may be rougher than before. (5) Developability is good even at a sleeve speed (10 cm / sec or less) lower than before.

[0050]

【Example】

Production Example Production of Insulating Magnetic Toner A toner material having the following composition was preliminarily mixed. Parts represent parts by weight. Styrene-acrylic resin (trade name: Almatex PA-201, manufactured by Mitsui Toatsu Chemicals, Inc., volume resistivity = 5 × 10 ¹⁵ Ωcm) 63.0 parts Magnetite (trade name: MG-WMK, Mitsui Kinzoku Kogyo) 35.0 parts Charge stabilizer (detailed below) 2.0 parts 3 kg of the above-mentioned raw material is mixed with a 20-liter mixer (trade name: trade name: 5 × 10 ⁸ Ωcm).
Henschel mixer, manufactured by Mitsui Miike Seisakusho Co., Ltd.)
The mixture was mixed at 00 rpm for 5 minutes. This was melt-kneaded by a twin-screw extruder (trade name: PCM-30, manufactured by Ikegai Iron Works Co., Ltd.), pulverized by a jet mill, and classified by an airflow classifier to obtain a volume-based average particle size of about 11 μm. 5μ or less and 20μ
A toner substantially not containing the above was used as a sample. In order to mainly improve the fluidity of this toner, 0.3 parts of hydrophobic silica was added to 100 parts by weight of the toner and dry-mixed.

Trial Production Example Trial Production of Copy Tester A printing test was actually performed on the above toner using an experimental machine obtained by modifying a commercially available copy machine. As the copying machine, a machine using a positively charged Se (surface potential of +800 V) photoconductor and a copying machine using a negatively charged OPC (surface potential of -600 V) photoconductor were used. The former is referred to as experimental machine A, and the latter as experimental machine B. The same developing device was used for each experimental machine. The structure and setting conditions of the developing device are as follows.

Basic mechanism of the developing device: ・ Internal magnetic pole: 8 poles, 1000 gauss, rotating in the opposite direction to the photoconductor at 1000 rpm ・ Conductive sleeve: 24 mm in diameter, rotating in the same direction as the photoconductor at a peripheral speed of 15 cm / sec ( 10cm / sec relative speed to photoconductor
・ Doctor blade-conductive sleeve gap: 0.3mm ・ Photoconductor-conductive sleeve gap: 0.3mm ・ Sleeve is electrically grounded

(Examples 1 to 8)
The substances shown in the table were selected.

Table 1 Examples Charge Stabilizer Volume Resistance Ωcm 1 Nigrosine Dye (Note 1) 2 × 10 ⁹ 2 Nigrosine Dye (Note 2) 8 × 10 ¹⁰ 3 Nigrosine Dye (Note 3) 2 × 10 ⁸ 4 Aniline Black (reagent) 6 × 10 ⁸ 5 Spiron black (Note 4) 5 × 10 ⁸ 6 crude nigrosine dye 5 × 10 ⁵ 7 azo metal-containing dyes (Note 5) 6 × ¹⁰ 10 8 azo metal-containing dyes (Note 6 3 × 10 ¹¹ 9 Quinacridone pigment (Note 7) 8 × 10 ¹² 10 Phthalocyanine blue (Note 8) 1 × 10 ¹¹ (Note 1) Nigrosine base EX: Orient Chemical Co., Ltd.
(Note 2) Bontron N-2: Orient Chemical Industry Co., Ltd.
(Note 3) Bontron N-07: manufactured by Orient Chemical Industry Co., Ltd. (Note 4) Spiron Black SB: manufactured by Orient Chemical Industry Co., Ltd. (Note 5) Spiron Black THR: manufactured by Hodogaya Chemical Industry Co., Ltd. (Note 6) Bontron S-34: manufactured by Orient Chemical Co., Ltd. (Note 7) KET RED 310: manufactured by Dainippon Ink and Chemicals, Inc. (Note 8) Lionol Blue SL: Toyo Ink Manufacturing Co., Ltd.
Made

50 g of each of the above toners is put into a developing device,
A solid black image continuous printing experiment was performed on 50 sheets, and the reflection density of a 3 × 3 cm square solid black portion of the first sheet and the 50th sheet was measured (reflection densitometer, Macbeth RD-918). This was carried out on experimental machines A and B with the same toner. The results are shown in Table 2.

Table 2 Printing Test Image Density Example Example Tribo-Charging Polarity with Resin A Experimental Machine A Experimental Machine B Experimental Machine B Initial 50 Sheets Initial 50 Sheets 1 Positive 1.32 0.37 1.49 1.42 2 Positive 1.31 0.85 1.40 1.32 3 Positive 1.36 0.25 1.43 1.34 4 Positive 1.38 0.32 1.41 1.34 5 Positive 1.38 0.40 1.38 1.334 6 Positive 1.37 0.35 1.39 1.317 Negative 1.37 1.38 1.39 0.58 8 Negative 1.32 1.34 1.30 0.77 9 Negative 1.39 1.37 1.38 1.14 10 Negative 1.47 1.41 1.32 0.98 11 Positive / Negative 1.41 1.43 1.42 1.40 1.40

In the initial image development, the toner according to the present invention utilizes charges induced by electrostatic induction, so that an electrostatic latent image of either polarity, either positive polarity or negative polarity, is developed equally well. It turns out. However, by continuously printing solid black images, toner with the same polarity as the electrostatic latent image accumulates in the toner layer. In the case of using the toner, the density of the image significantly decreased, and was not suitable. (The underlined image density values in the table show the results according to the present invention. The reflection density is practically 1.2 or more, more preferably 1.3 or more.) In Example 1, the environment was 7 ° C./20% RH, 23 ° C./50%
A similar printing test was conducted by changing the RH to 30 ° C. and 85% RH. However, no deterioration in image density and image quality was observed in any environment because triboelectric charge was not used for charging.

Example 11 A printing test was performed in the same manner as in Examples 1 to 10, except that one part of each of the charge stabilizers used in Examples 1 and 7 was used. In this case, as shown in Table 2, it was found that the image density was stabilized with respect to the electrostatic latent images of both polarities, and that both positive / negative and normal / reverse development could be performed with the same toner.

(Comparative Examples 1 to 9) As comparative examples, various substances shown in Table 3 were evaluated in the same manner as in Examples 1 to 11. (Since the volume resistivity of carbon black is small in Comparative Examples 8 and 9, only 1.0 part was used, and styrene-acrylic resin was used in 64.0 parts.) The results are shown in Table 4.

Table 3 Comparative Example Charge Stabilizer (trade name ) Volume resistance Ωcm 1 Quaternary ammonium salt (Note 1) 1 × 10 ¹⁵ 2 Quaternary ammonium salt (Note 2) 1 × 10 ¹⁶ 3 Boron compound (Note 3) ^{) 5 × 10 13 4 Cr (} 3 -valent) complexes (Note 4) 3 × 10 ¹⁵ 5 Zn complex (Note 5) 3 × 10 ¹⁴ 6 azo pigment (Note 6) 5 × 10 ¹⁴ 7 phthalocyanine Green (Note 7) 2 × 10 ¹⁴ 8 carbon black (Note 8) 2 × 10 ³ 9 carbon black (Note 9) 4 × 10 ² (Note 1) TP-302: Hodogaya Chemical Co., Ltd. (Note 2) Bontron P-51: Orient Chemical Co., Ltd. (Note 3) LR-147: Nippon Carlit Co., Ltd. (Note 4) Bontron PNR-BE: Orient Chemical Co., Ltd. (Note 5) Bontron E-84 Orient Chemical Co., Ltd. )
(Note 6) Lionol Yellow FGN-T: manufactured by Toyo Ink Mfg. Co., Ltd. (Note 7) Lionol Green 6Y-501: manufactured by Toyo Ink Mfg. Co., Ltd. (Note 8) Mitsubishi Carbon 44: Mitsubishi Chemical Industry Co., Ltd. (Note 9) Conductex SC: manufactured by Columbia Carbon Co., Ltd.

Table 4 Printing Test Image Density Comparison Example Triboelectricity Polarity Test with Resin A Experimental Machine A Experimental Machine B Experimental Machine B Initial 50 sheets Initial 50 sheets 1 Positive 0.90 0.95 1.36 1.37 1.37 2 Positive 1.06 1.19 1.40 1.33 3 Negative 0.35 0.88 0.46 0.22 4 Negative 1.40 1.36 1.16 0.25 5 Negative 1.37 1.34 0.84 0.32 6 Negative 1.40 1.40 1.23 1.05 7 Negative 1.45 1.46 1.20 0.88 8-1.42 0.75 1.28 1.13 9- 1.34 1.18 1.24 1.03

In Comparative Examples 1-2 and 4-7, the volume resistivity was high, and the effect of triboelectric charging was greater than the effect of electrostatic induction or dielectric polarization. In terms of the developing property and the image density decrease after 50 sheets of solid black. However, in the development for the latent image polarity having an appropriate property, it is stable as in Examples 1 to 11. However, the above three environmental conditions (7 ° C., 20% R
H, 23 ° C./50% RH, 30 ° C./85% RH), the image density changed in a humidity-dependent image test of triboelectric charging, which was unsuitable. Therefore, it is understood that these are different from the developing method according to the present invention. In Comparative Examples 8 and 9, electrostatic latent images of both polarities were developed in the same manner because of low volume resistivity. However, since the charge retention and dissipative properties were inferior, the image density was reduced as the number of printed sheets was increased and the image density was unsuitable. Met. Comparative Example 3
Was poor in triboelectric chargeability and image density was insufficient in both polarities.

(Reference Example 1) Toners were produced in the same manner as in Examples 1 to 11, except that the toner raw materials were changed with the focus on the amount of magnetic powder as follows. The raw materials used are the same as in Example 1.

Table 5 Raw material formulation (% by weight) Sample name in experimental machine B Resin magnetite charge stabilizer Test result A 88 10 2 Toner excess B 78 202 2 Slightly poor (scattering) Example 1 63 35 2 Good C48 50 2 Good

The best amount of magnetic powder was 35 to 50%. Regarding the toner samples A and B, there is no problem with respect to the developability of the electrostatic latent image, and since the magnetic force of the toner carrier is constant, it is considered that the developability is simply inappropriate in this experimental machine.

Reference Example 2 When the charge stabilizer was 10 ⁴ Ωcm or less, as shown in Table 6, a printing test was carried out using an experimental machine B while changing the amount of carbon black added. The carbon black used in Comparative Example 9 was used.

Table 6 Raw Material Formulation (% by Weight) Image Density in Experimental Machine B Sample Name Resin M (*) C (**) Initial 50 Sheets D 65 35 0 1.35 0.88 E 64.9 350 .1 1.26 0.95 Comparative Example 9 64 35 1.0 1.24 1.03 F62 35 3.0 1.19 1.01 G58 35 7.0 1.18 1.09 *: Magnetite * *:Carbon black

Even if a small amount of carbon black was added, the image density was lowered in accordance with the amount, and the electrostatic transferability was deteriorated.

(Reference Example 3) A trial production was performed in the same manner as in Example 1 except that the amount of the charge stabilizer added to the toner used in Example 1 was changed, and a printing test was performed. The results are shown in Table 7.

Table 7 Raw Material Formulation (% by Weight) Image Density in Experimental Machine B Sample Name Resin Mac “ Netite Charge Stabilizer Initial 50 Sheets H 64 35 1 1.46 1.40 Example 1 63 35 2 1.49 1.42 I 61 354 4.38 1.40 J 57 358 1.40 1.31

Although the toner J had an excessive amount of addition, the specific volume resistance of the toner was lowered, and the toner J was slightly unsuitable.
Everything else was good.

[0072]

[0073]

[0074]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the concept of the developing method of the present invention. (A) Enlarged view in the circle of FIG. 1 (b) Enlarged view of the charged state of toner alone particles (c) Concept of charged state in toner magnetic brush Cross section showing

FIG. 2 is a cross-sectional view illustrating the concept of the toner carrier of the present invention.

Reference Signs List 1 toner carrier 2 magnetic pole 3 toner particles 4 electrostatic image carrier 5 electrostatic image 6 magnetic pole 7 conductive sleeve 8 ... Doctor blades

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-54-134640 (JP, A) JP-A-56-78846 (JP, A) JP-A-62-70862 (JP, A) JP-A-1- 250963 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08 G03G 9/08

Claims (1)

(57) [Claims] 1. A thermoplastic resin comprising at least a thermoplastic resin, a magnetic powder, a charge stabilizer, and, if necessary, a colorant, wherein the thermoplastic resin has a volume resistivity of about 1 × 10 ¹⁴ Ωcm or more. Is about 1 × 10 ⁴ to 1 × 10 ¹² Ωcm
Wherein the magnetic powder and the coloring agent have a volume resistivity of about 1 ×.
10 ⁴ to 1 × 10 ¹² Ωcm and a volume resistivity of about 1
0 ⁴ [Omega] cm the magnetic one-component toner which is substantially free of the following materials, using a magnetic held to at least the developing field surface conductive toner carrier is, electrostatic formed electrostatic image bearing member A latent image is visualized by bringing said magnetic one-component toner into contact with a latent image and mainly charging by electrostatic induction or dielectric polarization by an electric field of said electrostatic latent image; Development method.