JPS5944627B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In particular, the present invention uses an insulating magnetic toner or an insulating one-component developer that contains only toner as a main component and does not contain carrier particles, and electrostatically converts a toner image created by a conventionally known method. The present invention relates to an image forming method in which a final image is obtained by transferring onto plain paper.

Plain paper here refers to regular paper that has not been electrically insulated, and does not refer to electrostatic recording paper whose surface layer is coated with resin. Conventionally, the magnetic brush method, cascade method, liquid development method, and the like are known as methods for developing electrostatic images that have been generally used in devices applying electrophotography or electrostatic recording methods.

Each of these methods is an excellent method for obtaining good images, but on the other hand, they have drawbacks common to two-component developers, such as fatigue of the carrier and fluctuations in the mixing ratio of carrier and toner. On the other hand, single-component developers containing only toner as a main component and containing no carrier particles are essentially free from the above-mentioned drawbacks, and can be used, for example, by touch-down method, impression method, or induction development with conductive toner. Much is known about the law.

However, each of these methods has new problems to be overcome, and few of them have been put into practical use.
The MagneDry method, which is a type of induction development method, uses a conductive and ferromagnetic toner, and its details are disclosed in German Published Patent Application No. 2313297. This method has the advantage of being able to develop both positive and negative electrostatic charge images with the same toner, but on the other hand, because the toner is conductive, when electrostatically transferring an image onto plain paper, the image becomes extremely blurry. It has its drawbacks. When electrostatic recording paper is used as the transfer paper, the sharpness during electrostatic transfer is improved, but it has drawbacks that plain paper does not have, such as the cost of the recording paper and the difficulty of writing with ink. The present invention provides the essential advantages of the one-component developer (hereinafter sometimes referred to as insulating magnetic toner) as described above, and also provides sharp transferred images on plain paper.

The one-component developer used in the present invention does not contain carrier particles and has only toner as its main component, and has ferromagnetism and excellent insulation properties, and is necessary for development due to the mutual friction of toner particles. This means that a substantial charge can be obtained.

As the magnetic material used in the one-component developer, magnetite satisfies all the conditions and is most suitable for the purpose.

Of course, fine powders of various ferrites, iron, cobalt, nickel, etc. can also be used depending on the combination with the resin.
In addition, the resin used is selected taking into account the frictional charging properties with the magnetic material used, the manufacturing method and conditions, the coatability for the magnetic material, the ease of fixing with heat, etc., but includes styrene resin, acrylic resin, Suitable resins may be used as a mixture or copolymer of one or more of vinyl resins, epoxy resins, cellulose resins, polyurethane resins, and the like.

Further, if necessary, a charge control agent or the like may be added, and an auxiliary agent such as silica may be added to the toner to improve fluidity.
The one-component developer used in the present invention can be produced by selecting an appropriate combination from the above-mentioned magnetic materials and resins and using a known toner manufacturing method.

Conventionally, the most widely used method for producing pigments is a method in which resin and pigment are heated and mixed using two rolls, etc., and then pulverized. A drying method may also be used. Since it is an essential requirement for the one-component developer used in the present invention that the faces of the magnetic fine particles are substantially exposed on the particle surface, it is important to pay particular attention to this point during production.

This condition mainly depends on the type of magnetic material and resin used, and the content of the magnetic material, but is also influenced to some extent by manufacturing conditions. In the spray drying method, the better the dispersion, the better the coating of the magnetic particles with the resin.
During spray drying, the smaller the amount of solvent, the higher the rotational speed of the disk, and the lower the blowing temperature, the better the magnetic particles will be coated with the resin. Care must be taken when exposing the surface of the magnetic particles to an excessive degree, since the resistivity of the toner decreases and the amount of triboelectric charge of each toner particle cannot be increased. The above-mentioned toner manufacturing method is described in Japanese Patent Laid-Open No. 51-26046 by the same applicant as the present applicant.

Next, the first part up to development in the image forming method of the present invention.
This will be explained based on the diagram.

Created by the above method and with a specific resistance of 1014Ω-
? The above-mentioned one-component developer is housed in a hopper 1 as shown in FIG. 1, and the sleeve-shaped sleeve is made of a non-magnetic material and has a group of magnets 2 with alternating magnetic poles placed at the bottom of the hopper opening. Rotate the rotating member 3 in the direction of the arrow 4,
The one-component developer is held on the rotary member 3 by magnetic force to form a toner layer 5, and while the toner layer 5 rotates on the rotary member 3 while standing up, friction between toner particles causes the developer to form a toner layer 5. The toner charge substantially required for development is generated, and the toner is brought into contact with the electrostatic latent image supporting member 8 moving in the direction of arrow 7 at the position of the main magnet 6 to perform development.

Of course, in this configuration, a dedicated charging means for obtaining the amount of charge on the toner, such as applying a corona discharge, is not used to introduce charge. By the above method, an electrostatic latent image formed on a zinc oxide photoreceptor, a Se-polyvinylcarbazole composite photoreceptor, or a selenium photoreceptor could be developed.

Of course, reproduction of gradation images such as optical wedges was also obtained.
It is clear from the following several actual and experimental results that the image forming method according to the present invention relies on mutual friction between the insulating and ferromagnetic toner particles themselves.

First, the ferromagnetic and insulating toner prepared by the above-described method by containing ferromagnetic fine powder in the resin is conveyed through the developing device by magnetic force and brought into contact with a positively or negatively charged selenium plate. When development was carried out, normal images could be obtained in all cases. Furthermore, when the polarity of the developed toner was confirmed by measurement, it was negative and positive, respectively, and had a polarity opposite to that of the latent image. Of course, the toners used were all insulative and had a high specific resistance of 1014 Ω or more as described above, and the same was true for the toners to be used thereafter.
Next, a negative electrostatic latent image is created on the zinc oxide photosensitive plate, and development is performed by slightly weakening the magnetic force of the developing device. Not only the latent image area is developed, but also a small amount of the outside along the latent image area is developed. It was also observed that toner adhered to the area, that is, the area where the electric field was generated in the opposite direction to the latent image area. Further, when the amount of electric charge of several kinds of developed toners was measured, the value was 2.times.10@-6 to 1.4.times.10@-5 coulombs per unit true volume (cubic centimeter). This value is slightly insufficient to or approximately equal to the amount of charge on the toner generated by friction between the carrier and toner in two-component development. As a result of a simple experiment, for example, the amount of charge obtained by stirring the same resin powder is 1.
It was less than 0-0 clones/d. In addition, under the same development conditions, a zinc oxide photoconductor that is not charged with corona is rubbed against the toner layer on the developing device. After developing a zinc oxide photoreceptor having a latent charge image and sufficiently irradiating it with light to eliminate the excess latent image charge, the charge polarity of the developed toner was measured and found that the charge was positive. Next, when the developed toner was moved by placing a magnet on the back side of the photoreceptor and frictionally charged with the zinc oxide photoreceptor, the toner exhibited negative polarity again. From the above experimental examples, we found that there are positive and negative charges in the toner group, and these charges are not brought in from outside the toner layer, but are predominantly caused by mutual friction between the toners. It is assumed that it was That is, these toner particles were analyzed using an electron microscope to
When observed under magnification of 1,000 times, it was found that there were many fine protrusions on the particle surface, the size of which corresponded to the size of the ferromagnetic fine powder contained in the particles. The exposed ferromagnetic fine powder rubs against the resin part on the surface of other toner particles, and the ferromagnetic fine powder part becomes negatively charged and the resin part becomes positively charged. As a result, the surface of the toner particle is charged with positive and negative charges. Although charged surfaces are scattered, it is thought that as a result of combining them, there are toner particles that appear to be positively charged and toner particles that appear to be negatively charged.
As mentioned above, the development method related to the present invention is a mutual friction method using insulating ferromagnetic toner, and is different from the dielectric development method using conductive toner. It will be understood that the development method is also different.

As shown above, it was possible to obtain an image using a one-component developer mainly composed of ferromagnetic and insulating toner, but it is difficult to obtain a final image with good sharpness by electrostatic transfer onto plain paper. There are still problems to be overcome.

In insulating toner containing ferromagnetic fine powder, such as the developer used in the present invention, insulation is defined by specific resistance as in the conventional concept, and this is necessary simply because a toner with high specific resistance is produced. Naturally, the transferred image is not sharp.

Table 1 shows the relationship between the specific resistance of the prototype toner and the sharpness of the image electrostatically transferred onto plain paper. The sharpness was evaluated in descending order of ◎○∆×, and those of △ or better were considered acceptable for practical use.

At first glance, it can be understood that sharpness cannot be guaranteed solely on the condition that the resistance is high. In addition, cases in which the toner particles agglomerate and have already substantially lost the sharpness of the image during development, which is seen in monocomponent development of insulating toner containing ferromagnetic fine powder, are excluded from the beginning. This is a moot point.

The resistance measurement according to the above has a bottom made of brass material,
Using a container with a side wall plate made of acrylic resin having a thickness of 5U1, samples were placed approximately uniformly to a thickness of 5 mm into the container whose inner wall had been thoroughly cleaned, and tapping was performed approximately 10 times for each container to compress the sample. An additional 5 m is added to the thickness reduction caused by
After adding the sample almost uniformly to a thickness of m and performing lid-tapping 10 times, a brass electrode was applied to the top and a pressure of 1k was applied.
g/c! A voltage of 100 V was applied, and the measurement was carried out when the absorbed current was sufficiently reduced and the measured current became substantially flat. The final thickness of the sample layer was about 4 μ, and the measurement time was 15 to 30 minutes after voltage application. In addition, in the actual development state of the toner, the compressive force applied to the toner is dominated by the attractive force due to magnetic force, so it appears that the toner during development is used in a state where the contact resistance is higher than in the above measurement. We believe that the cause of the blurring (decreased sharpness) shown in Table 1 above is not due to the simple resistance value of the toner particles, but is due to the substantial exposure state of the ferromagnetic fine powder on the surface of each toner particle. I thought it was in. In other words, the thickness of the toner image that is developed and transferred is at most 2 to 8 layers on average based on the number of particles with an average diameter of about 10 μm, so even if it shows a high resistance in the normal resistance measurement method, in reality it is It was thought that charges were exchanged between the exposed ferromagnetic fine powder, the transfer paper, and others, and the charges entered the particles through electrical weaknesses within the toner particles, resulting in blurring. Therefore, the following measurement method was used to define the ease with which charges can enter. Hereinafter, the numerical value obtained by the measurement method described below will be referred to as the potential decay rate or leakage of the insulating toner (developer).

[Measurement method]

The explanation will be based on FIG. 2.

1. A zinc oxide photoreceptor is used, and after a predetermined potential is applied by ordinary corona discharge, a certain area is developed with an insulating toner.

Then, light irradiation is instantaneously applied so that the latent image (charge) within the area is not completely erased, but almost erased and a toner potential is generated. For example, 200~3001u with fluorescent light
x light irradiation, and irradiation time is 0.5~ depending on the thickness of the developing layer.
Let it be 3 seconds. 2. After cutting off the light irradiation, a translucent electrometer was placed on the sample within 2 to 3 seconds to record the dark decay for a short time (within 1 minute), and point A at time t1 in the figure was demand.

3. B after measuring point A and after 1 minute in the dark decay state
Find points.

4. Irradiation is then performed using the same light source.

At that time, the potential rise point C based on which the residual latent image in the middle is erased is determined, and at the same time, the potential V after 3 minutes from t1 is determined.
Find the point D that is 2. 5. By the above method, points A, B,
After obtaining the characteristic curves C and D, draw a virtual line parallel to the AB curve from the point C, and draw an intersection point E (potential V,) with the line extending from the time t1 toward the toner layer potential side. seek.

6. By substituting the above-mentioned values of V and V2 into the following equation, the ease with which charges penetrate into the toner layer, that is, the potential attenuation rate (V leak) is determined.

The potential V1 at point E in the above is the case where there is no latent image,
Moreover, it can be regarded as the initial potential of the toner layer when almost no potential attenuation occurs due to light irradiation.

Furthermore, although charge intrusion from the transfer paper may be a problem during measurement, it is important to obtain a peak value of C, and also to make the height of BC as small as possible relative to the height of 0A. is important. This is because the initial instantaneous exposure before placing the light transmission type electrometer is too low, and if the potential rises after the electrometer is placed, that is, the distance between BC is long, it is difficult to place the light transmission type electrometer. Under light irradiation in such a state, the direction in which the light enters is restricted, or the light irradiation causes the function of erasing the latent image and the penetration into the toner layer to occur at the same time. This is because generation may not be obtained.

Of course, this is different for toner whose potential is attenuated or zero. It is important to note here that the first instantaneous irradiation is scattered light, so we used a fluorescent lamp for indoor lighting.

However, the influence of light intensity was not so large. Furthermore, if the toner layer is placed thickly on the zinc oxide photoreceptor, the attenuation rate of the potential decreases to some extent, so it is necessary to specify the thickness of the toner layer. The thickness can be measured by measuring the weight per unit area of the toner layer used for measuring the potential attenuation, and dividing it by the specific gravity.
The result of this calculation is the plate-like thickness of the toner with zero porosity, but since the actual measurement of the thickness is somewhat ambiguous, it is also important to know not only the thickness but also how uniform the toner is on the zinc oxide surface. Since the degree of variation in toner adhesion to the toner also contributes to the measurement of the potential, the above-mentioned "calculated thickness", which incorporates these factors into the calculation, was determined for convenience. Next, to give an actual measurement example, an average of 1
The calculated thickness of toner particles of prescription A with a diameter of 0 μ is 8.0
It should be noted that the diameter of Formulation B observed in the 2nd and 3rd layers is 5.87μ, and that of the 2nd layer of Formulation C is 3.11μ, which is smaller than the diameter of one toner particle. .

The thickness required for measuring the leakage is the thickness of the toner layer actually used, and the calculated thickness is within 3 μm to 11 μm. The potential decay rate of the samples shown in Table 1 was measured and compared with the blurring, or sharpness, during transfer, and the results were as shown in Table 2.

From the above table, it can be seen that the sharpness, which could not be matched by specific resistance, shows a fairly good correspondence with the measurement of the potential decay rate.

It is unclear why the potential attenuation rate and specific resistance are not proportional, but it appears that the particle size distribution shape and fluidity of the toner when packing the toner into the resistance measuring electrode are also problems.

Furthermore, the resistance was measured by applying a pressure of 100 kg/Cd and making the sample into a tablet shape, but this also did not show a good correlation with the sharpness. Therefore, in order to see a direct correlation with the blurring during transfer, it is necessary to use this potential attenuation rate measurement method, which measures a form similar to the intrusion of charges that occurs during transfer.

For these reasons, in the case of a one-component toner containing ferromagnetic fine powder that is electrostatically transferred onto plain paper, it is insufficient to simply limit the specific resistance, and it is preferable to also specify the potential attenuation rate. is required to be less than 50% from Table 2.

A method for producing toner particles which are insulating and ferromagnetic and develop by mutual friction with a low potential attenuation rate is first to reduce the content of ferromagnetic fine powder.

However, in such insulating one-component development, it is difficult to apply a bias voltage, so a magnetic bias is applied instead. It should be noted that since a magnetic field is applied to the ferromagnetic powder, it is not possible to reduce the amount of ferromagnetic fine powder below the required amount. Also resin 40
Even if the amount of ferromagnetic fine powder is the same 60 parts by weight, the potential attenuation rate can be reduced by selecting the resin and solvent. That is, it is sufficient to select a material that has a high degree of coverage in relation to the ferromagnetic fine powder. Further, even when a charge control agent is used, it is better to use a good polymeric charge control agent using a dye. Also, depending on the manufacturing method, it is possible to create a product with a low potential decay rate.

These matters will be described later with examples.
The toner we initially produced as a prototype showed good development due to mutual friction, but there were many problems during transfer.

First, I will show some examples of them. was dissolved and dispersed in a mixed solvent of 70 parts of toluene and 30 parts of acetone, and the solid content was 60 parts.
After dispersing in a magnetic ball mill for 32 hours, the above mixed solvent was further added to adjust the solid content to 20%, and the mixture was granulated by a rotating disk type 3 spray drying method. The thus obtained black toner particles having an average particle diameter of about 10 μm were developed and transferred using the apparatus described later in Example 1, and the image developed on the photosensitive plate was an extremely good gradation image. However, there was a big disappointment in the transferred image. The potential decay rate of this toner was 75.6%. Example 2 was produced using the same manufacturing method as Example 1, and a toner having an average size of 10 μm was obtained.

Although the developed image had good gradation, the transferred image was not good. The potential decay rate of this toner was 52%. Embodiments will be described below with reference to FIG. 1 and FIG. 3, which shows an image forming apparatus according to the present invention including a transfer process.

Similar to Examples 1 and 2, Example 1 was dissolved and dispersed in a mixed solvent of 70 parts of toluene and 30 parts of acetone, and the solid content was 60 parts by weight. After dispersing in a magnetic ball mill for 32 hours, the above mixed solvent was further added to make the solid content 20% by weight, and the mixture was granulated by a rotating disk spray drying method.

To the obtained toner particles having an average particle size of about 10 μm and a maximum and minimum width of 3 μm to 30 μm, 0.3% by weight of silica (Aerosil 200 Nippon Aerosil Co., Ltd.) was added as an auxiliary agent to improve fluidity, and the hopper shown in FIG. 1 and a brass sleeve 3
Rotate the toner to the sleeve 3 using the magnetic force of the fixed magnet 2.
While holding it on top, I pulled it out of the hopper. The thickness of the toner 5 on the sleeve was 1 mm. The toner thickness is determined by determining the gap between the sleeve 3 and the lower end 9 of the hopper 1. The magnetic flux density of the fixed developing magnet 6 on the sleeve 3 was set to 900 Gauss, and the gap between the photoreceptor 8 and the sleeve 3 in the developing section was set to 1.4 degrees. This developing device is designated by the symbol 10 in FIG. In the apparatus shown in FIG. 3, a belt 13 is stretched over drums 11 and 12, and a zinc oxide photoreceptor 14 is placed on the belt.
After moving the charger 15 and the optical slit 15' in the direction of arrow 16 to create an electrostatic latent image with a maximum potential of 350 V, the drum 11 is rotated in the direction of arrow 16a and the sleeve 3 is rotated in the direction of arrow 4. I developed it. On the other hand, transfer paper tray 17
Plain paper 18 is placed on top, and paper feed rollers 19 and 20 are rotated in synchronization with the movement of the zinc oxide photoreceptor 14.
Plain paper 18 was fed along the paper feed guide plate 21, and toner was transferred on the transfer electrode 22 by corona discharge to ensure close contact with the photoreceptor 14. Thereafter, the plain paper 18 was separated by a separating head 23 and thermally fixed by a fixing device 24 to obtain a final image. The image obtained was a gradation image with no imperfections. The potential decay rate of the above toner is 5.2%.

In this embodiment, it is possible to convert the transfer device to an electrostatic transfer roller. Example 2 was the same as Example 1 except that the solvent was changed.

1 10 parts ethyl alcohol/90 parts dichloroethane and 2
The test was carried out using two mixed solvents of 10 parts of methylcellosolve/90 parts of ethyl acetate.

The manufacturing conditions are the same as in Example 1. Obtained average 10
0.3% by weight of silica (anilosil 200
(manufactured by Nippon Aerosil Co., Ltd.) and measured the potential decay rate, it was 1.0 in the case of the former solvent. , 19.6% for the latter
It was hot. When images were formed using these toners using the apparatus of Example 1, sharp transferred images were obtained.

Example 3 (-NONl4lCor1yo7 [N; Particles were granulated in the same manner as in Example 1 using a mixed solvent of 70 parts of toluene/30 parts of acetone as the solvent.

This is nothing but a case in which the above-mentioned copolymer was used as a polymer charge control agent in place of 2 parts of nigrosine SSB, which is a dye, as the charge control agent in Example 2. The potential attenuation rate in this example was 4.4%. Of course, a good gradation image was obtained during development, and the transferred image on plain paper was also sharp. In addition, in this example, the dye was changed to a polymeric charge control agent, and in addition to the simple effects expected, the styrene (90 mol%)/dimethylaminoethyl methacrylate (10 mol%) copolymer was used as a polymeric charge control agent. In relation to 1004, it was seen that it had the effect of improving the degree of coverage of the magnetic powder. Although no particular example will be given except for one example in Example 4, all of the Examples in which the conditions were changed little by little showed results in which the potential attenuation rate was small. Example 4 Two carbon blacks (MA-100) were added to Example 3.
Added part.

The rest is exactly the same as in Example 3. Although the obtained toner had an increased black color, the potential decay rate remained at 17.4%.
Despite the addition of carbon, the increase in potential decay rate was small. Example 5: Engineering; 'IJ▲'● V@↓
u 1J
The mixture was thoroughly kneaded in a pressurized kneader.

After cooling, this was coarsely pulverized and further finely pulverized using a dinit mill. Next, the pulverized toner was blown into a spray dryer using an air jet nozzle and instantaneously treated with hot air at 250° C. to produce a toner.

These toners were classified into particles of 10 μm on average using a zigzag classifier. To this was added 0.2% by weight of silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) as a fluidity aid, and when the image was developed and transferred using the apparatus of Example 1, a uniform gradation image was obtained.
The potential decay rate of this toner was 36%. Example 6 The manufacturing method was the same as in Example 5.

When 0.2% by weight of silica (R972 manufactured by Nippon Aerosil Co., Ltd.) was added to the obtained toner having an average particle size of 10 μm and the toner was developed and transferred using the apparatus of Example 1, a sharp gradation image was obtained. The potential decay rate was 23%. Example 7 was pulverized and dispersed using a pencil mixer, and thoroughly kneaded on two heated rolls.

After cooling, this was coarsely pulverized and further finely pulverized using a hammer mill. Next, the toner was introduced into a spray dryer using an air jet nozzle and instantly treated with hot air at a temperature of 270°C. Further, a zigzag classifier was used to obtain a toner having an average particle size of about 10 μm. Also, silica (R-97
2 (manufactured by Nippon Aerosil Co., Ltd.) in an amount of 0.1% by weight, it was possible to obtain a transferred image on plain paper in the same manner as in the above example.

The image was a sharp gradation image, and the potential attenuation rate was 4%. Example 8 was directly mixed and kneaded using a pressurized kneader without premixing.

Next, this was cooled and pulverized, introduced into a spray dryer through an air jet nozzle, and spheroidized with hot air at 250°C. Furthermore, after obtaining a toner with an average particle size of 10μ using a zigzag classifier, silica (R-972) was used as a fluidity aid.
When 0.2% by weight of Nippon Aerosil (manufactured by Nippon Aerosil Co., Ltd.) was added and development and transfer were performed in the same manner as in the above example, a sharp gradation image was obtained. When the potential decay rate was measured, it was found to be almost zero.
In addition, setting the potential attenuation rate to zero means that the potential attenuation is zero according to the method of measuring the potential attenuation rate, and is different from the fact that the ferromagnetic powder is completely covered. Mutual friction was also confirmed in the toner of this example by the experimental method for confirming mutual friction described above. Example 9 was kneaded directly in a kneader, pulverized, blown into a spray dryer with an air jet nozzle, and heated with hot air at 180°C to form spheres.

Next, 0.7% of silica (manufactured by M-5 Gear Pot Co., Ltd.) was added, and a zigzag classifier was used to obtain a particle size of 4μ to 30μ on average.
A toner of μ was obtained. Next, development and transfer were performed using the apparatus shown in FIG.

However, the photoreceptor 14 is SVPVK instead of an oxidized sub-sharp photoreceptor.
A composite photoreceptor was used. A scorotron equipped with a grid was used as the charger 15 to adjust the charging level of the photoreceptor. In addition, the gap between the sleeve 3 of the developing device and the Se//PVK photoreceptor passing along the drum 16 was changed to 1.25 mm, and the position of the main magnet was compared to that of the zinc oxide photoreceptor.
The sleeve 3 is set to be slightly tilted in the direction of rotation. The rest is the same as the example for the zinc oxide photoreceptor. The developed image obtained under these conditions exhibited strong characteristics of mutual friction, and a small amount of toner adhered to the reverse electric field generation area at the outer periphery of the latent image area, resulting in an unsatisfactory image. Since the Se/PVK layer is negatively charged, the toner adhering to the latent image area has positive polarity, and the toner adhering to the outer periphery has negative polarity. This image was then transferred onto plain paper by the transfer device 22 (minus discharge), but since only the positive toner of the positive image was transferred during the transfer, an excellent gradation image was obtained. Furthermore, the sharpness against transfer blur was extremely good. The potential decay rate of this toner was 1.9. As described above, the image forming method of the present invention uses an insulating toner containing ferromagnetic fine powder capable of mutual friction development and a potential attenuation rate of 50% or less. Because it performs electrostatic transfer onto plain paper, it has the advantages of one-component development and creates sharp images on plain paper.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a front view of a developing device, FIG. 2 is a curve diagram showing the relationship between toner layer potential and time, and FIG. 3 is a front view of a copying device. . 1 is a hopper, 2 is a fixed magnet, 3 is a sleeve, 5 is a toner, 6 is a fixed developing magnet, 8 is a photoreceptor, 10 is a developing device, 11 and 12 are drums, 14 is a zinc oxide photoreceptor, and 15 is Charger, 15' optical slit, 18 transfer paper, 19,
20 is a paper feed roller, 22 is a transfer electrode, 23 is a separation head, and 24 is a fixing device.

Claims (1)

[Claims] 1. Toner particles can be charged predominantly by friction between them,
Toner particles containing ferromagnetic fine powder as the main component have a specific resistance of 10^ so that toner particles with both positive and negative polarities can be formed.
It is an insulating one-component developer with a resistance of 1^4 Ω・cm or more, and is measured using the following measurement method a, after forming a toner layer on a zinc oxide photoreceptor, on the photoreceptor used to form the toner layer. while applying a first light irradiation capable of substantially erasing the latent image of the toner layer, b) the potential A of the toner layer immediately after the dark decay state (t_1) due to the light interruption and at the end of the dark decay one minute later; From B and the peak potential C of the toner layer obtained at the initial stage of bright decay due to the subsequent second light irradiation,
The initial potential value V_1 of the toner layer is determined, c, the potential value V_2 of the toner layer in the light decay state due to the second light irradiation, which is 3 minutes after the start of measurement (t_1) immediately after the dark decay state. , d, and the related formula (V_1-V_2/V_1) x 100% A developer having a potential decay rate whose value is 50% or less is attracted onto the conveying member using a magnet. At the same time, the magnet is guided to the developing section through relative rotation between the magnet and the conveying member, and the electrostatic latent image on the electrostatic latent image support member is developed to form a toner image, and then the toner image is electrostatically An image forming method characterized by sequentially transferring onto recording paper by a transfer means.