JP2001166526A - Method of nonmagnetic single component development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of nonmagnetic single-component development by which clogging of the toner easily caused between a developing roller and a doctor blade can be more surely prevented. SOLUTION: A nonmagnetic single component toner having 7 to 10 μm volume average particle diameter with external addition of hydrophobic silica by 0.5 to 2.0 mass % is used in the method of nonmagnetic single component development. From the experimental result, the toner (having <=5% distribution in number of particles having <=2 μm diameter) with good evaluation for toner clogging by visual check shown as (○) in the table is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic one-component developing method for more reliably preventing toner clogging which easily occurs between a developing roller and a doctor blade.

[0002]

2. Description of the Related Art Conventionally, there is an electrophotographic image forming apparatus using toner. Normally, this image forming apparatus includes a series of image forming processes of forming an electrostatic latent image on a photoconductor, forming the electrostatic latent image into a toner image (developing), and transporting the toner image to a position where the toner image is transferred to a sheet. The image forming unit for performing the above is incorporated.

FIG. 7 is a side sectional view showing a main part of a developing subunit paired with a drum subunit of such an image forming unit. The developing sub-unit 1 shown in FIG.
A photosensitive drum 2, a developing roller 3 that is in pressure contact with the photosensitive drum 2, and a toner container 4 that rotatably supports the developing roller 3 in an opening on a lower side surface, are provided with a toner 5, a stirrer 6, a supply roller 7, a doctor blade 8, a scooping sheet 9, and the like, which are disposed so as to be buried in the toner 5. The photosensitive drum 2, the developing roller 3 and the supply roller 7 rotate in the directions indicated by arrows in FIG.

The photoreceptor drum 2 is formed by uniformly applying a photoconductive member on the surface of a conductive metal roller, and an electrostatic latent image is formed on a peripheral surface formed of the photoconductive member to rotate the photoconductive member. I do.
The developing roller 3 is formed, for example, by applying a semiconductive urethane rubber around a metal core, a bias voltage is applied to the core, and the toner 5 is carried and conveyed on the surface to form the toner on the photosensitive drum 2. Is formed (developed) into a toner image. Stirrer 6
Is stirred so that the toner 5 in the toner container 4 is not solidified.

[0005] The supply roller 7 is also formed by coating a semiconductive urethane rubber around a metal core, and is arranged so that the urethane rubber layer on the surface is pressed against the developing roller 3. The toner 5 is once scraped off, and the fresh toner 5 stirred by the stirrer 6 is supplied to the developing roller 3. The doctor blade 8 serving as a toner regulating member is provided with a tip of a stainless steel plate having a spring property.
The toner 5 is guided between the doctor blade 8 and the developing roller 3 by the tip bent at an obtuse angle that is bent at an obtuse angle larger than the degree, and is disposed so that the bent portion is in contact with the developing roller 3. The toner 5 attached to the developing roller 3 is thinned to a predetermined thickness and the toner 5
Is given an appropriate triboelectric charge. The scooping sheet 9 is configured to prevent the leakage of the toner 5 in the toner container 4 and to allow the toner 5 remaining on the developing roller 3 to enter the toner container 4.

Although not particularly shown, a negative bias voltage is applied to the core of the developing roller 3, and a negative bias voltage is also applied to the other doctor blade 8. Conventionally, the toner 5
The negative bias voltage of the doctor blade 8 is considerably higher than the negative bias voltage of the developing roller 3 so as to compensate for the insufficient supply power of The toner 5 charged to a weak polarity is attracted to the developing roller 3. As a result, most of the toner 5 escapes from the doctor blade 8 into the toner container 4 as shown by the arrow A in the figure, and the other portion is attracted to the developing roller 3 by the electric field and the surface of the developing roller 3 And is transferred to the image portion of the electrostatic latent image on the peripheral surface of the photosensitive drum 2.

By the way, when the above-mentioned electrophotographic image forming apparatus becomes familiar, high resolution is required for an image to be formed, and accordingly, the particle size of the toner is also reduced.
Smaller particle sizes are being used.

However, in the image forming apparatus configured as described above, a sufficient charge is given to the toner 5 having a small particle size to provide a high-quality image free from background fog (non-image portion, that is, toner stain on a white background portion). In order to obtain the required value, it is necessary to press the doctor blade 8 against the developing roller 3 with a considerably large pressure to regulate the layer thickness of the toner 5 to a constant value and frictionally charge the toner.

However, when a large pressure is applied to the toner 5 on the developing roller 3 as described above, the pressure and the heat generated by the friction cause the resin component of the toner 5 (the non-magnetic one-component toner has a fluidity). (Silica, which is a hydrophobic resin, is externally added for the sake of improvement.) Melt and agglomerate, and these are embedded in the surface layer of the sponge body of the developing roller 3 or fixed to the tip of the doctor blade 8. I do.

When the aggregated toner is embedded in the surface layer of the developing roller 3 or adheres to the tip of the doctor blade 8 as described above, it becomes impossible to form a uniform toner layer on the developing roller 3 and, therefore, the photosensitive drum 2, the electrostatic latent image could not be developed correctly, which hindered image formation.

As described above, a relatively large potential difference is formed between the doctor blade 8 and the developing roller 3 in order to reinforce the toner supply force of the supply roller 7. The electric field from the doctor blade 8 to the developing roller 3 forms a repulsive force between the toner 5 and the doctor blade 8, which is a factor that hinders the triboelectric charging of the toner by the doctor blade 8.

When the relative humidity of the environment increases, the toner 5 absorbs moisture and the chargeability decreases. As a result, the amount of low-charge toner and toner of the opposite polarity increases, and these toners adhere to the photosensitive drum 2 regardless of the potential of the electrostatic latent image or against it. In other words, the above-described background fogging phenomenon in which the toner is transferred to the white print occurs here again, causing a problem of deteriorating the image quality.

In order to solve the above-mentioned problems, the applicant of the present invention disclosed in Japanese Patent Application No. 11-270422 a method in which the bending angle at the tip of the doctor blade was made acute and the bending radius R was set to 0.
25 mm <R <0.45 mm, and the doctor blade is set at 0 ° to 9 ° with respect to the tangent line of the contact portion with the developing roller.
It is arranged at an angle of 0 °, preferably 15 ° to 20 ° so that unnecessary toner does not enter between the doctor blade and the developing roller to form an unnecessarily thick toner layer. An improvement was proposed so that a toner having an extremely thin layer thickness can be formed, and there is no unevenness in charging, and therefore, a high-quality image without fogging or blurring can be formed.

Similarly, by changing the bias voltage of the doctor blade in accordance with the environmental humidity, the water content of the doctor blade is reduced to 0.1.
It has been proposed that even a toner of 8% or more can provide a sufficient charge amount, and can form a high-quality image with little fogging and blurring regardless of changes in environmental humidity.

Further, a large number of fine openings are formed obliquely in the scooping sheet and provided so as to be in sliding contact with the peripheral surface of the developing roller.
Almost all of the toner remaining on the developing roller without being involved in the development is easily collected on the supply roller side, so that the entire surface of the developing roller can be replenished with fresh toner. We have proposed a structure that can form high-quality images that are not affected by image quality.

Further, based on various experimental results in order to supply the optimum toner by the developing device having the above-mentioned structure, the toner is added with 0.5% by mass to 2% by mass of hydrophobic silica. A magnetic toner is used. In this toner, the mass distribution of the toner having a particle size of 5 μm or less is 4% or less, preferably 3% or less, and the CV value is 27 or less, preferably 2% or less.
A non-magnetic one-component developing method constituted as 4 or less was proposed.

[0017]

However, the configuration of the toner in the non-magnetic one-component developing method proposed above is correct in concept, but the particle size distribution of the toner is simply defined (regulated) by the mass distribution. Therefore, the distribution of the number of toner particles by particle size changes due to a change in classification conditions, etc., and the characteristics of the toner as a whole change. For this reason, if the toner is regulated by the mass distribution as described above, the optimum toner configuration state is not necessarily maintained. It turned out to be impossible. For example, when a large number of fine powders of 1 μm or less are contained, it has been found that the regulation based on the mass distribution cannot sufficiently prevent toner clogging.

This is because the mass distribution of the toner is a mass distribution proportional to the cube of the toner particle size.
This is because when there are many very fine toners such as φ, the number of individual toners may not appear in the mass distribution. In other words, the mass distribution may not be a measure for restricting the allowable value of the number of fine powder solids when a large number of extremely fine powders are contained. That was confirmed by subsequent pursuit.

Similarly, the regulation based on the CV value, that is, “(standard deviation of toner distribution / average particle size of toner) × 100” is also intended to suppress the deviation of mass distribution. In addition, it cannot be a means for sufficiently controlling the fine powder toner.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances,
An object of the present invention is to provide a non-magnetic one-component developing method that more reliably prevents toner clogging that easily occurs between a developing roller and a doctor blade.

[0021]

The non-magnetic one-component developing method of the present invention is a non-magnetic one-component developing method using a non-magnetic toner in which 0.5 to 2% by mass of hydrophobic silica is externally added to a toner. The toner has a volume average particle diameter of 7 μm or more.
The number distribution of the mixed toner having a volume particle size of 2 μm or less is 5% or less.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view schematically showing an internal configuration of a color image forming apparatus equipped with a developing device for realizing a non-magnetic one-component developing method according to an embodiment. First, the overall configuration will be described with reference to FIG. As shown in FIG. 1, the color image forming apparatus (main unit) 10
Has an openable / closable tray 11 on the rear surface (left side in the figure), and a paper cassette 12 detachable from the front of the main unit (right side in the figure) at the lower part. A large number of sheets are placed and stored in the sheet cassette 12. An upper lid 13 is provided on the upper surface of the main body device 10. A power switch, a liquid crystal display device, a plurality of input keys, and the like are arranged on the front side of the upper lid 13 although not shown in the drawing. The upper lid 13 forms a paper discharge tray 14 at the rear thereof together with the upper surface of the rear of the main body device 10.

Inside the main body device 10, a flat loop-shaped paper transport belt (hereinafter, simply referred to as a belt) 15 is disposed substantially in the center and extends back and forth. It is held by a driving roller 16 and a driven roller 17. The belt 15 is driven by a driving roller 16 and circulates in a counterclockwise direction indicated by an arrow R in the figure. Four photosensitive drums 18 (18a, 18b, 18) serving as electrostatic latent image carriers are provided on the upper circulating portion of the belt 15.
c, 18d) are juxtaposed in a multi-stage manner in the sheet transport direction (from right to left in the figure).

Each of the photosensitive drums 18 is surrounded (hereinafter, only the peripheral devices around the photosensitive drum 18d are denoted by reference numerals), and the cleaner 21,
Initializing charging brush 22, writing head 23, and developing device 2
4 are arranged. Although not shown, a contact-type transfer unit is connected to the photosensitive drum 18 via the belt 15.
To form a transfer portion.

The developing unit 24 forms a developing unit by bringing a developing roller 25 as a toner carrier rotatably supported in a lower opening thereof into contact with the peripheral surface of the photosensitive drum 18.
The write head 23 is disposed on the back surface of the upper lid 13 via a support member 26, moves up and down in a circular locus as the upper lid 13 opens and closes, and descends when the upper lid 13 is closed. The recording section is formed by being positioned between the initialization charging brush 22 and the developing roller 25.

At the upstream end of the upper circulation section of the belt 15,
The suction roller 27 is driven by the driven roller 17 via the belt 15.
To form a paper carrying portion. The suction roller 27 presses the paper conveyed to the paper conveyance unit against the belt 15 while applying a suction bias to the paper, and applies the belt 15.
Paper is electrostatically attracted to the paper.

The photosensitive drum 1 at the uppermost stream in the paper transport direction
8a, the photosensitive drum 1 at the most downstream position from the developing device 24
Up to the developing device 24 corresponding to 8d, each developing device 24 has M (magenta), C (cyan), and three subtractive primary colors.
Each toner of Y (yellow) and Bk (black) toner dedicated to printing of a black portion of a character or an image are stored.

A pair of standby rollers 28 is disposed further upstream (to the right in the drawing) in the transport direction than the belt 15, and a paper feed guide path 29 is disposed below the standby roller pair 28. A roller pair 31 is provided. Feeding roller pair 31
The paper feed end of the paper cassette 12 described above is located upstream (below). A paper feed roller 32 is disposed above a paper feed end of the paper cassette 12. The paper feed roller 32 takes out one uppermost sheet stored in the paper cassette 12 and feeds it to the feed roller pair 31 every one rotation.

On the other hand, a fixing device 33, a pair of paper discharge rollers 34, and a switching lever 35 are provided downstream of the belt 15 in the paper transport direction (left side in the drawing). The fixing device 33 includes a pressure contact roller, a fixing roller, a heating roller, a paper separating claw, a peripheral surface cleaner, an oil applying member,
It is composed of a thermistor or the like, and heat-fixes the toner image transferred on the paper to the paper surface.

When the switching lever 35 is at the lower position as shown in the figure, it guides the paper to be discharged to the paper discharge tray 14 via the upper discharge path 36 and the paper discharge roller pair 37. On the other hand, when rotating upward, the sheet is guided to the opening / closing tray 11 opened on the rear surface of the main unit.

An electrical unit 38 on which a circuit board can be mounted is provided between the belt 15 and the paper cassette 12, and a control device including a plurality of electronic components is mounted on the circuit board. Although not specifically shown, the control device includes a controller unit and an engine unit, and the controller unit includes a CPU (Central Processing Unit), a ROM (Read Only Memory), an EEP
It includes a ROM (rewritable read memory), a frame memory, an image data transfer circuit, and the like, analyzes print data input from a host computer or the like, creates print data, and transfers the print data to the engine unit.

The engine unit includes a CPU, a ROM, and the like.
On the input side, data and command signals from the controller unit, the output of the temperature sensor, the output of the paper detection sensor, etc. are input, and on the output side, a motor driver that drives a motor (not shown), and the drive of the motor is transmitted to each unit. Driver for switching the driving system to be performed, a print driver for driving the write head 23 based on the print data, an initialization charging brush 2
2. A bias power supply driver for supplying a predetermined bias voltage to a developing roller 25, a transfer device, a suction roller 27, a supply roller described later, a doctor blade, a scooping sheet, and the like are connected. The engine unit controls the driving of each unit based on data and command signals from the controller unit, the output of the temperature sensor, the output of the sheet detection sensor, and the like.

The basic operation of the color image forming apparatus 10 will be described below. First, when the power is turned on and the paper quality, the number of sheets to be used, the print mode, and other designations are input as a key input or a signal from a host device to be connected, the feed roller 32 is driven by a drive mechanism (not shown). By rotating, the paper loaded in the paper cassette 12 is fed to the standby roller pair 28 via the feed roller pair 31.
The standby roller pair 28 temporarily stops rotating, and waits for the transport timing in a state where the leading end of the sheet is brought into contact with the holding portion formed by the pair of rollers.

Subsequently, the driving roller 16 rotates in the counterclockwise direction, and the driven roller 17 is driven to rotate in the counterclockwise direction. As a result, the upper circulating portion of the belt 15 abuts on the four photosensitive drums 18 and circulates in the counterclockwise direction as a whole as shown by the arrow B in the figure.

At the same time, the developing units 24 and the photosensitive drums 18 are sequentially driven in accordance with the printing timing. The photosensitive drum 18 rotates clockwise, the initialization charging brush 22 applies a uniform high negative charge to the peripheral surface of the photosensitive drum 18, and the writing head 23 controls the photosensitive drum 18.
The peripheral surface is exposed according to the image signal. As a result, an electrostatic latent image composed of the high negative potential portion due to the initialization and the low negative potential portion whose potential has been attenuated by exposure is formed.
The developing roller 25 of the developing device 24 transfers the toner to the low potential portion of the electrostatic latent image to form a toner image on the peripheral surface of the photosensitive drum 18 (reversal development).

When the leading end of the toner image on the peripheral surface of the photosensitive drum 18a at the most upstream position is rotated and conveyed to the portion facing the belt 15, the printing start position of the paper coincides with the facing portion. The standby roller pair 28 starts rotating and feeds the sheet to the sheet carry-in section. The driven roller 17 and the suction roller 27 hold and transport the fed sheet together with the belt 15. The sheet is attracted to the belt 15 and is conveyed to the first transfer section formed by the photosensitive drum 18a and the transfer device.

The transfer unit applies a transfer current output from a transfer bias power supply to the sheet via the belt 15. The transfer current applied from the transfer device causes the photosensitive drum 18
The M (magenta) toner image on a is transferred to the sheet.
Subsequently, the C (cyan) toner image is transferred at the second transfer portion from the upstream formed by the photoconductor drum 18b and the transfer device, and is further transferred from the upstream formed by the photoconductor drum 18c and the transfer device. The Y (yellow) toner image is transferred at the second transfer portion. Then, a Bk (black) toner image is sequentially transferred at a most downstream transfer portion formed by the photosensitive drum 18d and the transfer device.

The paper on which the toner images of four colors have been transferred in this manner is separated from the belt 15 and carried into the fixing device 33. The fixing device 33 thermally fixes the toner image on the paper. After the image is fixed, the sheet is discharged by the discharge roller pair 34 with the toner image facing up on the opening / closing tray 11 on the rear surface or the toner image facing down on the upper discharge tray 14.

FIG. 2 is a side sectional view schematically showing an enlarged main part of the developing unit 24. Developing device 24 shown in FIG.
Is basically the same as the configuration of the developing sub-unit 1 shown in FIG. That is, the developing device 24 includes a housing 41 also serving as a toner hopper, and the developing roller 25 described above is rotatably held in a lower opening of the housing 41.
A stirrer 43 is disposed inside the toner container 1 and accommodates a non-magnetic one-component toner 42 and is buried in the toner 42.
It has.

A supply roller 44 made of a sponge body is disposed at the lowermost portion in pressure contact with the developing roller 25.
The developing roller 25 is provided with a leaf spring-shaped doctor blade 45 as a toner layer regulating member that is pressed against the downstream side in the rotation direction (counterclockwise direction in the drawing) from the pressing portion.
Further, a conductive scooping sheet 46 is disposed in contact with the lower peripheral surface.

In order to form a stable toner image on the photosensitive drum 18, a developing bias voltage “−250 V” is applied to the developing roller 25 from a bias power supply 47. Further, the supply bias voltage “−500 V” is applied to the supply roller 44 from another bias power supply 48.

The doctor blade 45 has an acute bending angle at the tip and a bending radius R of 0.25 mm <R <
0.45 mm, and arranged at an angle of 0 ° to 90 °, preferably 15 ° to 20 ° with respect to the tangent line of the contact portion with the developing roller. A bias voltage is applied.

Although not particularly shown, the scooping sheet 46 is provided with a large number of fine openings formed obliquely so as to be in sliding contact with the peripheral surface of the developing roller.
Appropriate voltage V3 is applied.

FIG. 3 shows that the developing device 24 having the above-mentioned structure is filled with non-magnetic one-component toners having various particle size distributions in which 0.5% to 2% by mass of hydrophobic silica is externally added. FIG. 9 is a table showing the results of an experiment in which continuous printing was performed and the presence or absence of a toner clogging phenomenon was examined between the time when the toner was not used and the time when the toner was exhausted. FIG. 9A shows the experiment No. from the left end column. , Toner clogging (visual judgment result), 5μ
m>% by mass (% by mass of particles of 5 μmφ or less), 2 μm>
The number% (number% of particles of 2 μmφ or less) is shown.

In the above experiment, 280 g of the toner 42 was charged into the developing device 24. Thus, in this example,
Printing was performed on A4 size paper at a printing rate of 5%, and approximately 6,500 sheets could be printed before the toner was exhausted. To determine toner clogging, print all solid prints on plain paper and OHP paper every 1000 sheets, visually check for white streaks caused by toner clogging, and transparently adhere the toner layer on the developing roller. The film was peeled off with a tape, and the presence or absence of a conveyance failure caused by the toner clogging was visually checked to determine.

The sample toner used in the above experiment was
A phthalocyanine pigment as a colorant, an organometallic complex as a negative charge control agent, a fixing release, and a polyester resin which is generally used for toners and is composed of a diol such as a bisphenol derivative, a polyhydric alcohol and a dicarboxylic acid such as maleic acid, and a tricarboxylic acid. A mixture obtained by kneading low-molecular-weight polypropylene as an agent, pulverizing with a jet mill, classifying into an arbitrary particle size distribution, and externally adding silica fine particles subjected to hydrophobizing treatment as a fluidization and chargeability improver using a mixer. It was used.

The average particle size of each sample toner was adjusted to be 8.5 μm in mass average. In the particle size and the particle size distribution, the mass distribution and the particle size were measured by a measuring device called a Coulter counter, and the number distribution of 2 μmφ or less was measured by using a measuring device called a particle analyzer.

The externally added hydrophobized silica had a relatively large average particle size of 40 nm and an average particle size of 8 nm.
m having a small particle size of m, and the external additive amount was processed so as to be 1.4% by mass and 0.35% by mass, respectively, based on the toner.

Experiment No. In No. 1, the proportion of the fine powder having a diameter of 5 μmφ or less is 5% or more in the mass distribution, and the proportion of the fine powder having a diameter of 2 μmφ or less is 10% or more in number. In the solid printing described above in this printing experiment, intense white stripes occurred.

Experiment No. 2 through Experiment No. 2. 4 and Experiment Nos. 9 and Experiment No. In No. 10, the proportion of fine powder having a diameter of 5 μmφ or less is 5% or less in a mass distribution, and the proportion of fine powder having a diameter of 2 μmφ or less is 5% or less in a number distribution. In this case, no white stripes were observed in all solid printing.

Experiment No. 5 to Experiment No. 5. In the case of No. 8, although the proportion of fine powder of 5 μmφ or less is less than 5% in the mass distribution, the amount of fine powder of 2 μmφ or less is 5% to 7% or more in the number distribution. There has occurred.

From these experimental results, it can be seen that the configuration of the toner that does not generate white streaks in all solid printing, that is, does not cause toner clogging in the developing device, is only required to reduce the mass distribution of particles having a particle size of 5 μm or less to 5% or less. Insufficient, and it is necessary to regulate the number distribution. Then, in the number distribution in that case, the distribution ratio of particles having a particle size of 2 μm or less is 5%.
It is clear that the following can prevent the toner clogging from occurring.

By the way, in the experiment No. of FIG. 5 to Experiment No. 5. As seen in the configuration of the sample toner of No. 8,
Despite classifying with a jet mill so as to reduce the proportion of particles having a diameter of 5 μm or less due to mass distribution, it is inexplicable that the number of fine powders having a diameter of 2 μm or less has increased in the number distribution. This was for the following reasons.

FIG. 4 is a side sectional view schematically showing the structure of a jet mill (classifier) for producing toner having a desired particle size distribution for practical use or for use in the above experiments. In the figure, first, the toner raw material appropriately pulverized is indicated by an arrow C in the figure.
As shown in the figure, the material supply port 54 on the upper side of the classifier 53
Supplied from The supplied toner raw material is dispersed by the swirling airflow indicated by the arrow D in the classifier 53.

Thus, the lower umbrella 55 and the classifier 5
In the classifying chamber in which 6 is disposed, a semi-free vortex is formed by the secondary airflow that flows in uniformly from the peripheral louver portion.
In this classifying chamber, coarse powder and fine powder are classified by centrifugal force, and the fine powder is discharged to the outside from the side discharge port together with the exhaust gas through the central discharge path 57 from the gap between the umbrella 55 and the classification plate 56 facing each other. . On the other hand, the coarse powder moves from the peripheral part of the classification chamber to the lower part, is discharged from the lower product discharge port, and is stored in a product tank (not shown).

In such a classifier 53, in order to impart a desired particle size distribution to the toner to be produced, the flow rates of the primary air flow and the secondary air flow and the umbrella 55 at the center of the classifier 53 are required.
And classifying by adjusting the gap B between the
Thus, a desired particle size distribution is provided.

Then, in order to separate and remove the fine powder,
When the gap B is widened and the classification is performed by reducing the flow rates of the primary air flow and the secondary air flow, fine powder is removed in terms of mass distribution, and a toner having a sharp particle size distribution is obtained. However, when this commercialized toner is observed with a SEM, actually, a finer differential toner of 1 μm or less remains in the toner having a normal particle size of 5 μmφ to 9 μmφ without being blown into the airflow, and this is the normal particle size. It was observed that the toner adhered to the toner.

And this is 5 μmφ by the mass distribution.
Despite the classification by a jet mill so as to suppress the proportion of the following particles to a low level, the number of fine powders of 2 μmφ or less in the number distribution was increased.

FIG. 5A shows the results of Experiment No. FIG. 4 is a diagram showing a particle size distribution based on a mass distribution of the toner used in No. 2 measured by a Coulter counter, and FIG. 4B is a diagram showing a particle size distribution based on a number distribution similarly measured by a particle analyzer.

FIG. 6A shows the results of Experiment No. 7 is a diagram showing a particle size distribution based on a mass distribution measured by a Coulter counter of the toner used in No. 7, and FIG. 2B is a diagram showing a particle size distribution based on a number distribution similarly measured by a particle analyzer.

When comparing FIG. 5 (a) and FIG. 6 (a),
Experiment No. 7, the mass distribution of the toner used in Experiment N
o. The distribution is more concentrated and sharper than the mass distribution of the toner used in 2, and it seems that there is no problem. But,
Comparing the number distributions shown in FIG. 5 (b) and FIG.
Experiment No. The toner used in Experiment No. 2 shows about “10 + 65 = 75 (pieces)”, whereas the toner used in Experiment No. 2 In the toner used in No. 7, approximately “5”
+ 175 = 180 (pieces) ", which indicates that the number is extremely large.

In particular, in the number distribution of FIG. 6B, as the particle size of the fine powder gradually decreases from 3 μm to 2.5 μm, 2 μm, and 1.5 μm, the number of the fine powder sharply increases. .

Here, an ultrafine toner having a particle size of 1 μm or less cannot be clearly measured by a Coulter counter or a particle analyzer. 5-Experiment No. 5 As can be seen from the number distribution of Fig. 8 and Fig. 6 (b), as the number of fine powders increases, the number of fine powders near 1µmφ increases rapidly, so the number of fine powders of 1µmφ or less will also increase. Can be easily estimated.

That is, when classifying the toner, the umbrella 55
When the classification is carried out by reducing the flow rate of the primary airflow and the secondary airflow by widening the gap B between the airflow and the classification plate 56, the fine powder as seen in the mass distribution is sorted to a satisfactory level. However, the number of fine powders will be increased. Experiments have shown that toner having a larger number of fine particles having a diameter of 2 μmφ or less causes toner clogging when the toner is used.

The present invention has been made based on the results of these experiments. In other words, when the particle size distribution of a toner having a large amount of fine powder and causing toner clogging is viewed from the number-based particle size distribution, the ratio of the number of particles having a diameter of 2 μmφ or less exceeds 5%. This is based on the fact that it has been confirmed that toner clogging will not occur.

[0066]

As described above in detail, according to the present invention, based on the results obtained by various experiments, 0.5% to 2% by mass of hydrophobic silica is externally added. Number distribution of 2 μmφ or less with a diameter of 7 μm to 10 μm
% By using a non-magnetic one-component toner configured to be less than 0.1%, the toner clogging that easily occurs between the developing roller and the doctor blade is more reliably prevented, and the entire surface of the developing roller is always fresh. The toner can be replenished, so that a high-quality image that is not affected by the development history can always be formed.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing an internal configuration of a color image forming apparatus equipped with a developing device for realizing a non-magnetic one-component developing method according to an embodiment.

FIG. 2 is a side sectional view schematically showing an enlarged main part of a developing device of the color image forming apparatus of FIG. 1;

FIG. 3 is a table showing experimental results obtained by examining whether or not a toner clogging phenomenon has occurred in a non-magnetic one-component toner having various particle diameter distributions by using the developing device of FIG. 2;

FIG. 4 is a side sectional view schematically showing a structure of a jet mill (classifier) for producing toner having a desired particle size distribution for practical use or for the experiment of FIG.

FIG. 5 (a) is an experiment No. of FIG. FIG. 4 is a diagram showing a particle size distribution of the toner used in No. 2 based on a mass distribution measured by a Coulter counter, and FIG. 4B is a diagram showing a particle size distribution by a number distribution similarly measured by a particle analyzer.

6 (a) is an experiment No. of FIG. FIG. 7 is a diagram showing a particle size distribution based on a mass distribution measured by a Coulter counter of the toner used in FIG. 7, and FIG. 4B is a diagram showing a particle size distribution based on a number distribution similarly measured by a particle analyzer.

FIG. 7 is a side sectional view showing a main part of a developing sub-unit paired with a drum sub-unit of an image forming unit of a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Development subunit 2 Photoreceptor drum 3 Developing roller 4 Toner container 5 Toner 6 Stirrer 7 Supply roller 8 Doctor blade 9 Scooping sheet 10 Color image forming apparatus (main body device) 11 Opening / closing tray 12 Paper cassette 13 Top lid 14 Discharge tray 15 Belt (paper transport belt) 16 Drive roller 17 Follower roller 18 (18a, 18b, 18c, 18d) Photoreceptor drum 19 Write head insertion groove 21 Cleaner 22 Initializing charging brush 23 Write head 24 Developing device 25 Developing roller 26 Support Member 27 Suction roller 28 Standby roller pair 29 Paper feed guide path 31 Feed roller pair 32 Paper feed roller 33 Fixer 34 Paper discharge roller pair 35 Switching lever 36 Discharge path 37 Paper discharge roller pair 38 Electrical unit 41 Housing 42 Non-magnetic One-component toner 43 Stirring member 44 Supply roller 45 Doctor blade 46 Scooping sheet 47, 48, 52 Bias power supply 49 Variable bias power supply 53 Classifier 54 Material supply port 55 Umbrella 56 Classification plate 57 Central discharge path

Continued on the front page (72) Inventor Kosuke Sugama 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo Office F-term (reference) 2H005 AA08 CB13 EA05 EA07 FA07

Claims (1)

[Claims] 1. A toner containing 0.5% by mass of hydrophobic silica.
A non-magnetic one-component developing method using a 2% by mass externally added non-magnetic toner, wherein the toner has a volume average particle diameter of 7 μm to 10 μm, and a number distribution of mixed toner having a volume particle diameter of 2 μm or less. A non-magnetic one-component developing method characterized in that the content is 5% or less.