JP3370346B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to an image forming equipment,
In particular, the formation of an electrostatic latent image on an image bearing member such as a photosensitive member, and developing the electrostatic latent image relates to an image forming equipment for recording onto a transfer material such as paper.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus or an electrostatic printer, after an electrostatic latent image is formed on a photoconductor, a developer is electrostatically attached to the electrostatic latent image to form a developer image. Is formed, and then the developer image is transferred to a sheet to form an image. After the transfer, the electrostatic latent image and the developer that cannot be transferred still remain on the photoconductor, so the residual developer is removed by a cleaning device, and then the electrostatic latent image is removed by a neutralization device. There is.

By the way, in recent years, there has been a demand for downsizing of the apparatus. For example, Japanese Patent Application Laid-Open No. 47-11538 discloses that
A method is disclosed in which the developing device and the cleaning device are combined into one device to reduce the size of the device. In this method, in one developing device, the electrostatic latent image is developed when the photosensitive drum passes the first time, and then the electrostatic latent image is passed the second time to clean the residual image after transfer. There is. However, in this conventional method, the residual image is removed from the developing device when the photosensitive drum passes the second time, so that the recording speed is halved and the peripheral speed of the photosensitive drum is reduced. There is a problem that a recording area larger than the size of the entire surface cannot be obtained. For this reason, it is inevitable that the photosensitive drum must have a relatively large size, and the device cannot be made sufficiently small.

On the other hand, in US Pat. No. 3,649,262, during the first passage of the electrostatic latent image, the electrostatic latent image is developed and the developer remaining after the previous transfer is disclosed. A method of solving the speed-related drawback by using a developing device which performs cleaning at the same time is disclosed. According to this method, the size of the machine can be reduced and waste toner is not generated.

[0005]

Generally, in an image forming apparatus for recording on PPC paper or the like, paper dust falls inside the device and the paper dust attached to the image carrier is collected by a cleaner. However, in a cleanerless recording device without a cleaner, the paper dust adhered to the image carrier is collected by the developing device, and the paper dust deteriorates the developer inside the developing device, resulting in fog and lowering of image density. It was a cause of various problems.

The adverse effect of the paper powder mixed in the developer is more remarkable when the developing / cleaning means is a contact developing device or the transfer means is a contact transfer device. That is, when the transfer device is a contact type, the adhesion of the paper to the image carrier is improved, the transfer efficiency is improved, the transfer efficiency does not decrease due to environmental conditions, and the cleanerless process does not have a cleaner. Is an effective transfer method, but paper dust is easily generated because the paper is squeezed during transfer.

Further, when the contact developing system, especially the contact one-component developing system using a conductive (resistive) roller is used in the developing and cleaning device, good cleaning property is exhibited and no image memory is generated. However, in such a contact developing method, the paper powder adhered to the photoconductor is easily taken into the developing device, and this paper powder deteriorates the developer inside the developing device, resulting in a decrease in image density and an increase in fog. There has occurred.

These problems are caused by the fact that the filler, which is one of the constituents of the paper contained in the paper dust, has the same charge polarity as the toner, so that the charge amount of the toner inside the developing device is reduced, and It is generated by charging the opposite polarity.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming equipment which allows to perform a good no fogging or paper dirty printing.

[0010]

In order to solve the above problems, the present invention provides an image forming apparatus using a transfer material containing a filler having a charging property that does not impair the charging property of the toner.

That is, according to the present invention, an electrostatic latent image forming means for forming an electrostatic latent image on an image carrier and a developer is supplied to the electrostatic latent image to make the electrostatic latent image visible. Developing means, a transfer means for transferring the developer image formed on the image bearing member to a transfer material, and a non-pausing developer remaining on the image bearing member after transfer.
A non-patterning means for turning into a non -pattern
In the image forming apparatus having a mechanism for returning to the developing unit to recover the reduction has been developer, wherein the transfer material, blanking the blow-off charge amount Qp and the developer of filler contained therein
There is provided an image forming apparatus characterized in that a low-off charge amount Qt satisfies the following formula (1) or (2) and a filler has a Mohs hardness of 2 to 7: When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2)

Further, according to the present invention, an electrostatic latent image forming means for forming an electrostatic latent image on an image carrier and a developer is supplied to the electrostatic latent image to visualize the electrostatic latent image. Developing means, a transfer means for transferring the developer image formed on the image bearing member to a transfer material, and a non-pausing developer remaining on the image bearing member after transfer.
A non-patterning means for turning into a non -pattern
In an image forming apparatus having a mechanism for recovering the converted developer and returning it to the developing means, the transfer material contains a first filler and a second filler having different mohs hardnesses, The filler has a moth hardness of 2 or less, the second filler has a moth hardness of 2 to 7, and the blow-off charge amount Qp of at least one of the first and second fillers is
There is provided an image forming apparatus characterized in that a developer having a blow-off charge amount Qt satisfying the following expression (1) or (2) is used. When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2)

Further, desirably, the transfer material for an image forming apparatus of the present invention comprises a filler having a polarity opposite to that of the developer and a filler having a low hardness for improving the manufacturability of the transfer material. Used in the mixing ratio of.

[0014]

The above-mentioned problem caused by the mixing of paper powder into the developer is that the filler such as talc contained in the paper powder comes into contact with the developer inside the developing device to reduce the charge amount of the developer, or the polarity. It is generated by inverting.

Therefore, the material to be transferred for an image forming apparatus of the present invention contains a filler having a predetermined charging characteristic which does not impair the electrostatic charge of the developer even when the developer is brought into contact with the developer, whereby the developer is It is possible to prevent the charge amount from being reduced and the polarity to be reversed. As a result, it is possible to prevent fogging and stains on the back of the paper.

Further, in particular, a filler having a high hardness (calcium carbonate, titanium dioxide, etc.) having a polarity opposite to that of the developer, and another filler having a low hardness and improving the productivity of the transferred material. By using a predetermined mixing ratio, it is possible to achieve both the prevention of fogging and the backside of paper and the productivity of the transferred material.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows an image forming apparatus in which the material to be transferred of the present invention is used.
A photosensitive drum 1 as an image carrier having a recording surface smaller than the area of an image to be recorded (that is, having a small diameter) is rotatably provided in the direction of arrow A. Photoconductor drum 1
Is formed of an organic photoconductor (OPC) photoconductive material. Around the photosensitive drum 1, a charge removing unit 7 and a transfer residual toner non-patterning unit are sequentially arranged along the rotation direction thereof.
2, a scorotron charger 3, a laser device 4, a development cleaning device 5, and a transfer roller 6 are provided.

The transfer residual toner non-patterning means 2 is 1
It has a brush 2a made of a fiber (trade name: trading card, Kynol, etc.) having an electric resistance of 0 ³ to 10 ⁹ Ωcm, and the brush 2a is arranged so as to be in sliding contact with the photosensitive drum 1, and the plus 200 to A voltage of 1200 V is applied. Further, the scorotron charger 3 is configured to charge the surface of the photoconductor drum 1 to −450 to −800 volts substantially uniformly and negatively. Leh
The device 4 irradiates the surface of the photosensitive drum 1 with the laser beam 8 in accordance with the image information to be recorded, and forms an electrostatic latent image on the charged area.

Further, the developing and cleaning device 5 comprises a hopper 9 for accommodating a so-called one-component developer T having a triboelectric charging property,
The developing roller 1 that conveys the developer T into the hopper 9 toward a position facing the photosensitive drum 1 and returns the developer T remaining on the photosensitive drum 1 into the hopper 9.
0 is provided. The developing roller 10 has 10 ² ~ 1
0 ⁸ Conductive surface layer 11 having an electric resistance of Ωcm, and urethane foam rubber, silicone rubber, or EPDM inside the conductive surface layer 11.
The elastic layer 12 made of, for example, is arranged to form an elastic roller as a whole.

An elastic blade 13 made of phosphor bronze, urethane, or silicon resin for forming a thin layer is pressed against the developing roller 10 while frictionally charging the developer T, and the developing passing therethrough is carried out. The agent T is charged with negative triboelectrification having the same polarity as that of the photosensitive drum 1 to form a developer layer of about 1 to 3 layers. The surface of the developing roller 10 should be selected in consideration of triboelectric charging with the developer T, and in consideration of appropriate elasticity and friction.

The surface layer 11 of the developing roller 10 is formed, for example, by coating a mixture of urethane resin with 10 to 30 weight percent of conductive carbon. Furthermore,
A bias power source 14 is connected to the developing roller 10 and is electrically connected to the surface layer 11. As a result, a predetermined developing bias is applied during development and cleaning. A sponge-like developer carrying roller 15 is provided in the hopper 9, and plays a role of preventing aggregation of the developer T in the hopper 9 and carrying and feeding.

The transfer roller 6 is substantially the photosensitive drum 1.
Is provided below the surface of the photoconductor drum 1 so as to face the peripheral surface of the photoconductor drum 1 via the paper transport path 16. Transfer roller 5
Has a structure similar to that of the developing roller 10, but the surface layer 1
The electric resistance of 1 is 10 ⁵ It is about 10 ¹⁰ Ωcm. By the transfer roller 6, the back surface of the sheet conveyed here
A voltage of 0 to 2000 V is applied to electrostatically attract the toner, and the toner image is transferred from the photosensitive drum 1 to the paper.

Since such a contact type transfer means exerts stable transfer characteristics even when the humidity is high, it is effective in reducing the amount of residual developer remaining on the transfer sheet and reducing the cleaning load. It also removes paper dust and prevents it from entering the developer.

The conductive brush 2a of the untransferred toner depatterning means 2 is brought into sliding contact with the rotation of the photosensitive drum 1, is connected to the bias power source 23, and a voltage of 200 to 1500 V is applied to the photosensitive drum 1. The upper transfer residual developer is temporarily adsorbed. Since most of the transfer residual toner has a negative polarity, it is adsorbed to the transfer residual toner non-patterning means 2. However, some of the transfer residual toner of the fog toner is positively charged, and these toners are adsorbed. It passes without passing through, but it is not a problem because it is a very small amount. The transfer residual toner temporarily trapped in the transfer residual toner non-patterning unit 2 has a positive charge in a time corresponding to the conditions such as the applied bias, the resistance of the brush 2a, the toner particle size, and the resistance. From the electric field formed by the injected brush 2 a and the photosensitive drum 1, the photosensitive drum 1
Returned to. The time from the transfer residual toner being trapped by the transfer residual toner non-patterning means 2 to the time of receiving the charge injection and being returned to the photosensitive drum 1 again depends on the particle size of the toner, the resistance, etc. as described above. , Will have a distribution with some width. Therefore, the transfer residual toner is not patterned. Further, the mechanical cleaning effect of the brush 2a also contributes to the non-patterning of the transfer residual toner. However, not all the toner is returned to the photoconductor, but the toner gradually accumulates on the brush 2a.

The toner returned to the photosensitive drum has a positive polarity which is the opposite polarity to the regular polarity, but when the photosensitive drum 1 is charged by the scorotron charger 3, it is exposed to the negative corona and the toner Also has a negative polarity and is cleaned by the developing and cleaning device 5.

Next, the resistance of the conductive brush 2a of the transfer residual toner depatterning means 2 will be described. If the resistance of the brush 2a is too large, the responsiveness of the potential at the tip of the brush 2a deteriorates, and the time constant of the operation of returning the toner to the photoconductor through the charge injection from the adsorption of the toner by the brush 2a increases. As a result, there are problems that the untransferred image of the high-frequency line image cannot be sufficiently patterned, the toner cannot be sufficiently returned to the photoconductor, and the toner accumulation increases. If the resistance of the brush 2a is too low, the bias leaks to the photoconductor, and the photoconductor is destroyed. Therefore, the resistance of the brush 2a is 10 ³ ~ 10 ⁹ Ω
Is desirable.

Further, the photoconductor drum 1 is also positively charged by the brush a, but the potential at this time changes depending on the amount of transfer residual toner and the like, so the charging device is a scorotron charger as in this embodiment. Is desirable. In this way, since the transfer residual toner is trapped and swept out in a short cycle, the amount of toner remaining on the brush 2a is very small. However, when printing continuously, the amount of trapped toner gradually accumulates, and when it exceeds the allowable amount, it scatters, or the brush suddenly ejects a large amount of toner, resulting in image defects. Occurs.

Therefore, the transfer residual toner depatterning means 2
By arranging the above position above the photosensitive drum 1 or on the developing device side from above, it is possible to prevent the developer T adhering to the brush 2a from falling and scattering in the machine.

Below the photosensitive drum 1, a paper feed unit 19 for supplying the paper P to the transport path 16 is provided. The paper feeding unit 19 stores paper P to which an image is transferred. Above the paper feed unit 19, a paper feed roller 20 that supplies the paper P from the paper feed unit 19 to the transport path 16 by rotation is provided. The conveyance path 16 is provided with a fixing device 21 that fixes the toner image after transfer onto the paper P, and fixes the toner image on the paper P by heat and pressure.

Next, the operation of the electronic copying apparatus according to this embodiment will be described. The photoconductor drum 1 is rotated in the direction of arrow A so that the peripheral surface of the photoconductor drum 1 is covered by the scorotron charger 3
Is charged to about -450 to 800 volts. continue,
A laser beam 8 is emitted from the laser device 4 to the charged area to expose it, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. This electrostatic latent image is then conveyed to the developing and cleaning position facing the developing and cleaning device 5. Developing roller of developing cleaning device 5
A developer (hereinafter referred to as a toner) T is sent from the toner 10 , and the developer T elastically contacts the electrostatic latent image with a nip width due to the deformation, and the toner T is attached to form a toner image. In this case, the toner T adheres to the light irradiation area and undergoes so-called reversal development.

The toner T is about -5 to 30 μc due to friction with the blade 13 and the surface layer 11 of the developing roller 10.
/ G (micro coulomb / gram) is charged,
A voltage of about -150 to 450 volts is applied to the developing roller 10. The toner image after development is next transferred to the transfer roller 6
It is conveyed to the transfer area facing. On the other hand, the paper P is sent from the paper feeding unit 19 to the transfer area in synchronization with the rotation of the photosensitive drum 1 by the rotation of the paper feeding roller 20.

The rear surface of the paper P is charged by the transfer roller 6 to a positive polarity. Therefore, the toner image on the surface of the photosensitive drum 1 is electrostatically attracted to the paper P and transferred. Here, the transfer roller 6 is a direct current.
A voltage of 600 to 2000 V is applied to the rotating shaft by a power source , and a silicone resin provided at both ends of the transfer roller 6 is mixed with conductive carbon in an amount of 5 to 40 weight percent to form a roller surface. 10 ⁵ to 10 ⁹
A voltage is applied to the conductive surface of Ωcm.

In the transfer method using the transfer roller, as shown in FIG. 2, the transfer efficiency does not depend on the environment (particularly humidity). However, in corona transfer, as shown in FIG. 3, transfer efficiency decreases in a humid environment.

This means that, in a recording apparatus having no cleaning device as in the present invention, the residual transfer toner rapidly increases under high humidity, and cleaning of a so-called cleanerless recording apparatus having no conventional cleaning device is performed. The largest cause of defects.

[0036] From the above, the roller transfer method, chestnut
It is very effective in the Nares process , and the same can be said for the contact type transfer device using a brush or the like.

By the way, on the surface of the photosensitive drum 1 after the transfer, there are toner images and electrostatic latent images which remain slightly after the transfer and cannot be completed. These toner images and electrostatic latent images are conveyed to the transfer residual toner depatterning means 2 and depatterned. Transfer residual toner non-patterning means 2
Then, the brush 2a is brought into contact with the toner image and the electrostatic latent image, and electrostatic and mechanical forces are applied to the brush 2a finely to the unreadable state, and as described above, the remaining image is disturbed.

The toner T scattered on the surface of the photosensitive drum 1 is distributed in a sufficiently small mist state and no longer has information as characters or images. The electrostatic latent image remaining on the photoconductor is erased by the charge eliminating means (red LED), and the process returns to the charging step.

The photosensitive drum 1 charged by the scorotron charger 3 is charged and then exposed by the laser device 4 to form an electrostatic latent image, and again (second time), the developing cleaning facing the developing cleaning device 5 is performed. Reach the position. In this case, the second
In the electrostatic latent image formed at the second time, even in the exposed portion (image portion to which toner should be attached) and the non-exposed portion, the roller transfer significantly reduces, and the remaining toner is almost evenly and sufficiently thin in advance. Since they are scattered, exposure unevenness does not occur. Therefore, even if you put it in the second development,
Since the residual potential becomes uniform after exposure, a uniform toner image can be obtained.

[0040] In this case, as described above, developing low
With La 10 has elasticity 30 to 70 ° in JIS hardness measurement ^method, 11 to have a conductivity of 2 ~10 ^8, 20~150g / cm to the developing roller 10 as a linear load
By applying a load of 1, and pressing and sliding with a speed difference of 1.5 to 4 times, a contact width (nip) of 1 to 4 mm is generated, and the residual toner and the developing roller 10 are in this nip.
Since the upper toner T is disturbed and rubbed, a strong frictional force is generated, and the cleaning ability is enhanced. Moreover, since the developer is formed only by the toner T, there is no deterioration in image quality such as streaks and crimps. In the non-exposed portion, the attraction force due to the developing bias exceeds that of the photosensitive drum 1, so the adhered toner T is attracted to the developing cleaning device 5 one after another and collected. That is, by applying a developing bias of an appropriate value (-150v to -450v in the embodiment) between the residual potential of the exposed portion and the potential of the non-exposed portion to the developing roller 10, the developing roller 10 exposes the exposed portion. The new toner adheres to the toner, and at the same time, the residual toner that adheres to the non-image area (non-image portion) is attracted to and collected by the developing roller 10. In this case, since the residual toner is small and dispersed in the transfer residual toner non-patterning means 2 into a small mist in advance, the developing and cleaning device 5 can efficiently collect the residual toner, resulting in defective recovery. Never. In this way, the photosensitive drum 1 is rotated in an overlapping manner and used in duplicate, and one recorded image is obtained.

In the contact one-component developing system as shown in the above-mentioned embodiment, the developing roller is close to the photosensitive drum 1 which is an image bearing member, so that a magnetic field which is generally used conventionally is used. It is known that the cleaning performance is higher than that of the brush development method (two-component, magnetic one-component). By combining the contact one-component development and the contact transfer method as in this embodiment, an image is obtained in a cleanerless process. Good application can be performed without causing memory or fogging.

The image non-patterning member (brush) 2a temporarily adsorbs the transfer residual toner, and by further injecting an electric charge, the toner is re-adhered to the photoconductor 1, thereby performing non-patterning. In the embodiment, a DC bias having a polarity opposite to that of the toner is applied to the brush 2a. Brush 2
Many toners temporarily adsorbed (trapped) on a
It reattaches to the photoconductor drum 1, but one part cannot be reattached,
It is possible that the brush 2a gradually accumulates. Therefore, in the embodiment, the print start operation and / or the end operation and the operation of discharging the toner accumulated in the brush 2a when the machine power is turned on (discharge mode) are performed. In the ejection mode, a bias that positively ejects the accumulated toner may be applied. For example, it is also effective to apply a bias of -200 to -800v having a reverse polarity to the bias applied during the printing operation (normal mode), or to turn the bias ON / OFF in small steps (DC discharge). mode). However, even if such a measure is taken, when printing including a large amount of a portion having a high image density is repeatedly performed, toner is accumulated on the brush 2a and toner scattering occurs.

Therefore, when an AC bias is applied in the discharge mode, the toner that has considerably entered the depth of the brush 2a can be sufficiently discharged, and the toner brush 2a can be discharged.
No longer accumulated. As a proper AC bias,
Voltage is 300 ~ 700vrms, frequency 100 ~ 2kHz,
The superimposed DC component is +300 to -300v. Even if the above AC bias is applied in a printing mode other than the ejection mode, good patterning can be performed.

A continuous printing test was conducted using the image forming apparatus shown in FIG. 1 described above. As the printing chart, a chart having characters on the left half and a white background on the right half was used. As the paper, the A paper shown in Table 1 below was used.

[0045]

[Table 1]

This A sheet is made of 100% talc as a filler.
%, And the ash content is 7.3%. However, 20
When 0 sheets were printed, the fog in the white background portion on the right half surface increased and the image density also decreased from 1.4 to 1.2.
When the fogging on the drum was sampled by taping on the right half surface, 10% of the fogging on the drum occurred. The on-drum fog Fd is calculated by the following equation. The initial fog on the drum is
It was 1.6%. Fd = (reflectance when the tape is placed on a blank sheet)-(reflectance when the sample is placed on a blank sheet (1)

At this time, the transfer roller was contaminated with the fog toner and the back side of the sheet was stained. The charge amount Q of the toner layer formed on the developing roller at the start of the test was measured using an apparatus as shown in FIG.

The suction nozzle 200 shown in FIG.
02, and sucks the toner layer formed on the developing roller 10. When the toner is sucked, the mirror image charge of the toner flows from the developing roller to the ground, and thus the charge amount q is measured by the minute ammeter 201. Further, the toner charge amount Q is calculated by the following equation by measuring the weight difference Δm of the developing device before and after suction. Q = q / Δm (2) The initial toner charge amount according to this measuring method is −8.2 μc.
/ G.

However, the charge amount after the completion of 2k sheets is -7.6 on the left half surface of the roller (the half surface on which characters were printed).
On the other hand, the right half surface (the half surface on which the white background was printed) showed a remarkable decrease in charge amount of -4.7 μc / g. Further, when the toner inside the developing device was analyzed at the end of 2k sheets, paper powder was mixed, and when the surface of the roller was analyzed, adhesion of talc, which is a filler of paper, was found on the right half surface. This is because toner is not consumed at all on the right half surface, and a cleaning electric field is constantly generated, and paper dust is unilaterally collected, so that talc, which is a component of paper, adheres and accumulates on the roller. On the other hand, it is considered that the talc does not adhere to the roller so much because the left half surface consumes the toner.

Next, in order to confirm that the decrease in the charge amount is caused by the talc in the paper powder, the developing device is charged with about 0.
When 6 g of talc was mixed and image formation was performed, the fog on the drum was 40%, and the charge amount of the toner at this time was −0.5 μc / g. Therefore, when all the toner inside the developing device was discarded and new toner was replenished, the fog on the drum was reduced to 18.5% and the charge amount was −
Although it became 3.8 μc / g, it does not recover to the initial state. So, when I printed about 30 solid black images,
2.1% fog on the drum, -7.7 μc / g charge amount
It has returned to almost the initial state. In order to know the charge amount of this talc, the weight ratio to the acrylic resin coated carrier is 5
% With a ball mill and measured with a blow-off charge amount measuring device (manufactured by Toshiba Chemical), -30.
It showed a strong negative polarity of 0 μc / g.

From the above experimental results, talc, which is one component of the paper powder mixed in the developing device, contacts the toner inside the developing device or adheres to the developing roller to reduce the negative charge amount of the toner. It was found that fogging occurs by reducing the size or reversing the polarity.

In a cleanerless device such as the device used in this embodiment, the generated paper dust is inevitably collected in the developing device, and it is very difficult to prevent the mixture of paper dust. . Therefore, in order to know the amount of paper dust collected in the developing device, the developing device is removed in the apparatus of FIG. 1 , a blade cleaning device is arranged instead, 5000 sheets of blank paper are continuously passed, and the cleaner is collected. The amount of paper dust was measured. As a result, as shown in Table 2 below, about 600 mg of paper dust was recovered after passing 5000 sheets. Therefore, it is possible to considerably reduce the amount of paper dust by providing a paper dust removing roller before transfer and applying an AC bias to the transfer residual image disturbing member.

[0053]

[Table 2]

FIG . 6 is a graph showing the relationship between the amount of mixed paper dust, the toner charge amount, and the fog on the drum when the paper dust of the paper A is gradually added to the developing device (toner amount 40 g). . As is clear from this graph, when the amount of paper powder mixed exceeds approximately 200 mg, the toner charge amount decreases,
Fogging on the drum is increasing. Further, if the fogging on the drum exceeds 4%, the backside of the paper is stained. Therefore, as described above, even if the amount of paper dust is reduced by various measures, it cannot be said that it is a sufficient measure considering the life of the developing device is about 10 k sheets.

Similarly, when the relationship between the amount of mixed paper powder and the fog on the drum and the charge amount was examined for the paper C whose filler was calcium carbonate (CaCO ₂ ), the fog on the drum was increased even if the amount of paper powder mixed increased. 2000 is hardly seen, but 2000
When it was more than mg, lumpy fogging was observed. this is,
It is considered that the toner aggregation was caused with calcium carbonate as the nucleus. The charge amount gradually increased as the mixed amount increased, and suddenly decreased when the mixed amount increased above a certain level. Next, the filler is kaolin (Al ₂ O ₃ · 2SiO ₂ ·
A similar test was conducted on paper B which is 2H ₂ O). When it exceeds 800 mg, the fog similar to that of paper A occurs, and when the mixing amount increases, the charge amount decreases. is not. The characteristics of talc, kaolin and calcium carbonate as fillers are shown in Table 3 below.

[0056]

[Table 3]

Next, in order to select the filler for the paper, the charge amount of the resin having a simulated particle size of about 1 μm is about −30 to +40 μc /
g, various resins having a Mohs hardness of about 1 to 8 were prepared, and the resins were mixed in a developing device, and the developing device was rotated for about 30 seconds. Tested for the appearance of dirt. The resin charge amount is the same as that of the talc charge amount measurement.
The value of the charge amount measured by a blow-off charge amount measuring device after stirring for 0 minutes. When the charge amount of the toner used in this example is measured by this method, it is -16.0 μm.
It was c / g.

According to the above experiment, 600 mg for 5 k sheets
It is expected that a certain amount of paper dust will be mixed in, and if the life of the developing device is set to 10 k sheets, approximately 0.08 g of the filler will be mixed in the developing device.
The test was conducted by mixing 0.08 g of resin with respect to 0 g. FIG. 7 shows the relationship between the chargeability and hardness of the mixed resin, the charge amount of the toner layer formed on the developing roller, and the fog amount on the drum. From these results, the following can be seen. 1. As the charge amount of the resin is larger (-), the charge amount of the toner is lower and the fog on the drum is increased, and the backside of the paper is more likely to be stained.

2. Even if the chargeability of the resin is similar, the lower the hardness, the greater the influence of the chargeability of the resin on the toner charge amount. If the chargeability of the resin is negative,
The toner has a low charge amount, a large amount of fog on the drum, stains on the back of the paper occur, and the image density is low. On the other hand, if it is positively large, the toner charge amount becomes too high, and the image density decreases. This is because if the hardness is low, the toner sticks to the roller or blade, and the toner is often charged by the filler and friction.

3. If the charge amount of the resin is too large (+), the toner charge amount is not a big problem (although it is slightly low), but the fog on the drum is increased. This is caused by the aggregation of the (−) toner with the (+) resin as the nucleus. 4. If the hardness of the resin is too high, the photoconductor drum and the toner coating blade are scratched, and streaks occur in solid and halftone (occurs when the Mohs hardness is 7 or more).

Summarizing the above results, in the paper filler, the charge amount Qp satisfies the relationship between the charge amount (blow off value) Qt of the toner and the following formula (3) or (4), and the Mohs hardness is 2 If it is about 7 to 7, good printing can be performed without causing back stains, fogging, and halftone and solid scratches throughout life. When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (3) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (4) Further, the long life of the developing device If desired, it is desirable that Qt and Qp have opposite polarities.

Next, as a filler, kaolin (Al ₂ O ₃
・ 2SiO ₂ · 2H ₂ O), calcium bicarbonate (CaC
20 sheets with two sheets (sheet B, sheet C) using O ₂ ).
A running test of k sheets was performed. Kaolin has a Mohs hardness of 2.5 and a charge amount of -16.0 μc / g, and calcium bicarbonate has a Mohs hardness of 3.5 and a charge amount of +17.2 μc / g.

As the running chart, as in the case of the paper A, a character whose left half surface is a character and whose right half surface is a white background is used. 20
FIG. 8 shows changes in image density, fogging on the drum, and charge amount in the left and right halves during k printing.

On sheet C, the toner charge amount was maintained at 7.5 μc / g even after printing 20 k sheets, the image density was not reduced, the backside of the image was not generated, and the fog on the drum was 3.0%.
On the other hand, in the case of the paper B, the charge amount on the right half surface of the paper B was good up to 10 k, but the charge amount on the right half surface started to decrease from around 15 k sheets, and after printing 20 k sheets, the toner charge amount on the right half surface was 5%. 0.1 μc / g, and fog on the drum was 8.2.
%, The image density decreased by 1.15, and the back of the paper was stained.

If the formula (3) or (4) is satisfied, printing of approximately 10 to 15 k sheets can be generally endured. However, when the life is further extended, the charging polarity of the filler is opposite to that of the toner. More preferably, it is polar.

However, it is difficult to select one filler which satisfies the above characteristics, and when a filler having a high hardness is used, the paper manufacturing facility is easily damaged and the productivity becomes a problem. Therefore, we use high-hardness filler and low-hardness filler to prevent sticking of rollers and blades inside the developing device with high hardness filler, and to prevent paper manufacturability and damage to the photoconductor drum with soft filler. Thought to do. Further, in order not to impair the charging property of the developer when mixed in the developing device, at least one kind of filler should satisfy the charging property of the formula (3) or (4), and more desirably, the toner. It is desirable to have opposite charging properties.

In order to know what the ratio of the resin having a high hardness and the resin having a low hardness should be, the ratio of the hard resin and the soft resin is changed and mixed into the developing device by using the following four resins. Then, the charge amount and the fog on the drum were measured. (A) A blend of a resin having a hardness of 3.5 and a charge amount of +20.4 (μc / g) and a resin having a hardness of 1.5 and a charge amount of −25.7 (μc / g). (B) A blend of a resin having a hardness of 3.5 and a charge amount of −25.7 (μc / g) and a resin having a hardness of 1.5 and a charge amount of +20.4 (μc / g).

The particle size of the resin was about 1 μm, and the mixing amount was 0.08 g for the two resins in total. The test results are shown in FIG. From FIG. 9, it can be seen that the influence of the chargeability of the soft resin becomes stronger as the mixing amount of the soft resin increases. Therefore, if the soft resin has the (-) polarity, the charge amount decreases, the fog on the drum increases, and the image density also decreases as the soft ratio increases. The mixing ratio is 50:50 because
The mixing ratio of the softer resin should be low. On the other hand, when the polarity of the soft resin is (+), when the mixed amount increases, the soft resin adheres to the roller or blade (not to filming) and increases the toner charge amount. When the mixing ratio is 55:45 or more, the image density becomes 1.2 or less.

Therefore, the mixing ratio of the soft resin may be about 1: 1 or less. That is, it was found that when two kinds of fillers are used, the mixing ratio of the fillers having a soft Mohs hardness of 2 or less should be about 50% or less with respect to the entire amount of the filler. Further, if the content ratio of the filler of the hard resin is large, the photosensitive drum may be scratched and the life of the paper manufacturing facility may be shortened. Therefore, the mixing ratio of the soft filler should be 5% or more. I won't.

Next, the ash content, which represents the amount of filler in the paper, was examined. Paper F using calcium carbonate as a filler
Then, in a paper G in which calcium carbonate and talc are mixed by 50%, 1.2 g (corresponding to printing of 10 k sheets) of paper powder of paper in which ash content is changed to 2 to 18% is mixed into a developing device to The charge amount and the fog on the drum were measured (FIG. 7). In the case of paper F containing only calcium carbonate as a filler,
Even if the amount of filler is increased and the ash content becomes 18%, the charge amount does not change significantly, but the toner agglomerates due to calcium carbonate, which tends to be positively charged as the nucleus, and agglomerated fogging occurs, and the ash content becomes 16%. When it exceeds, the amount of fog on the drum exceeds 4%,
The back of the paper becomes dirty.

On the other hand, in the paper G in which talc and calcium carbonate are mixed, agglomerated fogging does not occur, but when the ash content exceeds 15%, the talc in the filler adheres to the developing roller and the toner charge amount is increased. And the fog on the drum exceeds 4%. Therefore, the ash content is about 15
If it is less than%, good printing can be performed without fog or stain on the back of the paper. If the ash content is 3% or less, problems such as opacity, smoothness, and manufacturability of the paper occur. Therefore, the ash content is 3 to 15%.

When corona transfer is used, the amount of paper dust generated is smaller than that in contact transfer, so the amount of paper dust (that is, filler) mixed in the developing device is small. Further, even if the fog toner is generated on the drum to some extent, unlike the contact transfer, the back surface of the paper is not stained. Therefore, it has chargeability that satisfies the above-described formula (3) or (4) and has a Mohs hardness of 2
With the papers containing the fillers of 7 to 7, good printing can be performed in a life test of 20 k sheets without fogging or reduction in image density. From these results, it is expected that the chargeability and hardness of the filler contribute to the reduction of the charge amount and the fogging on the drum. From these results, it is expected that the chargeability and hardness of the filler contribute to the reduction of the charge amount and the fogging on the drum.

From the above, two or more kinds of materials are used as the paper filler, and at least one of them has the charging characteristic satisfying the expression (3), and preferably has the charging property of the opposite polarity to the toner and has the charging property. Of these, at least one type has a Mohs hardness of 2 or less, and the mixing ratio of the fillers having a Mohs hardness of 2 or less may be 5 to 50% of the entire filler, and further, the ash content of the paper showing the total amount of the filler. May be 5 to 15%. By using the above-described paper in a cleanerless process printing apparatus, it is possible to perform good printing with an image density of 1.2 or more and without fog or stain on the back of the paper.

Although the contact one-component developing device is used as the developing cleaning device and the contact transfer is used as the transfer device as an example, the transfer device is a general transfer device such as a corona transfer device. The cleaning device may be
It may be a two-component, one-component magnetic brush developing device, a jumping developing device, or the like. Further, the invention is not limited to the cleanerless device using the developing and cleaning device, but can be widely applied to a device of a type in which toner is collected and returned into the developing device.

[0075]

As described above, according to the present invention,
In an image forming apparatus having a mechanism for recovering the developer remaining on the image carrier after transfer and returning the developer to the developing unit, a predetermined amount of developer that does not impair the charge of the developer even when contacted with the developer as a material to be transferred. Using a material containing a filler with charging characteristics, it is possible to obtain a good image without image density reduction, fog and stains on the back of the paper, and to extend the life of the device. It was

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus using a transfer material of the present invention.

FIG. 2 is a graph showing the characteristics of roller transfer.

FIG. 3 is a graph showing the characteristics of charger transfer.

FIG. 4 is a schematic view of a suction type toner charge amount measuring device.

5 is a view showing a suction nozzle forming a part of the apparatus shown in FIG.

FIG. 6 is a graph showing the relationship between the amount of mixed paper powder, the amount of toner charge, and the fog on the drum.

FIG. 7 is a graph showing the relationship between the blow-off charge amount of resin, the toner charge amount, and the fog on the drum.

FIG. 8: Papers with different fillers A. FIG. 5 is a graph showing the relationship among the number of printed sheets, the toner charge amount, the fog on the drum, and the image density when a life test is performed using B and C.

FIG. 9 is a graph showing the relationship between the mixing ratio of two kinds of resins having different hardnesses, which are used in a simulated manner, the toner charge amount, the fog on the drum, and the image density.

FIG. 10 is a graph showing the relationship between the amount of ash showing the content of filler, the toner charge amount, and the fog on the drum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Transfer residual toner non-patterning means, 3 ... Scorotron charger, 4 ... Laser device, 5 ... Development cleaning device, 6 ... Transfer roller, 7 ... Electrification means, 9 ... Hopper, 10 ... Development Roller, 11 ... Conductive surface layer, 12 ... Elastic layer, 15 ... Conveying roller, 16 ... Conveying path, 19 ... Paper feeding unit, 20 ... Paper feeding roller.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-162560 (JP, A) JP-A-61-67038 (JP, A) JP-A-3-62042 (JP, A) JP-A-3- 4283 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 7/00 G03G 15/08 G03G 21/10

Claims (4)

(57) [Claims] 1. An electrostatic latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for supplying a developer to the electrostatic latent image to visualize the electrostatic latent image. A transfer means for transferring the developer image formed on the image carrier to a transfer material, and a non-patterning means for unpatterning the developer remaining on the image carrier after the transfer. In an image forming apparatus having a mechanism for collecting the converted developer and returning it to the developing unit, a blow-off charge amount Qp of a filler and a blow-off charge amount Qt of a developer contained therein are used as the transfer target material. An image forming apparatus characterized in that a filler satisfying the following formula (1) or (2) and having a Mohs hardness of 2 to 7 is used. When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2) 2. An electrostatic latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for supplying a developer to the electrostatic latent image to visualize the electrostatic latent image. A transfer means for transferring the developer image formed on the image carrier to a transfer material, and a non-patterning means for unpatterning the developer remaining on the image carrier after the transfer. In an image forming apparatus having a mechanism for recovering the converted developer and returning it to the developing means, the transfer material contains a first filler and a second filler having different mohs hardnesses, Filler mode
The hardness of the second filler is 2 or less, and the hardness of the second filler is 2 to
7 and the blow-off charge amount Qp of at least one of the first and second fillers and the blow-off charge amount Qt of the developer satisfy the following formula (1) or (2): An image forming apparatus characterized by. When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2) 3. An electrostatic latent image forming step of forming an electrostatic latent image on an image carrier, and a developing step of supplying a developer to the electrostatic latent image to visualize the electrostatic latent image. A transfer step of transferring the developer image formed on the image carrier to a transfer material, and a non-patterning step of un-patterning the developer remaining on the image carrier after the transfer, In the image forming method in which the converted developer is recovered and returned to the developing unit, the blow-off charge amount Qp of the filler and the blow-off charge amount Qt of the developer contained in the transfer target material are expressed by the following formula. An image forming method characterized by using (1) or (2) and using a filler having a Mohs hardness of 2 to 7. When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2) 4. An electrostatic latent image forming step of forming an electrostatic latent image on an image carrier, and a developing step of supplying a developer to the electrostatic latent image to visualize the electrostatic latent image. A transfer step of transferring the developer image formed on the image carrier to a transfer material, and a non-patterning step of un-patterning the developer remaining on the image carrier after the transfer, In the image forming apparatus in which the solidified developer is collected and returned to the developing means, the first material having different mohs hardness is used as the material to be transferred.
And the second filler, wherein the first filler has a hardness of 2 or less, the second filler has a hardness of 2 to 7, and the first and second fillers An image forming method characterized in that at least one of a filler blow-off charge amount Qp and a developer blow-off charge amount Qt satisfies the following formula (1) or (2). When Qt is negative Qp ≧ Qt and | Qp | ≦ 2 × | Qt | (1) When Qt is positive Qp ≦ Qt and | Qp | ≦ 2 × | Qt | (2)