JPH0815987A - Developing method and device for development - Google Patents

Abstract

PURPOSE:To reproduce an excellent image quality equal to or superior to the printing and the photographing, and to surely avoid the reduction of a development density and the transfer defect while effectively preventing the toner cloud from occurring, in the type adopting two component developer. CONSTITUTION:At the time of adopting the toner of <=6mum particle size, the static charge condition of the toner satisfies the next equation, y<=-3.5x+34.5 (where the mark (y) indicates the absolute value of the developing toner charge amount per unit area, and (x) indicates the transferring frequency). Moreover, with regard to the type provided with a developer peeling means 9 on the downstream side of the development opening 5 of a developer carrier 6, the developer G layer deposited on the surface of developer carrier 6 is normally held in contact with inner wall of the developing housing 4 or the wall surface of the mounting member 10 in the developing housing over the entire area on the shaft direction of the developer carrier 6 on the upstream side and the downstream side of the development opening 5 of the developer carrier 6. Then, with regard to the type not provided with the developer peeling means 9, the change of the developer G is accelerated by the forcedly pressing means 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for developing a latent image formed by an electrophotographic method or an electrostatic recording method and its apparatus, and more particularly to a developing method using a two-component developer and its development method. Regarding the improvement of the device.

[0002]

2. Description of the Related Art Generally, in an image forming method such as an electrophotographic method or an electrostatic recording method, for example, a two-component developer is used to attach toner to an electrostatic latent image on a latent image carrier to make it visible. The method is adopted. In this type of developing method, not only the density but also the electrostatic latent image must be faithfully developed in order to obtain an image of high quality which is true to the original, but high image quality can be obtained by reducing the toner particles. It is well known (for example, JP-A-58-184156).
No. JP-A-58-184157).

In our investigation, the relationship between the toner particle size and the character reproducibility (grade) was investigated by using the screen ruling as a parameter, and FIG. 21 (in the figure, lpi is lines)
22 is obtained, and the relationship between the screen ruling and the character reproducibility (grade) is examined by using the toner particle size as a parameter.
The result is as follows (however, the carrier has a particle size of 20μ
However, the toner particle size is about 6 μm or less, and an analog image or 350
It was found to be a digital image of pixel / inch or more.

[0004]

However, in the two-component development, when the toner particle size is reduced, a toner cloud is likely to occur, and when the toner charge amount is increased to prevent it, a desired development density cannot be obtained. Was found. In addition, especially when performing multiple transfer as in a color image forming apparatus, if the toner charge amount is increased in order to prevent the toner cloud of small particle size toner, transfer failure is likely to occur, and in order to prevent it, the transfer voltage or transfer current value is increased. It has been found that a large value causes a transfer voltage or transfer current generating member to generate a spark discharge from a surrounding metal component or a transfer failure due to a discharge generation in a transfer nip region.

According to the present invention, in a type using a two-component developer, high-quality image quality equal to or higher than that of printing or photography is reproduced, and generation of toner cloud is effectively suppressed, while lowering development density and transfer failure. An object of the present invention is to provide a highly reliable developing method and an apparatus thereof that can be reliably avoided.

[0006]

First, in the developing method according to the first aspect of the present invention, as shown in FIGS. 1A and 2, single-color or multi-color toners are used on the latent image carrier 1. Electrostatic latent image Z
A developing device 3 used in an image forming method in which the developed toner image TZ is electrostatically transferred or sequentially multi-transferred onto the transfer medium 2 after developing the latent image carrier of the developing housing 4. 1 is provided with a developing opening 5 and a developing agent carrier 6 in which a magnet member 8 is fixedly installed in a rotatable non-magnetic sleeve 7 is provided at a portion facing the developing opening 5. With the two-component developer G carried on the surface of the developer carrying body 6, the latent image carrying body 1 is passed through the developing opening 5.
In addition to developing the electrostatic latent image above, at least a pair of adjacent magnetic poles (repulsive magnetic poles) of the same polarity (repulsive magnetic poles), scraper, and other developer peeling means 9 are provided on the downstream side of the developing opening 5 of the developer carrier 6. Assuming a developing device, a toner having an average particle size of 6 μm or less is used, and a toner charging condition is y ≦ −3.5x + 3.
4.5 (however, y: absolute value of developing toner charge amount per unit area, x: number of times of transfer) is satisfied, and the developer is provided in the upstream and downstream regions of the developing opening 5 of the developer carrier 6. The developer G layer carried on the surface of the carrier 6 is always in contact with the inner wall of the developing housing 4 or the wall surface of the mounting member 10 in the developing housing over the entire axial direction of the developer carrier 6. To do.

The developing method according to the second invention of the present application is
As shown in FIGS. 1B and 2, after the electrostatic latent image Z on the latent image carrier 1 is developed by using monochromatic or plural-color toners, the developed toner image TZ is transferred onto the transfer medium 2. A developing device 3 used in an image forming method in which electrostatic transfer or sequential multiple transfer is performed, and a developing opening 5 is opened in a portion of a developing housing 4 facing a latent image carrier 1 and the developing opening 5 is formed. A developer carrier 6 having a magnet member 8 fixedly installed in a rotatable non-magnetic sleeve 7 is provided at a portion facing the opening 5 for use, and the magnet member 8 has an even number of magnetic poles 8a and 8b of different polarities.
And a two-component developer G carried on the surface of the developer carrier 6 to develop the electrostatic latent image on the latent image carrier 1 through the developing opening 5. Assuming an apparatus, a toner having an average particle size of 6 μm or less is used, and the toner charging condition is y ≦ −3.5x + 34.5 (however,
y: absolute value of developing toner charge amount per unit area, x:
The number of transfers is satisfied.

The developing method according to the present invention is applicable to both contact development and non-contact development. Further, although only the DC bias may be used as the developing bias, from the viewpoint of further improving the developing property, it is preferable to apply an AC bias of DC superimposition, and the voltage waveform of the AC bias is a rectangular wave, a sine wave, Triangular wave, sawtooth wave, etc. may be selected appropriately.

In the invention of an apparatus that embodies such a developing method, it is preferable to make various innovations as described below. For example, the inner wall of the developing housing 4 or the mounting member 10 in the developing housing 4 is made of a magnetic material, and the magnetic poles 8 are provided inside the developer carrying member 6 facing in the vicinity thereof.
a and 8b are arranged, the two-component developer G is filled along the magnetic field formed in the gap between the magnetic body and the magnetic poles 8a and 8b, and the airtightness (shield) of the gap is kept good. By designing as described above, it is possible to further enhance the sealing effect of the toner cloud.

A seal for preventing the developer G from leaking from the gap between the developer carrier 6 and the developing housing 4 at a position corresponding to a region where the developer G layer does not exist at the end of the developer carrier 6. By providing the means, it is possible to enhance the sealing effect of the toner cloud at the end portion of the developer carrying member 6. As the sealing means, for example, the inner wall of the developing housing 4 made of a magnetic material facing the magnetic poles 8a and 8b in the developer carrying body 6 or the mounting member 10 in the developing housing 4 may be the developer G layer of the developer carrying body 6. It is extended to a non-existing region so that the shield region of the developer G is expanded to the outside of the developer existing region, or the developer carrier in the region where the developer G layer at the end of the developer carrier 6 does not exist. An example is one in which an elastic body that is in contact with the developer carrying body 6 or a magnetic body that is not in contact with the developer carrying body 6 is provided on the outer periphery of the roller 6.

Further, in the apparatus invention embodying the developing method of FIG. 1 (b), from the viewpoint of improving the exchangeability of the developer G, the developer G is provided at a position close to the developer carrying member 6. It is preferable to provide a forced pressing means 11 that is strongly pressed against the developer carrying member 6 and is forcibly partly replaced with the developer G carried on the developer carrying member 6.

Furthermore, a carrier having an average particle diameter of 45 μm or less is used, a bias voltage containing an alternating component is applied between the developer carrying member 6 and the latent image carrying member 1, and the frequency f of the alternating voltage is applied. Is set to satisfy 6,000 ≦ f (Hz), thereby widening the allowable range of the toner of 6 μm or less in the environment and eliminating the toner adhesion (fogging) to the non-image area, and By increasing the developing efficiency, the toner can be used with a relatively high toner charge amount even within the limit of ³⁰ μC / cm ³ or less, and it is possible to improve the graininess and enhance the safety of the ner cloud.

The relationship between the developing gap, which is the distance between the latent image carrier 1 and the developer carrier 6, and the peak-to-peak voltage of the alternating voltage is 2.0 × 10 ⁶ V / m ≦ peak-to-peak voltage / developing gap. ≤
If it is set to 5.0 × 10 ⁶ V / m, it will peak under the above-mentioned conditions (carrier having an average particle diameter of 45 μm, frequency f of alternating voltage of developing bias is 6,000 ≦ f (Hz)). Since the inter-voltage / developing gap is 2.0 × 10 ⁶ V / m or more, the developing efficiency is improved, and the toner can be used with a relatively high toner charge amount even within the control of ³⁰ μC / cm ³ or less, and the graininess is improved. It is possible to improve and improve the safety of the toner cloud. On the other hand, when the peak-to-peak voltage / developing gap is 5.0 × 10 ⁶ V / m or less, discharge in the developing gap can be prevented and a good developing state can be maintained.

If a carrier having a volume resistivity of 10 ¹⁰ Ωcm or less is used, the toner can be used with a relatively high toner charge amount even within the limit of y determined by the transfer performance, and the graininess is improved. It is possible to improve the safety of the toner cloud.

When a digital latent image having a line number of 350 pixels / inch or more is targeted for development, it is possible to achieve both line reproducibility and graininess in an image using toner of 6 μm or less.

In a device such as a laser for writing an electrostatic latent image on a latent image carrier 1 charged by a light beam, if the beam diameter is 60 μm or less, the number of lines is 350 pi.
It is possible to further improve the graininess in an image of xel / inch or more.

[0017]

In the technical means as described above, FIG.
According to the developing method shown in (a), first, the average particle size is 6 μm.
By using a toner of m or less, high-quality image quality equal to or higher than that of printing or photography is realized. And y ≦ −3.5
By satisfying x + 34.5 (where y is the absolute value of the developing toner charge amount per unit area, and x is the number of times of transfer), stable transfer performance of toners of a plurality of colors is secured. That is, when multiple color toners are transferred in a multiple manner, the subsequent toner will not be sufficiently transferred and a transfer failure will occur unless a transfer current sufficient to overcome the charge of the previously transferred toner is passed to the transfer portion. Therefore, y should be as low as possible. If it exceeds the above range, the transfer current value or voltage must be increased to the extent that there is a risk of spark discharge in the machine body or transfer failure due to discharge in the transfer nip area occurs. , Stable transfer performance cannot be obtained.

Further, q / d for toner of 6 μm or less
(Q: toner charge amount (fc: femto [10 ^-15 ] coulomb), d: toner particle size (μm)) is 0.5 fc / μ
When it is less than m, a toner cloud is generated. This is because the image quantity of the toner and the carrier is weakened by the decrease of the charge amount of the toner, and the toner cloud is easily generated, but the inner wall of the developing housing 4 or the member 10 attached to the inner wall of the developing housing 4 is easily generated. Since the developer G layer and the developer G layer are constantly in contact with each other over the entire area in the rotation axis direction of the developer carrier 6, the gap between the developer carrier 6 and the developing housing 4 should be filled with the developer. Therefore, even if a toner cloud is generated in the developing housing 4, the toner cloud is confined in the developing housing 4 by the filled developer G and hardly leaks to the outside from the gap portion.

Further, in the developing method shown in FIG. 1 (b), a toner having an average particle diameter of 6 μm or less is used and the toner charging condition is y ≦ −3.5x + 34.5 (where y:
The action relating to satisfying the absolute value of the developing toner charge amount per unit area, x: the number of times of transfer is similar to the developing method shown in FIG. 1A, but different from the developing method shown in FIG. Since the developing device adopting this developing method has a structure in which the magnetic members 8 in the developer carrying member 6 are alternately arranged with the magnetic poles 8a and 8b having an even number of different polarities, the developer carrying device is originally carried. The developer G is less likely to be peeled from the body 6, and the generation of the toner cloud itself is suppressed. However, when the forced pressing means 11 is provided, a toner cloud is likely to occur, so it is preferable to mount the mounting member 10.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described below with reference to the drawings. However, the dimensions, characteristics, and other parameters of the components described in this embodiment do not limit the present invention unless otherwise specified. Example 1 An example of an electrophotographic color image forming apparatus to which the present invention is applied is shown in FIG. In the figure, reference numeral 21 is a photosensitive drum as a latent image carrier that rotates in the a direction, and 22
Is a charger that charges the photosensitive drum 21, 23 is an exposure unit such as a laser scanning unit that forms an electrostatic latent image on the charged photosensitive drum 21, and 24-27 are, for example, cyan, magenta, yellow, and black toners. Is a two-component magnetic brush developing device in which each of the developing devices 24 to 27 is housed.
Is rotatively moved by a rotary system and is selectively set at a developing position for each color image forming cycle.

Reference numeral 28 denotes a transfer drum which rolls in contact with the photosensitive drum 21, and the transfer drum 28 is provided at a portion of the transfer drum 28 facing the contact portion with the photosensitive drum 21.
81 is provided, and a charge is applied to the film 282 for forming the drum surface of the transfer drum 28 by this corotron 281, and the toner image on the photosensitive drum 21 is transferred to the recording paper 29 held on the transfer drum 28 by this transfer electric field. It is what makes me. Reference numeral 30 is a pre-transfer charger that adjusts the charging potential of the toner image on the photosensitive drum 21.

Then, the recording paper 29 is wound and held on the transfer drum 28 from the paper feeding unit 31 through the conveying device 32, and after repeating the transfer process of each color toner,
The toner image is sent to the carrying device 33, and the toner image is fixed by the fixing device 34, and then discharged to the discharge tray 35. Also, reference numeral 36
Is a blade cleaning type cleaner for removing the toner remaining on the photosensitive drum 21.

In the image forming process of the color image forming apparatus according to this embodiment, the photosensitive drum 21 is rotated for each color image forming cycle, and the photosensitive drum 21 is wound around the transfer drum 28 while being repeatedly charged, exposed, developed and transferred. The toner images of respective colors are sequentially transferred onto the recording paper 29, and the unfixed toner image on the recording paper 29 is fixed by the fixing device 34, and then the recording paper 29 is ejected.

Next, the developing devices 24 to 27 used in the color image forming apparatus according to this embodiment will be described in detail with reference to FIG. Since the developing devices 24 to 27 have the same basic configuration, the developing device 24 will be described below as an example. In the figure, the developing device 24 includes a developing opening 42 at a portion of the developing housing 41 facing the photosensitive drum 21.
Is provided, and the developing roll 43 is disposed at a portion facing the developing opening 42. In the developing roller 43 in this embodiment, a magnet roller 45 is fixedly installed in a rotatable non-magnetic developing sleeve 44. The magnet roller 45 is provided with magnetic poles 451 to 455, and at least the developing roller 43 is developed. The adjacent magnetic poles 452 and 453 located on the downstream side of the use opening 42 have the same pole (N in this embodiment).
The remaining three magnetic poles 451, 454, 455 have different polarities from the adjacent magnetic poles.

Then, around the developing roll 43, the two-component developer G in which the toner 46 and the carrier 47 are mixed becomes a magnetic brush by the magnetic force of the developing roll 43, and is conveyed along the developing sleeve 44 rotating in the direction of arrow b. To be done.
The magnetic brush rubs and develops the electrostatic latent image previously formed on the photosensitive drum 21 in the developing opening 42 of the developing housing 41.

Then, the developer G, which has been developed, is conveyed further downstream in accordance with the rotation of the rotating developing sleeve 44. At this time, since the magnetic poles 452 and 453 of the magnet roll 45 have the same polarity, the magnetic absorption force between the magnetic poles 452 and 453 is zero or weak, so that the developer G separates from the developing roll 43, and the pair of screw augers. It is conveyed and stirred by 48. The pair of screw augers 48 are arranged along the axial direction of the developing roll 43 at the front and rear positions of the developing housing 41, and convey the developer G in mutually opposite directions, during which toner is replenished from the toner replenishing port 411. The developer G is transferred through the opening at the end of the partition wall 49.

Further, the magnetic pole 453 of the magnet roll 45
New developer G is sucked into the area, and the developing sleeve 44
While the developer G made of a magnetic brush is conveyed in accordance with the rotation of, the trimming bar 50 regulates the developer G layer made of a magnetic brush to a constant thickness. A bias power source 51 supplies a DC superimposed AC bias voltage to the developing roll 43.

In such a developing device 24, in this embodiment, both the toner 46 of the developer G and the carrier 47 having different average particle diameters were used. Toners 46 having different average particle diameters were prepared by kneading, changing the conditions of pulverization and sizing, and applying an appropriate external additive. On the other hand, the carrier 47 is
After sintering, a suitable coating agent was applied and sieved to prepare. Further, the moving speed of the photosensitive drum 21 is set to 160 mm / sec, and the developing sleeve 44 is moved in the same direction as the photosensitive drum 21 by 33 mm.
It was rotated at 6 mm / sec. In addition, the bias power source 41
Of the direct current component of -500V and the amplitude value of the alternating current component of 0 to 3.
0KV (Peak to Peak), frequency 1 to 20
Experiments were conducted at KHz.

First, the carrier coating agent, the average particle diameter of the toner, the toner concentration, and the development potential contrast were changed, and development and multiple transfer were performed by the above method. The toner density is properly adjusted so that the image density becomes 1.2 or more and the fog does not occur by combining the toners of different particle diameters with only the DC development bias, and the development bias is set to Vp-p (Pea).
k to Peak voltage) = 1.2 KV and the DC component was changed to −500 V to change the frequency. As shown in FIG. 5, fog occurred on the low frequency side, and the degree of fog decreased as the frequency increased. It became. The smaller the toner particle size, the higher the frequency at which fog does not occur, but the fog does not occur at about 6 KHz or higher.

Further, the frequency of the alternating developing bias is 6 KHz.
In each case, the image density was higher than the DC developing bias alone by 30% or more. Also, at this time, 3 to 10 at the same time
A line / mm printed original was copied, and the copy image and the printed original and the photographic image of the printed original were compared with the naked eye. It was confirmed to be comparable, but it was confirmed that the toner of 7 μm or larger is inferior.

Next, these developers were left to stand for a day and night in an environment of high temperature and high humidity (30 ° C., 82% RH) and low temperature and low humidity (9 ° C., 27% RH), respectively. When copying was performed by adjusting the toner density so as to maintain the same image density as above in each combination by the developing bias, the combination of the toner of 6 μm or less and the carrier of 60 μm caused fog under low temperature and low humidity conditions. Then, the same experiment was carried out using a carrier of 45 μm, and fog occurred in the toner of 2.5 μm or less. still,
With the 1.5 μm toner, fog occurred at low temperature and low humidity under all conditions. This is because the amount of toner that can be held on the carrier surface is small with the combination of a carrier with a relatively large particle size and a toner with a small particle size, and the absolute amount of toner that contributes to development is insufficient, so keep a certain image density. It is assumed that when toner is added to the toner, the amount of toner that cannot be contacted with the surface of the carrier and is not charged increases, resulting in fog. This depends on the charging characteristics of the toner and the carrier, and although it cannot be said in a general sense, the toner particle size is approximately 10
It is desirable to use a carrier having a particle size equal to or less than twice the particle size.

Further, when the developing gap is varied between 0.2 and 0.6 mm and the AC developing bias Vp-p is varied between 0 and 3.0 KV, approximately [Vp-p / developing gap] is 5.0 ×. 10 ⁶
At V / m, dielectric breakdown occurred at high temperature and high humidity, causing image quality defects. Further, when [Vp-p / developing gap] is less than 2.0 × 10 ⁶ V / m, the developing density decreases,
The image quality has deteriorated. The result is shown in FIG.

Next, after changing the coating amount of the 45 and 20 μm carrier and measuring the resistivity, the developing gap was set to 0.4 m.
m, AC development bias Vp-p = 1.2 KV, and frequency = 6 KHz. At this time, 1V / μm
When the carrier resistance was 10 ¹⁰ Ωcm or more, an image defect occurred at the rear end of the halftone solid patch, but the carrier resistance was 10 ¹⁰
Below Ωcm, the degree was significantly improved. This is shown in FIG.

At normal temperature and humidity (20 ° C, 50% RH)
Under the environmental conditions close to, the frequency of the AC developing bias was shaken using several combinations of the toner particle size and the carrier particle size to copy the digital electrostatic latent image of 200 pixels / inch. When the graininess in all gradation regions was measured and the respective peak values were compared, the graininess was good for toner of 6 μm or less at a developing bias frequency of 6 KHz or higher, but the best graininess for frequencies of 8 KHz or higher. was gotten. Therefore, when the frequency of the AC developing bias was fixed to 9 KHz, the optical system was replaced and the laser beam diameter was set to 65 μm and the electrostatic latent image was shaken at 100 to 800 pixels / inch, the toner of 6 μm or less was 200 pixels.
Good graininess was obtained at 1 / inch or more. At the same time, when the laser beam diameter was swung at 30 to 130 μm, good graininess was obtained at 70 μm or less for toner of 6 μm or less. These results are shown in FIGS. 8 and 9, respectively.

Here, using toner having an average particle diameter of about 9 μm and about 5 μm and a ferrite carrier having an average particle diameter of 45 μm, the cycle of development and transfer is repeated in the order of yellow, magenta, and cyan, and on the film 282 of the transfer drum 28. The toner images of three colors were superposed on the recording paper 29 in FIG. At that time, the toner charge amount was changed by changing the toner concentration and a part of the carrier coating agent, and further, the developing potential condition was changed to change the toner development amount M per unit area. FIG. 10 is a plot of transfer current value conditions where the transfer rate is 85% or more and there is no transfer unevenness in image quality. Incidentally, the recording paper 29 conveys A3 plain paper in a vertical feed, the transfer drum 28 gives an electric charge from the inside of the film 282 by the corotron 281, and the shield current of the corotron 281 is fed back to the power source to obtain a net transfer current value. I monitored.

As a result, when the weight of the developing toner is large, the toner charge amount is large, and the number of times of multiple transfer is increased, the transfer current value must be increased, but when the transfer current value exceeds 40 μA. The risk of generating discharge marks (white spots in the image due to discharge) increases.

The results are summarized in FIG. It can be seen that it is necessary that y ≦ −3.5x + 34.5, where x is the number of transfers and y is the amount of developing toner charge per unit area. y was calculated by (q / m) × M.
However, q is the charge amount of the toner, m is the weight of the toner, and M is the toner development amount per unit volume. Although q / m is determined by a known method such as a charge spectrograph method or a blow-off method, the charge spectrograph method is used in this example. That is, q / d is obtained by image analysis from the charge spectrograph method (RBLewis, EWConnors, RFKoehler: Journal of the Electrophotographic Society, 22 (1), 85 (1983)), and the calculation formula q / m = q / ρV = q / {(4/3) ・ π
(D / 2) ³ ρ} = 6q / πd ³ ρ, the toner specific charge q /
m was calculated. Here, d is the toner particle diameter (diameter), ρ is the specific gravity of the toner, and V is the toner volume. At this time, the charge spectrograph is calibrated by applying a part of the toner developed on the metal piece to the charge spectrograph and blowing off the rest with an air gun, and obtaining q / m from the charge amount and weight change of the metal piece before and after that. , The parameters of the charge spectrograph were adjusted so that they would match.
A KEITHLEY electrometer 617 was used for measuring the amount of charge, and a zartorius R180D was used for measuring the weight.

A smaller amount of developing toner is more advantageous for transfer, but if it is excessively small, unevenness becomes noticeable after fixing and the image quality is degraded. This changes depending on the gloss after fixing, but if the surface of the toner image is smoothed so as to obtain the transparency required for the OHP sheet, a high gloss image is inevitably obtained even on plain paper. At this time, the weight of the developing toner needs to be approximately 0.6 mg / cm ² or more for the toner having a specific gravity of 1. Therefore, the limit of the toner charge amount that can be transferred is determined according to the number of times of transfer. On the other hand, the toner charge amount is q / d (q: toner charge amount, d: toner particle size) ≦ as a condition for suppressing the toner cloud generated from the developing device.
0.45fc / μm, q / v∞q / d
^Since it becomes ³ , the range of electric charges that can be used becomes narrower as the toner has a smaller particle diameter. Therefore, when the location where the toner cloud is mainly generated is examined, the repulsion magnetic pole 45 of the same pole in FIG.
It was found that the developer G was a portion separated from the developing roll 43 between 2 and 453.

However, in this embodiment, the size of the gap between the portion of the developing roller 43 closer to the developing opening 42 than the repulsive magnetic pole 452 and the lower portion of the developing housing 41 is such that the developer G conveyed as the developing sleeve 44 rotates. Since the thickness is set to be slightly smaller than the layer thickness, the developer G is constantly filled in the gap between the portion of the developing roll 43 and the lower portion of the developing housing 41.
Even if the toner cloud is generated at the repulsion magnetic poles 452 and 453, the toner cloud is blocked by the wall of the developer G, and the situation that the toner cloud leaks to the outside from the developing opening 42 is suppressed to some extent.

Further, in this embodiment, when an existing developing device is used, the portion of the developing roller 43 closer to the developing opening 42 than the repulsive magnetic pole 452 and the developing housing 4 are used.
It is possible that the size of the gap with the lower part of 1 is originally wider than the layer thickness of the developer G conveyed by the rotation of the developing sleeve 44. In such a case, for example, as shown in FIG. Further, a spacer member 61 for gap adjustment is provided in the lower portion of the developing housing 41, which faces the developing opening 42 side portion from the repelling magnetic pole 452 of the developing roll 43, and the developer is interposed between the spacer member 61 and the developing roll 43. It suffices to secure a gap that is slightly narrower than the layer thickness of G.

Example 2 The developing device according to this example has a basic structure similar to that of Example 1 as shown in FIG. 13, but unlike Example 1, the repelling magnetic pole of the developing roll 43 is different. A long magnetic plate 7 made of, for example, iron is provided on the lower portion of the developing housing 41 facing the 452.
1 is provided along the axial direction of the developing roll 43. According to this embodiment, the repulsion magnetic pole 452 and the magnetic plate 71 are
Since a magnetic field is formed between the developer G and the developer G, the developer G is arranged along the magnetic field and a curtain is formed by the developer G, and the amount of the toner cloud leaking to the outside is drastically reduced. In particular, in the first embodiment, when the inner wall of the developing housing 41 or the gap between the spacer member 61 and the developing roll 43 is set to be rough, the inner wall of the developing housing 41 or the spacer member 61 is made to have the developer G on the developing roll 43. It is difficult to bring the developer G into proper contact with the layer, sometimes it is separated from the developer G layer, and sometimes too close to the developing roll 43 to block the flow of the developer G and cause the developer G to overflow from the developing device. Therefore, it is necessary to set the gap between the inner wall of the developing housing 41 or the spacer member 61 and the developing roll 43 with a certain degree of accuracy. In this embodiment, the developing roll 43 and the magnetic plate 71 are used. Since it is possible to roughly set the gap dimension between and, the manufacturing becomes simple.

In this embodiment, the magnetic plate 71 may have a length corresponding to the peripheral surface of the roll body 431 of the developing roll 43, as shown in FIG. Since a part of the toner cloud was found at the end of the developing roll 43 that was off the roll body 431,
As shown in FIG. 14B, the magnetic plate 7 having a length dimension from the roll body 431 of the developing roll 43 to the end portion thereof.
If 2 is provided, the toner cloud generated from the end portion of the developing roll 43 is also effectively suppressed.

Further, in this embodiment, FIG.
As shown in (b), the roll body 431 of the developing roll 43.
It is preferable to provide the seal member 73 around the end of the. The seal member 73 used in this embodiment is, for example, a semi-ring-shaped magnetic body that is in non-contact with the roll body 431 that surrounds at least the toner cloud generating portion side of the periphery of the end portion of the roll body 431. A magnetic field is formed between the end peripheral surface and the seal member 73, and the developing roll 43
It is designed to contain the toner cloud generated at the edge of the. The seal member 73 may be an elastic member that makes elastic contact with the peripheral surface of the end portion of the roll body 431, but it is preferable to use a magnetic material like in terms of durability.

In this embodiment, for example, the magnetic plate 72,
For the magnetic material as the seal member 73 and the developing device in which the magnetic material is added to the trimming bar 50 to further enhance the sealing effect, a carrier having an average particle diameter of about 45 μm is used, and the toner particle diameter is changed to measure the toner cloud amount. Was done.
As a comparative example, a developing device of a conventional type (having a developing roll having a magnetic pole arrangement as shown in FIG. 4 and having a gap between the developer located downstream of the opening of the developing device and the developing housing) is used. Was used. At this time, the toner cloud amount is determined by the opening portion (developing opening 42) of the developing device while copying 100 sheets of JISA3 size recording paper.
The toner flowing out from the developing roll 43 at the opening of the developing device
Received by trays provided on the upstream side and the downstream side in the traveling direction,
It was determined by performing the overlay measurement. The result is shown in FIG.

According to the figure, in this embodiment, q / d at which the toner cloud amount rises (q: toner charge amount, d: toner particle size) can be significantly reduced as compared with the comparative example. Be understood.

FIG. 17 shows both the limit of the toner charge amount that can be transferred according to the number of transfers and the limit determined from the viewpoint of toner cloud suppression. The upper limit of q / v (q: toner charge amount, v: toner volume) is determined by the number of transfers, and q / d (q: toner charge amount, d: lower limit of toner particle size is determined by toner cloud suppression. The developing device according to No. 2 had almost no latitude for toner of 6 μm, and there was no latitude for toner of 5 μm or less.However, by using the developing device of this embodiment, the latitude was expanded to about 2 to 2.
Up to about 2.5 μm toner can be used.

[Embodiment 3] FIG. 18 shows Embodiment 3 of the developing device to which the present invention is applied. In addition, regarding the same constituent members as those in the first embodiment,
The same reference numerals are given and detailed description thereof is omitted here. In the drawing, in the developing device according to this embodiment, assuming that the toner particle size (6 μm or less) and toner charging conditions (transfer count x and developer toner charge amount per unit area y) are substantially the same as in Embodiments 1 and 2. , Y ≦ −3.5x + 34.5), but has a magnet roll 83 different from those of the first and second embodiments. The magnet roll 85 includes magnetic poles 851 to 854 having different polarities (S, N, S, N in this embodiment).
Order) is an even number. Therefore, according to this embodiment, it is possible to obtain substantially the same high-quality developability as in Embodiments 1 and 2, and since the repulsive magnetic poles of the same polarity are not provided adjacent to each other, the toner in that portion is not provided. The cloud itself does not occur, and even if the gap between the developing roll 43 and the inner wall of the developing housing 41 or the spacer member 61 is set larger than the developer G layer thickness as shown in the first embodiment, the developing device It was confirmed that the toner cloud leaking from the opening of the was drastically reduced. However, it is needless to say that it is preferable to adopt the seal structure for the toner cloud as in the second embodiment.

On the other hand, in this embodiment, since the existing developer G on the developing roll 43 is not peeled off, it is difficult to replace the developer. For this reason, in this embodiment, the screw auger 48 for circulating the developer (at least the screw auger near the developing roll 43) is disposed close to the developing roll 43, and the screw auger 48 moves toward the developing roll 43 side. The supply force of the developer G is increased so that the developer G is replaced on the developing roll 43 when the developer G is supplied. Also, screw auger 4
Since 8 is disposed near the developing roll 43, it is possible to reduce the space under the developing roll 43.
As a result, the space occupied by the developing housing 41 becomes compact.

Example 4 FIG. 19 shows Example 4 of the developing device to which the present invention is applied. The same components as those in Example 3 are used in Example 3
The same reference numerals are given and detailed description thereof is omitted here. In the drawing, the basic structure of the developing device according to the present embodiment is substantially the same as that of the third embodiment, but further upstream of the trimming bar 50 with respect to the moving direction of the surface of the developing roll 43 inside the developing housing 41. And a long pressing member 90 having an angle that presses the developer G toward the developing roll 43 side as the developer G is conveyed by the magnetic force of the magnetic pole inside the developing roll 43. is there.
Therefore, according to this embodiment, in addition to the operation substantially similar to that of the third embodiment, the presence of the pressing member 90 causes
Replacement of the developer G on the developing roll 43 is promoted, and long-term stability of developing performance is ensured. To confirm this, when the relationship between the number of copies and the solid density depending on the presence or absence of the pressing member 90 is examined, the result as shown in FIG. 20 is obtained, and the pressing member 90 ensures the long-term stability of the developing performance. It is understood that it has an effect on the

The pressing member 90 is the trimming bar 5
It is preferable to have a gap away from 0 and allowing the developer G returned from the trimming bar 50 to escape. Also in this embodiment, it is needless to say that it is preferable to adopt the seal structure for the toner cloud as in the second embodiment.

In this embodiment, a carrier having an average particle diameter of about 45 μm was used in a developing device having a seal structure for the toner cloud, and the toner particle diameter was changed to measure the toner cloud amount as in the second embodiment. As a result, substantially the same result as in FIG. 16 was obtained. Furthermore, q / v,
When the relationship between q / d and the toner particle size was examined, the results similar to those in FIG. 17 were obtained.

[0052]

As described above, according to the present invention, a toner of 6 μm or less can be used, which not only improves the character quality, but also improves the image density and the fog even in such a small particle size toner. It was possible to obtain a high-quality image with no graininess and good graininess.

Further, according to the present invention, even if the toner having a small particle size is used, the leakage of the toner cloud can be effectively made by devising the magnetic pole arrangement of the developer carrier and by providing an appropriate seal structure. Can be prevented.

Further, in the type in which the leakage of the toner cloud is suppressed by the magnetic pole arrangement of the developer carrying member, there is a technical problem that it is difficult to replace the developer on the developer carrying member. In the present invention, by providing the forced pressing means for forcibly pressing the new developer against the developer carrying member, the replacement of the developer on the developer carrying member is promoted, and the developing performance is reduced in a short time. The situation can be effectively prevented.

[Brief description of drawings]

1A and 1B are explanatory views showing a developing method and an apparatus therefor according to the present invention.

FIG. 2 is an explanatory diagram showing a multiple transfer type image forming method to which the present invention is effectively applied.

FIG. 3 is an explanatory diagram illustrating a specific example of a color image forming apparatus in which the developing device according to the first embodiment is used.

FIG. 4 is an explanatory diagram illustrating details of the developing device according to the first embodiment.

FIG. 5 is a graph showing the relationship between AC developing bias frequency, toner particle size, and fog.

FIG. 6 is a graph showing the relationship between development density and AC development bias VP-P / development gap and dielectric breakdown.

FIG. 7 is a graph showing the relationship between carrier resistivity and halftone edge image loss.

FIG. 8 is a graph showing the relationship among the number of pixels, toner particle size, and graininess.

FIG. 9 is a graph showing the relationship among laser beam diameter, toner particle diameter / line number, and graininess.

FIG. 10 is a graph showing a relationship between a toner charge amount and an optimum transfer current value.

FIG. 11 is a graph showing the relationship between the number of transfers and the amount of developing toner charge per unit area.

FIG. 12 is an explanatory diagram illustrating a modified example of the developing device according to the first embodiment.

FIG. 13 is an explanatory diagram illustrating details of a developing device according to a second embodiment.

14A is an arrow view seen from the XIV direction in FIG. 13, and FIG. 14B is an explanatory diagram showing a development example of FIG.

15A is an explanatory view showing details of an end seal structure of a developing roll of the developing device according to Embodiment 2, and FIG. 15B is a view seen from the arrow B direction of FIG.

16 is a graph showing the relationship between toner charge amount / toner particle size and toner cloud amount in Example 2. FIG.

FIG. 17 is a graph showing the relationship between toner charge amount / toner particle size, toner charge amount / toner volume, and toner particle size in Example 2;

FIG. 18 is an explanatory diagram illustrating details of a developing device according to a third embodiment.

FIG. 19 is an explanatory diagram illustrating details of the developing device according to the fourth embodiment.

FIG. 20 is a graph showing the relationship between the number of copies and the solid density of the developing device according to the fourth embodiment.

FIG. 21 is a graph showing the relationship between toner particle size and character reproducibility using the screen ruling as a parameter.

FIG. 22 is a graph showing the relationship between screen ruling and character reproducibility with the toner particle size as a parameter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 2 ... Transfer medium, 3 ... Developing device, 4 ...
Developing housing, 5 ... developing opening, 6 ... developer carrier,
7 ... Sleeve, 8 ... Magnet member, 8a, 8b ... Magnetic pole, 9 ...
Developer stripping means, 10 ... Mounting member, 11 ... Forced pressing means, G ... Two-component developer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Taku Fukuhara, 2274 Hongo, Ebina, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Tatsuo Okuno, 2274, Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Nobuhiro Katsuta 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor Yuichi Fukuda 2274 Hongo, Ebina City, Kanagawa Prefecture (72) Inventor Osamu Handa 2274 Hongo, Ebina City, Kanagawa Prefecture Address: Fuji Xerox Co., Ltd. (72) Inventor, Kiyoshi Shigehiro, 2274 Hongo, Ebina, Kanagawa Prefecture, Fuji Fuji Xerox Co., Ltd. (72) Inventor, Yoshinori Machida, 2274, Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd.

Claims (5)

[Claims] 1. An electrostatic latent image (Z) on a latent image carrier (1) is developed with a single color toner or a plurality of color toners, and then the developed toner image (TZ) is transferred onto a transfer medium (2). A developing device (3) used in an image forming method in which electrostatic transfer or sequential multiple transfer is performed, in which a developing opening () is formed in a portion of a developing housing (4) facing a latent image carrier (1). 5) is provided, and a developer carrier (6) in which a magnet member (8) is fixedly installed in a rotatable non-magnetic sleeve (7) is provided at a portion facing the developing opening (5). , Develop the electrostatic latent image on the latent image carrier (1) through the developing opening (5) with the two-component developer (G) carried on the surface of the developer carrier (6), and In the developing device in which the developer peeling means (9) is provided on the downstream side of the developing opening (5) of the agent carrier (6), the average particle size is A toner of μm or less is used, and the toner charging condition satisfies y ≦ −3.5x + 34.5 (where y is the absolute value of the development toner charge amount per unit area, x is the number of times of transfer), and the developer is carried. Development opening (5) of body (6)
The developer (G) layer carried on the surface of the developer carrier (6) in the upstream and downstream regions of the developer carrier (6) over the entire axial direction of the developer carrier (6) or the development housing (4). A developing method characterized in that the wall surface of the mounting member (10) in the housing is always brought into contact with the wall surface. 2. An electrostatic latent image (Z) on a latent image carrier (1) is developed with a single-color or multi-color toner, and then the developed toner image (TZ) is transferred onto a transfer medium (2). A developing device (3) used in an image forming method in which electrostatic transfer or sequential multiple transfer is performed, in which a developing opening () is formed in a portion of a developing housing (4) facing a latent image carrier (1). 5) is provided, and a developer carrier (6) in which a magnet member (8) is fixedly installed in a rotatable non-magnetic sleeve (7) is provided at a portion facing the developing opening (5). , The magnet member (8)
Magnetic poles (8a, 8b) having an even number of different polarities are alternately arranged on the surface, and a developing opening (5) is formed by the two-component developer (G) carried on the surface of the developer carrier (6). In a developing device for developing an electrostatic latent image on the latent image carrier (1) through a toner having an average particle diameter of 6 μm or less and a toner charging condition of y ≦ −3.5x + 34.5 (however, , Y: absolute value of developing toner charge amount per unit area, and x: number of transfers). 3. The developing device for carrying out the method according to claim 1 or 2, wherein the inner wall of the developing housing (4) or the mounting member (10) in the developing housing (4) is a magnetic body, and faces the vicinity thereof. A developing device in which magnetic poles (8a, 8b) are arranged inside a developer carrier (6). 4. The developing device for carrying out the method according to claim 1 or 2, wherein the developer (G) at the end of the developer carrying member (6).
Development characterized in that a seal means for preventing leakage of the developer (G) from the gap between the developer carrier (6) and the development housing (4) is provided at a position corresponding to the region where the layer does not exist. apparatus. 5. The developing device for carrying out the method according to claim 2, wherein the developer (G) is strongly pressed against the developer carrying member (6) side at a position close to the developer carrying member (6) to develop. A developing device, comprising: forcibly pressing means (11) for partially forcibly replacing the developer (G) carried on the agent carrier (6).