JPS60178476A - Charge image developing device - Google Patents

Abstract

PURPOSE:To obtain an image excellent in quality with less fogging and high density by using a friction charging type one-component magnetic toner and rotate both a magnet roll and a sleeve simultaneously, and charging toner particles to a sufficient value and obtaining a conveyance quantity required to obtain sufficient recording density. CONSTITUTION:The magnet roll 4 and sleeve 51 are both allowed to rotate as shown by arrows; and the peripheral speed Se of the sleeve 5 and the rotating speed Mg of the magnet roll 4 are so set that 0<Se<500(mm./s) (at a 0-300rpm rotating speed rpm when the sleeve is of 30mm.phi) and 0<Mg<3,000(rpm). Then, the gap (g) between the sleeve surface and a control plate 7 is narrowed down so that Te<G, where Te is the thickness of the toner layer on the sleeve and G is a development gap, performing development without contacting. Further, an agitator 10 is provided to mix the whole toner in a toner hopper 9 sufficiently, and the development is carried out excellently with friction having type magnetic toner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to electrophotography or electrostatic recording, and particularly to a developing device suitable for obtaining images using triboelectrically charged component magnetic toner. It is.

[Background of the invention]

Conventionally, one method of developing a charge latent image on a recording medium formed by electrophotography or electrostatic recording using colored toner is to mix magnetic powder such as magnetite with an organic polymer resin and apply a magnetic There is a developing method using a one-component magnetic toner that has target attraction properties.

FIG. 1 explains a conventionally used reversal development method.

When the charge image 3 formed on the recording medium 2 of the substrate 1h moves in the direction of the arrow, it comes close to or comes into contact with the magnetic brush f' formed from the magnetic toner 6Vc on the sleeve 5,
Six magnetic toner particles are attached to areas where there is no or little charge. To do this, an electric field between the sleeve 5 and the recording medium 2 created by a bias power source 8 connected to the non-magnetic metal sleeve 5 causes charge to be injected from the sleeve 5 into the toner particles, or a regulating plate is used to charge the toner particles. 7. It is necessary to use one of two methods: to impregnate the toner with a charge control agent that is charged by friction with the sleeve 5, and to sufficiently charge the toner before development.

The magnetic toner 6 is conveyed on the sleeve 5 by rotating one or both of the mag roll (multipolar magnetic member) 4 and the sleeve 5, and a charge image is developed.

The regulating plate 7 controls the total thickness of the toner layer.

In the above explanation, the toner particles are charged in advance by full use of friction before development, and the latent image surface is The method of adhering toner particles to the recording medium has the advantage that the toner particles that have been developed and adhered to the recording medium can be efficiently, stably and easily transferred to ordinary plain paper.
Since the developer is a single component, it is difficult to control the charge on the particles, making it difficult to obtain good images.

Therefore, even in regular development such as that used in ordinary copying machines, when using the above-mentioned charged toner, a magnetic blade etc. The toner layer on the sleeve is made very thin, and the gap between the recording medium and the sleeve is 0.
1~Q, 'l, mm In addition, a complicated mechanism such as superimposing direct current and alternating voltage is applied to the sleeve, and extremely high precision is required to obtain a good image. Adjustments will be necessary. Moreover, in reversal development, in which toner is deposited in areas with no charge, the electric field formed by the charge pattern is complex, which not only disrupts the image, but also causes toner to adhere to unnecessary areas when trying to increase the density of the image area. This has the disadvantage that toner tends to adhere to it and cause fogging (background stains).

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device which eliminates the above-mentioned drawbacks, produces images with less capri, a high a degree, and high quality.

[Summary of the invention]

In order to achieve the above object using a triboelectrically charged component magnetic toner, the present invention satisfies the following three conditions: (1) both the mag roll and the sleeve are rotated simultaneously to provide a sufficient amount of charge to the toner particles; (2) The development gap between the sleeve and the recording medium allows the magnetic brush of the magnetic toner formed on the sleeve to come into strong contact with the surface of the recording medium. (3) to provide stirring means to sufficiently mix the entire toner in the toner reservoir that supplies the toner to the sleeve, and to develop without contact. That's true.

[Embodiments of the invention]

FIG. 2 shows an embodiment of a developing device using the present invention.

Make both the mag roll 4 and the sleeve '5 rotatable in the direction of the arrow in Figure 2, and set the circumferential speed of the sleeve 5 to 5dkO<8h.
< 500 (mm/s) (For a 30rnmφ sleeve, the sleeve rotation speed is 0 to 300rp III) -
Rotation of rgfl-ru 4 aMg k O<Mg <aoo
o (rpm), and narrow the gearing g between the sleeve surface and the regulating plate 7 so that the thickness T of the toner layer on the sleeve is in the relationship between the developing gearing G and To<G. A stirrer 10 is provided to enable non-contact development and to ensure that all the toner in the toner hopper 9 is sufficiently mixed.
It is characterized by the ability to perform good development even with triboelectrification type and magnetic toner.

Conventionally, when using non-triboelectric magnetic toner, that is, non-charged magnetic toner, there is no need to stir the toner in the toner hopper (container), and it is sufficient to at most prevent toner bridges from occurring, and the rotation of the sleeve and mag roll is sufficient. Although there are differences in the development characteristics, any combination of directions is possible, and it is also possible to rotate only one direction. However, unlike two-component developers, charged one-component magnetic toner has a triboelectric charge of 1υ.
I] Because the toner does not have a carrier to control it, it is charged by friction between toner particles and friction with the sleeve, regulating plate, and toner container, so it provides the toner with the necessary and stable force for charging. There must be. Therefore, the way the sleeve and mag roll are rotated is important. Furthermore, if the toner particle size distribution or compositional variation distribution changes, the amount of charge of the toner changes, so these distributions should rarely change significantly during development.

The above-mentioned specific example will be explained in detail below. When development is carried out by rotating the sleeve in the device shown in Figure 2 (the rotation direction of the sleeve is the direction in which the toner is pulled out from the toner hopper, passing under the regulating plate and onto the sleeve), the density of the printed image is as indicated by the dotted line in Figure 3. , and decreases with the number of sheets printed. The reason for this is that the amount of charge on the toner particles decreases, and when the relationship between the number of printed sheets and the amount of charge on the toner is actually examined, the characteristics shown by the dotted line in Figure 4 are shown. The reason why the toner charge amount decreases in this way is
This is because rotation of the sleeve alone cannot sufficiently triboelectrically charge the toner particles. To eliminate this drawback, the rotation of the mag roll is added to the rotation of the sleeve. In this way, the agitation force of the toner and the number of times the toner particles come into contact with the surface of the metal sleeve increases, so the image characteristics become as shown by the solid line in Figure 3, and the image density decreases even after repeated printing. The amount of charge is also 4th.
As shown by the solid line in the figure, it can be made not to change depending on the number of printed sheets. The desired circumferential speed of the sleeve is 50~2 Q Q
mm/s (3Q m mφ sleeve approximately 50~20
0rpm), mag roll rotation speed is 700~isoorp
It is m. If the rotation is too low, the image density will decrease, and if the rotation is too high, a load will be applied to the toner, causing aggregation and poor conveyance.

Next, we will discuss the issue of conveyance amount. As explained above, a sufficient amount of charge can be obtained by rotating the mag roll, but the charged toner becomes difficult to move on the sleeve because the mirror image force moves across the metal sleeve surface. , it is not possible to obtain a sufficient amount of conveyance to achieve the concentration only by rotating the mag roll.

Therefore, when examining the relationship between mag roll rotation speed and image density, the result is as shown by curve a in FIG. 5.

In the case of the conventionally used charge injection type magnetic toner, the characteristics shown in curve gb in FIG. 5 can be obtained by only rotating the mag roll, and the image density can be increased only by increasing the number of rotations of the mag roll. In the case of triboelectric magnetic toner, adding sleeve rotation to mag roll rotation increases the amount of conveyance and improves the image density to the characteristic of curve C in Figure 5, which is a parallel shift of the characteristic of curve a in Figure 5. It is possible to obtain a satisfactory concentration. To further reduce the effects of image forces, it is preferable to provide a high resistance or insulating layer on the sleeve that is thicker than the toner radius. Further, in order to make frictional charging more stable, it is preferable to make the sleeve surface uneven.

Next, the reason why the thickness T of one layer of toner on the sleeve is set to be less than the developing gear G will be described.

- The charged state of each toner particle in component magnetic toner is different from conventional charge injection type magnetic toner or two-component developer that uses a mixture of carrier and toner gold, and it is not possible to make the charge amount of each toner particle uniform. , has a certain degree of distribution, and some of them have a charge opposite to the desired polarity. Therefore, when toner particles are pressed against the recording medium and come into contact with it, in reversal development, the toner easily adheres to the electrically charged areas that correspond to the background area.
Causes capri. In addition, in the case of triboelectric magnetic toner, the toner particles are charged and retain their full charge, so if the toner particles have the same polarity, static repulsion is likely to occur, so if the toner layer on the sleeve is made thicker, Toner scattering occurs in the upper part of the layer, that is, the part where the magnetic attraction is weak, and this is also a cause of capri. Therefore, T, T
As an example of hG, if the Guyang G is Q, 5 mm, and the gap glQ is set to about 45 mm, the relationship between the bias voltage Vb and the image density will be as shown by the dotted line in Figure 6, and the image density will be increased. However, when the bias voltage is increased, the concentration of Capri also increases. On the other hand, if g'ko is set to 35 mm or less so that T, ku G, the relationship between bias voltage and concentration becomes as shown by the solid line in Figure 6, and even if the bias voltage is changed, the concentration of Capri remains unchanged. Characteristics that hardly change can be obtained. On the other hand, the density in the image area is slightly lowered, but the desired density can be compensated for by adjusting the bias voltage. The reproduction of halftones is rather excellent. This is thought to be because the rotation of the mag roll gives movement to the toner, and development is performed without the brush coming into contact with the recording medium. The thickness T of a single layer of toner on the sleeve varies depending on the strength of the magnetic field of the mag roll and the amount of magnetic powder impregnated in the toner, but usually, for the gap g,
Since it is about 1.1 to 1.4 times, the setting of gap g is
It is preferable to set G/1.1 to 1.4 or less. For example, Q=Q
, when 5mm, 0.05≦g≦0.35 (ROM)
, When Q=0.4 ROM, 0.05≦g≦0
．． 3 was good.

The reason why the direction of rotation of the mag roll is reversed to the direction of rotation of the sleeve to accelerate the movement of toner on the sleeve will be explained.

FIG. 7 shows four examples in which the sleeve and mag roll are combined in all rotational directions. If the mag roll is fixed and only the sleeve is rotated, the toner will be transported in the direction of rotation of the sleeve. Conversely, if the sleeve is fixed and only the mag roll is rotated, the toner will be transported in the direction opposite to the rotation direction of the mag roll. do. When both rotations are combined, Fig. 7, B, C
This method fully accelerates toner transport. In Fig. 2, the condition f of Q = 9.5 mm and g = 0.2 mm,
When the differences in the development characteristics of each method shown in FIG. 7 are investigated, the result is l/I: as shown in FIG. FIG. 8 shows the bias voltage V
Due to the relationship between b and the density of the solid black image, the A method has a curve like the one shown in Figure 8, which has poor developability, and the D method has a curve like the one shown in Figure 8, with variations in characteristics. This results in uneven density in the image. The characteristics shown in Figure 8 were smooth in the two BIC methods.

From the above experimental facts, in order to obtain good images, it is better to further accelerate the conveyance of toner by rotation of the sleeve by rotation of a mag roll.

Next, the reason why the toner stirring device 10 must be provided in the toner hopper 9 will be described.

As mentioned above, unlike conventional charge injection type or two-component magnetic toner, the charge state of -component magnetic toner is that the charge amount of each toner particle cannot be made uniform and a certain degree of distribution occurs. Do you want to develop it? Toner particles under favorable conditions are selectively developed, and only toner particles that are difficult to develop remain in the toner hopper 9. That is, the particle size distribution and charge distribution state of the toner near the sleeve in the toner pumper change. Therefore, even if there is toner in the homper,
A problem arises in that the developed density is not achieved. Such a thing did not occur with conventional toner. To alleviate this selective development phenomenon, move the toner in the toner pumper back and forth, left and right.

A device 10 that stirs the entire mixture from top to bottom is required.

FIG. 9 shows a rotating shaft of the stirring device shown in FIG. 2, which shows one embodiment of the present invention. Fig. 9 shows a simple structure in which a stirring blade 11 is attached to the center of rotation 12, but by placing this device in a pumper and rotating it at about 10 to 20 rpm, the toner can be sufficiently stirred. can,
This solves the problem of toner remaining in the hopper that is difficult to develop.

Figure @10 is another embodiment of a developing device using the present invention.

The major differences from the developing device shown in FIG.
The point is that it uses . After the development is completed, the toner remaining on the sleeve 5 and conveyed is scraped off with a V-dope 13 placed against the sleeve, and the belt stirring device 14 with a plate made of rubber is rotated to remove the toner. At the same time, the toner is placed on a plate and transported. Since the dish hits the dusting rod 15 and is knocked off between the blade 13 and the regulation plate 7, it is possible to always use sufficiently stirred toner for development, with toner particle size distribution and charge distribution being approximately constant. .

The blade 13Fi shown in FIG. 10 which scrapes off the toner on the sleeve once subjected to development is effective in preventing the above-mentioned selective development, and is preferably applied to FIG. 2 as well. However, Fig. 2.

It is not possible to realize long-term stable development by omitting the stirring device shown in FIG. 10, that is, by using only the blade 13.

[Effects of the Invention] As described above, according to the present invention, toner that always has a particle size distribution in a substantially constant range and is charged with a charge distribution in a substantially constant range by friction is supplied onto the sleeve from within each toner container,
The cooperation between the sleeve and the mag roll rotation gives the toner a large movement and can obtain the triboelectrification # required for development.
The amount of toner conveyed necessary for development can be secured, and bacteria density images can be obtained even though the gap between the recording medium and the sleeve can be made thicker than before, while the capri is reduced by suppressing contact between the recording medium and the toner brush. Images with good halftone reproducibility can be stably obtained over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing reversal development using a one-component magnetic toner, Fig. 2 is a configuration diagram of a developing device according to an embodiment of the present invention, and Figs. 3 to 6 are experiments showing the effects of the present invention. A diagram showing the results, FIG. 7 is a schematic diagram explaining mag roll rotation and sleeve rotation of the present invention, FIG. 8 is a diagram showing the experimental results of the example in FIG. 7, and FIG. 9 is a configuration of the stirring section of the stirring device. 10 are configuration diagrams of a developing device showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Recording body, 3... Charge image, 4...
...Mag roll, 5...Sleeve, 6...-component magnetic toner, 7...Regulation plate, 8...Bias power supply, 9
... Toner pumper, 10 ... Stirring device, 11 Stirring blade, 13 ... Pond, 14 ... Stirring belt, 15
... Duster stick. Rate 1I211 2 figures of shadows and 3 figures'' Bino ■η 5 figures 7 one row 1 and Hojo to Hihira (r, P, m)! (Vb (V) Voltage Vb (V) Figure 7)

Claims (1)

[Claims] 1. In a device that develops an electrical latent image formed on a recording medium using a friction band* type magnetic toner that is charged by friction, the toner in the replenishment toner container is stirred, and a portion of the toner used for development and the toner are mixed. A means for mixing the toner with the toner in the container and supplying the mixed and agitated toner onto the non-magnetic metal sleeve for conveying the toner, a member for regulating the amount of toner supplied from the toner container onto the sleeve, a means for rotating the sleeve for conveying the toner; means for rotating a multipolar magnetic member provided within the sleeve, the direction of rotation of the sleeve is a direction in which toner is drawn out from the toner container through the toner regulating member, and the direction of rotation of the multipolar magnetic member is in a direction opposite to that of the sleeve. A charge image developing device characterized in that the number of rotations is higher than that of the sleeve, and the thickness of a layer of toner formed on the sleeve is smaller than the gap between the recording medium and the surface of the sleeve.