JPS58205166A - Developing method - Google Patents

Abstract

PURPOSE:To obtain a copy having good quality, by setting the gaps between a regulating blade and a developing sleeve as well as between said sleeve and a photoreceptor under prescribed conditions thereby increasing the balance range between the gap of the regulating blade and the developing gap and increasing the process speed of the photoreceptor. CONSTITUTION:A developer 3 having a magnetic component is attracted by magnetic force onto the surface of a rotatable developing sleeve 2 made of a non-magnetic material contg. a rotatable magnet roll 1, and the electrostatic latent image formed on the photoreceptor is developed by the magnetic brush formed by the developer 3. The rotating direction of the roll 1 and the rotating direction of the sleeve 2 in this stage are made different and the gap between a blade 6 regulating the height of the tuft (a) in the developing layer on the sleeve 2 and the sleeve 2, as designated as d1, and the gap between the sleeve 2 and the photoreceptor, as designated as d2, are so set as to attain d1>=d2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing method applicable to electrophotographic copying machines and the like.

Since ftYl, a method of developing an electrostatic latent image on the surface of a photoreceptor using a magnetic developer has been proposed, for example, in JP-A-5
As described in Japanese Patent No. 2-17881, rotation 1
A fixed magnetic pole is placed inside a developing sleeve made of a non-magnetic material capable of generating 1 J. A rotary sleeve type device that develops a latent image is known. Alternatively, as described in Japanese Patent Application Laid-Open No. 52-67336, there is a magnet roll rotating type in which a developing sleeve made of a non-polar material is fixed and a magnetic roll placed inside the developing sleeve is rotated to develop the latent image. Mome is also known.

Furthermore, recently, as described in JP-A-54-116233 and JP-A-54-119936, the developing sleeve and magnet roll are rotated in opposite directions. A formula has been proposed.

However, these three h° formulas each have the following problems. For example, the sleeve rotation type or the non-sleeve rotation type has the disadvantage that it is difficult to obtain an even image. This is because the developer used in these devices is fine, has poor powder flow, is sensitive to humidity, pressure, and foreign matter such as paper sakaki, and is sensitive to foreign matter such as the developing sleeve]-! ,,1. ．． Since it becomes difficult to convey the developer uniformly, a uniform 1:: image cannot be obtained.

In addition, with the sleeve rotation type, smear-free type, and trawl rotation type, the developer density is difficult to reduce, it is easy to produce young fruits during processing, it is difficult to remove fog, the sharpness is poor, and the speed is high. @Cchiru issues such as not being applicable to development.

In this regard, a recently proposed method of rotating the developing sleeve and the magnet roll in the same direction can solve the above-mentioned problem. In other words, it can be said that the present invention has been significantly improved in terms of uniform developer transport and stable images. However, the drawback of the method of rotating the developing sleeve and the magnet roll in the same direction is the gap between the developing sleeve and the regulating blade for regulating the height of the developing layer X'f formed on its surface. The blade gap) and the gap between the developing sleeve and the photoreceptor (developing gap) are very delicate.1-The blade gap itself is very small.

This is a very important song order.

In other words, the blade gear: □The essence of the knob and the developing gap 1
This is because, in order to release the button, not only the accuracy of the photoreceptor, the developing sleeve, and the doctor blade, but also the accuracy of the various parts to which these parts are attached and their attachment must be as high as possible.

Here, the concept of optimal values for the blade gap and development gap will be explained.

FIG. 1 is a conceptual diagram showing a state in which magnetic developer 3 stands up when attached to a rotatable developing sleeve 2 having a built-in rotatable magnet roll 1. As shown in FIG. When the developing sleeve 2 and the magnet roll 1 are in the zero position, as shown in Fig. 1, the developer above the magnetic poles forms a high spike as shown by a, and the developer between the magnetic poles forms a high spike as shown by b. Creating low spikes 3. Figure 2 is a conceptual diagram of the developing device shown in Figure 1 when the sleeve and magnet roll are rotated. Figure 3 shows the developing layer in Figure 2 viewed under a microscope from direction C. It is an enlarged cross-sectional view when observed at. As shown in FIG. 3, the developing sleeve 2. When the magnet roll 1 rotates, it consists of two layers: a developing layer 4 with a high density on the side near the developing sleeve 2 and a developing layer 5 with a low density on the side near the surface of the developing layer. Note that 63. in Figure 3. da is the height of the spikes of the developing layer 4.5 from the developing sleeve.

Curves 1 and 2 in FIG. 4 show changes in copy density when the gap between the photoreceptor surface and the developing sleeve (development gap) is changed. 65 on the positive axis in Figure 4. d4 is a length corresponding to ds and da in FIG. In other words, when the development gap reaches the height of the spike ds, contact between the developer and the electrostatic latent image begins, and development begins. When the development gap is between d4 and d5, the smaller the gap, the higher the density of the copy obtained. The highest density can be obtained when the development gap is around d4, but if it becomes too small, the density becomes low (1:1). This is because if the photoreceptor penetrates into the developing layer 4, which has a high density, the developer transported by the developing device will no longer be able to pass through the developing gear, resulting in the formation of a developing layer.
In even worse cases, excessive pressure is applied to the developer between the development gaps, making normal development impossible.

That is, in this type of development method, the optimum values of the blade gap and the development gap are always limited to a narrow range of the d4 side.

Next, considering the relationship between the regulating blade gap and the height of the spikes of the developing layer, this depends on the material of the regulating blade, the rotation ratio of the developing sleeve and the red roll, and the rotation direction of the developing sleeve and magnet roll. dependent. Practically, the characteristic required for the regulation mode gap is that the blade gap can be set large for a given developing gear sag. If the blade gap is small, developer clogging is likely to occur between the regulating blade and the developing sleeve, which is a serious problem in practice.

The present invention further improves the drawbacks of the above-mentioned developing method in which the developing sleeve and the magnetic roll are rotated in the same direction. A.) is coated on the surface of a developing sleeve made of a non-conductive material by magnetic force, and a photoconductor VC such as a photoconductor drum is formed by the magnetic brush formed by the developer. When developing an electrostatic latent image, a regulating blade and a developer are used to make the rotating direction of the -7g non-sotrol and the developing sleeve different, and to regulate the height of the developing layer of the developing sleeve ball. The gist of this is to set d1≧d2, where dl is the gap with the sleeve and d2 is the gap between the developing sleeve and the photoreceptor.

The present invention has the following features compared to conventional methods, particularly a developing method in which a developing sleeve and a magnet roll are rotated in the same direction. That is, the first advantage of the present invention is that, compared to the conventional method, the range in which the regulating blade gap and the developing gap are balanced is wide. As mentioned above, the optimum image can be obtained by positioning the latent image on the photosensitive drum within a very limited range near the boundary between the developing layer 4 and the developing layer 6 in FIG. Curve 1 and curve n in FIG. 4, which have been explained above, are 5. This figure shows a comparison between the conventional method and the present invention. As is clear from FIG. 4, in the conventional method 1, the development gap range is d4 or d4 as shown by 11 in FIG.
Although limited to a slightly smaller area, the U according to the present invention
Since the density is higher in the range of horizontal axis d3 to d4 in Fig. 4 compared to 1, the setting range of the development gap is e2 in Fig. 4.
It becomes wider as shown in .

This reason is based on the difference in developer transport speed between the conventional method and the method of the present invention. The conveying speed of the developer due to the rotation of the developing tube 11 and the magnet roll is approximately determined by the following equation.

The conveying speed by the developing sleeve is Vs, and the conveying speed by the magnetic roll is Vm, where: D=Outer diameter of the developing sleeve (cm '1h: Height of spikes of developer 1αl P: Number of magnetic poles of the magnet roll Ns, Nm Rotational speed (rpm,) of the varnish leaf and magnet roll The conveying speed of the developer in the conventional method is Vs and Vm in opposite directions, so Vs is Vs − Vm −−43). and Vm are in the same direction, so Vtotal = Vs + Vm --(4)
becomes.

As an example, D:=3CIn, h=0.05GI, P:
=8.

N5 = 60rpm, Nm21ooorpm Calculated using Hhi, the conveyance speed in the conventional method is 16.7/sec.
In contrast, in the present invention, 3s, 9a/sec
becomes.

As an example, D=3cm, h-α06("Fll, P
=8, NS =6Orpm, Nm =100Orpm
m (7), the conventional method is 2.1 cm/s
ec, whereas in the present invention it is 26.3cTn/
sec, and it can be seen that in any case, the developer transport speed according to the present invention is very advantageous compared to the FIY1 To method.

The second feature of the present invention is that, compared to conventional methods, it is possible to increase the speed of the photoreceptor. In general, in the magnetic bluff development method, the higher the developer transport speed, the higher the image density1.As explained in the first feature, the developer transport speed of the VC of the present invention is higher than that of the conventional method. Therefore, it is clear that this is a developing method that can be applied at high speed.

The third feature of the present invention is that when the development gap is kept constant, the gap between the regulation blades for regulating the height of the spikes of the development layer can be reduced compared to any conventional method. be.

When the developing gap is kept constant at 6, it is necessary to adjust the regulating blade to optimize the contact between the developing layer and the photoreceptor.

If you want clear development that is faithful to the original without edge effects, the development gap must be 0.5ffff or less. In the conventional method, development, gear tube io, 4 to 0.611
If 1M, the blade gap is 0.20-0.26
I have to set it to my friend. In the initial state when the developer is fresh, it is possible to obtain a straight image using the setting conditions described in 1-1. However, after making many copies, paper dust, foreign objects, and developer mixed into the developer may With a blade gap of 0.20 to 0.25 Jff due to the presence of blockfish particles, there is a problem in that developer clogging occurs due to coarse foreign particles mixed in between the blade and the sleeve. First, the relationship between the regulating blade gap and the height of the spikes of the developing layer will be explained. FIG. 6 is a schematic diagram of the apparatus used in the experiment. In the figure, a developer is placed on the surface of the developing sleeve 2, and the developer is placed on the surface of the developing sleeve 2. The rotation speed and rotation direction of the magnet roll 1, the blade gap d1 between the regulating blade 6 and the developing sleeve 2
The height of the spikes of the high-density development layer 4 and the low-density development layer 6 formed on the development position point e was measured when changing the development position e.

In this case, the height of the developed layer was measured using a scaled microscope 8 under illumination from a lamp 7 shown in FIG. The measurement results are shown in FIG.

In FIG. 6, the horizontal axis represents the ratio of the rotational speeds of the magnet roll and the developing sleeve, and the vertical axis represents the height of the spikes of the developing layer 4.6 with respect to the blade gear d1.

As is clear from FIG. 6, the spike height is determined by the rotation ratio of the magnet roll and the developing sleeve.

The solid line in FIG. 6 is the measurement result when a blade made of non-magnetic material is used, and the dotted line is the measurement result when a blade made of ferromagnetic curved material a is used. Here, the spike height of the developing layer 4 in the conventional method is set to 1. In addition, the spike height of the developing layer 6 is represented by lines B1 and B2. -15
, the height of the spikes of the developing layer 4 in the present invention is the line C+, 02
Also, the height of the spikes of the developing layer 6 is expressed by the line T, D2. As is clear from FIG. It makes small changes that are completely different depending on the direction of rotation. In the example of Confucian Song, the height of the spike is larger than the blade gap, and as the rotation ratio increases, the height of the spike 1''Z-- becomes even larger by V.On the other hand, in the present invention, the height of the spike is larger than the blade gap. The height L shows a decrease as the rotation ratio increases Vζ.From this, as explained in Fig. 4, the blade gap dl
When set to , the appropriate gap can be inferred from the line showing the change in the developing layer 4 in Figure A. This is because the gap exists near the boundary between the developing layers 4 and 5.

To express this relationship concretely with numerical values, when the rotation ratio of the magnet roll and the developing sleeve is 20, the blade gap dl:o, and 5#ff, the appropriate developing gap is as shown in Fig. 6, which is the conventional development gap. For non-magnetic blades according to the method, J° point ~ 1.0 JFIl! , for magnetic blades, g
However, according to the present invention, the non-magnetic blade has a h-point of ~0.6 mm, and the magnetic plate has a h-point of ~0.6 mm.
It becomes 0.3ffff.

That is, from the opposite perspective, it can be seen that when the developing gap is constant, this developing method can maximize the gap of the regulating blade compared to any conventional method. In particular, when used in combination with the ferromagnetic regulation blade described in Japanese Patent Application Laid-Open No. 53-125844, even more remarkable effects can be obtained.

A fourth feature of the present invention is that the developed copy image is very good. One of the reasons for this is that, as mentioned above, in the present invention, the developer conveyance speed is constant, so that sufficient development is achieved, and the developer conveyance direction is only one direction, so it is kept constant by the regulating plate. The reason for this is that the thickness of the developing layer at the developing point is always constant. On the other hand, in the conventional method, the developer transport speed is slow and the developer is transported in both directions, so it cannot be stabilized using only the regulation blade, and the 11.
E is unstable.

Compared to the conventional method, its advantages in terms of image defects include less fogging, a smaller gamma value, and a lower halftone image current Pl:
Good thing, solid painting ('I four sides of enon shell 9
The advantage is that there is less carrier adhesion.

Carrier adhesion is a phenomenon in which carrier adheres to a portion of the photoreceptor where the potential contrast is strong at the boundary between the image area and the non-image area of the electrostatic latent r, and both copies C are significantly damaged.

In the case of the carrier of a normal double-tray tray developer, it contains particles and is dense like iron powder and easily magnetized, so toner! Unless If is extremely low, use a carrier with a small particle size, such as those described in Tondo No. 33152, JP-A-53-33633, and JP-A-67-10160. In conventional development methods, images were often damaged by carrier adhesion, but the present invention has completely solved this problem. For example, FIG. 7 shows an example of a comparison of the amount of carrier adhesion in copy images obtained by the conventional RTT method and the method of the present invention. The vertical axis is the number of carrier particles adhering to a given image, and the horizontal axis is the direct current development (Ias) value.

As shown in FIG. 7, the amount of carrier attached largely depends on the developing bias. At low bias, carrier adhesion is not a problem. However, it is difficult to remove fog at a low bias due to the residual potential of the photoreceptor. Since this fog is caused by the optical characteristics of the photoreceptor, it is not possible to completely eliminate fog even if the exposure sensitivity is increased. In order to completely remove fog, it is necessary to apply a developing bias of at least 100 to 16 ov.

Curve E in FIG. 7 represents the carrier adhesion in the image obtained by the conventional method, and curve F represents the carrier adhesion in the image obtained by the method of the present invention. In the conventional method, the SOV bias is the limit, and fog is sensitive to variations in the residual potential of the photosensitive drum and optical fatigue of the photosensitive drum, making it difficult to stably obtain fog-free images. In addition, in the conventional method, it was necessary to set the exposure to a high value of 11 in order to remove the fog, which had the disadvantage that the thin lines tended to jump, but in the method of the present invention, the curve F in FIG. As can be seen, the ability to apply a bias of 170 to 180 V made it possible to stably obtain images with good sharpness of thin lines and no fog.

A fifth feature of the present invention is that there is little scattering of developer from the developing device. The conventional method is sleeve! .

Due to the flow of the two developing layers trying to move in opposite directions, there was a lot of scattering of the developer from the developing device. However, in the present invention, the developer is transported only in one direction, so the developing agent does not flow out of the developing device. There is little scattering of the agent.

As is clear from the explanation in 1. below, the present invention has many excellent features, and is particularly effective when applied to electrostatic transfer type electrophotographic copying machines.

It is conceivable that rotating the P1 magnet roll and the developing sleeve in opposite directions would generate resistance and generate heat due to eddy currents in the developing sleeve, which cannot be ignored. It was confirmed that there were no problems during long-term copying experiments.

On the other hand, if the developing sleeve and magnet roll are rotated in the same direction, the flow of developer conveyance on the developing sleeve will be increased.
E. It could be seen that it was rather unnatural to have the rain flow direction.

In the present invention, it goes without saying that good development can be carried out whether the developer is transported in the forward direction or the photoreceptor is rotated in the opposite direction.

[Brief explanation of the drawing]

Figure 1 shows the developing sleeve 1- when the developing device is stopped.
2 is a schematic cross-sectional view showing how the developer on the developing sleeve stands up when the developing device is in operation. FIG. Figure 4 is an enlarged cross-sectional view of the developing layer in Figure 4. Figure 4 is a diagram showing the change in copy density depending on the contact between the latent image surface of the photoreceptor and the developing layer. Figure 6 is a diagram showing the method for measuring the spike height of the developing layer. The schematic diagram shown in Figure 6 shows the rotation ratio and rotation number of the developing sleeve and Mada Sotrol.
A characteristic diagram showing changes in the regulation blade gap and the spike height of the developing layer due to changes in the direction and the material of the regulation blade,
FIG. 7 is a characteristic diagram showing an example of a comparison of carrier/rear adhesion and damage in copy images obtained by the conventional method and the method of the present invention. 1...Madafutsutrol, 2...Developing sleeve, 3...Magnetic r1 developer, 6...
- Regulation blade. Name of representative: Patent attorney Toshio Nakao and 1 other person5.
) Fig. 1 Fig. 3 [, 4 Fig. 4 a Image gap (ηm) Fig. 5 Fig. 6 Ua ul,)v4'7X CV)423

Claims (4)

[Claims] (1) A developer having a magnetic component is attached by magnetic force to the surface of a rotatable non-magnetic developing sleeve containing a rotatable magnet roll, and a magnetic brush is formed by the developer. When the electrostatic latent image formed on the photoreceptor is developed by /, the magnet roll is rotated. and the direction of rotation of the developing sleeve are different from each other, and "a gap f between a regulating blade provided near the developing sleeve and the developing sleeve for regulating the height of spikes of the developing layer on the developing sleeve. d +, and the gap between the developing sleeve and the photoreceptor is d2, and it is set so that d1-d2'f!: 4jJ. (2) A developing method according to claim (1), characterized in that a ferromagnetic material is used as a material of a regulating blade that regulates the height of spikes of the developing layer. (3) The developing method according to claim 1 or 2, wherein the number of rotations of the magnet roll is set to 6, where S is the number of rotations of the M1 developing sleeve. . (4) A developing method according to claim (1) or (2), characterized in that a developer comprising a carrier and a toner is used as the developer having a magnetic component.