JPH0128382B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner layer forming device in a developing device that uses a one-component magnetic toner as a developer.

As a conventional developing method using a one-component magnetic toner, a developing method using a conductive magnetic toner disclosed in US Pat. No. 3,909,258 and the like is known and widely used. However, such development methods require that the toner be inherently conductive, and the conductive toner is capable of applying an electric field to transfer the toner image on the latent image-bearing member to the final image-supporting member (such as plain paper). Although the reason for this is not fully elucidated, it has been difficult to use it for transcription.

The present applicant has proposed a new developing method that eliminates the drawbacks of the conventional developing method using one-component magnetic toner (for example, Japanese Patent Laid-Open No. 18659/1983).

In this method, an insulating magnetic toner is uniformly applied onto a cylindrical developer support member having a magnet inside, and is developed by facing the latent image holding member without contacting it. At this time, a low frequency alternating voltage is applied between the developer support member and the base conductor of the latent image holding member to cause the toner to reciprocate between the developer support member and the latent image holding member, thereby eliminating background fog. It has no limitations on gradation, and can perform good development without thinning at the edges of the image.

In this developing method, since the toner is an insulator, transfer is easy.

In such a developing method, it is extremely important to uniformly apply the toner onto the developer support member. In other words, if the toner layer on the developer support member becomes excessively thick, not only will the toner be rubbed against the latent image holding member, but also the toner will likely become insufficiently triboelectrically charged due to friction with the developer support member. When the toner becomes thin, the amount of toner provided for development becomes insufficient, resulting in an unsatisfactory density of the developed image.

One method for forming a uniform toner layer on the developer support member is to use a coating blade at the outlet of the toner container, as shown in FIGS. 1 and 2.

What is shown in Fig. 1 is an elastic blade 1 made of rubber or the like.
is pressed against the developer support member 2, thereby regulating the thickness of the toner layer 3.

By these methods, it has become possible to form a substantially uniform toner layer on the developer support member 2. However, it has been experimentally found that it is difficult to stably form a uniform toner layer on the developer support over a long period of time in practice. In particular, when a toner with significantly poor fluidity or agglomerated toner is used, it tends to be more difficult to form a uniform toner layer.

The present invention relates to a developing device that is capable of forming a stable toner layer when forming the toner layer by the above-described method.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner layer forming apparatus that can form a stable and uniform toner thin layer. The toner layer forming apparatus of the present invention that achieves this object has a magnet on the surface of a developing support member having a magnet inside.
In a toner layer forming device that forms a magnetic toner layer for developing a latent image held on a latent image holding member, the surface of the development supporting member has a peak height H of 1/4 to 1/4 of the average particle diameter of the toner. 3 times, and the distance D between the peaks is larger than the height H of the peaks.
This toner layer forming apparatus is characterized in that a magnetic toner layer is formed on the surface by an elastic blade pressed against the surface.

That is, the surface of the developer supporting member 2 is provided with irregularities 4 of about several μm. By providing the unevenness 4, the toner is mechanically loosened by sliding contact with the uneven surface of the support member 2 supporting the toner at the disposed portion of the elastic blade 1 shown in FIG. 1, and uniform application is achieved. becomes possible.

That is, since the magnetic toner is rubbed onto the uneven surface of the developer support member with an elastic blade, the magnetic toner is sufficiently loosened, and even though the elastic blade is in pressure contact with the developer support member, the surface of the developer support member is Since the surface is uneven, the toner conveying force is strong, and a uniform magnetic toner layer can pass through this elastic blade portion and exit.

Figures 2a to 2d are four cross-sectional views of the surface shape of the developer support member used in the experiment.
In figure a, both the valleys 4-2 and the peaks 4-2 of the unevenness 4 are sharp.

Although it is possible to form a uniform toner layer with this shape, the density of the developed image is extremely low, and the outline of the line in the developed image is not straight and when magnified, it has a thin sawtooth shape. It was found that the image shows the Also, Figure 2 b shows valley 4-1 and mountain 4-
2. Both are rounded, Figure 2 c is valley 4-1
is rounded, and in Figure 2 d, mountain 4-2 is rounded. In the examples shown in FIGS. 2b, c, and d, it has been found that good developed images can be obtained as long as the size of the unevenness 4 satisfies the conditions described below.

That is, regarding the size of the unevenness 4, the height H of the peaks shown in FIG. 3 is preferably about 1/4 to 3 times the average particle diameter of the toner, and optimally 1/3 to the same size. . When the peak height H is smaller than 1/4 of the average particle diameter of the toner, there is almost no effect of providing the unevenness 4, and when it is 3 times or more, the density of the developed image becomes low and background fog is likely to occur.

Since the particle size of commonly used toner is about 5 to 20 microns, the optimum size of the unevenness 4 is about 2 to 20 microns. Further, the distance D between the peaks must be greater than the height H of the peaks. When the peak height H is smaller than the peak height H, the density of the developed image becomes low, and when the peak interval D is too wide, the effect of the unevenness is lost.
In this case, a pattern due to the unevenness 4 of the developer support member appears in the image, but as a result of experiments, the pattern of the unevenness 4 does not appear if the distance is smaller than the distance between the developer support member 2 and the latent image holding member 5, and the pattern is sufficient. I found out that it has a great effect.

The causes of these things are not known in detail, but are estimated as follows.

If the peak 4-2 is sharp as shown in Figure 2 a, the electric field will be concentrated in this area and the electric field due to the latent image will not reach the toner particles sufficiently, resulting in insufficient development. It is estimated that In terms of electric field concentration, the shape shown in Figure 2c has a sharp peak at the peak 4-2, so
This is the same as in Figure 2a, but since the valley 4-1 is large and has a rounded shape, the capacity of the valley 4-1 is the largest among the figures a to d. Therefore, the amount of toner used for development increases, and the drawbacks caused by electric field concentration are covered.

In particular, in a configuration in which the developing section has a magnetic pole as shown in FIG. 1, the toner between the valleys 4-1 becomes brush-like due to the influence of the magnetic field, and the height thereof is sufficiently higher than the top of the peaks 4-2. This can be observed with a magnifying glass.

The height H of the peak 4-2 needs to be large enough to mechanically loosen the toner, but if it is too high, the toner will not be loosened and the height H will fall into the valley 4-1.
The injected toner is not sufficiently charged and development is not performed properly. Furthermore, under the action of the magnetic field, the toner does not remain on the valleys 4-1 but also forms brushes on the peaks 4-2. When the height of the peaks 4-2 is high, the toner in the deep valleys 4-1 forms a tall brush on the peaks 4-2, which rubs against the latent image holding member 5. This may cause fogging.

If the interval D between the peaks 4-2 is smaller than the height of the peaks 4-2, the toner between the valleys 4-1 will be electrically shielded and will not be used for development, or the toner and the development The adhesive force between the agent supporting members 2 is also strengthened. Therefore, it is desirable that the distance between mountains 4-2 be relatively wide. However, in this case, the pattern of the developer supporting member 2 may appear on the image. However, it has been found that when the distance between the peaks 4-2 is smaller than the distance between the developer support member 2 and the latent image holding member 5, this effect hardly appears.

It is presumed that this is because when the toner moves from the developer support member 2 to the latent image holding member 5, it does not necessarily move in the vertical direction to the developer support member, but some of the toner moves in an oblique direction.

The unevenness 4 having such a shape and size can be made by either a chemical method or a mechanical method.

As a chemical method, by corroding the surface of a developer support member made of stainless steel or the like with various acids, ferric chloride solutions, etc., irregularities as shown in FIGS. 2b and 2d are formed on the surface.

As a mechanical method, the shape as shown in FIG. 2c can be obtained by a so-called blasting process in which bead-shaped abrasives (glass beads, martensite, etc.) are applied.

In either case, it is also possible to round the peaks of the ridges by, for example, applying a very weak electric field polishing after the unevenness has been created. Note that when manufacturing the developer support member by machining, it is possible to create unevenness by leaving marks; It is uniformly connected in the circumferential direction of the agent support member and has no effect.

In order to achieve the object of the present invention, it is necessary that the depressions be random or continuous in the longitudinal direction of the developer support member.

Furthermore, in the case of blasting, it is important that the abrasive be in the form of beads. sandy (amorphous)
If this abrasive is used, the surface shape becomes as shown in FIG. 2a, and good results cannot be obtained.

The toner layer forming device of the present invention can form a stable and uniform toner thin layer, and also allows the elastic blade to rub the toner on the uneven surface of the developer support member, thereby making sufficient contact between the surface and the toner while loosening the toner. Therefore, sufficient frictional electrification of the toner can be achieved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a developing device using an elastic blade, Figures 2 a to d are enlarged sectional views showing the surface shape of the developer support member used in the experiment, and Figure 3 is the uneven surface of the developer support member. FIG. 3 is an enlarged cross-sectional view showing the relationship between the height H of the peaks and the distance D between the peaks. 1...Elastic blade, 1'...Magnetic blade, 2
...developer supporting member, 3...toner layer, 4...irregularities, 5
...Latent image holding member.

Claims (1)

[Claims] 1. On the surface of a developer supporting member having a magnet inside,
In a toner layer forming device that forms a magnetic toner layer for developing a latent image held on a latent image holding member, the surface of the developer supporting member has a peak height H that is 1/4 of the average particle diameter of the toner. It is an uneven surface in which the distance D between the peaks is larger than the height H of the peaks,
A toner layer forming apparatus characterized in that a magnetic toner layer is formed on the surface by an elastic blade pressed against the surface. 2. The toner layer forming apparatus according to claim 1, wherein the toner layer is developed in an alternating electric field formed between a developer supporting member and a latent image holding member.