JPH07281518A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of forming a developed image of high quality with good reproducibility by one-component non-magnetic developer. CONSTITUTION:As for the developing device constituted of a toner container 28 for containing the one-component non-magnetic developer, a developing roll 21 arranged at the opening part of the toner container 28, an elastic blade 23 arranged so as to form the thin layer of the toner on the surface of the developing roll 21 and so that one end of the blade may be fixed on the toner container 28, the other end may be in non-contact with the developing roll 21 and the prescribed surface may be in press-contact with the peripheral surface of the developing roll 21, and a photoreceptive drum 33 arranged opposite to the developing roll 21 with the thin layer formed, provided that (mu) denotes coefficient of internal friction of the toner, (mur) denotes coefficient of kinetic friction between the circumferential surface of the developing roll 21 and the toner, (mub) denotes coefficient of kinetic friction between the surface of the elastic blade 23 and the toner, by using the developer, the developer carrier and the developer coating member so as to satisfy mui,<mub<mur, the toner layer is sheared and the extremely thin and uniform toner layer can be stably formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device.

[0002]

2. Description of the Related Art As a developing device using electrophotographic technology, technical progress has been made with a two-component developer comprising a toner and a carrier and a one-component developer comprising only a magnetic toner. Furthermore, it has been developed into a developing device using a one-component non-magnetic developer that can eliminate the drawbacks of the one-component developer consisting of only magnetic toner. However, since it uses a one-component non-magnetic developer, it has the only major problem that it is difficult to stably form a uniform thin toner layer on the surface of the movable developer carrier. Practical use was hindered. Therefore, the present inventors have already developed the developing device shown in FIG. 1 (Japanese Patent Application No. 57-155).
No. 934), and succeeded in forming a thin layer of a non-magnetic developer. According to the present invention, the developing roller 1 as a movable developer carrier is provided with a rubber blade 2 as an elastic blade so as to make surface contact with its free end, that is, the downstream side of the flow of the developer. Is applied to the surface of the developing roll 1 by the rubber blade 2 to form a thin toner layer, which is opposed to the photosensitive drum 5 as a latent image holding member to develop the electrostatic latent image. The container 3 is composed of a synthetic metal piece 6 and a side wall 7.

According to the above-described developing device, it is possible to set a large contact area between the surface of the developing roll and the elastic blade, and moreover, since the edge of the elastic blade does not contact the surface of the developing roll, the pressing force is locally applied. You can avoid joining. As a result, it is possible to alleviate the non-uniformity of the pressure contact force caused by the subtle defects such as setting conditions and mechanical precision, wear, etc., and to form a more uniform developer layer. Also,
Due to the large contact area between the surface of the developing roll and the elastic blade, the developer will be rubbed under the pressure contact force for a longer time when passing through this contact portion, and as a result, the developer will be uniform. In addition, a sufficient charge is given. Therefore, it is possible to form a uniform thin layer of the developer having a sufficient charge, so that the electrostatic latent image can be well developed.

However, the following problems were found in the above-mentioned developing device by the experiments conducted by the inventors of the present invention.

That is, since the above-mentioned invention uses the non-magnetic toner, it is suitable for color development. However, since color toners are colored with different dyes or pigments for each color, even if they are manufactured by using the same resin as a matrix, their physical properties are usually different for each color. Of course, even if the toner is colored with the same substance, the physical characteristics of the toner are greatly different depending on the materials such as resins and additives, the toner particle size distribution, the particle shape, and the manufacturing method. In fact, as a result of conducting experiments using various toners having different physical characteristics, the apparatus of the invention does not always work well for all toners, and when a certain toner is used, the developer carrying member is It was not possible to stably form a uniform thin toner layer on the surface of the toner, and therefore the formed developer had defects such as uneven density, insufficient density, and background fog.

For this reason, when the toner thin layer becomes non-uniform, it is impossible to obtain a good quality developed image on the latent image holding member by any developing method.

[0007]

As described above, it is difficult to uniformly form an extremely thin thin layer in a developing device using a conventional one-component non-magnetic developer, and therefore a high quality developed image is obtained. Could not be formed with good reproducibility.

The present invention has been made in view of the above problems, and it is difficult to uniformly form an extremely thin thin layer. Therefore, a developing device capable of forming a high quality developed image with good reproducibility. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a developer container for accommodating a one-component non-magnetic developer, and a roller-shaped developer carrying member rotatably supported in an opening of the developer container. Body, and one end is fixed to the developer container and the other end is not in contact with the carrier so as to form a thin layer of the developer on the surface of the carrier, and a predetermined surface is the circumference of the carrier. The developer coating member is disposed so as to be in pressure contact with the surface, and the latent image holding member is disposed so as to face the carrier on which the thin layer is formed. The internal friction coefficient of the developer is μi. , Μi <μb <μr, where μr is the coefficient of kinetic friction between the peripheral surface of the carrier and the developer, and μb is the coefficient of kinetic friction between the surface of the developer coating member and the developer. A developer, a developer carrier and a developer applying member are used so that That is a developing apparatus.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic view showing the developing device of the present invention. The developing roll 21 is rotatably supported in the clockwise direction (arrow). The developing roll 21 is an AC power source 22,
And a DC power supply 22 ', and an AC voltage having a peak value difference of 1.8 kV and a frequency of 1 kHz is applied.
The developing roll 21 is, for example, a 24 mm aluminum cylinder whose surface is roughened by sandblasting, and the surface of which is hard chrome plated to a thickness of 5 μm, and the final surface roughness is 3 μm. Here, the surface roughness is the 10-point average roughness of JIS standard (JIS B060
According to 1). The first elastic blade 23 is made of, for example, a phosphor bronze plate having a thickness of 0.2 mm, a length of 270 mm, and a width of 35 mm. One end of the elastic blade 23 is fixed to the support 25 by a mounting screw 24, and the other end of the elastic blade 23 is in pressure contact with the surface of the developing roll 21 within a certain area of its side surface. However, the edge of the first elastic blade 23, that is, the free end, is not in contact with the surface of the developing roller 21. The pressure contact force P ₁ of the first elastic blade 23 against the developing roll 21 is set to 78 g / cm, for example. Here, P ₁ is the current pressure P _t of the blade linear pressure is calculated from the rotational axis direction of the blade developing roll length l _b (27cm) at _{P 1 = P t / l b} , ie unit length It is the pressure per hit.

Further, the second elastic blade 26 is made of a polyester film having a thickness of 75 mm, for example. One end of the elastic blade 26 is fixed to the support 27,
On the other end side, like the first elastic blade 23, a certain area of the side surface not including the edge is pressed against the developing roll 21. Such second elastic blade 26
The contact pressure P ₂ of the developing roller 21 against the developing roll 21 is set to 10 g / cm. That is, the first elastic blade 23
And the pressure contact force of the second elastic blade 26. The relationship between P ₁ and P ₂ is P ₁ > P ₂ . In the figure, the toner 29 is stored in the toner container 28. The toner container 28 is basically composed of the upper part of the developing roll 21, first and second elastic blades 23 and 26, and further, the supports 25 and 27, the container walls 30 and 31, and the developing roll. It is composed of a pair of side frames (not shown) arranged in parallel to both ends of 21. The supports 25 and 27 and the container walls 30 and 31 are fixed to the pair of side frames, and the developing roll 21 is also rotatably supported by the similar side frames. A stirring blade 32 for stirring the stored toner 29 is provided in the toner container 28, and the stirring blade 32 is rotatably supported by the pair of side frames.

The developing device having the above-described structure has, for example, an outer diameter of 78.
The developing roller 21 with respect to the selenium-based photosensitive drum 33 of mm.
And the drum 33 are arranged so that the minimum gap between them is 0.2 mm. The drum 33 rotates counterclockwise, and an electrostatic latent image having a maximum surface potential of 900 V is formed on the surface of the drum 33 by a corona charger and an image exposure device (not shown). In the copying apparatus including the developing device and the photosensitive drum, when the developing roll 21 and the photosensitive drum 33 are rotated, the toner 2 in the toner container 28 is discharged.
9 is made thin by the first elastic blade 23, and at the same time, a negative electrostatic charge is imparted by frictional charging. The toner conveyed with the rotation of the developing roll 21 approaches the electrostatic latent image on the photosensitive drum 33, and flies in the gap between the developing roll 21 and the photosensitive drum 33 by the Coulomb force and adheres to the surface of the drum 33. As a result, a developed image is formed.

In the above-mentioned method, the internal friction coefficient of the toner 29 is μi, the kinetic friction coefficient between the peripheral surface of the developing roll 21 and the toner 29 is μr, and the kinetic friction coefficient between the surface of the elastic blade 23 and the toner 29. Is μb, μi <
By using the developing roll, the elastic blade and the toner such that μb <μr, an extremely thin and uniform toner layer can be formed on the peripheral surface of the developing roll 21, and the toner particles are uniformly and sufficiently charged, which is excellent. It is possible to obtain a clear image.

[0015]

4 is a partially enlarged view of the developing device of the present invention, and FIG.
The principle diagram for explaining the shearing of the toner layer is shown in FIG.

The conditions for shearing the toner layer will be described with reference to FIGS. 3 and 4A to 4D. Developer 2
If the friction coefficient and the frictional force among the three members, 9, the developing roll 21, and the developer coating / coating member 23 are as shown in Table 1 below, F = μN between the pressure N acting on the developer and the frictional force F. Relationship is established.

[0017]

[Table 1] In order for the shearing action to occur in the toner layer with the movement of the developing roll, it is necessary to satisfy the relationship of F'i, Fi <F'b, Fb, F'r, Fr (1). Under this condition, slippage occurs between the developer coating member developer, the developing roll and the developer,
The toner layer is sheared. The toner layer, which is finally made into a single layer by repeated shearing, must be released under the pressure of the developer applying member while being attached to the surface of the developing roll (shown in FIGS. 4C and 4D). For this purpose, it is necessary that a slip occurs between the developer and the developer applying member, and it is necessary to satisfy the condition of F'b, Fb <F'r, Fr (2).

From the above formulas (1) and (2), the conditions for obtaining a thin layer of toner on the surface of the developing roll are F'i, Fi <F'b, Fb <F'r, Fr (3) or μ ′ I, μi <μ′b, μb <μ′r, μr (4) However, the pressure N acting on the toner layer was always constant.

Generally, when considering a stress state in a powder layer such as a toner, the mechanical behavior of the powder layer is based on a critical balance state (or a degrading equilibrium state). That is, when a constant compressive stress σ is applied to any one surface in the powder layer and shear stress γ is applied along that surface, slip occurs at the limit value of γ and γ is a value larger than that. I won't. Since the limit values γ correspond to the values of various compressive stresses σ, respectively, they are represented by a single line on the plane having the relations σ and γ as coordinate axes,
This is called the destruction envelope. The breakdown envelope is (1) in FIG.
When expressed by a straight line as in (2), Coulomb's law concerning solid friction can be applied, and r = μiσ + C = σtan φ ₁ + C (5) I can decide. Here, μi is the internal friction coefficient, φ ₁ is the internal friction angle, and C is the powder adhesion and cohesiveness. In the non-adhesive powder, C = 0 in the formula (5), that is, (1) in FIG. 5 corresponds to this. What is represented by a straight line like (1) and (2) in the figure is called Coulomb powder. (3) in the figure is a non-Coulomb powder, which is represented by the following equation (γ / C) ⁿ = (σ + σ _r ) / σ _r (6). Where σ _r is the tensile strength of the powder layer,
n indicates a shearing index, and when n = 1, it becomes a Coulomb powder. Non-Coulomb powders generally have n> 1, and the larger n is, the worse the fluidity is. The direct one-side shear method is known as a measuring method. In principle, as shown in FIG. 6, upper and lower cells 51, 52 are stacked and filled with powder, one cell (fixed cell) 52 is fixed, and vertical stress σ is applied to move the movable cell 51 in the horizontal direction. The stress γ when the powder layer is sheared by pulling is measured. By measuring γ for different values of σ, a fracture envelope can be obtained and the internal friction coefficient of the powder can be known.

[0020]

EXAMPLE This example was carried out using the developing device shown in FIG.

The internal friction coefficient of the toner layer was measured using the shear cell shown in FIG. The condition at this time is shear cell 5
Outer diameter 76 mm, inner diameter 61 mm, height 5 m as 1, 52
Using a ring of m, the height of the toner layer is 5m both above and below
m, the shear rate was 0.1 mm / sec, and the vertical loading range was changed. Further, as shown in FIG. 7, the friction coefficient between the developing blade and the toner and between the developing roll and the toner is the same as that of the elastic blade or the developing roll and the fixed flat plate 53 (size 100 mm × 1).
The measurement was performed by placing the above-mentioned movable cell 51 on (00 mm) and pulling the movable cell 51 in the direction of the arrow under a load-loaded state. The conditions at this time are that the toner layer height is 5 mm, the cell moving speed is 0.1 mm / sec, and the preload is 400 g / cm.
² , and the load was changed from 50 g / cm ² to 400 g / cm ² .

An example of the measurement result of the shear stress of the toner layer is shown in FIG. 8, and the inclination of the fracture envelope obtained from this result, that is, the internal friction coefficient μi of the toner layer is 0.53. Further, as a result of performing the above-described measurement on five types of toners A, B, C, D and E having different resin compositions, pigments, particle size distributions, etc., the internal friction coefficient is 0.42, 0.49, 0 in order. .5
It was 3, 0.58 and 0.64.

On the other hand, as the flat plate 53 in FIG. 7, five types of aluminum plates shown in Table 2 below corresponding to the developing rolls and five types of phosphor bronze plates shown in the same table corresponding to elastic blades are prepared. did.

[0024]

[Table 2] When the friction coefficient μr between the developing roll and the toner was measured using the Al plate a in Table 2, it was found that the toners A, B, C, D and E having the above-mentioned internal friction coefficient μi were in order of 0. It was 48,0.50,0.52,0.54,0.57. When the Al plate of e is used, μr is the toner A to
0.50, 0.52, 0.54, 0.5 for E
It was 7,0.60. In addition, the device shown in FIG.
When the kinetic friction coefficient μb between the elastic blade and the toner was measured using the phosphor bronze plate of a in the inside, for the toners A, B, C, D and E having the above-mentioned internal friction coefficient μi,
0.48, 0.51, 0.52, 0.54, 0.5
It was 7. When the phosphor bronze plate of e in the table is used, .mu.b is 0.50, 0.5 for toners A to E in this order.
It was 3,0.55,0.57,0.60.

However, the internal friction coefficient described above is applied to the developing device using the above-mentioned developing roll 21 shown in FIG. 2 which corresponds to the Al plate of e in Table 2 (Al roll having a surface roughness of 3 μm). Toners A, B, C having μi
D and E were put in, and a toner layer was formed on the peripheral surface of the developing roll 21 using the elastic blade 23 corresponding to the phosphor bronze plate in Table 2 above, and the internal friction coefficient μi of the toner and the elastic roll and toner The quality of the toner layer in relation to the coefficient of kinetic friction μr, and the quality of the toner layer in relation to the coefficient of internal friction μi of the toner and the coefficient of kinetic friction μb between the elastic blade and the toner were examined. The results are shown in FIGS. 10 and 11. The circles in these figures indicate that a uniform toner layer having a thickness of 13 to 70 μm was obtained, and the crosses indicate that a uniform toner layer was not obtained. From the results of FIGS. 10 and 11, it is understood that the relationship of μi <μb (7) μi <μr (8) must be satisfied in order to obtain a uniform thin toner layer.

Further, the toner A having the above-mentioned internal friction coefficient (0.42) is put in the movable cell 51 of the apparatus of FIG. 7, and the Al plates of a to e in Table 2 and the a to e of the table. When the coefficient of kinetic friction with respect to the phosphor bronze plate was measured, the results shown in Table 3 below were obtained.

[0027]

[Table 3] The correlation between the numerical values shown in Table 3 and the uniformity of the toner layer actually formed is shown in FIG. From these results, it is possible to surely form a uniform thin toner layer by setting so that the relationship of the following expression μb <μr (9) is satisfied. However, as shown in FIG.
There is also a point that a good toner layer is partially formed in the region of ≧ μr (for example, μb = 0.63, μr = 0.5).
7). These points are distributed in a region where μr is large, and when μi <μr and μr is sufficiently large, it is possible to form a uniform thin toner layer even if μb ≧ μr. However, in order to increase the kinetic friction coefficient μr between the developing roll and the toner, it is necessary to roughen the surface of the developing roll, and when a thin layer of toner is ejected to form a developed image on the photosensitive drum, The difference in electric field strength between the peaks and valleys of the rolls becomes large, which may lead to deterioration of image quality such as roughness.

Therefore, considering the above reason and the fact that the equation (2) estimated from the model of FIG. 4 agrees with the equation (9), the toner thinness which satisfies the condition of the equation (9) is uniform. It is preferable from the viewpoints of layer formation and good image formation. Therefore, by summing up the equations (7), (8), and (9), μi <μb <μr (10) is obtained, and this condition is given by the formula (4) which is the condition estimated from the model of FIG. I am doing it. Equation (4) includes the coefficient of static friction μ′r, but from the above experimental results,
It can be seen that the main factor that governs the toner thin layer formation process is the kinetic friction coefficient μr. This suggests that slippage or rolling occurs between the developing roll and the toner and between the elastic blade and the toner during the shearing process of the toner layer under the pressure contact of the elastic blade.

When a thin toner layer was formed under the condition satisfying the above expression (10) and a latent image was actually developed using this, a good developed image free from unevenness, fog, density defect, etc. was obtained. It was Incidentally, the optimum range of the developing conditions is the distance between the developing roll and the photosensitive drum 0.1 to 0.25 mm, the maximum surface potential of the drum 400 to 1000 V, and the pressure 3 of the first elastic blade
0 to 180 g / cm, AC developing bias 800 to 230
It was 0 V (peak value difference), 600 to 1500 Hz, and DC developing bias was 100 to 500 V.

[0030]

As described above, according to the present invention, it is possible to provide a developing device capable of forming a high quality developed image with good reproducibility by using a one-component non-magnetic developer.

[Brief description of drawings]

FIG. 1 is a schematic view of a developing device.

FIG. 2 is a schematic view of a developing device for explaining the present invention.

FIG. 3 is a schematic diagram showing a toner layer forming process.

FIG. 4 is a schematic diagram schematically showing a toner layer forming process.

FIG. 5 is a cross-sectional view showing a basic type of powder destruction envelope.

FIG. 6 is a sectional view showing a shearing device used in a direct one-sided shear test of toner.

FIG. 7 is a schematic view showing an apparatus for measuring a coefficient of kinetic friction between a developing roll and toner or between an elastic blade and toner.

FIG. 8 is a diagram showing an example of data of shear stress of a toner layer measured by the shearing device shown in FIG.

9 is a diagram showing a fracture envelope obtained from the data in FIG.

FIG. 10 is a characteristic diagram showing a relationship between a friction coefficient of a toner and a developing roll and a formed toner thin layer.

FIG. 11 is a characteristic diagram showing the relationship between the friction coefficient of the toner and the elastic blade and the formed toner thin layer.

FIG. 12 is a characteristic diagram showing the relationship between the friction coefficient of the developing roll and the elastic blade and the formed toner thin layer.

[Explanation of symbols]

21 ... Developing roll, 23 ... First elastic blade, 26 ... Second elastic blade, 2
8 ... Toner container, 33 ... Photosensitive drum

Claims (1)

[Claims] 1. A developer container for accommodating a one-component non-magnetic developer, a roller-shaped developer carrier disposed in an opening of the developer container and rotatably supported, and a surface of the carrier. So as to form a thin layer of the developer,
A developer coating member, one end of which is fixed to the developer container and the other end of which is not in contact with the carrier, and a predetermined surface of which is in pressure contact with the peripheral surface of the carrier, and the thin layer is formed. And a latent image carrier arranged so as to face the carrier, the internal friction coefficient of the developer is μi, and the kinetic friction coefficient between the peripheral surface of the carrier and the developer is μr. When the coefficient of kinetic friction between the surface of the developer applying member and the developer is μb, the developer, the developer carrier and the developer applying member are used so that μi <μb <μr. Characteristic developing device.