JPH0766217B2 - Development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrostatic copying machine using electrophotography, or a printer of the same, and more particularly to a one-component developing device.

[Prior Art and Problems to be Solved] Conventionally, substances for controlling the charge amount (hereinafter referred to as tribo) of dry type one-component magnetic toner, such as gas phase silica (hereinafter referred to as dry silica) and wet process silica ( It is known that (hereinafter referred to as dry silica) is externally added to the toner.

For example, for a negative polarity toner containing 60 parts by weight of magnetite in styrene acrylic, dry negative silica showing a strong negative property (adding HMDS at a ratio of 10 parts by weight per 100 m ² to 100 m ² of vapor phase method silica and heating. By externally printing (processed), tribo as a developer is increased. When a developing thin layer is formed on the sleeve 8 by using this developer such as known jumping development as shown in FIG. 2, the image density is higher than that of the developer without silica added,
It is widely known that an image with less shading can be obtained.

[Problems that the invention is trying to solve]

However, with a developer to which negative-characteristic silica that is strong against negative toner is externally added, a sleeve ghost, which is a history of a print pattern, occurs on the developing sleeve, and this also appears on the print image. As shown in FIG. 3, the sleeve ghost generated in the case of the developer in which negative silica is externally added to the negative toner becomes a positive ghost. That is, since the non-printing portion (white background) continues, only the thin development is performed even if the printing is performed (a), and the dark development is performed because the printing is continued (b). Get out. The mechanism of this ghost formation is deeply related to the layer of fine powder (particle size of 5 to 6 microns or less) formed on the sleeve according to the experiments and consideration by the present inventors. That is, there is a clear difference in the particle size distribution of the toner lowermost layer of the developing sleeve between the toner consuming portion and the toner non-consuming portion,
A fine powder layer is formed on the non-consumed portion and the toner bottom layer. Since the fine powder has a large surface area per volume, the amount of triboelectric charge per mass is large compared to a large particle size, and due to its own mirroring force,
Strongly restrained electrostatically. For this reason, the toner on the portion where the fine powder layer is formed cannot be sufficiently frictionally charged with the developing sleeve, so that the developing ability is deteriorated and appears as a sleeve ghost on the image. The sleeve ghost described above is a phenomenon that occurs because the charging of the toner largely depends on the triboelectric charging with the developing sleeve together with the formation of the fine powder layer. Therefore, in order to solve the sleeve ghost, the mirroring force acting between the sleeve and the sleeve of the charged fine toner near the surface of the sleeve may be removed or reduced by some method.

[Means for solving problems]

According to the present invention, when a negatively charged one-component toner is used, a resin layer containing conductive fine particles having an average particle size of about 20 mm and surface conductive fine particles on the surface of the developer carrier. And the conductive fine particle-containing resin layer has an average volume resistivity in the range of 10 ² to 10 ⁻⁶ Ω · cm and a thickness of
The conductive particles are between 0.5 micron and 30 micron, and the conductive fine particles appear on the surface layer, and the size of secondary particles formed by the conductive fine particles and the resin is 1.0 micron or less. By having a thin layer containing fine particles, sleeve ghost (positive ghost)
Can be solved.

〔Example〕

Example 1 In this example, as shown in FIGS. 1a and 1b, a resin layer containing conductive fine particles having an average particle size of about 20 mm was provided on the surface of the developer carrier, and Fine particle-containing resin layer 1
Has an average volume resistivity in the range of 7 × 10 ^{1 to} 7 × 10 ^-2 Ω · cm and a thickness of 0.5 μm to 30 μm.
Moreover, the conductive fine particles appear on the surface layer, the size of the secondary particles 3 made of the conductive fine particles and the resin is 1.0 micron or less, and the secondary particles 3 are formed so that the outermost surface layer has a gravel shape. A conductive fine particle layer that is distributed is provided on a developer carrying member that has been blasted with Alundum # 400. It should be noted that the gravel road shape indicates the outermost layer portion in which the size of the secondary particles is about 0.1 μm to 0.3 μm and the interval between the secondary particles is about 0.1 μm to 0.4 μm.

Here, FIG. 1a shows a cross-sectional view of the developer carrier,
FIG. 1b shows a perspective view of the developer carrying member.

As described in the conventional example, a positive sleeve ghost often occurs when a toner having a negative polarity is used. This is because the polymer resin originally has the property of being easily charged to the negative polarity, and in the positive polarity toner, the charge-up phenomenon described in the conventional example does not easily occur. The charging of the toner itself near the surface of the developer carrying member can be carried out by the method of leaking to the developer carrying member in the present invention. Various surface treatment methods have been proposed for the conventional developer carrier, but these are mainly macroscopic phenomena in the developing process, and so-called leak sites in the insulating toner are actively provided. Not the way. The present invention makes it possible to cause a charge leak in an insulating toner by arranging a mixture of conductive fine particles and fine particles having surface lubricity in a gravel path at a portion in contact with the toner. is there.

Hereinafter, this embodiment will be described.

First, the relationship between the content of carbon as the conductive fine particles and the sleeve ghost when negative toner was used was examined.
A thermosetting phenol resin was used as the resin. The examination results are shown below.

The carbon used here is RAVEN 1035 from Colombian Carbon. The coating was performed by coating the surface of a developer carrier blasted with Alundum # 400 by a dipping method or a spray method by about 1.0 to 1.5 microns. In this experiment, since phenol resin, which is one of the thermosetting resins, is used
Thermal curing was performed at a temperature of C-30 minutes. When a sleeve ghost was compared with a developer carrier (hereinafter referred to as a coat sleeve) thus completed using a toner having a negative polarity, the positive ghost was improved as the formulations 1 to 3 were performed. . The development at this time was performed using a non-contact jumping development method. The developing bias was an AC bias Vpp of 1600 V, a frequency of 1800 Hz, and the developer carrier of the present invention had an interval of about 300 μm. Also, when the film thickness was changed from 0.5 to 30 microns, the prescription was 1.0 to 3.0.
About micron is effective for sleeve ghost, less effective for film thickness less than that, and when it is thick, so-called toner charge phenomenon occurs in toner, resulting in extreme decrease in density and improvement in sleeve ghost. Was not done.

Therefore, the inventors considered that there is a close correlation between the film resistance and the sleeve ghost against these phenomena, and proceeded with the experiment using conductive carbon having higher conductivity.

That is, a study was conducted using conductive carbon instead of the above-mentioned formulation 2.

(Prescription 4) The effect conditions and the film formation method are as described above.

Moreover, about the film thickness, 0.5-30 micrometers was examined. As a result, when the negative toner was evaluated under the same developing conditions as the above in a low humidity environment where the positive sleeve ghost is said to be the most severe, it tended to be better than in the above Formulas 1 to 3. The effect was recognized when the amount of conductive carbon was changed from 20% to 90% with respect to the resin. However, the tendency in the film thickness was the same as that of the formulations 1 to 3 although the allowable range was widened. However, when a negative polarity toner is used, the positive sleeve ghost is not perfect under low humidity, which is said to be severe. Therefore, the inventors have again considered the viewpoint of the charge leak site of the fine powder toner from a viewpoint other than the resistance.

It is clear that the resistance of the coat layer is certainly effective in the above-mentioned formulations 1 to 4, but the resistance should be lower without the coating alone.

On the other hand, the inventors of the present invention noted the following. If a state in which the charge of the toner is formed in a concave-convex shape (for example, a gravel shape) in the coat film, so-called charge concentration occurs due to the conductive particles and the charge flows to the sleeve. This allows the fine powder that has been charged to be removed.

From this viewpoint, the average particle size of the secondary particles, which is a mixture of the resin and the conductive carbon, was changed by changing the dispersion state in the above-mentioned formulation 4, and the positive sleeve ghost and the size of the secondary particles were changed. There was a correlation with the distribution.
That is, according to the observation with the scanning electron microscope,
(1) When the average size of the secondary particles is about 1 micron or less, almost complete effect is exhibited against sleeve ghost even in low humidity, but when it is more than that, the effect is reduced. (2) If the secondary particles are so dense that no secondary particles are present and there are no gaps, that is, if a substantially flat film is formed, the effect is reduced and the secondary particle spacing is about an average.
The effect should be recognized in the case of 0.05 μm to 2.0 μm. In addition, the depth of the voids at this time should be about one or more of the average size of the secondary particles. That is, within the range of film thickness 0.1μ
m to 30.0 μm. (3) Although the film resistance has a range when the sleeve ghost is effective, the shape of the portion of the film that contacts the toner is more important than the volume resistance of the film.

The following table summarizes the above results.

Here, the uniqueness of the present invention will be described again. Originally, the developer carrying member in the insulating toner used a conductive sleeve, which is a well-known fact. However, as described above, the sleeve ghost is generated when the negative polarity toner is used. This is repeated, because the fine powder toner is electrically attracted to the sleeve by the mirroring force of the toner itself. According to the present invention, the charge of the fine powder toner is easily leaked. From a macroscopic point of view, it can be considered that the contact resistance between the toner and the developer carrying member is reduced. That is, in the present invention, the size of the secondary particles formed between the conductive fine particles and the resin is set to 1 micron or less, and the surface layer of the film is formed into a gravel path to reduce the apparent contact resistance (leakage). Creating a site)
succeeded in. In addition, the volume resistivity of the coating film is naturally in the range because a phenomenon called a charge jump occurs macroscopically on the insulating toner unless an electrically conductive sleeve is used, and a decrease in development density occurs with the sleeve ghost. It will be limited. In addition, for the thin film thickness, the lower limit is naturally determined from the relationship between the density of leak sites due to the toner and the secondary particles. Further, with respect to the upper limit of the film thickness, it is clear that the conductive fine particle-containing resin layer of the present invention has a high volume resistivity with respect to a metal, so that the effect is reduced if the thickness is made too thick.

The inventors of the present invention have analyzed the finely charged fine particles present on the surface of the developer carrier in positive ghost as follows, and confirmed that the developer carrier of the present invention surely prevents the fine particle charge. It was confirmed.

It has been conventionally known that positive ghosts are likely to occur due to continuous printing of white areas, and are less likely to occur at black areas. Therefore, the effect was confirmed by comparing the tribo of the toner in the upper layer portion and the tribo of the toner in the lower layer portion in the thin layer coat of the developer. FIG. 5 shows the difference between the toner tribo of the white part and the black part. The horizontal axis represents the toner coating position, and the vertical axis represents the tribo difference, that is, tribo difference (ΔQ / M) = white portion Q / M−black portion Q / M.

The tribo difference of the conventional sleeve is that the toner-tipped toner is present in the lower layer of the toner coat as shown by the broken line, whereas the toner-tipped toner is considerably reduced in this embodiment (prescription 4). I understand.

As described above, by applying the coating of the present invention to the conventional conductive sleeve, it is possible to obtain a developer carrying member having an effect more than that of metal against positive ghost. The same effect was obtained by applying the present invention to a mirror surface and a sleeve having roughness other than No. 400. Further, similar effects were obtained not only for plasts having irregularly shaped particles such as alundum but also for those using spherical particles.

In this embodiment, as the developing device configuration, a thin layer of the developer is formed by the metallic blade 9 as shown in FIG. 4a, but in addition to this, as shown in FIGS. 4b and 4c. The same effect was obtained with a developing device using an elastic blade. In addition, almost the same effect was obtained for the one coated on an aluminum sleeve having a substantially mirror surface.

That is, the present invention is established regardless of the surface state of the developer carrying member. Also, not only aluminum sleeves but also SUS ones are applicable.

The thermosetting resin used in this example was a phenol resin, but a butyral resin was also used.

[Other Examples]

(Embodiment 2) In this embodiment, in order to further secure the effect on the positive sleeve ghost particularly in low humidity, the mechanical adsorption force of the fine powder developer carrier is higher than that of the first embodiment. From the viewpoint of weakening the temperature, graphite carbon was mixed on the surface of the developer carrier as conductive fine particles having solid body lubricity. The other conditions are the same as in Example 1. In this case, a complete developer carrier for a positive sleeve ghost was obtained.

(Prescription 5) (Embodiment 3) In this embodiment, carbon as conductive fine particles and graphite as conductive fine particles having lubricity are dispersed in a photo-effect resin, and the average particle diameter is 20 mm on the surface of the developer carrier. It has a resin layer containing conductive fine particles of the order of microns, and this conductive fine particle-containing resin layer has an average volume resistivity of 10 ² to 1
It is in the range of 0 ^-2 Ω · cm, the thickness is between 0.5 micron and 5 micron, the size of secondary particles due to the conductive fine particles and the resin is 1.0 micron or less, and the outermost layer is It is shown that the positive sleeve ghost in the negative toner can be eliminated or reduced by forming the coat film in which the secondary particles are distributed so as to have a gravel shape.

The formulation of the coating agent in this example is shown below.

When the sleeve ghost was evaluated in the same manner as in the above examples, almost satisfactory results were obtained for the above film thickness.

In the examples, the thermosetting resin and the photocurable resin are used, but an aqueous polymer such as casein, glue, TiO ₂ ,
Similar effects were obtained when the SnO ₂ , Si alkoxide-based conductive ceramics were dispersed in a binder and applied to the present invention.

Further, although conductive carbon was used as the conductive fine particles in the examples, the case of using metal fine particles also holds true from the logic of the present invention.

In the examples, the average volume resistivity of the conductive-containing resin layer was 7 × 10 ^{1 to} 7 × 10 ⁻² Ω · cm.
According to the logic of the present invention, 7 × 10 ⁻² to 10 ⁻⁶ holds.

〔The invention's effect〕

As described above, the developer carrier surface has a resin layer containing conductive fine particles having an average particle diameter of about 20 mm, and the conductive fine particle-containing resin layer has an average volume resistivity of
It is in the range of 10 ² to 10 ^-6 Ω ・ cm, and the thickness is 0.5 micron to 30
The size of the secondary particles of the conductive fine particles and the resin is 1.0 micron or less, and the secondary particles are distributed so that the outermost surface layer has a gravel shape. By providing a developing device having the characteristic conductive fine particle-containing thin layer on the surface of the developer carrying member, it is possible to solve the positive toner ghost of the negative toner, which remarkably appears particularly in an environment under low humidity. In addition, it also has the following effects.

1) Higher development efficiency.

2) Reversal fog is reduced.

[Brief description of drawings]

FIG. 1a is a partially enlarged cross-sectional view of a developer carrier according to the present invention, FIG. 1b is a perspective view of FIG. 1a, FIG. 2 is a conventional developing device, and FIG. 3 is a sleeve. 4A, 4B, and 4C are explanatory views of a developing device equipped with the developer carrier of the present invention, and FIG. 5 is an explanatory view of effects of the present invention. 1 ... Conductive resin layer of the present invention 2 ... Conventional developer carrier 3 ... Secondary particles of conductive fine particles and resin 5 ... Developer hopper 6 ... Developer 7 ... Development magnet 8a ... ... Sleeve 8b ... Conductive resin layer of the present invention 9 ... Developing blade 11 ... Elastic developing blade

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Moto Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Suwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Yasushi Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kimio Nakahata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-58-208769 (JP, A) JP-A-56-77870 (JP, A) JP-A-55-26517 (JP, A) Practical application Sho-57-133051 (JP, U)

Claims (5)

[Claims] 1. A one-component toner that is negatively charged is used to form a thin layer of a developer on the surface of a developer carrier, and a minute distance is provided between the surface of the developer carrier and the surface of the electrostatic image carrier. A developing device for visualizing an electrostatic image by transferring a developer from the surface of a developer carrier to the surface of an electrostatic image carrier while maintaining a constant interval, wherein the surface of the developer carrier contains conductive fine particles. The resin layer containing conductive fine particles has an average volume resistivity in the range of 10 ² to 10 ⁻⁶ Ω · cm and a thickness of 0.5 μm to
Conductive fine particle-containing thin particles having a size of 30 μm or less, the size of the secondary particles of the conductive fine particles and the resin is 1.0 μm or less, and the secondary particles are distributed so that the outermost layer has irregularities. A developing device having a layer on the surface of a developer carrier. 2. The developing device according to claim 1, wherein the resin layer contains conductive fine particles having lubricity. 3. The developing device according to claim 1, wherein a thermosetting resin is used as the resin layer. 4. A photocurable resin is used as the resin layer, and the conductive fine particle-containing resin layer has a thickness in the range of 0.5 μm to 5 μm. Developing device. 5. The developing device according to claim 1, wherein the developer is a magnetic toner.