JPH04223487A - Developing device - Google Patents

Abstract

PURPOSE:To offer a developing device which can attain compatibleness of two contradictory requirements; improvement of image reproducibility and no-generation of deterioration of a charge applying process to toner on a developer having magnetic one-component system toner. CONSTITUTION:In the developing device having magnetic toner 4 having the volume average grain diameter of Rmum incorporating a magnetic substance, a developer carrier 2a carrying the developer incorporating the magnetic toner 4 on the surface of the carrier 2a, and a regulating member 3 regulating the coating of the developer on the developer carrier 2a, saturation magnetization sigmasemu/g in the magnetic field 1k oersted of the magnetic toner 4 satisfies the following conditions, sigmas<36.8-1.85R, and a characteristic that an elastic body regulating member is used for the regulating member 3 is obtained.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art Hitherto, as a dry developing method for electrophotography, two methods have been commonly used: a method using a magnetic one-component toner as a developer, and a method using a two-component developer, a carrier and a toner. The two developing methods using the above-mentioned developer have the following advantages, namely, the one-component developing method allows the development device configuration to be miniaturized, and the two-component developing method allows sufficient charge to be applied to the toner. , has the advantage of wide design tolerance.

However, as can be seen from the fact that the above advantages are intended to compensate for the shortcomings of each system, the one-component system has a narrow design tolerance for the toner and developing system because the process of imparting charge to the toner is insufficient. However, the two-component method has the disadvantage that the device configuration becomes complicated because the mixed concentration of toner and carrier must be controlled to a constant value.

[0004] Also, the copied images by each method are as follows:
In magnetic one-component development methods, the toner is developed in the form of chains (commonly called "ears") during development, so the resolution in the horizontal direction of the image tends to be worse than in the vertical direction. However, two-component development methods tend to leave scratches from the magnetic brush.

[0005]

[Problem to be solved by the invention] As mentioned above,
The disadvantages of the above-mentioned magnetic one-component development system are that the charge imparting process is insufficient, and the other is that image reproducibility is poor due to the toner containing magnetic material. There are two points.

One can easily imagine a method of reducing the proportion of magnetic material in the toner as a solution to poor image reproducibility, but in general, current development systems depend on the absolute value of the specific charge of the toner. Therefore, it becomes difficult to develop a toner containing a reduced amount of magnetic material for the following reasons.

That is, when the radius of one toner is r, the amount of charge is Q, the density is ρ, and the weight of the toner is M, the specific charge Q/M of the toner can be expressed by the following formula. Q/M
=3Q/4πρr3 The density of the magnetic substance in a general magnetic one-component toner is several times larger than the density of the binder resin. Therefore, the toner density ρ decreases as the amount of magnetic material in the toner decreases, and the specific charge conversely increases. As is well known, an increase in specific charge tends to cause image density to decrease. In particular, as is clear from the above equation, this tendency becomes more pronounced as the toner particle size becomes smaller.

Furthermore, in the magnetic one-component developing system, the toner transport system is greatly influenced by the fluidity of the toner. It is a well-known fact that the fluidity of toner deteriorates as the amount of magnetic material contained in a magnetic one-component toner is reduced. It is also a generally well-known fact that deterioration in the fluidity of toner causes poor coating, deterioration of the process of imparting charge to the toner, and the like.

Therefore, conventionally, image reproduction has been achieved by using a magnetic single-component toner with a volume average particle diameter of R μm and a saturation magnetization σsemu/g of 36.8-1.85R in a magnetic field of 1K Oersteds. Generally, a balance is struck between the characteristics of the toner and the process of imparting a charge to the toner. It is an empirically known fact that in order to solve poor image reproducibility, in an attempt to reduce the proportion of magnetic material in toner, saturation of a magnetic single-component toner with a volume average particle diameter of R μm in a magnetic field of 1 K Oersteds was applied. magnetization σ
When semu/g satisfies the following condition σs<36.8-1.85R, it is difficult to achieve both image reproducibility and the process of imparting charge to the toner in a development method using magnetic one-component toner. , the problem was that the design tolerance was very narrow.

[0010] Accordingly, it is an object of the present invention to solve the above problems.

That is, the present invention relates to a developing device using a developer containing a magnetic one-component toner, and meets two contradictory requirements: improvement of image reproducibility and no deterioration of the process of imparting charge to the toner. It is an object of the present invention to provide a developing device that can achieve both of the following.

The present invention also relates to a developing device using a developer having a magnetic one-component toner, which has a volume average particle diameter Rμ.
The saturation magnetization σsemu/g in a magnetic field of 1K oersted of a magnetic one-component toner of m is determined by the following condition σs<36.8-
It is an object of the present invention to provide a developing device that can expand the design tolerance range without causing deterioration of the process of imparting charge to toner even when poor image reproducibility is solved by satisfying 1.85R.

[0013]

[Means for Solving the Problems and Effects] According to the developing device of the present invention, a magnetic toner containing a magnetic material and having a volume average particle diameter of R μm and a developer carrying a developer containing the magnetic toner are carried on the surface. In a developing device having a regulating member for regulating the application of developer on the developer carrier, the saturation magnetization σs(
emu/g) satisfies the following condition σs<36.8-1.85R, and the regulating member is an elastic regulating member, thereby achieving the above object.

The developing device of the present invention has a volume average particle diameter of R μm.
The saturation magnetization σs at 1K Oersted of the magnetic toner of
When emu/g satisfies the following condition σs<36.8-1.85R, poor image reproducibility is solved, and furthermore, the regulation member that regulates the application of the developer on the developer carrier is replaced with an elastic regulation member. As a result, the toner is pressed onto the developer carrier by the elastic force of the elastic body, so the amount of charge does not decrease, and therefore the process of imparting charge to the toner does not deteriorate.

[0015]

Embodiment Embodiment 1 An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a developing device which is an embodiment of the present invention. In the figure, 1 is an image carrier (hereinafter a photosensitive drum is shown as an example) that rotates in the direction of arrow a, and 2a is 1
A developer carrier (hereinafter, a non-magnetic metal developing sleeve is shown as an example) rotates in the direction of arrow b. Reference numeral 3 denotes an elastic blade used as an elastic regulating member for regulating the amount of developer on the developer carrier, which is one of the features of the present invention.In the present invention, as shown in FIG. The elastic blade 3 is brought into contact with the elastic blade 3 at an angle toward the downstream side, that is, in a counter direction. 2b is a permanent magnet, and as shown in FIG. 1, it is arranged inside the developing sleeve 2a. The distance between the developing sleeve 2a and the photosensitive drum 1 is approximately 250 μm, and a developing bias for transferring toner from the developing sleeve 2a to the photosensitive drum 1 is applied to the conductive portion of the sleeve 2a by a power source 5. The elastic blade 3 is a blade made of rubber, plastic, etc. with an appropriate elastic modulus, and the pressure at the contact point is determined by displacing the blade in a set manner as shown in Fig. 1, and applying pressure evenly to the contact generatrix area. Alternatively, as shown in FIG. 2, a constant pressure may be applied using a load 7 centered on the rotating shaft 6, or a so-called equalized uniform load method fixed to the developing device frame may be used. 4 is one of the features of the present invention, where the saturation magnetization σs (emu/g) in a magnetic field of 1K Oersteds satisfies the following condition σs<36.8
This is a magnetic one-component toner that satisfies -1.85R.

The magnetic material contained in the toner includes:
These include metal oxides containing elements such as iron, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon.

The magnetic material used in the examples of the magnetic toner of the present invention is spinel type iron oxide obtained by the synthesis method shown below.

<Synthesis example> As a reactor, the internal capacity is 180 liters.
A bubble oxidation type reaction tower was used. Industrial iron sulfate is dissolved in water to prepare 40 liters of a solution with a ferrous iron concentration of 135 g/l. Separately, 40 liters of a solution with a caustic soda concentration of 183 g/l was prepared, and the above-mentioned iron sulfate solution was added to this solution while stirring to effect neutralization, so that the residual caustic soda was 5 g/l. To this, industrial zinc hydroxide solution pH 11.3, zinc concentration 40g/
1 was added to prepare a reaction solution with a ferrous iron concentration of 40 g/l. While maintaining the temperature of the reaction solution at 80° C., oxidizing air was blown in at a rate of 10 l/mm to carry out an oxidation reaction. The reaction was completed in about 7 hours. This slurry was then washed and dried to obtain spinel type iron oxide.

The obtained magnetic material has a horizontal Feret diameter of 0.
27μm, BET specific surface area 8.8m2/g, saturation magnetization σ
s30.3 emu/g, coercive force Hc 174 oersteds, and residual magnetization σr 5.1 emu/g.

According to the study of the present applicant, the binder resin 100
Toner containing 80 parts by weight of the above magnetic material and having a volume average particle diameter of 8 μ (toner with saturation magnetization σs of about 13.5 emu/g in a magnetic field of 1 K Oersted), and binder resin 1
00 parts by weight contains magnetite (FeO Fe
Toner with a volume average particle diameter of 8 μ containing 80 parts by weight of
emu/g toner) (hereinafter, the former is referred to as σs1
2 toner, the latter being referred to as conventional toner), and when the fluidity of both was measured, it was found that the values were almost the same. In addition, when the above two toners were mixed with iron powder carrier (200/300 manufactured by Powder Tech Co., Ltd.) and the specific charge of the toner was measured by the blow-off method, both values were found to be almost the same within the range of the electrophotographic development system. It was a value that could be determined.

That is, the applicant has proposed that by using the above magnetic material, the saturation magnetization σse in a magnetic field of 1K Oersteds
A magnetic one-component toner whose mu/g satisfies the following condition σs<36.8-1.85R can be obtained with fluidity and charge amount almost equivalent to those of conventional toners.

[0023] The present applicant also conducted the following study regarding imparting electric charge to toner. That is, the magnetic toner layer is thinned by the magnetic field between the internal magnet 2b of the developing device as shown in FIG. The σs1/2 toner and the conventional toner are placed in a well-known conventional developing device in which the magnetic one-component toner receives an electric charge through frictional charging with the developing sleeve 2a. The specific charge was measured.

As a result, the value of the specific charge of the above-mentioned conventional toner showed a value close to the value of the specific charge obtained by the above-mentioned blow-off method, but the value of the specific charge of the above-mentioned σs1/2 toner was similar to the value of the specific charge obtained by the above-mentioned blow-off method. It has become smaller.

This is because the charging of the toner in the developing device as shown in FIG. 3 depends on the force of pressing the magnetic one-component toner against the developing sleeve, and the pressing force is the force between the magnetic toner and the magnet 2b. This is thought to be due to dependence on magnetic attraction force. Therefore, the above σs1/2 toner has a weaker magnetic adsorption force with the magnet 2b than the conventional toner, so the process of imparting charge to the toner is insufficient, and as a result, the specific charge value is small. Conceivable.

Therefore, the present applicant tilted the elastic blade 3 toward the downstream side with respect to the rotating direction of the developing sleeve 2a as shown in FIG. A configuration was adopted in which the σs1/2 toner was strongly pressed against the developing sleeve. Further, the contact point of the elastic blade was positioned opposite to one pole of the magnet 2b.

As a result, the specific charge of the σs1/2 toner was found to be approximately the same as that of the conventional toner.

That is, the magnetic substance contained in the magnetic one-component toner is made of a metal oxide, has a saturation magnetization σs of 10 to 40 emu/g in a magnetic field of 1 K Oersted, and has a horizontal Feret diameter of 0.05 to 0.5 μm. As a magnetic material,
Furthermore, the saturation magnetization σsemu/g of the magnetic one-component toner in a magnetic field of 1K Oersteds satisfies the following condition σs<36.
．． The magnetic one-component toner has a volume average particle diameter Rμm that satisfies 8-1.85R, and also has elasticity in order to regulate the amount of developer on the developer carrier and stabilize the process of imparting charge to the toner. By using an elastic blade as the body regulating member, it has become possible to achieve two contradictory goals: improving image reproducibility and expanding the allowable design range of the process of imparting charge to toner.

The magnetic material used in the present invention is not limited to this example, and has a saturation magnetization σs of 10 to 40 emu/g in a magnetic field of 1 K Oersted, and a horizontal Feret diameter of 0.05 μm to 0.5 μm. Any magnetic material may be used.

Further, the position of the elastic blade used in the present invention is not limited to that shown in FIG. 1, but may be as shown in FIG. 4, for example.

<Example 2> According to the study by the present applicant, the saturation magnetization σs in the magnetic field of 1K Oersted used in Example 1 is 10 to 40 emu/g, and the Feret diameter in the horizontal direction is 0.
05 μm to 0.5 μm, 40 parts by weight of hematite (α-Fe2O3), which has a very small saturation magnetization σs, is added to 100 parts by weight of the binder resin, and the saturation magnetization σs in a magnetic field of 1K Oersteds is about 60 emu/ A toner with a volume average particle diameter of 8μ containing 40 parts by weight of magnetite (FeO Fe2O3) (toner with a σs of about 13.5 emu/g in a magnetic field of 1K Oersteds) and 100 parts by weight of a binder resin in a magnetic field of 1K Oersteds. Magnetite (FeO・
Toner containing 80 parts by weight of Fe2O3) with a volume average particle diameter of 8μ (σs in a magnetic field of 1K Oersteds is approximately 27emu)
/g of toner) (hereinafter, the former will be referred to as a blended toner and the latter as a conventional toner), and the fluidity of both was measured, and it was found that the values were almost the same. In addition, when the above two toners were mixed with an iron powder carrier (200/300 manufactured by Powder Tech Co., Ltd.) and the specific charge of the toner was measured using the blow-off method, both values were found to be almost the same within the range of the electrophotographic development system. It was a value that could be determined.

When the above blended toner was put into the developing device of Example 1, the above blended toner was found to have σs1 of Example 1.
/2 toner showed almost the same characteristics.

That is, the magnetic one-component toner contains at least two metal oxides with different saturation magnetizations σs in a magnetic field of 1K Oersteds, and the saturation magnetization σsemu/g of the magnetic toner in a magnetic field of 1K Oersteds satisfies the following condition σs<36. By satisfying .8-1.85R, it is possible to simultaneously achieve the two contradictory goals of improving image reproducibility and expanding the allowable design range of the process of imparting charge to toner.

<Example 3> One of the features of the present invention is
The elastic regulating member that regulates the amount of developer on the developer carrier is not limited to the shape of the elastic blade of the first embodiment, and as shown in FIG. 5, an elastic roller 9 may be brought into contact with the developing sleeve. It may also be used. In the present invention, by using urethane as the elastic roller and rotating the elastic roller in the direction of arrow c in FIG. 5, the same effect as the elastic blade of Example 1 could be obtained.

[0035]

As explained above, according to the configuration of the present invention, two contradictory demands are met: improvement of image reproducibility of magnetic one-component toner and prevention of deterioration in the process of imparting charge to the toner. The design tolerance can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device that is an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a method for adjusting the contact pressure between the elastic blade and the developing sleeve shown in FIG. 1;

FIG. 3 is a sectional view of a conventional developing device.

FIG. 4 is an explanatory diagram of another arrangement position of the elastic blade in FIG. 1;

FIG. 5 is an explanatory diagram of an elastic roller.

[Explanation of symbols]

1 Photosensitive drum 2a Developing sleeve 2b Magnet 3 disposed in the developing sleeve Elastic blade 4 Magnetic one-component toner 8 Magnetic blade 9 Elastic roller 9

Claims (3)

[Claims] [Claim 1] Volume average particle diameter Rμm containing magnetic material
of magnetic toner, a developer carrier that carries a developer containing the magnetic toner on its surface, and a regulating member that regulates application of the developer on the developer carrier. Saturation magnetization σ in a magnetic field of 1K Oersteds
s (emu/g) under the following condition σs<36.8-1.85
A developing device that satisfies R and is characterized in that the regulating member is an elastic regulating member. 2. The magnetic substance contained in the magnetic toner is made of a metal oxide, and the saturation magnetization σs of the magnetic substance in a magnetic field of 1 K Oe is 10 to 40 emu/g.
, and the horizontal Feret diameter is 0.05 μm to 0.5 μm
The developing device according to claim 1, characterized in that: 3. The magnetic toner contains at least two metal oxides having different saturation magnetizations σs in a magnetic field of 1K Oe, so that the magnetic toner has the following saturation magnetization σs (emu/g) in a magnetic field of 1K Oersteds. 2. The developing device according to claim 1, wherein the condition σs<36.8-1.85R is satisfied.