JP3139116B2 - Development roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is an electrophotographic copying machine, it relates to a developing roll of a printer or the like.

[0002]

2. Description of the Related Art Generally, an electrophotographic copying machine is constructed as shown in FIG. 5, and copying is performed as follows. That is, the photosensitive drum 1 rotating in the direction of the arrow around the axis 1 a is uniformly charged by the corotron 2. Reference numeral 3 denotes an exposure mechanism through which the slit exposure 8 of the original light image reaches the surface of the photosensitive drum 1, and an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 1. Reference numeral 4 denotes a developing roll incorporated in the case 4a, which is frictionally charged by sliding contact of the layer forming member 12, and toner in the case 4a is adhered. Then, the toner flies toward the electrostatic latent image on the surface of the photosensitive drum 1, and a toner image is formed on the surface of the photosensitive drum 1. This toner image is transported by the paper feed roller 6 as shown by the arrow, transferred onto the copy paper 11 via the transfer device 5, and fixed on the copy paper 11 by the fixing roll 7. Copying is performed in this manner. In the drawing, reference numeral 9 denotes a cleaner for removing transfer residual images and residual toner on the surface of the photosensitive drum 1, and reference numeral 10 denotes an eraser lamp for making the photosensitive drum 1 zero and preparing for the next charging.

When the toner is non-magnetic, this type of developing roll 4 is generally constituted by a metal shaft (core metal) 41a and a conductive layer 42a on the outer periphery thereof, as shown in FIG. If it has, as shown in FIG. 7, it is constituted by a metal sleeve (core bar) 41b, end caps 41c at both ends thereof, a magnet shaft 41d in the metal sleeve 41b, and a conductive layer 42b on the outer periphery of the metal sleeve 41b. ing. In the figure, 4
3 is a bearing.

[0004]

The conductive layers 42a and 42b of the developing roll 4 are formed from the viewpoint of cost reduction and the like.
Recently, a coating material is used in which a conductive material such as a carbon powder and a conductive metal oxide is dispersed in a synthetic matrix (binder), and this is coated on the surface of the metal sleeve. However, the developing roll obtained by using the above carbon powder causes fog (for example, black spots are formed on white paper) because the residual charge of the toner is easily released.
However, there is a problem that it is difficult to control the electric resistance, and as a result, unevenness of the copied image occurs. Further, the developing roll obtained using the conductive metal oxide powder has an advantage that a uniform copied image can be obtained because the control of electric resistance is relatively easy, but the residual charge of the toner is hard to escape, As a result, there is a problem that image density is reduced and fog occurs.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a developing roll capable of obtaining a uniform and sufficient copy image density and having excellent fog resistance.

[0006]

To achieve the above object, according to an aspect of the developing roll of the present invention is a developing roll conductive polymer layer on the outer periphery of the shaft body is formed, the conductive polymer layer Is formed of a conductive paint in which two types of conductive metal oxide powders having the following properties (A) and different particle sizes having different properties are dispersed and contained in a binder resin. (A) The particle size Mp of the conductive metal oxide powder M is Mp> 0.
1 μm, the particle size Np of the conductive metal oxide powder N is Np <
0.1 μm and the particle size of both is inequality Mp> 2N
Two kinds of conductive metal oxide powders having different particle sizes satisfying p.

[0007]

The present inventors have conducted a series of studies in order to obtain a developing roll having a uniform and sufficient image density and excellent fog resistance. As a result, the conductive metal oxide powder having a large particle size (average particle size) and the conductive metal oxide powder having a small particle size have two different types of conductive metal oxide powder. When two types of conductive metal oxide powders having a specific relationship are used and used as a material for forming a conductive polymer layer of a developing roll, a conductive material having a small particle size is interposed between conductive metal oxide powders having a large particle size. The metal oxide powder enters, the electric charge smoothly flows between the conductive metal oxide powders, and the residual electric charge of the toner is easily released. Therefore, the present inventors have found that it is easy to control the toner flying from the roll, and that a uniform and sufficient image density can be obtained, and further excellent fog resistance can be obtained.

Next, the present invention will be described in detail.

[0009] The developing roll of the present invention comprises a shaft and a conductive polymer layer formed on the outer periphery of the shaft.

The shaft is not particularly limited.
A metal core made of a solid metal body, or a metal cylindrical body whose inside is hollowed out is used.

The conductive polymer layer formed on the outer periphery of the shaft body is formed using a conductive paint containing a binder resin and two types of conductive metal oxide powders M and N having different particle sizes. The thickness of the conductive polymer layer is generally 5
It is preferable to set the thickness to 0 to 300 μm.

The binder resin is not particularly limited and may be a conventionally known binder resin.
An acrylic resin, a melamine resin, a phenol resin, an epoxy resin and the like can be given. These are used alone or in combination.

The two types of conductive metal oxide powders M and N having different particle sizes include conductive titanium oxide, tin oxide,
Zinc oxide and the like may be mentioned, and the same or different ones may be used. These may be used alone or in combination. Then, the conductive metal oxide powder M
Must exceed 0.1 μm, and the particle size Np of the conductive metal oxide powder N must be less than 0.1 μm. Further, the relationship between the two particle sizes must satisfy the following inequality.

Mp> 2Np That is, by using particles having different particle sizes at a boundary of 0.1 μm as described above, the conductive metal oxide powder having a small particle size is separated from the conductive metal oxide powder having a large particle size. And the flow of charge between the powder particles becomes smoother,
The residual charge of the toner is easily escaped. For this reason, a sufficient image density is obtained, and the fog resistance is also improved. Further, it is preferable that the electric resistances Mv and Nv of the two types of conductive metal oxide powders M and N having different particle sizes satisfy the following inequality.

Mv <Nv Mv: electric resistance of the conductive metal oxide powder M Nv: electric resistance of the conductive metal oxide powder N

Further, the electric resistance RMv of the conductive paint containing only the conductive metal oxide powder M and the electric resistance Rm of the conductive paint containing only the conductive metal oxide powder N are described.
Nv preferably satisfies the following inequality. What
In the present invention, the electric resistance of the conductive paint refers to the conductive paint.
Of a roll with a conductive polymer layer
It refers to qi resistance. RMv <RNv

By having the above-described electrical resistance, the flow of charges between the conductive metal oxide powder M particles can be made smoother, and as a result, a more sufficient image density can be obtained and the fog resistance can be improved. Will be improved.

It is preferable that the addition amounts Mc and Nc of the two types of conductive metal oxide powders M and N having different particle sizes and the total compounding amount of the two are set within a range satisfying the following conditions. . Mc is 20 parts or more and 150 parts or less and Nc is 50 parts or more and 150 parts or less with respect to 100 parts by weight (hereinafter abbreviated as “parts”) of the binder resin. Further, the total amount (Mc + Nc) of both is set to 70 to 250 parts. That is, when the addition amounts of Mc and Nc are less than 20 parts and less than 50 parts, respectively, it is difficult to set the electric resistance of the developing roll to 10 ¹⁰ Ω · cm or less, and a decrease in image density due to a charge-up phenomenon occurs. There is a tendency. If the addition amounts of Mc and Nc exceed 150 parts, respectively, and the total amount (Mc + Nc) of both exceeds 250 parts, the addition amount of the conductive metal oxide powder is excessive, coating is difficult, and it is difficult to form a roll. Because.

The conductive coating composition may optionally contain other additives, such as fillers, in addition to the above components, if necessary. Examples of the filler include titanium oxide, calcium carbonate, talc, crew, and the like.

The conductive coating material, which is a material for forming the conductive polymer layer on the outer periphery of the developing roll of the present invention, is prepared by, for example, adding two types of conductive metal oxide powders M and N having different particle sizes to a binder resin.
And other additives are mixed, mixed and stirred using a ball mill or the like, and the mixture is dissolved in an appropriate solvent (xylene, methanol, etc.).

The developing roll of the present invention can be produced by using the above conductive paint, for example, as follows.
That is, the conductive paint is applied to the outer peripheral surface of the metal sleeve by dipping or the like and dried to form a conductive polymer layer. More specifically, the conductive paint is stored as a dipping liquid in a tank 17 as shown in FIG. Next, the metal sleeve 12 is set upright, and is repeatedly immersed in the conductive paint to form a conductive polymer layer on the outer peripheral surface of the metal sleeve 12. At this time, it is preferable that the conditions such as the viscosity of the conductive paint, the rate of elevating and lowering, the number of times of elevating and lowering be set so that the liquid film of the conductive paint is in the range of 50 to 300 μm. The film on which such a liquid film is formed is dried at a temperature of about 60 ° C. for 1 hour to remove the solvent, and subsequently heated at a temperature of 150 ° C. for 30 minutes to form a conductive polymer layer. Thus, a developing roll having a structure as shown in FIG. 1 can be manufactured. In the figure, 12 is a metal sleeve, and 13 is a conductive polymer layer.

FIG. 2 shows another embodiment of the developing roll of the present invention. Reference numeral 14 denotes a metal cylinder.
The conductive polymer layer 13 is formed on the outer peripheral surface of the substrate. Fifteen
Is an end cap.

FIG. 3 shows still another embodiment of the developing roll of the present invention. Reference numeral 42 denotes a magnet shaft. The metal sleeve 16 on which the conductive polymer layer 13 is formed is coaxially provided with a gap around the magnet shaft 42. End caps 41 are fitted into the left and right ends. In the figure,
43 is a bearing.

The electric resistance of the conductive polymer layer formed on the outer peripheral surface of the developing roll thus obtained is 10 ¹⁰ Ω ·
cm or less. That is, by setting the electric resistance value of the conductive polymer layer to 10 ¹⁰ Ω · cm or less, it is possible to prevent a decrease in image density due to a charge-up phenomenon.

[0025]

As described above, in the developing roll of the present invention, the conductive metal oxide powder having a large particle size (average particle size) and the conductive metal oxide powder having a small particle size Conductive metal oxide powders of different types, which have different particle sizes, and have a specific relationship between the two particle sizes, use a conductive paint dispersedly containing two types of conductive metal oxide powders. A polymer layer is formed. For this reason, the conductive metal oxide powder having a small particle size enters between the conductive metal oxide powders having a large particle size, and the charge flows smoothly between the conductive metal oxide powders, so that the residual charge of the toner is easily released. Therefore, it is easy to control the toner flying from the roll, and a uniform and sufficient image density can be obtained, and further excellent fog resistance can be obtained. Thus, the developing roll of the present invention is optimal in electrophotographic copying machines, a developing roll such as a printer.

Next, examples will be described together with comparative examples.

[0027]

Examples 1 to 8 and Comparative Examples 1 to 4 First, three kinds of conductive materials having the characteristics shown in Table 1 below were prepared. In addition, the electric resistance in a table | surface was measured as follows. That is, a metal plate (a metal cylinder having an outer diameter d) -a powder-metal plate whose electric resistance is to be measured is placed inside a resin cylinder having an inner diameter d (the outer diameter is arbitrary) and an electric resistance of 10 ¹⁴ Ω · cm or more. In order,
The powder was pressed at a pressure of 100 kg / cm ² and the electric resistance was measured. When the value at this time is ρ and the thickness of the green compact is t, the electric resistance ρc of the powder was calculated according to the following formula (the electric resistance in Table 1 is the value of ρc).

[0028] ρc = ρS / t (It should be noted, S = πd ^2/4)

[0029]

[Table 1]

The components shown in Tables 2 and 3 below were blended in the proportions shown in the same table, mixed and stirred using a ball mill, and the mixture was dissolved in 100 parts of methanol to prepare a conductive paint. did. Next, a conductive polymer layer was formed on the outer peripheral surface of the metal sleeve serving as the core metal by applying a conductive paint by a dipping method and drying. Thus, a developing roll having the structure shown in FIG. 1 was obtained.

[0031]

[Table 2]

[0032]

[Table 3]

The electrical resistance, the image density of the developing roll and the fogging index of the thus obtained Examples and Comparative Examples were measured. The results are shown in Tables 4 to 8 below. Further, the electric resistance of the conductive paint containing each of the conductive metal oxide powders alone was measured. The results are shown in Tables 4 to 8 below. It is to be noted that the image density, the current
The image roll is incorporated into an electrophotographic copying machine to perform image output,
In this image output, a solid black copy was taken at the maximum density, and the density of the copy was measured with a reflection densitometer manufactured by Macbeth. Then, those having measured values of 1.3 or more were evaluated as ○, and those having 1.2 to 1.3 were evaluated as Δ. Also,
The fogging index is calculated at any of 10 points (1
(0 mm × 10 mm), and the fogging amount was measured.
It was shown by an index when it was set to 00. In addition, the electric resistance was measured by using a measurement system shown in FIG. 8B with 20 electrodes 21 having the shape shown in FIG. 8A formed on the roll surface. In the figure, 20 is a roll, 21a is a main electrode, 2
1b is a guard electrode. The electric resistance values in Examples and Comparative Examples are average values of the measured values at 20 points.

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

[0038]

[Table 8]

From the results of Tables 4 to 8, it was found that
The developing roll had a higher image density and a lower fog index than the comparative example. From this, it can be seen that the products of Examples have sufficient image density and are excellent in fog resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a developing roll of the present invention.

FIG. 2 is a sectional view showing another embodiment of the developing roll of the present invention.

FIG. 3 is a sectional view showing still another embodiment of the developing roll of the present invention.

FIG. 4 is an explanatory view showing a method of manufacturing the developing roll of the present invention.

FIG. 5 is a configuration diagram illustrating a copying mechanism of the electrophotographic copying machine.

FIG. 6 is a sectional view showing a conventional developing roll.

FIG. 7 is a sectional view showing another conventional developing roll.

FIG. 8A is an explanatory view showing the shape of an electrode formed on the roll surface when measuring the electric resistance of the developing roll,
(B) is an explanatory view showing a measurement system of the electric resistance value of the developing roll using the same.

[Explanation of symbols]

 12 metal sleeve 13 conductive polymer layer

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akihiko Kaji Komaki-shi, Aichi 3600 Gezu, Kitai-gaiyama Tokai Rubber Industry Co., Ltd. (56) References JP-A-3-24570 (JP, A) JP-A-3-20763 (JP, A) JP-A-4-24670 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15 / 08 501 G03G 15/02 101 G03G 15/16 103 G03G 21/06 F16C 13/00

Claims (2)

(57) [Claims] 1. A developing roll in which a conductive polymer layer is formed on the outer periphery of a shaft body, wherein the conductive polymer layer has the following characteristic (A) in a binder resin and has a different particle size. A developing roll formed of a conductive paint in which various kinds of conductive metal oxide powders are dispersed and contained. (A) The particle size Mp of the conductive metal oxide powder M is Mp> 0.
1 μm, the particle size Np of the conductive metal oxide powder N is Np <
0.1 μm and the particle size of both is inequality Mp> 2N
Two kinds of conductive metal oxide powders having different particle sizes satisfying p. 2. The electric resistance Mv of the conductive metal oxide powder M.
2. The developing roll according to claim 1, wherein the electrical resistance Nv of the conductive metal oxide powder N satisfies the following inequality. Mv <Nv