JP3279965B2 - Conductive composite fiber and contact charging brush comprising the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composite fiber which can be used as a charging brush for uniformly charging the surface of an image carrier (photoreceptor) in an image forming apparatus such as an electrophotographic copying machine or a printer. It is about.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic copying machine or a printer, the surface of a photoconductive photosensitive member is uniformly charged, and an electrostatic latent image is formed by exposure. The toner is electrostatically attached to the toner image and developed, and the obtained toner image is transferred and fixed on a recording sheet to visualize the image. Since untransferred toner remains on the photoreceptor surface after the transfer, cleaning and removal are performed by a cleaning device, and the same operation as described above is repeated to continuously form an image.

Conventionally, a corona charging device including a metal wire and a shield electrode has been used as a charging device for uniformly charging the surface of a photoreceptor, but it is expensive at several thousand volts (5 kV).
(Approximately 8 kV) and a problem such as generation of harmful ozone to a human body and a photoreceptor at the time of corona discharge. Recently, a conductive rubber roller, a brush in which conductive fibers are planted or a conductive brush is used. A charging device of a contact charging system in which a relatively low voltage (approximately 1 to 2 kV) is applied to a conductor such as a conductive blade and the conductor is brought into contact with a photoreceptor to directly charge the same is proposed and put to practical use. (For example, JP-A-6-67510, JP-B-6-752)
No. 21).

Conventional brush-type yarns of a brush-type charging device include conductive regenerated cellulosic fibers obtained by uniformly dispersing conductive carbon black in cellulose (JP-A-61-7561).
No. 81) is used, but regenerated cellulose has a high hygroscopicity, so that the electrical resistance tends to decrease remarkably under high humidity. To cause image quality unevenness. In addition, since carbon black is uniformly dispersed at a high concentration, the fibers are brittle, and there are problems such as inferior mechanical properties as a brush.

On the other hand, as a raw material for the brush, a conductive component comprising a thermoplastic polymer containing conductive fine particles such as carbon black, which has been conventionally used for antistatic of a fiber material such as clothing, and a fiber-forming heat-sensitive material. Conductive conjugate fibers (JP-A-51-143723, JP-A-54-30919) in which a non-conductive component composed of a plastic polymer is composited have been reported. When used as a brush yarn, there is a problem that uniform charging cannot be performed.

[0006]

The present invention is suitable for a raw material of a charging brush which does not change its electrical resistance under any environmental conditions, has excellent mechanical properties, and can uniformly charge the surface of a photoreceptor. To provide a conductive composite fiber.

[0007]

That is, a conductive conjugate fiber used for a contact charging brush of an electrophotographic image forming apparatus, wherein the conjugate fiber is formed of a conductive polymer comprising a thermoplastic polymer containing conductive fine particles. The component and a non-conductive component made of a thermoplastic polymer are joined together, the cross section is a multi-lobed shape having at least four protrusions, and the conductive component is at the tip of all the protrusions. Polyamide having a composite structure arranged so as to be exposed, and wherein the thermoplastic polymer constituting the conductive component and the thermoplastic polymer constituting the non-conductive component are mainly composed of monomer units having 10 or more carbon atoms. A conductive conjugate fiber selected from the group consisting of aromatic polyester and polyolefin, and a contact charging brush for an electrophotographic image forming apparatus comprising the fiber.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the conductive fine particles used in the present invention, any known conductive carbon black, conductive metal oxide and the like can be used. Considering the conductivity, the volume resistivity of the conductive fine particles in powder form is 10 ⁴ Ω.
cm or less.

The diameter of the particles is at least 0.5 μm, preferably at least 0.5 μm, in order to prevent abrasion damage of the photoreceptor.
It is 0.1 μm or less. As an example of such particles, conductive carbon black has a high volumetric resistivity of the order of 10 ^-2 Ωcm, has high conductivity, and a small and uniform particle having a particle size of the order of 0.01 μm can be easily obtained. It is.

The thermoplastic fiber-forming polymer forming the non-conductive component in the present invention is preferably a fiber-forming polymer whose mechanical properties as a brush are stable under any environmental temperature and humidity. Nylon 11 with low water absorption,
Preference is given to long-chain-length polyamides such as nylon 12 and the like whose main component is a monomer unit having 10 or more carbon atoms, aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyolefins such as polyethylene and polypropylene. Among them, nylon 12 has excellent wear resistance and is particularly suitable as a brush material.

It is important to use a thermoplastic polymer containing conductive fine particles that has stable conductivity at ambient temperature and humidity. In particular, aromatic polyesters such as polyamides and polyethylene terephthalate having 10 or more carbon atoms of monomers such as nylon 11 and nylon 12 having low water absorption described above, and polyethylene terephthalate and polybutylene terephthalate,
Polyolefins such as polyethylene and polypropylene are preferred.

It is preferable that both components use the same type of polymer so that the layer of the non-conductive component and the conductive component does not peel off or drop off during spinning or drawing. However, if the adhesiveness of the two components is improved by adding a mutual affinity improver to either the non-conductive component or the conductive component, a polymer different from the non-conductive component can be used. It is.

The content of the conductive particles in the conductive component varies depending on the conductive performance and particle size of the conductive particles and the conductive performance required as a charging brush material. But,
From the viewpoint of the spinnability and the conductivity of the composite fiber, 10 to 35% by weight is optimal in most cases.

In the present invention, the composite form of the conductive component and the non-conductive component and the cross-sectional shape of the fiber are important. That is, it is important that the cross section of the fiber is a multi-lobed shape having at least four protrusions, and that the conductive component is arranged so as to be exposed at the tips of all the protrusions. FIG.
4 to 4 show examples of composite structures suitable for the present invention. 1 and 2 show examples of the present invention in a four-leaf shape, FIG. 3 shows a six-leaf shape, and FIG. 4 shows a flat shape having six leaves. With such a structure, when the fiber is used for a charging brush, the conductive component disposed on the protrusion of the fiber always comes into contact with the photoreceptor surface, so that the photoreceptor surface can be uniformly charged evenly. Becomes possible.

The preferred exposure ratio of the conductive component to the length of the cross section of the fiber varies depending on the size of the projections, the number of projections, and the cross-sectional shape (flatness) of the fibers. To perform, usually at least 30
% Or more is preferable, and 40% or more is more preferable.

The proportion of the conductive component in the fiber cross section is preferably 50% or less in consideration of spinnability. Figure 1
No. 4 is an example satisfying these conditions.

The conductive conjugate fiber of the present invention can be produced by a conventionally known melt spinning method. At this time, various conditions (temperature, stretching speed, etc.) may be set according to the characteristics of the polymer to be used.

Since the conductive conjugate fiber of the present invention is used as a brush, the single yarn denier is preferably 1 to 20 denier.

[0019]

The present invention will be specifically described below with reference to examples.

(Measurement of Volume Resistivity) The volume resistivity of the polymer was determined by preparing a strand having a diameter of about 2 mm,
The electrical resistance was measured and calculated at a temperature and humidity of 20% RH, a length of 10 cm, and a DC voltage of 100 V. Further, the volume resistivity of the fiber was determined by measuring a sample obtained by bundling 100 single yarns each having a length of 10 cm and bonding both ends to a metal terminal with a conductive adhesive under a constant temperature and humidity conditions and a DC voltage of 1000 V. The electric resistance value was measured and calculated below.

(Evaluation of Charging Property of Brush) The brush was mounted on a charging device of a copying machine, a bias voltage of 1000 V was applied, and the image quality was visually inspected at various temperatures and humidity. The following evaluation was performed according to the degree of unevenness of the image quality. "○": no unevenness "△": unevenness "x": significant unevenness

(Production of conductive polymer) 30 parts by weight of conductive carbon black, 69 parts by weight of 12 nylon (Daiamide L1600 manufactured by Daicel Huls) and 1 part by weight of an amide wax (dispersant) were obtained by melting and mixing. The conductive polymer is referred to as CP1. The volume resistivity of CP1 is 1.3.
× 10 ³ Ωcm.

Example 1 A composite structure as shown in FIG. 1 was prepared by mixing the polymer CP1 and ordinary 12 nylon (Daiamide L1801 manufactured by Daicel Huls) at a composite ratio (volume ratio of conductive component: nonconductive component) of 1: 8. Combined and spun from an "x" shaped orifice at a temperature of 270 ° C, cooled and oiled, spinning speed 600m / m
in. And then 2.6 on a hot roller at 80 ° C.
The yarn Y1 of 300 denier / 50 filament (single yarn 6 denier) was obtained.

For comparison, the following four yarns were produced. (Comparative Example 1) Spinning and stretching were performed in the same manner as in Y1, except that the composite structure was changed to that shown in Fig. 5, to produce a 300-denier / 50-filament yarn Y2.

(Comparative Example 2) The composite ratio (volume ratio of the conductive component to the nonconductive component) was set to 1:10 to form a composite structure as shown in FIG. 6, and the “Y” shape was formed at a temperature of 270 ° C. Spinning speed 600m / m while spinning, cooling and oiling from orifice
in. And then stretched in the same manner as the yarn Y1 to 300
A denier / 50 filament yarn Y2 was produced.

Comparative Example 3 Spinning and drawing were carried out in the same manner as in Y1 except that the composite structure was made as shown in FIG. 7 and the diameter of the spinning orifice was 0.25 mm to produce a yarn Y4 of 300 denier / 50 filaments. .

Comparative Example 4 20% by weight of carbon black
The mixture was dispersed and mixed to produce a 300-denier / 50-filament rayon yarn Y5.

The volume resistivity under certain conditions of Y1 to Y5 was measured. Table 1 shows the results.

Using these yarns, pile length 5 mm, pile density 100,000 filament / in ² , width 30 m
m brush cloth (cotton base cloth), conductive carbon latex (surface resistance 10 ³ Ω) is applied to the back surface, and the diameter is 30
It was wound around a metal lot of mm to prepare a charging brush.

The brush was attached to an electrophotographic copying machine, and the state of the image under various conditions was observed. Table 1 shows the results
Shown in

[0031]

[Table 1]

As is clear from Table 1, the volume resistivity of the rayon yarn Y5 containing carbon black fluctuated at ambient temperature and humidity, and image quality unevenness occurred at low humidity and high humidity. In addition, the yarn Y2 in which the conductive component is not arranged on the protrusion, the yarn Y3 having a three-leaf cross section (the number of protrusions is 3), and the yarn Y4 in which the conductive component is exposed on the fiber surface but has a circular cross section are ,
Although there was almost no change in volume resistivity under any temperature and humidity conditions, the image quality was poor regardless of the temperature and humidity conditions. On the other hand, the conductive conjugate fiber of the present invention provided good image quality under any temperature and humidity atmosphere.

[0033]

As described above, the conductive conjugate fiber of the present invention is made of a fiber material whose conductivity and fiber mechanical properties are not affected by environmental temperature and humidity, and has at least four protrusions having a fiber cross-sectional shape. The conductive component is arranged so as to be exposed at the tips of all the projections in a multi-leaf shape having the same. Therefore, when the brush made of the conjugate fiber of the present invention is used for a contact charging brush of an electrophotographic copying machine or printer,
The conductive component is always in contact with the photoreceptor, and the fiber strength is the same as that of ordinary synthetic fiber, and the conductivity is stable without being affected by the environmental temperature and humidity. The body surface can be charged uniformly, and high quality image can be stably provided. According to the conductive conjugate fiber of the present invention, a charging brush for an electrophotographic image forming apparatus having no charging unevenness and having mechanical properties similar to those of a general synthetic fiber can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a conductive conjugate fiber of the present invention.

FIG. 2 is a cross-sectional view of an example of the conductive conjugate fiber of the present invention.

FIG. 3 is a cross-sectional view of an example of the conductive conjugate fiber of the present invention.

FIG. 4 is a cross-sectional view of an example of the conductive conjugate fiber of the present invention.

FIG. 5 is a cross-sectional view of an example of a conductive conjugate fiber outside the scope of the present invention.

FIG. 6 is a cross-sectional view of an example of a conductive conjugate fiber outside the scope of the present invention.

FIG. 7 is a cross-sectional view of an example of a conductive conjugate fiber outside the scope of the present invention.

[Explanation of symbols]

 1 conductive component 2 non-conductive component

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-46265 (JP, A) JP-A-4-275572 (JP, A) JP-A-57-167416 (JP, A) JP-A-6-265 11916 (JP, A) JP-A-9-101650 (JP, A)

Claims (2)

(57) [Claims] 1. A conductive conjugate fiber used for a contact charging brush of an electrophotographic image forming apparatus, wherein the conjugate fiber is
A conductive component made of a thermoplastic polymer containing conductive fine particles having a particle size of 0.5 μm or less is bonded to a non-conductive component made of a thermoplastic polymer, and the cross section thereof has at least four protrusions. Having a composite structure in which the conductive component is disposed so as to be exposed at the tips of all the protrusions, and a thermoplastic polymer and a non-conductive component that constitute the conductive component The conductive conjugate fiber is characterized in that the thermoplastic polymer constituting the above is selected from the group consisting of polyamides, aromatic polyesters and polyolefins having a main component of a monomer unit having 10 or more carbon atoms. 2. A contact charging brush for an electrophotographic image forming apparatus comprising the fiber according to claim 1.