JPH047570A - Conductive roll - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a conductive roll used as a developing roll of an electrophotographic copying machine.

[Conventional technology]

An electrophotographic copying machine forms a document image as an electrostatic latent image on the surface of a photosensitive drum, attaches toner to this to form a toner image, and copies this toner image by transferring it to copy paper. It is. This type of electrophotographic copying machine is generally constructed as shown in FIG. 2, and copies are made in the following manner. That is, ■ is a photosensitive drum that rotates in the direction of the arrow around the shaft 1a. A corona charger 2 charges the outer peripheral surface of the photosensitive drum 1 positively or negatively by corona discharge. Reference numeral 3 denotes an exposure device which causes slit exposure of the original optical image to reach the surface of the photosensitive drum 1. As a result, an electrostatic latent image corresponding to the original image is formed on the uniformly charged surface of the photosensitive drum 1. A developing roll 4 is built in the case 4a, and causes the toner in the case 4a to adhere to the electrostatic latent image to form a toner image. Reference numeral 5 denotes copy paper, which is transported in the direction of the arrow, and in the process the toner image on the surface of the photosensitive drum 1 is transferred thereto. 6 is a transfer device for transferring the toner image. Reference numeral 7 designates a static eliminator that removes the electrical charge on the surface of the photosensitive drum 1, and reference numeral 8 designates a cleaner that removes transfer residual images and the like from the surface of the photosensitive drum 1. A fixing roll 9 fixes the toner image on the copy paper 5 onto which the toner image has been transferred.

[Problem to be solved by the invention]

In electrophotographic copying machines having such a structure, there has been a recent demand for improved image quality of copied images, and it is desired that even minute images can be obtained in a clear state. However, at the current stage, it cannot be said that imparting electric charge to the developer such as toner is sufficient, and even for the developer once imparted with electric charge, the charge is removed from the conductive material component contained in the developing roll 4. The effect is a loss of charge, which poses a problem with respect to the formation of high quality reproduced images.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a conductive roll such as a developing roll that can form high-quality copied images.

[Means to solve the problem]

In order to achieve the above object, the conductive roll of the present invention is a conductive roll in which a conductive layer is formed along the circumference on the outer periphery of a shaft body, the conductive layer comprising a phenol novolac resin and a rosin phenol resin. The base material is a cured resin derived from a resin and a hardening agent, and conductive material particles are dispersed in the base material.

[Effect]

The present inventors have conducted extensive research focusing on the constituent materials of the developing roll in order to solve the above-mentioned conventional drawbacks. As a result, when a combination of phenol novolac resin and rosin phenol resin is used as the conductive resin material constituting the developing roll, the amount of charge increases significantly when positively charged toner is positively charged due to the action of the rosin phenol resin. This invention has been achieved by discovering that this can be improved.

The conductive roll of the present invention is composed of a shaft and a conductive layer formed on the outer periphery of the shaft.

The shaft body is not particularly limited, and a metal core made of a cylindrical body, a hollow metal cylindrical body, or the like may be used.

As the forming material (conductive resin material) of the conductive layer formed along the circumference on the outer periphery of the shaft, a phenol novolak resin, a rosin phenol resin, a hardening agent, and conductive material particles are generally used.

The above-mentioned phenol novolak resin is not particularly limited, and conventionally used phenol novolak resins can be used as they are.

Further, the rosin phenol resin used in combination with the above-mentioned phenol novolac resin is obtained by reacting rosin and phenol in the presence of an acid, as represented by the following formula.

The ratio of the phenol novolac resin and rosin phenol resin used is 80% of the phenol novolac resin.
From the ratio of 20 parts of rosin phenol resin to 0 parts by weight (hereinafter abbreviated as "parts"), 50 parts of phenol novolak resin
part of rosin phenolic resin to 50 parts of rosin phenolic resin. Within this range, the effect of significantly improving the amount of charge on positively charged toner can be obtained.

The total content of such phenol novolak resin and rosin phenol resin should be set within the range of 20 to 70% by weight of the entire conductive resin material to improve the charge amount and improve the development roll. Preferable from the viewpoint of mechanical strength and the like.

The curing agent serves as a curing agent for the phenol novolak resin and rosin phenol resin, and hexamethylenetetramine is usually used.

Further, examples of the conductive material particles include carbon black graphite, C-5nO, C-Tfo2, and the like.

In addition to the above ingredients, glass fiber, fillers such as calcium silicate (wollastonite), mold release agents such as stearic acid, flame retardants such as calcium hydroxide, and plasticizers such as furfural and polycresyl phosphate. In addition, coloring agents such as dyes and pigments are used as necessary. Therefore, in addition to the cured resin derived from the phenol novolac resin, the rosin phenol resin, and the curing agent, the base material in the present invention also contains other component materials as necessary.

When blending the above-mentioned component raw materials, if at least one of C-Ti0□ and C-3nO□ among the conductive material particles is used in combination with rosin phenol resin, the synergistic effect will increase the positive charge on the positively charged toner. The effect of further improving the quantity can be obtained.

The conductive roll of the present invention can be manufactured using the above raw materials, for example, in the following manner.

First, the above-mentioned phenol novolac resin and rosin phenol resin are used, and other additives are appropriately blended therein to form a base component material, and the above-mentioned conductive material particles are further blended into this. In this case, the proportion of conductive material particles used is
20 to 3 parts per 100 parts of the resin (phenol novolak resin rosin phenol resin) in the above base component material
From the viewpoint of effectiveness, it is preferable to mix it in a proportion of 50 parts. Next, such a blend is mixed and kneaded using a conventionally known mixer such as a kneader, and then pulverized to form a pellet or the like. In addition, in the above-mentioned mixing and kneading, in addition to blending the raw materials and then adding and mixing them as described above, each raw material is also sequentially added, mixed and kneaded according to the recipe table. Next, the conductive resin material obtained as described above is extruded into a cylindrical shape using an extrusion molding machine or the like, and as shown in FIG. do. In this external fitting, an adhesive containing fine conductive material particles such as metal powder is applied to the outer peripheral surface of the core bar 11 or the inner peripheral surface of the cylindrical molded body, and this is applied to the conductive adhesive layer 13. Become.

In the conductive roll obtained in this way, the conductive layer 12
is made of the above-mentioned conductive resin material, and due to the action of the rosin phenol resin in the material, it is possible to significantly improve the amount of positive charge on the positively charged toner.

The conductive roll of the present invention is generally used as a developing roll in electrophotographic copying machines, but is also widely applied to facsimile machines, printers, and the like.

〔Effect of the invention〕

As described above, the conductive roll of the present invention has a structure in which the conductive layer has a base material of a cured resin derived from a phenol novolac resin, a rosin phenol resin, and a hardening agent, and conductive material particles are dispersed in the base material. Therefore, the effect of significantly improving the amount of positive charge on the positively charged toner can be achieved by the action of the rosin phenol resin. Therefore, when this is used in a developing roll of an electrophotographic copying machine or the like, it is possible to obtain the effect of increasing the quality of the copied image.

Next, examples will be described.

〔Example〕

The raw materials shown in the table below were blended in the proportions shown in the table. Then, these were uniformly mixed and kneaded using a kneader, and then pulverized to form pellets with a particle size of approximately 0.1 to 2 mm.

Next, a developing roll having an outer diameter of 25 mm and a conductive layer having a thickness of 2 mm was made using the conductive resin material thus obtained. The electrical resistance of the obtained developing roll and the effect of improving the amount of charge on negatively charged toner and the effect of improving the amount of charge on positively charged toner are also shown in the same table.

Note that the charge amount is based on the charge amount of Comparative Example 1 as 1oo, and based on this, a larger value indicates an improvement in the charge amount, and a lower value indicates a decrease in the charge amount (see the margin below). ) As is clear from the above table, according to the actual height measurement, it is possible to obtain a significant improvement in the amount of charge for positively charged toner, and to obtain a high quality and clear copy image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electrophotographic copying machine, and FIG. 2 is a block diagram of an embodiment of the present invention. 11... Core metal 12... Conductive layer 13... Conductive adhesive layer Patent applicant Tokai Rubber Industries Co., Ltd. Fuji Xerox Co., Ltd.

Claims (1)

[Claims] (1) A conductive roll in which a conductive layer is formed along the circumference on the outer periphery of a shaft body, the conductive layer containing a hardened resin derived from a phenol novolac resin, a rosin phenolic resin, and a hardening agent. 1. A conductive roll comprising a base material having conductive material particles dispersed in the base material.