JPH047572A - Conductive roll - Google Patents

Abstract

PURPOSE:To form a copy image of high picture quality by using setting resin which is derived from epoxy resin, a tert-butyl phenol novolak resin setting agent as the base material of a conductive layer and dispersing conductive particles in the base material. CONSTITUTION:The conductive roll is constituted by forming the conductive layer 12 on the outer periphery of a shaft body 11 along the circumference, and the conductive layer 12 is formed by using setting resin, derived from the epoxy resin, tert-butyl phenol novolak resin setting agent, as the base material and dispersing conductive particles in the base material. Namely, the epoxy resin and tert-butyl phenol novolak resin (tBu-phenol novolak) are used in combination as the conductive resin material which constitutes a developing roll, and then when negative electrostatically charged toner is charged electrostatically to the negative polarity by the developing roll which uses the conductive roll, the electrostatic charging quantity of negative charges is improved since the tert-buthy group is high in electron donative ability. Consequently, the picture quality increase effect of the copy image is obtained.

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, 1 is a photosensitive drum that rotates in the direction of the arrow around an axis 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 represents a static eliminator that removes the electrical charge on the surface of the photosensitive drum 1, and 8 represents a cleaner that removes transfer residual images and the like from the surface of the photosensitive drum l. 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, and the conductive layer is made of epoxy resin and tertiary resin.
The structure is such that a cured resin derived from a t-butylphenol novolak resin curing agent is used as a base material, 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 epoxy resin and tert-butylphenol novolac resin (hereinafter abbreviated as rtBu-phenol novolac) is used as the conductive resin material constituting the developing roll, the tert-butyl group becomes electron-donating. The inventors have discovered that the amount of negative charge can be greatly improved when a negatively charged toner is negatively charged with a developing roll using the developed roller.

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.

The material for forming the conductive layer (conductive resin material) that is formed along the circumference of the shaft is generally an epoxy resin and a tert-butylphenol novolac resin (hereinafter abbreviated as rtBu-phenol novolac). ) and conductive material particles are used.

The above-mentioned epoxy resin is not particularly limited, and conventionally used epoxy resins can be used as they are. Particularly suitable among epoxy resins are those with an epoxy equivalent of 160 to 230 and a melting point of 60 to 100°.
An epoxy phenol novolak (glycidyl etherified O-talesol novolac) type epoxy resin having a C2 molecular weight of 500 to 2,500 is preferred.

Furthermore, the tBu-phenol novolak used in combination with the epoxy resin acts as a curing agent for the epoxy resin, and the OH groups of the tBu-phenol novolak are equivalent to the epoxy groups of the epoxy resin. It is blended as follows. Such a tBu-phenol novolac is represented by the following general formula (%), and it is preferable to use one in which n in the above general formula is in the range of 0 to 4.

The ratio of the epoxy resin to the tBu-phenol novolak used is set so that the epoxy groups of the epoxy resin and the OH groups of the tBu-phenol novolak are equal in amount, as described above, but there are no strict rules. It is not required that the amount be equal to .

The total content of such tBu-phenol novolak and epoxy resin is 2% of the entire conductive resin material.
It is preferable to set the amount within the range of 0 to 70% by weight from the viewpoint of the effect of improving the amount of charge and the mechanical strength of the developing roll.

Further, examples of the conductive material particles include carbon black, graphite, CTiOz, CZnO, and the like.

In addition to the above-mentioned component materials, glass fibers, calcium silicate (wollastonite), etc. are used as fillers. In addition, a mold release agent such as stearic acid, a flame retardant such as calcium hydroxide, a plasticizer such as furfural or polycresyl phosphate, and a coloring agent such as a dye or pigment are used as necessary. Therefore, in this invention,
In addition to the cured resin derived from the epoxy resin and tBu-phenol novolak, the base material also contains other component materials as required.

In particular, when forming a conductive layer on the outer periphery of the shaft by blending the above-mentioned epoxy resin and a curing agent made of tBu-phenol novolac, C-ZnO among the above-mentioned conductive material particles should be mixed with tBu-phenol novolak. When used in combination with the above, due to the synergistic effect, the amount of negative charge on the negatively charged toner can be further improved.

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

First, the above-exemplified epoxy resin and tBu-phenol novolac are used, and other additives are suitably blended into this to form a base component material, and the above-mentioned conductive material particles are blended into this. In this case, the conductive material particles should be used at a ratio of 20 to 350 parts per 100 parts by weight (hereinafter abbreviated as "parts") of the resin (epoxy resin + tBu-phenol novolac) in the base component material. is preferable in terms of effectiveness. Next, such a blend is mixed and kneaded using a conventionally known mixer such as a kneader, and then pulverized to form pellets 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 1.
It becomes 3.

In the conductive roll thus obtained, the conductive layer 2 has a base material (base layer) of a cured resin derived from an epoxy resin and a tBu to phenol novolac curing agent, and conductive material particles are contained in this base layer. It is in a dispersed state. Therefore, due to the action of the tBu-phenol novolak in the mother layer, it is possible to significantly improve the amount of negative charge on the negatively 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, in the conductive roll of the present invention, the conductive layer is
The base material is a cured resin derived from an epoxy resin and a tBu-phenol novolac curing agent, and the conductive material particles are dispersed in the base material. It is possible to achieve a significant effect of improving the amount of charge on negatively charged toner. 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 about 0.1 to 2 m.

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 are also shown in the same table. Note that the charge amount is based on the charge amount of Comparative Example 1 as 100, and a larger value indicates an improvement in the charge amount, and a lower value indicates a decrease in the charge amount.

(The following is a blank space) As is clear from the above table, according to the actual height measurement, it is possible to obtain a significant improvement effect in the amount of charge for negatively charged toner, and to obtain a high quality and clear copy image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an electrophotographic copying machine. 11... Core bar 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, wherein the conductive layer is made of epoxy resin and T.
1. An electrically conductive roll comprising, as a base material, a cured resin derived from an ert-butylphenol novolak resin curing agent and conductive material particles dispersed in the base material.