JPH047571A - Conductive roll - Google Patents

Abstract

PURPOSE:To form a copy image of high picture quality by using specific setting resin for 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 the setting resin, derived from resin A between tert-butyl phenol novolak resin A and phenol novolak resin B and a setting agent, and dispersing conductive material particles in the base material. Namely, a material consisting principally of tert-butyl phenol novolak resin (tBu-phenol novolak) is used as the conductive resin material which constitutes the developing roll and when negative electrostatically charged toner is charged electrostatically to the negative polarity by using the developing roll which uses the roll, the electrosatic charging quantity of negative charges to the negative electrostatically charged toner is improved since the tert-buthy group is high in electron donative ability. Consequently, the picture quality increase effect of the copy image can be 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 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 images 1 to 1 on the copy paper 5 to which the toner images have 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 the following (A) component. The base material is a cured resin derived from at least component (A) of the components (B) and a curing agent, and conductive material particles are dispersed in the base material.

(A) tert-butylphenol novolac resin.

(B) Phenol novolak resin.

[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, tert-
When using a resin whose main component is butylphenol novolac resin (hereinafter abbreviated as rtBu-phenol novolac), the tert-butyl group is rich in electron donating properties, so a developing roll using this resin can be used to generate negatively charged toner. The present invention was achieved by discovering that when negatively charged toner is charged, the amount of negative charge on negatively charged toner is significantly 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.

The materials for forming the conductive layer (conductive resin material) that are formed along the circumference of the shaft are generally a phenol novolac resin, a curing agent, conductive material particles, and one of the phenol novolac resins. tBu-phenol novolak, which is used in place of part or all of the tBu-phenol novolac.

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

In addition, tBu-phenol novolac used in place of part or all of the above phenol novolak resin is
It is represented by the following general formula (% formula %), and it is preferable to use one in which n in the above general formula is in the range of 0 to 4.

Regarding the ratio of the phenol novolak resin and tBU-phenol novolak resin, it is most effective to use tBu-phenol novolak in place of all of the phenol novolak resin. However, within the range in which 80 to 40% by weight (hereinafter abbreviated as "%") of the phenol novolac resin is replaced with tBU-phenol novolac, there is not much difference in effect from replacing the entire phenol novolak resin.

The total content of such tBu-phenol novolak and phenol novolac resin should be set so that it is within the range of 20 to 70% of the entire conductive resin material, to improve the effect of improving the amount of charge and developing. This is preferable from the viewpoint of the mechanical strength of the roll.

The curing agent includes the phenol novolak resin and t
It serves as a curing agent for Bu-phenol novolak, and hexamethylenetetramine is usually used.

Further, examples of the conductive material particles include carbon black graphite, C-ZnO, C-TiO2, and the like.

In addition to the above ingredients, fillers such as glass fiber, calcium silicate (wollastonite), mold release agents such as stearic acid, flame retardants such as calcium hydroxide, furfural, polycresyl phosphate, etc. plasticizers and dyes,
Coloring agents such as pigments are used as necessary.

Therefore, in the present invention, the base material includes, as necessary, other component raw materials other than the above, in addition to the phenol novolac resin, the cured resin derived from the tBu-phenol novolac, and the curing agent.

In particular, the tBu-phenol novolak is used in place of part or all of the phenol novolak resin,
When forming a conductive layer on the outer periphery of the shaft by blending a curing agent etc. with this, among the above-mentioned conductive material particles, especially C-Zn
When O is used in combination with tBu-phenol novolak, the synergistic effect results in a significant improvement in the amount of negative charge on the negatively charged toner.

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 phenol novolac resin, tBU-phenol novolak, is used, and other additives are suitably blended therein to form a base component material, and the above-mentioned conductive material particles are blended into this. In this case, the proportion of the conductive material particles used is the resin (phenol novolac resin + tBu - phenol novolac 100 parts by weight (hereinafter abbreviated as "parts") in the base component material).
From the viewpoint of effectiveness, it is preferable to mix in the ratio of 20 to 350 parts. 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, when performing the above-mentioned mixing and purification, in addition to blending the raw materials as described above and then adding and mixing, each raw material is sequentially added and mixed according to the recipe table.
Kneading is also carried out. 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 manner, the conductive layer 2 is made of a hardening resin derived from a phenol novolac resin, tBu-phenol novolac which is partially or completely replaced with the hardening agent, and a hardening agent. ), and conductive material particles are dispersed in this base material. Therefore, due to the action of the tBu-phenol novolac in the base material, 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 applicable 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
At least a portion of the phenol novolac resin is tBu-
The base material is a cured resin derived from the substituted phenol novolac and a curing agent, and the conductive material particles are dispersed in the base material, so the electron donating property of tBu-phenol novolak It is possible to achieve a significant effect of improving the amount of charge on negatively charged toner. Therefore, when this is used in 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 having a particle size of about 0.1 to 2ffIff1.

Next, a developing roll having an outer diameter of 2511II11 and a conductive layer thickness of 2 m 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 amount of charge is based on the amount of charge of Comparative Example 1 as 100,
Based on this, a larger value indicates an improved charge amount, and a lower value indicates a decreased 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 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, the conductive layer comprising at least (A) of the following components (A) and (B). 1. A conductive roll having a base material made of a cured resin derived from a hardening agent and a hardening agent, and having conductive material particles dispersed in the base material. (A) tert-butylphenol novolac resin. (B) Phenol novolac resin.