JPH0416973A - Conductive resin material - Google Patents

Abstract

PURPOSE:To obtain the conductive resin material which can form copied images having high image quality by using an epoxy resin and tert-butyl/phenol novolak resin. CONSTITUTION:The conductive resin material is constituted to contain the following components (A) to (D): (A) the epoxy resin, (B) tert-butyl/phenol novolak resin, (C) a filler, and (D) a conductive material. Namely, if the material formed by making combination use of the epoxy resin and the tert-butyl/phenol novolak resin is used as the conductive resin material of a conductive layer 2 constituting a developing roll, the electrostatic charge quantity of the negative charges to a negatively charged toner is greatly improved as the tert-butyl group thereof has an excellent electron donating characteristic. The electrostatic charge quantity to the negatively charged toner is greatly improved in this way and the effect of enhancing the image quality of the copied images is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive resin material that is a component of a developing roll used in an electrophotographic copying machine or the like.

[Conventional technology]

-S, the electrophotographic copying machine is adapted to copy in the following manner. That is, the outer circumferential surface of a photosensitive drum that rotates around its axis is positively or negatively charged by ion charging by a corotron or frictional charging by a charging roll, and the surface of the photosensitive drum is exposed to a slint of a light image of the original. is projected to form an electrostatic latent image corresponding to the original optical image. Then, the developing roll and the toner are brought into contact and the toner is charged by the friction, and the toner is attached to the electrostatic latent image on the photosensitive drum by the electric attraction force B, forming a toner image, and this toner image is transferred to the copy paper. Copies are made by transferring and fixing the image onto a computer.

[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 charging toner and other developers is sufficient, and even once charged, the charge is removed by the neutralizing effect of the conductive material component in the developing roll. This poses a problem when it comes to forming high-quality copied images.

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

[Means for Solving the Problems] In order to achieve the above object, the conductive resin material of the present invention is configured to contain the following components (A) to (D).

(A) Epoxy resin.

(B) tert-butylphenol novolac resin.

(C) Filler.

(D) Conductive 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 on the negatively charged toner is greatly improved when the negatively charged toner is negatively charged with a developing roll using the developing roll.

The conductive resin material of the present invention includes epoxy resin (component (A)), tBu-phenol novolak (component (B)),
It is obtained using a filler (component (C)) and a conductive material (component (D)). Usually, the conductive resin material of the present invention is in the form of pellets or powder.

The epoxy resin of component (A) is not particularly limited, and conventionally used epoxy resins can be used as they are. Particularly suitable among epoxy resins are those having an epoxy equivalent of 160 to 230. An epoxyphenol novolak (glycidyl etherified 0-talesol novolac) type epoxy resin having a melting point of 60 to 100°C and a molecular weight of 500 to 2,500 is preferred.

In addition, t used in combination with the epoxy resin of the above component (A),
The Bu-phenol novolak acts as a curing agent for the epoxy resin, and the OH of the tBu-phenol novolak acts as a curing agent for the epoxy resin.
The groups are blended in equal amounts. Such tBu-
The phenol novolak is represented by the following general formula, and it is preferable to use one in which n in the above general formula is within 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 it within the range of 0 to 70% from the viewpoint of the effect of improving the amount of charge and the mechanical strength of the developing roll.

Used with the above (A) component and (B) component (
Examples of the filler of component C) include glass fiber calcium silicate (wollastonite).

Examples of the conductive material of component (D) include carbon black graphite C-TiO2, C-ZnO, and the like.

In addition to the above components (A) to (D), mold release agents such as stearic acid, flame retardants such as calcium hydroxide, furfural, polycresyl phosphate, etc., and dyes,
Coloring agents such as pigments are used as necessary.

When blending the above-mentioned components (A) to (D), if C-' Z n O is used in combination with tBu phenol novolac among the conductive materials, the synergistic effect will increase the negative charge on the negatively charged toner. The effect of further improving the quantity can be obtained.

The conductive resin material of the present invention can be manufactured using the above-mentioned raw materials, for example, in the following manner. That is, the above-mentioned epoxy resin (component (A)) and tBu-phenol novolak (component (B)) are used, and the above-mentioned (C
) Component materials and other additives are appropriately blended to form a base component material, and the conductive material of component (D) is blended with this. In this case, the ratio of the conductive material used is 2 parts by weight (hereinafter abbreviated as "parts") to 100 parts by weight of the resin (epoxy resin + tBu-phenol novolak) in the base component material.
From the viewpoint of effectiveness, it is preferable to mix in a proportion of 0 to 350 parts. Next, such a compound is passed through a conventionally known kneader.
It can be obtained by mixing and kneading in a mixer such as , and then pulverizing 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.

The conductive resin material of the present invention thus obtained is
Usually, it is extruded into a cylindrical shape using an extrusion molding machine or the like, and is fitted around the outer periphery of the core bar 1 as a conductive layer 2, as shown in the drawings. In this case, when externally fitting, an adhesive containing fine conductive material particles such as metal powder is applied to the outer peripheral surface of the core bar 1 or the inner peripheral surface of the cylindrical molded body, and this forms a conductive adhesive layer. It becomes 3. In the developing roll thus obtained, the conductive layer 2 is made of the conductive resin material of the present invention, and the amount of negative charge on the negatively charged toner is reduced by the action of tBu-phenol novolak in the material. Significant improvement effects can be achieved.

Note that the above developing roll can be used not only for electrophotographic copying machines, but also for electrophotographic copying machines.
Widely used for facsimiles, printers, etc.

〔Effect of the invention〕

As described above, the conductive resin material of the present invention contains an epoxy resin, a tBu-phenol novolac filler, and a conductive material, and since the above-mentioned epoxy resin and tBU-phenol novolak are used together, the developing roll can be In this case, due to the electron donating property of tBuphenol novolac, 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 2IITI11.

Next, a developing roll having an outer diameter of 25 mm and a conductive layer 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]

The drawing is a configuration diagram of a developing roll using the conductive resin material of the present invention. 1... Core metal 2... Conductive layer 3... Conductive adhesive layer Patent applicant Tokai Rubber Industries Co., Ltd.

Claims (1)

[Claims] (1) A conductive resin material characterized by containing the following components (A) to (D). (A) Epoxy resin. (B) tert-butylphenol novolac resin. (C) Filler. (D) Conductive material.