JPH0416974A - Conductive resin material - Google Patents

Abstract

PURPOSE:To obtain the conductive resin material which can form copied images having high image quality by incorporating a tert-butyl/phenol novolak resin into the specific conductive resin material. CONSTITUTION:The following components (A) to (D) are incorporated as the conductive resin material and this member is so constituted as to contain the tert-butyl/phenol novolak resin in place of at least a part of the component (A). (A) the phenol novolak resin, (B) a hardener, (C) a filler, and (D) a conductive material. Namely, if the material formed by using the tert-butyl/phenol novolak resin as its essential component 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 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.

[Prior Art] Generally, an electrophotographic copying machine makes copies 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 slit of an optical 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 electric attraction to form a toner image, and this toner image is transferred to copy paper. Copies are made by fixing the image.

[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 due to the static elimination 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 a conductive resin material containing the following components (A) to (D), ) A structure is adopted in which a tert-butylphenol novolac resin is contained in place of at least a part of the components.

(A) Phenol novolac resin.

(B) Hardening agent.

(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, as the conductive resin material constituting the developing roll, tert,
- When using a resin whose main component is butylphenol novolak resin (hereinafter abbreviated as rtBu-phenol novolac), the tert-butyl group is rich in electron donating properties, so a developing roll using it can produce a negatively charged toner. The present inventors have discovered that when toner is negatively charged, the amount of negative charge on the negatively charged toner is significantly improved, and the present invention has been achieved.

The conductive resin material of the present invention includes a phenol novolak resin (component (A)), a cured iJ (component (B)), a filler (component (B)), and a filler.
(C) component>, conductive material <(D) component>, and the above (
A) tB used in place of some or all of the ingredients
It is obtained using u-phenol novolac. usually,
This conductive resin material is in the form of pellets or powder.

The phenol novolak resin of component (A) is not particularly limited, and conventionally used phenol novolak resins can be used as they are.

In addition, the tBu-phenol novolak used in place of part or all of the phenol novolak resin of component (A) is represented by the following general formula, and n in the above general formula is O to 4. It is preferable to use a range.

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 of the phenol novolak resin is replaced with tBu-phenol novolak, there is not much difference in effect from replacing the entire phenol novolak resin.

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

The curing agent for component (B) serves as a curing agent for the phenol novolac resin and tBu-phenol novolac for component (A), and hexamethylenetetramine is usually used.

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

Further, examples of the conductive material of component (D) include car Δ;

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

When blending the above components (A) to (D), if C-ZnO among the conductive materials is used in combination with tBu-phenol novolak, the synergistic effect will reduce the amount of negative charge on the negatively charged toner. Significant improvement effects 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-exemplified phenol novolak resin (component (A)), t
Using Bu-phenol novolac, the above (B)
The (C) component material and other additives are appropriately blended to form a base component material, and the (D) component conductive material is blended therewith. In this case, the proportion of the conductive material used is the resin (phenol novolac + tBu-
From the viewpoint of effectiveness, it is preferable to blend the compound in an amount of 20 to 350 parts per 100 parts by weight (hereinafter referred to as "parts") of the phenol novolak. 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.

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 composed of the conductive resin material of the present invention, and due to the action of tBu-phenol novolac,
It is possible to significantly improve the amount of negative charge on negatively charged toner.

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.

[Effects of the Invention] As described above, the conductive resin material of the present invention contains a phenol novolac resin, a curing agent, a filler, and a conductive material, and at least a part of the phenol novolac resin is tBu.
Since the tBu-phenol novolak is substituted with the tBu-phenol novolak, when a developing roll is constructed with this, the electron-donating property of the tBu-phenol novolak can significantly improve the charge amount of the 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 with a particle size of 0.1 to 2Il [II+II].

Next, using the conductive resin material thus obtained, a developing roll having an outer diameter of 25 mm and a conductive layer thickness of 2[II[Il] was prepared. 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]

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 containing the following components (A) to (D), characterized by containing a tert-butylphenol novolac resin in place of at least a part of the component (A). conductive resin material. (A) Phenol novolac resin. (B) Hardening agent. (C) Filler. (D) Conductive material.