JPS6266268A - Carrier for developing electrostatic image - Google Patents

Abstract

PURPOSE:To form stably high quality images with no fog for a long period by forming a coating layer contg. silicone oil besides silicone resin. CONSTITUTION:A coating layer of silicone resin contg. silicone oil is formed on the surface of the core material of a carrier. The silicone oil used may be represented by the formula. Methylsilicone oil having methyl groups as R1-R3 in the formula is preferably used. When the methylsilicone oil is used, the coating layer has superior water repellency, so the triboelectric chargeability of the resulting carrier is not deteriorated by moisture and is extremely stabilized. The amount of the silicone oil used is 2-25wt%, preferably 5-15wt% of the amount of the silicone resin. In case of <2wt%, the effect of the silicone oil can not be expected. In case of >25wt%, the coating layer is softened and the durability is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, etc. The present invention relates to a carrier for developing an electrostatic image, and particularly relates to a carrier for developing an electrostatic image of a resin-coated type having a coating layer made of a silicone resin.

[Conventional technology]

In recent image forming methods, methods using electrostatic latent images are widely used. In electrophotography, for example, an electrostatic latent image is formed by imparting a uniform electrostatic charge to a photoconductive photoreceptor and then performing imagewise exposure. Such an electrostatic latent image is developed with a developer, and the resulting toner image is transferred to transfer paper or fixed as it is to form a visible image.

As a method for developing an electrostatic latent image, a two-component developer consisting of toner and a carrier containing a magnetic material is used, and the developer is made to stand on the surface of a developer carrier by magnetic force to form a magnetic brush. However, a method is widely used in which the magnetic brush rubs the surface of the latent image carrier to electrostatically adhere the toner particles in the magnetic brush to the electrostatic latent image on the latent image carrier.

As carriers used in such development methods, carriers made of particles of ferromagnetic materials such as iron, ferrite, and magnetite have conventionally been known, but when such carriers are used, the developer During use, toner components may transfer and adhere to the surface of the carrier, reducing the triboelectric charging properties between the toner and the carrier, or the ferromagnetic particles described above are highly hygroscopic and may cause the toner to adhere to the surface of the carrier in a humid environment. There are problems such as early deterioration of triboelectrification between the carrier and the carrier.

[Problems to be solved by the invention]

In order to eliminate these problems, a carrier has been developed in which the surfaces of the above-mentioned ferromagnetic particles are coated with a resin. This resin-coated carrier has superior triboelectric charging stability and durability in repeated use compared to conventional carriers, and in particular, carriers whose carrier core material is coated with silicone resin are superior to other carriers. Its properties are superior to those of carriers coated with resin.

However, even with such a silicone resin-coated carrier, if it is used repeatedly over a long period of time, the triboelectric charging properties may deteriorate due to moisture, or the toner substance may adhere to the surface of the carrier particles due to friction with the toner, causing friction. It has been found that there are problems such as a decrease in charging properties, and eventually fogging occurs in the formed visible image, or the image quality becomes unstable.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide a coating layer with excellent water resistance and slipperiness, stable triboelectric charging properties, and a long-term fog-free coating. An object of the present invention is to provide a carrier for electrostatic image development that enables the formation of images of good quality.

[Means for solving problems]

The electrostatic image developing carrier of the present invention is characterized in that it has a coating layer made of a silicone resin containing silicone oil on its surface.

According to such a configuration, since the coating layer contains silicone oil in addition to the silicone resin, the silicone oil imparts excellent to-water properties to the carrier, so that the coating layer is formed only with the silicone resin. The stability of triboelectrification against moisture is significantly better than when the carrier particles are exposed to moisture, and the silicone oil significantly improves the slipperiness of the surface of the carrier particles, resulting in much better releasability of the surface of the carrier particles. This prevents toner substances from adhering to the surface of the carrier particles, and since silicone oil and silicone resin are highly compatible, silicone oil can be stably contained in the coating layer for a long period of time. As a result, the triboelectric charging property becomes stable over a long period of time, and it becomes possible to stably form a fog-free image of good quality over a long period of time.

The present invention will be explained in detail below.

In the present invention, a carrier for electrostatic image development is constructed by providing an IW layer made of a silicone resin containing silicone oil on the surface of a carrier core material.

In the present invention, a coating layer made of a silicone resin containing silicone oil refers to a coating layer in which the silicone oil is present as it is, or a coating layer in which the silicone oil is present as a result of a partial reaction with the silicone resin. It includes both a coating layer and a coating layer.

Examples of the silicone oil used in the present invention include those represented by the following general formula (A).

General formula (A) R1R1Rs+Si-○±, 5i-R3RtR where R+, Rz, R2 represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxyl group, an acyloxyl group, a phenyl group, a phenoxy group, n represents a positive integer.

Among these, the above-mentioned R1, RZ, R1 are particularly preferable.
is a methyl silicone oil in which the methyl group is a methyl group, and when such methyl silicone oil is used, excellent tθ aqueous properties can be obtained in the coating layer, and therefore triboelectric charging properties in the carrier do not deteriorate even in the presence of moisture. It becomes extremely stable.

The silicone oil is of the above R3, R2, R1 types,
0.6 to 1,000,0OOcp depending on the number of n, etc.
A variety of viscosities over a range of s can be obtained.

In the present invention, any of these may be used in forming the coating layer, but those with a viscosity of 100.0OOcps or less are practically preferred, and from the viewpoint of properties and handling, those with a viscosity of 1 to 10,000 cps are more preferred. preferable.

When a silicone oil made of polyorganosiloxane containing a hydrogen atom, a halogen atom, an alkoxyl group, and an acyloxyl group is used as R1, R2, and R8 above, the silicone oil is used as a silicone resin on the surface of the coating layer. Therefore, it is possible to obtain a carrier in which the silicone oil is firmly and stably present on the surface of the coating layer.

Specific examples of the silicone oil used in the present invention include those commercially available under the names shown below, but the silicone oil is not limited to these exemplified substances.

K F -50, 54, 56, 69, 92, 76, 96
L, 96H, 99,410,412゜901.961゜K S -61,700,701,702,703,7
04,707,712,713゜714.722,72
5,740,742,751,780,782,785
゜786.787,788゜K P -301, 310, 320, 321, 330,
331,340° Polon-MR, MC;, MF
-1, MK -206°MN.

(All of the above are manufactured by Shin-Etsu Chemical Co., Ltd.) The proportion of silicone oil used is 2 to 25% by weight, preferably 5 to 15% by weight based on the silicone resin.

If this ratio is too small, no effect can be expected from the silicone oil, while if it is too large, the coating layer becomes soft and its durability decreases.

In the present invention, the silicone resin used together with silicone oil to form the coating layer is not particularly limited, but
For example, condensation reaction type silicone resins that are cured by the reactions shown in (1) and (2) below can be particularly preferably used.

■Heating dehydration condensation reaction R, Rs -O-5i-○H+ HO-3i-0-heating
11 ■ Room temperature humidity curing reaction R4Rs -O-3i-OX + XO-3i-0-128O
In the formula X l 1, Ox represents an alkoxy group, a ketoxime group, an acetoquine group, an aminoxy group, or the like.

Particularly preferred among such condensation reaction type silicone resins are those in which the substituent is a methyl group. The coating layer obtained using a condensation reaction type silicone resin in which the substituent is a methyl group has a dense structure and has a very good 1G water resistance, with a resistance of 1! It can be used as a carrier with extremely good properties.

In the present invention, as the silicone resin, either a heat-curable silicone resin or a room-temperature-curable silicone resin can be used. When using a room-temperature-curable silicone resin, heating to a particularly high temperature is recommended for curing. Since this is not necessary, the carrier of the present invention can be easily manufactured.

Room temperature curable silicone resin is a silicone resin that cures at a temperature of about 20 to 25 degrees Celsius or slightly higher than this in a normal atmosphere.
It does not require temperatures exceeding ℃.

In forming the coating layer, a mixture of silicone resin and other resin may be used. Examples of such other resins include acrylic resins, styrene resins, epoxy resins, urethane resins, polyamide resins, polyester resins, acetal resins, polycarbonate resins, phenolic resins, vinyl chloride resins, vinyl acetate resins, cellulose resins, and polyolefin resins. , their copolymer resins, blended resins, and the like.

As the carrier core material, materials conventionally used as carrier core materials such as glass beads and metal particles can be used, but in order to enable development by the magnetic brush method, which is advantageous as a development method, magnetic particles are used. It is preferable to use Such magnetic materials include ferrite, magnetite, iron, cobalt, nickel, and other ferromagnetic metals or alloys, or compounds containing these elements, or materials that do not contain ferromagnetic elements but are subjected to appropriate heat treatment. It is possible to use alloys which exhibit ferromagnetism due to ferromagnetism, such as a type of alloy called a Heusler alloy containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, among others. As a carrier core material, the weight average particle size is usually 1 to 1.
A thickness of 1000μ is used, and a thickness of 5 to 500n is particularly preferred.

In manufacturing the carrier of the present invention, a solution of silicone resin and silicone oil dissolved in a solvent is applied to the surface of carrier core particles by a method such as a dipping method, a spray method, or a fluidized bed method, and then is heated and dried to volatilize and remove the solvent, and the coating layer is cured during or after drying to form a coating layer made of silicone resin containing silicone oil.

Other additives may be added to the coating solution for forming the coating layer, if necessary. The solvent is not particularly limited as long as it dissolves the silicone resin and silicone oil, but examples include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran, dioxane, and higher alcohols. , or a mixed solvent thereof can be used.

The temperature when curing the coating layer is, for example, 80 to 300°C.
The temperature is about 250°C or lower, preferably 250°C or lower. If this temperature is high, the silicone oil may be crosslinked and cannot exist on the surface of the coating layer, and in this case, the effect of containing the silicone oil may not be obtained. That is, in order to reliably obtain the effect of containing silicone oil, it is necessary to bond the silicone oil with the silicone resin without crosslinking it on the surface of the coating layer, and to orient the hydrophobic groups of the silicone oil on the surface of the coating layer. It is preferable to contain it in a state where it is

When a room temperature curing silicone resin is used as the silicone resin, it is possible to firmly bond the silicone oil to the silicone resin on the surface of the coating layer by appropriately selecting the curing temperature. With ↑a, it is possible to obtain a carrier having a coating layer having extremely good aqueous properties and high mold releasability. In addition, during drying, metal soaps such as lead, iron, cobalt, tin, manganese, and zinc such as octylic acid and naphthenic acid may be used as drying accelerators, and organic amines such as ethanolamine may also be used as drying accelerators. It can be used effectively.

The thickness of the coating layer thus obtained is usually 0.1 to 20 mm.
It is m.

Further, the average particle size of the carrier of the present invention is, for example, 1 to 1000.
n, preferably about 5 to 200 n.

The toner constituting the developer together with the carrier of the present invention is not particularly limited, and any known toner can be used.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1 (Preparation of coating solution) A solution of 235 g of dimethyldichlorosilane and 170 g of methyltrichlorosilane dissolved in 1200 d of toluene was dropped into 800 tZ water preheated to 70° C. using a dropping funnel to hydrolyze the chlorosilane. .

The active silanol groups thus generated are polymerized by a dehydration condensation reaction and retained in the toluene layer formed by dropping. The separated aqueous layer was removed, the toluene layer was washed with water, and the dehydration condensation reaction was further advanced to obtain a 40% by weight toluene solution of a siloxane oligomer having a hydroxyl group.

A silicone resin solution was prepared by adding 235 g of tri(methylethylketoxime)-methoxysilane and 20 g of dibutyltin diacetate to this toluene solution.

Next, 10 g of silicone oil rKF19J (manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 250 g of this silicone resin solution.
g was added and mixed to prepare a coating liquid.

(Manufacture of carrier) This coating liquid is applied to 500 g of spherical ferrite powder with an average particle size of 100 μm using a fluidized bed apparatus, and then cured to form a carrier having a coating layer made of silicone resin containing silicone oil. I got it. The thickness of the coating layer was about 1 layer. This career is called “Career 1”
shall be.

(Manufacture of toner) Styrene-acrylic copolymer with a weight average molecular weight of 12 x 10' (styrene/n-butyl acrylate = 75
/25) 100 parts by weight of carbon black "Mogull-LJ" (manufactured by Caboft), and 3 parts by weight of low-molecular IT polypropylene "Viscol 660PJ (manufactured by Sanyo Chemical Industries, Ltd.) were mixed, and mixed with two rolls. After melting and kneading, the mixture was crushed and classified to obtain a toner having an average particle size of 12x.This toner is referred to as "Toner 1".

(Actual photocopying test) A developer was prepared by mixing 95 parts by weight of the carrier 1 and 5 parts by weight of toner 1, and this developer was used repeatedly using a modified electrophotographic copying machine r U-Bix 2500. When a copy image was formed using the same method, a good copy image without fogging was still obtained even after the number of times the copy image was formed exceeded 80,000 times.

Comparative Example 1 A carrier was obtained in the same manner as in Example 1, except that the silicone resin solution was used as it was as a coating liquid without adding and mixing silicone oil.

This carrier will be referred to as "comparison carrier 1."

Using Comparative Carrier 1, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As a result, good images could be formed until the number of copied images reached 50,000. However, the number of times the copy image is formed is To, 00
After 0 times, the quality of the copied image deteriorated and fogging occurred.

〔Effect of the invention〕

As explained in detail above, since the carrier of the present invention has a coating layer made of a silicone resin containing silicone oil, the silicone oil imparts excellent water repellency to the carrier, and therefore the silicone resin The stability of the triboelectric properties against moisture is significantly better than when a coating layer is formed solely with silicone oil, and the silicone oil significantly improves the slipperiness of the surface of the carrier particles. The moldability is much better, preventing toner substances from adhering to the surface of the carrier particles, and the silicone oil and silicone resin are highly compatible, so the silicone oil remains stable in the coating layer for a long period of time. As a result, the triboelectric properties become stable over a long period of time, making it possible to stably form fog-free images of good quality over a long period of time. Become.

Claims (1)

[Scope of Claims] 1) A carrier for electrostatic image development, characterized in that it has a coating layer made of a silicone resin containing silicone oil on its surface. 2) The carrier for electrostatic image development according to claim 1, wherein the silicone oil is dimethyl silicone oil. 3) The carrier for electrostatic image development according to claim 1 or 2, wherein the content ratio of silicone oil to silicone resin is 2 to 25% by weight.