JPS59200262A - Carrier material for electrophotography - Google Patents

Abstract

PURPOSE:To improve durability and electrostatic chargeability on surface by treating the surface of magnetic powder with a silane coupling agent contg. chlorine and specific compds. contg. a vinyl group. CONSTITUTION:The surface of magnetic powder is treated by using a silane coupling agnet contg. chlorine and a compd. contg. a vinyl group having >=100mol.wt. 1 or >= 2 kinds of compds. among liquid polybutadiene, modified liquid polybutadiene, etc. are used as the comp. contg. a vinyl group having >=100mol.wt. For example, ClC3H6Si(OCH3)3, etc. are used as the silane coupling agent contg. chlorine. The magnetic powder is dipped under agitation into a soln. consisting of said liquid polybutadiene and an org. solvent and the powder is dried, thereby manufacturing a carrier. A coating layer is further formed on the carrier subjected to such surface treatment by using, for example, a methyl methacrylate/styrene copolymer. Such carrier material has excellent durability and electrostatic chargeability on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carrier material for electrophotography.More specifically, the present invention relates to a carrier material for electrophotography having improved durability 8 and surface chargeability.

Conventionally, as a method for developing an electrostatic latent image using toner 7, a cascade development method and a magnetic brush development method are known.

In both of these methods, a two-component developer is used, and this two-component developer consists of a mixture of toner particles with a particle size of 10-odd μm and carrier particles with a particle size of about 25 μm to about 200 μm. Electrostatic forces of opposite polarity created by contact of the particles hold the toner particles to the surface of the carrier particles. When this developer contacts the electrostatic latent image on the photoconductor, toner particles are attracted to the latent image to form an image. In this case, the toner particles must have the correct chargeability S and charge size 7 to ensure that they are preferentially C-double deposited on the desired image area on the photoconductor.

Currently, carriers for electrophotography have a diameter of approximately 25μη2~
Granules of iron, ferrite, steel, glass, etc. of approximately 200 μη2 are commonly used. If these particulates are used as a carrier as they are, the following drawbacks are likely to occur. That is, (1) the volume resistance of the carrier is low, and normal images cannot be obtained during copying (2).

(11) Due to the long-term mechanical collision between the carrier and the toner, thermoplastic resin, which is the main component of the toner, adheres to the carrier surface and forms a film.

As a result, the amount of frictional electrification of the toner becomes non-uniform, making it impossible to obtain a copy with a good image.

G11) Non-uniform charging similar to (11) occurs due to moisture absorption on the carrier surface in a high humidity environment.

(1) In the case of iron or steel, the surface is hardened by moisture and oxygen in the air, causing subtle changes in surface characteristics.

So, what are the drawbacks? In order to solve this problem (2. Methods of treating the surface of the carrier 7 have been proposed, among which coating the carrier particles 7 with a polymer such as methyl methacrylate/styrene copolymer is often practiced. Generally, it seems that the method of spraying and drying the carrier particles (2) in a fluidized bed of the polymer solution (2) is adopted (1).Also, by using the carrier as a core and carrying out suspension polymerization in a system containing monomers, A coating method has also been proposed.As polymers for coating carrier particles, in addition to the above-mentioned methyl methacrylate/styrene copolymer, epoxy resins and fluoropolymers (% KBE 49 51950), alkoxyvinyl silane compounds, and Examples include a copolymer with acrylic ester or styrene (Japanese Patent Application Laid-Open No. 50-147947).

By employing such a polymer-coated carrier, the above-mentioned drawbacks may be temporarily resolved, or they may be used for a long time (two times).
Second, the polymer detaches from the carrier surface, and even a polymer-coated carrier cannot be said to be a durable carrier material.

In view of the above-mentioned current situation regarding carrier materials (1), the inventors have conducted intensive research and found that carrier materials whose surfaces are heat-plasticized with a certain compound enable toner charge stability and long-lasting properties. We have completed the present invention Z by discovering that it is also excellent.

That is, the present invention provides an electrophotographic carrier material whose surface is treated with a chlorine-containing silane coupling agent and a vinyl group-containing compound having a molecular weight of 100 or more.

7 Rankasof containing chlorine according to the present invention.

As the ring agent, for example, C(l C3l-I6S
i (OCH3)3, ClC3J(6S i (OC
2I-I5)a etc. can be opened.

In addition, vinyl group-containing compounds with a molecular weight of 100 or more according to the present invention (1) include liquid polyfridiene, modified liquid polybutadiene, (meth)acrylate or polymer, α-olefin, styrene or its derivatives, divinylbenzene, etc. ZA (can be done. Here, (meth)acrylate means acrylate or methacrylatene.

The present invention (1) Examples of carriers that can be used include particles conventionally used as carrier IJ carriers, such as iron, ferrite, steel, glass, and sand with a particle size of about 25 μm to about 200 μ2 nm. .

In the present invention (2S, the surface of the carrier particles (1) is treated with the chlorine-containing silane coupling agent (11) and the vinyl group-containing compound σ11 with a molecular weight of 100 or more), (i)? (11) and (ill) to coat the surface of (1) with Y (!ri and 011).

The following method is exemplified as a specific method.

b) Above (1) and above (ii)' in an inert organic bath medium
A method of adding Y, heating and mixing, and then adding the above G11) and further heating and mixing.

(11) above and 01 above in an inert organic medium.
A method of heating and mixing 1), then adding 1 inch of the above and further heating and mixing.

...) A method of charging the above (1), (11) and 0:1) Bi in an inert organic layer medium and heating and mixing.

The amount of the chlorine-containing silane coupling agent used according to the present invention is approximately 0.1 to 5 parts by weight, preferably 0.5 to 15 parts by weight per d1 carrier particles.

The appropriate amount of the vinyl group-containing compound having a molecular weight of 100 or more is 2 to 4 times the amount (by weight) of the above-mentioned polymerization agent.

It can be easily inferred that in the treatment process of carrier particles related to the present invention (1), the chlorine-containing silane coupling agent is bonded to the carrier surface through a chemical reaction with the carrier surface.On the other hand, the silane coupling agent and the molecular weight 100
Whether or not the vinyl group-containing compounds mentioned above bond through chemical reactions (the latter two are not clear).

Examples of inert organic solvents that can be used for surface treatment of carrier particles include benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, and cyclohexanone. There are no particular restrictions on the amount of these solvents used, but it may be adjusted so that the viscosity of the mixture system becomes appropriate.

When manufacturing the carrier material YM of the present invention, it is essential to treat the carrier particles with both a chlorine-containing silane camping agent and a vinyl group-containing compound with a molecular weight of 100 or more, and only one of the compounds can be used. Carrier materials that have been treated with only one or both compounds will not have satisfactory performance.

In addition, it is not possible to further coat the carrier material surface-treated by methods (a), (b), 09, etc. with a polymer such as methyl methacrylate/styrene copolymer, as is generally done. There is nothing wrong with that.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples. Note that all parts in Examples and Comparative Examples are by weight.

(Example 1) 4 flask with cooling tube, iron particles (Japanese iron powder)
F-250) 100 parts, methyl ethyl ketone 300 parts,
CβC3H6Si, a chlorine-containing silane coupling agent
(OCH3) and 3 parts of maleated polybutadiene (BN-1000 from Nippon Soda) were heated at 80C.
After stirring for an hour, the iron particles were washed with a large amount of methyl ethyl ketone and then dried.

Next, the surface-treated iron particles were coated with a methyl methacrylate (MMA)/styrene (St) copolymer (copolymerization molar ratio MMA/St of 250,150, molecular weight of approximately 200,000). was used as a carrier material for an electrophotographic developer.

For coating, a fluidized bed coating tester (manufactured by Fuji Sangyo Co., Ltd.) was used.The MMA/St copolymer was used as a toluene solution with a solid content of 5%.

Next, 95 parts of the carrier material and toner (styrene (St)
/butyl acrylate) (BA) copolymer, copolymerization molar ratio st >BA=85/15, molecular weight approximately 100,000 as the main component, and contains a small amount of carbon blank. ) 5 parts were mixed to make an electrophotographic developer.2 <Evaluation of toner charge stability (TEC stability)> Toner charge amount test consisting of a one-hole drum wrapped with polyester film and a magnetic brush type developing unit. Load the Hokkaido developer into the device and rotate the magnetic brush. Rotate 8
A portion of the toner after a certain period of time and the toner before rotation (hereinafter referred to as initial stage) are sampled, and the amount of charge (TEC) thereof is measured using a blow-off tester (manufactured by Tokyo Yusen Denki ■). Calculate the rate of change in TEC after 8 hours of rotation with respect to the initial TEC,
TEC stability is expressed as a number from 1 to 5. The correspondence between numerical values and rate of change is as follows.

Numerical value Rate of change (ch) 5 0-20 4 21-40 3 41-60 2 61-80 τ 1 81-100 The larger the value, the better the TEC stability.

<Evaluation of TEC distribution stability> The toner used in the above <Evaluation of TEC stability> was specially
The distribution of TEC was investigated using a toner particle characteristic measuring device described in Japanese Patent No. 56-212442. The toner distribution curve after 8 hours of rotation and the initial toner distribution curve were compared, and the TEC distribution stability after 8 hours of rotation was expressed as a numerical value of 1 to 3. The meanings of the numbers are as follows.

Numerical value Meaning 3 - The TEC distribution pattern after 8 hours is the same as the initial one, and the TEC distribution stability is good in the evening.

2 - The TEC distribution pattern after 8 hours is slightly wider than the initial one, and the TEC distribution stability is average;

- The TEC distribution pattern after 8 hours is wider than the initial one, indicating that the TEC distribution stability is poor.

The results of the evaluation of TEC stability and TEC distribution stability are shown in Table-1.

(Example 2) Surface-treated iron particles were obtained in the same manner as in Example 1, except that 3 parts of butyl acrylate was used for casting the maleated polybutadiene used in Example 1.

Thereafter, in accordance with the method of Example 1, the iron particles were further coated with a methyl methacrylate/styrene copolymer to prepare a carrier material to prepare an electrophotographic developer. The TEC stability and TEC distribution stability of the developer were evaluated in the same manner as in Example 1. These results are shown in Table-1.

(Example 3) Instead of the maleated polybutane diene used in Example 1, Dialene 168 (Mitsubishi Kasei ■, carbon number 16-18) was used.
Surface-treated iron particles were obtained in the same manner as in Example 1, except that 3 parts of α-olefin, which is the main component, and 300 parts of toluene were used for methyl ethyl lactone.

Thereafter, in accordance with the method of Example 1, the iron particles were further coated with methyl methacrylate/styrene copolymer to form a carrier material to prepare an electrophotographic developer. The TEC stability and aTEC distribution stability of the developer were evaluated in the same manner as in Example 1. These results are shown in Table-1.

(Comparative Example 1) An electrophotographic developer was prepared according to the method of Example 1 using the iron particles used in Example 1 as a carrier material without any surface treatment or coating. The TEC stability and TEC distribution stability of the developer were evaluated in the same manner as in Example 1.

These results are shown in Table-1.

(Comparative Example 2) The iron particles used in Example 1 were coated with the methyl methacrylate/styrene copolymer used in Example 1 without being subjected to surface treatment, and used as a carrier material. Hereinafter, an electrophotographic developer was prepared according to the method of Example 1. For the developer,
TEC stability and TEC distribution stability were evaluated in the same manner as in Example 1. These results are shown in Table-1.

(Comparative Example 3) Iron particles 1 used in Example 1 were placed in a 4-tube flask with a cooling tube.
0'O part, 7300 parts of methyl ethyl keto, and 1 part of the silane coupling agent used in Example [2] were taken, and iron particles surface-treated with only the silane coupling agent were obtained in the same manner as in Example 1.

This was further coated with the methyl acrylate/styrene copolymer used in Example 1 and used as a carrier material to prepare an electrophotographic developer. The TEC stability and TEC distribution stability of the developer were evaluated in the same manner as in Example 1. These results are shown in Table-1.

Table-1 Patent applicant: Kao Soap Co., Ltd. Agent Mochizuki Keibu

Claims (1)

[Scope of Claims] 1. An electrophotographic carrier material surface-treated with a chlorine-containing silane coupling agent and a vinyl group-containing compound having a molecular weight of 100 or more. 2. The carrier material for electrophotography according to claim 1, wherein the vinyl group-containing compound having a molecular weight of 100 or more is one or more compounds selected from the group consisting of liquid polybutadiene and modified liquid polybutadiene.