JPS62229161A - Developer for electrophotography and its production - Google Patents

Abstract

PURPOSE:To obtain a carrier which has stable electrostatic chargeability, has uniform grain sizes even after production and does not require a sieving operation by bringing a dispersion contg. polymer particles and core material into contact with each other, then subjecting the same to a heating treatment so that the core material has the coating layer of a uniform thickness on the surface. CONSTITUTION:The dispersion contg. various polymer particles is prepd. and the polymer particles are monodispersed in the dispersion. The polymer particles to be used have generally about uniform grain sizes and the variance of the grain sizes is preferably about + or -1mum. Water, various alcohols, etc., are used for the dispersion medium in the dispersion. The core material and the dispersion are brought into contact with each other by spraying or the like to stick the polymer particles in the dispersion onto the surface of the core material. The core material stuck with the polymer particles is subjected to the heating treatment to melt the polymer particles sticking thereto and to accelerate the melt-sticking, by which the melt-stuck film having the excellent adhesiveness to the surface of the core material is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a two-component electrophotographic developer comprising a carrier and a toner, and a method for producing the same.

(Prior art) In electrophotography, the dry developer used to develop an electrostatic image formed on a photoconductor by a magnetic brush method is a two-component system consisting of toner and carrier. It will be done. The developer typically consists of a mixture of relatively fine toner particles and relatively large carrier particles, the toner particles being held to the surface of the carrier particles by electrostatic forces of opposite polarity created by the contact of the particles. When this developer comes into contact with the electrostatic charge image on the photoreceptor, toner particles are attracted to the electrostatic charge image to form an image. In this case, the toner particles must have the correct chargeability and charge magnitude so that they are preferentially attracted to the desired image area of the photoreceptor.

By the way, the conventional dry developer used in electrophotography is
Due to repeated contact and collision between the carrier particles and toner particles or between the developer and the mechanical parts of the developing machine, some of the toner particles physically adhere to the surface of the carrier particles and form a film. Therefore, when such a situation begins to occur, the carrier particle surface
As the film of toner material gradually grows thicker, the originally necessary frictional zone between carrier particles and toner particles turns into frictional charging between toner particles, and the triboelectrical properties of the developer as a whole deteriorate. As a result, a so-called background smudge development occurs in which a large number of toner particles adhere to the background portion of the copy image, resulting in deterioration of the copy image.

In order to solve these problems, various methods have been proposed for manufacturing a carrier by coating the surface of a core material with a resin.

Among these methods, there is a method in which the resin to be coated is dissolved in a suitable solvent, and the resulting resin solution is applied to the surface of the core material by spraying or dipping to serve as a carrier.

(Problems to be Solved by the Invention) However, the carrier produced by the above method has the following problems.

The first problem is to ensure that the thickness of the resin film covering the core material is uniform.
Since it is difficult to achieve a predetermined thickness, the chargeability on the surface of the carrier varies depending on the location, resulting in non-uniformity. The second problem is that it is extremely difficult to reduce the amount of coating on each particle of the core material to m,
Even if a core material with a uniform particle size distribution is used, two or more core materials often stick together, resulting in a problem of large variations in the particle size of the carrier.

When such a problem occurs, not only the amount of charge on the surface of the carrier and the magnitude of the charge do not reach a desired constant value, but also the sieving of the manufactured carrier requires work.

The present invention eliminates the disadvantages mentioned above, has a coating layer with a uniform thickness on the surface of the core material, has stable charging properties, and has a uniform particle size even after production, making it easy to sieve. The purpose of the present invention is to provide an electrophotographic developer that does not require a carrier.

[Structure of the Invention] (Means and Effects for Solving the Problems) The electrophotographic developer of the present invention is characterized in that it consists of a toner and a carrier whose core material is coated with a fused film of polymer particles. The method for producing the carrier is characterized in that the carrier is produced by bringing a dispersion containing polymer particles into contact with a core material and then subjecting the carrier to heat treatment.

The carrier in the present invention is composed of a core material and a polymer particle fused film, which will be described later, which uniformly covers the surface of the core material.

Examples of the core material include powders of iron, nickel, cobalt, and alloys thereof with appropriate addition of other elements, and magnetic powders of oxides such as ferrite. Among these, iron powder is particularly suitable, and any type of iron powder can be used.
For example, pure iron powder such as reduced powder, atomized powder, electrolytic powder, or those whose surfaces have been subjected to oxidation treatment can be used.

The particle size of the core material is not particularly limited, but is 10 to
The thickness may be appropriately selected within the range of 200 μm.

The fused film that is formed by covering the surface of the core material is a film that is formed by sticking the following polymer particles onto the surface of the core material using the method described below, and then fusing them. .

Examples of the polymer particles include particles of a polymer of any one monomer selected from among ethylene, styrene, butadiene, vinyl acetate, acrylic esters, and derivatives thereof, or copolymers of two or more monomers; Examples include particles of fluorine-based polymers containing fluorine atoms in their structural units. Thus, examples of these polymer particles include polyethylene, polystyrene, polybutadiene, polyvinyltoluene, polyisoprene, polychloroprene, polyvinyl acetate, polyethyl acrylate, styrene-butadiene copolymer, styrene-methyl methacrylate copolymer, Alternatively, polyvinyl fluoride, polyvinylidene fluoride, polytrifluorochloroethylene,
Polytetrafluoroethylene, tetrafluoroethylene/hexafluoropylene copolymer, tetrafluoroethylene/ethylene copolymer, trifluorochloroethylene/ethylene copolymer, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer Polymers, vinylidene fluoride/propene hexafluoride copolymer rubber, polyfluoroalkyl group-containing acrylic (or methacrylic) acid ester copolymers, and the like can be mentioned.

Each of these polymer particles may be used alone, or two inserts -1- may be used in an appropriate combination.

It is further preferable that the fused film according to the present invention contains a predetermined amount of a charge control agent. The charge control agent mentioned here is
A substance having the function of adjusting the chargeability of the carrier surface by being present in the fusion film, thereby adjusting the relationship of electrostatic force between the carrier and the toner.

Such charge control agents include anionic surfactants,
Any one or two of various surfactants, such as cationic surfactants, nonionic surfactants, anionic and nonionic surfactants, and amphoteric surfactants.

The carrier according to the present invention can be produced, for example, as follows.

First, a dispersion containing various polymer particles as described above is prepared. What is important at this time is to monodisperse the polymer particles in the dispersion. This is to ensure that the finally formed coating film on the surface of the core material has a uniform thickness.

It is preferable that the polymer particles used generally have a substantially average particle size and have a variation in particle size of about ±lpm. Although the particle size can be changed as appropriate depending on the particle size of the core material used, it is preferable that the particle size is 10 μm or less. Using more than 10 polymer particles makes it difficult to obtain a stable monodisperse dispersion.

It is from.

In the dispersion, examples of the dispersion medium used include water, various alcohols, and various ketones.

Water-alcohol, water-ketone, etc. are preferable, and it is preferable that the polymer particles are dispersed therein in an amount of 1 to 7% by weight.

When containing a charge control agent, the surfactant as described in -1- is added in an amount of 0.01 to 0.01 to
It is sufficient to add 2% by weight.

Next, the core material and the dispersion are brought into contact by dropping a predetermined amount of the obtained dispersion onto the core material powder and stirring the whole, or by spraying the core material powder while fluidizing it. The polymer particles in the dispersion are then stuck onto the surface of the core material.

Note that, prior to this step, it is effective to treat the surface of the core material with a surface treatment agent, which will be described later, in order to uniformly stick the polymer particles in the dispersion.

As the surface treatment agent to be used, at least one of a titanium-based coupling agent, a silane-based coupling agent, an aluminum-based coupling agent, and a phosphoric acid ester is most suitable, but in addition, It is also possible to use an indium-based coupling agent, a chromium-based coupling agent, a zirconium-based coupling agent, or the like. The amount of these surface treatment agents used is 0.1 to 5% relative to the core material.
It suffices if it is capacity %. Specific examples of these organic compounds or organometallic compounds are listed below.

Examples of titanium-based coupling agents include isopropyl)su(N-amineethyl-aminoethyl)titanate, isopropyltriisostearoyltitanate, 4
-Amine benzenesulfonyl dodecylbenzenesulfonyl ethylene nathanate, tetra(2,2 diallyloxymethyl-1-butyl)bis(ditridecylphosphite) titanate, tetraoctylbis(ditridecylphosphite) titanate, dicumiphenyloxyacetate Examples include titanates.

Examples of silane-based coupling agents include γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and N-β(aminoethyl). -γ-aminopropylmethyldimethoxysilane and the like.

Typical examples of aluminum-based coupling agents include ethyl acetoacetate; examples of aluminum diisopropylate esters include dioctyl phosphate, monoisodecyl phosphate, di(off] xyethoxyethyl) phosphate-1, and mono(methylphenoxy). (ethyl) bosphate, etc.

By drying the surface of the core material coated with polymer particles naturally or at a temperature of 100° C. or lower, the dispersion medium can evaporate and the polymer particles can be fused together. However, it is possible to form a fused film with excellent adhesion to the surface of the core material by applying heat treatment at a temperature higher than 1 to melt the adhering polymer particles and promote the fusion phenomenon. I can do it. The treatment temperature at this time varies depending on the type of polymer particles used, but it may normally be arbitrarily selected within the temperature range of 100 to 350°C. It goes without saying that the application of temperatures that would cause thermal decomposition or thermal deterioration of the polymer particles should be avoided. The atmosphere during the treatment may be an air atmosphere, but when the treatment temperature is 250° C. or higher, it is preferable to use an inert gas to suppress oxidation of the surface of the core material. Further, the time between treated surfaces is usually within 1 hour.

In this way, the carrier, which is one component of the developer of the present invention, is produced.

The toner, which is the other component of the developer of the present invention, is not particularly limited and may be anything that can be used as a toner, for example, natural resin, synthetic resin, or a combination of natural and synthetic resins as appropriate. Examples include those in which various well-known dyes are dispersed in the mixture.

(Example) Example 1 Flat amorphous iron powder with a particle size of 74 to 149 μm was selected as the core material, and this iron powder i. While stirring o o o g,
Here, there are 10 polyacrylic acid particles with an average particle size of 0.2 μm.
Dispersion dispersed in wt% water
was dripped.

In addition, this dispersion contains a surfactant (CI2H
xO (CH2 CH2 0) 3SO3Na) is 0.
03% by weight was added.

The obtained treated core material was left to dry at room temperature for 24 hours,
The mixture was then heated at 180°C for 0.5 hour in the air. When the surface of the obtained powder was observed using a scanning electron microscope (SEM), it was found that the entire surface was covered with a film (fused film) having a uniform thickness. Furthermore, there were almost no powders with a diameter of 150 μm or more.

This powder was used as a carrier, and 40 parts by weight of a commercially available magnetic brush toner (toner for Toshiba's BD3504) was placed in a polyethylene container, and the whole was heated to 75 rp.
The mixture was stirred at m for 1 hour to obtain a developer for electrophotography.

When an electrostatic latent image on a selenium photoreceptor was developed using this developer, all the copy images obtained were of excellent image quality with no fogging, and even after 20,000 times of development, the initial image quality was excellent. It was held.

Example 2 Except that the dispersion used was one in which tetrafluoroethylene hexafluoropropylene copolymer particles with an average particle size of 0.2 μm were dispersed in 50% by weight water.
A carrier was produced in the same manner as in Example 1. Example 1
Almost the same results were obtained.

Example 3 The same core material as in Example 1 was selected, and 1000 g of this powder was
Isopropyl I.lis(dioctylpyrophosphate) titanate was added in an amount corresponding to 0.7% by volume of the core material and thoroughly stirred.

Next, 1 of the dispersion used in Example 2 was added to this.
0rn! After the addition and thorough stirring, the mixture was left to stand at room temperature for 12 hours to air dry. After that, the powder was placed in the atmosphere for 2
The mixture was heated at 00°C for 15 minutes to form a carrier. According to SEM observation, a fused M film with a uniform thickness was formed on the surface of the carrier.

A developer was prepared by stirring 1,000 g of this carrier and 40 g of toner, which was obtained by kneading styrene-acrylic resin, carbon, and microcrystalline units and then pulverizing and classifying, at 110 rpm for 1 hour.

When the same developing operation as in Example 1 was carried out using this developer, all of the obtained copy images were of excellent image quality with no fogging, and even after 30,000 times of development, the image quality was equivalent to the initial image quality. there were.

Examples 4 to 6 The surface treatment agents used were γ-glycidoxypropyl I.rimethoxysilane (0.3% by volume), ethyl acetoacetate aluminum diisopropyle-1 (1% by volume), dioctyl. Three types of carriers were prepared in the same manner as in Example 3, except that the carriers were phosphate (0.2% by volume), and were designated as Example 4 carrier, Example 5 carrier, and Example 6 carrier, respectively. .

When developers were prepared and developed using these three carriers in the same manner as in Example 3, almost the same results as in Example 3 were obtained in all cases.

Example 7 The same core material as in Example 1 was selected, and 1000 g of this powder was
A solution 20- of the same powder in which 0.7% by volume of tetraoctyl bis(ditridecyl phosphinate) was diluted in isopropyl alcohol was sprayed onto the sample.

While stirring the whole, the isopropyl alcohol is evaporated, and a dispersion Ion is prepared in which 5% by weight of methyl polyacrylic particles with an average particle size of 1 unit are dispersed in water.
/ was sprayed.

The obtained treated powder was heated in the atmosphere at 150°C for 3 minutes to form a carrier. According to SEM observation, a fused film of uniform thickness was formed on the surface of the carrier.

When a developer was prepared using this carrier in the same manner as in Example 3 and a developing operation was performed, almost the same results as in Example 3 were obtained.

Example 8 Amorphous iron powder (particle size 63 to 1.491 zm) that had been oxidized and had an oxygen content of 1.2% by weight was selected as the core material. After surface treatment in the same manner as in Example 7, 1000 g of this powder was fluidized to form a dispersion in which 20% by weight of vinylidene fluoride resin particles of carp with an average particle size of 1 were dispersed in methyl isobutyl ketone. 50i was sprayed. This powder was dried in a λr at 300° C. for 10 minutes to form a carrier. SEM
According to observation, a uniform fused film was formed on the surface of the carrier.

When a developer was prepared using this carrier in the same manner as in Example 2 and a developing operation was performed, a copy image of good quality was obtained with no lag, and the quality was equivalent to the initial image quality even after 30,000 times of development. ! Comparative Example Using the iron powder used in Example 1 as a carrier, a developer was prepared from this and the toner used in Example 1 in the same manner, and the same image durability test was conducted. 1.5000
After the first development, the image quality began to deteriorate and the image became blurred and unreliable.

[Effects of the Invention] As is clear from the above explanation, the carrier, which is the component of the developer of the present invention, has a substantially constant thickness of the fused film formed on the surface of the core material, and Since there is little variation in film thickness between carriers or between different surface portions of the same carrier, the amount of charge and charge on the carrier surface are stable.

Since this fused film has excellent adhesion to the surface of the core material, it is unlikely that the S will peel off during use and the surface of the core material will be exposed.

Furthermore, during the manufacture of the carrier, the polymer particles exist in a monodisperse state and adhere to the surface of the core material, so there is almost no binding between the core materials, and the particle size of the obtained carrier is the same as that of the core material used. There is no variation much greater than the variation in particle size.

Furthermore, if the dispersion contains a charge control agent, it will be incorporated into the resulting fused film, making it easier to control the charge on the carrier. This means that any toner can be selected as a mating material.
This means that this is an extremely beneficial effect. In addition, the method for producing the developer of the present invention does not require any special equipment, and also has excellent productivity.
It also has high industrial value.

Procedural amendment April 28, 1986

Claims (5)

[Claims] (1) An electrophotographic developer comprising a toner and a carrier in which a core material is coated with a fused film of polymer particles formed using a dispersion containing polymer particles. (2) The polymer particles contained in the dispersion are each polymer or copolymer of two or more of ethylene, styrene, butadiene, vinyl acetate, acrylic ester, and derivatives thereof, or have fluorine atoms in the structural unit. Claim 1, which is a fluoropolymer containing
Electrophotographic developer described in Section 1. (3) In the method for producing an electrophotographic developer comprising a carrier and a toner, the carrier is produced by bringing a core material into contact with a dispersion containing polymer particles and then subjecting the dispersion containing polymer particles to a heat treatment. A method for producing a featured electrophotographic developer. (4) The method for producing an electrophotographic developer according to claim 3, wherein the core material is surface-treated with a surface treatment agent before the dispersion and the core material are brought into contact with each other. (5) The polymer particles contained in the dispersion are each polymer or copolymer of two or more of ethylene, styrene, butadiene, vinyl acetate, acrylic ester, and derivatives thereof, or have fluorine atoms in the structural unit. 4. The method for producing an electrophotographic developer according to claim 3, which is a fluorine-based polymer containing.