JPH03185456A - Planar magnetic material toner - Google Patents

Abstract

PURPOSE:To enhance the quality and density of images and to eliminate the staining of a background by using a specific FeOx magnetic material for a toner. CONSTITUTION:This toner consists of a binder resin and the FeOx magnetic material. The FeOx having >=0.15 mum and <0.5 mum average grain size and >=1.33 and <1.4 x is used as this magnetic material. The magnetic material is preferably compounded at 20 to 120 pts. wt. per 100 pts. wt. binder resin. Polyester, styrene/acryl resin, etc., are usable for the binder resin. FeO1.33, FeO1.35, etc., are usable for the magnetic material. A lubricant, fixing assistant, polishing agent, etc., may be used at need for the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a toner used in electrophotography, electrostatic recording, etc., and particularly relates to an insulating flat magnetic toner.

(Prior art and its problems) Conventionally, as an electrophotographic method, U.S. Patent No. 2,297.6
Specification No. 91, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666.363), and Japanese Patent Publication No. 43-2
Although many methods are known, such as those described in U.S. Pat. An electrical latent image is formed on the surface, and then the latent image is developed with toner to become a visible image, and if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, etc. , to obtain a copy.

Various developing methods are known for making electrostatic latent images visible using toner. For example, U.S. Pat.
The magnetic brush method described in US Patent No. 2
, 618,552, and the powder cloud method, fur brush development method, and liquid development method described in U.S. Pat. No. 2,221,776. It has been known.

Among these developing methods, the magnetic brush method, cascade method, liquid developing method, etc., which use a developer mainly consisting of toner and carrier, are in particular widely put into practical use. All of these methods are excellent methods that can produce good images relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier. There is.

In order to avoid such drawbacks, various development methods using a one-component developer made only of toner have been proposed, but among them, many methods using a developer made of magnetic toner particles are superior.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive toner. In this method, conductive toner is supported on a cylindrical conductive sleeve that has magnetism inside, and is brought into contact with an electrostatic image to develop it. At this time, in the developing section,
A conductive path is formed by the toner particles between the recording medium surface and the sleeve surface, and charges are guided from the sleeve to the toner particles through this conductive path, and the toner particles form an image due to the Coulomb force between them and the image area of the electrostatic image. It adheres to the area and is developed.

This developing method using conductive toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, since the toner is conductive, the developed image can be transferred from the recording medium to the final product such as plain paper. It has the disadvantage that it is difficult to electrostatically transfer it to a permanent support member.

As a developing method using a high-resistance toner that can be electrostatically transferred, there is a developing method that utilizes dielectric polarization of toner particles. However, such methods inherently have drawbacks such as slow development speed and insufficient density of developed images, and are difficult to employ in practice.

Another developing method using high-resistance toner is a method in which toner particles are triboelectrified by friction between toner particles or friction between toner particles and a sleeve, etc., and then developed by contacting an electrostatic image holding member. Are known. However, these methods have drawbacks such as the number of times the toner particles come into contact with the frictional member is small and frictional charging tends to be insufficient, and the charged toner particles tend to aggregate on the sleeve due to the strong Coulomb force between them and the sleeve. This makes it difficult to adopt in practice.

However, in JP-A-55-18656, a new developing method was proposed which eliminated the above-mentioned drawbacks. This involves applying a very thin layer of toner onto the sleeve, triboelectrically charging it, and then developing it in close proximity to the electrostatic image. In this method, by applying an extremely thin layer of toner onto the sleeve, the chances of contact between the sleeve and the toner are increased, and sufficient frictional electrification is possible.
The toner is supported by magnetic force, and by moving the magnet and toner relative to each other, the toner particles are deagglomerated and have sufficient friction with the sleeve. By developing the image facing the image without contacting it, excellent images can be obtained by preventing blurring of the image.

The developing device used in such a developing method is characterized by its simple structure and very small size.

For this reason, for example, in high-speed machines, there is more space around the photoconductor, so it is possible to arrange several developers of other colors and change the color with a single touch, or to use laser light at the same time as analog light to This provides advantages such as the ability to easily write and copy text at the same time as copying.

Particularly in the case of small machines, the overall size can be made lighter and smaller, making it a necessary technology for personalizing copying machines.

In addition, even in printers such as small LBPs (laser beam printers), in order to achieve the contradictory performance of being quiet and high speed, which dot printers and thermal transfer printers do not have, it is necessary to take up a large amount of developer space. The fact that it is small, simple, and light is very effective.

However, because this developing method is simple, lightweight, and uses a small developing device, the toner used in this method has better overall image quality, durability, and stability, unless it has higher performance than conventional toner. This includes the problem of not being able to obtain In other words, the performance of such toner is often directly reflected in the performance of the system.

By the way, the copying machines themselves have changed from the conventional analog type, making it possible to use digital latent images, and as a result latent images can now be written more minutely than ever before. A toner that can sufficiently follow such a fine latent image must have a high-resolution developing ability. Furthermore, as copying machines are moving toward higher speeds, toners must meet high requirements such as high resolution, high speed development, and high durability.

When using this type of development method in a printer, the same high level of performance is required, but in terms of high durability, the output frequency is high because it is used as output for a computer, and the durability is better than that of a copier. There are some tough ones.

Furthermore, it is no longer sufficient for an image to simply be black. In the case of copying machines, it is especially necessary to faithfully reproduce photographs (that is, reproduce halftones), and in the digital latent image method, halftones are expressed by differences in the density of cotton, so line thickness is always If they are not the same, it will not be possible to express the intermediate tones in the same way, which will cause a problem.

Reproduction of such gradation is also highly required, especially for digital latent image printers, and it is not possible with conventional toners to consistently output the same halftones at the beginning and end of life. It can be said that there is no.

Furthermore, with regard to environmental stability, as copiers have become more personalized and LBPs have become more popular in households due to lower prices,
They are now often used in harsh environments where they were not previously used. In order to meet these strict demands, research and development of toner is being carried out diligently.

Magnetic materials are contained in a large proportion of toner, and are an important element in terms of toner performance. Although various proposals have been made regarding magnetic materials for toner, there is a strong demand for further improvement in performance.

In particular, if too much magnetic material is added to the toner, it will deteriorate the fixing properties, so it is necessary to use a smaller proportion to fully satisfy the performance.In addition, the charging properties of the toner, especially the control of the amount of charge, and the durability It is known that magnetic toner has an effect on changes over time, environmental characteristics, etc., and it is necessary to develop a magnetic toner that fully satisfies these factors.

In particular, various shapes of magnetic bodies have been proposed, and although some are effective, there is a desire for magnetic bodies with even better performance.

Among the proposals for magnetic toner, JP-A-61-138959
The magnetic toner using platelet-like particles or scale-like particles described in the publication has excellent coloring properties and is effective as a color magnetic toner, but on the other hand, in the presence of a colorant, And X of FeOx which is particularly preferable is 1.33≦x<1
．． 5, and the diameter of the magnetic particles is preferably 0.5 to 2.
When it is 5 μm, in the development of insulating magnetic toner,
Various problems related to charge control occur, such as a charge-up phenomenon in which the amount of charge increases abnormally, a decrease in the amount of charge at high temperatures, and deterioration of durability characteristics, and it cannot be said to be sufficient.

Therefore, a first object of the present invention is to provide a toner with high image quality, high density, and no background stains.

A second object of the present invention is to provide a toner with good fixing properties.

A third object of the present invention is to provide a toner that does not cause a decrease in image density due to charge-up or uneven coating of the toner on a sleeve.

A fourth object of the present invention is to provide a toner that has good durability and stability even on high-speed machines.

A fifth object of the present invention is to provide a toner with excellent environmental stability.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a toner comprising a binder resin and a FeOx-based magnetic material, in which the average diameter of the magnetic material is 0.15 μm.
m or more and less than 0.5 μm, and X of FeOx is 1.3
The flat magnetic toner is characterized in that the magnetic flux density is 3 or more and less than 1.4.

(Function) Although not bound by any theory, the plate-shaped Fe0w-based magnetic material used in the present invention often exists flat near the surface of the toner due to its shape. Compared to a magnetic material, the toner contacts the surface of a toner carrier such as a sleeve more effectively, and the amount of charge on the toner can be appropriately controlled.Therefore, various problems of the prior art are solved, and the present invention described above A magnetic toner is provided that achieves the above objectives.

On the other hand, if a conventional magnetic toner is attempted to work in the same way, it is necessary to increase the content of the magnetic material, which may adversely affect the fixing performance, image quality, and durability of the toner.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

If X of FeOx of the flat magnetic material used in the present invention is larger than 1.4, the color becomes red and the electrical resistance of the magnetic material increases, which may cause a charge-up phenomenon. If it is small, heat resistance will decrease. Moreover, if the diameter is smaller than 0.15 μm, the color becomes red, which is undesirable, and the heat resistance is also deteriorated. Furthermore, the dispersibility with the binder resin also deteriorates. On the other hand, if the thickness is larger than 0.5 μm, a charge-up phenomenon occurs, the environmental characteristics deteriorate, and the durability deteriorates. Preferably from 0.2 μm to 0.4 μm, more preferably from 0.25 μm to 0.35 μm
It is.

To find the average diameter of a magnetic material, take a 10,000x photograph with a transmission electron microscope (TEM), enlarge it 4x, and then arbitrarily select 100 pieces from the 4'0.000x photograph. A magnetic material was selected, the horizontal Feret diameter was measured, and the average value was calculated.

The diameter is measured in the surface direction, not in the thickness direction.

Further, the ratio of diameter to thickness is preferably 2 to 10.

Also, the magnetic properties of the flat magnetic material are at 1OKOe)
lc70 to ioo, δ, 85 to 89, δ15 to 1
3 is a preferred range.

The above-mentioned flat magnetic material may be manufactured by any generally known method.Also, a black flat magnetic material may be obtained by reducing α-iron oxide (or wet method). A black tabular magnetic material may be obtained from tabular iron carbonate.

As mentioned above, the specific magnetic material is preferably used in an amount of 20 to 120 parts by weight, more preferably 40 to 80 parts by weight, per 100 parts by weight of the binder resin described below.

If the amount used is less than the above range, there will be problems such as a decrease in transportability and uneven toner coating, resulting in a decrease in image density and background stains.On the other hand, if the amount used exceeds the above range, the image This is undesirable since there are problems such as a decrease in transferability, a decrease in transferability especially in a high-temperature environment, and a decrease in image density.

Furthermore, in terms of the direction of the particle size of the toner, it has been considered to reduce the particle size from the viewpoint of high image quality, etc., but this direction causes problems such as charge-up and background stains, and the toner of the present invention It is also effective in improving the problem of

Binder resins used in the toner of the present invention include polystyrene, polyp-chlorostyrene, polyvinyltoluene,
Homopolymers of styrene and its I analytes, such as styrene-p-chlorostyrene copolymer and styrene vinyltoluene copolymer, and copolymers thereof: styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer , copolymers of styrene and acrylic esters such as styrene-n-butyl acrylate copolymer; styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer Copolymers of styrene and methacrylic esters such as polymers; multi-component copolymers of styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene- Styrenic copolymers of styrene and other vinyl monomers such as butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide,
Epoxy resins, polyvinyl butyral, polyacrylic acid, phenolic resins, aliphatic or alicyclic hydrocarbon resins, petroleum resins, chlorinated paraffins, etc. can be used alone or in mixtures.

In particular, low molecular weight polyethylene, low molecular weight polypropylene,
Ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, higher fatty acids, polyamide resins, polyester resins, etc. can be used alone or as a mixture.

More desirable results can be obtained when the polymer, copolymer, or polymer blend used as the binder resin contains a vinyl aromatic or acrylic monomer represented by styrene in an amount of 40% by weight or more.

Additives may be mixed with the toner as necessary, such as lubricants such as Teflon and zinc stearate, or fixing aids (for example, low molecular weight polyethylene, low molecular weight polypropylene, etc.). , fluidity imparting agents, and anti-caking agents (for example, colloidal silica).

Further, examples of the polishing agent include cerium oxide, strontium titanate, etc., and examples of the electrical resistance adjusting agent include tin oxide.

The flat magnetic toner of the present invention comprising the above components can be produced by a conventionally known method, and the production method is not particularly limited.

(Example) Next, the present invention will be described in more detail according to Examples and Comparative Examples. In the text, parts or percentages are based on weight unless otherwise specified.

Example 1 Polyester resin 100 parts Negative charge control agent 2 parts Mold release agent
3 parts flat magnetic body A (diameter 0.33μ
60 parts of FeO+, 31) were heat-kneaded for about 15 minutes in a roll mill with a set temperature of 140°C, and after cooling, they were coarsely and finely ground, and then the fine powder and coarse powder were cut using an air classifier to form the present invention. of toner powder was obtained.

The average particle size of the above toner powder is Coulter Counter's T.
Measurement was performed using an A-n type, and the volume average diameter was 9.0 μm, and the standard deviation was divided by the average particle size to obtain a variation coefficient of 30% expressed in %.

Add hydrophobic colloidal silica to this toner powder.

It was externally added at a rate of 0.5% using a Henschel mixer to form a developer. This was tested on a Canon copier NP-8580.

As a result, in an intermittent durability test under a low-temperature, low-humidity environment, images of high quality, high image density, and no background stains were obtained that were stable for a long period of time. In addition, particularly in a fixing test immediately after the copying machine was turned on and ready for use, it showed good fixing properties.

Furthermore, it performed very well in tests under high temperature and high humidity conditions.

Comparative Example 1 A toner was prepared in the same manner as in Example 1 except that the flat magnetic material was changed to cubic magnetite with an average particle size of 0.32 μm. The average particle size of the obtained toner powder was 9.1 μm
, the coefficient of change was 33%.

As a result of similar tests on this toner, under a low-temperature, low-humidity environment, there was a decrease in image quality due to charge-up, a decrease in image density, and the occurrence of background stains.

Example 2 Styrene-acrylic resin 100 parts Positive charge control agent 2 parts Mold release agent
3 parts flat magnetic body B (diameter 0.27μ
In the same manner as in Example 1, 60 parts of FeO+, as) were converted into a toner to obtain a toner powder of the present invention. The average particle size of the toner powder was 8.2 μm, and its variation coefficient was 29%. 0.6% of positively charged hydrophobic colloidal silica was externally added to this toner powder to prepare a developer.

This was tested on a Canon copier NP-1215.

As a result, in an accelerated deterioration test in which the developing machine was taken out of the machine in a low-temperature, low-humidity environment and the sleeve was rotated idly, the image quality, image density, and background stains were excellent even after 10 hours. Furthermore, the fixing properties were also very good, and the results were also very good in high temperature and high humidity tests.

Comparative Example 2 A toner was produced in the same manner as in Example 2, except that cubic magnetite with a particle size of 0.27 μm was used as the flat magnetic material in Example 2. The average particle size of the toner was 7.9 μm, and the variation coefficient was 30%.

This toner was similarly evaluated. As a result, in an accelerated test under a low temperature and low humidity environment, abnormal coating occurred on the sleeve after about 3 hours, resulting in a decrease in image quality, a decrease in image density, and background stains.

Example 3 The polyester resin of Example 1 was replaced with a styrene acrylic resin, the flat magnetic material was replaced with an average particle size of 0.4 μm, and FeO+
, s. Example 1 except that 80 parts of the flat magnetic material C were used.
Created in the same way. The average particle size of the obtained toner was 6.2
μm, and the variation coefficient was 31%. 0.8% hydrophobic colloidal silica was externally added to this to prepare a developer.

This is Canon's laser beam printer LBP-8
It was evaluated as 11. As a result, extremely high image quality, low temperature and low humidity,
High image density was maintained stably even during high-temperature, high-humidity durability. or,
The fixing properties were also very good.

(Effects) According to the present invention as described above, a toner is provided that has good fixing properties and environmental stability, and is capable of forming images of high image quality, high density, and no background stains.

Furthermore, these toners do not cause a decrease in image density due to charge-up or uneven coating of the toner on the sleeve, and have excellent durability and stability even in high-speed machines.

Claims (2)

[Claims] (1) In a toner comprising a binder resin and an FeO_x-based magnetic material, the average diameter of the magnetic material is 0.15 μm or more;
A flat magnetic toner having a diameter of less than 0.5 μm, and x of FeO_x being 1.33 or more and less than 1.4. (2) The weight ratio of the binder resin and the magnetic material is 100% of the binder resin.
2. The flat magnetic toner according to claim 1, wherein the magnetic material is contained in a range of 20 to 120 parts by weight per part by weight.