JPS6026953A - Magnetic color toner - Google Patents

Abstract

PURPOSE:To improve a toner in triboelectric performance and to obtain a sharp image by specifying the contents of gamma-Fe2O3 and colloidal silica in the toner. CONSTITUTION:A toner contains gamma-Fe2O3 and colloidal silica in amts. of >=80wt% and 0.02-5wt% of the total content of a magnetic material, respectively. The toner has 0.5-20muQ/g triboelectrifiable absolute amt., 50-250Oe coercive force when a 10kOe external magnetic field is impressed, 15-40emu/g saturation magnetization, and 1.5-20emu/g residual magnetization. The toner can be spread in a thin layer more stably and more uniformly on the surface of a toner carrying body and a superior image is obtained by adding the colloidal silica to said magnetic toner in an amt. of 0.02-5wt% of the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner used in electrophotography, electrostatic printing, magnetic recording, etc., and particularly relates to sepia or red magnetic color toner.

Conventionally, as an electrophotographic method, U.S. Patent No. 2,297,69
Although many methods are known, as described in HA Specification No. 1, Japanese Patent Publication No. 42-23910, and Japanese Patent Publication No. 43-24748, etc., generally, photoconductive substances are used and various methods are used. An electrical latent image is formed on the photoreceptor by a means, and then the latent image is developed using toner, and if necessary, the toner image is transferred to a transfer material such as paper, and then heated, pressure, solvent vapor, etc. It is used to fix the image and obtain copies.

Various methods are also known for visualizing electrical latent images using toner.

For example, the magnetic brush method described in U.S. Pat. No. 2,874,063, the cascade development method described in U.S. Pat. No. 2,618,552, and U.S. Pat. No. 2,221.
A number of development methods are known, such as the powder method and fur brush development method described in No. 776, and liquid development.

Among these developing methods, in particular, the magnetic brush method, cascade method, and
Liquid development methods and the like have been widely put into practical use. These methods are excellent methods in which good images can be obtained with relatively stable b deviations, 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.

In order to avoid such drawbacks, various development methods have been proposed that use one-component developers that provide good toner quality, but among these, many are superior to methods that use developers made of magnetic toner particles.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. In this system, a conductive magnetic developer is supported on a cylindrical conductive sleeve having 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 through this conductive path, electric charges are conducted to the toner particles (from the sleeve), and between them and the image area of the electrostatic image. Due to the Coulomb force, the B toner particles adhere to the image area and are developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, because 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.

There is a developing method that utilizes dielectric polarization of toner particles as a developing method using high-resistance magnetic toner that can be transferred electrostatically, but such a method inherently has a slow developing speed and the density of the developed image is low. However, it has disadvantages such as not being able to obtain a sufficient amount of carbon dioxide, making it difficult to use in practice.

Other developing methods using high-resistance magnetic toner include
A known method is to triboelectrically charge toner particles by friction between toner particles or friction between toner particles and a sleeve or the like, and then develop the toner particles by bringing them into contact with an electrostatic image holding member. However, these methods tend to cause insufficient frictional charging due to the small number of times of contact between the toner particles and the friction member, and the Coulomb force between the charged toner particles and the sleeve is strong and they tend to aggregate on the sleeve. It has many drawbacks and is difficult to use in practice.

The present applicant has previously proposed a new developing method that eliminates the above-mentioned drawbacks in Japanese Patent Application Laid-Open No. 54-42141. This involves applying a very thin layer of magnetic toner onto a toner carrier, triboelectrically charging it, and then placing it in close proximity to an electrostatic image under the action of a magnetic field, facing it without contact, and developing it. be.

According to this method, by applying an extremely thin layer of magnetic toner on the toner carrier, the opportunity for contact between the toner carrier and the toner is increased, and sufficient frictional electrification is possible, and the toner is supported by magnetic force. In addition, by moving the magnetic field and the entire toner relative to each other, the toner particles are disaggregated and are sufficiently rubbed against the toner carrier, and the toner is supported by magnetic force and is transferred to the electrostatic image through a gap. Excellent images can be obtained by developing the materials facing each other to prevent blemish formation.

Furthermore, the jumping development method using an insulating component magnetic toner has the great advantage that it is possible to transfer to plain paper using corona discharge for transfer.

(5) Further, the residual toner on the toner carrier moves as it is around the outer periphery of the toner carrier, returns to the toner supply section, and is used again, repeating the cycle.

In general, one-component development methods using magnetic toner do not use a carrier, so there is no need to adjust the mixing ratio of carrier and toner, and a stirring operation is especially required to mix the carrier and toner sufficiently and uniformly. Since the developing device does not require a large amount of space, it has the advantage that the entire developing device can be constructed simply and compactly.

However, in all developing methods using -component developers, it is necessary to form a relatively thin and uniform layer of toner on the developer carrying member, but environmental conditions, toner physical properties, physical properties of the developer carrying member surface, etc. It is difficult to obtain a uniform layer of toner, and uneven coating of toner on the developer carrier often occurs, especially in low humidity environments, and image density decreases in high humidity environments.

Furthermore, magnetic toner is charged in the developing device by friction between toner particles and friction between toner particles and a toner carrier (6), and retains an electrostatic charge. The number of times the particles come into contact with the friction member is small, and frictional charging tends to be insufficient.

Further, charged toner particles have the disadvantage that the Coulomb force between them and the toner carrier becomes strong and they tend to aggregate on the toner carrier.

An object of the present invention is to provide a sepia or red magnetic color toner that does not suffer from the above-mentioned drawbacks.

Another object of the present invention is to provide a magnetic color toner that has extremely good charging properties and provides clear images.

Another object of the present invention is to provide a magnetic color toner in which image density does not decrease with repeated copying.

Yet another object is to provide a magnetic color toner in which image density hardly decreases under low or high humidity conditions.

The aspects of the present invention described above are such that the absolute value of the charge amount of the toner is
Coercive force (He) of 50 to 2500 when measured with a total external magnetic field of 10 koe applied at 0.5 to 20 μQ/g.
e, saturation magnetization (σs) of 15 to 40 emu/g, residual magnetization (σr) of 1.5 to 20 emu/g, and 80% by weight or more of the total amount of magnetic material contained in the toner is γ- Fe2O3, colloidal silica'k 0.0
This is achieved by having a weight of 2 to 5 qb.

That is, when an external magnetic field of 10 koe is applied and the magnetic properties of the toner are measured, the coercive force (He) is 50 to 3000.
e, saturation magnetization (σs) of 15 to 40 emu/g, residual magnetization (σr) of 1.5 to 20 emu/, and when the toner is in the range of 9, a thin layer of toner can be applied to the toner carrier.

However, if the magnetic properties of the toner are below the above range, the magnetic interaction between the toner and the magnetic field generated by the magnetic field generating means inside the toner carrier may be insufficient, and the toner may move relative to the magnetic field due to the rotation of the toner carrier. The effect of disaggregating the toner particles is reduced, making it difficult to apply a thin layer to the surface of the toner carrier and causing problems such as uneven coating. In addition, if the magnetic properties of the toner are above this range, the initial toner will be coated in a thin layer on the surface of the toner carrier and uneven coating will not occur, but the action of the magnetic field will be strong during development and the toner will be applied to the surface of the toner carrier. It is strongly attracted by the magnetic field and the image density decreases. Furthermore, if the magnetic properties of the toner exceed this range, if the toner is left in a developing device that has an internal magnetic field or is used for a long time, the toner may become strongly magnetized due to the action of the magnetic field inside the toner carrier. As a result, the toner particles aggregate, making it difficult to apply the toner to the surface of the toner carrier, causing problems such as uneven coating.

The magnetic properties of toner are measured as follows. Using a vibrating sample magnetometer (manufactured by Toei Kogyo), measure the toner to be tested by approx.
501n9, apply an external magnetic field of 10 koe, and record the magnetic hysteresis on a record. ) to measure the magnetic properties of the magnet. As a measurement method, the toner to be tested is weighed to approximately 501n9' and placed in a sample case. Lightly compress it in that state, close the lid, accurately weigh the total weight, and subtract the weight of the sample case to obtain the true weight. Attach this to a vibrating rod and apply the specified vibration. In this state, an external magnetic field (9) of 10 koe f is applied and gradually reduced, and at the same time recording begins on the recorder. The value of magnetization when the external magnetic field is set to 00e is the residual magnetization σr, and then a reverse magnetic field is gradually applied and the magnetization when the value reaches 10 koe is σS (saturation magnetization). σS, σr in the magnetic field on the + side and σB, σ on the one side
Since r is slightly different, calculate both values, average value, get the correct σB and σr, divide the direct reading from this hysteresis loop by the true weight, and use the magnetization per gram as data (unit: is emu/9). The coercive force is determined by directly reading all the recorded X-axis values of the hysteresis loop (unit: Oe). Note that before measurement, nickel is used as a standard sample and the output is adjusted.

In the present invention, 0.02 to 5 wt% of colloidal silica is externally added to the magnetic toner having the above-mentioned magnetic properties, based on the total toner.Thus, a thin layer of toner is applied to the surface of the toner carrier. When the amount of colloidal silica (10) is less than 0.02 wt%, the coating of a thin layer of toner on the surface of the toner carrier becomes stable. There is no equalizing and homogenizing effect, and 5
If it exceeds wt% f, problems such as poor line reproducibility and spotting will occur. In particular, colloidal silica is 0.05
When added to ~3 wt% toner, very good and clear images are obtained. Colloidal silica used in the present invention includes, for example, fine silica powder with a primary particle size of 15 to 200 mμ produced by vapor phase oxidation of a silicon halide compound or produced by various precipitation methods from an aqueous solution, and a silane coupling agent. The above-mentioned fine silica powder treated with an organic treatment agent such as the above is used.

Furthermore, a magnetic toner having magnetic properties within the above-mentioned range and containing a predetermined amount of colloidal silica, the absolute value of the toner charge amount being in the range of 0.5 to 20 μQ/9. As a result, a thin layer of toner is uniformly applied to the surface of the toner carrier under various environmental conditions, and image changes due to environmental conditions are significantly reduced. Particularly good results can be obtained when the absolute value of the toner charge amount is within the range of 1 to 10 μvg. That is, the absolute value of the amount of charge mentioned above is 0.5μQ/
If it is less than g, the coating thickness on the surface of the toner carrier will be too thin under high temperature and high humidity conditions, the image density will be low, the image reproducibility will be very poor, and a poor image will be obtained without sharpness, making it unsuitable for practical use. do not have. On the other hand, when the absolute value of the toner charge amount is 20 μvg or more, the toner charge amount becomes too large under low humidity, and the Coulomb force between the charged toner particles and the toner carrier increases, causing the toner particles to carry the toner. The strong attraction to the body surface prevents toner particles from adhering to the electrical latent image from the surface of the toner carrier, causing a decrease in image density and poor image quality. Furthermore, agglomeration tends to occur on the toner carrier, which causes uneven coating on the toner carrier and uneven images. The amount of charge of the toner here is the amount of charge of the toner applied to the surface of the toner carrier, and is a value measured by directly sucking the toner on the surface of the toner carrier using the well-known suction type Faraday cage method. .

The toner binder used in the present invention includes:

A wide variety of known materials can be used, including polystyrene and polyP-chlorostyrene.

Monopolymers of styrene and its substituted products such as polyvinyltoluene; styrene-P-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer , styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl Styrene-maleic acid ester copolymers, etc. 13) Thyrenic copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, l-lipropylene, polyester, triurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin,
Modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, mother rough wax, etc. can be used alone or in combination.

As the magnetic material used in the present invention, any magnetic material whose magnetic properties fall within the above-mentioned range when a toner containing 40 to 100 parts by weight of the magnetic material is formed can be used.
In order to obtain the seguia or red magnetic color toner which is the object of the present invention, 80% by weight or more of the total amount of magnetic material is γ-F.
e Must be 20.5. The reason for this is
Most other magnetic materials have a black or dark brown color, and can be mixed within 20% by weight, but if the amount exceeds that, the color of the toner will deteriorate ( 1
4) Because you end up doing it. Conversely, γ-F containing zinc etc.
a205 ferrite, γ-Fa20. Preferably, the magnetic material of the present invention is one in which a part of the material is pregelatinized.

In addition, various dyes and pigments of yellow, orange, red, and sepia color having a desired hue can be used in combination with the toner of the present invention, if necessary.

In addition, other additives include tin oxide fine powder, charge control agents, metal complex salts, etc. for charge control and prevention of aggregation.
Fluororesin powder, metal salts of higher fatty acids, etc. can be added, but for the purposes of the present invention, those having a black or similar hue are not preferred.

Further, the developing method applied to the toner of the present invention is not particularly limited, but includes the magnetic brush method described in U.S. Pat. No. 2,874,063, U.S. Pat.
The cascade development method described in the specification of the issue, JP-A-5
4-42141, JP-A-55-18656, etc., and a method using an electrically conductive magnetic toner described in U.S. Pat. No. 3,909,258. There are several methods, including a method using high-resistance magnetic toner, an impression method, a powder cloud method, and a fur brush method. Alternatively, it may be one that develops a magnetic latent image. In particular, the toner of the present invention is
141, No. 55-18656, etc., a one-component magnetic toner is supplied to the surface of a rotatable toner carrier equipped with a magnetic field generating means fixed inside, and the toner is applied by a toner application thickness regulating member. When used in a developing method in which the thin layer of toner on the surface of a carrier is opposed to the surface of an electric latent image holder with a gap therebetween, it exhibits excellent performance.

The details of the present invention will be illustrated below by way of examples.

Example 1 Styrene-butyl methacrylate copolymer (monomer ratio 7
:3) 100 parts by weight, γ-Fst205 (He165
0e, σs 67. Oemu/,! i'-σr 16
．． 1 emu/J9 BET surface area 5.0m/'g)6
0 parts by weight of Cr salt of ditertiary-butylsalicylic acid, Cr salt type weight parts of ditertiary-butylsalicylic acid were mixed in a high-speed mixer, melt-kneaded on a roll mill at about 150°C, cooled, pulverized in an air jet mill, and further 5 parts by weight in an air classifier. The particles of ~25μ were used as a toner.

Further, to this toner, 0.4 wt % of hydrophobic colloidal silica, which was produced by a vapor phase oxidation method and whose surface was treated with a silane coupling agent, was externally added.

The above toner was applied to a commercially available copying machine (product name NP-400RE manufactured by Canon), and the amount of charge on a 30φ stainless steel sleeve was measured to be -6μVy.Furthermore, the vapor characteristics were Hc1650e, 6g, 24.56mu/I! ,σ,5
．． It was 15 emu/i.

This toner was applied to the above-mentioned copying machine NP-400RE and image evaluation was performed. In the initial state, the temperature is normal temperature and humidity, low temperature and low humidity (10℃, 10%), and high temperature and high humidity (35℃).

85%), a thin layer of toner can be uniformly applied to the 30φ stainless steel sleeve that is the toner carrier.
The image density was 1.2.0.9.1.1, respectively, and a clear and good image was obtained. Durability tests were carried out for 50,000 sheets in each environment, and the toner coating on the sleeve remained uniform and stable, with no change from the initial state, and the image density was 1.3 (17). ) Stable at 1.2 and 1.2, and no change in image quality was observed ◎ Comparative Example 1 Electrostatic charging on the sleeve was carried out in the same manner as in Example 1 except that ditertiary-butylsalicylic acid was removed. The amount is 0.3μ
An experiment similar to Example 1 was conducted in which a toner with magnetic properties equivalent to those of Example 1 was obtained at 100 g, but the initial density was low at around 0.6 even at room temperature and humidity, and the image was not reproduced. I could only obtain images with noticeable roughness and severe dust particles, and almost no images could be obtained under high temperature and high humidity conditions.

Comparative Example 2 A toner with a charge amount on the sleeve of 22 μWfl was obtained in the same manner as in Example 1, except that the amount of the Cr salt of ditertiary-butylsalicylic acid was increased. An experiment was conducted in the same manner as in Example 1, but under low temperature and low humidity conditions, the coating on the sleeve was thicker from the beginning than in Example 1, and the image density was 0.70.
It was low. When this Toner 1 was subjected to a durability test under low temperature and low humidity conditions, coating unevenness occurred after approximately 1,300 sheets, and the image density decreased to 0.45 (18), so the durability test was discontinued.

Comparative Example 3 Approximately 50 pieces of the magnetic material of Example 1 were α-Fe20.
γ-Fe2O3, α-Fe 203 eutectic (Hcl 600e, 0g 33.8 emu/g
,σr12.5emu/gBET surface area5.0 m2/
A toner was obtained in the same manner except that g) was changed. The magnetic properties of this toner were measured: Ha 1590e, σs 1
2.4 emu/! g, σr4.5 emu/g), and the charge amount was 7 μQ15/g. A test similar to Example 1 was conducted using this toner. At room temperature and humidity, the toner coating on the sleeve was very uneven from the beginning, and uneven coating occurred after several dozen sheets, making it unsuitable for practical use. It was something.

Comparative Example 4 The magnetic material of Example 1 was made into acicular γ-Fa203 (He 3
000ebσ! +66. Oemu/El, σr 3
3. Oemu/, 9, BET surface area 8.8 m2/
g)) A toner was obtained in the same manner as in Example 1, and the same test was conducted, and the image density was 0 even at room temperature and humidity.
．． It was low at 57, but I could only get an image of Satsuki that stood out. The amount of charge of this toner on the tube 17 is 3.5μQ/
It was 11.

Example 2 The magnetic material of Example 1 was converted into γ-Fe2O3 (Hcl 750e
.

σs 75.9 emu/9σr 21.3 emu/
The toner was obtained in the same manner as in Example 1 except that the magnetic properties were He 1750s, σs
27.7 emu/, 9%σr-7, 5emu/g
The amount of charge on the stainless steel sleeve of NP-400RE was -5.3 μσg. When this toner was tested in the same manner as in Example 1, a clear, high-density image was obtained, and the durability and environmental tests were as good as in Example 1.

Example 3 80 parts by weight of styrene-butyl methacrylate copolymer, 20 parts by weight of styrene-butadiene copolymer, 2 parts by weight of nigrosine
Part by weight, partially pregelatinized γ-Fe2O3 (He 1650
e, +7F+ 62.3 emu/,! i', or
23.8 emu/9BET surface area 5.8 m2/fi
) A toner was obtained in the same manner as in Example 1 using all 60 parts by weight. Colloidal silica made by precipitation method.
5 wtS k externally added. The charge amount of this toner is +6.5μQ on the developing sleeve of a commercially available copying machine PC-20, and the magnetic property is He 1650esσs 22.7e
mu/, 9, σr 8.4 emu/,! It was i'.

Kono Toner Th When applied to a commercially available copying machine PC-20 (Canon Ring), a clear image with a deep sepia color was obtained, and a good image was obtained even after 5000 copies.
The results of the environmental test were also good as in Example 1.

(21)

Claims (1)

[Claims] At least 80% by weight of the total amount of magnetic material contained in the toner
F e 20 s, and colloidal silica is 0.
02 to 5% by weight), the absolute value of the toner charge amount is 0.5 to 20 μQ/l, and 1
When an external magnetic field of 0 koe was applied and measured, the coercive force (H
e) 50-2500s, saturation magnetization C (1m) 15-4
0 emu/, 9% residual magnetization (σr) 1.5~20e
A magnetic color toner characterized by having magnetic properties of mul&.