JPS59226354A - Electrophotographic insulating magnetic toner - Google Patents

Abstract

PURPOSE:To enhance electrostatic chargeability, to improve transferability, and to prevent scattering, poor or uneven transfer, etc. by adding an fine inorg. powder contg. a specified amt. of ZnO on the outside of a toner. CONSTITUTION:An fine inorg. powder of >=98.0% purity ZnO is added to the outside of a toner in an amt. of 0.1-10.0wt% of the toner. A content of a fine magnetic powder in a binder resing is 30-90wt%. The fine inorg. powder thus added is weakly positively charged. It holds a funtion as a triboelectric carrier to the magnetic toner and it has a chance of triboelectrification enough to keep a sufficient charge amt. on a developing sleeve between the magnetic toner and the inorg. powder. As a result, since the magnetic toner can be charged highly negatively and development and transfer are carried out in that state, disturbance of an image, such as trailed traces, can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner used for developing an electrical latent image or a magnetic image in an electrophotographic method or an electrostatic printing method, and in particular to a magnetic toner for electrophotography which has significantly improved image quality. Regarding toner.

Conventionally, regarding electrophotography, U.S. Patent No. 229769
1 Specification 5% Publication No. 1982-23910 (U.S. Patent No. 5666563), Japanese Patent Publication No. 43-24748
As described in U.S. Pat. Perform layer image formation. Development is carried out by allowing a fine powder electrostatic substance, toner, and toner to adhere to the obtained electrostatic image. The toner is attracted to the electrostatic latent image depending on the amount of light applied to the layer, forming a toner image with shading. This toner image is transferred to a support surface such as an abrasive or cloth as required, and permanently fixed on the support surface by heating, pressure, or the like. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed to the photoconductor layer.

In addition to the fixing method described above, it is also possible to use other means such as solvent treatment and overcoat treatment.

There are many known development methods for this electrophotography.
Until now, development methods such as the cascade development method described in U.S. Pat. No. 2,618,552 and the magnetic brush method described in U.S. Pat. No. 2,874,066, which are development methods that are mixed with carrier particles and used as a two-component toner, have been widely used. .

All of these methods are excellent methods in which relatively good images can be obtained, 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 a single-component developer that improves the appearance of the toner, but among these, many methods that use a developer made of magnetic toner particles are superior, as disclosed in the U.S. patent. No. 3.9 G 9.258 proposes a developing method using an electrically conductive magnetic toner. In this method, a conductive magnetic developer is supported on a cylindrical conductive toner carrier (sleeve) having magnetism inside, and is brought into contact with an electrostatic image to develop it.

At this time, in the developing device, a conductive path is formed by the toner particles between the recording medium surface and the sleeve surface, and a charge is conducted to the sleeve through this conductive path to the image area of the electrostatic image. Due to the Coulomb force between the images, 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.

As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, there is a developing method that utilizes dielectric polarization of toner particles. However, such a method has disadvantages such as a slow development speed and an inability to obtain a developed image with sufficient density, making it difficult in practice.

Other developing methods using high-resistance magnetic toner include
Friction between toner particles, # between toner particles and sleeve
Friction of toner particles by rubbing etc.? A method is known in which the toner particles are brought into contact with the n'i'lf image holding member and developed. However, in these methods, the number of times of contact between the toner particles and the friction member is small, and the frictional electrification is reduced. This has been difficult in practice due to disadvantages such as the fact that the charged toner particles tend to become insufficiently charged, and the Coulomb force between the charged toner particles and the sleeve becomes strong and they tend to aggregate on the sleeve.

The applicant previously proposed in Japanese Patent Application Laid-Open No. 55-42141 a new representation method that eliminates the above-mentioned drawbacks.

This is achieved by coating a very thin layer of insulating magnetic toner on the sleeve, triboelectrifying it, and then placing it very close to an electrostatic image under the action of a magnetic field, causing the toner to fly. It is to be developed.

According to this method, by applying an extremely thin layer of magnetic toner onto the sleeve, the degree of contact between the sleeve and the toner is increased, and sufficient frictional electrification is possible.The toner is supported by magnetic force, and the magnet and toner are connected. By moving the toner particles relative to each other, the aggregation of the toner particles is released, and the toner particles are sufficiently rubbed against the sleeve. The toner is supported by magnetic force, and the toner is developed by facing the electrostatic image without coming into contact with it. Excellent images can be obtained by preventing external blurring.

However, in this method, the amount of triboelectric charge held by the toner particles coated on the sleeve is significantly smaller than the amount of triboelectric charge that the toner particles have in normal two-component development.

If such magnetic toner that retains only a weak amount of charge is used, it will cause defects on the image.

In other words, this is because toner having only a weak charge amount is attached only with a weak adhesion force to the photoconductive layer and the transfer support during the development and transfer process due to electrostatic attraction. For example, in the case of corona transfer, for a given corona transfer voltage, the smaller the charge of the toner, the weaker the toner's adhesion to the transfer support, and at the same time, the image (particularly the line characters) is disturbed, resulting in so-called blurring. Furthermore, when the transferred image enters the fixing roller, the edges of the image on the support are disturbed and so-called trailing occurs.

As a process measure to deal with the defects induced in toner having a small load ηti as described above, there is a method of increasing the corona transfer voltage to increase the adhesion between the support and the toner. However, in this case, the resistance of the support (transfer paper) is relatively low and transfer omissions are likely to occur. In addition, uneven transfer of solid portions (due to uneven thickness of the transfer paper) is likely to occur as uneven density.

An object of the present invention is to provide a magnetic toner for electrophotography in which the weak charging property of the magnetic toner, which is essentially inherent in the jumping development-one-component magnetic toner system, is significantly improved.

Another object of the present invention is to provide a magnetic toner for electrophotography which has improved transferability, widens the process latitude in the transfer process, and overcomes defects such as unevenness, transfer omissions, and uneven transfer.

It has been found that the present invention can be achieved by externally adding inorganic fine powder containing 98.0% or more of zHo to a magnetic toner.

The inorganic fine powder applied to the present invention is weakly positively charged when the charge amount is measured by the two-component mesh method. Of course, the magnetic toner is highly negatively charged in the above charge amount measurement.

In this way, when a weakly positively charged inorganic fine powder is added and mixed with magnetic toner and placed on a developing sleeve, the frictional electrification of the magnetic toner is caused by the inorganic fine powder, in addition to the conventional developing sleeve and toner mutually. It is thought that friction between the two sides acts as an important factor. That is, the fine powder appears in the magnetic toner and maintains the function as a friction carrier, and the opportunity for frictional contact to maintain a sufficient amount of charge on the developing sleeve is ensured between the magnetic toner and the inorganic fine powder. be done. Therefore, magnetic toner can have a high amount of negative charge, and development and transfer are performed in this state, so it is thought that the above-mentioned image disturbance (tailing) does not occur.

At this time, what should be considered for percentage scratches is that any combination of a weakly positively charged substance on the one hand and a negatively charged magnetic toner on the other hand will not cause any disturbance in image quality. isn't it. This is because whether or not the toner can have a high negative charge amount when combined with a magnetic toner depends on the frictional charge with the added material, and measuring the charge amount using the two-component mesh method is only for the time being. This is because it is easy.

In fact, in the process of completing the present invention, the inventors discovered a substance that has a weak positive charge using the two-component mesh method, but does not have any effect on image quality disturbance.

However, the inorganic fine powder provided in the present invention is ZnO9B.
, Owt% or higher purity is preferable, more preferably s
It is preferably 99.0 wt% or more.

10.0 It is desirable that the inorganic fine powder be contained in an amount of 0.1 to 5 wt%, preferably 0.2 to 5 wt%, based on the toner.

The particle size is preferably 2.0 microns or less and preferably in the range of 02 to 15 microns.

As the binder resin used in the present invention, all known binder resins can be used, but examples include monopolymers of styrene and its substituted products such as folystyrene, bo+)P-chlorostyrene, and polyvinyltoluene; -Chlorus fL/
copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate 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-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-hinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer Polymethyl methacrylate,
Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic resin Hydrocarbon resin.

Aromatic petroleum resins, chlorinated paraffins, paraffins, waxes, etc. can be used alone or in combination.

When this binder resin contains a magnetic substance and is formed into particles, the particle size is preferably 5 to 20 microns, which is the general toner particle size.

The magnetic substances contained in the binder resin include magnetite, which is a ferromagnetic element and alloys and compounds containing these.
Hematite, ferrite, and other alloys and compounds of iron, cobalt, nickel, manganese, and other ferromagnetic alloys can be used as appropriate.

Its particle size is 100 to 800 m7I, preferably 6
00 to 500 mμ, 30 to 7 for polymer particles
0 weight φ preferably 40 to 65% by weight, more preferably 5
It is suitable to contain 0 to 60% by weight.

In addition, this magnetic toner contains a charge control agent, a flow modifier,
The present invention will not be hindered in any way even if coloring agents, lubricants, etc. are added and contained as necessary.

To measure the amount of charge in the present invention, test substances are mixed at a ratio of 10:1. The mixture is carefully evaluated at 05 to 1.5 f, and is suctioned at a pressure of 253H20 on a metal 100 mesh screen connected to an electrometer, and the amount of toner sucked and its electric charge are separated at that time. , find the amount of charge per unit weight. The inorganic fine powder (Zn density) measured by this method showed 0.5 to 0.95 μc/?

The present invention will be explained in more detail with reference to Examples below.

Example 1 Styrene-butyl acrylate copolymer 100
Part EFT-10 [J [X Toda Kogyo magnetite]
60 parts Charge control agent 2 parts The above materials were mixed and pulverized to obtain a one-component magnetic toner having a particle size of 5 to 30 μm. The toner contains 0.0% hydrophobic colloidal silica.
A toner for visualization was prepared by externally adding 3 wt % of zinc oxide fine powder (manufactured by Sakai Chemical Co., Ltd., purity 990%, average particle size 08 μm).

Images were produced using the magnetic toner of the present invention in the following manner using the apparatus shown in the figure. A positive electrostatic latent image is formed on a well-known CDS photoreceptor, and as shown in the figure, the sleeve surface magnetic flux density is 700 Gauss, the distance between the ear cutting blade and the sleeve surface is 2 mr+, and the sleeve is fixed with a rotating magnet (sleeve circumferential speed is the same as that of the drum, but the direction of rotation is opposite), and the distance between the surface of the photosensitive drum and the sleeve is 0.25.
Set in the throat, 1.2 KHz 1.2 KV in the sleeve
The magnetic toner is used for development by applying an alternating current of 150 V and a direct current bias of +150 V, and then the back side of the transfer paper is
．． The powder image was transferred while irradiating a direct current corona in the range of 0 to 10 ZO to obtain a copied image. The remaining developer on the photosensitive drum was removed using a magnetic brush cleaner, and the fixation was carried out using a commercially available ordinary copier (product name: NP-200, r, manufactured by Canon).
I went there using

The resulting image was clear and free from tailing and blurring within the above transfer voltage range.

In addition, a uniform solid image with no density unevenness due to transfer defects or transfer unevenness was obtained even in the border area.

Subsequently, the transfer voltage was fixed at 5.9 KV and 10,000 sheets were continuously copied, and the images after 10,000 sheets had the same image quality as the initial image.

Comparative Example 1 Example 1 was prepared by externally adding and mixing only 0.3% of hydrophobic colloidal silica to the same magnetic toner as in Example 1 to obtain a toner for imaging.
When we conducted the same test as above, we increased the transfer voltage by +5. Q.K.
up to V]; When it was removed, there were no transfer defects or uneven transfer, but the pressure was very uneven, and conversely, 7. OKV'
In the case of 1:, the hardness and blurring were improved to some extent, but solid black areas were affected, transfer omissions, and transfer ratio unevenness of 1 degree occurred, making it unsuitable for use. I fixed the transfer voltage at 59KV and made continuous copies of 10,000 sheets, but in the early stages, there was a lot of effort and unevenness, and after 10,000 sheets, there were always transfer omissions in solid black areas, and the transfer density was poor. Unevenness was observed.

Comparative Example 2 A commercially available atomized zinc fine powder (
A toner for imaging was obtained by externally adding and mixing 06% hydrophobic colloidal silica (purity: 85φ, average particle size: 25 μm), and the same test as in Example 1 was conducted.

As a result, similar to Comparative Example 1, defects on the image were observed.

Example 2 Polyester resin 100 parts cop-1 (
After 55 parts (manufactured by TDK Magnetite) and 2 parts (2 parts) of a charge control agent were mixed and pulverized and classified, a one-component magnetic toner having a particle size of 5 to 30 μm was obtained. The toner contains 0.3w of hydrophobic colloidal silica.
A toner for visualization was prepared by externally adding 4.0 wt% of t% zinc oxide fine powder (manufactured by Sakai Chemical Co., Ltd., purity 990, average particle size 0.8 μm). When this toner was printed using a commercially available NP-400RE copying machine, a good image was obtained with no blurring, no transfer defects, and no uneven transfer density.

[Brief explanation of the drawing]

The figure is a sectional view of an embodiment of a developing process to which the toner of the present invention can be applied. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Nonmagnetic cylinder, 6... Magnetic roll, 4... Hopper, 5... Doctor blade, 6... Magnetic toner. Patent applicant Canon Co., Ltd. Agent Patent attorney Yu Kano 4

Claims (3)

[Claims] (1) The step of forming an electrical latent image on the latent image holding layer, in which the insulating toner disposed on the toner holding member and at least the non-latent image area of the latent image holding layer are closely opposed to each other so as not to come into contact with each other. The toner used in the image forming method, which includes the step of developing the latent image and the step of transferring the obtained toner image to a transfer member, may contain an inorganic fine powder having a purity of 98.0% or more of ZnO. Characteristic insulating magnetic toner for electrophotography. (2) 0.1 to 10.0 of inorganic fine powder to toner
The insulating magnetic toner for electrophotography described in the Patent Hjr Required Range Paragraph 1 is externally added in a wt% range. (3) The insulating magnetic toner for electrophotography according to claim 1, which contains 30 to 90 wt% of magnetic fine powder based on the binder resin.