JPS58136045A - One-component electroscopic magnetic developer - Google Patents

Abstract

PURPOSE:To increase the density and to control the change with the passage of time, by kneading an electrically insulating resin binder with ferro-magnetic powder and red iron oxide in a certain ratio. CONSTITUTION:A homo- or copolymer of a mono- or diethylenic unsatd. monomer such as an aromatic vinyl monomer or an acrylic monomer with >=5X 10<13>OMEGA-cm electric resistance is blended with red iron oxide[iron (III) oxide]and magnetite. By substituting red iron oxide for part of magnetite, high electrification is enabled by the charge retentivity of red iron oxide. It is desirable to use the binder by 230-40pts.wt. per 100pts.wt. magnetite and red iron oxide mixed preferably in 95:5-50:50 weight ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a component-based electroscopic magnetic developer (more specifically, a ferromagnetic powder such as magnetite and red iron oxide in a weight ratio of 95:5 to 50:50). The present invention relates to a one-component electroscopic magnetic developer comprising powder particles of a crosstalk composition dispersed in an electrically insulating resin binder.

Conventionally, when developing an electrostatic latent image, a component-based magnetic developer has been developed in which powder of a ferromagnetic material is contained in developer particles as a developer capable of developing a latent image without using a special carrier. The agent is widely known. Magnetite is mainly used as this ferromagnetic material due to its magnetic properties and black coloring.

During development of a static image using a one-component magnetic developer, each developer particle has a static attractive force (Coulomb force) between it and the electrostatic latent image, and magnetic brush formation. The magnetic attraction force between the magnet and the magnet acts simultaneously, and particles on which the Coulomb force acts more strongly are attracted to the static latent image, while particles on which the magnetic attraction force acts more strongly Developing sleeve upper ζ
This remains, and development is performed according to the electrostatic latent image on the substrate.

However, the known one-component magnetic developer is still unsatisfactory for the purpose of stably forming images of sufficiently high density over a long period of time. In other words, in a -component magnetic developer, since there is no carrier, the developer particles must be charged by friction between the particles, but charging due to self-friction is not possible in a two-component developer. Compared to electrification, it is inferior in potential height and stability. Furthermore, in the -component developer ζ, there is a considerable distribution in the magnitude of the magnetic attraction of individual particles, and particle components with large magnetic attraction remain and accumulate on the developing sleeve. During long-term use, the amount of fresh developer supplied onto the sleeve gradually decreases, and the amount of developer that can be transferred to the electrostatic latent image side decreases significantly. This is thought to be because the developer particles are classified by air classification, and as a result, the developer contains fine particles with a significantly high concentration of magnetite.

In order to prevent such defects, it is possible to greatly reduce the # of magnetite in the crosstalk composition for forming the developer, but in this case, the electroscopic property of the final developer particles, i.e. There is a problem in that the property of being charged by friction is significantly reduced and the image density is reduced.

The present inventors kneaded ferromagnetic powder such as magnetite and red iron in an electrically insulating resin binder in a fixed ratio, and created a one-component electrodetecting magnetic material in the form of powder particles by using this mixed wire composition in the form of powder particles. When used as a developer, it is possible to maintain the triboelectrification of the developer particles at an excellent level, while maintaining a relatively uniform distribution of magnetic attraction of individual particles to 4f, which reduces the concentration of particle components onto the developer sleeve. It has been found that the tendency of residual accumulation can be significantly prevented, and images with high density can be stably formed over long periods of copying work.

In the present invention, when a resin binder is mixed with a ferromagnetic powder such as magnetite, which is a red to brown pigment mainly composed of cloudy red iron oxide (nI), the triboelectric charging properties of developer particles can be significantly improved. Based on the new knowledge that it can be improved. That is, red iron has a tendency to be triboelectrically charged more positively than magnetite, and has the characteristics of being more insulating than magnetite. When powder particles made of red iron and magnetite dispersed in a resin are rubbed against each other, the exposed portion of red iron on the surface of the particles becomes positively charged and the exposed portion of magnetite becomes negatively charged, but the red iron has already been charged. As mentioned above, when the magnetite concentration in the developer composition is reduced, the potential due to triboelectric charging tends to decrease, but in the present invention, by replacing a part of the magnetite with red iron, It becomes possible to charge the powder particles rather strongly.

Furthermore, the red iron iron used in the present invention is a non-magnetic material, and has characteristics that are significantly different from magnetite, but while magnetite has a true specific gravity of 5.2,
Its true specific gravity is 5.1 to 5°2 = 5-, and its properties are very similar to magnetite.

Thus, when magnetite and red iron are dispersed in the electrically insulating resin binder, both are dispersed in the binder in a relatively uniform composition ratio. Thus, when such a mixed wire composition is cooled, pulverized, and further classified to form developer particles, each developer particle contains magnetite, which is a magnetic material, and red iron, which is a nonmagnetic material. By adjusting the composition so that these are contained in a substantially constant composition ratio, it is possible to significantly suppress the possibility that powder particles having a significantly high m degree of magnetite will be produced.

For the above reasons, it will be understood that when the one-component electroscopic magnetic developer of the present invention is used, a high density image can be stably formed throughout a long copying operation.

In the developer of the present invention, it is also important to use ferromagnetic powder such as magnetite and red iron in a weight ratio of 95:5 to 50:50, particularly 95:5 to 70:30. That is, if the weight ratio of Penga 6-1 is less than the above range, the objective of the present invention, which is to prevent the generation of particle components with an abnormally high magnetite concentration and increase the amount of triboelectrification of the particles, is disadvantageous. When the amount ratio of -10,000 Red Garlic exceeds the above range, the magnetic fishing boat's ability of the particles to attract the particles becomes weaker, the particles become more conductive, and furthermore, the color becomes red or close to brown, which is characteristic of Red Garlic. Not preferred for the purposes of the present invention.

In the present invention, the electrically insulating resin binder is 25% per 1100 ffiit parts of magnetite and red iron.
It is preferred to use amounts of 0 to 40 parts by weight, especially 190 to 50 parts by weight. In other words, if the amount of resin is less than the above range, it tends to be unsatisfactory in terms of triboelectricity, while if it is used in an amount greater than the above range, the chargeability and magnetic properties will also be poor. Furthermore, it tends to be unsatisfactory in terms of friction band acidity.

In the present invention, red iron oxide having any particle shape and size can be used, but for the purpose of the present invention, it is made of non-friable agglomerates of cubic particles and has a particle size of 1 to 10 microns, particularly Red iron in the range of 1.5 to 5 microns is preferably used.

The red iron oxide consisting of cubic particles of non-friable acromerate preferably used in the present invention is produced by the following method, although it is not limited thereto.

That is, a weak alkaline aqueous solution such as aqueous ammonia is added to an aqueous solution of iron sulfate ('lrD) to form a precipitate of iron (III) hydroxide. , the pseudoglue-like precipitate of iron hydroxide is transformed into fine cubic hematite. That is, at this time, the weak burqa IJ'L is used,
By adjusting the pH of the mother liquor to a condition close to the acidic side, fine cubic particles that are easily agglomerated are generated.
By aging at a temperature of 50 to 260° C. for a long time of 50 hours or more, and roasting if necessary, the above-mentioned red iron oxide having the particle shape is obtained.

Furthermore, magnetite (
FasO4) may also have any particle shape and size, but the number average particle size is less than 1 micron, especially 0.
．． It is particularly desirable to use magnetite particles that are as fine as 1 to 0.7 f ron but have a large apparent density of 0.45 f 7 m1 or more.

The fine magnetite particles suitable for the present invention generally have the morphology of cubic particles to slightly rounded amorphous particles, and are defined as the ratio of longest dimension/shortest dimension. It is desirable that the shape anisotropy is in the range of 1.0 to 5.5, preferably 1 to 6.In addition to the above-mentioned magnetite, the ferromagnetic powder may include various ferrites, such as synthetic ferrites such as ZnFe2Q4. You can also use

By using a combination of red iron oxide and magnetite having such particle characteristics in accordance with the preferred width of the present invention, an electroscopic magnetic developer that meets the above-mentioned purpose of the present invention by %ζ can be obtained. In other words, since the aforementioned coarse red iron particles are used, there is a tendency for the red iron particles to be exposed on the surface of the molded developer particles. This is done so that the image density is significantly improved.

Furthermore, by using fine particles as magnetite, it is possible to ensure that magnetite is contained in each developer particle, and the charging due to mutual friction between the two can be further ensured. Not only that, but by making the red to brown red iron oxide into coarse particles and the black magnetite into fine particles, the hue of the developer as a whole can be made to be almost pure black and cloudy.

As the electrically insulating resin binder, any developer resin binder having an electrical resistance of 5 x 10"Ω or more when measured alone is used, and generally various mono- or diethylene-based resin binders are used. Saturated monomers, particularly homopolymers and copolymers of (α) a vinyl aromatic monomer and (b) an acrylic monomer, are used.

As a vinyl aromatic monomer, in the following formula, R8 is a hydrogen atom, a lower (carbon number or less) alkyl group, or a halogen atom, and R7 is a lower alkyl group, an IW substituted atom such as a halogen atom, etc. and n is an integer of 2 or less including zero, such as styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, vinylnaphthalene, etc. can.

Among these, styrene and vinyltoluene are preferred.

As an acrylic yarn monomer, the following formula % formula % In the formula, R8 is a hydrogen atom or a lower alkyl group, and R
4 is a hydroxyl group, an alkoxy group, a hydroxyalkoxy group,
Acrylic monomers represented by: amine group or aminoalkoxy group, such as acrylic acid, methacrylic acid, ether acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-
Ethylhexyl acrylate, 2-ethylhexyl acrylate, 3-hydroxypropyl acrylate, 2-
Examples include hydroxyethyl methacrylate, 6-amituprobyl acrylate, 5-N,N-diethylaminoprobyl acrylate, and acrylamide.

Other monomers used in combination with these monomers (al or (b) or alone) include, for example, the following formula % formula % where l?!l is a hydrogen atom, a lower alkyl group or a chlorine atom, such as butadiene, isoprene, chlorobrene, etc. (this also applies to other ethylenically unsaturated monomers such as maleic anhydride, fumaric acid, crotonic acid, itaconic acid, etc.) Carboxylic acids or their esters, vinyl esters such as vinyl acetate, vinylpyridine, vinylpyrrolidone, vinyl ethers, acrylonitrile,
Vinyl chloride, vinylidene chloride, etc. can also be mentioned.

The molecular weight of these vinyl polymers is 3,000 to 3
00,000. % is preferably in the range of 5,000 to 200,000.

The developer of the present invention is obtained by kneading the aforementioned resin binder, magnetite, and red iron under conditions in which the resin binder is melted, cooling and pulverizing the mixed wire composition, and classifying the pulverized product.

Prior to kneading and granulating the developer components, auxiliary components of the developer known per se may be blended in a known formulation (for example, to improve the color tone of the developer, ζ, carbon black, etc.). Pigments such as -13=acid violet and dyes such as -13=acid violet can be used alone or in combination of two or more in an amount of 0.5 to 5% by weight based on the total weight.Also, for the purpose of increasing the amount, calcium carbonate, A filler such as finely powdered silicic acid can be blended in an amount of up to 20% by weight based on the total amount.In the method of fixing the developer with a hot roll, silicone oil, low molecular weight olefin resins,
One agent can be used to prevent offset of various waxes, etc. in an amount of 2 to 15% by weight based on the total weight. Further, in applications where the developer is fixed with a pressure roll, a pressure fixing agent such as paraffin wax, various animal/vegetable waxes, fatty acid amide, etc. may be used in an amount of 5 to 30% by weight based on the total amount. Further (
In order to prevent developer particles from agglomerating each other and improve their fluidity, polytetrafluoroethylene fine powder,
0.1 fluidity improver such as finely powdered silica per total
It may be blended in an amount of 1.5% by weight.

Although the particle size of the developer particles is related to resolution and other factors, it is generally in the range of 5 to 55 microns, and it is desirable that the particle size be at least twice the particle size of agglomerated red red iron.

n electrophotographic copying method using the developer of the present invention (herein, the formation of an electrostatic latent image can be carried out by a method known per se; for example, on a conductive substrate -1-); ,'N.

After the electrolytic layer is uniformly charged, it can be imagewise exposed to form a p-electromagnetic latent image.

The surface of the substrate having this static TM image is brought into contact with the magnetic brush of the magnetic developer described above to form a visible image of the developer.

The process of developing an electrostatic latent image using the developer of the present invention is as follows:
The developer hopper is filled with the one-component magnetic developer described above. A non-magnetic sleeve is rotatably provided at the lower end opening of the hopper, and a magnet is provided inside the sleeve so as to be rotatable in the opposite direction to the sleeve.

In this way, when the sleeve and magnet are rotated, a brush layer of magnetic developer is formed on the sleeve, and after this brush layer is cut into appropriate lengths tC and ζ with a cutting board, a selenium developer rotating in the same direction as the sleeve is formed. Make light contact with the drum,
The electrostatic image on the selenium drum is developed with a magnetic developer.

Next, the developer image on the substrate A is brought into contact with the transfer paper, and corona charging with the same polarity as the electrostatic latent image described above is applied from the back side of the transfer paper, thereby transferring the developer image onto the transfer paper.

In the present invention ζ, the transferred image can be fixed by any method such as heat roller fixing, flash rung fixing, or pressure roller fixing depending on the type of developer.

The developer of the present invention is particularly useful for developing p-type photosensitive plates having a positive latent image, such as selenium photosensitive plates and organic photoconductor photosensitive plates. Conventional triboelectric-component magnetic developers can generally be used to develop photosensitive plates with negatively charged latent images, but they cannot be used to develop positively charged latent images on p-type photosensitive plates as described above. The results are extremely unsatisfactory. On the other hand, according to the present invention, excellent effects can be achieved in developing and transferring such positive charge latent images.

The invention is illustrated by the following example.

Example 1 A mixture consisting of the compositions shown in Table 1 was cross-melted at 145°C for 60 minutes using a 6-roll mill, and after cooling, it was coarsely ground using a cutting mill and crushed to a size of 0.5 to 2 mm. . Next, the powder was finely pulverized using a jet mill and classified using a zigzag classifier to obtain magnetic toners CA-B, C1D, and E with sizes of 8 to 25μ.
%F, G, H). Furthermore, in order to improve fluidity, hydrophobic silica (R-97210, 3% manufactured by Nippon Aerosil Co., Ltd.) was added.
They were mixed and surface treated.

Using these prepared magnetic toners, the following 1. A copying test was conducted.

In a copying machine that uses a selenium drum (outer diameter 150 s + m) as a photoreceptor, the strength of the magnetic field on the developing sleeve (outer diameter 63 m) containing a built-in magnet via a non-magnetic member is approximately 90 m.
0 Gauss, and the above magnetic toner was placed on a developing roller of a so-called double-rotation system in which the magnet and sleeve could be rotated independently, and the spacing between the ear cutting plate and the sleeve was set at 0.0 Gauss.
The magnetic toner was arranged so that it could be supplied from a hopper to a part of the developing roller, and the distance between the surface of the photoreceptor and the developing roller was 0.5 mm. Under rotating conditions such that the developing sleeve and photoreceptor rotate in the same direction and the magnet rotates in the opposite direction, charging (+6.7 KV),
Exposure, development, transfer (+6.5 KV), constant fixing with a heater roller, and fur brush cleaning were performed. However, the copying speed was set so that 25 copies could be made per minute on A4 size paper. The transfer paper used was high-quality paper with a thickness of 80 μm. FIG. 2 shows the image density of the copy as a result of the copying test. The image density was determined by measuring solid black areas using a commercially available reflection densitometer (manufactured by Konishiroku Photo Industry).

=18- -19- According to the results, a magnetic toner dispersed in an electrically insulating resin binder at a weight ratio of magnetite and bengalane of 95:5 to 50:50 had a higher image density than a magnetic toner containing only magnetite. Gave expensive copies.

Also, for reference, when the amount of frictional charge of the magnetic toner was measured using a commercially available blow-off powder charge measuring device (manufactured by Toshiba Chemical), it was -22,5 μolff# for α toner, and -25,8 μolff# for -toner. f%k toner is -20.2μc
/f was shown.

Example Z Average particle size 0.7μ, apparent density 0.53f/door 1 magnetite 40% by weight (hereinafter expressed as %), average particle size 15μ
of red iron 5% and styrene/acrylic copolymer resin 5%
A magnetic toner having a composition of 5% is prepared in the same manner as in Example 1.

The following continuous copying test was conducted using this produced magnetic toner.

In a copying machine using an organic semiconductor drum as a photoreceptor, the above magnetic toner is applied onto a 20-developing roller with a built-in magnet via a non-magnetic member, with a spacing of 0.3 square meters between the cutting plate and the developing roller. Charging, exposure, development, Transfer fixation and fur brush cleaning were performed.

After making 30,000 copies, the image density remained stable at 1.40 to 1.51 with no toner accumulation on the developing roller.
I was able to obtain a copy of.

[Brief explanation of drawings]

FIG. 1 is a microscopic photograph of Red Red Garlic used in Example 1 of the present invention, and FIG. 2 is a graph showing the image density of a copy corresponding to the mixing ratio of Red Red Garlic. Patent applicant: Sanda Kogyo Co., Ltd. 21-L/To milk 2

Claims (4)

[Claims] (1) One-component electrodetection system consisting of powder particles of a crosstalk composition in which ferromagnetic powder such as magnetite and red iron are dispersed in an electrically insulating resin binder at a weight ratio of 95:5 to 50:50. Magnetic developer. (2) The developer according to claim 1, wherein the resin binder is present in an amount of 40 to 20 parts by weight per 100 parts by weight of the total amount of the ferromagnetic powder and red red iron. (3) The developer according to claim 1, wherein the red red iron is composed of non-friable agglomerates of cubic particles and has a particle size of 1 to 10 microns. (4) The developer according to claim 1, wherein the ferromagnetic powder has a particle size of 0.1 to 1.0 microns.