JPS5921549B2 - electrostatic image developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a one-component developer used for developing electrostatic images.

Conventionally, two-component developers containing carrier and toner have been used in magnetic brush methods, cascade methods, liquid development methods, etc., and have been prized as useful developers for forming images by electrophotography. On the other hand, it has drawbacks peculiar to two-component developers, such as carrier fatigue and fluctuations in the mixing ratio of carrier and toner.

Furthermore, many component-based developers have already been disclosed in US patents and Japanese patents, and for example, those used in the touchdown method, impression method, bristle brush method, powder cloud method, etc. are known. None of these have been put into practical use. However, recently, a one-component developer whose main component is a conductive magnetic toner containing a magnetic material has been developed, and such a developer is disclosed in West German Patent Publication No. 2313297.
It is stated in the No.

A developer using this conductive magnetic toner has the advantage of being able to develop an electrostatic charge image of either positive or negative polarity, but on the other hand, since the toner is conductive, once the developed image is There is a drawback that when transferring images to other areas, the sharpness of the image tends to decrease and it is difficult to obtain a good transferred image. For the reasons mentioned above, there has been a demand for a one-component developer whose main component is an insulating magnetic toner that does not reduce the sharpness of the image even when a transferred image is formed.
For example, it is disclosed in Japanese Patent Publication No. 49-17739 and is already known.

The insulating magnetic toner, which is the main component of this developer, is a colorant,
It is a capsule type product in which a core made of a soft solid polymer such as a reaction product of isopropylidene diphenoxypropanol and adipic acid and a magnetic material is coated with a resin such as styrene. This resinous magnetic toner certainly has excellent transfer properties, and since it uses a soft solid polymer as a core material, it has excellent pressure fixing properties.

However, to charge this toner, an external charging device such as a corona discharge is required.Although it is possible to uniformly charge a flat object such as an electrophotographic photosensitive plate, a group of fine particles such as toner can be uniformly charged. However, it is extremely difficult to charge the toner toner, and therefore it is impossible to obtain a good toner image. An object of the present invention is to provide a one-component developer for electrophotography that does not use carrier particles and does not cause deterioration of the developer due to fatigue of the carrier. Another object of the present invention is to develop a one-component developer for electrophotography which is capable of producing an image with high sharpness when a toner image formed on a photosensitive plate for electrophotography is electrostatically transferred to form a transferred image. The aim is to provide agents for

Still another object of the present invention is to develop a one-component electrophotographic developer capable of forming a toner image by developing an electrostatic latent image by frictional charging generated by friction between toner particles without using a corona charger or the like. The aim is to provide agents for

The present inventors have proposed a toner which contains a magnetic material and a resin as main components, and optionally contains a pigment and/or a charge control dye, and which has electrically insulating properties as a whole, the magnetic material being on the surface of the toner particles. It has been found that the above object can be achieved by using a one-component developer whose main component is a magnetic toner which is made to be substantially exposed.

That is, by having the above-mentioned structure, the developer which has magnetic toner as a main component according to the present invention does not require a dicarrier, which is different from conventional two-component developers, and therefore the developer having the magnetic toner as a main component does not suffer from fatigue deterioration of the developer due to the carrier. Also, there is an advantage that there is no fluctuation deterioration of the image due to fluctuations in toner density with respect to the carrier.

Further, the magnetic toner according to the present invention has a volume resistivity of 1014Ω (7
) Since it is made electrically insulating, it has the advantage that a sharp transferred image can be obtained without image disturbance during transfer. Furthermore, the magnetic toner of the present invention is charged as a result of friction between the particles, with some toner being charged positively and others negatively, and the electrostatic attraction between the toner particles causing toner flow. Because sex becomes extremely poor,
It must have a fluidity of over 30 on the force fluidity index. The magnetic toner used in the developer of the present invention has a resin component and a finely divided magnetic material as main components, and contains a colorant and/or a charge control agent as necessary. Various thermoplastic resins are used to provide insulation. Preferred thermoplastic resins include styrene resins such as polystyrene and polyparachlorostyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. Acrylic resin consisting of a single or copolymer, vinyl resin consisting of a single or copolymer of vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propylate, vinyl benzoate, vinyl butyrate, etc., vinyl methyl ether, Vinyl ether resin consisting of a single or copolymer of vinyl isobutyl ether, vinyl ethyl ether, etc., vinyl ketone resin consisting of a single or copolymer of vinyl methyl ketone, vinyl hexyl ketone, N-vinylpyrrole, N-vinylcarbazole, N-vinyl N-vinyl resin consisting of a single or copolymer of indole, N-vinylpyrrolidone, etc., rosin-modified phenol-formalin resin, oil-modified epoxy resin, polyurethane resin, cellulose resin, vinyl resin, epoxy resin, cellulose resin, polyurethane resin, etc. An appropriate one or a mixture or copolymer of two or more of these can be used. In the toner of the present invention, a colorant and a charge control agent may be added as necessary.

As a coloring agent, it has conventionally been used in electrophotographic toners. For example, carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow,
Ultramarine Bruni, DuPont Oil Red, Quinoline Yellow, and mixtures thereof are used. However, if the magnetic material serves as a coloring agent, the coloring agent may not be added. As the charge control agent, for example, Fetschwarz-HBN (Color Index HBN 26150) and alcohol-soluble Nigro-N (
Color Index 71650415), Sudan Chief Schwartz BB (Color Index, 462615)
0), chromogenic ETCO (color index f) 14645), etc. are preferably used.

In order to produce the magnetic toner which is the main component of the developer of the present invention, for example, 50 parts of triiron tetroxide is used per 100 parts by weight of the toner.
~65 parts by weight (approximately 10 parts by weight of magnetic material per 100 parts by weight of resin)
0 to 190 parts by weight), add a charge control agent and/or a coloring agent as necessary, mix with, for example, a diroll mill, heat-grind, and then crush and classify with, for example, a ball mill or dinit crusher, preferably, e.g. U.S. Patent No. 33389
The toner resin is manufactured by subjecting it to hot air treatment at a temperature higher than its softening point using a rotary spray dryer as disclosed in the specification of No. 91, or by spheroidizing the toner resin, or by adding 50 to 50 to 100% of the magnetic material to 100 parts by weight of the toner.
Add 65 parts by weight of a charge control agent and/or colorant as necessary, and further add an organic solvent such as toluene, acetone, or ethyl acetate, mix and disperse in a ball mill, and heat the mixture with hot air at a temperature higher than the softening point of the resin. It is produced by feeding the powder and granulating it in a furnace, for example, by the above-mentioned rotary spray drying method. The developer containing the magnetic toner of the present invention as a main component is a developer that can be applied to both positively charged photoreceptors and negatively charged photoreceptors. Although the present invention can be applied to other photosensitive plates, it is preferable to use a negatively charged zinc oxide photosensitive plate to form excellent images.

In the magnetic toner used in the developer of the present invention, both a positively charged toner and a negatively charged toner are formed due to mutual friction, and if a negatively charged photoconductor is developed, only the positively charged toner is formed. Although consumed, the remaining toner is again mutually triboelectrically charged to form toner that is positively and negatively charged at the same rate as before development.

Therefore, even as development progresses, the toner is not biased toward one polarity, and a substantially constant ratio of positive and negative toner is maintained.
Therefore, it is only necessary to replenish toner consumed as development progresses as needed. Therefore, the developer is easier to handle than conventional two-component developers, and the apparatus is also simplified. The magnetic toner of the present invention is made by uniformly dispersing fine magnetic particles in a resin as described above, but if the temperature and dispersion time during granulation are excessive, the exposure of the magnetic powder may be small. Therefore, charging due to mutual friction is not performed smoothly, resulting in a toner that is not suitable for the present invention.

The characteristics of the developer of the present invention, in terms of -G, are that it consists of particles containing an appropriate amount of ferromagnetic powder in a resin, and a large number of surfaces of the magnetic powder are exposed on the surface of the particles. It is a developer whose main component is a ferromagnetic and insulating toner, which imparts positive and negative charges to the toner particles through the frictional charging effect between the particles, and which produces spikes of toner particles using a magnet. It performs a developing action.

Therefore, the developing device using the developer of the present invention can be a slightly simplified version of the magnetic brush developing device, and in particular, a very simplified one in terms of toner replenishment.
On the other hand, the toner used has unique properties compared to conventional toners, such as the necessary triboelectric charging properties, good spike formation, and good fluidity required since no carrier particles are used. The developer of the present invention is an extremely unique and revolutionary product that concentrates only on the toner to perform the functions that conventionally were performed using the two components of toner and carrier. The effects obtained by this method are far superior to any conventional developer and development method using the same in terms of equipment simplification and ease of maintenance.

The developer of the present invention fulfills the role played by iron powder as a carrier in the conventional magnetic brush development method, for example, by imparting electric charge to toner particles, and by creating spikes with a magnet to rub the electrostatically charged image on the support surface. Since both of these can be accomplished using a single component toner, the composition and particle structure of the toner must be made to suit the purpose.The first function is to mutually impart a charge. However, it is generally known that when particles of the same substance rub against each other, the amount of charge cannot be very large.

The amount of charge of toner particles developed by the magnetic brush method, cascade method, etc. is approximately 10-5 coulombs/c-In3.
However, the results of a simple experiment show that, for example, the amount of charge obtained by stirring resin powder is 10-coulomb/? It was below. On the other hand, in order to perform the other functions that the toner particles of this developer should possess, such as magnetic spike formation and rubbing on the electrostatic charge image surface, the toner itself must have magnetism. We considered mixing and dispersing fine powder of magnetic material into resin.

The magnetic material used is desirably black in view of its properties as a toner, and if it is not black, it is necessary to further add a black pigment such as carbon black. Magnetite (triiron tetroxide) is a suitable magnetic material in this sense. As a preliminary experiment, we made several types of toner using the spray drying method by changing the mixing ratio of epoxy resin and magnetite. In a range where the magnetite content was up to 60% of the total toner content, generally speaking, the higher the magnetite content, the better the fluidity of the toner and the better it stood. Next, the inventors used these magnetic toners to investigate the relationship between the content of magnetic material (triiron tetroxide) in the magnetic toners, the developability on various photosensitive plates, and the imageability of transferred images. The following experiment was conducted using a developing device.

In FIG. 1, reference numeral 1 is a permanent magnet with N and S poles arranged alternately, and a non-magnetic block inserted therein and hardened with adhesive.

2 is a non-magnetic metal plate such as brass (aluminum), 3 is a magnetic toner attached to its surface, 4 is a photosensitive plate, and 5
The photosensitive layer 6 is a conductive substrate, and an electrostatic charge image is formed on the photosensitive layer 5 by the usual curling method.

Although not shown, an appropriate spacer is inserted between the metal plate 2 and the photosensitive layer 5 to maintain a gap of about 1 inch, and during the developing operation, the metal plate 2 is slid from side to side to prevent the tip of the toner. slides on the latent image surface. Note that the photosensitive plate 4 is moved slowly, for example from left to right, so that the entire surface is developed. Using this developing device, experiments were conducted on several types of toner and photosensitive plate combinations, and the results shown in Table 1 were obtained. In Table 1, the left-hand column for each photoreceptor shows the evaluation of the as-developed image, and the right-hand column shows the evaluation of the image corona-transferred onto white paper. The types of photoreceptors include binder-type zinc oxide photoreceptors, selenium photoreceptors, polyvinyl carbazole trinitrofluorenone photoreceptors, and polyvinyl carbazole layer-selenium layer laminated photoreceptors.

Further, the zinc oxide photoreceptor and the polyvinylcarbazole layer-selenium layer composite photoreceptor exhibit only negative charging, while the polyvinylcarbazole trinitrofluorenone photoreceptor and selenium photoreceptor exhibit j-image properties of both positive and negative charging. The left side of each photoreceptor shows the developability, and the right side shows the image quality after transfer. Judgment of image quality is ◎, O, △, ×, ××, ×××, 6
Displayed in stages. As is clear from Table 1, when the amount of magnetic material is 70% by weight, the developability is good, but the transferability tends to deteriorate, which is not preferable.

If the amount is less than 50% by weight, the amount of magnetic material exposed on the toner particle surface is small, and the generation of electric charge due to mutual friction between particles is small, resulting in a decrease in image density. That is, if the amount of magnetic material is too large, the transferred image will be disturbed and the sharpness of the image will be reduced. This decrease in sharpness is considered to be due to the fact that the resistivity of the toner decreases as the content of triiron tetroxide increases.

For example, FIG. 2 shows the relationship between the content of triiron tetroxide and the specific resistance of the toner.

At this time, the specific resistance was measured at a pressure of 1 kg/Cr! ? , the applied voltage is 100 V, and the thickness of the sample layer is about 4! ! The test was carried out under conditions of Tm. From FIG. 2, it is determined that when the content of triiron tetroxide reaches 70% by weight, the specific resistance decreases extremely, causing the transferred image to be disturbed and the sharpness to decrease.The magnetic toner of the present invention has at least specific resistance. It is desirable that the resistance is 1014Ω or more. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto.

Example 1 The above composition was dispersed in a porcelain ball mill for 32 hours and then granulated by a rotating disk spray drying method.

The conditions for spray drying were as follows: Thus, the average particle size was approximately 10μ.
Black spherical toner particles were obtained.

Next, remove the developing device from a commercially available Ubix 800 copying machine (manufactured by Konishiroku Photo Industry Co., Ltd.), press the copy button, and when the electrostatic latent image has been created on the master paper, switch the power switch. to stop the cutting machine.

After pulling out the master stand under a safe light and developing with the above toner using the device based on the principle shown in Figure 1, load the master stand again, turn off the power to the charging and exposure equipment, and press the copy button. When the image was transferred onto plain paper, a good image was obtained. Example 2 Priorite ACL The above composition was dispersed in a porcelain ball mill for 16 hours and then granulated by a rotating disk spray drying method.

The conditions were as follows. Thus, the average particle size of approximately 1
0μ black spherical toner particles were obtained.

Next, an image was produced using this toner in the same manner as in Example 1, and good results were obtained. Example 3 Pentaline A The above composition was dispersed in a porcelain ball mill for 4 hours and then granulated by a rotating disk spray drying method.

The conditions were as follows. Thus, the average particle size of approximately 1
0μ black spherical toner particles were obtained.

Next, development and transfer were performed using this toner in the same manner as in Example 1, and a good image was obtained. Example 4 The above composition was prepared in a porcelain ball mill.

After 5 hours of dispersion, the mixture was granulated by a rotating disk spray drying method.

The conditions were as follows. Thus, the average particle size of approximately 1
0μ black spherical toner particles were obtained.

Next, development and transfer were performed using this toner in the same manner as in Example 1, and a good image was obtained. It has been previously confirmed in another experiment that all the resins used in the above examples are positively triboelectrified with respect to magnetite (Mapico Black), and the toner particle surface was determined by electron micrographs to show the size of the magnetite particles. It was observed that there were uniform fine irregularities corresponding to .

Example 5 The above composition was kneaded in a two-roll mill at 65°C for 10 minutes, then ground in a dinit grinder, and then milled at 50°C.
After pulverizing 0g with water in a porcelain ball mill for 16 hours,
It was dried for one week in an air stream at 40°C.

Further, this powder was atomized using a two-fluid nozzle, ejected into a dryer, and spheroidized by sending hot air (190° C.). Thus, black spherical toner particles having an average particle size of about 10 microns were obtained. Next, development and transfer were performed using this toner in the same manner as in Example 1, and a good image was obtained. Although all of the toners used in the above five examples were composed of spherical particles, spherical shape is not necessarily an essential condition for the present invention.

However, in our experiments, spherical toner tended to have better fluidity on average than non-spherical toner that had been crushed. Of course, pulverized toners such as No. 5 have also been obtained with sufficient fluidity to be used in the method of the present invention. There is no particular critical value for this fluidity limit, but for example, a Carr fluidity index of 30 or less is almost impossible, and a Carr fluidity index of 50 or more is desirable. Example 6 The above composition was dispersed in a porcelain ball mill for 16 hours and then granulated by a rotating disk spray drying method.

The conditions were as follows. Thus, the average particle size is 10
Black spherical toner particles of μ were obtained.

Next, development and transfer were carried out using this toner in the same manner as in Example 1, and it was evident that the image quality was slightly improved compared to Example 1 due to the inclusion of the charge control dye. It was done. Comparative Example 1 The above composition was dispersed in a porcelain hole mill for 12 hours and then granulated by a rotating disk spray drying method.

The conditions were as follows. Thus, the average particle size of approximately 1
0μ black spherical toner particles were obtained.

Next, when an image was produced using this toner in the same manner as in Example 1, the transferred image was distorted and the fine print was difficult to read.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a simple developing apparatus for carrying out the developing method of the present invention.

Claims (1)

[Claims] 1. The main components are resin and magnetic material, and the fine particles of the magnetic material are uniformly dispersed in the resin, and the fine particles are substantially exposed on the resin surface at the particle surface, and the volume as a whole is A type consisting of electrically insulating particles with a resistance of 10^1^4 Ωcm or more, exhibiting fluidity exceeding Kerr's fluidity index of 30, and capable of generating the charge necessary to form an image by friction between the particles. An electrostatic image developer whose main component is toner.