JPH03122666A - Developer - Google Patents

Abstract

PURPOSE:To prevent the developer from causing carrier attraction, etc., and to obtain images which fog less and have high image quality by using the developer under specific conditions and incorporating particles having <=250 mesh particle size in the grain size distribution of a carrier into the developer in an <=8wt.% range. CONSTITUTION:The developer used for a developing mechanism to be impressed with >=250V potential contains <=8wt.% particles having <=250mesh particle size in the grain size distribution of the carrier of the developer. The developer is preferably used for a positive chargeable photosensitive body (OPC) in this case. A photosensitive body formed by combining a charge generating material and a charge transfer material is usable as the positive chargeable photosensitive body. The images which are free from the fogging and have the high image quality are obtd. without generating the carrier attraction in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developer, and more specifically, a developer that can obtain a high-temperature image even with a developing mechanism with a small potential difference and that does not cause so-called carrier attraction. Regarding no developer.

(Conventional technology) In the field of commercial electronic copying, for developing electrostatic images.

Magnetic brush development using a two-component magnetic developer is widely used. Two-component magnetic developers are widely used as a mixture of a magnetic carrier made of iron or sintered ferrite particles, and toner particles made of a fixing resin dispersed with colorants, charge control agents, etc. It is used.

A typical developing mechanism section that uses a developer has a structure as shown in FIG. be done. The toner 6 is supplied into the lower developing device 10 through the feeder-equipped supply port 8.
The two-component developer 14 is agitated together with the carrier therein by an agitator 12, 12.

A developing sleeve (developer carrier) 16 having a large number of polar magnets is disposed inside the developing device 10, and the developing sleeve 16 is filled with toner #! The developer 14 after obtaining a friction charge is supplied,
Further, a magnetic brush 18 is formed on the sleeve surface by the developer. The magnetic brush 18 has a panicle length adjusted by a panicle cutting mechanism 20, and the magnetic brush 18 is connected to an electrophotographic photosensitive drum (image carrier).
22 and is transported to the nip position with light #24.

The distance between the photosensitive drum 22 and the developing sleeve 16 is DD−.
The developing sleeve 16 and the photosensitive drum 22 are rotatably supported by a machine frame (not shown) and move in the same direction (arrows) at the nip position (rotating directions are opposite to each other). It is driven so that

A corona charger 26 connected to a variable high voltage power supply 24 and an exposure optical system 28 are arranged around the photoreceptor drum 22.
is disposed upstream of the developing device 1o to form an electrostatic latent image with a predetermined surface potential. Further, a bias power supply 33 equipped with a voltage adjustment mechanism 30 is connected between the photosensitive drum 22 and the developing sleeve 12, and the photosensitive layer 2
An arbitrary value (bias potential) which is the same polarity as the surface potential and lower than the surface potential can be applied to the surface potential. Further, a transfer mechanism 34 for transferring the toner image to a copying machine is provided around the photosensitive layer 24 and downstream of the developing section.

In such a configuration, the developer 14 is in the development sleep 1
A magnetic brush 18 is formed on the photosensitive layer 2 at the nip position.
4 to form a visible image 36 of toner on the photosensitive layer 24. The formed visible image 36 is transferred to a transfer material (not shown), and then the toner image is fixed by the transfer mechanism 34 to form a direct image.

(Problems to be Solved by the Invention) Incidentally, when forming this image, it is required that the optical density of the image area is high and that toner adhesion to the background area, that is, fogging is small.

As a means of obtaining such high-quality images with less fog, a method of increasing the bias potential has been considered. Also,
By increasing the bias potential, problems caused by low-charge toner can be eliminated, and the amount of light required to reach the photoreceptor layer can be reduced, thereby increasing the speed of development.

However, there is a problem in that an increase in the bias potential increases charge repulsion between the magnetic carrier and the developing sleeve, making carrier attraction more likely to occur.

In addition, in recent years, organic photoreceptors have been used as photoreceptors for electrophotography because they have good processability and are advantageous in terms of manufacturing cost, and also have a large degree of freedom in functional design. There are two types of organic photoreceptors: negatively charged types and positively charged types, but since negatively charged types cause pollution of the copying environment, the use of positively charged photoreceptors (OPC) is expected. has been done.

However, the residual potential of such positively charged photoreceptors tends to be larger than that of conventional Se-based photoreceptors, and when using a positively charged photoreceptor, the bias potential must be set to 250 V.
Must be used above. As shown in FIG. 2, it has been found that when the bias potential is high, the conventional developer (indicated by the broken line △) frequently causes carrier attraction.

Therefore, an object of the present invention is to provide a developer which can be used at a bias potential of 250 V or more and which can provide high quality images without causing problems such as carrier attraction and fogging.

Another object of the present invention is to provide a developer for OPC, which has recently been frequently used, particularly a positively charged type developer for OPC.

(Means for Solving the TIA Problem) According to the present invention, there is provided a developer used in a developing mechanism to which a bias potential of 250 V or more is applied, which has a carrier particle size distribution of 250 mesh or less. An object of the present invention is to provide a developer characterized in that particles having a particle size account for 8% by weight or less.

The present invention also provides a developer for a positively charged organic photoreceptor.

(Function) The present invention uses a developer carrier having a particle size distribution of 250 mesh or less and octafold % or less in development that deviates from the conventional development conditions in which a bias potential of 250 V or more is applied. This is based on the knowledge that high-quality images without fog can be obtained without causing so-called carrier attraction.

As shown in FIG. 2, in the conventional developer, carrier attraction increases as the bias potential increases.

This is understood to be because the magnetic carrier gradually increases its charge repulsion with the developing sleeve, making it easier for the carrier to transfer to the photoreceptor. It is generally believed that the current value and other electrostatic effects of magnetic carriers are largely influenced by carrier attraction, and the particle size of the carriers is not given much importance because all carriers are uniformly charged. There wasn't.

However, in the developer of the present invention, by controlling the particle size distribution of the magnetic carrier of 250 mesh or less to 8% by weight or less, particularly 5% by weight or less, carrier attraction can be significantly suppressed even when the bias potential increases.

The particle size distribution of the microparticle size carrier of 250 mesh or less is 8
By weight% or less, compared to conventional carriers,
This means that a part of the micro-particle carriers have been removed.

Development under such high bias potential conditions can reduce fog and obtain high-quality images, as described above. In addition, even in a bad environment where low-charged toner is generated, the effect is small, and the amount of light required for the photoreceptor layer can be reduced, so the speed of the apparatus can be increased.

Furthermore, increasing the bias potential can reduce the influence of the residual potential of the photoreceptor. That is, even if the residual potential of the photoreceptor is as high as at least 150 V, by increasing the bias potential, the photoreceptor can provide excellent image quality without causing fogging.

Positively charged photoreceptors (
OPC), etc., and this OPC has conditions under which the developer of the present invention can be suitably used. Further, an increase in the bias potential lowers the development potential difference given by the difference between the bias potential and the surface potential, and in some cases, low potential development is forced. Such low potential development deteriorates tonality and image density. However, in the aforementioned DD-g, 1.
Less than 2mm, especially 1. If the developing condition is less than 0 mm, excellent gradation and image density can be maintained, and carrier drag will not occur. From this reason as well, the developer of the present invention can be fully applied to positively charged organic photoreceptors (preferred embodiments of the invention) Preferred embodiments of the developer according to the present invention will be described below.

The developer of the present invention is a two-component developer consisting of a magnetic carrier and a toner, and the magnetic carrier, toner, and developer will be explained in detail in turn.

11. In the present invention, any magnetic carrier can be used as long as the particle size distribution is within the above-mentioned range, and it is preferable to mainly use ferrite particles whose surfaces are coated with a resin. can.

That is, carrier particles are generally preferably spherical, and those with a particle size distribution of 250 mesh or less satisfy the range of 8% by weight or less, and in particular, those that satisfy the range of 5 weight% or less, To prevent carrier pull even in a state where the bias potential is high. With a magnetic carrier having such a particle size distribution, no fogging is observed and high quality images can be obtained.

In addition, in the present invention, 50% diameter D5 of 1 weight average particle diameter
It is preferable to use a carrier in which o satisfies the range of 70 μm to 120 μm, and the removal of carriers with a particle size of 250 mesh or less and the raising of the particle size based thereon are as follows:
It also has the effect of reducing the torque of the photoreceptor drum and the drum circumferential friction force.

The saturation magnetization of the magnetic carrier is 50 to 70 etxu/g
It is desirable to meet the following range. Furthermore, when 200V is applied to the carrier used in the present invention, the current value is 0.
．． 5 to 5μA, especially 0. It is desirable that the carrier satisfies the range of 5 to 2 μA, and the flow rate of the carrier is 15 to 35 μA.
sec150g, especially 2o to 33 sec150g
It is desirable to meet the following range.

Specifically, as a ferrite, 1, for example, iron zinc oxide (Zn
Fe204), iron yttrium oxide (Y3Fe5O12
), iron cadmium oxide (CdFe204), iron gadolinium oxide (CdFe20,2), iron oxide complex (PbFe
l 2o19), iron nickel oxide (NiFe204),
Neodymium iron oxide (NdFe03), barium iron oxide (
BaFe120. g), magnesium iron oxide (MgFe
Sintered ferrite particles with a composition consisting of one or more of iron manganese oxide (MnFe204), lanthanum iron oxide (LaFeOs), etc. are used, and in particular Cu, Zn, MW, Mn, and A soft ferrite containing at least one, preferably two or more metal components ψ selected from the group consisting of Ni, such as copper-zinc-magnesium ferrite, is used.

As the coating resin, one or more of silicone resin, fluororesin, acrylic resin, styrene resin, styrene-acrylic resin, olefin resin, ketone resin, phenol resin, xylene resin, diallyl phthalate resin, etc. can be used. can be used. Among these resins, straight silicone resins, ie, silicone resins made of organopolysiloxanes such as dimethylpolysiloxane, diphenylsiloxane, and methylphenylpolysiloxane, and having a network structure are most preferred. Reticulation (crosslinking) of silicone resin involves the presence of hydrolyzable functional groups such as trimethoxy groups or functional groups such as silanol groups in organopolysiloxane units, and if necessary, after hydrolysis treatment, a silanol condensation catalyst is added. It is done by making it act. The amount of resin coating is generally 0.5 to 3 parts by weight, particularly 0.8 parts by weight per 100 parts by weight of ferrite.
A range of 1.5 parts by weight is desirable.

The toner used in the present invention is one in which a colorant and a charge control agent, or a toner compounding agent known per se, is blended into a fixing resin medium.

First, as the fixing resin medium, styrene resin, acrylic resin, or styrene-acrylic copolymer resin is generally used. Examples of the styrene-based polymer include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, and vinylnaphthalene. Among these, styrene is preferred.

On the other hand, examples of the acrylic monomer include ethyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, acrylic acid, and methacrylic acid. In addition to those mentioned above, ethylenically unsaturated carboxylic acids and their anhydrides, such as maleic anhydride, fumaric acid, maleic acid, crotonic acid, and itaconic acid, can also be used.

Styrene-acrylic copolymer resin is one of the suitable resin media, and the styrene monomer (A) and acrylic monomer (B) have a ratio of A:B=50:50 to 90. : 10, special! , :60:40 to 85:15. Further, it is preferable that the resin used generally has an acid value of 0 to 25. Further, from the viewpoint of fixing properties, it is preferable that the toner has a glass transition temperature (Tg) of 50 to 65°C.

As the coloring agent to be contained in the resin, the following inorganic or organic pigments, dyes, etc. may be used alone or in combination of two or more. Carbon black such as furnace black and channel black: Iron black such as triiron tetroxide Titanium dioxide such as nil-chile type or anatase type: Phthalocyanine blue: Phthalocyanine green: Cadmium yellow:
Molybrene Orange: Pyrazolone Red: Fast Violet B, etc.

As the charge control agent, any charge control agent known per se, for example, oil-soluble dyes such as nigrosine base (CI 50415), oil black (CI 26150), spirone black, naphthenic acid metal salts, fatty acids and soaps,
Resin acid soap etc. are used.

The particle size of the toner particles is 8 to 14 μm on a volume basis, especially 10 μm as measured by a Coulter counter.
The particle size is preferably in the range of 12 μm to 12 μm, and the particle shape may be amorphous produced by melt-kneading and pulverizing, or spherical produced by dispersion or suspension polymerization.

The L1 upper developer usually contains the above-mentioned magnetic carrier and toner in a ratio of 99:
It is desirable to mix and use them at a weight ratio of 1 to 90:10, particularly 98:2 to 95:5.

Further, it is desirable that the initial charge amount of the developer satisfies the range of 5 to 25 μc/z, particularly 10 to 20 pc7g, as measured by a blow-off method. The apparent specific gravity of the developer is 1
．． 7 to 2. 1 g/cm3, especially 1.8 to 2.
Those satisfying the range of 0 g/am3 are preferred for the purposes of the present invention.

The developer of the present invention is used at a bias potential of 250 V or more, and the image carrier and the developer carrier may be of a flat type or a drum type as shown in FIG.
Any bias potential may be used as long as the bias potential satisfies the above range.

A developer with a bias potential of 250 V, especially 280 V or more provides high quality images with less fog, and a developer that takes into account the above carrier requirements does not cause carrier pull. Furthermore, due to the increase in bias potential, the developer of the present invention is desirably used under conditions where the development potential difference is 500V or less, particularly 480V or less. In such low potential development,
Furthermore, it is desirable to shorten the Dos width than before, and D
The o-s width is 1. Less than 2mm, especially 1. It is desirable to make it less than 0 mm. Also, depending on the reduction tJs of DD-8, the ear cutting width can be set to 0, 5 to 1. 3mm, especially 0. 7
to 0. It is desirable to provide it within a range of 9 mm.

As the photoreceptor, photoreceptors used in conventional electrophotography methods, such as selenium photoreceptors, amorphous silicon photoreceptors, zinc oxide photoreceptors, cadmium selenide photoreceptors, cadmium sulfide photoreceptors, etc., can be used. However, if these are used in the Dn-a width as described above, development with excellent gradation and image density can be provided.

Furthermore, in the present invention, it is preferable to use the developer in a positively charged photoreceptor (OPC), since a positively charged photoreceptor mainly contains a charge generating material and a charge transporting material mixed in one layer. Electrons and holes move inside, and one of them becomes a trap, and the residual potential tends to increase. Such a photoreceptor with a high residual potential must be used at a bias potential of at least 250 V or more, and in some cases, 280 V or more. The developer of the present invention provides excellent images even at such bias potential and does not cause carrier attraction.

As a specific positively charged photoreceptor, a photoreceptor combining a well-known charge generating material and a charge transporting material can be used.
In particular, organic photoreceptors such as those disclosed in Japanese Patent Application No. 62-27158, which were previously proposed, are desirable.

(Effects of the Invention) According to the present invention, the developer is heated under specific conditions, and particles having a particle size of 250 mesh or less in the particle size distribution of the carrier are made to have a particle size of 8% by weight or less. The agent does not cause carrier attraction and can provide high-quality images with little fog. Furthermore, the developer is not affected by adverse environments in which low-charge toner and the like are likely to be generated, making it possible to speed up the development operation.

In addition, the developer of the present invention tends to be frequently used recently,
It can be sufficiently applied as a developer for OPC used under high bias potential.

(Example) Examples and comparative examples are shown below. Note that the present invention is not limited to the scope of the embodiments.

The components of the developer and the developing conditions were set as shown below.

The Hirooka magnetic carrier used was an acrylic resin-coated ferrite carrier, and its basic characteristics are shown in Table 1.

Toner is styrene acrylic resin, carbon black,
Others were used as raw materials. The particle size is 10 to 14 μm.

The developer was a mixture of toner and carrier at a weight ratio of 4.5:95.5, and its basic characteristics are shown in Table 1.

Table 1 shows the width of 1 raw green soybean, the period of ear cutting, the developing potential difference, the bias potential, and the photoreceptor.

Table 1 shows the results of development (carrier extraction 1 image density) using the developer of the above conditions and components.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the developing mechanism, and FIG. 2 is a characteristic diagram showing the relationship between bias potential and carrier attraction.

Claims (2)

[Claims] (1) A developer used in a developing mechanism where a bias potential of 250 V or more is applied, and the particle size distribution of the carrier of the developer contains 8% by weight or less of particles having a particle size of 250 mesh or less. A developer characterized by: (2) The developer according to claim 1, wherein the image carrier is a positively charged organic photoreceptor.