JPS6371862A - Developer composition - Google Patents

Abstract

PURPOSE:To prevent a carrier from attaching to a background, to extend the life of a developer, and to obtain stable copies by attaching carbon black particles to the surface of the toner particles. CONSTITUTION:The developer is obtained by mixing the carrier particles having an average particle diameter of 20-50mum prepared by dispersing a fine magnetic powder into a binder resin, with the toner particles having an average particle diameter of 5-20mum prepared by dispersing a colorant into a binder resin, and attaching the carbon black particles to the surface of the toner particles, thus permitting the carrier to be prevented from attaching to a fixed image and the background part of a photoconductive layer by using this developer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dry developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, it relates to a new two-component developer.

BACKGROUND OF THE INVENTION As developing methods currently used in copying machines, the cascade developing method and the magnetic brush developing method are well known. In the magnetic brush development method that is currently widely used, the average particle size of carriers is 60 μm to 200 μm.
iron powder or ferrite, etc., with an average particle size of 10 μm ~/
! A 92-component developer is used by mixing non-magnetic particles (toner) of fpyn. The toner is held on the surface of the carrier particles by frictional charging with the carrier, and is carried along with the carrier to the surface of the photoreceptor by the magnetic force of the magnetic roll, where the toner is developed in accordance with the electrostatic latent image on the photoreceptor.

This toner image is then transferred and fixed onto a support such as paper to produce a copy.

The so-called conductive carrier, which uses iron powder or ferrite as a carrier without being coated with resin, comes close to the photoreceptor during development and acts as a developing electrode, resulting in good gradation and wide solid black areas. Copies that are uniform in area can be obtained.

However, the disadvantage is that the life of the developer is short.

Recently, an attempt has been made to use particles as a carrier in which magnetic powder is dispersed in a binder resin and whose particle size is approximately equal to that of the toner, mixed with the toner, and used as a developer for a magnetic brush.

The special feature of this developer is that it can uniformly develop a large black area over a wide area, and can produce copies with excellent gradation and without fine lines or wrinkles. Further, since the weight of the carrier can be reduced due to the difference in specific gravity between the resin and the iron powder, deterioration of the developer due to collision between the carrier and toner can be alleviated, and the life of the developer can be extended.

However, it has been found that when development is carried out using such a carrier whose particle size is approximately equal to that of the toner, there is a drawback that the carrier adheres to the background portion of the latent image. This does not occur with conventional large-particle carriers, but because the carrier particles are made smaller, the magnetic force held by the carrier becomes weaker, so the electrostatic attraction between the photoreceptor and the carrier holds the carrier on the sleeve of the developing machine. It is thought that the stronger the magnetic attraction, the more likely it is to stick to the background.

Furthermore, if such adhesion occurs, not only the toner but also the carrier will be transferred at the same time, resulting in a copy with high background density and stains. Furthermore, even if the resistance of the carrier is increased as a means for preventing transfer of the carrier, this phenomenon cannot be prevented.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate such drawbacks, and it is an object of the present invention to provide a dry type developer in which the carrier does not adhere to the background area.

Another object of the present invention is to provide a dry developer with a long life.

Still another object of the present invention is to provide a dry developer that produces stable copies over a wide range of toner concentrations.

Another object of the present invention is to provide a dry developer which has excellent gradation and can produce high quality copies.

Structure of the present invention The present invention involves dispersing magnetic fine powder in a binder resin and dispersing the powder with an average particle size of 2.
Carrier particles having a particle size of 0 μm to 50 μm and a colorant dispersed in a binder resin have an average particle size of 3 to 50 μm. 2
A dry developer containing toner particles having a particle diameter of 0 μm is characterized in that carnon black particles are attached to the surface of the toner particles.

Structure and effects of the present invention (1) Chiaria (a) The binder resin used in the binder resin carrier is polystyrene,
? Reacrylate, Primethacrylate, -Reacrylonitrile, -Reether, Polyvinyl chloride,
In addition to thermoplastic resins such as thermoplastic 4-lyesters, homopolymers of vinyl resins, copolymer resins that combine one or more of these monomers, or mixtures thereof, polyurethane resins, modified acrylic resins, phenolic resins, and polymers. Other resins such as resins and area resins can also be used.

The number average molecular weight of the binder resin is /0.00
0~70.000! The average molecular weight is ko,ooo~/
! 0.000 is preferred. If the molecular weight is too small, the binder resin becomes brittle and the carrier is easily crushed, while if the molecular weight is too large, production becomes difficult.

(b) Magnetic Fine Powder The magnetic fine powder used in the carrier particles includes any material exhibiting magnetism.

Examples include metals such as iron, nickel, and cobalt, metal oxides, and alloys. As a material often used,
Triiron tetroxide, iron sesquioxide, cobalt-added iron oxide,
There are ferrite, nickel fine powder, etc. The amount of magnetic fine powder is based on the total amount of carrier particles! θ~tOi weight is preferable, and 60~tOi weight is more preferable.If the amount of magnetic fine powder is SO118% or less, the magnetic force held by the carrier is weak, so the magnetic attraction toward the developing roll is weakened, and the carrier is more likely to be developed in the background.

Moreover, if the amount of the magnetic fine powder exceeds 0x, 0x, or more, the binding force between the binder resins becomes weak and the carrier becomes brittle and easily destroyed, which is particularly preferable.

The particle size of the magnetic fine powder is preferably about 0.02 to 0 μm, more preferably about 0.02 to 0 μm.The shape of the magnetic fine powder is not particularly limited, and may be granular or acicular magnetic. Any of the fine powders may be used, and furthermore, a predetermined amount of magnetic fine powders of different shapes may be mixed for use. When acicular magnetic fine powder is used, the carrier moves more rapidly on the developer sleeve and the carrier layer on the developer sleeve becomes thicker than when only granular magnetic fine powder is used. .

(e) Conductivity modifier, charge control agent The Φ spear 7 particles may contain a conductivity modifier or charge control agent as a component other than the above. Known conductivity regulators can be used, including conductive powders such as carbon black, aluminium powder, and silver powder.

Further, the magnetic fine powder can also play a role as a conductivity modifier. The amount of the conductivity modifier in the carrier composition varies depending on the type and amount of magnetic fine powder contained in the carrier.

The carrier used in the present invention has an applied voltage of so or oo.

Electrical resistivity at k-/o 10Ω ~ 1O16
The amount of the conductivity modifier is preferably determined so that the electrical resistivity of the carrier falls within the above-mentioned range. When the electrical resistivity of the carrier is 70 Ω1 or less,
Charge is injected into the carrier, making it easier to develop an electrostatic latent image or background area on the photoreceptor.

As a result, the amount of carrier consumed increases or the background area of the copy is undesirably smeared.If the electrical resistivity of the carrier exceeds 10Ω, solid black areas will not be developed uniformly and the quality of the copy will deteriorate. do.

Known charge control agents can be used, including nigrosine dyes, quaternary ammonium salts, and basic dyes (
(methylene violet, Victoria Del., etc.), phthalocyanine and other systems, or dyes containing transition metals such as chromium.

(d) Carrier The average particle diameter of the carrier is preferably in the range of 0 to 30 μm, and more preferably in the range of -0 to 0 μm. As the average particle size decreases, the magnetic attraction that the carrier particles experience from the magnetic roll decreases. When the average particle size of the carrier becomes 20 μm or less, the force of holding the carrier on the sleeve of the existing machine due to the above-mentioned magnetic attraction becomes inferior to the electrostatic attraction that acts on the photoreceptor and the carrier particles, causing the carrier to stick to the photoreceptor. It becomes easier to develop. Furthermore, if the particle size of the carrier becomes smaller, the fluidity of the carrier deteriorates, and the flowability of the developer in the developing machine deteriorates, resulting in insufficient blending of the voice image agent or uneven toner concentration, which is undesirable. When the average particle size is 50 μm or more, there is no difference in particle size from conventionally used carrier particles such as iron powder, so the superiority in fine line reproducibility and resolution achieved by reducing the particle size of the carrier is lost.

(e) Manufacturing method of carrier The method of manufacturing the carrier is not particularly limited, and may be performed using a kneading-pulverization method, a spray drying method, suspension polymerization, or emulsion polymerization.
'hffi graft polymerization method is a typical manufacturing method. It is desirable to minimize the generation of small particle size carriers during carrier production. When a pulverization method is required in the manufacturing process, it is preferable to use a pulverization method that generates a small amount of fine powder, and in this respect, a mechanical pulverization method is more preferable than a jet pulverization method.

In addition, if fine carrier particles of 70 μm or less, free magnetic fine powder, carbon black, etc. are generated during carrier production, they are classified and removed, and the weight percentage containing particles of 10 μm or less is preferably less than IO, preferably less than Kuchi. If these fine powders or fine carriers are present, toner may be charged to the same polarity as the photoconductor, or the toner may be insufficiently charged, or the carrier may adhere to the background, resulting in deterioration of image quality or the inside of the device. cause contamination.

(1) Toner The toner used in the present invention is a non-magnetic particle having an average particle size of 3 μm to 10 μm, in which a colorant is dispersed in a binder resin.

(a) Binder resin used in toner Binder resins include vinyl resins such as polystyrene, I-lyethylene, deli-detetrapyrene, and polyWPa vinyl;
Polyacrylate, polymethacrylate, polyacrylonitrile, I-reather, thermoplastic polyester, polyvinyl chloride, cellulose resin, polycargonate, and copolymerized, grafted and crosslinked resins of their monomers are used. Furthermore, depending on the purpose, these resins can be used not only as a single type but also as a mixture of more than one type. Pressure fixable toners using so-called pressure-sensitive deformable materials as part of the binder resin, such as adhesive materials such as ionomer isothermally crosslinked polymers, block copolymers, etc., can also be used in the lid of the present invention.

The glass transition temperature T'gs or molecular properties of the binder resin of the toner used in the present invention differs depending on the purpose and cannot be specified in part.

6) Colorant Any suitable pigment or dye can be used as a colorant in the toner of the present invention, preferably in an amount sufficient to color the binder resin, generally up to 13% by weight of the toner, preferably /-
It is used in an amount of 20% by weight. For example, Kagen Deluxe, Nigrosine dye, Aniline Blue, Alcoyl Del-1 Chrome Yellow, Tarte 2 Marin Del-1 DuPont Oil Red, Quinoline Yellow, Methylene Blue, Lid'Cyanine Blue, I-Rachite Green,
Examples include lamp black, rose bengal, and dyes containing transition metals such as copper or chromium.

(c) Toka: The average particle size of the toner of the present invention should be S to -0, preferably 7 to 1 μm. When the average particle size of the toner is 5 μm or less, even if an external additive is added to improve the fluidity, the fluidity of the toner is insufficient and the toner cannot be sufficiently dispensed into the developing machine. Furthermore, it is undesirable that the fluidity of the toner is poor and that the developer is insufficiently mixed within the developing machine. Furthermore, if the average particle diameter of the toner is 20 μm or more, the resolution is reduced and the roughness of the image becomes noticeable, making it impossible to obtain good copies.

((Production method of toner) The method of producing the toner of the present invention is not particularly limited. A kneading-pulverization method, a Sugere dry method, and a direct polymerization method using suspension polymerization or emulsion polymerization are known as representative production methods. However, any manufacturing method can be used.

In addition, during toner production, fine powder toner of 7 μm or less and free Kagen! If rack, magnetic fine powder, etc. are generated, it is recommended to classify them. The presence of these fine powders and fine toner particles causes deterioration of image quality and contamination of the inside of the apparatus. Furthermore, cleaning the photoconductor surface is extremely inconvenient. Therefore, it is desirable to remove fine powder toner of 7 μm or less, preferably 5 μm or less, free Kazen black, magnetic powder, etc., by a classification operation or the like.

01D Carbon Black (a) Adhering Cargen Black Particles The toner according to the present invention contains casen black as a toner component.

Is this a car in the toner particles? When mixed with carbon black, carbon black is attached to the surface of the toner particles. Usually, carbon black is used as a coloring agent mixed in the toner, and when the toner is charged, this carbon black is released and mixed.

However, in the present invention, the object of the present invention can be achieved by actively containing and using carbon black in an amount greater than the amount of free carbon black. The amount of carbon black is 0.3 g/kg by weight based on the toner.
pc%, preferably 0-'I N#% to o, Rijyu Takachi. Carbon black ffs having a primary particle size of 0.03 μm or less can be used without any particular problem. In order to uniformly disperse carbon black on the toner surface, powdery carbon black is more preferable than granulated carbon black, which is granulated during carbon black production.

In praise of free carbon black, o, ooi precious chi~
The carbon black content of the present invention is 7 to 2 orders of magnitude larger than that.

(b) Attachment method A known method can be used to attach carbon black to the surface. Cars using well-known mixers such as T-type mixers and rotary vane mixers? 71 racks can be attached.

OV) 3J agent The toner and carrier according to the present invention are mixed and used as a developer. The toner and carrier to be combined are selected in consideration of the amount of triboelectric charge caused by mutual particles. If the amount of charge on the toner is small, the toner scatters violently and the copying machine is likely to be contaminated. Also, the background part of the copy is likely to get dirty.
On the other hand, if the amount of charge is too high and the amount of charge is too high, the developing density will be insufficient. Furthermore, as the amount of charge on the toner increases, the amount of charge held by the carrier also increases, so the carrier is developed in the background area, a large amount of carrier in the developer is consumed, and the developed carrier is further transferred to the background area, making it difficult to copy. This will stain the background of the object. Therefore, the amount of charge of the toner is 3 to 3 at 10%, assuming that the toner is 7tlily to the developer.
/! μC/g is preferably 3~2 μC/9 is 4 tons. The amount of charge on the toner depends on the difference between the photoreceptor and the developing bias! Qθ
In the case of V, it is calculated from the weight of the toner developed on the photoreceptor and the amount of charge held by this toner. When the toner charge amount is 3 μC/g or less, toner scattering and background staining are likely to occur as described above. If the amount exceeds 15 μc and 7 g, the image density tends to be insufficient and a phenomenon occurs in which the carrier is developed in the background area.

The resin used for the carrier particles and toner particles must be selected so that the toner charge amount falls within the above range. That is, the resin used for the toner and carrier particles is not the above-mentioned binding resin, but the toner band 1! The amount is selected to be in the range 3 μC/i to 15 μC/g. Things that affect the chargeability of toner particles include not only the crystalline XI resin used in the toner and carrier, but also conductivity modifiers such as magnetic powder and carno black, as well as charge control agents. Since the band shape of the particles varies greatly depending on the composition of the binder resin and other additives in the toner and carrier particles, the preferred combination of the binder resin used in the toner and carrier particles changes depending on the composition ratio of other compositions. do.

The electrification series of the binder resin can be used as a guideline for selecting the binder resin used to maintain a preferable amount of charge on the toner particles. - For example, when a polyester resin is selected as the binder resin of the toner (or carrier), a resin containing an amine group or imide group with relatively strong normal conductivity is used as the main binder resin of the carrier (or toner). If used, the amount of charge on the toner increases, which is preferable. However, as described above, the electrification series of the resin alone cannot be used as a criterion for selecting a carrier or a binder resin for toner.

The developer of the present invention is used as a dry developer in electrophotography. The developer according to the present invention can be used in a magnetic brush developing device of the sleeve rotating type, the so-called magnetic roller rotating type in which the sleeve is fixed and the magnet inside the Uleap rotates, or the sleeve and magnetic roll both rotating type.

The non-magnetic toner is transported by magnetic particles functioning as a carrier to the electrostatic latent flaw development position using one of the above developing machines, and there the non-magnetic toner is moved onto the photoconductor by electrostatic adsorption or the like. to develop the electrostatic latent image on the photoconductor, and then transfer and fix the toner image to transfer paper using a corona charger. When the developer according to the present invention is used, carrier adhesion is not observed in the fixing area or in the background area on the photoconductor, as is the case with conventional methods.

As described above, the developer using toner to which carbon black is attached according to the present invention does not cause problems when the carrier adheres to the background area, compared to the developer using toner to which carbon black is not attached. Although the details of this reason are unknown, it is thought that a part of the specific charge generated on the carrier is discharged with the help of carbine black on the surface of the toner, and the amount of charge on the carrier is appropriately controlled. If the amount of carbine black is less than O0J ft%, it is not possible to completely prevent the carrier from adhering to the background part, and if the amount of carbon black is more than 100% by weight, carbine black will be loosely scattered, damaging the copying machine or the copied material. Undesirable phenomena such as contamination occur.

In addition to carbine black, external additives may be used in the toner of the present invention in order to maintain fluidity and cleanability of the toner particles.

External additives include zinc stearate, calcium stearate, previnylidene fluoride, alumina, and silicon oxide. Seven or a mixture of two or more of these are used as external additives for toner particles.

The weight percentage of toner in the developer is preferably 3 to 3]. If the toner fraction in the developer is less than 3, sufficient image density cannot be obtained.

On the other hand, if the toner fraction in the developer is greater than =S, the toner will not have a sufficient amount of charge and will stain the background area.
Toner scattering becomes severe, which is not desirable.

Examples Some examples of the present invention are shown below. Of course, the present invention is not limited to these examples.

In the text, "part" means "rim part".

Carrier reference example/triiron tetroxide (manufactured by F'da Kogyo Co., Ltd., trade name EFT-10 (1
)O) Aj part car? black (Kyaget Co., Ltd. f)
f BPL) 3 parts were melt-kneaded, cooled and pulverized to obtain magnetic fine powder.

This fine powder was classified using an air classifier to obtain fine particles of 10 μm or less, and the average particle size of the particles was 30 μm or less.
μm, this magnetic fine powder was used as a carrier.

Carrier reference example Part 3: Produced in the same manner as Carrier reference example/The fine particles were 10μ.
m or less was 5% by weight and the average particle size was 33 μm, so
This magnetic fine powder was used as a carrier.

Carrier reference example 3 Triiron tetroxide (manufactured by Toda Kogyo Co., Ltd., trade name MTA71/-06
5th car is 7 black (BPL made by Caget)
The fine particles produced in the same manner as in 3-Part Carrier Reference Example had a weight percent drop of 10 μm or less and an average particle size of 25 μm, so this magnetic fine powder was used as a carrier.

Career reference example Hiro 50th car? black (used in carrier reference example)
Three-Part Carrier The fine particles produced in the same manner as in Reference Example 1 had a triple thickness of 708 m or less and an average particle size of 2 g, so this magnetic fine powder was used as a carrier.

Carrier reference example 3 The fine powder particles classified with carrier reference example / have IOpm or less of 3! The average particle size was 77 μm at tIi amount.

These particles were used as a carrier to examine the effect of particle size.

Among the above carrier reference examples, reference examples/~da are compatible with the present invention, and reference fJ& is not compatible with the present invention.

Toner reference example/Graft copolymer with polypropylene (pp) as the trunk and styrene-n-butyl methacrylate copolymer as branches (
A; 2/30//l'') A j part and styrene-n-butyl methacrylate crosslinked copolymer (70/30) 2
! Mixing part r and IO part of Cargon Black, melting and kneading,
It was pulverized to obtain fine particles with an average particle size of 13 μm. The fine particles were mixed with 0.23-1 CA% of calcium stearate and 0.73% by weight of silicon oxide using a V-type blender to prepare a toner.

Toner reference example Cotner reference example / To the fine particles obtained in Toner Reference Example / before adding external additives with an average particle diameter of 3 μm, an amount of Cargen Black (Mokik 1ioo manufactured by Kyaget Co., Ltd.) was mixed with a V-type delander to form a toner. .

Toner Reference Example 3 Graft copolymer (!, 2/
3v10) 43 m g) +-Reference example/Te 23 parts of the used crosslinked copolymer and 70 parts of cargoon black were mixed, melt-kneaded, and pulverized to produce an average particle size of 3.61 Jj.
n fine particles were obtained. This was used as a toner.

Toner Reference Example Average particle diameter obtained in Hirotoner Reference Example 3/3. ! Car for 1Mn particle? hmm! Rack (Mokiku made by Kyaget Co., Ltd./
300) 0. ．． 3% by weight and polyvinylidene fluoride θ
, Daju Notification: q6 was mixed in a V-type blender to make a toner.

Toner Reference Example 3 90 parts of Prioride ACL (manufactured by Gutdeyer Chemical Co., Ltd., styrene/acrylic acid ester copolymer) and 90 parts of Caden Black IO were melt-kneaded, cooled and solidified, and then pulverized to obtain an average particle size of //, Sμm. Fine particles were obtained. To this, Karne Black (Mokarkza 00 manufactured by Cabot Corporation) was mixed with 0.3% by weight of zinc stearate in a V-type blender to obtain a toner.

Among the above toner reference examples, those that are compatible with the present invention are:
Reference example Ko, da toner, reference example /.

3.3 is not compatible with the present invention.

'#, Examples and comparative examples

Claims (1)

[Claims] Magnetic fine powder is dispersed in a binder resin to obtain an average particle size of 20 μm to 5 μm.
Carbon black particles were attached to the surface of the toner particles in a dry developer in which carrier particles having a diameter of 0 μm were mixed with toner particles having an average particle size of 5 μm to 20 μm by dispersing a colorant in a binder resin. A dry type developer characterized by: