JPH0227365A - Carrier for photographic developer - Google Patents

Abstract

PURPOSE:To stabilize the triboelectrostatic charge characteristics of the carrier for a copying developer and to prolong the service life thereof by coating the core material of the carrier with a specific 1st polymer, a 2nd polymer to be adhered to the core material and a specific additive. CONSTITUTION:The carrier core material may be magnetic metals such as iron and nickel or the alloys thereof, or the bonded matter of an oxide or nonmagnetic material. A fluoropolymer such as polyvinylidene fluoride is used as the 1st polymer and copolymer of styrene and methyl methacrylate, etc., having the good mechanical characteristics and adhesive strength to the carrier core material are preferable as the 2nd polymer. A release property is maintained without exerting adverse influence to the film formability and the triboelectrostatic charge control of the toner by incorporating the metallic salt of stearic acid such as zinc stearate as an additive at 0.01-40wt.% into the coating material. The weight of the coating material with respect to the core material is preferably 0.05-20wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a carrier for an electrophotographic developer, that is, a carrier that constitutes an electrophotographic developer together with a toner.

[Prior Art] Conventionally, electrophotography has been described in U.S. Patent No. 22!378.
No. 91, Special Publication No. 1972-23910, Special Publication No. 43-
As described in Japanese Patent No. 24748, etc., electrostatic charges are applied to the photoconductive layer in a negative manner by corona discharge, and a light image corresponding to the original is exposed to the photoconductive layer, thereby eliminating the charges in the exposed areas and forming a latent image. Perform formation.

Development is carried out by depositing a fine powder electrostatic substance, so-called toner, on the obtained electrostatic latent image.

The toner is attracted to the electrostatic latent image depending on the amount of charge on the photoconductive layer, forming a toner image with shading. This toner image is transferred to a support surface such as paper or cloth as required, and permanently fixed on the support surface using a suitable fixing means such as heating, pressure, solvent treatment, or overcoating. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed onto the photoconductive layer.

In developing the electrostatic latent image, the toner is mixed with carrier having relatively large particles and used as an electrophotographic developer. The compositions of both the toner and the carrier are chosen such that, due to their mutual contact friction, the toner assumes a polarity opposite to the charge on the photoconductive layer. Further, as a result of the contact friction between the two, the carrier electrostatically adheres the toner to the surface, transports it as a developer through the developing device, and also supplies the toner onto the photoconductive layer.

There are many known methods for developing a developer. Cascade development method described in US Pat. No. 2,818,552, US Pat. No. 28,740 [(Magnetic brush method described in No. 3, US Pat.
There are the touchdown method described in No. 95847, and the fur brush development method. Particularly typical developing methods are known as the cascade method and the magnetic brush method. In the cascade method, non-magnetic particles such as glass peas are used, and fine powder toner is attached to the surface to form a developer. When this developer cascades over the surface of the photoconductive layer bearing the electrostatic latent image, the toner selectively adheres only to the band '11f portion of the electrostatic latent image and does not adhere to the uncharged portion, thereby preventing development. Let's do it.

Further, the magnetic brush method uses magnetic particles such as copper and ferrite as carriers. A developer consisting of toner and magnetic carrier is held by a magnet, and the magnetic field of the magnet arranges the developer in a brush shape. When this magnetic brush contacts the surface of the electrostatic latent image on the photoconductive layer, only toner is attracted from the brush to the electrostatic latent image to effect development. Touchdown development involves transporting the developer material to the latent image supporting surface by a support layer such as a web or sheet. ! Development is performed according to the image.

In conventional technology, single particles of glass, ferrite, copper, etc. have been used as carriers, but such carriers do not have all the required properties such as triboelectric properties and mechanical properties. Nothing satisfied me at all. For this reason, it has been proposed to use as a carrier a material whose surface is coated with a coating material. For example, JP-A-39-358H, JP-A-49-51950, JP-A-49-123.
Publication No. 037, etc.

[Problem to be Solved by the Invention 1 There are various properties that the coated carrier must satisfy, but the following points are particularly important. The first thing to consider is charging characteristics.

In other words, due to the contact friction between the toner and the carrier, the desired polarity and charge amount are imparted to the toner particles! The carrier must have surface properties such that j.

Second, in continuous copying of multiple sheets using an electrophotographic device, the carrier is used repeatedly, and during this time carrier particles interact with each other.
Alternatively, large continuous mechanical impacts such as multiple collisions between the carrier and the developing device may cause cracking, chipping, or abrasion of the carrier coating. Therefore, carrier nuclei are formed on the surface, and the efficiency of triboelectric charging between the carrier and toner phase is reduced. To prevent this, the carrier coating must have sufficient wear resistance and high adhesive strength to the carrier core. Furthermore, the coating layer of the carrier must have releasability so that the toner particles do not fuse to the carrier surface even during continuous copying of a large number of sheets.

However, with the coating methods proposed so far,
It is not fully satisfactory for use as a developer. For example, a method has been proposed in which styrene-acrylic resin is coated on the surface of the carrier core material, but although styrene-acrylic resin has high adhesive strength with the carrier core material, the surface energy is too large, and the toner can be coated with a small number of copies. The particles are fused to the surface of the carrier particles, which poses a problem in durability. In addition, carriers coated with fluorine-containing resin have low surface energy, making it difficult for toner to stick to the carrier surface, and have high mold releasability.Also, they have excellent charging properties, but the adhesive strength with the carrier core material is weak. There is a drawback that the coating layer easily peels off from the carrier core material. Furthermore, there has been a proposal to use a mixture of a styrene-acrylic resin and a fluorine-containing resin as a coating layer, but the disadvantages of poor toner fusion to the carrier surface and poor charging properties have not yet been fully resolved.

[Means and effects for solving the problems] The present invention provides a coated carrier for electrophotographic development that improves the above-mentioned drawbacks, and aims to: (4) The coating layer has strong adhesive strength to the carrier core material and is difficult to peel off even when mixed and agitated. It has good mold releasability and does not adhere to the carrier surface.

The present invention provides a coating in which the carrier core material contains a fluorine-containing polymer as a first polymer, a second polymer having strong adhesive properties to the carrier core material, and further a stearate metal salt as an additive. This is an electrophotographic developer carrier coated with a material.

Examples of metal stearates used in the present invention include barium stearate, calcium stearate, zinc stearate, aluminum stearate, magnesium stearate, zinc stearate/barium stearate complex, zinc stearate/calcium stearate complex, etc. It will be done.

These stearic acid metal salts are added to the coating material at a concentration of 0.01 to 40%.
It is preferable to contain it in an amount of 0.1 to 20% by weight (preferably 0.1 to 20% by weight).

If the ratio of the metal stearate is 40% by weight or more, it will adversely affect the film-forming properties of the coating material and the charge control of the toner. On the other hand, the proportion of stearic acid metal salt is 0.01% by weight.
If it is below, the releasability between the coating layer and the toner will be insufficient and the toner will fuse to the carrier surface, making it impossible to perform stable toner charge control.0 As an example of the fluorine-containing resin used in the present invention, Polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, halofluoropropylene such as polytrifluorochloroethylene, copolymers of vinylidene fluoride and 7-acrylic monomer, te]chloroethylene and Joint body with hexafluoropropylene,
Copolymer of vinyl fluoride and vinylidene fluoride, copolymer of vinylidene fluoride and tetrafluoroethylene, copolymer of vinylidene fluoride and ehesafluoropropylene, tetrafluoroethylene and vinylidene fluoride, and non-fluorine Fluoro terpolymers such as terpolymers of chemical monomers are preferred.

On the other hand, a second poly having adhesive properties to the core material of the carrier may be used, for example, a copolymer of styrene and methyl methacrylate, a terpolymer of styrene, methyl methacrylate and an organosilane, 14-soluble acrylic, methyl methacrylate and Methacrylic acid copolymer, styrene and methacrylic acid copolymer, polymethacrylonitrile and its copolymer, acrylonitrile copolymer, copolymer containing methacrylic acid and its salts
Polysulfone, polycarbonate, polyester, polyamide, etc. are preferred. In particular, the second polymer is preferably a styrene-acrylic copolymer in view of good mechanical properties and adhesion to carrier core materials such as metals, metal oxides, and ferrite.

In the present invention, the coating amount of the L fertilizer solution covering material on the core material is 0.05 to 20 tonne%, especially 0.1 to 10% by weight, based on the carrier core material.
Weight percent is preferred.

In addition, the content of fluorine-containing polymer in the coating material is 20 to 80
Weight: preferably j-%. Considering the adhesion with the carrier core material, the strength of the coating layer, and the toner fusion to the coating layer, the content of fluorine-containing polymer in the coating material j,) is 80
If it is more than 20% by weight, the adhesion and strength of the coating layer will be somewhat insufficient, and if it is less than 20% by weight, the toner fusion to the coating layer and charging properties will be poor.

As the material of the carrier core material used in the present invention, for example, surface-oxidized or unoxidized metals such as iron, nickel, cobalt, manganese, chromium, rare earths, and their alloys or oxides can be used.

Moreover, there are no special restrictions on the manufacturing method.

Carrier particles generally have an average particle size of 30 to 2004 tm.
, preferably 40-100μ layer, 0 particle size is 30#L
If it is smaller than m, the carrier is likely to be developed on the latent image holder, and the PPi image holder and the cleaning blade are likely to be damaged. On the other hand, if the particle size is larger than 200 IL layer, the toner retention ability of the carrier will be reduced, resulting in uneven solid images, toner scattering, and fogging. The carrier core material may be made of only a magnetic material or may be a combination of a magnetic material and a non-magnetic material.

The method for manufacturing the coated carrier in the present invention involves dissolving and dispersing the coating resin and the stearate metal salt in an organic solvent to prepare a coating solution, mixing this with the carrier core material, and then using a rotary drying method or a fluid flow method. The carrier core material is coated with a resin containing a metal stearate by drying using a bed coater method.

The organic solvent used in the above manufacturing method may be any solvent as long as it dissolves the coating resin used in the present invention, such as acetone, methyl ethyl ketone, toluene,
A solvent such as xylene, tetrahydrofuran, dioxane, or a mixture thereof is used.

On the other hand, as the binder resin of the toner used in the present invention,
Monopolymers of styrene and its substituted products such as polystyrene, poly p-chlorostyrene, polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, Styrene-ethyl methacrylate copolymer, styrene-methacrylic butyl copolymer, styrene-acrylic-aminoacrylic copolymer, styrene-
Aminoacrylic copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer Styrenic copolymers such as styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; methyl methacrylate,
Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic resin Hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes, etc. can be used alone or in combination.

In the toner, any suitable pigment or dye can be used as a colorant. Examples include known dyes and pigments such as carbon black, iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow.

In addition, amine compounds, quaternary ammonium compounds, and organic dyes, especially basic dyes and their salts, as charge control agents.
Benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin γ and crystal violet may be added.

[Example] Next, the present invention will be described in detail with reference to Examples. All parts in the following formulations are parts by weight.

Example 1 60 g of polyvinylidene fluoride, 60 g of styrene-methyl methacrylate (70:30) copolymer, and 15 g of 4F lead stearate were each dissolved in 5 volumes of acetone-methyl ethyl ketone (mixing ratio 1:1) mixed solvent. Next, 10 kg of ferrite particles with an average particle size of 60 gm were coated with this coating liquid using a fluidization bed device to obtain a coated carrier of the present invention, and fine particles with an average particle size of 11 uL consisting of 0.8 part of colloidal silica was added to 100 parts to prepare a toner.

The coated carrier thus formed and the toner were mixed at 92°C.
:8 to 1lfU to prepare a developer.

When this developer was copied using an MP-5040 (Canon copier) in a constant temperature and humidity (23.0°C, 60% RH) environment, an image with excellent clarity and gradation was obtained. Obtained. Moreover, even after 100,000 copies were continuously made, the images remained as good as the initial ones.

By the way, there is almost no change in the amount of electrostatic charge of the toner in the developer by the blow-off method at the initial stage of copying and after 10,000 copies have been made. It was 2.1 c/g and 1007 pots c/g.

Further, the coated carrier was stirred in a ball mill for 80 hours, and the coating layer of the carrier before and after stirring was extracted and the change in weight was measured. As a result, almost no peeling of the coating material was observed. Further, in observation using an electron microscope (manufactured by Hitachi, Ltd., 5-aoo), almost no change in the surface of the carrier was observed before and after stirring in a ball mill.

Furthermore, when the toner was separated from the developer at the initial stage and after copying 100,000 copies using air, and the surface of the carrier coating was observed using an electron microscope, almost no toner fused substances were observed in either case.

On the other hand, when we performed the same double extraction in harsh environments of high temperature and high humidity (32°5°C, 80% R) and low temperature and low humidity (10°C, 10% RH), good images were obtained in both cases. The amount of electrostatic charge on the toner was also almost unchanged from that under constant temperature and humidity conditions.

Comparative Example 1 Image printing was carried out in the same manner as in Example 1 except that zinc stearate was removed from the carrier coating material of Example 1. From the initial stage to nearly 50,000 sheets, gradation with excellent clarity was obtained. A certain image was obtained, but after continuous copying up to 100,000 sheets, ground blurring and toner scattering occurred, although this was not at a level that would pose a practical problem.

By the way, the amount of electrostatic charge of the toner in the developer by the blow-off method at the initial stage of copying and after copying 100,000 sheets is 11.9 pots q/
g to 7.0 #Lc/g.

Furthermore, when the carrier-coated surface after continuous copying of 100,000 copies was observed using an electronic S microscope, a small amount of toner fusion was observed in some areas.

Example 2 Polyvinylidene fluoride-tetrafluoroethylene copolymer (75:25>80 g, styrene-butyl methacrylate copolymer (80:20) sog, aluminum stearate 20 g and acetone-methyl ethyl ketone (mixing ratio t: B A coating solution was prepared by dissolving it in a mixed solvent. 10 kg of ferrite particles with an average particle size of 50 μm were coated with this coating solution using a fluidization bed device to obtain a resin-coated carrier containing aluminum stearate. .

The coated carrier thus formed and the toner used in Example 1 were mixed at a weight ratio of 90+10 to form a developer. When images were produced using this developer in the same manner as in Example 1, good images were obtained as in Example 1.

Even in continuous copying of 10,000 copies, a good image is maintained from the beginning to the end, and the amount of electrostatic charge of the toner in the developer is 12.5.
There is almost no change from pc/g to 10.9 sc/g after copying 100,000 sheets, so the interaction between the toner and the coated carrier of the present invention is the same as in the initial stage, and the carrier coating layer is not about to crack and the toner is melted. It is surmised that this normal relationship with no wear and tear is maintained even after 100,000 copies have been made.

Further, the coated carrier was stirred in a ball mill for 80 hours in the same manner as in Example 1, but almost no peeling of the coating material was observed.

Furthermore, when the toner was separated from the developer after copying 10,000 copies using air, and the carrier-coated surface was observed using an electron microscope, almost no toner fusion was observed.

On the other hand, when images were similarly produced in harsh environments of high temperature and high humidity (32.5°C, 90% RH) and low temperature and low humidity (10°C, 10% RH), good images were obtained in both cases, and the toner The amount of static charge was also almost unchanged from that under constant temperature and humidity conditions.

Example 3 In Example 1, the stearic acid metal salt was replaced with barium stearate, and the same effect as Habo was obtained.

Example 4 A toner was prepared by adding 0.6% by weight of colloidal silica to 100 parts of fine particles having an average particle size of 10 gm and consisting of 5 parts of carbon black.

Next, 10 kg of iron powder particles having an average particle size of 70 .mu.m were coated with the same coating solution as that prepared in Example 1 using a fluidizing bed apparatus to obtain a coated carrier of the present invention. The thus formed coated carrier and toner were mixed at a weight ratio of 94=6 to form a developer.

When this developer was copied using a commercially available MP-5000 (Canon Copy M) in a constant temperature and humidity environment (23.5°C, 60% RH), an image with excellent gradation was obtained. It was done.

Moreover, even after 100,000 copies were continuously made, the images remained as good as the initial ones.

By the way, the static load of toner in the developer by the blow-off method at the initial stage of copying and after 10,000 copies was almost unchanged, being -9.5 c/g and -8°4 c/g. .

On the other hand, when images were similarly produced in harsh environments of high temperature and high humidity (32.5°C, 90% RH) and low temperature and low humidity (10°C, 10% RH), good images were obtained in both cases. The amount of electrostatic charge on the toner was also almost unchanged from that under constant temperature and humidity conditions.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a carrier for an electronic copying developer that has stable triboelectric charging characteristics and has a long service life.

Claims (1)

[Claims] The core material of the carrier is coated with a coating material containing a fluorine-containing polymer as a first polymer, a second polymer having adhesive properties to the carrier core material, and further a metal stearate as an additive. A carrier for an electrophotographic developer characterized by: