JP2546564B2 - Electrophotographic carrier particles coated with a polymer mixture - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates generally to carrier compositions, and more particularly, the invention relates to electrophotographic carrier compositions coated with a polymer mixture. In one embodiment of the invention, the carrier particles are triboelectric.
It consists of a core with a coating on its surface formed from a mixture of polymers that are not close to each other. Further, in another aspect of the invention, the carrier particles are provided with a polymer mixture of some type to the carrier to provide insulating particles having a relatively constant conductivity parameter, and are marked by a coating used by the triboelectric charge on the carrier. It is prepared by a variable dry coating method. The carrier particles prepared by the dry coating method of the present invention are useful in electrostatographic imaging systems, especially electrostatographic imaging methods. In addition, the substantially insulating carrier particles prepared by the method of the present invention are useful in imaging processes where a relatively constant conductivity parameter is desired. Furthermore, in each of the above imaging methods, the triboelectric charge on the carrier particles can be preselected by the polymer composition applied on the carrier core. Prior art Electrostatographic and electrostatographic processes are well known. The method involves forming an electrostatic latent image on a photoreceptor, then developing and then transferring the image to a suitable substrate. Many different types of electrostatographic imaging processes are known, for example insulating developer particles or conductive toner compositions, depending on the development system used. Furthermore, what is important with the above developer compositions is the appropriate triboelectric charge value associated therewith. This is because these values enable continuous constant development with high quality and excellent resolution.

Further, carrier particles used in the development of electrostatic latent images are well known in many patents, eg, US Pat. No. 3,59.
No. 10,000. These carrier particles consist of various cores, including steel, on which have a coating of fluoropolymers or terpolymers with styrene, methacrylate and silane compounds. Recent efforts have been devoted to obtaining coatings for carrier particles for the purpose of improving development quality, obtaining reusable particles and not adversely affecting the imaging member in any practical way. . Many of the current commercial coatings degrade rapidly, especially when used in continuous electrostatographic processes, causing the entire coating to separate from the carrier core in chips or flakes.
It also drops off when it collides with the device members and other carrier particles and makes frictional contact. These flakes or chips generally cannot be regenerated from the developer mixture,
The triboelectric charging properties of the carrier particles are adversely affected, so that the carrier coating provides only images with low resolving power as compared to the composition retained on the core substrate surface. Moreover, another problem encountered with some prior art carrier coatings is varying triboelectric charging properties, especially due to changes in relative humidity. This variation in triboelectric charging properties results in development with poor quality background deposits.

US Pat. No. 4,233,387 also describes a coating carrier component for an electrostatographic developer mixture which comprises fine toner particles attached to the surface of the carrier particles. In particular, the U.S. patent discloses an average carrier core particle having an average diameter of about 30 microns to about 1,000 microns, and about 0.05% to about 3.0% by weight of thermoplastic resin particles based on the weight of the coated carrier particles. Disclosed are coated carrier particles obtained by mixing with. The resulting mixture is then mixed with the thermoplastic resin particles by mechanical adhesion (impactio).
n) and / or dry mix until attached to the carrier core by electrostatic adsorption. Then mix the mixture at about 320 °
The thermoplastic resin particles are melted and fused to the carrier core by heating to a temperature of F (about 160 ° C.) to about 650 ° F. (343.3 ° C.) for 20 minutes to 120 minutes. Although the developer and carrier particles prepared by the method of the U.S. patent are suitable for their intended purpose, the conductivity values of the resulting particles are in all cases not constant, for example, when the amount of carrier coating is varied. There is a change in triboelectric charging properties, and in addition, in the '387 U.S. patents, carrier and developer mixtures having only certain triboelectric charging properties were intended for certain conductivity values or properties. Sometimes obtained. According to the invention, the conductivity of the resulting carrier particles is substantially constant, and the triboelectric value depends on the polymer mixture used to carry out the coating process, for example from -15 microcoulombs / g to -70 microcoulombs. Coulomb / g
It can be selected to change significantly above.

Further with respect to the prior art, carriers obtained by applying an insulating resin coating to a porous metal carrier core using the solution coating method are in many respects undesired. For example, the coating material is usually present in the pores of the carrier core, rather than the surface of the carrier core, and thus is not useful for triboelectric charging when the coated carrier particles are mixed with finely divided toner particles. Attempts to solve this problem by increasing the carrier coating amount by as much as 3% or more resulted in the use of excess solvent,
Furthermore, these treatments usually result in poor quality products. Also, solution coated carrier particles, when combined with fine toner particles, in some cases provide triboelectric charge values that are too low in many applications. The powder coating method of the present invention overcomes these deficiencies and allows for the generation of highly useful triboelectric charge values on fine toner particles.
The carrier particles also have a substantially constant conductivity.
Moreover, when resin-coated carrier particles are prepared by the powder coating method of the present invention, the majority of the coating material can be fused to the carrier surface, thereby reducing the number of toner adhesion sites on the carrier material.
Furthermore, the method of the present invention provides the desired triboelectric charging properties and conductivity values independent of each other;
For example, the triboelectric charging parameter is such that US Pat. No. 4,233,387 states that increasing the amount of coating on the carrier particles results in increased triboelectric charging properties.
It does not rely on the amount of carrier coating as believed in the case of the method of No. Thus, the carrier compositions and methods of the present invention allow for the preparation of developers with selected triboelectric charging properties and / or conductivity values in many different combinations.

Thus, for example, according to the present invention, about 10 −6 mhos (cm) − when measured in a magnetic brush conduction cell.
A developer having a conductivity of 1 to 10-17 mho (cm) -1 and a triboelectric charge value of about -8 to -80 microcoulombs / g on carrier particles as measured by the known Faraday cage method is prepared. it can. Thus, the developers of the present invention can be prepared to have constant conductivity values and various triboelectric charging properties, for example, by maintaining the same amount of carrier particles coated and varying the polymer coating ratio. . Similarly, a developer composition having a constant triboelectric charge value and varying conductivity can be prepared by keeping the polymer ratio constant and varying the amount of coating on the carrier particles. Other patents of interest include:
U.S. Pat. No. 3,939,086 (see column 6), which teaches steel carrier beads having a polyethylene coating; U.S. Pat. No. 4,264,697; which discloses dry coating and fusion processes. , 53
No. 3,835; No. 3,658,500; No. 3,79
No. 8,167; No. 3,918,968; No. 3,92
No. 2,382; No. 4,238,558; No. 4,310
No. 611; No. 4,397,935; and No. 4,43.
There is 4,220. OBJECT OF THE INVENTION The object of the invention is to provide a carrier composition which overcomes some of the above-mentioned drawbacks.

Yet another object of the present invention is to provide carrier particles having a coating of a mixture of dissimilar polymers, ie, a mixture of polymers at different positions in a triboelectric system, for example. Yet another object of the present invention is to provide carrier particles having insulating properties consisting of a core with a coating formed from a polymer mixture. Yet another object of the present invention is to provide carrier particles comprising a core having a coating formed from a polymer mixture having a triboelectric charge value of about -10 microcoulombs / g to about -70 microcoulombs / g at the same coating amount. That is. Also,
Yet another object of the present invention is to provide a positively charged or negatively charged toner composition comprising carrier particles having a coating of a certain polymer mixture. SUMMARY OF THE INVENTION The above and other objects of the invention are achieved by providing a developer composition comprising toner particles and carrier particles prepared by a powder coating method and comprising a core having a coating comprising a polymer mixture. . More specifically, the carrier particles used are low density porous magnetic or magnetically attractable metal core carrier particles, about 0.0 based on the weight of the coated carrier particles.
5 to about 3% by weight of the polymer mixture is mixed until mechanical adhesion or electrostatic adsorption of the polymer mixture onto the carrier core occurs; the mixture of carrier core particles and polymer is, for example, from about 200 ° F. to about 550. ° F (heated to a temperature of about 93.3 ° C to about 287.8 ° C for about 10 to about 60 minutes to melt the polymer and fuse it with the carrier core particles; cool the coated carrier particles; It can be prepared by classifying the particles to the desired particle size.

In a particular embodiment of the present invention, the first
There is provided carrier particles comprising a core having a coating comprising a dry polymer component of and a second dry polymer component. Thus, the carrier composition comprises a known core material, including steel, having a dry polymer coating mixture thereon. Thereafter, the developer composition of the present invention can be formed by mixing the carrier particles with a toner composition composed of resin particles and pigment particles.
A variety of suitable solid core carrier materials can be used as long as the objects of the invention are achieved. Important characteristic core properties include the property that allows the toner particles to obtain a positive or negative charge and the property that the carrier core provides the desired fluidity in the developer reservoir within the electrostatographic imaging device. is there. Also important for the carrier core properties is that the carrier has the desired magnetic aging properties and the proper magnetic properties that enable magnetic brush formation in the magnet development process. Examples of carrier cores that can be used are iron, steel, ferrites, magnetite, nickel and mixtures thereof. The preferred carrier core is ferrite, and steel grit or sponge iron having an average particle size of about 30 microns to about 200 microns.

Examples of polymer coatings used for the carrier particles of the present invention include those that do not approximate triboelectric systems. Specific polymer mixtures used include polyvinylidene fluoride and polyethylene, polymethylmethacrylate and copolyethylene-vinyl acetate, copolyvinylidene fluoride-tetrafluoroethylene and polyethylene, polymethylmethacrylate and copolyethylene-vinyl acetate, and polymethylmethacrylate. And polyvinylidene fluoride. Other related polymer mixtures not specifically mentioned here can also be used as long as the object of the invention is achieved. Further with respect to polymer coating mixtures, the term "approximate" as used herein means that the choice of each polymer is indicated by its position in the triboelectric system.
Thus, for example, a first polymer can be selected that has a triboelectric charge value significantly lower than the second polymer. For example, the triboelectric charge of a steel carrier core with a polyvinylidene fluoride coating is about -75 microcoulombs / g. However, the same carrier but with a polyethylene coating has a triboelectric charge value of about -17 microcoulombs / g. The proportion of each polymer present in the carrier coating mixture can vary depending on the particular components used, the amount of coating and the properties desired. Generally, the polymer mixture used is from about 10 to about 90% by weight of the first polymer and from about 90 to about 1.
It contains 0% by weight of the second polymer. Preferred is about 40
To about 60% by weight of the first polymer and about 60 to about 40% by weight
Using a polymer mixture having a second polymer of In one embodiment of the invention, when a high triboelectric charging value is desired, i.e., -50 microcoulombs / g or greater, about 90% by weight of a first polymer such as polyvinylidene fluoride and 10 A weight percentage of a second polymer such as polyethylene is used. On the other hand, when a low triboelectric charging value of about −20 microcoulombs / g or less is required, about 10% by weight of the first polymer and 9% by weight of the first polymer are used.
0% by weight of the second polymer is used.

Also, in accordance with a preferred embodiment of the present invention, a 10 volt impact across a 0.1 inch (2.54 mm) gap containing carrier beads suitably held by, for example, a magnet, results in about 10-15 m.cm. -1 to about 1
Carrier particles having a relatively constant conductivity of 0-9 mho-cm-1 and triboelectric charge values of about -15 microcoulombs / g to -70 microcoulombs / g are obtained, these parameters being It depends on the coating used and the proportion of each polymer used as described above. A variety of effective and suitable means can be used to apply the polymer mixture coating to the carrier particle surface. Examples of typical means for this purpose are cascade roll mixing, or tumbling, milling, shaking mixing, electrostatic powder mass spraying, fluidized bed, electrostatic mixing of a mixture of carrier core material and each polymer. It is to combine by the disk processing method and the electrostatic curtain method. Following application of the polymer mixture, heating is disclosed to effect the flow of coating material over the carrier core surface.
The concentration of the coating material powder particles and the parameters of the heating process can be selected to allow the formation of a continuous film of coating material on the surface of the carrier core or to coat only the working surface of the carrier core. When the use surface of the metal carrier core is uncoated or exposed, the carrier particles are electrically conductive when the carrier material comprises a metal.
Conductivity can include various suitable values. However, in general, this conductivity will be about 10- when the coating coverage is in the range of about 10% to about 100% of the carrier core, as measured, for example, with a 0.1 inch magnet brush at an applied potential of 10 volts. 9 to about 10-17 mho-cm-1.

Specific examples of the fine toner resin used in the developer composition of the present invention include polyamide, epoxy, polyurethane, diolefin, vinyl resin, and polymer esterification of dicarboxylic acid and diol containing diphenol. There is a thing. Specific vinyl monomers that can be used include
Styrene; p-chlorostyrene; vinylnaphthalene; ethylene; propylene; unsaturated monoolefins such as butylene and isobutylene; vinyl chloride, vinyl bromide,
Vinyl halides such as vinyl fluoride; vinyl acetate,
Vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl alpha-chloro acrylate, methyl methacrylate. ,
Vinyl esters such as esters of monocarboxylic acids including ethyl methacrylate and butyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide; vinyl ethers including vinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether; vinyl methyl ketone, vinyl hexyl Vinyl ketones such as ketones and methyl isopropenyl ketone; vinylidene halides such as vinylidene chloride and chlorofluorovinylidene; N-vinyl indole,
There are N-vinylpyrrolidene; styrene butadiene copolymers; and mixtures thereof, or other similar materials.

One preferred toner resin is the transesterification product of a dicarboxylic acid and a diol containing a diphenol (US Pat. No. 3,590,000).
No.). Other preferred toner resins include styrene / methacrylate copolymers, styrene / butadiene copolymers, polyesters obtained by the reaction of bisphenol A with propylene oxide, and dimethyl terephthalate, 1,3-putanediol, 1,2-propanediol and There are branched polyester resins obtained by reaction with pentaerythritol. Generally, about 1 to about 5 parts by weight of toner particles are mixed with about 10 to about 300 parts by weight of carrier particles prepared according to the present invention. Many well known suitable pigments or dyes can be used as colorants for toner particles, such as carbon black, nigrosine dyes, lamp blacks, iron oxides, magnetite and mixtures thereof. The pigment, preferably carbon black, should be present in an amount sufficient to highly color the toner composition. That is, the pigment particles are present in an amount of about 3 to about 20% by weight, based on the total weight of the toner composition, although higher or lower amounts of pigment particles can be used as long as the objects of the invention are achieved.

When the pigment particles comprise a mixture of iron oxides (FeO.Fe2O3), including magnetite, a commercially available material as mapico black, the pigment particles are present in the toner composition in an amount of from about 10 to about 70 weight percent. %, Preferably present in an amount of about 20 to about 50% by weight. The resin particles are present in a sufficient and effective amount, i.e. about 90% by weight resin material is used when 10% by weight pigment such as carbon black is included. However, generally, as long as the objects of the invention are achieved, the toner composition comprises from about 85 to about 97 wt% toner resin particles and from about 3 to about 15 wt% pigment particles such as carbon black. Also within the scope of the invention is a color toner composition comprising toner resin particles, carrier particles and magenta, cyan and / or yellow particles as pigments or colorants, and mixtures thereof. More specifically, specific examples of the magenta substance that can be used as a pigment include 1,9-dimethyl-substituted quinacridone and C in the color index.
I60720, Anthraquinone shown as Dispersed Red 15, CI26 on color index
050, a diazo dye shown as CI Solvent Red 19, and the like. Cyan substances that can be used as pigments include copper tetra-4 (octaethyl sulfonamide) phthalocyanine, CI74160 for color index,
X-copper phthalocyanine pigment, shown as CI Pigment Blue, and CI 698 to Color Index
10, anthrathrene blue and the like shown as Special Blue X-2137. Specific examples of yellow pigments that can be used include diarylide yellow 3,3-dichlorobenzidine acetoacetanilide, CI 12700 in color index, monoazo pigment shown as CI solvent yellow 16, and freon yellow in color index. Nitrophenylamine sulfonamide designated as SE / GLN, C
I Despersed Yellow 33,2,5-dimethoxy-4
-Sulfoneanilide phenylazo-4'-chloro-
2,5-dimethoxyacetoacetanilide, permanent yellow FGL and the like. These pigments are generally present in amounts of about 1 to about 15% by weight based on the weight of the toner resin.

Further, for the purpose of improving the positive charging property of the developer of the present invention, and as an optional component, a charge promoting additive such as alkylpyridinium halide (see US Pat. No. 4,298,672); organic Sulfate or sulfonate compounds (see US Pat. No. 4,338,390); Distearyl dimethyl ammonium sulfate (Toner Compositions With Ammonium Sulfate Charge Enhancing Additive)
positions With Ammonium S
ulfate Charge Enhancing A
U.S. Patent Application No. 645,5.
No. 660); and other similar known charge promoting additives. These additives are usually added to the toner in an amount of about 0.
It is present in an amount of 1 to about 20% by weight. The toner compositions of the present invention can be prepared in a number of known ways, such as by melt blending the toner resin particles of the present invention and a pigment or colorant followed by mechanical milling. Other methods include those well known in the art such as spray drying, melt dispersion, dispersion polymerization and suspension polymerization. In one dispersion polymerization method, a solvent dispersion of resin particles and pigment particles is spray dried under controlled conditions to obtain the desired product.

The toner and developer compositions of this invention can also be used in electrostatic electrophotographic imaging processes involving conventional photoreceptors, such as inorganic and organic photoreceptor imaging members. Examples of imaging members are selenium, selenium alloys, and selenium or selenium alloys with additives such as halogens or dopants. In addition, organophotoreceptors can also be used, examples of which are multilayer photosensitive devices consisting of a transport layer and a photoexcitation layer (see US Pat. No. 4,265,990) and other similar multilayer photosensitive devices. There is. Examples of excitation layers include trigonal selenium, metal phthalocyanines, metal-free phthalocyanines, and vanadyl phthalocyanines. As the charge transfer layer, the aryldiamine disclosed in the above '990 US patent can be used. The photoexcited pigments include squaraine compounds and thiapyrylium substances. These multi-layered members are usually negatively charged and require positively charged toner. Other photosensitive devices useful in the present invention include polyvinylcarbazole, 4-dimethylaminobenzylidene, benzhydrazide, 2-benzylidene-aminocarbazole, 4-dimethylamino-benzylidene, (2-nitro-benzylidene) -p-bromo. Aniline, 2,4-diphenyl-quinazoline, 1,2,4-triazine, 1,5-diphenyl-3-methylpyrazoline 2- (4'-dimethylaminophenyl) -benzoxizole, 3-aminocarbazole, polyvinylcarbazole- Trinitrofluorenone charge transfer complex, and mixtures thereof. Further, the developer composition of the present invention comprises an electrostatographic imaging method and apparatus using a mobile transport means and a mobile charging means, and an electrostatographic imaging method using a deflectable flexible multilayer imaging member. Particularly useful in methods and apparatus (US Pat. No. 4,3,4)
94,429 and 4,368,970).

The images obtained with the developer compositions of this invention have acceptable solid images, good halftones and the desired line resolution and are substantially free of background deposits. Further, with respect to the method of forming the carrier particles of the present invention, an uncoated carrier core and polymer powder mixture is first obtained, usually from a commercially available source of material. The individual components for coating are
For example, from Ben Walt Company, 301F Kinal (Kyn
ar), polymist B6 from Allied Chemical Company
(Polymist B6) and from other sources. In general, these polymers are in the proportions mentioned above, for example 1: 1, 0.1: 0.9 and 0.
Mix in a ratio such as 5: 0.5. Mixing, for example,
This can be done by a number of known methods, including a two-bend mixing device. Thereafter, the carrier core polymer mixture, in a preferred embodiment, is placed in a mixing device at about 1% by weight, based on the weight of the core, and the mixture is mixed until the polymer mixture is evenly distributed and mechanically or electrically deposited on the carrier core. Do on time. The resulting coated carrier particles are then placed in a rotary tube furnace and maintained for a time sufficient for the polymer mixture to melt and fuse to the carrier core. In FIG. 1, 78% by weight of styrene-butadiene, 16% by weight of magnetite commercially available as mapico black, 4% by weight of carbon black and 2% by weight of antistatic additive distearyldimethylammonium methylsulfate.
4% by weight of a toner composition; and 0.7% by weight of a coating of a polymer mixture of 40% by weight of polyvinylidene fluoride and 60% by weight of polymethylmethacrylate, and 96% by weight of carrier particles of a steel core. 5 is a graph plotting the negative triboelectric charge (microcoulomb / g) of the carrier for 1000 imaging cycles with the agent composition. The values given in this graph are for aluminum, a photoexcitation layer consisting of trigonal selenium dispersed in polyvinylcarbazole on the aluminum, and 50% by weight N, N′-dispersed in 50% by weight polycarbonate. Diphenyl-N, N '
-Bis (3-methylphenyl) [1,1-biphenyl]
Obtained on a Xerox Corporation imaging tester having a photosensitive imaging member consisting of a charge transport layer of -4,4'-diamine. This graph shows that the triboelectric charge and the inferred carrier coating ratio remain relatively constant, ie, values of around -30 and 40:60 polymer ratio, respectively, over 50,000 imaging cycles. (% By weight).

In FIG. 2, a steel core, obtained in a Faraday cage according to the procedure described below, is formed of a steel core, on which a coating of various polymer ratios of 301F polyvinylidene fluoride and polyethylene B available from Allied Chemical Co. is prepared. 3 is a plot of negative triboelectric charge values of carrier particles having each value obtained at 1% coating weight. Also, according to the method of the present invention, carrier particles having a positive triboelectric charge of about 10 to about 80 microcoulombs / g can be obtained, for example, by using polyethylene and polymethylmethacrylate as the carrier coating. Examples The following examples are provided to further clarify the invention and it should be understood that these examples are for illustrative purposes only and do not limit the scope of the invention.
Parts and percentages are by weight unless otherwise noted. COMPARATIVE EXAMPLE 1 Carrier particles were mixed with Tonioro (T
oniolo) Polyvinylidene fluoride 6 which can obtain powdered steel core 68040 g as quinal 301F
It was prepared by coating with 80 g (1% coating amount). The coating is a Munso (Munso) rotating these ingredients for 60 minutes at 27.5 RPM.
n) by mixing in an MX-1 mini mixer. When measured by visual observation, polyvinylidene chloride was uniformly distributed and electrostatically adsorbed on the carrier core. The carrier particles obtained were then placed in a rotary tube furnace at a rate of 105 g / min. 503 ° F in this furnace
Maintaining a temperature of (261.7 ° C), the polymer was melted and fused into the core.

The developer composition is then treated with 97.5 g of the carrier particles prepared above with 92% by weight of styrene n-butyl methacrylate copolymer resin (58% by weight styrene, 42% by weight n-butyl methacrylate). 10
It was prepared by mixing with a toner composition consisting of wt% carbon black and 2 wt% of the charge promoting additive cetylpyridinium chloride. The triboelectric charge on the carrier particles was then measured by the well-known Faraday Cage method and a charge of -68.3 microcoulombs / g was measured on the carrier. In addition, the conductivity of the carrier, measured by forming a 0.1 inch (2.54 mm) long magnetic brush of carrier particles and measuring the conductivity by applying a 10 volt potential to the brush, is 10-15.
It was mho cm-1. Therefore, the carrier particles are insulating. In all examples triboelectric charge and conductivity values were obtained by the above procedure. Comparative Example 2 The procedure of Comparative Example 1 was repeated, except that polyvinylidene fluoride 10
2.0 g (0.15% coating amount) was used. A triboelectric charge of -33.7 microcoulombs / g was obtained on the carrier. The carrier particles are 10-9 mho-cm-
It had a conductivity of 1. That is, these particles are considered to be electrically conductive. Therefore, the coating amount is 1% ~
By changing to 0.15%, there is a remarkable change in conductivity, that is, the carrier particles change from the insulating property of Comparative Example 1 to the conductive property of this example, and the triboelectric value is -68.
Increased from 3 to -33.7. Example 1 A developer composition of the present invention was prepared by repeating the procedure of Comparative Example 1, except that 1% of polyvinylidenequinal fluoride 301F as a carrier coating and polyethylene (available as Polymist B6 from Allied Chemical Co.). 680 g of a polymer mixture of: 9 (polymer mixture 1.0% coating amount) was used. A triboelectric charge of -17.6 microcoulombs / g was obtained on the carrier particles. The carrier particles are 10-15 mho-cm-
It was insulating in that it had a conductivity of 1.

Accordingly, carrier particles were obtained which were insulating and had a relatively low triboelectric charge, ie -17.6 microcoulombs / g. Example 2 A developer composition was prepared by repeating the procedure of Example 1,
Polyvinylidene fluoride 301F and polymist B
A 9: 1 ratio polymer mixture of polyethylene, available as 6, was used as the carrier coating. About 68
0 g of polymer mixture, ie 1.0% coating amount, was used as it was. -6 on carrier coating
A triboelectric charge of 3 microcoulombs / g was obtained and the resulting insulating carrier particles had a conductivity of 10-15 mho-cm-1. Thus, for example, toner particles having a higher negative tribo, i.e., -63 microcoulombs / g, as compared to the developer of Example 3 having a polymer mixture ratio of 9: 1 instead of 1: 9, are used in Example 1. Of the developer of -17.6 microcoulomb / g. Example 3A developer composition was prepared by repeating the procedure of Example 1,
As the carrier coating, a polymer mixture of polyvinylidene fluoride quinal 301F and high density 10.962 g / ml polyethylene FA520 (available from USI Chemical Co.) in a mixing ratio of 3: 2 was used. About 3
40 g of polymer mixture was used, i.e. 0.5% coating weight. A triboelectric charge of -29.8 microcoulombs / g was obtained on the carrier particles. The resulting insulating carrier particles had a conductivity value of 10-14 mho-cm-1. EXAMPLE 4 A developer composition was prepared by repeating the procedure of Example 1, but using copolyvinylidene fluoride-tetrafluoroethylene (available from Penworth Company as quinal 7201) and a high density of 0.2 as a carrier coating.
A polymer mixture with a mixing ratio of 7: 3 with 962 g / ml polyethylene (available as Microsen FA520 from USI Chemical Company) was used. About 272 g of polymer mixture, i.e. 0.4% coating weight, was added. A triboelectric charge of -47.6 microcoulombs / g was obtained on the carrier particles. The resulting insulating carrier particles had a conductivity value of 10-14 mho-cm-1. Example 5A developer composition was prepared by repeating the procedure of Example 4,
Copolyvinylidene fluoride-tetrafluoroethylene (available as Penal 7201 quinal 7201) and low density 0.924 g as a carrier coating.
/ Ml polyethylene (FN51 from USI Chemical Co., Ltd.
(Available as 0) and a mixing ratio of 7: 3. About 476 g of polymer mixture, i.e. 0.7
% Coating amount was added. -42 on carrier particles
A triboelectric charge of microcoulomb / g was obtained. The resulting insulating carrier particles had a conductivity value of 10-15 mho-cm-1. Example 6 A developer composition was prepared by repeating the procedure of Example 4,
As a carrier coating, quinal 7201 and copolyethylene-vinyl acetate (FE from USI Chemical Co.
Available as 532) and about 476 g of polymer mixture with a mixture ratio of 7: 3.
A 0.7% coating amount was added. A triboelectric charge of -33.7 microcoulombs / g was obtained on the carrier particles. The obtained insulating carrier particles are 10-15 m
It had a conductivity value of cm-1. Example 7A developer composition was prepared by repeating the procedure of Example 6,
A polymer mixture of polyvinylidene fluoride (available from Penwort as Quinal 301F) and polymethacrylate (available from Fuji Xerox) in a mixing ratio of 2: 3 was used as the carrier coating. About 476 g of polymer mixture, i.e. 0.7% coating weight, was added. A triboelectric charge of -29.5 microcoulombs / g was obtained on the carrier particles. The obtained insulating carrier particles had a conductivity of 10-15 mho-cm-1.

In each of the above embodiments, the conductivity value is obtained as described above. In particular, these values were obtained by forming a magnetic brush with each carrier particle produced. The brush was present in one electrode bath consisting of a magnetic force as one electrode and a non-magnetic steel surface as the counter electrode. A 0.100 inch (2.54 mm) gap was maintained between the two electrodes and a 10 volt bias was applied to this gap. The current through the brush was recorded and conductivity was calculated based on the measured current and geometry. More specifically, the conductivity of mho cm-1 is the product of the current and the brush thickness of about 0.254 cm divided by the product of the applied voltage and the effective electrode area. Insulating developers provide high copy quality images for both lines and halftones, while solid image areas are of substantially poor quality. In contrast, conductive developers provide improved solid image areas with low line resolution and poor halftones. For triboelectric values in microcoulombs / g, the developer material was red devil paint shaker (Red Devil).
It was measured by placing it in an 8 ounce glass vase containing 2.75 wt% toner composition placed on a Paint Shaker) and stirred for 10 minutes. The pot was then removed and the sample from the pot was placed in a known triboelectric Faraday cage device. The apex triboelectricity of the carrier particles was then measured.

Other modifications of the present invention will be apparent to those skilled in the art from the description given herein, and these modifications shall fall within the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a graph plotting triboelectric charge during an imaging cycle with a developer containing a carrier composition of the present invention.

FIG. 2 is a graph plotting the negative triboelectric charge values for carrier particles having various ratios of polymer ratio coatings of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-130050 (JP, A) JP-A-58-208754 (JP, A) JP-A-60-176053 (JP, A) JP-A-54- 110839 (JP, A) JP-A-56-113146 (JP, A) JP-A-55-67754 (JP, A) US Patent 3939086 (US, A) "Iromura" Vol. 50, No. 9 (1977) Pages 31-32

Claims (6)

(57) [Claims] 1. A core particle having a coating comprising a fusion film of a mixture of a first polymer and a second polymer which are not close together in a triboelectric system, said mixture comprising polyvinylidene fluoride and polyethylene; polymethylmethacrylate. And copolyethylene vinyl acetate; copolyvinylidene fluoride-tetrafluoroethylene and polyethylene;
Copolyvinylidene fluoride-selected from the group consisting of tetrafluoroethylene and copolyethylene vinyl acetate; and polymethylmethacrylate and polyvinylidene fluoride, said coating being present in an amount of 0.05 to 3% by weight, based on the weight of the core particles. And the first polymer is one of the polymer blends.
The second polymer is present in an amount of 0 to 90% by weight, the second polymer is present in an amount of 90 to 10% by weight of the polymer mixture, and the coating has a triboelectric charging value of -8 to -80 microcoulombs / g. A carrier composition for an electrophotographic toner, comprising: 2. A carrier composition according to claim 1, wherein the polymer mixture comprises polyvinyl fluoride and polyethylene. 3. A carrier composition according to claim 1, wherein the polymer mixture consists of polymethylmethacrylate and copolyethylene-vinyl acetate. 4. The carrier composition according to claim 1, wherein the polymer mixture comprises copolyvinylidene fluoride-tetrafluoroethylene and polyethylene. 5. The carrier composition according to claim 1, wherein the polymer mixture comprises polymethylmethacrylate and polyvinylidene fluoride. 6. The carrier composition according to claim 1, wherein the carrier core is selected from the group consisting of iron, ferrite, steel and nickel.