JPH05127432A - Carrier for electrostatic charge image developing and its production - Google Patents

Abstract

PURPOSE:To obtain a coating layer having high wear resistance and to increase thermal stability by coating the carrier core material with a compsn. containing at least polycarbodimide resin and treating the coated carrier by heating at specified temp. or higher. CONSTITUTION:This electrostatic charge image development carrier consists of the carrier core material coated with a compsn. containing at least polycarbodimide resin. After coating the carrier core material with a compsn. containing at least polycarbodimide resin, the carrier is subjected to heat treatment at >=120 deg.C. The polycarbodimide resin is synthesized by decarbonation condensation reaction of a compd. having >=2 isocyanate groups at the molecular end in the presence of a catalyst which promotes carboimidization. The carbodimide resin has carbodimide group in its molecular structure and causes inner crosslinking reaction by heating at >=120 deg.C. Thus, tougher coating films is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for electrostatic images of electrophotography and electrostatic recording, and more particularly to a dry two-component developer comprising a carrier and a toner.

[0002]

2. Description of the Related Art In electrophotography, a photosensitive member having a photoconductive layer is provided with a uniform surface charge in a dark place, and then an electrostatic image is formed by imagewise exposure, and the electrostatic image is developed. To form a visible image.

Generally, the method for developing such an electrostatic image is roughly classified into a wet developing method and a dry developing method. The wet developing method is a method of developing using a liquid developing agent in which various pigments and dyes are dispersed as fine particles in an insulating organic liquid, and the dry developing method is a method of developing carbon black in a natural or synthetic resin. Is a developing method using a toner containing a colorant such as the above. In this dry development method, a so-called bristle brush method using a developer containing only the toner as a main component, an impression method, a powder cloud method, a mixture of a carrier made of iron powder or glass beads, and the toner is used. There are so-called magnetic brush method and cascade method used as a developer.

By these developing methods, toner particles having a charge contained in the developer adhere to the electrostatic image to form a visible image. This visible image is transferred onto the photoreceptor as it is by heat, pressure, solvent vapor or the like, or is fixed onto paper or other record carrier.

Carriers of the dry two-component type developer which is the object of the present invention are roughly classified into conductive carriers and insulating carriers.

Oxidized or non-oxidized iron powder is usually used as the conductive carrier. In a developer containing the iron powder carrier as a component, the triboelectric chargeability against the toner is unstable, and the developer is not developed. There is a drawback that the visible image formed by the agent causes fogging. That is, as the toner particles adhere to the surface of the iron powder carrier particles as the developer is used, the electric resistance of the carrier particles increases, the bias current decreases, and the triboelectrification becomes unstable. The image density of the visible image is reduced and the fog is increased. Therefore, when copying continuously with an electronic copying machine using a developer containing an iron powder carrier, the developer deteriorates in a small number of times, so it is necessary to replace the developer at an early stage, so that good images can be continuously reproduced. I can't get it.

As the insulating carrier, iron,
A typical example is a carrier in which the surface of a carrier core material made of a ferromagnetic material such as nickel or ferrite is uniformly coated with an insulating resin. In the developer using this insulative carrier, the toner particles are much less fused to the carrier surface than in the case of the conductive carrier, and at the same time, the triboelectrification property between the toner and the carrier can be controlled and the durability can be improved. Is relatively excellent. It also has the advantage that it can be used in high-speed electronic copying machines. However, in this insulative carrier, the coating layer that covers the surface of the carrier core material has sufficient abrasion resistance (durability), and the coating layer is well fixed so that the toner film is not formed on the carrier surface. It is required to have an antistatic property and to obtain a charged state of a desired strength (charging property) by friction with a specific toner used together with a carrier.

That is, the insulating carrier is rubbed with other carrier particles, toner particles, container walls, etc. in the developing device. When the coating layer is abraded by the friction, the stability of the charging property caused by the friction with the toner is generated. Are lost, and the toner particles cannot be given a desired charge state. Further, even if the coating layer of the insulating carrier has sufficient abrasion resistance, if the adhesiveness to the core material is poor, the coating layer is peeled off or crushed by the above-mentioned friction, and the charging property is similarly lost. Like Furthermore, when toner adheres to the surface of the coating layer to form a coating, the charging characteristics also become unstable. In either case, it is necessary to replace the entire developer with a new one as soon as possible.

Conventionally, there has been no insulating carrier satisfying all of these.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems; (1) a carrier having a coating layer having high abrasion resistance and a method for producing the same, (2) a carrier having a coating layer having excellent thermal stability, and A manufacturing method thereof, and (3) a carrier having stable triboelectricity at high speed and long-term use and having high durability, and a manufacturing method thereof.

[0011]

The above object of the present invention is achieved by an electrostatic image developing carrier characterized in that the surface of a carrier core material is coated with a composition containing at least a polycarbodiimide resin. Can be obtained by a method for producing a carrier for electrostatic image development, characterized in that the surface of a carrier core material is coated with a composition containing at least a polycarbodiimide resin and then heat-treated at a temperature of 120 ° C. or higher.

The polycarbodiimide resin according to the present invention is synthesized by a decarboxylation condensation reaction of a compound having two or more isocyanate groups at the terminals in the presence of a catalyst for promoting carbodiimidization.

Further, the carbodiimide resin has a carbodiimide group in its molecular structure, and when heated to 120 ° C. or higher, an internal cross-linking reaction is caused to form a stronger film. When a compound containing two or more active hydrogen groups in the molecule is added to the carbodiimide resin as a cross-linking agent, the curing reaction proceeds rapidly, and a high-strength coating film can be formed.

The compound having two or more isocyanate groups at the terminal used in the present invention is, for example, 2,
4-tolylene diisocyanate, 2,6-tolylene diisocyanate, mixture of 2,4- and 2,6-tolylene diisocyanate, crude tolylene diisocyanate, methylene diphenyl diisocyanate, crude methylene diphenyl diisocyanate, 4,4 ', 4 " -Triphenylmethylene triisocyanate, 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-
Tetraisocyanate, xylene diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate methyl ester, polymethylene polyphenyl isocyanate, hydrogenated methylene diphenyl isocyanate, m-phenylene diisocyanate, naphthylene-1,5-
Diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl isocyanate, 3,3'- Examples thereof include dimethyl-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate and isophorone diisocyanate. or,
It is also possible to use a so-called terminal isocyanate prepolymer obtained by using these organic polyisocyanates with respect to the polyfunctional hydrogen compound in a stoichiometric excess.
These include, for example, terminal isocyanate prepolymers of 4,4'-diphenylmethane diisocyanate and poly-ε-caprolactone diol, polytetrahydrofuran ether diol, and the like.

Various catalysts can be used as the catalyst for promoting the carbodiimidization of isocyanate, but 1-phenyl-2-phospholen-1-oxide, 3-methyl-2-phospholen-1-oxide, 1-phenyl- 2-phosphorene-1-sulfide, 1-
Ethyl-2-phosphorene-1-oxide, 1-ethyl-3-methyl-
2-phospholen-1-oxide, these 3-phospholen isomers and the like are preferable in terms of yield and the like.

The cross-linking agent is, in principle, a compound or mixture containing two or more active hydrogen groups in the molecule, such as amino-S-triazine, 1-phenyl-3,5-diaminotriazine, 1-methyl-3, Triazine derivatives such as 5-diaminotriazine and 1,3,5-trihydroxytriazine; 3,9-bis [2- (3,5-diamino-2,4,6, -triazaphenyl) ethyl] -2, 4,8,10, -Tetraoxaspiro [5,5] undecane, cyanuric acid and its substituted compounds; hydroquinone, 4,
Compounds having a phenolic hydroxyl group such as 4'-isopropylidenediphenol; diimide compounds such as urea, dicyandiamide, pyromellitic diimide; pyromellitic anhydride, 3,3'-4,4'-benzophenone tetracarboxylic acid anhydride Examples thereof include dianhydrides; polyfunctional epoxy compounds and the like.

In the production of the carrier used in the present invention, at least a polycarbodiimide resin is dissolved in an organic solvent to prepare a coating solution, which is applied to the surface of the carrier core material by, for example, a dry spray method to form a coating layer. After that, the carrier used in the present invention is obtained by further heating. The heating temperature must be 120 ° C or higher.

Specifically, for example, in a fluidizing bed apparatus, the carrier core material is raised to an equilibrium height by a rising pressurized gas flow, and the coating liquid is sprayed by the time the core material falls again. Apply. This coating is repeated to form a coating layer in advance. When there is an aggregated carrier, it can be sieved to finally obtain the carrier of the present invention having a desired film thickness. The thickness of the coating layer is in the range of 0.05 to 20 μm, preferably 0.1 to 2 μm.

The organic solvent used in the above production is
Any solvent can be used as long as it can dissolve the resin containing the polymer of the present invention as a main component, and for example, toluene, tetrahydrofuran, dioxane, dimethyl sulfoxide, or a mixed solvent thereof is used.

As the material of the carrier core material in the present invention, those conventionally used as the carrier core material such as sand, glass and metal can be used. In particular, a substance which is strongly magnetized in that direction by magnetism, For example, ferrite, magnetite, iron, cobalt, nickel, and other metals exhibiting ferromagnetism, or alloys or compounds containing these metals, but containing no ferromagnetic element, but exhibiting ferromagnetism by appropriate heat treatment Suitable alloys include, for example, alloys of the type called Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide. The particle diameter of these carrier core materials is 30 to 1000 μm, preferably 50 to 500.
μm. The carrier of the present invention has an absolute value of 5 to 40 μC / toner with respect to the toner used together under normal use conditions.
It is preferable to give a charge of g.

The carrier according to the present invention can constitute a two-component developer with any toner. Among them, preferable toners include those using polyester resin or styrene / acrylic resin as the binder.

To produce the toner used in the present invention, a colorant is contained in the binder, various additives are added if necessary, and the mixture is mixed by a ball mill or the like.
The toner used in the present invention can be obtained through the steps of blending, pulverizing, and classifying.

It can be obtained by a production method other than the above, for example, a spray drying method, an interfacial polycondensation method, a suspension polycondensation method, a solution polycondensation method, or the like.

The particle size of the toner obtained by the above method is 1
˜50 μm, preferably 5˜30 μm.

Specific examples of the colorant contained in the toner include carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue or a mixture thereof. be able to.

Further, examples of the additive added as necessary include an offset preventive agent, a charge control agent and the like.

The above-mentioned developer is obtained by mixing the carrier of the present invention with the toner, and the mixing ratio thereof is preferably 0.3 to 20 parts by weight with respect to 100 parts by weight of the carrier.

The carrier of the present invention is coated with a thermosetting polycarbodiimide resin, and has improved adhesion to the core material and good abrasion resistance, so that it can be used in a developing device at high speed or for a long period of time. Even when used, the coating resin does not peel off. Further, since it is also thermally stable, it is less dependent on the environment, and stable triboelectric charging properties can always be obtained.

[0029]

EXAMPLES Next, the present invention will be described in detail with reference to Examples.

(Production of Carrier) Carrier 1 15 g of polycarbodiimide (1) having the following structure prepared by synthesizing tolylene diisocyanate with 3-methyl-1-phenyl-2-phosphorene oxide as a catalyst is dissolved in 500 ml of toluene to obtain a polymer solution. Was prepared. 1 kg of spherical ferrite particles (average particle size 80 μm) as a carrier core material was spray-coated with a fluidized bed coating method, and then dried.
The carrier 1 of the present invention was produced by heat treatment at 0 ° C. for 20 minutes.

Carrier 2 The carrier 2 of the present invention was produced in the same manner as the carrier 1 using the polycarbodiimide (2) having the following structure obtained from 4,4'-diphenylmethane diisocyanate.

Carrier 3 Polycarbodiimide (3) having the following structure obtained from hexamethylene diisocyanate is used, and 1,3,
Carrier 3 of the present invention was produced in the same manner as Carrier 1 by adding 1 g of 5-triamino-S-triazine at the same time.

Carrier 4 A carrier 4 for comparison was produced in the same manner as Carrier 1 except that polystyrene (molecular weight Mw = 10,000) was not used.

[0034]

[Chemical 1]

(Production of Toner) Toner 1 Copolymer 100 obtained by reacting styrene, methyl methacrylate, and butyl methacrylate (molar ratio 50/20/30)
Parts by weight, carbon black "Mogul L" (manufactured by Cablack) 10 parts by weight, low molecular weight polypropylene "Viscole"
660 p "(manufactured by Sanyo Kasei Co., Ltd.), kneaded by a heating roll, cooled, coarsely crushed, further finely pulverized by an ultrasonic jet mill, and classified by an air classifier to obtain colored fine particles. It was

Hydrophobic silica fine powder "Aerosil R-972" (manufactured by Aerosil) to 100 parts by weight of the colored fine particles.
0.8 parts by weight were mixed with a V-type mixer to obtain a toner having an average particle size of 11 μm.

(Preparation of Developer) 1,96 parts by weight of carrier and 1,4 parts by weight of toner were mixed with a YGG mixer (manufactured by Yayoi Co., Ltd.) at 100 rpm for 20 minutes to prepare a developer.

Carriers 2 to 4 are used and developers 2 to 4 are used in the same manner.
Was prepared.

(Evaluation of Developer) The developer was 5% under an environmental condition of a temperature of 33 ° C. and a relative humidity of 80% by a modified electrophotographic copying machine “U-Bix5000” (manufactured by Konica Corporation).
Ten thousand running tests were performed.

For the evaluation, the coverage rate, charge amount, image, continuous copy number (durability), specific resistance, and image quality of 5th generation copy were examined, and the results are summarized in Table 1.

[0041]

[Table 1]

The meanings of the terms in Table 1 are as follows.

The "coverage" was calculated by heating the coated carrier at a high temperature and calculating the weight of the resin relative to the carrier core material from the amount of carbon dioxide produced. The manufactured carrier was used before the start of running. After running, the developer was washed with water containing a surfactant to remove the toner, and a carrier dried at 40 ° C. for 24 hours was used.

The "charge amount" is the value of the triboelectric charge amount per 1 g of the developer measured by the blow-off method.

"Dmax" represents the maximum image density and is expressed as the relative density of the developed image when the image density of the original image is 1.3.

The "fog" is expressed by the relative density of the developed image when the density of the original image is set to 0.

“5th generation copy” means 1 copy of the original image.
This is the fifth copy when the first-generation copy is the second-generation copy. The image quality of the fifth generation copy is indicated by x when it is less than the practical level, Δ when it is at the practical level limit, and by ◯ when it is better than the practical level.

"Durability" means that the fog value of a developed image is 0.
It is the number of copies when the value becomes 03 or more or the value of Dmax becomes 0.7 or less. In addition, the number of copies when the 5th generation copy has reached the practical level is also shown. It should be noted that the number of copied sheets of "50,000 sheets or more" means that neither the fogging value nor the Dmax value reached the above-mentioned limit value even after copying 50,000 sheets.

The "specific resistance" was calculated by applying 100 V to a carrier layer of 1 cm under the conditions of an electrode area of 1 cm ² and a load of 1 kg, and converting the current value flowing therethrough. For the measurement, the manufactured carrier was used at the start of running, and the carrier from which the toner was removed by blow-off after the start of running was used.

[0050]

EFFECTS OF THE INVENTION (1) Since the abrasion resistance is good and the coating layer is not peeled off, the coating film always has stable triboelectric chargeability, so that a high quality image can be obtained for a long period of time.

(2) Since the polycarbodiimide resin of the present invention has high solubility in an organic solvent, it can be manufactured by a dry spray method or a dipping method.

Claims (2)

[Claims] 1. A carrier for electrostatic image development, characterized in that the surface of a carrier core material is coated with a composition containing at least a polycarbodiimide resin. 2. A method for producing a carrier for electrostatic image development, which comprises coating the surface of a carrier core material with a composition containing at least a polycarbodiimide resin and then heat-treating it at a temperature of 120 ° C. or higher.