JP2759516B2 - Developer for developing electrostatic images - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electrostatic image used for developing an electric latent image in an electrophotographic method or an electrostatic printing method.

[Related Art] In recent years, as image forming apparatuses such as color copiers have become widespread, their uses have been diversified and the demands for image quality have become strict. 2. Description of the Related Art In copying an image such as a general photograph, catalog, or map, it is required to reproduce very finely and faithfully without being crushed or interrupted even in a minute portion.

Further, in an image forming apparatus such as an electrophotographic color copying machine which has recently used a digital image signal, a latent image is formed by collecting dots of a constant potential, and a solid portion, a halftone portion and a light portion are formed. Is expressed by changing the dot density. However, in a state where the toner particles do not adhere to the dots and the toner particles protrude from the dots, it is not possible to obtain the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image. There is a problem. Further, when the resolution is improved by reducing the dot size in order to improve the image quality, the reproducibility of a latent image formed from minute dots becomes more difficult, and the resolution and especially the gradation of the highlight part are increased. The image tends to be poor in quality and lacks in sharpness.

On the other hand, for the purpose of improving image quality,
It has been proposed to reduce the particle size of the toner. But,
With this, some problems arise. Among them, it is particularly important to suppress toner scattering while securing image density. In other words, when the particle diameter of the toner is reduced, the surface of the magnetic particles is covered with a small amount of toner. Therefore, in order to prevent the toner from scattering, the toner concentration must be reduced. However, when the toner density is reduced, the image density is also reduced. As described above, hitherto, it has been difficult to balance toner scattering and image density.

[Problems to be Solved by the Invention] An object of the present invention is to provide a developer having high image density, excellent fine line reproducibility, and excellent highlight gradation.

It is a further object of the present invention to provide a developer in which toner is less likely to be scattered under a wide range of operating conditions, such as long-term running, rapid replenishment of toner, and long-term storage.

[Means and Actions for Solving the Problems] Specifically, the present invention relates to a toner having at least a nonmagnetic colorant-containing fine particle and a fluidity-imparting agent, and a developer for developing an electrostatic image containing magnetic particles. When the agglomeration degree of the developer is a% and the agglomeration degree of only the magnetic particles is b%, the following expressions 10 <a <50,3 <b <10,4 <a / b <10 are satisfied; The volume average diameter of the toner is 6 to 10 μm, and 5 μm
15 to 40% by number of toner particles having the following particle size, and 0.1 to 0.1% of toner particles having a particle size of 12.7 to 16.0 μm.
5.0% by volume, toner particles having a particle size of 16 μm or more are contained at 1.0% by volume or less, and 6.35 to 10.1 μm toner particles are represented by the following formula: Wherein the average particle size of the magnetic particles is 20 to 60 μm.

That is, the present inventors have conducted intensive studies and found that the cohesion of the developer and the magnetic particles is closely related to toner scattering, and that when the above conditions are satisfied, toner scattering is extremely reduced. .

Of the variables a / b, b in the denominator is a measured value of only magnetic particles, and has a meaning of correcting measurement conditions and the like. Therefore, if the value of a / b is large, it indicates that the attractive force between the toner and the magnetic particles is strong and it is difficult to separate them.When considered as a developer, the replacement of the toner is poor, and the replenishment toner is It cannot contact and scatters as it is. Conversely, if a / b is small, it indicates that the attractive force between the toner and the magnetic particles is weak, and even if the toner is in contact with the magnetic particles, the toner is easily scattered.

The attraction between the toner and the magnetic particles is considered to be mainly due to the Coulomb force. However, in the ordinary measurement of the charge amount, the charge amount and the toner scattering do not always show a good correlation. That is, factors that affect the toner scattering include the toner concentration, the distribution of the charge amount, the attractive force other than the Coulomb force, the shape and the particle size distribution of the toner and magnetic particles, and the like in addition to the charge amount. However, the factor of the agglomeration degree of the present invention shows a good correlation with toner scattering, and the developer whose a / b satisfies the above condition has very little toner scattering.

It is also important that a / b satisfies the above condition in terms of the other image density. That is, when a / b is large, the toner and the magnetic particles are not separated, so that the toner is not developed and the image density is reduced. Conversely, if a / b is small, fog increases.

The present inventors have further adopted the following configuration in order to achieve both image density and toner scattering.

As the fluidity imparting agent, the absolute value of the triboelectric charge amount with the magnetic particles is 50 μc / g or more, and the specific surface area S _A by the BET method is 80.
A hydrophobic inorganic oxide A of about 300 m ² / g based on the resin particles in an amount of m wt%, and an absolute value of a triboelectric charge amount with the magnetic particles of not more than 20 μc / g. Surface area S _B
Contains 30 to 200 m ² / g of a hydrophilic inorganic oxide B in an amount of n wt% with respect to the resin particles, and satisfies the following formula: S _A ≧ S _B , m ≧ n, 0.3 ≦ m + n ≦ 1.5 This is a developing agent for developing an electrostatic image.

As fluidity-providing agent, an absolute value of triboelectric charge quantity of the magnetic particles is the specific surface area S _A by the BET method in 50μc / g or more 80~300m
By using the hydrophobic inorganic oxide A of ² / g, the fluidity of the toner is improved, the contact between the magnetic particles and the toner is increased, and when the toner is replenished, the toner is quickly charged and the toner is not easily scattered. Becomes

In combination with this, the absolute value of the triboelectric charge quantity of the magnetic particles is the specific surface area S _B by the BET method in the following 20μc / g 30~20
By using 0 m ² / g of the hydrophilic inorganic oxide B, the charge amount of the toner can be reduced. Simply lowering the charge amount of the toner is disadvantageous for toner scattering, but a decrease in the charge amount increases the developability of the toner. Therefore, in order to obtain the same image density as when the hydrophilic inorganic oxide B is not used, the toner density can be reduced, which is advantageous for toner scattering. At first glance, this relationship seems to be a mere trade-off, but when considering toner replenishment, the lower toner concentration (in the case of the present invention) has more room to accept replenished toner.
Eventually, it is advantageous for toner scattering.

Further, by using the two kinds of fluidity-imparting agents in combination and setting the addition amount in the above range, a suitable charge amount and a suitable fluidity can be obtained, so that the developability is also good.

Further, in the present invention, the latent image formed on the photoreceptor is faithfully reproduced, and the gradation of the highlight portion, which is a minute latent image, is excellent, and the resolution is excellent. The following configuration was adopted in order to achieve good development with a consumption amount, no carrier adhesion, good developer transportability, high image density and no toner scattering.

The reason why the above-described effects can be obtained in the toner of the present invention is not necessarily clear, but is presumed as follows.

That is, one feature of the toner of the present invention is that 15 to 40% by number of toner particles having a particle diameter of 5 μm or less. Conventionally, toner particles having a particle size of 5 μm or less have difficulty in controlling the charge amount or impair the fluidity of the toner, and as a component that scatters the toner and soils the machine, and further as a component that causes image fogging.
It was thought that aggressive reduction was necessary.

However, according to the study of the present inventors, it has been found that toner particles of about 5 μm are essential components for forming high quality image.

For example, by using a non-magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm and a two-component developer having a carrier, the surface potential on the photoreceptor is changed, and a large development potential contrast from which a large number of toner particles are easily developed is obtained. Develop the latent image with the changed latent image potential on the photoreceptor to a halftone, and even to a small minute dot latent image where only a few toner particles are developed, and remove the developed toner particles on the photoreceptor. When collected and measured for toner particle size distribution, many non-magnetic toner particles of 8 μm or less, especially 5 μm
It has been found that non-magnetic toner particles of a large degree are present on the latent image of fine dots. That is, when non-magnetic toner particles having a particle size of about 5 μm are smoothly supplied to the development of the latent image on the photoreceptor, the image is faithful to the latent image, does not protrude from the latent image, and is truly excellent in reproducibility. Can be obtained.

Further, in the non-magnetic toner of the present invention, 12.7 ~ 16.0
One feature is that the particles in the μm range are 0.1-5.0% by volume.

This is related to the above-mentioned necessity of the presence of the non-magnetic toner particles having a particle size of about 5 μm. However, the non-magnetic toner particles having a particle diameter of 5 μm or less surely reproduce a latent image of fine dots faithfully. Has the ability, but itself quite cohesive,
Therefore, the fluidity of the non-magnetic toner may be impaired.

The present inventors have proposed the above-mentioned 2 for the purpose of improving fluidity.
By adding more than one kind of inorganic oxide, the fluidity was improved, but only by adding the inorganic additive,
It was confirmed that the conditions for satisfying all items such as image density, toner scattering and fog were very narrow. Therefore, the present inventors have further studied the particle size distribution of the toner. As a result, 15 to 40% by number of non-magnetic toner having a particle size of 5 μm or less are contained, and the toner particles of 12.7 to 16.0 μm are added. 0.
It has been found that the content of 1 to 5.0% by volume solves the problem of fluidity and achieves high image quality. That is, it is considered that the toner particles having a size in the range of 12.7 to 16.0 μm have an appropriately controlled fluidity with respect to the non-magnetic toner particles having a size of 5 μm or less. This provides a sharp image with excellent resolution and gradation in density.

Further, for the toner particles of 6.35 to 10.1 μm, between the volume% (V), the number% (N) and the volume average particle size (v), One of the features is that the negative chargeable color toner of the present invention satisfies the following relationship.

The present inventors have studied the state of the particle size distribution and the development characteristics and found that there is a state of existence of the particle size distribution most suitable for achieving the object as shown by the above formula.

That is, when the particle size distribution is adjusted by general air classification, a large value indicates that toner particles of about 5 μm that faithfully reproduces a minute dot latent image increase, and a small value indicates that the particle size is 5 μm. It is understood that the degree of toner particles indicates a decrease.

Therefore, v is in the range of 6 to 10 μm, and
When the above relational expression is further satisfied, good toner fluidity and faithful latent image reproducibility are achieved.

Further, the content of the non-magnetic toner particles having a particle size of 16 μm or more is set to 1.0% by volume or less, and the smaller the amount, the better.

The magnetic particles of the present invention are different from conventionally known magnetic particles, in that the average particle diameter is small, the amount of fine powder, and the amount of coarse powder are controlled, so that the particle size distribution is very narrow and sharp cut. Therefore, there is almost no ultrafine powder that adversely affects the carrier adhesion, and the particles are uniform and small in particle diameter. Therefore, the rise of the triboelectric charging property with the toner is also preferably improved. In addition, due to the small particle size and uniformity, the amount of toner having good chargeability that can be included in the particles is much larger than that of the magnetic particles having a large particle size. When broad magnetic particles having a particle diameter are used, a phenomenon in which the fine powder particles often adhere to the carrier on the photoreceptor during development occurs. Further, the toner mixed with the coarse powder particles often has a charge amount that is too high in terms of charge, and is often difficult to develop.

Further, the amount of coarse powder indicating the amount of coarse particles of 250 mesh-on is closely related to the sharpness of the image, and is preferably 1 to 7% by weight. If the amount is more than 7% by weight, the toner carrying ability of the carrier is reduced, the scattering of the toner to non-images is increased, and the resolution of the image is reduced and the roughness is likely to become apparent. Therefore, the content of 250 mesh or more is preferably 7% by weight or less, and more preferably 5% by weight or less.

On the other hand, when the content is less than 1% by weight, the fluidity of the developer is deteriorated, and the bias of the developer in the developing device is caused, so that it is difficult to obtain a stable image.

The average diameter of the magnetic particles is preferably from 20 to 60 µ, more preferably from 30 to 56 µ. At an average particle diameter of less than 20 μm, carrier adhesion to the photoreceptor increases drastically, and magnetic particles having an average diameter of more than 60 μm deteriorate highlight reproduction of color copying.

As the hydrophobic inorganic oxide used in the present invention, a negatively chargeable inorganic oxide having a specific surface area of 80 m ² / g or more and an absolute value of a triboelectric charge amount with magnetic particles of 50 μc / g or more is preferable. A preferred example is a treated silica fine powder obtained by subjecting a silica fine powder generated by gas phase oxidation of a silicon halide compound to a hydrophobic treatment. It is particularly preferable that the treated silica fine powder is obtained by treating the silica fine powder such that the degree of hydrophobicity measured by a methanol titration test shows a value in the range of 30 to 80.

The hydrophobizing method is applied by reacting with silica fine powder or chemically treating with an organic silicon compound which physically adsorbs.

As a preferred method, silica fine powder produced by vapor phase oxidation of a silicon halide is treated with an organosilicon compound.

Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane, trimethylchlorosilane,
Trimethylethoxysilane, dimethyldichlorosilane,
Methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α
-Chloroethyltrichlorosilane, ρ-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane,
Triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane,
Dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane and 2 to 12 siloxane units per molecule with terminal positions The units used are dimethylpolysiloxanes containing hydroxyl groups bonded to one Si each. These are used alone or as a mixture of two or more.

The treated silica fine powder preferably has a particle size in the range of 0.003 to 0.1 μm. Commercial products include Taranox-500 (Talco), AEROSIL R-972
(Nippon Aerosil).

On the other hand, as the hydrophilic inorganic oxide, alumina and titanium oxide are preferable because a sharp particle size can be obtained relatively easily by a gas phase method, but there are no particular restrictions on the production method and crystal structure. However, it is not preferable that the particles have an extremely square shape or a needle shape.

As the binder used in the negatively-chargeable colorant-containing resin particles of the present invention, various material resins conventionally known as electrophotographic toner binder resins are used.

For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer, styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer Phenolic resin, epoxy resin, acrylic phthalate resin, polyamide resin, polyester resin, maleic acid resin and the like. In addition, the production method of any resin is not particularly limited.

The effect of the present invention is remarkable when a polyester resin having a high negative chargeability is used among these resins. That is, the polyester-based resin has excellent fixability and is suitable for a color toner, but has a high negative charging ability and tends to be excessively charged. A toner is obtained.

In particular, (Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2
~ 10. A) a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid) Acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are more preferred because they have sharp melting properties.

In particular, from the viewpoint of light transmission with a trapene, the apparent viscosity at 90 ° C. is 5 × 10 ^{4 to} 5 × 10 ⁶ poise, preferably 7.5 × 10 ⁴ poise.
２2 × 10 ⁶ poise, more preferably 10 ⁵ to 10 ⁶ poise, and the apparent viscosity at 100 ° C. is 10 ^{4 to} 5 × 10 ⁵ poise, preferably 10 ^{4 to} 3 × 10 ⁵ poise, more preferably 10 ⁴ to 2
Color O with good light transmittance due to × 10 ⁵ poise
As a result, good results can be obtained in fixing property, color mixing property and high-temperature offset resistance as a full-color toner. 90 ℃
The absolute value of the difference between the apparent viscosity P ₂ at apparent viscosity P ₁ and 100 ° C. in ^{the, 2 × 10 5 <| P} 1 -P 2 | < particularly preferably in the range of 4 × 10 ^6.

As the coloring agent, known dyes and pigments, for example, phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used widely. The content thereof is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin so as to be sensitive to the light transmittance of the OHP film.

The toner according to the present invention may contain a charge control agent for stabilizing the charge characteristics. At that time, a colorless or light-colored charge control agent that does not affect the color tone of the toner is preferable.
In the present invention, when a negatively charged developer is used, the present invention becomes more effective. In this case, as the negatively charge controlling agent, for example, a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex of di-tert-butylsalicylic acid or Organometallic complexes such as zinc complex). When the negative charge control agent is added to the toner, it is added in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.

As the magnetic particles used in the present invention, for example, surface oxidized or unoxidized iron, nickel, copper, zinc, cobalt,
Metals such as manganese, chromium, and rare earths and alloys or oxides thereof and ferrites can be used. In addition, there is no particular limitation on the manufacturing method.

In the present invention, the surface of the magnetic particles is coated with a resin or the like.A method of dissolving or suspending a coating material such as a resin in a solvent and applying the coating material to adhere to the magnetic particles, or simply a powder method Any of the conventionally known methods, such as a method of mixing with, for example, can be applied. In order to stabilize the coating layer, it is preferable that the coating material be dissolved in a solvent.

The coating material on the surface of the magnetic particles varies depending on the toner material, for example, amino acrylate resin,
Acrylic resins or copolymers of these resins and styrene resins are preferred. As the negatively charged resin, silicone resin, polyester resin, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, and the like are located on the negative side in the charging series, and are suitable, but are not necessarily limited thereto. .

Most suitable for the present invention are acrylic resins or copolymers of these resins and styrene resins.

In selecting the coating material, it is necessary to take into account the charge retention ability from the viewpoint of preventing toner scattering. For example,
Even if the charging ability is high, if the charging is not stable and the leak is fast, toner scattering will occur.

The most suitable material for the magnetic particles used in the present invention is 98% or more of Cu—Zn—Fe (composition ratio (5 to 20): (5 to 20%).
20): Ferrite particles having a composition of (30 to 80)), which are easy to smoothen the surface and have a stable charging ability,
In addition, the coating can be stabilized.

The coating amount of the compound may be appropriately determined so that the charge imparting property of the magnetic particles satisfies the above-mentioned conditions, but is generally 0.1 to 30% by weight (preferably 0.3 to 20% by weight) based on the magnetic particles of the present invention. % By weight).

In the present invention, a fatty acid metal salt as a lubricant, such as zinc stearate, aluminum stearate, or the like, or a fine powder of a fluorine-containing polymer, such as polytetrafluoroethylene, polyvinylidene fluoride, and tetrafluoroethylene-vinylidene fluoride Fine powder of a ride copolymer, or an abrasive such as cerium oxide, silicon carbide, strontium titanate or tin oxide,
A conductivity imparting agent such as zinc oxide may be added.

To prepare the negatively-chargeable colorant-containing resin particles according to the present invention, a pigment or a dye as a colorant, a charge control agent, and other additives are added to the thermoplastic resin by a mixer such as a ball mill as necessary. After mixing well, heat roll, kneader, melt using a hot kneader such as extruder,
The pigments or dyes are dispersed or dissolved in the resin mixed with each other by kneading and kneading, and after cooling and solidification, pulverization and strict classification are performed to obtain the colorant-containing resin particles according to the present invention. I can do it.

Hereinafter, a method of measuring characteristic values used in the present invention will be described.

(1) Measurement of agglomeration degree (separation of magnetic particles) For example, 500 mesh is set in a container to which a mesh as shown in FIG.
Suction is performed as shown in FIG. The magnetic particles remaining in the container are used for the main measurement. In this separation method, it was confirmed that magnetic particles finer than 500 mesh were removed, but had little effect on the results of this measurement. (Results of Comparison of Magnetic Particles Used in the Present Invention with Magnetic Particles Before Mixing with Toner) (Measurement of b Value) 10 g of magnetic particles separated from the developer are weighed. As a measuring device, a powder tester (manufactured by Hosokawa Micron)
Is used. 200 mesh, 150 mesh, and 100 mesh sieves are set on the shaking table in the order of narrower meshes, that is, 200 mesh, 150 mesh, and 100 mesh so that the 100 mesh sieve is at the top.

The input voltage to the shaking table was set to 12.0 V, and 10 g of magnetic particles accurately weighed on the set 60 mesh screen
And shake for 15 seconds. Thereafter, the weight of the sample remaining on each sieve is measured to obtain the degree of aggregation based on the following equation.

(Measurement of a value) 10 g of the developer to be measured is put in a 50 cc polybin and stirred for 1 minute. Next, the cohesion of the developer is measured under the same conditions as those for measuring the cohesion of the magnetic particles. In the same manner as above except that the magnetic particles were changed to the developer, the cohesion degree of the developer and the value of a / b were obtained.

(2) Measurement of Particle Size of Toner The particle size distribution of the toner can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-An interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution using Model II (manufactured by Coulter) and CX-1
A personal computer (manufactured by Canon Inc.) is connected, and a 1% aqueous NaCl solution is prepared using primary grade sodium chloride as an electrolyte. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
After a dispersion treatment for minutes, the Coulter Counter TA-II
According to the mold, the particle size distribution of particles of 2 to 40 μ was measured on the basis of the number, using a 100 μ aperture as the aperture, and then the value according to the present invention was determined.

(3) Measurement of Friction Charge Amount FIG. 1 is an explanatory diagram of a friction charge amount measuring device. First, a mixture of particles to be measured and magnetic particles used as a developer is prepared. The mixing ratio is 5 parts by weight for 95 parts by weight of magnetic particles in the case of toner and colorant-containing fine particles, and 2 parts by weight in 98 parts by weight of magnetic particles in the case of a fluidity imparting agent. .

The particles to be measured and the magnetic particles are placed in a measurement environment and left for 12 hours or more, then put into a polyethylene bottle, and sufficiently mixed and stirred.

Next, a mixture of particles and magnetic particles whose triboelectric charge amount is to be measured is placed in a metal measuring container 2 having a conductive screen 3 of 500 mesh (which can be appropriately changed to a size that does not allow magnetic particles to pass) at the bottom. A metal lid 4 is provided. At this time, the weight of the entire measurement container 2 is weighed and defined as W ₁ (g). next,
In the suction device 1 (at least a portion in contact with the measuring container 2 is an insulator), the pressure of the vacuum gauge 5 is adjusted to 250 mmAq by adjusting the air volume control valve 6 by suctioning from the suction port 7. In this state, suction is sufficiently performed (about 2 minutes) to remove toner by suction. The potential of the electrometer 9 at this time is set to V (volt). Where 8
Is a capacitor and the capacity is C (μF). Also,
The weight of the whole measuring container after suction is weighed and is defined as W ₂ (g). This triboelectric charge amount T (μc / g) is calculated as follows.

(4) Magnetic particle size distribution measurement method 1. Measure about 100 g of a sample to the order of 0.1 g.

2. Standard sieve of 100 Mesh to 400 Mesh (hereinafter referred to as sieve)
And stack them in order of size 100, 145, 200, 250, 350, 400 from the top, place a saucer on the bottom, put the sample in the top sieve and cover it.

3. This is sifted by a vibrator at 285 ± 6 horizontal revolutions per minute and 150 ± 10 vibrations per minute for 15 minutes.

4. After sieving, measure the iron powder in each sieve and tray to the nearest 0.1 g.

5. Calculate to the second decimal place by weight percentage and round to the first decimal place according to JIS-Z8401.

However, the size of the sieve frame is 200 mm inside diameter above the sieve surface,
The depth from the top surface to the sieve surface is 45mm.

The sum of the weights of iron powder in each part shall not be less than 99% of the mass of the starting sample.

The average particle size is determined from the above measured particle size distribution according to the following equation.

For a carrier of 500 mesh or less, a 50 g sample amount is 500
It is put on a mesh standard sieve, sucked from below, and calculated from the weight loss.

(5) Hydrophobicity Measurement The methanol titration test is an experimental test for confirming the hydrophobicity of a silica fine powder having a hydrophobized surface.

The "methanol titration test" defined herein for evaluating the degree of hydrophobicity of the treated silica fine powder is performed as follows. 0.2 g of the test silica fine powder is added to 50 ml of water in a 250 ml Erlenmeyer flask. Methanol is titrated from the burette until all of the silica is wetted. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed by the suspension of the entire amount of the fine silica powder in the liquid, and the degree of hydrophobicity is expressed as the percentage of methanol in the liquid mixture of methanol and water at the end point.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples. still,
“%” And “parts” indicate weight% and parts by weight.

Example 1 Polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Di-tert-butylsalicylic acid chromium complex 4 parts was sufficiently premixed with a Henschel mixer,
The mixture was melt-kneaded at least twice with a three-roll mill, cooled, and coarsely ground to a particle size of about 1 to 2 mm using a hammer mill. Next, it was pulverized by a pulverizer using an air jet method. Furthermore, the obtained finely pulverized material is classified by a multi-segment classifier, and the volume average particle diameter is 8.3 μm, 5 μm or less is 25 number%, 12.7 μm or less.
16μ is 1.6% by volume, 16μ or more is practically 0%, Was obtained.

The specific surface area by the BET method is 100 m ² / g with respect to 100 parts of the colorant-containing resin particles, and the specific surface area by the BET method is 250 m ² / g with 0.3 part of alumina fine powder having a charge amount of −3 μc / g. ,
0.5 parts of silica fine powder (charge amount -80 μc / g) hydrophobized with hexamethyldisilazane was combined and externally added to obtain a cyan toner. For reference, a classification process using a multi-divided classifier is schematically shown in FIG. 2, and a cross-sectional perspective view (three-dimensional view) of the multi-divided classifier is shown in FIG.

Cu-Zn-Fe-based ferrite particles surface-coated with styrene-acrylic acid-2-ethylhexyl methacrylate copolymer (6 parts of the cyan toner) (carriers in Table 2)
94 parts were mixed to prepare a developer.

The cohesion of this developer was 40%, and the cohesion of the ferrite particles was 7.5%, a / b = 5.3.

Using this developer, a commercially available plain paper copying machine (manufactured by CLC-1 Canon) was modified so that the peripheral speed of the sleeve was 280 mm / sec, and a running test of 30,000 sheets was conducted at normal temperature and normal humidity (23 ° C, 60 ° C).
% RH), low temperature and low humidity (15 ℃, 10% RH), high temperature and high humidity (32.5 ℃,
(85% RH), a high-quality image with a sufficient image density was obtained in any environment, and toner scattering in the copying machine was not conspicuous.

Comparative Example 1 The procedure of Example 1 was repeated, except that only 1.0 part of the alumina fine powder used in Example 1 was used as the fluidity-imparting agent. Yes, a /
b was 1.7. Also, as a result of the test, remarkable toner scattering occurs under high temperature and high humidity, and even under normal temperature and normal humidity,
The running test was stopped at 5,000 sheets because toner scattering occurred.

Example 2 As a fluidity imparting agent, the specific surface area by the BET method was 220 m ² / g.
0.6 parts of silica fine powder hydrophobized with dimethyldichlorosilane and 0.3 parts of titanium oxide fine powder (charge amount +5 μc / g) with a specific surface area of 60 m ² / g by BET method Except for, the aggregating degree of the developer was 35% and a / b was 4.7. In addition, as a result of the test, good results in which both toner scattering prevention and high image density were achieved were obtained.

Comparative Example 2 As a magnetic particle, a styrene-acrylic copolymer (3: 6: 1) composed of styrene-methyl methacrylate-2-hydroxyethyl acrylate (3: 6: 1) was coated with a resin obtained by cross-linking with hexamethoxymethylsilane. Except for using -Zn-Fe-based ferrite particles (Table 2 carriers), the same procedure as in Example 1 was carried out. The coagulation degree of the developer was 68%, and the coagulation degree of the magnetic particles alone was: 4.0%, a / b
Was 17. Further, as a result of the test, the image density was low under a low temperature and a low humidity, and further decreased as the running was advanced. In addition, when running was started after standing for one day and night under high temperature and high humidity, toner scattering was noticeable up to about 50 sheets in the initial stage.

Example 3 In Example 1, the volume average particle diameter 8.0 μ 5 μ or less is 36 number% 12.7 to 16 μ 1.6 volume% 16 μ or more Substantially 0% Was carried out in the same manner as in Example 1 except for using the colorant-containing resin particles having a cohesiveness of the developer of 31% and a / b = 4.1.
Met. Then, good results were obtained in the image output test.

[Effects of the Invention] The present invention can improve the fluidity imparting agent to make the aggregation degree of the developer and the magnetic particles appropriate, thereby preventing toner scattering and providing an image of excellent quality. It is.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a triboelectric charge measuring device, FIG. 2 is an explanatory diagram of a classification process using a multi-division classification device, and FIG. 3 is a sectional perspective view of the multi-division classification device.

Claims (2)

(57) [Claims] 1. A developer for electrostatic image development containing magnetic particles and toner having at least non-magnetic colorant-containing fine particles and a fluidity imparting agent, wherein the developer has an agglomeration degree of a% and only the magnetic particles B
%, The following formulas 10 <a <50, 3 <b <10,4 <a / b <10 are satisfied, and the volume average diameter of the toner is 6 to 10 μm and the particle diameter is 5 μm or less. Contains 15 to 40% by number of toner particles,
0.1 to 5.0% by volume of toner particles having a particle diameter of 12.7 to 16.0 μm, and toner particles having a particle diameter of 16 μm or more
1.05% by volume or less and 6.35 to 10.1 μm of toner particles are represented by the following formula: Wherein the average particle size of the magnetic particles is 20 to 60 μm. 2. _A hydrophobic inorganic oxide as the fluidity-imparting agent, having an absolute value of a triboelectric charge amount with the magnetic particles of 50 μc / g or more and a specific surface area SA of 80 to 300 m ² / g by a BET method. things a are contained m% by weight relative to the resin particles, and the absolute value of the triboelectric charge quantity of the magnetic particles is less than or equal 20μc / g, specific surface area S _B by the BET method of 30 to 200 m ² / g The hydrophilic inorganic oxide B is contained in an amount of n wt% with respect to the resin particles, and satisfies the following formula: S _A ≧ S _B , m ≧ n, 0.3 ≦ m + n ≦ 1.5. Developer for developing electrostatic images.