JP3168366B2 - Two-component developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called two-component developer in which a small amount of toner is dispersed in a medium called a carrier, and more particularly to a two-component developer having remarkably improved image quality and durability.

[0002]

2. Description of the Related Art In recent years, with the widespread use of image forming apparatuses such as electrophotographic copiers, their uses have been diversified, and demands for higher definition and higher image quality have been increasing in the market. In the technical field, attempts have been made to achieve high image quality by reducing the particle size of the toner.However, as the particle size becomes smaller, the surface area per unit weight increases, and the amount of charge of the toner tends to increase. There is a concern about low image density and deterioration in durability. In addition, since the charged amount of the toner is large, the adhesion between the toners is strong, the fluidity is reduced, and problems occur in the stability of toner supply and in the application of tribo to the supplied toner.

[0003] Several developers have been proposed for the purpose of improving image quality. JP 5
Japanese Patent Application Laid-Open No. 1-3244 proposes a non-magnetic toner intended to improve the image quality by regulating the particle size distribution. The toner is mainly composed of a toner having a particle size of 8 to 12 μm, and is relatively coarse. According to the study of the present inventors, it is difficult for the toner to have a dense “glue” to a latent image, In addition, from the characteristic that 5 μm or less is 30 number% or less and 20 μm or more is 5 number% or less, there is a tendency that the particle size distribution is broad and the uniformity is lowered.
In order to form a clear image using such a coarse toner particle and a toner having a broad particle size distribution, it is necessary to fill the gap between the toner particles by thickly overlapping the toner particles. There is also a problem that it is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density increases.

Japanese Patent Application Laid-Open No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former, but the size of particles having an intermediate weight is 8.5 to 8.5.
There is still room for improvement as a toner having a high resolution of 11.0 μm and high resolution.

Japanese Patent Application Laid-Open No. 58-129439 proposes a non-magnetic toner having an average particle diameter of 6 to 10 μm and a maximum number of particles of 5 to 8 μm, but 15% by number or less of particles of 5 μm or less. There is almost no effect in sharpness.

According to the study by the present inventors, it has been found that toner particles of 5 μm or less clearly reproduce the outline of a latent image and have a main function of dense toner gluing on the entire latent image. Was done. In particular, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contoured edge portion has a higher electric field strength than the inside, and due to the quality of the toner particles collected in this portion,
The sharpness of the image quality is determined. According to the study of the present inventors, 5 μm
It has been found that the amount of particles less than m is effective in solving the problem of sharpness of image quality.

Therefore, Japanese Patent Application Laid-Open No. 2-222966 proposes a toner containing 15 to 40% by number of toner particles having a particle size of 5 μm or less, whereby a considerable improvement in image quality has been achieved. Improved image quality is also desired.

In Japanese Patent Application Laid-Open No. 2-877, 5 μm
The following toner containing 17 to 60% by number of toner particles has been proposed. By this, the image quality and the image density are surely stable, but an original which consumes a large amount of toner such as a photo original is continuously printed. In such a case, it was also found that the particle size distribution of the toner was changed only by taking measures as the toner, and it was difficult to always obtain a constant image.

On the other hand, Japanese Patent Application Laid-Open Nos. 51-3238, 58-144839 and 61-20264 disclose the average particle size and the particle size distribution of the carrier.
No. 6 publication. JP-A-51-3238 refers to a rough particle size distribution. However, it does not specifically disclose the magnetic properties closely related to the developability of the developer and the transportability in the developing device. Further, all the carriers in the examples are about 80% by weight at 250 mesh or more.
The average particle diameter is also 60 μm or more.

Japanese Patent Application Laid-Open No. 58-144839 discloses only the average particle size, and the amount of fine powder which affects the adhesion of the carrier to the photoreceptor and the coarse powder which affects the sharpness of the image. The quantity is not described in detail with reference to the quantity. Further, Japanese Patent Application Laid-Open No. 61-204646 discloses a combination of a copying machine and an appropriate developer as the gist of the invention, and does not specifically describe the particle size distribution and magnetic properties of the carrier. Furthermore, it does not even disclose why the developer is effective in the copying machine.

Japanese Patent Application Laid-Open No. 49-70630 discloses that
The magnetic force of the carrier is described, but these are iron powder having a higher specific gravity than ferrite as a carrier material, and have a high saturation magnetization. Conventionally, these iron powder carriers have been used in many cases. However, since the specific gravity is large, the copying apparatus is liable to increase in weight and the driving torque is overloaded, and the environment is highly dependent.

Further, the ferrite carrier described in Japanese Patent Application Laid-Open No. 58-23032 is for a material having a large number of porous holes, and such a carrier easily generates an edge effect and has low durability. It turns out to be poor.

Until now, a developer capable of continuously copying an image having a large image area with a small amount of developer and satisfying the characteristic characteristic of color copying in which an edge effect does not occur even after durability has been desired. ing. Although studies have been made on developers and carriers, most of them have been proposed in consideration of black-and-white copying, and very few have been proposed as applicable to full-color copying. In addition, a carrier having an ability to continuously copy an image having an image area of 20% or more, which is almost a solid image, a reduction in edge effect, and an ability to maintain uniformity of image density in one copy is available. Long awaited.

In view of this, Japanese Patent Application Laid-Open No. 2-281280 proposes a carrier having a narrow particle size distribution in which the amount of fine powder and the amount of coarse powder are controlled, thereby achieving a carrier having improved development characteristics.

However, as described above, the demand for high definition and high image quality of the copying machine is increasing in the market, and in the technical field, it is intended to achieve high image quality by reducing the particle size of the toner. Attempts have been made, however, as the particle size becomes smaller, the surface area per unit weight increases, and the amount of charge of the toner tends to increase.

As described above, attempts have been made to further reduce the diameter of the carrier for the purpose of preventing the image density from being reduced and the durability from being reduced due to the reduction in the particle diameter of the toner, or improving the development efficiency. However, in such carriers,
At present, it is not possible to obtain sufficient quality to cope with a change in the charge amount due to durability.

The present inventors have proposed an image forming method comprising:
As a result of intensive studies on highlight reproducibility and fine line reproducibility, when a toner having a specific particle size distribution and a spherical carrier are used, high image quality with excellent image density, highlight reproduction, fine line reproduction, etc. It has been found that stabilization of their durability can be achieved by improving the fluidity of the developer.

First, as an adverse effect when the carrier and the toner are reduced in particle size, the fluidity of the developer is reduced, and the developer in the developing device is hardly circulated. As a countermeasure for this, there is a change in apparatus conditions such as increasing the stirring intensity in the developing device, but this is not preferable because it causes a problem such as shortening the durability life of the developer. Therefore, it is important to ensure a certain level of fluidity as a developer. To ensure the fluidity of the developer,
Several means are conceivable.

The present inventors have found that it is effective to control the carrier fluidity as one of them.

The present inventors have also found that it is effective to further incorporate a resin having a low surface energy into the coating resin of the resin-coated carrier in order to improve the fluidity of the developer.

[0021] What defines the fluidity of the carrier is:
JP-A-63-41865 and JP-A-1-2596.
No. 2 discloses this. However, when a smaller carrier is used in the present invention, J
It is difficult to perform measurement by IS-Z2502, and it is difficult to obtain reproducibility.

Further, the above publication is limited only to the carrier, and does not include the influence of the chargeability on the toner side and other additives. Therefore, even if the fluidity of the carrier is constant, a good result is not always obtained in reality. For this reason, it is important to pay attention to the developer fluidity including the effect of the chargeability and the toner surface. Furthermore, it is important to control the ratio of these two types of fluidity in order to reduce the influence of toner density fluctuation and the temperature and humidity of the use environment.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-component developer which solves the above-mentioned problems.

A further object of the present invention is to provide a two-component developer which is clear and has excellent gradation.

It is a further object of the present invention to provide a two-component developer having good transportability in a developing device.

It is a further object of the present invention to provide a two-component developer which does not change its performance over a long period of use.

It is a further object of the present invention to provide a two-component developer which does not change its performance with respect to environmental changes.

A further object of the present invention is to provide a two-component developer capable of obtaining a high image density with a small consumption.

A further object of the present invention is to provide a two-component developer capable of forming a toner image excellent in resolution, gradation and fine line reproducibility even in an image forming apparatus using a digital image signal. It is.

[0030]

The present invention relates to a two-component developer containing at least a nonmagnetic colorant-containing resin particle, a toner having an external additive, and a carrier,

(1) The toner has a weight average particle size of 3 to 7 μm, contains 10 to 70% by number of toner particles having a particle size of 4 μm or less, and contains 2 to 8% or more of toner particles having a particle size of 8 μm or more. -20% by volume, 10.08
contains 6% by volume or less of toner particles having a particle size of not less than μm,

(2) The fluidity (A) of the carrier is 10
16 (sec / 50 g),

(3) The fluidity (B) of the developer is 22 to 5
5 (sec / 50 g),

(4) A two-component developer characterized in that the ratio B / A of the carrier fluidity (A) to the developer fluidity (B) is 1.8 to 3.7.

The present invention will be described in more detail.

As the toner, toner particles having a particle diameter of 4 μm or less are 10 to 70% by number of the total number of particles, preferably 15 to
60% by number is good. 1 toner particle having a particle size of 4 μm or less
When the content is less than 0% by number, the amount of non-magnetic toner particles effective for high image quality is small, and in particular, as the toner is used by continuing copying or printing, the effective non-magnetic toner particle component is reduced. The balance of the particle size distribution of the non-magnetic toner indicated by (1) is deteriorated, and the image quality may be gradually reduced.

If it exceeds 70% by number, toner particles are likely to aggregate with each other, and the toner particles tend to be larger than the original particle size, resulting in poor image quality, reduced resolution, or The density difference between the edge portion and the inside of the latent image is increased, and the image tends to be slightly hollow.

Further, particles having a particle size of 8 μm or more are 2.0 to 20.0%.
%, Preferably 3.0 to 18.0% by volume.
Volume% is good. If the content is more than 20.0% by volume, the image quality is deteriorated, and the development is performed more than necessary, that is, the toner is overloaded, which leads to an increase in toner consumption. On the other hand, 2.0
If the amount is less than the volume%, there is a possibility that the image quality may be deteriorated due to a decrease in fluidity regardless of how the toner formulation is devised.

In order to further improve the effect of the present invention, 5.04 is used for the purpose of improving the chargeability of the toner.
The particles having a particle size of μm or less are more than 40% by number and 90% by number or less, preferably more than 40% by number and 80% by number or less,
Further, it is more effective that the particles having a particle size of 10.08 μm or more are set to 0 to 6% by volume, preferably 0 to 4% by volume.

On the other hand, the carrier preferably has a weight average particle size of 15 to 45 μm,
m is preferably 1-20%, more preferably 2-10%, even more preferably 2-6%.
%, And the carrier particles smaller than 16 μm are preferably 3% or less, more preferably 1% or less, and still more preferably 0.5% or less.

If the amount of the fine powder exceeds the above-mentioned value, the allowable range of developing conditions for carrier adhesion becomes small, and if the amount of carrier particles smaller than 22 μm is less than 1%, the magnetic brush becomes sparse. In addition, the rise of the charge of the toner is deteriorated, and the toner is easily scattered or fogged.

As described above, as an adverse effect caused by reducing the particle size of the carrier and the toner, the fluidity of the developer is reduced, and the developer in the developing device is hardly circulated. As a countermeasure for this, there is a change in apparatus conditions such as increasing the stirring intensity in the developing device, but this is not preferable because it causes a problem such as shortening the durability life of the developer. Therefore, it is important to ensure a certain level of fluidity as a developer. As a means for ensuring the fluidity of the developer, it is effective to control the shape of the carrier. That is, the fluidity is improved by increasing the sphericity of the carrier particles.

In general, it is difficult to increase the degree of spheroidization as the particle size of the carrier is reduced. However, in order to adjust the degree of spheroidization as described above, adjustment of manufacturing conditions, for example, a spray drying method is required. When used, the viscosity of the slurry can be adjusted, the temperature, and the use of additives can be used, but there is no particular limitation. In other methods, the sintering temperature can be adjusted. Further, it is effective to include a silicon-based or fluorine-based material having a low surface energy in the coating resin of the resin-coated carrier in terms of improving fluidity.

As a method for measuring the fluidity of the developer, JIS-
In the case where the method is carried out based on Z2502, when applied to the toner and the carrier having a small particle size according to the present invention, the flowability of the developer becomes worse than that of the normal particle size, so that the outlet of the funnel is easily clogged. Therefore, reproducibility and measurement accuracy are extremely deteriorated. Therefore, the present inventors have conducted studies and found that a larger judging means can be used as a preferable judging means by measuring the outlet diameter of the funnel.

That is, the desirable fluidity of the developer in the present invention is 22 to 55 (sec / 50 g). It is more preferably from 23 to 48 (sec / 50 g), and even more preferably from 24 to 46 (sec / 50 g). If the time is longer than 55 seconds, the fluidity is poor, and charging of the supplied toner cannot be performed smoothly, resulting in image deterioration. If the time is less than 22 seconds, a phenomenon in which the developer flows as a small lump is observed, and toner scattering and ground fogging occur.

In the present invention, the flow rate of the carrier is 10 to 16 (seconds / 50 g), preferably 10 to 1
4 (sec / 50 g). If the time is longer than 16 seconds, the fluidity is poor and the fineness of the image is poor. If the time is shorter than 10 seconds, the shape of the carrier must be substantially spherical, and the apparent density must be increased. This limits the material and increases the cost.

Further, in the present invention, the ratio between the fluidity (A) of the carrier and the fluidity (B) of the developer is also important.
Is 1.8 to 3.7, and preferably 1.9 to 3.6. The reason is that when the value of the fluidity of the developer is lower than the value of the fluidity of the carrier and the flow speed is 1.7 or less, the mixing property between the replenished toner and the developer tends to be inferior. It is easy to cause fog.

On the other hand, when the flow rate of the developer is low and the flow rate of the developer is low with respect to the flow rate of the carrier, the image quality is slightly degraded as the number of copies increases, and toner scattering is likely to occur.

Incidentally, the magnetic properties of the carrier are affected by the magnet roller built in the developing sleeve, and greatly affect the developing properties and the transportability of the developer.

The saturation magnetization of the carrier is 50 to 90 e
When the value is mu / g, the image is excellent in uniformity and gradation reproducibility, and is suitable.

Further, if the residual magnetization and coercive force of the carrier are too high, good transportability of the developer in the developing device is hindered,
As an image defect, blurring or uneven density in a solid image is likely to occur, and the developing ability is reduced. Therefore, in order to maintain the developability, the residual magnetization is preferably 10 emu / g or less, more preferably 5 emu / g or less, and preferably the coercive force is 40 emu / g or less.
It has been confirmed that it is less than Oersted (3000 Oersted, with respect to the applied magnetic field), more preferably 30 Oersted or less, even more preferably 10 Oersted or less.

Further, according to the present invention, as an external additive of the toner,
It is desirable to contain titanium oxide fine particles. In particular, anatase-type titanium oxide fine particles subjected to a surface treatment while hydrolyzing a coupling agent in an aqueous system are extremely effective in terms of stabilizing charging, imparting fluidity, and the like. This has not been achieved with the commonly known hydrophobic silica as a flow improver.

The reason is that the silica fine particles themselves have strong negative chargeability, whereas the titanium oxide fine particles have almost neutral chargeability. Conventionally, it has been proposed to add hydrophobic titanium oxide. However, titanium oxide fine particles originally have a smaller surface activity than silica, and hydrophobicity has not always been sufficiently achieved. In addition, when a large amount of a treating agent or the like is used or a highly viscous treating agent is used, the degree of hydrophobicity is certainly increased, but coalescence of the particles occurs, and the ability to impart fluidity is reduced. And stabilization of fluidity have not always been achieved.

On the other hand, although hydrophobic silica is excellent in its fluidity-imparting ability, when it is contained in a large amount, on the contrary, due to its strong chargeability, it causes electrostatic aggregation, and its fluidity-imparting ability decreases. There is a tendency. In this regard, as the amount of titanium oxide increases, the fluidity of the toner improves.

The particle size is 0.0
1 to 0.2 μm is desirable. If the particle size is larger than 0.2 μm, toner charging due to poor fluidity becomes non-uniform, resulting in toner scattering and fogging. Also 0.
When the thickness is smaller than 01 μm, the toner is easily embedded on the surface of the toner, so that the toner deteriorates quickly and the durability is reduced. This tendency is particularly remarkable in the case of a sharp melt color toner. The particle size of titanium oxide can be measured with a transmission electron microscope.

In the present invention, as a method for treating titanium oxide, a method in which titanium oxide is mechanically dispersed in an aqueous system so as to have a primary particle size and the coupling agent is hydrolyzed is effective. Yes, it is preferable in that no solvent is used.

The titanium oxide of the present invention is suitable for satisfying the developer fluidity and obtaining good results.

When the particle size of the toner is reduced, the surface area per weight increases, and excessive charging due to rubbing is liable to occur. On the other hand, titanium oxide fine particles which can control charging and impart fluidity have a great effect. The content of titanium oxide suitable for the present invention is 0.5 to 5% by weight, preferably 0.7 to 3% by weight, more preferably 1.0 to 2.5% by weight.

The toner according to the present invention may contain a charge control agent in order to stabilize the charge characteristics. Examples of the negative charge control agent at that time include, but are not particularly limited to, organometallic complexes such as a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex or a zinc complex of di-tert-butylsalicylic acid). 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.

Generally, good results can be obtained when the mixing ratio of the toner and the carrier according to the present invention is 2 to 12% by weight, preferably 3 to 9% by weight as the toner concentration in the developer. If the toner concentration is less than 2% by weight, the image density is too low to be practical, and if it exceeds 10% by weight, fog and scattering inside the machine are increased, and the useful life of the developer is shortened.

Examples of the coloring agent used in the present invention include magnetite, carbon black and the like, as well as known dyes and pigments such as phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, It can be used widely such as permanent yellow and benzidine yellow.
The content is 1 to 100 parts by weight of the binder resin.
It is not more than 2 parts by weight, preferably 0.5 to 9 parts by weight.

Additives may be added to the toner of the present invention as needed as long as the properties of the toner are not impaired. Examples of such additives include Teflon, zinc stearate, and polyvinylidene fluoride. Lubricants, fixing aids (eg, low molecular weight polyethylene, low molecular weight polypropylene, etc.), and organic resin particles.

In the production of the toner of the present invention, the constituent materials are well kneaded by a hot kneader such as a hot roll, kneader, extruder, etc., and then mechanically pulverized and classified to obtain the toner. After dispersing a material such as a colorant in the method obtained by spray drying, or
After mixing the predetermined material with the monomer that should constitute the binder resin,
Each method such as a polymerization toner production method of obtaining a toner by polymerizing this emulsion suspension can be applied.

As the binder used in the toner of the present invention, various material resins conventionally known as toner binder resins for electrophotography are used.

For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer and styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer 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 carrier used in the developer of the present invention is preferably a carrier coated with a resin, and an electrically insulating resin is used as a coating resin on the surface of the carrier, which is appropriately selected depending on a toner material and a carrier core material. . In the present invention, in order to improve the adhesion to the carrier core material surface, at least one monomer selected from acrylic acid (or ester thereof) monomer and methacrylic acid (or ester thereof) monomer is used. It is desirable to contain, but there is no particular limitation. In particular, when polyester resin particles having high negative chargeability are used as a toner material, it is possible to further use a copolymer with a styrene monomer for the purpose of stabilizing charging. It is preferable that the copolymer weight ratio be 5 to 70% by weight.

Examples of the monomer for producing a coating resin for a carrier core material usable in the present invention include styrene-based monomers such as styrene monomer, chlorostyrene monomer, α-methylstyrene monomer and styrene-chlorostyrene monomer. Examples of the system monomer include acrylate monomers (methyl acrylate monomer, ethyl acrylate monomer, butyl acrylate monomer, octyl acrylate monomer, phenyl acrylate monomer, 2-ethylhexyl acrylate monomer), and methacrylate monomer. (Methyl methacrylate monomer, ethyl methacrylate monomer, butyl methacrylate monomer, phenyl methacrylate monomer) and the like, but are not particularly limited.

In order to achieve the fluidity of the present invention, it is possible to use a silicone resin such as polysiloxane or a fluorine resin such as polyvinylidene fluoride alone or together with another resin as a coating material.

As the material of the core material of the carrier used in the present invention, for example, metals such as iron, nickel, cobalt, manganese, chromium, rare earths and the like, and their alloys or oxides, magnetic materials dispersed or not oxidized. Although resin particles and the like can be used, ferrite particles are more preferably used than metal oxides.

There is no particular limitation on the manufacturing method.

When the average particle size of the carrier is less than 4 μm, the carrier is easily developed (transferred together with the toner) on the latent image holding member, and the latent image holding member and the cleaning blade are easily damaged. Even when the thickness is less than 10 μm, the same tendency is likely to occur due to a difference in development conditions. Such a carrier core material may be composed of only a magnetic material, may be composed of a combination of a magnetic material and a non-magnetic material, and may be a mixture of two or more magnetic particles. May be.

As a method of coating the surface of the carrier core material with the above coating resin, the resin is dissolved or suspended in a solvent and applied to the surface of the core material, and the resin is coated with a core material made of magnetic particles or the like. It is preferable to use a method in which a solvent is used, but a dry pressure bonding method using no solvent is also possible, and there is no particular limitation.

The treatment amount of the coating resin is generally 0.1 to 3 with respect to the carrier core material in total from the film forming property and durability of the coating material.
0% by weight (preferably 0.5 to 20% by weight) is desirable.

The method for measuring the characteristic value of the developer of the present invention will be described below. (1) Magnetic properties of carrier: BHU-60
Type magnetization measurement device (manufactured by RIKEN) is used. Specifically, about 1.0 g of a measurement sample was weighed, the inner diameter was 7 mm, and the height was 1
The cell is packed in a 0 mm cell and set in the above-mentioned device. In the measurement, an applied magnetic field is gradually applied to change the maximum to 3,000 Oe. Next, the applied magnetic field is decreased, and finally a hysteresis curve of the sample is obtained on the recording paper. Than this,
Obtain the saturation magnetization, residual magnetization, and coercive force. (2) Measurement of the particle size distribution of the carrier: The measurement was performed using an SRA type Microtrac particle size analyzer (Nikkiso Co., Ltd.) with a range setting of 0.7 to 125 μm. (3) Measurement of toner particle size: The particle size distribution can be measured by various methods. In the present invention, the measurement is performed using a Coulter counter.

That is, a Coulter counter TA-II type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) for outputting the number average distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) are connected. The electrolyte is 1% sodium chloride.
% NaCl aqueous solution is prepared. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, is used as a dispersant in 100 to 150 ml of the electrolytic aqueous solution.
Add 5 ml, and further add 2-20 mg of the measurement sample.
The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the volume and number of the toner were measured using the Coulter Counter TA-II, using a 100 μm aperture as the aperture. The volume distribution and number distribution of 〜40 μm were calculated. Then, according to the present invention, the weight-average weight average diameter (D
4) (The median value of each channel is taken as a representative value for each channel), the amount of weight-based coarse powder (1
6.0 μm or more), and the number-based fine powder number (5.04 μm or less) determined from the number distribution. (4) Hydrophobicity measurement: The methanol titration test is an experimental test for confirming the hydrophobicity of a titanium oxide fine powder having a hydrophobized surface.

The "methanol titration test" defined herein for evaluating the degree of hydrophobicity of the treated fine titanium oxide powder is carried out as follows. 0.2 g of the test titanium oxide fine powder was added to 50 m of water in a 250 ml Erlenmeyer flask.
Add to l. Methanol is titrated from the burette until all of the titanium oxide is wetted. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed as the entire amount of titanium oxide fine powder is suspended 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. (5) Carrier fluidity measurement method: In this experiment, the carrier fluidity was measured as follows.

The carrier was heated at a temperature of 23 ° C. ± 2 ° C. and a humidity of 60%.
After leaving for 24 hours in an environment of ± 3%, measurement is performed. The measuring method is based on JIS-Z2502, but the heating and drying steps are omitted. Here, the measuring device is as shown in FIG. 1, but a modified funnel as shown in FIG. 2 (a is a plan view, b is a cross-sectional view) is used. (6) Developer Fluidity Measurement Method: In this experiment, the developer fluidity was measured as follows.

That is, the toner and the carrier are mixed at an actually used toner concentration (0.5 to 20%),
After 24 hours in an environment of 3 ° C. ± 2 ° C. and humidity 60% ± 3%, measurement is performed. The measuring method is based on JIS-Z2502, but the heating and drying steps are omitted. Here, the measuring device is as shown in FIG. 1, but a modified funnel as shown in FIG. 2 (a is a plan view, b is a cross-sectional view) is used.

[0079]

EXAMPLES Parts means parts by weight.

Example 1 A polyester resin obtained by condensing 100 parts of propoxylated bisphenol and fumaric acid 4 parts 4 parts of a chromium complex of di-tert-butylsalicylic acid 4 parts of chromium complex salt of di-tert-butylsalicylic acid were sufficiently premixed with a Henschel mixer, and then biaxially mixed. The resulting mixture was melt-kneaded by a type extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified by a multi-segment classification device, and 2 to 8 μm was selected so as to have the particle size distribution of the present invention, thereby obtaining colorant-containing resin particles.

The particles were added to hydrophilic anatase type titanium oxide fine particles (particle size: 0.05 μm, BET: 120 m ² /
g) while mixing and stirring in an aqueous system, while n-C ₄ H ₉ Si
(OCH ₃ ) ₃ is dispersed in an aqueous system, and is added to and mixed with the titanium oxide fine particles while hydrolyzing so that the solid content is 20% by weight so that the particles do not coalesce, and then dried and crushed. The obtained degree of hydrophobicity was 70% and the average particle size was 0.05 μm.
m of titanium oxide was mixed with a Henschel mixer to obtain a cyan toner.

This cyan toner has a weight average particle diameter of 5.7 μm, 19.8% by number of toner particles of 4 μm or less, 53.2% by number of toner particles of 5.04 μm or less, and 7.3% by weight of toner particles of 8 μm or more. 4% by volume, 0.6% by volume of toner particles of 10.08 μm or more
Met.

A carrier was mixed with 7 parts of the cyan toner so that the total amount of carrier A in Table 1 was 100 parts to prepare a developer.

When the carrier fluidity and the developer fluidity were measured, they were 11.6 (sec / 50 g) and 34.7, respectively.
(Second / 50 g), and the value of developer fluidity / carrier fluidity was 3.0. (Hereinafter, the carrier fluidity, the developer fluidity, and the ratio between them are shown in Table 2.) A commercially available Canon color copier CLC-
The test was carried out under a 23 ° C./60% temperature and humidity environment using a 500 (partial modification of the screw shape of the developing device, a built-in magnet roller of a 5-pole configuration having a developing sleeve of 960 gauss in the developing sleeve) (development conditions V _cont = 350V, V _back =-
130V). As a result, the image density excellent in image fineness was stable at 1.5 to 1.6 even after 10,000 sheets of printing, and good results were obtained.

Example 2 Example 1 was the same as Example 1 except that the mixing amount of titanium oxide during the production of the toner was changed from 1.5 to 2.2%.
When image formation was performed in the same manner as in Example 1, good results were obtained.

Example 3 Example 1 was repeated except that the mixing amount of titanium oxide was changed from 1.5% to 1.3% during the production of the toner, and the carrier B in Table 1 was used instead of the carrier A. When image formation was performed in the same manner as in Example 1, good results were obtained.

Example 4 Example 1 was repeated except that the mixing amount of titanium oxide during toner production was changed from 1.5 to 1.8%, and the carrier B was replaced with the carrier A shown in Table 1. When image formation was performed in the same manner as in Example 1, good results were obtained.

Example 5 An image was formed in the same manner as in Example 1 except that the carrier C shown in Table 1 was used instead of the carrier A as a carrier. Is 1
After 10,000 copies, the image was slightly inferior to Example 1 in terms of image fineness. However, there were no problems such as fog and scattering, and good results were obtained.

Comparative Example 1 An image was formed in the same manner as in Example 1 except that titanium oxide mixed during the production of the toner was not subjected to a hydrophobic treatment. Although the fineness of the image was slightly inferior, the fine line reproducibility became slightly worse as the number of copies increased.

Comparative Example 2 2.2 Silicic acid fine powder (BET 170 m ^{2 /} g) treated in Example 3 with hydrophobic treatment with dimethyldichlorosilane instead of mixing 1.3% of titanium oxide during toner production
When image formation was performed in the same manner as in Example 3 except that% was used, the fog tended to worsen, albeit slightly, as the number of copies increased.

Comparative Example 3 In Example 5, the titanium oxide mixed during the production of the toner was obtained by treating the titanium oxide fine particles in a dimethylpolysiloxane gas phase of 5,000 centistokes in a solid content of 30% by weight based on the solid content. Hydrophobicity 90%, average particle size 0.
Using titanium oxide of 07 μm, the mixing amount is 1.5 to 2.
When image formation was performed in the same manner as in Example 4 except that the amount was changed to 2%, toner scattering and fogging were slightly inferior during 10,000-sheet running.

Comparative Example 4 In Example 5, 1.5% of titanium oxide was used during toner production.
Instead of mixing, silicate fine powder (BET 170 m ² / g) which has been subjected to a hydrophobizing treatment with dimethyldichlorosilane is added to 0.1%.
When image formation was performed in the same manner as in Example 4 except that 7% was used, the image quality deteriorated, and fog increased slightly after copying 10,000 sheets.

COMPARATIVE EXAMPLE 5 In Example 3, 1.5 parts of titanium oxide were added during the production of the toner.
%, But instead of using 0.7% of a silicic acid fine powder (BET 170 m ² / g) subjected to a hydrophobizing treatment with dimethyldichlorosilane, an image was formed in the same manner as in Example 3. Although a good image was obtained, toner scattering slightly occurred during copying of 10,000 sheets.

Comparative Example 6 An image was formed in the same manner as in Example 1 except that Carrier D having a lower sphericity than Carriers A, B and C in Table 1 was used instead of Carrier A. Although almost the same image as that of No. 1 was obtained, toner scattering slightly increased after copying 10,000 sheets, and particularly, the fineness of the image deteriorated. A good sphericity ratio means that many particles close to a true sphere are contained by carrier particle observation using a scanning electron microscope (SEM). In addition, poor sphericity means that particles close to a true sphere found by the same method are few and many are irregularly shaped.

Comparative Example 7 An image was formed in the same manner as in Example 1 except that the carrier E having a large particle diameter was used instead of the carrier A. The toner scattering at the time of copying 10,000 sheets was slightly inferior. And the reproducibility of the fine line was slightly inferior.

Comparative Example 8 An image was formed in the same manner as in Example 5 except that the carrier F having a small particle diameter was used instead of the carrier C. The reproduction of fog and fine lines at the time of copying 10,000 sheets was performed. The sex was slightly inferior.

Table 2 shows the evaluation results of the above Examples and Comparative Examples.
Are shown together.

[0098]

[Table 1]

[0099]

[Table 2]

[0100]

According to the present invention, there is provided a two-component developer in which the toner having a small particle diameter is improved in chargeability and durability. By using the two-component developer of the present invention, the number of copies can be increased. In this case, stable charging is maintained, and a high-quality image can be obtained over a long period of time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring the flow rates of a carrier and a developer.

FIG. 2 is an explanatory view of a funnel in the apparatus of FIG.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/08-9/10

Claims (3)

(57) [Claims] 1. A two-component developer containing toner and carrier having at least a non-magnetic colorant-containing resin particles and an external additive, (1) a weight average particle diameter of the toner be 3~7μm , 4
10 to 70% by number of toner particles having a particle size of μm or less
Toner particles having a particle size of 8 μm or more
Contains 20% by volume and has a particle size of 10.08 μm or more
That the toner particles are contained less than 6% by volume, (2) fluidity of the carrier (A) is 10 to 16 (sec / 5
(3) The fluidity (B) of the two-component developer is 22 to 55.
(Second / 50 g), and (4) the ratio B / A of the fluidity (A) of the carrier to the fluidity (B) of the two-component developer is 1.8 to 3.7. Two-component developer. 2. The two-component developer according to claim 1, further comprising at least titanium oxide fine particles as an external additive. 3. A toner having a particle size distribution of 5.04 μm.
2. The two-component developer according to claim 1, wherein more than 40% by number of toner particles having a particle size of m or less are present.