JPH06289648A - Developer and developing method - Google Patents

Abstract

PURPOSE:To provide a developer showing no change in performance even used for a long term so that picture images of high quality with high picture density and no fog can be obtd. CONSTITUTION:This developer is used for such a developing method that a magnetic brush having 5-20 volume % toner particles is formed in a developing zone formed by a latent image holder and a developer carrier and an AC electric field at >=2.5kHz frequency is applied on the brush. In the distribution of particle size of the developer the toner, the proportion of particles having 2.0-4.0mum particle size is 15-40% in number, and the proportion of particles having 4.0-8.0mum particle size is >=60% in number. The charge amt. of the toner when mixed with an iron powder carrier is >=¦-30¦muC/g.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer and a developing method for developing an electrostatic latent image in an image forming method such as electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art In recent years, with the widespread use of image forming apparatuses such as electrophotographic copying machines, their applications have been widespread and demands on their image quality have become strict. When copying an image such as a general document or photograph, it is required to reproduce extremely finely and faithfully without crushing or breaking even a minute portion. Recently, in an image forming apparatus such as an electrophotographic printer that uses a digital image signal, a latent image is formed by collecting dots, and a reproducibility of a smaller latent image is required.
In particular, when trying to obtain a full-color image, the reproducibility of the latent image becomes more important because the ratio of minute dots increases in order to express a wide range of colors.

Heretofore, some developers have been proposed for the purpose of obtaining a good image. JP-A-5
In JP-A 8-129437, the average particle size is 6 to 10 μm.
A non-magnetic toner having a maximum number of particles of 5 to 8 μm has been proposed, but the number of particles of 5 μm or less is as small as 15% by number or less, and as a high resolution toner that faithfully reproduces a minute dot latent image. Still, there is still room for improvement. According to Japanese Patent Application Laid-Open No. 2-282755, toner particles of 5 μm or less clearly reproduce a minute dot latent image, and have a main function for dense toner paste on the entire latent image. It is said that particles of 5 μm or less are effective in solving the problem of highlight gradation. Based on such knowledge, Japanese Patent Laid-Open No. 2-282755 proposes a toner containing 15 to 40% by number of toner having a particle diameter of 5 μm or less.

Further, in JP-A-2-877, 5 μ
A toner containing 17 to 60% by number of toner having a particle diameter of m or less is proposed.

However, the studies by the present inventors have revealed that the inclusion of a certain amount of toner having a particle diameter of 5 μm or less does not work in all aspects. Of the toner with a particle size of 5 μm or less,
It was found that unless the toner having a particle diameter of 2.0 to 4.0 μm is set to a certain ratio or less, the fog is deteriorated and the effect of improving the image quality is canceled.

So far, there have been few discussions about toner particles having a particle size of 2.0 to 4.0 μm. Japanese Patent Laid-Open No. 60-140361 exemplifies that the toner content of particles having a particle diameter of 2.5 μm or less is 0% and 4%, but the average particle diameter at this time is as large as 9.5 μm. However, it is not possible to expect a great effect for improving the image quality as in the present invention. The claim of this publication does not include particles having an average particle size of 1/4 or less, but if this is applied to the present invention, in the case of the present invention, since the average particle size is about 6 to 7 μm, it is 2 μm or less. I'm discussing. Therefore, the technology is different from the present invention.

Further, in JP-A-2-284151, the content ratio of the toner having a particle diameter of 2.0 to 2.5 μm is exemplified. From this, the content ratio of 2.0 to 4.0 μm is estimated. However, it is difficult to discuss.

Further, Japanese Patent Application Laid-Open No. 2-877 discloses some toner particle size distribution data, but according to the study by the present inventors, the particle size distribution is controlled as in the prior art. It was found that the improvement of the image quality is not sufficient only by itself. That is, as the particle size of the toner becomes smaller, the charge per particle sharply decreases, and the fidelity to the latent image deteriorates. Therefore, the image quality does not improve as expected, or the fog worsens in severe cases. Also,
When the particle size of the toner becomes small, it is generally necessary to set the toner concentration in the developer low in order to avoid toner scattering, but this also reduces the toner supply amount to the latent image, so Hinder the improvement of

Further, according to the studies made by the present inventors, it has been found that when the toner particle size is made small, the image quality is changed by the developing bias, and the effect of making the toner small is sufficiently exerted, and It has been found that the frequency of the AC component is particularly important for overcoming the adverse effects.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer and a developing method which have high image density, excellent fine line reproducibility and fine dot reproducibility, and which can obtain an image without fog. is there.

Further, an object of the present invention is to provide a developing agent and a developing method capable of obtaining a high image density with a small consumption amount.

Further, an object of the present invention is to provide a developing agent and a developing method which have no change in performance with respect to environmental changes.

Further, an object of the present invention is to provide a developing agent and a developing method which do not change in performance after being used for a long time.

Further, an object of the present invention is to provide a developing agent and a developing method capable of obtaining an OHP image having good translucency.

[0015]

The above objects can be achieved by the following constitutions.

That is, in a developer comprising a resin particle containing at least a binder resin and a colorant, a non-magnetic toner containing at least a fluidity-imparting agent, and a carrier, the toner has a particle size distribution of 2. The content of toner particles having a particle size of 0 to 4.0 μm is 15 to 40% by number,
The content of toner particles having a particle diameter of 4.0 to 8.0 μm is 60.
% Or more, and the charge amount of the toner when mixed with the iron powder carrier is |-
Achieved with a developer that is 30 | μC / g or more.

Further, using this developer, a magnetic brush is formed in the developing area defined by the latent image carrier and the developer carrier so that the volume ratio of the toner particles is 5 to 20%. This is achieved by a developing method which applies an alternating electric field having an alternating component with a frequency above 2.5 kHz.

The present invention will be described in detail below.

According to the study by the present inventors, in the toner particle size distribution, the content ratio of the toner particles having a particle size of 2.0 to 4.0 μm is 15 to 40% by number, and the content of 4.0 to 8. 0μ
It was found that the content of the toner particles having a particle diameter of m of 60% by number or more is optimal for forming a high quality image. More preferably, the content of the toner having a particle diameter of 2.0 to 4.0 μm is 20 to 35% by number and 4.0.
The content of toner having a particle size of ˜8.0 μm is 65% by number or more, and the content of toner having a particle size of more than 8.0 μm is 1
It is preferably 0% or less.

When the particle size distribution of the toner developed into a minute latent image is measured, it is smaller than the particle size distribution of the original toner, and it is conventionally known that there are many toner particles of 5 μm or less. However, according to the study of the present inventors, it was found that the toner having a particle diameter of 2.0 to 4.0 μm needs to be controlled separately. That is, a certain condition is necessary for the toner having a particle diameter of 2.0 to 4.0 μm to exert the effect of improving the image quality, and one of them is to set the content rate to an appropriate range. . When the content is 15% by number or more, even a minute latent image can be reproduced without protruding and the image quality is improved. However, when it exceeds 40% by number,
Fogging becomes worse, and a phenomenon in which even if a latent image should be present, the image is hardly developed begins to occur. A possible reason for this is that the toner having such a small particle size has a small amount of electric charge per particle and is not faithful to the electric field of the latent image. For example,
Since the toner having a particle diameter of 3.0 μm has a surface area that is 1/4 that of a toner having a particle diameter of 6.0 μm, the charge amount per toner particle should also be 1/4. In this way, 2.0-
The content of the toner having a particle diameter of 4.0 μm needs to be strictly controlled.

It is difficult to measure the content of toner having a particle size of 2.0 to 4.0 μm by 40% by number or less (normal condition, 100 μm aperture) with a particle size of less than 2.0 μm. The toner content will also be reduced (if a general classification method is used). It is considered that the toner having a particle diameter of less than 2.0 μm also has a large adverse effect on the image quality due to the above mechanism. Also,
A toner having a particle diameter of 4.0 μm or less, particularly a toner having a particle diameter of less than 2.0 μm occupies a large surface area of the carrier for its weight, and therefore a large content causes toner scattering. From these aspects as well, the content of the toner having a particle size of 2.0 to 4.0 μm needs to be 40 number% or less.

On the other hand, the toner having a particle diameter of 4.0 to 8.0 μm contributes to the improvement of the image quality and has less harmful effects, and it is preferable that the content rate is as large as possible. 60 pieces%
With the above, the effect of improving the image quality is sufficiently exhibited. Further, since the toner having this particle size is thinly and uniformly fixed on the image, the image density becomes high even with a small amount of toner. As a result, if copying is performed with the same image density, the toner consumption amount is small, and since the toner layer is thin, the transparency of the OHP image is also good.

In the present invention, a toner having a particle size of more than 8.0 μm is also included, but a large toner having a particle size of more than 16 μm disturbs the image and therefore is substantially not contained (0% in volume distribution). preferable.

As mentioned above, the improvement of the image quality is not sufficient only by controlling the particle size distribution. The present inventors have found that the chargeability of the toner is important as a condition for improving the image quality, and the charge amount needs to be increased.
The reason is considered to be the decrease in the amount of electric charge per particle due to the decrease in the surface area. What actually affects the image quality is the amount of toner charge when used as a developer,
As a method, it is important to give the toner itself a negative charging property.
The charge amount must be 0 | μC / g or more. Thereby, the charge amount of the toner in the developer is different from that obtained by relying on the positive chargeability of the coating resin of the carrier, and even if the contact frequency with the carrier varies, the chargeability of the negative chargeability of a certain degree is obtained. It becomes the range. As a result, the distribution of the charge amount becomes sharp and the image quality is improved. Further, since the carrier is not relied upon, the toner has a sufficient negative charging property even when the carrier is spent due to durability, and the life of the developer is extended.

As the binder resin used in the present invention, various conventionally known resins can be used.

For example, polystyrene, styrene-styrene copolymers such as styrene-butadiene copolymer and styrene-acrylic copolymer, ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer. Polymers, phenolic resins, epoxy resins, acrylic phthalate resins, polyamide resins, polyester resins, maleic acid resins and the like. In addition, the manufacturing method and the like of each resin are not particularly limited.

Among these resins, a polyester resin having an acid value of 5.0 or more is preferable. As a result, stable charging can be quickly obtained, and charge-up can be eliminated. As a result, a high-quality image can be stably obtained, and fluctuations in image density during running are small. Polyester resin has excellent fixability and is suitable for color toners.

[0028]

[Chemical 1]

(Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2 to 10. ), A bisphenol derivative or a substitution product represented by the formula (1) is used as a diol component, and a carboxylic acid component composed of a carboxylic acid having a valence of 2 or more or an acid anhydride thereof or a lower alkyl ester thereof (eg, fumaric acid, maleic acid, maleic anhydride, phthalate). An acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) is more preferable because it has a sharp melting property.

As the cross-linking agent, a compound mainly having two or more polymerizable double bonds may be used. Examples thereof include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters having two double bonds such as ethylene glycol acrylate; divinylaniline and divinyl ether. Also, a compound having three or more vinyl groups can be used. These cross-linking agents are used alone or as a mixture, and when the addition amount is based on the binder resin, it is necessary to use 0.01 to 5 parts by weight of the binder resin at the time of synthesis in terms of offset resistance and fixing property. Is preferred.

Even if a wax-like substance such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, sazol wax, and paraffin wax is added to the non-magnetic toner for the purpose of improving releasability at the time of heat roll fixing. good. The amount of these release agents applied is 0.1 to 8 parts by weight, preferably 0.5 to 5 parts by weight, based on the binder resin.

Further, in the present invention, since a negatively chargeable resin is used, the toner exhibits negative chargeability without using a charge control agent, but it is preferable to add a charge control agent. As the charge control agent that can be used in the present invention, for example, organic metal complexes and chelate compounds are effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and chromium 3,5-ditertiary-butylsalicylate. There is. In particular, acetylacetone metal compounds (including monoalkyl-substituted compounds and dialkyl-substituted compounds) and salicylic acid-based metal compounds (including monoalkyl-substituted compounds and dialkyl-substituted compounds) are preferable, and ditertiary-butylsalicylic acid chromium or zinc It is preferable that the compound does not affect the color tone of the toner. The applied amount of these charge control agents is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on the binder resin.

On the other hand, in the present invention, the magnetic brush is formed in the developing region defined by the latent image carrier and the developer carrier so that the volume ratio of the toner particles is 5 to 20%. It is more preferably 6 to 15%. The present inventors have found that it is preferable to control the toner supply amount in the vicinity of the latent image within a certain range in order to faithfully develop the latent image. The volume ratio of toner particles is calculated as follows.

[0034]

[Equation 1]

Here, M is the coating amount of the developer per unit area of the developer carrier (sleeve) (g / cm ² ), and h is the re-proximity distance (cm) between the latent image carrier and the developer carrier. ), Ρ is the true density of the toner particles (g / cm ³ ), T / (T + C) is the toner concentration (weight ratio) of the developer, and σ is the peripheral speed ratio of the latent image carrier and the developer carrier (developer). The peripheral speed of the carrier / the peripheral speed of the latent image carrier).

When the volume ratio of the toner particles is less than 5%, the toner is less supplied to the latent image, so that the effect of reducing the toner particle size is not sufficiently exerted.
High quality images cannot be obtained. Further, the amount of toner particles attached to the latent image carrier becomes too small, and the conditions for transfer to paper, separation of paper, and cleaning of toner become strict.

On the contrary, when the volume ratio of the toner is more than 20%, the adhesion of the toner to the non-image area is increased and the fog is deteriorated, and the toner developed on the image area becomes excessive, so that the latent image is faithfully reproduced. It cannot be reproduced. In addition, the developed toner layer becomes thick and OHP transparency deteriorates, and the toner consumption also increases.

In the present invention, an alternating electric field having an AC component with a frequency of 2.5 kHz or higher is applied to the developing section. The frequency is preferably 3.0 kHz or higher, and more preferably 4.
It is 0 kHz or more. By increasing the frequency of the alternating-current component of the alternating electric field applied to the developing section, the present inventors
It was found that the effect due to the small toner particle size is increased and the adverse effect is prevented. As described above, even if the particle size of the toner is reduced, it does not directly relate to good image quality. The smaller the particle size of the toner, the more advantageous it is when the toner tries to line up with the shape of the latent image faithfully. However, if the particle size is simply reduced, the amount of charge per particle will be small, so that the toner will be faithful to the electric field of the latent image. Property deteriorates, and the latent potential of the toner cannot be fully brought out. This decrease in the fidelity of the latent image to the electric field can be compensated by increasing the frequency of the alternating electric field. It is considered that this is because if the frequency is high, the number of times of contact with the latent image carrier increases, and as a result, the fidelity is improved even if the probability of faithfully adhering to the latent image is low. This effect is, of course, in the halftone part, which is a collection of minute latent image dots,
It is also demonstrated in the solid part where the latent image is clear,
The image density of the solid portion also becomes high. Adhesion of toner to the non-image area is also reduced, so that fogging is also eliminated. In the present invention,
The main component is a toner having a particle size of 2.0 to 8.0 μm in the number distribution, but the potential of the toner of this particle size can be fully brought out.

Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, hansa yellow G and rhodamine 6.
Conventionally known dyes and pigments such as G, rhodamine lake, chalco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triarylmethane dyes, monoazo dyes and disazo dyes may be used alone or in combination.

As the additives used for the purpose of imparting various characteristics in the present invention, for example, the following ones are used.

1) Flowability-imparting agents: metal oxides (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Those subjected to a hydrophobic treatment are more preferable.

2) Abrasive: Metal oxide (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (calcium sulfate, etc.) , Barium sulfate, calcium carbonate), etc.

3) Lubricants: Fluorine-based resin powder (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salts (zinc stearate, calcium stearate), etc.

4) Charge controllable particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.), carbon black, spherical resin fine particles (average particle size 0.05 to 3 μm), etc.

These additives are used in an amount of 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner particles. These additives are
They may be used alone or in combination.

Further, the developer of the present invention is a mixture of the non-magnetic toner and a carrier. As the carrier that can be used in the present invention, known carriers can be used, for example, iron powder, ferrite powder, magnetic powder such as nickel powder, glass beads, and the like, and the surface thereof is treated with a resin or the like. The ones that have been done are listed. Further, as the resin for coating the carrier surface, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, silicone resin, fluorine-containing resin, A polyamide resin, an ionomer resin, a polyphenylene sulfide resin, or the like, or a mixture thereof can be used. As a preferable mixing ratio of the carrier and the toner, it is preferable to mix 30 to 500 parts by weight of the carrier with 10 parts by weight of the toner. The average particle size of the carrier is 5
It is preferably about 80 μm.

To prepare the non-magnetic toner of the present invention, a binder resin, and if necessary, a colorant, a charge control agent and other additives are thoroughly mixed with a mixer such as a Henschel mixer, and then heated rolls are used. It can be obtained by thoroughly kneading the constituent materials using a heat kneader such as a kneader or an extruder kneader, then mechanically crushing and classifying. Alternatively, a method in which a material such as a colorant is dispersed in a binder resin solution and then spray-dried, or a predetermined material is mixed with a monomer that constitutes the binder resin, and then suspension polymerization is performed. The toner can also be obtained by a method such as a method for producing a polymerized toner.

The measuring method according to the present invention will be described below.

(1) Particle size distribution measurement The particle size distribution of the toner can be measured by various methods.
In the present invention, it is suitable to use 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 number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) are connected. As the electrolytic solution, an approximately 1% NaCl aqueous solution is prepared using first-grade sodium chloride. For example ISOTON
-II (made by Coulter Scientific Japan) can be used. As the measuring method, the electrolytic aqueous solution 10
A surfactant, preferably 0.1 to 5 ml of alkylbenzene sulfonate is added as a dispersant to 0 to 150 ml, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter counter TA-II type was used to use a 100 μm aperture as an aperture.
The toner volume and number were measured to calculate the volume distribution and number distribution of particles of 2 to 40 μm. Then, the content ratio of the number-based fine powder according to the present invention (2.0 to 4.0 μm, 4.0
˜8.0 μm) was determined.

(2) Measurement of triboelectric charge amount The measuring method will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view of an apparatus for measuring the charge amount of toner. First, about 20 g of a mixture (weight ratio 1:19) of toner and iron powder (EFV 200 300) whose triboelectric charge is to be measured is put in a polyethylene bottle having a capacity of 50 ml and shaken by hand 500 times. About 0.5 g of the mixture is placed in a metal measuring container 2 having a screen 3 of 500 mesh on the bottom, and a metal lid 4 is placed on it. At this time, the entire measuring container is weighed to obtain W ₁ (g).
Next, in the suction device 1 (at least the portion in contact with the measurement container 2 is an insulator), suction is performed from the suction port 7 (the air volume control valve 6 is adjusted to keep the pressure of the vacuum gauge 5 at 250 mmAq). In this state, suction is carried out for 1 minute or more, preferably 2 minutes to suck and remove the toner. The potential of the electrometer 9 at this time is V
(Bolt). Here, 8 is a capacitor, and the capacitance is C (μF). Next, the total weight of the measuring container after suction is weighed to obtain W ₂ (g). The triboelectric charge amount (μC / g) of this toner is calculated by the following formula.

[0053]

[Equation 2]

The toner and iron powder to be measured were at 23 ° C. and 60
What is left for 12 hours or more in the% RH environment is used. Also, the shaking and measurement environments are 23 ° C. and 60% RH.

[0055]

EXAMPLES The present invention will be specifically described below with reference to examples. All parts in the following formulations are parts by weight.

Example 1 Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts (acid value 9.0) C.I. I. Pigment Blue 15: 3 5 parts Di-tert-butylsalicylic acid chromium compound 4 parts

The above materials were sufficiently premixed with a Henschel mixer, melt-kneaded with a three-roll mill three times, cooled, roughly crushed to about 1 to 2 mm with a hammer mill, and then finely crushed by an air jet system. Finely crushed with. Furthermore, the obtained finely pulverized product was classified to obtain colorant-containing resin particles.

To 100 parts of the obtained resin particles, 1.2 parts of hydrophobic acid value titanium (BET specific surface area of 110 m ^{2 /} g) was mixed with a Henschel mixer to obtain a toner.

The data of the particle size distribution of the obtained toner are shown in Table 1.
Shown in.

[0060]

[Table 1]

When the charge amount of this toner when mixed with the iron powder carrier was measured, it was -42 μC / g.

A styrene-acryl copolymer was coated on a Cu-Zn-Fe type ferrite carrier having a weight average diameter of 35 μm in an amount of 0.5 wt% to prepare a carrier.

95 parts of this carrier and 5 parts of the above toner were mixed to prepare a developer.

Using this developer, a commercially available plain paper color copying machine (color laser copier 500, manufactured by Canon Inc.) was remodeled to produce an image. The peripheral speed of the photoconductor tram is 160m
The peripheral speed of the sleeve is 300 mm / sec.
And An AC component having a frequency of 5.0 kHz and a potential difference of 2.0 kV from peak to peak was applied to the sleeve. The volume ratio of the toner in the developing area was 10%.

The obtained image had a high density of 1.55 and was clear without any fog. At this time, when a minute latent image was formed on the photosensitive drum and the developing state of the toner was observed, it was confirmed that even dots having an average diameter of about 20 μm had the same size and shape. Also, OHP
The translucency of the image was also good. After that, 5000 more copies were made, but the fluctuation of the image density during that time was as small as 0.1, and the toner consumption was smaller than that of the conventional toner.
It was also economical. Further, the images after 5,000 sheets had almost the same fog and sharpness as the initial images.

Comparative Example 1 The same as Example 1 except that the conditions of fine pulverization and classification in Example 1 were changed to obtain the particle size distribution shown in Table 2 and the addition amount of titanium oxide was set to 0.9%. Drawing out.

The charge amount of the toner when mixed with iron powder is -3.
The volume ratio of the toner in the developing area was 10%.

The obtained image had a high density of 1.52 and was clear without fog, but the smoothness of the highlight portion, which is a collection of minute dots, was obtained in Example 1.
Inferior to Even when observing the developability for minute latent images,
The dot size and shape were more uneven than in Example 1.

Comparative Example 2 Image formation was performed in the same manner as in Example 1 except that the mixing ratio of the toner and the carrier was changed to 97 parts of the carrier for 3 parts of the toner and the peripheral speed of the sleeve was 200 mm / sec. went.

The volume ratio of the toner in the developing area is 4.
It was 0%.

The obtained image had a low density of 1.30, and the smoothness of the highlight portion was inferior to that of Example 1. In addition, when the developability of a minute latent image was observed, the dot size and shape were more uneven than in Example 1.

[0072]

[Table 2]

Comparative Example 3 Resin particles were obtained in the same manner as in Example 1 except that the formulation was as follows.

100 parts of polyester resin obtained by condensing propoxylated bisphenol and fumaric acid (acid value 5.5) C.I. I. Pigment Blue 15: 3 6 parts Chromium compound of di-tert-butylsalicylic acid 1 part

Alumina (B
1.3 parts of an ET specific surface area of 150 m ^{2 /} g) was mixed with a Henschel mixer to obtain a toner.

The data of the particle size distribution of the obtained toner are shown in Table 3.
Shown in. The charge amount of toner when mixed with iron powder is -26μ
It was C / g.

Using this toner, images were formed in the same manner as in Example 1. The volume ratio of toner in the developing area is 9
%Met.

The obtained image had a high density of 1.61, but was inferior to Example 1 in the smoothness of the highlight portion, which is a collection of minute dots. Even in the observation of the developability for a minute latent image, the size and shape of the dots were more uneven than in Example 1.

Comparative Example 4 Image formation was carried out in the same manner as in Example 1, except that the frequency of the alternating electric field applied to the sleeve was set to 1.8 kHz.

The image obtained had a density of 1.40 and the image of Example 1
And the smoothness of the highlight part was also inferior to that of Example 1. In addition, when the developability of a minute latent image was observed, the dot size and shape were more uneven than in Example 1.

Example 2 In the same manner as in Example 1, yellow toner, magenta toner and black toner were obtained.

Yellow toner The colorant is C.I. I. Pigment Yellow 17.4, except that it has been changed.

Content of toner having a particle diameter of 2.0 to 4.0 μm 27.7 number% Content of toner having a particle diameter of 4.0 to 8.0 μm 69.2 number% When mixed with iron powder Toner charge amount −46 μC / g 4 parts of this toner was mixed with 96 parts of the same carrier as in Example 1 to obtain a developer. The volume ratio of toner in the developing area is 10
%Met.

Magenta toner The colorant is C.I. I. Pigment Red 122.5 parts, except that the same.

Content of toner having a particle size of 2.0 to 4.0 μm 25.2 number% Content of toner having a particle size of 4.0 to 8.0 μm 67.6 number% When mixed with iron powder Toner charge amount -41 μC / g This toner was used as a developer in the same manner as in Example 1. The volume ratio of the toner in the developing area was 10%.

Black toner Same as above except that the colorant was changed to 6 parts of carbon black.

Content of toner having a particle size of 2.0 to 4.0 μm 26.1 number% Content of toner having a particle size of 4.0 to 8.0 μm 69.1 number% When mixed with iron powder Toner Charge-39 μC / g This toner was used as a developer in the same manner as in Example 1. The volume ratio of the toner in the developing area was 10%.

Using these developers and the developer of Example 1, full color images were formed in the same manner as in Example 1.

The obtained image had good color reproducibility in a portion where fine dots of each color such as skin color were overlapped, and the dots were uniform and smooth. When each color is evaluated individually,
The image density of the yellow toner was 1.63, the image density of the magenta toner was 1.59, and the image density of the black toner was 1.61. Also, for each color,
Even in the case of observing the developing property for a fog and a minute latent image, Example 1
As good as. After that, 5000 copies were made, but the fluctuation of the image density during that period was small and the toner consumption was also small. Further, the images after 5,000 sheets were obtained with almost the same color reproducibility, fog, and sharpness as in the initial stage.

Example 3 In the same manner as in Example 1 except that the conditions for fine pulverization and classification in Example 1 were changed to obtain the particle size distribution shown in Table 3 and the amount of titanium oxide added was 1.4%. Drawing out.

The charge amount of the toner when mixed with iron powder is -5.
It was 0 μC / g, and the volume ratio of the toner in the developing area was 10%.

The obtained image had a high density of 1.56 and was clear without fog. The smoothness of the highlight portion, which is a collection of minute dots, was also good as in Example 1. However, in the observation of the developability for a minute latent image, the dot size and shape were slightly uneven as compared with those in Example 1, but were good.

Example 4 Polyester resin obtained by condensing propoxylated bisphenol with terephthalic acid and trimellitic acid 100 parts (acid value 11.0) carbon black 5 parts low molecular weight propylene-ethylene copolymer 3 parts disazo dye Chromium compound 4 parts

The above materials were sufficiently premixed by a Henschel mixer and kneaded by a twin-screw kneading extruder. It was roughly crushed to about 1 to 2 mm by using a hammer hammer mill and then finely crushed by a fine crusher using an air jet system.
Furthermore, the obtained finely pulverized product was classified to obtain colorant-containing resin particles.

To 100 parts of the obtained resin particles, 1.0 part of hydrophobic alumina (BET specific surface area of 150 m ^{2 /} g) was mixed with a Henschel mixer to obtain a toner.

The data of the particle size distribution of the obtained toner are shown in Table 3.
Shown in. The toner charge when mixed with iron powder is -40μ
It was C / g.

The mixing ratio of the toner and the carrier is toner 4
Carrier for the part (the same as that of the first embodiment) 96
Part and

A plain paper copying machine N available on the market using this developer.
P-7550 (manufactured by Canon Inc.) was modified to draw an image. An AC component having a frequency of 3.0 kHz and a peak-to-peak potential difference of 1.5 kV was applied to the sleeve.
The volume ratio of the toner in the developing area was 8%.

The obtained image had a high density of 1.43 and was clear without any fog. 100 more after that
Copies of 00 sheets were made, but the fluctuation of the image density during that time was 0.
It was as small as 05 and the toner consumption was also small. Further, the images after 10,000 sheets had almost the same fog and sharpness as the initial images.

[0100]

[Table 3]

[0101]

According to the present invention, not only the toner particle size distribution is controlled, but also the toner charge amount is increased and the frequency of the AC component of the alternating electric field applied to the developing section is increased to prevent fog. You can get a good quality image for a long time.

[Brief description of drawings]

FIG. 1 is a device for measuring a charge amount of toner.

Claims (2)

[Claims] 1. A developer comprising a resin particle containing at least a binder resin and a colorant, a non-magnetic toner containing at least a fluidity-imparting agent, and a carrier, the latent image carrier and the developer carrier. Development in which a magnetic brush is formed so that the volume ratio of the toner particles is 5 to 20%, and an alternating electric field having an AC component with a frequency of 2.5 kHz or more is applied to the development area defined by A developer used in the method, wherein the content of toner particles having a particle diameter of 2.0 to 4.0 μm is 15 to 40% by number in the particle size distribution of the toner,
The content of toner particles having a particle diameter of 4.0 to 8.0 μm is 60.
% Or more, and the charge amount of the toner when mixed with the iron powder carrier is |-
30 | μC / g or more, The developer characterized by the above. 2. A magnetic brush is formed in a developing area defined by a latent image carrier and a developer carrier using a developer so that the volume ratio of toner particles is 5 to 20%. .5k
In a developing method in which an alternating electric field having an AC component of a frequency of Hz or higher is applied, as the developer, a resin particle containing at least a binder resin and a colorant and a fluidity-imparting agent are used. The toner comprises a magnetic toner and a carrier, and in the particle size distribution of the toner, the content of the toner particles having a particle size of 2.0 to 4.0 μm is 15 to 40% by number,
The content of toner particles having a particle diameter of 4.0 to 8.0 μm is 60.
% Or more, and the charge amount of the toner when mixed with the iron powder carrier is |-
30 | μC / g or more, a developing method characterized by using a developer.