JP2999245B2 - Magenta toner for electrophotography for negative charging - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magenta toner for electrophotography for negative charging, and more particularly, to a colorant containing a quinacridone-based pigment as a main component. The present invention relates to a negative charging electrophotographic magenta toner capable of forming a high-density image with a sharp hue and excellent image reproducibility without occasional toner scattering.

(Prior Art) In the field of commercial electrophotographic copying and electrophotographic printing, a method of forming a positively charged electrostatic image is generally adopted in order to minimize the amount of ozone generated during charging. And
Therefore, as a developing toner used for developing the electrostatic image, a negative charging toner is widely used.

On the other hand, in recent years, laser beam printers and digital copiers have been developed, and in such image forming apparatuses,
The operation of writing a latent image on a negatively charged organic photoreceptor with a laser and performing reversal development with a negatively charged toner has been adopted, and a higher quality toner has been required for the negatively charged toner.

The developing toner is formed by granulating a resin composition containing a fixing resin, a colorant and a charge control agent as essential components to a toner particle size, generally an average particle size of 5 to 15 μm. In the case of a negative charging toner, a toner having a negative charge control action during frictional charging is used as a charge control agent.

In the conventional toner charge control method, the control of the average value of the toner charge amount of the entire toner is controlled by selecting the type of charge control agent and adjusting the amount of addition. However, in this method, even if it is possible to control the average value of the charge amount of the entire toner, it is very difficult to exactly control the distribution of the charge amount of the toner particles.

Conventionally, it is already known that a toner particle contains a plurality of charge control agents having a charging performance of opposite polarities. For example, JP-A-54-34243 discloses an electrostatic charge comprising toner and a carrier. An image developer is described in which the toner is a negatively chargeable toner containing a dye which is positively charged by friction with a carrier.

JP-A-57-196264 discloses an electrically insulating fixing medium, an electrically insulating magnetic one-component developer comprising a magnetic material powder and a charge control agent dispersed in the fixing medium. The developer, wherein the charge control agent comprises a combination of a negative or positive charge control agent and a charge control agent of the opposite polarity in a weight ratio of 1: 0.05 to 1: 1.5. Have been.

Recently, in a full-color toner for forming an image by superimposing magenta, cyan, yellow, and black color toners, an organic colorant is used in a cyan toner, a magenta toner, and a yellow toner. In black toner, carbon black is mainly used as a colorant.

(Problems to be Solved by the Invention) In the conventional negative charging toner, the type and amount of the charge control agent are adjusted so that the average value of the charge amount is a value that can be sufficiently satisfied. In addition, the tendency that the distribution of the charge amount becomes considerably wide is inevitable. Of particular concern here is that
The charge amount is considerably higher than the average value, and a highly charged toner which is not consumed for development is always generated at a certain frequency (distribution amount). Another problem is that a low-charged toner having a charge amount considerably lower than the average value and causing toner scattering is generated at a certain frequency.

The former highly charged toner particles are strongly adsorbed to the surface of the carrier particles and exist in a state in which they are hardly separated, and significantly impair the frictional charging performance of the carrier particles. Therefore, even if the toner has relatively few problems at the beginning of the development,
As the development time elapses, the ratio of the uncharged or low-charged toner increases, causing problems such as toner scattering, fogging, and image density reduction.

In the method of combining a positively chargeable dye (charge control agent) with a charge control agent for negative charging, which is found in the prior art, the distribution of the charge amount can be freely shifted to a higher charge amount side or a lower charge amount side. Even if the advantage of obtaining the toner can be obtained, this method is still sufficiently satisfactory from the viewpoint that the distribution of the toner charge amount is sharpened and the generation of the highly charged toner and the lowly charged toner is suppressed to a level that is negligible or negligible. It was not something you could do.

Further, an organic colorant is used in the color toner, but the mechanical impact force in the stirring operation in the developing device is often denatured by heat or the like generated thereby,
As a result, the charging characteristics of the toner fluctuate, and the state may not be maintained even if the charge amount distribution is sharp and good in the initial step.

A desired color image (full-color image) is obtained by superimposing the color toners (cyan, yellow, magenta) of each color. The toner is not developed (transferred) and cannot be reproduced in a desired color.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks in the conventional magenta toner for negative charging, to appropriately adjust the charge amount of the toner, and to keep the average value of the charge amount of the toner in the optimum range with respect to prevention of toner scattering and image density. At the same time, the distribution of the toner charge amount is sharp, and there is almost no occurrence of highly charged toner that is not used for development or low charged toner that causes toner scattering. An object of the present invention is to provide a magenta toner for charging.

Another object of the present invention is to provide a negative charging magenta having excellent image reproducibility, in which the distribution of the toner charge amount is sharp, the charge rises quickly during charging, and the charging characteristics are less deteriorated during long-term operation. To provide toner.

(Means for Solving the Problems) According to the present invention, a quinacridone pigment is used as a coloring agent in a negative charging electrophotographic toner containing a fixing resin, a coloring agent, and a negative charging control agent. A quaternary ammonium salt containing an oxyacid anion, which is incompatible with the fixing resin, but has a positive charge control action with a positive dispersibility, as a charge control aid,
An electrophotographic magenta toner for negative charging, characterized by being contained in a toner, is provided.

The charge control agent (A) and the charge control aid (B) are A: B =
It is preferably present in a weight ratio of 1: 0.05 to 1: 1, especially 1: 0.1 to 1: 0.7, and in a total amount of 0.5 to 5 parts by weight, especially 2 to 4 parts by weight, per 100 parts by weight of the fixing resin. Good to use.

(Function) The magenta toner for electrophotography for negative charging of the present invention contains, as essential components, a fixing resin, a colorant having a quinacridone pigment as a main component, and a charge control agent for negative charging.
Along with the negative charge control agent, a charge control auxiliary agent which is incompatible with the fixing resin but has dispersibility and has a charge control action of a polarity opposite to that of the negative charge control agent is contained. That is a remarkable feature.

That is, the present invention uses a positively chargeable dye that is incompatible with the fixing resin but is dispersible in place of the conventionally used positively chargeable dye that is compatible with the fixing resin. When combined with a charge control agent for negative charge as a charge control aid, the charge amount of the toner can be suitably adjusted, and the distribution of the charge amount of the toner can be significantly sharper than that of a conventional toner. As a result, it is based on a new finding that the generation of highly charged toner not used for development and low charged toner that causes toner scattering can be effectively suppressed.

In the present invention, it is also important to use a quinacridone pigment as a coloring agent. That is, when a quinacridone-based pigment is used in the toner in combination with the charge control agent and the charge control auxiliary agent, denaturation due to impact force or heat is suppressed even in a continuous stirring operation, and variation in the charge amount distribution can be reduced. You can.

Making the charge amount distribution of the toner significantly sharper than that of the conventional toner is particularly important when obtaining a full-color image (multicolor image) by overlapping the toner. That is, in a full-color image, if any toner adheres (exists) to an unnecessary area in the development and transfer steps, the color of the image obtained by superposition changes and the image is not faithfully reproduced on the original.

FIG. 2 shows the charge control agent for negative charging (Comparative Example 1).
FIG. 3 shows the toner A using the toner A alone, FIG. 3 shows the toner B using the positive charge dye (see Comparative Example 2) in combination with the negative charge controller, and FIG. 5 is a graph showing the results of measuring the distribution of the charge amount of toner C using a charge control assistant (see Example 1) that satisfies the requirements of the present invention. Table 1 below summarizes the characteristic values of the charge amount distribution for these toners A, B, and C.

In this specification, the distribution of the charge amount of the toner is obtained by the following method.

Measurement of charge amount distribution The charge amount measuring device will be described below. As shown in FIG.
The apparatus includes a separating unit 2 for separating the toner from the developer, a measuring unit 3 for measuring the charge amount distribution of the separated toner, and a suction device 10 such as an air pump.

The separating unit 2 and the measuring unit 3 are separated by a partition plate 7, and the housing 1 is located slightly below the partition plate 7.
A communication hole 1a for introducing air into the housing 1
Is provided. An air rectifying filter 8 is provided slightly below the communication hole 1a.

The separating unit 2 is provided with the developer held on the magnet 4,
The compressed air is blown by the air needle 5, and only the lightweight toner is blown up and scattered, leaving the carrier magnetically attracted to the magnet 4.

A funnel 6 supported by a partition plate 7 is provided between the separation unit 2 and the measurement unit 3. The receiving port 6d at the upper end of the funnel 6 protrudes above the partition plate 7, and the front recess 6a at the lower end penetrates the filter 8 and faces the measuring unit 3 side.

The measuring unit 3 applies a DC power source R to the pair of electrode rods 9a and 9b embedded in the side wall of the housing 1,
A horizontal parallel electric field is formed between the electrode rods 9a and 9b. 10 is a filter.

The suction device 11 is connected to the through hole 1a from outside the housing 1.
A main airflow that flows to the measuring section 3 through the rectifying filter 8 and an airflow that sucks toner into the funnel 6 are formed above the funnel 6.

According to this charge amount measuring device, the toner particles separated by the separating unit 2 and collected by the funnel 6 and introduced into the measuring unit 3 fall vertically by the airflow by the suction device 11, and fall into the electrode rod 9a, It passes between 9b and lands on the filter 10. At this time, the toner particles fall in the horizontal parallel electric field between the electrode rods 9a and 9b while receiving the horizontal Coulomb force H and the vertical gravity V according to the charge amount. The light is dispersed on the filter 10 at positions corresponding to the mass and the charge amount. Then, from the distribution of the falling positions of the toner particles, the charge amount distribution of the toner is calculated by image processing.

The charge distribution curves in FIGS. 1, 2 and 3 are measured by this method.

On the other hand, in the toner A using the negative charge control agent alone, as shown in FIG. 2, a large amount of the highly charged toner in the a region exists, and a considerable proportion of the oppositely charged toner and the 0 charged toner in the d region are present. Included in. Further, in the toner B of the prior art in which a positively chargeable dye is combined with a negatively chargeable control agent, the average value of the charge amount can be shifted to the lower charge amount side as shown in FIG. The width is almost the same as that of the toner A, and the amount of the highly charged toner in the area a is small but still present, and the proportion of the oppositely charged toner or 0 charged toner in the area d is increased. On the other hand, in the toner C of the present invention in which a negative charge control agent and a fixing resin immiscible type positive charge control material are combined as an auxiliary agent, as shown in FIG. As the amount of the toner present increases, the width of the charge amount distribution becomes extremely narrow, and the amount of the highly charged toner in the a region and the amount of the oppositely charged toner in the d region and the amount of the 0 band toner are reduced (here, eliminated).
I understand what you can do.

Table 1 shows that the above toners A, B and C were used to continuously copy 1000 sheets using a laser beam printer LPX-1 (manufactured by Mita Kogyo Co., Ltd.) with a remodeling machine (remodeled into a reversal development system). This is an evaluation of the image density (ID), the image fogging density (FD), and the state of toner scattering around the developing device at the time of performing.

From FIGS. 1 to 3 and Table 1, it is confirmed that the toner of the present invention can be improved to a preferable charging characteristic capable of suppressing fluctuations in image density, image fogging and toner scattering.

FIG. 4 shows an initial toner charge amount distribution when a 10,000 sheet copy test was performed using the toner C of the present invention (see Example 1) and a toner charge amount distribution after 10,000 sheet copy. FIG. 5 shows the initial toner charge amount distribution and the initial toner charge distribution when a 10,000-sheet copy test was performed using toner D as a colorant other than a quinacridone pigment (CI Pigment Red 57, see Comparative Example 3). FIG. 7 is a diagram illustrating a toner charge amount distribution after copying million sheets. As is clear from the figure, the toner C of the present invention using a quinacridone pigment can maintain a sharp charge amount distribution for a long period of time, and the toner D using a coloring agent other than the quinacridone pigment has a long term copy test. It can be seen that the initial sharp charge amount distribution becomes broad and a large amount of defective toner is generated. this is,
In the toner of the present invention, even when the development is performed for a long period of time as well as in the initial stage of development, the fluctuation of the image density does not cause fogging and toner scattering, and has an effect on charging characteristics and prevention of deterioration thereof. Is shown.

In the toner of the present invention, the fact that the distribution of the charge amount is sharpened by using the charge control aid for the positive charge, which is incompatible with the fixing resin, was found as a phenomenon as a result of numerous experiments. Although the reason is not clear, the positively chargeable dye compatible with the fixing resin has no effect of sharpening the distribution, and the negative charge control agent has a positive charge in the compatible or dispersed matrix. It is presumed that the dispersion structure in which the charge control assistant for use is dispersed with a macroscopic particle size acts to reduce the number of highly charged toners and negatively charged toners. In general, one of the significant drawbacks of combining a negative charge control agent with a positive charge control agent as an auxiliary is that, even if the charge on the toner particles is ultimately controlled to be negative, When the developer is stirred in a developing device, the rise of charge is delayed. On the other hand, in the toner having the composition and the dispersion structure of the present invention, the rise of the charge when the developer is started to be stirred and the charging is started is similar to the negatively chargeable toner containing only the negatively chargeable charge controlling agent. It also has the advantage of being fast.

Further, the use of a quinacridone pigment as a coloring agent can stably maintain the above-mentioned action for a long period of time.

(Preferred Embodiment of the Invention) Charge Control Aid The charge control aid used in the present invention is incompatible with the fixing resin but has dispersibility and reverse polarity to that of the negative charge control agent. , And specifically, a quaternary ammonium salt is used.

Suitable quaternary ammonium salts include those of the formula In which R is at least one long-chain alkyl or long-chain alkenyl group, provided that at least two of them are lower alkyl groups or benzyl groups.
It is a lower alkyl group, a benzyl group, a long-chain alkyl group or a long-chain alkenyl group, and A ^- represents an oxygenate anion.

Can be mentioned. Examples of the oxyacid anion include phosphorus oxyacids such as orthophosphoric acid and pyrophosphoric acid,
Examples include anions such as molybdic acid, tungstic acid, antimonic acid, and bismuthic acid. These quaternary ammonium salts are particularly suitable for the purpose of sharpening the distribution of the charge amount without delaying the rise of the charge of the toner.

Charge Control Agent As the charge control agent used in combination with the charge control aid, any charge control agent known per se can be used as long as it does not hinder color development of the colorant and hue development. . For example, metal-containing monoazo dyes, aromatic dicarboxylic acids, and metal complex compounds of aromatic oxycarboxylic acids can be mentioned.

In the present invention, the charge control agent and the charge control aid
It is preferred to use 1: 0.05 to 1: 1, especially 1: 0.1 to 1: 0.7 weight ratio, and to use these combinations in total of 1 to 5 parts by weight, particularly 2 to 4 parts by weight per 100 parts by weight of the fixing resin. Should be present in an amount of

Fixing Resin As the fixing resin, a known fixing resin which is not compatible with the charge control assistant but exhibits dispersibility is used. Since these fixing resins charge the toner with a negative charge, it is desirable that the fixing resin has a tendency to be charged with a negative charge. For example, a styrene resin, an acrylic resin, or a styrene-acryl copolymer resin may be used. Commonly used.

As the styrene monomer used for these resins,
The following formula In the formula, R ₁ is a hydrogen atom, a lower (C 4 or less) alkyl group or a halogen atom, and R ₂ is a hydrogen atom or a substituent such as a lower alkyl group or a halogen atom. Such as styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, and vinylnaphthalene. Among them, styrene is preferred.

On the other hand, as the acrylic monomer, the formula In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and R ₄ is a hydrogen atom or a substituted or unsubstituted alkyl group having up to 18 carbon atoms, such as ethyl acrylate, methyl methacrylate, Butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylic acid, methacrylic acid and the like. As the acrylic monomer, in addition to those described above, other ethylenically unsaturated carboxylic acids or anhydrides thereof,
For example, maleic acid, fumaric acid, maleic acid, crotonic acid, itaconic acid, etc. or their anhydrides can be used.

Styrene-acrylic copolymer resin is one of the suitable resin media, and styrene monomer (A) and acrylic monomer (B) are A: B = 50: 50-90. :Ten,
In particular, the range is preferably 60:40 to 85:15. Further, the resin used generally preferably has an acid value of 0 to 25. Further, from the viewpoint of fixability, the glass transition temperature (Tg) is preferably 50 to 75 ° C.

Colorant As the colorant contained in the resin, one or more magenta colorants containing a quinacridone pigment as a main component are used.

Specific examples of the quinacridone pigment include CI Pigment Red 122 (quinacridone magenta), CI Pigment Red 192, CI Pigment Red 209, CI Pigment Violet 19 (Quinacridone Violet), and the like.

In addition, by using a quinacridone pigment as a main component, a magenta color is well developed, the hue is clear, and there is no fading and durability is obtained.

Toner The particle size of the toner particles is preferably in the range of 5 to 15 μm, particularly 7 to 12 μm in terms of volume-based median diameter measured by a Coulter counter, and the particle size is produced by a melt-kneading / pulverization method. In addition, they may be amorphous or spherical, produced by a dispersion or suspension polymerization method.

The toner of the present invention exhibits excellent chargeability when used as a two-component magnetic developer in combination with a magnetic carrier known per se. As the magnetic carrier, a ferrite carrier or an iron powder carrier is used, and these can be used either uncoated or resin-coated. Generally, ferrite carriers are preferred.

Conventionally, as ferrite, for example, acid value iron zinc (ZSnFe
₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe ₂ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), iron oxide Lead (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), neodymium iron oxide (NdFeO ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), magnesium iron oxide (MgF
e ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LeFeO ₃ ), and the like. At least one metal component selected from the group consisting of Mg, Mn and Ni
Soft ferrites containing species, preferably two or more, such as copper-zinc-magnesium ferrite, are used, but these ferrites are also preferably used in the present invention.

Various types of coating resins for magnetic carriers, such as acrylic resins, styrenic resins, silicone resins, fluorine resins, and various amino-modified resins, are known, but they positively control the charge of the resin-coated magnetic carrier. Accordingly, it is preferable that the toner charge is indirectly controlled to be negative. Of course, in the present invention, even if such a carrier coat resin layer does not exist, it is natural that the control of the charge is performed effectively and reliably. The carrier's saturation magnetization is
It is preferably in the range of 40 to 75 emu / g, especially 45 to 70 emu / g. As the magnetic carrier, a ferrite carrier that satisfies the above conditions, particularly a spherical ferrite carrier, is preferable, and its particle size is 20 to 140 μm, particularly 50 to 100 μm.
m is desirable.

The mixing ratio between the toner and the magnetic carrier varies depending on the physical properties of the toner and the magnetic carrier, but is preferably in the range of generally 1:99 to 10:90, more preferably 2:98 to 5:95 by weight. . Further, it is generally desirable that the electric resistivity of the whole developer is in the range of 5 × 10 ^{9 to} 5 × 10 ¹² Ω · cm, preferably 5 × 10 ^{9 to} 5 × 10 ¹¹ Ω · cm.

In developing an electrostatic image, after mixing the toner and the magnetic carrier, a magnetic brush having a predetermined length is formed on a developing sleeve having a magnet roll therein, and the magnetic brush and a photoconductor having an electrostatic image are formed. The magnetic brush and the electrostatic image holding photoreceptor are brought close to each other in a printing operation or in an electric field to which an oscillating electric field is applied.

(Effects of the Invention) According to the present invention, in a magenta toner for electrophotography for negative charging containing a fixing resin, a colorant having a quinacridone pigment as a main component and a charge control agent for negative charging, the fixing resin Is incompatible, but has a dispersibility and a charge control aid having a charge control action of a polarity opposite to that of the charge control agent for negative charge, so that the charge amount of the toner can be suitably adjusted. It can be adjusted and eliminates various drawbacks of the conventional negatively charged toner.The average value of the toner charge amount is in the optimal range for toner scattering prevention and image density, and the toner charge amount distribution is sharp. The present invention provides a negatively charged toner having almost no unused high charged toner and low charged toner which causes toner scattering. The toner of the present invention has a sharp distribution of toner charge amount,
Since there is an advantage that charge rises quickly during charging and the deterioration of charging characteristics during long-term operation is small, it is possible to obtain an image with a clear hue and good reproducibility especially when used as a full-color toner. .

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1) Styrene-acryl copolymer 100 as fixing resin
Parts by weight, CI Pigment Red 122 as colorant
5 parts by weight, 1.5 parts by weight of low molecular weight polypropylene as an anti-offset agent, 2 parts by weight of an aluminum complex of an aromatic dicarboxylic acid as a charge control agent for negative charging, and a charge control auxiliary incompatible with a fixing resin. 0.5 parts by weight of a quaternary ammonium salt of the following formula Was melt-kneaded by a twin-screw extruder, and the kneaded product was cooled, pulverized and classified to obtain a toner having an average particle diameter of 11 μm. The average particle diameter of the toner and the resin coating is 85 μm.
The ferrite carrier was mixed and stirred at a toner concentration of 4.5% to obtain a developer, and the charge distribution was measured by a toner charge distribution measuring device shown in FIG. FIG. 1 shows the result.

Next, the above-mentioned developer was modified with a laser beam printer LPX-1 manufactured by Mita Kogyo Co., Ltd. equipped with an organic photoreceptor for negative charging (remodeled to a reversal development system) (photoreceptor surface potential: −
(700 V, developing bias potential: -500 V), and continuous image formation was performed on 1000 sheets, and the image characteristics were observed. As a result, a good image was obtained without any decrease in image density, image fogging, and toner scattering shown in Table 1. Was. Further, a continuous image formation of 10,000 sheets was performed to track the fluctuation of the toner charge amount distribution.
As shown in the figure, the toner charge amount distribution was maintained in a good condition at the initial stage and after 10,000 sheets without fluctuating.

(Example 2) In Example 1, 5 parts by weight of CI Pigment Red 209 was used as a coloring agent, and 0.5 part by weight of a quaternary ammonium salt represented by the following formula was used as a charge control aid incompatible with a fixing resin. Except for the above, a toner was prepared in the same manner.

Thereafter, a developer was obtained in the same manner as in Example 1, and image characteristics were observed by continuous image formation of 1000 sheets.
Fluctuations in the toner charge amount distribution during continuous image formation on sheets were tracked. As a result, a good image was obtained as in Example 1.
There was no toner scattering inside the machine. In addition, the toner charge amount distribution was sharp, as in Example 1, and the charge amount distribution in which there was almost no high-charge-range toner or 0 to reverse-polarity toner was maintained.

(Comparative Example 1) A toner was prepared in the same manner as in Example 1, except that no charge control auxiliary agent was used. The toner charge amount distribution was measured in the same manner as in Example 1. The results are shown in FIG. In observation of image characteristics by continuous image formation of 1000 sheets, the image density was unstable and occasionally dropped. Further, image fogging and toner scattering also occurred.

Comparative Example 2 A toner was prepared in the same manner as in Example 1, except that 0.5 parts by weight of CI Solvent Red 81 compatible with the fixing resin was used instead of the charge control aid. And
The toner charge amount distribution was measured in the same manner as in Example 1. The results are shown in FIG. Further, in observation of image characteristics by continuous image formation of 1000 sheets, image fog and toner scattering were severe. Although the image density was satisfactory to some extent, density unevenness occasionally occurred.

Comparative Example 3 A toner was prepared in the same manner as in Example 1, except that 5 parts by weight of CI Solvent Red 57 was used as a coloring agent. Observation of image characteristics by continuous image formation of 1000 sheets and fluctuation of toner charge amount distribution by copying of 10,000 sheets were traced in the same manner as in Example 1. The results are shown in FIG.

In the continuous image formation of 1000 sheets, a good image similar to that of Example 1 was obtained, but the toner charge amount distribution gradually deteriorated, and the distribution gradually became broader as is apparent from the figure.
Poor charge amount toner was generated, and the image gradually deteriorated.

Comparative Example 4 A toner was prepared in the same manner as in Example 1, except that 5 parts by weight of CI Pigment Red 31 was used as a coloring agent. Observation of image characteristics by continuous image formation of 1000 sheets and change in toner charge distribution by copying of 10,000 sheets were tracked in the same manner as in Example 1.
In the continuous image formation of 00 sheets, a good image similar to that of Example 1 was obtained, but the toner charge amount distribution gradually deteriorated, the distribution gradually became broader, a defective charge amount toner was generated, and the image gradually deteriorated. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a special curve of the toner charge amount distribution of the present invention, and FIG. 2 is a diagram showing a characteristic curve of the charge amount distribution of the toner using the negative charge control agent alone. FIG. 3 is a diagram showing a characteristic curve of a charge amount distribution of a toner using a charge control agent for negative charge and a positively chargeable dye (compatible with a fixing resin); FIG. 5 is a characteristic curve showing the variation of the charge amount distribution of the toner of the present invention and the toner of the comparative example. FIG. 6 is a schematic arrangement of a charge amount measuring device used for measuring the charge amount distribution of the toner. FIG.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiro Watanabe 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Yoshihisa Kuramae 1-2-2 Tamazo, Chuo-ku, Osaka-shi, Osaka No. 28 Mita Kogyo Co., Ltd. (56) References JP-A-1-155361 (JP, A) JP-A-2-22670 (JP, A) JP-A-53-127726 (JP, A) JP-A-54 JP-A-134441 (JP, A) JP-A-59-136747 (JP, A) JP-A-62-53944 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (3)

(57) [Claims] An electrophotographic toner for negative charging containing a fixing resin, a colorant and a charge control agent for negative charging, wherein a quinacridone pigment is used as a coloring agent and the toner is incompatible with the fixing resin. Wherein a quaternary ammonium salt containing an oxyacid anion having dispersibility and a positive charge control action is contained in the toner as a charge control aid, Magenta toner for photo. 2. The method according to claim 1, wherein the quaternary ammonium salt is represented by the following formula: (R) ₄ —N ⁺ · A ^{− wherein} at least one of R is a long-chain alkyl group or a long-chain alkenyl group. , and the on condition that at least two lower alkyl group or a benzyl group of the four, a lower alkyl group, a benzyl group, a long chain alkyl group or long chain alkenyl group, a ^- represents an oxygen acid The magenta toner according to claim 1, which represents an anion. 3. The method according to claim 1, wherein the charge control agent and the charge control aid are in a ratio of 1: 0.05
At a weight ratio of 1: 1 and a total of 0.1 per 100 parts by weight of fixing resin.
The magenta toner according to claim 1, which is present in an amount of 5 to 5 parts by weight.