JP2999249B2 - Electrophotographic yellow toner for negative charging - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a negatively chargeable yellow toner for electrophotography, and more particularly, to a toner containing a benzidine-based pigment as a colorant and having a toner charge amount at the time of use. The present invention relates to a negative charging electrophotographic yellow toner capable of forming a high-density image with little fluctuation of toner.

(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, a negatively charged toner is widely used as a developing toner used for developing the electrostatic image.

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 negatively charged toner has been required.

The yellow toner for development is obtained 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 having an average particle size of 5 to 15 μm. , For negative charging toner,
As a matter of course, a charge controlling agent having a negative charge controlling action at the time of triboelectric charging is used.

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 is described, wherein the charge control agent comprises a combination of a weight ratio of a negative or positive charge control agent and a charge control agent having a polarity opposite thereto from 1: 0.05 to 1: 1.5. ing.

Further, recently, full-color development for forming an image by superimposing yellow, cyan, magenta color toner and black toner has been performed. An organic colorant is used in the cyan toner, magenta toner, and yellow toner used in the full-color development, and carbon black is used as the colorant in the black toner.

(Problems to be Solved by the Invention) In the conventional negatively chargeable 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 much higher than the average value, and a highly charged toner that is not consumed for development is necessarily 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 is often denatured by a mechanical impact force or heat generated by a stirring operation in a developing device,
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 of each color (cyan, yellow, magenta). However, if the charging characteristics of the toner fluctuate, the toner image is transferred to an area to be developed (transferred) in the developing step and the transferring step. The toner is not developed (transferred) and cannot be developed into a desired color.

Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages of the conventional negatively charged yellow toner, to have an average value of the toner charge amount in an optimum range with respect to toner scattering prevention and image density, and to have a sharp distribution of toner charge amount. Accordingly, an object of the present invention is to provide a yellow toner for negative charging, which has almost no high-charged toner not used for development and low-charged toner that causes toner scattering.

Another object of the present invention is to provide a yellow toner for negative charging, which has a sharp distribution of toner charge amount, has a fast rise of charge during charging, and has little deterioration in charging characteristics during long-term operation.

(Means for Solving the Problems) According to the present invention, in a negative charging electrophotographic toner containing a fixing resin, a colorant and a negative charge control agent, the fixing resin is a polyester resin. A benzidine pigment is used as a colorant, and a quaternary ammonium salt containing an oxygenate anion, which is incompatible with the fixing resin but has a dispersibility and a positive charge control effect. A negative charge electrophotographic yellow toner, which is contained in a toner as a charge control aid.

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

(Operation) The electrophotographic yellow toner for negative charging of the present invention contains a polyester resin for fixing, a benzidine pigment and a charge control agent for negative charging as essential components. A remarkable feature is that it contains a charge control aid that is incompatible with the polyester resin as the fixing resin, but has a dispersibility and a charge control action of a polarity opposite to that of the negative charge control agent. It is.

In other words, the present invention provides a positive charge, which is incompatible with a polyester resin as a fixing resin but has a dispersive property, instead of a positively chargeable dye which is compatible with a conventionally used fixing resin. When a control substance is used in combination with a charge control agent for negative charge as a charge control aid, the distribution of the toner charge amount can be remarkably sharper than that of a conventional toner, and as a result, the This is based on a novel finding that the generation of a high-charge toner that is not used or a low-charge toner that causes toner scattering can be effectively suppressed.

In the present invention, it is also important to use a polyester resin as the fixing resin. This polyester resin has a sufficient triboelectric charge (negative charge) on the resin itself, and has various types of polycarboxylic acids and polyhydric alcohols that can be used as an esterifying agent, so that the characteristics of the resin can be freely controlled. It is possible to easily obtain a polyester resin in which the charge control aid is incompatible and dispersible, and can be used as a fixing resin capable of effectively exhibiting the above-mentioned effects of the present invention.

In the present invention, the use of a benzidine pigment as a colorant is also important. That is, the benzidine-based pigment does not significantly affect the electrical properties of the fixing resin, and is excellent in thermal stability. When such a benzidine-based pigment is used together with the charge control agent and the charge control aid described above, the toner characteristics are less likely to be modified by the impact force or heat in the continuous stirring operation, and the charge amount distribution is sharpened. Can be maintained for a long time.

It is especially important to obtain a full-color image (multicolor image) after superimposing the toners, in order to make the charge amount distribution of the toner significantly sharper than that of a conventional toner. That is, in a full-color image, even a little toner adheres (exists) to an unnecessary area in the development and transfer steps.
Then, the color of the image obtained by the superposition changes, and the image is not faithfully reproduced with respect to 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 shows that, using the toners A, B, and C, a laser beam printer LPX-1 (trade name, manufactured by Mita Kogyo Co., Ltd.) The image density (ID), image fog density (FD), and toner scattering around the developing device during continuous copying are evaluated.

From FIGS. 1 to 3 and Table 1, it can be seen that the toner of the present invention having a remarkably sharpened charge amount distribution can sufficiently suppress fluctuations in image density, image fogging and toner scattering.

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 passes through the filter 8 and faces the measuring section 3.

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 communication hole 1a from outside the housing 1.
A main airflow that flows to the measuring section 3 through the rectifying filter 8 and the airflow that sucks the 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, 3, 4, 5 and 6 are measured by this method.

That is, the toner A using the negative charge control agent alone
In FIG. 2, as shown in FIG. 2, a large amount of the high charge amount toner in the region a exists, and a considerable amount of the oppositely charged toner and the zero charge toner in the region d. Further, in the toner B of the prior art in which a positive charge dye is combined with a negative charge control agent, the average value of the charge amount can be shifted to the lower charge amount side as shown in FIG. The difference is almost the same as that of the toner A, and the amount of the high charge amount toner in the area a decreases but still exists, and the presence of the oppositely charged toner or the zero charge toner in the area d increases.

On the other hand, in the toner C of the present invention in which a negative charge control agent and a positive charge control material which is incompatible with the polyester resin are used as an auxiliary agent, as shown in FIG.
The abundances of the toners b and c increase, and the width of the charge amount distribution is remarkably narrowed, and the amount of the high charge amount toner in the region a and the amount of the oppositely charged toner and the amount of the 0 charge toner in the region d are reduced (they are eliminated here).
I understand what you can do.

On the other hand, FIG. 4 shows the initial toner charge amount distribution when a copy test of 20,000 sheets was performed using the toner C of the present invention (see Example 1), and the toner charge after copying 20,000 sheets and 20,000 sheets. FIG. 5 shows the initial toner when a copy test of 20,000 sheets was performed using toner D using a colorant other than a benzidine pigment (here, CI Pigment Yellow 138, Comparative Example 3) as a colorant. FIG. 6 is a diagram showing a charge amount distribution and a toner charge amount distribution after copying 10,000 sheets and 20,000 sheets. FIG. 6 shows a toner using a fixing resin other than polyester (here, a styrene-acrylic resin, see Comparative Example 4). FIG. 9 is a diagram illustrating an initial toner charge amount distribution when a copy test of 20,000 sheets is performed using E, and a toner charge amount distribution after copying 10,000 sheets and 20,000 sheets.

As is apparent from the figure, the toner C of the present invention using the above-described charge control agent and charge control aid together with the polyester resin and the benzidine pigment can maintain a sharp charge amount distribution for a long period (20,000 sheets). . On the other hand, a toner D using a colorant other than a benzidine pigment
Shows that the initial sharp charge amount distribution becomes broad in a long-term copy test, and that when the number of copies reaches 10,000 to 20,000, a large amount of defectively charged toner is generated. Further, a toner E using a styrene-acrylic resin as a fixing resin is used.
It can be seen that the characteristics similar to those of the toner C can be maintained from the initial to the 10,000th sheet, but the distribution of the charge amount also fluctuates broadly after the 20,000th sheet copy.

From these results, the toner of the present invention is free from fluctuations in image density, fogging, and toner scattering, not only during the initial stage of development but also when development is performed for a long period of time. It is effective.

In the toner of the present invention, the fact that by using an incompatible type positive charge control aid for the polyester resin as a fixing resin, the distribution of the charge amount becomes sharp,
It was found as a result of a number of experiments as development, and the reason is not clear, but the positive charge dye compatible with the fixing resin has no effect of sharpening the distribution, the negative charge control agent Is dispersed or dispersed in a matrix, the charge control aid for positive charge is dispersed with a larger particle size, and the dispersed structure acts to reduce the number of highly charged toner and negatively charged toner. It is presumed that.
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 of the composition and the dispersion structure of the present invention, the rising of the charge when the developer is started to be charged and the stirring is started,
An advantage is also obtained that it is fast as in the case of a negatively chargeable toner containing only a negatively chargeable charge control agent.

(Preferred Embodiment of the Invention) Charge Control Aid The charge control aid used in the present invention is incompatible with a polyester resin as a fixing resin, but has dispersibility and a charge control agent for negative charge. Has an opposite polarity charge control action. Specifically, a quaternary ammonium salt containing an oxyacid anion is used.

Suitable quaternary ammonium salts include those of the formula In the formula, R represents a lower alkyl group or a benzyl group under the condition that at least one of them is a long-chain alkyl group or a long-chain alkenyl group, and at least two of them are a lower alkyl group or a benzyl group. , A long-chain alkyl group or a long-chain alkenyl group, and [A] ⁻ represents an oxygenate anion.

The compound represented by these can be mentioned.

Examples of the oxyacid anion include anions of phosphorus oxyacids such as orthophosphoric acid and pyrophosphoric acid, and anions such as molybdate, 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.

As the negative charge control agent used in combination with the negative charge control agent, any negative charge control agent known per se can be used.A suitable negative charge control agent is 1: Metal compounds of type 1 or 2: 1 metal complex dyes, aromatic dicarboxylic acids and aromatic oxycarboxylic acids can be mentioned.

In the present invention, the charge control agent and the charge control aid are preferably used in a weight ratio of 1: 0.05 to 1: 1, particularly 1: 0.1 to 1: 0.7, and the combination thereof is a polyester as a fixing resin. It is preferred that the resin be present in a total amount of 1 to 5 parts by weight, especially 2 to 8 parts by weight, per 100 parts by weight of the resin.

Fixing Resin In the present invention, as described above, the use of a polyester resin as the fixing resin is also an important feature.

As the polyester resin, it is possible to use a polyester resin known per se, which has no compatibility with the charge control assistant but exhibits dispersibility.

In general, Wherein R is an ethylene group or a propylene group;
Or n is a positive integer. It is preferable to use a polyester resin obtained by polycondensation of a diol component represented by the following formula and a polycarboxylic acid or an acid anhydride or a derivative thereof as an acid component.

The diol component represented by the above formula includes polyoxypropylene-2,2-bis (4-hydroxyphenyl)
Examples thereof include propane, polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane, and polyoxypropylene-polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane.

As the carboxylic acid component, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, Linoleic acid, 1,2,4 benzene tricarboxylic acid, 1,2,5 benzene tricarboxylic acid, 1,2,4 cyclohexane tricarboxylic acid, 2,5,7 naphthalene tricarboxylic acid, 1,2,4 naphthalene tricarboxylic acid, 1 , 2,5 hexanetricarboxylic acid, 1,2,4 butanetricarboxylic acid, 1,3-
Dicarboxy-2-methylcarboxypropene, 1,3-
Examples thereof include dicarboxy-2-methyl-2-methylcarboxypropanetetra (methylenecarboxy) methane, 1,2,7,8-octanetetracarboxylic acid, trimer of embol and their acid anhydrides.

This polyester resin is produced by polycondensing the diol component and the polycarboxylic acid component.In this case, the number of carboxyl groups in the carboxylic acid component is 1.2 to the number of hydroxyl groups in the diol component. To 0.
8, particularly preferably from 1.1 to 0.9, and as the catalyst, tin oxide, zinc oxide, titanium oxide, dibutyltin oxide, dibutyltin dilaurate and the like are used. At the time of the reaction, other diol components such as ethylene glycol and bisphenol A can be used in a range of 10 mol% or less in addition to the etherified bisphenol represented by the above general formula.

Benzidine pigment As described above, in the present invention, as a yellow colorant, one or two of benzidine pigment as a main component.
The use of more than one species is also an important feature.

Examples of the benzidine pigments include CI Pigment Yellow 1 (Hanza Yellow G), CI Pigment Yellow 2 (Hanza Yellow GR), CI Pigment Yellow 12 (Benzidine Yellow G), CI Pigment Yellow 13 (Benzidine Yellow GR), and CI Pigment. Yellow 14 (Vulcan First Yellow G), and the like.

Further, the above-mentioned benzidine-based pigment as a main component, and other yellow colorants, for example, graphite, titanium yellow,
Quinoline yellow lake and other coloring agents may be used in combination.

The benzidine pigment is preferably used in an amount of 1 to 20 parts by weight, particularly 3 to 10 parts by weight, per 100 parts by weight of the polyester resin as the fixing resin.

By using a benzidine-based pigment as a main component, yellow coloring is good, the hue is clear, and there is no fading and durability.

Toner The particle diameter 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 shape was produced by a melt-kneading / pulverization method. It may be amorphous or spherical, produced by a dispersion or suspension polymerization method.

The toner of the present invention is used in combination with a magnetic carrier known per se, as a two-component magnetic developer,
Excellent chargeability is exhibited. As the magnetic carrier, a ferrite carrier or an iron powder carrier can be used, but it is generally preferable to use a ferrite carrier. These may be uncoated or resin-coated.

Conventional ferrite carriers include, for example, zinc iron oxide (ZnFe ₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), and gadolinium iron (Gd ₃ Fe).
₂ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe
₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFeO ₃ ), iron barium oxide (BaFe ₁₂ O ₁₉ ), iron magnesium oxide (MgFe ₂ O ₄ ), iron manganese oxide (MnFe)
Sintered ferrite particles having a composition of one or more of ₂ O ₄ ) and lanthanum iron oxide (LaFeO ₃ ) are used, and are particularly selected from the group consisting of Cu, Zn, Mg, Mn and Ni. Soft ferrites containing at least one, preferably two or more metal components, such as copper-zinc-magnesium ferrite, are used, and these ferrites are also suitably 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. The charge of the resin-coated magnetic carrier is positively controlled. 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 charge control is performed effectively and reliably. The saturation magnetization of the carrier is preferably in the range of 40 to 75 emu / g, especially 45 to 70 emu / g. As the magnetic carrier, a spherical ferrite carrier is particularly preferable, and the particle size thereof is 20 to 14.
It is preferably in the range of 0 μm, especially 50 to 100 μm.

The mixing ratio of the toner and the magnetic carrier varies depending on the physical properties thereof, but is preferably in the range of generally 1:99 to 10:90, particularly preferably 2:98 to 5:95 by weight. Also,
The electric resistivity of the entire developer is 5 × 10 ^{9 to} 5 × 10
It is preferably in the range of ¹² Ω · cm, particularly 5 × 10 ^{9 to} 5 × 10 ¹¹ Ω · cm.

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

(Effect of the Invention) According to the present invention, in a negative band electrophotographic toner containing a fixing resin, a colorant and a negative charge control agent,
The fixing resin is a polyester resin and the colorant is a benzidine pigment, and is incompatible with the fixing resin, but has a dispersibility and a charge control having a polarity opposite to that of the negatively-charged charge control agent. By incorporating a charge controlling aid having an effect into the toner, various disadvantages of the conventional negatively charged toner can be solved, the excellent tint of the benzidine pigment can be maintained as it is, and the average charge amount of the toner can be maintained. The value is within the optimal range for toner scattering prevention and image density, and the toner charge amount distribution is sharp, and negatively charged toner that has little charged toner that is not used for development or lowly charged toner that causes toner scattering. A yellow toner is provided. The toner of the present invention has the advantages that the charge amount distribution is sharp, the charge rises quickly during charging, and the charging characteristics are less deteriorated during long-term operation. In addition, it is possible to obtain an image with a clear hue and good reproducibility.

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

Example 1 100 parts by weight of a polyester resin as a fixing resin, 175 parts by weight of CI Pigment Yellow 175 as a colorant, 2 parts by weight of an aluminum complex of an aromatic dicarboxylic acid as a charge control agent for negative charging, and Quaternary ammonium salt of the following formula as a compatible charge control aid 0.5 parts by weight 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. Then, this toner and resin-coated ferrite carrier having an average particle size of 85 μm were mixed and stirred at a toner concentration of 4.5% to obtain a developer, and the charge amount distribution was measured by a toner charge distribution measuring device shown in FIG. did. 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 (the developing unit was remodeled to a reversal development system) (photoreceptor surface potential: -700 V, (Development bias potential: -500 V), 1000 images were continuously formed, and the image characteristics were observed. As shown in Table 1, a decrease in image density, image fog,
It was a good image with no toner scattering. In addition, 20000
When a continuous image was formed on the sheets and the variation of the toner charge amount distribution was traced, as shown in FIG. 4, the toner charge amount distribution was maintained in a good condition even in the initial to 20,000 sheets.

Example 2 In Example 1, CI Pigment Yellow was used as a coloring agent.
A toner was prepared in the same manner except that 13 parts was changed to 5 parts by weight, and 0.5 parts by weight of a quaternary ammonium salt of the following formula was used as a charge control aid incompatible with the fixing resin.

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 in the machine. Further, the toner charge amount distribution was sharp as in the case of Example 1, and the charge amount distribution in which there was almost no high-charge area 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 the charge control auxiliary agent was not used. The toner charge amount distribution was measured in the same manner as in the example, and 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 CISolvent Yellow 56 compatible with the fixing resin was used instead of the charge control assistant. Then, the toner charge amount distribution was measured in the same manner as in the example.
The result was shown in the figure. Further, image fogging and toner scattering were severe in observation of image characteristics by continuous image formation of 1000 sheets. Although the image density was satisfactory to some extent, density unevenness occasionally occurred.

Comparative Example 3 In Example 1, CI Pigment Yellow 1 was used as a colorant.
A toner was prepared in the same manner except that 5 parts by weight of 38 was used. In the same manner as in the example, the image characteristics of the continuous image formation of 1000 sheets were observed, and the fluctuation of the toner charge amount distribution after the image formation of 20,000 sheets was traced. The results shown in FIG. 5 were obtained.

In the continuous image formation of 1000 sheets, a good image similar to that in Example 1 was obtained, but the distribution of the toner charge amount gradually deteriorated after 8,000 sheets, and became broad, and the image became poor after 10,000 sheets.

Comparative Example 4 A toner was prepared in the same manner as in Example 1 except that 100 parts by weight of a styrene-acrylic resin was used as a fixing resin. When the toner charge amount distribution was measured in the same manner as in the example, the distribution width was narrower than that in FIG. 2, but there were still many toners near 0 charge and highly charged toner in area a.

Further, when a continuous image was formed on 1000 sheets in the same manner, image fogging, toner scattering, and fluctuation of image density occasionally occurred.

[Brief description of the drawings]

1 and 4 are graphs showing characteristic curves of the charge distribution of the toner of the present invention. FIGS. 2, 3, 5 and 6 are graphs showing the characteristic of the charge distribution of the comparative (conventional) toner. FIG. 7 is a diagram showing a curve, and FIG. 7 is a schematic layout diagram of a charge amount measuring device used for measuring a charge amount distribution of toner.

Continuation of the front page (72) Inventor Akihiro Watanabe 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Industry Co., Ltd. (72) Inventor Yoshihisa Kuramae 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka (56) References JP-A-1-155361 (JP, A) JP-A-2-22670 (JP, A) JP-A-53-127726 (JP, A) JP-A-54-134441 ( 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] 1. A negative charging electrophotographic toner containing a fixing resin, a colorant and a negative charge control agent, wherein the fixing resin is a polyester resin, and a benzidine pigment is used as a colorant. A quaternary ammonium salt containing an oxygenate anion, which is incompatible with the fixing resin but has dispersibility and a positive charge control effect, is contained in the toner as a charge control aid. A yellow toner for electrophotography for negative charging. 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 ruled proviso 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 Indicates an anion. The yellow toner according to claim 1, wherein 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 yellow toner according to claim 1, which is present in an amount of 5 to 5 parts by weight.