JPH04195164A - Negatively chargeable electrophotographic toner - Google Patents

Abstract

PURPOSE:To effectively restrain occurrence of a highly charged toner not to be used for development and that of a lowly charged toner ready to cause its scattering by combining a positively chargeable material incompatible with a fixing resin but dispersible in it as an auxiliary charge controller with a negatively chargeable charge controller. CONSTITUTION:The toner contains the fixing resin, a colorant, and the negatively chargeable charge controller, and further the auxiliary charge controller incompatible with the fixing resin but dispersible in it and having a charge controlling action in polarity reverse to the charge controller, thus permitting the obtained negatively chargeable toner to have an average toner charge amount in an optimum range for preventing toner scattering and stabilizing image density and to have a sharp distribution of toner charge amount free from almost all of the highly charged toner not to be used for development and a lowly charged toner ready to cause its scattering.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a negatively charged electrophotographic toner,
More specifically, the present invention relates to a negatively charged electrophotographic toner that does not cause toner scattering and can form high-density images.

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

On the other hand, in recent years, the development of laser beam printers and digital copying machines has progressed, and in these image forming devices, a process is adopted in which a latent image is written on a negatively charged organic photoreceptor using a laser and then reversely developed using negatively charged toner. is,
Negative charging toner is also available.

There is a growing demand for higher quality products.

A developing toner is made 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 negatively charged toner, as a matter of course, a charge control agent having a negative charge control effect during triboelectric charging is used.

In conventional toner charge control systems, the average value of the toner charge amount for the toner as a whole is controlled by selecting the type of charge control agent and adjusting the amount added. However, in this method, although it is possible to control the average value of the charge amount of the toner as a whole, it is difficult for the device to precisely control the distribution of the charge amount of the toner particles.

Conventionally, it has already been known that toner particles contain a plurality of charge control agents having chargeability of opposite polarity. Among the image developers, there is described an electrostatic image developer characterized in that the toner is a negatively charged toner containing a dye that becomes positively charged when rubbed with a carrier.

JP-A-57-196264 discloses an electrically insulating magnetic component developer comprising an electrically insulating fixing medium, a magnetic material powder dispersed in the fixing medium, and a charge control agent. The charge control agent is a negative or positive charge control agent and a charge control agent of opposite polarity in a ratio of 1:0.0.
A developer is described which is characterized in that it consists of a combination in a weight ratio of 5 to 1:1.5.

(Problems to be Solved by the Invention) In conventional negatively charged toners, even if the type and amount of charge control agent added are adjusted so that the average value of the charge amount is a sufficiently satisfactory value, , it is inevitable that the distribution of the amount of charge becomes quite wide. A particular problem here is that the amount of charge is considerably higher than the average value, and highly charged toner that is not consumed for development inevitably occurs at a frequency (amount of distribution).

Another problem is that the amount of charge is considerably lower than the average value, and low charge toner that causes toner scattering occurs frequently.

The former highly charged toner particles are strongly electrically adsorbed to the surface of the carrier particles and exist in a state where they are difficult to separate from, significantly impairing the triboelectric charging performance of the carrier particles. For this reason, even if the toner has relatively few problems at the beginning of development, as development time progresses, the proportion of uncharged or low-charge toner increases, causing toner scattering, fogging, and image density. Problems such as deterioration will occur.

In the method of combining a positively chargeable dye (charge control agent) with a charge control agent for negative charge as seen in the prior art, the charge amount distribution can be shifted quite freely toward the high school graduate@ amount side or the low charge amount side. Even though this method has the advantage of sharpening the toner charge amount distribution and suppressing the generation of highly charged toner and low charged toner to a negligible level, it is still not fully satisfactory. It was not possible.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of conventional negatively charged toners, to be able to suitably adjust the amount of charge of the toner, and to ensure that the average value of the amount of charge of the toner is within the optimum range in terms of toner scattering prevention and image density. Another object of the present invention is to provide a negatively charged toner having a sharp toner charge amount distribution and containing almost no highly charged toner that is not used for development and lowly charged toner that causes toner scattering.

Another object of the present invention is a toner band! To provide a toner for negative charging, which has a sharp radius distribution, has a rapid charge rise during charging, and has little deterioration of charging characteristics during long-term operation.

(Means for Solving the Problems) According to the present invention, in a negatively charging electrophotographic toner containing a fixing resin, a colorant, and a negatively charging toner swelling agent, a An electrophotographic toner for negative charging, characterized in that the toner contains a charge control auxiliary agent that is compatible but dispersible and has a charge control action of opposite polarity to that of the charge control agent for negative charging. is provided.

In the present invention, quaternary ammonium salts, especially quaternary ammonium salts containing oxyacid anions as anions, are used as charge control aids.
It is preferable to use grade ammonium salts.

The charge control agent (A) and the charge control aid (B) are A:
B=1: 0.05~]:1 especially 1:0.1~
They are preferably present in a weight ratio of 1:O7 and used in a total amount of 0.5 to 5 parts by weight, particularly 2 to 4 parts by weight per 100 parts by weight of fixing resin.

(Function) The electrophotographic toner for negative charging of the present invention contains a fixing resin, a colorant, and a charge control agent for negative charging as essential components. A notable feature is that it contains a charge control auxiliary agent that is incompatible with the resin or has dispersibility and has a charge control effect with a polarity opposite to that of the charge control agent for negative charging.

That is, in place of the conventionally used positively chargeable dye that is compatible with the fixing resin, the present invention uses a positively charge controlling substance that is incompatible with the fixing resin but has dispersibility. ,
When combined with a charge control agent for negative charging as a charge control aid, the toner charge amount distribution can be made significantly sharper than that of conventional ones, resulting in highly charged toner that is not used for development. This is based on new knowledge that the generation of low-charge toner, which causes toner scattering, can be effectively suppressed.

Figure 2 of the accompanying drawings shows toner A using only a charge control agent for negative charging (Comparative Example 1), and Figure 3 shows toner A using a charge control agent for negative charging in combination with a positively charging dye (see Comparative Example 2). The distribution of charge amount was measured for Toner B used in the above-mentioned test, and Toner C used in Figure 1 in which the negative charge toner was used in combination with a charge control aid (see Example 1) that satisfies the requirements of the present invention. This is a graph showing the results. Further, Table 1 below summarizes the characteristic values of the charge amount distribution for these toners A, B, and C.

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

Measurement of Charge Amount Distribution This charge amount measuring device will be explained below. As shown in FIG. It has a measuring section 3 that measures the charge amount distribution of the separated toner, and a suction device 10 such as an air pump.

The separating section 2 and the measuring section 3 are separated by a partition plate 7, and a communication hole for introducing air into the housing 1 is provided in the side wall of the housing 1 slightly below the partition plate 7.
is provided. An air rectifying filter 8 is disposed slightly below the communication hole 1a.

The separating unit 2 uses an air needle 5 to blow compressed air onto the developer held on the magnet 4, leaving behind the carrier magnetically attracted to the magnet 4, and blowing only the lightweight toner upward and scattering it. let

A funnel 6 supported by a partition plate 7 is provided between the separating section 2 and the measuring section 3. A receiving opening 6d at the upper end of the funnel 6 protrudes above the partition plate 7, and a recessed portion 6a at the lower end passes through the filter 8 and faces the measuring section 3 side.

The measurement unit 3 applies a DC power supply R to a pair of electrode rods 9a and 9b embedded in the side wall of the housing 1, thereby forming a horizontal parallel electric field between the electrode rods 9a and 9b.

10 is a filter.

The suction device 11 connects the communication hole 1 from the outside of the housing 1.
A and the rectifying filter 8 to form a main air flow that flows to the measuring section 3, and at the same time, an air flow that sucks the toner into the funnel 6 is formed above the funnel 6.

According to this electrification lt measuring device, the toner particles separated by the separating section 2, collected by the funnel 6, and introduced into the measuring section 3 are carried by the airflow by the suction device 11 and fall vertically, and the toner particles are vertically dropped by the electrode rod 9a. .

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 being subjected to a Coulomb force H in the horizontal direction according to the amount of charge and gravity ■ in the vertical direction, so that the toner particles are On the filter 10, it is dispersed at positions corresponding to its quality 1 and amount of charge. Then, from the distribution of the falling positions of the toner particles, the toner charge amount distribution is calculated by image processing.

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

That is, toner A using only the negatively charged JltJ control agent
As shown in FIG. 2, there is a large amount of highly charged toner in the d range, and a considerable proportion of oppositely charged toner and O-charged toner in the d range are also included. In addition, in the prior art toner B in which a positively chargeable 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 width of the toner is almost the same as that of toner A, and although the highly charged toner in the d range disappears, it still exists, and the ratio of the oppositely charged toner and O-charged toner in the d range increases. On the other hand, in the toner C of the present invention, in which a negatively charging I'Il# agent and a fixing resin-incompatible positive charge control substance are combined as auxiliary agents, the proper charging range is reached as shown in FIG. , It is understood that the amount of c toner present increases and the width of the charge amount distribution becomes significantly narrower, making it possible to reduce the amount of highly charged toner in the d region and the oppositely charged toner and zero charged toner in the d region (here, they are eliminated). be done.

In addition, Table 1 uses the above toners A, B and C,
Laser beam printer LPX-1 (manufactured by Sanda Kogyo Co., Ltd.)
Product name) 1 with a modified machine (modified to reverse development method)
The image density (ID), image fog density (FD) and toner scattering around the developing device were evaluated when 000 sheets were continuously copied.

From FIGS. 1 to 3 and Table 1, it is confirmed that the toner of the present invention can be modified to have preferable charging characteristics that can suppress fluctuations in image density, image fogging, and toner scattering.

The toner of the present invention does not cause fluctuations in image density, fog, or toner scattering, not only during the initial stage of development but also when development is performed for a long period of time, and is extremely effective in preventing charging characteristics and deterioration thereof. It shows.

In the toner of the present invention, the fact that the charge amount distribution becomes sharper by using a fixing resin-incompatible positive charging charge control agent was discovered as a result of numerous experiments. Although the reason is not clear,
A positively chargeable dye that is compatible with the fixing resin has no effect on sharpening the distribution, and a charge control agent for positive charges is contained in macroscopic particles in a matrix in which a control agent for negative charges is compatible or dispersed. It is presumed that the dispersed structure, which is dispersed in size, acts to reduce the number of highly charged toners and negatively charged toners. In general, one of the major drawbacks that arises when a negative charge control agent is combined with a positive charge control agent as an auxiliary agent is that even if the charge of the toner particles is ultimately controlled to be negative, the toner and carrier When a developer consisting of is stirred in a developing device, the charge rises slowly. On the other hand, in the toner having the composition and dispersion structure of the present invention, the charge rise when the developer starts to be stirred and charged is similar to that of the negatively chargeable toner containing only the negatively chargeable charge suppressing agent. This also has the advantage of being faster.

(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 has a polarity opposite to that of the charge control agent for negative charging. Specifically, a quaternary ammonium salt is used.

Suitable quaternary ammonium salts include the formula % where R is at least one long-chain alkyl group or long-chain alkenyl group, and at least two of them are lower alkyl groups or benzyl groups. Under the condition that it is a base,
It is a lower alkyl group, benzyl group, long-chain alkyl group or long-chain alkenyl group, and A 1 represents an anion, particularly preferably an oxyacid anion.

Examples include compounds represented by Examples of the oxyacid anion include phosphorus oxyacids such as orthophosphoric acid and pyrophosphoric acid, and anions such as molybdic acid, tungstic acid, antimonic acid, and bismuth acid. These quaternary ammonium salts are particularly suitable for the purpose of sharpening the charge amount distribution without slowing down the charge rise of the toner.

Charge control agent Negative charge I! used in combination with the above charge control aid!
As the auxiliary agent, any negative charge control agent known per se can be used on the condition that it does not interfere with the color development and hue development of the colorant. Suitable negative charge control agents include 1:1 type or 2:1 type metal complex dyes, naphthene salt metal salts, and especially % formula % where A and B are each a diazo component having a phenolic hydroxyl group at the ortho position and It is a metal complex dye represented by the following formula, where M represents a chromium, iron or cobalt metal, and [Y] is an organic or inorganic cation. Typical examples thereof are: C,1, Asindo blank 123 chromium-containing dye C,I, Solvent blank 22C,1, Solvent black 23 C,1, Solvent black 28 C,I, Solvent blank 42C,I,
Solvent Blank 43 grade.

In the present invention, the charge I control agent and the charge riql# auxiliary agent are mixed in a ratio of 1:0.05 to 1:1, particularly l:o, 1 to 1:1.
A weight ratio of 1:0.7 is preferably used, and the combination is preferably present in a total amount of 1 to 5 parts by weight, especially 2 to 4 parts by weight per 100 parts by weight of fixing resin.

Fixing Resin As the fixing resin, there is used a fixing resin known per se that is not compatible with the charge III additive but exhibits dispersibility. Since these fixing resins charge the toner negatively, it is desirable that they have a tendency to be negatively charged. For example, styrene resins, acrylic resins, or styrene-acrylic copolymer resins are preferred. Commonly used.

The styrenic monomer used in these resins has the following formula: CH=C l where R1 is a hydrogen atom and lower (L'd) s number is 4)
alkyl group, 6. or a halogen atom, and R2 is a hydrogen atom or a substituent such as a lower alkyl group or a halogen atom. -Methylstyrene, α-chlorostyrene, vinylxylene, vinylnaphthalene, etc.
, 7=I can do it. Among these, styrene is 1
4' No 4.

On the other hand, acrylic 1' blindness, amount (as a book, in formula 1, R
2 is a hydrogen atom or a lower alkyl group, R4 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,
These include 2-ethylhexyl methacrylate, acrylic acid, and methacrylic acid. In addition to the above-mentioned acrylic monomers, other ethylenically unsaturated carboxylic acids and their anhydrides, such as maleic acid, fumaric acid, maleic acid,
Crotonic acid, itaconic acid, etc. or anhydrides thereof can also be used.

Styrene-acrylic copolymer resin is suitable as #1 lipid medium, and styrene monomer (A')
and acrylic monomer (B), A:B==50:
It is preferably in the range of 50 to 90:10, particularly 60:40 to 85:15. Further, it is preferable that the resin used generally has an acid value of 0 to 25. Further, from the viewpoint of fixing properties, it is preferable that the toner has a glass transition temperature (Tg) of 50 to 75°C.

Colorant As the colorant contained in the resin, the following inorganic or organic pigments, dyes, etc. may be used alone or in combination of two or more. Carbon black such as furnace black and channel black; iron black such as triiron tetroxide; titanium dioxide such as rutile type or anatase type; phthalocyanine blue; phthalocyanine green; cadmium yellow; molybdenum orange; pyrazolone red; fast violet B, etc.

Toner The particle size of the toner particles is preferably in the range of 5 to 15 μm, particularly 7 to 12 μm, as measured by a volume-based median diameter using a coulter counter, and the particle size is manufactured by melt-kneading and pulverization. It may be amorphous or spherical produced by dispersion or suspension polymerization.

By combining the toner of the present invention with a magnetic carrier known per se and using it as a two-component magnetic developer,
Excellent charging properties are exhibited. As the magnetic carrier, a ferrite carrier or an iron powder carrier is used, and these carriers may be uncoated or resin-coated. Ferrite carriers are generally preferred.

Conventional ferrites such as iron zinc oxide (ZnFe2
04), iron oxide intram (YJe, 0.2), iron cadmium oxide (CdFe20.), iron gadolinium oxide (Gd3Fe20+2), iron copper oxide (CuFe20+)
, iron oxide complex (PbFe, 20+,), iron nickel oxide (
NiFel:! 0. ), iron neodymium oxide (tTdFe
Os) - barium iron oxide (BaFe120+o), magnesium iron oxide (MgFeaOa).

Iron manganese oxide (MnFe204), iron lanthanum oxide (
Sintered ferrite particles having a composition consisting of one or more types such as L a F e 03) are used, and in particular C
Soft ferrite containing at least one, preferably two or more metal components selected from the group consisting of u, Zn, Mg, Mn and Ni, such as copper-zinc monomagnesium ferrite, is used. ferrite is preferably used in the present invention.

As the coating resin for the magnetic carrier, acrylic f
Various types of resins are known, such as M resin, styrene resin, silicone resin, fluorine resin, and various amine-modified resins.1. Preferably, the toner charge is indirectly controlled to be negative by controlling the charge of the resin-coated magnetic carrier to be positive.

Of course, in the present invention, charge control can be performed effectively and reliably even without such a carrier resin layer. The saturation magnetization of the carrier is 40 to 75e+!
lu/g, particularly preferably in the range of 45 to 70e u/g. The magnetic carrier is preferably a ferrite carrier that satisfies the above conditions, especially a spherical ferrite carrier, and its particle size is 20 to 140μ, especially 5.
It is desirable that the thickness be in the range of 0 to 100 μn.

The mixing ratio of the toner and magnetic carrier varies depending on the physical properties of the toner and magnetic carrier, but the weight ratio is generally 1:99 to 10:90, particularly 2:98 to 5:95.
It is desirable that it be within the range of . Further, the electrical resistivity of the IIL image material as a whole is 5 x 10' to 5 x
1012Ω・am, preferably 5x109 to 5X]
It is generally desirable that it be in the range of O.Ω.cm.

To develop an electrostatic image, after mixing the toner and magnetic carrier, a magnetic brush of a predetermined length is formed on a developing sleeve having a magnet roll inside, and this magnetic brush and a photoreceptor having an electrostatic image are connected. The magnetic brush and the electrostatic image holding photoreceptor are brought into close proximity to each other in an electric field to which an oscillating electric field is applied.

(Effects of the Invention) According to the present invention, in a negatively charged electrophotographic toner containing a fixing resin, a colorant, and a negatively charged charge control agent,
By incorporating a charge control aid into the toner, which is incompatible with the fixing resin but has dispersibility and has a charge control action of the opposite polarity to that of the charge control agent for negative charging, it is possible to Eliminates various drawbacks of negatively charged toner, and the average value of toner charge is in the optimum range for toner scattering prevention and image density, and the distribution of toner charge is sharp, so it is not used for development. A negatively charged toner is provided that is free of highly charged toner and lowly charged toner that causes toner scattering. The toner of the present invention has a toner band tffi
In addition to having a sharp distribution of , the charge rises quickly during charging, and the charging characteristics are less likely to deteriorate during long-term operation.

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

However, the present invention is not limited to this.

(Example 1) Styrene-acrylic copolymer as fixing resin 10
0 parts by weight, 8 parts by weight of carbon black as a coloring agent, low molecular weight polypropylene as an anti-offset agent
1.5 parts by weight, aluminum complex of aromatic dicarboxylic acid as charge control agent for negative charging 2 parts by weight, styrene-
A quaternary ammonium salt of the following formula as an auxiliary agent for charge i that is incompatible with the acrylic copolymer. p by a two-axis refiner? 8. After melt kneading and cooling the kneaded material,
The powder was crushed and classified to obtain a toner having an average particle size of 11 μm. The average particle size of this toner and the resin coated product was 85.
A developer was prepared by mixing and stirring μrn ferrite carrier at a toner concentration of 4.5%, and the charge distribution was measured using a toner charge distribution measuring device shown in the m4 diagram. The result is the ft51 diagram.

Next, the above developer was applied to a modified Sanda Kogyo laser beam printer LPX-1 equipped with a negatively charged organic photoreceptor (the development method was modified to an inverted GL image method) (the photoreceptor surface potential knee was 700 V, Continuous image formation was performed on 1000 sheets at a bias potential of 500 V). As a result, no decrease in image density or image fogging occurred, and there was no toner scattering at all.

Details are shown in Table 1.

(Example 2) A toner having an average particle size of 11 μm was obtained in the same manner as in Example 1, except that 5 parts by weight of C1 Pigment Red 237 was used as a charge control aid. Thereafter, a developer was obtained in the same manner as in Example 1, and images were continuously formed on 1000 sheets. As a result, similar to Example 1, good images were obtained, and there was no toner scattering inside the machine. Further, the toner charge amount distribution was also sharp as in Example 1.

(Comparative Example 1) A toner was prepared in the same manner as in Example 1 except that the charge control auxiliary agent was not added. When the toner charge amount distribution was measured in the same manner as in Example 1, the results were shown in FIG. Then, when 1000 images were continuously formed in the same manner, the image density was unstable and the image density occasionally dropped.

Additionally, image fogging and toner scattering occasionally occurred.

(Comparative example 2) In Example 1, instead of the charge I11 auxiliary agent.

C that is compatible with the fixing resin; 1. solvent yellow
A toner was prepared in the same manner except that 2 parts by weight of 56 was used. Then, the toner charge amount distribution was measured in the same manner as in Example Y, and the results were shown in FIG. 3. Furthermore, when 1000 images were continuously formed in the same manner, image fogging and toner scattering were severe. Further, 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 2 parts by weight of C, I, and Basic Blue, which are compatible with the fixing resin, were used instead of the charge control aid. Then, when the charge amount distribution of the toner was measured in the same manner as in Example 1, it showed a form similar to that shown in FIG. 3. Similarly, 100
When continuous image formation was performed on 0 sheets, image fogging and toner scattering were severe. Further, although the image density was satisfactory to some extent, density unevenness occasionally occurred.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a characteristic 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 a toner using only a charge control agent for negative charging. , FIG. 3 is a diagram showing the characteristic curve of the charge amount distribution of a toner using a charge control agent for negative charging and a positively charging dye (comparable to the fixing resin), and FIG. FIG. 2 is a schematic layout diagram of a charge amount measuring device that uses a toner band to measure the amount distribution. Patent applicant Sanda Kogyo Co., Ltd. Figure 4

Claims (5)

[Claims] (1) A negatively charged electrophotographic toner containing a fixing resin, a colorant, and a negatively charged charge control agent, which is incompatible with the fixing resin but has dispersibility and is negatively charged. An electrophotographic toner for negative charging, characterized in that the toner contains a charge control auxiliary agent having a charge control action of opposite polarity to that of the charge control agent for electrophotography. (2) The toner according to claim 1, wherein the charge control aid is a quaternary ammonium salt. (3) The toner according to claim 1, wherein the charge control aid is a quaternary ammonium salt containing an oxyacid anion as an anion. (4) The charge control aid has the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, at least one of R is a long-chain alkyl group or a long-chain alkenyl group, and at least two of them are Under the condition that it is a lower alkyl group or a benzyl group,
It is a lower alkyl group, a benzyl group, a long-chain alkyl group, or a long-chain alkenyl group, and A represents an anion. The toner according to claim 1, which is a compound represented by: (5) The charge control agent and the charge control aid are present in a weight ratio of 1:0.05 to 1:1, and in a total amount of 0.5 to 5 parts by weight per 100 parts by weight of the fixing resin. Toner listed.