JPH08254852A - Electrophotographic toner - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an electrophotographic toner having a high rate of rise in charge by using a small amount of a charge control agent. [Constitution] The ratio of the loss permittivity of the toner to the loss permittivity of the binder resin is set in the range of 1.2 to 2.3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used for developing an electrostatic latent image in electrophotography or the like. More specifically, it relates to improvement of the charging speed of toner.

[0002]

2. Description of the Related Art In electrophotography, a photoconductive insulator (such as a photocondrum) is provided with a uniform electrostatic charge by corona discharge or the like, and an optical image is formed on the photoconductive insulator by various means. Irradiation forms an electrostatic latent image. here,
Develop by charging fine powder called toner, and the charged toner adheres to the latent image by electric attraction.
Visualization is performed, and the toner image is transferred to paper or the like as needed, and then the toner image is fixed on a recording medium such as paper by a means such as pressurization, heating, or irradiation with light to obtain a copy. is there.

Conventionally, a toner is made of a binder resin made of a natural or synthetic polymer substance, a substance such as carbon black or a dye, which plays a role of controlling coloring and charge, and waxes, alone or in combination. 5 to 5 of these dispersed in a binder resin
Particles finely pulverized to about 20 μm are used. Toner for developing an electrostatic latent image is iron powder, magnetite,
By mixing with iron or metal oxide such as ferrite, or a carrier substance (carrier) obtained by applying various coatings to the above substances, they are triboelectrically charged (two-component developing method). When the toner is used alone, it is frictionally charged by rubbing the toner against a wall surface of the developing device or a member such as a magnet roll in the developing device (one-component developing method).

When a large amount of toner is printed at high speed in electrophotography, a large amount of toner is consumed. Therefore, the supplied toner must be quickly raised to a printable charge amount. Since flash fixing, which is a typical optical fixing, is non-contact fixing, it does not deteriorate the resolution of an image during development. There is no waiting time after the power is turned on, and quick start is possible. Even if the recording paper is jammed in the fixing device due to system down, it does not ignite. Glued paper,
It can be fixed regardless of the material and thickness of the recording paper, such as preprinted paper or paper with different thickness. It has features such as, and is used for high-speed, large-volume printing. In such a printer, it is especially necessary to quickly charge the toner.

[0005]

The saturated charge amount and charge rising speed of the toner are determined by the balance of the constituent elements of the toner, that is, the charge control agent such as the binder resin, carbon and dye. The charge rate and the saturated charge amount can be increased by increasing the amount of the charge control agent, but the charge control agent is expensive and it is not desirable to use it in a large amount. Also, the use of large amounts can adversely affect other properties of the toner. Heretofore, there has been no study on a method for increasing the rate of charge increase when a small amount of charge control agent or the same amount of charge control agent is used.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrophotographic toner having a high charge rising speed by using a small amount of a charge control agent.

[0007]

It is known that the charging of toner is determined by the balance between the accumulation and leakage of generated charges, and an equation for the change of specific charge with time according to this is known (see below). References 1 and 2). [Reference 1] Kenichi Karakida: The 60th Research Forum of the Electrophotographic Society, p. 1, (1987) [Reference 2] Norie Matsui, Kozo Oka: Journal of Electrophotographic Society, p.
307, Vol. 27, No. 3 (1988) The electric charge is generated by friction between a carrier such as a carrier (two-component development), a printer member such as a blade (one-component development) and the toner, and the degree of charge leakage varies. If it does not change, it is considered that the higher the rate of charge accumulation per unit time, the higher the rate of increase in charging. In addition, the leakage of charge is
It is thought that it occurs toward the ground through the carrier or the printer member, or into the air, and if the degree of charge accumulation does not change, the greater the leakage of charge, the faster the time to reach the saturated charge amount, that is, It is predicted that the rate of increase in charge tends to increase and the saturated charge amount tends to decrease.

In practice, it is difficult to fix one of the charge accumulation and the leakage and to change only the other, and in many cases it can be said that it is determined only by the balance between the two. However, the charge accumulation and the leakage dominate. Is certain. Toner has a high resistivity in the insulator region, ie it is a dielectric. Then, the real number part (storage permittivity, ε ') and the imaginary number part (loss permittivity,
Each ε '') is expected to be related to charge accumulation and leakage. Therefore, the dielectric property is likely to be related to the charging speed of the toner.

As a result of studies, the inventors have found that the loss permittivity (ε ″) of the toner has a correlation with the charging rate of the toner, and that the higher the loss permittivity, the higher the charging rate. It came to eggplant. Other dielectric properties, storage permittivity (ε ′) and dissipation factor (tan δ) have no clear correlation with the charging rate.

The loss permittivity is an amount corresponding to conductivity.
According to the studies by the inventors, the loss permittivity of the toner is increased based on the value of the binder resin, which accounts for the majority of the weight fraction, and the inclusion of other components. Therefore, if the binder resin changes, the value of the base also changes, so the relationship with the charging speed cannot be determined by the absolute value of the loss permittivity. It can be seen that the relationship with the charging rate is determined by the amount of change from the base value or the change ratio. As a result of the examination, it was found that the toner has a sufficient charging rate if the loss permittivity of the toner is 1.2 or more with respect to the loss permittivity of the binder resin. When the loss permittivity ratio exceeds 2.3, the charging speed is high, but the saturated charge amount exceeds the proper range. In addition, the amount of charge tends to gradually increase with friction and is not suitable for use in electrophotography.

Means for adjusting the loss permittivity of the electrophotographic toner and the loss permittivity of the binder resin are not unconditional.
It has to be empirical and experimental. The loss permittivity of the binder resin is determined according to the type of resin and its manufacturing method.
The loss dielectric constant of the toner depends on the type and amount of the charge control agent contained in the binder resin, but the actual amount used is small, so other conditions than this amount, in this case, the dispersion state of the conductive component It is considered to be an important factor. This changes depending on the toner manufacturing (kneading) conditions. Specifically, it seems that the value of the loss permittivity tends to increase as the kneader rotation speed increases. However, the dispersed state changes with temperature, so it cannot be said that the relationship always holds. The loss dielectric constant of a toner is affected by the dispersion state of carbon and dye in the toner. The dispersion state is determined by how the rotational shear of the kneader is transmitted to the carbon and the dye through the resin. This changes depending on the resin viscosity, and at low viscosity, the shear may not be transmitted regardless of the kneader rotation speed. However, even in a high-viscosity state, if the number of revolutions is increased too much, the high share is achieved only in the vicinity of the teeth, but there is a case where little share is applied at a position slightly apart.

By adjusting the loss permittivity ratio in this way, the amount of the charge control agent in the toner can be reduced by about 50% as compared with the conventional typical example. As the toner binder, carbon, colorant, charge control agent, waxes and the like used in the present invention, known materials usually used in electrophotography can be used. As the toner binder resin, polyester resin, epoxy resin or the like can be used. In the flash fixing method, prompt melting of toner and penetration into paper are required, and a polyester resin is preferably used as a resin satisfying these requirements.

In high-speed printing, amorphous silicon is often used as a photoconductor, and in this case, the toner needs to be positively charged. Polyester resin
Since it is often negatively charged, it is positively charged by using a charge control agent such as a nigrosine type or a quaternary ammonium salt type. If a negative charge is originally charged positively, the charge amount may be low, depending on the amount and condition of the charge control agent added.
It often takes a long time to start up, and it is necessary to consider the rise of charging.

The toner used in the present invention can be manufactured by a conventionally known method. That is, a binder resin, a colorant, and optionally carbon, a charge control agent, etc. are melt-kneaded by, for example, a pressure kneader, a roll mill, an extruder, etc. and uniformly dispersed, and for example, finely pulverized by, for example, a jet mill. A desired toner can be obtained by classification with a classifier such as an air classifier. Further, if necessary, silica powder, fluororesin powder, titanium oxide fine powder, or the like can be added as an external additive to the manufactured toner.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 As a binder resin, 5 parts by weight of carbon black (Mogal L, made by Cabot) as a coloring material to 92 parts by weight of polyester resin (1) (Diacron ER-501, made by Mitsubishi Rayon), Nigrosine dye (Oil Black BY, Orient Chemical)
Add 3 parts by weight, and press a kneader to 140 ° C, 100r.
Melt kneading was performed for 30 minutes at pm to obtain a toner mass. The cooled toner lump was made into a coarse powder toner having a particle diameter of about 2 mm by a Rotoplex pulverizer. Then, the toner is finely pulverized using a jet mill, and the pulverized product is classified by an air classifier,
A positively charged toner A having a particle size of 5 to 20 μm was obtained.

The dielectric properties of Toner A are determined as follows.
I have 450 kg weight of toner powder / cm ²Compressed at
Molding (KBr tablet molding machine, hand press: SSP
-10A, manufactured by Shimadzu Corporation), and then dielectric loss measuring device
(TR-10C, WBG-9, BDA-9, SE-4
3, TO-10, manufactured by Ando Electric Co., Ltd., and applied voltage 20
V, frequency 1000 Hz, storage permittivity (ε '),
Calculate loss permittivity (ε '') and dielectric loss (tan δ)
I have

The charging speed and the saturated charge amount were determined as follows. 6 parts by weight of A toner and 94 parts by weight of magnetite carrier (manufactured by Kanto Denka Kogyo Co., Ltd.) were placed in a polybin, stirred by a ball mill, and sampled at appropriate intervals
The charge amount was determined by the blow-off method (TB-100, manufactured by Toshiba Chemical). This was plotted on a graph, and a curve fit was performed by the following formula described in the above-mentioned Document 2 to obtain a time constant τ of rising of charging.

Q _max −q = (q _max −q _o ) exp (−t / τ) where q: toner charge amount t: mixing time τ: time constant of charge rise q _max : when t = 0 Q q _o : When t = ∞, 6 parts by weight of the qA toner and 94 parts by weight of magnetite carrier (manufactured by Kanto Denka Kogyo Co., Ltd.) are taken to prepare a developer, and FACOM is used.
A printing test was conducted using a modified 6700 laser printer.

Example 2 A polyester resin (1) was used as a binder resin, and the kneading conditions were 140 ° C. and 20 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining a positively charged toner B having a particle size of up to 20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

Example 3 A polyester resin (1) was used as a binder resin, and the kneading conditions were 130 ° C. and 20 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining a positively charged toner C having a particle size of up to 20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

Example 4 Polyester resin (2) (Pryoton 5120, manufactured by Goodyear) was used as a binder resin, and the kneading conditions were 140 ° C. and 100 rpm for 30 minutes. Particle size 5 to 20 μm
After obtaining the positively charged toner D, the dielectric constant and the charging time constant were determined, and a printing test was performed.

Example 5 A polyester resin (2) was used as a binder resin, and the kneading conditions were 140 ° C. and 20 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining the positively charged toner E having a particle size of up to 20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

Example 6 A polyester resin (2) was used as a binder resin, and the kneading conditions were 130 ° C. and 20 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining a positively charged toner F having a particle size of up to 20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

Comparative Example 1 Polyester resin (1) was used as the binder resin, and the kneading conditions were 130 ° C. and 50
The rpm was set to 30 minutes, and the particle size was 5 to 5 in the same manner as in Example 1.
After obtaining the positively charged toner G of 20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

[Comparative Example 2] Polyester resin (1) was used as the binder resin, and the kneading conditions were 140 ° C and 30 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining a positively charged toner H of ˜20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted.

[Comparative Example 3] Polyester resin (2) was used as the binder resin, and the kneading conditions were 130 ° C and 50 ° C.
The rpm was set to 30 minutes, and the particle size was 5 to 5 in the same manner as in Example 1.
After obtaining the positively charged toner I of 20 μm, the dielectric constant and the time constant of charging were obtained and a printing test was conducted.

[Comparative Example 4] Polyester resin (2) was used as a binder resin, and the kneading conditions were 140 ° C and 30 ° C.
It was set to 0 rpm for 30 minutes, and the particle size was 5 in the same manner as in Example 1.
After obtaining a positively charged toner J of ˜20 μm, the dielectric constant and the charging time constant were determined and a printing test was conducted. The results of the above Examples and Comparative Examples are shown in Table 1 and FIGS. When the ratio of loss permittivity was 1.2 or less, fog occurred due to insufficient charging, and when 2.3 or more, after 40 minutes, the charge amount increased and the optical density of the printed matter decreased. If the ratio of loss permittivity is in the range of 1.2 to 2.3, good printing can be obtained.

[0029]

[Table 1]

[Brief description of drawings]

FIG. 1 shows the relationship between the dielectric constant ratio of toner and polyester resin (1) and the time constant of charge increase in Examples.

FIG. 2 shows the relationship between the dielectric constant ratio of toner and polyester resin (2) and the time constant of charge increase in Examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Naito No.35 Saho, Shrine-cho, Kato-gun, Hyogo Prefecture (No address) Inside Fujitsu Peripheral Machinery Co., Ltd. Address within Fujitsu Limited (72) Inventor Norio Saruwatari 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Within Fujitsu Limited

Claims (5)

[Claims] 1. A dry toner containing a binder resin as a main component, wherein the ratio of the loss permittivity of the toner to the loss permittivity of the binder resin is in the range of 1.2 to 2.3. toner. 2. The electrophotographic toner according to claim 1, wherein the binder resin of the toner is a polyester resin. 3. The toner for electrophotography according to claim 1, wherein carbon and a nigrosine dye are contained as essential constituents of the toner. 4. The toner for electrophotography according to claim 1, wherein carbon and a quaternary ammonium salt dye are contained as essential constituents of the toner. 5. The toner for electrophotography according to claim 1, which is used in electrophotography in which a flash fixing system is adopted for toner fixing.