JPH06282097A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide an electrophotographic toner excellent in fluidity, caking resistance and chargeability and with a black-spot picture flaw hardly generated. CONSTITUTION:This electrophotographic toner consists essentially of a binder resin and a colorant, 0.05-1.0wt.% of the fine particles having <=16nm primary average diameter are added to the toner particles having 3-10mum average diameter, and AXB <=0.2 and 0.05 <=BXC <=0.30 are fulfilled. In the inequalities, A is the ratio of the fine particle desorbed from the toner particle to the total amt. of the fine particle added when an ultrasonic vibration (20W output and 20kHz frequency) is applied in the toner dispersion, B is the wt.% of the fine particle added to the toner particle and C is the ratio of the fine particle desorbed from the toner particle to the total wt.% of the fine particle added when an ultrasonic vibration (60W output and 20kHz frequency) is applied in the toner dispersion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing and the like.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat. No. 2,297,691 and JP-B-42-23910 are known.
And Japanese Patent Publication No. 43-24748. These methods use a photoconductive substance to form an electrostatic latent image on a photoreceptor, develop it with toner, transfer the toner image to paper, etc., if necessary, and then heat or use solvent vapor. The image is fixed and a copy image is obtained. A method of visualizing an electrostatic latent image with toner is described in, for example, the magnetic brush method described in US Pat. No. 2,674,063 and the US Pat. No. 2,616,552. Cascade Method, US Pat. No. 2,22
The powder cloud method and the like described in the specification of 1,776 are known. Dry developers used in such an electrophotographic method are roughly classified into a one-component developer using a toner itself in which a colorant is dispersed in a binder resin and a two-component developer in which a carrier is mixed with the toner. be able to. When performing a copying operation using these developers, it is necessary that the developers have excellent fluidity, anti-caking property, fixing property, charging property, cleaning property and the like in order to have process compatibility. . Then, in order to improve fluidity and anti-caking property, it is often practiced to add fine particles such as silica to the toner. By the way, the process compatibility also greatly depends on the state when the fine particles are attached to the surface of the toner particles.
For example, fine particles that have weak adhesion to toner particles or have not yet adhered to the toner particles easily migrate and adhere to the photosensitive layer, causing image defects in black spots. JP-A-63-85756, JP-A-63-139366, JP-A-3-293676.
Issue).

[0003]

However, if the adhesive force with the toner particles is made too strong, the fine particles are embedded in the toner particles, and the proportion of the fine particles that should function effectively with respect to the added amount decreases, and the desired amount is reduced. Although the amount of addition must be further increased in order to obtain the toner characteristics, the surface area of the mother particles is limited. Therefore, if the coverage of the toner exceeds 100%, the number of fine particles with weak adhesion will increase and transfer to the photoconductor. The rate of adhesion increases and image defects occur. The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide an electrophotographic toner excellent in fluidity, anti-caking property, and electrostatic property. Another object of the present invention is to provide an electrophotographic toner in which black dot image defects are less likely to occur.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on the relationship between the adhesion of fine particles to toner particles and the toner characteristics such as improvement in fluidity and image quality. It has been found that the above object is achieved when the amount and the adhesive force of fine particles have a predetermined relationship,
The present invention has been completed. That is, the electrophotographic toner of the present invention contains a binder resin and a colorant as essential components,
Toner particles having an average particle size of 3 to 10 μm have a primary average particle size of 1
It is characterized in that fine particles of 6 nm or less are added and the following formula is satisfied. A × B ≦ 0.2 0.05 ≦ B × C ≦ 0.30 [where A is ultrasonic vibration (output 20
(W, frequency 20 kHz) for 1 minute with respect to the total amount of fine particles desorbed from the toner particles, B is the weight% of the fine particles added to the toner particles, and C is ultrasonic vibration (output) in the toner dispersion liquid. 60W, frequency 20kHz) 3
In the present invention, toner for developing an electrostatic charge image by electrostatic recording method, electrostatic printing method or the like in addition to the electrophotographic method is shown. Is also referred to as an electrophotographic toner for convenience.

The present invention will be described in detail below. As described above, the toner for electrophotography of the present invention comprises toner particles containing the binder resin and the colorant as essential components, and the particles having an average particle diameter in the range of 3 to 10 μm have a primary average particle diameter of 1
Fine particles of 6 nm or less are added. Examples of the binder resin for the toner particles include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; ester vinyls such as vinyl acetate, vinyl propionate and vinyl benzoate; acrylic. Α of methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, etc.
-Methylene aliphatic monocarboxylic acid esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl butyl ether; homopolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone, or copolymers thereof. A polymer can be illustrated. Particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymers, styrene-alkyl acrylate copolymers, polyethylene, polypropylene and the like. Further, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like can be mentioned.

As the colorant for the toner particles, carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp. Black, Rose Bengal, C.I.
I. Pigment Red 48: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 12
2, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 97, C.I. I. Pigment Blue 1
5: 1, C.I. I. Pigment Blue 15: 3 and the like can be illustrated as a typical example. When used as a magnetic toner, a part or all of the colorant may be replaced with magnetic powder. Examples of such magnetic powder include magnetite, ferrite, iron powder, nickel and the like.

As the toner particles of the present invention containing a binder resin and a colorant as essential components, those having an average particle size of 3 to 10 μm are used. When the particle size is less than 3 μm, it is difficult to obtain the adhesion strength of the fine particles as compared with the conventional toner particles, while when the particle size is larger than 10 μm, the adhesion strength of the fine particles to the toner particles becomes too strong. The diameter needs to be in the above range.

In the present invention, the fine particles externally added to the toner particles include, for example, SiO ₂ , TiO ₂ , Al ₂ O ₃ ,
CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , M
gO, BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ ,
CaO · SiO ₂ , K ₂ O · (TiO ₂ ) _n , Al ₂ O
_{3 · 2SiO 2, CaCO 3,} MgCO 3, BaS
Examples thereof include inorganic fine powders such as O ₄ and MgSO ₄ , resin fine powders such as polystyrene, polyvinylidene fluoride, epoxy resin, and methacrylate resin. Among these fine particles, silica, titania and alumina are preferably used, but silica fine particles are particularly preferable. Further, the fine particles may be untreated, or may be hydrophobized with a hydrophobizing agent such as a silane coupling agent or surface-treated with a quaternary ammonium salt or silicone oil. .

These fine particles have a primary average particle size of 16 nm.
The following are used: When the particle size is larger than 16 nm, the adhesion strength of the fine particles to the toner particles becomes too strong, and the fluidity deteriorates in relation to the average particle size of the toner particles,
Caking easily occurs. Therefore, the average primary particle diameter of the fine particles needs to be within the above range. Further, the addition amount of the fine particles to the toner particles is 0.05 to
1.0% by weight, preferably 0.1-0.5% by weight is suitable.

As a means for holding the fine particles on the surface of the toner particles, an ordinary mixer such as a ball mill or a V type mixer can be used, but it is preferable to use a so-called high speed fluidized agitator. Examples of the high-speed fluidized agitator include a Henschel mixer, a mechanofusion system (manufactured by Hosokawa Micron), a nara hybridization system (manufactured by Nara Machinery Co., Ltd.), and a mechanomill (manufactured by Okada Seiko). However, the device for holding the fine particles on the surface of the toner particles is not limited to these. When a Henschel mixer is used as an example, fine particles can be favorably attached by appropriately adjusting the shape of the stirring blade, the peripheral speed, the mixing time, and the like. When the fine particles are held in the toner particles, for example, if the peripheral speed of the mixer is increased or the mixing time is lengthened, the adhesion strength becomes stronger. However, if the peripheral speed is increased or the mixing time is lengthened, the temperature in the tank rises, and fusion or aggregation of toner particles does not occur. Therefore, in order to keep the temperature below room temperature, preferably below 10 ° C., cold water or The mixing tank may be cooled with cooling brine or the like.

In the toner of the present invention, it is important that the following relationship be satisfied between the toner particles and the externally added fine particles. A × B ≦ 0.2 0.05 ≦ B × C ≦ 0.30 A: Total amount of fine particles detached from the toner particles when ultrasonic vibration (output 20 W, frequency 20 kHz) is applied for 1 minute in the toner dispersion liquid. Proportion to Addition Amount B: Weight% of fine particles added to toner particles C: Total addition amount of fine particles desorbed from toner particles when ultrasonic vibration (output 60 W, frequency 20 kHz) is applied for 30 minutes in the toner dispersion liquid To

When determining the above A and C, the adhesion strength of the fine particles to the toner particles in the present invention is measured as follows. That is, 2 g of toner particles are added to 40 ml of a 0.2% aqueous surfactant solution, and the toner particles are sufficiently dispersed so as to be wet with the aqueous solution. In this state, ultrasonic vibration with a frequency of 20 kHz is applied with a predetermined output for a predetermined time, and the amount of fine particles desorbed from the toner particles is measured.
Specifically, the ratio of the amount of fine particles desorbed after applying ultrasonic vibration for 1 minute at an output of 20 W to the amount of fine particles adhering before applying ultrasonic vibration is A, and similarly, at an output of 60 W, 3
The above ratio after applying ultrasonic vibration for 0 minutes is C. The above A and C change by increasing or decreasing the addition amount of the fine particles. However, if the addition amount is too small or too large, the relation of the above formula may not be satisfied, so the addition amount is Usually, the above range is suitable.

If desired, the toner of the present invention may contain additives such as a charge control agent and a release agent. When used as a two-component developer, iron powder, glass beads, ferrite powder, nickel powder, or those having a resin coating on the surface thereof are used as the carrier.

[0014]

In the electrophotographic toner of the present invention, the fine particles externally added to the toner particles satisfy the relation of the above formula, and the fine particles which are easily detached from the toner particles are removed. The rate of migration and attachment to the body decreases,
The occurrence of image defects can be suppressed for a long period of time.
That is, if the adhesion strength of the fine particles to the toner particles is too weak, the fluidity is good, but the chargeability is high and a good copy density cannot be obtained. On the other hand, if the adhesion strength is too high, the chargeability is low and a good copy density is easily obtained, but the fluidity is poor and problems such as poor toner replenishment and caking occur. On the other hand, in the present invention in which the toner particles having an average particle diameter of 3 to 10 μm and the fine particles having a primary average particle diameter of 16 nm or less are combined, the fluidity and the charging property are greatly related to the adhesion strength. It is possible to achieve both chargeability and adhesion to the photoconductor.

[0015]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. The following "parts" mean "important parts". Example 1 Styrene-n-butyl acrylate (85:15) copolymer 85 parts Carbon black (BP1300, manufactured by Cabot) 10 parts Polypropylene wax 5 parts (Viscole 660P, manufactured by Sanyo Chemical Industries) Melt kneading the above components , Pulverize, classify and average particle size 9μ
m black particles were obtained. Next, silica (RX200, manufactured by Nippon Aerosil Co., Ltd.) shown in Table 1 was added to the toner particles as an external additive, and the mixture was mixed with a Henschel mixer having a capacity of 5 l in which the temperature of the mixing tank was cooled to 5 ° C. to obtain a toner. It was The particle size of the toner was measured with a particle size analyzer (TA-II, manufactured by Coulter Counter, Inc.) having an aperture diameter of 100 μm.

Example 2 Styrene-n-butyl acrylate (85:15) copolymer 83 parts Carbon black (BPL, Cabot Co.) 10 parts Charge control agent (TRH, Hodogaya Chemical Co., Ltd.) 1 part Polypropylene wax (Viscole 660P) 6 parts The above components are melt-kneaded, pulverized and classified to have an average particle size of 7 μm.
m black particles were obtained. Next, silica (R812, manufactured by Nippon Aerosil Co., Ltd.) was added to the toner particles as an external additive, and a toner was obtained in the same manner as in Example 1. Example 3 After obtaining black particles having an average particle size of 9 μm in the same manner as in Example 1, silica (TS720, manufactured by Cabot Corporation) was added as an external additive, and a toner was obtained in the same manner as in Example 1.

Comparative Example 1 After obtaining black particles having an average particle size of 9 μm in the same manner as in Example 1, RX200 was added as an external additive, and a toner was obtained in the same manner as in Example 1. Comparative Example 2 After obtaining black particles having an average particle size of 9 μm in the same manner as in Example 1, RX200 was added as an external additive, and a toner was obtained in the same manner as in Example 1. Comparative Example 3 After obtaining black particles having an average particle size of 7 μm in the same manner as in Example 2, RX200 was added as an external additive, and a toner was obtained in the same manner as in Example 1. Comparative Example 4 After obtaining black particles having an average particle size of 7 μm in the same manner as in Example 2, silica (R972, manufactured by Nippon Aerosil Co., Ltd.) was added as an external additive, and a toner was obtained in the same manner as in Example 1. .

With respect to each of the obtained toner particles, the adhesion strength of fine particles was measured by the following method, and the numerical values A and C of desorbed silica were obtained according to the above formula. 2 g of toner particles are sufficiently dispersed in 40 ml of a 0.2% concentration Triton solution (polyoxyethylene octyl phenyl ether having a degree of polymerization of 10, manufactured by Wako Pure Chemical Industries), and an ultrasonic oscillator with an oscillation frequency of 20 kHz is immersed in the ultrasonic wave. The silica was desorbed by operating a sonic vibrating device (ultrasonic homogenizer US300T, manufactured by Nippon Seiki Seisakusho) at an output of 20 W for 1 minute and at an output of 60 W for 30 minutes. Then, a 50 cc centrifuge with a sedimentation tube (compact cooling high-speed centrifuge Model M160-IV,
The toner particles were separated under a condition of 1000 rpm × 2 min by applying Sakuma Seisakusho Co., Ltd., and after removing the supernatant liquid, the particles were washed twice with pure water and dried. Molded dry toner, fluorescent X-ray analyzer (System 3370, manufactured by Rigaku Corporation)
The amount of silica remaining in the toner particles was determined by. The above measurement results are shown in Table 1 together with external additives and mixing conditions. The "silica addition amount B" in Table 1 is represented by wt% with respect to the toner particles.

[0019]

[Table 1]

Preparation of Developer For each toner obtained in Examples 1 to 3 and Comparative Examples 1 to 4, a methyl methacrylate polymer (Mw; 8.5 ×) was used.
10 ⁴ ) 1.0 part of ferrite 10 having an average particle size of 40 μm
A carrier prepared by coating 0 part of the carrier was mixed with a V-type blender so as to have a concentration of 5% to prepare a developer.

Continuous copying test For each of the prepared developers, an electrophotographic copying machine (FX-
5030, manufactured by Fuji Xerox Co., Ltd.), 15,000 copies were continuously made, and the copy density, fog, black spots on the copy, charge amount and toner density were measured, and these characteristics were evaluated.・ Copy density ・ ・ ・ Measured with Macbeth densitometer ・ Fog ・ ・ ・ Judged by comparing with samples from G1 (good) to G5 (bad) ・ Black spots on copy ・ ・ ・ Visual evaluation ・ Charge amount and toner density ・ ・ ・ Blow-off charge Measurement with a volume measuring machine (TB-200, manufactured by Toshiba Chemical Co.) The results are shown in Table 2.

[0022]

[Table 2] As shown in Table 2, when the toners of the respective examples are used, the density maintenance property, fog, and
It can be seen that both the black spots on the copy and the toner concentration maintaining property are superior to the toners of the comparative examples that do not satisfy the above expression.

[0023]

In the electrophotographic toner of the present invention, since the fine particles externally added to the toner particles satisfy the relationship of the above formula, the fluidity, the caking resistance and the charging property are excellent, and the toner is also photosensitive. Adhesion of fine particles to the body is reduced, and image defects such as the generation of black dot images can be suppressed for a long period of time.

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[Procedure amendment]

[Submission date] April 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

[Table 1]

Front page continued (72) Inventor Eimi Takahashi 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. An electrophotographic toner containing at least a binder resin and a colorant, having an average particle size of 3 to 10 μm.
A toner for electrophotography, characterized in that fine particles having a primary average particle size of 16 nm or less are added to the toner particles, and the following formula is satisfied. A × B ≦ 0.2 0.05 ≦ B × C ≦ 0.30 [where A is ultrasonic vibration (output 20
(W, frequency 20 kHz) for 1 minute with respect to the total amount of fine particles desorbed from the toner particles, B is the weight% of the fine particles added to the toner particles, and C is ultrasonic vibration (output) in the toner dispersion liquid. 60W, frequency 20kHz) 3
Represents the proportion of the total amount of fine particles released from toner particles when added for 0 minutes]