JPH01112255A - Electrostatic image developing toner - Google Patents

Abstract

PURPOSE:To enhance cleanability and to stably form an image free from black spots by incorporating fine inorganic particles and fine organic particles having an average particle diameter of <=3mum of their primary particles and larger than that of the primary particles of the inorganic particles. CONSTITUTION:The toner comprises, as essential components, binder resin particles, the fine inorganic particles, and the fine organic particles having an average particle diameter of <=3mum of their primary particles and larger than that of the primary particles of the inorganic particles, thus permitting the obtained tone to achieve good cleaning in a state of reduced contact pressure of a cleaning blade to an latent image bearing body, and consequently, to prevent scratching of the surface of said by due to the inorganic particles, and to stably form images free from black spots in a large number of times.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to developing an electrostatic latent image formed on the surface of a latent image carrier in, for example, electrophotography, electrostatic recording, electrostatic printing, etc. This invention relates to toner for developing electrostatic images.

[Technology background]

In general, in electrophotography, a latent image carrier having a photosensitive layer made of a photoconductive material is given an electrostatic charge, and then the surface of the latent image carrier is exposed to light. A corresponding electrostatic latent image is formed, and this electrostatic latent image is developed by the developer conveyed to the development area by the developer conveyance carrier to form a toner image. This toner image is transferred to a transfer material such as paper and then fixed by heating, pressure, etc. to form a copy image. On the other hand, after the transfer step, the latent image carrier is neutralized, the remaining developer after transfer is cleaned, and then the latent image carrier is used for forming the next copy image.

Therefore, in order to achieve good development, a ladle must be able to stably transport the appropriate amount of toner to the development area using a developer transport carrier, and for this purpose, the toner must have high fluidity. It is said that

From this point of view, toners have conventionally been prepared by adding and mixing fine silica powder to binder resin particles.

[Problem that the invention seeks to solve]

However, in toners mixed with fine silica powder, the fine silica powder is quite hard, so when cleaning the residual toner with a cleaning blade placed in contact with the latent image carrier with a large pressure contact force, the fine silica powder is caught between the cleaning blade and the latent image carrier, and the surface of the latent image carrier is rubbed, resulting in a problem in that the surface of the latent image carrier is likely to be damaged. When the surface of the latent image carrier is damaged in this way, fine silica powder, etc. is embedded in the wound and cannot be cleaned. There is a problem in that this adheres and is fixed, resulting in black spot-like stains (black spots) on the image.

In addition, with toner mixed with fine silica powder, a filming phenomenon occurs in which toner substances adhere to the surface of the developer transport carrier and form a film as images are repeatedly formed. There is a problem in that the transportability of the toner by the carrier deteriorates, and the amount of toner transported to the development area gradually decreases, resulting in a decrease in image density.

In addition, toner containing fine silica powder has a large electrostatic adhesion force to the latent image carrier.
There is a problem in that the transfer rate of a toner image formed by development onto a transfer material is generally low, resulting in a decrease in image density.

In particular, when the toner is used as a one-component developer, since the toner contains magnetic powder, the number of molecules of the toner increases, resulting in a further decrease in the transfer rate.

The present invention has been made based on the above-mentioned circumstances, and is capable of stably forming an image with good cleaning performance and no black spots over many times, and also prevents the filming of the developer transport carrier. The present invention provides a toner for electrostatic image development, which can stably transport toner to a developing area without causing generation of toner, and can form an image with a high transfer rate and high image density.

[Means for solving problems]

The electrostatic image developing toner of the present invention comprises binder resin particles, inorganic fine particles, and organic fine particles in which the average diameter of the secondary particles is 3 μm or less and larger than the average diameter of the primary particles of the inorganic fine particles. It is characterized by being

[Function and effect of the invention]

According to the present invention, organic fine particles are contained together with inorganic fine particles, and the average diameter of the primary particles of the organic fine particles is 3 μm.
or less and larger than the average diameter of the primary particles of the inorganic fine particles, good developability is exhibited due to the effect of improving the fluidity of the toner by the inorganic fine particles, and the so-called lubricating effect of the organic fine particles forms the latent image of the toner. Since the physical adhesion to the carrier is weakened, residual toner can be easily cleaned. Therefore, it is possible to achieve good cleaning with a small pressure contact force of the cleaning blade against the latent image carrier, and as a result, damage to the surface of the latent image carrier due to inorganic fine particles can be prevented, and there is no black spot. Images can be stably formed many times.

The so-called lubricating action of the organic fine particles suppresses the occurrence of the filming phenomenon of the developer transport carrier due to toner substances, and the organic fine particles also provide appropriate polishing performance, so that the toner substances temporarily adhere to the developer transport carrier. Even if it does, it is easily removed, and as a result, even when images are formed many times, the ability of the developer transport carrier to transport toner to the development area becomes stable, resulting in a decrease in image density. Never.

Since the physical adhesion of the toner to the latent image carrier is weakened by the so-called lubricating action of the organic fine particles, the transfer rate of the toner image formed by development to the transfer material increases, and as a result, the image Images with high density can be formed.

Furthermore, as a result of the high transfer rate, the amount of residual toner remaining on the latent image carrier without being transferred is reduced, and from this point of view as well, cleaning of the residual toner becomes easier.

[Specific structure of the invention]

In the present invention, binder resin particles, inorganic fine particles, -
A toner for electrostatic image development is constituted by using as an essential component organic fine particles whose secondary particles have an average diameter of 3 μm or less and are larger than the average diameter of the primary particles of the inorganic fine particles. The electrostatic image developing toner of the present invention is a one-component developer that does not contain a carrier;
Alternatively, it can be applied to any type of two-component developer that mixes a carrier.

It is necessary that the average diameter of secondary particles (particles separated into individual unit particles) of the organic fine particles is 3 μm or less and larger than the average diameter of the primary particles of the inorganic fine particles. Especially 0
．． A range of 1 to 2 μm is preferred.

When the average diameter of the primary particles of the organic fine particles is too large, the toner transfer rate decreases and the image density decreases.

Further, when the average diameter of the primary particles of the organic fine particles is smaller than the average diameter of the primary particles of the inorganic fine particles, cleaning failure occurs.

The proportion of the organic fine particles is preferably 0.01 to 3.0% by weight, particularly preferably 0.1 to 2.0% by weight, based on the total toner. When the proportion of organic fine particles is too small, the toner transfer rate tends to decrease, the toner transportability tends to decrease, and furthermore, cleaning defects tend to occur. On the other hand, if it is too large, the triboelectric charging properties of the toner are likely to be inhibited.

The organic substance for forming the organic fine particles is not particularly limited, but vinyl polymers are preferred because they are relatively hard and provide appropriate polishing performance.

Such vinyl polymers can be produced by various polymerization methods, such as emulsion polymerization and vJ turbidity polymerization, but emulsion polymerization is preferred because small-diameter, spherical organic fine particles can be efficiently obtained. In particular, in systems in which the monomer used to obtain the vinyl polymer itself has an emulsifying effect, it is preferable to obtain the vinyl polymer by emulsion polymerization without using an emulsifier.

Examples of the vinyl polymer include acrylic polymers, styrene polymers, vinyl group-containing fluororesins, and among them, acrylic polymers are preferred.

Acrylic polymers are homopolymers or copolymers obtained by polymerizing monomers selected from acrylic acid, acrylic esters, methacrylic acid, and methacrylic esters. Acrylic monomers used to obtain such acrylic polymers include acrylic acid,
Methyl acrylate, ethyl acrylate, n-acrylate
Butyl, isobutyl acrylate, propinope acrylate n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate) 2-chloroethyl acrylate, phenyl acrylate, α-chloroacrylic acid Methyl, methacrylic acid, metinope methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, inbutinope methacrylate, n-octyl methacrylate, dodecinope methacrylate, lauryl methacrylate, methacrylic acid 2
-Ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylamine ethyl methacrylate, diethylaminoethyl methacrylate, and the like.

Among the acrylic polymers, polymethyl methacrylate is particularly preferred. With polymethyl methacrylate, uniform and small-diameter organic fine particles can be easily obtained,
In addition, it is possible to obtain a suitable polishing performance and suitably weaken the physical adhesion of the toner to the latent image bearing member or the developer transporting carrier, so that an excellent effect can be exhibited.

Furthermore, since there is no risk of inhibiting the triboelectric charging properties of the toner, stable developing performance can be obtained.

The acrylic polymer may be copolymerized with other monomers, if necessary.

In this case, it is preferable to use the acrylic monomer in a proportion of 50% by weight or more in the monomer composition. Such other monomers include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene. , p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, I) n-dodecylstyrene, p-methoxystyrene, p- Styrenic monomers such as phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene,
Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl esters such as vinyl acetate, vinyl acetate, and vinyl benzoate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone; Dienes such as butadiene and isoprene; unsaturated carboxylic acids such as maleic acid and fumaric acid; and others.

It is necessary that the average diameter of the secondary particles (particles separated into individual unit particles) of the inorganic fine particles is smaller than the average diameter of the primary particles of the organic fine particles.

When the average diameter of the primary particles of the inorganic fine particles is too large, damage occurs to the surface of the latent image carrier. Practically, the average diameter of the primary particles of the inorganic fine particles is preferably 2 μm or less, particularly 1 μm or less.
It is preferably less than μm.

The proportion of the inorganic fine particles is preferably 0.05 to 2.0% by weight, particularly preferably 01 to 1.0% by weight, based on the total toner.

When the proportion of inorganic fine particles is too small, the fluidity of the toner decreases, while when the proportion is too large, the surface of the latent image carrier is likely to be damaged.

The constituent materials of the inorganic fine particles are not particularly limited, but include, for example, oxides such as silica, titanium oxide, aluminum oxide, zirconium oxide, barium titanate, lead titanate, and barium carbonate; nitrides such as silicon nitride and boron nitride; and carbide. Carbides such as silicon, aluminum carbide, titanium carbide;
Others can be mentioned. These inorganic fine particles may be surface-treated.

Particularly preferred are silica fine particles or surface-treated silica fine particles. As the surface treatment agent, for example, a silane coupling agent, a titanium coupling agent, etc. can be used. The surface-treated silica fine particles are highly stable against environmental changes such as temperature and humidity, so that the environmental dependence of the triboelectric charging property of the toner can be suppressed to a small level.

Two or more types of inorganic fine particles may be used in combination. In this case, it is preferable to always use silica fine particles or surface-treated silica fine particles.

The above organic fine particles and inorganic fine particles are preferably used by being added to and mixed with the binder resin particles from the outside. Specifically, by mixing binder resin particles, organic fine particles, and inorganic fine particles using a mixing device such as a V-type blender, organic fine particles and inorganic fine particles are present on the surface of the binder resin particles. It is preferable to let

The binder resin particles are particles in which, for example, a magnetic substance, a colorant, an offset inhibitor, a charge control agent, etc. are contained in a binder resin.

The binder resin is not particularly limited, and various resins can be used. Specifically, styrene resins, acrylic resins, styrene-acrylic copolymer resins, epoxy resins, polyester resins, etc. can be mentioned.

These resins may be used in combination.

The styrene/acrylic copolymer resin used as the binder resin is a resin made of a copolymer of a styrene monomer and an acrylic monomer. Styrene monomers include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert. -butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-
Examples include nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3°4-dichlorostyrene, and the like.

Acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, and n-acrylate.
-Octyl, dodecyl acrylate, lauryl acrylate, 2-ethylhexynopea acrylate, stearyl acrylate, 2-chloroethinopea acrylate, phenyl acrylate, methyl α-chloroacrylate, methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, propinope methacrylate n-butyl methacrylate, isobutyl methacrylate, n-octinope methacrylate dodecinope methacrylate lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, methacrylic acid Mention may be made of diethylaminoethyl, diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, and others.

Magnetic substances include substances that are strongly magnetized in the direction of a magnetic field, such as metals or alloys that exhibit ferromagnetism such as iron, ferrite, and magnetophyte, nickel, and cobalt, compounds containing these elements, and ferromagnetic elements. Alloys that do not contain manganese and copper but become ferromagnetic through appropriate heat treatment, such as manganese-copper-aluminum, manganese-copper-tin, etc. Alloys called Heusler alloys that contain manganese and copper, dioxide Chromium, and others can be mentioned. The average particle size of the magnetic material is 0.1
It is preferable that it is uniformly dispersed and contained in the form of a fine powder of ~1 μm. When the toner is used as a -component developer, the content of the magnetic material is preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight, based on the total toner.

Examples of colorants include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, fucrocyanine blue, malachite green offsalate,
Mention may be made of lamp black, rose bengal, mixtures thereof, and others.

Examples of anti-offset agents include low softening point polyolefins, high melting point paraffin waxes, silicone resins, fatty acid esters or partially saponified products thereof, fatty acid amide compounds, higher alcohols, and the like.

Examples of the charge control agent include metal complex dyes, nigrosine dyes, ammonium salt compounds, and the like.

〔Example〕

Examples of the present invention will be specifically described below, but the present invention is not limited to these Examples.

Example 1 Styrene/acrylic copolymer resin (single composition: 65 parts by weight of styrene, 5 parts by weight of α-methylstyrene, 10 parts by weight of methyl methacrylate, 1 part by weight of n-butyl acrylate)
8 parts by weight, 56 parts by weight of divinylbenzene (2 parts by weight),
Magnephyto rBL-100J (manufactured by Chikun Kogyo Co., Ltd.) 40
Parts by weight, low molecular weight polypropylene "Viscol 660"
Mix 2 parts by weight of PJ (manufactured by Sanyo Chemical Industries, Ltd.),
The mixture was milled, pulverized, and classified to obtain a binder resin particle powder with an average particle size of 12 μm.

Inorganic fine particle powder “R-972” is added to this binder resin particle powder.
J (hydrophobic silica fine particles, average diameter of -order particles -0,
The present invention was prepared by mixing 0.5 wt. Toner T1 for electrostatic image development was obtained.

Using this toner T1, an electrophotographic copying machine rU-Bix 1200J (Konishi Using a modified machine (manufactured by Rokusha Kogyo Co., Ltd.), a real-photographing test was carried out 50,000 times under normal conditions, and the amount of toner conveyed to the developing area and changes in image density over time were investigated. The results are shown in FIGS. 1 and 2 by curve T1. As can be seen from these results, changes over time in the amount of toner conveyed to the development area and image density were small, and good images could be stably formed many times. In addition, when the images were visually observed to check for the occurrence of black spots, it was found that 50.00
No black spots were observed until the 0th test.

On the other hand, for comparison, a comparative toner t1 was produced in the same manner as above except that no organic fine particles were used.
1 was used to conduct a live-action test similar to the above. The results are shown in FIGS. 1 and 2 by curve t1. As can be understood from these results, the toner transport amount and image density began to decrease from around 15,000 times, and at 20,000 times, the image density became considerably low at 1.0 or less. Also 1
From around 0.000 times, black spots began to appear on the image.

Example 2 Various toners were produced in the same manner as in Example 1, except that the average diameter of the primary particles of the organic fine particles was varied.

Using each of these toners, a photocopying test was conducted in the same manner as in Example 1, and the transfer rate of the toner image obtained by development onto transfer paper was investigated. The results are shown in Figure 3. As can be understood from the figure, when the average diameter of the primary particles of organic fine particles is 3 μM or less, the transfer rate is 80% or more, which is sufficient for practical purposes, whereas when the average diameter exceeds 3 μm, the transfer rate is This decreases considerably and poses a practical problem.

Example 3 Styrene-acrylic copolymer resin (single composition: 65 parts by weight of styrene, 5-type middle part of α-methylstyrene, 10 parts by weight of methyl methacrylate, 1 part by weight of n-butyl acrylate)
8 parts by weight, 100 parts by weight of divinylbenzene (2 parts by weight), 10 parts by weight of carbon black "Mogull LJ" (manufactured by Cabot Corporation), and 4 parts by weight of low molecular weight polypropylene "Viscol 660PJ (manufactured by Sanyo Chemical Industries, Ltd.).
Mixed, kneaded, crushed, and classified to have an average particle size of 12μ
A counterfeit binder resin particle powder was obtained.

Inorganic fine particle powder [R-972
J (hydrophobic phosphoric acid fine particles, average diameter of -order particles -0,
016 μm, manufactured by B Hon Aerosil Co., Ltd.) in a proportion of 0.4% by weight and organic fine particle powder (polymethyl methacrylate fine particles, average diameter of -0.5/711 particles) in a proportion of 0.8% by weight, An electrostatic image developing toner according to the present invention was obtained.

A two-component developer was prepared by mixing 4 parts by weight of this toner with 96 parts by weight of a carrier made of ferrite powder rF-100J (manufactured by Nippon Tetsuko Co., Ltd.) having an average diameter of 120 μm.

Using this two-component developer, an electrophotographic copying machine rU-[] is equipped with a latent image carrier made of a selenium/tellurium photoreceptor and is equipped with a cleaning device having a cleaning blade. Ix 1800J (manufactured by Konishiroku Photo Industry Co., Ltd.) was used in a modified machine to perform 50,000 live-action tests under normal conditions, and the amount of toner conveyed to the development area and changes in image density over time were investigated.
The amount of toner conveyance and image density remained stable until the number of times the toner was conveyed. Furthermore, when the images were visually observed to check for the occurrence of black spots, no black spots were observed until 50,000 times.

On the other hand, for comparison, a comparative toner was manufactured in the same manner as above except that organic fine particles were not used, and a two-component developer was prepared in the same manner as above using this comparative toner and a live-action test was conducted. When this was repeated, the image density began to decrease after about 10,000 times, and fog and black spots began to appear on the image.

Example 4 Inorganic fine particle powder rR-972J (hydrophobic silica fine particles, -
Average diameter of secondary particles = 0.016 μm 0.4% by weight (manufactured by Nippon Aerosil Co., Ltd.), inorganic fine particles (silicon carbide fine particles, average diameter of secondary particles - 1.0JIm).

0.4% by weight of organic fine particle powder (polymethyl methacrylate fine particles, -average particle size -0,
A toner for developing an electrostatic image according to the present invention was obtained by mixing 0.8% by weight of 0.8% by weight.

Using this toner, a two-component developer was prepared in the same manner as in Example 3, and an actual photographic test was conducted. As a result, the toner transport amount and image density were stable up to 50,000 times. Furthermore, when the images were visually observed to check for the occurrence of black spots, no black spots were observed until 50,000 times.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the change over time in the amount of toner transported in the live-action test, Figure 2 is a diagram showing the change in image density over time in the live-action test, and Figure 3 is the transfer rate of toner images to transfer paper in the live-action test. FIG. Figure 1: Filial 2nd Figure: Zen Shaping Review (10,000 times)

Claims (1)

[Scope of Claims] 1) The invention comprises binder resin particles, inorganic fine particles, and organic fine particles in which the average diameter of the primary particles is 3 μm or less and larger than the average diameter of the primary particles of the inorganic fine particles. Characteristic toner for developing electrostatic images. 2) The toner for electrostatic image development according to claim 1, wherein the inorganic fine particles are made of silica or surface-treated silica. 3) The toner for electrostatic image development according to claim 1, characterized in that the toner contains two or more types of inorganic fine particles. 4) The toner for electrostatic image development according to claim 3, wherein one of the inorganic fine particles is made of silica or surface-treated silica. 5) The toner for electrostatic image development according to any one of claims 1 to 4, wherein the organic fine particles are made of a vinyl polymer. 6) The toner for electrostatic image development according to claim 5, wherein the vinyl polymer is an acrylic polymer. 7) The toner for electrostatic image development according to claim 6, wherein the acrylic polymer is polymethyl methacrylate.