JPS62269150A - Electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To obtain a sharp high-quality image near a print by specifying weight average particle diameter, and regulating the weight content of particles having particle diameters of >=8mum to <=5%, and the number content of particles having particle diameters of <=2mum to <=15%. CONSTITUTION:The toner particles have a weight average particle diameter of 3-5mum, the weight content of particles having particle diameters of >=8mum to <=5%, and the number content of particles having particle diameters of <=2mum to <=15%. It is preferred that both contents of >=8mum particles and <=2mum particles are as small as possible in order to enlarge the allowances of each development process, such as an electric field and a development gap, thus permitting the obtained image to be free from fog, superior in resolution, and high in image quality near the print.

Description

[Detailed Description of the Invention] 1. The present invention relates to a toner for developing an electrostatic latent image, particularly a new toner in which a gap between magnetic poles on the back side of a developer carrier exists in a developing section, and an alternating electric field is applied to the gap in this developing section. The present invention relates to a small particle size toner with a narrow particle size distribution width that is suitably used in a two-component non-contact developing method.

11 Aiyori Conventionally, as a non-contact development method, insulating magnetic toner or non-magnetic toner is thinly applied on the surface of a developer carrier.
A gap is formed between the surface of this thinned developer and the surface of the latent image carrier in the developing section, and an alternating electric field is applied to the developing section to cause the toner to drip from above the developer carrier. A method for developing an electrostatic Ns image on a latent image holder is disclosed in Japanese Patent Application Laid-open No. 55-1.
It is disclosed in Japanese Patent No. 8656.

However, such a developing method has the following problems. In other words, if you try to reliably charge each toner particle on the developer carrier surface to the desired polarity, the thickness of the toner layer on the developer carrier surface will inevitably become thinner, and the developed density of the solid black area will not be sufficient. A high value cannot be obtained; more specifically, when a single character-shaped PF3 image is developed.

Not only the toner on the surface of the developer carrier facing the latent image, but also the toner in the surrounding area gathers around the character latent image area due to the alternating electric field, so that a developed image with a sufficiently high density can be obtained. On the other hand, when an electrostatic latent image with solid black areas or thick lines is developed, the thin layer of toner on the surface of the developer carrier tends to be insufficient to obtain a high density, and the edges of the latent image tend to be insufficient. Toner collected on the image, resulting in image quality that lacked toner in solid black areas.

This lack of toner concentration in solid black areas is more noticeable when developing with non-magnetic toner made mainly of resin than when developing with magnetic toner made of resin and magnetic material. It is. Therefore, the problem became more serious when color development was performed than black and white development. especially,
For high-quality development aiming for Victorian colors,
knee.

The darkening effect and lack of density in solid black areas become serious problems.

Therefore, as a technique for overcoming the above-mentioned drawbacks, the present applicant has previously proposed an improved developing method in which the magnetic poles of the magnetic field generating means on the back surface of the developer carrier are located in the developing section (Unexamined Japanese Patent Publication No. However, studies on toners suitable for this developing method have not necessarily been sufficient.In other words, non-magnetic toner particles with a weight average particle size of a few tens of micrometers, which are currently commonly used, have not been sufficiently investigated. If used as is, the roughness will cause toner scattering during the development and transfer process, so the characteristics of the improved development method may not be fully utilized, and resolution will not be improved sufficiently, resulting in fine lines. It is difficult to reproduce the dots and dots as clearly as in printing.

In order to obtain high-quality images, it is thought that it is necessary to make toner particles finer, but if the toner particles are finer particles with an average particle size of 10 gm or less, especially 5 gm or less,
The effects of mirror image force and van der Waals force appear on the Coulomb force during development, and toner particles adhere to the ground area of the image background, causing so-called fog, which causes a direct current bias to the developer carrier. Application of voltage also makes it difficult to prevent fogging, and (2) it becomes difficult to control triboelectric charging of toner particles, making aggregation more likely.

Therefore, the side effects mentioned above are more noticeable with micronization! It has been difficult to actually use micronized toner particles because of the problem that clear images cannot be obtained.

1 to 11 The main object of the present invention is to develop an electrostatic charge image applied to a new two-component non-contact developing method in which a gap between magnetic poles on the back side of a developer carrier exists in a developing section and an alternating electric field is applied to the gap in this developing section. An object of the present invention is to provide a toner for developing an electrostatic image, which is a toner for developing an electrostatic charge image and can provide a clear high-quality image similar to that of printing.

11.1 The electrostatic image developing toner of the present invention was developed to achieve the above object, and the distance between the magnetic poles of the magnetic field generating means provided on the back surface of the developer carrier is the same as that of the developer carrier. The developer carrier and the latent image carrier are arranged so that the latent image carrier is located in a developing section facing each other with a constant development gap, and the developer carrier is composed of toner particles and carrier particles, and Development in which a layer of two-component developer whose thickness is regulated to be smaller than the gap is formed on a developer carrier, and the latent image on the latent image carrier is developed while applying an alternating electric field to the development gap. The toner used in the method has an ff1fi average particle diameter of 3 to 3.
5 gm, the weight content of particles with a particle size of 8 gm or more is 5% or less, and the number content of particles with a particle size of less than 2 pm is 15% or less. In order to ensure that the various process conditions (electric field, development gap, etc.) of the developing method used here can be widened, toner particles of 8 pm or more,
The content of particles less than 2 pm is preferably as low as possible.

In other words, the present inventors have deeply studied the process of a new two-component non-contact developing method in which the gap between the magnetic poles on the back side of the developer carrier exists in the developing section, and an alternating electric field is applied to the gap in the developing section. We discovered that toner with a small particle size (which was difficult to use in the development method of The present invention was completed based on the knowledge that

The present invention will be explained in more detail below.

; The electrostatic image developing toner of the present invention has an average particle size of about 10 #Lm compared to a conventionally used toner.

It is a special toner having a small particle size with a weight average particle size of 57 zm or less, and the content of coarse particle toner or ultrafine particle toner is suppressed to a certain percentage or less.

Generally, as the average particle size of toner particles becomes smaller, the amount of charge on the toner particles qualitatively decreases in proportion to the square of the particle size.
Adhesive forces such as image forces and van der Waals forces become relatively large, making it difficult for toner particles to separate from carrier particles, and once toner particles adhere to non-image areas of the latent image carrier surface, they become By rubbing with a conventional magnetic brush, it is not easily removed and fogging occurs.

In the conventional magnetic brush development method, such problems became noticeable when the average particle size of toner particles was 10 gm or less.

However, in the developing method using the toner of the present invention, this problem is solved by applying alternating electric fields between the developer carrier and the latent image carrier to perform development.

That is, the toner particles adhering to the developer layer are easily moved away from the developer layer and transferred to the image area and non-image area on the surface of the latent image carrier due to electrically applied vibrations, and are also easily separated from the developer layer. and developer layer thickness.

If the gap is thinner than the gap between the latent image carrier surface and the developer carrier surface, toner particles with a low charge amount will hardly migrate to the image area or non-image area, and the gap between the latent image carrier surface and the developer carrier surface will be reduced. Since there is no rubbing, there is no possibility of adhesion to the latent image carrier due to frictional charging, and toner particles having a particle size of about I μm can now be used. Therefore, a clear toner image with good reproducibility can be obtained by faithfully developing electrostatic Hs#L.

Furthermore, since the alternating electric field weakens the bond between the toner particles and the carrier particles, the adhesion of carrier particles associated with the toner particles to the latent image carrier surface is also reduced. In particular, when the thickness of the developer/layer is made thinner than the gap between the latent image carrier surface and the developer carrier surface, toner particles with a large amount of charge are exposed to alternating electric fields in the image area and non-image area. The toner particles vibrate, and depending on the strength of the electric field, the carrier particles also vibrate, causing the toner particles to selectively migrate to the image area on the latent image carrier surface, which greatly reduces the adhesion of the carrier particles to the latent image carrier surface. will be reduced to Depending on the electric field, toner particles in the non-image area may or may not reach the non-image area. The same applies to carriers.

What is more important in the developing method using the toner of the present invention is that the latent image carrier and the magnetic poles of the magnetic pole generating means (between N1 and 51 in FIG. 1, which will be described later) face each other in the developing area. It is that you are. This makes it possible to perform two-component non-contact development with almost no developer spikes and a smaller distance between the latent image carrier and the developer carrier than ever before, resulting in sharp, blur-free images. An image is obtained.

On the other hand, as mentioned above, as the average particle size of toner increases, image roughness and scattering become noticeable.Normally, in terms of image resolution, even toner with an average particle size of about 10 lm is not practical for practical use. is not a problem, but the average particle size is 5gm
If atomized toner is used below, the resolving power will be significantly improved and a clear, high-quality image with faithful reproduction of gradation differences etc. will be provided.

In the present invention, the weight average particle diameter of the toner particles is less than 3 gm, or 5. When Bcm is exceeded, image resolution sharply decreases, and when the weight content of coarse toner with a particle size of 8 gm or more exceeds 5%, toner scattering occurs; When the number content exceeds 15%, fog becomes 111%.

In order to obtain the small particle diameter toner of the present invention having such a particle size distribution, a binder resin consisting of a conventionally known vinyl-based thermoplastic resin, non-vinyl thermoplastic resin, etc., as described below, and a pigment or a coloring agent are used. After thoroughly mixing the dye and charge control agents and additives added as necessary using a ball mill or other mixer, they are melted and kneaded using a heat kneader such as a heated roll, kneader, or extruder. By mixing and kneading, the pigment or dye is dispersed or dissolved in the resins that are made compatible with each other. After cooling and solidifying this product, it is pulverized and further classified to obtain a predetermined ratio of coarse toner with an average particle size of 3 to 51 Lm, and moreover, a coarse toner with a particle size of 8 uLm or more and an ultrafine toner with a particle size of less than 2 μm. What is necessary is to obtain a toner whose content is controlled to be .

Examples of toner binder resins that can be used in the uninvented toner include monopolymers of styrene and its substituted products such as polystyrene and polyvinyltoluene; styrene-methyl methacrylate copolymers, styrene-acrylonitrile copolymers, and styrene. - Styrenic copolymers such as phthadiene copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin.

Polyvinyl butyral, polyacrylic acid resin, rosin,
Examples include modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, and paraffin wax. These binders can be used alone or in combination.

Colorants used in the toner of the present invention include carbon black, lamp black, and iron black.

Ultramarine blue, nigrosine dye, aniline black, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, sevenanoazo dye, disazo dye Any conventionally known dyes and pigments such as pigments can be used alone or in combination.

The amount of these colorants added is 100% of toner binder resin.
It is desirable that the amount is 2 to 30 parts by weight.

Further, in order to impart desired triboelectric charging properties to the toner of the present invention, a conventionally known charge control agent can be added. Examples of such charge control agents include 1, for example, azine dyes containing an alkyl group having 2 to 16 carbon atoms; basic dyes; metal salts of higher fatty acids; metal complexes of salicylic acid, naphthoic acid, guicarboxylic acid such as CO1Cr and Fe; etc. are used. These amounts are 0 parts per 100 parts of toner binder resin.
It is desirable to use 01 to 20 parts by weight.

The toner of the present invention may be mixed with additives as necessary, such as lubricants such as Teflon and zinc stearate, or abrasives such as cerium Mide and silicon carbide, or Examples include fluidity agents such as colloidal, silica, and flunimium oxide, anti-caking agents, conductivity imparting agents such as carbon black and tin mide, and fixing aids such as low molecular weight polyethylene.

In addition to the toner manufacturing method that includes the melting, mixing, and pulverizing steps described above, the uninvented toner can also be produced by mixing a specified material with the monomer that constitutes the toner binder resin and emulsifying and suspending it in a suitable dispersion medium. It can also be obtained by using a polymerization toner manufacturing method in which the toner is produced by polymerizing the toner.

When using this suspension polymerization method, one or more polymerizable monomers and dyes and pigments (if necessary, charge control agents, additives, crosslinking agents such as divinylbenzene, etc.) are added to the toner binder resin. , azobisin butyronitrile (A
A polymerizable mixture obtained by mixing a polymerization initiator such as IBN) into an aqueous dispersion medium containing, for example, about 0.1 to 30% of a suitable dispersant, and heated at 50°C or higher while stirring. The toner of the present invention can be obtained by polymerizing at a temperature of .

Examples of the dispersant include gelatin, starch, polyvinyl alcohol, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, viscosity, silicic acid, metal oxides, colloidal silica, and other powders. Can be done.

In addition, when the polymer composition contains an ionic substance, for example, a cationic substance or anionic substance such as a nitrogen-containing polymerizable monomer or poorly water-soluble amines, when dispersed in water, the dispersed particles are In the case of being charged to either positive or negative polarity, an ionic dispersant 1 that is charged to the other polarity when dispersed in water, such as negatively charged colloidal silica, positively charged aluminum oxide, etc., is suspended. It can be effectively used as a stabilizer.

Further, a surfactant such as sodium dodecylbenzenesulfonate may be added to the dispersant to promote the action of the dispersant.

After washing the fine particulate polymer obtained by the suspension polymerization method described above, it is treated by filtration, decantation, centrifugation, etc., and the particles are collected and dried to obtain a toner.

When this suspension polymerization method is used, the toner particle size and particle size distribution are controlled mainly by the amount of dispersant relative to the amount of polymerizable monomer,
The larger the amount of dispersant relative to the zero-polymerizable monomer, which is controlled by adjusting the stirring speed during polymerization, and the higher the stirring speed, especially the stirring speed at the initial stage of polymerization, the smaller the particle size of the resulting toner. Further, if necessary, the toner obtained by the above polymerization method may be classified to obtain a toner having a particle size distribution suitable for the toner of the present invention.

As described above, the toner for developing electrostatic images of the present invention can be produced by a pulverization method or a polymerization method, but the method is not limited thereto.

FIG. 1 is a schematic side sectional view showing one tooth of a developing device applied to the toner of the present invention. In FIG. It is a latent image holding layer and may be an insulating layer or an electrophotographic photoreceptor layer, shown here as a photosensitive drum 1. 2 is a developer carrier, which is made of a non-magnetic material, and is indicated by an arrow. This is a conductive sleeve that rotates in the A direction. Reference numeral 3 denotes a magnetic field generating means fixedly provided inside the sleeve, which in this example is a magnet roller having four magnetic poles.

In the developing area, the magnetic pole N! of the magnet roller 3 inside the sleeve 2 with respect to the photosensitive drum l. and magnetic pole S1 are arranged to face each other. 4 is a developer in which magnetic particles (carrier) containing magnetic powder in a resin are mixed with non-magnetic particles (toner) having a smaller average particle diameter and mainly made of resin. Photosensitive drum l rotating in the direction of arrow B
A developing bias is applied between the back electrode 11 and the sleeve 2 by a DC power supply 5 and an AC power supply 6. 7
8 is an elastic member, 8 is a toner supply roller, 9 is a developer layer thickness regulating member, and here a doctor blade is shown.

11] As described above, according to the present invention, the gap between the magnetic poles of the magnetic field generating means on the back surface of the developer carrier is located in the developing section where the latent image carrier and the developer carrier face each other with a constant development gap. , and used in a method of developing a latent image on a latent image carrier by applying an alternating electric field to the development gap while maintaining a development gap larger than the thickness of a two-component developer layer consisting of toner particles and carrier particles. The toner has a weight average particle size of 3 to 5 gm, and the weight content of coarse toner with a particle size of 8 pm or more is 5% by weight.
Hereinafter, by using the toner of the present invention in the above-mentioned developing method, a toner with a small particle diameter in which the number content of ultrafine toner with a particle diameter of less than 2 m is 15% or less can be obtained, and there is no fog and resolution is obtained. You can obtain high-quality images that are close to those of excellent printing.

1 Cliff 1 Next, the present invention will be explained in more detail with reference to Examples.
This is not intended to limit the invention in any way.

In the following examples, the particle size of the toner is Coulter Counter Type, aperture diameter 1100.
p was measured using a polystyrene standard sample.

In the following examples, all "1 part" expressing quantitative ratios are parts by weight.

The mixture was kneaded using two rolls heated to 150°C. After the kneaded material was left to cool naturally, it was roughly pulverized with a cutter mill, and further pulverized into powder with a particle size of 1 to 10 pm using a pulverizer using a jet stream (Labojet manufactured by Ehon Pneumatic Co., Ltd.). Next, a classifier (Fulpine 100 manufactured by HEYMA IV, West Germany)
MZR) was used to remove the ultrafine powder toner at a rotation speed of 2000 rpm, and then to remove the coarse powder toner at a rotation speed of 11000 rpm, resulting in a weight average particle size of 4.5 pm and a particle size as measured by the coulter counter. The weight content of coarse powder toner of 8gm or more is 3.0ffi
Table 1 and Figure 2 below show the data of the 0 particle size distribution in which a small particle size toner was obtained with a particle size distribution in which the number content of ultrafine toner with a particle size of less than 2 gm was 12.0%. .

15 g of the above toner, 85 g of carrier with an average particle size of 40 pm made of iron chloride and epoxy resin, and hydrophobic silica (AERO3IL R manufactured by Nippon Aerosil Co., Ltd.)
A development test was conducted under the following conditions using a developer mixed with 0.15 g of 972).

Referring to FIG. 1, a drum having a selenium photoreceptor 12 was used as the photoreceptor drum l. When the latent image potential on the photosensitive drum l is +600 V and the background potential is OV, the developing bias voltage applied to the sleeve 2 has a peak-to-peak value of 130 V.
+1so to AC voltage of 0VPP, frequency 3.0KHz
A superimposed DC voltage of V was used. The distance between sleeve 2 and drum 1 is 300 pm, and the developer layer thickness in the development area is 200 pm.
gm, and magnets were used whose magnetic force distributions in the vertical and horizontal directions on the surface of the developing sleeve 2 were as shown in FIGS. 3 and 4, respectively.

After developing with the toner of the present invention under the above conditions, the toner image was transferred onto plain paper and fixed through a heat roller fixing device with a surface temperature of 150°C. The results are shown in the examples below,
The results are shown together with comparative examples in Table 2 below.

After kneading and coarsely pulverizing the same toner constituent materials as in Example 1, changing the air flow conditions of a pulverizer using a jet stream, the toner was powdered with a particle size of 5 to 151 Lm. After pulverization, ultrafine powder and coarse powder were removed using a classifier in the same manner as in Example 1 to obtain a toner having a particle size distribution shown in Table 1.

A development test was conducted using this toner under the same conditions as in Example 1.

Tables 1 and 5 were prepared in the same manner as in Example 1, except that the coarse toner particles were not removed using a classifier.
A development test was conducted in the same manner as in Example 1 using a toner having the particle size distribution shown in the figure.

Using a toner manufactured in the same manner as in Example 1, except that the ultrafine powder toner was not removed using a classifier,
A development test was conducted in the same manner as in Example 1.

After mixing for 5 minutes at 60°C and IOORPM using stirring χ,
Furthermore, 4 hours with Attritor (MA-ISD, manufactured by Mitsui Miike)
After stirring, add 2°2-7 zobisu(2,
A solution prepared by dissolving 2 g of 4-dimethylvaleronitrile) and 2.2-7 zobisisobutyronitrile Ig at a temperature of 60°C was added to a solution of 7mino-modified silica (Japan 7 Erosyl).
Co., Ltd., AER6SII, 200.100 parts by weight was reacted with 5 parts by weight of aminopropyltriethoxysilane') 15 g and distilled water 600 g, N/1011! A mixture with 20 g of acid was added to a stainless steel container (capacity @ 2 t) and heated at 60°C in a nitrogen gas atmosphere.
10. Using a K homo mixer (manufactured by Tokushu Kika Kogyo). OO
I wore it for 1 hour at Orpm. Further, this mixed system was heated and stirred at 1100 rpm and 1OHr at 60° C. using a paddle stirring blade to complete the polymerization.

The polymerization product was cooled, dehydrated, further washed with a sodium hydroxide solution, and then dehydrated using a classifier (West German HEYMA I).
Using V company Alpine 100MZR), rotation speed 20
00Orpm'T! 1llj powder toner, remove fine particles such as unreacted substances, and continue to rotate at a rotation speed of 11,000 Orp, remove coarse powder toner, and have a weight average particle size of 4. Opm, particle size 8
A small particle size toner was obtained in which the weight content of coarse toner of gm or more was 1% by weight, and the number content of awI small toner of particle size less than 2 μm was 5%. A development test was conducted using this toner under the same conditions as in Example 1.

L Kasa 1'' A toner having a particle size distribution shown in Table 1 was obtained in the same manner as in Example 2, except that the amount of amine-modified silica added was 8 g. A development test was conducted using this toner under the same conditions as in Example 1.

A toner was obtained in the same manner as in Example 2 except that the coarse toner powder was not removed using a classifier. A development test was conducted in the same manner as in Example 1 using this toner.

A toner was produced in the same manner as in Example 2, except that the ultrafine powder toner was not removed using a classifier.

A development test was conducted in the same manner as in Example 1 using this toner.

The weight average particle diameter, etc. of the toner obtained as described above are summarized in Table 1, and the results of the development test are summarized in Table 2.

Table 1 The methods for measuring fog, resolution, and similarity to printing shown in Table 2 above, as well as the criteria for these criteria, are as follows.

(Fog) When the reflection density value of the non-image area (value excluding paper density) is 0 or more and less than 0.01, it is marked O, and when it is 01 or more and less than 0.03, it is marked Δ, and 0. Cases of 03 or higher were marked with an x.

(resolution) Mark O if the resolution is 7.1 lines/mm or more.

The case where it was greater than 5.0 lines/mm and less than 7.1 lines/mm was marked with an x, and the case where it was 5.0 lines/mm or less was marked with an X.

(Similarity to printing) Fluctuations in the optical reflection density inside each image (optical reflection inside the image) when the same line images of the original printed manuscript and the copy are scanned with a micro-scanning densitometer □ The difference between the maximum value and the minimum value of the density) is designated as Δ (print) and Δ (copy), respectively, and when the difference between Δ (print) and Δ (copy) is 0.1 or less, it is marked O, 0. A value of greater than 1 and less than 0°2 was marked with Δ, and a value of 0.2 or more was marked with X.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view showing an example of a developing device to which the toner of the present invention is applied, FIG. 3 is a vertical magnetic field distribution diagram of the magnet roller in the device shown in FIG. 1, and FIG. 2 is a horizontal magnetic field distribution diagram of the magnet roller in the apparatus, FIG. 2 is a graph showing the particle size distribution of the toner of the present invention obtained in Example 1, and FIG. 5 is a graph showing the particle size distribution of the toner of Comparative Example 2. It is a graph. In the figure, 1 is a photosensitive drum, 2 is a sleeve, 3 is a magnet roller, 4 is a developer, 5.6 is a developing bias power source, and 9 is a doctor blade. ff1 = 1st = Figure 1 Figure 2 (Example 1) Male 5 Country (Comparative Example 2) a tun (PITI) Figure 3

Claims (1)

[Scope of Claims] The developer is arranged so that the magnetic poles of the magnetic field generating means provided on the back surface of the developer carrier are located in a developing section where the developer carrier and the latent image holder face each other with a constant development gap. A carrier and a latent image holder are arranged, and a layer of a two-component developer consisting of toner particles and carrier particles and regulated to have a layer thickness smaller than the development gap in the development section is applied to the developer. A toner formed on a carrier and used in a developing method of developing a latent image on a latent image carrier while applying an alternating electric field to the development gap, the toner having a weight average particle size of 3 to 5 μm and a particle size of 8 μm or more. A toner for developing an electrostatic image, characterized in that the weight content of particles is 5% or less, and the number content of particles with a particle diameter of less than 2 μm is 15% or less.