JP3270198B2 - Electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image carrier and a toner carrier which are arranged at a predetermined interval, and the toner is carried on the toner carrier at a thickness smaller than the interval. Flying and developing the electrostatic latent image on the electrostatic latent image carrier,
It relates to a toner used in a so-called non-contact developing method.

[0002]

2. Description of the Related Art An electrostatic latent image carrier and a toner carrier are arranged at a predetermined interval, and toner is carried on the toner carrier to a thickness smaller than the interval. Japanese Patent Publication No. 41-9475 describes a developing method of developing an electrostatic latent image on a body by flying it (hereinafter referred to as non-contact development). However, in order for the toner to fly to the electrostatic latent image, it is necessary that the toner particles are individually charged to a desired polarity, that the particles are easily separated individually, and that the toner particles fly easily in accordance with the electrostatic field. Is an important condition.

[0003] In order to achieve the above, an attempt has been made to improve the flying property of toner by applying an alternating electric field between a toner carrier and an electrostatic latent image as a developing method. In addition, as a toner suitable for non-contact development, silica is used as an external additive of the toner (Japanese Patent Publication No. 63-42783), or a method of specifying the true specific gravity, the filling density and the charge amount of the toner (Japanese Patent Application Laid-Open No. 60-8 / 1985).
7343), a method of defining the particle size distribution (Japanese Patent Laid-Open No. 62-1)
03675).

[0004] However, although each of them has an effect locally on the developing property of the toner, it is hard to say that the flying property of the toner is satisfied. Further, in the non-contact development, as in the case of the conventional contact development, even if a high-density copy image is obtained with unused toner, if the toner agitation continues in the in-machine developing device such as long-term running, the fluidity of the toner itself is poor. It is known that the flying from the toner carrier to the electrostatic latent image carrier becomes extremely poor, which leads to a decrease in image density and image deterioration.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner having high density and high quality with little image deterioration over a long period of time in non-contact development.

[0006]

According to the present invention, in non-contact development, the adhesive force per contact point between toner particles affects the flying performance, and the adhesive force per contact point between toner base particles is smaller than the toner. The present inventors have found that the effect of suppressing the deterioration of the flying property at the time of use is given, and have reached the present invention. Here, the toner base particles referred to in the present invention are a fixing resin, a charge control agent,
Particles obtained by mixing, kneading and pulverizing and classifying a release agent and a colorant mean particles obtained by attaching externally added particles to the surface of the particles are defined as toner particles. The toner refers to a toner obtained by adding an external additive to the toner base particles.

That is, the constitution of the present invention is an electrophotographic toner as described in the claims. In summary, in a toner used for non-contact development, the adhesive force between the toners is less than a certain value. It is limited to. That is, if the adhesive force between the toners is large, the flying of the toner is suppressed and the image density is reduced. Originally, van der Waals force, liquid bridging force, etc. act strongly between toner particles used in electrophotography. Therefore, in actual use, a method of adding a fluidity improver to the toner surface to reduce the above-mentioned force between particles is used. Has been taken.

[0008] However, the addition of a fluidity improver to the toner improves the flying performance of the toner on the photoreceptor, but it is still insufficient for a high-density, high-quality image. This is because the adhesive force between the toner particles on the toner carrier is not sufficiently reduced, and the adhesive force between the toner particles is larger than the electric field from the toner carrier to the electrostatic latent image. That is,
If the toner has a small adhesive force, a sufficient image can be obtained.

The adhesive force per toner contact point in the present invention can be determined from the breaking stress per unit area of the packed layer of the pressed powder and the number of contact points of the particles per unit area. The number of contact points of the particles can be estimated from the packing density and the particle size of the particles. The flying of the toner onto the electrostatic latent image is sufficiently improved by defining the adhesion between the toners as a calculation as described above.

The present inventor has found the adhesive force between particles at the contact point between particles using the breaking stress per unit area of the packed bed in which the powder is pressed, and obtained the present invention. It was just. Specifically, the powder is filled in the two-part cell shown in FIG.
Pressurize at 1 kg / cm ² in advance. By fixing the lower cell and pulling the upper cell in the direction of consolidation of the packed bed to measure the stress F when the powder layer breaks, the breaking stress (F) per unit area between the powders is obtained (hereinafter referred to as the powder). Vertical tensile strength). The number N of contact points of the particles is estimated from the packing density (ε) and the volume average particle diameter (D _P ) of the powder when the powder is pressure-filled into the two-divided cell,

[0011]

(Equation 1)

## EQU1 ## Adhesion force f _P per contact point of particles is

[0013]

(Equation 2)

Is calculated by In the present invention, if the adhesive force per contact point of the toner particles is 0.015 dyne or less, the electric field force of the electrostatic latent image becomes sufficiently larger than the adhesive force between the toner particles, and a sufficient amount of toner It was found that the aircraft could fly and obtain a high-density image.

In general, toner used in electrophotography is deteriorated when used for a long period of time, and the image density and image quality are reduced. This is because long-term use causes stress of agitation in the developing machine, and external additives distributed on the toner surface are buried in the toner, so that the toners easily come into contact with each other and the adhesive force between the toners increases. It is. In this case, since the toner base particles are exposed on the surface, the adhesion of the base particles greatly affects the deterioration of the toner after long-term use. That is, it has been found that a toner having a small adhesive force of the toner base particles has a great effect on image density and image quality deterioration over a long period of use.

In particular, it has been found that if the adhesive force per contact point of the toner base particles is 0.020 dyne or less, sufficient image density and image quality can be ensured even when the toner is used for a long period of time. That is, when mechanical energy is applied to the toner, even when the externally added fluidity imparting agent is buried in the toner base particles, the adhesive force between the toner base particles is kept small and high for long-term running and storage. A toner having high density and low image deterioration is provided.

The components of the toner of the present invention may be the same as those of a conventional toner, and include a fixing resin, a charge control agent, a release agent, a colorant and a fluidity imparting agent. As examples of the type of the fixing resin used in the present invention, all of those which have been used as a binder resin for a toner can be applied.

Specifically, styrene such as polystyrene, polychloroethylene and polyvinyltoluene, and homopolymers of substituted styrenes; styrene-P-chlorostyrene copolymer, styrene-propylene copolymer, and styrene-vinyltoluene copolymer Styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-
Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer,
Styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl Ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid Copolymers, styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate,
Polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin,
Modified rosin, terpene resin, phenolic resin and the like can be mentioned. However, since 80 to 95% of the main component of the toner is a resin, the selection of the adhesive force of the fixing resin itself greatly affects the adhesive force.

That is, the smaller the adhesive force of the fixing resin itself, the smaller the adhesive force of the toner base particles, which greatly affects the developability of the toner. In particular, by using a styrene butyl acrylate copolymer, the adhesive force can be significantly reduced.
The amount of styrene butyl acrylate copolymer used is 3
When the content is 0% by weight or more, there is an effect of lowering the powder vertical tensile breaking strength of the toner base particles.

As the release agent, all of the release agents which have been used up to now as toner release agents can be applied. In addition to synthetic waxes such as polyethylene and polypropylene having a low molecular weight, candelilla wax, carnauba wax, rice wax, wood wax and the like. Plant waxes such as wax and jojoba oil, animal waxes such as beeswax, lanolin, and spermaceti, mineral waxes such as montan wax and ozokerite, hydrogenated castor oil, hydroxystearic acid, fatty acid amide, phenol fatty acid ester, etc. And the like can be used.

Examples of the charge control agent include nigrosine, 4
Examples include quaternary ammonium salts, metal-containing azo dyes, and salicylic acid complex compounds. As the coloring agent, all of conventionally used pigments and dyes can be applied. Specifically, ultramarine, nigrosine dye, aniline blue, calco oil blue,
Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, rhodamine 6C lake, quinacridone, benzidine yellow, malachite green, hansa yellow G, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dye Pigments, disazo dyes and pigments, trisazo dyes and the like can be mentioned.

The fluidity-imparting agent to be added to and mixed with the toner base particles of the present invention is, for example, a lubricant such as Teflon or zinc stearate, or an abrasive such as cerium oxide or silicon carbide, or a carbon black or tin oxide. Examples include a conductivity-imparting agent, a fixing aid such as a low-molecular-weight polyolefin, and a wax, and, for example, colloidal silica, aluminum oxide, and titanium oxide. The addition amount is 0.1% by weight to 10% by weight, preferably 0.2% by weight to 5% by weight based on the toner base particles.

When the average volume particle diameter of the toner used in the present invention is 7 μm to 13 μm, the flying property of the toner can be ensured. If the average volume particle diameter is smaller than 7 μm, the adhesive force between toner particles, particularly the liquid crosslinking force between the particles, becomes large, so that the toner is prevented from separating from the toner carrier and flying to the electrostatic latent image is suppressed. On the other hand, if it is larger than 13 μm, the image clarity deteriorates (image blur and bleeding occur).

FIG. 2 shows an outline focusing on a developing roller portion of a typical developing device useful for carrying out this image forming method, but the present invention is not limited to the above. In FIG. 2, toner 6 of the present invention contained in a toner tank 7 is forcibly brought to a toner supply member (such as a sponge roller or a fur brush) 4 by a stirring blade (toner supply unit auxiliary member) 5 and 6 is supplied to the toner supply member 4. On the other hand, the developing roller 2 that has completed the development rotates in the direction of the arrow and reaches a contact portion with the toner supply member (sponge roller) 4. The toner supply member 4 rotates in a direction opposite to that of the developing roller 2, charges the developing roller 2 and the toner 6, and causes the toner 6 to adhere to the developing roller 2. Further, the developing roller 2 rotates, and the toner adhered on the developing roller 2 is stabilized by the toner layer thickness regulating member (elastic blade) 3 while controlling the thickness, and reaches the developing area 8. In the development area 8, the latent image is developed by non-contact development. Here, a DC voltage or the like is applied to the developing roller 2 and the toner supply member 4 to apply an electric field in a direction in which the toner is held on the developing roller, thereby suppressing the toner from flying to portions other than the electrostatic latent image portion and forming an optimal image. Can be controlled.

Next, the mechanism of toner adhesion to the developing roller 2 of this type (electrode type) will be described.
As an example of the developing roller, as shown in FIG. 3, for example, a dielectric portion 10 and a conductive portion 9 are mixed on a surface thereof with a small area. As for the size of the area, assuming that the shape is a circle, minute areas having a diameter of 30 to 2000 μm, preferably 100 to 400 μm are dispersed randomly or according to a certain regulation. As the area ratio, the area of the insulating portion is preferably in the range of 50 to 80%.

The toner adhesion is as follows. First, the developing roller 2 that has completed the development rotates in the direction of the arrow and comes into contact with the toner supply member 4. Here, the remaining toner in the non-image portion that has not been developed is mechanically and electrically scraped off by the toner supply member 4, and the dielectric portion is charged by friction.
At this time, the charges of the developing roller 2 and the toner by the previous development are fixed and initialized by friction. Next, the toner carried by the supply member 4 is charged by friction and adheres electrostatically to the dielectric portion of the developing roller 2. At this time, the polarity of the toner is opposite to the charge of the photosensitive member, and the dielectric portion of the developing roller 2 has the same polarity.

At this time, the electric field on the developing roller 2 is a microfield (closed electric field) 11 as shown in FIG.
Thus, the electric field has a large electric field gradient, and the toner can be adhered in multiple layers. Further, since the adhered toner has a closed electric field, it is strongly pulled toward the developing roller 2 and is hardly separated. The toner layer thickness of the toner layer is further controlled by the toner layer thickness regulating member 3, so that the toner in the developing area 8 becomes an electric field that easily adheres to the photoreceptor, and the toner is developed.

In order to produce a developing roller in which the dielectric portion 10 and the conductive portion 9 are mixed in a small area on the surface, for example, a metal roller having a groove formed on the surface by iris knurling or the like is used. For example, a metal surface coated with grooves is coated with, for example, a fluorine resin, cured and dried, and then the surface of the roller is cut or polished so that the conductive surface is mixed in a small area, and the conductive portion area is 2
Grind to 0-50%. Of course, instead of the developing roller shown here, a metal member subjected to a sandblast treatment or a metal member coated with a thin layer of resin can be used. In addition, a developing method in which a regulating member is provided by two-component magnetic brush development to perform non-contact development may be used.

[0029]

The present invention will be described in more detail with reference to the following examples. In addition, the amount (part) of each component described in an Example represents a weight part. Example 1 Binder resin Styrene-butyl methacrylate copolymer 84 parts Release agent Carnauba wax 4 parts Colorant carbon black 4 parts Charge control agent Zinc salicylate 7 parts A mixture of the above composition is melt-kneaded, cooled, and then hammer milled. And then finely pulverized by a fine pulverizer using an air jet method. The obtained finely pulverized product was classified to obtain toner base particles having an average particle size of 11 μm. Further, 1.2 parts of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base particles to obtain a toner.

Next, the powder vertical tensile breaking strength was measured. The measurement was performed using Shimadzu powder adhesion measuring device ED-2000H type. 10 g of the above toner is filled in a two-piece cell 14 having a cross section of 10 cm ^{2, and} a constant pressure is charged under a load of 10 kg for 5 minutes to prepare a measurement sample. The lower cell 13 is fixed by a Shimadzu powder adhesion measuring device, and the upper cell 12 is fixed. tensile fracture stress F (powder vertical when tensile powder layer is broken in the filling layer compaction direction
Force) to determine the adhesive force per contact point.
The filtrate was 0.013dyne. Similarly, the powder vertical tensile breaking force of the toner base particles was measured, and the
The adhesive force was 0.022 dyne.

A dielectric unit and a conductive unit are mixed in a very small area, and a developing device equipped with a developing roller having an area ratio of 50% is prepared, and the toner is mounted on the developing device.
An image was produced at 450 (manufactured by Ricoh) using a chart having a black ratio of 3%. Further, running was performed continuously for 2,000 sheets, and an image was displayed again. The results are shown in Table 1. The fixability is shown as a result of evaluating dirt on the fixing roller after running the above 2,000 sheets on a five-point scale.

Examples 2 to 4 and Comparative Examples 1 to 3 In the same manner, Examples 2 to 4 and Comparative Examples 1 to 3 were evaluated in the same manner. Materials used and each toner,
Table 1 shows the adhesive force of the toner base particles per particle contact point and the evaluation results of each example.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

As described above, by using the toner of the present invention, a high-density, high-quality image can be formed even by the non-contact developing method, and the toner does not deteriorate for a long time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a two-part cell,

FIG. 2 is an explanatory diagram of an example of a developing device using the toner of the present invention,

FIG. 3 is an explanatory diagram of a developing roller suitable for the toner of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image roller 2 Developing roller 3 Toner layer thickness regulating member (elastic blade) 4 Toner supply member 5 Stirring blade 6 Toner 7 Toner tank 8 Developing area 9 Conductor section 10 Dielectric section 11 Closed electric field by microfield 12 Two-part cell (Upper) 13 Two-part cell (Lower) 14 Sample cell 15 Switch 16 Coil spring 17 Electronic balance 18 Motor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Masuda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-5-19529 (JP, A) JP-A Heihei JP-A-4-318560 (JP, A) JP-A-4-337738 (JP, A) JP-A-4-9863 (JP, A) JP-A-4-44054 (JP, A) JP-A-59-198470 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] An electrostatic latent image carrier and a toner carrier are arranged at a fixed interval, toner is carried on the toner carrier to a thickness smaller than the interval, and the toner is transferred to the electrostatic latent image carrier. A toner obtained by applying an external additive to toner base particles containing a fixing resin, a release agent, and a colorant as main components, which is used in a developing method of developing the toner by flying on the electrostatic latent image. After applying a load of 1 kg / cm ² to the toner, the adhesive force per toner contact point due to vertical tensile fracture of the toner is 0.015 dy.
electrophotographic toner wherein the ne or less. 2. The electrophotographic apparatus according to claim 1, wherein the adhesive force per toner contact point due to vertical tensile fracture after applying a load of 1 kg / cm ² to the toner base particles is 0.020 dyne or less . Toner .