JP3121364B2 - toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying a non-magnetic one-component developer to which an auxiliary agent is externally added as needed to a developer carrier which is driven to rotate, and to a surface of the developer carrier. The electrostatic latent image formed on the latent image carrier is carried by the developer carrier in a developing region where the latent image carrier and the developer carrier are opposed to each other. Further, the present invention relates to an image forming method for visualizing an image with the developer and a toner used therefor .

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copier, a printer or a facsimile, which forms an electrostatic latent image on a latent image carrier and visualizes the latent image with a developer to obtain a recorded image, a powdery image is formed. Dry developing devices using a developer are widely used.

As such a powdery developer, a two-component developer having a toner and a carrier and a one-component developer not containing a carrier are known, and the former two-component developer is used. In the two-component developing method, a relatively stable and good recorded image can be obtained, but the deterioration of the carrier and the fluctuation of the mixing ratio of the toner and the carrier are apt to occur, the maintenance of the apparatus is complicated, and the structure of the entire apparatus is large. It has a disadvantage that it is easy to change.

[0004] From such a viewpoint, a one-component developing system using a one-component developer which does not have the above-mentioned disadvantages has attracted attention. One-component developer is composed of only toner,
In some cases, an auxiliary agent is externally added as necessary. As the toner, there are a magnetic toner in which magnetic powder is kneaded into each toner particle itself, and a non-magnetic toner containing no magnetic material. Here, since the magnetic material is generally opaque,
When a color image including a full-color image and a multi-color image is formed with a magnetic toner, a developed visible image becomes unclear and a vivid color image cannot be obtained. Therefore, it is desirable to adopt a one-component developing method using a non-magnetic toner especially for color development.

In a developing device employing a one-component developing system, a one-component developer is carried on a developer carrier and conveyed, and the developer carrier and the latent image carrier are opposed to each other. In the region, the electrostatic latent image formed on the latent image carrier is visualized with a developer, but in order to form a high-quality visible image of a predetermined density, a large amount of sufficiently charged toner is required. It is necessary to convey the latent image to a developing area and visualize the latent image with the toner.

In the case where a magnetic toner is used, the above-described requirement can be relatively easily satisfied because the one-component developer can be carried on the developer carrier by utilizing the magnetic force of a magnet provided in the developer carrier. It is possible to satisfy

However, when a non-magnetic one-component developer is used, it cannot be supported on a developer carrier by magnetic force, so that it is difficult to satisfy the above requirements. Various measures have been proposed for this,
For example, JP-A-61-42672 discloses that a layer of a dielectric (insulator) is formed on the surface of a developer carrying member (developing roller), and a developer supplying member comprising, for example, a sponge roller. Are pressed against each other to frictionally charge them with different polarities, and a non-magnetic toner charged with a polarity opposite to that of the dielectric is electrostatically attached to the dielectric, and the one-component developer is transported to the developing area. A way to do that has been proposed. However, even with this method, the strength of the electric field formed in the vicinity of the dielectric surface cannot be sufficiently increased, so that it is difficult to carry a large amount of toner on the surface of the developing roller, and the developing roller can be transported to the developing area. Insufficient amounts of the agent make it difficult to form a high-density visible image.

It is also known to apply an electric field between the developing roller and the developer supply member in such a direction that the non-magnetic toner electrostatically moves to the developing roller side. However, it is difficult to attach a sufficient amount of toner to the developing roller.

[0009] The toner supply member includes 10 ² to 10 ⁶
Ωcm conductive foam (JP-A-60-229067), elastic body with skin layer (JP-A-60-229060) and fur brush
(Japanese Patent Application Laid-Open No. 61-42672) and the like, and as a developing roller, a metal body having irregularities on its surface (Japanese Patent Application Laid-Open No. 60-53976), an insulating coated roller body ( JP-A-55-46768) Medium resistance coated roller (JP-A-58-132)
No. 768) and an electrode roller having an insulating surface and a conductive surface (JP-A-53-36245).

In a developing apparatus using a non-magnetic one-component developer, a sponge roller is disclosed in JP-A-60-229067, an elastic roller is disclosed in JP-A-62-229060,
In 52663, using a fur brush or the like, a charge is applied to the toner by frictional charging between the toner and the replenishing member, and further, by friction in contact with the developing roller, the toner is electrostatically attached to the developing roller, Further, the latent image on the photoreceptor is developed by controlling the toner layer using a layer thickness regulating member such as a blade. As the material of the developing roller, various materials such as an insulating material, a medium-resistance material, and a laminated material are used.

According to the methods shown in these references, toner is adhered to the developing roller by friction between the toner replenishing member and the developing roller. Is difficult to obtain, resulting in insufficient toner adhesion . The need for a large amount of this adhesion also makes non-magnetic one-component development difficult.

Further, as shown in Japanese Patent Application Laid-Open No. 54-51841, the one-component developer on the developing roller after passing through the developing area is scraped off, and the surface layer of the developing roller is removed. On the other hand, there has been proposed a technique in which a corona discharge is performed to apply a charge, and then a non-magnetic toner is positively electrostatically adhered to a developing roller by a developer supply member. Also, the amount of developer carried on the surface of the developing roller cannot be increased, and a large amount of developer cannot be transported to the developing area.

As a method of solving these problems, the present inventors have previously described a one-component system comprising a non-magnetic toner in which an auxiliary agent is externally added to a rotatable developer carrier, if necessary. A developer is supplied, the developer is carried on the surface of the carrier and transported, and the latent image carrier and the developer carrier are formed on the latent image carrier in a developing region facing each other. In a developing method of visualizing an electrostatic latent image by the developer carried on a developer carrying member, the developing device selectively holds electric charges on the surface of the developer carrying member so as to be in the vicinity of the carrier carrying surface. An image in which a large number of minute closed electric fields are formed, charged toner is sucked by the closed electric field, and a developer is adhered to and carried on the surface of the developer carrier, and the electrostatic latent image is visualized by the carried developer. Method of formation "was proposed.

In this method, a large number of minute electric fields (microfields) are formed in the vicinity of the surface of the developer carrier, so that the intensity of the electric field can be significantly increased as compared with the conventional method, and a sufficiently charged large amount of electric fields can be obtained. This has many advantages such that the non-magnetic toner can be carried on the developer carrier and transported to the development area.

[0015]

However, according to the subsequent studies by the present inventors, according to the developing method in which a large number of minute closed electric fields (microfields) are formed near the surface of the developer carrier as described above. When using a conventionally known toner as it is, the toner layer on the developer carrier is
It is difficult to always stabilize as two or more layers, the toner layer becomes thinner, the amount of toner to be developed decreases, the density of the image area decreases, and the toner layer becomes uneven, causing uneven development. Or fogging may occur, furthermore, a filming phenomenon often occurs on the developer carrier, the microfield effect decreases, and the toner holding amount on the developer carrier decreases. It has been found that problems such as difficulty in sufficiently developing the toner on the latent image carrier occur.

Accordingly, an object of the present invention is to provide a toner capable of stably and uniformly laminating two or more layers on a developer carrier in the above-described image forming method, and the use of the toner.
It is another object of the present invention to provide the image forming method .

[0017]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a toner containing a binder resin and a colorant and having a specific average particle size and a specific particle size distribution is suitable for the above purpose. Having found this, the present invention has been completed.

That is, according to the present invention, by holding electric charges selectively on the surface of the developer carrying member, a large number of minute closed electric fields are formed in the vicinity of the surface of the developer carrying member. A non-magnetic one-component developer composed of a toner to which an auxiliary agent is externally added as necessary, is supplied onto the body, and the developer is carried on the surface of the developer carrier by the minute electric field. Used in an image forming method for making an electrostatic latent image a visible image by using at least a binder resin and a colorant, and further comprising 1 coarse particle having a volume average particle diameter of 12 μm or less and a particle diameter of 25 μm or more. % By weight or less. According to the present invention,
For example, the charge is selectively retained on the surface of the developer carrier.
This allows a large number of minute static
To form an auxiliary field on this developer carrier as needed
Supply a non-magnetic one-component developer consisting of toner with external additives
To supply the developer by the minute closed electric field to a developer carrier
The electrostatic latent image is visible on the surface and the developer
An image forming method for forming an image, wherein the toner is
Image forming method characterized by using different toners provided
Is done.

As described above, the toner of the present invention comprises at least a binder resin and a colorant, and has a volume average particle diameter of 12 μm or less and coarse particles having a particle diameter of 25 μm or more.
% By weight or less.

According to the study of the present inventors, in a developing method for forming a minute closed electric field, when coarse particles are mixed in the toner, the toner layer on the developer carrier is always stabilized with two or more layers. This makes the toner layer thin, resulting in uneven development and fogging. In order to prevent this, it has been found that in the toner having a volume average particle diameter of 12 μm or less, it is necessary that the coarse particles having a particle diameter of 25 μm or more be 1% by weight or less.

As the binder resin used in the toner of the present invention, all of those conventionally used as binder resins for toner are applied. Specifically, polystyrene,
Homopolymers of styrene such as polychlorostyrene and polyvinyltoluene and substituted products thereof; styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / vinylnaphthalene 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-chloromethacrylic acid Methyl 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 copolymers such as polymers, styrene / acrylonitrile / indene copolymers, styrene / maleic acid copolymers, styrene / maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate Vinyl, poly Tylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. These may be used alone or in combination of two or more.

As the colorant used in the toner of the present invention, all of pigments, dyes and polarity control agents conventionally used as colorants for toner are applied. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, calco oil blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, hansa yellow G, rhodamine 6C lake, Chrome yellow, quinacridone, benzidine yellow, malachite green, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dyes, disazo dyes, trisazo dyes, nigrosine, quaternary ammonium salts, metal-containing Examples include azo dyes, metal salts of salicylic acid and salicylic acid derivatives, and mixtures thereof.

Furthermore, in the toner of the present invention, in order to impart release properties, low molecular weight polyethylene, other synthetic waxes such as polypropylene, candelilla wax, carnauba wax, rice wax, Japan wax, ho
Vegetable waxes such as jojoba oil ; beeswax, lanolin,
Animal waxes such as whale wax; mineral waxes such as montan wax and ozokerite; and oil waxes such as hardened castor oil, hydroxystearic acid, fatty acid amide, and phenol fatty acid ester can be contained.

The toner of the present invention may contain various plasticizers in addition to the binder resin, the colorant, and the like, for the purpose of adjusting the thermal, electrical, and physical properties of the toner as necessary.
It is also possible to add auxiliary agents such as (dibutyl phthalate, dioctyl phthalate, etc.) and resistance adjusting agents (tin oxide, lead oxide, antimony oxide, etc.).

Further, the toner of the present invention may contain additives other than the above-mentioned binder resin, colorant, auxiliary and the like, if necessary. Examples of the additive include fluidity imparting agents such as colloidal silica, titanium oxide, and aluminum oxide.

By selectively holding electric charges on the surface of the toner and developer carrier of the present invention, a large number of minute closed electric fields are formed in the vicinity of the surface of the developer carrier. Supplying a non-magnetic one-component developer composed of a toner to which an auxiliary agent is externally added, if necessary, causing the developer to be carried on the surface of the developer carrier by the minute closed electric field; It is particularly useful in an image forming method for visualizing a latent image.

Hereinafter, such an image forming method will be described. FIG. 1 shows an outline of a typical developing device useful for carrying out this image forming method, focusing on a developer carrier. FIG.
, The toner 60 contained in the toner tank 70
Is forcibly brought to a toner supply member (such as a sponge roller or a fur brush) 40 by a stirring blade (toner supply auxiliary member) 50, and the toner 60 is supplied to the toner supply member 40. On the other hand, the developer carrier (developing roller)
Rotates in the direction of the arrow (for example, 400 rpm), and reaches a contact portion with the toner supply member 40. The toner supply member 40 rotates in the opposite direction to the developer carrier 20 (for example, 300 rpm), and
And charge the toner 60, and put the toner 60 on the developer carrier 20.
To adhere. Further, the developer carrier 20 rotates, and the toner adhered on the developer carrier 20 is stabilized in thickness while being controlled by the toner layer thickness regulating member (elastic blade) 30, and reaches the developing region 80. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, a direct current may be applied to the developer carrier 20 and the toner supply member 40.
An optimum image can be controlled by applying a bias such as AC, DC superimposed AC, or pulse.

Next, the mechanism of toner adhesion to the developer carrier 20 of this type (electrode type) will be described.
As an example of the developer carrying member 20, as shown in FIG. 2, for example, a dielectric portion and a conductor portion are mixed on a surface thereof with a small area. As for the size of the area, assuming that the shape is circular, minute areas having a diameter of 10 to 500 μm are dispersed randomly or according to a certain rule. As the area ratio, the area of the dielectric portion is preferably in the range of 20 to 60%.

The toner adhesion is as follows. First, the developer carrier 20 that has completed the development rotates in the direction of the arrow and comes into contact with the toner supply member 40. 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 40, and the dielectric portion is charged by friction.
At this time, the charges of the developer carrier 20 and the toner by the previous development are fixed and initialized by friction. Next, the toner carried by the supply member 40 is charged by friction,
Electrostatically adheres to the dielectric portion of the developer carrier 20. At this time, the polarity of the toner is opposite to the charge of the photosensitive member, and the dielectric portion of the developer carrier 20 has the same polarity. At this time, the electric field on the developer carrier 20 becomes a microfield (closed electric field) as shown in FIG. 2, and becomes an electric field with a large electric field gradient, so that the toner can be attached to multiple layers. Also, since the attached toner has a closed electric field,
The developer is strongly pulled toward the developer carrier 20 and is hard to be separated.

The toner layer further includes a toner layer thickness regulating member.
The toner layer thickness is controlled by 30 and reaches the developing area 80.
The electric field between the developer carrier 20 and the electrostatic latent image carrier (photoreceptor) 10 in the developing area 80 increases the electrode effect, and the toner on the developer carrier 20 is transferred to the electrostatic latent image carrier 10. The electric field is easily adhered, and development is performed.

Although many types of parts can be used for the developing device, as shown in Table 1, when only the preferable materials are used from the viewpoint of releasability from toner and durability.

[0032]

[Table 1]

Next, the method for producing the developer carrier used in the present invention will be described. For example, the following method is employed. (i) First, a metal roller whose surface is grooved is manufactured. The groove is formed by a method such as iris knurling. The grooves have a pitch of 0.1 to 0.5 mm and are processed at an angle of about 45 degrees with respect to the longitudinal direction of the roller. (See FIG. 3 (a)) (ii) Next, for example, a fluororesin
(Lumiflon LF200; manufactured by Asahi Glass Co., Ltd.), 10
Cure and dry at 0 ° C for about 30 minutes. The coating thickness is set so that the grooves are completely filled. [See; FIG. 3 (b)] (iii) Subsequently, the surface of the roller is cut or polished so that the conductive surface is mixed in a small area, and the conductive area is reduced to 20%.
Cut to ~ 60%. [See; FIG. 3 (c)]

In the developing method in which a large number of micro electric fields (microfields) are formed in the vicinity of the surface of the developer carrier, the toner layer on the developer carrier is always stabilized by using two or more layers. It is necessary to prevent the amount of toner to be developed from becoming thinner and reduce the density of the image area, and to prevent the toner layer from becoming uneven and causing uneven development or fogging. However, when the toner of the present invention is used, a multi-layered toner layer is stably formed on the developer carrying member.

[0035]

The present invention will be described in more detail with reference to the following examples. Parts represent parts by weight.

Example 1 Binder resin Styrene / acrylic copolymer 95 parts Release agent Low molecular weight polypropylene 5 parts Colorant carbon black 8 parts Charge control agent Nigrosine 2 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by a pulverizer using an air jet method. The obtained finely pulverized product was classified to have an average particle size of 11 μm. 0.2 parts of colloidal silica was added to and mixed with 100 parts of the particles to obtain the toner of the present invention. The ratio of coarse particles having a particle diameter of 25 μm or more was 0.3%.

Next, a developing roller having a cross section as shown in FIG. 3 (c) [FIG. 3 (a)] (dielectric and conductive portions are mixed in a very small area, and their area ratio is 50% Things)
Prepared a developing device equipped with the above, when the toner is attached to such a developing device, and an image is taken out, high image density, no background stain, no partial blurring or unevenness, and a clear image is obtained. Obtained.

Example 2 Binder resin 95 parts of styrene / acrylic copolymer Release agent 5 parts of low molecular weight polypropylene Colorant 8 parts of carbon black Charge control agent 2 parts of zinc salicylate

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to have an average particle size of 9 μm. 0.3 parts of titanium oxide was added to and mixed with 100 parts of the present particles to obtain a toner of the present invention. Coarse particles having a particle diameter of 25 μm or more were 0.2%.

Next, a developing roller having a cross section as shown in FIG. 3 (c) [FIG. 3 (a)] (dielectric part and conductor part are mixed in a small area, and their area ratio is 50% Things)
Prepared a developing device equipped with the above, when the toner was mounted on such a developing device and an image was taken out, there was no background stain at high image density, and no clear blur or unevenness was observed, and a clear image was obtained. Obtained.

Comparative Example Binder Resin Styrene / acrylic copolymer 95 parts Release agent Low molecular weight polypropylene 5 parts Colorant carbon black 8 parts Charge control agent Nigrosine 2 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to have an average particle size of 11 μm. 0.2 parts of colloidal silica was added to and mixed with 100 parts of the particles to obtain a toner. The coarse particles having a particle diameter of 25 μm or more were 1.1%.

Next, a developing roller having a cross section as shown in FIG. 3 (c) (FIG. 3 (a)) (dielectric part and conductor part are mixed in a very small area, and their area ratio is 50% Things)
Was prepared, and the toner was attached to the developing device, and an image was formed. As a result, although the image density was high and the background was not stained, partial blurring and unevenness were observed.

[0045]

According to the present invention, the toner of the present invention comprises at least a binder resin and a colorant, and has a volume average particle size of 12 μm or less and 1% by weight or less of coarse particles having a particle size of 25 μm or more. Therefore, by selectively holding electric charges on the surface of the developer carrier, a number of minute closed electric fields are formed in the vicinity of the surface of the developer carrier, and auxiliary electric fields are formed on the developer carrier as necessary. A non-magnetic one-component developer composed of a toner externally added with a developer is supplied, and the developer is carried on the surface of the developer carrier by the minute closed electric field. good in the image forming method of reduction
Book used to apply, Ru using the toner to the image forming method
According to the image forming method of the present invention , two or more layers of the toner can be stably and uniformly laminated on the developer carrier, and as a result, a high-density and high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a developing device that forms a microfield electric field on a developer carrier useful for carrying out the present invention, focusing on a developer carrier portion.

FIG. 2 is a schematic cross-sectional view for explaining a state in which a closed electric field is generated by a microfield on a developer carrier in the apparatus shown in FIG.

3 (a) to 3 (c) are schematic cross-sectional views showing surface states in a process of manufacturing a developer carrier used in a developing device of the type shown in FIG.

[Explanation of symbols]

 10 Electrostatic latent image carrier 20 Toner transport member 30 Toner layer thickness regulating member 40 Toner supply member 50 Stirrer blade 60 Toner 70 Toner tank 80 Development area

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-101557 (JP, A) JP-A-53-36245 (JP, A) JP-A-49-126856 (JP, A) JP-A-60-1985 78460 (JP, A) JP-A-61-87177 (JP, A) JP-A-62-143074 (JP, A) JP-A-2-214874 (JP, A) (58) Fields investigated (Int. ^7, DB name) G03G 9/08 G03G 13/08 G03G 15/06

Claims (2)

(57) [Claims] An electric charge is selectively retained on a surface of a developer carrier to form a large number of minute closed electric fields near the surface of the developer carrier. Accordingly, a non-magnetic one-component developer composed of a toner externally added with an auxiliary agent is supplied, and the developer is carried on the surface of the developer carrier by the minute closed electric field, and the electrostatic latent image is formed by the carried developer. A toner for use in an image forming method for forming a visible image, comprising at least a binder resin and a colorant, and having a volume average particle diameter of 12 μm or less and 1% by weight or less of coarse particles having a particle diameter of 25 μm or more. A toner characterized by the following. 2. An electric charge is selectively retained on the surface of the developer carrier to form a large number of minute closed electric fields near the surface of the developer carrier. Accordingly, a non-magnetic one-component developer composed of a toner externally added with an auxiliary agent is supplied, and the developer is carried on the surface of the developer carrier by the minute closed electric field, and the electrostatic latent image is formed by the carried developer. An image forming method for visualizing an image, wherein the toner according to claim 1 is used as the toner.