JPH05273782A - Toner - Google Patents

Abstract

PURPOSE:To provide a toner used for an image forming method in which the toner can be stably and uniformly deposited in two or more layers on a developing roller, suppresses filming on the developing roller to give images of high density and high quantity for a long period by forming lots of small closed electric fields near the surface of the developing roller, depositing a developer on the surface of the roller to visualize electrostatic latent images. CONSTITUTION:This toner contains a binder resin and a coloring agent and has 2-500kg.cm/cm Izod impact strength when the toner is formed in a plate. This toner is used for an image forming method to visualize electrostatic latent images. In this method, small closed electric fields are produced near the surface of the developing roller by selectively giving charges on the surface of the roller, on which a nonmagnetic one-component developer comprising a toner, if necessary with external additives, is supplied. Thus, the developer is deposited on the surface of the roller by the small closed electric fields to visualize electrostatic latent images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies a non-magnetic one-component developer to which an auxiliary agent is externally added, if necessary, to a developing roller which is rotationally driven, and the developer is applied to the surface of the developing roller. The latent image carrier is carried and conveyed, and in the developing area where the latent image carrier and the developing roller face each other, the electrostatic latent image formed on the latent image carrier is visualized by the developer carried on the developing roller. The present invention relates to a toner used in an image forming method for converting into a toner.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a printer or a facsimile, which forms an electrostatic latent image on a latent image carrier and visualizes it with a developer to obtain a recorded image, a powdery material is used. A dry developing device using a developer is widely adopted. As the powdery developer, a two-component developer containing a toner and a carrier and a one-component developer containing no carrier are known. Two-component development using the former two-component developer is known. The method can obtain a relatively stable and good recorded image, but on the other hand, deterioration of the carrier and variation of the mixing ratio of the toner and the carrier are likely to occur, maintenance of the apparatus is complicated, and the structure of the entire apparatus tends to be large. It has drawbacks.

From this point of view, a one-component developing system using a one-component developer which does not have the above-mentioned drawbacks has been attracting attention. The one-component developer consists of toner only,
In some cases, an auxiliary agent is externally added to the toner if necessary and the toner and the auxiliary agent are mixed. 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 substance. Here, since the magnetic substance is generally opaque, when a color image including full color and multi-color is formed with magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained. Therefore, especially for color development, it is desirable to adopt the one-component development method using non-magnetic toner.

By the way, in a developing device adopting a one-component developing system, a one-component type developer is carried on a developing roller and conveyed, and in the developing area where the developing roller and the latent image carrier face each other, The electrostatic latent image formed on the image carrier is visualized by a developer, but in order to form a high-quality visible image with a predetermined density, a large amount of sufficiently charged toner is conveyed to the development area. However, it is necessary to visualize the latent image with such toner. When a magnetic toner is used, the magnetic force of a magnet provided inside the developing roller can be utilized to carry the one-component developer on the roller, so that the above-mentioned requirements can be satisfied relatively easily. is there.

However, when a non-magnetic one-component developer is used, it cannot be carried on the developing roller by magnetic force, so that it is difficult to satisfy the above-mentioned requirements. Various countermeasures against this have been proposed in the past,
For example, in Japanese Patent Laid-Open No. 61-42672, a dielectric (insulator) layer is laminated on the surface of a developing roller, and a developer supply member composed of, for example, a sponge roller is pressed against the layer, and both layers are formed. A method has been proposed in which the non-magnetic toner charged with the opposite polarity to this dielectric is electrostatically adhered to the dielectric, and the one-component developer is conveyed to the development area. There is. However, even with this method, the strength of the electric field formed in the vicinity of the surface of the dielectric cannot be sufficiently increased, so that it is difficult to carry a large amount of toner on the surface of the developing roller, and it is possible to convey the toner to the developing area. It is difficult to form a high-density visible image because the amount of the agent is insufficient. A configuration is also known in which an electric field in a direction in which non-magnetic toner is electrostatically transferred to the developing roller side is applied between the developing roller and the developer supply member. It is difficult to attach a sufficient amount of toner to the roller.

Further, as the toner supply member, 10 ² to
Conductive foam of 10 ⁶ Ω · cm (JP-A-60-2290)
57), an elastic body with a skin layer (JP-A-60-229).
No. 060) and fur brush (JP-A-61-426).
No. 72) and the like, and as a developing roller, a metal body having irregularities on its surface (JP-A-60-53976) and an insulating coating roller body (JP-A-55-46768). JP-A-58-13278), an electrode roller having an insulator and a conductive surface (JP-A-53-36245), and the like. Further, in a developing device using a non-magnetic one-component developer, a sponge roller in JP-A-60-229057, an elastic roller in JP-A-62-229060, a fur brush in JP-A-61-52663, etc. The toner is charged by frictional charging between the toner and the replenishing member, and the toner is electrostatically attached to the developing roller by friction during contact with the developing roller.
Further, a toner layer is controlled by using a layer thickness regulating member such as a blade to develop the latent image on the photoreceptor. Various materials such as an insulating material, a medium resistance material, and a laminated material are used as the material of the developing roller.

According to the method shown in these references, toner is attached to the developing roller by friction between the toner replenishing member and the developing roller. Is difficult to obtain and, as a result, toner adhesion is insufficient. Further, when comparing the color toner with the black toner, the adhesion amount of the black toner is about 0.4 to 0.5 mg / cm ^{2 in} order to obtain the required density, whereas the color toner has the adhesion amount of the black toner of about 0.4 to 0.5 mg / cm ² . 1.5-2
Double the amount attached is required. The need for this large amount of adhesion also makes non-magnetic one-component development difficult. Further, as shown in JP-A-54-51841, etc., after scraping off the one-component developer on the developing roller after passing through the developing area, corona is applied to the surface layer of the developing roller. A technique has also been proposed in which an electric charge is applied by discharging and then a non-magnetic toner is electrostatically and positively adhered onto a developing roller by a developer supplying member.
Even with this configuration, the amount of developer carried on the surface of the developing roller cannot be increased, and a large amount of developer cannot be conveyed to the developing area.

As a method of solving these problems, the inventors of the present invention have previously described "a one-component developer composed of a non-magnetic toner in which an auxiliary agent is externally added to a developing roller which is rotationally driven, if necessary. Is supplied, and the developer is carried on the surface of the developing roller and conveyed, and the electrostatic latent image formed on the latent image carrier is developed in the developing area where the latent image carrier and the developing roller face each other. In a developing method in which the developer carried on the developing roller is visualized, a large number of minute closed electric fields are formed in the vicinity of the surface of the developing roller by selectively retaining electric charges on the surface of the developing roller. Then, an image forming method has been proposed in which the charged toner is attracted by the closed electric field, the developer is attached to the surface of the developing roller and carried, and the electrostatic latent image is visualized by the carried developer.

In this invention, since a large number of minute closed electric fields (microfields) are formed in the vicinity of the surface of the developing roller, the electric field strength can be remarkably increased as compared with the prior art, and a sufficiently charged large amount of non-fields can be formed. It has many advantages that the magnetic toner can be carried on the developing roller and conveyed to the developing area. However, according to the subsequent studies by the present inventors, in the developing method for forming such a minute closed electric field (microfield), when the conventionally known toner is used as it is, the toner on the developing roller is not changed. It is difficult to always stabilize the toner layer with two or more layers, the toner layer becomes thin and the amount of toner to be developed decreases, the density of the image area becomes low, and the toner layer becomes non-uniform and development is performed. This may cause unevenness or fogging.Furthermore, a filming phenomenon often occurs on the developing roller, the microfield effect is reduced, the toner holding amount on the developing roller is reduced, and It has been found that there arises a problem that it becomes difficult to sufficiently develop the toner on the image carrier.

[0010]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned technical background, and its object is to enable two or more layers to be stably and uniformly laminated on a developing roller and to have the developing roller. Filming is suppressed and high density and high quality images can be provided for a long period of time. Therefore, by selectively retaining electric charges on the surface of the developing roller, a large number of micro-closed areas are formed near the surface of the developing roller. An electric field is formed, and a non-magnetic one-component developer composed of a toner to which an auxiliary agent is externally added is supplied onto the developing roller, and the developer is carried on the surface of the developing roller by the minute closed electric field. It is an object of the present invention to provide a toner that can be suitably used in an image forming method in which an electrostatic latent image is visualized by the carried developer.

[0011]

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 Izod impact value when formed into a plate is suitable for the above purpose. That is, the present invention has been completed. That is, according to the present invention, a large number of minute closed electric fields are formed in the vicinity of the surface of the developing roller by selectively retaining electric charges on the surface of the developing roller, and assisting the developing roller as needed. A non-magnetic one-component developer composed of toner to which an agent is added is supplied, the developer is carried on the surface of the developing roller by the minute closed electric field, and the electrostatic latent image is visualized by the carried developer. A toner used in an image forming method, characterized in that the toner contains at least a binder resin and a colorant and has an Izod impact value of 2 to 500 kg · cm / cm when the toner is formed into a plate. Toner is provided.

The toner of the present invention contains the binder resin and the colorant as described above, and has an Izod impact value of 2 to 500 kg.cm/cm, preferably 4 to 1 when formed into a plate.
It is characterized in that it is 00 kg · cm / cm. In addition,
In the present invention, as a method of measuring the Izod impact value,
According to "JIS K-7110, Impact Test Method for Hard Plastics", a sample was prepared by pressure molding by melting toner to form No. 1 test piece.
By the way, the Izod impact value is a scale indicating the mechanical strength of the toner, and is specifically measured when the toner is formed into a plate.

According to the research conducted by the present inventors, when the Izod impact value of the toner is within the above range, the toner is less likely to be pulverized on the developing roller, and the toner particles are made uniform and stable. It was found that two or more layers can be laminated, and filming on the developing roller and fog development at the time of development are reduced.

The Izod impact value of the toner is 2 kg · c
If it is less than m / cm, the mechanical strength is weak, and the toner is pulverized due to friction with the toner layer regulating member and the latent image carrier on the developing roller, resulting in filming on the developing roller and fogging during development. Development is likely to occur. Also,
If it exceeds 500 kg · cm / cm, the strength will be too strong. Therefore, the developing roller is abraded, and the area ratio of the dielectric part to the conductive part on the developing roller, which will be described later, changes greatly, and the trapping force of toner particles due to the microfield effect decreases. In any case, the intended purpose of the present invention cannot be achieved.

The binder resin used in the toner of the present invention is
All of those which have been used as a binder for toner so far can be applied. Specifically, styrene such as polystyrene, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer Including resin, saturated polyester resin, unsaturated polyester resin, epoxy resin,
Examples thereof include phenol resin, maleic acid resin, coumaronic acid resin, chlorinated paraffin, xylene resin, vinyl chloride resin, polypropylene and polyethylene. It goes without saying that two or more kinds of these binder resins may be appropriately mixed and used. Of these, use of polystyrene, styrene resin, and epoxy resin is advantageous.

The toner of the present invention contains a colorant. As the colorant used in the toner of the present invention,
All of the pigments and dyes conventionally used as colorants for toner are applied. Specifically, carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, chalco oil blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6C rake, Chrome yellow,
Examples include quinacridone, benzidine yellow, malachite green, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dyes and pigments, disazo dyes and pigments, trisazo dyes and pigments, and mixtures thereof.

The toner of the present invention may contain a charge control agent, a fluidizing agent or a releasing agent, if necessary. As the charge control agent, a nigrosine dye, a quaternary ammonium salt, or an agent that imparts positive polarity to the toner,
There are basic dyes, amino acid-containing polymers, and the like, and those that impart negative polarity include chromium-containing monoazo dyes,
Examples thereof include chlorinated organic dyes and metal salts of salicylic acid derivatives. Examples of the fluidizing agent include inorganic oxides such as SiO ₂ and TiO ₂ whose surfaces are hydrophobized, inorganic fine particles such as SiC, and metallic soaps such as zinc stearate.

As the release agent, in addition to synthetic waxes such as low molecular weight polyethylene and polypropylene, plant waxes such as candelilla wax, carnauba wax, rice wax, wood wax and jojoba oil; beeswax, lanolin, Animal waxes such as whale wax; mineral waxes such as montan wax and ozokerite; hydrogenated castor oil, hydroxystearic acid, fatty acid amide,
Examples include oil-based waxes such as phenol fatty acid ester.

In addition to the above-mentioned components, the toner of the present invention contains various plasticizers (dibutyl phthalate, dibutyl phthalate, etc.) for the purpose of adjusting the thermal properties, electrical properties, physical properties, etc. of the toner as required.
It is also possible to add auxiliary agents such as dioctyl phthalate) and resistance adjusting agents (tin oxide, lead oxide, antimony oxide, etc.).

The toner of the present invention selectively holds an electric charge on the surface of the developing roller to form a large number of minute closed electric fields in the vicinity of the surface of the developing roller, and if necessary, on the developing roller. A non-magnetic one-component developer composed of a toner to which an auxiliary agent is added is supplied, and the developer is carried on the surface of the developing roller by the minute closed electric field, and the electrostatic latent image is visualized by the carried developer. In the image forming method
Especially useful.

The image forming method will be described below. FIG. 1 shows an outline centering on a developing roller portion of a typical developing device useful for carrying out this image forming method. In FIG. 1, the toner 60 of the present invention contained in the toner tank 70 is forcibly drawn to the toner supply member (sponge roller or fur brush) 40 by the stirring blade (toner supply auxiliary member) 50, and the toner 60 is discharged. Is supplied to the toner supply member 40. On the other hand, the developing roller 20 that has completed development rotates in the direction of the arrow (for example, 400 rpm).
Then, it reaches the contact portion with the toner supply member (sponge roller) 40. The toner supply member 40 rotates in the opposite direction to the developing roller 20 (for example, 300 rpm), charges the developing roller 20 and the toner 60, and causes the toner 60 on the developing roller 20.
Attach. Further, the developing roller 20 rotates, and the toner adhered on the developing roller 20 is stabilized by the toner layer thickness regulating member (elastic blade) 30 while the charge is stabilized and reaches the developing area 80. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, a bias such as DC, AC, DC superimposed AC, or pulse may be applied to the developing roller 20 and the toner supply member 40 to control an optimum image.

Next, the mechanism of toner adhesion to the developing roller 20 of this type (electrode type) will be described. As an example of the developing roller 20, for example, as shown in FIG. 3, a dielectric portion and a conductor portion are mixed in a minute area on the surface thereof. The size of the area is
When the shape is circular, minute areas having a diameter of 10 to 500 μm are dispersed randomly or according to a certain rule. As for the area ratio, the area of the insulating part is 20
The range of -60% is preferable.

Toner adhesion is as follows. First, the developing roller 20 that has completed development contacts the toner supply member 40 by rotating in the direction of the arrow. The residual toner in the non-image area that has not been developed is mechanically and electrically scraped by the toner supply member 40, and the dielectric portion is charged by friction. At this time, the electric charges of the developing roller 20 and the toner due to the previous development are constant and initialized by friction. Next, the toner carried by the supply member 40 is charged by friction and electrostatically adheres to the dielectric portion of the developing roller 20. At this time, the polarity of the toner is opposite to that of the charge on the photosensitive member, and the dielectric portion of the developing roller 20 has the same polarity.
At this time, the electric field on the developing roller 20 becomes a microfield (closed electric field) as shown in FIG. 2, and becomes an electric field having a large electric field gradient, so that the toner can be attached in multiple layers. Further, since the adhered toner has a closed electric field, the toner is strongly attracted to the developing roller 20 side and becomes difficult to separate. This toner layer further includes the toner layer thickness regulating member 3
The toner layer thickness is controlled by 0, and the toner in the developing area 80 becomes an electric field that easily adheres to the photoconductor, and development is performed. Although many kinds of developing device parts can be used, Table 1 shows only the preferable materials in terms of releasability from toner and durability.

[0024]

[Table 1]

In order to manufacture a developing roller having a surface in which a dielectric portion and a conductor portion are mixed in a small area, for example, first, a metal whose groove is processed by iris red processing or the like is first formed on the surface. A roller is produced (in this case, the groove has a pitch of 0.1 to 0.5 mm and is machined at an angle of about 45 ° with respect to the longitudinal direction of the roller).
(A)] Next, the grooved metal surface is coated with, for example, a fluororesin (Lumiflon LF200; manufactured by Asahi Glass Co., Ltd.) and cured and dried at 100 ° C. for about 30 minutes (the coating thickness is such that the groove is completely filled). [Refer to FIG. 3
(B)] Then, the surface of the roller is ground by cutting or polishing so that the conductive surface is mixed in a minute area, and the conductive area is cut to 20 to 60% [see FIG. 3 (c)].
Method is adopted.

In the developing system for forming a micro-field electric field on the developing roller, when the conventionally known toner is used as it is, the toner layer on the developing roller is always stabilized as two layers or more. However, the toner layer becomes thinner and the amount of developed toner decreases, resulting in lower density in the image area, uneven toner layer and uneven development, and fogging. There is. Further, with the conventional toner, the filming phenomenon often occurs on the developing roller, but when the filming is formed on the developing roller, the microfield effect is reduced and the toner holding amount on the developing roller is reduced. However, it becomes difficult to sufficiently develop the toner on the latent image carrier.
However, when the toner of the present invention is used, pulverization of the toner on the developing roller is suppressed, and as a result, filming on the developing roller is suppressed, so that a sufficient microfield effect is exerted. With the toner of the invention,
High-density and high-quality images can be obtained over a long period of time.

[0027]

The present invention will be described in more detail with reference to the following examples. In addition, a part represents a weight part. Example 1 Binder resin Styrenic polymer 85 parts Phenyl ether polymer 10 parts Release agent Low molecular weight wax 5 parts Colorant carbon black 8 parts Charge control agent Salicylic acid derivative zinc salt 4 parts Melt kneading the mixture of the above composition After cooling, coarse pulverization was performed using a hammer mill, and then fine pulverization was performed using an air jet type fine pulverizer. The resulting finely pulverized product was classified to have an average particle size of 9 μm. Toner was obtained by adding 0.4 parts of silica fine powder to 100 parts of the present particles and mixing. The Izod impact value of the toner obtained by melting and flattening the toner before mixing the obtained silica fine powder was 88 (kg · cm / c).
m). Next, a developing roller (FIG. 3 (a)) having a cross section as shown in FIG. 3 (c) (dielectric part and conductive part are mixed in a minute area, and the area ratio thereof is 60%) is provided. When a developing device was prepared, and the toner was attached to the developing device and an image was formed, a clear image with high image density and no background stain was obtained. Further, after running 5000 sheets continuously, the toner was not filmed on the developing roller and a clear image was maintained.

Example 2 Binder resin Styrene-methacrylic acid polymer 85 parts Polycarbonate 10 parts Release agent Low molecular weight wax 5 parts Coloring agent Carbon black 10 parts Charge control agent Salicylic acid derivative zinc salt 5 parts Melting the mixture of the above composition After kneading and cooling, coarse pulverization was performed using a hammer mill, and then fine pulverization was performed using an air jet type fine pulverizer. The obtained finely pulverized product was classified to have an average particle size of 8 μm. Toner was obtained by adding 0.3 parts of fine silica powder to 100 parts of the present particles and mixing. The Izod impact value of the toner when the toner before being mixed with the obtained silica fine powder was flattened by melting was 50 kg · cm / cm.
Met. Next, the development provided with a developing roller (FIG. 3 (a)) having a cross section as shown in FIG. 3 (c) (dielectric part and conductive part are mixed in a minute area, and the area ratio is 50%) An apparatus was prepared, the above toner was attached to the developing apparatus, and an image was printed. As a result, a clear image having a high image density and no background stain was obtained. Further, even after running 5000 sheets continuously, the toner was not filmed on the developing roller and a clear image was maintained.

Comparative Example 1 Binder resin Styrenic polymer 95 parts Release agent Low molecular weight wax 5 parts Colorant carbon black 10 parts Charge control agent Salicylic acid derivative zinc salt 4 parts Melt kneading the mixture of the above composition and cooling after hammering Coarse pulverization was performed using a mill, and then fine pulverization was performed using an air jet type fine pulverizer. The resulting finely pulverized product was classified to have an average particle size of 9 μm. 0.4 part of silica fine powder was added to 100 parts of the particles and mixed to obtain a comparative toner. The Izod impact value of the toner when the toner before being mixed with the obtained silica fine powder was melted and flattened was 0.5 kg.
It was cm / cm. When an image was formed using this toner in the same manner as in Example 1, the image density was low, and uneven density was observed in some places. Further, the toner was filmed on the developing roller after running 5000 sheets.

Comparative Example 2 Binder resin Styrene-methacrylic acid polymer 95 parts Release agent Low molecular weight wax 5 parts Colorant carbon black 10 parts Charge control agent Salicylic acid derivative zinc salt 4 parts Melt kneading the mixture of the above composition, After cooling, it was coarsely pulverized using a hammer mill and then finely pulverized by an air jet type fine pulverizer. The obtained finely pulverized product was classified to have an average particle size of 8 μm. 0.4 part of silica fine powder was added to 100 parts of the particles and mixed to obtain a comparative toner. The Izod impact value of the toner when the obtained silica fine powder was mixed and flattened by melting the toner was 1.8 kg.
It was cm / cm. When an image was formed in the same manner as in Example 2 using this toner, the image density was low, and density unevenness was observed in some places. Further, the toner was filmed on the developing roller after running 5000 sheets.

[0031]

INDUSTRIAL APPLICABILITY The toner of the present invention can stably and evenly stack two or more layers on the developing roller, suppress filming on the developing roller, and provide a high density and high quality image for a long period of time. Therefore, the toner of the present invention forms a large number of minute closed electric fields near the surface of the developing roller by selectively retaining electric charge on the surface of the developing roller, and assists the developing roller on the surface of the developing roller as needed. Supplying a non-magnetic one-component developer consisting of toner with external additives
It is suitably used for an image forming method in which the developer is carried on the surface of the developing roller by the minute closed electric field and the electrostatic latent image is visualized by the carried developer.

[Brief description of drawings]

FIG. 1 is a schematic sectional view centering on a developing roller portion showing an example of a developing device in which a microfield electric field is formed on a developing roller useful for carrying out the present invention.

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

3A to 3C are schematic cross-sectional views showing a surface state in a manufacturing process of a developing roller used in the developing device of the type shown in FIG.

[Explanation of symbols]

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

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/08 7810-2H

Claims (1)

[Claims] 1. A large number of minute closed electric fields are formed in the vicinity of the surface of the developing roller by selectively retaining an electric charge on the surface of the developing roller, and an auxiliary agent is externally applied to the developing roller as needed. An image forming method in which a non-magnetic one-component developer composed of added toner is supplied, the developer is carried on the surface of the developing roller by the minute closed electric field, and the electrostatic latent image is visualized by the carried developer. The toner for use in, containing at least a binder resin and a colorant, and having an Izod impact value of 2 to 2 when the toner is formed into a plate.
A toner having a weight of 500 kg · cm / cm.