JPH10232507A - Toner for developing electrostatic charge image and image forming method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a toner for developing an electrostatic charge image having satisfactory transferability, ensuring a long service life at the time of use in a developer and having satisfactory faithful reproducibility of an initial image even at the time of use over a long period of time by specifying the amt. of toner particles having specified circularity or below obtd. by a pulverizing method. SOLUTION: This toner for developing an electrostatic charge image contains <=50% toner particles having circularity (SF) of <0.95 produced by a pulverizing method. The circularity SF represented by the equation SF=[(area of toner)/(peripheral length of toner)<2> ].4π is a shape factor expressing the complexity of the peripheral shape of the toner and it becomes closer to 1.00 as the peripheral shape of the toner becomes more circular. The circularity may be measured with a flow type particle image analyzer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image used in an electrophotographic method, an electrostatic printing method and the like, and an image forming method using the same.

[0002]

2. Description of the Related Art In the case of a dry method, an electrostatic image formed by an electrophotographic method, an electrostatic printing method, an electrostatic recording method or the like is generally developed with a dry toner containing a binder resin and a colorant as main components. It is transferred and fixed on copy paper. The dry toner used at this time, when manufactured by a pulverization method, has more contact points with the photoreceptor and is harder to separate from the photoreceptor as compared with a spherical toner because the shape is square and irregular. Therefore, in the above-described transfer process, all of the developed toner is not transferred, and is collected in the next cleaning process while remaining on the photoconductor.

In recent years, there has been a strong demand for a machine without waste toner from the viewpoints of economy, maintenance-free, and environmentally-friendly disposal, and a recycling system in a copying machine has been constructed and addressed. ,
To build such a system, a certain amount of space is required in the copier, and a recent trend of downsizing demands a smaller and lighter model. In that respect, it is necessary to increase the toner transfer rate. It is considered that the most appropriate method is to take measures to eliminate waste toner as much as possible or to construct a simple recycling system. For this reason, if a transfer rate of 100% is ideally obtained, a recycling system is not necessary. However, on the other hand, the demand for higher image quality in the market has been to reduce the toner particle size year by year, and the smaller the particle size, the larger the specific surface area of the toner itself. It can be said that the method is moving toward a method in which the toner is hardly peeled off from the photoreceptor and is hardly transferred.

Further, as disclosed in JP-A-59-46664, the method includes a step of electrostatically transferring a toner image formed on the surface of an electrostatic charge holding member to a transfer material such as a sheet mainly made of paper. In an image forming apparatus, an electrostatic charge holding member such as a rotating cylindrical shape or an endless belt shape is used, and a transfer device to which a bias is applied is pressed against the transfer device, and a transfer material is passed between the two. An apparatus for transferring the toner on the holding member to a transfer material has already been proposed. Compared with a conventional transfer device using corona discharge, such an apparatus transfers the transfer material while pressing the electrostatic charge holding member against the transfer material, so that the adhesion between the electrostatic charge holding member and the transfer material is improved. It is easy to obtain a high quality transfer image.

However, when an abutting pressure is applied, pressure is also applied to the toner image on the electrostatic charge holding member to cause aggregation, and adhesion occurs between the toner and the electrostatic charge holding member. In this case, a phenomenon occurs in which a portion having strong adhesion is not transferred. This phenomenon is particularly noticeable in line images, and is called “depressing development” in which the center is not transferred, and has been regarded as a problem. It has been widely taken up and its solution is eagerly awaited. To cope with such a problem, Japanese Patent Application Laid-Open No. 4-27443 discloses a method in which specific resin fine particles which act as spacer particles between the toner and the electrostatic charge holding member are added. However, a method for preventing adhesion of the toner to the electrostatic charge holding member due to aggregation of the toner has already been proposed.

[0006]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a good transferability, a long life when used in a developer, and a good reproducibility of an initial image even when used over time. To provide a toner for developing an electrostatic latent image. A second object of the present invention is to provide an image forming method which has a high transfer efficiency, has no omission during transfer, has a long life when used as a developer, and has a good fidelity of an initial image even when used over time. To provide.

[0007]

Means for Solving the Problems As a result of intensive studies on the toner for developing an electrostatic image, the present inventor has determined that the amount of toner obtained by a pulverization method having a circularity of a certain value or less as described below. It has been found that the above-mentioned task can be achieved. The present invention has been made based on this.

According to the present invention, first, the following equation (Equation 1)
Wherein the content of toner particles produced by a pulverization method having a circularity (SF) represented by the following formula is 50% or less in all the toners.

## EQU1 ## Secondly, the toner circularity (SF) = [toner area / (toner perimeter) ² ] × 4π <0.95. A toner is provided. Third, in the first and second aspects, there is provided an electrostatic image developing toner having a toner particle content (number) having a particle size of 3 μm or less of 10% or less.

According to the present invention, fourthly, an image forming method in which a transfer means is brought into contact with a part of an electrostatic charge holding member via a transfer material and a toner image is electrostatically transferred to the surface of the transfer material. Wherein the content of toner particles produced by a pulverization method having a circularity represented by the above formula (Formula 1) in the total toner of 45% or less is used. Is done.

In the present invention, the toner circularity (SF) defined by the toner circularity (SF) = [toner area / (toner peripheral length) ² ] · 4π is a shape index representing the complexity of the shape around the toner. Thus, the shape around the toner is smoother, and the closer the shape is to a circle, the closer to 1.00. This circularity can be measured using, for example, a flow-type particle image analyzer (FPIA-1000, manufactured by Toa Medical Electronics Co., Ltd.).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, the above formula (Equation 1) is used in all the toners.
When the ratio of the toner satisfying the condition is smaller than 50%, the shape of the toner is close to a circle (sphere), the number of contacts with the electrostatic charge holding member is reduced, the transfer efficiency is increased, and the life of the developer is reduced to the carrier surface. It has been found that the toner fusing phenomenon, that is, the so-called spent phenomenon, is unlikely to occur, and is therefore increased. This is 55%
Is considered to be the polarization point of the transfer efficiency. At this time, if the number of toner measurement samples is 800 or more, stable data can be obtained.
Better if more than 000. When the number of toner measurement samples is smaller than 800, it has been found that the value of the difference between the two toners having different transfer characteristics becomes small, and that the repetition accuracy is slightly reduced.

However, as a toner having a smooth and round surface, a toner produced by a polymerization method (polymerized toner) is generally known. It has also been found that the use of such a toner improves transfer efficiency and improves problems such as missing during transfer. However, although the polymer toner is too round, its adhesion to the electrostatic charge holder is reduced, but it has a disadvantage that it is difficult to scrape off in the cleaning process and the toner cannot be completely removed. There is also a disadvantage that the cost is considerably higher than the toner obtained by the crushing method. Therefore, if the above-mentioned drawbacks can be solved with a toner manufactured by a crushing method,
An electrophotographic system is successfully established, and it is more effective in terms of cost.

As far as the spheroidization of the toner produced by the pulverization method is concerned, a method of improving the toner surface by using mechanical energy is described in, for example, Japanese Patent Publication No. 7-38079.
As described in Japanese Unexamined Patent Publication (Kokai) No. H10-260, it is already known and known. However, the surface modification and toner production conditions according to the present invention have not been clarified yet.

The toner of the present invention can provide a clear copy image with higher image quality and no image defects by providing a toner having an average particle diameter of 5 to 9 μm on a volume basis and a good transfer rate. In digital copiers and printers, dots are formed on a latent image on a photoreceptor by laser light emitted from a laser optical system.Since the dot diameter is at most about 20 μm, the smaller the toner particle size is, the better. . However, when the volume average particle diameter of the toner is 5 μm or less, the productivity of the toner becomes extremely poor, and the yield also becomes poor, so that it is difficult to industrially produce the toner. Further, when the volume average particle diameter of the toner is 9 μm or more, problems such as deterioration of dot reproducibility and deterioration of image quality are observed.

The present invention provides a toner in which the content (number) of toner particles having a volume average particle size of 3 μm or less is 10% or less. It was also found that the life of the developer further increased because the phenomenon of fusion of the toner to the carrier surface, that is, the so-called spent phenomenon, hardly occurred.

Further, the present invention relates to an image forming method provided with a system for transferring a toner image electrostatically to the surface of a transfer material by bringing a transfer means into contact with a part of the electrostatic charge holding member via a transfer material. The toner used in the process has a circularity (SF) represented by the above formula (1), and the content of the toner particles manufactured by a crushing method in the total toner is 45% or less. By using a toner having the following characteristics, the transfer rate is good, and the hollow phenomenon, which is a problem unique to this system, can be eliminated. Here, when the proportion of the toner satisfying the expression (Equation 1) is less than 45%, the shape of the toner is closer to a circle (sphere), the number of contacts with the electrostatic charge holding member is reduced, and the transfer efficiency is reduced. It has been found that the hollowing-out phenomenon, which is a problem peculiar to this system, can be eliminated, and the life of the developer increases because the phenomenon of fusion of the toner to the carrier surface, that is, the so-called spent phenomenon, hardly occurs. This is considered that 45% is a branch point of the transfer rate.

In the present invention and the toner used in the method of the present invention, at least the toner satisfying the above formula (Equation 1) needs to be manufactured by a pulverization method. Other toners may be produced by a production method other than the pulverization method, for example, a polymerization method, but may be produced by a pulverization method, but those produced by a pulverization method are most preferred. Further, it may be a mixture of a toner manufactured by a pulverization method and a toner manufactured by a polymerization method.

Next, the materials used in the toner of the present invention will be described in detail. Examples of the binder resin used in the present invention include homopolymers of styrene such as polystyrene, poly p-chlorostyrene, 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-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 Styrene-based copolymers such as copolymers and styrene-maleic acid ester copolymers may be mentioned. In addition, the following resins can be mixed and used. Polymethyl methacrylate,
Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic Hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
And paraffin wax.

Particularly preferred binder resins for pressure fixing include the following, and these can be used in combination. Polyolefin (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polytetrafluoroethylene, etc.), epoxy resin, polyester resin, styrene-butadiene copolymer (monomer ratio 5 to 30: 9)
5-70), olefin copolymer (ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer,
Ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, ionomer resin), polyvinylpyrrolidone, methyl vinyl ether-
Maleic anhydride copolymer, maleic acid-modified phenolic resin, phenol-modified terpene resin.

The toner of the present invention further contains a magnetic material and can be used as a magnetic toner. Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, hematite, and ferrite, metals such as iron, cobalt, and nickel, and aluminum, cobalt, copper, lead, magnesium, tin, and zinc of these metals. , Antimony, beryllium, pismuth, cadmium, calcium,
Alloys of metals such as manganese, selenium, titanium, tungsten, and vanadium and mixtures thereof are given. These ferromagnetic substances preferably have a particle size of about 0.1 to 2 μm, and the amount contained in the toner is about 20 to 200 parts by weight, particularly preferably 100 parts by weight, based on 100 parts by weight of the resin component. It is 40 to 150 parts by weight.

As the charge control agent contained in the toner of the present invention, all conventionally known charge control agents can be used. Examples of the positive charge control agent include nigrosine, lake pigments of basic dyes, and quaternary ammonium salt compounds.Examples of the negative charge control agent include metal salts of monoazo dyes, salicylic acid, naphthoic acid, and metal complexes of dicarboxylic acid. And the like.

The toner of the present invention may optionally contain additives. Examples of the additive include a lubricant such as Teflon and zinc stearate or an abrasive such as cerium oxide and silicon carbide, or colloidal silica, for example.
Examples thereof include a fluidity-imparting agent such as aluminum oxide, an anti-caking agent, a conductivity-imparting agent such as carbon black and tin oxide, and a fixing aid such as a low-molecular-weight polyolefin.

As the colorant used in the toner of the present invention, all those known for toners can be used. As the black colorant, for example, carbon black, aniline black, furnace black, lamp black and the like can be used. As the cyan coloring agent, for example, phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, ultramarine blue and the like can be used. As the magenta colorant, for example, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake, and the like can be used. As the yellow colorant, for example, chrome yellow, benzidine yellow, Hanza yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used.

The toner of the present invention may be used as a one-component developer or a two-component developer. Further, when used as a two-component developer, the toner of the present invention is used by mixing with a carrier powder. As the carrier that can be used in the present invention, all known carriers can be used, for example, iron powder, ferrite powder, powder having magnetic properties such as nickel powder, glass beads, and the like, and their surfaces are treated with a resin or the like. And the like.

The resin powder that can be coated on the carrier in the present invention includes styrene-acrylic copolymer,
Silicone resin, maleic acid resin, fluorine resin, polyester resin, epoxy resin and the like are available. In the case of a styrene-acrylic copolymer, if it exceeds 30 to 90% by weight, the coating film becomes hard and easily peels off, shortening the life of the carrier. Further, the resin coating of the carrier may contain an adhesion-imparting agent, a curing agent, a lubricant, a conductive material, a charge control agent, and the like, in addition to the above resin.

[0026]

EXAMPLES Next, the present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. All parts are parts by weight.

Regarding the evaluation contents of Examples 1 and 2 and Comparative Example 1, a change in image quality and transfer efficiency at the start and after 150,000 sheets of images were output for each toner using a Ricoh copier FT-5500. An average test was performed. Example 3
Regarding the evaluation contents of Comparative Example 2, the Ricoh Copier FT-5500 was modified and a transfer roller on a cylinder was installed in the transfer section. With respect to the subsequent change in image quality, the average transfer efficiency, and the fourth aspect, a test was performed for missing images during transfer. The transfer efficiency was measured by the following equation. The amount of each adhered toner was evaluated by attaching the toner to the release tape using a release tape and evaluating the weight thereof.

Next, a production example of a carrier having a silicone resin in a coating layer will be described. These can be performed by known means. (Example of carrier production) Composition of coating layer forming liquid Silicone resin solution (KR250 manufactured by Shin-Etsu Silicone Co., Ltd.) 100 parts Carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 4 parts Toluene 100 parts The above formulation was dispersed with a homomixer for 30 minutes. A coating layer forming liquid was prepared. This coating layer forming liquid was applied with a volume average particle size of 100
A carrier A having a coating layer formed on the surface of 1000 parts of a spherical ferrite having a diameter of 1000 μm was obtained using a fluidized bed type coating apparatus.

Examples 1-4 and Comparative Examples 1 and 2 Polyester resin (weight average molecular weight 250,000) 75 parts Styrene-methyl methacrylate copolymer 15 parts Oxidized rice wax (acid value 15) 3.5 parts Carbon black ( 9 parts, manufactured by Mitsubishi Carbon Co., Ltd. 9 parts Quaternary ammonium salt compound 1 part After sufficiently stirring and mixing the mixture having the above composition in a Henschel mixer, the mixture was rolled at a temperature of 130 to 140 ° C. to about 3 with a roll mill.
After heating and melting for 0 minutes and cooling to room temperature, the obtained kneaded material was pulverized and classified by a jet mill to obtain a toner having a particle size of 5 to 12 μm. At this time, the shape index of the toner was changed depending on the toner residence time in the jet mill. To 2.5 parts of this toner, 97.5 parts of carrier A were mixed by a ball mill to obtain a developer.

Table 1 shows the percentage of toner having a circularity of 0.95 or less in all toners in each developer, the content (number) of fine powder having a toner particle diameter of 3 μm or less, and the total toner in repeated measurement (N = 5). The value of the standard deviation (variation) of the toner abundance having a circularity of 0.95 or less is shown. Table 2 shows the evaluation results of each developer.

[0031]

[Table 1]

[0032]

[Table 2] The image evaluation (solid uniformity, fine line reproducibility, dot reproducibility, transfer omission) was determined in the following five stages according to the change. ◎: Very good ○: Good ●: Normal △: Bad ▽:
Very bad

[0033]

As described above, claims 1, 2 and 3
By using the specific toner as described in the developer, the transfer is good, a long life is obtained when the toner is used in the developer, and the faithful reproducibility of the initial image is excellent even when used over time. An electrostatic latent image developing toner can be obtained. In addition, by using a specific toner as described in claim 4 in the developer, the transfer efficiency is high, and there is no omission during transfer.
When used as a developer, a long life is obtained, and even when used over time, a toner for developing an electrostatic latent image having good reproducibility of an initial image can be obtained.

Claims (4)

[Claims] 1. A circularity (S) represented by the following equation (Equation 1)
A toner for developing an electrostatic charge image, wherein the content of the toner particles produced by the pulverization method having F) in all the toners is 50% or less. ## EQU1 ## Toner circularity (SF) = [toner area / (toner perimeter) ² ] × 4π <0.95 2. The electrostatic image developing toner according to claim 1, wherein the volume average particle diameter is 5 to 9 μm. 3. The toner according to claim 1, wherein the content (number) of toner particles having a volume average particle diameter of 3 μm or less is 10% or less. 4. An image forming method in which a transfer unit is brought into contact with a part of an electrostatic charge holding member via a transfer material, and a toner image is electrostatically transferred to a surface of the transfer material. An image forming method using a toner having a content of 45% or less in the total toner of toner particles produced by a pulverization method having a circularity represented by the following formula: