JPH09325522A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method by which electrification and carrying of a toner can be stabilized for a long term, stable image density can be obtd. without fog or irregular density, and dart or mixing of colors are hardly caused. SOLUTION: By this method, an image is formed by developing an electrostatic latent image on a latent image holding body using a developer layer on a developer carrying body. The developer carrying body has a surface resin layer. As for the developer, a toner containing a charge controlling agent expressed by formula is used. In formula, M is a metal element selected from zinc, iron, nickel and cobalt, and R<1> and R<2> are hydrogen or 1 to 6C alkyl groups. Moreover, this method is carried out under the condition of 0.03<=M/D<=0.09, wherein M (mg/cm<2> ) is the toner weight in a unit area on a developer carrying body and D (μm) is the volume average particle diameter of the toner.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an image forming method using a non-magnetic one-component developer.

[0002]

2. Description of the Related Art At present, as a dry developing method in various electrostatic copying systems put into practical use, a two-component developing system using a carrier such as toner and iron powder and a one-component toner developing system using no carrier are known. Have been. In the two-component developing method, toner particles adhere to the surface of the carrier to deteriorate the developer, and since only the toner is consumed and the concentration ratio of the toner in the developer decreases, the toner and the carrier are separated from each other. Since a concentration controller or the like for keeping the mixing ratio constant is required, there is a drawback that the developing device becomes large. On the other hand, the one-component developing method is becoming the mainstream of the developing method because it does not use the carrier and does not have the above-mentioned problems and has advantages such as a reduction in size and weight of the apparatus.

The one-component developing system includes a magnetic one-component developing system using a magnetic toner and a non-magnetic one-component developing system using a non-magnetic toner. The magnetic one-component developing method is to hold and develop magnetic toner using a developer carrier having a magnetic field generating means such as a magnet provided therein, and has been put into practical use in small printers in recent years. This method is difficult to use for colorization because the toner used contains a black magnetic material such as magnetite inside. On the other hand, the non-magnetic one-component developing method is suitable for colorization because it does not use a magnetic material for toner, and since it does not use a magnet for a developer carrying member, it can be made lighter in weight and lower in cost. In recent years, it has begun to be put to practical use in small full-color printers and the like.

By the way, the two-component developing system has a stable charging and conveying member called a carrier, and the magnetic one-component developing system has a stable conveying and layer forming means called a magnetic force of a magnet roll. On the other hand, the non-magnetic one-component developing system is not provided with such stable charging and conveying means. Therefore, in the non-magnetic one-component developing method, it is necessary to hold the toner mainly on the developer carrying member by electrostatic force, and therefore the toner of this method has higher charging and stable charging characteristics. Required to have.

Conventionally, in order to stabilize the charge of the toner, a charge control agent has been added to the inside of the toner. As typical negatively chargeable charge control agents, metal-containing monoazo complexes such as chromium-containing azo dyes and metal-containing salicylic acid compounds such as chromium, iron and zinc are used. Among these charge control agents, the metal-containing azo dye can obtain a high charge amount relatively quickly, but is inferior in charge maintainability,
When used for non-magnetic one-component development, there is a problem that fog or dirt is likely to occur due to a decrease in charge amount after long-term use. Further, the metal-containing salicylic acid compound is excellent in charge maintaining property as compared with the metal-containing azo dye, and among them, the chromium-containing salicylic acid compound has a fast charging start-up, and since a high charging property is obtained, it is generally used. However, when used for non-magnetic one-component development,
Since the charge distribution is wide and the charge exchange property is poor, the toner is deteriorated by long-term use, and problems such as fogging and low image density due to an increase in reverse polarity toner are likely to occur. Further, since a metal such as aluminum or stainless steel is generally used as the developer carrying member, there is a problem that it is not possible to give a sufficient charge to the toner. In fact, it is practically used in combination with the above charge control agent.

In recent years, a large number of surface-treated developer carrying members (charging members) have been proposed, but even if they are applied to an image forming method using a non-magnetic one-component toner, the charging property is insufficient. Or, on the contrary, the amount of charge is excessive and the amount of toner conveyed onto the developer carrier becomes too large, and eventually the distribution of the amount of charge of toner becomes broad, causing fogging and dirt inside the machine. The problem of dirt has not been solved yet. As described above, in the non-magnetic one-component developing method, many problems still remain with respect to toner charging and stabilization of toner layer formation.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances in the prior art, and has been made to solve the problems. That is, it is an object of the present invention to provide an image forming method that stabilizes the charging and conveyance of toner for a long period of time and can obtain a stable image density without fog or density unevenness. Another object of the present invention is to provide an image forming method in which dirt, color mixing, etc. are unlikely to occur for a long period of time in a non-magnetic one-component developing system.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, carried a developer having a surface resin layer formed of a resin having a specific charging property. By using a toner to which the body and a specific charge control agent are added, and by defining the ratio of the particle diameter of the toner to be used and the weight of the toner carried on the developer carrying member within a certain range, the above object is achieved. They have found that they can be achieved, and have completed the present invention.

That is, the image forming method of the present invention is an image forming method of developing an electrostatic latent image on a latent image carrier by using a developer layer on the developer carrier. As the developer, a developer having a surface resin layer is used.
A toner containing a charge control agent represented by the following formula (1) is used, the toner weight per unit area on the developer carrying member is M (mg / cm ² ), and the volume average particle diameter of the toner is D.
(Μm), the value of M / D is 0.03 to 0.09
It is characterized in that it is performed in the range of.

Embedded image (In the formula, M represents a metal element selected from zinc, iron, nickel and cobalt, and R ¹ and R ² each represent hydrogen or an alkyl group having 1 to 6 carbon atoms.) In the present invention, development As the agent carrier, it is preferable to use one having a surface resin layer containing a solid lubricant having a particle size in the range of 0.2 to 10 μm. Further, it is preferable to use a non-magnetic one-component toner as the developer.

[0010]

Embodiments of the present invention will be described below in detail. The image forming method of the present invention comprises a latent image forming step of forming a latent image on a latent image holding member, and a latent image on the latent image holding member is formed by using a developer formed in a thin layer on a developer carrying member. It is used in an image forming apparatus having a developing step of developing, a transfer step of transferring a toner image on a latent image carrier to a transfer body, and a fixing step of thermally fixing the toner image on the transfer body, and particularly yellow, magenta, It is used in a full-color developing device that uses four color toners of cyan and black.

As the latent image forming step, a conventionally known method can be applied, and the latent image holding member such as a photosensitive layer or a dielectric layer is statically formed by an electrophotographic method or an electrostatic recording method. Form a latent image. Examples of the photosensitive layer of the latent image carrier used in the present invention include known materials such as organic materials and amorphous silicon. Further, as the cylindrical holder, one obtained by a known manufacturing method such as extruding aluminum or aluminum alloy and then surface-treating it can be used.

In the developing step, a thin layer of toner supplied by a toner supply roll is formed on a rotary cylinder of a developer carrying member (hereinafter referred to as "developing roll") by an elastic blade or the like to the developing nip. The developing roll is brought into contact with the latent image carrier that holds the electrostatic latent image in the developing section, or a certain gap is provided and a bias is applied between the developing roll and the latent image carrier. Meanwhile, the electrostatic latent image is developed with toner.

The developing roll used in the present invention is a polishing roll.
Aluminum, SU that has undergone surface treatment such as blasting
A surface resin layer is formed by coating a specific resin on the surface of a metal substrate such as S stainless steel. In the present invention, as the resin used for forming the surface resin layer of the developing roll, various resins such as polyethylene resin, styrene resin, polymethylmethacrylate (PMMA) resin, phenol resin, epoxy resin, polyester resin, polyurethane resin and silicone resin can be used. Although various resins can be used, PMMA resins, phenol resins, silicone resins, etc., which have a charging property without being substantially affected by changes in the environment, are preferable for facilitating charge control.

Further, in the present invention, it is preferable to add a solid lubricant to the surface resin layer of the developing roll. As the solid lubricant, for example, molybdenum disulfide, boron nitride, graphite, etc. are appropriately used in consideration of the dispersibility in the resin, the chargeability of the toner, the transportability of the toner, etc. The average particle size is preferably in the range of 0.2 to 10 μm. The average particle size of the solid lubricant is 0.
If it is less than 2 μm, the effect of suppressing toner adhesion is insufficient due to charge-up on the surface of the developing roll, while if it is more than 10 μm, the dispersion in the surface resin layer of the developing roll is reduced and the toner charge amount is reduced. The distribution becomes broad. The amount of the solid lubricant is preferably in the range of 20 to 70% by weight in the surface resin layer. If the amount added is less than 20% by weight, the effect of suppressing toner adhesion due to charge-up becomes insufficient, while if it exceeds 70% by weight, the strength of the surface resin layer decreases and the surface resin layer of the developing roll peels off. Problems such as occur.

As a method for producing the developing roll used in the present invention, if necessary, a solid lubricant is dispersed in a solution in which the above resin is dissolved, and then a known coating method such as spraying or dipping is used. Examples thereof include a method of coating on the surface of the substrate, drying, or curing if necessary. The toner layer is formed on the developing roll by bringing the elastic blade into contact with the surface of the sleeve. As the material of the elastic blade, it is preferable to use a rubber elastic body such as silicone rubber or urethane rubber. Even if an organic substance or an inorganic substance is added to and dispersed in these elastic bodies in order to control the toner charge amount. Good.

As a method of developing the four-color toner, four developing machines are arranged around the photoreceptor, and for each toner,
A method of repeating the charging, exposure and development processes for 4 cycles,
In addition, a method of charging, exposing and developing four-color toner in one cycle is used. As a method of superimposing the four color toners, a method of transferring the toner image formed on the photoconductor one by one onto a transfer drum around which a transfer paper is wound and superimposing the toner image, and a method of superimposing the toner image formed on the photoconductor. After transferring the color toner image on the transfer body and superimposing the color toner image on the transfer body, collectively transferring the image onto the transfer paper, or by superimposing the color toner image on the photoreceptor and then transferring the image onto the transfer paper collectively Used. As a transfer unit, a known unit such as a contact type in which a transfer roll is pressed against a latent image holding member or a non-contact type using a corotron is used.

In the cleaning step, the toner remaining on the latent image carrier without being used for transfer in the transfer step is
The cleaning means to be removed by a cleaner includes known means such as blade cleaning or roller cleaning.
For the blade cleaning, an elastic rubber such as silicone rubber or urethane rubber is used. The fixing process is
The toner image transferred to the transfer body is fixed by a fixing device. As a fixing means, a heat fixing method using a heat roll is preferable, and oil is applied in order to prevent gloss and improve OHP image quality. Roller fixing and oilless fixing in which a releasing agent is added to toner are performed for downsizing of the apparatus.

The developer used in the present invention contains at least a binder resin, a colorant and a charge control agent, and fluidized fine particles are externally added to toner particles obtained by adding a release agent or the like as necessary. In particular, it is a toner used in a non-magnetic one-component developing system.

The charge control agent used in the developer of the present invention is a charge control agent represented by the following formula (1), that is, a metal-containing salicylic acid compound.

Embedded image (In the formula, M represents a metal element selected from zinc, iron, nickel, and cobalt, and R ¹ and R ² each represent hydrogen or an alkyl group having 1 to 6 carbon atoms.) In the metal-containing salicylic acid compound represented by the formula, M is most preferably zinc among the above metal elements. R ¹ and R ² are more preferably hydrogen or an alkyl group having 4 or less carbon atoms from the viewpoint of dispersibility and fixability in a binder resin. These charge control agents have a narrow charge distribution and a good charge exchange property, even though they have a low charge amount, as compared with conventionally used chromium-containing salicylic acid compounds. Even if there is deterioration, the generation of reverse polarity toner is small,
Problems such as fog and low image density are unlikely to occur. The charge control agent is used in the toner in an amount of 0.1 to 10% by weight, preferably 1 to 6% by weight, depending on the required charge amount.

The binder resin of the developer used in the present invention includes styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl acetate, vinyl propionate, vinyl benzoate and butyric acid. Vinyl esters such as vinyl, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate α-methylene, etc. Homopolymerization of aliphatic monocarboxylic acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone And it can be exemplified a copolymer. Particularly typical binder resins include polystyrene and
Styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, polypropylene, and further, polyester , Polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.

Examples of toner colorants include carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black and rose bengal. , C.I. I. Pigment Red 4
8: 1, C.I. I. Pigment red 122, C.I. I.
Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I.
I. Pigment yellow 17, C.I. I. Pigment
Blue 15: 1, C.I. I. Pigment Blue 15: 3
Etc. can be given.

Further, a releasing agent may be added to the developer used in the present invention for the purpose of improving gloss and offset resistance. As the release agent, paraffins having 8 or more carbon atoms, polyolefins and the like are preferable, and examples thereof include paraffin wax, paraffin latex, microcrystalline wax, polypropylene, polyethylene and the like, and these are used alone or in combination. . The amount added is preferably in the range of 0.3 to 10% by weight.

In the present invention, for the purpose of imparting appropriate fluidity and chargeability to the developer, it is preferable to use the fluidizing agent fine particles as an external additive. Examples of the fluidizing agent fine particles include inorganic fine powder of hydrophobic silica, titania, alumina, etc., fine powder of organic compound such as fatty acid or its derivative and its metal salt, resin such as fluorine resin, acrylic resin or styrene resin. Fine powder and the like can be used, and these are used alone or in combination of two or more kinds. In particular, the inorganic fine powder having an average particle diameter of 10 to 500 nm is effective in suppressing an increase in the amount of toner conveyed due to charge-up. These fluidizing agent fine particles are used in an amount of 0.1 to 3 parts by weight, preferably 0.3 to 1.5 parts by weight, based on 100 parts by weight of the toner. If the amount of external addition is less than 0.1 parts by weight, the surface coverage of the toner particles with the fine powder is low,
The toner cannot be provided with sufficient fluidity. on the other hand,
If the amount of external addition is more than 3 parts by weight, fine particles tend to adhere to the surface of the photoconductor to easily cause comet and filming.

The particle size of the toner used in the present invention is preferably in the range of 4 to 10 μm in volume average particle size, more preferably 6 to 9 μm. Volume average particle size is 4μm
The following materials are apt to cause fog and dirt because they cannot form a layer satisfactorily because their fluidity is significantly reduced. On the other hand, when the particle size is 10 μm or more, not only the resolution is lowered and a high image quality cannot be obtained, but also the charge amount per unit weight of the developer is lowered, so that the layer formation maintainability is low and fog and dirt are apt to occur.

In the present invention, the weight of the toner conveyed onto the developing roll is represented by M (mg / cm ² ), and
When the volume average particle diameter of the toner used is represented by D (μm), it is necessary to perform image formation when the value of M / D is within the range of 0.03 to 0.09. If the value of M / D is smaller than 0.03, a sufficient image density cannot be obtained, and uneven density occurs. On the other hand, when the value of M / D is larger than 0.09, the distribution of the charge amount of the toner becomes wide, and fog and dirt are likely to occur.

The toner used in the present invention can be manufactured by any known method, but a kneading and pulverizing method is particularly preferable. That is, toner particles obtained by premixing a binder resin, a colorant, a charge control agent, etc., melt-kneading with a kneader, cooling the obtained kneaded product, pulverizing and classifying In addition, a method of adding and mixing fluidizing agent fine particles as an external additive is preferable. As the kneader, a Banbury mixer, a pressure kneader, a continuous mixer, an extruder, or the like is used.

The reason why the configuration adopted in the present invention is effective is considered as follows. First, the surface of the developing roll is provided with a surface resin layer coated with a resin having a relatively low charging property, so that the toner can be charged. Furthermore, since the toner used in the present invention contains a specific negative charge control agent, even if the toner deteriorates due to continuous use, the charge exchange property is good, so the toner charge distribution Is sharp and the amount of charge is not significantly reduced, so that it is possible to obtain an image of excellent image quality, which is free from fluctuations in image density, low developability, fog and stains inside the machine. However,
If the surface resin layer of the developing roll is simply charged, the toner existing in the vicinity of the surface is charged up and adheres strongly to the surface of the developing roll. When the toner is formed, the amount of conveyance increases, and the mutual charging between the toner particles reduces the electrostatic charge of the toner particularly in the upper layer portion, which may cause fog or dirt. Therefore, when the solid lubricant is further dispersed in the surface resin layer of the developing roll, even if the toner in the vicinity of the surface is charged up, the surface resin layer itself has slipperiness, It is effective for suppressing the strong adhesion of the toner to the surface of the developing roll and the increase in the amount of the toner conveyed. Further, when an inorganic oxide having a relatively large particle size is used as an external additive of the toner, the external additive acts as a roller between the toners under the pressure of the layer forming blade, which also suppresses an increase in the carry amount. It is effective to do. In the present invention, the toner weight per unit area on the developing roll is determined by measuring the toner transferred using a tape having a fixed area after the toner is conveyed onto the developing roll using an apparatus described later. Determined by The particle size of the toner used in the present invention was measured with a particle size analyzer TAII manufactured by Coulter Counter Co., Ltd. and an aperture diameter of 100 μm.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. Example 1 <Developing roll> A resin solution prepared by ultrasonically dispersing a composition made of the following materials on a substrate made of aluminum having a surface roughness (Ra) of 0.4 μm and blasted with a thickness of 10 μm was used.
m with a push-up coater, 120 ° C
For 1 hour to produce a developing roll. Resin: Polymethylmethacrylate (PMMA) resin 10 parts by weight Solid lubricant: Molybdenum disulfide (average particle size 0.5 μm) 5 parts by weight Solvent: Methyl ethyl ketone 15 parts by weight <Toner> Binder resin: Polyester resin 92 parts by weight (terephthalate) Acid / bisphenol A ethylene oxide adduct) (weight average molecular weight Mw: about 10,000, Tg: 67 ° C.) Pigment: Copper phthalocyanine blue pigment 4 parts by weight Charge control agent: 3,5-ditert-butyl zinc salicylate 4 parts by weight After mixing the above materials with a Henschel mixer, use an extruder to set temperature 120 ° C, screw speed 3
Melt kneading was carried out under the conditions of 00 rpm and a supply speed of 150 kg / h. The obtained kneaded product was cooled, coarsely pulverized, finely pulverized by a jet mill, and further classified by an air classifier to obtain a volume average particle diameter D ₅₀ of 8.0 μm. Toner particles are obtained. Next, 100 parts by weight of the obtained toner particles were mixed with 0.5 part by weight of silica treated with silicone oil and 1.0 part by weight of titanium oxide having a particle diameter of 30 nm with a Henschel mixer to obtain a toner. The above-described developing roll and toner are used in the image forming apparatus shown in FIG. 1, and are used in a high-temperature and high-humidity environment (temperature 28 ° C./85% RH) and a low-temperature and low-humidity environment (temperature 10 ° C./humidity 3).
(0% RH), 5,000 print tests were performed. Table 1 shows the results.

(Image Forming Apparatus) FIG. 1 shows an image forming apparatus used for image formation for evaluating image quality and the like in the present invention. The photosensitive drum 1 and the developing roll 3 were arranged so as to have a constant gap. The photosensitive drum 1 is charged by a roll charger 2 and then exposed to laser light to form an electrostatic latent image, and an AC voltage and a DC voltage are applied to the developing roll 3 and the developer supply roll 4. Then, the electrostatic latent image was developed. Layer forming blade 5 made of silicone rubber
Was brought into contact with the developing roll 3 at a constant linear pressure to form a thin layer of toner. Reference numeral 6 denotes a roll transfer device, and reference numeral 7 denotes a blade type cleaner.

Example 2 Except that graphite (average particle diameter 4 μm) was used as the solid lubricant added to the surface resin layer of the developing roll,
An image was formed and evaluated in the same manner as in Example 1. Comparative Example 1 An image was formed and evaluated in the same manner as in Example 1 except that the chromium salicylate compound was used as the charge control agent of the developer. Comparative Example 2 An image was formed in the same manner as in Example 1, except that an aluminum base (Ra: 1 μm) having no surface resin layer was used as a developing roll, and a toner not containing titanium oxide was used. An evaluation was performed.

[0031]

[Table 1] In Table 1, A is a high temperature and high humidity environment (temperature 28 ° C., humidity 85% R
H) is the measurement and evaluation, and C is the measurement and evaluation in a low-temperature and low-humidity environment (temperature 10 ° C., humidity 30% RH). In “density unevenness”, ○ indicates a density difference of 0.1.
Less than, Δ represents a concentration difference of less than 0.1 to 0.3, ×
Indicates that the density difference is 0.3 or more. In “fogging” and “in-machine dirt”, ○ means that there is no occurrence and is good, Δ means that there is some occurrence, and X means that there is occurrence and there is a problem. In the “Comprehensive Evaluation”, ○ means good, Δ means usable level, and × means a problem.

[0032]

According to the image forming method of the present invention, even if the toner is deteriorated due to continuous use, the charge distribution of the toner is sharp and the decrease in the charge amount is small, so that the image density does not fluctuate over a long period of time. It is possible to obtain an image with excellent image quality that does not cause low developability, fogging and stains inside the apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus used for image formation for evaluating image quality and the like in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Roll charger, 3 ... Development roll, 4 ... Developer supply roll, 5 ... Layer forming blade, 6 ...
Roll transfer unit, 7 ... blade type cleaner.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroe Okuyama 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor, Kotaro Yoshihara, 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (3)

[Claims] 1. An image forming method for developing an electrostatic latent image on a latent image holding member using a developer layer on a developer carrying member,
The developer carrier having a surface resin layer is used, the toner containing the charge control agent represented by the following formula (1) is used as the developer, and the developer carrier has a unit area per unit area. When the toner weight is M (mg / cm ² ) and the volume average particle diameter of the toner is D (μm), the value of M / D is 0.03 to
An image forming method, wherein the image forming method is performed in the range of 0.09. Embedded image (In the formula, M represents a metal element selected from zinc, iron, nickel, and cobalt, and R ¹ and R ² each represent hydrogen or an alkyl group having 1 to 6 carbon atoms.) 2. The surface resin layer has a particle size of 0.2 to 10 μm.
2. The image forming method according to claim 1, wherein a developer carrier containing a solid lubricant having a range of m is used. 3. The image forming method according to claim 1, wherein a non-magnetic one-component developer is used as the developer.