JPH09325599A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method capable of holding a high electrostatic charging performance and a stable carrying performance even in the case of using toner in which electrostatic charging control agent, capable of obtaining stable image density free from fogging and uneven density, and also suppressing the occurrence of dirt and color mixture, etc., irrespective of repeated use for a long period. SOLUTION: In this method, an image is formed by developing an electrostatic latent image on an electrostatic latent image holding body by using a developer layer on a developer carrier. In this case, as the developer carrier, a carrier provided with a surface resin layer containing resin having a triboelectrostatic charging amount is within +1 to +30μc/g is used, and also, provided that M(mg/cm<2> ) denotes a toner weight per unit area on the developer carrier, D(μm) denotes the volumetric mean grain size of toner, the image is formed within the extent where M/D is 0.03 to 0.09.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a specific developer and a developer carrier.

[0002]

2. Description of the Related Art At present, as a dry developing method in various electrostatic copying methods which have been put into practical use, a two-component developing method using a carrier such as toner and iron powder and a one-component developing method not using a carrier are known. ing. 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 toner concentration ratio in the developer decreases, the mixing ratio with the carrier Must be kept constant, and therefore
Although the developing device has a drawback of increasing in size, the one-component developing system does not have such a problem and has advantages such as downsizing of the device, and is becoming the mainstream of the developing system.

[0003] The one-component toner developing system is classified into 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 a method of holding and developing a magnetic toner using a developer carrier having a magnetic field generating means such as a magnet provided therein.
In recent years, many have been put to practical use in small printers and the like. However, since the magnetic toner used contains a black magnetic substance such as magnetite inside, there is a problem that it is not suitable for colorization. On the other hand, the non-magnetic one-component developing method does not use a magnetic material for the toner, so that colorization is possible.
Further, since a magnet is not used for the developer carrying member, it is possible to reduce the weight and cost, and in recent years, it has begun to be put into practical use in small full-color printers and the like.

However, for example, in the two-component developing system, there is a stable charging and conveying member called carrier, and in the magnetic one-component developing system, there is a stable conveying and layer forming means such as the magnetic force of a magnet roll. The component developing system does not have such stable charging and conveying means,
Since it is necessary to hold the toner mainly on the developer carrier by electrostatic force, this toner is required to have higher charging characteristics and stable charging characteristics. When the toner is low in charge, problems such as fog in the non-image area and dirt on the machine due to dirt and color mixing are likely to occur, and therefore a further stabilization design is required.

Conventionally, a charge control agent is added to the inside of the toner in order to improve the charge amount of the toner, and thereby a relatively high charge amount is achieved, but the charge in the toner is not less than a certain amount. No effect can be obtained without adding a control agent, and there are various problems such as adversely affecting the fixing performance and color characteristics by increasing the addition amount, so overall satisfactory characteristics have not been obtained. Is the current situation.
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, but there are still problems. The actual situation is that the toner is blended with a charge control agent and put into practical use.

In recent years, a number of surface-treated developer carrying members (charging members) have been proposed, but even if they are applied to a method for developing a non-magnetic one-component toner, the charging property is insufficient. On the contrary, the amount of charge becomes excessive and the amount of toner conveyed on the developer carrier becomes too large.
The charge distribution of the toner becomes broad, and the problem of fouling and dirt inside the machine due to dirt has not been solved. Therefore, there are still many problems concerning stabilization of charging and layer formation in non-magnetic one-component development.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation in the prior art, and aims to solve the problems. That is, an object of the present invention is to form an image in which, even when a toner containing no charge control agent is used, a sufficiently high chargeability and stable transportability are maintained and a stable image density without fog or density unevenness is obtained. To provide a method. Another object of the present invention is to provide an image forming method in which dirt, color mixing, and the like are less likely to occur even after repeated use over a long period of time.

[0008]

The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and as a result, have dispersed a surface resin layer containing a resin having a specific chargeability and a solid lubricant. By using a developer carrying member having a surface resin layer, and performing image formation by making the ratio of the amount of toner conveyed onto the developer carrying member and the particle diameter of the toner used within a certain range. , It has been found that the above object can be achieved.

That is, the image forming method of the present invention is an image forming method for developing an electrostatic latent image on an electrostatic latent image holding member by using a developer layer on a developer carrying member. A carrier having a surface resin layer containing a resin having a triboelectric charge amount in the range of +1 to +30 μc / g is used, and
The toner weight per unit area on the developer carrier 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.

As the developer carrier used in the present invention, it is preferable to use a developer whose surface resin layer contains a lubricant having an average particle diameter of 0.2 to 10 μm. It is preferable to use a developer carrying member containing 20 to 70% by weight of the developer. The developer used in the present invention is preferably a non-magnetic one-component toner, and the surface of the toner particles has an average particle size of 10 to 500 n.
It is preferable that fine particles in the range of m are externally added.

[0011]

Embodiments of the present invention will be described below in detail. The image forming method of the present invention includes a latent image forming step of forming a latent image on a latent image holding member, and forming a latent image on the latent image holding member by using a thin layer-formed developer on a developer holding member. Used in an image forming apparatus having a developing step of developing, a transfer step of transferring a toner image on a latent image holding member to a transfer member, and a fixing step of thermally fixing the toner image on the transfer member,
It is used in a full-color developing device using four color toners of yellow, magenta, 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. As the photosensitive layer of the latent image carrier used in the present invention, known materials such as organic materials and amorphous silicon can be used. 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 holder that holds the electrostatic latent image in the developing section, or the developing roller and the latent image holder are arranged at a certain interval, and a bias is applied between the developing roller and the latent image holder. Meanwhile, the electrostatic latent image is developed with toner.

The developing roll used in the present invention is a polishing,
Aluminum, SU that has undergone surface treatment such as blasting
A surface resin layer is formed by using a specific resin on the surface of a metal base such as S stainless steel. In the present invention, the resin used for forming the surface resin layer of the developing roll is required to have a charge amount in the range of +1 μc / g to +30 μc / g, and particularly for negatively charging the toner. In addition, it is preferable to use a positively chargeable resin that is positively charged, such as nylon, epoxy resin, or melamine resin. When a resin having a charge amount less than +1 μc / g is used for the surface resin layer, the charge amount of the toner becomes insufficient, and in particular, a toner containing no charge control agent has a problem that fog or dirt occurs. . On the other hand, the charge amount is +
On the other hand, when a resin larger than 30 μc / g is used, on the contrary, the charge amount of the toner becomes excessive, and a sufficient image density cannot be obtained.

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 balance of dispersibility in resin, toner chargeability, toner transportability, etc. , 0.2 to 10 μm is preferable. Particle diameter of solid lubricant is 0.2 μm
If it is smaller than 10 μm, the effect of suppressing toner adhesion is insufficient due to charge-up on the surface of the developing roll, while if it is larger than 10 μm, the dispersion in the surface resin layer of the developing roll is reduced, resulting in a broad charge distribution of the toner. become. 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 is insufficient, while if it exceeds 70% by weight, the strength of the surface layer of the carrier decreases and problems such as peeling of the surface layer occur. To do.

The developing roll used in the present invention can be produced by a known coating method such as spraying or dipping after a solid lubricant is dispersed in a solution prepared by dissolving the above resin, if necessary. Examples thereof include a method of coating on the surface of the substrate and 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. In order to control the toner charge amount, an organic substance or an inorganic substance is added and dispersed in the elastic body. Good.

As a method of developing four-color toner, four developing machines are arranged around the photoconductor and each toner is
A method of repeating the charging, exposure and development processes for 4 cycles,
Also, a method of charging, exposing and developing four color toners 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 holding member without being transferred in the transfer step is removed by a cleaner, and the cleaning means used in the present invention is known as blade cleaning or roller cleaning. The following are listed. For the blade cleaning, an elastic rubber such as silicone rubber or urethane rubber is used. In the fixing step, the toner image transferred onto the transfer body is fixed by a fixing device, and a heat fixing method using a heat roll is preferable as the fixing means. Further, roller fixing in which oil is applied to improve gloss and OHP image quality, and oilless fixing in which a releasing agent is added to toner for downsizing of the apparatus are performed.

The developer used in the present invention is as described above.
It is a toner that basically does not require a charge control agent, and is particularly used as a non-magnetic one-component toner.
Examples of the binder resin used for this toner include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate. Α-methylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and dodecyl methacrylate. , Homopolymers and copolymers of 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. Can Shimesuru. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include polymers, polyethylene and polypropylene, and further examples include polyester resin, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.

As the toner colorant, 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, Rose Bengal, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 122,
C. I. Pigment Red 57: 1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 1
2, C.I. I. Pigment Yellow 17, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 3 and the like are used.

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

In the developer of the present invention, in order to impart appropriate fluidity and chargeability, it is preferable to use fine particles by externally adding fine particles to the surface of the toner particles. The fine particles used include fine particles of inorganic oxides such as hydrophobic silica, titania and alumina, fine particles of organic compounds such as fatty acids or their derivatives and metal salts thereof, resins such as fluororesins, acrylic resins or styrene resins. Such as fine powder,
These may be used alone or in combination. In the present invention, these fine particles have an average particle size of 10 to 500.
The range of nm can be used. Further, it is preferable to use two or more kinds of these fine particles in combination, and those within this range are effective in suppressing an increase in the transport amount due to charge-up. These 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 particles. If the amount of external addition is less than 0.1 parts by weight, the surface coverage of the toner with the fine powder will be low, so that the toner cannot be provided with sufficient fluidity. On the other hand, when the amount of external addition is more than 3 parts by weight, the fine powder adheres to the photosensitive drum, and comet and filming are likely to occur.

The particle size of the developer 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. When the volume average particle diameter is 4 μm or less, the fluidity is remarkably reduced, so that the layer formation becomes poor and fogging and dard are likely to occur. On the other hand, when the particle size is 10 μm or more, not only the resolution decreases and high image quality cannot be obtained, but also the charge amount per unit weight of the developer decreases, so that it is difficult to maintain the layer formation and fogging or dirt easily occurs. Become.

In the present invention, the weight of the toner carried on 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 less than 0.03, 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 broad and fogging and dirt are likely to occur.

The developer used in the present invention can be produced by any known method, but a kneading and pulverizing method is particularly preferable. That is, after preliminarily mixing the binder resin, the colorant and the like, the mixture is melt-kneaded using a kneading machine, the obtained kneaded product is cooled, pulverized and classified to obtain toner particles, A method of adding and mixing fluidizing agent fine particles as an 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, by coating the surface of the developing roll, which corresponds to the carrier of the two-component developer, with the resin having the above-mentioned triboelectric charge amount, it is possible to impart the charge to the toner containing no charge control agent. Become. However, simply increasing the charge amount of the surface resin layer causes the toner existing in the vicinity of the surface of the developing roll to be charged up and adhere strongly to the surface, so that the toner layer is further formed on the toner layer. When the toner is formed, the amount of conveyance is increased, and the mutual charging between the toner particles reduces the charging of the toner particularly in the upper layer portion, which may cause fog or dirt. Therefore, in such a case, by dispersing a solid lubricant further in the surface resin layer of the developing roll, even if the toner near the surface is charged up, the surface resin layer itself has slipperiness. Therefore, there is an advantage that it is possible to prevent the toner from strongly adhering to the surface of the developing roll, and also to suppress an increase in the toner transport amount. Furthermore, when fine particles having a relatively large particle size are used as the external additive of the toner, the external additive acts as a roller between the toners under the pressure of the layer forming blade,
This is effective in suppressing an increase in the toner conveyance amount. In addition,
In the present invention, the charge amount of the resin used for the surface resin layer is
Using a blow-off electrification meter (manufactured by Toshiba Chemical Co.), 30 g of 100 μm iron powder and 1.2 g of resin pulverized to 10 to 12 μm were stirred for 120 seconds by a turbula mixer and then determined by measurement. . The measurement environment is a temperature of 22 ° C. and a humidity of 55% RH. The particle size of the toner was measured with a particle size analyzer TAII (manufactured by Coulter Counter) and an aperture diameter of 100 μm. Further, the toner weight per unit area on the developing roll was determined by transporting the toner onto the developing roll using a device described later and then measuring the transferred toner using a tape having a constant area.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. Example 1 <Developing roll> A resin solution in which the following composition was ultrasonically dispersed was blast-treated onto an aluminum substrate blasted to have a surface roughness (Ra) of 0.4 μm, and the resin solution was pushed up to a thickness of 10 μm. Was applied and dried at 120 ° C. for 1 hour to obtain a developing roll. Resin: Epoxy resin (charge amount: +8 μc / g) 20 parts by weight (Brand name: Epicoat 1004, Showa Shell Co., Ltd.) Solid lubricant: Molybdenum disulfide (0.5 μm) 10 parts by weight Solvent: Methyl ethyl ketone 30 parts by weight <Toner > Binder resin: Polyester resin 96 parts by weight (terephthalic 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 After mixing with a mixer, set the temperature by an extruder at 120 ℃, 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 is cooled, coarsely pulverized, then finely pulverized by a jet mill, and the pulverized product is further classified by an air classifier to have a volume average particle diameter D ₅₀ of 8.0.
μm toner particles were obtained. Next, the obtained toner particles 1
0.5 parts by weight of silica treated with silicone oil
A toner was obtained by mixing an external additive consisting of 1.0 part by weight of titanium oxide having a particle size of 30 nm and 30 parts by weight with a Henschel mixer. The developing roll and toner described above,
It was used in the image forming apparatus shown in FIG. 1 under the conditions of M / D shown in Table 1 under the environment of temperature 22 ° C. and humidity 55% RH.
000 sheets of images were formed and evaluated.

(Image Forming Apparatus) FIG. 1 shows an image forming apparatus used in image formation for evaluating image quality 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 Polyisocyanate (charge amount: +18 μc / g, trade name: D11) was used as the resin for the surface resin layer of the developing roll.
An image was formed and evaluated in the same manner as in Example 1 except that 0N, manufactured by Takeda Pharmaceutical Co., Ltd.) was used, and ethyl acetate was used as the solvent. Comparative Example 1 Polymethylmethacrylate resin (charge amount: −5 μc / g, trade name:
An image was formed and evaluated in the same manner as in Example 1 except that BR80, manufactured by Mitsubishi Rayon Co., Ltd. was used. Comparative Example 2 Example 1 was repeated except that an aluminum substrate (Ra: 1 μm) having no surface layer was used as a developing roll, and a toner to which titanium oxide was not added was used as an external additive.
An image was formed and evaluated in the same manner as in.

Table 1 shows the results obtained in the above Examples and Comparative Examples.

[Table 1] In the “density unevenness”, ○ indicates a density difference of less than 0.1,
Δ indicates a density difference of 0.1 to less than 0.3, and X indicates a density difference of 0.
Indicates three 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 barely usable level, and × means problem.

[0031]

The image forming method of the present invention uses a developing roll having a specific surface resin layer and regulates the relationship between the amount of toner conveyed onto the developing roll and the particle size of the toner used. As a result, even if the toner deteriorates due to continuous use, the charge distribution of the toner is sharp, the decrease in the charge amount is small, the image density does not fluctuate over a long period, and there is no low developability, fog, or stain inside the machine. It is possible to obtain an image with excellent image quality.

[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.

Front page continuation (72) Kotaro Yoshihara, 1600 Takematsu, Minamiashigara-shi, Kanagawa, Fuji Xerox Co., Ltd. Etsuo 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd.

Claims (5)

[Claims] 1. An image forming method for developing an electrostatic latent image on an electrostatic latent image holding member by using a developer layer on the developer holding member, wherein the developer holding member has a triboelectric charge amount of +1 to +1. +30
A toner having a surface resin layer containing a resin in the range of μc / g is used, the toner weight per unit area on the developer carrying member is M (mg / cm ² ), and the toner volume average particle diameter is D. (Μm), the value of M / D is 0.03 to 0.
The image forming method is performed in the range of 09. 2. The surface resin layer has an average particle size of 0.2 to 10
The image forming method according to claim 1, wherein a developer carrying member containing a lubricant of μm is used. 3. The image forming method according to claim 1, wherein a non-magnetic one-component toner is used as the developer. 4. The image forming method according to claim 3, wherein a developer is used in which fine particles having an average particle diameter in the range of 10 to 500 nm are attached to the surface of toner particles. 5. The amount of solid lubricant in the surface resin layer is 20 to
3. The image forming method according to claim 2, wherein a developer carrier containing 70% by weight is used.