JPH1020584A - Electrostatic charge image forming method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method being excellent in the development selectivity of the charge quantity of consumed toner and having a high capacity for developing even after the lapse of time for copying and the output of an image of high quality by using a specific parameter. SOLUTION: In an electrostatic charge image forming method using at least an electrostatic charge image developing device and a developer, the value of a parameter α in an equation Q/M=(Q/M)0 +αt for expressing a change in the charge quantity Q/M of toner in a developing part is set <=0.03. At this time, M denotes toner mass, Q denotes the charge quantity and Q/M denotes the toner charge quantity per unit mass. Then, (Q/M)0 denotes an initial stage toner charge quantity and (t) denotes the number of copies. The equation expresses the selectivity of the charge quantity of the consumed toner in a combination of a developing device and the developer, in the developing part and the parameter α is called a development selection coefficient (the charge quantity). When the value of the parameter α is >=0.01 to <=0.03, dependency on the concn. of the toner is low so that a photosensor as a concentration sensor can be stably controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image forming method and apparatus used in an electrophotographic method, an electrostatic printing method and the like.

[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, etc. is generally a binder resin triboelectrically charged by a carrier formed of a metal powder or the like, and colored. After the dry toner containing the agent as a main component is developed by an electric field, it is transferred and fixed on copy paper. At this time, in order to obtain a high-quality image, one of the most important technical issues is how to express the latent image formed on the photoreceptor by development using toner in any situation. Various studies are currently underway.

Generally, in a copying machine, the image density is adjusted to be constant by controlling the toner density in a developing device. As such a toner density control method, conventionally, a predetermined reference image pattern is formed on a photoreceptor, the reference image pattern is optically measured, compared with a preset reference density, and the comparison result is obtained. A method of supplying a toner into a developing device by calculating a toner supply amount in accordance with the above formula and controlling a toner supply control unit based on the calculated toner supply amount is widely used. In this method, since the toner reference image pattern on the photoconductor can be directly controlled, it is hardly affected by deterioration of the photoconductor, and the image density can be relatively easily controlled. However, the control of the image density using the sensor is specifically performed by changing the toner density in the developing section and setting the toner charge amount in the toner developing section to an appropriate value. If the change value of the toner charge amount with respect to the change of the toner density at the time of development does not have a magnitude within a certain suitable range, the image density control by the sensor cannot be performed. Therefore, this method largely depends on the developing conditions and the developer characteristics, so that complicated control is inevitable.

Therefore, in the development stage of a copying machine, in order to use the sensor effectively, the developing condition and the developer are determined by fine adjustment by a matching test between the copying machine and the developer. There is a long-awaited need for a characteristic value to be used as an index of gender. However, even when the sensor is used, the humidity and the like inside the apparatus change due to changes in the external environment and the like, and when the characteristics of the photosensitive member and the developing characteristics change significantly, the density of the image pattern greatly deviates from the target. In the control by the sensor, since the control is performed by changing only the toner density, the use range of the toner density is inevitably increased, the load on the developer is increased, and in the case of excessive toner replenishment, the In the case of insufficient replenishment, there are problems such as "carrier adhesion" and "deterioration of developer life".

For this reason, Japanese Patent Laid-Open No. 1-295281 has proposed a method of providing a toner density sensor in a developing device and controlling the toner density by the toner density sensor. Japanese Patent Application Laid-Open No. 2-269371 proposes a technique in which the surface potential of a photoreceptor is measured by an electrometer, and the developing bias is changed and controlled based on the measured potential so that the developing potential becomes constant. According to the image density control methods described in these publications,
Since the toner concentration in the developing machine or the surface potential of the photoreceptor can be directly measured, the above-mentioned problems can be solved.
In Japanese Patent Application Laid-Open No. 1-295281, a sensor for measuring a reference pattern formed on a photoreceptor and a toner density sensor for measuring toner density are required, and the number of sensors is increased. The image forming apparatus has a problem that not only the structure becomes complicated but also the cost increases.
In Japanese Patent Application Publication No. 2000-133, it is necessary to control the toner supply not only by the developing bias but also by some other method, or to keep the toner concentration in the developing unit constant. It is necessary to perform control, and not only is the control complicated, but also there is a problem that the use range of the toner density is greatly different due to the weighting of the two controls of “toner supply amount control” and “image forming condition control”. . A method that solves these problems and eliminates the need for a toner density sensor is proposed in Japanese Patent Application Laid-Open No. Hei 7-271117. However, any kind of sensor is required, and the configuration and control are not simplified. is the current situation.

With respect to toner used in various developing devices, there has been a demand for means for quantitatively expressing and defining a desired condition of a toner having no density dependency, that is, a toner having no development selectivity.

[0007]

SUMMARY OF THE INVENTION The present invention has excellent development selectivity of the amount of toner consumed by using specific parameters, has high developing ability over time of copying, and has high image quality. In addition, an optimal combination of a developing device and a developer constituting an image forming method and apparatus capable of stably controlling an optical sensor is realized. Furthermore,
An object of the present invention is to provide an image forming method and apparatus which does not require a toner density sensor under specific parameter conditions.

[0008]

As a result of extensive studies, the present inventors have found that the toner in the developing section in a copying experiment using an A4 image area 6% chart with no toner supplied using an electrostatic image forming apparatus. Focusing on the change in the charge amount Q / M, a specific parameter relating to the change in the toner charge amount Q / M is as follows:
The present invention was found to be excellent in the selectivity of the consumed toner and to be an index for obtaining a high-quality image that is stable over time.

That is, the present invention provides the following (1) to (4).

(1) In the electrostatic image forming method using at least the electrostatic image developing device and the developer, the value of the parameter α in the following general formula (1) showing the change of the toner charge amount Q / M in the developing section. Is less than or equal to 0.03.

Q / M = (Q / M) ₀ + αt (1) (where M is the toner mass, Q is the charge amount, Q / M is the toner charge amount per unit mass, and (Q / M) ₀ (2) The value of the parameter α is 0.01 or less, and the toner density sensor is not used. (1)
The electrostatic image forming method as described in the above.

(3) In an electrostatic image forming apparatus including at least an electrostatic image developing device and a developer, a value of a parameter α in the following general formula (1) indicating a change in a toner charge amount Q / M in a developing section. Is not more than 0.03.

Q / M = (Q / M) ₀ + αt (1) (where M is the toner mass, Q is the charge amount, Q / M is the toner charge amount per unit mass, and (Q / M) ₀ Is the initial toner charge amount and t is the number of copies.) (4) The value of the parameter α is 0.01 or less, and the electrostatic image developing apparatus does not have a toner density sensor. The electrostatic image forming apparatus as described in the above.

As a result of an examination based on the above equation (1), a developing process apparatus having a system for detecting an image pattern on a photoreceptor by an optical sensor and limiting a toner supply amount and a developer for electrostatic charge development are described. It has been found that when the value of the parameter α in the general formula is 0.03 or less, a high-quality image having a stable image density over time can be obtained.

That is, the above equation (1) expresses the selectivity of the toner charge amount consumed in the combination of the developing device and the developer in the developing section, and the parameter α is the development selection coefficient (charge amount). It can be called. That is, the parameter α is calculated from the charge amount distribution held at the initial start,
This means that it is caused by the distribution of the charge amount distributed to the toner particles contributing to the development, and is considered to express the selectivity of the toner charge amount contributing to the development. α
Is larger than 0.03, the change in toner charge due to the change in toner density during development is too large, and the toner charge changes sensitively even with a slight change in toner density. However, there are disadvantages such as that the toner density range becomes slightly smaller than the toner charging area suitable for development.

On the other hand, if the value of the parameter α in the above equation (1) is not more than 0.03 and not less than 0.01, the dependency on the toner density is small, so that the optical sensor serving as the density sensor is stable. Can be controlled.

In particular, if the value of the parameter α in the above formula (1) is 0.01 or less, the toner concentration dependency of the toner charge amount during development is further reduced, so that the amount of toner in the developing device decreases. Also, the toner charge amount at the development site does not change.
This means that the image density does not change, and since the margin of the image density for the change in the toner density is very large, an image having the desired image density can be obtained even by periodically replenishing the toner at a constant rate. A system that detects an image pattern on the photoreceptor by an optical sensor and controls the amount of toner replenishment can construct a sensorless system that is not particularly required.

The parameter α defined in the present invention is obtained by a copying experiment in a state where toner is not supplied as described above, but this is a method for calculating the α value. When the value of the parameter α in the combination of the agents is 0.03 or less, the electrostatic image forming method and apparatus in the toner replenishment state are not limited to the toner image replenishment state electrostatic image forming method and apparatus.

Next, the materials used for the toner of the present invention will be described in detail.

The binder resin used in the present invention includes styrene such as polystyrene, poly p-chlorostyrene, and polyvinyl toluene, and a homopolymer of a substituted product thereof; styrene-p-chlorostyrene copolymer, and styrene-propylene. Copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-
Octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-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-based copolymers such as styrene-maleic acid copolymer and styrene-maleic acid ester copolymer are exemplified. Further, the following resins can be used in combination.
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.

Further, as the binder resin particularly suitable for pressure fixing, the following can be mentioned, and they 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, ethylene-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.

Further, the toner of the present invention further contains a magnetic material and can be used as a magnetic toner. As the magnetic material contained in the magnetic toner of the present invention, magnetite,
Metals such as iron oxides such as hematite and ferrite, iron, cobalt and nickel or aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony beryllium, bismuth, sudomium, calcium, manganese, selenium, titanium, Examples include alloys of metals such as tungsten and vanadium, and mixtures thereof.

These ferromagnetic materials have an average particle size of 0.1 to 2
μm is desirable, and the amount contained in the toner is about 20 to 200 parts by weight per 100 parts by weight of the resin component, and particularly preferably 40 to 200 parts by weight based on 100 parts by weight of the resin component.
It is 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 positive charge control agents include nigrosine, basic dyes, lake dyes of basic dyes, quaternary ammonium salt compounds, and the like.As negative charge control agents, metal salts of monoazo dyes, salicylic acid, naphthoic acid, dyes And metal complexes of carboxylic acids and the like.

The toner of the present invention may be mixed with known additives as necessary. Examples of the additive include a lubricant such as Teflon and zinc stearate or a polishing agent such as cerium oxide and silicon carbide; a fluidity imparting agent such as colloidal silica and aluminum oxide; a caking inhibitor; or carbon black and tin oxide. And a fixing aid such as a low-molecular-weight polyolefin.

As the colorant, any known colorants 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 coloring agent, 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.

As the carrier that can be used in the present invention, all known carriers can be used. For example, magnetic powders such as iron powder, ferrite powder and nickel powder, glass beads, etc. And the like.

The resin powder that can be coated on the carrier in the present invention includes a 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, those having a styrene content of 30 to 90% by weight are preferred. In this case, if the styrene content is less than 30% by weight, the developing characteristics are low, and if the styrene content exceeds 90% by weight, the coating film becomes hard and easily peels off, shortening the life of the carrier.

The resin coating of the carrier according to the present invention 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-mentioned resin.

The electrostatic image developing device used in the present invention comprises:
There is no particular limitation, as long as the parameter α in the above formula (1) can be 0.03 or less in relation to the developer. Although the electrostatic image forming apparatus of the present invention includes the electrostatic image developing device and the developer as essential components, other known additional components may be added.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. All parts are parts by weight.

First, a production example of a carrier having a silicone resin used in the present embodiment and the like in a coating layer will be described. This can be performed by known means.

Carrier Production Example 1 Composition of Coating Layer Forming Liquid Silicon 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. Thus, a coating layer forming liquid was prepared. The coating layer forming solution was prepared with an average particle size of 100 μm
A carrier A having a coating layer formed on the surface of 1,000 parts by weight of the spherical ferrite was obtained using a fluidized bed type coating apparatus.

Carrier Production Example 2 Composition of Coating Layer Forming Solution Silicon Resin Solution (KR250 manufactured by Shin-Etsu Silicone Co., Ltd.) 100 parts Chloro group-containing silane coupling agent 5 parts Carbon black (# 44 manufactured by Mitsubishi Kasei Corporation) 4 parts Toluene 100 Part The above formulation was dispersed with a homomixer for 30 minutes to prepare a coating layer forming liquid. The coating layer forming solution was prepared with an average particle size of 100 μm
A carrier B having a coating layer formed on the surface of 1,000 parts by weight of the spherical ferrite using a fluidized bed type coating apparatus was obtained.

Carrier Production Example 3 Composition of Coating Layer Forming Liquid Silicon resin solution (KR250 manufactured by Shin-Etsu Silicone Co., Ltd.) 100 parts Aminosilane coupling agent 5 parts Carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 4 parts Toluene 100 parts The mixture was dispersed with a homomixer for 30 minutes to prepare a coating layer forming liquid. The coating layer forming solution was prepared with an average particle size of 100 μm
A carrier C having a coating layer formed on the surface of 1,000 parts by weight of the spherical ferrite by using a fluidized bed type coating apparatus was obtained.

Example 1 Polyester using the following developer 15 parts Styrene methyl acrylate 80 parts Low molecular weight polypropylene 5 parts Rhodamine dye 0.3 part The mixture of the above composition was thoroughly stirred and mixed in a Henschel mixer, and then roll-milled. About 3 at a temperature of 130-140 ° C
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 20 μm. To 3.5 parts of the toner, the carrier A
96.5 parts were mixed with a ball mill to obtain a developer.

Using a commercially available copying machine FT-4500 manufactured by Ricoh Co., Ltd. having an optical sensor for controlling the toner density, a copying experiment was conducted with the above-mentioned developer without toner supply. The value of the parameter α representing the development selectivity was 0.013. The copy image chart used at this time had an A4 image area of 6%. By using this image forming method, as shown in Table 1,
Even after running 140,000 sheets (with toner replenishment) using the Ricoh copier FT-4500, a good image was obtained as in the start.

Example 2 The following developer was used.

Polyester resin (weight average molecular weight 250,000) 80 parts Styrene-methyl methacrylate copolymer 20 parts Acid value rice wax (acid value 15) 5 parts Carbon black (Mitsubishi Carbon Co. # 44) 8 parts Quaternary ammonium 3 parts of salt compound The mixture having the above composition was thoroughly stirred and mixed in a Henschel mixer, and then roll-milled at a temperature of 130 to 140 ° C. for about 3 hours.
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 20 μm. To 2.5 parts of this toner, carrier B9
7.5 parts with a ball mill and charge amount 20.1 μC
/ G of developer. The developer has a combination having a small toner charging ability and a very large carrier charging ability.

Using a commercially available copying machine FT-4500 manufactured by Ricoh Co., Ltd. having an optical sensor for controlling the toner density, a copying experiment was performed with the developer without toner supply. The value of the parameter α representing the development selectivity was 0.008. The copy image chart used at this time had an A4 image area of 6%.
As shown in Table 1, good images were obtained after running 140,000 sheets (with toner replenishment) using the Ricoh copying machine FT-4500 as shown in Table 1 by using this image forming method. .

Example 3 In the image evaluation using the developer of Example 2, the copier FT-4500 to be used was modified, the sensor for controlling the toner density was removed, and the toner supply was quantitatively performed (every 100 copies). Approximately 4 to 6 g), and a running test of 120,000 sheets was performed. By using this image forming method, as shown in Table 1, Ricoh copier FT-4500
Even after running 140,000 sheets using (with toner replenishment), a good image was obtained as in the start.

Comparative Example 1 The following developer was used.

Polyester resin (weight average molecular weight 250,000) 80 parts Styrene-methyl methacrylate copolymer 20 parts Acid value rice wax (acid value 15) 5 parts Carbon black (Mitsubishi Carbon Co. # 44) 8 parts Quaternary ammonium Salt compound 11 parts After sufficiently mixing and mixing the mixture having the above composition in a Henschel mixer, the mixture was roll-milled at a temperature of 130 to 140 ° C. for about 3 hours.
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 20 μm. To 2.5 parts of the toner, a carrier C9 was used.
7.5 parts with a ball mill, and charge amount 20.6 μC
/ G of developer. The developer has a combination having a very large toner charging ability and a small carrier charging ability.

Using a commercially available copying machine FT-4500 manufactured by Ricoh Co., Ltd. having an optical sensor for controlling the toner density, a copying experiment was carried out with the developer and without toner supply. The value of the parameter α representing the development selectivity was 0.036. The copy image chart used at this time had an A4 image area of 6%.
In the use of this image forming method, as shown in Table 1, after running 140,000 sheets using the Ricoh copier FT-4500 (with toner replenishment), a good image cannot be obtained as in the start. Was.

[0046]

[Table 1]

[0047]

As described above, the value of the parameter α is set to 0.
03 or less, an electrostatic image forming method which has excellent development selectivity of the amount of charge of the consumed toner, has high developing ability and high image quality over time, and can stably control the optical sensor; The device can be configured. In particular, by setting the value of the parameter α to 0.01 or less, it is possible to eliminate the need for the toner density sensor in the image forming method and in the image forming apparatus.

Claims (4)

[Claims] In an electrostatic image forming method using at least an electrostatic image developing device and a developer, a value of a parameter α in the following general formula (1) indicating a change in a toner charge amount Q / M in a developing section is determined. An electrostatic image forming method characterized by being 0.03 or less. Q / M = (Q / M) ₀ + αt (1) (where M is the toner mass, Q is the charge amount, Q / M is the toner charge amount per unit mass, and (Q / M) ₀ is the initial toner The charge amount and t represent the number of copies.) 2. The electrostatic image forming method according to claim 1, wherein the value of the parameter α is 0.01 or less, and the toner density sensor is not used. 3. In an electrostatic image forming apparatus comprising at least an electrostatic image developing device and a developer, a value of a parameter α in the following general formula (1) indicating a change in a toner charge amount Q / M in a developing section is determined. An electrostatic image forming apparatus characterized by being 0.03 or less. Q / M = (Q / M) ₀ + αt (1) (where M is the toner mass, Q is the charge amount, Q / M is the toner charge amount per unit mass, and (Q / M) ₀ is the initial toner The charge amount and t represent the number of copies.) 4. The electrostatic image forming apparatus according to claim 3, wherein the value of the parameter α is 0.01 or less, and the electrostatic image developing apparatus does not have a toner density sensor.