JPH04338977A - Nonmagnetic one-component development method - Google Patents

Abstract

PURPOSE:To provide the nonmagnetic one-component development method which uses a nonmagnetic toner, improves the rise of electrification in order to obtain an extremely good development characteristic, obviates the degradation in the density of solid black images and decreases drawbacks liable to arise with a nonmagnetic one-component contact system, such as fusion of the toner to a developing roll and the damage to the surface of a photosensitive body. CONSTITUTION:The developer to be used in the nonmagnetic one-component method of a contact type is formed by sticking hydrophobic silica and magnetic powder to the surface of the nonmagnetic toner essentially consisting of a binder resin and coloring agents. The hydrophobic silica has the state in which a part thereof is fixed to the surface of the nonmagnetic toner. The magnetic powder is particles of a size 0.5 to 3.0mum.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type nonmagnetic one-component developing method for developing an electrostatic latent image using a nonmagnetic toner.

0002

[Prior Art] Conventional methods of developing using an electrostatic latent image and toner include a two-component developing method using a two-component developer mainly consisting of toner and a carrier, or a two-component developing method using only a magnetic toner. There is a one-component developing method using a one-component developer, and various proposals have been made regarding each developing method.

A two-component developing method using a non-magnetic toner and a carrier has the following disadvantages compared to a one-component developing method. ■A toner concentration sensor is required to control the mixing ratio of toner and carrier. ■The life of the developer is short. ■Care must be taken when handling the developer stirring mechanism, and equipment such as the developing machine becomes large.

[0004] Further, the following points are listed as disadvantages of the one-component system using magnetic toner. ■The charging member is a sleeve or blade, and compared to a carrier, charging stability and charging ability are weaker. ■The precision of the developing machine is necessary to uniformly form the magnetic brush. (2) Transfer and fixing properties are inferior to non-magnetic toners, and the surface of the photoreceptor is more likely to be damaged.

[0005] Considering these problems comprehensively and considering the miniaturization of the device, it is believed that a single-component developing method using non-magnetic toner is extremely effective, and in recent years, non-magnetic single-component developing methods Developing methods using .

In the one-component development method using non-magnetic toner, in the process of forming a toner layer on a developing roll carrying a developer, the developer is applied to a blade for regulating the toner layer or to a toner layer on the developing roll. Since triboelectric charging is performed only by the toner supply roller provided for forming the toner, sufficient triboelectric charging is difficult to be performed.

[0007] Therefore, with the non-magnetic one-component development method, there is no problem at all as long as normal character images are printed, but when printing with many solid black areas, the density of the solid black areas decreases. This phenomenon may occur. This is thought to occur because the toner is not sufficiently tribo-electrified, so that a toner layer with sufficient tribo-charging properties is not formed on the developing sleeve.

[0008] In order to form a toner layer with sufficient triboelectric charging properties, it is sufficient to perform sufficient charging only by friction with the blade or toner supply roller, but the so-called developer charging required for this is sufficient. It has been difficult with the prior art to improve the rise characteristics of .

[0009]

[Problems to be Solved by the Invention] In order to obtain extremely good development characteristics in a non-magnetic one-component developing method using non-magnetic toner, the present invention aims to improve the charging start-up and reduce the density of solid black images. The object of the present invention is to provide a developing method that is free from toner fusing to the developing roll and damage to the photoreceptor surface, which are disadvantages that tend to occur in non-magnetic one-component contact systems.

0010

[Means for Solving the Problems] As a result of intensive studies to solve the problems of the conventional contact type non-magnetic one-component developing method, the present inventors have developed a technology for post-processing agents for the surface of non-magnetic toner. To obtain a non-magnetic one-component developing method that eliminates a decrease in the density of a solid black image while obtaining good charging properties, and reduces the occurrence of toner fusion to a developing roll and damage to a photoconductor by adding a specific device. It turns out that it is possible.

That is, the present invention provides a photosensitive material that supplies a developer to a developing roll, forms a thin layer of the developer on the developing roll using a regulating member, and charges the developer to retain an electrostatic latent image. In a contact-type non-magnetic one-component developing method in which an electrostatic latent image is developed by contacting the body and then transferred to paper, the developer is a non-magnetic toner whose main components are a binder resin and a colorant. Hydrophobic silica and magnetic powder are attached to the surface, and a part of the hydrophobic silica is stuck to the non-magnetic toner surface, and the magnetic powder is 0.5 to 3
．． This is a non-magnetic one-component developing method characterized by particles having a diameter of 0 μm.

The present invention will be explained in detail below. FIG. 1 is a schematic diagram of a developing device used in the contact type non-magnetic one-component developing method of the present invention. In the figure, 1 is a photosensitive drum which is a cylindrical electrostatic latent image holder, 2 is a hopper, and 3
4 is a developer, 4 is a regulating member such as a doctor blade, 5 is a developing roll provided with a toner carrying layer, 6 is a toner supply roll, and 7 is an agitator. In this developing device, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by electrophotography. A developer 3 is stored in the hopper 2, and the developer is carried by a regulating member 4 on the surface of the toner carrying layer of the developing roll 5 to a constant layer thickness, and is conveyed to the surface of the photoreceptor. . At this time, the developer is triboelectrically charged by the regulating member, and the regulating member may be connected to a direct current or alternating current power source to generate an electric field between the toner carrying layer and the regulating member. The developer carried on the toner carrying layer of the developing roll 5 is conveyed by the rotation of the developing roll 5 and comes into contact with the photoreceptor drum 1 having an electrostatic latent image, so that the electrostatic latent image is visualized. .

The toner carrying layer is formed on an elastic roll, and the roll is preferably made of a conductive material or has a conductive layer so that a bias voltage can be applied. The toner carrying layer is made of a thin resin layer with appropriate elasticity, such as fluorine-containing resin,
Resins having film-forming properties are used, such as silicone resins, polyester resins, and polycarbonate resins. The thickness of the toner carrying layer is formed in a range of 10 to 200 μm. Further, as the elastic material constituting the roll, various rubbers such as silicone rubber, sponge rubber, urethane foam, etc. are used, and these may contain conductive powder. Further, the surface may be coated with a conductive paint.

The non-magnetic toner constituting the one-component developer used in the present invention contains a binder resin and a colorant as main components.

[0015] As the binder resin, in addition to those conventionally used in dry toners for electrophotography, any resin that could not be used due to charge controllability etc. can be used. For example, polystyrene, polyester, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, polyamide, polyethylene, maleic acid resin, acrylic resin, epoxy resin, xylene resin, coumaron resin, ketone resin, petroleum resin, phenol. Examples include resin.

Examples of colorants include carbon black, acetylene black, lamp black, channel black, funeral blue, permanent blue, nigrosine blue, phthalocyanine blue, rose bengal, C.I. I. Pigment Red 122, C. I.
Pigment Yellow 12 etc. can be mentioned. These colorants are appropriately blended in an amount of 1 to 10 parts by weight based on 100 parts by weight of the binder resin. The non-magnetic toner may contain other components, such as a known charge control agent, if desired. Non-magnetic toners having a particle size of less than about 30 μm are preferably used.

In the present invention, the non-magnetic toner includes:
Hydrophobic silica is blended, and at that time, a portion of the hydrophobic silica is fixed to the surface of the toner particles, and a portion of the hydrophobic silica is held in an attached state. The adhesion referred to in the present invention means that toner particles and hydrophobic silica come into point contact during mixing, and at least either the toner particles or the hydrophobic silica at the contact point is caused by compressive force, frictional force, and impact force during mixing. Heat is generated instantaneously to a temperature higher than the melting point of the silica, indicating a phenomenon of adhesion due to fusion, and refers to a state in which a portion of the hydrophobic silica is embedded in the toner particles. On the other hand, adhesion refers to a state in which hydrophobic silica is sprinkled on the surface of toner particles, and refers to a state in which hydrophobic silica is not embedded in toner particles.

[0018] In order to fix a part of the hydrophobic silica to the non-magnetic toner and keep the part attached, a larger amount of hydrophobic silica than usual is used, preferably for the non-magnetic toner. , 0.6% by weight or more, and the hydrophobic silica is mixed in two or more portions. In that case, the ratio of hydrophobic silica to be fixed to the non-magnetic toner and hydrophobic silica to be attached is 40:60 to 90:10.
It is preferable to keep it within the range of .

In order to fix a part of the hydrophobic silica to the non-magnetic toner and make it adhere to the non-magnetic toner, it is necessary to use a mixer such as a Henschel mixer, a super mixer, etc., which are normal powder mixers, a hybridizer, an Ongmill, etc. This can also be carried out using a so-called surface modification machine such as . When using a powder mixer such as a Henschel mixer or a super mixer, a relatively long processing time is required, but when using a so-called surface modification machine, the same process can be achieved in a relatively short time. It is efficient and has the following effects. For example, first, a predetermined amount of hydrophobic silica is blended into a non-magnetic toner, and the mixture is mixed with the above-mentioned mixer until the hydrophobic silica is fixed on the surface of the toner particles by heating near the melting point of the binder resin. Then, the remaining amount of hydrophobic silica is added to the non-magnetic toner and mixed for a short time under mild mixing conditions.

The hydrophobic silica used in the present invention can be easily obtained by replacing the terminal silanol group of a conventional hydrophilic silica molecule with an organosilicon halide or alcohol. Such hydrophobic silica fine powder is easily available as a commercial product (
For example, Aerosil R-972 manufactured by Nippon Aerosil, H2000 manufactured by Hoechst, etc.).

Next, magnetic powder, which is another feature of the present invention, will be explained. In the present invention, magnetic powder is attached to the surface of the toner particles of the non-magnetic toner together with the above-mentioned hydrophobic silica. By adhering magnetic powder to toner particles, the charge build-up characteristics are improved and image density is prevented from decreasing in originals with many solid black areas. Although it is not clear why the charging characteristics improve when magnetic powder is attached to non-magnetic toner, it is probably because the surface of the toner particles becomes non-uniform by attaching magnetic powder. If we focus only on the charging rise characteristics, it is possible to achieve the objective to some extent without particularly limiting the size of the magnetic powder, but this may cause the toner to fuse to the developing roll and damage the photoreceptor surface. In order to prevent this, the size of the magnetic powder added to the non-magnetic toner is an important factor. That is, the size of the magnetic powder used in the present invention must be 0.5 to 3.0 μm. The reason for this is that if the thickness is less than 0.5 μm, it becomes difficult for the cleaning blade to clean the magnetic powder on the surface of the photoreceptor, causing damage, whereas if it is larger than 3.0 μm, contact between the photoreceptor and the developing roll, or Magnetic powder is pressed between the contact between the photoreceptor and the cleaning blade and is easily damaged.

Magnetic powder having a particle size of 0.5 to 3.0 μm may be directly attached to the surface of a non-magnetic toner, or magnetic powder generally available on the market may have a primary particle size of 0. .2 to 0.4 μm, and multiple primary particles form aggregates of 5 to 10 μm. Therefore, after putting the magnetic powder and non-magnetic toner into a mixer such as a Henschel mixer, 5 while adjusting the rotation speed of the stirring blade.
~10μm aggregates are dispersed to 0.5~3.0μm
A magnetic powder may be formed and attached to the surface of the non-magnetic toner.

[0023] Furthermore, the shape of the magnetic powder used in the present invention is preferably cubic in order to prevent damage to the photoreceptor when the magnetic powder separates from the non-magnetic toner. If the amount of magnetic powder attached to the non-magnetic toner is too large, it will cause more scratches on the photoreceptor, and if it is too small, it will not contribute to improving the rise of chargeability. Preferably, it is 8% by weight. As such magnetic powder,
Magnetite, hematite, ferrite, etc., which are compounds of iron, cobalt, nickel, manganese, zinc, etc., specifically EPT-500 and EPT- manufactured by Toda Kogyo Co., Ltd.
1000, or BL-220 or B manufactured by Titanium Kogyo Co., Ltd.
There are L-200 etc.

In the present invention, hydrophobic silica (partly fixed, partially attached) and magnetic powder can be attached by the following method, and from the viewpoint of manufacturing cost, (1) or (2) is preferred.
It is preferable to carry out this method.

(1) Put the non-magnetic toner, magnetic powder and hydrophobic silica into a mixer, and after adhering the magnetic powder to the surface of the toner particles and fixing the hydrophobic silica, add the hydrophobic silica again. method of attaching hydrophobic silica. (2) A method in which non-magnetic toner and hydrophobic silica are placed in a mixer to adhere the hydrophobic silica to the surface of the toner particles, and then magnetic powder and hydrophobic silica are placed in the mixer to adhere the magnetic powder and hydrophobic silica. . (3) Put the non-magnetic toner and magnetic powder into a mixer, and after adhering the magnetic powder to the surface of the toner particles, add hydrophobic silica and perform fixing treatment, then put the hydrophobic silica into the mixer again to make it hydrophobic. How to attach silica. (4) Put the non-magnetic toner and hydrophobic silica into a mixer,
A method in which hydrophobic silica is adhered to the surface of toner particles, then magnetic powder is added to perform adhesion treatment, and then hydrophobic silica is placed in a mixer again to adhere hydrophobic silica. (5) Put the non-magnetic toner and hydrophobic silica into a mixer,
A method in which hydrophobic silica is fixed to the surface of toner particles, then hydrophobic silica is added again to perform the adhesion treatment, and then magnetic powder is placed in a mixer to make the magnetic powder adhere.

[0026]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. Note that the parts described below refer to parts by weight.

Example 1 The raw materials were mixed, melt-kneaded, crushed and classified according to the following composition,
A non-magnetic toner having an average particle diameter of 12 μm was obtained. Styrene acrylic copolymer
92 copies (
Manufactured by Fujikura Kasei Co., Ltd. TTR-563) Polypropylene wax
Part 2 (Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) Chromium-containing metal dye
1 part (Orient Chemical Industry Co., Ltd. Bontron S-34) Carbon black
5 parts (MA-100, manufactured by Mitsubishi Chemical Industries, Ltd.) 0.4 parts of hydrophobic silica (manufactured by Hoechst, trade name H2000) was added to the above non-magnetic toner.
Weight% and magnetite (manufactured by Toda Kogyo Co., Ltd., product name: EPT-
500) was added in an amount of 0.5% by weight, and the mixture was stirred for 30 minutes while passing cooling water through a Henschel mixer to fix hydrophobic silica and magnetic powder on the surface of the non-magnetic toner. Further, 0.2% by weight of the same hydrophobic silica was added and stirred for 2 minutes to obtain a developer used in the present invention. When the surface of the developer was observed using an electron microscope, it was found that the magnetite on the surface of the developer was aggregated to a size of 1.0 to 2.0 μm. Using the obtained developer, a commercially available non-magnetic one-component development printer (LP1060-SP3 manufactured by Ricoh Co., Ltd.) having the developing mechanism shown in Fig. 1 was used.
Normal temperature and humidity (20℃, 60%RH), low temperature and low humidity (10℃,
When printing was performed under various environments (15% RH) and high temperature and high humidity (30°C, 80% RH), there was no change compared to the initial image even after printing 10,000 sheets, and the uniformity of the black solid area was improved. was also good. Additionally, there is no occurrence of toner fusing to the developing roll or damage to the photoreceptor drum.
The results were good.

Comparative Example 1 0.6% by weight of only the same hydrophobic silica as in Example 1 was added to the non-magnetic toner of Example 1, and 2% by weight was added in a Henschel mixer.
A comparative developer was obtained by stirring for a minute. As in Example 1, a commercially available printer (LP1060-SP manufactured by Ricoh Co., Ltd.
3) was used to print under each environmental condition. As a result, under each environment, the density of the black solid image decreased in the portion that appeared to be after the second cycle of the developing roll, and a uniform image could not be obtained. Further, at low temperature and low humidity, a significant decrease in image density appeared.

Comparative Example 2 0.4% by weight of the same hydrophobic silica as in Example 1 was added to the non-magnetic toner of Example 1, and the mixture was stirred for 30 minutes while passing cooling water through a Henschel mixer to fix the hydrophobic silica. I let it happen. Furthermore, 0.2% by weight of the same hydrophobic silica was added,
A comparative developer was obtained by stirring for 2 minutes. As in Example 1, a commercially available printer (Ricoh LP
1060-SP3) under each environmental condition. As a result, under each environment, the density of the black solid image decreased in the portion that appeared to be after the second cycle of the developing roll, and a uniform image could not be obtained. Table 1 summarizes the above results. In addition, the image density in the table was measured with a Macbeth reflection densitometer, and the fog was measured with a Hunter whiteness meter. Furthermore, the black solid uniformity was evaluated by visual inspection of the black solid image, and a uniform black solid image was evaluated as ○, and a black solid image with unevenness was evaluated as poor.

[0030]

[Table 1] Next, the triboelectric charging build-up characteristics of the developers of Example 1, Comparative Example 1, and Comparative Example 2 were evaluated. The measurement method is as follows. ■Put 100 parts of non-coated iron powder carrier and 10 parts of developer into a beaker. ■Stir the sample in the beaker with a magnetic stirrer,
Measure the amount of triboelectric charge at each rotation speed of the magnetic stirrer. At this time, the amount of triboelectric charge was measured using a magnetic blow-off method. The magnetic blow-off method separates the developer from the carrier using a difference in magnetic force and measures the charge remaining on the carrier. The measurement results are shown in Table 2, and a graph of the results is shown in FIG. As is clear from Table 2 and FIG. 2, in the developer of Example 1, the amount of triboelectric charge reaches a saturation value at a small number of revolutions and exhibits a high value.

[0031]

[Table 2]

[0032]

Effects of the Invention As described above, the present invention fixes a part of the hydrophobic silica to the surface of a non-magnetic toner, adheres a part of it, and further increases the size of the magnetic powder to 0.5 to 3.0 μm. Since the toner is attached in such a manner that the developer is charged quickly, it is possible to prevent the toner from fusing to the developing roll and damaging the photoreceptor drum. Therefore, according to the present invention, it is possible to print a uniform image without decreasing the density of a solid black image.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a one-component developing device for carrying out the present invention. 1...Photosensitive drum, 2...Hopper, 3
...developer, 4...regulating member, 5...developing roll, 6...toner supply roll, 7...stirrer.

Claims (3)

[Claims] 1. Supplying a developer to a developing roll, forming a thin layer of the developer on the developing roll using a regulating member, applying an electric charge to the developer, and bringing it into contact with a photoreceptor holding an electrostatic latent image. In a contact-type non-magnetic one-component development method in which an electrostatic latent image is developed using a wafer and then transferred to paper, the developer has a hydrophobic property on the surface of a non-magnetic toner whose main components are a binder resin and a colorant. Silica and magnetic powder are attached, and part of the hydrophobic silica is stuck to the non-magnetic toner surface, and the magnetic powder is particles of 0.5 to 3.0 μm. Characteristic non-magnetic one-component development method. 2. The non-magnetic one-component developing method according to claim 1, wherein the amount of hydrophobic silica deposited is 0.6% by weight or more based on the non-magnetic toner. 3. The non-magnetic one-component developing method according to claim 1, wherein the magnetic powder has a cubic shape and the amount of adhesion is 0.1 to 0.8% by weight based on the non-magnetic toner. .