JPH0114583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method using an insulating developer.

Conventionally, developing methods for electrophotography, electrostatic recording, etc. are broadly classified into dry developing methods and wet developing methods. The former method is further divided into a method using a two-component developer and a method using a single-component developer. Two-component developing methods include a magnetic brush method using an iron powder carrier, a cascade method using a bead carrier, a fur brush method using fur, etc., depending on the type of carrier for conveying the toner.

Furthermore, the one-component development methods include the powder cloud method, in which toner particles are sprayed, and the contact development method, in which toner particles are brought into direct contact with the electrostatic latent image surface. (also called donor development), jumping development method in which toner particles are not brought into direct contact with the electrostatic latent image surface, but are charged and flown toward the latent image surface by the electric field of the electrostatic latent image; magnetic conduction There is the MagneDry method, which develops by bringing a toner into contact with the electrostatic latent image surface. Two-component development methods necessarily use a developer mixture of carrier particles and toner particles, and usually a developer is used, and as the development process progresses, toner particles are consumed in much larger quantities than carrier particles. As a result, the mixing ratio of the two changes, resulting in fluctuations in the density of the suspended image, and the carrier particles, which are difficult to consume, deteriorate due to long-term use, resulting in a reduction in image quality.

On the other hand, in one-component developing methods, the Magne-Dry method using magnetic toner and the contact developing method that does not use magnetic toner, the toner comes into contact with the entire surface of the surface to be developed, that is, the image area and the non-image area, indiscriminately. As a result, there is a problem in that toner tends to adhere even to non-image areas, resulting in so-called background fog and dirt. (This fog stain was also a drawback of two-component development.)
Further, even in the powder cloud method, it is inevitable that toner particles in a powder state adhere to non-image areas, and the method also has the disadvantage that background fog cannot be removed.

Furthermore, in the so-called jumping development method, which belongs to the one-component development method, after toner is uniformly applied to a carrier such as a sheet, the toner is placed facing an electrostatic holding surface with a small gap, and an electrostatic image is transferred from the toner carrier. A method is known in which toner is attracted and adhered to a holding surface by the electric charge of an electrostatic image, thereby developing the image. (U.S. Patent No.
2839400, etc.) This method has the advantage that not only the toner is not attracted to the non-image area where there is no static charge, but also the toner and the non-image area do not come into contact, so the above-mentioned fogging is less likely to occur. . Furthermore, since carrier particles are not used, there is no variation in the mixing ratio as described above, and there is no deterioration of the carrier particles.

However, in this method, an electric field is applied in advance to adhere the toner to the toner carrier sheet, but it is difficult to apply the toner uniformly and thinly, and uneven application is likely to occur. Another drawback is that when the applied toner layer faces an electrostatic image, it is difficult to release the toner uniformly to the electrostatic image.

In this regard, in the developing device proposed in JP-A-54-43027 and JP-A-55-18656, which has magnetic toner, a movable toner carrier (sleeve roller), and a stationary magnet inside the carrier, A developing device is provided in which a toner thickness regulating member made of a magnetic material is disposed close to the outer surface of the sleeve roller facing the magnetic pole of the magnet, and can uniformly and thinly apply toner on the outer surface of the sleeve roller. It can be said that this electrostatic image developing apparatus eliminates the above-mentioned drawbacks and has high fidelity and stable image quality.

An object of the present invention is to provide a developing method with excellent durability such as continuous use characteristics.

Another object of the present invention is to provide a developing method that is stable against environmental changes such as high temperature and high humidity.

Specifically, the present invention arranges an electrostatic image holder that holds an electrostatic image on its surface and a developer carrier that carries an insulating developer on its surface with a certain gap in a developing section. , a one-component developer containing a silicate fine powder containing 0.1 to 20% by weight of alumina and a positively charged toner is triboelectrically charged, and the triboelectrically charged developer is placed on the developer carrier through the gap. It also relates to a developing method, characterized in that the developer is supported in a thin thickness and the developer is transferred to the electrostatic image holder in a developing section for development.

In addition to anhydrous silicon dioxide (silica), silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be used as the silicate fine powder here. .

The inventors of the present invention have found that when copying is continued repeatedly using a conventionally known jumping developer, the image density decreases and the image quality deteriorates, especially in the case of high temperature and high humidity. As a result of repeated studies on this point, we found that one of the causes is the stability and reliability of the charge control component, and that these causes change the adhesion of developer powder onto the sleeve and the transfer of developer powder from the sleeve. I found out that it was for the purpose of

Conventionally known charge control agents used in such dry developing toners include amino compounds, quaternary ammonium compounds, organic dyes, especially basic dyes and their salts, and benzyldimethyl-hexadecyl ammonium chloride, decyl -trimethylammonium chloride, nigrosine base,
Nigrosine hydrochloride, safranin γ, crystal violet, etc. are used. Nigrosine base and nigrosine hydrochloride are often used as positive charge control agents.
These are usually added to thermoplastic resins, heated, melted and dispersed, finely pulverized, and adjusted to a suitable particle size as necessary before use.

However, these dyes used as charge control agents have complex structures, inconsistent properties, and poor stability. In addition, it may decompose or change in quality due to decomposition during thermal kneading, mechanical impact, friction, changes in temperature and humidity conditions, etc., resulting in a phenomenon in which charge controllability is reduced.

Therefore, when a toner containing these dyes as a charge control agent is used for development in a copying machine, the dye decomposes or changes in quality as the number of copies increases, causing deterioration of the toner during durability.

Furthermore, since it is extremely difficult to uniformly disperse these dyes as charge control agents in thermoplastic resins, they have the fatal drawback of causing a difference in the amount of frictional charge between the toner particles obtained by crushing them. have. For this reason, various methods have been used to more uniformly disperse these dyes into resins. For example, basic nigrosine dyes are used by forming salts with higher fatty acids in order to improve their compatibility with thermoplastic resins, but unreacted fatty acids or salt dispersion products are often exposed on the toner surface. This contaminates the carrier or toner carrier, causing a decrease in toner fluidity, fog, and a decrease in image density. Alternatively, in order to improve the dispersion of these dyes into the resin, a method has been adopted in which the dye powder and the resin powder are mechanically pulverized and mixed beforehand and then hot-melted and kneaded, but the inherent poor dispersion is , cannot be avoided, and the reality is that sufficient uniformity of charge has not yet been obtained for practical use.

In addition, many charge control dyes are hydrophilic,
Due to poor dispersion in these resins, the dye is exposed on the toner surface when it is crushed after melt-kneading. When these toners are used under high humidity conditions, they have the disadvantage that good quality images cannot be obtained because these dyes are hydrophilic.

In this way, when conventional dyes with charge control properties are used in toner, they can be applied to the surface of toner particles between toner particles, between toner and carrier, or between toner and toner carriers such as sleeves. This causes variations in the amount of charge generated, leading to problems such as development fog, toner scattering, and carrier contamination.
Furthermore, these phenomena become particularly noticeable when a large number of copies are made, resulting in a result that is practically unsuitable for copying machines.

Furthermore, under high humidity conditions, the toner image transfer efficiency is significantly reduced, making it unusable. Furthermore, when the toner is stored for a long period of time even at room temperature and humidity, the toner often aggregates and becomes unusable due to the instability of the charge control dye used.

Conventionally, examples of adding fine powder silica called colloidal silica (for example, Aerosil 200, R972, manufactured by Nippon Aerosil Co., Ltd.) to toner are known. However, such substances do not necessarily have sufficient stability, and addition of such silica changes chargeability, making them unsuitable for toners that require positive charge control.

The present inventor has conducted extensive research with the aim of solving the various problems associated with conventional chargeable toners as described above, and producing high-quality images by being strongly and uniformly charged and visualizing the electrostatic charge image. It was discovered that an electrophotographic developer exhibiting various excellent properties can be obtained by incorporating a fine silicate powder containing alumina in a silicon yeast body into a developer. Furthermore, it has been found that it is very effective to apply this developer to a developing device having a sleeve roller.

The developing process used in the present invention will be explained. FIG. 1 shows a cross-sectional view of one embodiment of the developing process used in the present invention. In the figure, the electrostatic image holder 1 moves in the direction of the arrow. The non-magnetic cylinder 4b, which is a developer carrier, rotates in the developing section so as to move in the same direction as the surface of the electrostatic image carrier. A multipolar permanent magnet 9 is arranged in the non-magnetic cylinder 4b so as not to rotate. The one-component insulating magnetic developer 11 sent from the developer container 12 is applied onto the non-magnetic cylindrical surface, and the friction between the cylindrical surface and the toner particles causes the toner particles to have a polarity opposite to that of the electrostatic image charge. Gives a charge. Furthermore, by arranging the iron doctor blade 10 close to the cylindrical surface (with an interval of 50 μm to 500 μm) and facing one magnetic pole (S pole in the figure) of the multipolar permanent magnet 9, the thickness of the toner layer can be reduced. thinly (30μ~
300μ) and uniformly regulated. By adjusting the rotational speed of the cylinder 4b, the surface speed and preferably the internal speed of the developer layer are made to be substantially equal to or close to the speed of the electrostatic image holding surface. As the doctor blade 10, a permanent magnet may be used instead of iron to form opposing magnetic poles. Further, an alternating current bias may be applied between the developer carrier and the electrostatic image holding surface in the developing section.
This AC bias has f of 200 to 4000Hz and Vpp of 500
~3000V is fine.

As described above, in this developing step, the non-magnetic cylinder 4b containing the multipolar permanent magnet 9 was used in order to stably hold the one-component magnetic developer on the developer carrier. Further, in order to form a thin and uniform developer layer, a doctor blade 10 made of a magnetic thin plate or a permanent magnet was placed close to the surface of the cylinder 4b. When a magnetic doctor blade is used in this way, opposing magnetic poles are formed between the magnetic poles of the permanent magnet contained in the developer carrier, and the toner particle chains are forced to stand up between the doctor blade and the developer carrier. This is advantageous in controlling the thickness of the developer layer in other parts of the developer carrier, for example, in the development part facing the electrostatic image surface. Further, by imparting such forced movement to the developer, the developer layer becomes more uniform, thereby achieving a thin and uniform toner layer formation that could not be achieved with a non-magnetic doctor blade. Moreover, since the gap between the doctor blade and the sleeve can be set wide, there is also the effect of preventing the destruction and aggregation of toner particles. When the toner particles are transferred in the developing area, they are transferred to the electrostatic image side due to the attraction action of the electrostatic image or the action of an alternating current bias.

As the binder resin for toner used in the developing method of the present invention, various material resins conventionally known as toner binder resins for electrophotography are used.

For example, styrene copolymers such as polystyrene, polystyrene/butadiene copolymer, styrene/acrylic copolymer, ethylene copolymers such as polyethylene, polyethylene vinyl acetate copolymer, polyethylene vinyl alcohol copolymer, and phenolic copolymers. These include resins, epoxy resins, allyl phthalate resins, polyamide resins, polyester resins, maleic acid resins, and the like. Furthermore, there are no particular restrictions on the manufacturing method of any of the resins. This is because conventionally, resins produced by emulsion polymerization or the like tend to contain impurities and are difficult to use, but the present invention allows them to be used easily, and the range of resin selection is greatly expanded. This is also a great effect of the present invention.

The magnetic powder to be contained in the toner includes ferromagnetic elements and alloys and compounds containing them.
There are conventionally known magnetic materials such as alloys and compounds of iron such as magnetite, hematite, and ferrite, cobalt, nickel, and manganese, and other ferromagnetic alloys. Generally used magnetic powder has an average particle size of 0.05 to 5μ, preferably 0.1 to 1μ. This magnetic powder is preferably contained in the toner in an amount of 10 to 70% by weight, preferably 15 to 30% by weight. With this content, an appropriate magnetic moment is activated in the above-mentioned developing method, a good image can be created, and the fixing property is also excellent.

As the coloring material used in the toner, conventionally known carbon black, iron black, etc. can be used, and all conventionally known dyes as positive charge control agents can be used in combination with the alumina-containing silicate fine powder used in the present invention. can do.

Various dyes include, for example, benzyldimethyl-hexadicylammonium chloride, decyl-trimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin gamma and crystal violet.

The method for producing the alumina-containing silicate fine powder used in the present invention is disclosed in US Pat. No. 3,007,878, for example.
After drying the water-dispersed colloidal silica particle sol obtained by the known method described in No. 3956171, etc. at a temperature of about 100°C, it is pulverized using a jet air stream or by a ball mill or the like. The particles may be pulverized using a device and adjusted to an appropriate particle size. The commercially available colloidal silica particle sol used as a raw material here includes those commercially available under the following trade names, for example.

Ludotux 130 Ludotux AM Ludotux WP manufactured by DuPont Co., Ltd. Examples of commercially available silicate fine powders include MOX80, MOX170, and COK84 (Nippon Aerosil Co., Ltd.).

The primary particle size of the alumina-containing silicate fine powder is
It is preferable to use it by adjusting it to 0.01 to 2μ.

Further, the alumina content of the alumina-containing silicate fine powder used in the present invention is 0.1 to 20% by weight of the weight of the silicate fine powder, and the above-mentioned characteristics are achieved by containing alumina of 0.1 to 20% by weight. be satisfied.

Furthermore, various organic treatments may be performed for the purpose of making the alumina-containing silicate fine powder used in the present invention hydrophobic.

When adding the alumina-containing silicate fine powder to the developer in an amount in the range of 0.01 to 20 wt% (preferably 0.1 to 15 wt%), a developer exhibiting positive chargeability with excellent stability can be obtained. It will be done. In particular, 0.01 to 3 wt% of the fine powder to be added is based on the weight of the developer.
It is more preferable to attach the toner particles to the surface of the toner particles.

The method for adding alumina-containing silicate fine powder to a developer is to add a binder resin,
When heat-kneading dyes and pigments, they can be added at the same time.If they are to be attached to the surface of toner particles, they are crushed after heat-kneading to reduce the toner particle size to a few microns or more.
After reducing the size to several tens of microns, alumina-containing silicate fine powder may be added using a mixer.

The first characteristic of the positively charged toner used in the developing method of the present invention constructed as described above is not only charge control using an unstable dye, which is conventionally known as a charge control agent, but also the use of silicic acid containing alumina. Because the control is carried out using fine salt powder, there is no variation in the amount of frictional charge between toner particles, especially when used as a toner for the developing method of the present invention, and since the amount of charge is large, it is difficult to prevent conventional methods. There is no development fog, toner scattering, or toner aggregation, and there is no deterioration due to long-term use of the toner, and high-quality images can be used for a long period of time.
There are several additional properties that are of practical importance. One of them is that because of the stable positive charge controllability due to the interaction between silica and alumina of the silicic acid fine powder used in the present invention, there is almost no decrease in the amount of charge due to environmental changes such as temperature and humidity, and in particular, It has the surprising property that the transfer efficiency at high humidity is almost the same as at normal humidity.

Another feature is that conventional pigments and dyes that control positive charge have selectivity with the binder resin used due to their poor dispersibility, and it was not possible to combine them with any resin. There is no selectivity between the silicic acid fine powder used in the present invention and the resin, and it can be combined with any resin, allowing a wide range of applicable toner compositions to be selected. For example, in addition to heat fixing toner, pressure fixing toner,
Can be used for capsule toner.

The basic configuration and features of the present invention have been described above, and the method of the present invention will be specifically explained below based on Examples. However, this does not in any way limit the embodiments of the present invention. Parts in the examples are parts by weight.

Example 1 A mixture consisting of 100 parts by weight of zinc oxide, 20 parts by weight of styrene-butadiene copolymer, 40 parts by weight of n-butyl methacrylate, 120 parts by weight of toluene, and 4 parts by weight of 1% rose bengal methanol solution was dispersed and mixed in a ball mill for 6 hours. did. This was applied to a 0.05 mm thick aluminum plate using a wire bar to a dry coating thickness of 40 μm, and the solvent was evaporated with hot air to create a zinc oxide binder photoreceptor in the form of a drum. This photoreceptor was subjected to -6 KV corona discharge to uniformly charge the entire surface, and then an original image was irradiated to form an electrostatic latent image.

The developer carrier was a stainless steel cylindrical sleeve with an outer diameter of 50 mm. The magnetic flux density on the sleeve surface is 700 Gauss, and the distance between the ear cutting blade and sleeve surface is 0.2 mm. This sleeve rotation magnet fixed (sleeve peripheral speed is the same as that of the drum, rotation direction is opposite) type developer was set at a distance of 0.25 mm between the photosensitive drum surface and the sleeve surface, and the sleeve was supplied with 400Hz 1000V AC and -150V DC. A bias was applied.

Next, Picolastic D-150 (Etsuo Petrochemical Polystyrene resin)
100 parts methylene blue chloride 5 parts magnetite 50 parts Mix the above materials well in a blender and then heat to 150°C.
The mixture was kneaded using two heated rolls. After the kneaded material is left to cool naturally, it is coarsely pulverized using a cutter mill, then pulverized using a pulverizer using jet air flow, and further classified using an air classifier to obtain a fine powder with an average particle size of 10 to 20μ. Obtained as a chargeable toner. In this fine powder,
MOX80 (Japan Aerosil Co., Ltd., alumina content 0.3
~1.3% by weight) based on the weight of the developer was mixed in a Henschel mixer and adhered to the toner surface to form a developer. Put this developer into the developer container,
Triboelectrically charging the sleeve to give it a positive charge, coating the stainless steel cylindrical sleeve with a thin layer using a blade, and developing the electrostatic latent image on the photoreceptor with a developer;
The toner image on the photoreceptor is heated to -7KV from the back of the transfer paper.
The powder image was transferred while irradiating with a direct current corona to obtain a duplicate image. For fixing, use a commercially available plain paper copier (product name
NP-5000 (manufactured by Canon) was used. The images obtained were clear, had high density (1.36) and resolution, and were free from fog. It also had an excellent durability of 20,000 sheets, and even under environmental conditions of 35°C and 85%, the density was as high as 1.32, and the transfer efficiency was good at 90%.

Comparative Example 1 A developer was prepared in the same manner as in Example 1, except that MOX80 was not added, and development, transfer, and fixing were performed using the same equipment. The image density was as low as 0.63, and only an unclear image with a lot of fog was produced. I couldn't get it. 35℃,
Under 85% environmental conditions, the density was extremely low at 0.32, making the image impractical.

Example 2 Epicote #1007 (Ciel Chemical Epoxy Resin)
100 parts Spirit Black AB2 2 parts Magnetite 60 parts The above materials were made into a toner by the method of Example 1, and Ludtux AM (manufactured by Dupont) was used for this toner.
After drying at 100℃, pulverize with a jet mill to adjust the average particle size to 0.8μ, then apply fine silica powder to the developer.
The developer was 1.5wt% added using a Henschel mixer. When a transfer-fixed image was created using this developer using the method of Example 1, the image density was
The image had a high value of 1.35, had no fog, and had excellent gradation and resolution. Good durability, 15000
The transferred image after printing had a good density of 1.32 with no change and no fogging at all. 35℃, humidity 85%
High concentration of 1.25 even under environmental conditions and transfer efficiency of 85%
It was excellent.

Comparative Example 2 A developer was prepared in the same manner as in Example 2, except that Ludotux AM was dried and finely powdered silica was not added.
When developing, transferring, and fixing were carried out using a similar device, the image density was as low as 0.63, and only unclear images with a lot of fog were obtained. Under the environmental conditions of 35°C and 85%, the density was extremely low at 0.32, making the image impractical.

Example 3 PE130 (polyethylene, Hoechst AG) 100 parts Lilvent Black 3 5 parts Alumina-containing silica produced in Example 2 20 parts Magnetite 50 parts After mixing the above materials well in a blender, approx.
The mixture was kneaded with two rolls heated to 150° C., and crushed and classified in the same manner as in Example 1 to obtain a developer. The image was developed by the method of Example 1, transferred onto plain paper, and fixed under pressure using a pressure roller to obtain an image. The image density is
The image density is as high as 1.32 and the image density after 15,000 sheets is 1.25.
It was high enough. The image quality was good, there was no fog, and the image had high resolution. Also, 35℃, 85%RH
The image density under high humidity conditions was as high as 1.30, and the image quality was exactly the same as under normal humidity.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a developing process applicable to the present invention. 1... Electrostatic image holder. 4...Nonmagnetic cylinder. 10
...Doctor Blade. 11...Insulating developer.

Claims (1)

[Claims] 1. An electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating developer on its surface are arranged with a certain gap in the developing section, and 0.1 to 20% by weight of alumina is placed. triboelectrically charging a one-component developer containing fine silicate powder and a positively charged toner, and supporting the triboelectrically charged developer on a developer carrier to a thickness thinner than the gap; A developing method comprising transferring the developer to the electrostatic image holder in a developing section to perform development.