JPH0473788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing an electrostatic latent image formed on a surface of a latent image carrier, and particularly a method for developing an electrostatic latent image formed on a toner carrier by forming a thin and uniform insulating nonmagnetic toner layer on a toner carrier. It's about how to do it.

Conventionally, the following methods are known as developing methods using one-component nonmagnetic or weakly magnetic toners.

For example, in an electrostatic image development method in which a developer carrier holding a developer on its surface is opposed to a latent image carrier to develop an electrostatic image on the surface of the carrier, the developer is stored in a developer storage means. When the developer under the developer carrier is pumped up onto the developer carrier, vibration is applied to the developer in the pumped-up portion to activate it and form a developer layer of a predetermined thickness on the surface of the developer carrier. There is a developing method in which the film is then subjected to development.

In addition, there is a rotatable magnetic roller that adsorbs a magnetic carrier to charge the one-component non-magnetic toner particles to form a magnetic brush, and a rotatable magnetic roller that transfers the toner particles of the roller and charges the electrostatic image carrier on the electrostatic image carrier. It has a developing roller for developing an image, maintains a distance between the electrostatic image holder and the developing roller in the developing section,
There is a method in which the length is set larger than the thickness of the toner coating layer on the developing roller and the electrostatic image is developed.

The movable developer carrying means carries and conveys the developer and supplies it to the latent image holding member, the developer replenishing means, and the movable developer carrying means receives the developer from the developer replenishing means and develops the image on the movable developer carrying means. A movable applicator for applying a developer, which has a fiber brush that carries a developer on its surface, contacts the movable developer carrier, and moves in the same direction as the movable developer carrier at this abutting portion. There is a method in which toner is uniformly applied to the surface of the movable developer carrying means using a movable coating means that moves at a higher speed than the movable developer carrying means, and development is carried out by bringing this coated layer close to the electrostatic latent image area. .

Compared to conventional developing methods using one-component toner, these methods apply strong pressure when applying the toner to the toner carrier, which tends to increase the amount of triboelectric charge on the toner, and the friction increases with development time. This method has the drawback that the image density of the resulting copy changes over time as the amount of electrical charge increases, and the quality of the copy cannot be kept constant.

In addition, these methods are methods in which insulating non-magnetic or weakly magnetic toner is supported on a carrier mainly by non-magnetic force in a developing section and developed. The forces that cause the toner to be supported on the carrier are mainly electrostatic attraction and physical adhesion, and in this respect, conventional insulating magnetic toner that supports the toner on the carrier by magnetic force, electrostatic force, etc. Various problems arise compared to the developing method using . For example, many toners are developed in a relatively thin and uneven manner onto the carrier. Furthermore, for example, even if the toner is applied relatively uniformly, so-called background fog occurs in which toner adheres to non-image areas. Furthermore, even if the toner is applied thinly and uniformly, the amount of toner adhering to the image area is insufficient, resulting in an image with low density. Additionally, many toners, even when applied thinly and evenly, can produce very poor images with low fidelity and low resolution. Furthermore, repeated use of a large amount of toner results in decreased image density and poor quality images. Furthermore, many toners have the problem of sometimes causing a decrease in image density or sometimes causing background fog due to environmental changes such as high temperature and high humidity or low temperature and low humidity.

In addition, in the development method using one-component magnetic toner, since the magnetic toner particles contain a large amount of magnetic powder, they are not only more expensive than toners that are non-magnetic or weakly magnetic, but also produce beautiful colors. Colorization was difficult.

An object of the present invention is to provide a new developing method using an insulating non-magnetic or weakly magnetic toner which solves the above-mentioned problems. That is, an object of the present invention is to provide a developing method with high fidelity and stable image quality. Another object of the present invention is to provide a developing method that eliminates background fog development and provides a high-resolution image that is uniform and has sufficient density in the image area.

Another object of the present invention is to provide a developing method using an insulating non-magnetic toner that has excellent durability such as continuous use characteristics.

Another object of the present invention is to provide a developing method using an insulating nonmagnetic toner that is stable against environmental changes such as high temperature and high humidity, and low temperature and low humidity.

Another object of the present invention is to provide a developing method that provides images with sharp hues.

Specifically, the present invention provides an electrostatic image holding body that holds an electrostatic image on its surface and a toner carrying body that carries and conveys nonmagnetic toner on its surface, which are separated from each other for a certain period of time in a developing section. The magnetic particles for toner application and the volume average particle diameter of 10 to 20 μm and volume distribution are
A developer container storing non-magnetic toner with a true specific gravity of 1.2 or less and 50% or more of 5.04 to 20.2 μm is disposed on the toner carrier, and the toner carrier is placed on the upstream side of the toner outlet of the developer container. A fixed magnet for forming a magnetic brush made of toner application magnetic particles is disposed inside the toner carrier so as to be in contact with the toner application magnetic particles, and as the toner carrier rotates, the toner application magnetic particles are By circulating the non-magnetic toner in a developer container, a thin layer of the non-magnetic toner is formed on the toner carrier while taking in the non-magnetic toner, and the non-magnetic toner on the toner carrier is The present invention relates to a developing method characterized in that the electrostatic image is developed by transferring the electrostatic image to the electrostatic image holder in a developing section.

In the above-mentioned developing method of the present invention, it is preferable to apply an alternating current and/or direct current bias between the toner carrier and the electrostatic image holder in the developing section, if necessary.

The present inventors investigated various developing methods using conventionally known non-magnetic or weakly magnetic toners, and found that in order to solve the above-mentioned problems, compared to developing methods using magnetic toners, We have found that it is important to more precisely control the amount of electrostatic charge and fluidity of the toner on the toner carrier in the developing section. For example, if the amount of charge is low, the toner will not be applied uniformly on the toner carrier, and development will not be possible, and even if the amount of charge is increased, even if it is applied evenly, the value will not be appropriate. If the value is too high, the electrostatic attraction with the toner carrier is too strong, making it difficult for the toner to transfer to the electrostatic image carrier, resulting in a decrease in image density. , resulting in the appearance of low-quality images.

In addition, if the fluidity is poor, it is difficult to apply uniformly, and even if uniformly applied, smooth development will not be possible. Therefore, in order to uniformly apply a non-magnetic or weakly magnetic toner containing a magnetic material with a specific gravity of only about 1.2 onto a toner carrier in a state where sufficient development is possible, it is necessary to precisely control the amount of electrostatic charge and fluidity of the toner. Therefore, it was concluded that it is necessary to appropriately adjust the particle size distribution of the toner. It goes without saying that, in general, the amount of electrostatic charge and fluidity of toner largely depend on its particle size distribution.

The present invention solves the above-mentioned requirements due to the method of developing a non-magnetic or weakly magnetic toner with a true specific gravity of 1.2 or less on a carrier mainly by non-magnetic force in the developing section. This is achieved by adjusting the particle size distribution.

The non-magnetic or weakly magnetic toner having the particle size distribution of the present invention was uniformly coated on the carrier by the coating method described below, and exhibited good development. Furthermore, this remained unchanged even under high temperature and high humidity environments, low temperature and low humidity environments, and even after long-term image production.

The particle size distribution of the toner can be measured using commonly available particle size distribution measuring devices such as a particle counter (Particle Data Co., Ltd.), a Hiatsuku Automatic Particle Size Distribution Analyzer (Hiatsuku Royco Co., Ltd.), a laser granulometer (CILAS Co., Ltd.), Measurements can be made using all types of equipment, including Microtrack (LEEDS & NORTHRUP), Micron Photosizer (Seishin Enterprises), Luzex (Nihon Regulator), and Coulter Counter (Coulter Electronics).

As the binder resin for the toner, monopolymers of styrene and its substituted products such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, and styrene-vinyl Toluene 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-methyl chloromethacrylate 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- Styrenic copolymers such as maleic acid copolymers and styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester resins, 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, paraffin wax, etc. can be used alone or in combination.

As the coloring material used in the toner, conventionally known carbon black, dyes, pigments, etc. can be used.
Conventionally known positive or negative charge control agents can be used in the present invention.

Toner is mixed with magnetic particles such as iron powder, nickel powder, ferrite powder, etc., and used as a developer for electrical latent images.

The non-magnetic toner used in the present invention is, for example,
It is manufactured by the conventionally known methods of kneading, pulverizing, and classifying, or by dispersing it in a liquid phase or gas phase and granulating it. Alternatively, it may be microencapsulated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiment examples using figures.

FIG. 1 is a diagram showing an example of a developing method using an insulating nonmagnetic toner and magnetic particles for toner application. In FIG. 1, 1 is an electrostatic image carrier, 2 is a toner carrier, 3 is a hopper (that is, a developer container), 6 is a bias power source for development, 5 is a non-magnetic toner, 50 is a fixed magnet, 52 is a magnetic brush made of a mixture of magnetic particles and non-magnetic toner for toner application;
Reference numeral 58 indicates a toner thickness regulating blade. The magnetic brush 52 formed on the toner carrier 2 is circulated by rotating the toner carrier 2, and the hopper 3
The non-magnetic toner inside is taken in and uniformly coated on the toner carrier 2 in a thin layer. The one-component non-magnetic toner 5 on the toner carrier 2 is produced by opposing the toner carrier 2 and the electrostatic image carrier 1 at a distance greater than the toner layer thickness.
is developed by flying onto the electrostatic charge image on the electrostatic image holder 1. The charge amount and thickness of the toner layer are determined by the magnetic brush 5.
This is controlled by the size of the brush and the degree of circulation of the brush. Between the electrostatic image carrier 1 and the toner carrier 2
is set to be larger than the toner layer thickness. The developing bias may be applied by the developing bias power supply 6.

FIG. 2 is a diagram showing still another example of the embodiment of the present invention. In FIG. 2, numeral 1 denotes a cylindrical electrophotographic photoreceptor that moves in the direction of arrow a. A non-magnetic sleeve 2, which is a toner carrier, is provided with a gap between the photoreceptor 1 and the photoreceptor 1. As shown in FIG. This sleeve 2 rotates in the direction of arrow b as the photoreceptor 1 moves. A fixed permanent magnet 50 is provided within the sleeve 2 as a magnetic field generating means. Reference numeral 3 denotes a hopper as a developer supply container, which, together with the sleeve 2, accommodates a developer mixture containing non-magnetic toner 5 and magnetic particles 60.

A magnetic brush made of magnetic particles 60 is formed near the nozzle surface of the sleeve 2 corresponding to the magnetic pole 62 of the magnet 50. When the sleeve 2 is rotated in the direction of arrow b, the magnetic brush circulates in the direction of arrow c near the magnetic pole 62 by appropriately selecting the arrangement position of the magnetic pole 62 and the fluidity and magnetic properties of the magnetic particles 60. A circulation layer 66 is formed.

On the other hand, at a point 68 on the downstream side of the magnetic pole 62 in the rotational direction of the sleeve, a magnetic blade 64 as a magnetic particle restraining member made of a magnetic material is placed at an appropriate distance from the sleeve 2. The sleeve is disposed so as to be inclined downstream in the direction of movement of the sleeve, with an angle δ formed between the line n and the center line l of the blade. The magnetic particles 60 are restrained at a point 68 on the surface of the sleeve 2 by a balance between the restraining force based on gravity, magnetic force, and the effect of the presence of the magnetic blade 64, and the conveyance force in the direction of movement of the sleeve 2, and are restrained to some extent. A stationary layer 65 is formed which is movable but mostly immobile. A magnetic particle layer consisting of the circulation layer 66 and the stationary layer 65 is formed on the surface of the sleeve 2. The magnetic particle layer contains toner 5, and the magnetic particles of stationary layer 65 are restrained on the sleeve surface by the aforementioned balance between the restraining force and the conveying force, but the toner is substantially non-magnetic. Therefore, it is not restrained by the magnetic field of the magnetic pole 62, and is coated uniformly and thinly on the sleeve surface by the mirroring force, and is transported as the sleeve rotates, facing the surface of the photoreceptor 1, and subjected to development. be done.

In the circulation layer 66, the arrow C
The magnetic brush is circulated as shown in FIG.
The non-magnetic toner 5 is taken in from the hopper 7 and returned to the lower part of the hopper 3, and this cycle is repeated thereafter. The magnetic blade 64 does not directly participate in this circulation.

The developing method used here is
The method described in Publication No. 32375 is preferred. A voltage is applied between the electrophotographic photoreceptor 1 and the toner carrier 2 by a bias power supply 6 . The bias power source 6 may be an alternating current or a direct current, but it is preferably one in which alternating current and direct current are superimposed. The developer provided by the development is supplied to the toner carrier 2 from the circulation layer 66, and the shortage in the circulation layer 66 is supplied to the developer layer 67 by the aforementioned environmental movement.

[Example 1] Styrene-BMA copolymer 100 parts by weight Phthalocyanine pigment 10 parts by weight Nigrosine 2 parts by weight The above materials were thoroughly mixed in a blender and then heated to 150°C.
The mixture was kneaded using two heated rolls. After the kneaded material was left to cool naturally, it was roughly pulverized with a cutter mill, then pulverized with a pulverizer using a jet air flow, and further classified using an air classifier to obtain a volume average particle size of 13.2 μm.
A toner with a particle diameter of 82% from 5.04 to 20.2 .mu.m was obtained (measurement was carried out using a Coulter Counter TA- manufactured by Coulter Electronics. The same applies to the following examples). The true specific gravity was 1.05.

Meanwhile, 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 in a ball mill for 6 hours. Mixed. This is 0.05
The coating was applied to a mm-thick aluminum plate using a wire bar so that the dry coating thickness was 40 μm, and the solvent was evaporated with hot air to create a zinc oxide binder-based 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.

20 g of the positively charged non-magnetic toner was mixed in advance with 20 g of iron powder carrier, and the mixture was placed in the developing device shown in FIG. When a uniform coating was obtained, the electrostatic latent image formed above was developed.

The toner carrier 2 is a stainless steel cylindrical sleeve with an outer diameter of 50 mm, the distance between the photosensitive drum surface and the sleeve surface is set to 0.25 mm, and the sleeve is supplied with a voltage of 400 Hz, 1000 V.
An alternating current of 150 V and a direct current bias of -150 V were applied.

Next, the powder image was transferred while irradiating -7 kV direct current corona from the back side of the transfer paper to obtain a copy image. Fixing was carried out using a commercially available plain paper copying machine (trade name: NP-5000, manufactured by Canon).

The resulting transferred image has a sufficiently high density of approximately 1.3,
There was no fogging at all, there was no toner scattering around the image, and the image was good with high resolution. Durability was continuously examined using the above toner, and the transferred images after 10,000 sheets were also completely uncolored compared to the initial images.

In addition, when the environmental conditions were set to 35℃ and 85%, the image density was almost the same as normal temperature and humidity, and a clear blue image was obtained without fogging or scattering, and the durability was almost unchanged until 10,000 sheets were printed. Nakatsuta. Next, a transferred image was obtained at a low temperature of 10°C and 10% humidity, and the image density was high, solid black areas were developed and transferred extremely smoothly, and the image was excellent with no scattering or hollow spots. Durability tests were conducted under these environmental conditions in continuous and intermittent modes, and the density fluctuation was ±0.2 up to 10,000 sheets, which was sufficient for practical use.

[Comparative Example 1] The toner of Example 1 was changed in crushing conditions and classification conditions, and the volume average particle size was 8 μm, and 48% of the particles were 5.04 to 20.2 μm.
And so. When this was coated on a holder in the same manner as in Example 1, the coating was uniform but thicker, and as compared to Example 1, good development could not be achieved.

[Comparative Example 2] The toner of Example 1 was changed to different grinding conditions and classification conditions, and the volume average particle size was 23 μm, and 36% of the particles were 5.04 to 20.2 μm.
And so. When this was applied onto a holder in the same manner as in Example 1, the application was not as uniform as in Example 1, and even when developed, the image had a lot of fog.

[Example 2] 20 g of the toner of Example 1 was mixed with 50 g of ferrite carrier in advance, and the mixture was placed in the developing device shown in FIG. When the sample was loaded and developed in the same manner as in Example 1, similar good results were obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing different types of developing devices used to carry out the developing method of the present invention. 1... Electrostatic image holder, 2... Toner carrier (non-magnetic sleeve), 3... Hopper (developer container),
5... One-component non-magnetic toner, 6... Development bias power supply, 50... Permanent magnet, 52... Magnetic brush,
58... Regulation blade, 60... Magnetic particle, 64
...Magnetic blade, 66... Circulating layer.

Claims (1)

[Claims] 1. An electrostatic image carrier that holds an electrostatic image on its surface and a toner carrier that carries and conveys non-magnetic toner on its surface are arranged with a certain distance between them in a developing section. and magnetic particles for toner application with a volume average particle size of 10~
A developer container storing non-magnetic toner having a true specific gravity of 1.2 or less and having a diameter of 20 μm and a volume distribution of 5.04 to 20.2 μm for 50% or more is disposed on the toner carrier, and the developer container is placed on the upstream side of the toner outlet of the developer container. A fixed magnet for forming a magnetic brush made of magnetic particles for toner application is disposed inside the toner carrier so as to be in contact with the toner carrier, and the toner is applied as the toner carrier rotates. By circulating magnetic particles in the developer container, a thin layer of the non-magnetic toner is formed on the toner carrier while taking in the non-magnetic toner, and a thin layer of the non-magnetic toner is formed on the toner carrier. A developing method, wherein the electrostatic image is developed by transferring the non-magnetic toner to the electrostatic image holder in a developing section.