JPH0458028B2 - - 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 carrying member holding a developer on its surface is opposed to a latent image holding member to develop an electrostatic image on the surface of the holding member, the developer stored in the developer storage means is used. When pumping up the developer under the developer carrier 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 gap between the electrostatic image holder and the developing roller in the developing section,
There is a method of developing an electrostatic image by setting the gap length to be larger than the thickness of the toner coating layer on the developing roller.

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 triboelectric charge amount of 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 charged 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. There are various disadvantages compared to developing methods using . For example, a phenomenon occurs that many toners are not applied relatively thinly and uniformly on the carrier. Furthermore, for example, even if the toner is applied relatively uniformly, toner adheres to non-image areas, resulting in so-called background fog. 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 more toner results in decreased image density and lower quality images. Furthermore, many toners have the disadvantage that they sometimes cause a decrease in image density or sometimes cause background fog due to environmental changes such as high temperature and high humidity, 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 that overcomes the above-mentioned drawbacks.
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 the background fog phenomenon 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.

The feature is that the electrostatic image carrier that holds the electrostatic image on the surface and the toner carrier that carries the toner on the surface are arranged with a certain gap in the developing section, and the humidity is 60% at 25℃. The present invention provides a developing method in which a toner having a degree of aggregation of 30% or less is supported on a toner carrier to a thickness thinner than the gap, and the toner is transferred to the electrostatic image holder in a developing section for development.

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 drawbacks, 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 uniform 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 will be too strong, making it difficult for the toner to transfer to the electrostatic image carrier, resulting in a decrease in image density and This results in the appearance of a quality image.

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 the toner onto the 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, and for this purpose, the degree of aggregation and true It was concluded that it is necessary to adjust the specific gravity appropriately.

The present invention solves the above-mentioned requirements caused by the method of carrying and developing toner having non-magnetism or weak magnetism on a carrier mainly by non-magnetic force in the developing section, by adjusting the agglomeration degree and true specific gravity of the toner. This is achieved by making adjustments.

The non-magnetic or weakly magnetic toner having a degree of agglomeration and true specific gravity as in the present invention can be uniformly coated onto a carrier by many coating methods as described below, and exhibits a good development state. . Furthermore, there was no change in the performance even under high temperature, high humidity, low temperature and low humidity environments, or after long-term image display.

That is, in the present invention, an electrostatic image carrier that holds an electrostatic image on its surface and a toner carrier that carries and conveys nonmagnetic toner on its surface are arranged with a certain gap in a developing section, A developer container storing magnetic particles for toner application and non-magnetic toner is disposed on the toner carrier, and the magnetic particles for toner application are placed in contact with the toner carrier upstream of the toner outlet of the developer container. A fixed magnet for forming a magnetic brush of particles is disposed inside the toner carrier, and the toner application magnetic particles are circulated within the developer container as the toner carrier rotates. , forming a thin layer of the non-magnetic toner on the toner carrier to be thinner than the gap while taking in the non-magnetic toner, and converting the non-magnetic toner on the toner carrier into the electrostatic image in a developing section. A developing method in which the electrostatic image is developed by transferring the electrostatic image to a holding body, wherein the non-magnetic toner has a degree of aggregation of 30% or less at a temperature of 25° C. and a humidity of 60%, and the magnetic particles for toner application are One side of each rectangular parallelepiped circumscribing the particle is a>b>c or a
>b=c or a=b>c so that a, b,
It relates to a developing method characterized by having a shape in which the average b/a is 0.4 to 1.0 and the average c/a is 0.4 to 0.95 when c is defined.

Humidity at 25°C in the toner used in the present invention
The reason why the degree of aggregation at 60% is 30% or less is because if the degree of aggregation is larger than the above range, the electrostatic attraction between the toner and the toner carrier will be too strong, making it difficult for the toner to transfer to the electrostatic image carrier. As a result, image density may be reduced.

Furthermore, in the toner used in the present invention,
The reason why the true specific gravity is 1.2 or less is because if the true specific gravity is larger than the above range, it becomes difficult for the toner to transfer to the electrostatic image carrier, resulting in a decrease in image density.

Furthermore, in the magnetic particles for toner application preferably used in the present invention, one side of each rectangular parallelepiped circumscribing the magnetic particles is a>b>c or a>b=
When a, b, and c are defined so that c or a=b>c, the average of b/a is 0.4 to 1.0 and c/a
Using magnetic particles having a shape with an average of 0.4 to 0.95, for example, if the shape is perfectly spherical, fog may occur due to the brush circulation being too fast or the ability to regulate the amount of toner applied. disadvantages such as the occurrence of On the other hand, if the shape is flat like a thin plate, for example, the circulation of the brush may be poor, or the force regulating the amount of toner applied may be too large, resulting in a local density drop or, in some cases, partial image loss. Problems such as white spots may occur. Therefore, it is preferable that the shape of the magnetic particles be in an intermediate range between a completely spherical shape and a flat shape.

In the present invention, the shape of this intermediate region is defined as follows. First, measure the magnetic particles at an appropriate magnification.
Photographs will be taken using a SEM (scanning electron microscope).
At this time, take several screens in which the electron beam is hitting the same particle perpendicularly to the sample stage on which the magnetic particle is placed, and another screen in which it is hitting as horizontally as possible.
Now draw a rectangular parallelepiped that circumscribes one particle. Furthermore, a, b, and c are set so that each side of this rectangular parallelepiped satisfies a>b>c, a>b=c, or a=b>c, and a, b, and c are actually measured.

The above operation is performed randomly for at least 20 particles or more, and the average of b/a and c/a is determined.

In the present invention, magnetic particles having a shape with an average b/a of 0.4 to 1.0 and an average c/a of 0.4 to 0.95 are preferred, and more preferably b/a
is 0.5 to 1.0c/a is preferably in the range of 0.5 to 0.9.

As such magnetic particles for toner application, metals such as iron, nickel, cobalt, manganese, chromium, rare earths, and alloys or oxides thereof, whose surface is oxidized or unoxidized, and their alloys or oxides can be used. Alternatively, it may be coated with a suitable treatment agent. Moreover, there are no special restrictions on the manufacturing method.

The method for measuring the degree of aggregation used in the present invention is to place toner on a sieve, apply vibrations, and measure the proportion of toner remaining on the sieve.

According to this method, the larger the proportion of toner remaining on the sieve, the greater the degree of toner aggregation, indicating that toner particles tend to aggregate and behave. Specifically, it is measured using a powder tater manufactured by Hosokawa Micrometics Laboratory at a temperature of 25±1°C and a humidity of 60±5%.

Arrange the 60 mesh, 100 mesh, and 200 mesh sieves in this order, top to bottom, and set them on the shaking table.
Place 2g of toner on a 60 mesh sieve,
Apply a voltage of 47V to the vibration system and give it vibration for 40 seconds.

After completion, the weight of the toner remaining on each sieve is measured, weighted by 0.5, 0.3, and 0.1, and added to express the degree of aggregation as a percentage.

As the binder resin for the toner, monopolymers of styrene and its substituted products such as polystyrene, polyP-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-alpha 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-
Styrenic copolymers such as acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; 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, 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.

In order to use the toner as a magnetic toner, it may contain magnetic powder. Such magnetic powder is a substance that is magnetized when placed in a magnetic field, and includes powders of ferromagnetic metals such as iron, cobalt, and nickel, and alloys and compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is preferably 15% by weight or less based on the weight of the toner.

For toner, use iron powder, glass beads,
It is mixed with carrier particles such as nickel powder or ferrite powder and used as a developer for electrical latent images.

Furthermore, the toner used in the present invention may be produced by any method. For example, there are those that undergo kneading, pulverization, and classification as conventionally known, and those that are dispersed in a liquid phase or gas phase and granulated. Alternatively, it may be microencapsulated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiment examples and with reference to the drawings.

FIG. 1 is a diagram showing still another example of the embodiment. In the figure, 1 is an electrostatic image carrier, 2 is a toner carrier, 3 is a hopper which is a developer container, 5 is a non-magnetic toner, 50 is a fixed magnet, 51 is a magnetic particle,
Reference numeral 52 indicates a magnetic brush using a toner mixture, and reference numeral 58 indicates a blade for regulating the toner thickness. A magnetic brush 52 formed on the toner carrier 2 is circulated by rotating the toner carrier 2, takes in the toner in the hopper 3, and uniformly coats the toner carrier 2 in a thin layer. The toner carrier 2 and the electrostatic image carrier 1 are opposed to each other with a gap larger than the toner layer thickness, and the one-component nonmagnetic toner 5 on the toner carrier 2 is flown onto the electrostatic charge image on the electrostatic image carrier 1. Let it develop. The amount of charge and thickness of the toner layer are controlled by the size of the magnetic brush 52 and the degree of circulation of the brush. The gap between the electrostatic image carrier 1 and the toner carrier 2 is set to be larger than the toner layer thickness.

a, b, and c indicate the rotation directions of the electrostatic image carrier and the toner carrier magnetic brush, respectively. d indicates magnetic particles not bound by magnetic poles.

The present invention will be explained in detail in the following examples. Note that all parts in the following formulations are parts by weight.

[Example 1] Styrene-butyl methacrylate (75:25) copolymer 100 parts Phthalocyanine pigment 8 parts Nigrosine 2 parts The above materials were thoroughly mixed in a blender and then heated to 150°C.
The mixture was kneaded using two heated rolls. After allowing the kneaded product to air, it was roughly pulverized using a cutter mill, then pulverized using a pulverizer using a jet air flow, and further classified using an air classifier to obtain a powder of 5 to 20 μm.
The measurements were carried out using a Coulter Counter TA- manufactured by Coulter Electronics. (The same applies to the following examples). A blue toner was obtained by adding 0.5 part of colloidal silica to the above powder.

This toner had a true specific gravity of 1.03 and a degree of aggregation of 13.8%.

As the magnetic particles, sponge iron powder with a particle size of 70 to 100 μm was used. When the magnetic particles were observed with a scanning electron microscope, the average b/a was 0.71 and the average c/a was 0.63.

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 with 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-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.

When the toner was put into a developing device as shown in FIG. 1, a uniform application state was obtained.
The electrostatic latent image formed above was developed. In this case, the toner carrier 2 was a stainless steel cylindrical sleeve with an outer diameter of 50 mm, and the distance between the photosensitive drum surface and the sleeve surface was set to 0.25 mm, and an alternating current of 400 Hz, 1000 V, and a direct current bias of -150 V were applied to the sleeve.

Next, the powder image was transferred while irradiating -7 KV direct current corona from the back side of the transfer paper to obtain a copied image. For fixing, use a commercially available plain paper copier (product name: NP-5000,
(manufactured by Canon).

The resulting transferred image had a sufficiently high density of 1.3, had no fogging, had no toner scattering around the image, and was a good image with high resolution. Durability was continuously examined using the above toner, and the transferred images after 10,000 sheets were also completely devoid of color compared to the initial images.

In addition, when the environmental conditions were set to 35℃ and 85%, the image density was 1.23, a value that was almost unchanged from normal temperature and humidity, and a clear blue image was obtained without fogging or scattering, and the durability was up to 10,000 sheets. There was almost no change. Next, a transferred image was obtained at a low temperature of 10° C. and 10% humidity, and the image density was as high as 1.35. Even solid black areas were developed and transferred extremely smoothly, resulting in an excellent image with no scattering or voids. 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] A blue toner with a true specific gravity of 1.03 and a cohesion degree of 31.3% was obtained in the same manner as in Example 1 except that 0.2 parts of colloidal silica was added. and the image quality also deteriorated.

[Comparative Example 2] A blue toner with a true specific gravity of 1.38 and a cohesion degree of 19.6% was obtained in the same manner as in Example 1 except that 40 parts of magnetite was added and kneaded. and the color tone also decreased.

[Comparative Example 3] The same procedure as in Example 1 was carried out except that iron powder having a flaky flat shape with an average of b/a of 0.55 and an average of c/a of 0.25 was used as the magnetic particles. When an image was produced, poor circulation of the magnetic particles occurred, causing a partial decrease in density.

[Example 2] In the same manner as in Example 1 except that perylene red pigment was used as the pigment in Example 1, a true specific gravity of 1.05,
A red toner with a degree of cohesion of 11.8% was obtained, and when images were produced, good results similar to those of Example 1 were obtained.

[Example 3] An image was produced in the same manner as in Example 1 except that ferrite particles having an average b/c of 0.94 and an average of c/a of 0.89 were used as the magnetic particles, and the results were good. I got good results.

[Example 4] Image formation was carried out in the same manner as in Example 1, except that slightly flat iron powder with an average of b/a of 0.57 and an average of c/a of 0.52 was used as the magnetic particles. In the end, we obtained good results.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a specific example of a developing device used to carry out the developing method of the present invention. 1... Electrostatic image carrier, 2... Toner carrier, 3
... Hopper, 5 ... Insulating non-magnetic toner, 50
... Permanent magnet, 51 ... Magnetic particle, 52 ... Magnetic brush, 58 ... Regulation blade.

Claims (1)

[Scope of 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 gap in a developing section. , a developer container storing magnetic particles for toner application and non-magnetic toner is disposed on the toner carrier, and a developer container for toner application is placed in contact with the toner carrier upstream of a toner outlet of the developer container. A fixed magnet for forming a magnetic brush made of magnetic particles is disposed inside the toner carrier, and the toner applying magnetic particles are circulated within the developer container as the toner carrier rotates. forming a thin layer of the non-magnetic toner on the toner carrier to be thinner than the gap while taking in the non-magnetic toner; A developing method of developing the electrostatic image by transferring it to an image carrier, wherein the non-magnetic toner has a degree of aggregation of 30% or less at a temperature of 25°C and a humidity of 60%, and the toner coating magnetic particles are One side of each rectangular parallelepiped circumscribing the magnetic particles is a>b>c or a
>b=c or a=b>c so that a, b,
A developing method characterized by having a shape in which the average b/a is 0.4 to 1.0 and the average c/a is 0.4 to 0.95 when c is defined.