JPH02281280A - Electrophotographic color developer and developing method using the same - Google Patents

Abstract

PURPOSE:To obtain copies superior in image quality in repeated copying operations by using a toner small in particle diameter and magnetic particles having a specified average particle diameter, a specified particle diameter distribution, and specified magnetic characteristics as the carrier. CONSTITUTION:When the toner as small in particle diameter as 6 - 11mum is used, the carrier to be used has an average particle diameter of 20 - 60mum, contains a fine powder of <=350 mesh in an amount of <=40wt.%, a fine powder of <=400 mesh in an amount of <=20wt.%, an ultrafine powder of <=500 mesh in an amount of 1 - 8wt.%, substantially not particles of <=11mum diameter measured by the microtrack method, and coarse particles of >=250 mesh in an amount of 7 - 10wt.%, and the magnetic particles to be used have a saturated magnetization of 55 - 75emu/g in a magnetic field of 3,000 oersted, a residual magnetization of <=10emu/g, and a coercive force of <=10 oersted, thus permitting copies superior in image quality to be obtained even after repeated copying operations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic color developer and a developing method, and more particularly to an improvement in an electrophotographic carrier useful for full-color copying electrophotography.

[Prior Art] Conventionally, regarding electrophotography, U.S. Patent No. 2.29
7.691, Special Publication No. 1977-23910, Special Publication No. 1977
As described in Japanese Patent No. 24748, electrostatic charge is applied to the photoconductive layer by corona discharge, and by exposing the photoconductive layer to a light image corresponding to the original, the charge in the exposed area is extinguished and the latent Perform image formation. Development is carried out by depositing a finely powdered electrostatic substance, so-called toner, on the obtained electrostatic latent image.

The toner is attracted to the electrostatic latent image depending on the amount of charge on the photoconductive layer, forming a toner image with shading. This toner image is transferred to a supporting surface such as paper or cloth as required, and permanently fixed to the supporting surface using a suitable fixing means such as heating, pressure, solvent treatment, or overcoating. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed onto the photoconductive layer.

In the development of an electrostatic latent image, the toner is mixed with a carrier having relatively large particles and used as an electrophotographic developer. The compositions of both the toner and the carrier are chosen such that, due to their mutual contact friction, the toner assumes a polarity opposite to the charge on the photoconductive layer. Also, as a result of contact friction between the two,
The carrier electrostatically deposits the toner on the surface, transports it as a developer through the development device, and also supplies the toner onto the photoconductive layer.

There are many known methods for developing a developer. Cascade development method described in U.S. Patent No. 2,818,552, magnetic brush method described in U.S. Patent No. 2,874,063, touchdown method described in U.S. Patent No. 2,895,847, etc.', developer carrying There is the so-called J/B development method, which is disclosed in Japanese Patent Laid-Open No. 62-63970, in which development is performed by applying a bias electric field consisting of an AC component and a DC component between a developing sleeve and a photoconductive layer. .

A typical method is the magnetic brush method. That is, magnetic particles such as steel or ferrite are used as carriers, and a developer consisting of toner and magnetic carrier is held by a magnet, and the magnetic field of the magnet arranges the developer in a brush shape.

When this magnetic brush contacts the electrostatic latent image surface on the photoconductive layer, only toner is attracted from the brush to the electrostatic latent image to effect development.

When a large number of sheets are continuously copied using an electronic copying device using a single-component developer, initially images are clear and of good quality, but after tens of thousands of sheets have been copied, the edge effect with many capri becomes noticeable and The result is an image with poor tonality and clarity.

In color copying using chromatic toner, continuous gradation is an important factor that affects image quality, and the occurrence of an edge effect in which only the peripheral areas of the image occur after copying multiple sheets is due to the gradation of the image. will be greatly damaged. This improves copying reproducibility, including color reproducibility in color copying, by forming a pseudo contour using an edge effect near the actual contour. In addition, the image area used in conventional black and white copying is less than 10%, and images such as letters, literature, and reports are mostly line images, whereas in color copying, the image area is is at least 20% or more, and solid images with gradation, such as photographs, catalogs, maps, and paintings, occupy a considerable degree of sharpness or area.

When continuous copying is performed using such originals with large image areas, copies with high image density are usually obtained at the beginning, but gradually the toner cannot be replenished to the two-component developer in time, and the density decreases. The replenishment toner and carrier may be mixed with each other in an insufficiently charged state, causing fog, or causing partial toner concentration (indicating the mixture ratio of toner and carrier) on the developing sleeve. There is a tendency for the image to increase or decrease, causing blurring of the image and making it impossible to obtain uniform white density of the image. This tendency is more noticeable when the diameter of the toner is reduced.

This is because the amount of toner contained in the developer (that is, toner concentration) is too low, or the rapid rise of frictional charging between the supplied toner and the carrier in the two-component developer is poor.
It is thought that insufficient development and fogging occur due to uncontrollable and insufficiently charged toner being involved in development. As a color developer, it is essential to have the ability to consistently output high-quality images in continuous copying of documents with large image areas. Conventionally, in order to deal with originals with large image areas and extremely high toner consumption, improvements have been made to developing devices rather than improvements to the developer itself. That is, in order to increase the chances of the developing sleeve coming into contact with the electrostatic latent image, attempts have been made to increase the circumferential speed of the developing sleeve or to make the developing sleeve larger in diameter.

Although these measures improve the developing ability, they also cause contamination inside the machine due to toner scattering from the developing device and overload on the developing device drive, which significantly limits the device life. Furthermore, in some cases, a large amount of developer is put into the developing device to compensate for the lack of developing capacity of the developer, but this also increases the cost due to the increased weight of the copying machine and the larger size of the device. , which is not very desirable, as it results in an overload on the driving of the developing device, as described above.

As an indication of the average particle size and particle size distribution of the carrier,
JP-A-51-3238, JP-A-58-14483
No. 9 and Japanese Unexamined Patent Publication No. 61-2041+46.

JP-A-51-3238 refers to a rough particle size distribution. However, it does not specifically disclose the magnetic properties that are closely related to the developability of the developer and the transportability within the developing device. Further, all the carriers in the examples have a mesh size of 250 or more, which accounts for about 80% by weight or more, and an average particle size of 60μ or more.

Furthermore, JP-A-58-144839 merely discloses the average particle diameter, but also mentions the amount of fine powder that affects the adhesion of carrier to the photoreceptor and the amount of coarse powder that affects the sharpness of the image. However, considering the characteristics of color copying, the distribution is not described in detail.

Further, JP-A-61-204846 makes the gist of the invention a combination of a copying device and a suitable developer, and does not specifically mention the particle size distribution or magnetic properties of the carrier. Furthermore, it is not even disclosed why the developer is effective for the copying device.

Additionally, JP-A-49-70630 describes the magnetic force of carriers, but these are based on iron powder, which has a higher specific gravity than ferrite, as the carrier material, and has a high saturation magnetism. . These iron powder carriers have been widely used in the past, but due to their high specific gravity, they tend to increase the weight of the copying device and overload the drive torque.
It is also highly dependent on the environment.

Furthermore, the ferrite carrier described in JP-A-58-23032 is a porous material with many pores, and such a carrier is prone to edge effects and has poor durability. However, it has been found to be unsuitable as a color carrier.

Until now, there has been a long-awaited developer that can make it possible to continuously copy images with a large image area with a small amount of developer, and that satisfies the characteristics peculiar to color copying without producing edge effects even after durability. Although developers and carriers have been studied, most of them have been proposed with black-and-white copying in mind, and very few have been proposed for full-color copying. In addition, it has the ability to continue copying images with an image area of 20% or more, which is close to a solid image, the reduction of edge effects, and the ability to maintain uniformity of image density among copies. A long-awaited career is in demand.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic color developer and a developing method that do not cause a decrease in image density or blur even when a color original with a large image area is continuously copied. be.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic color developer and a developing method that allow color copies with suppressed edge effects to be obtained even after repeated copying.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic color developer and a developing method that allow rapid rise in frictional charging between toner and carrier.

An object of the present invention is to provide an electrophotographic color developer and a developing method in which triboelectric charging is less dependent on the environment.

An object of the present invention is to provide an electrophotographic color developer and a developing method that have good transportability within a developing device.

[Means and effects for solving the problem] The inventors have 6
The present invention was arrived at as a result of extensive research into the optimal carrier for color copying using toner with a small particle diameter of ~11 microns.

Specifically, in the present invention, the average particle size is 2O-1i0μ, the amount of fine powder of 350 mesh or less is 40% by weight or less, the amount of fine powder of 400 mesh or less is 20% by weight or less, and the amount of fine powder of 400 mesh or less is 20% by weight or less, The amount of ultra-fine powder is 1 to 8% by weight, and furthermore, the amount of 11μ or less as measured by Microtrack is substantially 0, and the amount of coarse powder of 250 mesh or more is 10 to 7% by weight.
% by weight, a saturation magnetization of 55 to 75 emu/g in response to an applied magnetic field of 3000 oersteds, a residual magnetization of toemu/g or less, and a coercive force of 106 e or less are used as carriers for electrophotography. .

The electrophotographic carrier used in the present invention differs from conventionally known carriers in that it has a small average particle size and controls the amount of fine powder and coarse powder, resulting in a very narrow particle size distribution and sharp cut. Because of this, there is almost no ultrafine powder that adversely affects carrier adhesion, and the carrier is uniformly small in particle size. Therefore, the rise in triboelectricity with the toner is also favorably improved.

Furthermore, since the carrier is small in particle size and homogeneous, the amount of toner with good charging properties that can be contained in the carrier is much larger than that in a carrier with a broad particle size. When a carrier with a broad particle size is used, the fine powder carrier sometimes causes a phenomenon in which the carrier adheres to the photoreceptor during development. Further, the toner mixed with the coarse powder carrier often has an excessively high charge amount, resulting in a toner that is difficult to develop.

The content of ultrafine powder of 500 mesh or less is 1 to 8% by weight, preferably 2 to 6% by weight. If it exceeds 8% by weight, carrier adhesion and smooth frictional electrification with the toner are hindered, and the edge effect tends to grow.

If the amount is less than 1% by weight, the magnetic brush will become loose and the charging of the toner will be slow, causing toner scattering and fogging.

Further, the amount of coarse powder showing a carrier amount of 250 meshes or more is closely correlated with the sharpness of the image, and needs to be 1 to 7% by weight. If it exceeds 7% by weight, the toner transporting ability of the carrier will be reduced, toner scattering onto non-image areas will increase, and image resolution will be reduced and roughness will become more apparent. Therefore, the content of 250 mesh or more should be 7% by weight or less, preferably 5% by weight or less.

On the other hand, if it is less than 1% by weight, the fluidity of the developer deteriorates, causing the developer to shift in the developing device, making it difficult to obtain a stable image.

The average particle size of the carrier is preferably 20-60μ, more preferably 30-56μ. When the average particle size is less than 20 μm, carrier adhesion to the photoreceptor increases dramatically, and when the average particle size exceeds 60 μm, highlight reproducibility in color copying deteriorates.

The magnetic properties of the carrier are influenced by the magnetic roller built into the developing sleeve, and have a large effect on the development properties and transportability of the developer.

In the present invention, a two-component developer consisting of magnetic particles and insulating color toner is circulated and conveyed by fixing the magnetic roller on a developing sleeve with a built-in magnetic roller and rotating the developing sleeve by itself. When developing the electrostatic latent image carried on the surface of the electrostatic latent image carrier with a developer, (1) the developing sleeve has an outer diameter of 32 mm, and the magnetic roller has a five-pole configuration having repulsive poles; ■
The magnetic flux density in the development area is 600 to 1200 Gauss, and the saturation magnetization of the carrier is 75 emu to 55 emu.
When this is the case, it is suitable for color copying since it has excellent image uniformity and gradation reproducibility.

If the saturation magnetization exceeds 75 emu/g (for an applied magnetic field of 3000 oersteds), brush-like spikes composed of carrier and toner on the developing sleeve facing the electrostatic latent image on the photoreceptor during development. The image becomes stiff and stiff, resulting in poor gradation and reproduction of intermediate tones. Also, 5
If it is less than 5 cmu/g, it will be difficult to properly hold toner and carrier on the developing sleeve, and problems such as carrier adhesion and toner scattering will likely occur.

Furthermore, if the residual magnetization and coercive force of the carrier are too high, good conveyance of the developer in the developing device will be hindered, and image defects such as blurring and uneven density in solid images will likely occur, reducing the developing ability. This will result in a decline in therefore,
Unlike general black and white copying, in order to maintain developability in color copying, the residual magnetization must be 10 cmu/g or less.
It is preferably 5 emu/g or less, more preferably substantially 0, and the coercive force is 106 e or less (3000 oersted,
It is important that the applied magnetic field is preferably less than or equal to 6.06e, more preferably substantially O.

Next, an example of a developing device according to the present invention will be explained with reference to FIG.

The latent image carrier 1 is made of a-5t, Cds, ZnO2,0P
II: A photosensitive drum having a photoconductive insulating material layer such as a-5e.

The latent image carrier 21 is rotated in the direction of arrow a by a drive device (not shown). A developing sleeve 22 is in close proximity to or in contact with the latent image carrier 21, and is made of a non-magnetic material such as aluminum or 5O5316. The developing sleeve 22 has a right half-circumferential surface extending into the container 36 through a horizontally elongated opening formed in the lower left wall of the developing container 36 in the longitudinal direction of the container, and a left substantially half-circumferential surface exposed outside the container so as to be rotatably supported on a bearing. It is installed horizontally and is driven to rotate in the direction of the arrow.

Reference numeral 23 designates a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is inserted into the developing sleeve 22 and positioned and maintained at the position and orientation shown in the figure. It remains fixed in its position. This magnet 23 has four magnetic poles: an N-pole magnetic pole 23a, an S-pole magnetic pole 23b, an N-pole magnetic pole 23c, and an S-pole magnetic pole 23d. The magnet 23 may be an electromagnet instead of a permanent magnet.

Reference numeral 24 has a base fixed to the side wall of the container on the upper edge side of the opening of the developer supply device in which the developing sleeve 22 is disposed, and the tip side is made to protrude inside the container 36 beyond the position of the upper edge of the opening and extend along the longitudinal direction of the upper edge of the opening. The non-magnetic blade is a non-magnetic blade as a developer regulating member disposed in a horizontal direction, and is made by bending, for example, 5IJS31B into a dogleg shape in cross section.

Reference numeral 26 denotes a magnetic particle limiting member whose upper surface is in contact with the lower surface side of the non-magnetic blade 24 and whose front end surface is a developer guide surface 261. A portion constituted by the non-magnetic blade 24, the magnetic particle limiting member 26, etc. is a regulating portion.

27 is a magnetic particle with a resistance value of 107ΩcI11 or more,
Preferably, ferrite particles of 108 Ωcm or more (maximum magnetization 55 to 75e target u/g) are coated with an electrically insulating resin of 0.05 to 10% by weight to form 109 Ωcm to 1014 Ω.
cm may be used.

The resistance value of the magnetic particles was measured using a measuring electrode area of 40 m2.
Using a sandwich type cell with a distance between electrodes of 51 ft 0.4 cm, an applied voltage E (V/cm) between both electrodes was applied under a pressure of 1 kg to one electrode, and magnetic properties were detected from the current flowing through the circuit. The method used is to obtain the resistance value of the particles.

3F is a non-magnetic toner.

Reference numeral 40 denotes a sealing member for sealing the toner accumulated in the lower portion of the developer container 36, which is elastic and curved in the direction of rotation of the sleeve 22, and elastically presses the surface side of the sleeve 22. This sealing member 40 has an end on the downstream side in the rotational direction of the sleeve in a contact area with the sleeve so as to allow the developer to enter the inside of the container.

H is a toner replenishment roller that operates according to the output obtained from a toner concentration detection sensor (not shown). Examples of the sensor that can be used include a developer volume detection method, a piezoelectric element, an inductance change detection element, an antenna method using alternating bias, and an optical density detection method. By stopping the rotation of the roller, the non-magnetic toner 37 is replenished. The fresh developer supplemented with the toner 37 is mixed and stirred while being conveyed by the screw 61. Therefore, triboelectricity is applied to the replenished toner during this conveyance. Reference numeral 63 denotes a partition plate which is cut out at both ends in the longitudinal direction of the developing device, and the fresh developer conveyed by the screw 61 is passed to the screw 62 at this portion.

Further, the S magnetic pole 23d is a transport pole. The recovered developer after development is collected into a container, and the developer in the container is further conveyed to a regulating section.

Further, near 23d, the fresh developer conveyed by the screw 62 provided close to the sleeve is exchanged with the recovered developer after development.

Reference numeral 64 denotes a conveying screw that equalizes the amount of developer in the axial direction of the developing sleeve.

Note that this configuration is also effective when magnetic particles and non-magnetic or weakly magnetic toner are mixed in the developer container.

The distance d2 between the end of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 300 to 1000μ11, preferably 400μ
~900 μm. If this distance is smaller than 300 μm, magnetic particles, which will be described later, will tend to clog between the gaps, causing unevenness in the developer layer, and it will not be possible to apply the developer necessary for good development, resulting in a developed image with a thin and uneven density. There are drawbacks that can only be obtained. d2 is preferably 4001 or more in order to prevent uneven coating (so-called blade clogging) due to unnecessary particles mixed in the developer. Also 1
If it is larger than 000 μm, the amount of developer applied onto the developing sleeve 22 will increase, making it impossible to regulate the prescribed developer layer thickness.
As more magnetic particles adhere to the latent image carrier, circulation of the developer and development regulation by the developer limiting member 26, which will be described later, are weakened, leading to insufficient triboelectricity of the toner, which tends to cause fogging.

The angle θ1 is between -5° and 356°, preferably between 06° and 25°. When θ1 is 5°, the thin layer of developer formed by magnetic force, mirror force, cohesive force, etc. acting on the developer becomes sparse and uneven, and when θ>35@, the non-magnetic blade The amount of developer applied increases, making it difficult to obtain a predetermined amount of developer.

Even when the sleeve 22 is rotated in the direction of the arrow, this magnetic particle layer has a magnetic force 1 and a restraining force based on gravity and the sleeve 22
The movement slows down as it moves away from the sleeve surface due to balance with the conveying force in the direction of movement. Of course, some things fall due to the influence of gravity.

Therefore, the arrangement positions of the magnetic poles 23a and 23d and the magnetic particles 27
By appropriately selecting the fluidity and magnetic properties of the magnetic particle layer, the closer the magnetic particle layer is to the sleeve, the more it is transported toward the magnetic pole 23a, forming a moving layer. Due to the movement of the magnetic particles, the magnetic particles are conveyed to the development area as the sleeve 22 rotates and are subjected to development.

As the toner binder resin used with the carrier of the present invention, the following can be used.

For example, polystyrene, chloropolystyrene, poly-α-
Methylstyrene, styrene-chlorostyrene copolymer,
Styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-
Vinyl acetate copolymer, styrene-maleic acid copolymer,
Styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate) copolymers, etc.), styrene-methacrylate ester copolymers (styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-phenyl methacrylate copolymers, etc.) ), styrene resins such as styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic ester copolymer (styrene or a homopolymer or copolymer containing a styrene substitute), vinyl chloride resin, Styrene-vinyl acetate copolymer, lysine-modified maleic acid resin, phenol resin, epoxy resin,
Polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin,
Examples include silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, and polyvinyl butyral resin. In the practice of the present invention, particularly preferred resins include styrene-acrylic acid ester resins and polyester resins.

In particular, the following formula (wherein R is ethylene or propylene group, X%
Each y is an integer of 1 or more, and the average value of x+y is 2 to 10. ) as a diol component, and a carboxylic acid component consisting of a divalent or higher carboxylic acid, its acid anhydride, or its lower alkyl ester, such as fumaric acid, maleic acid, maleic anhydride, and phthalic acid. , terephthalic acid, trimellitic acid, pyromellitic acid, etc., are more preferable for use in color toners because they have sharp melting characteristics.

As the carrier used in the present invention, known materials can be used as long as they do not interfere with the gist of the present invention, such as surface oxidized or unoxidized iron, nickel, copper, zinc, cobalt, manganese, chromium, rare earth. metals such as metals, their alloys or oxides, and ferrites. Preferably, ferrite selected from zinc, copper, nickel, and cobalt metals can be used from the viewpoint of magnetic properties.

The particle size distribution may be controlled by any method as long as it satisfies the above particle size distribution, but it is preferable to use a mesh for the coarse powder side and air classification for the fine powder side.

It is also possible to coat the surface of the carrier with a resin or the like. As a method, a method in which a coating material such as a resin is dissolved or suspended in a solvent and applied and adhered to the carrier, a method in which the coating material is simply mixed in powder form, etc. can be applied.

Substances that adhere to the carrier surface vary depending on the toner material, but include, for example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal complex of ditertiary butylsalicylic acid, styrene resin, It is appropriate to use acrylic resin, polyacid, polyvinyl butyral, nigrosine, aminoacrylate resin, basic dye and its lake, fine silica powder, fine alumina powder, etc. singly or in combination.

The amount of the above compound to be treated may be appropriately determined so that the carrier satisfies the above conditions, but generally the total amount is 0.1 to 30% by weight (preferably 0.2 to 30% by weight) based on the carrier of the present invention.
20% by weight) is desirable.

In the present invention, a particularly preferred embodiment is a combination of styrene-2-ethylhexyl acrylate-methyl methacrylate (20-60:5-30:10-50).

Further, as the ferrite, a ternary ferrite of Cu-Zn-Fe is particularly preferable.

When preparing a two-component developer by mixing with the 6-11μ color toner used in the present invention, the mixing ratio is 2.0% to 12% by weight, preferably 3.0% as a toner concentration in the developer. Good results are usually obtained between % and 10% by weight. If the toner concentration is less than 2.0%, the image density will be low enough to be unpractical, and if it is more than 12%, fogging and in-machine scattering will increase even if a carrier within the particle size distribution range of the present invention is used, and the service life of the developer will be shortened. is easy to shorten.

As the coloring agent used when forming a color developer together with the carrier of the present invention, examples of the dye include C,1, Direct Red 1, C,1, Direct Red 4, C,1, Acid Red 1, C,I Basic Red 1, C,1, Modern Tread 30, C,1, Direct Blue 1, C,1, Direct Blue 2, C,
1, Acid Blue 9, C, 1, Acid Blue 15,
There are C,1, Basic Blue 3, C,R, Basic Blue 5, C,1, Mordand Blue, etc.

Pigments include Naphthol Yellow S, Banza Yellow G, Permanent Yellow NCG, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Permanent Red 4R, Watching Red Calcium Salt, Brilliant Cardin 3B, First Violet B1 Methyl Violet Examples include Lake, Phthalocyanine Proof Earth Sky Blue, and Indan Stremblu-BC.

Preferably, the pigments are disazo yellow, insoluble azo, and copper phthalocyanine, and the dyes are basic dyes and oil-soluble dyes.

Particularly preferably C, 1, Pigment Yellow 17, C,
1, Pigment Yellow 15, C,1, Pigment Yellow 13, C,1, Pigment Yellow 14, C,1,
Pigment Yellow 12, C, 1, Pigment Red 5
,C,I.

Pigment Red 3, C, 1, Pigment Red 2, C
, 1, Pigment Red 6, C, 1, Pigment Red 7, C, 1, Pigment Blue 15, C, 1, Pigment Blue 16, 2 to 2 carboxybenzamidomethyl groups
Examples include a copper phthalocyanine pigment having three carboxybenzamidomethyl groups, or a copper phthalocyanine pigment having the structural formula (1) shown below, which is a Ba salt in which the phthalocyanine skeleton is substituted with two to three carboxybenzamidomethyl groups.

(The following is a blank space) n=2 to 3 or -H, and R and R' represent an alkylene group having 1 to 5 carbon atoms. However, this excludes the case where all of x1 to x4 are -H. ] As a dye, C, 1, Solvent Red 49. C,I
Solvent Red 52, C, 1, Solvent Red 10
9, C,1, Basic Red 12, C,1, Basic Cret 1, C,1, Basic Red 3b, etc.

The method for measuring particle size distribution in the present invention is as follows.

1. Weigh approximately 100g of the sample to the nearest 0.1g.

2. For the sieve, use a standard sieve of 100Mesh to 400Mesh (hereinafter referred to as sieve), and 100.145.20 from the top.
0°250, 3.50.400 sizes are stacked in order, a tray is placed at the bottom, and the sample is placed in the top sieve and covered with a lid.

3. Shake this with a vibrator for 15 minutes at a horizontal rotation rate of 285±6 times per minute and an impulse rate of 150±1o times per minute.

4. After sieving, weigh out the iron powder in each node and tray to the nearest 0.1 g.

5. Calculate the weight percentage to the second decimal place, JISZ84
Round to the first decimal place by 01.

However, the inner diameter of the sieve frame above the sieve surface is 200 mm.
, the depth from the top surface to the sieve surface is 45 mm.

The total weight of the iron powder in each part shall not be less than 99% of the starting mass of the sample.

Further, the average particle diameter is determined from the above-mentioned particle size distribution measurement values according to the following formula.

(145MEsl (remaining amount of sieve) x 1224 (200M
Remaining amount of ESH sieve) x 90 + (Remaining amount of 250 MESH sieve) x 68 + (Remaining amount of 350 MESH sieve) x 52 + (4
00MESH sieve remaining amount) x 38 + (total sieve passing amount) x 1
7) The amount of carrier less than 500 mesh is calculated from the weight loss by placing a 50 g sample on a 500 mesh standard sieve and suctioning it from below.

For measuring the magnetic properties of carriers, the device is BHU-
A 60-inch magnetization measuring device (manufactured by Riken Keizai) is used.

The measurement sample weighed approximately 1.0 g, had an inner diameter of 7 mmφ, and a height of 10 mm.
Fill it into a cell of 1.0 mm in size and set it in the above-mentioned apparatus.

For measurements, the applied magnetic field is gradually applied and varied up to a maximum of 3,000 oersteds. Then, the applied magnetic field is reduced, and finally a hysteresis curve of the sample is obtained on recording paper. From this, saturation magnetization and residual magnetization.

Find the coercive force.

[Examples] The present invention will be explained in detail below using Examples. Part 1”
means parts by weight.

Example 1 Yellow, magenta, cyan, and black color toners were applied to 100 parts of a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid using the colorant and charge control agent in the prescribed amounts shown in Table 1. Obtained.

The manufacturing method is to pre-mix the above prescription amounts thoroughly using a Henschel mixer, melt-knead at least twice using a Miki roll mill, cool, and then coarsely grind to about 1 to 2 mm using a hammer mill, and then air It was pulverized to a particle size of 30 am or less using a jet type pulverizer. Furthermore, the obtained finely pulverized product was classified to select a particle size of 2 to 12 μ so as to have the particle size distribution of the present invention, and fine silica powder treated with hexamethyldisilazane as a flow improver was added to each classified product.
A color toner was prepared by externally adding 0.5 parts to 00 parts and 0.3 parts of alumina. The volume average particle size of this toner is 7.8
It was μ.

4 to 6 parts of these color toners were mixed with carrier (2) shown in Table 2 in a total amount of 100 parts to prepare a developer.

This carrier is styrene-2-ethylhexyl acrylate-methyl methacrylate (st-2E) IA-M
MA) copolymer (copolymerization ratio 45:20:35) to about 0
It was a coated ferrite carrier coated with a film thickness of , 5μ.

The 500 mesh pass rate was 3.7%.

Furthermore, it was confirmed by Microtrack that the content of magnetic particles of 11 μm or less was substantially zero.

The developer concentration of each color toner is 4%, 4%,
5% and 6%.

A commercially available Canon color copier (C
LC-1) was modified to incorporate a 5-pole magnetic roller with a main developing pole of 980 gauss into a developing sleeve with a sleeve diameter of 32 mm, and the peripheral speed of the sleeve was increased to 28 mm.
The speed was set to 0 mm/sec, and a test was conducted using an original with an image area of about 40% in full color mode.

As a result, a full-color image was obtained that faithfully reproduced the original color chart with little edge effect even after printing 15,000 sheets. Moreover, images without blurring or density reduction were obtained even during continuous copying, and transport within the copying machine and developer concentration detection were also good and stable. In addition, low temperature and low humidity (
15℃, 10%RH) and high temperature (35℃, 85%RH)
) A full-color image with excellent colors was obtained even under the environment of I). 0) Even when an IP film was used, the toner permeability was very favorable.

Fruit 81 (+TL colorant for Smagenta C, R, Paysic Red 12゜0
．． Part 8, C, 1, Disperse Violet 31°0.
A single-color magenta toner durability test was conducted using Carrier (2) in Table 2 instead of 2 parts, and even after 2,000,000 copies, good image density and clear images were obtained. The carrier's 500 mesh pass rate at this time was 2.9%.

Button 101 Using Carrier O in Main Table 2, change the colorant for cyan to 6.0 parts of C,1, Pigment Blue 15, and change the colorant for yellow to 2.3 parts of C,1, Disperse Yellow 54. and in a high temperature environment (32.5°C, 85% RH) in the same manner as in Example 1 except that an original with an image area of 50% was used.
When tested in Example 1, a desirable image with no fog and good color balance was obtained, but it was slightly inferior to Example 1. The 500 mesh pass rate at this time was 2%.

Comparative Example 1 Image printing was carried out in the same manner as in Example 2 except that carrier O in Table 2 was used, and the decrease in image density was 01 greater than in Example 1 at low temperature and low humidity.

The carrier's 500 mesh pass rate at this time was 7.3%.
Met.

- A test was carried out in the same manner as in Example 2 except that the carrier was changed to carrier [F] shown in Table 2. However, during continuous copying, the image density gradually decreased and the edges were more sharp than in the Example. This resulted in poor tone reproducibility.

The 500 mesh pass rate at this time was 0.2%.

Comparative Example 3 A test was conducted in the same manner as in Example 2, except that the carrier was thoroughly cut so that 250 meshes or more were virtually zero and changed to carrier [F] in Table 2. Initially, the test was very good. Although an image was obtained, the image area was 6 at low temperature and low humidity.
When continuous copying was performed using a small consumption chart on the order of %, uneven image density occurred, and the developer in the developer container was unevenly distributed.

The carrier's 500 mesh pass rate at this time was 5.2%.
Met.

(The following is a blank space) [Effects of the Invention] The present invention uses magnetic particles having a specific particle size distribution and magnetic properties as a carrier for toner with a small particle diameter of 6 to 11 μm, so that image quality can be maintained even with repeated copying. Copies with excellent quality can be obtained, and transportability within the developing device is also good.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a developing device according to the present invention.

Claims (3)

[Claims] (1) A two-component system containing at least magnetic particles and insulating color toner, in which both the magnetic roller and the developing sleeve are fixed on a developing sleeve with a built-in magnetic roller, or the developing sleeve is rotated with the magnetic roller fixed. An electrophotographic color developer used in a method of circulating an electrophotographic color developer and developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier with the two-component developer. (a) the volume average particle size of the insulating color toner is from 6 to 11;
(b) the weight average particle diameter of the magnetic particles is 20 to 60 μ, the amount of fine powder of 350 mesh or less is 40% by weight or less, the amount of fine powder of 400 mesh or less is 20% by weight or less, The amount of ultrafine powder of 500 mesh or less is 1 to 8% by weight, the amount of coarse powder of 250 mesh or more is 1.0 to 7% by weight, and the saturation magnetization of the magnetic particles in response to an applied magnetic field of 3000 Oe is 55 to 75 emu. /g, residual magnetization is 10 emu/g or less, and coercive force is 10 μe or less. (2) On a developing sleeve with a built-in magnetic roller, the magnetic roller is fixed and the developing sleeve is rotated to circulate and convey a two-component electrophotographic color developer containing at least magnetic particles and insulating color toner. In the method for developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier with the two-component developer, (a) the developing sleeve has an outer diameter of 32 mm, and the magnetic roller has a repulsion pole. (b) the magnetic flux density in the development region is 600 to 1200 Gauss, and (c) the two-component developer described in claim (1) is used. Image development method. (3) The electrostatic latent image developing method according to claim (2), wherein the magnet roller has substantially five magnetic poles.