JPH07191493A - Electrostatic latent image developer - Google Patents

Abstract

PURPOSE:To enhance the reproducibility of lines and to faithfully and advantageously develop a latent image formed on a photoreceptor by electrostatic latent image developer. CONSTITUTION:This is the electrostatic latent image developer 30 obtained by mixing electric field conditioner constituted of binding resin and magnetic powder in developer obtained by mixing at least carrier and toner. The electrostatic charging of toner does not depend on frequency that the toner comes contact with the carrier or the other member but depends on the movement of the charge in the toner by the electrical conductive effect of the electric field conditioner. By the electric field conditioner, the electric charge is taken from the toner electrostatically charged much because the contacting frequency is many and the electric charge is imparted to the toner electrostatically charged little. Therefore, the distribution of the electrostatic charge quantity of the toner is more uniformized than a simple contact type electrostatic charge method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developer, and more particularly to a novel electrostatic latent image developer mainly applied to electrophotographic developing systems such as printers and facsimiles.
The present invention relates to a developer that can be suitably applied to any developing method as long as it is a printing method for developing an electrostatic latent image.

[0002]

2. Description of the Related Art Conventionally, various electrophotographic developing methods for developing an electrostatic latent image have been proposed, which are roughly classified into a one-component developing method and a two-component developing method. Among these methods, the one-component developing method uses a developer composed of only toner that is developed into an electrostatic latent image on a photoreceptor. Further, this one-component developing system includes a type using a magnetic toner and a non-magnetic toner, and both types form a thin developer layer on a toner carrier. Further, in the two-component developing system, a developer having a mixing ratio of 95 to 98% carrier and 2 to 5% toner is used on a weight basis. Note that the toner at this time is a non-magnetic toner, and if the mixing ratio is 5% or more, fogging of the toner occurs in the non-printed portion, resulting in deterioration of image quality.

Further, a method has been proposed in which the toner of the developer in this two-component developing system is used as a magnetic toner to increase the mixing ratio of the toner, which is between the above-mentioned one-component developing system and two-component developing system. Because there is
It is also called the 1.5-component developing method. This 1.5-component developing system uses carrier 30-80%, toner 20-70
The developer is constituted by a mixing ratio of%. And this 1.
The five-component developing method is similar to the above-described two-component developing method in that a sleeve containing a magnet roll is used as a toner carrier, and a developer layer having a layer thickness larger than that of the one-component developing method is formed on the toner carrier. I am doing it. Therefore, in the 1.5-component developing method, although the carrier mixing ratio is low,
The thick layer on the sleeve not only causes a lot of fogging of the toner on the non-printed portion, but also has a problem that the sharpness of lines and characters becomes dull.

Further, the magnetic brush in the 1.5-component developing system is characterized in that the spike height is lower than that of the magnetic brush formed of the sleeve and the magnet roll in the 2-component developing system. Since the distance between the photoconductor sleeve and the photoconductor sleeve can be reduced by the lower amount, the 1.5-component developing method is more faithful to the development of the electric field between the photoconductor and the sleeve. It has the advantage that

[0005]

However, even with this 1.5-component developing system, the reproducibility of fine lines was not satisfactory. For example, while the laser dot diameter is about 80 μm, the line thickness is 100-
Even if an image having a size of 150 μm and a 1-dot space between lines is printed, the image is often printed, and the same print result as when a filled image is output appears. In addition, there is an inherent problem that the toner is scattered around the characters and the sharpness of the characters becomes dull if the laser dots are not faithfully reproduced.

The present invention has been made to solve the above problems, and in a developing system for developing an electrostatic latent image, the reproducibility of lines is improved and the latent image formed on the photosensitive member is improved. It is an object of the present invention to provide an electrostatic latent image developer capable of advantageously performing faithful development.

Another object of the present invention is to provide an electrostatic latent image developer in which the conductivity of the developer is increased so that the toner to be developed is uniformly charged.

[0008]

In order to achieve the above-mentioned object, the electrostatic latent image developer of the present invention comprises a binder in which at least a carrier and a toner are mixed, and a binder resin and magnetic powder. It is a mixture of the constituted electric field adjusters.

The volume resistance of the electric field adjusting agent is 8 × 1.
It has a conductivity of 0 ⁸ Ωcm or less, and can make the triboelectric charge amount of the toner uniform.

[0010]

The electrostatic latent image developer of the present invention having the above-mentioned constitution is a toner in which the developer in which at least the carrier and the toner are mixed contains the electric field adjuster composed of the binder resin and the magnetic powder. The charge amount of can be made uniform.

Generally, since the toner and the carrier are triboelectrically charged to give the toner a charge amount, the charge amount of the toner is determined by the number of times of contact between the toner and the carrier if there is no electric field adjusting agent. At this time, there are some toners having a high charge amount and some toners having a low charge amount. Therefore, the toner charge amount can vary greatly. When the electric field adjusting agent is mixed in the developer, the electric charge can be taken from the toner having a high charge amount and the electric charge can be given to the toner having a low charge amount.

An electric field is formed between the developing sleeve, which is a carrier for the developer, and the photoconductor, which is an electrostatic latent image carrier. The toner is developed by the electric field between the developing potential given to the developing sleeve and the potential on the photoreceptor on which the electrostatic latent image is formed. The dielectric constant can be increased by mixing the electric field adjuster with the developer existing during this period. The toner of the developer layer having a high dielectric constant is faithfully developed to the electrostatic latent image formed on the support.

[0013]

SPECIFIC STRUCTURE Such an electrostatic latent image developer according to the present invention has a carrier, an electric field adjusting agent and a toner mixed in a predetermined ratio, and carrier: electric field adjusting agent: toner = 10 to 80: by weight. The range of 10 to 60:10 to 80 is preferable.

If the proportion of the carrier in the electrostatic latent image developer is 10% or less, the chance of contact with the toner is reduced and the toner is not frictionally charged, so that the charge amount of the toner becomes uneven. Become. This is because when the mixture ratio is 80% or more, when the toner consumption amount for the electrostatic latent image becomes large, the toner cannot be replenished in time, and the black density of the image decreases.

If the electric field adjusting agent is less than 10%, its effect is not sufficiently exerted, and a factory of image quality cannot be expected. Also, 60%
With the above mixing ratio, not only the toner charge is adjusted, but also the toner itself is charged and charged in the same manner as the toner, and it is developed on the photoconductor, so that the uniformity of charging is lost, increasing fog and uneven black density. Will occur.

When the mixing ratio of the toner becomes 10% or less,
When the amount of toner consumed for the electrostatic latent image becomes large, the toner cannot be replenished in time and the black density decreases. 8
When the mixing ratio of the toner is 0% or more, the contact charging opportunity of the toner is reduced, and the image is developed without sufficient charging, so that an image with a lot of fogging and scattering is obtained.

The carrier constituting the electrostatic latent image developer according to the present invention is known as a hard carrier, and a carrier core material made of magnetic powder or its surface is coated with a suitable resin. Things are used. Incidentally, the raw material for the carrier core material may be any powder that exhibits magnetism such as iron, nickel, cobalt, and ferrite, and any of them may be used. Using the raw material, it is calcined, crushed to an average particle size of 2 μm or less, and granulated to a predetermined particle size, and then at a temperature of 1250 to 1350 ° C. for 3
After calcination for ~ 5 hours, crush or classify to 20 ~ 10
It can be manufactured as particles having an average particle diameter of about 0 μm. Further, the carrier can be used in the state of the carrier core material thus obtained as it is, or can be used by being coated with a suitable resin. As the coating resin, fluorine resin, styrene resin, acrylic resin,
Silicon resin, epoxy resin, polyester resin, polyalkylene resin and the like can be mentioned. Using one or more of these resins, the surface of the carrier core material is coated,
Finishing into a carrier is also advantageous.

The carrier is not limited to a hard carrier, and a soft carrier containing a magnetic powder in a resin can sufficiently obtain the effect.

The toner, which is one component of the electrostatic latent image developer according to the present invention, is composed of a binder resin, magnetic powder, a release agent, a charge control agent and the like as in the conventional case. Among them, as the binder resin, polystyrene, polyacrylate, polymethacrylate, vinyl resin, polyester resin, polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, polyether, polycarbonate, cellulose resin, polyamide, and these. Copolymers of monomers that give the resin can be used, and among them, a copolymer of a styrene monomer and an acrylic monomer is advantageously used.

As the magnetic powder, any material can be used as long as it exhibits magnetism or can be magnetized. For example, a metal such as iron, manganese, nickel, cobalt, chromium, or the like can be used. A metal oxide such as magnetite, hematite or ferrite can be made into a fine powder and used as a magnetic powder material.

As the release agent, polyalkylene or natural wax can be used, and specific examples thereof include polyethylene, polypropylene, carnauba wax, candelilla wax, rice wax and the like. You can As the charge control agent, nigrosine dye, quaternary ammonium salt, alkoxylated amine, alkylamide, metal complex of azo dye,
Examples include metal salts of higher fatty acids. The mixing ratio of these toner components is generally 30 to 98% by weight of binder resin, 0 to 60% of magnetic powder, 0.5 to 10% of release agent, and 0.1 of charge control agent. The ratio is about 5%.

Further, it is generally desirable that the average particle diameter of the toner is appropriately selected within the range of 5 to 15 μm. If the average particle diameter is smaller than 5 μm, it is difficult to handle the toner as a powder, the fluidity is lowered, and it becomes difficult to uniformly perform triboelectric charging. On the other hand, with a toner having a large particle size of more than 15 μm, the resolution of the developed image becomes poor, which is common in current printers.
It becomes difficult to obtain a resolution of 0 dpi.

The electrostatic latent image developer of the present invention mixes at least the above carrier and toner, and further mixes particles serving as an electric field adjusting agent, and its average particle diameter is preferably 5 to 20 μm. . This electric field adjuster is composed of at least a binder resin and magnetic powder, and the binder resin is the same as the binder resin of the toner: polystyrene, polyacrylate, polymethacrylate, vinyl resin, polyester resin, polyethylene, polypropylene, polyvinyl chloride. ,
Copolymers of polyacrylonitrile, polyethers, polycarbonates, cellulosic resins, polyamides, and the monomers that give these resins can be used.
Further, as the magnetic powder, any material can be used as long as it exhibits magnetism or is magnetizable, for example, metal such as iron, manganese, nickel, cobalt chrome, magnetite, hematite, ferrite Such a metal oxide can be made into a fine powder and used as a magnetic powder material.

A charge control agent and a conductive material can be further added to the constituent material of the electric field adjusting agent depending on the developing conditions and the developer mixing conditions. As the charge control agent, for example, a positively chargeable charge control agent such as a nigrosine dye or a quaternary ammonium salt and a negative charge control agent such as a metal complex of an azo dye or a metal salt of a higher fatty acid are used. You can Examples of the conductive material include metal powders such as titanium oxide, nickel, cobalt, manganese, and iron, and organic conductive materials such as carbon black.

The mixing ratio of the binder resin and the magnetic powder is preferably in the range of binder resin: magnetic powder = 10 to 60:40 to 90. When the volume resistance is 8 × 10 ⁸ Ωcm or more, A conductive material is mixed to lower the volume resistance value. If the binder resin content is 10% or less, the binder resin cannot surround the magnetic powder and particles cannot be formed. Further, when the content is 60% or more, the electric conductivity effect of the electric field adjusting agent becomes insufficient, and the volume resistance does not become 8 × 10 ⁸ Ωcm or less even when a conductive material is added in addition to the magnetic powder.

The amount of magnetic powder is 40 as in the binder resin.
If the amount of the magnetic powder is less than 100%, a sufficient volume resistance cannot be obtained, and if the content is more than 90%, the binder resin is insufficient and desired particles cannot be formed.

The volume resistance is calculated from the electric conductivity when the electric field adjusting agent is in the form of pellets and an AC potential of 10 V having a frequency of 1 kHz is applied.

In order to adjust the electrostatic latent image developer of the present invention by containing such an electric field adjusting agent in the developer, the carrier, the electric field adjusting agent and the toner are weighed in a desired ratio,
Mix all at once with a mixer to make.

By the way, such an electrostatic latent image developer according to the present invention is applied to a printing method of developing an electrostatic latent image by being filled in various devices of an electrophotographic developing system. The developing principle will be described with reference to FIG. 1 showing the case where the developer of the present invention is filled in a laser beam printer.

First, the exemplary laser beam printer is
Around the photoconductor 10 in which a photoconductive layer is applied to an aluminum conductive tube, a charger 12 for applying a surface potential to the photoconductor 10, a laser scanner 14 for providing image information, and an electrostatic latent image on the photoconductor. Developing device 16 for developing toner onto the photoconductor, transfer device 20 for transferring the development of the toner formed on the photoconductor to a recording medium 18 such as paper, and photoconductor not transferred by the transfer device 20. The cleaning device 22 for removing the toner on the recording medium 10 is an electrophotographic system. Further, a thermal fixing device 24 for fixing the toner image on the recording medium 18 by heat melting is provided.

In the developing device 16, a non-magnetic sleeve 28 is stored around the magnet roll 26 so that they can be rotated relatively in opposite directions, while the sleeve 28 is The photoconductor 10 is configured to rotate in the opposite direction. The electrostatic latent image developer 30 according to the present invention is filled in the developing device 16 and agitated by an appropriate agitating means so as to come into contact with the sleeve 28. The sleeve 28 must be rotated in order to convey the developer 30, but the magnet roll 26 does not necessarily need to be rotated and may be stationary.

Further, the developer 30 is applied to the sleeve 28.
Are mixed in the carrier confinement chamber 32 located at the position. In the carrier confining chamber 32, the developer 3 mixed in advance is mixed prior to the start of development.
0, that is, at least an electrostatic latent image developer according to the present invention, which is a mixture of carrier, toner and electric field adjuster, is filled. The carrier and the electric field adjusting agent in the developer 30 do not exist or move except on the carrier confining chamber 32 and the sleeve 28. This is because even if the carrier is conveyed to the photoconductor 10 by the sleeve 28, the carrier and the electric field adjusting agent are not developed on the photoconductor 10. However, the toner is
As it is developed and consumed up, the carrier confinement chamber 32
The toner is supplied from a toner box (not shown) provided so as to communicate with the toner according to the consumption of the toner.

Further, in the developing device 16, since the developer 30 is in contact with the sleeve 28, the developer 30 in which the carrier and the toner are mixed with the electric field adjusting agent is present on the sleeve 28. Further, in order to make the developer layer formed on the sleeve 28 uniform, a blade 34 is provided at an interval from the sleeve 28 where the developer layer is formed. This sleeve 28
The distance between the blade 34 and the blade 34 affects the image quality, and is therefore generally set to be narrower than the gap (usually 250 to 450 μm) between the photoconductor 10 and the sleeve 28. For example, if the gap between the photoconductor 10 and the sleeve 28 is 350 μm, the gap between the blade 34 and the sleeve 28 is controlled to be 200 to 300 μm.

In the charger 12, 3-5 kV
A voltage of about a certain level is applied to cause corona discharge, and a surface potential of about +700 V is formed on the photoconductor 10. The charger 12 includes a scorotron that applies a predetermined surface potential to the photoconductor 10 by corona discharge, and a member such as a semiconductive brush, a roller, or a blade that contacts the photoconductor 10 to give a predetermined surface potential. Can be used.

By the way, the image information converted into an electric signal is converted into an optical signal from the laser scanner 14 to the photoconductor 10.
And the potential of the filtered portion of the light is lowered by the action of the photoconductive layer on the surface thereof, and an electrostatic latent image having a different potential distribution is formed on the photoconductor 10.

Then, the sleeve 28 in the developing device 16
The developer 30 conveyed by means forms a developer layer having a predetermined thickness on the surface of the sleeve 28, and the developer layer contacts the photoconductor 10 and is formed on the photoconductor 10. Only the toner is developed on the electrostatic latent image. The undeveloped carrier, electric field adjusting agent, toner and the like are conveyed again into the carrier confining chamber 32 and used for triboelectric charging of the toner. The electrostatic latent image on the photoconductor 10 is reduced by the exposure of the laser scanner 14 under the condition that the surface potential applied from the charger 12 is 700V to 100V. Has been formed. On the other hand, the sleeve 28 is applied with a potential of 600 V as a bias potential, whereby the positively charged toner is developed on the potential portion of 100 V on the photoconductor 10. In addition,
The chargeability of the toner used for this purpose is positively charged here, but even if it is negatively charged, it can be applied by setting the potentials given to the respective members to opposite polarities.

The toner image thus formed on the photoconductor 10 is transferred onto the recording medium 18 such as paper by using the transfer device 20, and further recorded by the heat fixing device 24. The toner is fixed on the medium 18, whereby a desired recorded image can be obtained.

In such a developing operation, the electrostatic latent image developer according to the present invention contains the carrier confining chamber 3 of the developing device 16.
2 is pre-filled, and the electric field adjusting agent is mixed with the developer to effectively form a conductive layer for smooth transfer of charges to and from the toner surface, thereby charging the toner. By making the amount uniform, it is possible to faithfully develop the electrostatic latent image formed on the photoconductor 10 with the toner.
It is possible to form a good toner visible image on the image surface.

[0039]

EXAMPLE An example of embodying the present invention will be shown below.
The electrostatic latent image developer will be described in more detail.

First, the carrier CR used for the electrostatic latent image developer is A silicon coated ferrite carrier B silicon coated magnetite carrier, all of which have an average particle diameter of 50 μm and are manufactured by Powder Tech Co., Ltd. The toner TN is a styrene-acrylic type carrier. Resin 40 parts by weight UNI 3000 [styrene-acrylic resin manufactured by Sanyo Chemical Industry Co., Ltd.] Magnetite 45 parts by weight EPT 1000HDH [manufactured by Toda Industry Co., Ltd.] Polypropylene 5 parts by weight TP-32 [manufactured by Sanyo Chemical Industry Co., Ltd.] Nigrosine dye 2 parts by weight N-01 [Orient Chemical Co., Ltd.] materials are mixed in a mixer, melt-kneaded to form a toner material in bulk, and then coarsely pulverized to about 1 to 2 mm, and further 100 parts by weight of raw toner is obtained by pulverizing and classifying to form raw toner having an average particle diameter of 9 μm. Stirring and mixing 0.5 part by weight of hydrophobic silica for silica to obtain toner TN in a state of being dispersed in the raw toner surface.

The electric field adjusting agent FAP is as follows: composition 1 styrene-acrylic resin 30 parts by weight UNI 3000 [Sanyo Chemical Co., Ltd. styrene-acrylic resin] magnetite 70 parts by weight EPT 1000HDH [Toda Kogyo KK] ] Azo dye metal complex 2 parts by weight S-34 [manufactured by Orient Chemical Co., Ltd.] Composition 2 Styrene-acrylic resin 50 parts by weight UNI 3000 [Sanyo Chemical Co., Ltd. styrene-acrylic resin] Magnetite 50 parts by weight EPT 1000 [manufactured by Toda Kogyo Co., Ltd.] carbon black [manufactured by Mitsubishi Kasei Co., Ltd.] 10 parts by weight of a material having a composition are mixed by a mixer and melt-kneaded to form a bulk electric field conditioner material, Coarse pulverization to about 1 to 2 μm, fine pulverization and classification to obtain an average particle size of 9 μm
To form a raw electric field conditioner, and 0.1 part by weight of hydrophobic silica is mixed with 100 parts by weight of the raw electric field conditioner and stirred,
An electric field conditioner FAP in which silica was dispersed on the surface of the raw electric field conditioner was obtained.

In the above composition 1, the volume resistance is 3 × 10 ⁸ Ωc.
An electric field conditioner FAP having a magnetic flux density of 60 emu / g at m was obtained. With the composition 2, an electric field regulator FAP having a volume resistance of 2 × 10 ⁷ Ωcm and a magnetic flux density of 45 emu / g was obtained.

For comparison, an electric field adjuster FAP of composition 2 containing no carbon black was prepared. The volume resistance was 6 × 10 ¹⁰ Ωcm of the electric field adjuster FAP.

Regarding the various developers 30 thus obtained,
Using a laser beam printer as shown in FIG.
In the carrier confinement chamber 32, each developer 30
Meanwhile, the toner box is filled with only the toner TN corresponding to each developer, and the electrostatic latent image on the photoconductor 10 is developed.
The image transferred onto the above and fixed was evaluated in terms of density, fog and line scattering rate, and the results are shown in Table 1.

[0045]

[Table 1]

The evaluation method for each evaluation item is as follows:
It is as follows.

For the density measurement, a Macbeth transmission densitometer [TD-904 manufactured by Macbeth Co., Ltd.] was used to measure the transmission density of the solid black portion of the print sample, and based on the light transmittance T thereof, -log The value calculated based on the formula T is output. The smaller the value, the denser the print. The diameter for measuring the transmission density is 5 mm.
It is φ and can be measured if there is a solid black portion of at least about 5 mm square.

In the fogging measurement, the whiteness W is measured using a spectrocolorimeter [MSCM manufactured by Suga Test Instruments Co., Ltd.]. This whiteness W is measured by the C light source in the Lab color system,

[0049]

[Equation 1]

It is the value obtained by The whiteness W is determined from the whiteness within a diameter range of 30 mmφ. Here, the difference between the whiteness W of the printed back side of the print sample and the whiteness W of the printed portion on the printed side (front side) is evaluated. The smaller the value, the more the fog does not occur. There is.

Further, in the line-to-line scattering rate measurement, the ratio of the toner TN scattered between the printed lines is measured by using a PIAS image processing device. Specifically, a print area between three lines of a print pattern formed from a line group of one dot and three spaces is captured as image data, and a density of a certain threshold level is set. The data is binarized into a form that can be used for analysis, and the data is processed to calculate the ratio of toner TN scattered between lines. The larger the value, the greater the value. , And that the sharpness of letters or lines deteriorates.

As is clear from the results shown in Table 1, the electrostatic latent image was developed using the developer according to the present invention, and in the image output, in addition to sufficient density and low fog, While it has been shown that the line-to-line scattering rate is low, and that it is possible to improve the sharpness of characters or lines, in the comparative example showing the case where the electric field adjusting agent FAP having a high volume resistivity is added. , Both have high line-to-line scattering rate,
It was inferior in sharpness of letters or lines.

[0053]

As is apparent from the above description, according to the electrostatic latent image developer of the present invention, the charge of the toner is prevented by mixing the electric field adjusting agent in the mixture of the carrier and the toner. The electric charge in the toner is transferred by the conductive effect of the electric field adjusting agent, not by the number of times the carrier or other member comes into contact. The electric field adjuster deprives the charge of the toner that has been charged a lot due to a large number of contacts, and provides the charge to the toner having a low charge, so that the distribution of the charge amount of the toner becomes more uniform than the simple contact charging. .

Further, since the electrostatic latent image developer is present in the electric field formed between the sleeve, which is the developing carrier, and the electrostatic latent image on the photosensitive member, the induction rate in the electrostatic latent image developer is increased to improve the fidelity. It works so as to develop the toner into a latent image.

Further, since only the toner is developed into the electrostatic latent image and the electric field adjusting agent is conveyed to the sleeve together with the carrier, and contributes to the charging of the toner again in the carrier confining chamber. Without affecting the transfer efficiency from the body to the recording medium, without increasing the extra waste toner,
Economical toner consumption can be achieved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a configuration of a main part of a laser beam printer to which an electrostatic latent image developer according to the present invention is applied.

[Explanation of symbols]

 10 Photoreceptor 12 Charging Device 14 Laser Scanner 16 Developing Device 18 Recording Medium 20 Transfer Device 22 Cleaning Device 24 Thermal Fixing Device 26 Magnet Roll 28 Sleeve 30 Developer 32 Carrier Confining Chamber 34 Blade

Claims (2)

[Claims] 1. An electrostatic latent image developer characterized in that an electric field adjuster composed of a binder resin and magnetic powder is mixed with a developer in which at least a carrier and a toner are mixed. 2. The volume resistance of the electric field adjusting agent is 8 × 10 ⁸
The electrostatic latent image developer according to claim 1, which has an Ωcm or less.