JPH08328291A - Developer and image forming device - Google Patents

Abstract

PURPOSE: To provide a developer capable of developing at a desired development density even if a latent image formed on a latent image carrying member is developed by a contactless development system. CONSTITUTION: This developer utilized at the time of developing the latent image formed on the latent image carrying member 1 by the contactless development system is formed by adhering external additives of an average grain size of 20 to 100nm at a covering rate of 20 to 80% to the toner particles. The electrostatic charge quantity qa of the toners after the adhesion the external additives and the electrostatic charge quantity qb before the adhesion of the external additives satisfies the relation |qa |<|qb |.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer and a developer, and more specifically, an image forming method for developing a latent image formed on a latent image carrier by a non-contact developing method. The present invention relates to improvements in devices and developers.

[0002]

2. Description of the Related Art In recent years, color formation has progressed in image forming apparatuses, and as one technique therefor, a batch transfer system for performing so-called overdevelopment has been proposed. The batch transfer type image forming apparatus described above repeats a process of developing a latent image formed on a latent image carrier to form a toner image a plurality of times to form a multicolor toner image on the latent image carrier. After forming
This is a system in which the multicolor toner images are collectively transferred to a transfer material. In this batch transfer type image forming apparatus, since the toner images are superposed on the latent electrostatic image bearing member, there is little color misregistration, and since the multicolor toner images are transferred to the transfer material all at once, the transfer material is transferred. Since there is no need for a transfer drum for transporting the sheet to the transfer position a plurality of times, there is an advantage that the apparatus can be downsized. In this batch transfer type image forming apparatus, since the toner image is formed on the latent image carrier, it is necessary to form the toner image on the latent image carrier on which the toner image is formed. There is. Therefore, in this batch transfer type image forming apparatus, the developer is held at a distance from the latent image carrier so as not to disturb the toner image formed on the latent image carrier, and, for example, It is necessary to develop the toner by a so-called non-contact developing method in which the toner flies toward the latent image carrier by an alternating electric field.

However, when a one-component developer is used in this non-contact developing type image forming apparatus, since there is a gap between the developer and the latent image carrier, the force of the electric field acting on the developer is used. Weakens the toner and makes it difficult for the toner to fly, lowers the development density, and it is necessary to fly the toner from the state of contacting only the developer carrier, that is, the physical adhesive force acting between the developer carrier and Since it is necessary to fly the toner against the toner, it becomes difficult for the toner to fly and there is a problem that the developing density is lowered. In addition,
The physical adhesive force referred to here is, for example, page 152 of "Basics and Applications of Electrophotography" (edited by the Institute of Electrophotography, June 1, 1988).
It is believed that van der Waals force and Coulomb force are dominant, as described in "Corona Publishing" on the 5th.

When a two-component developer is used in the non-contact developing type image forming apparatus, the development density is lowered due to the same cause as when the one-component developer is used. When the strength of the electric field acting on the toner is increased by increasing the strength of the alternating electric field in order to compensate for the decrease in the development density, the carrier flies with the toner and the carrier is transferred onto the latent image carrier. However, there is a problem in that due to the adhesion of the carrier, a white portion (white blank) is formed in the image, and a desired image quality cannot be obtained.

Incidentally, Japanese Patent Laid-Open No. 6-43694 discloses that
A technique is disclosed in which an inorganic external additive having an average particle size of 50 to 120 nm is attached to toner particles, and a toner having an improved charge amount after the external additive is attached is used. However, since this technique improves the charge amount of toner, the development density does not increase.

Further, when the color two-component developer is used in the non-contact development type image forming apparatus, the development density is lowered or the carrier is lowered due to the same cause as in the case of using the two-component developer. However, there is a problem that the image quality is deteriorated due to the adherence of the particles on the latent image carrier.

By the way, when a two-component developer for color is used, JP-A-62-182775,
JP-A-6-27718, JP-A-6-043694
Japanese Patent Laid-Open Publication No. 2003-242977 proposes a technique of attaching an external additive to toner particles to reduce the physical adhesive force acting between the toner and the carrier and to secure a desired developing density.

However, JP-A-62-182775
In the publication, since an external additive having a small particle diameter such as 7 to 20 nm is used, the external additive is buried in the toner particles over time, and its charging characteristics and the like are changed, which results in long-term The desired development density cannot be obtained over the entire range.

Further, in JP-A-6-27718 and JP-A-6-043694, the average particle size is 50-12.
Since the external additive having a large particle size of 0 nm is used, the physical adhesive force acting between the toner and the carrier can be reduced, but on the other hand, the toner attached to the latent image carrier and There is a problem that the physical adhesive force acting between the latent image carrier and the latent image carrier is reduced. Therefore, when such a toner is used in the overlapping developing method, when the toner image is formed on the latent image bearing member on which the toner image is formed, the toner on the latent image bearing member is in the latter stage. It is scraped off in the developing process and enters the developing device in the subsequent stage (hereinafter, this phenomenon is referred to as mixing), and in the long term, the color reproducibility of the developing in the subsequent stage is lowered, or the developer in the subsequent stage is deteriorated. The chargeability of the toner deteriorates, the developability of the toner deteriorates, and fog occurs. It should be noted that, when the alternating electric field is used in the non-contact developing system, this phenomenon of mixing causes the toner between the latent image bearing member and the developer bearing member from the developer bearing member to the latent image bearing member. The electric force in the developing direction for transferring the toner and the electric force in the opposite direction for transferring the toner from the latent image carrier to the developer carrier, which are opposite to each other, act alternately. Is caused by. It is also possible to adjust the strength of the alternating electric field and the like to prevent the mixture, but the adjustment is extremely difficult in consideration of the development density.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer capable of developing a latent image formed on a latent image bearing member at a desired developing density even if the latent image is developed by a non-contact developing method. To provide.

A second object of the present invention is to develop a latent image formed on a latent image bearing member by a non-contact developing method so that the latent image can be developed at a desired developing density.
An object of the present invention is to provide a developer that does not cause blank areas.

Next, a third object of the present invention is to develop a latent image formed on a latent image carrier to a desired value over a long period of time even if the latent image is overdeveloped by a non-contact developing method. Stable,
Another object of the present invention is to provide a color developer that hardly causes color mixing.

A fourth object of the present invention is to provide a non-contact developing type image forming apparatus capable of developing at a desired developing density.

[0014]

Therefore, a first invention of the present application relates to a developer used when developing a latent image formed on a latent image bearing member by a non-contact developing method, wherein the above-mentioned developer is used. Is an average particle size of 20 nm or more with respect to the toner particles 10
The external additive having a thickness of 0 nm or less is attached at a coverage of 20% or more and 80% or less, and the charge amount q _a of the toner after the external additive is attached and the toner before the external additive is attached The developer has _a charge amount q _b and a relationship of | q _a | <| q _b |.

The second invention of the present application relates to a developer used for developing a latent image formed on a latent image bearing member by a non-contact developing method, wherein the developer comprises a carrier and a toner. The above toner has a coating rate of 2 with an external additive having an average particle size of 20 nm or more and 100 nm or less with respect to toner particles
0% or more and 80% or less, the toner charge amount q _a after the external additive is attached and the toner charge amount q _b before the external additive is attached are | q _a The developer satisfies the relationship of | <| q _b |.

Next, a third invention of the present application relates to a color developer which is used when a latent image formed on a latent image bearing member is developed in a non-contact development method. Consists of carrier and toner, and the toner is
An external additive having an average particle size of 20 nm or more and 50 nm or less is attached to the toner particles at a coverage of 20% or more and 50% or less, and the toner charge amount q _a after the external additive is attached The charge amount q _b of the toner before attaching the external additive is
The color developer satisfies the relationship of q _a | <| q _b |.

Further, a fourth invention of the present application uses the developer according to any one of the first to third inventions to form a latent image formed on a latent image carrier by a non-contact developing system. An image forming apparatus for developing.

In the above first and second inventions,
The average particle size of the external additive is preferably 20 nm or more and 100 nm or less. When the average particle diameter of the external additive is less than 20 nm, the physical adhesion force (for example, Van der Waals force or Coulomb force) acting between the toner and the developer carrier or the carrier cannot be sufficiently reduced. Therefore, the desired development density cannot be obtained. When the average particle diameter of the external additive exceeds 100 nm, the physical adhesive force can be reduced by increasing the distance between the toner and the carrier, but the fluidity of the toner and the developer is lowered and the developer is Due to the aggregation, the developer is unevenly conveyed, and the image is uneven in density.

On the other hand, in the third invention, the average particle diameter of the external additive is 20 nm or more and 50 nm or less, preferably 40 nm or less. The average particle size of the external additive is 20 nm
If it is less than the above range, the external additive will be buried in the toner particles over time and its chargeability will change, so that the desired developing density cannot be obtained for a long period of time. When the average particle size of the external additive exceeds 50 nm, the toner is significantly scraped during the overdevelopment.

In the first and second inventions, the coverage of the external additive adhered to the toner particles is preferably 20% or more and 80% or less. 20% coverage
When the amount is less than the range, the fluidity of the toner and the developer is poor, so that the developer aggregates to cause uneven transport of the developer and uneven density in the image. If the coverage exceeds 80%, the coverage of the external additive with respect to the toner particles becomes excessive, so that the charge amount of the toner and thus the physical adhesion force are extremely reduced, and the toner easily floats, and the toner cloud Will occur.

On the other hand, in the third invention, the coverage of the external additive adhered to the toner particles is preferably 20% or more and 50% or less. When the coverage is less than 20%, the toner cannot have stable fluidity and chargeability. If the coverage exceeds 80%, the toner is remarkably scraped during the overdevelopment. The term "coverage ratio" as used in the present invention means that the toner surface is photographed with a scanning electron microscope SEM at a magnification of 30,000 or more, and 10 images are taken. Is an average value calculated from the ratio (a / t × 100) of the total cross-sectional area a of the external additive adhering to the toner particle surface and the surface area t of the toner particle.

Further, in the above first to third inventions,
The toner has a charge quantity of q after the external additive is attached.
is _a, if the charge amount of the toner before adhering the external additive was q _b, they _{| q a | <| q b} | a good thing that meet the relationships. When the charge amount of the toner increases when the external additive is attached (| q _a |> | q _b |), the external additive has a large charge and the physical adhesive force acting on the toner is large. Therefore, the developability is lowered. In addition, when the charge amount of the toner does not change even if the external additive is attached (| q _a |
= | Q _b |) does not generate an electrostatic adhesive force between the toner and the external additive, so that the external additive is easily detached and the effect of the external additive is lost.

The toner charge amount as referred to in the present invention means the toner charge amount when the toner and the carrier are mixed and measured by the blow-off method, and the toner charge amount before the above external additive is attached. The mixing ratio of the toner and the carrier when measuring the amount is the same as the mixing ratio of the toner and the carrier when measuring the charge amount of the toner after the external additive is attached.

In the first invention, the carrier mixed with the toner for measuring the charge amount of the toner is styrene-normal-butyl methacrylate (B
MA) copolymer (St / nBMA = 85/15) 30w
t% and 70 wt% of granular magnetite (EPT-1000: manufactured by Toda Kogyo Co., Ltd.) are mixed to form an average particle size of 45 μm. Further, in the above first invention,
When the toner and the carrier are mixed, the toner concentration is 5 to
The charging method was 15 wt%, and 100 cc of a mixture of the toner and the carrier was placed in a 2000 cc (sectional area 100 cm ² , height 20 cm) cylindrical container.
It is a value after being oscillated for 100 reciprocations (1 minute) with an amplitude of 30 cm up and down.

The developer of the present invention will be described in detail below.

The toner is composed of toner particles and an external additive attached to the surface of the toner particles. The average particle size of the toner is
The average particle size may be about 20 μm, but the average particle size may be 10 mm or less in consideration of image quality such as resolution of fine lines. On the other hand, when the average particle diameter of the toner is less than 5 μm, the physical adhesive force acting between the toner and the carrier becomes dominant, so that the developing density is lowered and the toner is apt to aggregate. , Handling problems may occur.

The charge amount of the toner is 5 to 50 in absolute value.
It is desirable to be in the range of μc / g, preferably 10 to 40 μc / g. If the charge amount is too high, the physical adhesive force acting between the toner and the carrier becomes too high, and the toner does not fly. If the charge amount is too low, the physical adhesive force acting between the toner and the carrier becomes too weak, and a toner cloud due to free toner occurs, causing fog in printing.

Examples of the external additive include titanium oxide, magnesium titanate, barium titanate, potassium titanate, strontium titanate, silica, zinc oxide, chromium oxide, cerium oxide, zirconium oxide, antimony trioxide, alumina, carbonized. Inorganic powders such as silicon, calcium carbonate, magnesium oxide, and magnesium carbonate, and organic fine powders such as polyester resins such as polymethylmethacrylate and polyacrylate, polyurethane resins, and polycarbonate resins can be used. Further, these materials can be used alone or in combination in order to give desired fluidity and chargeability as a toner, and those whose surface characteristics are changed to change their characteristics are used. It is also possible.

In addition to these external additives, the average particle size is 20 nm in order to finely control the chargeability and fluidity.
Of less than 20 nm may be added to the surface of the toner particles, but organic fine particles of less than 20 nm or inorganic fine powder will be buried in the toner particles and the charge amount of the toner will change over time. Therefore, the addition amount in that case is 50% of the above external additive.
% Or less, preferably 30% or less. When an inorganic powder having a hygroscopic property such as titanium oxide, silica oxide, or alumina is used as an external additive, it is preferable to perform a hydrophobizing treatment in consideration of environmental stability. The hydrophobic treatment is a dialkyldihalogenated silane,
It can be carried out by reacting a silane coupling agent such as trialkylhalogenated silane, alkyltrihalogenated silane or hexaalkyldilasilane or a hydrophobizing agent such as dimethyl silicone oil with the fine powder at a high temperature.

The toner particles are composed of a main binder resin and a colorant.

As the main binder resin for the toner,
For example, polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer There are a combination, a polyester resin, a polyurethane resin, and the like, and a single or a plurality of binder resins are mixed and used as necessary. The main binder resin is preferably a polymer having a number average molecular weight of 10,000 or less, because different color toners need to be melt-fixed favorably at the time of fixing, and preferably, the number average molecular weight is 5,
It is desirable that the polymer is 000 or less. However, if the number average molecular weight is less than 2,000, the toner itself is deformed by heat during continuous printing, and thermal agglomeration of the developer is likely to occur. Therefore, the number average molecular weight of the binder resin for the toner is 2,000. The above is desirable.

The toner particles may contain an olefin-based homopolymer or copolymer such as low molecular weight polyethylene, ethylene or propylene, or carnauba in order to enhance the releasability from the roll and prevent toner offset during heat roll fixing. Wax or wax components such as fatty acid esters such as maleic acid ethyl ester and stearic acid methyl ester may be added. At this time, the addition amount of the wax component is 0.5 wt% or more and 10 wt% with respect to the toner.
The following is desirable. If the amount added is less than this, the effect of the wax component will not be obtained. On the other hand, if the addition amount is larger than this, the toner is likely to be deformed by heat, the chargeability of the developer is changed, and stable image density cannot be obtained. In addition, in order to increase the mechanical strength of the toner and to enhance the cohesive force of the toner at the time of heat roll fixing and prevent toner offset, the toner particles may have a high molecular weight polymer having a weight average molecular weight of 100,000 or more and a cross-linking agent. A polymer may be included.
The content of the high molecular weight polymer and the crosslinked polymer is preferably 20 wt% or less with respect to the toner. If the content is more than this range, different color toners do not melt and fix well during fixing, causing a problem in color reproducibility. Further, the toner particles may contain a charge control agent such as an ammonium salt compound or a metal complex dye.

As the above-mentioned colorant, carbon black, nigrosine, graphite or the like is used as a black type. As the chromatic color system, (yellow or orange pigment), C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 1
2, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 93,
C. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 174,
Quinoline yellow, and as (magenta or red pigment), C.I. I. Pigment Red 5, C.I.
I. Pigment Red 48, C.I. I. Pigment Red 53, C.I. I. Pigment Red 57, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123,
C. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I.
I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I.
Pigment Red 222, Pigment Orange,
Furthermore, as (Cyan or green pigment),
C. I. Pigment Green 7, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I.
I. Pigment Blue 15: 3, C.I. I. Pigment Blue 60, aniline blue or the like known colorant is used. The content of these toner colorants is preferably 0.5% by weight or more and 20% by weight or less with respect to the toner. If it is less than 0.5% by weight, the coloring property is not sufficient and a clear image cannot be obtained. If it exceeds 20% by weight, unevenness in image quality occurs due to poor dispersion of the colorant in the toner.

Next, the carriers used in the second and third inventions of the present application will be described.

The average particle size of the carrier is 35 μm or more, 6
It is preferably 0 μm or less. When the average particle diameter is 60 μm or less, the magnetic brush becomes dense and the image does not become uneven.
If the average particle size is less than 35 μm, the magnetic restraining force of the carrier is weakened, so that the carrier adheres to the latent image carrier. The electric resistance of the carrier is 10 ⁸ Ω. cm or more is preferable. The resistance value is 10 ⁸ Ω. If it is less than 10 cm, charges are injected into the carrier particles and the carrier adheres to the latent image carrier, or leakage of the developing bias occurs. Here, the resistance value is measured by the following method. 10 g of the carrier is put in a cylindrical molding container having a diameter of 40 mm,
Pressure molding was performed at a pressure of 10 tons, the molded sample was sandwiched between electrodes, the voltage was changed to measure the current value, and the relationship curve between the electric field and the volume resistance value was plotted from the thickness of the sample,
The resistance value at 1000 V / cm is adopted.

The carrier may be a magnetic carrier composed of a magnetic substance alone, a resin-coated carrier in which the surfaces of the particles are coated with a resin, or a mixture of magnetic fine powder and a binder resin. It may be a polymer carrier formed in this way. Since the polymer carrier has weaker magnetization intensity and lighter specific gravity than the magnetic carrier, carrier scattering is less likely to occur, the surface of the latent image bearing member is less likely to be damaged, and moreover stress on the toner when mixed. Has the merit that it can be made smaller.

The magnetic properties of the polymer carrier are 60 emu.
/ Cm ³ or more and 120 emu / cm ³ or less are desirable. When the magnetization intensity is less than 60 emu / cm ³ , the magnetic restraining force is weak, and the carrier flies and adheres to the latent image carrier. On the other hand, the strength of magnetization is 120 emu / cm
^When it exceeds ³ , the developing agent becomes rough and the density unevenness occurs in the image. As a polymer carrier,
In order to bind the magnetic powder and maintain the shape of the carrier, the content of the magnetic powder in the binder resin is 80 wt.
% Is the upper limit. If the content of the magnetic powder is further increased, it becomes brittle and cannot serve as a carrier. Also,
When the content of the magnetic powder is small, the magnetic force of the carrier is lowered, so that the phenomenon that the carrier adheres to the latent image carrier occurs.
From these things, the content of the magnetic powder of the polymer carrier used in the present invention is preferably about 60 to 80 wt%.

As the binder resin of the polymer carrier,
Various examples can be given, and examples thereof include acrylic resins, polyester resins, and epoxy resins. Further, as the magnetic fine powder, magnetite fine powder,
Examples include ferrite fine powder. The size of the magnetic powder is preferably 0.1 μm or more and 0.5 μm or less in consideration of dispersibility in the binder resin. 0.1 μm
If it is less than the above, aggregation of the magnetic powder is observed and good dispersion cannot be expected. When it exceeds 0.5 μm, the protrusion of the magnetic powder from the surface of the polymer carrier is conspicuous, and when the developer is mixed, the carrier is disintegrated with the protrusion as a starting point over time, which is not preferable.

There are various methods for producing the polymer carrier, for example, a method of melting and kneading the polymer and the magnetic powder with a Banbury mixer, a kneader, an extruder, etc., cooling, pulverizing and classifying, Alternatively,
There is a spray dry method in which magnetic powder is mixed and dispersed in a polymer solution and then spray-dried. It is also possible to use a suspension polymerization method in which a monomer constituting a polymer and a predetermined material are dispersed in an appropriate solvent and the suspension is polymerized to obtain a desired carrier.

[0040]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1 An example of the developer according to the first invention of the present application will be described.

The toner particles used in the developer have an average particle size of 7 by kneading and pulverizing 95 wt% of polyester as a binder resin and 5 wt% of carbon black as a colorant.
It is formed to have a thickness of μm and has a negative charging property.

As the external additive adhering to the above-mentioned developer, titanium oxide having an average particle diameter of 20 nm and an average particle diameter of 100 nm were prepared.

Then, in this example, as shown in Table 1, the toner particles and the external additive were mixed by a Henschel mixer to form four kinds of developers.

The charge characteristics of each of the above four kinds of developers were measured by the blow-off method. As a result, for all the developers, the charge amount q _a of the toner after the external additives were attached
And the amount of charge q _b of the toner before attaching the external additive are | q _a
The relationship of | <| q _b | was satisfied.

The charge quantity q _a of the toner after the above-mentioned external additives are attached is determined by the styrene-n-BMA copolymer (St
/ NBMA = 85/15) 30 wt% and granular magnetite (EPT-1000 (registered trademark): manufactured by Toda Kogyo Co., Ltd.) 7
0 wt% is mixed to form a carrier having an average particle diameter of 45 μm, the carrier and the four types of developers are mixed at a toner concentration of 8 wt%, and 100 cc of the mixture of the carrier and toner is 2000 cc (a cross-sectional area of 100 cm. ⁽² , height is 20 cm) and is a measured value after being charged by being oscillated for 100 reciprocations (1 minute) with an amplitude of 30 cm up and down. The charging amount q _b of the toner before the deposition of the external additive, and mixing the carrier and the toner particles in the toner concentration 8 wt%, is a measure of the after vibrated by the vibration condition it .

[0047]

[Table 1]

Then, using the image forming apparatus shown in FIG. 1, the developing densities of the above four kinds of developers are measured.

In FIG. 1, 1 is the process speed 11
A drum of an organic photoreceptor having a diameter of 160 mm rotating at 0 mm / s, 2 is a uniform charging device, 3 is an exposing device, 4, 5, 6, and 7 are four developing devices, 8 is a pre-transfer charging device, and 9 is Transfer device, 10 is a peeling device, 11 is a cleaning means, 12 is a static eliminator, 13
Is a paper guide, and 14 is a conveyor belt. The potential of the non-exposed portion of the photoconductor 1 is -550v and the potential of the exposed portion is -150v. Each of the developing devices 4, 5, 6, 7
Is made of aluminum with anodized surface 3
It has a cylindrical sleeve having a diameter of 18 mm rotating at 30 mm / s, a mag roll having a magnetizing width of 3 mm for the N pole and the S pole disposed inside the sleeve, and a trimmer pressed against the surface of the sleeve. . The trimmer has a thickness of 0.2.
It is arranged at the contact position of the mm SUS plate and the sleeve,
It is made of urethane rubber having a thickness of 1 mm that charges the developer, and the urethane rubber is pressed against the sleeve by a pressing force of a linear pressure of 100 g / cm. The developer transport amount on the sleeve is 120 g / m ² .

In the image forming apparatus, the distance between the photoconductor 1 and the sleeve is set to 0.15 mm, and an AC voltage (frequency 8 kHz,
Vp-p 0.5 kV, duty 50%, rectangular wave) and DC voltage (-500 v) are applied as a developing bias to develop the latent image formed on the photoconductor 1 by the non-contact developing method. ing.

Then, the above four kinds of developers are applied to the developing device 4.
Put it in, develop a solid image for each,
Measure the toner weight per 10mm x 10mm of solid image
Decided Table 2 shows the results. Real developer toner weight
Usable area is 10.0 g / cm ²It is more than the above. Table 2
As is clear from the figure, the toner weight of all four types of developer
The amount is 10.0 g / cm²With the above, all developers are
It turned out to be usable.

Further, instead of the above black toner, 85 wt% polyester and 15 wt% pigment yellow
% Of the toner particles made of 87% polyester
% And toner particles composed of 13% by weight of red pigment and magenta toner similarly having external additives attached thereto, or toner particles composed of 87% by weight of polyester and 13% by weight of blue pigment. Similarly, the same results were obtained with Sian toner to which an external additive was attached.

Therefore, the average particle size is 20 with respect to the toner particles.
20% or more and 8% or more of external additives having a thickness of 100 nm to 100 nm
The toner charge amount q _a after the external additive is attached is 0% or less, and the toner charge amount q _b before the external additive is attached is | q _a | <| It is understood that the desired development density can be obtained with the developer satisfying the relationship of q _b |.

[0054]

[Table 2]

Comparative Example 1 A comparative example with respect to Example 1 will be described.

The developers T5 to T16 of this comparative example are shown in Table 3.
An external additive having a material and an average particle diameter as shown in FIG.

Further, the above 12 kinds of developers were carried out.
When the charging property was measured by the same method as in Example 1, it was found that
The developer (T5 to T12) to which the external additive made of tan is attached is
| Q _a| <| Q_b│ relationship was met, but made of silica
| Q for the developers (T13 to T16) with external additives attached
_a｜ ＞ ｜ q_bIt became a relationship of |.

[0058]

[Table 3]

Then, in the same manner as in Example 1, the above 12
When the developing densities of the types of developers were measured, the results shown in Table 4 were obtained. That is, T5, T6, T9,
The developer of T10 and T13 to T16 is 10 mm × 10 m
The toner weight per m was less than 10.0 g / cm ^2, and it was found that the toner was not a practical developer.

In the measurement of the development density, T1
It was found that the toners of T1 and T12 are not practical developers because toner cloud is generated.
It was also found that the developers of Nos. 8, T9 and T10 were not practical developers because density unevenness occurred in a solid image.

[0061]

[Table 4]

It is considered that the above problems occur in these twelve kinds of developers for the following reasons. When the average particle size of the external additive is less than 20 nm (T5, T
In 6), since the physical adhesive force acting between the developer and the sleeve (developer carrying member) cannot be weakened, the required development density cannot be obtained. When the average particle size of the external additive exceeds 100 nm (T7,
At T8), the flowability of the developer is reduced and the developer agglomerates, so that the developer is unevenly conveyed and the density is uneven. When the coverage of the external additive is less than 20% (T9, T10)
In addition, since the developer cannot be provided with the required fluidity and the developer is aggregated, the developer is unevenly conveyed and the density is uneven. When the coverage of the external additive exceeds 80% (T11, T1
In 2), since the physical adhesive force acting between the developer and the sleeve (developer carrying member) cannot be weakened, the required development density cannot be obtained. Further, since the physical adhesive force acting between the developer and the sleeve (developer carrier) is extremely reduced, a toner cloud is generated. When the chargeability of the toner is improved by adding the external additive (T13 to T16), the Coulomb force acting between the developer and the sleeve (developer carrying member) becomes strong, so that the developer and the sleeve are increased. The physical adhesive force acting between the (developer carrying member) and the (developing agent carrying member) is improved, and the required developing density cannot be obtained.

Example 2 An example of the two-component developer according to the second invention of the present application will be described.

The toner used in the above developer is the same as that in the first embodiment. Therefore, all four types of toner have an average particle size of 20 nm or more and 100 n
An external additive of m or less is adhered at a coverage of 20% or more and 80% or less.

The carrier used in the developer is a mixture of magnetic fine powder (70 wt% magnetite) and polymer resin (30 wt% styrene acrylic), and has an average particle diameter of 45 μm and saturation magnetization with respect to an applied magnetic field of 1000 Oersted. 80 emu / cm ³ , remanent magnetization 12.8 emu /
cm ³ , carrier resistance is about 10 ¹² Ω · cm, and carrier density is 2.2 g / cm ³ .

Then, in this embodiment, the carrier and the four types of toner are mixed at a toner concentration of 8 wt%,
When the charging characteristics of each toner were measured, the charge amount q _a of the toner after the external additive was attached and the charge amount q _b of the toner before the external additive was attached were | The relationship of q _a | <| q _b | was satisfied.

Next, a solid image is developed by a non-contact developing method using an image forming apparatus similar to that of the first embodiment, and the toner weight of the solid image is measured, and the toner weight is 10 mm.
The white spots in the solid image per × 10 mm were examined. As a result, as shown in Table 5, it was found that all of the four types of developers had a toner weight of 10.0 g / cm ² or more and were practically applicable, and that white spots did not occur. .

[0068]

[Table 5]

Further, instead of the above black toner, 85 wt% polyester and 15 wt% pigment yellow
% Of the toner particles made of 87% polyester
% And toner particles composed of 13% by weight of red pigment and magenta toner similarly having external additives attached thereto, or toner particles composed of 87% by weight of polyester and 13% by weight of blue pigment. Similarly, the same results were obtained with Sian toner to which an external additive was attached.

Therefore, the average particle size is 20 with respect to the toner particles.
20% or more and 8% or more of external additives having a thickness of 100 nm or more
The toner charge amount q _a after the external additive is attached is 0% or less, and the toner charge amount q _b before the external additive is attached is | q _a | <| It can be seen that in the developer satisfying the relationship of q _b |, a desired development density is obtained and white spots do not occur.

The image forming apparatus uses a two-component developing device, as compared with the image forming apparatus of the first embodiment.
The rotation speed of the sleeve (developer carrying member) of the two-component developing device is 198 mm / s, and the distance between the photosensitive member and the sleeve is 0.5.
mm, the thickness of the developer layer on the sleeve is 0.3 mm, the voltage applied between the photoconductor and the sleeve has a frequency of 6 kHz,
AC voltage of Vp-p1.6kV, duty 50% and-
The difference is that the DC voltage of 500 V is superposed.

Comparative Example 2 A comparative example with respect to Example 2 will be described.

In this comparative example, 12 used in Comparative Example 1 was used.
Twelve types of developers were prepared by mixing the types of toner and the carrier used in Example 2.

Further, when the charging characteristics of the above-mentioned 12 kinds of developers were measured in the same manner as in Example 2, the toner (T5-T5) to which the external additive made of titanium oxide was adhered was measured.
T12) satisfies the relationship of | q _a | <| q _b |
Toner to which an external additive made of silica is attached (T13 to T1
In 6), the relationship is | q _a |> | q _b |.

Then, in the same manner as in Example 2, the above 12
When the development densities of the types of developers were measured, the results shown in Table 6 were obtained. That is, T5, T6, T9,
The developer of T10 and T13 to T16 is 10 mm × 10 m
It was found that the toner weight per m was less than 10.0 g / cm ² and white spots were generated in the image, so that it was not a practical developer. Further, in the measurement of the development density, it was found that the developer of T11 and T12 was not a practical developer because the toner cloud was generated.
It was also found that the developers of T7, T8, T9 and T10 are not practical developers because density unevenness occurs in a solid image.

[0076]

[Table 6]

It is considered that the above problems occur in these twelve kinds of developers for the following reasons. When the average particle diameter of the external additive of the toner is less than 20 nm (T
5, T6) cannot weaken the physical adhesive force acting between the toner and the carrier, so that the required developing density cannot be obtained. Further, the carrier adheres to the photoreceptor due to the above-mentioned physical adhesive force, and white spots are generated. When the average particle diameter of the external additive of the toner exceeds 100 nm (T7, T8), the developer deteriorates in fluidity and agglomerates, causing uneven transport of the developer and uneven density. When the coverage of the toner external additive is less than 20% (T9,
At T10), since the physical adhesive force acting between the toner and the carrier cannot be weakened, the required developing density cannot be obtained. Further, the carrier adheres to the photoreceptor due to the above-mentioned physical adhesive force, and white spots are generated. Furthermore, since the developer cannot be provided with the required fluidity and the developer aggregates, uneven transport of the developer occurs and uneven density occurs. When the coverage of the toner external additive exceeds 80% (T1
1, T12), the physical adhesive force acting between the toner and the carrier is extremely reduced, so that a toner cloud is generated. When the chargeability of the toner is improved by adding the external additive (T13 to T16), the Coulomb force acting between the toner and the carrier becomes strong, so that the physical force acting between the toner and the carrier is increased. Adhesion is improved, and the required development density cannot be obtained. Further, the carrier adheres to the photoreceptor due to the above-mentioned physical adhesive force, and white spots are generated.

Example 3 An example of the two-component developer according to the third invention of the present application will be described.

The toner particles used in the above developer are polyester (number average molecular weight: 4,300, weight average molecular weight: 9,800, Tg = 58 ° C.) 94 wt% and resinocarmine 6B (resinocolor) 6 wt%. It is formed by kneading and pulverizing so as to have an average particle size of 7 μm.
Has a negative charging property. The average particle size was measured with a Coulter counter (manufactured by Coulter).

The external additive attached to the toner particles is polymethyl methacrylate (number average molecular weight: 30,000,
Weight average molecular weight: 112,800, Tg = 80 ° C.) and average particle diameters of 20 nm, 40 nm and 50 nm were prepared.

The carrier used in the developer is a styrene-acrylic copolymer (number average molecular weight: 23,000).
0, weight average molecular weight: 98,000, Tg = 78 ° C)
30 wt%, carbon black (basic carbon black: pH = 8.5) 3 wt%, granular magnetite (maximum magnetization 80 emu / g, particle size 0.5 μm) 67 wt
% Is kneaded and pulverized, and then classified, and has an average particle diameter of 45 μm, a specific gravity of 2.2 and an electric resistance value of 10 ¹² Ωcm, and has a positive charging property. The average particle size was measured by Microtrac (manufactured by Nikkiso Co., Ltd.).

In this embodiment, first, the toner particles and the external additives are mixed at a coverage of 20% or 50% to form a negatively chargeable magenta toner, and then the magenta toner. And the carrier and the toner concentration (T
C: Toner Concentration) 10w
In combination with t%, as shown in Table 7, six types of developers having different average particle diameters of external additives and different coverages were formed.

[0083]

[Table 7]

Further, the toner band in these developers is
The electrical characteristics were measured by the blow-off method.
The toner charge after applying the above external additives.
Quantity q _aAnd the amount of charge of the toner before attaching the external additive q_bAnd
| Q_a| <| Q_bThe relationship of | was satisfied. In addition, above
Charge amount q of toner before adhering additive_bThe above Tona
-When combining particles and the above carrier at 10 wt%
It is the value measured by the blow-off method for the charging characteristics of the toner.
It

Next, using the image forming apparatus shown in FIG.
Changes in the development density of each of the above-mentioned developers and the occurrence status of contamination were examined.

In FIG. 2, 21 is the process speed 3
An OPC photosensitive drum having a diameter of 84 mm rotating at 00 mm / s, 22 is a uniform charger for charging the photosensitive drum to -550 V, and 23 is a photosensitive member potential at a resolution of 400 dpi-
Exposure device for exposing up to 150 V, 24 and 25 are two developing devices, 26 is a transfer device, 27 is a peeling device, 28 is a cleaning means, 29 is a static eliminator, 30 is a paper guide, and 31 is a conveyor belt. Is. Each of the developing devices 24, 25
As shown in FIG. 3, the surface is made of aluminum whose surface is anodized, and has a diameter of 25 m that rotates at 600 mm / s.
m cylindrical sleeve 32 and fixedly arranged inside the sleeve 32, and the magnetic flux density on the sleeve 32 becomes 500 G 7
A magnet roll 33 having two magnetic poles formed thereon, a developer layer layer thickness regulating member 34 that is pressed against the surface of the sleeve 32 to even out the developer layer supplied onto the sleeve 32, and the sleeve 3.
2 adjacent to each other, and has a paddle 35 for mixing and charging the developer and supplying the same to the sleeve 32.

In the image forming apparatus, the distance between the photoconductor 1 and the sleeve 32 is set to 0.5 mm, the thickness of the developer layer on the sleeve 32 is set to 0.4 mm, and the sleeve 32 and AC voltage (frequency 8 kHz, Vp-p1.5 kV) and DC voltage (-500
v) is applied as a developing bias to develop the latent image formed on the photoconductor 1 by the non-contact developing method.

Further, the developing device 24 was charged with the magenta developer, and the developing device 25 was charged with Sian developer. The Sian toner is a mixture of Sian toner, the carrier, and a toner concentration of 10 wt%, and the Sian toner is polyester (number average molecular weight: 4,
300, weight average molecular weight: 9,800, Tg = 58 °
C) 94 wt% and cyanine blue 4938 (Dainichi Seika) 6 wt% were kneaded and pulverized, and Sian toner particles having an average particle size of 7 μm, and polymethacrylic acid having an average particle size of 40 nm adhered to the surface at a coverage ratio of 50%. It is composed of an external additive made of methyl and has a negative charging property. The developing toner weight (Mt [g / m ² ]) of the cyan dye on the photoconductor at the start of printing is 8.0 g / m ² . Further, in the image forming process by the image forming apparatus, first, the surface of the photoconductor 1 is charged to −550 V by the uniform charger 22 (FIG. 4A), and the photoconductor 1 is exposed by the exposure device 23.
The surface is exposed to −150 V (FIG. 4 (b)) and is developed by the developing device 24 (FIG. 4 (c)) to form a magenta toner image on the photoconductor 1, and then a magenta toner image is formed. Charger 2
2 again charges the surface of the photoconductor 1 to −550 V (see FIG.
(A)), the surface of the photoreceptor 1 is exposed to −15 by the exposure device 23.
It is exposed to 0 V (FIG. 5B), and the developing device 2
5 (FIG. 5 (c)), the cyan toner image is formed on the photoconductor 1 by superposing it on the magenta toner image.

Changes in the development density of the above-mentioned developer and mixing of
Specifically, the occurrence status is as described above when printing starts.
Weight of developing toner on photoreceptor of Sian developer (Mt [g
/ M ²]) Is 7.8 to 8.0 g / m.²As above each
Adjust the toner density of magenta developer to 10,0
Make 00 continuous prints, before and after
Change rate of the development density Mt of the
The generation level of color was examined. From the image density, Mt
Desirable level is 8.0 g / m²Above, also used
The level without any problems is 7.0 g / m²As above
Bell is 6.5g / m²That is all.

Then, the change rate ΔMt of the development density is
When Mt (before) at the start of printing and Mt (after) at the end of continuous printing of 10,000 sheets are defined as ΔMt = Mt (after) / Mt (before). Incidentally, a desirable level for ΔMt is 0.85 or higher, and a usable level is 0.80 or higher. Further, the level of occurrence of color mixing was obtained by calculating the area ratio of magenta toner in the cyan image, and defining this as the color mixing ratio [%]. By the way, the level with which there is no problem in the color mixing ratio is less than 1.0%, and the usable level is 1.0% or more and less than 1.2%.

In the above continuous printing of 10,000 sheets, one cycle is to set a pause time of 30 seconds after performing continuous printing of 100 sheets.
It was repeated 0 times, and the cyan developer in the second developing device was replaced with the magenta developer in the first developing device.

As a result, as shown in Table 8, in all the above-mentioned developers, Mt is 6.5 g / m ² or more, the development density change rate ΔMt is 0.80 or more, and the color mixture rate is Is also less than 1.2%, and even when the latent image formed on the latent image carrier is overdeveloped by the non-contact development method, the development density is stable at a desired value for a long period of time, and the color mixture does not occur. It turned out to be unlikely. Further, with all of the above-mentioned developers, the density did not decrease or white spots did not occur immediately after the start of printing.

[0093]

[Table 8]

Further, a similar experiment was conducted using a ferrite carrier in place of the polymer carrier, and it was confirmed that there was some practicality, although the performance was a little poor. The reason why the performance of the ferrite carrier is poor is that since the ferrite carrier has a large specific gravity, stress on the toner during mixing becomes large, and as a result, the chargeability of the toner deteriorates quickly. Conceivable.

Comparative Example 3 A comparative example (No. 1) with respect to Example 3 will be described.

In the developers D7 to D20 of this comparative example, the materials as shown in Table 9 and the external additives having the average particle diameter are adhered at the coverage shown in the table.

[0097]

[Table 9]

Then, in the same manner as in Example 3, the above 14
Changes in the development density of the types of developers and the occurrence of contamination were examined <The results are shown in Table 10. As shown in Table 10, for all the developers, the Mt was less than 6.5 g / m ² , the development density change amount was less than 0.8, or the color mixture rate was 1.2 or more, which was not practical. I knew it wasn't.

[0099]

[Table 10]

It is considered that the above-mentioned problems occur in the above 14 kinds of developers for the following reasons. A developer using an external additive having a small average particle size (D13 to
In D16), since the external additive is buried in the toner particles, the effect of reducing the physical adhesive force exerted between the toner and the carrier by the external additive is weakened, and the change in the development density is increased. (Actually, when the developers D13 to D16 were observed with a scanning microscope (SEM), it was observed that the external additive was buried. On the other hand, the external additive having a thickness of 20 nm or more was not observed. ). A developer using an external additive having a large average particle size (D17 to
In D20), the physical adhesive force acting between the toner and the carrier is reduced, and the physical adhesive force acting between the toner and the photoconductor is also reduced, so that the color mixture ratio is 1.2 or more. become. Developers with small external additive coverage (D7, D9, D1
At a coverage ratio of 10%), the developer has poor fluidity and agglomerates, so that a large amount of toner having a reduced charge amount or toner charged with an opposite polarity is generated, that is, toner charging failure occurs, and thus development is performed. The change in concentration becomes large. A developer with a large external additive coverage (D8, D10, D1
(2: coverage rate 60%), the physical adhesive force acting between the toner and the carrier becomes small, and the physical adhesive force acting between the toner and the photoconductor also becomes small. It becomes 1.2 or more.

From the above results, the particle size of the external additive is 20.
It is understood that the thickness is not less than 50 nm and not more than 50 nm, and the coverage of these external additives with respect to the toner particles is preferably not less than 20% and not more than 50%.

Comparative Example 4 A comparative example (No. 2) with respect to Example 3 will be described.

The developer of this comparative example is different from the developer of Example 3 in that the material of the external additive is changed from polymethylmethacrylate to polytetrafluoroethylene (Teflon: registered trademark). In addition, in this comparative example, as shown in Table 11, the average particle size is 15, 20, 40, 50, 60 nm.
20 kinds of developers were formed by using the toner prepared by preparing the external additive (1) and coating the surface of magenta toner particles with a coverage of 10, 20, 50, 60%. Also,
When the charging characteristics of the toners of the above 20 kinds of developers were measured by the same method as in Example 3, the charge amount q _a of the toner after the external additive was attached and the toner before the external additive was attached of the amount of charge q _b and is | q _a |> | had become of the relationship | q _b. The reason for the above relationship is that since polytetrafluoroethylene has a charging order on the negative polarity side of the toner, it is largely charged on the negative polarity side by contact with the carrier, and as a result, the charge amount of the toner is It is considered that it becomes larger on the negative polarity side.

[0104]

[Table 11]

Then, in the same manner as in Example 3, the above 20
When it was tried to examine the change in the development density of the types of developers and the occurrence of mixing, as shown in Table 12, for all the developers, fogging and unevenness occurred in the image immediately after the start of image formation, and I couldn't stand it.

The reason why the above-mentioned problem occurs is that the toner is highly charged on the negative polarity side, and therefore Mt is 8.0 g.
/ M ² or more, it is necessary to extremely improve the toner density.
As a result, it is considered that the toner is not sufficiently restrained by the carrier and a toner cloud is generated to cause fog. Also, since the toner concentration is too high, the developer is It is considered that the fluidity of the toner deteriorates and aggregates, resulting in uneven transport of the developer.

[0107]

[Table 12]

[0108]

As described above, the developer according to the first invention of the present application has an average particle size of 20 nm or more with respect to toner particles.
The external additive having a thickness of 00 nm or less adheres at a coverage of 20% or more and 80% or less, and the charge amount q _a of the toner after the external additive is adhered and the toner before the external additive is adhered Since the charge quantity q _b satisfies the relationship of | q _a | <| q _b |, even if the latent image formed on the latent image carrier is developed by the non-contact development method, the desired development density is obtained. Development can be performed.

The developer according to the second aspect of the present invention comprises a carrier and a toner, and the toner has an average particle size of 20 nm or more and 100 n or more with respect to the toner particles.
m or less of the external additive is attached at a coverage of 20% or more and 80% or less, and the charge amount q _a of the toner after the external additive is attached and the toner before the external additive is attached Since the charge quantity q _b satisfies the relationship of | q _a | <| q _b |, even if the latent image formed on the latent image carrier is developed by the non-contact developing method, the desired developing density is obtained. Development can be carried out and white spots do not occur.

Next, the color developer according to the third aspect of the present invention comprises a carrier and a toner, and the toner has an average particle size of 20 nm or more and 50 n or more with respect to the toner particles.
m or less of the external additive is attached at a coverage of 20% or more and 50% or less, and the charge amount q _a of the toner after the external additive is attached and the toner before the external additive is attached Since the amount of charge q _b satisfies the relationship of | q _a | <| q _b |, even if the latent image formed on the latent image carrier is overdeveloped by the non-contact development method, the development density is long-term. Is stable at almost a desired value over a long period of time, and color mixing hardly occurs.

Further, an image forming apparatus according to a fourth invention of the present invention uses the developer described in any one of the first to third inventions to form a latent image on a latent image carrier. Is developed by a non-contact developing method, so that development can be performed at a desired developing density.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus used for evaluation of a developer of Example 1.

FIG. 2 is a schematic diagram of an image forming apparatus used for evaluation of a developer of Example 3.

3 is a schematic diagram of a developing device in the image forming apparatus in FIG.

4 is an explanatory view (No. 1) of an image forming process by the image forming apparatus of FIG.

5 is an explanatory view (No. 2) of an image forming process by the image forming apparatus of FIG.

[Explanation of symbols]

 1: Photoreceptor (latent image carrier).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigenori Ando 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Shinji Sasahara, 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (5)

[Claims] 1. A non-contact type latent image formed on a latent image carrier.
The smell of the developer used when developing with the development method
The developer has an average particle size of 20 n with respect to the toner particles.
20% or more and 80% or more of the external additive having a thickness of m or more and 100 nm or less
% Or less, and the above-mentioned external additive was attached.
Charge amount of the subsequent toner q_aAnd toner before attaching external additives
-Charge amount q_bAnd is | q _a| <| Q_bSatisfy the relationship
A developer characterized by being present. 2. A developer used for developing a latent image formed on a latent image carrier by a non-contact developing method, wherein the developer comprises a carrier and a toner, and the toner is a toner particle. With an average particle size of 20 nm or more 10
The external additive having a thickness of 0 nm or less is attached at a coverage of 20% or more and 80% or less, and the charge amount q _a of the toner after the external additive is attached and the toner before the external additive is attached charge quantity q _b and is | q _a | <| developer characterized in that it satisfies the relation | q _b. 3. A color developer which is used when a latent image formed on a latent image bearing member is overdeveloped by a non-contact developing method, wherein the color developer comprises a carrier and a toner. The toner comprises an external additive having an average particle size of 20 nm or more and 50 nm or less adhered to the toner particles at a coverage of 20% or more and 50% or less, and the toner charge amount after the external additive is adhered. q _a and the charge amount of the toner before the external additive adhering q _b and is _{| q a | <| q b} | color developer, characterized in that it meets the relationship. 4. The color developer according to claim 3, wherein the carrier is a polymer carrier formed by mixing fine magnetic powder and a binder resin. 5. An image characterized by developing a latent image formed on a latent image bearing member by a non-contact development method, using the developer according to any one of claims 1 to 4 as a developer. Forming equipment.