JPH041767A - Electrostatic charge image developer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application'] The present invention relates to an electrostatic image developer, and more particularly to a two-component developer for developing an electrostatic image formed in electrophotography. .

[Prior Art] What is electrophotography? U.S. Patent No. 2.297.6! Many methods are known, as described in Specification H etc.
Generally, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, the latent image is developed using toner, and the toner image is transferred to a transfer member such as paper as necessary. After the transfer, the image is fixed using heat, pressure, solvent vapor, etc. to obtain a copy.

Furthermore, various methods have been proposed as methods for developing with toner or methods for fixing toner images, and methods suitable for each image forming process are adopted.

In recent years, high-speed copying and high image quality have been required for electrophotography, and developers are required to have even higher durability.

Generally, toner is manufactured by melt-mixing coloring agents such as dyes and pigments and additives such as charge control agents in a thermoplastic resin, uniformly dispersing the mixture, and then using a pulverizer or a classifier to form the desired particles. Methods of manufacturing toner having a diameter are known.

Toner produced by these pulverization methods requires brittleness in the binder resin in order to provide sufficient pulverization properties, and in addition, since pulverization method toners have sharp protrusions, they are further pulverized in the developing device. or susceptible to powdering. As a result, increased fogging and scattering inside the machine occur, which is undesirable.

Addition of a crosslinking agent is generally used as a method of imparting brittleness, but this method is not suitable for low-temperature fixing of toners. Furthermore, the toner produced by the pulverization method is -E
Since Q has an amorphous shape, there is a limit to faithfully reproducing the latent image, which is disadvantageous for achieving high image quality. In order to achieve high image quality in the pulverization method, it is necessary to pulverize into smaller particles. However, it is difficult to balance the brittleness of the binder resin, which is related to the crushing efficiency, and the thermal properties, which are related to fixability and storage stability, and it has been impossible to fully satisfy these properties.

As opposed to these irregularly shaped toners, spherical toners have been proposed. For example, in Japanese Patent Publication No. 56-13945, a spherical toner is obtained by a melt spray method, and in Japanese Patent Publication No. 57-51576, a small amount of an organic solvent is added to an amorphous toner, and the mixture is stirred under cooling. A method of obtaining spherical toner by this method is further disclosed in Japanese Patent Publication No. 36-10231, Japanese Patent Application Laid-Open No. 59-53856, and Japanese Patent Application Laid-open No. 59-5385.
No. 9-61842 and the like disclose a method of obtaining a spherical toner using a polymerization method.

Since these spherical toners have a uniform shape, a latent image, especially an edge portion, can be faithfully developed, so that they are suitable for achieving high image quality. Furthermore, when a spherical toner is obtained by a polymerization method, it is easy to reduce the particle size of the particles, and the toner becomes suitable for achieving high layer image quality.

On the other hand, as a carrier, an example is JP-A-64-81966.
JP-A-2003-100001 discloses a method for obtaining a carrier that can improve image quality and extend the life of the developer.

[Problems to be Solved by the Invention] An object of the present invention is to provide a developer that can be stirred and mixed with a small load. Furthermore, the other purpose is to have excellent durability,
An object of the present invention is to provide a developer having good development characteristics.

[Means for Solving the Problems] An object of the present invention is to provide an electrostatic image developer containing a toner containing at least a colorant and a binder resin, and a carrier.
The toner has a relationship of 1.00≦r/R≦1.20 between an inscribed circle of radius r that touches the toner projection plane at at least three points and a circumscribed circle of radius R. , the carrier is 100V/
The specific resistance value when a DC electric field of cm is applied is 1. Ox
This is achieved using an electrostatic image developer characterized in that the resistance is 10" to 1.Ox 1015 Ω"cm.

The present invention will be described in detail below.

As a result of extensive studies, the present inventors have found that a developer consisting of toner and carrier that satisfies the above requirements can be stirred and mixed with a small load, has excellent durability, and exhibits good development characteristics. I found out.

That is, in a two-component developer consisting of at least a toner and a carrier, it is desired that the toner and carrier be sufficiently stirred and mixed, and that the toner be quickly charged to a constant charge (2). Therefore, simply carrying out strong agitation and mixing will cause the toner to become spent, which will significantly reduce not only the durability but also the developability. Therefore, at least a substantially spherical toner and a specific resistance value of 1. OX I (19-1.0
By using a developer composed of a carrier of ×10 15 Ω·cm, the spherical toner present between the carriers acts as a roller, improving the fluidity of the developer. A developer with excellent fluidity enables sufficient stirring with less energy, quickly charges the toner to a constant IF charge amount, and provides excellent development characteristics. Furthermore, it prevents toner from becoming spent and improves durability.

As described above, the toner particles in the present invention are preferably substantially spherical, and between an inscribed circle of radius r and a circumscribed circle of radius R that touch the projection plane of the toner particles at least three points. It is preferable that there is a relationship of 1.00≦r/R≦1.20. As r/R increases, the shape moves away from a spherical shape, and when it exceeds 1.20, the characteristics of a spherical toner no longer appear.

The volume average particle diameter of these spherical toners is 2 to 20 μm, preferably 3 to 12 μm, and more preferably 4 to 8 μm.

In the present invention, the projection plane of toner particles means at least 2000 times or more, preferably 5000 times or more, using an electron microscope.
Mean image obtained by focusing on the contour of the particle at magnification.

On the other hand, regarding the carrier, the specific resistance value when a DC electric field of 100 V/cm is applied is 1. OX 109-1,
It is preferable that OXl015Ω·cm. Specific resistance value is 1. When OX is larger than 10"Ω・cm, not only does it take time for the toner to reach the appropriate amount of charge, but it also causes a charge-up phenomenon, increases the cohesive force between toner carriers, and as a result deteriorates fluidity. On the other hand, if it is smaller than 1.0 x 10'' Ω·cm, the charge charged on the toner tends to leak, causing problems such as toner scattering under high humidity or after being left unpreferably.

Examples of methods for obtaining the substantially spherical toner 7 used in the present invention include the above-mentioned method of spheronizing an irregularly shaped toner and polymerization method.

The polymerized toner used in the present invention can be obtained by the following method. That is, a monomer system in which release agents, colorants, charge control agents, polymerization initiators, and other additives are added to polymerizable monomers and uniformly dissolved or dispersed using a homogenizer, ultrasonic disperser, etc. It is dispersed in an aqueous phase containing a dispersion stabilizer using a conventional stirrer, homomixer, homogenizer, etc. Preferably, the stirring speed and time are adjusted so that the monomer droplets have a predetermined toner particle size, generally 30 μm or less, and after that, the particle state is maintained by the action of a dispersion stabilizer, and the particle size is maintained. It is sufficient to perform stirring to an extent that sedimentation is prevented. The polymerization temperature is set to 40°C or higher, and for boat fishing, the polymerization is carried out at a temperature of 50 to 90°C. After the reaction is completed, the generated toner particles are collected by washing and filtration, and then dried. In the suspension polymerization method, the monomer system is usually 10
It is preferable to use 300 to 3000 parts by weight of water as a dispersion medium per 0 parts by weight.

Examples of polymerizable monomers that can be used in the above polymerized toner include styrene, 0-methylstyrene, m-methylstyrene, and p-methylstyrene.
- Styrenic monomers such as methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate・Acrylic acid esters such as dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate・Methacrylic acid esters such as isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.Other acrylonitrile and methacrylate Examples include monomers such as nitrile and acrylamide.

These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or styrene derivatives alone or in combination with other monomers from the viewpoint of the development characteristics and durability of the toner.

The dispersion medium used in the present invention may include any suitable stabilizer, such as polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salt of carboxymethylcellulose, polyacrylic acid and its salts, starch. - Tricalcium phosphate, aluminum hydroxide, magnesium hydroxide, calcium metasilicate, barium sulfate, bentonite, etc. can be used by dispersing them in the aqueous phase.This stabilizer should be used in an amount of 100 parts by weight of the polymerizable monomer. , it is preferred to use 0.2 to 20 parts by weight.

In addition, due to the fine dispersion of these stabilizers,
0.1 parts by weight of surfactant may be used. This is to promote the intended action of the above-mentioned dispersion stabilizers, and specific examples include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, and lauric acid. Sodium/potassium stearate/
Examples include calcium oleate.

It is more preferable to add and polymerize a polymer/copolymer having a polar group as an additive to the monomer system. Furthermore,
In the present invention, a monomer system containing a polar group-containing polymer/copolymer or cyclized rubber is suspended in an aqueous phase in which a dispersant having an opposite charge to the polar polymer is dispersed, and polymerization is carried out. It is preferable to do so. That is, the cationic or anionic polymer/copolymer or cyclized rubber contained in the monomer system is polymerized with the oppositely charged anionic or cationic dispersant dispersed in the aqueous phase. The particles are electrostatically attracted to each other on the surface of the particles that become the toner, and the dispersant covers the particle surface to prevent the particles from coalescing and stabilize them, and the polar polymer added during polymerization gathers on the surface of the particles that become the toner. Therefore, it takes on a kind of shell-like shape, and the resulting particles become pseudo-capsules. A relatively high molecular weight polar polymer/copolymer or cyclized rubber is used to give toner particles excellent properties such as printability and development abrasion resistance, while a relatively low molecular weight internally provides fixing properties. By performing polymerization in a manner that contributes to improvement, it is possible to obtain a toner that satisfies the contradictory requirements of fixing properties and blocking properties. Examples of polar polymers/copolymers and counterloading dispersants that can be used in the present invention are shown below.

(1) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, or copolymers with styrene and unsaturated carboxylic acid esters.

(2) Examples of anionic polymers include nitrile monomers such as acrylonitrile, halogen-containing monomers such as vinyl chloride, unsaturated carboxylic acids such as acrylic acid and methacrylic acid,
Other examples include unsaturated dibasic acids, unsaturated dibasic acid anhydrides, polymers of nitro monomers, and copolymers with styrene monomers. Furthermore, cyclized rubber may be used instead of these polar polymers.

(3) As the anionic dispersant, fine silica powder is preferably used, especially with a BET specific surface area of 200 m27 g.
The above colloidal silicas are suitable.

(4) As the cationic dispersant, aminoalkyl-modified colloidal silica (preferably has a BET specific surface area of 20
Examples include hydrophilic positively chargeable silica fine powder such as 0m27g or more), aluminum hydroxide, and the like.

It is preferable to use such a dispersant in an amount of 0.2 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer. More preferably, it is 0.3 to 15 parts by weight.

As the polymerization initiator, any suitable polymerization initiator such as 2,2-azobis-(2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, 1.
1-azobis(cyclohexane-1-carbonitrile)
, 2,2°-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxy carbonate, cumene hydroperoxide ,2
．． Examples include peroxide-based polymerization initiators such as 4-dichlorobenzoyl peroxide and lauroyl peroxide. These polymerization initiators are generally 0.5 to 1 % of the polymerizable monomer.
An addition amount of 0% by weight is sufficient.

Further, in order to impart various properties to the toner, for example, the following substances may be added. Note that, from the viewpoint of durability when added to the toner, these additives preferably have a particle size of 1710 or less of the volume average diameter of the toner particles.

l) Fluidity imparting agent: Metal oxides (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Each of them is more preferably subjected to hydrophobization treatment.

2) Abrasives: Metal oxides (strontium titanate, cerium oxide,
aluminum oxide, magnesium oxide, chromium oxide, etc.), nitrides (silicon nitride, etc.), carbides (silicon carbide, etc.), metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), etc.

3) Lubricant: Fluorine resin powder (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), etc.

4) Charge controllable particles: Metal oxides (metal tin, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.), carbon black, etc.

These additives are used in an amount of 0 per 100 parts by weight of toner particles.
．． 1 to 10 parts by weight are used, preferably 0.1 to 5 parts by weight.
Parts by weight are used. These additives may be used alone or in combination.

As the colorant used in the present invention, known colorants can be used, such as carbon black, iron black, C, 1,
Direct Red 1, C, 1, Direct Red 4, C
,1, Acid Red 1. C, 1, Basic Red 1
, C,1, Modern Tread 30, C,1, Direct Blue 1, C,1, Direct Blue 2, C,I.

Acid Blue 9, C, 1, Acid Blue 15, C,
I.

Basic Blue 3, C, 1, Basic Blue 5, C
Dyes such as ,1, Mordand Blue, C,1, Direct Green 6, C,1, Basic Green 4, C11, Basic Green 6, yellow lead, cadmium yellow,
Mineral Fast Yellow, Navel Yellow Naphthol Yellow S, Hansa Yellow 61 Permanent Yellow NCG, Tartrazine Lake, Molybdenum Orange, Permanent Orange GTR, Benzidine Orange G1 Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Brilliant Carmine 3
B, Fast Violet B1 Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Quinacridone, Rhodamine B,
There are pigments such as Phthalocyanine Blue First Sky Blue Pigment Green B, Malachite Green Lake, and Final Yellow Green G.

In particular, when obtaining toner using a polymerization method, it is necessary to pay attention to the polymerization inhibiting property and aqueous phase migration property of the colorant.
Preferably, surface modification, for example, hydrophobic treatment using a substance that does not inhibit polymerization, is performed.

Further, in order to improve the release properties during hot roll fixing, waxes, such as hydrocarbon compounds, which are generally used as release agents may be added to the toner. Waxes used in the present invention include paraffin/polyolefin waxes and modified products thereof, such as oxides and grafted products, as well as higher fatty acids, metal salts thereof, and amide waxes. These waxes are prepared using the ring and ball method (
Softening point according to JIS K 2531) is 40-130℃
, preferably one having a temperature of 50 to 120°C,
If the softening point is 40° C. or lower, the blocking resistance and shape retention of the toner will be insufficient, and if the softening point is 130° C. or higher, the releasability effect will be insufficient.

In the present invention, it is desirable to add a charge control agent to the toner material for the purpose of controlling the chargeability of the toner. As these charge control agents, known ones can be used.
For example, positive charge control agents include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, amine and polyamine compounds, and negative charge control agents include salicylic acid metal compounds, monoazo dye metals, etc. Examples include compounds, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and the like.

The carrier used in the present invention has a national resistance value of 1.0 when a DC electric field of 100 V/cm is applied. OX109
~1. Any known OXIO"Ωcm can be used. In the present invention, the method of measuring the specific resistance value is exemplified by the method shown in FIG. The specific resistance value of the carrier can be determined by applying a voltage of 100 V using the device shown in Figure 1, measuring the minute current flowing at that time, and calculating the specific resistance ρ (Ω・am
), but since the carrier is a powder, it may change depending on the filling rate, so care must be taken.

[Example] Hereinafter, the present invention will be explained in detail based on an example. still,
All parts are by weight.

The above formulation was heated to 60°C in a container to dissolve or disperse it, and then 10 parts of 2,2'-azobis-2,4-dimethylvaleronitrile was added as an initiator to prepare a monomer system.

Separately, 10 parts of aminoalkyl-modified colloidal silica was added to 1200 parts of ion-exchanged water, and the above monomer system was added to a dispersion medium system adjusted to pH 6 with hydrochloric acid, and the mixture was heated for 6 hours under a nitrogen atmosphere.
Recycling and dispersion treatment was carried out at 0°C for 20 minutes at 8000 rpm using a Hyline Mill Model 25 (Tokushu Kikako Pear Type) to granulate the monomer system.

Furthermore, the polymerization temperature was heated to 60°C with a paddle stirring blade, and when it was confirmed that the degree of polymerization exceeded 95% by measuring the residual monomer by gas chromatography, the polymerization temperature was raised to 80°C, and the paddle stirring blade was heated to 60°C. The stirring blade was changed to a T, K, type homomixer (Special Machine Kako Pear type), and stirring was performed at 5000 rpm for 15 minutes. After that, stirring was continued with the paddle stirring blade again to complete the polymerization. Reaction product After cooling, add sodium hydroxide and dissolve the dispersant, wash with water,
A spherical toner was obtained by filtration and drying. The particle size of this toner was measured using a Coulter counter (aperture diameter 100).
gm), the volume average diameter was 4.2 μm.
Met.

Further, this toner had r/R=1.00.

To 100 parts of this toner, 1.0 part of fine silica powder having a specific surface area of 20 On+2/g by the BET method and hydrophobized with hexamethyldisilazane was mixed. Further, for 6 parts of the toner, a specific resistance value of 1.0×10′2Ω・c
94 parts of carrier m were mixed to prepare a developer.

The developer obtained in this way was used with Canon CLC-
The power when the sleeve was rotated was measured to be 9.6W.

Further, when image printing was performed, the copies were clear and no fogging occurred even after 50,000 copies were made.

The granulation process was carried out under a nitrogen atmosphere using a Hyline Mill Model 25 at 60°C/8000 rpm/20 minutes.
Under a nitrogen atmosphere, at 60°C using a homomixer.
The same procedure as in Example 1 was carried out except that the dispersion treatment conditions were changed to /6500 rpm/60 minutes, and a spherical toner with a volume average diameter of 12.2 parts m in a Coulter counter (aperture diameter 1100p) and a glass transition point of 56°C was used. Obtained.

Further, this toner had r/R=1.00.

For 10 parts of this toner, the specific resistance value is 5.0x1012
90 parts of a carrier of Ω·cm was mixed to prepare a developer.

The developer obtained in this way was used with Canon CLC-
The power when the sleeve was rotated was measured to be 1O, 8W.

Further, when image printing was performed, the copies were clear and no fogging occurred even after 50,000 copies were made.

The above mixture was melted and kneaded in a roll mill at 150°C to obtain a colored resin kneaded product. This was heated to 200°C, melted, and supplied to a two-fluid nozzle using hot compressed gas at approximately 500°C and 13kg/cm" to be atomized. The sprayed particles were immediately cooled, classified, and sent to a coulter. Volume average diameter measured by counter (aperture diameter 1100p) is 7.8μm
A spherical toner was obtained. Also, this toner has r/R=
It was 1.05.

To 100 parts of this toner, 0.6 part of the hydrophobized silica fine powder used in Example 1 was mixed. To 8 parts of the toner, a carrier 9 having a specific resistance value of 1.0 XIO"Ω・cm
Two parts were mixed to form a developer.

The developer obtained in this way was used with Canon CLC-
When the sleeve was placed in the developing device No. 1 and the power during rotation was measured, it was found to be 9. It was OW.

Further, when image printing was performed, the copies were clear and no fogging occurred even after 50,000 copies were made.

The above formulation was sufficiently premixed using a Henschel mixer, melt-kneaded at least twice using a three-roll mill, coarsely ground using a hammer mill after cooling, and finely ground using a jet mill, followed by air classification. Colored resin particles having a volume average diameter of 11.5 μm as measured by a Coulter counter (aperture 100 μm) were obtained.

After externally adding and mixing positively charged hydrophilic colloidal silica to the particles, the particles were dispersed in water and placed in a flask at 75°C/3 with stirring.
Heat treatment was performed for 0 minutes to form a spherical shape. After further cooling, treatment with sodium hydroxide was performed to dissolve the silica, followed by washing with water, filtration, and drying to obtain a spherical toner having a volume average diameter of 9.5 μm as measured by a Coulter counter (aperture diameter i00#Lm). . Further, this toner had r/R=1.10.

To 100 parts of this toner, 0.5 part of the hydrophobized silica fine powder used in Example 1 was mixed. For 10 parts of the toner, the specific resistance value is 2. OXIO”ΩCm carrier 90
These parts were mixed to prepare a developer.

The developer obtained in this way was used with Canon CLC-
When the sleeve was placed in developing device No. 1 and the power during rotation was measured, it was 11.3 W.

Further, when image printing was performed, the copies were clear and no fogging occurred even after 50,000 copies were made.

Comparison ■In Example 1, the specific resistance value of the carrier used was 1.
．． A developer was prepared in the same manner except that OXIO"Ωcm was used. This developer was placed in a Canon CLC-1 developing device, and the power when the sleeve rotated was measured. It was 12.0W.

Furthermore, when the image was printed, the image density was low (a satisfactory image could not be obtained).

In Example 1, the specific resistance value of the carrier used is 1
．． OX]0'Ω・CI? A developer was prepared in the same manner as above, except that 1 was used. This developer was put into a CLC-1 developing device manufactured by Canon Inc., and the power when rotating the sleeve was measured and found to be 9.4 W.

Further, when image printing was performed, toner scattering and fogging occurred in the image printing immediately after being left unused.

11 obtained without spheronizing treatment in Example 4
．． The 5 μm colored resin particles had r/R > 1.20.

0.5 part of the hydrophobized silica fine powder used in Example 1 was mixed with 100 parts of the colored resin particles to obtain a toner. Specific resistance value 2 x 10”Ω for 10 parts of the toner
- 90 parts of CII+ carrier was mixed to prepare a developer.

The developer obtained in this way was used with Canon CLC-
When the sleeve was placed in developing device No. 1 and the power when rotating was measured, it was 14.5 W.

Also, when I printed out the images, the fogging started to become noticeable around 40,000 copies.

[Effects of the Invention] As described above, according to the present invention, a developer that can be easily stirred and mixed with a small load can be obtained. As a result, a developer can be obtained that prevents the toner from becoming spent, has excellent durability, and has good development characteristics.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram schematically showing an apparatus for measuring the electrical resistance value of a carrier. 1... Main electrode 2... Upper electrode 3... Insulator 4... Ammeter 5... Voltmeter 6.
... Constant voltage device 7 ... Carrier 8 ... Measurement cell

Claims (1)

[Scope of Claims] In an electrostatic image developer containing a toner containing at least a colorant and a binder resin, and a carrier, the toner has an inscribed circle with a radius r that touches the projection plane of the toner at at least three points. and the circumscribed circle of radius R have a relationship of 1.00≦r/R≦1.20, and the carrier is 100V/R≦1.20.
The specific resistance value when a DC electric field of cm is applied is 1.0×
An electrostatic image developer characterized by having a resistance of 10^9 to 1.0 x 10^1^5 Ω·cm.