JPH0251504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel electrophotographic developer used in electrophotography and the like.

In electrophotography, an electrostatic latent image is first formed by utilizing the properties of photoconductors such as cadmium sulfide, polyvinylcarbazole, selenium, and zinc oxide. For example, applying a charge uniformly on the photoconductor layer,
Imagewise exposure is performed to form an electrostatic latent image, which is then developed with toner powder charged to the opposite polarity to that of the electrostatic latent image, and further transferred and fixed onto a transfer sheet as required.

Among these, in the case of a device that has a transfer process,
Usually, residual toner on the photoreceptor that has not been transferred to the transfer sheet is removed and the photoreceptor is used repeatedly.

The remaining toner on the photoreceptor is generally removed by bringing a cleaning member into contact with the photoreceptor, such as a blade cleaning method, a fur brush cleaning method, or a magnetic brush cleaning method. In this case, since the cleaning member is pressed against the photoreceptor with an appropriate pressure, the photoreceptor may be scratched or the toner may stick to the photoreceptor during repeated use. When a cleaning failure occurs, the resulting image shows dot-like or streak-like contamination, and is judged to be impractical for practical use. In order to avoid this phenomenon in which the toner fuses to the photoreceptor, it is known to add a friction-reducing substance to the toner. However, although this method is certainly effective in preventing cleaning failures such as toner sticking, it has the following problems.
In other words, conventionally known friction-reducing materials
In order to be effective under poor cleaning conditions such as low temperature and low humidity, a large amount of additive is required, which causes problems such as not being able to obtain clear images, and formation or adhesion on the surface of the photoreceptor due to repeated use. It becomes difficult to remove low electrical resistance materials such as paper dust and ozone adducts, and the latent image on the photoreceptor is significantly damaged by low electrical resistance materials, especially in high temperature and high humidity environments. be.

On the other hand, the use of so-called vinylidene polyfluoride powder as a friction reducing substance is known, for example, in Japanese Patent Publication No. 48-8136, Japanese Patent Publication No. 48-8141, Japanese Patent Publication No. 1130-1973, etc. ing.

However, the inventors of the present invention have conducted studies to overcome the above-mentioned problems, and have found that using a large amount of polyvinylidene fluoride using known methods or currently in general use may cause toner problems related to poor cleaning. Although fusion can be prevented,
On the other hand, there are problems in that the sharpness of the image is significantly reduced, the latent image on the photosensitive plate is easily disturbed under high temperature and high humidity, there is a lack of stability during durability, and the photosensitive plate is easily damaged. Due to these problems, it became clear that it was difficult to use in practice.

The present inventors have arrived at the present invention as a result of intensive research to solve the above-mentioned problems.

An object of the present invention is to provide a developer that does not cause disturbance of latent images even under high temperature and high humidity conditions.

An object of the present invention is to provide a developer capable of producing clear images.

An object of the present invention is to provide a developer that is electrically stable during copying durability and provides stable images.

Furthermore, the object of the present invention, in addition to the above-mentioned object, is to
It is an object of the present invention to provide a developer that does not cause adhesion of toner components to a photosensitive plate or damage to the photosensitive plate due to toner components.

That is, the present invention provides the following method when measured in acetone by ^F19 nuclear magnetic resonance method: indicates the area of the absorption peak at approximately −27.5 ± 1 ppm, and Sc is approximately −45.8 ± 1 ppm
The area of the absorption peak in Sd is approximately 48.1±
Indicates the area of absorption peak at 1ppm (however,
1,1,2-trichloro-1, as a standard substance
The present invention relates to an electrophotographic developer characterized by having a vinylidene fluoride polymer that satisfies the following:

These F ¹⁹ NMR absorption spectra are, for example,
As shown in J. Polymer Sci Al page 1305 (1963), -CF ^* ₂ - of vinylidene fluoride polymer
This absorption is based on the chemical shift of .

That is, the absorption at −23.5 ppm is due to the repetition of regular head-to-tail bonds of CF ₂ —CH ₂ units. -27.5ppm absorption is -CH ₂ -CH ₂ -C
CF ₂ absorption occurs in a chain containing a CH _{2 --CH 2} bond, such as F ^* ₂ --CH ₂ --CF 2 --. -Absorption of 45.8ppm is-
CF ₂ ―CH ₂ ―CF ^* ₂ ―CF ₂ ―CH ₂ ― as in CF ₂
-CF ^* ₂ absorption in a chain containing a _CF2 bond.

-48.1ppm absorption is -CH ₂ -CH ₂ -CF ^* ₂ -
CH ₂ --CH ₂ bond and CF ₂ -- as in CF ₂ --CH ₂ --
CF ^* ₂ absorption in a chain containing both _CF2 bonds.

The inventors believe that by regular repetition of bonds
The ratio of the area of the peak in the F ₁₀ -NMR absorption spectrum to the peak due to the anomalous addition bond is (Sb+Sc+
Sd)/Sa≧0.20 (where, Sa, Sb, Sc, Sd are −
By using a developer composition with absorption peak areas of 23.5, -27.5, -45.8, and -48.1 ppm, the above-mentioned problems can be overcome and the latent image will not be disturbed at high temperature and high humidity. It has been found that clear and stable images without contamination due to poor cleaning can be obtained even at low temperatures and low humidity.

NMR peak ratio of the present invention (Sb+Sc+Sd)/Sa
The condition of ≧0.20 indicates that the developer composition of the present invention contains a vinylidene fluoride polymer with many abnormal addition bonds, that is, (-
This indicates that there are many structures in which CF ₂ --CH ₂ )- is not arranged regularly.

This is contrary to the conventional idea of obtaining a polymer as uniform as possible in order to improve mechanical properties and lower surface free energy.

However, the present inventors recognized that anomalous addition bonds are important to achieve the purpose of the present invention, and the NMR peak ratio (Sb + Sc + Sd) / Sa ≥ 0.20
It was revealed that the effect was fully expressed under the following conditions.

In other words, it has high lubricity and moderate abrasive power, which prevents toner and paper dust from adhering to the photoreceptor surface, allowing it to produce clear images without contamination even under high temperature and high humidity conditions of 32.5°C and 90% RH. This makes it possible to obtain accurate images.

Incidentally, polyvinylidene fluoride powder such as Kynar, which has been conventionally used in developers, is (Sb+Sc+Sd)/as described in Comparative Example 1 etc.
Sa was less than 0.20.

Furthermore, with the developer composition of the present invention, a uniform toner charge can be formed during durable copying, so a stable image with high density can be obtained. This is because CF ₂ in vinylidene arsenide polymer
It is thought that this is because the molecules are partially oriented in the same direction within a single lattice, which makes it easy to adopt a conformation with a large dipole moment, giving high dielectric properties.

It is a fact that has never been suggested that physical properties can be determined by limiting specific peak ratios by F ₁₉ NMR, and that the corresponding substance can produce the above-mentioned unique effects.

In the present invention, it is preferable that (Sb+Sc+Sd)/Sa≧0.20 in the peak ratio due to chemical shift of CF ^* ₂ by F ₁₉ -nuclear magnetic resonance of the developer composition.

F ¹⁹ - Measurement method using nuclear magnetic resonance is as follows. The sample is extracted at a temperature ranging from room temperature to 50°C, and the acetone or deuterated acetone solution is used for measurement. Measurement was carried out using FX made by JEOL Ltd.
Using a 90Q type high-resolution NMR device, the observation frequency
84.25MHz, observation width 9000Hz offset frequency
Measured at 55.33KHz.

Chemical shift is 1,1,2-trichlor-
Shown based on 1,2,2-trifluoroethane. At this time, the four chemical shifts of CF ₄ are -23.5±1ppm, -27.5±1ppm, -45.8±1ppm,
It was -48.1±1ppm. At this time, when the toner extract and the vinylidene fluoride polymer were measured, the chemical shifts of both were substantially the same, with no difference. Sa, Sb, Sc, and Sd were determined from the integral values of these peaks.

The vinylidene fluoride polymer used in the present invention is a homopolymer of vinylidene fluoride and a copolymer of vinylidene fluoride with ethylene, vinyl fluoride, trifluoroethylene, tetrafluoroethylene, or the like.

The particle size of the vinylidene fluoride polymer used in the present invention is preferably 0.05 to 1 μm, particularly 0.1 to 0.5 μm. If the particle size is 1.0 μm or more, the dispersion between toner particles will not be sufficient, and it will not be possible to impart fluidity and lubricity to the toner.
It is not effective. Also, below 0.05μm,
Since the surface of the toner is covered with ultrafine particles, the charging properties of the toner are impaired and no effect can be obtained. Also,
The shape should preferably be close to a powder-like spherical shape.

The amount of the specific vinylidene fluoride polymer of the present invention added to the toner is 0.01 to 2.0 wt%, particularly 0.02 to 2.0 wt%.
1.0% is preferred. If the amount added is more than 2.0 wt%, problems such as a decrease in image density will occur, and if it is less than 0.01 wt%, it will not be effective as it will not be enough to increase the slipperiness of the toner.

The weight average molecular weight of the vinylidene fluoride polymer of the present invention is smaller than that conventionally used, and is 10
Preferably between 10,000 and 800,000.

Furthermore, it is also possible to use vinylidene fluoride polymer particles surface-treated with a surfactant, a charge processing agent, or the like.

The particle size of the vinylidene fluoride polymer was determined by taking a secondary electron image taken with a scanning electron microscope at a magnification of 2,000 to 50,000 times and determining the number average particle size of its primary particles.

There are various methods for measuring the weight average molecular weight Mw, which results in slight differences. Therefore, it is measured by the following measurement method. That is, by gel permeation chromatography (GPC), 300μ of THF was injected at a temperature of 40°C, a solvent of tetrahydrofuran, a measured flow rate of 1.0ml/min, and a concentration of 0.1wt%. When measuring the molecular weight of a sample, a calibration curve prepared using a monodisperse polystyrene standard sample is used.
Although the column is not limited to this in any way,
For example, there is A-80M manufactured by Syodekus.

The binder resin for the toner used in the present invention is as follows:
Monopolymers of styrene and its substituted products such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-
Vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene- α-Methyl chlormethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Combined, styrene
Styrenic copolymers such as isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, Polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic carbon resin, aromatic Petroleum resins, chlorinated paraffin, paraffin wax, carnauba wax, etc. can be used alone or in combination.

If necessary, conventionally known carbon black, copper phthalocyanine iron black, etc. can be used as coloring materials for the toner used in the present invention, and all conventionally known positive or negative charge control agents can be used in the present invention. .

Furthermore, the toner of the present invention has a volume resistivity of 10 ¹⁰ Ω.
cm or more, especially 10 ¹² Ωcm or more is preferable. The volume resistivity mentioned here is calculated by molding the toner at a pressure of 100Kg/cm ² and applying an electric field of 100V/cm to it.
It is defined as a value converted from the current value one minute after application.

The toner of the present invention can be mixed with carrier powder such as iron powder, glass beads, nickel powder, ferrite powder, etc., if necessary, and used as a two-component developer for electrical latent images.

Further, the present invention may contain magnetic powder if necessary. The magnetic powder used is a substance that becomes magnetized when placed in a magnetic field, and includes powders of ferromagnetic metals such as iron, cobalt, and nickel, or alloys and compounds such as magnetite, γ-Fe ₂ O ₃ , and ferrite. .

In particular, in order to exhibit the above-mentioned effects, it is preferable that the BET specific surface area by the nitrogen adsorption method be 2 to 20.
m ² /g, particularly 2.5 to 12 m ² /g, and preferably a magnetic powder having a Mohs hardness of 5 to 7.

The content of this magnetic powder is preferably 10 to 70% by weight based on the toner.

By using such magnetic powder in the developer composition of the present invention, a polishing effect is exhibited, and abnormal adhesion of toner onto the photosensitive plate and damage to the photosensitive plate are suppressed, and images with high density and no stains are produced. It can be grown.

When producing toner, the constituent materials are thoroughly kneaded using a thermal kneading machine such as a hot roll, kneader, or extruder, and then obtained by mechanical crushing and classification, or in a binder resin solution. method obtained by spray drying after dispersing the material in
Alternatively, various methods can be applied, such as a polymerization toner manufacturing method in which a monomer to constitute the binder resin is mixed with a predetermined material to form an emulsified suspension and then polymerized to obtain a toner.

Furthermore, the toner used in the present invention has a BET specific surface area of 0.5 to 500 ^{m 2} /g, especially 50 m 2 /g, determined by nitrogen adsorption method.
It is preferable to add ~400 m ² /g of non-magnetic inorganic fine powder. This is because the addition of such fine powder reduces the disturbance of the latent image as described above. This is thought to be because such fine powder has a large specific surface area, so that the low-resistance substance adhering to the drum is adsorbed or attached to its surface and removed.
Examples of such non-magnetic inorganic fine powder include:
Alumina, titanium dioxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, silicon carbide,
Examples include powders or particles of various inorganic oxide pigments, chromium oxide, cerium oxide, red iron, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silica fine powder, etc., but titanate metal salts , silicon carbide, cerium oxide, and silica fine powder are particularly preferred.

The silica fine powder referred to herein is a fine powder having Si--O--Si bonds, and includes both those manufactured by a dry method and those manufactured by a wet method.

The silica fine powder referred to herein may be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate. The particle size is the average primary particle size,
It is desirable that it be within the range of 0.01 to 2μ. Also, it is desirable that the material contains 85% by weight or more of SiO ₂ .

The developer composition of the present invention is more effective when combined with fine silica powder. That is,
This is thought to be because when ordinary polyvinylidene fluoride is used simultaneously with silica fine powder, the silica fine powder is embedded in polyvinylidene fluoride, but sufficient effects cannot always be obtained with silica fine powder. However, in the present invention, the silica fine powder is appropriately dispersed between the vinylidene fluoride polymer particles, and does not inhibit mutual fluidity, but rather enhances it, resulting in a toner with excellent oil lubricity and dispersibility. There is.

They also enhance each other's electrical characteristics.

This makes it possible to achieve the desired effect of the present invention with a smaller amount of vinylidene fluoride polymer.

When using the toner of the present invention, photoreceptors include cadmium sulfide, selenium, zinc oxide, organic photoconductor (OPC), amorphous silicon (α-
However, in the present invention, as an excellent combination of the developer and photoreceptor of the present invention,
Organic photoconductor (OPC) and amorphous silicon (α-Si) are preferred.

In addition, when using the toner of the present invention, cleaning methods include blade cleaning method,
A fur brush cleaning method, a magnetic brush cleaning method, etc. are used, but in the present invention, a blade cleaning method is preferable in view of the excellent combination of the developer of the present invention and the photoreceptor. Further, immediately before the cleaning process, a static elimination process or the like may be provided as necessary to facilitate toner cleaning.

The basic configuration and features of the present invention have been described above, and the method of the present invention will be specifically explained below based on Examples. However, this does not in any way limit the embodiments of the present invention. Parts in the examples are parts by weight.

Example 1 Styrene-butyl methacrylate-dimethylaminoethyl methacrylate (weight ratio 7:2.5:
0.5) 100 parts by weight of copolymer, BET specific surface area 5m ² /
40 parts by weight of magnetite were mixed and melted and kneaded at 160°C in a roll mill. After cooling, it is roughly pulverized using a hammer mill, and then finely pulverized using a jet pulverizer.

Next, it was classified using an air classifier to obtain a black powder with a volume average particle size of approximately 13 μm.

To 100 parts by weight of this black powder, 0.5% hydrophobic colloidal silica and 0.5% vinylidene fluoride polymer (trade name Holaflon 1000VLD) with a number average particle size of 0.30μ and an average weight molecular weight of 300,000 were added to form a developer. I made it into a thing.

This developer composition was added to (CD ₃ ) ₂ CO and mixed, and after separating insoluble magnetite and others, it was measured by high-resolution F ¹⁹ nuclear magnetic resonance, and the result was -23.5, -
There were four peaks due to chemical shifts of 27.5, -45.8, and -48.1 ppm, and the value of (Sb+Sc+Sd)/Sa was 0.214. A measurement chart is shown in the attached drawing.

Apply this toner to a commercially available copier (product name: Canon).
When we conducted a running test of 1000 sheets using the NP150Z (OPC photoreceptor, blade cleaning method used), clear and stable images were obtained.

Add this toner to 30℃90%RH, 15℃10%
A similar running test was conducted in a RH environment, and the results were good, with no image contamination due to latent image disturbances or streaks due to poor cleaning. Furthermore, no scratches were found on the photoreceptor during the running test.

Example 2 (Sb+Sc+Sd)/Sa was added to the black powder of Example 1.
is 0.22, number average particle size 0.25μ, average weight molecular weight 45
By adding 0.3% of vinylidene fluoride polymer,
When the developer composition was subjected to a running test in the same manner as in Example 1, good stable images were obtained in both low temperature, low humidity and high temperature and high humidity environments, as in Example 1.

Example 3 Adding (Sb+Sc+Sd)/Sa to the black powder of Example 1
is 0.43, number average particle size 0.30μ, average weight molecular weight 28
0.3% of vinylidene fluoride copolymer copolymerized with trifluoroethylene was added to prepare a developing composition, and a running test was conducted in the same manner as in Example 1. Good and stable images were obtained in both high temperature and high humidity environments.

Comparative Example 1 In Example 1, (Sb+Sc+
The same procedure was carried out except that 0.5% polyvinylidene fluoride with Sd)/Sa of 0.18, average particle size of 0.5 μm, and weight average molecular weight of 550,000 was used.
In 90% of the environments, defective images occurred due to disturbances in the latent image.

Comparative Example 2 (Sb+Sc+Sd)/Sa by NMR in Example 1
When 0.4% of polyvinylidene fluoride with an average particle diameter of 0.4 μm and a weight average molecular weight of 550,000 was added and the same test was performed, the image density decreased due to running, and furthermore, the image density decreased due to running. 90%
A defective image occurred on RH.

[Brief explanation of drawings]

The accompanying drawing shows a high resolution F ¹⁹ nuclear magnetic resonance chart of the developer of the present invention.

Claims (1)

[Claims] When measured in acetone by 1 F ¹⁹ nuclear magnetic resonance method, the formula (Sb+Sc+Sd)/Sa≧0.02 [wherein, Sa represents the area of the absorption peak at about −23.5±1 ppm, Sb shows an absorption peak area at approximately −27.5±1ppm, and Sc exhibits an area of approximately −45.8±1ppm.
The area of the absorption peak in Sd is approximately 48.1±
Indicates the area of absorption peak at 1ppm (however,
1,1,2-trichloro-1, as a standard substance
2,2-trifluoroethane is used)]. 2. The electrophotographic developer according to claim 1, wherein the vinylidene fluoride polymer is a homopolymer of vinylidene fluoride.