JPS61277964A - Developer - Google Patents

Abstract

PURPOSE:To improve the stability of a developer against an environmental change such as high temp. and high humidity or low temp. and low humidity by incorporating the pulverous silica powder which is treated with a silicone oil and has a specific degree of hydrophobicity therein. CONSTITUTION:This developer contains the pulverous silica powder of which the surface is treated with the silicone oil. The degree of hydrophobicity of the treated pulverous silica powder is >=90%. The pulverous silica powder is preferably formed by the vapor phase oxidation of the halogen compd. of silicon and is known as dry process silica or fumed silica. The pulverous silica powder is preferably treated with 0.2-70wt% silicone oil and the treatment by the silicone oil is made within an A/10+ or -A/20pts.wt. (A: the specific surface area of the pulverous silica powder) for each 100pts.wt. silica. The high-quality image which maintains the high density even in the environment of high temp. and high humidity or low temp. and low humidity and is free from fogging and scttering to the periphery of the latent image is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for developing electrostatically charged images in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, the present invention relates to an electrophotographic developer that is uniformly and strongly negatively charged in a direct or indirect electrophotographic development method and provides high-quality images with little environmental dependence.

Conventionally, as an electrophotographic method, U.S. Patent No. 2,297.69
Specification No. 1, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666.363), Japanese Patent Publication No. 43-247
Publication No. 48 (U.S. Patent No. 4,071,361)
Many methods are known, such as, but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is converted into developer powder (hereinafter referred to as toner). ), and if necessary, transfer the toner image to a transfer material such as paper, then heat.

Copies are obtained by fixing using pressure, a heat-pressure fixing roller, solvent vapor, or the like. Furthermore, when a process for transferring a toner image is included, a process for removing residual toner on the photoreceptor is usually provided.

Development methods for visualizing electrical latent images using toner include, for example, the magnetic brush method described in U.S. Pat. No. 2,874,063 and the magnetic brush method described in U.S. Pat. No. 2,618,552. Cascade development method and 2,221,7
There is a powder cloud method described in the specification of No. 76.

Also, as a method of using magnetic toner, US Patent No. 3,
909,258, a method using electroconductive toner, a method using galvanic polarization of toner particles, a method of charge transfer by toner disturbance, and
JP-A-54-42141, JP-A-55-1865
There is a method of developing a latent image by flying toner particles as described in Japanese Patent No. 6.

Conventionally, toners used in these development methods are fine powders in which dyes and pigments are dispersed in natural or synthetic resins. Finely pulverized particles of about 1 to 30 IL are used as toner. As the magnetic toner, one containing magnetic particles such as magnetite is used. In the case of a system using a so-called two-component developer, the toner is usually mixed with carrier particles such as glass beads and iron powder.

In order to form a visible image of good quality in such a method using a dry developer, it is necessary for the developer to have high fluidity and uniform chargeability. Addition and mixing of silica fine powder to toner powder has been carried out. However, since fine silica powder is hydrophilic as it is, the developer to which it is added causes agglomeration due to moisture in the air.

The fluidity may be reduced, or in extreme cases, the charging performance of the developer may be reduced due to moisture absorption by the silica.Therefore, it is recommended to use silica fine powder treated to make it hydrophobic, as disclosed in Japanese Patent Laid-Open No. 46-5.
No. 782, JP-A-48-47345, JP-A-48-4
No. 7346, etc. Specifically, fine silica powder is used, which is made hydrophobic by, for example, reacting fine silica powder with an organosilicon compound such as dimethyldichlorosilane to replace the silanol groups on the surface of the fine silica powder with organic groups. However, although these fine silica powders have been made hydrophobic to some extent, the degree of hydrophobization is not sufficient, and for example, the charging performance of the developer deteriorates at high temperatures. With the advent of small and inexpensive copying machines, facsimile machines, laser printers, etc. for personal use, they can be used not only in places with relatively good environmental conditions, but also in ordinary homes, where they can be used at high temperatures for long periods of time. It is necessary to maintain good copy quality and image quality even when left in high humidity, and conventional hydrophobized silica fine powders have some unsatisfactory performance aspects.

On the other hand, in the case of magnetic toner, the toner itself has a strong abrasive effect, and a photoconductor with a relatively low surface hardness such as selenium or OPC is used as the photoconductor, and a fairly strong pressure contact with the photoconductor is performed using a blade cleaning method. When cleaning is performed in various ways, toner externally added with silica fine powder treated with conventional silane coupling agents tends to scratch the surface of the photoreceptor excessively, resulting in white spots and scratches on the photoreceptor. Conventionally, in order to avoid this phenomenon, toner contamination such as toner fusion, black spots, or filming is likely to occur, and in severe cases, image defects may occur. It is also known to add lubricants such as fatty acid metal salts such as zinc stearate, but many of these lubricants have strong polarity, and if they adhere to the surface of the photoreceptor, they can cause problems such as image blurring due to high humidity. This often occurs and is not satisfactory.

The present inventors investigated various types of silica fine powder and found that the above problems can be avoided by using silica fine powder that has been treated with silicone oil and has a degree of hydrophobicity of 90% or more. .

That is, an object of the present invention is to provide a developer for electrostatic charge development that is stable against environmental changes such as high temperature and high humidity, low temperature and low humidity, and can always exhibit good characteristics.

Another object of the present invention is to provide a developer with excellent durability that can provide stable images even when a large number of images are formed over a long period of time in electrophotography including processes such as development, fixing, and cleaning. It is about providing.

Another object of the present invention is to solve various problems associated with conventional chargeable toners, to produce high-quality toners that are uniformly charged, visualize electrostatic charge images, and do not cause fogging or scattering of toner around edges. The purpose of the present invention is to provide a developer that produces images.

has a fine silica powder whose surface has been treated with silicone oil, and the treated fine silica powder has a degree of hydrophobicity of 90% or more.

The silica fine powder used in the present invention is preferably silica fine powder produced by vapor phase oxidation of a silicon halide compound, so-called dry process silica, or fumed silica, which is manufactured by a conventionally known technique. For example, it utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is as follows.

SiC 4+2H2+02→5i02+4HC In addition, in this manufacturing process, a composite fine powder of silica and other metal oxides can be obtained by using other metal/\halogen compounds, such as aluminum chloride or titanium chloride, together with silicon halogen compounds. are also possible and inclusive.

The average primary particle size of the particles is preferably within the range of 0.001 to 2, particularly preferably 0.00
It is preferable to use silica fine powder within the range of 2 to 0.2 degrees.

Commercially available silica fine powders produced by vapor phase oxidation of silicon halogen compounds preferably used in the present invention include those commercially available under the following trade names.

AEROSIL (Japan Aerosil■
130t 200t
T 300! /380 tt TT 600/l
MOX 80tt
MOX 170AERO3IL (Japan Aerogino IJ, l) COK 84Ca-0
-SiL (CABOT Co,) M-
5/IMS-7 //
MS-75//
HS-5/I
EH-5 Wacker
HDK N20 (WACKERN20(WACKER-CHF V
IS//
N20E〃
T30〃
T40 The silicone oil used in the present invention is generally represented by the following formula.

Preferred silicone oils have a viscosity of approximately 50-1000 centistokes at 25°C, such as dimethyl silicone oil and alkyl-modified silicone oil.

α-methylstyrene-modified silicone oil, chlorphenyl silicone oil, fluorine-modified silicone oil, etc. are preferred 6. From the purpose of the present invention, silicone oil containing a large amount of -OH groups, -COOH groups, -NH2 groups, etc. is not preferred. .

Known techniques are used for the silicone oil treatment; for example, fine silica powder and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silicone oil may be injected onto the base silica. It's also good.

Alternatively, it may be prepared by dissolving or dispersing silicone oil in a suitable solvent, mixing it with the base silica fine powder, and removing the solvent.

The degree of hydrophobicity of fine silica powder in the present invention uses a value measured by the following method. Of course, other measurement methods can also be used while referring to the measurement method of the present invention.

After pouring 100m of pure water and 1g of sample into a sealed container, collect the water layer, measure the transmittance at a wavelength of 500nm using blank pure water without fine silica powder as a standard, and calculate the transmittance value. This is the degree of hydrophobicity of the treated silica.

The degree of hydrophobicity of the silica fine powder in the present invention is 90% or more (more preferably 95% or more). If the degree of hydrophobicity is less than this, a high-quality image cannot be obtained due to moisture adsorption of the silica fine powder under high humidity.

On the other hand, the degree of hydrophobicity obtained by the above method is different from that obtained by the conventional methanol method (the degree of hydrophobicity is defined as the maximum amount of methanol required), and the uniformity of the surface treatment of silica can also be seen. It has also been found that if the hydrophobization is uneven even with the prescribed amount, the degree of hydrophobization becomes small.

In the present invention, so-called dry silica is preferably used because, in the case of dry silica, the particle size of fine silica powder is generally smaller than that of so-called wet silica, and the effect of improving the fluidity of the developer is greater. In addition, in wet silica fine powder, the internal structure of the silica fine powder particles is rough, and the inside of the particles has many silanol groups and contains a large amount of processing agent residues such as Na2O, SO32-, etc. during manufacturing, and these are This is because they tend to adsorb a large amount of moisture, and even if surface treatment is performed, the moisture resistance of the developer to which these silica fine powders are added tends to deteriorate. This is because the dry silica fine powder does not have the above-mentioned problems and can obtain good characteristics.

The present inventors believe that silicone oil treatment has better moisture resistance than fine silica powder treated with conventionally known silane coupling agents or the like as follows. The silane coupling agent is S on the surface of silica fine powder.
The i-0H (silanol group) reacts with the methoxy or ethoxy group of the silane coupling agent, changing the silanol group to a 5i-0-Si bond type, but it reacts with all the silanol groups on the silica surface. It is difficult to
Some silanol groups remain. These residual silanol groups adsorb moisture under high humidity conditions, but this is only inhibited by steric hindrance caused by the silane coupling agent molecules, and even if the coupling agent molecules are made larger, the remaining silanol groups will not completely absorb moisture. It is possible to completely cover the silanol groups on the surface of the silica fine powder by applying a dung-preventing oil to prevent water adsorption. Therefore, it is thought that silicone oil-treated silica fine powder dramatically improves moisture resistance. Another advantage of silicone oil treatment is that unlike silane coupling agents, which are fixed to the surface of fine silica powder by chemical bonds, it is a surface-applied type and because of the lubricity of silicone oil. Even if the surface of the photoreceptor is strongly rubbed during blade cleaning or the like, there is very little risk of scratching or scratching the surface of the photoreceptor.

In addition, the above-mentioned silicone oils generally have strong negative chargeability, except for amino-modified ones, so adding silica fine powder treated with this oil to the developer imparts a uniform and strong negative charge to the developer. I can think about sexuality. This characteristic is particularly effective when forming a toner image at a location where the potential of the photoreceptor is low, such as in reversal development.

The silica fine powder in the present invention is preferably treated with 0.2 to 70% by weight of silicone oil, and more preferably within the range of silicone oil treatment.

Here, the specific surface area of silica fine powder is N in the BET method.
This is the value obtained from 2 adsorption. The reason for limiting the above treatment amount is that if the amount of silicone oil treated is too small, the surface of the fine silica powder will not be completely covered with silicone oil, and the degree of hydrophobicity of the silica will not increase. This increases the tendency for the fine powder to absorb moisture and make it impossible to obtain high-quality copy images. In addition, if the amount of silicone oil treated is too large, free silicone oil will be formed on the surface of the silica fine powder, so when it is added to the developer, the fluidity cannot be sufficiently improved. This is because silicone oil contaminates the photoreceptor, making it impossible to form good images.

Within the range of the amount of silicone oil treated in the present invention, it is thought that the silicone oil exists in a substantially uniform layer on the surface of the silica, and as a result, the above-mentioned problems do not occur.
It has a high degree of temperature resistance and can also have lubricity to the surface of the photoreceptor.

The applied amount of these treated silica fine powders to toner is 0.01 to 100 parts by weight of developer (toner).
20 parts by weight, more preferably o, i to 3 parts by weight.

Examples of the binder resin for the toner used in the present invention include polystyrene, styrene-butadiene copolymer, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, styrene hebinyltoluene copolymer, etc. Homopolymers of styrene and its substituted products and copolymers thereof; styrene and acrylics such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer, etc. Copolymers of styrene and methacrylic acid esters such as styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic tMn-butyl copolymer; Multicomponent copolymers with acrylic esters and methacrylic esters; other styrene-7 cyclonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-butadiene copolymers, styrene-vinyl methyl ketone copolymers, styrene-acrylonitrile -indene copolymer,
Styrenic copolymers of styrene and other vinyl threads, such as styrene-maleic acid ester copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, Acrylic acid, phenolic resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, etc. can be used alone or in combination.

In particular, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid ester copolymer are used as binder resins for toners used in pressure fixing systems.

Higher fatty acids, polyamide resins, polyester resins, etc. can be used alone or in combination.

More preferable results can be obtained when the polymer, copolymer, or polymer blend used contains a vinyl aromatic or acrylic monomer represented by styrene in an amount of 40 wt % or more.

Any suitable pigment or dye can be used as a coloring agent in the toner. For example, there are known dyes and pigments such as carbon black redone and benzidine yellow.

When the toner is a magnetic toner, ferromagnetic elements such as iron, cobalt, and nickel, or iron, cobalt, nickel, and the like such as magnetite, hematite, and ferrite are used.
It may contain a magnetic material such as an alloy or compound of manganese or other ferromagnetic alloy.

Additives may be mixed with the toner as necessary, such as lubricants such as Teflon and zinc stearate, fixing aids (such as low molecular weight polyethylene), and conductivity imparting agents. Examples include metal oxides such as tin oxide.

The developer (toner) of the present invention configured in this manner has high flexibility even under environments of high temperature, high temperature, low temperature and low humidity, and can provide high quality images without fogging or scattering around the latent image. .

In addition, the silica fine particles used in the present invention are generally dry silica with a strong negative charge, and are further treated with silicone oil, which has a negative charge, so when added externally to the toner, they impart a strong and uniform charge to the toner. can give. This characteristic is particularly effective in zero reversal development, which is performed in facsimile machines, laser printers, etc., which have become popular in recent years.

The charge of the electrostatic latent image is small in the image area, and the charge on the photoconductor is large in the background area, so if toner with a small amount of charge is present, the toner will ride on the background with a large charge on the photoconductor, resulting in reverse fog. This is because it may cause Furthermore, this property of imparting a strong negative charge is also effective for magnetic-component toners whose toner charge tends to fluctuate.

The basic structure and features of the present invention have been described below, and the method of the present invention will be specifically explained based on Examples. However, the embodiments of the present invention are not limited thereby, and the numbers in the examples are parts by weight.

<Example 1> The above mixture was heated to a temperature of 150°C to 160°C using a roll mill.
After cooling, the mixture was pulverized by a jet mill using a well-known method, and air classification was performed to obtain a classified magnetic toner product having a size of 5 to 20 JL.

Next, colloidal silica fine powder Aerosil #200 (manufactured by Nippon Aerosil Co., Ltd., specific surface area approximately 200 m 2 / g
) l O0 part is dimethyl silicone oil KF-9
After treatment with 20 parts of 6100cs (manufactured by Shin-Etsu Chemical) diluted with a solvent, a dry heat treatment was performed at 250° C. to obtain dimethyl silicone oil-treated colloidal silica fine powder.

The obtained dimethyl silicone oil-treated colloidal silica fine powder was 0.4% for 100 parts of the magnetic toner classified product described above.
A magnetic toner was obtained. The degree of hydrophobicity of the treated colloidal silica was 98%. Then, the obtained magnetic toner was supplied to a commercially available copying machine NP-1502 (manufactured by Canon) that had been modified to use a selenium drum as a photoconductor, and the drum charge amount was +800 V and the developing bias V.
An image output test was conducted under the conditions of p p 1300 U, frequency 1600 Hz, and drum-sleeve pressure 1lli270 IL.
Under the conditions of H), it was about 1.3. High temperature and high humidity conditions (3
2.5℃.

When the magnetic toner of the present invention was left under 85% RH and an image reproduction test was performed, the image density was 1.1 in the morning after one day of being left.
The image density was 1.0 even after being left for -week. In addition, durability tests were conducted for 30,000 sheets under various environments, and there were virtually no image defects such as filming or missing image areas.

Comparative Example 1> Colloidal silica fine particles R-972 (manufactured by Nippon Aerosil Co., Ltd., prepared by treating dry silica with dimethyldichlorosilane) were added to 100 parts of the classified product used in Example 1.
A magnetic toner to which 0.4 part (hydrophobicity: 88%) was externally added was used as a magnetic toner for comparison, and the same test as in Example 1 was conducted, and the image density was high under normal temperature and normal humidity conditions.

There were no problems with durability, but it was
At 0% RH), scratching occurred on the surface of the selenium drum, and a phenomenon of missing image areas due to this was observed. Furthermore, in a test under high temperature and high humidity conditions, the image density became 0.9 after being left for one day, and decreased to 0.6 after being left for one week.

<Example 2> 100 parts of colloidal silica particles #300 (manufactured by Nippon Aerosil Co., Ltd.) were added to olefin-modified silicone oil (KF
Colloidal silica treated with olefin-modified silicone oil (hydrophobicity 99%) treated with 35 parts of -415 Shin-Etsu Chemical
) was prepared in the same manner as in Example 1, except that a magnetic toner was used, and an image quality test was conducted in the same manner.The image density was 1.2 at room temperature and humidity, and the image density was 1.2 when left at high temperature and humidity for one week. However, the image density decreased only to 0.9. Furthermore, there were no problems in image development tests and durability tests under low temperature and low humidity conditions.

<Example 3> 100 parts of colloidal silica particles #200 (manufactured by Nippon Aerosil Co., Ltd.) were mixed with fluorine-modified silicone oil (FLloo
Colloidal silica treated with fluorine-modified silicone oil (hydrophobicity 9) treated with 15 parts (Shin-Etsu Chemical)
A magnetic toner was prepared in the same manner as in Example 1, except that 5%) was used, and an image reproduction test was conducted in the same manner.The image density was 1.2 at room temperature, and 1. Even after being left for a week, the image density remained 1.0, and the results of the durability test were also good.

<Example 4> Colloidal silica (hydrophobicity degree 94%) was prepared by treating 100 parts of colloidal silica fine powder #200 (manufactured by Nippon Aerosil Co., Ltd.) with 15 parts of α-methylstyrene modified silicone oil (KF-410 manufactured by Shin-Etsu Chemical). A magnetic toner was produced in the same manner as in Example 1, except for the use. When the obtained magnetic toner was applied to a laser beam printer LBP-CX, it was rated at 200% at room temperature and humidity. The line density was 1.3, and the density remained 1.0 even after being left in high temperature and high humidity for one week.

Further, in a durability test of 4,000 sheets at low temperature and low humidity, the cleaning performance was good, and there was virtually no occurrence of filming or the like. Further, no occurrence of fog such as reverse fog was observed.

<Example 5> Colloidal silica #j, 30 (manufactured by Nippon Aerosil Co., Ltd.) 1
When 00 parts were replaced with dimethyl silicone oil (K) and tested in the same manner, the line concentration remained 1.0 even after being left under high temperature and high humidity for a week, and there was almost no dusting around the line. .Furthermore, the results of the low temperature and low humidity durability test were also good.

Comparative Example 2> Colloidal Silica #200 (manufactured by Nippon Aerosil Co., Ltd.) 1
00 parts of α-methylstyrene modified silicone oil (KF
-410) When a test was conducted in the same manner as in Example 4 except for using 10 parts of colloidal silica (hydrophobicity: 80%), the line density was 1.3 at normal temperature and normal humidity. 1.0 after being left in high temperature and high humidity for 1 day, 0 after being left for 1 week.
The concentration dropped to 7.

Comparative Example 3 Colloidal silica R-812 (untreated with silicone oil)
A test was conducted in the same manner as in Example 4, except that Nippon Aerosil (manufactured by Nippon Aerosil, hydrophobicity 99.8%, hexamethyldisilazane treatment) was used. There were no problems at room temperature and humidity, but after leaving it for one week at high temperature and high humidity. The concentration dropped to 0.6. or,
Under low temperature and low humidity conditions, reverse fog was observed.

Claims (2)

[Claims] (1) 90% hydrophobicity treated with silicone oil
A developer characterized by having the above fine silica powder. (2) The developer according to claim 1, wherein the silica fine powder is produced by vapor phase oxidation of a silicon halide compound.