JPH07117767B2 - Image forming method - Google Patents

Description

The present invention relates to an image forming method using a developer for developing an electrostatically charged image in electrophotography, electrostatic recording, electrostatic printing and the like. More specifically, in the electrophotographic process, a photoreceptor with low surface hardness such as OPC is used, and a developer suitable for cleaning such as blade cleaning method that presses against a strong photoreceptor is used. Image forming method.

[Conventional technology]

Conventionally, as an electrophotographic method, U.S. Pat.No. 2,297,691, Japanese Patent Publication No. 42-23910 (US Pat. No. 3,666,363), Japanese Patent Publication No. 43-24748 (US Pat. No. 4,071,361).
A number of methods are known, but generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the latent image is developed with a powder ( (Hereinafter referred to as toner), the toner image is transferred to a transfer material such as paper, if necessary, and then fixed by heating, pressure or solvent vapor to obtain a copy. When the method has a step of transferring a toner image, it usually has a step of removing the residual toner on the photoconductor.

A developing method for visualizing an electric latent image using toner is, for example, a magnetic brush method described in U.S. Pat.No. 2,874,063, a cascade developing method described in U.S. Pat. No. 2,618,552 and 2,221,776. The powder cloud method and the like described in the book are available. Further, as a method of using a magnetic toner, a magnet dry method using a conductive toner described in US Pat. No. 3,909,258, a method of using dielectric polarization of toner particles, a method of charge transfer by disturbance of toner In addition, Japanese Patent Laid-Open No. 54-42141 proposed by the present applicant in recent years
JP-A-55-18656 and JP-A-55-18656 disclose a method in which toner particles are made to fly to develop a latent image.

As a toner applied to these developing methods, a fine powder in which a dye or a pigment is dispersed in a natural or synthetic resin is conventionally used. For example, particles in which a colorant is dispersed in a binder resin such as polystyrene and finely pulverized to about 1 to 30 μm are used as a toner. A magnetic toner containing magnetic particles such as magnetite is used. In the case of using a so-called two-component developer, it is usually used as a toner mixed with carrier particles such as glass beads and iron powder.

In the method using such a dry developer, in order to form a visible image with good image quality, the developer needs to have high fluidity and have uniform chargeability,
For this reason, it has been customary to add fine silica powder to toner powder. However, since the fine silica powder is hydrophilic as it is, the developer to which it is added causes agglomeration due to moisture in the air to lower the fluidity,
In extreme cases, moisture absorption of silica lowers the charging performance of the developer. Therefore, it is preferable to use a fine powder of silicic acid which has been subjected to a hydrophobic treatment.
And JP-A-48-47346. Specifically, for example, a silicic acid fine powder is used which is obtained by reacting silicic acid fine powder with an organic silicon compound such as dimethylchlorosilane to substitute silanol groups on the surface of the silicic acid fine powder with organic groups to make the silicic acid fine powder hydrophobic.

In recent years, compact and inexpensive personal-use copiers and laser printers have appeared, and in these compact machines, a cartridge type method in which a photoconductor, a developing device, a cleaning device and the like are integrated is used from the standpoint of maintenance-free. Since the cartridge is disposable, an expensive photoreceptor cannot be used, and so-called OPC or the like is used as the photoreceptor.

Further, as a form suitable for personal use, it is necessary to downsize a copying machine or a laser printer itself, and a drum having a small photosensitive drum is required.

Further, as the cleaning device, so-called blade cleaning which can simplify the device is used.

Similarly, as a developer, it is desirable to use a magnetic one-component developer because the structure of the developing device can be simplified.

In such a magnetic toner, the cleaning effect of the toner itself is strong, and a cleaning method such as a blade cleaning method using a photoconductor having a low surface hardness such as OPC is used as a photoconductor to perform pressure contact with a strong photoconductor. When carried out, in the toner externally added with the silicic acid fine powder treated with the conventional silane coupling agent or the like, white blank development by scratching the surface of the photoconductor, toner fusion by scratching the photoconductor, Contamination of the photoconductor, such as black spots or filming, is likely to occur, and in the extreme case, image loss will occur. In order to avoid this development, the lubricant in the conventional toner,
For example, a method of adding a fatty acid metal salt such as zinc stearate is also known, but many of these lubricants have strong polarity, and if they adhere to the surface of the photoconductor, they may cause adverse effects such as image deletion under high humidity. Many were not satisfied.

[Problems to be solved by the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to use a photoreceptor having a low surface hardness, and to perform a cleaning such as a blade cleaning method in which a pressure contact with a strong photoreceptor is performed. An object of the present invention is to provide an image forming method using a developer which does not cause image loss due to abrasion or contamination.

A second object of the present invention is to provide an image forming method using a developer capable of obtaining a high image density without causing an adverse effect such as image deletion under high humidity conditions.

A third object of the present invention is to provide an image forming method using a developer having excellent durability.

A fourth object of the present invention is to prevent image defects due to abrasion or contamination of the surface of the photoconductor that occurs when cleaning the photoconductor having a surface hardness of 30 g or less, under high humidity conditions. It is intended to provide an image forming method exhibiting high durability without causing an adverse effect such as image deletion.

[Means for solving problems]

The present invention forms an electric latent image on a photoreceptor having a surface hardness of 30 g or less, develops the electric latent image with a developer to form a toner image, and transfers the formed toner image from the photoreceptor to a transfer material. An image forming method in which residual developer components on the photoconductor after transfer are removed by a cleaning means. A negatively charged silicic acid treated with hexamethyldisilazane and further treated with silicone oil. An electrostatic latent image is developed with a negatively chargeable developer containing fine powder and toner, and the remaining developer components on the photoreceptor after transfer are cleaned with a rubber blade in the presence of the fine silica powder. The present invention relates to an image forming method.

The advantage of the silicone oil treatment in the present invention is that the silane coupling agent is fixed on the surface of the silicic acid fine powder by a chemical bond, because it is a surface coating type and because of the lubricity of the silicone oil. If the surface of the photoconductor is strongly rubbed during blade cleaning or the like, it is difficult to scrape or damage the surface of the photoconductor. Here, although there is a treatment with only silicone oil, a large amount of silicone oil is required to completely cover the surface of the silicic acid fine powder only with the treatment with silicone oil, which easily forms aggregates and causes scratches on the photoreceptor. The drawback is that it is easy.

In the silicic acid fine powder in the present invention, since the silicic acid fine powder is first treated with a silane coupling agent, it is possible to reduce the amount of silicone oil that causes the aggregates, and to overcome the above-mentioned drawbacks, silicon It is possible to take advantage of the oil treatment.

Further, since the above silicone oil generally has a strong negative chargeability except for those which have been amino-modified, by adding silica fine powder treated with this to a developer, the developer is uniformly and strongly charged. Can be given.

The fine silicic acid powder in the developer used in the present invention is a so-called dry process which is well-formed for vapor phase oxidation of a silicon halogen compound or a dry silica which is called fumed silica, and a so-called wet silica which is produced from water glass or the like. Although both can be used, dry silica having less silanol groups on the surface and inside the silicic acid fine powder and having no production residue such as Na ₂ O and SO ₃ ^2- is preferable.

Further, in the case of dry silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound in the manufacturing process. They are also included.

The particle size is preferably in the range of 0.001 to 2 μ as an average primary particle size, and particularly preferably, silica fine powder in the range of 0.002 to 0.2 μ is used.

In the present invention, hexamethyldisilazane is used as the silane coupling agent.

The silane coupling agent treatment of the silicic acid fine powder is a dry treatment in which the vaporized silane coupling agent is reacted with the silicic acid fine powder made into a cloud by stirring or the like, or the silicic acid fine powder is dispersed in a solvent. The treatment can be carried out by a generally known method such as a wet method in which a silane coupling agent is dropped.

The silicone oil used in the present invention is generally represented by the following formula: R: C _{1 to} C ₃ alkyl group R ′: Silicone oil modifying group such as alkyl, halogen modified alkyl, phenyl, modified phenyl, etc. R ″: C _{1 to} C ₃ alkyl group or alkoxy group, for example, dimethyl silicone oil, alkyl Modified silicone oils, α-methylstyrene modified silicone oils, chlorophenyl silicone oils, fluorine modified silicone oils, etc. Also, the silicone oils preferably have a viscosity at 25 ° C. of about 50 to 1000 centistokes. Silicone oil whose molecular weight is too low may generate rare components due to heat treatment, etc.
On the other hand, if the molecular weight is too high, the viscosity becomes too high and the treatment operation becomes difficult.

A known technique is used for the method of treating silicon oil. For example, silica fine powder and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicone oil onto the base silica. Is also good. Alternatively, it may be prepared by dissolving or dispersing silicon oil in an appropriate solvent, mixing with silica fine powder of the base, and then removing the solvent.

As a feature of the present invention, since it is necessary that silicon oil is exposed on the surface from the lubricity of fine silicic acid powder,
An important point of the present invention is the order of treatment of the silica fine powder. The silicic acid fine powder of the present invention must first be treated with a silane coupling agent and then with silicone oil.

In addition, the amount of silicon oil to be treated can be small, because the fine silica powder has been made hydrophobic in the previous stage.
(A: specific surface area of fine silica powder), more preferably A / 25 /
It is preferably within a range of ± A / 40. Here, the specific surface area of the silicic acid fine powder is a value obtained from N ₂ adsorption in the BET method. The reason why the treatment amount is limited is that if the treatment amount of silicone oil is too small, the same result as that of the treatment with the silane coupling agent is obtained, and defects such as fusion are generated during cleaning.

Also, if the amount of silicone oil treated is too large, the agglomerates of the above-mentioned fine particles of silicic acid are likely to be formed, and moreover, free silicone oil is likely to be produced, which improves the fluidity when applied to a developer. There are drawbacks such as the inability to do so.

The amount of the treated silica fine powder applied to the developer is 0.01 to 20 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the developer (toner).

The developer used in the present invention has a large number of rotations of the drum per one electrophotographic process and a large curvature. Therefore, when the blade cleaning method is adopted, the pressing force to the surface of the photoconductor must be large. It is very effective for small-diameter drums (diameter 50mmφ or less) where the surface of the photoconductor is likely to be damaged.

The photoconductor used in the present invention is mainly OPC, and its surface hardness was measured as follows. Using a Haydon 14 type scratch hardness meter, using a diamond needle of R0.01mm, scratch the surface of the photoconductor with a load applied, and the width of the scratch
The hardness is expressed by the amount of load when it becomes 40μ.

Further, for the blade cleaning, a currently used rubber plate pressure contact type can be used. For example, this blade generally has a rubber strength of 20 to 60 ° and an invasion amount of about 0.1 to 2 mm at the time of blade cleaning, but is not limited to this value.

Examples of the binder resin of the toner used in the present invention include homopolymers of styrene and its substitution products such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer. And copolymers thereof; copolymers of styrene and acrylic ester such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer; styrene- Copolymers of styrene and methacrylic acid ester such as methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer; of styrene and acrylic acid ester and methacrylic acid ester Multi-component copolymer; other styrene-acrylonitrile copolymer, styrene -Styrene and other vinyl-based monomers such as vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester copolymer Styrene-based copolymer with; polymethylmethacrylate, polybutylmethacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, Chlorinated paraffin and the like can be used alone or in combination.

In particular, as a binder resin for toner that is subjected to a pressure fixing method, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, higher fatty acid, polyamide resin, polyester resin, etc. Can be used alone or in combination.

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, more desirable results are obtained. Any suitable pigment or dye can be used as a colorant in the toner. For example, there are known dyes and pigments such as carbon black, iron black, phthalocyanine blue, county blue, quinacridone, and benzidine yellow.

When the toner is a magnetic toner, a ferromagnetic element such as iron, cobalt, nickel, or iron, cobalt, nickel, such as magnetite, hematite, or ferrite,
An alloy or compound such as manganese, or a magnetic material such as another ferromagnetic alloy may be contained.

You may mix an additive with a toner as needed. Examples of such additives include lubricants such as Teflon and zinc stearate, fixing aids (such as low molecular weight polyethylene), and metal oxides such as tin oxide as a conductivity-imparting agent.

The developer (toner) of the present invention having such a constitution can obtain good cleaning characteristics even under the environment of high temperature and high humidity, low temperature and low humidity and the like.

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

[Example 1] The above mixture is kneaded by a roll mill at 150 to 160 ° C., cooled, and then ground by a jet mill by a well-known method and air classification is performed for 5 to 20
A magnetic toner classified product of μ was obtained.

Next, after silicane coupling was applied to 20 parts of hexamethylene disilazane (HMDS) to the silica fine powder, Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.) (the specific surface area of the silica fine powder treated with hexamethyldisilazane is It was about 190 m ² / g), dimethyl silicone oil KF-
96100cs (Shin-Etsu Chemical Co., Ltd.) 10 parts diluted with a solvent is treated again, dried and heated at 250 ° C., treated with hexamethyldisilazane and then treated with dimethyl silicone oil. A fine powder of silicic acid was obtained, and 0.4 part was externally added to 100 parts of the magnetic toner classified product to obtain a negatively chargeable magnetic toner (that is, a negatively chargeable developer). The hydrophobicity of this treated silicic acid fine powder was 98%.
This magnetic toner was remodeled so that a commercially available copying machine (FC-3 Canon; drum diameter 30φmm) could be developed by reversal, surface hardness
Drum charge using 21g OPC drum −700V, V _DC 500V,
When the development bias V _{PP was} 1600 V, the frequency was 1800 Hz, the drum-sleeve distance was 270 μ, and the OPC drum surface was cleaned by a blade cleaning method using a rubber blade, an image formation test was performed and a good image was obtained. Using this device, a durability test was performed under low temperature and low humidity and high temperature and high humidity. Even after running 5000 sheets, there were no image defects such as filming, toner fusion, drum scratches, image deletion, and white spots. .

Example 2 The operation described in Example 1 above was repeated. However, in the case of this example, the treatment amount of dimethyl silicone oil was set to 3 parts. Using this silica fine powder, 5000
The sheet was durable, but the result was good.

Example 3 The operation described in Example 1 above was repeated. However, in the case of this example, the treated amount of dimethyl silicone oil was 12 parts. Using this silica fine powder, 5000
The sheet was subjected to durability test, but the result was good and no image deletion or toner fusion occurred.

[Comparative Example 1] The same test as in Example 1 was conducted by using 100 parts of the classified product used in Example 1 and 0.4 parts of silicic acid fine particles merely subjected to the silane coupling treatment. However, under high temperature and high humidity, image deletion occurs on about 3000 sheets, and
Under low temperature and low humidity, toner fusion occurred from about 3,500 sheets to the drum surface.

Comparative Example 2 The operation described in Comparative Example 1 was repeated. However, in the case of this example, 0.03 part of zinc stearate was added to the external additive in addition to 0.4 part of silica fine particles. When the same test as in Example 1 was conducted, fusion did not occur at the endurance of 5000 sheets under low temperature and low humidity, but image deletion occurred at about 2000 sheets under high temperature and high humidity.

〔The invention's effect〕

As described above, in an electrophotographic process in which a rubber blade or the like is pressed against a photoreceptor having a small surface hardness, a silane coupling agent is used for the cleaning, and then a silicon oil-treated fine silicate powder is used. The developer containing a body can avoid image loss due to abrasion or contamination of the surface of the photoconductor under each environment and obtain a good image. Further, in a small-diameter drum having a large curvature, this effect is remarkable, and exhibits a cleaning characteristic capable of improving the durability of the photoconductor.

Claims (3)

[Claims] 1. A latent image is formed on a photoconductor having a surface hardness of 30 g or less, a toner image is formed by developing the latent image with a developer, and the formed toner image is transferred from the photoconductor to a transfer material. Is an image forming method in which the residual developer components on the photoconductor after the transfer are removed by a cleaning means, and after being treated with hexamethyldisilazane, it is further treated with silicone oil. An electrostatic latent image is developed with a negatively chargeable developer containing acid fine powder and toner, and the remaining developer components on the photoreceptor after transfer are cleaned with a rubber blade in the presence of the fine silica powder. An image forming method comprising: 2. The image forming method according to claim 1, wherein the photosensitive member is a photosensitive drum having a diameter of 50 mm or less. 3. The image forming method according to claim 1 or 2, wherein the toner is a magnetic toner.