JPH0421859B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a developer for developing latent images in electrophotography, electrostatic recording, electrostatic printing, magnetic recording, etc. Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Although a number of methods are known, such as those described in the patent specification, generally a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then a developing powder (hereinafter referred to as toner) is formed. The toner image is developed using a developer having the following properties, and the toner image is transferred to a transfer material such as paper as necessary, and then fixed by heat, pressure, solvent vapor, etc. to obtain a copy. Furthermore, when a step of transferring a toner image is included, a step of 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, the cascade development method described in U.S. Pat. No. 2,618,552, and U.S. Pat.
The powder cloud method described in U.S. Pat.
A method using a conductive magnetic toner described in Japanese Patent Publication No. 3909258, a method using various insulating magnetic toners described in Japanese Patent Publication No. 41-9475, etc. are known. As toners applied to these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. For example, particles obtained by dispersing a colorant in a binder resin such as polystyrene and pulverizing the particles to about 1 to 30 μm 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. As charge control agents used in such dry developing toners, for example, amino compounds, quaternary
class ammonium compounds and organic dyes. Common charge control agents include benzylmethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride, nigrosine base, nigrosine hydrochloride, safranin gamma and crystal violet. In particular, nigrosine base and nigrosine hydrochloride are often used as charge control agents. These are usually added to thermoplastic resins, heated, melted and dispersed,
This is finely pulverized and adjusted to an appropriate particle size as necessary for use. However, these dyes used as charge control agents have complex structures, inconsistent properties, and poor stability. In addition, decomposition or deterioration occurs due to decomposition during thermal kneading, mechanical impact, friction, changes in temperature and humidity conditions, etc., resulting in a phenomenon in which charge controllability deteriorates. Therefore, when a toner containing these dyes as a charge control agent is used for development in a copying machine, the dye decomposes or changes in quality as the number of copies increases, and the toner tends to deteriorate during durability. Further, most of the charge control dyes are hydrophilic, and due to poor dispersion in these resins, the dyes are exposed on the toner surface when the toner is crushed after melt-kneading. When using the toner under high humidity conditions,
Since these dyes are hydrophilic, they have the disadvantage that good quality images cannot be obtained. In this way, when a conventional dye with charge controllability is used in a toner, toner particles may be dispersed between toner particles, between toner and carrier, or between toner and toner carrier such as a sleeve. The amount of charge generated on the surface varied, and problems such as development fog, toner scattering, and carrier contamination were likely to occur. In addition, many conventional toners are unusable under high-humidity conditions, as their free-flowing properties are reduced and the toner image transfer efficiency is significantly reduced. In order to overcome the various deficiencies associated with conventional toners as described above, the present applicant previously filed a patent application filed in 1983-
No. 154938 discloses a developer characterized by containing fine silicic acid powder synthesized by a wet method and having a pH value of 6 to 11 when dispersed in distilled water at 4% by weight. proposed. However, even if this developer is used, if it is stored in high temperature and high humidity for a long period of time, the amount of triboelectric charge will decrease significantly, and
It was found that the free flow properties were reduced and the copy quality was significantly inferior. The object of the present invention is to provide a developer having excellent physical and chemical properties that overcomes the above-mentioned deficiencies. That is, the present invention can be applied at a temperature of 400°C or higher (preferably 450°C to 1500°C, particularly preferably 500°C to
The present invention provides a developer for developing electrostatic latent images characterized by containing fine silicic acid powder synthesized by a wet method and heat-treated at a temperature of 1000° C.) and a positively charged toner. Various conventionally known methods can be used to produce the silicic acid fine powder used in the present invention by a wet method. For example, the decomposition of sodium silicate with an acid can be expressed by the general reaction formula (the reaction formula is omitted below): Na ₂ O x SiO ₂ + HCl + H ₂ O → SiO ₂ * nH ₂ O + NaCl Other ammonia salts or alkalis of sodium silicate After decomposition with salts and generation of alkaline earth metal silicates from sodium silicate,
A method of decomposing with an acid to produce silicic acid, a method of converting a sodium silicate solution to silicic acid using an ion exchange resin,
There are methods that use natural silicic acid or silicates. As the silicic acid fine powder referred to herein, any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be used. The silicic acid fine powder used in the present invention is obtained by heat-treating these silicic acid fine powders at a temperature of 400°C or more. This may be carried out by leaving it for an appropriate period of time, for example, 10 minutes to 10 hours, at a temperature of 0.degree. C. or above. There are no particular restrictions on the heat treatment method, and any method can be applied as long as it does not significantly deteriorate the properties of the developer. In the present invention, the developer containing fine silicic acid powder synthesized by a wet method and heat-treated at a temperature of 400°C or higher is used between toner particles or between a toner and a carrier in the case of one-component development, such as a toner and a sleeve. The amount of frictional charge between the toner carrier and the toner carrier is stable and uniform, preventing fogging, toner scattering,
A developer that does not cause toner aggregation and has a high number of durable copies.A developer that reproduces stable images unaffected by changes in temperature and humidity.A developer that has high transfer efficiency, especially in extremely high humidity conditions. Furthermore, even if the developer is stored at high temperature and high humidity for a long period of time, the amount of triboelectric charge decreases very little, and the quality of copying hardly deteriorates. This seems to be due to the following reasons. That is, the silicic acid fine powder synthesized by the wet method is used, and the silicic acid fine powder synthesized by the wet method is porous and has many capillaries on the surface.
This is believed to be because heat treatment at a temperature of 400° C. or higher causes condensation of silanol groups with each other, and as a result, the capillaries are considerably eliminated and the surface is stabilized. When heat-treated at less than 400°C, adsorbed water is removed during heating and the water content of the silicic acid fine powder decreases, but when returned to room temperature, water is absorbed again and the water content becomes the same amount as before the heat treatment. However, when heat treated at 400°C or higher, the hydroxyl groups on the surface of the silicic acid fine powder particles condense and release water, so even if the temperature is returned to room temperature, the water content will be significantly lower than before the heat treatment. In the present invention, the heat treatment time varies depending on the treatment temperature, the particle size of the silicic acid fine powder, and other characteristics, but is in the range of about 1 minute to 10 hours, and the heat treatment results in a moisture absorption amount of within about 5% by weight (particularly preferably). (within 3% by weight) as a guideline. The amount of moisture absorbed is determined by heating the heat-treated silicic acid fine powder left on a saturated aqueous solution with a liquid base of sodium thiosulfate at 78% humidity for about one week at 20°C and increasing the temperature by 2°C/min using a thermobalance. Measure the heating loss curve from room temperature to 400℃, and determine the amount of moisture absorption. The particle size of the silicic acid fine powder of the present invention is preferably within the range of 0.01 to 2μ as an average primary particle size. In addition, the applied amount of these silicic acid fine powders is effective when the amount is 0.01 to 20% based on the weight of the developer, and particularly preferably when it is added in an amount of 0.1 to 3%, it has excellent charging properties and excellent stability. Indicates flow characteristics.
Regarding the preferred form of addition, it is preferable that 0.01 to 3% by weight of the silicic acid fine powder based on the weight of the toner be attached to the surface of the toner particles. Commercially available fine silicic acid powder synthesized by a wet method used in the present invention includes, for example, those commercially available under the following trade names. Carplexes Shionogi & Co., Ltd. Nipseal Nippon Silica Toxil, Fine Seal Tokuyama Soda Vita Seal Tagi Hi Silton, Silnetx Mizusawa Kagaku Starsil Kamishima Kagaku Himezil Ehime Pharmaceutical Thyroid Fuji Davison Kagaku Hi-sil Pittsburgh Plate Glass
Co. (Pittsburgh Plate Glass) Durosil Ultrasil Fiillstoff−
Gesellscheft Marquart
Manosil Hardman and Holden
(Hardman and Holden) Hoesch Chemische Fabrik
Hoesch K-G Sil-Stone Stoner Rubber
Co. (Stoner Lover) Nalco (Nalco) Nalco Chem Co. (Nalco Chemical) Quso (Quso) Philadelphia Quartz Co. (Philadelphia Quartz) Santocell (Santocell) Monsanto・chemical
Co. (Monsanto Chemical) Imsil Illinois Minerals Co. Calcium Silikat
Chemische Fabrik Hoesch K-G Calsil Fiillstoff-Gesellschaft
Marquart Fortafil Imperial Chemical Industries, Ltd. Microcal Joseph Crosfield &
Sons, Ltd.
Hardman and Holden Manosil Hardman and Holden
(Hardman and Holden) Vulkasil Farbenfabiken
Bryer, A.-G.
Buyer) Tufknit Durham Chemicals,
Ltd. (Doulham Chemicals) Silmos Shiraishi Kogyo Starex Kamishima Kagaku Furikosil Takihii These can be used after being adjusted to have an average primary particle size in the range of 0.01 to 2μ. In the present invention, as mentioned above, silicic acid fine powder synthesized by a wet method and heat-treated at a temperature of 400°C or higher is used and exhibits an effect, but among such wet silicic acid fine powder, particularly , the silicic acid fine powder
Particularly desirable are those containing 85% or more SiO ₂ . The silicic acid fine powder synthesized by a wet method, which is the raw material for the silicic acid fine powder used in the present invention, has a pH value of 6 to 6 when the silicic acid fine powder is dispersed at 4% by weight in water.
It is preferably 11 (more preferably 7 to 9). This is thought to be influenced by the various elements contained in the raw materials used to synthesize the silicic acid fine powder or in the treatments used during the synthesis process, and the incorporation of alkali metal elements has a favorable effect. it is conceivable that. Among these, experiments have revealed that those mixed with an appropriate amount of sodium ions have a particularly effective effect. In order to positively and stably charge the toner, it is particularly preferable to use silicic acid that satisfies the above PH conditions and contains an appropriate amount of sodium ions.The preferred sodium content that provides the above PH value is Na. Convert to ₂ O
It is 0.01-10%. This is because sodium ions mixed into the SiO ₂ lattice near the surface of the fine silicic acid powder added to the toner or sodium ions attached to the surface of the fine silicic acid powder absorb some adsorbed moisture inside or on the surface of the fine powder. This is thought to be because it is effective in forming stable charges through interaction with That is, among the silicic acid fine powder synthesized by the wet method used in the present invention, the pH of the water dispersion system is 6 to 11.
In particular, the sodium content in the silicic acid fine powder is 0.01 to 10% in terms of _Na2O (the sodium content necessary to maintain a particularly preferable pH of the aqueous dispersion is 0.1 to 10%). It is preferable to use silicic acid fine powder containing 2.0%). Next, examples of particularly preferred silicic acid fine powders synthesized by the wet method used in the present invention will be given. Of course, this example does not limit the scope of the claims of the present invention.

【table】

[Table] Furthermore, the surface of the silicic acid fine powder synthesized by these wet methods may be treated with an organic substance before use. As the binder resin of the toner used in the present invention, monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers;
Styrene-propylene copolymer, 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-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer,
Styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-
Styrenic copolymers such as butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, Butyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic carbonized Hydrogen resin, aromatic petroleum resin, chlorinated paraffin, paraffin,
Wax etc. can be used alone or in combination. As the coloring material used in the toner, conventionally known carbon black, iron black, etc. can be used, and when used in combination with the silicic acid fine powder used in the present invention, conventionally known charge control agents, including the above-mentioned charge control agents, are preferably used. It can be used. Furthermore, in order to use the toner of the present invention as a magnetic toner, it may contain magnetic powder. As such magnetic powder, materials that are magnetized when placed in a magnetic field are used, such as powders of ferromagnetic metals such as iron, cobalt, and nickel, or magnetite, γ-
There are alloys and compounds such as hematite and ferrite. The content of this magnetic powder is 15% based on the weight of the toner.
~70% by weight. Furthermore, the toner of the present invention is mixed with carrier particles such as iron powder, glass beads, nickel powder, ferrite powder, etc., as required, and used as a developer for electrical latent images. The developer of the present invention can be applied to various developing methods. For example, magnetic brush development method, cascade development method, method using conductive magnetic toner described in U.S. Pat. No. 3,909,258, JP-A-53-
Method using high-resistance magnetic toner described in JP-A-31136, JP-A-54-42141, JP-A-55-18656
There are methods described in Japanese Patent Publication No. 54-43027, fur brush development method, powder cloud method, impression development method, etc., but the most preferable development method for the developer of the present invention is the following method. It is. That is, an electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating developer on its surface are arranged with a certain gap in the developing section, and the image is heat-treated at 400°C. A developer containing fine silicic acid powder synthesized by a wet method is supported on a developer carrier to a thickness thinner than the gap, and the developer is transferred to the electrostatic image carrier in a developing section for development. This is the way to do it. This method will be specifically explained. FIG. 1 shows a cross-sectional view of one embodiment of the developing process according to this method. In the figure, the electrostatic image holder 1 moves in the direction of the arrow. The non-magnetic cylinder 2, which is a developer carrier, rotates in the developing section so as to move in the same direction as the surface of the electrostatic image carrier. A multipolar permanent magnet 3 is arranged inside the nonmagnetic cylinder 2 so as not to rotate. One-component insulating magnetic developer 6 sent from developer container 4
is applied onto a non-magnetic cylindrical surface, and friction between the cylindrical surface and the toner particles imparts a charge of opposite polarity to the electrostatic image charge to the toner particles. Furthermore, an iron doctor blade 5 is placed close to the cylindrical surface (at intervals of 50 μm or more).
500 .mu.), and is arranged to face one magnetic pole (in the figure, the S pole) of the multipolar permanent magnet 3, thereby regulating the thickness of the toner layer to be thin (30 .mu. to 300 .mu.) and uniform. By adjusting the rotational speed of the cylinder 2, the surface speed and preferably the internal speed of the developer layer are made to be substantially equal to or close to the speed of the electrostatic image holding surface. Instead of iron, a permanent magnet may be used as the doctor blade 5 to form opposing magnetic poles. Further, an alternating current bias may be applied between the developer carrier and the electrostatic image holding surface in the developing section. This AC bias f is 200 ~
It is good if it is 4000Hz and Vpp is 500 to 3000V. As described above, in this developing step, the non-magnetic cylinder 2 containing the multipolar permanent magnet 3 was used in order to stably hold the one-component magnetic developer on the developer carrier. Further, in order to form a thin and uniform developer layer, a doctor blade 5 made of a magnetic thin plate or a permanent magnet was placed near the surface of the cylinder 2. Using a magnetic doctor blade in this way,
Opposing magnetic poles are formed between the magnetic poles of the permanent magnet included in the developer carrier, and by forcibly raising toner particle chains between the doctor blade and the developer carrier, other parts on the developer carrier, For example, this is advantageous in controlling the thickness of the developer layer in the development area facing the electrostatic image surface. Further, by imparting such forced movement to the developer, the developer layer becomes more uniform, thereby achieving a thin and uniform toner layer formation that could not be achieved with a non-magnetic doctor blade. Moreover, since the gap between the doctor blade and the sleeve can be set wide, there is also the effect of preventing the destruction and aggregation of toner particles. When the toner particles are transferred in the developing area, they are transferred to the electrostatic image side due to the attraction action of the electrostatic image or the action of an alternating current bias. Here, if the insulating developer does not have magnetism, the doctor blade does not need to be magnetic, nor does it need to have a magnet inside the sleeve. 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, this does not in any way limit the embodiments of the present invention. Example 1 100 parts by weight of a positively charged toner prepared from 100 parts by weight of styrene-butyl methacrylate, 60 parts by weight of magnetite, 3 parts by weight of nigrosine, and 100 parts by weight of silica (trade name, Nip Seal ER, manufactured by Nippon Silica Kogyo).
A developer was prepared by adding 1.0 part by weight of silicic acid fine powder produced by heat-treating the mixture at 800°C for 1 hour. On the other hand, the OPC photoreceptor was subjected to -6KV corona discharge to uniformly charge the entire surface, and then an original image was irradiated to form an electrostatic latent image. The developer carrier was a stainless steel cylindrical sleeve with an outer diameter of 50 mm. The magnetic flux density on the sleeve surface was 700 Gauss, and the distance between the ear cutting blade and the sleeve surface was 0.25 mm. This sleeve rotating magnet fixed (sleeve circumferential speed is the same as that of the drum, rotation direction is opposite) type developer is connected to the surface of the photosensitive drum.
Set the distance between the sleeve surfaces to 0.25mm, and
An alternating current of 1200 Hz and 1200 V and a direct current bias of -150 V were applied. The developer is applied to this developer to develop the latent image, and then a toner powder image having a positive triboelectric charge is transferred while irradiating -7KV DC corona from the back side of the transfer paper to obtain a copy image. Ta. Fixing was carried out using a fixing device of a commercially available plain paper copying machine (trade name: NP-5500, manufactured by Canon). As shown in Table 2, a fog-free image with an image density of 1.25 was obtained. A durability test of 50,000 sheets was conducted, and good results were obtained with almost no decrease in image density. Furthermore, this developer is
Images were taken after being stored in a %RH environment for one month, and images comparable to those before storage were obtained. Examples 2 to 9 The heat treatment temperature of silicic acid fine powder was 430°C,
480℃, 500℃, 600℃, 700℃, 900℃, 1000℃,
Good results were obtained when the same procedure as in Example 1 was carried out except that the temperature was changed to 1200°C. Example 10 Styrene-butyl methacrylate copolymer
100 parts by weight Carbon Black 6 Nigrosine 2 Mix the above materials well in a blender and then heat to 150℃
The mixture was kneaded using two heated rolls. The kneaded material was allowed to cool naturally, and then coarsely pulverized using a cutter mill, pulverized using a pulverizer using jet air flow, and further classified using an air classifier to obtain toner having a particle size of 5 to 20 μm. For 100 parts by weight of this toner, add silica (product name,
HiSeal 233, Pittsburgh Plate Glass Co.)
A developer was obtained by adding 90 parts by weight of carrier iron powder (250 to 400 mesh) to 10 parts by weight of a mixture of 0.8 parts by weight of silicic acid fine powder produced by heat treating at 800 DEG C. for 5 hours. Using this developer, the latent image on the OPC photoreceptor was developed using a magnetic brush method, and the resulting powder image was transferred to transfer paper using a -7KV direct current corona, and then fixed with a hot roll. A clear image was obtained. High temperature and ultra high humidity (35℃90
%RH) for one month, and even after that, clear images were obtained with almost no decrease in image density compared to before storage. Comparative Example 1 The same procedure as in Example 1 was carried out except that silicic acid fine powder was not used, but only poor images were obtained. Comparative Example 2 The same procedure as in Example 1 was carried out except that silicic acid fine powder that had not been heat treated was used. Clear and capri-free images were obtained, but at high temperatures and extremely high humidity (35℃)
When I tried to image it after storing it at 90% RH for one month, I could only get a poor image. Comparative Example 3 Fine silica powder (Aerosil 200, dry process silica manufactured by Nippon Aerosil Co., Ltd.) was placed in a closed Henschel mixer heated to 70°C, and treated with alcohol so that the treatment amount was 10% by weight based on the fine silica powder. The diluted γ-aminopropyltriethoxysilane was added dropwise while stirring at high speed. The obtained treated silica fine powder was dried at 120°C to obtain positively chargeable silica fine powder treated with an aminosilane coupling agent. One part by weight of the aminosilane coupling agent-treated silica fine powder was added to 100 parts by weight of the toner of Example 1 to obtain a developer. When this developer was used to obtain an image in the same manner as in Example 1, the image density was as low as 0.85, the line drawing was scattered, and the solid black was noticeably rough. We investigated the durability and found that the density decreased to 0.65 after printing 5,000 sheets. When an image was obtained at 35° C. and 85%, the image density was as low as 0.72, fogging, scattering, and roughness increased, and the image quality decreased. Table 2 shows the evaluation of each example and comparative example.

【table】

[Table] The degree of aggregation was measured using a powder tester manufactured by Hosokawa Micromeriteisk. The smaller the numerical value, the better the free flow property.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a developing process to which the developer of the present invention can be applied. 1... Electrostatic image holder, 2... Non-magnetic cylinder, 5...
...Doctor blade, 6...Developer.

Claims (1)

[Claims] 1. A developer for developing an electrostatic latent image, comprising silicic acid fine powder synthesized by a wet method and heat-treated at a temperature of 400° C. or higher, and a positively charged toner.