JPH0349104B2 - - 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, etc. Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Although a number of methods are known, such as those described in the above 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 if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, solvent vapor, etc. to obtain a copy. 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, 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 benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium 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, it is added to a thermoplastic resin, heated and melted and dispersed, and then finely pulverized and adjusted to an appropriate particle size as necessary before 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 development with decreased charge controllability. 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, in the present invention, synthesis is performed by a wet method, and then
heat treatment at a temperature of 400°C or higher, preferably 450°C to 1500°C, particularly preferably 500°C to 1000°C,
The present invention provides a developer characterized by containing a toner and silicic acid fine powder obtained by subjecting the surface to a coupling treatment following the heat treatment. Various conventionally known methods can be applied to produce the silicic acid fine powder used in the present invention by a wet method. For example, the decomposition of sodium silicate by acid can be expressed using the general reaction formula (the reaction formula is omitted below): Ma ₂ O, xSiO ₂ + HCl + H ₂ O → SiO ₂・nH ₂ O +
NaCl Other methods include decomposition of sodium silicate with ammonia salts or alkali salts, generation of alkaline earth metal silicate from sodium silicate and then decomposition with acid to form silicic acid, method of converting sodium silicate solution into ion exchange resin There are methods such as using silicic acid, and using natural silicic acid or silicate. The silicic acid fine powder mentioned here includes anhydrous silicon dioxide (silica), aluminum silicate,
Any silicates such as sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be applied. The fine silicic acid powder used in the present invention is obtained by heat-treating these fine silicic acid powders at a temperature of 400°C or higher and then coupling the surface. Fine silicic acid powder may be added and left at a temperature of 400° C. or higher for an appropriate period of time, for example, 10 minutes to 10 hours. 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 can be used between toner particles, between a toner and a carrier, or between a toner and a sleeve in the case of one-component development. The amount of frictional charge between the developer and the toner carrier is stable and uniform, there is no fogging, toner scattering, or toner aggregation, and the developer is durable and has a high number of copies, and is not affected by changes in temperature and humidity. A developer that reproduces stable images that are free from damage.A developer that has high transfer efficiency even in extremely high humidity conditions.
Furthermore, even if stored at high temperature and high humidity for a long period of time, the developer exhibits very little decrease in triboelectric charge and exhibits almost no deterioration in copy quality. 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 further coupling treatment makes the surface extremely stable. 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, it absorbs moisture and the water content becomes the same as before heat treatment. However, 400℃
When the above heat treatment is performed, the hydroxyl groups on the surface of the silicic acid fine powder particles condense and release water, so that even when the temperature is returned to room temperature, the water content is 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 1 minute to 10 hours, and the heat treatment results in a moisture absorption of approximately 5% by weight or less (particularly preferably). (within 3% by weight) as a guideline. The amount of moisture absorbed is measured by heating a heat-treated silicic acid fine powder that has been left on a saturated aqueous solution with a liquid base of sodium thiosulfate at 78% humidity for about a week at 20°C and using a thermobalance to increase the temperature by 2°C/min. Measure the heating loss curve from room temperature to 400℃, and determine the amount of moisture absorption. Further, as the coupling agent used in the coupling treatment in the present invention, any coupling agent that reacts with the hydroxyl group on the surface of the silicic acid fine powder may be used, but well-known silane coupling agents and titanium coupling agents are preferred. Specifically, methyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl)-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, isopropyltriisostearoyl Titanate, Isopropyl tridodecyl benzene sulfonyl titanate, Isopropyl tris (dioctyl pyrophosphate) titanate, Tetraisopropyl bis (dioctyl phosphite) titanate, Tetraoctyl bis (ditridecyl phosphite) titanate, Isopropyl trioctanoyl titanate, Isopropyl Dimethacrylylisostearoyl titanate, Isopropyl isostearoyl diacryl titanate, Isopropyl tri(dioctyl phosphatate) titanate, Isopropyl tricylphenyl titanate, Isopropyl tri(N-aminoethyl-aminoethyl) titanate, Dicumyl phenyloxyacetate titanate, Dicumyl phenyloxyacetate titanate Isostearoyl ethylene titanate, bis(dioctylpyrophosphate) ethylene titanate, bis(dioctylpyrophosphate) oxycetate titanate, tetra(2,2-diallyloxymethyl-
Examples include 1-butyl)bis(di-tridecyl)phosphorite titanate. As a method for treating silicic acid fine powder with a coupling agent, either a dry method or a wet method can be adopted, and a wide range of treatment methods can be used. for example,
Fine silicic acid powder and an appropriate amount of coupling agent are put into a mixed acid such as a Henschel mixer or a ball mill, and dry mixed. Alternatively, after dissolving the coupling agent in a suitable solvent, adding and mixing fine silicic acid powder and removing the solvent, or simultaneously melting and kneading the fine silicic acid powder and the binder resin. Various methods are used, including a method of adding a coupling agent, and a method of dissolving a binder resin in a solution containing a coupling agent, adding fine silicic acid powder, and then obtaining toner powder by spray drying. It will be done. The amount of coupling agent to be treated with respect to the silicic acid fine powder is 0.01 to 10% by weight (preferably 0.1 to 5% by weight).
weight%) is desirable. This is because a treatment amount of less than 0.01% by weight will have no effect, and a treatment amount of more than 10% by weight will increase the amount of unreacted coupling agent, which may cause problems in other processes such as development. It is. 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 application 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 improves chargeability and fluidity with excellent stability. Show 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. Carplex Shionogi & Co., Ltd. Neep Seal 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 Fiillstoff-Gesellschaft Ultrasil Marquart Manosil Hardman and Holden
(Hardman and Holden) Hoesch Chemische Fabrik Hoesch
K-G (Hiemitsussie Vabrik Betsuyu) Sil-Stone Stoner Rubber
Co. Nalco Chem.Co. Quso Philadelphia Quartz Co. Santocell Monsanto.Chemical
Co. (Monsanto Chemical) Imsil (Imsil) Illinois Minerals Co. (Isonois Minerals) Calcium Silikat (Calcium Silikat)
Chemische Fabrik Hoesch.K-G Calsil Fiillstoff-Gesellschaft
Marquart Fortafil Imperial Chemical
Industries, Ltd. (Inverial Chemical
Industries) Microcal Joseph Crosfield &
Sons.Ltd. Manosil Hardman and Holden
(Hardman and Holden) Vulkasil Farbenfabriken
Bryer, A.-G. 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, a fine silicic acid powder synthesized by a wet method is used and the surface is subjected to a heat treatment at a temperature of 400°C or higher and a coupling treatment. Among these, those in which the silicic acid fine powder contains 85% or more of SiO ₂ are particularly desirable. 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.
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 the processing agents used during the synthesis process, and the incorporation of alkali metal elements seems to have a favorable effect. It is thought that there are. 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 good 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 0.01~ converted to Na ₂ O
It is 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 Na ₂ O (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.

[Example 1]

Styrene-butyl methacrylate copolymer
100 parts by weight of magnetite 60 and nigrosine 2 synthesized by a wet method were thoroughly mixed in a blender and then melt-kneaded in a roll mill. After cooling, it was coarsely pulverized using a hammer mill, and then finely pulverized using a supersonic jet pulverizer. The toner was 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, Nip Seal ER, Nippon Silica Kogyo Co., Ltd.)
was heat treated at 800℃ for 1 hour, and then 2
0.8 parts by weight of silicic acid fine powder obtained by treatment with vinyltrimethoxysilane in a weight percent was added and mixed to prepare a developer. 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. Sleeve surface magnetic flux density 700 Gauss,
The distance between the ear cutting blade and the sleeve surface is 0.25 mm. The developing device is fixed with a rotary magnet (sleeve circumferential speed is the same as that of the drum, but the direction of rotation is opposite).
The voltage was set to 0.25 mm, and a 1200 Hz 1200 V alternating current and -150 V direct current bias were applied to the sleeve. The developer was applied to this developing device to develop the latent image, and then the powder image was transferred while irradiating -7 KV direct current corona from the back side of the transfer paper to obtain a copied image. For fixing, use a commercially available plain paper copier (product name, NP-
5500, manufactured by Canon). A clear and good image without fogging 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 placed in an environment of high temperature, ultra-high humidity, 35℃ and 90%RH.
After storing it for several months, I took out the image, and the image I obtained was comparable to the one before storage. [Examples 2 to 9] The heat treatment temperature of silicic acid fine powder was 430°C,
480℃, 500℃, 600℃, 700℃, 900℃, 1000℃,
When the same procedure as in Example 1 was carried out except that the temperature was changed to 1200°C, good results were obtained. [Examples 10 and 11] The same procedure as in Example 1 was carried out except that the amount of silane coupling agent added was changed to 1% by weight and 4% by weight, and a high density image without fogging was obtained. It was done. [Example 12] The same procedure as in Example 1 was conducted except that a titanium coupling agent (TTS) was used instead of the silane coupling agent, and a clear, high-density image was obtained. [Example 13] 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. After the kneaded material was left to cool naturally, it was coarsely pulverized using a cutter mill, then pulverized using a pulverizer using jet air flow, and further classified using an air classifier to obtain toner with a particle size of 5 to 20μ. . Silica fine powder obtained by heat-treating 100 parts by weight of this toner with silica (trade name: HiSeal 233, Pittsburgh Plategrast Co., Ltd.) at 800°C for 2 hours, and then treating with 1% by weight of vinyltoluethoxysilane. Mixed with 1 part by weight
Carrier iron powder (250-400 mesh) in 10 parts by weight
A developer was obtained by adding 90 parts by weight. 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 DC 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, there was almost no decrease in image density compared to before storage, and clear, fog-free images were obtained. [Example 14] Styrene-butyl acrylate copolymer
0.5 weight percent of the silicic acid fine powder used in Example 1 was added to a toner prepared from 100 parts by weight of 50 parts by weight of magnetite, 2 parts of metal-containing dye, and 2 parts of polyethylene to prepare a developer. This developer is applied to a commercially available plain paper copier (product name:
NP201 (manufactured by Canon) and imaged.
Clear images with high resolution were obtained. [Comparative Example 1] The same procedure as in Example 1 was carried out except that the 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. Although clear and fog-free images were obtained, the high temperature and ultra-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. Table 2 shows the evaluation of each example and comparative example.

[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. DESCRIPTION OF SYMBOLS 1...Electrostatic image holder, 2...Nonmagnetic cylinder, 5...Doctor blade, 6...Developer.

Claims (1)

[Claims] 1. An electrostatic image characterized by containing a toner and silicic acid fine powder synthesized by a wet method, then heat treated at a temperature of 400°C or higher, and then subjected to a coupling treatment on the surface after the heat treatment. Developer for development.