JP2818778B2 - Dry two-component negatively chargeable developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dry two-component negatively chargeable developer, and more particularly, to an electrostatic image formed by electrophotography, electrostatic recording, electrostatic printing, or the like. The present invention relates to a two-component negatively chargeable developer used for imaging.

[Conventional technology]

Developers used in electrophotography and the like are broadly classified into dry-type developers and wet-type developers, and both dry-type developers and wet-type developers (liquid developers) have advantages and disadvantages. The former dry developer is more often used because the product can be obtained in a dry state. As the dry developer, a one-component developer consisting of only a toner and a two-component developer consisting of a mixture of a toner and a carrier are known. At present, a one-component developer can maintain a constant charge amount. Because of the difficulty, two-component developers are more often used.

However, even in this dry two-component developer, the toner component adheres to the carrier surface in accordance with the use frequency (use period), and the performance of the carrier tends to gradually decrease. Such a decrease in the performance of the carrier naturally affects the charge amount of the toner and hinders obtaining a good image.

However, attempts to remove the defects of the two-component developer have been made everywhere. For example, (1) coating the carrier surface with a low surface energy substance such as a silicone resin to form the carrier surface; (2) An organic group is bonded to silicon to prevent toner contamination and to obtain a developer having excellent durability (JP-B-44-27879, JP-A-54-21730, etc.). By incorporating hydrophobized silicon dioxide fine particles into the toner and mixing it with the carrier, the toner filming phenomenon on the photoreceptor and carrier surface is prevented, and a long-term stable developer is provided. (Japanese Patent Application Laid-Open No. Sho 46-5792) and the like have been proposed. However, according to these two-component developers (1) and (2), although the durability is very excellent, the background fogging of these developers when the negatively charged toner is replenished is caused. There is an inconvenience that often occurs.

[Problems to be solved by the invention]

The present invention prevents toner contamination of the carrier and the photoreceptor, and does not cause ground fogging even when the negatively charged toner is replenished in the developer. Therefore, many high-quality copies can be obtained over a long period of time. And a dry two-component developer.

[Means for solving the problem]

The dry two-component negatively chargeable developer according to the present invention comprises: (a) a toner containing at least a binder resin and a colorant, and having hydrophobic silica having a degree of hydrophobicity of 10 to 40 supported on the surface thereof;
(B) It is characterized by comprising a mixture with a silicon resin-coated carrier.

The present inventors have now conducted a detailed study on the development of ground fogging when the hydrophobic silica-containing negatively chargeable toner is supplied to a two-component developer comprising the toner and a silicone resin-coated carrier. It was confirmed that the hydrophobic silica-containing toner initially showed positive polarity when mixed with the silicon resin-coated carrier, and then turned to negative polarity. On the other hand, the two-component developer composed of a mixture of the negative polarity toner containing hydrophilic silica and the silicon resin-coated carrier was obtained immediately after the negative polarity toner containing hydrophilic silica was replenished in the developer. Even with small stirring, the toner did not show a positive polarity, but the toner containing hydrophilic silica had poorer fluidity of the toner than the toner containing hydrophobic silica, and the toner was transferred from the toner tank to the developing device toner. Was found to be unstable. In consideration of such development, the present inventors prepared silica with reduced hydrophobicity,
When the toner containing the toner was replenished into the developer, the toner did not have a positive polarity and no fogging occurred. At this time, the fluidity of the toner is
Although it was slightly inferior to the case where silica having a hydrophobicity of 40 or more was mixed, the toner supply stability was good.

 The present invention has been made based on such findings.

 Hereinafter, the present invention will be described in more detail.

As described above, the dry two-component developer according to the present invention is:
A toner containing at least a colorant and a binder resin and having hydrophobic silica having a degree of hydrophobicity of 10 to 40 adhered to the surface thereof (hereinafter, may be referred to as “component A”); (May be referred to as "B component")
Consists of a mixture with

The "hydrophobic silica" in the component A is obtained by first obtaining a fine powder of silicon dioxide (hydrophilic silica) by an arbitrary method, for example, a method of hydrolyzing silicon tetrachloride in an oxyhydrogen flame or a method of precipitating an aqueous solution of sodium silicate. The hydrophilic silica can be produced by making the hydrophilic silica hydrophobic. The hydrophilic silica is made hydrophobic by substituting a silanol group on the silica surface with an organic silicon compound.

The typical examples of the hydrophobic silica used in the present invention are as follows, but are not necessarily limited thereto, and the use thereof may be singly or in combination of two or more.

Dimethyldichlorosilane, trimethylchlorosilane,
Methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α
-Chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane,
Chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyl-tris (β-methoxyethoxy) silane, γ-methacryl Oxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyl-trichlorosilane, decyl-
Trichlorosilane, nonyl-trichlorosilane, (4-
(t-propylphenyl) -trichlorosilane, (4-t
-Butylphenyl) -trichlorosilane, dibenzyl-
Dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl-dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, dihexadecyl-dichlorosilane, (4-t-butylphenyl) -octyl-dichlorosilane, dioctyl-dichlorosilane, didecenyl-dichlorosilane, didecenyl-dichlorosilane , Di-2-ethylhexyl-dichlorosilane, di-3,3-dimethylpentyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-
Chlorosilane, tridecyl-chlorosilane, dioctyl-methyl-chlorosilane, octyl-dimethyl-chlorosilane, (4-t-propylphenyl) -diethyl-chlorosilane, octylmethoxysilane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilane, Hexaphenyldisilazane, hexatolyldisilazane and the like.

 The degree of hydrophobicity of the hydrophobic silica is 10-40.

The “degree of hydrophobicity” in the present invention is a value measured by a methanol titration method. For example, 50 ml of pure water is placed in a 100-150 ml container, and 0.2 g of silica is added. Then, with gentle stirring with a magnetic stirrer, methanol is added from the puret whose tip is immersed in water at the time of dropping, and the number of ml of methanol dropped when the floating silica starts to sink is defined as the degree of hydrophobicity. In this case, methanol has a surface-active action, and the silica that floats as methanol drops drops into water via methanol (that is, starts to sink). The greater the number, the greater the hydrophobicity of the silica.

As the binder resin in the component A, conventionally known binder resins can be widely used, for example, styrenes such as styrene and parachlorostyrene, vinyl naphthalenes such as vinyl chloride, vinyl bromide, vinyl fluoride, and vinyl acetate. Vinyl esters such as vinyl propionate, vinyl benzoate and vinyl butyrate, for example, methyl acrylate,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloro acrylate, phenyl ethyl acrylate, α-methyl methyl acrylate, methyl methacrylate, ethyl methacrylate, Α such as butyl methacrylate
Esters of methylene aliphatic monocarboxylic acids, acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; -A polymer obtained by polymerizing monomers such as N-vinyl compounds such as vinylpyrrole, N-galvazole, N-vinylindole and N-vinylpyrrolidone, or a copolymer obtained by combining two or more of these monomers. Non-vinylic thermoplastic resins such as copolymers or mixtures thereof, or rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyurethane resins, cellulose resins, polyether resins, and the like and And a mixture of Le resin. Particularly, materials limited to pressure fixing materials include polyolefins (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polytetrafluoroethylene, etc.), epoxy resins, polyester resins (acid value
10 or less), styrene-butadiene copolymer (monomer ratio 5-30: 95-70), olefin copolymer (ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer,
Ethylene-methacrylic acid ester copolymer, ethylene-
Vinyl chloride copolymer, ethylene-vinyl acetate copolymer,
Ionomer resin), polyvinylpyrrolidone methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, and the like.

As the coloring agent in the component A, conventionally known pigments and dyes are used. Specific examples include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, dubon oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, lamp black, oil black, azo oil black, rose bengal And mixtures thereof.

Further, it is advantageous to add a negatively chargeable adjusting agent to the component A. Known negative charge control agents can also be applied as they are, specifically, Japanese Patent Publication No. 41-20153 and No. 43-27596.
Metal complex salts of monoazo dyes described in JP-A-44-6397, JP-A-45-26478, etc .;
No., JP-B-58-41508, JP-B-58-7384, JP-B-59
Salicylic acid, dialkyl salicylic acid, naphthoic acid, dicarboxylic acid Zn, A
Metal complexes such as l, Co, Cr, Fe, etc .; and sulfonated copper phthalocyanine pigments.

In the component A, the hydrophobic silica (particle size of about 5 nm to 3 μm) is carried (adsorbed and adhered) on the surface of the toner (particle diameter of about 1 to 25 μm) with at least a colorant and a binder resin as main components. It is made of what was done. The amount of the hydrophobic silica fine powder in the component A is suitably from 0.02 to 10.0% by weight, preferably from 0.1 to 2.0% by weight.

Examples of the silicone resin used for the component B (silicone resin-coated carrier) include a conventionally known straight silicone resin and a silicone resin modified with alkyd, acrylic, epoxy, or the like.

The weight ratio of component A / component B in the developer of the present invention is suitably such that the coverage of component A on the surface of component B is 5 to 80%.

〔Example〕

Next, examples will be described. Here, both parts and% are based on weight.

Example 1 A mixture of 100 parts of a styrene-2 ethylhexyl acrylate copolymer, 10 parts of carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), 3 parts of a chromium-containing monoazo dye, 3 parts was melted and kneaded by a hot roll mill. Coarsely pulverized, and then finely pulverized by a jet mill. The obtained finely pulverized product was classified by an air classifier to obtain a negative toner A having a volume average particle size of about 10 μm.

In addition, dimethyldichlorosilane is allowed to act on the gas-phase-process silica fine powder obtained by hydrolysis of silicon tetrachloride,
A weakly hydrophobic silica having a degree of hydrophobicity of 25 was obtained. Subsequently, 0.5% of the weakly hydrophobic silica was added to the toner A and mixed with a Henschel mill side to produce a toner A-1 according to the present invention.

On the other hand, a silicone resin solution (SR-2400 manufactured by Toray Silicone Co., Ltd.) was added to 1000 parts of spherical ferrite having an average particle size of about 100 μm.
100 parts to form a coating layer using a fluidized bed type coating device,
A carrier B according to the present invention was manufactured. Next, the toner A-
1 and Carrier B to prepare the developer of the present invention, and then store the developer in a commercially available electrophotographic copying machine (FT-6550, manufactured by Ricoh Co., Ltd.) and supply 100,000 sheets while replenishing toner A-1. Was tested to evaluate the durability of the developer and the background fog when the toner A-1 was supplied.

 The results are summarized in Table 1.

Example 2 Toner A obtained in Example 1 was added with 0.5% of hydrophobic silica shown in Table 1 and mixed with a Henschel mixer to produce Toner A-2 according to the present invention.

Next, the toner A-2 and the carrier B obtained in Example 1 were mixed to prepare a developer of the present invention, and the developer was stored in an electrophotographic copying machine (FT-6550). While replenishing the toner No. 2, a copy test was performed on 100,000 sheets to evaluate the durability of the developer and the background fogging at the time of toner replenishment. The results are summarized in Table 1.

Example 3 Toner A obtained in Example 1 was added with 0.5% of hydrophobic silica shown in Table 1 and mixed with a Henschel mixer to produce toner A-3 according to the present invention.

Next, the toner A-3 and the carrier B obtained in Example 1 are mixed to prepare a developer of the present invention, and the developer is stored in an electrophotographic copying machine (copier FT-6550). While replenishing the toner A-3, a 100,000-sheet copy test was performed to evaluate the durability of the developer and the background fogging when replenishing the toner.
Table 1 summarizes the results.

Example 4 A mixture composed of 100 parts of a polyester resin synthesized from bisphenol A and terephthalic acid, 10 parts of carbon black (# 44 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.), 10 parts of zinc salt of salicylate 2 parts was melted and kneaded with a hot roll mill, and cooled. It was coarsely pulverized by a hammer mill and then finely pulverized by a jet mill. The obtained finely pulverized product was classified by an air classifier to obtain a negative toner C having a volume average particle size of about 10 μm according to the present invention.

Further, dimethyldichlorosilane was allowed to act on the fine silica powder obtained by hydrolysis of silicon tetrachloride to obtain weakly hydrophobic silica having a hydrophobicity of 25. Subsequently, 0.5% of this weakly hydrophobic silica was added to the toner C and mixed with a Henschel mill side to produce a toner C-1 according to the present invention.

On the other hand, 100 parts of an acrylic modified silicone resin (manufactured by Toray Silicone Co., Ltd.) is formed on 1000 parts of spherical magnetite having an average particle diameter of about 100 μm using a fluidized bed type coating apparatus to form a coating layer, thereby producing the carrier D according to the present invention. did.

Next, the toner C-1 and the carrier D are mixed to prepare the developer of the present invention, and the developer is stored in an electrophotographic copying machine (FT-6550). After conducting a copy test of 10,000 sheets, the durability of the developer and the toner C-
The ground cover at the time of one replenishment was evaluated. Table 1 summarizes the results
Shown in

Example 5 Toner C obtained in Example 4 was mixed with 0.5% of hydrophobic silica shown in Table 1 using a Henschel mixer to produce Toner C-2 according to the present invention.

Next, the toner C-2 and the carrier D obtained in Example 4 were mixed to prepare a developer of the present invention, and the developer was stored in an electrophotographic copying machine (FT-6550). While replenishing the toner No. 2, a copy test was performed on 100,000 sheets to evaluate the durability of the developer and the background fog when the toner C-2 was replenished. The results are summarized in Table 1.

Example 6 Toner C obtained in Example 4 was mixed with 0.5% of hydrophobic silica shown in Table 1 and mixed with a Henschel mixer to produce Toner C-3 according to the present invention.

Next, the toner C-3 and the carrier D obtained in Example 4 were mixed to prepare a developer of the present invention, and the developer was stored in an electrophotographic copying machine (FT-6550). A copy test was performed on 100,000 sheets while the toner No. 3 was replenished, and the durability of the developer and the background fog when the toner C-3 was replenished were evaluated. The results are summarized in Table 1.

Comparative Example 1 A developer was prepared in exactly the same manner as in Example 1 except that hydrophobic silica was not used. Next, this comparative developer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 (1 ′, 2 ′ and 3 ′) Except that dimethyldichlorosilane, octylmethoxylane, and hexamethyldisilazane shown in Table 1 having a degree of hydrophobicity of 5 were used, exactly the same as Example 4 was used. I made a developer. Next, this comparative developer was evaluated in the same manner as in Example 4, and the results are summarized in Table 1.

Comparative Example 3 (1 ', 2' and 3 ') Developed in the same manner as in Example 1 except that dimethyldichlorosilane, octylmethoxylane and hexamethyldisilazane shown in Table 1 having a degree of hydrophobicity of 4 were used. I made a medicine. Next, this comparative developer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4 (1 ', 2', and 3 ') A developer was prepared in the same manner as in Example except that dimethyldichlorosilane, octylmethoxylane, and hexamethyldisilazane shown in Table 1 having a hydrophobicity of 7 were used. Was made.
Next, this comparative developer was evaluated in the same manner as in Example 4, and the results are summarized in Table 1.

Note 1) Regarding the evaluation results on durability and fogging at the time of toner replenishment, ○ indicates that there was no problem with 100,000 sheets, and X indicates that there was a problem.

Note 2) Concerning toner replenishment stability, a continuous replenishment test was performed using FT-6550, and those with stability were represented by 、, and those that became unstable with respect to the remaining amount of toner and changes in temperature and humidity were represented by x.

〔The invention's effect〕

According to the use of the dry two-component negatively chargeable developer of the present invention, contamination of the carrier and the photoreceptor by toner is prevented, excellent durability is exhibited, and the ground fogging when toner is supplied to the developing device is achieved. It became possible to prevent the phenomenon.

Continuation of the front page (72) Inventor Yasutaka Iwamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-62-180375 (JP, A) JP-A-62-182752 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 9/08 G03G 9/113

Claims (1)

(57) [Claims] 1. A dry two-component system comprising a mixture of a toner containing at least a binder resin and a colorant and carrying on its surface hydrophobic silica having a hydrophobicity of 10 to 40, and a silicon resin-coated carrier. Negatively chargeable developer.