JPH03192267A - Negatively chargeable dry binary system developer - Google Patents

Abstract

PURPOSE:To prevent the stain of a carrier and a photosensitive body with a toner and base fog and to improve durability by mixing a toner contg. at least a binding resin and a colorant and supporting hydrophobic silica having a specified hydrophobic degree and hydrophilic silica on the surface with a silicone resin coated carrier. CONSTITUTION:A toner contg. at least a colorant and a binding resin and holding hydrophobic silica having >=40 hydrophobic degree and hydrophilic silica stuck to the surface is mixed with a silicone resin coated carrier to obtain the developer. The hydrophilic silica is fine silicon dioxide powder and is obtd. by hydrolyzing silicon tetrachloride in an oxyhydrogen flame or causing precipitation in an aq. sodium silicate soln. and the hydrophilic silica is made hydrophobic by substituting an organosilicon compd. for silanol groups on the surface of the silica to obtain the hydrophobic silica. The stain of the carrier and a photosensitive body with the toner and base fog are prevented and durability is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dry two-component negatively chargeable developer, and more specifically, it is used to develop electrostatic images formed by electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to a two-component negatively charged developer used for imaging.

[Conventional technology]

Developers used in electrophotography are roughly divided into dry and wet types, and both dry and wet type developers (liquid developers) each have their own advantages and disadvantages. The former dry type developer is more commonly used because the product can be obtained in a dry state. There are two types of dry developers: one-component developer consisting only of toner and two-component developer consisting of a mixture of toner and carrier. Two-component developers are more commonly used because they are difficult to maintain.

However, even in this dry type two-component developer, toner components tend to adhere to the surface of the carrier depending on the frequency of use (period of use), and the performance of the carrier gradually deteriorates. Such a deterioration in the performance of the carrier naturally affects the amount of charge on the toner, making it difficult to obtain good images.

However, attempts to eliminate the defects of such two-component developers have been made, for example,
(1) By coating the carrier surface with a low surface energy material such as silicone resin, toner contamination on the carrier surface is prevented and a developer with excellent durability is obtained (Japanese Patent Publication No. 44-27879, Japanese Unexamined Patent Publication No. 54-21
730, etc.), (2) containing in the toner silicon dioxide fine particles made hydrophobic by bonding an organic group to silicon;
By mixing this with a carrier, it is possible to prevent the toner filming phenomenon on the photoconductor and carrier surface, provide a stable developer over a long period of time, and obtain a large number of copied images (Japanese Patent Application Laid-Open No. 46-11102). -5782) etc. have been proposed. However, although these two-component developers (1) and (2) have excellent durability, these developers suffer from background fogging when negatively charged toner is replenished. This is an inconvenience that often occurs.

[Problem to be solved by the invention]

The present invention prevents toner contamination of the carrier and photoreceptor, and also prevents background fog from occurring even when negatively charged toner is replenished into the developer. Therefore, a large number of high-quality copies can be produced over a long period of time. The present invention provides a dry two-component developer.

[Means to solve the problem]

The dry two-component negatively charged developer of the present invention (a) contains at least a binder resin and a colorant, and has hydrophobic silica and hydrophilic silica having a degree of hydrophobicity of 40 or more supported on the surface. and (b) a silicone resin-coated carrier.

The present inventors have once again investigated in detail the phenomenon that causes background fog when a negatively charged toner containing hydrophobic silica is replenished into a two-component developer consisting of a mixture of the toner and a silicone resin-coated carrier. As a result, it was confirmed that this hydrophobic silica-containing toner exhibited positive polarity when initially mixed with the silicone resin-coated carrier, and then changed to negative polarity. On the other hand, a two-component developer consisting of a mixture of a negative toner containing hydrophilic silica and a silicone resin-coated carrier is used immediately after replenishing the negative toner containing hydrophilic silica. Although the toner did not show positive polarity even with a small amount of stirring, the toner containing hydrophilic silica showed a3It
Compared to toners containing aqueous silica, toner fluidity was poor, and toner replenishment from the toner tank to the developing device was not stable. Taking this phenomenon into consideration, the present inventors prepared both hydrophobic silica and hydrophilic silica, and when replenishing toner containing these into a developer, the toner became positively polarized. It also no longer caused any ground fog. At this time, the fluidity of the toner was as favorable as when hydrophobic silica was mixed, and the toner replenishment stability was also good.

The present invention has been made based on this knowledge.

The present invention will be explained in more detail below.

As mentioned above, the dry two-component developer according to the present invention contains at least (1) a coloring agent and (2) a binder resin, and on the surface (1) hydrophobic silica with a degree of hydrophobicity of 40 or more and (2) hydrophilic silica. It consists of a mixture of the adhered toner (hereinafter sometimes referred to as "component A") and a silicone resin-coated carrier (hereinafter sometimes referred to as "component B").

"Hydrophilic silica" in the ^ component means silicon dioxide fine powder produced by any method. That is, it can be produced, for example, by hydrolysis of silicon tetrachloride in an oxyhydrogen flame or by precipitation with an aqueous sodium silicate solution. On the other hand, the "hydrophobic silica" in component A can be produced by making this hydrophilic silica hydrophobic. Note that hydrophilic silica is made hydrophobic by substituting silanol groups on the silica surface with an organic silicon compound.

Representative examples of the hydrophobic silica used in the present invention are shown below, but they are not necessarily limited to these, and they may be used alone or in combination of two or more.

Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, P-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, P-chlorophenyltrichlorosilane, 3-Chlorpropyltrichlorosilane, 3
- Chlorpropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyl-tris(
β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyl 1-lyacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyl-trichlorosilane, decyl-trichlorosilane, nonyl-trichlorosilane, (4 -t-
(propylphenyl)-trichlorosilane, (4-t-butylphenyl)-trichlorosilane, dibendyludichlorosilane, dihexyldichlorosilane, dioctyl-dichlorosilane, dinonyl-dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, dihexane Decyl-dichlorosilane, (4-t-butylphenyl)-octyl-dichlorosilane, dioctyl-dichlorosilane, dibutenyl-dichlorosilane, divinyldichlorosilane, 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, octyltrimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilazane, hexaphenyldisilazane, hexatolyldisilazane, and the like.

The degree of hydrophobicity of hydrophobic silica must be 40 or more,
If the degree of hydrophobicity is 40 or less, fluidity will not be imparted to the toner sufficiently.

Note that the "degree of hydrophobicity" in the present invention is a value measured by methanol titration. For example, 100-10
Put 50mQ of pure water in a 0-l50 container and add 0.2g+7
) Add silica. Then, while gently stirring with a magnetic stirrer, methanol is added from a billet whose tip is immersed in water during dropping, and the success or failure of the dropped methanol when the floating silica begins to sink is determined as the degree of hydrophobicity. In this case, methanol has a surfactant effect, and as the methanol is dripped, the floating silica dissolves (i.e. begins to sink) in the water via the methanol.
The greater the degree of hydrophobicity (the greater the amount of methanol dropped), the greater the hydrophobicity of silica.

In order to obtain the effects of the present invention, the mixing ratio (weight ratio) of hydrophobic silica and hydrophilic silica is preferably in the range of 80:20 to 30:0.

As the binder resin for component A, a wide variety of conventionally known binder resins can be used, such as styrenes such as styrene and parachlorostyrene, vinylnaphthalene, vinyl chloride, vinyl bromide, vinyl fluoride, and vinyl acetate. , vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-acrylate Chlor, phenyl ethyl acrylate, methyl α-chloroacrylate, methyl methacrylate,
Esters of α-methylene aliphatic monocarboxylic acids such as ethyl methacrylate and butyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether, such as vinyl methyl ketone, Polymers obtained by polymerizing monomers such as vinyl ketones such as vinylhexyl ketone, N-vinyl compounds such as N-vinylpyrrole, N-galbazole, N-vinylindole, and N-vinylpyrrolidone, or these monomers. copolymers or mixtures thereof, or non-vinyl thermoplastic resins such as rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyurethane resins, cellulose resins, polyether resins, etc. Mixtures of these and the above-mentioned vinyl resins can be mentioned. In addition, materials particularly limited to pressure fixing materials include polyolefins (low molecular weight polyethylene, low molecular weight polypropylene, oxidized polyethylene, polytetrafluoroethylene, etc.), epoxy resins, polyester resins (acid value 10
(below), styrene-butadiene copolymer (monomer ratio 5
~30:95-70), olefin copolymers (ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate) copolymers, ionomer resins, etc.), polyvinylpyrrolidone methyl vinyl ether-maleic anhydride copolymers, maleic acid-modified phenol resins, phenol-modified terpene resins, and the like.

As the coloring agent in 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, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, lamp black, oil black, azo oil black, and rose bengal. and mixtures thereof.

Furthermore, it is advantageous to add a negatively chargeable regulator to the A component. Known negative chargeability adjusters can be used as they are, and specifically, Japanese Patent Publication Nos. 41-20153 and 43-
No. 27596, No. 44-6397, No. 45-2647
Metal complex salts of monoazo dyes described in publications such as No. 8; Japanese Patent Publication No. 55-42752, Japanese Patent Publication No. 58-4150
No. 8, Special Publication No. 58-7384, Special Publication No. 59-7385
Salicylic acid, dialkyl salicylic acid, naphthoic acid, dicarboxylic acid Zn, ^Q,
Examples include metal complexes such as Co, Cr, and Fe, and sulfonated copper phthalocyanine pigments.

Component A contains at least a colorant and a binder resin as main components, and the above-mentioned hydrophilic silica (particle size of about 5 nm to 3/J@) and hydrophobic silica (particle size of about 5 nm to 3/J@) are added to the surface of the toner (particle size of about 1 to 25 nm). 3) is supported (adsorbed/attached). The total amount of hydrophilic silica fine powder and hydrophobic silica fine powder in component A is (1
, 02-10, 0 weight 2 preference L <!; [), 1-2
．． Approximately 0 parts and 1% is appropriate.

Examples of the silicone resin used for component B (silicon resin-coated carrier) include straight silicone resins, which are also conventionally known, and silicone resins modified with alkyd, acrylic, or epoxy.

The toner (core material), hydrophobic silica, and hydrophilic silica can be mixed using a rotary mixing and stirring device such as a Hentzel mixer, super mixer, speed kneader, or pipe retizer. It is also possible to provide adhesion.

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

〔Example〕

Next, examples will be shown. Both parts and percentages herein are based on weight.

Example 1 A mixture consisting of 3 parts of a chromium-containing monoazo dye was melted and kneaded in a hot roll mill, cooled, coarsely ground in a hammer mill, and then finely ground in a jet mill. The obtained finely ground material is classified using a wind classifier,
Negative polarity toner A having a volume average particle diameter of about 10 was obtained.

This toner A was mixed with hydrophobic silica and hydrophilic silica (Japan Yourosil Co., Ltd. 1A-300) shown in Table 1 using a Hentzel mixer to produce toner A-1 according to the present invention.

On the other hand, spherical ferrite 1000 with an average grain size of about 1100p
In the part, silicone resin solution (Toshi Silicone Co., Ltd. 1% 5R
Carrier B according to the present invention was manufactured by forming a coating layer on 100 parts of -2400) using a fluidized bed coating device.

Next, after mixing toner A-1 and carrier B to prepare the developer of the present invention, a commercially available electrophotographic copying machine (Ricoh Co., Ltd. FT
-6550), and a 100,000 copy test was carried out while replenishing the toner A-1.

The durability of the developer and the background fog when toner A-1 was replenished were evaluated.

The results are summarized in Table-1.

Example 2 Toner A obtained in Example 1 was treated with hydrophobic silica and hydrophilic silica (A-2 manufactured by Nippon Yourosil Co., Ltd.) shown in Table 1.
00) and mixed using a Henschel mixer to produce toner A-2 according to the present invention.

Next, toner A-2 and carrier B obtained in Example 1
After preparing the developer of the present invention by mixing the toner A-
A 100,000 copy test was conducted while replenishing toner No. 2 to evaluate the durability of the developer and the background fog during toner replenishment. The results are summarized in Table-1.

Example 3 Hydrophobic silica and hydrophilic silica shown in Table 1 were added to toner A obtained in Example 1, and mixed using a Henschel mixer to produce toner A-3 according to the present invention6. , toner A-3 and carrier B obtained in Example 1
After preparing the developer of the present invention, the developer is stored in an electrophotographic copying machine (copying machine FT-6550), and without replenishing toner A-3, it is possible to make 10,000 copies. A test was conducted to evaluate the durability of the developer and the background fog during toner replenishment.The results are summarized in Table 1. Example 4 Carbon black (#44 manufactured by Mitsubishi Chemical Industries, Ltd.) 10
A mixture consisting of two parts of zinc salt of salicylate was melted and mixed in a hot roll mill, cooled, coarsely ground in a hammer mill, and then finely ground in a jet mill. The obtained finely ground material is classified using a wind classifier,
Negative polarity toner C with a volume average particle diameter of about 10 μs according to the present invention
I got it.

Toner C-1 was mixed with hydrophobic silica and hydrophilic silica shown in Table 1 using a Henschel mixer to produce toner C-1 according to the present invention.

On the other hand, spherical magnetite with an average particle diameter of 100
100 parts of an acrylic modified silicone resin (Toshiba Silicone Co., Ltd., $1) was applied to the carrier to form a coating layer using a fluidized bed coating device, thereby producing a carrier D according to the present invention.

Next, after preparing the developer of the present invention by mixing toner C-1 and carrier D, the developer
While storing the developer and replenishing toner C-1,
A 100,000-sheet copying test was conducted to evaluate the durability of the developer and background fog when toner C-1 was replenished. The results are summarized in Table-1.

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

Next, toner C-2 and carrier D obtained in Example 4
After preparing the developer of the present invention, the developer is stored in an electrophotographic copying machine (FT-6550) and the toner C-
While replenishing Toner C-2, a 100,000 copy test was conducted to evaluate the durability of the developer and background fog when replenishing Toner C-2. The results are summarized in Table-1.

Example 6 Hydrophobic silica and hydrophilic silica shown in Table 1 were added to Toner C obtained in Example 4 and mixed in a Henschel mixer to produce Toner C-3 according to the present invention.

Next, toner C-3 and carrier D obtained in Example 4
After preparing the developer of the present invention by mixing the toner C-
A 100,000 copy test was conducted while replenishing Toner C-3 to evaluate the durability of the developer and background fog when replenishing Toner C-3. The results are summarized in Table-1.

Comparative Example 1 (1'2' and 3') Same as Example 1 except that dimethyldichlorosilane, octylmethoxyrane, and hexamethyldisilazane shown in Table 1 in which the degree of hydrophobicity of hydrophobic silica was 40 or less were used. A developer was prepared in the same manner as in Example 1. Next, this comparative developer was evaluated in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 2 (1'2' and 3') A developer was prepared in the same manner as in Example 1.2 or 3, except that hydrophilic silica was not contained. Next, this comparative developer was evaluated in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 3 (1'2' and 3') Example 1 or 2 except that hydrophobic silica was not contained.
A developer was prepared in the same manner. Next, this comparative developer was evaluated in the same manner as in Example 4, and the results are summarized in Table 1.

Note 1) Note 2) Regarding the evaluation results regarding durability and fogging during toner replenishment, O indicates that there was no problem after 100,000 copies, and × indicates that there was a problem.

Concerning toner replenishment stability, a continuous replenishment test was conducted using FT-6550, and stable toner replenishment was evaluated as 0, and unstable toner replenishment due to changes in the remaining amount of toner or temperature and humidity was represented as x.

(Effects of the Invention) According to the use of the dry two-component negatively chargeable developer of the present invention,
Contamination of the carrier and photoreceptor with toner is prevented, and it exhibits excellent durability, and it is also possible to prevent background fogging when toner is replenished to the developing device.

Claims (1)

[Claims] (1) A dry-type secondary toner comprising a mixture of a toner containing at least a binder resin and a colorant and carrying hydrophobic silica and hydrophilic silica having a hydrophobicity of 40 or more on the surface, and a silicone resin-coated carrier. Component-based negatively chargeable developer.