JP3027588B2 - Developer for electrostatic image - Google Patents

Description

The present invention relates to electrophotography of a copying machine, a laser printer and the like,
The present invention relates to an electrostatic image resolving agent used for developing an electrostatic image in electrostatic recording, electrostatic printing, and the like.

2. Description of the Related Art Electrophotography has been widely known, for example,
A visible image is formed through the following steps.

The photoconductive insulator layer is uniformly charged by corona discharge or the like, and selectively irradiated with light by image exposure or scanning exposure with a laser beam to dissipate the charged portion to form an electrostatic latent image. .

This latent image is visualized with a developer called toner to form a visible image (developing step).

The visible image is transferred directly or onto another substrate such as paper (transfer step), and then fixed (fixing step).

There is also known a method of forming an electrostatic latent image by selectively charging with a pin electrode.

In any case, the developer has a great effect on the success or failure of the developing step, the transfer step, and the fixing step.
Strict characteristics are required to determine the image characteristics and the running cost of the apparatus.

Developers are broadly classified into two-component developers composed of a toner and a carrier, and one-component developers having a toner function as a carrier. The development method is broadly classified into a normal development method in which the latent image is adhered to the latent image bearing portion of the photoconductor and a reversal development method in which the toner adheres to the non-carrying surface of the latent image. Is an important issue.

It has been conventionally proposed to add silica as an external additive to a toner to impart appropriate fluidity and charge stability.

For example, Japanese Patent Publication No. Sho 54-16219 discloses that submicron silica is added to a toner having a particle size of about 30 μm or less. However, this developer has problems in durability stability in many cases, and it has been difficult to store silica fine powder in a toner for a long period of time.

JP-A-58-60754 proposes that silica fine powder synthesized by a wet method is subjected to hydrophobic treatment with silicone oil and added to the toner. However, uniform treatment is difficult with this hydrophobic treatment method,
Processing unevenness is likely to occur. Further, when silica which has been subjected to a hydrophobizing treatment by this method is added to the toner, there is a problem that the fluidity of the toner is impaired and the stability during continuous printing is poor.

Further, Japanese Patent Application Laid-Open No. Sho 59-176753 describes that silica or the like is subjected to a hydrophobic treatment with a silane coupling agent and the resultant is fused to the toner surface. But,
With such a coupling agent treatment, sufficient hydrophobicity cannot be obtained, and there is a problem that the toner fused with the toner tends to cause image deterioration.

SUMMARY OF THE INVENTION The present invention is to provide a developer for an electrostatic charge image which has stable fluidity and chargeability and does not cause image deterioration even after continuous printing.

Constitution of the Invention The developer for an electrostatic image of the present invention is a silica powder synthesized by a wet method, the surface of which is hydrophobized by a gas phase reaction with a dimethylsilane compound or a trimethylsilane compound. Contains 70 or less hydrophobized wet silane powder.

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

The wet silica, unlike the dry silica, has fine pores in its internal structure and contains many water molecules bonded to silanol groups on the surface of the pores by van der Waals force. These water molecules, unlike surface adsorbed water, exist relatively stably even due to environmental changes. Therefore, when added to the toner, the triboelectric potential does not rise excessively during the triboelectric charging, and the toner can be provided with a stable chargeability required for development.

In the present invention, such wet silica is further treated by a gas phase reaction with a dimethylsilane compound and / or a trimethylsilane compound, whereby the silanol groups on the silica surface are reacted with the treating agent, and a hydrophobic treatment is performed. FIG. 1 and FIG. 2 show examples of this reaction. This reaction can be carried out, for example, by a gas phase reaction (solid-gas phase reaction) in which the treating agent gas and silica are brought into contact in the presence of an inert gas such as nitrogen gas.

In order to improve the hydrophobicity, the silanol groups on the silica surface and the treating agent sufficiently react to minimize the amount of the silanol groups exposed on the silica surface, preferably substantially exposing the silanol groups on the silica surface. It is important not to. However, in practice, as shown in FIGS. 1 and 2, even when dimethyl or trimethylation is performed in a gas phase to make it hydrophobic, it is necessary to completely react with all silanol groups and block the silanol groups. Can not.
This is due to steric hindrance of the methyl group in the treating agent, and unreacted silanol groups remain. It is preferable to use a dimethylsilane compound and a trimethylsilane compound in combination, in order to avoid steric hindrance and reduce the amount of unreacted silanol groups. The amount of unreacted silanol groups is determined by the dibutylamine (DBA) adsorption method.
Alternatively, the degree of hydrophobicity can be measured by a methanol method. In the present invention, the DBA adsorption amount (mg-molg / kg)
Hydrophobic wet silane of 70 or less is preferred, more preferably
It is 60 or less, more preferably 30 or less.

The wet-process silica is obtained by various conventionally known production methods, and is precipitated by, for example, neutralization with an acid or alkali metal salt of an aqueous solution of sodium silicate and a decomposition reaction.

Na ₂ O.3.3SiO ₂ + H ₂ SO ₄ → 3.3SiO ₂ .nH ₂ O + Na ₂ SO _{4 As} wet silica, various commercially available products can be used. For example, Carprix (Shinogi Pharmaceutical), Nip Seal (Japan) Silica), Fine Seal (Tokuyama Soda), Vita Seal (outer wooden manure), Shilton, Silnex (Mizusawa Chemical), Star Sil (Kamijima Chemical), Syloid (Fuji Devison Chemical), and others.

As the wet silica, fine particles having an average primary particle size of 0.01 to 2 μm are preferable.

As the dimethylsilane compound and the trimethylsilane compound, those having a functional group that reacts with a silanol group are used, and dimethyldichlorosilane, trimethylchlorosilane, hexamethyldisilazane, allyldimethylchlorosilane, benzyldimethylchlorosilane, and bromomethyl Examples thereof include dimethylchlorosilane, chloromethyldimethylchlorosilane, divinyldichlorosilane, and dimethylvinylchlorosilane. Of these, dimethylchlorosilane, trimethylchlorosilane, and hexamethyldisilazane are particularly preferred.

The hydrophobized wet silane of the present invention contains 0.1 to 0.1% in the toner.
It is preferable to mix 2% by weight.

The toner particles used in the present invention are not particularly limited,
It may contain a binder resin, a colorant, a charge control agent, a fixing improving aid, and the like. In the case of a one-component system, a magnetic substance is blended, and in the case of a two-component system, a carrier is powder-mixed.

As the binder resin, a polystyrene resin, a polyester resin, or the like is used. Examples of the polystyrene resin include homopolymers of styrene monomers such as styrene, α-methylstyrene, and α-chlorostyrene; copolymers of these styrene monomers; copolymers of styrene monomers with other monomers copolymerizable with the styrene monomers. Polymers.
Other copolymerizable monomers include propylene, butadiene, vinyl chloride, vinyl acetate, maleic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate , Ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate,
An acrylate or methacrylate such as phenyl methacrylate is exemplified.

The polyester resin is obtained by polycondensation or co-condensation polymerization of an alcohol component and a carboxylic acid component. Specific examples of each component used include the following.

Examples of the divalent or trivalent or higher alcohol component include the following.

1) Diols: ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5- Pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

2) Bisphenols; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxyprolenated bisphenol A;

3) Trihydric or higher alcohols; sorbitol, 1,2,3,
6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropane Triol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like.

Examples of the divalent or trivalent or higher carboxylic acids include divalent or trivalent carboxylic acids, acid anhydrides and lower alkyl esters thereof, and the following carboxylic acids are exemplified.

4) divalent carboxylic acids; maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, Or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dosesenyl succinic acid,
Alkyl or alkenyl succinic acid such as isododecyl succinic acid and isododecenyl succinic acid;

5) Trivalent or higher carboxylic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4- Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,
1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid and the like.

Acid anhydrides or lower alkyl esters of these carboxylic acids can also be used.

Various colorants and pigments such as carbon black are used as colorants; magnetite and ferrite are used as magnetic substances; quaternary ammonium compounds are used as charge control agents;
Nigrosine, nigrosine base, crystal violet, 1,2-type chromium alloy complex salt dyes and the like; olefin waxes such as low molecular weight polypropylene, low molecular polyethylene or modified products thereof can be used as an anti-offset agent and fixing aid.

The toner of the present invention can be produced by a conventional method, for example, a twin-screw extruder,
It is obtained by melt-kneading each component with a kneader or the like, pulverizing with a jet mill or the like, and classifying.

The toner of the present invention contains hydrophobic silica as an external additive, is mixed with a carrier to form a two-component developer, contains a magnetic substance, and becomes a one-component developer, or contains a photoconductive material to form a photoconductive material. It can take various forms of use such as as a toner.

Effects of the Invention According to the present invention, the charge stability of a developer is improved by blending a wet silica which has been subjected to a hydrophobic treatment by a gas phase reaction using a dimethylsilane compound or a trimethylsilane compound as an external additive into a toner. This makes it possible to prevent deterioration in image quality even after printing a large number of sheets, and to effectively prevent fogging of images and scattering of toner.

Example 1 (Preparation of hydrophobized silica) The silica fine powder shown in Table 1 below (each having an average primary particle size of about 0.03 μm) was added to the silica fine powder in an amount of 5%.
By treating with a surface treating agent at a weight% of weight, hydrophobic silica having an average particle size of 0.5 μm was prepared. DBA for these hydrophobic silicas
The adsorption amount, the value measured by the hydrophobic methanol method, and the Q / M using an iron powder carrier were measured, and the results are summarized in Table 1 below.

(1) Hydrophobizing Method (Silica Nos. 1 to 3, 6) The silica fine powder was subjected to a hydrophobizing treatment by bringing it into contact with a surface treating agent at a temperature of 400 ° C. in the presence of nitrogen.

(2) Hydrophobizing Method (Silica No. 4) A silane coupling agent was dissolved in water, sprayed on silica fine powder during high-speed stirring, and then heated and dried to obtain surface-treated silica.

(3) Hydrophobization method (Silica No. 5) Silicone oil is added dropwise while stirring the silica fine powder at high speed. Further curing was performed at 150 ° C. for 30 minutes to obtain surface-treated silica.

(4) Measurement method of DBA adsorption amount 250 mg of a dry sample was precisely weighed in a 250 ml stoppered Erlenmeyer flask.
To this, add 50 ml of N / 500-n dibutylamine solution (petroleum benzene solvent) with a pipette and shake frequently for 20 minutes.
Leave for about 2 hours at ° C.

Aspirate 25 ml of the supernatant with caution with a pipette, transfer to an Erlenmeyer flask, add 5 ml of chloroform, and 2 to 3 drops of indicator (0.1% by dissolving crystal violet in acetic anhydride), purple color turns blue. Titrate with an N / 100-perchloric acid solution (acetic anhydride solvent) until (A ml).

Separately, blanking is performed for 25 ml of N / 500-n-dibutylamine (B ml), and the DBA adsorption amount is calculated by the following equation.

DBA adsorption amount (mg-mole / kg) = 80 (BA) f where f is the titer of N / 100-perchloric acid (5) Measuring method of hydrophobicity by methanol method Water / methanol was added to a 10 ml test tube. Pour 5 ml of the liquid with the ratio set constant.

A small amount of a sample is added to the test tube with an earpick spatula, shaken twice twice, and the degree of hydrophobicity is defined as the ratio of methanol at which clouding begins.

(6) Measured by blow-off method using Q / M iron powder carrier,
The sec value is shown.

Example 2 (Preparation and evaluation of developer) Polyester binder 85% by weight Polypropylene wax 5% by weight Carbon black 9% by weight Charge control agent 1% by weight After thoroughly mixing the above components with a mixer, kneading, coarse pulverization and fine grinding were performed. The mixture was pulverized and classified to obtain a classified toner having an average of 10 μm.

To this, 1.0% by weight of each surface-treated silica fine powder prepared in Example 1 was added and mixed for 2 minutes with a super mixer to obtain a toner.

Further, 100 parts of a ferrite carrier coated with silicone (average 100 μm) was added to 4 parts of the toner and mixed to prepare a developer, and the image was evaluated with a Kyocera laser beam printer F-800, and the result was described later. The results are shown in Table-2.

(1) Q / M (charge amount) It was measured by the blow-off method and showed a value of 30 sec.

(2) Fluidity Use a powder tester (manufactured by Hosokawa Micron Corporation)
Set the two-stage screen of mesh and 100 mesh, set the scale of vibration to 3, measure the remaining amount of 20 mesh screen, the larger the value of the fluidity (%), the worse the fluidity, the following criteria Was evaluated.

◎: 20% or less :: 20 to 50% ×: 50% or more (3) Image density Using a Kyocera laser printer F-800, initial and 100,000 sheet development were measured with a Macbeth densitometer.

This test was performed at 23 ° C-55% RT (under normal temperature and humidity) and 35 ° C-
The test was performed under two conditions of 20% RT (under high temperature and low humidity).

(4) Fog Fog was judged by the limit sample (under normal temperature and normal humidity conditions).

Judgment criteria ：: No fog is observed at all ○: Fog cannot be discerned with the naked eye △: Fog can be confirmed with the naked eye ×: Fog is clearly confirmed (5) Toner scattering inside the machine Using the same laser printer, 10 After printing every 10,000 sheets, it was visually observed, and the in-flight scattering was evaluated based on the following criteria. The results are shown in Table 1 below (under normal temperature and normal humidity).

Judgment criteria ◎: No scattering ○: Good scattering △: A little scattering ×: Large scattering

[Brief description of the drawings]

FIG. 1 and FIG. 2 are explanatory views of the hydrophobizing treatment of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Noda 704 Matabe, Noshino, Tamashino-cho, Tamaki-cho, Mie Prefecture 19 Inside the Mie Tamaki Factory of Kyocera Corporation (56) References JP-A-46-5782 (JP, A) JP-A-48-47346 (JP, A) JP-A-55-159450 (JP, A) JP-A-59-81650 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 9/08-9/097

Claims (1)

(57) [Claims] 1. A silica powder synthesized by a wet method, wherein the surface is hydrophobized by a gas phase reaction with a dimethylsilane compound or a trimethylsilane compound, and the adsorbed amount of dibutylamine is 70 or less. A developer for an electrostatic image, comprising a body.