JPS62180373A - Electrostatic image developer - Google Patents

Abstract

PURPOSE:To stably form an image having good image quality without fogging at a high density by incorporating a copolymer of an acrylic monomer and styrene monomer having an electron withdrawing substituent as a binder into a toner and providing a coating layer formed by curing a silicone resin onto the particle surface of a carrier. CONSTITUTION:An electrostatic image developer is constituted of the toner formed by contg. the copolymer of the acrylic monomer and styrene monomer having the electron withdrawing substituent as the binder and the carrier formed by providing the coating layer formed by curing of the silicone resin onto the surface of the carrier core material. The electron withdrawing substituent is exemplified by a fluorine atom, bromine atom, nitro group, etc. The copolymer to be used as the binder contains preferably >=10wt% high mol.wt. component having >=100,000mol.wt. The performance to prevent the generation of the so- called offset in which part of the toner constituting the image is transferred onto the surface of a fixing roller in the stage of fixing and that the transferred toner is transferred again onto transfer paper carried to the fixing roller to stain the image is obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a developer for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, etc., particularly a toner. This invention relates to a so-called two-component electrostatic image developer comprising a carrier and a carrier.

[Technology background]

In recent image forming methods, methods using electrostatic latent images are widely used. In electrophotography, for example, an electrostatic latent image is formed by imparting a uniform electrostatic charge to a photoconductive photoreceptor and then performing imagewise exposure. Such an electrostatic latent image is developed with a developer, and the resulting toner image is transferred to transfer paper or fixed as it is to form a visible image.

As a method for developing an electrostatic latent image, a two-component developer consisting of toner and a carrier containing a magnetic material is used, and the developer is made to stand on the surface of a developer carrier by magnetic force, and a magnetic brush is used. A method is widely used in which toner particles in the magnetic brush are electrostatically attached to the electrostatic latent image on the latent image carrier by rubbing the surface of the latent image carrier with this magnetic brush. .

As carriers used in such development methods, carriers made of particles of ferromagnetic materials such as iron, ferrite, and magnetite have conventionally been known, but when such carriers are used, the developer During use, toner components may transfer and adhere to the surface of the carrier, reducing the frictional electrification between the toner and the carrier, or the ferromagnetic particles described above are highly hygroscopic and may not be used in a humid environment. However, there are problems in that the triboelectricity between the toner and the carrier deteriorates early.

[Problems to be solved by the invention]

In order to eliminate these problems, a carrier has been developed in which the surfaces of the above-mentioned ferromagnetic particles are coated with a resin. This resin-coated carrier has superior stability in triboelectric charging properties and durability in repeated use compared to conventional carriers, and in particular, carriers made by coating the surface of the carrier core material with silicone resin are superior to other carriers. Its properties are superior to carriers coated with resin.

However, in such silicone resin-coated carriers, the silicone resin itself has low triboelectric charging ability;
In an electrostatic image developer composed of this carrier and a toner containing a styrene-acrylic copolymer as a binder, there is a problem in that the amount of charge of the toner is insufficient, resulting in low image density.

In response to this, a technique was developed in which the toner contains a charge control agent such as a dye (Japanese Patent Laid-Open No. 57-19165
(See Japanese Patent Application Laid-Open No. 152256/1982).

However, in this technology, when a silicone resin-coated carrier is used repeatedly over a long period of time, a phenomenon occurs in which the dye contained in the toner adheres to the surface of the carrier particles, resulting in a decrease in triboelectric charging properties. There is a point.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its object is to stably obtain triboelectric charging properties between the toner and the carrier even when the carrier is used repeatedly over a long period of time, and to achieve stable triboelectrification properties. It is an object of the present invention to provide an electrostatic image developer capable of stably forming images of high density, fog-free, and good quality over many times.

[Means for solving problems]

The electrostatic image developer of the present invention is an electrostatic image developer comprising a toner and a carrier, wherein the toner is a copolymer of an acrylic monomer and a styrene monomer having an electron-withdrawing substituent. as a binder, and the particles of the carrier have a coating layer formed by hardening a silicone resin on their surfaces.

According to this configuration, the toner contains a copolymer of an acrylic monomer and a styrene monomer having an electron-withdrawing substituent as a binder, so that the electron-withdrawing substituent is Due to its presence, the toner exhibits excellent negative triboelectric charging ability, and therefore, it is no longer necessary to include a charge control agent such as a dye in the toner. Problems such as a decrease in triboelectric charging properties due to dye transfer and adhesion to the latent image support, and a decrease in the performance of the latent image support due to transfer and adhesion of the dye to the latent image support do not occur. Since it has a coating layer made of
The surface has a high slipperiness, which prevents deterioration of triboelectric charging properties due to the adhesion of toner substances to the surface of the carrier particles (this results in excellent durability for repeated use, and as a result, a good toner with high density and no capri) is produced. It becomes possible to stably form high-quality images over a long period of time.

The present invention will be explained in detail below.

In the present invention, a toner containing as a binder a copolymer of an acrylic IHT compound and a styrene monomer having an electron-withdrawing substituent, and a silicone resin cured on the surface of a carrier core material. A carrier provided with a coating layer constitutes an electrostatic image developer.

In the above, the electron-withdrawing substituent is a substituent with a positive Hammett constant, preferably a Hammett constant of +0.2.
Above, particularly preferred is a substituent of +0.4 or more. When the Hammett constant is too small, it becomes difficult to charge the toner sufficiently negatively.

Specific examples of such electron-withdrawing substituents include fluorine atom, bromine atom, nitro group, cyano group, trifluoromethyl group, carboxyl group, and acetyl group.

As a styrenic monomer having an electron-withdrawing substituent,
For example, fluorostyrene, bromostyrene, nitrostyrene, cyanostyrene, trifluoromethylstyrene,
Examples include acetylstyrene and carboxystyrene.

Examples of acrylic monomers used together with the above-mentioned styrene monomers to constitute the toner binder include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, methacrylic acid 2 - Amount of α-methylene aliphatic monocarboxylic acid esters such as ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate 7-minoethyl methacrylate, diethylamine ethyl methacrylate, etc. Acrylic acid or methacrylic acid such as acrylonitrile, methacrylonitrile, acrylamide, etc. Acid derivative;
Others can be mentioned.

These styrenic monomers and acrylic monomers are
One type or a combination of two or more types can be used.

The binder used in the toner is a copolymer of a styrene monomer having an electron-withdrawing substituent and an acrylic monomer, and such a copolymer contains a high molecular weight component having a molecular weight of 100,000 or more. It is preferable that the content is 10% by weight or more, and in this case, a part of the toner constituting the image is transferred to the surface of the fixing roller during fixing, and this is transferred again to the transfer paper etc. that is sent next. This provides performance that prevents the occurrence of the so-called offset phenomenon that contaminates images. A copolymer containing such a high molecular weight component can be easily obtained by appropriately selecting polymerization conditions or by using a suitable crosslinking agent to form a crosslinked polymer.

The toner constituting the electrostatic image developer of the present invention contains a colorant and other additives as necessary.

Examples of colorants to be included in the toner include carbon black, nigrosine dye (C01, P&L50415B
), aniline blue (C, 1, Na50405), calco oil blue (C, 1, max axoic Blue
3), chrome yellow (C, L 14090), ultramarine blue (C, 1, N1177103), DuPont oil red (c, 1.Na26105), quinoline yellow (C11, Na47005), methylene blue chloride (C, [, 11k152015), Phthalocyanine Blue (C,1, 74160), Malachite Green Offsalate (C,1,N142000),
Lamp black (C, 1, Na 7?266), rose bengal (C, 1, Na 45435), mixtures thereof, and others may be mentioned. These colorants need to be contained in a sufficient proportion to form a visible image with sufficient density, and are usually contained in an amount of 1 to 20 parts by weight per 100111 parts of toner.

Other additives include anti-offset agents, fluidity improvers, etc. As anti-offset agents,
For example, polyolefin wax, carnauba wax, alkylene bis fatty acid amide compound, etc. can be used, and examples of the fluidity improver include fine silica powder.

In the present invention, the carrier constituting the electrostatic image developer together with the toner has a coating layer formed by hardening a silicone resin on its surface.

Such silicone resins include, but are not particularly limited to,
For example, condensation reaction type silicone resins that are cured by the reactions shown in (1) and (2) below can be particularly preferably used.

■ Heating dehydration condensation reaction R+ Rt 0-5t OH+ HO-5i-0- ■ Room temperature moisture curing reaction R, Rt -O-5i-OX + Xo-Smi〇=In the formula, O
X represents an alkoxy group, a ketoxime group, an acetoxy group, an aminoxy group, or the like.

Particularly preferred among such condensation reaction type silicone resins are those in which the substituent is a methyl group. A coating layer obtained from a condensation reaction type silicone resin in which the substituent is a methyl group has a dense structure, has good aqueous properties, and can be used as a carrier with good moisture resistance.

As the silicone resin used for the rIIIWM of the carrier, either a heat-curing silicone resin or a room-temperature-curing silicone resin can be used. When using a room-temperature-curing silicone resin, it is necessary to heat it to a particularly high temperature in order to cure it. The carrier can be manufactured easily since it is not necessary to do so.

Room temperature curable silicone resin is a silicone resin that cures at a temperature of about 20 to 25 degrees Celsius or slightly higher than this in a normal atmosphere.
It does not require temperatures exceeding ℃.

As the silicone resin used to form the coating layer of the carrier, the above-mentioned silicone resins may be used alone or in combination, or the above-mentioned condensation reaction type silicone resin mixed with other resins may be used. Good too. Examples of such other resins include acrylic resin,
Examples include styrene resin, epoxy resin, urethane resin, polyamide resin, polyester resin, acetal resin, polycarbonate resin, phenol resin, vinyl chloride resin, vinyl acetate resin, cellulose resin, polyolefin resin, copolymer resins of these resins, blended resins, etc. be able to.

As the carrier core material, materials conventionally used as carrier core materials such as glass beads and metal particles can be used, but in order to enable development by the magnetic brush method, which is advantageous as a development method, magnetic particles are used. Preferably, such magnetic materials include metals or alloys exhibiting ferromagnetism such as iron, cobalt, and nickel, including ferrite and magnetite, or compounds containing these elements, or compounds containing ferromagnetic elements. Alloys that exhibit ferromagnetism through appropriate heat treatment, such as alloys called Heusler alloys containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide. , and others can be used. As a carrier core material, the weight average particle size is usually 1
"1000.gm is used, especially 5-5
00n is preferred.

In manufacturing the carrier, a solution of the silicone resin as described above is dissolved in a solvent, for example, by a dipping method, a spray method,
It is applied to the surface of carrier core material particles by a method such as a fluidized bed method, and then usually heated and dried to volatilize and remove the solvent, and the applied layer is cured during or after drying to form a coating layer. .

Other additives may be added to the coating solution for forming the coating layer as necessary, and the solvent is not particularly limited as long as it dissolves the silicone resin, but for example, aromatic solvents such as toluene and cylene can be used. Wli group hydrocarbons; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran, dioxane, higher alcohols, or mixed solvents thereof can be used.

When using heat-curable silicone resin, 200~
It is necessary to heat at 250°C, and when using a room temperature curing silicone resin, it is not necessary to heat it to a particularly high temperature for curing, but it is necessary to heat it at a temperature of 150 to 250°C to accelerate curing. You can also heat it inside. In addition, during drying, metal soaps such as lead, iron, cobalt, tin, manganese, and zinc such as octylic acid and naphthenic acid may be used as drying accelerators, and organic amines such as ethanolamine may also be used as drying accelerators. It can be used effectively.

The thickness of the coating layer thus obtained is usually 0.1 to 20
(preferably μ-o).

Further, the average particle size of the carrier is, for example, 1 to 1000 aa.

Preferably it is about 5 to 200 μm.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1 (Binder) l) Binder A Copolymer of m-nitrostyrene and n-butyl acrylate (weight ratio = 75:25) (Electron-withdrawing substituent: nitro group (Hammett constant: 0.7
1), Weight average molecular weight Mw: 110,000,
High molecular weight component with a molecular weight of too, ooo or more = 25% by weight) 2) Binder B Copolymer of m-trifluoromethylstyrene, methyl methacrylate and n-butyl acrylate (weight ratio = 507
20: 30) (Electron-withdrawing substituent; trifluoromethyl group (Hammett constant F 0.43), weight average molecular IMw: 120
,000, high molecular weight component with a molecular weight of 100,000 or more: 22 m star%) 3) Binder C Copolymer of p-bromustyrene and acrylic fJ1 n-butyl (weight ratio = 75:25) (Electron-withdrawing substituent: Bromine atom (Hammett constant: 0.2
32), weight average molecule fftMw: 110,000
, high molecular weight component with a molecular weight of 100.000 or more = 20
4) Comparative Binder D Copolymer of styrene and n-butyl acrylate (weight ratio -
75: 25) (electron-withdrawing substituent: none, weight average molecule 11Mw: 1
20.000, high molecular weight component with a molecular weight of 100.000 or more: 23% by weight) (Manufacture of toner) 0 Binder-A 100 parts by weight 0 Carbon black 10 parts by weight "Mogul LJ (manufactured by Cabo Soto) 0 Wax
3 parts by weight “Viscol 660PJ
(Manufactured by Sanyo Chemical Industries, Ltd.) The above substance was melted and kneaded using two rolls, then ground and classified to produce a toner having an average particle size of It)an.

This toner is referred to as "toner l".

(Manufacture of carrier) Condensation reaction type silicone resin solution r SR-2411J
(manufactured by Toray Silicone Co., Ltd.) using a fluidization head device at a temperature of 80°C with an average particle size of 1.
00 μm spherical ferrite particles (manufactured by Nippon Tetsuko Co., Ltd.)
0 parts by weight was coated and further heat treated at 200° C. for 1 hour to obtain a carrier having a coating layer made of silicone resin. The thickness of the coating layer was approximately 1 trm. This carrier will be referred to as "Gearial I".

(Actual photo test) 3.5 parts by weight of the above toner 1 and 96 parts by weight of the above carrier 1
．． 5 parts by weight to prepare a developer, and using this developer, an electrophotographic copying machine r U-Bix 2500J (
When duplicated images were repeatedly formed using a modified machine (manufactured by Konishiroku Photo Industry Co., Ltd.), the number of duplicated images formed was 60,000.
Even after repeated printing, a copy image of good quality with high image density and no capri was obtained.

Further, when the charge amount of the toner I was measured by a blow-off method, it was -21.0 (〆/g), indicating sufficient negative chargeability.

Comparative Example 1 A toner was produced in the same manner as in Example 1, except that 100 parts by weight of Comparative Binder D was used instead of the binder. This is referred to as "comparison toner l".

A developer was prepared using Comparative Toner 1 and Carrier I in the same manner as in Example 1, and when a similar actual copying test was conducted using this developer, the number of times copying images were formed was 2,000.
After the number of times exceeded 0, the image density decreased and fogging occurred significantly.

In addition, for comparison, the amount of charge of Nar I was measured in the same manner as in Example 1, and it was -10.3 (t!c/g), which showed low negative chargeability.

Example 2 A toner was manufactured in the same manner as in Example 1 except that 100 parts by weight of binder B was used instead of binder A. This is referred to as "toner i".

A developer was prepared using this toner 2 and carrier L in the same manner as in Example 1, and when a similar actual copying test was conducted using this developer, the number of times a copy image was formed was 50.
Even after more than 1,000 repetitions, a copy image of good quality and high image density and no fogging was obtained.

Further, when the charge amount of Toner 2 was measured in the same manner as in Example 1, it was -17.6 (〆/g), indicating sufficient negative chargeability.

Example 3 A toner was manufactured in the same manner as in Example 1 except that 100 parts by weight of binder C was used instead of binder A. This will be referred to as "toner 3."

A developer was prepared using this toner 3 and carrier 1 in the same manner as in Example 1, and when a similar actual copying test was conducted using this developer, the number of times of formation of a copy image was so
, ooo times, the image density was still high and a good quality copy image without fogging was obtained.

Further, when the charge amount of Toner 3 was measured in the same manner as in Example 1, it was -18.4 (〆/g), indicating sufficient negative chargeability.

〔Effect of the invention〕

As explained in detail above, the electrostatic image developer of the present invention is
Since the toner contains a copolymer of an acrylic monomer and a styrene monomer having an electron-withdrawing substituent as a binder, the toner has excellent negative properties due to the presence of the electron-withdrawing substituent. It shows the triboelectric charging ability of
Therefore, it is no longer necessary to include a charge control agent such as a dye in the toner, and problems caused by the dye, such as deterioration of triboelectric charging properties due to transfer and adhesion of the dye to the surface of the carrier particles, occur. On the other hand, the carrier has a coating 31 on the surface of which silicone resin is hardened! Because it has a layer, the surface has high slipperiness and triboelectric charging properties are less likely to deteriorate due to adhesion of toner substances to the carrier particle surface, resulting in excellent durability during repeated use.As a result, high density This makes it possible to stably form images of good quality without fog over a long period of time.

Claims (1)

[Scope of Claims] 1) An electrostatic image developer comprising a toner and a carrier, wherein the toner comprises a copolymer of an acrylic monomer and a styrene monomer having an electron-withdrawing substituent as a binder. An electrostatic image developer, characterized in that the particles of the carrier have a coating layer formed by hardening a silicone resin on the surface thereof. 2) Claim 1, wherein the electron-withdrawing substituent in the styrene monomer is at least one of a fluorine atom, a bromine atom, a nitro group, a cyano group, a trifluoromethyl group, a carboxyl group, and an acetyl group. electrostatic image developer.