JPH01108557A - Carrier for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To improve durability by coating the surface of core particles with a coating material contg. a polymer which consists essentially of a specific imide group-contg. unsatd. monomer and hydroxyl group-contg. unsatd. monomer as well as an amino resin and/or alkyl etherified amino resin. CONSTITUTION:The surface of the core particle is coated with the coating material contg. the polymer which consists essentially of the specific imide group-contg. unsatd. monomer expressed by the formula I and hydroxyl group- contg. unsatd. monomer as well as the amino resin and/or alkyl etherified amino resin. In the formula I, R1 denotes hydrogen or methyl group; R2 denotes an alkylene group of 1-6C or bivalent org. group having alicycle or arom. ring; R3 denotes the formulas II, III, etc.; Y1-Y8 denote hydrogen, alkyl group of 1-3C. The excellent durability is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carrier for a two-component dry developer useful for developing electrostatic images formed in electrophotography.

(Prior Art) In electrophotography, after a photoreceptor is uniformly charged, the photoreceptor is exposed to a light image based on an original image.

An electrostatic latent image corresponding to the original image is formed on the photoreceptor by eliminating or reducing the charge on the light-irradiated area, which is then composed of carrier particles and toner particles. The method of obtaining a copy by visualizing it using a so-called two-component dry developer is well known. In this two-component dry developer, minute toner particles are held on the surface of relatively large carrier particles by electric force generated by friction between nine particles, and when they come close to an electrostatic latent image, the electrostatic latent image is The attraction force on the toner particles in the direction of the latent image due to the electric field that is formed overcomes the bonding force between the toner particles and carrier particles, and the toner particles are attracted and adhered onto the electrostatic latent image, making the electrostatic latent image visible. It is something. The developer is used repeatedly while replenishing the toner consumed by development.

Therefore, the carrier must always impart the desired polarity and sufficient charge to the toner particles during long-term use. However, conventional carriers cause friction with toner particles,
A toner film is formed on the surface of the carrier due to collisions or the heat generated by these, resulting in so-called spent, and as a result, the triboelectric charging properties of the carrier deteriorate over time, making it necessary to replace the entire developer. arise.

In order to prevent such spent, methods of coating the surface of the carrier with various resins have been proposed, and although this has greatly improved the durability of the developer, no satisfactory product has yet been obtained.

(Problems that the EA is trying to solve) For example, carriers coated with a resin such as styrene-methacrylic acid ester copolymer have excellent wear resistance, but this resin itself is relatively hard and brittle. , easy to peel off when carriers collide with each other.

Covering effectiveness is reduced.

In addition, the carrier coated with tetrafluoroethylene polymer is 9
Spent is difficult to occur due to low surface energy, but
It is difficult to manufacture because it is difficult to dissolve in solvents, b, ! Ta.

There are drawbacks such as difficulty in adjusting triboelectric charging ability by mixing with other resins.

In addition, it has been proposed to reduce spent by coating silicone resin, another low surface energy resin, but since the mechanical strength of the silicone resin itself is weak, the silicone resin on the carrier surface may be coated during agitation in the developing machine. wears out, and frictional charging with toner particles becomes unstable, deteriorating the quality of copied images.

The present invention solves these problems and provides a highly durable carrier.

(Means for Solving Problems) The present invention is based on the general formula (1) [wherein R1 is hydrogen or a methyl group eR2 is an alkylene group having 1 to 6 carbon atoms or a divalent group having an alicyclic ring or an aromatic ring] represents an organic group, R13 represents =6~ + Yt + Yz + Ys + Y4 t
Ys e Ya t Yy and Y8 are each independently,
Hydrogen, an alkyl group having 1 to 3 carbon atoms.

Indicates SOsH or -N3 s Zt t Zz t
Zs + Z4 and Z5 each independently represent hydrogen or an alkylene group having 1 to 5 carbon atoms, and Ys is -C-, -C
H-, -C-.

Hs CH3 ■ -CH2-CH2-, -CH2-CH- or -〇H=C
Indicates H-. ] A polymer containing an imide group-containing unsaturated monomer and a hydroxyl group-containing unsaturated monomer as essential components, and a coating material containing an amino resin and/or an alkyl etherified amino resin. The present invention relates to a carrier for developing an electrostatic image, the surface of which is coated.

First, the monomer represented by general formula (I) will be described. The imide group-containing unsaturated monomer represented by the general formula CI) is produced by a known method.

Specific examples of the imide group-containing unsaturated monomer represented by general formula (1) are as follows.

C) (3 Hs 〇〇0 CH3〇H2 The polymer constituting the coating material of the carrier for developing an electrostatic image according to the present invention is one of the imide group-containing polymerizable unsaturated monomers represented by the general formula (1). It contains at least one type of monomer as a component, which improves wear resistance.In particular, when the monomer represented by the general formula (11) is contained in the polymer in an amount of 20 to 70% by weight as a component, the above-mentioned effects can be obtained. This is preferable because it improves significantly.

Examples of hydroxyl group-containing unsaturated monomers include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate. hydroxyalkyl methacrylates such as glycerin, monoacrylates or monomethacrylates of polyhydric alcohols such as trimethylolpropane, N-methylol acrylamide.

Examples include N-methylol methacrylamide.

These hydroxyl group-containing polymerizable unsaturated monomers are preferably contained in the 9-polymer in an amount of 5 to 35% by weight from the viewpoint of good carrier properties. is preferred.

House styrene, 0
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n -Octylstyrene.

p-n-nonylstyrene tP-n-f silstyrene, p
-n-dodecylstyrene, n-methoxystyrene, p-
Styrene and its derivatives such as phenylstyrene, n-chlorostyrene, 3,4-dichlorostyrene, ethylene,
Propylene, butylene.

Ethylenically unsaturated monoolefins such as inbutylene, vinyl chloride, vinylidene chloride, vinyl bromide.

Vinyl halides such as vinyl fluoride, vinyl acetate.

Vinyl esters such as vinyl propionate, vinyl penzoate, vinyl butyrate, and methyl acrylate.

Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate.

2-chloroethyl acrylate, phenyl acrylate, α
- Methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate
-octyl, dodecyl methacrylate, methacrylic acid 2-
Ethylhexyl.

Stearyl methacrylate, phenyl methacrylate.

α-methylene aliphatic monocarboxylic acid esters such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, and diethylaminoethyl methacrylate.

Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acrylic acid, methacrylic acid, maleic acid,
Fumaric acid, etc., vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropyl vinyl lactone, N-
N-vinyl compounds such as vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone, monofunctional monomers such as vinylnaphthalene salts, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and their derivatives. .

Polyfunctionality such as diethylene carboxylic acid esters such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate, and trimethylolpropane triacrylate, and divinyl compounds such as N,N-divinylaniline, divinyl ether, and divinyl sulfite. Examples include monomers.

Here, when a polyfunctional monomer is used in combination, it is preferable to use it in a small amount as much as possible, and it is particularly preferable that it is contained in the polymer in an amount of 0 to 5% by weight as a constituent component.

9 As a polymerization catalyst during polymerization, benzoyl peroxide, di-t
Peroxide-based radical initiators such as ert-butyl peroxide, azobisisobutyronitrile.

An azo radical initiator such as azobisvaleronitrile is used. In the case of emulsion polymerization, water-soluble polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate, and potassium perchlorate.

Perchloric acid) Perdate salts such as IJum, and salts of rogenic acid such as potassium chlorate and potassium bromate.

Hydrogen peroxide etc. can be used.

The polymerization catalyst is preferably used in an amount of 0.1 to 10% by weight based on the total monomers.

Polymerization methods include solution polymerization and suspension polymerization.

Bulk polymerization method, emulsion polymerization method, etc. can be performed.

Since the obtained polymer is dissolved in a solvent and applied to a carrier, a solution polymerization method is preferred. Polymerization is about 80-130
Preference is given to carrying out the reaction at a reaction temperature of .degree.

Preferably, reaction times are about 2 to 10 hours.

If the molecular weight of the obtained polymer is too small, the durability tends to decrease, so the molecular weight is 20,000 to 1,000. O
It is preferable to have a weight average molecular weight in the range of OO, and from the viewpoint of blocking properties, it is preferable to have a glass transition point (Tg) of 50° C. or higher. Note that the weight average molecular weight in the present invention is measured by gel permeation chromatography using a standard polystyrene calibration curve.

In addition, the obtained polymer preferably has a hydroxyl value adjusted to 20 to 150 from the viewpoint of good properties, particularly 20 to 150.
It is preferable to adjust it to 75.

Used in the present invention. What is amino resin?

Alkyl etherified amino resins are amine resins obtained by addition-condensation reaction with formaldehyde of amino compounds such as urea, melamine, benzoguanamine, acetoguanamine, etc. alone or in combination of two or more. methanol.

It is obtained by etherification with alcohols such as ethanol, propatool, n-butanol, and isobutanol.

In the present invention, the polymer and the amino resin and/or the alkyl etherified amino resin are preferably blended so that the solid content weight ratio of the former to the latter is 9515 to 70/30, particularly 85/15 to 70/30. Preferably, the ratio is 75/25. If the amount of amino resin and/or alkyl etherified amino resin is too large, the resin film on the surface of the carrier will become brittle and easily peel off. On the other hand, if the amount is too small, sufficient hardness cannot be obtained and spent tends to occur.

The coating material in the present invention includes a polymer containing the monomer represented by the general formula (I) as described above and a hydroxyl group-containing monomer as essential components, and an amino resin and/or an alkyl etherified amino resin. resin.

For example, styrene-acrylic acid ester copolymer.

It may contain a styrene-methacrylic acid ester copolymer, a silicone resin, a fluorine-containing resin, and the like.

In this case, it is preferable that the content of the monomer generally represented by 2m is 20% by weight or more in the total coating material (solid content).

The core particles (carrier core material) in the present invention include:

Average particle size of iron, nickel, cobalt, ferrite, etc. 30
A magnetic material with a diameter of μm to 300 μm is preferably used. If the average particle size is 30 μm or less, the carrier will adhere to the surface of the photoreceptor, not only damaging the photoreceptor but also significantly deteriorating the quality of the image. In addition, the average particle size is 300 μm
If this is the case, the amount of toner that can be carried on the surface of the carrier is small, and the quality of images tends to fluctuate during continuous copying.

As a method for forming a resin coating on core particles.

A magnetic material is immersed in a solution of a resin dissolved in an organic solvent such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, butyl acetate, methyl cellosolve, chloroform, tetrahydrofuran, etc., and its surface is coated with the resin solution.

There are methods of drying, methods of spraying the solution onto the magnetic material in a fluidized bed, and further drying. The temperature during drying is 140-20
Preferably it is 0°C.

In order to form a sufficient coating, the resin concentration of the solution is preferably 3 to 30% by weight.

The thickness of the coating layer is preferably about 0.1 to 10 μm.

The toner used with the carrier according to the present invention may be a conventional toner such as a thermoplastic resin such as a styrene-acrylic ester copolymer, a styrene-methacrylic ester copolymer, a polyester resin, or an epoxy resin. Pigments such as carbon black, dyes and magnetite, charge control agents such as nigrosine, azo dyes, salicylic acid derivatives and their metal salts, fixing property improvers such as polypropylene, polyethylene and carnauba wax, etc. are mixed thoroughly, and the mixture is heated. It can be obtained by thoroughly melting and kneading in a mixer such as a roll mill or a co-kneader, followed by cooling, pulverization, and two classifications. Additionally, the toner material was added during resin polymerization.

So-called polymerized toners can also be used. Furthermore, these toners contain fluidity improvers such as hydrophobized silica, alumina, molybdenum disulfide, and titanium oxide, zinc stearate,
Cleanability improvers such as magnesium stearate and zinc laurate may also be added.

The amount of toner used for the carrier is 2.
It is preferable that the toner covers 0 to 90 inches. 2 (If it is less than l, the image density will be lower!
If it exceeds 9 liters, it is not preferable because fog increases and toner scatters.

(Example) Next, the present invention will be specifically described in detail based on Examples.
The present invention is not limited to this.

In addition, in the following, "part" means "part by weight".

Example 1 A mixed solution of 140 parts of xylene and 60 parts of methyl isobutyl ketone was charged into a flask equipped with a stirrer and a reflux condenser, and while keeping the temperature at 100°C, 100 parts of phthalimidoethyl methacrylate, 40 parts of styrene, and 2B parts of butyl methacrylate were added. , 2-hydroxyethyl methacrylate 30
parts, 2 parts of methacrylic acid, 3 parts of azobisisobutyronitrile
A mixed solution of 100 parts of toluene and 100 parts of toluene was added dropwise over 2 hours, and the reaction was continued for another 4 hours at the same temperature to obtain a copolymer resin solution. What is the weight average molecular weight of the copolymer resin?

The glass transition temperature ('I'g) was approximately 45,000°C and 73°C.

75 parts of the obtained copolymer resin (solid content) and 25 parts of isobutyl etherified melamine resin (Melan 28°, trade name of Hitachi Chemical Co., Ltd.) were mixed.

Dilute with solvent toluene so that the solid content is 10% by weight,
This was used as a carrier coating solution.

This solution was coated on the surface of 5 kl of amorphous iron oxide having an average particle size of 70 μm using a fluidized bed type coating device, and further heated and dried at 150° C. for 1 hour to obtain a resin-coated carrier.

To 95 parts of this carrier, mix 5 parts of positively charged toner (toner for 8F-7ss, Sharp ■ product) to make a developer, and use it for a copying machine (modified 8F-755, manufactured by Sharp ■). When I made 10,000 copies using 9
No change in image.

Good copies were obtained with no fogging.

US Structural formula styrene/butyl methacrylate copolymer resin [styrene/
Butyl methacrylate ratio 70/30 (weight ratio) 9 weight average molecular weight approximately 120,000] was diluted with a solvent toluene to a solid content of 10% to prepare a carrier coating solution. Using this solution, a coated carrier was obtained in the same manner as in Example 1.

The obtained carrier was tested under the same conditions as in Example 1. After copying 10,000 copies, one image had a kana blur.

Comparative Example 2 When amorphous iron oxide with an average particle size of 70μ, which was used as a material for resin coating, was used as a carrier and tested under the same conditions as in Example 1, fogging became severe after 5000 copies were made, and 9 images were distorted. There has occurred.

(Effect of the invention) The carrier according to the present invention has excellent durability.

Claims (1)

[Claims] 1. General formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼ (I) [However, in the formula, R_1 is hydrogen or a methyl group, and R_2 is an alkylene group having 1 to 6 carbon atoms or a fatty acid group. Represents a divalent organic group having a ring or an aromatic ring, R_3 represents ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and Y_1, Y_2, Y_3, Y_4, Y_5, Y
_6, Y_7, and Y_8 each independently represent hydrogen, an alkyl group with 1 to 3 carbon atoms, halogen, ▲a mathematical formula, a chemical formula, a table, etc.▼, ▲a mathematical formula, a chemical formula, a table, etc.▼, -
NO_2, -SO_2H or -N_3, Z_1, Z_2, Z
_3, Z_4 and Z_5 each independently represent hydrogen or an alkyl group having 1 to 5 carbon atoms, and Y_9 is -CH_2-, ▲
There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -CH_-CH_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or -CH=CH-. ] The surface of the core particles is coated with a polymer containing an imide group-containing unsaturated monomer and a hydroxyl group-containing unsaturated monomer as essential components, and a coating material containing an amino resin and/or an alkyl etherified amino resin. A carrier for developing electrostatic images coated with.