JPS632078A - Carrier for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain a carrier having excellent durability by coating the surface of core particles with a coating material formed by incorporating an cyclopentyl acrylate component and/or cyclopentyl methacrylate component therein and incorporating a copolymer having a specific hydroxyl value and amino resin or alkyl etherified amino resin. CONSTITUTION:The surface of the core particles is coated by the coating material contg. the cyclopentyl acrylate component and the cyclopentyl methacrylate component and contg. the copolymer having 20-150 hydroxyl value and amino resin or alkyl etherified amino resin. The copolymer constituting the coating material is satisfactory if the copolymer contains the cyclopentyl acrylate and/or cyclopentyl methacrylate even at a small ratio. The effect thereof is remarkably higher if the cyclopentyl acrylate and/or cyclopentyl methacrylate is incorporated at >=30wt% in the entire coating material (solid content). The copolymer (I) and the alkyl etherified amino resin (II) is preferably so compounded that the solid content weight ratio of (I)/(II) attains 95/5-70/30, more particularly preferably 85/15-75/-25.

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 latent images formed in electrophotography.

(Prior Art) In electrophotography, after a photoreceptor is uniformly charged, a light image based on an original image is exposed to the photoreceptor, and the charge on the light irradiated area is erased or reduced, so that the original image is transferred to the photoreceptor. A method for obtaining a copy by forming an electrostatic latent image corresponding to the image and then developing it using a so-called two-component dry developer consisting of carrier particles and toner particles is well known.

In this two-component dry developer, minute toner particles are held on the surface of relatively large carrier particles by the electric force generated by the friction of rain particles, and when they come close to the 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 collisions, resulting in so-called spent, and as a result, the triboelectric charging properties of the carrier deteriorate over time of use, making it necessary to replace the entire developer.

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

(Problems to be Solved by the Invention) For example, a carrier coated with a resin such as styrene-methacrylate copolymer has excellent wear resistance, but this resin itself is relatively hard and brittle. When carriers collide with each other, they tend to peel off, reducing the coating effect.

In addition, the carrier coated with tetrafluoroethylene polymer is
Spent is difficult to occur due to low surface energy, but
It is difficult to manufacture because it is difficult to dissolve in solvents, and it also has 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 the Problems) The present invention provides a copolymer (1) containing a cyclopentyl acrylate component and/or a cyclopentyl methacrylate component and having a hydroxyl value of 20 to 150, and an amino resin or an alkyl ether. The present invention relates to a carrier for electrostatic charge development, in which the surfaces of core particles are coated with a coating material containing an amino resin (I[).

The copolymer constituting the coating material in the present invention only needs to contain at least a small amount of cyclopentyl acrylate and/or cyclopentyl methacrylate, thereby improving flexibility and abrasion resistance. In particular, it is preferable to contain 30% by weight or more of the cyclopentyl acrylate component and/or the cyclopentyl methacrylate component in the total coating material (solid content) because the above-mentioned effects are significantly improved. In addition, if the molecular weight of the copolymer is too small, the durability tends to decrease, so it is preferable that the copolymer has a weight average molecular weight in the range of 20,000 to t, ooo, ooo, and from the viewpoint of prongability, it is 50" It is preferable to have a glass transition point (Tg) of C or more.The weight average molecular weight is measured by gel permeation chromatography using a standard polystyrene calibration curve.

The above-mentioned copolymers include cyclopentyl acrylate and/or cyclopentyl methacrylate and 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
Hydroxyalkyl acrylates such as 2-hydroxybutyl acrylate, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate, monoacrylates or monomethacrylates of polyhydric alcohols such as glycerin, trimethylolpropane, etc. It is obtained by copolymerizing a hydroxyl group-containing monoethylenically unsaturated monomer such as , N-methylol acrylamide, or N-methylol methacrylamide with other polymerizable monomers as necessary.

Other polymerizable monomers mentioned above include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-
-n-butylstyrene, pter t-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, n- methoxystyrene,
p-phenylstyrene, n-chlorostyrene, 3.4-
Styrene and its derivatives such as dichlorostyrene, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride, vinyl acetate, and propion. vinyl esters such as vinyl acid, vinyl henzoate, vinyl butyrate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-acrylate
Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate , isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate α-methylene aliphatic monocarboxylic acid esters such as acrylonitrile, methacrylonitrile, acrylamide, acrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-methacrylate Acrylic acid or methacrylic acid m4 such as hydroxypropyl, and in some cases, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. can also be used.

Also, vinyl methyl ether, vinyl ethyl ether,
Vinyl ethers such as vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropyl vinyl ketone, N-vinyl compounds such as N-vinylvirol, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone, Vinylnaphthalene salts and the like can be used alone or in combination of two or more.

In the copolymerization, a peroxide radical initiator such as benzoyl peroxide or di-tert-butyl peroxide, or an azo radical initiator such as azobisisobutyronitrile or azobisvaleronitrile is used as a polymerization catalyst. In addition, as water-soluble polymerization initiators (in the case of emulsion polymerization method), persulfates such as potassium persulfate and ammonium persulfate, perchlorates such as potassium perchlorate and sodium perchlorate, potassium chlorate, and bromate Salts of halogen acids such as potassium, hydrogen peroxide, etc. can be used.

Polymerization methods include solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization, but solution polymerization is preferred because the copolymer is dissolved in a solvent and applied to a carrier. The polymerization is carried out at a reaction temperature of about 80-130°C and a reaction time of about 2-10 hours.

In the present invention, the amino resin is an amino resin obtained by addition-condensation reaction with formaldehyde of amino compounds such as urea, melamine, benzoguanamine, acetoguanamine, etc. alone or in combination with formaldehyde. The resin refers to the amine resin in methanol,
It is obtained by etherification with alcohols such as ethanol, propatool, n-butanol, and isobutanol.

In the present invention, the copolymer (1) and the amino resin or alkyl etherified amino resin (II) are (1) / (
II) is preferably blended in a solid content weight ratio of 9515 to 70/30, particularly 85/15 to 75
Preferably, it is used so that it becomes 25. (II) If there is too much of the component, the resin film on the carrier surface will become brittle.
It will peel off easily.

On the other hand, if the amount is too small, sufficient hardness cannot be obtained and spent tends to occur.

In addition to the above-mentioned cyclopentyl acrylate and/or cyclopentyl methacrylate and hydroxyl group-containing copolymer and amino resin, the coating material in the present invention includes other resins, such as styrene-acrylic ester copolymer,
It may contain styrene-methacrylic acid ester copolymer, silicone resin, fluorine-containing resin, etc., but the content of cyclopentyl acrylate component and/or cyclopentyl methacrylate component is 30% by weight of the total coating material (solid content). %
It is preferable to set it to the above value.

The carrier core material in the present invention includes iron, di-butyl, cobalt, ferrite, etc. with an average particle size of 30 μm to 300 μm.
Magnetic materials are preferably used.

If the average particle size is 30 μm or less, carriers will not only adhere to the surface of the photoreceptor, but also cause TM damage to the photoreceptor.
Image quality deteriorates significantly. In addition, the average particle size is 300
If it is .mu.m or more, the amount of toner that can be carried on the carrier surface decreases, and the quality of images tends to fluctuate during continuous copying.

A method for forming a resin coating on a magnetic material is to immerse the magnetic material in a solution in which a resin is dissolved in an organic solvent such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, butyl acetate, methyl cellosolve, chloroform, or tetrahydrofuran. However, there are methods in which the surface is coated with a resin solution and then dried, and methods in which the solution is sprayed onto the magnetic material in a fluidized bed and further dried. The temperature during drying is preferably 140 to 200°C.

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

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

Toners used with the carrier according to the present invention include conventionally known toners, such as toners made of thermoplastic resins such as styrene-acrylic ester copolymers, styrene-methacrylic ester copolymers, polyester resins, and epoxy resins. , carbon black, dyes, pigments such as magnetite, charge control agents such as nigrosine, azo dyes, salicylic acid derivatives and their metal salts, and fixing property improvers such as polypropylene, polyethylene, carnauba wax, etc., and heat roll mill. It can be obtained by thoroughly melting and kneading in a kneader such as , Konida, etc., followed by cooling, pulverizing, and classifying. Further, the toner material is added at the time of 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% of the area. If it is less than 20%, the image density will be low and 9.
If it exceeds 0%, 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, 140 parts of cyclopentyl acrylate, 28 parts of butyl methacrylate, and 2 parts of methacrylic acid were added. - A monomer mixture of 30 parts of hydroxyethyl, 2 parts of methacrylic acid and 3 parts of abbisisobutyronitrile was added dropwise over 2 hours, and then reacted at the same temperature for an additional 4 hours,
A copolymer resin solution was obtained. The weight average molecular weight of the copolymer resin was about 45,000, and the 'rg was 73°C.

75 parts (solid content) of the obtained copolymer resin (1) and 25 parts of isobutyl etherified melamine resin (Furan 28, trade name of Hitachi Chemical Co., Ltd.) were mixed, and a solvent was added so that the solid content was 10% by weight. It was diluted with toluene to prepare a carrier coating solution.

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

To 95 parts of this carrier, mix 5 parts of positively chargeable toner (toner for SF-755, Sharp (+1 product)) to make a developer, and make a developer for a copying machine (SF-755 modified machine, Sharp interlayer). When 10,000 copies were made using this method, good copies were obtained with no image change and no fogging.

Comparative Example 1 Styrene/butyl methacrylate copolymer resin (Il) [Styrene/butyl methacrylate ratio 70/30 (weight ratio),
weight average molecular weight of approximately 120,000] was diluted with a solvent toluene to a solid content of 10% to prepare a carrier coating solution. A coated carrier was obtained in the same manner as in Example 1 using this solution.

The obtained carrier was tested under the same conditions as in Example 1. After copying 10,000 copies, there was considerable fog in the images.

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 images were distorted. Occurred.

(Effects of the Invention) The carrier according to the present invention has excellent durability as shown in the examples.

, J.

Claims (1)

[Scope of Claims] 1. Contains a cyclopentyl acrylate component and a cyclopentyl methacrylate component, and has a hydroxyl value of 20 to 150
A carrier for electrostatic charge development, in which the surfaces of core particles are coated with a coating material containing a copolymer and an amino resin or an alkyl etherified amino resin. 2. The carrier according to claim 1, wherein the coating material contains 30% by weight or more of a cyclopentyl acrylate component and a cyclopentyl methacrylate component.