JP2630761B2 - Carrier for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for developing an electrostatic image, that is, a carrier constituting an electrostatic image developer together with toner.

[0002]

2. Description of the Related Art In electrophotography, an electrostatic charge image is formed by image exposure after a uniform surface charge is applied to a photoreceptor comprising a photoconductive element in a dark place, and the electrostatic charge image is formed by a developer. By developing, a visible image is formed.

The method of developing such an electrostatic image can be roughly classified into a liquid developing method and a dry developing method. The liquid developing method is a method in which development is performed using a liquid developer in which various pigments and dyes are dispersed as fine particles in an insulating organic liquid, and the dry developing method is a method in which carbon black is contained in a natural or synthetic resin. This is a method using fine powdered electrophoretic powder, usually called toner, which contains a coloring agent such as a dispersion. In the latter method, the toner is charged to a polarity opposite to the polarity of the charge of the electrostatic image, and the charged toner is electrostatically attached to the electrostatic image to form a visible image. In this dry development method, a method using a so-called one-component developer containing only the toner as a main component and a so-called two-component developer in which a carrier made of iron powder or glass beads is mixed with the toner are used. The former includes a bristle brush method, an impression method, and a powder cloud method, and the latter includes a magnetic brush method and a cascade method.

[0004] The visible image formed by the toner adhering to the electrostatic image by the above-described developing method is directly transferred onto a photoreceptor or onto a paper or other image support, and then heated. , Pressure, solvent vapor and the like.

The present invention relates to a carrier for a two-component developer used in a magnetic brush method or a cascade method among the above-mentioned developing methods, that is, a carrier which is mixed with a toner and used for developing an electrostatic image. Things.

The carrier for developing an electrostatic image can be roughly classified into a conductive carrier and an insulating carrier. Oxidized or unoxidized iron powder is usually used as the conductive carrier. However, the developer containing the iron powder carrier has unstable triboelectric charging characteristics with respect to the toner. There is a drawback that fogging occurs in the visible image formed by the method. That is, the toner particles adhere to the surface of the iron powder carrier particles due to friction with the toner and become contaminated, so that the electric resistance of the carrier particles increases, the bias current decreases, and the frictional charging characteristics become more unstable. ,
The image density of the visible image decreases, and fog increases. Therefore, when copying is continuously performed by an electronic copying machine using a developer containing an iron powder carrier, the developer deteriorates in a small number of copies, and it is necessary to replace the developer at an early stage, resulting in a high cost. Become.

On the other hand, as an insulating carrier, a carrier in which the surface of core particles made of a magnetic material is generally covered with a coating layer of an insulating resin is typical. In the developer containing the insulating carrier as a component, the toner particles adhere to the surface of the carrier particles very little to be contaminated, and it is possible to control the frictional charging characteristics of the carrier and the toner, and to improve the durability. This is advantageous in that it is particularly suitable for high-speed electronic copiers in that it has excellent service life and a long service life.

As the insulating resin for forming the coating layer on the core particles, a styrene-based polymer, an acrylic polymer or a styrene-acrylic copolymer as shown in JP-A-47-13954 has an adhesive force to the core particles. Is large and preferred.

[0009]

However, the insulating carrier coated with the above-mentioned polymer or copolymer is mixed and stirred with the toner to give a charge to the toner,
That is, there is a disadvantage that the so-called charging rise speed is slow. When the speed of the rise of the charge is slow, the amount of the toner that is not charged or the toner that does not have a sufficient charge increases in the developer, and the toner separates from the carrier with copying, causing so-called toner scattering. The toner scattering contaminates the inside of the apparatus, and in a severe case, is discharged outside the apparatus, and contaminates the surrounding environment.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a carrier for developing an electrostatic image, which has a long service life and a fast charging speed.

[0011]

The object of the present invention is to provide a magnetic material comprising a styrene-based polymer, an acrylic polymer and a styrene-based polymer.
This can be achieved by using a carrier for developing an electrostatic image containing a fatty acid metal salt on the carrier surface coated with at least one selected from acrylic copolymers.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The carrier according to the present invention is, for example,
A solution in which at least one selected from a styrene-based polymer, an acrylic-based polymer, and a styrene-acryl-based copolymer is dissolved in an appropriate solvent is applied to the surface of the magnetic material,
Thereafter, the fatty acid metal salt can be added to the carrier produced by evaporating the solvent at a desired temperature, and the carrier can be produced by a method such as mixing and stirring with appropriate strength. Further, the carrier according to the present invention is a solution in which at least one selected from a styrene-based polymer, an acrylic-based polymer and a styrene-acryl-based copolymer is dissolved in an appropriate solvent, and further, a fatty acid metal salt is micro-dispersed. It can also be produced by applying the composition on the surface of the composition and then evaporating the solvent.

In the present invention, any styrene polymer, acrylic polymer or styrene-acryl copolymer can be used, but the weight average molecular weight is 500
Those having 0 to 500,000 are preferred. Average molecular weight of 5
If it is less than 000, the strength of the resin is poor and the coating is easily broken, and if it exceeds 500,000, the solubility in a solvent is poor and it is difficult to form a coating. Typical styrene compounds serving as constituent units of a styrene polymer or a styrene-acrylic copolymer include styrene, α
-Methylstyrene, vinyltoluene, 4-bromostyrene, 4-chloro-5-fluorostyrene, 2-chlorostyrene, 2,5-dichlorostyrene, 2,5-difluorostyrene, 2,4-dimethylstyrene, Examples thereof include 4-ethoxystyrene, 4-ethylstyrene, 4-hexyldecylstyrene, 3-oxymethylstyrene, 4-iodostyrene, 4-isoventoxystyrene, 4-nonadecylstyrene, and mixtures thereof.

Representative substituted and unsubstituted acrylate and methacrylate compounds which are constituent units of the acrylic polymer or the styrene-acrylic copolymer include methyl acrylate, ethyl acrylate, and the like.
Tert-butyl acrylate, neopentyl acrylate, α-methyl acrylate, isobutyl acrylate, cyclohexyl acrylate, dodecyl acrylate,
Hexyldecyl acrylate, isopropyl acrylate,
Tetradecyl acrylate, ethylene glycol dimethacrylate, sec-butyl acrylate, 2-n-ter
t-butylaminoethyl methacrylate, 2-butyl methacrylate, glycidyl methacrylate, methacrylic acid 2
-Chloroethyl, 3,3-dimethylbutyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid 2
-Methoxyethyl, pentyl methacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, propyl methacrylate, 2-ethylhexyl acrylate, and mixtures thereof.

Of the above compounds, styrene-acrylic copolymers have good coating properties, and copolymers composed of styrene and methyl methacrylate are more preferred because they have very good coating properties. As the fatty acid constituting the fatty acid metal salt used in the present invention, for example, caprylic acid,
There are pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, arachinic acid, behenic acid, lignoceric acid, serotinic acid and mixtures thereof. Salts include, but are not limited to, metal salts such as lithium, sodium, potassium, copper, silver, magnesium, calcium, zinc, strontium, cadmium, barium, aluminum, tin, lead, iron, nickel, and the like. Among these, a metal salt of stearic acid is particularly effective and effective for improving the rate of rise in charging.

In the present invention, the amount of the fatty acid metal salt contained on the carrier surface is preferably in the range of 0.001% by weight to 0.04% by weight based on the entire carrier. When the content of the fatty acid metal salt is less than 0.001% by weight, the effect of increasing the charging rise speed is insufficient, and when it exceeds 0.04% by weight, the charging sequence of the carrier is gradually changed, and the On the other hand, it is difficult to provide a desired charging property.

The amount of the fatty acid metal salt on the carrier surface can be determined as follows. As an example, a method for determining zinc stearate on the carrier surface will be described.

1. About 5 g of carrier in a 100 cc beaker
And stir it.

2. An appropriate amount of acetone is added, and a magnet is arranged at the bottom of the beaker so that the carrier is fixed to the bottom of the beaker so that the carrier does not flow out, and only the carrier coating layer is eluted.

The operation of 3.2 is repeated to completely remove the coating layer.

4. Dry the carrier core remaining in the beaker on a hot plate.

5. Weigh the carrier core.

6. The coverage is determined from the following equation.

[0024] 7. Put about 100g of carrier in a 1 liter beaker
The coating layer is eluted in the same manner as described above.

8. The solvent is removed from the eluted solution using an evaporator, and the solution is further dried under reduced pressure.

9. The remaining resin is pelletized, and the amount of zinc stearate in the resin is quantified by X-ray fluorescence analysis.

10. The amount of zinc stearate (wt%) in the carrier is determined from the following equation.

[0028] Other fatty acid metal salts can be quantified in the same manner as described above.

The magnetic material used in the present invention includes, for example, iron, nickel, ferrite, cobalt and the like.
The particle size of the magnetic material is 30 to 10 after coating with the resin.
00 microns, preferably 40-200 microns. If the particle diameter is less than 30 microns, the carrier has a small magnetization, so that the carrier easily scatters from the sleeve and adheres to the photoreceptor, and if it exceeds 1000 microns, the image quality is poor.

Any toner can be used as the toner constituting the developer in combination with the carrier of the present invention. In particular, those having fine particles of hydrophobic silica, alumina, titania or the like on the surface are further charged. This is preferable because the rising speed is fast and a clear image can be obtained.

[0031]

The effects of the present invention will be clarified with reference to the following examples, but the present invention is not limited to these embodiments.

(Production Example 1) The monomer composition ratio of styrene and methyl methacrylate was 40:60 and the weight average molecular weight was 1
A coating liquid was prepared by dissolving 15 g of a 20000 styrene-methyl methacrylate copolymer in 300 ml of methyl ethyl ketone.
150 (manufactured by Nippon Tekko Co., Ltd.) was coated using a spira coater (manufactured by Okada Seiko Co., Ltd.) to produce a carrier having a coating layer having an average film thickness of 1.0 μm. This is referred to as “carrier A”.

(Production Example 2) 1 kg of carrier A and zinc stearate "Zinc stearate S" (manufactured by NOF Corporation)
50 mg was placed in a V-type mixer "micro-type see-through mixer" (manufactured by Tsutsui Chemical Co., Ltd.) and mixed at a rotation speed of 70 rpm for 20 minutes to produce a carrier having zinc stearate on the surface. This is called “carrier B”.

(Production Example 3) A carrier was produced in the same manner as in Production Example 2 except that zinc stearate was used in an amount of 5 mg. This is called “carrier C”.

(Production Example 4) 10 mg of zinc stearate
A carrier was produced in the same manner as in Production Example 2 except for the above.
This is called “carrier D”.

(Production Example 5) 500 m of zinc stearate
A carrier was produced in the same manner as in Production Example 2 except that the amount was changed to g. This is called “carrier E”.

(Production Example 6) A carrier was produced in the same manner as in Production Example 2 except that zinc stearate was changed to aluminum stearate (manufactured by Tokyo Chemical Industry Co., Ltd.). This is referred to as “carrier F”.

(Production Example 7) A carrier was produced in the same manner as in Production Example 2, except that zinc stearate was changed to sodium stearate (manufactured by Tokyo Chemical Industry Co., Ltd.). This is referred to as “carrier G”.

(Production Example 8) A carrier having a coating layer having an average film thickness of 1.1 μm was produced in the same manner as in Production Example 1, except that the styrene-methyl methacrylate copolymer was a styrene polymer having a weight average molecular weight of 130,000. This is referred to as “carrier H”.

(Production Example 9) A carrier was produced in the same manner as in Production Example 2 except that the carrier A was changed to the carrier H. This is called “carrier I”.

(Production Example 10) A carrier having a coating layer having an average film thickness of 1.0 μm was produced in the same manner as in Production Example 1, except that the styrene-methyl methacrylate copolymer was changed to a methyl methacrylate polymer having a weight average molecular weight of 120,000. This is called “carrier J”.

(Production Example 11) A carrier was produced in the same manner as in Production Example 2 except that the carrier A was changed to the carrier J.
This is referred to as “carrier K”.

(Production Example 12) Spherical ferrite F-15
A carrier having a coating layer having an average film thickness of 1.1 μm was produced in the same manner as in Production Example 1 except that spherical iron powder DSP-138 (manufactured by Dowa Iron Powder Co., Ltd.) was substituted for 0. This is called “carrier L”.

(Production Example 13) A carrier was produced in the same manner as in Production Example 2, except that the carrier A was changed to the carrier L.
This is called “carrier M”.

(Production of Toner) A composition ratio of styrene, methyl methacrylate and butyl acrylate is 70: 1.
5:15, a resin having a weight average molecular weight of 120,000 and a number average molecular weight of 6,600, 100 parts by weight, 10 parts by weight of carbon black Mogal L (manufactured by Cabot), and 3 parts by weight of polypropylene wax 660P (manufactured by Sanyo Chemical) After mixing, kneading and pulverizing and classifying, a toner having an average particle size of 10 μm was obtained. 100 parts by weight of this toner and hydrophobic silica R-97
2 (manufactured by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer.

This toner is referred to as “toner A”.

299 g of terephthalic acid, 211 g of polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, and pentaerythritol 82
g was placed in a round bottom flask equipped with a thermometer, a stainless steel stirrer, a glass nitrogen gas inlet tube and a falling condenser, the flask was set on a mantle heater, and nitrogen gas was passed through the nitrogen gas inlet tube. After the introduction, the temperature was raised while keeping the inside of the flask in an inert atmosphere. Then, 0.05 g of dibutyltin oxide was added and reacted at a temperature of 200 ° C. while following the reaction at the softening point, thereby producing a polyester resin having a chloroform-insoluble content of 17% by weight. This is designated as "polyester resin A". Ring and ball softening point of this polyester resin A (JISK1351)
-1960. ) Was 131 ° C.

100 parts by weight of the polyester resin A,
Carbon black “Mogal L” (Cabot) 1
0 parts by weight and low molecular weight polypropylene "Viscol 66"
3P of "0P" (manufactured by Sanyo Chemical Co., Ltd.) was melt-kneaded and pulverized and classified to obtain a toner having an average particle diameter of 10 µm.

100 parts by weight of this toner and hydrophobic silica R
-972 0.8 parts by weight were mixed with a Henschel mixer. This toner is referred to as “toner B”.

100 parts by weight of a resin having a composition ratio of styrene, methyl methacrylate and butyl acrylate of 70:15:15, a weight average molecular weight of 120,000 and a number average molecular weight of 6,600, and 10 parts by weight of carbon black Mogal L (manufactured by Cabot Corporation) Part and polypropylene wax 66
3 parts by weight of 0P (manufactured by Sanyo Chemical Co., Ltd.) were mixed, ground, and pulverized to obtain a toner having an average particle diameter of 10 μm. This toner 10
0 parts by weight, 0.8 parts by weight of hydrophobic silica R-972 (manufactured by Nippon Aerosil Co., Ltd.) and 0.1 parts by weight of zinc stearate zinc stearate S were mixed with a Henschel mixer.

This toner is referred to as “toner C”.

Using a developer in which each of the toners A, B, and C and the carriers A to M were combined, measurement of a charging start speed and measurement of toner scattering were performed.

Table 1 below shows combinations of the toner and the carrier.

[0054] To measure the charging rise speed, 19 g of the carrier and 1 g of the toner were placed in a 20 cc glass sample tube, and the amplitude was 30 μm.
cm, mixing with a mixer that reciprocates at a speed of 130 strokes / min. Was used as an index.

As for the toner scattering state, an actual photographing test of 20,000 copies was performed using an electrophotographic copying machine U-Bix 1600, and the toner scattering state after 10,000 and 20,000 copies was expressed in the following six stages. Table 2 shows the experimental results.

[0056] As described above, all of the comparative carriers have a slow charge rise and cause a large amount of toner scattering, whereas the carriers of the present invention have a fast charge rise and a good performance with little toner scattering.

[0057]

As described in detail above, the carrier of the present invention exhibits good performance with a high charge rising speed, little toner scattering, and a long service life.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroki Kabashima 2970, Ishikawa-cho, Hachioji-shi, Tokyo Inside Konica Corporation (56) References JP-A-58-216261 (JP, A)

Claims (1)

(57) [Claims] 1. An electrostatic image developing carrier comprising a magnetic material coated with an acrylic polymer, wherein the carrier surface contains a fatty acid metal salt.