JPS5814148A - Electrostatic image developing agent - Google Patents

Abstract

PURPOSE:To enable good fixing using a heating roller without causing offset phenomenon, by using a developer comprising carriers of iron powder coated with a resin and a toner containing a specified styrene type resin as a binder and furthermore polypropylene. CONSTITUTION:A developer consists of carriers made of iron particles coated with a resin, and a toner comprising a styrene type resin containing a >=10wt% polymer component having mol.wt. as high as >=100,000 and furthermore, polypropylene. For example, 100pts.wt. styrene-acrylic resin containing 25wt% said polymer component, 3.5wt% low softening point polypropyrene, 10pts.wt. carbon blck are incorporated, and a toner having 11.6mum average particle diameter is prepared by an ordinary process. A developer is obtained by mixing this toner with said carriers so as to adjust toner concn. to 5wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

In electrophotography, a photoreceptor comprising a photoconductive element is provided with a uniform surface charge in the dark, exposed to light to form an electrostatic charge image, and then developed to form a visible image.

Generally, methods for developing such electrostatic images are broadly classified into liquid development methods and dry development methods. The liquid development method uses a liquid developer consisting of fine particles of pigment or dye dispersed in an insulating organic liquid (2), while the dry development method uses a natural or synthetic resin. This is a developing method that uses a mixture of a toner containing a colorant such as carbon black dispersed therein and a carrier such as iron or glass beads. In general, carriers can be divided into insulating carriers and conductive carriers. Oxidized or unoxidized iron powder is used as the conductive carrier. Insulating carriers include iron, nickel, cobalt,
A typical example is a carrier in which the surface of carrier core particles made of a magnetic material such as ferrite is coated with an insulating resin.

Dry development methods include the so-called bristle brush method, impression method, and powder cloud method that use a developer containing only the above-mentioned toner as a main component, as well as methods that use a mixture of toner and a carrier made of iron powder or glass beads as a developer. There are the so-called magnetic brush method and cascade method used as a method.

By these developing methods, electrostatic particles such as charged toner particles contained in the developer adhere to the electrostatic charge image to form a visible image. This visible image is transferred directly onto a photoreceptor or onto another image support such as paper by heat, (3) pressure, solvent vapor, etc., and is then fixed.

The present invention relates to a developer used in the magnetic brush method and the cascade method among the above-mentioned developing methods, that is, an electrostatic image developer composed of toner and carrier.

Conventional fusing involves a photoconductive photoreceptor supporting an electrostatically charged image;
Alternatively, the toner image obtained by development is directly fused onto the electrostatic recording body, or the toner image obtained by development is transferred from the photoconductive photoreceptor or electrostatic recording body onto a transfer sheet such as paper. This is done by first transferring the image to a paper and then fusing it. In this case, the toner image is fused either by contact with solvent vapor or by heating.

As the heating method, a non-contact heating method using an electric furnace and a pressure heating method using a heating roller are generally adopted.

The pressure heating method using a heating roller performs fixing by passing the toner image surface of the sheet to be fixed while being in pressure contact with the surface of the heating roller whose surface is made of a material that has releasability for the toner. This method is generally called the heated roller fixing method.

In this method, the surface of the heating roller and the toner image surface of the fixing sheet come into pressure contact, so the thermal efficiency when fusing the toner image onto the fixing sheet is extremely good, and the fixing can be performed quickly. Therefore, it is extremely effective particularly for transfer type electrophotographic copying machines intended for high-speed copying.

However, in this method, since the heating surface and the toner image come into pressure contact in a heated and molten state, a part of the toner image adheres to the surface of the heating roller and is transferred, causing stains on the next sheet to be fixed. Something happened. This is a so-called offset phenomenon. Therefore, one of the essential requirements in the heat fixing method is to prevent toner from adhering to the surface of the heating roller.

Conventionally, in order to prevent toner from adhering to both surfaces of the heating roller, for example, the surface of the heating roller is made of a material with excellent mold release properties such as fluorine resin, and (5) the surface is further coated with an offset prevention liquid such as silicone oil. The surface of the heating roller is coated with a thin film of liquid by supplying the liquid.

Although this method is extremely effective in preventing the offset phenomenon, it generates an odor due to heating of the offset prevention liquid and requires a device to supply the offset prevention liquid. Since the mechanism of the copying device is important and high precision is required to obtain stable results, there is a drawback that the copying device becomes expensive. However, if the anti-offset liquid is not supplied, toner will adhere to the surface of the fixing roller and an offset phenomenon will occur, so despite these drawbacks, it is necessary to supply the anti-offset liquid. is the current situation.

Japanese Patent Publication No. 52-3304 describes in detail the toner containing an anti-offset agent developed to compensate for these drawbacks. By using a toner containing an anti-offset agent, even when silicone oil is not supplied to the surface of the fixing roller (6), it is possible to perform efficient (good heated roller fixing) without generating an offset phenomenon. Therefore, the mechanism of the fixing device can be simplified, and for example, the accuracy, stability, and reliability of high-speed copying machines incorporating such a fixing device can be improved, and the cost can also be reduced. It has the advantage of being configurable.

However, the toner containing the anti-offset agent itself has poor flowability (does not exhibit free flow).

When a developer is created by mixing a toner containing an anti-offset agent and an uncoated iron powder carrier, the anti-offset agent that was present on the surface of the toner particles is transferred to the surface of the uncoated carrier during long-term use. It moves and contaminates or adheres to the surface of the carrier, deteriorating the developer. Moreover, at present, complete anti-offset properties cannot be obtained simply by containing polypropylene, which is a general anti-offset agent. Therefore, in order to improve the non-offset property, a combination of resins and resins each having a certain degree of non-offset property is required.

(7) That is, it is a toner using a binder consisting of a resin having a high molecular weight component and polypropylene.

On the other hand, toners whose binder is a styrene resin containing a high molecular weight component with a molecular weight of 100,000 or more has very good non-offset properties, but due to the high molecular weight component contained, the toner has a softening point. is high (on the contrary, the fixing property is poor. Therefore, in this case, it is necessary to lower the softening point by adding a low molecular weight component, and to decide the binder resin by considering the balance between the offset generation temperature and the softening point. .

However, in this case, since a corresponding amount of low molecular weight components are mixed in, the durability as a developer deteriorates. That is, the low molecular weight resin dislocates onto the surface of the uncoated iron powder carrier and stains the surface of the carrier. That is, the polypropylene as an offset inhibitor and the low molecular weight components of the resin contaminate the carrier surface.

As a result, in a developer composed of an uncoated carrier and a toner made of a resin containing polypropylene and a low molecular weight component, the triboelectric charging characteristics of the toner become unstable during long-term use, resulting in changes in image density and capri. Occur.

Specifically, as the developer is used, polypropylene, which is an anti-offset agent, and resin with a low molecular weight component adhere to the surface of the iron powder carrier particles, which increases the electrical resistance of the carrier particles and reduces the asumi flow. Moreover, the triboelectric charging properties become unstable, resulting in a decrease in the density of the formed image and an increase in capri. Therefore, it becomes necessary to replace the developer at an early stage, resulting in high costs.

In order to solve the above-mentioned drawbacks, it has been strongly desired to develop a highly durable developer containing a toner as a constituent component, which contains an anti-offset agent and whose binder is composed of a resin having a low molecular weight component and a high molecular weight component.

An object of the present invention is to use a toner that can perform efficient (favorable heating P-L) fixing without causing offset phenomenon even when a fixing roller that does not supply an anti-offset liquid to its surface is used. The purpose of the present invention is to provide a developer that can achieve high durability.

The present inventors have developed a toner comprising a resin-coated iron powder carrier and (9) a toner containing polypropylene and using a styrene resin as a binder containing 10 weight or more of a high molecular weight component having a molecular weight of 100,000 or more. It has been found that a developer achieves the above objectives.

In other words, the developer of the present invention has a structure that prevents polypropylene, which is an anti-offset agent, and a low molecular weight resin contained in the toner surface from dislocating or fusing onto the surface of the resin-coated carrier. They have found that it is particularly suitable for high-speed electrophotographic copying machines because it is significantly less in amount than when a coated carrier is used and has excellent durability.

In the present invention, the resin for coating the iron powder particles of the carrier includes styrenes such as p-chlorostyrene and methylstyrene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl heptadide; vinyl acetate; , vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dode(10) acrylate, n-octyl acrylate, 3-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate,
Esters of α-methylene aliphatic monocarboxylic acids such as butyl methacrylate; vinyl ethers such as acrylonitrile, methacrylonitrile, acrylamide, vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether; vinyl methyl ketone, vinyl hexyl ketone, methyl Homopolymers made by polymerizing monomers such as vinyl ketones such as isopropenyl ketone, and other resins such as epoxy resins, rosin-modified phenol-formalin resins, cellulose resins, polyether resins, polyvinyl butyral resins, polyester resins, and styrene resins. Resins such as butadiene resin, polyurethane resin, polyvinyl formal resin, melamine resin, polycarbonate resin, and fluororesin such as Teflon can be used alone or in a blend.

Among these, styrene-acrylic resins ((11) styrene-methyl methacrylate, styrene-butyl methacrylate, etc.), epoxy resins, styrene-butadiene resins, butyral resins, cellulose resins, etc. are particularly useful.

When the photoreceptor is made of an organic photoconductive substance, cadmium sulfide, or the like and has negative charging characteristics, resins such as fluororesin such as Teflon, vinyl chloride vinyl acetate resin, and polyester resin are suitable.

In order to manufacture the carrier used in the present invention, the above-mentioned resin is dissolved in a solvent to prepare a coating liquid, and this coating liquid is applied to the surface of iron powder as carrier core particles. For this application, a dipping method, a spray method, etc. can be used, but a fluidized bed method is particularly preferred. This fluidized bed method uses a pressurized gas flow that rises in a fluidized bed device to raise and suspend the core particles to an equilibrium height, and the coating liquid is removed until the core particles fall again. This is a method in which the coating is applied to each particle by spraying from above, and this is repeated to form a coating film of a desired thickness, and by this method it is possible to apply uniform coating to each particle.

Other resins with good compatibility may be mixed and dissolved in the coating liquid.

The solvent used in the above may be one that dissolves the resin (for example, alcohols such as methanol, ethanol, butanol, and ingropanol; halogenated hydrocarbons such as methylene chloride, dichloroethane, and trichloroethylene; Aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; organic solvents such as tetrahydrofuran and dioxane, or mixed solvents thereof are also used.

In the above, the iron powder as the core particle has a particle size of 1
The thickness of the resin coating layer is preferably 0 to 1000 microns, especially 20 to 300 microns, and the thickness of the resin coating layer is preferably 0.1 to 10 microns, especially 0.2 to 5 microns.

The carrier thus obtained is preferably insulative and spherical, but even if it is conductive or non-spherical, the effects of the present invention will not be lost. The styrenic resin used as the binder is a styrene homopolymer or copolymer. Examples of styrenes include t hastyrene,
0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene,
2.4-dimethylstyrene, p-n-butylstyrene,
p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p- Examples include phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene.

When the styrene resin is a styrene copolymer, a styrene-acrylic copolymer is particularly preferred.

Here is the acrylic monomer for the acrylic component:
For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate,
Acrylic (14) lauryl ruate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, globil methacrylate, n-butyl methacrylate, inbutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate α- amine ethyl, diethylaminoethyl methacrylate, etc.
Methylene aliphatic monocarboxylic acid esters; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, and others. These monomers can be used alone or in combination. In particular, a terpolymer consisting of the three components styrene-methyl methacrylate-butyl methacrylate is preferred.
Mention may be made of butadiene copolymers.

The above styrene resin must contain 10% by weight or more of a high molecular weight component with a molecular weight of 100,000 or more; if it is not used, a high offset generation temperature cannot be obtained. .

A styrenic resin containing such a high molecular weight component can be easily obtained by appropriately selecting polymerization conditions or by forming a crosslinked polymer using a crosslinking agent or the like.

The molecular weight in this specification refers to the gel weight under the following conditions.
Permeation chromatography (Gel permeation)
It is determined by the measurement chromatography method. Tetrahydrofuran was flowed at a flow rate of 1 g/min at a temperature of 25°C, and the concentration was 0.4 g.
/dt of tetrahydro7 run solution as sample weight 8m
g and perform measurement. When measuring the molecular weight of a sample,
Measurement conditions are selected in which the molecular weight distribution of the sample is inscribed within a range in which the logarithm of the molecular weight and the count number of a calibration curve created using several types of monodisperse polystyrene standard samples are a straight line. The above measurement was performed using HLC-802 manufactured by Toyo Soda Co., Ltd.
Using a UR device, the column is TSK-GEL/CMH6
It was used.

A styrene-acrylic resin containing 10 weight or more of a high molecular weight component having a molecular weight of 100,000 or more can be produced, for example, as follows.

Synthesis Example 0.1 g of partially saponified polyvinyl alcohol "Gohsenol GH-17J (manufactured by Nippon Gosei Co., Ltd.)" was placed in a separable flask with a capacity of 1 t, and dissolved in 100% of distilled water. After adding, suspending and dispersing and replacing the gas phase with nitrogen gas, the temperature was raised to 80°C.
Maintain this temperature for a period of time to polymerize. Then temperature 40℃
Monomer mixture B shown in the table below was added thereto, and stirring was continued for 2 hours at a temperature of 40°C. Then, polyvinyl alcohol partially saponified f[gohsenol GH-
17J O, 4g 1r water 100d separately vI
i and add the aqueous solution to the suspension system. Then 80℃
(17) The temperature was raised again and the temperature was maintained for 8 hours to carry out polymerization, and the temperature was further raised to 95°C and maintained for 2 hours to complete the polymerization. Thereafter, it is cooled, dehydrated, washed repeatedly, and dried to obtain a resin. This resin has a number average molecular weight of 1. lX10', ratio of weight average molecular weight MW to number average molecular weight Mn Mw/M
n was 4.5, and the softening point was 140±2° C. when measured by the ring and ball method specified in JIS K2531-1960.

In addition, α-methylstyrene (dimer) is described in U.S. Patent No. 2
Synthesized according to the description in No. 429719, t, = 2
．． 4-diphenyl-4-methyl-1-bentent 2.4
-Diphenyl-4-methyl-2-ben(18) It is a mixture with thene and has a refractive index of 1.569.

Since the polypropylene contained in the toner of the developer of the present invention requires a relatively low fusing temperature, it is desirable that the polypropylene has a relatively low molecular weight, and has an average molecular weight of 1000 to 4.
5,000, particularly preferably an average molecular weight of 2,000
~20,000 can be effectively used. In addition, polypropylene having a softening point of 80°C to 180°C according to the ring and ball method is preferred, particularly preferably 100°C.
℃~160℃.

These useful polypropylenes are commercially available from Sanyo Chemical Industries, Ltd. under the trade names of ``Viscoll 550PJ'' and ``Viskol 660PJ''.The amount of polypropylene added to the toner is generally 0.1 parts by weight of the resin component of the toner. ~50 parts by weight, particularly preferably 1 to 2 parts by weight
It is 0 parts by weight.

The toner of the present invention is made of the above-mentioned styrene resin, and contains a colorant and a property improver added as necessary in a binder containing polypropylene.

Coloring agents include carbon black, digloscine (19) dye (C81, 450415B), and aniline blue (C, I).

450405), Calcooilb/I/-(C,
1,4azoecBlue3), Chrome x Low (C0
I. ,% 14090), ultramarine blue (C
,I. 477103), DuPont Oil Red (C
,1,/l626105), quinoline yellow (C
.

1, A 47005), methylene blue chloride (
c, r. Taka52015), Phthalocyanine Blue (C
,I. 74160), malachite green offsalate (C,I.442000λ lamp black (C0I)
, 477266), Rose Bengal (C, 1, 44
5435), mixtures thereof, and others. These colorants need to be contained in a sufficient proportion to form a visible image of sufficient density, and are usually about 1 to 20 parts by weight per 100 parts by weight of the binder.

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

[Manufacture of carrier]

[E
1 kg of FV8 J (manufactured by Nippon Tetsuko Co., Ltd.) was placed in the coating solution, and after removing the supernatant liquid, it was dried by blowing hot air while stirring in a photographic vat, and then the powder was heated to a temperature of 100°C.
The carrier was heat-treated for 2 hours in an open air conditioner, thereby obtaining a carrier 1 having a resin coating. The volume resistivity of this carrier 1 was 2.3×10′Ω·cm.

In addition, "the volume resistivity IJ is 10 dl in area and 1 c in depth.
The value was measured under the condition that 1 g of the sample was placed in a container with a recess of m in diameter and the inner circular bottom was a brass electrode plate, and a brass electrode weighing 1 kg was placed on the sample layer from above. be.

2) Carrier 2 3 g of cellulose acetate butyrate resin and 30 g of methyl ethyl ketone
Prepare a coating solution by dissolving in 0 sg, 200 to 300
1 kg of mesh steel iron powder [DSP-179DJ (manufactured by Dowa Iron Powder Co., Ltd.) was added to the coating solution, and after removing the supernatant liquid, it was dried by blowing hot air while stirring with a photographic vat, and then dried. The powder was heat-treated for 1 hour in an open air at 120°C (21°C), thereby obtaining a carrier 2 having a resin coating. The volume resistivity of this carrier 2 was 4.5×10”Ω·cm.

3) Carrier 3 3 g of methyl methacrylate-ethyl acrylate copolymer resin with an average molecular weight of 100,000 was mixed with 300 g of methyl ethyl ketone.
- Using the coating liquid dissolved in the liquid, apply 200 to 300 meshes of sintered iron powder I TEFVS J (manufactured by Nippon Iron Powder Co., Ltd.) 1k
A carrier 3 having a resin coating was obtained in the same manner as in the production of carrier 1 except that g was used. The volume resistivity of this carrier 3 was i,5xio'Ω·cm.

4) Carrier 4 Prepare a coating solution by dissolving 20g of epoxy resin in 300ml of methyl ethyl ketone, and use a fluidized bed device to coat 1kg of spherical steel powder with an average particle size of 100 microns at a fluidized drying temperature of 60°C. The powder was then heat treated in an open air at a temperature of 100° C. for 2 hours, thereby obtaining a carrier 4 having a resin (22) coating. The volume resistivity of this carrier 4 was 10'4 Ω·Cm or more.

5) Carrier 5 A carrier 5 having a resin coating was obtained in the same manner as in the manufacture of carrier 4 except that polyvinyl butyral resin "Eslec BJ (manufactured by Tanezu Kagaku Co., Ltd.) was used instead of the epoxy resin. This gear 9 F50 volume resistivity is 6.8 x 1
It was 0''Ω·cm.

6) Carrier 6 Use styrene-butyl methacrylate resin with an average molecular weight of 130,000 as a coating resin 1 to iron powder 1'': DI9P
A carrier 6 having a resin coating was obtained in the same manner as the carrier 4 except that -135CJ (manufactured by Dowa Iron Powder Co., Ltd.) was used. Volume resistivity 1j, 1o of this carrier 6
It was 14Ω·cm or more.

[Manufacture of toner]

1) Toner 1 Styrene-acrylic resin "S (23) Ledge" containing 25% by weight of high molecular weight components with a molecular weight of 100,000 or more (Sekisui Chemical Co., Ltd. $4!7100 parts by weight) and low softening point polypropylene [Viscol 660PJ (manufactured by Sanyo Chemical Industries, Ltd.) and 10 parts by weight of carbon black were mixed in a ball mill, and the average particle size was Toner 1 was obtained.

2 Toner 2 15 weight parts of high molecular weight components with a molecular weight of 100,000 or more, 100 parts by weight of SS-certified styrene-2-ethylhexyl acrylate (softening point 138°C), 5 parts by weight of low softening point polypropylene "Viscol 660PJ, and carbon Toner 2 with an average particle size of 12.9 microns was obtained in the same manner as Toner 1 using 10 parts by weight of black.

3) Toner 3 100 parts by weight of a styrene-acrylic resin (sample manufactured by Omizu Kagaku Co., Ltd.) containing 38 parts by weight of a high molecular weight component having a molecular weight of ioo, ooo or more, and low softening point polypropylene [Viscol 550P J (Sanyo Chemical Industries, Ltd.) Toner 3 with an average particle size of 12.9 microns was produced in the same manner as Toner 1 using 24 parts by weight of Toner 3 and 10 parts by weight of carbon black.
I got it.

One of the carriers 1 to 6 described in Examples above and one of the toners 1 to 3 are mixed in the combination shown in the following table in a ratio that gives the toner concentration (wt%) shown in the same table, and a total of 611. The electrophotographic copying machine 1'-U is manufactured using the electrostatic charge generating agent of the present invention.
-BiX W (modified type)” (Konishi Roku Photo Industry Co., Ltd.)
Durability tests were conducted using continuous copying for each printing agent. The results are shown in the table. In addition, "high molecular weight component" in the table means that the molecular weight of the binder of the toner is 100.
,000 or more components.

(25) As can be understood from the results above, the electrostatic charge of the present invention g1
The developer does not cause fogging even after being subjected to a large number of developments (it can achieve good development and has great durability, and it also does not cause image staining due to offset phenomenon). A duplicate image is obtained.

Comparative Example 1 8% by weight of high molecular weight components with molecular weights of ioo, ooo or more
A comparative developer with a toner concentration of 5 weight was prepared by using a toner obtained in the same manner as in the production of Toner 1, except that the styrene-acrylic resin contained therein was used as the binder (26), and Carrier 1 described above. When a durability test similar to that in Example was conducted, before the number of copies reached 10,000, staining due to the offset phenomenon became severe and fogging also occurred, so the experiment was discontinued.

Comparative Example 2 A comparative developer with a toner concentration of 5 weight was prepared using 200 to 300 mesh iron powder [Erv-IIIJ (manufactured by Nippon Tetsuko Co., Ltd.) and Toner 1 described above, and a durability test was conducted on the same machine as in the example. As a result, although the fixing properties were sufficient, fogging occurred before the number of copies reached 10,000, so the experiment was discontinued.

Agent: Patent Attorney Masahiko Ooi

Claims (1)

[Claims] 1) Specially designed to consist of a carrier made of iron powder particles coated with resin, a styrene resin containing 10% by weight or more of a high molecular weight component with a molecular weight of 100,000 or more as a binder, and a toner containing polypropylene. An electrostatic image developer.