JPS61163347A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain a toner sufficient in fixability, superior in offset resistance and storage stability, and good in high-speed copying aptitude by using a binder resin obtained by melt kneading a specified noncross-linked vinyl polymer and a cross-linked polymer. CONSTITUTION:The binder resin is obtained by mixing the noncrosslinked vinyl polymer having a weight average mol.wt. of 10,000-50,000, and a glass transition point of 40-80 deg.C and contg. no gel fraction. with a cross-linked polymer having a glass transition point of 30-70 deg.C and contg. a gel fraction in an amt. of 5-70wt% in a mixing weight ratio of (20-95):(80-5). Each polymer has, preferably, >=40wt% styrene units as the polymer constituents, and each polymer separately prepared is heat kneaded. A colorant and/or a magnetic powder is added to this binder resin before or after the kneading step. It is an important point to microdisperse both of resins in the heat kneading step. The use of such a binder resin permits the obtained toner to be prevented from fogging, and enhanced in developing performance, to cause no caking, and to be good in stability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toner for developing an electrostatic image formed on a photoreceptor in electrophotography, electrostatic recording, and the like.

BACKGROUND OF THE INVENTION It is well known to form and develop images on the surface of photoconductive materials by electrostatic methods. U.S. Patent No. 2.297,69
The basic xerographic method described in No. 1 applies a uniform electrostatic charge onto a photoconductive insulating layer.

An electrostatic latent image is formed by exposing the layer to a bright and dark image to eliminate the charge in the bright image area, and a fine powder called toner is electrostatically attached to the image, which corresponds to the electrostatic latent image. Form a toner image. The toner image is then transferred to the surface of an image support such as paper.

The image is fixed by heating, for example.

Several methods are known for attaching toner to an electrostatic latent image to be developed. For example, U.S. Patent 2.618,5
In the method described in No. 52, a developing material consisting of toner powder and a powder called a carrier having a relatively large particle size relative to the toner whose surface is electrostatically coated is moved over an electrostatic latent image. The method of developing by glazing is known as the cascade development method.

In this method, the carrier powder is selected to triboelectrically charge the toner powder to the desired polarity.

Other methods of developing electrostatic latent images are described in US Pat.
There is a magnetic brush development method described in US Pat. No. 874,063. In this method, a developer containing toner and magnetic carrier is supported by a magnet, and the magnetic field of the magnet aligns the magnetic carrier in a brush-like shape, and the magnetic brush is brought into contact with or close to the electrostatic latent image. The toner is deposited onto the latent image by electrostatic attraction.

Others include liquid development as described in U.S. Pat. No. 4899,335, fur brush development as described in U.S. Pat. No. 490λ974, and U.S. Pat.
．． The touchdown development method described in No. 432 is known.

The developed toner image is transferred onto an image support such as paper by corona discharge or the like. The transferred toner image is easily removed from the image support.

Therefore, it is necessary to fix it on a support.

Fixing methods include a method of melting the toner by heating;
A method of dissolving toner using a solvent.

A method of deforming toner by applying pressure is known. Among these methods, the method of fixing by heating, especially the method called heated roll fixing in which the image is passed through two heated rolls, is the most common because it is superior in energy efficiency, economical efficiency, and high-speed fixing. is being carried out.

In this heating roll fixing system, the temperature of the heating roll is usually set within a temperature range of 150 to 220 DEG C. for reasons such as the melting characteristics of the toner's binder resin, economy such as power consumption, and copying speed. From the viewpoint of fixing properties, it is advantageous for the binder resin of the toner used in this method to have a low glass transition point or a low molecular weight. However, from the viewpoint of the storage stability of the toner, it is impossible to lower the glass transition point to a particularly low temperature, and the temperature is limited to a certain level or higher.

Furthermore, when a low molecular weight resin is used, a phenomenon called offset, in which toner transfers from the image support to the heating roll during fixing and adheres thereto, tends to occur. Furthermore, this is disadvantageous in terms of the mechanical strength of the toner.

For the reasons mentioned above, until now there has been no technology using a binder resin made of a resin having a specific degree of dispersion with respect to one molecular weight; a binder resin made of a low molecular weight resin and a high molecular weight resin; or a binder resin made of a crosslinked polymer. Some are known.

For example, in JP-A-50-134652.

A method is described in which a resin having a weight average molecular weight to number average molecular weight ratio of 3.5 to 40 is used as a binder resin.

In addition, Japanese Patent Application Laid-open No. 114245/1983 discloses that the molecular weight is i.
, o o o~4. OOO has a glass transition point of 40~
Low molecular weight polymer with low temperature meltability of 60℃ and high fluidity, 2 weight average molecular weight of 500,000 or more and glass transition point of 35 to 60.
A method using a polymer having a temperature of 0.degree. C. as a binder resin is described.

In JP-A-56-16144, the molecular weight distribution curve measured by gel permeation chromatography has a molecular weight i of 9, a region of o oo to 80.000, and a region of 100.00.
A method is described in which resins each having at least one maximum value in the ranges of 000 to 000 to 000 and 000 are used as a binder resin.

All of the methods described in the above publications contain non-crosslinked low molecular weight polymers and high molecular weight polymers in the binder resin of the toner, thereby suppressing the occurrence of offset phenomenon while maintaining fixing properties. The purpose is to

For example, JP-A-49-101031 describes a method in which a vinyl polymer reacted with a crosslinking agent is used as a binder resin.

Further, a method using a crosslinked polymer as a binder resin is also known in US Pat. No. 3,938,992.

(Problems to be Solved by the Invention) However, the improvement in anti-offset properties is insufficient with resins in which only the degree of dispersion is specified, and with the above-mentioned binder resins consisting of low molecular weight polymers and high molecular weight polymers, both Because non-crosslinked polymers are used, molecular interactions occur between low molecular weight polymers and high molecular weight polymers, which limits fixing properties due to the properties of high molecular weight polymers, and Generally, due to the characteristics, prevention of the offset phenomenon was insufficient.

When a crosslinked polymer is used as a binder resin, its elastic properties are too strong, resulting in poor fixing properties. In particular, when fixing at high speed, the fixing performance becomes insufficient. In addition, the mechanical strength is too high and the crushability is often poor.

The present invention was made based on one or more circumstances,
Its purpose is to have sufficient fixing properties, and
It has excellent properties to prevent offset phenomenon and also has excellent storage stability. The object of the present invention is to provide an electrophotographic toner particularly suitable for high-speed copying.

Another object of the present invention is to provide an electrophotographic toner that has excellent crushability and developability.

(Means for Solving the Problems) The present invention provides (a) a weight average molecular weight of 10.000 to 50;
．． 000 and a glass transition point of 40 to 80°C and 20 to 95% by weight of a non-crosslinked vinyl polymer containing no gel content;
The present invention relates to an electrophotographic toner containing a binder resin consisting of 80 to 5% by weight of a crosslinked polymer containing 70% by weight.

The non-crosslinked vinyl polymer of the present invention refers to one kind of monofunctional vinyl monomer or a copolymer of 28 or more monomers.
A mixture of such polymers may also be used.

Here, the monofunctional vinyl monomers include styrene,
Styrene derivatives such as p-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate.

Stearyl acrylate, lauryl acrylate, oleyl acrylate, cetyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, glycidyl acrylate, hydroxyethyl acrylate, hydroxy acrylate Pupil, hydroxybutyl acrylate.

Monofunctional acrylic acid derivatives such as (N,N-dimethylamino)ethyl acrylate, (N,N-diethylamino)ethyl acrylate, morpholinoethyl acrylate, piperazinoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate , butyl methacrylate, hexyl methacrylate, octyl methacrylate, stearyl methacrylate, lauryl methacrylate, oleyl methacrylate, cetyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate , glycidyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, methacrylic acid (
N,N-dimethylamino)ethyl, methacrylic acid (N,
N-diethylamino)ethyl, morpholinoethyl methacrylate.

Monofunctional methacrylic acid derivatives such as piperazinoethyl methacrylate, and maleic anhydride, maleic acid, methyl maleate, and dimethyl maleate.

Ethyl ileate, dimethyl maleate, butyl maleate, diptyl maleate, octyl maleate, dioctyl maleate, glycidyl maleate, diglycidyl maleate, N-methylmaleimide, N-ethylmaleimide.

N-propylmaleimide, N-butylmaleimide, N-hexylmaleimide.

Examples include maleic acid derivatives such as N-octylmaleimide, and vinyl monomers such as vinyl acetate and vinyl chloride.

As the non-crosslinked polymer, a polymer containing 40% by weight or more of styrene as a component is preferred from the viewpoint of the relationship between melt viscosity characteristics and glass transition point, which are major factors in fixability, and economic efficiency.

The non-crosslinked vinyl polymer has a weight average molecular weight of 10.000 to 50.0 as measured by conventional gel permeation chromatography in terms of standard polystyrene.
00. Preferably 20,000 to 40. OOO is used. Here, the weight average molecular weight is 10. If it is less than OO0, it will be difficult to cross lines during toner production, and the mechanical strength will be insufficient, resulting in poor durability.9. This causes capri and scattering, which reduces developability and forms a film of toner on the photoreceptor.

It also causes a phenomenon that deteriorates images, that is, filming. In addition, it tends to cause poor cleaning of the photoreceptor. Furthermore, if the weight average molecular weight exceeds 50,000, fixing properties will be insufficient.

In addition, the non-crosslinked vinyl polymer has a glass transition point of 40~
A polymer having a temperature of 80°C, preferably 50-70°C is used. If the glass transition point is below 40°C, storage stability is poor6. If the temperature exceeds 0.degree. C., the fixing properties will be insufficient.

In the present invention, the glass transition point is measured by DSC. Alumina as a standard sample.

Approximately the same amount of sample is heated at a rate of 20° C./min and its endothermic curve is measured. On the endothermic curve, the point obtained by extrapolating the baseline (non-endothermic) and endothermic state lines is defined as the glass transition point.

The non-crosslinked vinyl polymer used does not contain any gel content. In the present invention, the gel content refers to the chloroform-insoluble content. The method for measuring chloroform-insoluble content is to add 1 g of a sample to approximately 1009 ml of chloroform and leave it at room temperature for 3 days.

The sample is filtered using two types of filter paper according to the JIS-P3801 standard, and the uneluted portion is washed three times with about 100 g of chloroform, and the dry weight of the uneluted portion is measured to determine the gelled portion in the sample.

As the crosslinked polymer, a crosslinked vinyl polymer obtained by copolymerizing one or more of the above monofunctional vinyl monomers with a polyfunctional vinyl monomer is used.

Examples of polyfunctional vinyl monomers include divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, butylene glycol diacrylate, and butylene glycol dimethacrylate.

Hexanediol diacrylate, hexanediol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate.

Bifunctional compounds such as polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, and s-2-bis(4-acryloxyjethoxyphenyl)propane. vinyl monomer, trimethylolpropane triacrylate -
to.

Examples include trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

In addition, as a crosslinked polymer, a crosslinked polymer made by copolymerizing a monofunctional vinyl monomer with a polymer having an average of two or more copolymerizable vinyl groups in the molecule, such as unsaturated polyester or maleic acid-terminated acrylic polymer, etc. Polymers, known non-crosslinked polymers having functional groups capable of crosslinking reaction, which are crosslinked with a crosslinking agent, etc. can also be used. The crosslinked polymer used in the present invention is a crosslinked vinyl polymer obtained by copolymerizing and crosslinking a polyfunctional vinyl monomer for reasons such as ease of production, stability, and a small amount of unreacted materials remaining. Polymers are preferred. Further, the crosslinked polymer preferably contains 40 weight or more of cystyrene as a component for the same reason as the non-crosslinked vinyl polymer.

The crosslinked polymer in the present invention has a gel content, that is, a chloroform-insoluble content as determined by the above-mentioned measuring method, of 5 to 70% by weight, preferably 10 to 50% by weight. If the gel content is less than 5% by weight, the effect of preventing the offset phenomenon and the mechanical strength of the toner will be poor.

In addition, because the molecular compatibility with the non-crosslinked vinyl polymer becomes too good, the fixing properties may be reduced. Furthermore, if the gel content exceeds 70% by weight, the crosslinkability with non-crosslinked vinyl polymer components, pigments, and other additives will be extremely poor, causing scattering, capri, etc., and deteriorating the image.

The glass transition point of the crosslinked polymer is 30 to 7 according to the measurement method described above.
0°C, preferably 40-60°C.

If the glass transition point is less than 30°C, the storage stability will be poor, and if it exceeds 70°C, the crosstalk will be poor and the strength of the fixed image will likely decrease. The glass transition point of the crosslinked polymer is the same as that of the non-crosslinked vinyl polymer or 5°C.
It is preferable that it be as low as possible.

This is because crosslinked polymers tend to have better storage stability than non-crosslinked vinyl polymers having the same glass transition point.

In the present invention, the non-crosslinked vinyl polymer and the crosslinked vinyl polymer are produced by a well-known polymerization method such as a solvent removal method, suspension polymerization method, emulsion polymerization method, or bulk polymerization method after solution polymerization of raw material monomers. Manufactured by polymerization. Among these, suspension polymerization is preferred from the viewpoint of economy and ease of handling. Toner for electrophotography requires stability against humidity.

As the binder, a lipophilic vinyl polymer is preferably used. For these reasons, 2 For example, sparingly soluble inorganic salts such as calcium phosphate and calcium carbonate.

It is particularly preferable to produce by an aqueous suspension polymerization method using a water-soluble polymer such as polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, or sodium polymethacrylate as a dispersant.

The ratio of non-crosslinked vinyl polymer/crosslinked polymer is 2 by weight.
0/80~9515. Preferably 40/60 to 80/2
It is blended with 0. When this ratio is less than 20/80, the elasticity is too strong, and the fixing property at high speed is inferior to the fixing property %. If it exceeds 9515, the strength effect of the crosslinked vinyl polymer will be small, the effect of preventing the offset phenomenon will be weakened, and the mechanical strength will also be reduced.

The toner for electrophotography in the present invention contains two coloring agents and/or magnetic powder.

Examples of colorants include carbon black, nigrosine dye, aniline blue, alcohol blue, chrome yellow, and ultramarine blue.

DuPont Oil Red, Monoline Yellow, Malachite Green Oxalate, Lamp Black.

There are rose bengal and mixtures thereof. The amount of colorant varies depending on the material used.

It is preferably used in an amount of 3 to 20% by weight based on the total weight of the toner, but is not limited thereto.

Magnetic powders include ferrite, magnetite, etc.
It is used in an amount of 30 to 60% by weight based on the total weight of the toner.

When using colorants together with magnetic powder.

Preferably, the amount of the colorant is 10% by weight or less based on the total weight of the toner.

It is also possible to use any other known additives in the electrophotographic toner of the present invention.

For example, low-molecular-weight polyethylene, low-molecular-weight polypropylene, long-chain fatty acids and their esters, derivatives such as amides, paraffin wax, castor wax, carnauba wax, and other waxes can be used as fixing or offset prevention improvers. .

The electrophotographic toner according to the present invention is manufactured by any known kneading method. Of them.

Particularly preferred is one in which the binder resin is heated to a certain degree of melting state and then mixed by applying mechanical shearing force.

For example, there are methods such as passing the toner mixture between two heated rolls, stirring and mixing with a heated screw, and methods of forcing the molten toner compound through pores using pressure, but these methods have similar effects. There is no limitation as long as there is.

In the present invention, the non-crosslinked vinyl polymer and the crosslinked vinyl polymer must be separately manufactured and then mechanically melt-kneaded. In this case, a colorant and/or magnetic powder and other additives may be present at the same time.

Melt mixing of a non-crosslinked vinyl polymer and a crosslinked polymer is necessary because it is not a so-called molecular ``compatibility,'' but a ``microdispersion''.Therefore, although there are differences depending on the mixing method,
Melt kneading should neither be insufficient nor excessive. In the present invention, the gel content of the crosslinkable vinyl polymer is particularly limited, but if it is used within this limited range, the minimum necessary crosstalk, that is, colorants such as pigments and dyes, will be reduced. The purpose can be achieved with just the amount of crosstalk required to achieve uniform distribution. The colorant and/or magnetic powder and other additives may be kneaded with the binder resin after such mixing.

In the present invention, if the melt crosstalk is insufficient, the colorant and/or magnetic powder cannot be uniformly dispersed, and phenomena such as toner scattering and capri occur, resulting in poor developability. On the other hand, if it is too long, the non-crosslinked vinyl polymer and the crosslinked vinyl polymer become molecularly "compatible", resulting in poor fixing properties, especially fixing properties at high speeds. The optimum degree of melt mixing varies depending on the type and composition of the polymer, the type and composition of additives, and the mixing machine.

It will be determined on a case-by-case basis.

In the present invention, the toner composition that has been appropriately melted and kneaded is pulverized to an average particle size of about 5 to 30 microns by a well-known method. In this case, all known mechanical grinding methods such as hammer mills and jet mills can be used. Furthermore, the toner after pulverization can be classified by two well-known methods, if necessary.

(Example) The present invention will be explained in detail by way of examples.

Hereinafter, "parts" represent "parts by weight."

1. Polymer production: 2. In a cylindrical separable flask reactor equipped with a stirrer, cooling tube, nitrogen gas introduction tube, thermometer, and temperature control detector.
Partially saponified polyvinyl alcohol 0.2% aqueous solution 100
A mixture of vinyl monomers shown in Tables 1 and 2 and benzoyl peroxide as a polymerization initiator was added and polymerized by heating at 85°C for 6 hours under a nitrogen stream and then at 95°C for 2 hours with stirring. I let it happen. After cooling the inside of the reactor to 50'C.

The polymerization mixture was filtered under reduced pressure, and the obtained polymer beads were washed with 100 parts of tap water and filtered under reduced pressure. This operation was repeated 5 times. After washing, the obtained polymer beads were dried in a dryer at 50° C. for 24 hours.

The physical properties of the obtained polymer are also shown in Tables 1 and 2.

The polymer obtained by the formulation shown in Table 2 is a non-crosslinked polymer, and the polymer obtained by the formulation shown in Table 2 is a crosslinked polymer.

Example 1 Non-crosslinked polymer UC-160 parts, crosslinked polymer UL-14
0 parts, 10 parts of carbon black, 3 parts of Bontron E81 (negative charge control agent manufactured by Orient Chemical ■), and 2 parts of low molecular weight polypropylene.

The mixture was kneaded 5 times using two rolls heated to 100°C. This was coarsely pulverized with a hammer mill, then finely pulverized with a jet mill, and then classified to obtain a toner having an average particle size of about 13 μm. This was mixed with iron oxide powder EFV200/300 (manufactured by Nippon Tetsuko Powder ■) as a carrier to give a toner concentration of 5% to prepare a developer.

This developer was put into a developing machine of an improved copying machine NC3000 (■Copia), and an unfixed image of 1/3 black was created on A4 paper.

Next, the upper part of the unfixed black peta image is Teflon.

A fixing test was conducted using a heated roll type fixing tester with a silicone rubber lower part, by changing the roll temperature in steps of 10° C. from 100° C. to 240° C. at a linear speed of 800 c+n/min. How to judge fixability.

lX Place ``Sekai tpu Hakuro Sai ≠ Zero # Gi 1'' on the fixed image.

After applying a load of ``KxOOg/an'', it was slowly peeled off and the image density (hereinafter abbreviated as ID) was measured.The temperature at which fixing was completed was determined by the ratio of ID before and after the cellophane tape peeling test of 95- That's all.

Table 3 below shows the experimental results compared to the number of crosstalks with two rolls.
Shown below.

Table 3 Experimental Results In addition, in the table above, the hot offset Miyako temperature is determined by the number of times of crosstalk when the roll part in contact with the black peta part is wetted again with the white part. A continuous copying test of 20,000 sheets was conducted using the toner three times at 30° C. and humidity of 80° C., but no capri or the like occurred and the developability was extremely good. In addition, in order to examine the mechanical strength, the particle size distribution t-X was plotted at the initial stage and after 20,000 sheets were copied, and the fine powder of 5 μ or less increased from 0.64 inch to 0.5 inch, which is sufficient for the mechanical strength. I made a ditch. Further, the toner was placed in a desiccator at a temperature of about 80° C. and stored at 50° C. for 24 hours, but no caking occurred and the storage stability was extremely good.

Examples 2 to 5 Experiments similar to those in Example 1 were conducted using the combinations and blending amounts of non-crosslinked polymers and crosslinked polymers shown in Table 4.

The results are shown in Table 4.

Comparative Examples 1 to 4 Experiments similar to those in Example 1 were conducted using the combinations and blending amounts of non-crosslinked polymers and crosslinked polymers shown in Table 5. The results are also shown in Table 5.

Comparative Example 5 In correspondence with Example 1, the following test was conducted to see the difference from "compatibility" in the molecular state.

160 parts of non-crosslinked polymer UC-29.88 parts of styrene;
It was dissolved in 10 parts of butyl acrylate and 0.12 parts of divinylbenzene, 0.8 parts of benzoyl peroxide was added thereto, and polymerized in the same manner as the other polymers. Using 100 parts of this polymer, a toner was prepared in the same manner as in Example 1, and the same experiment was conducted. The results are shown in Table 6 together with the results of Example 1.

Table 6 Experimental Results From this test, when comparing Example 1 and Comparative Example 5 (both crosstalks 3 times), it can be seen that Example 1 has excellent fixing properties.

(Effect of the invention) The electrophotographic toner according to the present invention has excellent fixing properties.

Also, it is less prone to offset and has excellent durability and storage stability.

Claims (1)

[Claims] 1. (a) Weight average molecular weight is 10,000 to 50,00
0 and a glass transition point of 40 to 80°C and a non-crosslinked vinyl polymer containing no gel content of 20 to 95% by weight; and (b) a glass transition point of 30 to 70°C and a gel content of 5% by weight.
An electrophotographic toner comprising a binder resin comprising 80 to 5% by weight of a crosslinked polymer containing 70% by weight. 2. The electrophotographic toner according to claim 1, wherein the binder resin is obtained by melt-kneading the non-crosslinked vinyl polymer and the crosslinked polymer. 3. The non-crosslinked vinyl polymer and the crosslinked polymer are
3. The electrophotographic toner according to claim 1 or 2, each of which contains 40% by weight or more of styrene as a polymer component.