JPS6291959A - Toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain a toner for developing electrostatic charge image having superior stability of charge and excellent fixing characteristics by using a binder resin prepd. by using a specified polymn. initiator being constituted to have a specified mol.wt. distribution. CONSTITUTION:The binder resin is one contg. a copolymer of monomer mixture selected from styrene and its derivs., acrylic esters and/or methacrylic esters, maleic acid or its esters copolymerized in the presence of a polymn. initiator having a 10hr half value period temp. >=110 deg.C at by 0-40 deg.C higher temp. than the 10hr half value period temp. of the initiator. If a vinyl copolymer obtd. by using a polymn. initiator having 10hr half value period temp. below 110 deg.C is used for the toner, the electric charge of the toner is insufficient and unstable. A representative polymn. initiator having a 10hr half value period temp. >=110 deg.C is dicumyl peroxide.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to toner used for developing electrostatic images formed in electrophotography, electrostatic printing, electrostatic recording, etc. Regarding sex toner.

[Description of prior art]

Image forming methods conventionally known as electrophotography, electrostatic printing, electrostatic recording, etc. all include the step of visualizing the formed electrostatic image using colored fine powder called toner. I'm here. For example, electrophotography is described in US Pat. No. 2,297,691, Japanese Patent Publication No. 42
Although various methods are known, as described in Japanese Patent Publication No. 23910 and Japanese Patent Publication No. 43-24748,
Generally, an electrostatic charge image is formed on the surface of a photoreceptor using a photoconductive substance by various methods, and then the electrostatic charge image is developed with toner, and if necessary, the toner image is transferred to a transfer material such as paper. After the image is transferred, it is fixed by heating, pressure, etc. to obtain a copy.

The process of developing an electrostatic charge image involves attracting toner particles charged with a polarity opposite to that of the electrostatic charge image by electrostatic attraction.
The electrostatic charge image is visualized by adhering it to the electrostatic charge image on the surface of the photoreceptor, and this developing method includes
For example, cascade development using a glass bead carrier as described in U.S. Pat. No. 2,618,552, magnetic brush development using an iron powder carrier as described in U.S. Pat. No. 2,874,065. Fur brush development method using a cylindrical brush made of beaver hair instead of carrier particles, U.S. Pat. No. 2,221,7
Powder cloud development method using toner particles in a spray state as described in US Pat. No. 76, and US Pat.
．． A magnetodynamic method using a one-component conductive magnetic toner described in Japanese Patent No. 909.258 is known. Furthermore, as a method using component-based toner, a development method using insulating magnetic toner has been devised, and this development method has been widely applied because it is less dependent on the material of the transfer sheet and the development system can be simplified. ing.

Toners applied to these developing methods are generally prepared by mixing and dispersing a coloring agent in a thermoplastic resin and then pulverizing the mixture. As the thermoplastic resin, polystyrene resin is the most common, but polyester resin, epoxy resin, acrylic resin, urethane resin, etc. are also used. Carbon black is most widely used as a coloring agent, and in the case of magnetic toner, iron oxide-based black magnetic powder is often used. In the case of a system using a so-called two-component developer, the toner is usually mixed with carrier particles such as glass beads and iron powder.

The toner image on the final copy imaging member, such as paper, is permanently affixed to the support by heat, pressure, or the like. Conventionally, this fixing process often uses heat.

In addition, the heating fixing method has replaced the old oven fixing method, but in recent years, copying work has become more efficient, energy efficient, and copying machines have become smaller, faster, and more sophisticated.In recent years, a heat roll type fixing method with good thermal efficiency has become available on the market. They now account for the majority of the population.

This method attempts to fix the toner onto the paper by thermocompression bonding using a heating roller, and it is possible to obtain a satisfactory fixed image at a lower temperature than the non-contact heating method using a hot wire. It also has many advantages, such as being able to increase speed.

Generally, toners used for a specific fixing method cannot be used for other fixing methods, and as fixing methods change, various toner materials suitable for heat-pressure fixing using heated rollers have been proposed. However, in these proposals, the molecular weight distribution of the binder resin, the degree of crosslinking, the mixture of different resins,
In addition, a wide range of technical innovations have been made, such as the addition of mold-releasing substances.

In addition, as mentioned above, methods using insulating magnetic toner are attracting attention as a developing method, and efforts are being made to actively develop toner materials that are compatible with this developing method, especially materials that take into account the charge stability of insulating toner. is being carried out.

Charge control of an insulating toner using a single-frequency charge is generally carried out by incorporating a charge control substance, such as a metal complex dye, into the toner, or by introducing a specific functional group into the toner resin body. However, styrene resins, especially styrene-acrylic copolymer resins, which have been widely used as toner resins in recent years, inherently have negative chargeability as toners, and in addition, charge control agents with negative control properties are used. It is generally put into practical use by using it in combination.

Examples of insulating toners using the above-mentioned styrene/acrylic resins include Japanese Patent Publication No. 58-25265 and Japanese Patent Application Laid-open No. 56-16144, but these resins and toner compositions depend on their developability, Although the heat fixability is at a practical level, it is difficult to use under harsh environmental conditions or usage conditions.
For example, they are unsatisfactory in developability under high humidity or fixing power in high-speed processes. Recently, there has been an extremely strong demand for improving the reliability of copying machines in particular. Additionally, copying machine manufacturers are currently striving to develop and produce copying machines with longer lifespans from the viewpoint of maintenance-free use. Under these circumstances, a review of the toner properties revealed that the conventional insulating toner using styrene/acrylic resin as a binder resin was insufficient.

Research is still being conducted on binder resins for toners that are suitable for hot roller constant adhesion methods, and up to now, binder resins with various components and resins whose molecular weight has been adjusted mainly by crosslinking or other means have been developed. Although various efforts have been made, it is still difficult to say that the ideal form of the binder resin has been clearly defined.

In addition, in order to improve the fixing properties, especially the offset resistance properties, efforts have been made to add low molecular weight polyolefins, their base plasticizers, etc.; There are various problems such as impairing the fluidity of the toner and promoting toner aggregation, and no good one has been found yet. However, the most important thing is to improve the resin component of the binder resin, and it is thought that there is a limit to the improvement that can be made using the above-mentioned auxiliary agents. As mentioned above, some attempts have been made to adjust the molecular weight of the binder resin, but the extent to which it is better to apply crosslinking to broaden the distribution is unclear, and it is not clear what specific range is best. . Until now, the molecular weight distribution has generally been a single peak, and the range of the average value and the width of the distribution have been expressed in terms of dispersion (weight average molecule it/number average molecular weight by GPC, MY/MN). However, with binder resins in this category, the overall performance of dry toner that is constantly worn by a hot roller, which requires a variety of complex performances as described above, is mainly focused on fixing characteristics and development. There is no sexual satisfaction.

[Purpose of the invention]

An object of the present invention is to provide a toner for electrostatic image development that solves all of the above-mentioned problems. That is, the main object of the present invention is to provide a negatively charged toner having extremely stable polarity and a long life.

Another object of the present invention is to provide a toner for developing electrostatic images that has excellent fluidity, does not cause aggregation, and has excellent impact resistance.

Another object of the present invention is to provide a toner for developing electrostatic images that has good fixing properties, good anti-offset properties, and is suitable for constant fixation on a heated roller.

Yet another object of the present invention is to provide a toner for developing electrostatic images with less adhesion to a carrier, a toner holding member, or the surface of a photoreceptor.

[Structure of the invention]

In order to achieve the above object, the present inventors have conducted intensive research and found that by using a resin as a binder resin that is polymerized using a specific initiator and has a specific molecular weight distribution,
It has been found that a toner for developing electrostatic images having excellent charge stability and very good fixing properties can be obtained.

That is, the toner for developing electrostatic images of the present invention (hereinafter referred to as toner) contains (capacitated styrene and its derivatives, (B) acrylic ester and/or methacrylic ester, (C) malein dispersion) as a binder resin. or esters thereof, and the monomer or monomer mixture is heated to a temperature at which the half-life temperature at 10 hours is 110°C.
In the presence of a polymerization initiator that is more than 10% of the polymerization initiator,
It is characterized by containing a product obtained by copolymerization at a temperature 0 to 40°C higher than the half-life temperature.

The main feature of the toner of the present invention lies in the binder resin used, particularly the polymerization initiator used to polymerize or copolymerize at least one of the monomers (A), (B), and (C).

The present inventors have found that when the 10 hour half-life temperature of the polymerization initiator used differs, the charge strength of the toner using the copolymer differs.

That is, a toner using a vinyl copolymer obtained using a polymerization initiator whose 10 hour half-life temperature is lower than 110°C has a small charge amount and is unstable; A copolymer using a polymerization initiator with a temperature as high as 110° C. can be used alone as a binder for a toner to obtain a toner exhibiting extremely good and strong negative chargeability. Note that the amount of charge of the toner of the present invention is determined by Coulter.
Using a counter (manufactured by Coulter Co., Ltd.), the amount of triboelectric charge ( It was measured using a method of measuring μc/ri.

Examples of the polymerization initiator having a 10 hour half-life temperature of 110°C or higher include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, α
, α'-bis(1,-butylperoxydiimprovil)benzene, t-butylperoxycumene, di-t-butylperoxide, 2,5-dimethyl-2,5-di(t
-butylperoxy)hexyne and other organic peroxides can be used.

Component Fi(4) of the binder resin used in the toner of the present invention
It consists of a group of six monomers: styrene and its derivatives, (B) acrylic acid ester and/or methacrylic acid ester, and (C) maleic acid or its ester. Specifically, (A) is styrene, α-methylstyrene, p
-chlorostyrene, etc. (B) includes methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, As (C), maleic acid, butyl maleate, methyl maleate, dimethyl maleate, etc. are used.

The ratio of each group of monomers constituting the binder resin of the present invention is 50 to 80 mol %, 5 to 30 mol % (B),
It is preferable that (C) be 10 to 40 mol.

The binder resin used in the toner of the present invention is a polymerization initiator having a 10 hour half-life temperature of 110° C. or higher by adding the above-mentioned mixture of seven monomers in the presence of an organic solvent capable of dissolving the copolymer of these monomers. It is obtained by solution polymerization at a polymerization reaction temperature that is 0 to 40°C higher than the 10 hour half-life temperature of the polymerization initiator, and the organic solvent is one that is suitable for the polymerization reaction temperature. Select and use.

Further, by slightly crosslinking the binder resin used in the toner of the present invention, the fixing properties and anti-offset properties of the resulting toner are improved. There are various methods for slightly crosslinking, but for example, when obtaining the copolymer which is the binder resin of the present invention, there is a method in which a crosslinkable monomer is added to the monomer mixture and then copolymerized. It is valid.

As the crosslinking monomer, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, such as ethylene glycol diacrylate,
Carboxylic acid esters and divinyl compounds having two double bonds, such as ethylene glycol dimethacrylate and 1.6 butanediol dimethacrylate; divinyl compounds such as vinyl ether, divinyl sulfide, divinyl sulfone, and six or more double bonds; Compounds having vinyl groups are used alone or as a mixture. Among them, divinylbenzene is effective.

Such crosslinkable monomers are used in (4)(B) (C
) per 100 parts by weight of the monomer mixture. Q, 0
．． It is contained in an amount of 2 to 5 parts by weight, preferably 0.8 to 2.5 parts by weight.

Another feature of the binder resin used in the toner of the present invention is its molecular weight distribution. That is, the molecular weight distribution of the binder resin used in the toner of the present invention has at least three maximum points or shoulders in a chromatogram measured by gel permeation chromatography, and the molecular weight distribution corresponds to the maximum point with the lowest molecular weight. Molecule i-Ma is 200
It is characterized in that Mc/Ma, which is a ratio of the molecular weight Me corresponding to the maximum point with the highest molecular weight to the molecule JIMa corresponding to the maximum point with the lowest molecular weight, is in the range of 0 to 80,000 and is 150 or more. Furthermore, according to a preferred embodiment of the present invention, the three maximum points or shoulders have a molecular weight of 10
5-8 x 104 (area A), molecular weight 3 x 105-1
06 (area B), molecular weight 3 x 106 or more (area C)
When there is at least one in each region and the height is HaSHblHc, the ratio of these is
Ha*Hb: Hc=j:0.2~1.0:0
．． It is characterized by being 1 to 0.6.

When using a binder resin having a specific molecular weight distribution as described above, it is possible to obtain a toner that has good fixing properties, excellent offset resistance, and is suitable for fixed fixation on a hot roller for the reasons described below. It is something that can be done.

That is, among the components that give these molecular weight regions ASB and C, those in region B basically satisfy the various characteristics of a heat-fixed dry toner. On the other hand, area A is extremely important in order to improve the fixing force to the transfer material by heat-pressure welding). Those in the range C have extremely good toner offset resistance of the roller when the heated roller is fixed, and also improve the peelability of the fixed transfer material from the roller, as well as improve the toner copying durability and the environment. Dependency also plays an important role.

Furthermore, in order to improve the fixing force by heat pressure welding, and at the same time improve the roller offset phenomenon during constant fixation of heat roller 2, and at the same time satisfy copying durability and environmental dependence, the range of area C must be maximized. The ratio Mc/Ma between the point molecular weight Me and the maximum point molecule i'Ma in the range of region A, and the heights HaSHb and HeO of the maximum points in the three regions are very important factors.

Here, the height H of the maximum point or shoulder is the length of the perpendicular line from each maximum point or shoulder of the chromatogram chart on the PC to the baseline. It is obtained by taking the curve point as a reference and drawing a perpendicular line to the baseline.

As mentioned above, blood is related to the fixing of the toner to the transfer agent or the minimum temperature at which it can be fixed, and Me is related to the high temperature offset resistance of the toner to the heated roller or the high temperature offset starting temperature.

Therefore, it is preferable to make Mc smaller to ensure a lower fixing temperature, and at the same time to make Mc larger so as not to impair high temperature offset resistance, and to widen the temperature range in which toe fixation is possible. From this point of view, when Mc/Ma is 150 or more, the fixable temperature range is wide, and the heat roll fixing has good comprehensiveness, that is, it can be fixed sufficiently with a relatively low capacity heat source, and there is almost no offset of the toner to the heat roll. Various properties such as smooth paper ejection from the rollers can be obtained. Further, in terms of durability, an improvement can be obtained by increasing Mc.

Furthermore, the maximum point in region A, which is a factor that determines the fixing force due to heat pressure welding, that is, the minimum temperature that can be fixed by a heat roller, is that the lower the molecular weight, the lower the fixing temperature, which is preferable in terms of fixing force, but conversely The roller offset and transfer paper peelability are poor. Therefore, the molecular weight Ma at this maximum point is preferably from 2,000 to 80,000, and more preferably from 5,000 to 20,000.

Further, the maximum point of the high molecular weight portion in region C is important for anti-offset properties, and as mentioned above, the above-mentioned region size exhibits favorable characteristics at ℃ which complement each other. By adjusting the balance between the tabs, areas A and C, effective fixing force and good anti-offset properties can be achieved. For that purpose,
The ratio of molecular weights at each maximum point, MC/Ma, is required to be 150 or more.

Furthermore, in order to improve the conventional problems, molecular weight regions A and B
It is also important that the height ratio Ha/Hb/HC of each maximum point of , C works extremely effectively. If the molecular weight Ma and MbSMC at the maximum point are the qualitative factors of the binder,
The height of the maximum point HaSHb.

Hc is a quantitative fx element, and the balance between Ha and HbSHc is important for toner heat fixing properties, durability, and manufacturing workability such as heat kneading and pulverization.

Ha:Hb:Hc is preferably 1:0.2
-10: 0.1-0.6, more preferably i:o, 4-0.8:CL15-0.4. If Ha is too large compared to Hb, the releasability of the offset transfer paper to the roller during fixing will be poor, the cohesiveness will increase, and the durability of the toner will likely deteriorate. On the other hand, if it is too small, the toner fixing properties will be insufficient. In addition, if Hc is too large compared to Hb, the toner will have poor flow properties during heating and will not be sufficiently fixed, and during toner production, the crushability will be extremely poor and the particle size of the toner will not be suitable. It will no longer be effectively crushed. On the other hand, if it is too small, sufficient non-offset and peelability cannot be ensured during fixing.

The binder resin used in the toner of the present invention has three molecular weight regions A.
, B, and C each have a maximum point or a shoulder, and the maximum point molecular weight Ma, Mc is Ma = 1000 to 80000, Mc/
'Ma≧150, but the chromatogram showing the molecular weight distribution differs slightly depending on the measurement method. Therefore, in the present invention, each value is defined by the chromatogram and molecular weight numerical value obtained based on the following measurement method.

That is, Takafusa Seisakusho H8G1 and H8G40 were used as columns.
, H8CN3 was set in series on a gel ξ-meation chromatograph LC-3A at an oven temperature of 40°C, and tetrahydrofuran (THF) was added as a solvent at a fluid pressure of 90 Kq/1 m2 (under D conditions, at a flow rate of t7117 per minute). 500 mL of THF sample solution with a concentration of 0.49/dl.
Inject μl. The sample is dissolved in THF, filtered with a membrane filter (TM-2P 0.45 μm manufactured by Toyo Roshi KK), and injected 1 hour after dissolution.

The molecular weight of the sample was measured using polystyrene standard samples (manufactured by Pressure Chemical) at 6 points (2 million, 600,000, 233,000,
50,000, 17,500, 2,200) to create a calibration curve and determine the molecular weight. The standard sample was prepared by mixing equal amounts of 3 of the above 6 points: 2,000,000, 26,60,000, and 17,500.
A THF solution was prepared at a concentration of E/dl, and 500 μl was injected 24 hours after dissolution. Also, 600,000, 50,000, 2
Similarly, the three points of 200 were mixed in equal amounts to give 0.411/d11.
A THF solution was prepared and injected in the same manner. The detector used was a differential refractometer RID-2A.

When a general polymerization method is used, the molecular weight distribution usually has a single peak. However, the binder resin used in the toner of the present invention has a specific molecular weight distribution as described above by copolymerizing it using a specific polymerization initiator at a specific polymerization reaction temperature. can be obtained.

Furthermore, although the binder resin used in the toner of the present invention exhibits slightly different values depending on the type and composition of monomers contained as components, the softening point according to the ring and ball method is approximately 1.
The temperature is preferably 00 to 150°C, and a glass transition point of 40 to 80°C is effective. More preferably, the glass transition point is 50 to 65°C.

If the softening point is lower than 100°C, photoconductor contamination due to toner film formation and toner durability deterioration are likely to occur;
If the temperature exceeds 0° C., fixing efficiency decreases due to an increase in fixable temperature, and pulverization efficiency also decreases. When the glass transition point is lower than 40° C., thermal aggregation and caking are extremely difficult to occur during toner storage, and aggregation troubles are also likely to occur in copying machines. On the other hand, if the glass transition point exceeds 80° C., the thermal fixing efficiency will deteriorate.

Furthermore, the MI of the binder resin used in the toner of the present invention
(Melt index) is preferably in the range of 0.25 to 5, and more preferably in the range of 1.2 to 4 under the measurement conditions of 125° C. and 216011. If MI is smaller than 0.5, it will lead to an increase in toner fixing temperature and a decrease in fixing efficiency, while if MI is larger than 5,
On the contrary, this is because the high temperature offset phenomenon during fixing becomes more likely to occur.

In addition, the softening point (sp) by the ring and ball method is JIS K2
531, and the melt index (MI) is JI.
Measured using SK7210. Glass transition point (Tg)
was measured using a differential thermal analyzer DTA-30M at a heating rate of 15° C./min and samples 10 to 15 jy.

In addition to the binder resin component described above, the toner of the present invention contains, for example, silicone resin, polyester, polyurethane, polyamide,
Epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin,
It may also contain aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc.

In the toner of the present invention, a colorant or, if necessary, an auxiliary agent such as a charge control agent can be dispersed in the binder resin.

As the colorant, dyes and pigments conventionally used in electrostatic image toners may be used, but when used as a color toner, the following dyes and pigments are particularly preferred.

That is, for yellow toners, for example, benzidine yellow (C, 1, Pigment Yellow 12, etc.), monoazo dye R (C, K, Nrubento Yellow 16, etc.), nitrophenylamine sulfonamide' (C0I).

For example, quinacridone magenta pigments (C, 1,
pigment red 122), anthraquinone dyes,
For cyan toners such as diazo dyes (C, R, Solvent Red 19), copper 7 talocyanine (C,
I, Pigment Blue is), Indan Stremblin, Te.

When the toner of the present invention is a magnetic toner, magnetic particles are contained in the toner. Magnetic particles may be any material that exhibits magnetism or can be magnetized, such as metals such as evaporator, iron, manganese, nickel, cobalt, and chromium, magnetite, hematite, various 7E-poorites, manganese alloys, and other strong particles. Magnetic alloys, etc., have an average particle size of about 0.
A fine powder of 0.05 to 5 μm (more preferably 0.1 to 2 μm) can be used. The amount of magnetic particles contained in the magnetic toner is 15 to 70% by weight (more preferably 25 to 45%) of the total weight of the toner.

Alternatively, 10 to 40% by weight of hydrophobic silica or the like may be contained in the toner as a fluidity improver. Of course, this fluidity improver may be used by being mixed outside the toner particles, and the amount added in that case is 0.1 to 5% by weight (toner weight fit).

The toner of the present invention is composed of a binder resin, magnetic fine particles, a colorant, a charge control agent, etc., and has strong resistance to the load applied in the developing device, and does not deteriorate due to being crushed in a durability test. Never. However, because the toner particles are hard, materials used in the copying machine, such as the surface of the photoreceptor, the cleaning member, the surface of the developing sleeve, the carrier particles, etc., may be easily abraded or scratched. In such a case, the melt viscosity at 140°C may be 10
~1060PS, preferably 102-105 CPS
It is preferable to add a small amount of an olefin homopolymer or olefin copolymer. When adding this additive, if it is added outside the toner particles, the weight ratio with the toner will change during repeated use and the development characteristics will change, so it is recommended not to include this additive in the toner. good. Olefin polymer with the above viscosity range is added to the developer powder.
．． When 5 to 5 weight i-% is contained, the dispersibility and compatibility of pigments and magnetic fine particles with toner are improved, and the surface of the photoreceptor,
The negative effect on cleaning members, etc. is reduced. Examples of the olefin-based homopolymer or copolymer used herein include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ether acrylate copolymer, and polyethylene skeleton There are ionomers and the like, and the above-mentioned copolymers preferably contain 50 moles or more (more preferably 60 moles or more) of olefin monomers.

The melt viscosity was measured using the Brookfield method, using a B-type viscometer equipped with a small sample adapter.

Next, an electrophotographic method to which the toner of the present invention is applied will be explained.

The process of developing the electrical latent image with toner includes the above-mentioned magnetic brush method, cascade development method, powder cloud method, the method using conductive magnetic toner described in U.S. Pat. No. 5,909,258, and There is a method using a high-resistance magnetic toner, which is described in JP-A No. 53-31136. A developer using the toner of the present invention is also suitable for a developing method using a so-called one-component developer containing magnetic particles.

The process of transferring the developed image formed using the toner of the present invention to the transfer target includes a corona transfer method, a bias transfer method, an electrostatic transfer method such as a method using a conductive roller, a method of transferring using a magnetic field, etc. is used.

Furthermore, a blade cleaning method, a fur brush cleaning method, or the like is applied to the step of removing residual toner on the photosensitive layer or the insulating layer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Xylene 4209 was placed in a 214-day round bottom flask equipped with a thermometer, a nitrogen inlet tube, a stirring bar, and a water-cooled Dimroth type condenser, and the temperature was raised to the xylene reflux temperature in an oil bath equipped with a heater.

The above mixture was added dropwise to this under reflux over 3 hours and 20 minutes. After the dropwise addition was completed, a polymerization reaction was carried out for 4 hours, and then the solvent was removed by ordinary distillation under reduced pressure to obtain a polymer.

Next, the materials consisting of were mixed in a Henschel mixer and melted and kneaded in a roll mill.

After cooling, it was coarsely pulverized using a hammer mill, and then finely pulverized using a supersonic jet pulverizer. The obtained product was classified using an air classifier, and particles of approximately 5 to 35 μm were collected to form a classified toner product. To 100 parts by weight of this product, 0.4 parts by weight of hydrophobic colloidal silica powder was added and mixed to obtain a toner. The tribocharge amount of this toner is -15μc/I
Met.

Next, images were created using this toner.

To produce an image, a commercially available plain paper copying machine (NP-500RE manufactured by Canon) was used, and the image was fixed on designated copy paper by standard heat roll fixing.

The initial copy image was a good image with no fog, and even after a running test of 50,000 sheets, a good copy image with sufficient image density was obtained. Furthermore, no scratches or toner fusion were observed on the photosensitive drum, cleaning unit, developing sleeve, etc.

In addition, the fixing properties are very good, with no problems in the fixing power in a running test of 50,000 sheets, the amount of offset is small, and there are almost no jams caused by paper clinging to the rollers during paper ejection. Overall, it was satisfactory. Furthermore, even in a continuous copying test at the start of work in a 10°C environment, no tumbles due to insufficient fixing power occurred.

Example 2 A copolymer was obtained by carrying out a polymerization reaction in the same manner as in Example 1 except that the above formulation was used.

The following materials were melted, mixed, and pulverized in the same manner as in Example 1 to obtain a toner with a particle size of 5 to 30 microns. For 100 parts of this toner, add iron powder carrier (Japanese iron powder EFV 3
00-500) were mixed to obtain a developer. The triho charge amount of the toner in this developer was -13 μC/y.

Next, apply this developer to a dry copying machine (product name: NP manufactured by Canon).
5000), a clear, fog-free image was obtained. Incidentally, the image reflection density was 1.45 and the fog reflection density was 0.02.

In addition, as a durability test, a copy run of 100,000 copies was performed, and copies were obtained that were comparable to the initial images.

Examples 6 to 9 and Comparative Example 1 Copolymers were produced in the same manner as in Example 1, except that the monomers, crosslinking monomers, and polymerization initiators in Example 1 were changed as shown in the table below. This was used to make a toner.

The results are listed in the table below along with the results of Example 1.2.

Comparative Example 2 The same procedure as in Example 1 was carried out except that monobutylmaleic acid was not added, but a practical image could only be obtained at about 500
It was 0 degrees. The amount of triboelectric charge of this toner is -6μ
The value was as low as c/g.

Comparative Example 3 When the same procedure as in Example 1 was carried out except that divinylbenzene was not added, the image was almost as good as in Example 1, but an offset phenomenon immediately appeared.
The offset toner that could not be removed by the cleaning web of the fixing device after copying several dozen sheets appeared as a black line on the image when the web was removed, making it completely impractical. When we investigated the fixing properties in detail using a separate fixing device, we found that although the fixing point was slightly lower than that of Example 1, it showed poor thermal characteristics with offset appearing immediately after fixing and no practical fixing range at all. I understand.

[Summary of effects of the invention]

The toner of the present invention is extremely stable, has strong negative chargeability, has excellent fluidity, does not cause agglomeration, and has excellent impact resistance. In addition, the molecular weight distribution of the binder resin used in the toner of the present invention has a desirable distribution from the viewpoint of fixing properties and anti-offset properties, and the toner of the present invention using such a binder resin can be used at a constant temperature with a heated roller. It can be used as a toner suitable for the printing method.

Claims (3)

[Claims] (1) Consisting of at least a binder resin and a colorant, and the binder resin comprises (A) styrene and its derivatives, (B)
acrylic ester and/or methacrylic ester,
and (C) a monomer mixture consisting of at least one monomer selected from each of the groups (A) to (C) of maleic acid and its esters, which has a half-life temperature of 1 for 10 hours.
A toner for developing an electrostatic image, characterized in that it is obtained by copolymerizing in the presence of a polymerization initiator having a temperature of 10°C or higher at a temperature from 0 to 40°C higher than the 10-hour half-life temperature of the polymerization initiator. . (2) Electrostatic image development according to claim (1), wherein the binder resin is obtained by adding a crosslinkable monomer to a monomer mixture and copolymerizing the mixture. toner. (3) The polymerization initiator is dicumyl peroxide, 2,5-
Dimethyl-2,5-di(t-butylperoxy)hexane, α,α'-bis(t-butylperoxydiisopropyl)benzene, t-butylperoxycumene, di-t
-butyl peroxide, and 2,5-dimethyl-2,
The toner for developing an electrostatic image according to claim 1 or claim 2, wherein the toner is selected from the group consisting of 5-di(t-butylperoxy)hexyne.