JPS5914747B2 - Toner for developing electrostatic images - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a toner for developing electrostatic images, and particularly relates to a toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc. More specifically, even in the case of a pressure-bonding heating method using a heated roller, no offset phenomenon occurs, the resolution and sharpness are good, and fogging can be suppressed, and it has good fluidity and storage stability. The present invention relates to a toner for developing an electrostatic image. Methods for developing electrostatic images are broadly divided into liquid development methods that use a developer in which colorants such as various pigments and dyes are finely dispersed in an insulating solvent, cascade methods, and bristle brush methods. There is a so-called dry development method that uses a fine powder developer called dry toner, which uses a natural or synthetic resin and a colorant such as carbon black dispersed in a natural or synthetic resin. The invention relates to a toner used in the latter dry development method. Conventionally, toner for dry electrostatic image development has generally been made by melt-kneading a pigment such as carbon black in a thermoplastic resin to form a uniform dispersion, and then using an appropriate pulverizer35 to reduce the particles required for the toner. It is manufactured by a method of pulverizing it into a powder of a diameter (see, for example, Japanese Patent Application Laid-Open No. 51-3244). Although the toner produced by this method can have various excellent properties, it also has various drawbacks. For example, there are restrictions on the use of raw materials. That is,
Since the process of melting and pulverization is required, it is necessary to fluidize at an appropriate temperature to achieve a state in which colorants such as pigments can be mixed uniformly, and the equipment used to crush the mixture system must be able to produce the desired particles. It is required to be able to process the diameter at a considerable speed. However, using materials that are easy to crush, on the other hand,
Furthermore, it is easily crushed, leading to drawbacks such as staining of equipment and fogging of images. In addition, if a material that is easily melted is used, the toner may become caked and the surface of the photoconductive layer may become dirty (
This also leads to toner filming). In addition, coloring agents such as pigments that were buried in the resin may spill onto the surface during crushing, resulting in local unevenness of triboelectric charging characteristics.Furthermore, depending on the type of coloring agents such as pigments, Problems may also arise in terms of moisture resistance, etc. Another major disadvantage is that the shape of toner produced by the pulverization method is amorphous, which tends to cause aggregation (blocking) between toner particles, resulting in poor stability during toner storage and dispensing during toner supply. Characteristics, transfer efficiency,
Furthermore, it may affect the sharpness of the developed image and may act as an undesirable factor in the cleaning characteristics in the case of repeated use. , has become a problem. For toner produced by these pulverization methods, for example, Japanese Patent Publication No. 36-10231, Japanese Patent Publication No. 47-51830, Japanese Patent Publication No. 5
No. 1-14895, No. 5317735, No. 53-17
As described in Japanese Patent Application No. 736 and No. 53-17737, toners produced by the so-called polymerization method have been proposed. These are manufactured by the so-called suspension polymerization method, in which a mixture of polymerizable monomers, polymerization initiators, colorants, etc. is suspended in water and polymerized to directly manufacture the toner. What they all have in common is that they are all close to spherical in shape. An example of this is that a coloring agent such as a pigment is included inside the toner. The toner obtained by this polymerization method is
Although the drawbacks of the toner obtained by the above-mentioned pulverization method could be compensated for, a new drawback has arisen in that the toner deteriorates rapidly due to changes in the amount of charge during continuous copying. In other words, for the substantially spherical toner obtained by the polymerization method, during continuous copying, the ratio of the large particle size toner used for development is
This is more noticeable than with amorphous toner, and the change in charge amount during continuous copying is correspondingly large, giving unfavorable results in terms of long-run characteristics. Particularly when recycled toner is used, disadvantages such as a decrease in image density and the occurrence of fog appear. In electrostatography, fixing is performed after developing an electrostatic charge image using toner. Generally, fixing is performed by developing an electrostatic charge image onto a photoconductive photoreceptor or electrostatic recording medium that carries the electrostatic charge image. The toner image thus obtained is either directly fused, or the toner image obtained by development is transferred from the photoconductive photoreceptor or electrostatic recording medium onto a transfer sheet such as paper, and then This is done by fusing it onto a transfer sheet. At that time, the toner image is fused by either contact with solvent vapor or heating, and the heating methods generally include a non-contact heating method using an electric furnace and a pressure bonding heating method using a heating roller. . The pressure heating method using a heating roller usually performs fixing by passing the toner image surface of the sheet to be fixed through pressure contact with the surface of the heating roller whose surface is made of a material that has releasability for toner. In this method, the surface of the heating roller and the toner image surface of the fixing sheet come into pressure contact, so the toner image is fused onto the fixing sheet. Since it has extremely good thermal efficiency and can perform fixing quickly, it is particularly suitable for transfer-type electrophotographic copying machines intended for high-speed copying. However, in this method, the surface of the fixing roller and the toner image come into pressure contact with each other in a heated and molten state, so a part of the toner image adheres to the surface of the fixing roller and is transferred, and is then reprinted onto the next sheet to be fixed. This transfer may cause a so-called offset phenomenon, which may cause stains on the sheet to be fixed. Therefore, one of the essential requirements in the heated roller fixing method is to prevent toner from adhering to the roller surface. Conventionally, in order to prevent toner from adhering to the surface of the fixing roller, for example, the roller surface was made of a material such as a fluorine-based resin that has excellent release properties against toner, and the surface was further coated with an offset prevention liquid such as silicone oil. The roller surface is coated with a thin film of liquid by supplying liquid. Although this method is effective in preventing toner offset, the offset prevention liquid generates an odor when heated and requires a device to supply the offset prevention liquid. However, since the mechanism of the copying device becomes complicated and high precision is required to obtain stable results, the copying device becomes expensive. However, if offset prevention liquid is not supplied, toner will adhere to the surface of the fixing roller and an offset phenomenon will occur, so despite these drawbacks, supply of offset prevention liquid is unavoidable. is the current situation. On the other hand, techniques have been proposed in which various additives are used in toner for the purpose of preventing offset. For example, there are techniques described in Japanese Patent Publications No. 51-11492 and No. 5147622, and these techniques are effective in the kneading method, but in producing toner by suspension polymerization, polymerizable monomers are Since the polymerization reaction is carried out in a state where all the various additives, including colorants, are contained, it is necessary to select compounds that do not affect the polymerization reaction.
There are restrictions such as the inability to use compounds that are difficult to dissolve in monomers. SUMMARY OF THE INVENTION An object of the present invention is to provide a new toner for developing electrostatic images that overcomes the various drawbacks of the amorphous toner and substantially spherical toner described above. One of the objects of the present invention is that even when using a fixing roller to which no offset prevention liquid is supplied to the surface of the fixing roller, it is possible to perform efficient and good heat roller fixing without causing toner offset phenomenon. The present invention provides a toner for developing electrostatic images. Another object of the present invention is to provide a toner for developing electrostatic images that has good fluidity and excellent storage stability. Still another object of the present invention is to provide a toner for developing electrostatic images that has good resolution and sharpness and causes less fog. Another object of the present invention is to provide a toner for developing electrostatic images with a good transfer rate. Still another object of the present invention is to provide a toner for developing electrostatic images with small changes in charge amount during continuous copying. Still another object of the present invention is to provide a toner for developing electrostatic images with good recycling characteristics. The above-mentioned objects of the present invention are to
It has a substantially spherical shape with a ratio of 1.00≦a/b≦1.05, a particle size of 1 to 30 microns, and a main particle size of ±3
Contains 70% by weight or more of particles within microns, and contains α/β monounsaturated ethylenic monomer as a constituent unit as the main resin component, and is produced by suspension polymerization and its weight average This is achieved by an electrostatic image developing toner (hereinafter referred to as the toner of the present invention) having a molecular weight of 80,000 or more. While researching toner production methods using suspension polymerization, the present inventors analyzed the resins of toners produced under various polymerization conditions, and found that by using resins with molecular weights within a certain range, It was discovered that this method is effective in preventing offset, etc., and the present invention was completed. In other words, if the molecular weight of the resin produced is small, an offset phenomenon will occur during fixing, causing the paper to wrap around the roller, and the toner may aggregate, impairing fluidity and making it difficult to develop. They discovered that there were times when they could no longer provide services. The present invention will be explained in detail below. In general, toner is composed of a resin component, a colorant component consisting of a pigment or dye, and additive components for adjusting the physical properties and development characteristics of the toner, including a plasticizer and a charge control agent. As components, various natural or synthetic resins and polymers may be used alone or in appropriate mixtures. The toner for developing electrostatic images according to the present invention contains a resin containing an α/β unsaturated ethylenic monomer as a constituent unit and has a weight average molecular weight of 80,000 or more (hereinafter referred to as the resin of the present invention). The toner is characterized in that it contains the resin of the present invention as a main resin component of the toner. That is, by containing the resin of the present invention in the toner in an amount of at least about 60% by weight, preferably at least 75% by weight based on the total resin components of the toner, the above objects of the present invention are achieved, and in particular, The toner offset phenomenon with respect to the heat fixing roller is effectively prevented. The first feature of the present invention is that it contains an α/β monounsaturated ethylenic monomer as its main component. It may be any copolymer made of two or more types of monomers, or it may be a mixed polymer obtained by appropriately combining such homopolymers or copolymers. A second feature of the present invention is that the weight average molecular weight of the resin of the present invention obtained by suspension polymerization is 80,000 or more. When the resin of the present invention is composed of one type of homopolymer or copolymer, this value is the value that each of these polymers has, and when the resin of the present invention is a mixed polymer, this value is the value that each of these polymers has. , is the value for the entire mixed polymer. In other words, in the case of a mixed polymer, the weight average molecular weight of each individual polymer to be mixed does not necessarily have to be 80,000 or more, and the value of the entire mixed polymer obtained by mixing must be within the above range. It is fine as long as it is inside.
As mentioned above, the resin of the present invention has a weight average molecular weight (IVw) of 80,000 or more. Note that the value of Mw can be measured by various methods, and may vary slightly depending on the measurement method. Therefore, in the present invention, the value of Mw is defined as that measured by the following measuring method. In other words, each of these values is determined by gel vermi- cation chromatography (
GPC) under the conditions described below. At a temperature of 40° C., a solvent (tetrahydrofuran) is flowed at a flow rate of 1.2 ml per minute, and a sample solution of tetrahydrofuran with a concentration of 0.27/20 d is injected at 3η as the sample weight to perform measurements. When measuring the molecular weight of a sample, the molecular weight distribution of the sample is measured using several types of monodisperse polystyrene standard samples, and the measurement is performed so that the logarithm of the molecular weight and the count number of the calibration curve are in a straight line. Select conditions.
The reliability of this measurement was determined using the NBS7O6 polystyrene standard sample [Mw=28.8×
104, Mn (number average molecular weight) = 13.7 x 104, M
w/Mn=2,11] pulse CMn is 2.11±0.10
Confirm by: Any GPC column may be used as long as it satisfies the above conditions, such as TSK-GEL. There is GMH6 [manufactured by Toyo Soda Co., Ltd.]. Examples of the α/β monounsaturated ethylenic monomer used as a constituent component of the resin of the present invention include styrene, o
-Methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2
・4-dimethylstyrene to p-n-butylstyrene, p-
p-n-hexylstyrene to tert-butylstyrene,
p-n-octylstyrene, p-n-nonylstyrene,
Pn-decylstyrene, p-n-dodecylstyrene, p
- Styrenes such as methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene, vinylnaphthalenes, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene, vinyl chloride, Vinyl esters such as vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl alkurate, propyl acrylate, acrylic n-octyl acid,
Dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate α-methylene aliphatic monocarboxylic acid esters such as aminoethyl, diethylaminoethyl methacrylate, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc. Vinyl ethers, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl getone,
Examples include N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidene. Note that the resin of the present invention also includes those formed by acetalizing a polymer, such as polyvinyl acetals such as polyvinyl butyral. Among these monomers, resins containing α-methylene aliphatic monocarboxylic acid esters or aromatic vinyl compounds and α-methylene aliphatic monocarboxylic acid esters as main constituents are particularly effective in the present invention. A resin containing both of these monomer components and, in particular, at least about 30 mol% of styrene not only does not cause the toner offset phenomenon, but also has the triboelectrification properties and additive properties required for toners. It is particularly effective in the present invention because it has excellent properties in the manufacturing process such as uniform dispersibility of the agent. In the present invention, when the ratio of the long diameter (a) to the short diameter (b) of the toner particles exceeds 1.05, the toner particles are substantially the same as conventional irregularly shaped toners, and the fluidity, transfer efficiency, resolution, sharpness, etc. When compared with a substantially spherical toner in which 1≦a/b≦1.05, it gives unfavorable results. Further, if toner with a particle size of less than 1 micron is present, fogging will occur more frequently, and conversely, if toner with a particle size of more than 30 microns is present, unfavorable results will be produced in terms of image distortion and resolution. Furthermore, if the amount of toner with a main particle size within ±3 microns is less than 70% by weight, especially 65% by weight or less, the change in the amount of charge during continuous copying becomes large, giving unfavorable results in terms of long-run characteristics and toner recycling characteristics. In addition, in this specification, the weight % of toner having a main particle size within ±3 microns
means that if the average particle size of the toner is X microns,
It represents what percentage by weight of toner from -3 to X+3 is included in the total toner. The toner of the present invention is manufactured by a suspension polymerization method. That is, a polymer composition consisting of a polymerizable monomer, a colorant, a charge control agent, a polymerization initiator, etc. is dispersed in water, and the mixture is dispersed at room temperature in the presence of a dispersion stabilizer using a dispersing machine capable of applying high-speed shearing at room temperature. ~10000r. p. Suspend by high-speed stirring for 100 m, and when the required particle size distribution is achieved while observing with a microscope, switch to low-speed stirring, for example, 100 to 800 rpm, raise the temperature to 40 to 85° C., complete polymerization, wash with water, The toner of the present invention is obtained by filtering and drying. When producing the toner of the present invention, in order to make the weight average molecular weight (Mw) of the resin of the present invention 80,000 or more,
Various amounts and conditions such as the type and combination of polymerizable monomers, the type and amount of colorant such as carbon black, other additives, amount of polymerization initiator, polymerization temperature, polymerization time, etc. However, it can be determined, for example, as follows, with reference to the fact that, in general, when the amount of polymerization initiator is large and the polymerization temperature is high, the weight average molecular weight becomes small. That is, after fixing the amount of monomer, colorant, and other additives necessary for the toner to a certain amount, the amount of polymerization initiator,
By varying the polymerization temperature, the desired weight average molecular weight can be obtained by performing several experiments to determine the conditions. On the other hand, particle size and particle size distribution are controlled by the degree of shearing, the time of shearing, the shape of the disperser, the type and amount of dispersion stabilizer used, the ratio of monomer to water, the viscosity of the polymer composition, etc. It is known that the larger the shear rate, the larger the amount of dispersion stabilizer used, the smaller the ratio of polymerization composition to water, and the lower the viscosity of the polymerization composition, the smaller the particle size produced. It is being However, these factors interact with each other, and it is difficult to control all factors, so we applied shear while observing with a microscope and confirmed that the particle size and particle size distribution required in the present invention were achieved. The most suitable method for obtaining the toner of the present invention is to then switch to ordinary stirring and polymerize. Any coloring agent such as a pigment or dye can be added to the toner of the present invention, if necessary. These colorants are known and include, for example, carbon black (including prepolymerized or grafted carbon black). Nigrosine dye, aniline blue, calco oil full, chrome yellow ultramarine blue, Dupont oil red, quinoline yellow, methylene chloride, phthalocyanine blue, malachite green oxalate, lamp black, oil black, azo oil black, Rose Bengal and mixtures thereof. Also, where conventional xerographic reproduction of printed documents is desired, the toner may be made from a black pigment, such as carbon black, or a black dye, such as Amaplast black dye. The amount of the colorant used in the toner of the present invention may vary widely, but is usually 1 to 20 parts by weight per 100 parts by weight of the polymerizable monomer. When the toner of the present invention is used as a one-component developer, any magnetic material can be added. The magnetic substance used in the present invention is a substance that is strongly magnetized in the direction of a magnetic field, is preferably black in color, is well dispersed in the resin, is chemically stable, and has a particle size of 1μ or less. Since it is desirable to easily obtain fine particles, magnetite (triiron tetroxide) is most preferred. Typical magnetic or magnetizable materials include metals such as cobalt, iron, and nickel; aluminum, cobalt, copper, iron, lead, magnesium, nickel, tin, zinc, antimony, perylium, bismuth, cadmium, calcium, and manganese. , selenium, titanium, tungsten,
Alloys of metals and mixtures thereof such as vanadium; metal compounds including metal oxides such as aluminum oxide, iron oxide, copper oxide, nickel oxide, zinc oxide, titanium oxide and magnesium oxide; Refractory titanides such as; carbides such as tungsten carbide and silica carbide; ferrites and mixtures thereof, etc. may be used. These ferromagnetic materials have an average particle size of 0.1
It is preferable that the amount is about 1 μm, and the amount contained in the toner of the present invention is about 50 to 160 parts by weight per 100 parts by weight of the resin component.
Parts by weight are desirable, particularly preferably resin components 1
The amount is 90 to 130 parts by weight. When producing the toner of the present invention, polymerization may be carried out using a polymerization initiator if necessary. As the polymerization initiator used in the present invention, a normal oil-soluble initiator is used at a normal temperature range. For example, benzoyl peroxide, lauryl peroxide, 2,2'-azobisisobutyronitrile, 2,2/-azobis(2,4-dimethylvaleronitrile), orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, etc. are used. It will be done. In order to form an image by, for example, electrophotography using the toner of the present invention, a selenium photoreceptor, or zinc oxide, cadmium sulfide,
Cadmium selenide, cadmium selenide sulfate, lead oxide,
A photoreceptor in which a photosensitive layer containing an inorganic photoconductive material such as mercury sulfide dispersed in a binder resin is provided on a conductive support, or an organic photoconductive material such as anthracene or polyvinylcarbazole is used as necessary. A photoreceptor is used, in which a photosensitive layer containing a binder resin and a photosensitive layer is provided on a conductive support. The surface of the photosensitive layer of such a photoreceptor is charged entirely by corona discharge using, for example, a corotron or scorotron charger, and then imagewise exposed to light to form an electrostatic charge image. This electrostatic charge image is then developed, for example, by a cascade method or a magnetic brush method, with a developer comprising, for example, a mixture of the toner of the present invention and a glass beads or iron powder carrier to form a toner image. This toner image is pressed onto a transfer paper under corona discharge, for example, and transferred onto the transfer paper. The toner image transferred onto the transfer paper is pressed and heated to be fixed by a hot roll coated with a fluorine-based resin or silicone rubber having a releasable property. At this time, since the toner of the present invention contains α/β monounsaturated ethylenic monomer as a constituent unit as a main resin component and has a weight average molecular weight of 80,000 or more, it is necessary to use silicone oil in particular. The offset phenomenon can be prevented without replenishing the liquid, and the fixing performance can be improved. The invention will be illustrated by the following examples. In addition, "parts" shown in the following examples indicate "parts by weight" unless otherwise specified.Example 1 Styrene, butyl methacrylate,
Carbon Black #30 (Mitsubishi Chemical Industries, Ltd.) as a coloring agent
Co., Ltd.], 2.2″Azobis-(2.
Polymerization compositions shown in Table 1 below were prepared using 4-dimethylvaleronitrile). Meanwhile, in a separate flask with a capacity of 21, 3 parts of tricalcium phosphate and 0.04 parts of sodium dodecylbenzenesulfonate.
1 part, distilled water was added thereto, the polymer composition was added thereto, and T. K. The mixture was stirred using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and dispersed while being observed under a microscope. When the particle size is too large, change to a regular stirrer and increase the stirring speed to 100r.
．． p. The polymerization was completed under the polymerization conditions shown in Table 1 while stirring at m. No change in particle size was observed until the polymerization was complete. After the polymerization was completed, the solid particles were treated with hydrochloric acid and washed with water to obtain a two-component toner. The obtained toners are all substantially spherical, with a major axis (a) and a minor axis (b).
) was within the range of 1≦a/b≦1.05. In addition, the results of the main particle size, the amount of toner within ±3% of the main particle size measured with a Coulter counter, and the weight average molecular weight of the resin were as shown in the table. Here, the weight % of toner having a main particle size within ±3 μm indicates what percentage by weight of toner with a particle size of 7 μm to 13 μm is contained in the total toner when the average particle size of the toner is 10 μm. A developer is prepared by mixing each of the toners in the table above with a resin-coated iron powder carrier having a particle size of about 50 to 80 microns;
These developers were used to develop electrostatic images formed by ordinary electrophotography, and image tests were conducted to determine resolution, fog, and changes in the amount of charge during continuous copying with a built-in toner recycling device (initial , after 10,000 copies), what is the image density?
The results obtained are shown in the table. As is clear from the table, toners [B], [C], [D], [F] and [G] of the present invention
Because the particle size distribution is narrow, there is little fog and there is no change in the amount of charge. However, it gives an image with good image density, but
Comparative toners [H] and [1] have a wide particle size distribution, so
There was also a lot of fog, especially in [H], a decrease in resolution was observed. Furthermore, due to variations in the amount of charge, some development was observed in which the image density decreased. Furthermore, since the comparative toner [J] had a particle size distribution exceeding 30 μm, the resolution was poor and image distortion was observed.
Furthermore, since the comparative toner [K] contained less than 70% by weight of toner having a main particle size within ±3 μm, the amount of charge varied greatly and did not have long-run characteristics. Regarding offset property, after developing the electrostatic charge image,
The toner image is transferred onto transfer paper, and the surface is coated with fluorine resin (FE).
16 using a fixing roller made of
The toner image was fused and fixed by pressure contact at 5 to 175°C. To determine whether the fused toner image is then transferred to the surface of the fuser roller, resulting in offset development,
After performing each fixing operation, the transfer paper without toner image is brought into pressure contact with the fixing roller under the same conditions as above,
Staining caused by toner offset on the transfer paper was observed. As a result, as shown in the table, when comparative toners [A] and [E] having weight average molecular weights outside the invention were used, significant staining due to toner offset was observed on the transfer paper; Invention toner [B], [C]
, [D], [F] and [G] are toners other than the present invention, but toners [H], [1], which use the resin of the present invention,
When [J] and [K] were used, no stains were generated on the transfer paper, and it was observed that no toner offset phenomenon occurred. This result was exactly the same even when this fixing operation was repeated. Furthermore, 50℃
When a blocking test was conducted in a constant temperature room, no clumping was observed in any of the samples. Comparative Example 1 Two-component toner 1 [L] was obtained in the same manner as in Example 1 using the same polymerization composition and polymerization conditions as Toner [B] in Example 1. The ratio of the major axis (a) to the minor axis (b) of the obtained toner [L] was a/b-1.1. In addition, the main particle size, particle size distribution, amount of toner within ±3 μ of the main particle size, and resin weight average molecular weight were measured in the same manner as in Example 1. The results were as follows. Main particle size (μ
)-13 Particle size distribution (μ) -5 to 30 Toner amount (wt%) within main particle size ±3μ - weight average molecular weight (Mw) of resin -9. 9×104 Using the above toner, an image test was conducted in the same manner as in Example 1, and the following results were obtained regarding toner fluidity, transfer efficiency, resolution, and sharpness. That is, compared to toner [B] of Example 1, the fluidity is slightly worse, but not only is there a drawback that the transfer efficiency is significantly worse, but the resolution is 5 lines/M77.
1, and a decrease in resolution was observed. Note that the sharpness was the same. Comparative Example 2 The above substances were melted, kneaded, and pulverized as shown in JP-A No. 51-3244, etc., and a particle size of 1 to 30 was obtained using a classifier.
The particles were classified so that particles having a main particle size within ±3 μ accounted for 70% by weight to obtain a negatively chargeable two-component toner [M]. This toner [M] had a/b of 2.0. Next, the toner [M] was spray-dried to form spheres as shown in Japanese Patent Application Laid-Open No. 50-45639 and US Pat. No. 3,392,139. That is, a/b-1.5 by 10 spray drying.
toner [N], and a/b-1.05 toner by spray drying 100 times.

I got [0]. As mentioned above, in order to make the toner obtained by the pulverization method spherical to a/b-1.05 like the toner of the present invention, it was necessary to spray dry the toner 100 times. Toner obtained by this

[0] could not be used practically because its thermal deterioration was unavoidable and the offset characteristics and anti-blocking characteristics of the toner deteriorated. Comparative Example 3 The above materials were heated, pressurized, and stirred as shown in US Pat. No. 3,674,736. However, it was not possible to obtain a substantially spherical toner having a/b-1.05 or less. Therefore, styrene/butyl acrylate (120/80) copolymer resin (Mw = 50,000)
As a result of heating, pressurizing, and stirring this toner in the same manner as above, a substantially spherical toner [P] with a/b-1.05 was obtained. However, this toner [P] had poor blocking properties and was not suitable for practical use. Further, when the above substance was heated and dispersed at 100°C as described in the above-mentioned US Pat. No. 3,674,736, a/b-
1.04, particle size is 1 to 30μ, and main particle size ±3
A toner [Q] containing 72% by weight of particles within μ was obtained.

Claims (1)

[Claims] 1. The ratio of the major axis (a) to the minor axis (b) of the particle is 1.00≦a
/b≦1.05 and has a substantially spherical shape with a particle size of 1
Contains 70% by weight or more of particles with a particle size of ~30 microns and a main particle size within ±3 microns, and contains α・
Contains β-unsaturated ethylenic monomer as a structural unit,
Further, a toner for developing an electrostatic image, which is produced by a suspension polymerization method and has a weight average molecular weight of 80,000 or more. 2. A toner for developing electrostatic images, characterized in that the main resin component according to claim 1 is contained in an amount of 60% by weight or more based on the total resin components of the toner.