JP3529105B2 - Toner for developing electrostatic images - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image formed in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, the present invention relates to a binder resin. 2. Description of the Related Art Generally, in electrophotography, electrostatic recording, and the like, an electrostatic latent image formed on a latent image carrier made of a photoconductive photoreceptor or a dielectric is developed. To
Using a toner that has been thinned by a blade or the like on a toner supply roller such as a developing sleeve, and appropriately charged and finely powdered, developed and, if necessary, transferred a toner image to a transfer material such as paper, Fixing is performed by heating pressure, solvent vapor, etc. to obtain a copy. [0003] In the toner applied to these developing methods, an oil coating machine is provided in a fixing device or a release agent is used in the toner in order to improve the offset property at a fixing portion. However, when an oil applicator is installed in the fixing device,
This may cause an increase in cost or necessitate repair of a failure, which increases the burden on the user, which is not preferable. Also, when a large amount of release agent is used in the toner, a spent phenomenon of the toner on the photoreceptor or the carrier is observed, and the image is disturbed or the density is lowered due to the deterioration of the charge, which is not preferable. The phenomenon described above is a phenomenon that is also observed in a kneading type toner or a polymerization type toner.However, in the case of a polymerization type toner, if a release material is present on the surface of the toner, the transfer rate is deteriorated, and an obtained image is not obtained. It becomes very thin. Further, the poor transfer rate causes an increase in the amount of cleaning toner, which may cause cleaning failure. [0004] As described above, the fixing characteristics are improved by improving the fixing device and the toner prescription. Regarding the toner formulation, attempts have been made to improve the fixing properties by adding a release material or by limiting the molecular weight distribution, but at present, sufficient properties have not yet been obtained. Examples in which the thermal properties of the toner polymer are improved are described in JP-A-64-13558, JP-A-1-143661,
-201452, Japanese Patent Application Laid-Open No. 3-139661, etc., which differs from the contents of the present invention. Further, since high image quality is required in the future market, the particle diameter of the toner has been reduced. Japanese Patent Application Laid-Open No. 2-287278 discloses a small particle size toner having a volume average particle size of 6 to 9 μm, but a toner having a volume average particle size of 5 μm or less has not yet been observed. Further, when the toner has a small particle size, the number of toners in the heat fixing roller system becomes very large as compared with the conventional toner of about 10 μm, so that sufficient thermal energy can be supplied to all the toner particles. become unable. Therefore, there is a problem that a fixing failure occurs in the thermal characteristics of the conventional toner. As a method of improving this fixing failure,
In a conventional kneading and pulverizing type toner, low temperature fixing is performed by using polyester. This improves the thermal characteristics of the toner and reduces the softening temperature of the flow tester to 7
It becomes possible to set the outflow starting temperature to 0 ° C. or less and 100 ° C. or less. However, with the polymerized toner according to the present invention, it was practically impossible to obtain polyester particles having a uniform particle size and a small particle size. SUMMARY OF THE INVENTION In the present invention, in order to suppress the offset of the toner in the fixing process, the offset is prevented without using a release agent, and good transferability is exhibited. It is intended to provide a toner capable of obtaining an image. Means for Solving the Problems As a result of intensive studies for solving the above problems, the constitution of the present invention has a volume average particle diameter of 0.1.
A toner 5～2Myuemu, volume average particle diameter (D _v) and the ratio of the number average particle diameter (D _p) is D _v / D _p = 1~1.2, the softening temperature in the flow tester toner Is 70 ° C
The toner for developing an electrostatic charge image has a flow start temperature of 100 ° C. or less and a difference between the flow start temperature and the softening temperature of 35 ° C. or less. A commonly used copy paper has a paper fiber thickness of 20 to 50 μm, which overlaps and has a certain direction and is a paper. Therefore, the surface of the paper has irregularities on the order of several tens of μm, and the toner particles can easily enter the gaps between the fibers. This phenomenon is 5 μm
The appearance of many toner particles buried under the fibers is observed by an optical microscope or the like. As the size of the toner particles is further reduced, the amount of toner at the time of transfer, which enters the concave portion under the fiber of the paper, increases, and the toner particle decreases at the convex portion of the fiber. In such a state, the toner particles hardly come into direct contact with the fixing roller, and the heat energy is transferred through the paper fibers. In such a case, a polymer having ordinary thermal characteristics (glass transition temperature, softening temperature, outflow start temperature) has a high fixing temperature, and cannot be said to be a preferable toner in terms of energy saving. Therefore, as the thermal characteristics of the polymer constituting the toner, it is necessary that the softening temperature is 70 ° C. or less and the outflow starting temperature is 100 ° C. or less. If the softening temperature and the outflow start temperature are higher than these temperatures, it becomes impossible to fix the image with a general copying machine. On the other hand, when the particle size is 2 μm or more, the amount of toner sunk under the fiber of the paper decreases, so that an offset phenomenon is easily generated at the time of fixing, which is not suitable for the object of the present invention. On the other hand, when the thickness is 0.5 μm or less, the transferability deteriorates, and the phenomenon that the image density decreases and the cleaning performance deteriorates is observed. Further, a good result can be obtained if the binder resin contains a crosslinking component by a polyfunctional monomer. Further, in order to obtain an image corresponding to high-resolution writing, which is a characteristic of the small particle size toner, it is preferable that the particle size distribution is sharp. This is because if the particle size distribution is broad, even if the writing is at a high resolution, the writing cannot be faithfully developed. In other words, a phenomenon occurs in which the characteristics of the small particle size toner are weakened if a true image cannot be realized. More importantly, Tf-T
If m exceeds 35 ° C., fixing becomes insufficient, an unfixed image is generated, and a problem occurs in practical use. The toner particles used in the present invention need to contain a gel component in the polymer. The presence of the gel component can more effectively achieve the object of the present invention. An appropriate amount of this gel component is 10 to 60
wt%. By containing this gel component,
In the fixing step, internal cohesive failure following adhesion to the fixing roller is avoided. As the toner particles, particles obtained by a usual kneading / pulverizing method or a polymerization method may be used. In the production method by the polymerization method, there are the following examples. After a polymer dispersant such as polyvinylpyrrolidone was completely dissolved in a hydrophilic organic solvent such as methanol, styrene, an acrylic monomer, a chain transfer agent, and a cross-linking agent were mixed, and nitrogen gas was introduced to degas. The polymerization is started by adding a polymerization initiator at 60 ° C., and after 20 hours, a crosslinking agent (polyfunctional monomer) is added together with styrene, and the polymerization is further started to obtain. At this time, it is necessary that a gel component is contained in the polymer particles as a preferable condition. In the case of a kneading type toner, it can be obtained by adding a highly crosslinkable polymer at a later stage of kneading. As the highly crosslinkable polymer used at this time, a polymer having a long distance between crosslink points is preferable. The polymer having a long distance between crosslinking points can be obtained by using a polyfunctional monomer having a large molecular weight. The monomers forming the binder resin used in the present invention include styrene, o-methylstyrene,
m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-
Styrenes such as nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene; ethylene, propylene, butylene, Ethylenically unsaturated monoolefins such as isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl propionate; methyl acrylate and ethyl acrylate; Α-methylene aliphatic monocarboxylic esters such as n-butyl acrylate, methyl methacrylate and ethyl methacrylate; vinyl ethers such as vinyl methyl ether; vinyl ketones such as vinyl methyl ketone; N-vinyl pyrrole; Vinyl carbazole, N-vinyl in Lumpur, can be exemplified N- vinyl compounds such as N- vinylpyrrolidone. These monomers can be used alone or in combination of two or more. In the toner of the present invention, additives such as a colorant and a charge controlling agent can be used. Examples of such additives include metal chelate dyes such as carbon black, oil black, nigrosine dye and metal-containing dye, aniline dye, and the like. Calco oil blue, chrome yellow, ultramarine blue, methylene blue chloride, phthalocyanine blue, rose bengal, other dyes or pigments are included. In the toner of the present invention, a fluidizing agent can be used. For example, inorganic oxides such as SiO ₂ and TiO ₂ having a hydrophobic surface,
Inorganic fine particles such as SiC, metal soap such as zinc stearate,
Others can be used. Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. The amounts of each component described in Examples and Comparative Examples are based on weight. Example 1 Base particles were produced by a dispersion polymerization method as described below. In a 500 ml three-necked flask equipped with a stirring blade and a cooler, 300 parts of methanol and 30 parts of ion-exchanged water were added.
Polymer dispersant Gantret (average molecular weight 40,000) 6.4
The mixture was added little by little while stirring, and completely dissolved.
Further, the following composition was added and completely dissolved. Styrene 25.6 parts n-butyl methacrylate 6.4 parts 2,2′-azobisisobutyronitrile 0.2 parts dodecyl mercaptan 0.2 parts 5-ethyl-2- (hydroxy-1,1- 0.45 parts of acrylic acid ester of (dimethylethyl) -5- (hydroxymethyl) -1,3-dioxane While stirring these, the inside of the flask was purged with nitrogen gas and allowed to stand for 1 hour. The polymerization was started while stirring at a stirring speed of 200 rpm in a constant temperature water bath at 60 ° C. ± 0.1 ° C. After 15 minutes from heating, the liquid began to become cloudy, and was a stable dispersion that became cloudy even after polymerization for 20 hours. A part of the sample was subjected to measurement by an internal standard method by gas chromatography, and as a result, it was confirmed that the polymerization rate was 85%. The resulting dispersion was cooled and centrifuged at 2000
Upon centrifugation at rpm, the polymer particles settled out completely and the upper liquid was clear. The supernatant was removed, and 200 parts of methanol was newly added, followed by stirring and washing for 1 hour. The operation of centrifuging and washing with methanol was repeatedly filtered. The filtered product was dried under reduced pressure at 50 ° C. for 24 hours to obtain white styrene / n-butyl methacrylate particles in a yield of 95%. The resulting particles have a volume average particle size D _v = 1.5 μ
m, the number average particle diameter D _p was 1.4 μm. The softening temperature of the flow tester was 63 ° C and the outflow starting temperature was 90 ° C.
° C. The gel content was 25%. [Hereinafter, these polymerized particles will be referred to as (A)] Next, 1.0 part of Oil Black 803 (Orient Chemical Co., Ltd.) is dissolved in 200 parts of methanol by heating, then cooled and filtered with a 1 μm filter to obtain a dye solution. Was prepared. Next, 24 parts of the polymer particles (A) were added to the filtrate to disperse, and 5
The mixture was heated and stirred at 0 ° C. for 1 hour. Thereafter, the dyed resin particle dispersion (B) was cooled to room temperature and filtered to obtain colored resin fine particles. After vacuum drying at room temperature for 24 hours,
And then mixed to obtain a toner. Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amount of dodecyl mercaptan was reduced to 1/2 to obtain colored resin fine particles.
The resulting particles volume average particle size D _v = 0.88 .mu.m, was the number-average particle diameter D _p = 0.80 .mu.m. The softening temperature of the flow tester was 68 ° C., and the outflow starting temperature was 94 ° C. The gel content was 33%. This at room temperature
After vacuum drying for 4 hours, 1.5 parts of silica was added and mixed to obtain a toner. Example 3 Polymerization was carried out in the same manner as in Example 1 except that the amount of dodecyl mercaptan was doubled to obtain colored resin fine particles. The resulting particles volume average particle size D _v = 1.9 .mu.m, was the number-average particle diameter D _p = 1.7 [mu] m. The flow tester had a softening temperature of 70 ° C. and an outflow starting temperature of 90 ° C.
The gel content was 48%. After vacuum drying at room temperature for 24 hours, 1.5 parts of silica was added and mixed to obtain a toner. Table 1 shows the evaluation results of the samples manufactured by changing the conditions in the above manner. Comparative Example 1 Styrene monomer 50 parts n-butyl methacrylate 20 parts Butanediol dimethacrylate 2 parts Low molecular weight polypropylene 660P (manufactured by Sanyo Chemical) 3 parts Bontron E81 (manufactured by Orient Chemical) 5 parts Graft carbon black 30 parts The mixture was dispersed in a ball mill for 10 hours. In this dispersion, 2,2'-azobisisobutyronitrile and sodium nitrite are each dissolved one part at a time, and then added to 250 parts of a 2% aqueous solution of polyvinyl alcohol, and TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) 10 at 6000 rpm
The mixture was stirred for minutes to obtain a suspension. The suspension was placed in a 500 ml four-neck separable flask equipped with a three-one motor driven stirring blade, a cooler, a gas inlet tube, and a thermometer, and stirred at room temperature for 30 minutes under a nitrogen stream to remove oxygen in the flask with nitrogen. Was replaced. Then, in a hot water bath at 70 ° C for 8 hours x 90r
The mixture was stirred at pm to complete the polymerization and produce suspended polymer particles. The obtained particles had a volume average particle size D _v = 7.9 μm and a number average particle size 5.2 μm. The softening temperature of the flow tester was 65 ° C, and the outflow starting temperature was 133 ° C. The gel content was 5%. After drying the suspension polymer particles, 100 parts of the suspension polymer particles and 1.5 parts of silica were mixed to obtain a toner. Comparative Example 2 The following was added to a flask equipped with a reflux condenser, a stirrer, and a thermometer, and the temperature was raised to 70.degree. Ion-exchanged water 225 parts Sodium polyoxyethylene phenyl ether sulfate 5 parts Potassium peroxosulfate 3 parts Next, the following mixture was added, and polymerization was carried out for 2 hours.
After the temperature was raised to 0 ° C. and the polymerization was further performed for 2 hours, the mixture was cooled to room temperature to obtain a styrene resin particle dispersion. Methyl methacrylate 5 parts Methyl acrylate 25 parts Styrene 65 parts Butadiol dimethacrylate 2 parts The above dispersion was colored in the same manner as in Example 1 to obtain colored resin particles after filtration. The resulting colored particles have a volume average particle size D
_v = 0.18 μm and the number average particle diameter was 0.13 μm. The softening temperature of the flow tester was 80 ° C, and the outflow starting temperature was 131 ° C. After drying the particles, the particles 1
A toner was prepared by mixing 00 parts with 1.5 parts of silica. Comparative Example 3 A toner was produced in the same manner as in Example 1, except that no ion-exchanged water was used during the polymerization of the particles. As for the thermal characteristics of the obtained toner, the softening temperature of the flow tester was 75 ° C., and the outflow starting temperature was 130 ° C. The volume average particle size was 4.8 μm. Comparative Example 4 A toner was produced in the same manner as in Example 1, except that dodecyl mercaptan was not used during the polymerization of the particles. The thermal characteristics of the obtained toner were as follows: the softening temperature of the flow tester was 89 ° C., and the outflow starting temperature was 145 ° C.
Met. The volume average particle size was 1.8 μm. [Table 1] Evaluation Method The wrapping property of copy paper, which indicates the releasability of the toner, was tested using a fixing machine for a medium-speed copying machine under the fixing conditions shown in Table 2. An unfixed image having the toner adhered to the leading end 30 mm width of the copy paper was prepared by a normal developing and transferring process, and this was used as a fixing sample. Insert this sample into the fuser,
It was determined whether or not it would wind around the fixing roller. The set temperature of the fixing roller was changed in the range of 160 to 210 ° C., and the test was performed every 5 ° C. Table 3 shows the results. [Table 2] [Table 3] As described above, the volume average particle size is 0.5 to 2
A toner [mu] m, a volume average particle diameter (D _v) and the number ratio of the average particle diameter (D _p) is _{D v / D p = 1~1.2,} T m in the flow tester of the toner 70 Below ℃, T _f
Is 100 ° C. or less, and _Tf− T _m is 35 ° C. or less. By using the electrostatic image developing toner, a high-resolution image is obtained and a good image without offset to the fixing roller is obtained. Is obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/00

Claims (1)

(57) [Claim 1] A toner containing at least a styrene-based polymer in a binder resin and having a volume average particle size of 0.5 to 2 μm, and having a volume average particle size (D _v ) and a number average particle size. the ratio of particle size (D _p) is D _v / D _p = 1~1.2, at the softening temperature in the flow tester of the toner (T _m) is 70 ° C. or less, the flow beginning temperature (T _f) is 100 ° C. Wherein T _f -T _m is 35 ° C. or less.