JP2006145800A - Toner and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner having good charging performance and a good yield by regulating a coverage of fine silica particles as an external additive to fine base particles having unevenness in particle size according to the particle size range, and to provide a method for manufacturing the toner. <P>SOLUTION: Fine base particles based on a binder resin are classified into a group of particles in a small particle size range and a group of particles in a large particle size range in a classification step 10, the particles in the large particle size range are covered with fine silica particles in a first covering step 20, and the particles in the small particle size range are covered with fine silica particles in a second covering step 21. A coverage of the fine silica particles in the second covering step is made larger than that in the first covering step. The fine base particles thus covered in the covering steps are mixed in a mixing step 30 to manufacture the objective toner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toner used for developing an electrostatic latent image in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine, and a manufacturing method thereof.

  In an electrophotographic image forming apparatus, various toners for developing an electrostatic latent image formed on the surface of a photosensitive drum have been developed. For example, a colorant, a charge in a binder resin Known is one in which the surface of a base fine particle to which a control agent, a release agent, a fixing aid and the like are added is coated with an external additive.

By coating the surface of the base fine particles with an external additive, the toner can be provided with stable chargeability and fluidity. However, when the external additive is excessively added, not only does the toner charge amount increase and the image quality is affected, but the external additive is liberated and adversely affects the toner fixing. In addition, when the external additive is insufficient, the charge amount of the toner is reduced, image deterioration such as fogging occurs, and filming on the photosensitive drum is likely to occur. Thus, the amount and characteristics of the external additive that coats the surface of the toner base fine particles are important factors that determine the charging characteristics of the toner. For this reason, various improvements have been made regarding external additives. For example, Patent Document 1 describes that the surface of a fine silicate powder is treated with hexamethylsilazane as an external additive for toner particles, and the coverage is 60% to 100%. Further, Patent Document 2 describes that inorganic fine particles are heated and fixed in a hot air flow field on the surface of base fine particles made of a binder resin having a colorant, and the coverage of the inorganic fine particles is set to 46% or more. Has been. Further, in Patent Document 3, in the electrostatic image developing toner, the externally added fine particles are fixed on the surface of the base fine particles, and the specific surface area of the toner after fixing to the specific surface area of the base fine particles before fixing is determined by the BET method. The ratio is 3.2 or less, and the absolute value of the charge amount of at least one of the externally added fine particles is 300 μC / g or more.
JP 11-95480 A JP 2000-338712 A JP 2003-215838 A

  The toner base fine particles can be obtained by using a thermoplastic resin as a binder resin and melt-kneading, pulverizing, and classifying the binder resin together with additive components such as a colorant, a charge control agent, and a release agent. The base fine particles obtained by pulverization in this way have large particle size variations. Therefore, when the external additive is mixed with the base fine particles and the surface of the base fine particles is coated, the coverage of the external additive coated on the surface varies depending on the particle size of each base fine particle. That is, the external additive easily adheres to the surface of the base fine particles having a large particle size and the coverage is increased, but the external additive is difficult to adhere to the base fine particles having a small particle size and the coverage is reduced. Tend. This is presumably because the base fine particles having a small particle diameter enter between the base fine particles having a large particle diameter, and the base fine particles having a large particle diameter are more likely to adhere to the external additive when mixed with the external additive. Since the mixing ratio of the external additive is determined based on the average particle diameter of the base fine particles, the coverage of the external additive has to be small for the base fine particles smaller than the average particle diameter.

  As described above, when the coverage of the base fine particles varies depending on the particle size, the charging performance varies depending on the particle size, which causes image deterioration due to poor charging of the toner. For this reason, it is conceivable that the base fine particles coated with the external additive are further sieved to make the base fine particles have the same particle size, but wasteful toner that is not used is generated, resulting in poor yield.

  Therefore, the present invention adjusts the coverage of the post-treatment agent fine particles containing external additives to the base fine particles having a variation in particle size for each particle size range, and has good characteristics such as charging performance and good yield. An object of the present invention is to provide a toner and a manufacturing method thereof.

  The toner according to the present invention is a toner comprising base fine particles mainly composed of a binder resin and post-treatment fine particles covering the surface of the base fine particles, and relates to the base fine particles having a predetermined particle size range. The coverage of the post-treatment agent fine particles is set to be smaller than the coverage of the post-treatment agent fine particles with respect to the base fine particles having a particle size range smaller than the particle size range. Further, the post-treatment agent fine particles are silicate fine particles.

  A method for producing a toner according to the present invention includes a classification step of classifying base fine particles mainly composed of a binder resin into a plurality of particle size ranges, and a post-treatment agent for the classified base fine particles in a first particle size range. The first coating step for coating the fine particles, and the coverage of the base fine particles in the second particle size range smaller than the first particle size range than the coverage of the post-treatment agent fine particles in the first coating step The second coating step for coating the fine particles of the post-treatment agent so as to increase, and the mixing step for mixing the base particles coated in the first and second coating steps, respectively. Further, the post-treatment agent fine particles are silicate fine particles.

  By having the above-described configuration, the coverage of the post-treatment agent fine particles with respect to the base fine particles having a predetermined particle size range is smaller than the coverage of the post-treatment agent fine particles with respect to the base fine particles having a particle size range smaller than the particle size range. Since it is set to be small, the coverage of the post-treatment agent fine particles with respect to the base fine particles in the small particle size range becomes larger than the coverage of the base fine particles in the larger particle size range, and also to the base fine particles in the small particle size range. Good characteristics such as charging performance are imparted. Therefore, even with respect to the base fine particles having a large variation in particle diameter, it becomes a toner in which characteristics such as good charging performance are imparted to the individual base fine particles, and excellent image quality can be formed. In addition, since characteristics such as good charging performance can be imparted to the base particles having a small particle diameter, which has been poorly charged, the toner yield can also be improved.

  When the post-treatment agent fine particles are silicate fine particles, the base fine particles having a small particle size range tend to have a higher charge amount than their weight, but the larger the silicate fine particle coverage, the larger It becomes possible to set the charge amount to almost the same level as the base fine particles in the particle size range. In addition, the base fine particles having a small particle size range tend to deteriorate in fluidity because they enter between the base fine particles having a large particle size range, but the fluidity is improved by increasing the coverage of the silicate fine particles. You can also.

  In the toner production method according to the present invention, the base fine particles are once classified into a plurality of particle size ranges, and then coated after being coated so that the coverage of the post-treatment agent fine particles is different for each particle size range. Therefore, the coverage can be easily adjusted according to the size of the particle size in the particle size range. Accordingly, even when base particles having a large variation in particle diameter are used, a toner having characteristics such as good charging performance as a whole can be produced, and since mother particles having a small particle diameter can also be used, the yield can be improved. It becomes possible.

  Here, the base fine particles are those in which various additive components such as a colorant, a charge control agent, and a release agent are contained in a binder resin as a main component. The post-treatment agent fine particles are fine particles added to the surface of the base fine particles, and include external additives such as silicate fine particles.

  Further, the coverage is an area ratio in which the surface of the base microparticles is covered with the post-processing agent microparticles, and can be obtained, for example, by a ratio of the total projected area of all the silicate microparticles to the total surface area of the base microparticles. it can.

First, when the true specific gravity of the base microparticles [rho _t, the radius of the base microparticles 1 particles and r _t, weight W _t and surface area S _t of the base microparticles 1 particles are obtained by the following equation.

When the true specific gravity of the post-treatment agent fine particles is ρ _s and the radius of one post-treatment agent fine particle is r _s , the weight W _s and the projected area S _s of one post-treatment agent fine particle can be obtained by the following equations. The projected area is calculated by a cross-sectional area passing through the center of the post-processing agent fine particles.

Next, _assuming that the addition rate of the post-treatment agent fine particles is X%, the number N _s of post-treatment agent fine particles for one base particle can be obtained by the following equation.

  And the coverage C is calculated | required from the following formula | equation as a ratio of the projection area of post-processing agent microparticles | fine-particles with respect to the surface area of a base particle.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  The base fine particles used in the present invention can be produced according to a known method by adding various additive components such as a colorant, a charge control agent, and a release agent to the binder resin as a main component.

  Examples of the binder resin include styrene resins, polyester resins, vinyl chloride resins, phenol resins, epoxy resins, ionomer resins, polyurethane resins, silicone resins, ketone resins, xylene resins, polyvinyl butyral resins, and the like. Examples of the resin include a styrene resin, a polyester resin, and an epoxy resin. These resins may be used alone or in combination.

  A known pigment or dye can be used as the colorant. For example, a colorant such as titanium oxide, carbon black, alumina white, calcium carbonate, bitumen, phthalocyanine blue, phthalocyanine green, benzine yellow, nigrosine dye, azo dye or pigment is used alone or in combination. Moreover, it is preferable that content of a coloring agent shall be 3-20 weight part with respect to 100 weight part of binder resin.

  Examples of the charge control agent include positive charge control agents such as nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds, imidazole compounds, polyamine resins, and metals containing Cr, Co, Al, Fe and the like. Examples include negatively charged charge control agents such as azo dyes, salicylic acid metal compounds, calixarene compounds, and alkylsalicylic acid metal compounds. The charge control agent is added as necessary while observing the charging characteristics of the toner, but is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  Examples of the mold release agent include polyethylene wax, polypropylene wax, and paraffin wax. Offset resistance can be improved by adding a mold release agent.

  In addition to the additives described above, a low melting point material may be added in order to improve fixability.

  Add the above additives to the binder resin, mix with a known mixer, melt and knead under specified conditions, crush the solidified with a crusher such as a crusher or jet mill, The fine particles can be produced by classification with a classifier. A known method may be used as a method for producing such base fine particles. The average particle diameter of the base fine particles is preferably 5 μm to 9 μm. The particle diameter of the base fine particles can be measured using a measuring device such as a multisizer.

  As an example of the fine particles of post-treatment agent used in the present invention, silicate particles will be described. As typical silicate fine particles, for example, anhydrous silicon dioxide (silica) can be cited as a typical example, but silicates such as aluminum silicate, sodium silicate, potassium silicate, and magnesium silicate can also be used. . The particle diameter of the silicic acid fine particles is preferably 10 nm to 500 nm.

  Next, a process for producing toner will be described. FIG. 1 is a schematic view relating to a toner manufacturing process. In the classification step 10, the base fine particles containing the binder resin as a main component and containing the above-described additives are classified into two particles having a large particle size range and one having a small particle size range. The classification is performed using a known classifier such as an air classifier. Since the base fine particles are already classified and arranged in a predetermined particle size range, they are further subdivided into two particle size ranges: those having a smaller particle size range and those having a larger particle size range. The small particle size range is set to an average particle size that is about 1 to 2 μm smaller than the average particle size of the base particles, and the large particle size range is set to be about 1 to 2 μm larger than the average particle size of the base particles. Subdivide.

  For example, if the average particle size of the base particles is 7 μm, the particle size range with a small particle size is preferably 6 μm, and the particle size range with a large particle size is 8 μm. The particle size range to be subdivided is desirably subdivided as much as possible. However, when the particle diameters of the base microparticles are uniform to some extent, the effect can be sufficiently achieved by subdividing into about two.

  The finely divided base fine particles are mixed with silicate fine particles by a known mixer in separate coating steps 20 and 21 so as to cover the surface thereof. Base particles having a larger particle size range are mixed with silicate particles in the first coating step 20, and mother particles having a smaller particle size range are mixed with silicate particles in the second coating step 21. . The addition rate of the silicic acid fine particles to be mixed is obtained by the above-described calculation formula based on a preset coverage. The coverage is set so that the base fine particles having a smaller particle size range have a larger particle size.

  In the mixing step 30, the base fine particles respectively coated in the first coating step 20 and the second coating step 21 are mixed so as to be evenly distributed to each other to produce a toner.

  The manufactured toner has a higher coverage of the silicate fine particles of the base particles in the particle size range with a smaller particle size, so that more silicate particles adhere to the base particles in the particle size range with a larger particle size. Accordingly, the charging performance is suppressed, and the fluidity is improved.

  As the base fine particles, those having a particle diameter range of 3 μm to 11 μm of 90% or more and an average particle diameter of 7 μm were prepared. The base fine particles are mainly composed of a styrene-acrylic polymer as a binder resin, 7 parts by weight of carbon black as a colorant, 0.5 parts by weight of nigrosine dye as a charge control agent, and 100 parts by weight of a binder resin. A mold was prepared by adding 2 parts by weight of a mixture of polyethylene wax and polyethylene wax, and an appropriate amount of fixing aid.

  The base fine particles were classified by an air classifier and subdivided into particle size ranges of 3 μm to 7 μm and 7 μm to 11 μm. When the particle size range is 3 μm to 7 μm, the average particle size is 6 μm, and when the particle size range is 7 μm to 11 μm, the average particle size is 8 μm.

  Next, the surface of the base fine particles was coated with anhydrous silicon dioxide (silica) having a particle size of 50 nm as silicate fine particles. The amount added to the base microparticles is 2 parts by weight for 100 parts by weight of the base microparticles for base particles with a particle size range of 3 μm to 7 μm, and for 100 parts by weight of the base particles for base particles with a particle size range of 7 μm to 11 μm. 1 part by weight was added, and the mixture was stirred for 5 minutes at room temperature using a Henschel mixer (Mitsui Mining Co., Ltd.).

When the coverage was calculated for these two base fine particles, for the base particles having a particle size range of 3 μm to 7 μm, the true specific gravity of the base particles was ρ _t 0.3, the true specific gravity of the silica fine particles was ρ _s 0.3. Then, the radius r _{t of the} base fine particles is 6/2 μm, the radius r _{s of the} silica fine particles is 0.05 / 2 μm, and the addition rate X is 2%. .

In the base particles having a particle size range of 7 μm to 11 μm, the radius r _t of the base particles is 8/2 μm, the radius r _{s of the} silica particles is 0.05 / 2 μm, and the addition rate X is 1%. Is calculated as follows.

  Accordingly, the base particles having a smaller particle size range are set to have a higher coverage than the parent particles having a larger particle size range.

Next, the base particles having different coverages were put together in a Henschel mixer (Mitsui Mining Co., Ltd.) and mixed for 2 minutes. When development was performed using the toner thus produced, an image with good image quality free from fogging could be formed.
[Comparative example]

  Using the same base particles as in the examples, the same silicate particles as in the examples were added without classification. The addition amount of the silicic acid fine particles was 1.5 parts by weight with respect to 100 parts by weight of the base fine particles. Silica fine particles were added to the base fine particles and stirred with a mixer, and the surface of the base fine particles was coated with the silica fine particles. The coverage in this case is calculated as follows.

  However, as shown in the examples, silicate fine particles are added in the same manner with respect to those having a mean particle size of 8 μm and those having a mean particle size of 6 μm included in the base fine particles, Each coverage is calculated as follows when the average particle diameter is 8 μm.

  Further, when the average particle size is 6 μm, the calculation is performed as follows.

  Accordingly, the coverage of particles having a small particle size range tends to be smaller than that of particles having a large particle size range. For this reason, the charging performance of the toner having a small particle diameter becomes high and fog is likely to occur, which adversely affects the image quality.

It is explanatory drawing of the manufacturing process regarding embodiment which concerns on this invention.

Explanation of symbols

10 classification process 20 first coating process 21 second coating process 30 mixing process

Claims (4)

  A toner comprising matrix fine particles mainly composed of a binder resin and post-treatment fine particles that coat the surface of the matrix fine particles, and covering the post-treatment fine particles with respect to the matrix fine particles in a predetermined particle size range A toner having a rate set smaller than a coverage of the post-processing agent fine particles with respect to the base fine particles having a particle size range smaller than the particle size range.   The toner according to claim 1, wherein the post-treatment agent fine particles are silicate fine particles.   A classification step of classifying the base fine particles mainly composed of a binder resin into a plurality of particle size ranges; a first coating step of coating the post-treatment agent fine particles on the classified base particles of the first particle size range; The post-treatment agent fine particles are applied so that the coverage of the base fine particles in the second particle size range smaller than the first particle size range is larger than the coverage of the post-treatment agent fine particles in the first coating step. A toner manufacturing method comprising: a second coating step for coating; and a mixing step for mixing the base fine particles respectively coated in the first and second coating steps.   The toner manufacturing method according to claim 3, wherein the post-treatment agent fine particles are silicate fine particles.

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