JP2005140965A - Nonmagnetic single component toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonmagnetic single component toner having suppressed filming, fog or the like for long-term use and capable of forming an image with stable picture quality. <P>SOLUTION: In the toner prepared by mixing and adding at least two kinds of external additives to toner particles containing at least a polyester resin and a coloring pigment, the external additives are silica fine particles having 5 to 100 nm average particle size and silica melamine composite fine particles having 300 to 1,000 nm average particle size. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-magnetic one-component developer, and more particularly to a non-magnetic one-component developer for developing an electrical latent image in electrophotography and electrostatic printing.

  Conventionally, as described in, for example, Patent Document 1 below, electrophotography is generally a charging process for uniformly charging a photoconductor containing a photoconductive substance, and exposing the surface of the photoconductor. An exposure process for forming an electrostatic latent image, a development process for visualizing the electrostatic latent image on the surface of the photoreceptor to a toner image, a transfer process for transferring the toner image carried on the surface of the photoreceptor to the surface of the paper, and It consists of a fixing process in which the toner image is fixed on the paper by means such as heating and pressing.

  Of these, the two-component development method and the one-component development method are generally known in the development process. In recent years, the one-component development method has been widely used because of advantages such as maintainability, size reduction, weight reduction, and cost reduction. However, in the one-component development system, there are still many problems to be improved. As a one-component development system, a developing roller arranged close to or in contact with the photosensitive member, a supply roller that supplies toner to the developing roller, and a toner on the developing roller that is in contact with the developing roller are thinned to give a charge. A one-component developing system including a regulating blade is known.

  One-component development methods include magnetic one-component systems and non-magnetic one-component systems, but magnetic one-component systems are not suitable for full-color image forming apparatuses because it is necessary to use a black magnetic material together. . On the other hand, a non-magnetic one-component system is suitable for a full-color image forming apparatus because it does not use a magnetic material or the like.

  In the non-magnetic one-component developing method, as described above, it is necessary to bring a regulating blade into contact with the developer on the developing roller in order to give a charge. At this time, the developer passes through the gap between the developing roller and the regulating blade, so that the developer is formed into a thin film on the surface of the developing roller to be charged, and thereafter the electrostatic latent image formed on the photoconductor is developed. I do.

  In order to perform appropriate development on the photosensitive member by the one-component development method, it is very important to always form a stable thin toner layer on the developing roller. In recent years, a toner having a low softening point is generally used as the colorization and the fixing temperature are lowered (energy saving). In the above-described non-magnetic one-component development method, the binder resin used for full-color toner in particular has such a low softening point, and therefore, problems such as toner fusing and adhering to the regulating blade are often cited as compared with black toner. It is done. When such fusing or fixing occurs, a thin layer is not uniformly formed on the developing roller, white streaks or the like are generated on the image, and sufficient charge is not imparted to the toner. This causes problems such as toner scattering in the developing machine.

  In the non-magnetic one-component development method, the toner on the developing roller is charged with contact with the regulating blade. In order to uniformly charge the toner on the developing roller, it is essential to impart fluidity to the toner. As external additives used for imparting fluidity, inorganic fine particles such as silica, alumina and titania are mainly used. For example, Patent Document 2 below proposes a non-magnetic one-component toner in which the external addition with silica, titania or the like is defined by the coverage to provide fluidity. As described above, in the non-magnetic one-component developing method, the regulating blade contacts the developing roller to apply a charge, and when the toner on the developing roller passes through the gap, a large mechanical stress is applied to the toner particles. . As a result, the external additive on the toner surface is embedded in the toner, and the toner characteristics may change.

US Patent No. 2,297,691 JP-A-8-137122 JP 2002-327036 A JP-A-7-114214 JP 2003-57869 A

  The present invention has little change in the surface state of toner particles even for long-term use, suppresses adverse effects such as filming and fusing, and is excellent in image quality stability such as maintaining image density and low fog. Another object of the present invention is to provide a non-magnetic one-component toner.

  As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by adding a specific external additive to toner particles containing at least a polyester resin and a color pigment. Reached.

  That is, the present invention relates to a toner obtained by mixing and adding at least two or more external additives to toner particles containing at least a polyester resin and a color pigment, and the silica fine particles having an average particle diameter of 5 to 100 nm. And silica / melamine composite fine particles having an average particle diameter of 300 to 1000 nm. In particular, the silica fine particles are preferably composed of silica fine particles having an average particle diameter of 5 to 20 nm and silica fine particles having an average particle diameter of 20 to 100 nm.

  In a toner obtained by mixing and adding two or more external additives, a combination of silica fine particles having an average particle diameter of 5 to 100 nm and silica / melamine composite fine particles having an average particle diameter of 300 to 1000 nm as an external additive can be used for a long time. It is possible to obtain a non-magnetic one-component toner capable of suppressing adverse effects such as filming and fogging during use and capable of forming a stable image quality.

Hereinafter, the nonmagnetic one-component toner of the present invention will be described in detail.
The polyester resin used in the present invention comprises a polycondensation of a polyol and a polybasic acid, and may be a polyester resin having a crosslinked structure by polymerizing a trifunctional or higher polyfunctional component in at least one as necessary. .

  Among the polyols used for the synthesis of the polyester resin, the diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, trimethylene glycol, 1,4. -Butanediol, 1,4-butenediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and the like can be mentioned.

  Examples of phenols include bisphenol A alkylene oxide adducts such as bisphenol A, hydrogenated bisphenol A, and polyoxyethylenated bisphenol A, 1,2,4-benzenetriol, hydroquinone, and the like.

  Examples of the trivalent or higher polyols related to the crosslinking of polyester include glycerin, 1,2,4-butanetriol, 1,2,5-pentanetriol, 2-methylpropanetriol, 2-methyl-1,2, Examples include 4-butanetriol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, and sucrose. It is done.

  On the other hand, polybasic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1, Examples include 5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and acid anhydrides or lower alkyl esters thereof.

  Examples of the tribasic or higher polybasic acid related to the crosslinking of the polyester resin include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2 , 5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexatricarboxylic acid, and acid anhydrides and lower alkyl esters thereof.

  Any appropriate pigment or dye is used as the colorant contained in the non-magnetic one-component toner according to the present invention. For example, carbon black, lamp black, iron black, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine pigment, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, anthraquinone dye, Any conventionally known dyes and pigments such as monoazo and disazo dyes can be used alone or in combination. The addition amount of these colorants is preferably 2 to 10 parts by weight with respect to 100 parts by weight of the polyester resin.

  Any known charge control agent can be used. For example, there are nigrosine dyes, amino group-containing vinyl copolymers, quaternary ammonium salt compounds, polyamine resins, imidazoles, etc. for positive charging, and metals such as chromium, zinc, cobalt, and aluminum for negative charging. Known metal-containing azo dyes, salts of salicylic acid or alkylsalicylic acid with the aforementioned metals, metal complexes, and the like are known. The amount used is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the resin. In this case, the charge control agent may be added to the resin, or may be used in a form adhered to the toner particle surface. The addition amount of these charge control agents is preferably 0.1 to 4.0 parts with respect to 100 parts by weight of the polyester resin.

  Examples of mold release agents include petroleum waxes such as paraffin wax and microcrystalline wax, synthetic waxes such as polyethylene wax, Fischer-Tropsch wax and amide wax, and animal and plant waxes such as carnauba wax, candelilla wax and rice wax. desirable.

  The release agent is dispersed in the toner and bleeds (elutes) on the surface of the toner at the time of thermocompression bonding by a fixing roller, thereby exhibiting release properties and acting as an offset preventing agent. Therefore, the melting point of the release agent and the dispersion state in the toner are greatly involved in preventing offset.

  The addition amount of the release agent is preferably 0.5 to 5.0 parts, more preferably 1.5 to 3.5 parts with respect to 100 parts by weight of the polyester resin. When the addition amount of the release agent is 1.5 parts or less, the effect of preventing offset cannot be expected, and when it is 3.5 parts or more, phenomena such as filming can be considered.

  Considering the maintenance of image density and long-term transition in long-term use, at least one silica fine particle is used as an external additive to the toner surface of the present invention, and the average particle of silica is used from the viewpoint of toner fluidity and developability. The diameter is desirably 5 to 100 nm. Further, the silica fine particles are preferably a combination of at least two types having an average particle size of 5 to 20 nm and an average particle size of 20 to 100 nm.

  Silica fine particles having an average particle size of 5 to 20 nm are excellent in the effect of imparting fluidity to toner particles, and silica fine particles having an average particle size of 20 to 100 nm are effective in maintaining the life characteristics of the toner. Therefore, in consideration of long-term use of the toner, it is preferable to combine two kinds of silica fine particles having an average particle diameter of 5 to 20 nm and an average particle diameter of 20 to 100 nm, compared to adding only one kind of silica fine particles having an average particle diameter of 5 to 100 nm. More desirable.

  When the silica fine particle is 5 nm or less, it can be considered to be embedded in the toner particle. Further, there may be a problem that a sufficient charging effect cannot be expected. On the other hand, when the silica fine particles are 100 nm or more, it is considered inappropriate because the fluidity imparting effect to the toner particles cannot be expected.

  The amount of silica fine particles added is desirably 0.5 to 5.0 parts. When the external addition amount is 0.5 parts or less, sufficient fluidity cannot be imparted to the toner particles. In the case of 5.0 parts or more, there is a possibility that the toner may be melted during fixing and the fixing strength may be significantly reduced.

  Further, it is desirable that the silica fine particles have been subjected to a hydrophobizing treatment. For the hydrophobizing treatment, the silica fine particles are provided by reacting or physically adsorbing an organosilicon compound, a silane compound, or the like. Examples of organosilicon compounds include silicone oil, and silane compounds include hexamethylene disilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyldichloro. Silane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane , Dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, , 3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and the like.

  Silica / melamine composite fine particles used as an external additive can be produced according to Patent Document 3. Silica-melamine composite fine particles intervene on the toner particle surface to act as a spacer against mechanical stress caused by the developing roller and the regulating blade, and suppress the embedding of the external additive in the toner particles. . Therefore, the toner surface change is small even with long-term use, and the fluidity of the toner can be maintained. In addition, a stable charge imparting effect can be maintained.

  The average particle size of the silica / melamine composite fine particles is preferably 300 to 1000 nm. When the average particle size is 300 nm or less, the effect of suppressing the embedding of the external additive cannot be expected against the mechanical stress caused by the regulation blade as described above. When the average particle diameter is 1000 nm or more, it is difficult to externally add the toner particles.

  The external addition amount of silica / melamine composite fine particles to the toner particles is desirably 0.05 parts to 2.0 parts. When the external addition amount is 0.05 parts or less, the number of inclusions on the toner surface is small, and the effect of suppressing the embedding of the external additive cannot be expected. It is difficult to attend.

  In Patent Documents 4 and 5, a non-magnetic one-component toner using a melamine resin as an external additive is provided. However, in the non-magnetic one-component development system in which the toner particles on the surface of the developing roller are subjected to a large mechanical stress when passing through the regulating blade, filming on the photosensitive drum may occur if conditions such as an increase in the temperature in the copying machine overlap. There is a possibility of inducing fusion on the regulating blade. By coating the surface of melamine fine particles, which are an organic substance, with silica, which is an inorganic substance, it is possible to suppress fusion to each developing member.

  The polyester resin, color pigment, release agent, and charge control agent are mixed in advance with a high-speed stirrer such as a super mixer, kneaded with a biaxial continuous extruder or kneader, two rolls, etc., and then quickly cooled while rolling. To do. The cooled kneaded product was roughly crushed by a cutter mill, and then a non-magnetic one-component toner was obtained using a jet airflow pulverizer and an airflow classifier. The toner particle diameter was measured with a multisizer manufactured by Coulter. The particle diameter of the toner is preferably 6.0 to 11.0 μm, and more preferably 7.0 to 9.5 μm.

  As a method for externally adding the inorganic fine particles to the toner surface, there is a high-speed stirrer that gives a shearing force such as a Henschel mixer or a super mixer by appropriately blending the toner particles and the inorganic fine particles. Next, as a method of removing foreign matters and coarse particles at the time of external addition, sieving using an ultrasonic sieve, a vibrating sieve such as a gyro shifter, or a rotary sieve such as a turbo screener can be mentioned. Toner can be obtained.

The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist.
The method for preparing the toner particles in the present invention is as follows.

Table 1 shows toner constituent materials in each of Examples and Comparative Examples. Here, the addition amount of a constituent material is as follows with respect to 100 parts of polyester resins.
-Color pigment 5.0 parts-Charge control agent 1.0 part-Wax 2.0 parts

  The toner constituent materials are mixed in advance by a super mixer, kneaded by a biaxial continuous extruder, and then rapidly cooled while being rolled by two rolls subjected to water cooling. The cooled kneaded product was roughly crushed with a cutter mill, and then adjusted to a volume average particle size of about 8.2 μm using a jet airflow pulverizer and an airflow classifier. The toner particle diameter was measured with a multisizer manufactured by Coulter.

[Example 1]
Further, with respect to 100 parts of the toner particles obtained as described above, 1.5 parts of silica fine particles A (30 nm) and 0.2 parts of silica / melamine composite fine particles (650 nm) were externally added and mixed with a super mixer, and mesh # After sieving at 200, non-magnetic one-component toner particles were obtained.

[Example 2]
Similarly to Example 1, with respect to 100 parts of the toner particles obtained as described above, 1.5 parts of silica fine particles B (8 nm), 1.5 parts of silica fine particles C (50 nm), and silica / melamine composite fine particles (650 nm) 0 2 parts were externally mixed with a super mixer and sieved with mesh # 200 to obtain non-magnetic one-component toner particles.

[Comparative Example 1]
As in Example 1, 1.5 parts of silica fine particles A (30 nm) and 0.2 parts of melamine fine particles (350 nm) were externally added and mixed with 100 parts of the toner particles obtained as described above by using a super mixer. After sieving at 200, non-magnetic one-component toner particles were obtained.

[Comparative Example 2]
As in Example 1, 1.5 parts of silica fine particles B (8 nm), 1.5 parts of silica fine particles C (50 nm), and 0.2 parts of melamine fine particles (350 nm) are added to 100 parts of the toner particles obtained as described above. After external addition with a super mixer and sieving with mesh # 200, non-magnetic one-component toner particles were obtained.

[Comparative Example 3]
In the same manner as in Example 1, 1.5 parts of silica fine particles A (30 nm) were externally added and mixed with 100 parts of the toner particles obtained as described above using a super mixer, sieved with mesh # 200, and then nonmagnetic. One-component toner particles were obtained.

[Comparative Example 4]
Similarly to Example 1, 1.5 parts of silica fine particles B (8 nm) and 1.5 parts of silica fine particles C (50 nm) were externally added and mixed with 100 parts of the toner particles obtained above by a super mixer. After sieving with # 200, non-magnetic one-component toner particles were obtained.

[Evaluation methods]
(1) Evaluation machine A full color copying machine (ARC260) manufactured by Sharp Corporation was used.

(2) After obtaining 10 continuous blown solid images, the stain on the white background was evaluated based on the following legend.
(Legend) ◎: No problem at all, ○: Slightly soiled, but practically no problem, △: Partially soiled, ×: Severely soiled

(3) Gently place 30 g of apparent density non-magnetic one-component toner on a funnel with mesh, and place a cup (30 cc) under the funnel. The toner on the mesh is gently swirled with a brush at a constant speed to disperse and drop the toner. The weight of the toner dropped into the cup is weighed, and the apparent density is calculated from the following formula.
Apparent density = (toner weight) / (cup volume (30 cc)) [g / cc]
The apparent density was evaluated based on the following legend.
(Legend) ◎: 4.20 or less to 4.00 or more, ○: less than 4.00 to 3.80 or more, x: less than 3.80

(4) Image Density A solid portion of the transfer paper imaged by a reflection densitometer RD918 manufactured by Macbeth was measured and evaluated based on the following legend.
(Legend) ◎: 1.65 or less to 1.55 or more, ○: less than 1.55 to 1.45 or more, Δ: less than 1.45 to 1.35 or more, x: less than 1.35

(5) The white background portion of the fog transfer paper and the white portion of the 5% band image drawn by the above evaluation machine were measured at the same position with a whiteness meter Σ90 manufactured by Nippon Denshoku Co., Ltd. The fog was calculated.
(Legend) Through 10000 sheets, ◎: less than 0.60, ○: less than 0.80, Δ: less than 1.00, x: 1.00 or more

(6) After 10,000 sheets were passed by a filming evaluation machine, the toner drum was confirmed by visually observing the surface of the photosensitive drum.
(Legend) ○: No problem, x: Filming occurred The above items were comprehensively judged based on the following legends, and were evaluated as comprehensive evaluation.
(Comprehensive evaluation) (double-circle): It is excellent, (circle): There is no problem in practical use, X: There exists a problem in practical use.

  From Table 2, the toners of Examples 1 and 2 using silica fine particles having an average particle diameter of 5 to 100 nm and silica / melamine composite fine particles having an average particle diameter of 300 to 1000 nm as the external additive are excellent in comprehensive evaluation. On the other hand, the toners of Comparative Examples 1 to 4 which do not use these in combination are inferior in overall evaluation.

Claims (2)

  In a toner obtained by mixing and adding at least two or more kinds of external additives to toner particles containing at least a polyester resin and a color pigment, the external additive has silica fine particles having an average particle diameter of 5 to 100 nm and an average particle diameter of 300 to A non-magnetic one-component toner characterized by being a fine particle of 1000 nm silica / melamine composite.   2. The non-magnetic one-component toner according to claim 1, wherein the silica fine particles are composed of silica fine particles having an average particle diameter of 5 to 20 nm and silica fine particles having an average particle diameter of 20 to 100 nm.