JP2010152203A - Positively charged red toner for electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positively charged red toner for electrophotography that has early rise of charging, stable electrostatic chargeability and good flowability, and that is free from lowering of image density in running and the occurrence of fog or supply fog. <P>SOLUTION: The positively charged red toner for electrophotography contains at least a polyester in resin and a benzyl tributyl ammonium in a charge control agent. Also, an external additive is characterized by externally adding a fumed silica which is obtained by having the surface with an average particle size of 7-15 nm subjected to hydrophobic treatment by hexamethyldisilazane. An initial charging amount in the developer which is stirred and mixed with carrier is ≥7 μC/g, and the charging amount is 16 to 30 μC/g and a fall rate is ≥70% when stirred for a long time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positively charged red toner for photography used in an electrophotographic apparatus that performs printing at a printing speed of 46 ips or more.

  In general, in an electrophotographic image forming method, an electrostatic latent image formed on a latent image carrier is developed using a developer (toner), and then transferred to a transfer sheet or the like and fixed. Is obtained. This toner is required to be fine particles, excellent fluidity, and appropriately charged powder.

  At this time, the toner is required to have a charge amount by friction with the carrier, and stability over time and charge rise are required as important characteristics. In addition, since the toner is uniformly frictionally charged with the carrier at this time, the toner is required to have a certain fluidity.

  Recently, the speed of electrophotographic apparatuses has been increased, and in the field of color toners, development of a toner having excellent charging performance suitable for high-speed development is desired. The toner used in the high-speed developing device has excellent characteristics that the toner instantaneously reaches a desired charge amount in the developing device, that is, a so-called charge rising property, and has a high charge amount. It is required that the charge does not fluctuate even when it is stirred for a long time.

  By the way, the color toner is used in combination of four colors, cyan toner, yellow toner, magenta toner, and black toner, for full color printing or process color printing for reproducing photographs, paintings, etc. There is monocolor printing in which a mark, an illustration, a color character, and a solid portion are printed using toner, for example, blue toner, green toner, and red toner. Among them, red toner used for displaying seals, vermilion stamps, correction symbols such as letters, underlines, and important characters is frequently used.

  Conventionally, many techniques have been disclosed for color toners used in electrostatic image developing apparatuses, and various positively charged red toners such as JP-A Nos. 2004-117649 and 2003-302793 have been disclosed. The technology has been proposed.

JP 2004-533953 A JP 2004-117649 A JP 2003-302793 A

  Toners are mainly classified into toners that are positively charged and toners that are negatively charged mainly for the reason of the electrophotographic apparatus. Among these, positively charged red toners are made up of negatively charged elements such as polyester resins and azo dyes. Overcoming this is a major challenge.

  In general, a positively charged color toner uses a quaternary ammonium salt or the like as a charge control agent, but there are some which have good charging stability with stirring time with a carrier, but the rise of charging is slow due to the negative charging element. There is a drawback. As described above, in the case where an azo group is used in the positively charged toner particles, particularly in the pigment, it is very difficult to control the charge because the red toner particles include both positively charged elements and negatively charged elements.

  For this reason, high speed printers with a large variation in the stirring time for each particle, for example, 46 ips or more, have been particularly troublesome in charge control. Also in the above-mentioned patent document, the characteristics required for positively charged color toners used in electrophotographic apparatuses of this level of development speed, that is, having a high charge amount, excellent charge rise characteristics, and stable charge characteristics It was difficult to realize that

  Generally, an external additive such as silica is used for the toner in order to obtain charge and fluidity. However, the conventional external additive does not satisfy all of the rise of charge, charge stability, and fluidity in the high-speed printer as described above.

  The present invention has been made in order to solve the above-mentioned conventional problems, and has quick charge rise, stable chargeability, good fluidity, image density reduction during running, fog and replenishment fog. An object is to provide a positively charged red toner for electrophotography that does not occur.

In order to achieve the above object, the first means of the present invention comprises at least a polyester as a resin
Contains benzyltributylammonium in the charge control agent,
The external additive is externally added with fumed silica whose surface has an average particle diameter of 7 to 15 nm hydrophobized with hexamethyldisilazane, and the external additive is treated with aminosilane in addition to at least the hydrophobizing process. In addition to the hydrophobization treatment with hexamethyldisilazane, a mixture treated with cyclic silane is used in combination, and the total amount of the two types of external additives is 0.4 mass% to 1. And the ratio of the two external additives is 1: 3 to 3: 1,
The initial charge amount in the developer stirred and mixed with the carrier is 7 μC / g or more, the charge amount when stirred for a long time is 16 μC / g to 30 μC / g, and the drop rate is 70% or more. It is characterized by this.

  The second means of the present invention is characterized in that, in the first means, the average particle diameter is 8 to 12 μm.

  A third means of the present invention is characterized in that, in the first or second means, the fine powder content of 4 μm or less is 18 number% or less.

  According to a fourth means of the present invention, in the first to third means, the circularity is 0.8 to 1.0.

  The fifth means of the present invention is characterized in that in the first to fourth means, carnauba wax and / or rice wax is used as the wax.

  The present invention is configured as described above, and is positively charged red toner for high-speed electrophotographic apparatus of 46 ips or more, has stable chargeability, good fluidity, reduced image density during running, fogging, A toner that does not generate replenishment fog can be provided.

As a result of intensive studies, the present inventor has used benzyltributylammonium as a charge control agent in order to obtain stable charging, and a surface having an average particle diameter of 7 to 15 nm is used as a silane cup in order to obtain rising of charge and fluidity. The inventors have found that it is effective to externally add fumed silica hydrophobized with a ring agent, and the present invention is characterized by the following (1) to (5).
(1) At least polyester as a resin, benzyltributylammonium as a charge control agent, and externally added fumed silica having a surface with an average particle size of 7 to 15 nm hydrophobized with hexamethyldisilazane, The external additive is a combination of at least the treatment with aminosilane in addition to the hydrophobization treatment and the treatment with cyclic silane in addition to the hydrophobization treatment with hexamethyldisilazane. The total amount of the additive is 0.4% by mass to 1.0% by mass with respect to the toner base material, and the ratio of the two external additives is 1: 3 to 3: 1. The initial charge amount in the developer is 7 μC / g or more, the charge amount when stirred for a long time is 16 μC / g to 30 μC / g, and the drop rate is 70% or more. .
(2) The average particle size is 8 to 12 μm.
(3) The fine powder content of 4 μm or less is 18% by number or less.
(4) The circularity is 0.8 to 1.0.
(5) Carnauba wax and / or rice wax are used as the wax.

  The present invention relates to a red toner, but the red pigment is not limited to an azo type, and a yellow pigment may be used in combination to obtain a yellowish red toner. For example, as a red colorant, quinacridone C.I. I. Pigment Red 122, azo-based C.I. I. Pigment Red 22, C.I. I. Pigment Red 23, C.I. I. Pigment Red 31, C.I. I. Pigment Red 48: 3, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 184, C.I. I. Pigment Red 185, C.I. I. Pigment Red 221 etc. As the yellow colorant, azo C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 155, a benzimidazolone-based C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 154, C.I. I. Pigment Yellow 180, etc.

  These may be used alone or in combination of two or more. However, the pigment is preferably from 0.3 to 20% by mass, particularly preferably from 5 to 10% by mass, based on the resin.

  In the toner of the present invention, various known waxes such as polyethylene wax, polyamide wax, polypropylene wax, Fischer-Tropsch wax and the like can be appropriately used as a release agent. Among them, higher fatty acid ester compounds and / or Or it is preferable to use the wax containing an aliphatic alcohol compound as a mold release agent. Among waxes containing a higher fatty acid ester compound and / or an aliphatic alcohol compound, it is particularly preferable that carnauba wax and rice wax are further combined.

  It is essential for the charge control agent to contain benzyltributylammonium. In general, in the case of a positively charged color toner, since it is desired to use a white color from a transparent color that does not impair the color tone, quaternary ammonium salts, imidazole metal complexes, salts, and the like are used. In the charging of the red toner using the toner, only the above charge control agent was able to obtain the charging stability in which the charging does not increase excessively with the stirring time for a long time, specifically, the charging amount does not exceed 30 μC / g.

  Regarding the external additive in the toner of the present invention, it is essential to externally add fumed silica whose surface having an average particle diameter of 7 to 15 nm is hydrophobized with a silane coupling agent. However, the external additive is a combination of the hydrophobization treatment and aminosilane treatment and the hydrophobization treatment and cyclic silane treatment, and the total amount of the two external additives is the toner base. The ratio of the two external additives is from 1: 3 to 3: 1 with respect to the agent.

  As will be shown later in the Examples, a fumed silica surface-treated with aminosilane and hexamethyldisilazane having an average particle size of 7 to 15 nm in a red toner containing polyester as a resin and benzyltributylammonium as a charge control agent is externally added. Although there is some shortage in the rise of the charge, it becomes very fluid. However, the addition amount is 3.0% by weight or less based on the toner base material. It is a well-known fact that the greater the amount added, the better the fluidity. In that case, depending on the number of printed sheets, the external additive adheres to the photoconductor, or the external additive peeled off from the toner adheres to the carrier side. There is a possibility that the phenomenon of lowering the charge occurs. It is a well-known fact that the smaller the silica particle size, the better the fluidity. However, silica with a particle size of 7 nm or less is immediately embedded in the toner due to agitation stress and does not play its original role. Thus, the particle diameter from which fluidity is obtained is most preferably 7 to 15 nm.

  In addition, in charging, it has succeeded in obtaining from the experimental results that external addition of fumed silica having an average particle diameter of 7 to 15 nm and surface-treated with cyclic silane and hexamethyldisilazane has the greatest effect on the rise. . However, under these conditions, the charge rise is good, but the fluidity has not been improved. Therefore, as a result of intensive studies, the present inventor has found that the above-mentioned problems can be solved by externally adding the two types of external additives together under the following mixing conditions. That is, the total amount of the two types of external additives is preferably 0.4% by mass to 1.0% by mass with respect to the toner base material, and the ratio is preferably 1: 3 to 3: 1.

  The toner of the present invention has an initial charge amount of 7 μC / g or more in the developer stirred and mixed with the carrier, a charge amount of 16 μC / g to 30 μC / g when stirred for a long time, and a drop rate. Needs to be 70% or more. The initial charge amount mentioned here is the value of the charge amount when a developer with a toner concentration of 3.0% is stirred for 20 seconds at 67 rpm in 20 cc polybin, and this value is 7 μC / g when the experiment is repeated. This is due to the discovery that the above is an index that does not cause replenishment fogging in printing. Also, the amount of charge when stirred for a long time shows the value when stirred for 3600 seconds under the same conditions, and as a result of continuous printing, the charge as a developer increases, and as a result the image density decreases. This is due to the discovery that this value is 30 μC / g or less as an index in order not to cause the phenomenon. At this time, if the charge amount is 16 μC / g or less, the proportion of low-charged toner increases, which may cause fog on the printed matter without being controlled on the mag roll. For this reason, the charge amount when stirred for 3600 seconds needs to be 16 μC / g to 30 μC / g.

The drop rate is calculated from the amount of drop when 5 g of the toner is placed on a sieve having a radius of 45 mm and 75 mesh and is vibrated for 60 seconds under an amplitude of 0.35 mm. This is because the developer and the carrier are not mixed well, and in the actual machine, the frictional charging is not sufficiently performed, and a problem such as fogging or replenishment fogging occurs.
In the toner of the present invention, the average particle size is preferably 8 to 12 μm. Above this, the resolution is lowered, and below this, there are problems such as toner scattering.

  In addition, regarding the fine powder content, the fine powder content of 4 μm or less is preferably 18% by number or less, and more preferably 10% by number or less. By doing so, the quality improvement effect in the fluidity and the storage stability is remarkably exhibited, and the toner replenishment property in the developing machine and the charge rising property of the toner are improved.

  In the toner of the present invention, the circularity is desirably 0.8 to 1.0. With an irregularly shaped toner having an average circularity of less than 0.8 and far from a spherical shape, satisfactory transferability and high-quality images without dust cannot be obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the master batch is manufactured by using Pigment Red 184 and a polyester resin at a weight ratio of 1: 1 for red, and manufactured by Pigment Yellow 180 and a polyester resin at a weight ratio of 1: 1 for yellow. It is.

Example 1
Resin Polyester 85% by mass
Colorant (masterbatch) red 5% by mass
Colorant (masterbatch) Yellow 3% by mass
Charge control agent benzyltributylammonium 2% by mass
The mixture of the above composition is melt-kneaded with a twin-screw kneader, and the kneaded product is finely pulverized to a mean particle size of 9 μm with a jet mill pulverizer equipped with a flat plate-type collision plate in the pulverizing section, and further finely classified. Thus, fine particles having a weight average particle size of 10 μm and 4 μm or less and a fine powder content of 8% by number were obtained. Furthermore, using a Henschel mixer, the following external additives were externally added to obtain a red toner for electrophotography.
0.25% by mass of fumed silica (external additive A) whose surface was treated with hexamethyldisilazane and aminosilane on the surface having an average particle diameter of 7 to 15 nm
Fumed silica (hereinafter referred to as external additive B) of 0.25% by mass having a surface with an average particle size of 7 to 15 nm hydrophobized with hexamethyldisilazane and a silane coupling agent
(Examples 2 to 5)
The same raw material as in Example 1 was kneaded and pulverized and classified by the same formulation ratio and method as in Example 1 to produce fine particles having the same particle size distribution as in Example 1. Further, an external additive shown in FIG. 1 was externally added thereto using a Henschel mixer to obtain a red toner for electrophotography.

(Comparative Examples 1-10)
The same raw material as in Example 1 was kneaded and pulverized by the same prescription ratio and method as in Example 1 to produce fine particles having the same particle size distribution as in Example 1. Further, an external additive shown in Table 1 was externally added thereto using a Henschel mixer to obtain a red toner for electrophotography.

  The above toner is printed with a monochrome high-speed continuous form printer at a printing speed of 46 ips and evaluated. The comparison result by Examples 1-5 and Comparative Examples 1-10 is shown in FIG. The carrier used was ecoferrite coated with fluorine resin.

  The evaluation method is as follows.

  The fog was evaluated using a Spectro Color Meter SE2000 manufactured by Nippon Denshoku Industries Co., Ltd. ΔE between the white background after printing and the white background before printing was calculated, and the average of the four measurements was taken as the fogging amount. The smaller the value, the less fogging. At that time, the fog was evaluated as a density on the recording material of less than 0.3% as ◯ and 0.3% or more as x. The sample to be evaluated was the one after 100KFt printing.

  The evaluation of replenishment fogging is performed by printing 10 pages of 40% printing density continuously after printing 20 pages of images with 5% printing density. As soon as the printing density is increased from 5% to 40%, a large amount of toner is supplied from the toner hopper in the developing machine and is put into the mag roll. When replenishment fogging occurs, the toner cannot be charged with the carrier at this time, and is not electrostatically attached but passes directly to the photosensitive member, causing an image density difference in the printed matter. The evaluation was evaluated as ○ × depending on whether or not this phenomenon occurs. The sample to be evaluated was the one after 100KFt printing.

  The rising of the charge and the charge stability were as follows. The developer with a toner concentration of 3.0% was stirred under the above conditions, the charge amount when stirred for 10 seconds was Q10, and the charge amount when stirred for 1 hour was Q3600.

  Regarding the sieve drop rate, 5 g of the toner was vibrated under the above conditions, and the sieve drop rate (% by mass) was calculated from the amount of toner remaining on the sieve. The result is shown in FIG.

It is a figure which shows the ratio of the external additive in Examples 1-5 and Comparative Examples 1-10. It is a figure which compares and shows the various characteristics in Examples 1-5 and Comparative Examples 1-10.

Claims (5)

At least polyester to resin,
Contains benzyltributylammonium in the charge control agent,
The external additive is externally added with fumed silica whose surface has an average particle diameter of 7 to 15 nm hydrophobized with hexamethyldisilazane, and the external additive is treated with aminosilane in addition to at least the hydrophobizing process. In addition to the hydrophobization treatment with hexamethyldisilazane, a mixture treated with cyclic silane is used in combination, and the total amount of the two types of external additives is 0.4 mass% to 1. And the ratio of the two external additives is 1: 3 to 3: 1,
The initial charge amount in the developer stirred and mixed with the carrier is 7 μC / g or more, the charge amount when stirred for a long time is 16 μC / g to 30 μC / g, and the drop rate is 70% or more. A positively charged red toner for electrophotography.   2. The positively charged red toner for electrophotography according to claim 1, wherein the average particle diameter is 8 to 12 [mu] m.   3. The positively charged red toner for electrophotography according to claim 1, wherein the content of fine powder of 4 μm or less is 18% by number or less.   The positively charged red toner for electrophotography according to any one of claims 1 to 3, wherein the circularity is 0.8 to 1.0.   The positively charged red toner for electrophotography according to any one of claims 1 to 4, wherein carnauba wax and / or rice wax are used as the wax.

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