JP2007086469A - Electrophotographic toner and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner with which the degradation in the amount of electrostatic charge hardly occurs. <P>SOLUTION: The electrophotographic toner formed by making a cyclic siloxane compound adhere to the surface of a toner parent particle is characterized by making the cyclic siloxane compound having a structure of formula (1) adhere to the surface of the toner parent particle. In the formula, n is either of 3 or 10; R is any of hydrogen, 1-3C alkyl group, 1-3C denatured alkyl group; and R' is any of an alkyl group, unsaturated aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, condensed ring hydrocarbon group, and their modified groups. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner used for image formation by electrophotography and a method for producing the same.

  Toner in an electrophotographic development process is attached to an image carrier (for example, a photoreceptor) from a developing roller or the like, and further transferred from the image carrier to a transfer medium.

  At this time, an image defect called so-called character omission may occur.

  In electrophotographic development, the latent image on the image carrier is developed by the adhesion of toner, the developed image is transferred onto a transfer medium, and the image on the transfer medium is fixed to obtain a copy. I can do it.

  Among these processes, in particular, the toner on the image carrier is not uniformly transferred onto the paper in the transfer process, and a part of the transferred image remains on the image carrier and a part of the transferred image is lost. .

  This omission is likely to appear at the center of a line or point, which is called a so-called character omission.

  This missing character is not a big problem in terms of image interpretation, but it is a serious problem for applications requiring high image quality such as copying of photographic images.

  In order to solve such a problem, a linear silicone oil such as dimethylpolysiloxane has been conventionally attached to the surface of the toner base particles (for example, Patent Document 1).

Japanese Patent Publication No. 8-16791

  However, the toner produced in this way has problems such as fogging due to a decrease in the amount of charge with time during continuous printing of a large number of sheets.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an excellent toner for electrophotography in which the charge amount is difficult to decrease and a method for producing the same.

  The present invention has solved the above problems by the following technical configuration.

  (1) An electrophotographic toner obtained by adhering at least a cyclic siloxane compound to the surface of toner base particles.

  (2) An electrophotographic toner obtained by adhering at least a cyclic siloxane compound having a structure represented by the following general formula (1) to the surface of toner base particles.

（ただしｎは３ないし１０のいずれか、Ｒは水素、炭素数１〜３のアルキル基、炭素数１〜３の変性アルキル基のいずれか、Ｒ′はアルキル基、不飽和脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、縮合環炭化水素基およびこれらの変性基のいずれかである。）

(Where n is any of 3 to 10, R is hydrogen, an alkyl group having 1 to 3 carbon atoms, or a modified alkyl group having 1 to 3 carbon atoms, R 'is an alkyl group or an unsaturated aliphatic hydrocarbon group) , An alicyclic hydrocarbon group, an aromatic hydrocarbon group, a condensed ring hydrocarbon group, or a modified group thereof.)

  (3) A toner for electrophotography characterized by comprising a cyclic siloxane compound and a flow modifier coexisting on the surface of toner base particles constituting the toner for electrophotography of (1) or (2).

  (4) The electrophotographic apparatus as described in any one of (1) to (3) above, wherein 0.01 to 2.0 parts by weight of a cyclic siloxane compound is blended with 100 parts by weight of toner base particles. toner.

(5) The electrophotographic toner according to any one of (1) to (4), wherein the cyclic siloxane compound has a kinematic viscosity at 25 ° C. of 30 mm ² / s or less.

  (6) The toner for electrophotography according to any one of (1) to (5), wherein the cyclic siloxane compound has a structure represented by the following formula (2).

  (7) a step of obtaining a kneaded product by hot-melting and kneading a compound comprising a binder resin and a charge control agent as main components, a step of pulverizing and classifying the kneaded product to obtain toner base particles, and the toner base particles being cyclic A method for producing an electrophotographic toner comprising: a step of mixing and stirring with a siloxane compound to obtain a mixture; and a step of mixing and stirring a flow modifier in the mixture.

  According to the present invention, it is possible to provide an excellent electrophotographic toner in which the charge amount is less likely to decrease.

  As a result, it is possible to provide an electrophotographic toner that is less likely to cause missing characters and fog even when a large number of sheets are continuously printed.

  As a result of intensive studies on the above problems, it has been found that the toner for electrophotography is stable because the amount of charge is less likely to be reduced by attaching a cyclic siloxane compound represented by the following formula (1) to the surface of the base particles. It was.

（ただしｎは３ないし１０のいずれかが好ましく、さらに好ましくは３〜７、さらに好ましくは３〜５、もっとも好ましくは５である。Ｒは水素、炭素数１〜３のアルキル基、炭素数１〜３のアルキル変性基のいずれかが好ましく、さらに好ましくは水素、炭素数１〜３のアルキル基のいずれか、もっとも好ましくはメチル基である。Ｒ′はアルキル基、不飽和脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、縮合環炭化水素基およびこれらの変性基のいずれかが好ましく、さらに好ましくはアルキル基、フェニル基、ビニル基およびこれらの変性基のいずれか、もっとも好ましくはメチル基である。）

(However, n is preferably any of 3 to 10, more preferably 3 to 7, more preferably 3 to 5, and most preferably 5. R is hydrogen, an alkyl group having 1 to 3 carbon atoms, or 1 carbon atom. Is preferably any one of ˜3, more preferably hydrogen, any one of 1 to 3 carbon atoms, and most preferably a methyl group, R ′ being an alkyl group or an unsaturated aliphatic hydrocarbon group. , An alicyclic hydrocarbon group, an aromatic hydrocarbon group, a condensed ring hydrocarbon group and any of these modified groups are preferred, more preferably any of an alkyl group, a phenyl group, a vinyl group and any of these modified groups, Most preferably, it is a methyl group.)

  This will be described with reference to FIG.

  1A and 1B are explanatory views of the toner for electrophotography of the present invention, in which FIG. 1A is a diagram of toner base particles, FIG. 1B is a diagram in which a cyclic siloxane compound is added, and FIG. The figure of the state which added the agent, (d) is a figure of the state which changed with time.

  11 is toner base particles, 12a is a cyclic siloxane compound, and 13 is a flow modifier.

  When the cyclic siloxane compound 12a is added to the toner base particles 11 as shown in FIG. 1A, the cyclic siloxane compound 12a has a low molecular weight and a low kinematic viscosity as shown in FIG. Regardless of the unevenness of the particles 11, the surface of the toner base particles 11 can be covered without any problem, which is considered to prevent the chargeability from being lowered.

  Then, as shown in FIG. 1 (c), when a flow modifier 13 such as hydrophobic silica is further adhered thereto, the flow modifier is firmly attached over time as shown in FIG. 1 (d). 13 is held, which is also considered to prevent a decrease in chargeability.

  One type of cyclic siloxane compound can be used, but it is also possible to use a mixture of a plurality of types as required.

  The selection and mixing ratio of the cyclic siloxane compound are ultimately determined by the charging characteristics, fluidity, etc. of the desired toner.

The dynamic viscosity of the cyclic siloxane compound used in the present invention is preferably 30 mm ² / s or less at 25 ° C., more preferably 10 mm ² / s or less, and most preferably 5 mm ² / s or less.

When the kinematic viscosity of the cyclic siloxane compound exceeds 30 mm ² / s, mottle is likely to occur, which is not preferable.

  The amount of the cyclic siloxane compound used in the present invention is preferably 0.01 to 2.0 parts by weight, more preferably 0.01 to 1.0 parts by weight, most preferably 100 parts by weight of the toner. 0.01 to 0.1 part by weight.

  In this case, if the amount is less than 0.01 part by weight, the object of the present invention cannot be achieved, and if it exceeds 2.0 parts by weight, the fluidity between toner particles is unfavorably deteriorated.

  There is also a method in which a powdery external additive such as silica is treated with a hydrophobic material with a cyclic siloxane compound and the silica is adhered to the toner. However, the surface of the toner base particles cannot be covered with the cyclic siloxane compound without any problem. The effect of the invention cannot be obtained.

  In the present invention, a cyclic siloxane compound as a liquid external additive is directly adhered to the surface of the toner base particles by stirring with a mixer such as a Henschel mixer or a super mixer, thereby providing a sufficient effect without harm even in a small amount. I can do it. Further, spraying or the like can be performed while the toner base particles are being stirred.

  The electrophotographic toner of the present invention is produced as follows.

  That is, the method for producing an electrophotographic toner of the present invention comprises a step of obtaining a kneaded product by hot-melting and kneading a formulation mainly comprising a binder resin and a charge control agent, and crushing and classifying the kneaded product to obtain a toner base. A step of obtaining particles, a step of mixing and stirring the toner base particles with a cyclic siloxane compound, and a step of mixing and stirring a flow modifier in the mixture.

  More specifically, the toner base particles used in the electrophotographic toner are a binder resin, a charge control agent, and other additives, if necessary, blended into a predetermined composition, and this mixture is mixed with a biaxial kneader, It is manufactured by melt-kneading using an extruder, roll mill or the like, pulverizing the obtained lump by mechanical pulverization means such as a jet mill, and classifying it into particles having a predetermined particle size by a classifier.

  Further, it may be a suspension polymerization method or a spray drying method.

  Binder resins include styrene-acrylic resins, polystyrene, polyethylene, vinyl resins, polyacrylates, polymethacrylates, polyvinylidene chloride, polyacrylonitrile, polyethers, polycarbonates, polyesters, cellulosic resins, and copolymers of these monomers. In addition to thermoplastic resins such as resins, thermosetting resins such as modified acrylic resins, phenol resins, melamine resins, and urea resins can be used. A mixture of these may also be used.

  As the charge control agent, any charge control agent used for toners can be used, but iron-based metal-containing dyes, chromium-based dyes, nigrosine compounds, quaternary ammonium salts, and the like that particularly improve frictional chargeability can be preferably used. .

  Other additives that may be added as needed include colorants such as carbon black and colorants, fixing aids such as low molecular weight polypropylene, mold release agents, and magnetic powder.

  The toner for electrophotography of the present invention is obtained by attaching a cyclic siloxane compound to the obtained toner base particles.

  Further, the toner base particles constituting the present invention may be externally added with a flow modifier described below in combination with a cyclic siloxane compound, if necessary.

  As the flow modifier, hydrophobic silica, colloidal silica, fatty acid metal salt, alumina, titanium compound, resin fine particles and the like can be appropriately used.

  The obtained electrophotographic toner can be used as a one-component developer, or can be mixed with a carrier and used as a two-component developer.

  Any carrier can be used as long as it is a known carrier. From the viewpoint of magnetic force, charging characteristics, shape, etc., for example, a ferrite carrier or a granulated magnetite carrier produced by a spray dry-granulation-firing process is preferable. Can be used.

The present invention will be described below with reference to examples.
<Method for producing toner base particles>
Styrene-acrylic acid copolymer resin (trade name: TTR-591, manufactured by Fujikura Kasei Co., Ltd.)
90.0 parts by weight of charge control agent (Nigrosine compound, trade name: CCA3, manufactured by Chuo Gosei Co., Ltd.) 3.6 parts by weight of carbon black (trade name: Mitsubishi Carbon # 40, manufactured by Mitsubishi Chemical Corporation) 4.6 parts by weight of low molecular weight polypropylene (Product name: Viscol 660P, manufactured by Sanyo Chemical Industries)
1.8 parts by weight

  The raw materials having the above blending ratio are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air classifier, resulting in a volume average particle size (D50) of 9 Toner base particles for a non-magnetic one-component developer of 0.0 μm were obtained. The volume average particle diameter (D50) is a volume-based integrated 50% value by Coulter counter TA-II type.

  The cyclic siloxane compounds shown in Table 1 were adhered to the surface of the base particles to prepare toners for electrophotography of the present invention shown in Examples 1 to 4 below.

Example 1
To 100 parts by weight of the toner base particles, 0.06 part by weight of dimethyl cyclic siloxane (D5) represented by the formula (2), which is a cyclic siloxane compound, was added and stirred with a super mixer.

  After stirring, 0.4 wt% of hydrophobic silica coated with linear dimethyl silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a flow modifier and mixed and stirred. The toner for electrophotography of Example 1 was obtained.

(Example 2)
An electrophotographic toner of Example 2 was obtained in the same manner as in Example 1 except that the cyclic siloxane compound used in Example 1 was used instead of the dimethyl cyclic siloxane (D4) represented by the formula (3). .

(Example 3)
An electrophotographic toner of Example 3 is obtained in the same manner as in Example 1 except that the cyclic siloxane compound used in Example 1 is used in place of the vinylmethyl cyclic siloxane (V4) represented by the formula (4). It was.

Example 4
The electrophotographic toner of Example 4 was prepared in the same manner as in Example 1 except that the cyclic siloxane compound used in Example 1 was used in place of the fluorinated alkyl cyclic siloxane (F3) represented by Formula (5). Obtained.

(Comparative Example 1)
In Example 1, hydrophobic silica coated with D4 was used without using a cyclic siloxane compound and instead of hydrophobic silica coated with linear dimethyl silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.). A toner for electrophotography of Comparative Example 1 was obtained in the same manner as Example 1 except that it was used.

(Comparative Example 2)
In Example 1, an electrophotographic toner of Comparative Example 2 was obtained in the same manner as in Example 1 except that the cyclic siloxane compound was not added.

(Comparative Example 3)
Example except that the cyclic siloxane compound used in Example 1 was used instead of the linear silicone oil (trade name: KF96-50CS, manufactured by Shin-Etsu Chemical Co., Ltd.) shown in Table 1 and Formula (6). In the same manner as in Example 1, an electrophotographic toner of Comparative Example 3 was obtained.

（ただしｋは１以上の整数）

(Where k is an integer greater than 1)

  Next, a copy test was performed on the toners for electrophotography obtained in Examples 1 to 4 and Comparative Examples 1 to 3.

<Copy test>
Under normal temperature and humidity (25 ° C./55% RH, hereinafter referred to as N / N), under high temperature and high humidity (30 ° C./80% RH, hereinafter referred to as H / H), and under low temperature and low humidity (10 ° C./20 % RH (hereinafter referred to as L / L)), a continuous 3000 page copy test was conducted with a commercially available laser printer (printing speed A4 paper 25 sheets / min) using a non-magnetic one-component minus toner, and the developing sleeve charge amount was evaluated. Went.

  Furthermore, in the N / N copy test, image density, fogging, and missing characters were evaluated.

  A specific evaluation method is shown below.

  In order to obtain the developing sleeve charge amount A, the developing device containing the electrophotographic toner is allowed to stand for 24 hours, and then the stirrer of the developing device is stirred for 10 minutes, and then obtained by the following measuring device.

  FIG. 2 is a schematic view of a measuring apparatus for obtaining the developing sleeve charge amount A. FIG.

  In FIG. 2, 31 is a developing sleeve, 32 is an electrophotographic toner, 33 is a suction machine, 34 is a Q meter, and 35 is a filter.

  Here, the suction device 33 sucks the suction port close to the surface of the electrophotographic toner 32 on the surface of the developing sleeve 31 and sucks it using a vacuum cleaner or the like.

  Further, the Q meter is measured using a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical.

  Specifically, the developing sleeve charge amount A can be obtained as follows.

  (1) Put two paper filters 35 on the suction nozzle of the suction machine 33 so as to overlap each other.

  (2) The weight ma (g) before suction of the suction nozzle is measured.

  (3) The electrophotographic toner 32 adhering to the surface of the developing sleeve 31 is sucked by a suction nozzle for one minute while being moved 20 cm in the longitudinal direction of the developing sleeve 31, and the charge amount q (μc) is obtained by a Q meter 34. .

  (4) The weight mb (g) of the suction nozzle to which the toner for electrophotography after suction is attached is measured.

(5) Then, the weight m (g) of the attracted electrophotographic toner is obtained from mb-ma, and the developing sleeve charge amount A can be obtained by the following equation.
A = q / m (μc / g)

  Image density: The reflection density of the solid image portion was measured with a Macbeth reflection densitometer (RD-914).

  Fog: The reflection density of the non-image area was measured with a Macbeth reflection densitometer (RD-914).

  Missing characters: 30 symbols “i” were printed on the A4 plate, and the presence or absence of missing characters was visually examined.

  Table 2 shows the result of the copy test.

  As is apparent from Table 2, the charge amount of the developing sleeve is not reduced so much after 3000 page copying from the initial stage (hereinafter referred to as the end stage, the same applies to the table) in Examples 1 to 4 in any environment. In Comparative Examples 1 to 3, the decrease is significant.

  In particular, Example 1 showed an excellent developing sleeve charge amount stably in all environments.

  The image density was not significantly different between the example and the comparative example.

  Fog appeared in Comparative Example 3.

  Missing characters appeared at the end of Comparative Examples 1-2.

FIG. 3 shows changes in the developing sleeve charge amount and fog in the N / N copy test.
3A and 3B are graphs showing changes in the developing sleeve charge amount and the fog in the copy test, wherein FIG. 3A is a graph showing the change in the developing sleeve charge amount with respect to the number of prints, and FIG. 3B is a graph showing the change in fog with respect to the number of prints. It is a graph to show.
As is apparent from FIG. 3, in Example 1, the charge amount was kept high and the fogging was kept low in any number of printed sheets as compared with Comparative Example 3.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an electrophotographic toner of the present invention, where (a) is a diagram of toner base particles, (b) is a diagram showing a state where a cyclic siloxane compound is added, and (c) is a state where hydrophobic silica is further added. (D) is a figure of the state which changed with time. Schematic diagram of a measuring device for determining the charge amount of the developing sleeve 7 is a graph showing changes in the developing sleeve charge amount and fog in a copy test, where (a) is a graph showing change in the developing sleeve charge amount with respect to the number of prints, and (b) is a graph showing change in fog with respect to the number of prints.

Explanation of symbols

11 Toner base particle 12a Cyclic siloxane compound 13 Flow modifier 31 Developing sleeve 32 Toner for electrophotography 33 Suction machine 34 Q meter 35 Filter

Claims (7)

An electrophotographic toner obtained by adhering at least a cyclic siloxane compound to the surface of toner base particles. An electrophotographic toner obtained by adhering at least a cyclic siloxane compound having a structure represented by the following general formula (1) to the surface of toner base particles.

(Where n is any of 3 to 10, R is hydrogen, an alkyl group having 1 to 3 carbon atoms, or a modified alkyl group having 1 to 3 carbon atoms, R 'is an alkyl group or an unsaturated aliphatic hydrocarbon group) , An alicyclic hydrocarbon group, an aromatic hydrocarbon group, a condensed ring hydrocarbon group, or a modified group thereof.) 3. An electrophotographic toner comprising a surface of toner base particles constituting the electrophotographic toner according to claim 1 or 2, wherein a cyclic siloxane compound and a flow modifier are present together. 4. The electrophotographic toner according to claim 1, wherein 0.01 to 2.0 parts by weight of a cyclic siloxane compound is blended with 100 parts by weight of toner base particles. The electrophotographic toner according to claim 1, wherein the cyclic siloxane compound has a kinematic viscosity at 25 ° C. of 30 mm ² / s or less. 6. The electrophotographic toner according to claim 1, wherein the cyclic siloxane compound has a structure represented by the following formula (2).

A step of obtaining a kneaded product by hot-melting and kneading a blend resin and charge control agent as main components, a step of pulverizing and classifying the kneaded product to obtain toner base particles, the toner base particles and a cyclic siloxane compound; A method for producing an electrophotographic toner, comprising: a step of mixing and stirring to obtain a mixture; and a step of mixing and stirring a flow modifier in the mixture.

Images