JPH087455B2 - Dry toner for electrophotography - Google Patents

Description

The present invention relates to a dry toner for developing an electrostatic charge image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method or the like.

[Conventional technology]

Conventionally, the dry toner for electrophotography is dry-blended with a binder resin, a colorant, a charge control agent, and other additives that are added as necessary to a desired composition, and the mixture is melt-kneaded to obtain the soul The product was pulverized by mechanical pulverization means, and then classified to have an average particle size of 10 to 20 μm.

However, in the dry toner for electrophotography according to the conventional manufacturing technique, the metal-containing dye or the nigrosine dye used as the charge control agent is not uniformly melt-dispersed in the binder resin. Therefore, the charge amount of the toner during frictional electrification between the individual toner particles and the carrier is unavoidably uniform, and therefore, the conventional dry toner for electrophotography is used for long-term continuous copying, and the image density is reduced and non-image is generated. There were problems such as increased fog in the area.

In order to solve the above problems, mother particles of a colorless resin are prepared by a suspension polymerization method or the like, and a coloring agent, a charge controlling agent, or the like, is mixed with the child particles on the surface of the mother particles, and mechanically attached. A method has been proposed in which a toner is formed by applying a strain force and fixing the toner. However, in this method, depending on the method of adhering the child particles to the mother particles and the material of the child particles, the child particles cannot be sufficiently adhered to the surface of the mother particles, and the unadhered child particles may be spent on the carrier during actual imaging. This has been a cause of problems such as filming on the photosensitive member, toner scattering from the developing device, and deterioration of toner fluidity.

[Problems to be Solved by the Invention]

The present invention provides a novel dry toner for electrophotography, which has stable image characteristics without deterioration of image density or fog on non-image areas in long-term continuous copying.

[Means for solving the problem]

The present invention has been made in view of the above problems,
The outline is as follows.

That is, the present invention relates to a dry method for electrophotography, characterized in that resin particles having an average particle diameter of 0.05 to 2 μm, which are provided with a charging property, are fixed to the surface of colored particles composed of at least a binder resin and a direct colorant. Toner.

 The present invention will be described in detail below.

For the colored particles constituting the present invention, a binder resin, a colorant, and other additives that are added as necessary are dry-blended into a desired composition, and this mixture is used as an extruder.
It is melt-kneaded using a roll mill or the like, and the obtained soul-like substance is crushed by a machine-provided crushing means such as a jet mill to be classified into particles having an average particle diameter of 2 to 15 μm.

As the above-mentioned binder resin, it is possible to use all those which are generally used as binder resins for electrophotographic dry toners, for example, styrene resin, polyacrylic ester resin, styrene-acrylic ester copolymer. Examples thereof include polymer resins, polyvinyl oxide, polyvinyl acetate, polyvinylidene chloride, phenol resins, epoxy resins, polyester resins and the like.

Further, as the colorant, it is possible to use all those generally used as a colorant for a dry toner for electrophotography, for example, carbon black, a monoazo red pigment, a disazo yellow pigment, a quinacridone magenta pigment. , Anthraquinone dyes and the like.

Other additives added as necessary include, for example, polytetrafluoroethylene powder, lubricants such as metal salts of higher fatty acids, abrasives such as cerium oxide, fixing aids such as low molecular weight polyethylene and low molecular weight polypropylene. Can be mentioned.

The colored particles constituting the present invention can be obtained by a polymerization method other than the melt kneading method as described above. That is, it is also possible to form a colored particle by adding a colorant and other additives to be added to the monomer, mixing and dispersing or dissolving the monomer to obtain a polymerization composition, and polymerizing the polymerization composition. .

In this case, as a method for polymerizing the monomer, a suspension polymerization method, an emulsion polymerization method, or the like can be appropriately used. If a polymerization initiator or a polymerization catalyst is required in the polymerization, this is used as a polymerization composition. It can also be added to things.

On the other hand, the resin particles which are the other constituent elements of the present invention are negatively or positively charged in a thermoplastic resin component such as styrene-acrylic ester resin, epoxy resin, polyester resin, low molecular weight polypropylene and low molecular weight polyethylene. Average particle size with the introduction of polar groups with properties of 0.05 to 2
It is a fine particle of μm and can be obtained by a suspension polymerization method, an emulsion polymerization method, or the like. That is, in order to impart chargeability to the resin particles, various polar groups such as a sulfone group and a carboxyl group for the negative polarity, and an amino group and an amide group for the positive polarity are introduced into the resin itself, which is desirable. The charging polarity can be obtained.

Other methods for imparting electrostatic properties to resin particles include azo-based metal-containing dyes, chlorinated polyesters, if they have negative polarity.
Chlorinated paraffin and other positive polarity nigrosine dyes, aliphatic metal salts, quaternary ammonium salts and other charge control agents can be obtained by polymerizing with the above-mentioned thermoplastic resins, or thermoplastic resins and charge control agents. Can be obtained by melt-kneading and pulverizing and classifying.

The glass transition temperature of the resin particles in the present invention is preferably 50 ° C. or higher in order to maintain the storage stability of the dry toner for electrophotography after fixation. Further, the melt viscosity characteristic of the resin particles measured by an elevated flow tester is (a) in relation to the applied temperature and the melt viscosity as shown in FIG.
3 × 10 ⁶ POISE at 85 ℃, (B) 5 × 10 ⁴ POISE at 120 ℃
ISE, (c) Point given by 5 × 10 ⁴ POISE at 205 ° C, (d) 3 × 10 ⁶ POISE at 170 ° C (a), (b),
It is preferable to have a melt viscosity characteristic in a region connecting (c) and (d) with a straight line, that is, in a region A. The resin particles in the B region, which have a higher melt viscosity characteristic than the A region, are less likely to stick to the colored particles because they have a higher melt viscosity, and the resin particles in the C region, which have a lower melt viscosity characteristic than the A region, have a strong cohesive property. As a result, the resin particles are not well dispersed in the colored particles, and the resin particles do not uniformly adhere to the surface of the colored particles.

Next, the means for fixing the resin particles to the colored particles will be described in detail.

In the present invention, in order to fix the resin particles to the colored particles, first, the resin particles 0.1 to 100 parts by weight of the colored particles are added.
100 parts by weight, preferably 3 to 60 parts by weight, are mixed by a mixer typified by a Henschel mixer to disperse the resin particles on the surface of the colored particles. Next, this mixed powder is applied to a powder surface reforming machine (such as Nara Hybridizer of Nara Machinery Co., Ltd. and Ong Mill of Hosokawa Micron Co., Ltd.) to apply compression and frictional force to both mixed particles (hereinafter referred to as surface Resin particles are fixed to the surface of the colored particles (referred to as modification treatment).

〔Example〕

Next, the present invention will be described with reference to examples. All parts in the examples are parts by weight.

Example 1 After stirring the above materials with a Henschel mixer for 10 minutes, melt kneading with an extruder, and then finely pulverizing with a hammer mill or jet mill to obtain an average particle diameter of 9μ with an air flow classifier.
The particles were classified into m to obtain colored particles.

Next, 1 part of the resin particles described below was added to 100 parts of the colored particles.
0 parts were mixed for 10 minutes at 2000 rpm using a Henschel mixer.

The mixed powder obtained by the above operation was applied to Nara Hybridizer (NHS-1 manufactured by Nara Machinery Co., Ltd.), and 6400 rpm
The surface modification treatment was performed twice for 5 minutes to fix the resin particles to the surfaces of the colored particles.

To 100 parts of this powder, 0.4 part of hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) was externally added to obtain a dry toner for electrophotography according to the present invention capable of being negatively charged.

Example 2 After stirring the above materials with a Henschel mixer for 10 minutes, melt kneading with an extruder, and then finely pulverizing with a hammer mill or jet mill to obtain an average particle diameter of 8 μm with an air flow classifier.
To obtain colored particles.

Next, 15 parts of the same resin particles as in Example 1 were mixed with 100 parts of the colored particles, and the surface modification treatment was performed twice by the same method as in Example 1 to fix the resin particles to the surface of the colored particles. After that, hydrophobic silica was externally added to obtain a dry toner for electrophotography according to the present invention, which can be negatively charged.

Example 3 A polymerizable monomer composition having the following composition was polymerized by a suspension polymerization method to obtain colored particles having an average particle size of 7 μm.

Resin particles 1 described below with respect to 100 parts of the obtained colored particles
Electron according to the present invention capable of being negatively charged by externally adding hydrophobic silica after 0 parts of surface modification treatment was performed twice by the same method as in Example 1 to fix the resin particles on the surface of the colored particles. A photographic dry toner was obtained.

Example 4 To 100 parts of the colored particles of Example 3, 10 parts of the resin particles described below were subjected to surface modification treatment 3 times in the same manner as in Example 1 to fix the resin particles to the surface of the colored particles. After that, hydrophobic silica was externally added to obtain a dry toner for electrophotography according to the present invention, which can be positively charged.

The iron powder carrier 100 of 6 parts each of the dry toner for electrophotography according to the present invention based on the above Examples 1 to 4 is used.
To prepare a developer. When a continuous copying test was conducted using a commercially available copying machine using these developers, the results shown in Table 1 were obtained.

As is clear from the results in Table 1, the dry toner for electrophotography according to the present invention has a stable charge amount, so that the image density remains high even after continuous copying of 30,000 sheets. There was no fog and the resolution was good.

〔The invention's effect〕

As described above, according to the present invention, since the resin particles having chargeability are uniformly fixed to the surface of the colored particles, a dry toner for electrophotography having good charging characteristics and image characteristics in continuous copying is obtained. To be

[Brief description of drawings]

 FIG. 1 is a diagram showing melt viscosity characteristics of resin particles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Ebioka 3-1, Somune-cho, Shizuoka-shi, Shizuoka Pref., Yoshio Sugano (56) (JP, A) JP 62-237462 (JP, A) JP 2-294659 (JP, A) JP 1-105261 (JP, A) JP 62-246074 (JP, A)

Claims (3)

[Claims] 1. An average particle size, which is imparted with electrostatic properties, is 0.05 on the surface of colored particles comprising at least a binder resin and a colorant.
A dry toner for electrophotography, characterized in that resin particles of ˜2 μm are fixed. 2. The dry toner for electrophotography according to claim 1, wherein the glass transition temperature of the resin particles is 50 ° C. or higher. 3. The relationship between the applied temperature and the melt viscosity of the resin particles is (a) 3 × 10 ⁶ POISE at 85 ° C., (b) 12
5 × 10 ⁴ POISE at 0 ℃, (C) 5 × 10 ⁴ POI at 205 ℃
SE, (d) is characterized by having a melt viscosity characteristic within a region connecting points (a), (b), (c), and (d) given by 3 × 10 ⁶ POISE at 170 ° C. with a straight line The dry toner for electrophotography according to claim 1.