JPS61117565A - Production of toner composition for electrophotography - Google Patents

Abstract

PURPOSE:To decrease the variance of the specific charge of a toner and to obtain excellent printed image by dissolving a binder resin, coloring agent and charge control agent into a solvent to prepare a uniform soln., evaporating the solvent therefrom and pulverizing the resulted toner lump material to form pulverous powder. CONSTITUTION:91pts.wt. Epoxy resin as the binder resin, 3pts.wt. nigrosine dye as the charge control agent and 33pts.wt. carbon black as the coloring agent are added under stirring each slightly into the methyl ethyl ketone in a beaker and the mixture thereof is thoroughly stirred. The soln. of the resulted uniform compsn. is vacuum-dried at 50 deg.C to evaporate the entire solvent. The resulted black lump material is pulverized after cooling to obtain the toner compsn. having 5-20mu grain size. Such toner compsn. is mixed with iron powder as a carrier by which a developer having 4wt% toner concn. is obtd. The sharp printed image without fogging is thus stably obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrophotography technology. More particularly, the present invention relates to a method for producing toner compositions that can be advantageously used in electrophotographic processes. The toner composition according to the present invention can be used in a wide range of electrophotographic development devices.
- Examples include LED printers, light emitting diodes, etc.
It can be used for printer devices such as printers.

[Conventional technology]

For example, a Rede printer is an output device that writes output information from a computer onto a photosensitive drum using a laser beam, and then prints the information on recording paper at high speed and with high quality using an electrophotographic process. Here, the laser light from the semi-source is modulated by an ultrasonic light modulator into a blinking signal according to output information from the computer, and then scanned onto the photosensitive drum by a rotating polygon mirror. In this way, when a laser beam is irradiated onto a photosensitive drum whose entire surface has been charged in advance, the stain is lost due to the photoconductive effect only in the irradiated area, creating a latent image corresponding to the output information. is written. To develop this latent image, toner as a developer is attached to the latent image area on the photosensitive drum. A toner usually consists of a binder resin, a colorant, and a charge control agent dispersed in the binder resin. After the development is completed, the recording paper is pressed onto the photosensitive drum to which the toner image has been adhered and transferred, and then the transferred toner image on the recording paper is fixed by applying heat. For such image fixing, fixing methods such as flash fixing and hot roll fixing are widely used.

By the way, conventional toner for electrophotography (referred to as 6-toner composition in the present invention) is usually produced by heating toner-forming components such as a binder resin, a colorant, and a charge control agent with a heating kneader or the like to melt them. However, in this toner production method, the viscosity of the binder resin when melted is high, so it is difficult to disperse the charge control agent in the melted binder resin, and as a result, the strength of the binder is reduced. In other words, uneven distribution of the charge control agent occurs, that is, non-uniform dispersion occurs.

If such a bias exists in the charge control agent, the toner specific charge will vary from one toner to another obtained through subsequent steps such as pulverization. Here, "toner specific charge" refers to the toner mass ratio achieved when the obtained toner is mixed with a carrier (carrier material) such as iron powder or glass beads and charged by the friction of the carrier. means the amount of charge □.

In fact, if the specific charge of the toner is high, the print density will be low, and conversely, if the specific charge of the toner is low, the toner will scatter when mixed with the carrier, contaminating the inside of the device, and the toner will fog up on the print background during printing. Inconvenient problems arise, such as the so-called capri phenomenon occurring due to the adhesion of particles. Such problems are particularly noticeable when there are variations in the toner specific charge.

[Problem that the invention seeks to solve]

The problems to be solved by the present invention are as is clear from the description of the prior art described above, and the disadvantages caused by variations in toner specific charge caused by the conventional toner manufacturing method, namely, low print density. , equipment contamination, fogging phenomenon, etc. In other words, the present invention eliminates these drawbacks, improves the dispersibility of the charge control agent in the binder resin, reduces variations in toner specific charge, and provides a toner for electronic display with less toner scattering and capri. It is an object of the present invention to provide a method for producing a composition.

[Means for solving problems]

The present inventors have recently discovered that in producing an electrophotographic toner composition having a colorant and a charge control agent dispersed in a binder resin, the above-mentioned toner-forming properties can be improved using a conventional production method. Rather than heating, melt-kneading the ingredients, the binder resin, colorant, and charge control agent are dissolved in a solvent to form a homogeneous solution, the solvent is evaporated from this solution to obtain a toner mass, and the toner mass is then processed. It has been discovered that the above-mentioned problems can be solved by pulverizing the toner mass into a fine powder.

A homogeneous solution 12 of toner-forming components, for example, first dissolving a binder resin in a solvent, then adding a colorant and a charge control agent to this resin solution and uniformly mixing and dissolving; binder resin, colorant; It can be prepared by adding the charge control agent to the solvent all at once or in portions, and then uniformly mixing and dissolving the charge control agent. Furthermore, in order to achieve uniform mixing and dissolution, it is recommended to use regular stirring operations.

Finally, in order to crush the toner agglomerates into fine powder, it is recommended to use a combination of crushing operations such as coarse crushing, medium crushing, and fine crushing, and classification operations.

Binder resins that may be advantageously used in the practice of the present invention include natural or synthetic resin materials commonly used for the same purpose in this technical field, such as epoxy resins, styrenic resins (styrene-acrylic resins), etc. It is.

Colorants useful in the present invention are pigments commonly used in the art, such as carbon black, iron black, and the like. Charge control agents useful in the present invention include resin materials and dyes commonly used in this field, such as nigrosine dyes and monoazo dyes.

These toner-forming components can be dissolved in any inorganic or organic solvent, such as methyl ethyl ketone. Furthermore, these toner-forming ingredients can be formulated as desired depending on the properties of the ingredients and the desired results.

By the way, there is currently no known reliable method for measuring the variation in toner specific charge cited above. The present inventors therefore analogized the variation in toner specific charge using the following method: Figure 1 shows the relationship between the amount of charge control agent and toner specific charge when a charge control agent is added to toner. This is a graph generally showing. From this figure, it can be seen that the toner specific charge increases as the charge control agent is added, and tends to be saturated when the amount of the charge control agent exceeds a certain value. Therefore, it is understood that even if the amount of charge control agent increases in each toner, the toner specific charge hardly increases beyond a certain value.

In relation to the above facts, the relationship between the amount of charge control agent and the number of toners, and the relationship between the specific charge of the toner and the number of toners, for the well-dispersed toner (curve ■) and the poorly dispersible toner (curve ■), respectively. The second section generally shows the relationship between
Reference is made to the diagram and the graph in FIG. From these graphs, it can be seen that when the variation in the amount of charge control agent in the toner is large (curve ■), the average toner specific charge is smaller than when the variation is small as in curve I (
A>B). Since the average toner specific charge can be easily measured by a conventional method, it is possible to easily infer the variation in the charge control agent in the toner, that is, the variation in the jjl+) toner specific charge, from the measured value of the average toner specific charge. . Note that this method can be applied only to toners having the same composition.

〔Example〕

Example 1: Epoxy resin (Evicron EXA-1191, manufactured by Dainippon Ink and Chemicals) as a binder resin, nigrosine dye (Oil Black BY, manufactured by Orient Chemical Exhibition) as a charge control agent, and carbon black (Kyaget Co., Ltd.) as a coloring agent. A toner composition was prepared containing P2K Pearls L) manufactured by Co., Ltd. with the following composition: Epoxy resin 91 parts Nigrosine dye 3 parts Carbon black 3 parts These materials were added little by little to methyl ethyl ketone in a beaker while stirring. , and mix under stirring.
continued over time. The resulting homogeneous solution was then vacuum dried at 50°C. The entire amount of methyl ethyl ketone used as a solvent was evaporated to give a black toner mass.

After cooling this toner mass to room temperature, it was coarsely pulverized with a rotoplex type pulverizer, and the coarsely pulverized toner was further pulverized with a jet mill (PJM pulverizer manufactured by Nippon Pneumatic Industries). Furthermore, the obtained toner fine powder was classified using an air classifier (manufactured by Lupine Co., Ltd.) to have a particle size of 5 to 20.
A toner composition of μm was obtained.

The toner composition obtained as described above was mixed with iron powder (EFV 250 manufactured by Nippon Iron Powder Co., Ltd.) as a carrier to prepare a developer for a magnetic brush having a toner concentration of 4% by weight. A series of printing tests were conducted using this developer in a flash fixing type laser printer (F-6715D manufactured by Fujisoku Co., Ltd.). Toner specific charge during printing is 15μC/
It was determined that ll. As a result of this printing test, even after printing 100,000 sheets continuously, clear printing without fogging was stably obtained, and there was almost no contamination inside the device due to toner scattering.

Example 2: The procedure described in Example 1 above was repeated. However, in this example, instead of adding the epoxy resin, nigrosine dye, and carbon black all at once to methyl ethyl ketone, the entire amount of the epoxy resin is first dissolved in methyl ethyl ketone, and then the nigrosine dye and carbon black are added to the epoxy resin solution. Carbon black was added little by little and mixed and dissolved.

The results of a series of printing tests were the same as those of Example 1 above.

Example 3 (comparative example): The procedure described in Example 1 above was repeated. However, in the case of this example, methyl ethyl ketone was not used in the preparation of the toner composition, and instead, 91 parts by weight of epoxy resin, 3 parts by weight of nigrosine dye, and 3 parts by weight of carbon black were used.
The mixture was kneaded for about 1 hour using a pressure kneader heated to 0°C.

After cross-mixing, the resulting toner mass was cooled and then coarsely pulverized, finely pulverized, and classified in the same manner as in Example 1 to obtain a toner composition having a particle size of 5 to 20 μm.

Next, a magnetic brush developer was prepared from the above toner and the iron powder described in Example 1 in the same manner as in Example 1, and a series of printing tests were conducted in the same manner as in Example 1.

In this example, the toner specific charge during printing was 10 μC/g. As a result of the printing test, it was found that fogging occurred in the printing background area, and that contamination had already occurred inside the device due to toner scattering after printing 10,000 sheets.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the variation in toner specific charge that could not be avoided until now due to the manufacturing method, so it is possible to prevent contamination inside the device caused by toner scattering, and At the same time, it is possible to achieve excellent printing without fogging.

[Brief explanation of the drawing]

FIG. 1 is a graph generally showing the relationship between the amount of charge control agent and the toner specific charge, and FIGS. 2 and 3 are graphs showing the relationship between the amount of charge control agent and the number of toners, and the toner 2 is a graph generally showing the relationship between specific charge and the number of toner particles. In the figure, the curve ■ indicates a toner with good dispersion, the curve ■ indicates a toner with poor dispersion, and A and B indicate the average specific charge of the toner.

Claims (1)

[Claims] 1. A method for producing an electrophotographic toner composition having a colorant and a charge control agent dispersed in a binder resin, the method comprising: dispersing the binder resin, the colorant, and the charge control agent in a solvent; A toner composition for electrophotography, which is characterized by dissolving to prepare a homogeneous solution, evaporating the solvent from this solution to obtain a toner mass, and then crushing the toner mass to form a fine powder. Production method. 2. First, dissolve the binder resin in a solvent, then add the colorant and charge control agent to this resin solution and mix uniformly.
The manufacturing method according to claim 1, which involves dissolving. 3. The manufacturing method according to claim 1, wherein the binder resin, colorant, and charge control agent are added to the solvent all at once or in portions, and then uniformly mixed and dissolved.