JPH03114060A - Negatively chargeable toner for electrostatic photography - Google Patents

Abstract

PURPOSE:To enable a toner to have good negative chargeability even at the time of successively copying of a large amount by using a carbon black having an active hydrogen content of 15.0X10<-5> - 30.0X10<-5>mol/g in the surface as a colorant. CONSTITUTION:The toner to be used is prepared by mixing a resin, the carbon black having the active hydrogen content of 15.0X10<-5> - 30.0X10<-5>mol/g in the surface as the colorant, a dyestuff, and auxiliary additives when needed, sufficiently kneading the mixture in a kneader with heating rolls, then pulveriz ing it, further, when needed, finely pulverized with a jet mill, and classified to form the toner having a particle diameter distribution of 5 - 25mum, thus permitting the obtained toner to be improved in negative chargeability even at the time of a large amount copying.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a negatively charged toner for developing an electrical latent image in electrophotography or electrostatic recording.

<Prior art and problems to be solved by the invention> Conventionally, the method of developing an electrostatic latent image with powdered toner was to mix toner powder with magnetic iron powder and hold it in a magnet to form a brush-like image. There is a magnetic brush method in which the mixture is developed by sliding it over an electrostatic latent image, or a toner powder is mixed with a carrier such as a glass bulb and adhered to the surface of the carrier, and this is scattered on the electrostatic latent image. A cascade method is known in which the film is developed using a cascade method.

In all of these developing methods, the toner is mixed with magnetic iron powder or glass spheres, the toner is triboelectrically charged, and the toner is adhered to the electrostatic latent image mainly by Coulomb force, thereby developing the toner. That is, if the polarity of the toner is different from that of the electrostatic latent image, the toner will adhere to the charged electrostatic latent image area, and if the toner is the same, it will adhere to the uncharged non-electrostatic latent image area, thereby preventing development. It will be done.

As carriers used in the magnetic brush method or the cascade method, in addition to the above-mentioned iron powder and glass spheres, those coated with a thin resin film are generally used. As mentioned above, the toner is charged by mixing with these carriers and friction, but the charging polarity depends on the colorant and resin constituting the toner.

In addition to controlling the polarity, the resin also has the purpose of fixing the toner powder, and since the coloring properties and storage stability of the toner change depending on the resin, it is difficult to satisfy the controllability of charge polarity. It also satisfies fixability and other properties.
--Selecting the right resin is not an easy task. 1. Moreover, if the object to be fixed, the fixing device, etc. are different, the required toner requirements will also be different, making it extremely difficult to select the optimal toner.

Note that JP-A No. 50-5052 describes a toner containing an oxidized car and 1ζ blank, but with prior art techniques such as 1 and r, it is still possible to obtain a sufficient negative charge even with 1 or more. It was not possible to impart the properties 1.:;-1.

The present invention improves the above-mentioned drawbacks, and reduces the negative impact even when copying a large number of sheets in succession. Means for Solving the Problems It is an object of the present invention to provide a controlled and stable I/N for electrostatic photography. This was done as a result of consideration, and the outline is at least about colorants and trees)11
In an electrostatic photographic toner consisting of 1. The active hydrogen content on the surface is 15゜0XIO-'”-
A carbon blank of 30.0×10-' mol/g is used.

A carbon blank is generally considered to be a compressed polycyclic aromatic carbon compound, and has carbon atoms arranged in a hexagonal network and has 3 to 5 layer planes stacked in parallel at approximately equal intervals. Near the surface, the crystallites are arranged in parallel j7, but inside the crystallites are irregularly oriented.

A small amount of carboxyl groups, hydroxyl groups, and carbonyl functional groups are present at the edges of the crystallites on the surface of J-. Generally, the properties of carbon black are influenced by these functional groups. The present inventors have conducted a series of studies related to carbon black for toners, and found that the chargeability of carbon black is dominated by active hydrogen present in the surface functional groups. .0×lo”5~30.0×lo-
It has been found that it is good to use carbon black of 'mol/g.

・, Effect> In the present invention, the amount of active hydrogen is 15.0×lo-' m
If it is less than ol/g, the triboelectric chargeability of the carbon black tends to be positive chargeability L, which makes it impossible to impart good negative chargeability to the toner, which is the objective of the present invention.

On the other hand, the amount of active hydrogen is 30.0×lo-' nioi/g
If it exceeds , the dispersibility of the carbon black into the binder resin of the toner becomes poor due to the functional groups introduced excessively into the surface of the carbon black, making it impossible to obtain stable triboelectric charging properties.

Incidentally, the amount of active hydrogen on the surface of carbon black is measured as follows. That is, drop a diethyl ethyl solution of diazomethane onto the carbon brane.
4 Ru, -Toni Carb〉'Black! All of the second active hydrogens (hydrogens of the human 1 coxyl group and carbonyl group) are exchanged with methyl groups. Hydroiodic acid with a specific gravity of 1.7 is added to the treated Chikara-Pon black and when heated, the methyl group becomes methyl iodide and vaporizes. When this methyl iodide gas is mixed with a silver nitrate solution, the methyl iodide turns into silver iodide and precipitates. From the weight of this silver iodide, the amount of original methyl groups, that is, the amount of active hydrogen, can be measured. When we investigated the relationship between the amount of surface active hydrogen and the triboelectricity of iron powder using this method, we found that the closer the amount of active hydrogen was to 0, the more positively charged it was. Conversely, when the amount of active hydrogen increases, it becomes negatively charged, and the amount of charge varies depending on the amount of active hydrogen and the type of carbon black, but on average 1-i5. o X 10-'~17,0
The chargeability approaches 0 at xlo-' mol/g. Therefore, carbon black can be selected depending on the purpose of the toner. Moreover, the amount of surface active hydrogen can be artificially changed by chemical treatment.

Methods for increasing active hydrogen in carbon blank include potassium dichromate, perbenzoic acid, potassium permanganate, lithium aluminum hydride, sodium borohydride,
Treat with phenylazide, aniline, etc. To reduce it, there is a method of treatment with diazomethane, trimethylchlorosilane, dimethyl sulfate, etc. By processing in this way and using a carbon blank that matches the purpose of the toner, the amount of charge of the toner can be stabilized, and the dispersibility and dispersion stability of the resin used in the toner can be improved. Furthermore, since the portion of the toner having the opposite charge is reduced, the image quality is improved, especially white spots (white spots) in solid black areas are eliminated, and the recording density can be increased.

Furthermore, almost all resins conventionally used in toners can be used as the toner resin of the present invention, such as polystyrene, polyester, polyamide, polyethylene, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, maleic resin, etc. Examples include acid resins, acrylic resins, epoxy resins, xylene resins, coumaron resins, ketone resins, petroleum resins, phenol resins, rosin-terpene resins, and the like.

In addition to the above-mentioned materials, the toner of the present invention may optionally include:
Dyes and various auxiliaries and additives can be added.

To make the toner of the present invention, as in the conventional method, resin, carbon black, dye, and if necessary, auxiliary agents are mixed, thoroughly kneaded in a kneader with heated rolls, and then pulverized. It is sufficient to classify it into about 25μ.

<Example> Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 200 g of a carbon blank was placed in a No. 11 round bottom flask, and 150 g of a 15% potassium dichromate aqueous solution was slowly added dropwise thereto, followed by stirring for 6 hours after the dropwise addition was completed. After removing the upper supernatant by decantation, the solid was placed in 21 water, stirred well and allowed to stand. After removing the supernatant, the solid was filtered, washed well with water, dried thoroughly, and then When the amount of active hydrogen was measured using the method, it was 21.7X10-
It was 5 mol/g. This carbon blank is 5
Parts by weight, styrene acrylic resin (styrene/n-butyl acrylate ratio = 7.8/2.2, number average molecular weight 75
000, number average molecular weight/weight average molecular weight ratio = 3.66
) and 5 parts by weight of a dye (Spiron Black BHH, manufactured by Odougaya Chemical Industry Co., Ltd.) was heat-kneaded, cooled, pulverized with a hammer mill, further pulverized with a jet mill, and classified. A toner having a particle size distribution of 25 μm was produced.

Example 2 200 g of carbon black was placed in a round bottom flask (No. 11), and 150 g of a 15% by weight aqueous solution of potassium permanganate was slowly added dropwise thereto. After the addition was completed, the mixture was stirred for 6 hours. After removing the upper supernatant by decantation, the solid was placed in 21 water, stirred well and allowed to stand. After removing the supernatant, the solid was filtered, washed well with water, dried thoroughly, and then When the amount of active hydrogen was measured using the method, it was 15.1X10
-5 mol/g. A toner was produced using this carbon black in the same manner as in Example 1.

Comparative Example 1 100 g of a carbon blank was placed in a 1β round-bottomed flask, and after replacing the gas inside with dry nitrogen, the entire flask was cooled on ice. A solution prepared by dissolving 10 g of diazomethane obtained by hydrolyzing nitrosomethylurea in 150 g of ice-cooled purified diethyl ether was added dropwise to the flask over 10 minutes. The resulting mixture was stirred overnight under water cooling. Ether was removed to obtain dry carbon black. As a result of this treatment, all active hydrogens that can be measured by the final method are methylated.

Next, carbon black 200 before the above diazomethane treatment
g was placed in a No. 11 round bottom flask, the gas inside was replaced with dry nitrogen, and the whole was cooled with water. In this flask, 2.4 g of diazomethane obtained by hydrolyzing nitrosomethylurea
A solution prepared by dissolving this in 150 g of ice-cooled purified diethyl ether was added dropwise over 10 minutes. After stirring until the temperature reached room temperature, ether was removed to obtain diazomethane-treated carbon black.

The diazomethane-treated carbon black obtained here,
The amount of methyl groups in the fully methylated carbon black,
The amount of active hydrogen in the lydiazomethane-treated carbon black was determined by the method described above, and the difference between the two was determined to be 4.1xto-s mo.
It was determined that l/g. A toner was produced using this carbon black in the same manner as in Example 1.

A developer was prepared by mixing 5 parts by weight of each of the toners obtained above with 100 parts by weight of iron powder (manufactured by Nippon Tetsuko Co., Ltd., TEF V 200/300), and a developer was prepared by mixing 5 parts by weight of each toner obtained above with 100 parts by weight of iron powder (manufactured by Nippon Tetsuko Co., Ltd., TEF V 200/300).
When recording was performed using a C copying machine and the characteristics were compared, the results shown in Table 1 were obtained.

Table 1 <Evaluation method> - Density of solid black area: by Macbeth reflection densitometer - White spots on solid black area: Visually measure the degree of occurrence of white spots - Dispersibility of carbon black in toner: Toner Sprayed on a glass plate and thermally melted, then observed the molten film under a microscope. In the table, the recording characteristics and dispersion stability are as follows: ○...Very good△...Good×...Poor××...Very As shown in Table 1, the toners of Examples using chemically treated carbon black to increase the amount of surface active hydrogen had good recording characteristics and carbon dispersibility. or,
When the frictional charge amount of the toner of Example 1 was measured using a blow-off charge amount measuring device, it was -22 μc/g at the start of copying, and was -21 μc/g even after 5,000 sheets were continuously copied. It exhibited almost stable negative chargeability even during the copying process. Further, the toner of the comparative example using carbon whose surface active hydrogen was reduced by chemical treatment had poor recording characteristics and carbon dispersibility.

<Effects of the Invention> As described above, the toner of the present invention has good negative chargeability even when a large number of sheets are continuously copied due to the use of carbon black with an amount of active hydrogen in a specific range as a colorant, and has excellent Recording characteristics can be provided.

Claims (1)

[Claims] In an electrostatic photographic toner comprising at least a colorant and a resin, the active hydrogen content on the surface of the colorant is 1.
5.0×10^-^5~30.0×10^-^5mol
A negatively charged electrostatic photographic toner characterized by using carbon black of /g.