JPH0648390B2 - Toner - Google Patents

Description

TECHNICAL FIELD The present invention relates to a toner, and more particularly to a toner for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like.

(Background of the Invention) Generally, a toner for developing an electrostatic latent image used in an electrophotographic copying machine or a laser printer mainly contains a colorant and a thermoplastic binder resin. This colorant,
In particular, carbon black is often used as a black colorant. Since carbon black has a low surface electric resistance,
The cohesiveness is high, resulting in insufficient dispersion of carbon black when the toner composition is pulverized to produce a toner having a predetermined particle size. If the dispersibility of the colorant is poor, the chargeability becomes unstable, and the toner scatters frequently. In addition, the image quality may be poor and the halftone portion may be uneven. In order to improve the image quality, the particle size of the toner may be reduced. However, if the particle size is reduced, problems such as fluidity and heat resistance of the toner may occur. There are various difficulties to overcome.

In particular, the above-mentioned drawbacks tend to result in poor dispersibility of the coloring agent (carbon black) when the gelling component of the resin is increased or the molecular weight distribution is widened to prevent offset in the oilless fixing method. Will increase.

Therefore, a material having good dispersibility in place of the carbon black is desired, but carbon black is still used from the viewpoints of price, handling, particle size, and compatibility with other components.

(Object of the Invention) The present invention provides a toner which is excellent in charging rise and has less toner scattering, or a toner which has good gradation reproducibility of image quality and fine line reproducibility and does not cause unevenness in a halftone portion. To aim.

(Structure of the Invention) That is, the present invention provides a toner containing a binder resin and activated carbon.

The present invention is characterized by containing activated carbon as a colorant. Activated carbon has high surface electrical resistance and low cohesiveness, and therefore has better dispersibility than carbon black. When the dispersibility is improved, the variation in charging property is eliminated and the toner is not scattered. Further, the gradation reproducibility of image quality and the reproducibility of fine lines are improved, and unevenness in the halftone portion does not occur.

The activated carbon used in the present invention may be any activated carbon such as coconut husk and charcoal. The particle size of the activated carbon is preferably about 5 μm or less. The activated carbon has a large number of pores on its surface, but the number thereof is not particularly limited. Further, as the activated carbon, a commercially available activated carbon can be used as it is without pretreatment.

Even if activated carbon is used in combination with conventional carbon black, the effects of the present invention can be sufficiently obtained. Activated carbon should be at least 5 in the colorant
The effect of the present invention is sufficiently observed when the content is 0% by weight. Therefore, in addition to activated carbon, conventional carbon black and other colorants may be used together. Examples of carbon black include furnace black, channel black, and acetylene black. Examples of other coloring agents that can be used include iron black, cupric oxide, manganese dioxide, and alinine black, but they are not limited to these, regardless of whether they are organic or inorganic, as long as they have no pollution and coloring power. It is not something that will be done.

The amount of activated carbon added is 1 to 20 parts by weight, preferably 5 to 15 parts by weight, of the binder resin. It has a drawback that the coloring power of the toner is less than 1 part by weight, which is weak. If it is added in an amount of more than 20 parts by weight, the charging property will be poor and the melt viscosity of the toner will be high. In addition, the fixability becomes poor.

As the binder resin used in the toner of the present invention, any binder resin conventionally used as a binder resin for toner may be used. As an example of the binder resin, a vinyl polymer resin, a polyester resin, an epoxy resin, a mixture thereof, or the like may be used.

Vinyl polymerized resins include styrene, methyl styrene,
Copolymers of styrene aromatic vinyl monomers such as α-ethylstyrene, β-methylstyrene, chlorostyrene and vinylnaphthalene with vinyl monomers having a functional group such as carboxyl group, hydroxyl group, amino group and glycidyl group, or these functional groups An example is a copolymer of monomers having a group. Examples of the monomer having a functional group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate and their corresponding methacrylates;
Hydroxyethyl acrylate, 2 hydroxypropyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate and corresponding methacrylates; N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminopropyl acrylate , N, N-dimethylaminobutyl acrylate, and their corresponding methacrylates; glycidyl acrylate, glycidyl methacrylate, etc., but vinyl containing carboxyl group, amino group (including primary to quaternary), hydroxyl group, glycidyl group The monomer is not limited to the above monomers. In addition to these monomers, vinyl monomers having no functional group, such as vinyl chloride and butylene vinyl monomers, and /
Alternatively, a vinyl monomer having an ester bond such as vinyl acetate may be used in combination.

Particularly preferred resins are polymers containing both amino and hydroxyl groups at the same time, including copolymers of aromatic vinyl monomers, vinyl monomers having amino groups and vinyl monomers having hydroxyl groups. A vinyl monomer having an amino group and a hydroxyl group in one molecule may be used, or a polymer having an amino group and a polymer having a hydroxyl group may be blended and used.

Examples of the thermoplastic polyester resin that can be used in the present invention include bisphenol type polyesters described in JP-A-57-37353 and JP-A-59-204848.
Suitable are those having an ester bond, such as rosin glycidyl ester type polyesters and polyesters such as polyethylene terephthalate as disclosed in Japanese Patent Laid-Open Publication No. 2003-242, but not limited thereto. If necessary, it is possible to use a crosslinked product by using a polyhydric alcohol or a polycarboxylic acid together. When a thermoplastic resin other than a polyester resin is used as the thermoplastic resin of the present invention, its gelling density is preferably 5% by weight or more, more preferably 10 to 50% by weight.

Further, the above polyester and styrene or a styrene-acrylic resin can be used in combination.

The toner of the present invention may contain a charge control agent, an offset preventing agent, etc. in addition to the colorant and the binder resin.
Examples of the charge control agent include, for example, nigrosine oil black and oil-soluble dyes such as crystal violet as typical ones that impart positive chargeability to the toner.
Further, typical examples of imparting a negative chargeability include metal complex salt dyes such as barracchin dyes and orazole dyes. Examples of the anti-offset agent include, for example, low molecular weight polyethylene, low molecular weight polypropylene,
Examples thereof include oxidized polyethylene and oxidized polypropylene.

The addition amount of the above-mentioned additive is not particularly limited, but it is preferably used in a ratio of 2 to 7 parts by weight with respect to 100 parts by weight of the resin component.

The toner of the present invention is obtained by thoroughly mixing the composition obtained by mixing the various components described above, further mixing until sufficiently uniform, then kneading, cooling, pulverizing with a pulverizer such as a jet pulverizer, and removing by classification. A toner having a particle size of 5 to 25 μm and an average particle size of about 12 μm is obtained.

(Effects of the Invention) Since the toner of the present invention has good dispersibility of activated carbon, the rise of charging is good and the toner is less scattered. In addition, the gradation reproducibility and fine line reproducibility of the image quality are good, and unevenness in the halftone portion does not occur. Since it is also used as a food additive for activated carbon, there is no problem in terms of safety. Further, since the image quality is improved by using the activated carbon, the toner particle size can be increased to a required range, and there is an advantage in manufacturing such as pulverization.

(Examples) The present invention will be described in more detail with reference to Examples. In the examples, parts and percentages are by weight unless otherwise indicated.

Example 1 A toner for developing an electrostatic latent image was obtained using the following components.

Ingredients Weight part Thermoplastic polyester resin 100 (acid value: 20.3KOHmg / g, softening point 123.5 ° C, glass transition point: 68.3 ° C) Activated carbon ¹ 6 Offset additive additive ² 3 Charge control agent ³ 2 ¹ Takeda Pharmaceutical Company Limited Marketed as Shirasagi A-1. ² Oxidized polypropylene commercially available from Sanyo Chemical Industries as Viscole TS-200. ³ Commercially available as Spiron Black TRH from Hodogaya Chemical Industry.

The raw materials having the above composition were well mixed in a Henschel mixer, kneaded, cooled, coarsely pulverized, further finely pulverized with a jet pulverizer, and then classified to have a particle size of 4 to 20 μm and an average particle size of 11.5.
A toner (1) having a size of μm was obtained. To the obtained toner, 0.2% by weight of hydrophobized silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added and surface-treated by stirring.

Example 2 A toner was prepared using the following components.

Ingredients by weight Thermoplastic styrene-acrylic copolymer resin (softening point 130
℃, 100 glass transition point 65 ° C) Activated carbon of Example 1 5 Additive for offset prevention ⁴ 5 Charge control agent of Example 1 4 ⁴ Commercially available from Sanyo Kasei Co., Ltd. as Viscole 660P.

A toner (2) having the same composition as in Example 1 but having an average particle size of 11.4 μm was obtained. A surface treatment was also performed in the same manner.

Comparative Example 1 For comparison, a toner using only carbon black as a colorant was prepared.

The composition of Example 1 was the same as Example 1 except that 6 parts by weight of carbon black (carbon black commercially available as Special Black 6 from Tegusa Co., Ltd.) was used in place of the activated carbon, and the average particle size was 11.5 μm. Toner
I got (3). A surface treatment was also performed in the same manner.

Comparative Example 2 In this comparative example as well, a toner was similarly prepared using carbon black instead of activated carbon.

In the composition of Example 1, carbon black (carbon black # 4 from Mitsubishi Kasei Co., Ltd.) was used instead of activated carbon.
A toner (4) having an average particle diameter of 11.4 μm was obtained in the same manner with the same composition components except that 6 parts by weight of 4) were used.
The surface treatment was performed in the same manner as in Example 1.

Comparative Example 3 Also in this example, a toner was prepared by using carbon black instead of activated carbon.

In the composition of Example 2, carbon black (carbon black MA from Mitsubishi Kasei Co., Ltd.) was used instead of activated carbon.
Toner (5) having an average particle size of 11.6 μm was obtained in the same manner except that 5 parts by weight of -100 was used. Similarly, the surface treatment was performed in the same manner as in Example 2.

Experimental Example 1 50 g of each toner was placed in a polyethylene bottle of 1 together with 450 g of a carrier (binder type magnetic carrier using styrene-acrylic copolymer resin; average particle size 35 μm), and the charge amount when mixed at a rotation speed of 250 rpm was measured. The measurement was performed after 1 hour, 3 hours, 5 hours, and 10 hours. The results are shown in Table-1.

From the above results, the charge amounts of the toners of Examples 1 and 2 according to the present invention are stable.

Experimental Example 2 A copying machine (EP-650) using the (+) chargeable Se-based photoconductor using each of the developers (1) to (5) prepared as described above.
Z-Minolta Camera Co., Ltd.)
The fineness of the halftone portion, the gradation reproducibility and the fine line reproducibility were evaluated, and the evaluation results shown in Table 2 were obtained.

The fixing of the copying machine is provided with a fixing device using an oilless type Teflon-coated aluminum roller. Also, the fineness of the halftone portion is visually evaluated, the gradation reproducibility is evaluated by using the Kodak Gray Skele 20-step Q-13, and the fine line reproducibility is evaluated by DataQuest. This was performed by using the chart AR-4 manufactured by the company.

From the above results, it is clear that the toner according to the present invention (Examples 1 and 2) is also excellent in gradation reproducibility and fine line reproducibility, and is also excellent in fineness of texture or texture. is there.

Example 3 This example shows an example of determining a suitable particle size range of activated carbon.

In the composition of Example 1, the average particle of activated carbon is 1.0 μm,
Toners (6), (7), and (8) were obtained with the same composition and method as in Example 1 except that the thickness was changed to 7.5 μm and 10 μm.

The charge amount of the obtained toner after 10 hours was measured in the same manner as in Experimental Example 1. In addition, an actual copying test was conducted using the same machine as in Experimental Example 2 to examine whether or not fog and filming occurred.

From Table 3, toners (1) and (6) using an average particle size of less than 5 μm have good charging rise, good fog and filming, but toners using a particle size of more than 5 μm ( Fog and filming occur in 7) and (8). Therefore, it is suitable that the activated carbon has an average particle size of 5 μm or less.

Example 4 This example shows an example showing a proper addition amount range of activated carbon.

In the composition of Example 1, 5 parts by weight of activated carbon was added,
8 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25
Toners (9), (10), (11), (12), (13), and (14) were obtained by the same method and composition as in Example 1 except that parts by weight were changed, and the same method as in Experimental Example 1 After 10 hours, the amount of charge was measured. The results are shown in Table-4.
Shown in.

From the above results, the chargeability is stable when the amount of activated carbon added is in the range of 5 to 15 parts by weight, but the toners (13) and (14) added with 15 or more parts by weight have low chargeability and fogging. A lot of toner is scattered. Also, in the composition of Example 4, activated carbon 1
Carbon black MA- in 2 parts by weight, 4 parts by weight
Toners (15), (16) and (17) were obtained by adding 1 part by weight of each of 8 (manufactured by Mitsubishi Kasei Co., Ltd.). This toner was subjected to an actual copying test in the same manner as in Experimental Example 2 to examine fineness of texture, gradation reproducibility and fine line reproducibility. The results are shown in Table-5.

Claims (1)

[Claims] 1. A toner containing a binder resin and activated carbon.