JP2946523B2 - Two-component positively charged developer - Google Patents

Description

The present invention relates to a two-component positively chargeable developer used in the field of electrophotography and the like.

(Prior Art and Problems to be Solved) Conventionally, a two-component developer composed of a carrier and a toner has been used as a developer for developing an electrostatic charge image formed on a latent image holding surface such as an electrophotographic photosensitive member. One-component developers (magnetic toners) that do not require a developer and a carrier are known.

The toner particles that constitute these developers are usually resins,
Colored fine particles containing a colorant, a charge control agent and the like as components.
In a one-component developer, magnetic fine particles such as magnetite having magnetism are used as a coloring agent.

Known resin components such as a styrene resin, an epoxy resin, and a polyester resin can be used as the resin component in these toners.

However, developers using a positively charged toner that contains a dye such as nigrosine as a charge control agent in an epoxy resin or polyester resin with excellent low-temperature fixability and vinyl chloride contamination resistance are used as plain paper copiers, printers, etc. When used repeatedly, the following problems occur practically.

(A) Since the inherent chargeability of the resin has OH groups and COOH groups, the resin is negatively chargeable, and the frictional chargeability becomes non-uniform. Further, the frictional chargeability becomes unstable over time due to mixing with the carrier. Various non-uniformity and instability tend to cause various image defects such as insufficient image density and deterioration of fog.

(B) The ratio at which the developed toner particles are effectively transferred to paper or the like, that is, an image whose transfer efficiency is low tends to cause unevenness and blurring.

(C) The resistance of the developer changes due to unstable frictional charging characteristics over time due to mixing with the carrier, and the image quality such as gradation and resolution changes.

(Means for Solving the Problems) The inventors of the present invention have intensively studied to solve the above-mentioned problems of the conventional toner and to obtain a two-component positively chargeable developer satisfying various required characteristics. The inventors have found a two-component positively chargeable developer in which the triboelectricity of each particle is uniform and stable over time, the change in the resistance of the developer is small, and the transferability is good.

That is, the gist of the present invention is at least a resin, a coloring agent,
In a two-component positively chargeable developer comprising a toner comprising a charge control agent and an external additive and an iron powder carrier, the resin is a polyester resin having an acid value of 5 KOH / mg or less, and the external additive is SiO 2 _{2 is} a fine particle powder, and a triaminotriphenylmethane-based compound represented by the following general formula as the charge control agent with respect to 100 parts by weight of the resin
0.05 to 10 parts by weight of a two-component type positively chargeable developer.

(R represents an alkyl group having 1 to 5 carbon atoms.) Hereinafter, the present invention will be described in detail.

As the colorant in the toner constituting the two-component positively chargeable developer of the present invention, various known colorants can be used.
Examples include inorganic pigments such as carbon black, navy blue and titanium oxide, organic pigments such as azo-based and phthalocyanine-based pigments, and anthraquinone-based dyes. These include the necessary amount in the toner to obtain a clear visible image,
Usually, the amount is 20 parts by weight or less, preferably 10 parts by weight or less based on 100 parts by weight of the resin.

The binder resin used in the present invention is a polyester resin having an acid value of 5 KOH / mg or less.
If it is higher than / mg, the negative charge property of the resin itself becomes strong, and sufficient positive charge characteristics cannot be obtained even if a positive charge control agent is added. The toner of the present invention using such a resin, in combination with a specific charge control agent to be used, can obtain excellent charging characteristics, and has excellent resistance to vinyl chloride contamination, and in this sense, is particularly suitable as a toner for a printer. is there.

As the charge control agent used in the present invention, a triaminotriphenylmethane-based compound represented by the above-mentioned general formula (hereinafter referred to as a TAPM compound) is used as an essential component, and other known positive control agents such as nigrosine-based dyes and quaternary ammonium salts are used. A charge control agent may be used in combination as long as the charge characteristics of the toner are not disturbed.

The charge control agent is added in an amount of 0.05 to 1 based on 100 parts by weight of the resin.
0 parts by weight, preferably 0.1 to 7 parts by weight. The amount of the TAPM compound as an essential component is 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the resin.

In addition, as a component of the positively chargeable toner of the present invention, a fine particle powder of SiO ₂ is included as an external additive, and other components, for example, a low-molecular-weight olefin polymer, TiO ₂ , Various internal or external additives such as ultrafine particle powders such as Al ₂ O ₃ and Fe ₃ O ₄ may be included, but they should be of such an extent as not to impair the object of the present invention.

As a method for producing the toner, the above-mentioned components may be blended, mixed, kneaded in a kneader or the like, cooled, pulverized and classified, and externally added with a stirrer or the like as necessary. The volume average particle diameter of the toner is preferably 5 to 20 μm as measured by a Coulter counter.

When the toner of the present invention is mixed with a carrier and used as a two-component developer, iron powder can be suitably used as the carrier. Further, a so-called coating carrier coated with various resins or the like for the purpose of improving durability during continuous use may be used. The average particle size of the carrier is 10
~ 200 µm is preferred. The mixing weight ratio of the carrier and the toner is preferably 100: 1 to 10.

When the above toner is used as a single-component developer containing a magnetic powder therein, examples of the magnetic powder include fine magnetite powder and ferrite powder. Is from 10 to 80% by weight, preferably from 20 to 70% by weight.

Hereinafter, the present invention will be described in more detail by examples,
The present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples, "parts" indicates "parts by weight". The charge amount was measured using a blow-off charge amount measuring device.

(Example 1) Toner raw materials were mixed at the following mixing ratio, kneaded by an extruder, cooled, pulverized and classified, and 0.2 parts of hydrophobic silica was dispersed at high speed with respect to 100 parts of the classified toner by high-speed stirring. At least, a toner A having an average particle diameter of 12.5 μm was obtained.

Polyester resin A is a polyester mainly composed of bisphenol A and terephthalic acid, and has a resin acid value of 0.7 KOH / m
g, and the acid value was measured according to JIS K-6901 except that a mixture of toluene and methanol at a volume ratio of 9: 1 was used as a solvent for dissolving the sample.

Note that Copy Blue PR is a TAMP compound in which R is a methyl machine.

Then, “Developer A” was prepared by mixing 2 parts of toner A and 98 parts of spherical iron powder carrier having an average particle diameter of 100 μm, and a continuous printing test was performed using a reversal developing non-impact printer equipped with a selenium photoreceptor. Was.

As a result, there was almost no change in the image quality over 100,000 pages from the beginning, and the charge amount also showed a very small change as shown in Table 1.

(Example 2) Table 1 shows the results of print tests in which toner B and developer B were prepared in the same manner as toner A and developer A, except that the above formula was used.

As a result, there was almost no change in the image quality over 100,000 pages from the initial stage, and the charge amount slightly increased in the initial stage, but the power was relatively low.

(Example 3) Bontron P-51 is a quaternary ammonium salt charge control agent.

Table 1 shows the results of a print test in which the toner C and the developer C were adjusted in the same manner as the toner A and the developer A except that the above-mentioned composition was used.

As a result, there was almost no change in the image quality over 100,000 pages from the beginning, and the charge amount was slightly reduced at the beginning, but the change was relatively small.

(Example 4) Table 1 shows the results of a printing test in which toner D and developer D were prepared in the same manner as toner A and developer A except that the above-mentioned composition was used.

As a result, there was almost no change in the image quality over 100,000 pages from the beginning, and the charge amount was very little changed from the beginning.

(Example 5) Table 1 shows the results of a printing test in which the toner E and the developer E were adjusted in the same manner as the toner A and the developer A except for using the above-mentioned composition.

As a result, there was almost no change in the image quality over 100,000 pages from the beginning, and the charge amount also had relatively little change from the beginning.

(Comparative Example 1) Table 2 shows the results of a print test in which the toner F and the developer F were adjusted in the same manner as the toner A and the developer A except for using the above-mentioned composition.

As a result, the initial image quality was good, but the charge amount tended to increase with time, and accordingly, the print density gradually decreased and the voids worsened.

(Comparative Example 2) Table 2 shows the results of a printing test in which the toner G and the developer G were adjusted in the same manner as the toner A and the developer A except for using the above-mentioned composition.

As a result, the initial image quality was good, but the amount of charge tended to decrease over time, and fog gradually worsened.

(Comparative Example 3) Table 2 shows the results of print tests in which the toner H and the developer H were adjusted in the same manner as the toner A and the developer A except for using the above-mentioned composition.

As a result, fog was worse than at the beginning, the charge amount was changed at a low level over time, and the image was not fished.

(Effects of the Invention) As described above, by using the two-component positively chargeable developer of the present invention, a long-life developer with high quality image quality and little deterioration in performance over time can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-123372 (JP, A) JP-A-2-501506 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08 CA (STN)

Claims (1)

(57) [Claims] 1. A two-component positively chargeable developer comprising an iron powder carrier and a toner comprising at least a resin, a colorant, a charge control agent and an external additive, wherein said resin has a polyester having an acid value of 5 KOH / mg or less. a system resin, said external additive is a fine powder of SiO _2, and the charge control agent as triamino triphenylmethane compound represented by the following general formula per 100 parts by weight of the resin 0.05
A two-component positively chargeable developer, characterized by containing up to 10 parts by weight. (R represents an alkyl group having 1 to 5 carbon atoms.)