JPH01273056A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To prevent sticking of a toner to a sleeve by using a binder resin and coloring agent as the essential component of the toner and further incorporating conductive zinc oxide in the form of superfine powder having an average primary grain size and specific volume resistivity of respectively specific values or below into the toner. CONSTITUTION:The toner consists essentially of the binder resin and the color ing agent and further, the conductive zinc oxide in the form of the superfine powder having <=80mmu average primary grain size and <=8,000OMEGAcm specific volume resistivity is incorporated into the toner. The sticking of the toner to the sleeve cannot be prevented and the damage of the surface of a photosensi tive body and the white speck phenomenon of an image are generated if the average primary grain size of the conductive zinc oxide is larger than 80mmu. The sticking of the toner to the sleeve cannot be prevented if the specific vol ume resistivity is larger than 8,000OMEGAcm. The average primary grain size and the specific volume resistivity are, therefore, confined to the above-mentioned ranges, by which the desorption of the toner from the toner particle surface is decreased and the sticking of the toner to the sleeve is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic toner for developing electrostatic latent images in electrophotography, electrostatic recording, and the like.

Dry developers for electrophotography are divided into one-component developers containing only toner and two-component developers containing carrier. Two-component developers have the advantage of being able to stably supply an appropriate amount of toner, but have the problem of toner adhesion to the sleeve.

As a method for preventing sleeve adhesion, a method is known in which conductive zinc oxide having an average primary particle size of 100 mμ to 1 μm is deposited on the surface of toner particles. This method prevents the toner charge from accumulating during continuous copying by controlling the resistance or charge of the toner. However, with this method, it is difficult to completely prevent sleeve adhesion, and zinc oxide aggregates are formed in the developer, resulting in white spots on the image. Further, in a blade cleaning type copying machine, definitive damage or black spots occur on the surface of the photoreceptor. Furthermore, even if the above-mentioned zinc oxide is added, the fluidity of the toner is not improved, but on the contrary, it has the disadvantage of deteriorating the fluidity of the toner. As a result of conducting research to eliminate these drawbacks, the present inventor found that when the primary particle size of zinc oxide is large, zinc oxide easily detaches from the surface of toner particles during continuous copying, causing sleeve adhesion. , and by using zinc oxide with a specific particle size, desorption from the toner particle surface is significantly reduced.
It has been found that it is possible to prevent toner from adhering to the sleeve.

The present invention is based on this knowledge, has a binder resin and a colorant as main components, and has an average primary particle size of 8077 μm.
This is an electrophotographic toner characterized by containing ultrafine conductive zinc oxide having a volume resistivity of 8000 Ωm or less.

The conductive zinc oxide used in the present invention has an average primary particle size of 80 to 71μ or less and a volume resistivity of 8000Ωcrn (
The measured pressure is 100 kg/Crn2) or less. If the average primary particle size is larger than 80,771μ, it is not possible to completely prevent toner from adhering to the IJ-tube, resulting in toner adhesion to the photoreceptor, damage to the surface of the photoreceptor, and white spots on the image. . Further, if the volume resistance is greater than 8000 Ω, it is not possible to completely prevent toner from adhering to the sleeve.

Average primary particle size is 80771μ or less, volume resistivity is 80
As the conductive zinc oxide having a conductivity of 00 Ωm or less, commercially available products are usually used.

The binder resin may be a natural resin, a semi-synthetic resin, or a synthetic resin, such as polystyrene, a homopolymer of styrene or its derivatives such as polyvinyltoluene, a styrene-methyl acrylate copolymer, and a styrene-methyl methacrylate. Styrene-acrylic copolymers such as copolymers, polymethyl methacrylate, polyesters, etc. are used.

As the colorant, for example, carbon black, red iron oxide, titanium oxide, Fast Yellow, Pigment Orange R, phthalocyanine full, phthalocyanine green, etc. are used.

The toner of the present invention preferably contains a charge control agent such as a metal-containing azo dye or nigrosine.

When producing the toner of the present invention, a colorant and, if necessary, a charge control agent are added to the binder resin, and the mixture is melt-kneaded.

The mixing ratio of each component is preferably 1 to 20 parts by weight of the colorant and 0.1 to 5 parts by weight of the charge control agent per 100 parts by weight of the binder resin. The mixture is then cooled, ground, and classified to form a fine powder with an average particle size of 6 to 20 microns.

The fine powder thus obtained has an average primary particle size of BO
By adding 0.01 to 10% by weight, preferably 0.1 to 3% by weight of ultrafine conductive zinc oxide having a volume resistivity of 8000 Ωm or less and mixing uniformly, the desired toner can be obtained. It will be done. This toner contains 0.0 hydrophobic silica.
It may be contained in a proportion of 1 to 5% by weight.

In the toner of the present invention, ultrafine electrically conductive zinc oxide is attached to the surface of the particles whose main components are a binder resin and a colorant, and the detachment of zinc oxide is extremely small. Therefore, when this toner is used, it is possible to completely prevent the two-component developer from adhering to the sleeve. Furthermore, since there is almost no formation of zinc oxide aggregates, white spots do not occur on the image, there is no critical damage to the photoreceptor, there is no black spot, and the toner has good fluidity.

The volume resistivity in the following side is determined by putting 10 g of the sample into a cylinder with an inner diameter of about 25 mm, and applying it to 100 klil/c using a hydraulic machine.
The thickness and electrical resistance of the sample at that time were measured and calculated using the following formula.

In the formula, the symbol means the thickness of the sample (m), S means the inner area of the cylinder (4,91ffi2), and R means the electrical resistance (Ω).

Example 1 90 parts by weight of styrene-butyl acrylate-1 copolymer,
6 parts by weight of low molecular weight polypropylene, 5 parts by weight of carbon black
Parts by weight and 2 parts by weight of the metal-containing dye (charge control agent) were sufficiently predispersed, and then melt-kneaded in a Banbury mixer. After cooling this mixture, it was pulverized using a jet mill and classified to obtain a powder with an average particle size of 11.4 μm. To this powder, 05% by weight of conductive zinc oxide having an average primary particle diameter of about 15 mμ and a volume resistivity of about 7000 Ω was added and mixed uniformly with a high-speed stirrer to obtain a toner. A developer was prepared by mixing 4 parts by weight of this toner with 200 parts by weight of Ferray, and the developer was put into a dry copying machine (PC: SE blade cleaning method) and 50,000 copies were made continuously. No sleeve adhesion, no definitive damage to the drum, no black spots, no white spots on the image, etc. were observed. Also, the fluidity of the toner measured by the method below is 0.
．． It was 249,710 seconds.

Measurement of fluidity of toner: Using a powder tester (Model PT-E manufactured by Micron Laboratory), 20 g of toner was
Place it on the mesh sieve and check the RH of the powder tester.
Set the EO5TAT scale to 4, vibrate the sieve for 10 seconds, and measure the weight of the toner remaining on the sieve after 10 seconds.

Toner with a small amount remaining in the sieve is judged to have good fluidity.

Example 2 1.5% by weight of conductive zinc oxide having an average primary particle size of about 80 mμ and a volume resistivity of 1000 Ωα was added to the powder with an average particle size of 11.4μ obtained in Example 1. A toner and a developer were prepared in the same manner as in Example 1. This developer was used in the same copying machine as in Example 1.

Example 1
Similar good results were obtained. Note that the fluidity of the toner was 0.40.9710 seconds.

Example 6 A toner and a developer were prepared in the same manner as in Example 1 except that 0.6% by weight of hydrophobic silica was added to the toner of Example 1. Put this developer into the same copying machine as in Example 1.
When continuous copying was performed for 10,000 sheets, good results similar to those in Example 1 were obtained. Furthermore, the liquidity of S- is 0.17
, 9710 seconds.

Example 4 90 parts by weight of styrene-methacrylate-butyl acrylate copolymer, 6 parts by weight of low molecular weight polypropylene, 5 parts by weight of red colorant (5PILON RED GRCH) and 2 parts by weight of charge control agent (BONTRON P-51) were used in Example 4. It was treated in the same manner as in 1 to obtain a red powder with an average particle size of Z8μ. To this powder, 1.0% by weight of zinc oxide and 0.4% by weight of hydrophobic silica with an average primary particle diameter of about 40 mμ and a volume resistivity of about 5000 Ωσ are added, and the mixture is uniformly mixed with a high-speed stirrer to form a red toner. I got it. Next, a developer was prepared by mixing 5 parts by weight of red toner with 100 parts by weight of fluorine-coated ferrite carrier. When this developer was placed in a dry copying machine (photoreceptor: OPC, grade cleaning method) and 50,000 sheets were continuously copied, the same results as in Example 1 were obtained. The fluidity of the toner was 0.68 g for 710 seconds.

Example 5 1.5% by weight of zinc oxide and 0.4% by weight of hydrophobic silica as in Example 2 were added to the red powder with an average particle size of Z8μ obtained in Example 4, and the mixture was homogenized using a high-speed stirrer. A red toner was obtained. Add 4 parts by weight of this toner to 1 part by weight of ferrite.
00 parts by weight to prepare a developer. When this developer was placed in the same copying machine as in Example 4 and 50,000 sheets were continuously copied, the same results as in Example 1 were obtained. The fluidity of the toner was 1.0Jj9710 seconds.

Comparative Example 1 A toner and developer were prepared in the same manner as in Example 3 except for the conductive zinc oxide. This developer was placed in the same copying machine as in Example 1, and a continuous copying test was conducted. As a result, sleeve adhesion occurred after approximately 1,500 sheets. Even after copying 50,000 copies, no significant damage to the photoreceptor, no black spots, and no white spots on the images were observed. Note that the fluidity of 1.sup.- was 0.6 g/10 seconds.

Comparative Example 2 Using powder with an average primary particle size of 150 mμ as zinc oxide,
A toner and a developer were prepared in the same manner as in Example 1 in other respects. When this developer was placed in the same copying machine as in Example 1 and 40,000 sheets were continuously copied, sleeve adhesion occurred after approximately 20,000 copies were made, and a decrease in image density and an increase in capri were observed. . Furthermore, after 40,000 copies, white streaks due to scratches on the photoreceptor and small white spots caused by transfer of zinc oxide aggregates were observed. The fluidity of the toner is 1.6. ! It was 9/10 seconds.

Comparative Example 6 Using powder with an average primary particle size of 800 mμ as zinc oxide,
A toner and a developer were prepared in the same manner as in Example 4 in other respects. This developer was placed in the same copying machine as in Example 4 and continuous copying was performed. As a result, sleeve adhesion occurred after approximately 10,000 copies were made, and a decrease in image density and an increase in fog were observed. In addition, white streaks, black spots, and white spots due to scratches on the photoreceptor appeared in the image after 20,000 copies. The fluidity was 3.4!9710 seconds.

Claims (1)

[Claims] The main components are a binder resin and a colorant, and the average primary particle size is 80 mμ or less, and the volume resistivity is 8000 Ω.
An electrophotographic toner characterized by containing ultrafine conductive zinc oxide having a particle size of 1 cm or less.