JPH02170167A - Electrophotographic composition - Google Patents

Abstract

PURPOSE:To enhance the insulating characteristic of the compsn. and to speed up the restoration of resistance by using specific fine crystal powder as a photoconductive pigment. CONSTITUTION:At least the photoconductive inorg. pigment (A) and a binder resin are incorporated into the above compsn. and the fine crystal powder having <=1ppm deviation from the stoichiometric compsn. is used as the compo nent A. Zinc oxide, titanium oxide, zinc sulfide, etc., are usable as the compo nent A and a sensitizing dyestuff, such as cyanine dyestuff, can be added to the compsn. The addition of coloring agents at need to the compsn. is possible as well. This compsn. is usable for a photosensitive body or photoconductive toner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic composition that can be used in copying machines, printers, facsimile machines, and the like.

[Prior Art] As a conventional electrophotographic composition using a photoconductive pigment, for example, dye-sensitized Zn○ is used as a photoconductive agent.

Using an inorganic material such as dye-sensitized TiO2 or an organic photoconductor such as phthalocyanine, quinacridone, or benzidine, a known insulating thermoplastic resin is used as a binder, and a coloring agent is selected as necessary to produce cyan or magenta. , toner colored yellow and black has been used as a developer. The inorganic material used in this case is usually prepared under conditions in which it contains an excess of metal elements in order to exhibit photoconductivity. In addition, as an example of a process using them, Japanese Patent Application Laid-Open No. 6031
There was one shown in 150.

A visible light source has been used as a light source for conventional image forming apparatuses using photoconductive toner. In addition, in recent years, research has been carried out on processes using light sources in the near-infrared region. An example of using a near-infrared sensitized photoreceptor is an electrophotographic photoreceptor disclosed in JP-A-57-72150.

[Problem N to be Solved by the Invention] However, the following problems have been pointed out in conventional electrophotographic compositions, and solutions are desired.

1. Photoconductive agents generally have a memory effect, and recovery of dark resistance after stopping light irradiation is slow, making continuous high-speed processing difficult.

2. Electrophotographic compositions are prepared under conditions in which an excessive amount of photoconductive agent is used in order to efficiently develop photoconductivity, but when used as a toner, the dark resistance value is low and the commonly used electrostatic transfer method is used. becomes difficult.

Therefore, in the present invention, by using microcrystals in which the deviation from the stoichiometric composition of the photoconductive agent used in electrophotographic compositions is 1 ppm or less, continuous high-speed continuous The purpose is to enable the process.

[Means for Solving the Problems] The electrophotographic composition of the present invention comprises at least a photoconductive pigment and a binder resin, in which the photoconductive inorganic pigment has a stoichiometric composition. It is characterized by being a microcrystalline powder with a deviation of 1 ppm or less.

[Function] It is a well-known fact that the conductive mechanism of inorganic pigments as photoconductive agents is mediated by oxygen atoms such as 02- and 03- adsorbed on the surface. In order to develop conductivity through light irradiation, it is necessary to release the electrons trapped by the adsorbed oxygen atoms and desorb the oxygen. It is thought that the memory effect occurs because the photoresponsiveness is accompanied by the movement of such atomic groups. The basic mechanism is the same when a sensitizing dye is used, and it has a memory effect.

In the present invention, the deviation in the stoichiometric composition of the photoconductive agent is reduced to 1 ppm.
By doing the following, there are very few cavities in the bulk, so the insulation is high, and there are no electrons trapped by adsorbed oxygen atoms, so even if an excess of photoconductive agent is added, the composition shows high resistance. It becomes possible to use the electrostatic transfer process. The development of photoconductivity is due to carriers generated in the sensitizing dye by light irradiation. Electrons are injected into the conduction band of zinc oxide and contribute to conductivity, and holes interact with the electron-donating material to form the dye. can be recycled and used repeatedly. Since this mechanism mainly involves the movement of charge, the dark resistance recovers much more quickly than in the case of movement of atomic groups mediated by oxygen, and the memory effect is suppressed. Therefore, when applied to electrophotographic materials, continuous high-speed processing becomes possible.

Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

[Example] The composition of the electrophotographic composition of the present invention is shown below.

It basically consists of a photoconductive agent, a sensitizer, and a binder resin, and if necessary, a coloring agent is used.

The following photoconductive agents are used.

Zinc oxide, titanium oxide, zinc sulfide 1, cadmium sulfide.

Any dye can be selected as the sensitizer depending on the photoconductive material and the sensitive wavelength range. For example, triphenylmethane dye, diallylmethane dye, monomethine cyanine, trimethine cyanine, pentamethine cyanine, heptamethine cyanine, styryl dye, oxonol, merocyanine, complex cyanine, azenium dye, azo dye, anthraquinone dye, indigo dye, vinylene. A dye, azomethine, is used. Examples of these types of dyes include rose bengal, acridine orange, rhodamine B1 erythrosin, eosin, fluorescein, brilliant green, crystal violet, and the like.

When coloring is required, known organic pigments and dyes are used depending on each color. For example, nigrosine, aniline blue
Calco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, oil black, azo oil black, rose bengal, etc.

As the binder resin, known insulating thermoplastic resins can be used, including acrylic resins and their copolymers such as polyacrylate and polymethacrylate, styrene resins and their copolymers such as polystyrene and poly-1-methylstyrene, Polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polyester resins and copolymers thereof, polycarbonate resins, cellulose resins, and polyarylate resins are used alone or in combination. Further, in order to impart electron-donating properties to the resin, a carbazole resin or the like is used.

Further, when a known insulating thermoplastic resin is used as the binder resin, an electron donating substance is added. Examples include polymeric charge transfer agents such as methylpolysilane and propylpolysilane; Molecular charge transfer agents may be used alone or in combination.

The electrophotographic composition of the present invention is applied to a photoreceptor or a photoconductive toner. A specific example is shown below.

[Example 1] A photoconductive toner used in a developer was prepared using the electrophotographic composition according to the present invention.

The composition and manufacturing method of the photoconductive toner (hereinafter referred to as phototoner) are shown below.

Zinc oxide: 40 parts by weight Sensitizing dye: 0.04 parts by weight Ethyl alcohol: 80 parts by weight As a light source, anything in the ultraviolet to visible to near-infrared regions is possible, but cheap and small semiconductor lasers are suitable. Think of it as a writing system. For this reason, a cyanine dye with the following structure was adopted as a sensitizing dye sensitive to the near-infrared region.

Sensitizing dye of Example 1 The above materials were mixed and uniformly dispersed and adsorbed using ultrasonic waves.

Next, the solvent ethyl alcohol is removed by centrifugation to obtain dried dye-adsorbed zinc oxide.

Next, a colored resin solution is prepared. The following composition was dissolved and compatible in a toluene solvent.

Acrylic resin...40 parts by weight Hydrazone compound...40 parts by weight Black dye-1...20 parts by weight Black dye-1 has the property of transmitting near infrared light and is the second
As shown in the figure, it has a naphthalene ring and an azo coupling, Me is Cr, Xi, X3 is a long chain methyl group, X2. The one in which X4 was a long-chain ethyl group was used.

The above-mentioned dye-adsorbed zinc oxide is added to this solution, and further subjected to ultrasonic dispersion so that it is uniformly dispersed in the resin. In this manner, the raw material solution was prepared to have a solid content of 5%, and a phototoner having a thickness of approximately 10 μm was prepared by spray drying.

Next, FIG. 1 schematically shows the process of an image forming apparatus using the photoconductive toner of the present invention. The basic configuration is drums,
Consists of a two-component developer, writing optical system, corona transfer device, heat roll, and cleaning brush.

Next, the process will be explained. The drum surface is made of dielectric material, and the inner conductive substrate is grounded. While a developing electric field is being applied by the two-component magnetic brush 2, an exposure system 3 irradiates light to form an image. Since zinc oxide is sensitized to near-infrared rays using a sensitizing dye, an inexpensive semiconductor laser can be used as the light source. When irradiated with light, only the conductive toner is injected with charge and further adhered to the dielectric surface. In the transfer section, an image is formed on the paper by normal electrostatic transfer through the plain paper 8. Since the phototoner of the present invention has almost no memory effect, the resistance in the transfer area is restored to high insulation, making electrostatic transfer possible. The image on the transfer paper is permanently fixed by a heat roll 6. The toner remaining on the drum is removed by a cleaning brush 7. When an image was actually formed through this process, a printing speed of 20 PPM was obtained at a resolution of 300 DPI. For the black solid image, O and D values of 1°5 or more were ensured. In addition, good images were obtained with good reproducibility in 10,000 printing tests. The light amount of the exposure system at this time is 10erg
/cm2 was written. In this method, development and exposure are performed simultaneously, increasing speed, and since only one layer is developed by charge injection, it is possible to print with clear images without background smearing. In the present invention, since the process of developing photoconductivity is not mediated by oxygen, there is no need to make the surface of the developer porous, and the ratio of photoconductive agent to binder resin can be determined in consideration of fixing properties. Printing is now possible. These printing results indicate that the photoresponsiveness of the photoconductive toner, the fixability of the toner to plain paper, and the black print density are functioning as desired.

[Example 2] By using the electrophotographic composition of the present invention, high insulating properties are ensured, so the surface of the toner has an excess of zinc oxide to ensure photoresponsiveness, and the inner core contains an excess of resin to ensure fixability. A double-structured microcapsule toner can be produced.

The composition and manufacturing method of the micro-buself toner are shown below.

First, using acrylic particles with a particle size of 10 μm, black dye-
The particles are directly stained in the alcohol solution of 1 and used as inner core particles.

Next, prepare the following solution.

Zinc oxide...75 parts by weight Cyanine dye...0.075 parts by weight Ethyl alcohol...150 parts by weight Butyral resin...25 parts by weight The same sensitizing dye as in Example 1 was used.

First, the above materials were mixed except for the resin, and uniformly dispersed and adsorbed using ultrasonic waves.

A zinc oxide dispersed resin solution is prepared by adding a resin to this dispersion and performing ultrasonic dispersion in the same manner. Furthermore, inner core particles are added to this resin solution and subsequently uniformly dispersed using ultrasonic waves. In this way, the raw material solution was prepared to have a solid content of 10%, and a phototoner whose surface was coated by a spray drying method was prepared. Approximately 1 μm according to electron microscope observation
It was confirmed that the zinc oxide dispersed film was coated with a thickness of .

When the process of Example 1 was performed using this micro-force self-adhesive toner, good printing was obtained. This indicates that insulation on the surface is ensured, triboelectric charging properties and transferability work as expected, and photoresponsiveness, fixing properties with inner core particles, and coloring properties function as designed.

[Example 3 An electrophotographic photoreceptor was produced according to the following composition.

Zinc oxide...80 parts by weight Sensitizing dye...0.08 part by weight Ethyl alcohol...160 parts by weight The same sensitizing dye as in Example 1 was used.

The above materials were mixed and uniformly dispersed and adsorbed using ultrasonic waves.

Next, the solvent ethyl alcohol is removed by centrifugation to obtain dried dye-adsorbed zinc oxide.

The dye-adsorbed zinc oxide and the binder resin are mixed and dispersed in a solvent. As the resin, a carbazole resin with strong electron donating properties was used. The structure is shown below.

-CH-CH2- glance C=0 -H (CH’2)3 The following materials were dissolved in toluene solvent.

Carbazole resin: 20 parts by weight The above dye-adsorbed zinc oxide was added to this solution, and further ultrasonically dispersed to obtain uniform dispersion in the resin to prepare a photosensitive layer forming solution.

This photosensitive layer forming solution was applied onto A1 vapor-deposited PET using a wire bar and dried in a dryer.

If left as is, the surface will be uneven and not durable, so a thin protective film will be applied. Any hard resin can be used as the protective film, and this time we used polycarbonate to coat it.

An electrophotographic photoreceptor was produced using the electrophotographic composition of the present invention through the above steps.

The coating thickness after drying was adjusted to about 10 to 20 μm.

The xerographic characteristics of the electrophotographic photoreceptor produced as described above were measured using 5P-428 manufactured by 110 Denki. The light source used was a halogen lamp whose light intensity was 1 μW/cm 2 separated by an interference filter. The measurement conditions were 5 tat-1, corona applied voltage -5 kV, Da
rk Decay 4 seconds, Light Dec
ay 4 seconds, cleaning 2 seconds. As a result of the measurement, the charging potential V [1700V.

Half-exposure ff1E I/210 e r g / c
m2. The residual potential VR was about 0■. Using this photoreceptor, a repeated test of charging and light irradiation was conducted for 3 seconds per cycle, and there was no particular change in the amount of charge or sensitivity characteristics even after repeating the test 10,000 times. This is 20 pages
It shows that it can be used with PM high-speed machines, and it also shows that the durability has been dramatically improved. By using the electrophotographic composition of the present invention, these products maintain high insulating properties and chargeability even when zinc oxide is excessive, and since the process does not require the presence of oxygen, it is possible to apply a protective film, making it durable. It is thought that the characteristics have improved.

[Example 4] Using the materials shown in the table below as the composition of zinc oxide powder,
A phototoner was prepared and its electrophotographic properties were evaluated. manufacturing method,
The evaluation was the same as in Example 2.

Table 1 As can be seen from this table, zinc in zinc oxide is
Under conditions exceeding m, high insulation properties cannot be ensured and charging properties are difficult, leading to phenomena such as background fogging and low density.

Although the examples have been described above, the process using the electrophotographic composition of the present invention is applicable not only to the above examples but also to all processes using photoconductive pigments.

By using microcrystalline powder with a deviation of 1 ppm or less, it is now possible to provide an electrophotographic composition with high insulation properties and quick resistance recovery.

If an image forming apparatus using the electrophotographic composition according to the present invention is used, it is possible to perform high-speed printing while maintaining chargeability, sensitivity, etc., and it is possible to obtain clear images with good reproducibility. has.

[Brief explanation of the drawing]

Country 1 is a diagram showing an image forming process when the electrophotographic composition of the present invention is used as a toner. FIG. 2 is a diagram showing the composition of the black dye used in the photoconductive toner of the present invention. 1. Drum 2, two-component magnetic brush developer 3, exposure system 4, photoner 5, corona transfer device 6, heat roll 7° cleaning brush 8, plain paper 9, dielectric substrate 10, conductive substrate and above Applicant: Seiko Epson Corporation Figure 2

Claims (1)

[Claims] An electrophotographic composition comprising at least a photoconductive inorganic pigment and a binder resin, wherein the photoconductive inorganic pigment is a microcrystalline powder having a deviation from a stoichiometric composition of 1 ppm or less. Photographic composition.