JPH02199457A - Electrophotographic composition - Google Patents

Abstract

PURPOSE:To enhance the dispersability of the pigment in the compsn. by using a polymer contg. a polar group as a binder resin. CONSTITUTION:This compsn. is the compsn. used for forming a photosensitive body or photoconductive toner and is formed by incorporating at least the photoconductive pigment (e.g. titanium oxide) and the binder resin consisting of the polymer contg. the polar group (A). A (co)polymer which consists of (meth)acrylate, vinyl acetate, etc., as a starting raw material is usable as the component A. Then, the dispersibility of the pigment is enhanced and, therefore, the electrostatic chargeability and sensitivity of the compsn. are improved.

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 an image forming device using a conventional photoconductive pigment, for example, dye-sensitized ZnO or dye-sensitized TiO2 is used as a photoconductive agent.
Using inorganic materials such as phthalocyanine, quinacridone, benzidine and other organic photoconductors, using a known insulating thermoplastic resin as a binder, and selecting a coloring agent as necessary to produce cyan, magenta, yellow and black colors. It has been used as a colored toner or photoreceptor. In addition, as an example of a process using them, JP-A-60-
There was one shown in 31150.

Examples of using a semiconductor laser as a writing light source include JP-A-59-78358, which uses zinc oxide sensitized to near-infrared light, and JP-A-59-78358, which uses titanium dioxide sensitized to near-infrared light. An example is an electrophotographic photoreceptor disclosed in Japanese Patent Application Laid-Open No. 57-72150.

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

1. Inorganic pigments used in electrophotographic processes are highly hydrophilic and have poor dispersibility in lipophilic resins.

Therefore, in the present invention, the binder resin of the electrophotographic composition is a polymer containing a polar group, thereby increasing the dispersibility with the inorganic pigment and enabling an electrophotographic process with excellent charging ability and photosensitivity. The purpose is to

[Means for Solving the Problems] The electrophotographic composition of the present invention comprises at least a photoconductive pigment and a binder resin, wherein the binder resin is a polymer containing a polar group. It is characterized by

[Function] The charge retention ability and carrier transport ability in a pigment/binder mixed system depend on the dispersion state of the pigment in the binder.

It is said that dipolar interaction at the interface is dominant in terms of dispersion, and substances with polar groups interact well with each other due to electrostatic action and are dispersed.

In the case of inorganic pigments, the polarity of the charges is large, so in order to ensure high dispersibility, the resin selected has polar groups in its side chains. These polar groups include C
=〇There are those with double bonds, OH groups, sulfone groups, etc.

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

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

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

The following photoconductive pigments are used.

Zinc oxide, titanium oxide, zinc sulfide, 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 dye. , azomethine is used. Examples of these types of dyes are Rose Bengal, Acridine Orange, Rhodamine B, Erythrosine,
Eosin, fluorescein, brilliant green,
There are crystal violets, etc.

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 which is a feature of the present invention, a polymer copolymer starting from acrylic ester, methacrylic ester, vinyl acetate, etc. is selected.

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. In this example, an acrylic acid ester copolymer was used as the binder resin. An acrylic copolymer used as a binder resin was prepared by reacting monomers of methyl acrylate, butyl methacrylate, and butyl acrylate in a solution. Using this resin, the following composition was dissolved in a toluene solvent to make them compatible.

Acrylic copolymer...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. When the dispersion was placed on a glass slide and observed under a microscope, it was found that the pigment was evenly dispersed down to the primary particles. 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. The developed conductive toner is irradiated with corona by a corona charger 12 to recover its resistance, and an image is formed on the paper by normal electrostatic transfer through plain paper 8 in a transfer section. Next, it is permanently fixed using 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 10er
Writing was performed in g/cm2. 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. These printing results are pigment/
This shows that the dispersibility of the resin has improved, contributing to charging properties and carrier transport properties. This also shows that the photoresponsiveness of the photoconductive toner, the fixability of the toner to plain paper, and the black printing flow rate are functioning as desired.

[Example 2] An experiment was conducted by changing the resin used in the coarse toner as follows. Other materials, compositions, and manufacturing methods are the same as in Example 1.

Polyvinyl butyral has OH groups in it and is a highly polar resin. Among these butyrals, one having a low proportion of OH groups is selected and mixed with methacrylate to cause an acrylic polymerization reaction. After this reaction, a polymerized resin having an inter-polymer network structure in which butyral is incorporated into the acrylic resin is obtained. By incorporating butyral into methacrylate, the resin has improved water resistance and is highly polar.

The photoner using this resin had a shorter dispersion time with ultrasonic waves than that of Example 1, making it possible to produce the photoner efficiently. In addition, this phototoner has sufficient chargeability and photosensitivity, and when an image was actually formed, 30
A printing speed of 20 PPM was obtained at a resolution of 0 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.

[Example 3] The following pigment binder resin was prepared.

In addition to methyl acrylate and butyl acrylate, the first
Solution polymerization was performed by mixing the monomers shown in the table.

Table 1 Compared to ordinary acrylic resins, adding a monomer having a polar group to the starting material made it possible to introduce a polar group to the end of the polymer, making it possible to produce a polar resin.

When a photoner was produced using this resin, it was confirmed by microscopic observation that the dispersibility of the pigment was significantly improved. When this was evaluated using the process of Example 1, it was possible to print with good resolution, O, and D values.

[Example 4] An electrophotographic photoreceptor was produced using the resin of Example 3.

The manufacturing procedure is shown below.

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.

Next, the dye-adsorbed zinc oxide and the binder resin are mixed and dispersed in a solvent. The following materials were dissolved in toluene solvent.

Acrylic copolymer: 20 parts by weight The above-mentioned 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. Both the dispersion time and the dispersibility were significantly improved compared to the conventional ones, as in the case of producing Fouiner.

This photosensitive layer forming solution was applied onto A1 vapor-deposited PET using a wire bar and dried in a dryer to produce an electrophotographic photoreceptor. 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 Kawaguchi Electric Membrane 5P-428. The light source used was a halogen lamp whose light intensity was 1 μW/cm 2 separated by an interference filter. Measurement conditions are 5tat-1, corona applied voltage -5kV, Dark
Decay 4 seconds, Light Decay
4 seconds, cleaning 2 seconds. As a result of the measurement, the charging potential Vθ700V.

Half-reduction exposure amount E l /210 e r g / cm
2. The residual potential VR was about 0■. Using this photoreceptor, we conducted a repeated test of charging and light irradiation for 3 seconds per cycle, and found that even after 1000 cycles, the amount of charge
There was no particular change in sensitivity characteristics. This is 20PPM
It is thought that the improved dispersibility effectively contributed to the charging ability and carrier transport ability. Furthermore, repeated tests confirmed an improvement in the durability of the membrane, which is thought to be due to the improved dispersibility, which made the membrane tougher.

[Example 5] A process experiment was conducted using the materials shown in the table below as resins used in photo toner. For comparison, cases using other resins are also shown. The composition, manufacturing method, and evaluation of the phototoner were the same as in Example 1.

Table 2 As is clear from this table, printing quality is also good when using a polar resin, which is a feature of the present invention.
Polystyrene, polyethylene, and polycarbonate had a lot of background fog, resulting in unclear printing.

[Example 6] A process experiment was conducted using the material shown in Example 5 as a resin used in an electrophotographic photoreceptor.

The composition, manufacturing method, and evaluation of the electrophotographic photoreceptor were the same as in Example 4. When a polar resin is used as a photoreceptor, the print quality is good, but when using polystyrene, polyethylene, or polycarbonate, the initial charge amount is small, resulting in unclear prints such as background fog.

It goes without saying that the resin used in the electrophotographic composition of the present invention is not limited to the above-mentioned types and compositions, and that resins other than the above-mentioned resins can also be used as long as they have polarity.

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.

[Effects of the Invention] As described above, according to the present invention, an electrophotographic composition comprises at least a photoconductive pigment and a binder resin, and the binder resin contains a polar group. The use of polymers has made it possible to provide developers and photoreceptors with good pigment dispersibility.

If an image forming apparatus using the electrophotographic composition according to the present invention is used, clear printing is possible due to improved charging properties and sensitivity, and it is possible to obtain highly reliable images with good reproducibility. Kudzu has the effect of

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of 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 Exposure system Photoner Corona transfer device Heat roll Cleaning brush Plain paper Dielectric substrate Conductive substrate Applicant Seiko Epson Corporation Agent Patent attorney Kizobe Suzuki (@!1 name) X knee C0O
R, -3OaR. Alkyl group, hydroxyl group (R: alkali metal or hydrocarbon group)

Claims (1)

[Claims] 1. An electrophotographic composition comprising at least a photoconductive pigment and a binder resin, wherein the binder resin is a polymer containing a polar group.