JPS58150956A - Charge carrying organic substance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to charge transporting organic materials used in particular in electrophotography.

In electrophotography, pairs of charge carriers are created by light rays, such as light or X-rays, absorbed in a semiconductor. Under an electric field, pairs of charge carriers are separated and a charge pattern is formed on the surface of the recording material, of which the irradiated semiconductor forms part. Therefore, in the whole process, 1,
It is necessary that at least a charge be formed, and 2. that the formed charge be able to migrate towards the interfacial surface. Furthermore, it is necessary that the particular material on which the charges or turns are stored has a high dark resistance.

Elemental selenium possesses all of the above-mentioned properties required of a material suitable for electrophotography. In the future, selenium will be replaced by organic materials. However, to date it has been found that it is not possible for organic materials to satisfy all of the optimal properties.

Therefore, at the same time as developing organic materials, new structures for electrophotographic recording materials were also developed.

Two layer structures are often used, where the first layer contains a charge generating material and the second layer contains a charge transporting organic material.

A type of charge transporting organic material of particular interest is shown, for example, in US Pat. No. 3,711,280. Metallocene or metallocene derivatives are used as actual charge transport materials. The dispersion or solution of the metallocene derivative has film-forming properties,
A polymeric binder that is hydrophobic is added. A large number of suitable binders are shown in the above patents. However, such charge-transporting organic materials containing metallocene derivatives dissolved or dispersed in the film-forming compound are difficult to use because the metallocene or metallocene derivative evaporates from the film-forming compound under elevated temperatures, e.g., 50°C. It has been found that the charging properties of the electrophotographic recording material decrease the longer it is left at elevated temperature, especially when it is deposited on a selenium layer.

The purpose of this invention is that even if kept at a temperature of about 50°C for a long time,
It is an object of the present invention to provide a charge transporting organic material containing a metallocene derivative and a film-forming compound whose electrophotographic properties are unchanged from the original.

The present invention provides a charge transporting organic material that is a copolymer of a metallocene derivative and a phenyl compound. By copolymerizing the metallocene derivative with the film-forming compound instead of dissolving or dispersing it, it is ensured that the metallocene derivative is tightly bound and does not evaporate from the film-forming compound even at elevated temperatures. Among the binders shown in US Pat. No. 3,711.280, polystyrene and other phenyl compounds, such as those having alkyl groups, have been found to be particularly advantageous. However, nitrogenated phenyl compounds such as nitrogenated polystyrene are less suitable.

Copolymers of metallocene derivatives, ie, copolymers of vinyl ferrocene and film-forming agents such as vinylpyrinone, are known, and are described in, for example, Chemical Abstracts Vol.
．． 82 (1975) A163013P. The copolymers shown therein are vinylferrocene,
Based on film-forming monomers, electron-accepting compounds, and complex-forming compounds. With prolonged operation, such materials become non-conductive in the exposed areas, thus making it possible to make multiple copies of the film-formed charge pattern. However, the material of this invention behaves quite differently. This is because the materials of this invention can transport charge even after exposure.

As the 5-metallocene derivative, particularly ferrocene derivatives and metallocene derivatives having the same ionic bond energy ratio as ferrocene can be used. For example, cobaltocene has a too large proportion of ionic bond energy. Among ferrocene derivatives, vinylferrocene, which has the simplest structure and is one of the cheapest, is the most suitable ferrocene derivative.

In the copolymer of the present invention, it is particularly preferable that the ratio of ferrocenyl groups to tophenyl groups is 1 nia. As the proportion of phenyl groups increases, phenyl series? This is advantageous because the film-forming ability of the remer becomes remarkable, but the charge transport ability due to the ferrocenyl group deteriorates. However, as the content of ferrocenyl groups increases, although the charge transport ability improves, it becomes impossible to form a continuous layer necessary for making electrophotographic recording materials. After all, the usual objective is achieved when the ratio of ferrocenyl groups to phenyl groups is about 1:5 to 1:9.

As mentioned above, it is desirable that the content of ferrocenyl groups is high, but this will reduce the film-forming ability of the copolymer. If the content of ferrocenyl groups is high, the polymer coated in the form of a layer on the carrier will crack slightly. However, this is because the copolymer has a softening agent (
This can be prevented by adding the metallocene, preferably a copolymerized metallocene derivative. When vinyl ferrocene is used as the metallocene derivative, it is preferred to use about 12% by weight of ferrocene as the softening agent. If less than about 5% by weight of ferrocene is added, no softening effect is observed. On the other hand, if the amount of ferrocene exceeds 20 wt.

As the content of phenyl groups in the copolymer decreases, the adhesion of the polymer layer to the carrier or support also deteriorates. In this case, if hydroxyacrylate is further copolymerized for the purpose of improving adhesive strength, the adhesive strength will be improved. However, beyond a certain limit, this hydroxyacrylate has an adverse effect on the residual potential of the recording material. The residual potential is a specific potential that a maximally charged recording material has after exposure. If 2-hydroxy-ethyl acrylate is used, no more than two 2-hydroxy-ethyl acrylate groups should be used for every about every 20 ferrocenyl groups, so as not to harm the residual potential.

The copolymer of the present invention is suitable for use as a layer without adding any other additives, such as a charge-generating substance, but the copolymer containing the charge-generating substance in a dissolved or dispersed state is suitable for use as a layer. It is possible to form a coalescing layer. As such a dissolved charge generating substance, an organic dye such as copper phthalonanine can be used, while as a dispersed charge generating substance, for example, sulfide powder or cadmium selenide powder can be used. Powders can be used.

The copolymers of the present invention not only have very high temperature stability as far as electrophotographic properties are concerned, but also have more favorable residual potential values than non-copolymerized materials. Thus, for example, in a two-layer recording (copy) material consisting of a substrate, a copper phthalocyanine layer, and a ferro7ine layer, dissolved in polystyrene, the residual potential is 1 when exposed after initially applying 1800 V. 200V, whereas a copolymer of vinylferrocene and styrene having the same structure has a residual potential of only -100V.

The invention will be explained in further detail with reference to the following examples.

Example 1 Commercially available vinylferrocene and styrene were used as starting materials. The mass, vinylferrocene, was cleaned by sublimation under vacuum at 60°C. A female fixing agent, which is thought to interfere with polymerization to polystyrene, was removed from commercially available styrene by distillation under vacuum. These purification steps (
7) After that, 1.15g vinyl ferrocent, 2.7g9
- of styrene and 40 μm of azobisisobutyronitrile were carefully stirred and heated to 80° C. for 4 hours until a reddish-brown mass of transparent solid formed.

During this time, some of the vinylferrocene sublimed in the cold part of the reaction vessel. As a result, the content of ferrocenyl groups during copolymerization is always smaller than the value expected from the charging molar ratio. The actual ratio of ferrocenyl and phenyl groups was confirmed by nuclear magnetic resonance spectroscopy.

The copolymer layer was dissolved in 201 nl of benzene, and the
The copolymer was again precipitated by using m1 of methanol. The resulting precipitate was washed with methanol until the supernatant became colorless. The copolymer was then dried at 80°C under 1 Torr. This gave 1.8 g of a copolymer in which there was one ferrocenyl group for every nine phenyl groups.

0.4 g of the copolymer was dissolved in 30 ml of toluene and coated onto an aluminum plate using a spiral film forming device. After evaporation of the bath medium, a defect-electron-(hole)-transport layer with a size of approximately 10-11 μm was obtained.

Example 2 A copolymer was prepared in the same manner as in Example 1.

Next, 0.4 g of copolymer and 0.05 I of ferrocene as a softener were dissolved in 30 ml of toluene and then deposited as in Example 1. Such a layer, unlike that of Example 1, no longer showed a tendency to crack.

(a) Amorphous selenium containing 7.5% tellurium or (b)
A 1 μm thick layer of β-copper phthalocyanine is deposited on an aluminum foil, and a copolymer containing ferrocene as a softening agent is applied onto this layer. The copy material created in this way can be heated up to -800% by corona.
? Charged up to 100%. However, because the charge-generating materials were different, they were highly sensitive to light of different wavelengths. In the case of 0), the residual potential after exposure to light with a wavelength of 450 nm and 2 μJ/cm 2 was -120 delts. In the case of (b), the residual potential after exposure to light with a wavelength of 530 nm and 50 μJ/cm2 is -160? It was Ruto.

Example 3 1 g (4.7 mmol) of sublimated vinyl ferrocene, 3.35 g (32 mmol) of freshly diluted styrene, 0.026 g (0.23 mmol) of 2-hydroxyethyl acrylate and 65 da (0.4 mmol)
) was reacted with α,α'-azobisisobutyronitrile and purified in the same manner as in Example 1. According to nuclear magnetic resonance absorption spectroscopy, this copolymer contained eight phenyl groups per ferrocenyl group.

Dissolve 0.8g of copolymer in 411Ll of toluene,
It was coated on an aluminum plate using a spiral film forming device.

When the toluene evaporated, a layer was obtained which had the same electrophotographic properties as the layer of Example 1, but with significantly improved adhesion to aluminum.

Example 4 1.6 g of cadmium selenide was stirred into the copolymer-toluene solution of Example 3 and dispersed using an ultrasonic disintegrator. Using a spiral film forming device, the obtained dispersion was applied onto an aluminum foil that had been previously polished with toluene.
It was dried at 120°C for 2 hours. The same dispersion was similarly applied and dried to form a thicker layer.

The total layer thickness was approximately 34 μm. -7 due to corona
00,t' Silt It was possible to provide a negative charge. The residual potential of the recording (copy) material after a 10 lux second exposure with a tungsten filament rung is only -90
? It was Ruto. This value is considerably lower than that using ferrocene dissolved in polystyrene.

The ratio of ferrocenyl group to tophenyl group is 1 to 1
: Various copolymer layers between
defective electrons (holes) by
The effective mobility of was measured. When the ratio is 1:25, the effective mobility is 6X10. 1.13, 3X], O,1:
9 is 2X10. 1:7 is 7 x 10 c
m/V·sec. However, if the ratio of 13-phenyl groups is greater than 1:13, the residual potential after exposure will be too high, which is of little interest for practical applications. Layers with a proportion of phenyl groups less than 1 nia are too brittle. However, this drawback is
This can be overcome by adding a softening agent such as ferrocene at the beginning. It has been found that when the ratio of ferrocenyl groups to phenyl groups is about 1:5, it becomes brittle even if a softener is added.

The examples described above merely describe suitable methods for forming a layer of copolymer on a substrate.

However, the copolymer layer can also be formed, for example, by compact molding in a molding solution, or by melt casting or by vapor deposition under vacuum. However, while it is easy to form individual layers using compact molding, it is almost impossible to form layered structures. Vapor deposition and melting methods tend to crystallize the layer, making it difficult to obtain reproducible results. Furthermore, a portion of the copolymer is dispersed by heating. Using vapor deposition methods, it is also difficult to form layers with large surfaces.

After all, the adhesion of the 0 copolymer layer to the metal substrate, where it is most advantageous to make the layer from solution, is not only improved by copolymerizing the hydroxyacrylate. Other acrylates such as methacrylates can also be used.

Takehiko Suzue, patent attorney, 15- −403=

Claims (9)

[Claims] (1) A film-forming charge-transporting organic material consisting of a copolymer of a metallocene derivative and a phenyl compound. (2) The substance according to claim 1, wherein the phenyl compound is styrene. (3) The substance according to claim 1 or 2, wherein the metallocene derivative is a ferrocene derivative. (4) The substance according to claim 3, wherein the ferrocene derivative is vinylferrocene. (5) The ratio of ferrocenyl group to phenyl group is 1:5
The substance according to claim 3 or 4, wherein the ratio is between 1:9 and 1:9. (6) The substance according to any one of claims 1 to 5, which contains a metallocene as a softening agent. (7) A material according to claim 4, which contains 5 to 20 moles of ferrocene as a softening agent. (8) The material according to any one of claims 1 to 7, wherein hydroxyacrylate is further copolymerized. (9) The amount of hydroxyacrylate copolymerized is 00
The substance according to claim 8, which has a content of 5 molt or less. 11. The material according to claim 1, further comprising a charge generating material.