JPH0365961A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve sensitivity and stability by dispersing a part of at least X type phthalocyanine or tau type phthalocyanine in the form of molecules into a binder high polymer. CONSTITUTION:The X or tau type phthalocyanine dispersed in the form of particles in the binder high polymer and the charge generating agent dispersed in the form of particles therein are made to exist in the binder high polymer. Such particle dispersion is attained by dissolving the X type or tau type phthalocyanine into a suitable solvent and selecting such a high olymer which dissolves in this solvnt as a binder. The formation of the photosensitive body into such single layer constitutin is thus possible. The structure and process are simplified in such a manner and the high performance and high sensitivity and durability similar to the performance, sensitivity and durability of a two- layer type are improved with the positive charge photosensitive body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photographic photoreceptor, and more particularly to an electrophotographic photoreceptor that is ideal for a positive charging system and consists essentially of a charge generating agent and a binder polymer.

Conventional technology Compared to inorganic photoreceptors, organic photoreceptors (abbreviated as OPC) have advantages such as being able to synthesize materials with high sensitivity to various wavelengths through molecular design, being non-polluting, and being superior in productivity and economy. It is known for its low cost and is currently undergoing active research and development. Significant improvements have also been made in terms of durability and sensitivity, which had previously been considered problems with organic photoreceptors.
Some of them have been put into practical use and are now becoming the mainstay of electrophotographic photoreceptors.

OPC is usually composed of a double layer structure consisting of a charge generation layer (CGL) that absorbs light and generates carriers and a charge transfer layer (CTL) that moves the generated carriers. It is being Materials used for CGL (abbreviated as CGM) include various perylene compounds,
Various organic materials are being investigated, such as various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes.

On the other hand, materials used for CTL (abbreviated as CTM) include various hydrazone compounds, oxazole compounds,
Triphenylmethane compounds, arylamine compounds, etc. have been developed.

These materials are formed on a substrate such as a drum or belt by a relatively simple i-coating method together with a binder polymer.

Binder polymers used for this purpose include:
Examples include polyester resin, polycarbonate resin, acrylic resin, and acrylic-styrene resin. Generally, in such a double layer structure, the CG layer is coated with a thickness of several microns for high sensitivity ratio, while the CT layer is coated with a thickness of several tens of microns. At this time, for reasons such as strength and printing durability, the CG layer is usually formed on the substrate side and the CT layer on the surface side. In such a configuration, only those in which the CTM operates to move holes have been put into practical use.
The double layer photoreceptor is of a negative charging type.

Problems to be Solved by the Invention However, such a negative charging method has a problem in that oxygen in the air turns into ozone due to the negative charge used for charging. Ozone is not only harmful to the human body, but also often reacts with photoreceptors, shortening the life of the photoreceptor.

Furthermore, such a two-layer system has problems such as (1) the manufacturing process becomes complicated, and (2) stability becomes a problem due to peeling between layers.

In order to solve these problems, positive charging type organic photoreceptors are currently being developed.

Conventionally, in order to achieve positive charging (11CGL layer and CT
An inverted two-layer structure in which the L layer is configured inversely to the negatively charged case, and (2
) Single-layer structures in which various CGMs and CTMs are dispersed in binder polymers have been studied. The inverted two-layer structure does not solve the same problems of manufacturing process complexity and delamination as in the case of the negative charging method. Further, there are problems in that a CG layer, which essentially needs to be made thin, is placed on the surface of the photoreceptor, resulting in a decrease in printing resistance and a deterioration in life characteristics.

On the other hand, the single-layer type photoreceptor that diffracted positive charges was inferior to the two-layer type in terms of sensitivity, charging characteristics (charge for charging is difficult to be carried), and residual potential. The reason for the inferior sensitivity was that charge generation and movement occurred randomly within the single layer, and the problems with the single layer photoreceptor were sensitivity, charging characteristics, and residual potential.

As described above, all conventional OPCs have some kind of problem. Therefore, with a single layer type positively charged photoreceptor, 2
If it can achieve the same high sensitivity, residual potential, and charging characteristics as the layered type, it is considered to be an ideal photoreceptor.

An object of the present invention is to solve the above-mentioned drawbacks of conventional OPCs and to provide a photoreceptor for electrophotography that has high performance, high sensitivity, and excellent durability.

Means for Solving the Problems In order to solve the above problems, we investigated positively charged single-layer organic photoreceptors having various configurations. As a result, we used various perylene compounds, various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, azulenium dyes, etc. as CGMs, and further developed suitable materials for these CGMs. X type of quantity or τ
The inventors have discovered that a single-layer organic photoreceptor made of a combination of phthalocyanine-type phthalocyanine and a suitable binder polymer exhibits excellent photosensitivity in a positive charging system, leading to the present invention.

As described above, the first feature of the structure of the present invention is that it does not contain CTM, and in this structure, conventional single-layer organic photoreceptors were formed from a mixture of CGM and CTM. It has an essentially different configuration compared to the .

As described above, the structure of the present invention does not require CTM, which has conventionally been considered to be a hexa-type, but this means that the added X-type or τ-type phthalocyanine has charge transfer ability under certain conditions. Moreover, unlike conventional CTM, it has the ability to move negative charges.

We investigated various such conditions and clarified that such positive charge transfer ability is due to X-type or τ-type phthalocyanine molecularly dispersed in the binder polymer. On the other hand, the charge generation ability is mainly due to the charge generation agent dispersed in the form of particles in the binder polymer. That is, the second feature of the present invention is that the X-type or τ-type phthalocyanine that is molecularly dispersed and the charge generating agent that is particle-dispersed are present in the single layer.

The organic photoreceptor having such a structure has the following characteristics compared to conventional photoreceptors.

■ The manufacturing process is simple because it has a single layer structure.

■ Much higher sensitivity than conventional single-layer OPC.

■ Shows excellent characteristics especially in positive charging method.

■ Superior stability and special electric properties compared to conventional single-layer structure OPC.

■ Since it has a single layer structure, it has excellent printing resistance.

As is clear from the above, in this case, at least a portion of the X-type or τ-type phthalocyanine must be dispersed in the polymer binder in molecular form. In order to realize such molecular dispersion, X-type or τ
Mold lid □It is necessary to dissolve cyanine in a suitable solvent and select a polymer that dissolves in this solvent as a binder.

Solvents that dissolve X-type or τ-type phthalocyanine suitable for such purposes include nitrobenzene, chlorobenzene, dichlorobenzene, dichloromethane, trichloroethylene, chlornaphthalene, methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, Examples include 1,4-dioxane, N-methylpyrrolidone, tetracyclized carbon L-bromobutane, ethylene glycol, sulfolane, ethylene glycol monobutyl ether acetoxyethoxyethane, pyridine, and the like.

On the other hand, acetone, cyclohexane, petroleum ether, nitromethane, methoxyethanol, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, ethyl acetate, isopropyl alcohol, diethyl ether, methyl ethyl ketone, ethanol, hexane, propylene carbonate, butylamine, water,
Such solvents do not dissolve X-type or τ-type phthalocyanine.

Therefore, in the present invention, these solvents cannot be used alone. When using these solvents, it is necessary to use them in combination with a solvent that dissolves the X-type casing or the τ-type phthalocyanine mentioned above.

Charge generating materials that are well used in the present invention include phthalocyanine compounds, perylene compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, various phthalocyanine pigments, trisazo pigments, azulenium dyes, etc. There is. Representative examples of these CGMs are shown below.

(11 (21 (sl (6) IO4) The binder polymer used in the present invention preferably has a solvent common to the above-mentioned X-type or τ-type phthalocyanine. Polymers suitable for these purposes include: Polyester, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl formal, polyacrylonitrile, polymethyl methacrylate, polyacrylate, and copolymers thereof, poly(vinyl chloride/ Poly(vinyl acetate/vinyl alcohol), poly(vinyl chloride/vinyl acetate/maleic acid), poly(ethylene/vinyl acetate), poly(vinyl chloride/vinylidene chloride), cellulose polymers, etc.These polymers can be used alone or as a mixture of two or more types.Of course, as mentioned above, two or more types of solvents can be combined, and one solvent can dissolve the X-type or τ-type phthalocyanine, and the other solvent can dissolve the binder. Since it is possible to dissolve the molecules, the binder polymer according to the present invention is not limited to the above-mentioned polymers.

The optimum ratio of the weight of the above-mentioned X-type or τ-type phthalocyanine and charge generating agent to the weight of the binder polymer is between 1:1 and 1=10.

It was a cabinet. X-type l or τ-type phthalocyanine is required in an amount of 10% by weight or more for various charge generating agents.

If the amount of the binder polymer is less than this range, the photosensitive properties (potential attenuation properties due to light) will be excellent, but the charging properties will deteriorate and it will generally be difficult to apply a potential of 300 V or more.

On the other hand, if the amount of the binder polymer is greater than the above range, the photosensitivity will deteriorate.

Conventional single-layer OPC buttons have used a mixture of CTM and CGM. In this purpose OCTM and 1~,
These include hydrazone compounds, oxazole compounds, triphenylmethane compounds, and arylamine compounds.

Addition of these materials has little effect on the photosensitivity when the amount added is 5% or less, but when added in an amount of 5% or more, the photosensitivity and charging stability are significantly deteriorated. That is, the conventional CTM has a negative influence on the configuration of the present invention, and is essentially unnecessary.

By combining such materials, for example, a thread (
(see Example 1), the half-reduced exposure sensitivity due to positive charging is 1.
6lux, 5eeO high sensitivity (charged potential 600V) was achieved. On the other hand, the sensitivity due to negative charging is 12 l
ux, see (charged potential 120V).

Its characteristics were significantly inferior to positive charging.

However, this system is very stable, and the characteristic due to positive charging is 10
There was almost no change even after 00 repeated tests.

The conductive support serving as the substrate of the organic photoconductive layer is not particularly limited, and can be appropriately selected depending on the intended use. Specifically, metals such as aluminum, glass, paper, plastic, or the like with a conductive layer formed on the surface by a method such as metal vapor deposition are preferably used.

Moreover, it can take various shapes such as a drum shape, a belt shape, and a sheet shape.

The electrophotographic photoreceptor according to the present invention described above is
For example, it can be used in various recording systems such as copying machines, printers, facsimiles, etc., and its uses are not limited in any way. Note that the electrophotographic photoreceptor according to the present invention is not limited to the above-mentioned example, and for example, if necessary, a surface protective layer made of an insulating resin may be further formed on the organic photoreceptor layer, or a photoreceptor layer may be formed on the photoreceptor layer. It is also possible to provide a prosodic layer between the substrate and the substrate.

Function The positively charged single layer type OPc according to the present invention has an unprecedented structure and can realize excellent characteristics as a photoreceptor, and has the following characteristics compared to conventional photoreceptors. ■The manufacturing process is simple because it has a single layer structure. ■Conventional single-layer OPC
It is much more sensitive than ■Excellent characteristics especially in positive charging method.

■It has superior stability and chargeability compared to conventional single-layer structure OPC. ■It has a single layer structure, so it has excellent printing resistance.

EXAMPLES Next, the present invention will be described in more detail, including examples and comparative examples.

Example 1 - X-type metal-free phthalocyanine (abbreviated as XPc, manufactured by Dainippon Ink ■, Fastogen Blue)
e) 8120B), literature (Ricoh Techini
-cal Report No. 8 November
Three components, consisting of a trisazo compound (the above compound (13)) synthesized by the method of J. Er. After dispersing and thoroughly mixing and kneading, the resulting solution was applied onto an aluminum drum using the dip method, and treated in vacuum at 120'C for 1 hour to form an OPC layer (thickness 10
~20 μm) was formed.

The photosensitive characteristics of the photoreceptor obtained in this way were
Using a PA-8100 paper analyzer, irradiate white light from tungsten to measure photosensitivity due to positive charging (
The half-life exposure amount ('E 1/2 ) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. XPc,
Table 1 shows the properties when the weight ratio of compound (13) and PVB was varied.

As is clear from the results in Table 1, the appropriate weight ratio of XP(!+(13) and PVB is between 1:1 and 1=10, and a composition within this range has good charging characteristics and sensitivity characteristics. The characteristics can be obtained.The ratio of XPc and (13) is 1:1.
It can be seen that good characteristics are obtained in the range of 0 to 5:1.

Comparative Example 1 - For comparison, the characteristics when a mixed solvent of acetone and DMF was used as a solvent at the same tank bottom as in Example 1 are shown. Acetone and DMF dissolve PVB but not XPc. Therefore, in such a manufacturing method, XPc is mixed in the PVB in the form of particles, and it is considered that XPc dispersed in the form of molecules does not exist. The results are shown in Table 2.

As shown in the results in Table 2, the sensitivity due to positive charging, E1/2, is significantly worse than the results in Table 1. You can see that it is necessary to be dispersed.

Example 2 - τ-type metal-free phthalocyanine (abbreviated as τPc, manufactured by Toyo Ink ■, Liopoton THP),
Literature (Ricoh Technical Report Ricoh T
electrical report No. 8N
trisazo compound (said compound (13)) synthesized by the method of Ove-mber, 14 (1982),
and polyvinyl butyral CPVB (abbreviated as S-LEC BM-2 manufactured by Tanemizu Chemical Industry Co., Ltd.) in tetrahydrofuran and thoroughly mixed and kneaded. The resulting solution was coated on an aluminum drum by the dip method and heated under vacuum for 120 minutes. '
Treated with C for 1 hour to form a 020 layer (thickness 10-20 μm)
was formed. The photosensitive characteristics of the photoreceptor obtained in this way were irradiated with white light from tungsten using an EPA-8100 paper analyzer manufactured by Yoro Denki ■, and the photosensitivity due to positive charging (half-reduced exposure amount, E j /2) was determined. Measure, 1
The photosensitivity after 000 repeated tests was also measured in the same manner.

Table 3 shows the properties when the weight ratios of τ-type phthalocyanine, compound (13), and PVB were varied.

Example 3 - X-type metal-free phthalocyanine (abbreviated as XPc, manufactured by Jin Nippon Ink ■, Fastogen Blue)
e) 8120B), the above compound (13), and various binder polymers were mixed in a ratio of 0.2: 0.4: 1.8, dissolved in tetrahydrofuran, thoroughly mixed and kneaded, and the resulting solution was mixed with aluminum. It was coated onto a drum by the dip method, treated in a vacuum at 120°C for 1 hour, and then opened.
A layer c (thickness: 10 to 20 μm) was formed.

The photosensitive characteristics of the photoreceptor obtained in this way were
Using a PA-8100 paper analyzer, irradiate white light from tungsten to measure photosensitivity due to positive charging (
The half-life exposure amount (E 1/2 ) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. The results are shown in Table 4.

From these results, it is clear that τ-type phthalocyanine exhibits excellent photosensitivity properties similar to X-type phthalocyanine.
In the case of compound (13) dispersed in particle form with c, a photoreceptor with excellent characteristics can be formed regardless of the type of polymer.

Example 4 - X-type metal-free phthalocyanine (abbreviated as XPc, manufactured by Dainippon Ink ■, Fastogen Blue)
e) 8120B), various CGMs shown above, and polyvinyl butyral (abbreviated as PVB, S-LEC BM-2 manufactured by Tanemizu Chemical Industry Co., Ltd.) at 0.2
: 0.4 : 1.8 weight ratio, dissolved and dispersed in tetrahydrofuran, thoroughly mixed and kneaded, and the resulting solution was applied onto an aluminum drum by dip method.
An OPC layer (thickness 10-20 μrn) was formed by treatment at 120° C. for 1 hour in vacuum.

The photosensitive characteristics of the photoreceptor obtained in this way were
Using a PA-8100 paper analyzer, irradiate white light from tungsten to measure photosensitivity due to positive charging (
The half-life exposure amount (E 1/2) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. The results are shown in Table 5.

Table 5 As is clear from the results, the method of the present invention can be applied to various conventionally known CGMs.

Since each of these CGMs has an excellent charge generation ability with respect to light of a specific wavelength, a characteristic photoreceptor can be obtained with each system.

Example 6 Among the photoreceptors prepared by the method of Example 1, the ratio of XPc, compound (13), and PVB was 0.2:0.4:
1.8 was selected and a continuous printing resistance test was conducted. A test was conducted using A4 test paper, and it was found that it operated stably even after continuous testing of 30,000 sheets.

As described above, it has been found that the method of the present invention is superior in terms of printing durability compared to conventional two-layer type photoreceptors or single-layer type photoreceptors.

Effects of the Invention As described above, the electrophotographic photoreceptor according to the present invention has an X-type housing or a τ-type phthalocyanine, a charge generating agent,
It consists of a binder polymer, and at least a part of X-type or τ-type phthalocyanine is molecularly dispersed in the binder polymer. It is a positively charged single-layer photoreceptor, and compared to conventional photoreceptors, It has high sensitivity and excellent stability, and is also characterized by an extremely easy manufacturing method, making it suitable for use as an electrophotographic photoreceptor and in various recording devices. ,There is expected.

Claims (2)

[Claims] (1) X-type phthalocyanine or τ-type phthalocyanine,
It consists of a charge generating agent, a binder polymer, and at least
A photoreceptor for electrophotography, characterized in that a part of type phthalocyanine or τ type phthalocyanine is dispersed in a molecular form in a binder polymer. (2) An electrophotographic photoreceptor in which the weight ratio of the weight of the X-type phthalocyanine or τ-type phthalocyanine according to claim 1 plus a charge generating agent to the binder polymer is in the range of 1:1 to 1:10.