JPH03274562A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance simplicity in the manufacturing process, printing resistance, sensitivity characteristics, electric charging characteristics, and residual potential characteristics by forming the photosensitive layer composed of a binder polymer. a charge generating material molecularly dispersed into the binder polymer and a charge generating material granularly dispersed into the polymer. CONSTITUTION:The photosensitive layer is composed of the binder polymer, the charge generating material molecularly dispersed into the binder polymer, and the charge generating material granularly dispersed into the binder polymer. The presence of the at least 2 kinds of charge generating materials molecularly and granularly dispersed into the binder polymer imparts superior sensitivity in the wavelength region in accordance with the charge generating materials to be used, and reduces residual potential. The part of the charge generating material is molecularly dispersed into the binder polymer by dissolving the charge generating material in a proper solvent and selecting the binder polymer soluble in this solvent, thus permitting simplicity of the manufacturing process, printing resistance, sensitivity characteristics, charging characteristics, and residual potential characteristics to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrophotographic photoreceptor that is suitable for positive charging type electrophotography and is substantially composed of a charge generating agent and a binder polymer.

Compared to inorganic window photomaterials, conventional technology-based photoconductors (hereinafter abbreviated as OPC) have advantages such as being able to synthesize materials with high intensity at various wavelengths through molecular design, being non-polluting, and being more productive and economical. It has characteristics such as excellent performance and low cost, and is currently undergoing active research and development. Significant improvements have also been made in terms of durability and irritability, which were conventionally regarded as problems with OPC, and some of these improvements have been put into practical use, and are now becoming the mainstay of photoreceptors for electrophotography.

OPC is usually used in a double layer structure consisting of a charge generation layer (hereinafter referred to as 00 layer) that absorbs light and generates carriers and a charge transfer layer (hereinafter referred to as CT layer) that moves the generated carriers. Efforts are being made to increase its sensitivity. 00
The materials used for the layer (hereinafter abbreviated as CG agent) include:
Various perylene compounds, various phthalocyanine compounds,
Thiapyrylium compounds, ansuanthrone compounds,
Various organic materials are being investigated, such as squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes. On the other hand, materials used for the CT layer (hereinafter abbreviated as CTI) include various hydrazone compounds,
Oxazole compounds, triphenylmethane compounds,
Arylamine compounds, etc. have been developed.

In recent years, OPC has been used as a photoreceptor for digital recording in laser printers and other devices.
There is a growing demand for use in the near-infrared region corresponding to nm), and OPCs with high sensitivity characteristics in this region have been developed.
is actively being developed. As a photoreceptor for such areas,
Organic photoreceptors have an advantage over inorganic photoreceptors in terms of sensitivity.

The CG agent and the CT agent are coated together with a binder polymer onto a substrate such as a drum or belt using a relatively simple coating method to form a layer. Binder polymers used for this purpose include polyester resins, polycarbonate resins, acrylic resins, acrylic-styrene resins, and the like.

Generally, in a double layer structure, the CG layer is coated to a thickness of several microns, and the CT layer is coated to a thickness of several tens of microns, in order to increase sensitivity. 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 is formed on the front side. As CT agents, only those that operate by the movement of holes have been put to practical use, so in the above layer structure, this double layer photoreceptor is negatively charged. However, in this negative charging method, (1) Oxygen in the air becomes ozone due to the negative charge used for electrification, (
There were problems such as 2) incomplete charging and (3) being easily affected by the surface properties of the drum. Ozone is not only harmful to the human body, but also often reacts with photoreceptors, shortening the life of the photoreceptor. Charging instability often leads to poor image quality, and the strong influence of the drum surface texture requires the drum surface to have a mirror finish or an undercoat, increasing manufacturing costs. Leads to. Furthermore, such a two-layer system has problems such as (4) the manufacturing process becomes complicated, and (5) stability becomes a problem due to interlayer peeling.

In order to solve these problems, there is currently active development of OPC using a positive charging method. In order to realize the positive charging method, we have developed (a) an inverted two-layer structure OPC in which the C0 layer and the CT layer have the opposite layer structure to that of the negative charging method, and (b) a CG agent and a CT agent. In addition, single-layer OPC in which a binder polymer is dispersed, and (C) a single-layer OPC1 in which copper phthalo/anine is dispersed in a polymer have been studied.

In the inverted two-layer structure shown in (a), the complexity of the manufacturing process and the problem of interlayer peeling remain unsolved, as in the case of the negative charging method. Furthermore, since the CG layer, which essentially needs to be made thin, is placed on the surface side of the photoreceptor, there are problems of decreased printing resistance and deterioration of life characteristics.

On the other hand, a photoreceptor aiming for a positive charging method using a single layer of (bl (C)) has a higher charge than a conventional two-layer photoreceptor using a negative charging method.
It was inferior in terms of sensitivity characteristics, charging characteristics (it is difficult to carry charge for charging), and residual potential (large residual potential). The sensitivity was poor because the generation and movement of charges occurred randomly within one layer. As described above, the problems with single-layer photoreceptors are sensitivity, charging characteristics, and residual potential.

Problems to be Solved by the Invention However, a single-layer positive charging type photoreceptor essentially does not have the disadvantages of a multilayer type negative charging type photoreceptor, nor does it have the disadvantages of a reverse layer type positive charging type photoreceptor. Therefore, if a single-layer positive charging type photoreceptor can achieve the same high sensitivity, residual potential, and charging characteristics as a two-layer type photoreceptor, it will be an ideal photoreceptor.

The purpose of this invention is to eliminate the above-mentioned drawbacks of conventional positively charged single-layer photoreceptors and to provide a positively charged single-layer OPC 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 OPCs having various configurations. the result,
They discovered that if a charge generating agent dispersed in molecular form and a charge generating agent dispersed in particulate form were present in the binder polymer, excellent photoreceptor characteristics could be exhibited in a positive charging system. This invention was completed.

Therefore, the gist of the present invention is an electrophotographic photoreceptor comprising a binder polymer, a charge generating agent molecularly dispersed in the binder polymer, and a charge generating agent dispersed in particulate form.

Function The positively charged single-layer 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. .

■ Since it basically has a single layer structure, the manufacturing process is simple.

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

■Higher sensitivity than conventional single-layer OPC.

■ Superior stability and chargeability compared to conventional single-layer OPC.

■ Shows excellent characteristics especially in the positive charging method.

■ Excellent residual potential characteristics.

Example The present invention will be explained in detail below.

A feature of the structure of the electrophotographic photoreceptor according to the present invention is that the charge generating agent exists in at least two types of states: molecular dispersion and particulate dispersion in the single layer.

The sensitivity of the photoreceptor according to this invention is 1.0 to 3.01u.
x, sec, which is significantly higher sensitivity than conventional single-layer OPC. Further, the OPC of the present invention exhibits excellent sensitivity to light in a wavelength range depending on the type of charge generating agent used, and the residual potential is generally 30 V or less.

The charge generating agents used in this invention include various perylene compounds, various crystalline phthalocyanines, various metal phthalocyanines, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes. Used effectively. Examples of compounds that can be used particularly effectively include some of the substances shown below.

(The following is a blank space) The OPC having such a configuration has the following characteristics compared to a conventional photoreceptor.

■ Since it has a single layer structure, the manufacturing process is simple and it has excellent printing resistance.

■ Compared to conventional single-layer structure OPC, it has much higher sensitivity and excellent chargeability and residual potential characteristics.

■ Shows excellent characteristics especially in the positive charging method.

As is clear from the above description, in this case, it is necessary that a portion of the charge generating agent be dispersed in molecular form in the polymer binder.

In order to achieve such molecular dispersion, it is preferable to dissolve the charge generating agent in a suitable solvent and to select a polymer that is soluble in this solvent as the binder.

Solvents suitable for this purpose include nitrobenzene, chlorhenzene, dichloromenzene, dichloromethane, trichloroethylene, chlornaphthalene, methylnaphthalene, henzene, toluene, xylene, tetrahydrofuran, cyclohexanone, 1,4-dioxane, N-methylpyrrolidone, Examples include carbon tetrachloride, bromobutane, ethylene glycol, sulfolane, ethylene glycol monobutyl ether, acetoxyethoxyethane, pyridine, and the like. The solvents used in this invention are not limited to those mentioned above, and these solvents may be used alone or as a mixture of two or more.

The binder polymer used in this invention is preferably one that dissolves in the above-mentioned solvent for dissolving the charge generating agent. Polymers suitable for this purpose include polyester,
Polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyvinyl butyral, polyvinyl acetoacetal, polystyrene, polyacrylonitrile, polymethyl methacrylate, polyacrylate,
Polycarbazole and their copolymers, poly(vinyl chloride/vinyl acetate/vinyl alcohol), poly(vinyl chloride/vinyl acetate/maleic acid), poly(ethylene, vinyl acetate), poly(vinyl chloride/vinylidene chloride)
, cellulose polymers, various siloxane polymers, and the like. The binder polymer used in this invention is not limited to the above-mentioned polymers. These polymers are
It can be used alone or as a mixture of two or more types. When using a combination of two or more types of solvents, it is possible to dissolve the charge generating agent (electrode-accepting substance) with one solvent and dissolve the binder polymer with the other solvent.

The optimum ratio of charge generating agent to binder polymer is between 21 and 1:10 by weight. If the amount of the charge generating agent (photosensitive material) is larger than the above ratio range, the photosensitive characteristics will be excellent, but the charging characteristics will be poor, and generally 500
It becomes difficult to apply a higher potential. On the contrary,
If the amount of the binder polymer is greater than the above ratio range, the photosensitivity will deteriorate.

What is important in the method for obtaining the photoreceptor of this invention is to perform sufficient kneading in order to create stable two states of molecular dispersion and particulate dispersion. Generally, in order to create such a stable crosstalk state, one
It takes more than a day. If stirring is insufficient,
The photosensitivity is poor, the residual potential is large, and practical properties cannot be obtained.

By combining such materials, for example, in a system using the compound (1) and polyvinyl butyral at a weight ratio of 1:4, the half-light sensitivity due to positive charging is 1.61 u.
x, 5ecO high sensitivity (charged potential 800■) has been achieved,
Sensitivity at 600nm is 1.5cd/μJ5 Residual potential is 2
It was below 0V. On the other hand, the sensitivity due to negative charging is
201ux, sec (1! Fitii rank 350V)
The dark decay characteristics were also extremely poor, and these characteristics were significantly inferior to positively charged ones. Further, this system was very stable, and the characteristics due to positive charging hardly changed even after 1000 repeated tests. Furthermore, this photoreceptor exhibited excellent heat resistance, and its properties hardly changed even after treatment at 100''C for 8 hours.

Note that the photoreceptor of the present invention may further contain other charge generating agents. These charge generating agents include the various crystalline metal-free phthalocyanine compounds, perylene compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, various phthalocyanine pigments, trisazo pigments, and azulenium pigments as described above. , etc.

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, silver, 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 can be used in various recording systems such as copying machines, printers, facsimile machines, etc., and its uses are not limited in any way. In addition,
The electrophotographic photoreceptor according to the present invention is not limited to the above-mentioned examples, but may include, for example, further forming a surface protective layer made of an insulating resin on the organic photoreceptor layer, or forming an insulating layer and a substrate on the organic photoreceptor layer. A blocking layer may also be provided in between.

Next, examples of the present invention will be described in more detail together with comparative examples. The scope of this invention is not limited to the following examples.

Example 1 - Compound (1) and polyvinyl butyral (hereinafter abbreviated as PVB, S-LEC BM-2 manufactured by Tanemizu Chemical Industry Co., Ltd.) in a ratio of 1:3
It was weighed according to the weight ratio of First, PVB was dissolved in a mixed solvent of tetrahydrofuran and methylnaphthalene, and then compound (1) was added and stirred for 3 days to thoroughly knead. The resulting solution was applied onto an aluminum drum by the dip method and treated in vacuum at 120'C for 4 hours to form a 020 layer (about 15 μm thick).

The photosensitive characteristics of the photoreceptor obtained in this way were used by Rodenki EPA.
Using a paper analyzer model -8100, white light from tungsten was irradiated to measure the photosensitivity due to positive charging (half-decreased exposure amount, E, 8), and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, the wavelength characteristics at 650 layers m were measured. Charge potential (6KV charge) is 650V
and the photosensitivity by white light (E, 8) 1.51 ux,
sec, photosensitivity after 1000 repetitions (E, 8) 1
．． 61ux, sec, wavelength characteristics (photosensitivity at 650 layers m) 1.2cj/μJ, residual potential 1 second after light irradiation of 101ux) 10■.

Example 2 - Compound (2) and polyester (weight ratio 1:3) were treated in the same manner as in Example 1, and after stirring and kneading the molecules for 5 days, the resulting solution was placed on an aluminum drum by the dip method. It was coated and treated in vacuum at 100° C. for 1 hour to form a 020 layer (15 μm thick).

The photosensitive characteristics of the photoreceptor obtained in this way were used for EP manufactured by Rodenki.
Using an A-8100 paper analyzer, irradiate white light from tungsten and measure the photosensitivity due to positive charging (half-reduction exposure, E, /l), and measure the photosensitivity after 1000 repeated tests in the same way. did.

Furthermore, the wavelength characteristics at 550 layer m were measured. Charged potential (
6KV charge) is 750■, and the photosensitivity by white light (
E+/z) 1.81ux, sec, photosensitivity after 1000 repetitions (El/ri is 2.01ux, sec, wavelength characteristics (photosensitivity at 550 layers m) 1.0cd/
The residual potential (after 1 second of 101 ux light irradiation) was 15 μJ. From this result, compound (2) is similar to compound (1)
It was revealed that it exhibited excellent photosensitivity characteristics.

Example 3 Compound (3) and various binder polymers were mixed at a weight ratio of 1=4, dissolved in tetrahydrofuran and methylnaphthalene, and thoroughly stirred and kneaded for 7 days. The 020 layer (thickness: 15 to 20 .mu.m) was formed by coating on top by the dip method and treating in vacuo at 120'C for 4 hours.

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-decrease exposure amount (E18) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner.

Furthermore, the wavelength characteristics at 550 layer m were measured. The properties obtained are shown in Table 1.

Table 1 As is clear from the results, the method of this invention:
It can be applied to a wide range of binder polymers.

Example 4 - Compound (4) and polycarbonate (hereinafter abbreviated as PC)
were weighed at a weight ratio of 1:3. First, PC was dissolved in a mixed solvent of tetrahydrofuran and methylnaphthalene, and then compound (4) was added and stirred for 3 days to thoroughly knead.

The obtained solution was applied onto an aluminum drum by the dip method and treated in vacuum at 120°C for 4 hours to form an OPC layer (
A thickness of approximately 15 μm) was formed.

The photosensitivity characteristics of the photoreceptor obtained in this way were evaluated by irradiating white light from tungsten using an EPA-8100 paper analyzer manufactured by Yoroden Sin, and determining the photosensitivity due to positive charging (half-reduced exposure amount, E, /,). The photosensitivity after repeating the test 1000 times was also measured in the same manner.

Furthermore, the wavelength characteristics at 650 nm were measured. Charged potential (
6KV charge) is 650V, and the photosensitivity by white light (
E+/l) 2.51++x, sec, photosensitivity (E+8) after 1000 repetitions is 2.81ux, sec, wavelength characteristics (photosensitivity at 650 nm) 0.8cd/
The residual potential (potential after 1 second of 101ux light irradiation) was 30V.

Example 5 - Compound (5) and polystyrene (weight ratio 1:3) were treated in the same manner as in Example 1, and after thorough stirring and kneading,
The obtained solution was applied onto an aluminum drum using the dip method.
0PCIi (thickness: 15 μm) was formed by processing in vacuum at 100° C. for 1 hour.

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-decrease exposure amount (E2m) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner.

Furthermore, the wavelength characteristics at 700 nm were measured. Obi tt position (
The 6KV band t) is 750v, and the photosensitivity due to white light (
E, 8) is 2.81 ux, sec, photosensitivity after 1000 repetitions (E + 8) is 3.01 ux, sec, wavelength characteristics (photo sensitivity at 700 nm) is 0.7 cd/μJ,
The residual potential (1 second after 101ux light irradiation) was 15V. From this result, it was found that compound (5) exhibited excellent photosensitive properties.

Example 6 The photoreceptor produced by the method of Example 1 was subjected to a continuous printing resistance test. The test was conducted using A4 test paper, and it was found that it operated stably even after continuous testing of 50,000 sheets. As described above, the photoreceptor of the present invention is also superior in terms of rigidity resistance than conventional two-layer photoreceptors or multi-layer photoreceptors.

Effects of the Invention The electrophotographic photoreceptor according to the present invention is a positively charged single-layer photoreceptor, which has higher sensitivity and excellent stability than conventional photoreceptors, and is also easier to manufacture. The process is also extremely easy, and it is expected to be applied to various recording devices as electrophotographic photoreceptors.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a binder polymer, a charge generating agent molecularly dispersed in the binder polymer, and a charge generating agent dispersed in particulate form. 2. The electrophotographic photoreceptor according to claim 1, wherein the weight ratio of the charge generating agent to the binder polymer is within the range of 2:1 to 1:10.