JPH03287171A - Electrophotographic sensitive body and manufacture of same - Google Patents

Abstract

PURPOSE:To obtain an organic photosensitive body high in performance and sensitivity and superior in durability by stirring a mixture of an X-type metal- free phthalocycnine (H2-Pt) and its solvent and a polymer and changing the crystal system of a part of the phthalocycnine. CONSTITUTION:The X-type metal-free phthalocycnine (H2-Pc) is placed together with the solvent capable of dissolving at least a part of the phthalocycnine and, when needed, a binder polymer in a reactor, sufficiently stirred and mixed, resulting in change of the crystal system, and rise of the solution viscosity, changes of absorption spectra and crystal structure, and enhancement of sensitiv ity are observed during the course of reaction, thus permitting the photosensitive body higher in sensitivity and stability than the conventional photosensitive body to be easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor for forming an electrophotographic image and a method for manufacturing the same.

Conventional technologyOrganic photoreceptors (abbreviated as OPC) have the following advantages: compared to inorganic photoreceptors, materials with high sensitivity to various wavelengths can be synthesized through molecular design, are non-polluting, are superior in productivity and economy, and are inexpensive. It has the following characteristics 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, and some of these improvements have been put into practical use, and they are now becoming the mainstay of photoreceptors for electrophotography.

OPC is usually used with a double layer structure consisting of a charge generation layer (abbreviated as CGL) that absorbs light and generates carriers and a charge transfer layer (abbreviated as 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,
Various hydrazone compounds, oxazole compounds, triphenylmethane compounds, arylamine compounds, and the like have been developed as materials used for CTL (abbreviated as CTM).

Furthermore, in recent years, there has been a strong demand for the use of these organic photoreceptors in the near-infrared region, which is compatible with semiconductor laser light (780-830 nm), as photoreceptors for digital recording in laser printers, etc. Organic photoreceptors with high sensitivity characteristics are being actively developed in this area. As a photoreceptor in such a region, an organic photoreceptor has an advantage over an inorganic photoreceptor in terms of sensitivity.

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

Binder polymers used for this purpose include:
Examples include polyester resin, polycarbonate resin, acrylic resin, acrylic-styrene resin, and the like. Generally, in a double layer structure, the CG layer is coated to a thickness of about 1 micron to increase sensitivity, while the CT layer is coated to a thickness of 10 to 20 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, since only a CTM in which the CTM operates by the movement of holes has been put into practical use, the double layer photoreceptor is of a negative charging type.

Problems to be Solved by the Invention However, in such a negative charging method, (1) the negative charge used for charging causes oxygen in the air to become a 5-thin, and (2) the charging is unstable. (3) There was a problem that it was easily affected by the tram surface.

Ozone is not only harmful to the human body, but also often reacts with photoreceptors, shortening the life of the photoreceptor. However, the instability of charging often leads to a decline in image quality, and the large influence on the drum surface requires the drum to be mirror-finished or undercoated, leading to increased manufacturing costs. Furthermore, when using such a two-layer method, (4) the manufacturing process becomes complicated and the yield rate becomes poor, (5) stability becomes a problem due to delamination between layers, etc. In order to solve these problems, development of organic photoreceptors using a positive charging system is currently underway. Conventionally, in order to achieve positive charging, (1) an inverted two-layer structure OPC in which the CGL layer and CTL layer are configured in the opposite way to the negative charging case, (2) various CG
A single-layer structure OPC in which M and CTM are dispersed in a binder polymer, and (3) a single-layer structure OPC1 in which copper phthalocyanine crystals are dispersed in particles in a polymer have been studied.

6 . . . Among these, the inverted two-layer structure (1) does not solve the problems of complexity in the manufacturing process and interlayer peeling similar to those of the negative charging method. Furthermore, problems arise in that the CGL layer, which essentially needs to be made thin, is placed on the surface of the photoreceptor, resulting in decreased printing resistance and deterioration in life characteristics. On the other hand, (2) (3)
A single-layer photoreceptor that aims to be positively charged using this method has better sensitivity characteristics, charging characteristics (it is difficult for charging charges to accumulate), and residual potential (the residual potential is larger) than the conventional negatively charged two-layer photoreceptor.
It was inferior in that respect. The reason for the poor sensitivity was that charge generation and movement occurred randomly within the single layer, and the problems with single-layer photoreceptors were sensitivity, charging characteristics, and residual potential.

However, in the case of a single layer type positively charged photoreceptor, there is essentially no disadvantage of the multilayer type negatively charged type photoreceptor, and there is also no disadvantage of the reverse layer type positively charged type photoreceptor. Therefore, it is a single layer type and a positive charge type.
If high sensitivity, residual potential, and charging characteristics similar to those of the two-layer type can be achieved using this method, it would be considered an ideal photoreceptor.

An object of the present invention is to solve the above-mentioned drawbacks of the single-layer positive charging method 7.2 photoreceptor and to provide an organic photoreceptor 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. especially,
Metal-free phthalocyanine (H2-P) with various crystal structures
We developed a photoreceptor consisting of a binder polymer and a binder polymer. As a result, we have developed a new photoreceptor and its manufacturing method in which the crystal system of at least a portion of the photoreceptor is changed by stirring X-type H2-Pc with a solvent and a polymer that dissolves the phthalocyanine. It can also be said that this photoreceptor is composed of at least phthalocyanine dispersed in molecular form in a binder polymer and X-type phthalocyanine dispersed in particulate form. With this photoreceptor, we have realized a photoreceptor that has far superior charging characteristics, sensitivity characteristics, and durability compared to conventional single-layer positive charging OPCs, and have accomplished the present invention. Therefore, the photoreceptor of the present invention contains at least a new phthalocyanine made from X-type metal-free phthalocyanine, and in some cases, two types of phthalocyanine, the former phthalocyanine and the X-type metal-free phthalocyanine as a starting material, are simultaneously contained. Sometimes there is a bite.

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. ■Higher sensitivity than conventional single-layer OPC, especially less delay in photoresponse. ■Excellent characteristics especially in positive charging method. ■It has superior stability and chargeability compared to conventional single-layer structure OPC. ■6
It exhibits excellent sensitivity in the wavelength range of 00 to 80 Qnm.

■It has a single layer structure, so it has excellent printing resistance. ■Excellent residual potential characteristics.

Example Examples of the present invention will be described in detail below.

Regarding H2-pc') (Erox Corporation developed X-type H2-Pc with excellent electrophotographic properties, and its synthesis method,
9. - Research on the relationship between crystal type and electrophotographic properties, structural analysis, etc. (USP 3,357,989) X type H
2-Pc is produced by converting β-type H2-Pc synthesized by a conventional method into α-type by treating with sulfuric acid and subjecting it to ball milling for a long time. The crystal is clearly different from the conventional α-type and β-type. FIG. 1 shows the X-form H2-PcOX ray diffraction pattern (measured using CLIKα radiation). The diffraction line is 2
θ near, 4.9.0, 15.1, 16.5.

17.2.20.1.20.6.20.7,2],,4
．． 22.2.23.8.27.2゜28.5, 30.3
Appears in °. The most intense diffraction line is the one near 75° (corresponding to the interplanar spacing d-11,8A), and if its intensity is 1, then the intensity of the diffraction line near 9.1° (corresponding to interplanar spacing a
-=9.3A) is 0.66.

This strength ratio is hardly affected by the grain type of the crystal. Furthermore, the absorption spectrum of the X-type H2-Pc is clearly different from that of the α-type and β-type. Figure 2 shows the X type H2-
The absorption spectrum of Pc is shown. This difference in spectra due to the difference in crystal type is due to the difference in the stacking state of the Pc molecule in the crystal state, and it has been reported that the X-form H2-Pc has a dimeric structure.

The present invention is carried out using type X phthalocyanine among these phthalocyanines as a starting material. Interestingly, even when α-type and β-type notarocyanine are used as the original material, the crystal system does not change as in the present invention. Below, typical techniques of the present invention will be explained.

First, the X-type phthalocyanine is placed in a reaction vessel together with a solvent capable of dissolving at least a portion of the X-type phthalocyanine, a button, and, if necessary, a binder polymer, and thoroughly stirred and mixed. The important point of the production method of the present invention is to use a soluble solvent and perform sufficient kneading. Generally, one day or more is required to create such a stable state using a normal stirring method. As this reaction progresses, an increase in solution viscosity, a change in absorption spectrum, a change in crystal structure, and an improvement in photosensitivity are observed.

An example of an X-ray diffraction diagram of a photoreceptor obtained by such a method is shown in FIG. This diffraction pattern is clearly different from the diffraction pattern shown in FIG. 1 shown above.

It is clearly different from the diffractograms of shredded α-type and β-type H2-Pc. Here, a comparison will be made with the 2PcOX ray diffraction diagram in the X-type shown in FIG. Figure 3 is 2θ-21 compared to Figure 1.
Diffraction lines of 4° or more tend to disappear, and diffraction lines around 16.5° tend to increase. The most notable change is
The most characteristic 7.5° (d=11.8A
), 91° (d=9.8A) Of the two diffraction lines near 75°, only the diffraction line near 75° has selectively disappeared. This is clearly confirmed by the method of the present invention.
This indicates that a part of 2-Pc has changed to a new crystal system. The degree, time, temperature, etc. of these kneading vary depending on the solvent used and the type of polymer. In order to obtain the most excellent properties as a photoreceptor, the treatment with this solvent may be insufficient or too advanced. To determine the appropriate degree of reaction, look at the 75° x-ray pattern mentioned above.
, the diffraction line intensity ratio (In, s/I9.
It is desirable that 8) is between 1 and 01.

An example of the absorption spectrum of a photoreceptor produced by such a method is shown in FIG. This absorption spectrum is clearly different from the absorption spectrum in FIG. 2, which is another evidence that a new crystal form has been generated by the method of the present invention. Also, this spectrum is different from the spectrum in Figure 2 above at a wavelength of 50 nm.

Two absorption lines at 690 nm are large.

These absorptions are considered to be absorptions of molecularly dispersed phthalocyanine, and indicate the possibility that molecularly dispersed phthalocyanine is trapped in the photoreceptor obtained by the method of the present invention. That is, the present invention is a method of changing at least a part of the crystal system of X-type phthalocyanine to another crystal system or amorphous type (or molecular dispersion).

Among crystalline phthalocyanines other than the α-type, β-type, and X-type described above, there is one called τ-type. This is α, β, X
The molded crystal was placed in an inert solvent with a grinding aid at 5-10°C for 2
Obtained by ball milling for 0 hours. That X
The line diffraction diagram is shown in FIG. 5, and the absorption spectrum is shown in FIG. 6.

The X-ray diffraction pattern of the τ crystal is essentially similar to the new crystal system of the present invention. However, the lines on the high angle side have slightly different buttons, so it is not clear whether they are the same crystal or not. In the case of this τ type crystal, the ratio of the intensity of the diffraction line near 7.5° and the intensity of the diffraction line near 9.1° is 1:08.

Solvents suitable for the purpose of the present invention include nitrobenzene,
Chlorobenzene, dichlorobenzene, dichloromethane,
Trichlorethylene, chlornaphthalene, methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, 1,4-dioxane, N-methylpyrrolidone, carbon tetrachloride, bromobutane, ethylene glycol, sulfolane, ethylene glycol monobutyl ether, acetoxyethoxyethane, pyridine , etc. can be raised.

The binder polymer according to the present invention is X-type H2-Pc
It is best to use one that dissolves in the solvent that dissolves it. Polymers suitable for these purposes include polyester, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyvinyl butyral, polyvinyl acetoacetal, polystyrene, polyacrylonitrile, polymethyl methacrylate, and polyvinyl acetate. Acrylate, 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), melamine resins, alkyd resins, cellulose polymers, various silochitin polymers,
Examples include urethane resin. These polymers may be used alone or as a mixture of two or more. Of course, as mentioned above, it is possible to combine two or more types of solvents, so that one solvent dissolves the X-type l-12-Pc and the other solvent dissolves the binder polymer. Therefore, the binder polymer according to the present invention is not limited to the above-mentioned polymers.

The optimal ratio of the X-form I-(2-Pc and the binder polymer) described above is between 1:■ and 1:10 in terms of weight ratio.

If the amount of photosensitive material is greater than this ratio, the photosensitive characteristics will be excellent, but if the charging characteristics are poor, generally 500
It is difficult to apply a potential higher than 15 ・＼. On the other hand, if the amount of the binder polymer is greater than the above range, the photosensitivity will deteriorate.

As a conductive support serving as a substrate for an organic photoconductive layer, 4'
, h-, and can be appropriately selected depending on the intended use. Specifically, metals such as aluminum, glass, paper, or plastics on which a conductive layer is formed by metal vapor deposition or the like are preferably used. Moreover, it can take various shapes such as a drum shape, a belt shape, and a sheet shape.

The sensitivity of the photoreceptor according to the present invention is 10-3.01ux, se
c, which is significantly higher sensitivity than conventional single-layer OPC, and this is the first feature of the photoreceptor of the present invention. Further, the OPC of the present invention exhibits excellent sensitivity to light in the wavelength range of 600 to 800 nm, and has a residual potential of 30 V or less. For example, in a system using phthalocyanine and polyvinyl butyral at a weight ratio of 1:4 (see Example 2), a high sensitivity (charging potential of 800 V) with a half-reduced exposure sensitivity of f 1.11 ux, sec due to positive charging was achieved. The sensitivity at 800 nm was 237/μJ1 and the residual potential was 20 V or less. On the other hand, the sensitivity due to negative charging is 251ux, sec
(Charging potential: 350 V) The dark decay characteristics were also extremely poor, and these characteristics were significantly inferior to those with positive charging. Additionally, this system is very stable, with positive charging characteristics of 100
There was almost no change even after 0 repeated tests. Furthermore, this photoreceptor exhibited excellent heat resistance, and its properties hardly changed even after treatment at 120° C. for 8 hours.

The second feature of the photosensitive properties of the present invention is single layer type electron charging, op
The time delay in photoresponse to light irradiation, which is characteristic of c., is hardly observed. This situation is shown in FIG. FIG. 7(a) shows the characteristics of a ten-charged single-layer photoreceptor produced by a conventional method, in which X-type H2-Pc is dispersed in the form of particles in a binder. On the other hand, b) is a characteristic of the photoreceptor according to the present invention, in which X-type H2-Pc and a metal-free phthalocyanine of a different crystal system are present in the binder. (a
) and (b), it is clear that in (a) a clear delay in response to light irradiation is observed, whereas in (b) this delay is almost eliminated. This is one of the reasons why the photoreceptor of the present invention has high sensitivity, and indicates the possibility that the photoconductor mechanism of the present invention is fundamentally different from that of conventional photoreceptors.

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 to thin tubes. 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 blocking layer between the substrate and the substrate.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1] X-type metal-free phthalocyanine (abbreviated as X-type H2-PC, manufactured by Dai Nippon Ink ■, Phanutogen Blue (li'asto
gen Blue) 8120B) and polyester (abbreviated as PET, manufactured by Toyobo ■, Byron 200)
was dissolved in 18 b/d tetrahydrofuran, thoroughly mixed, and then kneaded for 2 days. The obtained solution was applied onto an aluminum tram by a dip method and treated in vacuum with 120''Cf for 1 hour to form an OPC layer (thickness: 10 to 20 μm).

The X-ray diffraction pattern of the photoreceptor thus obtained was analyzed using an X-ray diffractometer (manufactured by Rigaku Denki, R, ADB 5Y).
STEN). The light source is CuKa line. In addition, its photosensitive characteristics were evaluated using EPA-81 manufactured by Yoro Denki.
Using a 00-type paper analyzer, white light from tungsten was irradiated to measure the photosensitivity due to positive charging (half-decreased exposure amount, EV2), and the photosensitivity after 1000 repeated tests was also measured in the same manner.

Furthermore, wavelength characteristics in the range of 400 to 11,000 nm were measured.

In the X-ray diffraction diagram when the weight ratio of phthalocyanine and PET is 1:4, the diffraction line intensity ratio (111,8/I9.8) is 0.8, and the intensity ratio in the case of 1 raw material X type H2-Pc is 15
The intensity of the diffraction lines was significantly changed compared to the previous one. However, this strength ratio is phthalocyanine and PET19...-
7 was almost constant regardless of the weight ratio. Table 1 shows the photosensitive characteristics when the weight ratio of phthalocyanine and PET was varied.

Table 1 As is clear from these results, a suitable ratio of X-type 1-12-Pc to PET is between 1:1 and 1:10, and a composition within this range provides good charging and sensitivity characteristics. I can do things.

[Example 2] X-type metal-free phthalocyanine (abbreviated as X-type Hz-Pc,
Manufactured by Dai Nippon Ink ■, Fastogen Blue (Fastog
En Blue) 8120B) and polyvinyl butyral (abbreviated as PVB, Eslenok BM-2 manufactured by Tanemizu Chemical Industry Co., Ltd.) were dissolved in tetrahydrofuran, thoroughly mixed and kneaded, and then the resulting solution was applied onto an aluminum drum by the dip method. This was treated in vacuum at 120° C. for 1 hour to form an OPC layer (thickness: 10 to 20 μm). The photosensitive characteristics of the photoreceptor obtained in this way were evaluated using EPA manufactured by Yoro Denki.
Using a vapor analyzer model -8100, white light from tungsten was irradiated to measure the photosensitivity due to positive charging (half exposure amount, Ev'z), and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, 400-1100
The wavelength characteristics in the 0n range were measured. The intensity ratio of the diffraction lines in the X-ray characteristics (111,8/I9.
8), the trigrams and photosensitive characteristics are shown in Table 2.

Table 2 21...-122...-1 For comparison, the characteristics of the same composition as in Example 2 but using n-butyl alcohol as the solvent are shown. n-Butyl alcohol dissolves FiPVB but does not dissolve H2-Pc type X. Therefore, in this manufacturing method, X
Type I (2-Pc was mixed in the form of particles and no new crystals were present. The results are shown in Table 3.

Table 3 From this result, in the method of the present invention, the intensity ratio (I 11.8/19.8) of the diffraction line by X-ray diffraction is 08 to 01.
It was found that excellent characteristics were exhibited when the value was between 1 and 2. It can be seen that when the intensity ratio is less than 0.1, the photosensitive properties are excellent, but the repetition stability is lacking and it is not practical.

[Hitting example I]

As shown in this result, the sensitivity due to positive charging, E1/2, is significantly worse than the results in Tables 1 and 2.
Type TT2- A part of Pc changes into a new crystal23 \-
It can be seen that it is necessary for the present invention to do the following.

[Example 3] X-type H2-Pc (manufactured by Dai-Nippon Ink ■, Fastgen Blue) 8120
B) and various binder polymers were mixed in a ratio of 1=4, dissolved in tetrahydrofuran, thoroughly mixed and kneaded, and then the resulting solution was coated on an aluminum drum by the dip method and heated at 120°C in vacuum for 1 hour. After time processing, 010
A layer (10-20 μm thick) was formed. In both samples, the intensity ratio according to the X-ray diffraction described earlier is 0, 8-0.5.
The reaction time was adjusted so that the

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 (El/2) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, 400-1
The wavelength characteristics were measured in a range of 0,000 m2. The obtained properties are shown in Table 4.

Margin Table 4 Below: As is clear from these results, the method of the present invention can be applied to a wide range of polymers.

[Example 4] Of the photoreceptors produced by the method of Example 1, type X H2PC and P
A sample with an ET ratio of 1:4 was selected and a continuous printing resistance test was conducted. The test was conducted using A4 test paper, but
It was found that it operated stably 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 photoreceptors25.

Effects of the Invention As described above, the method for producing an electrophotographic photoreceptor according to the present invention is particularly effective for positively charged single-layer photoreceptors, and this method is superior to conventional photoreceptors. A photoreceptor with higher sensitivity and excellent stability can be easily manufactured.

The photoreceptor produced by the method of the present invention is expected to be applied as an electrophotographic photoreceptor to various recording devices such as copying machines and printers.

[Brief explanation of the drawing]

Figure 1 shows the X-ray diffraction of type X metal-free phthalocyanine26.
- FIG.

Claims (6)

[Claims] (1) An electrophotographic photoreceptor in which at least a part of the crystal system is changed by treating X-type metal-free phthalocyanine with a solvent and a polymer that dissolve the phthalocyanine. (2) An electrophotographic photoreceptor comprising a binder polymer, a phthalocyanine molecularly dispersed in the binder polymer, and an X-type phthalocyanine dispersed in particulates. (3) The weight ratio of the metal-free phthalocyanine according to claim 1 or claim 2 and the binder polymer is 1:1 to 1:10.
Electrophotographic photoreceptors in the range of . (4) A method for producing an electrophotographic photoreceptor in which a type X metal-free phthalocyanine is stirred together with a solvent that dissolves the phthalocyanine and a binder polymer to form at least a portion of new metal-free phthalocyanine crystals. (5) The method for producing an electrophotographic photoreceptor according to claim 4, wherein a metal-free phthalocyanine mixture of a new metal-free phthalocyanine crystal and an X-type metal-free phthalocyanine is obtained. (6) The method for producing an electrophotographic photoreceptor according to claim 4 or 5, wherein the weight ratio of the metal-free phthalocyanine to the binder polymer is in the range of 1:1 to 1:10.