JPH0466507B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor used in a laser beam printer using a semiconductor laser. [Prior art] Phthalocyanine compounds exhibit photoconductivity.
Since its discovery in 1968, a great deal of research has been conducted on it as a photoelectric conversion material. In recent years, with the development of non-impact printing technology, much research has been conducted to develop laser beam printers that use semiconductor lasers as writing heads. In a laser beam printer used in electrophotography, a uniformly corona-charged photoreceptor is first irradiated with a laser beam modulated based on an input signal, and an image is formed by a toner phenomenon. Such a laser recording method improves the image quality, and in particular, the use of a semiconductor laser has the advantage of simplifying the device, making it smaller, and making it possible to reduce the cost. Currently, most of the oscillation wavelengths of semiconductor lasers that operate stably are in the near-infrared region (λ>780nm).
That is, the recording photoreceptor used therein needs to have high sensitivity in a long wavelength region of 780 nm or more. In this case, the half-decrease exposure amount E1/2 of monochromatic infrared light irradiation required for practical sensitivity is 10 erg/cm ² or less. Among photoconductive substances that exhibit high sensitivity in such long wavelength regions, phthalocyanine compounds are attracting particular attention. Conventionally, electrophotographic photoreceptors have been made of selenium, tellurium,
Inorganic compounds such as cadmium sulfide, zinc oxide,
Alternatively, organic compounds such as polyN-vinylcarbazole and bisazo pigments are used. However, these cannot be said to have sufficient photosensitivity in the long wavelength range of 780 nm to 900 nm, and in recent years, photoreceptors using an alloy of selenium, tellurium, and arsenic or photoreceptors using dye-sensitized cadmium sulfide have been developed.
Although it has been reported that they have high sensitivity in the long wavelength region around 800 nm, they are all highly toxic and their environmental safety is being reconsidered as a social issue. In addition, it is thought that it is possible to extend the photosensitive region of a photoreceptor using amorphous silicon to a long wavelength region by using a specific doping method and manufacturing method, but at present, the film formation rate is slow and there are problems with mass production, making it difficult to use. It's hard to say that it's a photoreceptor for the price. Among the phthalocyanine compounds that have been studied so far, compounds that exhibit high sensitivity in the long wavelength region of 780 nm or more include χ-type metal-free phthalocyanine,
Examples include ε-type copper phthalocyanine and vanadyl phthalocyanine. On the other hand, in order to increase sensitivity, a laminated photoreceptor using a vapor-deposited film of phthalocyanine as a charge generation layer has been studied. Some have been obtained. Documents related to such metal phthalocyanines include, for example, Japanese Patent Applications No. 56-96040, No. 56-33977, No. 57-146538, No. 57
-153982, 57-141581, 57-142458, 57-
146538, 58-40789, etc. [Problems to be solved by the invention] However, the production of the vapor deposited film requires a high vacuum exhaust device, which increases the equipment cost, making the organic photoreceptor as described above unavoidably expensive. . On the other hand, a laminated type photoreceptor has been studied in which the phthalocyanine is not deposited as a vapor-deposited film but as a resin dispersion layer, this is used as a charge generation layer, and a charge transport layer is coated on top of the layer. As a photoreceptor, metal-free phthalocyanine (patent application 1982-
No. 66963) and indium phthalocyanine (No. 66963) and indium phthalocyanine
No. 58-220493), and these are relatively highly sensitive photoreceptors, but the former has the disadvantage that sensitivity rapidly decreases in the long wavelength region of 800 nm or more, and the latter When the generating layer is made of a resin dispersion system, it has drawbacks such as insufficient sensitivity for practical use. Furthermore, when a photoreceptor using these phthalocyanine derivatives as a charge-generating material is used in a printer that uses a semiconductor laser as a light source, the interference of the laser light causes shading in the printed image (so-called interference fringes, moiré phenomenon). This has drawbacks such as the inability to form images with uniform density. The present invention improves these drawbacks and
An object of the present invention is to provide an electrophotographic photoreceptor that exhibits high photosensitivity in a wide wavelength range, particularly in a long wavelength region of 800 nm or more, and does not cause interference fringes in images. [Means for Solving the Problems] The present invention solves the above problems by providing an electrophotographic photoreceptor characterized by having a photosensitive layer in which α-type titanyl phthalocyanine and β-type titanyl phthalocyanine are dispersed in a binder. This is the solution. Both the α-type and β-type titanyl phthalocyanine used in the present invention have the general formula (hereinafter referred to as general formula ()). (In the formula, X ₁ , X ₂ , X ₃ , and X ₄ are each independently C
or Br, and k, , m, and n each independently represent a number from 0 to 4. ) is a compound having the structure represented by Among the compounds of general formula (), non-halogen-substituted compounds and monohalogen-substituted compounds are particularly preferred. The α-form titanyl phthalocyanine used in the present invention is, for example, dichlorotitanium phthalocyanine obtained by reacting titanium tetrachloride (or tetrabromo titanium) and phthalodinitrile in an α-chloronaphthalene (or α-bromonaphthalene) solvent. The product obtained by hydrolyzing TiC ₂ Pc) [or dibromotitanium phthalocyanine (TiBr ₂ Pc)] with aqueous ammonia, 2-ethoxyethanol, diglyme, dioxane, tetrahydrofuran, N,N-dimethylformamide,
It can be produced by treatment with an electron-donating solvent such as N-methylpyrrolidone, pyridine, or morpholine. α-type titanyl phthalocyanine thus obtained (k=0,= in the general formula ())
Fig. 1 shows an X-ray diffraction pattern using Cu-Ka rays of the compound with m = 0, m = 0, n = 0. This α-form titanyl phthalocyanine has an X-ray diffraction pattern of 7.6,
10.2, 12.6, 13.2, 15.1, 16.2, 17.2, 18.3, 22.5,
Bragg angle 2θ of 24.2, 25.3, 28.6, 29.3, 31.5
(However, this includes an error range of ±0.2.) It has a characteristic peak. In the other α-type titanyl phthalocyanines used in the present invention, the above specific peak is observed in common in their X-ray diffractograms, despite differences in the halogen atoms, their substitution positions, or the number of substitutions. The β-type titanyl phthalocyanine used in the present invention can be produced by recrystallizing the α-type titanyl phthalocyanine from α-chloronaphthalene or α-bromonaphthalene. The X-ray diffraction pattern of the β-type titanyl phthalocyanine thus produced is shown in FIG. This β-type titanyl phthalocyanine is 7.4, 9.2, 10.3, 13.0, 14.9, 15.3, 15.9,
It has a characteristic peak at each Bragg angle 2θ of 18.6, 20.6, 23.2, 25.5, 26.2, 27.0, and 32.7. Other β-type titanyl phthalocyanines used in the present invention also have the above-mentioned specific peak in common in their X-ray diffractograms, despite differences in the halogen atoms, their substitution positions, or the number of substitutions. A mixed system of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine can be prepared by simply mechanically mixing the pure α-type titanyl phthalocyanine and β-type titanyl phthalocyanine as described above, but as an example of another method, α-form titanyl phthalocyanine can be transformed into β-form by applying mechanical strain force.
It is known that a crystal transition occurs to form titanyl phthalocyanine.Using this phenomenon, by processing α-form titanyl phthalocyanine for a certain period of time using a ball mill, etc., a certain proportion of α-form titanyl phthalocyanine and β-form titanyl can be obtained. Titanyl phthalocyanine mixed with phthalocyanine can also be prepared. The mixing ratio of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine is preferably 20:80 to 99:1 in weight ratio of α-type to β-type, and 50:50-99:1.
is more suitable. The titanyl phthalocyanine used in the present invention is preferably one that has been sufficiently ground into fine particles using a grinding device such as a ball mill, sand mill, or attritor. At this time, commonly used glass beads, steel beads, and alumina beads can be used as a grinding agent, and if necessary, a grinding aid such as common salt or bicarbonate of soda can also be used. When a dispersion medium is required during grinding, it is preferable to use a dispersion medium that is liquid at the temperature during grinding, such as 2-ethoxyethanol, diglyme, dioxane, tetrahydrofuran, N,N-dimethylformamide, N-
Solvents such as methylpyrrolidone, pyridine, morpholine or polyethylene glycol can be used. As the resin used as a binder in the present invention, resins that are generally used as binders for electrophotographic photoreceptors can be used, and preferred examples include phenol, resin, urea resin, melamine resin, epoxy resin, Silicon resin, vinyl chloride-vinyl acetate copolymer, butyral resin, xylene resin, urethane resin, acrylic resin, polycarbonate resin, polyacrylate resin, saturated polyester resin, phenoxy resin, etc. can be used. The electrophotographic photoreceptor of the present invention can have various structures. Examples are shown in FIGS. 4-7. The photoreceptor shown in FIG. 4 has a photosensitive layer 2a formed by dispersing α-type titanyl phthalocyanine 3 and β-type titanyl phthalocyanine 4 in a binder 5 on a conductive support 1. The photoreceptor shown in FIG. 5 has a photosensitive layer 2b formed on a conductive support 1, in which α-type titanyl phthalocyanine 3 and β-type titanyl phthalocyanine 4 are dispersed in a charge transport medium 6 consisting of a charge transport substance and a binder. It is something. The photoreceptor shown in FIGS. 6 and 7 includes a charge carrier generation layer 7 made of an α-type titanyl phthalocyanine 3 and a β-type titanyl phthalocyanine 4 dispersed in a binder 5, and a charge carrier-generating layer 7 made of a charge transport substance and a binder. Photosensitive layer 2c or 2d consisting of layer 8
are set up respectively. In the case of the photoreceptor shown in Figure 4, α-type titanyl phthalocyanine 3 and β-type titanyl phthalocyanine 4
performs both the generation and transport of charge carriers necessary for optical attenuation. In the case of the photoreceptor shown in FIG.
is formed, α-form titanyl phthalocyanine 3
and β-type titanyl phthalocyanine 4 act as charge carrier generating substances. This charge transport medium 6 has the ability to accept and transport charge carriers generated from titanyl phthalocyanine. That is,
In the photoreceptor shown in FIG. 5, the generation of charge carriers necessary for light attenuation is performed by titanyl phthalocyanine,
On the other hand, the transport of charge carriers is mainly carried out by the charge transport medium 6.
This is done by In the case of the photoreceptor shown in FIGS. 6 and 7, the α-type titanyl phthalocyanine 3 and the β-type titanyl phthalocyanine 4 contained in the charge carrier generation layer 7 generate charge carriers, while the charge transport layer 8
receives injection of charge carriers and transports them. The photoreceptor shown in FIG. 4 can be produced by dispersing titanyl phthalocyanine in a binder solution, coating this dispersion on a conductive support, and drying it.
The photoreceptor shown in FIG. 5 can be produced by dispersing titanyl phthalocyanine in a solution containing a charge transporting substance and a binder, coating this dispersion on a conductive support, and drying it. The photoreceptor shown in FIG. 6 is made by coating a conductive support with a dispersion obtained by dispersing titanyl phthalocyanine in a binder solution.
It can be produced by drying, applying a solution of a charge transport substance and a binder dissolved in a solvent thereon, and drying. The photoreceptor shown in Figure 7 is a dispersion obtained by coating a solution of a charge transport substance and a binder dissolved in a solvent on a conductive support, drying it, and then dispersing titanyl phthalocyanine in the binder solution. It can be produced by applying a liquid and drying it. Coating is usually carried out by dipping or using a roll coater, wire bar, doctor blade, etc. The thickness of the photosensitive layer is 3 to 50 .mu.m, preferably 5 to 20 .mu.m for the photoreceptors of FIGS. 4 and 5.
In the case of the photoreceptor shown in FIGS. 6 and 7, the thickness of the charge carrier generation layer is 5 μm or less, preferably 0.01 μm or less.
2μ, and the thickness of the charge transport layer is 3 to 50μ, preferably 5 to 20μ. The ratio of the phthalocyanine compound in the photosensitive layer of the electrophotographic photoreceptor of the present invention is 0.05 to 0.05 to
90% by weight, preferably 15-50% by weight, and the proportion of charge transport material is 10-90% by weight, preferably 10-50% by weight.
60% by weight, and the proportion of charge generating material is 10-70% by weight, preferably 30-50% by weight. Incidentally, in producing any of the photoreceptors shown in FIGS. 4 to 7, a plasticizer can be used together with a binder. In order to obtain even better sensitivity, the electrophotographic photoreceptor according to the present invention may contain a charge transport substance and a charge generation substance in the photosensitive layer together with titanyl phthalocyanine, if necessary. Charge transport materials are classified into hole transport materials and electron transport materials. Examples of hole transport materials include indoline compounds, quinoline compounds, and triphenylamine compounds, and examples of electron transport materials include bisazo compounds. When used, it is more preferable to use at least one hole transport substance and at least one electron transport substance in combination. Examples of the charge generating substance include perylene compounds and bisazo compounds. As an indoline compound, for example, the general formula (In the formula, R ₁ represents an alkyl group, an aralkyl group, or an aryl group that may have a substituent,
R ₂ and R ₃ each independently represent a hydrogen atom, a halogen atom, or an alkyl group, an aralkyl group, or an aryl group which may have a substituent, and R ₄ represents a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. represents an alkyl group or an aralkyl group, and R ₅
and R ₆ represent an alkyl group, an aralkyl group, or an aryl group which may each independently have a substituent, and R ₅ and R ₆ may be combined with each other to form a ring. ) Indoline compounds and general formulas represented by (In the formula, A represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R' ₁ and R' ₂ each independently represent a hydrogen atom, a halogen atom, or a substituent. _R′3 represents a hydrogen atom, a halogen atom, or an alkyl group or an aralkyl group that may have a substituent. Examples are listed in Tables 1 and 2.

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[Table] As a quinoline compound, for example, the general formula (In the formula, B represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and R ₁ , R ₂ , and R ₃ are each independently a hydrogen atom, a halogen atom, or a substituted Represents an alkyl group, aralkyl group or aryl group which may have a group, R ₄ is a hydrogen atom,
Represents an alkyl group or an aralkyl group that may have a halogen atom or a substituent. ) can be mentioned. Preferable examples of quinoline compounds are summarized in Table 3.

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[Table] As a triphenylamine compound, the general formula (In the formula, Ar ₁ , Ar ₂ and Ar ₃ represent a substituted or unsubstituted aromatic carbocyclic group and a substituted or unsubstituted aromatic heterocyclic group.) , suitable examples are listed in Table 4.

[Table] Other well-known charge transport substances can also be used, such as derivatives of heterocyclic compounds such as pyrazole, pyrazoline, oxadiazole, thiazole, and imidazole, hydrazone derivatives, triphenylmethane derivatives, poly-N- Examples include vinyl carbazole and its derivatives. As the bisazo compound used in the present invention,
Any suitable bisazo compound that is generally used in electrophotographic photoreceptors may be used as the fifth compound.
They are summarized in a table.

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[Table] Perylene compounds that can be used in combination with titanyl phthalocyanine as a charge generating substance in the present invention include, for example, the general formula (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group, aryl group, alkylaryl group, or amino group.) Perylene compounds represented by the following can be mentioned. Preferable examples of perylene compounds are listed in Table 6.

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[Table] As the conductive support of the photoreceptor of the present invention, for example, a metal plate drum or metal foil made of aluminum or the like, a plastic film deposited with a metal such as aluminum, or paper subjected to conductive treatment is used. In the electrophotographic photoreceptor according to the present invention, an adhesive layer or a barrier layer can be provided between the conductive support and the photosensitive layer, if necessary. Materials for these layers include polyamide, nitrocellulose, casein, polyvinyl alcohol, etc., and the film thickness is preferably 1 μm or less. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Charge transfer substance No. or charge generation substance in Examples
No. indicates the No. of specific examples of indoline compounds, quinoline compounds, triphenylamino compounds, bisazo compounds, and perylene compounds described in Tables 1 to 5 in the specification. All "parts" in each example indicate "parts by weight" unless otherwise specified. [Example] Production of a mixture of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine α-type titanyl phthalocyanine 88 in which k, m, and n are all 0 in the general formula ()
% by weight and 12% by weight of β-type titanyl phthalocyanine was ground for 64 hours in a ball mill using alumina beads as a grinding agent. The X-ray diffraction pattern of this mixture is shown in FIG. In this X-ray diffraction diagram,
7.6, 9.2, 10.3, 12.4, 13.2, 15.0, 16.2, 18.3,
20.6, 22.5, 24.2, 25.3, 26.2, 27.0, 28.6, 29.3
It has a characteristic peak at each Bragg angle 2θ. Production Example of Electrophotographic Photoreceptor 1 Mixture of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine refined as described above 3
1 part of saturated polyester resin ("Vylon 200" manufactured by Toyobo Co., Ltd.) and 210 parts of chloroform were mixed for 18 hours in a ball mill using alumina beads, and the resulting dispersion was placed on an aluminum-deposited polyester film using a wire bar. A charge generation layer having a dry film thickness of 0.3 μm was formed. On this charge generation layer,
Charge transfer substance No.T-33 (5 parts), polycarbonate resin (“Panlite-1250W” manufactured by Teijin Kasei Ltd.) 5
A photoreceptor for electrophotography was prepared by applying a solution of 65 parts of chloroform dissolved in 65 parts of chloroform using a wire bar to form a charge transfer layer with a dry film thickness of 10 μm. The sensitivity of this photoconductor is measured using a paper analyzer.
SP-428" (manufactured by Kawaguchi Electric Seisakusho Co., Ltd.), the photoreceptor was first charged by corona discharge at an applied voltage of -6 kV in a dark place, and the initial potential (V ₀ ) was measured.
The sample was left in the dark for 10 seconds, and the surface potential retention rate (V ₁₀ /V ₀ ) was measured after 10 seconds. Next, the light sensitivities E _1/2 and E _1/5 were determined by irradiating light from a tungsten lamp at a surface illuminance of 5 lux and measuring the time until the surface potential decreased to 1/2 or 1/5. It was measured. In addition, the surface potential (V ₁₅ ) 15 seconds after the start of exposure was also measured in the same manner. The light is further divided into 830nm (light intensity 10mw/
m ² ), and similarly the light sensitivity (E _1/2 , _1/5 )
was measured. The spectral sensitivity of this photoreceptor is shown in Figure 8.
Practical sensitivity of photoreceptors for laser printers in a wide range of 520 to 900 nm E _1/2 = 10erg/cm ² (E _1/2 ^-1 = 0.1
cm ² /erg). On the other hand, the same paint as in Example 1 was applied onto a transparent PET film, dried, and the visible absorption spectrum of this paint film was measured. The absorption spectrum is shown in FIG. As is clear from this spectrum, this coating film, that is, the charge generation layer of this example, exhibits maximum absorption at 650 nm and 800 nm. Example 2 The mixing ratio of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine was 60% by weight for α-type and 40% by weight for β-type.
A photoreceptor was prepared in the same manner as in Example 1, except for using weight %, and the characteristics of the photoreceptor were measured in the same manner as in Example 1. Comparative Example 1 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 using only the β-type titanyl phthalocyanine used in Example 1 as the titanyl phthalocyanine, and the characteristics of the photoreceptor were measured in the same manner as before. . The photoreceptor characteristics of Examples 1 to 2 and Comparative Example 1 are summarized in Table 7.

[Table] Examples 3 to 6 Mixture 3 of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine refined as described above
1 part of saturated polyester resin ("Vylon 200" manufactured by Toyobo Co., Ltd.) and 210 parts of various solvents shown in Table 8 below were mixed for 18 hours in a ball mill using alumina beads, and the resulting dispersion was aluminum-evaporated. It was applied onto a polyester film using a wire bar and dried to form a charge generation layer with a dry thickness of 0.3 μm. Other than that, a laminated electrophotographic photoreceptor was produced in the same manner as in Example 1, and light separated into 830 nm (light intensity
10mw/m ² ), the sensitivity of the photoreceptor (E _1/5 )
were measured and summarized in Table 8.

[Table] Examples 7 to 12 In Example 1, other charge transport substances shown in Table 9 were used instead of charge transport substance No. T-33,
Various photoreceptors were created. The sensitivity (E _1/5 ) of the photoreceptor was measured by inputting light separated into 830 nm (light intensity: 10 mw/m ² ) into this photoreceptor, and the results are summarized in Table 9.

[Table] Examples 13 to 18 In the photoreceptor of Example 1, the charge generation layer contains
Various photoreceptors were prepared in which 30% by weight of the charge generating substance listed in Table 10 was added to a mixture of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine. Table 10 summarizes the characteristics of each photoreceptor.

〔Effect of the invention〕

The electrophotographic photoreceptor of the present invention has a photosensitive layer in which α-type titanyl phthalocyanine and β-type titanyl phthalocyanine are dispersed in a binder, and thus has high sensitivity in a wide wavelength range from 500 to 900 nm. It is especially excellent as a photoreceptor for laser beam printers and liquid crystal printers that use light sources of around 700 to 900 nm. The electrophotographic photoreceptor of the present invention can be used not only for laser beam printers but also for semiconductor lasers etc.
It can also be applied to various other optical recording devices using an 850 nm light source.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction diagram of α-type titanyl phthalocyanine. FIG. 2 is an X-ray diffraction diagram of β-type titanyl phthalocyanine. FIG. 3 is an X-ray diffraction diagram of a mixture of α-type titanyl phthalocyanine and β-type titanyl phthalocyanine. 4 to 7 are enlarged partial cross-sectional views of the electrophotographic photoreceptor according to the present invention. 1... Conductive support, 2a, 2b, 2c, 2d
...Photosensitive layer, 3...α-type titanyl phthalocyanine, 4...β-type titanyl phthalocyanine, 5...
Binder, 6... Charge transport medium, 7... Charge carrier generation layer, 8... Charge transport layer. FIG. 8 is a diagram showing the spectral sensitivity of the electrophotographic photoreceptor of Example 1. FIG. 9 is a diagram showing the visible absorption spectrum of the charge generation layer of the photoreceptor of Example 1.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer comprising α-type titanyl phthalocyanine and β-type titanyl phthalocyanine dispersed in a binder. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a charge transporting substance. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a charge transporting substance and a charge generating substance. 4. Claim 2 or 3, wherein the charge transport substance is at least one compound selected from the group consisting of indoline compounds, quinoline compounds, triphenylamine compounds, and bisazo compounds.
The electrophotographic photoreceptor described in . 5. The electrophotographic photoreceptor according to claim 3, wherein the charge generating substance is a perylene compound or a bisazo compound.