GB2265724A - Electrophotographic photoreceptor - Google Patents

Abstract

An electrophotographic photoreceptor comprises alpha -form copper phthalocyanine composition obtained by treating a copper tetranitrophthalocyanine and copper phthalocyanine simultaneously to convert the crystalline form into alpha -form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine to the alpha -form copper phthalocyanine composition is limited to a particular range. The photoreceptor has a high photosensitivity and an excellent durability. The photoreceptor may have two photo-sensitive layers, the lower layer containing alpha copper phthalocyanine, perylene, anthanthrope or quinacridone pigment and the upper layer containing the above composition. Alternatively, a charge transparent layer containing a hydrazone may also be present.

Description

ELECTROPHOTOGRAPHIC PHOTORECEPTOR BACKGROUND OF THE INVENTION This invention relates to an electrophotographic photoreceptor wherein an a-form copper phthalocyanine composition composed of a tetranitro copper phthalocyanine and copper phthalocyanine having a specific structure is used as a photoconductive material.

Electrophotographic photoreceptors presently used are mostly in a functionally separating type containing a charge generation material having photosensitivity at a wavelength of light source and a charge transport material having a high charge transport rate. The charge generation material is a photoconductive material, such as an azo pigment, a perylene pigment or a phthalocyanine pigment or the like, and the charge transport material is a hydrazone compound, a styryl compound, a pyrazoline compound, a triphenylamine compound or the like.

On the other hand, there are single layer-type photoreceptors wherein a pigment having photosensitivity at a wavelength of light source is dispersed in a binder resin, and the photoconductive material is an azo pigment, a quinacridone pigment, a perylene pigment, an anthraquinone pigment, a phthalocyanine pigment or the like.

The above photoreceptors using copper phthalocyanine as the photoconductive material have some problems, such as low sensitivity or sensitivity deviation or decrease in charge acceptance caused by repeated use.

SUMMARY OF THE INVENTION An object of the invention is to provide an electrophotographic photoreceptor having a high photosensitivity and an excellent durability by using copper phthalocyanine as the photoconductive material.

The present invention provides an electrophotographic photoreceptor which has achieved the above object, and comprises an a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (A) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (A) to the a-form copper phthalocyanine composition being 2 wt. % to 20 wt. %.

In the formula, each one nitro group is substituted in 1-position or 4-position, 8-position or ll-position, 15-position or 18-position, and 22-position or 25-position, respectively.

The present invention provides another electrophotographic photoreceptor which also has achieved the above object, and comprises a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (B) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (B) to the a-form copper phthalocyanine composition being 1 wt. % to 10 wt. %.

In the above formula.

In the formula, each one nitro group is substituted in 2-position or 3-position, 9-position or 10-position, 16-position or 17-position, and 23-position or 24-position, respectively.

The present invention provides a further electrophotographic photoreceptor which also has achieved the above object, and comprises a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (A) and a tetranitro copper phthalocyanine (B) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (A) to the a-form copper phthalocyanine composition being not more than 15 wt. %, the ratio of the tetranitro copper phthalocyanine (B) being not more than 8 wt. %, and the ratio of the sum of the tetranitro copper phthalocyanine (A) and the tetranitro copper phthalocyanine (B) to the a-form copper phthalocyanine composition being not more than 20 wt. %.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph showing a X-ray diffraction pattern of an a-form copper phthalocyanine composition used in the invention.

Figures 2 through 5 are sectional views of electrophotographic photoreceptors embodying the invention, respectively.

Figure 6 is a graph showing light decay curve of an electrophotographic photoreceptor of the invention.

1 ... Conductive substrate 2 ... Photosensitive layer 3 ... First photosensitive layer 4 ... Second photosensitive layer 5 ... Charge generation layer 6 ... Charge transport layer DETAILED DESCRIPTION OF THE INVENTION Preferred forms of the electrophotographic photoreceptor of the invention are single layers alone of the photosensitive layer, laminates of a first photosensitive layer containing a pigment and a second photosensitive layer containing the a-form copper phthalocyanine composition laminated thereonto, and laminates of a charge generation layer containing the a-form copper phthalocyanine composition and a charge transport layer.

In the electrophotographic photoreceptor of the invention, the photosensitivity can be changed by changing the ratio of tetranitro copper phthalocyanine (A) and/or (B) to copper phthalocyanine composition. In the case that the ratio of the tetranitro copper phthalocyanine (A) and/or (B) is less than the aforementioned range, photosensitivity is insufficient as the photoreceptor. On the other hand, in the case that the ratio is more than the aforementioned range, charge acceptance is insufficient. A preferable range is 3 to 15 wt. % in the case of the tetranitro copper phthalocyanine (A) 0.2 to 4 wt. % in the case of the tetranitro copper phthalocyanine (B). In the case of a combination of the tetranitro copper phthalocyanines (A) and (B), a preferable range is 1 to 10 wt. % of the tetranitro copper phthalocyanine (A) and 0.1 to 2 wt. % of the tetranitro copper phthalocyanine (B).

Copper phthalocyanine and tetranitro copper phthalocyanines (A) and (B) can be prepared according to a known synthesis of copper phthalocyanine, such as disclosed in GB 464126, GB 476243, J. Coord. Chem., 19(4), 295-301, 1989 or the like.

The a-form copper phthalocyanine composition can be prepared by the acid pasting method, the acid slurry method, the low temperature sublimation method or the like. In the invention, it is important that tetranitro copper phthalocyanine is uniformly distributed among the a-form copper phthalocyanine crystals in the a-form copper phthalocyanine composition, and in this regard, the acid pasting method is the most preferable. In the acid pasting method, phthalocyanine (copper phthalocyanine and copper tetranitrophthalocyanine) is dissolved in sulfuric acid, and the sulfuric acid solution is poured into a great quantity of water to convert the crystal form to a-form. The photoreceptor properties in the invention cannot be obtained by mere mixing of tetranitro copper phthalocyanine with a-form copper phthalocyanine.

An X-ray diffraction pattern of the a-form copper phthalocyanine composition used in the invention is shown in Figure 1. As the crystal forms of copper phthalocyanine, there are a-form, form, x-form and T-form. In the case of form crystal, diffraction peaks appear at diffraction angles (2 ) of 6.5 , 7.0 , 9.7 , 15.2 , 15.9 , 23.7 , 24.8 26.4 and 27.3 , and accordingly, it can be seen from the diffraction patterns of Figure 1 that the copper phthalocyanine composition of the invention belongs to a-form.

Some embodiments of the photoreceptor of the invention are illustrated in Figures 2 through 5.

The electrophotographic photoreceptor of Figure 2 is composed of a photosensitive layer 2 containing the a-form copper phthalocyanine composition on a conductive support 1.

The electrophotographic photoreceptor of Figure 3 is composed of a first photosensitive layer 3 containing a pigment on a conductive support 1 and a second photosensitive layer containing the a-form copper phthalocyanine composition formed further thereon.

The electrophotographic photoreceptor of Figure 4 is composed of a charge generation layer 5 containing the a-form copper phthalocyanine composition on a conductive support 1 and a charge transport layer 6 formed further thereon. A small amount of charge transport material may be added to the charge generation layer 5.

The electrophotographic photoreceptor of Figure 5 is composed of a charge transport layer 6 on a conductive support 1 and a charge generation layer 5 further thereon.

The a-form copper phthalocyanine composition of the invention can be used not only as a photoconductive material of single layer-type photoreceptor but also as a charge generation material of functionally separating type photoreceptor. Moreover, in the case of using copper phthalocyanine pigment or the like as a charge generation material, it is, in general, combined with a charge transport material in hole type. When it is combined with a charge treansport material in electron transport type, photosensitivity is minor. However, the aform copper phthalocyanine composition of the invention exhibits good properties by combining with either of the hole type change transport material or the electron transport type one.

In the electrophotographic photoreceptor of the invention, the photosensitive layers 2, can be prepared by dispersing the a-form copper phthalocyanine composition in a binder resin and applying onto the conductive support 1.

The second photosensitive layer 4 and the charge generation layer 5 may be formed by applying a dispersion of the a-form copper phthalocyanine composition onto the conductive substrate 1, the first photosensitive layer 3 or the charge transport layer 6 or by depositing the a-form copper phthalocyanine composition thereonto. As the binder resin, there are thermoplastic resins, such as polyester resin, polycarbonate resin and polyvinyl butyral resin, and thermosetting resins having a high volume specific resistance, such as polyurethane resin, epoxy resin, melamine resin, formalin resin and phenol resin. A suitable content of the a-form copper phthalocyanine composition in the resin is 10 to 60 wt. %, preferably 20 to 30 wt. %.

The pigment contained in the first photosensitive layer 3 in the electrophotographic photoreceptor of the invention may be anyone which can injects carrier produced in the a-form copper phthalocyanine composition contained in the second photosensitive layer 4 by irradiation of light and transports efficiently. As such a pigment, there are phthalocyanine pigments, perylene pigments, anthraquinone pigments, squarylium pigments, azo pigments, quinacridone pigments, and the like. A low molecular charge transport material or the a-form copper phthalocyanine composition used in the second photosensitive layer may be incorporated into the first photosensitive layer containing a pigment.

As the blendable low molecular charge transport materials, there are hydrazone compounds, styryl compounds, triphenylamine compounds, and the like.

The photosensitive layer 3 containing a pigment may be prepared by dispersing the pigment into the binder resin, and applying onto the conductive support. As the binder resin, there are thermoplastic resins, such as polyester resin, polycarbonate resin and polyvinyl butyral resin, and thermosetting resins having a high volume specific resistance, such as polyurethane resin, epoxy resin, melamine resin, formalin resin and phenol resin. A suitable content of the pigment in the resin is 10 to 60 wt. %, preferably 20 to 40 wt. %.

The charge transport material and the binder resin used for the charge transport layer 6 may be those used in conventional electrophotographic photoreceptors. Such a charge transport material includes polyvinyl carbazole, hydrazone compounds, styryl compounds, triphenylamine compounds, quinone compounds, thioxanthone compounds, and the like. The binder resin may be anyone being excellent in adhesiveness and being insulating material.

The charge transport layer 6 may be prepared by dispersing the charge transport material into the binder resin, and applying onto the conductive support 1 or the charge generation layer 5. Either of the photosensitive layers 2,3,4 the charge generation layer 5 and/or the charge transport layer 6 may be blended with a plasticizer for the improvement in plasticity, adhesiveness and mechanical strength, an antioxidant for the improvement in chamical strength to the extent so as not to degrade the photosensitive properties of the photoreceptor. The photoreceptor is provided optionally with an intermediate layer in order to improve the adhesiveness to the conductive support 1 or to inhibit the injection of carrier from the conductive support 1, a surface-protective layer in order to improve mechanical properties, or the like.

As the coating means of the photosensitive layers 2,3, 4, the charge generation layer 5, the charge transport layer 6, and/or the intermediate layer, etc., doctor blade, wire bar, roll coater or the like are, in general, usable.

In the case of the electrophotographic photoreceptor of Figure 2, the thickness of the photosensitive layer 2 is usually 5 to 50 pm, preferably 10 to 20 pm. When an intermediate layer or a surface-protective layer is provided, its thickness is preferably less than 1 pm.

In the case of the electrophotographic photoreceptor of Figure 3, the thickness of the first photosensitive layer 3 is 5 to 50 pm, prefeably 10 to 20 pm, and the thickness of the second photosensitive layer 4 is 0.2 to 5 pm, preferably 0.5 to 2 pm. When an intermediate layer or a surface-protective layer is provided, its thickness is prefeably less than 1 pm.

In the case of the electrophotographic photoreceptors of Figures 4 and 5, the thickness of the charge generation layer 5 is less than 5 pm, preferably 0.1 to 1 pm, and the thickness of the charge transport layer 6 is 5 to 50 pm, preferably 10 to 20 pm. When an intermediate layer or a surface-protective layer is provided, its thickness is preferably less than 1 pm.

The conductive support 1 may be those used in conventional ones, such as metal supports, e.g. aluminum, stainless steel, copper or brass, inslating supports onto which aluminum, indium oxide or the like is deposited, and so on.

The a-form copper phthalocyanine composition used in the invention has a high sensitivity and is excellent in durability due to its chemical stability, compared with conventional a-form copper phthalocyanine. The electrophotographic photoreceptor of the invention has a high sensitivity and is excellent in durability and resistance to printing. Moreover, since the a-form copper phthalocyanine composition used in the invention has absorption in a broad range from visible region to infrared region, the electrophotographic photoreceptor of the invention is applicable to laser printer, liquid crystal shutter printer, LED printer, copying apparatus, computerized type-setting system, and the like.

In the case of using in a positive charged type, the generation of ozone is little caused in the charging process. Electrophotographic photoreceptors as shown in Figure 2 or Figure 3 exhibit induction phenomenon specific to the pigment dispersed type photoreceptor in a region of very low quantity of light as well as high sensitivity, they can be used as an electrophotographic photoreceptor having a high resolution not affected by the light distribution at edge portions of a spot of irradiated light, nor light leaked through a liquid crystal shutter.

EXAMPLES Example 1 9.2 g of copper phthalocyanine and 0.8 g (8 wt. %) of tetranitro copper phthalocyanine (A) were dissolved into 100 g of sulfuric acid, and the solution was poured into 2 1 of ice water to obtain an a-form copper phthalocyanine composition. 5 g of the a-form copper phthalocyanine composition was mixed with a polymer solution prepared by dissolving 20 g of polyester resin into 180 g of cyclohexanone, and dispersed by a shaking type dispersing machine for 3 hours. The solution obtained was applied onto an aluminum deposited polyester film by a wire bar to form a photosensitive layer 17 pm in dry thickness.

The electrophotographic photoreceptor thus prepared was charged by corona discharge at + 6 kV at a dark place and then exposed to W lamp at an intensity of illumination of 2.5 p W/cm2 for 20 seconds, in order to examine the photoreceptor properties. Measured photoreceptor properties were initially charged potential VO after charging, time to necessary for dark-decaying from 620 V to 600 V in the surface potential, quantity of exposed light E1/2 necessary for light-decaying from 600 V to 300 V and residual potential Vr after light irradiation for 20 seconds.

Furthermore, similar operations were repeated 1000 times as to the electrophotographic photoreceptor, and VO (1000), to (1000), E1/2 (1000) and Vr (1000) were measured to evaluate durability. The results were shown below. A light decay curve obtained by irradiating light at time to after charging was shown in Figure 6. As can be seen from Figure 6, the electrophotographic photoreceptor of the invention has a high sensitivity, and exhibits induction phenomenon specific to the pigment dispersion-type photoreceptor in a region of very weak light quantities.

VO = 780 V to = 15 sec.

E1/2 = 1.8 pJ/cm2 Vr = 36 V VO (1000) = 765 V to (1000) = 13 sec.

E1/2 (1000) = 1.6 pJ/cm Vr (1000) = 42 V Example 2 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that the a-form copper phthalocyanine composition used was composed of 2 wt.

% of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 1. The light decay curve was similar to Example 1.

Example 3 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that thermosetting-type melamine resin was used as the binder resin. The photoreceptor properties were shown in Table 1.

The light decay curve was similar to Example 1.

Example 4 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that the a-form copper phthalocyanine composition was composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine and the binder resin was thermosetting-type melamine resin. The photoreceptor properties were shown in Table 1. The light decay curve was similar to Example 1.

Example 5 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that the a-form copper phthalocyanine composition was composed of 4 wt. % of tetranitro copper phthalocyanine (A), 1 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine and the binder resin was thermosetting-type mealmine resin. The photoreceptor properties were shown in Table 1. The light decay curve was similar to Example 1.

Table 1 Photoreceptor Example2 Example3 Example4 Example5 Properties Vo cV] 796 867 872 836 to DsecX 16 18 16 16 E1/2 [ J/cm] 1.5 1.6 -1.2 1.0 Vr [V] 30 43 38 32 Vo (1000) EV] 779 841 869 824 to (1000) Lsecj. 14 16 16 16 E1/2 (1000) NJ/cm2 1.3 1.4 1.1 0.9 Vr (1000) [V] 40 50 43 36 Comparative Example 1 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that conventional a-form copper phthalocyanine alone obtained by the acid pasting method was used as the photoconductive material. The photoreceptor properties were shown below.

As can be seen from the results, initial photosensitivity was very low, and charge acceptance was sharply decreased by repeated use.

VO = 765 V to = 13 sec.

E1/2 = 43.3 pJ/cm2 Vr = 283 V VO to000) =321 V Vr (1000) = 134 V Compararive Example 2 An electrophotographic photoreceptor was prepared under the conditions similar to Example 1, except that the mixture of conventional a-form copper phthalocyanine obtained by the acid pasting method and tetranitro copper phthalocyanine (B) in the same content as Example 2 was used as the photoconductive material. The photoreceptor properties were shown below. As can be seen from the results, charge acceptance was low, and photosensitivity was very small, and accordingly, it was unsuitable to put to practial use.

VO = 196 V Vr = 121 V Comparative Examples 3-7 Using the a-form copper phthalocyanine compositions wherein the contents of tetranitro copper phthalocyanines (A), (B) were varied, electrophotographic photoreceptors were prepared under the conditions similar to Example 1.

The photoreceptor properties of them were measured, and the results were shown in Table 2.

As can be seen from the results of Table 2, in the case that the tetranitro copper phthalocyanine content of the a-form copper phthalocyanine composition is less than the range of the invention, photosensitivity is insufficient as photoreceptor. In the case that the content is more than the rangeof the invention, charge acceptance is sharply decreased.

Table 2 Comparative3 Comparative4 Comparative5 Comparative6 Conparative7 Photoreceptor A B A B A B A B A B Properties (wt.%)(wt.%) (wt.%)(wt.%) (wt.%)(wt.%) (wt.%)(wt.%) (wt.%)(wt.%) 1.2 0 50 0 0 0.3 0 20 20 5 Vo (V) 878 225 883 198 176 to (sec.) 20 18 E1/2 (J/om2) 36.5 34.8 Vr (V) 232 181 218 171 123 Vo (1000) (V) 576 523 to (1000) (sec.) E1/2 (1000) ( J/cm) Vr (1000) (V) 246 211 Example 6 Using 10 g of copper phthalocyanine as the pigment, a-form copper phthalocyanine was prepared by the acid pasting method. 5 g of the a-form copper phthalocyanine was mixed with a polymer solution prepared by dissolving 20 g of polyester resin into 180 g of cyclohexanone, and dispersed by a shaking type dispersing machine for 3 hours. The solution obtained was applied onto an aluminum deposited polyester film by a wire bar to form a first photosensitive layer 16 pm in dry thickness.

Subsequently, 9.2 g of copper phthalocyanine and 0.8 g (8 wt. %) of tetranitro copper phthalocyanine (A) were dissolved into 100 g of sulfuric acid, and the solution was poured into 2 1 of ice water to obtain an a-form copper phthalocyanine composition. A dispersion composed of 1 g of the a-form copper phthalocyanine composition, 4 g of polyester resin and 36 g of cyclohexanone was prepared similarly, and applied onto the first photosensitive layer so that the total dry thickness of the first and second photosensitive layers was 17 pm to obtain an electrophotographic photoreceptor.

As to the electrophotographic photoreceptor thus prepared, photoreceptor properties were measured similar to Example 1, and the results were shown in Table 3. A light decay curve was measured by irradiating light at time to after charging, and the results as shown in Figure 6 were obtained similar to Example 1. As can be seen from the results, the electrophotographic photoreceptor of the invention has a high sensitivity, and exhibits induction phenomenon in a region of very weak light quantities.

Example 7 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the a-form copper phthalocyanine composition used was composed of 2 wt.

% of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Example 8 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the a-form copper phthalocyanine composition was composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine and the binder resin for dispersing the pigment was thermosetting-type melamine resin. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Example 9 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the following perylene pigment was used as the pigment. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Example 10 An electrographic photoreceptor was prepared under the conditions similar to Example 6, except that the pigment was replacedby the following pigment. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Example 11 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the c-form copper phthalocyanine composition was composed of 4 wt. % of tetranitro copper phthalocyanine (A), 1 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Example 12 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the perylene pigment used in Example 9 was used as the pigment, the following hydrazone compound was added in an amount of 5 wt. % of the pigment as the low molecular charge transport material, and the a-form copper phthalocyanine composition composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine was used. The photoreceptor properties were shown in Table 3. The light decay curve was similar to Example 6.

Table 3 Photorecepeor Example6 Example7 Example8 Example9 Example10 Example Example2 Properties Vo tVs 806 800 878 738 721 752 726 t EseeJ 18 18 17 14 16 16 14 E112 2 E1/2 [ J/cm] 1.9 1.4 1.5 2.4 3.2 2.6 2.0 Vr [V] 43 38 46 68 75 75 61 V (1000) (V) 800 796 860 728 714 738 718 to (1000) (secj 17 17 16 11 18 14 13 E1/2 (1000) [ J/cm] 1.7 1.3 1.4 2.1 3.4 2.2 1.8 Vr (1000) CV] 48 42 49 73 73 81 70 Comparative Example 8 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the perylene pigment used in Example 9 was used instead of the a-form copper phthalocyanine composition. The photoreceptor properties were shown below. As can be seen from the results, photosensitivity was very low, and it was unsuitable for practical use.

VO = 725 V to = 23 sec.

Vr = 412 V Comparative Example 9 An electrophotographic photoreceptor was prepared under the conditions similar to Example 6, except that the pigment used in Example 10 was used instead of the a-form copper phthalocyanine composition. The photoreceptor properties were shown below. As can be seen from the results, photosensitivity was very small, and accordingly, it was unsuitable to put to practical use.

V = 733 V 0 to = 31 sec.

Vr = 481 V Example 13 9.2 g of copper phthalocyanine and 0.8 g (8 wt. %) of tetranitro copper phthalocyanine (A) were dissolved into 100 g of sulfuric acid, and the solution was poured into 2 1 of ice water to obtain an a-form copper phthalocyanine composition. 5 g of the a-form copper phthalocyanine composition was mixed with a polymer solution prepared by dissolving 20 g of polyester resin into 180 g of cyclohexanone, and dispersed by a shaking type dispersing machine for 3 hours. The solution obtained was appied onto an aluminum deposited polyester film by a wire bar to form a charge generation layer 0.5 pm in dry thickness.

Subsequently, 10 g of the hydrazone compound used in Example 12 as the charge transport material was dissolved into a polymer solution prepared by dissolving 10 g of polycarbonate resin into 90 g of cyclohexane. The solution obtained was applied onto the charge generation layer by a wire bar to form a charge transport layer 17 pm in thickness, and an electrophotographic photoreceptor was completed.

The electrophotographic photoreceptor thus prepared was charged by corona discharge at -6 kV at a dark place and then exposed to W lamp at an intensity of illumination of 2.5 pW/cm2 for 20 seconds, in order to examine the photoreceptor properties. Measured photoreceptor properties were initially charged potential VO after charging, time to necessary for dark-decaying from -620 V to -600 V in the surface potential, quantity of exposed light E1/2 necessary for light-decaying from -600 V to -300 V and residual potential Vr after light irradiation for 20 seconds.

Furthermore, similar operations were repeated 1000 times as to the electrophotographic photoreceptor, and VO (1000), to (1000), E1/2 (1000) and Vr (1000) were measured to evaluate durability. The results were shown in Table 4.

Example 14 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that the a-form copper phthalocyanine composition used was composed of 2 wt.

% of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 4.

Example 15 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that thermosetting-type melamine resin was used as the binder resin of the charge generation layer. The photoreceptor properties were shown in Table 4.

Example 16 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that the a-form copper phthalocyanine composition composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine was deposited on the aluminum substrate polyester film to form a charge generation layer 0.5 pm in thickness. The photoreceptor properties were shown in Table 4.

Example 17 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that the a-form copper phthalocyanine composition composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine was used, and as shown in Figure 5, the charge transport layer was formed on the conductive support of the aluminum deposited polyester film, and the charge generation layer was laminated thereonto. The photoreceptor properties were shown in Table 4.

Example 18 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that the a-form copper phthalocyanine composition was composed of 4 wt. % of tetranitro copper phthalocyanine (A), 1 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine and the binder resin was thermosetting-type mealmine resin. The photoreceptor properties were shown in Table 4.

Table 4 Photoreceptor Example13 Example14 Examples Examplel6 Examplel7 Example18 Properties V0 EV] -782 -793 -867 -862 873 -843 to [secJ 12 16 18 19 19 18 E1/2 tpJ/cm3 1.6 1.3 1.6 1.2 1.6 1.3 Vr [V] -48 -43 -43 -40 51 -48 V0 (1000) tV] -777 -789 -841 -860 861 -836 to (1000) [secj 10 15 16 17 18 16 E1/2 (1000) [ J/cm] 1.7 1.5 1.4 1.3 1.4 1.2 Vr (1000) CV] -53 -52 -50 -44 53 -51 Comparative Example 10 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that conventional a-form copper phthalocyanine alone obtained by the acid pasting method was used as the charge generation material in the charge generation layer. The photoreceptor properties were shown below. As can be seen from the results, initial photosensitivity was very low, and charge acceptance was sharply decreased by repeated use.

V = -785 V to = 18 sec.

E1/2 = 28.4 pJ/cm2 Vr = -226 V VO (1000) = -421 pJ/cm2 Vr (1000) = -184 V Compararive Example 11 An electrophotographic photoreceptor was prepared under the conditions similar to Example 13, except that the mixture of conventional a-form copper phthalocyanine obtained by the acid pasting method and tetranitro copper phthalocyanine (B) in the same content as Example 2 was used as the charge generation material to form the charge generation layer. The photoreceptor properties were shown below. As can be seen from the results, charge acceptance was low, and photosensitivity was very small, and accordingly, it was unsuitable to put to practial use.

Vo = -399 V Vr = -114 V Example 19 5 g of the a-form copper phthalocyanine composition containing 8 wt. % of tetranitro copper phthalocyanine (A) and 20 g of polyester resin were dissolved in 180 g of cyclohexanone, and the mixture solution was dispersed by a shaking type dispersing machine for 3 hours. The solution obtained was applied onto an Al deposited polyester film by a wire bar to form a charge generation layer 0.5 pm in dry thickness. Subsequently, 10 g of the following thioxanthone derivative was dissolved as the charge transport material into a polymer solution prepared by dissolving 10 g of polycarbonate resin into 90 g of cyclohexanone. The mixture solution obtained was applied onto the charge generation layer by a wire bar to form a charge transport layer 20 pm in thickness, and an electrophotographic photoreceptor was completed.

As to the electrophotographic photoreceptor thus prepared, the photoreceptor properties were measured similar to Example 1, and the results were shown in Table 5.

Example 20 An electrophotographic photoreceptor was prepared under the conditions similar to Example 19, except that the a-form copper phthalocyanine composition used was composed of 2 wt.

% of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 5.

Example- 21 An electrophotographic photoreceptor was prepared under the conditions similar to Example 19, except that the a-form copper phthalocyanine composition was composed of 2 wt. % of tetranitro copper phthalocyanine (A), 3 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine. The photoreceptor properties were shown in Table 5.

Example 22 An electrophotographic photoreceptor was prepared under the conditions similar to Example 19, except-that thermosetting-type melamine resin was used as the binder resin. The photoreceptor properties were shown in Table 5.

Example 23 An electrophotographic photoreceptor was prepared under the conditions similar to Example 19, except that the a-form copper phthalocyanine composition was composed of 2 wt. % of tetranitro copper phthalocyanine (B) and copper phthalocyanine and the binder resin was thermosetting-type melamine resin. The photoreceptor properties were shown in Table 5.

Table 5 Photoreceptor Examplel9 Example20 Example21 Example22 Example 23 Properties Vo CVg 760 755 780 780 776 to [sec.] 14 15 10 17 15 E1/2 [ J/cm] 2.5 2.1 2.7 2.3 2.1 Vr Cv) 30 32 45 29 32 Vo (1000) EV] 750 740 730 768 786 to (1000) [secj 12 10 13 15 17 E1/2 (1000)[ J/cm] 2.3 2.1 2.4 2.1 2.3 V (1000) [V] 35 38 31 48 46

Claims (1)

1. CLAIMS 1. An electrophotographic photoreceptor comprising an a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (A) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (A) to the a-form copper phthalocyanine composition being 2 wt. % to 20 wt. %.

   In the formula, each one nitro group is substituted in l-position or 4-position, 8-position or 11-position,

   15-position or 18-position, and 22-position or

   25-position, respectively.

   2. The electrophotographic photoreceptor of claim 1 wherein said treating is conducted by the acid pasting method.

   3. The electrophotographic photoreceptor of claim 1 or 2 which comprises a photosensitive layer being a single layer.

   4. The electrophotographic photoreceptor of claim 1 or 2 which comprises two photosensitive layers, the lower photosensitive layer comprising a pigment, and the upper photosensitive layer comprising the ct-form copper phthalocyanine composition.

   5. The electrophotographic photoreceptor of claim 1 or 2 which comprises a charge generation layer and a charge transport layer, and the charge-producing layer containing the a-form copper phthalocyanine composition.

   6. An electrophotographic photoreceptor comprising an a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (B) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (B) to the a-form copper phthalocyanine composition being 1 wt. % to 10 wt. %.

   In the formula, each one nitro group is substituted in

   2-position or 3-position, 9-position or 10-position,

   16-position or 17-position, and 23-position or

   24-position, respectively.

   7. The electrophotographic photoreceptor of claim 6 wherein said treating is conducted by the acid pasting method.

   8. The electrophotographic photoreceptor of claim 6 or 7 which comprises a photosensitive layer being a single layer.

   9. The electrophotographic photoreceptor of claim 6 or 7 which comprises two photosensitive layers, the lower photosensitive layer comprising a pigment, and the upper photosensitive layer comprising the ct-form copper phthalocyanine composition.

   10. The electrophotographic photoreceptor of claim 6 or 7 which comprises a charge generation layer and a charge transport layer, and the charge-producing layer containing the ct-form copper phthalocyanine composition.

   11. An electrophotographic photoreceptor comprising an a-form copper phthalocyanine composition obtained by treating a tetranitro copper phthalocyanine (A) and a tetranitro copper phthalocyanine (B) having the formula I and copper phthalocyanine simultaneously to convert the crystalline form into a-form as a photoconductive material, and the ratio of the tetranitro copper phthalocyanine (A) to the ct-form copper phthalocyanine composition being not more than 15 wt. %, the ratio of the tetranitro copper phthalocyanine (B) to the ct-form copper phthalocyanine composition being not more than 8 wt. %, and the ratio of the sum of the tetranitro copper phthalocyanine (A) and the tetranitro copper phthalocyanine (B) to the a-form copper phthalocyanine composition being not more than 20 wt. %.

   In the formula, in the tetranitro copper phthalocyanine (A), each one nitro group is substituted in l-position or 4-position, 8-position or 11-position, 15-position or 18-position, and 22-position or 25-position, respectively, and in the tetranitro copper phthalocyanine (B), each one nitro group is substituted in 2-position or 3-position, 9-position or 10-position,

   16-position or 17-position, and 23-position or 24position, respectively.

   12. The electrophotographic photoreceptor of claim 11 wherein said treating is conducted by the acid pasting method.

   13. The electrophotographic photoreceptor of claim 11 or 12 which comprises a photosensitive layer being a single layer.

   14. The electrophotographic photoreceptor of claim 11 or 12 which comprises two photosensitive layers, the lower photosensitive layer comprising a pigment, and the upper photosensitive layer comprising the a-form copper phthalocyanine composition.

   15. The electrophotographic photoreceptor of claim 11 or 12 which comproses a charge generation layer and a charge transport layer, and the charge generation layer containing the a-form copper phthalocyanine composition.