JPS6059588B2 - electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor in which a photosensitive layer comprising a combination of a carrier generation phase and a carrier transport phase is provided on a conductive support.

In general, with the exception of a few substances such as amorphous selenium, it is difficult to form a film on the surface of substances that generate carriers by absorbing visible light. It has the disadvantage of poor charge retention.

On the contrary, materials that have excellent film-forming ability and can retain a charge of 500 V or more for a long time with a thickness of about 10 microns generally have the disadvantage of not having sufficient photoconductivity due to absorption of visible light. have. For this reason,
Recently, photosensitive layers have been developed by combining a carrier generation phase made of a substance that absorbs visible light and generates charge carriers, and a carrier transport phase that transports either positive or negative charge carriers or both of the charge carriers generated in this carrier generation phase. It was proposed to configure the

In this way, by dividing charge carrier generation and transport into separate phases, a wide range of materials can be selected and can meet the various properties required in the electrophotographic process, such as charge retention and surface strength. It has now become possible to improve or improve sensitivity to visible light, stability during repeated use, etc. 7 Conventionally, the following types of photoreceptors are known.

(1) Carrier generation phase layer (hereinafter simply referred to as 1 carrier generation layer).

) is composed of amorphous selenium, and the carrier transport phase layer (
Hereinafter, it will simply be referred to as one carrier transport layer. ) Polly N
- A photosensitive layer composed of vinyl carbazole (hereinafter referred to as RPVK) and laminated. (2)
The carrier generation layer is made of amorphous selenium, and the carrier transport layer is made of 2,4,7-trinitro-9-fluorenone (
Hereafter referred to as RTNFJ.

) and has a laminated photosensitive layer. (
3) A photosensitive layer in which the carrier generation layer is composed of a perylene derivative and the carrier transport layer is composed of an oxadiazole derivative (U.S. Pat. No. 3,871)
88 trowel specification).

(4) A photosensitive layer in which the carrier generation layer is made of chlordian blue or methylskarylium and the carrier transport layer is made of a pyrazoline derivative, which are laminated (see JP-A-51-90827). (5) P
A photosensitive layer in which phthalocyanine constituting a carrier generation phase is dispersed in a carrier transport layer containing VVK.

(6) A photosensitive layer in which phthalocyanine constituting a carrier generation phase is dispersed in a carrier transport layer containing TNF.

As described above, electrophotographic photoreceptors equipped with photosensitive layers having many two-phase structures are known, and they are easy to manufacture, have sufficient electrophotographic properties, and are stable against environmental changes. Until now, no electrophotographic photoreceptor with excellent properties has been known.

For example, when PVK is used to construct a carrier transport layer, the coating film shrinks significantly during the drying process.
For this reason, there is a drawback that the formed photosensitive layer peels off from the conductive support. Furthermore, when TTSJF or an oxadiazole derivative is dissolved in a solvent together with a resin binder to form a carrier transport phase or carrier transport layer, there is a drawback that crystal precipitation of the above-mentioned compound often occurs. Further, in a photoreceptor having a two-layer structure, the carrier generation layer is made up of an organic pigment such as chlordian blue or scarillium, and the carrier transport layer is made up of a pyrazoline derivative having various substituents or PVK. According to Merz's research on the injection efficiency of positive sign carriers (holes) from the carrier generation layer to the carrier transport layer, PV
The injection efficiency is the lowest when K is used as the material for the carrier transport layer, and when a pyrazoline derivative is used, the injection efficiency varies greatly depending on the type of substituent. It is said that the lower the ionization potential of , the higher the injection efficiency. However, PVK can constitute a good carrier transport layer for a carrier generation layer made of amorphous selenium.

In this way, a carrier transporting substance that is effective for a specific carrier-generating substance is not always effective for other carrier-generating substances, and a carrier-generating substance that is effective for a specific carrier-generating substance is not always effective for other carrier-generating substances. Nor can it be said that it is always effective for other carrier transport substances. If the combination of these two substances is inappropriate, not only will the electrophotographic sensitivity become low, but also the discharge efficiency will be poor, especially in low electric fields, so the so-called residual potential will increase, and in the worst case, repeated use will cause damage. Potential accumulates in the area, making it practically unusable for electrophotographic purposes. In this way, there is no legal way to select a suitable combination of the constituent substances of the carrier generation phase and the constituent substances of the carrier transport phase, and it is necessary to practically determine an advantageous combination from among many substance groups. . An object of the present invention is to provide an electrophotographic photoreceptor that does not have the drawbacks of conventional electrophotographic photoreceptors as described above, has very high sensitivity to visible light, and can therefore always form clear images. shall be.
Another object of the present invention is to provide an electrophotographic photoreceptor that has high sensitivity, high mechanical strength, and extremely low residual potential, and can therefore be used repeatedly. The present invention will be explained below with reference to the drawings.

In the present invention, as shown in FIG. 1, a carrier generation layer 2 containing a carrier generation substance described later as a main component is formed on a conductive support 1, and a carrier generation layer 2 containing a carrier generation substance described below as a main component is formed on this carrier generation layer 2. A carrier transport layer 3 containing a carrier transport substance as a main component is laminated to form a photosensitive layer 4. The carrier generation layer 2 and the carrier transport layer 3 constitute a photosensitive layer 4. Here, as the material of the conductive support 1, for example, a sheet of metal such as aluminum, nickel, copper, zinc, palladium, silver, indium, tin, platinum, gold, stainless steel, brass, etc. can be used. The present invention is not limited to these, and the conductive support 1 may be constructed by providing a conductive layer 1B on an insulating substrate 1A, as shown in FIG. 2, for example.

In this case, the substrate 1A is suitably flexible, such as paper or a plastic sheet, and has sufficient strength against stress such as bending and tension. The conductive layer 1B can also be provided by laminating metal sheets, vacuum depositing metal, or by other methods. The carrier generation layer 2 is made of a carrier generation substance described later alone, or a suitable binder resin is added thereto, or a substance having a high mobility for carriers of specific or non-specific polarity, that is, a carrier transport substance is added. It can be formed by

Specific forming methods include a method in which a carrier-generating substance is vacuum-deposited on the support, and a method in which a carrier-generating substance dissolved or decomposed in a suitable solvent is coated and dried.

In this latter method, binder resins or carrier transport substances may be added, in which case
The ratio of carrier generating substance: binder resin: carrier transporting substance is preferably 1:0 to 100:0 to 50 by weight.
:0-10:0-50 is preferable.

Examples of binder resins used here include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, and melamine. Addition polymer resins such as resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more of the repeating units of these resins, such as vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-acetic acid Examples include vinyl-maleic anhydride copolymer resin.

However, the binder resin is not limited to these, and all resins commonly used for such purposes can be used. As carrier transport substances having high mobility for carriers of specific or non-specific polarity that can be added to the carrier generation layer, certain carrier transport substances described below, which are used in the construction of the carrier transport layer 3 etc. in the present invention, may be used. Although it may be used as part or all of the carrier transport material, other carrier transport materials may be used in consideration of the performance as an electrophotographic photoreceptor.

Furthermore, this carrier generation layer may contain a residual potential lowering agent, a fatigue reducing agent, or the like, if necessary.

The thickness of the carrier generation layer 2 formed as described above is preferably 0.005 to 20 microns, particularly preferably 0.1 to 5 microns.

The carrier transport layer 3 is formed by applying a coating solution obtained by dissolving or dispersing a hydrazone derivative described below as a carrier transport substance in an appropriate solvent together with an appropriate binder resin or other additives as required. How to dry and others! It can be formed by law. Examples of binder resins used here include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, Feznol resin, polyester resin, alkyd resin, polycarbonate resin, and silicone resin. , addition polymer resins such as melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more of the repeating units of these resins, such as vinyl chloride-vinyl acetate copolymer resins, chloride resins, etc. Examples include vinyl-vinyl acetate-maleic anhydride copolymer resin.

However, the binder resin is not limited to these, and all resins commonly used for such purposes can be used. The blending ratio of the binder resin and the carrier transport substance is preferably 10 to 500 parts by weight per 10 parts by weight of the binder resin, and when polycarbonate is used as the binder resin, 20 parts by weight per 10 parts by weight of the binder resin. It is preferred to use up to 10 parts carrier transport material as this provides excellent electrophotographic properties.

The thickness of this carrier transport layer 3 is between 2 and 100 microns, preferably between 5 and 30 microns. In the present invention, the carrier generating substance contained in the carrier generating layer 2 as its main component is selected from compounds represented by the following general formulas [A], [B] and [C].

General formula [A] General formula [C] In the above formula, X represents a halogen atom, a nitro group, a cyano group, an acyl group, or a carboxyl group, n is an integer of 0 to 4, and m is an integer of 0 to 6. represents.

Specific examples of compounds of the anthoanthrone pigment represented by the general formula [A] are as follows. [A1] Specific compound examples of the dibenzpyrenequinone pigment represented by the general formula [B] are as follows.

Specific examples of the vilantrone pigment represented by the general formula [C] are as follows.

In the present invention, the carrier transport substance contained in the carrier transport layer 3 as its main component has the following general formula [P
] from the hydrazone derivatives shown below.
General formula [P] (wherein R1 and R2 each represent an alkyl group, an aralkyl group, or an aryl group that may have a substituent, and A is an aromatic hydrocarbon group that may have a substituent or Represents a heterocyclic group, and n is 1 or 2.

) Representative specific examples of the hydrazone derivative represented by the general formula [P] are as follows.

The above-mentioned hydrazone derivatives may be used not only one type, but also a mixture of two or more types, and further a mixture of one or more of the hydrazone derivatives and one or more other carrier transport substances. You can also do that. And in the last case, it is possible that the hydrazone derivative and the other carrier transport substance may form a charge transfer complex, thereby increasing the mobility of carriers of a particular sign in the carrier transport layer. can be controlled arbitrarily, and it is also possible to effectively eliminate internal traps. Furthermore, this carrier transport layer may contain a suitable plasticizer, residual potential lowering agent, fatigue reducing agent, and other substances as required. Since the electrophotographic photoreceptor of the present invention has the above-mentioned structure, as is clear from the Examples and Comparative Examples described later, it has extremely high sensitivity compared to the conventional one having two photosensitive layers. Since the maximum spectral sensitivity is in the central part of the visible light region, the color sensitivity is excellent, and as a result, it is possible to form a copied image with extremely good resolution and gradation reproducibility.

Furthermore, the electrophotographic photoreceptor of the present invention has high charge retention and surface strength, and has an extremely low residual potential. Therefore, even after repeated use, the electrophotographic photoreceptor exhibits stable performance and does not cause charge accumulation.

In the formation of the carrier generation layer 2 and the carrier transport layer 2, shrinkage of the film body or crystallization of the contained substances does not occur, and therefore problems of peeling and clouding do not occur. In the present invention, as shown in FIG. 3, an intermediate layer 5 is provided on a conductive support 1, a carrier generation layer 2 is formed thereon, and a carrier transport layer 3 is formed thereon. good.

This intermediate layer 5 prevents injection of free carriers from the conductive support 1 to the photosensitive layer 4 when the photosensitive layer 4 is charged, and also integrally adheres the photosensitive layer 4 to the conductive support 1. It acts as an adhesive layer to hold the material in place. Materials for the intermediate layer 5 include metal oxides such as aluminum oxide and indium oxide, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, polyurethane resins, phenolic resins, polyester resins, and alkyd resins. , polycarbonate resin, silicone resin, melamine resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and the like can be used. Further, as shown in FIG. 4, a carrier transport layer 3 is formed on the conductive support 1 with or without the intermediate layer 5, and a carrier generation layer 2 is formed thereon. Layer 4 may also be configured.

Further, as shown in FIG. 5, the photosensitive layer 4 is formed by dispersing the above-mentioned carrier-generating substance 21 in the carrier-transporting phase 31 containing the above-mentioned hydrazone derivative to form a carrier-generating phase. You can also do that.

In this case, 0.1 to 1 part of the carrier generating substance is added to 100 parts by weight of the material forming the carrier transport phase 31.
00 parts by weight, preferably 1 to 5 parts by weight. If the proportion of the carrier-generating substance is too small, the sensitivity of the photoreceptor will be reduced, and if the proportion is too large, the strength of the photosensitive layer 4 will generally be reduced. As described above, various mechanical configurations can be adopted in the present invention, but
Those skilled in the art will be able to select a preferable mechanical configuration as well as the polarity to which the photosensitive layer 4 should be charged in the electrophotographic process.
Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1 Exemplary carrier generating material [A3] (Antannarone pigment 1 Monolite Red 2 YJC.I.N0
．． 59300) was vapor-deposited for 3 minutes at an evaporation source temperature of 35 (range) in a vacuum atmosphere of 0-4T0rr for 3 minutes to form a carrier generation layer with a thickness of about 0.5 micron.

Next, 7.5 g of the exemplified hydrazone derivative [P4] and 10 g of polycarbonate resin 1 Panlite L-1250J (manufactured by Teijin Chemicals) were dissolved in 100 mt of tetrahydrofuran, and this solution was poured onto the carrier generation layer using a doctor blade. The electrophotographic photoreceptor of the present invention was prepared by coating the film on the substrate and drying it at a temperature of 70'C for 1 hour to form a carrier transport layer with a thickness of about 10 microns.

This is assumed to be 1 J for one sample. This sample 1 was tested using an electrostatic copying paper tester model SP-428. J (manufactured by Kawaguchi Electric Seisakusho), the voltage applied to the discharge electrode of the charger was set to 1, and the charging operation was performed for 5 seconds. VO 11
The half-reduced exposure amount Ell2(I
xsec) was measured.

The results are shown in Table 1. Examples 2 to 5 In each of these Examples, hydrazone derivatives [Pl3], [Pl9], [P24], and [P26] were used as carrier transport substances instead of [P4]. A total of four types of electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 1.

These samples were numbered 1 sample 2 to 1 sample 5, and the charged potential VO and half-decreased exposure amount Ell2 were measured in the same manner as sample 1. The results are shown in Table 1. RCTM represents a carrier transport material, and JCTL represents a carrier transport layer.

Examples 6 to 8 In each of these Examples, exemplary substance [A2] (anthrone pigment Jr Indanthrene Brilliant Orange GKJC.I.NO.59) was used as a carrier generating substance.
3O5), [B3] (Dibenzpyrenequinone pigment 1 Indanthrene Golden Yellow RKJC.I.NO.
59lO5) and [C4) (Vilanthrone Pigment 1 Paliogen Red 3340J) were used in place of the exemplified substance [M], respectively, to a thickness of 0.5
A micron carrier generation layer was formed, and then a carrier transport layer was formed in the same manner as in Example 1 using the exemplified hydrazone derivative [P4] as a carrier transport substance, thereby forming a total of three types of electrophotographic photoreceptors of the present invention. 6. j~1 Samples 8J were used, and the charging potential ■O and half-decreased exposure amount Ell2 of each sample were measured in the same manner as Sample 1.

The results are shown in Table 2. RCGMJ indicates a carrier generating substance.

Example 9 Vinyl chloride-vinyl acetate-maleic anhydride copolymer "ESLEK-10J" (manufactured by Sekisui Chemical Co., Ltd.) was applied to a conductive support made by vapor-depositing aluminum on a base made of polyethylene terephthalate having a thickness of 100 microns. An intermediate layer with a thickness of about 0.1 micron is provided, and an exemplified carrier-generating substance [A3
] was added to the dispersion obtained by ultrasonic dispersion,
A carrier generation layer having a thickness of 2 microns was formed by coating on the intermediate layer by a wire spray coating method and drying.

On this carrier generation layer, a carrier generation layer having a thickness of 10 microns was formed in the same manner as in Example 1 using the exemplified hydrazone derivative [P4] as a carrier transport substance, thereby producing an electrophotographic photoreceptor of the present invention. .

When one sample was 9J and measurements were performed in the same manner as sample 1, VO = -713 (V), Ell2 = 2.7
(Ix.sec). Example 10 An exemplary hydrazone derivative LCP4) was used as a carrier transport material, and 7.5 g of the hydrazone derivative LCP4) and 10 g of polycarbonate resin were dissolved in 100 ml of 1,2-dichloroethane. A3〕1.5
This dispersion was applied in the same manner to the same conductive support as in Example 9 with the same intermediate layer provided thereon, and then heated at a temperature of 70°C for 1 hour. An electrophotographic photoreceptor of the present invention having a photosensitive layer having a thickness of 12 microns was prepared by drying.

This is assumed to be 10 J for one sample. The photosensitive layer of sample 10 was
As shown in the figure, it has a structure in which a carrier generating substance 21 is dispersed in a carrier transporting phase 31. When this sample 10 was measured in the same manner as sample 1, VO=-835 (V), Ell2=4.7 (Ix.
sec).

When a photocopying test was carried out with each of Samples 1 to 10 obtained in each of the above examples installed in an electronic copying machine RU-BiX2OO [■ (manufactured by Konishiroku Photo Industry Co., Ltd.), it was found that sufficient image density was obtained. It was possible to obtain a good copy image with no fog.

Comparative Example 1 A bisazo pigment having the above structure was used as a carrier generating substance, and 1 g of the bisazo pigment and a polyester resin "Vylon 2" were added.
00. J (manufactured by Toyobo Co., Ltd.) 1g and 1,2-dichloroethane? ml and subjected to a dispersion treatment using a two-hole ball mill, and this dispersion was applied to the same conductive support as in Example 9 with the same intermediate layer provided,
It was dried to form a carrier generation layer with a thickness of 1 micron.

On this carrier generation layer, a carrier transport layer with a thickness of 10 microns was formed in the same manner as in Example 1 except that an exemplary hydrazone derivative [Pl3] was used as a carrier transport substance,
An electrophotographic photoreceptor was produced. When this was designated as 1 comparative sample 1J and measured in the same manner as sample 1, VO = -715 (V) and Ell2 = 4.0 (1x.sec), which were compared to the electrophotographic photoreceptor of the present invention. Sensitivity was low. Comparative Example 2 Chlordiane blue was used as a carrier generating substance,
0.5g of it was made of ethylenediamine, n-butylamine, and tetrahydrofuran, the weight ratio of which was 1.2:
Comparative Example 1 was dissolved in 75 g of a mixed solution of 1.0:2.2.
A carrier generation layer of 0.2 g/d was formed in the same manner as in .

On this carrier generation layer, a carrier transport layer having a thickness of 10 microns was formed in the same manner as in Example 1 using the exemplified hydrazone derivative [P4] as a carrier transport substance, thereby producing an electrophotographic photoreceptor.

This was used as comparative sample 2, and measurements were carried out in the same manner as sample 1. VO=-710 (V), Ell2=3.1
(Ix.sec), the sensitivity was lower than that of the electrophotographic photoreceptor of the present invention. Comparative Examples 3 to 5 Examples of carrier-generating substances [A3
Electrophotographic photoreceptor 1 Comparative sample 3J-1 Comparative sample 5J were prepared in the same manner as in Example 1, except that the following was used in place of . .

The results are shown in Table 3. Comparative sample 3: Algol yellow (anthraquinone pigment) Comparative sample 4: Comparative sample 5: Comparative example 6 Exemplified hydrazone derivatives [P4
Example 1 was carried out in the same manner as in Example 1, except that 1,1-bis(4-N,N-diethylamino-2-methylphenyl)-1-phenylmethane was used instead of ] to form a carrier transport layer with a thickness of 11 microns. An electrophotographic photoreceptor was produced.

When this was used as 1 comparative sample 6J and measurements were performed in the same manner as sample 1, VO = -638 (V), Ell2 = 2
．． 5 (IxIsec). Next, each of Sample 1 and Comparative Sample 6 was installed in an electronic copying machine RU-BiX2OOORJ, and a continuous copying test was performed. The measurement was performed using a 4D-1D model J (manufactured by Monroe Electronics Inc.).

The results are shown in Table 4. As judged from the results in Table 4, when an aryl alkane compound that is not the hydrazone derivative of the present invention is used as a carrier transporting substance, as in Comparative Sample 6, the carrier generating substance is of the present invention. However, it is clear that the repeatability is inferior.

That is, the potential of the background portion of the image increases significantly due to continuous copying a large number of times, and the resulting copied image has a large amount of fog and cannot be put to practical use. . Comparative Examples 7 to 12 Exemplary carrier transport substances [P4
Electrophotographic photoreceptors 1 comparative sample 7J to 1 comparative sample 12J were prepared in the same manner as in Example 1 except that the following were used instead of
were prepared, and measurements were performed on each of them in the same manner as Sample 1.

The results are shown in Table 5. Comparative sample 7: N-ethylcarbazole Comparative sample 8: Anthracene Comparative sample 9: Fluorenone Comparative sample 10: 2,4,7-trinitro 9-fluorene
Fluorenone comparative sample 11: 2,4,5,7-tetranitrofluorenone Comparative sample 12: polyvinylcarbazole As a result, both when using the carrier-generating substance used in the present invention and when the carrier-transporting substance is not a specific one, It is clear that an electrophotographic photoreceptor with high sensitivity cannot be obtained.

As is clear from the above explanation, even when the carrier transporting substance used in the present invention is used, when a carrier generating substance other than that used in the present invention is used as a carrier generating substance, and the carrier used in the present invention Even when a generating substance is used, if a carrier transporting substance other than that used in the present invention is used as a carrier transporting substance, the resulting electrophotographic photoreceptor will have extremely low sensitivity, and sufficient characteristics may not be obtained. I can't.

However, as in the present invention, by combining a specific carrier-generating substance and a specific carrier-transporting substance,
It is possible to obtain an excellent electrophotographic photoreceptor having a high sensitivity that was previously unexpected.

[Brief explanation of the drawing]

FIG. 1 is an explanatory enlarged sectional view showing an example of the structure of the electrophotographic photoreceptor of the present invention, FIG. 2 is an explanatory enlarged sectional view showing a modified example of the conductive support, and FIGS. 3 and 4 are respectively FIG. 5 is an explanatory enlarged sectional view showing another example of the structure of the present invention. FIG. 5 is an enlarged sectional view for explaining still another example of the structure of the invention. DESCRIPTION OF SYMBOLS 1... Conductive support, 1A... Insulating substrate, 1B... Conductive layer, 2... Carrier generation layer, 3...・Carrier transport layer, 4...
...Photosensitive layer, 5...Intermediate layer, 21...
Carrier generating substance, 31...Carrier transport phase.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer comprising a combination of a carrier generation phase and a carrier transport phase provided on a conductive support, wherein the carrier generation phase has the following general formula [A] andanthrone pigment represented by the following general formula [B], and a dibenzpyrenequinone pigment represented by the following general formula [C]
The carrier transport phase contains as a main component at least one selected from the group consisting of pyranthrone pigments represented by the following, and the carrier transport phase contains a hydrazone derivative represented by the following general formula [P] as a main component. An electrophotographic photoreceptor. General formula [A] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ General formula [B] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ General formula [C] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, represents a halogen atom, a nitro group, a cyano group, an acyl group, or a carboxyl group, n represents an integer of 0 to 4, and m represents an integer of 0 to 6.) General formula [P] ▲ Numerical formula, chemical formula, There are tables, etc. ▼ (In the formula, R_1 and R_2 each represent an alkyl group, an aralkyl group, or an aryl group that may have a substituent,
A represents an aromatic hydrocarbon group or a heterocyclic group which may have a substituent, and n is 1 or 2. )2 The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is constituted by a laminate of a layer of the carrier generation phase and a layer of the carrier transport phase. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is configured such that the carrier generation phase is dispersed in a carrier transport phase.