JP2005121727A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charge electrophotographic photoreceptor having high sensitivity, low residual potential, and stable electrostatic characteristics and photochemical durability for repeated use. <P>SOLUTION: A charge transfer complex having the following properties is used for an electron transport substance in the positive charge photoreceptor. The complex formed of a quinone compound and a hole transport substance is expressed by general formula (I), and the strongest peak of the IR absorption spectrum of the complex appearing at 1,600 to 1,700 cm<SP>-1</SP>assigned to the quinone structure is shifted toward a higher wave number by ≥3 cm<SP>-1</SP>compared with the quinone compound before the formation of the charge transfer complex. In formula (I), D represents a hole transport compound, X an oxygen atom or a compound of formula (II) or (III), each of R1 to R14 a hydrogen atom, halogen atom, alkyl group, aralkyl group or alkoxy group and may be identical to or different from others, and n is an integer of 1 or 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic photoreceptor for use in electrophotography. More specifically, the present invention relates to a novel charge transfer complex having excellent electron transportability, and a positive sensitivity having excellent sensitivity, light fatigue, and environmental stability using the same. The present invention relates to an organic electrophotographic photosensitive member for charging.

The electrophotographic method is a skillful combination of photoconductivity and electrostatic phenomenon as revealed by Carson in U.S. Pat. No. 2,297.691, and the electrophotographic photosensitive member is placed in a dark place. After the surface is uniformly charged by corona discharge or the like, the surface of the charged electrophotographic photosensitive member is exposed to form an electrostatic latent image of a light image, and a colored charge powder (toner) is formed on the surface. It is a kind of image forming method that is attached to a visible image. Currently, as this electrophotographic technology is widely used in copying machines, laser printers, etc., the environmental conditions for use have expanded from office use to home use, and the reliability and safety of these wide use environments are also improved. There is a strong demand.

Conventionally, as electrophotographic photoreceptors, photoreceptors mainly composed of an inorganic photoconductive material such as amorphous silicon, selenium, zinc oxide, cadmium sulfide have been widely used. However, since such inorganic photoreceptors do not have satisfactory characteristics such as photosensitivity, durability, and safety, many organic electronic materials have been developed. In recent years, charge generating substances and charge transporting substances have been developed. The used organic electrophotographic photosensitive member is increasingly used.

Such an organic electrophotographic photosensitive member is classified into a positive charging photosensitive member and a negative charging photosensitive member according to an electrophotographic charging method. The layer structure of the photoconductor includes a single-layer type photoconductor in which charge generation and charge transport are made of the same layer, and a stacked type photoconductor in which charge generation and charge transport are made of separate layers depending on the operation mechanism.

  By the way, in the charge transport material which is the main functional component of the organic electrophotographic photosensitive member, the material having excellent charge transport ability was a hole transport material, so that it was put into practical use except for a special layer structure. Many of the electrophotographic photosensitive members are negatively charged electrophotographic photosensitive members, and the electrophotographic charging method is also a negative charging method.

However, the negative charging method has problems such as the generation of a lot of harmful ozone and nitrogen oxides and the difficulty of uniform charging by corona discharge.
On the other hand, the positive charging method does not have the disadvantages of the negative charging method described above, and can be applied to toners of amorphous silicon and selenium positively charged inorganic photoreceptors and many process technologies. The appearance of an organic photoreceptor for charging has been desired.

The positively charged organic photoconductors developed so far include single-layer photoconductors consisting of a charge transfer complex of polyvinylcarbazole (PVK) and trinitrofluorenone (TNF), and charge generating materials and hole transporting materials. There were single layer type photoreceptors dispersed in the adhesive, but the former was low sensitivity and trinitrofluorenone was a carcinogen, the latter was low sensitivity and low charge retention, and repeatedly Both are not currently used due to problems such as degradation of electrical characteristics during use.

The deterioration of the electrical characteristics of the single layer type photoreceptor composed of the charge generation material and the hole transport material described above is caused by accumulation of electrons in the photosensitive layer without being sufficiently transported. Until now, many electron transport materials have been developed.

Examples of the charge transport material having an electron transporting ability include the above-described charge transfer complexes such as PVK and TNF (for example, see Patent Document 1), dicyanomethylenefluorene carboxylate compound (for example, see Patent Document 2), anthraquinodimethane A compound (for example, see Patent Document 3), a diphenyldicyanoethylene compound (for example, see Patent Documents 4 to 5), a naphthoquinone compound (for example, see Patent Documents 6 to 8), a benzoquinone compound having a specific redox potential (for example, Patent Document 9), diphenoquinone compounds (for example, see Patent Document 10), stilbene quinone compounds (for example, see Patent Document 11), azomethine quinone compounds (for example, see Patent Document 12), quinone systems such as Schiff base quinone An electron transport material is disclosed.

However, the mobility of charge transport complexes and electron transport materials with nitro and cyano groups is low, making it difficult to obtain highly sensitive photoconductors. Substances with nitro and cyano groups are also carcinogenic. Since there are concerns about health and safety concerns, there have been no practical examples.

On the other hand, quinone-based electron transfer substances have been disclosed in large numbers because there are few hygiene problems such as carcinogenicity. However, the mobility of low molecular weight quinone compounds such as benzoquinone compounds and naphthoquinone compounds is low and still does not have sufficient electron transport capability. The reason for this low mobility is that the conjugated system necessary for electron emission is small compared to the quinone group, which is an electron accepting group, so that the conjugated system is large and the molecular weight is large. Transport materials have been proposed.

Among these compounds having a large conjugated system and a high molecular weight, there are diphenoquinone compounds and stilbenequinone compounds as compounds that have attracted particular attention. However, since these high molecular weight quinone compounds have low solubility in organic solvents and low affinity with the binder resin, crystallization is likely to occur in the photosensitive layer. When crystallization occurs, it becomes a noise in the output image, so that it is difficult to contain a sufficient amount in the photosensitive layer.

In order to improve the disadvantages of diphenoquinone, improvement techniques such as improved solubility and prevention of crystallization have been proposed by adding diphenoquinone having an asymmetric structure or a low molecular weight benzoquinone derivative as an auxiliary component. , Its mobility is still low, compared to negatively charged photoconductors using hole transport materials, the problem of low sensitivity and high residual potential, sensitivity due to charge accumulation during repeated use, charge retention, Problems such as changes and deterioration of basic electrical characteristics such as residual potential have not been solved.

In addition, when these compounds are applied to a single-layer type photoreceptor coexisting with a hole transport material, forming a charge transfer complex with the hole transport material reduces the effective light transmittance due to coloring and the mobility. (For example, Non-Patent Document 1 and Patent Document 9). For this reason, when a hole transport material is allowed to coexist, a problem that does not form a charge transfer complex and a problem in manufacturing technology are caused.

Furthermore, a problem of the electron transport material having a quinone structure is that the quinone structure is easily hydroquinoneized by protons. The hydroquinone compound does not have an electron transporting ability, but also acts as a trap for mobile charge (electrons), and causes a significant deterioration in electrical characteristics such as sensitivity even in the presence of a small amount. In order to prevent this, improvements such as the introduction of bulky substituents that block the quinone group and the use of substances with a high reduction potential have been proposed, but under the high electric field used in the electrophotographic process. However, it is still inadequate, and it is difficult to prevent the reaction with protons generated from moisture in the atmosphere due to light, and the electrical characteristics of the parts exposed to light change when the photoconductor is replaced or manufactured. Therefore, there is a problem that light exposure traces having different image densities are generated on the output image.

To date, many of the layer configurations of positively charged photoconductors using the above-described electron transfer materials are single layer types. The reason for this is that when an electron transport material having a low mobility as described above is used, the single-layer configuration in which the average transport distance of electrons is short is lower than the multi-layer photoreceptor in which the transport distance of electrons is long. Because it is advantageous for transport materials, the single-layer type requires only one photosensitive layer coating, reduces manufacturing costs, and does not have a thin film part like the charge generation layer of a multilayer photoconductor. This is because the reason that it is difficult to be influenced by defects on the surface of the base tube, which is the base, has been considered.

However, it has gradually become clear that the single layer type, which has been considered as an ideal layer structure, has many drawbacks. For example, the single layer type is insensitive to defects under the photosensitive layer such as scratches on the substrate, but is sensitive to defects such as scratches on the surface of the photoreceptor due to cleaning blades, toner additives, paper dust, etc. Is likely to appear as noise on the image. Such noise on an image causes a problem when applied to a device that outputs a document that requires reliability. Since the charge mobility depends on the strength of the electric field, it is difficult for the residual potential to reach the level of the multilayer photoreceptor, and a high gradation image that requires a high contrast development potential. For example, it is not suitable for output. For this reason, high stability and high mobility that can be applied to single-layer positively charged photoconductors with high sensitivity and low residual potential as well as highly reliable stacked positively charged photoconductors. Therefore, an electron transfer material that has high affinity with the binder resin and is difficult to crystallize is demanded.
US Pat. No. 3,484,237 JP-A-61-148159 JP 63-170257 A JP-A 63-175860 Japanese Patent Laid-Open No. 63-174993 JP-A 63-85749 Japanese Patent Laid-Open No. 06-110227 Japanese Patent Laid-Open No. 09-151157 Japanese Patent Laid-Open No. 05-45908 Japanese Patent Laid-Open No. 01-206349 Japanese Patent No. 2805376 JP 2000-199979 A Yokoyama et al .; Journal of the Electrophotographic Society, Volume 30, P274 (1991)

In view of the above problems, an object of the present invention is an electron having high mobility, high affinity with a binder resin, hardly crystallizing in a photosensitive layer, hardly attacked by protons, and highly stable to light. To provide a transport material.

As another object, by applying such an electron transport material to the photoreceptor, a single layer type of positive charge with high reliability and high sensitivity without light exposure traces due to light deterioration and little potential fluctuation during repeated use. The object is to provide a photoreceptor and a multilayer photoreceptor.

As a result of intensive studies on various organic materials in order to achieve the above object, the present inventor has found that the following specific charge transfer complexes described below have been used in electron transport materials that have been considered to be a cause of deterioration in conventional characteristics. Was found to be an excellent electron transport material that solves the problems of conventional electron transport materials and positively charged photoreceptors, and the present invention has been completed.

The electron transport material according to the present invention is a charge transfer complex represented by the following general formula I formed by a quinone compound that is an electron-withdrawing molecule and a hole-transport compound that is an electron-donating molecule. The strongest absorption peak position appearing at 1600 to 1700 cm ⁻¹ belonging to the quinone structure of the spectrum is characterized by being shifted to a higher wavenumber side by 3 cm ⁻¹ or more than the quinone compound before the charge transfer complex formation. It is a charge transfer complex.

ただし、式中Ｄは正孔輸送化合物を示し、Xは酸素原子、もしくは一般式ＩＩもしくは一般式ＩＩＩを示し、Ｒ１〜Ｒ１４は同じでも異なっていてもよい水素原子、ハロゲン原子、アルキル基、アラルキル基またはアルコキシ基を示す。また、ｎは１もしくは２の整数である。

In the formula, D represents a hole transport compound, X represents an oxygen atom, or general formula II or general formula III, and R1 to R14 may be the same or different hydrogen atom, halogen atom, alkyl group, aralkyl. Represents a group or an alkoxy group. N is an integer of 1 or 2.

  The electron transport material which is a charge transfer complex according to the present invention has excellent mobility, and when used as an electron transport material of a single layer type photoreceptor or a multilayer photoreceptor, the residual potential is low, and A positively charged photoreceptor having excellent sensitivity can be provided.

Further, in the charge transport material according to the present invention, when the charge transport composition contains two or more charge transfer complexes having different shift wave numbers in the infrared absorption spectrum, the charge transport material has excellent stability to light. By using the transport composition as a charge transport material for a single layer type or a multilayer type photoreceptor, a positively charged photoreceptor excellent in photochemical light fatigue resistance can be provided.

Thus, although the charge transport complex according to the present invention is an electron transport material from the viewpoint of excellent material chemistry and electronic material, the charge transfer complex according to the present invention is charged from the viewpoint of material chemistry. The superiority over the quinone compound not forming the transfer complex can be explained as follows.

1. Since the molecule is asymmetric in three dimensions, it is difficult to crystallize.
2. The chemically active quinone structure is three-dimensionally shielded and protected, and has increased chemical stability against chemically active species including protons.
3. The fact that the absorption position of quinone has shifted to the high wavenumber side indicates that it has changed to another substance in terms of structural chemistry, and physically, the binding energy of quinone (> C = O) has increased. This indicates that the physical strength has increased.
4). As described above, since the charge transfer complex according to the present invention is chemically and physically increased in strength and stability, the stability is enhanced against chemical and physical external fluctuation factors. It is a factor that improves photochemical stability.
5). In addition, when charge transfer complexes having different shift wave numbers of quinone groups (> C═O) coexist, they act as quenchers because they absorb harmful light wavelength components from each other and widen the energy bandwidth.

From the viewpoint of electron transport ability, the superiority over quinone compounds not forming a charge transfer complex can be explained as follows.

1. Since charge transfer complexes are strongly separated and polarized in the molecule, the charge transfer complex easily accepts a charge opposite to the polarity compared to a neutral molecule. In addition, the accepted charge quickly moves to the charge release portion via the charge transfer complex forming bridge, and from this, the charge is easily released to the adjacent charge transfer complex.

2. In addition, this charge transfer complex is difficult to crystallize because the shape of the molecule is three-dimensionally lost, and it is difficult to crystallize in the photosensitive layer. Therefore, the fact that the intermolecular distance, which is a charge transport material, is short is advantageous for charge hopping and leads to an improvement in charge transport ability.

Further, the mechanism of charge transport by the charge transfer complex is completely different from a composition comprising a hole transport material and an electron transport material (hereinafter abbreviated as a charge transport composition) not forming a charge transfer complex. In the case of a single-layer type photoconductor having a similar composition, charge transport in the charge transport composition is carried out by holes and electrons, so that movement of holes and electrons in the same layer by electric attraction is performed. While charge accumulation and mobility decrease are inevitable, charge transport in charge transfer complexes is carried out by electrons, so there is no positive or negative electrical interaction, and charge transfer area density is charged. Since the hole transport route of the transport composition becomes the electron transport route and doubles, the mobility and charge accumulation are reduced, and the sensitivity during repeated use in the electrophotographic photoreceptor is reduced. An increase in the residual potential appears as an effect that can be prevented.

The charge transfer complex of the present invention consisting of an electron transporting quinone compound and a hole transporting compound has excellent electron transporting properties compared to the raw material electron transporting quinone compound, and is not repeatedly accumulated. Even in such a case, it is possible to obtain single-layer and multi-layer positively charged electrophotographic photoreceptors having excellent sensitivity and stable electrical characteristics. In addition, by using a charge transfer agent composed of a charge transfer complex having a different absorption wave number due to a quinone structure due to formation of a quinone structure, an excellent positively charged electrophotographic photosensitive member in which no deterioration with respect to light is observed is provided. I can do it.

The charge transfer complex represented by the general formula I as an electron transport material according to the present invention is formed by a chemical reaction between a quinone compound and a hole transport material which is an electron donating molecule, and the reaction center is a quinone structure. The amine group structure in the hole transport material is deeply involved, but the ease of reaction varies depending on the steric hindrance and electrical properties due to the substituents of both. However, as a quinone compound suitable for the present invention, a quinone compound having a very high reduction potential is usually obtained because it becomes difficult to react if the reduction potential is too high, and the resulting charge transfer complex tends to be unstable. The compound is not preferred, and is preferably −1 V or less when the reduction potential is taken as a representative index. More preferably, -0.8V or less is preferable. However, it is not limited as long as the charge transfer complex obtained is stable and the shift wave number of quinone is 3 cm ⁻¹ or more because of the interaction with the hole transport material.

The specific compounds of the quinone compounds constituting the typical charge transfer complexes according to the present invention used in Examples and Comparative Examples of the present invention are shown below. However, it is not limited to this.

  In addition, hole transport materials as electron donating molecules that are another constituent of the charge transfer complex according to the present invention include conventionally known hydrazone compounds, carbazole compounds, butadiene compounds, stilbene compounds, arylamines. Although it is necessary to have an amine group structure in the hole transport material molecule, specific compounds of the hole transport compounds used in Examples and Comparative Examples of the present invention are shown below. . However, it is not limited to this.

By the way, the formation of a charge transfer complex involves an electron-withdrawing quinone molecule and an amine group structure which is an electron-donating group. If there are multiple amine structures in the hole transport material, this number However, the range in the present invention is that the molar ratio of the quinone compound to the hole transport material which is an electron donating molecule is 1/1 or 2/1. Is preferred.

The charge transfer complex according to the present invention can be produced by the following method. (1) A method of precipitating a product by reacting a quinone compound and an electron donating compound in a solvent in which both are soluble and the resulting complex is insoluble or insoluble. (2) A method in which the raw material and the product of the quinone compound and the electron donating compound are reacted in a soluble solvent, and then the product is precipitated by adding a poor solvent of the product. (3) A method in which both raw materials and the product are reacted in a solvent in which both the raw materials and the product are soluble and the poor solvent of the product is added, or the reaction solvent is distilled off to precipitate the product. (4) Similarly, a common crystal precipitation method such as a method of precipitating the product is possible by reacting both raw materials and the product in a soluble solvent and cooling. Moreover, the charge transfer complex of this invention can be obtained by combining these.

The compound obtained by the above method is not a simple mixture of molecules but a novel charge transfer complex. The product absorption spectrum is the sum of the individual absorption spectra of the quinone compound and the electron donating substance. However, it can be confirmed that the substance is different from the raw material by the appearance of a new absorption peak or the disappearance of the original individual absorption peak. appears at 1700 cm ^-1, is identified by the strongest absorption shift wavenumber of about charge transfer complex formed of peak positions appearing in 1600～1700Cm ^-1 attributable to the stretching vibration of the quinone group.

Hereinafter, a specific configuration of a preferred example of the photoreceptor of the present invention will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing various configuration examples of the photoreceptor.

When the charge transfer complex of the present invention is applied to a single layer type photoreceptor as a charge transport material, a charge generation transport coating solution in which the charge transfer complex of the present invention is dissolved in a binder solution in which the charge generation material is dispersed is electrically conductive. A single layer type photoreceptor can be obtained by coating and drying on a conductive substrate. At this time, the content of the charge transfer complex in the total solid content of the photosensitive layer is preferably 30 to 60% by weight from the viewpoint of the strength of the coating of the photosensitive layer and the electrical characteristics. Increasing the content more than this decreases the film strength of the photosensitive layer. On the other hand, if the content is less than this, the hopping distance of the charge becomes long, so that the mobility is lowered, which is not preferable because the sensitivity is lowered or the residual potential is repeatedly increased. The amount of the charge generating agent in the charge generating / transporting layer is preferably 0.4 to 2.5% by weight in the total solid content.

In addition, in a laminated type photoreceptor in which a conductive support / charge generation layer / charge transport layer containing a charge transport material is sequentially laminated, the blending ratio of the charge transfer complex as the charge transport material is as follows. The content in the total solid content is preferably 36 to 60% by weight.

In addition to the charge transfer complex of the present invention, the charge generation / transport layer and the charge transport layer may contain a known hole transport material or electron transfer material in combination.

Further, the charge generation / transport layer and the charge transport layer have a limit of transporting charge carriers, and thus the film thickness cannot be increased more than necessary, but the range of 5 to 40 μm, particularly 10 to 30 μm is preferable.

Further, the charge transfer complex of the present invention has a function as a stabilizer against light in addition to the function as an electron transport material. When the charge transfer complex of the present invention is used as such a light stabilizer, the effect is strongly exerted when the shift wave number of the quinone group of the charge transfer complex used as the electron transfer material is different. And since the addition amount in the case of using for such a purpose does not need to be concerned with charge transport, the content rate with respect to an electron transfer substance is sufficient even if it is 10 weight% or less, and is substantially 0 A sufficient effect is exhibited even at 5 to 5% by weight.

Examples of the charge generating material used in the electrophotographic photoreceptor according to the present invention include 1) azo pigments such as monoazo, bisazo, trisazo, etc. (2) phthalocyanine pigments such as metal phthalocyanine and nonmetal phthalocyanine (3) indigo, thioindigo, etc. Indigo pigments (4) Perylene pigments such as perylene acid anhydrides and perylene imides (5) Polycyclic quinine pigments such as anthraquinone and pyrenequinone (6) Squalilium dyes (7) Pyryllium salts, thiopyrylium salts (8) Organic charge generation materials such as triphenylmethane dye (9) and inorganic charge generation materials such as selenium and amorphous silicon can be used.

The binder used in the electrophotographic photoreceptor according to the present invention can be selected from a wide range of binder resins, such as polycarbonate, polyester, polyarylate, butyral resin, polystyrene, polyvinyl acetal, diallyl phthalate resin, acrylic resin, Examples include, but are not limited to, methacrylic resin, vinyl acetate resin, phenol resin, silicone resin, polysulfone, styrene-butadiene copolymer, alkyd resin, epoxy resin, urea resin, vinyl chloride-vinyl acetate copolymer. It is not a thing. These resins may be used alone or in combination as a copolymer polymer.

Further, a lubricant such as an antioxidant, an ultraviolet absorber, a plasticizer, or silicone oil can be added to the photoreceptor as necessary.

As a conductive substrate that can be used in the electrophotographic photoreceptor according to the present invention, a metal plate such as aluminum, nickel, copper, and stainless steel, a metal drum or metal foil, a thin film of aluminum, tin oxide, and copper iodide was applied. A plastic film, glass, etc. are mentioned. Further, an alumite or resin blocking layer (intermediate layer) may be provided on the surface of these conductive substrates.

When forming a charge generation / transport layer of a single layer type photoreceptor or a charge transport layer of a multilayer type photoreceptor, an appropriate organic solvent is used, and a dip coating method, a spray coating method, a spinner coating method, a roller coating method, a Meyer bar A coating method such as a coating method or a blade coating method can be used.

Hereinafter, a synthesis example of the charge transfer complex of the present invention and a result of application to a photoreceptor will be specifically described based on examples.

(Synthesis Example of Charge Transfer Complex) 27.6 parts by weight (0.1 mole part) of the quinone compound (I1) and 28.6 parts by weight (0.05 mole part) of the hole transport material (II1) were heated. After completely dissolving with stirring in 200 parts of tetrahydrofuran, remove about 10% by weight of the initial crystals and about 10% by weight of crystals contained in the residual mother liquor, while precipitating while evaporating the solvent under reduced pressure on a rotary evaporator. The precipitated crystals were filtered, washed with cooled methanol, and dried to obtain a charge transfer complex (CT1) which is a charge transfer complex compound having a molar ratio of (I1) to (II1) of 2/1.

Further, in the same manner as the synthesis method of (CT1), (I1), (I2), (I3) of the quinone compounds and (Ia1), (Ia2) used for the comparative examples and (II1) of the hole transport material -(II9) were combined in Table 3 to obtain (CT2) to (CT20) of charge transfer complexes, and (NCT1) and (NCT2) used for comparison.

(Analysis / Evaluation) Elemental analysis values of the obtained charge-transfer complex almost coincided with theoretical calculation values. Among these charge transfer complexes, infrared absorption of the charge transfer complex (CT1) and its raw materials (I1) and (II1), and the charge transfer complex (CT11) and its raw materials (I2) and (II2) The spectrum and main absorption peak positions are shown in FIGS. As can be seen from FIGS. 3, 4, and Table 1, the peak position and relative intensity of the formed charge transfer complex are different from those of the raw material. Moreover, since it was not the synthetic sum of the infrared absorption spectrum intensity of a raw material, it was confirmed that the quinone compound of the raw material has changed into another substance (charge transfer complex).

Also features in the present invention, the absorption position after forming the charge transfer complex formed prior to the quinone (stretching vibration of C = O) is changed to 1650.77Cm ^-1 from 1646.91Cm ^-1 in (CT1) Yes. Moreover, changes are changing (CT11) in the 1606.41Cm ^-1 to 1612.2Cm ^-1, respectively ^3.86Cm -1, the new substance from the fact that has been shifted 5.79Cm ^-1 wavenumber It was shown that Here, the summarized results in (CT1) to (CT20), (NCT1), and (NCT2) are shown in Table 2.

注）ＣＴ：電荷移動錯体

Note) CT: Charge transfer complex

A photoconductor was prepared using the charge transfer complex obtained above as an electron transfer material, and the effect was examined. The evaluation relating to the content of the photoreceptor of the present invention was performed by the following method.

(Evaluation of basic electrical characteristics) The basic electrical characteristics of the electrophotographic photosensitive member are as follows: after adjusting the corona charger so that the surface potential is 600 Volt, charging → 5 seconds exposure in the dark → 5 seconds exposure (light adjusted to 780 nm) An intensity of 1 μW light) was taken as one cycle, and this was repeated for 10,000 cycles, and changes in surface potential (Vo), charge retention (Vk5), sensitivity (E1 / 2), and residual potential (Vr) were measured. Here, Vo is the surface potential immediately after charging, the charge retention rate (Vk) is the surface potential retention rate from the surface potential (Vo) immediately after charging to just before the exposure after 5 seconds, and the sensitivity (E1 / 2) is The exposure energy required to reduce the surface potential immediately before exposure to ½, and the residual potential (Vr) are the surface potential after exposure for 5 seconds. Further, as a reference value, a single-layer positively charged photoreceptor used in a Brother laser printer (HL1060) was used as a comparison.

(Photodegradation durability characteristics) The durability of photoconductor degradation due to light is obtained by exposing a photoconductor with a portion of the surface of the photoconductor light-shielded with black paper to 1000 lux fluorescent light for 1 hour. This photoconductor was printed 2000 sheets with a positively charged laser printer (manufactured by Brother Industries, Ltd. HL-1060) and durability against photodegradation of the photoconductor due to the difference in image density between the exposed portion and the non-exposed portion due to black paper. Sex was evaluated.

(Production and evaluation of multilayer photoconductor)
Comparative Example 1: A charge generation layer solution in which 50 parts by weight of polyvinyl butyral resin and 50 parts by weight of X-type metal-free phthalocyanine are dissolved and dispersed in tetrahydrofuran is applied onto a cylindrical aluminum base tube whose surface is anodized by dip coating. After drying to form a 0.2 μm thick charge generation layer, 55 parts by weight of a polycarbonate resin and 45 parts by weight of a comparative compound (NCT1) as a charge transport material were dissolved in 500 parts by weight of tetrahydrofuran. The charge transport layer solution was applied by a dip coating method and then dried to prepare a laminated photoreceptor (sensitivity ratio 1) composed of a 17 μm charge transport layer.

Comparative Example 2: A multilayer photoreceptor (sensitivity ratio 2) having the same film thickness as that of the example was prepared by replacing 45 parts by weight of the charge transport material (NCT1) of Comparative Example 1 with 45 parts by weight of (NCT2).

Example 1: A charge generation layer solution in which 50 parts by weight of polyvinyl butyral resin and 50 parts by weight of X-type metal-free phthalocyanine are dissolved and dispersed in tetrahydrofuran is applied to a cylindrical aluminum tube whose surface is anodized by dip coating. After drying and forming a 0.2 μm thick charge generation layer, 500 parts by weight of tetrahydrofuran and 55 parts by weight of polycarbonate resin and 45 parts by weight (0.04 mole part) of the charge transport material (I1) are formed thereon. A charge transport layer solution (0.04 (charge transport material mole part) / 100 parts by weight of total solids) in which lysate is applied is applied by a dip coating method, dried, and a laminated photoreceptor comprising a 17 μm charge transport layer (Feel 1A) was created.

Next, in order to compare the charge transport capability per molecule of the charge transfer complex and the quinone compound of the starting material, the charge transport material mole parts / total solids weight parts of the charge transport layer composition should be equal (sensitivity). 1A) (CT1) is a starting material of (CT1) (I1) A tetrahydrofuran solution consisting of 22.9 parts by weight (0.04 moles) and 77.1 parts by weight of polycarbonate is the same charge generation as (Sensitive 1A) Comparative laminate type photoreceptor comprising a charge transport layer of 17 μm on the layer (sensitivity 1A)

Next, a solution obtained by adding 1 part by weight of (CT20) of the charge transport material (CT1) having the charge transport layer composition of (Sense 1A) to the charge transport layer solution of (Sense 1A) (Sense 1A) ) On the same charge generation layer as in (1), a laminated type photoconductor (sensitivity 1B) is prepared, and the photosensitivity, sensitivity ratio 1, sensitivity ratio 2, sensitivity 1A, sensitivity ratio 1A, and sensitivity 1B are prepared. Electrophotographic basic electrical characteristics and photochemical photodegradation durability were investigated.

(Examples 2 to 20) The charge generating material, charge transporting material, and additive of the photosensor of Example 1 with Sensitivity 1A, Sensitivity 1A, and Sensitivity 1B were replaced with the constituent materials shown in Table 3 (Sense 1A). , (Sensitivity 1A), (Sensitivity 2B), (Sensitivity 2A) to (Sensitivity 20A), (Sensitivity 2A) to (Sensitivity 20A), (Sensitivity 2B) to (Sensitivity 20B) are created. did.

In all of (Sense 1A) to (Sense 20A) prepared above, crystallization in the charge transport layer did not occur. On the other hand, in the case where the charge transport material in Example 1 (Sense 1A) was replaced with the same parts by weight (45 parts by weight) of I1, I2, and I3, I1, I2, and I3 were all deposited in the charge transport layer, Evaluation as a photoconductor was not possible.

注）ＴｉＯＰｃ＝チタニルフタロシアニン、Ｈ２Ｐｃ＝Ｘ型無金属フタロシアニン

Note) TiOPc = titanyl phthalocyanine, H2Pc = X-type metal-free phthalocyanine

(Evaluation) Table 3 shows typical examples of the electrical characteristics of the photoreceptors prepared in the examples.
Table 3 (the sensitive 1A) (sensitive ratio 1), (sensitive ratio 2), as can be seen from the results of (sensitive 3A), the absorption of quinones 1600～1700Cm ^-1 is ^{3 cm -1} following are the initial The characteristics were poor, and further, the repetition characteristics had large potential fluctuations and were not suitable for actual use.

In addition, in comparison of (sensitivity 1A) and (sensitivity ratio 1A), which is a comparison of charge transport capacity per molecule between the charge transfer complex and the quinone-based molecule of the starting material, (sensitivity ratio 1A) is the initial sensitivity, charge retention. In addition to being inferior to (sensitivity 1A) in all of the ratio and residual potential, a decrease in sensitivity and an increase in residual potential were observed due to repetition, which is not suitable for practical use. It was shown that the transfer complex is superior to the quinone molecule as a starting material, and a photoreceptor having excellent characteristics can be obtained.

In addition, the charge transport material is a single component (feeling 1A), but the effect of light irradiation traces was inconspicuous in the initial image of the laser printer, but the portion irradiated with light as the running was repeated The difference in density between the non-irradiated part and the non-irradiated part became remarkable, but (Sensitive 1B) showed no light irradiation marks in the initial image and the image after 1000 copies, and the charge transfer complex of the present invention It has been shown to be an excellent light stabilizer.

Also in Examples 2 to 20, all of the charge transfer complex electron transfer agents have a sensitivity ratio 2A to a sensitivity ratio 20A corresponding to a sensitivity ratio 1A made from a quinone compound before formation of the charge transfer complex. As a result, the decrease in sensitivity and the increase in the residual potential were the same as those of the feeling 1A, whereas the feeling 2A to the feeling 20A showed almost no change in electrical characteristics due to repetition. From these results, it was shown that the charge transfer complex of the present invention was superior in charge transport capability per molecule than the quinone compound.

(Production and evaluation of single-layer type photoreceptor)
Comparative Example 3: 45 parts by weight of a comparative compound (NCT1) was used as a charge transport material in a solution obtained by dispersing 1 part by weight of an X-type metal-free phthalocyanine in a tetrahydrofuran solution in which 54 parts by weight of polycarbonate was dissolved in 600 parts by weight of tetrahydrofuran. The charge generation and transport layer solution in which the solution is dissolved is coated and dried on a cylindrical aluminum base tube whose surface is anodized by the dip coating method, and a single layer type photoconductor comprising a charge generation and transport layer having a thickness of 22 μm (photosensitive layer). A ratio 3) was created.

Comparative Example 4: A single layer type photoreceptor (sensitivity ratio 4) was prepared by replacing the charge transport material (NCT1) of the single layer type photoreceptor (sensitivity ratio 3) of comparative example 3 with the same weight part of (NCT2).

Example 21: Charge transfer complex () as a charge transport material in a solution obtained by dispersing 1 part by weight of an X-type metal-free phthalocyanine as a charge generation material in a tetrahydrofuran solution in which 54 parts by weight of polycarbonate is dissolved in 600 parts by weight of tetrahydrofuran A charge generation and transport liquid in which 45 parts by weight of Chemical Formula 1 is dissolved is applied and dried on a cylindrical aluminum base tube whose surface is anodized by a dip coating method to form a charge generation and transport layer having a thickness of 22 μm. A single layer type photoreceptor (single sensitivity 21A) was prepared. The obtained photoreceptor had an excellent appearance without crystallization.

Next, a charge generation and transport liquid obtained by further adding 0.5 parts by weight of CT10 as an additive to the charge generation and transport liquid composition of the single sensitivity 21A is treated in the same manner as the above photoreceptor (single sensitivity 21A). (Single sense 21B) was created.

Examples 22 to 40: Example 21 The charge generating substance and the charge transporting substance in the photosensitive element 21A are replaced with the charge generating and charge transporting substances in Examples 22 to 40 in Table 2 to obtain the single feeling 22A to 22A. In the senses 40A and the senses 22B to 40B corresponding to the senses 21B, 0.5 parts by weight of the charge transfer complex additive shown in Table 2 was prepared in the same manner as the senses 21B.

Table 4 shows the electrical characteristics of the single layer type photoreceptors prepared in Examples 21 to 40. In addition, the electrical property by the presence or absence (single-sensitivity A and single-sensitivity B) of the charge transfer complex of a different quinone absorption shift wave number as an additive added for the stabilization by light was a substantially the same value.

From the results of Table 4 (Evaluation of a single layer type photosensitive member), as compared to the single sense 21A, sensitive ratio of 3 to shift the absorption wave number of quinones 1600～1700Cm ^-1 it was made from ^{3 cm -1} or less of the charge transfer complex, A photosensitive member having a sensitivity ratio of 4, a single sensitivity of 23A, and the like has a charge retention rate (Vk) sensitivity (E1 / 2), compared to a single layer type photosensitive member made of a charge transfer complex having a shift wave number of 3 cm ⁻¹ or more. Initial characteristics such as residual potential (Vr) are inferior. Furthermore, the charge retention rate (Vk) sensitivity (E1 / 2) and residual potential (Vr) characteristics are greatly changed by 10,000 repeated use, and it is used for the laser printer HL1060 used as a reference material. The present invention also has excellent charge retention (Vk), sensitivity (E1 / 2), residual potential (Vr), and repeatability with respect to a single-layer type photoreceptor using diphenoquinone and a hole transport agent. It has been shown that the charge transfer complex is an electron transfer material having an excellent electron transport ability.

Further, when comparing the light sensitivity 21A and the light sensitivity 21B of Example 21 with respect to light fatigue resistance in an environment of high temperature and high humidity at a temperature of 35 ° C. and a humidity of 90%, the light sensitivity 21A causes light fatigue marks in the initial image. This fatigue fatigue mark is further emphasized when running on, but no light fatigue trace was observed in the initial image and the image after running the actual machine. In addition, even in the single senses 22B to 40B in Examples 22 to 40, the photoconductor was excellent in resistance to light without causing light fatigue marks.

  Since it is stable to light, there is no need for light shielding during manufacture or replacement of the photoreceptor. In addition, since it is for positive charging, harmful ozone can be reduced, so it can be applied to office and home use laser printers that require a safer environment and more reliable images.

Schematic diagram of single-layer type electrophotographic photoreceptor Schematic diagram of multilayer electrophotographic photoreceptor Infrared absorption spectrum comparison chart of charge transfer complex (CT1) and raw materials (I1, II1) of synthesis example Infrared absorption spectrum comparison chart of charge transfer complex (CT11) and raw material (I2, II2) of synthesis example

Explanation of symbols

1 Conductive substrate 2 Blocking layer (intermediate layer)
3 Charge Generation Layer 4 Charge Transport Layer 5 Charge Generation Transport Layer

Claims (4)

In an electrophotographic photosensitive member in which a photosensitive layer containing a charge generating material and a charge transport material is provided on a conductive substrate, the charge transport material is a quinone compound that is an electron-withdrawing molecule and a positive compound that is an electron-donating molecule. The strongest absorption peak appearing at 1600-1700 cm ⁻¹ belonging to the quinone structure of the infrared absorption spectrum of the charge transfer complex represented by the following general formula I formed with the pore transport compound is a quinone system before the charge transfer complex is formed. An electrophotographic photosensitive member, characterized in that it is a charge transfer complex shifted by a high wave number by 3 cm ^-1 or more as compared with a compound.

In the formula, D represents a hole transport compound, X represents an oxygen atom, or general formula (II) or (III), and R1 to R14 may be the same or different from each other, a hydrogen atom, a halogen atom, or an alkyl group. Represents an aralkyl group or an alkoxy group. N is an integer of 1 or 2. The electrophotographic photoreceptor according to claim 1, wherein the charge transport material is a composition containing two or more charge transfer complexes having different shift wave numbers of infrared absorption spectra in the charge transfer complex according to claim 1. Transfer complex composition. 3. A positively charged layered electrophotographic photoreceptor, wherein the electrophotographic photoreceptor according to claim 1 and 2 is laminated in the order of a conductive substrate / charge generation layer / charge transport layer. 3. A positively charged single layer type electrophotographic photosensitive member according to claim 1, wherein the charge generating material and the charge transporting material are in the same layer.

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