JPH07160020A - Electron carrying material consisting of diester type bis-naphthalimido - Google Patents

Abstract

PURPOSE:To provide a new organic electron carrying material which is especially useful for construction of an electrophotography sensitive body used for positive electrification type electrophotography technology which is a low ozone system suitable for environmental protection in particular. CONSTITUTION:Diester type bis-1,8-naphthalimido compound and the like in which any hydrogen atoms combined with a naphthalene skelton can be replaced with electron attractive group shown in the formula is used for an electron carrying material. In the formula, X indicates a hydrogen atom or a electron attractive group, R1 indicates a hydrocarbon residual group capable of having substituent, R2 indicates a hydrocarbon residual group capable of having single combination or substitutent, and R1 and R2 can be equal to each other or not.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a diester type bis-1,
The present invention relates to a novel electron-transporting material composed of 8-naphthalimide compounds, and more specifically, it is suitable for use in an electrophotographic photoreceptor, particularly an electrophotographic photoreceptor for a positive charging type (or positive / negative charging type) electrophotographic system, Regarding new electron transport materials.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member utilizing an organic photo-semiconductor as an active ingredient, aromatic amine compounds such as poly-N-vinylcarbazole and triphenylamine derivatives and aromatic compounds such as carbazole aldehyde-hydrazone derivatives have been used. Hydrazone compounds, or 1,
A charge transporting material having a hole transporting ability (that is, a hole transporting material) such as a stilbene compound such as a 1,4,4-tetraphenylbutadiene derivative, a triphenylmethane dye, a fluorane dye, ( Thio) pyrylium salt dyes, phthalocyanine pigments, bisazo pigments, perylene pigments, etc. are combined with a coloring material (that is, a charge generating material) that generates an electric charge (electron / hole pair) by light absorption, and thus conductive. Formed as a single-layer type or laminated type (function separation type) photosensitive layer on a photosensitive support, electrostatically charging the surface of the photosensitive layer in the dark with negative polarity, and performing image exposure to generate the exposed portion The holes of the generated electrons and holes are moved to the surface of the photosensitive layer to neutralize the negative charge image-wise and form an electrostatic latent image composed of the negative charge (after that, a charge called toner is applied). Coloring Body deposited by electrostatic attraction to allowed to visualization, i.e. is developed) type, an electrophotographic photosensitive member suitable for use in so-called negatively charged electrophotographic method has been mainly used.

In the negative charging type electrophotographic method, which has been the mainstream in the past, there is a problem that a large amount of ozone generated in the negative electrostatic charging process due to corona discharge causes corrosion of a photoconductor and other equipments, and in particular environmental pollution. It has occurred, and there has been a strong demand for improvement.

However, in the case of the positive charging type electrophotographic method, which is a method of charging an electrostatic charge of the opposite polarity to that described above, ozone generation is extremely small, so that it becomes a method particularly suitable for environmental protection, and in the future The positive charging type electrophotographic system must be the mainstream, and therefore, the realization of the positive charging type electrophotographic photosensitive member is urgent.

To that end, contrary to the above, a charge-transporting substance (that is, an electron-transporting material), which is mainly excellent in electron-transporting ability, has become an urgently needed material. In other words, in the positive charging type electrophotographic system, electrostatic charges having a positive polarity are charged on the surface of the photosensitive layer of the electrophotographic photosensitive member, and similarly, image exposure is performed and electrons generated in exposed areas and electrons out of holes are generated. One is moved to the surface of the photosensitive layer to neutralize the positive charge imagewise, and an electrostatic latent image consisting of the positive charge is formed (after this,
Since it is necessary to attach toner by electrostatic attraction to develop it), an electron transport material, which is a charge transport material having an excellent electron transport capability, is indispensable.

However, there are not many examples of such electron transfer type organic charge transporting materials (electron transporting materials), and there are only a few tetracyanoethylene, tetracyanoquinodimethane, chloranil, 2,4,7-trinitrofluorenone, 9 -Dicyanomethylenefluorene-4-carboxylate compound,
4-dicyanomethylene-2,6-diphenyl-4H-thiopyran-1,1-dioxide derivative, 2- (4-biphenylyl) -5- (4-tert-butylphenyl)
-1,3,4-oxadiazole derivative or 3,
Only 5,3 ′, 5′-tetraalkyl-4,4′-diphenoquinones and the like have been announced, and the electron transporting ability of these substances is not yet sufficient.

Further, Japanese Patent Laid-Open Nos. 5-19505 and 5-5
No. 25136 discloses a naphthalenedicarboxylic acid imide compound, and it is judged from the description that the compound is a kind of organic electron transport material. However, even with these, it must be said that the ability as an electron transport material is still at an unsatisfactory level.

The present invention is based on the unpublished diester type bis-
The present invention provides a novel electron transport material composed of 1,8-naphthalimide compounds, and by using one kind or two or more kinds of the compounds, more excellent positive charge type (or positive / negative charge type) electrons can be obtained. This enables the assembly of a photographic photoreceptor.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel organic electron transporting material which enables the assembly of an excellent positive charging type (or positive / negative charging type) electrophotographic photosensitive member.

[0010]

The object of the present invention is to chemically synthesize the diester type bis-1,8-naphthalimide compounds represented by the above formula 1 and utilize them as electron transport materials. Solved by In Formula 1,
X is a hydrogen atom or a halogen atom, a nitro group, a cyano group, an electron-withdrawing group such as a carboxylic acid ester group, R ¹
Is an aliphatic or aromatic hydrocarbon residue such as an alkylene group, a cycloalkylene group, an aralkylene group, or an arylene group which may have a substituent, and R ² may have a single bond or a substituent. It represents an aliphatic or aromatic hydrocarbon residue such as an alkylene group, a cycloalkylene group, an aralkylene group and an arylene group, and R ¹ and R ² may be the same or different.

In the present invention, 1,8-naphthalimide in which any hydrogen atom directly bonded to the naphthalene nucleus of the 1,8-naphthalimide skeleton may be substituted with an electron-withdrawing group such as a halogen atom or a nitro group. The bis-1,8-naphthalimide compounds having a diester structure, which are bound by a hydrocarbon residue through an ester bond introduced into the N-substituent of the compound, are adopted as novel electron transport materials. By covalently bonding the two 1,8-naphthalimide skeletons, the mobility of charge carriers such as electrons is greatly increased. This is considered to be the reason why the electron transport material has remarkably high performance.

The diester-type bis-1,8-naphthalimide compounds newly provided by the present invention refer to the method described in the literature (Organic Synthetic Chemistry: Volume 14, No. 7, 459, published in 1956). Then, first, 1,8-naphthalic anhydride, which may have an electron-withdrawing group in the naphthalene nucleus, is condensed with a primary amine having an -OH group to form an -OH group on the N-substituent. After synthesizing the 1,8-naphthalimides that it has, and then reacting 2 moles of this with 1 mole of various dicarboxylic acid dihalides in a basic medium, obtaining solvent-soluble crystals in good yield I was able to.

These crystals are particularly useful as an electron transporting material in an electrophotographic photoreceptor, and in combination with a charge generating material and, if necessary, another material (for example, a hole transporting material), a polyester-based material, Disperse in a polymer binder such as polycarbonate or poly (meth) acrylate to form a single-layer or multi-layer coating layer on the conductive support, which may have a barrier layer. For example, it was discovered for the first time in the present invention that an excellent positive charging type (or positive / negative charging type) electrophotographic photosensitive member can be provided by functioning as a high performance electron transporting material.

The compounds provided by the present invention utilize their high electron-transporting ability to form a barrier layer (which selectively transfers electrons) between the conductive support and the electrophotographic photosensitive layer. Can also be used as a material for the undercoat layer).

[0015]

EXAMPLES Next, the present invention will be described more specifically by way of examples. The parts and% shown below are based on weight unless otherwise specified.

Example 1 (Synthesis Example) N-2'-hydroxyethyl-4-nitro-1,8-naphthalimide (melting point 1
(50.5-151.5 ° C) 5.72 parts of 2-butanone 5
In addition to 0 volume part, phthalic acid dichloride 2.4
When 4 parts was added and 3 parts by volume of pyridine was added dropwise with stirring at room temperature, heat generation was observed. Then, after heating and refluxing for 3 hours on an oil bath, when pouring into a large amount of water, a brownish precipitate was generated. After stirring for a while, crystals were separated by suction filtration, washed with water, and dried. did. The crude crystals thus obtained were recrystallized from N, N-dimethylformamide, the brownish prism crystals were separated by suction filtration, washed with cold 2-butanone and dried to obtain 5.02 parts of purified crystals. (Yield 71.4%). Melting point 202.
0 to 203.0 ° C. Mass number m by mass spectrometry (FD method)
/ Z = 702 (calculated value C ₃₆ H ₂₂ N ₄ O ₁₂ = 702.6
0).

The FT-infrared spectrum (KBr tablet method) of the thus obtained crystal is shown in FIG. In FIG. 1, 3,
Several characteristic absorption bands of alkane around 000 cm ^-1 ,
At 737 cm ^-1 , the ester bond νC = O was 1,709
cm ^-1 and 1,663Cm ^-1 to 6-membered cyclic imide bond νC
= O, the characteristic absorption bands of the nitro group are clearly observed at 1,529 cm ^-1 and 1,348 cm ^-1 respectively. From the above results, it can be seen that the compound represented by the following formula 2 was obtained.

[Chemical 2]

Examples 2 to 8 (Synthesis Example) The compounds shown in Table 1 below were synthesized in the same manner as in Example 1. As a raw material primary amine having a —OH group, p-β-aminoethylphenol was used in Example 4, and 1-amino-2-propanol was used in Examples 6 and 7.

[0019]

[Table 1]

Example 9 (Example of use in electrophotographic photoreceptor) 1 part of α-type oxytitanium phthalocyanine as a charge generating material and 1 part of a diester type bis-1,8-naphthalimide compound according to the present invention as an electron transporting material. The compound synthesized in Example 1 (abbreviated as ETM-1) is 100
Parts, 75 parts, 50 parts, 25 parts or 0 parts, and 0-part, 25 parts, 5 parts of p-dibenzylaminobenzaldehyde-diphenylhydrazone (abbreviated as HTM) as a hole transport material.
0 part, 75 parts or 100 parts (that is, the total of the electron transport material and the hole transport material is 100 parts), and 1 part of polyester (Vylon-200 manufactured by Toyobo Co., Ltd.) as a polymer binder is used.
00 parts, and tetrahydrofuran 1,30 as the solvent
0 parts were mixed, placed in a closed container together with glass beads, shaken and dispersed for 2 hours using a paint conditioner device, and then the glass beads were removed by sieving to prepare 5 kinds of coating solutions for electrophotographic photoreceptors. . Then, these coating solutions were applied onto an aluminum plate using an applicator so that the thickness of the coating layer after drying was 20 ± 3 μm, and the temperature was 80 ° C.
After drying for 1 hour in a drier, the mixture was left at room temperature for 1 night or more in a black bag.

The electrophotographic photosensitive member thus prepared was evaluated for electrophotographic characteristics under positive charging (or negative charging) by an electrostatic recording tester (SP-428 manufactured by Kawaguchi Denki Co., Ltd.). Measurement conditions: Applied voltage + 6.0kV (or -6.0k
V) Static No. 3 (Turntable rotation speed mode) Light source Tungsten lamp White light Sample surface illuminance 10 lux

The measurement results are shown in Table 2 (or Table 3). In Table 2 (or Table 3), V ₀ (volt) is the initial surface potential after application of a positive (or negative) voltage, Vd ₁₀ ( bolt)
Is the potential after 10 seconds in the dark (at which time exposure begins),
DD ₁₀ (%) is Vd ₁₀ / V ₀ × 100, Vl ₁ (volt) is the surface potential after 1 second from the start of exposure, and the difference between Vd ₁₀ and Vl ₁ represents the photosensitivity. The higher the light attenuation, the higher the sensitivity. Also E
_1/2 (lux · sec) indicates the exposure amount required to reduce the surface potential to 1/2 of Vd ₁₀ by exposure (potential half exposure amount), and the smaller the number, the higher the practical sensitivity. Represents

[0023]

[Table 2]

[0024]

[Table 3]

From Table 2, it can be seen that the photoconductor of Sample No. (5), which uses only the hole transport material (HTM) as the charge transport material, has a slight electron transporting ability, and thus exhibits a small light attenuation (photosensitivity). However, the light attenuation (photosensitivity) of the sample to which the diester-type bis-1,8-naphthalimide compound of the present invention, which is considered to be an electron transporting material, is increased, and particularly the light attenuation (photosensitivity) of the sample (2) is increased. ) Has reached its maximum, dark decay is small (DD ₁₀ is large), and the most excellent result as a positive charging type electrophotographic photosensitive member is obtained.

In addition, in Table 3 in the case of negative charging, the photosensitivity of the sample (2), in particular, the value of the potential half exposure (E _1/2 ) almost agrees with that in the case of positive charging. This shows that if the mixing ratio of the compound according to the present invention and the hole transport material is appropriate, a positive / negative charging type electrophotographic photosensitive member whose sensitivity does not change during positive / negative charging can be prepared.

Comparative Example 1 N-2, which is not a bis form, is a compound other than the present invention as a comparative compound.
A test similar to that in Example 9 was performed using'-acetyloxyethyl-4-nitro-1,8-naphthalimide (abbreviated as Ref) as an electron transport material. The results are shown in Table 4.

[0028]

[Table 4]

In the case of this comparative example, no data showing good photosensitivity was obtained, and further dark decay was remarkable, and therefore the initial potential (Vd ₁₀ ) was extremely small and the chargeability was poor. Only unsuitable electrophotographic photoreceptors could be given. Then, since a good result was not obtained in positive charging, the test with negative charging was not performed.

In Table 2, Table 3 or Table 4, − indicates that the surface potential was not optically attenuated to Vd ₁₀ × _1/2 , and E _1/2 could not be obtained.

Other diester type bis-type compounds provided by the present invention
All of the 1,8-naphthalimide derivatives, especially the electrophotographic photoreceptors in combination with various hole transport materials, gave a large light attenuation (photosensitivity) in both positive and negative charging and were superior as electron transport materials.

[0032]

As is apparent from the examples, the novel diester-type bis-1,8-naphthalimide compounds according to the present invention have an electron transporting capacity higher than that without bis-formation and a potential in the dark. It also has a large retention property, and thus is an excellent electron transport material and is also excellent as a material for an electrophotographic photoreceptor. When these are used as a charge transport material, only a positive charging type electrophotographic method can be used. Not
The positive and negative charging type electrophotographic system becomes possible, and in particular, it becomes possible to provide a new positive charging type electrophotographic photosensitive member which is preferable in environmental protection.

[Brief description of drawings]

FIG. 1 is one of diester-type bis-1,8-naphthalimide compounds, which are new electron transport materials according to the present invention,
FT-infrared spectrum diagram (KBr tablet method) of phthalic acid di {β-N- (4-nitro-1,8-naphthalimide) ethyl} ester (compound obtained in Example 1).

Claims (1)

[Claims] 1. An electron transport material comprising diester-type bis-1,8-naphthalimide compounds represented by the following formula 1. [Chemical 1] (In Formula 1, X is a hydrogen atom or an electron-withdrawing group, R ¹ is a hydrocarbon residue which may have a substituent, R ² is a single bond or a hydrocarbon residue which may have a substituent. And R ¹ and R ² may be the same or different.)