JP2610941B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high sensitivity and durability widely used in electrophotographic application fields such as electrophotographic copying machines, laser beam printers, CRT printers, and electrophotographic plate making systems. The present invention relates to an electrophotographic photoreceptor excellent in the above.

[Prior art] In recent years, various organic photoconductive materials have been developed as photoconductive materials for electrophotographic photoreceptors. Among photoreceptors using these organic photoconductive materials, particularly, a charge generation layer and a charge transport layer have been already used. The stacked function-separated type is commercialized and installed in copiers and printers. However, these photoreceptors generally have mechanical durability against abrasion and scratches caused by rubbing of the photoreceptor surface, and decrease in sensitivity, fluctuation in residual potential, decrease in charging ability, and electrophotographic characteristics against image blur. Was not sufficiently durable.

In order to improve mechanical durability, JP-A-56-25746, JP-A-56-25749, and a fluorine-based resin powder on the photoconductor surface layer as described in JP-A-61-123850, etc. It is known to disperse lubricant powder such as polyolefin resin powder and carbon fluoride.

However, whereas since the photoreceptor does not distribute the lubricant powder surface degraded by active species of the ozone and NO _X, etc. produced during the corona discharge shaved surface not always new deterioration has appeared, smooth In the case of the photoreceptor in which the material powder is dispersed, the amount of shaving is remarkably reduced, so that a new surface does not sufficiently appear.

Therefore, the present inventors use a compound having an oxidation potential of 0.6 V or more as a charge transport material contained in the surface layer,
Image blur when lubricant powder is dispersed is eliminated
63-30850).

However, as a new problem with this photoreceptor, if the photoreceptor is continuously used and then notified in a copying machine for a long time, the charging ability of the part of the photoreceptor close to the charger that performs corona discharge apparently decreases, and It has been pointed out that a phenomenon in which white stripes occur, that is, a so-called white drop occurs. This white drop is a peculiar phenomenon when a charge transporting substance having an oxidation potential of 0.6 V or more is used, and is not seen at all in a charge transporting substance having a low oxidation potential of less than 0.6 V.

Generation of white spots are attributable to ozone and NO _X generated during similar corona discharge and an image blur of the foregoing, when the oxidation potential of the charge transporting material is less than 0.6V, the charge transport material itself photoreceptor surface in receiving oxidized by the action of ozone and NO _X while the image blur lower resistance is occurring, the oxidation potential is 0.6V
More oxidation a charge generating substance ozone and NO _X in the charge transporting material is less susceptible to oxidation can penetrate to the photosensitive member deep inside the case of the charge transport material, hole injection from infrastructure in order to reduce the resistance of Is promoted, and apparently the potential does not increase, and white dropout is presumed to occur. Although this apparent potential drop occurs even during continuous use, the drop in surface potential occurs uniformly on the surface of the photoreceptor and is not recognized as a partial drop in potential. upon standing after, it is to significantly surfaced local potential drop becomes a white spot at extremely high charger vicinity ozone and NO _X concentrations.

[Problems to be Solved by the Invention] The present invention is to provide an electrophotographic photoreceptor having high durability and solving the above-mentioned problems. That is, an object of the present invention is to provide an electrophotographic photoreceptor having a high durability, in which abrasion on the surface due to friction and generation of scratches are small and a high-quality image free of images and white spots is obtained. Another object of the present invention is to provide an electrophotographic photoreceptor having good cleaning properties and high durability without toner adhesion to a surface layer. Still another object of the present invention is to provide an electrophotographic photosensitive member having high durability and capable of always obtaining a high-quality image without accumulation of residual potential in a repeated electrophotographic process.

[Means for Solving the Problem] The problem is that, in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, at least a layer farthest from the support has a lubricant powder and an oxidation potential of 0.6 V Less than a charge transport layer,
And an electrophotographic photoreceptor characterized by containing compounds represented by the following general formulas (1) and (2).

General formula (1) (Where X ₁ and X ₂ are And R ₁ and R ₂ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ) General formula (2) (In the formula, X ₃ and X ₄ are respectively an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms.) In the present invention, the compounds represented by the general formulas (1) and (2) addition of an effect of protecting the charge transport material from the oxidizing action of ozone and NO _X. That is, the general formula (1),
The compound of (2) prefers ozone and NO over charge transport materials.
It is subject to the oxidizing action of _X , and its oxidatively degraded product does not adversely affect other electrophotographic characteristics. Hereinafter, the present invention will be described in detail.

The photosensitive layer containing an organic photoconductive material in the present invention is a single-layer photoreceptor in which a charge-separating material and a charge-transporting material are mixed, or a charge-generating layer containing a charge-generating material and a charge-transporting material. It takes the form of a laminated photoreceptor in which a charge transporting layer containing the same is laminated.

As the charge generating substance, a pyrylium, a thiopyrylium dye, a phthalocyanine pigment, an anthrone pigment, a perylene pigment, a dibenzopyrene quinone pigment, a pyranthrone pigment, a trisazo pigment, a disazo pigment, an azo pigment, an indigo pigment, a quinacridone pigment, or the like is used. be able to.

The charge transport material having an oxidation potential of less than 0.6 V in the present invention is a hydrazone compound, a stilbene compound, a carbazole compound, a pyrazoline compound, an oxazole compound, a thiazole compound, a triarylmethane compound, or a polyarylalkane. Selected. Also,
These charge transport materials may be used in combination of two or more.

Since the charge transport material generally has a low molecular weight and cannot form a film itself, it is necessary to use a resin having film forming properties as a binder. The binder resin is not particularly limited as long as it is a polymer compound having a film-forming property.However, polymethacrylic acid esters, polycarbonate, polystyrene, and the like have a certain degree of hardness by themselves and do not hinder carrier transport. Preferred are arylate, polyester, polysulfone and the like.

The binder resin contained in the layer farthest from the conductive support is usually 1 to 100 parts by weight of the charge transporting substance.
About 0 to 1000 parts by weight are used.

As the lubricant powder used in the present invention, for example, ethylene tetrafluoride resin powder, ethylene trifluoride chloride resin powder, ethylene hexafluoride propylene resin powder, ethylene dichloride ethylene chloride resin powder, Fluorinated resin powder such as a copolymer of a monomer constituting a polymer of the above; polyethylene resin powder, polypropylene resin powder, polyolefin resin powder such as a copolymer of a monomer constituting such a polymer; carbon fluoride Is mentioned. Among these, ethylene tetrafluoride resin, vinylidene fluoride resin, and polyethylene resin are preferable from the viewpoint of slipperiness, abrasion resistance, and mold release properties. These lubricant powders can be used in combination of two or more.

The content of the lubricant powder dispersed in the layer farthest from the conductive support is determined by the sum of the charge transporting substance and the binder (and, if the layer contains a charge generating substance, further the charge generating substance). 1.0 to 30% by weight based on the amount is appropriate,
-20% by weight is preferred.

If the content is less than 1.0% by weight, the effect of surface modification by the dispersion of the lubricant powder is not sufficient, while if it exceeds 30% by weight, the light transmittance is reduced and the mobility of the carrier is also reduced. There is.

Examples of the compounds represented by the general formulas (1) and (2) used in the present invention include the following compounds.

These compounds include one of a phenol derivative having a hindered phenol group known as a radical scavenger or an antioxidant such as plastic and rubber, and a phosphorus-based compound known as a hydroperoxide decomposer. It is one of. These compounds may be used in combination of two or more.

The total content of the compounds represented by the general formulas (1) and (2) contained in the layer farthest from the conductive support is the sum of the charge transport material and the compound (when the layer contains a charge generating material). In general, 0.1 to 30% by weight, and preferably 0.2 to 10% by weight, of the total amount of the charge generating substance and the binder are appropriate. When the amount of the additive is less than 0.1% by weight, the effect of preventing deterioration is small, and when the amount exceeds 30% by weight, adverse effects such as a decrease in sensitivity and an increase in residual potential tend to occur.

When producing the electrophotographic photoreceptor of the present invention, as the conductive support, a support having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel , Indium, gold, platinum, and the like can be used. In addition, plastic, titanium oxide, and oxide having a layer in which aluminum, an aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, or the like is formed by a vacuum evaporation method can be used. It is possible to use a support in which conductive particles such as tin are coated on a plastic or the conductive support together with a suitable binder, a support in which conductive particles are impregnated in plastic or paper, or a plastic having a conductive polymer. it can.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, It can be formed of gelatin, aluminum oxide, or the like.

The thickness of the undercoat layer is 0.1 μm to 40 μm, preferably 0.3 μm.
μm to 3 μm is appropriate.

As a method of dispersing the lubricant powder, general dispersing means such as a homogenizer, an ultrasonic wave, a ball mill, a vibration mill, a sand mill, an attritor, and a roll mill can be used. After the lubricant powder is added to the binder dissolved in an appropriate solvent, it is dispersed by the above dispersion method. This is prepared by mixing an appropriate amount of a solution in which a binder, a charge transport material and the compound represented by the general formula (1) are dissolved.
In addition, it is also possible to add various dispersing aids to improve dispersibility when dispersing the lubricant powder.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, and a curtain coating method. Drying is preferably performed by touch drying at room temperature and then heating and drying. The heating and drying can be performed at 30 ° C. to 200 ° C. for 5 minutes to 2 hours in a stationary or blown state.

In the present invention, the oxidation potential reference electrode saturated calomel _{electrode, 0.1N (n-Bu) 4} N + ClO 4 - with acetonitrile solution as an electrolytic solution, and sweeping the potential of the working electrode by the potential sweeper, resulting current The peak position of the potential curve was determined as the oxidation potential value.

Specifically, to dissolve the sample to a concentration of about 5～10Mmol% in the electrolytic solution of _{0.1N (n-Bu) 4 N} + ClO -4 acetonitrile. Then, a voltage is applied to this sample solution, and a current change when the voltage is changed linearly from a low potential is measured to obtain a current-potential curve. The potential value corresponding to the first inflection point of the current value in this current-potential curve was defined as the oxidation potential.

Hereinafter, the present invention will be described with reference to examples. Parts in Examples are parts by weight.

Example 1 An 80φ × 360 mm aluminum cylinder was prepared as a conductive support.

On the other hand, 100 parts of conductive powder coated with tin oxide containing 10% of antimony oxide to 75% by weight of titanium oxide is composed of 100 parts of resole phenolic resin, 30 parts of methanol, and 100 parts of methyl cellosolve. To the solution,
It was well dispersed in a ball mill to give a coating. This paint was applied on the support by dip coating and cured by heating at 140 ° C for 30 minutes.
m of the conductive undercoat layer was provided.

On top of this, 1 part of a polyamide resin (6-66-610-12 quaternary nylon copolymer) and 3 parts of an 8-nylon resin (methoxymethylated 6 nylon, methoxylation ratio of about 30%) were mixed with 50 parts of methanol and 40 parts of butanol. The coating solution dissolved in the solvent consisting of the above parts was applied by a dipping method, dried at 70 ° C. for 10 minutes, and an undercoat layer having a thickness of 0.5 μm was formed.

Next, 10 parts of a bisazo pigment of the following structural formula (3) and 5 parts of a polyvinyl butyral resin And 100 parts of cyclohexanone were dispersed in a sand mill using 1φ glass beads for 20 hours. To this dispersion was added 50 to 100 parts of tetrahydrofuran (as appropriate), and the dispersion was coated on the undercoat layer, and dried at 100 ° C. for 5 minutes to form a 0.12 μm thick charge generation layer.

Next, ethylene tetrafluoride resin powder, a fluorinated acrylic oligomer as a dispersant, and an oxidation potential of 0.
57V hydrazone compound of the following formula (CT-1) A bisphenol Z-type polycarbonate resin was prepared as a binder. First, polycarbonate resin 20
Parts, 20 parts of a hydrazone compound and 0.6 parts of a fluorinated acrylic oligomer are dissolved in 100 parts of monochlorobenzene. Then, 6 parts of a tetrafluoroethylene resin powder was added thereto, and dispersed in a stainless steel ball mill for 40 hours to obtain a compound of the following structural formula (5) (corresponding to the above-mentioned general formula (1) (abbreviated as MB).
P-1) and a compound of the structural formula (6) (the aforementioned general formula (2)
Was added to 20 parts of a dichloromethane solution prepared by dissolving 0.4 part of each (abbreviation: P-EPQ-1) to prepare a charge transport layer coating solution. This solution was applied on the charge generation layer,
The resultant was dried with hot air at 60 ° C. for 60 minutes to form a charge transport layer having a thickness of 20 μm.

The photoreceptor created for this purpose has a blade penetration of 1.1m
m, attached to a Canon copier NP-3525 modified to have a cleaning mechanism with a relative speed of the sponge roller of 102%, and the durability was evaluated. No blurring occurred even after the durability test of 100,000 sheets. A high quality copy was obtained. At this time, the amount of reduction in the thickness of the photoreceptor was 1.5 μm. In addition, using another photoreceptor manufactured in the same way, after performing 5,000 continuous copies, the photoreceptor was left in the copier for 3 days,
At this time, the surface potential was measured. At this time, the portion of the photoreceptor located immediately below the corona charger during the standing was marked, and the potential difference (ΔV _D ) from the other portions was determined. Did not.

Examples 2 to 14 Hereinafter, as the lubricant powder, polyvinylidene fluoride resin powder, polydifluoroethylene dichloride resin powder, polyethylene powder, carbon fluoride, and the CT as a charge transport material.
-1, Structural formula (7) having an oxidation potential of 0.54 V (abbreviated as CT-2),
A compound of structural formula (8) (abbreviated as CT-3) having an oxidation potential of 0.47 V Photoreceptors manufactured in the same manner as in Example 1 using the compounds shown in Table 1 in addition to the MBP-1 and P-EPQ-1 as the compounds corresponding to the general formulas (1) and (2) Table 2 summarizes the results of the same evaluation as in Example 1.

Examples 15 to 20 Table 2 shows the evaluation results of the photoconductors manufactured in the same manner as in Example 1 except that the amounts of the compounds represented by formulas (1) and (2) were changed.

Comparative Examples 1 to 11 From the composition of the example, the lubricant powder or the general formula (1),
A photoreceptor lacking the compound represented by (2) was prepared and evaluated in the same manner as in Example 1. Further, the oxidation potential shown in Table 3 was 0.
Table 4 shows the evaluation results of the photoreceptor using the charge transport material of 6 V or more and the photoreceptor using the additive of Table 1 alone.

As shown in Table 4, the photoreceptors to which the compounds represented by the general formulas (1) and (2) were not added or used in combination were 3,000 to 3,000.
Blurring occurred from about 4000 sheets, and the image was indistinguishable after 100,000 sheets of durability test.

In addition, the photoreceptor without addition of the tetrafluoroethylene resin powder, which is a lubricating powder, starts to fog from about 35,000 sheets due to a sharp decrease in the thickness of the photoreceptor surface in an endurance test.
After the endurance test of 10,000 sheets, it was difficult to distinguish it from characters.

The photoreceptor using a charge transport material with an oxidation potential of 0.6 V or higher did not blur during the durability test, but when left in a copying machine for 3 days, the potential under the charger was significantly reduced. White spots occurred on the top.

Example 21 In the same manner as in Example 1, up to the undercoat layer was coated on an 80φ cylinder substrate. Next, a solution prepared by dissolving 15 parts of the hydrazone compound (CT-1) used in Example 1 and 10 parts of a polycarbonate Z resin in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied on the undercoat layer, and charge transported to a thickness of 15 μm. A layer was formed.

Next, 4 parts of disazo pigment having the following structural formula, polycarbonate Z resin 10 parts and 50 parts of cyclohexanone were dispersed in a sand mill using 1φ glass beads for 20 hours to prepare a charge generation layer dispersion.

Next, ethylene tetrafluoride resin powder, a fluorinated acrylic oligomer as a dispersant, a hydrazone compound (CT-
1) A polycarbonate Z resin was prepared. First, 10 parts of a polycarbonate resin, a hydrazone compound, and 0.15 part of a fluorine-based acrylic oligomer are dissolved in 10 parts of dichloromethane and 40 parts of monochlorobenzene. Then, 1.5 parts of polytetrafluoroethylene resin powder was added thereto, and the mixture was dispersed in a stainless steel ball mill for 40 hours. Further, each of the compounds represented by the general formulas (1) and (2) used in Example 1 was added to this solution at a concentration of 0.1%.
3 parts were added to prepare a charge generation layer solution. A paint in which the charge generation layer dispersion liquid and the charge transport layer liquid were mixed at a ratio of 1: 1 was applied on the charge transport layer to form a charge generation layer having a thickness of 5 μm.

The copier used in Example 1 was modified so that it could be further positively charged, and this photoreceptor was evaluated in the same manner as in Example 1.
No blurring occurred even after the endurance test of 10,000 sheets, and high-quality copies could be obtained. At this time, the amount of decrease in the thickness of the photoconductor is 2.5
μm. Further, the potential difference between the other portions in portions even when left a durability test after the photoreceptor in the copying machine hits the site just below the charger ([Delta] V _D) is almost observed no white spots did not occur.

Comparative Example 12 As a comparative example of Example 21, a photoreceptor to which the compounds represented by the general formulas (1) and (2) were not added was produced and subjected to the same evaluation, but blurring began to occur from about several thousand sheets. .

[Effect of the Invention] As described above, the electrophotographic photoreceptor containing the lubricant powder of the present invention, the charge transport substance having an oxidation potential of less than 0.6 V, and the organic compound having a specific structure is mechanically durable. It is extremely high in stability and potential stability in a corona discharge environment, and can always provide a stable and high-quality image. Further, the electrophotographic photoreceptor of the present invention can be used as a photoreceptor of a printer to which electrophotography is applied, such as a laser beam printer, an LED printer, an LCD printer, and a CRT printer, in addition to a normal copying machine.

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Claims (5)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein at least the layer farthest from the support comprises a lubricant powder, a charge transport material having an oxidation potential of less than 0.6 V, and An electrophotographic photoreceptor comprising a compound represented by the formula (1) or (2). General formula (1) (Where X ₁ and X ₂ are Wherein R ₁ and R ₂ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ) General formula (2) (In the formula, X ₃ and X ₄ are each an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms.) 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure composed of a charge generation layer and a charge transport layer, and the charge transport layer is provided on the charge generation layer. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure comprising a charge generation layer and a charge transport layer, and the charge generation layer is provided on the charge transport layer. 4. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer comprises a single layer containing a charge generating substance and a charge transporting substance. 5. The electrophotographic photoreceptor according to claim 1, wherein the lubricant powder is a fluororesin powder, a polyolefin resin powder or a carbon fluoride powder.