JPH0534939A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high durability and high sensitivity by which the sensitive body can be put to practical use by specifying the glass transition temp. of the electric charge transferring layer of an org. sensitive body causing no environmental pollution and easy to mass- produce. CONSTITUTION:When a photosensitive layer contg. an electric charge generating layer and an electric charge transferring layer as essential constituent elements is formed on an electric conductive substrate to obtain an electrophotographic sensitive body, the glass transition temp. of the electric charge transferring layer is regulated to 50-70 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly sensitive and highly durable electrophotographic photoreceptor.

[0002]

2. Description of the Related Art In recent years, electrophotographic copying machines and printers have been remarkably developed, and various types of models having various forms, types, and functions have been developed according to their uses, and correspondingly, photoconductors used for them have also been developed. A wide variety of things are being developed. Conventionally, inorganic compounds have been mainly used as electrophotographic photoreceptors from the viewpoint of sensitivity and durability. For example, zinc oxide, cadmium sulfide, selenium, etc. can be mentioned. However, these often use harmful substances, and their disposal poses a problem and causes pollution. When using selenium, which has good sensitivity,
It is necessary to form a thin film on the conductive substrate by a vapor deposition method or the like, which is inferior in productivity and causes a cost increase.

In recent years, amorphous silicon has attracted attention as a non-polluting inorganic photoconductor, and research and development thereof have been advanced. However, although these are also excellent in sensitivity, the productivity is extremely poor because the plasma CVD method is mainly used when forming a thin film, and the photoreceptor cost and the running cost are large.

On the other hand, the organic photoreceptor can be incinerated,
It has the advantage of being pollution-free, and many of them can be formed into thin films by coating and are easy to mass-produce. Therefore, it has an advantage that the cost can be significantly reduced and that various shapes can be processed according to the application. However, with respect to the organic photoconductor, problems remain in its sensitivity and durability, and it is strongly desired to develop an organic photoconductor with high sensitivity and high durability. Various methods have been proposed as means for improving the sensitivity of the organic photoconductor, but at present, a function-separated photoconductor mainly having a two-layer structure in which the functions are separated into a charge generation layer and a charge transport layer has become mainstream. There is. For example, the charge generated in the charge generation layer by exposure is injected into the charge transport layer, transported through the charge transport layer to the surface, and the surface charge is neutralized to form an electrostatic latent image on the surface of the photoreceptor. To be done. Compared to the single-layer type, the function-separated type has a smaller possibility of trapping the generated charges, and each layer can efficiently transport the charges to the surface of the photoconductor without hindering the function of each layer (US Patent (2803541).

As the organic charge generating material used in the charge generating layer, a compound which absorbs the energy of irradiated light and efficiently generates charges is selected and used.
Azo pigments (JP-A-54-14967), metal-free phthalocyanine pigments (JP-A-60-19146), metal phthalocyanine pigments (JP-A-57-146255), and squarium salts (JP-A-63). -113462 gazette) etc. can be mentioned. As the charge transport material used in the charge transport layer, it is necessary to select a compound having a high charge injection efficiency from the charge generation layer and a high charge mobility in the charge transport layer. For that purpose, a compound having a small ionization potential and a compound which easily generates a cation radical are selected. For example, a triarylamine derivative (JP-A-58-123542) and a hydrazone derivative (JP-A-57-101844) are selected. , Oxadiazole derivatives (JP-B-34-5466), pyrazoline derivatives (JP-B-52-4188), stilbene derivatives (JP-A-58-198043), triphenylmethane derivatives (JP-B-45-555). Gazette), 1, 3-
Butadiene derivatives (JP-A-62-287257) and the like have been proposed.

[0006]

However, the above-mentioned organic photoconductor is still unsatisfactory in terms of sensitivity because of insufficient charge mobility as compared with the inorganic photoconductor. Further, in a series of electrophotographic processes such as charging, exposure, development, transfer, and charge elimination, the photoreceptor is required to have durability because it is subjected to extremely severe conditions, but satisfactory ones have not yet been obtained. For these reasons, various organic photoconductors have been developed in the art to improve them. Among them, attempts have been actively made to improve the sensitivity of the electrophotographic photosensitive member by developing a charge generating material having a high charge generating efficiency and a charge transporting material having a large charge mobility. It has been pointed out.

That is, the charge mobility of the charge transport material used in the electrophotographic photosensitive member is generally highly dependent on the electric field, and for example, the most frequently used hydrazone compound is 2 ×.
The electric field of 10 ⁵ V / cm is 10 ⁻⁶ cm ² / V · s, whereas the electric field of 2 × 10 ⁴ V / cm is 10 ⁻⁷ cm ^2.
/ V · s or less. As a result, the photoconductor using them gives high sensitivity immediately after being charged and exposed, but the sensitivity sharply decreases as the surface potential is neutralized by photocurrent. As a result, space charge accumulates,
The residual potential increases, the surface potential becomes unstable, the charge transport material deteriorates, and the sensitivity and durability decrease.

Since the dependence of the charge mobility on the electric field depends on the activation energy of the charge transfer and the temperature, various attempts have been made to improve the dependence on the electric field. For example, as an improvement method by reducing the activation energy,
Attempts have been made to reduce impurities as much as possible to eliminate traps, but it is impossible to completely remove impurities because the charge transport material is an organic substance, and satisfactory results have not been obtained. Also, the molecular design of the charge transport material that reduces the activation energy has been studied, but the cause of reducing it has not been clarified yet, and satisfactory results have not been obtained for this (for example, Journal of Applied Physics, Vol. 69, No. 2, 821 (1991)).

On the other hand, regarding temperature, it is known that the closer the operating temperature is to the glass transition point of the charge transport layer, the smaller the electric field dependence of the charge mobility is (for example, chemicals).
Physics Letters, Vol. 153, No. 5, 422 (1988)). That is, when the photoconductor is used near the glass transition point of the charge transport layer, the residual potential is small and high sensitivity and high durability can be obtained. However, the glass transition point of the charge transport layer of a commonly used photoreceptor is 100
Since it is around ℃, it is not practical to use a copying machine, printer, etc. at such a high temperature, and even if only the periphery of the photoconductor is kept at that temperature, the charge transport material and the binder are easily oxidized and decomposed. On the contrary, the durability is lowered. Further, in the vicinity of such a glass transition point, the wear resistance of the charge transport layer decreases, which also decreases the durability. As described above, it has been practically impossible to reduce the electric field dependency by adjusting the use temperature of the charge transport layer.

[0010] Therefore, the fact that the glass transition point of the charge transport layer itself is optimized to improve the electric field dependence of the charge mobility has not been known in the past. By the way, with respect to the glass transition point of the binder used in the photosensitive layer, there is an invention in which it is set in a specific temperature range for the purpose of improving the mechanical strength, coating property, coatability, durability and the like of the photosensitive layer. Although reported (Japanese Patent Application Laid-Open No. 58-192040 and Japanese Patent Application Laid-Open No. 58-19204).
No. 1, JP-A-58-189642, JP-A-SHO-5
No. 8-193549, JP-A-58-70230, etc.), but none of them has improved the electric field dependence of the charge mobility.

The object of the present invention is exactly this point, and as a solution to such a problem, by lowering the glass transition point of the charge transport layer as compared with the conventional one, it is possible to obtain high sensitivity and high durability which can be put to practical use. An object is to provide an electrophotographic photoreceptor.

[0012]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention provides an electrophotographic photosensitive member comprising a conductive support and a photosensitive layer having a charge generation layer and a charge transport layer as essential components, and the glass transition point of the charge transport layer is 50 ° C. The present invention relates to an electrophotographic photosensitive member having a temperature of 70 ° C. or lower.

Examples of the base material of the conductive support in the present invention include metals such as aluminum and nickel, metal evaporated polymer films, metal laminated polymer films, and the like, and the shape thereof is, for example, a drum shape or a sheet. The shape may be any shape, such as a belt shape and a belt shape. The charge generation layer in the present invention comprises a charge generation material and, if necessary, a binder, an additive and the like, and examples of the manufacturing method thereof include a coating method, a vapor deposition method, a CVD method and the like.

The charge generating material is not particularly limited as long as it absorbs light of a specific wavelength and efficiently generates charges, and either an organic material or an inorganic material can be used. .. Examples of organic materials include perylene pigments, polycyclic quinone pigments, metal-free phthalocyanines, metal phthalocyanines, bisazo pigments, trisazo pigments, thiapyrylium salts, squarium salts, and azurenium pigments, which are mainly dispersed in a binder. Used. Examples of the inorganic material include selenium, selenium alloy, cadmium sulfide, zinc oxide, amorphous silicon, amorphous silicon carbide and the like.

The binder used as necessary includes
There is no particular limitation, for example, polycarbonate,
Condensation polymers such as polyarylate, polyester, polyamide; polyethylene, polystyrene, polyacrylate, polymethacrylate, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, styrene-acryl copolymer, styrene- Addition polymers such as maleic anhydride copolymers and acrylonitrile-butadiene copolymers; polysulfones, polyether sulfones, silicone resins, phenoxy resins and the like are preferably used. Of these, alone or in admixture of two or more. You may use. The amount of the binder used is 0.
1% to 80% by weight, preferably 10% by weight
It is 70% by weight. If the amount is more than 80% by weight, the sensitivity of the photoconductor is sharply reduced.

Additives used as required include
Examples thereof include antioxidants, ultraviolet absorbers, dispersants, pressure sensitive adhesives, sensitizers and the like. The film thickness of the charge generation layer produced using the above materials is 0.1 μm to 5.0 μm, preferably 0.1 μm to 2.0 μm. 0.1
If it is less than μm, the sensitivity is insufficient, and if it is more than 5.0 μm, the charging characteristics are deteriorated.

The charge transport layer in the present invention is usually provided as a thin film on the charge generating layer. The glass transition point of the charge transport layer in the present invention is 50 ° C. or higher and 70 ° C. or lower (measured by a differential thermal analysis method or a viscoelasticity measurement method). Within this range, the electric field dependence of the charge mobility is small, and for example, when a hydrazone compound is used as the charge transport material, an electric field of 2 × 10 ⁵ V / cm produces 10 ⁻⁶ cm ² / V ·
It is of the order of s, and the charge mobility does not decrease remarkably even in the electric field of 2 × 10 ⁴ V / cm.
^-Keeps the order of ^-6 cm ² / ^Vs. Thereby, the sensitivity and durability can be improved. If the glass transition point of the charge transport layer is less than 50 ° C., the abrasion resistance is lowered, and if it exceeds 70 ° C., the electric field dependence of the charge mobility becomes large, which is not preferable.

Here, as a method of adjusting the glass transition point of the charge transport layer, for example, the following three methods are used because it comprises a charge transport material, a binder, and an additive added as necessary. is there. 1) A charge transport material having a low melting point is used. 2) A binder having a low glass transition point is used. 3) Additives such as plasticizers are used. Any of the above methods can be used, and these can be used alone or in combination. Among them, the method of using a binder having a widest selection range and a low glass transition point is particularly effective.

The charge transporting material in the present invention is not particularly limited as long as the glass transition point of the charge transporting layer is 50 to 70 ° C. after preparation, and for example, a hydrazone compound, a stilbene compound, a butadiene compound. , Triarylamine compounds, bistriarylamine compounds, carbazole compounds, polyvinylcarbazole compounds, oxadiazole compounds, oxazole compounds, pyrazoline compounds, triphenylmethane compounds and the like. In the present invention, those having a low melting point are preferably used, and the melting point thereof is usually 50 to 250 ° C, preferably 70 to 200 ° C. You may use these individually or in mixture of 2 or more types.

As the binder in the present invention, a binder having a low glass transition point and excellent mechanical properties and abrasion properties so that the glass transition point of the charge transport layer is 50 to 70 ° C. after preparation. There is no particular limitation. Specifically, for example, condensation type polymers such as polycarbonate, polyarylate, polyester, polyamide; polyethylene, polystyrene, polyacrylate, polymethacrylate, polyvinyl butyral, polyvinyl acetal,
Addition polymers such as polyvinyl formal, polyacrylonitrile, polyacryloamide, styrene-acrylic copolymer, styrene-maleic anhydride copolymer, acrylonitrile-butadiene copolymer; polysulfone, polyether sulfone, silicone resin, phenoxy resin And the like, and these may be used alone or in combination of two or more. At this time, the glass transition point is 50 ° C. or higher 14
Those having a temperature of 0 ° C. or lower are preferably used.

The content of the binder in the present invention is 0.1 to 80% by weight of the charge transport layer, preferably 1%.
It is 0% to 70% by weight. If it is less than 0.1% by weight, abrasion resistance and coating property are deteriorated, and if it is more than 80% by weight, the sensitivity of the photoreceptor is drastically decreased due to decrease in charge mobility. Examples of additives used as necessary include antioxidants, ultraviolet absorbers, lubricants, plasticizers, and the like. Among these, antioxidants and plasticizers are also effective for adjusting the glass transition point of the charge transport layer. The addition amount of these is usually 10% by weight or less of the charge transport layer, and if it exceeds 10% by weight, the charge mobility is lowered.

In the present invention, the glass transition point of the charge transport layer is adjusted to 50 ° C. or higher and 70 ° C. or lower by appropriately selecting the charge transport material, binder and additive as described above.

For preparing the charge transport layer in the present invention, for example, a dip coating method, a spray coating method, a roll coater method or the like can be used. The thickness of the charge transport layer produced is 10 μm to 50 μm, preferably 10 μm to
It is 30 μm. If the film thickness is larger than 50 μm, it takes a long time to transport the charges, and the probability of trapping the charges is large, which causes a decrease in sensitivity.
On the other hand, when it is less than 10 μm, the mechanical strength is lowered,
It is not preferable because the life of the photoreceptor is short.

In the present invention, if necessary, an intermediate layer such as an adhesive layer or a barrier layer may be provided between the conductive support and the charge generating layer. For example, polyamide, polyvinyl butyral or the like may be provided in these layers. The insulating resin, the conductive inorganic fine powder dispersed in the insulating resin, or the conjugated polymer such as polypyrrole ion-doped into the conductive polymer can be used. A protective layer may be provided on the surface of the photoconductor.

In using the electrophotographic photosensitive member of the present invention, the surface of the photosensitive member is first charged negatively by a corona charger or the like. After charging, by exposure, charge is generated in the charge generation layer, and positive charges are injected into the charge transport layer,
This is transported to the surface through the charge transport layer, and the surface negative charges are neutralized. On the other hand, negative charges remain in the unexposed areas. In the case of regular development, positively charged toner is used, and the toner is attached to the portion where the negative charge remains to be developed. In the case of reversal development, negatively charged toner is used, and the toner adheres to the portion where the charge is neutralized, and the toner is developed. The electrophotographic photosensitive member according to the present invention can be used in any developing system and can provide high image quality.

In the present invention, when the charge transport layer is provided between the conductive support and the charge generating layer, first the surface of the photoreceptor is positively charged, and after exposure, the negative charge generated is generated in the photoreceptor. The surface charges will be neutralized and the positive charges will be transported to the conductive support through the charge transport layer.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 4.1 g of X-type metal-free phthalocyanine, polyvinyl butyral (S-REC W-200, manufactured by Sekisui Chemical Co., Ltd.)
1 g, cyclohexanone 200 g, and glass beads (diameter 1 mm) 650 g were put in a sand mill and dissolved and dispersed for 2 hours to prepare a charge generation layer coating material. An aluminum cylinder (40 mm in diameter) having a mirror-finished surface using the coating composition was dip-coated so that the film thickness after drying was 0.15 μm, and dried at 70 ° C. for 1 hour. Next, equation (1)

[0029]

[Chemical 1]

80 g of the hydrazone compound represented by and 80 g of a polyester resin (Vylon 200, Tg = 67 ° C., manufactured by Toyobo Co., Ltd.) were dissolved in 450 g of chloroform to prepare a coating material for the charge transport layer. The coating material was applied onto the charge generation layer previously applied so that the film thickness after drying would be 25 μm, and dried at 70 ° C. for 1 hour. The glass transition point of the charge transport layer separately prepared by the same method was measured by the differential thermal analysis method (D
When measured by SC210, manufactured by Seiko Denshi KK, it was 59 ° C.

The electrophotographic characteristics of the drum-shaped electrophotographic photosensitive member produced as described above were evaluated by a drum xerographic tester (evaluation temperature of the photosensitive member was 25 ° C.). -5.5
When charged with a corona voltage of kV, the initial surface potential V
₀ was -750V. The surface potential V ₂ after standing for 2 seconds in the dark became −740V. The oscillation wavelength is 780
nm semiconductor laser (1 μW) was irradiated and the half-exposure amount E _1/2 was determined to be 0.28 μJ / cm ² .
Residual potential V _R was -0.2V.

After repeating the above operation 5,000 times, V
_0, V _2, E _1/2, was measured V _R, respectively -
750V, -740V, 0.30 μJ / cm ² , -1.
It was 3 V and showed high sensitivity and high durability. Next, the electrophotographic photosensitive member manufactured by the same method as above was mounted on a commercially available laser beam printer of the reversal development system by the blade cleaning system, and a print test was conducted. as a result,
The initial image density was 1.4 (using a Macbeth densitometer), and the image density after printing 50,000 sheets was 1.3, which showed no blurring of letters or memory phenomenon while maintaining high density. It turned out that it was a high-performance photoconductor.

Example 2 In Example 1, instead of the polyester resin as the binder of the charge transport layer, a methacrylic resin (Acrypet M) was used.
D, Tg = 97 ° C., manufactured by Mitsubishi Rayon Co., Ltd. An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that it was used. The glass transition point of this charge transport layer is 6
It was 8 ° C. As a result, the initial V ₀ , V ₂ , E _1/2 ,
V _R, respectively -750V, -730V, 0.30μJ
/ Cm < ² >, -0.4V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 , and V _R were measured, and were -730 V, -720 V, and 0.30 μ, respectively.
J / cm ² , -1.7V, showing high sensitivity and high durability.

Example 3 In Example 1, instead of the polyester resin as the binder of the charge transport layer, a phenoxy resin (PKHH, Tg) was used.
= 100 ° C., manufactured by Union Carbide Co., Ltd.), an electrophotographic photosensitive member was produced in the same manner as in Example 1,
evaluated. The glass transition point of this charge transport layer is 68 ° C.
Met. As a result, initial V ₀ , V ₂ , E _1/2 , V _R
Are -740V, -730V, 0.28μJ / c, respectively.
m ^2, was -0.4V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 , and V _R were measured, and they were −730 V, −720 V, and 0.29 μJ /, respectively.
It was cm ² and −1.0 V, and showed high sensitivity and high durability.

Comparative Example 1 In Example 1, except that a polycarbonate resin (Lexan 131-111, Tg = 137 ° C., manufactured by Engineering Plastics Co., Ltd.) was used as the binder for the charge transport layer instead of the polyester resin. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1. The glass transition point of this charge transport layer was 101 ° C. As a result, initial V ₀ , V ₂ , E _1/2 , and V _R are −7, respectively.
80V, -760V, 0.42μJ / cm ² , -38V
Met. Next, after repeating the above operation 5,000 times,
When V ₀ , V ₂ , E _1/2 and V _R were measured, they were −760 V, −740 V, 0.45 μJ / cm ² and −8, respectively.
The voltage was 6 V, which was inferior in both sensitivity and durability.

Example 4 In Example 1, instead of the X-type metal-free phthalocyanine as the charge generating material, the formula (2) was used.

[0037]

[Chemical 2]

An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that dibromoanthanthrone represented by the formula (1) was used. The glass transition point of this charge transport layer was 59 ° C. It was The obtained photoreceptor is -5.5 kV
When charged at a corona voltage of, the initial surface potential V ₀ was −720V. The surface potential V ₂ after standing for 2 seconds in the dark became −710V. Then, a halogen lamp with an illuminance of 5 lux was irradiated to determine the half-exposure amount E _1/2, which was 1.1 lux · sec, and the residual potential V _R was −.
It was 0.2V. Next, after repeating the above operation 5,000 times, V ₀ , V ₂ , E _1/2 and V _R were measured, and they were −710 V, −700 V, 1.1 lux · sec, respectively.
It was −2.8 V, and showed high sensitivity and high durability.

Comparative Example 2 In Example 4, except that a polycarbonate resin (Lexan 131-111, Tg = 137 ° C., manufactured by Engineering Plastics Co., Ltd.) was used instead of the polyester resin as the binder for the charge transport layer. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 4. The glass transition point of this charge transport layer was 101 ° C. As a result, initial V ₀ , V ₂ , E _1/2 , and V _R are −7, respectively.
50V, -730V, 1.4lux · sec, -43V
Met. Next, after repeating the above operation 5,000 times,
When V ₀ , V ₂ , E _1/2 and V _R were measured, they were −730 V, −720 V, 2.4 lux · sec and −1, respectively.
It was 32 V, which was inferior in both sensitivity and durability.

Example 5 In Example 1, instead of the hydrazone compound represented by the formula (1) as the charge transport material, the formula (3) was used.

[0041]

[Chemical 3]

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that the triarylamine compound represented by the formula (1) was used. The glass transition point of this charge transport layer was 63 ° C. As a result, the initial V ₀ , V ₂ , E
_1/2, V _R respectively -730V, -720V, 0.2
It was 3 μJ / cm ² and 0V. Next, after the above operation was repeated 5,000 times, V ₀ , V ₂ , E _1/2 and V _R were measured and found to be −720 V, −710 V and 0.24 μ, respectively.
J / cm ² , -1.1V, showing high sensitivity and high durability.

As described above, the electrophotographic photoreceptors of the present invention shown in Examples 1 to 5 have a glass transition point of the charge transport layer within the range of 50 to 70 ° C., and have high sensitivity and high durability. However, in Comparative Examples 1 and 2 in which the glass transition point was as high as 101 ° C., both sensitivity and durability were inferior.

[0044]

According to the present invention, by setting the glass transition point of the charge transport layer to 50 ° C. or higher and 70 ° C. or lower, it can be put to practical use in an organic photoreceptor having advantages such as no pollution and easy mass production. A highly sensitive and highly durable electrophotographic photoreceptor can be obtained.

Claims (1)

Claim: What is claimed is: 1. An electrophotographic photosensitive member comprising a conductive support and a photosensitive layer having a charge generation layer and a charge transport layer as essential components on the conductive support, and a glass of the charge transport layer. Transition point is 5
An electrophotographic photoreceptor having a temperature of 0 ° C. or higher and 70 ° C. or lower.