JPH04125565A - Organic electrophotographic sensitive drum and cylindrical conductive body used for this drum - Google Patents

Abstract

PURPOSE:To enhance the productivity of the photosensitive body and to lessen unequal characteristics by specifying the heat conduction quantity per unit area to the volumetric heat capacity of a cylindrical conductive base body. CONSTITUTION:This photosensitive drum is provided with the photosensitive layer formed by applying a coating liquid contg. a photoconductive org. compd. on the cylindrical conductive base body and drying the coating. The value of k/d is specified to >=0.1 where the volumetric heat capacity of the base body is designated as D (cal/cm<2>.K) and the heat conduction quantity per unit area of the base body as k (cal/sec.K). The base body is formed at the thickness at which the value of k/d attains >=0.1 according to the outside diameter of the base body and the base body is preferably formed of aluminum or a material essentially consisting of the aluminum.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention provides an organic electronic device having a photosensitive layer formed by coating and drying a coating liquid containing a photoconductive organic compound on the surface of a cylindrical conductive substrate. The present invention relates to a photographic photosensitive drum and a cylindrical conductive substrate used therein.

[Conventional technology]

The currently used manufacturing method for organic electrophotographic photosensitive drums involves applying a coating solution containing a binder resin, such as a dispersion of an organic photoconductive pigment or a solution of an organic photoconductive compound, onto a cylindrical conductive substrate and drying it. A method is adopted in which photosensitive drums are manufactured through the following steps.

This manufacturing method is applicable to 5e-Te system, ^s, Se3 system,
Continuous production is possible, and it can be said to be advantageous in terms of process, compared to manufacturing methods using vapor deposition or plasma CVD processes on photosensitive drums such as the a-3l series.

A photosensitive drum to which this manufacturing method can be applied is prepared by coating and drying a dispersion of an organic pigment such as a phthalocyanine compound or an azo compound to form a charge generation layer, and then applying a pyrazoline compound, a hydrazone compound, or an oxazoide compound thereon. Diazole compound.

A functionally separated organic electrophotographic photosensitive drum has been developed in which a charge transport layer is formed by coating and drying a binder resin solution containing styryl compounds, etc., and it has advantages not only in terms of characteristics but also in terms of production such as processability and cost. As a result, its range of applications is expanding.

[Issues that Hathu tries to solve]

However, in the above-mentioned manufacturing method, non-uniform heating during coating and drying causes uneven charging and uneven sensitivity, which are problematic in terms of the characteristics of the photosensitive drum, and causes a decrease in process yield. Due to non-uniform heating, the vaporization rate of the solvent in the coating solution varies locally, resulting in non-uniform concentrations of functional substances such as photoconductive compounds in the photosensitive layer, and non-uniform morphology of the photosensitive layer. As a result, it is thought that unevenness in characteristics occurs. In order to avoid such problems, conventionally, in the drying process, the solvent was vaporized in the coating machine's natural state, and the coating film was made to have no fluidity, and then hot air was dried to remove the remaining solvent and cure the coating. However, there were problems such as it was time consuming and the yield was not necessarily good.

The present invention solves the above-mentioned problems, and provides an electrophotographic photosensitive drum and an electrophotographic photosensitive drum used therein, which can be manufactured with high productivity using a coating and drying process, and which have stable and good properties with little unevenness. The problem is to provide a cylindrical conductive substrate.

[Means to solve the problem]

In order to solve the above problems, according to this publication, a coating liquid containing a photoconductive organic compound is applied to a cylindrical conductive substrate.
In an organic electrophotographic photosensitive drum having a photosensitive layer formed by drying, the volumetric heat capacity of the cylindrical conductive substrate is d.
cal /ctl-, and the amount of heat conduction per unit cross section of the cylindrical conductive substrate is k cat /5ec-
When the value of /d of the cylindrical conductive substrate is 0
．． 1 or more.

The cylindrical conductive substrate used in such a photosensitive drum has a wall thickness of 0.0000000000000000000000000000000000000000000000000000000000,000.
This is a cylindrical conductive substrate with a diameter of 1.

The material for the cylindrical conductive substrate is preferably aluminum or a material containing aluminum as a main component.

[Effect]

When applying a coating liquid to an H-cylindrical conductive substrate and drying it, a method is adopted in which a large number of substrates are placed in a dryer in order to increase productivity. At this time, the substrate is statically covered, and the hot air generated by the dryer is blown against the substrate unevenly; Even if the structure of the dryer is devised so that hot air at a constant temperature is always blown over the entire substrate, there will always be an upwind side and a leeward side of the hot air, making it difficult to uniformly heat the entire substrate. It is. This is
During drying, a difference in temperature distribution occurs on the substrate, resulting in uneven characteristics of the photosensitive drum.

In view of this, as a result of repeated and intensive studies focusing on the thermal characteristics of cylindrical conductive substrates, we have found that a substrate manufactured to satisfy a specific relationship between the specific heat and thermal conductivity of the substrate is used. It has been found that the above-mentioned drying problems can be solved by this method. In other words, in order to minimize the difference in temperature distribution of the substrate during drying, which causes unevenness in characteristics such as uneven charging of the photosensitive drum, it is necessary to spread heat as quickly as possible on the inner surface of the substrate to prevent heat from accumulating locally. That's fine. The degree of heat diffusion is determined by the ratio of the amount of heat conduction per unit cross section, which is a measure of the ease of heat transfer, and the volumetric heat capacity, which is a measure of the ease of warming.

When the volumetric heat capacity of the substrate is d cal /ci -K and the amount of heat conduction per unit cross section is k cal /5ec-, if the value of /d is 0.1 or more, there is a problem with the drying conditions by the dryer. Differences in temperature distribution of the substrate during drying due to uniformity can be suppressed within a range that does not pose a practical problem.

In order to make the value of /d of the cylindrical conductive substrate 0.1 or more, it is necessary to set the thickness of the substrate to an appropriate value depending on the outer diameter of the substrate. Naturally, this wall thickness will change if the material of the base changes.

In this way, the value of /d is 0,
By using one or more cylindrical conductive substrates, it is possible to produce a highly productive organic electrophotographic photosensitive drum using a coating and drying process, and to obtain a stable and good organic electrophotographic photosensitive drum with little unevenness in characteristics.

〔Example〕

The relationship between the characteristic unevenness caused by the drying process of the photosensitive drum and the thermal characteristics of the substrate is shown below.

The investigation was conducted using a charge generation layer of a functionally separated organic electrophotographic photosensitive drum. The coating solution for the charge generation layer was prepared by dispersing titanyl phthalocyanine in a polyester resin using THF as a solvent using a vibration mill. , the pigment to binder ratio is 10%, and the solid content ratio is 2%. This coating solution was applied by a dip method onto substrates having different thermal properties, and then dried in a hot air dryer for 1 hour while blowing hot air at 120°C at a flow rate of 0.5 m for 7 minutes.

The film thickness after drying was 0.2 μm. On the charge generation layer thus formed, a polycarbonate solution containing p-diethylaminobenzaldehyde-N,N-diphenylhydrazone was applied as a charge transport layer to a dry film thickness of 20 μm.
A photosensitive drum was prepared by coating and drying so as to give a thickness of m.

The cylindrical conductive substrate used had an outer diameter of 80 g and a length of 340 mm, and was made of different materials and wall thicknesses.
Shown in the table.

Table 1 Thermal conductivity was measured by cutting the substrate 1 into an I0m square as shown in FIG. 3 and using a conventional method. Substrate (^) or D)
Although they are made of the same material, the thickness of the base body is different, and the amount of heat conduction per unit cross section is different.

A dryer shown in FIG. 4 was used to dry the coating film in order to minimize the effects of drying conditions and dryer structure. In FIG. 4, air heated by a heater 101 is blown into the upper hollow part of the dryer by a blower 102 through a ventilation duct H, 03. The hot air is always uniformly sent through the upper mesh 1104 from top to bottom over the entire surface of the upper mesh 104. The hot air that has heated and dried the substrate 105 is discharged to the outside of the dryer through the lower mesh 106. Dryer internal volume 0.2m', air volume 0.5m'/min,
When we investigated the relationship between the drying time and the temperature difference between the upper and lower parts of the substrate when the hot air temperature was 120°C and the number of substrates was 16, we found that the fifth
The results shown in the figure were obtained. Each am is the base (A)
, (B), (C), and (D), and show the temperature difference between a position X 5 cm from the top and a position Y 5 cm from the bottom of the substrate.

As seen in FIG. 5, the temperature rise at the initial stage of drying differs greatly between the upper and lower parts of the substrate depending on the substrate. In other words, there are large differences in temperature distribution depending on the substrate. Photosensitive drums manufactured under such conditions will have significantly different degrees of characteristic unevenness depending on the thermal characteristics of the substrate.

FIG. 2 shows potential characteristic distributions of photosensitive drums manufactured using substrates (B) and (D) in Table 1, respectively. The potential characteristics were measured by charging the sample with a corona charger of v to an applied voltage of -6 using a process simulator, and then exposing it to light. There were four measurement points in the axial direction of the photosensitive drum. In Figure 2, the horizontal axis shows the axial distance of the photosensitive drum, the vertical axis shows the surface potential, and each plot shows the average surface potential of the surface potential around the measurement point, and the vertical line in each plot shows the surface potential around the surface. The maximum and minimum potential values are connected to show the dispersion. In addition, the dark potential,
The solid line for both the open-circuit potential and the photosensitive drum using the substrate (B);
The dotted line relates to the photosensitive drum using the substrate (D).

As seen in FIG. 2, the photosensitive drum using the substrate (B) has less unevenness and is better in both the dark area potential and the bright area potential than the photosensitive drum using the substrate (D).

The cause of potential unevenness is thought to be that during drying, dispersed pigment particles cause localized non-uniform agglomeration and concentration changes due to differences in drying speed due to differences in temperature distribution of the substrate. .

In order to reduce the difference in temperature distribution of the substrate during drying, it is necessary to use a substrate that has a large amount of heat conduction and does not cause a temperature gradient, and has a small specific heat so that the temperature quickly changes when heat is transferred. Something that rises is desirable.

As a result of examining the relationship between the thermal characteristics of the substrate (^) or F) shown in Table 1 and the potential unevenness of the photosensitive drum, we found that the volumetric heat capacity dcal/c of the substrate and the amount of heat conduction per unit cross section It was confirmed that a substrate having thermal characteristics with a relationship of /d≧01 between k cal /sac -K can be dried uniformly and a photosensitive laminate with small potential unevenness can be obtained. . The relationship between potential unevenness and i is shown in FIG. 1. When k/d<0.1, large potential unevenness occurs, which is undesirable.

The above-mentioned /d represents how quickly the temperature distribution can be made uniform when non-uniform temperature distribution occurs on the substrate during the drying process. Since the thermal properties of the substrate play an essential role in making the temperature distribution uniform during the drying process, the present invention is also effective when applied to various photosensitive drums.

Specific examples will be described in detail below.

Example 1 A photosensitive drum was manufactured using a cylindrical conductive substrate having an outer diameter of 80 mm, a length of 340 μm, and a thermal resistance shown in Table 1. The ratio of the volumetric capacity dcal/cm3- of each substrate to the thermal conductivity per unit cross section kcal/5ec-/d
is the value shown in Table 2.

Table 2 A charge generation layer coating solution having the following composition was applied onto these substrates and dried to form a charge generation layer having a thickness of 70.2 μm. Next, a charge transport layer coating liquid having the following composition is applied on top of this.
It was dried to form a charge transport layer having a thickness of 20 μm (7) to prepare a photosensitive drum.

Coating liquid for charge-generating layer - 1 part by weight of α-type metal-free phthalocyanine 100 parts by weight of tetrahydrofuran Coating liquid for charge-transporting layer - 4 parts of tetrahydrofuran, toluene
The 4 parts by weight coating solution for the charge generation layer was dispersed in a vibrating mill for 3 hours before use. The coating was done by the dip method, and the drying was done at 120°C using the dryer shown in Figure 4.
The test was carried out for 1 hour while blowing hot air at a flow rate of 0.5 m + 7 minutes.

Table 3 shows the results of examining the difference between the maximum and minimum charged potential within the photoreceptor for each of the photoreceptor drums thus obtained.

Table 3 Further, the relationship between k/d and potential unevenness is shown in FIG.

From Table 3 and Figure 1, as for the thermal characteristics of the substrate, when the value of /d is less than 0.1, potential unevenness is likely to occur on the photosensitive drum due to the drying process. It can be seen that the value of hani/d must be 1 or more.

Example 2 In Example 1, the substrates used are (^) and (B).

Example 1 except that the four types (C) and (D) were used, and the drying conditions at the time of forming the charge generation layer were changed as shown in Table 4.
A photosensitive drum was produced in the same manner as above, and the potential unevenness of the obtained photosensitive drum was examined. The results are shown in Table 4.

From Table 4, it can be seen that as the air volume becomes extremely large and as the hot air temperature becomes high, potential unevenness is more likely to occur.
This tendency is remarkable when the /d of the substrate is less than 0.1,
k/d is 0. ] or above is desirable.

〔Effect of the invention〕

According to this invention, the value of /d regarding the thermal characteristics of a cylindrical conductive substrate used in an organic electrophotographic photosensitive drum is selected to be 0. IB
By using a substrate with such specified thermal properties, it is possible to manufacture an organic electrophotographic photosensitive drum with high productivity using a method that employs a coating and drying process, and which is stable and good with little unevenness in properties. can be obtained. It is preferable to use aluminum or a material containing aluminum as a main component as the material for such a base because it has good productivity, is lightweight, and is easy to handle.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between /d and potential unevenness of the photosensitive drum substrate, and Fig. 2 is a diagram showing the relationship between the photosensitive drum using the substrate (B) and the photosensitive drum using the substrate CD) in the axial direction of the photosensitive drum. A diagram showing the surface potential characteristic distribution, Fig. 3 is a perspective view of the sample to be measured for heat conduction per unit cross section of the substrate, Fig. 4 is a conceptual diagram of the dryer used in the example, and Fig. 5 is the same as Fig. 4. A diagram showing the relationship between the drying time in the dryer and the temperature difference between the upper and lower parts of the substrate.

Claims (1)

[Scope of Claims] 1) An organic electrophotographic photosensitive drum comprising a photosensitive layer formed by coating and drying a coating liquid containing a photoconductive organic compound on a cylindrical conductive substrate, wherein The volumetric heat capacity is dcal/cm^3・K, and the amount of heat conduction per unit cross section of the cylindrical conductive substrate is kcal/se.
An organic electrophotographic photosensitive drum characterized in that the cylindrical conductive substrate has a k/d value of 0.1 or more when c·K. 2) A cylindrical conductive substrate used in an organic electrophotographic photosensitive drum, with a volumetric heat capacity of dcal/cm^3·K,
When the amount of heat conduction per unit cross section is kcal/sec・K, the value of k/d is 0 depending on the outer diameter of the cylindrical conductive substrate.
．． A cylindrical conductive substrate having a wall thickness of 1 or more. 3) The cylindrical conductive substrate according to claim 2, wherein the cylindrical conductive substrate is made of aluminum or a material containing aluminum as a main component.