JPS63261266A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity of a photosensitive body by using a bisphenol Z type polycarbonate specified in molecular weight for the binder polymer of an electric charge transfer layer. CONSTITUTION:The photosensitive body is formed by successively laminating on a conductive substrate 31 an undercoat layer 33, a charge generating layer 35 made of indium phthalocyanine, and a charge transfer layer 37 containing a hydrazone derivative (B) dispersed into the binder polymer (A) prepared by using the bisphenol A type polycarbonate having a molecular weight of about 20,000-40,000 represented by the formula shown on the right. 1,2,3,4- tetrahydroquinoline-6-carboxyaldehyde and the like can be used for the derivative (B). The layer 35 can be formed by the vapor deposition method or the like, and the layer 37 can be formed by the dip coating method and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor, and particularly relates to a functionally separated type electrophotographic photoreceptor with excellent sensitivity.

(Prior Art) Electrophotographic photoreceptors (hereinafter sometimes abbreviated as photoreceptors) are well known and are expected to be incorporated into, for example, copiers, printers, and the like.

Such photoreceptors have various structures, but in recent years, the mainstream of development has been functionally separated electrophotographic photoreceptors in which a charge generation layer and a charge transport layer are laminated on a conductive support. It becomes. Regarding this, the applicant of this application also disclosed in Japanese Patent Application Laid-open Nos. 59-44054 and 59-174845,
We proposed a functionally separated electrophotographic photoreceptor using a specific phthalocyanine or a mixture thereof in the charge generation layer. The structure of such a conventional photoreceptor will be described in more detail below by giving an example. That is, a charge generating layer is formed by depositing a charge generating substance on a conductive support, and then a solution of a mixture of a charge transporting material and a binder polymer dissolved in an organic solvent is applied and dried to form a charge generating layer. It forms a layer.

Here, in order to deepen the understanding of the photoreceptor as described above, an example of the use of such a photoreceptor will be briefly described. Figure 3 (A) is a perspective view schematically showing an example of a Hitotsubashi structure of a photoreceptor. This figure shows a photosensitive drum 1 that has a charge generation layer and a charge transport layer sequentially provided on the surface of a drum-shaped conductive support.
1 is shown. Further, FIG. 3(B) is a diagram schematically showing the configuration of a laser beam printer incorporating this photosensitive drum 11.

In such a laser beam printer, the photosensitive drum 11 is rotated in a predetermined direction during use. Furthermore, such a laser beam printer has a photosensitive drum 1.
The charger 1 is placed around the photoreceptor drum 11 in a position facing the photoreceptor drum 11 and along the rotational direction of the photoreceptor drum 11.
3. A laser light source 15, a developing device 17, and a transfer device 19 are sequentially provided. As the photosensitive drum 11 rotates, the following processes are sequentially performed, and as a result, an image is formed on the recording medium.

First, the charger 13 charges the photoreceptor drum 11.
The partial area facing 3 is charged. Thereafter, when this charged area faces the laser light source 15, an electrostatic latent image is formed on the surface of the photoreceptor by selective irradiation of image information (responsive laser light). When it faces a developing device 17 provided downstream, it is developed with toner.The image-shaped toner on the photoreceptor is transferred onto a recording medium 21 at a position where a transfer device 19 is provided. The toner transferred onto the medium 21 is subjected to a predetermined printing process, etc., and an image is formed on the recording medium 21.

The photoreceptor used in such devices must be charged with a small amount of energy, and the initial potential and residual potential after charging must be constant even after repeated charging many times. It has basic characteristics such as not being affected by ambient temperature, and the necessary sensitivity.

By the way, as already explained, the charge transport layer of a functionally separated photoreceptor is made by dispersing a charge transport material in a binder polymer. As such binder polymers, styrene resin, acrylic jugetsuji, polyester jugetsuji, hisphenol A type polycarbonate resin, etc. are known, and among these resins, bisphenol A type polycarbonate resin (see (V) below) is known. Formula) has been frequently used because it is superior to other resins in both charge retention and compatibility with charge transport materials.

The conventional sphenol A type polycarbonate resin that has been used in this way has a molecular weight of about 30,000.

(Problem to be solved by the invention) However, even if various functionally separated photoreceptors are constructed using various conventionally known resins as described above as binder polymers, there may be problems due to differences in the resins. The sensitivity of the photoreceptor did not improve. In particular, the inventor of this application used indium phthalocyanine as the charge generating layer as disclosed in JP-A-59-44054 and JP-A-59-174,845, and furthermore, the binder polymer resin was as described above. When various photoreceptors were constructed and the ability to improve the sensitivity of these photoreceptors was investigated, no improvement in sensitivity was found due to differences in resin.

On the other hand, in devices such as laser beam printers,
One important requirement is the ability to perform high-speed printing, and this requirement will become increasingly important in the future. Conventionally, the printing speed of optical printers such as small laser printers was about 10 pages/minute, but from now on, medium-speed printers of about 30 pages/minute,
High-speed blinking of 40 sheets/minute or more is increasing. In addition, even in low-speed printers with a printing speed of about 10 sheets/min, the size of printers is becoming increasingly smaller, and the diameter of the photoreceptor drum must be reduced. As the drum diameter becomes smaller, the time from charging to exposure and development becomes shorter.

As described above, in printers with any printing speed, the linear velocity of the photoreceptor drum tends to increase, but since the output of the light source remains constant, as a result (the time for exposing the photoreceptor to light becomes shorter). Therefore, a highly sensitive photoreceptor is required.

. Therefore, in order to make such an attempt possible, it is desired to develop a photoreceptor that is more sensitive than the conventional one.

This invention has been made in view of the above-mentioned points, and therefore, the purpose of this invention is not only to have the above-mentioned basic characteristics but also to provide an electrophotographic device with higher sensitivity than the conventional one. The purpose is to provide a photoreceptor.

(Means for Solving the Problems) In order to achieve this objective, the inventor of this application has conducted various experiments. As a result, in a functionally separated type photoreceptor, the charge generation layer is indium phthalocyanine, the charge transport material is a hydrazone derivative, and the resin that makes up the binder polymer is changed to various types. As a result of investigation, it was discovered that the sensitivity of a photoreceptor can be dramatically improved by using a certain type of resin as a binder polymer.

Therefore, according to the present invention, there is provided a functionally separated type electronic device comprising, on a conductive support, a charge generation layer of indium phthalocyanine, a charge transport layer having a charge transport material of a hydrazone derivative and a binder polymer of the charge transport material. In photographic photoreceptors, the binder polymer has a molecular weight of approximately 20,000~
It is characterized by being composed of about 40,000 bisphenol Z type polycarbonate (cyclohexyl type polycarbonate).

Further, in carrying out the present invention, the charge transport material is 1.2
, 3.4-tetrahydroquinoline-6-carpoxyaldehyde hydrazo, p-diethylaminobenzaldehyde diphenylhydrazone, or ethylcarbazolyldiphenylhydrazone.

(Function) According to such a configuration, as is clear from the experimental results described later, a photoreceptor with dramatically higher sensitivity can be obtained while the basic characteristics are the same as those of the conventional photoreceptor.

Although it is not clear why the sensitivity is increased like this,
Bisphenol Z-type polycarbonate resins having a molecular weight of about 20,000 to about 40,000 are believed to further enhance the charge transport properties of the charge transport material. In addition, it is thought that this is because carriers generated in the indium phthalocyanine charge generation layer are efficiently injected into the charge transport layer containing bisphenol Z type polycarbonate resin with a molecular weight of about 20,000 to about 40,000. It will be done.

(Examples) The present invention will be explained below using the following examples and comparative examples. However, although the embodiments of this invention described below are described with preferred designated materials and numerical conditions within the scope of this invention, these are merely illustrative and this invention does not apply to these materials and numerical conditions. It is clear that the conditions are not limited only.

In addition, FIG. 1 shows electrophotographic photoreceptors (
Hereinafter, it may be abbreviated as photoreceptor. ) is a cross-sectional view schematically showing the structure of a part of a photoreceptor. The part referred to here is I-I in Figure 3(A).
It corresponds to the part cut along the line. Although the photoreceptor in FIG. 1 is of a negatively charged type, the photoreceptor of the present invention is not limited to the structure shown in this figure, and may have other structures, for example, a subbing layer may be provided. It should be understood that it may be of a certain type (see FIG. 4) or of a positively charged type (see FIG. 5) (details will be described later).

In this example, the conductive support was 40 mm in diameter;
An aluminum pipe base (hereinafter sometimes abbreviated as base) with a total length of 250 mm is used. In FIG. 1, the part indicated by 31 corresponds to a part of this base.

A charge generation layer 33 of indium phthalocyanine is formed on the surface of the substrate 31 . In the case of this example, this indium phthalocyanine is a mixture of a phthalocyanine in which the central metal is indium and chlorine is bonded to this indium, and a phthalocyanine in which a portion of the hydrogen in the benzene ring surrounding the phthalocyanidi ring is replaced with chlorine. , that is, Japanese Patent Application Laid-Open No. 59-44054 (assuming that this is disclosed,
A vapor-deposited film of this was formed on the substrate 31 to a thickness of about 0.2 μm to form a charge generation layer 35. The thickness of the charge generation layer can be changed depending on the design, but in this embodiment, the thickness is preferably in the range of about 0.03 to about 0.3 um.

Next, on this charge generation layer 35, a coating liquid 11F for forming a charge transport layer having the following composition is applied! : charge transport layer 37 with a thickness of about 15 um by dip coating method.
The photoreceptor of Example 1 was obtained. The thickness of the charge transport layer can be changed depending on the design, but
Film thicknesses in the range of about 10 to about 25 um are preferred for this embodiment.

Coating solution 1> ■・・・Binder polymer Bisphenol Z with a molecular weight of about 20,000 to about 40,000 (viscosity average)
type polycarbonate (formula (I) below, Ubiloshi Z20
0, handmade by Mitsubishi Gas Chemical). 600z ■・・・Charge transport material 1.2.3.4-tetrahydroquinoline-6-carboxaldehyde hydrazone (formula (II) below, JP-A-1986
No. 0-146248, manufactured by Asan Fragrance Industry Co., Ltd.). 600
9゜■ Chloroform (special grade reagent, manufactured by Kanto Katei, containing 0.5% ethanol to prevent decomposition). 2000 mρ.

Application 11 A charge generation layer 35 is formed on the same substrate 31 as in Example 1 in the same manner as in Example 1.

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of about 15 um was formed by dip coating using a coating liquid 2 for forming a charge transport layer having the composition shown below. I got a body.

<Coating Solution 2> (2), (2)... The binder polymer and chloroform were the same as in Coating Solution 1.

■・・・Charge transport material p-diethylaminobenzaldehyde diphenylhydrazone (formula (III) below, (JP-A-60-146248)
Publication No.), (manufactured by Asan Fragrance Industry Co., Ltd.). 6009° Example 1
A charge generation layer 35 is formed on the same substrate 31 in the same manner as in Example 1.

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of about 15 um was formed by a dip coating method using a coating liquid 3 for forming a charge transport layer having the composition shown below. I got a body.

<Coating solution 3> (1), (2)... The binder polymer and chloroform were the same as in coating solution 1.

■...Charge transport material ethylcarbazolyldiphenylhydrazone (rV
) formula, Japanese Patent Application Laid-Open No. 61-40104, (manufactured by Anan Perfume Sangyo Co., Ltd.). 6009° A charge generation layer 35 is formed on the same substrate 31 as in Example 1 in the same manner as in Example 1.

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of about 15 um was formed by a dip coating method using a coating liquid 11 for forming a charge transport layer having the composition shown below. I got a body.

<Coating solution 11> ■・・・Binder polymer bisphenol A type polycarbonate Lexan +
4l-IN (molecular weight approximately 30,000, manufactured by Engineer Plastics). 6009° ■, ■... The hydrazone derivative and chloroform were the same as in Coating Solution 1.

Comparison ±2 A charge generation layer 35 is formed on the same substrate 31 as in Example 1 in the same manner as in Example].

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of about 15 μm was formed by a dip coating method using a coating liquid 12 for forming a charge transport layer having the composition shown below. I got a body.

Coating solution 12> ■... Binder polymer Same as Comparative Example 1, Lexan + 4l-Nl (molecular weight: about 30,000, manufactured by Engineer Plastics). 6o○9゜■,■
...The hydrazone derivative and chloroform were used in the same manner as in Coating Solution 2.

Comparison 1 A charge generation layer 35 is formed on the same substrate 31 as in Example 1 in the same manner as in Example 1.

Next, a charge transport layer 37 having a layer thickness of approximately 15 μm was formed on this charge generation layer 35 by a dip coating method using a coating liquid 13 for forming a charge transport layer having the composition shown below. I got a body.

Coating solution 13> ■... Binder polymer Same as Comparative Example 1, Lexan+4l-II+ (molecular weight approximately 30,000, manufactured by Engineer Glasstic). 6009゜■,
(2) Hydrazone derivative and chloroform were used in the same manner as in Coating Solution 3.

A charge generation layer 3518 is formed in the same manner as in Example 1 on the same substrate 31 as in Example 1.

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of about 15 um was formed by a dip coating method using a coating liquid 14 for forming a charge transport layer having the composition shown below. I got a body.

Coating Solution 14> ■...Binder Polymahisphenol A type polycarbonate Panlite L-1250 (molecular weight approximately 30,000, manufactured by Konjin Kasei). 600
9゜■,■...The hydrazone derivative and chloroform were the same as in Coating Solution 1.

Comparison A charge generation layer 35 is formed in the same manner as in Example 1 on a substrate 31 similar to that in Example 1.

Next, on this charge generation layer 35, a charge transport layer 37 having a layer thickness of approximately 15 um was formed by a dip coating method using a coating liquid 15 for forming a charge transport layer having the composition shown below. I got a body.

<Coating solution 15> ■・・・Binder polymer bisphenol A type polycarbonate Tanolon A
2200 (molecular weight approximately 30,000, manufactured by Mitsui Koyu Chemical). 60
0q.

(2), (2)...The hydrazone derivative and chloroform were used in the same manner as in Coating Solution 2.

Comparison 1 A charge generation layer 35 is formed on the same substrate 31 as in Example 1 in the same manner as in Example 1.

Next, a charge transport layer 37 having a layer thickness of about 1511 m was formed on this charge generation layer 35 by a dip coating method using a coating liquid 168 for forming a charge transport layer having the following composition. I got it.

<Coating Solution 16> ■...Binder Polymer: Brim Top Tsukufu 025AC, which is Mahisphenol A type polycarbonate, has a molecular weight of approximately 30,000, manufactured by Mitsubishi Kasei). 600
9゜■,■...Hydrazone derivative and chloroform were used in the same manner as coating solution 3 (strained).

The photoreceptors of Examples 1 to 3 and the photoreceptors of Comparative Examples 1 to 6 were each charged using a corona discharger so that the initial surface potential reached -7° OV. After that, 670
Exposure of 0.5 uJ/cm2 was performed by irradiating monochromatic light with a wavelength of nm for 10 m5ec.

Immediately after the end of exposure, the change in surface potential of each photoreceptor was measured using TR2.
The photoresponse characteristics were investigated using a high-speed surface potentiometer equipped with a 362A translucent probe manufactured by Company 0. AUT this measurement result
The data were stored in NISC: Company 121 type digital memory and analyzed.

Further, after each photoreceptor was charged, the photoreceptor was left in a dark place, and the surface potential was measured from immediately after charging to 10 seconds later to investigate dark decay characteristics.

In Figure 2, time is plotted on the horizontal axis and surface potential of the photoreceptor is plotted on the vertical axis, and the photoresponse characteristic a of a typical photoreceptor is shown as a solid line, and its dark decay characteristic is shown as a broken line. It is a characteristic curve diagram. In this example, the surface potential of the photoreceptor after 0.2 seconds has passed after the exposure of 0.5 uJ/cm2 is completed is approximately -4
00V, indicating that the attenuation potential VL of the surface potential is 300V.

The photoresponse characteristics and dark decay characteristics of each of the photoreceptors of Examples 1 to 3 and Comparative Examples 1 to 6 were investigated as described above.

Based on the photoresponse characteristics, the difference between the initial potential of each photoreceptor and the surface potential after 0.2 seconds has elapsed from the end of exposure, that is, the attenuation voltage VL8 is determined. Also, based on the dark decay characteristic, the surface potential V when 1 second has passed after the end of charging. The surface potential V immediately after being charged. Divided by the dark decay rate V,. /Find VO.

Attenuation voltage VL of each photoreceptor and dark decay rate V + o/V
.

and are shown in Table 1.

Table 1 However, the initial potential of the photoreceptor is V. is -700V.

Consider the results in Table 1.

First, a group of photoreceptors having the same charge transport material, namely a group of Example 1, a group of Comparative Example 1 and a group of Comparative Example 4, a group of Example 2, a group of Comparative Example 2 and a group of Comparative Example 5; 3. In the three groups of Comparative Example 3 and Comparative Example 6, the sensitivity of each photoreceptor within the group is compared. As is clear from the comparison results, in all groups, the sensitivity of the photoreceptor of the example in which the binder polymer was composed of bisphenol Z type polycarbonate having a molecular weight of about 20,000 to about 20,000 was lower than that of the photoreceptor of the comparative example. I can see that it is dramatically higher than that of .

Further, among the photoreceptors of Examples 1 to 3, the photoreceptor of Example 3 in which the charge transport material was composed of ethylcarbazolyldiphenylhydrazone had a photoreceptor of 0.5 LI J/cm
The surface potential attenuated to 190V for exposure No. 2. Therefore, according to the photoreceptor of Example 3, 0.5u
Despite the extremely low exposure amount of J/crn2,
Since the initial potential of -700 V can be attenuated to a potential closer to OV than -90 V within 0.2 SeC, this photoreceptor can be said to be extremely sensitive.

Roughly considering the dark decay rates of the photoreceptors of Examples 1 to 3, these values pose no practical problems, so it can be determined that the basic properties such as charging properties are also equivalent to conventional photoreceptors. .

In the above-mentioned embodiments, the charge generation layer was formed according to Japanese Patent Application Laid-open No. 59-44.
Although the explanation is given using an example of indium phthalocyanine disclosed in Japanese Patent Application Laid-open No. 054, this charge generation layer is made of indium phthalocyanine in which the central metal is indium and one chlorine is bonded to this indium, that is, JP-A-59. −
Even in the case of using indium phthalocyanine disclosed in No. 174845, the same results as in the examples were obtained.

Furthermore, even when the charge generation layer is composed of chloroindium phthalocyanine in which hydrogen in the benzene ring surrounding the phthalocyanine ring is replaced with 1 to 16 chlorine atoms, the same effect as in the example can be obtained. You can expect it. In general, the same effects as in the examples can be expected even with indium phthalocyanine in which the chlorine of the above-mentioned indium phthalocyanine is replaced with another halogen atom.

However, the present invention is not limited to the embodiments described above.

The above-mentioned embodiments have been described using examples in which the charge generation layer is directly formed on the conductive support 31. However, as shown in FIG. 4, which is a cross-sectional view corresponding to FIG. This invention can be applied. In such a case, the undercoat layer 33 can be formed by, for example, a dip coating method.

Further, the thickness and material of the undercoat layer 33 can be selected according to the design. Well-known materials for the undercoat layer include, for example, polyvinyl alcohol, polyvinyl butyral, and the like.

In general, the present invention can be applied to a photoconductor in which the stacking order of the charge generation layer and the charge transport layer is reversed from that of the photoconductor of the embodiment, as shown in FIG. 5, which is a cross-sectional view corresponding to FIG. It can be applied. In the case of such a structure, an overcoat layer 39 is provided on the charge generation layer 35 to ensure printing durability of the photoreceptor and to enable charge transport. Such an overcoat layer 39 can be formed by mixing a binder polymer and, for example, trinitrone fluorenone in a weight ratio of 1:1, and coating a solution obtained by dissolving these in trichlene on the charge generation layer. I can do it.

In the examples, a comparison is made between a bisphenol Z type polycarbonate resin having a molecular weight of about 20,000 to about 40,000 and a bisphenol A type polycarbonate resin having a molecular weight of about 30,000. This is because the molecular weight of currently available Tosuphenol Z type polycarbonate resins is from about 20,000 to about 40,000. Therefore, when bisphenol Z type polycarbonate is used as a binder polymer,
It is to be understood that the molecular weight of the polyponate that can improve the sensitivity of the photoreceptor may range from about 20,000 to about 40,000 as described above.

(Effects of the Invention) As is clear from the above description, the present invention (according to this invention) provides a charge generation layer of indium phthalocyanine on a conductive support, a charge transport material of a hydrazone derivative, and a binder of the charge transport material. An electrophotographic photoreceptor comprising a charge transport layer having a polymer, a binder polymer (
By using this bisphenol Z type polycarbonate having a molecular weight of about 20,000 to about 40,000, a photoreceptor can be obtained whose basic properties such as dark decay characteristics are substantially the same as conventional ones, but whose sensitivity is dramatically higher. I was able to do it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the photoreceptor of the present invention, FIG. 2 is a diagram for explaining the photoresponse characteristics and dark decay characteristics of the photoreceptor, and FIG. 3(A) is an example of the photoreceptor. Perspective view shown in Figure 3 CB
) is a diagram schematically showing the configuration of a laser beam printer in order to explain an example of the use of the photoconductor, and FIGS. 4 and 5 are cross-sectional views showing a photoconductor of a modified example to which the present invention can be applied. be. 31... Conductive support (aluminum base) 33...
- Undercoat layer, 35...charge generation layer 37...
charge transport layer, 39... overcoat layer. Patent applicant: Oki Electric Industry Co., Ltd. 31-... Conductive support (aluminum base) 35...
-Charge generation layer 37 --- Charge transport layer Figure 1 shows the photoreceptor of an example. θ θ5 Time (sec) Figure 2 shows the characteristics of the photoreceptor. Figure 2 shows the photoreceptor and examples of its use. Fig. 3 33: A diagram showing a photoconductor with a modified example of an undercoat layer. Fig. 4 39: A diagram showing a photoconductor with a modified example of an overcoat layer.

Claims (4)

[Claims] (1) In a functionally separated electrophotographic photoreceptor comprising a charge generation layer of indium phthalocyanine on a conductive support, a charge transport layer having a charge transport material of a hydrazone derivative, and a binder polymer of the charge transport material. An electrophotographic photoreceptor, characterized in that the binder polymer is bisphenol Z-type polycarbonate having a molecular weight of about 20,000 to about 40,000. (2) The electrophotographic photoreceptor according to claim 1, wherein the hydrazone derivative is 1,2,3,4-tetrahydroquinoline-6-carboxaldehyde. (3) The electrophotographic photoreceptor according to claim 1, wherein the hydrazone derivative is p-diethylaminobenzaldehyde diphenylhydrazone. (4) The electrophotographic photoreceptor according to claim 1, wherein the hydrazone derivative is ethylcarbazolyldiphenylhydrazone.