JPH0317654A - Photosensitive body having memory - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body having memory in an infrared region and high sensitivity by using a substance having absorption in the infrared region for an electric charge generating layer and an electron transfer type substance for a charge transfer layer. CONSTITUTION:The charge generating layer 14 is obtained by forming a switching layer 12 made of a polycarbonate type resin having a Cu.TCNQ complex dispersed into it on a conductive substrate 10 made of Cu, and vapor depositing an about 500Angstrom thick phthalocyanine film having absorption in the infrared region on the layer 12. The charge transfer layer 16 is obtained by coating the layer 14 with the electron transfer type substance in a thickness of 10 - 20mum, and acceptance potential can be enhanced by laminating a charge transfer complex layer 13 made of PVK.TeNF in a thickness of 0.1 - 5mum on the layer 12, and a potential acceptance is enhanced and the contrast of a print can be further enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a memory photoreceptor that can be used as a photoreceptor for electrophotography, particularly a memory photoreceptor that can be used as a photoreceptor for laser printers. It's about the body.

[Prior Art] FIG. 5 is an explanatory diagram showing the cross-sectional structure of a conventional memory photoreceptor disclosed in Japanese Patent Application Laid-Open No. 60-208771. A layer 2 is provided on which a charge generation/transport layer or a charge acceptance layer 3 is further provided. Here, the switching layer 2 is made of Cu-TCN which becomes a highly conductive state in a high electric field and maintains this high conductive state.
A polymer dispersed film of Q complex is used, and PVK-TeNF is used as the charge generation transport layer or the charge acceptance layer 3.

FIG. 6 shows the relationship between applied voltage and current for the switching layer 2 made of a polymeric decomposed film of Cu-TCNQli, and curve 1 shows the relationship between the voltage and current for the untreated switching layer 2. Relationship, curve 2 shows a similar relationship for switching layer 2 after application of high voltage.

As is clear from these curves, this switching layer 2 has a high resistance state A with a gentle slope and a low resistance state B with an extremely large slope (curve l), and once in a high conductivity state (ON STATE). Then, the high resistance state A almost disappears (curve 2), that is, this switching layer 2 has ifflji dependence, and according to one electric field direction, switching occurs at a certain electric field strength. Figure 7 shows Cu-TCNQ in switching layer 2 and PV
K-TN. The llI body is added to the charge generation transport layer or the charge acceptance layer 3.
2 is a diagram showing the relationship between the surface potential of a photoconductor and time, in which curve (1) is the surface charge potential of an untreated photoconductor, curve (2) is the surface charge potential after the start of exposure, and curve (2) is the surface charge potential of the untreated photoconductor;゜) is the surface charging potential when the main charging and exposure are performed after pre-charging and uniform exposure within the limit where no switching operation is performed (however, the surface potential of the photoreceptor after main charging is the same) (The applied voltage was adjusted so that the photoreceptor had a high conductivity due to charging exposure.) Curve (3) shows the surface charging potential when the photoreceptor whose switching layer has become highly conductive due to charging exposure is recharged.

In FIG. 4, V. is high resistance state (OFF STATE)
is the initial saturation charging potential of the photoconductor equipped with the switching layer 2 at . ■, is the saturation charging potential of the photoreceptor equipped with the switching layer 2 in a high conductivity state (ONSTATE),
The memory effect (F) is expressed by the following formula. Next, the principle of forming a memory image and the principle of forming an electrostatic image of this memory photoreceptor will be explained below with reference to Figures 8-A to 8-F.

First, as shown in Figure 8-A, the surface of the photoreceptor 4 is charged with a constant polarity by the corona charger 5 (
pre-charged). In the example shown in the figure, the surface of the charge receiving layer 3 is positively charged, and the conductive substrate 1 is negatively charged.

Next, the surface of the photoconductor 4 charged in this way is
As shown in Figure B, uniform exposure is performed using the light source 6 (pre-uniform exposure). By uniformly exposing the charge receiving layer 3, charges (
carriers) are generated, and the resulting holes (+) are at the stacking interface,
That is, it moves to the interface with the switching layer 2 and is accumulated there.

This pre-charging and pre-uniform exposure are performed as long as a high electric field is not applied to the switching layer 2. Thus, although a certain amount of positive charge is accumulated at the interface between the charge receiving layer 3 and the switching layer H2, the switching layer 2 is still maintained in a high resistance state (OFF STATE). Next, the surface of the photoreceptor 4, which has been pre-charged and pre-uniformly exposed, is charged to a constant polarity with a corona charger 5°, as shown in FIG. Expose to light (main charging and image exposure). Due to this main charging and image exposure, as shown in Figure 8-D, the surface charge remains as it is in the dark area D, but in the bright area L, the charge receiving layer 3 remains the same as shown in Figure 8-B. generation of charges (carriers) and movement of holes (+) to the interface with the switching layer 2, the accumulation of charges exceeds the above-mentioned limit, and a high electric field is applied to the switching layer 2. .

As a result, as shown in FIG. 8-E, the switching layer 2
The bright part L of is in a highly conductive state (ON) due to the applied high electric field.
STATE), that is, is induced into a low resistance state, and the dark part D of the switching layer 2 is in a high resistance state! ! J (OFF
STATE) remains, and in the bright area L, electrons (1) from the conductive substrate l are easily injected.

When electrons (-) are injected into the photoreceptor 4 from the conductive substrate l in this state, the electrons (-) are in a highly conductive state in the bright area L that has already been exposed, as shown in Figure 8-F. The charge is injected into the charge generation/transport/charge acceptance layer 3 via the switching layer 2, reaches the surface of the photoreceptor 4 through the layer 3, erases the positive charges (+) on the surface, and forms a charge image. (electrostatic image formation/process).

Although not shown, a copy or printed matter can be obtained by developing this charge image with toner by a method known per se and transferring the formed toner image onto paper or the like. Thus, by performing the charging process a desired number of times as shown in FIG. 8-F after forming the memory image once shown in FIGS. 8-A to 8-E, it is possible to make a desired number of copies.

[Problems to be Solved by the Invention] However, the conventional memory photoreceptors described above have memory properties limited to the visible region and do not have memory properties in the infrared region. There was a problem in that a semiconductor laser (780 nm, 830 nm), which had a wavelength of 100 nm, could not be used as an exposure light source (problem 1).

In addition, the above-mentioned conventional memory photoreceptor has a low receptive potential of the photosensitive layer, resulting in poor printing contrast and poor memory performance, resulting in the problem that the number of sheets that can be printed with one exposure is small ( Problem 2).

The present invention has been made in order to solve these problems, and it is possible to obtain a highly sensitive memory photoreceptor having memory properties in the infrared region, improve the contrast by increasing the receptive potential, and improve the memory property. The object of the present invention is to obtain a memory photoreceptor that can increase the number of prints by improving the properties of the photoreceptor.

[Means and effects for solving the problem] The memory photoreceptor according to claim 1 has a switching layer that causes switching from a high resistance state to a low resistance state being laminated on a conductive substrate, and a switching layer that causes switching from a high resistance state to a low resistance state. A charge generation layer having absorption in the infrared region is laminated thereon, and a charge transport layer made of an electron transfer type substance is laminated on the charge generation layer, thereby solving the above problem (1).

Here, as the conductive substrate, conductive metal substrates such as copper, aluminum, tinplate, etc., conductive treated paper, NESA glass, etc. are used, and these are used in the form of sheets or drums.

The switching layer has an electrical resistance (R,) in a high resistance state (OFFSTATE) of 10" to 1014 Ω1cm.
In particular, it is desirable to be in the range of lO9 to 1011 Ω-cm from the viewpoint of charge retention, while R and the electrical resistance in the low resistance state (ON S TATE) (RL: Ω-cm)
The ratio (R./RL) is from IXIO' to IXIO'
From the viewpoint of contrast, it is desirable that the value be within the range of .

As a switching layer having the above-mentioned characteristics, tetracyanoethylene (TCNE), tetracyanoquinodimethane (TCNQ), tetracyanonaphthoquinodimethane (T
NAP). 2.3.5.6-tetrafluoro-7.7.
8. Complexes of cyano group-containing electron-accepting substances such as 8-tetracyanoquinodimethane (TCNQF.) with copper or silver are preferably used, but other switching layers with similar properties can also be used. be able to.

These complexes can be formed directly on the conductive substrate in the form of a thin crystalline film by means such as vapor deposition, or they can be formed as microcrystals in a resin binder and then provided on the conductive substrate. You can also do that.

As the resin binder, electrically insulating resins such as polyester resins, acrylic resins, styrene resins, polycarbonate resins, vinyl chloride-vinyl acetate copolymers, phenoxy resins, epoxy resins, silicone resins, and alkyd resins are used.

The microcrystalline complex and resin binder are used in a weight ratio of 1:4 to 4:1. These resin binders are dissolved in a solvent such as tetrahydrofuran, chloroform, dioxane, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, etc. to decompose the microcrystalline complex, coated on a conductive substrate, and dried to form a switching layer. Let it form.

Examples of materials that can be used in the charge generation layer include phthalocyanine, squarylium, azulenium salts, naphthalocyanine, 4,4°-bis[2-hydroxy-3-(2.
4-dimethylphenyl)carbamoyl l-naphthylazo]-1,4-distyrylbenzene, chlorodiane blue τ type 1 metal roof talocyamine, l-(p
-dimethylaminocinamilidene)-5-isopropyl-
3.8-dimethylazulenium salt, 2.7-bis[2-
Hydroxy-3-(2-chlorophenylcarbamoyl)
-1-naphthilazo]-9-fluorenone, Rhodamine B,
Examples include indigo, thioindigo, bisphenol-A-polycarbonate, aryl-substituted siabyllium dye, chlorodiane blue, and N,N'-dimethylperilimide. Note that the charge generation layer can be formed by depositing these substances that have absorption in the infrared region, or by immersing these materials deposited on the substrate in an organic solvent so that they have absorption in the infrared region. You can also shift it. Examples of electron transfer type substances include 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone, and 2-nitro-9-fluorenone.
, 4,5.7-tetranitro-9-fluorenone, 2-
Nitrobenzothiophene, 2,4,8-trinitothioxanthone, dinitroanthracene, dinitroacridine, dinitroanthraquinone, tetracyanoquinodimethane, and the like can be used. The charge transport layer is made of the above-mentioned electron transfer type substance and a resin binder,
For example, the layers are laminated by a coating method such as a bar coating method, a dip coating method, or a blade coating method.

Here, as the resin binder, electrically insulating resin such as polyester resin, acrylic resin, styrene resin,
Polycarbonate resin, vinyl chloride-vinyl acetate copolymer, phenoxy resin, epoxy resin, silicone resin,
Alkyd resin etc. are used.

The thickness of the charge transport layer is preferably 10 to 20 μm. This is because if the charge transport layer is thinner than 10 μm, carrier generation efficiency becomes low and the sensitivity is lowered, and if the charge transport layer is thicker than 2 OLLm, the acceptance potential during charging becomes small.

In the memory photoreceptor according to the second aspect, a switching layer that causes switching from a high resistance state to a low resistance state is laminated on a conductive substrate, and a PVK layer is formed on this switching layer.
-A charge transfer complex layer made of TeNF is laminated to a thickness of 0.1 to 5 μm, and charges are generated on this charge transfer complex layer.
The above problem 2 can be solved by laminating photoreceptor layers with transport and receptor properties.
This is the solution.

Here, the charge transfer complex layer. The reason why O. This is because if it is less than 1 μm, the effect will be small, and if it exceeds 5 μm, the accepted potential due to the second charging will be higher than the accepted potential due to the first charging, and no memory effect will be observed. Further, the conductive substrate and the switching layer are the same as in the memory photoreceptor according to claim 1, and the photoreceptor layer is the same charge generation layer and charge transport layer as in the memory photoreceptor according to claim 1. It can be constructed from. In this case, the thickness of the charge transport layer is preferably 10 to 20 μm. If the charge transport layer has a thickness of less than -10 .mu.m, the charge receptivity is low, and if it exceeds 20 .mu.m, the charge receptivity is good, but does not decrease even when exposed to light, that is, the photosensitivity becomes low.

[Example 1 Example 1 Laying Light] Deaf Jiu Xianmeng As shown in FIG. 1, a conductive substrate 10 made of a Cu substrate
A switching layer 12 made of a dispersed film of a polycarbonate resin containing a Cu-TCNQ complex is provided thereon, and a charge generation layer 14 is formed by vapor-depositing phthalocyanine that absorbs in the infrared region to a thickness of about 500 nm. Further, an electron transfer material was applied thereon to a thickness of 10 to 20 μm to form a charge transport layer 16.

The following charging and exposure test was conducted using the photoreceptor manufactured as described above.

That is, as shown in FIG.
kV for the first time, and the photoreceptor in this state was irradiated with monochromatic light (l OmW/cm") with a wavelength of 780 nm (corresponding to the process shown in Figure 8-C). The photoreceptor was subjected to a second corona charge at +6 kV (corresponding to the step shown in Figure 8-F).

This photoreceptor has an acceptance potential of ■ during the first corona charging.

was +650V, but in the second corona charging after irradiation with light with a wavelength of 780nm, the accepted voltage Vl was +40V.
It only reached 0V. That is, this photoreceptor is
Memory effect (■.1 V.)/V at a wavelength of 780 nm, that is, in the infrared region. It was observed that the This acceptance potential ■1 increases with time, but by 50%
It took about three hours to recover. That is, the first (■
. −V, )/V. is 100, after 3 hours (vo
-v. )/V. became 50. From this, it was found that this memory property can be maintained for a considerably long time, and a considerably large number of copies can be made.

Example 2 ΔUpper J-tip 1 As shown in FIG. 3, a conductive substrate 10 made of a Cu substrate
On top is a switching layer consisting of a polycarbonate-based resin dispersed film containing a Cu-TCNQ complex. 12 was provided, and PVK-"1" eNFF was applied thereon to a thickness of 0.1 to 5 μm to form a PVK-TeNF layer 13. On top of this, phthalocyanine was vapor-deposited to a thickness of approximately 500 μm. A charge generation layer 14 was formed, and an electron transfer material was further provided thereon to a thickness of 10 to 20 am to form a charge transport layer 16.

The following charging-exposure test was conducted using the photoreceptor manufactured as described above.

That is, as shown in FIG.
kV for the first time, and then the photoreceptor in this state is exposed to monochromatic light with a wavelength of 780 nm (10 mW/cm").
) was used for a second corona charge at +6kV. This photoreceptor has an acceptance potential of V at the first corona charging.

became +soov, but in the second corona charging after irradiation with light with a wavelength of 780 nm, the acceptance potential vI became +38
It took about 5 hours for the memory effect to recover by 50%. In other words, this experiment revealed that the receptive potential and memory ability were improved. [Effects of the Invention] As explained above, the invention described in claim 1 has a photosensitive layer consisting of two layers, a charge generation layer and a charge transport layer, and a substance having absorption in the infrared region as the charge generation layer. Since an electron transfer type material is used as the transport layer, it is possible to provide memory properties in the infrared region, and therefore, a semiconductor laser, which is currently most commonly used, can be used as an exposure light source.

Further, the invention as recited in claim 1 has the effect that the memory property is maintained for a long time, so that it is possible to print a large number of sheets. Furthermore, the invention described in claim 1 has the effect that the contrast of printing can be improved because the acceptance potential of the photosensitive layer is increased. In the invention according to claim 2, as described above, a charge transfer complex layer made of PVK-TeNF is laminated with a thickness of 0.1 to 5 μm on the switching layer, so that the acceptance potential can be improved. Therefore, it has the effect of further improving the contrast of printing. Further, the invention as claimed in claim 2 has the advantage that the memory property is maintained for a long time, so that it is possible to print a large number of sheets.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the invention as claimed in claim 1,
FIG. 2 is a graph showing changes in acceptance potential when the photoreceptor shown in FIG. 1 is charged and exposed to light; FIG. Figure 3 is a graph showing changes in acceptance potential when a photoreceptor is charged and exposed to light, Figure 5 is a cross-sectional view of a conventional photoreceptor, and Figure 6 is a graph showing changes in applied voltage and switching layer of a conventional photoreceptor. FIG. 7 is a graph showing the relationship between the surface potential of a conventional photoreceptor and time. 10... Conductive substrate, l2... Switching layer, l3... PVK/TeNF layer, 14... Charge generation layer, 16... Charge transport layer.

Claims (2)

[Claims] (1) A switching layer that causes switching from a high resistance state to a low resistance state is laminated on a conductive substrate, a charge generation layer that absorbs in the infrared region is laminated on this switching layer, and this charge generation layer A memory photoreceptor characterized by having a charge transport layer made of an electron transfer type material laminated thereon. (2) A switching layer that causes switching from a high resistance state to a low resistance state is laminated on a conductive substrate, and a charge transfer complex layer made of PVK/TeNF is placed on top of this switching layer to a thickness of 0.1 to 5 μm. 1. A photoreceptor with memory properties, characterized in that a photoreceptor layer having charge generation, transport and reception properties is laminated on the charge transfer complex layer.