JPS63172168A - Photosensitive body - Google Patents

Abstract

PURPOSE:To improve the electric charge transferring ability, and to reduce the residual potential of the titled body by using the electric charge transfer layer which is formed by plasma- polymerizing a hydrocarbon, and is composed of a noncrystalline solid contg. carbon and hydrogen atoms as a constituting atom, and contains continuously a fluorine atom as a chemically modified substance in a larger amount at the electric chrge generating layer side in the direction of the film thickness of the titled body. CONSTITUTION:The charge transfer layer is formed by plasma-polymerizing the hydrocarbon in a gaseous state, and is composed of the noncrystalline solid contg. the carbon and the hydrogen atoms as the constituting atom, and contains continuously the fluorine atom as the chemically modified substance in the larger amount at the electric charge generating layer side in the direction of the film thickness of the titled body. The titled body is composed of the at least the charge generating layer and the charge transfer layer, and the charge transfer layer comprises at least one layer composed of the carbon layer contg. the hydrogen atom. Said carbon layer contg. the hydrogen atom varys from the noncrystalline to the diamond according to the hydrogen content and the production method. The charge transfer layer contains the fluorine atom in the larger amount at the charge generating layer side and adversely, in the lesser amount at the opposite side. Thus, the injection of charge from the surface or the substrate of the titled body is prevent, and the dark attenuation characteristics of the titled body is improved. The sensitivity of the titled body is improved by preventing the injection of charge from the substrate or the surface thereof.

Description

[Detailed description of the invention] ζIzumi, ΔMeki Gua Ritsu The present invention relates to photoreceptors, particularly electrophotographic photoreceptors.

Prior art Invention of the Carlson method (1938, USP 222176)
) Since then, the application field of electrophotography has continued to make remarkable progress, and various materials have been developed and put into practical use for electrophotographic photoreceptors.

The main electrophotographic photoreceptor materials conventionally used include inorganic substances such as amorphous selenium, selenium arsenide, selenium telluride, cadmium sulfide, zinc oxide, amorphous silicon, polyvinyl carbazole, metal phthalocyanine,
Examples include organic substances such as disazo pigments, trisazo pigments, perylene pigments, triphenylmethane compounds, triphenylamine compounds, hydrazone compounds, styryl compounds, pyrazoline compounds, oxazole compounds, and oxadiazole compounds.

In addition, the configurations include a single-layer structure in which these substances are used alone, a binder-type structure in which they are dispersed in a binder, and a laminated structure in which a charge generation layer and a charge transport layer are provided for each function. Can be mentioned.

However, the conventionally used electrophotographic photoreceptor materials each have drawbacks.

One of these is their toxicity to the human body, and all inorganic substances, except for the amorphous silicon mentioned above, have unfavorable properties.

In addition, in order for an electrophotographic photoreceptor to be actually used in a copying machine, it must always maintain stable performance even when exposed to harsh environmental conditions such as charging, exposure, development, transfer, neutralization, and cleaning. However, all of the organic substances mentioned above have poor durability and many unstable factors in terms of performance.

In order to solve such problems, in recent years, amorphous silicon (hereinafter abbreviated as a-9i) manufactured by plasma chemical vapor deposition method (hereinafter referred to as plasma CVD method) has been used for photoreceptors, especially electrophotographic photoreceptors. It has been adopted.

The a-3i photoreceptor has various excellent properties. But a
-S i has a large dielectric constant ε of about 12, so there is a problem in that a film thickness of at least about 25 μm is essentially required in order to obtain a sufficient surface potential as a photoreceptor. a
In the plasma CVD method, the -9i photoreceptor requires a long time to produce because the film deposition rate is slow, and the longer the production time becomes, the more difficult it becomes to obtain a homogeneous a-Si film. As a result, the a-3i photoreceptor has drawbacks such as a high probability of image defects such as white spot noise and high raw material costs.

Although various attempts have been made to improve the above drawbacks, it is essentially not desirable to make the film thinner than this.

On the other hand, the a-Si photoreceptor also has drawbacks such as poor adhesion between the substrate and a-9i, as well as poor corona resistance, environmental resistance, and chemical resistance.

In order to solve such problems, it has been proposed to provide an organic plasma polymerized film as an overcoat layer or undercoat layer of the A-9T photoreceptor. An example of the former is
For example, JP-A-59-214859, JP-A-51
-46130, JP-A-50-20728, etc. are known, and examples of the latter include, for example, JP-A-60
-63541, JP 59-13674.2, JP 59-38753, JP 59-28
Publication No. 161, Japanese Unexamined Patent Publication No. 56-60447, etc. are known.

Organic plasma polymerized films can be prepared from all kinds of organic compound gases such as ethylene gas, benzene, and aromatic silanes (e.g., A, T, Be1l).
, M, 5hen, et al., Journal of Applied Polymer Science
orApplied Polymer 5cienc
e), Vol. 17, pp. 885-892 (1973), etc.)
However, organic plasma-polymerized films prepared by conventional methods are used only for applications requiring insulation. Therefore, these films were considered to be insulating films having an electrical resistance of about <10'' ΩCM like ordinary polyethylene films, or at least were used with the understanding that they were such films.

On the other hand, in recent years, thin films of diamond-like carbon have been proposed in the semiconductor field, but nothing is known about their charge transport properties.

The technique described in Japanese Patent Application Laid-Open No. 60-61761 discloses a photoreceptor coated with a diamond-like carbon insulating film having a thickness of 500 to 2 μm as a surface protective layer.

This carbon thin film is intended to improve the corona discharge resistance and mechanical strength of the a-Si photoreceptor. The polymer membrane is very thin, and charges move through the membrane through the tunnel effect, so the membrane itself does not require charge transport ability. Furthermore, there is no mention of the carrier transport properties of organic plasma polymerized films, and a
- It does not solve the above-mentioned essential problem of Si.

JP-A-59-214859 discloses a technique in which an organic hydrocarbon monomer such as styrene or acetylene is coated as an overcoat layer with a thickness of about 5 μm by plasma polymerization. This improves the peeling, durability, pinholes, and production efficiency of the a-3T photoreceptor. There is no description whatsoever regarding the carrier transport properties of organic plasma polymerized films, and it does not solve the above-mentioned essential problems of a-Si.

JP-A-51-46130 discloses that an organic hydrocarbon monomer such as styrene or ethylene is applied onto a poly-N-vinylcarbazole organic optical semiconductor to a thickness of 3 μm to 0.001 μm on the surface. A photoreceptor having a plasma polymerized film formed thereon is disclosed. The purpose of this technology is to make it possible to use poly-N-vinylcarbazole photoreceptors, which could only be used with positive charging, with bipolar charging.

This film is very thin at 0.001 to 3 μm and is used as a protective film like an overcoat. It is thought that the polymeric membrane is very thin and does not require charge transport ability. Also,
There is no description whatsoever regarding the carrier transportability of the polymer membrane, and it does not solve the above-mentioned essential problems of a-Si.

JP-A No. 50-20728 discloses a sensitizing layer on a substrate,
A technique has been disclosed in which an organic photoconductive electrical insulator is sequentially deposited and a glow discharge polymer film with a thickness of 0.1 to 1 μm is formed thereon, but this film is made to withstand wet development. It is intended to protect the surface and is used as an overcoat.

Polymerized membranes are very thin and do not require charge transport capabilities.

Furthermore, there is no description whatsoever regarding the carrier transport properties of the polymeric membrane, and it does not solve the above-mentioned essential problems of a-Si.

JP-A No. 60-63541 discloses a photoreceptor using a diamond-like film of 200 to 2 μm in thickness as an a-St undercoat layer, but the film does not improve the adhesion between the substrate and a-Si. The purpose is to improve The polymeric membrane can be very thin, and charges move through the membrane by tunneling.

Japanese Patent Application Laid-open No. 59-136742 discloses that about 5μ
A semiconductor device is disclosed in which an organic plasma polymerized film and a silicon film of m are sequentially formed. However, although the purpose of this organic plasma polymerized film is to prevent the diffusion of aluminum, which is a substrate, into a-St, there is no description of its manufacturing method, film quality, etc. Furthermore, there is no description whatsoever regarding the carrier transport properties of organic plasma polymerized films, and a-
It does not solve the above-mentioned essential problem of S i.

JP-A-59-28161 discloses a photoreceptor in which an organic plasma polymerized film and an a-Si are sequentially formed on a substrate. The organic plasma polymerized film is an undercoat layer that takes advantage of its insulating properties and functions as a blocking layer, adhesion layer, or peel prevention layer. Polymerized membranes can be very thin, charges move through the membrane by tunneling, and the membrane itself does not require charge transport capabilities. In addition, there is no description whatsoever regarding the carrier transport properties of the organic plasma polymerized film, and it does not solve the above-mentioned essential problems of a-9i.

JP-A No. 59-38753 discloses that 10-10
0 organic plasma polymerized thin film was formed, and a-
A technique for depositing a 9i layer is disclosed. The organic plasma polymerized film is an undercoat layer that takes advantage of its insulating properties, and functions as a blocking layer or a peel-preventing layer. Polymerized membranes can be very thin, charges move through the membrane by tunneling, and the membrane itself does not require charge transport capabilities. Further, there is no description whatsoever regarding the carrier transport properties of the organic plasma polymerized film, and it does not solve the above-mentioned essential problems of a-St.

As mentioned above, conventionally, it has been proposed to use an insulating organic plasma polymerized film or a diamond-like film for the overcoat layer or undercoat layer, but the movement of charges caused by these films is basically due to the tunnel effect. This is due to an electrical breakdown phenomenon.

That is, the tunnel effect occurs when electrons pass through the insulating layer when the thickness thereof is extremely small (generally on the order of angstroms).

On the other hand, electrical breakdown occurs when a small amount of charge carriers in a layer are accelerated by an electric field and acquire enough energy to ionize atoms of the insulator, and the ionization increases the number of carriers and the same process repeats. This is a phenomenon in which carriers increase in a mouse-like manner, which occurs in the case of extremely high electric fields (generally 100 V/μ or higher).

For example, in the case of a photoreceptor structure in which an insulator and a semiconductor are laminated,
Charges generated in a semiconductor travel through the film due to the electric field, but cannot pass through the insulator at low electric fields. If the insulating layer is thin, this can be ignored as a surface potential, or
Since the effect on so-called development characteristics in electrophotography is extremely small, deterioration of characteristics due to the presence of the insulating layer is not a problem. Next, consider the effects of repeated use. Charges accumulate in the insulating layer due to repeated use, but when a high electric field (for example, 100 V/μ or more) is achieved due to the accumulated charges, no further electric field is applied due to electrical breakdown.

For example, when an insulating material that causes electrical breakdown at 100 V/μl is vtDed to a thickness of 0.1 μl, the increase in so-called residual potential due to the insulating layer is only IOV even after repeated use.

For the above reasons, when a general insulating material is used for the photoreceptor, the film thickness must be approximately 5 μm or less. Otherwise, the increase in residual potential due to the insulating layer will exceed 500 V, causing fog in the copied image and making it unusable.

Problems to be Solved by the Invention As mentioned above, organic polymer films conventionally used in photoreceptors have been used as undercoat layers or overcoat layers, but these do not require a carrier transport function. It is a film, and it is used based on the judgment that the organic polymer film is insulating. Therefore, its thickness is at most 5μ
It is used only as an extremely thin film, about the size of a shoulder, and carriers pass through the film due to the tunnel effect, or if a tunnel effect cannot be expected, the film is thin enough that the residual potential does not pose a problem in practical use. It is only used in

While considering the application of organic polymer films to a-Si photoreceptors, the present inventors found that organic polymer films, which were originally thought to be insulating, showed a decrease in electrical resistance when the hydrogen content reached a certain level. However, it was discovered that by further adding fluorine atoms, it began to exhibit better charge transport properties.

By utilizing this new knowledge, the present invention solves the problems of conventional a-Si photoreceptors, namely a-'Si photoreceptors.
The present invention is a photoreceptor using an organic polymer film, especially an organic plasma polymer film, which solves all problems in film thickness, manufacturing time, manufacturing cost, etc., and has completely different purpose of use and characteristics from conventional ones. As a charge transport layer in a photoreceptor, it has a hydrogen-containing carbon film that has excellent charge transport ability, has a small residual potential even when the film thickness is 5 μm or more, and has excellent physical properties.

Means for Solving the Problems The present invention is based on the new finding that a hydrogen-containing carbon film exhibits a better charge transport function when combined with a charge generating layer and by adding fluorine atoms. It is something. That is, the present invention provides a laminated photoreceptor having at least a charge generation layer and a charge transport layer, in which the charge transport layer is formed by plasma polymerizing hydrocarbons in a gas phase, and is composed of non-containing materials composed of carbon and hydrogen as constituent atoms. It is a crystalline solid;
The present invention also relates to a photoreceptor characterized in that it contains a large amount of fluorine atoms as a chemical modifier continuously in the thickness direction on the charge generation layer side.

In order to be used as an electrophotographic photoreceptor, the laminated charge generation layer and charge transport layer must have a dark resistance of 109 Ωcm or more and a light-to-dark resistance ratio (i.e., gain) of 10" to 1.
Approximately 0.04 is required.

The photoreceptor of the present invention is composed of at least a charge generation layer and a charge transport layer, and has a layer of carbon (hereinafter referred to as CHI) containing at least -8 hydrogen as the charge transport layer, and is expected to satisfy the above characteristics. Features.

-1-a nr + 7-t-Ph Eshi 1h ρ 9 Shizan Koru Ryo Miko is 0, 1~67' atomic% (hereinafter a
tm, %), preferably 1 to 60 atm, %,
More preferably, it is 30 to 60 atm%. 0,
If it is smaller than 1 atm, 67 atm, dark resistance suitable for electrophotography cannot be obtained.

%, there is no charge transport ability.

The hydrogen-containing carbon film in the present invention has an amorphous or diamond-like shape depending on its hydrogen content and manufacturing method.

In most cases, it takes an amorphous form, and the film itself is soft and has high resistance. On the other hand, the obtained manufacturing method and conditions, e.g.
In the plasma CVD method, a diamond-like carbon film can be obtained when the hydrogen content is about 40 atm, % or less, and such a film is hard with a Vickers hardness of 2000 or more and an electrical resistance of 10"Ω・CJI or more. However, all carbon films exhibit high charge transport properties.

The hydrogen stand m and structure in the C:II film of the present invention can be quantified by elemental analysis, infrared absorption spectroscopy, 'H-NMR or 13C-NMR.

In the C:II film of Wood 91'll"l, fluorine atoms are continuously and non-uniformly contained in a large amount on the charge generation layer side in the film thickness direction as a chemical modifying substance.

By including fluorine atoms in the C:H film, injection of carriers from the charge generation layer is promoted, carrier mobility during charge transport is improved, and sensitivity is also improved.

The charge transport layer of the present invention contains more fluorine atoms on the charge generation layer side and less on the opposite side. By doing so, charge injection from the surface or substrate is prevented, and dark decay characteristics are improved.

That is, for example, when the charge transport layer is on the surface side of the charge generation layer, fewer fluorine atoms are contained on the surface side, suppressing the injection of charged charges from the surface and reducing dark decay. Prevention can be measured. Furthermore, when the charge transport layer is located on the substrate side relative to the charge generation layer, fewer fluorine atoms are contained on the substrate side, which suppresses charge injection from the substrate and prevents dark decay. It also improves the adhesion between the substrate and the charge transport layer.

When considering the charge transport layer divided into multiple regions in the film thickness direction, the amount of fluorine atoms to be included during charge transport is 04 to 2 for all atoms in the region closest to the charge generation layer side.
8 atm, %, preferably 0.3-15 μmm, %, more preferably 0.5-1 Oatm.

%. When the amount is less than 0.0, 1'jtm, %, suitable charge transport properties are not necessarily guaranteed, and sensitivity decreases or residual potential is likely to occur, and sensitivity stability over time is also not guaranteed. 28 atm, if it is more than %,
When added in an appropriate amount, fluorine atoms guaranteed suitable charge transport properties and prevention of residual potential generation, but on the contrary, they showed the effect of reducing charging ability and furthermore, lowering dark resistance after a period of time, making storage difficult for several months. This leads to a decrease in charge retention ability. Furthermore, film-forming properties are not necessarily guaranteed, resulting in peeling of the film, oily state, or powdery state. The region opposite to the charge generation layer contains as little fluorine atoms as possible within the range of m. However, the charge transport layer is formed so that the concentration of sulfur atoms changes continuously from the charge generation layer side to the opposite side. Continuously means that there is no region in which fluorine atoms are not contained in each of the divided regions from the charge generation layer side of the charge transport layer to the opposite side thereof, and the present invention As described above, fluorine atoms are continuously contained in the charge transport layer of the photoreceptor.

It is preferable for the concentration of fluorine atoms in the charge generation layer to vary smoothly from the side of the charge generation layer to the opposite side, for example, in a linear continuous manner, from the viewpoint of charge transportability.
The present invention is not particularly limited to such changes.

Fluorine atoms in the charge transport layer can be detected by Auger spectroscopy, organic elemental analysis, etc., and the distribution of m in the thickness direction of the charge transport layer can be measured.

The charge generation layer is not particularly limited, and may be made of amorphous silicon (including various different elements to change the a-8iX characteristics).
For example, C, OlS, N, P, B.

(may contain halogen, Ge, etc., and may have a multilayer structure), Se film, 5e-As film, 5e-Te bladder, CdS film, inorganic substances such as zinc oxide, bisazo pigment, triaryl Methane dyes, thiazine dyes, oxazine dyes, xanthine dyes, cyanine dyes, styryl dyes, pyrylium dyes, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, Examples include organic substances such as bisbenzimidazole pigments, induthrone pigments, squarylium pigments, and phthalocyanine pigments.

Other materials can be used as long as they absorb light and generate charge carriers with extremely high efficiency.

As will be described later, the charge generation layer may be provided at any position on the photoreceptor, for example, it may be provided on the top layer, bottom layer, or intermediate layer. The layer thickness depends on the type of material, especially its spectral absorption characteristics, exposure light source, purpose, etc., but is generally set so that it absorbs 90% or more of light of 555 nm. a-
In the case of 9t:H, it is about 0.1 to 1 μm.

For normal electrophotography, the thickness of the C:H charge transport layer is 5 to 5
A suitable thickness is 0 .mu.m, particularly 7 to 20 .mu.m, and if it is thinner than 5 .mu.m, the charging ability is low and sufficient density of the copied image cannot be obtained. If it is thicker than 50 μm, it is not preferable in terms of productivity.

This C:8 layer has light transmittance, high dark resistance, and is rich in charge transport properties, and transports carriers without causing charge traps even when the film thickness is 5 μm or more as described above.

Invention C: The 8 layers are formed through an ion state such as ionization vapor deposition or ion beam deposition, or a plasma state such as a direct current, high frequency, or microwave plasma method.
Low pressure CVD method, vacuum evaporation method, sputtering method, optical CV
It may be formed by a method of forming from neutral particles such as method D, or a combination thereof. However, for example, when the charge generation layer is formed by high-frequency plasma or CVD, it is preferable to form the C:H film by the same method, as this leads to savings in manufacturing equipment cost and process labor.

C: As a carbon source for forming HFi, C11-
1t, C, [(,, C21-1,, C, I-I,
,CH,,C,H,,.

C, I (QS C, H,, C31-18, CH3CH
Examples include OS C5Ha, CIor(, e, etc.).

C: t as a fluorine source containing fluorine atoms in the 8th layer
ccf2*Ft, (j-IC12Ft, Cl4P3,
CF Ct Fe, CsF 51C-F lo, Ct
Examples include F4, CeH5C2F3, F2, HF, and the like.

As carrier gas, Ht, Ar, Ne, He
etc. are appropriate.

1 to 12 are schematic cross-sectional views showing one embodiment of the photoreceptor of the present invention. In the figure, (1) shows a substrate, (2) shows a C:H film as a charge transport layer, and (3) shows a charge generation layer. The diagonal lines in the charge transport layer (2) in FIGS. 1 to 3 represent the concentration distribution of fluorine atoms. For example, in FIG. It represents the state of being. In the photoreceptor of the embodiment shown in FIG. 1, for example, it is charged ten times and then the image @! When exposed to light, charge carriers are generated in the charge generation layer (3) and the electrons neutralize the surface charges. On the other hand, holes are transported to the substrate (1) side, guaranteed by the excellent charge transport properties of the C:H film (2) containing fluorine atoms. The charge transport layer contains many fluorine atoms on the charge generation layer side to effectively inject carriers from the charge generation layer, and contains less on the substrate side to suppress charge injection from the substrate. , and the adhesion to the substrate (1) is improved.

The photoreceptor shown in Figure 2 is an example in which a C:H film (2) is used as the top layer, and by containing more fluorine atoms on the charge generation layer side of the charge transport layer, charge carriers are transferred from the charge generation layer. By making the injection more effective and containing less charge on the surface side, the injection of charge from the surface can be suppressed.

The photoreceptor shown in FIG. 3 has a C:H film (2) with a charge generating 5 (
In the example above and below 3), carrier injection from the a-SiTL color generation layer into the charge transport layer (2) is effectively performed, and injection of surface charges and charges from the substrate is suppressed. , and the adhesion to the substrate (1) is also improved.

The photoreceptors shown in FIGS. 4 to 6 are examples of the photoreceptors shown in FIGS. 1 to 3 in which a surface protective layer with a thickness of 0.01 to 5 μm is further provided as an overcoat layer (4).
Charge generation layer (3) or charge transport layer C: Hffl (2
) and to improve the initial surface potential. The surface protective layer may be formed of any known material, and in the present invention, it is desirable to provide it by organic plasma polymerization from the viewpoint of the manufacturing process. Invention C:H membranes may also be used.

The photoreceptors shown in FIGS. 7 to 9 are examples in which C:HIli used as a charge transport layer is used as an undercoat layer (5) on a substrate (1) as a barrier layer or as an adhesive layer.

Of course, other known materials may be used for the undercoat layer. In this case as well, it is preferable to use the plasma polymerization method. The barrier layer has a rectifying function of effectively blocking charge injection from the substrate (1) and transporting the charges generated in the charge generation layer (3) to the substrate side. Also, the barrier layer I! ! 2. The thickness is preferably 0.01 to 5 μm. Furthermore, the photoreceptor shown in FIGS. 7 to 9 may be provided with an overcoat layer (4) shown in FIGS. 4 to 6 on the substrate (FIGS. 10 to 12).

In order to incorporate fluorine atoms into the C:I-1 layer, a suitable gaseous compound containing these elements may be brought into an ionized state or a plasma state together with a hydrocarbon gas to form a film.

The C:H charge transport layer of the photoreceptor of the present invention may further contain nitrogen, oxygen, sulfur and/or various metals.

Generally, N1, N I-13, NtOSN are used as nitrogen sources.
OSNol or the like is used, and by mixing this, the interface barrier with the charge generation layer can be reduced. By introducing nitrogen, -N is added to the C:I-1 film.
Since a group such as Hz-1-N=N-1-NH- is generated and exists, it acts as a donor, making it easier for the pole to move.

Examples of oxygen sources include 01, o3, NtO, No, etc., and by mixing them, the charging ability is improved. Furthermore, in the case of plasma CVD, introducing oxygen (0) has the secondary effect of increasing the film formation speed.

As a sulfur source, CS t, (CtHs)'ts, HtS
.

Examples include S Fe, S67, etc. Mixing sulfur is effective in preventing previous absorption and interference. Additionally, the introduction of sulfur (S) has the secondary effect of increasing the film formation speed.

By adding a small amount of Si or Ge, a hard film with wear resistance and water repellency can be formed. In addition, the introduction of both facilitates the injection of charge from the charge generation layer, and has a favorable effect on lowering the residual potential and increasing sensitivity.

The photoreceptor of the present invention has a charge generation layer and a charge transport layer. Therefore, at least two steps are required to manufacture it. When using, for example, an a-Si layer formed using a glow discharge decomposition device as the charge generation layer, it is possible to perform plasma polymerization using the same vacuum device,
Therefore, it is particularly preferable to form the a-cTi transport layer, surface protective layer, barrier layer, etc. by plasma polymerization.

The charge transport layer of the electrophotographic photoreceptor according to the present invention includes, for example,
Molecules in the gas phase are decomposed by discharge under reduced pressure, and activated neutral species or charged poles contained in the generated plasma atmosphere are diffused onto the substrate, induced by electric force, magnetic force, etc., and regenerated on the substrate. It is preferably produced from a so-called plasma polymerization reaction, in which it is deposited as a solid phase by a bonding reaction.

FIGS. 13 and 14 show a capacitively coupled plasma CVD apparatus which is a photoreceptor manufacturing apparatus according to the present invention. FIG. 13 shows a parallel plate plasma CVD apparatus, and FIG. 14 shows a cylindrical plasma CVD apparatus.

First, explanation will be given using FIG. 13.

In FIG. 13, (701) to (706) are the first to sixth tanks in which the raw material compound and carrier gas, which are in a gas phase at room temperature, are sealed, and each tank is connected to the first to sixth control valves (707). ~ (712) and the first to sixth flow rate controllers (
713) to (71g).

In the figure, (719) to (721) are first to third containers filled with raw material compounds that are in a liquid or solid phase at room temperature, and each container is connected to a first to third heater (721) for vaporization.
22) to (724), and each container is connected to the seventh to ninth R section valves (725) to (727) and the seventh to ninth flow rate controllers (72g) to (730). has been done.

After these gases are mixed in a mixer (7:(1)), they are sent to the reaction chamber (733) via the main pipe (732).

The pipes along the way can be heated by appropriately placed pipe heaters (734) so that the gas, which is the vaporized raw material compound that is in a liquid or solid state at room temperature, does not condense on the way. .

Inside the reaction chamber, there is a ground electrode (735) and a power application electrode (73).
6) are installed facing each other, and each electrode is connected to an electrode heater (7).
37) allows for heating.

Is there matching for high frequency power on the power application electrode? 5 (73g) to a high frequency power source (739) and a matching machine for low frequency power (7
A low frequency power source (741) is connected through a low-frequency power source (741) and a DC power source (743) is connected through a low-pass filter (742), and power with different frequencies can be applied by a connection selection switch (744).

The pressure inside the reaction chamber can be adjusted by a pressure control valve (745), and the pressure inside the reaction chamber can be reduced through an exhaust system selection valve (746), a diffusion pump (747), and an oil rotary pump (748).
, or by using a cooling exclusion bag U (749), a mechanical booster pump (75G), or an oil rotary pump.

The exhaust gas is further rendered safe and harmless by an appropriate exclusion device (753) before being exhausted into the atmosphere.

These exhaust system pipings are also heated by appropriately placed piping heaters to prevent the vaporized gas from the raw material compound, which was in a liquid or solid phase at room temperature, from condensing on the way.
It is said that heating is possible.

For the same reason, the reaction chamber can also be heated by a reaction chamber heater (751), and a conductive substrate (752) is installed on the IX electrode arranged inside.

In FIG. 13, the conductive substrate (752) is the ground electrode (752).
35), but the power application electrode (73
6) may be fixedly arranged, or may be further arranged on both sides.

The apparatus shown in FIG. 14 is basically the same as the apparatus shown in FIG.
52) is cylindrical in shape. The substrate also serves as a ground i-pole (735), and both the power application electrode (736) and electrode heater (737) have a cylindrical shape.

In the above configuration, the reaction chamber includes a diffusion pump (747)
Reduce the pressure in advance to about 10-4 to 10-1' by
Check the degree of vacuum and remove the gas sucked into the device.

At the same time, the electrode heater (737) heats the electrode (736) and the conductive substrate (752) fixedly disposed on the electrode to a predetermined temperature.

Next, the raw material gas is transferred from the first to sixth tanks (701) to (706) and the first to third containers (719) to (721) to the first to ninth flow controllers (713) to (718).
, (728) to (730) to react while making constant flow m! (733) and the reaction chamber (733) by the pressure control valve.
33) Maintain a constant reduced pressure inside.

After the gas flow rate has stabilized, press the connection selection switch (744)
For example, a high frequency power source (739) is selected, and high frequency power is applied to the power application electrode (736).

A discharge starts between both electrodes, and a convex plate (752
) a solid-phase a-C film is formed on the top.

The fluorine atoms contained in the a-C film are contained in the reaction chamber (733).
By adjusting the amount of the fluorine atom-containing compound introduced into the charge generation layer using the flow controller, it is possible to make the charge generation layer contain a large amount of fluorine atoms continuously and non-uniformly in the film thickness direction.

The present invention will be explained below with reference to Examples.

Example 1 Charge transport color forming step (CTL): In the glow discharge decomposition apparatus shown in FIG. , second, and third control valves (707,
708 and 709), and the first tank (701)
Hydrogen gas, ethylene gas from the second tank (702), and carbon tetrafluoride gas from the third tank (703) were supplied to the 11th and 3rd tanks at an output pressure of 1.0 kg/am'', respectively.
It was made to flow into the flow rate controllers (713, 714, and Hifu 15). Then, adjust the scale of each flow rate controller to set the hydrogen gas flow rate to 408 CCms and the ethylene gas flow rate to 30 se.
cm, and the flow rate of carbon tetrafluoride gas was set to 12 sec, and flowed into the reaction chamber (733) from the main pipe (732) via an intermediate mixer (731). After each flow rate stabilizes, the pressure inside the reaction chamber (733)
The pressure control valve (745) was adjusted so that the pressure was 0.0 Torr. On the other hand, as a conductive substrate (752),
Using an aluminum substrate measuring 0 x width 50 x thickness 3 x 3, pre-heated to 250°C, and with the gas flow rate and pressure stable, a high-frequency power source ( 739) and applied 200 Watt power to the power application electrode (736) at frequencies 13 and 5.
The plasma polymerization reaction was started by applying below 6 MHz. After 10 minutes, the flow of carbon tetrafluoride gas n was increased to 12
secm, and 19 minutes after the start of the reaction,
It was set at 120 sec. During this time, power and pressure were kept constant. In this state, the reaction was continued, and 5 hours after the start of the reaction, the reaction was stopped.

By the above procedure, an a-C film having a thickness of 19 μm was formed as a charge transport layer on the conductive substrate (752). After the film formation is completed,
The control valve was closed and the inside of the reaction chamber (733) was sufficiently evacuated.

Auger analysis was performed on the a-C film obtained as described above, and it was found that m of the contained fluorine atoms was 12 seconds for all +1v1 atoms of carbon tetrafluoride.
The layer of m is 0,5 atm,%, and the carbon tetrafluoride flow rate is l.
The 20 sccm layer was 3.1 atm,%.

Charge generation layer forming step (CGL) a-9i): Next, the first control valve (707) and the sixth control valve (712) are opened, and hydrogen gas is removed from the first tank (701) and the sixth tank ( 706) at an output pressure of Ikg/cy.
t", the first and sixth flow controllers (713 and 7
18) It was allowed to flow into the interior. The scales of each flow rate controller were adjusted to set the flow rate of hydrogen gas at 300 sccm and the outflow of silane gas at IOOsccm, which then flowed into the reaction chamber (733). After each flow rate stabilized, the reaction chamber (7
The pressure regulating valve (745) was adjusted so that the pressure inside 33) was 0.8 Torr. On the other hand, the conductive substrate (752) on which the a-C film is formed is heated to 250°C, and the high-frequency power supply (752) is heated to 250°C and the gas flow rate and pressure are stabilized.
39), a power of 200 Watt was applied to the power application electrode (736) at a frequency of 13.56 MHz to generate glow discharge. This discharge was carried out for 20 minutes, and the thickness was 0.
．． A 4μ order a-St:H charge generation layer was formed.

Characteristic.

When the obtained photoreceptor was used in a commonly used Carlson process, the maximum charging potential (hereinafter referred to as V max) was -
In other words, since the total photoreceptor film thickness is 19.4 μl, the charging capacity per 1 μl (hereinafter referred to as C, A) is extremely high at 51.5 V, which indicates that sufficient charging performance can be achieved. It was understood that they had. Also, V in the dark
The time required for dark decay from max to a potential of 90% of V max (hereinafter referred to as Td) was about 25 seconds, and from this fact it was understood that it had sufficient charge retention performance. In addition, the amount of light required to achieve bright attenuation H from V max to a potential of 20% of V max (hereinafter referred to as E) is 2°512L11[-5ec, which indicates that there is sufficient photosensitivity. It was understood that it has good performance.

From the above, the photoreceptor according to the present invention shown in this example has excellent performance. Further, when an image was formed and transferred to this photoreceptor using the commonly used Carlson process, a clear image was obtained.

Example 2 Charge generation layer forming step (CG LXa-S i): 1st
The control valve (707) and the sixth control valve (712) are released, and hydrogen gas from the first tank (701) and silane gas from the sixth tank (706) are supplied to the first tank under an output pressure of 1 and 97cx''. , and the sixth flow rate controller (713 and 718)
It flowed inside. The flow rate of hydrogen gas was set to 300 seconds and the flow rate of silane gas was set to 100 seconds by adjusting the filtration scale of each flow rate controller, and the gases were caused to flow into the reaction chamber (733). After each flow rate is stabilized, the reaction chamber (733)
Pressure regulating valve (7) so that the internal pressure is 0.8 Torr.
45) was adjusted. On the other hand, the conductive substrate (752) has 25
After heating to 0℃ and keeping the gas flow rate and pressure stable, a high frequency power source (739) is used to generate a frequency of 13.56M I.
-200W to the power application electrode (736) under Iz
A power of t was applied to generate a glow discharge. This discharge was carried out for 20 minutes to form an a-Si:H charge generation layer having a thickness of 0.4 μm.

After the film formation was completed, power application was stopped, the control valve was closed, and the inside of the reaction chamber (733) was sufficiently evacuated.

Charge transport layer forming step (CTL): ri*IQ1sa711--=su)fFl-iIt1)ri
Q (Inl-f)\1. First, after creating a high vacuum of about 10 Torr inside the reactor (733), the first, second, and third control valves (707, 70
8, and 709), hydrogen gas from the first tank (701), ethylene gas from the second tank (702), and carbon tetrafluoride gas from the third tank (703) at output pressures of 1 and 0 kg, respectively. /cm" into the No. 11 second and third flow rate controllers (713, 714, and 715). Then, by adjusting the scale of each flow rate controller, the flow rate of hydrogen gas was set to 40 seconds, The flow rate of ethylene gas is 305
ccn, and the flow rate of carbon tetrafluoride gas to 120 se
cm, and flowed into the reaction chamber (733) from the main pipe (732) via an intermediate mixer (731). After each flow rate stabilizes, the pressure regulating valve (745) is adjusted so that the pressure in the reaction chamber (733) becomes 1.0 Torr.
) was adjusted. On the other hand, as the conductive substrate (752),
Using an aluminum substrate measuring 50 cm long x 50 cm wide x 3 cm thick, the high-frequency TL was preheated to 250°C and connected using the connection selection switch (744) with the gas flow rate and pressure stable. Source ('tmf, -krh enter 1-ff1f'Ifil+n buds r7'2A)1.
-9nn W-v++ maca frequency 13.56MH
The plasma polymerization reaction was started by applying the voltage below z. After 4 hours and 40 minutes, the flow of carbon tetrafluoride gas m was increased to 12 seconds per minute.
ecm and was set to 12 seconds 4 hours and 49 minutes after the start of the reaction. During this time, power and pressure were kept constant. The reaction continued in this state and was stopped 5 hours after the start of the reaction.

By the above procedure, an a-C film having a thickness of 19 μm was formed as a charge transport layer. After the film formation is completed, close the control valve and close the reaction chamber (7
33) Thoroughly evacuated the inside.

When the a-C film obtained as described above was subjected to an Ohm analysis, the amount of fluorine atoms contained in the layer with a carbon tetrafluoride flow rate of 12 sec was 0.5 atm based on the total amount of fluorine atoms. ,%, carbon tetrafluoride flow rate is 120
The layer of secm was 3,1 atm,%.

Characteristics: When the obtained photoreceptor was used in a commonly used Carlson process, V max was +l100V, that is, since the total photoreceptor film thickness was 19.4μl, the charging ability per 1μl was se, 7V. It was understood from this that it had sufficient charging performance. Also, Vm in the dark
The time required for dark decay from ax to a potential of 90% of V max was 30 seconds, and from this it was understood that it had sufficient charge retention performance. Also, V may,
When the brightness was attenuated from Vmax to a potential of 20% of Vmax, the required light m was 4,0Qux-sea, and from this it was understood that it had sufficient photosensitivity performance.

From the above, the photoreceptor according to the present invention shown in this example has excellent performance. Further, when an image was formed and transferred to this photoreceptor using the commonly used Carlson process, a clear image was obtained.

Example 3 CTL process: In the glow discharge decomposition apparatus shown in FIG.
After creating a high vacuum of about 10-'' Torr inside the reactor (733), the fourth control valve (710) is opened and the fourth control valve (710) is opened.
Argon gas is supplied from the tank (704) at an output pressure of 1.0
4th flow control'' under Kg/ax''? 5 (716), at the same time, the ninth control valve (727) is released and the third container (
721) from 2.2.2-trifluoroethyl methacrylate [CH,=C(CH3)C00CH,CP,] under the third temperature controller (724) (temperature 40°C) and the ninth flow rate controller (730). Then, adjust the scale of each flow rate controller to set the argon gas flow rate to 40 se
cm.

The flow rate of the 2,2.2-trifluoroethyl methacrylate gas was set to 30 seconds, and the gas flowed into the reaction chamber (733) from the main pipe (732) via the mixing P3 (731). After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure in the reaction chamber (733) was 0.3 Torr. On the other hand, the conductive substrate (752) has a length of 50×width of 50×thickness of 311 mm.
Using an aluminum laminated substrate of 20 to the application electrode (736)
A plasma polymerization reaction was performed for 20 minutes by applying a power of 0 Watt at a frequency of 13.56 MHz, and the conductive substrate (
752), a 1 μm thick a-C film was formed thereon as a charge transport layer. After the film formation was completed, power application was stopped, the control valve was closed, and the inside of the reaction chamber (733) was sufficiently evacuated.

Subsequently, the fourth control valve (710) is released and the fourth tank (
704), the output pressure of argon gas is 1 and 0 kg, respectively.
7cm'' into the fourth flow controller (716), simultaneously releasing the eighth regulating valve (726) and releasing the second container (720).
More IH.

IH,2I(,2H-heptafluorodecyl methacrylate [CHt=C(CHJCOOCHt(CFt)al
The argon gas flowed into the eighth flow rate controller (729) under the second temperature controller (723 40 sccm, and I H,1)[,21-I,
The flow M of 2H-hebutafluorodecyl methacrylate gas was set to 30 sccm, and the flow was carried out from the main pipe (732) to the reaction chamber (73) via the mixer (731) on the way.
3) It flowed into the interior. After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure in the reaction chamber (733) was 0.3 Torr.

When the gas flow rate and pressure are stable, connect the high frequency source (744) that has been connected in advance using the connection selection switch (744).
39) and applied 200 W to the power application electrode (736).
Att power was applied at a frequency of 13.56 MHz to carry out the plasma polymerization reaction for about 5 hours. After the film formation is completed,
The application of electric power was stopped, the control valve was closed, and the inside of the reaction chamber (733) was sufficiently evacuated.

Auger analysis was performed on the a-C film obtained as described above, and it was found that the amount of fluorine atoms contained in the part formed with 2,2,2-trifluoroethyl methacrylate was approximately 10 atomic%, l H, l
The amount of fluorine atoms contained in the film formed from I-1, 2H, 21-1-hebutafluorodecyl methacrylate was 28 at % based on the total constituent atoms. Also, the film thickness is 28μ! Met.

CGL (a-9i) step: Next, the 1st section valve (707) and the 6th control valve (712
) and release hydrogen gas from the first tank (701) and silane gas from the sixth tank (70B) to the output pressure! k
The first and sixth flow controllers (713,
and 718). The scales of each flow rate controller were adjusted to set the flow rate of hydrogen gas to 3 Q Q sccm and the flow rate of silane gas to l Q Osccm, which were then caused to flow into the reaction chamber (733). After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure inside the reaction chamber (733) was 0.8 Torr. On the other hand, the conductive substrate (752) on which the a-C film is formed is heated to 200°C, and while the gas flow rate and pressure are stable, the high frequency power supply (739) is heated to a frequency of 13.56 μl-Iz. A power of 200 Watts was applied to the power application electrode (736) to generate glow discharge. This discharge was performed for 20 minutes to form an a-Si:H charge generation layer with a thickness of 0.4 μl.

Skin: When the film-formed portion of the obtained laminated film was used in a commonly used Carlson process, V max was -800V, that is, the total photoreceptor film thickness was 28.4μ, so C, A
, was extremely high at 2B, 2V, and from this it was understood that it had sufficient charging performance. Furthermore, the Td was approximately 15 seconds, and from this fact it was understood that it had sufficient charge retention performance. Also, E is 2.0 Qux-sea,
From this, it was understood that the film had sufficient photosensitivity performance.

From the above, the photoreceptor according to the present invention shown in this example has excellent performance. Further, when an image was formed and transferred to this photoreceptor using the commonly used Carlson process, a clear image was obtained.

Comparative Example 1 Charge Transport Layer Formation Step (CTL): In the glow discharge decomposition apparatus shown in FIG. Second and third control valves (707, 7
08 and 709), hydrogen gas from the first tank (701), and air gas from the second tank (702).
And from the third tank (703), carbon tetrafluoride gas was flowed into the first, second and third flow rate controllers (713, 714, and 715) under an output pressure of 1,000 kg/ax, respectively. Then, adjust the scale of each flow rate controller so that the flow rate of hydrogen gas is 40 secms and the flow rate of ethylene gas is 30 secms.
secm, and the flow rate of carbon tetrafluoride gas to 120sec.
After the flow rate of each intermediate mixer (731) was stabilized, the pressure control valve (745) was adjusted so that the pressure in the reaction chamber (733) was 1.0 Torr. On the other hand, the conductive substrate (752) is
A high-frequency power source (739) using an aluminum substrate measuring 50 x width x 3 RR, preheated to 250°C, and connected with a connection selection switch (744) with the gas flow rate and pressure stable. and applied 200 Watt power to the power application electrode (736) at a frequency of 13.5.
A plasma polymerization reaction was performed for about 5 hours by applying a frequency of 6 MHz, and a 20 μl thick a-C was deposited on the conductive substrate (752).
The membrane was formed as a charge transport layer.

After the film formation was completed, power application was stopped, the control valve was closed, and the reaction chamber (733) was sufficiently evacuated.

When the a-C film obtained as described above was subjected to Auger analysis, the amount of halogen atoms, that is, fluorine atoms contained therein was 3.1 at % based on the total constituent atoms.

Charge generation layer forming step (CG L) (a-S i):
Next, silane gas is supplied from the first control valve (707) and the sixth control valve and sixth tank (706) at an output pressure of I k
g/c*'0) Lower T: 1st, and U 6th flow rate control! (
713 and 718). Adjust the scale of each flow rate controller to set the hydrogen gas flow m to 300 scc+n,
The flow m of silane gas was set at 100 sccm and flowed into the reaction chamber (733). After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure inside the reaction chamber (733) was 0.8 Torr. On the other hand, a-
The conductive substrate (752) on which the C film is formed is 250
℃, and with the gas flow rate and pressure stable, 200 Watt power was applied to the power application TL pole (736) at a frequency of 13.56 MHz from the high frequency power source (739) to generate glow discharge. Ta. This discharge was performed for 20 minutes, and a-3t:H? A lX charge generation layer was formed.

Characteristics: When the obtained photoreceptor was used in a common Carlson process, V max was -700V, that is, the total photoreceptor film thickness was about 20.4μ, so C and A were 3C.
The voltage was extremely high at 3V, and from this fact it was understood that it had sufficient charging performance. Furthermore, the Td was approximately 15 seconds, and from this it was understood that it had sufficient charge retention performance.

In addition, E was 2°5 Qux-sec, and from this it was understood that the film had sufficient photosensitivity performance.

From the above, the photoreceptor according to the present invention shown in this example has excellent performance. However, it was found that the photoreceptor shown in Example 1 was inferior in charging performance and charge retention performance.

Comparative Example 2 CTL process: In the glow discharge decomposition apparatus shown in FIG.
After making the inside of the reactor (733) a high vacuum of approximately IO-'Torr, the fourth control valve (710) is opened and the fourth control valve (710) is opened.
Argon gas is supplied from the tank (704) at an output pressure of 1,
0 Kg/cm'' into the fourth flow controller (716), simultaneously releasing the eighth regulating valve (726) and releasing the second container (
720) from IH, IH, 2H, 2H-heptafluorodecyl methacrylate [CI-Iyo = C (CHJCOO
CI(t(CF) flows into 111-11, and under the second temperature controller (723
9) It was allowed to flow into the interior. Then, adjust the scale of each flow controller to set the argon gas flow rate to 40 sec and I
The flow rate of H9IH, 2H, 2H-heptafluorodecyl methacrylate gas was set to 30 sec, and flowed into the reaction chamber (733) from the main pipe (732) via the mixer (731) midway. After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure in the reaction chamber (733) was 0.3 Torr. On the other hand, as the conductive substrate (752), use a 50 x 50 x 3 degree thick aluminum substrate, heat it to 200°C in advance, and when the gas flow rate and pressure are stable, switch the connection selection switch in advance. (744), turn on the high frequency power supply (739) connected to the power application electrode (736), and
A plasma polymerization reaction was performed for about 5 hours by applying a power of 0 Watt at a frequency of 13.56 MHz, and the conductive substrate (
752), an a-C film was formed thereon as a charge transport layer. After the film formation was completed, power application was stopped, the section valve 5.1 was closed, and the inside of the reaction chamber (733) was sufficiently evacuated.

1; above 11-1. Hisaji Temami conducted Auger analysis of Su.3-C pus2 and found that the amount of halogen atoms, i.e., fluorine atoms, contained was 28% of all fluorine atoms.
It was atomic%. Further, the film thickness was 27 μm.

CGL (a-Si) process: Next, the first control valve (707) and the sixth control valve (712
) and hydrogen gas from the first tank (701) and silane gas from the sixth tank (706) at an output pressure of 1k.
g/ax", the first and sixth flow controllers (713,
and 718). The scale of each flow rate controller was adjusted to set the flow rate of hydrogen gas to 300 sec and the flow rate of silane gas to 100 sec.
3) It was allowed to flow into the interior. After each flow rate became stable, the pressure control valve (745) was adjusted so that the pressure inside the reaction chamber (733) was 0.8 Torr. On the other hand, the conductive substrate (752) on which the a-C film is formed is heated to 200°C, and when the gas flow rate and pressure are stable, high frequency?
I! A power of 200 Watts was applied from the source (739) to the power application electrode (736) at a frequency of 13.56 MHz to generate glow discharge. This discharge was carried out for 20 minutes,
A 0.4 μm thick a-9t:H charge generation layer was formed.

Characteristics: When the film-formed portion of the obtained laminated film was used in a commonly used Carlson process, V wax was -350V, that is, the total photoreceptor film thickness was 27.4μ, so C, A
, was low at 12.8V, and Td was also low at about 3 seconds. Further, the amount of light required for bright attenuation from -350V to -100V was 4°8 f2ux-see. From this, it was understood that C, A, and Td were low and insufficient.

Effects of the Invention According to the present invention, when the charge transport layer contains fluorine atoms, the charge transport ability is improved, and furthermore, by containing more fluorine atoms on the charge generation layer side and less on the opposite side, the charge generation layer improves. Injection of carriers from the substrate into the charge transport layer is promoted, and charge injection from the substrate or surface can be suppressed, resulting in improved sensitivity of the photoreceptor.

[Brief explanation of the drawing]

1 to 12 show schematic cross-sectional views of the photoreceptor of the present invention. FIG. 13 and FIG. 14 are diagrams showing an example of an apparatus for manufacturing a photoreceptor. The symbols in the figure are as follows. (1)...Substrate (2)...Charge transport layer (a
-C layer) (3)...charge generation layer (4)...overcoat layer (5)...undercoat layer (701) to (706)...tank (707) to (712) and (725) ~ (727)・
...Control valve (713) ~ (71g) and (72g) ~ (
730)...Flow ffi controller (mass flow controller) (719) to (721)...Container (722) to
(724)... Heater (731)... Mixer
(732)...Main pipe (733)...Reaction chamber (
734)...Pipe heater (735)...Ground electrode
(736)...Power application electrode (737)...Power heater (738)...High frequency power matching device (739)
...High frequency power supply (740) ...Low frequency power matching box (741) ...Low frequency power supply (742) ...Low pass filter (743) ...DC power supply (744)
... Connection selection switch (745) ... Pressure control valve (
746)...Exhaust system selection valve (747)...Diffusion pump (748)...Oil rotary pump (749)...Cooling exclusion device (750)...Mechanical booster pump (751)
... Reaction heater (752) ... Conductive substrate (75
3)...Exclusion device

Claims (1)

[Claims] 1. In a laminated photoreceptor having at least a charge generation layer and a charge transport layer, the charge transport layer is an amorphous solid formed by plasma polymerizing hydrocarbons in a gas phase and whose constituent atoms are carbon and hydrogen. A photoconductor characterized in that it contains a large amount of fluorine atoms as a chemical modifier continuously in the thickness direction on the charge generation layer side.