JP2009109810A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and image forming method, effectively restraining the occurrence of negative ghost while effectively performing static elimination. <P>SOLUTION: This image forming apparatus includes: a positively charged single layer type electrophotographic photoreceptor having a photosensitive layer containing at least binder resin, a charge generating agent, a hole transport agent, an electron transport agent, and an optical absorption agent; a charging means; an exposure means; a developing means; a transfer means; a fixing means; and a static elimination means. In this image forming method, an X-type metal-free phthalocyanine is used as the charge generating agent, the film thickness of the photosensitive layer is set to a value ranging from 20 to 50 μm, and when the maximum absorption wavelength of the optical absorption agent is λ1<SB>max</SB>nm, and the wavelength of exposure light radiated from the exposure means is λ<SB>0</SB>nm, the λ1<SB>max</SB>nm satisfies the expression (1): 450≤λ1<SB>max</SB>≤λ<SB>0</SB>-200, and further the wavelength of static elimination light radiated from the static elimination means is set to a value of 580 nm or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method. In particular, the present invention relates to an image forming apparatus and an image forming method capable of effectively suppressing the occurrence of a negative ghost that is likely to be generated by performing a static elimination process.

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic system such as a copying machine or a printer, an organic photoreceptor having a photosensitive layer made of an organic material has been widely used from the viewpoint of safety and ease of processing.
Such an organic photoreceptor includes a layered electrophotographic photoreceptor obtained by laminating a charge generation layer containing a charge generation agent and a charge transport layer containing a charge transfer agent, and a charge generation agent and a charge generation agent in the same layer. And a single-layer electrophotographic photosensitive member containing a charge transfer agent.
Moreover, although the hole transport agent and the electron transport agent exist in the charge transport agent described above, a compound having a sufficient electron transport ability has not been developed yet.
Therefore, in general, a laminated electrophotographic photoreceptor uses a hole transporting agent as a charge transporting agent, so that the charging type is a negative charging type.
However, when the electrophotographic photosensitive member is negatively charged, ozone or the like is remarkably generated as compared with the case where the electrophotographic photosensitive member is positively charged. Therefore, the photosensitive layer is likely to be deteriorated or adversely affect the human body. There is a problem of becoming.
In this regard, a single layer type electrophotographic photoreceptor can contain a hole transport agent and an electron transport agent in the photosensitive layer, and therefore can be easily positively charged. Can effectively solve the problem of ozone generation.
However, in such a positively charged single layer type electrophotographic photosensitive member, residual charges are likely to be generated in the photosensitive layer due to insufficient electron transporting ability of the electron transporting agent. There has been a problem that the image quality is reduced and the exposure memory is likely to be generated.

Accordingly, a static elimination method for efficiently removing such residual charges has been proposed (for example, Patent Documents 1 to 3).
That is, Patent Document 1 discloses a method characterized by using irradiation of light-emitting diode light that emits light having a visible region maximum absorption wavelength ± 10 nm of a photosensitive layer in static elimination of a predetermined single-layer type electrophotographic photosensitive member. Has been.
Further, in Patent Document 2, the wavelength of light emitted from the charge eliminating means is set to a wavelength in the range of the half-width of the maximum absorbance in the absorbance characteristics of the photoreceptor film or the charge generation material contained in the photoreceptor film. A method is disclosed.
Further, in Patent Document 3, in the charge removal of a predetermined single layer type electrophotographic photosensitive member, the wavelength λ ₀ of the exposure light source and the charge removal light wavelength λ ₁ satisfy the relationship of λ ₀ −200 nm ≦ λ ₁ ≦ 780 nm. A method characterized by this is disclosed.
And certainly, if it is the static elimination method disclosed by these patent documents 1-3, static elimination efficiency can be improved and the fall of a charging potential and generation | occurrence | production of exposure memory can be suppressed to some extent.
Japanese Patent No. 3257910 (Claims) JP-A-7-234618 (Claims) JP 2001-350329 A (Claims)

However, even with the static elimination methods disclosed in Patent Documents 1 to 3, it is difficult to remove residual charges in the deep layer of the photosensitive layer.
As a result, especially when the photosensitive layer is made thick, or when the image forming speed is increased, the charge generated by the static elimination light is less likely to move due to the residual charge in the deep layer of the photosensitive layer, There has been a problem that the charged potential in the photosensitive layer becomes non-uniform.
As a result of the non-uniform charging potential in the photosensitive layer, a phenomenon in which the image density slightly decreases (hereinafter referred to as negative ghost) tends to occur at the corresponding portion in the formed image, particularly when a full-color image is formed. However, there was a new problem that such negative ghosts were easily noticeable.

Therefore, as a result of intensive studies, the present inventors have used a specific compound as a charge generating agent in an image forming apparatus equipped with a positively charged single-layer type electrophotographic photosensitive member, and the film thickness of the photosensitive layer within a predetermined range. In addition, a light absorber having a predetermined light absorption characteristic is added, or a compound having a predetermined light absorption characteristic is added as a charge transport agent, and the wavelength of the static elimination light irradiated from the static elimination means is predetermined. In the range described above, it has been found that while neutralization can be effectively performed, the occurrence of negative ghosts can also be effectively suppressed, and the present invention has been completed.
That is, an object of the present invention is to provide an image forming apparatus and an image forming method using the same that can effectively suppress the occurrence of negative ghosts while effectively performing static elimination.

According to the present invention (hereinafter sometimes referred to as the first invention), a photosensitive layer comprising at least a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent. An image forming apparatus comprising a positively charged single-layer type electrophotographic photosensitive member having a charging means, an exposure means, a developing means, a transfer means, a fixing means, and a charge eliminating means, X-type metal-free phthalocyanine is used as the charge generating agent, the photosensitive layer thickness is set to a value in the range of 20 to 50 μm, and the maximum absorption wavelength of the light absorber is set to λ1 _max (nm). Λ 1 _max (nm) satisfies the relational expression (1) when the wavelength of the exposure light to be applied is λ ₀ (nm), and the wavelength of the static elimination light emitted from the static elimination means is 580 nm or less. An image forming apparatus is provided, which is described above. It is possible to solve the problem.
450 ≦ λ1 _max ≦ λ ₀ −200 (1)
That is, by adding a light absorber having a predetermined light absorption characteristic to the photosensitive layer of the positively charged single-layer type electrophotographic photosensitive member and setting the wavelength of the static elimination light within a predetermined range, It is possible to limit the portion where the process is performed to the vicinity of the surface layer of the photosensitive layer.
As a result, it is possible to suppress the generation of excessive charges in the photosensitive layer due to the static elimination light while effectively eliminating the residual charges mainly generated in the vicinity of the surface layer of the photosensitive layer by the exposure light.
Further, by suppressing the generation of excessive charges due to the static elimination light, it is possible to efficiently eliminate the residual charges in the deep layer of the photosensitive layer.
Therefore, it is a positively charged single layer type electrophotographic photosensitive member in which residual charges are likely to be generated, and it is possible to effectively perform negative ghosting while effectively eliminating static electricity even though the photosensitive layer has a predetermined thickness. Generation can be effectively suppressed.
In the first invention, the light absorber having a predetermined light absorption property may have a charge transporting ability. Even in this case, the light absorber is composed of an electron transport agent and a hole. The compound is different from the transport agent.
That is, in the first invention, even if the light absorber has a charge transporting ability, the light absorber is added as a light absorber, and separately, an electron transport agent and a hole transport agent. Is added as an electron transporting agent and a hole transporting agent.

In constituting the image forming apparatus of the present invention, the light absorber is selected from the group consisting of a trinitrofluorenone derivative, a benzofuran derivative, a bisnaphthylquinone derivative, an indenopyrazine derivative, a diphenoquinone derivative, and an azoquinone derivative, at least A kind of compound is preferred.
With such a configuration, it is possible to limit the portion of the photosensitive layer where the charge is removed, to the vicinity of the surface of the photosensitive layer, while suppressing the deterioration of the electrical characteristics of the electrophotographic photosensitive member.

In configuring the image forming apparatus of the present invention, it is preferable that the addition amount of the light absorber in the photosensitive layer is set to a value in the range of 5 to 100 parts by weight with respect to 100 parts by weight of the binder resin.
By configuring in this way, it is possible to more effectively remove the residual charge generated by the exposure light while limiting the portion of the photosensitive layer to be neutralized to the vicinity of the surface layer of the photosensitive layer.

In configuring the image forming apparatus of the present invention, it is preferable to set the irradiation amount of the static elimination light to a value within the range of 1 to 10 μJ / cm ² .
With such a configuration, it is possible to more effectively remove the residual charge generated by the exposure light while limiting the portion of the photosensitive layer to be neutralized to the vicinity of the surface layer of the photosensitive layer.

In configuring the image forming apparatus of the present invention, it is preferable that the static elimination light source used in the static elimination means is an LED.
With this configuration, the wavelength of the static elimination light can be easily adjusted to a value within a predetermined range.

In configuring the image forming apparatus of the present invention, it is preferable to set the wavelength of the exposure light emitted from the exposure unit to a value in the range of 590 to 790 nm.
By comprising in this way, a charge can be efficiently generated from a charge generating agent and a clear electrostatic latent image can be formed on the surface of the photosensitive layer.
On the other hand, since charges are generated efficiently, residual charges are inevitably generated. However, according to the present invention, the occurrence of negative ghosts can be effectively suppressed regardless of the residual charges. .

In configuring the image forming apparatus of the present invention, the image forming apparatus is preferably a full-color image forming apparatus.
With such a configuration, as a result of the color shading in the formed image being easily noticeable, negative ghosts are likely to occur. However, according to the present invention, the occurrence of such negative ghosts can be effectively suppressed.
Therefore, a high-quality full color image can be stably formed.

Further, another aspect of the present invention (hereinafter sometimes referred to as the second invention) is a positively charged single layer type having a photosensitive layer containing a binder resin and a charge transport agent on at least a substrate. An image forming apparatus including an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit, and an X-type non-metal as a charge generating agent While using phthalocyanine, the film thickness of the photosensitive layer is set to a value in the range of 20 to 50 μm, the maximum absorption wavelength of the charge transfer agent is λ2 _max (nm), and the wavelength of the exposure light irradiated from the exposure means is λ _{In the case of 0} (nm), λ2 _max (nm) satisfies the relational expression (2), and the wavelength of the static elimination light emitted from the static elimination means is set to a value of 580 nm or less. Device.
450 ≦ λ2 _max ≦ λ ₀ −200 (2)
That is, by adding a compound having a predetermined light absorption property as a charge transfer agent to the photosensitive layer of the positively charged single-layer type electrophotographic photosensitive member, and setting the wavelength of the static elimination light within a predetermined range, the photosensitive layer The portion to be neutralized in can be limited to the vicinity of the surface layer of the photosensitive layer.
As a result, it is possible to suppress the generation of excessive charges in the photosensitive layer due to the static elimination light while effectively eliminating the residual charges mainly generated in the vicinity of the surface layer of the photosensitive layer by the exposure light.
Further, by suppressing the generation of excessive charges due to the static elimination light, it is possible to efficiently eliminate the residual charges in the deep layer of the photosensitive layer.
Therefore, it is a positively charged single layer type electrophotographic photosensitive member in which residual charges are likely to be generated, and it is possible to effectively perform negative ghosting while effectively eliminating static electricity even though the photosensitive layer has a predetermined thickness. Generation can be effectively suppressed.
In the second invention, unlike the first invention, it is not necessary to add a light absorber separately from the electron transport agent and the hole transport agent.
In other words, the electron transport agent and / or the hole transport agent may be any compound having a predetermined light absorption property, and it is not necessary to add another light absorber.

Another embodiment of the present invention is a positively charged single-layer type electron having a photosensitive layer containing at least a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent. An image for forming an image on a transfer object by performing a charging process, an exposure process, a developing process, a transfer process, a fixing process, and a charge eliminating process on the photographic photoreceptor. In this method, X-type metal-free phthalocyanine is used as a charge generator, the film thickness of the photosensitive layer is set to a value in the range of 20 to 50 μm, and the maximum absorption wavelength of the light absorber is λ1 _max (nm) When the wavelength of the exposure light irradiated in the exposure process is λ ₀ (nm), λ1 _max (nm) satisfies the relational expression (1), and further, the wavelength of the static elimination light irradiated in the static elimination process Image forming method, characterized in that the value is 580 nm or less It is.
450 ≦ λ1 _max ≦ λ ₀ −200 (1)
That is, according to the image forming method of the present invention, a positively charged single layer type electrophotographic photoreceptor containing a specific charge generating agent and a light absorber having a predetermined light absorption characteristic and having a predetermined film thickness is used. In addition, since the neutralization light having a predetermined wavelength is irradiated as the neutralization step, it is possible to effectively suppress the occurrence of negative ghost while performing the neutralization effectively.

Further, another aspect of the present invention provides a charging step for a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer containing at least a binder resin, a charge generating agent, and a charge transporting agent. An image forming method for forming an image on a transfer object by performing an exposure step, a development step, a transfer step, a fixing step, and a charge removal step, and the charge generation agent Exposure light irradiated in the exposure process using X-type metal-free phthalocyanine, a film thickness of the photosensitive layer in the range of 20 to 50 μm, and a maximum absorption wavelength of the charge transport agent of λ2 _max (nm) the wavelength of the case of the lambda ₀ (nm), characterized in that .lambda.2 _max (nm) is satisfied equation (2), further, that the following values 580nm wavelength of discharging light emitted in the neutralization step Image forming method.
450 ≦ λ2 _max ≦ λ ₀ −200 (2)
That is, according to the image forming method of the present invention, a positively charged single-layer type electrophotographic photoreceptor containing a specific charge generating agent and a charge transporting agent having a predetermined light absorption characteristic and having a predetermined film thickness is used. In addition, since the neutralization light having a predetermined wavelength is irradiated as the neutralization step, it is possible to effectively suppress the occurrence of negative ghost while performing the neutralization effectively.

[First Embodiment]
The first embodiment of the present invention is a positively charged single layer type electron having a photosensitive layer including at least a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent. An image forming apparatus including a photographic photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit, and an X-type metal-free phthalocyanine as a charge generating agent , The photosensitive layer thickness is set to a value in the range of 20 to 50 μm, the maximum absorption wavelength of the light absorber is λ1 _max (nm), and the wavelength of the exposure light irradiated from the exposure means is λ _0. (Nm), λ1 _max (nm) satisfies the following relational expression (1), and the wavelength of the static elimination light emitted from the static elimination means is set to a value of 580 nm or less. Device.
450 ≦ λ1 _max ≦ λ ₀ −200 (1)
Hereinafter, the image forming apparatus as the first embodiment will be specifically described for each component.

1. Basic Configuration The image forming apparatus includes at least a positively charged single layer type electrophotographic photosensitive member, which will be described later, a charging unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit.
Hereinafter, as a specific example, the basic configuration of the image forming apparatus of the present invention will be described with reference to the full-color image forming apparatus 10 shown in FIG.
That is, the full-color image forming apparatus 10 includes an endless belt (conveying belt) 15, and the endless belt 15 conveys the recording paper fed from the paper feeding cassette 18 toward the fixing unit 20. It is configured. Further, on the upper side of the endless belt 15, a magenta developing unit 11M, a cyan developing unit 11C, a yellow developing unit 11Y, and a black developing unit 11BK are arranged along the conveyance direction of the recording paper. .
Further, positively charged single-layer type electrophotographic photosensitive members 13M to 13BK are arranged facing the developing rollers 12M to 12BK, respectively. Further, around these positively charged single layer type electrophotographic photosensitive members 13M to 13BK, charging means 14M to 14BK for charging the surfaces of the positively charged single layer type electrophotographic photosensitive members 13M to 13BK and positively charged single layers, respectively. Exposure means 15M to 15BK and the like for forming electrostatic latent images are arranged on the surfaces of the type electrophotographic photoreceptors 13M to 13BK.
Therefore, the electrostatic latent images formed on the positively charged single layer type electrophotographic photosensitive members 13M to 13BK corresponding to the respective colors are developed by the developing units 11M to 11BK corresponding to the respective colors.
Further, transfer means 16M to 16BK for sequentially transferring the respective color developer images onto the recording paper conveyed by the endless belt 15 are respectively positively charged single layer type electrophotographic photosensitive members via the endless belt 15. It is arrange | positioned on the opposite side of the bodies 13M-13BK.
Next, cleaning devices 23M to 23BK having cleaning blades 22M to 22BK for removing the untransferred developer remaining on the positively charged single layer type electrophotographic photoreceptors 13M to 13BK after the transfer of the respective color developer images are provided. The image carriers 13M to 13BK are arranged around.
Further, on the downstream side of the cleaning means 23M to 23BK, static elimination for neutralizing residual charges generated in the photosensitive layers of the positively charged single-layer type electrophotographic photoreceptors 13M to 13BK when an electrostatic latent image is formed. Means 24M-24BK are arranged.
As described above, when the image forming apparatus is configured as a full-color image forming apparatus, the density of the color in the formed image becomes conspicuous, and as a result, negative ghosts are likely to occur. The occurrence of negative ghost can be effectively suppressed.
Therefore, a high-quality full color image can be stably formed.

2. 1. Static elimination means (1) Wavelength of static elimination light The present invention is characterized in that the wavelength of static elimination light emitted from the static elimination means 24M to 24BK shown in FIG. 1 is set to a value of 580 nm or less.
The reason for this is that the wavelength of the static elimination light is set to a value of 580 nm or less, which is shorter than the absorption peak of the X-type metal-free phthalocyanine as the charge generating agent, and as described later in the section of the electrophotographic photoreceptor, This is because by adding a light absorbent having a predetermined light absorption characteristic to the photosensitive layer, the portion of the photosensitive layer where the charge is eliminated can be limited to the vicinity of the surface layer of the photosensitive layer.
As a result, it is possible to suppress the generation of excessive charges in the photosensitive layer due to the static elimination light while effectively eliminating the residual charges mainly generated in the vicinity of the surface layer of the photosensitive layer by the exposure light.
Further, by suppressing the generation of excessive charges due to the static elimination light, it is possible to efficiently eliminate the residual charges in the deep layer of the photosensitive layer.
Therefore, it is possible to effectively suppress the occurrence of negative ghost, which is considered to be caused by the interaction between the residual charge in the deep layer of the photosensitive layer and the charge generated from the surface layer to the middle layer of the photosensitive layer due to static elimination light. .

Next, a negative ghost generation mechanism and a suppression mechanism will be specifically described with reference to FIGS.
First, FIG. 2A shows the distribution of charges in the photosensitive layer when the conventional static elimination is performed.
That is, in the conventional static elimination, in order to improve the static elimination efficiency, static elimination light having a wavelength that is largely absorbed by the charge generating agent has been used.
For example, FIG. 3 shows a light absorption spectrum of X-type metal-free phthalocyanine as a charge generating agent, and it can be seen that the wavelength efficiently absorbed in such a compound is in the range of 590 to 790 nm.
Therefore, in the conventional static elimination, if X-type metal-free phthalocyanine is used as a charge generating agent, for example, as shown in FIG. 2A, the static elimination is performed using a 630 nm static elimination light.
However, even in the case of using a neutralizing light having a wavelength that is efficiently absorbed by such a charge generating agent, the neutralizing light is not completely absorbed by the charge generating agent in the vicinity of the surface layer of the photosensitive layer. It reaches the middle layer of the layer and generates charges there.
Therefore, as shown in FIG. 2A, the electric charge 312 generated by the static elimination light is distributed from the surface layer to the middle layer of the photosensitive layer 304.
Of course, since the residual charge 310 due to the exposure light is generally generated in the vicinity of the surface layer of the photosensitive layer 304, it is possible to obtain a sufficient static elimination effect even with conventional static elimination.
Accordingly, the residual charge 310 by the exposure light and the charge 312 generated by the discharge light are generally canceled out by the charging process on the surface of the photosensitive layer, and the surface of the photosensitive layer is uniformly positively charged.

However, it is known that part of the exposure light may reach the deep layer of the photosensitive layer 304 and generate a residual charge 310 ′ in the deep layer of the photosensitive layer 304.
The residual charge 310 ′ in the deep layer of the photosensitive layer 304 cancels out the positive charge generated by the static elimination light, and thus the negative charge 312 generated by the static elimination light is prevented from moving to the surface of the photosensitive layer.
As a result, it is difficult to uniformly positively charge the surface of the photosensitive layer even when the photosensitive layer surface is charged, especially when the photosensitive layer is made thick or when the image forming speed is increased. In particular, it is considered that a negative ghost is likely to occur in a full-color image in which the color density in the formed image is easily noticeable.

On the other hand, as shown in FIG. 2B, when the wavelength of the static elimination light is set to a value of 580 nm or less, for example, 500 nm, and a light absorber 315 having a predetermined light absorption characteristic is added to the photosensitive layer. Since the light absorbing agent 315 having the predetermined light absorption characteristic specifically absorbs the static elimination light having the predetermined wavelength, the portion of the photosensitive layer 304 that is neutralized is placed near the surface layer of the photosensitive layer 304. It can be limited.
As a result, since it is possible to suppress the generation of excessive charges due to the static elimination light up to the middle layer of the photosensitive layer 304, the charges 310 and 312 can be quickly canceled by the charging process.
Then, by quickly canceling the charge on the surface of the photosensitive layer, the residual charge 310 ′ existing in the deep layer of the photosensitive layer 304 can be efficiently moved to the surface of the photosensitive layer 304 and canceled by the charging process.
Accordingly, the surface of the photosensitive layer can be uniformly positively charged, and the occurrence of negative ghost can be suppressed.
2A to 2B, the positive charge in the photosensitive layer can be moved relatively efficiently because the hole transport agent is superior to the electron transport agent in terms of charge transport ability. Therefore, the description is omitted for the sake of convenience, and only negative charges that remain in the photosensitive layer and easily become residual charges are described.

A schematic diagram of an image in which a negative ghost is generated is shown in FIG.
That is, in the formed image 501, the image density of the portion corresponding to the front-circumferentially formed image 502 in the electrophotographic photosensitive member is slightly lowered, and a negative ghost 503 is generated.
As described with reference to FIG. 2A, this is due to the interaction between the residual charge in the deep layer of the photosensitive layer generated by the exposure light in the previous round image formation and the charge generated by the subsequent charge removal light. This is considered to be caused by the non-uniform charge state on the surface of the layer.

(2) Irradiation amount Moreover, it is preferable to make the irradiation amount of static elimination light into the value within the range of 1-10microJ / cm < ² >.
The reason for this is that by setting the irradiation amount of the neutralizing light within such a range, the portion of the photosensitive layer that is neutralized is limited to the vicinity of the surface layer of the photosensitive layer, and the residual charge generated by the exposure light is more effectively reduced. This is because the charge can be removed.
That is, if the dose of the charge removal light is less than 1 μJ / cm ² , it is difficult to generate a sufficient charge for charge removal near the surface of the photosensitive layer. On the other hand, when the irradiation amount of the static elimination light reaches a value exceeding 10 μJ / cm ² , even if it is a light absorbent having a predetermined light absorption characteristic, it becomes difficult to sufficiently absorb the static elimination light, and the static elimination is performed. This is because it may be difficult to limit the portion to be formed to the vicinity of the surface of the photosensitive layer.
Therefore, it is more preferable to set the irradiation amount of the static elimination light to a value within the range of 1.5 to 9 μJ / cm ² , and further preferably to a value within the range of ^{2 to} 8 μJ / cm ² .

(3) Type The type of static elimination means used in the present invention is not particularly limited, and for example, the following types of static elimination means can be used.
・ LED chip array type (Multiple LED chips arranged in the longitudinal direction)
・ Fuse lamp type (white light)
-Light guide type In addition, it is more preferable that the static elimination light source used in a static elimination means is LED.
This is because, in the case of an LED, the wavelength of the static elimination light can be easily adjusted to a predetermined range, and it is inexpensive and economically advantageous.
Therefore, it is more preferable to use an LED chip array type static elimination means among the types of static elimination means described above.
As the light emitting diode, any light emitting diode can be used among PN junction type diodes such as GaAs, GaAs _1-x , P _x , GaP, Al _x , Ga _1-x and As.

3. Type of electrophotographic photosensitive member (1) In the image forming apparatus of the present invention, the electrophotographic photosensitive members 13M to 13BK shown in FIG. 1 are positively charged single layer type electrophotographic photosensitive members.
The reason for this is that a single-layer type electrophotographic photosensitive member can be configured as a positively charged type, which is generally difficult for a laminated type electrophotographic photosensitive member, and is effective in generating ozone and the like in the charging process. This is because it can be suppressed.
On the other hand, in the positively charged single layer type electrophotographic photoreceptor, since the electron transporting ability of the electron transport agent is still insufficient, residual charges tend to be generated in the photosensitive layer. When the static elimination method is performed, negative ghost is likely to occur.
In this respect, in the present invention, as described in detail in the section of the static elimination means, the wavelength of the static elimination light is set within a predetermined range, and as described later, the light absorption having a predetermined light absorption characteristic with respect to the photosensitive layer. Since the agent is added, it is possible to effectively suppress the occurrence of negative ghost even though the positively charged single layer type electrophotographic photosensitive member is adopted as the electrophotographic photosensitive member.

(2) Basic Configuration As shown in FIG. 5A, the positively charged single layer type electrophotographic photosensitive member 13 according to the present invention has a single photosensitive layer 304 provided on a substrate 302.
Such a photosensitive layer contains at least a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent having predetermined light absorption characteristics.
In the single-layer electrophotographic photosensitive member of the present invention, as shown in FIG. 5B, an intermediate layer 306 is formed between the substrate 302 and the photosensitive layer 304 within a range that does not impair the characteristics of the photosensitive member. The positively charged single layer type electrophotographic photosensitive member 13 ′ may be used.

(3) Substrate As the substrate, various conductive materials can be used. For example, a metal such as aluminum, a plastic material on which a metal is deposited, or conductive fine particles such as carbon black is dispersed. The plastic material etc. which are formed are mentioned.
Further, the shape of the substrate may be any of a sheet shape, a drum shape and the like according to the structure of the image forming apparatus to be used.
Moreover, when making the shape of a base | substrate into a drum shape, it is preferable to make the outer diameter into the value within the range of 10-40 mm.
The reason for this is that by setting the outer diameter of the substrate within such a range, the number of rotations of the electrophotographic photosensitive member increases and negative ghosts are likely to occur. However, in the present invention, the generation of such negative ghosts is effective. This is because it can be suppressed.
Therefore, the outer diameter of the substrate is more preferably set to a value within the range of 15 to 30 mm, and further preferably set to a value within the range of 20 to 25 mm.

(4) Photosensitive layer In the present invention, an X-type metal-free phthalocyanine represented by the following formula (1) is used as a charge generating agent added to the photosensitive layer.
The reason for this is that the type of the charge generating agent is limited to X-type metal-free phthalocyanine, and a light absorbing agent having a predetermined light absorbing property is added as will be described later, and as described in detail in the section of the static eliminating means. This is because, by setting the wavelength of the static elimination light within a predetermined range, the portion of the photosensitive layer where static elimination is performed can be limited to the vicinity of the surface layer of the photosensitive layer.
Needless to say, the X-type metal-free phthalocyanine can efficiently generate charges by exposure light, so that a clear electrostatic latent image can be formed on the surface of the photosensitive layer.

In the present invention, a light absorber having a predetermined light absorption characteristic is added to the photosensitive layer.
More specifically, when the maximum absorption wavelength of the light absorber is λ1 _max (nm) and the wavelength of the exposure light irradiated from the exposure means is λ ₀ (nm), λ1 _max (nm) has the following relationship: A light absorber satisfying the formula (1) is added.
450 ≦ λ1 _max ≦ λ ₀ −200 (1)
The reason for this is that if the light absorbing agent has a light absorption characteristic that satisfies the relational expression (1), the neutralizing light having a wavelength of 580 nm or less is specifically absorbed, while the absorption of the exposure light is suppressed. This is because it can be done.
Therefore, the portion of the photosensitive layer where the charge is removed can be limited to the vicinity of the surface layer of the photosensitive layer without hindering the formation of an electrostatic latent image by exposure light.
That is, when the maximum absorption wavelength λ1 _{max in} the light absorber becomes a value less than 450 nm, there is an overlap range between the light absorption wavelength region in the light absorber and the light absorption wavelength region in the X-type metal-free phthalocyanine as the charge generating agent. Too small. As a result, even if the wavelength of the static elimination light is appropriately adjusted, the static elimination effect near the surface of the photosensitive layer may be insufficient. On the other hand, when the maximum absorption wavelength λ1 _max in the light absorber exceeds a value of λ ₀ -200 (λ ₀ : wavelength of exposure light), the light absorption wavelength region in the light absorber and the X-type absence as the charge generation agent. The overlapping range with the light absorption wavelength region in metal phthalocyanine becomes excessively large. As a result, not only the static elimination light but also the exposure light is easily absorbed by the light absorber, and thus the amount of charge generated by the exposure light may be insufficient.
Accordingly, when the maximum absorption wavelength of the light absorber is λ1 _max (nm) and the wavelength of the exposure light irradiated from the exposure means is λ ₀ (nm), λ1 _max (nm) is expressed by the following relational expression (1 ′ ) Is more preferable, and it is more preferable that the following relational expression (1 ″) is satisfied.
450 ≦ λ1 _max ≦ λ ₀ −220 (1 ′)
460 ≦ λ1 _max ≦ λ ₀ −230 (1 ″)

Note that the light absorber having predetermined light absorption characteristics may have a charge transporting ability, but even in this case, the light absorber is different from the electron transport agent and the hole transport agent. This is a compound.
That is, even when the light absorber has charge transporting ability, the light absorber is added as a light absorber, and separately, the electron transport agent and the hole transport agent are the electron transport agent and the hole transport agent. It shall be added as a transport agent.

The light absorber having a predetermined light absorption property is at least one compound selected from the group consisting of a trinitrofluorenone derivative, a benzofuran derivative, a bisnaphthylquinone derivative, an indenopyrazine derivative, a diphenoquinone derivative, and an azoquinone derivative. Preferably there is.
The reason for this is that, by using a light absorber having a predetermined light absorption property as such a compound, while suppressing the electrical properties of the electrophotographic photoreceptor from being lowered, the portion of the photosensitive layer where the charge is removed, This is because the exposure can be limited to the vicinity of the surface.
For example, specific examples of these compounds include compounds (LAM-1 to 4) represented by the following formulas (2) to (5).
In addition, all the compounds (LAM-1 to 4) represented by the formulas (2) to (5) are electron transporting compounds having an electron transporting ability.

Further, the constituent material of the photosensitive layer other than the charge generating agent and the light absorbing agent having a predetermined light absorbing property is not particularly limited, and various conventionally known materials can be used.
For example, examples of the binder resin include a polycarbonate resin, a polyester resin, and a polyarylate resin.
Examples of the hole transporting agent include triphenylamine compounds, hydrazone compounds, enamine compounds, and the like.
Furthermore, examples of the electron transport agent include quinone compounds, diphenoquinone compounds, fluorenone compounds, and the like.

Moreover, it is preferable to make the addition amount of X-type metal-free phthalocyanine as a charge generating agent a value within the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.
The reason for this is that by adjusting the amount of X-type metal-free phthalocyanine as a charge generating agent within such a range, the amount of charge generated by static elimination light and exposure light is adjusted to a suitable range, and negative ghosts are generated. It is because it can suppress more effectively.
That is, when the amount of X-type metal-free phthalocyanine added is less than 0.5 parts by weight, the generation of electric charges due to static elimination light becomes insufficient, and it becomes difficult to eliminate the residual potential due to exposure light. This is because it may be difficult to sufficiently generate even the charge due to the exposure light. On the other hand, when the amount of X-type metal-free phthalocyanine added exceeds 10 parts by weight, the amount of charge generated by exposure light increases excessively, and the residual charge cannot be sufficiently removed even by static elimination light. This is because it may be difficult to effectively suppress the negative ghost.
Therefore, the amount of X-type metal-free phthalocyanine added in the photosensitive layer is more preferably set to a value in the range of 1 to 7 parts by weight with respect to 100 parts by weight of the binder resin, and in the range of 2 to 5 parts by weight. More preferably, the value of

Moreover, it is preferable to make the addition amount of the light absorber in a photosensitive layer into the value within the range of 5-100 weight part with respect to 100 weight part of binder resin.
The reason for this is that by setting the amount of the light absorber having a predetermined light absorption characteristic within such a range, the portion of the photosensitive layer where the charge is removed is limited to the vicinity of the surface of the photosensitive layer, but more effectively. This is because residual charges generated by exposure light can be removed.
That is, when the addition amount of the light absorber having a predetermined light absorption characteristic is less than 5 parts by weight, the static elimination light reaches the middle layer of the photosensitive layer, and the portion of the photosensitive layer where static elimination is performed is exposed to the photosensitive layer. This is because it becomes difficult to limit to the vicinity of the surface of the layer. On the other hand, when the amount of the light absorber having a predetermined light absorption characteristic exceeds 100 parts by weight, the light absorber excessively absorbs the static elimination light and generates a charge necessary for static elimination. This may be difficult.
Therefore, it is more preferable that the addition amount of the light absorber in the photosensitive layer is a value within the range of 10 to 90 parts by weight with respect to 100 parts by weight of the binder resin, and a value within the range of 20 to 80 parts by weight. More preferably.

  In addition, it is preferable that the addition amount of a positive hole transport agent and an electron transport agent shall be the value within the range of 1-120 weight part with respect to 100 weight part of binder resin, respectively.

Further, the film thickness of the photosensitive layer is set to a value within a range of 20 to 50 μm.
This is because when the film thickness of the photosensitive layer is in this range, particularly 30 μm or more, the distance of charge movement in the photosensitive layer increases, so that residual charges tend to occur and negative ghosting occurs. It tends to be easier.
On the other hand, according to the present invention, as described in detail in the section of the static elimination means, it is possible to effectively suppress the occurrence of such a negative ghost.
If the film thickness of the photosensitive layer is excessively small, it may be difficult to form a uniform photosensitive layer, or film defects may easily occur. On the contrary, if the film thickness of the photosensitive layer is excessively large, residual charges may be excessively accumulated, and it may be difficult to obtain predetermined electrical characteristics.
Therefore, the film thickness of the photosensitive layer is more preferably set to a value within the range of 22 to 40 μm, and further preferably set to a value within the range of 25 to 35 μm.

In addition, as shown in FIG. 6 illustrating the light absorption spectrum of the photosensitive layer, the absorbance value (X1) with respect to the static elimination light in the photosensitive layer and the photosensitive layer configured without adding a light absorbent having a predetermined light absorption characteristic. It is preferable that the absorbance value (Y1) with respect to the static elimination light in the layer satisfies the following relational expression (2).
The characteristic curve A in FIG. 6 shows the light absorption spectrum of the photosensitive layer (added with the light absorber), and the characteristic curve B shows the light absorption spectrum of the photosensitive layer formed without adding the light absorber. Furthermore, the characteristic curve C shows the light absorption spectrum of the light absorber itself.
1.5 ≦ X1 / Y1 ≦ 10 (3)
The reason for this is that by configuring as above, the balance between the static elimination light absorbed by the light absorbent having a predetermined light absorption characteristic and the static elimination light that is absorbed by the charge generation agent and generates a charge is further suitable. This is because it can be adjusted within a range.
That is, when the value of X1 / Y1 is less than 1.5, the proportion of static elimination light absorbed by the light absorber having a predetermined light absorption characteristic is excessively reduced, and the portion where static elimination is performed in the photosensitive layer. This is because it may be difficult to limit the value to the vicinity of the surface layer of the photosensitive layer. On the other hand, when the value of X1 / Y1 exceeds 10, the proportion of the static elimination light absorbed by the charge generating agent is excessively reduced, the amount of charge generated by the static elimination light is insufficient, and the residual charge is sufficiently high. This is because it may be difficult to remove the charge.
Therefore, the value of X1 / Y1 preferably satisfies the following relational expression (3 ′), and more preferably satisfies the following relational expression (3 ″).
2 ≦ X1 / Y1 ≦ 8 (3 ′)
2.5 ≦ X1 / Y1 ≦ 7 (3 ″)

4). Charging means The charging means 14M to 14BK shown in FIG. 1 include a discharge wire and are disposed above the positively charged single-layer type electrophotographic photosensitive members 13M to 13BK. This is a device for uniformly charging 13BK.
More specifically, the types of the charging means 14M to 14BK include a scorotron including a discharge wire,
Alternatively, a non-contact type charging device such as corotron may be used.

5). Exposure Units 15M to 15BK shown in FIG. 1 form electrostatic latent images on positively charged single-layer electrophotographic photosensitive members 13M to 13BK based on a document image read from an image data input unit (not shown). It is a device for making it.
Further, the wavelength of the exposure light emitted from the exposure means is not particularly limited. For example, the light absorption of the X-type metal-free phthalocyanine as a charge generator such as a value of 540 nm or less or a value exceeding 800 nm. The wavelength may be relatively low in efficiency.
However, when the wavelength of the exposure light is excessively deviated from the absorption peak of the X-type metal-free phthalocyanine, it becomes difficult not only to generate charges efficiently from the charge generator, but also to the deep layer of the photosensitive layer by the exposure light. In some cases, the residual charge generated during the process tends to increase, making it difficult to suppress the occurrence of negative ghosts.
Therefore, it is preferable to set the wavelength of the exposure light irradiated from the exposure means to a value within the range of 590 to 790 nm.
That is, by setting the wavelength of the exposure light in such a range, charges can be efficiently generated from the charge generating agent, and a clear electrostatic latent image can be formed on the surface of the photosensitive layer.
On the other hand, since charges are generated efficiently, residual charges are inevitably generated. However, according to the present invention, the occurrence of negative ghosts can be effectively suppressed regardless of the residual charges. .
Therefore, it is more preferable to set the wavelength of the exposure light irradiated from the exposure means to a value within the range of 620 to 785 nm.

6). Developing Units The developing units 11M to 11BK shown in FIG. 1 are apparatuses that form toner images by supplying toner to the surfaces of the positively charged single layer type electrophotographic photoreceptors 13M to 13BK on which electrostatic latent images are formed. .
The developing means is not limited to the tandem type.

7). The transfer means 16M-16BK shown in FIG. 1 are devices for transferring the toner images of the positively charged single-layer type electrophotographic photosensitive members 13M-13BK to a sheet, and are an intermediate transfer belt 15 and a transfer roller 16M. It is preferable to have ~ 16BK.

8). Cleaning blades 22M to 22BK shown in FIG. 1 are devices for cleaning deposits such as residual toner remaining on the positively charged single layer type electrophotographic photoreceptors 13M to 13BK, and have a hardness of 60 to 80. It is preferable that a blade made of rubber (for example, urethane rubber) is in pressure contact with the positively charged single layer type electrophotographic photosensitive member at a linear pressure of 10 to 40 N / m.

9. Fixing Unit The fixing unit 20 is a device for fixing the transferred toner image on a sheet.
That is, the fixing unit 20 is a device that heat-fuses the toner transferred to a transfer member such as paper by a heat roll.

[Second Embodiment]
The second embodiment includes a positively charged single layer type electrophotographic photosensitive member having a photosensitive layer containing a binder resin and a charge transport agent on at least a base, a charging unit, an exposure unit, An image forming apparatus including a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit, wherein X-type metal-free phthalocyanine is used as a charge generating agent, and the film thickness of the photosensitive layer is within a range of 20 to 50 μm. And the maximum absorption wavelength of the charge transfer agent is λ2 _max (nm), and the wavelength of the exposure light irradiated from the exposure means is λ ₀ (nm), λ2 _max (nm) is a relational expression An image forming apparatus characterized by satisfying (2) and further having a wavelength of static elimination light emitted from the static elimination means having a value of 580 nm or less.
450 ≦ λ2 _max ≦ λ ₀ −200 (2)
Hereinafter, an image forming apparatus according to the second embodiment will be described focusing on differences from the first embodiment.
That is, in the second embodiment (second invention), unlike the first embodiment (first invention), the electrophotographic photosensitive member does not use a light absorber having a predetermined light absorption characteristic. Instead, a compound having a predetermined light absorption characteristic is used as the charge transport agent.
Therefore, the contents relating to the compound having a predetermined light absorption property as the charge transport agent will be mainly described.

  First, examples of the compound having a predetermined light absorption property as a charge transporting agent include the electron transporting compounds (LAM-1 to 4) represented by the above formulas (2) to (5). .

Moreover, it is preferable that the addition amount of the compound having a predetermined light absorption property as a charge transport agent in the photosensitive layer is set to a value within the range of 5 to 100 parts by weight with respect to 100 parts by weight of the binder resin.
The reason for this is that the amount of charge removal in the photosensitive layer is limited to the vicinity of the surface layer of the photosensitive layer by making the addition amount of the compound having a predetermined light absorption property as the charge transporting agent within such a range. This is because the residual charges generated by the exposure light can be effectively eliminated.
Moreover, it is because a predetermined sensitivity characteristic required for forming an electrostatic latent image can be obtained.
That is, when the amount of the compound having a predetermined light absorption property as a charge transporting agent is less than 5 parts by weight, the static elimination light reaches the middle layer of the photosensitive layer, and the portion where static elimination is performed in the photosensitive layer This is because it may be difficult to limit the surface area to the vicinity of the surface of the photosensitive layer, or the absolute amount of the charge transfer agent may be insufficient, and it may be difficult to obtain predetermined sensitivity characteristics. On the other hand, when the amount of the compound having a predetermined light absorption property as the charge transport agent exceeds 100 parts by weight, the compound excessively absorbs the static elimination light and generates a charge necessary for static elimination. This is because it may be difficult to do so.
Therefore, the addition amount of the compound having a predetermined light absorption property as the charge transport agent in the photosensitive layer is more preferably set to a value within the range of 10 to 90 parts by weight with respect to 100 parts by weight of the binder resin. More preferably, the value is within the range of 20 to 80 parts by weight.

Further, the absorbance value (X2) with respect to the static elimination light in the photosensitive layer and the absorbance value (Y2) with respect to the static elimination light in the photosensitive layer constituted without adding a compound having a predetermined light absorption property as a charge transfer agent. It is preferable that the following relational expression (4) is satisfied.
1.5 ≦ X2 / Y2 ≦ 10 (4)
The reason for this is that, by configuring in this way, a static elimination light that is absorbed by a light absorbent having a predetermined light absorption characteristic as a charge transport agent, a static elimination light that is absorbed by the charge generation agent and generates a charge, This is because the balance can be adjusted to a more suitable range.
That is, when the value of X2 / Y2 is less than 1.5, the proportion of static elimination light absorbed by the compound having a predetermined light absorption characteristic as a charge transfer agent is excessively reduced, and static elimination is performed in the photosensitive layer. This is because it may be difficult to limit the portion formed to the vicinity of the surface layer of the photosensitive layer. On the other hand, when the value of X2 / Y2 exceeds 10, the proportion of the static elimination light absorbed by the charge generating agent is excessively reduced, the amount of charge generated by the static elimination light is insufficient, and the residual charge is sufficiently high. This is because it may be difficult to remove the charge.
Therefore, it is more preferable that the value of X2 / Y2 satisfies the following relational expression (4 ′), and it is even more preferable that the following relational expression (4 ″) is satisfied.
2 ≦ X2 / Y2 ≦ 8 (4 ′)
2.5 ≦ X2 / Y2 ≦ 7 (4 ″)

Also in the second embodiment, the negative ghost suppressing mechanism does not use a light absorbent having a predetermined light absorption characteristic in the electrophotographic photosensitive member, but instead has a predetermined light absorption characteristic as a charge transport agent. The description is the same as that described in the first embodiment, except that the compound is used.
The electrophotographic photosensitive member is the same as in the first embodiment except that a light absorber having a predetermined light absorption property is not used and a compound having a predetermined light absorption property is used instead as a charge transport agent. Thus, the image forming apparatus as the second embodiment can be configured.

[Third Embodiment]
The third embodiment is a positively charged single-layer type electrophotographic photosensitive member having a photosensitive layer containing at least a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent. In contrast, an image forming method for forming an image on a transfer object by performing a charging step, an exposure step, a development step, a transfer step, a fixing step, and a charge eliminating step. In addition, X-type metal-free phthalocyanine is used as the charge generating agent, the photosensitive layer thickness is set to a value in the range of 20 to 50 μm, and the maximum absorption wavelength of the light absorber is λ1 _max (nm). When the wavelength of the exposure light irradiated in the step is λ ₀ (nm), λ1 _max (nm) satisfies the relational expression (1), and the wavelength of the static elimination light irradiated in the static elimination step is 580 nm or less. Is an image forming method characterized by
450 ≦ λ1 _max ≦ λ ₀ −200 (1)

Alternatively, in the third embodiment, a positive charging single layer type electrophotographic photosensitive member having a photosensitive layer containing at least a binder resin, a charge generating agent, and a charge transporting agent, a charging step, and an exposure An image forming method for forming an image on a transfer object by carrying out a process, a developing process, a transfer process, a fixing process, and a charge eliminating process, and an X type as a charge generating agent The wavelength of the exposure light irradiated in the exposure process, using metal-free phthalocyanine, the photosensitive layer thickness in the range of 20-50 μm, and the maximum absorption wavelength of the charge transfer agent as λ2 _max (nm) Is λ ₀ (nm), λ 2 _max (nm) satisfies the relational expression (2), and the wavelength of the static elimination light irradiated in the static elimination step is set to a value of 580 nm or less. An image forming method.
450 ≦ λ2 _max ≦ λ ₀ −200 (2)
Hereinafter, the image forming method as the third embodiment will be described focusing on differences from the first and second embodiments, taking a full-color image forming method using a full-color image forming apparatus as an example.

First, the positively charged single-layer type electrophotographic photoreceptors 13M to 13BK of the image forming apparatus 10 shown in FIG. 1 are rotated at a predetermined process speed (peripheral speed) in the direction indicated by the arrow, and the surface thereof is charged by the charging means 14M. Charge to a predetermined potential with ~ 14BK.
Next, the surfaces of the positively charged single layer type electrophotographic photoreceptors 13M to 13BK are exposed by the exposure means 15M to 15BK through a reflection mirror or the like while being optically modulated according to the image information. By this exposure, an electrostatic latent image for each color is formed on the surfaces of the positively charged single layer type electrophotographic photosensitive members 13M to 13BK.
Next, based on these electrostatic latent images, latent image development is performed by the developing units 11M to 11BK. Developers of respective colors (magenta, cyan, yellow, and black) are accommodated in the developing units 11M to 11BK, and the developers are electrostatically charged on the surfaces of the positively charged single layer type electrophotographic photoreceptors 13M to 13BK. A developer image is formed by adhering corresponding to the latent image.
Further, the recording paper is conveyed to the lower part of the positively charged single layer type electrophotographic photosensitive members 13M to 13BK along a predetermined transfer conveyance path. At this time, the developer image can be transferred onto the recording material by applying a predetermined transfer bias between the positively charged single layer type electrophotographic photoreceptors 13M to 13BK and the transfer means 16M to 16BK.

Next, the recording paper onto which the developer image has been transferred is separated from the surface of the positively charged single-layer type electrophotographic photoreceptors 13M to 13BK by a separating unit (not shown), and conveyed to the fixing unit 20 by the conveying belt 15. The Next, the developer image is fixed on the surface by being heated and pressed by the fixing unit 20, and then discharged to the outside of the image forming apparatus 10 by a discharge roller.
On the other hand, the image carriers 13M to 13BK after the transfer of the developer image continue to rotate, and the untransferred developer remaining on the surfaces of the positively charged single layer type electrophotographic photosensitive members 13M to 13BK is provided in the cleaning units 23M to 23BK. The cleaning blades 22M to 22BK are scraped off.
Further, residual charges in the photosensitive layers of the positively charged single-layer type electrophotographic photoreceptors 13M to 13BK are removed by static elimination light irradiated from the static elimination means 24M to 24BK. At this time, in the present invention, as described in detail in the first and second embodiments, the portion to be neutralized is limited to the vicinity of the surface layer of the photosensitive layer, and the residual charges existing in the deep layer of the photosensitive layer are efficiently processed. Therefore, it is possible to effectively suppress the occurrence of negative ghosts.

In carrying out the image forming method of the present invention, the linear velocity of the positively charged single layer type electrophotographic photosensitive member is set to 150 to 300 mm / sec. It is preferable to set the value within the range.
The reason for this is that by setting the linear velocity of the positively charged single-layer type electrophotographic photosensitive member within such a range, the number of rotations of the electrophotographic photosensitive member increases and negative ghosts are likely to occur. This is because the occurrence of such a negative ghost can be effectively suppressed.
Therefore, the linear velocity of the positively charged single layer type electrophotographic photosensitive member is 160 to 250 mm / sec. Is more preferably in the range of 165 to 200 mm / sec. It is more preferable to set the value within the range.

  Hereinafter, the present invention will be described in more detail based on examples. Needless to say, the following description exemplifies the present invention, and the scope of the present invention is not limited to the following description without any particular reason.

[Example 1]
1. Production of Positively Charged Single-Layer Electrophotographic Photoreceptor In a stirring vessel, 2.7 parts by weight of X-type metal-free phthalocyanine represented by formula (1) as a charge generating substance and the following formula ( 6) 50 parts by weight of a stilbeneamine compound represented by the formula, 30 parts by weight of a quinone compound represented by the following formula (7) as an electron transport agent, and a compound represented by the formula (4) as a light absorber. (LAM-3) 30 parts by weight (maximum absorption wavelength λ1 _max : 486 nm), 100 parts by weight of a bisphenol Z-type polycarbonate resin having an average molecular weight of 30000 as a binder resin, and 700 parts by weight of tetrahydrofuran as a solvent were accommodated. Thereafter, the mixture was mixed and dispersed with a ball mill for 50 hours to prepare a coating solution. Next, the obtained coating solution is applied on a substrate made of an aluminum tube by a dip coating method, followed by hot air drying at 130 ° C. for 45 minutes, and a positively charged single layer type electron having a thickness of 30 μm and a diameter of 30 mm. A photographic photoreceptor was obtained.

2. Measurement of Absorbance Absorbance (X1) for static elimination light and absorbance (Y1) for exposure light in the photosensitive layer were measured.
That is, the photosensitive layer coating solution prepared in the production of the positively charged single-layer type electrophotographic photosensitive member was applied to the OHP sheet so as to have a film thickness of 10 μm to obtain a measurement material.
Subsequently, the absorbance (X1) with respect to static elimination light (wavelength: 500 nm) and the absorbance (Y1) with respect to exposure light (wavelength: 780 nm) in the obtained measurement data were respectively measured with a spectrophotometer (HITACHI, U-3000 Spectrometer). ) And X1 / Y1 was calculated. The obtained results are shown in Table 1.
In addition, about the light absorbency (X1) with respect to static elimination light, since it was a big value of 2 or more, the exact value was not able to be measured. Therefore, an accurate value cannot be calculated for the value of X1 / Y1.

3. Evaluation of Negative Ghost Using the obtained positively charged single layer type electrophotographic photosensitive member, negative ghost was evaluated.
That is, the obtained positively charged single-layer type electrophotographic photosensitive member was assembled to a printer (LS-5030 modified by Kyocera Mita Co., Ltd.), and the black image pattern 510 shown in FIG. 10 sheets were printed continuously.
Drum linear speed: 168mm / sec
Drum: φ30 positively charged single layer type OPC
Charging: Scorotron charging exposure: Laser scanner development: Touchdown development transfer: Intermediate transfer system cleaning: Counter blade system neutralization: LED light neutralization drum charging potential: 420V
Laser: Laser wavelength 780 nm, laser exposure 0.9 μJ / cm ²
Static elimination: LED wavelength 500 nm, LED exposure 4.0 μJ / cm ²
Light emitting diode: GaAs

Subsequently, in the last image obtained, whether or not a negative ghost was generated was visually confirmed and evaluated according to the following criteria. The obtained results are shown in Table 1.
0: Negative ghost is not confirmed 1: Slightly negative ghost is confirmed 2: Slightly negative ghost is confirmed 3: Slightly negative ghost is confirmed 4: Negative ghost is confirmed 5: Clearly negative Ghost is confirmed

[Example 2]
In Example 2, negative ghost was evaluated in the same manner as in Example 1 except that the wavelength of the static elimination light was changed to 550 nm. The obtained results are shown in Table 1.

[Comparative Example 1]
In Comparative Example 1, negative ghost was evaluated in the same manner as in Example 1 except that the wavelength of the static elimination light was changed to 630 nm. The obtained results are shown in Table 1.

[Comparative Example 2]
In Comparative Example 2, negative ghost was evaluated in the same manner as in Example 1 except that the wavelength of the static elimination light was changed to 730 nm. The obtained results are shown in Table 1.

The image forming apparatus and the image forming method according to the present invention contain a specific charge generating agent and a light absorber having a predetermined light absorption characteristic or a charge transport agent having a predetermined light absorption characteristic. In addition, by setting the wavelength of the static elimination light within a predetermined range, it is possible to effectively eliminate static charges, but it is also possible to effectively suppress the occurrence of negative ghosts.
As a result, even if a positively charged electrophotographic photosensitive member having the property of easily generating residual charges is used as the electrophotographic photosensitive member and the film thickness is set to a predetermined thickness, the static elimination is effectively performed. However, the occurrence of negative ghosts can be effectively suppressed.
Therefore, the image forming apparatus and the image forming method according to the present invention are expected to significantly contribute to speeding up of various image forming apparatuses such as copiers and printers and high quality of formed images.

FIG. 1 is a diagram for explaining the configuration of the image forming apparatus of the present invention. FIGS. 2A to 2B are views for explaining a negative ghost generation mechanism and a suppression mechanism. FIG. 3 is a diagram provided for explaining the light absorption spectrum of X-type metal-free phthalocyanine. FIG. 4 is a diagram for explaining a schematic diagram of a negative ghost. FIGS. 5A to 5B are views for explaining the configuration of the positively charged single layer type electrophotographic photosensitive member in the present invention. FIG. 6 is a diagram provided for explaining the light absorption spectrum of the photosensitive layer. FIG. 7 is a diagram for explaining an image pattern for evaluating the occurrence of a negative ghost.

Explanation of symbols

10: Full-color image forming apparatus, 11M to 11BK: Developing means, 12M to 12BK: Developing roller, 13M to 13BK: Positively charged single layer type electrophotographic photosensitive member, 14M to 14BK: Charging means, 15M to 15BK: Exposure means, 16M -16BK: transfer means, 18: paper feed cassette, 20: fixing means, 22M-22BK: cleaning blade, 23M-23BK: cleaning means, 24M-24BK: static elimination means, 302: substrate, 304: photosensitive layer, 306: intermediate Layer, 500: negative ghost image, 501: formed image, 502: pre-rounded formed image, 503: negative ghost, 510: image pattern for negative ghost evaluation

Claims (10)

A positively charged single-layer type electrophotographic photosensitive member having a photosensitive layer containing a binder resin, a charge generating agent, a hole transporting agent, an electron transporting agent, and a light absorbing agent on at least a substrate. An image forming apparatus comprising a charging unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, and a charge eliminating unit,
While using X-type metal-free phthalocyanine as the charge generating agent, the photosensitive layer has a thickness in the range of 20 to 50 μm, and
When the maximum absorption wavelength of the light absorber is λ1 _max (nm) and the wavelength of the exposure light emitted from the exposure means is λ ₀ (nm), λ1 _max (nm) is expressed by the relational expression (1). Satisfied,
An image forming apparatus characterized in that the wavelength of the static elimination light emitted from the static elimination means is set to a value of 580 nm or less.
450 ≦ λ1 _max ≦ λ ₀ −200 (1)   The light absorber is at least one compound selected from the group consisting of a trinitrofluorenone derivative, a benzofuran derivative, a bisnaphthylquinone derivative, an indenopyrazine derivative, a diphenoquinone derivative, and an azoquinone derivative. The image forming apparatus described in 1.   3. The image formation according to claim 1, wherein an addition amount of the light absorber in the photosensitive layer is set to a value within a range of 5 to 100 parts by weight with respect to 100 parts by weight of the binder resin. apparatus. The image forming apparatus according to any one of claims 1 to 3, wherein an irradiation amount of the static elimination light is set to a value within a range of 1 to 10 µJ / cm ² .   The image forming apparatus according to claim 1, wherein the static elimination light source used in the static elimination unit is an LED.   The image forming apparatus according to claim 1, wherein the wavelength of exposure light emitted from the exposure unit is set to a value within a range of 590 to 790 nm.   The image forming apparatus according to claim 1, wherein the image forming apparatus is a full-color image forming apparatus. A positively charged single layer type electrophotographic photosensitive member having a photosensitive layer containing a binder resin and a charge transfer agent on at least a substrate, and a charging unit, an exposure unit, a developing unit, and a transfer unit, An image forming apparatus comprising a fixing unit and a charge eliminating unit,
While using X-type metal-free phthalocyanine as the charge generating agent, the photosensitive layer has a thickness in the range of 20 to 50 μm, and
When the maximum absorption wavelength of the charge transfer agent is λ2 _max (nm) and the wavelength of exposure light emitted from the exposure means is λ ₀ (nm), λ2 _max (nm) is expressed by the relational expression (2). Satisfied,
An image forming apparatus characterized in that the wavelength of the static elimination light emitted from the static elimination means is set to a value of 580 nm or less.
450 ≦ λ2 _max ≦ λ ₀ −200 (2) A charging step for a positively charged single layer type electrophotographic photoreceptor having a photosensitive layer containing at least a binder resin, a charge generator, a hole transport agent, an electron transport agent, and a light absorber; An image forming method for forming an image on a transfer object by performing an exposure step, a development step, a transfer step, a fixing step, and a static elimination step,
While using X-type metal-free phthalocyanine as the charge generating agent, the photosensitive layer has a thickness in the range of 20 to 50 μm, and
When the maximum absorption wavelength of the light absorber is λ1 _max (nm) and the wavelength of the exposure light irradiated in the exposure step is λ ₀ (nm), λ1 _max (nm) is expressed by the relational expression (1). Satisfied,
A method of forming an image, characterized in that the wavelength of the static elimination light irradiated in the static elimination step is set to a value of 580 nm or less.
450 ≦ λ1 _max ≦ λ ₀ −200 (1) For a positively charged single-layer type electrophotographic photosensitive member having a photosensitive layer containing at least a binder resin, a charge generator, and a charge transport agent, a charging step, an exposure step, a development step, and a transfer step And an image forming method for forming an image on a transfer object by performing a fixing step and a charge removal step,
While using X-type metal-free phthalocyanine as the charge generating agent, the photosensitive layer has a thickness in the range of 20 to 50 μm, and
When the maximum absorption wavelength of the charge transfer agent is λ2 _max (nm) and the wavelength of exposure light irradiated in the exposure step is λ ₀ (nm), λ2 _max (nm) is expressed by the relational expression (2). Satisfied,
A method of forming an image, characterized in that the wavelength of the static elimination light irradiated in the static elimination step is set to a value of 580 nm or less.
450 ≦ λ2 _max ≦ λ ₀ −200 (2)