JP2001066799A - Image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image blurring due to repulsion of electric charges which migrate in an electric charge transfer layer(CTL), ensure sufficient potential by electrification and attain satisfactory development, even if the CTL is made thin and an undercoat layer(UL) is made thick. SOLUTION: This image-forming device has at least a photoreceptor, an electrifying means, an image exposure means and a developing means, and part of light used for exposing an original by the image exposure means forms an image on the photoreceptor through an optical lens. The photoreceptor is a function separated photoreceptor having an undercoat layer(UL) 25, an electric charge generating layer(CGL) 31 and an electric charge transfer layer(CTL) 33 on the electrically conductive substrate 21, a thickness (Tctl) of the CTL is 20 μm or smaller and the Tct1 and the thickness (Tul) of the UL satisfy th relation Tu1>Tctl/3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine and a printer to which an electrophotographic technique is applied.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic photosensitive member used in the above image forming apparatus has a single-layer photosensitive member in which a single photosensitive layer is provided on a conductive support as shown in FIG. As shown in FIG. 4, a function-separated type laminated photoreceptor for incoherent light having a laminated structure in which a photosensitive layer is composed of a charge generation layer (CGL) and a charge transport layer (CTL), and a laminated photosensitive for coherent light as shown in FIG. There is a body. A single-layer photoreceptor has a simple structure and is inexpensive, but it is difficult to obtain sufficient sensitivity. The incoherent light photoreceptor of FIG. 4 has no undercoat layer (UL) or an extremely thin (1 μm or less) undercoat layer (UL).
The photoreceptor for coherent light in FIG. 5 has an undercoat layer but is thin. In the undercoat layer (UL) of the photoreceptor for coherent light, writing light (coherent) is multiple-reflected between the surface layer of the photoreceptor (surface of CTL) and the conductive support, causing sensitivity unevenness due to the interference effect. It is provided to prevent this interference effect in order to generate an unnecessary stripe pattern on the image, and has a thickness of several μm, preferably 5 μm or less. The thickness of the charge transport layer is usually 20 to 40 μm.
It is.

[0003]

The function-separated type photoreceptor shown in FIGS. 4 and 5 has a higher photosensitivity than the single-layer photoreceptor shown in FIG. 3 and is the mainstream of organic photoreceptors. . However, since the charge generation layer (CGL) is below the charge transport layer (CTL), the charge generated by the writing light is repelled by each other's electric field while moving in the CTL and diffuses laterally, so that the image is blurred. Phenomenon occurs. A first object of the present invention is to solve this image blur.

Therefore, to solve this image blur, CT
It is conceivable that the thickness of L is 20 μm or less, preferably 15 μm or less. However, if the thickness of CTL is 2
If the thickness is reduced to 0 μm or less, the electrostatic capacity of the photoconductor increases, and a sufficient potential cannot be obtained. This phenomenon is particularly remarkable when the CTL layer thickness is smaller than 15 μm. The reason is that the electrostatic withstand voltage of the CTL is 40 to 50 V / μm, and it is preferable to use the CTL at 30 V / μm or less for safety. Therefore, a photosensitive member of 20 μm has a voltage of
It is desirable to use the photoreceptor charged at 450 V or less, and in a blade cleaning device (used in most cases), the photoreceptor is shaved with a blade. ~ 40μ
Generally, the thickness is further increased to m. Further, the UL layer of the conventional coherent light photoreceptor only shares a partial pressure of 20% of the voltage due to the charged charges, and does not provide a sufficient withstand voltage against electrostatic breakdown. A second object of the present invention is to increase the thickness of the UL layer so that the UL layer has a sufficient withstand voltage to secure a required charging potential, and to perform sufficient charging and eventually sufficient development.

[0005]

According to the present invention, first, at least a photoreceptor, a charging means, an image exposing means, and a developing means are provided, and the image exposing means exposes the original to light. In an image forming apparatus for forming an image on a photosensitive member through an optical lens, the photosensitive member is formed on a conductive substrate by an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CT).
L) wherein the CTL has a thickness (Tctl) of 20 μm or less, and the Tctl and U
An image forming apparatus is provided in which the thickness (Tul) of L satisfies the relationship of Tul> Tctl / 3.

Second, in an image forming apparatus having at least a photoreceptor, a charging unit, an image exposing unit, and a developing unit, the image exposing unit divides a light image into minute pixels and exposes the image with incoherent light. Wherein the photoreceptor is on a conductive substrate,
A function-separated type photoconductor having an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CTL).
Has a thickness (Tctl) of not more than 20 μm and
An image forming apparatus is provided, wherein the thickness (Tul) of 1 and UL satisfies the relationship of Tul> Tctl / 3.

Third, in an image forming apparatus having at least a photoreceptor, a charging unit, an image exposing unit, and a developing unit, wherein the image exposing unit divides a light image into minute pixels and exposes the image with coherent light. Wherein the photoconductor is a function-separated type photoconductor having an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CTL) on a conductive substrate;
Has a thickness (Tctl) of not more than 20 μm and
An image forming apparatus is provided, wherein the thickness (Tul) of 1 and UL satisfies the relationship of Tul> Tctl / 2.

[0008] Fourthly, it has at least a photoreceptor, a charging unit, an image exposing unit, a developing unit, and a gradation expressing unit, and the image exposing unit corresponds to an original image having image data containing gradation information. The light image is divided into pixels, the photosensitive member is exposed to incoherent light, and an electrostatic latent image is formed on the photosensitive member.The gradation expressing means shows an image forming method based on gradation. A drive signal having a predetermined minimum value is given to the image exposure means based on the image data of the original image, and the photoconductor is provided on a conductive support with an undercoat layer (UL), a charge A function-separated type photoreceptor having a photogenerating layer (CGL) and a charge transport layer (CTL);
L has a thickness (Tctl) of 20 μm or less;
The thickness (Tul) of tl and UL satisfies the relationship of Tul> Tctl / 2, and the photoconductor at the predetermined minimum value of the drive signal, at the maximum exposure in the exposure distribution on the photoconductor surface, It has a differential sensitivity of 1/3 or less of the maximum differential sensitivity of the photoreceptor, and the exposure distribution has a writing energy distribution P (x, y) at coordinates (x, y) on the photoreceptor surface.
y, t) [watt / m ² ] is expressed by E (x, y) [joule / m ² ] obtained by integrating the exposure time (t), and the sensitivity at the predetermined minimum value of the drive signal is obtained. In the photoconductor region at an exposure amount equal to or more than の of the maximum exposure in the exposure distribution on the body surface, the smaller one of the exposure diameters measured in the main scanning direction or the sub-scanning direction is defined as the exposure diameter Db. And the exposure diameter Db is Db> Tctl
The image forming apparatus is characterized by satisfying the following.

Fifth, there is provided at least a photoreceptor, a charging unit, an image exposing unit, a developing unit, and a gradation expressing unit, and the image exposing unit corresponds to an original image having image data including gradation information. The light image is divided into pixels and the photosensitive member is exposed to coherent light to form an electrostatic latent image on the photosensitive member. The gradation expressing means indicates a gradation-based image forming method, A drive signal having a predetermined minimum value is given to the image exposing means based on the image data of the image. The photoreceptor comprises an undercoat layer (UL), a charge generation layer on a conductive support. Layer (CGL), charge transport layer (CT
L), wherein the thickness (Tctl) of the CTL is 20 μm or less, and the thickness (Tul) of the Tctl and UL satisfies the relationship of Tul> Tctl / 2; The photoreceptor has a differential sensitivity equal to or less than 1/3 of the maximum differential sensitivity of the photoreceptor at the predetermined minimum value of the drive signal and the maximum exposure in the exposure distribution on the photoreceptor surface; Are coordinates (x,
y), the write energy distribution P (x, y,
t) E (x, y) [joule / m ² ] obtained by integrating [watt / m ² ] with respect to the exposure time (t), and the photoconductor surface at the predetermined minimum value of the drive signal In the photoconductor region at an exposure amount equal to or more than 最大 of the maximum exposure in the above exposure distribution, the smaller one of the exposure diameters measured in the main scanning direction or the sub-scanning direction is defined as an exposure diameter Db, An image forming apparatus is provided, wherein the exposure diameter Db satisfies Db> 2Tctl.

Sixth, in the image forming apparatus described in the first aspect, the thickness (Tul) of the Tctl and the UL is Tul.
> Tctl / 2 is provided.

Seventh, in the image forming apparatus described in the second aspect, the thickness (Tul) of the Tctl and the UL is Tul.
> Tctl / 2 is provided.

Eighth, in the image forming apparatus described in the third aspect, the thickness (Tul) of the Tctl and the UL is Tul.
> Tctl is provided.

Ninth, in the image forming apparatus described in the fourth aspect, the thickness (Tul) of the Tctl and the UL is Tul.
> Tctl is provided.

Tenthly, in the image forming apparatus described in the fifth aspect, the thickness (Tul) of the Tctl and the UL is Tul.
> Tctl is provided.

Hereinafter, the present invention will be described in detail. By reducing the thickness of the CTL as described above, it is possible to prevent the charge generated in the CGL from being repelled by the electric field of each other while moving through the CTL, thereby preventing the charge from being diffused. If the same charge is applied to the photosensitive member, the surface potential of the photosensitive member becomes low, and sufficient development cannot be performed. In the conventional device, a thin line with a particularly low contrast cannot be reproduced clearly, and in some cases, it cannot be reproduced at all. In a conventional analog photoreceptor, the UL layer is of such an extent that the conductive support is pretreated to prevent charge injection from the conductive support into CGL and CTL and to uniformly coat the CGL. Was. Therefore, its thickness was very thin and negligible compared to the thickness of CTL.

In contrast to the conventional photoconductor, the photoconductor used in the image forming apparatus according to the first aspect of the present invention is C
The thickness (Tctl) of the TL is 20 μm or less and the T
ctl and UL thickness (Tul) are Tul> Tctl /
3 is satisfied. According to such a configuration, a sufficient potential can be secured, and a thin line with low contrast can be clearly reproduced.

The image forming apparatus according to the second aspect of the present invention is used for digital writing using an LED array. As described above, sufficient development cannot be performed only by reducing the CTL. In particular, with the conventional device, a thin line written with light having a relatively small energy cannot be developed clearly. Since the LED light is incoherent light, the photoconductor used in a copying machine or a printer using the LED array writing head does not need to have a light diffusion function in the UL layer, and can use an analog photoconductor. . As described above, in the conventional analog photoconductor, the thickness of the UL is negligible compared to the thickness of the CTL.

On the other hand, the photosensitive member used in the image forming apparatus according to the second aspect of the present invention has a CTL thickness (T
(ctl) is 20 μm or less, and the Tctl and the thickness (Tul) of the UL satisfy the relationship of Tul> Tctl / 3. According to such a configuration, a sufficient potential can be secured, and a fine line written with light having relatively small energy can be clearly developed.

The image forming apparatus according to the third aspect of the present invention is used for digital writing by an LD. As described above, sufficient development cannot be performed only by reducing the CTL. In the prior art, particularly thin lines written with light of relatively small energy cannot be clearly developed. On the other hand, the photoreceptor used in the image forming apparatus according to the third aspect of the present invention has a CT
L has a thickness (Tctl) of 20 μm or less and
tl and the thickness of the UL (Tul) are Tul> Tctl / 2
It satisfies the relationship of According to such a configuration, a sufficient potential can be secured, and a fine line written with light having relatively small energy can be clearly developed.

The image forming apparatus according to the fourth aspect of the present invention is used for digital writing using incoherent light, and has the gradation expression means specified as described above. Although sufficient development cannot be performed only by reducing the CTL as described above, the photoreceptor used in the image forming apparatus according to the fourth aspect of the present invention has a CTL having a thickness (Tctl) of 20 μm or less. And the Tctl and the thickness (Tul) of the UL are Tul> T
ctl / 2, and the exposure diameter Db and CTL
And the thickness (Tctl) satisfies the relationship of Db> Tctl. According to such a configuration, a potential potential for performing sufficient development can be secured and the spread of electric charges can be reduced, so that an isolated dot with the minimum writing energy can be stably reproduced.

The image forming apparatus according to the fifth aspect of the present invention is used for digital writing using coherent light, and has the gradation expressing means specified as described above. Although sufficient development cannot be performed only by reducing the CTL as described above, the photoreceptor used in the image forming apparatus of the present invention described in the fifth aspect is a C photoconductor.
The thickness (Tctl) of the TL is 20 μm or less and the T
ctl and UL thickness (Tul) are Tul> Tctl /
2 and the exposure diameter Db and the thickness (Tctl) of the CTL satisfy the relationship of Db> 2Tctl. According to such a configuration, a potential potential for performing sufficient development can be secured and the spread of electric charges can be reduced, so that an isolated dot with the minimum writing energy can be stably reproduced.

The image forming apparatus according to the sixth aspect is characterized in that the Tc of the photosensitive member used in the image forming apparatus according to the first aspect is used.
The relation between tl and UL thickness (Tul) is expressed as Tul> Tct.
When the thickness is set to 1/2 and Tul is further increased, the effect obtained by the first device can be further improved.

In the image forming apparatus described in the seventh aspect, the Tc of the photosensitive member used in the image forming apparatus described in the second aspect is used.
The relation between tl and UL thickness (Tul) is expressed as Tul> Tct.
When the thickness is set to l / 2 and Tul is further increased, the effect obtained by the second device can be further improved.

The image forming apparatus according to the eighth aspect is characterized in that the Tc of the photosensitive member used in the image forming apparatus according to the third aspect is used.
The relation between tl and UL thickness (Tul) is expressed as Tul> Tct.
By setting l to further increase Tul, the effect obtained by the third device can be further improved.

The image forming apparatus according to the ninth aspect is characterized in that the Tc of the photosensitive member used in the image forming apparatus according to the fourth aspect is used.
The relation between tl and UL thickness (Tul) is expressed as Tul> Tct.
By setting l to further increase Tul, the effect obtained by the fourth device can be further improved.

The image forming apparatus according to the tenth aspect is characterized in that the Tc of the photosensitive member used in the image forming apparatus according to the fifth aspect is used.
The relation between tl and UL thickness (Tul) is expressed as Tul> Tct.
By setting l to further increase Tul, the effect obtained by the fifth device can be further improved.

Here, "Db" defined in the fourth and fifth image forming apparatuses is, for example, the power distribution of the exposure beam whose half diameter in the main scanning direction is 30 μm and half diameter in the sub-scanning direction. In the case of a 50 μm Gaussian distribution laser exposure apparatus, the exposure amount distribution when a 34 μm width exposure is performed in the main scanning direction is a Gaussian distribution with a half value diameter of approximately 40 μm for the main and 50 μm for the sub. Diameter Db is 40 μm
That is.

The "differential sensitivity" means that the attenuation characteristic of the photoreceptor is measured by using light having the same wavelength as that used in the image exposure apparatus or light having the same wavelength so that the measurable area is (substantially) uniform. It is defined by the relationship between the potential V (E) obtained at the time of exposure and the exposure amount E. The differential sensitivity means that the photoconductor surface potential at a certain exposure amount E is V (E), and the photoconductor surface potential at the time when the exposure amount is increased by a small value ΔE is V (E).
(E + ΔE) is defined as follows.

[0029]

## EQU00001 ## Differential sensitivity = [V (E + .DELTA.E) -V (E)] /. DELTA.E Generally, the differential sensitivity decreases as the exposure amount increases.

Hereinafter, the structure and operation of the photosensitive member employed in the image forming apparatus of the present invention will be described in detail. The capacity Cpc of the photoconductor is

## EQU2 ## Cpc = 1 / (εctl · Tctl + εcgl)
・ Tcgl + εul ・ Tul) (where εctl, εul, εcgl are CT
Dielectric constant of L, UL and CGL
constant). ), But in general,

[0031]

## EQU3 ## There is a relationship of .epsilon.ctl to .epsilon.ul to .epsilon.cgl = 3. By the way, in the conventional analog photoconductor,

[0032]

## EQU4 ## There is a relation of Tctl >> Tcgl to Tul, and it can be said that the capacity of the photoconductor is almost inversely proportional to the thickness of the CTL (Tctl). Therefore Tc
When tl is reduced, the capacitance Cpc of the photoconductor increases.

On the other hand, the electric charge Q given to the photoreceptor has various restrictions and cannot be made too large. Therefore, when Tctl is reduced,

[0034]

## EQU5 ## In some cases, the photoconductor surface potential Vpc given by Vpc = Q / Cpc cannot secure a magnitude required for the image forming process. Therefore, the relationship of the present invention

[0035]

By satisfying Tul> Tctl / 2, Tctl is reduced to reduce the diffusion of electric charges in the CTL, and even if the blur amount of the latent image is reduced, Tu is reduced.
Since 1 is not negligible, the capacitance does not unnecessarily increase, and the potential required for development can be secured with the minimum necessary charge. As a result, a potential potential necessary for development is secured, and fine lines with low contrast, which are difficult to reproduce, can be copied clearly.

[0036]

A description will be given of a case where a laminated photoreceptor comprising CTL, CGL, UL and a conductive support is used in an analog copying machine. In the process of wet coating CTL on CGL, CTL
The coating liquid permeates the CGL and the charge transport material (CTM) comes into contact with the charge generation material (CGM), and the interface becomes a charge generation site. When the surface of the photoreceptor is uniformly charged (negatively charged) by the charger, charges of the opposite polarity (positive polarity) induced by the charge are induced in the conductive support. The dark resistance of the organic photoreceptor is sufficiently high, and the injection of charges (holes) of the conductive support may be considered to be zero. Therefore, CGL (CGM
Around). That is, CTL
And the voltage applied to the conductive support is shared by CTL and UL (CGL is also shared, but can be neglected because its thickness is thin).

When light is irradiated from the exposure apparatus, a certain percentage of the light is absorbed by CGM to generate excitons. Excitons are C
Electrons and holes are generated as a pair when they diffuse in the GM and reach the charge generation site (see the description of FIGS. 6 and 7 and the following drawings. However, FIG. 6 shows the UL layer and the conductive support). Absent). The holes are attracted by the photoreceptor surface charge (-) and conduct through the CTL (hopping between CTMs),
It reaches the photoreceptor surface and neutralizes the surface charge. During this conduction, the charges of the holes are repelled, spread laterally, and create a (blurred) surface charge distribution larger than the spot diameter of the light. Similarly, the other half-generated electron, the other half, is also UL
It is believed that the layer diffuses laterally and conducts. However, this does not create a blurred spread of the counter charge. Because the counter charge is in the conductive support, charge rearrangement occurs, resulting in a distribution that depends only on the surface charge neutralized with holes. That is, the spread of the charges in the UL layer can be ignored (only the CTL contributes to the spread of the charges).

In FIG. 6, M and G ^* represent a CTM molecule and a photoexcited CGM, respectively. The CTM molecules in the CGL are those which have permeated the CTL formed by the wet coating method into the CGL before the CTL is dried. Optical carrier generation site is CGM of molecular order in CGL.
/ CTM interface. FIG. 7 is a schematic diagram of photocarrier generation in the laminated photoreceptor, showing that photon absorption and carrier generation occur at different sites, and that carrier generation and carrier injection occur simultaneously.

[0039]

FIG. 1 is a conceptual diagram of an image forming apparatus according to the present invention, and FIG. 2 is a function-separated type photosensitive used in the image forming apparatus according to the present invention. It is a schematic sectional drawing which shows an example of a body. By setting the CTL at 20 μm and forming a 10 μm undercoat layer (UL) under the CTL and CGL, the exposure potential is set to a charging potential of −700 V, and the background portion (reflection density 0.1 of the original) becomes −80 V. A developing device using a two-component developer containing a positively charged toner,
By developing with a developing bias of -200 V, a low-contrast fine line could be well developed. In addition, even when used for a long time under these conditions, it could be used without any problem.

[Second Embodiment] (Digital Copier, Incoherent Light) The writing in the first embodiment is digital writing using an LED array, the writing density is 600 dpi for main and sub, and the multi-value writing: the relative lighting time depends on the image data. 0, 1/4,
Adjustable to 2/4, 3/4, 4/4. CTL 1
By forming an undercoat layer (UL) of 6 μm under the CTL and CGL to a charge potential of −600 V, in a region of a predetermined size of the photoconductor where the light attenuation characteristic of the photoconductor can be measured, The exposure was adjusted so that the potential when the pixels were sequentially exposed at the maximum relative exposure time of 4/4 was -120V. A developing device using a two-component developer containing a negatively charged toner. By performing negative-positive development with a developing bias of -400 V, even when reproducing one dot line with a minimum relative exposure time of 1/4. Could be developed. In addition, even when used for a long time under these conditions, it could be used without any problem.

[Embodiment 3] (Digital copier, coherent light) Writing in Embodiment 1 is performed by LD raster scan, the writing density is 600 dpi for main and sub, and multi-level writing: From 0/255 at power depending on image data. The adjustment was made in 256 steps including up to 1/255. CTL 15μ
m, and forming a 10 μm undercoat layer (UL) under the CTL and CGL, thereby setting the charging potential to −600 V, and in the measurement size region of the photoconductor where the light attenuation characteristic of the photoconductor can be measured, The exposure was adjusted so that the potential when the pixels were sequentially exposed at the maximum power of 255/255 was -150V. With a developing device using a two-component developer containing a negatively charged toner, by performing negative-positive development with a development bias of -400 V, good development is achieved even when one dot line is reproduced at a power of 16/255. I was able to. In addition, even when used for a long time under these conditions, it could be used without any problem.

Fourth Embodiment (Digital Copier, Incoherent Light) The writing in the first embodiment is digital writing using an LED array, and the writing density is 600 dpi for both main and sub, four-level writing: relative to LED by image data. The lighting time was OFF, 1/3, 2/3, or 3/3. By making the CTL 12 μm and forming a 6 μm underlayer (UL) under the CTL and CGL, −500
And a potential of -60 V when a pixel is sequentially exposed for a maximum relative exposure time of 3/3 in a region of a predetermined size of the photoconductor where the light exposure attenuation characteristic of the photoconductor can be measured.
The exposure was adjusted so that A developing device using a two-component developer containing a negatively charged toner;
By performing negative-positive development with a development bias of 30 V,
One isolated dot was also successfully developed. In addition, even when used for a long time under these conditions, it could be used without any problem.

[Embodiment 5] The writing in the embodiment 1 is performed by LD raster scan, and the writing density is 600 d
pi, binary writing: lighting of the LD was either ON or OFF depending on the image data. The CTL is 10 μm, and a 10 μm undercoat layer (U
By forming L), the charge potential is set to −500 V, and in a region of the measurement size of the photoconductor where the light attenuation characteristic of the photoconductor can be measured, the potential when the LD is turned on and the pixels are sequentially exposed is −. The exposure was adjusted to 70 V. By performing negative-positive development with a developing bias of -350 V with a developing device using a two-component developer containing a negatively charged toner, one isolated dot could be successfully developed. In addition, even when used for a long time under these conditions, it could be used without any problem.

[0044]

As described above, according to the image forming apparatus of the first aspect, a function-separated type photoconductor is used as a photosensitive member of an image forming apparatus having an exposure unit for forming a latent image by forming an image of reflected light from a document. Using a photoconductor, the thickness of the charge transport layer (Tc
tl) is set to 20 μm or less, and the thickness (Tul) of the Tctl and the undercoat layer (UL) satisfies the relationship of Tul> Tctl / 3, whereby a sufficient potential is secured. Thus, a thin line with low contrast, which cannot be obtained with a conventional analog photoconductor, can be clearly reproduced.

According to a second aspect of the present invention, there is provided an image forming apparatus having an exposing means for dividing a light image into minute pixels and exposing the image with incoherent light, wherein a function-separated type photosensitive member is used. 1, the thickness (Tctl) of the charge transport layer of the photoconductor is set to 20 μm or less, and
l and the thickness (Tul) of the undercoat layer (UL) are Tul> Tc
The configuration satisfies the relationship of tl / 3, whereby a sufficient potential can be ensured, and a portion written with relatively weak light in a highlight portion can be clearly developed.

According to a third aspect of the present invention, there is provided an image forming apparatus having an exposing means for dividing an optical image into minute pixels and exposing the image with coherent light, wherein a function-separated type photoreceptor is used. The thickness (Tctl) of the charge transport layer
0 μm or less, and the Tctl and the undercoat layer (UL)
Has a thickness (Tul) satisfying the relationship of Tul> Tctl / 2, whereby a sufficient potential can be secured, and a portion of the highlight portion written with relatively weak light is also sharp. And can be developed.

According to a fourth aspect of the present invention, there is provided an image forming apparatus including an exposure unit for dividing a light image into minute pixels and exposing the image with incoherent light, and a gradation expression unit. A function separation type laminated photoreceptor is used as the photoreceptor to be used, and the thickness (Tctl) of the charge transport layer of the photoreceptor is set to 20 μm or less; In addition, the Tctl and the thickness (Tul) of the undercoat layer (UL) are Tul> Tctl
/ 2 and the exposure diameter Db and Tctl are Db
> Tctl, which can secure a potential potential for performing sufficient development and reduce the spread of electric charges, thereby stabilizing isolated dots having the minimum writing energy. Can be reproduced.

According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising an exposure unit for dividing an optical image into minute pixels and exposing the image with coherent light, and a gradation expression unit. An exposure amount at which the differential sensitivity of the photoreceptor is sufficiently small can be obtained. A function-separated type laminated photoreceptor is used as the photoreceptor, and the thickness of the charge transport layer (T
ctl) is 20 μm or less, and the thickness (Tul) of the Tctl and the undercoat layer (UL) is Tul> Tctl / 2.
And the exposure diameter Db and Tctl are Db> 2.
In this configuration, a potential satisfying Tctl is satisfied. According to this configuration, a potential potential for performing sufficient development can be secured and the spread of electric charges can be reduced, so that isolated dots having the minimum write energy can be stably formed. Can be reproduced.

According to a sixth aspect of the present invention, in the image forming apparatus of the first aspect, the Tctl (thickness of the charge transport layer) is used.
And Tul (the thickness of the undercoat layer) as Tul> Tctl
/ 2, and the effect obtained by the device of claim 1 can be further improved.

According to a seventh aspect of the present invention, in the image forming apparatus of the second aspect, the Tctl (thickness of the charge transport layer) is used.
And Tul (the thickness of the undercoat layer) as Tul> Tctl
/ 2, and the effect obtained by the device of claim 2 can be further improved.

According to an eighth aspect of the present invention, in the image forming apparatus of the third aspect, the Tctl (thickness of the charge transport layer) is used.
And Tul (the thickness of the undercoat layer) as Tul> Tctl
Therefore, the effect obtained by the device according to claim 3 can be further improved.

According to a ninth aspect of the present invention, in the image forming apparatus of the fourth aspect, the Tctl (thickness of the charge transport layer) is used.
And Tul (the thickness of the undercoat layer) as Tul> Tctl
Thus, the effect obtained by the device of claim 4 can be further improved.

According to a tenth aspect of the present invention, in the image forming apparatus of the fifth aspect, the relationship between Tctl (thickness of the charge transport layer) and Tul (thickness of the undercoat layer) is Tul> Tc.
tl, and the effect obtained by the device of claim 5 can be further improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an image forming apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a function-separated-type laminated photoconductor used in the image forming apparatus of the present invention.

FIG. 3 is a schematic sectional view showing an example of a conventional single-layer photoreceptor.

FIG. 4 is a schematic cross-sectional view showing an example of a conventional function-separated type laminated photoreceptor.

FIG. 5 is a schematic sectional view showing an example of a conventional function-separated type laminated photoconductor.

FIG. 6 is a schematic view showing a structure of a laminated photosensitive layer manufactured by a wet coating method.

FIG. 7 is a schematic diagram illustrating generation of photocarriers in a laminated photoconductor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 plain paper 2 paper feeder 3 feed belt 4 fixing device 5 image forming device 6 photosensitive drum 7 charging device 8 developing device 9 transfer device 10 cleaning device 11 exposure device 21 conductive support 23 photosensitive layer 25 undercoat layer 31 Charge generation layer 33 Charge transport layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/04

Claims (10)

[Claims] 1. An image forming apparatus comprising at least a photosensitive member, a charging unit, an image exposing unit, and a developing unit, wherein the image exposing unit forms a part of light, which has exposed an original, on a photosensitive member through an optical lens. In the apparatus, the photoconductor is a function-separated photoconductor having an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CTL) on a conductive support;
L has a thickness (Tctl) of 20 μm or less and
An image forming apparatus, wherein the thickness (Tul) of tl and UL satisfies the relationship of Tul> Tctl / 3. 2. An image forming apparatus comprising at least a photoreceptor, a charging unit, an image exposing unit, and a developing unit, wherein the image exposing unit divides a light image into minute pixels and exposes the image with incoherent light. The photoreceptor is a function-separated type photoreceptor having an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CTL) on a conductive support;
Has a thickness (Tctl) of not more than 20 μm and
An image forming apparatus, wherein a thickness (Tul) of 1 and UL satisfies a relationship of Tul> Tctl / 3. 3. An image forming apparatus comprising at least a photoreceptor, a charging unit, an image exposing unit, and a developing unit, wherein the image exposing unit divides a light image into minute pixels and exposes the image with coherent light. A photoconductor is formed on a conductive support by forming an undercoat layer (UL), a charge generation layer (CGL), and a charge transport layer (CT).
L) wherein the CTL has a thickness (Tctl) of 20 μm or less, and the Tctl and U
An image forming apparatus, wherein the thickness (Tul) of L satisfies the relationship of Tul> Tctl / 2. 4. An image forming apparatus comprising at least a photoconductor, a charging unit, an image exposing unit, a developing unit, and a gradation expressing unit, wherein the image exposing unit corresponds to an optical image corresponding to an original image having image data including gradation information. Is exposed to the photoreceptor with incoherent light to form an electrostatic latent image on the photoreceptor, and the gradation expressing means indicates a gradation-based image forming method, A driving signal having a predetermined minimum value is given to the image exposing means based on the image data of (1), wherein the photoreceptor comprises an undercoat layer (UL), a charge generation layer (CGL), charge transport layer (CT
L), wherein the thickness (Tctl) of the CTL is 20 μm or less, and the thickness (Tul) of the Tctl and UL satisfies the relationship of Tul> Tctl / 2; The photoreceptor has a differential sensitivity equal to or less than 1/3 of the maximum differential sensitivity of the photoreceptor at the predetermined minimum value of the drive signal and the maximum exposure in the exposure distribution on the photoreceptor surface; Are coordinates (x,
y), the write energy distribution P (x, y,
t) E (x, y) [joule / m ² ] obtained by integrating [watt / m ² ] with respect to the exposure time (t), and the photoconductor surface at the predetermined minimum value of the drive signal In the photoconductor region at an exposure amount equal to or more than 最大 of the maximum exposure in the above exposure distribution, the smaller one of the exposure diameters measured in the main scanning direction or the sub-scanning direction is defined as an exposure diameter Db, The image forming apparatus, wherein the exposure diameter Db satisfies Db> Tctl. 5. An image forming apparatus comprising at least a photoreceptor, a charging unit, an image exposing unit, a developing unit, and a gradation expression unit, wherein the image exposing unit corresponds to an optical image corresponding to an original image having image data including gradation information. Is exposed to the photoconductor with coherent light to form an electrostatic latent image on the photoconductor, and the gradation expressing means indicates an image forming method based on gradation, and A drive signal having a predetermined minimum value is given to the image exposure means based on the image data, and the photoconductor is provided on a conductive support with an undercoat layer (U
L), a function-separated type photoreceptor having a charge generation layer (CGL) and a charge transport layer (CTL), and having a thickness (T
ctl) is 20 μm or less, and the thickness (Tul) of the Tctl and the UL satisfies the relationship of Tul> Tctl / 2, and the photosensitive member is arranged on the photosensitive member surface at the predetermined minimum value of the drive signal. The maximum exposure in the above exposure distribution has a differential sensitivity of 1/3 or less of the maximum differential sensitivity of the photoconductor, and the exposure distribution has coordinates (x, y) on the surface of the photoconductor.
, The write energy distribution P (x, y, t)
E (x, y) [joule / m ² ] obtained by integrating [watt / m ² ] with respect to the exposure time (t),
The exposure diameter measured in the main scanning direction or the sub-scanning direction in the photoconductor region at an exposure amount equal to or more than の of the maximum exposure in the exposure distribution on the photoconductor surface at the predetermined minimum value of the drive signal The image forming apparatus is characterized in that the smaller one of the exposure diameters is an exposure diameter Db, and the exposure diameter Db satisfies Db> 2Tctl. 6. The image forming apparatus according to claim 1, wherein
The thickness (Tul) of Tctl and UL is Tul> Tctl
An image forming apparatus that satisfies the relationship of (1/2). 7. The image forming apparatus according to claim 2, wherein
The thickness (Tul) of Tctl and UL is Tul> Tctl
An image forming apparatus that satisfies the relationship of (1/2). 8. The image forming apparatus according to claim 3, wherein
The thickness (Tul) of Tctl and UL is Tul> Tctl
An image forming apparatus that satisfies the following relationship: 9. The image forming apparatus according to claim 4, wherein
The thickness (Tul) of Tctl and UL is Tul> Tctl
An image forming apparatus that satisfies the following relationship: 10. The image forming apparatus according to claim 5, wherein Tctl and UL have a thickness (Tul) of Tul> Tc.
tl satisfying the following relationship: tl.