JP2001222121A - Electrophotographic photoreceptor and electrophotographic process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor capable of stably obtaining a latent image of a high γphotoreceptor. SOLUTION: The electrophotographic photoreceptor has a photosensitive layer formed by mixing fine powder 1 of a P-type semiconductor with fine powder 2 of an N-type semiconductor and shaping the mixture into a thin layer with a binder having >=1013 Ω-cm volume resistivity and a transparent high electric insulating layer attached to the surface of the photosensitive layer in one body.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor and an electrophotographic method, and more particularly, to a photoreceptor having a novel digital characteristic used in electrophotography, and more particularly to a conventional KIP method. The present invention relates to a photoreceptor which has been used in a known electrophotographic method and which exhibits a particularly high γ characteristic. Conventionally, "KIP method requires an impurity level and thus requires a high sensitivity in which the photosensitive material must be an intrinsic semiconductor. γ characteristics cannot be expected ”.

[0002]

BACKGROUND OF THE INVENTION The inventor of the present application is an inventor of a high-gamma electrophotographic photoreceptor (see Japanese Patent Publication No. 5-19140 and U.S. Pat. No. 4,963,452) and a KIP method (Japanese Patent Publication No. Sho.
No. 3,2627, and U.S. Pat. No. 3,457,070). The KIP method is described in R. M.
Schaffert's book "Electrophototo"
Graphy, page 107 to page 111, Th
e Katsurakawa Electrophotot
It is introduced as an optic process. Originally, the expression of the high γ characteristic is mainly due to the charge amplification action in the photosensitive layer, and the amplification action is mainly caused by the so-called avalanche phenomenon in the intrinsic semiconductor under a high electric field. The avalanche phenomenon is also known for inorganic materials such as Si and Ge, but phthalocyanine is attracting attention as an organic material showing avalanche particularly strongly due to its special structure. For this reason, many high gamma photoreceptors use phthalocyanine.

On the other hand, in the KIP method, a) the surface of the photoreceptor is covered with a transparent insulating layer, the latent image is a charge image on the surface of the insulating layer, and once formed, the latent image does not disappear even by photoexcitation. b) The latent image forming step is a first charging step of uniformly charging to a certain polarity, and a second charging step of irradiating the photoreceptor with a light image while charging to a polarity opposite to the first charging step. Consists of This is completely different from the conventional Carlson method.
KIP method (Japanese Patent Publication No. 43-2627 and U.S. Pat.
No. 3,457,070) is also called an inversion electric field method, and it has been considered in principle that the PIP phenomenon caused by a trap level in a photosensitive semiconductor governs the formation of a latent image. Since the trap referred to here is considered to be mainly caused by impurity levels in the semiconductor, it has been considered that the PIP phenomenon does not occur in an intrinsic semiconductor containing no impurities.
Therefore, it was considered that a high γ photoconductor using an intrinsic semiconductor does not have KIP characteristics. But KIP
The excellent properties of the law are difficult to discard. The wish that the high γ KIP method existed was a matter of course. In particular, a high γ photoreceptor using phthalocyanine is excellent in high γ characteristics, but there is a problem that phthalocyanine is deteriorated by ozone, and if the high γ KIP method is established, the insulating layer on the surface of the photoreceptor is converted from ozone to a photosensitive layer. There is hope that it will protect it. A long-term stable operation cannot be expected with a photoreceptor having no overcoat, such as a high γ photoreceptor disclosed in Japanese Patent Publication No. 5-19140.

[0004]

As described above, high γ
The characteristic and the KIP characteristic are in exactly the opposite positions in the conventional theory regarding the involvement of the impurity level, and it is better that the high γ characteristic has no impurity, and the KIP characteristic has a high value if the conflicting requirements of requiring the impurity are satisfied. The γKIP photoreceptor does not hold. In the process of challenging this seemingly impossible task, the present inventor has stated that the fact that a photoreceptor made of a high-resistance binder by mixing pure ZnO fine particles and pure phthalocyanine fine particles exhibits high γ characteristics. Encountered. It is natural that phthalocyanine is used to show high γ characteristics, but it was important information that a kind of hysteresis phenomenon associated with high γ characteristics was also observed. One of the problems as a kind of harmful effect in the operation of the high γ photoreceptor is the fact that when images are formed continuously, charges are unevenly distributed and a history is formed. In order to cancel this, an appropriate AC electric field must be applied to eliminate “distribution of charges”. The fact that "distribution of charges must be forcibly removed by an AC electric field" means that the localized charges are temporarily trapped in a quasi-equilibrium state, if any. That is, there is a kind of trap phenomenon. This trapping phenomenon is particularly remarkable in "a photoreceptor in which ZnO fine particles and phthalocyanine fine particles are mixed", and the high γ characteristic is also remarkable in this type of photoreceptor. Therefore, the “photosensitive layer in which ZnO fine particles and phthalocyanine fine particles are mixed” is 5 to 10 μm
When a transparent insulating layer having a thickness of 5 mm was attached by coating, a KIP latent image was obtained by a KIP image forming method. Both ZnO and phthalocyanine used are pure materials containing no impurities.
There is no impurity that causes the PIP phenomenon. Nevertheless, KIP characteristics were exhibited. Why "Zn
Did the photosensitive layer containing a mixture of O particles and phthalocyanine particles show KIP characteristics? What can be considered is that "the contact point between the ZnO particles and the phthalocyanine particles forms a PN junction." In this way, it was explained that the high γ characteristics were strongly exhibited and the KIP characteristics were also exhibited. You.

[0005]

In order to achieve the above object, an electrophotographic photoreceptor according to the present invention is characterized in that a P-type semiconductor fine powder and an N-type semiconductor fine powder are mixed and have a volume of at least 10 ¹³ Ω-cm. It has a photosensitive layer thinned with a binder having a specific resistance, and a transparent electrically insulating layer integrally attached to the surface of the photosensitive layer. Further, the electrophotographic method according to claim 2 is characterized in that a P-type semiconductor fine powder and an N-type semiconductor fine powder are mixed and thinned with a binder having a volume resistivity of 10 ¹³ Ω-cm or more; An electrophotographic photoreceptor having a transparent electrically-high insulating layer integrally attached to the surface of the layer; a first step of performing a first charge of a certain polarity on the electrophotographic photoreceptor; After the first step, a second step of exciting the electrophotographic photoreceptor with an optical image while performing a second charge having a polarity opposite to that of the first step;
After the step, a third step of photo-exciting the entire electrophotographic photosensitive member holding the latent image is further provided.
In addition, the electrophotographic method according to the third aspect is characterized in that a P-type semiconductor fine powder and an N-type semiconductor fine powder are mixed and thinned with a binder having a volume resistivity of 10 ¹³ Ω-cm or more; An electrophotographic photoreceptor having a transparent electrically-high insulating layer integrally attached to the surface of the layer; a first step of performing a first charge of a certain polarity on the electrophotographic photoreceptor; After the first step, a second step of irradiating light, and after the second step, the electrophotographic photoreceptor is excited by a light image while performing a second charging having a polarity opposite to that of the first step. And a fourth step of photo-exciting the entire electrophotographic photosensitive member holding the latent image after the third step. The electrophotographic photoreceptor according to claim 4, wherein the P-type semiconductor fine powder, the N-type semiconductor fine powder,
A thin photosensitive layer containing a binder having a volume resistivity of not less than 0 ¹³ Ω-cm; and a transparent layer having a volume solid resistance of not less than 10 ¹³ Ω-cm formed integrally with the photosensitive layer. And an electrically insulating layer. According to a fifth aspect of the present invention, in the electrophotographic photoreceptor of the fourth aspect, the P-type semiconductor fine powder is phthalocyanine, and the N-type semiconductor fine powder is ZnO dye-sensitized with rose bengal. is there. An electrophotographic method according to claim 6, wherein the photosensitive layer is made thin by including a P-type semiconductor fine powder, an N-type semiconductor fine powder, and a binder having a volume resistivity of 10 ¹³ Ω-cm or more. And 10 ¹³ Ω-
and an electrophotographic photosensitive member having a transparent electric high-insulating layer having a volume solid resistance of not less than 1 cm, and a charging step of performing a first charge of a certain polarity on the electrophotographic photosensitive member, and after the charging step, A latent image forming step of exciting the electrophotographic photosensitive member with a light image to form a latent image on the electrophotographic photosensitive member while performing a second charging having a polarity opposite to the first charging; And a latent image holding step of photo-exciting the entire electrophotographic photoreceptor for holding the latent image thereafter, wherein the light image is generated by a laser. The diameter of the toner dot formed by changing the amount of light emission is controlled. An electrophotographic method according to claim 7, wherein the photosensitive layer is made thin by including a P-type semiconductor fine powder, an N-type semiconductor fine powder, and a binder having a volume resistivity of 10 ¹³ Ω-cm or more. And an electrophotographic photosensitive member having a transparent electrically high insulating layer having a volume solid resistance of 10 ¹³ Ω-cm or more formed integrally with the photosensitive layer. And a photo-excitation of the entire electrophotographic photoreceptor to form a polarization state, and after this polarization formation step, the light is applied while performing a second electrification having a polarity opposite to the first electrification. A latent image forming step of exciting the electrophotographic photoreceptor with an image to form a latent image on the electrophotographic photoreceptor, and after the latent image forming step, further excites the entire electrophotographic photoreceptor holding the latent image An electrophotographic method comprising:
The light image is due to a laser, and the laser
The diameter of the toner dot formed by changing the amount of light emission is controlled.

(Operating Principle of High γ KIP Photoreceptor) There is almost no literature on the reason why high γ characteristics are exhibited. However, since the present inventor is an inventor of the high γ photoreceptor, he naturally has a hypothesis regarding “the reason why the high γ characteristics are exhibited”. This hypothesis is strongly related theoretically to the present invention. FIG. 1 is a simplified equivalent circuit of a photoconductor showing a high γ characteristic. In other words, the high γ characteristic is the characteristic of the photoconductor that responds greatly to the light input in a non-linear manner, unlike the conventional classical Carlson method photoconductor that responds in proportion to the light input. It refers to a photoreceptor that has an increased response over an increase in light input as the input increases. This type of response cannot occur unless there is a non-linear photoresponse in the photoreceptor or a type of amplification. A in FIG. 1 indicates, for example, a photoconductive semiconductor such as phthalocyanine. B is A
A and B are drawn separately for the sake of showing the factor that amplifies the electric charge that has passed through, and A and B are drawn separately for the sake of display as an equivalent circuit. However, A and B are inseparable in the particles of a material such as phthalocyanine which is apt to cause the avalanche phenomenon. It is. That is, in the phthalocyanine particles, the resistance is reduced according to the light input and the charge is allowed to pass, and at the same time, the passing charge is amplified, so that free charges equal to or higher than the density of the free charge generated according to the light input are generated.
The circuit indicated by C and the parallel capacitance in FIG. 1 represents a thin layer of binder. The free charge group reaching the point E in the figure is further amplified in the next phthalocyanine particle to increase the density. Avalanche that causes amplification occurs more strongly as the electric field intensity increases, and the relationship between the amplification factor α and the electric field intensity E is represented by α = Kexp (−1 / E). The free charge density at the point E in the figure can be calculated, and similarly, the variation of the free charge density over the entire photosensitive layer can be calculated. FIG. 2A shows the result of calculating the light response at a certain electric field strength of a photoreceptor using phthalocyanine as a photosensitive material based on the above-described concept. As seen in FIG.
Since the measured and calculated results agree well, the hypothesis that "high γ characteristics are dominated by avalanche in phthalocyanine particles" is valid in general. FIG. 2B shows a graph of a real number scale actually measured for reference.
As shown in FIG. 2A, the calculation taking into account the avalanche well explains the measurement result of the high γ photoreceptor, but it is important to remember that the calculation is “the movement of the electric charge is stored in each stage of the calculation”. It is done under the condition of saying. That is, the movement of the electric charge is temporarily trapped. In fact,
What actually becomes a defect in the operation of the high γ photoconductor is the “history phenomenon”. If a high γ photoreceptor is used repeatedly, a previous history may appear and disturb the image. There is also a complaint that the photosensitive curve shifts to the high sensitivity side due to repeated use, and that stable characteristics cannot be obtained. In severe cases, the charge retention ability is lost by repeated use. As described above, the hysteresis phenomenon occurring in the high γ photoconductor is only a serious defect in the Carlson method, but from the standpoint of pursuing “high γ KIP”, the “hysteresis phenomenon” is a kind of “trap phenomenon”. "Zn
It is considered that the reason why the KIP characteristic was observed in the special photosensitive layer "O + phthalocyanine" is due to the material arrangement as shown in FIG. As shown in FIG. 3, the average particle size of phthalocyanine which is a P-type semiconductor fine powder is, for example, 0.01%.
.About.0.05 .mu.m, whereas the N-type semiconductor fine powder Z
Since the average particle size of nO is as large as 0.1 to 0.5 μm, for example, and the charging characteristics of both are opposite polarities, it is considered that the phthalocyanine particles surround the ZnO particles. The fine powder is, for example, an average particle size of 0.01 to 0.
It is about 5 μm. Since phthalocyanine is P-type and ZnO is N-type, the contact point between the two forms a PN junction. In FIG. 3, the ZnO particles are PN
It is in a state of being wrapped in a junction. If free charges exist in the ZnO particles for any reason, the free charges are prevented from exiting the particles by a high-resistance PN junction and become a kind of trapped state. P
The trap charge formed by the N junction is released because the resistance of the PN junction disappears when excited by light. The release of the trapped charge by light is the same as the trap by the impurity level.
Very similar to the phenomenon. Actually "ZnO + phthalocyanine"
Is easily lost by light irradiation.

[0007]

EXAMPLES (Example 1) "ZnO + phthalocyanine"
An example of a high γ KIP photoconductor having a photoconductive layer thinned with a binder having a volume resistivity of 10 ¹³ Ω-cm or more will be described. Metal-free phthalocyanine 6.0 g (Dainichi Chemical Co., average particle size 0.02 μm) ZnO 46.0 gr (Sakai Chemical Co., average particle size 0.2 μm) Polyester resin・ ・ ・ ・ 138.0gr (Dai Nippon Ink Co., Ltd., trade name Beckolight 54-409) Melamine resin ・ ・ ・ ・ ・ ・ 39.0gr (Dai Nippon Ink Co., Ltd., trade name Super-Beckamine L
-117-60) Cyclohexanone ..... 300.0 gr was put into a vibrating stirrer and stirred for 120 minutes to obtain a coating liquid having a viscosity of 420 cp. Mixing casein · · · · · 4.0Gr iodine · · · · · 0.4Gr ethyl alcohol ····· 20.0gr 5% ammonia H ₂ O ··· 200.0gr on one side of the Al foil having a thickness of 100μm were prepared separately Apply the dried liquid to a thickness of 1 μm after drying.
After drying, apply the above coating solution to the gelatin surface
m, heated in an atmosphere of 150 ° C. for 60 minutes, and then stored at room temperature to complete formation of a substrate having a photosensitive layer.
Acrylic resin ・ ・ ・ ・ ・ ・ 80.0 gr (Mitsubishi Rayon Co., Ltd., product name: Dianal LR-214) Toluene ・ ・ ・ ・ ・ ・ A mixture of 80.0 gr is applied by dipping and dried completely. An overcoat film (the overcoat film is a transparent electrically insulating layer integrally attached to the surface of the photosensitive layer) was formed so that the thickness of the film became 8 μm. High γ in this process
The trial production of the KIP photoconductor has been completed. The characteristics of the prototyped high γ KIP photoreceptor were examined by the apparatus shown in the sectional view of FIG. This device is basically an image forming device.
All the elements that form the image are provided. FIG. 4 (A)
FIG. 4B is a diagram showing an eraser operation which is a former stage of image formation, and FIG. 4B is a diagram showing an image formation stage. There is no reason to say that the eraser and the image must be separated, but only for the production of the device, which is divided into two parts. FIG.
The AC corona (A) erases the previous history in the photosensitive layer by using the function of the light irradiated on the photosensitive member by the lens L. The photoreceptor from which the previous history has been erased is transferred to the apparatus shown in FIG. 4B and the next image forming process is started. The device shown in FIG.
FIG. 4A is the same as the device shown in FIG. 4A except that the photosensitive member has a first corona for charging negatively and second and third coronas for charging positively next. ). In FIG. 4B, reference numeral 10 denotes a moving body that moves horizontally on the photoconductor in the direction of an arrow. The moving body 10 includes a wire for performing negative charging (−DC corona) and a positive charging (+ DC corona).
A light-shielding plate S ₁ that shields a wire for performing (− corona), a wire for performing − charging (−DC corona), a wire for performing − charging (−DC corona), and a wire for performing + charging (+ DC corona). + charge (+ DC corona) light shielding plate S ₂ for shielding on the wire to perform are provided each. In particular, the corona for performing the + charge is divided into two, and consideration is given to irradiating the optical image by the lens L between the two + charges (the second corona for performing the + charge and the + The light-shielding plate S is not provided between the third corona and the third corona. The method in which a light image is given between these two positive charges is a method in which the irradiation effect of the light image is maximized by the KIP method. Irradiation "is further enhanced in the effect of the second charging step. That is, after the first step of performing the first charge of the polarity on the electrophotographic photoreceptor, in this embodiment, the first charge of-, and then the second charge of the opposite polarity to that of the first step, in this embodiment, + The electrophotographic photoreceptor is excited by a light image while performing the charging (second step). Note that the above-described first step and second step are performed in a dark room, and after the second step,
Take out the electrophotographic photoreceptor from the dark room, the entire photoreceptor holding the latent image, for example, by exposing to room light,
Photoexcitation (third step). Therefore, specifically, the free charge corresponding to the light irradiation is first obtained under the condition that the first + corona is charged to a certain potential + and the electric field of the second polarity is applied to the photosensitive layer to a certain degree. Movement occurs and the second
The + corona compensates for the decrease in the surface potential of the photoconductor due to the charge transfer generated by light irradiation, and forcibly increases the surface potential of the photoconductor.
Forcibly determine the potential. For reference, FIG. 5 shows a corona arrangement in an image forming process that is almost ideal. The + DC corona 2 in FIG.
It is a discharger provided with a grid called a so-called scorotron. In this type of corona discharger, the charging potential is freely changed by the voltage of the grid, and the charging potential is stabilized at a certain value. As described above, the role of the + DC corona 2 is to determine the latent image potential of the light image bright portion. As a digital electrophotographic latent image, the light image dark portion has a negative potential and the light bright portion has a certain positive value. Most rarely. If the potential of the portion to be developed is constant in this manner, the density of the developed visible image is also constant, and the most favorable situation for recording can be realized. FIG. 7 shows the sensitivity curve of the photoconductor of Example 1 measured experimentally using the apparatus shown in FIG. In FIG. 7, since the light amount side is drawn on a log scale, γ is estimated from this sensitivity curve. In FIG. 7, since the grid voltage of the + corona 2 is selected so that the surface potential of the member to be charged is +200 Volt, the charging potential of the light image portion is +200 Volt.
The light image dark portion is not as stable as the light image bright portion, but falls within a certain potential of-if the trapped charge density induced by DC charging is constant. In the curve of FIG. 7, the negative charging potential is -2000 Volt
And the + charge potential was selected to be +200 Volt. As shown in the figure, when the light input is 1 μJ / cm ² or less, the photoconductor surface potential is about −50 Volt. However, when the light input is 1.6 μJ / cm ² or more, the photoconductor surface potential becomes +200 Volt. While the light input changes from 1 μJ / cm ² to 1.6 μJ / cm ² , the photoreceptor surface potential changes from -50 Volt to +200 Volt. When expressed by γ, γ = 8.0. The feature of the image obtained by the high γ KIP method is that the dark portions of the light image are negatively charged and the light image portions are charged to the opposite polarity such that they are positively charged.
The developed visible image is an image in which the brightness and darkness are clear (the SN ratio is high) (if the charged polarity of the toner is clear). In addition, once a latent image is created, it will not be attenuated unless a special erasing step is given.
Unlike the classical Carlson method latent image held on the semiconductor surface, it does not change due to temporal factors, and always provides a stable image. In particular, in the case of a digital image, if the signal input is ON, the image signal is also ON and the signal input is O
If it is FF, the image signal must also be OFF. Moreover, both the ON level and the OFF level must always be stable. High γ KIP method answers this demand well O
_It offers a "stable electrophotographic method" that has withstood ₃ and could not be reached by any method in the past. Photoconductor surface
An 8 µm insulating layer does not hinder the creation of latent images of lines or dots of the order of 10 µm. This seems to be because the electric field applied to the insulating layer is almost perpendicular to the surface direction of the photoconductor. Next, a cylindrical photoreceptor used for a practical image forming apparatus was prototyped. Basic configuration of photoreceptor is Example 1.
Is the same as The photoreceptor is practical because it has a cylindrical shape.

(Embodiment 2) First, an Al cylinder having a diameter of 80 mm and a thickness of 1 mm serving as a base of a photoreceptor was prepared. Al
The outer surface of the cylinder is machined to a surface roughness of 1s or less.
In order to form a casein film on the outer surface of the Al cylinder for bonding adjustment with the photosensitive layer, casein ・ ・ ・ ・ ・ ・ 4.0 gr iodine ・ ・ ・ ・ ・ ・ 0.4 gr ethyl alcohol ・ ・ ・ ・ ・ ・ 20.0 gr H ₂ O + 0.5% ammonia ...
It was applied to a thickness of 1 μm and dried. Separately, metal-free phthalocyanine for photosensitive layer: 6.0 gr (Daiichi Seika, average particle size: 0.02 μm) ZnO: 46.0 gr (Sakai Chemical Co., average particle size: 0.2 μm) Polyester resin: 138.0gr (Dai Nippon Ink Co., Ltd., trade name Beckolight 54-409) Melamine resin: 39.0gr (Dai Nippon Ink Co., Ltd., trade name: Super Beckamine L-117)
-60) Cyclohexanone ・ ・ ・ ・ ・ ・ Prepare a coating solution with a composition of 300.0gr, apply it to the casein surface with a ring coater so that the film thickness after complete drying becomes 20μm, and after pre-drying, The solvent was completely removed by heating in an atmosphere of ° C for 60 minutes. The cylinder returned to normal temperature is a cylinder provided with a photosensitive layer. Next, in order to attach the insulating layer on the surface, first, the photosensitive layer was coated with silicone resin ... 40.0gr (Shin-Etsu Chemical Co., Ltd., product name: KR-216) Toluene ... 160.0gr A surface insulating layer having a thickness of 8 μm (a surface insulating layer is a transparent electrically insulating layer integrally attached to the surface of the photosensitive layer) was obtained by a dipping method of dipping in a liquid and gently pulling up. After drying in an atmosphere at 100 ° C. for 60 minutes, the production of a cylindrical high γ KIP photoconductor was completed. The obtained cylindrical high γ KIP photoreceptor was mounted on a measuring device shown in FIG. 6, and various characteristics were examined. FIG. 6 is substantially the same as the image forming apparatus, and is a measuring instrument only in that a potential measuring instrument is placed at the developing position. The electrometer and the developer can be replaced. The photoreceptor drum is first photoexcited by the eraser A and erased by the AC corona, and reaches the B-DC corona. The surface of the photoreceptor is uniformly charged to a potential (-2000 Volt) by the DC corona B (first step). Next, it is charged to + by the + coronas C and D, and is irradiated with a light image in E in the process of being charged to the + (second step). In the process so far, the dark portion of the light image (the portion not exposed to the image light) is negatively charged, and the light image bright portion (the portion where the image light is irradiated) is a positively charged latent image formed on the surface of the photoreceptor. Next, when a uniform post light is received by F, the uneven distribution of the charge inside the photosensitive layer disappears, and the actual charge on the surface of the photosensitive member remains as a latent image (third step). The + portion of the real charge image easily absorbs the-toner to form a toner image. The portion where this toner is adsorbed is the light image bright part, and the light image dark part is negatively charged.
No toner is attached at all, and a visible image with a very clear difference in brightness is obtained. Next, at H, the toner image is transferred to a transfer sheet, and fixed by a fixing device not shown in the figure to complete the print. Note that the first and second embodiments described above
In “ZnO + phthalocyanine”, the first step was charged to − and the second step was charged to +.
Since the photoconductor is dependent on the photoconductor, a second process after the first process of performing the first charge of a certain polarity on the photoconductor is performed while performing the second charge of the opposite polarity to the above-described first process. The electrophotographic photoreceptor may be excited by an image. The peripheral speed of the photosensitive drum is fixed at 80 mm / sec. However, if the peripheral speed of the light image is large, even if the peripheral speed is further increased, the image forming operation is not hindered. When considered as a printer, it is the fixing unit that determines the printing speed (the one that takes the longest time). Charging and development by the corona do not take much time. Even if the charge image is formed inside the photoreceptor by light, even if the peripheral speed reaches 1000 mm / sec or more, if the amount of light is increased, no problem occurs. Although it is not the gist of the present invention to discuss development, the ability as a printer is evaluated by a visible image, and the quality of the toner determines the quality of the visible image. The department that was behind in the development of printers in the past was toner. In the stage of creating a latent image, the development of toner required to express 1200 dpi dots was neglected, for example, saying (1200 dpi is required). Was. For example, in a 1,200 dpi laser printer, the size of the dots that compose the screen is 21.2 μm φ, so it must be 2 μm toner to completely represent this as a dot. However, the toner actually made is 4.5 μm at the finest, and a toner of this particle size can express only 45 μm dots, and the resolution limit is 560 dpi. The most recent object of the high γ KIP method is a photoreceptor used for a laser beam printer, which aims to transmit a complex image such as an X-ray image to a remote place by facsimile, for example. Conventionally,
The cleaning with a blade was performed to remove the toner remaining in the transfer because the amount of toner and the toner particle size were not uniform, and a large amount of toner remained, so that cleaning had to be performed. If the particle size of the toner and the amount of charge are uniform, complete transfer is performed, and cleaning is not required. Although problems relating to development and transfer are not the focus of the present invention, the high γKI
In order for P to demonstrate its true value, it cannot be discussed outside the visualization stage. The present invention contemplates an electrophotographic photoreceptor for use in a laser printer that provides a digital light signal to the photoreceptor. A latent image corresponding to a light image bright portion has a positive charging potential. " The edge of the latent image of the dot has a considerably sharp potential gradient due to the effect of high γ in addition to the sharp distribution of light from the laser. In addition to the above-described effect unique to the KIP (parts exposed to light and parts not exposed to light are charged to opposite polarities), the dot latent image is extremely steep as shown in FIG. Will have a rich edge. When the conventional function-separated Carson method photoconductor is used in a laser printer (the image is sweet regardless of the laser)
He was criticized because dots were not independent. The latent image produced by the high γ KIP photoreceptor is 1
Since each dot latent image is completely independent, there is no room for the above criticism. The salient features of our method are:
"In the second step, the charge of the polarity opposite to that of the first step, in this embodiment, the charge is positive. In other words, the portion where light is incident is charged negatively, and the portion where light is not incident is positively charged. I do it ". This is shown in FIG. 8. As is apparent from FIG. 8, the toner of “−” is applied to the charged portion (the portion where no light is incident) due to the electric repulsive force. Can not be attached at all. The toner of-is adsorbed to the portion charged to + (the portion where light is incident). It is the generality of the KIP electrophotography that a latent image in which the light image light portion and the light image dark portion are charged with polarities opposite to each other is formed. In the high γ KIP method, since the high γ characteristic is added to the generality of the KIP electrophotographic method, a latent image having a sharp edge almost like a rectangular wave as shown in FIG. 8 can be formed. In addition to the generality of KIP electrophotography, "the latent image once formed does not disappear even when exposed to light", the "latent image of the KIP method is a real charge image on the insulating layer on the surface of the photoreceptor." Therefore, an image having a much higher SN ratio and higher resolution than any conventional electrophotographic method can be obtained. However, in the above-mentioned embodiment, A) the trap formed as a result of the first negative charging lacks certainty, and B) the trap is hardly formed when left in a high humidity atmosphere for a long time. occured. The present inventor carried out the following Example 3 to correct this point, and confirmed that both disadvantages were completely eliminated.

Example 3 Al having a diameter of 80 mm and a thickness of 1 mm
A cylinder was prepared. The surface is finished to less than 1s roughness. First of all, casein on the surface of this cylinder 40 g iodine 0.4 g ethyl alcohol 20 gr H ₂ O + 0.5% Ammonia ・ ・ ・ ・ ・ ・ ・ The liquid after mixing is dried with a ring coater to a thickness of 200gr.
It was applied and dried to a thickness of 1 μm. Separately, metal-free phthalocyanine ・ ・ ・ ・ ・ ・ ・ ・ ・ 7.6gr (Dainichi Seika Co., Ltd., average particle size 0.02 μm) ZnO ・ ・ ・ 10.0gr (Sakai Chemical Co., Ltd., average particle size) Diameter 0.2μm) Silicone epoxy varnish ・ ・ ・ ・ ・ ・ 90.0gr (Shin-Etsu Chemical Co., Ltd., product name ES1001N) Cyclohexanone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Prepare a coating liquid of 140.0gr and use a ring coater. Coating was performed on the casein surface so that the film thickness after complete drying became 20 μm, and after preliminary drying at room temperature, heating was performed in an atmosphere at 150 ° C. for 60 minutes to completely remove the solvent. The cylinder returned to room temperature is a cylinder provided with a photosensitive layer. Next, in order to attach the insulating layer on the surface, acrylic resin .......... 5.0 gr (manufactured by Mitsubishi Rayon Co., Ltd., product name "Dianal LR-214") Toluene ... 80.0 gr is applied to the surface of the photosensitive layer by dipping, and the overcoat layer (the overcoat layer is a transparent electric height integrally attached to the surface of the photosensitive layer) so that the thickness after complete drying is 8 μm. It is an insulating layer.) In this process, the trial production of the high γ KIP cylindrical photoconductor was completed. Just in case 1
A photosensitive layer and an insulating layer were attached to the Al foil having a thickness of 00 μm in the same steps as described above, and a flat high γ KIP photosensitive member was produced. The two types of high γ KIP photoreceptors made are shown in Fig. 4.
This was closely examined by a device obtained by modifying a part of the device shown in FIG. First, a flat high γ KIP photoreceptor is examined by using the apparatus shown in FIG. 4, and as a result, it is very effective to irradiate light after the first-charging to make a trap targeted for the first-charging. The thing was confirmed. This is considered to mean that the charge does not move in the photosensitive layer called (ZnO + phthalocyanine) unless light is irradiated. Needless to say, trapped charges generated in accordance with the first negative charging are stored immediately below the insulating layer. In order to generate the trapped charges, it is necessary to generate and move free charges. (ZnO + phthalocyanine)
It is understood that free charge is generated in the layer, and excitation by light is required for the free charge to move directly below the insulating layer. This point is significantly different from the classic KIP phenomenon that occurs in the photoconductor containing impurities. FIG. 9 is a partial modification of the device shown in FIG. As shown in FIG. 9, the moving body 10 moves in the direction of the arrow on the photoconductor, and the moving body 10 includes a first-corona (wire) and a second-corona (wire).
A lamp is provided between the + corona (wire) and the first
The lamp is irradiated with light immediately after the charging. That is, after the first step of performing the first charge of the polarity on the electrophotographic photoreceptor, in this embodiment, the first charge of-, the lamp is irradiated with light (second step). Light from the lamp is shielded from light by the light shielding plate S ₁ as unexpected fall in the second + corona. (First
The corona, ramp, and second corona) are a group of moving objects 10
To move. That is, after the above-described second step by the movement of the moving body 10, the above-described electrophotographic photosensitive is performed by a light image while performing the second charge of the opposite polarity to the above-mentioned first step, in this embodiment, + charge. Excites the body (third
Process). The above-described first, second, and third steps are performed in a dark room (not shown). After the third step, the electrophotographic photosensitive member is taken out of the dark room to hold a latent image. The entire photoconductor is photo-excited, for example, by exposing it to room light (fourth step). As a result, the light image from the enlarger is projected onto the photoreceptor surface from the gap between the second two + coronas. The moving speed of the (corona ramp) group is about 88 mm / sec. The distance between the first-corona and the second + corona should be 50mm or more, and the lamp is rated 15v
olt incandescent bulb plus 10-13 volts.
It is about 10 μJ / cm ² . -6700volt for the first corona
Is added, and the surface of the insulating layer of the photoreceptor is -2 by this corona.
Charged to 000volt. +5300 volts for the second + corona
The corona changes the surface of the insulating layer at the light image portion to +200 volts. The light image dark part is -50 volt. Dark part
Although the difference in potential is small at -50 volts and the bright portion is +200 volts, when this latent image is developed with toner, the toner selectively adheres only to the light image bright portion without adhering to the dark portion of the light image. Since the dark portion of the light image is negatively charged, the toner is repelled and cannot be attached at all. From this experiment, it was found that the photoreceptor of Example 3 had optimal characteristics for a laser dot printer. In order to apply this result to a cylindrical photoreceptor, the apparatus of FIG. 6 was modified as shown in FIG. FIG. 10A shows a -DC corona, and D shows a + DC corona. +
There are two DC coronas. Light excitation by a lamp is performed between A and D. An optical image is projected between the two + DC coronas. In a laser printer, point E is irradiated with laser light. Point G is where the measuring and developing devices come. Post light is applied between the points G and D. The role of the post light is to eliminate the distributed charges in the photosensitive layer, and the post light clarifies the actual charge latent image on the surface of the insulating layer. In the subsequent development, the toner adheres only to the area where the light was applied by E. That is, the photosensitive drum is
, And reaches the -DC corona of A first. −DC
The surface of the photoreceptor is uniformly charged to a negative potential by the corona A (first step). -Immediately after charging, light is irradiated by a lamp (second step) to form a trap. Then + corona C, D
Is charged to +, but is irradiated with a light image in E in the process of being charged to + (third step). In the process so far, the dark portion of the light image (the portion not exposed to the image light) is negatively charged, and the light image bright portion (the portion where the image light is irradiated) is a positively charged latent image formed on the surface of the photoreceptor. Next, when a uniform post light is received at F, the uneven distribution of the charge inside the photosensitive layer disappears, and the actual charge on the surface of the photoconductor remains as a latent image (fourth step). The + portion of the real charge image easily absorbs the-toner to form a toner image. The portion where the toner is adsorbed is a light image bright portion, and the light image dark portion is negatively charged, so that no toner adheres, and a visible image with a very clear difference in brightness is obtained. Next, at H, the toner image is transferred to a transfer sheet, and fixed by a fixing device not shown in the figure to complete the print. FIG. 11 shows the sensitivity curve of the photoreceptor of Example 3 which was closely examined using the apparatus of FIG. γ ≒ 8 and high γ. With this degree of γ, the portion where the laser light signal is incident is certainly visualized by the toner in combination with the characteristic of the high γ KIP method that the toner adheres only at the portion where the optical signal is incident. The photoconductor of Example 3 was placed in a high humidity atmosphere of 85% or more.
After standing for more than an hour, the characteristics were examined, and it was confirmed that the image forming properties had sufficient moisture resistance without any decrease. This is the effect of using silicone epoxy as the binder. Hereinafter, it is needless to say that the toner is transferred to the paper at the transfer portion and is thermally fixed to form a print. In the case of “ZnO + phthalocyanine” in Example 3 described above, the first step was charged negatively and the third step was charged positively. However, since the polarity of charging depends on the photoreceptor, After the first step of performing the first charge of a certain polarity, the third step after the second step of irradiating light performs the second charge of the opposite polarity to the first step described above. However, the electrophotographic photosensitive member may be excited by a light image. In addition, phthalocyanine is described as an example of the P-type semiconductors of Examples 1, 2, and 3 described above. However, the present invention is not limited to this, and may be, for example, Si or the like. As an example of the N-type semiconductor, ZnO is mentioned, but the present invention is not limited to this, and for example, Cd
S, ZnS or the like may be used. Also, a transparent electric high-insulation material is prepared by mixing a P-type semiconductor fine powder and an N-type semiconductor fine powder and integrally attached to the surface of a photosensitive layer thinned with a binder having a volume resistivity of 10 ¹³ Ω-cm or more. The layer is, for example, 10 ¹³
It has a volume resistivity of Ω-cm or more.

In the above embodiment, it was found that it was difficult to use the photosensitive member repeatedly. This is because the ZnO used in the above embodiment can be excited only by light having a wavelength shorter than 388 mμ. The trap that occurs in the mixture of ZnO and phthalocyanine is supported by the very high resistance of the contact between ZnO and phthalocyanine. To release the created trap, either ZnO or phthalocyanine must be excited with light. FIG. 12 shows an image forming apparatus for operating the photoconductor. As shown in FIG. 12, irradiation of polarized light is performed immediately after the first charging. The role of this polarized light is
The purpose is to excite the photosensitive layer to form polarized charges required for the KIP method, and to remove trap charges near the electrode that are unnecessary and harmful for the KIP method. That is, the drum of the photoreceptor 10 rotates as shown in FIG. 12, and reaches the -DC corona of A first. The surface of the photoreceptor 10 is uniformly charged to a negative potential by the DC corona A (first step). Immediately after charging, light is irradiated by the lamp P (second step) to form a trap. Next, it is charged to + by + corona C and D, but it is L at E in the process of charging to +.
A light image is irradiated (third step). In the process up to this point, the dark portion of the light image (the portion not exposed to the image light) is negatively charged, and the light image bright portion (the portion where the image light is exposed) is the positively charged latent image.
Formed on 10 surfaces. Next, when a uniform post light is received by F, the uneven distribution of the charge inside the photosensitive layer 10 disappears, and the actual charge on the surface of the photosensitive member 10 remains as a latent image (fourth step).

FIG. 13 is a schematic representation of the polarization charge necessary for the KIP method and the trap charge near the electrode that is unnecessary and harmful to the KIP method. Reference numeral 13 denotes a photosensitive layer, and 13 denotes an electrode. As shown in FIG. 13, trapped charges in the vicinity of the electrode 13 are present in a portion far from the surface of the photosensitive layer 12, so that light for removing the trapped charges is absorbed by the photosensitive layer 12 on the way, and only a small amount of light reaches. Further, since the polarized light shown in FIG. 12 is, for example, an incandescent light bulb P, the component which originally excites ZnO is very small. Together, in the KIP method using (phthalocyanine + ZnO 2) as a photosensitive material, trapped charges near the electrode 13 remain without being released. The trapped charges at the position B 'in FIG. 13 are harmful and useless to the image formation.

In the second step of the KIP method described above, the trapped charges are at the position of A 'in FIG. 13, but move to the position of B' in FIG. 13 in the light image portion of the third step. That is, the presence of trapped charges at the position B 'in FIG. 13 means that the state is in the state of the light image portion in the third step. When this trap charge is carried over to the next cycle, the history of the previous cycle enters the next cycle. The above is a description of the inconvenience that occurs in the KIP method photoreceptor using (phthalocyanine + ZnO 2) as a photosensitive material. To eliminate this inconvenience, the trapped charge at the position B ′ in FIG. 13 must be erased.
The trapped charge at the position B 'in FIG. 13 is a photosensitive layer having a thickness of d.
Since light is absorbed by the photosensitive layer 12, the light absorbed by the photosensitive layer 12 reaches only (absorbed residue). To release the trap, either phthalocyanine or ZnO may be photoexcited. In the present invention, (phthalocyanine + CdS) is basically considered instead of (phthalocyanine + ZnO). However, CdS cannot be used at present due to pollution. PbO can be used instead of CdS, but at present
PbO also has the potential for pollution. As the safest material,
An experiment with (ZnO 2 sensitized by Rose Bengal) was selected, and it was found that the apparatus shown in FIG. 12 works completely as a KIP method. In general (Zn sensitized by Rose Bengal
O) is considered to have a short life because rose bengal is destroyed by ultraviolet rays. However, in the apparatus shown in FIG. 12, since there is no chance that ultraviolet rays are given to the photoconductor 10, rose bengal is not destroyed. By repeating latent image formation experimentally,
Even after several hundred thousand cycles, no signs of dysfunction of the ZnO sensitized with Rose Bengal were observed. That is, several hundred thousand cycles of complete images without previous history were obtained by the apparatus of FIG. Of course, neither phthalocyanine nor (ZnO 2 sensitized with Rose Bengal) is pollutant, so this photoreceptor 10 has no risk of pollution.

(Embodiment 4) P-type semiconductor fine powder (for example,
High γ KIP photoreceptor 10 having a photosensitive layer 12 in which a phthalocyanine) and an N-type semiconductor fine powder (for example, ZnO dye-sensitized with Rose Bengal) are thinned with a binder having a volume resistivity of 10 ¹³ Ωcm or more. Examples of the present invention will be described. First, to make ZnO sensitized with Rose Bengal, ZnO: 100gr (Sakai Chemical Co., average particle size 0.2μm) Tetrachlorotetraiodofluorescein (Rose Bengal) Precursor) (Rose Bengal acid) 0.1 g Toluene 200 gr Tetrahydrofuran 10 gr And mix in a ball mill for 1 hour.
Heating at 0 ° C. for 1 hour gave sensitized ZnO. Next, the photosensitive layer
Sensitized ZnO for the purpose of making 12 .. 100gr metal-free phthalocyanine 46.0gr (Daiichi Seika Co., Ltd., average grain Diameter 0.02 μm) Polyester resin ··· 138.0 gr (Mitsui Toatsu Chemicals Co., Ltd., trade name P-645) Melamine resin ··· 39.0 gr (manufactured by Mitsui Toatsu Chemicals Co., Ltd., trade name: Uban 20-HS) Cyclohexanone: 400gr is put into a vibrating stirrer and mixed for 120 minutes for a photosensitive layer of 420cp. A coating liquid was obtained. An 80 μm thick A1 foil is used as a supporting electrode, and a coating liquid for a photosensitive layer is applied to the surface thereof using a ring coater so that the thickness after drying becomes 20 μm.
Heat for 120 minutes in an atmosphere at a temperature of
Finished the production of 12.

Next, an acrylic resin is used as a coating liquid for the electric high insulating layer 11 (a transparent electric high insulating layer has a volume resistivity of, for example, 10 ¹³ Ω-cm or more). ······· 80.0gr (Mitsubishi Rayon Co., Ltd., trade name: Dianal LR 214) Is coated on the surface of the photosensitive layer 12 by a ring coater so that the thickness after drying becomes 8 μm. After coating, heat in an atmosphere of 150 ° C for 60 minutes. After heating and cooling, the production of the electrophotographic photoreceptor 10 (hereinafter referred to as “photoreceptor”) was completed.

The photoreceptor 10 manufactured as described above is mounted on the image forming apparatus shown in FIG.
The properties and lifetime of the slab were investigated. FIG. 12 is a conceptual diagram of the image forming apparatus. A for −DC corona, C and D for + corona, E
Denotes laser light (L light image), F denotes post light, G denotes developer, H denotes transfer corona, L denotes lamp, P denotes paper to be transferred, and S denotes shielding plate. I have. The + corona is divided into two (C and D in the figure), and the laser beam E is projected toward the photoreceptor 10 between the two coronas. The polarized light is shown as (lamp L) in the figure, and the polarized light erases the history and forms effective polarization.
FIG. 12 shows a latent image forming apparatus for measurement. In a practical image forming apparatus, a cleaner is provided between A and H. In order to observe electrical and physical phenomena, it is easier to observe without a cleaner.

FIG. 14 is a graph showing the photosensitive characteristics of the photosensitive member 10 obtained by using the apparatus shown in FIG. As shown in FIG. 14, the light image dark portion is -50 Volt, and the light image bright portion is +200 Volt. If light is not incident, it is -50 Volt, and if light is incident, it is +200 Volt. A typical digital response,
This is a characteristic required by laser printers. γ is (γ
≒ 8), which can be said to be high γ. -50Vol in the dark part of the light image in Fig. 14
t is a numerical value determined by the minus corona of A in FIG. 12, and +200 Volt of the light image portion is the plus / minus of C and D in FIG.
It is a numerical value determined by corona. When the latent image created by the image forming apparatus shown in FIG. 12 is visualized by the developing device G, it forms an image having a sharp edge which cannot be seen in other electrophotographic methods. As a test, when one pulse of light from the laser was injected into point E in FIG. 12, a latent image of one laser pulse was formed on the photoreceptor 10, and the latent image was in accordance with the designed laser luminescent spot. To make a visible image of diameter. It was found that the photoreceptor 10 faithfully changes the laser emission into a latent image. With the conventional Carlson method, it is extremely difficult to faithfully produce a one-pulse laser latent image.
The photoreceptor 10 created a latent image of one laser pulse, as shown in FIG.
This is considered to be due to the photosensitive characteristics shown in FIG. FIG. 15 is a diagram comparing a latent image formed by the Carlson method with laser light and a latent image formed by the high γ KIP method. As is clear from FIG. 15, the latent image of the Carlson method has no portion that adsorbs toner, and the latent image of the high γKIP method has a portion that adsorbs negative toner. The relationship between the latent image and the charged toner in the high γ KIP method is exactly the same as the relationship between the chemical offset master and the oil-based ink. Fig. 15 (C)
Fig. 15 (A) and Fig. 14 show the latent images of the high γ KIP method.
Is derived from As shown in Fig. 15 (A), the laser light
Since one part of the latent image formed by the P method is + and the other part is-, when developed with negative toner, toner adheres only to the + part and no toner adheres to the other parts. There is no doubt that the resulting image will have a high S / N ratio and good image quality if the toner does not adhere to the back which occupies most of the screen and the toner adheres only to the signal portion. The Carlson latent image in FIG. 15B is developed by a so-called (reversal development) developing method. For example, even if toner adheres between a and c, from where a and c I don't know until. That is, the edge of the toner image is not clear. It is this uncertainty of the edge that has traditionally been regarded as having poor image quality in electrophotographic printers, and the (edge uncertainty) disappears with the adoption of the high γ KIP method. The image formed by the photoreceptor 10 expresses one laser pulse as a dot.
This is due to the inherent function of the high γ KIP method as described above.

The laser light has been described as an example for the sake of simplicity. However, the light source is not limited to a laser.
Even if it is an LED, a halo will be created around the projected light image. Not a laser or LED image, but a microfilm image also has blurred areas around the image. The blurred portion is a portion having a small amount of light, and is the same as a portion having a small amount of laser light. Visualization of microfilm images by the high γ KIP method produces less blurred images than visualization by other methods, including silver halide photography.
In the first to third embodiments, there was a problem with the history erasure. However, in the present embodiment, since the N-type semiconductor excited by the remaining light of the light absorbed by the P-type semiconductor is used, The history is completely erased and a complete image is created each time. In this explanation, the P-type semiconductor is responsible for avalanche,
Although an example of working as a P-type high γKIP photoconductor has been described, a case in which an N-type semiconductor exhibits avalanche and works as an N-type high γKIP photoconductor is considered in the future. It should be noted that the high γKIP photoreceptor using the photosensitive material of the present invention in which the P-type semiconductor fine powder and the N-type semiconductor fine powder are mixed functions as a P-type high γKIP photoconductor, but also as an N-type high γKIP photoconductor. I will add. Since the present invention is intended to increase the γ of the KIP photoreceptor, it is expected that the effect of increasing the γ will appear even when applied to the NP method using a photoreceptor having the same structure as the KIP photoreceptor. The power supply of the electric field applied to the portion D of the latent image forming apparatus in FIG. 12 was changed to an AC power supply, and the apparatus was modified to work as the NP method. As a result of mounting the photoreceptor 10 on this device and forming a latent image, the expected result was obtained that the dark portion of the light image was at a potential and the light image portion was 0 Volt, but the conventional method using CdS It was judged that the result was not particularly excellent as compared with the result of the NP photoreceptor. The teaching of this result is that the effect of increasing γ is difficult to recognize in electrophotography in which the light image area becomes 0 Volt like the NP method. Even with the Carlson method, the effect of increasing γ is unlikely to appear. When (γ ≒ ∞), the edge of the image becomes sharp and the improvement of the image quality is clear, but the effect does not appear immediately because γ is slightly increased.

(Embodiment 5) In Embodiment 5, a laser is used as the L light image E on the photoconductors of the above-described Embodiments 1 to 4, and a point-like latent image on the photoconductor is changed by a change in the light emission amount of the laser. Is controlled. That is, as described above, the N-type semiconductor fine powder, the P-type semiconductor fine powder, and 10 ¹³ Ω-c
The photosensitive member having a thinned photosensitive layer containing a binder having a volume resistivity of not less than m and a transparent electric high insulating layer integrally attached to the surface of the photosensitive layer has a high γK
Acts as an IP photoreceptor, especially when used in a laser printer, creates a point-like latent image reliably in response to each laser emission and visualizes the latent image with a toner. It gives excellent results.

Next, the present inventor paid attention to the fact that the sign of the latent image changes from-to + at the boundary of the incident light amount L _S in the photosensitive characteristics of the high γ KIP photosensitive member shown in FIG. The amount of laser light can be varied by controlling the voltage of a laser drive circuit (not shown). FIG. 17 shows the light amount distribution when the light emission amount of the laser changes. Figure 17 is strongly and when the emitted, while indicating two stages of when weak light emission, it is possible to voltage as soon as the middle of the emission of L ₁ and L ₂ to give. The horizontal axis of FIG. 17 indicates the distance from the laser emission center. Les represented by L ₂ - The - if light them incident on the photosensitive member having the characteristic of FIG. 17, L ₂ is greater in amount than that because the amount of light becomes L _S at a distance of d _2/2 from the center The portion produces a positive polarity latent image, while the portion having a light intensity smaller than L _S produces a negative polarity latent image. The latent image created by this laser light is
Toner - if developed with only a + portion of the latent image toner - are adhered can diameter circle d _2. On the other hand, at L _{1 where the} light amount is large,
Adheres - toner to a circle of diameter d _1. Thus, the laser
If the light emission intensity changes, the diameter of the circular image formed by the toner changes. The edge of the toner image of this circle is clear and sharp. In a conventional laser printer using the Carlson method, the laser
The diameter of the toner dot formed by the laser light is determined by the way of stopping the laser light, and the diameter of the toner dot does not change unless the optical system that projects the laser light is changed. I was thinking. However, if the high γ KIP method is used, the toner dot diameter changes if the light emission amount of the laser is changed. Conventionally, in a Carlson laser printer, laser light is projected as a light image having a constant diameter. Toner of fixed diameter
There is no way to change the density of the toner dots in order to express the shading with dots. To change the diameter of the toner dot, it is necessary to change it from the optical system. High γ KIP photoreceptor
In the case of expressing light and shade by changing the amount of light emitted from the laser, if the amount of light is quadrupled, the toner dot diameter is also approximately doubled. If the light emission amount is changed from 1 mW to 10 mW using a 10 mW laser, the toner dot diameter becomes about three times. Laser
Controlling the amount of light emission is simply an operation of changing the applied voltage, and can be easily performed. If you stick to the Carlson method, you must change from the optical system to change the toner dot diameter. To change the shading without changing the toner dot diameter, the emission density must be changed.
For this purpose, the emission time of the laser must be changed, but this requires a huge amount of calculation, which is impractical. The high γ KIP method described above means that the high γ KIP photoconductor (high γ electrophotographic photoconductor) is subjected to a first charge of a certain polarity (for example, −) and the entire high γ KIP photoconductor is photo-excited (overall exposure). A polarization forming step of forming a polarization state by performing the polarization, and after this polarization forming step, exciting the high γ KIP photoreceptor by an optical image while performing a second charging of a polarity (for example, +) opposite to the first charging. A latent image forming step of forming a latent image on the high γ KIP photoreceptor, and after this latent image forming step, the entire high γ KIP photoreceptor holding the latent image is further photo-excited (exposed entirely) to retain the latent image. Or high γK
A charging step of performing a first charge of a certain polarity on the IP photoreceptor (high γ electrophotographic photoreceptor), and after this charging step, performing a second charge having a polarity opposite to the first charge by an optical image. A latent image forming step of exciting the high γ KIP photoconductor to form a latent image on the high γ KIP photoconductor, and after the latent image forming step,
Further, the entire high γ KIP photoconductor holding the latent image is photo-excited (overall exposure) to hold the latent image. The light image is from a laser.

On the other hand, using a high γ KIP photoreceptor, the laser
The method of controlling the diameter of the toner dot formed by changing the light emission amount of the laser beam is to specify the light emission position of the laser at the same time as specifying the light emission position of the laser. It is possible to obtain a means of expressing light and shade simply by modifying the electric circuit. For example, a continuously changing shading can be realized only by smoothly changing the laser voltage. If this is to be accomplished using laser light of a fixed diameter, both the optical system and the rotation of the polygon mirror must be changed. This is not possible. Even with the conventional Carlson method laser printer, there are not few attempts to change the toner dot diameter. In the invention of the same inventor (Koichi Kinoshita) as the present inventor (see Japanese Patent Publication No. 6-3551),
A method has been proposed in which the toner dot diameter is controlled by changing the amount of laser light emission using a high-γ Carlson method photoreceptor, but this method is intended to increase the toner dot diameter. However, the toner dot diameter cannot be reduced. Eventually, the diameter of the toner dot could not be changed significantly, and the edges of the toner dot tended to be unclear. On the other hand, in the method of changing the amount of laser light emitted by the high γ KIP method, each of the toner dots produced is independent, and the edges of the dots are clear and sharp. The result is a high quality image comparable to offset printing.

[0021]

According to the electrophotographic photoreceptor of the present invention, a P-type semiconductor fine powder and an N-type semiconductor fine powder are mixed, and a thin layer is formed with a binder having a volume resistivity of 10 ¹³ Ω-cm or more. By using the photosensitive layer, high γ characteristics can be obtained and a stable latent image can be obtained. According to the electrophotographic method of the present invention, the photosensitive layer is obtained by mixing a P-type semiconductor fine powder and an N-type semiconductor fine powder and thinning the mixture with a binder having a volume resistivity of 10 ¹³ Ω-cm or more. A high γ characteristic can be obtained, and a stable latent image can be obtained. Also,
According to the electrophotographic method of the third aspect, a first step of performing a first charge of a certain polarity on the electrophotographic photoreceptor,
After the step, a second step of irradiating light is provided, so that the trap formed as a result of the charging in the first step increases certainty,
A stable latent image can be obtained. According to the electrophotographic photoreceptor of the present invention, sensitization was achieved with Rose Bengal.
ZnO is excited by the illuminated white light, provides an image with no previous history, and can withstand repeated use of the photoreceptor. According to the electrophotographic method of the sixth or seventh aspect, it is possible to obtain a high-quality image in which the edges of dots are clear and sharp.

[Brief description of the drawings]

FIG. 1 is a simplified equivalent circuit of a photoconductor showing a high γ characteristic.

FIG. 2 (A) shows a calculation result and a measurement result of a light response at a certain electric field intensity of a photoreceptor using phthalocyanine as a photosensitive material, and FIG. 2 (B) shows a measurement result. It is a graph of the obtained real number scale.

FIG. 3 is a material layout diagram of ZnO and phthalocyanine constituting a photoreceptor of one embodiment of the present invention.

FIG. 4A is a diagram illustrating an eraser operation which is a preceding stage of image formation, and FIG. 4B is a diagram illustrating an image formation stage.

FIG. 5 is a diagram illustrating a corona arrangement in an image forming process that is close to ideal.

FIG. 6 is a view showing a high γ KIP photosensitive member according to an embodiment of the present invention mounted on a measuring device.

FIG. 7 is a diagram showing a sensitivity curve of the photoconductor of one embodiment (Example 1) of the present invention.

FIG. 8 is a diagram illustrating a dot latent image of a photoconductor according to an embodiment of the present invention.

FIG. 9 shows an example in which the method of another embodiment of the present invention is applied to a flat high γ KIP photoconductor.

FIG. 10 shows an example in which the method of another embodiment of the present invention is applied to a high γ KIP cylindrical photoreceptor.

FIG. 11 is an embodiment (third embodiment) of the present invention;
FIG. 4 is a diagram showing a sensitivity curve of the photoconductor of FIG.

FIG. 12 shows a high γKIP according to an embodiment of the present invention.
FIG. 3 shows a diagram in which a photoconductor is mounted on a measuring device.

FIG. 13 is a diagram schematically illustrating a polarization charge required for the KIP method and a trap charge near an electrode unnecessary and harmful to the KIP method.

FIG. 14 is a graph showing the photosensitive characteristics of the photosensitive member obtained in Example 4 using the apparatus shown in FIG.

FIG. 15A is a graph showing a light amount distribution of a laser;
(B) shows a Carlson method latent image, and (C) shows a high γKIP method latent image.

FIG. 16 is a diagram showing the photosensitive characteristics of a high γ KIP photoconductor.

FIG. 17 is a diagram showing a light amount distribution when the light emission amount of the laser changes.

[Explanation of symbols]

 1 P-type semiconductor fine powder 2 N-type semiconductor fine powder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 5/09 101 G03G 5/147 502 5/147 502 15/02 102 15/02 102 15/24 15 / 043 B41J 3/00 M 15/04 G03G 15/04 120 15/24 F term (reference) 2C362 AA33 AA54 AA63 CA10 CB05 CB59 CB80 2H003 AA02 BB11 BB13 CC01 2H068 AA08 AA15 AA19 AA26 AA31 BA38 FB13 FC32 FA32 FC05 2H076 AB02 AB09 DA11 DA26 2H078 AA02 BB05 CC01 DD02 DD15 DD68

Claims (7)

[Claims] 1. A photosensitive layer obtained by mixing a P-type semiconductor fine powder and an N-type semiconductor fine powder and thinning it with a binder having a volume resistivity of 10 ¹³ Ω-cm or more, and integrally with the surface of the photosensitive layer. An electrophotographic photoreceptor having a transparent electric high insulation layer attached thereto. 2. A photosensitive layer in which a P-type semiconductor fine powder and an N-type semiconductor fine powder are mixed and thinned with a binder having a volume resistivity of 10 ¹³ Ω-cm or more; An electrophotographic photosensitive member having a transparent electric high insulation layer attached thereto; and a first charging device having a first polarity having a certain polarity on the electrophotographic photosensitive member.
And after the first step, a second step of exciting the electrophotographic photoreceptor with an optical image while performing a second charge having a polarity opposite to that of the first step; and a second step of And a third step of photo-exciting the entire electrophotographic photoreceptor holding the latent image. 3. A photosensitive layer obtained by mixing a P-type semiconductor fine powder and an N-type semiconductor fine powder and thinning it with a binder having a volume resistivity of 10 ¹³ Ω-cm or more, and integrally with the surface of the photosensitive layer. An electrophotographic photosensitive member having a transparent electric high insulation layer attached thereto; and a first charging device having a first polarity having a certain polarity on the electrophotographic photosensitive member.
And after the first step, a second step of irradiating light, and after the second step, performing the second charging of the opposite polarity to that of the first step by the optical image A third step of exciting the electrophotographic photosensitive member, and after the third step, a fourth step of optically exciting the entire electrophotographic photosensitive member holding a latent image. Electrophotographic method. 4. A photosensitive layer thinned to include a P-type semiconductor fine powder, an N-type semiconductor fine powder, and a binder having a volume resistivity of 10 ¹³ Ω-cm or more, and an integrated photosensitive layer. An electrophotographic photoreceptor, comprising: a transparent electrically-high insulating layer having a volume solid resistance of 10 ¹³ Ω-cm or more, which is formed by a method. 5. The electrophotographic photosensitive member according to claim 4, wherein the P-type semiconductor fine powder is phthalocyanine, and the N-type semiconductor fine powder is ZnO dye-sensitized with rose bengal. 6. A thin photosensitive layer containing a P-type semiconductor fine powder, an N-type semiconductor fine powder, and a binder having a volume resistivity of 10 ¹³ Ω-cm or more, and an integrated photosensitive layer. An electrophotographic photosensitive member having a transparent electrically high insulating layer having a volume solid resistance of 10 ¹³ Ω-cm or more, and a first charging of a certain polarity on the electrophotographic photosensitive member. Forming a latent image on the electrophotographic photosensitive member by exciting the electrophotographic photosensitive member with a light image while performing second charging having a polarity opposite to that of the first charging after the charging step. And a latent image holding step of photo-exciting the entire electrophotographic photoreceptor for holding the latent image after the latent image forming step, wherein the optical image is a laser image. And a laser produced by changing the amount of light emitted from the laser. The diameter of Tsu bets control - an electrophotographic method which is characterized in that Le. 7. A thin photosensitive layer containing a P-type semiconductor fine powder, an N-type semiconductor fine powder, and a binder having a volume resistivity of 10 ¹³ Ω-cm or more, and a photosensitive layer integrated with the photosensitive layer. An electrophotographic photosensitive member having a transparent electrically high insulating layer having a volume solid resistance of 10 ¹³ Ω-cm or more, and performing a first charge of a certain polarity on the electrophotographic photosensitive member, A polarization forming step of photo-exciting the entire electrophotographic photoreceptor to form a polarization state; and after the polarization forming step, a second polarization having a polarity opposite to that of the first charging.
A latent image forming step of exciting the electrophotographic photoreceptor with a light image to form a latent image on the electrophotographic photoreceptor while charging the electrophotographic photoreceptor; A latent image holding step of photo-exciting the entire photographic photoreceptor, wherein the light image is generated by a laser, and is formed by changing a light emission amount of the laser. An electrophotographic method comprising controlling the diameter of a toner dot.