JPH0656498B2 - Photoreceptor and image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoconductor and an image forming method, and more particularly to a photoconductor and a color image forming method for forming a color image using electrophotography.

B. Prior art Conventionally, when obtaining a multicolor image using electrophotography,
Although many methods and devices used therefor have been proposed, they can be generally classified as follows. One of them is to repeat latent image formation and development with color toners according to the number of separated colors using a photoconductor so that colors are superposed on the photoconductor, or transferred onto a transfer material every time development is performed, and then transferred onto a transfer material. This is a method of overlapping colors. As another method, an apparatus having a plurality of photoconductors corresponding to the number of separated colors is used, and light images of the respective colors are simultaneously exposed to the respective photoconductors, and the latent image formed on the respective photoconductors is colored. The toner is developed with toner, transferred sequentially onto a transfer material, and the colors are superimposed to obtain a multicolor image.

However, in the above-mentioned first method, since the latent image formation and the development process must be repeated a plurality of times, it takes a long time to record an image, and it is extremely difficult to increase the speed, which is a major drawback. Further, the above-mentioned second method is advantageous in terms of high speed because a plurality of photoconductors are used in parallel, but the apparatus is complicated because a plurality of photoconductors, an optical system, a developing means, etc. are required. However, the size is large, the price is high, and the utility is poor. Further, both of the above methods have a serious drawback that it is difficult to align the images when repeating image formation and transfer a plurality of times, and it is not possible to completely prevent color misregistration of the images.

In order to fundamentally solve these problems, the present inventor has previously proposed a method of recording a multicolor image on a single photoreceptor with one image exposure. This is as follows.

That is, a plurality of color separation filters (filters that substantially transmit only light having a specific wavelength range) are arranged in a fine linear or mosaic pattern on a photosensitive layer having sensitivity over the entire visible light range. First, an image is exposed on the entire surface of a photoconductor to form a primary latent image on the photoconductive layer below each filter according to the decomposed image density.
By exposing the entire surface with the specific light that passes through the decomposition filter, the electrostatic image (hereinafter referred to as the secondary latent image) corresponding to the primary latent image is formed only on the filter portion of the filter. The color corresponding to the type, preferably developed with color toner of a color that is a complementary color of the color that passes through the filter,
Further uniformly charge, and then repeat the same overall exposure, development, and recharging operations for each decomposed image to form a multicolored image on the photoconductor, and transfer it once to make many multicolor images on the transfer material. A color image is recorded.

C. Object of the Invention The present invention is a further development of the above-described photoconductor and image forming method, and an object thereof is to rapidly and easily produce a multicolor image free from color misregistration by a single image exposure. It is an object of the present invention to provide a novel photoconductor capable of recording and to provide an image forming method capable of forming a multicolor image by a high speed and simple process using the photoconductor.

D. Structure of the Invention That is, the photoreceptor according to the present invention is characterized by having a photoconductive layer composed of a plurality of portions having mutually different spectral sensitivity distributions, and an insulating layer provided on the photoconductive layer. is there.

Further, the image forming method according to the present invention comprises a step of image-exposing a photoconductor having a photoconductive layer having a plurality of portions having different spectral sensitivity distributions and an insulating layer provided on the photoconductive layer; , And a step of repeating the operation of performing the entire surface exposure with the specific light for generating a potential pattern on the specific photoconductive layer portion and the development.

(E) Examples Hereinafter, examples in which the present invention is applied to a multicolor image forming photoconductor (hereinafter, simply referred to as a photoconductor) and a multicolor image forming process will be described in detail. In the following description, only a full-color reproduction photoreceptor having three types of photoconductive portions having a spectral sensitivity distribution only for red light, green light, and blue light as a photoconductive layer will be described. The toner color is not limited to the above.

FIG. 1A schematically shows a cross section of a photoreceptor according to the present invention. The photoconductive layer 2 is provided on the conductive member or the substrate 1. The photoconductive layer has photoconductive portions 2R, 2G, and 2B having a required spectral sensitivity distribution, for example, red (R), green (G), and blue.
(B) contains a large number of sensitive photoconductive parts. The insulating layer 3 is laminated on the photoconductive layer.

The conductive substrate 1 may be made of a metal such as aluminum, iron, nickel, or copper, or an alloy thereof, and may be formed into a cylindrical shape, an endless belt shape, or the like having an appropriate shape and structure as necessary.

The photoconductive layer 2 is formed to a thickness of 10 to 100 μm, and is a photoconductive material such as sulfur, selenium, amorphous silicon or an alloy containing sulfur, selenium, tellurium, arsenic, antimony, etc .; or zinc, aluminum, antimony, Inorganic photoconductive substances such as oxides, iodides, sulfides, and selenides of metals such as bismuth, cadmium, and molybdenum; organic light such as vinylcarbazole, anthracenephthalocyanine, trinitrofluorenone, polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene Conductive substances dispersed in an insulating binder resin such as polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, polycarbonate, acrylic resin, silicon resin, fluororesin, epoxy resin, charge generation and transfer On separate layers It can be configured by a function-separated type laminated body or the like which is designed to be carried.

The insulating layer 3 is formed to have a thickness of 10 to 100 μm and can be made of a transparent insulating material such as various polymers and resins.

The photoconductive layer 2 has colored portions 2R, 2G, and 2B which are photoconductive portions having different spectral sensitivity distributions. These colored portions have a required spectral sensitivity as shown in FIG. 1A (a). It can be formed by adhering the photoconductive substance possessed on the conductive layer 1 in a predetermined pattern by means such as printing. Or Figure 1A (b)
As described above, the charge generation layer 2b (which is composed of portions having different spectral sensitivities) is printed on the charge transport layer 2a formed in advance on the conductive layer 1 or on the photosensitive layer 2 ', It may be formed by adhering to a predetermined pattern by means such as vapor deposition. Further, the photoconductive portions 2R, 2G, and 2B can be randomly arranged to form a photosensitive layer.

FIG. 2 illustrates the shape and arrangement of the photoconductive layer of the photoreceptor according to the present invention. Here, B, G, and R are portions sensitive to blue, green, and red, respectively.

FIG. 2 (a) shows a linear shape. For example, when the photoconductor is a drum shape, the linear shape may be orthogonal to the rotation direction or may be parallel. Further, each of the various photoconductive portions may be configured so that the plurality of types of photoconductive portions densely surround the drum-shaped photosensitive member in a spiral shape. Alternatively, it is preferable to form a mosaic pattern as shown in FIGS. 2 (b) and 2 (c).

The size of each photoconductive portion is preferably 30 to 500 μm as a color repeating width (1 in FIG. 2). When the size of each photoconductive portion is too small, it becomes easy to be influenced by the adjacent portions of other colors, and when the width of one of the photoconductive portions becomes the same as or smaller than the particle diameter of the toner particles. Also difficult to create. On the other hand, if the size of the photoconductive portion is too large, the resolution and color mixing of the image are deteriorated and the image quality is deteriorated. 2 (a) to 2 (c) show the case where photoconductive portions having spectral sensitivity are provided in red, green and blue. The array may be arranged such that the micro-photosemiconductor portions are separated from each other or in close contact with each other, but if sufficient insulation is maintained in the dark part, they are arranged in close contact with each other in terms of image clarity. Good to do.

The spectral sensitivity characteristic of the photoconductor is determined by the spectral sensitivity characteristic of the photoconductive portion, the exposure light source, and the spectral characteristic of the color correction filter interposed therebetween.

For example, when the spectral sensitivity characteristic of each photoconductive portion is as shown in FIG. 3, the spectral characteristic of the exposure light source and the filter may be smooth. On the other hand, when the spectral sensitivity characteristic of the photoconductive portion is as shown in FIG. 4, the exposure light source and the filter are used to further cut off the ultraviolet and infrared portions so that B,
The balance of the transmittance of the exposure light source and the filter is adjusted so that G and R have uniform spectral sensitivity characteristics. Note that the filter here includes not only a filter provided between the exposure light source and the photosensitive layer, but also an insulating layer constituting the photoconductor.

It is preferable that the spectral characteristics of the photoconductive portions overlap as shown in FIGS. 500m if not overlapping
Images around m and 600 mm may not be reproduced.

It is preferable that the whole surface exposure is performed by, for example, avoiding overlapping wavelength ranges so that a potential pattern is generated only on a specific kind of optical semiconductor. Further, unlike FIG. 2, when the photoconductive portions are randomly arranged, the size of each photoconductive portion is preferably 30 to 150 μm. In this case, the obtained image tends to be rough compared to the regulated arrangement shown in FIG. 2, and its size is preferably 30 to 80 μm.

An example of a method of manufacturing the above-described photoconductor, for example, the photoconductor of FIG. 1 (a) will be specifically described. This method is (A) ~
Carry out as in (D).

(A). Photoconductive particles for B, G, and R, dyes, and adhesives are mixed in a solvent, and spherical particles B and G having an average particle size of 30 to 300 μm with a uniform particle size by a spray drying method. , R for each conductive particle is created. These are conventionally known (JP-A-51
-129232, JP-A-53-79542, etc.) can be used.

(B). After mixing the three types of particles, for example, FIG. 1B (a)
Next, a thin adhesive member is attached to the conductive substrate 1 by 0.001 to 1
The photoconductive particles 2'B, 2'G,
The 2'R is evenly attached so as to form a substantially monolayer.

As the adhesive member at this time, it is preferable to use a resin that adheres the conductive substrate and the photosensitive layer, and it is particularly preferable to use a thermosetting member.

(C). An insulating layer may be provided directly on the surface of the photosensitive layer, but it is desirable to smooth the photosensitive layer in advance as shown in FIG. 1B (b).

For example ,. Smooth with heat or pressure.

For this purpose, the binder resin of the photoconductive particles needs to be deformable by heat or pressure.

． A blocking layer is provided to prevent the entry of a solvent when the insulating layer or the adhesive layer is provided on the photosensitive layer.

(D). The insulating layer 3 is provided by providing a shrink tube or an adhesive to attach the sheet to the photosensitive layer, or by applying a solvent having a resin forming the insulating layer.

In addition to this, a method of sequentially printing solutions for B, G, and R photoconductors can be used.

By providing the photoconductive portion only by printing or the like, unevenness is likely to occur on the surface.

In this case, after performing the smoothing treatment as described in (C) above, the insulating layer is provided as described in (D) above.

Next, a method for manufacturing the above-mentioned photoreceptor will be specifically described.

Preparation Method of Photoreceptor (1) Photosensitive liquids having spectral sensitivities for blue, green, and red were prepared. As shown in Table 1 below, these are a mixed solution of zinc oxide, its sensitizing dye, a binder and a solvent.

These sensitizing solutions were intermittently applied in 100 μm square by intaglio printing on a 120φ aluminum drum substrate (Fig. 2 (C)).
Print so that it has the configuration of. l is 300 μm. ). First, the blue photosensitive solution was applied and then dried, then the green photosensitive solution was printed and dried, and then the red photosensitive solution was printed and dried. The photosensitive layer thus formed had a thickness of about 25 μm. The central portion of each mosaic photosensitive layer was slightly raised, and smoothing was performed by rotating while pressing a metal roller for smoothing processing.

Next, a shrink tube having a thickness of 20 μm was overlaid and then heat-shrinked to manufacture a photoconductor shown in FIG. 2 (C).

Preparation Method of Photoreceptor (2) After adjusting the viscosity of the previously prepared photosensitive solution with a solvent, spherical particles having an average particle size of 60 μm were prepared by a spray dry method. Next, each of the particles thus prepared is uniformly mixed in an equal amount. 0.1mm adhesive layer on 120φ aluminum drum substrate
It is provided by coating to a thickness of μm and sprinkled with particles in which B, G, and R are uniformly mixed. The excess particles are then blown off with air to form a monolayer. In this way, a substantially uniform particle monolayer was formed. Next, the aluminum drum base and the metal roller pressed against the aluminum drum base were pressed and rotated while being heated to bring the particles into close contact with the base and to provide a smooth photosensitive layer having a thickness of 40 μm. Then, a shrink tube having a thickness of 30 μm was superposed and then heat-shrinked to manufacture a photoconductor in which photoconductive portions were randomly arranged.

Preparation Method of Photoreceptor (3) After adjusting the viscosity of the previously prepared photosensitive solution with a solvent, spherical particles having an average particle size of 80 μm were prepared by a spray drying method. Next, a hexagonal adhesive layer having a side of 50 μm and a thickness of 0.1 μm (so as to have the configuration of FIG. 2B) is printed on a 120φ aluminum drum substrate. Particles for blue are attached to this, and the aluminum substrate is heated to be lightly fixed.

Next, an adhesive layer is provided by shifting the position by the same operation, particles for green are attached, and the aluminum base is fixed by heating.

Similarly, the red particles are fixed. The photosensitive member thus formed had a thickness of about 70 μm and a raised central portion, and the substrate was further heated for smoothing treatment for smoothing. As a result, the particles were well bonded. Next, a shrink tube having a thickness of 30 μm was superposed and then heat-shrinked to manufacture a photoconductor shown in FIG. 2 (b).

Next, a process of forming a multicolor image using the above-mentioned photoconductor will be described with reference to FIG. In the figure, a part of a photoconductor using an n-type (that is, high electron mobility) optical semiconductor such as zinc oxide whose photosensitivity is easy to control is taken out, and an image forming process there is schematically shown. The cross-sectional hatching of each part is omitted. In the figure, 1 and 2 are conductive substrates, B, G, and R are photoconductive layers having spectral sensitivity, and 3 is an insulating layer. Also, the graphs below each figure show the potentials on the surface of each part of the photoconductor.

First, as shown in FIG. 5 [1], when a positive corona discharge is applied to the entire surface by the charger 4 while the entire surface is exposed with white light, a positive charge is generated on the surface of the insulating layer 3, and in response to this. Negative charges are induced at the interface between the photoconductive layer 2 and the insulating layer 3.

Next, as shown in FIG. 5 [2], an AC or negative discharge is applied by the charger 5 equipped with an exposure slit, and the insulating layer 3
While erasing the surface charges, the colored image is exposed, for example, the reflected light of the red portion of the original, that is, the red image is exposed L _R. Since the red light passes through the insulating layer 3 and makes the photoconductive portion 2R of the photoconductive layer 2 thereunder conductive, the positive charge on the insulating layer 3 is erased and the charge in the photoconductive portion 2R is also erased. . On the other hand, since the photoconductive portions 2G and 2B having spectral sensitivity to green and blue do not sense red light, some positive charges of the insulating layer and negative charges of the photoconductive layer 2 remain as they are. This charging may be performed until the surface potential becomes negative.

The above corresponds to the formation of the first latent image, but at this stage,
Not only the 2R portion where the charge is erased, but also the portions where the charge remains 2G and 2B do not function as an electrostatic image because they have the same potential on the surface of the insulating layer 3.

In FIG. 3 [2], the case where the potential after charging is almost zero is shown, but the potential may be negative.

Then, as shown in FIG. 5 [3], the entire surface is exposed with light of a color in which only one of the photoconductive portions has a spectral sensitivity, for example, blue light L _B obtained by the light source 6B and the blue filter F _B. When given, the 2B portion having spectral sensitivity to blue light becomes conductive,
A part of the negative charges of the photoconductive layer 2 and the charges of the conductive substrate 1 are neutralized to generate a potential pattern only on the surface of the 2B portion.

No change occurs in the 2G and 2R portions where blue light is not felt. Then, the yellow toner TY in which the charge image is negatively charged
When developed with a developer containing, the toner adheres only to the insulating layer 3 having a potential, and development is performed (FIG. 5 [4]).

Then, as shown in FIG. 5 [5], charging is performed by the charger 14 in order to erase the generated potential difference. At this time, if blue light is exposed at the same time, the charge can be erased more completely.

Next, as shown in FIG. 5 [6], when the entire surface is exposed with the green light L _G , a potential pattern is formed on the 2G portion as in the case of the entire surface exposure with the blue light (the irradiation as the entire surface exposure light has already been performed. It does not matter if it contains a blue component.) If this is developed with magenta toner TM as shown in FIG. 5 [7], magenta toner TM adheres only to the portion of the filter G.

Then, after recharging in the same manner as in FIG. 5 [5], the entire surface is exposed to red light, but since there is no electric charge in the 2R portion, no potential pattern is formed, and even if development is performed with cyan toner, cyan toner is not used. Does not occur. The entire surface exposure light may include already-irradiated blue and green components.

By transferring the toner image thus obtained onto a transfer material such as a copy or paper and fixing it, a red image is reproduced on the transfer material by mixing the yellow toner and the magenta toner.

For other colors, color reproduction is performed by the combination of the three-color separation method and the three primary color toners as shown in Table 2 below.

In this table, Is the state of the first stage of electrostatic image formation, Is the completed electrostatic image, Indicates that development has been performed, and ↓ indicates that the state in the upper column is maintained as it is. The blank columns represent the parts where no electrostatic image exists.

Although the above description is based on an example using an n-type optical semiconductor layer, it is a p-type such as selenium (that is, having a large hole mobility).
Of course, it is also possible to use an optical semiconductor layer, and in this case, only the positive and negative signs of charges are reversed, and the basic processes are all the same. If it is difficult to inject charges during primary charging, uniform irradiation with light is also used.

As is clear from the above description, according to the present embodiment, after the multi-color image forming photoconductor having a fine color separation function is exposed to an image while being charged, one of a plurality of types of photoconductive portions is formed. The step of developing the film by exposing the whole surface to specific light so that only the seed exhibits spectral sensitivity is repeated according to the number of types of the photoconductive portion. That is, a photoconductor having a photoconductive layer having a fine color separation function is imagewise exposed (after the step of FIG. 5 [2], and then exposed over the entire surface with three color separation light (steps of FIG. 5 [3] and [6]). ) Is applied, a latent image is formed for each photoconductive portion, development is performed using toner of a corresponding color (steps [4] and [7] in FIG. 5), and this is repeated to obtain a multicolor image. So according to this process,
In a photosensitive layer having photosensitivity over the entire visible light range, a plurality of photoconductive parts having a color separation function are arranged in combination in the form of fine lines or mosaics, and an insulating layer is further provided on the photosensitive layer. On the photoconductive portion, a body is first subjected to imagewise exposure to form a primary latent image corresponding to the resolution image density, and then the entire surface is exposed to light sensed only by the first photoconductive portion. A secondary latent image is formed only on the first and second portions, and an electrostatic image corresponding to the image exposure intensity in the primary latent image forming process is formed. Then, it is developed with color toner of the corresponding color, and then uniformly recharged. By repeating the same operation for each separated image, a multicolor image is formed on the photoconductor, and a single transfer is performed on the transfer material. It is possible to record multicolor images at once. When an image is to be obtained, a developing device having black toner is newly provided, and a potential pattern is formed by normal primary charging, secondary charging and simultaneous image exposure, and uniform exposure with white light, and development is performed with toner. Alternatively, the Y, M, and C toners are superposed on the potential pattern generated by the uniform exposure and developed.

FIG. 6 is a schematic diagram of an image forming portion of a color copying machine suitable for carrying out the above process of this embodiment. In the figure, reference numeral 41 denotes a photoconductor drum composed of the photoconductor having the configuration shown in FIG. 1, and rotates in the direction of arrow a during the copying operation. The photoconductor drum 41 is rotated and irradiated with light as necessary, and is charged with electric charge on the entire surface by the charging electrode 4. The electrode 5 provided with the next exposure slit is an alternating current, or a corona discharge having the opposite sign to the electrode 4. While receiving the exposure L of the document D, the primary latent image process is completed. Next, the light source 6B and the light source blue filter F _B
The whole surface is exposed to the blue light obtained by the combination with the above, and a yellow latent image is formed. Next, this is developed by the developing device 17Y loaded with yellow toner. Then electrode 14
Then, the surface of the photoconductor is made to have a uniform potential, and then the entire surface is exposed by the green light from the light source 6G and the green light source filter F _G, and the development is performed by the developing device 17M loaded with magenta toner. Further, the photoconductor is uniformly charged by the electrode 15, and the entire surface is exposed by the red light from the light source 6R and the red light source filter F _R, and development is performed by the developing device 17C loaded with cyan toner. As a result, a multicolor image is formed on the photosensitive drum. The resulting multicolor toner image is recharged by the pre-transfer belt electrode 11,
It is transferred by the transfer electrode 9 onto the copy paper 8 supplied by the paper feeding means. The paper carrying the transferred multicolor toner image is separated from the photoconductor drum by the separation electrode 10 and fixed by the fixing device 12 to be a completed multicolor copy, which is ejected out of the machine. The photosensitive drum 41 that has finished the transfer is erased by the static elimination electrode 16 while irradiating with static elimination light (preferably white light) if necessary, and the cleaning blade 13 removes the toner remaining on the surface and is used again. .

In the above image forming process, the developer used may be either a so-called one-component developer using a non-magnetic toner or a magnetic toner, or a so-called two-component developer in which a toner and a magnetic carrier such as iron powder are mixed. You can In the development, a method of directly rubbing with a magnetic brush may be used, but in particular, at least after the second development, in order to avoid damage to the formed toner image, the developer layer on the development sleeve is a photoreceptor surface. It is essential to use a non-contact development method that does not rub the surface. This non-contact method uses a one-component or two-component developer having a non-magnetic toner or a magnetic toner whose coloring can be freely selected, and an alternating electric field is formed in the developing area to develop an electrostatic image support (photoreceptor) and a developer. The layer is developed without rubbing the layer. This will be described in detail below.

In the repeated development using the alternating electric field as described above, it is possible to repeat the development several times on the photoconductor on which the toner image is already formed, but if the proper development conditions are not set, the latter stage of the development, The toner image formed on the photoconductor in the previous stage is disturbed, or the toner already attached on the photoconductor returns to the developing sleeve which is the developer transport body, and this causes the developer of a different color from the developer in the previous stage to be discharged. There is a problem that color mixture occurs when it enters the developing device in the subsequent stage that is stored.

From the above consideration, the image forming conditions for performing recording with a desired density and without image disturbance and color mixture using the one-component developer or the two-component developer are the one-component developer and the two-component developer. It became clear that there was a process in which each was used. This developing condition is basically that the developer layer on the developing sleeve is operated without rubbing or contacting the photoreceptor. For this purpose, the gap between the image carrier and the developing sleeve is kept larger than the thickness of the developer layer on the developing sleeve (provided that there is no potential difference between the two). More desirable conditions are the step of forming a latent image on the image carrier and the development of the latent image using a one-component developer to form a plurality of toner images on the image carrier. In the process, when the amplitude of the AC component of the developing bias is V _AC (v), the frequency is (Hz), and the gap between the image carrier and the developer carrier that conveys the developer is d (mm), 0.2 It is to satisfy ≦ V _AC / (d ·) ≧ 1.6.

Further, in the step of forming a latent image on the image carrier, the image forming method of developing the latent image using a developer composed of a plurality of components, to form a plurality of toner images on the image carrier, At each development step, the amplitude of the AC component of the development bias is
V _AC (V), frequency (Hz), and the gap between the image carrier and the developer transporter that transports the developer is d (mm), 0.2 ≦ V _AC / (d ·) {(V It is preferable to satisfy _{AC /} d) -1500} /≦1.0.

That is, the present inventor has studied the method for forming an image by repeating the latent image formation and development, and as a result, an AC bias,
It has been found that there is a region in which a high-quality image can be obtained without causing image distortion or color mixing, depending on how to select development conditions such as frequency and frequency.

In the method of sequentially superimposing toner images on an image carrier (for example, a photoconductor drum), it is necessary to perform development at an appropriate density without disturbing the toner image formed on the image carrier at the previous stage during development. Here, "overlapping" means that a toner image is previously formed on the image bearing member, and then a toner image is formed on the image bearing member by recharging and uniform exposure with specific light. This means forming a toner image by adhering toner onto the electrostatic latent image from one or a plurality of developing devices.
As a result of examination, in order to satisfy this condition, the gap d (mm) between the image carrier and the developer transporter in the developing area (hereinafter, sometimes simply referred to as the gap d), the amplitude V _AC of the AC component of the developing bias. It was found that it was difficult to obtain an excellent image even if the values of the frequency and the frequency (Hz) were determined independently, and that these parameters are closely related to each other. Therefore, an experiment was conducted by using the color copying machine shown in FIG. 6 while changing the parameters such as the voltage and frequency of the AC component of the developing bias and using the one-component magnetic toner in the developing device 17 as shown in FIG. As a result, the results shown in FIGS. 8 and 9 were obtained. A toner image is previously formed on the photosensitive drum 41. This developing device 17 corresponds to each of the developing devices 17Y, 17M, and 17C shown in FIG. 6, and rotates the sleeve 7 and / or the magnetic roll 43 to cause the developer De to move around the sleeve 42. The developer De is supplied to the developing area E by being conveyed in the direction of arrow B on the surface. The developer De is a one-component magnetic developer. 70 wt% of a thermoplastic resin, 10 wt% of a pigment (carbon black), 20 wt% of a magnetic substance, and a charge control agent were kneaded and pulverized to have an average particle diameter of 15 μm, and silica. The one added with a fluidizing agent such as The charge amount is controlled by a charge control agent. Magnetic roll 43 is in the direction of arrow A, sleeve 7
Is rotated in the direction of arrow B, developer D
Is conveyed in the direction. The thickness of the developer De is regulated by the spike-height regulating blade 40 made of a magnetic material during transportation.
A stirring screw 42 is provided in the developer reservoir 47 to sufficiently stir the developer De.
When the toner in 47 is consumed, the toner supply roller
By rotating 39, the toner T is replenished from the toner hopper 38.

A DC power supply 45 is provided between the sleeve 7 and the photosensitive drum 41 to apply a developing bias, and the developer De is vibrated in the developing area E, so that the developer De is transferred to the photosensitive drum 41. An AC power supply 46 is provided in series with the DC power supply 45 so as to be sufficiently supplied. R is a protective resistance.

In FIG. 8, the gap d between the photosensitive drum 41 and the sleeve 7 is set to 0.
7 mm, the developer layer thickness is 0.3 mm, the DC component of the developing bias applied to the sleeve 7 is 50 V, the frequency of the AC component of the developing bias is 1 KHz, and the charging potential of the photoconductor by uniform exposure after charging is 500 V. At this time, the relationship between the amplitude of the AC component and the image density of the black toner image formed on the non-exposed portion (the exposed portion potential is 0 V) on the photosensitive drum 41 is shown. The amplitude E _AC of the _AC electric field strength is the amplitude V _AC of the AC voltage of the developing bias.
Is a value obtained by dividing by the gap d. Curves A, B shown in FIG.
C is the average charge amount of the magnetic toner is −5 μc / g, −
It is a result when using those of 3 μc / g and −2 μc / g. The three curves A, B, and C are large in image density when the amplitude of the AC component of the electric field is 200 V / mm or more and 1.5 KV / mm or less, and are formed on the photosensitive drum 41 in advance when 1.6 KV / mm or more. It was observed that the toner image on the surface was partially destroyed.

FIG. 9 shows a change in image density when the AC component frequency of the developing bias is 2.5 KHz and the AC electric field strength and the like are changed under the same conditions as in the experiment of FIG.

According to this experimental example, the amplitude E _{AC of the AC} electric field strength is 500
Greater image density at V / mm or more and 3.8 KV / mm or less, 3.2
At KV / mm or more, a part of the toner image previously formed on the photosensitive drum 41 was destroyed.

As can be seen from the results shown in FIGS. 8 and 9, the image density changes so as to saturate or slightly decrease at a certain amplitude, but the value of this amplitude changes from the curves A, B, and C. As can be seen, the toner is obtained without depending much on the average charge amount of the toner. The reason is considered as follows. That is, it is expected that the charge amount of the one-component developer is widely distributed over the positive and negative sides due to mutual friction between the toner particles. Therefore, the average charge amount becomes a small value, but in reality, a large charge amount, for example, a size of 20 μc /
Toners of g or more are also present at a constant rate, and it is considered that such toner is mainly developed. Even if the average charge amount is controlled by the charge control agent, the proportion of the toner having such a large charge amount does not change significantly, and as a result, it is considered that changes in the developing characteristics are hardly observed.

When experiments similar to those shown in FIGS. 8 and 9 were conducted under different conditions, the relationship between the amplitude E _AC of the _AC electric field strength and the frequency could be arranged and the results shown in FIG. 10 were obtained.

The area indicated by in FIG. 10 is the area where uneven development is likely to occur, the area indicated by is the area in which the effect of the AC component does not appear, and the area indicated by is the area where the already formed toner image is easily destroyed. This is a particularly preferable region where the effect of the AC component appears, a sufficient developing density is obtained, and the toner image already formed is not destroyed.

This result indicates that the amplitude of the AC electric field strength is required to develop the next (post-stage) toner image at an appropriate density without destroying the toner image previously (previous stage) formed on the photosensitive drum 41. It also indicates that there is an appropriate range for the frequency and its frequency, and the cause is considered to be due to the reasons described below.

Image density with respect to the amplitude E _AC of the alternating electric field intensity, the area is increasing, i.e., for example, for the density curve A of Figure 8, the region where the amplitude E _AC of the alternating electric field intensity is 0.2~1KV / mm is The AC component of the developing bias serves to easily exceed the threshold value for the toner to fly from the sleeve, and even a toner having a small charge amount is attached to the photosensitive drum 41 to perform the development. Therefore, the image density increases as the amplitude E _{AC of the AC} electric field strength increases.

On the other hand, there are several reasons why the image density saturates or decreases slightly as the amplitude of the AC electric field increases (for example, in the case of the density curve A of FIG. 8, the AC electric field amplitude E _AC is 1 KV or more). Conceivable. As the amplitude E _{AC of the AC} electric field strength increases, the toner vibrates strongly, the clusters formed by aggregation of the toner are easily broken, and only the toner having a large electric charge is selectively attached to the photoconductor drum 41. Toner with a small charge is less likely to be developed. Further, the toner having a small electric charge has a weak mirror image force even if it adheres to the photoconductor drum 41 once, so that the toner easily returns to the sleeve 7 by an AC bias. Further, when the amplitude of the electric field strength of the AC component is too large, the charge on the surface of the photoconductor drum 41 leaks, which makes it difficult for the toner to be developed. In fact, it is considered that these causes overlap and the image density is saturated or lowered.

On the other hand, when the amplitude E _AC of the _AC electric field strength is increased, as described above, the toner image previously formed on the photosensitive drum 41 is destroyed, and the greater the AC component, the greater the degree of destruction. It is considered that this is because a force that pulls back the toner adhered on the photoconductor drum 41 to the sleeve 7 by an AC component. When toner images are successively superposed and developed on the photoconductor drum 41, it is a fatal problem that the already formed toner image is destroyed during the subsequent development.

Also, as can be seen by comparing the results of FIG. 8 and FIG. 9, when experiments were performed by changing the frequency of the AC component, the image density tends to decrease as the frequency increases. This is because the toner particles cannot follow the change of the electric field, so that the vibrating range is narrowed and the toner particles are less likely to be attracted to the photosensitive drum 41.

Based on the above experimental results, the present inventor
The amplitude of the AC component of the developing bias is V _AC (v) and the frequency is (H
z), when the gap between the photosensitive drum 41 and the sleeve 7 is d (mm), if the development is performed under the condition of 0.2 ≦ V _AC /(d·)≦1.6, the photosensitive drum is already
It was concluded that the subsequent development can be performed at an appropriate density without disturbing the toner image formed on the 41. In order to obtain a sufficient image density and not disturb the toner image formed up to the preceding stage, the image density is a region where the image density tends to increase with respect to the AC electric field in FIGS. 6 and 7, 0.4 ≦ V It is more desirable to satisfy the condition of _AC / (d ・) ≦ 1.2. Furthermore, it is more desirable to satisfy the condition of 0.6 ≦ V _AC /(d·)≦1.0, which is a region slightly lower than the saturation of the image density.

In order to prevent uneven development due to the AC component, the frequency of the AC component is set to 200Hz or higher, and the developer is set to the photosensitive drum 4.
When a rotating magnetic roll is used as the means for supplying 1 to 1, the frequency of the alternating component is more preferably 500 Hz or more in order to eliminate the influence of the AC component and the beat generated by the rotation of the magnetic roll.

Next, an experiment was conducted using the two-component developer in the developing device 17 as shown in FIG. 7 in the same manner as above, and the results shown in FIGS. 11 and 12 were obtained. The developer De is a two-component developer composed of a magnetic carrier and a non-magnetic toner, and the carrier has an average particle size of 20 μm, a magnetization of 30 emu / g and a resistivity of 10
It is a carrier prepared by dispersing fine iron oxide in a resin so that it exhibits a physical property of ¹⁴ Ω-cm.
After tapping in a container having a sectional area of 0.50 cm ^2, a load of 1 kg / cm ² on packed particles, applying a voltage to the electric field of 1000V / cm is generated between the load and a bottom electrode It is a value obtained by reading the current value at that time. The toner used was one in which a small amount of a charge control agent was added to 90 wt% of a thermoplastic resin and 10 wt% of a pigment (carbon black), and the mixture was kneaded and pulverized to have an average particle size of 10 μm. The toner was mixed at a ratio of 20 wt% with respect to 80 wt% of the carrier to obtain a developer D.
The toner is negatively charged by friction with the carrier.

FIG. 11 shows a gap d between the photosensitive drum 41 and the sleeve 7 of 1.
0mm, developer layer thickness 0.7mm, photoconductor charging potential 500V,
The DC component of the developing bias is 50V, and the frequency of the AC component is 1
AC component amplitude and photosensitive drum 41 when set to KHz
3 shows the relationship with the image density of the black toner image formed in the non-exposed area (the exposed area potential is 0 V). The amplitude E _AC of the _AC electric field strength is a value obtained by dividing the amplitude V _AC of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in FIG. 9 indicate that the toner has an average charge amount of -30 μc / g, -20 μc / g, and -15 μc / g, respectively.
This is the result when a charge-controlled one is used. A,
The amplitude of the AC component of the electric field is 20 for both the three curves B and C.
It was observed that the effect of the AC component appeared at 0 V / mm or more, and that the toner image previously formed on the photosensitive drum was partially destroyed at 2500 V / mm or more.

FIG. 12 shows a change in image density when the AC component frequency of the developing bias is 2.5 KHz and the _AC electric field strength E _AC is changed under the same conditions as in the experiment of FIG.

According to this experimental example, the amplitude E _{AC of the AC} electric field strength is 500
If it exceeds V / mm, the image density becomes large, and if it is not shown, it becomes 4 KV / mm or more, and a part of the toner image previously formed on the photosensitive drum 41 is destroyed.

As can be seen from the results shown in FIGS. 11 and 12, the image density changes such that the image density becomes saturated or slightly decreased at a certain amplitude, and the value of this amplitude can be seen from the curves A, B, and C. As described above, the toner can be obtained without depending much on the average charge amount of the toner. The reason is considered as follows.
That is, in the two-component developer, the toner is charged by the friction with the carrier and the mutual friction between the toners, even though it is not as much as the one-component developer, and it is expected that the charge amount of the toner is distributed over a wide range. It is considered that the toner having a large charge amount is preferentially developed. Even if the average charge amount is controlled by the charge control agent, the proportion of the toner having such a large charge amount does not change significantly, and as a result, it is considered that the change in the development characteristics is tentatively observed but not observed. .

When experiments similar to those shown in FIGS. 9 and 10 were conducted under different conditions, the relationship between the amplitude E _AC of the _AC electric field strength and the frequency could be arranged and the results shown in FIG. 13 were obtained.

In FIG. 13, a region indicated by is a region where uneven development is likely to occur, a region indicated by is a region in which the effect of an AC component does not appear, a region indicated by is a region where destruction of a toner image already formed is likely to occur, Is a region where the effect of the AC component appears, a sufficient developing density is obtained, and the toner image already formed is not destroyed, and is a particularly preferable region.

The result is that the amplitude of the AC electric field strength and its frequency are required to develop the next (post-stage) toner image at an appropriate density without destroying the toner image formed on the photoconductor drum 41 in the previous stage. Therefore, there is an appropriate area, and the cause is the same as in the case of the one-component developer described above.

That is, the image density with respect to the amplitude E _AC of the alternating electric field intensity, the region is increasing, for example, for the density curve A of FIG. 11, the region where the amplitude E _AC of the alternating electric field intensity is 0.2~1.2KV / mm Has a function of facilitating the AC component of the developing bias to exceed the threshold value for flying toner from the sleeve, and even toner with a small charge amount is attached to the photoconductor drum 41 and is used for development. Therefore, the image density increases as the amplitude of the AC electric field strength increases.

On the other hand, in the area where the image density is saturated with respect to the amplitude E _AC of the AC electric field strength, the curve A in FIG.
For the region where _AC is 1.2 KV / mm or more, this development can be explained as follows. That is, in this region, the toner vibrates strongly as the amplitude of the AC electric field strength increases, and the clusters formed by aggregation of the toner are easily broken, and only the toner having a large charge is selectively transferred to the photosensitive drum 41. Toner particles that are attached and have a small charge are less developed. Further, the toner having a small electric charge has a weak mirror image force even if it adheres to the photoconductor drum 41 once, so that the toner easily returns to the sleeve 7 by an AC bias. Further, since the amplitude of the electric field strength of the AC component is too large, the charge on the surface of the photosensitive drum 41 leaks,
The development that the toner is hard to be developed easily occurs. In fact, it is considered that these factors are overlapped and the image density is constant as the AC component increases.

Further increasing the AC electric field strength, for example the curve A in FIG.
When the amplitude is set to 2.5 KV / mm or more under the condition obtained, the toner image previously formed on the photosensitive drum 41 is destroyed as described above, and the greater the AC component, the greater the degree of destruction. I understood. It is considered that this is because a force that pulls back the toner adhered on the photoconductor drum 41 to the sleeve 7 by an AC component.

When the toner images are successively superposed on the photosensitive drum 41 and developed, it is a fatal problem that the already formed toner image is destroyed during the subsequent development.

Further, as can be seen by comparing the results of FIG. 11 and FIG. 12, an experiment was conducted by changing the frequency of the AC component, and the higher the frequency, the lower the image density. The reason is that the range of vibration is narrowed because it cannot follow the change of the electric field, and it becomes difficult to adhere to the photosensitive drum 41.

Based on the above experimental results, the present inventor
Amplitude of AC component of developing bias is V _AC (V) frequency is (H
z), when the gap between the photosensitive drum 41 and the sleeve 7 is d (mm), develop under the condition of 0.2 ≦ V _AC / (d ·) {(V _AC /d)-1500}/≦1.0 If you already have a photoconductor drum
It was concluded that the subsequent development can be performed at an appropriate density without disturbing the toner image formed on the 41. In order to obtain sufficient image density and not disturb the toner image formed up to the previous stage, 0.5 ≦ V _AC / (d ·) {(V _AC / d) -1500} / ≦ It is more preferable to satisfy 1.0. In particular, if 0.5 ≦ V _AC / (d ・) {(V _AC /d)-1500}/≦0.8 is satisfied, a clearer and more color-free multicolor image can be obtained, even if it is operated many times. It is possible to prevent mixing of different color toners into the developing device.

Further, in order to prevent development unevenness due to the AC component, the frequency of the AC component is 200 Hz or higher as in the case of using the component developer, and a rotating magnetic roll is used as a means for supplying the developer to the photosensitive drum 41. In this case, it is more desirable that the frequency of the AC component is 500 Hz or higher in order to eliminate the influence of the AC component and the beat generated by the rotation of the magnetic roll.

Although the image forming process based on the present invention is as illustrated above, the subsequent toner images are sequentially developed on the photosensitive drum 41 at a constant density without destroying the toner image formed on the photosensitive drum 41. To this end, as the development is repeated, a toner having a large charge amount is sequentially used.

The amplitude of the electric field strength of the AC component of the developing bias is gradually reduced.

The frequency of the AC component of the developing bias is gradually increased.

It is more preferable to employ each of these methods alone or in any combination.

That is, the toner particles having a larger charge amount are more likely to be affected by the electric field. Therefore, if toner particles having a large charge amount are attached to the photoconductor drum 41 in the initial development, when the subsequent development is performed,
The toner particles may return to the sleeve. Therefore, the above-mentioned is to prevent the toner particles from returning to the sleeve during the subsequent development by using the toner particles having a small charge amount for the initial development. Is
This is a method of preventing the toner particles already adhering to the photosensitive drum 41 from returning by sequentially decreasing the electric field strength as the development is repeated (that is, as the development is performed in the subsequent stage). As a specific method for reducing the electric field strength, there are a method of sequentially lowering the voltage of the AC component and a method of widening the gap d between the photosensitive drum 41 and the sleeve 7 in the subsequent development. Further, the above is a method of preventing the return of the toner particles already adhering to the photosensitive drum 41 by increasing the frequency of the alternating-current component as the development is repeated. They are,
Although they are effective when used alone, they are more effective when they are used in combination such that the toner charge amount is sequentially increased and the light flow bias is sequentially decreased as the development is repeated. Further, when the above three methods are adopted, it is possible to maintain an appropriate image density or color balance by adjusting the DC bias, respectively.

Next, a specific experimental example actually conducted by the present inventor will be described.

That is, when a multicolor image was recorded under the conditions shown in Table 3 below, good recording on each surface was possible.

Not limited to the developing method described above, as a modified example of the developing method performed without rubbing the photosensitive member, only the toner is taken out from the composite developer onto the developer carrier, and one component by the toner is generated in the alternating electric field. Method of developing (Japanese Patent Laid-Open No. 59-42565)
No. 58-231434), a method of providing a linear or mesh control electrode and performing development with a one-component developer in an alternating electric field (JP-A-56-125753), and providing a similar control electrode. It goes without saying that the method of developing with a two-component developer in an alternating electric field (Japanese Patent Application No. 58-97973) is also included in the multicolor image forming method of the present invention.

In the above embodiments, the corona transfer is used as the toner image transfer method, but other methods can also be used. For example, when the adhesive transfer described in JP-B-46-41679 and JP-A-48-22763 is used, transfer can be performed without considering the polarity of the toner. Further, a method of directly fixing to the photoconductor such as electro-fax can also be adopted.

In addition, the layer structure of the photoconductor is provided with a transparent insulating layer, a photoconductor layer, a conductive layer, and a filter, and primary and secondary charging from the transparent insulating layer side is performed, and image exposure from the filter side is performed. It is also possible to adopt a configuration in which development is performed from the transparent insulating layer side by applying from the back surface.

Further, all the above explanations refer to the so-called three color separation photosensitive layer and three
Although the example of the color copying machine using the primary color toner has been described, the embodiment of the present invention is not limited to this, and it can be widely used in various multicolor image recording devices, color photographic printers and the like. It goes without saying that the spectral sensitivity of the decomposition photosensitive layer and the corresponding combination of toner colors can be arbitrarily selected according to the purpose. Further, the structure of the photosensitive layer of the photoconductor is not limited to that described above, and its pattern, arrangement, etc. can be variously changed. Further, it is also possible to apply primary latent image formation in which image exposure is performed simultaneously with primary charging and secondary charging, image exposure after primary charging, and primary latent image formation in which secondary charging is performed.

It should be noted that the term "charging" in the present specification includes cases in which the surface potential becomes 0 when the "charging" is performed or the surface charge disappears.

Further, in the above description, the spectral characteristics of the light for whole surface exposure are
Green (G), blue (B), and red (R), but not limited to this, the point is that a specific photosensitive portion (a kind of However, the spectral characteristics may be such that a potential pattern is formed only in (not limited to).

F. Effects of the Invention As described above, in the present invention, since the photoconductive layer itself of the photoconductor is composed of a plurality of photoconductive portions having different spectral sensitivity distributions,
It is not necessary to separately provide a color separation filter, and the layer structure of the photoconductor is significantly simplified.

Further, since the insulating layer is provided on the photoconductive layer composed of a plurality of parts having different spectral sensitivity distributions, the photoconductive layer is protected by the insulating layer, and the durability of the color separation characteristic is excellent. , It is stable over a long period of time and is unlikely to deteriorate.

Furthermore, since the insulating layer is provided on the photoconductive layer composed of a plurality of portions having different spectral sensitivity distributions, the surface layer portion is also excellent in insulating property, and an excellent photoreceptor can be obtained.

Moreover, using this photoreceptor, after the formation of the first electrostatic latent image, the steps of whole surface exposure and development with light of a specific wavelength that produces a potential pattern in only one kind of photoconductive portion are repeated, The entire surface charging and image exposure that required multiple times in the past can be done only once, there is no need to align various images during transfer, and the device can be made smaller, faster, and more reliable. You can The recorded matter obtained also has a high image quality with no color shift.

[Brief description of drawings]

The drawings show an embodiment of the present invention, wherein FIGS. 1A (a) and 1 (b) are cross-sectional views of each photoconductor, and FIGS. 1B (a) and 1 (b) are manufacturing processes of the photoconductor. Sectional views, FIGS. 2 (a), (b), and (c) are sectional views showing the manufacturing process of the photoconductor, and FIGS. 3 and 4 are spectrum diagrams showing two examples of the spectral characteristics of the photoconductive portion. , FIG. 5, [1], [2], [3], [4], [5],
[6] and [7] are process flow diagrams showing the image forming process, FIG. 6 is a schematic view of a color copying machine, FIG. 7 is a sectional view of a developing device, and FIGS. 8 and 9 are single-component developers. Fig. 10 is a graph showing the relationship between the amplitude and frequency of the AC bias when a one-component developer is used. Figs. 11 and 12 are two-component developers. Is a graph of the data obtained when, and 13th is a graph showing the relationship between the amplitude of the AC bias and the frequency when the two-component developer is used. In the reference numerals shown in the drawings, 1 ... conductive substrate 2 ... photoconductive layer 2R, 2G, 2B ... photoconductive portion 3 ... insulating layer 4 ... primary charger 5 ... secondary charger 7 , 7Y, 7M, 7C …… Developing sleeve 8 …… Copy paper 14,15 …… Recharging device 17,17Y, 17M, 17C …… Developing device 41 …… Photosensitive drum F _B …… Blue filter F _G …… Green filter F _R ...... Red filter L _R ...... Red light L _B ...... Blue light L _G ...... Green light TY ...... Yellow toner TM ...... Magenta toner D ...... Developer T ...... Toner.

Claims (2)

[Claims] 1. A photoconductor comprising a photoconductive layer composed of a plurality of portions having different spectral sensitivity distributions, and an insulating layer provided on the photoconductive layer. 2. A step of image-exposing a photoconductor having a photoconductive layer composed of a plurality of portions having spectral sensitivity distributions different from each other and an insulating layer provided on the photoconductive layer; An image forming method comprising: a step of repeating an entire surface exposure with a specific light for generating a potential pattern on the layer portion and a developing operation.