JPS62205369A - Formation of multicolor image - Google Patents

Abstract

PURPOSE:To form an excellent color image with no color mixing in a fast, simple process by performing entire-surface exposure to wavelength-distributed light transmitted through a toner image on a photosensitive body. CONSTITUTION:A charge density layer is formed by single-time image exposure at the boundary between a photoconductive layer 2 and an insulating layer which includes color filters R, B, and G on the photosensitive body which has a color separating function. A latent image is formed on filters B by entire- surface exposure using light transmitted through the filters B, etc., and the image is developed with toner T1 of corresponding color. Then, entire-surface exposure is carried out with wavelength-distributed light L transmitted through the toner T1, etc., and development using toner T2 of corresponding color is performed to superpose the images of the toner particles T1 and T2 one over another at the end part excellently. Similarly, the process is repeated to form an excellent color image which has no color mixing in the fast, image process.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an image forming apparatus for forming an image on a photoreceptor, and in particular, it relates to an image forming apparatus for forming an image on a photoreceptor, particularly for forming a multicolor image on a photoreceptor used in electrophotography. The present invention relates to an image forming method for forming an image.

Traditionally, in obtaining multicolor images using electrophotography,
Although many methods and devices used therefor have been proposed, they can generally be classified into the following types. Part 1
One method is to repeat latent image formation and development with color toner using a photoreceptor according to the number of separated colors, and then overlap the colors on the photoreceptor, or transfer the colors to a transfer material each time the development is performed. This is a method of layering.

Another method uses a device that has multiple photoreceptors corresponding to the number of separated colors, and simultaneously exposes each photoreceptor with a light image of each color, and the latent image formed on each photoreceptor is colored. The image is developed with toner, transferred sequentially to a transfer material, and the colors are superimposed to obtain a multicolor image.

However, in the first method described above, the latent image formation and development process must be repeated multiple times, so it takes time to record the image, and a major drawback is that it is extremely difficult to speed up the process. In addition, the second method described in ``2'' uses multiple photoreceptors in parallel, so it is advantageous in terms of high speed, but it requires multiple photoreceptors, optical bodies, optical systems, developing means, etc. This makes the device complicated, large, expensive, and impractical.

In addition, both of the above methods have the major disadvantage that it is difficult to align the images when repeating four image formations and transfers multiple times, and it is not possible to completely prevent color shift of the images. There is. In order to fundamentally solve these problems, the present inventor previously proposed a method of recording a multicolor image on a single photoreceptor through one image exposure. One of these is as follows.

In other words, multiple color separation filters (each filter section substantially transmits only light in a specific wavelength range) are combined in a fine linear or mosaic pattern on a photosensitive layer that is sensitive to the entire visible light range. Using a photoconductor with an insulating layer arranged on it, first image exposure is applied to the entire surface of the photoconductor, and charges are distributed in the photoconductive layer below each filter according to the resolved image density (hereinafter referred to as the primary latent image). Then, by exposing the entire surface to light that passes through the first color separation filter, an electrostatic image (hereinafter referred to as this) corresponding to the intensity of the first latent image formation process is formed only on the photoconductive layer under the filter. The secondary latent image is developed with a color toner of a color corresponding to the type of filter that formed it, preferably a complementary color to the color that passes through the filter, and is further uniformly charged. A multicolor image is formed on the photoreceptor by repeating the same whole-surface exposure, development, and recharging operations, and the multicolor image is recorded on the transfer material at once by two transfers.

However, with the above method, it is difficult to produce toners and filters that are ideally transparent only in a specific wavelength range. Furthermore, in order to prevent a decrease in the sensitivity of the photoreceptor, it is better for the spectral transmittance of the filter to be as high as possible, but if the spectral transmittance of the filter is increased, it will inevitably become transparent to other wavelengths of light. This will result in

Furthermore, in the above method, the entire surface of the photoreceptor is exposed to specific light to release the charge on the photosensitive layer corresponding to a specific filter, but regarding the exposure light, the entire surface exposure light generally has a wavelength distribution. Furthermore, each filter has a slight transmittance for wavelengths other than specific wavelengths. Further, the toner already attached blocks part of the entire surface exposure light. Therefore, full-surface exposure also releases a considerable amount of charge in other filter parts.
Alternatively, the charge on a part of the specific filter may not be sufficiently released due to toner already attached.

This means that a sufficient potential pattern is not generated in a specific filter section, or that a potential pattern is generated in other filter sections. In conventional image formation using a photoreceptor with a transparent insulating layer, such as the NP or KIP method, it was sufficient to provide a sufficient amount of exposure at any wavelength to which the photoreceptor is sensitive, but with this method, toner It is necessary to consider translucency and the order of toner development. Furthermore, it is not possible to provide an unlimitedly strong specific full-surface exposure.

C1 Object of the Invention The object of the present invention is to create a multicolor image by a high speed and simple process by using a photoreceptor that can quickly and easily record a multicolor image without color shift by - times of image exposure. An object of the present invention is to provide an image forming apparatus capable of achieving excellent color reproduction.

28 Structure of the Invention The present invention provides a method for charging a photoreceptor having a color separation function and, after image exposure,
In a multicolor image forming method in which a plurality of toner images of different colors are superimposed on the photoconductor by repeating full-surface exposure and development with specific light, the electrostatic photograph is The present invention provides a multicolor image forming method characterized by using light having a wavelength distribution that substantially transmits each toner constituting a toner image formed on a photoconductor, and also includes In an image forming apparatus in which a photoreceptor having a color separation function is charged and exposed to an image, the entire surface is exposed to specific light and development is repeated, and the light intensity of the entire surface exposure is such that the potential generated by the entire surface exposure is approximately saturated. , 0.7Lo≦L≦5L for o.

=7- An image forming method is provided.

The image forming method according to the present invention includes a step of imagewise exposing the photoreceptor, comprising a layer consisting of a plurality of color separation portions that mainly transmit light in different wavelength ranges; The present invention is characterized by the step of applying full-surface exposure to light to form a potential pattern on at least one of the portions, and repeating the development operation for each type of color-separated portion.

E. Examples Hereinafter, examples in which the present invention is applied to a multicolor image forming photoreceptor (hereinafter simply referred to as photoreceptor) and a multicolor image forming process will be described in detail. In the following explanation, we will only discuss a full-color reproduction photoreceptor using red, green, and blue filters that transmit only red, green, and blue light as separation filters, but we will discuss the colors of the separation filters and their combinations. The color of the toner is not limited to the above. FIG. 1 illustrates the shape and arrangement of a filter according to the invention. Here, BSG.

R indicates blue, green, and red filter sections, respectively.

FIG. 1(A) shows a linear type. For example, if the photoreceptor is drum-shaped, the linear type may be perpendicular to the rotation direction, parallel, or oblique.

FIGS. 1(B) and 1(C) are mosaic-like, and the size of each filter portion is preferably 10 to 500 μm in length, as indicated by Q in FIG. In this case as well, the direction of Q may be perpendicular to the rotational direction of the photoreceptor, parallel to it, or oblique to it.

If the size of the filter part is too small, it will be easily influenced by adjacent parts of other colors, and if the width of one filter part is equal to or smaller than the particle size of the toner particles, it will be difficult to create. Become.

Also, if the size of the filter section becomes too large, the resolution of the image will deteriorate.
Image quality deteriorates due to poor color mixing.

The shape and arrangement are not limited to those shown in FIG. 1, and may be of any kind.

FIG. 2 schematically shows a cross section of a photoreceptor that can be used in the present invention. A photoconductive layer 2 is provided on a conductive member or substrate 1, and a required color separation filter such as red (R
), green (G), and blue (B) filter sections are laminated.

The conductive substrate 1 may be made of metals such as aluminum, iron, nickel, copper, or alloys thereof, and may have a cylindrical shape or have an appropriate shape and structure as required for forming an endless belt.

The photoconductive layer 2 is made of a photoconductor such as sulfur, selenium, amorphous silicon or an alloy containing sulfur, selenium, tellurium, arsenic, antimony, etc., or zinc, lead, mercury, cadmium,
Inorganic photoconductive substances such as molybdenum and other metal oxides, iodides, sulfides, and selenides, azo-based, disazo-based, trisazo-based, and phthalocyanine-based dyes, vinylcarbazole, trinitrofluorenone, polyvinylcarbazole, and oxa It is formed by dispersing a resin and a charge transporting substance such as a diazole, a hydrazone compound, a dirubene derivative, or a styryl derivative, and then coating the resin.

Examples of such binder resin include insulating resins such as polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, polycarbonate, acrylic resin, phosphor resin, fluororesin, and epoxy resin. Also used is a functionally separated photoelectric body that is divided into a charge generation layer and a charge transfer layer.

The insulating layer 3 is made of a transparent insulating material, such as various polymers,
It can be made of resin or the like, and has a colored portion on its surface or inside that acts as a color separation filter. As shown in FIG. 2(A), the colored portion is formed by applying a colored insulating material to the photoconductive layer 2 by adding a coloring agent such as a dye or pigment having a desired color to the photoconductive layer 2 in a predetermined manner by printing, resisting, vapor deposition, or the like. Attach it to the pattern. In this case, each color of paint is printed multiple times (for example, three times). Alternatively, as shown in FIG. 2(B), a coloring agent is attached in a predetermined pattern to a colorless insulating layer 3bJ- that has been uniformly formed in advance on the photoconductive layer 2-H by means such as printing, photoresist, vapor deposition, etc. It can be formed by Furthermore, even if a film-like insulating material on which a colored portion is formed in advance is attached to the photoconductive layer, it is possible to
Photoreceptors having the structures A) and (B) can be constructed. Furthermore, the surface of the formed colored part is further coated with an insulating material 3.
It may be covered with C and have a structure as shown in FIG. 2(C) or (D).

Note that FIGS. 1(A) to (C) and FIGS. 2(A) to (D) all show cases in which so-called three-color separation filters of red, green, and blue are provided.

Next, the process of forming a multicolor image using the above-mentioned photoreceptor will be explained with reference to FIG. The figure schematically shows the image forming process in a portion of a photoreceptor that uses an n-type (that is, high electron mobility) photosemiconductor such as cadmium sulfide as a photoconductive layer. In addition, cross-sectional hatching of each part is omitted. In the figure, 1 and 2 are a conductive substrate and a photoconductive layer, respectively, and 3 is an insulating layer including three color separation filter sections R, G, and B. Further, the graph at the bottom of each figure shows the potential on the surface of each part of the photoreceptor.

First, as shown in FIG. 3 [1], when a positive corona discharge is applied to the entire surface by the charger 4, a positive charge is generated on the surface of the insulating layer 3, and correspondingly, a positive charge is generated on the surface of the insulating layer 3. A negative charge is induced at the interface.

-12= Next, as shown in FIG. 3 [2], alternating current or negative discharge is applied by the charger 5 equipped with an exposure slit, and the insulating layer 3
A colored image exposure, for example, a red image exposure LR, is applied while erasing the surface charge.

The red light passes through the red filter section R of the insulating layer 3, and in order to make the photoconductive layer 2 below it conductive, the charges in the photoconductive layer 2 are erased in the same filter section. On the other hand,
Since the green color filter section 3G and the blue color filter section 3B do not transmit red light, the negative charges on the photoconductive layer 2 remain as they are. Further, due to the action of the charger 5, the charge distribution on the insulating layer 3 changes so that the surface potential of the photoreceptor becomes uniform.

The primary latent image is formed in the manner described above.

The portions of the document irradiated with the green and blue components also give similar results for each filter section.

The primary latent image is a state in which all color components exist as an image-like charge distribution under each filter section.

At this stage, not only the portions on the photoconductive layer 2 where the charges have been erased, but also the portions where the charges remain have the same potential on the surface of the photoreceptor, and therefore do not function as an electrostatic image.

In addition, in FIG. 3 [2], the potential after charging (J is approximately zero is shown), but it may be charged to a negative value.

Next, as shown in FIG. 3 [3], when the entire surface is exposed to light that passes through one of the filters included in the insulating layer 3, for example, blue light T, 8 obtained by the light source 6B and the blue filter FB. , the photoconductive layer 2 below the filter 3 that transmits blue light becomes conductive, and a part of the negative charge of the photoconductive layer 2 in this part and the charge of the conductive substrate 1 are neutralized, and the surface of the filter B becomes conductive. A potential pattern is generated by the electric charge. In the part of the GSR that does not transmit blue light (J change does not occur. This is the second latent image. Then, when the charged image on filter B'2 is developed with a developer containing negatively charged yellow toner TY, Toner adheres only to the surface of the portion of the film 23 where the potential is relatively high, and development is performed (FIG. 3 [4]).

Next, in order to eliminate the generated potential difference, the surface potential is made uniform by the charger 8 as shown in FIG. 3 [5], and then the surface potential is made uniform as shown in FIG.
6], when the entire surface is exposed with green LG, a second latent image is formed in the green filter portion G, as in the case of blue light.

If this is developed with magenta toner TM as shown in FIG. 3 [7], magenta toner TM will adhere only to the filter G portion. Subsequently, as shown in FIG. 3 [8], after making the surface potential uniform in the same way, the entire surface is exposed to red light, and the second latent image appearing on the red filter portion R is developed with cyan toner TC.

In the illustrated example, since there is no charge in the photoconductive layer 2 of the red filter R, no potential difference is generated even when the entire surface is exposed, and no cyan toner is attached even when development is performed with cyan toner.

When the thus obtained toner image is transferred onto a transfer material such as copy paper and fixed, a red image is reproduced on the transfer material by a mixture of yellow toner and magenta toner. In addition,
It is desirable that the image exposure be performed with light in which the ultraviolet and infrared regions are cut.

As for other colors, as shown in Table 1 below, color reproduction is performed by combining the three-color separation method and three primary color toners. This method is basically additive color mixing, but the toner is developed,
Due to the transfer, separation, and fixing processes, a state in which the particles are spread out and adhered to a specific filter portion actually occurs, and subtractive color mixing is also performed. This achieves high image density.

In this table, the symbol r"l is the state in the first latent image formation stage, the symbol "○" is the second latent image formation stage, the symbol "・" is the state in which development has been performed, and the symbol "↓" is the state on the upper shelf. Indicates that the state is maintained as is.

A blank column represents the absence of an image on the photoconductive layer.

161-I9- The above explanation is based on an example using an n-type optical semiconductor layer, but p-type (i.e., high hole mobility) such as selenium
Of course, it is also possible to use a photo-semiconductor layer; in this case, the basic processes are all the same except that the positive and negative signs of the charges are all reversed. If it is difficult to inject charge during negative charging, uniform irradiation with light may be used before or after primary charging, or at the same time.

As is clear from the above description, according to this embodiment, after the multicolor image forming photoreceptor is charged and subjected to imagewise exposure, the entire surface is exposed to light that passes through one of a plurality of types of filters. The steps of applying and developing are repeated depending on the type of filter.

That is, a fine color separation filter is placed on the photoreceptor, and after image exposure (step [2] in FIG. 3), the entire surface is exposed to three-color separated light (steps [3] and [6] in FIG. 3). A second latent image is formed for each color portion of the color separation filter, and developed using toner of the corresponding color (steps [4] and [7] in Figure 3), and this process is repeated to form multiple latent images. Obtain a color image. Therefore, according to this process, a photoreceptor is used, in which a plurality of color separation filters are arranged in a combination of fine lines or mosaics on a photoconductive layer that is sensitive to the entire visible light range. Image exposure is applied to form a primary latent image in the photosensitive layer below each filter according to the resolved image density, and then the entire surface is exposed to light passing through the first color separation filter to form a first latent image on the cough filter section. A second latent image is formed in accordance with the first latent image.

Then, it is developed with a color toner of a color corresponding to the color of the filter, preferably a color complementary to the color transmitted through the filter, and the same operation is repeated for each color separation image to form a multicolor image on the photoreceptor. A multicolor image can be recorded on the transfer material at once by forming a multicolor image.

FIG. 4 is a schematic diagram of an image forming apparatus for a color copying machine showing an embodiment of the present invention suitable for carrying out the above process. In the figure, reference numeral 41 denotes a photosensitive drum having the structure shown in FIGS. 1 and 2, which rotates in the direction of arrow a during a copying operation. While rotating, the photoreceptor drum 41 is irradiated with light as needed, and the entire surface is charged with a charging electrode 4, and an alternating current or a corona discharge of the opposite sign to that of the electrode 4 is generated from the next electrode 5 having an exposure slit. The image exposure of the manuscript is given while receiving the
The primary latent image formation process is completed. Next, the entire surface is exposed to blue light obtained by the combination of the light source 6B and the light source blue filter FB, and a second latent image of the yellow component is formed. Next, this is developer 1 loaded with yellow toner.
Developed with 7Y. Subsequently, after the surface of the photoreceptor is brought to a uniform potential by the electrode 14, the light source 6G and the green light source filter PC are connected.
The entire surface is exposed to green light from the image forming apparatus, and the image is developed by a developing device 17M loaded with magenta toner. Further, the potential of the photoreceptor is made uniform by the electrode 15, and the entire surface is exposed to red light from the light source 6R1 and the red light source filter PR, and the photoreceptor is developed by the developer 17C loaded with cyan toner.

As a result, a multicolor image is formed on the photoreceptor drum.

The obtained multicolor toner image is charged by J' on the pre-transfer charging electrode 11, and then transferred by the transfer electrode 9 onto the copy paper 8 fed by the paper feeding means.

The copy paper carrying the multicolor toner image to be transferred is separated from the separation electrode I.
The photoreceptor is separated from the photoreceptor drum by O and fixed by the fixing device 18 to become a completed multicolor copy, which is then removed from the machine and discharged. After the transfer, the photosensitive drum 41 is irradiated with static eliminating light, static electricity is eliminated by the static eliminating electrode 19, and residual toner on the surface is removed by the cleaning blade 13, and the drum 41 is used again.

-4] In the image forming process described above, the developer used is either a so-called two-component developer that uses non-magnetic toner or magnetic toner, or a so-called two-component developer that mixes toner and magnetic gear such as iron powder. can also be used. During development, a method of directly rubbing with a magnetic brush may be used, but especially after at least the second development,
In order to avoid damage to the formed toner image, it is essential to use a non-contact development method in which the developer layer of the developer transporter does not rub against the surface of the photoreceptor.

This non-contact method uses a two-component or two-component developer containing non-magnetic toner or magnetic toner that can freely select color retention, forms an oscillating electric field in the development area, and
Developing is performed without rubbing the developer layer. This will be explained in detail below.

In repeated development using an oscillating electric field as described above, it is possible to repeat the development several times on a photoreceptor on which a toner image has already been formed, but if appropriate development conditions are not set, during subsequent development, This may disturb the toner image formed on the photoconductor in the previous stage, or the toner already attached to the photoconductor-L may return to the developer conveying body, which may contain a developer of a different color from the developer in the previous stage. There is a problem in that it invades the developing device in the subsequent stage, causing color mixing.

Basically, to prevent this, the developer layer on the developer transporting member should be operated without rubbing or contacting the photoreceptor.

That is, the gap between the photoreceptor and the developer transport member is maintained larger than the thickness of the developer layer on the second developer transport member (provided that there is no potential difference between them).

Experiments conducted by the present inventors have revealed that desirable development conditions exist in order to more completely avoid the above-mentioned problems and further form each toner image with sufficient image density.

These conditions include the gap d (mm) between the photoreceptor and the developer transporter in the development area (hereinafter sometimes simply referred to as gap d), the amplitude VAC and the frequency f ( It has become clear that it is difficult to determine and obtain the value of Hz) alone, and that these parameters are closely related to each other. The progress will be explained below.

The experiment was conducted using the color copying machine shown in FIG. 4, and the developing device 17Y and 1. When forming a two-color toner image with IM, the influence of parameters such as the voltage and frequency of the AC component of the developing bias of the developing device 17M was investigated.

Figure 5 shows each developer shown in Figure 4], 7Y, 1.7M,
This shows the basic structure of +70, in which the sleeve 7 and/or the magnetic roll 43 rotate to convey the developer De on the circumferential surface of the sleeve 7 in the direction of arrow B, and the developer De is transferred to the developing area. It is supplied to E.

As the magnetic roll 43 rotates in the direction of the arrow B and the sleeve 7 rotates in the direction of the arrow B, the developer De is conveyed in the direction of the arrow B. The thickness of the developer De is regulated by a spike 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, and when the toner in the developer reservoir 47 is consumed, the toner supply roller 39 rotates. , toner 'F is replenished from the toner hopper 38.

Further, between the sleeve 7 and the photosensitive drum 41, a DC power source 45 and an AC power source 46 are provided in series without applying a developing bias. R is a protective resistance.

The developer De, initially stored in the developing device 17M, is a -component magnetic developer, containing 70 wt% of thermoplastic resin and pigment (
carbon black)] Owt%, magnetic material 20wt%, and a charge control agent are kneaded and pulverized to have an average particle size of 15 μm, and a fluidizing agent such as silica is further added.

The amount of charge is controlled by a charge control agent.

As a result of the experiment, the results shown in FIGS. 6 and 7 were obtained.

FIG. 6 shows a developing device 17M in which the gap d between the photoreceptor drum 41 and the sleeve 7 is 0.7 mm, and the developer layer thickness is OJ.
mm, the DC component of the developing bias applied to the sleeve 7 is 50 V, and the frequency of the AC component of the developing bias is Ikllz.
Under these conditions, the surface potential of the photoreceptor after uniform exposure after charging was 50
It shows the relationship between the amplitude of the alternating current component and the image density of the black toner image when the 0■ area is developed. Note that at this time, a two-component developer consisting of yellow toner and carrier is stored in the developing device 17Y. The amplitude EAC of the AC electric field strength is the value obtained by dividing the amplitude VAC of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in FIG. 6 indicate that the average charge amount of the magnetic toner is -511 c/g, respectively.
-3pc/g.

This is the result when -27tc/g was used.

In the three curves ASB and C, the image density is high when the amplitude of the alternating current component of the electric field is 200 V/mm or more and 1.5 kV/mm or less, and when the amplitude is 6 kV/mm or more, the image density is high. It was observed that the toner image that had been previously formed was partially destroyed.

Figure 7 shows the frequency of the AC component of the developing bias at 2.5k.
tlz, and shows the change in image density when changing the alternating current electric field strength, etc. under the same conditions as in the experiment shown in FIG.

According to this experimental result, the amplitude of the AC electric field strength is EA
When C is 500 V/mm or more and 3.8 kV/mm or less, the image density is high, and when it is 3.2 kV/mm or more (not shown in FIG. 6), part of the toner image previously formed on the photoreceptor drum 41 is section was destroyed.

As can be seen from the results in Figures 6 and 7, the image density changes to become saturated or slightly decrease after a certain amplitude, but the value of this amplitude can be seen from the curves ASB and C. As such, it does not depend much on the average charge amount of the toner.

Now, when experiments similar to those shown in FIGS. 6 and 7 were conducted while changing the conditions, the relationship between the amplitude EAC of the alternating current electric field strength and the frequency could be sorted out, and the results shown in FIG. 8 were obtained.

In FIG. 8, the area shown in (A) is an area where uneven development is likely to occur, the area shown in (B) is an area where the effect of the AC component does not appear, and the area shown in (C) is an area where toner has already been formed. Areas where image destruction is likely to occur, (D), (E)
(E) is a particularly preferred region, where the effect of the alternating current component appears, a sufficient developing density is obtained, and a portion of the already formed toner is not destroyed.

This result shows that in order to develop the next (later stage) toner image at an appropriate density without destroying the toner image previously formed on the photoreceptor drum 41 (at the previous stage), the amplitude of the alternating current electric field strength must be This shows that there is an appropriate range for that frequency.

Based on the above experimental results, the present inventor set the amplitude of the AC component of the developing bias to V AC (V ), the frequency to f (llz), and the gap between the photoreceptor drum 41 and the sleeve 7 to d (mm) in each developing process. ), then if development is performed under conditions that satisfy 0.2≦v AC/ (d - f)≦1.6, subsequent development can be carried out without disturbing the toner image already formed on the photoreceptor drum 41. They concluded that it can be done at an appropriate concentration. In order to obtain sufficient image density and not disturb the toner image formed up to the previous stage, the image density should be 0.4, which is the region in which the image density tends to increase with respect to the alternating current electric field, as shown in FIGS. 6 and 7. ≦V AC/ (d − f) l; It is more desirable that the condition of 1.2 is not satisfied. Further, within this region, it is more desirable that the electric field is slightly lower than that at which the image density is saturated, and that 0.6≦V AC/(d −D≦1.0) is not satisfied.

In addition, in order to prevent uneven development due to the alternating current component, the frequency F of the alternating current component is set to 200 Hz or more, and when a rotating magnetic roll is used as a means for supplying the developer to the photoreceptor drum 41, the alternating current component and the magnetic roll are In order to eliminate the effect of beat caused by the rotation of the AC component, the frequency of the AC component is set to 5.
It is more desirable to set the number to 001 (z or more).

Next, an experiment was conducted using a color copying machine shown in FIG. 4 in the same manner as above using a two-component developer. The developer De stored in the developing device 17M is a two-component developer consisting of a magnetic carrier and a non-magnetic toner, and the carrier has an average particle size of 20
A carrier made by dispersing fine iron oxide in a resin so as to exhibit physical properties of μm1 magnetization of 30 emu/g and resistivity of 1014 Ω-cm.The resistivity of particles is 0.50 cm.
After tapping in a container with a cross-sectional area of m',
This value is obtained by applying a load of IJ/cm' on the packed particles and reading the current value when applying a voltage that generates an electric field of 1000 V/cm between the load and the bottom electrode. . The toner contains 90wt% thermoplastic resin.
A small amount of a charge control agent was added to 10 wt % of pigment (carbon black), which was then kneaded and ground to give an average particle size of 10 μm. The toner is 20w for the carrier 80wt%.
They were mixed at a ratio of t% to form a developer De. Note that the toner is negatively charged due to friction with the carrier.

The results of this experiment are shown in FIGS. 9 and 10.

FIG. 9 shows the condition that the gap d between the photosensitive drum 41 and the sleeve 7 is 1.0 mm, the thickness of the developer layer is 0.7 mm, the DC component of the developing bias is 50 V, and the frequency of the AC component is 1 kHz. 3 shows the relationship between the amplitude of the AC component and the image density of a black toner image when developing a region where the surface potential of the photoreceptor is 500 V after exposure to light.

Note that the developing device 17Y stores a two-component developer consisting of yellow toner and carrier. The amplitude EAC of the AC electric field strength is the value obtained by dividing the amplitude VAC of the AC voltage of the developing bias by the gap d.

Curves A and BSC shown in FIG. 9 are the results when toners whose average charge amounts were controlled to -30 μc/g, −20 μc/g, and −15 μc/g, respectively, were used.

The three curves A, B, and C all show that the effect of the AC component appears when the amplitude of the AC component of the electric field is 200 V/mm or more.
When the voltage was set to 500 V/mm or more, it was observed that the toner image previously formed on the photoreceptor drum was partially destroyed.

Figure 10 shows that the frequency of the AC component of the developing bias is 2.5.
kHz, and shows changes in image density when alternating current electric field strength EAC is changed under the same conditions as in the experiment shown in FIG.

According to this experimental result, the amplitude EAC of the alternating current electric field strength
When the voltage exceeds 500 V/mm, the image density becomes high, and when the voltage exceeds 4 kV/mm (not shown), part of the toner image previously formed on the photoreceptor drum 41 is destroyed.

As can be seen from the results in Figures 9 and 10, the image density changes to become saturated or to decrease slightly after a certain amplitude, and the value of this amplitude corresponds to curves A, B, C.
As can be seen, it does not depend much on the average charge amount of the toner.

Now, when experiments similar to those shown in FIGS. 9 and 10 were conducted while changing the conditions, the relationship between the amplitude EAC of the alternating current electric field strength and the frequency f was sorted out, and the results shown in FIG. 11 were obtained.

In FIG. 11, the area shown in (A) is an area where uneven development is likely to occur, the area shown in (B) is an area where the effect of the AC component does not appear, and the area shown in (C) is an area where uneven development is likely to occur. area where destruction of the toner image is likely to occur, (D),
(E) is a region in which the effect of the alternating current component appears, a sufficient development density is obtained, and the already formed toner image is not destroyed, and (E) is a particularly preferred region.

This result shows that in order to develop the next (later) toner image at an appropriate density without destroying the toner image formed in the previous stage on the photoreceptor drum 41, as in the case of -component developer, This shows that there is an appropriate range for the amplitude of the alternating current electric field strength and its frequency.

Based on the above experimental results, the present inventor has determined that in each development step,
When the amplitude of the AC component of the developing bias is VAC (V), the frequency is f (Hz), and the gap between the photosensitive drum 41 and the sleeve 7 is d (mm), 0.2≦V AC/ (d-D ( If development is performed under conditions that satisfy (VAC/d)-1500)/f≦1.0, subsequent development can be performed at an appropriate density without disturbing the toner image already formed on the photoreceptor drum 41'2. It was concluded that 0.5≦V AC/ (d - f) is required among the above conditions in order to obtain sufficient image density and not disturb the toner image formed up to the previous stage. ((V AC/ (1) 1.500)/ f≦1.
It is more preferable to satisfy 0. Furthermore, among these, especially 0.5≦■ΔC/(d-f) ((V8C/d)-1500) / I≦0.
When 8 is satisfied, a clearer multicolor image without color turbidity can be obtained, and even if the developing device is operated many times, it is possible to prevent toner of a different color from being mixed into the developing device.

In addition, in order to prevent uneven development due to the AC component, the frequency of the AC component is set at 200
When using a rotating magnetic roll as a means for supplying the developer to the photoreceptor drum 4, the alternating current component must be controlled by the alternating current component in order to eliminate the influence of the beat caused by the rotation of the magnetic roll. It is more desirable that the frequency be 500 Hz or higher.

The image forming process is as exemplified above, but without destroying the toner image formed on the photoreceptor drum 41, subsequent toner images are sequentially transferred to the photoreceptor drum 41 at a constant density.
2. For development, as the development is repeated, (1) use toners with sequentially larger charges.

■Sequentially reduce the amplitude of the AC component of the developing bias.

■ Sequentially increase the frequency of the AC component of the developing bias.

It is more preferable to employ these methods individually or in any combination.

−33= That is, the larger the amount of charge, the more easily the toner particles are affected by the electric field. Therefore, if highly charged toner particles adhere to the photoreceptor drum 41 during initial development, these toner particles may return to the sleeve during subsequent development.

Therefore, the above-mentioned point (2) is to prevent the toner particles from returning to the sleeve during the subsequent development by using toner particles with a small amount of charge in the initial development.

(2) By sequentially decreasing the electric field strength as development is repeated (that is, as development progresses to later stages),
This method prevents toner particles already attached to the photoreceptor drum 41 from returning.

Specific methods for reducing the electric field strength include a method in which the voltage of the alternating current component is gradually lowered, and a method in which the gap d between the photoreceptor drum 41 and the sleeve 7 is made wider as the developing stage progresses.

In addition, the above-mentioned (2) is achieved by sequentially increasing the frequency of the AC component as the development is reversed.
This method prevents toner particles already attached to the surface from returning.

These ■■■ are effective even when used alone, but for example,
It is even more effective to use a combination of, for example, increasing the toner charge amount and decreasing the alternating current bias sequentially as development is repeated. Furthermore, when the following three methods are adopted, appropriate image density or color balance can be maintained by adjusting the DC biases respectively.

Next, the relationship between the filter provided on the front surface of the photoreceptor shown in FIGS. 1 and 2, the light source that exposes the entire surface from the front surface, and the attached color toner will be explained. As already mentioned, the entire surface exposure light generally has a wavelength distribution. Furthermore, each filter has a slight translucency beyond the specific wavelength range.

For this reason, the entire surface exposure light also releases a considerable amount of charge in other filter parts, which means that a potential pattern is generated in the other filter parts as well.

Therefore, the image forming apparatus according to this method has a problem in that it is not possible to provide unlimited exposure over the entire surface.

The inventors set conditions for the amount of light for full-surface exposure to produce sufficient potential contrast for a specific filter, while not producing potential contrast for other filters. This condition is also important in the case of a photoreceptor in which the filters partially overlap each other.

Reducing the size of the filter will improve the resolution of the reproduced image, but for this purpose, it is necessary to align B, G, and R with extremely high precision when manufacturing the filter, but in reality Overlap and misalignment of several microns are unavoidable.

The photoconductive layer under this overlapping portion has a lower transmittance than a portion of the filter during imagewise exposure, so that charges are not released. In other words, it will be the same as the black background part of the original. If this area is fully exposed to light, a potential pattern will be generated in this area, and toner will also adhere to the area corresponding to the white original.

In this case as well, limiting the amount of exposure light over the entire surface has the effect of preventing the generation of potential patterns.

Since the transmittance is high in the portion where the filter is not attached due to the positional shift, the charge of the photosensitive layer is sufficiently released during imagewise exposure, so that the potential contrast caused by full-surface exposure is small.

This prevents toner from adhering to the highlighted areas and causing no problems.

Figure 12 shows red (R), green (G), and
This is an example showing the transmittance of each blue (B) filter, and shows the transmittance of each filter with respect to light wavelength. Both filters have a tailed shape.

In addition, Fig. 13 shows an example showing the relative output with respect to the light wavelength of a fluorescent lamp for full-surface exposure. Fig. 13(a) is a blue fluorescent lamp, Fig. 13(b) is a green fluorescent lamp, C) shows the characteristics of a red fluorescent lamp.

It is shown that each color fluorescent lamp has a slight wavelength distribution in other color portions as well, but this was cut out by a filter in advance.

Figure 14 shows the relationship between the exposure amount and the potential difference generated by exposing the entire surface of the photoreceptor surface from the front of the filter shown in Figure 12 to the fluorescent lamp shown in Figure 13 as a parameter. ), green (G), and blue (B), the curves show bends, and LRO1L in the figure
Inflection points as shown by GO and LBO were obtained.

The reason that the potential contrast (8 V) decreases in the order of blue (B), green (G), and red (R), and that the potential is not easily saturated depending on the total exposure amount is due to the decay of trapped charges in the photosensitive layer. This is due to the fact that the entire surface exposure passes through , and other filter sections. In particular, green light is difficult to saturate with full exposure.
The blue (B) and red (R) shapes shown in Fig.
) and the light wavelength distribution of the green fluorescent lamp as shown in Figure 13(b) partially overlap,
This is because part of the light enters the photoreceptor under the blue (B) and red (R) filters, and charges are released.

The following two trends were observed, but at the inflection points LRO, T, Go, and LBO in Figure 14, the potentials generated by full-surface exposure did not nearly reach saturation for each color light. It was defined as light ftt Lo. Let the uniform exposure amount LR of red (R) light be LRO, similarly, let the overall exposure amount LG of green (G) light be LGO, and the overall exposure amount 11LB of blue (B) light.
When LBO is taken as LBO, the difference between the white background potential and black background potential of the surface potential of photoreceptor 2 in Example 2 due to each specific light is approximately VB = 250V and VC = 270V, respectively.
.

VB = 300V.

Next, let's look at the exposure amounts for full-face exposure for the three colors of red (R), green (G), and blue (B), which are lights for which the potential generated by full-face exposure is almost saturated! ! Image evaluation of color expression was performed on images when LRo, LGO, and LBO were changed as standards.

Some of the filters have yellow toner, magenta toner,
Apply cyan toner accordingly.

Table-2 TJR= L RO, T, G= T, Go, LB=
n, L BO”1 test (Table-2), L
When B=0.6L BO, insufficient density was observed in the yellow image. On the other hand, T,, B= 6 L
When it was set as BO, the yellow toner also adhered to some of the other filters, resulting in color turbidity and deterioration in image quality.

L B = 0.7~5.0LBO especially 0.9~3.0L
Regarding BO, good color reproduction was achieved for each color.

Table-3 LR=LRO, LG=n2LGO, LB=LBO" In the test (Table-3), LG=0.6LG.

In this case, a lack of density was observed in the magenta image. On the other hand, when LG=6LGO, magenta toner also adhered to some of the other filters, resulting in color turbidity and deterioration in image quality.

L G = 0.7~5.0LGO especially 0.9~3.0L
Regarding GO, good color reproduction was achieved for each color.

Table-4 LR=r++LRO, LG= LGO, LB= LBO
In the above test (Table-4) LR = 0.6L RO
When this was done, insufficient density was observed in the cyan image. On the other hand, when L R = 6 L RO, cyan toner adhered to some of the other filters, resulting in color turbidity and deterioration in image quality.

L R = 0.7~5.0LRO especially 0.9~3.0L
Regarding RO, good color reproduction was achieved for each color.

The above test is for two-color light, full-surface exposure amount saturated light m
The test results are as follows: L R = niL RO.

In the case where LG=nzL Go, LB=nlL BO, and the overall exposure amount was changed by changing n2 and n3, the same trends and results as those described above were obtained. From the above results, preferred nl+
12+n3 is 0.7 to 50, particularly preferably 0
．． It was 9-3.0.

By the way, you can change any color to yellow, magenta, or noan (3
In principle, it is possible to express primary colors using toner. However, in ordinary recorded materials, black often needs to be particularly emphasized compared to other colors, as it represents sharp parts such as characters and lines. In addition, in order to express black with three primary color toners using this method, it is required that the three types of toner images be mixed and that the spectral transmittance of each toner be close to ideal.
These are technically difficult. In particular, a color recorded image consisting of a specific toner image attached only to a specific filter tends to lack density, especially black density. In order to solve this problem, the image forming method described above is often equipped with a developing device that stores black toner in addition to the three primary colors. When expressing various colors using the method described above, there are the following two methods.

■ A method that does not directly overlap toners of different colors.

■ Method of directly overlapping toners of different colors.

■ is a multicolored toner T + as shown in FIG. 15(A),
By distributing T2 on the photoreceptor 1'' without overlapping, subtractive color mixture may sometimes occur in a pseudo manner on the recording paper during the transfer and fixing steps.

In (2), toner of a different color is superimposed on a toner image of a certain color and developed by controlling the latent image potential and the developing bias.

However, in case (2), since the toner images of each color are attached at the same position so as not to overlap, the toner T to be developed is
1. There is a problem in that the amount of T2 deposited is significantly reduced. This makes it impossible to produce a color tone with the desired density.

In addition, in case (2), if a large amount of toner is attached so as to protrude from a part of the specific filter, even if the entire surface exposure light is irradiated from above the previously developed toner T (Fig. 15B)
, the toner T2 is absorbed by the toner TI and does not sufficiently reach the photosensitive layer, and a potential pattern is not completely formed, resulting in a significantly reduced amount of toner T2 that is developed later, as shown in FIG. 15(C).

An object of the present invention is to provide a method that can easily form an image with good color balance and no image blur.

That is, in the image forming method according to the present invention, a latent image formed by subjecting an image carrier having a photoconductive layer to a first full-surface exposure is developed with a first toner TI, and then a second full-face exposure is performed. An image forming method in which a latent image formed by applying the toner is developed with a second toner, characterized in that the transmittance of the first toner T1 to the irradiation light used for the second full-surface exposure is sufficiently large. be. By doing this, a sufficient potential contrast is generated due to the entire surface exposure regardless of toner adhesion, and as a result, sufficient toner T is adhered as shown in FIG. 15(d).

In particular, each toner constituting the toner image already formed on the photoreceptor exhibits a reflectance of 40% or more for a wavelength having a maximum spectral distribution of light for full-surface exposure. The problem was solved by a multicolor image forming method.

As mentioned above, this problem basically lies in the blocking of light due to the toner adhesion amount distribution due to the single layer of toner already formed on the surface of the photoconductor during full-surface exposure, but the light is blocked by the toner adhesion amount distribution. It is often difficult to directly measure the amount of effective transmitted light that reaches the photoreceptor directly under the layer that has been exposed, and the inventors' studies have shown that the reflectance is within the range of effective exposure under practical conditions as described above. It has become clear that there is a correlation with the amount of transmitted light, that is, the amount of effective transmitted light.

Therefore, the reflectance of the toner layer according to the present invention can be understood to have the same meaning as its effective transmittance.

That is, the present invention uses exposure light that has high transmittance to a layer of toner already formed on the photoreceptor, thereby allowing the light to reach the photoreceptor covered with a layer of toner. This is to form superimposed toner images.

It should be noted that since each toner image usually consists of one to two layers of toner particles, the reflectance is a value measured using a sample in which toner particles are uniformly formed into almost one layer.

Specifically, sprinkle an appropriate amount of toner on the adhesive side of Maitatsu Label manufactured by Nichiban Co., Ltd. with a medicine spoon, and smooth the toner with your fingers to remove the excess and create the desired toner adhesion area on the adhesive side. It is removed from the area. If necessary, remove the label (due to the measuring device, this area needs to be at least φ-30mm). Then, gently rub the label with your finger in this way until the toner no longer sticks to your finger. The desired sample is obtained.

This sample was measured using a Hitachi spectrophotometer 330.
Measure the spectral transmittance using

Although the method of the present invention can be applied to the formation of multicolor images using a combination of toners of arbitrary colors, it can be particularly preferably used for the formation of so-called full-color images using yellow, magenta, and cyan toners. .

There is no particular restriction on the light for full-surface exposure used in the method of the present invention for the first exposure when no toner is present on the photoreceptor, and for the second and subsequent full-surface exposures, the light has already been formed on the photoreceptor. It is sufficient that the light has a wavelength at which each toner constituting the 1-toner image has a reflectance of 40% or more. The light source is not particularly limited, but monochromatic light from an LED fluorescent lamp, colored light obtained by using a white light source such as a halogen lamp or a white fluorescent lamp in combination with various filters, etc. are preferably used. For example, one having an overall exposure distribution having the spectral characteristics shown in FIG. 13 is used.

More preferably, the light for full-surface exposure for forming each of the yellow, magenta, and cyan toner images is blue light whose spectral distribution maximum wavelength is 450±40 nm, green light whose maximum wavelength is 550±40 nm, and 650±40 nm. 40nm
It is preferable that the spectral reflectance of each toner constituting each toner image formed on the photoreceptor is 40% with respect to the light of the wavelength.

More preferably, a blue filter in which each of the filters has a maximum wavelength of spectral transmittance of 450±40 nm, 55
Using a green light filter with a wavelength of 0±40 nm and a red light filter with a wavelength of 650±40 nm, the spectral reflectance of each l·toner constituting each toner image formed on the photoreceptor is 40% for the wavelength. It is preferable.

Hereinafter, the relationship between the exposure light and the spectral reflectance of the toner in the method of the present invention will be explained in the case of forming a full-color image.

FIG. 16 shows the spectral reflectance of full-color yellow (C), magenta (M), and cyan (0) color toners used in the examples described below. On the contrary, cyan toner strongly absorbs the long wavelength side of 550 nm and above.

In addition, this spectral reflectance is also common for full color use).

As is well known, the combination of full-surface exposure light and toner color to obtain a full-color image is blue/yellow, green: magenta, and red/nidian. It is necessary not to absorb light,
In this case, it is most preferable to use yellow, magenta, and cyan in that order.

First, the entire surface is exposed to blue light to form a yellow image. At this time, since no toner image is formed on the photoreceptor, there is no problem due to light absorption.

FIG. 16(B) is a spectral transmittance curve of a general mosaic blue filter for three-color separation similar to FIG. 12. Next, the entire surface is exposed to green light, the wavelength of which is preferably in the region where the reflectance of the yellow toner, which has previously formed the image, is 40% or more.

FIG. 16(G) is an example of the green filter spectral distribution.

Next, red exposure is performed, but since yellow and magenta images are superimposed on the photoreceptor, the wavelength of the red light is likely to be in the region where the reflectance of magenta I/ner is 40% or more. desirable.

In addition, yellow toner also has a reflectance of 40% or more in this region, and by using red light in this wavelength range, the conditions of the method of the present invention are satisfied. It is possible to form a correct cyan image by superimposing the correct cyan image without receiving (3). If the light corresponding to the area with lower toner reflectance is used, the total exposure light amount reaching the filter as explained in Fig. 15 will be reduced. As a result, a sufficient potential pattern is not generated and toner is not deposited on necessary areas, making it impossible to obtain a desired color image.

If the three-color images are formed in any other order, the superimposition of the images as shown in Table 1 will be hindered due to light absorption by the previously formed toner image, which is undesirable.

Table-5 The table shows the overall exposure light/toner combinations, ○, △, ×
respectively indicate whether the next image formation using the previously formed toner is possible, intermediate, or impossible.

() indicates the time of image formation during the final full-surface exposure.

In this case, even if the entire surface is irradiated with a sufficient amount of exposure light, there is little possibility that potentials will be generated in other filter parts, so (x) can also be used.

As for the whole surface exposure, the case of using FIG. 13 or a single light source having an even narrower distribution and effectively transmitting only a specific filter will be described.

In this case, the amount of light for full-surface exposure may be larger than the above range from this point of view, but it is the same that a wavelength at which toner absorption is small should be selected in consideration of the relationship with toner absorption. It is necessary to satisfy the following conditions.

In order to satisfy the conditions of the present invention using a single light source, the maximum wavelength of the spectral distribution must have a reflectance of 40 in the reflection region of the toner deposited first.
% or more, and furthermore, those whose spectral transmittance is 40% or more with respect to the filter through which the wavelength should be transmitted.
In the case of the toner and filter shown in FIG. 6, in the case of full-color exposure shown in FIG. 13, when a full color image is to be formed, the order of image formation is preferably yellow, magenta, cyan, or yellow, cyan, magenta, or magenta, cyan, yellow.

Among these, it can be performed in the order of magenta, cyan, and yellow in particular, which encodes the order of color reproduction that is sensitive to the human eye and provides preferable results.

Next, development suitable for the method of the present invention will be described.

There are no particular limitations on the development method, conditions, equipment, etc. for the development in forming a multicolor image by the method of the present invention, but the toner should be The developer layer contained therein does not come into direct contact with the surface of the photoreceptor. It is preferable to use a developing method called non-contact development.

FIG. 5 shows an example of a developing device suitable for performing the above-mentioned non-contact development. 40 is a layer thickness regulating blade that regulates the thickness of the developer layer formed on the developing sleeve 7; 44 is the developing sleeve 7;
2, a scraper blade for removing the developer layer after development; 42, a stirring rotor for stirring the developer in the developer reservoir 47; 38, a toner hopper; 39, a toner hopper 38;
A toner replenishing roller 45 and 46 which has a recess into which the toner enters the surface replenishes toner from the developer reservoir 47, applies a bias voltage that may have a vibrational component to the developing sleeve 7 via a protective resistor R, and performs development. This is a power source for forming an electric field between the sleeve 7 and the photoreceptor 41 to control the movement of toner, and the figure shows that the developing sleeve 7 and the magnet 43 rotate in the directions of the arrows. , even if the developing sleeve 7 is fixed, the magnet body 43 is fixed, or the developing sleeve 7 and the magnet body 43 are fixed.
Even if they rotate in the same direction.'' When the magnet body 43 is fixed, normally, in order to make the magnetic flux density of the magnetic pole facing the photoreceptor 41 larger than the magnetic flux density of other magnetic poles, the magnetization is strengthened or a magnetic pole of the same or different polarity is placed there. Two magnetic poles are sometimes provided close to each other.

In such a developing device, the magnetic pole of the magnet body 23 is usually 500 to 500.
It is magnetized to a magnetic flux density of 1500 Gauss, and the developer in the developer reservoir 47 is attracted to the surface of the developing sleeve 7 by the magnetic force, and the attracted developer is transferred to the layer thickness regulating blade 44.
The developer layer is formed with its thickness regulated by , and the developer layer moves in the same direction or in the opposite direction to the direction of the rotation arrow of the photoreceptor 41, so that the surface of the developing sleeve 7 faces the surface of the photoreceptor 41. The electrostatic image on the photoreceptor 41 is developed in the developing area, and the remainder is removed from the surface of the developing sleeve 7 by a scraper blade 44 and returned to the developer reservoir 47.

As the developer used in the method of the present invention, a one-component non-magnetic developer or a so-called one-component magnetic developer that uses only a magnetic toner containing a magnetic material can be used. A so-called two-component developer consisting of a mixture of a non-magnetic toner and a magnetic carrier is used, which makes it possible to obtain a toner with a clear color without the need to contain a magnetic substance, and toner charge control can be easily controlled. It is preferable. In particular, when magnetic carriers are used in resins such as styrene resins, vinyl resins, epoxy resins, rosin-modified resins, acrylic resins, polyamide resins, epoxy resins, and polyester resins, triiron tetraoxide, γ-ferric oxide, and chromium dioxide ,
Dispersed particles of ferromagnetic or paramagnetic substances such as manganese oxide, ferrite, manganese-copper alloy, etc.
Alternatively, it is preferable to use an insulating carrier having a resistivity of 10 8 Ωcm or more, preferably 10 I 3 Ωcm or more, which is made by coating the surface of these magnetic particles with a resin as described above. If this resistivity is low, the developing sleeve 7
When a bias voltage is applied to the carrier particle, is there an electric charge?
, ij are injected, causing problems that carrier particles tend to adhere to the surface of the photoreceptor 41 and that a sufficient bias voltage is not applied.

In particular, when the carrier adheres to the image forming body 41, it does not adversely affect the tone of the color image.

The resistivity was determined by placing particles in a container with a cross-sectional area of 0.50 cm' and tapping, then applying a load of I kg/cm2 on the packed particles, and measuring the relationship between the electrode that also served as the load body and the bottom electrode. This value is obtained by reading the current value when a voltage that generates an electric field of 100 OV/cm is applied.

Furthermore, if the average particle size of the carrier is less than 571 m, the magnetization will be too weak, and if it exceeds 50 μm, the image will not be improved.
In addition, breakdown and discharge tend to occur, making it impossible to apply high voltage, so the average particle size should not exceed 57 zm.]
The thickness is preferably 250 μm or less, and can be easily set so that only toner adheres to the electrostatic image and no fogging occurs without fear of leakage. Note that in order to more effectively control the development movement of toner by applying such a bias voltage,
- The toner may also contain a magnetic material such as that used in magnetic carriers to the extent that color clarity is not impaired.

The above is the welfare of the developing device and developer preferably used in the method of the present invention, but the present invention is not limited thereto.
The developing device and developer described in each of the publications No. 553 to 116554 may be used, and more preferably, the developing device and developer described in Japanese Patent Application Nos. 58-57446 and 58-96900 to 96903 previously filed by the applicant of the present application may be used. No. 58-97973
Non-contact development with a -component developer or two-component developer, that is, an image carrier (When there is no potential difference between the surface of the photoreceptor and the developing sleeve) Conditions are set so that the thickness of the developer layer formed on the developing sleeve is thinner than the gap between the surface of the image carrier and the developing sleeve. It is best to develop with

[Example I]

Image formation was performed using the image forming apparatus shown in FIG. 4. The image carrier 41 has a nickel base, a 5e-Te photosensitive layer with a long wavelength sensitization of 60 μm in thickness, and a structure shown in FIGS. 1(a) and 2(C) with a thickness of +7I1 m. A color separation filter with a thickness of 2 It m and a color separation filter with a thickness of 2 It m and a filter size Q of 100 μm and a color separation filter having a spectral characteristic shown in FIG.
A photoreceptor is provided by adhering the film provided on the second polyester film to the photosensitive layer, and its peripheral speed is 180
/sec. This image carrier 41 is heated by a DC scorotron corona discharger 4 so that the surface level of the image carrier 41 is 120.
It was charged to 00V.

For the three color lights of red (R), green (G), and blue (B), the first
The exposure amount is ffi L RO using the entire surface exposure light shown in FIG.

Image evaluation of color expression was performed on images with twice the size of LGO and LBO.

Next, while performing image exposure, the image carrier 41 was charged to a surface potential of +500V using a secondary charger 5 consisting of a Scotron corona discharger having an alternating current component. During image exposure, infrared and ultraviolet light was cut off using a filter in advance.

Next, by performing uniform exposure through a blue filter, the white area of the original +48QV and the black area of the original approximately 3
An electrostatic image was formed with a contrast of 00v. This potential contrast is approximately 1 when using a transparent insulating layer.
/3.

This electrostatic image was developed using a developing device 17Y as shown in FIG.

In developing device 17Y, magnetite is 80wt% in the resin.
Contains dispersed particles, average particle size is 2571m, magnetization is 20cm
The second carrier with u/g1 resistivity of 1014 Ωcm or more:
A developer consisting of a positively charged non-magnetic toner with an average particle diameter of 10 μm, which is made by adding 10 parts by weight of a benzine derivative as a yellow pigment to a styrene-acrylic resin and other charge control agents, is used so that the ratio of the toner to the developer is 20 wt%. It was used under the following conditions. Further, the outer diameter of the developing sleeve 7 is 30 mm, its rotation speed is 1100 rpm, and the N of the magnet body 43 is 30 mm.

The magnetic flux density of the S magnetic pole is 900 Gauss, and the rotation speed is lQOOr.
p.m.

The thickness of the developer layer in the developing area is OJmm, the gap between the developing sleeve 7 and the image carrier 41 is 0.5 mm, and the developing sleeve 7 is
+400v DC voltage and 2,0KHz, 1000
The non-contact development conditions were such that a superimposed voltage of an AC voltage of V was applied.

Incidentally, while the electrostatic image was being developed by the developing device 17Y, the other developing devices 17M and 17C, also shown in FIG. 2, were kept in a non-developing state. This can be done by disconnecting the developing sleeve from the power supply 45, 46 and leaving it in a floating state, or by grounding it, or actively applying a DC bias to the developing sleeve with the same polarity as the electrostatic image, or with the opposite polarity or with the same polarity as the toner charge. This is achieved by applying a voltage, and among these, it is preferable to apply a DC bias voltage. Further, the driving of the developing device was stopped during non-developing time.

It is assumed that the developing devices 17M and 17C are also developed under the same non-contact developing conditions as the developing device 17Y, so the developing sleeves.
The second developer layer does not need to be removed. This developer 17M
In this case, the developer in the developer 1.7Y is changed to a toner containing boritungstophosphoric acid as a magenta pigment instead of a yellow pigment.
For C, a developer was used in which the toner was changed to a toner containing a copper phthalocyanine derivative as a cyan pigment. Of course, color toners based on other pigments or dyes can be used, and the order of developing colors can be appropriately determined so as to obtain a clear color image.

In particular, the order of developing colors may be related to the sharpness of the color image and the potential contrast that can be obtained, and therefore needs to be carefully determined.

The surface of the image carrier 41 developed by the developer 17Y was recharged to a surface potential of +600 V by a scorotron corona charger, and then uniformly exposed to light through a green filter. The potential of the electrostatic image thus obtained was +550V for the white background and -250V for the black background. This electrostatic image was developed in developer 1.7M under the same conditions as in developer 1.7Y, except that a voltage of +500 cm for the DC component and 2.5 KI to Tz, 2000 cm for the AC component was applied to the developing sleeve. Developed.

Similarly, a scorotron corona charger increases the surface potential to +
After being recharged to 700 μm, uniform exposure was performed through a red filter. As a result, an electrostatic image of +350V on the black background part is formed with respect to +600V on the white background part, and this electrostatic image is applied to the developing sleeve with a DC component of 630V and an AC component of 2.
Developing was carried out in the developing device 17C under the same conditions as in the developing device 17Y except that a voltage of 5 KHz and 12000 V was applied.

When this third development is performed and a three-color image is formed on the image carrier 41, the corona discharger 11 is activated, thereby making it easier to transfer the color image. The image was transferred to a copy paper 8 by a transfer device 9, separated by a separator 10, and fixed by a heat roller fixed fixer 18.

The image carrier 41 to which the color image has been transferred is subjected to static electricity removal by the static eliminator 19 while being irradiated with white light, and the cleaning device 1
The remaining toner was removed from the surface by the cleaning blade No. 2, and when the surface on which the color image was formed passed through the cleaning device 12, one cycle process of color image recording was completely completed.

[Example 2] Image formation was performed using the image forming apparatus shown in FIG. 4. The image carrier 41 has a 60 μm thick As25es photosensitive layer on a nickel base, and a 20 μm thick As25es photosensitive layer on a nickel base.
Each filter size has the structure shown in FIG. 1 (, ) and FIG. 2 (e) of m, and has the spectral characteristics shown in FIG. 12!
, 50 μm, and 1250 μm, each with a thickness of 2 μm, was provided on a polyester film with a thickness of 15 μm, and a photoreceptor was provided by adhering the film to the photosensitive layer, and the peripheral speed was 180 mm/see. did. This image carrier 41 was charged with a DC scorotron corona discharger 4 so that the surface level of the image carrier 41 was -2000V.

For the three color lights of red (R), green (G), and blue (B), the first
Using the full-face exposure light shown in FIG. 3, the exposure amount is LRO, at which the potential generated by full-face exposure is approximately saturated.

It was four times more than LGO and LBO. This is done in consideration of the fact that as the filter size becomes smaller, the proportion of adhesion outside a specific filter increases. Image evaluation of color expression was performed in the same manner.

Next, while performing image exposure, the image carrier 41 was charged with a secondary charger 5 consisting of a Suftron corona discharger having an alternating current component so that the surface potential of the image carrier 41 was +200 cm. During image exposure, infrared and ultraviolet light was cut off using a filter in advance.

Next, by uniformly exposing the image through a green filter, an electrostatic image having a contrast and a last of about 300 cm was formed, with +180 V for the white background of the original and -150 V for the black background of the original. This potential contrast was about 1/3 of that when a transparent insulating layer was used.

This electrostatic image was developed using a developing device 17Y as shown in FIG.

In the developing device 17Y, the magenta developer in Example 1 was used. The outer diameter of the developing sleeve 7 is 30 mm, the rotation speed is 1100 rpm, the magnetic flux density of the N and S magnetic poles of the magnet body 43 is 900 Gauss, and the rotation speed is 1. OOOrpm, the thickness of the developer layer in the developing area is 0.7 mm, the gap between the developing sleeve 7 and the image carrier 41 is 1.0 mm, and the developing sleeve 7 has +
Non-contact development conditions were used in which a superimposed voltage of 100 V DC voltage and 2.5 KHz, 2000 V AC voltage was applied.

Incidentally, while the electrostatic image was being developed by the developing device 17Y containing magenta toner, the other developing devices 17M and 17c, also shown in FIG. 2, were kept in a non-developing state.

That is, disconnecting the developing sleeve from the power source 45, 46 and leaving it in a floating state, or grounding it.
or positively electrostatic image on the developing sleeve (or with the same polarity)
- This is achieved by applying a DC bias voltage of the opposite polarity or the same polarity as the charging of the energizer, and it is particularly preferable to apply a DC bias voltage. Further, the driving of the developing device was stopped during non-developing time. Since the developing devices 1.7M and 17C are also assumed to perform development under the same non-contact developing conditions as the developing device 17Y, the developer layer on the developing sleeve does not need to be removed. The cyan developer in Example 1 was used in the developing device 17M, and the yellow developer in Example 1 was used in the developing device 17C.

Of course, color toners based on other pigments or dyes can be used, and the order of developing colors can be appropriately determined so as to obtain a clear color image. especially,
The order of colors to be developed may be related to the sharpness of the color image and the potential contrast obtained, so it must be carefully determined.

The surface of the image carrier 41 developed by the developer 17Y was recharged to a surface potential of +300 cm by a scorotron corona charger having an AC component, and then uniformly exposed to light through a let filter. The potential of the electrostatic image thus obtained was +250V for the white background and -50V for the black background. This electrostatic image is transferred to a developing sleeve using a DC component element tso.
v, AC component 2.5KHz.

Developing device 1 except for applying a voltage of 2000V? Developing was carried out under the same conditions as in Y, using the developing device 17M replaced with one having cyan toner.

Similarly, after being recharged to a surface potential of +400 cm using a scorotron corona charger having an AC component, uniform exposure was performed through a blue filter.

To this, the background part → -300■, the black part +
A 50V electrostatic image is formed, and this electrostatic image is transferred to a developing sleeve with a DC component of +200cm and an AC component of 2.5K HZ, 20
Developing was carried out under the same conditions as in developer +7Y, except that a voltage of 00V was applied, using developer 7C, which was replaced with a developer having magenta toner.

When this third development is performed and a three-color image is formed on the image carrier 41, the corona discharger 1.1 is activated to facilitate the transfer of the color image. Then, the image was transferred onto copy paper 8 using a transfer device 9, separated using a separator 10, and fixed using a heat roller fixer 18.

The image carrier 41 to which the color image has been transferred is subjected to static electricity removal by a static eliminator 19 while being irradiated with white light, residual toner and toner are removed from the surface by a cleaning blade of the cleaning device 19, and the color image is removed. When the image-formed surface passes through the cleaning device 12, one cycle process of color image recording is completely completed.

Not limited to image forming apparatuses using the developing method described in Table 7 below,
As a modification of the developing method without rubbing the photoreceptor, a method is proposed in which only the toner is extracted from the composite developer onto a developer transport carrier and one-component development is performed using the toner in an alternating electric field (Japanese Patent Laid-Open No. No. 59-42565, patent application No. 58-2314
No. 34), a method of developing with a two-component developer in an alternating electric field by providing a linear or mesh control electrode (Japanese Patent Application Laid-open No. 56
-125753), and an apparatus using a method of developing with a two-component developer in an alternating electric field (Japanese Patent Application No. 58-97973) is also applicable to the multicolor image forming apparatus method according to the present invention. Needless to say, it is included.

In the above embodiments, corona transfer is used as the toner image transfer method, but other methods may also be used. For example, Japanese Patent Publication No. 46-41679, 4g-
When the adhesive transfer method described in Japanese Patent No. 22763 is used, transfer can be performed without considering the polarity of the toner. Furthermore, a method of directly fixing a photoreceptor, such as electrofax, can also be adopted.

Furthermore, the layer structure of the photoreceptor is changed by providing an insulating layer, a photoconductive layer, a transparent conductive layer, and a filter as shown in Japanese Patent Application No. 59-1.99547. It is also possible to adopt a configuration in which development is performed from the insulating layer side by applying imagewise exposure or full-surface exposure.

In the present invention, the preferable full-surface exposure photoelectricity is the same for a portion of the color filter and a portion of the transparent filter as disclosed in Japanese Patent Application No. 59-198167 and No. 59-198166, in which a portion of the filter is transparent or opaque.

Further, the present invention includes primary charging, secondary charging with a polarity substantially opposite to the -order charging, recharging after image exposure for smoothing the potential pattern, whole surface exposure with specific light, and development with a specific color toner. It can also be used in an image forming method that returns the image. (Japanese Patent Application No. 60-229524) Furthermore, the present invention is
201085 and 60-245177, a photoreceptor consisting of an insulating layer and a photosensitive layer having a color separation function was similarly subjected to primary charging, secondary charging, and simultaneous image exposure, followed by full-surface exposure with specific light and specific light. Development with color toner, image forming method that repeats recharging to smooth the potential pattern, primary charging, secondary charging with substantially opposite polarity to secondary charging, and smoothing of the potential pattern after image exposure. It can also be used in an image forming method in which recharging, full-surface exposure with specific light, and development with specific color toner are repeated.

In this case, since the spectral sensitivity distribution of the photosensitive layer is often sensitive to other wavelength ranges as well as color separation filters, exposure of the entire surface to specific light produces a potential pattern in other parts as well. Color mixing and resolution loss may occur. Good color reproduction can be achieved by properly exposing the entire surface to specific light.

In addition, all of the above explanations have been made regarding examples of color copying machines that use so-called three-color separation filters and three primary color toners, but embodiments of the present invention are not limited to this, and various types of multicolor image recording It can be widely used in devices, color electrophotographic printers, etc. It goes without saying that the combination of the color of the separation filter and the color of the toner corresponding thereto can be arbitrarily selected depending on the purpose.

In the multicolor image forming process described above, each full-surface exposure light does not necessarily have to be B SG or R light.

That is, as shown in Japanese Patent Application No. 59-198127, in the filter section through which the entire surface of the photoreceptor has already been exposed,
Since the charge at the interface between the insulating layer and the photoconductive layer has already disappeared, there is little change in the surface potential even if light passes through it again. Therefore, for example, instead of performing full-surface exposure in the order of blue light, green light, and red light, the order is blue light, cyan light, and white light;
Even if the yellow toner, magenta toner, and cyan toner are developed in this order, a multicolor image with good color reproduction of the original can be obtained. Of course, the exposure is not limited to this, and the entire surface may be exposed with light having other spectral distributions.

As mentioned above, when the entire surface exposure light passes through a part of the filter on the photoreceptor more than once, the light should be removed after development to completely erase the charge on the interface between the insulating layer and the photoconductive layer. It is further desirable to irradiate. (Special application 1981-1981 LI
No.) In this case, it is preferable to set the irradiation light intensity to the same light intensity as the entire surface exposure light intensity described above.

Further, the filter structure of the photoreceptor is not limited to a double filter structure, and its pattern, arrangement, etc. can be changed in various ways.

Functions and Effects of the Invention As described above, the present invention can completely or sufficiently prevent the mixing of potential patterns corresponding to different color information in a multicolor image forming photoreceptor, and therefore subtractive color mixing using color-separated potentials can be realized. Therefore, a multicolor image with high density and good color reproduction can be obtained.

Moreover, using this photoreceptor, after forming a first latent image by imagewise exposure, the entire surface exposure and development steps are repeated to form a potential pattern in at least one of the color separation functional parts, which conventionally requires multiple times. Only one image exposure is required, there is no need to align various images during image exposure or transfer, and the apparatus can be made smaller, faster, and more reliable. The resulting recorded matter also has high image quality with no color shift, no color mixture, and good color reproduction.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show embodiments of the present invention, and include FIG. 1 (A
), (B), and (C) are plan views showing the arrangement of filters on the surface of each photoreceptor. FIGS. 2(A), (B), (C), and (D) are cross-sectional views of the photoreceptor. Figure 3 [:1), (2), (3), (4,), (5),
[6], [7], and [8] are process flow diagrams showing image forming steps. FIG. 4 is a schematic diagram of a color copying machine. FIG. 5 is a sectional view of the developing device. FIGS. 6 and 7 are graphs of experimental data for development using a one-component developer. FIG. 8 is a graph showing the optimum conditions for development using a one-component developer. FIGS. 9 and 10 are graphs of experimental data for development using a two-component developer. FIG. 11 is a graph showing the optimum conditions for development using a two-component developer. FIG. 12 is a graph showing the transmittance of each filter. FIG. 13 shows the wavelength characteristics of fluorescent lamps: (a) blue, (b) green, and (C) red fluorescent lamps. FIG. 14 is a graph showing the relationship between the overall exposure amount of each color and the potential difference of the photoreceptor. FIGS. 15 (Δ), (B), (C), and (D) are cross-sectional views showing the state of toner adhesion to the photoreceptor. FIG. 16 is a spectral transmittance curve of the filter. l... Conductive substrate 2... Photoconductive layer 3... Insulating layer containing a color separation filter 4.1.4.15... Charger 5... Charger 8 with an exposure slit.・・Copy paper], 7.17Y, 17M, 17C・・Developer 41・
Photoreceptor drum R...Red filter section G...Green filter section B...Blue filter section T'B...Blue filter PG...Green filter F'R...Red filter L R...Red light LB... Blue light LG...Green light TY...Yellow toner TM...Magenta toner Ds/Developer T... Toner applicant Konishi Roku Photo Industry Co., Ltd. Figure 1 uI + 1 + - ■ Threat - U + □ Reita ← - Figure 7 Figure 6 Figure 8 J IKHzJ EAC[Kv7mml f UKH=1 Figure 1G Anti-fog procedure amendment 1, Indication of the case 1986 Patent Application No. 4.9090 2, Name of the invention Multicolor image Formation method 3, relationship with the case of the person making the amendment Patent applicant address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Contact address: Konishiroku Photo Industry Co., Ltd., 1-Sakura-cho, Hino-shi, Tokyo, 191 Japan (Telephone: 0425- 83-152
1) Patent Part 4, date of amendment order Voluntary /1107\5
, Section 1 of Claims 1 of the specification to be amended, and Section 1 of ``Detailed Description of the Invention''. 6. Contents of amendment (1) First, claim 1 of the specification is corrected as shown in the attached sheet. (2) "Detailed explanation of one invention in the specification" has been corrected as follows. No. Paper Claims (1) After charging and image exposure of a photoreceptor having a color separation function, by repeating full-surface exposure with specific light and development,
In a multicolor image forming method in which a plurality of toner images of different colors are superimposed and formed on the photoreceptor, each toner constituting the toner image already formed on the photoreceptor during the entire surface exposure is used for the entire surface exposure. A multicolor image forming method characterized by using light having a wavelength distribution that is substantially transmitted. (2) Full-surface exposure having a wavelength at which the reflectance of each toner constituting the toner image formed on the photoreceptor is 40% or more is used. multicolor image forming method. (3) The multicolor image forming method according to claim 1 or 2, wherein the plurality of l/toner images are toner images made of yellow, magenta, and cyan toners, respectively. (4) Blue light having a maximum wavelength of spectral distribution of 45 (1!240 nm) as light for full-surface exposure to form each of the yellow, magenta, and cyan toner images;
5501: green light that is 40nm, 650:, +40
A patent characterized in that the spectral reflectance of each toner constituting each toner image formed on the photoconductor is in the 40% range λ- with respect to the light of the wavelength using red light having a wavelength of Claims 1 to 3 - 144 p-h->1m
The multicolor image forming method described in μU. (5) The color separation means is composed of a filter, and a blue filter whose maximum spectral transmittance wavelength is 450 ± 40 nm and a green filter whose maximum spectral transmittance is 550 ± 40 nm are used, and the color separation means is a filter that has a peak wavelength of 450 ± 40 nm and a green filter that has a maximum wavelength of spectral transmittance of 550 ± 40 nm. Hikari-Jin-Citeichi 650
Red light having a wavelength of ±40 nm is used, and the spectral reflectance of each toner constituting each toner image formed on the photoreceptor 1 is 40% or more with respect to the light of the wavelength. A multicolor image forming method as described in claims 1 to 4. (6) The formation order of the plurality of toner images is yellow,
A patent in which the order of magenta, yellow, and cyan toner images is Any one of claims 1 to 5 (a multicolor image forming method as described in (7) Claims in which the toner development is performed under conditions where the developer layer and the surface of the photoreceptor are not in contact with each other. The multicolor image forming method according to item 1'.(8) The light ffi L of the entire surface exposure is 0.0000000000000 with respect to the light amount L o at which the potential generated by the entire surface exposure is approximately saturated.
7La≦L≦5L. A multicolor image forming method according to claim 1, characterized in that: (9) The light fiL of the entire surface exposure is particularly preferably 0.
9La≦L≦3L. A multicolor image forming method according to claim 8, characterized in that: -2, --

Claims (9)

[Claims] (1) A multicolor image forming method in which a photoconductor having a color separation function is charged and exposed to image, and then a plurality of toner images of different colors are formed in a superimposed manner on the photoconductor by repeating full-surface exposure with specific light and development. Multicolor image formation, characterized in that for the whole surface exposure, light having a wavelength distribution that substantially transmits each toner constituting the toner image already formed on the photoreceptor at the time of the whole surface exposure is used. Method. (2) Multi-coloring according to claim 1, characterized in that full-surface exposure having a wavelength at which the reflectance of each toner constituting the toner image formed on the photoreceptor is 40% or more is used. Image forming method. (3) The multicolor image forming method according to claim 1 or 2, wherein the plurality of toner images are toner images made of yellow, magenta, and cyan toners, respectively. (4) Blue light whose spectral distribution maximum wavelength is 450±40 nm as light for full-surface exposure to form each of the yellow, magenta, and cyan toner images;
Using green light with a wavelength of ±40 nm and red light with a wavelength of 650±40 nm, the spectral reflectance of each toner constituting each toner image formed on the photoconductor is 40% with respect to the light of the wavelengths.
A multicolor image forming method according to any one of claims 1 to 3, characterized in that: (5) A blue filter in which the color separation means is composed of filters, each of which has a wavelength of maximum spectral transmittance of 450±40nm, 550±40nm;
m, a red light having a wavelength of 650±40 nm is used, and a spectral reflectance of each toner constituting each toner image formed on the photoreceptor is 40 nm with respect to the light of the wavelength. %. The multicolor image forming method according to any one of claims 1 to 4. (6) The multicolor image forming method according to any one of claims 1 to 5, wherein the plurality of toner images are formed in the order of yellow and cyan toner images. (7) The multicolor image forming method according to claim 1, wherein the toner development is performed under conditions where the developer layer and the surface of the photoreceptor are not in contact with each other. (8) The light amount L of the full surface exposure is 0.7 L_ with respect to the light amount L_0 at which the potential generated by the full surface exposure is approximately saturated.
The multicolor image forming method according to claim 1, characterized in that 0≦L≦5L_0. (9) The light amount L of the entire surface exposure is particularly preferably 0.9
9. The multicolor side image forming method according to claim 8, wherein L_0≦L≦3L_0.