JPS6148872A - Formation of color image - Google Patents

Abstract

PURPOSE:To transfer a toner image to transfer paper by one positioning operation by forming a toner image on the 1st and the 2nd photosensitive bodies and performing transfer operation twice. CONSTITUTION:The 1st photosensitive body 1 formed by providing a conductive base 2 with a photoconductive layer 3 which has photosensitivity to the 1st chromatic color B is charged electrostatically and irradiated with a light image containing the component of the chromatic color B of a color image to form an electrostatic latent image, which is developed with the toner YT of the complementary color of the chromatic color B. Then, the 2nd photosensitive body 1a formed by laminating photoconductive layers 3a and 4a photosensitive to the 2nd chromatic color G and the 3rd chromatic color R on a conductive base 2a is charged twice to the different polarities to polarize both photoconductive layers 3a and 4a to the different polarities and then irradiated with light images containing components of the chromatic colors G and R of the color image to form an electrostatic latent image; the electrostatic latent image of the photoconductive layer 4a photosensitive to the chromatic color R is developed with toner MT of the complementary color of R and the latent image of the photoconductive layer 3a photosensitive to the chromatic color G is developed with toner MT of its complementary color. Then, the toner images YT, CT, and MT on the 1st and the 2nd photosensitive bodies 1 and 1a are transferred to the same transfer material 32.

Description

[Detailed description of the invention] Ritsuka Ritsuka The present invention relates to a color image forming method.

The conventional color image forming method involves exposing a photoconductor to light through blue, green, and red filters, and then applying the resulting electrostatic latent image to toner of its complementary colors, yellow, magenta, and cyan. The most common method is to develop and transfer these toner images onto the same transfer paper in an overlapping manner. In this case, it is necessary to correctly position each toner image and transfer it to the transfer paper, but this positioning is very difficult, and correct positioning inevitably increases the cost of the apparatus. In the conventional method described above, the toner image transfer operation must be performed by positioning at least twice, so the difficulty associated with positioning is particularly significant.

From the above viewpoint, two photoconductors are used, and toner images of two colors are formed on each of them, for example, black and red toner images are formed on one photoconductor, and blue and green toner images are formed on the other photoconductor. , and a method of transferring these to the same transfer paper has been proposed. According to this method, the toner image can be transferred onto the transfer paper with only one positioning, and the drawbacks of the above-mentioned methods can be alleviated. However, it is not easy to obtain a full-color image with natural colors using the method according to this proposal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image forming method that allows a toner image to be transferred to a transfer paper through one-time positioning, and that also allows a natural full-color image to be easily obtained.

In order to achieve the above-mentioned object, the present invention provides a first photoreceptor in which a photoconductive layer having photosensitivity to at least a first chromatic color (A) is provided on a conductive base material, and a color image is produced by IF electrophoresis. Said first
An optical image containing the chromatic color (A) component.

1st I! The surface of the three-photon material is irradiated to form an electrostatic latent image, the latent image is developed with an α-color toner that is complementary to the first chromatic color, and a second chromatic color CB) is applied to the conductive substrate. A second photoreceptor in which photoconductive layers each having photosensitivity are stacked on a third chromatic color (C) is charged with different polarities at least twice to polarize both photoconductive layers to different polarities, A light image containing the second and third chromatic color CB, C) components of the color image is irradiated onto the surface of the second photoreceptor to form an electrostatic latent image, and a third chromatic color (C
), the electrostatic latent image of the photoconductive layer is developed with a β-color toner of its complementary color, and the electrostatic latent image of the photoconductive layer is developed with a second chromatic color (B), which is photosensitive. A color image forming method is proposed, which is characterized in that the electrostatic latent image on the IX layer is developed with toner of one color complementary to the latent image, and the toner images on the first and second photoreceptors are transferred onto the same transfer material.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a color copying machine as an example of an image forming apparatus that implements the method according to the present invention, and this copying machine includes first and second photoreceptors 1. Two photoreceptors are provided. In this example, these photoreceptors are formed into a drum shape and are driven to rotate in a clockwise direction. In the illustrated example, a toner image is formed using yellow toner on the first photoreceptor 1, and a toner image is formed using cyan toner and magenta toner on the second photoreceptor 1a, but this combination may be arbitrary.

As schematically shown in FIGS. 1 and 2(a), the first photoreceptor 1 is mounted on a conductive base material 2 made of, for example, an aluminum drum, and is coated with light having photosensitivity to at least a first chromatic color A. It is constructed by laminating conductive layers 3. In this example, the chromatic color A is selected from one of the three primary colors of light, red, blue, and green, and in this example, this is blue.6 For example, an aluminum drum (S
e) is vacuum-deposited to a thickness of 60 μm to constitute a photoconductive layer 3, which is used as a first photoreceptor. As described above, the photoconductive layer 3 made of selenium has a photosensitivity Sλ shown by the solid line S1 in FIG.
500 nm).

On the other hand, as schematically shown in FIGS. 1 and 3(a), the second photoreceptor 1a is a conductive substrate 2a such as an aluminum drum that has photosensitivity only for the second chromatic color. 1st to have
It is formed by laminating a photoconductive layer 3a and a second photoconductive layer 4a which transmits a second chromatic color B and has photosensitivity to a third chromatic color C. In this case as well, in this embodiment, the chromatic colors B and C are composed of the three primary colors of light, and in this embodiment, B is green and C is red. To give a specific example, the first photoconductive layer 3a is a layer in which selenium containing 10% tellurium, that is, an S e -Te alloy, is vacuum-deposited to a thickness of 60 μm on a conductive base material 2 a of aluminum (as necessary). (denoted as L layer according to the
The second photoconductive layer 4a consists of a layer (also referred to as M layer) overcoated by a dipping method on the 1M layer, and a zinc oxide resin layer dye-sensitized with methylene blue on the 1M layer to a thickness of 15
It consists of μ coated using a dipping method. The photosensitivity of the second photoconductor J54'a is shown by the dashed line SU2 in FIG.
It can be seen that it is sensitive to red light with a wavelength of 0 nm.

In this example, the second photoconductive layer 4a is also sensitive to near-infrared light of 700 nm or more, but the reason for this will be explained later. Daiichi Kosen again? The L layer of the TC layer 3a has a sensitivity Sλ to light having a wavelength of blue-green light (or longer), as shown by the solid line SL2 in FIG.
Mffl has a light transmittance T shown by the broken line TM2 in FIG.
A has substantially photosensitivity only to light of g (second chromatic color). The first photoconductive layer 3a may be composed of a single layer of photoconductive material having photosensitivity only to green light. In addition,
Since the M layer only functions as a green filter, MFIj is omitted in FIG. 3, and the first photoconductive FS 3 a is shown to be composed of only the L layer.

Referring again to FIG. 1, a contact glass 5 is located at the top of the copying machine, and a document 6 to be copied is placed on top of the contact glass 5.The copying machine shown in FIG. In the example, as shown in FIG. 2(a) and FIG. 3(c), the white background part W has a black part BL, a cyan part C, a magenta part M, a yellow part Y, a red part R1, a green part G, and a blue part. Assume that the document 6 of section B on which seven color images are formed is to be copied.

The operation of copying the above-mentioned original will be explained below in order for each photoreceptor. FIGS. 4 and 5 are graphs showing changes in the surface potential of the photoreceptor in each copying process.

[1] During the copying operation, the first photoreceptor 1 is rotated clockwise as shown in FIG.
The surface of the photoreceptor 1 is charged to a predetermined polarity (positive in this example) in the dark.In this example, it is assumed that the surface potential of the first photoreceptor 1 after charging is about +750V (see Fig. 4). )).

The surface of the first photoreceptor described above is irradiated with the optical image of the document 6 shown in FIG. A light source 9 located below illuminates the original 6 while scanning, and the reflected light is reflected by the first to third mirrors 10, 11, which also scan.
．． 12, passes through the imaging lens 13, is reflected by the dichroic mirror 14 and other mirrors 15 and 16, and is reflected by the first
It reaches the photoreceptor 1. The dichroic ink mirror 14 has a reflectance distribution shown by the broken line R1 in FIG. 6, and reflects blue light and transmits green and red light. A light image of (first chromatic color A component) is formed, and an electrostatic latent image corresponding to this is formed. That is, the white area W, cyan area C, and magenta area M of the original 6
The light reflected at the blue portion B includes blue wavelength light (400 to 500 nm), and the blue wavelength light is reflected by the dichroic ink mirror 14, so these document portions W, C,
The photoreceptor portions corresponding to M and B become bright exposed areas, and since the photoconductive layer 3 has photosensitivity to at least the blue color, its charge disappears and becomes approximately O■ (Fig. 2). (a)
and Figure 4 (b)). On the other hand, almost no light reaches the photoreceptor 1 from the black part Bi- of the original 6, and the light reflected by the yellow part Y, red part R1, and green part G does not contain any blue component light. The light is not reflected by the dichroic ink mirror 14.

Therefore, charges remain in the photoreceptor portions corresponding to these document portions BL, Y, R, and G, and positive electrostatic latent images BLI, Yl, and R1°Gl are formed as shown in FIG. 2(a). fart What is the surface potential of the latent image at this time?

Due to natural attenuation, etc., the potential is usually slightly lower than the potential immediately after charging, about +700 V in one example (see FIG. 4 (b)).

As described above, the photoconductor portion on which the latent image is formed is toner having a complementary color relationship with the first chromatic color A (chromatic color A in this example).
When passing through the yellow developing device 18 (FIG. 1) containing yellow toner YT (since yellow toner YT is blue), the negatively charged yellow toner YT forms positive latent images BLI, Yl, R1, Gl.
The yellow toner image is electrostatically attracted to the yellow toner image (FIG. 2(b), FIG. 4(c)).

[2] The second photoreceptor 1a is also rotated clockwise in synchronization with the first photoreceptor 1a, and at this time, the surface of the photoreceptor 1a is charged to a predetermined level in the dark by the primary charger 7a shown in FIG. It is charged with polarity (negative in this example). This is called -order charging, and due to this -order charging, the surface potential of the second photoreceptor 1 becomes, for example, about -2100V (Fig. 5 (a)), and at this time, as shown in Fig. 3 (a). As shown in FIG. captured by the side.

Next, as shown in FIG. 3(b), the secondary charger 8
By applying a voltage of, for example, +4.7 V to a, the surface of the second photoreceptor 1a is subjected to primary charging and reversible positive charging in the dark (secondary charging). As a result, a part of the negative charge on the surface of the photoreceptor due to the -order charging is discharged, and the surface potential is lowered by the positive charge captured by the first photoconductive layer 3a.

It becomes about -700v (Figure 3 (b) and Figure 5).
Figure (b)). At this time, the second photoconductive layer 4a has a thickness of -1400
V, the first photoconductive layer 3a is charged (polarized) to +700V.

On the other hand, the light from the original that reaches the dichroic mirror 14 during illumination of the original 6 described above is divided into green component light (500 to 600 nm) and red component light (600 to 600 nm).
00 to 700 nm) is the only dichroic mirror14
After being reflected by the mirror 19, this light reaches the second photoreceptor 1a, where it forms an optical image of green and red components. As a result, an electrostatic latent image is formed on the photoreceptor la, but this photoreceptor is charged twice with different polarities by primary and secondary charging as described above, and the first photoconductive layer 3a and the second photoconductor Jg4a are each polarized to different polarities.

The latent image is shown in FIGS. 3(C) and 5(C) and is formed as described below.

First, since almost no light reaches the photoreceptor 1a from the black area BL of the original 6, the surface potential state of the photoreceptor portion corresponding to the black area BL is almost the same as after secondary charging.In this example, natural attenuation, etc. The surface potential decreases slightly, including −
The voltage shall be 600V. In this way, a negative black latent image BLI is formed. Conversely, the surface potential of the second photoreceptor portion corresponding to the white background portion W is approximately Ov.

Blue light does not reach the second photoreceptor portion corresponding to the blue area, and even if it does, the second photoconductive layer 4a does not show sensitivity to blue light and the first photoconductor J? Since the M layer of J 3 a is a green filter, blue light does not pass therethrough, and the charges on both photoconductive layers 4a and 3a remain.

Therefore, like the part corresponding to the black part BL, this part becomes a blue latent image B1 with a surface potential of, for example, about -600V.

Since the light from the cyan color area C and the green area G of the original 6 does not contain light with a red wavelength (600 to 700 nm), the second photoconductor J of the photoreceptor portion that is irradiated with these lights
'34a does not become conductive, but since these lights contain green light, they pass through the M layer of the first photoconductive layer, which is a green filter, and pass through the first photoconductive layer 3a, which is sensitive to green light. becomes conductive and the charge here disappears. Therefore, the surface potential of these photoreceptor parts increases to the negative side compared to before irradiation, for example, about -1000V (theoretically it would be -1400V, but taking natural attenuation etc. into consideration, it was set to -1000V). .

In this way, a negative cyan latent image C1 is formed in these parts.
Similarly, negative green i9 t'RG 1 is formed.

Furthermore, the light from the magenta color part M, yellow part Y, and red part R of the original 6 has a red wavelength (600 nm to 700 nm).
Since the light of m) is included, the charges on the second photoconductive WJ4a that are irradiated with these lights disappear.

In this case, since the yellow light consists of red light and green light, this light passes through the M layer of the first photoconductive layer, which is a green filter, and charges the first photoconductive layer 3a, which is photosensitized to green. disappear, and the surface potential of this part becomes approximately Ov. In addition, magenta color light and red light have green wavelengths (500 nm to 600 r
+m), the first photoconductive layer 3a
The light does not pass through the M layer, and the charge on the first leading TL layer 3a does not disappear. Therefore, the surface potential of the photoreceptor portion irradiated with these lights is converted to a positive value of, for example, about +500V.

By irradiating the photoreceptor 1a with light from the original as described above, a negative cyan latent image Ct, a green latent image G1, a blue latent image B1, . A black latent image BL1 and a positive magenta latent image aM1. A red latent image R1 is formed respectively.

Among the latent images formed on the second photoreceptor 1a as described above, the latent images BLl, C1, G due to the charges on the second photoconductive layer 4a
1 and Bl are developed with toner of β color, which is a complementary color to color C, to which the photoconductive layer 4a has photosensitivity. In this example, the second
Since the photoconductive layer 4a has photosensitivity to red, it is at first glance conflicted with the cyan toner of its complementary color. That is, the cyan developing device 30 containing cyan toner CT (FIG. 1)
When a latent image passes through the latent image, the positively charged cyan toner CT with the opposite polarity to the latent image BLI, 'CI, Gl, Bl
to form a cyan toner image (Fig. 3(d)).
and Figure 5(d)).

Next, a blue latent image B1 to which cyan toner CT is attached and a magenta latent image M1. To the black latent image BLI and the red latent image R1, toner of γ color complementary to the color to which the first photoconductive layer 3a has photosensitivity, that is, magenta toner in this example, is attached. Treat as follows.

By setting the surface potential of the latent image to which the magenta toner is to be attached to a polarity different from that of other photoreceptor portions (including OV), the magenta toner can be attached only to this portion. For this purpose, the second photoconductive layer 4a is coated on the surface of the photoreceptor with red light (wavelength 600 to 700) to which the second photoconductive layer 4a is sensitive.
nm) to dissipate the charge on this layer 4a, recall the latent image b) stored in the first photoconductive layer 3a, and attach magenta toner to this. cyan toner has already adhered to it, and since this toner uses copper phthalocyanine, almost no red light passes through it, as shown in FIG. From this point of view, the surface of the photoreceptor after passing through the cyan developing device 30 shown in FIG.
The lamp 34 uniformly irradiates near-infrared light with a wavelength of about 00 nm to 750 nm. As can be seen from FIG. 8, light in this wavelength range can pass through the cyan toner on the photoreceptor and reach the surface of the photoreceptor, so that the second photoconductive layer 4a has photosensitivity even to near-red light. can eliminate the electric charge of

In this way, the surface potential of the latent images BLI, Bl is reversed to positive, and the latent images of BLI, Ml, R1, Bl become positive (third
Figure (e) and Figure 5 (e)).

Next, when the latent image passes through a magenta developing device 31 containing magenta 1 hener, the negatively charged magenta toner MT forms a predetermined latent image BLI, Ml.

It attaches to R1 and Bl (Fig. 3(f) and Fig. 5(f)).

Note that even if the light reflected by the original contains near-infrared light,
These can be cut by optical elements in the optical path up to the photoreceptor, so when exposing the photoreceptor, the second
The photoconductive layer 4a does not exhibit substantial sensitivity to near-infrared light, and the above-described effect can be obtained without any problem.

The toner image after development is transferred to the pre-transfer charger 18a (Fig. 1).
is uniformly charged positively or negatively. This charging aligns toners CT and MT with different charging polarities to one polarity,
Since it is prepared for transfer, the charging polarity may be either positive or negative.

In this example, this is set as negative.

[3] As described above, toner images are formed on the first and second photoreceptors, respectively, and these toner images are transferred to the transfer paper 32 conveyed by the transfer belt 33 shown in FIG.
On top, a transfer charger 35a.

35 (Fig. 3 (g), Fig. 2 (c)), and thus a full-color image that is the same as or similar to the original image is formed on the transfer paper, and in this case, the transfer operation is performed only twice. Therefore, the toner images on each photoreceptor can be aligned once and transferred to the transfer paper. The transferred color image is fixed by a fixing device (not shown), and each photoreceptor after the toner image is transferred is cleaned by a cleaning device 36,
The remaining toner is cleaned by 36a and the static electricity is removed, just as in a normal copying machine.

In the above embodiment, an electrostatic latent image is formed on each photoreceptor by illuminating and scanning a hard image on a document, but a printed color image can also be obtained from a soft color image. For example, using a laser that emits red, blue, and green light, or an LED array, etc., each photoreceptor can be exposed to light based on the image signal of a soft color image, and a latent image can be formed in the same manner as in the above embodiment. . In addition, when forming a latent image on a photoreceptor using a laser, LED array, etc., the photoreceptor is exposed to three types of light other than red, blue, and green, and each photoreceptor is The colors to which the first and second photoconductive sheets are sensitive may be set, and the toner used to form the color image may be the same as in the previous embodiment, so that the same results as in the previous embodiment can be obtained. Therefore, the aforementioned chromatic colors A, B, and C, in which the photoconductive layer of each photoreceptor has photosensitivity, do not need to be three primary colors.

In addition, chromatic color A in which the photoconductive layer of each photoreceptor has photosensitivity,
The combination of B and C is not limited to the illustrated example, and photoconductive layers having photosensitivity to each of the chromatic colors A, B, and C may be appropriately combined to constitute the first and second photoreceptors, and the combinations thereof may be combined. It is also possible to generate a potential on each photoreceptor so that a predetermined toner image can be obtained. However, if they are combined as in the illustrated embodiment, magenta toner and cyan toner are superimposed on one photoconductor and transferred to transfer paper.
Since no misalignment occurs between the toner images of magenta toner and cyan toner, it is possible to create a beautiful completed color image. As is well known, if the magenta toner image and the cyan toner image are even slightly misaligned on the transfer paper, it will be very noticeable, but even if the yellow toner image is slightly misaligned with these toner images, it will not be noticeable. This is because there is no such thing.

Furthermore, the order in which the toner images are transferred to the transfer paper is not limited to the illustrated embodiment; for example, the toner image of yellow toner may be transferred first, and then the toner images of magenta toner and cyan toner may be transferred. Of course.

In the illustrated embodiment, a dichroic mirror is used to guide only the light image of the necessary light wavelength component to each photoreceptor, but the second photoreceptor is irradiated with light from the original that does not pass through the dichroic mirror or filter. However, the first photoconductor may be illuminated with light from the FM document through a blue filter, or the blue filter may be placed in the optical path from the document to the first photoconductor. Alternatively, a layer having a filter function may be laminated on the photoreceptor, or the blue filter can be omitted by using a photoconductive layer of the first photoreceptor that is sensitive to only the blue component color. It is also possible to irradiate light from a document without passing through a filter.

The method of polarizing the first photoconductive layer and the second photoconductive layer of the photoreceptor is not limited to the illustrated embodiment, and various methods proposed in the prior art may be employed as appropriate.

As described above, according to the present invention, it is possible to obtain a natural full-color image with a small number of deviations in one position with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an example of a copying machine embodying the present invention, and FIGS. 2(a) to (c) are schematic explanatory diagrams showing an image forming/transfer process on a first photoreceptor. 3(a) to 3(g) are schematic explanatory diagrams similar to FIG. 2 for the second photoreceptor, and FIGS. 4 and 5 are graphs showing changes in surface potential of the first and second photoreceptors. , FIG. 6 and FIG. 7 are graphs showing the properties of the first and second photoreceptors, respectively, and FIG. 8 is a graph showing the transmittance of cyan toner. 1... First photoreceptor 1a... Second photoreceptor 2.
2a... Conductive base material 3.3a, 4a... Photoconductive layer BLI, CI, Ml, Yl, R1, Gl, Bl...
Latent image B LT, CT, MT, YT... Toner Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Wavelength On (nm) Figure 1 Wavelength Longevity (nm)

Claims (1)

[Scope of Claims] A first photoreceptor comprising a conductive base material and a photoconductive layer having photosensitivity to at least a first chromatic color (A) is charged, and a first chromatic color (A) of a color image is produced. A) The optical image containing the component is
The surface of the photoreceptor is irradiated to form an electrostatic latent image, and the latent image is transferred to the first
The second chromatic color (B) and the third chromatic color (C
) is laminated with a photoconductive layer having photosensitivity, respectively, and is charged with different polarities at least twice to polarize both photoconductive layers to different polarities from each other. The optical image containing the third chromatic color (B, C) components is
The surface of the photoreceptor is irradiated to form an electrostatic latent image, the electrostatic latent image of the photoconductive layer sensitive to a third chromatic color (C) is developed with a β color toner of its complementary color, and a second chromatic color (C) is developed. An electrostatic latent image on a photoconductive layer having photosensitivity to a chromatic color (B) is developed with a gamma color toner of its complementary color, and the toner images on the first and second photoreceptors are transferred onto the same transfer material. Characteristic color image forming method.