JPH0296781A - Image forming device - Google Patents

Abstract

PURPOSE:To permit a developing means which develops successively to obtain a sufficient developing contrast in an image forming device provided with plural developing means by specifying parts on an image carrier on which image exposing light is made incident. CONSTITUTION:The photosensitive drum 1 is provided with plural developing units, and a laser beam being a 2nd information signal 5 is made incident on the outer periphery of the photosensitive drum 1. Here, l2 is a distance between the part L2 on the photosensitive drum 1 and the part D2 on the photosensitive drum 1 facing the 2nd developing unit 6 developing a 2nd electrostatic latent image formed with a laser beam when a laser beam is made incident on the part L2. The distance l2 is set longer than a distance l1 between the part L1 on the photosensitive drum 1 and the part D1 on the photosensitive drum 1, which faces the 1st developing unit 4 developing a 1st electrostatic latent image formed with a laser beam when a laser beam is made incident on the part L1. Thus, the developing unit 6 developing successively can obtain a sufficient developing contrast.

Description

[Detailed Description of the Invention] ,-Itno! The present invention generally relates to an image forming apparatus, and in particular is used as a terminal equipment printer for various information devices such as computers, facsimiles, and CAD, and is capable of forming visible images in multiple colors in one print cycle. The present invention relates to a color image forming apparatus such as a multicolor electrophotographic copying machine.

[As is well known, in a color image forming apparatus such as this type of multicolor electronic X copying machine, the process of forming one image is
In many cases, an electrostatic recording method using electrophotography is used. Figure 3 shows a conventional color image forming apparatus in which the above-mentioned electrostatic recording method using electrophotography is adopted in the process of forming one image. It is. The JlE requirement of the color image forming apparatus shown in FIG. 3 seems to be 4 or less. II
In FIG. 3, the outer peripheral surface of the photosensitive drum L, which has a photoconductive layer coated on a conductive substrate and is rotatably supported in the direction of the arrow in FIG. (to negative polarity) and laser beam scanner.

The first information signal 3 is scanned onto the photoreceptor drum l using an LED, LCD, etc. (not shown), thereby forming a first static image 111 as a latent image (FIG. 4(a), V).

/ V L l ) is formed. The first electrostatic image Wj is reversely developed by a negatively charged developer stored in the first developing device 4 (FIG. 4(a), V
DILT), a visible image is formed by the developer.

The outer peripheral surface of the photoreceptor drum l on which the visible image is formed,
When the charger 11 charges the battery in a negative manner (for example, to a negative polarity), the first static ? The dark potential of the l1WI image is shown in Figure 4 (J
V illustrated in L).

4(b) to the VOZO shown in FIG. potential)
Also, V06. shown in FIG. 4(a). Figure 4 from Ding (
V illustrated in b). It rises to 2nd level (here,
I V OZ OI > l V (11L rule)
The second information signal 5 is scanned onto the photoreceptor drum l using the beam scanner, LED, LCD, etc. (not shown), so that the second static i! Latent image (Fig. 4(b), VLz
) is formed. The second static latent image is reversely developed by a negatively charged developer of a different color from the developer stored in the second developing device 6, and a visible image is formed by the developer. be done. The second developing device 6 may be of a non-contact developing type or a flexible type in order to avoid disturbing the visible image formed by the developer on the photoreceptor drum 1''2 by the first developing device 4. It is assumed that a contact development method is used. The visible image formed on the outer circumferential surface of the photoreceptor drum l through the above-mentioned process using a plurality of colors (in this example, two colors) of developer is as follows:
The image is transferred onto the transfer material 8-) 1 by the transfer charger 7, and the image is fixed by the fixing device 10. Photoreceptor drum 1]
- The remaining developer is removed by the cleaning device 9 to form a color image. tM is in a standby state to prepare for the execution of a re-Iff copy cycle! It becomes mu.

” - According to the color image forming apparatus having the above-mentioned configuration, for example, a color copy developed with a developer in which the color of the former and the color of the calculated value or data is different from the color of Image information that is easy to understand, such as a copy of a drawing developed with a developer of a different color from other parts, is obtained that is differentiated by the developer of multiple colors.

By the way, in the conventional color image forming apparatus having the above-mentioned configuration, as is clear by comparing and contrasting FIGS. 4(a) and 4(b), a second electrostatic charge is formed on the photosensitive drum l. The dark potential VOZO when the latent image is formed is higher than the dark potential VOI when the first latent image is formed on the photoreceptor drum i1-, so the second information signal The bright area potential VLZ due to the laser beam corresponding to the first information signal 3 is the bright area potential VLZ due to the laser beam corresponding to the first information signal 3.
− will be higher than. On the other hand, as described above, the second developing device 6 for developing the second electrostatic latent image employs a non-contact developing type or a flexible contact developing type. In order for the second developing device 6 to develop the second electrostatic latent image into an IIf visual image with sufficient image density and sharpness, the second electrostatic latent image must have a large latent image contrast (R, It is essential to have a difference Vi) between the bright ff! potential in the acid 7! latent image and the developing bias voltage. However, in the @2 second electrostatic PP1t, the difference value between the bright area potential Vt,z and the developing bias voltage (V, oc) is equal to the first electrostatic 7I! Bright area potential in latent image■
Since the value of the difference between the voltage and the developing bias voltage (Vo C) is smaller than the difference value between the voltage and the developing bias voltage (Vo C), it is not possible to obtain a sufficient developing contrast and an image with good quality cannot be obtained. Therefore, in order to ensure sufficient development contrast especially in the second electrostatic latent image, a method of increasing the developing bias voltage applied to the developing sleeve 6a of the second developing device 6 has been considered. When the developing bias voltage applied to the developing sleeve 6a of the second developing device 6 is set high, the visible image formed by the developer contained in the first developing device 4 is overlaid on the visible image formed by the developer contained in the second developing device. There was a problem in that the developer used in the process was fogged. Instead of the above-mentioned method, a method of lowering the optical attenuation potential due to the laser beam corresponding to the second information signal 5 was considered in order to lower the bright area potential V L Z in the second static tWj image. However, this method of reducing the optical attenuation potential due to laser light requires a high-output light source, which poses a problem in that the cost of the color image forming apparatus increases.

Therefore, the present invention was devised in order to solve the above-mentioned problems, and its purpose is to provide a plurality of developing units corresponding to each color of developer in order to accommodate the plurality of color developers individually. By providing an image forming apparatus that is capable of obtaining a good quality color image with sufficient development contrast using the second and subsequent developing units. be.

The above objects are achieved by an image forming apparatus according to the present invention. To summarize, the present invention includes an image carrier and a plurality of developing means arranged along the moving direction of the image carrier, and the image carrier is further provided than each of the developing means on the image carrier. In an image forming apparatus in which a latent image is formed by irradiating an image exposure light onto a region on the upstream side in the moving direction of a carrier, there is a difference between a region on the image carrier onto which the image exposure light is incident and a region on the image carrier. The distance between the developing means for developing a latent image formed by the irradiation of the imagewise exposure when the imagewise exposure is incident and the portion on the image @ carrier in a facing relationship is This image-forming rIt device is characterized in that it is set to become longer from the upstream side toward the downstream side in the direction of movement of the body.

five presentations 1 An embodiment of the present invention will be described below with reference to one drawing.

FIG. 1 shows a color image forming apparatus in which an electrophotographic electrostatic recording method is employed in the image forming process according to an embodiment of the present invention. (Although the overall configuration of an image forming apparatus according to an embodiment of the invention is already well known,
The [ff is as follows. That is, in FIG. 1, an image carrier, that is, a photosensitive drum 1 is disposed approximately at the center inside the color image forming apparatus main body (not shown) and is rotatably supported in the direction of arrow A in FIG. There is. In the vicinity of the outer peripheral surface of the photoreceptor drum 1, in the rotational direction l of the photoreceptor drum 1: a first charger 2, a developing means, that is, a first developer 4, a second developer, etc. Obi*Base11. Developing means or second developing devices 36 are arranged at predetermined intervals. In the gap defined by the first charger 2 and the first developer 4, a laser beam scanner,
The first information signal 3 is irradiated toward the outer peripheral surface of the photoreceptor drum l from an image exposure irradiation means such as an LED or an LCD (not shown). In the gap defined by the second charged $11 and the second developing device 6, the photoreceptor drum 1 is supplied from an image exposure irradiation means such as a laser beam scanner, an LED, an LCD (not shown), etc., as described above. The second information signal 5 is irradiated toward the outer circumferential surface of. The above configuration will be further explained as follows. The photoreceptor drum l is a photoreceptor drum in which an organic photosensitive agent is sprayed on the outer peripheral surface of an aluminum cylinder having a diameter of 60 mm. It is set to rotate in the direction of the arrow. The first charger 2 is configured to uniformly charge the outer peripheral surface of the photoreceptor drum 1 at a potential of 13 oov. The first information signal 3 is a laser beam, and the laser beam is applied to the outer peripheral surface of the photoreceptor drum l.
2, a first electrostatic latent image corresponding to document image information is formed on the outer peripheral surface of the photoreceptor drum l. The first developing device 4 is provided with a developing sleeve 4a facing the opening thereof, and a developing sleeve 4a facing the opening thereof.
A carrier consisting of ferrite particles of 0 to i 00=,
A two-component developer having 5 to 20 chromatic non-magnetic toner is contained therein. The second charger 11 is configured to uniformly charge the outer peripheral surface of the photoreceptor drum 1 at a potential of -800V (7). The second information signal 5 is
The laser beam scans the outer peripheral surface of the photoreceptor drum 1, thereby forming a second electrostatic latent image corresponding to the document image information on the outer peripheral surface of the photoreceptor drum 1. ing. The second developing device 6 is provided with a developing sleeve 6a facing the opening thereof, and -
A developer consisting of component magnetic toner is contained therein. Second
In the developing device 6, a thin layer of developer made of one-component magnetic toner is applied onto the outer peripheral surface of the developing sleeve 6a, and the second static latent image is visualized in a non-contact state. A non-contact developing device is used.

According to this embodiment, the laser beam as the second information signal 5 on the outer peripheral surface of the photosensitive drum 1 is incident on the irradiated area Lz of the photosensitive drum 1F and the area LZ. A second static region formed by the laser beam irradiation when the A distance intersection 2 between the second developing device 6 that develops the tl image and a portion DZ on the photoreceptor drum l in a facing relation is a laser beam that is the first information signal 3 with the outer peripheral surface of the photoreceptor drum 1. a region L1 on the photoreceptor drum 1 on which the light is incident, and a first static image formed by the irradiation of the laser light when the laser light is incident on the region L1; The distance is set to be longer than the distance 1+ between the developing unit 4 and a portion D+ on the photosensitive drum l that faces the developing device 4. As mentioned above, the distance Jl
ztMore than the above-mentioned distance intersection 1, it was decided to set:
This is due to the following circumstances.

In the image forming apparatus having the configuration shown in FIG. 1, the present inventors set the distance reference 1 to 10 mm, the distance 1z = lO,J, and 5.20.25 mm, respectively. The intensity of the laser beam that is the first information signal 3 and the intensity of the laser beam that is the second information signal 5 are both 2.5.
The surface potential of the photoreceptor drum l and the image quality of the visible image at the above-mentioned positions and Dz were investigated when set to pJ/crn'. As a result, in the portion DI, the surface potentials of the photoreceptor drums t and h are Vow (i.e., dark area potential) = -500V, VLI (i.e., bright area potential)
-100V, and a good image was obtained by applying a developing bias voltage in which an AC voltage component of 1600 Vp-p was superimposed on a DC voltage component of -500 V to the developing sleeve 4a. At the site Dz, the distance is 1ztlz
= 10, 15, 20, 25 mm, respectively, the surface potential of the photoreceptor drum l is Vozo (that is, $fl potential) potential of the part) = -550V
, and there was no change. Here, the distance intersection l is the intersection z
"10, 15, 20.25 mm, respectively, of the surface potential of the photoreceptor drum 11: V+-
1 (that is, the bright area potential of the second electrostatic latent image), and at the same time, a DC voltage component (V(1c) - 400v and an AC voltage component of 1200V) is applied to the developing sleeve 6a of the second developing device 6.
Table 1 shows the results of evaluating the image quality of an image obtained by applying a developing bias voltage with pp superimposed thereon in terms of four image densities and g-sharpness.

Table 1 fLl VLZ VLZ -V (1c Image quality 10mm -17OV 230V
X15mm -1O0V 300
V 020mm -6OV
340V @25mm -43
V 355V 0 Referring to Table 1, images of good quality were obtained when the distance Jl l z was set to 15 mm or more. The reason why such a result was obtained is that the longer the distance QZ is, the more the VLZ decreases due to optical attenuation of the residual potential caused by the laser beam, which is the second information signal 5, and the development contrast (i.e., VLZ
This is thought to be due to the increase in VG c). In each of the cases shown in Table 1 above, no fogging occurs on the image.If the DC voltage component of the developing bias voltage applied to the developing sleeve 6a of the second developing device 6 is set to -300V, When the distance statement 2 is set to 10 mm, the image brightness and sharpness of the obtained image are slightly improved, but the monocomponent magnetic toner stored in the second developing device 6 for the VozLr portion is Due to the fact explained above, it was found that fogging occurs in the second developing device 6.
In the second development step for visualizing the second electrostatic latent image carried out by It has become clear that the length of the distance uZ needs to be longer than the distance 1.

Next, as another embodiment of the present invention, an A-5+ photosensitive layer was coated on the outer peripheral surface of an aluminum cylinder with a diameter of 108 mm to a thickness of 30 mm on the photosensitive drum 1 shown in FIG. A photoreceptor drum is used, and the photoreceptor drum l is 400
A color image forming apparatus configured to rotate in the direction of the arrow in the IT diagram at a process speed of mm/sec will be described. Note that the other configurations are the same as those of the first embodiment, so explanations will be omitted. As above! !
In the configuration, the distance intersection between the portion LI on the photoreceptor drum 1 and the portion glue and the distance 211Z between the portion Lz and the portion nz on the photoreceptor drum 1 are both set to 20 mm. When the intensity of the laser beam that is the first information signal 3 and the intensity of the laser beam that is the second information signal 5 are both 2.5 l J/crn', the above part is D
The surface potential of the photosensitive drum l at Z is shown in Fig. 2(a).
It was as shown in (b). That is, the dark area potential VO on the surface of the photoreceptor drum 1 at the time of forming the first electrostatic latent image
I is 7 ports, = -500V, light area potential VL + Ha,
VL 1 = -6, Ov-c' ant, dark area potential vozo on the surface of the photoreceptor drum 1 during second electrostatic layer image formation
is Vo zo = -600V, bright area potential V L
Z is VLz = -250V, and the potential VOZL of the developer attachment site of the first developing device 4 is v.

ZLT=-430V. When performing reversal development on the bright area potential VL of the second static image in the second developing device 6, a DC voltage component of −300 V is applied to the developing sleeve 6a of the second developing device 6. Voltage component 1300Vp
When a developing bias voltage with -p superimposed is applied, the second
The one-component magnetic toner contained in the developing device 6 will also adhere to the portion f☆ of the voZ Lr.

Also, the DC voltage component of the developing bias voltage is -4O0V.
When set to , the voz L of the -component magnetic toner
Although it became possible to suppress adhesion to the r region, the 57-view image of the second electrostatic H9 image was inferior in both image density and sharpness. Therefore, the distance intersection 1 is set to 21 = 20 mm, and the distance # intersection 2 is set to 21 = 20 mm.
and D
The surface potential of the photosensitive drum 1 at z is shown in figure ff12 (
It was as illustrated in a) and (c). That is, v,
=-500V, VLI =-60V, Va z
o = -600V, Voz L = -430
V, VLZ = -80V. A portion of the bright area potential VLZ of the electrostatic Hs image of tj42 is applied directly to the developing sleeve 6a of the second developing device 6, and a developing bias voltage in which an AC m voltage component of 1300 Vp-p is superimposed on the voltage component -4O0v is applied. Where I applied it! The a-5i photoreceptor according to this embodiment, which was able to produce 111 two-color images with good image quality at high brightness, has a Δ) compared to the organic photoreceptor according to the first embodiment.
Since the capacitance is large, the dark potential V, zo on the surface of the photoreceptor drum 1-J and the first TI! , the potential V at the developer attachment site of the device 4. In order to reduce the difference value between the VOZN and the VoZL, it is necessary to improve the controllability of the corona current supplied to the photoreceptor drum 1. You can use a charger, but
Corona like this? A charger with excellent controllability of the tt flow is large and expensive. However, according to this embodiment.

A good image carrier using a photoreceptor with large capacitance! I
It has become possible to provide an inexpensive color image forming apparatus that can produce i-quality images. In addition, in FIG. 2, the symbol TN indicates color toner.

Next, as still another embodiment of the present invention, direct contact is made to the photoreceptor drum shown in figure tJ4i! ! , a 120 mm aluminum cylinder whose outer peripheral surface was coated with an organic photoreceptor was used, and the photoreceptor drum L was 120 mm thick.
The second developing device 6 is set to rotate in the direction of arrow A in FIG. 1 at a process speed of /see. A color image forming apparatus configured using a developing device will be described. Note that the other configurations are the same as those of the first embodiment, so explanations will be omitted. To further explain the second developing device 6 mentioned above,
The second developing device 6 is a developing device that employs a non-contact developing method, and is a two-component developer in which non-magnetic toner of 5 to 20 tons is mixed with an insulating carrier of 5 to 40 tons. Contains a system developer. The developer is carried on the developing sleeve 6a in a non-contact state with respect to the outer peripheral surface of the photoreceptor drum 1, and is applied to the developing sleeve 6a with a DC voltage component alternating FLi! By applying a developing bias voltage on which a pressure component is superimposed, the second electrostatic latent image described above is visualized. Since the second developing device 6 employs a non-contact developing method, a large developing contrast is required to visualize the latent image, but in the configuration shown in FIG. By setting the intersection 1 = 30 mm and the distance intersection 1 = 50 mm, it was possible to obtain a two-color image with good image quality.

As described above, according to the present invention, in an image forming apparatus that is equipped with a plurality of developing means corresponding to each color developer to individually accommodate a plurality of color developers, It is possible to provide an image forming apparatus capable of obtaining a sufficient development contrast and a color image of good quality by the second and subsequent developing means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an M factor showing an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of the operation of the image forming apparatus according to each embodiment of the present invention. FIG. 3 is an IJI diagram showing an image forming apparatus according to the prior art. FIG. 4 is an explanatory diagram of the operation of the image forming apparatus according to the prior art shown in FIG. 3. :Photosensitive drum:First information signal:First developer:Second information signal:TF42 developer

Claims (1)

[Scope of Claims] 1) An image bearing member and a plurality of developing means arranged along the moving direction of the image bearing member, wherein the developing means on the image bearing member are In an image forming apparatus in which a latent image is formed by irradiating an image exposure light onto a region on the upstream side in a moving direction of an image carrier, a region on the image carrier onto which the image exposure light is incident and the region. The distance between a developing means for developing a latent image formed by the irradiation of the imagewise exposure when the imagewise exposure is incident on the image carrier and a portion on the image carrier that is in a facing relationship is An image forming apparatus characterized in that the length of the image forming apparatus is set to increase from the upstream side to the downstream side in the moving direction. 2) The image forming apparatus according to claim 1, wherein each of the developing means accommodates a developer of a different color.