JPH0450886A - Recorder - Google Patents

Abstract

PURPOSE:To obtain a recorder without a cleaner which can output an excellent image under any condition by providing a moving member whose surface interposing an image supporting body is formed of a dielectric material and a means which forms a transfer electric field between the moving member and the surface of a latent image holding body. CONSTITUTION:A transfer device 5 is provided with the moving member 13 whose surface interposing the image supporting body in between the surface of the latent image holding body 1 is formed of the dielectric material and the transfer electric field forming means 16 which forms the transfer electric field between the moving member 13 and the surrfce of the holding body 1. Then, reverse electric charge is not injected to toner through a paper interposed between a photosensitive body 1 and the transfer device 5. Therefore, the toner left without being transferred arrives at the position of a uniformizing brush while always holding the electric charge of normal polarity. Besides, since transfer electric charge is not given to the photosensitive body 1 even when the paper does not exist, the toner is not discharged from the uniformizing brush. Thus, the excellent image is outputted under any condition.

Description

[Detailed Description of the Invention] [Object of the Invention'] (Industrial Application Field) The present invention relates to a recording device based on an electrophotographic method,
More specifically, the present invention relates to a cleanerless recording apparatus that performs image recording without using a cleaning device for cleaning residual toner after transfer.

(Prior Art) In a recording device based on an electrophotographic method, without using a cleaning device for cleaning residual toner after transfer,
A recording device (hereinafter referred to as a cleaner-less recording device) that collects transferred residual toner into the developing device at the same time as development is performed by a developing device is known, for example, from Japanese Patent Application Laid-open No. 59-133578 and Japanese Patent Application Laid-open No. 59-157681. .

These publications disclose the basic idea of the cleanerless recording device, and the gist thereof can be summarized as follows. That is, as shown in FIG. 8, which shows a cross-sectional view of the main structure, electrophotographic printers such as laser printers often use the well-known reversal development method. In the reversal development method, toner particles 2 charged to the same polarity as the photoreceptor 1 are used to adhere to areas on the surface of the photoreceptor 1 where there is no charge (or areas with a small amount of charge), The toner particles 2 are not attached to the portions where charges exist. In order to realize such selective toner adhesion, the toner carrier 4 in the developing device 3 is given a voltage Vb (
l VLl <I vbl <I Vol ) is applied, the toner adhesion to the photoconductor 1 is suppressed by the electric field between the charged part, and the toner 2 is adhered to the photoconductor 1 by the electric field between the non-charged part. let

The toner 2 adhering to the photoconductor 1 is transferred to a well-known corona transfer device 5.
The image is transferred to the image support 6 by. In general, not all toner is transferred in the transfer process (the remaining toner 2' is distributed in the form of an image on the surface of the photoreceptor after transfer). After collecting the untransferred toner 2' by the cleaner 7 shown,
The charge on the surface of the photoreceptor 1 is removed by the charge eliminating lamp 8, and the latent image forming process (uniform charging process by the charger 9 and exposure process by the light beam 10) is carried out again. On the other hand, in a cleanerless recording apparatus, the residual toner 2' is subjected to the developing process without using the cleaner 7, and the residual toner 2' is collected into the developing device 3 at the same time as the development.

Strictly speaking, of the latent image formed by exposure with the light beam 10, the residual toner remaining in the charged area (i.e., unexposed area or non-image area) is ensured to have the same polarity as the latent image by the charger 9. Since each toner particle 2 is charged to the toner carrier 4, it is transferred to the toner carrier 4 side by an electric field that suppresses the transfer of each toner particle 2 from the toner carrier 4 to the photoreceptor 1, that is, an electric field due to the potential difference between vO and Vb. At the same time, the non-electrified part,
That is, the transfer residual toner 2' existing in the exposed area or the image area receives the force directed from the toner carrier 4 toward the photoreceptor 1 and remains on the surface of the photoreceptor 1. New toner particles 2 are transferred from the toner carrier 4 to this uncharged portion, and cleaning is performed simultaneously with development.

In this manner, the cleaner-less recording apparatus does not require the cleaner 7 or the waste toner box for storing cleaned toner, that is, waste toner, making it easier to downsize and simplify the apparatus.

In addition, since the transferred residual toner 2' is collected in the developing device 3 and reused, it is economical because no waste toner is generated, and since the photoreceptor 1 is not rubbed by the cleaning blade, the photoreceptor 1 is not rubbed. Many benefits can be obtained, such as making it possible to extend the lifespan of the body 1.

However, in this cleanerless recording device,
Ghost images may appear due to the following reasons.

First, in a high-humidity environment, the paper used as the image support 6 absorbs moisture and becomes low in resistance, so that transfer efficiency generally decreases and a large amount of toner tends to remain on the surface of the photoreceptor. If the amount of transferred residual toner 2' becomes too large, it will not be possible to completely clean the developing position 3, and the transferred residual toner 2' will remain in the non-image area, resulting in a positive ghost on the white background area of the transferred image. (hereinafter referred to as positive ghost or positive memory).

Second, if the amount of transferred residual toner 2' becomes too large, the transferred residual toner 2' blocks the light beam 1O during the exposure process using the light beam 10, and the attenuation of the surface potential of the photoreceptor 1 is insufficient, resulting in the difference between Vo and vL. This results in an intermediate potential state (defined as VJL).

In such a region, the developing voltage becomes bvL', which is smaller than the developing voltages v, -Vz of the surrounding exposed areas, so the amount of toner transferred from the toner carrier 4 to the photoreceptor 1 is smaller than that of the surrounding area. Therefore, the residual toner image appears as a whiteout image (hereinafter referred to as a negative ghost or negative memory) in the image area of the transferred image.

This phenomenon is particularly noticeable in halftone images consisting of a set of halftone dot images or line images.

On the other hand, Japanese Unexamined Patent Publication No. 82-2H183 discloses that ghosts can be removed by applying a voltage to a conductive brush II having the cross-sectional shape shown in FIG. 9 and bringing it into light contact with the photoreceptor 1. ing. That is, a voltage having a polarity opposite to the charged polarity of the toner is applied to the conductive brush 11 by the DC power supply 12, and the untransferred toner 2' is once attracted to the brush 11 by Coulomb force. by this,
The amount of untransferred toner 2' on the surface of the photoreceptor 1 is significantly reduced, and the occurrence of the ghost is prevented.

(Invention or problem to be solved) However, the following two problems arise in the above method.

(2) Under high-humidity environmental conditions, the paper serving as the image support 6 retains (absorbs) a large amount of moisture, resulting in a significant decrease in resistance. As a result, the charge applied from the corona transfer device 5 to the paper 6 moves in the thickness direction of the paper 6 and reaches the toner particles on the surface of the photoreceptor 1, charging the toner to a polarity opposite to the original charging polarity. Even when toner particles charged to the opposite polarity come into contact with the conductive brush 11, they are not attracted to the brush 11 because they receive a repulsive force due to the electric field, and even after passing through the brush, the distribution state of the transferred residual toner image 2' remains almost in its original state. will remain the same. Therefore, in such a case, the occurrence of the ghost described above cannot be prevented.

(2) In the reversal development process, a voltage having a polarity opposite to that of the photoreceptor 1 is applied to the corona transfer device 5.

For example, when the photoreceptor 1 is of a negatively charged type, the transfer device 5 applies positive corona ions to the paper 6. However, paper 6
When cut paper of a predetermined size is used, the surface of the photoreceptor 1 is directly exposed to corona ions before the leading edge of the paper 6 reaches the transfer device 5 and after the trailing edge of the paper 6 passes through the transfer device 5. You will be bathed.

When the surface of the photoreceptor 1 whose polarity has been reversed to positive reaches the brush 11 to which a positive voltage is applied, the negative polarity toner that has been attracted to the brush 11 is expelled onto the surface of the photoreceptor 1 all at once. The ejected toner must be collected in the developing device at the developing position, but if the amount is large, it cannot be collected with one-time cleaning, and the negative memory is blocked by blocking the laser light during the next image exposure. bring.

By turning the transfer corona voltage on and off in accordance with the conveyance of the paper 6, the occurrence of the above problem can be somewhat suppressed, but since the corona charger usually has an opening of about 20m5, It is virtually impossible to turn on and off exactly according to the rear end.

On the other hand, the toner is discharged from the brush 11 from the photoreceptor 1.
This is particularly noticeable at locations where the surface potential changes rapidly. Therefore, when there is a difference in potential on the surface of the photoreceptor 1 corresponding to the edge of the paper 6, it is impossible to suppress the toner from being ejected.

The transfer corona voltage is turned on after the leading edge of paper 6 passes, and the transfer corona voltage is turned on after the leading edge of paper 6 passes.
Although the above problem can be solved to some extent by turning off the switch before the trailing edge of the paper 6 passes, a transfer failure occurs at the leading edge and trailing edge of the paper 6. Furthermore, when paper sheets of different sizes are used, it is inevitable that the surface of the photoreceptor 1 will be directly exposed to the transfer corona.

Because of these problems, it has been extremely difficult to completely prevent positive memory and negative memory in conventional cleanerless recording devices.

The present invention has been made in response to the above-mentioned circumstances, and an object of the present invention is to provide a cleanerless recording apparatus that can output good images under any conditions.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a latent image holding member, a means for forming a latent image on the surface of the latent image holding member, and a method for attaching toner to the formed latent image. a developing device that forms a toner image, a transfer device that transfers this toner image onto an image support, and a residual toner that disturbs the residual toner image that remains on the surface of the latent image carrier after transfer and makes the toner distribution uniform. In the recording device, the developing device sucks and collects residual toner into the developing device, and at the same time develops the latent image, the transfer device has an image support between it and the surface of the latent image carrier. A moving member having at least a surface made of a dielectric material or a high-resistance material to be held therebetween, and a transfer electric field forming means for forming a transfer electric field between the moving member and the surface of the latent image carrier. It is characterized by

(Function) In the present invention, since the surface of the transfer device that holds the image support conveyed between it and the surface of the latent image carrier is formed of a dielectric material or a high-resistance material, the photoreceptor and the transfer device are Reverse charges are no longer injected into the toner through the paper sandwiched between them. Therefore, the untransferred toner always reaches the uniformization brush position while maintaining the normal polarity of charge, and good uniformization is easily achieved. Further, even when no paper is present, no transfer charge is applied to the photoreceptor, so it is completely avoided that a large amount of toner is ejected from the equalizing brush.

In other words, it is possible to always output good images without memory under any conditions.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 7.

Embodiment 1 FIG. 1 is a cross-sectional view of the main parts of an example of a recording apparatus according to the present invention. Reference numeral 1 denotes an electrostatic latent image holding member, such as a photoreceptor, and a negatively charged organic photoreceptor drum. It is. 3 is a developing device, for example, a one-component non-magnetic developing device; 4 is a developing roller attached to the developing device, which lightly contacts the surface of the photoreceptor drum 1 through a toner layer carried on the surface;
It rotates at a circumferential speed that is about 1.2 to 4.0 times the circumferential speed of the photoreceptor drum 1 . The developing roller 4 is constructed by coating the surface of a conductive polyurethane rubber roller with a conductive urethane elastomer. 8 is a static elimination lamp, 9 is a scorotron charger, 10 is a laser beam, 1
Reference numeral 1 denotes a residual toner equalizing brush, whose basic structure is the same as that shown in FIG. 9 above.

Furthermore, 13 is an image support 6, for example, an endless dielectric film for conveying paper, for example, a thickness of 50 μm to 1++v.
A transfer belt (moving member) made of a polyethylene terephthalate film of about 100 mL is rotated in the direction of the arrow while being stretched by a drive roller 14 and a tension roller 15 while contacting the surface of the photoreceptor 1. Reference numeral 16 denotes a transfer channel as a transfer electric field forming means, which serves to apply a positive corona charge to the inside of the transfer belt 13, and the paper conveyed on the surface of the transfer belt 13 is transferred to the transfer belt 13.
It is electrostatically attracted to and reaches the transfer position.

The toner image on the surface of the photoreceptor 1 is transferred to the paper surface by the transfer electric field formed by the corona charge on the back surface of the transfer belt 13, and the remaining toner 2' on the surface of the photoreceptor 1 is
It is uniformized by the equalization brush 11, and the static elimination lamp 8,
After passing through the charger 9 and laser exposure 10, it reaches the developing position,
Cleaning is performed simultaneously with development.

The transfer corona caused by the transfer charge 1B acts only on the inside of the transfer belt 13, and since the corona charge does not reach the inside or surface of the paper, there is no possibility that the toner charge will be reversed. Further, even when no paper is present at the transfer position, the transfer corona does not reach the surface of the photoreceptor 1. Therefore, under any conditions, the equalizing brush 11
operates normally and can reliably suppress memory phenomena.

Note that the transfer corona may act on the outer surface of the transfer belt 13 before reaching the transfer position, and in this case, the surface charge may leak through the paper to the photoreceptor 1 side in a high temperature environment. However, since the amount of charge is very small, there is no problem in practice. The transfer belt 13 may have a resistance value of 10'Ω·cm to 1015Ω·C11, and may be of a type in which a transfer bias is applied from the inside, or may be a layered structure in which the inside is a conductor and the outside is a dielectric or resistor. It may be shaped.

Here, to explain the mechanism of memory generation in the cleanerless process, first, the developed toner layer and the untransferred toner layer (residual toner layer) are regarded as homogeneous dielectric layers, and the second
Analyze based on the model in the figure. That is, Gauss's law is applied to the second figure layer and Poisson's equation regarding the potential φ is solved.

divD =0 (1)d
iv D −q m / dr
(2) r r “div D-qkm / dt (3)
t t.

Here, the boundary condition is expressed as follows, where n is the unit vector in the X direction.

D φn■σp(4) (D −D ) ・n−σp(5)r
p (D − D ) ・n −0(8)t
r −D −n−σt(7) t φp (0) −0(8) φp (dp) −φp (dp)
(9) φp (dp + dr) −φp
(dp+dr) (10)φri (dp+d
r10 old) −Vb (11)σp −εp
(V/dp), (12)
By solving the above boundary value problem, the potentials φr and φt in the toner layer can be obtained. At a point XO where the electric field -dφ/dx becomes zero, the toner layer separates and development or cleaning is completed.

When xo<dp+dr, cleaning is x.

>dp+dr, development is performed and the photosensitive drum 1
The toner adhesion amount m on the surface is 5r(xo −dp
)/dr and m(xo -dp-dr)/dt+s
guided by r. However, the amount of residual toner is assumed to be r.

As a result of the above analysis, the following developing and cleaning equation was obtained. (Left below) Cleaning equation: Development equation: However, A-dp/ εp+dr/ t: r dt/
It was set as εt.

Due to the presence of residual toner, the value of Vp (-
Next, we will consider how the potential on the surface of the photoreceptor 1 changes. During the charging process, residual toner particles shield corona ions and reduce IVpl. Assuming that the toner particles are spherical and the coverage rate of the surface of the photoreceptor 1 by the toner is η, then η−πR”・mr(3/4 π, oR”) m3m
r/4, oR. If the surface potential of the entire photoreceptor 1 to which toner is attached is vl, the contribution of the toner-attached portion is v1, and the contribution of the non-toner 1 attached portion is Vo, then the capacitance CSC and surface charge density Q shown in FIG. ,tp
Using tQ, V, -V, +Vo (1B)■
-ηQ (1/C+1/C(17)t t
t p)■ −(1−η)Q/Q
(18) Op C, and these potentials are expected to show a linear dependence on m, and the experimental results shown in Figure 3 support this idea.In the experiment, it is possible to measure vl and Vl. and V
-V, -V, the following empirical formula was obtained.

Vo -1,20xlO' sr-500 (19)
Note that ■ corresponds to the initial potential in the exposure process.

By the way, as a result of comparing the theoretical formula (18) and the experimental formula (19), the actual coverage ratio η is only 19% of the theoretical value, and corona ions wrap around the surface of the photoreceptor 1 below the toner particles. It shows that it is crowded.

When laser exposure is performed through the residual toner with respect to the initial potential V in the exposure step, the light transmittance of the residual toner layer is l-η, so the incident energy of the laser beam is reduced to Io.
Then, the energy I reaching the surface of the photoreceptor 1 is
It is given by the following formula.

1-I (1-77) -1(1-3ar/4 ρ
R) (2G) Residual toner amount■ Area where r is large (sr>0.8X 10
10-2 (/m2)), toner particles overlap, so it was assumed that the transmittance of the laser beam was proportional to 11.r, and the proportionality multiplier was determined from experiments.

By the above laser exposure, the initial potential V on the surface of the photoreceptor 1 is
Since, for example, considering the generation and transport phenomenon of photocarriers in a laminated p-type organic photoreceptor, the optical attenuation characteristic of the surface potential Vp of the photoreceptor 1 can be approximated by the following three equations.

1≦11: V −K11+V+ (2
1) ■1≦I≦I 2: V −V2 exp(−
21) (22) 1 ≧ 12:
V −K3 1+V3 (
2B) An example when the initial potential V is -500V is shown in Figure 4.

1 to 3, ■1 to v3, and 11 to I2 are constants determined by comparison with experimental results, and V
The potential after exposure is the value multiplied by /-500 p
O.

Next, the results of calculating the simultaneous development and cleaning characteristics by substituting the surface potential Vp of the photoreceptor 1 obtained above into the cleaning equation will be shown. - Figure 5 shows the development characteristics, and due to the presence of residual toner, the image density decreased and the background density increased, and the experiment and theory were in agreement.

FIG. 6 shows the relationship between the amount of residual toner 1r and the amount of developed toner m, and the cleaning performance in the unexposed area is good, and the amount of residual toner is 0.55 x 1010-
2(/m') or less, it has been proven both experimentally and theoretically that the leaning is more or less complete.

By the way, the amount of residual toner is 0.55
kg/m2), a positive memory appeared on a white background.

In addition, the developed toner amount m in the high density area shows a tendency to increase once as the residual toner amount 1r increases and then decrease, and the decrease in the developed toner amount m is attributed to the light shielding effect in the exposure process. be understood.

Therefore, the amount of residual toner 11r> 0.24 X 1
In the range of O-2 (kg/m2), the developed toner amount m is less than the initial value (the value of m when sr-0), and negative memory is likely to occur. On the other hand, residual toner iLmr<0.24
In the area of X 1010-2 (7 m2), the density was already saturated, so no positive memory appeared even if the amount m of developing toner increased.

Furthermore, in halftones, the amount of residual toner is lower.
Negative memory occurs in this area. This phenomenon can be said to be because the increase in IVpl due to the light shielding effect is greater than the decrease in 1Vpl due to the shielding of corona ions. In this way, by optimizing the transfer conditions, the residual toner 1iar is suppressed as much as possible, and at the same time, by uniformizing the residual toner distribution using the equalizing brush 11, it is possible to reliably prevent the occurrence of the memory. possible and always (
Good images could be output (under any conditions).

In addition, in the above, dp, dt, dr-2X 10-5
5 ・5ir(m) in 1.1X10-5, K-2,0
, K5-3.77 X103 (Vs/kg),
e p, e r, ε t −3,4ε o,
1.0ε 01, lεo, io −5,5X 10
10-2 (/ra”), p-1,1, qt, q
r-0,84x 10-2-3. IX 1O-2(C/
kg) and Vb-200 (v).

Embodiment 2 FIG. 7 is a cross-sectional view showing another main part configuration example of the recording apparatus according to the present invention. Reference numeral 17 is a transfer roller that has both the moving member 13 and the transfer electric field forming means 16. An image support 6 to which developed toner adhered in a desired image is transferred to the surface of the photoreceptor serving as a latent image holding member is sandwiched between the surface of the photoreceptor drum 1 and the image support 6 plays a role in the transfer. I will do it. The transfer roller 17 has a structure in which a conductive elastic layer and a dielectric layer are sequentially coated around the shaft, and a transfer voltage is applied to the shaft by a power source (not shown).
A transfer electric field is formed between the surface of the photoreceptor 1 and the surface of the transfer roller 17, and the toner is transferred onto an image support, such as paper 6, which is held between them.

Even with the use of the transfer roller 17 having such a configuration, the surface dielectric layer of the transfer roller 17 prevents the movement of charges, so that memory generation due to charge reversal of residual toner and reverse polarity charging of the photoreceptor 1 is reliably prevented. Can be prevented.

In addition, in this embodiment, in the case of a configuration in which a high resistance layer of 10'Ω·σ or more is provided instead of the dielectric layer of the transfer roller 17, or without intervening a conductive elastic layer between the transfer roller 17 and the shaft. A case in which the entire structure is composed of only a high-resistance elastic layer having a resistance value of 10 7 Ω or more can also be used in the same manner. However, in the case of the transfer roller 17 having a dielectric layer provided on its surface, it is desirable to install a static eliminator or a charger to remove electric charges generated on the surface due to frictional charging or the like.

[Effects of the Invention] As described above, the present invention provides a cleaner that can easily prevent the polarity reversal of the residual toner charge after transfer and reverse polarity charging of the photoreceptor, and can always output good images without memory. It can function as a response recording device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the main part configuration of a recording apparatus according to the present invention, FIG. 2 is a schematic diagram showing a modeled development cleaning area in the recording apparatus according to the present invention, FIGS. 5 and 6 are characteristic diagrams showing theoretical diffraction and experimental results of the fleeceless process in the recording device according to the present invention, and FIG. 7 is a cross-sectional view showing another example of the main part configuration of the recording device according to the present invention. 8 and 9 are cross-sectional views showing different configurations of main parts of conventional recording apparatuses. 1...Latent image holder (photoreceptor) 2...
...Toner particles 2...Residual toner image 3...Developing device 4...Toner carrier 5... ...Transfer device 6...Image support 9...Charger (forming part of latent image forming means) lO...・Exposure beam (forms part of latent image forming means) 11... Residual toner image uniformizing member (conductive brush) 13... Transfer belt (moving member) )16・
......Transfer electric field forming means 17...
...Transfer roller (combined as a moving member and transfer electric field forming means) Applicant: Toshiba Corporation Tokyo Electric Co., Ltd.

Claims (1)

[Claims] A latent image carrier, a means for forming a latent image on the surface of the latent image carrier, a developing device for forming a toner image by attaching toner to the formed latent image, and a developing device for forming a toner image on the image support. and a residual toner image equalizing member that disturbs the residual toner image remaining on the surface of the latent image carrier after the transfer and makes the toner distribution uniform, and the residual toner is transferred by the developing device to the developing device. In a recording device that simultaneously develops a latent image by suction and collection, the transfer device has at least a surface formed of a dielectric material or a high-resistance material, and the image support is sandwiched between the transfer device and the surface of the latent image carrier. A recording apparatus comprising a member and a transfer electric field forming means for forming a transfer electric field between the movable member and the surface of a latent image carrier.