JPH0486878A - Recording device - Google Patents

Abstract

PURPOSE:To perform excellent printing without the omission of a line or a character by impressing the AC transfer bias of a proper frequency which satisfies a specified condition on a transfer means. CONSTITUTION:An electrostatic latent image is formed on a selenic photosensitive drum 1 by an exposing means. Normal developing with toner is performed by a two-component developing device 3 so as to develop the electrostatic latent image. The toner has a positive polarity and the toner image is carried to a transfer area with the rotation of the drum 1. A transfer material 4 is stocked in a cassette 5, inserted in the transfer area which is formed by the photosensitive drum 1 and a transfer roller 12 by an aligning roller 6, and the toner image is transferred to the transfer material 4 by the transfer roller. The AC bias which satisfies the following condition and biased to be positive is impressed on the driving shaft of the roller 12. Ft<=4000 and (FrXd)/V>=20, provided that Fe(Hz) denotes the frequency of the AC bias, d(mm) denotes a nip width formed by the transfer means and the image carrier, and V(mm/sec) denotes the moving speed of the image carrier. By impressing the AC bias, the floccuration of the toner in the transfer nip is prevented and the high-quality printing without the omission of the character or the line is performed.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention forms an electrostatic latent image on an image bearing member such as a photoreceptor, develops this electrostatic latent image, and prints it on a sheet of paper. The present invention relates to a recording device that records on a transfer material such as.

(Prior Art) As this type of recording device, an electrophotographic device, an electrostatic printer, and the like are known.

In these recording devices, after forming an electrostatic latent image on a photoreceptor,
A developer image is formed by electrostatically adhering a developer to the electrostatic latent image, and then the developer image is transferred to paper for recording. Furthermore, since the electrostatic latent image and developer that has not been transferred remain on the photoreceptor after transfer, the remaining developer is removed by a cleaning device, and then the electrostatic latent image is removed by a static eliminator. It is being removed.

As the transfer means, corona charger transfer is widely used. However, in corona charger transfer, a corona charge of opposite polarity to the developer is applied from the back side of the transfer material and the developer is electrostatically transferred to the transfer material, so the resistance of the transfer material increases due to the influence of humidity. There have been problems such as the transfer material changing easily and being difficult to transfer to transfer materials with low resistance.

Recently, contact-type transfer devices such as transfer rollers, transfer drums, and transfer belts have been proposed.

In these contact transfer devices, by appropriately selecting the resistance of the transfer members such as the rollers, drums, and belts mentioned above, and applying a DC bias of opposite polarity to the developer to the transfer members, a part of the transfer material is Although charge is applied,
Since the transfer is performed mainly by an electric field formed between the transfer member and the image carrier, transfer defects caused by environment dependence of transfer and the influence of resistance of the transfer material can be improved. In addition, these contact type transfer devices have good adhesion between the transfer material and the image carrier, and can perform stable transfer with high image quality.

(Problems to be Solved by the Invention) However, in the conventional contact transfer method, there is a problem in that transfer voids occur in images such as characters and lines. This is thought to be caused by toner aggregation occurring due to excessive pressure at the transfer nip. This is likely to occur if the transfer material is thick paper or hard material such as an OHP sheet.

This invention was made in view of the above circumstances, and aims to provide a clear image with no transfer defects. In order to achieve this, the present invention provides an image bearing member on which an image is formed when a developer is applied, and an AC bias biased to the opposite polarity to the toner polarity of the AC bias developer, which is brought into contact with the image bearing member. The developer image formed on the image bearing member is connected to a transfer means for transferring the developer image formed on the image carrier to a transfer member, and this transfer means satisfies the following conditions: Fr≦4000 and (Fr×d)/V≧20Fr(H2
): Frequency d(w) of AC bias: Nip width V (mm/5ee) formed between the transfer means and the image carrier: satisfies the condition of the moving speed of the image carrier. It is a recording device that

(Function) When an AC bias is applied as a transfer bias, the developer layer in the transfer nip is agitated by the AC electric field, which prevents toner aggregation due to overpressure in the transfer nip, and thick transfer material, It is possible to print high-quality images with no hollow characters or lines even on hard transfer materials.

(Example) First, a process using conventionally used corona transfer will be explained.

Figure 1 shows the Toshiba copier BD-511O used in the experiment.
This shows the layout around the process. The process speed is 120 mm/sec. In the figure, 1 is a selenium-based photoreceptor drum, and then an electrostatic latent image is formed by an exposure means (not shown). The toner is properly developed by the two-component developer 3, and the electrostatic latent image is visualized. The toner used here is of negative polarity. The toner image is transported to the transfer area as the photosensitive drum 1 rotates.

Paper, which is the transfer material 4, is stocked in a cassette 5, is fed in accordance with the timing of each process of charging, exposure, and development, and is formed by the aligning roller 6, photoreceptor drum 1, and transfer roller 12. inserted into the transcribed region. In this transfer area, the toner image is transferred onto the transfer material 4 by the transfer electric field generated by the transfer roller.

A highly biased AC bias is applied to the drive shaft of the transfer roller 12 by a power source (not shown). The transfer material 4 on which the toner image has been transferred is peeled off from the photosensitive drum 1 by an AC peeling charger 8 and guided to a fixing device 9 . The toner image on the transfer material 4 is heated and pressed by the fixing device 9, and after being fixed onto the transfer material 4, it is discharged from the machine.

Untransferred toner remaining on the photoreceptor 1 without being transferred is
It is removed by the cleaning device 10.

Thereafter, the entire surface of the photosensitive drum 1 is erased by the static eliminating lamp 11, and one cycle of the process is completed. As the cleaning method, a commonly used blade cleaning method is adopted.

FIG. 2 shows an enlarged view of the transfer area.

The transfer roller 12 is supported by a transfer roller support member 14, and a transfer cleaning blade 15 and a transfer roller discharge toner box 16 are also attached to the transfer roller support member 14. The transfer roller 12 is pressed against the photosensitive drum 1 by a spring 17 .

The spring 17 is stretched between the transfer roller support member 14 a and the spring support member 18 . The transfer roller support member 14 is supported by the transfer roller unit frame 19 so as to be rotatable about a fulcrum. The transfer roller 12 also serves as a transfer conveyance roller, and when the transfer roller 12 is used, the adhesion of the transfer material 4 to the photoreceptor drum 1 is improved, and transfer blur is significantly improved. Further, by using the transfer roller 12, deterioration of transfer in a humid environment is prevented.

The transfer bias conditions for good transfer are the bias component +
800v~+1500V, AC component 1200V~25
00V (peak to peak, same below), frequency 600
It ranged from 8z to 4kllZ.

These appropriate bias conditions are related to regular development, and a lower bias voltage is in a good range for reversal development. In addition, the shift occurs depending on conditions such as the surface potential of the photoreceptor drum 1 and the resistance of the transfer roller 12.

Further, when a contact type transfer method such as a transfer roller is used, the pressing force of the transfer member against the photoreceptor drum becomes an important factor. Therefore, the hardness of the transfer roller 12 is also an important factor; if the pressing force is too weak, the adhesion of the transfer material to the photoreceptor will deteriorate, resulting in transfer defects; if the pressing force is too strong,
If the roller hardness is too high, hollow characters will occur. Appropriate pressing force and roller hardness are as follows.

Pressure pressure: 60 to 280 g/d (the pressure force of the transfer roller on the photosensitive drum divided by the transfer nip) Roller rubber hardness: 10 to 60 degrees Within these conditions, the transfer nip is about 0.4 mm to 81.

Note that the conditions used in this example are shown below.

Transfer bias: DC+ 1300V, AC
1800Vpp.

kHz Roller rubber hardness = 30 degrees Transfer nip: 2.5 Next, the transfer efficiency of the transfer roller and corona transfer was compared.

The toner used is a general two-component toner A for BD-5110 (FIG. 3). The range of good transfer characteristics (operating environment) when the transfer roller 12 is used is shown in FIG. 3(a). FIG. 3(b) shows similar characteristics of corona transfer. As shown by this result, roller transfer has a transfer efficiency of 85% in the humidity range of 30 to 85% relative humidity.
The above is obtained.

On the other hand, in corona transfer, the humidity range is 30% to 50%.
A higher transfer efficiency cannot be obtained. In a humid environment, transfer efficiency decreases significantly.

Next, change the frequency of the applied bias from 200Hz to 5kHz.
By changing the number of lines, we evaluated the transfer hollowness of line images. This transfer void is a problem that tends to occur in the contact transfer method. As the transfer material, an OHP sheet was used, which is the least likely to cause voids in the transfer.

The results at this time are shown in FIG. The appropriate frequency is 700)
It was 1z to 4kt+z. Next, the transfer nip was changed from 11 to 5+ nm, and the frequency dependence of transfer voids was similarly investigated, and the results are shown in FIG. At this time, the rubber hardness of the transfer roller 12 and the spring coefficient of the spring were adjusted so that the pressing force per unit area at the transfer nip did not change.

The wider the transfer nip, the less voids will occur even at low frequencies. The electric field fluctuation within the transfer nip is 20
It can be seen that if it is more than 10 times, the effect of toner agitation appears and no transfer voids occur. However, if the frequency of the transfer bias is too high, the toner cannot follow changes in the electric field and the agitation effect is lost. If the bias frequency exceeds 4 kHz, transfer voids will occur.

Therefore, if the frequency of the transfer bias satisfies the following conditions, it is possible to perform good transfer without hollow areas in characters or line images.

Fr≦4000 or F r X d / V≦20Fr
: Bias frequency (Hz) d : Transfer nip (G) (2), Peripheral speed of photosensitive drum I+++m/5ee) FIG. 6 shows the structure of the transfer roller.

106 is a resistive layer, 107 is a conductive layer, 108 is an elastically deformable elastic layer, and 109 is a metal shaft. The resistive layer 106 is made of resin such as polyester, polyethylene, or vinyl chloride, or rubber in which conductive fine particles such as conductive carbon, copper, or nickel fine metal particles are dispersed.
Alternatively, a resistive sheet with excellent flexibility, such as a conductive polymer resin, can be used. The volume resistivity value is desirably in the range of 103 to 1025 Ω/gloss, as described later, and in particular 1
A range of 02 to 1022 Ω· is preferably used. Such volume resistance value can be easily controlled by changing the mixing ratio of conductive fine particles to the resin or rubber.

In addition, the volume resistance value of the resistive layer is affected by external pressure and/or
Alternatively, it is desirable that the change in environmental conditions such as temperature and humidity does not change or that the change is small.

Since the resin sheet structure does not have an internal air chamber, the resistance value is more stable with respect to temperature than the foam structure. With these characteristics, it is possible to transfer paper, envelopes, postcards, etc. of different thickness (i.e., between the toner image bearing member and the transfer roller that are in pressure contact), and even when the transfer roller is in contact with the toner image bearing member and the transfer roller. target toner transfer conditions can be maintained the same.

Further, it is desirable that the surface of the resistive layer 106 be smooth. When unnecessary toner accumulates on the surface of the resistive layer 106,
This will stain the back surface of the transfer material, but this toner removal becomes easier as the surface of the resistive layer 106 is smoother.

The thickness of the resistive layer 106 should be as thin as possible so as not to impair the flexibility of the elastic layer 108. l
A range of l11 is good. The conductive layer 107 can be made of a conductive resin such as polyester in which conductive fine particles such as conductive carbon are dispersed, a thin sheet of metal, a conductive adhesive, etc., and must have conductivity and flexibility. The volume resistivity must be lower than that of the resistive layer 106, less than or equal to 10'Ω·mark. Further, electrical connection between the conductive layer 107 and the resistive layer 1 must be ensured. The thickness of the conductive layer 107 is also preferably as thin as possible so as not to impair the flexibility of the elastic layer 108. By making the sum of the thicknesses of the resistive layer 1 and the conductive layer 2 less than 1710 times the thickness of the elastic layer 8, the function of the elastic layer 8 is maintained. The elastic layer 108 that can be elastically deformed is made of foamed rubber sponge, foamed polyethylene,
An elastic body that can be compressed and deformed, such as urethane foam, can be used.

Since the transfer roller 12 is used with a part of the toner image carrier in pressure contact, the elastic layer 108 needs to be flexibly deformed when the pressure is applied, and quickly return to its original shape when the pressure is released. However, it is necessary to operate stably. That is, a material with excellent creep resistance and plastic deformation resistance is desirable.

As the foam structure, any structure such as an open cell structure or a closed cell structure can be used, but an open cell structure is preferably used because its shape is stable regardless of the ambient humidity. be able to.

Any flexibility can be obtained for the elastic layer 108 by changing the constituent materials, foaming structure, degree of foaming, etc., and a hardness equal to or lower than the hardness of a sponge rubber with a closed cell structure of 30 is preferably used. .

The shaft 109 and the conductive layer 107 are electrically connected by applying a conductive substance 107' to both ends of the roller.

Using the transfer roller 6 as described above, the surface potential is +75
0V, transfer bias DC+1300V, AC1800
V.

Frequency: 2 kHz, roller pressing force: 100 g/d
When a printing test was carried out under the conditions of a transfer nip of approximately 2.5 liters and 1 m, it was possible to maintain good image quality with no decrease in transfer efficiency or transfer voids even after printing 80,000 sheets.

As an example, did you explain about the transfer roller?
In addition, it can be similarly applied to contact type transfer methods such as transfer belts and transfer drums.

As for the developing method, although two-component reversal development was explained in the embodiment, any known developing method may be used.

Next, an example will be shown in which this embodiment is applied to a machine using a cleanerless process, which also serves as a cleaning function for a developing device or an image carrier.

An example of the device configuration is shown in FIG.

FIG. 7 shows a recording device according to the present invention, in which a recording surface smaller than the area of the image to be recorded (that is, a small diameter) is provided as an image carrier approximately at the center of the main body H. A photosensitive drum 1 is provided rotatably in the direction of arrow A. The photoreceptor drum 1 is formed from an organic photoreceptor (○PC) type photoconductive material, and has a drum diameter of 40 mm.

Further, a developer stirring means 1 is provided around the photoreceptor drum 1.
3, a static eliminating means 11, a scorotron charger 2, a laser device 31, a developing cleaning device 3', and a transfer roller 12 are provided.

The developer stirring means 23 is made of fibers (trade name: Torayca, Kynol, etc.) having an electrical resistance of 10 3 to 10 9 Ω.
The brush 23a is arranged to be in sliding contact with the photoreceptor drum 1, and the brush 23a is biased to 800 to 2000V (peak to heat).
, a bias with a frequency of 300 to 4 kHz is applied. Further, the scorotron charger 2 is configured to negatively charge the surface of the photoreceptor drum 1 approximately uniformly to -450 to -800 cm.

The laser device 31 forms an electrostatic latent image on the charged area on which the surface of the photoreceptor drum 1 has been irradiated with the laser beam 28, depending on the image information to be recorded.

Further, in the developer cleaning device 3', a hopper 29 that stores a so-called one-component developer T that is triboelectrically charged is provided with a hopper 29 for transporting the developer T toward a position facing the photoreceptor drum 1, and for transporting the developer T toward a position facing the photoreceptor drum 1. A developing roller 24 is provided for returning the developer T remaining on the body drum 1 into a hopper 29.

The developing roller 24 has a conductive surface layer 27 having an electrical resistance of 102 to 108 Ωcm, and an elastic layer 26 made of urethane foam, silicone rubber, EPDM, etc. is disposed inside the surface layer 27, making the roller 24 elastic as a whole. It consists of

An elastic blade 30 made of phosphor bronze, urethane, silicone resin, etc. is pressed against the developer T to form a thin layer while frictionally charging the developer T.
A developer layer of about 3 to 3 layers is formed. Note that the surface of the developing roller 24 needs to be selected in consideration of frictional charging with the developer T and appropriate elasticity and frictional properties.

The material of the surface layer 27 is, for example, a mixture of urethane resin and 10 to 30% by weight of conductive carbon. Further, a bias power source 34 is connected to the developing roller 24, and the surface layer 27 is connected to a bias power source 34.
It is conducting. Thereby, a predetermined developing bias is applied during development and cleaning. A sponge-like developer conveying roller 25 is provided in the hopper 29.
It plays the role of preventing agglomeration of the developer T in the container 9 and transporting and supplying it.

The transfer roller 12 is provided substantially below the photoreceptor drum 1 so as to face the circumferential surface of the photoreceptor drum 1 via the paper conveyance path 35 .

The transfer roller 12 has the same structure as the developing roller 24, but the electrical resistance of the surface layer is 10 5 to 10 10 Ω·C. The transfer roller 12 transfers the toner image from the photoreceptor drum 1 onto the paper by applying an alternating current bias having a polarity opposite to the toner polarity (-) from the back side of the paper transported here.

Applied high power, DC +400-+1500V
.

Good transfer is performed at an AC of 400 to 2500 V peak to peak (hereinafter the same will be shown) and a frequency of 300 Hz to 4 kHz. This type of contact transfer means exhibits stable transfer characteristics even under high humidity conditions, so it is effective in reducing the amount of developer remaining after transfer and reducing the burden of cleaning, and also reduces paper dust in the transfer paper. Remove it and prevent it from getting mixed into the developer. Furthermore, since the applied bias is alternating current, the toner image is swayed within the transfer area nip, thereby preventing characters and lines from being missing in the transfer due to excessive pressure, which is a problem in the contact transfer method.

The static eliminating means 11 uses a red LED.

However, in order to remove the charge on the photoreceptor from the top of the transferred residual toner, a stronger light is required than the amount of light for removing static electricity provided by a normal cleaning device. The amount of light required is about 8 to 20 times the amount of light attenuated by half when a static elimination lamp is used as a light source. After passing through the static eliminating means 11, the electrostatic latent image on the image carrier 1 has been largely neutralized.

The conductive brush 23a of the developer stirring means 23 is brought into sliding contact with the rotation of the photoreceptor drum 1, and is connected to the bias power supply 32 to provide DCOV~800■, AC400~2000■,
In the range of frequency 3 (1011z to +iz to 4), the transferred residual toner is sufficiently disturbed and unbattered. Due to the alternating current electric field formed by the brush 23a and the photoreceptor drum 1, the transferred residual toner image is moved between the brush 23a and the photoreceptor drum 1. drum 1
As the transfer and counter-transfer are repeated, the shape of the brush surface is irregular, so the slamming of the untransferred toner is gradually disturbed. Further, the mechanical agitation effect by the brush 23a also contributes to the non-bumping of the transferred residual toner.

After the electrostatic latent image has been erased and the remaining 2-toner has been unbattered, the scorotron charger 2, which is the charging means, is charged.
As a result, the photoreceptor drum 1 is charged to a predetermined potential.

At this time, the toner scattered in the form of mist on the photoreceptor drum 1 is also negatively charged, and the toner is developed l+'i
It is cleaned in the cleaning device 3'.

Further, a paper feed unit 5 is provided below the photosensitive drum 1 to supply paper P to the transport path 35 . This paper feeding unit 5 stores a paper P on which an image is to be transferred. A paper feed roller 6 is provided above the paper feed unit 5 and supplies the paper P from the paper feed unit 5 to the transport path 35 by rotation.

Note that the conveying path 35 is provided with a fixing device 9 that fixes the toner image transferred to the paper P.

(The following is a blank space.) Next, the operation of the electronic copying apparatus according to this embodiment will be described. The photoreceptor drum 1 is rotated in the direction of the arrow, and the circumferential surface of the photoreceptor drum 1 is charged approximately -5 by the scorotron charger 2.
Charge to 00-800v. Subsequently, this charged area is exposed by irradiating the laser beam 28 from the laser device 31,
An electrostatic latent image is formed on the surface of the photoreceptor drum 1. The electrostatic latent image is then conveyed to a developing and cleaning position facing the developing and cleaning device 3'. Developer (toner) T is sent out from the developing roller 24 of the developing and cleaning device 3', and this contacts the electrostatic latent image elastically and with a nip width due to deformation, causing the toner T to adhere and forming a toner image. Form. In this case, the toner T adheres to the light irradiation area, resulting in so-called reversal development.

The toner T is charged to approximately -5 to 30 μc/g (microcoulombs/gram) due to friction between the blade 30 and the surface layer 27 of the developing roller 24.
4 is applied with a voltage of approximately -150 to 450V.

The developed toner image is then conveyed to a transfer area facing the transfer roller 12. On the other hand, the paper P is sent to the transfer area from the paper feed unit 5 by the rotation of the paper feed roller 6 in synchronization with the rotation of the photosensitive drum 1.

A positive bias is applied to the back surface of the paper P by the transfer roller 12, and the toner image on the surface of the photosensitive drum 1 is electrostatically attracted to the paper P and transferred. Here, the transfer roller 12 is biased to a positive voltage of 400 to 2000V by a power source 32,
A bias of 2500 V and a frequency of 300 Hz to 3.5 kHz is applied to the rotating shaft, and the roller surface is connected to the surface of the transfer roller 12 through conductive parts made of a silicone resin mixed with 5 to 40% by weight of conductive carbon provided at both ends of the transfer roller 12. 105-10
A voltage is applied to the conductive surface portion marked with 9Ω.

In addition, in order to clean the surface of the transfer roller 12 from foreign substances such as developer and paper dust, it is preferable to use a material that has a smooth surface and low friction.In this example, conductive polyfluoride resin is used. , conductive polyester, etc., and can be cleaned well with a cleaning blade.

In addition, as for the rubber hardness of the entire roller, a flexible one with a rubber hardness of 25 to 50'' was found to have a wide tolerance for the pressing force of the transfer roller 12 against the photoreceptor drum 1 according to comparative measurements using the JIS method.Corona transfer method If this is used in a so-called cleaner-less recording device that does not have a cleaning device, as shown in FIG. 3, residual toner after transfer increases rapidly under high humidity conditions, placing a large burden on the developer stirring means 23 and the developer cleaning device 3'. An increase in the amount of transferred residual toner means an increase in the amount of toner accumulated in the developer disturbance means 23, which may cause internal turbulence or a decrease in the ability to debatter the transferred residual toner. When the ability of the agent agitating means 23 to de-batter the residual toner after transfer is reduced, a memory of the residual toner may be generated, and the developing cleaning device 3- may not be able to perform sufficient cleaning, resulting in fogging. It is desirable for a contactless recording device to employ a contact transfer method.

From the above, contact-type transfer using the elastic conductive transfer roller 12 is extremely efficient and reduces residual toner in a wide range of environments. Since the paper powder on the host rock is also efficiently adsorbed and removed, the amount of deposits remaining on the photosensitive drum 1 after transfer is extremely reduced, and the charge reversal of the toner remaining after transfer does not occur, thereby preventing memory generation. I can do it.

Furthermore, since the transfer roller 12 is used to mechanically press the paper P, transfer omissions (partial non-transfer) are prevented, and the size and quality of the paper are less affected, resulting in clear images. or transcribed.

These effects are similar to those obtained by contact-type transfer methods other than the transfer roller, such as transfer methods using a transfer belt, transfer drum, transfer bar, or the like.

Further, the paper P after the transfer is sent to the fixing device 9, where the toner is melted and fixed on the paper P, and then discharged.

By the way, a small amount of the toner image and electrostatic latent image that were not completely transferred remain on the surface of the photoreceptor drum 1 after the transfer. The remaining electrostatic latent image is erased by the red LED II, which is a static eliminating means.

However, since the residual toner after transfer blocks the light, it is necessary to increase the amount of light for static elimination compared to an apparatus having a cleaner.

The amount of light required is eight times or more than the amount of light attenuated by half when the static elimination lamp is used as the light source.

Next, the transferred residual toner image is conveyed to the developer stirring means 23 and is unbattered. As described above, in the developer stirring means 23, the brush 23a is brought into contact with the toner image and the electrostatic latent image to apply electrostatic and mechanical forces to finely disturb the residual image to the point where it becomes illegible. Therefore, the developer stirring means 2
The toner T on the surface of the photoreceptor drum 1 after passing through the photoreceptor drum 1 is distributed in the form of a sufficiently small mist and no longer contains information as characters or images. In this way, after the transfer residual toner image is sufficiently debatified, the process returns to the charging step.

Photosensitive drum 1 charged by Scorotron charger 2
After being charged, it is exposed to light by the laser device 31 to form an electrostatic latent image, and reaches the developing cleaning device facing the developing cleaning device 3' again (for the second time).

In this case, in the electrostatic latent image formed the second time, the exposed areas (image areas to which toner should adhere) and non-exposed areas (non-image areas) have also been significantly reduced due to roller transfer. Since the residual toner is scattered almost uniformly and thinly enough, uneven exposure will not occur.

Therefore, even in the second development, after exposure. Since the residual potential becomes uniform, a uniform toner image can be obtained.

Also in this case, as mentioned above, the developing roller 24 is
IS rubber hardness 11 has an elasticity of 30 to 700 according to the FI standard method and has an electrical conductivity of 112 to 108, so a load of 20 to 150 g/cm as a line charge is applied to the developing roller 10, and a load of 1.5 to 4 times Due to the pressure-sliding contact with a speed difference, a bump) is generated in the contact width of 1 to 4 times, and in this nip, the residual toner and the toner T on the developing roller 24 are agitated and rubbed, so a strong frictional force is generated. and the cleaning ability is enhanced. Furthermore, since the developer is formed only from the toner T, no deterioration in image quality such as streaks or shading occurs. Further, in the non-exposed area, the adhering toner T is successively attracted to the developing cleaning device 3' and collected because the suction force due to the developing bias is stronger than that of the photosensitive drum 1. That is, by applying a developing bias of an appropriate value between the residual potential of the exposed area and the potential of the non-exposed area to the developing roller 24, new toner is transferred from the developing roller 24 to the exposed area, and At the same time, residual toner adhering to the non-image area (non-image area) is attracted from there to the developing roller 24 and collected.

In this case, the residual toner is small and the developer stirring means 2
3), the developing and cleaning device 3' can efficiently collect the residual toner without causing poor collection. 1 is rotated and used repeatedly to obtain - number of recorded images.

After development and cleaning, the toner image is transferred to the transfer roller]
The image is transferred onto the paper P at the position facing 2. below,
A similar process is repeated.

According to this embodiment, even if a photosensitive drum 1 with a small diameter is used, not only the memory image that has conventionally occurred can be eliminated, but also cleaning defects can be prevented.

Next, the effect of superimposing alternating current and direct current on the bias applied to the developer stirring means 23 and the transfer roller 6 will be explained.

Appropriate values for the applied voltage are that the DC component of the brush 23a is 0 to +800V, and the AC component is 800V to 2000V peak to beat.

Since an alternating current bias is applied to the developer-time peeling means 2, the remaining toner is removed from the brush 23a and the photoreceptor drum 1.
Transference and countertransference are repeated between them. Unlike a roller, the surface of the plan 23B is not uniform, so the position changes slightly as the photoreceptor drum 1 rotates, and depending on which part of the brush 23a it is attached to, it may The position at which it adheres to the photoreceptor drum 1 changes. Therefore,
As the transfer and countertransfer are repeated, the pattern gradually shifts, and patterns such as characters and lines remaining after transfer are disturbed, and after passing through the developer disturbance means 23, pattern information is lost.

As described above, by applying a bias that changes the AC component, it is possible to repeatedly cause the transfer and reverse transfer of the transfer remaining toner, thereby achieving non-bumping of the transfer remaining toner. Note that toner transfer and reverse transfer do not occur unless the potential difference between the brush 23a and the photoreceptor drum is 300 V or more, so the peak of the bias waveform is as shown in FIG.
It must be alternating with respect to the potential of the image area (that is, the potential of the exposed area).

For example, the surface potential is 1550■, and the exposed part potential is 7t.
)V, if the DC component is 0.2V, the effect can be obtained when the AC peak-to-peak is 740V or more.

However, in order to sufficiently debatter the residual toner remaining after transfer and prevent the occurrence of image memory, it is necessary to superimpose a DC bias opposite to the toner polarity to attract the toner, and while some toner is debattered, some of the toner remains on the photoreceptor. It is desirable to reverse transfer to.

Therefore, it is effective to apply a positive DC to the AC with a lower bias of ff1l. For example, DC component +200
In the case of V, a good effect can be obtained with AC of 1140V or more peak to peak.

However, when applying DC bias in ten directions,
Since the brush 23a is oriented in a direction that attracts toner, toner tends to accumulate on the brush 23a. Therefore, it is desirable to actively eject toner when printing newspapers, initializing operations, and completing printing operations. As the discharge operation, methods such as applying a negative direct current bias or applying a negative biased alternating current can be considered during the newspaper, initializing operation, or printing end operation.

In addition, in order to sufficiently prevent the residual image from being transferred,
It is necessary to perform the reciprocating movement of transference and countertransference multiple times.

FIG. 9 shows the configuration of the plan 23a, and this bra'/2
3 Use a, DC+ 400V and AC14 [1
Figure 10 shows the results of examining the occurrence of image memory by applying IV (peak to peak) and changing the frequency from 200 Hz to 5 kHz. 20 to 200 ura-, resistance value approximately 105 Ω, button fibers 41 are sewn to a cloth 42, which is caulked with an aluminum plate 43 to form a brush.The protruding length of the brush is approximately 8 mm. The length of the brush is longer at the portion that comes into contact with the rotation upstream of the photoreceptor drum.The width of the brush is about 5 degrees.

Here, the memory image in the cleanerless process will be explained.

If the transferred residual toner image is not sufficiently debatified and is exposed to corona during the charging process, the portions where there is no toner image will be charged to -550 cm. At this time, the untransferred toner is strongly negatively charged by the charging corona.

If this portion of the transferred residual toner image is a non-image area, that is, will not be exposed to light in the next process cycle, it should be removed from the photoreceptor drum 1 by the developer cleaner 5.

However, if there is a large amount of untransferred material and it has not been sufficiently unbattered, it will not be sufficiently cleaned, so it will be transferred by the transfer roller 2 and a black memory pattern on a white background will be called positive memory.

Furthermore, if a portion of the remaining transferred toner is in a solid or halftone image area, that is, an exposed area, in the next process cycle, the surface potential of the photoreceptor tram 1 is attenuated because the transferred remaining toner blocks exposure. do not. Or, it is attenuated or less than the area without transferred residual toner. If development is performed in this state, the developing electric field will be weakened in areas where there is untransferred toner, resulting in solids and halftones being omitted in the form of untransferred toner patterns, and the density becoming low.

This is called negative memory.

In general, negative memory (especially for halftones) tends to occur. FIG. 5 shows measurements of a negative memory with two dot lines in a halftone with an area ratio of 50% while changing the AC frequency. The white areas indicate the halftone density of the non-memory area, and the black areas indicate the density of the negative memory area (both measured with a microten cytometer). The difference between the two is
If the density difference is within 0.05, it can be judged by visual inspection that it is almost good.

be done.

As shown by the solid line in Figure 10, from approximately 300Hz to 4k
Good memory-free zero images could be obtained at frequencies up to Hz. The process speed of the example is 72 mm
/sec, and since the width of the brush is 5 mm, considering that the distance between the blank 23a and the image carrier 1 is also approximately 5 mm, the transition and countertransition are repeated approximately 20 times at the frequency of 30011z. In other words, it can be seen that by performing transfer/countertransference 20 times or more, non-transferred transfer residues are achieved.

Next, a similar test was conducted using a brush with a width of 2 mm. Good memory-free images could be obtained at frequencies from approximately 70011z to 4 kHz. By performing transfer/countertransfer of about 23 degrees, the unbattered image of the transferred residual image is achieved.

On the other hand, if the frequency is too high, the toner will not be able to follow changes in the electric field and will not be able to transfer or reverse transfer, resulting in a frequency of approximately 4 kH.
At frequencies exceeding z, it is not possible to decontaminate the residual toner after transfer.

With the device shown in Figure 7, Brassinokuiasu DC+400■
, A C1400V pIE, frequency 2kHz, transfer bias Dc + BOOL A C2100V pp,
Frequency 2kllz, surface potential 550■, exposed part potential -7
When a printing test was carried out on 20,000 sheets of newspaper with both the transfer bias and brush bias turned off under the condition of 0 V, good printing was maintained with no transfer omissions and no memory images.

As described above, by applying an alternating current bias to the developer-disturbing member and non-bumping the untransferred image, it is possible to perform good printing without charging unevenness or memory images.

The conditions for performing the above-mentioned non-bumping are the nip di (mm) formed by the image disturbing member and the image carrier, the moving speed V (mm/5ee) of the image carrier, and the frequency Fr1 of the applied AC bias. (fiz) must meet the following conditions.

Frl ≦4000katsu (Frl x d) /V
≧20 If the frequency is too high, the toner will not be able to follow changes in the electric field, and if the frequency is too low, the toner will not transfer or reverse transfer sufficiently between the image bearing member and the image disturbing member, and the remaining toner will not be transferred. De-blasting is not performed sufficiently, resulting in memory image and image unevenness.

In addition, by performing contact transfer, it is possible to perform good transfer with good transfer efficiency and no transfer omissions even in a humid environment, and furthermore, by applying AC noise, problems with the contact transfer method can be achieved. , it is also possible to prevent the occurrence of voids in the transfer of characters and line images.

In order to obtain the above effects, the transfer nip d2 (mm) formed by the image carrier and the transfer means, the moving speed V (mn/5ee) of the image carrier, and the frequency Fr2 (of the applied transfer bias) are required. Hz) must satisfy the following conditions.

Fr2 ≦4000 and (Frl xd)/V≧2
0 Using the device shown in Figure 1, set the plan bias to DC+400.
and A C1400V I)l), a frequency of 2 kHz was applied, and DC+ was applied as a transfer roller bias.
BOO ■ and A C2100V 1) I), frequency 2k
When a 30,000-sheet photoconductor test was carried out with II z applied and the photoreceptor surface potential at -550V and the exposed part potential at 70V, good image quality was maintained with no transfer defects and no unevenness in memory images or halftones. Ta.

In the above embodiment, the non-magnetic component development method was used as the most compact example, but the method is not limited to this, and other known magnetic component brush methods, fur brush methods, and cascade methods are also available. Needless to say, it is also possible to apply this method to legal matters.

In addition, as an example of a developer-disturbing member, one using a conductive or resistive brush was explained, but conductive or resistive members such as conductive or resistive rollers, sponges, rubber, cloth-like members, etc. Any member may be used as long as it comes into frictional contact with the image carrier without applying a bias.

Further, the transfer means may have a configuration in which an AC bias is applied to a conductive or resistive member such as a transfer heald or a transfer bar in addition to the transfer roller.

[Effects of the Invention] As explained above, according to the present invention, by employing a contact transfer device to which an AC transfer bias of an appropriate frequency is applied as a transfer means, good transfer can be achieved even in high humidity, and line and line transfer can be achieved. It is possible to perform good printing without missing characters during transfer. Furthermore, by installing this transfer device as a transfer means in a recording device using a cleanerless process, memory images can be eliminated and the life of the device can be extended.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a transfer device according to an embodiment of the present invention, Fig. 2 is an enlarged view of the transfer portion of Fig. 1, and Fig. 3 (a) is a diagram showing environmental characteristics of transfer efficiency of a transfer roller. , Figure 3(b) is a diagram showing the environmental characteristics of the transfer efficiency of corona transfer, Figure 4 is a diagram showing the transfer bias frequency and the occurrence of line hollowing, and Figure 5 is a diagram showing the change in the appropriate frequency due to the transfer nip. Figure 6 is a diagram showing an example of the transfer roller configuration, Figure 7 is a diagram showing the configuration when the present invention is applied to a cleanerless process, and Figure 8 is a diagram showing appropriate brush bias conditions (AC component). , FIG. 9 is a diagram showing an example of a brush configuration, and FIG. 10 is a diagram showing an appropriate range of brush bias frequency. 1... Photosensitive drum (image carrier) 3...
...Developer 3'...Developer cleaner 12...Transfer roller

Claims (1)

[Claims] (1) an image bearing member on which an image is formed by targeting the developer; and an AC bias that is in frictional contact with the image bearing member and biased to a polarity opposite to the toner polarity of the AC bias developer;
The developer image formed on the image carrier is connected to a transfer means for transferring the developer image to a transfer member, and this transfer means has the following conditions: Fr≦4000 and (Fr×d)/V≧20Fr (Hz
): AC bias frequency d (mm): Nip width formed between the transfer means and the image carrier V (mm/sec): satisfies the conditions of the moving speed of the image carrier. recording device.