JPS58162353A - Recording method - Google Patents

Abstract

PURPOSE:To make the image density at a background part low by providing a collecting means, to which a bias voltage whose polarity is the same as that of toners to be transferred, in the vicinity of a toner layer, removing the part corresponding to the toners of the background pattern, and performing transfer. CONSTITUTION:The negatively charged toner layer is formed in a doner 1. A positive charge is injected to the toners which are contacted with the doner by the image signal from a multiple needle electrode 4. Then a positively charged image pattern and the negatively charged background pattern are constituted. An AC voltage of about 100-150V is superimposed on the bias voltage of about +500-800V in the collecting means 6. The part corresponding to the negatively charged toners constituting the background pattern, whose attaching force to the doner 1 is weak, and which is located in the vicinity of a roll 60 of the means 6, is collected to the outer surface of the roll 60, and put into a recovering tool 61. Then, the positively charged toner constituting the image pattern is transferred to a recording medium S. Therefore the image density of the background part can be made sufficiently low and the resolution is not degraded.

Description

[Detailed description of the invention] The present invention relates to a recording method.

In a single layer of toner on a donor, by using charge injection into the toner, an image pattern and a background pattern to be a background for this image pattern are formed as toner charge distributions with opposite polarities, A recording method is known in which toner constituting an image pattern is directly transferred onto a recording medium according to its charge distribution pattern (Japanese Patent Laid-Open No. 55-8
No. 4955 Publication In this recording method, when the toner on the donor is transferred onto the recording medium, since the transfer is direct, not only the toner forming the image pattern but also the background and the toner forming the pattern are transferred. , directly contacts the recording medium, and a portion thereof is transferred to the recording medium. As a result, it has not been possible to sufficiently lower the density of the portion that should become the background of the resulting recorded image.

1 In order to solve this problem, a method was proposed in which an intermediate transfer medium is interposed between the donor and the recording medium (Patent Publication No. 157752/1982), but it is still difficult to achieve sufficient effects. Met.

Furthermore, a method has been attempted in which the surface of the donor and the surface of the intermediate transfer medium move at different speeds at the contact portion between the donor and the intermediate transfer medium, and by this method, -
The above problem of image density in the background area has been satisfactorily resolved.

However, on the other hand, there is a reduction in resolution in the recorded image due to the speed difference between the donor surface and the intermediate transfer medium surface, especially the surface). A new problem has arisen in which the resolution decreases in the direction corresponding to the direction of movement of the image.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording method as described above, which can sufficiently reduce the image density of the background portion of a recorded image without causing a decrease in resolution.

The present invention will be explained below.

The features of the present invention are as described below.

A collecting means to which a bias voltage of the same polarity as the charge polarity of the toner to be transferred is applied is brought close to the toner layer after the charge distribution has been formed, with a small gap therebetween.

The bias voltage is determined to be sufficiently lower than the discharge starting voltage depending on the size of the minute gap.

By means of this collection means, a considerable portion of the toner constituting the background butter 7 is removed onto the donor. Thereafter, the toner constituting the image pattern is transferred. Transfer may be performed directly or via an intermediate transfer medium. After the toner is removed by the collection means,
The background pattern toner remaining on the donor is
All of them have a strong adhesion to the donor, so they are not easily transferred, and therefore there is no risk that they will increase the image density in the background area. In this way, the collection means can solve the problem of image density in the background area, so when using an intermediate transfer medium, there is no need to provide a speed difference between the donor surface and the intermediate transfer medium surface, and therefore the intermediate transfer Even with a transfer method using a medium, there is no reduction in resolution.

Now, let's consider from a model perspective why the image density of the back bottle image increases in the conventional recording method.

The thickness of the toner layer formed on the donor is generally 2 to 3 times the average particle size of the toner, in other words, the number of toner layers formed is 2 to 3 layers. Therefore, let's consider that there are two layers of toner on the donor, and what kind of force acts on this layer during transfer.

FIG. 1 schematically shows a transfer section of a recording apparatus disclosed in Japanese Patent Application Laid-Open No. 55-84955.

, the reference numeral indicates the donor, the reference numeral T indicates the toner, the reference numeral S indicates plain paper as a recording medium (hereinafter referred to as "recording paper"), the reference numeral R indicates a transfer roller, and the reference numeral E indicates a transfer power source.

The peripheral surface of the donor D is made of conductive silicone rubber. The toner T shown in the figure is a toner forming a background pattern and is negatively charged. In other words, these [colors] should not be transferred if possible.

The transfer roller R is a metal roller, and a transfer voltage is applied between it and the donor D by a transfer power source Eo. Now,
In this state, consider the case where two layers of toner exist between the donor D and the recording paper S (Fig. 1 (1)) and the case where only one layer exists (Fig. 1 (■)). In the case of , let us consider the force acting on the toner on the recording sheet S side.

Then, in the state shown in FIG. 1 (I), the force acting on the toner on the recording paper S side is Fwt , Fce , Fid , which is directed toward the recording paper S side as a force toward the donor D side. As forces, Fwp , Fc t , Fi t
, Fx can be considered. Here, the force F'wt is the van der Waalska force between the toners, Fce is the electric force due to the transfer electric field, Fid is the mirror image force between the donor and the toner via the toner layer on the donor side, F'wp is toner and recording paper S
Fct is the Coulomb repulsion force between the toners, and Fx is the adhesion force such as the bolt effect, which is the force that acts between the toner and the recording paper.

On the other hand, in the state shown in FIG. 1 (It), the force acting on the toner T is F'wd as a force directed toward the donor D.

11i'ce, Fid, and the force directed toward the recording paper S is Fwp.

Fit and Fx are considered. The newly emerged force Fwd is the van der Waalska, Fwd between Toner and Donor D.
id is the mirror force of the toner charge due to the donor D.

In order to compare the forces shown in Fig. 1 (11) and the forces shown in Fig. 1 (■), the forces shown in Fig. 1 (13) and the forces shown in Fig. 1 (I
Taking the difference in force shown in I), we get (Fwd +Fid) - (F'wt-Fct +Fi
d). If we express these forces in concrete terms and perform all the calculations, the result will be approximately. The first term is based on van der Waalska, and the second term is
The term is an electrical force.

r represents the radius of the toner, a represents the amount of charge of the toner, and a represents the dielectric constant of air. In performing the calculations, the dielectric constant of the recording paper was 80%, and the dielectric constant of 10ε0 was adopted in accordance with the experimental results.

From this result, we can understand the following. In other words, among the toner layers on the donor that make up the background pattern, some are easily transferred to the recording paper, while others are difficult to transfer. ing. Things are easily transferred<<, things that are not are easily transferred.

Incidentally, in the state shown in FIG. 1 (1), the force acting on the toner on the recording paper S side is, and under these conditions, the toner on the recording paper S side is not transferred onto the recording paper S either. In the above equation, E is the transfer electric field acting on the toner, and d is the thickness of the recording paper S.

In this way, some toners are easily transferred to the background pattern, while others are difficult to transfer.
What was easily transferred was transferred together with the image pattern forming toner, increasing the density of the background portion of the recorded image.

Therefore, in the present invention, among the toners constituting the background pattern, those that are easily transferred are removed from the donor in advance by a collection means, and then the toner constituting the image pattern is transferred. This prevents the image density from increasing in the background portion of the recorded image.

The following will explain the specific example shown in the drawings.

In the example shown in FIG. 2, numeral 1 is a donor, numeral 2 is a hopper, numeral 3 is a doctor, numeral 4 is a multi-needle electrode, and numeral 5 is a doctor.
Reference numeral 6 indicates a transfer roller, and reference numeral 6 indicates a collection means.

The toner 1 is roller-shaped, and is made of a metal roller whose circumferential surface is covered with a layer of conductive silicone rubber.The toner 1 is arranged with its rotational axis perpendicular to the drawing, and has a rotational function in the direction of the arrow. and is electrically grounded.

The hopper 2 has an opening for supplying toner, and this opening is covered by the upper circumferential surface of the donor 1; the toner T stored inside the hopper 2 is disposed above the donor 1.
It is supplied from the opening to the upper circumferential surface of the donor 1 in the direction of the donor rotation axis.

The doctor blade 3 is electrically conductive and is disposed on the left side plate of the hopper 2, and its edge is brought into pressure contact with the circumferential surface of the donor 1 in the direction of the donor rotation axis by a pressing means 31.

The multi-needle electrode 4 is in the form of a thin plate whose longitudinal direction is perpendicular to the drawing, and on the 10,000 side end face along the longitudinal direction, minute end faces of a large number of embedded needle electrodes are arranged along the longitudinal direction. towards the direction;
The combustion regulators are arranged and exposed in a single row or in a plurality of rows, and this side end surface is brought into pressure contact with the upper left peripheral surface of the donor 1 over the longitudinal direction.

The transfer roller 5 is an electrically conductive roller, and the donor-i
It is provided in parallel with the donor 1, and is arranged so that it can convey the recording medium S under pressure in the direction of the arrow in cooperation with the donor 1.

1. The doctor 3 is connected to a power source El, and the transfer roller 5 is connected to a power source E2.

In this example, the collecting means 6 is a conductive roller 6.
0, a collection tool 61, and a blade 62. Roller 601'i, donor 1. To be more precise, it is provided parallel to the donor 1 with a minute gap between it and the toner layer formed on the donor 1, and is connected to the power source E3. This power source E3 is for bias voltage.

The edge of the blade 62 is pressed against the peripheral surface of the roller 60 (D) in a so-called counter direction.

During recording, the donor 1 rotates in the direction of the arrow.

Then, the toner T supplied to the donor 1 is formed into a uniform layer on the peripheral surface of the donor 1 by the action of the doctor 30. At this time, the negative charge applied to the doctor 3 causes the toner T to be injected with negative charge. Therefore,
The single layer of toner formed on the donor 1 is uniformly negatively charged.

When this single layer of toner passes through the position of the multi-needle electrode 4, an image signal is applied to the multi-needle electrode 4 as a positive voltage pulse signal. From the needle electrode driven by this signal,
Since a positive charge is injected into the toner that comes into contact with this, the toner into which the positive charge has been injected changes its charging polarity to positive polarity.

Therefore, one layer of toner that has passed through the position of the multi-needle electrode 4 is composed of positively charged toner and negatively charged toner. The distribution of positively charged toner forms an image pattern, and the distribution of negatively charged toner forms a background pattern.

A considerable portion of the negatively charged toner that constitutes this background pattern,
In other words, some of the weakly adhesive materials and relatively strong adhesive materials to the donor 1 are collected on the circumferential surface of the roller 60 and scraped into the collection tool 61 by the blade 62. Of course, since an electrical repulsive force acts between the positively charged toner and the roller 60, the positively charged toner is not collected.

The gap between the roller 60 and the toner layer is 0.3 to Q, 511
The bias voltage applied to this 1c is suitably about +500 to 700V. It has also been found that when an alternating current voltage of about 100 to 150 square meters is superimposed on the above-mentioned direct current voltage as a bias voltage, the effect of collecting negatively charged toner is increased.

Next, the positively charged toner constituting the image pattern is transferred onto the recording medium S according to the charge distribution pattern. The recording medium S is generally plain paper. The toner image obtained by the transfer is fixed onto the recording medium S by a fixing device (not shown).

In experiments, the apparatus shown in FIG. 2 produced recorded images with extremely low background image density, no background stains, and high resolution. Note that at this time, the eaves voltage from the power source E2 was -100V.

Figure 3 illustrates the process described above.

FIG. 1 m shows the formation of a layer of toner T and the injection of negative charges by the doctor 3, and FIG. 1 (It) shows the multi-needle electrode 4.
Fig. 2 schematically shows the injection of positive charges according to an image signal. The marks in Fig. 3 indicate the collection of negatively charged toner by the collecting means 60 and the roller 60, the transfer of positively charged toner (IV) in the same figure, and the state after transfer (■) in the same figure.

The toner T collected by the collection tool 61 may be disposed of as is, or may be transported to the hopper 2 by an appropriate transport means for reuse.

Incidentally, one of the features of the present invention is that the collecting means does not come into contact with the toner on the donor during collection, and this point will be briefly explained below.

From the standpoint of collecting the toner constituting the background pattern, it seems more efficient to bring the collecting means into even more contact with the toner. However, 2. When the collecting means is brought into contact with a single layer of toner, - due to the contact pressure caused by this contact, the bulk density of the toner in the single layer of toner increases and the volume resistance decreases, and the charge from the collecting means to the toner is reduced. Injection is more likely to occur. Considering that the bias voltage applied to the collection means has the same polarity as the charged polarity of the toner forming the image pattern, in other words, the polarity opposite to that of the toner forming the background pattern, this charge injection is mainly caused by This is performed for one pair of toners forming the background pattern 7.

When charge injection is performed in this way, some of the toner that makes up the background pattern reverses its polarity and becomes the same polarity as the toner that makes up the image pattern. It will rise.

In addition, if the collecting means and the toner layer are separated, there will be a mirror image between the collecting means and the toner forming the image pattern. A large force is applied, and therefore, a portion of the toner constituting the image pattern is also collected by the collecting means, resulting in a decrease in the density of the recorded image.

As a precautionary measure to prevent such problems, it is conceivable to cover the surface of the collection means with an insulating layer, but even with this, van der Waalska between the collection means and the image pattern separated toner can be prevented. In addition, due to the electric field acting on the collection section, charge injection from the donor to the toner constituting the image pattern is likely to occur, and as a result, the density of the image area in the recorded image is also reduced.

For this reason, the collection member and the toner layer are kept out of contact during collection.

In the example shown in FIG. 4, a belt-shaped rotating member is used as the collecting means. Please note that to avoid confusion,
The same reference numerals as in FIG. 2 are used in FIG. 4 and FIG.

The bias voltage of the collection means 7 shown in FIG. 4 is controlled by the switch Sw from the power source E31. By switching E32, its polarity can be switched.

When collecting toner, the switch Sw is closed to the power source E31 side. When toner is not collected, that is, when not recording, the switch Sw is closed to the power source E32 side. Then, by rotating both the donor 1 and the collecting means 7 in the direction of the arrow, the collected toner can be returned onto the donor.

In the example shown in No. 51 No. 1, the collecting means 8 includes the roller 80
, blade 81, and doctor 83 constitute the main parts. The blade 81 is supported by the swinging arm 82 and can move toward and away from the roller 80 . Also roller 8
0 is itself separable from donor 1.

3. Figure 5 (I) shows the state during collection. As the roller 80 moves away from the donor 1, the blade 81 presses its edge against the roller 80.

The collected toner is transferred to a roller 80 by a blade 81.
It is removed from the 0 circumferential surface.

Figure 5 shows the state at the time of non-recording. That is,
The roller 80 is in contact with the donor 1, and the blade 81 is spaced apart from the circumferential surface of the roller 80.

As the bias voltage to the roller 80, a negative voltage from the power source E2 is applied by switching the switch Sw. Donor 11 and roller 80 both rotate in the direction of the arrow. - The toner 7T on the roller 80 is formed into a uniform layer on the roller 80 by the action of the doctor 83, which is integrated with the roller 80 in response to the displacement of the roller 80. Then, at the contact portion between the roller 80 and the donor 1, it is returned onto the donor 1 by electrical force. The contact between the roller 80 and the donor 1 promotes toner return. At this time, the transfer roller 5 is retracted and released from contact with the donor I. This retraction of the transfer roller 5 is also performed in the example shown in FIG.

In the examples shown in FIGS. 4 and 5, the absolute value of the power source E32 may be approximately the same as the absolute value of the power source E31. It was found that the toner O return efficiency was improved by making the speed equal to the peripheral speed of the donor and f:J. In this case, it is more effective to make the circumferential speed of the belt or roller larger than the y-speed of the donor.

[Brief explanation of drawings]

, ig1 is a diagram to clarify the problems in the conventional recording method, and FIG. 2 is a front view schematically showing only the main parts of an example of an A-type apparatus implementing the present invention. 2 is a diagram for explaining the process of the present invention using the device shown in FIG. 2, and FIG. 4 is a front d diagram showing only the essential parts of another example of the device for carrying out the present invention. , FIG. 5 is a diagram illustrating another example of the apparatus for carrying out the present invention. 1... Donor. , 2...Hopper, 3...Doctor, l...Multi-needle electrode, 5...Transfer roller, 6...
- Collection means, 60... conductive roller, 61...
Collection tool, 62...brush door, El, E2...power supply,
E3... Power supply for bias T) 7 and ÷ 2 Procedural amendments (voluntary) 2 May 1980 1 Indication of the incident 1988 Patent Application No. 44852 2 Record of the name of the invention Method 3 Relationship with the case of the person making the amendment Appointment of patent applicant
Location 1-3-6 Nakamagome, Ota-ku, Tokyo Name (
674) Ricoh Co., Ltd.-4 Agent 156 Address 2-6-28-5 Sakuragaoka, Setagaya-ku, Tokyo
"Detailed Description of the Invention" column of the specification to be amended and Drawing 6 Contents of the amendment (11 M 7 ji 9th line 6') rFi
Correct it as t J f r FiTj. (2) “It is a repulsive force” and “F
Between ``X'' and ``FiT is the mirror image force between the transfer roller and the toner through the recording paper,'' is corrected. (4) Correct the formula on page 9, line 8. (5) Correct the formula as the 9th negative, 9th line from the bottom. (6) The code [FitJ in Figure 1 of the drawings is corrected to ``FiT'' as in the attached drawings. /'F')Z mouth

Claims (1)

[Scope of Claims] 1. In a single layer of toner on a donor, an image pattern and a background pattern to be a background for this image pattern are formed with opposite polarities, by using charge injection into the toner.・
In a recording method in which toner forming an image pattern is formed as a charge distribution of toner and is transferred onto a recording medium according to the charge distribution pattern, either directly or via an intermediate transfer medium, the charge of the toner to be transferred is A collecting means to which a bias voltage of the same polarity is applied is brought close to the toner layer after the charge distribution has been formed, with a minute gap therebetween, and the magnitude of the bias voltage is set to the size of the minute gap. The collecting means is set to be sufficiently lower than the discharge starting voltage according to the voltage, and after a considerable portion of the toner constituting the background pattern is removed from the donor, the toner constituting the image pattern is transferred. Recording method. 2. The recording method according to claim 1, wherein the collecting means has a rotating member in the form of a conductor, such as a roller or a belt. 3. The recording method according to claim 2, wherein the collecting means has a mechanism for removing toner from the rotating member. 4 In claim 2 or 3, it is possible to switch the polarity of the bias voltage applied to the rotating member, and during non-recording, a bias voltage with the opposite polarity to that during recording may be applied. A recording method characterized by causing the collected toner to return onto a donor. 5. The recording method according to claim 2, 3, or 4, characterized in that the rotating member is brought into contact with the donor during non-recording. 6. The recording method according to claim 5, wherein the donor and the rotating member that are in contact with each other during non-recording have different moving speeds at the contact portion.