JPS62291673A - Formation of outline image - Google Patents

Abstract

PURPOSE:To develop the positive image of an outline image by forming a developing process for normally developing an electrostatic latent image formed through a 2nd electrostatic charging process for executing recharging while impressing voltage having the same polarity as that of a 1st charging process by charged toner having the reverse polarity against the 1st charging process. CONSTITUTION:After exposing a negative image to the surface 1 of an electrostatic sensitive body to which the charge of fixed potential is applied by an electrostatic charger 2, a grid 42 is recharged while impressing voltage sufficiently lower than the surface potential of the non-image part of an electrostatic latent image formed by an exposure process 3 and having the same polarity as the charger 2 by a scorotron charger 4 to which DC voltage or alternate voltage having the same polarity as the charger 2 is impressed. The surface potential of the electrostatic latent image part other than the outline part of the image part is dropped down to almost the grid voltage and then the electrostatic latent image formed through the scorotron charger 4 is normally developed by the charged toner having the reverse polarity against the charger 2. Consequently, the charged toner is stuck to the outline part of the electrostatic latent image part with high potential and the outline image is turned to a positive image.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a contour image forming method as one of the image forming methods by electrophotography, and in particular to a method for forming a contour image using a negative original image, a laser, an LED, etc. The present invention relates to a method of forming a contour image corresponding to the contour outer periphery of a negative image formed by.

BACKGROUND OF THE INVENTION Conventional techniques and their problems In general, contour lines are a part of an image that contains a lot of information, and at the same time sufficiently express the characteristics of the image, and thus play an important role in the image. In contrast, images that have been converted into binary figures with contour lines are easier to identify than ordinary grayscale images.

Extremely easy to handle in various processes such as determination and transmission,
Converting an image into a binary figure by drawing a contour line is extremely effective in terms of image pattern recognition, image correction/enhancement, bandwidth compression, and the like. Also, for example, by repeating two copies and adding a colored outline around a black pattern to make it more noticeable, or by painting one pattern in different colors to create patterns with different colors, so-called It is also useful when preparing a coloring pattern.

By the way, conventional methods for forming contour images of this type include:
The present applicant has already developed static electricity using conductive toner. In a type of one-component toner development method that develops a latent image, a direct current having a potential intermediate between the maximum value of the surface potential of the member to be developed and the maximum /J% value and having a polarity opposite to that of the electrostatic latent image charge is used. proposed a method characterized by extracting the outline of an electrostatic latent image on a member to be developed by applying a bias between the member to be developed and a conductive toner carrier (Japanese Unexamined Patent Publication No. 51-1346).
(See Publication No. 35).

However, in this method, the contour formed as an electrostatic latent image is a negative image, and the conductive toner adheres to areas with a large potential difference based on the potential difference on the surface of the electrostatic latent image carrier, that is, areas other than the contour line. Therefore, the developed image is obtained only as a negative image. Normally, the required contour image is a positive image (black image), so in order to make a positive image, the negative contour image obtained by this method must be copied again using reversal development. have.

In order to solve the above problems, the contour image forming method according to the present invention includes: (1) a first charging step of applying a constant electric charge to the surface of an electrophotographic photoreceptor; (i) the first charging step; (i) an exposure step in which a negative image is exposed on the surface of the electrophotographic photoreceptor that has undergone the exposure step; and (i) an electrostatic latent image formed on a grid in the exposure step using a Suflotron charger on the surface of the electrophotographic photoreceptor that has undergone the exposure step; a second charging step of recharging while applying a voltage that is sufficiently lower than the surface potential of the non-image area and of the same polarity as the first charging step; and (iv) the image formed through the second charging step. A developing step of regularly developing the electrostatic latent image with a charged toner having a polarity opposite to that of the first charging step.

In other words, a negative image is exposed on the surface of the electrophotographic photoreceptor that has been charged with a constant potential in the first charging step (see (a) in FIGS. 3 and 6), and then in the second charging step. The surface potential of the electrostatic latent image non-image area formed on the grid in the exposure process is sufficiently lower and Recharging is performed while applying a voltage of the same polarity as in the first charging step. As a result, the surface potential of the non-image area of the electrostatic latent image drops to approximately the grid voltage, leaving the outline of the image area (see (b) in Figure 3). When the voltage is applied, the surface potential of the image area also increases slightly to approximately the grid voltage, except for the area near the contour area [see (b) in FIG. 6].

Next, the electrostatic latent image formed through the second charging step is normally developed using a charged toner having a polarity opposite to that of the first charging step. This leaves the static 'rI1. Charged toner is applied to the contour of the latent image area, and the contour image is developed as a positive image [see Figures 3 and 6 (
c) Reference m].

Embodiment [First embodiment, see FIGS. 1 to 3] FIG. 1 schematically shows an electrophotographic copying apparatus for carrying out the first embodiment, in which the electrophotographic photosensitive drum (1) has an outer periphery. It is a well-known device that has a photoconductive layer on its surface and can be rotated in the direction of arrow <8), and around it are the following members,
Equipment is installed.

The electrification charger (2) is for performing a first electrification that applies a constant electric charge to the surface of the photoreceptor drum (1), and a power source (21) is connected to the charge wire.

The exposure device (3) uses a well-known slit exposure method to place a static image of 7 mm on the surface of the photoreceptor drum (1) corresponding to a negative original image.
This is for forming a latent image, and is composed of an exposure lamp, a mirror, a lens, etc. In addition, exposure device (3)
As long as it can form a negative electrostatic latent image,
A scanning type exposure method using an electric signal such as a laser or LED may be used.

The suflotron charger (4) is connected to the exposure device (3).
) is used to perform a second charge on the surface of the photoreceptor drum (1) on which an electrostatic latent image has been formed. ) is M
i(43) is connected. A DC voltage with a polarity opposite to that of the charger (2) is applied from a power source (41) to the wire, and a voltage of -t'ji is applied to the grid (42).
(From (43), it is possible to apply a voltage that is sufficiently lower than the surface potential of the non-image area of the electrostatic latent image and has the same polarity as the charger (2). Note that the voltage applied to the grid (42) needs to be higher than the surface potential of the electrostatic latent image area whose potential has decreased in the exposure device (3).

The developing device (5) is a well-known magnetic brush system equipped with a developing sleeve (51) containing a magnet roller (52) magnetized with N and S poles on the periphery, and also functions as a developing electrode. An electric FA (53) for developing bias is connected to the developing sleeve (51).The developer is made of a mixture of a magnetic carrier and an insulating toner, and is charged to opposite polarities by frictional electrification. The toner is charged to a polarity opposite to that of the charger (2).Here,
If the insulating toner does not have magnetism, the developing sleeve (51) is supplied with a charger that is slightly higher than the surface potential of the non-image area of the electrostatic latent image that has decreased in the second charging process from the power source (53). A developing bias of the same polarity as (2) is applied. The insulating toner may have magnetism, and a bias of a voltage slightly lower than the surface potential of the non-image area of the electrostatic latent image lowered in the second charging step is applied to the developing sleeve (51). You can leave it there. Further, it is also possible to apply a developing voltage in which an alternating current voltage is superimposed.

If the toner has magnetism, it is possible to use only insulating toner.

The transfer charger (6) applies an electric field from the back side to the copy paper (10) being conveyed in the direction of arrow (b), and the developing device (5) applies an electric field to the surface of the photoreceptor drum (1). It is used to transfer the formed toner image onto the copy paper (10), and its charge wire is electrically connected! (61), a voltage having a polarity opposite to that of the insulating toner is applied.

The separation charger (7) applies an alternating current electric field to the copy paper immediately after transfer to remove static electricity from the copy paper (10) and separate it from the surface of the photoreceptor drum (1). An alternating current voltage is applied to the wire from electricity 1 (71).

The cleaning device (8) uses a blade method to remove toner remaining on the surface of the photoreceptor drum (1).

The eraser lamp (9) is used to remove charges remaining on the surface of the photoreceptor drum (1) by irradiating light in preparation for the next copying process.

Here, the polarity and voltage of each charger, etc. in the first embodiment will be shown.

[I] When using non-magnetic insulating toner Charge ~ [Power supply (21)] Positive polarity +5.5kV Scorotron charge + [Electricity 1 (4t)] Negative polarity -6
, OkV Grid [power supply (43)] Positive polarity +200v Grid-photosensitive drum distance (dg) 1.5mm Developing bias [Ml, source (53) positive polarity +300■ Transfer charger [voltage 1 (61) positive polarity +5 .5kV Non-magnetic insulating toner Negative polarity [1[] When using sensitive insulating toner Charger [M, Source (21) Positive polarity +5.5kV Sufroto a', -f Yasha [TfEi (41>]
- Negative polarity - 6, OkV Grid [TL source (43)] Positive polarity +200■ Grid-photosensitive drum distance (dg) 1.5 mm Developing bias ['rri source (53)] Positive polarity (DC)
+170V (AC) 350Vrms, 1kHz Development start potential +250V Magnetic insulating toner Negative polarity Note that all of these polarities may be reversed.
Of course, the voltage value is only an example.

The outline image forming method using the copying apparatus described above will be explained step by step.

(1) First charging step A charger (2) applies a constant electric charge to the surface of the photoreceptor drum (1). As a result, in the first embodiment, the surface potential of the photoreceptor drum (1) is +600V.

(i) Exposure step A negative original image is exposed to slit light on the surface of the photosensitive drum (1) charged to a potential of +600V to form a negative electrostatic latent image. In this case, as shown in (a) in Figure 3,
The potential of the portion corresponding to the image area (Δ>, (B) decreases to about +100V by light irradiation, and the potential of the portion corresponding to the non-image area remains at +600V.

(i) Second charging step The surface of the photoreceptor drum (1) on which the negative electrostatic latent image is formed is charged with a polarity opposite to that of the electrostatic latent image using a scorotron charger (4). Recharge.

At this time, a voltage of +200 V is applied to the grid (42) from TIl,m (43) when non-magnetic insulating toner and magnetic insulating toner are used. The voltage applied to the scorotron charger (4) has a polarity opposite to that of the first charging step, and the voltage applied to the grid (42) is sufficiently higher than the surface potential of the non-image area of the electrostatic latent image (<+600V). and has the same polarity as the first charging step. Note that the voltage applied to the grid (42) is higher than the surface potential (+100V) of the electrostatic latent image areas (A) and (B).

Electric lines of force shown by arrows in FIG. 2 are formed between the surface of the photosensitive drum (1) and the grid (42).

Then, the negative polarity ions generated from the charge wire are subjected to a sending force along the lines of electric force. In this case, the electric lines of force that direct negative ions toward the surface of the photoreceptor drum (1) in the vicinity of the grid (42) are only present in the background area excluding the outside of the contours of the image areas (A) and (B). It has not occurred. Therefore, negative ions are present in image areas (A) and (B) as shown by arrows →.
It reaches only the background part excluding the outside of the outline part, and eliminates the charge in the reached part to lower the potential to near the grid voltage (Vg).

That is, if we explain the surface potential of the photoreceptor drum (1), as shown in FIG. 3 (b), the image areas (A), (B)
The outside of the contour has a constant width and is at the initial surface potential of approximately +
It is left as a high potential part of 600v, and the image part (A
>, (B) is also left as a low potential part of approximately +100V, and the surface potential of the non-image part is the same as that of the image part (A) and (B).
The voltage decreases to approximately the grid voltage (Vg), leaving the outside of the contour. Specifically, -6, OkV to the scorotron charger'rrt source (41) when the insulating toner is non-magnetic and when it is magnetic.

Grid Z de' FF: When a voltage of +200V is applied to the source (43), the voltage decreases to around +200V.

In other words, in this second charging step, the image area (A),
This means that the outline in (B) is formed as a positive electrostatic latent image.

(iv> Developing step In the second charging step, the electrostatic latent image formed as a positive image of the contour portion is developed in the developing device (5). If the insulating toner does not have magnetism, Developing sleeve (51
) is applied with a developing bias of +30QV. This developing bias voltage (vb) is set to prevent toner from adhering to the non-image area of the electrostatic latent image (of course also to the image area) whose surface potential has decreased in the second charging process. It is slightly higher than the potential drop non-image area (+200V) and has the same polarity as the first charging step.

On the other hand, when the insulating toner has magnetism, the developing sleeve (51) has AC350V, 1kHz and DC+17V.
0V (7) Developing bias is applied. The developing bias voltage (Vb) is the potential of the non-image area (+20
0V). However, when an insulating toner having magnetism is used, there is a threshold value due to magnetic binding force, so development starts when the surface potential is around +250V. Therefore, toner does not adhere to and cover the electrostatic latent image area (of course, the image area) that has deteriorated in the second charging step.

As a result, the negatively charged insulating toner is attached to the high-potential areas of the photoreceptor drum (1), that is, the contour areas of the image areas (A) and (B), so to speak, and The toner image that has been formed by regular development is then transferred onto copy paper (10) by positive discharge from a transfer charger (6), and is formed as a copy image through a fixing device (not shown).

By the way, the reason why the grid voltage (Vg) is made sufficiently lower than the surface potential (+600V) of the non-image area of the electrostatic latent image is as follows.
This is because the surface potential of this non-image area is sufficiently lowered with respect to the original surface potential in the second charging step.

[111] An example will be shown in which the conditions of the scorotron charger (4) in the second charging step are changed when the non-magnetic insulating toner of the first embodiment is used. In this case, when using a non-magnetic insulating toner, the above [I
] Among the conditions, change the following items.

Scorotron charger [power supply (41)] polarity -7,
OkV Grid [power supply (43) positive polarity +300V Grid-photoreceptor drum distance (dg) 1.0mm Developing bias [voltage #1 (53)] positive polarity +250v In this modification, charging by scorotron charge ~ (4) Since the capacity becomes higher, the potential of the non-image area becomes higher than that of the image area (
Except for the outside of the outline of A) and (B), the grid voltage (
The voltage drops to around +230v, which is slightly lower than Vg).

The developing bias potential (Vb) is set to +250V, which is lower than the grid voltage (Vg) of +300V, but since the lowered surface potential is higher than +23GV, the electrostatic latent image does not appear. There is no chance of toner adhering to the image area.

In the first embodiment described above, the photoreceptor drum (
The distance It(dg) (see FIG. 2) between the surface of 1) and the grid 42) is 1.5 mm or 1,Q mm.

This value is larger than the setting of the scorotron charger that has conventionally been used in this type of electrophotographic copying machine. This is to increase the degree to which the electric lines of force are directed toward the surface of the photoreceptor in the edge portion (contour) of the plane image portion (A) or the line image portion (B), and to obtain a good contour image. The state of the electric lines of force changes depending on the pressure jilt (dg). That is, by varying the distance (dg), it is possible to arbitrarily change the width dimension of the contour line obtained as an image, and as the distance (dg) increases, the width dimension also tends to increase.

Note that this point also applies to the second embodiment described below.

[Second Embodiment, see Figures 4 to 6] This second embodiment is different from the first embodiment in that an alternating voltage is supplied from the power source (41') to the scorotron charge (4) that performs the second charging. The differences are that a voltage is applied and that a laser optical system is used as the exposure device 3. Figure 4 is different from Figure 1, Figure 5 is different from Figure 2, and Figure 6 is different from Figure 3. correspond to each. Therefore, the differences will be explained below.

Scorotron charger (4) C, n optical device M<3>
Shizuka! Electrophotographic photosensitive drum (1) on which a latent image is formed
A power source (41') is connected to the charge wire, and a grid (42') is connected to the charge wire.
The power supply (43) is disconnected. An alternating voltage is applied to the charge wire from electric m (41'), and the grid (
42), as in the first embodiment, a voltage is applied from the power source (43) that is sufficiently lower than the surface potential of the electrostatic latent image area and has the same polarity as the charger (2). ing. Note that the voltage applied to the grid 42) needs to be higher than the surface potential of the electrostatic latent image area whose potential has decreased in the exposure device (3).

In addition, the polarity and voltage of each charger etc. in the second embodiment are the same as those shown in the first embodiment, but
The voltage of the power supply (41') of Scorotron Charge (4) is AC±6.0 when using non-magnetic insulating toner. OKV, AC±6. even when using magnetic insulating toner. It is OkV.

Next, the outline image forming method will be explained step by step.

(i) First charging step A charger (2) applies a constant electric charge to the surface of the photoreceptor drum (1). In the second embodiment as well, the surface potential of the photosensitive drum 1) is +600V.

(i) Exposure step: The surface of the photosensitive drum (1) charged to a potential of +60 QV is irradiated with a laser to form a negative electrostatic latent image. In this case, as shown in FIG. 6(a), the image area (A),
The potential of the part corresponding to (B) is +100 by laser irradiation.
It decreases to about V, and the part corresponding to the non-image area is +600
It remains as a potential of V.

(i) Second charging step The photosensitive drum (1
) is recharged by a Suflotron charger (4) to which an alternating voltage is applied from a power source (41'). At this time, the grid (42) is supplied with +20V from the power supply (43) if non-magnetic insulating toner is used.
, +200 when using magnetic insulating toner
A voltage of v can be applied. The voltage applied to this grid (42) is the surface potential of the non-image area of the electrostatic latent image (+600V
) and has the same polarity as the first charging step.

Electric lines of force shown by arrows in FIG. 5 are formed between the surface of the photosensitive drum (1) and the grid (42).

Ions of negative and positive polarity generated from the charge wire to which an alternating voltage is applied are subjected to a transport force along the lines of electric force. In this case, the electric lines of force that direct negative ions toward the surface of the photoreceptor drum (1) in the vicinity of the grid (42) are only present in the background area excluding the inside of the contours of the image areas (A) and (B). It has not occurred. Therefore, as in the first embodiment, the negative ions are distributed in the image area (A) as indicated by the arrow →.
It reaches only the background part excluding the outside of the outline part in (B), eliminates the charge in the reached part, and lowers the electric potential to approximately the same as the grid voltage (Vg). Also, positive ions are indicated by the arrow →
As shown, the potential reaches only the central part of the surface image area (A) excluding the inside of the contour part, and the potential of the reached part is set to the grid voltage (V
g) to approximately the same potential.

That is, when explaining the surface potential of the photosensitive drum (1), as shown in FIG. 6(b), the image areas (A), (B)
) has a constant width on the outside of the contour and is at the initial surface potential of approximately +
It can remain as a high potential part of 600V, and the surface image part (
The inside of the contour part of A) and the line image part (B) are also almost + toov
The surface potential of the central part of the surface image part (A) remains at almost the grid voltage (Vg
), and the surface potential of the non-image area decreases to approximately the grid voltage (Vg), leaving the outer edges of the image areas (A) and (B). Specifically, if the insulating toner does not have magnetism, the Suflotron charger power supply (41' to 6.OkV, grid T
ri' To IR (43) (7) By applying +200V (7) voltage, the surface potential of the electrostatic latent image non-image area and the surface potential of the center part of the surface image area (A) rise to around +200V. Decrease and increase. Also, when the insulating toner has magnetism, the Sufrotron charge 'v Ti,1
(41') F (7) ±6. OkV, grid'w
When a voltage of +200V is applied to the source (43), the voltage similarly decreases and increases to around +200V.

In other words, in the second embodiment as well, the contours of the image areas (A) and (B) are formed as positive electrostatic latent images in the second charging step.

(iv) Developing step In the second charging step, the electrostatic latent image formed as a positive image of the contour portion is developed by a developing device (5). The development conditions and development mechanism here are the same as those in the first embodiment, but in the case of the second embodiment, the center of the electrostatic latent image surface image area (A) is Even if the potential of the area rises to approximately the same level as the grid voltage (Vg), toner will not adhere to the area and cause fogging.

Effects of the Invention As is clear from the above explanation, according to the present invention, as a second charging step, the surface of the electrophotographic photoreceptor that has undergone the negative image exposure step is exposed to a grid using a Suflotron charger. By applying a voltage sufficiently lower than the surface potential of the non-image area of the formed electrostatic latent image and having the same polarity as that of the first charging step, recharging is performed, so that the surface of the electrophotographic photoreceptor has no original image area. A positive electrostatic M in which the contour part remains as a high potential part, a latent image is completely formed, and in a further development step, the electrostatic latent image is regularly developed with a charged toner having a polarity opposite to that of the first charging step. Therefore, in this regular development, toner adheres to the contour portion of the negative original image, which is a high potential portion of the electrostatic latent image, and a contour image without toner fog can be obtained as a positive image.

[Brief explanation of drawings]

1 to 3 are for explaining a first embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of an electrophotographic copying apparatus;
FIG. 2 is a schematic diagram of the lines of electric force in the second charging step, and FIG. 3 is a graph showing the potential of the electrostatic latent image in each step. 4 to 6 are for explaining the second embodiment of the present invention. FIG. 4 is a schematic configuration diagram of an electrophotographic copying apparatus, and FIG. 5 is a diagram showing lines of electric force in the second charging step. The schematic diagram and FIG. 6 are graphs showing the potential of the electrostatic latent image in each step. (1)... Electrophotographic photosensitive drum, (2)... Charger, (21)... Power source, (3)... Exposure device, (4)... Scorotron charge ~, ( 41)
, (41')...power supply, (42)...grid, (
43)...tRl(5)...Developing device, (51)...
・Developing sleeve.

Claims (1)

[Scope of Claims] 1. A first charging step of applying a constant electric charge to the surface of the electrophotographic photoreceptor; and an exposure step of exposing a negative image to the surface of the electrophotographic photoreceptor that has undergone the first charging step. , the surface of the electrophotographic photoreceptor that has undergone the exposure step is charged with a scorotron charger to a grid that is sufficiently lower than the surface potential of the non-image area of the electrostatic latent image formed in the exposure step and has a first
a second charging step in which the electrostatic latent image formed through the second charging step is re-charged while applying a voltage of the same polarity as the charging step; A method for forming an outline image, comprising: a developing step of performing regular development with a charged toner;