JPS5995545A - Two-color picture forming method - Google Patents

Abstract

PURPOSE:To obtain a sharp dichroic picture by forming an electrostatic latent image on a photosensitive body in the opposite relation of a picture part potential to a two-color picture, developing the latent image with a developer consisting of nonmagnetic toner in the 1st color and high-resistance magnetic carriers in the 2nd color, and transferring the picture. CONSTITUTION:The rotating photosensitive body 1 is electrified positively by a corona charger 2 and exposed to the picture of an original to form a primary electrostatic latent image. The photosensitive body is then electrified negatively by a corona charger 6 and exposed to the same original through a red cutting filter 8. The electrostatic latent image having the opposite potential relation between the 1st color picture part and the 2nd picture part is developed by a magnetic brush developing device 10 and then charged by a corona charger 12 for transfer. The developing material for the device 10 uses the nonmagnetic toner in the 1st color and high-resistance magnetic carriers in the 2nd color which is electrified by friction to the polarity opposite to said toner, contains magnetic particulates dispersed in insulating resin, has >=10<12>OMEGA.cm and about 5-10mum particle size so that 50-75wt% carriers are incorporated on the basis of the whole of magnetic particles.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a two-color image forming method that uses a triboelectrically charged high-resistance magnetic carrier and a non-magnetic insulating toner as a developer to easily form a two-color image.

PRIOR ART A number of methods have already been proposed for forming two-color images; for example, Japanese Patent Laid-Open No. 55-117155
As shown in the above publication, a first photoconductive layer having photosensitivity to a first color (for example, red), an intermediate layer, and a second photoconductive layer (for example, black) are formed on a conductive substrate as a photoreceptor. A second photosensitive layer having photosensitivity is sequentially laminated, and through a predetermined process, the electrostatic latent images corresponding to the first color and second color images are made to have a relationship of opposite polarity. There is a type of toner that is formed into a visible image by developing it with two types of toners that are charged with opposite polarities and colored in different colors.

In addition to the above, a photoreceptor made by laminating a photoconductive layer having bipolar properties and photosensitivity to two colors on a conductive substrate is used as a photoreceptor, and through a predetermined process, @1 color, 2 colors An electrostatic latent image corresponding to the color image area is formed so as to have a relationship of opposite polarity, and 2
A two-color image forming method has also been proposed in which the image is developed using toners of different colors.

However, in two-color image forming methods including these methods, two developing devices are generally required because two types of toners of different colors are used, which inevitably increases the size of the copying machine. There are drawbacks. Although a method of developing two colors using one developing device has been proposed, capri or color mixture often occurs in the copied image, resulting in sharp two-color development.
It was not possible to obtain a color image.

Purpose of the Invention The present invention has been made in view of the above facts, and its purpose is to form a clear two-color image without fogging with extremely easy condition setting and a simple configuration. An object of the present invention is to provide a two-color image forming method.

SUMMARY OF THE INVENTION The first feature of the two-color image forming method according to the present invention is that it uses a non-magnetic insulating toner, which is frictionally charged to the opposite polarity to the toner and has a high resistance value of 10120 or more, A high-resistance magnetic carrier having a diameter of about 5 to 40 microns and made by dispersing magnetic fine powder in an insulating resin, in which the proportion of the magnetic fine powder to the whole particle is 50 to 75% by weight. The point is that a developer consisting of at least two components is used.

This developer has already been developed by the applicant in Japanese Patent Application Publication No. F@55-3.
This is disclosed in Japanese Patent No. 2073, and is extremely superior to conventional ones, especially in terms of resolution and latitude. More specifically, in the above-mentioned developer, the high-resistance magnetic carrier is produced by, for example, melting and mixing an insulating resin and a magnetic fine powder, cooling it, pulverizing it, and selecting the particle size to about 5 to 40 microns. Ru. Here, among the above insulating resins, polyethylene, polyacrylic acid ester,
Polymethyl methacrylate, polystyrene, styrene acrylic polymer, epoxy resin, coumaron resin, maleic acid resin, carbonic acid resin, fluoric acid resin, etc. can be used. Further, as the magnetic fine powder, Fe703FeO4, ferrite, magnetite, etc. may be appropriately selected. On the other hand, conventionally known non-magnetic insulating toners can be used, with an average particle size of about 5 to 50 microns and a volume resistivity of about 10.
It is 140 cm or more.

Then, the high-resistance magnetic carrier and the non-magnetic insulating toner are stirred and frictionally charged to opposite polarities, and developed by forming a magnetic brush using a magnetic brush development method and depositing the non-magnetic insulating toner in accordance with the latent image pattern. It is something to do.

The inventor of the present invention performed magnetic brush development under various conditions using the above-mentioned developer and discovered the following fact. That is, magnetic brush development is performed while applying a bias voltage to the development electrode. This bias pressure is set to be somewhat higher than the potential of the non-image area of the electrostatic latent image in order to prevent toner from adhering to the non-image area. The same method is used when developing with a magnetic brush using the above developer.
The inventor of the present application has stated that the first point is that non-magnetic insulating toner hardly adheres at a potential that is approximately equal to or near the bias voltage value, especially below the bias voltage value, and the second point is that, based on the bias voltage value, non-magnetic insulating toner tends to adhere It has been found that, in an inverse relationship to the latent image potential to which toner adheres, high-resistance magnetic carriers do not adhere to potentials up to a certain range of potential, but carriers adhere to potential areas exceeding that potential.

To explain this with reference to Figure 1, the vertical axis represents the image density, the horizontal axis represents the potential on the photoreceptor, and (A) and (B)
represent the amount of adhered non-magnetic insulating toner and high-resistance magnetic carrier depending on the potential, respectively. Furthermore, as will become clear from the description below, in order to obtain a two-color image in the wood F3A, the latent image potential portion corresponding to the first color image portion and the latent image potential portion corresponding to the second color image portion are required to have an inverse pattern. Therefore, for the purpose of matching this, for example, (Vl) is a latent image potential corresponding to both image areas of the first color with negative polarity, and (v2) is a potential of positive polarity corresponding to the image area of the second color. do. Further, (V, , ) is a bias voltage value set somewhat higher than the non-image area (white background area) potential (v3) and applied to the developing electrode, and (Vo) is a threshold potential of the combination of the magnetic field and the electric field.

As is clear from this figure, almost no non-magnetic toner adheres to the potential portion near the bias voltage (Vb), and in particular, no adhesion occurs at voltages below (Vb, ). On the other hand, when the potential is higher than (Vb), it adheres as shown in curve (A) to the potential area represented by the bend (Vl). On the other hand, high-resistance magnetic +m-carriers do not adhere to the threshold potential (Vo) based on the bias voltage (Vb), but the curve (B) shows the potential part (V2) exceeding that (VC). It sticks like that. This threshold potential (
Vo) depends on the magnetic force of the carrier itself, the magnetic force of the developing means itself, the latent image potential (v2), etc., but as is clear from the experimental examples described later, the absolute value is about 200 V with respect to the bias voltage (Vb). If there is a difference, carriers will adhere at a high concentration due to being higher than (V2) or (VC).

In this way, in the present invention, the non-magnetic insulating toner and the high-resistance magnetic carrier are attached to potential patterns of opposite polarity, and the high-resistance magnetic carrier has a particle size of 5 to 40 microns, which is approximately the same as that of the toner. Even when used for image formation, two-color images can be obtained because of its excellent resolution, good fixing properties, and the ability to be colored in desired colors.

FIG. 2 shows the configuration of a copying machine for carrying out the two-color image forming method according to the present invention, in which the photosensitive drum (1), which is sensitive to both positive and negative polarities and rotates counterclockwise, is first connected to the first corona charger. (2), the two-color original is uniformly charged to the first polarity, placed on a reciprocating document table (3), is exposed to light by an exposure lamp (4), and then exposed to light through a lens (5). A primary electrostatic latent image is formed by successive exposures.

This primary electrostatic latent image is then charged by a second corona charger (6) of a second polarity, and then the same document is exposed to light by an exposure lamp (7) and passed through a cut filter (8) and a lens (9). A secondary electrostatic latent image is formed.

In addition, (10) is a magnetic brush developing device for developing this secondary electrostatic latent image, and (11) is a corona for aligning the non-magnetic insulating toner and high-resistance magnetic carrier attached during development to either polarity. Charger (14) is a separating corona charger for separating the transferred transfer paper from the drum surface, (15) is a grade cleaner for removing residual developer, and (16) is for removing residual charge. It is an eraser lamp.

The above-mentioned magnetic brush developing device (10) uses the above-mentioned high-resistance magnetic carrier and non-magnetic insulating toner as a developer, and these are sufficiently stirred by the stirring roller (17) and frictionally charged to opposite polarities. be done. A magnetic roller (18) and a sleeve roller (19) are rotatable in the same direction at different speeds, and a secondary electrostatic latent image is developed by forming a magnetic brush on the sleeve roller. In addition, the sleeve roller (19) is connected to a DC voltage source (2
0)・A predetermined bias voltage (vb) is applied.

The specific structure of this developing device is, for example, disclosed in Japanese Patent Application Laid-open No. 5
5-414.60 can be used.

The two-color image forming method according to the present invention is carried out as follows using the copying machine having the following configuration. Rotating photoreceptor drum (L
) id4 is uniformly charged to a positive polarity by the first corona charger (2)K to a surface potential of (Vo) as shown in FIG. 3(a). Next, the two-color original is exposed to image light as shown in Figure 3(b).
A primary electrostatic latent image as shown in FIG. In this case, when an original containing a red image and a black image is used, the potential corresponding to the red image area due to image exposure is (Vo)
From (Vr) VC, ,, = If.The non-image area (white background area) attenuates to (Vg) close to 0, while the black image area attenuates (Vg).
) is approximately equal to

This primary electrostatic latent image having the potential pattern of (Vo, ), (Vr), (vg) is then transferred to the second corona charger (6).
It becomes negatively charged, as shown in FIG. 3(c). That is, due to negative polarity charging, the lowest non-image area potential (vg) is reversed and becomes negative polarity (vg), and the red image area potential (Vr) is also reversed to negative polarity (Vl), The potential (Vo) of the black image area remains positive (V2)
-1: Decreases. In this state, the same original is exposed again. However, at this time, exposure is performed with a red cut filter (8) interposed, and as a result, a secondary electrostatic latent image having the potential pattern shown in FIG. 3(d) is formed. Due to this exposure, the potential of the non-image area (Vg') attenuates to (v3) close to O, while the potential (vl) corresponding to the red and black image areas (■2
) is maintained until -1.

The secondary electrostatic latent image thus formed is then developed by a magnetic brush developing device (10). For example, as a non-magnetic insulating toner, the potential (V, A high-resistance magnetic carrier is tribo-electrified to a positive polarity (positive polarity) and colored red, and a high-resistance magnetic carrier is charged to an opposite polarity (negative polarity) to the potential (V2) of the black image area and is colored black. Use something similar. On the other hand, a DC voltage source (
2o) is set somewhat higher than digit (V3). By forming magnetic brush ears on the sleeve roller (19) and applying a bias voltage (Vb), (
Non-magnetic insulating toner is deposited between the voltage (V, ) @ of the red image area (vb) and the potential of the black image area (v2), and a high-resistance magnetic carrier is adhered between the voltage (Vo) and the potential of the black image area (v2).

To explain this specifically, as mentioned in connection with FIG. Red toner adheres to the red image area between Vb) and (Vl). Strictly speaking, the toner is (Vb
), it begins to adhere at a potential several tens of volts higher. on the other hand,
With respect to the potential where toner adheres relative to the bias voltage (Vb), a constant value (VC) is applied to the potential part in the opposite direction!
As mentioned above, high-resistance magnetic carriers do not adhere in .

This is (Vb),! in Figure 3(e). = (vo
) Corresponds to the potential of -4-, and there is a high resistance of black color between (VC) and the black image area potential (V2), which corresponds to the potential of -4-. Magnetic carriers adhere. In this way, two-color development is performed faithfully to the red and black original. In the above description, it has been explained that the toner and the carrier are frictionally charged positively and negatively, respectively, and colored red and black, but the relationship may be reversed. In this case, the bias voltage (Vb) is set not to a negative electrode potential that is somewhat higher than (V3) but to a lower positive electrode voltage.

As mentioned above, high-resistance magnetic carriers do not adhere to potentials within a certain range of (Vb), specifically about 200 volts, so in this sense, the potential that the gear should adhere to is at least (Vb)K. On the other hand, the potential must be sufficiently different from the absolute value of 200 volts. Furthermore, if two-color copying is not required, the toner carriers may be of the same color.

The two-color image developed on the photoreceptor drum (1) in this way is
Next, it is negatively or positively charged by a pre-charging corona charger (11). The purpose of this is to align the polarity of the high-resistance magnetic carrier to the same polarity as that of the toner. However, if the transfer is done by pressure or heat, it will be separated from 14) K and the fixing device (
21) to become the final copy. On the other hand, the residual developer on the photoreceptor drum (1) is removed by grade cleaner (1).
5), and then the residual charge is removed by an eraser lamp (16) to perform the next copy.

FIG. 4 shows another embodiment of a transfer type copying machine capable of carrying out the two-color image forming method according to the present invention. In the figure, (22) is a fixed document table on which a two-color document is placed.
Below that, a plurality of rollers (23) including a drive roller,
A photoreceptor belt (26) rotatably supported by (24) and (25) is provided. This photoreceptor belt (
An optical system unit (27) that can reciprocate and move integrally is provided between the document platen (22) and the document platen (22), and the unit has an optical system unit (27) that can evenly align the surface of the photoreceptor belt with the first polarity. A first focusing light transmitter such as Selfoc for subsequent projection (
30), a second corona charger (31) which is charged to a second polarity, and a second corona charger (31), such as a selfoc, which projects an original image illuminated by a second exposure lamp (32) through a cut filter (33). Focusing light transmitter (3
4).

During photographing, the optical system unit (27) is moved forward in the direction shown in the figure while the photoreceptor belt (26) remains stationary. As a result, the surface of the photoreceptor belt is uniformly charged to positive polarity by the first corona charger (28) as shown in FIG. 3(a) without being separated, and is successively exposed to lightning as shown in FIG. 3(b).
A primary electrostatic latent image is formed as shown in . This one
The next electrostatic latent image is sequentially formed and charged by the second corona charger (31) K of negative polarity to form the potential pattern shown in FIG. 3(c). (33) and the second convergent light transmitting member (34), and the planar portion of the photoreceptor belt facing the document table (22) is finally shown in FIG. 3(d).
) A secondary electrostatic latent image is formed as shown in FIG.

Once the secondary electrostatic latent image is formed, the photoreceptor-belt (26)
begins to rotate, and two-color development is carried out as shown in FIG. 3(e) under the application of a bias voltage (vb) by the magnetic brush developing device (10). The developed image is then charged by a pre-charging corona charger (11), transferred to transfer paper (13), and fixed by a heat roller (21).

As described above, in the copying machine having the configuration shown in Figs. 2 and 4, a photoreceptor having photosensitivity to both polarities is used to form a latent image to be finally developed by two image exposures. However, if the photoreceptor disclosed in the above-mentioned Japanese Patent Application Laid-open No. 55-117155 is used, a two-color image can be formed with one image flash, and a cut filter is not required. Specifically, this photoreceptor is as shown in FIG.
0a), a first photoconductive layer (40b), an intermediate layer (4,Oc
:' and a second photoconductive layer (40d) are sequentially laminated, and the first photoconductive layer (40b) is chargeable to a first polarity and is sensitive to light other than red light, while the first photoconductive layer (40b) is The two-photoconductive layer (40d) can be charged to the second polarity and has photosensitivity to red light.

FIG. 6 shows a schematic configuration of a copying machine that uses the above-mentioned photoreceptor (40) to obtain a two-color image. The unit irradiates the device with red light and performs positive primary charging. This allows the second photoconductive @
(40d) is made conductive, and the boundary between the second photoconductive layer (40d) and the intermediate layer (40c) has a positive charge.
) and the first photoconductive layer (4, Ob), negative charges are induced and distributed. Next, the photoreceptor (40) I/''i is charged with a negative polarity smaller than the primary charge by the second corona charger (43).
Next charging is performed, and the potential on the surface of the second photoconductive layer (40d) is reversed to negative polarity. As a result, an electric double layer is formed in the first and second photoconductive layers (40b) and (40d).

Next to the photoconductor (40) is a reciprocating document table (44).
The two-color original placed above is exposed by an exposure lamp (45) and sequentially projected through a lens (46). Due to this image exposure, the potential of the photoreceptor part corresponding to the white area becomes 0, while in the red area, only the second photoconductive layer (40d) becomes conductive, the electric double layer disappears, and the surface potential is reversed to positive polarity. . Note that the potential of the black portion remains negative. The electrostatic latent image thus formed is then developed in two colors by a magnetic brush developing device (10), the details of which are as described above. At this time, the bias voltage (Vb) may be set to the potential side of the polarity to which the non-magnetic insulating toner is desired to be attached. The rest of the structure is the same as in FIG. 2, so the same numbers are given to make it clear. Further, the process and photoreceptor for forming an electrostatic latent image corresponding to a two-color original are not limited to those described above, but are disclosed in Japanese Patent Application Laid-open No. 54-112634, Japanese Patent Laid-Open No. 55-7306, etc.
2, the method shown in J-publication etc. can be adopted,
In short, any method may be used as long as the latent image is formed so that the potentials corresponding to the first color and the second color have an inverse relationship.

An experimental example will be described below.

EXAMPLE First, the relationship between the bias voltage (Vb) and the reflection density of the attached non-magnetic insulating toner and high-resistance magnetic carrier was measured using the bias voltage (Vb) as a reference. Using the copying machine shown in Fig. 2, the photoreceptor drum (1) is 30 microns thick and is made by dispersing Cd511nCdCO3 photoconductive fine powder in a thermosetting acrylic resin together with a solvent on an aluminum drum with a diameter of 80 mm. A photoconductive layer was used, and an insulating protective layer made of acrylic resin having a thickness of 0.5 microns or less was sequentially laminated thereon. In addition, the developer is a non-magnetic insulating toner with a resistance value of 10 + 5 Ω, an average particle size of 14 microns on a steel plate, colored red and tribo-electrified to a positive polarity, and a high-resistance magnetic carrier with a resistance value of 1014 Ω.・It is colored black by containing carbon black and magnetite in a styrene acrylic polymer, and has an average particle size of 20E Cron, and the magnetic fine powder (magnetite) is 60% compared to the resin.
% by weight and was triboelectrically charged to negative polarity.

The mixing ratio of toner and carrier is 1:9, and the amount of charge is 11.
．． There is 6μC/grC.

Furthermore, the rotational speed of the photoreceptor drum was set to 110 mm/sec.

Makigno roller (18) and sleeve roller (19)
The rotational speed of the rollers was set to 1300 rpm and 3 Orpm respectively, the bias voltage (Vb) applied from the DC voltage source (20) to the sleep roller (19) was set to -50V, and the charging potential by the first corona charger (2) K was set to 1800 VK. Set.

Under the above conditions, the original was divided into three parts: white, red, and black, and the voltage applied to the second corona charger (6) was varied for each copy. The potentials of (Vl) and (V2) (see FIG. 3(d)) were changed. Then, develop two colors and apply bias voltage (
The Macbeth reflection density due to the adhesion of non-magnetic insulating toner between (Vb) and red image area potential (vl) is
The Macbeth reflection density due to the adhesion of high-resistance magnetic carriers between the black image area potential (V2) and the black image area potential (V2) was measured.

The results are as shown in FIGS. 7(a) and (b)K. In FIG. 7(a), the non-magnetic insulating toner is
It adheres to a potential that is somewhat higher than Vb) on the (Vl) side, and the concentration increases as the potential difference increases. Specifically v
, -Vb is -60V (Vl -1110V), the reflection density is 0.3, -120V is 0.5, and -150V is 0.
76, it becomes 0.95 at -200V.

As mentioned in Figure 3(e), this is true for (Vb) & (V,
) means that the toner adheres to the space between the two.

On the other hand, as shown in Fig. 7(b)K, the high-resistance magnetic carrier is
It does not adhere within a range of approximately 200V from the bias voltage (Vb), but begins to adhere at a potential difference greater than that.

When the threshold voltage v2-vb is 0.80.170V, the reflection density is equal to 0 and no carriers are attached. It does not adhere to a certain range of potential, and it is confirmed that it does not adhere between (Vb) and (vc) in Fig. 3(e).However, when V2-Vb is 2
At 00V, carriers start to adhere and the reflection density also becomes 26
0v at 0.2, 370v at 0.45, 440v at 0.6
07 at 4.470V. (V2) and (vc)
A carrier is attached between the two. In addition, Fig. 7 (a), (b)
The rise and slope of each curve can be controlled to some extent by the development conditions and the physical property values of toner and carrier, and in particular, carrier adhesion starts when there is a difference of about 200V from (Vb). Further, among the two-color developed products obtained as described above, there was no capri, although there was a difference in density, and the results were good.

Effects As is clear from the above explanation, the two-color image forming method according to the present invention can obtain a clear two-color image without capri with a single developing device under extremely easy condition settings.

Furthermore, the structure itself is simple and has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the adhesion amount of the non-magnetic insulating toner and high-resistance magnetic carrier used in the present invention and the potential based on the bias voltage, and FIG. A schematic configuration diagram of a copying machine that can be implemented, FIGS. 3(a) to 3(e) are diagrams showing a two-color image creation process, and FIG. 4 is another embodiment of a copying machine that can implement the method of the present invention. , FIG. 5 is a diagram showing a photoreceptor that can be used in the present invention, FIG. 6 is a diagram showing a schematic configuration of a copying machine employing the photoreceptor shown in FIG. 5, and FIGS. b) is a diagram showing the relationship between the reflection density change due to the adhesion of non-magnetic insulating toner and high-resistance magnetic carrier when the bias voltage and image area potential are changed. (1)...Photosensitive drum, (2)(28)...First
Corona charger, (6) (31)...Second corona charger, (10)...Magnetic brush developing device, (20)
...DC voltage source, (Vb) ...bias voltage, (V
C)...threshold potential, (vl)...first color image portion voltage, (V2)...second color image portion potential. Applicant: Minolta Camera Co., Ltd. Figure 1 Figure 2 Figure 3 (α) In Figure 7 I)) ta * (Vz-Vb)

Claims (1)

[Claims] (1) photoreceptor; second, a first step of forming an electrostatic latent image in which a first color image area potential and a second color image area potential have an inverse relationship corresponding to a two-color image; Using a developer consisting of a non-magnetic insulating toner of a first color that is tribo-charged to a polarity and an insulating resin that is tribo-charged to a second polarity, the electrostatic latent image is applied to a developing electrode by a magnetic brush development method. While applying a bias voltage set near the potential of the non-image area, non-magnetic insulating toner is applied to the first color image area.
A second step of developing by attaching a high-resistance magnetic carrier to the second color image area, and forming a two-color dual image according to claim 1, characterized in that the second color image area is attached to the image area with the following steps: Method.