JPH0557589B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a regular-reverse copying method that is capable of positive-positive copying for forming a positive copy image from a positive image and negative-positive copying for forming a positive copy image from a negative image.

BACKGROUND ART Reader printers are generally required to have both positive-positive and negative-positive copying functions because they have positive and negative microfilms. In addition, in recent years,
A reader printer that uses a powder image transfer type image forming method has been proposed, and in this image forming method, a photoreceptor is charged, image exposed, developed, and transferred to obtain an image on transfer paper. - Since powder images are formed under different conditions for positive and negative images, a slight change in conditions may cause a situation in which a good image cannot be obtained, especially during transfer. In particular, when environmental conditions change, particularly under high humidity, or when the transfer paper is changed, the transfer efficiency decreases, making it impossible to obtain a good image.

Purpose of the invention The present invention has been made in view of the above facts.
The purpose is to be able to consistently obtain good images with high transfer efficiency even when environmental conditions change or the type of transfer paper is changed, and the method itself is simple and easy to use. The object of the present invention is to provide a normal-reverse copying method that can perform negative-positive copying.

Embodiment FIGS. 1 a to e and 2 a to e show a series of steps of a normal-reverse copying method according to the present invention, and FIGS. 1 a to e relate to a method of obtaining a positive image copy from a positive image. Figures 2a to 2e show a series of steps in a method for obtaining a positive image from a negative image.

First, the positive-positive copying method shown in FIGS. 1a to 1e will be explained. In the first step, as shown in FIG. In this process, the corona electrode 3 of the scorotron charger 2 is connected to a high voltage source 4, the grid electrode 5 is connected to a DC bias voltage source 6, and the surface of the photoreceptor is connected to the voltage applied to the grid electrode 5. is charged to a potential approximately equal to . Incidentally, instead of this scorotron charger 2, a normal corotron charger may be used for charging. Further, the photoreceptor is a conductive substrate 1
The photoconductive layer 1b is laminated on the photoconductive layer 1b, and has photosensitivity to both positive and negative polarities. Such photoreceptors include those made by dispersing CdS/nCdCO ₃ (0<n≦4) photoconductive powder with a binder resin and coating it on a substrate, or amorphous silicon produced by glow discharge decomposition method. Can be used.

The second step is a step of exposing the positive image 7 to form an electrostatic latent image as shown in FIG. 1b, in which the potential of the image area is substantially maintained, but the potential of the non-image area is optically attenuated to a constant potential. The third step is to develop the electrostatic latent image thus formed, and as shown in FIG. Developing is carried out under the application of a bias voltage Vb1 that is approximately equal to or somewhat higher than the potential. Specifically, a two-component developer is used, and one example is a non-magnetic insulating toner and a developer that is triboelectrically charged with the toner and has a resistance value of 10 ¹² Ω.
cm or more, has a particle size of about 5 to 40 microns, is made by dispersing magnetic fine powder in an insulating resin, and the proportion of the magnetic fine powder to the whole particle is 50 to 75% by weight. At least two components can be used: a high-resistance magnetic carrier and a high-resistance magnetic carrier.

This developer has already been developed by the applicant in JP-A-55
Although it is disclosed in Publication No. 32073,
It is significantly superior to conventional lenses, especially in terms of resolution and tolerance. More specifically, in the above 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. Manufactured. Here, as the above insulating resin,
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. In addition, magnetic fine powders include Fe ₂ O ₃ and Fe ₃
O ₄ , ferrite, etc. may be selected as appropriate. On the other hand, conventionally known non-magnetic insulating toners can be used, and have an average particle size of about 5 to 50 microns and a volume resistivity of about 10 ¹⁴ Ω·cm or more.

Then, the high-resistance magnetic carrier and the non-magnetic insulating toner are stirred and frictionally charged to opposite polarities,
A magnetic brush tip is formed on the magnetic brush developing roller 8, and while applying a bias voltage Vb1, non-magnetic insulating toner is deposited by regular development at a potential between Vb1 and Vo1. Note that the developer is not limited to those mentioned above, and any known two-component developer can be used.

The fourth step is the step of transferring the developed image to the transfer paper 10, in which positive corona ions are applied from the back side of the transfer paper by the transfer corona charger 12 connected to the high voltage source 11. This is done by At this time, the transfer corona charger 12 is set so that the amount of corona discharge is larger than that in the case of negative-positive copying, which will be described later. This is because the force acting between the photoreceptor and toner in negative-positive copying is repulsion, whereas in positive-positive copying it is suction, and in addition, under high humidity conditions, the transfer conditions deteriorate significantly, causing corona discharge. By setting a large amount, a good image with excellent transfer efficiency can be obtained. The amount of corona discharge can be changed by, for example, changing the voltage or current applied to the corona electrode or changing the distance from the photoreceptor 1.
Various methods can be adopted.

The toner image thus transferred onto the transfer paper 10 is then fixed by a heat roller 13, as shown in FIG. 1e, and a positive copy image is finally obtained from the positive image.

Next, I will explain the negative-positive copying method.
The first step is to uniformly charge the photoreceptor 1 to a predetermined surface potential Vo2 with the scorotron charger 2 to a negative polarity, which is the opposite polarity to that in the case of positive-positive copying, as shown in FIG. 2a. 3 to negative high voltage source 14
This is done by applying a bias voltage to the grid electrode 5 from a negative DC bias voltage source 15 while applying a higher voltage.

The second step is to expose the negative image 16 to the photoreceptor 1, which has been uniformly charged to a negative polarity, to form an electrostatic latent image, as shown in FIG. Although not attenuated, the image area potential of the light irradiation section is attenuated to a constant potential. In the following third step, Figure 2c
As shown in , in the step of developing the electrostatic latent image, the same developer is used as in the case of positive-positive copying, and the same magnetic brush method is used. however,
At this time, a negative bias voltage Vb2 set approximately equal to the non-image area potential is applied to the developing roller 8 from the DC bias voltage source 17, and the toner is deposited between Vb2 and 0 volts by reversal development.

The fourth step is a step of transferring the reversely developed image, and as shown in FIG.
The amount of corona discharge at this time is set to be smaller than that in the case of positive-positive copying. In the case of negative-positive copying, this is
This is because the repulsive relationship between the toner and the photoreceptor makes it possible to transfer the toner with a smaller electrostatic attraction force than in the case of positive-positive copying. The transferred image is then fixed by a heat roller 13 as shown in FIG. 2e.

FIG. 3 shows the configuration of a reader printer capable of carrying out the above-described regular-reverse copying method according to the present invention,
The microfilm carried on the carrier 20 is detected by a lamp 21, and its image is guided to a screen 25 via a first scanning mirror 22, a swinging mirror 23, and a fixed mirror 24 at the time of reading. On the other hand, during printing, the swinging mirror 23 is retracted to the dashed line position, and the first scanning mirror 22 and the second scanning mirror 26, which is movable integrally with the mirror 22, first move to the dashed line position A, and then both move integrally to the broken line position B, scan the image on the microfilm in a slit shape, and expose this image onto the photosensitive drum 1 via the fixed mirror 27 and the slit 28.

Around the photoreceptor drum 1, there is the aforementioned scorotron charger 2 and a sleeve 29 that rotates together with the scorotron charger 2.
A developing roller 8 including a magnetic roller 30 provided therein, a transfer corona charger 31, a separation corona charger 31, a blade cleaner 32, and an eraser lamp 33 are provided.

The transfer paper 10 is transferred from the cassette 34 to the paper feed roller 3
5 or from a manual paper feed port 36 by a pair of feed rollers 37, and passes through a pair of rollers 38 and a pair of timing rollers 39 to reach the transfer position. When the transfer is completed, the transfer paper passes through the heat roller 13 and is discharged outside the machine.

At the start of copying, the photosensitive drum 1 rotates counterclockwise and the scorotron charger 2
When the microfilm carried on the carrier is a positive image, it is charged to a positive polarity, and when it is a negative image, it is charged to a negative polarity to a surface potential of Vo1 or Vo2. Subsequently, the microfilm is transferred to the first and second scanning mirrors 2.
2 and 26 are sequentially projected onto the photosensitive drum 1 to form an electrostatic latent image (corresponding to the second step in FIGS. 1b and 2b). The electrostatic latent image thus formed is then developed by the developing roller 8 under the application of a bias voltage of Vb1 for normal development and Vb2 for reversal development (Fig. 1c, 2). (corresponding to the third step in Figure c). The developed image is then transferred to the transfer paper 10 by the transfer corona charger 12, but the amount of corona discharge at this time is higher than that for positive-positive copying in order to obtain an image with high transfer efficiency under high humidity conditions. (corresponding to the fourth step in Figure 1 d and Figure 2 d). Next, the transfer paper 10 is separated from the drum surface by a separating corona charger 31 and fixed by a heat roller 13, while the remaining toner is removed from the photosensitive drum by a blade cleaner 32.
Further, residual charges are erased by the eraser lamp 33 in preparation for the next copy.

Experimental example In the reader printer shown in Figure 3, photoreceptor drum 1 is placed on an aluminum drum with a diameter of 80 mm.
A 30 micron thick photoconductive layer made by dispersing CdS/nCdCO ₃ photoconductive fine powder in a thermosetting acrylic resin with a solvent, and an insulating protective layer made of acrylic resin with a thickness of 0.5 micron or less on top of the photoconductive layer. A positive micro film is used, and a scorotron charger 2 is used to apply 570V to the grid electrode 5 under normal temperature and humidity conditions.
The drum surface was positively charged to 550V by applying a bias voltage of . Subsequently, images of the microfilm were sequentially projected by the first and second scanning mirrors 22 and 26 to form an electrostatic latent image. Next, a bias voltage is applied to the sleeve 29 of the developing roller 8 from a DC bias voltage source 9.
300V was applied as Vb1, and this electrostatic latent image was developed with a contrast of 550V to 300V. Note that the highest image portion potential is approximately 550V, and the non-image portion potential is 300V or less. At this time, the aforementioned high-resistance magnetic carrier and non-magnetic insulating toner were used as the developer. Specifically, the carrier has a resistance value of 10 ^{to 14} Ωcm, is made of styrene acrylic polymer, contains carbon black and magnetic fine powder, has an average particle size of 20 microns, and contains 60% by weight of magnetic fine powder based on the resin. Toner has a resistance value of 10 ¹⁵ Ω.
The carrier and toner were mixed in a carrier to toner ratio of 9:1.

This developed image is transferred to the corona charger 1.
2 to transfer paper 10 and transfer efficiency was measured. At this time, the output current (aluminum tube current) of the transfer corona charger 12 is changed from 13 μA to 50 μA for each copy.
When measured as variable, the characteristics shown by curve A in FIG. 4 were obtained. In addition, a negative film was used instead of a positive microfilm, and the drum surface was charged to -450V with Scorotron charger 2.
An electrostatic latent image was formed on the photoreceptor drum by successively projecting images of the negative film using the optical system described above. Next, the DC bias voltage source 17 applies the bias voltage Vb2 to the sleeve 29 of the developing roller 8.
300V was applied and this electrostatic latent image was developed in reverse with a contrast of 0V to -300V. Highest image potential is omitted.
0V, and the non-image area potential is -300 to -450V.

This developed image is transferred to the corona charger 1.
2 to the transfer paper 10, and the transfer efficiency was measured. When the output current of the transfer corona charger 12 was varied from 5 μA to 37 μA, the results shown by curve B were obtained.

The results shown in Fig. 4 show that although the optimum transfer conditions are different depending on positive-positive and negative-positive under normal temperature and normal humidity, the transfer efficiency is good as long as the output current of the charger 12 is within the above range.
At around 25 μA, good transfer efficiency common to positive-positive and negative-positive is achieved. As mentioned above, the reason why the optimum transfer conditions differ between positive and negative is due to the difference in the electrostatic attraction between the photoreceptor and the toner, and is derived from the potential of each image area. Under the same conditions as above,
However, when the same experiment was conducted under high temperature and high humidity,
In positive-positive copying, good images could not be obtained when the output current of the charger 12 was less than about 40 μA.
For these reasons, the optimum output current required for transfer is different between positive and negative, and especially for positive and negative.
This confirms that the positive value must be increased.

Effects As is clear from the above explanation, according to the normal-reverse copying method according to the present invention, it is possible to always obtain good images with stable transfer efficiency even under changes in environmental conditions, and the method The method itself is simple and has excellent effects, such as being able to easily obtain optimal positive-positive and negative-positive transfer images.

[Brief explanation of the drawing]

Figures 1 a to e and Figures 2 a to e are diagrams showing a series of steps of the regular-reverse copying method according to the present invention;
This figure shows the configuration of a reader printer that can carry out the method according to the present invention, and FIG. 4 is a diagram showing the relationship between the output current of the transfer corona charger and the transfer efficiency. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 2...Scorotron charger, 8...Developing roller, 9, 17...DC bias voltage source, 12...Corona charger for transfer.

Claims (1)

[Claims] 1. A first step of charging a photoreceptor; a second step of exposing a positive image or a negative image onto the photoreceptor to form an electrostatic latent image; and a development bias using a two-component developer. By switching the voltage, the positive latent image is normally developed as a positive image, while the negative latent image is reversely developed as a positive image.
and a fourth step of transferring under a larger amount of corona discharge than during positive copying.