JPH02184869A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a negative/positive image forming device such as a copying device installed in a reader printer or the like that performs regular (positive) development and reversal (negative) development. .

(Prior Art) In recent years, there has been a demand for microreader printers that make copies from microfilm to make copies not only from negative film but also from positive film. In response to these demands, it would be undesirable to prepare separate copying machines for negative film and positive film, as it would require the cost and space for the number of copying machines. Most users use negative film, and positive film is rarely used. Furthermore, even when using positive film, it is rare to frequently exchange negative and positive films.

Taking into consideration these requirements and usage methods, we have proposed a method of satisfying these requirements at low cost, in which the main body of the copying machine is one that includes a developing device or a developing device and various process equipment such as a drum cleaner. By replacing the kit,
A method has been devised to easily convert a negative film microprinter into a positive film microprinter.

(Problem to be Solved by the Invention) However, this method is not sufficient, for example, simply changing the toner in the developing device from a developer for negative film to a developer for positive film, and it may lead to wasteful consumption of toner. There was a problem in which the movement of the density adjustment volume's shading display and the actual copy's shading were reversed.

Furthermore, as copying machines have become smaller in recent years, the internal or external volume of the copying machine has become narrower, making it difficult to install large objects such as parts. Therefore, it is difficult to always provide process equipment dedicated to negative films and positive films inside the device.

Furthermore, in recent years, when designing microreader printers or laser beam printers (LBPs), etc., it is better to design based on a copier or LBP that has already been commercialized in terms of schedule and cost, and to improve the degree of completeness. Efficiency can also be improved in terms of reliability and reliability. Therefore,
Although it is desirable to design and commercialize an analog type printer that has a dual-use function that can be used in common with the regular development system and the reversal development system, the difficulties that arise in this case are described below. In other words, the following (1) and (2) standardization of reversal development (making a positive copy from a negative film, hereinafter referred to as NP) and regular development (making a positive copy from a positive film, hereinafter referred to as PP) ) Difficult due to reason (3).

(1) The polarity of some high-voltage process equipment is different. For example, in the above N-P, the primary charge and the transfer charge have different polarities, while in the P-P, the primary charge and the transfer charge have the same polarity.

(2) Setting values depending on image quality are different between NP and PP. For example, a) conditions for appropriate values (light amount, charging settings, etc.) are different. b) There is a significant difference in gradation and image density. C)
Depends on latent image contrast. In other words, primary charging (■
. :Dark potential), N-P is ■. By increasing the contrast by increasing the contrast, fogging does not occur even when the ``v''decreases; however, when the ``vo'' is high in P-P, characters tend to be blurred.

(3) In order to standardize the system, it is necessary to configure the system so that it can switch high voltages, but this requires a large capacity high-voltage relay for high-voltage switching, which requires a large amount of space. Furthermore, if each device is provided with a high voltage transformer, the total cost of the entire device will increase. Furthermore, sufficient consideration must be given to electrical safety, resulting in complicated wiring and connections. Therefore, even if a printer is equipped with a dual-use function, the current situation is that a person called a technician or a service person is responsible for switching the polarity, changing settings, switching the high voltage, replacing the transformer, etc., and it is the so-called user. It was difficult for me to respond on my own.

This invention was made in view of the above problems,
To obtain a negative/positive image forming apparatus that can easily switch high voltage by changing the polarity of the process equipment and changing the setting values of the process equipment without having process equipment dedicated for negative film and positive film installed inside. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, in the present invention, one type of image forming apparatus is replaced by replacing a process cartridge including a plurality of process devices provided according to copying modes. In a negative/positive image forming apparatus that selectively performs multiple copying modes including normal development mode or reverse development mode using It is characterized in that it has a high voltage generator unit with a generator and a signal source for generating signals for process changes.

(Function) The present invention having the above configuration is provided with each high voltage generator unit according to the copying mode, and the high voltage generator unit is provided with not only a high voltage generator but also a signal for changing the process. By providing a signal source that generates a There is no need for large-capacity photoelectric relays for high voltage switching. Further, by providing a signal source that generates a signal for changing the process, the polarity of the process equipment can be changed and the set value can be changed.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 shows a microreader printer showing a specific embodiment of the present invention. That is, in this microreader printer, the following four copy modes can be selected.

■ Obtain a black positive copy from negative film.

■ Obtain a black positive copy from positive film.

■ Obtain a red copy from negative film.

■ Obtain a red copy from positive film.

There are four modes.

In these four modes, when a process cartridge (hereinafter referred to as a cartridge) P prepared for each mode is inserted, a signal is emitted from a copy mode signal source 30 (described later) attached to this cartridge P, and a signal is generated to determine the type of toner. Alternatively, the image forming process for copying is changed to match the copy mode.

The basic image forming process of this microreader printer will be explained below.

In the device shown in the figure, A is the microfilm l as the original.
B is an illumination unit, B is an optical scanning mechanism unit, C is a copying mechanism unit having the cartridge P, and the means surrounded by double rectangles are signal generation sources S1, S2. Shows S3.

First, in the illumination section A, the microfilm 1 (for example, roll microfilm, microfiche film, microstrip film, etc.) It is searched by the illumination unit A using a search mechanism or manually and held stationary. The film frame image la of the illumination section A is illuminated from below by an illumination lamp 2 such as a spherical halogen lamp through a condenser lens 4, and the film-transmitted light of the illumination light enters the projection lens 5.

3 is a reflector for the illumination lamp 2, and E6 is an exposure amount control circuit for the lamp 2.

Next, in the optical scanning mechanism part B, 7 is an optical scanning unit formed by arranging first and second mirrors (plane mirrors) 8 and 9 facing each other on a common support member 9a so that the surfaces including the reflective surfaces intersect with each other at right angles. It is. This unit 7 is always on standby with the position indicated by the dashed dot line on the left side in the figure as its home position, and based on a scanning start command signal, a drive mechanism (not shown) moves the photosensitive drum 10 as an image forming body to the right to be described later.
It is driven forward in the direction of arrow a at a speed of 1/2 of the rotational circumferential speed of , and when it reaches the end point of the forward movement indicated by the two-dot chain line on the right side of the figure, it is driven backward in the direction indicated by the arrow, and the home position is on the left side of the figure. be returned to.

When the optical scanning unit 7 is on standby at the home position, the first mirror 8 is located outside the optical path of the projection lens 5, and the film frame image projection light emitted from the projection lens 5 is transmitted to a glue screen (not shown). direction (arrow β direction)
The image of the film frame image 1a is projected in an enlarged manner on the screen surface (reader state).

On the other hand, an enlarged copy of the film frame image 1a
When a copying switch (not shown) is turned on, the copying mechanism section C starts operating and the photosensitive drum 10
is driven to rotate in the direction of the arrow at a predetermined circumferential speed. Further, as described above, the optical scanning unit 7 is driven forward from the home position in the direction of the arrow a at a speed of 1/2 of the circumferential speed of the photosensitive drum 10.

During the forward movement of the optical scanning unit 7, the film frame image projection light from the projection lens 5 is sequentially scanned by the first mirror 8 and reflected to the second mirror 9, and from the second mirror 9 to the optical slit. The optical slit 1 passes through the slit 12 in the direction of the drum generatrix of the unit 11 and enters the exposure position d of the rotating photosensitive drum 10, that is, the enlarged projected image of the film frame image 1a passes through the slit 12 on the circumferential surface of the rotating photosensitive drum 10.
2, the slit exposure in the drum generatrix direction is used as main scanning,
Slit exposure (image exposure) is performed sequentially by using the movement of the drum surface as the photosensitive drum 10 rotates as sub-scanning.

The above illumination lamp 2 - condenser lens 4 -> projection lens 5 - first mirror 8 - second mirror 9 - optical slit unit 11
- The system that reaches the exposure position d of the photosensitive drum 10 is an optical system that performs image exposure on the photosensitive drum 10.

The photosensitive drum 10 of the apparatus of this example is made up of an OPC photosensitive member having a two-layer structure of a conductive layer and a photoconductive layer on the circumferential surface of a drum base, and undergoes the following processes sequentially during its rotational driving process. image formation is performed, and the desired film frame image 1 is
An enlarged image copy of a is output. That is, for example, the negative electrode is uniformly charged by the primary charger 21.

○ The above image slit exposure at exposure position d.

Through the above process of 0 and 0, an electrostatic latent image of a negative high potential dark area potential and a negative low potential bright area potential corresponding to the image exposure pattern is sequentially formed on the circumferential surface of the photosensitive drum 10.

0 Toner development of a latent image by the developing device 22.

At this time, when the microfilm 1 is a positive film and a positive copy is obtained (hereinafter referred to as PP), the toner in the developing device 22 is a positive (+) toner. On the other hand, when obtaining a positive copy using a negative film (hereinafter referred to as NP), negative (-) toner is used as the toner in the developing device 22.

Transfer material 24 of developed toner image by O transfer charger 23
Transcription to.

In the N-P copy mode here, the polarity of the transfer charger 23 is positive (+), which is the opposite polarity to the toner.

Similarly, in the PP copy mode, the transfer charge polarity is negative (-).

○ Static elimination needle electrode 2 from the photosensitive drum 10 surface of the transfer material 24
5, separation by bias, introduction into a fixing device (not shown), and discharge to the outside of the apparatus (copy output).

■ Cleaning of the photosensitive drum 10 surface after transfer by the cleaner 26.

Removal of residual electrostatic latent images and paper memory by O pre-exposure lamp 27.

■ Blank shutter 28 and blank exposure lamp 2
9 prevents excess toner from adhering to the non-image area of the film frame image 1a of the microfilm 1 in the process O. That is, in the case of negative film, the blank exposure lamp 29 does not operate and the blank shutter 2
In the case of positive film, the blank shutter 28 is not operated and the blank exposure lamp 29 is used to expose the non-image exposed area. These controls are performed by a blank exposure/blank shutter switching circuit E13.

Now, as described above in the outline of one embodiment of the microreader printer shown in FIG. 1, the individual image forming processes need to be changed as appropriate for negative film and positive film.

In the microreader printer of this embodiment, the following four copy modes can be selected as described above. That is, ■ Obtaining a black positive copy from a negative film (hereinafter referred to as N
-P -B) mode, ■ Obtaining a black positive copy from positive film (hereinafter referred to as P-P -B) mode, and ■ Obtaining a red copy from negative film (hereinafter referred to as N-P-R). ) mode and ■ Obtaining a red copy from positive film (hereafter P-P
-R) mode, and the following four modes.

In these four modes, by inserting the cartridge P prepared for each mode, the image forming process of copying corresponding to the type of toner or the copy mode is performed in accordance with the copy mode signal source 30 attached to these cartridges P. Be changed.

The relationship with which each copy image forming process is changed by the copy mode signal will be explained below. We will also explain in detail the reasons for the change and the problems that existed in the past.

First, the aforementioned cartridge P corresponding to the type (negative film or positive film) and color (black or red) of the microfilm l as the original to be copied is inserted into the main body of the microreader printer. Then, a signal is generated from the copy mode signal source 30 of a portion of the cartridge P. The generation and flow of this signal is shown in FIG. 3.The signal may be either a mechanical signal or an electrical signal. It should be noted that the microfilm l used as the original to be copied is such that the user of the machine can visually confirm and determine whether it is a negative film or a positive film. After selecting the cartridge P according to the determined original, the next step is to check the type of original (negative film or positive film) in the microreader printer.
It is necessary to change each process depending on the situation, but in this example, the high voltage generator (hereinafter referred to as H, 1 each of high pressure for separation and high pressure for developing bias generation (・V-
Tl, 2, 3.4 are made into units, and each process is automatically changed by replacing the H, ■, and T units H. Therefore, the H/V-T unit H and the cartridge P must be replaced bare.

FIG. 2 is a perspective view of the H/■/T unit H of FIG. 1. Space for storing the H, ■, and T units H must be secured in advance inside the copying section of the microreader printer.

In FIG. 2, there are two terminal plates 4 inside this copying section.
1.42 is provided, and each terminal board 41.42 is provided with a plurality of terminals, and these terminals are H, ■, and T.
It has a structure that fits and contacts the terminal on the unit H side. First, one terminal board 41 has a terminal 41-14 for receiving high-voltage electrical output from the H, ■, and T units H.
1-2.41-3.41-4 are provided. Among these, the terminal 41-1 is wired so that it can be connected to the primary charger 21, and the terminal 41-2 is similarly wired to the transfer charger 23.
The terminal 41-3 has a wiring connected to the static eliminating needle electrode 25, and the terminal 41-4 has wiring connected to the developing sleeve of the developing device 22. The other terminal board 42 has terminals 42-1, 42-2, 42-1 and 42-2 for receiving low-voltage electrical output from the H, ■, and T units H, respectively.
42-3.42-4.42-5°42-6.42-7 are provided. These seven terminals are connected to the primary charger 2.
Control signals issued to generate high voltage in process equipment such as 1, signals for determining processes according to negative film, positive film, or color (red or black), and high voltage processes such as transfer charger 23 This is a terminal that serves as a power source (low-voltage power source) to drive the device. In other words, the terminal 42-1 is a low voltage source of DC 24V, and the terminal 42
-2 is a terminal for GND (ground), terminal 42-
3 is a terminal for primary high voltage control, terminal 42-4 is a terminal for transfer high voltage control, terminal 42-5 is a terminal for high voltage control of static eliminating needle electrode 25, and terminal 42-6 is a terminal for high voltage control of developing device 22. The terminal 42-7, which is a terminal for controlling the developing bias, indicates whether the inserted cartridge P is for negative film or positive film, and what color the developer is (black or red).
This is a terminal that serves as a signal source for detecting whether the

Next, the terminals on the H-VT unit H side will be explained. H・
(2) Inside the T unit H, there are four transformers for generating high voltage: a primary high voltage transformer T1, a transfer high voltage transformer T, a static eliminating needle high voltage transformer Ts, and a developing bias high voltage transformer T4. Among these, the primary high voltage transformer T1 has terminal H
-1, and contacts the terminal 41-1 on the device main body side. Further, the transfer high voltage transformer T2 is connected to the terminal H-2 and comes into contact with the terminal 41-2 on the apparatus main body side. The static eliminating needle high voltage transformer T3 is connected to the terminal H-3 and the terminal 41-3 on the device main body side.
come into contact with. The developing bias high voltage transformer T4 is connected to the terminal H-
4 and contacts the terminal 41-4 on the device main body side.

In addition, the H/■/T unit H has terminals t-1, t-2, t- which serve as a signal source and low voltage source for outputting signals to each terminal provided on the terminal board 42 on the device main body side. 3, t-4,
It has t-5, t-6, and t-7. These terminals t-1
-t-7 is the terminal 42-1 to 42-7 on the device main body side.
contact with each.

By the way, as described above, in the negative/positive image forming apparatus of this embodiment, it is possible to select four copy modes combining negative film, positive film, black, or red. In order to prevent erroneous copying, the cartridge P and H-VT unit H must be correctly combined and inserted into the main body of the apparatus. Therefore, in order to detect whether this combination is correct, the terminal t-7 and the terminal 4 are connected to each other.
2-7 contacts have meaning. In other words, the signal from terminal t-7 is sent to terminal 42 to determine whether the correct H/■/T unit H has been inserted into the cartridge P that has already been inserted.
Confirm by receiving -7.

As mentioned above, depending on the copy mode selected from the four copy modes, not only the cartridge P but also the cartridge H
- By inserting the V-T unit H into the main body of the micro reader printer, the functions of the respective terminals H-1 to H-4 and t-1 to t-7 provided on the H, ■, and T units H It becomes possible to make necessary process changes according to the selected copy mode.

Next, as mentioned above, there are four copy modes: N-P, B, P-P.
- When converting -B, P-P-R, and N-P-R in the main body of -, we explain how each process element needed to be changed and the problems that existed in the past for each process element. Explain in detail.

[Setting the amount of charge by the primary charger] As described above, the microreader printer according to the embodiment of the present invention uses four types of cartridges P so that four copy modes can be taken.

Using these four types of cartridges P in each copy mode, standard originals commonly used on the market (negative film or positive film) can be printed at an appropriate density near the center of the same or approximately equivalent density adjustment volume. It is preferable to copy it with .

However, numerically speaking, the development characteristics of negative or positive films, black or red films are slightly different, and therefore it is necessary to correct the image forming process.

The V-D curve on the right side of FIG. 4 is the N-P- curve according to this embodiment.
B, P-P-B, and P-P-R are three types of toners representing the development density with respect to the potential change on the surface of the photosensitive drum 10, and the curves DI, Dll, and DII are N-P-B, respectively.
, P-P-B, and P-P.R toner V-D curves are shown. On the other hand, the EV curve on the left side of the figure shows the change in latent image potential when the image exposure amount is changed after the photosensitive drum 10 is charged with a predetermined potential by the primary charger 21. be.

Here, the potential V is selected so that an appropriate image and appropriate density can be obtained for the toner having the N-P-B copy mode, that is, the DI development characteristic.

In other words, when a predetermined amount of light is applied to microfilm 1 (negative film) in the EV curve in FIG. On the DI of the V-D curve, there is a potential VBI with a reflection density of 0.07 or less without fog and a density of 1.07 in the text area.
A potential ■L1 at which 0 is obtained is given.

Next, when microfilm 1, which is a positive film, is inserted under these charging conditions, that is, the EV curve remains V+, and a copy is made with P-P-B toner, the background part of the positive film is The relationship between the bright and dark areas of the text area is reversed, and a fog-free potential VL2 is given to the light amount EL of the background area on the V-D curve DIT of the positive film developer, but the text information area For the light ff1E, a problem arises in that only a potential VI12 and a reflection density of 0.9 can be obtained.

Therefore, cartridge P containing toner P-P-B
In this case, it becomes necessary to increase the current flowing through the primary charger 21. Therefore, the E-V curve in Figure 4 is ■,
Raise the potential so that it becomes 2. As a result, in the EV curve V2, the light amount E of the character information area of the positive film is
8 on the V-ri curve D II. 'That is, 1.
A reflection density of 0 is obtained.

Therefore, it is possible to obtain the same density with a standard original for N-P-B and P-P-B. Similarly, when a P-P-R toner is developed using the EV curve ■ used in N-P and B, the V-D curve of this toner is DIII, so the potential is VB3, i.e. 1.2
A reflection density of 5 is obtained. This would result in too high a concentration and increase fogging, so by reducing the current flowing through the primary charger 21 so as to obtain a reflection density of 1.0 similar to the N-P/B mode, as shown in FIG. E-V curve ■1 to ■.

decrease to. As a result, a potential V as' is obtained for the light amount of the character portion Ea, and a copy density of 1.0 and N-P-B
A reflection density similar to that obtained can be obtained.

In this way, depending on one type of toner, that is, the type of cartridge P, the toner's V-D curve DI, Dll, DIII
I: By selecting matching EV curves V+, V2, and Vs, the same reflection density can be obtained for different toners.

In addition, as another embodiment of the present invention, for example, P-P/R red toner can be used to match a specific toner or purpose of use, such as wanting to make copies a little lighter or darker. It is possible to prepare many types of cartridges P.

The above describes a method of changing the primary charging conditions, but as another example, it may be possible to affect one of the image forming processes such as the developing bias or the image exposure amount.
Since a large amount of operations are required depending on individual requirements, this problem can be solved by determining the combination of the H/2/T unit H and the cartridge P in each embodiment of the present invention.

[Image Exposure Settings] As described above, the microreader printer according to the embodiment of the present invention can obtain enlarged copies of negative and positive films. By the way, in a negative film, the background part is finished to a predetermined film density, and the text part is transparent. On the other hand, in a positive film, the background part is transparent and the text part is finished at a predetermined density.

In this way, even if two films with different properties are simply subjected to imagewise exposure with the same amount of light, it is not possible to obtain a proper image. Therefore, the standard negative film used in the market,
For positive films, the appropriate amount of light for negatives and positives is determined so that appropriate images can be obtained under standard image forming conditions.

For example, appropriate amounts of light for negatives and positives are determined and registered in the exposure amount control circuit E6 so that an appropriate image of each film described above can be obtained at the standard position or center position of the adjustment range of the density adjustment volume D4. Similarly, a film with a higher density than each of the films mentioned above.

Similarly, for light films, the exposure amount control circuit E6,
The appropriate exposure amount is controlled manually or automatically by controlling the terminal voltage of the illumination lamp 2 using signals from the signal generation sources Sl and S2. Note that the illumination lamp 2 is changed according to an instruction from the copy mode signal source 30 so as to provide an appropriate amount of light depending on the magnification magnification.

As a result, a proper image of a standard document at each magnification can be obtained at the center or standard position of the density adjustment volume D4.

In the above, the exposure amount of the illumination lamp 2 was changed so that an appropriate image could be obtained for each film or copy mode.
As another embodiment, the same effect can be obtained by changing the process conditions of the primary charger 21 or the H, ■, TD5, etc. for controlling the developing bias.

[Blanking Means Setting 1] As described above, the microreader printer according to the embodiment of the present invention obtains copies by using toner charged to opposite polarities for negative film and positive film, respectively.

At this time, except when developing a latent image corresponding to the document on the photosensitive drum 10 in each copy mode, the photosensitive drum l
It is undesirable for toner to adhere to O because it consumes excess toner and contaminates the inside of the machine. Therefore, each copy is The mode developing device 22 is provided with a copy mode signal source 30 for determining N-P or P-P.
Signals from 2 are outputted, and the means for preventing toner from adhering to the non-image area operates according to each copy mode.

For example, in the exposure system, the blank exposure lamp 29 and the blank shutter 28 are used as the signal generation source S according to each process mode.
For example, a blank exposure/blank shutter switching circuit E13 is operated by a signal from S3 and S3 to prevent toner adhesion.

On the other hand, in the development system, the development bias is set according to the latent image potential of the non-image area so that toner does not adhere, and the development bias is set based on the signals from the signal generation sources St and S3 according to each process mode (for development bias control). On the other hand, in the charging system, a pre-exposure lamp 27 is used to prevent toner from adhering to non-image areas, and to provide a preferably uniform latent image potential. ,
Based on the instruction from S3, the pre-exposure lamp 27 operates to prevent toner from adhering.

As described above, the exposure system, development system, and charging system operate individually or in combination to prevent toner from adhering to non-image areas.

[Density adjustment settings]

In microreader printers that obtain copies from both negative originals and positive originals, various problems have conventionally occurred because density adjustment in the N-P mode and P=P mode has been performed using one density adjustment volume.

First, since a common density adjustment lever is used in N-P and P-P modes, there are many adjustments that are unnecessary in a particular copy mode, narrowing the range to obtain an appropriate image, and making it difficult to use the above in actual operation. There was a problem in which the image density changed significantly when the lever was moved slightly.

Second, even if the document is a standard original, there is a problem in that an appropriate image cannot be obtained unless the density adjustment volume is located at a position offset from the center of the density scale.

Thirdly, in the NP mode and the PP mode, the lever movement of the density adjustment volume and the direction in which the copy density increases are reversed.

This embodiment solves the above-mentioned problems by always determining the appropriate volume variable range and increase/decrease direction according to each copy mode. The density adjustment VR (volume) D4 in FIG. 1 is NP.

It always determines an appropriate volume variable range and direction of increase/decrease according to the P-P copy mode.

These details are detailed below.

At present, the background transmission density of the negative microfilms used in the market is 0.6 to 1, with the center being 0.
．． In most cases, the background transmission density of positive microfilm is around 0.06 to 0, i44, with the background part transmission density being around 0.08.

FIG. 5 shows the exposure amount of the background part when a predetermined amount of light is applied to the microfilm I mentioned above, and the exposure amount on the horizontal axis also corresponds to the exposure amount of the EV curve in FIG. 4, and EL, Ea also corresponds to FIG.

In Fig. 5, assuming that Fl is a standard negative film and Fb is a standard positive film, latent image formation is performed in the fourth embodiment in order to set the exposure amount so as to obtain an image without fogging in the background area. The EV curve V1 shown in the figure is used, while the development process is an image forming process using the V-D curve DI in the NP mode and the V-D curve Dm in the PP mode. N-
In P mode, the exposure lamp voltage ■ in Fig. 6 is adjusted so that when film F is inserted, the exposure amount of the background part becomes EB.
If N is set, a fog-free copy can be obtained from the development characteristics of the curve DI. Similarly, in the P-P mode, when the film Fb is loaded, the lamp voltage ■9. By setting the following, you can obtain fog-free copies.

As mentioned above, regarding the center value of the density adjustment volume D4,
If the voltage is set so that the lamp voltage is VN in the NP mode and vo in the PP mode, an appropriate image can be obtained at the center of the volume for standard films F- and Fb.

The above describes an example in which the density adjustment volume D4 is adjusted by controlling the exposure amount of the exposure lamp 2 (see FIG. 7 described later), but the same applies to the case where the developing bias is controlled as shown in FIG. 1 or as described later. As shown in Figure 8, the center setting of the developing bias output is set for standard negative/positive film F in each mode.

Settings can be made so that an appropriate image can be obtained according to Fb.

Next, the variable width of each mode of the density adjustment volume will be described below.

First, in the NP mode, as shown in Fig. 5, a film F with a light background (transmission density 0.6) and a film F with a dark background (transmission density 1.4), which are negative films, are used.
Appropriate lamp voltage VNI for the standard film F mentioned above
When exposed at I, the exposure amount is ES for the film FC.
For C and film F, E Nd. Therefore, if the exposure amount is kept as it is, fog will occur in the background area of the film Fc as shown by the EV curve and V-D curve in FIG. 4, and the film Fa
There is no fogging, but light letters and thin small letters disappear and the letters become difficult to read.

Therefore, films F6 and F4 have the proper exposure amount E for image formation, film Fc has a voltage lower than the lamp voltage VNa, V N ct film Fd has a voltage higher than VNa.
. In this case, it is possible to set a preferable image for each film in which thin characters and small characters without fogging in the background are reproduced.

Similarly, for P-P mode, film F with a dark background
, (transmission density 0.14), light film Fc in the background
Even for (transmission density 0.06), if the voltage of the background part of each film is set as V, , V, (see Figure 6) so that the appropriate exposure amount EL mentioned above can be obtained, fog can be reduced. A proper image with no blemishes can be obtained.

In FIG. 5, E pan Eat is the exposure amount of the films F, Ft when the lamp voltage of Vp+ mentioned above is applied. Therefore, the variable voltage of the density adjustment volume D4 is from ■Nc to V□ in N-P mode, while P-P
mode is v2. to Vpf, and N-P becomes P-
It requires a larger variable width than the P mode, and also requires a larger voltage such as the standard voltage V N11+Vpb. Similarly, the variable range and center value of the density adjustment volume D4 may be set by controlling the developing bias voltage.

Next, the specific structure of the density adjustment volume D4 will be shown using examples of exposure amount control in FIG. 7 and development bias control in FIG. 8.

First, to explain in detail the example of controlling the exposure amount shown in FIG. It's in control. The control voltage (1) is supplied from a 24 V power source in order to generate the control signal VREkl. In the figure, VRI and VH2 are density adjustment volumes in P-PN-P mode, and they move simultaneously as two volumes. Regardless of the copy mode, these volumes VRI and VH2 reverse the direction of the power source V and zero potential so that when they move downward in the 1st direction of the scale, the copy becomes darker, and when they move upward in the 9th direction of the scale, the copy becomes lighter. The circuit is configured so that R
1. R2 is the density adjustment volume V in P-P mode
This is a resistor that sets the variable range of the upper and lower limits of RI, and the resistor R1 is determined so that the lamp voltage Vpf appears when the VRI is at the lower end of the scale 9, as shown in FIGS. 9 and 6.

Similarly, the resistance R2 of VH2 is determined according to the above-mentioned Vpe. Similarly, R3 in the NP mode. R4
are determined so that control voltages corresponding to VH@ and VNC are output, respectively. On the other hand, the density adjustment volumes VRI and VR
Standard lamp voltage at scale 5 of 2■. As shown in FIG. 6, <vN is determined by the resistance ratio of the resistor R2, the density adjustment volume VR2, and the resistor R4, and the density scale and resistance change of the volume VR2. Also, ■ and ゎ in the PP mode can be determined in the same manner.

As described above, the circuit in which each control voltage can be set is configured as shown in Fig. 7 so that the variable range in N-P mode is larger than that in P-P mode, so that the density scale and control in each copy mode can be adjusted. The relationship with voltage changes as shown in FIG.

Therefore, as shown in FIG. 6, the output of the exposure lamp also has a larger output range in the NP mode than in the PP mode.

In such a configuration, the relationship between the scale of the density adjustment volume D4 and the image (copy) density is also N-P and P-P as shown in FIG.
The image density changes regardless of the copy mode, and changes depending on the lightening direction. Also, with standard films on the market, a proper image can be obtained near density scale 5 regardless of the copy mode.

On the other hand, FIG. 8 shows an example of the density adjustment volume D4 when adjusting the density using the developing bias, but in this case as well, the purpose can be achieved with a control circuit (not shown) similar to that shown in FIG. I can do it. Incidentally, FIG. 1 is one example thereof.

As described above, according to this embodiment, the density adjustment volume D
4 to control the exposure lamp voltage or the developing bias voltage, the N-P mode is set to a larger predetermined voltage than the P-P mode, and its variable range is set wide, and By reversing the direction of increase/decrease, depending on the N-P mode and P-P mode,
It is possible to achieve a density adjustment volume D4 that is suitable for the density of a negative film or a positive film and does not include an unnecessary adjustment margin.

As explained above, H-V surrounded by the dashed line in Figure 1
- Since the T unit H is easily replaceable by the user in correspondence with the process cartridge P and the microfilm 1 as a document, sufficient versatility can be achieved to correspond to a variety of purposes in small quantities in copying machines, and it is safe and It has become highly reliable. It goes without saying that when switching from N-P mode to P-P mode, the copy sequence will be performed at a timing that corresponds to the mode.

(Effects of the Invention) As described above, according to the present invention, a process cartridge including a plurality of process devices provided according to the copy mode can be replaced, and at the same time, a high voltage generator and a process can be changed according to the copy mode. By replacing the high voltage generator unit equipped with a signal source that generates signals for Since there is no need for parallel installation, special considerations for electrical safety and complexity of wiring and connections can be avoided.

In addition, by providing a high voltage generator according to the copy mode, there is no need for a large capacity high voltage relay for high voltage switching.
In addition, by providing a signal source that generates a signal for changing the process, it is possible to change the polarity of high-voltage process equipment, such as a primary charger or a transfer charger, as necessary, and change the polarity to copy mode. The setting value can be changed accordingly.

[Brief Description of the Drawings] Figure 1 is a diagram for explaining the overall configuration of a microreader printer which is an embodiment of the negative/positive image forming apparatus of the present invention, and Figure 2 is a diagram for explaining the high voltage generation shown in Figure 1. 3 is a diagram for explaining the signal flow in FIG. 1, and FIG. 4 is a diagram for explaining the characteristics of the photosensitive drum (E-V
) and toner characteristics (V-D), Figure 5 is a diagram showing the exposure amount of the background area when a predetermined amount of light is applied to the microfilm, and Figure 6 is a diagram showing the relationship between the exposure lamp voltage (developing Figure 7 is a circuit diagram showing the configuration for adjusting the density adjustment volume by controlling the exposure lamp; Figure 8 is a diagram showing the relationship between the density adjustment volume (bias voltage) and the density scale; Figure 8 is a circuit diagram showing the configuration for adjusting the density adjustment volume by controlling the exposure lamp; FIG. 9 is a circuit diagram for setting the control signal voltage (V
REM) and the density scale, and FIG. 10 is a diagram showing the relationship between the image density and the density scale. Description of symbols B...Optical scanning mechanism section A...Illumination section C...Copying mechanism section P...Process cartridge H...High voltage generator unit 5l-33...Signal generation source 3rd Figure 2 Figure 5

Claims (1)

[Claims] A plurality of copy modes including a regular development mode or a reverse development mode can be created using one type of image forming apparatus by replacing a process cartridge including a plurality of process devices provided according to the copy mode. A negative/positive image forming apparatus that selectively performs the above-mentioned process cartridge, which is equipped with a high voltage generator corresponding to a copying mode and a signal source that generates a signal for changing the process, which is replaced at the same time as the process cartridge is replaced. A negative/positive image forming apparatus characterized by having a high voltage generator unit.