JPH03105357A - Electrostatic printing 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 Field of the Invention The present invention relates to an electrostatic printing device applying the principles of electrophotography.

BACKGROUND OF THE INVENTION Printing by electrophotography has been known for a long time. For example, the zero printing method disclosed in US Pat. No. 2,576,047, or the electronic printing apparatus disclosed in Japanese Patent Publication No. 1554/1984 can be cited. An electrostatic printing device that applies the principles of electrophotography produces non-photosensitive insulating images by fixing a toner image formed on a photoconductive sheet (photosensitive sheet) using electrophotography. That is, a printing master is formed on a photosensitive sheet, and then the printing master is uniformly charged and then uniformly irradiated with light to discharge the photosensitive parts, and then developed, to remove toner powder. This is a device that forms a new toner image by depositing it only on a non-photosensitive fixed toner image, and transfers it onto a suitable transfer material such as transfer paper. The process is repeated.

The image quality of printed matter obtained by this electrostatic printing device is
The image quality of printed matter is much more difficult to control than the quality of conventional copied images, as the characteristics of both the electrophotographic characteristics of the printing master and the electrostatic printing characteristics during printing will appear. becomes. Furthermore, when obtaining printed matter from an original using this electrostatic printing device, if the desired image quality is not obtained, the print master created during the electrostatic printing process will be wasted, making it both time- and economical. It will also be a big loss.

Such an electrostatic printing device generally stores a feed roll and a take-up roll of a photosensitive sheet formed from zinc oxide or the like in a photosensitive sheet holding drum that has a part cut out around the drum, and then unwinds the photosensitive sheet. The structure is such that the photosensitive sheet unwound from the roll is wound onto the outer peripheral surface of the photosensitive sheet holding drum, and the cut arrow portion of the holding drum is closed, leaving a gap for the photosensitive sheet to pass through (for example, Japanese Patent Application Laid-Open No. 1983-1999). See No. 136471 and Utility Model Application No. 6 3-2 1 9 7 7>.

With the drum structure of the electrostatic printing device constructed in this way, a print master is created by the above steps on the photosensitive sheet wound around the photosensitive sheet holding drum, and a predetermined number of sheets are printed using this print master. When the process is completed, a predetermined length of the photosensitive sheet is wound up by a take-up roll, and a new photosensitive sheet is wound onto the holding drum to be used for the next printing master production.

Problems to be Solved by the Invention The photosensitive sheets used in conventional electrostatic printing devices have conductive layers formed on both sides of a base paper, and a ZnO photosensitive layer is laminated on one of the conductive layers via a blocking layer. A relatively thick paper with a basis weight of 80 gsm was used as the base paper. However, since photosensitive sheets using such cardboard as the base paper are expensive, this has a significant impact on product development costs.

As a means to reduce the cost of photosensitive sheets, it is possible to reduce the thickness of the base paper to a weight of 62 gsm, 55 gsm, etc. By making the base paper thinner in this way, it is possible to increase the number of segments per roll of photosensitive sheet roll (one segment is wound exactly on the outer circumferential surface of the photosensitive sheet holding drum), which greatly increases It is possible to achieve significant cost reductions. However, it has been found that when the base paper of a photosensitive sheet is made thin in this manner, the photosensitive sheet absorbs moisture under high temperature and high humidity conditions, causing wrinkles and resulting in image quality defects such as white spots.

The present invention has been made in view of these points, and its purpose is to prevent the occurrence of moisture absorption wrinkles under high temperature and high humidity when using a photosensitive sheet made of thin base paper. It is an object of the present invention to provide an electrostatic printing device having the following features.

Means and operation for solving the problem The first solution is to house a photosensitive sheet feeding roll and a take-up roll in a photosensitive sheet holding drum with a part of its periphery cut out, and the photosensitive sheet is fed out from the feeding roll. In an electrostatic printing apparatus in which a photosensitive sheet is wound around the outer circumferential surface of the photosensitive sheet holding drum and a printing master is formed on the photosensitive sheet, a heating means is provided below the photosensitive sheet holding drum, A control means is provided for supplying power to the heating means when the device is powered off (when the plug is in an outlet!!J) and for cutting off power supply to the heating means when the device is powered on.

By operating the heating means at all times when the power of the apparatus is turned off in this manner, the heating means can warm and dehumidify the photosensitive sheet wound around the photosensitive sheet holding drum, thereby preventing the occurrence of wrinkles due to moisture absorption. be able to. Furthermore, when the power of the apparatus is turned on, the entire apparatus is warmed by the heat of the fixing device, etc., so active measures to dehumidify the photosensitive sheet are not required, and the power supply to the heating means is controlled to be cut off.

The second solution is that a predetermined tension is normally applied when winding a photosensitive sheet onto a photosensitive sheet holding drum, but a means is provided to release this tension when the device is not in use. . That is, a lock means for selectively locking the rotation of the feed roll is provided on the feed roll side, and a drive means for driving the take-up roll, a torque control means for controlling the torque of this drive means, and a take-up roller are provided on the take-up roll side. A reversal prevention means is provided to prevent the roll from reversing. Further, the locking means is unlocked when the device is powered off, and the locking means is activated when the device is powered on to lock the feeding roll,
A control means is provided for driving the driving means to apply a predetermined tension to the photosensitive sheet.

In this manner, by releasing the tension of the photosensitive sheet wound on the photosensitive sheet holding drum when the apparatus is not in use, it is possible to prevent wrinkles in the photosensitive sheet due to moisture absorption.

As a third solution, instead of releasing the tension, a means is provided to uniformly apply the tension to prevent moisture absorption wrinkles. That is, in the drum structure of the conventional electrostatic printing device, the photosensitive sheet fed out from the feeding roll is guided by a pair of guide rolls provided on both sides of the notch in the circumferential direction of the drum, while being guided by the photosensitive sheet on the outer peripheral surface of the photosensitive sheet holding drum. The guide roll is wound with a predetermined tension, and the diameter of the guide roll is the largest at the center in the axial direction and gradually decreases toward both ends, thereby preventing moisture absorption wrinkles.

If the diameter of the guide roll is uniform in the axial direction, play between the photosensitive sheet and the guide roll is likely to occur in the center, which increases the amount of displacement of the photosensitive sheet in the center, causing moisture absorption wrinkles in the center of the photosensitive sheet. It's easy to do. Therefore, by configuring the shape of the guide roll as described above, play between the photosensitive sheet and the guide roll can be eliminated, and the amount of displacement of the photosensitive sheet during winding can be made approximately uniform in the axial direction. . This makes it possible to eliminate variations in tension when winding up the photosensitive sheet, and prevent moisture absorption wrinkles from occurring due to uneven tension.

In addition to the above structure, the photosensitive sheet holding drum is provided with a plurality of axial slits that are slightly smaller than the width of the photosensitive sheet and slightly larger than the maximum image width of the photosensitive sheet, spaced apart in the circumferential direction. This slit portion absorbs variations in tension in the process direction (in the drum circumferential direction), making it possible to more uniformize the tension applied to the photosensitive sheet during winding.

The fourth solution is to prevent moisture absorption wrinkles from occurring on the photosensitive sheet side, rather than on the apparatus side. That is, the moisture content of the photosensitive sheet may be adjusted to a range of 6% to 10%, preferably 6.8% to 7.6%. Humidity control methods include, for example, a method in which humidity is controlled simultaneously during the final process, a method in which humidity is controlled offline after manufacturing, and the like. In addition, the method for measuring moisture content is JIS-P81
27. By adjusting the moisture content to a high level in advance in this manner, the photosensitive sheet does not absorb moisture to a large extent even under high temperature and high humidity conditions, and wrinkles due to moisture absorption can be prevented.

Example Embodiments of the present invention will be described in detail below based on the drawings.

In explaining the embodiments, we will first explain the overall structure of an electrostatic printing device suitable for applying the present invention, then analyze moisture absorption wrinkles on a photosensitive sheet, and finally explain solutions for moisture absorption wrinkles. do.

(1) Overall structure of the electrostatic printing device First, referring to FIGS. 1 and 2, 1 indicates the electrostatic printing device 1.
The main body is provided with a platen glass 3 on the top of which a document 2 to be copied or printed is placed. platen glass 3
is attached to the upper surface of a top cover 4 provided to cover the upper part of the main body 1, and a platen force bar 6 is attached to the top force bar 4 side via a hinge 5 on the platen glass 3. It can be opened and closed freely.

One end of the top cover 4 is pivotally attached to the main body l side by a support shaft 7, and the top cover 4 can be opened upward from the other end around the support shaft 7. On the back side of the top force bar 4, there is a light source 8 that scans and exposes the original 2 placed on the platen glass 3, and a light source 8 that directs the reflected light from the original 2 to a photosensitive sheet (sheet-like photoreceptor) 27, which will be described later. A guiding optical system 9 is provided.

The light source 8 is, for example, an annular halogen lamp, which is mounted on a lamp carriage 10 together with a reflector 8a that reflects the light emitted from the light source 8 toward the document 2, and scans the copy surface of the document 2 as the lamp carriage 10 moves. It is designed to be exposed to light.

The reflected light from the original 2 is guided to the lens carriage 1511+1 by the first mirror l2 mounted on the lamp carriage 10 and the second and third mirrors 13.14 mounted on the first mirror carriage l1. . The lens carriage 15 is movably attached to a guide rail 16 laid below and parallel to the platen glass 3, and the lens carriage 15 is provided with a lens 17 for condensing light.

A second mirror carriage 18 is provided behind the lens 17 and guided by a guide rail l6.A fourth mirror 19 is attached to the second mirror carriage 18, and the light is refocused by the lens 17. The reflected light from the original 2 is guided to the photosensitive sheet 27 side via the dustproof glass 20.

On the other hand, the lamp carriage 10 on which the light source 8 is mounted, the first
Mirror carriage 11, lens carriage 15 and second
The mirror carriage 18 is driven by the drive system 21 as follows. That is, the drive system 21 has a drive source composed of a DC servo motor (not shown), and this drive source drives each of the carriages 10.11 and 15.18 via a power transmission means 22 such as a wire. It is supposed to be done. Lens carriage l7 and second mirror carriage 1
8 is moved only when changing the magnification, and is fixed during scanning exposure. When displaying a same-size image of the original on the photosensitive sheet 27, the lamp carriage 10 is moved at the same speed as the circumferential speed of the photosensitive sheet 27, and the first mirror carriage 11 is moved at a speed of 172. will be moved.

In FIG. 1, reference numeral 25 denotes a photoreceptor unit, which has a scroll drum 26 that is rotated in forward and reverse directions by a main motor (not shown) at a speed of, for example, three steps in the forward direction shown by the arrow and one step in the reverse direction. There is. The photoreceptor unit 25 is configured to be pulled out from within the apparatus when replacing the photoreceptor sheet 27 or replenishing developer.

As shown in FIG. 3, a slit 26a is provided in the outer circumference of the scroll drum 26 in the axial direction, and a pair of guide rolls 3 are provided at both ends of the slit 26a in the circumferential direction.
0.31 is rotatably supported. Photosensitive sheet 27
is a feeding shaft 28 housed within the scroll drum 26.
The scroll drum 26 is wound into a roll and set, and is fed out to the outside of the scroll drum 26 through the slit 26a. In addition, the scroll drum 26
A master plate 29 is provided in the slit 26H to prevent toner from entering the scroll drum 26 during rotation.

As shown in FIG. 4, this master plate 29 has an outer circumferential surface 29a having the same curvature as the scroll drum 26, and is attached so that the outer circumferential surface 29a is slightly recessed into the outer circumferential surface of the scroll drum 26. ing. Also, on the inner circumferential side, inclined surfaces 29b and 29C with different angles are provided.
is taking shape. A notch 29a is provided in an outer circumferential surface 29a that is continuous with an inclined surface 29b located in the normal rotation direction of the scroll drum 26, so that when the master plate 29 passes through a developing device 45, which will be described later, the developer flows onto the scroll drum 26. In addition, one of the inclined surfaces 29b and 29c is formed at a steep angle, so that even if a part of the developer enters the scroll drum 26, this inclined surface By dropping the developer along 29C, the developer can be discharged to the outside of the scroll drum 26.

One end of the rolled photosensitive sheet set on the feeding shaft 28 is inserted into the slit 26a of the scroll drum 26.
The scroll drum 26 is taken out from a narrow gap between the guide roll 30 and the master plate 29 provided in the scroll drum 26 . The photosensitive sheet 27 taken out of the scroll drum 26 goes around the outer circumferential surface of the scroll drum 26 almost once, reaches the slit 26a, and connects the guide roll 31 and the master plate 29 provided on the opposite side of the slit. It is taken into the scroll drum 26 again through the narrow gap between them, and is wound onto a winding shaft 32 arranged in parallel with the feeding shaft 28.

The winding operation of the photosensitive sheet 27 and the rotating drive of the scroll drum 260 will be described later.

On the other hand, the following parts are arranged around the scroll drum 26 along the normal rotation direction of the scroll drum 26.

35 is a charging corotron (charger) that uniformly charges the photosensitive sheet 27 wound around the outer circumference of the scroll drum 26.
A static eliminating corotron (static eliminating device) 36 is provided on the upstream side of the photosensitive sheet 27 to eliminate charges on the photosensitive sheet 27.

Reference numeral 37 denotes an image area adjustment lamp for erasing the non-image area between the image areas on the photosensitive sheet 27 and the non-image areas on both sides of the image area, and is constructed as follows.

That is, the lamp case 37a has a slit-shaped opening on the side of the photosensitive sheet 27, and the inside of the lamp case 37a is divided into a plurality of lamp chambers, each of which accommodates a small-sized tungsten lamp. Each tungsten lamp is selectively turned on and off according to the document size to erase the electric charge on the non-image area on the photosensitive sheet 27.

At the lower edge of the slit-shaped opening 37b of the lamp case 37a, there is a light shielding plate 38 made of black Mylar sheet or the like.
are attached diagonally along the surface of the photosensitive sheet 27 to prevent a part of the light from leaking to the uniform exposure/discharge lamp 40 side. The uniform exposure/discharge lamp 40 is installed below the image area adjustment lamp 37, and in the printing mode, uniformly exposes the master image formed on the surface of the photosensitive sheet to form an electrostatic latent image for printing. The photosensitive sheet 27 is formed on the master and also lights up during cleaning.
It also has the function of facilitating cleaning by uniformly exposing the surface of the film.

A flash fixing device 41 is installed below the uniform exposure and static elimination lamp 40, and this flash fixing device 41 has an opening on the side of the photosensitive sheet 27, and a flash lamp 4lb is housed in a reflector 41a. has been done. This flash lamp 4lb blinks in synchronization with the rotation of the scroll drum 26 in the print mode, and the photosensitive sheet 27
It has the function of fixing the toner image formed on the photosensitive sheet 27 in a fixed width and creating a printing master on the photosensitive sheet 27, and the temperature of the photosensitive member installed upstream of the charging corotron 35 is According to the surface temperature on the photosensitive sheet 27 detected by the sensor 42, the voltage applied to the flash fixing device 4l from the flash fixing power source 43 is controlled.

Further, a developing device 45 is installed below the scroll drum 26, and this developing device 45 is composed of a developing unit 46 having a housing 46a with an open top, and a toner supply section 47. Guide rails 48 are laid on both sides of the lower part of the developing unit 46, and these guide rails 48 are placed on guide rolls 49 provided on the main body 1 side, so that the entire developing unit 46 is placed on the front side of the apparatus main body. It can be pulled out. Housing 46
Two mutually parallel developing rolls 50a and 50b are horizontally provided adjacent to the photosensitive sheet 27 in the opening a. These developing rolls 50a. A magnetic brush developing roll 50b is rotated in the same direction as the scroll drum 26 (clockwise in the figure) during development, and is wound around the outer circumferential surface of the scroll drum 26 by a magnetic brush of the developer formed on the outer circumferential surface. The electrostatic latent image on the photosensitive sheet 27 is developed. A stirring roll 51 is provided below each of the developing rolls 50a, 50b for supplying developer to the developing roll and stirring the developer in the housing 46a. A large number of buckets 51a are provided on the outer periphery of the stirring roll 51 at equal intervals in the circumferential direction, and as the stirring roll 51 rotates, these packets 51a scoop up the developer at the bottom of the housing 46a and transfer it to the developing roll 5Qa. , 50b.

Further, the developer supplied to the developing roll 50a by the stirring roll 51 is scraped off by a trimmer 52 installed near the developing roll 50a, and is shaped on the outer peripheral surface of the developing roll 50a. The height of the magnetic brush is regulated to be constant. The developer on the developing roll 50a is delivered to the developing roll 50b provided adjacent to the developing roll 50a, and the two developing rolls 50a,
The electrostatic latent image on the photosensitive sheet 27 is developed by the magnetic brush of the developer attached to the photosensitive sheet 50b. The developer that has completed the development of the electrostatic latent image on the photosensitive sheet 27 is scraped off from the outer peripheral surface of the developing roll 50b by a scraping replade 53 provided in contact with the developing roll 50b. The developer is uniformly mixed by a cloth mixer 54 provided below the scraping blade 53. An auger 57 is provided below the cross mixer 54 to mix the toner supplied from the toner supply section 47 and the developer dropped by the cross mixer 54 with the developer in the housing 46a.

The toner supply unit 47 includes a toner housing 47 whose bottom portion is pivotally attached to the side of the developing unit 46 by a bottle (not shown).
It has a. The upper part of the toner housing 47a is a semi-cylindrical cartridge guide 47b, and a cylindrical toner cartridge can be inserted and removed from the end side of this cartridge guide 47b. Further, an agitator 55 is provided below the cartridge guide 47b, and a toner supply roll 56 is provided at the lower opening of the toner housing 47a. The agitator 55 is mainly formed of a wire, for example, and rotates clockwise at a speed of about 7.3 rprn, so that the toner supplied from the toner cartridge is transferred to the toner supply roll 56 without causing a blocking phenomenon. Stir to reach the desired temperature.

The toner supply roll 56 provided at the lower opening of the toner housing 47a is made of foam such as polyurethane resin, and a portion of the toner enters into numerous holes provided on the surface. There is. The toner supply roll 56 is rotated at a speed of 4 rpm, which causes the toner supply roll 56 to rotate at a speed of about 0
．． 5 g of toner can be supplied into the housing 46a.

This developing device 45 is also used as a magnetic brush cleaning device for scraping off toner adhering to the photosensitive sheet 27 wound on the scroll drum 26.

When using it as a cleaning device, use the static eliminator Corotron 36! The charge on the photosensitive sheet 27 is neutralized and the charge eliminating lamp 40 is turned on to completely eliminate the charge on the photosensitive sheet 27. As a result, the developing rolls 50a, 50
The magnetic brush on b rubs against the residual toner on the photosensitive sheet 27 and scrapes it off. In this case, the rotation of the stirring roll 510 is stopped to stop supplying the developer to the developing roll 50a.

Further, 60 indicates a paper feeding device, which has multiple stages, for example, two
The tray is equipped with a paper load set 61. These paper cassettes 61 are removably mounted in a cassette holder 63 that can be freely pulled out toward the front of the main body l along guide rails 62. Reference numerals 60a and 60b are feed rolls that send out paper from within the paper cassette 6l. The paper sent out from the feed roll 60a or 60b is sent to a paper transport mechanism 64 that includes a transport roller 65 and a registration roller 66. Registration roller 66
The toner image is timed so as to match the toner image formed on the photosensitive sheet 27, and then sent to the transfer position. 67
is a transfer corotron (transfer device), which brings the paper into close contact with the photosensitive sheet 27 and transfers the toner image on the photosensitive sheet 27 onto the paper by performing corona discharge with a polarity opposite to that of the toner. act. The paper attracted to the photosensitive sheet 27 is peeled off by a peeling belt 68 formed of a thin metal plate made of stainless steel or the like provided on one end side (rear side) of the scroll drum 26, and transferred to a vacuum suction conveyance device 69. It is ready to be sent.

The paper onto which the toner image has been transferred by the transfer corotron 67 is sent to a fixing device 70 by a vacuum suction conveyance device 69. The fixing device 70 has a heat roll 7 with a built-in heat source.
1, and a pressure roll 72 that presses the paper to be fixed onto the heat roll 7l. The paper on which the toner image has been fixed by the fixing device 70 is discharged onto a paper discharge tray 74 by a discharge roll 73. The general structure of the electrostatic printing apparatus has been described above, and next, the driving of the photoreceptor unit 25 and the winding operation of the photoreceptor sheet 27 will be described.

Referring to FIG. 5, a sectional view of the drive mechanism of the photoreceptor unit 25 and the photosensitive sheet winding mechanism is shown. Also,
FIG. 6 is a sectional view taken along the line VI--VI of FIG. N5, and FIG. 7 is a sectional view taken along the line ■--■ of FIG.

First, the drive system for the scroll drum 26 will be explained.

The feeding shaft 28 is provided with a feeding roll 75 for winding the photosensitive sheet 27 into a roll, and the winding shaft 32 is provided with a winding roll 7 for winding up the photosensitive sheet 27.
6 is provided. The scroll drum 26, which rotatably accommodates the feed roll 75 and take-up roll 76 of the photosensitive sheet 27, is rotatably attached to a pair of side plates 77 provided on the main body of the apparatus. One end of a hollow shaft 79 made of a sintered oil-impregnated member that also serves as a bearing is fixed to a flange 78 provided on a part of the scroll drum 26, and a dog clutch 80 is installed in the middle of the hollow shaft 79. connected.

The dog clutch 80 is connected within a bearing support member 81 fixed to the outside of the side plate 77 to one end side of a hollow outer relay shaft 82 made of a sintered oil-impregnated member that also serves as a bearing. The outer relay shaft 82 is supported within the bearing support member 81 so as to be prevented from reversing by arranging a one-way clutch 83 for preventing reversal at a suitable position on its outer periphery.
The other end of the outer relay shaft 82 is connected to the inner periphery of an input gear 85 via a one-way clutch 84 for normal rotation.

The above is the drive system for the scroll drum 26, and next, the photosensitive sheet winding system will be explained.

A feed roll 75 arranged inside the scroll drum 26
A ratchet 86 for preventing rotation of the feed roll 75 is provided at one end of the shaft 28 of the scroll drum 2.
6 is rotated, the ratchet 86 is rotated by the spring 86a.
is engaged to hold the feed roll 75 so as not to rotate, and this ratchet 86 is disengaged by a release hand such as a solenoid (not shown), at which time the feed roll 75 is allowed to rotate. ing.

In addition, a take-up roll 76 is
A net gear 87 is attached to one end side of the shaft 32 of the roll.
A ratchet wheel 89 is provided integrally with the ratchet wheel 89, and a reversal prevention ratchet 88 biased by a spring 88a is engaged with the ratchet wheel 89. Thereby, the winding shaft 32 is held so as not to rotate in the direction opposite to the winding direction of the photosensitive sheet 27. The branet gear 87 is engaged with a sangya 90 whose shaft portion is rotatably inserted into the hollow shaft 79.
The j end is connected to the dog clutch 91 within the outer relay shaft 82.
This dog clutch 91 is connected to one end side of an inner relay shaft 92 rotatably provided within the outer relay shaft 82. A human power hub 93 and a clutch 94 are provided on the outer periphery of the other end of the inner relay shaft 92, and
The input gear 85 is connected to the input gear 85 via a one-way clutch 95 for reverse rotation arranged in series on the outside of the one-way clutch 84 for forward rotation in the axial direction.
is connected to the inner circumference of the

The operation of the scroll drum drive mechanism configured as described above will be described below. External drive input is from a motor (not shown) via a sprocket 97 provided at one end of a relay shaft 96, and an input gear 8 by a gear 98 provided at the other end.
5. When the scroll drum 26 is to be rotated steadily, the input is normally rotated. In response to this,
'C by the one-way clutch 84 for forward rotation in the manual gear 85
The driving force is transmitted to the outer relay shaft 82 and further transmitted to the hollow shaft 79 via the dog clutch 80,
Scroll drum 2 via 7 langes 78 fixed to 9
6 is rotated steadily at a desired rotation speed. At this time, the one-way clutch 83 for preventing reverse rotation in the bearing support member 81 does not engage because the outer relay shaft 82 rotates in the normal direction, so that the reverse rotation prevention function does not work. Also at this time, the scroll drum 26
Since the rotation stopper ratchet 86 provided on the shaft 28 of the inner feed roll 75 is locked by the action of a spring 86a, the take-up roll 76 side also holds the photosensitive sheet 2.
7, and the net gear 87 provided on the shaft 32 of the take-up roll 76 is prevented from rotating. Therefore, the sanghya 90 rotates at the same speed in the rotational direction of the scroll drum 26 as the scroll drum 26 rotates, but the rotation of the sangya 90 is transmitted from its shaft to the input hub 93 via the dog clutch 91. It only rotates the hub 93 and has no effect on the one-way reverse clutch 95.

Next, a case will be described in which the photosensitive sheet 27 wound around the outer peripheral surface of the scroll drum 26 is rolled up.

In the case of winding up the photosensitive sheet, the external drive input is reversed to rotate the input gear 85 in the opposite direction to that in the case of scroll drum drive. In response to this, a one-way reverse clutch 95 provided on the inner periphery of the input gear 85 operates to transmit driving force to the inner relay shaft 92, and this inner relay shaft 92
The sun gear 90 is rotated via the dog clutch 91, and the planet gear 87 is rotated by the rotation of the sun gear 90, and the rotation of the planet gear 87 rotates the shaft 32.
The take-up roll 76 is rotated through the wind-up roll 76 to wind up the photosensitive sheet 27 onto the take-up roll 76 .

At this time, the one-way clutch 84 for forward rotation provided in the input gear 85 does not operate for reverse rotation, so the scroll drum 26 does not rotate, but the ratchet 86 provided on the shaft 28 of the feed roll 75 is operated by a solenoid, etc. Since the locked state is released by the operation of the release means, the photosensitive sheet 1
- Winding up the 27 is easy.

The winding state of the photosensitive sheet 27 is detected by the photosensitive sheet feeding amount detection device, and when it is detected that feeding of the desired segment has been completed, the signal is sent to the control device, and the control device sends the signal to the feeding roll. A command is given to a release means such as a solenoid (not shown) of the rotation stop ratchet 86 of 75 to lock the rotation stop ratchet 86 again and stop the rotation of the feed roll 75. At this time, the rotation on the take-up roll 76 side continues;
Therefore, tension is gradually applied to the photosensitive sheet 27 as the take-up roll 76 rotates, and when the torque reaches the limit torque set in advance in the clutch 94, the external input is cut off by the clutch 94, and the take-up roll 76 At the same time as the rotation is stopped, the ratchet 88 for preventing reverse rotation is activated and becomes locked.

As a result, the photosensitive sheet 27 is uniformly brought into close contact with the outer peripheral surface of the scroll drum 26 under a constant tension, and this state is maintained thereafter.

At this time, the limit torque value of the clutch 94 is higher than the pulling load of the photosensitive sheet 27 in order to wrap the photosensitive sheet 27 evenly and sufficiently around the outer peripheral surface of the scroll drum 26, and Needless to say, the breaking tension is set to a value lower than the breaking tension of the bolt 27. Additionally, in this process, by locking the feed roll 75 with the rotation stop ratchet 86, a brake is applied to the take-up roll 76 side via the photosensitive sheet 27, and the rotation of the planet gear 87 on the take-up roll 76 side is stopped. In order to stop the scroll drum 26, a reversing force is applied to the scroll drum 26 by the rotating force of the sun gear 90 which has been engaged with the planetary gear 87, but this reversing force is applied to the housing of the bearing support member 81 by the one-way clutch 83 for preventing reverse rotation. This is prevented by the meshing and the scroll drum 26 does not rotate.

Next, the winding operation of the photosensitive sheet 27 is completed by cutting off the external drive input. The external drive input may be cut off by setting a delay time in advance and immediately after this time has elapsed.

Next, the operation of the electrostatic printing apparatus constructed as above will be briefly explained.

First, when the copy mode is selected and the start button is pressed, the scroll drum 26 begins to rotate at a medium speed, the photosensitive sheet 27 is uniformly charged by the charging corotron 35, and scanning is performed in synchronization with the rotation of the scroll drum 26. By exposure, an electrostatic latent image corresponding to the original is formed on the photosensitive sheet 27.

This electrostatic latent image is developed! 1145, the toner image is transferred onto a sheet of paper by a transfer corotron 67, and the toner image on this sheet is fixed by a fixing device 70 to obtain a copy. After transferring the toner image to the paper by transfer corotron 67, scroll drum 26 is rotated one more revolution for a cleaning cycle. In this cleaning cycle, the potential on the photosensitive sheet 27 is reduced to approximately 0 volts by the static eliminating corotron 36 and the static eliminating lamp 40.
The residual toner on the photosensitive sheet 27 is cleaned by the magnetic brush of the developing device 45. The above is the basic operation of Coby mode, and one copy can be made in two rotations. Photosensitive sheet 2 wound on scroll drum 26
7 is reusable after cleaning.

Next, the print mode will be explained. The printing mode consists of a plate-making step and a printing step. When automatic printing mode is selected, both modes operate continuously. When the start button is pressed, the scroll drum 26 begins to rotate at a medium speed, and the charged corotron 35 charges the photosensitive sheet 27.
is uniformly charged, an electrostatic latent image corresponding to the document is formed on the photosensitive sheet 27 by scanning exposure synchronized with the rotational speed of the scroll drum 26, and this latent image is developed by a developing device 45 and exposed to light. A toner image is formed on the sheet 27. Next, the scroll drum 26 is rotated at a low speed, and the photosensitive sheet 27 is
The toner image shaped above is fixed by a flash fixing device 41 to create a printing master. If left in this state, the electrical characteristics of the printing master will be poor, so the scroll drum 26
While rotating at high speed, the electrical characteristics of the master are adjusted by the charging corotron 35 and the transfer corotron 67. That is, during flash fixing, a low potential phenomenon appears on the master, which is thought to be due to the release of oxygen from the zinc oxide surface of the photosensitive sheet 27. In contrast, after fixing the master, while rotating the scroll drum 26 at high speed, the charging corotron 35 The transfer corotron 67 is discharged, and the air flow around the scroll drum is stopped to make the area around the master rich in ozone, thereby speeding up recovery of the charging characteristics of the master.

This completes the plate making step and continues the printing step. In the printing step, the scroll drum 2
6 is rotated at high speed, the printing master is uniformly charged with a charging corotron 35, and then the entire surface of the master is exposed with a uniform exposure lamp 40, leaving charges only in the toner image area. This is developed into a toner image by a developing device 45, transferred onto paper by a transfer corotron 67, and then fixed by a fixing device 70 to obtain a print image. Since the image exposure step is omitted in the print mode, the scroll drum 26 can be rotated at high speed, and A
The 4th edition can achieve a printing speed of 100 sheets per minute with 2 prints per revolution.

After printing is completed, the master is rolled up into the scroll drum 26 by the above-mentioned winding mechanism, and the unused surface of the photosensitive sheet 27 is set on the outer peripheral surface of the scroll drum 26.

The overall structure and basic operation of the electrostatic printing device are as described above. Conventionally, the base paper of the photosensitive sheet 27 is
GSM relatively thick paper was used. Therefore, moisture absorption wrinkles hardly occurred on the photosensitive sheet 27 under high temperature and high humidity conditions, and good copy images and print images could be obtained. However, when the photosensitive sheet 27 is made thinner to reduce costs as described above, a problem arises in that moisture absorption wrinkles occur in the photosensitive sheet under high temperature and high humidity conditions, which causes image defects. The present invention aims to provide an electrostatic printing device with good copy quality and print quality by using a photosensitive sheet that prevents the occurrence of moisture absorption wrinkles that occur when the photosensitive sheet is made thin and reduces costs. be.

Hereinafter, the results of analyzing moisture absorption wrinkles that occur when the photosensitive sheet is thinned will be explained, and then a solution to the moisture absorption wrinkles will be explained.

(2) Analysis of moisture absorption wrinkles on photosensitive sheet The photosensitive sheet 27 is constructed as shown in FIG.

That is, conductive layers 101 are provided on both sides of a base paper 100, and Zn○ is deposited on one conductive layer 101 via a blocking layer 102.
It is constructed by laminating photosensitive layers 103. Electrostatic printing device XP- manufactured by Fuji Xerox Co., Ltd. currently on the market
The photosensitive sheet 27 used in the base paper 100 is made of relatively thick paper of 80 gsm.
It is intended to use thin paper of 2 gSm. Below, X
The photosensitive sheet used for P-100 is called the current master, and the thinner photosensitive sheet is called the cost reduction master (C/
(abbreviated as D master).

(a) Check the occurrence of moisture absorption wrinkles at the beginning and end of winding of the current master and C/D master. According to this, between the winding side and the unwinding side (unwinding side), wrinkles are more likely to occur on the unwinding side. It was also confirmed that there were more wrinkles at the beginning and end of the winding of the photosensitive sheet than at the end of the winding. It was confirmed that moisture absorption wrinkles were more likely to occur at 28°C and 85°C.
It was confirmed that the product almost stopped after about 8 hours after being left in the A zone of 10%.

(b) Confirmation of the relationship between moisture absorption wrinkles and winding tension It was confirmed that the occurrence of moisture absorption wrinkles cannot be completely prevented in the C/D master even if the winding tension is changed. However, once the film was wound up, the tension was released and the film was left in the A zone for about 10 hours, and it was found that the occurrence of moisture absorption wrinkles was very slight and did not adversely affect the image quality.

(C) Measurement of the amount of displacement of the guide roll during lifting It was found that the amount of displacement of the guide roll on the winding side was larger than that of the guide roll on the unwinding side. Than this,
It was found that the tension applied to the photosensitive sheet on the unwinding side was small at the guide roll portion, and moisture absorption wrinkles were more likely to occur on the unwinding side.

Furthermore, it was confirmed that the amount of displacement near the center of the guide roll was large on both the winding side and the unwinding side, and play between the photosensitive sheet (master) and the guide roll was likely to occur. The results of this experiment revealed that in the current guide rolls, which have a uniform diameter in the axial direction, the tension applied to the photosensitive sheet at the guide roll portion varies greatly in the axial direction.

(d) Measurement of Master Shrinkage Rate and Elongation Rate It was found that between the current master and the C/D master, the C/D master is generally larger in terms of shrinkage rate and elongation rate. This is thought to be due to the fact that the base paper is made thinner in the C/D master.

(e) Checking whether water is being absorbed from the back side (conductive layer side) of the photosensitive sheet Using a normal scroll drum and a scroll drum with multiple axial slits in the circumferential direction of the drum, each A photosensitive sheet wound around a scroll drum was left in zone A and the state of moisture absorption wrinkles was compared.From the results of this experiment, it could not be determined whether water was mainly absorbed from the back side of the photosensitive sheet.However, It was confirmed that no wrinkles were generated in the slit portion.From this, it is thought that in the slit portion where the tension is considered to be uniform, wrinkles do not form even if water is absorbed because there is an escape route for the wrinkles.

(3) Solution to Moisture Absorption Wrinkles First Embodiment As shown in FIG. 105 is provided, and the drum heater 105 is controlled so that it is turned on when the device is powered off (in this case, the plug is always inserted into the ACIOOV outlet) and turned off when the device is powered on. Accordingly, the photosensitive sheet 27 on the scroll drum 26 is always warmed and dehumidified regardless of whether the apparatus is in operation or stopped, thereby preventing the generation of wrinkles due to moisture absorption in the photosensitive sheet.Power source of the apparatus The reason why the power supply to the drum heater 105 is turned off when the power is turned on is that when the power of the apparatus is turned on, the entire apparatus is warmed by the heat of the fixing device 70, etc., so active measures to dehumidify the photosensitive sheet are not required. Further, if power is continued to be supplied to the drum heater 105 while the apparatus is in operation, the photosensitive sheet 2
7. It is thought that the surface becomes too hot, causing problems such as deterioration of the photosensitive sheet.

The drum heater 105 is constructed as shown in FIGS. 9 and 10. That is, as shown in FIG. 9, a heating wire 107 is provided on a base plate 106 made of aluminum, and a holder 108 also made of aluminum is pressed from above to fix the heating wire 107.

In FIG. 9, 109 is a lead wire, and 110
is a connector. The drum heater 105 thus constructed is fixed to the main body of the apparatus with screws in an upright position as shown in FIG.

Although the drum heater 105 is always on when the apparatus is stopped (power is off), it was confirmed that the surface temperature of the drum heater 105 remains constant at about 113°C. At this time, the surface of the scroll drum 26 will be heated to about 37°C. Furthermore, when the device is turned on and placed in a ready state, the power to the drum heater 105 is turned off, but the temperature of the surface of the drum heater 105 at this time is approximately 30°C. , scroll drum 2
It was confirmed that the temperature of the 6 surface was approximately 36°C. From this, it can be seen that by using the drum heater when the device is powered off, the surface of the scroll drum can be heated to the same extent as when the device is in operation, so the photosensitive sheet wound on the surface of the scroll drum 26 can be heated. It has been confirmed that the use of the drum heater 105 can effectively prevent the occurrence of moisture absorption wrinkles on the photosensitive sheet without adversely affecting the photosensitive sheet.

Second Example From the above-mentioned analysis of moisture absorption wrinkles on the photosensitive sheet, it was found that when the winding tension was released after winding up the photosensitive sheet, the occurrence of moisture absorption wrinkles became slight. Control as follows.

That is, in FIG. 6, the ratchet 86 for stopping the rotation of the feed roll 75 is released by a release means such as a solenoid (not shown) when the power of the apparatus is turned off, and the photosensitive sheet wound on the scroll drum 26 is released while the apparatus is stopped. 27 is controlled to release the tension. Then, by turning off the release means in conjunction with turning on the power of the device, the rotation stopping ratchet 86 locks the feed roll 75, and the driving means (not shown) reverses the input gear 85 as shown in FIG. As a result, the one-way reverse clutch 95, the inner relay shaft 92, the dog clutch 9
1. Hollow shaft 79, Sangya 90 and Blanet Gya 87
The take-up roll 76 is rotated via the. Therefore, tension is gradually applied to the photosensitive sheet 27 as the take-up roll 76 rotates, and when the torque reaches the limit torque set in advance in the clutch 94, the external input is cut off by the clutch 94 and the tension is gradually applied to the photosensitive sheet 27 as the take-up roll 76 rotates. At the same time as the rotation is stopped, the ratchet 88 for preventing reverse rotation is operated to enter a locked state. As a result, the photosensitive sheet 27 is uniformly brought into close contact with the outer peripheral surface of the scroll drum 26 under a constant tension.

As explained above, in this embodiment, the tension of the photosensitive sheet on the scroll drum is temporarily released while the apparatus is stopped, and the tension is applied again to the photosensitive sheet on the scroll drum when the apparatus is turned on. Therefore, wrinkles in the photosensitive sheet due to moisture absorption can be prevented.

Third Example From the analysis of moisture absorption wrinkles in the photosensitive sheet described above, it has been found that moisture absorption wrinkles can be prevented by keeping the winding tension of the photosensitive sheet uniform. Therefore, in this embodiment, the 11th
A scroll drum 126 as shown in the figure is employed.

That is, while conventional guide rolls have a uniform diameter in the axial direction, the guide roll 127 of this embodiment has a shape that has a maximum diameter at the center in the axial direction and gradually decreases in diameter toward both ends. ing. By forming the guide roll 127 in such a shape, it is possible to eliminate the play of the photosensitive seal guide roll 127.

This makes it possible to eliminate variations in tension during winding up of the photosensitive sheet, and prevent moisture absorption wrinkles from occurring due to uneven tension.

Furthermore, the scroll drum 126 of this embodiment is provided with a plurality of slits 128 that extend in the axial direction and are spaced apart in the circumferential direction of the scroll drum. As a result, variations in tension in the process direction and in the drum circumferential direction can be absorbed by these slits 128, and the tension applied to the photosensitive sheet during winding can be made more uniform.

Fourth Embodiment The above-mentioned embodiments take measures to prevent moisture absorption wrinkles on the apparatus side, but this embodiment takes measures to prevent moisture absorption wrinkles on the photosensitive sheet side. As explained with reference to FIG. 8, the photosensitive sheet 27 has conductive layers 101 provided on both sides of a base paper 100, and a Zn○ photosensitive layer 103 laminated on one of the conductive layers 101 with a blocking layer 102 interposed therebetween. It is structured as follows. Conventional photosensitive sheets are humidity-controlled at the final stage of the manufacturing process so that the moisture content is 5.5%. When the moisture content of the photosensitive sheet 27 is adjusted to 5.5% by thinning the base paper to a weight of 62 gsm, the occurrence of moisture absorption wrinkles is noticeable under high temperature and high humidity. It was confirmed that when the moisture content is adjusted to 6.8%, it is possible to prevent the occurrence of moisture absorption wrinkles under high temperature and high humidity conditions.

The biggest cause of moisture absorption wrinkles is that the elongation rate of the thinned base paper due to water absorption is greater than that of a conventional photosensitive sheet using a 4180 gsm base paper. Therefore, by adjusting the moisture content to a high level in advance, the photosensitive sheet does not absorb moisture to a large extent even under high temperature and high humidity conditions, and it is possible to prevent wrinkles caused by stretching of the photosensitive sheet due to moisture absorption.

Effects of the Invention Since the electrostatic printing apparatus of the present invention is constructed as described in detail above, it has the effect that it is possible to use a photosensitive sheet made of a thin layer of base paper without causing moisture absorption wrinkles. By making the base paper thinner, it is possible to significantly reduce the cost of the photosensitive sheet.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an electrostatic printing device suitable for applying the present invention, Fig. 2 is an external perspective view of the electrostatic printing device, Fig. 3 is a side view of a photoreceptor unit, and Fig. 4 is a sectional view of the master plate, FIG. 5 is a sectional view of the scroll drum drive mechanism and photosensitive sheet winding mechanism, FIG. 6 is a sectional view of the 5rgJ along line VI-VI, and FIG. 8 is a composition diagram of a photosensitive sheet, FIG. 9 is a plan view of a drum heater, FIG. 10 is a sectional view taken along line X-X in FIG. 9, and FIG. 11 is a scroll according to an embodiment of the present invention. This is a schematic diagram of the drum structure. 5... Photoconductor unit, 6... Scroll drum, 7... Photosensitive sheet, 8... Feeding shaft, 2... Winding shaft, 5... Feeding roll, 6... Winding up Roll, 6... Ratchet for rotation stop, 8... Ratchet for preventing reverse rotation, 05... Drum heater, 26... Scroll drum, 27... Guide roll, 2 8... Slit .

Claims (1)

[Claims] A photosensitive sheet feeding roll and a take-up roll are housed in a photosensitive sheet holding drum having a part cut out around the drum,
An electrostatic printing apparatus in which a photosensitive sheet fed out from a feeding roll is wound onto the outer peripheral surface of the photosensitive sheet holding drum to form a printing master on the photosensitive sheet, wherein the photosensitive sheet has a water content of 6. An electrostatic printing device characterized in that it is a photosensitive sheet whose humidity is controlled to be 0% or more and 10.0% or less.