JPH0684067B2 - Laser plate making equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention forms an electrostatic latent image of an original image on a photoconductive sheet with laser light, and then develops the electrostatic latent image of the photoconductive sheet. The present invention relates to a laser plate making apparatus for making a plate for offset printing, in particular, a laser plate making apparatus for sequentially carrying out charging, laser exposure, development and fixing while conveying a photoconductive sheet inside the apparatus for the purpose of downsizing. Regarding

[Conventional technology]

A conventional example of such a laser plate making apparatus is Japanese Patent Application No. 58-1.
There is a plate-making device disclosed in Japanese Patent No. 49038 (see JP-A-60-40360). This plate-making device comprises a plurality of pairs of conveying rollers for conveying / sending the supplied photoconductive sheet, and a charger, a laser exposure section, and a developing device, which are sequentially arranged along the conveying path of the photoconductive sheet. And a fixing unit.

The supplied photoconductive sheet is first charged with a positive electrostatic charge on its surface by a charger.

Subsequent to the charging, the photoconductive sheet is selectively exposed by the laser light in accordance with the image data of the document in the laser exposure section, and an electrostatic latent image of the document image is formed on the photoconductive sheet. In this example, the laser light is blocked at the pixel portion of the electrostatic latent image, and the laser light is irradiated only to the portion other than the pixel. When irradiated with laser light, the positive positive charges on the photoconductive sheet are discharged. Thereby, only the pixel portion on the photoconductive sheet has a positive electrostatic charge.

The photoconductive sheet that has been laser-exposed and selectively discharged with a positive charge is passed through a developing unit filled with a developing solution in which toner is melted. The toner is previously charged with a negative electrostatic charge. As described above, since the positive electrostatic charge is charged in the pixel portion of the electrostatic latent image on the photoconductive sheet, negative toner is attached to this pixel portion and the electrostatic latent image on the photoconductive sheet is attached. The image is developed.

Thereafter, the photoconductive sheet containing the solvent (developing solution) is dried by heat to fix the original image. The photoconductive sheet after the fixing is sent out of the apparatus.

Here, the reason why the charging, the laser exposure, the development, and the fixing are sequentially performed while the photoconductive sheet is being conveyed in this manner is to downsize the entire apparatus. The total length of a typical photoconductive sheet can reach about 3/4 of the total length of such a device. Therefore, the tip of the photoconductive sheet reaches the developing unit, the fixing unit, and in some cases, outside the apparatus during exposure.

Since multiple pairs of transport rollers are provided between the laser exposure unit, the developing unit, and the fixing unit, it is possible that a part of the photoconductive sheet passes between the pairs of transport rollers with their leading ends during exposure. Become. Although each pair of conveying rollers is made of an elastic material such as rubber, the photoconductive sheet receives some impact at the moment the leading edge of the pair of conveying rollers is sandwiched between the pair of conveying rollers. Since the laser light applied to the photoconductive sheet is turned on / off according to the image data of the original, it is required that the photoconductive sheet during exposure be moved at a constant speed and maintain flatness. To be done. However, when a shock is applied to the leading end of the photoconductive sheet, it vibrates, making it impossible to maintain flatness and causing a slight change in speed at the moment of being sandwiched between the pair of conveying rollers. For this reason, when the electrostatic latent image of the original image is formed by the laser light, a positional deviation occurs, and the image quality of the plate deteriorates.

[Problems to be solved by the invention]

This invention has been made to deal with the above-mentioned circumstances,
It is an object of the present invention to provide a laser plate making apparatus which conveys a plate smoothly while keeping the flatness at a constant speed, without giving an impact to the plate being conveyed as much as possible, and in which a positional deviation does not occur during laser exposure.

[Means for solving problems]

In the laser plate making apparatus according to the present invention, the photoconductive sheet member is sequentially passed through the charging means, the laser exposure means, the developing means, and the fixing means by a plurality of rotating conveying roller pairs to form the plate of the original image on the photoconductive sheet member. In the laser plate making device to be made, at least a part of the photoconductive sheet member is provided at a position downstream of the laser exposure means in the conveyance direction among the plurality of conveyance roller pairs and at a position where the leading end of the photoconductive sheet member reaches during exposure in the laser exposure means. The photoconductive sheet member detecting means provided upstream of the predetermined conveying roller pair in the conveying direction, and the rollers forming the predetermined conveying roller pair when the detecting means detects the photoconductive sheet member It is provided with means for separating for a prescribed period so that they are separated at the moment when the tips of the members are sandwiched.

[Action]

According to the laser plate making apparatus of the present invention, at the moment when the photoconductive sheet member is sandwiched by the pair of conveying rollers, the rollers forming the pair of conveying rollers are spaced from each other. Never be given.

〔Example〕

An embodiment of a laser plate making apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing the outline of this embodiment. In FIG. 1, the paper feed cassette 12 is provided on the right side of the main body 10 and the paper discharge tray 14 is provided on the left side, and the photoconductive sheet as the material of the plate is conveyed from right to left. The transport path is indicated by a broken line.

Inside the paper feed cassette 12, for example, a large number of photoconductive sheets each having a conductive sheet coated with a photoconductive layer sensitive to laser light are stored. The bottom surface of the paper feed cassette 12 is not flat, and a slight step 12a is provided on the main body side. The step 12a makes it easier for the photoconductive sheets to come apart, and when the photoconductive sheets are taken out from the paper feed cassette 12, a plurality of sheets are prevented from being taken out in an overlapping manner.

The photoconductive sheets in the paper feed cassette 12 are taken out one by one by the supply roller 16 and sent to the conveyance path. Side guides are provided on both sides of the entrance of the transport path to accurately adjust the widthwise position of the photoconductive sheet in the transport direction.

Along the transport path, the tip sensor 20 and the first transport roller pair 2
2. A corona charger 24, a sheet supporting member 26, a second conveying roller pair 28, and a developing device 30 are sequentially provided.

FIG. 2 shows a detailed perspective view of the vicinity of the leading end detection sensor 20 and the first conveying roller pair 22 on the conveying path.

The front end detection sensor 20 is composed of an integrated light-transmitting / light-receiving optical sensor provided across the conveyance path, and when the light receiving section detects that the light beam from the light projecting section is blocked by the photoconductive sheet 32, The tip of the property sheet 32 is detected. The detection signal of the tip detection sensor 20 is used as the basis of various operation timings.

The upper roller 22a and the lower roller 22b, which form the first conveying roller pair 22, are made of an elastic member such as rubber, and have a gear mechanism provided at one end.
They are in contact with each other via 34 so that their axes are parallel. The gear mechanism 34 includes gears 40 and 42 connected to the shafts of the upper and lower rollers 22a and 22b, and gears 44 and 46 connecting the gears 40 and 42, respectively. The shafts of the gear 40 (upper roller 22) and the gear 44 are plates 52a, 5 provided at both ends of the conveying roller pair 22.
It penetrates 2b. The shaft of the upper roller 22a is connected to the rotary solenoid 50 via the lift mechanism 48.

The shaft of the gear 44 is rotated by the DC motor 56 via the belt 54. The rotation of the DC motor 56 is transmitted to the upper and lower rollers 22a and 22b of the conveying roller pair 22 via the gear mechanism 34. As a result, the upper and lower rollers 22a and 22b are rotated at a constant speed, and the photoconductive sheet 32 is smoothly conveyed.

Here, if the upper and lower rollers 22a and 22b are in contact with each other even at the moment when the photoconductive sheet 32 is sandwiched by the pair of transport rollers 22, the photoconductive sheet 32 is impacted as described above, which is not preferable. Therefore, in this embodiment, when the leading edge detection sensor 20 detects the leading edge of the photoconductive sheet 32, the rotary solenoid 50 is turned on for a predetermined period. Rotary solenoid
When 50 is turned on, the lift mechanism 48 is raised by a predetermined amount, and the plates 52a and 52b are rotated about the axis of the gear 44 by a predetermined angle φ. As a result, the upper roller 22a of the conveying roller pair 22 is separated from the lower roller 22b. The predetermined period during which the rotary solenoid 50 is turned on is set to be equal to the period during which the leading edge of the photoconductive sheet 32 is moved from the leading edge detection sensor 20 to the conveying roller pair 22. Therefore, the upper and lower rollers 22a and 22b are in contact with each other until the photoconductive sheet 32 detects the leading edge by the leading edge detection sensor 20 as shown in FIG. Therefore, at the moment when the photoconductive sheet 32 is sandwiched by the pair of conveying rollers 22, the upper roller 22a is lower than the lower roller 22b as shown in FIG. 3 (b).
Is separated from. Then, when the photoconductive sheet 32 is sufficiently sandwiched by the pair of transport rollers 22, the upper roller 22a again contacts the lower roller 22b via the photoconductive sheet 32 and transports the photoconductive sheet 32. As a result, the photoconductive sheet 32 is smoothly conveyed, and no positional deviation occurs when the electrostatic latent image of the original image is formed by the laser light.

Although not shown, the second conveying roller pair 28 is also configured similarly to the first conveying roller pair 22, and when detecting that the photoconductive sheet has been conveyed, the upper roller and the lower roller are separated for a predetermined period. . Therefore, at the moment when the front end of the photoconductive sheet is sandwiched by the second conveying roller pair 28, the upper and lower rollers are separated from each other. The position is not displaced when it is sandwiched by the pair of transport rollers 28.

A corona charger 24 and a sheet supporting member 26 are provided between the first conveying roller pair 22 and the second conveying roller pair 28. The photoconductive sheet exiting from the first conveying roller pair 22 is charged with a positive electrostatic charge on its surface by the corona charger 24. The sheet supporting member 26 flatly supports the photoconductive sheet being conveyed. The surface of the photoconductive sheet on the sheet support member 26 is exposed by the laser exposure unit 62.

The laser exposure unit 62 has a semiconductor laser 64, a polygon mirror 66 that scans the laser light emitted from the semiconductor laser 64 in one direction, and a scanning speed of the laser light scanned by the polygon mirror 66 on a plane. It comprises an fθ lens 68 and a reflection mirror 70. The laser light reflected by the reflection mirror 70 irradiates the photoconductive sheet on the sheet supporting member 26.

The semiconductor laser 64 is turned on (irradiated) / off (interrupted) according to binary image data showing black and white of a document (binary image) supplied by a floppy disk (not shown) or the like. In this embodiment, the laser light is blocked at the pixel (black) portion of the original image, and the positive electrostatic charge on the surface of the photoconductive sheet is left as it is. Laser light is radiated to the portion other than the pixel (white) to discharge the positive electrostatic charge on the surface of the photoconductive sheet. This forms an electrostatic latent image on the surface of the photoconductive sheet.

The photoconductive sheet 32 exiting from the second conveying roller pair 28 is passed through a developing device 30 filled with a developing solution in which toner is melted. Since the toner is previously charged with a negative charge,
Toner is attached to the pixel portion of the electrostatic latent image formed on the photoconductive sheet 32, and the electrostatic latent image is developed. The developing device 30 has a tank 72, a suction pump 74 provided under the tank 72 for circulating the developing solution, and a developing solution discharge pipe 76 for applying the developing solution from the suction pump 74 onto the photoconductive sheet 32. The developing device 30 further includes a lower guide plate 78 that is provided below the conveyance path of the photoconductive sheet 32 and is gently bent along the conveyance path, and a lower guide plate 78 that is provided above the conveyance path and is gentle like the lower guide plate 78. The curved photoconductive sheet 32 is provided between the lower guide plate 78 and the curved counter electrode 80. The lower guide plate 78 is grounded, a predetermined voltage is applied to the curved counter electrode 80 according to the polarity of the toner, etc., and a vertical electric field is applied between the lower guide plate 78 and the curved counter electrode 80 to enhance the developing efficiency. Lines of force are created.

Here, since the developing device 30 contains the developing solution, it is located at the lowest position in the transport path. Therefore, the transport path is not horizontal, and is bent halfway so that the developing device 30 tends to descend and the developing device 30 and subsequent components tend to rise. Therefore, the photoconductive sheet is bent when passing through the developing unit, but in this embodiment, the photoconductive sheet 32 is passed between the gently curved lower guide plate 78 and the curved counter electrode 80. Therefore, it can smoothly pass through the developing device 30. As a result, even if the laser exposure portion 62 forms an electrostatic latent image at the rear end of the photoconductive sheet while the front end of the photoconductive sheet is passing through the developing device 30, the conveyance is performed smoothly. Displacement is prevented.

The photoconductive sheet that has passed through the developing device 30 has the solvent squeezed out by a squeezing roller pair 82 similar to the conveying roller pair, is dried from below by a panel heater 84, and is further out of the main body 10 by a third conveying roller pair 86. The paper is conveyed and stored in the paper discharge tray 14. The aperture roller pair 82 and the third transport roller pair 86 are also configured similarly to the first transport roller pair 22, and when it is detected that the photoconductive sheet has been transported, the upper roller and the lower roller are separated from each other for a predetermined period. Therefore, at the moment when the front end of the photoconductive sheet is sandwiched between the aperture roller pair 82 and the third conveyance roller pair 86, the upper and lower rollers are separated from each other, and the rear end of the photoconductive sheet is laser-exposed. Even when the front end is pinched by the pair of squeezing rollers 82 and the pair of third conveying rollers 86, there is no displacement. The diaphragm roller pair 82 and the third conveying roller pair 86 are DC motors.
It is rotated by 89. The two transport motors are provided in this manner in order to reduce the load torque of the motor and to smoothly transport the photoconductive sheet.

A line flow fan 88 is provided above the developing device 30,
The hot air from this is blown onto the photoconductive sheet on the conveyance path immediately after the developing device 30 and the photoconductive sheet on the panel heater 84, and the photoconductive sheet is dried from above. This allows the photoconductive sheet after development to be quickly dried. The toner image is fixed on the photoconductive sheet by being dried.

As described above, according to this embodiment, the upper roller forming the conveying roller pair is separated from the lower roller immediately before the photoconductive sheet is sandwiched by the conveying roller pair, and the light is generated in the gap between the upper and lower rollers. The tip of the conductive sheet is inserted, then
Since the upper roller is brought into contact with the lower roller again, the photoconductive sheet member is not impacted when the photoconductive sheet is inserted into the pair of conveying rollers. As a result, the photoconductive sheet is smoothly conveyed at a constant speed while maintaining flatness, and positional deviation during laser exposure is prevented.

It should be noted that the present invention is not limited to the above-described embodiments, but can be variously modified. For example, the charger may charge the photoconductive sheet with a negative electrostatic charge contrary to the above description. In this case, a developing solution containing positively charged toner may be used. Further, in the case of reversal development, a developer containing positively charged toner may be used and the on / off of the laser light may be reversed.

〔The invention's effect〕

As described above, according to the present invention, at the moment when the photoconductive sheet is sandwiched by the pair of conveying rollers, the rollers forming the pair of conveying rollers are spaced from each other. Laser engraving device that does not cause shock to the photoconductive sheet during conveyance, smoothly conveys the photoconductive sheet at a constant speed while maintaining flatness, and does not cause misalignment during laser exposure. Can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of an embodiment of a laser plate making apparatus according to the present invention, and FIG. 2 is a front end detection sensor shown in FIG.
FIG. 3 is a perspective view showing a detailed structure in the vicinity of the first conveying roller pair;
FIGS. 4A and 4B are diagrams showing the operation of the first conveying roller pair in FIG. 1, and FIG. 4 is a perspective view showing the detailed structure of the developing device in FIG. 20 …… Tip detection sensor 22 …… 1st transport roller pair 24 …… Charger 28 …… 2nd transport roller pair 30 …… Developer 32 …… Photoconductive sheet 48 …… Lift mechanism 50 …… Rotary solenoid 62 …… Laser exposure part 82 …… Aperture roller pair 84 …… Panel heater 86 …… Third transport roller pair 88 …… Line flow fan

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-43668 (JP, A) JP-A-55-64268 (JP, A) Jikho 57-19719 (JP, Y2)

Claims (1)

[Claims] 1. A laser plate making apparatus for making a plate of an original image on a photoconductive sheet member by sequentially passing a photoconductive sheet member through a charging means, a laser exposing means, a developing means and a fixing means by a plurality of rotating conveying roller pairs. In the apparatus, at least a part of the photoconductive sheet member of the plurality of conveyance roller pairs is provided on the downstream side in the conveyance direction from the laser exposure means, and a part of the photoconductive sheet member is provided at a position where the tip of the photoconductive sheet member reaches during exposure in the laser exposure means. The photoconductive sheet member detecting means provided on the upstream side of the predetermined conveying roller pair in the conveying direction, and when the detecting means detects the photoconductive sheet member, the rollers forming the predetermined conveying roller pair are illuminated. A laser plate making apparatus comprising: a means for separating the conductive sheet member for a predetermined period so that the conductive sheet member is separated at the moment when the leading edge of the conductive sheet member is sandwiched.