JPS63113567A - Electrophotography printer - Google Patents

Abstract

PURPOSE:To record a continuous image having high reproducibility by providing a signal correcting means for correcting an image signal, based on an exposure quantity-to-toner image density characteristic of a photoconductive body, and linearizing the relation of a toner image density based on a signal after correction, and the image signal before correction. CONSTITUTION:A gradation characteristic of a photoconductive body 10, namely, a relation of an exposure quantity E-to-toner image density D is, generally, extremely non-linear. On the other hand, by setting a conversion characteristic in a D/A converter 43, and a modulation characteristic by a modulating circuit 25 and an optical modulator 24, the relation of an image signal Sd' before a D/A conversion and the exposure quantity can be set as a straight line (b) of the fourth quadrant. In a correction table, an image signal Sd is formed so as to be converted to an image signal Sd' by a characteristic shown by a curve (c) of the third quadrant, the relation of the image signal Sd and the toner image density D goes to linear as shown in the second quadrant. In such a way, by a variation of a prescribed quantity of the image signal Sd, and the toner image density D can be controlled at an equal density interval, and a continuous image can be recorded with high gradation reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a printer that records images by electrophotography, and particularly relates to an electrophotographic printer that is capable of recording high-gradation continuous-tone images. .

<Prior art> Conventionally, a uniformly charged photoconductor is irradiated with a light beam modulated based on an image signal that carries a continuous tone image to form an electrostatic latent image, and then ordinary electron beams are used to form an electrostatic latent image. Electrophotographic printers are known that use a photographic process to form hard copies of the images.

On the other hand, various electrophotographic methods have been proposed that allow continuous tone images to be recorded with good gradation reproducibility. For example, in Japanese Patent Publication No. 49-38172 by the present applicant, Shun develops an electrostatic latent image formed on a photoconductor into a toner image using a liquid developer, and presses an adhesive tape onto this toner image. An electrophotographic process is disclosed in which the toner image is peeled off and the tape is then adhered to the final support.

The liquid developer mentioned above is made by dispersing fine toner particles with an electric charge in an insulating liquid, and the toner particle size is usually 0.1 to 0.5 μm, which is smaller than that of a dry developer. Therefore, it is advantageous for recording continuous tone images.

As a method for transferring a toner image formed on a photoconductor to a support such as paper, a method of electrostatic transfer using a corotron is widely used. It has been recognized that there is a problem with poor transfer efficiency in high-density areas and low-density areas. On the other hand, the so-called adhesive transfer method in which a toner image is transferred to an adhesive layer as described above has a transfer efficiency of nearly 100% regardless of the image temperature, and is therefore also advantageous for recording continuous tone images.

(Problem that Te Ming is trying to solve) However, in the past, even if the above-mentioned wet development method and viscous transfer method were adopted, when recording a continuous tone image with high gradation, it was difficult to obtain an image with good gradation reproducibility. It was difficult to (q).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic printer that can record high-gradation continuous-tone images with good gradation reproducibility.

(Means for Solving the Problems) In the electrophotographic printer of the present invention, the problem that gradation reproducibility is impaired in electrophotography is solved by the gradation characteristics of the photoelectric material, that is, the exposure ff1E versus the toner image depth. This is based on the knowledge that the relationship between the photoconductors and the photoconductors is extremely nonlinear, as seen in the first quadrant of Figure 4. A charger that uniformly charges the photoconductor, a wet developer that performs the above-mentioned wet phenomenon, and an adhesive that presses a transfer sheet having an adhesive layer against the photoconductor and transfers a toner image to the adhesive layer. a transfer means, a sheet adhering means for adhering another sheet material to the adhesive layer of the transfer sheet to which the toner image has been transferred, and a 3i4 image signal carrying a continuous tone image to the uniformly charged photoconductor. Then, the image signal is applied to an electrophotographic printer equipped with a light beam irradiation means for irradiating a modulated light beam to form an electrostatic latent image, and the image signal is applied to the photoconductor's exposure amount versus toner image Q degree characteristic. The present invention is characterized in that a signal correction means is provided for making a linear relationship between the toner 9111 degrees based on the corrected signal and the image signal before correction.

(Function) If the relationship between the image signal and the toner image density can be made linear as described above, it will be possible to control the toner image density at equal density intervals by a constant change in the image signal, and it will be possible to control the toner image density at equal density intervals with good gradation reproducibility. Images can now be recorded.

(Examples) Hereinafter, the present invention will be described in detail based on examples not shown in the drawings.

FIG. 1 shows an electrophotographic printer according to a first embodiment of the present invention. A photosensitive drum 11 having a photoconductor 10 disposed on its circumferential surface is rotated in the direction of the arrow by a driving means (not shown). Around this photosensitive drum 11,
A charger 12 and an exposure section 1 are arranged along the rotational direction of the drum 11.
3, wet developing device 14, drum drying corona discharger 15,
Drum drying fan 16, adhesive transfer means 17, static eliminator 1
8, cleaning roller 19, cleaning blade 2
0 and an erase lamp 21 are arranged.

The exposure section 13 includes a laser light source 22 made of, for example, a semiconductor laser, a He-Ne laser, and the like.
An optical modulator 24 such as an AOM (acousto-optic modulator) that modulates the intensity of a light beam (laser beam) 23 emitted from the laser beam, a modulation circuit 25 that drives the optical modulator 24, and a modulated light beam. 23 is reflected and deflected, and the light 'fJT
An optical deflector 26, such as a polygon mirror, is mounted on the photoconductor 10 to scan it in a direction substantially perpendicular to the direction of rotation of the photoconductor (in the direction of the arrow), and the light beam 23 is focused on the photoconductor 10 to a uniform beam diameter. Scanning lens 2 consisting of an fθ lens that
7.

On the other hand, the adhesive transfer means 17 is moved by a known means in the direction of arrow B, and is a pressure roller that can take a position in pressure contact with the photoconductor 10 on the circumferential surface of the photoreceptor drum 11 and a position away from the photoconductor 10. 30, an adhesive sheet supply roller 33 for winding and storing a transparent adhesive sheet 32 as a transfer sheet on which a release paper 31 is attached, and the adhesive sheet supply roller 33.
and a pair of nip rollers 34 and 35 that sandwich the release paper 31 and the transparent adhesive sheet 32 between the pressure roller 30 and the pressure roller 30.
and a release paper winding roller 36 that winds up the release paper 31 that has been wrapped around one nip roller 35 and peeled off from the transparent adhesive sheet 32. This release paper winding roller 36 is rotationally driven in the direction of arrow C by a driving means (not shown). The transparent adhesive sheet 32 from which the release paper 31 has been removed is wound around the pressure roller 30 with its adhesive layer facing outward, and then passed between pressure rollers 37 and 38 consisting of a pair of nip rollers. These pressure rollers 37.3
8 are rotationally driven in the directions of arrows by driving means (not shown). These pressure rollers 37.3g constitute a sheet sticking means together with a sheet supply roller 40 that winds and stores a paper sheet 39 as an opaque support, and the paper sheet 39 pulled out from the sheet supply roller 40 is , and the transparent adhesive sheet 32 is overlapped with the transparent adhesive sheet 32 and passed between pressure rollers 37 and 38. Note that the paper sheet 39 used is, for example, a white one.

During image recording, the photosensitive drum 11 is rotated as described above. Then, a digital image signal Sd representing a continuous tone image is passed from an image signal supply device 41 to a correction table 42
The image signal S is sent to the Δ converter 43 and analogized by the D/Δ converter 43, and is sent to the modulation circuit 25 described above. Note that the image signal Sd is converted into an image signal Sd' in the correction table 42, and this conversion will be described in detail later.

The modulation circuit 25 modulates the optical modulator 24 based on the image signal S.
is driven, whereby the light beam 23 is intensity-modulated in accordance with the image signal S.

By rotating the photosensitive drum 11 as described above,
The photoconductor 10 is moved relative to the charger 12 and is uniformly 91 electrified by the charger 12 in the process. The uniformly charged photoconductor 10 is irradiated with the light beam 23 deflected by the optical deflector 2G as described above.

This light beam 23 passes over the photoconductor 10 by the deflection described above.
By rotating the photosensitive drum 11, the light beam 23 performs sub-scanning, and eventually the photoconductor 10 is scanned two-dimensionally by the light beam 23. As mentioned above, this light beam 23 is modulated based on the image signal S, and therefore, the electrostatic potential of the image carried by the image signal S appears on the photoconductor 10 irradiated with this light beam 23. An image is formed.

This electrostatic latent image is developed into a toner image by a wet developer 14. This wet type developing device 14 uses a liquid developer F, which is made by dispersing fine toner particles with an electric charge in an insulating liquid.
The electrostatic latent image is developed with toner by contacting the photoconductor 10 and causing toner particles to be attached to or removed from the photoconductor 10 by electrostatic attraction.

The density of the toner image thus formed changes in accordance with the intensity modulation of the light beam 23, and the gradation of the continuous tone image carried by the image signal Sd is realized.

After this development, the photosensitive drum 11 is dried by the drum drying corona discharger 15 and the drum drying fan 16.

When it is detected or determined by known means that the toner-developed portion of the photoconductor 10 has been fed just before the position facing the suppression roller 30, it is separated from the photoconductor drum 11 until then. The pressure roller 30, which had been previously used, is moved so as to press it against the photoreceptor drum 11, and at the same time, the release paper winding roller 36 and the pressure rollers 37, 38 are moved.
is driven. By rotating the release paper winding roller 36, the release paper 31 is peeled off from the adhesive layer of the transparent adhesive sheet 32, and the adhesive layer side of the transparent adhesive sheet 32 is pressed against the photoconductor 10 by the pressing roller 30. . Since the pressure roller 30 is driven to rotate by the photoconductor drum 11 and the pressure rollers 37 and 38 are rotated, the transparent adhesive sheet 32 comes into pressure contact with the photoconductor 10 and moves at the same speed as the photoconductor 10. At this time, as shown in detail in FIG.
Transferred to B32a. The transparent adhesive sheet 32 on which the toner image on the photoconductor 10 has been adhesively transferred in this manner is sent between pressure rollers 37 and 38, and a paper sheet 39 is bonded to the transparent adhesive sheet 32. The transparent adhesive sheet 32 and the paper sheet 39 that are stuck to each other are cut by a cutter 45.
The image is cut into image forming areas.

As a result, as shown in FIG. 3, a transparent adhesive sheet 32 is pasted on a paper sheet 39 as a support, and a print 50 with a continuous tone image recorded with toner T is placed between these two sheets 32 and 39. can get. In addition, if a transparent film sheet is used instead of the paper sheet 39 in FIG. 1, a transparent print can be obtained.

After the adhesive transfer of the toner image, the photoconductor 10 is transferred to a static eliminator 18
The charge is removed by the cleaning roller 19 and the cleaning blade 20, and the charge is optically removed by the erasing lamp 21, so that it can be used for the next image recording.

For the reasons mentioned above, wet development using the wet developing device 14 and adhesive transfer using the adhesive transfer means 17 are advantageous in recording continuous tone images. In addition, this device
Since the image signal Sd is corrected using the above-mentioned correction table 42, the gradation reproducibility is particularly excellent. This point will be explained below. Photoconductor 1
0 gradation characteristics, that is, exposure ff1E vs. toner image density e,D
Generally, the relationship is extremely nonlinear, as shown by curve a in the first quadrant of FIG. On the other hand, by setting the conversion characteristics in the D/A converter 43 and the modulation characteristics in the modulation circuit 25 and the optical modulator 24, the image signal S before D/Δ conversion is
It is possible to set the relationship between d' and the exposure distance as shown in the straight line in the fourth quadrant of FIG. The correction daple 42 is formed to convert the image signal Sd into an image signal Sd' with the characteristic shown by the curve C in the third quadrant of FIG. If such conversion is performed, the relationship between the image signal Sd and the image density from 1 to 1 becomes linear, as shown in the second quadrant of FIG. Therefore, it becomes possible to control the toner image depth at equal density intervals by changing the image signal Sd by a certain amount, and it becomes possible to record a continuous tone image with good tone reproducibility.

In the embodiment described above, the 1-Henner image on the photoconductor 10 is adhesively transferred to the transparent adhesive sheet 32, but as shown in the second embodiment apparatus of FIG. Alternatively, the toner image may be adhesively transferred to. That is, in this second embodiment apparatus, an opaque adhesive sheet 70 is used in place of the transparent adhesive sheet 32, for example, an opaque adhesive sheet 70 having an adhesive layer formed on the surface of a white paper sheet. A transparent sheet 71 as a cover sheet is stored, and the opaque adhesive sheet 70 km after the toner image transfer is pasted to the transparent sheet 71. A print can be formed.

Note that in FIG. 5, elements that are equivalent to those in FIG. 1 are given the same numbers, and a description thereof will be omitted.

In the case described above, since the toner image formed on the photoconductor 1o is reversed and transferred onto the opaque adhesive sheet 70, for example, as shown in FIG.
A signal inverter 72 is provided before or after the photoconductor 2, so that a desired image is formed on the photoconductor 10 with the front and back reversed.

In the embodiments described above, the adhesive sheet 32 or 70 bonded to the female pattern paper 31 is used, but other materials, such as those that are not sticky at room temperature but become sticky when heated, are used. It is also possible to use a sticky sheet provided with a heat-sensitive adhesive layer.

In such a case, for example, the pressure roller 30 may be formed as a heating roller, and the adhesive sheet may be heated when it is pressed against the photoconductor 10 of the photosensitive drum 11.

(Effects of the Invention) As explained in detail above, the electrophotographic printer of the present invention employs a wet printing method and an adhesive transfer method, as well as signal correction that linearly corrects the relationship between image signals and toner@density. By providing the means, it becomes possible to control the toner image 71 degrees at equal Wi degree intervals by a constant constant change of the image signal, and it becomes possible to record a continuous tone image with extremely excellent gradation reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a first embodiment of the device of the present invention, FIG. 2 is a side view showing an enlarged part of the device of the above embodiment, and FIG. 3 is a perspective view showing a print obtained by the device of the present invention. 4 is a graph illustrating the correction characteristics of the signal correction means in the apparatus of the present invention, and FIG. 5 is a schematic diagram showing a second embodiment of the apparatus of the present invention. 10... Photo S electric body 11... Photosensitive drum 12... Charger 13... Exposure section 14.
・Wet type developer 17 ・Adhesive transfer means 22 ・
...Laser light source 23...Light beam 24...
Light modulator 25...Modulation circuit 26...Light deflector 30...Press roller 31...Release paper 32...Transparent adhesive sheet 32a...Adhesive layer 37.38...Pressure roller 39 ...
Paper sheet 40... Sheet supply roller 41.
...Image signal supplier 42...Correction table 70.
... Opaque adhesive sheet 71 ... Transparent sheet 72 ...
・Signal inverter F...Liquid developer T...Toner Figure 2 Figure 3 Sd'

Claims (4)

[Claims] (1) A photoconductor, a charger for uniformly charging the photoconductor, and a light beam modulated based on an image signal carrying a continuous tone image irradiated onto the uniformly charged photoconductor; a light beam irradiation means for forming an electrostatic latent image using a liquid developer; a wet developing device for developing the electrostatic latent image into a toner image using a liquid developer; pressing a transfer sheet having an adhesive layer against the photoconductor; an adhesive transfer means for transferring the toner image onto the adhesive layer; a sheet adhering means for adhering another sheet material to the adhesive layer of the transfer sheet to which the toner image has been transferred; and a signal correction means for correcting the toner image density based on the exposure amount versus toner image density characteristic of the image signal to linearize the relationship between the toner image density based on the corrected signal and the image signal before correction. Photo printer. (2) The electrophotographic printer according to claim 1, wherein a transparent member is used as the transfer sheet, and an opaque sheet material is used as the other sheet material. (3) The electrophotographic printer according to claim 1, wherein the transfer sheet is made of an opaque material, and the other sheet material is a transparent sheet material. (4) The electrophotographic printer according to claim 1, wherein a transparent member is used as the transfer sheet, and a transparent sheet material is used as the other sheet material.