JPH0196677A - Adhesive transfer method - Google Patents

Abstract

PURPOSE:To improve the safety of a device and to prolong the life of a photoconductor by pressing a thermal head against the photoconductor from the opposite surface from the adhesive layer of a transfer sheet and also heating the transfer sheet. CONSTITUTION:The thermal head 30 is used instead of a heat pressure roll and this thermal head 30 pressed the transfer sheet 32 against the photoconductor 10 and also heats the transfer sheet 32. The heat generation part of the thermal head 32, therefore, comes into what is called linear contact with the transfer paper 32 and heat is not generated except at this contact part. Consequently, even when the thermal head 30 is used, the whole device such as an electrophotographic printer does not rise in temperature remarkably and the photoconductor 10 is also prevented from rising in temperature.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for transferring a toner image formed on a photoconductor by electrophotography onto a support, and in particular, a transfer method having an adhesive layer. This invention relates to an adhesive transfer method using a sheet.

(Prior art) Conventionally, an electrostatic latent image is formed by projecting an image of an original onto a negatively charged photoconductor or by irradiating a light beam modulated based on an image signal. 2. Description of the Related Art Electronic copiers or electrophotographic printers are known that develop an electrostatic latent image into a toner image and then transfer the toner image to a support such as paper.

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, an electrostatic latent image formed on a photoconductor is developed into a toner image using a developer, and then an adhesive tape is pressed onto the toner image to form a toner image. An electrophotographic process is disclosed in which the image is peeled off and the tape is then adhered to the final support.

As a method of transferring the toner image formed on a photoconductor to a support such as paper, 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 an extremely high transfer efficiency regardless of the image density, and is therefore advantageous for recording continuous tone images.

By the way, in carrying out the above-mentioned adhesive transfer method, it has been conventionally proposed to heat the transfer sheet pressed against the photoconductor from the side opposite to the adhesive layer. In other words, by doing so, the adhesiveness of the adhesive layer of the transfer sheet is increased, and the toner on the photoconductor is aggregated, thereby improving the transfer efficiency. Heretofore, heating of the transfer sheet has been accomplished specifically by incorporating a heating source into the pressure roller that presses the sheet against the photoconductor and maintaining the surface of the pressure roller at a high temperature.

(Problem to be solved by the invention) However, when heating the transfer sheet in this way,
Problems have been recognized in that the amount of heat generated from the suppression roller is large and the temperature of the entire apparatus such as an electrophotographic printer tends to rise, and as a result, the temperature of the photoconductor increases as a whole, accelerating thermal deterioration.

Therefore, an object of the present invention is to provide an adhesive transfer method that can solve the above problems.

(Means for Solving the Problems) As described above, the adhesive transfer method of the present invention is an adhesive transfer method in which a transfer sheet having an adhesive layer is pressed against a photoconductor to transfer a toner image onto the adhesive layer. In this method, a thermal head is used instead of using a heated pressure roller as described above, and the thermal head presses the transfer sheet against the photoconductor and heats the transfer sheet. That is.

(Function) The heat generating part of the thermal head is in line contact with the transfer sheet, and no heat is generated from any part other than this contact part, so even if this thermal head is used, the temperature of the entire device such as an electrophotographic printer will rise significantly. Therefore, temperature rise of the photoconductor is also prevented.

(Embodiments) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an example of an electrophotographic printer that transfers toner images by the method of the present invention.

A photosensitive drum 11 having a photoconductor 10 disposed on its circumferential surface is rotated in the direction indicated by the arrow by a driving means (not shown).

Around this photosensitive drum U, along the rotational direction of the drum 11, a charger 12, an exposure section 13, a wet developing device 14,
Squeeze corona discharger 15, drum drying fan 1B
, adhesive transfer means 17, static eliminator 18, cleaning roller 19, cleaning blade 20, and erasing lamp 21
is located.

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), which modulates the intensity of a light beam (laser beam) 23 emitted from the laser beam, and a modulation circuit 25 which drives this optical modulator 24.
Reflecting and deflecting the modulated light beam 23, the photoconductor lO
It consists of an optical deflector 26 such as a polygon mirror that scans the photoconductor in a direction substantially perpendicular to the direction of rotation of the photoconductor (direction of arrow A), and an fθ lens that focuses the light beam 23 to a uniform beam diameter on the photoconductor IO. A scanning lens 27 is provided.

On the other hand, the adhesive transfer means 17 is moved in the direction of arrow B by a known means, and the photoconductor lO on the circumferential surface of the photoreceptor drum 11 is
a thermal head 30 that can be in a position in pressure contact with the photoconductor 1O and a position apart from the photoconductor lO; a transfer sheet supply roller 33 that winds and stores a transparent transfer sheet 32 with a release paper 31 pasted thereon; A release paper 31 and a transparent transfer sheet 3 are placed between the roller 33 and the thermal head 30.
A pair of nip rollers 84.35 sandwich the transparent transfer sheet 3, and the transparent transfer sheet 3 is wrapped around one of the nip rollers 35.
and a release paper winding reroller 36 that winds up the release paper 31 peeled off from the paper 2.

This release paper winding roller 3B is rotationally driven in the direction of arrow C by a driving means (not shown). The transparent transfer sheet 32 from which the release paper 31 has been peeled off is hung on the thermal head 30 with its adhesive layer facing outward, and passed between pressure rollers 37 and 38 consisting of a pair of nip rollers. These pressure rollers 37 and 38 are driven to rotate in the directions of arrows, respectively, by driving means (not shown). These pressure rollers 37, 38 are connected to the paper sheet 3 as an opaque support.
Together with a sheet supply roller 40 that winds and stores sheets of paper, the sheet supply roller 4 constitutes a sheet pasting means.
The paper sheet 39 pulled out from the transparent transfer sheet 32 is superimposed on the transparent transfer sheet 32 and passed between the pressure rollers 37.3g. Note that the paper sheet 39 used is a white one, for example.

During image recording, the photosensitive drum 11 is rotated as described above, and the thermal head 30 is uniformly energized. 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 to a D/A converter 4.
The image signal S, which is converted into an analog signal by the D/A converter 43, 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 for gradation correction. Modulation circuit 25
drives the light modulator 24 based on the image signal S, whereby the light beam 23 is intensity-modulated in accordance with the image signal S.

The photosensitive drum 11 rotates as described above.
-, the photoconductor lO moves relative to the charger 12 and is uniformly charged by the charger 12.

The --like charged photoconductor IO is irradiated with the light beam 23 deflected by the optical deflector 2B as described above.

This light beam 23 passes over the photoconductor lO by the above deflection.
As the photosensitive drum 11 is rotated, the light beam 23 performs sub-scanning, and as a result, the photoconductor 10 is scanned two-dimensionally by the light beam 23. As mentioned above, the beam 23 is modulated based on the image signal S, and therefore, on the photoconductor lO irradiated with the light beam 23, an electrostatic latent image of the image carried by the image signal S is formed. 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 toner developed by contacting the photoconductor IO and causing toner particles to adhere to the photoconductor IO by electrostatic attraction.

The toner image thus formed is produced by a high-intensity light beam 2.
The area irradiated in step 3 has a lower density than the other, and the image signal S
The gradation of the continuous tone image that d is responsible for will be reproduced. After this development, the photosensitive drum 11 is dried by the squeezing 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 sent to just before the position facing the thermal head 30, it is separated from the photoconductor drum 11 until then. Thermal head 3
0 is moved so as to press against the photosensitive drum 11, and at the same time, the release paper winding roller 3B and the pressure roller 8
7. as is driven.

By rotating the release paper winder and reroller 3B, the release paper 31 is peeled off from the adhesive layer of the transparent transfer sheet 32, and the adhesive layer side of the transparent transfer sheet 32 is pressed against the photoconductor lO by the thermal head 8o. It will be done. The pressure rollers 37, 88 are rotated in synchronization with the photoconductor drum 11, so that the transparent transfer sheet 32 comes into pressure contact with the photoconductor 1G and moves at the same speed as the photoconductor 1O. At this time, as shown in detail in FIG. 2, the toner T on the photoconductor 10 is transferred to the adhesive layer 32a of the transparent transfer sheet 32. and,
Since the thermal head 3o that presses the transparent transfer sheet 32 against the photoconductor 10 is uniformly energized as described above, the transparent transfer sheet 32 pressed against the photoconductor 10
4j, heating is performed linearly over the entire width from the surface opposite to the adhesive layer 32a. This increases the adhesiveness of the adhesive layer 82a, and in addition, the toner T aggregates and becomes easier to peel off from the photoconductor 1o as a whole, so that the toner transfer efficiency is increased. As mentioned above, since the thermal head 3o heats the transfer sheet 32 extremely locally, the temperature of the entire electrophotographic printer does not rise significantly due to the heat generated by the thermal head 30, and therefore the photoconductor 1O also heats the transfer sheet 32 very locally. It is difficult for the temperature to rise in areas other than the area where the head 30 is pressed. .

The transparent transfer sheet 32, on which the toner image on the photoconductor 10 has been adhesively transferred, is sent between pressure rollers 37, 38,
``A paper sheet 39 is bonded to the transparent transfer sheet 32. Transparent transfer sheets 32 stuck to each other
, the paper sheet 39 is cut by a cutter 45 into image forming areas. As a result, as shown in FIG. 3, a transparent transfer sheet 32 is pasted onto a paper sheet 39 as a support.
A print 50 in which a continuous tone image is recorded with toner T is obtained between these two sheets.

After the adhesive transfer of the toner image, the photoconductor lO 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.

In the embodiment described above, the toner image on the photoconductor lO is adhesively transferred to the transparent transfer sheet 32, but as shown in FIG. 4, the toner image is adhesively transferred to the opaque transfer sheet. You can do it like this. That is, in the apparatus shown in FIG. 4, instead of the transparent transfer sheet 32, an opaque transfer sheet 70 having an adhesive layer formed on the surface of a white paper sheet, for example, is used. The adhesive layer is made of a material that does not have adhesive properties at room temperature but becomes adhesive when heated to a predetermined temperature.

Specifically, this adhesive layer may be formed from an adhesive generally called Riko hot melt adhesive.

This hot melt adhesive contains a thermoplastic resin, a tackifier, and waxes as components. Examples of thermoplastic resins include ethylene-vinyl acetate copolymer, polyethylene, acidic polypropylene, and ethylene-vinyl acetate copolymer.
Ethyl acrylate copolymer, polyamide, saturated copolymerized polyester resin, etc. are used. Tackifiers include rosin or its derivatives, natural resins such as pinene resins, aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, coumaron-indene resins, etc. synthetic resin is used. Also, as a wax,
paraffin wax, microcrystalline wax,
Low molecular weight polyethylene wax, alpha olefin wax, modified wax, etc. are used. In this device as well, the opaque transfer sheet 70 is heated to a predetermined temperature by the thermal head 30 when it is pressed against the photoconductor IO, thereby making the adhesive layer of the sheet 70 sticky. Note that in FIG. 4, elements that are equivalent to those in FIG. 1 are given the same numbers, and a description thereof will be omitted.

The opaque transfer sheet 70 with the toner image transferred in this way is
It is cooled before passing between a pair of transport rollers 71 and 72,
The adhesive layer is thereby cured. The opaque transfer sheet 70 that has passed between the transport rollers 71 and 72 is cut into image forming areas by the cutter 45. As a result, as shown in FIG. 5, a print 80 in which a continuous tone image is recorded with toner T on an opaque transfer sheet 70 as a support is obtained. In this print 80, since the adhesive layer has already been hardened as described above, the image will not be smeared even if the print surface is touched with a finger, and the print surface will not stick to the finger or the like.

In the case described above, since the toner image formed on the photoconductor 10 is reversed and transferred onto the opaque transfer sheet 70, the toner image formed on the photoconductor 10 is transferred onto the opaque transfer sheet 70, for example, at the front stage of the correction table 42 or as shown in FIG. A signal inverter 73 is provided at a later stage, etc.
The desired image is formed inside out on the photoconductor IO.

When using the transfer sheet 70 that becomes sticky when heated as described above, there is no need for a means for peeling off or winding up the release paper, and another sheet is attached to the transfer sheet 70 after the toner image has been transferred. There is also no need for a means for attaching the material, and the device can be made smaller and lighter.

(Effect of the invention) As explained in detail above, according to the adhesive transfer method of the present invention,
In addition to heating the transfer sheet to increase transfer efficiency or eliminating the need for release paper, heating the transfer sheet in this way does not increase the overall temperature of the device such as an electrophotographic printer, and also lowers the temperature of the photoconductor. Since no rise is caused, the safety of the device is increased and the life of the photoconductor is extended.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is a side view showing an enlarged part of the above-mentioned apparatus, and FIG. 3 is a perspective view showing a print obtained by the above-mentioned apparatus. FIG. 4 is a schematic view showing another example of an apparatus for implementing the method of the present invention, and FIG. 5 is a perspective view showing a print obtained by the apparatus of FIG. 4. lO... Photoconductor 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... Thermal head 31... Release paper 32... Transparent transfer sheet 32a...
・Adhesive layer 37.38...pressure roller 39・
... Paper sheet 40 ... Sheet supply roller 41 ... Image signal supply device 42 ... Correction table 70 ... Opaque transfer sheet 71.72 ... Conveyance roller 73 ... Signal inverter F ...・Liquid developer T
...Toner Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] An adhesive transfer method in which a transfer sheet having an adhesive layer is pressed against a photoconductor carrying a toner image on the surface to transfer the toner image to the adhesive layer, the transfer sheet comprising: An adhesive transfer method comprising: pressing a thermal head against the photoconductor from the side opposite to the adhesive layer; and heating the transfer sheet with the thermal head.