EP0778136A2

EP0778136A2 - Image recording apparatus

Info

Publication number: EP0778136A2
Application number: EP96308881A
Authority: EP
Inventors: Masaaki Ozaki; Masayoshi Tsunezawa; Masaya Nagata; Kaoru Higuchi
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 1995-12-07
Filing date: 1996-12-06
Publication date: 1997-06-11
Also published as: EP0778136A3; JP3200555B2; JPH09156137A

Abstract

An image recording apparatus includes a printing unit (100, 500) for making ink adhere to a recording medium (RM) without contact therewith to form an image on the recording medium (RM), and a dye receiving layer coating unit (200, 201, 202, 510) for coating an image formation surface of the recording medium (RM) with a dye receiving layer before the recording medium (RM) is transported to the printing unit (100, 500). The printing unit (100, 500) forms an image by vaporizing powdery sublimation dye ink and intermittently ejecting the vaporized ink in accordance with image data. The dye receiving layer coating unit (200, 201, 202, 510) makes dye receptor particles adhere to the recording medium (RM) electrostatically, or liquid dye receptor adhere to the recording medium (RM) by ejection, and thereafter fixes the dye receptor particles or the liquid dye receptor adhering on the recording medium (RM). A common fixing unit (14) may be used for the dye receiving layer coating unit (510) and the printing unit (500). In addition, a sensor (20) for deciding whether the recording medium (RM) is of specific paper with a preapplied dye receiving layer or of plain paper may be provided so as to operate the dye receiving layer coating unit (200, 201, 202, 510) only when the plain paper is detected.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to image recording apparatuses including a copying machine, a facsimile, and a printer, and more particularly to an image recording apparatus for recording an image by making ink adhere to a recording medium without contact therewith.

Description of the Related Art

As image recording apparatuses, image recording apparatuses employing an ink jet method or an electrostatic recording method have been proposed. According to the ink jet method, image recording is carried out by pressurizing liquid ink contained in a tank by piezoelectric elements or the like in accordance with electric signals corresponding to image data and ejecting the pressurized ink from nozzles. According to the electrostatic recording method, image recording is carried out by charging powdery or liquid (misty) ink, ejecting it from the nozzles by electrostatic suction force, and opening and closing shutters provided at tips of the nozzles in accordance with electric signals corresponding to image data.
However, the ink jet method causes problems that printing operation cannot be performed because sufficient pressurization in the ink tank is prevented by the air introduced into the tank, and that the nozzle is clogged up with ink and the recording medium is blurred with ink because liquid ink is used, resulting in degradation in image quality. The electrostatic recording method also causes problems that the clogging is produced by the ink particles agglomerated by blocking if the ink used is powder, and that the image quality is degraded by the clogging and blur with ink similarly to the ink jet method if the used ink is liquid.
As a method of solving the above-mentioned problems, a method of ejecting the vaporized ink to adhere onto the recording medium has been proposed. According to this method, the clogging of the nozzles is less likely to occur because gas is ejected, and both higher resolution and excellent gradation can be achieved because the pixels are recorded in the molecular state, allowing high quality print with less blur. An image recording apparatus using this method is disclosed in Japanese Patent Publication No. 56-2020. The above-mentioned conventional image recording apparatus will now be described in detail with reference to Fig. 14.
Referring to Fig. 14, the image recording apparatus includes a printing head 601, a heating apparatus 602, a charging electrode 603, electric field lenses 604 and 605, an electric field shutter 606, a back electrode 607, a power supply 610, and a signal source 611. Heating apparatus 602 includes a power supply 608 and an electric heater 609.
Ink Iℓ in printing head 601 is heated and vaporized by heating apparatus 602 constituted by electric heater 609 and power supply 608. Thus vaporized gaseous ink Ig is jetted out from printing head 601. At the same time, gaseous ink Ig is charged by power supply 610 inserted between charging electrode 603 and printing head 601 as it passed through charging electrode 603. Thus charged gaseous ink Ig is converged by electric field lenses 604 and 605. Thus converged gaseous ink Ig is controlled to a prescribed ejection amount by electric field shutter 606 of which operation is controlled by signal source 611, and sprayed toward back electrode 607, whereby an image is formed on a recording medium RM.
In the above mentioned conventional image recording apparatus, however, gaseous ink Ig is constantly ejected from printing head 601, whereby ink which is not actually used for recording is wasted, causing increase in the running cost. Furthermore, an apparatus for collecting the unused gaseous ink and an apparatus (not shown) for cleaning electric field shutter 606 and its vicinities are required, preventing reduction in size of the overall apparatus. Gaseous ink Ig is moved from printing head 601 to charging electrode 603 by increase in pressure in printing head 601 resulting from volume expansion by vaporization of ink I1 to cause gaseous ink Ig to jet out. Therefore, ejecting operation of gaseous ink Ig has poor response and is affected by the amount of ink I1 in printing head 601, causing degradation in printing quality such as unequal density.
In order to solve such problems as described above, we have proposed an image recording apparatus for carrying out printing operation by intermittently ejecting vaporized ink (United States Patent Application Serial No. 08/612,339 commonly assigned to the assignee of the present application). The above-mentioned image recording apparatus will now be described in detail with reference to Fig. 15. Note that the above application of the apparatus is already filed at the U.S. Patent and Trademark Office, but has not been published at the time when the present application is filed. The following description is given merely for the sake of understanding of the present application.
Referring to Fig. 15, the previously proposed image recording apparatus includes a printing head 1, a heating apparatus 2 including an electric heater 7, a charging electrode 3, an electric field shutter 4, a back electrode 5, and a control unit 6.
Powdery ink Ip is stored in printing head 1. At the lower part of printing head 1, heating apparatus 2 for heating ink Ip is provided. The heating apparatus is grounded. In the upper half portion of printing head 1, a wire electrode is provided as charging electrode 3 for charging the heated and vaporized ink Ip. An ejection hole for ejecting vaporized ink Ipg is provided at the upper portion of printing head 1, and electric field shutter 4 for controlling an ejection amount of vaporized ink Ipg is provided to surround the ejection hole. Electric field shutter 4 includes two electrode plates arranged to sandwich the wall at the upper portion of printing head 1. Shuttering operation of electric field shutter 4 is controlled by control unit 6. A recording medium RM is located over electric field shutter 4, and back electrode 5 is provided over recording medium RM.
In operation, ink Ip is heated and vaporized by heating apparatus 2 to gaseous ink Ipg. A positive voltage is applied to charging electrode 3, whereby corona discharge occurs therefrom toward heating apparatus 2, causing gaseous ink Ipg to be charged to a positive polarity. Next, a negative voltage is applied to back electrode 5 provided at the rear surface of the printing surface of recording medium RM, thereby attracting thus charged gaseous ink Ipg toward recording medium RM. At electric field shutter 4, a voltage corresponding to an output signal of control unit 6 in response to an electric signal of image data to be recorded is applied to the electrode on the side of recording medium RM and the electrode inside printing head 1. As a result, gaseous ink Ipg is controlled to pass or to be prevented from passing through electric field shutter 4. Gaseous Ipg which has passed through electric field shutter 4 is attracted by back electrode 5 to adhere to recording medium RM, forming a prescribed image thereon.
This image recording apparatus intermittently ejects ink, whereby both the amount of ink wasted and running cost are reduced.
However, the above-mentioned image recording apparatus which has been proposed but has not been published still has problems. More specifically, a specific recording medium RM with a preapplied dye receiving layer having superior color development for sublimation dye ink should be used when sublimation dye ink is used for ink Ip. Recording of excellent image is difficult for the sheets of plain paper which have not been subjected to special working. Increase in size of the apparatus itself should be avoided when an excellent image is to be formed on the sheets of recoding paper. In addition, it is preferable that an excellent image can be recorded on the sheets of either specific recording paper or plain paper.

SUMMARY OF THE INVENTION

The present invention is made to solve the above-mentioned problems, and it is an object of the present invention to provide an image recording apparatus capable of conducting excellent recording on the sheets of plain paper by ejecting vaporized sublimation dye ink.
It is another object of the present invention to provide an image recording apparatus capable of conducting excellent recording on the sheets of plain paper by ejecting vaporized sublimation dye ink, while allowing reduction in size.
It is a further object of the present invention to provide an image recording apparatus capable of conducting excellent recording on the sheets of both specific recording paper and plain paper by ejecting vaporized sublimation dye ink, while allowing reduction in size.
An image recording apparatus according to the present invention includes a printing unit for making ink adhere to a recording medium without contact therewith to form an image thereon, and a dye receiving layer coating unit for coating an image formation surface of the recording medium with a dye receiving layer before the receiving medium is transported to the printing unit.
Before ink is caused to adhere to the recording medium by the printing unit, the image formation surface of the recording medium is coated with a dye receiving layer. The presence of the dye receiving layer allows an excellent image to be formed even if the sheets of plain paper are used as recording medium. The printing unit makes ink adhere to the recording medium without contact therewith and therefore an image to be formed is less likely to be adversely affected by dye receiving layer coating if conducted right before image formation.
In one embodiment, the printing unit includes an ink reservoir for storing powdery sublimation dye ink, a heating apparatus for heating and vaporizing the sublimation dye ink stored in the ink reservoir, an ejecting apparatus for ejecting the sublimation dye ink vaporized by the heating apparatus onto the recording medium, and a controller responsive to image data corresponding to an image for controlling the ejecting apparatus to intermittently eject the heated sublimation dye ink. Since ink is intermittently ejected, the amount of wasted ink is reduced.
The dye receiving layer coating unit may include a reservoir for storing powdery dye receptor particles, a charging unit for charging the dye receptor particles, a holding unit for holding the dye receptor particles charged by the charging unit, and a transferring unit for electrostatically transferring the charged dye receptor particles onto the recording medium facing the holding unit. The dye receiving layer coating unit may be provided in the subsequent stage of the transferring unit, and may further include a fixing unit for fixing the dye receptor particles transferred onto the recording medium by the dye receiving layer coating unit.
An image recording apparatus of another embodiment further includes a fixing unit provided in the subsequent stage of the printing unit for simultaneously fixing the dye receptor particles transferred onto the recording medium by the dye receiving layer coating unit and the sublimation dye ink caused to adhere to the recording medium by the printing unit. Since the dye receptor particles and the sublimation dye ink can be fixed by the same fixing unit, increase in size of the apparatus can be prevented. Note that such fixing by the same fixing unit can be achieved because image quality will not be degraded even before fixing of the dye receiving layer so long as the printing unit can make ink adhere to the recording medium without contact therewith.
It is preferable that the dye receiving layer coating unit can selectively coat an arbitrarily portion of the recording medium with a dye receiving layer. An ion flow head, an ink jet, or the like can be used. In this case, coating of dye receiving layer can be carried out in the same region as an image recording region, thereby allowing reduction in the amount of dye receptor to be used.
More preferably, the recording medium further includes a recording paper decision apparatus provided in the upstream of the dye receiving layer coating unit in the path of the recording medium for deciding whether recording paper is specific paper with a preapplied dye receiving layer or plain paper. The dye receiving layer coating unit operates according to the result of decision by the recording paper decision apparatus. For example, a predetermined mark is attached to a sheet of specific paper, and an optical sensor for sensing whether the mark is attached to the recording medium or not can be used.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross sectional view showing the structure of an image recording apparatus according to a first embodiment of the invention.
Fig. 2 is a cross sectional view showing the structure of a dye receiving layer coating unit in an image recording apparatus according to a second embodiment of the invention.
Fig. 3 is a cross sectional view showing the structure of a dye receiving layer coating unit in an image recording apparatus according to a third embodiment of the invention.
Fig. 4 is a cross sectional view showing an ion flow head for writing an electrostatic latent image on a recording medium.
Fig. 5 is a cross sectional view showing the structure of an image recording apparatus according to a fourth embodiment of the invention.
Fig. 6 is a diagram showing a black mark for identification of specific paper provided on the rear surface of the sheet of specific paper.
Fig. 7 is a cross sectional view showing the structure of an image recording apparatus according to a fifth embodiment of the invention.
Fig. 8 is a cross sectional view showing a dye receiving layer sheet.
Fig. 9 is an enlarged view showing a heat element portion of a thermal head.
Fig. 10 is a top plan view showing the entire thermal head.
Fig. 11 is a cross sectional view showing the structure of an image recording apparatus according to a sixth embodiment of the invention.
Fig. 12 is a diagram of an ink jet head in Fig. 11 viewed from the nozzle direction.
Fig. 13 is a cross sectional view showing the structure of an image recording apparatus according to a seventh embodiment of the invention.
Fig. 14 is a cross sectional view showing the structure of a conventional image recording apparatus.
Fig. 15 is a cross sectional view showing the structure of our previously proposed image recording apparatus related to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Fig. 1, an image recording apparatus of a first embodiment is generally constituted by a printing unit 100 for intermittently ejecting vaporized sublimation dye ink selectively towards a recording medium RM for recording, and a dye receiving layer coating unit 200 for forming a dye receiving layer on the printing surface of the recording medium RM. Printing unit 100 and dye receiving layer coating unit 200 will now be described sequentially.
First, the structure and operation of printing unit 100 are described in the following. Printing unit 100 includes a printing head 1, a back electrode 5, and a control unit 6, wherein a heating apparatus 2, a charging electrode 3, and an electric field shutter 4 are formed integrally with printing head 1.
Powdery sublimation dye ink Iq is stored in printing head 1. At a lower part of printing head 1, heating apparatus 2 including an electric heater 7 for heating sublimation dye ink Iq is provided. Heating apparatus 2 is grounded. In the upper half portion of printing head 1, a thin wire electrode having a diameter in the range from 50 to 80 µm is provided as charging electrode 3 for charging heated and vaporized sublimation dye ink Iqg. An ejection hole for ejecting vaporized sublimation dye ink Iqg is provided at the upper portion of printing head 1, and electric field shutter 4 for controlling an amount of vaporized sublimation dye ink Iqg to be ejected is provided surrounding the ejection hole.
Electric field shutter 4 includes two electrode plates arranged to sandwich the wall at the upper portion of printing head 1. Operation of electric field shutter 4 is controlled by control unit 6. A recording medium RM is located over electric field shutter 4 such that a dye receiving layer RR faces electric field shutter 4, and back electrode 5 is provided over recording medium RM.
As coloring material for the ink, anthraisothiazole family, quinophtalon family, pyrazolonazo family, pyridonazo family, styryl family or the like can be used for yellow; anthraquinone family, dicyanoimidazole family, thiadiazoleazo family, tricyanovinyl family or the like can be used for magenta; azo family, anthraquinone family, naphthoquinone family, indoaniline family or the like can be used for cyan.
In printing operation, sublimation dye ink Iq is heated and vaporized by heating apparatus 2 to gaseous sublimation dye ink Iqg. A voltage in the range from +2 to 5 kV is applied to charging electrode 3, whereby corona discharge occurs toward heating apparatus 2 connected to the ground, and gaseous sublimation dye ink Iqg is charged to a positive polarity.
Then, a negative voltage in the range from -0.5 to-2kV is applied to back electrode 5 located over the rear surface of the printing surface of recording medium RM, thereby attracting gaseous sublimation dye ink Iqg thus charged to a positive polarity toward recording medium RM. A voltage is applied from control unit 6 to electrodes 4a and 4b of electric field shutter 4 in accordance with an electric signal of image data to be recorded so that a potential difference between electrode 4a on the side of recording medium RM and electrode 4b inside printing head 1 is in the range from 50V to 1kv. Gaseous sublimation dye ink Iqg has been charged to a positive polarity. Therefore, when a potential at electrode 4a on the side of recording medium RM is set to be higher than that at electrode 4b inside printing head 1, gaseous sublimation dye ink Iqg thus charged is prevented from passing through the ejection hole of electric field shutter 4. When a potential at electrode 4a on the side of recording medium RM is set to be equal to or lower than that at electrode 4b inside printing head 1, sublimation dye ink Iqg passes therethrough. Gaseous sublimation dye ink Iqg thus having passed through the ejection hole of electric field shutter 4 is sprayed toward back electrode 5 to adhere to and sink into dye receiving layer RR on recording medium RM for printing.
Through the above operation of printing unit 100, sublimation dye ink Iqg is vaporized to gaseous sublimation dye ink Iqg, which in turn is intermittently ejected from electric field shutter 4 in accordance with the electric signal responsive to the image data to be recorded to adhere to and sink into dye receiving layer RR on recording medium RM, thereby enabling a desired image to be formed. Therefore, the ejection operation of gaseous sublimation dye ink Iqg is controlled inside printing head 1 in accordance with the image data, whereby sublimation dye ink Iqg more than required will not be ejected. Thus, efficient printing can be achieved, allowing reduction in running cost.
Next, dye receiving layer coating unit 200 is described in the following. Dye receiving layer coating unit 200 includes a storing vessel 10 for storing powdery dye receptor particles RD, a charging member 11 for charging dye receptor particles RD, a holder 12 for holding thus charged dye receptor particles, a transferring unit 13 for transferring charged dye receptor particles onto recording medium RM, and a fixing unit 14 for fixing dye receptor particles thus transferred onto recording medium RM.
Dye receptor particles RD are preferably colorless. Dye receptor particles RD mainly contain polyester family and styrene acrylic family resin, and a charging control agent for stabilizing charging characteristics may be internally added thereto, and other fine particles for improving fluidity may be externally added thereto. Dye receptor particles RD preferably have a diameter in the range from 5 to 20 µm.
More specifically, dye receptor particles RD mainly contain binder resin like toner which is generally used as one component of developer for electric photography recording, and further contain internal and external additives. Dye receptor particles RD are different from toner in that toner contains a coloring agent for colors such as black, yellow, magenta, and cyan, while dye receptor particles are colorless and therefore do not contain a coloring agent.
Binder resin is not limited to particular resin so long as it is colorless and exhibits dyeing characteristics for sublimation dye, and may be any one of polyester family resin, vinyl chloride family resin, acrylic family resin, polyurethane family resin, vinyl chloride-vinyl acetate copolymer resin, silicon family resin, styrene resin, nylon family resin, polyallylate resin, AS resin, polycarbonate resin, cellulose family resin, and the like. These kinds of binder resin may be used alone or mixed with each other.
Internal additives include a charging control agent and a filing agent. The charging control agent is not limited to particular one, and any known material can be used as charging control agent. Colorless charging control agents having negatively charging characteristics include a metal complex of aromatic family dicarboxylic acid and a metal complex of salicylic acid.
External additives include a fluidizing agent. A fluidizing agent is inactive fine particles dispersed to serve as a spacer between dye receptor particles in order to reduce the force therebetween. The inactive particles include silica powder. Fine silica particles with a diameter in the range from 0.01 to 1 µm are preferable for dye receptor particles with a diameter in the range from 5 to 20 µm to effectively reduce the force between the dye receptor particles.
Charging member 11 is located to be pressed against holder 12, and frictionally charges dye receptor particles RD reaching the contact portion therebetween to form a thin layer of dye receptor particles RD on holder 12.
Holder 12 is formed of a conductive roller, and holds dye receptor particles RD in thin film by electrostatic force in response to application of bias voltage or grounding. In addition, holder 12 is spaced apart from recording medium RM so as not to be in contact therewith.
Combination of rigid body and elastic body may be used for charging member 11 and holder 12. When rigid body and elastic body are used for charging member 11 and holder 12, respectively, a metal sheet such as SUS sheet can be used for charging member 11, and a conductive solid roller or conductive spongy roller of urethane family or silicon family can be used for holder 12. On the contrary, when elastic body and rigid body are used for charging member 11 and holder 12, respectively, rectangle parallelepiped-shaped solid rubber of urethane family or silicon family can be used for charging member 11, and a metal roller of aluminum or the like can be used for holder 12. Note that it is appropriate for charging member 11 and holder 12 to be pressed against each other with a line pressure at the contact portion therebetween in the range from about 10 to about 200 gf/cm. It is appropriate to apply a bias voltage in the range from about 0 to about -200V to holder 12 to hold positively charged dye receptor particles RD at holder 12 by electrostatic force. In addition, it is appropriate to apply a bias voltage in the range from about 0 to about 200V to holder 12 to hold negatively charged dye receptor particles RD at holder 12 by electrostatic force.
Transferring unit 13 is formed of a corona discharging unit of corotron type, and located to charge the rear surface of recording medium RM. It is appropriate to apply a voltage in the range from about -1kv to transferring unit 13 to about -10kV to spray and transfer positively charged dye receptor particles RD onto recording medium RM. Meanwhile, it is appropriate to apply a voltage in the range from about 1kv to about 10kV to transferring unit 13 to spray and transfer negatively charged dye receptor particles RD onto recording medium RM.
Fixing unit 14 is constituted by a heat roller 14b including a heater lamp 14a therein, and a pressurizing roller 14c for pressing against heat roller 14b.
When a sheet of plain paper is used as recording medium RM and recording medium RM is transported to dye receiving layer coating unit 200 by a feeding system which is not shown to be coated with a dye receptor, dye receiving layer coating unit 200 operates as follows.
Dye receptor particles RD stored in reservoir 10 are guided to the contact portion between charging member 11 and holder 12, and then charged by friction to be held at a thin layer on holder 12. Recording medium RM is transported in the vicinity thereof so as not to be in contact with holder 12. Transferring unit 13 charges the rear surface of recording medium RM by corona discharge. The above-mentioned voltage is applied to transferring unit 13 so that the amount of charges is controlled to such a degree that the force of dye receptor particles RD attracted by holder 12 is larger than that of dye receptor particles RD spraying toward recording medium RM. Consequently, dye receptor particles RD are sprayed and transferred onto recording medium RM, and then transported to the subsequent fixing unit 14 while being held on recording medium RM. Fixing unit 14 is controlled to have a constant temperature in the range from 100°C to 200°C by a controller which is not shown. Recording medium RM holding dye receptor particles RD is passed between heat roller 14a and pressurizing roller 14c while the contact portion therebetween being heated and pressurized, whereby the dye receptor particles RD are fixed on recording medium RM and dye receiving layer RR is formed as a result.
An image recording apparatus according to a second embodiment of the invention will now be described. Referring to Fig. 2, a dye receiving layer coating unit in the image recording apparatus of the second embodiment can be replaced with that of the first embodiment shown in Fig. 1. In Figs. 1 and 2, the same parts, or the parts achieving the same function are denoted with the same reference numerals and characters. Therefore, detailed description thereof will not be repeated herein. The same is applied to Figs. 3 to 13.
A dye receiving layer coating unit shown in Fig. 2 includes a corona charging unit 15, and an electrode plate 22 disposed over the rear surface of a recording medium RM, both of which are arranged in such a position that the printing surface of recording medium RM is charged to a polarity opposite to dye receptor particles RD before recording medium RM is transported directly above a holder 12. This arrangement allows charged dye receptor particles RD to be transferred onto recording medium RM at such a position that recording medium RM faces holder 12. Note that it is appropriate to apply a voltage in the range from about 2 to about 7kV to corona charging unit 15 for positive charging and from about -2 to about -7kV for negative charging.
A dye receiving layer coating unit in an image recording apparatus of a third embodiment of the invention will now be described with reference to Fig. 3. The dye receiving layer coating unit shown in Fig. 3 is different from that in the image recording apparatus of the first embodiment shown in Fig. 1 in that a plate-shaped back electrode 16 extending from directly above a holder 12 to right before the contact portion of a fixing unit 14 is disposed over the path of a recording medium RM instead of transferring unit 13 shown in Fig. 1 so as to apply a voltage having a polarity opposite to charged dye receptor particles RD to back electrode 16. This arrangement allows charged dye receptor particles RD to be transferred onto recording medium RM and held thereat until being transported to fixing unit 14. It is appropriate to apply a voltage in the range from about -100V to about -3kV to back gate electrode 16 when positively charged dye receptor particles RD are sprayed and transferred onto recording medium RM. Meanwhile, it is appropriate to apply a voltage in the range from about 100V to about 3kV to back electrode 16 when negatively charged dye receptor particles RD are sprayed and transferred onto recording medium RM.
Ozone is generated in the first embodiment because a corona discharging unit is used in transferring unit 13 (Fig. 1). Meanwhile, the above-mentioned structure has an advantage that back electrode 16 is used in the dye receiving layer coating unit in Fig. 3 in place of transferring unit 13 in Fig. 1, whereby a voltage to be applied to back electrode 16 is smaller than that to be applied to transferring unit 13, generating no ozone.
Now, an embodiment capable of achieving coincidence of a dye receiving layer region of recording medium RM which is formed by the dye receiving layer coating unit with an image region which is subjected to recording at the printing unit will be described with reference to Fig. 4. With either transferring unit 13 of Fig. 1 or charging unit 15 of Fig. 2, recording medium RM can be only uniformly charged with respect to the widthwise direction of recording medium RM, which is perpendicular to the paper feeding direction of recording medium RM. In the present embodiment, transferring unit 13 or charging unit 15 is replaced with an ion flow head for writing an electrostatic latent image on recording medium RM, in order to selectively charge recording medium RM in the widthwise direction.
Referring to Fig. 4, the ion flow head includes a corona discharging unit 17, and a gate electrode 18 for controlling the path of ions generated by corona discharging unit 17 toward recording medium RM. In general, when an insulator (recording medium RM) is to be charged by the corona discharging unit, an opposite electrode should be placed over the rear surface thereof to attract corona ions toward the insulator. An electrode plate 19 disposed over the lower surface of recording medium RM and grounded as shown in Fig. 4 corresponds to the opposite electrode. Note that conductive holder 12 in Fig. 1 and electrode plate 22 in Fig. 2 each corresponds to the opposite electrode.
The above-mentioned ion flow head operates as follows. A high voltage in the range from 5 to 6kV is applied to corona discharging unit 17, and ions generated by corona discharge are controlled to pass or prevented from passing through gate electrode 18 by both the voltage applied to gate electrode 18 and the direction thereof, thereby forming an arbitrary charged region on recording medium RM. If the ion flow head is used instead of transferring unit 13 of Fig. 1 and charging unit 15 of Fig. 2 described above, coincidence of a dye receiving layer region which is formed at the dye receiving layer coating unit with an image region which is subjected to recording at the printing unit can be achieved, whereby dye receptor particles will not be wasted. Note that similar effects can be obtained by back electrode 16 shown in Fig. 3 when the back electrode 16 is divided into a plurality of electrodes in the widthwise direction of recording medium RM and a voltage is selectively and individually applied thereto.
An image recording apparatus according to a fourth embodiment will now be described with reference to Fig. 5. Since a printing unit and a dye receiving layer coating unit shown in Fig. 5 are similar to those shown in Fig. 1, the same portions are denoted with the same reference numerals and characters, and detailed description thereof will not be repeated herein.
Referring to Fig. 5, in the image recording apparatus of the fourth embodiment, a recording paper decision sensor 20 is provided in front of a dye receiving layer coating unit 200. Recording paper decision sensor 20 is a reflective optical sensor. If recording medium RM is a sheet of specific paper with a preapplied dye receiving layer, black mark 21 for distinguishing specific paper from plain paper is printed on the rear surface thereof as shown in Fig. 6. Recording paper decision sensor 20 decides that recording medium RM is of specific paper when it reads mark 21, and decides that recording medium RM is of plain paper when it cannot read black mark 21.
When recording paper decision sensor 20 decides that recording medium RM is of plain paper, a dye receiving layer is formed on the sheet of plain paper at dye receiving layer coating unit 200 and an image is recorded thereon at printing unit 100 in a manner similar to that described above. Meanwhile, when recording paper decision sensor 20 decides that recording medium RM is of specific paper, dye receiving layer coating unit 200 does not operate, and the sheet of specific paper is passed therethrough and is subjected only to image recording at printing unit 100. Note that when dye receiving layer coating unit 200 does not operate, dye receptor particles RD do not come into contact with the sheet of specific paper, and therefore the printing surface thereof will not be stained.
While the coating methods for electrostatically applying charged dye receptor particles for fixing have been described above, other coating methods will be described in the following.
Now, an image recording apparatus provided with a dye receiving layer coating unit 201 and employing another coating method according to a fifth embodiment will be described with reference to Fig. 7. Since printing unit 100 shown in Fig. 7 is similar to that shown in Fig. 1, the same portions are denoted with the same reference numerals and characters and detailed description thereof will not be repeated herein.
Referring to Fig. 7, dye receiving layer coating unit 201 includes a thermal head 300, a dye receiving layer sheet 320, a dye receiving layer sheet feeding roller 310, a dye receiving layer sheet wind-up roller 311, and a platen 312. With the above structure, dye receiving layer coating unit 201 thermally transfers a dye receiving layer sheet on a sheet of plain paper, thereby coating it with a dye receiving layer.
Dye receiving layer sheet 320 will now be described in detail. Referring to Fig. 8, dye receiving layer sheet 320 includes a base film 321, and a preapplied dye receiving layer 322 which can be separated therefrom by heating. As base film 321, a plastic film or sheet of various types which is formed of a single layer or stacked layers of polyethylene telephthalate, polyethylene naphtalate, polyimide, polyether imide, polycarbonate, polyether etherketone, polyallylate, polysulfone, polyether sulfone, or the like, having a thickness in the range from 4 to 10 µm can be used.
As dye receiving layer 322, resin similar to the above-mentioned binder resin of dye receptor particles can be used, including polyester resin, polyvinyl acetal family resin, urethane family resin, amide family resin, cellulose family resin, olefin family resin, vinyl chloride family resin, acrylic family resin, styrene family resin. The thickness thereof is preferably in the range from 5 to 10 µm.
Thermal head 300 shown in Fig. 7 will now be described in detail with reference to Figs. 9 and 10.
Referring to Fig. 9, a heating element portion includes a ceramic substrate 303, and a partial glaze 302, a heating element 301, a separate electrode 304, and a common electrode 305, which are sequentially formed on ceramic substrate 303. In addition, as shown in Fig. 10, thermal head 300 includes a plurality of heating elements 301 formed in array, which are controlled by a control unit (not shown) to be selectively driven by a driver IC 306 connected to respective separate electrodes 304 to generate heat.
Now, operation of dye receiving layer coating unit 200 thus structured will be described. Referring to Fig. 7, when a sheet of plain paper RM is transported under platen 312 by a paper feeding apparatus which is not shown, heating elements 301 of thermal head 300 press the sheet of plain paper RM against platen 312 with dye receiving layer sheet 320 sandwiched therebetween. This is achieved by a head up-and-down mechanism which is not shown. Heating elements 301 are heated to the temperature in the range from 100 to 150°C in this state, whereby dye receiving layer 322 is melted to be transferred and fixed on the sheet of plain paper RM. This operation is repeated while simultaneously feeding the sheet of plain paper RM and dye receiving layer sheet 320 being pressed against each other, whereby the sheet of plain paper RM is coated with a dye receiving layer. Dye receiving layer sheet 320 has been wound up in multiple layers around feeding roller 310 and sequentially fed to the pressing portion. At this time, base film 321 from which dye receiving layer 322 has been separated by thermal transfer is wound up and withdrawn around wind-up roller 311.
Furthermore, as shown in Fig. 9, the plurality of heating elements 301 on thermal head 300 are selectively driven, whereby coincident of the dye receiving layer coating region with the image recording region at printing unit 100 can be achieved. In this case, since the dye receiving layer is simultaneously transferred and fixed at the same place, reduction in size of the apparatus can be readily achieved.
An image recording apparatus for jetting out liquid dye receptor onto a sheet of plain paper by means of an ink jet head to coat the sheet of plain paper with a dye receiving layer according to a sixth embodiment will now be described with reference to Fig. 11. Since the printing unit shown in Fig. 11 is similar to that shown in Fig. 1, the same portions are denoted with the same reference numerals and characters and detailed description thereof will not be repeated herein.
Referring to Fig. 11, a dye receiving layer coating unit 202 includes an ink jet head 400 filled with liquid dye receptor 410, and a lamp fixing unit 420 which facilitates drying and fixing of ink.
Referring to Fig. 12, ink jet head 400 includes a plurality of nozzles 401, an ink chamber (not shown), and piezoelectric elements for causing change in pressure in the ink chambers, which are provided independently of each nozzle. Each nozzle can selectively jet out liquid dye receptor 410 toward a sheet of plain paper RM.
Solution of the above-mentioned binder resin in solvent can be used herein as liquid dye receptor. The solvent includes water, alcohol (ethanol, propanol etc.), cellosolve (methyl cellosolve, ethyl cellosolve etc.), aromatic (toluene, xylene, chlorbenzene etc.), ketone (acetone, methylethylketone etc.), ester family solvent (ethyl acetate, butyl acetate etc.), ether (tetrahydrofuran, dioxane etc.), chlorine family solvent (chloroform, trichloroethylene etc.), amide family solvent (dimethylformamide, N-methylpyrolidone etc.).
Dye receiving layer coating unit 200 thus structured operates as follows. First, when a sheet of plain paper RM is transported above ink jet head 400 by a paper feeding apparatus which is not shown, ink jet head 400 starts jetting out liquid dye receptor 410 toward the sheet of plain paper RM. Lamp fixing unit 420 located in the downstream is set to have such a calorific value that a temperature on the surface of the paper is in the range from 50 to 100°C in order to facilitate drying of liquid dye receptor 410 adhering to the sheet RM. This operation is repeated while transporting the sheet RM, whereby the sheet RM is coated with a dye receiving layer RR. In addition, the plurality of nozzles 401 of ink jet head 400 as shown in Fig. 12 are selectively driven, whereby coincidence of the dye receiving layer coating region with the image recording region at printing unit 100 can be achieved, eliminating a waste of dye receptor.
Fig. 13 shows an image recording apparatus according to a seventh embodiment of the invention. Referring to Fig. 13, this image recording apparatus includes a printing unit 500, and a dye receiving layer coating unit 510.
Dye receiving layer coating unit 510 is the same as that shown in Fig. 1 except that no fixing unit 14 is provided in unit 510.
Meanwhile, printing unit 500 is the same as that shown in Fig. 1 except that printing unit 500 further includes a fixing unit 14 located in the downstream of printing head 1. The same parts in Figs. 1 and 13 are denoted with the same reference numerals and characters and given the same names, and detailed description thereof will not be repeated herein.
Printing head 1 can make sublimation dye ink adhere to a recording medium RM without contact therewith. Therefore, sublimation dye ink can be made to adhere on recording medium RM by means of printing head 1 before fixing of dye receptor, and then, the dye receptor and sublimation dye ink can be simultaneously fixed at fixing unit 14, as in the seventh embodiment.
Generally, a fixing unit for fixing recording medium RM having sublimation dye ink adhering thereto must be provided in addition to the fixing unit for fixing the dye receptor. In the present embodiment, however, the dye receptor and sublimation dye ink can be simultaneously fixed at single fixing unit 14, whereby the apparatus can be reduced in size and of course the number of parts in the apparatus can be reduced, achieving reduction in manufacturing cost of the apparatus.
Note that fixing of both sublimation dye ink and dye receptor by the same fixing unit as in the present embodiment can be achieved not only by the image recording apparatus of the first embodiment but by the image recording apparatuses of the second to sixth embodiments so long as the printing unit can make sublimation dye ink adhere to the recording medium without bringing the printing head into contact with the recording medium.
As has been described above, in each embodiment of the present invention, a recording medium can be coated with a dye receiving layer prior to image recording by intermittent ejection of vaporized sublimation dye ink, thereby achieving excellent recording even on the sheets of plain paper. In addition, since dye receptor particles are fixed on the sheet of plain paper with pressure and heat, the dye receiving layer can be applied uniformly and time required for coating can be reduced. Furthermore, the dye receiving layer can be formed on the same region in the sheet of plain paper as an image region therein in accordance with image data, whereby the dye receptor particles will not be wasted as well as running cost can be reduced. Moreover, the kind of recording paper can be automatically determined, whereby an excellent image can be recorded on both specific paper and plain paper.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Claims

An image recording apparatus, comprising:
a printing unit (100, 500) for making ink (Iq) adhere to a recording medium (RM) without contact therewith to form an image on said recording medium (RM); and

a dye receiving layer coating unit (200, 201, 202, 510) for coating an image formation surface in said recording medium (RM) with a dye receiving layer (RR) before said recording medium (RM) is transported to said printing unit (100, 500).
The image recording apparatus according to claim 1, wherein
said printing unit (100, 500) includes

an ink storing member (1) for storing powdery sublimation dye ink (Iq),

heating means (7) for heating and vaporizing the sublimation dye ink (Iq) stored in said ink storing member (1),

ejecting means (3, 5) for ejecting the sublimation dye ink (Iqg) vaporized by said heating means (7) toward said recording medium (RM), and

control means (4a, 4b) for controlling said ejecting means (3, 5) to intermittently eject said heated sublimation dye ink in accordance with image data corresponding to the image.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit (200, 510) includes

a reservoir (10) for storing dye receptor particles (RD),

a charging unit (11) for charging said dye receptor particles (RD),

a holder (12) for holding the dye receptor particles (RD) charged by said charging unit (11), and

a transferring unit (13) for electrostically transferring said charged dye receptor particles (RD) onto said recording medium (RM) facing said holder (12).
The image recording apparatus according to claim 3, further comprising:
a fixing unit (14) provided subsequently to said printing unit (500) for simultaneously fixing the dye receptor particles (RR) transferred onto said recording medium (RM) by said dye receiving layer coating unit (510) and the sublimation dye ink caused to adhere to said recording medium (RM) by said printing unit (500).
The image recording apparatus according to claim 4, wherein
said fixing unit (14) includes

a fixing roller (14a, 14b, 14c) for fixing the dye receptor particles (RR) transferred onto said recording medium (RM) and said sublimation dye ink by heating with pressure.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit (200) includes

a reservoir (10) for storing dye receptor particles (RD),

a charging unit (11) for charging said dye receptor particles (RD),

a holder (12) for holding the dye receptor particles (RD) charged by said charging unit (11),

a transferring unit (13) for electrostatically transferring said charged dye receptor particles (RD) onto said recording medium (RM) facing said holder (12), and

a fixing unit (14) provided in a subsequent stage of said transferring unit (13) for fixing the dye receptor particles (RR) transferred onto said recording medium (RM) by said dye receiving layer coating unit (200).
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit includes

a reservoir (10) for storing dye receptor particles (RD),

a first charging unit (11) for charging said dye receptor particles (RD),

a holder (12) for holding the dye receptor particles (RD) charged by said first charging unit (11),

a second charging unit (15, 22) for charging said recording medium (RM) to polarity opposite to that of said first charging unit (11) before said recording medium (RM) is transported to a position facing said holder (12), and

a fixing unit (14) provided in a subsequent stage of said dye receiving layer coating unit for fixing the dye receptor particles (RR) transferred onto said recording medium (RM) by said dye receiving layer coating unit.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit includes

a reservoir (10) for storing dye receptor particles (RD),

a first charging unit (11) for charging said dye receptor particles (RD),

a holder (12) for holding the dye receptor particles (RD) charged by said first charging unit (11),

a second charging unit (16) extending over a prescribed region from a position facing said holder (12) to a position in a downstream along a path of said recording medium (RM) and provided on a side opposite to said holder (12) with respect to said recording medium (RM), for charging said recording medium (RM) to polarity opposite to that of said first charging unit (11), and

a fixing unit (14) provided directly subsequently to said second charging unit (16) for fixing the dye receptor particles (RR) transferred onto said recording medium (RM) by said dye receiving layer coating unit.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit includes

an ion flow head (17, 18, 19) capable of selectively coating an arbitrary portion of said recording medium (RM) with a dye receiving layer.
The image recording apparatus according to claim 2, further comprising:
recording paper deciding means (20) provided in an upstream of said dye receiving layer coating unit (200) in a path of said recording medium (RM) for deciding whether said recording medium (RM) is of specific paper with a preapplied dye receiving layer or plain paper, wherein

said dye receiving layer coating unit (200) operates in accordance with a result of the decision by said recording paper deciding means (20).
The image recording apparatus according to claim 10, wherein
a predetermined mark (21) is attached to a sheet of said specific paper (RM), and

said recording paper deciding means (20) includes an optical sensor (20) for detecting whether the predetermined mark is attached to said recording medium (RM) or not.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit (201) includes

a dye receiving layer sheet feeding unit (310) for feeding a dye receiving layer sheet (320) to a predetermined point on a path of the recording medium (RM), and

transferring means (300, 301, 312) for transferring a dye receiving layer (322) on said dye receiving layer sheet (320) onto a surface of the recording medium (RM) at said predetermined point.
The image recording apparatus according to claim 2, wherein
said dye receiving layer sheet (329) includes

a base film (321), and

a dye receiving layer (322) preapplied on the base film (321) and capable of being separated therefrom by heating,

said transferring means (300, 301, 312) includes

a thermal head (300, 301) provided at said prescribed point on one side of a path of the recording medium (RM), to which said dye receiving layer sheet (320) is supplied, for heating said dye receiving layer sheet (320) to press said dye receiving layer sheet (320) against said recording medium (RM), and

a platen (312) provided on a side opposite to said thermal head (300, 301) with respect to the path of said recording medium (RM), for supporting said recording medium (RM) against the pressure caused by said thermal head (300, 301), and

said dye receiving layer coating unit (201) further includes

a roller (311) for winding up said dye receiving layer sheet (320, 321) from which said dye receiving layer (322) has been separated by said thermal head (300, 301).
The image recording apparatus according to claim 13, wherein
said thermal head (300, 301) includes

a substrate (303),

a plurality of heating elements (301) arranged in an array on said substrate along a widthwise direction of said recording medium (RM), and capable of being driven individually, and

a driver (304, 305, 306) for selectively driving said plurality of heating elements.
The image recording apparatus according to claim 2, wherein
said dye receiving layer coating unit (202) includes

an ink jet head (400) for ejecting liquid dye receptor (410) onto a surface of the recording medium (RM), and

a lamp fixing unit (420) provided in a downstream of said ink jet head (400) in a path of said recording medium (RM) for drying and fixing the liquid dye receptor (410) adhering to the surface of said recording medium (RM).
The image recording apparatus according to claim 15, wherein
said ink jet head (400) has a plurality of nozzles (401) arranged in line in a widthwise direction of said recording medium (RM), said plurality of nozzles (401) are controlled individually.