JP2008149498A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method excellent in productivity and reliability in which the polarity of ions emitted from the discharge electrode of a heating discharge print head can be switched by switching the polarity of a voltage applied across the discharge electrode and a counter electrode arranged oppositely to the discharge electrode while holding a recording medium between, writing or erasure of an image can be carried out surely by one heating discharge print head without using an initialization means such as a restoration apparatus or a neutralization apparatus, and, in particular, a high-quality image can be formed in a short time by overwriting a new image while erasing an existing image and a recording medium of electrostatic developing system can be used repeatedly. <P>SOLUTION: The image forming method is arranged to perform writing or erasure of an image selectively by switching the polarity of a voltage applied across the discharge electrode of a heating discharge print head arranged oppositely to the recording surface of a recording medium and a counter electrode arranged on the backside of the recording medium, thereby switching the polarity of ions emitted from the discharge electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method in which an electric charge is selectively applied to an electrostatic development type recording medium by a heat discharge type print head to write or erase an image.

In recent years, as shown in (Patent Document 1), an ion irradiation method, which is an electrostatic latent image forming method different from the electrophotographic method, has been developed.
The electrophotographic method is a two-step process of uniform charging + exposure, and the electrostatic charge image is formed on the photoreceptor as an electrostatic latent image carrier by releasing the charge of the exposed part on the uniformly charged photoreceptor. On the other hand, in the ion irradiation method, in an atmosphere where ions can be generated (such as in the air), only selective charging (electrostatic latent image formation charging) by irradiation of ions generated by emission of electrons from the discharge electrode is performed. Since the formation of the electrostatic latent image can be completed on the electrostatic latent image bearing member (which is not necessarily a photosensitive member as long as it is an insulator), the electrostatic latent image forming method is simplified. .
Further, (Patent Document 2) discloses a specific shape of an ion irradiation type print head compatible with a horizontal printer and an image forming apparatus including the shape.
In particular, the heating and discharging methods shown in (Patent Document 1) and (Patent Document 2) are applied with a voltage (discharge control voltage) that generates a discharge by heating without generating a discharge when applied to a discharge electrode. Thus, by controlling the presence or absence of heating of the discharge electrode, the generation of ions is controlled by controlling the presence or absence of discharge, and it is not necessary to control the voltage applied to the discharge electrode. As a result, it is possible to control the occurrence of discharge with a driver IC that supports low withstand voltage such as 5V drive used for controlling heating by a heating resistor or the like, and is the most excellent control method from the viewpoint of discharge control. It can be said that there is.
Incidentally, as the digital paper at the present time, a minute ball is color-coded into two colors (for example, black and white), and a twist ball system that displays an arbitrary color by rotating the ball depending on the electrical characteristics of each color. Two colors (for example, black and white) of fine powder are mixed in, and an electrophoretic method in which only one color is floated and displayed due to the difference in electrical characteristics of each color of fine powder. In addition, there is a liquid crystal system that displays the background color of the part where the shutter is opened.
JP 2003-326756 A WO2005 / 087496

However, the above conventional techniques have the following problems.
(1) The electrostatic development type recording medium can be used repeatedly, and the heating and discharging type print heads of (Patent Document 1) and (Patent Document 2) are easy to control the discharge, and the electrostatic development system. However, when an image is formed on the recording medium, it is necessary to erase the image in advance. Initialization means must be provided, and the image forming apparatus is easily increased in size, and has a problem of lack of space saving and handling.
(2) Also, when a process for erasing an existing image is performed and then a process for forming a new image is performed, it takes time to form the image, the recording speed is likely to decrease, and the productivity is lacking. Had problems.
(3) When the recording medium supply unit includes a recording medium on which an image is formed and a recording medium on which no image is formed, the image is erased even on the recording medium on which no image is formed. The process to perform was required and had the subject that energy saving property and productivity were lacking.
(4) When an image detection unit for detecting the presence or absence of an image is provided to determine whether or not an image erasing process is necessary, the image forming apparatus is likely to be large in size and lacks space saving and handling properties. However, a process for detecting an image is required, and it takes time to form an image, resulting in a lack of productivity.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and by switching the polarity of a voltage applied between a discharge electrode of a heat discharge type print head and a counter electrode disposed opposite to the discharge electrode across the recording medium, the discharge electrode The polarity of the ions irradiated from the switch can be switched, and the writing or erasing of the image can be selectively performed reliably using only one heating / discharge type print head without using an initialization means such as a restorer or a static eliminator. In particular, by overwriting a new image while erasing an existing image, a high-quality image can be formed in a short time, and an electrostatic development recording medium can be used repeatedly. An object of the present invention is to provide an image forming method with excellent productivity and reliability.

In order to solve the above problems, an image forming method of the present invention has the following configuration.
According to a first aspect of the present invention, there is provided an image forming method using a heat discharge type print head having a discharge electrode having an electron emission site and a heating means for selectively heating the discharge electrode, and recording by the action of electric charge. An image forming method for writing or erasing an image on a medium, wherein the discharge electrode of the heat-discharge type print head is disposed opposite to a recording surface of the recording medium, and is disposed on a back surface of the recording medium. By switching the polarity of the voltage applied between the counter electrode and the opposite electrode, the polarity of ions irradiated from the discharge electrode is switched to selectively write or erase an image.
This configuration has the following effects.
(1) By switching the polarity of the voltage applied between the discharge electrode of the heat-discharge type print head arranged to face the recording surface of the recording medium and the counter electrode arranged on the back surface of the recording medium, Since it is possible to selectively perform writing or erasing of an image by switching the polarity of ions irradiated from the discharge electrode, there is no need to provide initialization means such as a restorer or a static eliminator in the image forming apparatus. The image can be reduced in size, and the image can be easily erased and written with only the heat discharge type print head, and the recording medium can be used repeatedly.
(2) By switching the polarity of the voltage applied between the discharge electrode and the counter electrode, the polarity of the ions irradiated from the discharge electrode can be switched. Therefore, depending on the type of the recording medium, An image can be formed by irradiating any negative ion, and a reversed image can be formed easily if necessary, and is excellent in versatility.

Here, the heat discharge type print head has a discharge control between the discharge electrode and a counter electrode disposed opposite to the discharge electrode with a recording medium disposed opposite to the heat discharge type print head. A potential difference corresponding to the voltage can be set to prepare for the discharge in a state where an electric field is formed. By selectively heating the discharge electrode by the heating means, a discharge is generated between the discharge electrode and the counter electrode, and the electric field is generated. Can move electrons or positive or negative ions to the recording medium side to give positive or negative charges to the recording surface, so just switch the polarity of the voltage applied between the discharge electrode and the counter electrode. The polarity of ions irradiated from the discharge electrode can be switched. The discharge control voltage refers to a voltage range in which discharge does not occur between the discharge electrode and the counter electrode of the heat discharge type print head only by the potential difference, but discharge occurs by heating the discharge electrode.
Since the potential difference between the discharge electrode and the counter electrode only needs to be the discharge control voltage, all the voltages corresponding to the discharge control voltage may be applied to the discharge electrode, and the counter electrode may be grounded. A voltage corresponding to the discharge control voltage may be distributed and applied to the discharge electrode and the counter electrode.

For example, the discharge electrodes can be formed in a comb shape by connecting one end portions of a plurality of discharge generation portions with a common electrode, or can be formed in a ladder shape or the like by connecting both end portions of the plurality of discharge generation portions with a common electrode. In addition, it can be formed in a single flat plate shape such as a rectangular shape or a square shape (see, for example, JP-A No. 2003-326756 and WO 2005/056297).
By providing a common electrode in the vicinity of the discharge generating part, such as a comb type or a ladder type, the cooling effect of the discharge electrode and the response to heating stop are improved by increasing the heat radiation area of the discharge electrode and increasing the heat capacity. Since a stable voltage can always be applied by reducing the resistance value, the discharge stability and the like can be further improved. Note that, in the discharge electrode formed in a flat plate shape, the heating position by the heating means becomes a discharge generation portion, and the portions other than the discharge generation portion become common electrodes.
In particular, in a discharge electrode formed in a comb shape, a ladder shape, or the like, when the width of the common electrode is wider than the width of the discharge generating portion, the cooling effect of the discharge electrode that is temporarily heated to 100 to 300 ° C. It can improve the heat and prevent the heat from burning so that it can stop the discharge quickly in response to the heating off, shorten the discharge time interval and switch the presence or absence of the discharge in a short time. Can be achieved. In addition, the resistance value of the common electrode can be reduced, and the potential difference generated between the discharge generators connected by the common electrode can be suppressed as much as possible, thereby reducing variations in the amount of ions generated in each discharge generator. And has excellent discharge stability.
Especially when the discharge electrode is formed in a comb shape or ladder shape, selective discharge can be reliably generated from a plurality of discharge generation portions, so it corresponds to a non-printing portion of a newly formed image. It is possible to accurately erase unnecessary portions in an existing image by accurately irradiating ions having a polarity opposite to that at the time of image formation, and to correspond to a print portion of an image to be newly formed, A new image can be overwritten by irradiation with ions for image formation. In addition, when the discharge electrode is formed in a flat plate shape, it is possible to easily irradiate the entire recording surface with ions having a polarity opposite to that at the time of image formation, and the existing image is completely erased and recorded. Since the entire medium can be initialized, the image quality is excellent in reliability.

The discharge electrode is formed by depositing a metal such as gold, silver, copper, or aluminum on the substrate by vapor deposition, sputtering, printing, plating, etc., and then patterning to form a discharge generating part or a common electrode by etching as necessary. A material in which at least a part of a metal such as stainless steel, copper, and aluminum is thinned by etching, cutting, or the like, and then patterned by etching, laser processing, or the like is suitably used. In addition, the discharge electrode may be formed using a conductive material such as carbon.
When the discharge electrode is formed on the substrate, the material of the substrate may be any material as long as the discharge electrode can be formed on the surface and has heat resistance to withstand the heating by the heating means. The substrate may be a hard substrate such as ceramic, or a flexible substrate formed of a thin film resin such as polyimide, aramid, or polyetherimide. When using a flexible substrate, it is excellent in shape flexibility, so after forming the discharge electrode in a flat state, it can be bent or curved as necessary to deform it into the desired shape, design flexibility, Excellent in mass production and versatility.
When the substrate is formed of a synthetic resin such as glass, polyimide, aramid, or polyetherimide, it is excellent in heat transfer, so that the discharge electrode can be heated by the heating means from the back side of the substrate.

When the discharge electrode is formed in a comb shape, the shape of each discharge generating portion can be formed in a substantially rectangular shape, trapezoidal shape, semicircular shape, bullet shape, or a combination thereof. Further, the peripheral length around the edge of the discharge generating portion can be increased by further dividing a part of the discharge generating portion with a slit or the like, or by forming an uneven portion on the peripheral portion (for example, WO2005 / 056297). Issue). Since the discharge electrode has a large amount of discharge from the periphery of the edge, it is possible to increase the amount of ions emitted and the intensity of the emitted light by increasing the discharge length from the discharge electrode by increasing the circumference around the edge. Control voltage and heating temperature can be set low, and energy saving and discharge generation efficiency are excellent. Moreover, since the discharge control voltage can be set low, the long life of the discharge electrode is also excellent.
Instead of dividing the end portion of the discharge electrode or forming the concavo-convex portion on the peripheral edge portion, a discharge hole portion may be formed in the discharge generating portion (near the heating position by the heating means). Thereby, electrons can be emitted from the periphery of the edge of the discharge hole, and the same effect as that obtained by dividing the end of the discharge electrode can be obtained. The shape of the discharge hole portion can be formed in various shapes such as a substantially circular shape, a substantially elliptical shape, a polygon such as a quadrangle and a hexagon, and a star shape. Further, the number and size of the discharge hole portions per location of the discharge generation portion (near the heating position by the heating means) can be appropriately selected and combined. In addition, the uneven | corrugated | grooved part and discharge hole part of a discharge electrode can be formed by the above-mentioned etching, laser processing, etc.

Further, a conductive material layer may be formed on at least the surface of the common electrode among the discharge electrodes. As a result, the resistance value of the common electrode can be further reduced, the potential difference generated between the respective discharge generating portions can be reliably reduced, and the discharge stability is excellent. The conductive material layer only needs to have conductivity superior to that of the discharge electrode, and can be easily formed by screen printing of silver paste or silver plating. By increasing the thickness of the conductive material layer, the resistance value of the common electrode can be reduced, and the discharge stability can be improved.
Although the thickness of the discharge electrode depends on the material, the thickness when formed of gold is preferably 0.1 μm to 100 μm. As the discharge electrode becomes thinner than 0.1 μm, it tends to be affected by wear, and the life of the discharge electrode tends to be shortened. As the discharge electrode becomes thicker than 100 μm, the heat capacity increases and the response to heating on / off decreases. There is a tendency to become easy and neither is preferable. By setting the thickness of the discharge electrode to 100 μm or less, it is possible to quickly recover from the heated state, and it is possible to increase the printing speed.

Any heating means for heating the discharge electrode may be used as long as it can selectively heat an arbitrary position (discharge generation portion) of the discharge electrode. The discharge electrode may be heated in close contact with the discharge electrode or separated from the discharge electrode. And may be heated.
As the heating means for heating in close contact with the discharge electrode, the same configuration as the thermal print head used in the conventional thermal facsimile can be suitably used. Specifically, the heat generation of the heating resistor is controlled by a driver IC electrically connected to the heating resistor. The driver IC is only required to be electrically connected to the heating resistor, and the driver IC can be arranged anywhere. For example, it may be disposed on a substrate on which a discharge electrode or a heating resistor is formed, or may be disposed on a printed wiring board or the like.
As a heating means for heating away from the discharge electrode, a method of irradiating laser light, a method of irradiating infrared rays, or the like can be suitably used. As a method of irradiating laser light, a combination of a laser irradiation unit and a polygon mirror or a galvanometer mirror, a method of serially scanning the laser irradiation unit, or the like is preferably used.

In addition to being formed integrally with the recording medium on the surface opposite to the recording surface of the recording medium, the counter electrode is formed on the recording medium mounting surface of the image forming apparatus and contacts the surface opposite to the recording surface of the recording medium. Alternatively, they are arranged close to each other.
In addition to the counter electrode that is formed in a substantially rectangular flat plate shape over almost the entire surface of the recording medium, a counter electrode that can be selected in units of rows or columns of display pixels of the recording medium is preferably used. It may be selectable. Specifically, it can be formed in a strip shape corresponding to each row or each column of display pixels of the recording medium, or can be formed in a matrix shape corresponding to each display pixel of the recording medium.

The recording medium used in this image forming method is not particularly limited as long as an image is formed by the action of electric charge, and a liquid crystal method, a toner display method, a twist ball method, an electrophoresis method, a powder transfer method, etc. are preferably used. It is done.
In addition to monochrome display such as monochrome, these are combined with a color filter having the three primary colors (R, G, B) in the additive color mixing method and a reflective layer having the three primary colors (Y, M, C) in the subtractive color mixing method, Color display can be performed by coloring the fine particles to the three primary colors (Y, M, C) in the subtractive color mixing method and arranging them for each color. In addition, one recording medium can be divided into a plurality of blocks, and different colors can be displayed for each block.
This image forming method can be used for a recording medium that is fixedly or detachably provided on an image forming apparatus (image display apparatus) and used as a display medium such as a signboard for displaying advertisements. Can be rewritten in a short time.

A second aspect of the present invention is the image forming method according to the first aspect, wherein the entire surface of the recording surface of the recording medium is irradiated with positive ions or negative ions to erase an existing image; And an image forming step of forming a new image by irradiating a negative ion or a positive ion on a print portion of a newly formed image in the recording surface of the recording medium. .
With this configuration, in addition to the operation of the first aspect, the following operation is provided.
(1) Since there is an image erasing process that erases an existing image by irradiating the entire recording surface of the recording medium with positive ions or negative ions, the existing image can be easily and surely referred to without referring to the data of the existing image. Can be erased, and the reliability of the image erasing process is excellent.
(2) An image forming process for forming a new image by irradiating negative or positive ions on a print portion of a newly formed image on the recording surface of the recording medium after erasing an existing image in the image erasing process. With this, a new image can be written and the reliability of the image quality is excellent.

  Here, in the image erasing process, there is no need to selectively discharge the recording medium and irradiate ions, and the entire recording surface of the recording medium is irradiated with positive ions or negative ions to erase the existing image. Therefore, the control is easy, the image can be erased in a short time, and the handleability is excellent.

A third aspect of the present invention is the image forming method according to the second aspect, wherein the image erasing step generates ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode. The image erasing voltage applying step for applying a voltage equal to or higher than the discharge control voltage is provided.
With this configuration, in addition to the operation of the second aspect, the following operation is provided.
(1) In the image erasing voltage application step, the discharge can be reliably performed only by applying a voltage (discharge generation voltage) higher than the discharge control voltage that generates ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode. An image erasing process for erasing an existing image can be performed, and it is not necessary to heat the discharge electrode with a heating means, and the control is easy and the handleability is excellent.

  Here, in the heating and discharging type print head, normally, while setting a potential difference corresponding to the discharge control voltage between the discharge electrode and the counter electrode, the generation of discharge is controlled by selectively heating the discharge electrode, Depending on the type of recording medium, positive or negative ions are irradiated onto the recording surface of the recording medium to write an image. However, when erasing an image, there is no need to selectively irradiate ions and recording is performed. Since it is only necessary to irradiate the entire surface with ions having a polarity opposite to that at the time of image formation, in the image erasing voltage application step, a voltage equal to or higher than the discharge control voltage at which discharge is generated only by applying between the discharge electrode and the counter electrode By applying (discharge generation voltage), the image erasing step can be performed by generating a discharge reliably and simply. By this image erasing step, the image can be written as usual after the existing image is erased.

A fourth aspect of the present invention is the image forming method according to the first aspect, wherein a non-printing portion of a newly formed image of the recording surface of the recording medium is irradiated with positive ions or negative ions. An image erasing process for erasing an existing image, and an image forming process for forming a new image by irradiating negative ions or positive ions on a print portion of an image to be newly formed in the recording surface of the recording medium; It has the structure equipped with these.
With this configuration, in addition to the operation of the first aspect, the following operation is provided.
(1) An image erasing process for erasing an existing image by irradiating a non-printed portion of a newly formed image on the recording surface of the recording medium with positive ions or negative ions, and a new one on the recording surface of the recording medium The image forming process for forming a new image by irradiating negative or positive ions on the printed portion of the image to be formed on the image can be surely overwritten regardless of the existing image. Excellent image quality reliability.
(2) Since the image erasing step and the image forming step can be performed based on the image data of a new image, it is not necessary to refer to the data of the existing image, and positive or negative with respect to the entire recording surface. Since a new image is overwritten by irradiating any of these ions, there is no need for fine alignment of the recording medium, control is easy, and image formation reliability is excellent.

  Here, the image erasing process and the image forming process are performed based on the image data of the new image. In the image erasing process, the non-printing portion of the image data of the new image has a polarity opposite to that at the time of image formation (printing portion). The image can be erased by irradiating the ions.

A fifth aspect of the present invention is the image forming method according to the second or fourth aspect, wherein the image erasing step includes ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode. An erasing discharge control voltage applying step for applying a discharge control voltage to be generated and a discharge electrode heating step for heating the discharge electrode by the heating means are provided.
With this configuration, in addition to the operation of the second or fourth aspect, the following operation is provided.
(1) An image erasing step includes an erasing discharge control voltage applying step for applying a discharge control voltage that generates ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode, and the discharge electrode is heated by a heating means. The discharge electrode heating step, the voltage value of the voltage applied directly to the discharge electrode in the erasing discharge control voltage applying step may be equal to or less than the discharge control voltage, Since it is not necessary to apply a voltage (discharge generation voltage) equal to or higher than a discharge control voltage that generates a discharge only by being applied between the counter electrode and the counter electrode, the energy saving property and the long life of the discharge electrode are excellent.

Here, in the discharge electrode heating step, all the discharge electrodes may be heated by the heating means regardless of the presence or absence of the existing image (regardless of whether the existing image is printed or non-printed). Based on the image data of the image, only the discharge electrode facing the non-printing part of the new image may be selectively heated by the heating means. When all the discharge electrodes are heated in the discharge electrode heating process, ions having the opposite polarity to those during image formation can be generated from all the discharge electrodes, and the existing image can be erased without defects and control. Is easy and reliable. Further, in the discharge electrode heating step, when only the discharge electrode facing the non-printing part of the new image is heated, ions having the opposite polarity to those at the time of image formation are generated only at the position corresponding to the non-printing part of the new image. Therefore, it is excellent in energy saving without generating unnecessary ions.
In the image forming step after the image erasing step, a discharge control voltage for generating image forming ions is applied between the discharge electrode and the counter electrode as usual, and the print portion is opposed to the image based on the image data of a new image. By selectively heating the discharge electrode with a heating means, ions for image formation are generated, and an image is written at a position corresponding to a print portion of a new image.

A sixth aspect of the present invention is the image forming method according to any one of the second to fifth aspects, wherein the image erasing step is performed in units of pages.
With this configuration, in addition to the operation of any one of claims 2 to 5, the following operation is provided.
(1) Since the image erasing process is performed in units of pages, an existing image displayed on the recording medium can be completely erased in advance and a new image can be written. The medium can be used repeatedly, and the reliability of the image quality is excellent.

Here, when the image erasing process is performed in units of pages, only the image erasing process is continuously performed on a plurality of recording media in addition to performing the image erasing process as a pre-process of the image forming process for each recording medium. It is also possible to prepare for the image forming step. When performing a large amount of printing in particular, the polarity of ions irradiated from the discharge electrode can be switched only once by performing the image forming process after initializing a plurality of recording media in the image erasing process. Since the image erasing process and the image forming process can be successively performed on a single recording medium, the time required for image formation can be shortened and the productivity is excellent. Further, the image forming apparatus is provided with a used recording medium container for storing a recording medium on which an image is formed, and an image erasing process is performed on the used recording medium when the image forming apparatus is not used. If the automatically initialized recording medium is replenished, a new image can be written by performing only the image forming process immediately at the time of use, and the handling property is excellent.
It is not necessary for the heat-discharge type print head to have discharge electrodes corresponding to the entire page, and by scanning a discharge electrode corresponding to one or more rows or one or more columns, the page can be scanned. It is only necessary that the image can be erased and written to the whole.

A seventh aspect of the present invention is the image forming method according to any one of the second to fifth aspects, wherein the image erasing step is performed in units of rows or columns of display pixels of the recording medium. have.
With this configuration, in addition to the operation of any one of claims 2 to 5, the following operation is provided.
(1) By performing the image erasing process in units of rows or columns of display pixels of the recording medium, it is possible to perform the image erasing process using a single heating / discharging type print head without causing displacement of the ion irradiation position. The image forming process can be performed continuously, and the reliability of the image quality is excellent.

Here, when the image erasing step is performed in units of rows or columns of display pixels of the recording medium, ions having a polarity opposite to that during image formation are generated between the discharge electrode and the counter electrode as described in claim 3. By applying an image erasing voltage application process that applies a voltage equal to or higher than the discharge control voltage to be applied, the entire row or column is applied regardless of the presence or absence of an existing image (regardless of whether the existing image is printed or not). By irradiating ions having the opposite polarity to that during image formation, the existing image can be surely erased, and the reliability is excellent. Further, as described in claim 5, an erasing discharge control voltage applying step for applying a discharge control voltage for generating ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode, and heating the discharge electrode You may perform the discharge electrode heating process heated with a means. At this time, in the same manner as described above, when all the discharge electrodes are heated in the discharge electrode heating step, the existing image is surely erased by irradiating the entire row or column with ions having the opposite polarity to that at the time of image formation. In the discharge electrode heating process, if only the discharge electrode facing the non-printing part of the new image is heated based on the image data of the new image, the non-printing part of the new image An existing image can be erased by irradiating only the corresponding position with ions having a polarity opposite to that at the time of image formation, so that unnecessary ions are not generated and energy saving is excellent.
The image erasing process may be performed one row or one column at a time, or may be performed multiple rows or multiple columns.

The invention according to claim 8 is the image forming method according to claim 4 or 5, wherein the image erasing step is performed in units of display pixels of the recording medium.
With this configuration, in addition to the operation of the fourth or fifth aspect, the following operation is provided.
(1) By performing the image erasing process for each pixel of the display pixels of the recording medium, an unnecessary image can be surely erased without generating wasteful discharge, and energy saving is excellent.

  Here, when the image erasing step is performed in units of display pixels of the recording medium, as described in claim 5, in the erasing discharge control voltage applying step, an image is formed between the discharge electrode and the counter electrode. A discharge control voltage that generates ions of reverse polarity is applied, and in the discharge electrode heating process, only the discharge electrode that faces the non-printed part of the new image is selected by the heating means based on the image data of the new image Heating may be performed.

As described above, according to the image forming method of the present invention, the following advantageous effects can be obtained.
According to invention of Claim 1, it has the following effects.
(1) Initialization means such as a restorer and a static eliminator in an image forming apparatus by selectively writing or erasing an image by switching the polarity of ions irradiated from the discharge electrode of one heating discharge type print head Therefore, the image forming apparatus can be reduced in size, and an image forming method excellent in resource saving that can repeatedly use a recording medium can be provided.
(2) Irradiating ions on the entire non-printed portion or the entire recording surface of the newly formed image with ions having a polarity opposite to that at the time of image formation, and then irradiating the printed portion of the newly formed image with ions for image formation. As a result, it is possible to provide an image forming method excellent in image quality reliability that can reliably erase an existing image and overwrite a new image.
(3) The polarity of ions irradiated from the discharge electrode can be switched simply by switching the polarity of the voltage applied between the discharge electrode and the counter electrode, and either positive or negative depending on the type of the recording medium It is possible to provide an image forming method excellent in versatility that can perform image writing and erasing by irradiating such ions and can easily form a reverse image.

According to invention of Claim 2, in addition to the effect of Claim 1, it has the following effects.
(1) In the image erasing step, by irradiating the entire recording surface of the recording medium with positive ions or negative ions, the existing image can be easily and surely erased without referring to the data of the existing image. It is possible to provide an image forming method excellent in the reliability of the image erasing process.
(2) As a subsequent process of the image erasing process, in the image forming process, negative ions or positive ions are irradiated to a newly printed image portion of the recording surface of the recording medium based on the image data of the new image. Thus, it is possible to provide an image forming method that can write a new image and that is excellent in reliability of image quality.

According to invention of Claim 3, in addition to the effect of Claim 2, it has the following effects.
(1) In the image erasing voltage application step, simply and reliably applying a voltage (discharge generation voltage) higher than the discharge control voltage that generates ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode. It is possible to provide an image forming method that is easy to control and excellent in reliability, which can perform an image erasing step of erasing an existing image by generating a discharge.

According to invention of Claim 4, in addition to the effect of Claim 1, it has the following effects.
(1) Based on the image data of a new image, ions having different polarities with respect to the non-printed part and the printed part of the newly formed image in the recording surface of the recording medium by the image erasing process and the image forming process Therefore, it is possible to securely erase unnecessary parts of an existing image and overwrite a new image without referring to the data of the existing image, and there is no need to perform fine alignment of the recording medium. Therefore, it is possible to provide an image forming method that is easy to control and excellent in image forming reliability.

According to invention of Claim 5, in addition to the effect of Claim 2 or 4, it has the following effects.
(1) By performing the image erasing step by the erasing discharge control voltage applying step and the discharge electrode heating step, the voltage value of the voltage applied directly to the discharge electrode in the erasing discharge control voltage applying step may be equal to or less than the discharge control voltage. The energy saving property that does not require the application of a voltage (discharge generation voltage) higher than the discharge control voltage between the discharge electrode and the counter electrode as in the case where the image erasing step is performed only by the image erasing voltage application step, and the discharge electrode It is possible to provide an image forming method having excellent long life.

According to invention of Claim 6, in addition to the effect of any one of Claims 2 thru | or 5, it has the following effects.
(1) By performing the image erasing process in units of pages, an existing image displayed on the recording medium can be completely erased in advance and a new image can be written. Thus, it is possible to provide an image forming method that can be used repeatedly and has excellent image quality reliability and resource saving.

According to invention of Claim 7, in addition to the effect of any one of Claims 2 thru | or 5, it has the following effects.
(1) By performing the image erasing process in units of rows or columns of display pixels of a recording medium, an existing image can be obtained simply by changing the polarity of ions irradiated from the discharge electrode using one heating / discharge type print head. An image forming method with excellent productivity and reliability that can overwrite a new image while erasing the image, and can form a high-quality image in a short time without causing a displacement of the ion irradiation position. Can be provided.

According to invention of Claim 8, in addition to the effect of Claim 4 or 5, it has the following effects.
(1) Providing an image forming method excellent in energy saving that can erase unnecessary images reliably without causing unnecessary discharge by performing the image erasing step in units of display pixels of a recording medium. can do.

An image forming method according to an embodiment of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1A is a schematic cross-sectional view showing a main part of a recording medium used in the image forming method in the first embodiment, and FIG. 1B is a main part showing an image erasing process in the image forming method in the first embodiment. FIG. 1C is a schematic cross-sectional view of an essential part showing an image forming process in the image forming method according to the first embodiment.
In FIG. 1, reference numeral 1 denotes an electrostatic development type recording medium which is used in the image forming method according to the first embodiment of the present invention and can write and erase an image by the action of electric charge, and 1a denotes a heating and discharging type print head 10 which will be described later. The recording surface 1 of the recording medium 1 to which electric charges are applied from 2 is a medium body in which an electrophoretic image display material capable of selectively displaying white and black is encapsulated, and 3 is a microcapsule encapsulated in the medium body 2 3a is negatively charged white colored particles encapsulated in the microcapsule 3, 3b is positively charged black colored particles encapsulated in the microcapsule 3, and 4 is the microcapsule 3 together with the colored particles 3a and 3b. The dispersion medium 5 encapsulated in the recording medium 1 is formed in a strip shape on the surface opposite to the recording surface 1a of the recording medium 1, and is disposed at the position of the microcapsule 3 corresponding to each column of display pixels of the recording medium 1. The counter electrode 10 is a heat-discharge type print head used in the image forming method in Embodiment 1 of the present invention, and 11 is a soft material such as a hard material such as ceramic or a thin film resin such as polyimide, aramid, or polyetherimide. A substrate of the heating / discharge type print head 10 which is formed of a material having the properties and on which heating means 12 and discharge electrodes 14 described later are laminated, and 12 is a heating of the heat discharge type print head 10 which selectively heats the discharge electrodes 14 described later. Means, 12a is a heating resistor of the heating means 12 arranged in parallel on the substrate 11 at a predetermined pitch, 12b is a driver IC of the heating means 12 that is electrically connected to each heating resistor 12a and controls the heat generation, 13 Is an insulating film that covers the heating resistor 12a and insulates the heating means 12 from a discharge electrode 14 to be described later, and 14 is a heat discharge type mark formed in a substantially rectangular flat plate shape. A discharge electrode of the head 10, 14 a is a discharge generating portion of the discharge electrode 14 that generates a discharge with the counter electrode 5 by being heated by the heating resistor 12 a, and 20 is an image used in the image forming method in the first embodiment. The forming device 21 sets a voltage to be applied between the discharge electrode 14 of the heating discharge type print head 10 and the counter electrode 5 of the recording medium 1 by selecting the voltage application unit V _H or −V _L with the switch unit 22. This is a potential difference setting unit of the image forming apparatus 20 that forms an electric field.

The voltage applied by the voltage application unit V _H generates a discharge between the discharge electrode 14 and the counter electrode 5 just by applying the voltage, and erases an image from the discharge electrode 14 to the recording surface 1 a of the recording medium 1. Therefore, the voltage applied at the voltage application unit −V _L does not generate a discharge when applied, and the heating means 12 does not generate a discharge. In order to form an image from the discharge electrode 14 to the recording surface 1a of the recording medium 1 by heating the discharge electrode 14 with the heat generating resistor 12a, thereby generating a discharge between the discharge electrode 14 and the counter electrode 5. This is a discharge control voltage that can be irradiated with negative ions.
The discharge electrode 14 was formed by depositing a metal such as gold, silver, copper, or aluminum by vapor deposition, sputtering, printing, plating, or the like, and then etching to form a pattern as necessary. The heating resistor 12a was made of TaSiO ₂ , RuO ₂ or the like.
Further, as the material of the counter electrode 5, the same material as that of the discharge electrode 14, ITO or the like is preferably used. However, when the medium body 2 is a transmissive type, or when the counter electrode 5 side is a display surface, The counter electrode 5 needs to be transparent.

As shown in FIG. 1A, for the recording medium 1 on which an image has already been formed, it is necessary to perform an image erasing process in order to erase the existing image.
In the image erasing step shown in FIG. 1B, as the image erasing voltage application step, the voltage application unit V _H is selected by the switch unit 21 of the potential difference setting unit 20, and positive ions having a polarity opposite to that at the time of image formation are selected from the discharge electrode 14. A voltage (discharge generation voltage) equal to or higher than the discharge control voltage for generating the voltage is applied between the discharge electrode 14 and the counter electrode 5. As a result, the entire recording surface 1a of the recording medium 1 is irradiated with positive ions, and the existing image is erased.
By performing an image erasing voltage application step of applying a voltage equal to or higher than a discharge control voltage for generating ions (in this case, positive ions) having a polarity opposite to that at the time of image formation between the discharge electrode 14 and the counter electrode 5, an existing image is obtained. Regardless of the presence or absence of the image (regardless of the printed or non-printed part of the existing image), the entire image can be erased reliably by irradiating the entire row or column with ions of the opposite polarity to that during image formation. Excellent reliability.

Next, an image forming process for forming a new image is performed.
In the image forming process shown in FIG. 1C, first, as a discharge control voltage application process, the voltage application unit -V _L is selected by the switch unit 21 of the potential difference setting unit 20, and discharge is not generated only by the application. A voltage is applied between the discharge electrode 14 and the counter electrode 5. Subsequently, as a discharge electrode heating step, the discharge electrode 14 is selectively heated by the heating means 12 based on the image data of a new image, whereby negative ions are irradiated to a desired position on the recording surface 1a of the recording medium 1. Then, a new image is formed.
Note that the image erasing step can be performed in any unit of page units of the recording medium 1 or row units or column units of display pixels of the recording medium 1.

In the present embodiment, the electrophoretic type in which the colored particles 3a and 3b are enclosed in the microcapsule 3 is used as the medium body 2 of the recording medium 1. However, the present invention is not limited to this. Any system such as a toner display system, a twist ball system, and a powder movement system can be used. In addition to a monochrome display such as monochrome, it is combined with a color filter having three primary colors (R, G, B) in an additive color mixing method or a reflective layer having three primary colors (Y, M, C) in a subtractive color mixing method, A device that performs color display by coloring twist balls or fine particles to the three primary colors (Y, M, C) in the subtractive color mixing method and arranging them for each color can also be used.
In this embodiment, an image is erased with positive ions and an image is formed with negative ions. However, whether to use positive ions or negative ions for erasing and forming an image depends on the recording medium 1. Depending on the type (configuration), it can be appropriately selected.

In the present embodiment, the discharge electrode 14 having the plurality of discharge generation portions 14a is formed in a single rectangular plate, but for example, one end of the plurality of discharge generation portions 14a is connected by a common electrode to form a comb shape. Alternatively, both ends of the plurality of discharge generating portions 14a may be connected by a common electrode to form a ladder type or the like (see, for example, WO2005 / 056297).
Further, instead of using the heating resistor 12a as the heating means 12, a method of irradiating laser light away from the discharge electrode 14 or a method of irradiating infrared rays may be used. By disposing the heating means so as to face the recording medium 1 with the discharge electrode 14 interposed therebetween, the discharge electrode 14 can be selectively heated from the outside.

  In the present embodiment, the counter electrode 5 is formed in a strip shape according to each column of the microcapsules 3 of the recording medium 1, but is not limited to this, and may be formed in a strip shape according to each row. The recording medium 1 may be formed in a substantially rectangular flat plate shape over almost the entire surface. Further, instead of forming the counter electrode 5 integrally with the recording medium 1, when the same counter electrode 5 is provided on the image forming apparatus 20 side and the medium body 2 is set in the image forming apparatus, the counter electrode 5 is opposite to the recording surface 1a. You may make it contact or adjoin to the side surface.

Since the image forming method of Embodiment 1 is configured as described above, it has the following operations.
(1) By switching the polarity of the voltage applied between the discharge electrode 14 of the heat-discharge type print head 10 and the counter electrode 5 of the recording medium 1 that are arranged opposite to each other with the recording medium 1 interposed therebetween, the discharge electrode Since the image can be selectively written or erased by switching the polarity of the ions irradiated from the image forming apparatus 20, it is not necessary to provide the image forming apparatus 20 with an initializing means such as a restorer or a static eliminator. 20 can be reduced in size, and the image can be easily erased and written only by the heat-discharge type print head 10, and the recording medium 1 can be used repeatedly.
(2) When the recording surface 1a is irradiated with ions having the opposite polarity to that at the time of image formation, the existing recording image can be completely erased and the entire recording medium 1 can be initialized. Excellent.
(3) Since the polarity of ions irradiated from the discharge electrode 14 can be switched by switching the polarity of the voltage applied between the discharge electrode 14 and the counter electrode 5, depending on the type of the recording medium 1, An image can be formed by irradiating either positive or negative ions at the time of image formation, and a reversed image can be easily formed if necessary, and is excellent in versatility.
(4) Since there is an image erasing process that erases an existing image by irradiating the entire recording surface 1a of the recording medium 1 with positive ions, an existing image can be easily and reliably referred to without referring to the data of the existing image. The image can be erased, and the reliability of the image erasing process is excellent.
(5) An image forming step of forming a new image by irradiating a negative ion to a print portion of an image to be newly formed in the recording surface 1a of the recording medium 1 after erasing an existing image in the image erasing step. By providing, a new image can be written, and the reliability of the image quality is excellent.
(6) In the image erasing voltage application step, it is ensured that only a voltage (discharge generation voltage) higher than the discharge control voltage for generating ions having a polarity opposite to that at the time of image formation is applied between the discharge electrode 14 and the counter electrode 5. Therefore, it is possible to perform an image erasing step of erasing an existing image by generating a discharge, and it is not necessary to heat the discharge electrode 14 with the heating means 12, and control is easy and excellent in handleability.
(7) When the image erasing step is performed in units of pages, the existing image displayed on the recording medium 1 can be completely erased in advance and then a new image can be written. The recording medium 1 can be used repeatedly, and the reliability of the image quality is excellent.
(8) When the image erasing process is performed in units of rows or columns of display pixels of the recording medium 1, the image erasing is performed without causing a displacement of the ion irradiation position by using one heating / discharge type print head 10. The image forming process can be performed following the process, and the reliability of the image quality is excellent.

(Embodiment 2)
FIG. 2A is a schematic cross-sectional view showing a main part of a recording medium used in the image forming method according to the second embodiment, and FIG. 2B is a main part showing an image erasing process in the image forming method according to the second embodiment. FIG. 2C is a schematic cross-sectional view of a main part illustrating an image forming process in the image forming method according to the second embodiment, and FIG. 3 is an image forming method used in the image forming method according to the first embodiment. It is a principal part schematic top view of the heating discharge type print head of an apparatus. In addition, the same code | symbol is attached | subjected to the thing similar to Embodiment 1, and description is abbreviate | omitted.
The image forming apparatus 20a used in the image forming method in the second embodiment is different from that in the first embodiment in that both ends of the plurality of discharge generating portions 14a of the discharge electrode 14 of the heating / discharge type print head 10a are connected by the common electrode 14b. And a point where the potential difference setting unit 20 a has voltage application units + V _L and −V _L selected by the switch unit 22.
It is.

The voltage applied at the voltage application unit + V _L does not generate a discharge only by being applied, and the discharge electrode 14 is heated by the heating resistor 12a of the heating means 12 so that the discharge electrode 14 and the counter electrode 5 are heated. The discharge control voltage is such that discharge occurs and positive ions for erasing the image from the discharge electrode 14 to the recording surface 1a of the recording medium 1 can be irradiated. Similarly to the first embodiment, the voltage applied by the voltage application unit -V _L does not generate a discharge by being applied, but the heating electrode 12 is heated by the heating resistor 12a of the heating means 12. The discharge control voltage is such that a discharge occurs between the discharge electrode 14 and the counter electrode 5, and negative ions for forming an image can be irradiated from the discharge electrode 14 to the recording surface 1a of the recording medium 1. .

As shown in FIG. 2A, for the recording medium 1 on which an image has already been formed, it is necessary to perform an image erasing process in order to erase the existing image.
In the image erasing process shown in FIG. 2B, first, as the erasing discharge control voltage application process, the voltage application unit + V _L is selected by the switch unit 22 of the potential difference setting unit 21a, and no discharge is generated only by applying the voltage application unit + V _L. A discharge control voltage having a polarity opposite to that at the time of formation is applied between the discharge electrode 14 and the counter electrode 5. Subsequently, as the discharge electrode heating step, only the discharge generating portion 14a of the discharge electrode 14 facing the non-printing portion of the new image is selectively heated by the heating means 12 based on the image data of the new image. The non-printing portion of the new image in the recording surface 1a of the recording medium 1 is irradiated with positive ions, and the image is erased.
In the discharge electrode heating step, when only the discharge generation portion 14a of the discharge electrode 14 facing the non-printing portion of the new image is heated based on the image data of the new image, the non-printing portion of the new image is supported. An existing image can be erased by irradiating only the position with ions having a polarity opposite to that at the time of image formation, so that unnecessary ions are not generated and energy saving is excellent.
In the discharge electrode heating step, the entire discharge electrode 14 may be heated. In that case, it is not necessary to refer to the image data, and control is easy. In addition, an existing image can be surely erased by irradiating the entire row with ions having a polarity opposite to that at the time of image formation.

Next, an image forming process for forming a new image is performed.
In the image forming process shown in FIG. 2C, first, the voltage application unit -V _L is selected by the switch unit 22 of the potential difference setting unit 21a, and a discharge control voltage that does not generate a discharge when applied is applied to the discharge electrode 14. It is applied between the counter electrode 5. Subsequently, as the discharge electrode heating step, recording is performed by selectively heating only the discharge generation portion 14a of the discharge electrode 14 facing the print portion of the new image based on the image data of the new image by the heating means 12. A negative image is irradiated on a print portion of a new image in the recording surface 1a of the medium 1 to form a new image.
The order of the image erasing process and the image forming process may be reversed.

  In the present embodiment, both ends of the plurality of discharge generators 14a are connected by the common electrode 14b to form the discharge electrode 14 in a ladder shape, but only one end of the plurality of discharge generators 14a is connected by the common electrode 14b. Then, it may be formed in a comb shape, or the discharge electrode 14 having a plurality of discharge generation portions 14a may be formed in a single rectangular plate as in the first embodiment. Further, instead of using the heating resistor 12a as the heating unit 12, a heating unit that irradiates light such as laser light or infrared light away from the discharge electrode 14 may be used.

Since the image forming method of the second embodiment is configured as described above, it has the following operations in addition to the same operations as (1) to (3) of the first embodiment.
(1) An image erasing step of erasing an existing image by irradiating positive ions to a non-printing portion of a newly formed image in the recording surface 1a of the recording medium 1, and a recording surface 1a of the recording medium 1 An image forming step of forming a new image by irradiating negative ions on the print portion of the image to be newly formed, so that the new image can be surely overwritten regardless of the existing image. Excellent quality reliability.
(2) Since the image erasing step and the image forming step can be performed based on the image data of a new image, there is no need to refer to the data of the existing image, and the positive or negative for the entire recording surface 1a. Since a new image is overwritten by irradiation with any negative ion, it is not necessary to finely align the recording medium 1, and control is easy and the reliability of image formation is excellent.
(3) In the image erasing step, an erasing discharge control voltage applying step for applying a discharge control voltage for generating ions having a polarity opposite to that at the time of image formation between the discharge electrode 14 and the counter electrode 5, and heating the discharge electrode 14 A discharge electrode heating step of heating by means 12, so that the voltage value of the voltage applied directly to the discharge electrode 14 in the erasing discharge control voltage applying step may be equal to or lower than the discharge control voltage. As described above, since it is not necessary to apply a voltage (discharge generation voltage) higher than the discharge control voltage that generates a discharge only by being applied between the discharge electrode 14 and the counter electrode 5, it is excellent in energy saving and the discharge electrode 14. Excellent long life.
(4) By performing the image erasing step for each pixel of the display pixels of the recording medium 1, an unnecessary image can be surely erased without causing unnecessary discharge, and energy saving is excellent.

  The present invention relates to the polarity of ions irradiated from the discharge electrode by switching the polarity of the voltage applied between the discharge electrode of the heat discharge type print head and the counter electrode arranged opposite to the discharge electrode across the recording medium. And can selectively perform writing or erasing of an image reliably using only one heating and discharging type print head without using an initialization means such as a restorer or a static eliminator. By overwriting a new image while erasing an existing image, a high-quality image can be formed in a short time, and the electrostatic development type recording medium can be used repeatedly. By providing an excellent image forming method, it is possible to promote the use of electrostatic development recording media.

(A) Main part schematic cross-sectional view showing a recording medium used in the image forming method in the first embodiment (b) Main part schematic cross-sectional view showing an image erasing process in the image forming method in the first embodiment, (c) Implementation Schematic cross-sectional view of the relevant part showing the image forming step in the image forming method of Embodiment 1 (A) Main part schematic sectional view showing a recording medium used in the image forming method in Embodiment 2 (b) Main part schematic sectional view showing an image erasing process in the image forming method in Embodiment 2 (c) Schematic cross-sectional view of the relevant part showing the image forming process in the image forming method according to mode 2. Schematic plan view of the main part of the heat-discharge type print head of the image forming apparatus used in the image forming method in the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording medium 1a Recording surface 2 Medium body 3 Microcapsule 3a, 3b Colored particle 4 Dispersion medium 5 Counter electrode 10, 10a Heat discharge type print head 11 Substrate 12 Heating means 12a Heating resistor 12b Driver IC
DESCRIPTION OF SYMBOLS 13 Insulating film 14 Discharge electrode 14a Discharge generating part 14b Common electrode 20, 20a Image forming apparatus 21, 21a Potential difference setting part 22 Switch part

Claims (8)

An image forming method for writing and erasing an image on a recording medium by the action of an electric charge using a heat discharge type print head having a discharge electrode having an electron emission site and a heating means for selectively heating the discharge electrode. There,
By switching the polarity of the voltage applied between the discharge electrode of the heat-discharge type print head arranged to face the recording surface of the recording medium and the counter electrode arranged on the back surface of the recording medium An image forming method comprising selectively performing writing or erasing of an image by switching the polarity of ions irradiated from the discharge electrode. An image erasing step of erasing an existing image by irradiating the entire recording surface of the recording medium with positive ions or negative ions, and a negative ion on a print portion of a newly formed image in the recording surface of the recording medium The image forming method according to claim 1, further comprising: an image forming step of forming a new image by irradiating positive ions. The image erasing step includes an image erasing voltage applying step of applying a voltage equal to or higher than a discharge control voltage for generating ions having a polarity opposite to that during image formation between the discharge electrode and the counter electrode. Item 3. The image forming method according to Item 2. An image erasing step of erasing an existing image by irradiating a non-printed portion of a newly formed image in the recording surface of the recording medium with positive ions or negative ions, and in the recording surface of the recording medium The image forming method according to claim 1, further comprising: an image forming step of forming a new image by irradiating negative ions or positive ions to a print portion of a newly formed image. In the image erasing step, an erasing discharge control voltage applying step for applying a discharge control voltage for generating ions having a polarity opposite to that at the time of image formation between the discharge electrode and the counter electrode; and The image forming method according to claim 2, further comprising: a discharge electrode heating step of heating at. The image forming method according to claim 2, wherein the image erasing step is performed in units of pages. 6. The image forming method according to claim 2, wherein the image erasing step is performed in units of rows or columns of display pixels of the recording medium. 6. The image forming method according to claim 4, wherein the image erasing step is performed in units of display pixels of the recording medium.

Images