JP2002156658A - Reversible image display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible image display medium which can be repeatedly used and can display a high-quality image. SOLUTION: In the reversible image display medium 13, at least two kinds of dry developing particles WP, BP having triboelectrification property and having different electrification polarity and different optical reflection densities from each other are housed in cells 116 between two substrates 111, 112 and an image can be displayed by forming an electrostatic latent image on one substrate 111 and driving the developing particles by the electric field based on the electrostatic latent image. The surface resistivity of the substrate 111 to be in contact with the developer is controlled to >=1×1012 Ω/unit square. The surface resistivity of the substrate 112 in contact with the developer is controlled to be between 1×106 Ω/unit square and 1×1012 Ω/unit square. The center line average roughness Ra of the substrate 111 in contact with the developer is controlled to be between 0.2 μm and 0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an image display medium. In particular, the present invention relates to a reversible image display medium capable of repeatedly performing image display and image deletion.

[0002]

2. Description of the Related Art Today's image displays include pencils, pens,
Manually write characters and graphics on an image display medium such as paper using paints, etc .; display documents and graphics created by a computer, word processor, etc. on a display such as a CRT display; This is done by, for example, displaying an output on a medium.

Further, a document, a figure, or the like, which is manually created on a medium such as paper, or a document, a figure, or the like on a medium such as paper output by a printer is printed on another medium such as paper using a copying machine or the like. In some cases, a copy is made, or transmitted by a facsimile machine or the like, and copied and output on a medium such as paper at a transmission destination.

[0004]

Among these image displays, characters, characters and the like are displayed on an image display medium such as paper using a pencil, a pen or the like.
Image display for displaying figures, etc., and image display for displaying characters, figures, etc. on an image display medium such as paper by an image forming apparatus such as an electrophotographic system, an ink spraying system, a thermal transfer system, etc., such as a printer, a copying machine, or a facsimile machine. Then, a clear image can be displayed at a high resolution, and the image is easy to see when viewing the image.

However, it is not possible to repeat image display and image deletion on an image display medium such as paper. When writing letters and the like using a pencil, the letters and the like can be erased to some extent with an eraser, but if the letters etc. are thinly written, they will be completely erased if they are written with normal darkness. It is difficult to leave, and it is difficult to reuse a medium, such as paper, on which an image has been displayed, unless the image is also displayed on the back side of the medium on which an image has not been displayed.

[0006] Therefore, a medium such as paper on which an image is displayed is discarded or incinerated after it has been used up, and a lot of resources are consumed. In printers and copiers, consumables such as toner and ink are also consumed. Further, in order to obtain a display medium such as new paper, toner, ink, and the like, resources such as a medium and energy for manufacturing the medium are further required. This is contrary to the demand for environmental load reduction required today.

In this regard, in the image display on a display such as a CRT display, image display and image deletion can be repeated. However, the image displayed on the display has a lower resolution than the image displayed on a paper or the like by a printer or the like, and there is a limit to obtaining a clear and fine image. Since the resolution is low, it is not suitable for displaying a text document mainly composed of characters. A sentence or the like that fits into about one screen is still good, but a sentence or the like that continues over a plurality of screens is difficult to read and sometimes difficult to understand. In addition, eyes are very apt to be tired in long-term visual work due to relatively low resolution and light emission from the display.

As an image display method capable of repeating image display and image deletion, electrophoretic display (EP
D) and twisted ball type display (TBD) have been proposed. More recently, the method introduced in "Japan Hardcopy '99 Transactions PP249-252" has been proposed.

In the electrophoretic display method, a sealed space is formed by arranging two substrates, at least one of which is transparent, at an interval with a spacer interposed therebetween to form a sealed space, in which particles having electrophoretic ability are formed. It is filled with a display liquid dispersed in a dispersion medium of a different color, and displays images in the color of the particles or the color of the dispersion medium by migrating particles in the display liquid in an electrostatic field. is there.

Such a display liquid is usually composed of a dispersion medium such as isoparaffin, fine particles such as titanium dioxide, a dye for imparting color contrast with the fine particles, a dispersant such as a surfactant, and additives such as a charge imparting agent. Is done.

However, in this electrophoretic display,
Since the contrast between the high refractive index particles (inorganic pigment) such as titanium dioxide and the insulating colored liquid is displayed, the degree of concealment of the colored liquid is inevitably low, and the contrast is reduced.

Furthermore, the types of dyes that can be dissolved in a high-concentration nonpolar solvent at a high concentration so as to enable electrophoresis of particles are limited. No black dye is known. Therefore, the background part is inevitably colored, and it is difficult to make the background part white and improve the contrast. When white particles for forming an image are put in the colored liquid, the colored liquid may enter between the substrate and the white particle layer moved to the image observation side substrate, or the colored liquid may be mixed between the white particles. And the contrast is reduced. Also, the resolution of the electrophoretic particles is low because it is difficult for the particles to be uniformly attached to the image observation side substrate.

Further, since the specific gravity difference between the particles and the dispersion medium in the display liquid is very large, and the particles are likely to settle and agglomerate,
The display contrast tends to decrease, and it is difficult to display images stably for a long period of time, and the previous display afterimage tends to occur. Further, the charging of the particles in the liquid greatly changes with time, and in this respect, the image display stability is also poor.

In the twisting ball type display method, a large number of microcapsules in which microspheres treated so that the half and the other half of the surface exhibit mutually different colors or optical densities together with an insulating liquid are held inside. Using an image display medium, a microsphere in the microcapsule is rotated by an electric field or a magnetic force to display an image in a predetermined color.

However, in this twisted ball type display, it is difficult to obtain a good contrast because an image is displayed by microspheres in an insulating liquid in a microcapsule, and in particular, a resolution is lowered because a gap is always formed between the microcapsules. . It is difficult to reduce the size of the microcapsule in order to improve the resolution in manufacturing the capsule.

"Japan Hardcopy '99 Transactions PP249
The image display method introduced in 252252 ”is a method in which two substrates each having an electrode and a charge transport layer laminated thereon are opposed to each other at a predetermined interval to form a sealed space, in which a conductive toner and a conductive toner and a conductive toner are formed. Insulating particles having different colors are enclosed, an electrostatic field is applied to charge and charge the conductive toner, and the conductive toner is moved by Coulomb force to display an image.

However, in the image display method utilizing the charge injection phenomenon, when the charge-injected conductive toner moves,
Insulating particles (for example, white particles that are put together to obtain the background color) hinder the movement of the conductive toner, and some toners stop moving. As a result, sufficient image density and contrast cannot be obtained, and the image display speed decreases. In order to solve this problem, high voltage driving is required. Also, the resolution is limited to the resolution determined by the electrodes. In addition, it is essential to employ an electrode, a charge injection layer, and a conductive toner, and there is a limitation in manufacturing.

Therefore, according to the present invention, image display and image erasure can be repeatedly performed, so that the use of consumables such as an image display medium such as paper and a developer and ink related to the conventional image formation can be reduced. It is an object of the present invention to provide a reversible image display medium capable of responding to today's environmental load reduction.

Another object of the present invention is to provide a reversible image display medium capable of displaying a high-contrast, high-quality image.

It is another object of the present invention to provide a reversible image display medium capable of displaying a high-resolution image with a high resolution.

Another object of the present invention is to provide a reversible image display medium capable of displaying images stably for a long period of time.

Another object of the present invention is to provide a reversible image display medium which is less likely to cause an afterimage and therefore exhibits good reversibility and can display a high quality image in this respect as well.

Another object of the present invention is to provide a reversible image display medium which requires a low driving voltage for image display.

[0024]

SUMMARY OF THE INVENTION The present invention provides the following first to fourth reversible image display media. (1) First reversible image display medium: two substrates facing each other with a predetermined gap;
One or two or more developer storage cells formed between two substrates and surrounded by a partition wall, and a dry developer included in each of the cells, wherein the dry developer includes: At least two kinds of dry developing particles having different charging polarities and different optical reflection densities and having triboelectric charging properties are included, and one of the two substrates has an image to be formed. By forming the corresponding electrostatic latent image, the developing particles can be driven by an electric field based on the electrostatic latent image to display an image, and the surface of the surface of the substrate on which the electrostatic latent image is formed is in contact with the developing particles. A reversible image display medium having a resistivity of 1 × 10 ¹² Ω / □ or more. (2) Second reversible image display medium: two substrates facing each other with a predetermined gap;
One or two or more developer storage cells formed between two substrates and surrounded by a partition wall, and a dry developer included in each of the cells, wherein the dry developer includes: At least two kinds of dry developing particles having different charging polarities and different optical reflection densities and having triboelectric charging properties are included, and one of the two substrates has an image to be formed. Forming the corresponding electrostatic latent image, the developing particles can be driven by an electric field based on the electrostatic latent image to display an image, and the developing particles on the other substrate facing the substrate on which the electrostatic latent image is formed Has a surface resistivity of 1 × 10 ⁶ Ω /
A reversible image display medium having a value of □ to 1 × 10 ¹² Ω / □. (3) Third reversible image display medium: two substrates facing each other with a predetermined gap;
One or two or more developer storage cells formed between two substrates and surrounded by a partition wall, and a dry developer included in each of the cells, wherein the dry developer includes: At least two kinds of dry developing particles having different charging polarities and different optical reflection densities and having triboelectric charging properties are included, and one of the two substrates has an image to be formed. By forming the corresponding electrostatic latent image, the developing particles can be driven by an electric field based on the electrostatic latent image to display an image, and the surface of the surface of the substrate on which the electrostatic latent image is formed is in contact with the developing particles. The resistivity is 1 × 10 ¹² Ω / □ or more, and the surface resistivity of the surface of the other substrate facing the substrate on which the electrostatic latent image is formed and which contacts the developing particles is 1 × 10 ⁶ Ω / □ or more. × 1
A reversible image display medium having a resistance of 0 ¹² Ω / □ or less. (4) Fourth reversible image display medium: two substrates facing each other with a predetermined gap;
One or two or more developer storage cells formed between two substrates and surrounded by a partition wall, and a dry developer included in each of the cells, wherein the dry developer includes: At least two types of different charging polarities, and different optical reflection densities from each other, including triboelectrically-charged dry developing particles, the surface of at least one of the substrates contacting the developing particles The center line average roughness Ra is 0.
A reversible image display medium having a size of 2 μm or more and 0.5 μm or less.

Each of the first to fourth image display media according to the present invention has an image to be displayed on the developing particles in a state where the developing particles contained in each cell of the image display medium are triboelectrically charged. By forming an electrostatic field corresponding to the above, the development can be performed by moving the developing particles by Coulomb force, and an image can be displayed.

The electrostatic field corresponding to the image to be formed can be obtained by providing electrodes on each of the medium constituting substrates, applying a voltage corresponding to the image to be formed between the electrodes, or applying an image to be formed on one of the substrates. Can be formed by forming an electrostatic latent image corresponding to.

Each image display medium according to the present invention comprises two substrates facing each other with a predetermined gap, and one or more substrates formed between the two substrates and surrounded by a partition wall. A developer containing cell, and a dry developer contained in each of the cells, wherein the dry developer has at least two kinds of frictions having different charging polarities and different optical reflection densities from each other. It contains dry developing particles having chargeability. Therefore, even after the image is displayed once, the image can be erased by applying a different electrostatic field, forming an alternating electric field or the like, or the image can be rewritten by applying a different electrostatic field. Therefore, there is no need to discard the image display medium on which the image has been displayed. Further, the developing particles are included in the cell, and therefore, there is no need to supply the developer from outside. As a result, the use of conventional image display media, such as paper, related to image display, and consumables, such as a developer, can be greatly reduced.

Further, unlike the conventional electrophotographic image formation, it is not necessary to dissolve and fix the toner on a sheet such as paper with heat, and the image forming energy required for this type of conventional image formation is not required. Can save most.

Thus, it is possible to meet today's environmental load reduction.

According to each image display medium of the present invention, the developer contained in the cell has a different optical reflection density (in other words, a "different contrast" or a "different color". )) At least two types of developing particles are included, and the developing particles are dry type developing particles, and the degree of hiding of the other type of developing particles by one type of developing particles is good. Images can be displayed.

The developer contained in the cell contains at least two types of mutually triboelectrically chargeable dry developing particles having different charging polarities. When an image is displayed, the developer is charged to the opposite polarity by friction charging. Since the particles move under the Coulomb force, the particles are easy to move, and in this respect, the image can be displayed with good contrast, the afterimage of the previous display hardly occurs, the image can be displayed at a high speed, and further, low voltage driving is possible. .

The dry-developed particles are less likely to settle and agglomerate because no liquid is interposed therebetween, as compared with, for example, the electrophoretic particles in the display liquid used for the electrophoretic image display described above. A decrease in contrast is unlikely to occur, and a long-term stable image display can be performed. Since the sedimentation and aggregation of the developing particles hardly occur, the afterimage of the previous display hardly occurs. Further, since dry development particles have less change over time in charging performance than particles in a liquid, stable image display can be performed for a long time in this respect as well.

Further, compared with the conventional image display by a CRT display or the like, the image can be displayed with a high resolution and easily to the eyes.

The respective image display media according to the present invention will be further described. Each of the first to third image display media can display an image by forming an electrostatic latent image on one of the substrates. In the first and third image display media, the surface of the substrate on which the electrostatic latent image is formed is in contact with the developing particles and has a surface resistivity of 1 × 10 ¹² Ω / □ or more.

According to the study of the present inventor, when an electrostatic latent image is formed and an image is displayed, if the surface resistivity of the surface of the substrate on which the electrostatic latent image is formed is in contact with the developing particles, the substrate is too small. Is difficult to hold the latent image, and the image is disturbed such as blurred image flowing.

In this regard, in the first and third image display media,
The surface resistivity of the surface of the substrate on which the electrostatic latent image is formed, which is in contact with the developing particles, is set to 1 × 10 ¹² Ω so that the latent image is preferably maintained.
/ □ or more, high quality images can be displayed accordingly. The upper limit of the surface resistivity is not particularly limited, but will be about 1 × 10 ¹⁶ Ω / □ in consideration of commercially available substrates and the like. However, it is not limited to this.

Each of the second and third image display media has a surface resistivity of 1 × 10 ⁶ Ω / □ or more and 1 × 10 ⁶ or more on the surface of the substrate facing the substrate on which the electrostatic latent image is formed, which is in contact with the developing particles. ¹² Ω
/ □ or less.

According to the study of the present inventor, if the surface resistivity of the surface of the substrate facing the substrate on which an electrostatic latent image is formed is in contact with the developing particles, the image display medium after image formation is overlaid. This makes it difficult to shield the substrate from static electricity. In other words, the substrate becomes susceptible to other charges such as charges on the image display medium superimposed on the substrate, and as a result, the image is easily broken and the image is stabilized. It becomes difficult to hold it. In addition, when erasing or rewriting an image, the latent image charge is not easily removed, and an afterimage is easily generated.

If the surface resistivity of the surface of the substrate facing the substrate on which the electrostatic latent image is to be formed is in contact with the developing particles, the discharge is likely to occur between the substrates. A uniform electric field cannot be obtained, and image unevenness is likely to occur.

In this regard, in each of the second and third image display media, the surface resistivity of the surface of the substrate facing the substrate on which the electrostatic latent image is formed, which is in contact with the developing particles, is reduced by 1 × to prevent the occurrence of such a problem. It is set to 10 ⁶ Ω / □ or more and 1 × 10 ¹² Ω / □ or less. Thus, the second and third image display media can stably hold the display image. In addition, afterimages are less likely to occur, and the occurrence of image unevenness can be suppressed, so that high-quality images can be displayed.

Further, in the fourth image display medium according to the present invention, the center line average roughness Ra of the surface of at least one of the substrates that contacts the developing particles is 0.2 μm or more and 0.5 μm or less.

According to the study of the present inventor, if the surface roughness of the surface of the substrate that comes into contact with the developing particles is too small, the van der Waals force between the developing particles and the substrate surface increases, and the particles adhere to the substrate surface. The adhesive force becomes large and it is difficult to separate from the substrate. Further, if the surface roughness of the surface of the substrate that contacts the developing particles is too large, the developing particles enter the unevenness of the substrate surface and are difficult to separate. As described above, if the surface roughness of the substrate surface is too small or too large, the adhered developing particles are difficult to separate, and this tends to cause an afterimage.

In this regard, in the fourth image display medium, the center line average roughness Ra of the surface of at least one of the substrates that comes into contact with the developing particles is set to 0.2 μm which can suppress the occurrence of such a problem.
m or more and 0.5 μm or less, high-quality images can be displayed by suppressing the occurrence of afterimages.

[0044]

Embodiments of the present invention will be described below.

The reversible image display medium according to the preferred embodiment of the present invention basically has the following structure.

That is, two substrates facing each other with a predetermined gap therebetween, one or more developer storage cells formed between the two substrates and surrounded by partition walls, and This is a reversible image display medium having a dry developer contained in each cell. The dry developer contains at least two types of dry developing particles having triboelectric charging properties, which have different charging polarities and different optical reflection densities.

According to the reversible image display medium, a predetermined electrostatic field is applied to the developing particles contained in each cell in a state where the developing particles are frictionally charged in correspondence with the image to be displayed. Then, the developing can be performed by moving the developing particles by the Coulomb force acting between the electrostatic field and the charged developing particles, and an image can be displayed with a predetermined contrast.

The electrostatic field can be formed, for example, by forming an electrostatic latent image on the outer surface of one of the two substrates and based on the electrostatic latent image. The formation of the electrostatic field may be performed simultaneously with the formation of the electrostatic latent image, or may be performed after the formation of the electrostatic latent image. Such an electrostatic field may be applied to a substrate opposite to the substrate on which an electrostatic latent image is formed, for example, by applying a bias voltage simultaneously with or after the formation of the electrostatic latent image, or by applying a bias voltage to the opposite substrate. It is obtained by setting the opposite substrate to a predetermined potential for forming an electrostatic field by grounding or the like.

Various materials can be selected and employed for the partition walls forming the substrate and the cells. As the substrate, a glass substrate, a rigid or flexible synthetic resin substrate, or the like can be employed. A flexible film-like substrate can also be employed.

At least one of the two substrates constituting the medium (the one disposed on the image observing side) may have a light transmitting property so that a displayed image can be visually recognized.

When forming an electrostatic latent image on a substrate, the substrate may be an insulating substrate.

The substrate on the side opposite to the substrate on which the electrostatic latent image is to be formed (for example, the substrate on the non-image observation side) may or may not be an insulating substrate. When an insulating substrate is used, this may be set to the ground potential, or when it is necessary to apply a bias voltage thereto, the insulating substrate may be left as it is.For example, a conductive film may be formed on the outer surface of the substrate, or the entire substrate may be used. It may be formed of a conductive material or a material containing a conductive material. In this way, the substrate can be easily grounded to a ground potential or a bias voltage can be applied to the substrate if necessary. Further, when the opposite substrate is an insulating substrate and a conductive film is formed on the outer surface thereof, or when the opposite substrate itself is a conductive substrate, there is an effect of shielding charges from other components. In addition, even when the media on which images are displayed are overlapped, the images are less likely to collapse, and the images can be held more stably.

When an image is displayed by forming an electrostatic latent image, if the surface resistivity of the surface of the substrate on which the electrostatic latent image is formed is in contact with the developing particles, the latent image is difficult to hold on the substrate. This causes image disturbance such as blurred image flowing.

Therefore, the surface resistivity of the surface of the substrate on which the electrostatic latent image is formed, which is in contact with the developing particles, is set to 1 × 10 ¹² Ω / □ or more so that the latent image is preferably maintained and a high quality image is displayed. It is better to be able to. The upper limit of the surface resistivity is not particularly limited, but will be about 1 × 10 ¹⁶ Ω / □ in consideration of commercially available substrates and the like. However, it is not limited to this.

When an image is displayed by forming an electrostatic latent image, if the surface resistivity of the surface of the substrate facing the substrate on which the electrostatic latent image is formed is in contact with the developing particles, it is too large.
When the image display medium after image formation is overlapped, it becomes difficult to electrostatically shield the substrate, in other words, it becomes susceptible to other charges such as charges on the image display medium stacked on the substrate, As a result, the image is easily broken, and it is difficult to stably hold the image. In addition, when erasing or rewriting an image, the latent image charge is not easily removed, and an afterimage is easily generated. If the surface resistivity of the surface of the substrate facing the substrate on which the electrostatic latent image is formed and which comes into contact with the developing particles is too small, discharge is likely to occur between the substrates, and as a result, a uniform electric field for image display is obtained. And image unevenness is likely to occur.

In this regard, the surface resistivity of the surface of the substrate facing the substrate on which an electrostatic latent image is to be formed, which is in contact with the developing particles, should be 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹² Ω / □ or less. Thus, the displayed image can be stably held. In addition, afterimages are less likely to occur, and the occurrence of image unevenness can be suppressed, so that high-quality images can be displayed.

Further, an image is displayed based on the electrostatic latent image.
Regardless, if the surface roughness of the surface of the substrate that contacts the developing particles is too small, the van der Waals force between the developing particles and the substrate surface increases, and the adhesion of the particles to the substrate surface increases. It is difficult to separate from the substrate. If the surface roughness of the surface of the substrate in contact with the developing particles is too large, the developing particles enter the unevenness of the substrate surface and are difficult to separate. As described above, if the surface roughness of the substrate surface is too small or too large, the adhered developing particles are difficult to separate, and this tends to cause an afterimage.

Regarding this point, generation of an afterimage is suppressed by setting the center line average roughness Ra of at least one substrate (particularly, the substrate on the image observation side) in contact with the developing particles to be 0.2 μm or more and 0.5 μm or less. To display high quality images.

The number, size, shape, distribution, arrangement (regular or irregular) of the developer containing cells are not particularly limited as long as images can be displayed. A developer movement suppressing member or a spacer for maintaining a gap between the substrates may be provided between the substrates. The partition wall constituting the cell may also serve as the developer movement suppressing member and the spacer.

In the case where an electrostatic latent image is formed on a substrate during image formation, if the gap between the substrates or the thickness of the substrate is large, the electric field applied to the developer is weakened, leading to a decrease in contrast. On the other hand, if the gap between the substrates is too small, the amount of developer that can be included is small, and the contrast is low. If the thickness of the substrate is too small, the substrate is easily bent, and uniformity of the gap between the substrates cannot be obtained,
Image unevenness is likely to occur. Therefore, the thickness of the substrate is 5
μm-100 μm, gap between substrates 20 μm-300
μm, and the thickness of the entire medium is suitably 30 μm to 500 μm.

With respect to the frictional charging of the developing particles, the developing particles may be stored in a developer storage cell and then triboelectrically charged by vibrating the developer particles. However, two or more types of developing particles may be mixed and stirred in advance. The developer particles triboelectrically charged may be accommodated in the cell. This makes it easier to obtain frictionally charged developing particles in a desired state. In any case, the developing particles are triboelectrically charged prior to image display.

The reversible image display medium may have an electrode or may have no electrode. When no electrode is provided on the substrate, the medium can be simplified accordingly, and a flexible film substrate or the like can be easily used as the substrate.

As an image display medium having electrodes, an electrode (preferably a transparent electrode) is formed on the inner surface of one substrate having light transmittance, and an electrode facing the electrode is formed on the inner surface of the other substrate. Can be exemplified.

The electrode on the inner surface of the other substrate may be composed of an individual electrode group formed for each pixel.

For an image display medium with electrodes, leads are connected to the electrodes, and the leads are desirably provided in a non-image display area having a partition wall or the like.

The developer contained in the developer accommodating cell has at least two kinds of different charge polarities and different optical reflection densities (in other words, “different contrast” or “different color”). It is preferable to include dry developing particles. As typical examples, positively chargeable (or negatively chargeable) black particles having light absorbency and negatively chargeable (or positively chargeable) white particles having light reflectivity can be given.

At least one of the at least two types of developing particles constituting the dry developer may be non-conductive particles. In this case, regardless of whether the image display medium has an electrode or not, the presence of the non-conductive particles causes
Various kinds of developing particles can be easily and reliably triboelectrically charged, so that a good image display can be performed.

Further, at least one of the at least two types of developing particles constituting the dry developer may be magnetic developing particles. When the magnetic developing particles are employed in this manner, a magnetic stirring force can be applied to the dry developing particles by a magnetic field in driving the developing particles by the electrostatic field, whereby the developing particles can be smoothly moved by the electrostatic field for image display. This makes it easier to move, further improving the contrast and driving at a lower voltage.

Furthermore, irrespective of whether or not the reversible image display medium has the electrodes, the presence of the magnetic particles allows the developer (developed particles) to be stirred by a magnetic field, for example, an oscillating magnetic field. In forming an image (image display) by stirring the developer, it is possible to initialize the medium or erase the previous image, and in the image display, the developing particles can be easily moved by the electrostatic field for the image display. Images can be displayed.

The stirring of the developing particles can be performed by applying an alternating voltage such as the application of an AC voltage or by applying mechanical vibration. Stirring can be performed by combining two or more of alternating voltage stirring, magnetic stirring, mechanical stirring, ultrasonic irradiation stirring, and the like.

It should be noted that one type of developing particles may be both non-conductive particles and magnetic particles.

In any case, if the developing particles are too small, the adhesive force becomes extremely large, causing sticking between the developing particles and lowering the developing efficiency. On the other hand, if the developing particles are too small, the charge amount of the particles becomes very large, so that an electric field for moving the particles in displaying an image must be made large, and therefore a high driving voltage is required.

If the size of the developing particles is too large, triboelectric charging cannot be performed well, and a sufficient moving speed of the developing particles cannot be obtained in an electrostatic field for displaying an image, or good contrast cannot be obtained.

In light of these facts and materials for obtaining developing particles having predetermined characteristics, it is appropriate that the non-conductive developing particles have a particle size of 1 μm to 50 μm, and the magnetic developing particles have a particle size of 1 μm to 100 μm. .

The developing particles can be formed from, for example, a binder resin, a colorant, or the like, or a colorant alone.
The following can be used for these. -There is no particular limitation as long as it can disperse a binder resin colorant, a magnetic substance, and the like, and are usually used as a binder. A typical example is a binder resin used for an electrophotographic toner.

For example, polystyrene resin, poly (meth) acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin, polyether resin, polysulfone resin, polyester resin, epoxy resin, urea resin, urethane Resin, urea resin, fluorine resin, silicon resin and copolymers thereof,
A block polymer, a graft polymer, a polymer blend, or the like can be used.

The glass transition point Tg may be quite high,
In some cases, it need not be a thermoplastic resin. -Colorant As the colorant, various organic or inorganic pigments and dyes as shown below can be used.

The black pigment includes carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.

Examples of the yellow pigments include graphite, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, banza yellow G, banza yellow 10G, benzidine yellow G, and benzidine. Yellow GR,
There are quinoline yellow lake, permanent yellow NCG, tartrazine lake and the like.

Examples of the orange pigment include red lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indathrene brilliant orange RK, benzidine orange G, and indathrene brilliant orange GK.

Red pigments include red iron, cadmium red, leadtan, mercury sulfide, cadmium, permanent red 4R, lithol red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine. Lake B, Alizarin Lake, Brilliant Carmine 3B and the like.

Examples of the violet pigment include manganese violet, fast violet B, methyl violet lake and the like.

As blue pigments, navy blue, cobalt blue, alkali blue lake, Victoria blue lake,
Phthalocyanine blue, metal-free phthalocyanine blue,
Phthalocyanine blue partially chlorinated products, Fast Sky Blue, Indaslen Blue BC and the like.

The green subjects include chrome green, chromium oxide, pigment green B, malachite green lake, and final yellow green G.

As white pigments, zinc white, titanium oxide,
Examples include antimony white and zinc sulfide.

The extender includes baryte powder, barium carbonate, clay, silica, white carbon, talc, alumina white and the like.

Various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

These colorants can be used alone or in combination.

Particularly in black and white display, carbon black is preferred as a black colorant, and titanium dioxide is preferred as a white colorant.

In particular, when the white pigment is kneaded with a molten binder resin (binder resin) to obtain the developing particles from the kneaded product, the amount of the white pigment used is determined in order to obtain sufficient whiteness. To 100 parts by weight of the starting monomer
The amount is desirably 0 parts by weight or more, preferably 20 parts by weight or more, and is desirably 60 parts by weight or less, preferably 50 parts by weight or less in order to ensure sufficient dispersibility of the white pigment. When the amount of the white pigment exceeds 60 parts by weight, the binding property between the pigment and the binder resin and the dispersibility of the pigment deteriorate. On the other hand, when the amount of the white pigment is less than 10 parts by weight, sufficient development particles of other colors cannot be obtained. No concealing properties are obtained.

Carbon black is preferable as the black colorant. However, in the case where the developing particles are to be magnetized, magnetic particles such as magnetite and ferrite and magnetic fine particles can be used as the colorant. -Other internal additives As internal additives preferably used other than the binder resin and the colorant, a magnetic substance, a charge control agent, a resistance adjuster and the like can be mentioned. -Charge control agent The charge control agent is not particularly limited as long as it gives charge to the developing particles by triboelectric charging.

Examples of the positive charge control agent include a nigrosine dye, a triphenylmethane compound, a quaternary ammonium salt compound, a polyamine resin, and an imidazole derivative.

Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, oil-soluble dyes containing gold (including metal ions and metal atoms), quaternary ammonium salt compounds, calixarene compounds, and boron-containing compounds. (Boron benzylate complex), nitroimidazole derivatives and the like.

In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide and ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments,
Resins containing fluorine, chlorine, nitrogen and the like can also be used as charge control agents. -Magnetic substance Magnetic particles and magnetic fine powder can be used, and examples thereof include ferromagnetic elements and alloys and compounds containing these, such as magnetite, hematite, iron such as ferrite, cobalt, nickel, and the like. Conventionally known magnetic materials such as alloys and compounds such as manganese and other ferromagnetic alloys may be contained. The shape of these magnetic powders is various, such as a granular shape, a needle shape, and a flake shape, and can be appropriately selected and used. -Resistance adjuster As the resistance adjuster, there are also the same as the above-mentioned magnetic powders and colorants, and it is preferable to use metal oxide, graphite, carbon black, etc. in various shapes such as flake, fiber, powder, etc. Can be.

Next, a production example of the developing particles will be described.

[0096] From among the binder resin, magnetic powder, colorant, charge control agent, resistance adjuster and other additives as described above, necessary ones are selected, sufficiently mixed by a predetermined amount, and pressurized. Heat kneading with a kneader or a twin-screw kneading device, etc.
After cooling, it is roughly pulverized by a hammer mill, a cutter mill or the like. Next, after further pulverizing with a jet mill, an ong mill or the like, the particles are classified using an air classifier or the like until the particles have a predetermined average particle size, thereby obtaining developed particles.

The thus-obtained particles having different charge polarities and different contrasts (optical reflection densities) are mixed and stirred at a predetermined ratio, whereby a developer having a predetermined charge amount can be prepared. At this time, a third component (particle) such as a fluidity improver may be added and mixed. -About such fluidizers As fluidity improvers, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite Diatomaceous earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride and the like.

In particular, fine powders such as silica, aluminum oxide, titanium dioxide and magnesium fluoride are preferable, and a fluidizing agent may be added alone or in combination.

As described above, the formation of an electrostatic field with respect to the developing particles on the reversible image display medium is intended to be displayed on, for example, the surface of one of the two substrates (for example, the substrate on the image observation side). An electrostatic latent image corresponding to an image can be formed, or an electrostatic latent image can be formed close to the electrostatic latent image based on the electrostatic latent image. In this case, the formation of the electrostatic field
It may be performed simultaneously with the formation or proximity of the electrostatic latent image, or may be performed after the formation of the electrostatic latent image. The formation of the electrostatic field can be performed, for example, by setting a predetermined potential for forming the electrostatic field on the substrate opposite to the substrate on which the electrostatic latent image is formed. The setting of the predetermined potential can be performed by, for example, applying a bias to the opposite substrate or setting the substrate to the ground potential.

The electrostatic latent image may be formed directly on the medium surface (substrate surface) using, for example, a direct electrostatic latent image forming apparatus, or may be formed outside the medium using an external electrostatic latent image forming apparatus. The electrostatic latent image may be formed by transferring the image onto the medium surface (substrate surface). The electrostatic latent image formed outside the medium using the external electrostatic latent image forming apparatus may be brought close to the medium surface (substrate surface).

As the direct electrostatic latent image forming apparatus, various discharge-type electrostatic latent image forming apparatuses which discharge an electrostatic latent image charge by discharging to the surface of a medium in accordance with an image to be displayed are to be displayed. Various charge-injection-type electrostatic latent image forming apparatuses that charge an electrostatic latent image by injecting a charge into a medium surface according to an image can be exemplified. Examples of the former include an ion flow type device and a multi-stylus type device having an electrostatic recording head in which recording electrodes are arranged in a predetermined direction (for example, a main scanning direction when a substrate is scanned by the device). As an example of the latter, a multi-stylus type device having an electrostatic recording head in which recording electrodes are arranged in a predetermined direction (for example, a main scanning direction when a substrate is scanned by the device) and adjacent control electrodes are arranged adjacent to the recording electrodes. Can be mentioned.

The external electrostatic latent image forming apparatus forms an electrostatic latent image corresponding to an image to be displayed on an electrostatic latent image carrier, and forms the electrostatic latent image on the electrostatic latent image carrier. Is transferred or brought close to the substrate surface. More specifically, an electrostatic latent image corresponding to an image to be displayed is formed on a photoconductor such as a photoconductor, and the electrostatic latent image on the photoconductor is transferred to or close to the substrate surface. And an electrostatic latent image corresponding to an image to be displayed on a dielectric, and the electrostatic latent image on the dielectric is transferred to or brought close to the substrate surface.

In displaying an image, an electric field forming apparatus including any one of the electrostatic latent image forming apparatuses can be employed.

As described above, when an electrostatic latent image is formed on an image display medium, whether the image is transferred, close to, or directly formed, image retention is improved. This is particularly advantageous in terms of image retention when using a highly fluid developer or a developer whose fluidity is increased by a developer stirring process prior to image display.

Note that for a reversible image display medium having a counter electrode, an electrostatic field for image display can be formed by applying a voltage between the counter electrodes. An electric field forming device for this medium will be exemplified later.

The formation of an electrostatic field on the developing particles in a reversible image display medium without electrodes or a medium having electrodes only on one substrate is performed by arranging electrodes on the outer surface of the medium and applying a voltage through this electrode. Can also be applied.

[0107] Regardless of whether a reversible image display medium with or without electrodes is employed, an image erasing process for erasing the previously displayed image may be performed before the image is displayed.

The image erasing process can be performed by, for example, forming an electric field for moving the developing particles constituting the developer in the image display medium, applying a stirring force to the developer, or both. The application of the stirring force, for example, to form an alternating electric field to the developer, to form an oscillating magnetic field,
Irradiation of ultrasonic waves, application of mechanical vibration, and combination thereof can be performed.

Therefore, in displaying an image, the image erasing device includes, for example, a device including an electric field forming device for forming an electric field for moving the developing particles, and a device including a stirring device for applying a stirring force to the developing particles. A device that includes both the electric field forming device and the stirring device can be appropriately used.

For example, under the electric field, one of the two types of developing particles having the same optical reflection density (in other words, “having the same contrast” or “having the same color”) is transferred to one substrate side. By collecting and developing the other developing particles having the same optical reflection density on the other substrate side, the image can be erased, and when a new image is formed next time, the developing particles only need to be moved only in the image area. Because it ’s good
As a result, image display is performed smoothly, reliably, and with high quality.

Further, for example, when the developer (developing particles) is stirred, the image is erased, and the charge amount and the fluidity of the developing particles are improved. In this case as well, the next image display becomes smoother.
High quality is ensured.

The electric field forming apparatus for erasing an image includes a pair of electrodes (usually a metal) or a dielectric disposed with a reversible image display medium therebetween, and a power supply for applying a bias voltage thereto. Can be exemplified.

In addition, various discharge type electric field forming devices for forming an electric field by discharging to an image display medium and various charge injection type electric field forming devices for forming an electric field by injecting charges into a reversible image display medium are exemplified. it can. Examples of the former include a corona charging device, an ion flow type electric field forming device, and a multi-stylus type electric field forming device having a head in which electrodes are arranged in a predetermined direction. As the latter example, electrodes are arranged in a predetermined direction. And a multi-stylus type electric field forming apparatus having a head in which adjacent control electrodes are arranged adjacent to the electrodes.

The following can be exemplified as the stirring device. A device for forming an alternating electric field on a reversible image display medium.

This device can be used when at least one of the developer particles is insulating. A device for forming an oscillating magnetic field on a reversible image display medium.

This device can be used when at least one of the developer particles contains a magnetic material. A device that irradiates a reversible image display medium with ultrasonic waves. A device that applies mechanical vibration to a reversible image display medium. A device combining two or more of the above devices.

As described above, when the developer (developing particles) is agitated, the charge amount and the fluidity of the developing particles are improved, and the next image display is smoothly, surely, and of high quality. .

Further, when the developer is stirred prior to the image display, the charge amount of the developing particles is stabilized, and in this respect, the image can be displayed well. Further, there is an advantage that the allowable range of chargeability and fluidity of the developer is widened.

Therefore, in the image display, regardless of whether a reversible image display medium with or without electrodes is employed, the above-mentioned image erasing process is also used, or separately from the image erasing process. The developer may be agitated.

When employing an image display medium without electrodes or an image display medium having electrodes only on one substrate,
For example, an electrostatic latent image corresponding to an image to be displayed is formed on the surface of the image display medium (substrate surface), and based on the electrostatic latent image, simultaneously with the formation of the electrostatic latent image or the electrostatic latent image. An electrostatic field for image display may be formed after image formation, and the developer may be agitated simultaneously with and / or before the formation of the electrostatic field.

In the case of an image display medium having a counter electrode, a voltage is applied between the electrodes to form an electrostatic field, and the developer is agitated before or simultaneously with the formation of the electrostatic field. be able to. Irrespective of the presence or absence of the electrodes, the developer agitation faces the image display medium conveyance path in the electrostatic field formation region by the electric field formation device or in the upstream side thereof, for example, in the relative conveyance direction of the image display medium to the electric field formation device. This can be done using a stirrer.

As for the developer stirring method and the stirring apparatus, the same stirring method and apparatus as those described in connection with the image erasing process can be employed.

By stirring the developer in displaying an image as described above, it is possible to further improve the contrast and further reduce the driving voltage.

When an electrostatic latent image is formed on the surface of the image display medium (substrate surface) in displaying an image, the surface of the medium is uniformly charged to a predetermined potential before the formation of the electrostatic latent image. An electrostatic latent image corresponding to the image to be displayed may be formed. Then, based on the electrostatic latent image, a predetermined electrostatic field corresponding to an image to be displayed on the developer particles in the developer accommodating cell may be formed to move the developer particles to display an image.

The electrostatic latent image on the medium is formed, for example, directly on the surface of the medium charged in the above-described charging step, or by forming the electrostatic latent image formed on the electrostatic latent image carrier outside the medium. It can be formed by transferring and forming on the surface of the medium charged in the charging step.

Even if the charge polarity of the area of the electrostatic latent image formed on the medium is the same as the charge polarity of the charge area by uniform charging of the medium surface prior to the formation of the electrostatic latent image, The polarity may be different, or 0 [V].

When the surface of the image display medium is uniformly charged to a predetermined potential in advance and an electrostatic latent image is written in the charged area, the charged developing particles in the developer storage cells can be moved. . Further, an electrostatic field sufficient to hold the moved developing particles at that position is formed. In other words, if the surface of the image display medium is uniformly charged to a predetermined potential in advance, and then the electrostatic latent image is written in the charged area, the image holding property is improved. This is particularly advantageous in terms of image retention when using a highly fluid developer or a developer whose fluidity is increased by a developer stirring process prior to image display. As a result, a high-quality image with excellent contrast can be stably displayed for a long time.

According to the various reversible image display media described above, a high-contrast, high-resolution, high-quality image can be stably displayed over a long period of time. Further, afterimages are less likely to occur, and therefore, good reversibility is exhibited. In this respect, a high-quality image can be displayed. It is possible to display images at high speed, and it is also possible to reduce the driving voltage. It is also possible to display an image with less image unevenness.

Hereinafter, specific examples of the developing particles and the developer will be described, and specific examples of a reversible image display medium, a reversible image display method, an image forming apparatus, and the like will be described with reference to the drawings. <Developing Particles and Developer> White developing particles WP 100 parts by weight of a thermoplastic polyester resin (softening point 121 ° C., glass transition point 67 ° C.), 40 parts by weight of titanium oxide (CR-50, manufactured by Ishihara Sangyo Co., Ltd.) Zinc salicylate complex (Orient Chemical: Bontron E) as a negative charge control agent
-84) 5 parts by weight were sufficiently mixed with a Henschel mixer, kneaded with a twin-screw extruder, and then cooled. The kneaded material was coarsely pulverized, then pulverized by a jet pulverizer, and classified by wind power to obtain a white fine powder having a volume average particle size of 10.1 μm. Thereafter, 0.3 parts by weight of hydrophobic silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: Aerosil R-972) were added to the white fine powder, and mixed with a Henschel mixer to obtain white developed particles WP. Black developing particles BP Styrene-n-butyl methacrylate resin (softening point 13
100 parts by weight, 2 parts by weight of carbon black (manufactured by Lion Yushi Co., Ltd., Ketjen Black) and silica (manufactured by Nippon Aerosil Co., Ltd. 200)
And 1.5 parts by weight of a magnetite-based magnetic powder (RB-BL
After 500 parts by weight (Titanium Industry Co., Ltd.) were sufficiently mixed with a Henschel mixer, the mixture was kneaded with a vented twin-screw kneader.

The kneaded product was cooled, coarsely pulverized by a feather mill, finely pulverized by a jet mill, and classified by an air classifier to obtain black particles BP having a volume average particle diameter of 25 μm. Preparation of Developer DL 30 g of the white particles and 70 g of the black particles were put in a polyethylene bottle, and mixed and stirred for 30 minutes while rotating on a ball mill base to obtain a developer DL. In this developer,
The white particles were negatively charged and the black particles were positively charged. <Reversible image display medium>-Reversible image display medium 11 The image display medium 11 is not a medium according to the present invention, but will be described for reference.

FIGS. 1 and 2 show an example of a reversible image display medium. The medium 11 shown in FIG. 1 and FIG.
1 and a second substrate 112. These substrates 11
Reference numerals 1 and 112 face each other with a predetermined gap therebetween. Partition walls 113 are provided between the substrates 111 and 112, and the partition walls 113 ensure a predetermined gap between the substrates. That is, the partition 113 also serves as a spacer between the substrates 111 and 112. The substrates 111 and 112 are connected and fixed to each other by a partition 113.

The first substrate 111 is a transparent substrate, and is formed of, for example, a light transmitting plate such as a transparent glass, a transparent resin film, or the like. This substrate 111 is a substrate on the image observation side.

The partition 113 is also provided with a developer containing cell 116.
(See FIG. 3). That is, the partitions 113 are formed upright on the inner surface of the first substrate 111 in a grid pattern as shown in FIG.
A plurality of developer accommodating cells 116 are formed in a rectangular shape with a part of 13 as a partition wall.

Each partition wall has a width α and a height h, and is formed such that the interval between adjacent partition walls is pt.

On the inner surface of the first substrate 111, the first electrode 11
4 are formed. The first electrode 114 is a transparent electrode in which a plurality of individual electrodes 114a are arranged in a grid pattern. Each individual electrode is formed of, for example, a transparent ITO film. The individual electrodes 114 a are arranged in each of the cells 116 at substantially the same interval as the thickness α of the wall 113. That is, here, one cell corresponds to one pixel.

The second substrate 112 is not necessarily required to be transparent, but is formed of, for example, a light-transmitting plate such as transparent glass, a resin film, or the like.

The second electrode 115 is provided on the inner surface of the second substrate 112 facing the first substrate 111. Second electrode 1
Reference numeral 15 is continuous over the entire image display area on the inner surface of the substrate 112. The second electrode 115 is not necessarily a transparent electrode, but may be, for example, indium tin oxide (ITO).
It may be formed on a transparent electrode formed as described above.

A dry developer DL containing white developer particles WP and black developer particles BP frictionally charged in each cell.
Is housed.

Each cell is sealed, and the developer DL does not leak from the cell.

The first electrode 1 on the image display medium 11
As shown in FIG. 4, each of the individual electrodes 114a lying laterally has a lead 110 connected thereto, and through these leads, an electrode selection circuit 117 as shown in FIG.
Connected to. A positive drive voltage generation circuit 118a, a negative drive voltage generation circuit 118b, and a display data control unit 119 are connected to the electrode selection circuit 117. A drive voltage is applied to each of the individual electrodes 114a independently from the electrode selection circuit 117, and a display data control unit 119 is provided with display data output means (not shown, such as a computer, a word processor, and a facsimile). Machine)
The display data is input from the controller and the electrode selection circuit 117 is controlled based on the display data. In other words, these electrode selection circuits and the like constitute an example of an electric field forming apparatus or an image forming apparatus for a reversible image display medium having a counter electrode.

Thus, a bias voltage is applied to the second electrode 115 of the image display medium 11 as, for example, a ground electrode or, if necessary, from a bias power supply (not shown) to the electrode 115, and the second electrode 115 is connected to each of the individual electrodes 114a. In the meantime, a predetermined voltage is applied from the positive drive voltage generation circuit 118a or the negative drive voltage generation circuit 118b via the electrode selection circuit 117 which is controlled so that a desired image is displayed by the display data control unit 119, A predetermined electric field is formed for each pixel. Thus, as shown in FIG.
At L, the developing particles WP and BP move from the state where the developing particles are mixed as shown in FIG. 2 according to the electric field.

According to the medium 11, an image can be displayed, for example, as shown in FIG. In FIG. 5, Bk is a black display portion, and W is a white display portion.

The rotating magnetic pole roller R shown by a chain line in FIG.
2 will be described later. -Reversible image display medium 12, 12 'FIG. 6 shows another example of the reversible image display medium.

The reversible image display medium 12 shown in FIG.
In the medium 11 shown in FIG. 1, at least the first substrate 111 is formed of a material having a light transmitting property and an insulating property, and the individual electrodes 114a are omitted.

In contact with the developer DL of the substrate 111 on the image observation side,
The inner surface to be touched has a surface resistivity of 1 × 10 ¹²Ω / □ or more
And the center line average roughness Ra is 0.2 μm or more and 0.5
μm or less.

Other points are the same as those of the medium 11 shown in FIG. In FIG. 6A, the same components and portions as those of the medium 11 are denoted by the same reference numerals as those of the medium 11.

The reversible image display medium 1 shown in FIG.
2 ′ is at least the second in the medium 11 shown in FIG.
The substrate 112 is formed of a material having both light transmittance and insulating properties, and the electrode 115 is omitted. In the medium 12 ', the substrate 112 is an image observation side substrate.

In contact with the developer DL of the substrate 112 on the image observation side,
The inner surface to be touched has a surface resistivity of 1 × 10 ¹²Ω / □ or more
And the center line average roughness Ra is 0.2 μm or more and 0.5
μm or less.

The other points are the same as the medium 11 shown in FIG. In FIG. 6B, the same components and parts as those of the medium 11 are denoted by the same reference numerals as those of the medium 11.

According to the medium 12 (or the medium 12 '), for example, the electrode 115 of the second substrate 112 (the electrode 114a for the medium 12') is used as a ground electrode, and further, for example, the first substrate 111 (the second electrode is used for the medium 12 '). A) arranging an electrode on the outer surface of the substrate 112) and selectively applying a voltage corresponding to an image to be formed between the electrode and the ground electrode;
b) directly forming an electrostatic latent image corresponding to the image to be formed,
c) The image carrier on which the electrostatic latent image corresponding to the image to be formed is formed is brought into contact (including proximity), and the image is displayed by applying a developing particle driving electric field to the developer DL based thereon. be able to.

The electrode 115 for the medium 12 and the electrode 114a for the medium 12 'are preferably electrodes having an intermediate resistance value. -Reversible image display medium 13 FIG. 7A shows another example of the reversible image display medium.

The reversible image display medium 13 shown in FIG.
In the medium 11 shown in FIG. 1, at least the first substrate 111 is formed of a material having a light transmitting property and an insulating property, and a first substrate electrode 114 and a second substrate electrode 115 are formed.
Is omitted.

In contact with the developer DL of the substrate 111 on the image observation side,
The surface resistivity of the inner surface to be touched is 1 × 10 ¹²Ω / □ or more
Of the inner surface of the opposite substrate 112 in contact with the developer DL.
The sheet resistivity is 1 × 10⁶Ω / □ or more 1 × 10¹²Ω / □ or less
It is.

The center line average roughness Ra of at least the inner surface of the substrates 111 and 112 that comes into contact with the developer DL is 0.2 μm or more and 0.5 μm or less.

The other points are the same as those of the medium 11 shown in FIG. 7, the same components and parts as those of the medium 11 are denoted by the same reference numerals as those of the medium 11. -Reversible image display medium 14 FIG. 8A shows another example of the reversible image display medium.

The reversible image display medium 14 shown in FIG.
In the medium 11 shown in FIG. 1, at least the first substrate 111 is formed of a material having a light transmitting property and an insulating property, and a first substrate electrode 114 and a second substrate electrode 115 are formed.
And a partition 113 composed of a plurality of partition walls 113a extending in parallel with the longitudinal side of the medium 14 is employed instead of the lattice-shaped partition (see also FIG. 9). A developer accommodating cell 116 is provided between each adjacent partition wall 113a. Each cell 116 has a developer D containing white developer particles WP and black developer particles BP frictionally charged with each other.
L is accommodated.

At the periphery of the medium 14, both substrates 111,
112 is heat-sealed to form a sealing portion 140. A portion 140a of the sealing portion 140, which is provided at both ends in the longitudinal direction of the vertical partition wall 113a and seals both ends of each cell, also serves as a partition wall forming the cell 116.

As shown in FIG. 9, each partition wall 113a has a width α and a height h, and the interval between adjacent partition walls 113a is pt.
It is formed as.

In each of the media 13 and 14, the surface resistivity of the inner surface of the substrate 111 on the image observation side which is in contact with the developer DL is 1 × 10 ¹² Ω / □ or more, and the opposite substrate 11
2 has a surface resistivity of 1 × 10
^{It is 6} Ω / □ or more and 1 × 10 ¹² Ω / □ or less.

The center line average roughness Ra of at least the inner surface of the substrates 111 and 112 which comes into contact with the developer DL is 0.2 μm or more and 0.5 μm or less.

According to the media 13 and 14, for example, a) an electrostatic latent image corresponding to an image to be formed is directly formed on the first substrate 111, and b) an electrostatic latent image corresponding to an image to be formed is formed. An image can be displayed by bringing the image carrier into contact with (including proximity to) the first substrate 111 and applying a developing particle driving electric field to the developer DL based on the contact. The second substrate 112 may be set to a ground potential or the like as necessary. -Reversible image display medium 15, 15 'FIG. 10 shows another example of the reversible image display medium.

The reversible image display medium 15 (1) shown in FIG.
5 ′) is a medium 13 (14) in which a conductive film 112A is provided on the outer surface of the second substrate 112.

In any of the media 15 and 15 ′, the surface resistivity of the inner surface of the substrate 111 on the image observation side, which is in contact with the developer DL, is 1 × 10 ¹² Ω / □ or more.
12 has a surface resistivity of 1 × 1 in contact with the developer DL.
0 ⁶ Ω / □ or more 1 × 10 ¹² Ω / □ or less.

The center line average roughness Ra of at least the inner surface of the substrates 111 and 112 that comes into contact with the developer DL of the substrate 111 is 0.2 μm or more and 0.5 μm or less.

The other points are the same as the medium 13 (14). In FIG. 10, the same components as the medium 13 (14),
Parts are given the same reference numerals as the medium 13 (14).

The image display on the mediums 15 and 15 ′ is performed by, for example, setting the conductive film 112 A to an appropriate potential such as a ground potential, and a) forming an electrostatic latent image corresponding to the image to be formed on the first substrate 1.
B) an image carrier on which an electrostatic latent image according to an image to be formed is formed is brought into contact with (including proximity to) the first substrate 111, and the developer particles are added to the developer DL based thereon. An image can be displayed by applying a driving electric field.

It is to be noted that, instead of providing the conductive film 112A, the second substrate 112 is made of a conductive material such as a substrate in which a conductive material is dispersed, and this is set to a ground potential. You may do it.

As described above, according to each image display medium described with reference to the drawings and the image display method using the same, image display and image deletion can be repeated. Also, the developing particles W
P and BP are contained in the cell, and do not require an external developer supply. Thus, the use of consumables such as a medium such as paper and a developer related to image display in the related art can be significantly suppressed. Further, since image energy does not require heat energy for fusing the toner to the medium as in the related art, the image forming energy can be reduced accordingly. Therefore, it is possible to meet today's environmental load reduction.

Since each of the media 11 to 15 'employs the dry developer DL containing the developing particles WP and BP having different colors, the other developing particles BP (or BP) formed by one developing particle WP (or BP) are used. Or WP), the degree of concealment is good, and an image can be displayed with good contrast.

The developing particles W contained in the cell 116
P and BP are frictionally charged to different charging polarities,
In the image display, it is easy to move due to the Coulomb force, and in this regard, the image can be displayed with good contrast, the afterimage of the previous display hardly occurs, the image can be displayed at a high speed, and the driving at a low voltage is possible.

Further, since the dry developer DL is employed as the developer, sedimentation and agglomeration of the developing particles are less likely to occur.
As a result, a decrease in contrast in image display is small and stable image display can be performed for a long period of time. Since the sedimentation and aggregation of the developing particles hardly occur, the afterimage of the previously displayed image is hardly generated. Since the dry developer DL has little change with time, stable image display can be performed for a long time in this respect as well.

In particular, in the medium 12 (12 '), the substrate 111 (112) on the image observation side where no internal electrode is provided.
In the case where an electrostatic latent image is formed on the
The inner surface of the substrate 111 (112) in contact with the developer DL of (12 ′) has a surface resistivity of 1 × 10 ¹² Ω / □ or more, so that the electrostatic latent image formed on the substrate can be held well. , It can display high quality images.

In the medium 12 (12 '), the substrate 111 (112) on the image observation side on which no internal electrode is provided.
The center line average roughness Ra of the inner surface of
Since it is m or less, unnecessary and strong adhesion of the developing particles to the substrate can be suppressed, and a high-quality image can be displayed by suppressing the occurrence of an afterimage.

In the case where an electrostatic latent image is formed on the image observation side substrate 111 on which the internal electrodes of the media 13, 14, 15, and 15 'are not provided and an image is displayed, the medium contacts the developer DL of the substrate 111. Since the inner surface has a surface resistivity of 1 × 10 ¹² Ω / □ or more, the electrostatic latent image formed on the substrate can be favorably held, and further, the surface resistivity of the inner surface of the substrate 112 that contacts the developer DL. Is 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹² Ω /
□ Because of the following, the displayed image can be stably held even when the image display media are overlaid, and afterimages are less likely to occur in image erasing or image rewriting, and the occurrence of image unevenness can be suppressed. Thus, high-quality images can be displayed.

Also, the center line average roughness Ra of at least the inner surface of the mediums 13, 14, 15, 15 ', which are not provided with the internal electrodes and which comes into contact with the developer DL of the substrate 111, is 0.2 μm or more. Since the thickness is 0.5 μm or less, unnecessary and strong adhesion of the developing particles to the substrate can be suppressed, and a high-quality image can be displayed by suppressing the occurrence of an afterimage.

[0176] Any of the media 11 to 15 'can display images with higher resolution than conventional electrophoretic displays and the like. In other media except the medium 11, since the resolution does not depend on the size of the pixel electrode 114a unlike the medium 11, an image can be displayed at a higher resolution.

Next, the media 12, 12 ', 13, 14, 1
An example of displaying an image using 5, 15 'will be described together with an image forming apparatus.

The image forming apparatus shown in FIG. 11 includes a photosensitive drum PC which is driven to rotate in the direction of the arrow in the figure. A scorotron charger CH is provided around the photosensitive drum PC.
A laser image exposure apparatus EX and an eraser lamp IR are arranged. An electrode roller R1 that is driven to rotate is disposed below the photosensitive drum PC. The electrode roller R1 is a developing electrode roller for forming an electrostatic field for displaying an image. A bias voltage can be applied to the roller R1 from the power supply PW1. The roller R1 may include a rotating magnetic pole roller R2 that is driven to rotate in the opposite direction to the roller R1 (or is driven to reciprocate).

The surface of the photosensitive drum PC is charged to the charger CH.
Then, the charged area is image-exposed by an exposure device EX to form an electrostatic latent image EI on the drum PC.
On the other hand, a bias is applied to the electrode roller R1 from the power supply PW1. In some cases, the electrode roller R1 may be set to the ground potential.

Then, the electrostatic latent image EI on the photosensitive drum PC
For example, the medium 13 or 14 is fed between the drum and the electrode roller R1 in synchronization with the above. At this time, the medium 13
The surface of (14) is uniformly charged to a predetermined potential in advance by a charger CRH such as a corona charger.

Thus, each cell 11 of the medium 13 (14)
An electrostatic field based on the electrostatic latent image EI is formed on the developing particles BP and WP of the developer DL contained in the developer 6, and the developing particles are formed by Coulomb force acting between the electrostatic field and the charged developing particles. Moves. Then, FIG. 7 (A) or FIG.
(A) As shown in FIG.
FIG. 7B or FIG. 8 when the BP is mixed.
As illustrated in (B), the white particles WP and the black particles BP each move according to the electric field. Thus, an image can be displayed with a predetermined contrast.

After the image is displayed as described above, the charge on the surface of the photosensitive drum PC is erased by the eraser lamp IR in preparation for the next print.

It is not always necessary to previously charge the surface of the medium 13 (14) with the charger CRH.

In this image display, the magnetic pole roller R
2 is provided, and when this is rotated, the developer DL in each cell 124 is agitated, and the developing particles BP and WP are easily moved, so that a better image can be displayed and the driving voltage can be reduced. Become.

The medium 11 shown in FIGS. 1 and 2 also has a rotating magnetic pole roller R as shown by a chain line in FIG.
2 can be adopted.

Instead of the magnetic pole roller R2, a magnet plate MG having alternately N poles and S poles is provided downstream of the medium conveyance path as exemplified by a chain line in FIG. A magnetic field may be formed.

Images can also be formed on the media 12, 12 'and the media 15, 15' by this image forming apparatus. When forming an image on the medium 12 or 15, instead of using the electrode roller R1, the second electrode 115 is
For 2 ′, the pixel electrode 114a is connected to the medium 15, 15 ′.
With regard to the above, the conductive film 112A can be grounded, or a bias can be applied thereto.

The image forming apparatus shown in FIG. 12 includes an ion flow type direct electrostatic latent image forming apparatus CR2. Device CR
2 is a corona ion generator c for generating corona ions
2 and corona ions generated in the generating section
3 (or 14) of the writing electrode e2 for leading to the surface of the first substrate 111, and a voltage for leading positive (or negative) corona ions to a pixel corresponding portion of the surface of the substrate 111 in accordance with an image to be displayed. A write electrode control circuit f2 for applying a voltage to the write electrode e2.

The corona ion generating portion c2 is provided in the shield case c21.
A corona wire c22 is formed by stretching a gold-plated tungsten wire having a diameter of 20 μm, and a positive (or negative) voltage (for example, 4 kV to 10 kV) is applied to this wire from a power source Pc2 to generate corona ions.

The write electrode e2 is connected to the medium 13 (or 1
4) The shield case c2 directed to the first substrate 111
1 and includes an upper electrode e21 and a lower electrode e22, through which a corona ion flow can pass.

The electrode control circuit f2 includes a control power supply Pc21,
Including a bias power supply Pc22 and a control unit f21,
The control unit f21 outputs an ion extraction voltage corresponding to the polarity of ions to be extracted toward the medium 13 to the electrodes e21 and e2.
2 can be applied.

Here, when a positive voltage is applied to the upper electrode e21 and a negative voltage is applied to the lower electrode e21 under the instruction of the controller f21, positive corona ions can be guided to the medium (FIG. 12A). . When a negative voltage is applied to the upper electrode e21 and a positive voltage is applied to the lower electrode e21, positive corona ions can be confined (FIG. 12B).

Further, an electrode roller R1 is provided so as to face the writing electrode e2, and a bias voltage is applied to the electrode roller R1 from the power supply PW1, or the roller R1 is set to the ground potential. The roller R1 incorporates a magnetic pole roller R2 that is driven to rotate.

Thus, the surface of the medium 13 (or 14) is uniformly charged in advance to a predetermined potential by a charger such as a corona charger, and the medium 13 (or 14) thus precharged is moved relative to the device CR2. Moving the electrode roller R1 in the medium feed direction and rotating the magnetic pole roller R2 in the opposite direction while moving the first substrate in accordance with the image to be displayed, under the instruction of the control unit f21. As shown in FIG. 12A, a positive corona ion is led to a predetermined pixel corresponding portion corresponding to an image to be displayed among a plurality of pixel corresponding portions on the surface of the surface 111, and FIG.
As shown in FIG. In this way, an image can be displayed on the medium 13 or 14 as illustrated in FIG. 7B or FIG. 8B.

It is not always necessary to charge the surface of the medium 13 (14) in advance.

The discharge wire c2 in the device CR2
2 can be replaced by a solid discharge element.

Images can be formed on the media 12, 12 'and the media 15, 15' by this image forming apparatus. When forming an image on the medium 12 or 15, instead of using the electrode roller R1, the second electrode 115 is
For 2 ′, the pixel electrode 114a is connected to the medium 15, 15 ′.
In this case, the conductive film 112A may be grounded or an appropriate bias may be applied thereto.

Further, the electrostatic latent image forming apparatus CR2 shown in FIG.
Uses the discharge phenomenon, but in addition to these devices,
Various discharge-type electrostatic latent image forming apparatuses can be used.

The image forming apparatus shown in FIG. 13 includes a multi-stylus type direct electrostatic latent image forming apparatus CR3. The device CR3 includes, for example, a multi-stylus head H3 having a plurality of electrodes e3 arranged in the main scanning direction with respect to the medium 15 (or 15 ′) and arranged close to the first substrate 111. A signal voltage is applied to apply an electrostatic latent image charge to a portion corresponding to a pixel on the surface of the first substrate 111 according to an image to be displayed on each electrode e3. Medium 15 (15 ')
For example, a bias is applied to the conductive film 112A of the second substrate 112, for example, or the conductive film 112A is grounded.
Then, the sheet is conveyed relatively to the head H3, whereby an image is displayed.

It should be noted that images can be formed on the mediums 12 and 12 'by this image forming apparatus. In that case, medium 1
A bias may be applied to the second electrode 115 or the electrode 114a of the medium 12 'as necessary.

Also, with respect to the media 13 and 14, an image can be formed by this image forming apparatus by bringing an external electrode to which a bias can be applied or grounded into contact with the outer surface of the second substrate 112 as necessary.

The image forming apparatus shown in FIG. 14 includes a charge injection type direct electrostatic latent image forming apparatus CR4. Device CR4
Is a multi-stylus type device having an electrostatic recording head H4 in which a plurality of recording electrodes e4 are arranged in the main scanning direction with respect to the medium, and adjacent control electrodes e41 are arranged adjacent to the recording electrodes e4. This head is arranged, for example, close to the medium, and a voltage of about の of the voltage (recording voltage) required for image recording is sequentially applied to the control electrode e41 of the head H4 sequentially, and the recording voltage of about 1 is applied to the recording electrode e4. By applying an image signal voltage of / 2, an electrostatic latent image can be formed on the medium located immediately below the recording electrodes.

Next, further specific examples of the reversible image display medium and image display using the same will be described. (Reversible image display medium D1) A medium of the same type as the reversible image display medium 13 shown in FIG. 7 and formed as follows.

That is, a 100 μm-thick film-shaped ultraviolet curable resin was brought into close contact with a first substrate 111 made of a transparent PET (polyethylene terephthalate) film having a thickness of 25 μm, and openings were formed in a predetermined pattern on the resin. A photomask was covered, and ultraviolet light was irradiated from above. Thereafter, development and washing were performed to form lattice-shaped partition walls 113 (see FIG. 3) on the substrate 111. Each partition wall 113a forming the partition wall 113 has a thickness (width) α = 50 μm, a height h = 100 μm, and a wall interval pt = 1 mm. This substrate 111 is a substrate on the image observation side (forms an electrostatic latent image).

Next, a surfactant solution was applied to the surface of the substrate 111 on which the partition walls 113 were formed, and dried to adjust the resistance.

The developer DL was put in each concave portion of the substrate 111 surrounded by the lattice wall 113. The developer was added so that the volume ratio of the developer contained to the volume of the concave portion was 30%.

Then, a photocurable adhesive 119a (see FIG. 7) is thinly applied only to the top surface of the wall 113 on the first substrate 111, and a PET film containing carbon black having a thickness of 25 μm is applied as the second substrate 112. The film was adhered to the adhesive, and the adhesive was cured by ultraviolet irradiation to adhere the film.

Thereafter, the periphery of the first and second substrates 111 and 112 was heat-sealed instead of being sealed with the epoxy resin adhesive 119b (see FIG. 1) shown in FIG.

Thus, a medium D1 of the type shown in FIG. 7 was obtained. (Reversible image display media D2 to D11) Except that the surface resistivity of the inner surface in contact with the developer DL of the substrate 111 on the side where an electrostatic latent image is formed is different, or further, the developer of the opposite substrate 112 The mediums D2 to D11 are the same as the medium D1 except that the inner surface in contact with the DL has different surface resistivity. (Reversible image display media D12 to D15) The same media D12 to D15 as the media D1 and the like except that the surface roughness of the surface of the substrate 111 that contacts the developer DL is variously different from that of the media D1 and the like.
It is. The surface roughness was varied by blasting, hot pressing and the like.

Table 1 summarizes the surface resistivity of the developer contact surfaces of the substrates 111 and 112 of each medium and the center line average roughness Ra of the developer contact surfaces of the substrate 111.

Note that, for any of the media D1 to D15, the surface roughness Ra of the developer contact surface of the substrate 112 is equal to 0.1.
25 μm.

[0212]

[Table 1]

FIG. 1 shows each of the media D1 to D15.
Flow-type direct electrostatic latent image forming apparatus CR2 shown in FIG.
The image was displayed by an image forming apparatus including

More specifically, the surface of the first substrate 111 is uniformly charged in advance to a negative potential (-500 V) by a corona charger (not shown), and the second substrate 112 of the precharged medium is grounded. A positive corona ion is guided to a predetermined pixel corresponding portion corresponding to an image to be displayed among a plurality of pixel corresponding portions on the surface of the first substrate 111 of the medium by setting the potential to a potential, and the portion is set to a positive potential, and Then, it was charged to a potential (+500 V) having the same absolute value as the above-mentioned negative charging potential (-500 V), and only the bias potential (ground potential here) was applied to the other pixels. As a result, the portion charged by the positive coronaine on and the portion which is not charged are set to the same potential (500 V) in absolute value, and
They were charged with opposite polarities. Thus, the image was displayed such that the portion on which the positive corona ions were superimposed was displayed white by the negatively chargeable white developing particles WP, and the portion where the positive corona ions were not superimposed was displayed black by the positively charged black developing particles BP. .

The image display is performed by using the magnetic pole roller R2.
Was rotated to exert a stirring action on the developing particles in the medium to smoothly display an image.

The contrast of the image formed using each of the media D1 to D15 was evaluated, and the initial image in image formation using each medium, the image after repeated image formation, and the stability thereof (the occurrence of an afterimage was suppressed). Evaluation).

The contrast was evaluated by measuring the image densities of the black portion and the white portion with a reflection densitometer (reflection densitometer manufactured by Konica: Sa
(Kura DENSIMETER PDA-65) and evaluated by the average concentration ratio. When the reflection density ratio was 5.0 or more, it was evaluated as good (○), and when the reflection density ratio was lower than that, it was evaluated as poor (x).

The evaluation of the repetition stability was performed by comparing the average image density in the initial formed image with the average image density in the 50th formed image in which the image was repeatedly formed. The change in average image density between the initial image and the 50th image is 0.2 or less, which is good (０．２), and larger than that is bad (×)
And

The surface resistivity was measured by ASTM D-25.
According to No. 7, it was measured under a 65% RH environment.

The center line average roughness Ra of the substrate was measured using a surface roughness measuring device Surfcom 554A (manufactured by Tokyo Seimitsu Co., Ltd.) and a soft material roughness measuring pickup E-DT-S02A.
It measured using.

The results of the image evaluation are shown in Table 2.

[0222]

[Table 2]

As can be seen from Table 2, when an electrostatic latent image is formed and an image is displayed, the surface resistivity of the surface of the substrate on which the electrostatic latent image is to be formed is 1 × 10 ¹² Ω / □. The above is appropriate, and the surface resistivity of the surface of the opposite substrate that comes into contact with the developer is suitably 1 × 10 ⁶ Ω / □ to 1 × 10 ¹² Ω / □.

The same can be said for image display media of the same type as the media 14, 15, 15 '.

The surface roughness of at least one of the substrates, particularly the surface of the substrate on the image observation side, which is in contact with the developer, is suitably 0.2 μm or more and 0.5 μm or less as the center line average roughness Ra. I understand.

The media 12, 12 ', 14, 15, 1
The same is true for image display media of the same type as 5 '.

[0227]

As described above, according to the present invention, image display and image erasure can be repeatedly performed, so that image display media such as paper, developer,
The use of consumables such as ink can be reduced, and a reversible image display medium capable of responding to today's environmental load reduction can be provided.

Also, according to the present invention, high contrast
Thus, a reversible image display medium capable of displaying a high-quality image can be provided.

Further, according to the present invention, image display is performed at a higher resolution than conventional electrophoretic image display media and twisted ball type image display media, and based on an electrostatic latent image without using a counter electrode. Then, it is possible to provide a reversible image display medium capable of displaying an image with higher resolution and higher quality.

Further, according to the present invention, it is possible to provide a reversible image display medium capable of displaying images stably for a long period of time.

Further, according to the present invention, it is possible to provide a reversible image display medium which hardly generates an afterimage and therefore exhibits good reversibility and can display a high-quality image also in this respect.

Further, according to the present invention, it is possible to provide a reversible image display medium requiring a low drive voltage for image display.

In particular, when an image is displayed by forming an electrostatic latent image, the surface resistivity of the surface of the substrate on which the electrostatic latent image is formed, which is in contact with the developer, should be 1 × 10 ¹² Ω / □ or more. In this case, the electrostatic latent image formed on the substrate can be satisfactorily held, and a high-quality image can be displayed accordingly.

When an image is displayed by forming an electrostatic latent image, the surface resistivity of the surface of the substrate on the side opposite to the substrate on which the electrostatic latent image is formed, which is in contact with the developer, is 1 × 10 ^6. When the value is Ω / □ or more and 1 × 10 ¹² Ω / □ or less, the displayed image can be stably held even when the image display media are overlaid,
Afterimages are hardly generated in image erasing or image rewriting, image unevenness can be suppressed, and a high-quality image can be displayed accordingly.

Further, the center line average roughness R of at least one substrate, for example, the surface of the image observation side substrate that comes into contact with the developer is used.
When a is 0.2 μm or more and 0.5 μm or less, unnecessary and strong adhesion of the developing particles to the substrate can be suppressed, and the generation of an afterimage can be suppressed, and a high-quality image can be displayed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a reversible image display medium with a counter electrode before image display.

FIG. 2 is a cross-sectional view of the medium shown in FIG. 1 in an image display state.

FIG. 3 is a perspective view of a first substrate and a grid-like partition formed on the first substrate in the medium shown in FIG. 1;

FIG. 4 is a plan view of a first substrate and individual electrodes formed on the first substrate in the medium shown in FIG.

FIG. 5 is a diagram showing an example of image display on the medium shown in FIG. 1;

6A is a cross-sectional view of another example of the reversible image display medium, and FIG. 6B is a cross-sectional view of still another example of the reversible image display medium.

7A and 7B show still another example of the reversible image display medium. FIG. 7A is a cross-sectional view of the reversible image display medium before displaying an image, and FIG. It is sectional drawing of an example.

8A and 8B show still another example of the reversible image display medium. FIG. 8A is a cross-sectional view of the reversible image display medium before displaying an image, and FIG. It is sectional drawing of an example.

FIG. 9 is a plan view showing a part of the medium shown in FIG.

FIG. 10A is a sectional view of still another example of the reversible image display medium, and FIG. 10B is a sectional view of still another example of the reversible image display medium.

FIG. 11 is a diagram illustrating a schematic configuration of an example of an image forming apparatus including an external electrostatic latent image forming apparatus.

FIG. 12 is a diagram showing a schematic configuration of an example of an image forming apparatus including an ion flow type direct electrostatic latent image forming apparatus.

FIG. 13 is a diagram illustrating a schematic configuration of an example of an image forming apparatus including a multi-stylus type direct electrostatic latent image forming apparatus.

FIG. 14 is a diagram illustrating a schematic configuration of an example of an image forming apparatus including a multi-stylus type electrostatic latent image forming apparatus having adjacent control electrodes.

[Explanation of symbols]

Reference Signs List 11 reversible image display medium 111 first substrate 112 second substrate 113 partition 113a partition wall α partition wall thickness pt adjacent partition wall interval h partition wall height 114 first electrode 114a individual electrode (pixel electrode) 115th 2 electrode 116 developer storage cell 110 lead part 117 electrode selection circuit 118a positive drive voltage generation circuit 118b negative drive voltage generation circuit 119 display data control unit DL developer WP white developing particles BP black developing particles Bk black display part W white Display part 12, 12 ', 13, 14, 15, 15' Reversible image display medium 140 Sealing part 140a Part of sealing part 120 112A Conductive film PC Photoreceptor drum CH Scorotron charger EX Laser image exposure device IR eraser Lamp R1 Electrode roller R2 Rotating magnetic pole roller PW1 Bias power supply CRH Charger MG Magnet plate CR2 Ion flow type direct electrostatic latent image forming device c2 Corona ion generator e2 Write electrode f2 Write electrode control circuit c21 Shield case c22 Corona wire Pc2 Power supply e21 Upper electrode e22 Lower electrode Pc21 Control power supply Pc22 Bias Power supply f21 Control unit CR3 Multi-stylus type direct electrostatic latent image forming apparatus e3 Electrode H3 Multi-stylus head CR4 Multi-stylus type electrostatic latent image forming apparatus with adjacent control electrodes e4 Recording electrode e41 Control electrode H4 Electrostatic recording head

Continued on the front page (72) Inventor Akihito Ikeside 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Masaharu Kanazawa 2-chome, Azuchi-cho, Chuo-ku, Osaka-shi, Osaka No. 3-13 Osaka International Building Minolta Co., Ltd. (72) Inventor Nozomi Yome 2-3-13 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Inventor Ryuji Kurita Osaka 5-2232-3-2-2-1116 Sayama, Osaka Sayama City

Claims (4)

[Claims] 1. Two or more substrates facing each other at a predetermined gap, one or two or more developer storage cells formed between the two substrates and surrounded by a partition wall. And a dry developer encapsulated in a cell, wherein the dry developer has at least two types of dry developing particles having triboelectric charging properties having different charging polarities and different optical reflection densities. Forming an electrostatic latent image corresponding to an image to be formed on one of the two substrates, thereby driving the developing particles with an electric field based on the electrostatic latent image to form an image. A reversible image display medium capable of displaying, wherein a surface resistivity of a surface of the substrate on which the electrostatic latent image is formed and which is in contact with the developing particles is 1 × 10 ¹² Ω / □ or more. 2. A method according to claim 1, wherein: two substrates facing each other with a predetermined gap therebetween; one or more developer storage cells formed between the two substrates and surrounded by a partition wall; And a dry developer encapsulated in a cell, wherein the dry developer has at least two types of dry developing particles having triboelectric charging properties having different charging polarities and different optical reflection densities. Forming an electrostatic latent image corresponding to an image to be formed on one of the two substrates, thereby driving the developing particles with an electric field based on the electrostatic latent image to form an image. The surface resistivity of a surface of the other substrate facing the substrate on which the electrostatic latent image is formed and contacting the developing particles is 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹² Ω / □ or less. Characteristic reversible image display medium. 3. two or more substrates facing each other at a predetermined gap; one or more developer storage cells formed between the two substrates and surrounded by a partition wall; And a dry developer encapsulated in a cell, wherein the dry developer has at least two types of dry developing particles having triboelectric charging properties having different charging polarities and different optical reflection densities. Forming an electrostatic latent image corresponding to an image to be formed on one of the two substrates, thereby driving the developing particles with an electric field based on the electrostatic latent image to form an image. The substrate on which the electrostatic latent image is formed has a surface resistivity of 1 × 10 ¹² Ω / □ or more, which is in contact with the developing particles, and the other substrate facing the substrate on which the electrostatic latent image is formed Has a surface resistivity of 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹² Ω
/ □ or less. 4. Two or more substrates facing each other at a predetermined gap, one or two or more developer storage cells formed between the two substrates and surrounded by a partition wall. And a dry developer encapsulated in a cell, wherein the dry developer has at least two types of dry developing particles having triboelectric charging properties having different charging polarities and different optical reflection densities. A center line average roughness Ra of a surface of at least one of the substrates contacting the developing particles is 0.2 μm or more;
A reversible image display medium having a size of 5 μm or less.