JP4129480B1 - Optical image storage method and display sheet used therefor - Google Patents

Abstract

There is no ultra-thin electronic paper that can form a bright monochrome or clear-color full-color image with a simple configuration. At least one of the transparent papers has fine particles in a gas or liquid medium. A display sheet is formed by sandwiching the dispersion system dispersed in the substrate, and the particles corresponding to the light image are moved by an electric field corresponding to the light image irradiated from the substrate provided with the transparent electrode on the inner surface. The present invention relates to a light image storage method characterized by creating a spatial distribution state and obtaining a light image perpendicular to a substrate and a display sheet used therefor, cyan particles sensitive to red as fine particles, magenta color sensitive to green By mixing and dispersing particles and yellow particles sensitive to blue, it is possible to irradiate a color light image and form a bright full-color positive image. Figure FIG. 1

Description

    At least one of them forms a display sheet by sandwiching a dispersion system in which fine particles are dispersed in a dispersion medium between transparent substrates, and an optical image irradiated from the transparent substrate provided with a transparent electrode on the inner surface. Correspondingly, the fine particles are moved by an electric field that is perpendicular or / and horizontal to the substrate to create a spatial distribution state of the particles corresponding to the optical image, thereby obtaining an optical image perpendicular to the substrate. Further, the present invention relates to a display sheet used therefor, and a full color image can be easily formed by mixing and dispersing C, M, and Y particles.

The demand for electronic paper that is thin, lightweight, easy to read and has low power consumption is extremely high. A cholesteric liquid crystal that changes the reflected color by spatially separating two colored particles by applying an electric field to a dispersion system in which fine particles of different colors and charge polarities are mixed and dispersed in an insulating liquid or gas body. Those using selective reflection, etc. have been put into practical use, and any of them is useful as a low power display device having a memory property that can maintain display even after the voltage is turned off. However, in order to display text information and image information, the panel and driver circuit are complicated, and a battery for switching the display must be mounted, and an ultra-thin and flexible one such as paper has not been developed. In addition, there is a strong demand for a full-color display that is bright and excellent in color purity. However, there is no reflective type that can realize a display comparable to a printed matter or a photograph in brightness and color purity.

As a light-input type electronic paper that forms a memory image corresponding to the irradiated light image without using a complicated XY matrix panel and driver configuration, a photoconductive layer, a liquid crystal such as cholesteric or electrochromic (EC) In addition, a method has been proposed in which a voltage is applied while irradiating an optical image on the layer stack to change the reflection state of the cholesteric layer or the EC layer in accordance with the optical image (Patent Documents 1 and 2). For color display, these three layers can be stacked and added color mixing by selective reflection at each cholesteric layer or subtractive color mixing of the stacked EC layers, but the multilayer structure makes the sheet structure complicated and sufficiently satisfactory. It has been difficult to realize a super thin sheet with good properties. In addition, those using selective reflection of cholesteric liquid crystal have a reflectivity of 50% or less in principle, making it difficult to realize a bright display.

Patent Literature: A method of forming an image by applying a voltage while irradiating a light-sensitive fine particle dispersion system and changing the charged state of the fine particle to create a spatial distribution state of particles corresponding to the incident light image It is stated in 3. However, in order to obtain an image with favorable contrast, a colored layer different from the color of the particles is provided on the substrate sandwiching the dispersion system, or when using bright particles, the dispersion medium is kept in a dark state, and the positive image is incident on the light image. It was inconvenient to observe from the opposite side. Basically, it looks at the particle image deposited on either side of the substrate, necessitates troublesome operations such as removing the dispersed particles with a transparent liquid, and forms a full-color image on the sealing sheet. No method was mentioned at all.

In Patent Documents 4 and 5, the first fine particles dispersed in the medium are irradiated with light to be charged, and the particles are moved by an electric field perpendicular to the substrate surface to conceal the moved particles by the second particles. (1) Use of particles charged by light irradiation (2) Color image is formed by C, M, Y color first particle group and white second particles, but C, M, Y particles Is charged with colored light that is not the main absorption wavelength. (3) Irradiates a light image from the back. (4) Sequential exposure for each colored light. (5) The particle dispersion medium is characterized by a gas body.

In Patent Document 6, a mixed particle system having different colors and charging polarities is sandwiched between electrodes provided with a photoconductive layer on one side, and the light image is selectively moved by applying voltage and irradiating the light image, thereby obtaining a light image. (1) Light image irradiation from the back side (2) Color image formation is characterized by a color addition method using a black and white particle dispersion system and R, G, B color filters provided on the display surface side.

JP 1995-199214 JP2002-040488 USP 4043655 JP2001-34200 JP2002-236298 JP2004-347719

The present invention relates to a light image storage method for changing the spatial distribution state of fine particles in a dispersion system into an image shape by using both light image incidence and voltage, and a display sheet used therefor, and stores the image with a simple sheet configuration. It is possible to reversibly form monochrome, multi-color and full-color images. Since the sheet on which the image is formed is not attached with any drive circuit or power source, it can be used in various fields as a monochrome or full-color ultra-thin display sheet that can update the display content exactly repeatedly.

    In order to solve the above-described problem, in the present invention, a dispersion system in which fine particles are dispersed in a medium is sandwiched between at least one transparent substrate, and the inner surface of each of both substrates or one of the inner surfaces thereof. It is configured so that a voltage can be applied to a pair of provided electrodes, and the fine particles are moved by an electric field corresponding to the light image irradiated from the transparent substrate side, so that light reflectivity or light transmission in a direction perpendicular to the substrate is achieved. The present invention relates to an optical image storage method characterized by changing the temperature and a display sheet used therefor

As shown in FIG. 1A, the optical image storage sheet of the present invention comprises a display sheet 5 composed of a spacer 9 provided between two substrates 1 and 2 that are transparent at least one of glass and plastic film. Between the substrates, a dispersion system 8 in which photosensitive fine particles 6 are dispersed in a dispersion medium 7 is filled. A transparent electrode 3 such as indium oxide is provided on the inner surface of the transparent substrate 1, and a transparent or opaque lower electrode 4 is provided on the inner surface of the lower substrate 2, so that a DC or AC voltage can be applied between the two electrodes. It is configured.

For example, if a DC voltage is applied between the electrodes in the dark state (first step) as shown in FIG. 1A, if the photosensitive fine particles 6 are negatively charged, the photosensitive fine particles 6 will be coulombic. It moves by being pulled by the anode 3 by the action of force, and is deposited on the anode 3. If a light image is irradiated (second step) as shown in FIG. 1B through the transparent substrate 1 and the transparent electrode 3 with voltage applied, if the photosensitive fine particles 6 are, for example, photoconductive, the electrical resistance of the particles. As a result of the charge being transferred to the anode and positively charged, the particles move toward the negative electrode 4 to form a particle distribution as shown in FIG. If the dispersion medium 7 is colored, for example, white and opaque, if the sheet 5 is viewed from the transparent substrate 1 side in the state of FIG. 1 (B), the region irradiated with light exhibits white, which is the color of the dispersion medium. The area where the light has not been exposed appears to be the color of the photosensitive fine particle 6, and if the photosensitive fine particle 6 is black, a positive image corresponding to the light image is observed. After the image is formed, light image irradiation and voltage application are unnecessary, and the formed image is maintained by the adhesion force of the particles to both electrodes after the voltage is removed, and is free from power consumption. It goes without saying that the halftone can be reproduced because the amount of particles toward the negative electrode 4 depends on the intensity of the irradiated light.

In the above, the photosensitive particles are accumulated on the transparent electrode in the first step ⇒ In the second step, an image is formed by a two-step process of light image irradiation in the state of voltage application. You may implement. This is because as soon as the negatively charged particles irradiated with light reach the electrode part, they transfer charges one after another to invert the charge, and toward the counter electrode, while in the unirradiated part, the particles are successively deposited on the electrode. When an appropriate particle distribution is achieved, voltage application and light image irradiation are stopped, but the particle distribution is maintained by the adhesion of the particles to both electrodes. This is called a one-step process.

The dispersion medium used in the present invention may be a liquid body such as various hydrocarbon-based insulating organic solvents and silicon oil, or a gas body such as air or nitrogen. In order to make the dispersion medium white, a white pigment such as titanium dioxide may be dispersed in the dispersion medium. However, if the charged polarity of the dispersed white pigment is the same as that of the non-irradiated photosensitive fine particles 6, it moves in the same manner as the photosensitive fine particles, and reduces the light energy irradiated to the photosensitive fine particles during light image irradiation. It is desirable that the white pigment is not charged, or has a mobility smaller than that of light-irradiated and unirradiated particles, or has the same polarity as that of the light-irradiated particles but much smaller mobility.

The particle distribution state in FIG. 1 (B) can be inverted as shown in FIG. 1 (C) by applying a reverse polarity pulse having an appropriate peak value and duration. That is, it means that negative / positive inversion of the input light image is possible. Although the dispersion medium has been described as being white, any color can be obtained by dissolving the dye or dispersing the pigment, and the color of the photosensitive particles and the colored dispersion medium so that the formed image can be easily seen visually. It is desirable to select them so that they have contrast in brightness or hue. The cell thickness is usually about several μ to 100 μ, the particle size of the photosensitive particles is about 50 nm to 10 μ, and the applied voltage is usually several volts to several thousand volts.

With fine particles that are not sensitive to normal light intensity, a particle distribution state as shown in FIG. 1A can be realized in a bright place. In this case, if a light image having a considerably higher intensity than that under normal illumination light is used, both the one-step process and the two-step process may be performed in a bright place. By performing ultraviolet light image irradiation using particles that are not sensitive to visible light but sensitive to ultraviolet light, both step processes can be performed under visible light.

If a transparent substrate is used for the back substrate 2 and the lower electrode 4, a light image may be irradiated from the back surface, and the light image forming operation can be easily performed in a bright place. In the case of back exposure, if black fine particles are dispersed in a white medium, a negative image is formed on the display surface side, but a negative light image may be irradiated or a reverse polarity voltage may be applied in the third step. Even when white light-sensitive fine particles are dispersed in a black dispersion medium, a positive image can be obtained by irradiation with a positive light image.

When a handwritten memo sheet is constructed by the optical image storage method of the present invention, if it is drawn with light stronger than illumination light using an electronic pen incorporating a laser diode (LD), LED element, etc., it should be handled in a bright place. Can be a rewritable electronic sheet.
Of course, it is possible to irradiate a light image by forming or closely exposing the display of a flat panel electronic display device such as a liquid crystal with backlight or an electroluminescence display device on the transparent electrode surface from the display surface side or the back surface side of the sheet. Alternatively, the line light image and the display sheet may be moved relative to each other in the vertical direction to sequentially irradiate the line light image.

FIG. 2 shows a light image storage method for forming a full-color image and a display sheet used therefor. The difference from FIG. 1 is cyan (C) colored particles having sensitivity to at least red (R) as photosensitive particles 6. Magenta (M) color particles sensitive to green (G) color and yellow (Y) color particles sensitive to blue (B) color are mixed and dispersed. The main absorption wavelengths of the C, M, and Y particles are R, G, and B light, and at least three kinds of fine particles that are sensitive to the respective absorption main wavelengths are mixed and dispersed.
It is desirable that each color particle has a charge of the same polarity when not irradiated with light. Either a one-step process or a two-step process may be used, and if a full-color image is irradiated with a voltage applied, the particle distribution corresponding to the color of the light image as shown in FIG. Achieved. In other words, the area irradiated with white appears almost white as it is directed to the lower substrate as a result of the C, M, and Y particles reversing the charge and hidden behind the white dispersion medium, and three colors are displayed in the black area not irradiated with the light image. Since the particles remain in the transparent electrode 3 as they are, the subtractive color mixture becomes black. The R (G, B) light irradiation area is a mixed color of M (C, Y), Y (M, C) particles remaining on the electrode 3 after moving only the C (M, Y) particles to the back surface. ) Present a color. In the C (M, Y) light irradiation region, the particles remaining on the electrode 3 are only C (M, Y) particles, and a positive image corresponding to the light image is formed. Multi-color display is obtained in a mixed dispersion system of two kinds of particles having different colors and sensitive wavelengths.

Patent Document 4 and Patent Document 5 propose a method in which C, M, Y and white particles are dispersed in a gas medium, and a light image is formed by light image irradiation and voltage application.
However, the C, M, and Y particles are charged by receiving colored light that is not each absorption main wavelength, optical image irradiation is fundamentally different from the present application in terms of light image irradiation from the back and light image irradiation in sequential exposure for each color light. In other words, in the case of particles charged at a wavelength other than the absorption main wavelength, such as C particles charged by G and B light, M particles charged by R and B light, Y particles charged by R and G light, for example, B (R, G) In light irradiation, C, M (M, Y; C, Y) particles move to the display surface side and certainly become positive B (R, G) color, but in white light irradiation, C, M, and Y particles are both This is because the display surface moves to the display surface and becomes black and reversed. Even when irradiated with C light (B + G light), M light (B + R light), or Y light (G + R light), the C, M, and Y particles move and become black, so that the simultaneous exposure is decent. This is because a color image cannot be formed.

In order to reproduce a color image in FIG. 2, a color image once irradiated is converted into a light image in the ultraviolet to blue region, and C, M, and Y color particles having sensitivity in the corresponding wavelength range are used to obtain a sufficiently bright place. However, in order to store the color image as it is in a bright place on the display sheet, it is necessary to sufficiently increase the intensity of the irradiation color image or to irradiate the color light image from the substrate 2 side.

When a full-color display storage device as shown in FIG. 2 is used as a handwritten electronic sheet, a selection switch is used by using a pen containing an R, G, B-LD or LED and an optical system for condensing the emitted light on the transparent electrode section. What is necessary is just to comprise so that a voltage can be applied between the electrodes of a sheet | seat while selecting a color and drawing a pattern on this electronic sheet | seat.

In order to erase the image, it is possible to erase the entire surface by applying a DC voltage sufficient for the particles to leave the electrodes to make the entire surface white or black, or by making the entire surface gray with an AC voltage. If any of the electrodes 3 to 4 is divided into strips or grids, a DC or AC voltage can be selectively applied between the divided electrode and the counter electrode to perform partial erasure corresponding to the shape of the divided electrode. is there.

If the electronic pen has a writing pressure detection function and is configured so that a voltage is applied between both electrodes at a predetermined writing pressure or higher, power consumption that continues to apply voltage to the display sheet during periods when drawing is not possible Image damage can be avoided.

A two-dimensional color image or a one-dimensional color image of a liquid crystal or electroluminescence display device is used as an input light image, and a light image is irradiated by imaging or closely exposing to a transparent electrode surface from the display surface side or back side of the sheet. What may be done is as described in (0016).

When black photosensitive particles are mixed with C, M, and Y particles, black reproducibility can be improved. The black photosensitive particles are panchromatic having sensitivity in the entire wavelength range of visible light and charged in the same polarity as the photosensitive particles in the dark.

1 and 2 describe the optical image storage method in which photosensitive particles are moved by a vertical electric field, the particles can also be moved by a horizontal electric field (lateral electric field).

FIG. 3 describes an optical image storage method using the horizontal electric field method and a sheet used therefor. A partition 10 is provided between an insulating transparent substrate 1 such as a plastic film or glass and the substrate 2 and is filled with a dispersion system 8 to form a cell 13. The transparent electrode 3 and the substrate 2 side are formed on the inner surface of the substrate 1. Are provided with electrodes 4 made of fine wires as shown in FIGS. The electrode 4 is connected to all the cells of the display sheet 5, and the display sheet together with the electrode 3 is handled as a two-terminal element.

When the photosensitive fine particles 6 dispersed in the cell are black light-absorbing and the dispersion medium is transparent, when the particles 6 are uniformly dispersed in the cell as shown in FIG. It is black opaque. When a light image is irradiated from the upper transparent substrate side while applying a DC voltage so that the electrode 3 becomes an anode between the electrodes 3 and 4, when the photosensitive fine particles 6 are negatively charged, the particles are applied to the anode 3. Collected, the charge is exchanged with the anode 3 to be positively charged and deposited on the linear electrode 4 toward the negative electrode 4. In the horizontal electric field method, since the dispersion medium is usually used in a transparent state, in this cell, the only thing that blocks light is the black particle layer deposited on the thin line. If this light absorption cross-section is small, the cell is substantially light transmissive. become. On the other hand, in the cell where no light is applied, the particles remain deposited on the electrode 3, so if the particles are uniformly deposited on the electrode 3 of the cell, it becomes opaque black, and a positive image is formed in a one-step process. Become.
Of course, a two-step process in which particles are once collected on the electrode 3 (FIG. 3 (C)) and a light image is irradiated while maintaining the voltage may be adopted, and a positive image is formed as shown in FIG. 3 (B). .

The electrode 4 may be opaque, and it is important to deposit the particles as thick as possible to minimize the light absorption cross section in order to increase the transmittance of the bright part as much as possible.

In the particle movement in the configuration of FIG. 3, a vertical and horizontal electric field are used in combination with the substrate, but for convenience it will be referred to as a horizontal (lateral) electric field method. The same applies hereinafter.

The linear electrode as shown in FIG. 4 is a thin film obtained by patterning a metal or transparent conductor such as aluminum, chromium, gold, tantalum or indium oxide by vapor deposition or sputtering, and patterned by photo treatment, or conductive paint, and ink jet drawing. For example, the conductive thick film may be provided. The width of the linear electrode is about several μ to several tens μ.

In order to form a full-color image on a horizontal electric field type display sheet, as described in (0018), cyan (C) color particles and green (G) color having sensitivity to at least red (R) color as photosensitive fine particles. Magenta (M) color particles having sensitivity to yellow and yellow (Y) color particles having sensitivity to blue (B) may be mixed and dispersed. It is desirable that each color particle has a charge of the same polarity when not irradiated with light. If the dispersion medium is transparent and the lower substrate side is white, a color positive image can be formed as in FIG.

Conventional electronic color image formation is (1) a combination of R, G, B juxtaposed color filters and a light valve that can be modulated in black and white (2) a three-layer stacked type of selective reflection layers for R, G, B light (3) C , M, Y modulation layer has to be realized in a three-layer laminated type. In (1), it was difficult to reduce the resolution and the light utilization rate. In (2) and (3), the panel configuration is inevitably complicated. In this application, the color of one cell can be arbitrarily changed according to the color of the irradiated light image by mixing and dispersing C, M, Y particles regardless of vertical type or horizontal type, thus overcoming the conventional difficulties. It is bright with a simple structure, excellent in color purity, and can form high-resolution images.

Although common to the vertical electric field method and horizontal electric field method, the transparent electrode on the light irradiation side is made of conductors, semiconductors, insulators, etc. to facilitate charge transfer with the light irradiated particles or to suppress charge transfer As necessary, the charge transfer control layer and the counter electrode side also include a charge blocking layer made of a conductor, semiconductor, insulator, etc., a threshold providing layer for stably depositing particles, and a conductive protrusion for converging the electric field on the electrode. It may be provided as appropriate.

Although it has been described that the charge polarity changes due to charge exchange with the electrode as a result of light irradiation in a liquid or gas dispersion medium, changes in the charge state of the light-irradiated particles (increase / decrease in charge amount, reversal of charge polarity, etc.) ) May occur not only by charge transfer with the electrode, but also by charge transfer with the dispersion medium, components in the dispersion medium, the substrate, and other dispersed particles. In the present application, the phenomenon in which the charged state of the fine particles is changed by light irradiation regardless of the presence or absence of an electric field (thus, the moving direction, the moving speed, the adhesion force to the electrode, etc.) is called a photoelectrophoresis phenomenon in a broad sense. The display sheets of FIGS. 1, 2, 3 and 5 of the present application use the photoelectrophoresis phenomenon for light image formation regardless of the vertical electric field type or the horizontal electric field type.

The following four cases can occur as the behavior when the photosensitive particles deposited on the electrode or dispersed in the dispersion medium absorb light regardless of the presence or absence of an electric field. 1) Polarity changes before light absorption (moving speed may be increased or decreased depending on the amount of charge): Named first particle group. 2) Those that have little charge absorb light and are charged positively or negatively: Name the second particle group 3) Charge amount increases with the same polarity as before light absorption (thus improving movement speed) ): Named the third particle group 4) Reduced charge amount with the same polarity as before light absorption (thus including the case where the moving speed is reduced and the charge disappears): Named the fourth particle group.

In the present application, all the first to fourth particle groups can be used for display using the vertical electric field configuration and the horizontal electric field configuration.
For example, if a voltage that attracts particles charged by light irradiation to the electrode 4 using the configuration shown in FIG. 1 or 3 is applied to the second particle group, a positive image is formed in one step.
In addition, when a voltage that attracts particles whose charge amount has been increased by light irradiation to the electrode 4 is applied to the third particle group using the configuration of FIG. 1 or FIG. 3, a positive image is formed in a one-step process. Become a negative statue

The second particle group and the fourth particle group can be effectively used in a transverse electric field configuration cell as shown in FIG. In FIGS. 5A and 5E, a pair of electrodes in a comb shape, a vortex shape, or the like as shown in FIGS. 4D to 4F is used. In the display sheet using the second particle group as shown in FIG. 5A, if a voltage is applied between the electrodes 3 and 4 to deposit the particles obtained by irradiating light to obtain the electric charge, it is positive in a one-step process. An image is obtained. The electrodes 3 and 4 in FIG. 5A may be provided on different substrates, or may be provided on the lower substrate. On the contrary, in the case of the fourth group particles, if a voltage for depositing unirradiated particles on the electrode 4 is applied, the particles that have lost their charge due to light irradiation maintain the dispersed state, and thus a negative image can be obtained in a one-step process. In the configuration shown in FIG. 5C, the electrodes 3 to 4 having the shapes shown in FIGS. 4A to 4C are used, but the electrode 3 is preferably transparent. Image formation is possible as in FIG. All of the cells having the configuration shown in FIG. 5 are opaque in a particle dispersion state and transparent in a state where particles are accumulated on a thin wire electrode.

In the present invention, the particle dispersion state means not only the colloidal state in which fine particles are stably uniformly dispersed in the liquid regardless of the specific gravity difference due to the Brownian motion, but also any one of the inner surfaces of the substrates 1 and 2 and the electrodes 3 and 4 or a part of both surfaces. This includes a state in which most of the particles are loosely adhered and a state in which the particles are loosely aggregated with each other to form a three-dimensional network structure between the electrodes or the substrates.

The transmittance in the bright state at the time of particle accumulation in the transverse electric field configuration cell will be described with reference to FIG. Assuming that all the particles in the cell filled with the dispersion system in which the photosensitive fine particles are dispersed at a concentration at which sufficient covering properties are obtained are accumulated on the upper substrate, the thickness of the particle layer at this time is d, which is a pixel. Let S be the area of the cell (A). In a bright state where the total area of the fine line-like electrode 4 that accumulates particles viewed from the display surface of one pixel is Δs and all the dispersed particles are accumulated in Δs, the thickness h of the particle layer on the electrode 4 is d * S / Δs. (B). The bright state is realized by maximizing S-Δs, that is, minimizing Δs. Δs / S is defined as the area ratio of the particle integrated electrode 4. If the area ratio is 10% and 20%, a transmittance of about 90% and 80% can be realized. However, the thickness h of the particle layer on Δs at this time is 10 times and 5 times of d, respectively. That is, a high transmittance can be realized by stacking particles as thick as possible on the integrated electrode 4 having an extremely small area, and the above high performance can be realized with a thin particle layer as d is small, that is, a particle having a high hiding power is used. . The concealing force should be selected so that the particle size is deeply related and the concealing force becomes high, as well as the characteristics of the particles themselves.

In order to stack the particles thickly in a minimum area Δs, the electrode 4 is provided on both substrates as shown in FIG. 5 (E) in addition to thinning the electrode 4 to converge the electric field. Since particles can be deposited on both electrodes (FIG. 5 (F)), the effect is the same as when the particles are deposited twice as thick, and contributes to a reduction in light absorption cross-section as viewed from the display surface (improvement of transmittance). .

Although an example of using photosensitive particles to form a spatial distribution of particles corresponding to a light image by light image irradiation has been described, particles can also be moved according to a light image by providing a photoconductive layer on the electrode surface. It is possible to make it.

FIG. 7 shows a light image sheet having this configuration. That is, it is similar to the light image sheet of FIG. 1 except that the transparent photoconductive layer 11 is provided on the transparent electrode 3.
A display system is configured by sandwiching a dispersion system in which particles of a different color from this are dispersed in an opaque dispersion medium between a pair of electrodes via a photoconductive layer.
If necessary, a uniform voltage of the wavelength felt by the transparent photoconductive layer is irradiated through the transparent electrode, and a DC voltage is applied in a state where the resistance value of the transparent photoconductive layer 11 is lowered to accumulate the fine particles 6 on the electrodes 3 to 4 ( If a DC voltage having a reverse polarity is applied while irradiating a light image (second step), the photoconductive layer of the light irradiating portion has a higher electric conductivity, so that a stronger electric field is distributed. Thus, the particles in this region move and deposit more quickly toward the opposite electrode, and an image is formed. In the case of a dispersion system in which charged black particles are dispersed in a white dispersion medium, a positive image is formed when black particles are deposited on the light image non-irradiated side, and in the opposite case, a negative image is formed.

When the dispersion medium is liquid, the dispersion medium 7 can be colored by dissolving the dye or dispersing the pigment. When the dispersion medium is a gas body, it is realized by dispersing fine particles having high fluidity.

The configuration in which the transparent photoconductive layer 11 is provided on the transparent electrode 3 of the horizontal electric field cell of FIG. 3 can also be used as a useful optical image storage display sheet. As in FIG. 7, in the light irradiation part, the electrical conductivity of the photoconductive layer is increased, so that charge transfer between the photoconductive layer and the particles is promoted, or a stronger electric field acts on the dispersed particles regardless of the presence or absence of photosensitivity. Thus, rapid particle movement can be realized, and the particle distribution can be made different from that of the non-light-irradiated part due to the difference in particle movement speed, so that a light image can be formed. In the case of the lateral electric field type sheet having the structure shown in FIG. 5, if a photoconductive layer is provided on the transparent electrode 3, an image can be formed even if non-photosensitive fine particles are used.

In Patent Document 6, a particle dispersion system having different charging characteristics and colors is sandwiched between transparent electrodes provided with a photoconductive layer, and image distribution is realized by applying voltage and light image irradiation to realize particle distribution corresponding to the light image. A method of forming is described. However, the light image irradiation is only from the back surface, and therefore it is essential that both the opposing electrode and the substrate are transparent, and the light image irradiation is performed from the display surface side by providing a transparent photoconductive layer on the display surface side. Since there is no mention of how to do this, it is unsuitable for applications such as drawing while viewing the display with an electronic pen.

In the case of the configuration of FIG. 7 in which a photoconductive layer is provided on the electrode, the fine particles need not be photosensitive, but can also be effectively used in the case of photosensitive particles. That is, a DC voltage is applied so that the photosensitive particles are attached to the photoconductive layer side in the same manner as in FIG. Illuminate the image. The particles irradiated with light, for example, facilitate charge transfer with the photoconductive layer having high conductivity and quickly become reverse polarity particles toward the electrode 4, but the electrical resistance of the photoconductive layer of the light irradiation portion decreases. As a result, a strong electric field is distributed to the dispersion system in this part, and as a result, the reversely polarized particles are promptly directed to the electrode 4 and an optical image is stored.

The photoconductive layer is transparent and panchromatic, and cyan (C) color particles having sensitivity to at least red (R) as light sensitive particles, and magenta (M) color having sensitivity to green (G) color. Needless to say, if yellow (Y) particles having sensitivity to blue (B) color are used, a full color image can be formed not only in the vertical electric field type shown in FIG. 7 but also in the horizontal electric field type cell structure shown in FIGS. Yes.
Even if the particles show any state of the first to fourth particle groups by light irradiation, by selecting the voltage pulse height, width, and polarity, the resistance reduction of the photoconductive layer can be used together, so the contrast is excellent. An image can be formed quickly.

Although common to the optical image storage sheets of FIGS. 1, 2, 3, 5, and 7, the state in which the photoconductive layer and the photosensitive particles are irradiated with light does not last forever. The time from the suspension of light irradiation and voltage application to the return of the charged particle state to the state before light irradiation is mainly determined by the properties of the photosensitive particles, dispersion medium, electrode, substrate, etc. As a matter of course, optical image formation should be finished within the time constant, and the pulse width of the applied voltage should be less than the time constant.

In the above cell configuration, an example in which all voltages for moving particles are performed using an external power source has been described. If a photovoltaic layer that generates voltage by light irradiation is provided, a display sheet that does not require an external power source can be configured.

If a photovoltaic layer is provided instead of the photoconductive layer in FIG. 7, the particles move according to the magnitude, polarity and polarity of the generated electromotive force corresponding to the incident light image pattern, and an image can be formed. . If the photovoltaic layer is transparent, it can be provided on the display surface side, and if it is opaque, it is provided on the back side, and a light image is irradiated from the back side. The present invention can also be applied to a horizontal electric field type cell as shown in FIGS.

If the photovoltaic layer is transparent and panchromatic and the fine particles are light sensitive, then a full color image can be formed using not only monochrome but also C, M, Y light sensitive particles. Even if the particles show any state of the first to fourth particle groups by light irradiation, the charged state of the photosensitive particles and the electromotive force of the photovoltaic layer are different between the light irradiation part and the non-irradiation part. By selecting the polarity and the polarity of the electromotive force, a positive or negative image can be selectively formed.

The photoconductive layer and the photovoltaic layer may be separated for each pixel (cell).

Although common to the optical image storage sheets of FIGS. 1, 2, 3, 5, and 7, the adhesion force to the electrode surface of the particles irradiated or not irradiated with light, that is, the threshold value, greatly affects image formation. This change in threshold value can be used effectively for image formation. For example, if there is a difference in the adhesion force on the electrode surface between the irradiated particle and the unirradiated particle (threshold property of electrode desorption when a reverse polarity voltage is applied), even if the charged polarity of the irradiated particle does not change It can be used effectively for image formation. When the threshold voltages of the light-irradiated particles and the unirradiated particles are set to V1 and V2, respectively, and a reverse polarity voltage V of V2> V> V1 is applied, only the light-irradiated particles are promptly directed toward the counter electrode, It can be deposited or dispersed. On the other hand, since the particles in the non-irradiated portion remain on the electrodes, the spatial distribution of the particles changes and an image is formed. On the other hand, at a voltage of V1> V> V2, on the contrary, the particles in the non-irradiated part quickly leave the electrode, and the negative / positive image is reversed. In order to erase the image, it is necessary to apply a reverse polarity DC voltage pulse or AC voltage equal to or higher than a threshold value at which the deposited particles on the electrode can once leave the electrode between the electrodes 3 and 4.

Although common to the optical image storage sheets of FIGS. 1, 2, 3, 5, and 7, in order to maintain the uniformity of the particle concentration within the sheet surface, a partition (partition) is provided between the substrates, and the dispersion system is a small rectangular parallelepiped or cylinder. It is desirable to confine them in a cell made of hexagonal columns or the like, or to confine the dispersion in capsule particles. FIG. 8A shows an example in which a cell is formed by providing partition walls between substrates, and FIG. 8B shows an example in which a dispersion system is confined in a capsule. A space other than capsule particles between electrodes is a transparent binder. Filled with resin 15.

In order to achieve excellent image contrast, it is desirable that the partition wall 10 has a thickness that is as thin as possible because the color does not change, and that the area ratio (aperture ratio) of the color change region is as high as possible.

Since whiteness is an important factor in electronic paper display, it is desirable that at least the side of the partition where the display is viewed is white. In the case of capsule particles, since the thickness of the capsule wall made of an organic resin is usually less than a micron, there is a merit that the partition wall is sufficiently thin. In FIG. 8B, the capsule is drawn as a sphere, but if the substrate gap is made smaller than the diameter of the capsule and each capsule is transformed into a rectangular parallelepiped as shown in FIG. 8C, the aperture ratio is improved. Contribute to.

In the case of using microcapsule particles, both substrates are fixed via a binder resin, but also in the case of a partition-type sheet, it is desirable that both substrates are fixed on the surface in contact with the partition.

Since the resolution depends on the cell size in the display sheet of the present application, the size of the cell or capsule particle should be about several tens of μ to about 100 μ in applications where high resolution is desired. When the cell pitch is 100 μm, an almost satisfactory resolution of 2970 × 2100 pixels (623.7 million pixels) can be obtained with A4 size (297 × 210 mm). Depending on the application, the cell pitch and capsule particle size may be larger. One pixel may be composed of many partition type cells or capsule particles.

1 and 2, the method of performing handwritten drawing display using an electroluminescent pen for photoimage formation has been described. The lateral electric field type sheet of FIGS. 3 and 5, the photoconductive layer or photovoltaic layer utilization sheet of FIG. Needless to say, it can also be applied.

If the display sheet of the present invention is formed on both sides of the substrate, for example, it can be used as a double-sided display sheet. FIG. 9 shows an example of a double-sided display sheet.
For example, a double-sided display sheet provided with display sheets on both sides as shown in FIGS. 1, 2, 3, 5, 7, and 8 uses paper or the like as a lower substrate, and preferably forms a permeation preventive layer for moisture, gas, etc. on both sides. A lower electrode is formed thereon, and a dispersion system is sandwiched between this electrode and two transparent plastic films provided with a transparent electrode, and the periphery is sealed with a spacer. Even if the electrode has a four-layer structure with electrodes on both substrates, the electrodes 3 can be connected to each other and the sheet can be connected to the outside as a two-terminal element. The optical images may be formed on both sides simultaneously or separately.

In order to save and bring a plurality of display sheets on which images are formed, whether a single-sided display sheet or a double-sided display sheet, in a loose-leaf format, a binding margin and a binding hole are provided outside the display area as shown in FIG. Easy to use. The display sheet of the present application can be constituted by a double-sided display sheet of about 240 μm, for example, even if the base paper is about 100 μm paper, the front substrate is about 20 μm plastic film, and the dispersion thickness is about 50 μm. Of course, it is also possible to make each of them thinner and have a thickness of about 100 μm, which is about the same as the thickness of a normal book or magazine, and it is possible to realize a flexible electronic display sheet that is literally suitable for being called electronic paper in terms of thickness and feel. .

When a plastic film or paper is used as the substrate material of the display sheet used in the present invention, the feature of continuous mass production by roll-to-roll can be exhibited.
FIG. 11 shows an example of manufacturing a display sheet by roll-to-roll. A roll-like film on which electrodes and the like are formed in advance is supplied from an upper roll, and for example, capsule particle ink dispersed in a binder resin is applied by printing or the like. On the other hand, both substrates are affixed so that there are no air bubbles left between the lower film substrate provided with a sealant such as UV seal resin, spacers, electrodes, etc. by punching holes for electrode extraction and printing or inkjet drawing. Combined with UV irradiation to fix. A binding hole 16 can be provided by punching or the like, or a sheet display sheet can be continuously produced by cutting into pieces. Of course, a long scroll type display sheet may be configured.

Although FIG. 11 shows an example of manufacturing a single-sided display sheet, it is of course possible to manufacture a double-sided display sheet by roll-to-roll.

Although the upper and lower substrate films are supplied in FIG. 11, the display sheet can be manufactured by roll-to-roll with a single roll film. In other words, as shown in FIG. 5 (A), the electrode may be only one side substrate. A display sheet can be obtained by printing a dispersion layer in the form of capsule particles or the like on a film provided with electrodes at a predetermined position and applying a transparent protective resin thereon.

In the partition type panel configuration, the partition is formed on the film with a photoresist or the like, or the film and the like that are pre-cured by applying a UV curable resin are embossed to form the partition and the cell, and then are fully cured to fill the dispersion system. It is also possible to manufacture a partition-type film panel by roll-to-roll by sealing with a pair of electrode-attached films.

The material used for this invention is described.
Various photosensitive fine particles described in US Pat. No. 3,384,488 can be used. That is, organic pigments such as anthoraquinone, quinacridone, azo, phthalocyanine, and triazine, amorphous silicon (a-Si), zinc oxide (ZnO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride Inorganic pigments or fine particles such as (CdTe) and selenium (Se) can be used. Even if the colorant fine particles have no photosensitivity, they can be used as photosensitivity colorant toner particles embedded in a resin medium together with the photosensitivity particles, or the particles can be coated with a photosensitizer such as a transparent photoconductor. Can be used. An encapsulated color material solution or color material dispersion system can also be used as fine particles, and the surface of the capsule particles may be coated with a photo-sensitive material such as a photoconductive agent in order to develop photo-sensitivity. The fine particles can be surface-modified by surface coating at the atomic or molecular level, or can be imparted with chargeability and good dispersibility by using a dispersant, a surfactant or the like.

In the dispersion system in which the dispersion system 8 in which fine particles for coloring and light-sensitive fine particles dispersed in a gas body such as air or nitrogen are dispersed has little resistance to selective movement of the light-sensitive particles, it has a high response speed. A display panel is possible, and the sheet can be solidified. It is known that the formation of minute irregularities on the surface of the fine particles further increases the fluidity, and that the surface treatment of the particles with a silane coupling agent or silicon oil is effective for controlling the chargeability and improving the fluidity.

As the photoconductive layer material, the same material as the photosensitive fine particles, or polyvinyl carbazole as the transparent photo semiconductor layer can be used. When the dispersion medium is a liquid, the specific gravity of the particles to be dispersed is desirably substantially equal to that of the dispersion medium. In the case of inorganic particles having a large specific gravity, it is effective to lower the apparent specific gravity as a toner form embedded in a resin having a small specific gravity.

Photovoltaic layers include various semiconductors such as phthalocyanine, pigments, organic semiconductors such as amorphous silicon, zinc oxide, titanium oxide, cadmium selenium, cadmium tellurium, gallium arsenide and other p-type and n-type PN junctions, PIN A bonding layer is used. In order to increase the photovoltaic power, a large number of p-n junctions are stacked and used.

When the dispersion medium is liquid, a variety of solvents such as silicon, petroleum, and halogenated hydrocarbons can be used. If the value is lowered, image formation and erasure are possible.

The present invention has the following effects.
Using a sealing sheet with a fine particle dispersion sandwiched between a pair of electrodes, using light image irradiation and voltage application together to create a spatial distribution of particles corresponding to the light image, light image erasure and new light image formation The optical image storage method and the display sheet used therefor are characterized in that they can be repeated, and full color formation is possible using C, M, and Y photosensitive fine particles. The display sheet can be as thin as paper, and when it is attached to a display rewriting machine that can generate a light image and a voltage to be applied to the sheet only when the display is updated, the image can be updated instantaneously. The paper can be used in various fields such as an electronic newspaper, an electronic book, a price tag, a poster, an advertisement signboard, a bulletin board, an electronic memo pad, an electronic painting, a menu sheet, a catalog, an IC card, and an OHP sheet.

FIG. 3 is a cross-sectional view and a principle explanatory view of a vertical electric field type optical image storage sheet of the present invention. FIG. 3 is a cross-sectional view and a principle explanatory view of a vertical electric field type full color optical image storage sheet of the present invention FIG. 2 is a transverse sectional view and a principle explanatory view of a horizontal electric field type optical image storage sheet of the present invention. Is a front view of the linear electrode used in FIG. Is another example of the horizontal electric field type optical image storage sheet of the present invention Sectional drawing showing the transmittance | permeability of the bright state of the horizontal electric field type | mold optical image memory sheet of this invention FIG. 2 is a cross-sectional view and a principle explanatory view of a light image storage sheet using the photoconductive layer of the present invention. Is a cross-sectional view of a cell configuration in which a dispersion system is separated by partition walls or encapsulation used in the present invention. FIG. 3 is a cross-sectional view of a double-sided storage sheet in which the optical image storage sheet of the present invention is provided on both sides of a base paper. Is an example of a display sheet provided with a binding hole for storing a plurality of display sheets of the present invention in a loose-leaf format Is an example of a process diagram for producing the display sheet of the present invention by roll-to-roll

Explanation of symbols

1: Transparent substrate 2: Lower substrate 3: Transparent electrode 4: Lower electrode 5: Display sheet 6: Photosensitive fine particles 7: Dispersion medium 8: Dispersion system 9: Spacer 10: Partition wall 11: Photoconductive layer 12: Photomask 13 : Cell 14: Capsule particle 15: Binder 16: Binding hole

Claims (10)

At least one of them forms a display sheet by sandwiching a dispersion system in which photosensitive fine particles are dispersed in a dispersion medium between a pair of transparent substrates, and a voltage is applied to a pair of electrodes provided on the substrate. In the photoelectrophoretic optical image forming method in which a light image is irradiated from the transparent substrate while being applied, the charged state of the light-irradiated fine particles is changed, and the fine particles are moved in accordance with the light image, the dispersion medium includes: It is transparent, at least one of the electrodes is made of a fine line electrode, and the other electrode is made of a transparent electrode, and the photosensitive fine particles are moved in a horizontal direction on the substrate and selectively deposited on the fine line electrode. Optical image storage method characterized in that a light image is obtained by modulating the light transmittance of the display sheet 2. The optical image storage method according to claim 1, wherein a transparent photoconductive layer or a transparent photovoltaic layer is provided on the transparent electrode. 3. The optical image storage method according to claim 1, wherein at least two types of photosensitive fine particles having different light wavelengths and different colors are mixed. Optical image storage 4. The optical image storage method according to claim 1, wherein the light-sensitive fine particles include at least cyan particles sensitive to red, magenta particles sensitive to green, and yellow particles sensitive to blue. 5. Optical image storage method 5. A double-sided storage display sheet, wherein the display sheet used in the optical image storage method according to claim 1 is configured to store optical images on both front and back sides. The display sheet according to any one of claims 1 to 5, wherein the dispersion system is filled in cells formed by partition walls provided between the substrates, or is confined in capsule particles. Display sheet The display sheet according to any one of claims 1 to 6, wherein the display sheet is manufactured roll-to-roll. The optical image storage method according to any one of claims 1 to 7, wherein the optical image is obtained by forming an optical image displayed on a liquid crystal or an electroluminescence display device in a one-dimensional or two-dimensional manner on the display sheet. Optical image storage method characterized by irradiation The optical image storage method according to claim 1, wherein the optical image is drawn by a pen having an electroluminescent element built therein. 10. A color light image storage method according to claim 9, wherein the pen is configured to selectively generate different color lights.

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