JP2006322971A - Electronic paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electronic paper enabling an observer to easily recognize visually that rewriting of an image has been normally carried out. <P>SOLUTION: The electronic paper 100 is constituted so that a dimmer layer 101 is arranged on an image display layer 102 having a memory function. When an image on the image display layer 102 is rewritten, an AC voltage is applied from an AC power source 107A to the dimmer layer 101 to make the dimmer layer 101 white, and the contrast of the image on the image display layer is temporarily lowered. Then, as time elapses, the dimmer layer 101 becomes transparent and the image on the image display layer 102 is displayed clearly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic paper having a light control layer.

  In recent years, a display recording medium (referred to as electronic paper or digital paper) having both the advantages of electronic display and paper has attracted attention as a display recording medium, in addition to paper media and electronic display devices.

Since this display recording medium has a memory property with respect to display, it is only necessary to apply writing energy by the image writing apparatus only when information is rewritten, and energy application for maintaining display is unnecessary. Therefore, after the information is written, only the display recording medium is separated from the image writing apparatus, and the information can be easily carried like a paper medium, stacked, arranged, or read by hand (for example, Patent Document 1). reference).
JP 2001-301233 A

  However, according to the conventional electronic paper, since the rewriting operation is performed in a very short time, the image before and after the rewriting is similar, for example, when only a part of a character or image is rewritten. There is a problem that it is difficult to visually recognize that the rewriting has been normally performed.

  Accordingly, an object of the present invention is to provide an electronic paper that allows an observer to easily recognize that image rewriting has been performed normally.

  In one embodiment of the present invention, in order to achieve the above object, an image display layer having a memory property and a light transmittance or reflectance change by applying a voltage are displayed on the image display layer. Provided is an electronic paper comprising a light control layer for adjusting the contrast of an image.

  When rewriting an image on the image display layer, the contrast of the image display layer is temporarily lowered using the light control layer, and the contrast is gradually increased after the image is rewritten, so that the image can be rewritten normally. It is possible to easily see what has been broken.

  As the light control layer, various materials such as a nematic polymer dispersion type liquid crystal, an electrochromic display element, a guest host liquid crystal, and a configuration in which positively or negatively charged particles are arranged in a dispersion liquid can be used.

  The light control layer may be provided on the observation side of the image display layer or may be provided on the opposite side of the image display layer from the observation side. By providing the light control layer on the observation side of the image display layer, the degree of freedom in driving the light control layer is increased.

  As a light control layer provided on the side opposite to the observation side of the image display layer, a transparent substrate positioned on the image display layer side, a counter substrate disposed facing the transparent substrate, and a transparent substrate disposed between the transparent substrate and the counter substrate Alternatively, a configuration may be provided that includes a first color liquid and a positively or negatively charged second color particle group that is provided in the liquid and moves between the transparent substrate and the counter substrate in accordance with an electric field. For example, when black is used as the first color and white is used as the second color, the contrast of the image displayed on the image display layer is lowered by moving the particle group to the transparent substrate side, and the liquid is transparent. By moving to the substrate side, the contrast of the image is improved.

  Further, as a light control layer provided on the side opposite to the observation side of the image display layer, a transparent substrate located on the image display layer side, a colored counter substrate disposed to face the transparent substrate, a transparent substrate and a colored counter substrate A structure including a liquid crystal layer disposed between and changing to a transmission state or a non-transmission state according to application of a voltage may be used. According to this configuration, the contrast of the image displayed on the image display layer is lowered by making the liquid crystal layer non-transmissive, and the contrast of the image is improved by making the liquid crystal layer transmissive.

  As the image display layer, a photo-writing display element including a pair of electrodes, a liquid crystal layer provided between the pair of electrodes, and a photoconductive layer may be used. When a voltage is applied to a pair of electrodes and pattern light corresponding to an image signal is applied to the photoconductive layer, the resistance value of the photoconductive layer decreases due to light irradiation, the partial pressure of the liquid crystal layer increases, and light reflection occurs. Since the rate increases, an image due to a change in light reflectance is displayed.

  The image display layer includes a pair of electrodes and a particle group having a predetermined charging characteristic that moves between the pair of electrodes in accordance with an electric field formed between the pair of electrodes by applying a voltage between the pair of electrodes. Alternatively, a toner display type display element may be used. By applying a voltage to the pair of electrodes, an electric field is generated between the pair of electrodes, the particles move according to the direction of the electric field, and an image is displayed by the particles attached to one of the pair of electrodes. The

  As the image display layer, a transmission / scattering display layer such as a ferroelectric liquid crystal can be used.

  The image display layer and the light control layer preferably share an electrode located between the image display layer and the light control layer. Thereby, a structure can be simplified.

  Both the image display layer and the light control layer may be operated by an AC power supply or may be operated by a DC power supply. Thereby, the structure of a power supply circuit can be simplified.

  In addition, the light control layer can use the same thing as the said image display layer. In addition to the above, as the image display layer and the light control layer, a thermal recording medium using a leuco dye, a liquid crystal having a memory property typified by a ferroelectric liquid crystal, and an electric for switching a display by moving charged particles. Display devices such as an electrophoretic method, a particle rotating method in which charged particles are rotated to switch display, and a magnetophoretic method in which particles are moved by magnetism to switch display may be used.

  According to the present invention, it is possible for an observer to easily recognize that image rewriting has been performed normally.

[First Embodiment]
(Structure of electronic paper)
1A and 1B are cross-sectional views of an electronic paper according to a first embodiment of the present invention. This electronic paper 100 is an image display layer 102 having a memory property, and a light control layer 101 which is located on the surface side (observation side) and whose light transmittance (reflectance) changes when an AC voltage is applied. With.

(Configuration of image display layer)
The image display layer 102 is an optically writable display element. As shown in FIGS. 1A and 1B, a pair of transparent substrates 106B and 106C made of PET (polyethylene terephthalate) films arranged opposite to each other, and their Reflectivity (transmittance) changes depending on a pair of transparent electrodes 105B made of ITO (indium tin oxide) provided on the inner side and an applied voltage between the pair of transparent electrodes 105B provided on the inner side thereof. Liquid crystal layer 111B in which cholesteric liquid crystal 108 is sealed in binder resin 104B, organic photoconductive layer 110 provided inside transparent electrode 105B on the back side, and light provided between liquid crystal layer 111B and organic photoconductive layer 110 It consists of an absorption layer 109.

(Configuration of light control layer)
As shown in FIGS. 1A and 1B, the light control layer 101 includes a transparent substrate 106A made of a PET film disposed to face the transparent substrate 106B provided on the surface side of the image display layer 102, and The pair of transparent electrodes 105A made of ITO provided inside the transparent substrates 106A and 106B, and the transmittance (reflectance) varies depending on the voltage applied between the pair of transparent electrodes 105A provided inside them. The liquid crystal layer 111A includes a nematic PDLC 103 sealed in a binder resin 104A.

  The nematic PDLC 103 has negative dielectric anisotropy, and, as shown in FIG. 1A, in a state where an AC voltage is applied from the AC power source 107A, the incident light is arranged in parallel with the transparent electrode 105A. As shown in FIG. 1B, the incident light is reflected and aligned vertically with respect to the transparent electrode 105A when no AC voltage is applied as shown in FIG.

(Operation of electronic paper)
Next, the operation of the electronic paper 100 will be described with reference to FIGS. 1 and 2. 2A and 2B show temporal changes in the states of the image display layer 102 and the light control layer 101, FIG. 2A shows image rewriting tamming of the image display layer 102, and FIG. 2B shows a change in transmittance of the light control layer 101. (C) shows the change in contrast of the observed image.

(1) Time t0
As shown in FIG. 2A, the time t0 represents the time when the image (previous image) before the screen of the electronic paper 100 is rewritten is displayed. FIG. 1B shows the state at time t0.

  At time t0, no voltage is applied to the light control layer 101, and the nematic PDLC 103 is arranged perpendicular to the transparent electrode 105A and transmits incident light. At this time, the image displayed on the screen of the electronic paper 100 viewed from the observer is the image itself displayed on the image display layer 102, and the contrast at that time is 100%.

(2) Time t1
The time t1 represents the time at the moment when the screen of the electronic paper 100 is rewritten. FIG. 1A shows the state at time t1.

  In the image rewriting, an AC voltage is applied to the pair of transparent electrodes 105B of the image display layer 102 from the AC power source 107B, and pattern light corresponding to the image signal is irradiated from the back side of the electronic paper 100 to the organic photoconductive layer 110. Is done. When the organic photoconductive layer 110 is irradiated with pattern light, the resistance value of the portion of the organic photoconductive layer 110 irradiated with light decreases, the partial pressure of the liquid crystal layer 111B increases, and the light reflectance increases. An image due to a change in light reflectance is displayed.

  When an AC voltage is applied from the AC power source 107A to the dimming layer 101 at time t1 or just before that time, the nematic PDLC 103 is arranged in parallel to the transparent electrode 105A and reflects incident light. At this time, the image displayed on the screen of the electronic paper 100 viewed from the observer is white, and the contrast ((maximum reflectance−minimum reflectance) / minimum reflectance) is about 0% with respect to the maximum contrast. It is.

(3) Time t1 to t2
When the application of voltage to the light control layer 101 is stopped after rewriting the image on the electronic paper 100, the arrangement direction of the nematic PDLC 103 starts to change from parallel to perpendicular to the transparent electrode 105A. Time t2 represents a time at which the direction in which nematic PDLCs 103 are arranged to change vertically.

  From time t1 to t2, the transmittance (reflectance) of incident light changes with the change in the direction in which nematic PDLCs 103 are arranged. At this time, the contrast of the image displayed on the screen of the electronic paper 100 viewed from the observer changes from about 0% to about 100%.

  In FIGS. 2B and 2C, the change in transmittance and contrast is shown to be linearly proportional to time, but it may not be linear in practice. Further, the time required for the change is not limited to that shown in FIG.

(4) After time t2 After time t2, the direction in which nematic PDLCs 103 are arranged is completely perpendicular to the transparent electrode 105A. This is the same as the state at time t0, and FIG. 1B also shows the state at time t2.

  Similar to time t0, after time t2, no voltage is applied to the light control layer 101, and the nematic PDLC 103 is aligned perpendicular to the transparent electrode 105A and transmits incident light. At this time, the image displayed on the screen of the electronic paper 100 viewed from the observer is the image itself displayed on the image display layer 102, and the contrast is about 100%.

(Effects of the first embodiment)
According to the first embodiment, the following effects can be obtained.
(A) At the moment when the image is rewritten, it appears to the observer that a white color is displayed on the screen of the electronic paper 100. Thereafter, the contrast of the image increases after a predetermined time, and the image appears to gradually appear on the screen of the electronic paper 100. As a result, the observer can easily recognize that the image has been rewritten normally.
(B) Since both the light control layer 101 and the image display layer 102 operate with an AC power supply, the configuration of the power supply circuit becomes easy, and there is little possibility that the operation becomes unstable due to interference.
(C) Since all the electronic paper 10 is made of a material that transmits light, illumination used for observation can be applied not only from the observer side but also from the back side.

[Second Embodiment]
(Structure of electronic paper)
3A and 3B are cross-sectional views of electronic paper according to the second embodiment of the present invention. The electronic paper 300 includes an image display layer 302 having a memory property, and a light control layer 301 that is positioned on the surface side (observation side), and whose light transmittance (reflectance) is changed by applying a DC voltage. With.

(Configuration of image display layer)
The image display layer 302 is a toner display type display element, and, as shown in FIGS. 3A and 3B, a pair of transparent substrates 306B and 306C made of PET films arranged opposite to each other, and inside each other, A plurality of strip-like transparent electrodes 305B and strip-like transparent electrodes 305C made of ITO provided so as to be orthogonal to each other, an insulating layer 310 provided on the inside thereof, and a support member 311 that forms a space 312 between the insulating layers 310; And positively charged black particles 308 enclosed in the space 312 and negatively charged white particles 309.

(Configuration of light control layer)
The light control layer 301 is an electrochromic display element, and as shown in FIGS. 3A and 3B, a PET film disposed to face a transparent substrate 306 </ b> B provided on the surface side of the image display layer 302. The transparent substrate 306A made of the above, a pair of transparent electrodes 305A made of ITO provided inside the transparent substrates 306A and 306B, and the transmittance according to the applied voltage between the pair of transparent electrodes 305A provided inside them A layer combining WO ₃ thin film 303 and polymer electrolyte 304, the (reflectance) of which changes.

Electrochromic display dimmer layer 301 which is an element, by applying a voltage between the pair of transparent electrodes 305A, and out ions and electrons between the polymer electrolyte 304 and WO ₃ thin film 303, WO ₃ thin film 303 in Change the valence of tungsten. Thereby, the transmittance (reflectance) can be changed by changing the absorption wavelength of light.

(Operation of electronic paper)
Next, the operation of the electronic paper 300 will be described with reference to FIGS. The temporal changes in the states of the image display layer 302 and the light control layer 301 are the same as those in the electronic paper according to the first embodiment, and are the same as those in FIG.

(1) Time t0
The time t0 in FIG. 2 represents the time when the image (previous image) before the screen of the electronic paper 300 is rewritten is displayed. FIG. 3B shows the state at time t0.

  At time t0, a DC voltage is applied from the DC power supply 307A in such a direction that the light control layer 301 transmits light. At this time, the image displayed on the screen of the electronic paper 300 viewed from the observer is the image displayed on the image display layer 302, and the contrast at that time is 100%.

(2) Time t1
The time t1 in FIG. 2 represents the time at the moment when the screen of the electronic paper 300 is rewritten. FIG. 3A shows the state at time t1.

  In rewriting the image, a DC voltage is selectively applied between the strip-shaped transparent electrodes 305B and 305C according to the image signal from the DC power supply 307B, and an electric field is formed between the strip-shaped transparent electrodes 305B and 305C. The positively charged black particles 308 and the negatively charged white particles 309 move according to the direction of the electric field, and an image is displayed by the black particles 308 and the white particles 309 attached to the band-like transparent electrode 305B on the surface side. .

At the time t1 or just before that, the DC power source 307A is connected in the direction opposite to the time t0, and the DC voltage is applied in such a direction that the light control layer 301 does not transmit light. At this time, the image displayed on the screen of the electronic paper 300 viewed from the observer is the color of the colored WO ₃ thin film 303, and the contrast of the image to be displayed is about 0%.

(3) Time t1 to t2
After the image on the electronic paper 300 is rewritten, when the direction of the DC voltage applied to the light control layer 301 is reversed again, the light control layer 301 starts to be transparent. The time t2 in FIG. 2 represents the time when the light control layer 301 becomes completely transparent.

  From time t1 to time t2, the contrast (reflectance) of incident light in the light control layer 301 changes, and the contrast of the image displayed on the screen of the electronic paper 300 viewed from the observer is about 0% to about 100%. Change toward.

(4) After time t2 The dimming layer 301 is completely transparent after time t2 in FIG. This is the same as the state at time t0, and FIG. 3B also shows the state after time t2.

  Similar to time t0, after time t2, the dimming layer 301 is completely transparent and transmits incident light. At this time, the image displayed on the screen of the electronic paper 300 viewed from the viewer is the image itself displayed on the image display layer 302, and the contrast thereof is about 100%.

(Effect of the second embodiment)
According to the second embodiment, the following effects can be obtained.
(A) At the moment when the image is rewritten, it seems to the observer that the color of the colored WO ₃ thin film 303 is displayed on the screen of the electronic paper 300. Thereafter, the contrast of the image increases after a predetermined time, and the image appears to gradually appear on the screen of the electronic paper 300. As a result, the observer can easily recognize that the rewriting of the image has been normally performed.
(B) Since the light control layer 301 using the electrochromic display element is thin, the electronic paper 300 can be thinned.
(C) Since both the image display layer 302 and the light control layer 301 operate with a DC power supply, the configuration of the power supply circuit is easy, and there is little possibility that the operation becomes unstable due to interference.

[Third Embodiment]
(Structure of electronic paper)
FIGS. 4A and 4B are cross-sectional views of electronic paper according to the third embodiment of the present invention. The electronic paper 400 is located on the image display layer 402 having a memory property and the back surface side (opposite side to the observation side), and the light transmittance (reflectance) is changed by applying an AC voltage. An optical layer 401.

(Configuration of image display layer)
The image display layer 402 is a transmission / scattering type display element such as a ferroelectric liquid crystal, and as shown in FIGS. 4A and 4B, a light transmission part 408 and a light scattering part 409 are formed according to an image, A strip-shaped transparent electrode and a transparent substrate (not shown) are provided. The light scattering unit 409 reflects white light and appears white, and the light transmission unit 408 transmits white light and appears black.

(Configuration of light control layer)
As shown in FIGS. 4A and 4B, the light control layer 401 includes a pair of transparent substrates 406 made of PET films arranged opposite to each other and white light provided on the back surface of the transparent substrate 406 on the back surface side. The scattering layer 410, a pair of transparent electrodes 405 made of ITO provided inside the pair of transparent substrates 406, and the transmittance (reflection) according to the applied voltage between the pair of transparent electrodes 405 provided inside them. The liquid crystal layer 411 in which the guest-host liquid crystal 403 is sealed in the binder resin 404.

  The guest-host liquid crystal 403 has positive dielectric anisotropy, and as shown in FIG. 4A, in a state where an AC voltage is applied, the incident-host liquid crystal 403 transmits incident light side by side perpendicular to the transparent electrode 405. As shown in FIG. 4B, incident light is reflected side by side in parallel with the transparent electrode 405 when no AC voltage is applied.

(Operation of electronic paper)
Next, the operation of the electronic paper 400 will be described with reference to FIGS. 4 and 5. FIG. 52 shows changes over time in the states of the image display layer 402 and the light control layer 401, (a) shows image rewriting tamming of the image display layer 402, and (b) shows changes in the transmittance of the light control layer 401. (C) shows the change in contrast of the observed image.

(1) Time t0
The time t0 represents the time when the image (previous image) before the screen of the electronic paper 400 is rewritten is displayed. FIG. 4B shows the state at time t0.

  At time t0, no voltage is applied to the light control layer 101, and the guest-host liquid crystal 403 is arranged in parallel to the transparent electrode 105A and reflects incident light. At this time, the color (for example, black) of the pigment of the guest host liquid crystal 403 is displayed on the light transmitting portion 408 of the image display layer 402, and the contrast of the image displayed on the screen of the electronic paper 400 at that time is 100%. And

(2) Time t1
The time t1 represents the time at the moment when the screen of the electronic paper 400 is rewritten. FIG. 4A shows the state at time t1.

  The rewriting of the image is performed by selectively applying a DC voltage from a DC power source (not shown) between the strip-shaped transparent electrodes according to the image signal. Thereby, the image of the transmission / scattering display element of the image display layer 402 is rewritten.

  When an AC voltage is applied from the AC power source 407 to the light control layer 401 at time t1 or just before that time, the guest-host liquid crystal 403 is aligned vertically with respect to the transparent electrode 405. Therefore, incident light passes through the light control layer 401 and reaches the light scattering layer (white) 310. At this time, the image displayed on the screen of the electronic paper 400 viewed from the observer is white, and the contrast is about 0%.

(3) Time t1 to t2
After rewriting the image on the electronic paper 400, voltage application to the light control layer 401 is stopped. Thereby, the direction in which the guest-host liquid crystal 403 is arranged starts to change from perpendicular to parallel to the transparent electrode 405. Time t2 represents the time at which the direction in which the guest-host liquid crystal 403 is arranged changes in parallel.

  From time t1 to t2, the transmittance (reflectance) of incident light changes with a change in the direction in which the guest-host liquid crystals 403 are arranged. At this time, the contrast of the image displayed on the screen of the electronic paper 400 viewed from the observer changes from about 0% to about 100%.

  In FIGS. 5B and 5C, the change in transmittance and contrast is shown to be linearly proportional to time, but in practice it may not be linear. Further, the time required for the change is not limited to that shown in FIG.

(4) After time t2 After time t2, the direction in which the guest-host liquid crystal 403 is arranged is completely parallel to the transparent electrode 405. This is the same as the state at time t0, and FIG. 4B also shows the state at time t3.

  Similar to time t0, after time t2, no voltage is applied to the light control layer 401, and the guest-host liquid crystal 403 is aligned perpendicular to the transparent electrode 405 and transmits incident light. At this time, the contrast of the image displayed on the screen of the electronic paper 400 viewed from the observer is about 100%.

(Effect of the third embodiment)
According to the third embodiment, the white of the light scattering layer 310 is displayed on the light transmitting portion 408 of the image display layer 402 at the moment when the image is rewritten, and is almost indistinguishable from the white color of the light scattering portion 309. . Thereafter, after a predetermined time, the color of the dye of the guest-host liquid crystal 403 is displayed on the light transmitting portion 408 of the image display layer 402 so that the contrast of the image is increased and the image gradually appears on the screen of the electronic paper 400. Looks like. As a result, the observer can easily recognize that the rewriting of the image has been normally performed.

  Note that the transparent substrate 406 on the back surface side of the light control layer 401 may be omitted. Further, the transparent substrate 406 on the surface side of the light control layer 401 may be omitted and shared with the substrate on the image display layer 402 side. Further, the transparent substrate 406 and the light scattering layer 410 on the back side of the light control layer 401 may be disposed upside down.

[Fourth Embodiment]
(Structure of electronic paper)
FIG. 6 is a cross-sectional view of electronic paper according to the fourth embodiment of the present invention. This electronic paper 600 uses a light scattering layer as the light control layer 601 in the third embodiment, and the other configuration is the same as that of the third embodiment.

(Configuration of image display layer)
Similar to the electronic paper according to the third embodiment, the image display layer 602 is a transmission / scattering type display element such as a ferroelectric liquid crystal. As shown in FIGS. 6A and 6B, the image display layer 602 corresponds to an image. A light transmission part 408 and a light scattering part 409 are formed, and a strip-shaped transparent electrode and a transparent substrate (not shown) are provided.

(Configuration of light control layer)
The light control layer 601 is a light scattering layer using an electrophoretic display element, and, as shown in FIGS. 6A and 6B, a pair of transparent substrates 606 made of PET films arranged opposite to each other, and the inside thereof A pair of transparent electrodes 605 made of ITO, a support member 610 providing a predetermined distance between the transparent electrodes 605, positively charged white particles 603 and a colored dispersion 604 enclosed between the transparent electrodes 605, Is provided.

  The light control layer 601 using the electrophoretic display element is a white particle that is positively charged according to the direction of the electric field formed between the transparent electrodes 605 by applying a DC voltage from the DC power source 607 between the transparent electrodes 605. 603 moves to one side of the pair of transparent electrodes 405. As a result, the light transmitting portion 608 of the image display layer 602 displays either the white color of the white particles 603 or the color (for example, black) of the colored dispersion 604.

(Operation of electronic paper)
Next, the operation of the electronic paper 600 will be described with reference to FIGS. FIG. 7 shows changes over time in the states of the image display layer 602 and the light control layer 601, (a) shows image rewriting tamming of the image display layer 602, and (b) shows a change in transmittance of the light control layer 601. (C) shows the change in contrast of the observed image.

(1) Time t0
The time t0 represents the time at which the image (previous image) before the screen of the electronic paper 600 is rewritten is displayed. FIG. 6B shows the state at time t0.

  At time t0, a DC voltage is applied from the DC power supply 607 in such a direction that the white particles 603 move to the transparent electrode 605 opposite to the image display layer 602. At this time, the color of the colored dispersion 604, for example, black, is displayed on the light transmission portion 608 of the image display layer 602. The contrast of the image displayed on the screen of the electronic paper 400 at this time is 100%.

(2) Time t1
The time t1 represents the time at the moment when the screen of the electronic paper 600 is rewritten. FIG. 6A shows the state at time t1.

  At the time t1 or just before that, the DC power source 607 is connected in the direction opposite to the time t0, and the white particles 603 move from the DC power source 607 in such a direction as to move to the transparent electrode 605 on the image display layer 602 side. Apply DC voltage. At this time, the image displayed on the screen of the electronic paper 100 as viewed from the observer is white, and the contrast is about 0%.

(3) Time t1 to t2
After rewriting the image on the electronic paper 600, the direction of the voltage applied to the light control layer 601 is reversed again. By reversing the direction of voltage application, the white particles 603 begin to move to the transparent electrode 605 on the opposite side of the image display layer 602. Time t2 represents the time when the white particles 603 have completely moved.

  At times t1 to t2, the contrast of the image displayed on the screen of the electronic paper 600 viewed from the observer is about 0% with the number of white particles 603 that have reached the transparent electrode 605 on the side opposite to the image display layer 602. It changes toward about 100%.

  In FIGS. 7B and 7C, the change in transmittance and contrast is shown to be linearly proportional to time, but it may not be linear in practice. Further, the time required for the change is not limited to that shown in FIG.

(4) After time t2 After time t2, the white particles 603 are completely transferred to the transparent electrode 605 on the side opposite to the image display layer 602. This is the same as the state at time t0, and FIG. 6B also shows the state after time t2.

  Similar to the time t0, after the time t2, the color of the colored dispersion 604 is displayed on the light transmitting portion 608 of the image display layer 602, and the contrast is about 100%.

(Effect of the fourth embodiment)
According to the fourth embodiment, the white of the white particles 403 of the light control layer 601 is displayed on the light transmitting portion 608 of the image display layer 602 at the moment when the image is rewritten, and the white of the light scattering portion 309 is displayed. Almost indistinguishable. After that, after a predetermined time, the color of the colored dispersion 604 of the light control layer 601 is displayed on the light transmission portion 608 of the image display layer 602, the image contrast is increased, and the image gradually appears on the screen of the electronic paper 600. Looks like it appears. As a result, the observer can easily recognize that the image has been rewritten normally.

  Note that black particles may be used instead of the white particles 603 of the light control layer 601, and a white dispersion may be used instead of the black colored dispersion 604. In this case, the direction of the DC voltage to be applied is different.

[Fifth Embodiment]
FIG. 8 shows electronic paper according to a fifth embodiment of the present invention. In the electronic paper 100, the transparent electrode 105A on the image display layer 102 side of the pair of transparent electrodes 105A provided in the light control layer 101 is omitted in the first embodiment, and the transparent electrode 105B of the image display layer 102 is omitted. The other configuration is the same as in the first embodiment. According to the fifth embodiment, the configuration of the electronic paper can be simplified by reducing one electrode.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, in each of the above embodiments, a specific combination of the light control layer and the image display layer has been described as an example, but other combinations may be used.

  The transparent substrate is not limited to the PET film, and various materials such as a glass substrate can be used. The transparent electrode is not limited to the ITO, and various materials such as tin oxide (TO), zinc oxide (ZnO), and tin cadmium oxide (CTO) can be used. In addition, the substrates 106C, 306C, and 606 on the side opposite to the observation side shown in FIGS. 1, 3, 6, and 8 may not be transparent, and various materials such as glass epoxy can be used. In addition, the electrodes 105B, 305C, and 605 on the side opposite to the observation side in FIGS. 1, 3, 6, and 8 may not be transparent, and various materials such as copper can be used.

(A), (b) is sectional drawing of the electronic paper which concerns on the 1st Embodiment of this invention. FIG. 4A illustrates temporal changes in the state of the image display layer and the light control layer of the electronic paper according to the first embodiment and the second embodiment. FIG. 5A illustrates image rewriting tamming of the image display layer. () Shows the change in the transmittance of the light control layer, and (c) shows the change in the contrast of the observed image. (A), (b) is sectional drawing of the electronic paper which concerns on the 2nd Embodiment of this invention. (A), (b) is sectional drawing of the electronic paper which concerns on the 3rd Embodiment of this invention. FIG. 6 shows temporal changes in the state of an image display layer and a light control layer of an electronic paper according to a third embodiment, (a) shows image rewriting tamming of the image display layer, and (b) shows transmission through the light control layer. (C) is a figure which shows the change of the contrast of the image to observe. (A), (b) is sectional drawing of the electronic paper which concerns on the 4th Embodiment of this invention. FIG. 6 shows temporal changes in the state of an image display layer and a light control layer of an electronic paper according to a fourth embodiment, (a) shows image rewriting tamming of the image display layer, and (b) shows transmission through the light control layer. (C) is a figure which shows the change of the contrast of the image to observe. It is sectional drawing of the electronic paper which concerns on the 5th Embodiment of this invention.

Explanation of symbols

100, 300, 400, 600 Electronic paper 101, 301, 401 Light control layer 102, 302, 402, 602 Image display layer 103 Nematic PDLC
104A, 104B, 404 Binder resin 105A, 105B, 305A, 305B, 305C, 405, 605 Transparent electrode 106A, 106B, 106C, 306A, 306B, 406, 606 Transparent substrate 107A, 107B, 407 AC power supply 108 Cholesteric liquid crystal 109 Light absorption Layer 110 Organic photoconductive layer 111A, 111B Liquid crystal layer 303 WO ₃ thin film 304 Polymer electrolyte 307A, 307B, 607 DC power supply 308 Black particles (positively charged)
309 White particles (negatively charged)
310 Insulating layer 311, 610 Support member 312 Space 403 Guest host liquid crystal 408, 608 Light transmission part 409, 609 Light scattering part 410 Light scattering layer (white)
601 Light scattering layer 603 White particles (positively charged)
604 Colored dispersion

Claims (14)

An image display layer having memory properties;
An electronic paper comprising: a light control layer that adjusts a contrast of an image displayed on the image display layer by changing a light transmittance or reflectance by applying a voltage.   The electronic paper according to claim 1, wherein the light control layer is a display element using a nematic polymer dispersed liquid crystal.   The electronic paper according to claim 1, wherein the light control layer is an electrochromic display element.   The electronic paper according to claim 1, wherein the light control layer is a display element using guest-host liquid crystal.   The electronic paper according to claim 1, wherein the light control layer is provided on the observation side of the image display layer.   The electronic paper according to claim 1, wherein the light control layer is provided on a side opposite to the observation side of the image display layer.   The light control layer includes a transparent substrate positioned on the image display layer side, a counter substrate disposed to face the transparent substrate, and a first color liquid disposed between the transparent substrate and the counter substrate. And a positively or negatively charged particle group of a second color that is provided in the liquid and moves between the transparent substrate and the counter substrate in accordance with an electric field. The electronic paper described.   The light control layer is disposed between the transparent substrate positioned on the image display layer side, a colored counter substrate disposed to face the transparent substrate, and between the transparent substrate and the colored counter substrate to apply a voltage. The electronic paper according to claim 6, further comprising a liquid crystal layer that changes to a transmissive state or a non-transmissive state according to the state.   2. The optical writing display element according to claim 1, wherein the image display layer includes a pair of electrodes, a liquid crystal layer provided between the pair of electrodes, and a photoconductive layer. Electronic paper.   The image display layer includes a pair of substrates and a display device of a toner display system including a group of particles disposed between the pair of substrates and having a predetermined charging property that moves between the pair of substrates according to an electric field. The electronic paper according to claim 1, wherein:   The electronic paper according to claim 1, wherein the image display layer is a transmission / scattering display layer such as a ferroelectric liquid crystal.   The electronic paper according to claim 1, wherein the image display layer and the light control layer share an electrode located between the image display layer and the light control layer.   The electronic paper according to claim 1, wherein the image display layer and the light control layer operate with an AC power source.   The electronic paper according to claim 1, wherein the image display layer and the light control layer operate with a DC power source.